HEAT PUMP CYCLE

Abstract

In a heat pump cycle, refrigerant tubes of an outdoor heat exchanger serving as an evaporator for evaporating refrigerant, and cooling fluid tubes of a radiator for dissipating heat from a coolant of an electric motor for traveling serving as an external heat source are bonded to the same outer fins. The heat contained in the coolant flowing through the cooling fluid tubes can be transferred to the refrigerant tubes of the outdoor heat exchanger via the outer fins. Thus, in the defrosting operation which involves defrosting the outdoor heat exchanger by flowing the coolant through the radiator, the loss in transfer of the heat contained in the coolant to the outdoor heat exchanger can be suppressed, and the heat supplied from the electric motor for traveling can be effectively used for defrosting the outdoor heat exchanger.

Description

CROSS REFERENCE TO RELATED APPLICATION

This application is based on Japanese Patent Applications No. 2010-132891 filed on Jun. 10, 2010, and No. 2011-123199 filed on Jun. 1, 2011, the contents of which are incorporated herein by reference in its entirety.

FIELD OF THE INVENTION

The present invention relates to a heat pump cycle for performing a defrosting operation to remove frost formed in a heat exchanger serving as an evaporator. More specifically, the invention relates to a heat pump cycle suitably used for an air conditioner for a vehicle that has a difficulty in obtaining a heat source for heating from a driving source for traveling.

BACKGROUND OF THE INVENTION

Conventionally, Patent Document 1 discloses a vapor compression refrigeration cycle (heat pump cycle) that performs a defrosting operation for melting and removing frost formed in a heat exchanger serving as an evaporator for evaporating refrigerant.

The heat pump cycle disclosed in Patent Document 1 is applied to an air conditioner for a hybrid car. The heat pump cycle is designed to be capable of switching between a heating operation for heating the interior of a vehicle by heating air blown into a vehicle compartment as a heat exchange fluid, and a defrosting operation for removing frost formed in an outdoor heat exchanger serving as the evaporator in the heating operation.

More specifically, in the defrosting operation, when the frost formation of the outdoor heat exchanger is detected, an internal combustion engine (engine) for outputting a driving force for vehicle traveling is initiated, and warm air blown from a radiator for dissipating heat from an engine coolant is blown into the outdoor heat exchanger to thereby defrost the outdoor heat exchanger.

In short, the heat pump cycle disclosed in Patent Document 1 is designed to remove the frost formed in the outdoor heat exchanger by melting the frost using waste heat of the engine as an external heat source.

PRIOR ART DOCUMENT

• Patent Document 1: Japanese Unexamined Patent Publication No. 2008-221997

However, the structure for transferring heat absorbed by the coolant from the engine to the evaporator via air might dissipate heat from the air (warm air) heated by the radiator into ambient air, thereby leading to the loss in heat transfer, as in Patent Document 1. In some cases, the waste heat from the engine as the external heat source cannot be effectively used for defrosting the evaporator.

As mentioned above, the waste heat from the engine cannot be effectively used for defrosting the evaporator, which takes a long time to perform the defrosting. And, during the defrosting operation, the engine has to continue working, causing the deterioration of the fuel efficiency of the vehicle. When the heating operation is stopped during the defrosting operation, a passenger cannot feel warm enough.

SUMMARY OF THE INVENTION

The present invention has been made in view of the forgoing points, and it is a first object of the present invention to provide a heat pump cycle that can effectively use the heat supplied from an external heat source during a defrosting operation.

Further, it is a second object of embodiments of the invention to provide a heat pump cycle applied to an air conditioner for a vehicle, which can achieve both the effective use of heat supplied from the external heat source, and the prevention of insufficient heating to a passenger during a defrosting operation.

To achieve the above object, according to a first exemplar of the present invention, a heat pump cycle includes: a compressor compressing and discharging refrigerant; a user-side heat exchanger exchanging heat between the refrigerant discharged from the compressor and a heat exchange fluid; a decompression device decompressing the refrigerant flowing from the user-side heat exchanger; and an outdoor heat exchanger which causes the refrigerant decompressed by the decompression device to exchange heat with outside air and to be evaporated. The heat pump cycle is adapted to perform a defrosting operation for defrosting the outdoor heat exchanger when the outdoor heat exchanger is frosted. The heat pump cycle further includes a heat-dissipation heat exchanger and a cooling fluid circuit switching device. The heat-dissipation heat exchanger is disposed in a cooling fluid circulation circuit for circulating a cooling fluid for cooling an external heat source, and is adapted to exchange heat between the cooling fluid and outside air. The cooling fluid circuit switching device is configured to switch between a cooling fluid circuit for allowing the cooling fluid to flow into the heat-dissipation heat exchanger, and a cooling fluid circuit for allowing the cooling fluid to bypass the heat-dissipation heat exchanger. In the heat pump cycle, the outdoor heat exchanger includes a refrigerant tube in which the refrigerant decompressed by the decompression device flows, a heat-absorption air passage for flowing the outside air is formed around the refrigerant tube, the heat-dissipation heat exchanger includes a cooling fluid tube in which the cooling fluid flows, a heat-dissipation air passage for flowing the outside air is formed around the cooling fluid tube, the heat-absorption air passage and the heat-dissipation air passage are provided with an outer fin that enables heat transfer between the refrigerant tube and the cooling fluid tube while promoting heat exchange in both of the outdoor heat exchanger and the heat-dissipation heat exchanger, and the cooling fluid circuit switching device performs switching to the cooling fluid circuit for flowing the cooling fluid into the heat-dissipation heat exchanger in at least the defrosting operation.

Because the cooling fluid circuit switching device performs switching to the cooling fluid circuit for flowing the cooling fluid into the heat-dissipation heat exchanger during the defrosting operation, the heat contained in the cooling fluid flowing through the cooling fluid tube can be transferred to the outdoor heat exchanger to defrost the outdoor heat exchanger.

At this time, outer fins are provided in the heat-absorption air passage and another heat-dissipation air passage to enable heat transfer between one refrigerant tube and another cooling fluid tube. Via the outer fins, the heat of the cooling fluid can be transferred to the outdoor heat exchanger.

As compared to the related art structure in which heat contained in the cooling fluid is transferred to the outdoor heat exchanger via air, the loss in heat transfer can be suppressed, and thus the heat supplied from the external heat source can be effectively used to defrost the outdoor heat exchanger during the defrosting operation. Further, the reduction in time required for the defrosting operation can also be achieved.

According to a second exemplar of the present invention, the heat pump cycle of the above first exemplar further includes: an indoor evaporator for allowing the refrigerant on a downstream side of the outdoor heat exchanger to exchange heat with the heat exchange fluid and to be evaporated; and a refrigerant flow path switching device configured to switch a refrigerant flow path in the heating operation in which the refrigerant discharged from the compressor flows into the user-side heat exchanger to heat the heat exchange fluid, and a refrigerant flow path in the cooling operation in which the refrigerant dissipating heat therefrom at the outdoor heat exchanger flows into the indoor evaporator to cool the heat exchange fluid. Furthermore, a flow direction of the refrigerant flowing through the refrigerant tube in the heating operation is the same as that of the refrigerant flowing through the refrigerant tube in the cooling operation.

This arrangement of the heap pump cycle can heat the heat exchange fluid by the user-side heat exchanger. Additionally, the heat pump cycle also includes an indoor heat exchanger, and thus can also cool the heat exchange fluid by use of the indoor heat exchanger.

During the heating operation, the flow direction of refrigerant flowing through the refrigerant tube is the same as that of refrigerant flowing through the refrigerant tube during the cooling operation. As viewed from the flow direction of the outside air, the positional relationship between a heat exchange region on a refrigerant inlet side of the outdoor heat exchanger and a heat exchange region on a refrigerant outlet side thereof does not change between the heating operation and the cooling operation.

Thus, the outdoor heat exchanger and the heat-dissipation heat exchanger are macroscopically regarded as one heat exchanger. In the cooling operation for dissipating heat from the refrigerant by the outdoor heat exchanger, a heat exchange region on the refrigerant inlet side of the outdoor heat exchanger for flowing the refrigerant having a superheat degree at a relatively high temperature is superimposed in the flow direction of the outside air, on a heat exchange region on the cooling fluid inlet side of the heat-dissipation heat exchanger for flowing the cooling fluid at a relatively high temperature. Further, a heat exchange region on the refrigerant outlet side of the outdoor heat exchanger for flowing the refrigerant having a superheat degree at a relatively low temperature is superimposed in the flow direction of the outside air, on a heat exchange region on the cooling fluid outlet side of the heat-dissipation heat exchanger for flowing the cooling fluid at a relatively low temperature. With this arrangement, the flow of the refrigerant and the flow of the cooling fluid flowing through both heat exchangers can be made parallel.

Further, with this arrangement, in the heating operation for evaporating the refrigerant by the outdoor heat exchanger, the heat exchange region on the refrigerant inlet side of the outdoor heat exchanger through which the refrigerant flows at a relatively low temperature can be superimposed on the heat exchange region on the cooling fluid inlet side of the heat-dissipation heat exchanger through which the cooling fluid flows at a relatively high temperature, in the flow direction of the outside air. Thus, the heat pump cycle of this embodiment can effectively suppress the frost formation caused in the heat exchange region on the refrigerant inlet side of the outdoor heat exchanger through which the refrigerant flows at a relatively low temperature.

According to a third exemplar of the present invention, the heat pump cycle of the above first or second exemplar is configured such that, in the defrosting operation, an inflow rate of the refrigerant flowing into the outdoor heat exchanger is decreased as compared to before transfer to the defrosting operation.

Thus, in the defrosting operation, heat transmitted to the outdoor heat exchanger via outer fins can be prevented from being absorbed in the refrigerant flowing through the refrigerant tube of the outdoor heat exchanger. As a result, the heat supplied from the external heat source can be used more effectively to defrost the outdoor heat exchanger during the defrosting operation.

Furthermore, as in a fourth exemplar of the present invention, the decompression device may be a variable throttle mechanism in which a throttle opening degree is variable, and the decompression device may increase the throttle opening degree in the defrosting operation as compared to before transfer to the defrosting operation. Thus, in the defrosting operation, high-temperature refrigerant discharged from the compressor can readily flow to the outdoor heat exchanger, thereby accelerating defrosting of the outdoor heat exchanger.

Furthermore, as in a fifth exemplar of the present invention, the heat pump cycle may further include an outflow rate adjustment valve configured to adjust an outflow rate of the refrigerant flowing from the outdoor heat exchanger, and the outflow rate adjustment valve may decrease the outflow rate of the refrigerant in the defrosting operation as compared to before transfer to the defrosting operation.

Furthermore, as in a sixth exemplar of the present invention, the outflow rate adjustment valve may be configured integrally with an outlet for the refrigerant of the outdoor heat exchanger. Thus, a refrigerant passage volume from a discharge port side of the compressor to an inlet side of the outflow rate adjustment valve can be reduced, thereby reducing a refrigerant flow amount flowing into the outdoor heat exchanger.

According to a seventh exemplar of the present invention, the heat pump cycle of any one of first to sixth exemplars further includes an outdoor blower which blows outside air toward both the outdoor heat exchanger and the heat-dissipation heat exchanger, and the outdoor blower increases an air blowing capacity when the compressor is stopped, as compared to before stopping the compressor.

When the compressor is stopped, the blowing capacity of the outdoor blower can be increased to thereby quickly increase the temperature of the outdoor heat exchanger to the same level as the outside air, which can further reduce the defrosting time. The term “when a compressor is stopped” means that the compressor is stopped not only during the defrosting operation, but also during the normal operation.

In an eighth exemplar of the present invention, the heat pump cycle according to any one of first to seventh exemplars is configured such that, in the defrosting operation, a heating capacity of the user-side heat exchanger for heating the heat exchange fluid is decreased as compared to before transfer to the defrosting operation.

Thus, the heating capacity of the user-side heat exchanger for the heat exchange fluid is decreased, so that the amount of heat absorbed from the refrigerant at the outdoor heat exchanger can be reduced to promote the defrosting. Specific means for decreasing the heating capacity of the user-side heat exchanger for the heat exchange fluid may include the reduction of a flow rate of refrigerant circulating through the cycle, and the reduction of a refrigerant pressure at the user-side heat exchanger.

According to a ninth exemplar of the present invention, in the heat pump cycle according to any one of the first to eighth exemplars, the heat-absorption air passage and the heat-dissipation air passage are configured such that volumes of the outside air flowing into the heat-absorption air passage and the heat-dissipation air passage are decreased in the defrosting operation.

Thus, the heat pump cycle can suppress the absorption of the heat transmitted to the outdoor heat exchanger via the outer fins, in the outside air flowing through the heat-absorption air passage and the heat-dissipation air passage during the defrosting operation, and thus can more effectively use the heat supplied from the external heat source to defrost the outdoor heat exchanger in the defrosting operation.

Specifically, an outdoor blower may be provided for blowing the outside air toward both the outdoor heat exchanger and the heat-dissipation heat exchanger. During the defrosting operation, the blowing capacity of the outdoor blower may be reduced to thereby decrease the volume of outside air flowing into the heat-absorption air passage and the heat-dissipation air passage.

Further, a shutter device (passage interruption means) may be provided for opening and closing an inflow route for allowing the outside air to flow into the heat-absorption air passage and the heat-dissipation air passage. During the defrosting operation, the shutter device may decrease a passage area of the inlet route of the outside air to thereby decrease the volume of outside air flowing into the heat-absorption air passage and the heat-dissipation air passage.

The term “decreasing the volume of outside air” means not only decreasing the volume of air as compared to the present volume of inflow air, but also setting the volume of air to zero (0) (that is, not allowing the outside air to flow thereinto).

In a tenth exemplar of the present invention, the heat pump cycle according to any one of first to ninth exemplars further includes an outdoor blower which blows outside air toward both the outdoor heat exchanger and the heat-dissipation heat exchanger. In this case, the heat-dissipation heat exchanger is located on a windward side in the flow direction of the outside air blown by the outdoor blower with respect to the outdoor heat exchanger.

Because the outside air whose heat is absorbed by the heat-dissipation heat exchanger flows into the outdoor heat exchanger, the heat of the cooling fluid can be transferred to the outdoor heat exchanger not only via the outer fins but also via air. Thus, during at least the defrosting operation, the heat supplied from the external heat source can be used more effectively to defrost the outdoor heat exchanger.

In an 11th exemplar of the present invention, in the heat pump cycle according to any one of first to tenth exemplars, at least one of the refrigerant tubes is located between the cooling fluid tubes, at least one of the cooling fluid tubes is located between the refrigerant tubes, and at least one of the heat-absorption air passage and the heat-dissipation air passage is formed as one air passage.

Thus, as compared to the case where the heat-dissipation heat exchanger and the outdoor heat exchanger are arranged in series with respect to the flow direction of the outside air, the cooling fluid tube and the refrigerant tube can be arranged close to each other. In other words, the cooling fluid tube can be positioned near frost formed in the refrigerant tube. Thus, during the defrosting operation, the heat supplied from the external heat source can be effectively transmitted to the outdoor heat exchanger to perform the defrosting operation.

According to a 12th exemplar of the present invention, the heat pump cycle of any one of first to 11th exemplars may be applied to an air conditioner for a vehicle, and may include an inside air temperature detection portion configured to detect an inside air temperature of a vehicle interior, and a frost formation determination portion configured to determine frost formation of the outdoor heat exchanger. In this case, the heat exchange fluid is air blown into the vehicle interior, the external heat source is a vehicle-mounted device generating heat in operation, the cooling fluid is a coolant for cooling the vehicle-mounted device, and the cooling fluid circuit switching device performs switching to the cooling fluid circuit for flowing the cooling fluid into the heat-dissipation heat exchanger when the frost is determined to be formed at the outdoor heat exchanger by the frost formation determination portion and an inside air temperature of the vehicle interior is equal to or more than a predetermined reference inside air temperature.

With this arrangement, the frost formation is determined by a frost formation determination portion, and when the temperature of an inside air within a vehicle compartment is equal to or more than a predetermined reference inside air temperature, the frosting operation is started. After the inside air temperature of the vehicle interior is warmed up to some degree, the defrosting operation can be started. Thus, during the defrosting operation, even in the use of means for decreasing the heating capacity of the air in the user-side heat exchanger, the heat pump cycle can prevent the passenger from feeling unsatisfied with heating.

According to a 13th exemplar of the present invention, the heat pump cycle of any one of first to 12th exemplars may be applied to an air conditioner for a vehicle. In this case, the heat pump cycle further includes a frost formation determination portion for determining frost formation of the outdoor heat exchanger. Furthermore, the heat exchange fluid is air blown into the vehicle interior, the external heat source is a vehicle-mounted device generating heat in operation, the cooling fluid is a coolant for cooling the vehicle-mounted device, the user-side heat exchanger is disposed in a casing forming therein an air passage, and an inside/outside air switching device for changing a ratio of introduction of inside air to outside air to be introduced into the casing is disposed in the casing. Furthermore, the cooling fluid circuit switching device performs switching to the cooling fluid circuit for flowing the cooling fluid to the heat-dissipation heat exchanger when the frost is determined to be formed at the outdoor heat exchanger by the frost formation determination portion, and the inside/outside air switching device increases the ratio of introduction of the inside air to the outside air as compared to before transfer to the defrosting operation when the frost is determined to be formed at the outdoor heat exchanger by the frost formation determination portion.

