Air conditioner for vehicle

Abstract

In a refrigerant cycle device for a vehicle air conditioner, a refrigerant flow switching device is configured to switch one of a cooling mode, a first heating mode and a second heating mode. In the first heating mode, refrigerant discharged from a compressor flows through a radiator, a heating decompression device and an exterior heat exchanger in this order, and the refrigerant flowing out of the exterior heat exchanger is introduced to a refrigerant suction side of the compressor while bypassing an evaporator. In contrast, in the second heating mode, the refrigerant discharged from the compressor flows into the radiator, and the refrigerant flowing out of the radiator is introduced to the refrigerant suction side of the compressor while bypassing both the exterior heat exchanger and the evaporator, so that the refrigerant radiates heat at the radiator.

Description

CROSS REFERENCE TO RELATED APPLICATION

This application is based on Japanese Patent Application No. 2010-003485 filed on Jan. 11, 2010, the contents of which are incorporated herein by reference in its entirety.

FIELD OF THE INVENTION

The present invention relates to a vehicle air conditioner provided with a refrigerant cycle device, which can selectively switch between a first heating mode and a second heating mode, in a heating operation for heating air to be blown into a vehicle compartment.

BACKGROUND OF THE INVENTION

In a conventional vehicle air conditioner having a refrigerant cycle device, an evaporator and a condenser are arranged in an air conditioning case located inside of a vehicle compartment, and an exterior heat exchanger is located outside of the vehicle compartment. A refrigerant flow switching valve is disposed in the refrigerant cycle device, so as to selectively switch any one of refrigerant cycles of a cooling mode, a heating mode and a dehumidifying mode. When the refrigerant cycle device is operated as a heat pump cycle, the heating mode is set, thereby performing a heating operation of a vehicle compartment (e.g., refer to JP Patent No. 3331765 corresponding to U.S. Pat. No. 5,526,650).

However, in the heating mode due to the heat pump cycle of the above refrigerant cycle device, it is difficult to keep the heating capacity at an extremely-low outside air temperature equal to or lower than −3° C., for example.

At the extremely-low outside air temperature, the exterior heat exchanger is easily frosted, and thereby it is necessary to switch the operation mode from the heating mode to a defrosting mode every when the exterior heat exchanger is frosted. Thus, it is impossible to continuously perform the heating operation of the vehicle compartment.

The present invention is made in view of the above problems, and it is an object of the present invention to provide an air conditioner for a vehicle, which can maintain a necessary heating capacity even in an extremely-low outside air temperature.

It is another object of the present invention to provide an air conditioner for a vehicle, which can continuously perform heating operation of a vehicle compartment even in an extremely-low outside air temperature.

According to an aspect of the present invention, an air conditioner for a vehicle includes a compressor configured to compress and discharge refrigerant, an exterior heat exchanger configured to perform heat exchange between the refrigerant and air outside of a vehicle compartment, an evaporator arranged in an air conditioning case to perform a heat exchange, between low-pressure and low-temperature refrigerant and air to be blown into the vehicle compartment, a radiator disposed to cool a high-pressure and high-temperature refrigerant by performing a heat exchange between the high-pressure and high-temperature refrigerant and air having passed through the evaporator, a refrigerant flow switching device configured to switch one of refrigerant cycles of a cooling mode, a first heating mode and a second heating mode, a first decompression device configured to decompress refrigerant at least in the refrigerant cycle of the cooling mode, and a second decompression device configured to decompress refrigerant at least in the refrigerant cycle of the first heating mode. The refrigerant cycle of the cooling mode is configured such that the refrigerant discharged from the compressor flows through the exterior heat exchanger, the first decompression device; the evaporator and a refrigerant suction side of the compressor in this order, so that the refrigerant absorbs heat at the evaporator and radiates heat at the exterior heat exchanger. The refrigerant cycle of the first heating mode is configured such that the refrigerant discharged from the compressor flows through the radiator, the second decompression device and the exterior heat exchanger in this order, and the refrigerant flowing out of the exterior heat exchanger is introduced to the refrigerant suction side of the compressor while bypassing the evaporator, so that the refrigerant absorbs heat at the exterior heat exchanger and radiates heat at the radiator. Furthermore, the refrigerant cycle of the second heating mode is configured such that the refrigerant discharged from the compressor flows into the radiator, and the refrigerant flowing out of the radiator is introduced to the refrigerant suction side of the compressor while bypassing both the exterior heat exchanger and the evaporator, so that the refrigerant radiates heat at the radiator. In addition, the refrigerant flow switching device switches the refrigerant cycle from the first heating mode to the second heating mode, when a physical amount having a relation with a heating capacity of the first heating mode becomes a value at which the heating capacity is low in the first heating mode.

In a condition in which the heating capacity in the first heating mode is low, the refrigerant cycle is switched to the second heating mode from the first heating mode, so as to heat air by using high-temperature gas refrigerant (hot gas) flowing into the radiator as a heating source. In the second heating mode, because the refrigerant does not flow into the exterior heat exchanger, and the exterior heat exchanger is not adapted as a heat absorber. Therefore, the exterior heat exchanger is not frosted, and it is unnecessary to perform a defrosting operation of the exterior heat exchanger in the second heating mode. Thus, it is possible to continuously perform the heating operation in an extremely-low outside air temperature, and thereby a necessary heating capacity can be obtained by setting the second heating mode.

The air conditioner may be provided with an air heater disposed in the air conditioning case at a downstream air side of the evaporator to heat air by using a heat source different from the refrigerant cycle. In this case, the radiator may be disposed in the air conditioning case at a downstream air side of the air heater, to heat air after passing through the air heater by performing heat exchange with refrigerant.

Alternatively, the refrigerant cycle of the second heating mode may be configured such that the refrigerant discharged from the compressor flows into the radiator, and the refrigerant flowing out of the radiator is introduced to the refrigerant suction side of the compressor after being decompressed by the second decompression device.

Furthermore, a third decompression device may be located to decompress the refrigerant discharged from the compressor, before flowing into the radiator in the second heating mode.

For example, an outside air temperature sensor may be disposed to detect an outside air temperature as the physical amount. In this case, the refrigerant flow switching device is configured to switch the refrigerant cycle from the first heating mode to the second heating mode when the outside air temperature detected by the outside air temperature sensor is lower than a predetermined temperature. Alternatively, a pressure detection device may be disposed to detect a refrigerant pressure at the refrigerant suction side of the compressor, as the physical amount. In this case, the refrigerant flow switching device may be configured to switch the refrigerant cycle from the first heating mode to the second heating mode, when the refrigerant pressure detected by the pressure detection device is lower than a predetermined pressure. Alternatively, a temperature detection device may be disposed to detect a refrigerant temperature at a refrigerant discharge side of the compressor, as the physical amount. In this case, the refrigerant flow switching device is configured to switch the refrigerant cycle from the first heating mode to the second heating mode, when the refrigerant temperature detected by the temperature detection device is higher than a predetermined temperature in the first heating mode.

The radiator may include a first radiator part disposed in the air conditionig case at a downstream air side of the evaporator to heat air after passing through the evaporator by using a liquid fluid flowing therein, and a second radiator part disposed to radiate heat from high-pressure and high-temperature refrigerant to the liquid fluid by performing heat exchange between high-pressure and high-temperature refrigerant and the liquid fluid. In this case, a liquid heater may be disposed to heat the liquid fluid flowing to the first radiator part.