Thus, even in the use of the means for decreasing the heating capacity of air in the user-side heat exchanger during the defrosting operation, the ratio of introduction of the volume of inside air having a high temperature to that of outside air is increased, which can prevent the passenger from feeling unsatisfied with heating.

According to a 14th exemplar of the present invention, the heat pump cycle of one of first to 13th exemplars is applied to an air conditioner for a vehicle, and the heat pump cycle further includes a frost formation determination portion configured to determine frost formation of the outdoor heat exchanger. In this case, the heat exchange fluid is air blown into the vehicle interior, the external heat source is a vehicle-mounted device generating heat in operation, the cooling fluid is a coolant for cooling the vehicle-mounted device, the user-side heat exchanger is disposed in a casing forming therein an air passage, an air outlet mode switching device for switching among air outlet modes by changing opening/closing states of air outlets for blowing the air into the vehicle interior is disposed in the casing, at least a foot air outlet for blowing the air to a foot of a passenger is provided as the air outlet, the cooling fluid circuit switching device performs switching to the cooling fluid circuit for flowing the cooling fluid into the heat-dissipation heat exchanger when the frost is determined to be formed at the outdoor heat exchanger by the frost formation determination portion, and the air outlet mode switching device performs switching to the air outlet mode for blowing the air from the foot air outlet when the frost is determined to be formed at the outdoor heat exchanger by the frost formation determination portion.

Further, even in the use of the means for decreasing the heating capacity of air in the user-side heat exchanger during the defrosting operation, switching is performed to an air outlet mode for blowing the air from a foot air outlet. For example, as compared to the case where the air is blown toward the face of the passenger, the heat pump cycle can prevent the passenger from feeling unsatisfied with heating.

According to a 15th exemplar of the present invention, the heat pump cycle of any one of first to 14th exemplars is applied to an air conditioner for a vehicle, and the heat pump cycle further includes a frost formation determination portion configured to determine frost formation of the outdoor heat exchanger. In this case, the heat exchange fluid is air blown into the vehicle interior, the external heat source is a vehicle-mounted device generating heat in operation, the cooling fluid is a coolant for cooling the vehicle-mounted device, the user-side heat exchanger is disposed in a casing for forming therein an air passage, a blower for blowing air toward the vehicle interior is disposed in the casing, the cooling fluid circuit switching device performs switching to the cooling fluid circuit for flowing the cooling fluid into the heat-dissipation heat exchanger when the frost is determined to be formed at the outdoor heat exchanger by the frost formation determination portion, and the blower decreases an air blowing capacity as compared to before the determination of the frost formation.

Moreover, even in the use of the means for decreasing the heating capacity of air in the user-side heat exchanger during the defrosting operation, blower decreases its blowing capacity, which can prevent the passenger from feeling unsatisfied with heating.

According to a 16th exemplar of the present invention, the heat pump cycle of any one of first to 15th exemplars may be applied to an air conditioner for a vehicle, and the heat pump cycle may further include a frost formation determination portion for determining frost formation of the outdoor heat exchanger. In this case, the heat exchange fluid is air blown into the vehicle interior, the external heat source may be a vehicle-mounted device generating heat in operation, the cooling fluid may be a coolant for cooling the vehicle-mounted device, the frost formation determination portion may determines that the frost is formed at the outdoor heat exchanger when a vehicle speed is equal to or less than a predetermined reference speed and when a temperature of the refrigerant on an outlet side of the outdoor heat exchanger is equal to or less than 0° C., and the cooling fluid circuit switching device may perform switching to a cooling fluid circuit for flowing the cooling fluid into the heat-dissipation heat exchanger when the frost is determined to be formed at the outdoor heat exchanger by the frost formation determination portion.

Specifically, when the frost is formed at the outdoor heat exchanger, the heat contained in a vehicle-mounted device can be effectively used to defrost the outdoor heat exchanger. Further, a frost formation determination portion determines that the frost is formed at the outdoor heat exchanger when the speed of the vehicle is equal to or less than a predetermined reference vehicle speed and the temperature of refrigerant on the outlet side of the outdoor heat exchanger is equal to or less than 0° C. In this way, the appropriate determination of frost formation is performed taking into consideration the vehicle speed.

According to a 17th exemplar of the present invention, in the heat pump cycle according to 16th exemplar, the frost formation determination portion may determine that the frost is formed at the outdoor heat exchanger, when the speed of the traveling vehicle is equal to or less than the predetermined reference speed, and when the temperature of the refrigerant on the outlet side of the outdoor heat exchanger is equal to or less than 0° C. The term “traveling vehicle” means that a vehicle whose speed is zero, that is, a stopping vehicle is not included.

According to an 18th exemplar of the present invention, the heat pump cycle of one of exemplars 12 to 17 further includes a coolant temperature detection portion configured to detect a temperature of the coolant flowing into a vehicle-mounted device. In this case, the cooling fluid circuit switching device performs switching to the cooling fluid circuit for flowing the cooling fluid into the heat-dissipation heat exchanger when a coolant temperature detected by the coolant temperature detection portion is equal to or more than the predetermined reference temperature.

In this way, heat contained in the coolant is dissipated from the heat-dissipation heat exchanger, which can protect the vehicle-mounted device from overheat. The heat dissipated from the heat-dissipation heat exchanger can be transferred to the outdoor heat exchanger, and then absorbed in the refrigerant. In the normal operation of the heat pump cycle, the indoor air can be effectively heated. As a result, the heating performance of the air conditioner for the vehicle can be improved.

According to a 19th example of the present invention, in the heat pump cycle of any one of first to 18th exemplars, the cooling fluid circulation circuit stores therein the heat contained in the external heat source when the cooling fluid circuit switching device performs switching to the cooling fluid circuit for allowing the cooling fluid to bypass the heat-dissipation heat exchanger.

Thus, when the defrosting operation is not necessary, the cooling fluid circuit switching device performs switching to a cooling fluid circuit for allowing the flow of the cooling fluid to bypass the heat-dissipation heat exchanger, which can store the heat contained in the external heat source, in the heat pump cycle. As a result, the heat stored during the defrosting operation can be used to complete the defrosting in a short time.

For example, according to a 20th exemplar of the present invention, the heat pump cycle of the 19th exemplar is applied to an air conditioner for a vehicle. In this case, the heat exchange fluid may be air blown into the vehicle interior, the external heat source may be a vehicle-mounted device generating heat in operation, the cooling fluid may be a coolant for cooling the vehicle-mounted device, and the cooling fluid circulation circuit may store heat dissipated from the vehicle-mounted device in the coolant when the cooling fluid circuit switching device performs switching to the cooling fluid circuit for allowing the cooling fluid to bypass the heat-dissipation heat exchanger.

According to a 21st exemplar of the present invention, the heat pump cycle of 19th exemplar is applied to an air conditioner for a vehicle. In this case, the heat exchange fluid may be air blown into the vehicle interior, the external heat source may be a heating element for generating heat by being supplied with power, the cooling fluid may be a coolant for cooling the heating element, and the cooling fluid circulation circuit may store the heat dissipated from the heating element in the coolant when the cooling fluid circuit switching device performs switching to the cooling fluid circuit for allowing the cooling fluid to bypass the heat-dissipation heat exchanger.

According to a 22nd exemplar of the present invention, the heat pump cycle of 21st exemplar is applied to an air conditioner for a vehicle. In this case, the heat exchange fluid may be air blown into the vehicle interior, a vehicle-mounted device generating heat in operation and a heating element for generating heat by being supplied with power may be provided as the external heat source, the cooling fluid may be a coolant for cooling the heating element and the vehicle-mounted device, and the cooling fluid circulation circuit may store the heat dissipated from at least one of the vehicle-mounted device and the heating element in the coolant when the cooling fluid circuit switching device performs switching to the cooling fluid circuit for allowing the cooling fluid to bypass the heat-dissipation heat exchanger.

Furthermore, as in a 23rd exemplar of the present invention, the heating element may be an amount of generated heat therefrom controlled based on an outside air temperature. Therefore, it can restrict unnecessary electrical power from being consumed in the heating element.

According to a 24th exemplar of the present invention, the heat pump cycle may further include: an outdoor unit bypass passage which causes the refrigerant decompressed by the decompression device to bypass the outdoor heat exchanger and to guide the refrigerant to a refrigerant outlet side of the outdoor heat exchanger; and an outdoor-unit bypass passage switching device configured to switch between a refrigerant circuit for guiding the refrigerant decompressed by the decompression device to the outdoor heat exchanger, and a refrigerant circuit for guiding the refrigerant decompressed by the decompression device toward the outdoor unit bypass passage. In this case, in the defrosting operation, the outdoor unit bypass passage switching device performs switching to the refrigerant circuit for guiding the refrigerant decompressed by the decompression device to the outdoor unit bypass passage.

The outdoor unit bypass passage switching device performs switching to a refrigerant circuit for guiding the refrigerant decompressed by decompression device to an outdoor unit bypass passage in the defrosting operation, which can prevent the heat transmitted to the outdoor unit heat exchanger via the outer fins from being absorbed in the refrigerant flowing through the outdoor heat exchanger during the defrosting operation.

Accordingly, the heat supplied from the external heat source can be used more effectively to defrost the outdoor heat exchanger during the defrosting operation. For example, in application to an air conditioner for a vehicle, the air can be heated by the user-side heat exchanger to achieve the heating of the vehicle interior.

According to a 25th exemplar of the present invention, the heat pump cycle may further include: an indoor evaporator which exchanges heat between the refrigerant on a downstream side of the outdoor heat exchanger and the heat exchange fluid; an evaporator bypass passage which causes the refrigerant on the downstream side of the outdoor heat exchanger to bypass the indoor evaporator and to guide the refrigerant to a refrigerant outlet of the indoor evaporator; and an evaporator bypass passage switching device configured to switch a refrigerant circuit for guiding the refrigerant on the downstream side of the outdoor heat exchanger to the indoor evaporator, and a refrigerant circuit for guiding the refrigerant on the downstream side of the outdoor heat exchanger to the evaporator bypass passage. In the defrosting operation, the evaporator bypass passage switching device performs switching to the refrigerant circuit for guiding the refrigerant on the downstream side of the outdoor heat exchanger to the indoor evaporator.

Thus, during the defrosting operation, the evaporator bypass passage switching device guides the refrigerant on the downstream side of the outdoor heat exchanger to an indoor evaporator side, so that the indoor evaporator can cool the heat exchange fluid by a heat absorption effect when the refrigerant is evaporated. For example, in application to the air conditioner for a vehicle, a dehumidification heating operation can be achieved in which the air cooled by the indoor evaporator is heated again by the user-side heat exchanger.

According to a 26th exemplar of the present invention, the heat pump cycle may be applied to an air conditioner for a vehicle. In this case, the heat exchange fluid is air blown into the vehicle interior, the user-side heat exchanger is disposed in a casing for forming therein an air blowing passage, and in the casing, an auxiliary heater is provided for heating the air blown into the vehicle interior using as a heating source, at least one of a heating fluid heated by a vehicle-mounted device that generates heat in operation, and a heating element that generates heat by being supplied with power.

Thus, even when the heating capacity of the user-side heat exchanger for the air is reduced by decreasing the refrigerant discharge capacity of the compressor during the defrosting operation, the air can be heated by an auxiliary heater. This arrangement can suppress the reduction in temperature of the air blown into the vehicle interior and thus can prevent the passenger from feeling unsatisfied with heating.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an overall schematic diagram showing refrigerant flow in a heating operation of a heat pump cycle according to a first embodiment.

FIG. 2 is an overall schematic diagram showing refrigerant flow in a defrosting operation of the heat pump cycle according to the first embodiment.

FIG. 3 is an overall schematic diagram showing refrigerant flow in a waste heat collecting operation of the heat pump cycle according to the first embodiment.

FIG. 4 is an overall schematic diagram showing refrigerant flow in a cooling operation of the heat pump cycle according to the first embodiment.

FIG. 5 is a schematic diagram showing a detail structure of an indoor air conditioning unit according to the first embodiment.

FIG. 6 is an overall schematic diagram showing refrigerant flow in a heating operation of a heat pump cycle according to a second embodiment.

FIG. 7 is an overall schematic diagram showing refrigerant flow in a defrosting operation of a heat pump cycle according to a third embodiment.

FIG. 8 is an overall schematic diagram showing refrigerant flow in a defrosting operation of a heat pump cycle according to a fourth embodiment.

FIG. 9 is an overall schematic diagram showing refrigerant flow in a defrosting operation of a heat pump cycle according to a fifth embodiment.

FIG. 10 is a perspective view of a heat exchanger structure according to a sixth embodiment.

FIG. 11 is an exploded perspective view of the heat exchanger structure according to the sixth embodiment.

FIG. 12 is a cross-sectional view taken along the line A-A in FIG. 10.

FIG. 13 is an exemplary perspective view for explaining the flow of refrigerant and the flow of coolant in the heat exchanger structure according to the sixth embodiment.

FIG. 14 is a flowchart showing a control flow of a vehicle interior linkage control according to a seventh embodiment.

FIG. 15 is a flowchart showing another control flow of the vehicle interior linkage control according to the seventh embodiment.

FIG. 16 is a flowchart showing another control flow of the vehicle interior linkage control according to the seventh embodiment.

FIG. 17 is a flowchart showing another control flow of the vehicle interior linkage control according to the seventh embodiment.

FIG. 18 is an overall schematic diagram showing refrigerant flow in a defrosting operation of a heat pump cycle according to an eighth embodiment.

FIG. 19 is an overall schematic diagram showing refrigerant flow in a defrosting operation of a heat pump cycle according to a ninth embodiment.

FIG. 20 is an overall schematic diagram showing refrigerant flow in a defrosting operation of a heat pump cycle according to a tenth embodiment.

FIG. 21 is an overall schematic diagram showing refrigerant flow in a defrosting operation of a heat pump cycle according to an eleventh embodiment.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

First Embodiment

Referring to FIGS. 1 to 5, a first embodiment of the present invention will be described below. In this embodiment of the present invention, a heat pump cycle 10 is applied to an air conditioner 1 for a vehicle of the so-called hybrid car, which can obtain a driving force for traveling from an internal combustion engine (engine) and an electric motor MG for traveling. FIG. 1 shows an entire configuration diagram of the air conditioner 1 for the vehicle of this embodiment.

The hybrid car can perform switching between a traveling state in which the vehicle travels obtaining the driving force from both engine and electric motor MG for traveling by operating or stopping the engine according to a traveling load on the vehicle or the like, and another traveling state in which the vehicle travels obtaining the driving force only from the electric motor MG for traveling by stopping the engine. Thus, the hybrid car can improve the fuel efficiency as compared to normal cars obtaining a driving force for traveling only from the engine.

The heat pump cycle 10 in the air conditioner 1 for the vehicle serves to heat or cool the air in the vehicle compartment to be blown into the vehicle interior as a space for air conditioning. Thus, the heat pump cycle 10 can switch between refrigerant flow paths to thereby perform a heating operation (heater operation) and a cooling operation (cooler operation). The heating operation is adapted to heat the vehicle interior by heating the air in the vehicle compartment as a heat exchange fluid as a normal operation. The cooling operation is adapted to cool the vehicle interior by cooling the air blown into the vehicle compartment.

Then, the heat pump cycle 10 can also perform a defrosting operation for melting and removing frost formed at an outdoor heat exchanger 16 serving as an evaporator for evaporating refrigerant in the heating operation, and a waste heat collecting operation for absorbing heat contained in the electric motor MG for traveling as the external heat source, in the refrigerant in the heating operation. In the entire configuration diagrams of the heat pump cycle 10 shown in FIGS. 1 to 4, the flow of refrigerant in each operation is designated by a solid arrow.

The heat pump cycle 10 of this embodiment employs a normal flon-based refrigerant as a refrigerant, and forms a subcritical refrigeration cycle whose high-pressure side refrigerant pressure does not exceed the critical pressure of the refrigerant. Into the refrigerant, a refrigerant oil for lubricating a compressor 11 is mixed, and a part of the refrigerant oil circulates through the cycle together with the refrigerant.

First, the compressor 11 is positioned in an engine room, and is to suck, compress, and discharge the refrigerant in the heat pump cycle 10. The compressor is an electric compressor which drives a fixed displacement compressor 11a having a fixed discharge capacity by use of an electric motor 11b. Specifically, various types of compression mechanisms, such as a scroll type compression mechanism, or a vane compression mechanism, can be employed as the fixed displacement compressor 11a.

The electric motor 11b is one whose operation (number of revolutions) is controlled by a control signal output from an air conditioning controller to be described later. The motor 11b may use either an AC motor or a DC motor. The control of the number of revolutions of the motor changes a refrigerant discharge capacity of the compression mechanism 11. Thus, in this embodiment, the electric motor 11b serves as a discharge capacity changing portion of the compressor 11.

A refrigerant discharge port of the compressor 11 is coupled to a refrigerant inlet side of an indoor condenser 12 as a user-side heat exchanger. The indoor condenser 12 is disposed in a casing 31 of an indoor air conditioning unit 30 of the air conditioner 1 for the vehicle. The indoor condenser 12 is a heat exchanger for heating that exchanges heat between a high-temperature and high-pressure refrigerant flowing therethrough and the air to be blown into the vehicle compartment and having passed through an indoor evaporator 20 described later. The detailed structure of the indoor air conditioning unit 30 will be described later.

A fixed throttle 13 for heating is coupled to a refrigerant outlet side of the indoor condenser 12. The fixed throttle 13 serves as a decompression device for the heating operation that decompresses and expands the refrigerant flowing from the indoor condenser 12 in the heating operation. The fixed throttle 13 for heating can use an orifice, a capillary tube, and the like. The outlet side of the fixed throttle 13 for heating is coupled to the refrigerant inlet side of the outdoor heat exchanger 16.

A bypass passage 14 for the fixed throttle 13 is coupled to the refrigerant outlet side of the indoor condenser 12. The bypass passage 14 causes a refrigerant flowing from the indoor condenser 12 to bypass the fixed throttle 13 for heating and guides the refrigerant into the outdoor heat exchanger 16. An opening/closing valve 15a for opening and closing the bypass passage 14 for the fixed throttle is disposed in the bypass passage 14 for the fixed throttle. The opening/closing valve 15a is an electromagnetic valve whose opening and closing operations are controlled by a control voltage output from the air conditioning controller.

The loss in pressure caused when the refrigerant passes through the opening/closing valve 15a is extremely small as compared to the loss caused in pressure when the refrigerant passes through the fixed throttle 13. Thus, when the opening/closing valve 15a is opened, the refrigerant flowing out of the indoor condenser 12 flows into the outdoor heat exchanger 16 via the bypass passage 14 for the fixed throttle. In contrast, when the opening/closing valve 15a is closed, the refrigerant flows into the outdoor heat exchanger 16 via the fixed throttle 13 for heating.

Thus, the opening/closing valve 15a can switch between the refrigerant flow paths of the heat pump cycle 10. The opening/closing valve 15a of this embodiment serves as a refrigerant flow path switching device. Alternatively, as such a refrigerant flow path switching device, an electric three-way valve or the like may be provided for switching between a refrigerant circuit for coupling the outlet side of the indoor condenser 12 to the inlet side of the fixed throttle 13 for heating, and another refrigerant circuit for coupling the outlet side of the indoor condenser 12 and the inlet side of the bypass passage 14 for the fixed throttle.

The outdoor heat exchanger 16 is to exchange heat between the low-pressure refrigerant flowing therethrough and an outside air blown from a blower fan 17. The outdoor heat exchanger 16 is a heat exchanger disposed in an engine room, and which serves as an evaporator for evaporating the low-pressure refrigerant to exhibit a heat absorption effect in the heating operation, and also as a radiator for dissipating heat from the high-pressure refrigerant in the cooling operation.

The blower fan 17 is an electric blower whose operating ratio, that is, whose number of revolutions (volume of air) is controlled by a control voltage output from the air conditioning controller. The outdoor heat exchanger 16 of this embodiment is integral with a radiator 43 to be described later, for exchanging heat between the coolant for cooling the electric motor MG for traveling and the outside air blown from the blower fan 17.

The blower fan 17 of this embodiment serves as an outdoor blower for blowing the outside air toward both the outdoor heat exchanger 16 and the radiator 43. The detailed structures of the outdoor heat exchanger 16 and the radiator 43 (hereinafter referred to as a “heat exchanger structure 70”) which are integral with each other will be described in detail below.

The outlet side of the outdoor heat exchanger 16 is coupled to an electric three-way valve 15b. The three-way valve 15b has its operation controlled by a control voltage output from the air conditioning controller. The three-way valve 15b serves as the refrigerant flow path switching device together with the above opening/closing valve 15a.

More specifically, in the heating operation, the three-way valve 15b performs switching to the refrigerant flow path for coupling the outlet side of the outdoor heat exchanger 19 to the inlet side of an accumulator 18 to be described later. In contrast, in the cooling operation, the three-way valve 15b performs switching to the refrigerant flow path for coupling the outlet side of the outdoor heat exchanger 16 to the inlet side of a fixed throttle 19 for cooling.

The fixed throttle 19 for cooling serves as decompression device for the cooler operation (cooling operation) for decompressing and expanding the refrigerant flowing from the outdoor heat exchanger 16 in the cooling operation. The fixed throttle 19 has the same basic structure as that of the above fixed throttle 13 for heating. The outlet side of the fixed throttle 19 for cooling is coupled to the refrigerant inlet side of an indoor evaporator 20.

The indoor evaporator 20 is disposed on the upstream side of the air flow with respect to the indoor condenser 12 in the casing 31 of the indoor air conditioning unit 30. The indoor evaporator 20 is a heat exchanger for cooling that exchanges heat between the vehicle indoor air and the refrigerant flowing therethrough to thereby cool the air within the vehicle interior. A refrigerant outlet side of the indoor evaporator 20 is coupled to an inlet side of the accumulator 18.

Thus, a refrigerant flow path for allowing the refrigerant to flow from the three-way valve 15b to the inlet side of the accumulator 18 in the heating operation serves as an evaporator bypass passage 20a for allowing the refrigerant on the downstream side of the outdoor heat exchanger 16 to bypass the indoor evaporator 20. The three-way valve 15b serves as evaporator bypass passage switching device for switching between a refrigerant circuit for guiding the refrigerant on the downstream side of the outdoor heat exchanger 16 to the indoor evaporator 20, and another refrigerant circuit for guiding the refrigerant on the downstream side of the outdoor heat exchanger 16 to the evaporator bypass passage 20a.

The accumulator 18 is a gas-liquid separator for the low-pressure side refrigerant that separates the refrigerant flowing thereinto into liquid and gas phases, and which stores therein the excessive refrigerant within the cycle. A vapor-phase refrigerant outlet of the accumulator 18 is coupled to a suction side of the compressor 11. Thus, the accumulator 18 serves to suppress the suction of the liquid-phase refrigerant into the compressor 11 to thereby prevent the compression of the liquid in the compressor 11.

Next, the indoor air conditioning unit 30 will be described below using FIG. 5. FIG. 5 shows an enlarged detailed configuration diagram, representing the indoor air conditioning unit 30 shown in FIGS. 1 to 4. The indoor air conditioning unit 30 is disposed inside a gauge board (instrument panel) at the forefront of the vehicle compartment. The unit 30 accommodates in a casing 31 serving as an outer envelope, a blower 32, the above-mentioned indoor condenser 12, and the indoor evaporator 20.

The casing 31 forms an air passage communicating with the vehicle compartment, through which air is blown into the vehicle interior. The casing 31 is formed of resin (for example, polypropylene) having some degree of elasticity, and excellent strength. An inside/outside air switch 33 for switching between the air (inside air) in the vehicle interior and the outside air to introduce the selected air is disposed on the most upstream side of the vehicle-interior air flow in the casing 31.

The inside/outside air switch 33 is an inside/outside air switching device for switching between suction port modes by continuously adjusting the opening areas of an inside air inlet for introducing the inside air into the casing 31 and an outside air inlet for introducing the outside air thereinto by an inside/outside air switching door to thereby continuously change the ratio of introduction of the inside air to the outside air.

The inside/outside air switch 33 is provided with the inside air inlet for introducing the inside air into the casing 31, and the outside air inlet for introducing the outside air thereinto. The inside/outside air switching door is positioned inside the inside/outside air switch 33 to continuously adjust the opening areas of the inside air inlet and the outside air inlet to thereby change the ratio of volume of the inside air to that of the outside air. The inside/outside air switching door is driven by an electric actuator (not shown) whose operation is controlled by a control signal output from an air conditioning controller.

The suction port modes switched by the inside/outside air switch 33 includes an inside air mode for introducing the inside air into the casing 31 by fully opening the inside air inlet, while completely closing the outside air inlet; an outside air mode for introducing the outside air into the casing 31, while completely closing the inside air inlet and fully opening the outside air inlet; and an inside-outside air mixing mode for simultaneously opening the inside air inlet and the outside air inlet.

A blower 32 for blowing the air sucked via the inside/outside air switch 33 into the vehicle interior is disposed on the downstream side of the air flow of the inside/outside air switch 33. The blower 32 is an electric blower which includes a centrifugal multiblade fan (sirocco fan) driven by an electric motor, and whose number of revolutions (volume of air) is controlled by a control voltage output from the air conditioning controller.

The indoor evaporator 20 and the indoor condenser 12 are disposed on the downstream side of the air flow of the blower 32, in that order with respect to the flow of the air in the vehicle interior. In short, the indoor evaporator 20 is disposed on the upstream side in the flow direction of the vehicle indoor air with respect to the indoor condenser 12.

An air mix door 34 is disposed on the downstream side of the air flow in the indoor evaporator 20 and on the upstream side of the air flow in the indoor condenser 12. The air mix door 34 adjusts the rate of volume of the air passing through the indoor condenser 12 among the air passing through the indoor evaporator 20. A mixing space 35 is provided on the downstream side of the air flow in the indoor condenser 12 so as to mix the air exchanging heat with the refrigerant and being heated at the indoor condenser 12 and the air bypassing the indoor condenser 12 and not being heated.

An opening hole for blowing the conditioned air mixed in the mixing space 35, into the vehicle interior as a space of interest to be cooled is disposed on the most downstream side of the air flow in the casing 31. Specifically, the opening holes include a defroster opening hole 36a for blowing the conditioned air toward the inner side of a front glass of the vehicle, a face opening hole 36b for blowing the conditioned air toward the upper body of a passenger in the vehicle compartment, and a foot opening hole 36c for blowing the conditioned air toward the foot of the passenger.

The defroster opening hole 36a, the face opening hole 36b, and the foot opening hole 36c have the respective downstream sides of the air flows thereof connected to a defroster air outlet, a face air outlet, and a foot air outlet provided in the vehicle compartment via ducts forming respective air passages.

The air mix door 34 adjusts the rate of volume of air passing through the indoor condenser 12 to thereby adjust the temperature of conditioned air mixed in the mixing space 35, thus controlling the temperature of the conditioned air blown from each air outlet. That is, the air mix door 34 serves as a temperature adjustment device for adjusting the temperature of the conditioned air blown into the vehicle interior.

In short, the air mix door 34 serves as heat exchanging amount adjustment device for adjusting the amount of heat exchanged between the refrigerant discharged from the compressor 11 and the air in the vehicle interior in the indoor condenser 12 serving as the user-side heat exchanger. The air mix door 34 is driven by a servo motor (not shown) whose operation is controlled based on the control signal output from the air conditioning controller.

The defroster opening hole 36a, the face opening hole 36b, and the foot opening hole 36c have, at the respective upstream sides of the air flows thereof, a defroster door 37a for adjusting an opening area of the defroster opening hole 36a, a face door 37b for adjusting an opening area of the face opening hole 36b, and a foot door 37c for adjusting an opening area of the foot opening hole 36c, respectively.

The defroster door 37a, the face door 37b, and the foot door 37c serve as air outlet mode changing device for changing the opening/closing state of each air outlet for blowing the air into the vehicle interior, and are driven by an electric actuator (not shown) whose operation is controlled based on a control signal output from the air conditioning controller.

The air outlet modes include a face mode for blowing air toward the upper half body of the passenger in the vehicle interior from the face air outlet by fully opening the face air outlet, a bi-level mode for blowing air toward the upper half body and the foot of the passenger in the vehicle interior by opening both the face air outlet and the foot air outlet, and a foot mode for blowing air mainly from the foot air outlet by fully opening the foot air outlet, while slightly opening the defroster air outlet.

The passenger can manually operate switches on an operation panel to be described later to thereby setting the defroster mode for blowing the air from the defroster air outlet toward the inner surface of the front glass of the vehicle by fully opening the defroster air outlet.

Next, a coolant circulation circuit 40 will be described below. The coolant circulation circuit 40 is a cooling fluid circulation circuit for cooling the electric motor MG for traveling by allowing the coolant (for example, ethylene glycol aqueous solution) as a cooling fluid to circulate through a coolant passage formed in the above electric motor MG for traveling, which is one of the vehicle-mounted devices generating heat in operation.

The coolant circulation circuit 40 is provided with a coolant pump 41, an electric three-way valve 42, the radiator 43, and a bypass passage 44 for allowing the coolant to flow bypassing the radiator 43.

The coolant pump 41 is an electric pump for squeezing the coolant into a coolant passage formed within the electric motor MG for traveling in the coolant circulation circuit 40, and whose number of revolutions (flow rate) is controlled by a control signal output from the air conditioning controller. Thus, the coolant pump 41 serves as a cooling capacity adjustment portion for adjusting the cooling capacity by changing the flow rate of the coolant for cooling the electric motor MG for traveling.

A three-way valve 42 switches between a cooling fluid circuit for flowing the coolant into the radiator 43 by connecting the inlet side of the coolant pump 41 to the outlet side of the radiator 43, and another cooling fluid circuit for flowing the coolant to bypass the radiator 43 by connecting the inlet side of the coolant pump 41 to the outlet side of a bypass passage 44. The three-way valve 42 whose operation is controlled by the control voltage output from the air conditioning controller serves as cooling fluid circuit switching device.

That is, as illustrated by a dashed arrow of FIG. 1 or the like, the coolant circulation circuit 40 of this embodiment can perform switching between the cooling fluid circuit for circulation of the coolant from the coolant pump 41, the electric motor MG for traveling, the radiator 43, and the cooling pump 41 in that order, and the cooling fluid circuit for circulation of the coolant from the coolant pump 41, the electric motor MG for traveling, the bypass passage 44, and the coolant pump 41 in that order.

Thus, when the three-way valve 42 performs switching to the cooling fluid circuit for allowing the coolant to bypass the radiator 43 during the operation of the electric motor MG for traveling, the coolant has its temperature increased without dissipating its heat into the radiator 43. That is, when the three-way valve 42 performs switching to the cooling fluid circuit for allowing the coolant to bypass the radiator 43, the heat (heat generated) contained in the electric motor MG for traveling is stored in the coolant.

The radiator 43 is a heat-dissipation heat exchanger that is disposed in an engine room, and which exchanges heat between the coolant and the outside air blown from the blower fan 17. As mentioned above, the radiator 43 is integrally structured with the outdoor heat exchanger 16 to form a heat exchanger structure 70.

Now, the details of the heat exchanger structure 70 will be described below. Each of the outdoor heat exchanger 16 and the radiator 43 in this embodiment is comprised of the so-called tank and tube heat exchanger which includes a plurality of tubes for allowing the refrigerant or coolant to flow therethrough, and a pair of tanks for collection and distribution which are positioned on both sides of the tubes and which are designed to collect or distribute the refrigerant or coolant flowing through the tubes.

More specifically, the outdoor heat exchanger 16 includes a plurality of the refrigerant tubes 16a for flowing the refrigerant therethrough. Further, the refrigerant tube 16a is a flat tube having a flattened cross section in the direction perpendicular to the longitudinal direction. The respective the refrigerant tubes 16a are laminated with a predetermined gap therebetween such that flat surfaces of the outer surfaces thereof are opposed to each other in parallel.

Thus, a heat-absorption air passage 16b to flow the outside air blown from the blower fan 17 is formed around the refrigerant tubes 16a, that is, between the adjacent the refrigerant tubes 16a.

The radiator 43 includes a plurality of cooling fluid tubes 43a for allowing the coolant to flow therethrough, and having a flattened cross section in the direction perpendicular to the longitudinal direction. Like the refrigerant tubes 16a, the cooling fluid tubes 43a are laminated with a predetermined gap therebetween. A heat-dissipation air passage 43b to flow the outside air blown from the blower fan 17 is formed around the cooling fluid tubes 43a, that is, between the adjacent cooling fluid tubes 43a.

In this embodiment, the respective tanks for collection and distribution of the outdoor heat exchanger 16 and the radiator 43 are partially made of the same material, and the heat-absorption air passage and the heat-dissipation air passage are provided with outer fins 50 made of the same substance. The outer fins 50 are bonded to both tubes 16a and 43a, so that the outdoor heat exchanger 16 and the radiator 43 are integral with each other to form the heat exchanger structure 70.

The outer fin 50 in use is a corrugated fin formed by bending a thin metal plate with excellent heat conductivity in a wave shape. A part of the outer fin 50 disposed in the heat-absorption air passage serves to promote the heat exchange between the refrigerant and the outside air, and another part thereof disposed in the heat-dissipation air passage serves to promote the heat exchange between the coolant and the outside air.

Further, each outer fin 50 is bonded to both the refrigerant tube 16a and the cooling fluid tube 43a, which enables the heat transfer between the refrigerant tubes 16a and the cooling fluid tubes 43a.

In this embodiment described above, the refrigerant tubes 16a of the outdoor heat exchanger 16, the cooling fluid tubes 43a of the radiator 43, the tanks for collection and distribution, and the outer fins 50 are all formed of an aluminum alloy, and integral with one another by brazing. Further, in this embodiment, the radiator 43 is integral with the outdoor heat exchanger 16 on the windward side in the flow direction X of the outside air blown by the blower fan 17.