BRIEF DESCRIPTION OF THE DRAWINGS

Other objects, features and advantages of the present invention will become more apparent from the following description made with reference to the accompanying drawings, in which like parts are designated by like reference numbers and in which:

FIG. 1 is a schematic diagram showing a refrigerant cycle in a cooling mode of a vehicle air conditioner, according to a first embodiment of the invention;

FIG. 2 is a schematic diagram showing a refrigerant cycle in a dehumidifying and heating mode of the vehicle air conditioner, according to the first embodiment;

FIG. 3 is a schematic diagram showing a refrigerant cycle in a first heating mode of the vehicle air conditioner, according to the first embodiment;

FIG. 4 is a schematic diagram showing a refrigerant cycle in a second heating mode of the vehicle air conditioner, according to the first embodiment;

FIG. 5 is a block diagram showing an electric controller of the vehicle air conditioner according to the first embodiment;

FIG. 6 is a flowchart showing an air conditioning control performed by the electric controller of the vehicle air conditioner, according to the first embodiment;

FIG. 7 is a Mollier diagram showing refrigerant states in the second heating mode of the vehicle air conditioner, according to the first embodiment;

FIG. 8 is a schematic diagram showing a refrigerant cycle in a second heating mode of a vehicle air conditioner, according to a second embodiment of the invention;

FIG. 9 is a Mollier diagram showing refrigerant states in the second heating mode of the vehicle air conditioner, according to the second embodiment;

FIGS. 10A and 10B are graphs showing relationships between an air temperature at an air inlet of a radiator, a compressor power, a heating capacity of the radiator, according to the second embodiment;

FIG. 11 is a schematic diagram showing a refrigerant cycle in a second heating mode of a vehicle air conditioner, according to a third embodiment of the invention;

FIG. 12 is a Mollier diagram showing refrigerant states in the second heating mode of the vehicle air conditioner, according to the third embodiment; and

FIG. 13 is a schematic diagram showing a refrigerant cycle in a second heating mode of a vehicle air conditioner, according to a fourth embodiment of the invention.

EMBODIMENTS

Embodiments for carrying out the present invention will be described hereafter referring to drawings. In the embodiments, a part that corresponds to a matter described in a preceding embodiment may be assigned with the same reference numeral, and redundant explanation for the part may be omitted. When only a part of a configuration is described in an embodiment, another preceding embodiment may be applied to the other parts of the configuration. The parts may be combined even if it is not explicitly described that the parts can be combined. The embodiments may be partially combined even if it is not explicitly described that the embodiments can be combined, provided there is no harm in the combination.

First Embodiment

In the present embodiment, an air conditioner 1 for a vehicle of the invention is mounted to an electrical vehicle (EV) driven by an electric motor for traveling, for example.

As shown in FIGS. 1 to 4, an air conditioner 1 for a vehicle of the present embodiment includes an interior air conditioning unit 10, and a refrigerant cycle device 20. In the air conditioner 1, an operation mode of the refrigerant cycle device 20 can be switched to a cooling mode shown in FIG. 1, a dehumidifying and heating mode shown in FIG. 2, a first heating mode shown in FIG. 3 and a second heating mode shown in FIG. 4. In FIGS. 1 to 4, arrows indicate the refrigerant flow directions in the respective operation modes.

The interior air conditioning unit 10 is located inside of an instrument panel (i.e., dash panel) positioned at the frontmost portion in a vehicle compartment. The interior air conditioning unit 10 includes an air conditioning casing 11 forming an outer shell and defining an air passage. In the air conditioning casing 11, a blower 12, an evaporator 13, a radiator 14 and the like are disposed.

The air conditioning casing 11 defines therein the air passage through which air flows into the vehicle compartment. The air conditioning casing 11 is made of a resin (e.g., polypropylene) having a suitable elasticity and being superior in the strength. An inside/outside air introduction box is located at the most upstream side to selectively introduce inside air or/and outside air into the air conditioning casing 11. Hear, inside air is air inside the vehicle compartment, and outside air is air outside the vehicle compartment. The inside/outside air introduction box is provided with an inside air introduction port 11a from which the inside air is introduced, an outside air introduction port 11b from which outside air is introduced, and an inside/outside air switching door 15 disposed to adjust a ratio between a flow amount of the inside air introduced from the inside air introduction port 11a and a flow amount of outside air introduced from the outside air introduction port 11b. The inside/outside air switching door 15 is driven by an electrical actuator such as servo motor.

The blower 12 is disposed in the air conditioning casing 11 at a downstream air side of the inside/outside air switching door 15, to blow air drawn via at least one of the inside air introduction port 11a and the outside air introduction port 11b toward the interior of the vehicle compartment. The blower 12 is an electrical blower in which a centrifugal multi-blade fan (e.g., sirocco fan) is driven by an electric motor.

An evaporator 13 is disposed in the air conditioning casing 11 at a downstream air side of the blower 12 to cross all the air passage area in the air conditioning casing 11. The evaporator 13 is a cooling heat exchanger in which a low-pressure and low-temperature refrigerant flowing therein is heat-exchanged with air blown by the blower 12 to cool the blown air.

At a downstream air side of the evaporator 13, the air passage of the air conditioning casing 11 is provided with a first air passage 16 through which air after passing through the evaporator 13 flows, a second air passage 17 used as a cool air bypass passage through which air after passing through the evaporator 13 flows while bypassing the radiator 14, and a mixing space 18 in which air from the first air passage 16 and air from the second air passage 17 are mixed. A partition wall 11c is provided in the air conditioning case 11 to partition the first air passage 16 and the second air passage 17 from each other.

The radiator 14 is disposed in the first air passage 16 to heat air passing through the first air passage 16. The radiator 14 is a heating heat exchanger configured to perform heat exchange between a high-pressure and high-temperature refrigerant flowing out of a compressor 21 and air after passing through the evaporator 13. Thus, the radiator 14 heats air after passing through the evaporator 13 in the first air passage 16, and thereby the radiator 14 can be adapted as a condenser in which refrigerant is cooled and condensed.

On the other hand, cool air having passed through the evaporator 13 flows into the mixing space 18 through the second air passage 17 used as the cool air bypass passage while bypassing the radiator 14. Thus, the temperature of air (i.e., conditioned air) mixed in the mixing space 18 can be adjusted by adjusting a ratio between a flow amount of air passing through the first air passage 16 and a flow amount of air passing through the second air passage 17.

In the present embodiment, an air mix door 19 is located at a downstream air side of the evaporator 13 and at an upstream air side of both the first air passage 16 and the second air passage 17. Furthermore, the air mix door 19 is configured to continuously change the ratio between the flow amount of air passing through the first air passage 16 and the flow amount of air passing through the second air passage 17.

The air mix door 19 is used as a temperature adjusting unit that adjusts the air temperature in the mixing space 18 so as to adjust the temperature of conditioned air to be blown into the vehicle compartment. The air mix door 19 is driven by an actuator such as servo motor.

Furthermore, at the most downstream air side, the air conditioning casing 11 is provided with plural air outlets from which conditioned air of the mixing space 18 is blown into the vehicle compartment that is a space to be air-conditioned. The air outlets are, for example, a face air outlet through which conditioned air is blown toward an upper side of a passenger in the vehicle compartment, a foot air outlet through which conditioned air is blown toward the foot area of the passenger in the vehicle compartment, and a defroster air outlet through which conditioned air is blown toward an inner surface of a windshield of the vehicle.