Now, an electric control unit of this embodiment will be described below. The air conditioning controller is comprised of the known microcomputer including a CPU, an ROM, and an RAM, and peripheral circuits thereof. The control unit controls the operation of each of the air conditioning controller 11, 15a, 15b, 17, 41, and 42 connected to its output by executing various operations and processing based on air conditioning control programs stored in the ROM.

A group of various sensors for control of air conditioning is coupled to the input side of the air conditioning controller. The sensors include an inside air sensor serving as inside air temperature detection portion for detecting a temperature of the vehicle interior, an outside air sensor for detecting a temperature of the outside air, a solar radiation sensor for detecting an amount of solar radiation in the vehicle interior, and an evaporator temperature sensor for detecting a temperature of blown air from the indoor evaporator 20 (evaporator temperature). And, the sensors also include a discharged refrigerant temperature sensor for detecting a temperature of the refrigerant discharged from the compressor 11, an outlet refrigerant temperature sensor 51 for detecting a refrigerant temperature Te on the outlet side of the outdoor heat exchanger 16, and a coolant temperature sensor 52 serving as coolant temperature detection portion for detecting a coolant temperature Tw of the coolant flowing into the electric motor MG for traveling.

In this embodiment, the coolant temperature sensor 51 detects the coolant temperature Tw of the coolant squeezed from the coolant pump 41. Alternatively, the coolant temperature Tw of the coolant sucked into the coolant pump 41 may be detected.

An operation panel (not shown) disposed near an instrument board at the front of the vehicle compartment is connected to the input side of the air conditioning controller. Operation signals are input from various types of air conditioning operation switches provided on the operation panel. Various air conditioning operation switches provided on the panel include an operation switch for the air conditioner for the vehicle, a vehicle-interior temperature setting switch for setting the temperature of the vehicle interior, and a selection switch for selecting an operation mode.

The air conditioning controller includes a control portion for controlling the electric motor 11b for the compressor 11, and the opening/closing valve 15a and the like which are integral with each other, and is designed to control the operations of these components. In the air conditioning controller of this embodiment, the structure (hardware and software) for controlling the operation of the compressor 11 serves as a refrigerant discharge capacity control portion. The structure for controlling the operations of the respective devices 15a and 15b serving as the refrigerant flow path switching device serves as a refrigerant flow path control portion. The structure for controlling the operation of the three-way valve 42 serving as the cooling fluid circuit switching device for coolant serves as a cooling fluid circuit control portion.

The air conditioning controller of this embodiment includes the structure (a frost formation determination portion) for determining whether or not the frost is formed at the outdoor heat exchanger 16, based on a detection signal from the above sensor group for the air conditioning control. Specifically, when the speed of a traveling vehicle is equal to or less than a predetermined reference value (in this embodiment, 20 km/h), and the refrigerant temperature Te on the outlet side of the outdoor heat exchanger 16 is equal to or less than 0° C., the frost formation determination portion of this embodiment determines that the frost formation is caused at the outdoor heat exchanger 16.

The determination using the frost formation determination portion is not limited thereto. Alternatively, for example, when the vehicle is stopped (specifically, the vehicle speed=0 km/h) with a vehicle system kept in operation, and the refrigerant temperature Te on the outlet side of the outdoor heat exchanger 16 is equal to or less than 0° C., the frost formation may be determined to be caused at the outdoor heat exchanger 16.

Next, the operation of the air conditioner 1 for the vehicle with the above arrangement in this embodiment will be described below. The air conditioner 1 for the vehicle of this embodiment can execute a heating operation for heating the vehicle interior, and a cooling operation for cooling the vehicle interior. In the heating operation, a defrosting operation and a waste heat collecting operation can also be carried out. Now, each operation will be explained in the following.

(a) Heating Operation

The heating operation is started when the heating operation mode is selected by the selection switch with the operation switch of the operation panel is turned on (ON). Then, in the heating operation, when the frost formation determination portion determines that the frost is formed at the outdoor heat exchanger 16, the defrosting operation is performed. When the coolant temperature Tw detected by the coolant temperature sensor 52 is equal to or more than the predetermined reference temperature (in this embodiment, 60° C.), the waste heat collecting operation is performed.

In the normal heating operation, the air conditioning controller closes the opening/closing valve 15a, and switches the three-way valve 15b to the refrigerant flow path for coupling the outlet side of the outdoor heat exchanger 16 to the inlet side of the accumulator 18. Further, the controller actuates the coolant pump 41 to squeeze the coolant in a predetermined flow rate, and switches the three-way valve 42 of the coolant circulation circuit 40 to the refrigerant flow path for allowing the coolant to bypass the radiator 43.

In this way, the heat pump cycle 10 is switched to the refrigerant flow path for allowing the refrigerant to flow as illustrated by the solid arrow in FIG. 1. The cooling fluid circulation circuit 40 is also switched to the cooling fluid flow path for allowing the refrigerant to flow as illustrated by the dashed arrow in FIG. 1.

The air conditioning controller with the above refrigerant flow path and cooling fluid circuit reads a detection signal from the sensor group for the air conditioning control and an operation signal from the operation panel. Based on the detection signal and the operation signal, a target outlet air temperature TAO is calculated as the target temperature of the air to be blown into the vehicle interior. Further, the operating states of various air conditioning control components connected to the output side of the air conditioning controller are determined based on the calculated target outlet air temperature TAO and the detection signal from the sensor group.

For example, the refrigerant discharge capacity of the compressor 11, that is, a control signal output to the electric motor of the compressor 11 is determined as follows. First, a target evaporator outlet air temperature TEO of the indoor evaporator 20 is determined based on the target outlet air temperature TAO with reference to a control map previously stored in the air conditioning controller.

Based on a deviation between the target evaporator outlet air temperature TEO and the blown air temperature from the indoor evaporator 20 detected by the evaporator temperature sensor, the control signal to be output to the electric motor of the compressor 11 is determined such that the blown air temperature of the air blown from the indoor evaporator 20 approaches the target evaporator outlet air temperature TEO by use of a feedback control method.

The control signal to be output to the servo motor of the air mix door 34 is determined based on the target outlet air temperature TAO, the blown air temperature of the indoor evaporator 20, and the temperature of the refrigerant discharged from the compressor 11 detected by the discharge refrigerant temperature sensor such that the temperature of air blown into the vehicle interior becomes a desired temperature set by the passenger using the vehicle indoor temperature setting switch.

During the normal heating operation, the defrosting operation, and the waste heat collecting operation, the opening degree of the air mix door 34 may be controlled such that the whole volume of air in the vehicle interior blown from the blower 32 passes through the indoor condenser 12.

A control signal to be output to an electric actuator of the inside/outside air switch 33 is determined with reference to a control map previously stored in the air conditioning controller. In this embodiment, basically, an outside air mode for introducing the outside air is given a higher priority. However, when the target outlet air temperature TAO becomes an ultra-high temperature to require high heating performance, or in the defrosting operation, an inside air mode for introducing the inside air is selected.

Control signals to be output to an electric actuator of each of the air outlet mode changing device 37a to 37c are determined with reference to a control map previously stored in the air conditioning controller. In this embodiment, as the target outlet air temperature TAO increases from a low-temperature range to a high-temperature range, the air outlet mode is switched from the face mode to the bi-level mode, and then to the foot mode in that order. Thus, in the heating operation, the foot mode is apt to be selected.

Then, the control signals determined as described above are output to various air conditioning control components. Thereafter, until the stopping of the air conditioner for a vehicle is requested by the operation panel, a control routine is repeated at every predetermined control cycle. The control routine includes a series of processes: reading of the detection signal and the operation signal, calculation of the target outlet air temperature TAO, determination of the operation states of various air conditioning control components, and output of the control voltage and the control signal in that order. Such repetition of the control routine is basically performed in other operation modes in the same way.

In the heat pump cycle 10 during the normal heating operation, the high-pressure refrigerant discharged from the compressor 11 flows into the indoor condenser 12. The refrigerant flowing into the indoor condenser 12 exchanges heat with the vehicle interior air blown from the blower 32 through the indoor evaporator 20 to dissipate the heat therefrom, so that the vehicle interior air is heated.

The high-pressure refrigerant flowing from the indoor condenser 12 flows into the fixed throttle 13 for heating to be decompressed and expanded by the throttle because the opening/closing valve 15a is closed. The low-pressure refrigerant decompressed and expanded by the fixed throttle 13 for heating flows into an outdoor heat exchanger 16. The low-pressure refrigerant flowing into the outdoor heat exchanger 16 absorbs heat from the outside air blown by the blower fan 17 to evaporate itself.

At this time, in the coolant circulation circuit 40, switching is performed to the cooling fluid circuit for allowing the coolant to bypass the radiator 43, which prevents the coolant from dissipating heat to the refrigerant flowing through the outdoor heat exchanger 16, and also prevents the coolant from absorbing heat from the refrigerant flowing through the outdoor heat exchanger 16. That is, the coolant never has a thermal influence on the refrigerant flowing through the outdoor heat exchanger 16.

Since the three-way valve 15b is switched to the refrigerant flow path connecting the outlet side of the outdoor heat exchanger 16 to the inlet side of the accumulator 18, the refrigerant flowing from the outdoor heat exchanger 16 flows into the accumulator 18 and is separated into liquid and gas phases. The gas-phase refrigerant separated into by the accumulator 18 is sucked by the compressor 11 and compressed again.

As mentioned above, in the normal heating operation, the air in the vehicle interior is heated by the indoor condenser 12 with heat contained in the refrigerant discharged from the compressor 11, which can perform the heating operation of the vehicle interior.

(b) Defrosting Operation

Next, the defrosting operation will be described below. In refrigeration cycle devices for evaporating the refrigerant by exchanging heat between the refrigerant and outside air in the outdoor heat exchanger 16, like the heat pump cycle 10 of this embodiment, when a refrigerant evaporation temperature as one of the temperatures of the outdoor heat exchanger 16 (specifically, the temperature of an outer surface of the outdoor heat exchanger 16, or the outdoor heat exchanger 16) becomes equal to or less than a frost formation temperature (specifically, 0° C.), the frost might be formed at the outdoor heat exchanger 16.

Such formation of the frost closes the heat-absorption air passage 16b of the outdoor heat exchanger 16 with the frost, which drastically reduces the heat exchange capacity of the outdoor heat exchanger 16. In the heat pump cycle 10 of this embodiment, when the frost formation is determined to be caused at the outdoor heat exchanger 16 by the frost formation determination portion in the heating operation, the defrosting operation is started.

In the defrosting operation, the air conditioning controller stops the operation of the compressor 11, and also stops the operation of the blower fan 17. Thus, during the defrosting operation, the flow rate of refrigerant flowing into the outdoor heat exchanger 16 is decreased, which leads to a decrease in volume of outside air flowing into the heat-absorption air passage 16b of the outdoor heat exchanger 16 and into the heat-dissipation air passage 43b of the radiator 43, as compared to the normal heating operation.

The air conditioning controller switches the three-way valve 42 of the coolant circulation circuit 40 to the cooling fluid circuit for allowing the coolant to flow into the radiator 43 as indicated by the dashed arrow in FIG. 2. Thus, the coolant circulation circuit 40 is switched to the cooling fluid circuit for flowing the refrigerant as indicated by the dashed arrow in FIG. 2 without circulation of the refrigerant through the heat pump cycle 10.

Thus, the heat contained in the coolant flowing through the cooling fluid tubes 43a of the radiator 43 is transferred to the heat-absorption air passages 16b of the outdoor heat exchanger 16 via the outer fins 50, whereby the defrosting operation of the outdoor heat exchanger 16 is carried out. That is, the defrosting is achieved which can effectively use the waste heat of the electric motor MG for traveling.

(c) Waste Heat Collecting Operation

Next, the waste heat collecting operation will be described below. Preferably, in order to suppress the over heat of the electric motor MG for traveling, the temperature of the coolant is maintained at a predetermined upper limit temperature or less. Further, in order to reduce the friction loss due to an increase in viscosity of oil for lubrication sealed into the electric motor MG for traveling, preferably, the temperature of the coolant is maintained at a predetermined lower limit temperature or more.

In the heat pump cycle 10 of this embodiment, when the coolant temperature Tw is equal to or more than the predetermined reference temperature (60° C. in this embodiment) during the heating operation, the waste heat collecting operation is performed. In the defrosting operation, the three-way valve 15b of the heat pump cycle 10 is performed in the same way as in the normal heating operation, but the three-way valve 42 of the coolant circulation circuit 40 is switched to the cooling fluid circuit for flowing the coolant into the radiator 43 as indicated by the dashed arrow in FIG. 3 in the same way as in the defrosting operation.

Thus, as illustrated by the solid arrow in FIG. 3, the high-pressure and high-temperature refrigerant discharged from the compressor 11 heats the air in the vehicle interior at the indoor condenser 12, and is then decompressed and expanded by the fixed throttle 13 for heating to flow into the outdoor heat exchanger 16 in the same way as in the normal heating operation.

Since the three-way valve 42 is switched to the cooling fluid circuit for flowing the coolant into the radiator 43, the low-pressure refrigerant flowing into the outdoor heat exchanger 16 absorbs both the heat contained in the outside air blown by the blower fan 17 and the heat contained in the coolant and transmitted thereto via the outer fins 50 to evaporate itself. Other actuations are the same as those in the normal heating operation.

As described above, in the waste heat collecting operation, the air in the vehicle interior is heated at the indoor condenser 12 with the heat of the refrigerant discharged from the compressor 11, which can perform heating of the vehicle interior. At this time, the refrigerant absorbs not only the heat contained in the outside air, but also the heat contained in the coolant and transmitted thereto via the outer fins 50, which can achieve the heating of the vehicle interior effectively using the waste heat of the electric motor MG for traveling.

(d) Cooling Operation

The cooling operation is started when the cooling operation mode is selected by the selection switch with the operation switch of the operation panel is turned on (ON). In the cooling operation, the air conditioning controller opens the opening/closing valve 15a, and switches the three-way valve 15b to the refrigerant flow path for connecting the outlet side of the outdoor heat exchanger 16 to the inlet side of the fixed throttle 19 for cooling. Thus, the heat pump cycle 10 is switched to the refrigerant flow path for flowing the refrigerant as indicated by the solid arrow in FIG. 4.

At this time, when the coolant temperature Tw is equal to or more than the reference temperature, the three-way valve 42 of the coolant circulation circuit 40 is switched to the cooling fluid circuit for flowing the coolant into the radiator 43. In contrast, when the coolant temperature Tw is less than the predetermined reference temperature, the three-way valve 42 is switched to the cooling fluid circuit for allowing the coolant to bypass the radiator 43. The flow of the coolant obtained when the coolant temperature Tw is equal to or more than the reference temperature is indicated by the dashed arrow in FIG. 4.

In the heat pump cycle 10 during the cooling operation, the high-pressure refrigerant discharged from the compressor 11 flows into the indoor condenser 12, and exchanges heat with the air in the vehicle interior blown from the blower 32 and having passed through the indoor evaporator 20 to dissipate heat therefrom. The high-pressure refrigerant flowing from the indoor condenser 12 flows into the outdoor heat exchanger 16 via the bypass passage 14 for the fixed throttle because the opening/closing valve 15a is opened. The low-pressure refrigerant flowing into the outdoor heat exchanger 16 further radiates heat toward the outside air blown by the blower fan 17.

Since the three-way valve 15b is switched to the refrigerant flow path for connecting the outlet side of the outdoor heat exchanger 16 to the inlet side of the fixed throttle 19 for cooling, the refrigerant flowing from the outdoor heat exchanger 16 is decompressed and expanded by the fixed throttle 19 for cooling. The refrigerant flowing from the fixed throttle 19 for cooling flows into the indoor evaporator 20, and absorbs heat from the air in the vehicle interior blown by the blower 32 to evaporate itself. In this way, the air in the vehicle interior can be cooled.

The refrigerant flowing from the indoor evaporator 20 flows into the accumulator 18, and is then separated into liquid and gas phases by the accumulator. The gas-phase refrigerant separated into by the accumulator 18 is sucked into and compressed by the compressor 11 again. As mentioned above, during the cooling operation, the low-pressure refrigerant absorbs heat from the air in the vehicle interior and evaporates itself at the indoor evaporator 20 to thereby cool the air in the vehicle interior, which can perform cooling of the vehicle interior.

As described above, the air conditioner 1 for the vehicle in this embodiment can perform switching among the refrigerant flow paths of the heat pump cycle 10, and among the cooling fluid circuits of the coolant circulation circuit 40 to thereby carry out various operations. Further, in the defrosting operation of this embodiment, the waste heat of the electric motor MG for traveling can be effectively used to defrost the outdoor heat exchanger 16 as will be described later.

More specifically, in this embodiment, the heat-absorption air passage 16b of the outdoor heat exchanger 16 and the heat-dissipation air passage 43b of the radiator 43 are provided with the outer fins 50 made of the same metal material to enable the heat transfer between the refrigerant tubes 16a and the cooling fluid tubes 43a. Thus, during the defrosting operation, the heat contained in the coolant can be transmitted to the outdoor heat exchanger 16 via the outer fins 50.

Therefore, this embodiment can suppress the loss in heat transfer as compared to the related art cycle in which heat contained in the coolant is transmitted to the outdoor heat exchanger 16 via air, and thus can effectively use the waste heat of the electric motor MG for traveling for defrosting the outdoor heat exchanger 16. Moreover, this embodiment can reduce the time for the defrosting operation.

During the defrosting operation, the operation of the compressor 11 is stopped and the flow rate of refrigerant flowing into the outdoor heat exchanger 16 is decreased (specifically, set to zero (0)) as compared to the time before the defrosting operation, which can prevent the heat transmitted to the outdoor heat exchanger 16 via the outer fins 50 from being absorbed in the refrigerant flowing through the refrigerant tubes 16a. Thus, the waste heat of the electric motor MG for traveling can be used more effectively to defrost the outdoor heat exchanger 16 during the defrosting operation.

In other words, during the defrosting operation, the operation of the compressor 11 is stopped to decrease the heating capacity for heating the air at the indoor condenser 12 (in this embodiment, such that the heating capacity is not exhibited), which decreases the amount of heat of the refrigerant absorbed in the outdoor heat exchanger 16. Thus, the waste heat of the electric motor MG for traveling can be used more effectively to defrost the outdoor heat exchanger 16 in the defrosting operation.

During the defrosting operation, the operation of the blower fan 17 is stopped to decrease the volume of outside air flowing into the heat-absorption air passages 16b and the heat dissipation air passage 43b (specifically, set to zero (0)), which can prevent the heat transmitted to the outdoor heat exchanger 16 via the outer fins 50 from being absorbed in the outside air flowing through the heat-absorption air passages 16b and the heat-dissipation air passage 43b. Thus, the waste heat of the electric motor MG for traveling can be used more effectively to defrost the outdoor heat exchanger 16 in the defrosting operation.

In the heat pump cycle 10 of this embodiment, during the normal heating operation, the three-way valve 42 of the coolant circulation circuit 40 is switched to the cooling fluid circuit for allowing the coolant to bypass the radiator 43 to thereby store the heat (generated heat) contained in the electric motor MG for traveling, in the coolant. Thus, during the defrosting operation, the defrosting operation can be completed by the stored heat in a short time.

In the heat exchanger structure 70 of this embodiment, the radiator 43 is arranged on the windward side of the flow direction X of the outside air blown by the blower fan 17 with respect to the outdoor heat exchanger 16. In other words, in the heat exchanger structure 70, the outdoor heat exchanger 16 and the radiator 43 are arranged in series such that the outside air flows from the radiator 43 to the outdoor heat exchanger 16.

Thus, the heat contained in the coolant can be transferred to the outdoor heat exchanger 16 not only via the outer fins 50, but also via air. That is, even when the blower fan 17 is stopped, the heat contained in the coolant can be transferred to the outdoor heat exchanger 16 by air pressure (ram air pressure) in the traveling direction of the traveling vehicle via the outside air passing through the heat exchanger structure 70. Thus, during the defrosting operation, the heat supplied from the electric motor MG for traveling can be used more effectively to defrost the outdoor heat exchanger 16.

The frost formation determination portion included in the air conditioning controller of this embodiment determines that the frost is formed in the outdoor heat exchanger 16 when the vehicle speed is equal to or less than the reference vehicle speed, and when the refrigerant temperature Te on the outlet side of the outdoor heat exchanger 16 is equal to or less than 0° C. Accordingly, the frost formation can be appropriately determined taking into consideration the vehicle speed.

That is, when the vehicle travels at low speed, the ram air pressure becomes lower and the volume of outside air flowing into the engine room is decreased. Thus, the volume of outside air flowing into each of the outdoor heat exchanger 16 and the radiator 43 is decreased. Thus, in the defrosting operation, the heat transferred to the outdoor heat exchanger 16 via the outer fins 50 is prevented from being absorbed in the outside air, which can achieve the effective defrosting.

Further, in the heat pump cycle 10 of this embodiment, when the coolant temperature Tw detected by the coolant temperature sensor 52 is equal to or more than the reference temperature, the waste heat collecting operation is performed by switching the three-way valve 42 to a cooling fluid circuit for flowing the coolant in the radiator 43. Thus, the heat contained in the coolant is dissipated by the radiator 43, which can protect the electric motor MG for traveling from over heat.

Additionally, in the waste heat collecting operation, the heat dissipated by the radiator 43 is transferred to the outdoor heat exchanger 16, and can be absorbed in the refrigerant, which can improve a coefficient of performance (COP) of the heat pump cycle 10, and thus can effectively heat the air in the vehicle interior. As a result, the heating performance of the air conditioner 1 for the vehicle can be improved.

In this embodiment, the three-way valve 42 is switched to the cooling fluid circuit for flowing the coolant into the radiator 43 to perform the waste heat collecting operation based on the reference temperature of 60° C. The reference temperature can be determined by the heat exchange performance or the like of the outdoor heat exchanger 16 and the like.

For example, when WW (g) is the weight of the coolant in the coolant circulation circuit 40, WG (g) is the amount of frost formed in the outdoor heat exchanger 16, TR (° C.) is the temperature of air blown from the outdoor heat exchanger 16, the amount of storage heat Qst stored in the coolant in the coolant circulation circuit 40 is represented by the following formula F1, and the amount of heat required for defrosting (hereinafter referred to as a “defrosting heat amount”) Qdf is represented by the following formula F2:

Qst=WW×Specific Heat of Coolant×(Tw−TR)  (F1)

Qdf=WG×Latent Heat of Vaporization of Water−Specific Heat of Water×

TR+Outdoor Heat Exchanger 16×Heat Capacity×TR+Amount of Heat

Dissipated into Air  (F2)

in which the storage heat amount Qst needs to exceed the defrosting heat amount Qdf in order to ensure the defrosting of the outdoor heat exchanger 16.

Further, when the heat capacity of the outdoor heat exchanger 16 and the amount of heat dissipated into air in the formula F2 are considered as ignorable ones, the minimum defrosting heat amount Qdf2 required to melt the frost formed at the outdoor heat exchanger 16 is represented by the following formula F3:

Qdf2=WG×Latent Heat of Vaporization of Water−Specific Heat of Water×TR  (F3)

Therefore, in order to perform the defrosting, at least the following formula F4 has to be satisfied:

Qst>Qdf2  (F4)

Substitution of the formulas (F1) and (F3) into the above formula (F4) can yield the following formula (F5):

Tw>TR+(WG×Latent Heat of Vaporization of Water−Specific Heat of

Water×TR)/(WW×Specific Heat of Coolant)  (F5)

Therefore, the temperature Tw satisfying the above formula F5 may be determined as the reference temperature.

In other words, the heat pump cycle of this embodiment includes coolant temperature detection portion (coolant temperature sensor 52) for detecting the coolant temperature Tw of the coolant flowing into the vehicle-mounted device (electric motor MG for traveling) generating heat in operation, and outdoor blown air temperature detection portion for detecting the air temperature TR of air blown from the outdoor heat exchanger 16. The cooling fluid circuit switching device (three-way valve 42) may perform switching to the cooling fluid circuit for allowing the cooling fluid (coolant) to flow into the heat-dissipation heat exchanger (radiator 43) when the coolant temperature TW detected by the coolant temperature detection portion (coolant temperature sensor 52) and the air temperature TR detected by the outdoor blown air temperature detection portion satisfy the following relationship:

Tw>TR+(WG×Latent Heat of Vaporization of Water−Specific Heat of

Water×TR)/(WW×Specific Heat of Coolant).

In the heat pump cycle 10 of this embodiment, during the heating operation (heater operation), the flow direction of refrigerant flowing through the refrigerant tubes 16a of the outdoor heat exchanger 16 is the same as that of refrigerant flowing through the refrigerant tubes 16a during the cooling operation (cooler operation). As viewed from the flow direction of outside air, the positional relationship between a heat exchange region on a refrigerant inlet side of the outdoor heat exchanger 16 and a heat exchange region on a refrigerant outlet side thereof does not change between the heating operation and the cooling operation. Therefore, the positional relationship between the temperature distribution of the heat exchange region of the outdoor heat exchanger 16 and the temperature distribution of the heat exchange region of the heat disspation heat exchanger 43 does not change.

That is, the outdoor heat exchanger 16 and the heat disspation heat exchanger 43 are macroscopically regarded as one heat exchanger structure 70. In that case, during the cooling operation for dissipating heat from the refrigerant at the outdoor heat exchanger 16, a heat exchange region on the refrigerant inlet side of the outdoor heat exchanger 16 for flowing the refrigerant having a superheat degree at a relatively high temperature can be superimposed in the flow direction of the outside air, on a heat exchange region on the cooling fluid inlet side of the heat disspation heat exchanger 43 for flowing the cooling fluid at a relatively high temperature. Further, a heat exchange region on the refrigerant outlet side of the outdoor heat exchanger 16 for flowing the refrigerant having a superheat degree at a relatively low temperature can be superimposed in the flow direction of the outside air, on a heat exchange region on the cooling fluid outlet side of the heat disspation heat exchanger 43 for flowing the cooling fluid at a relatively low temperature. With this arrangement, the flow of the refrigerant through the outdoor heat exchanger 16 and the flow of the cooling fluid through the heat disspation heat exchanger 43 can be made parallel to achieve the effective heat exchange.

Further, in the heating operation for evaporating the refrigerant at the outdoor heat exchanger 16, a heat exchange region on the refrigerant inlet side of the outdoor heat exchanger 16 for flowing the refrigerant at a relatively low temperature can be superimposed in the flow direction of the outside air, on a heat exchange region on the cooling fluid inlet side of the heat disspation heat exchanger 43 for flowing the cooling fluid at a relatively high temperature. As a result, the frost can be effectively prevented from being formed in the heat exchange region on the refrigerant inlet side of the outdoor heat exchanger 16 for allowing the refrigerant to flow therethrough at a relative low temperature.

Second Embodiment

Unlike the first embodiment, in this embodiment, as shown in the entire configuration diagram of FIG. 6, the indoor condenser 12 is removed, and a brine circuit 60 is provided for circulating brine, that is, a heating fluid by way of example. FIG. 6 is an entire configuration diagram showing refrigerant flow paths and the like during the heating operation in this embodiment, in which the flow of refrigerant in the heat pump cycle 10 is indicated by the solid line, and the flow of coolant in the coolant circulation circuit 40 is indicated by the dashed arrow.

In FIG. 6, the same or equivalent part as that of the first embodiment is designated by the same reference character. The same goes for the following other drawings.

Brine in this embodiment is a heating fluid for transferring heat contained in the refrigerant discharged from the compressor 11 to the air blown into the vehicle interior. Like the coolant as the cooling fluid, an ethylene glycol aqueous solution can be used. The brine circuit 60 includes a brine pump 61, a brine-refrigerant heat exchanger 62, and a heater core 63.

The brine pump 61 is an electric pump for squeezing the brine into the heater core 63 of the brine-refrigerant heat exchanger 62. The brine pump 61 has the same basic structure as that of the coolant pump 41 of the coolant circulation circuit 40. The brine-refrigerant heat exchanger 62 is a heat exchanger for exchanging heat between the refrigerant discharged from the compressor 11 and flowing through a refrigerant passage 62b, and the brine flowing through the brine passage 62a.

Specifically, the brine-refrigerant heat exchanger 62 can employ a double tube type heat exchanger structure comprised of an outer pipe forming the brine passage 62a, and an inner pipe disposed in the outer pipe for forming the refrigerant passage 62b. Alternatively, the refrigerant passage 62b may be formed as the outer pipe, and the brine passage 62a may be formed as the inner pipe. The refrigerant pipe forming the refrigerant passage 62b and the refrigerant pipe forming the brine passage 62a can be bonded together by brazing to form the heat exchanging structure and the like.

The heater core 63 is disposed in the casing 31 of the indoor air conditioning unit 30 of the air conditioner 1 for the vehicle. The heater core 63 is a heat exchanger for heating that exchanges heat between the brine passing therethrough and the vehicle-interior air having passed through the indoor evaporator 20. Thus, the heater core 63 of this embodiment serves as the user-side heat exchanger, which is the same as the indoor condenser 12. The structures and operations of other components in this embodiment are the same as those in the first embodiment.

Accordingly, even the operation of the air conditioner 1 for the vehicle of this embodiment can provide the same effects as those of the first embodiment. Further, since the brine circuit 60 is provided in this embodiment, the heating capacity of the heater core 63 can be easily adjusted by changing a coolant squeezing capacity of the brine pump 61.

Like the coolant, the brine in the brine pump 61 can also store the heat contained in the refrigerant discharged from the compressor 11 during the normal heating operation. Thus, even when the compressor 11 is stopped in the defrosting operation, the brine pump 61 can be operated to perform an auxiliary heating operation of the vehicle interior.

Third Embodiment

Unlike the heat pump cycle 10 of the first embodiment, as shown in the entire configuration diagram of FIG. 7, in this embodiment, an outdoor unit bypass passage 64 is added for allowing the refrigerant flowing from the fixed throttle 13 for heating or the bypass passage 14 for the fixed throttle to bypass the outdoor heat exchanger 16. And, an opening/closing valve 15c is further added for opening and closing the outdoor unit bypass passage 64.

FIG. 7 is an entire configuration diagram showing refrigerant flow paths during the defrosting operation in this embodiment, in which the flow of refrigerant in the heat pump cycle 10 is indicated by a solid line, and the flow of coolant in the coolant circulation circuit 40 is indicated by a dashed arrow.

The opening/closing valve 15c has the same basic structure as that of the opening/closing valve 15a disposed in the bypass passage 14 for the fixed throttle. The loss in pressure generated in the refrigerant passing through the opening/closing valve 15c when the opening/closing valve 15c is opened is much smaller than the loss in pressure generated in the refrigerant when the refrigerant passes through the outdoor heat exchanger 16.

Thus, when the opening/closing valve 15c is opened, most of the refrigerant flowing from the fixed throttle 13 for heating or the bypass passage 14 for the fixed throttle flows into the outdoor unit bypass passage 64, and hardly flows into the outdoor heat exchanger 16.

In this embodiment, in the defrosting operation, the air conditioning controller opens the opening/closing valve 15c without stopping the operation of the compressor 11, and in other operation modes, the opening/closing valve 15c is closed. Thus, during the defrosting operation, the flow rate of refrigerant flowing into the outdoor heat exchanger 16 is decreased. The structures and operations of other components in this embodiment are the same as those in the first embodiment.

Thus, even the operation of the air conditioner 1 for the vehicle of this embodiment can provide the same effects as those of the first embodiment. Further, since the operation of the compressor 11 is not stopped during the defrosting operation in this embodiment, the indoor condenser 12 can exhibit the heating capacity of the air with the heat contained in the refrigerant discharged from the compressor 11 to thereby perform the heating operation of the vehicle interior.

At this time, in the defrosting operation, the flow direction of refrigerant passing through the refrigerant tubes 16a of the outdoor heat exchanger 16 is the same as that in the heating operation (normal operation), which enables quick transfer from the normal operation to the defrosting operation, or from the defrosting operation to the normal operation. As a result, the defrosting time can be further reduced.

As viewed from the flow direction of the outside air, the positional relationship between the heat exchange region on the refrigerant inlet side of the outdoor heat exchanger 16 and the heat exchange region on the refrigerant outlet side thereof does not change with respect to the heat exchange region of the radiator 43, which can suppress large fluctuations in amount of heat transferred between the refrigerant flowing through the refrigerant tubes 16a of the outdoor heat exchanger 16 and the cooling fluid flowing through the cooling fluid tubes 43a of the radiator 43.

That is, when the heat exchange is performed between the refrigerant tubes 16a of the outdoor heat exchanger 16 via the outer fins 50 and the cooling fluid tubes 43a of the radiator 43, the relationship between the flow of the entire refrigerant in the outdoor heat exchanger 16 and the flow of the entire coolant in the radiator 43 might be changed from the opposite to the parallel, or from the parallel to the opposite in the related art. However, this embodiment can avoid such a situation.

As a result, the heat pump cycle of this embodiment can suppress the large fluctuations in amount of heat transfer between the refrigerant flowing through the refrigerant tubes 16a and the cooling fluid flowing through the cooling fluid tubes 43a, thus improving the flexibility in design of the outdoor heat exchanger 16 and the radiator 43.

Fourth Embodiment

This embodiment has the substantially same cycle structure as that of the heat pump cycle 10 of the third embodiment, but has a different control form of the air conditioning controller in the defrosting operation, which will be described below by way of example.

Specifically, in this embodiment, during the defrosting operation, the air conditioning controller opens the opening/closing valve 15a and the opening/closing valve 15c without stopping the operation of the compressor 11, and switches the three-way valve 15b to the refrigerant flow path for connecting the outlet side of the outdoor heat exchanger 16 (specifically, the outlet side of the outdoor unit bypass passage 64) to the inlet side of the fixed throttle 19 for cooling.

Thus, in this embodiment, in the defrosting operation, as shown in FIG. 8, the heat pump cycle 10 is switched to the cycle for circulating the refrigerant from the compressor 11, to the indoor condenser 12 (outdoor unit bypass passage 64), the fixed throttle 19 for cooling, the indoor evaporator 20, the accumulator 18, and the compressor 11 in that order.