The face air outlet, the foot air outlet and the defroster air outlet are selectively opened and closed by a door member. For example, a face door is located upstream of the face air outlet to adjust an open area of the face air outlet, a foot door is located upstream of the foot air outlet to adjust an open area of the foot air outlet, and a defroster door is located upstream of the defroster air outlet to adjust an open area of the defroster air outlet.

That is, the face door, the foot door and the defroster door are configured to form an air-outlet mode switching member, and are operatively connected each other to be driven by an electrical actuator via a link mechanism, thereby setting an air outlet mode.

The operation of the refrigerant cycle device 20 according to the present embodiment will be described.

The refrigerant cycle device 20 is configured to include the compressor 21, an exterior heat exchanger 22, a heating throttle 23, a cooling throttle 24 and an accumulator 25, in addition to the above-described evaporator 13 and the radiator 14. Respective components of the refrigerant cycle device 20 are connected by refrigerant piping to configure a refrigerant cycle. For example, in the refrigerant cycle device 20, a freon-type refrigerant may be used. In this case, a sub-critical refrigerant cycle is configured in the refrigerant cycle device 20. In the sub-critical refrigerant cycle, a refrigerant pressure on a high-pressure side discharged from the compressor 21 and before being decompressed becomes lower than the critical pressure of the refrigerant. Furthermore, a refrigerator oil is mixed to the refrigerant in order to lubricate the compressor 21, so that the refrigerator oil is circulated in the refrigerant cycle together with the refrigerant.

For example, in the present embodiment, the compressor 21, the radiator 14, the heating throttle 23, the exterior heat exchanger 22, the cooling throttle 24, the evaporator 13, the accumulator 25 and the compressor 21 are connected in series in this order, thereby forming a refrigerant cycle in the refrigerant cycle device 20.

The compressor 21 is disposed in an engine compartment to draw refrigerant, to compress the drawn refrigerant and to discharge the compressed refrigerant, in the refrigerant cycle device 20. For example, the compressor 21 is an electrical compressor in which a fixed-displacement compression mechanism with a fixed discharge capacity is driven by an electrical motor. The refrigerant discharge capacity of the compressor 21 can be changed and controlled by the rotational speed control of the electrical motor in an air conditioning electrical controller 40 (A/C ECU). As the fixed-displacement compression mechanism, various compression mechanisms such as a scroll-type compression mechanism, a vane-type compression mechanism or the like may be used.

The radiator 14 is a heat-radiation heat exchanger in which high-pressure and high-temperature refrigerant discharged from the compressor 21 is heat-exchanged with air blown by the blower 12, thereby radiating heat from the high-pressure and high-temperature refrigerant discharged from the compressor 21.

The heating throttle 23 is a heating decompression device for decompressing and expanding the refrigerant flowing out of the radiator 14 mainly in a first heating mode and in a second heating mode. As the heating throttle 23, a fixed throttle such as a capillary tube, an orifice or the like can be used. Alternatively, a variable throttle can be used as the heating throttle 23 to adjust a throttle passage area.

The exterior heat exchanger 22 is disposed in the engine compartment, such that the refrigerant flowing in the exterior heat exchanger 22 is heat-exchanged with outside air (i.e., air outside the vehicle compartment) blown by an exterior blower fan 22a. A refrigerant outlet side of the exterior heat exchanger 22 is coupled to the evaporator 13 via the cooling throttle 24.

The cooling throttle 24 is a cooling decompression device configured to decompress and expand the refrigerant flowing from the radiator 14, in the cooling mode. As the cooling throttle 24, a fixed throttle such as a capillary tube, an orifice or the like can be used. Alternatively, a variable throttle can be used as the cooling throttle 24 to adjust a throttle passage area.

The evaporator 13 is adapted to evaporate the decompressed refrigerant after passing through the cooling throttle 24 by performing heat exchange between low-pressure refrigerant and air blown by the blower 12. Therefore, air passing through the evaporator 13 is cooled and dehumidified.

The accumulator 25 is a low-pressure side gas-liquid separator, in which the refrigerant flowing therein is separated into gas refrigerant and liquid refrigerant, and surplus refrigerant is stored therein. A refrigerant suction port of the compressor 21 is connected to a gas refrigerant outlet of the accumulator 25.

The refrigerant cycle device 20 is provided with a first bypass passage 26 through which the refrigerant flowing out of the radiator 14 is introduced to the exterior heat exchanger 22 while bypassing the heating throttle 23, and a first electromagnetic valve 27 located to open and close the first bypass passage 26.

Furthermore, the refrigerant cycle device 20 is provided with a second bypass passage 28 through which the refrigerant flowing out of the exterior heat exchanger 28 is introduced to the accumulator 25 while bypassing the cooling throttle 24 and the evaporator 13, and an electrical three-way valve 29 located to open and close the second bypass passage 28. The electrical three-way valve 29 includes a refrigerant inlet connected to the exterior heat exchanger 22, a first refrigerant outlet connected to a refrigerant passage through which refrigerant flows to the evaporator 13, and a second refrigerant outlet connected to the second bypass passage 28. The electrical three-way valve 29 is configured to selectively switch one of the refrigerant passages connected to the first and second refrigerant outlets of the electrical three-way valve 29.

In addition, the refrigerant cycle device 20 is provided with a third bypass passage 30 through which the refrigerant flowing out of the heating throttle 23 is introduced to the second bypass passage 28 while bypassing the exterior heat exchanger 22, and a second electromagnetic valve 31 located to open and close the third bypass passage 30. In the example of FIG. 1, the downstream end portion of the third bypass passage 30 is directly connected to the second bypass passage 28. However, the downstream end portion of the third bypass passage 30 may be connected to a refrigerant passage between the evaporator 13 and the accumulator 25.

Because the first electromagnetic valve 27, the second electromagnetic valve 31 and the electrical three-way valve 29 are provided in the refrigerant cycle device 20, it is possible to switch one of a refrigerant cycle of the cooling mode, a refrigerant cycle of the dehumidifying and heating mode, a refrigerant cycle of the first heating mode and a refrigerant cycle of the second heating mode. Thus, the first electromagnetic valve 27, the second electromagnetic valve 31 and the electrical three-way valve 29 are adapted as a refrigerant cycle switching device.

Thus, in the cooling mode of the refrigerant cycle device 20 shown in FIG. 1, the first electromagnetic valve 27 is opened, and the electrical three-way valve 29 closes the second bypass passage 28 and opens the refrigerant passage connected to the evaporator 13, so that the refrigerant discharged from the compressor 21 is circulated as in the arrows of FIG. 1, in this order of the radiator 14, the first electromagnetic valve 27, the exterior heat exchanger 22, the electrical three-way valve 29, the cooling throttle 24, the evaporator 13, the accumulator 25 and the refrigerant suction side of the compressor 21.

In the dehumidifying and heating mode, both the first and second electromagnetic valves 27, 31 are closed, and the electromagnetic three-way valve 29 closes the second bypass passage 28 and opens the refrigerant passage connected to the evaporator 13, so that the refrigerant discharged from the compressor 21 is circulated as in the arrows of FIG. 2, in this order of the radiator 14, the heating throttle 23, the exterior heat exchanger 22, the electrical three-way valve 29, the cooling throttle 24, the evaporator 13, the accumulator 25 and the refrigerant suction side of the compressor 21.