The refrigerant flowing from the fixed throttle 19 for cooling takes latent heat of vaporization from the air upon evaporating at the indoor evaporator 20, so that the air can be cooled. Then, when the refrigerant discharged from the compressor 11 dissipates heat at the indoor condenser 12, the cooled air is re-heated. The structures and operations of other components in this embodiment are the same as those in the first embodiment.

Thus, even the operation of the air conditioner 1 for the vehicle of this embodiment can provide the same effects as those of the third embodiment. Further, in this embodiment, the air cooled by evaporating the refrigerant at the indoor evaporator 20 can be heated again by the indoor condenser 12 in the defrosting operation, which can achieve the defrosting and heating of the vehicle interior.

Fifth Embodiment

Unlike the heat pump cycle 10 of the first embodiment, as shown in the entire configuration diagram of FIG. 9, in this embodiment, a shutter device (passage interruption means) is added for opening or closing an inflow route for flowing the outside air into the radiator 43, by way of example. FIG. 9 is an entire configuration diagram showing refrigerant flow paths or the like in the defrosting operation of this embodiment, in which the flow of refrigerant in the heat pump cycle 10 is indicated by a solid line and the flow of coolant in the coolant circulation circuit 40 is indicated by a dashed arrow.

Specifically, a shutter device 65 is formed by combining a plurality of cantilever door plates. The shutter device 65 is designed to open the inflow route for flowing the outside air into the radiator 43 by displacing the door plate in the direction parallel to the flow of air from the blower fan 17, and to close the inflow route for flowing the outside air into the radiator 43 by displacing the door plate in the direction intersecting the air flow from the blower fan 17.

The radiator 43 is positioned on the windward side in the flow direction X of the outside air blown by the blower fan 17 with respect to the outdoor heat exchanger 16. The shutter device 65 closes the inflow route for flowing the outside air into the radiator 43 to thereby block the inflow route for flowing the outside air into the outdoor heat exchanger 16.

The shutter device 65 may be composed of a slide door or the like. The shutter device 65 is driven by a servo motor (not shown) whose operation is controlled by a control signal output from the air conditioning controller.

In this embodiment, in the defrosting operation, the shutter device 65 is operated to close the inflow route for flowing the outside air into the radiator 43, and in other operation modes, the shutter device 65 is operated to open the inflow route for flowing the outside air into the radiator 43. Thus, during the defrosting operation, the volume of outside air flowing into the heat-absorption air passage 16b and into the heat-dissipation air passage 43b is decreased. The structures and operations of other components in this embodiment are the same as those in the first embodiment.

Thus, even the operation of the air conditioner 1 for the vehicle of this embodiment can provide the same effects as those of the first embodiment. Further, in this embodiment, the shutter device 65 is operated to close the inlet route for flowing the outside air into the radiator 43 during the defrosting operation, which can prevent the inflow of the outside air into the heat-absorption air passages 16b and the heat dissipation air passage 43b due to the ram air pressure during the traveling of the vehicle.

Sixth Embodiment

In this embodiment, unlike the first embodiment, the specific structure of the heat exchanger structure 70 is modified, which will be described below by way of example. The details of the heat exchanger structure 70 will be explained below using FIGS. 10 to 13. FIG. 10 shows a perspective view of the contour of the heat exchanger structure 70 of this embodiment. FIG. 11 is an exploded perspective view of the heat exchanger structure 70. FIG. 12 is a cross-sectional view taken along the line A-A of FIG. 10. FIG. 13 is an exemplary perspective view for explaining the flow of refrigerant and the flow of coolant in the heat exchanger structure 70.

First, as shown in the exploded perspective view of FIG. 11, in the heat exchanger structure 70 of this embodiment, the refrigerant tubes 16a of the outdoor heat exchanger 16 are arranged in two lines and the cooling fluid tubes 43a of the radiator 43 are also arranged in two lines, in the flow direction X of the outside air blown by the blower fan 17. Further, the refrigerant tubes 16a and the cooling fluid tubes 43a are alternately arranged and laminated over each other.

Thus, in this embodiment, the heat-absorption air passage 16b and the heat-dissipation air passage 43b form one space. The outer fins 50 which are the same as those of the first embodiment are arranged in the heat-absorption air passage 16b and the heat-dissipation air passage 43b which form one space, and the respective outer fins 50 are bonded to the tubes 16a and 43a.

On one end side (lower end side shown in FIGS. 10 to 13) in the longitudinal direction of the refrigerant tubes 16a and the cooling fluid tubes 43a 43a, a tank 16c on the refrigerant side is provided for collecting or distributing the refrigerant flowing through the refrigerant tubes 16a. On the other end side (upper end side shown in FIGS. 10 to 13) in the longitudinal direction, a tank 43c on the cooling fluid side is provided for collecting or distributing the refrigerant flowing through the tubes 43a for cooling fluid.

The refrigerant side tank 16c and the cooling fluid side tank 43c have the same basic structure. First, the refrigerant side tank 16c includes a refrigerant side plate 161 for connection to the refrigerant tubes 16a and the cooling fluid tubes 43a which are respectively arranged in two lines, a refrigerant side intermediate plate 162 to be fixed to the refrigerant side connection plate 161, and a refrigerant side tank 163.

As shown in the cross-sectional view of FIG. 12, the refrigerant side intermediate plate 162 is fixed to the refrigerant side connection plate 161 to form a plurality of recesses 162b for forming a plurality of spaces in communication with the cooling fluid tubes 43a, between the refrigerant side connection plate 161 and the plate 162 itself. These spaces serve as a communicating space for the cooling fluid that connects and communicates the cooling fluid tubes 43a together arranged in two lines in the flow direction X of the outside air.

FIG. 12 shows the cross section of the surroundings of recesses 432b provided in the cooling fluid side intermediate plate 432 for clearly illustration. As mentioned above, since the refrigerant side tank 16c has the same basic structure as that of the cooling fluid side tank 43c, the refrigerant side connection plate 161 and the recesses 162b are represented in parentheses.

A through hole 162a is provided at a part of the refrigerant side intermediate plate 162 corresponding to the refrigerant tube 16a to penetrate both sides of the plate. The refrigerant tube 16a is inserted into the through hole. Thus, on one end of the refrigerant side tank 16c, the refrigerant tube 16a protrudes toward the refrigerant side tank 16c as compared to the cooling fluid tube 43a.

The refrigerant side tank 163 is fixed to the refrigerant side connection plate 161 and the refrigerant side intermediate plate 162 to form a collection space 163a for collecting therein the refrigerant and a distribution space 163b for distributing the refrigerant. Specifically, the refrigerant side tank 163 is formed by pressing a metal plate in double mountain shape (W-like shape) as viewed in the longitudinal direction.

The center of the double mountain shape of the refrigerant side tank 163 is bonded to the refrigerant side intermediate plate 162 to participate the tank 163 into the collection space 163a and the distribution space 163b. In this embodiment, the collection space 163a is disposed on the windward side of the flow direction X of the outside air, and the distribution space 163b is disposed on the leeward side of the flow direction X of the outside air.

One end of the refrigerant side tank 163 in the longitudinal direction is connected to a refrigerant inflow pipe 164 for flowing the refrigerant into the distribution space 163b, and to a refrigerant outflow pipe 165 for flowing the refrigerant from the collection space 163a. The other end of the refrigerant side tank 163 in the longitudinal direction is closed by a closing member.

On the other hand, the cooling fluid side tank 43c with the same structure as described above also includes a cooling fluid side connection plate 431, a cooling fluid side intermediate plate 432 fixed to the plate 431, and a cooling fluid side tank 433.

As shown in the cross-sectional view shown in FIG. 12, a refrigerant communication space that can communicate the two-lined the refrigerant tubes 16a together in the flow direction X of the outside air is formed by the recesses 432b provided in the cooling fluid side intermediate plate 432 between the cooling fluid side connection plate 431 and the cooling fluid side intermediate plate 432.

A through hole 432a is provided at a part of the cooling fluid side intermediate plate 432 corresponding to the cooling fluid tube 43a to penetrate both sides of the plate. The cooling fluid tube 43a is inserted into the through hole. Thus, on the side of the cooling fluid side tank 43c, the cooling fluid tube 43a protrudes toward the cooling fluid side tank 43c as compared to the refrigerant tube 16a.

Further, the cooling fluid side tank 433 is fixed to the cooling fluid side connection plate 431 and the cooling fluid side intermediate plate 432 to form a collection space 433a for collecting therein the cooling media and a distribution space 433b for distributing the cooling media. Specifically, in this embodiment, the distribution space 433b is disposed on the windward side of the flow direction X of the outside air, and the collection space 433a is disposed on the leeward side of the flow direction X of the outside air.

One end of the cooling fluid side tank 433 in the longitudinal direction is connected to a cooling fluid inflow pipe 434 for flowing the cooling fluid into the distribution space 433b, and to a cooling fluid outflow pipe 435 for flowing the cooling fluid from the collection space 433a. The other end of the cooling fluid side tank 43c in the longitudinal direction is closed by a closing member.

Thus, in the heat exchanger structure 70 of this embodiment, as shown in the exemplary perspective view of FIG. 13, the refrigerant flowing into the distribution space 163b of the refrigerant side tank 16c via the refrigerant inflow pipe 164 flows into each refrigerant tube 16a disposed on the leeward side in the flow direction X of the outside air among the refrigerant tubes 16a arranged in two lines.

And, the refrigerant flowing from each refrigerant tube 16a disposed on the leeward side flows into each refrigerant tube 16a disposed on the windward side in the flow direction X of the outside air via a space formed between the cooling fluid side connection plate 431 of the cooling fluid side tank 43c and the cooling fluid side intermediate plate 432.

Then, as indicated by a solid arrow in FIG. 13, the refrigerants flowing from the refrigerant tubes 16a disposed on the windward side are collected into the collection space 163a of the refrigerant side tank 16c, and then flow from the refrigerant outlet pipe 165. That is, in the heat exchanger structure 70 of this embodiment, the refrigerant flows turning around from the refrigerant tubes 16a on the leeward side to the cooling fluid side tank 43c, and the refrigerant tubes 16a on the windward side in that order.

Likewise, as illustrated by the dashed arrow in FIG. 13, the coolant flows turning around from the cooling fluid tubes 43a on the windward side to the refrigerant side tank 16c, and the cooling fluid tubes 43a on the leeward side in that order. The structures and operations of other components in this embodiment are the same as those in the first embodiment. Even the operation of the air conditioning 1 for the vehicle of this embodiment can provide the same effects as those of the first embodiment.

Further, in this embodiment, the refrigerant tubes 16a and the cooling fluid tubes 43a in the heat exchanger structure 70 are alternately arranged and laminated, so that the outdoor heat exchanger 16 can be effectively defrosted during the defrosting operation.

That is, in the heat exchanger structure 70 of this embodiment, the refrigerant tube 16a is disposed between the cooling fluid tubes 43a, and the cooling fluid tube 43a is disposed between the refrigerant tubes 16a, whereby the heat-absorption air passage 16b and the heat-dissipation air passage 43b form one air passage.

As compared to the case where the radiator 43 and the outdoor heat exchanger 16 are disposed in series with respect to the flow direction X of the outside air, in this embodiment, the tube 43ab for the cooling fluid and the refrigerant tube 16a can be arranged close to each other. Thus, the cooling fluid tube 43a can be disposed near the frost generated in the refrigerant tube 16a. As a result, the outdoor heat exchanger 16 can be effectively defrosted in the defrosting operation. The heat exchanger structure 70 of this embodiment may be applied to the heat pump cycles 10 of the second to fifth embodiments.

Seventh Embodiment

In the above first embodiment, the air conditioning controller stops the operation of the compressor 11 during the defrosting operation, by way of example. If the operation of the compressor 11 is stopped during the defrosting operation, the indoor condenser 12 cannot heat the air. As a result, the controller might blow the air having at a temperature lower than the temperature desired by the passenger in the vehicle. Once the defrosting operation is started, the passenger can feel unsatisfied with heating.

In contrast, in this embodiment, even when the air cannot be heated by the indoor condenser 12 in the defrosting operation, the vehicle interior linkage control is performed for suppressing the loss in heating to the passenger. The linkage control will be described below using the flowcharts shown in FIGS. 14 to 17.

FIG. 14 is a flowchart showing a basic control flow of the vehicle interior linkage control. The basic control flow is executed as a sub-routine which is an interrupt process for a main routine to be executed by the air conditioner 1 for the vehicle. When a defrosting flag deffg indicative of the execution of the defrosting operation does not become 1 within a predetermined time assigned as an execution time of the basic control flow, the operation returns to the main routine.

In step S100 of the basic control flow, a defrosting determination process is executed to determine whether or not the frost is formed at the outdoor heat exchanger 16 and whether or not the defrosting is performed. The details of the defrosting determination process will be described using FIG. 15. In step S101 of FIG. 15, the defrosting flag deffg or the like is initialized.

Subsequently, in step S102, it is determined whether or not the frost is formed at the outdoor heat exchanger 16. Specifically, when the temperature of the outer surface of the heat exchanger 16 is determined to be equal to or less than 0° C., the frost is determined to be formed, and then, the operation proceeds to step S103 with the deffg kept to 1 (deffg=1). In contrast, when the temperature of the outer surface of the outdoor heat exchanger 16 is determined not to be equal to or less than 0° C., the frost is determined not to be formed, and then, the operation returns to step S102 again with the deffg kept to zero (deffg=0).

In step S103, it is determined whether the engine is operated or not. When the engine is determined to be operated in step S103, the deffg is kept to 1 (deffg=1), and the operation proceeds to step S104. When the engine is determined not to be operated, the operation proceeds to an air conditioning mode changing control shown in step S200 of FIG. 14.

In step S104, like step S102, it is determined whether the frost is formed at the outer heat exchanger 16 or not. Specifically, when the temperature of the outer surface of the outdoor heat exchanger 16 is determined to be equal to or less than 0° C., the frost is determined to be formed, and then the operation proceeds to step S105 with the deffg kept to 1 (deffg=1). When the temperature of the outer surface of the outdoor heat exchanger 16 is determined not to be equal to or less than 0° C., the frost is determined not to be formed, and then the operation returns again to step S102.

In step S105, it is determined whether or not the coolant temperature Tw reaches the predetermined defrosting reference temperature KTwdef. In step S105, when the coolant temperature Tw is determined to reach the predetermined defrosting reference temperature KTwdef (in this embodiment, 10° C.), the outdoor heat exchanger 16 can be defrosted by flowing the coolant into the radiator 43, and then the operation proceeds to step S106 with the deffg kept to 1 (deffg=1).

In step S105, when the coolant temperature Tw is determined not to reach the predetermined defrosting reference temperature KTwdef, even if the coolant flows into the radiator 43, the outdoor heat exchanger 16 cannot be defrosted, and then the operation returns to step S102 again.

In step S106, it is determined whether or not an inside air temperature (temperature of the vehicle interior) Tr detected by the inside air sensor is equal to or more than a predetermined reference inside air temperature KTr (15° C. in this embodiment). In step S106, when the inside air temperature Tr is determined to be equal to or more than the reference inside air temperature KTr, the temperature of the vehicle interior is hot enough for a general passenger not to feel unsatisfied with the cold (hereinafter referred to as a “warm-up state”), and then the operation proceeds to step S107 with the deffg kept to 1 (deffg=1).

In step S106, when the inside air temperature Tr is determined not to be equal to or more than the reference inside air temperature KTr, the inside air temperature Tr is not increased until the warm-up state. In order to give the heating of the vehicle interior a priority over the defrosting operation, the operation returns again to step S102.

In step S107, it is determined whether or not the vehicle speed during traveling is equal to or less than a predetermined reference vehicle speed (20 km/h in this embodiment). In step S107, when the vehicle speed is determined to be equal to or less than the predetermined reference vehicle speed, like the first embodiment, the defrosting can be effectively performed together with the decrease in ram air pressure. Then, the operation proceeds to an air conditioning mode changing control shown in step S200 of FIG. 14 with deffg kept to 1 (deffg=1).

As can be seen from the above description, a control step S100 of this embodiment serves as a control portion with a frost formation determination portion for determining the frost formation of the outdoor heat exchanger 16. More specifically, the control steps S102 and S104 serve as the frost formation determination portion.

Then, the air conditioning mode changing control to be performed in step S200 will be described below using FIG. 16. The air conditioning mode changing control is to be exercised when the defrosting flag deffg is determined to be 1 by the defrosting determination process in step S100.

In step S201, first, a control signal to be output to the electric motor of the compressor 11 is determined such that the compressor 11 does not exhibit the refrigerant discharge capacity, that is, such that the compressor 11 is stopped. In the following step S202, a control signal to be output to the blower 32 is determined such that the air blowing capacity of the blower 32 is decreased by a predetermined capacity value from the present capacity.

In the following step S203, a suction port mode is set to the inside air mode. That is, the ratio of introduction of inside air to outside air is increased as compared to the state before the transmission to the defrosting operation. In step S204, an air outlet mode is set to the foot mode. That is, switching is performed to the air outlet mode for blowing the air mainly from the foot air outlet. Then, the operation proceeds to a defrosting start completion control shown in step S300 of FIG. 14.

The defrosting start completion control executed in step S300 will be described below using FIG. 17. In step S301, first, as described in the first embodiment, the three-way valve 42 of the coolant circulation circuit 40 is switched such that the coolant flows into the radiator 43. Further, the coolant squeezing capacity of the coolant pump 41 is maximized, the timer is actuated, and then the operation proceeds to step S302.

In step S302, it is determined whether the vehicle speed during traveling is equal to or less than a predetermined reference vehicle speed (in this embodiment, 20 km/h). When the vehicle speed is determined to be equal to or less than the reference vehicle speed in step S302, the effective defrosting can be achieved, and then the operation proceeds to step S303. When the vehicle speed is determined not to be equal to or less than the reference vehicle speed, the effective defrosting cannot be performed, and then the operation proceeds to step S304.

In step S303, it is determined whether or not the elapsed time of the defrosting operation exceeds a predetermined reference defrosting time using the timer actuated in step S301. When the elapsed time of the defrosting operation is determined to exceed the reference defrosting time, the operation proceeds to step S304. In step S304, at that time, the three-way valve 42 is switched such that the coolant flows into the bypass passage 44.

Then, the coolant squeezing capacity of the coolant pump 41 is changed to become the same squeezing capacity as that before the start of the defrosting operation, and the timer is reset. Thereafter, the operation proceeds to an air conditioning mode returning control shown in step S400 of FIG. 14. In the air conditioning mode returning control in step S400, the blowing capacity of the blower 32, the suction port mode, and the air outlet mode are returned to the same levels as those before the defrosting operation. Then, the operation proceeds to step S500.

In step S500, it is determined whether stopping of the vehicle system is requested or not. When the stopping of the vehicle system is not required, the operation proceeds to step S100. When the stopping of the vehicle system is required, the control processing is stopped. The structures and operations of other components of this embodiment are the same as those of the first embodiment.

Thus, this embodiment can obtain the same effects as those of the first embodiment. Additionally, in this embodiment, even when the air conditioning controller stops the operation of the compressor 11, and the indoor condenser 12 cannot exhibit the heating capacity during the defrosting operation, the above vehicle interior linkage control can be performed to prevent the passenger from feeling unsatisfied with heating.

That is, in this embodiment, as described in the control step S106, the defrosting operation is performed after the warm-up state is achieved, which can prevent the passenger from feeling unsatisfied with heating. As described in the control step S203, during the defrosting operation, the suction port mode is changed to the inside air mode. The inside air having a higher temperature than the outside air is circulated and blown, which can also prevent the passenger from feeling unsatisfied with heating.

As described in the control step S202, the blowing capacity of the blower 32 is decreased in the defrosting operation, which can prevent the passenger from feeling unsatisfied with heating even when the temperature of air blown into the vehicle compartment is decreased. At this time, as described in the control step S204, the air outlet mode is set to the foot mode, which can effectively prevent the passenger from feeling unsatisfied with the heating as compared to the case where the air is blown toward the passenger's face.

As can be seen from the above description, this embodiment can be considered as the example of application of the heat pump cycle 10 to the air conditioner) for a vehicle.

That is, this embodiment in one aspect includes a heat pump cycle which has a compressor for compressing and discharging refrigerant; a user-side heat exchanger (indoor condenser 12) for exchanging heat between the refrigerant discharged from the compressor and air blown into a vehicle interior; a decompression device (fixed throttle 13 for heating) for decompressing the refrigerant flowing from the user-side heat exchanger; an outdoor heat exchanger for allowing the refrigerant decompressed by the decompression device to exchange heat with outside air to evaporate itself; a heat-dissipation heat exchanger (radiator 43) disposed in a cooling fluid circulation circuit for circulating a cooling fluid for cooling a vehicle-mounted device (electric motor MG for traveling) generating heat in operation, and adapted to exchange heat between the cooling fluid and outside air to dissipate heat from the cooling fluid; a cooling fluid circuit for flowing the cooling fluid into the heat-dissipation heat exchanger (43); and cooling fluid circuit switching device (42) for performing switching to another cooling fluid circuit for allowing the cooling fluid to bypass the heat-dissipation heat exchanger (43). This embodiment also includes inside air temperature detection portion for detecting an inside air temperature in the vehicle interior; and a frost formation determination portion for determining frost formation at the outdoor heat exchanger. The outdoor heat exchanger includes a refrigerant tube for flowing the refrigerant decompressed by the decompression device. A heat-absorption air passage for flowing outside air is formed around the refrigerant tube. The heat-dissipation heat exchanger includes a cooling fluid tube for flowing the cooling fluid. An heat-dissipation air passage for flowing outside air is formed around the tubes for the cooling fluid. The air passage for the heat absorption and the air passage for the heat dissipation are provided with an outer fin that enables the heat transfer between the refrigerant tube and the cooling fluid tube, while promoting the heat exchange in both heat exchangers. When the frost is determined to be formed at the outdoor heat exchanger by the frost formation determination portion, and an inside air temperature Tr of the vehicle interior is equal to or more than a predetermined reference inside air temperature KTr, then the cooling fluid circuit switching device can perform switching to the cooling fluid circuit for flowing the cooling fluid to the heat dissipation heat exchanger.

This embodiment in another aspect includes the above heat pump cycle, a frost formation determination portion for determining the frost formation of the outdoor heat exchanger, and a casing for accommodating therein the user-side heat exchanger and for forming an air passage. An inside/outside air switching device (inside/outside air switch 33) is disposed in the casing to change the ratio of introduction of the inside air to the outside air to be introduced into the casing. When the frost is determined to be formed in the outdoor heat exchanger by the frost formation determination portion, the cooling fluid circuit switching device performs switching to a cooling fluid circuit for flowing the cooling fluid to the heat dissipation heat exchanger. When the frost is determined to be formed in the outdoor heat exchanger by the frost formation determination portion, the inside/outside air switching device can increase the ratio of introduction of the inside air to the outside air as compared to before transfer to the defrosting operation.

This embodiment in another aspect includes the above heat pump cycle, a frost formation determination portion for determining the frost formation of the outdoor heat exchanger, and a casing for accommodating therein the user-side heat exchanger and for forming an air passage. An air outlet mode switching device is disposed in the casing to switch among air outlet modes by changing opening/closing states of a plurality of air outlets for blowing the air into the vehicle interior. As the air outlet, a foot air outlet is provided for blowing the air toward at least the foot of a passenger. When the frost is determined to be formed at the outdoor heat exchanger by the frost formation determination portion, the cooling fluid circuit switching device performs switching to a cooling fluid circuit for flowing the cooling fluid to the heat dissipation heat exchanger. When the frost is determined to be formed at the outdoor heat exchanger by the frost formation determination portion, the air outlet mode switching device can perform switching to the air outlet mode for blowing the air from the foot air outlet.

This embodiment in another aspect includes the above heat pump cycle, a frost formation determination portion for determining the frost formation at the outdoor heat exchanger, a casing for accommodating the user-side heat exchanger therein and for forming an air passage, and blowing means (e.g., blower 32) disposed in the casing for blowing the air toward the vehicle interior. When the frost is determined to be formed at the outdoor heat exchanger by the frost formation determination portion, the cooling fluid circuit switching device performs switching to a cooling fluid circuit for flowing the cooling fluid into the heat-dissipation heat exchanger. When the frost is determined to be formed at the outer heat exchanger by the frost formation determination portion, the blower means can decreases its blowing capacity as compared to before the determination of the frost formation.

This embodiment in another aspect includes the above heat pump cycle, and a frost formation determination portion for determining the frost formation of the outdoor heat exchanger. When the vehicle speed of the traveling vehicle is equal to or less than a predetermined reference vehicle speed, and the refrigerant temperature on the outlet side of the outdoor heat exchanger is equal to or less than 0° C., the frost is determined to be formed at the outdoor heat exchanger. When the frost is determined to be formed at the outdoor heat exchanger by the frost formation determination portion, the cooling fluid circuit switching device can perform switching to the cooling fluid circuit for flowing the cooling fluid to the heat-dissipation heat exchanger.

Eighth Embodiment

Although in the above first and seventh embodiments, the operation of the compressor 11 is stopped during the defrosting operation by way of example, in this embodiment as shown in FIG. 18, the cycle structure of the heat pump cycle 10 is changed to achieve the heating of the vehicle interior, while performing the defrosting operation like the third embodiment by way of example. FIG. 18 is an entire configuration diagram of the heat pump cycle 10 during the defrosting operation in this embodiment, corresponding to FIG. 2 of the first embodiment.

Specifically, this embodiment differs from the first embodiment in that a variable throttle 83 for heating is employed which is capable of changing the opening degree of throttle as a decompression device for the heating operation. The variable throttle 83 for heating includes a valve body whose throttle opening degree is variable, and an electric actuator comprised of a stepping motor for changing the throttle opening degree of the valve body. The variable throttle 83 has its operation controlled by a control signal output from the air conditioning controller.

In this embodiment, the air conditioning controller controls the valve opening degree of the variable throttle 83 for heating to a predetermined opening degree in the heating operation and in the waste heat collecting operation, and increases the valve opening degree of the variable throttle 83 for heating in the defrosting operation, as compared to the heating operation and the waste heat collecting operation. Thus, in the defrosting operation, the high-pressure refrigerant with a higher temperature discharged from the compressor 11 is apt to flow into the outdoor heat exchanger 16 as compared to before the defrosting operation.

The structures and operations of other components of this embodiment are the same as those of the first embodiment. Thus, in the air conditioner 1 for the vehicle of this embodiment, the throttle opening degree of the variable throttle 83 for heating is increased in the defrosting operation, so that the high-pressure refrigerant at a high temperature can flow into the outdoor heat exchanger 16 to thereby promote the defrosting of the outdoor heat exchanger 16. Further, during the defrosting operation, the heating capacity of the indoor condenser 12 for heating the air can be exhibited to perform heating of the vehicle interior.

As viewed from the flow direction of the outside air, the positional relationship between a heat exchange region on a refrigerant inlet side of the outdoor heat exchanger 16 and a heat exchange region on a refrigerant outlet side thereof does not change with respect to a heat exchanger region of the radiator 43, which can suppress the large fluctuations in amount of the heat transfer between the refrigerant flowing through the refrigerant tubes 16a and the cooling fluid flowing through the cooling fluid tubes 43a, like the third embodiment.

Ninth Embodiment

As shown in the entire configuration diagram of FIG. 19, in this embodiment, the cycle structure of the heat pump cycle 10 is changed to achieve the heating of the vehicle interior, while performing the defrosting operation like the eighth embodiment by way of example. FIG. 19 is an entire configuration diagram of the heat pump cycle 10 in the defrosting operation according to this embodiment, which corresponds to FIG. 2 of the first embodiment.

Specifically, this embodiment differs from the first embodiment in that an outflow rate adjustment valve 84 is added for adjusting an outflow rate of the refrigerant flowing from the outdoor heat exchanger 16. The outflow rate adjustment valve 84 has the same basic structure as that of the variable throttle 83 for the heating of the eighth embodiment, and thus is integral with the refrigerant outlet of the outdoor heat exchanger 16.

In this embodiment, the air conditioning controller fully opens the valve opening degree of the outflow rate adjustment valve 84 in the heating operation, the waste heat collection operation, and the cooling operation, and reduces the valve opening degree of the outflow rate adjustment valve 84 in the defrosting operation as compared to in the heating operation, the waste heat collecting operation, and the cooling operation. Thus, in the defrosting operation, an inflow rate of the refrigerant flowing into the outdoor heat exchanger 16 is decreased as compared to before the transfer to the defrosting operation. The structures and operations of other components of this embodiment are the same as those of the first embodiment.

In the air conditioner 1 for a vehicle of this embodiment, the valve opening degree of the outflow rate adjustment valve 84 is decreased in the defrosting operation, so that the inflow rate of the refrigerant flowing into the outdoor heat exchanger 16 can be decreased, which can provide the same effects as those of the eighth embodiment.

Since the outflow rate adjustment valve 84 is integrally structured with a refrigerant outlet of the outdoor heat exchanger 16, the volume of the refrigerant passage leading from the discharge port of the compressor 11 to the inlet side of the outlet rate adjustment valve 84 can be decreased to thereby quickly decrease the flow rate of the refrigerant flowing into the outdoor heat exchanger 16.

Tenth and Eleventh Embodiments

In the above third, eighth, and ninth embodiments, the outdoor heat exchanger 16 exhibits the heating capacity to achieve the heating of the vehicle interior without stopping the operation of the compressor 11 in the defrosting operation, by way of example. In the ninth embodiment, as shown in FIG. 20, a PTC heater 85 is disposed in the casing 31 of the indoor air conditioning unit 30, and serves as a heating element for generating heat by being supplied with power.

The PTC heater 85 is disposed on the downstream side of the air flow of the indoor condenser 12, and generates heat by being supplied with power from the air conditioning controller in the defrosting operation. Thus, even when the air conditioning controller stops the operation of the compressor 11 during the defrosting operation, the PTC heater 85 can function as an auxiliary heater to heat the air, thereby achieving the heating of the vehicle interior.

In the eleventh embodiment, as shown in FIG. 21, a heater core 86 is provided for exchanging heat between the engine coolant as a heat fluid, and the air. The heater core 86 has the same basic structure as that of the heater core 63 of the second embodiment. The heater core 86 is disposed on the downstream side of the air flow of the indoor condenser 12 to allow the engine coolant to flow thereinto during the defrosting operation.

Thus, even when the air conditioning controller stops the operation of the compressor 11 during the defrosting operation, the heater core 86 can function as an auxiliary heater to heat the air, thereby achieving the heating of the vehicle interior. The heat fluid serving as a heat source for heating the air at the heater core 86 is not limited to the engine coolant, but may be coolant or the like for cooling the vehicle-mounted devices generating heat in operation, such as the electric motor MG for traveling, or an inverter.

Alternatively, both the PTC heater 85 of the tenth embodiment and the heater core 86 of the eleventh embodiment may be disposed on the downstream side of the air flow of the indoor condenser 12 to serve as the auxiliary heater. FIGS. 20 and 21 are the entire configuration diagrams of the heat pump cycle 10 in the defrosting operation according to the ninth and eleventh embodiment, respectively, and correspond to FIG. 2 of the first embodiment.

Other Embodiments

The present invention is not limited to the above embodiments, and various modifications and changes can be made to the above embodiments without departing from the scope of the invention as follows.

(1) In the above embodiments, the vehicle-mounted device (external heat source) generating heat in operation is the electric motor MG for traveling, by way of example, but the external heat source is not limited thereto. For example, when the heat pump cycle 10 is applied to the air conditioner 1 for the vehicle, an engine or an electric device, such as an inverter, for supplying power to the electric motor MG for traveling can be used as the external heat source.

In using the engine as the external heat source, the heat contained not only in the engine coolant, but also in engine exhaust gas may be used for defrosting. Further, in applying the heat pump cycle 10 to a stationary air conditioner, a cool storage, a cooling and heating device for a vending machine, and the like, the engine, the electric motor, and other electric devices which serve as the driving source for the compressor of the heat pump cycle 10 can be used as the external heat source.

(2) In the above embodiments, the electric three-way valve 42 is employed as circuit switching device for switching among the cooling fluid circuits of the coolant circulation circuit 40, but the circuit switching device is not limited thereto. For example, a thermostat valve may be used. Thermostat valve is a cooling fluid temperature-responsive valve comprised of a mechanical mechanism that opens and closes a cooling fluid passage by displacing a valve body using a thermo wax (temperature sensing member) whose volume is changed by the temperature. Thus, the use of thermostat valve can also remove the coolant temperature sensor 52.

(3) In the above embodiments, the refrigerant tubes 16a of the outdoor heat exchanger 16, the cooling fluid tubes 43a of the radiator 43, and the outer fins 50 are formed of an aluminum alloy (metal) and bonded together by brazing. Obviously, the outer fins 50 may be formed of other materials with excellent heat conductivity (for example, a carbon nanotube or the like), and these elements may be bonded together with other bonding means, such as an adhesive.

(4) In the above embodiments, in the normal heating operation, switching is performed to a cooling fluid circuit for allowing the coolant to bypass the radiator 43, which stores the heat dissipated from the electric motor MG for traveling in the coolant. Alternatively or additionally, a heat storage case (heat storing device) for accommodating a heat storing material, such as paraffin, may be disposed in the coolant circulation circuit 40, whereby the heat dissipated from the electric motor MG for traveling may be stored in the heat storage case in the normal heating operation.

Alternatively or additionally, a heating element (for example, PTC heater) that generates heat by being supplied with power may be disposed in the coolant circulation circuit 40, so that the heat dissipated from the heating element may be stored in the coolant in the normal heating operation. Alternatively, the heat dissipated from at least one of the vehicle-mounted device and the heating element that generates heat in the operation of the electric motor MG for traveling and the like may be stored in the coolant. At this time, the amount of heat generated in the heating element is desirably controlled to increase with decreasing outside air temperature so as to avoid the unnecessary power consumption.