In the first heating mode, both the first and second electromagnetic valves 27, 31 are closed, and the electromagnetic three-way valve 29 opens the second bypass passage 28 and closes the refrigerant passage connected to the evaporator 13, so that the refrigerant discharged from the compressor 21 is circulated as in the arrows of FIG. 3, in this order of the radiator 14, the heating throttle 23, the exterior heat exchanger 22, the electrical three-way valve 29, the accumulator 25 and the refrigerant suction side of the compressor 21.

In the second heating mode, the first electromagnetic valve 27 is closed, and the second electromagnetic valve 31 is opened, so that the refrigerant discharged from the compressor 21 is circulated as in the arrows of FIG. 4, in this order of the radiator 14, the heating throttle 23, the second electromagnetic valve 31, the accumulator 25 and the refrigerant suction side of the compressor 21.

The electric control portion of the present embodiment will be described with reference to FIG. 5. FIG. 5 is a block diagram showing the electric control portion of the vehicle air conditioner according to the first embodiment.

The air conditioning electrical controller 40 includes a microcomputer and a circumference circuit. The microcomputer includes CPU, ROM, RAM, etc. The air conditioning electrical controller 40 performs various calculations and processes based on control programs stored in the ROM, and controls operation of various components connected to an output side of the air conditioning electrical controller 40. The various components connected to the output side of the air conditioning electrical controller 40 includes the blower 12, the compressor 21, the exterior blower fan 22a, the electrical three-way valve 29, the first electromagnetic valve 27, the second electromagnetic valve 31, the actuators 51, 52, 53 and the like.

Sensors of a sensor group are connected to an input side of the air conditioning electrical controller 40, so that detection signals are input from the sensors to the input sides of the air conditioning electrical controller 40. For example, the sensor group includes an inside air sensor 41 adapted to detect an inside temperature Tr of the vehicle compartment, an outside air sensor 42 adapted to detect an outside air temperature Tam, a solar sensor 43 adapted to detect a solar radiation amount Ts entering into the vehicle compartment, a discharge temperature sensor 44 adapted to detect a refrigerant temperature Td discharged from the compressor 21, a discharge pressure sensor 45 adapted to detect a refrigerant pressure Pd (high-pressure side refrigerant pressure) discharged from the compressor 21, an evaporator temperature sensor 46 adapted to detect an air temperature TE flowing out of the evaporator 13, a suction temperature sensor 47 adapted to detect a refrigerant temperature Ts to be drawn into the compressor 21, and a suction pressure sensor 48 adapted to detect a refrigerant pressure Ps (low-pressure side refrigerant pressure) to be drawn to the compressor 21. Furthermore, the sensor group may further include a humidity sensor adapted to detect a relative humidity of air in the vehicle compartment near a window glass of the vehicle, a window glass temperature sensor adapted to detect a temperature in the vehicle compartment near a window glass of the vehicle, a window surface temperature sensor adapted to detect a surface temperature of a window glass of the vehicle, or the like.

As shown in FIGS. 1 to 4, the discharge temperature sensor 44 is arranged at a position downstream of a refrigerant discharge port of the compressor 21 and upstream of the radiator 14 in the refrigerant flow. The discharge pressure sensor 45 is arranged downstream of the radiator 14 and upstream of the first bypass passage 26, in the refrigerant flow. The suction temperature sensor 47 is arranged in the second bypass passage 28 at a position downstream of a connection portion connected to the third bypass passage 30 in the refrigerant flow, and the suction pressure sensor 48 is arranged downstream of the accumulator 25 and upstream of the refrigerant suction port of the compressor 21 in the refrigerant flow.

An operation panel 50 is located near the instrument panel at the front portion of the vehicle compartment. The operation panel 50 is connected to the input side of the air conditioning electrical controller 40, such that operation signals of various air-conditioning operation switches provided in the operation panel 50 are input to the air conditioning electrical controller 40. For example, the various air-conditioning operation switches include an operation switch of the air conditioner 1, a compressor operation switch for selectively operating and stopping the compressor 21, an operation mode selecting switch of the refrigerant cycle device 20, an air outlet mode selecting switch, and an air amount setting switch of the blower 12, a temperature setting switch of the vehicle compartment, an economic switch for outputting a power-saving priority signal to the refrigerant cycle device 20, and the like. When the power-saving priority signal is input to the refrigerant cycle device 20, a power saving control is performed in the refrigerant cycle device 20.

Next, operation of the air conditioner 1 according to the present embodiment will be described.

The air conditioning electrical controller 40 determines control target values of the various components of the air conditioner 1 based on an air conditioning load. For example, an air blowing amount (blower level) of the blower 12, an air suction mode, an air outlet mode, an open degree of the air mix door 19, an operation mode of the refrigerant cycle device 20 and the like are determined. Then, the various components of the air conditioner 1 are operated based on the control signals determined in and output from the air conditioning electrical controller 40.

FIG. 6 is a flowchart showing an example of an air conditioning control performed by the air conditioning electrical controller 40 in the air conditioner 1. Next, the control process for determining the operation mode of the refrigerant cycle device 20 will be described based on the flow diagram shown in FIG. 6.

At step S1, signals regarding the circumstances of the vehicle used for the air conditioning control, that is, detection signals from the above sensor group and operation signals from the operation panel 50 are read, and then the operation proceeds to step S2.

Next, at step S2, it is determined whether the compressor 21 is in an operation state. When the compressor 21 is in a stop state that is selected manually by the operation switch of the compressor 21 or the air conditioning electrical controller 40 performs a stop control of the compressor 21, the determination of step S2 is NO, and control process returns to step S1. In contrast, when the compressor 21 is in an operation state, the determination of step S2 is YES, and the control process of step S3 is performed.

At step S3, a target outlet air temperature TAO of blown air into the vehicle compartment is calculated. The target outlet air temperature TAO of blown air into the vehicle compartment is calculated based on the vehicle interior setting temperature Tset and the vehicle environment condition such as the inside air temperature, by using the following formula F1.

TAO=Kset×Tset−Kr×Tr−Kam×Tam−Ks×Ts+C   (F1)

Here, Tset is a set temperature of the vehicle compartment set by the temperature setting switch, Tr is a temperature inside of the vehicle compartment (inside air temperature) detected by the inside air sensor 41, Tam is an outside air temperature detected by the outside air sensor 42, and Ts is a solar radiation amount detected by the solar sensor 43. Furthermore, Kset, Kr, Kam and Ks are gains, and C is a constant value for a correction.

At step S4, any one operation mode of the refrigerant cycle device 20 is determined among the cooling mode, the dehumidifying and heating mode and the heating mode, based on the air temperature introduced from the inside air introduction port 11a and the outside air introduction port 11b, the air temperature of the vehicle compartment and the relative humidity in the vehicle compartment near the window glass, and the surface temperature of the window glass or the like, for example.

In addition to the operation mode of the refrigerant cycle device 20, a target rotational speed of the compressor 21, an open degree of the air mix door 19, an air blowing amount of the exterior blower fan 22a and the like are determined. Furthermore, in a case where the various components of the refrigerant cycle device 20 are required to be protected from heat, the target rotation speed of the compressor 21 is corrected to be reduced so that the refrigerant temperature discharged from the compressor 21 becomes lower than a predetermined value. That is, in this case, a power saving control of the compressor 21 is performed.

Then, at step S5, it is determined whether the operation mode determined at step S4 is a heating mode for heating the vehicle compartment. When the operation mode of the refrigerant cycle device 20 is determined to the cooling mode or the dehumidifying and heating mode, the determination of step S5 is NO, and it is determined whether the operation mode determined at step S4 is the cooling mode. When the operation mode of the refrigerant cycle device 20 is determined to the dehumidifying and heating mode, the control operation of step S7 is performed. In contrast, when the operation mode of the refrigerant cycle device 20 is determined to the cooling mode, the control operation of step S8 is performed.

At step S7, the air conditioning electrical controller 40 outputs control signals to various actuators, so as to set the dehumidifying and heating mode as the operation mode of the refrigerant cycle device 20. Specifically, the air conditioning electrical controller 40 outputs control signals to the first and second electromagnetic valves 27, 31, to cause the first and second electromagnetic valves 27, 31 to be closed. Furthermore, the air conditioning electrical controller 40 outputs control signals to the electrical three-way valve 29, to cause the electrical three-way valve 29 to close the side of the second bypass passage 28 and to open a refrigerant passage side of the evaporator 13. In addition, the air conditioning electrical controller 40 outputs control signals to the actuator 52 so that the first air passage 16 is fully opened, for example.

Thus, the air mix door 19 is operated to a position where the first air passage 16 is fully opened, and the heating and dehumidifying mode shown in FIG. 2 is performed. In the heating and dehumidifying mode, refrigerant is circulated as in the arrows shown in FIG. 2. In the heating and dehumidifying mode shown in FIG. 2, high-pressure and high-temperature refrigerant discharged from the compressor 21 is cooled in the radiator 14 to radiate heat, and low-pressure and low-temperature refrigerant decompressed in the cooling throttle 24 absorbs heat to be evaporated in the evaporator 13. Therefore, air blown by the blower 12 is cooled and dehumidified in the evaporator 13, and the dehumidified air is heated while passing through the radiator 14, and thereby dehumidified and heated air is blown into the vehicle compartment from at least one air outlet of the interior air conditioning unit 10.

When variable throttles are used as the heating throttle 23 and the cooling throttle 24, the open degrees of the heating throttle 23 and the cooling throttle 24 can be controlled in accordance with the calculated target outlet air temperature TAO. For example, when the temperature of air after passing through the radiator 14 is required to be made lower, the heating throttle 23 is fully opened, and the open degree of the cooling throttle 24 is set at a predetermined degree without being fully opened. In this case, refrigerant radiates heat at both of the radiator 14 and the exterior heat exchanger 22, and thereby the heat radiating amount of the radiator 14 is reduced, as compared with a case where heat is radiated only from the radiator 14. Therefore, the temperature of air after passing through the radiator 14 can be lowered.

In contrast, when the temperature of air after passing through the radiator 14 is required to be made higher, the cooling throttle 24 is fully opened, and the open degree of the heating throttle 23 is set at a predetermined degree without being fully opened. Thus, refrigerant absorbs heat from both of the evaporator 12 and the exterior heat exchanger 22, and thereby the heat absorbing amount can be increased, as compared with a case where heat is absorbed only from the evaporator 12. Therefore, the temperature of air after passing through the radiator 14 can be increased.

On the other hand, when fixed throttles are used as the heating throttle 23 and the cooling throttle 24, the exterior heat exchanger 22 is adapted as a radiator, a heat absorber or a simple refrigerant passage based on an outside air temperature Tam.

When the cooling mode is determined as the operation mode of the air conditioner 1 at step S6, control signals are output from the air conditioning electrical controller 40 to respective actuators so that the cooling mode shown in FIG. 1 can be set. Specifically, control signals are output from the air conditioning electrical controller 40 to the first electromagnetic valve 27, so that the first electromagnetic valve 27 is closed. Furthermore, the air conditioning electrical controller 40 outputs control signals to the electrical three-way valve 29, to cause the electrical three-way valve 29 to close the second bypass passage 28 and to open the refrigerant passage on the side of the evaporator 13. In addition, the air conditioning electrical controller 40 outputs control signals to the actuator 52 so that the first air passage 16 is fully closed and the second air passage 17 is fully opened.

Thus, the air mix door 19 is operated to a position where the first air passage 16 is fully closed, and the cooling mode shown in FIG. 1 is performed. In the cooling mode, refrigerant is circulated as in the arrows shown in FIG. 1. In the cooling mode shown in FIG. 1, high-pressure and high-temperature refrigerant is cooled in the exterior heat exchanger 22 to radiate heat, and low-pressure and low-temperature refrigerant absorbs heat to be evaporated in the evaporator 13. Therefore, air blown by the blower 12 is cooled and dehumidified in the evaporator 13, and the cooled air is blown into the vehicle compartment from at least one air outlet.

When it is determined that the operation mode is the heating mode at step S5, the control process of step S9 is performed.

At step S9, the air conditioning electrical controller 40 determines whether the first heating mode or the second heating mode is set based on the outside air temperature Tam. For example, at step S9, it is determined whether or not the outside air temperature Tam is higher than a predetermined temperature T1 (e.g., −3° C.). The predetermined temperature T1 is set, such that a necessary heating capacity cannot be obtained in the first heating mode when the outside air temperature is lower than the predetermined temperature T1.

When the outside air temperature Tam is higher than the predetermined temperature T1, the necessary heating capacity can be obtained by using the heat due to the first heating mode. In this case, at step S10, the air conditioning electrical controller 40 outputs control signals to various actuators, so as to set the first heating mode as the operation mode of the refrigerant cycle device 20. Specifically, at step S10, control signals are output from the air conditioning electrical controller 40 to the first and second electromagnetic valves 27, 31, so that both the first and second electromagnetic valves 27, 31 are closed. Furthermore, the air conditioning electrical controller 40 outputs control signals to the electrical three-way valve 29, to cause the electrical three-way valve 29 to open the side of the second bypass passage 28 and to close the refrigerant passage on the side of the evaporator 13. In addition, the air conditioning electrical controller 40 outputs control signals to the actuator 52 so that the first air passage 16 is fully opened and the second air passage 17 is closed.

Thus, the air mix door 19 is operated to a position where the first air passage 16 is fully opened, and the first heating mode shown in FIG. 3 is performed. In the first heating mode, refrigerant is circulated as in the arrows shown in FIG. 3. In the first heating mode shown in FIG. 3, high-pressure and high-temperature refrigerant is cooled in the radiator 14 to radiate heat, and low-pressure and low-temperature refrigerant absorbs heat to be evaporated in the exterior heat exchanger 22. Therefore, air blown by the blower 12 is cooled and dehumidified in the evaporator 13, and the air after passing through the evaporator 13 is heated while passing through the radiator 14, and thereby the heated air is blown into the vehicle compartment from at least one air outlet.

In contrast, when the outside air temperature Tam is lower than the predetermined temperature T1 at step S9, it is determined the necessary heating capacity cannot be obtained by setting the first heating mode, and thereby the second heating mode is set at step S11.

At step S11, the air conditioning electrical controller 40 outputs control signals to various actuators, so as to set the second heating mode as the operation mode of the refrigerant cycle device 20. Specifically, the air conditioning electrical controller 40 causes the first electromagnetic valve 27 to be closed, and causes the second electromagnetic valve 31 to be opened. In addition, the air conditioning electrical controller 40 causes the blower fan 22a to be stopped, and controls the actuator 52 so that the first air passage 16 is fully opened and the second air passage 17 is closed.