(5) In the above first embodiment, when the vehicle speed is equal to or less than the predetermined reference vehicle speed (20 km/h in this embodiment) and the refrigerant temperature Te on the outlet side of the outdoor heat exchanger 16 is equal to or less than 0° C., the frost formation determination portion is used to determine whether the frost is formed at the outdoor heat exchanger 16, by way of example. However, the determination conditions for the frost formation are not limited thereto.

For example, temperature detection portion for detecting the temperature of the outer fin 50 of the outdoor heat exchanger 16 may be provided, and when the temperature detected by the temperature detection portion is equal to or less than the predetermined frost formation reference temperature (for example, −5° C.), the frost may be determined to be formed.

(6) In the above embodiments, the means for stopping the operation of the blower fan 17 in the defrosting operation is used to decrease the volume of outside air flowing into the heat-absorption air passage 16b and the heat-dissipation air passage 43b, by way of example. Regardless of the normal operation and the defrosting operation, when the compressor 11 is stopped, the blowing capacity of the blower fan 17 may be increased until a predetermined time has elapsed. Thus, when the compressor 11 is stopped, the blowing capacity of the blower fan 17 can be increased, so that the temperature of the outdoor heat exchanger 16 can be quickly increased to the same level as the outside air temperature.

(7) The structures described in the above respective embodiments may be applied to other embodiments. For example, the vehicle indoor linkage control described in the seventh embodiment may be executed in the air conditioner for a vehicle to which the heat pump cycle 10 of each of the second to fifth, and eighth to eleventh embodiments is applied.

For example, when the vehicle interior linkage control of the seventh embodiment is applied to the heat pump cycle 10 of the third embodiment, the air conditioning controller may open the opening/closing valve 15c in the air conditioning mode changing control in the control step S200 without stopping the operation of the compressor 11. When applied to the fourth embodiment, the opening/closing valve 15a and the opening/closing valve 15c may be opened by air conditioning mode changing control in the control step S200.

Likewise, when applied to the eighth embodiment, the valve opening degree of the variable throttle 83 for heating may be reduced in the air conditioning mode changing control in the control step S200. When applied to the ninth embodiment, the valve opening degree of the outflow rate adjustment valve 84 may be reduced in the air conditioning mode changing control in the control step S200.

(8) Although in the above embodiments, normal flon-based refrigerant is used as the refrigerant, by way of example, the refrigerant is not limited thereto. Natural refrigerant, such as carbon dioxide, and a carbon-hydride refrigerant and the like may be used. Further, the heat pump cycle 10 may form a supercritical refrigeration cycle in which the pressure of refrigerant discharged from the compressor 11 is equal to or higher than the critical pressure of the refrigerant.

Claims

1-26. (canceled)

27. A heat pump cycle comprising:

a compressor compressing and discharging refrigerant;

a user-side heat exchanger exchanging heat between the refrigerant discharged from the compressor and a heat exchange fluid;

a decompression device decompressing the refrigerant flowing from the user-side heat exchanger;

an outdoor heat exchanger which causes the refrigerant decompressed by the decompression device to exchange heat with outside air and to be evaporated, the heat pump cycle being adapted to perform a defrosting operation for defrosting the outdoor heat exchanger when the outdoor heat exchanger is frosted;

an indoor evaporator for allowing the refrigerant on a downstream side of the outdoor heat exchanger to exchange heat with the heat exchange fluid and to be evaporated;

a refrigerant flow path switching device configured to switch a refrigerant flow path in a heating operation in which the refrigerant discharged from the compressor flows into the user-side heat exchanger to heat the heat exchange fluid, and a refrigerant flow path in a cooling operation in which the refrigerant dissipating heat therefrom at the outdoor heat exchanger flows into the indoor evaporator to cool the heat exchange fluid,

a heat-dissipation heat exchanger, disposed in a cooling fluid circulation circuit for circulating a cooling fluid for cooling an external heat source, the heat-dissipation heat exchanger being adapted to exchange heat between the cooling fluid and the outside air; and

a cooling fluid circuit switching device configured to switch between a cooling fluid circuit for allowing the cooling fluid to flow into the heat-dissipation heat exchanger, and a cooling fluid circuit for allowing the cooling fluid to bypass the heat-dissipation heat exchanger, wherein

the outdoor heat exchanger includes a refrigerant tube in which the refrigerant decompressed by the decompression device flows,

a heat-absorption air passage for flowing the outside air is formed around the refrigerant tube,

the heat-dissipation heat exchanger includes a cooling fluid tube in which the cooling fluid flows,

a heat-dissipation air passage for flowing the outside air is formed around the cooling fluid tube,

the heat-absorption air passage and the heat-dissipation air passage are provided with an outer fin that enables heat transfer between the refrigerant tube and the cooling fluid tube, while promoting heat exchange in both of the outdoor heat exchanger and the heat-dissipation heat exchanger,

the cooling fluid circuit switching device performs switching to the cooling fluid circuit for flowing the cooling fluid into the heat-dissipation heat exchanger in at least the defrosting operation,

a flow direction of the refrigerant flowing through the refrigerant tube in the heating operation is the same as that of the refrigerant flowing through the refrigerant tube in the cooling operation,

a heat exchange region at a refrigerant inlet side of the outdoor heat exchanger is overlapped in an outside air flow direction with a heat exchange region at a cooling fluid inlet side of the heat dissipation heat exchanger,

the outdoor heat exchanger is configured, such that relatively high-temperature refrigerant flows through the heat exchange region at the refrigerant inlet side of the outdoor heat exchanger in the cooling operation, and relatively low-temperature refrigerant flows through the heat exchange region at the refrigerant inlet side of the outdoor heat exchanger in the heating operation, and

the heat dissipation heat exchanger is configured, such that relatively high-temperature cooling fluid flows through the heat exchange region at the refrigerant inlet side of the heat dissipation heat exchanger in both the cooling operation and the heating operation.

28. The heat pump cycle according to claim 27, wherein in the defrosting operation, an inflow rate of the refrigerant flowing into the outdoor heat exchanger is decreased as compared to before transfer to the defrosting operation.

29. The heat pump cycle according to claim 27, wherein

the decompression device is a variable throttle mechanism in which a throttle opening degree is variable, and

the decompression device increases the throttle opening degree in the defrosting operation as compared to before transfer to the defrosting operation.

30. The heat pump cycle according to claim 27, further comprising

an outflow rate adjustment valve configured to adjust an outflow rate of the refrigerant flowing from the outdoor heat exchanger,

wherein the outflow rate adjustment valve decreases the outflow rate of the refrigerant in the defrosting operation as compared to before transfer to the defrosting operation.

31. The heat pump cycle according to claim 30, wherein the outflow rate adjustment valve is configured integrally with an outlet for the refrigerant of the outdoor heat exchanger.

32. The heat pump cycle according to claim 27, further comprising

an outdoor blower which blows the outside air toward both the outdoor heat exchanger and the heat-dissipation heat exchanger,

wherein the outdoor blower increases an air blowing capacity when the compressor is stopped, as compared to before stopping the compressor.

33. The heat pump cycle according to claim 27, wherein in the defrosting operation, a heating capacity of the user-side heat exchanger for heating the heat exchange fluid is decreased as compared to before transfer to the defrosting operation.

34. The heat pump cycle according to claim 27, wherein the heat-absorption air passage and the heat-dissipation air passage are configured such that volumes of the outside air flowing into the heat-absorption air passage and the heat-dissipation air passage are decreased in the defrosting operation.

35. The heat pump cycle according to claim 27, further comprising

an outdoor blower which blows the outside air toward both the outdoor heat exchanger and the heat-dissipation heat exchanger,

wherein the heat-dissipation heat exchanger is located on a windward side in the flow direction of the outside air blown by the outdoor blower with respect to the outdoor heat exchanger.

36. The heat pump cycle according to claim 27, wherein

at least one of the refrigerant tubes is located between the cooling fluid tubes,

at least one of the cooling fluid tubes is located between the refrigerant tubes, and

at least one of the heat-absorption air passage and the heat-dissipation air passage is formed as one air passage.

37. The heat pump cycle according to claim 27 being applied to an air conditioner for a vehicle, the heat pump cycle further comprising:

an inside air temperature detection portion configured to detect an inside air temperature of a vehicle interior; and

a frost formation determination portion configured to determine frost formation of the outdoor heat exchanger, wherein

the heat exchange fluid is air blown into the vehicle interior,

the external heat source is a vehicle-mounted device generating heat in operation,

the cooling fluid is a coolant for cooling the vehicle-mounted device, and

the cooling fluid circuit switching device performs switching to the cooling fluid circuit for flowing the cooling fluid into the heat-dissipation heat exchanger when the frost is determined to be formed at the outdoor heat exchanger by the frost formation determination portion and an inside air temperature of the vehicle interior is equal to or more than a predetermined reference inside air temperature.

38. The heat pump cycle according to claim 27 being applied to an air conditioner for a vehicle, the heat pump cycle further comprising

a frost formation determination portion for determining frost formation of the outdoor heat exchanger, wherein

the heat exchange fluid is air blown into the vehicle interior,

the external heat source is a vehicle-mounted device generating heat in operation,

the cooling fluid is a coolant for cooling the vehicle-mounted device,

the user-side heat exchanger is disposed in a casing forming therein an air passage,

an inside/outside air switching device for changing a ratio of introduction of inside air to outside air to be introduced into the casing is disposed in the casing, wherein

the cooling fluid circuit switching device performs switching to the cooling fluid circuit for flowing the cooling fluid to the heat-dissipation heat exchanger when the frost is determined to be formed at the outdoor heat exchanger by the frost formation determination portion, and

the inside/outside air switching device increases the ratio of introduction of the inside air to the outside air as compared to before transfer to the defrosting operation when the frost is determined to be formed at the outdoor heat exchanger by the frost formation determination portion.

39. The heat pump cycle according to claim 27 being applied to an air conditioner for a vehicle, the heat pump cycle further comprising

a frost formation determination portion configured to determine frost formation of the outdoor heat exchanger, wherein

the heat exchange fluid is air blown into the vehicle interior,

the external heat source is a vehicle-mounted device generating heat in operation,

the cooling fluid is a coolant for cooling the vehicle-mounted device,

the user-side heat exchanger is disposed in a casing forming therein an air passage,

an air outlet mode switching device for switching among air outlet modes by changing opening/closing states of air outlets for blowing the air into the vehicle interior is disposed in the casing,

at least a foot air outlet for blowing the air to a foot of a passenger is provided as the air outlet,

the cooling fluid circuit switching device performs switching to the cooling fluid circuit for flowing the cooling fluid into the heat-dissipation heat exchanger when the frost is determined to be formed at the outdoor heat exchanger by the frost formation determination portion, and

the air outlet mode switching device performs switching to the air outlet mode for blowing the air from the foot air outlet when the frost is determined to be formed at the outdoor heat exchanger by the frost formation determination portion.

40. The heat pump cycle according to claim 27 being applied to an air conditioner for a vehicle, the heat pump cycle further comprising

a frost formation determination portion configured to determine frost formation of the outdoor heat exchanger, wherein

the heat exchange fluid is air blown into the vehicle interior,

the external heat source is a vehicle-mounted device generating heat in operation,

the cooling fluid is a coolant for cooling the vehicle-mounted device,

the user-side heat exchanger is disposed in a casing for forming therein an air passage,

a blower for blowing air toward the vehicle interior is disposed in the casing,

the cooling fluid circuit switching device performs switching to the cooling fluid circuit for flowing the cooling fluid into the heat-dissipation heat exchanger when the frost is determined to be formed at the outdoor heat exchanger by the frost formation determination portion, and

the blower decreases an air blowing capacity, as compared to before the determination of the frost formation.

41. The heat pump cycle according to claim 27 being applied to an air conditioner for a vehicle, the heat pump cycle further comprising

a frost formation determination portion for determining frost formation of the outdoor heat exchanger, wherein

the heat exchange fluid is air blown into the vehicle interior,

the external heat source is a vehicle-mounted device generating heat in operation,

the cooling fluid is a coolant for cooling the vehicle-mounted device,

the frost formation determination portion determines that the frost is formed at the outdoor heat exchanger, when a vehicle speed is equal to or less than a predetermined reference speed, and when a temperature of the refrigerant on an outlet side of the outdoor heat exchanger is equal to or less than 0□□C, and

the cooling fluid circuit switching device performs switching to a cooling fluid circuit for flowing the cooling fluid into the heat-dissipation heat exchanger when the frost is determined to be formed at the outdoor heat exchanger by the frost formation determination portion.

42. The heat pump cycle according to claim 41, wherein the frost formation determination portion determines that the frost is formed at the outdoor heat exchanger, when the speed of the traveling vehicle is equal to or less than the predetermined reference speed, and when the temperature of the refrigerant on the outlet side of the outdoor heat exchanger is equal to or less than 0□□C.

43. The heat pump cycle according to claim 37, further comprising

a coolant temperature detection portion configured to detect a temperature of the coolant flowing into a vehicle-mounted device,

wherein the cooling fluid circuit switching device performs switching to the cooling fluid circuit for flowing the cooling fluid into the heat-dissipation heat exchanger when a coolant temperature detected by the coolant temperature detection portion is equal to or more than the predetermined reference temperature.

44. The heat pump cycle according to claim 27, wherein the cooling fluid circulation circuit stores therein the heat contained in the external heat source when the cooling fluid circuit switching device performs switching to the cooling fluid circuit for allowing the cooling fluid to bypass the heat-dissipation heat exchanger.

45. The heat pump cycle according to claim 44 being applied to an air conditioner for a vehicle, wherein

the heat exchange fluid is air blown into the vehicle interior,

the external heat source is a vehicle-mounted device generating heat in operation,

the cooling fluid is a coolant for cooling the vehicle-mounted device, and

the cooling fluid circulation circuit stores heat dissipated from the vehicle-mounted device in the coolant when the cooling fluid circuit switching device performs switching to the cooling fluid circuit for allowing the cooling fluid to bypass the heat-dissipation heat exchanger.

46. The heat pump cycle according to claim 44 being applied to an air conditioner for a vehicle, wherein

the heat exchange fluid is air blown into the vehicle interior,

the external heat source is a heating element for generating heat by being supplied with power,

the cooling fluid is a coolant for cooling the heating element, and

the cooling fluid circulation circuit stores the heat dissipated from the heating element in the coolant when the cooling fluid circuit switching device performs switching to the cooling fluid circuit for allowing the cooling fluid to bypass the heat-dissipation heat exchanger.

47. The heat pump cycle according to claim 44 being applied to an air conditioner for a vehicle, wherein

the heat exchange fluid is air blown into the vehicle interior,

a vehicle-mounted device generating heat in operation, and a heating element for generating heat by being supplied with power are provided as the external heat source,

the cooling fluid is a coolant for cooling the heating element and the vehicle-mounted device, and

the cooling fluid circulation circuit stores the heat dissipated from at least one of the vehicle-mounted device and the heating element in the coolant when the cooling fluid circuit switching device performs switching to the cooling fluid circuit for allowing the cooling fluid to bypass the heat-dissipation heat exchanger.

48. The heat pump cycle according to claim 46, wherein the heating element has an amount of generated heat therefrom controlled based on an outside air temperature.

49. The heat pump cycle according to claim 27, further comprising:

an outdoor unit bypass passage which causes the refrigerant decompressed by the decompression device to bypass the outdoor heat exchanger and to guide the refrigerant to a refrigerant outlet side of the outdoor heat exchanger; and

an outdoor-unit bypass passage switching device configured to switch between a refrigerant circuit for guiding the refrigerant decompressed by the decompression device to the outdoor heat exchanger, and a refrigerant circuit for guiding the refrigerant decompressed by the decompression device toward the outdoor unit bypass passage,

wherein in the defrosting operation, the outdoor unit bypass passage switching device performs switching to the refrigerant circuit for guiding the refrigerant decompressed by the decompression device to the outdoor unit bypass passage.

50. The heat pump cycle according to claim 27, further comprising:

an indoor evaporator which exchanges heat between the refrigerant on a downstream side of the outdoor heat exchanger and the heat exchange fluid;

an evaporator bypass passage which causes the refrigerant on the downstream side of the outdoor heat exchanger to bypass the indoor evaporator and to guide the refrigerant to a refrigerant outlet of the indoor evaporator; and

an evaporator bypass passage switching device configured to switch a refrigerant circuit for guiding the refrigerant on the downstream side of the outdoor heat exchanger to the indoor evaporator, and a refrigerant circuit for guiding the refrigerant on the downstream side of the outdoor heat exchanger to the evaporator bypass passage,

wherein in the defrosting operation, the evaporator bypass passage switching device performs switching to the refrigerant circuit for guiding the refrigerant on the downstream side of the outdoor heat exchanger to the indoor evaporator.

51. The heat pump cycle according to claim 27 being applied to an air conditioner for a vehicle, wherein

the heat exchange fluid is air blown into the vehicle interior, the user-side heat exchanger is disposed in a casing for forming therein an air blowing passage, and in the casing, an auxiliary heater is provided for heating the air blown into the vehicle interior using as a heating source, at least one of a heating fluid heated by a vehicle-mounted device that generates heat in operation, and a heating element that generates heat by being supplied with power.