Thus, the air mix door 19 is operated to a position where the first air passage 16 is fully opened, and the blower fan 22a is stopped, so that the second heating mode shown in FIG. 4 is performed at step S11. In the second heating mode, refrigerant is circulated as in the arrows shown in FIG. 4. That is, in the second heating mode, the refrigerant discharged from the compressor 21 flows into the radiator 14, the refrigerant flowing out of the radiator 14 is decompressed by the heating throttle 23, and is drawn to the refrigerant suction side of the compressor 21 while bypassing the exterior heat exchanger 22 and the evaporator 13.

Thus, in the second heating mode, high-pressure and high-temperature refrigerant discharged from the compressor 21 is heat-exchanged in the radiator 14 with air after passing through the evaporator 13, to radiate heat to the air. Thus, air passing through the radiator 14 is heated by the radiation heat of the refrigerant, and the heated air is blown into the vehicle compartment from at least one air outlet. The refrigerant flowing out of the radiator 14 is decompressed in the heating throttle 23, and is drawn to the refrigerant suction port of the compressor 21 via the second electromagnetic valve 31 and the accumulator 25.

FIG. 7 is a Mollier diagram showing refrigerant states in the second heating mode of the vehicle air conditioner, according to the first embodiment. In the second heating mode, as shown in FIG. 7, high-temperature and high-pressure refrigerant (hot gas refrigerant) discharged from the compressor 21 is radiated in the radiator 14 to be cooled and condensed, and becomes in a gas-liquid two-phase state. Then, the refrigerant of gas-liquid two-phase state flowing out of the radiator 14 is decompressed by the heating throttle 23 in iso-enthalpy to become in a gas state. In the hot gas refrigerant cycle due to the second heating mode, that is different from the heat pump cycle due to the first heating mode, the refrigerant does not absorb heat in the exterior heat exchanger 22, and thereby the heat radiation amount of the refrigerant in the radiator 14 is determined based on a compression work amount of the compressor 21. In the example of FIG. 7, the refrigerant flowing out of the radiator 14 becomes in a gas-liquid two-phase sate. However, the refrigerant flowing out of the radiator 14 may be in a gas state without being condensed, based on the physical property of the refrigerant.

According to the present embodiment, when the outside air temperature Tam is higher than the predetermined temperature T1, the air conditioning electrical controller 40 causes the refrigerant cycle device 20 to perform the first heating mode, so that the refrigerant cycle device 20 is operated as the heat pump cycle due to the first heating mode. In contrast, when the outside air temperature Tam is lower than the predetermined temperature T1, the air conditioning electrical controller 40 causes the refrigerant cycle device 20 to perform the second heating mode, so that the refrigerant cycle device 20 is operated as the hot gas cycle due to the second heating mode in which air to be blown into the vehicle compartment is heated by using hot gas refrigerant flowing into the radiator 14 from the compressor 21.

In the second heating mode, because the refrigerant does not flow into the exterior heat exchanger 22, the exterior heat exchanger 22 is not adapted as a heat absorber. Therefore, the exterior heat exchanger 22 is not frosted, and it is unnecessary to perform a defrosting operation of the exterior heat exchanger 22. Thus, it is possible to continuously perform the heating operation in an extremely-low outside air temperature, and thereby a necessary heating capacity can be obtained.

In contrast, in the first heating mode, the refrigerant pressure is reduced by the heating throttle 23 in order to the perform heat absorption of the refrigerant in the exterior heat exchanger 22. As a result, suction refrigerant pressure of the compressor 21 is lowered, and the compression ratio is increased in the compressor 21, thereby increasing the temperature of refrigerant discharged from the compressor 21. Thus, if the first heating mode is performed in an extremely-low outside air temperature, the temperature of the refrigerant discharged from the compressor 21 may become higher than a temperature resistance temperature of the components of the refrigerant cycle device 20. In this case, it is necessary to reduce the rotation speed of the compressor 21 to perform a power saving control, and thereby the heating capacity substantially becomes lower.

In the second heating mode, because the refrigerant does not absorb heat in the exterior heat exchanger 22, it can restrict the suction refrigerant pressure of the compressor 21 from being excessively lowered, and thereby it can restrict the refrigerant temperature discharged from the compressor 21 from being excessively increased, as compared with that in the first heating mode under the same outside air temperature. Accordingly, even when the second heating mode is performed in the extremely low outside-air temperature, it is unnecessary for the compressor 21 to perform the power saving control during the second heating mode.

Furthermore, in the present embodiment, because the second heating mode is performed in the extremely low outside-air temperature, it is unnecessary for the evaporator 13 to have a structure with a high-temperature resistance and a high-pressure resistance. Thus, a general evaporator can be used as the evaporator 13, thereby reducing the cost This is the same also in the following embodiments.

In the above-described embodiment, the position of the air mix door 19 in each of the cooling mode, the dehumidifying and heating mode, the first heating mode and the second heating mode is not limited to the examples shown in FIGS. 1 to 4. In the cooling mode, the dehumidifying and heating mode, the first heating mode and the second heating mode, the position of the air mix door 19 can be suitably adjusted, so that the temperature of conditioned air to be blown into the vehicle compartment can be adjusted.

Second Embodiment

In the present embodiment, the air conditioner 1 is typically used for a hybrid vehicle (HV) which is traveled by a vehicle driving source composed of an internal combustion engine 10 and an electrical motor for a vehicle traveling. In the second embodiment, a hot-water type heater core 61 is added to the interior air-conditioning unit 10, with respect to the first embodiment.

FIG. 8 is a schematic diagram showing an air conditioner for a vehicle according to the second embodiment of the invention. In the vehicle air conditioner 1, a coolant circuit 63 is provided such that the coolant of an engine (EG) 62 is circulated between the heater core 61 and the engine 62. The heater core 61 is a heating heat exchanger for heating air to be blown into a vehicle compartment by using engine coolant as a heat source. The heater core 61 is disposed in the air conditioning case 11 downstream of the evaporator 13 and upstream of the radiator 14 in an air flow direction.

Thus, the radiator 14 is located in the first passage 16 within the air conditioning case 11, at a downstream air side of the heater core 61, such that air having passed through the heater core 61 flows through the radiator 14 in the air conditioning case 11.

In the present embodiment, in a condition where the first heating mode is selected, the heating operation due to the first heating mode is performed when a coolant temperature of the heater core 61 is lower than a predetermined temperature, and the heating operation due to the heater core 61 is performed when the coolant temperature of the heater core 61 is higher than the predetermined temperature.

Furthermore, in the present embodiment, when the second heating mode is selected, the heating operation for heating air to be blown into the vehicle compartment is performed by using the heater core 61. For example, in a case where the second heating mode is performed by the air conditioning electrical controller 40 as the operation mode of the refrigerant cycle device 20, when the coolant temperature is lower than the predetermined temperature in a stop state of the engine 62, an engine operation-request signal is output from the air conditioning electrical controller 40 to an engine controller. Thus, the engine 62 is operated for the air conditioner 1, and thereby the coolant temperature is increased, and the air to be blown into the vehicle compartment is heated by the heater core 61. Therefore, in the second heating mode, the entire heating capacity for heating air in the vehicle air conditioner is the total of the heat radiation amount from the refrigerant in the radiator 14 and the heat radiation amount from the engine coolant in the heater core 61.

In the example of FIG. 8 of the second embodiment, the heater core 61 is located upstream of the radiator 14 in the air flow direction. However, the heater core 61 may be located downstream of the radiator 14 in the first air passage 16 of the air conditioning case 11 in the air flow direction. When the heater core 61 is arranged upstream of the radiator 14 in the air flow direction, the heat radiation amount of the radiator 14 can be more effectively increased as shown in FIG. 9, as compared with a case where the heater core 61 is arranged downstream of the radiator 14 in the air flow direction.

FIG. 9 is a Mollier diagram showing refrigerant states in the second heating mode of the vehicle air conditioner 1, according to the second embodiment. In the hot gas cycle of the second heating mode, a cycle balance is determined based on the work amount of the compressor 21 and the performance of the radiator 14. In the hot gas cycle, when the air temperature at the air inlet of the radiator 14 is increased from TO1 to TO2 (not shown), the refrigerant temperature on the high pressure side before decompressing is increased from T11 to T12, and thereby the refrigerant pressure of the high pressure side is increased from P1 to P2. In this case, the compression work amount of the compressor 21 is increased, and the refrigerant cycle is operated so that the heat radiation, amount of the radiator 14 is increased from Q1 to Q2.

Thus, in a case where the heat radiation amount of the heater core 61 is the same, by arranging the heater core 61 at an upstream air side of the radiator 14, the heating capacity of the radiator 14 can be increased as compared with a case where the heater core 61 is arranged downstream of the radiator 14 in the air flow direction.

According to the second embodiment, the heating capacity of the radiator 14 during the second heating mode can be increased, as compared with that during the first heating mode, as shown in FIGS. 10A and 10B. FIG. 10B is a graph showing a compressor power consumed in the compressor 21 with respect to the air temperature at the air inlet of the radiator 14, and FIG. 10A is a graph showing a heat radiation amount (heating capacity) of the radiator 14 with respect to the air temperature at the air inlet of the radiator 14.

As shown in FIG. 10B, when the first heating mode is performed in an extremely-low outside air temperature, the compression power is increased as the air temperature at the air inlet of the radiator 14 increases. However, in the first heating mode, when the air temperature at the air inlet of the radiator 14 is higher than the temperature Tx, the compressor power is not increased more than a predetermined power value and tends to become a predetermined power value. That is, in this case, the power saving control is performed.

Thus, as shown in FIG. 10A, when the first heating mode is set in a case where the air temperature at the air inlet of the radiator 14 is higher than the temperature Tx, the heat radiation amount (heating capacity) of the radiator 14 is set at a constant heating capacity Qx, and it is difficult to obtain a high heating capacity higher than the constant heating capacity Qx.

In contrast, when the second heating mode is set in an extremely-low outside air temperature, the power saving control can be avoided regardless of the air temperature at the air inlet of the radiator 14. Because the power saving control is not performed in the second heating mode, the compressor power consumed in the compressor 21 tends to continuously increase in accordance with an increase of the air temperature at the air inlet of the radiator 14, as shown in FIG. 10B. Thus, as shown in FIG. 10A, when the air temperature at the air inlet of the radiator 14 is equal to or higher than the predetermined temperature Ta (° C.), the heating capacity of the radiator 14 can be increased more than the heating capacity in the first heating mode.

Third Embodiment

FIG. 11 is a schematic diagram showing an air conditioner 1 for a vehicle, according to a third embodiment of the invention. In the present embodiment, a second heating throttle 71 for decompressing the refrigerant discharged from the compressor 21 is added with respect to the vehicle air conditioner 1 of the above-described first embodiment. The second heating throttle 71 for decompressing the refrigerant discharged from the compressor 21 may be added with respect to the vehicle air conditioner 1 of the above-described second embodiment.

More specifically, with respect to the structure of the vehicle air conditioner 1 of the above-described first embodiment, the second heating throttle 71, a fourth bypass passage 72 and an electromagnetic valve 73 are provided. The second heating throttle 71 is disposed to decompress the refrigerant discharged from the compressor 21 and before flowing into the radiator 14. The fourth bypass passage 72 is provided such that the refrigerant flows through the fourth bypass passage 72 while bypassing the second heating throttle 71. Furthermore, the electromagnetic valve 73 is disposed in the fourth bypass passage 72 to open or close the fourth bypass passage 72. As the second heating throttle 71, a fixed throttle or a variable throttle may be used.

The third bypass passage 30 of the present embodiment is provided to be different from the first embodiment, such that the refrigerant after passing through the radiator 14 is introduced into the second bypass passage 28 while bypassing the heating throttle 23 and the exterior heat exchanger 22. In the third embodiment, the heating throttle 23 described in the above first embodiment is adapted as a first heating throttle 23.

The air conditioning electrical controller 40 causes the electromagnetic valve 73 to be fully opened in the cooling mode, the dehumidifying and heating mode and the first heating mode. Therefore, the refrigerant cycles in the cooling mode, the dehumidifying and heating mode and the first heating mode are similar respectively to those described in the first embodiment.

In contrast, the air conditioning electrical controller 40 causes the electromagnetic valve 73 to be closed in the second heating mode. In the second heating mode, the refrigerant discharged from the compressor 21 is decompressed by the second heating throttle 71, and the decompressed refrigerant flows into the radiator 14. Then, the refrigerant flowing out of the radiator 14 is drawn to the refrigerant suction side of the compressor 21 while bypassing the first heating throttle 23, the exterior heat exchanger 22 and the evaporator 13.

FIG. 12 is a Mollier diagram showing refrigerant states in the second heating mode of the vehicle air conditioner 1, according to the third embodiment. In the example of FIG. 12, gas refrigerant decompressed by the second throttle 71 radiates heat in the radiator 14 without being condensed. According to the present embodiment, because the refrigerant discharged from the compressor 21 is decompressed by the second throttle 71 before flowing to the radiator 14, a refrigerant temperature T22 at the refrigerant inlet of the radiator 14 becomes lower than a refrigerant temperature T21 discharged from the compressor 21.

Thus, in the present embodiment, when the refrigerant temperature discharged from the compressor 21 is the same as that of the above-described first embodiment, the refrigerant temperature at the refrigerant inlet of the radiator 14 becomes lower, and a temperature difference between the refrigerant and air passing through the radiator 14 becomes smaller. Thus, the hot gas cycle shown in FIG. 12 can be easily balanced as compared with the hot gas cycle shown in FIG. 7.

Thus, according to the present embodiment, the compression work amount of the compressor 21 can be increased as compared with the second heating mode of the first embodiment, thereby obtaining a high heating capacity.

According to the third embodiment, the refrigerant cycle device 20 is provided with the second heating throttle 71, the fourth bypass passage 72 and the electromagnetic valve 73, with respect to the refrigerant cycle device 20 of the first embodiment. The other parts of the refrigerant cycle device 20 are similar to corresponding parts of the above-described first embodiment.

Fourth Embodiment

In the above-described first embodiment, as a radiator for radiating heat, the radiator 14 is used so as to heat air by directly performing heat exchange between the refrigerant and air. However, a radiator, in which high-temperature refrigerant is heat-exchanged with air through another liquid fluid such as the engine coolant, may be adapted instead of the radiator 14 of the above-described first embodiment.

FIG. 13 is a schematic diagram showing an air conditioner 1 for a vehicle, according to fourth embodiment of the invention. In the present embodiment, as shown in FIG. 13, a water-refrigerant heat exchanger 81 an a heater core 61 adapted instead of the radiator 14 of the second embodiment shown in FIG. 8, and the other components are similar to those of the above described second embodiment.

In the present embodiment, the heater core 61 is adapted as a first radiator part disposed downstream of the evaporator 13 in the air conditioning case 11 in the air flow direction, so that the engine coolant radiates heat to air by performing heat exchange between the engine coolant and air after passing through the evaporator 13.

The water-refrigerant heat exchanger 81 is a second radiator part connected to a downstream side of the compressor 21 and at an upstream side of the heating throttle 23 in a refrigerant flow, so as to radiate heat from the refrigerant to the engine coolant by performing heat exchange between the high-pressure and high-temperature refrigerant discharged from the compressor 21 and the engine coolant.

In the vehicle air conditioner 1 of the fourth embodiment, the water-refrigerant heat exchanger 81 is adapted to perform heat exchange between the refrigerant discharged from the compressor 21 and the engine coolant flowing through the heater core 61. Therefore, the engine coolant flowing through the heater core 61 can be heated by the high-temperature refrigerant in the water-refrigerant heat exchanger 81. In the second embodiment, the other parts may be similar to those of the above-described second embodiment. More specifically, in the dehumidifying and heating mode, the first heating mode or the second heating mode, the engine coolant can be heated by using the heat radiation of the refrigerant in the water-refrigerant heat exchanger 81, and then the air after passing through the evaporator 13 is heated by heat radiation of the engine coolant in the heater core 61.

Both the water-refrigerant heat exchanger 81 and the heater core 61 are adapted as a radiator in which the high-pressure and high-temperature refrigerant is heat exchanged with air after passing through the evaporator 13 via the engine coolant. Thus, even in this structure, it is possible to finally heat air after passing through the evaporator 13 by using the heat radiation from the refrigerant.

In the present embodiment, the compressor power tends to increase as the temperature of the engine coolant increases by the engine operation. Therefore, in the second heating mode, the heat radiation amount of the water-refrigerant heat exchanger 81 can be increased as compared with the first heating mode.

According to the fourth embodiment, because the water-refrigerant heat exchanger 81 is located outside of the air conditioning unit 10, the interior structure of the interior air conditioning unit 10 can be made simple, as compared with the structure of the second embodiment shown in FIG. 8.

Other Embodiments

Although the present invention has been fully described in connection with the preferred embodiments thereof with reference to the accompanying drawings, it is to be noted that various changes and modifications will become apparent to those skilled in the art.

(1) In the above-described embodiments, at step S9 in FIG. 6, one of the first heating mode and the second heating mode is determined based on the outside air temperature Tam. However, the first heating mode and the second heating mode may be switched based on a physical amount other than the outside air temperature Tam.

The physical amount is a physical amount having a connection with the heating capacity of the first heating mode. For example, the physical amount is a refrigerant pressure Ps at a refrigerant suction side of the compressor 21, a refrigerant temperature Ts at a refrigerant suction side of the compressor 21 or the like. In an extremely-low outside air temperature in which the heating capacity of the first heating mode is reduced, the suction side refrigerant pressure Ps is reduced, the refrigerant flow amount becomes smaller, and the refrigerant pressure discharged from the compressor 21 is increased.

A threshold value of the physical amount can be set based on the physical amount at which the heating capacity of the first heating mode is low and is insufficient for the heating operation. Then, the detected physical amount is compared with the threshold value. When the detected physical amount becomes a value at which a necessary heating capacity cannot be obtained by setting the first heating mode, the second heating mode is switched from the first heating mode.

For example, the suction pressure sensor 48 is disposed to detect the refrigerant pressure Ps at the refrigerant suction side of the compressor 21 in the first heating mode. Alternatively, the refrigerant pressure at the refrigerant suction side of the compressor 21 may be estimated based on the refrigerant temperature detected by the suction temperature sensor 47. When the detected or estimated refrigerant suction pressure Ps is lower than a first predetermined pressure P1, the refrigerant cycle may be switched to the second heating mode from the first heating mode. Furthermore, when the refrigerant suction pressure Ps detected in the second heating mode is higher than a second predetermined pressure (P1+α), the refrigerant cycle may be switched to the first heating mode from the second heating mode. The second predetermined pressure (P1+α) is set so that the refrigerant cycle is not directly switched to the first heating mode from the second heating mode, when the low-pressure side refrigerant pressure is increased by the second heating mode than that in the first heating mode after the refrigerant cycle is switched from the first heating mode to the second heating mode.

The refrigerant cycle may be switched to the second heating mode based on the suction side refrigerant pressure Ps in the first heating mode, not only in an extremely-low outside air temperature but also in a case where the heating capacity due to the first heating mode is low.

For example, the discharge temperature sensor 44 is set to detect the refrigerant temperature Td at the refrigerant discharge side of the compressor 21 in the first heating mode. When the discharge-side refrigerant temperature Td of the compressor 21 is higher than a first predetermined temperature, the refrigerant cycle is switched to the second heating mode from the first heating mode. In contrast, when the discharge-side refrigerant temperature Td of the compressor 21 is lower than a second predetermined temperature lower than the first predetermined temperature in the second heating mode, the refrigerant cycle is switched again to the first heating mode from the second heating mode. For example, the first predetermined temperature is set at 150° C. by considering the temperature area of the power saving control.

Alternatively, a refrigerant flow amount discharged from the compressor 21 may be detected by using a refrigerant flow sensor. In this case, when the detected refrigerant flow amount is lower than a predetermined flow amount, the refrigerant cycle may be switched to the second heating mode from the first heating mode.

(2) In the above-described embodiments, in the cooling mode shown in FIG. 1 or the dehumidifying and heating mode shown in FIG. 2, the refrigerant discharged from the compressor 21 flows in this order of the radiator 14, the exterior heat exchanger 22 and the evaporator 13. That is, the three heat exchangers of the radiator 14, the exterior heat exchanger 22 and the evaporator 13 are arranged in series in the refrigerant flow. However, the three heat exchangers of the radiator 14, the exterior heat exchanger 22 and the evaporator 13 may be arranged to be not in series.

For example, in the cooling mode shown in FIG. 1, a bypass passage through which the refrigerant bypasses the radiator 14 may be provided, such that the refrigerant discharged from the compressor 21 flows into the exterior heat exchanger 22 while bypassing the radiator 14.

Alternatively, in the dehumidifying and heating mode shown in FIG. 2, a bypass passage through which the refrigerant bypasses the exterior heat exchanger 22 may be provided, such that the refrigerant discharged from the radiator 14 flows into the evaporator 13 while bypassing the exterior heat exchanger 22. In addition, in the dehumidifying and heating mode, the refrigerant cycle may be configured such that the refrigerant discharged from the radiator 14 may flow in parallel with respect to the exterior heat exchanger 22 and the evaporator 13.

(3) In the above-described embodiments with the heater core 61, the engine coolant is used as a cooling fluid for cooling a heat generator such as an engine mounted to a vehicle. However, as the cooling fluid for cooling the heat generator, a cooling liquid other than water or a gas fluid may be used without being limited to the coolant. Furthermore, a cooling liquid fluid of a heat generator other than the engine may be used for heating air, or a liquid heater such as an electrical heater may be located to heat a liquid fluid thereby heating air via the heated liquid fluid.

(4) In the above-described second embodiment, the heater core 61 is disposed to increase the air temperature at the air inlet of the radiator 14. However, air flowing to the radiator 14 may be heated by a heater such as an electrical heater or a PTC heater or the like.

(5) The above described embodiments may be suitably combined if there is no contradiction therebetween.

Such changes and modifications are to be understood as being within the scope of the present invention as defined by the appended claims.

Claims

1. An air conditioner for a vehicle, comprising:

a compressor configured to compress and discharge refrigerant;

an exterior heat exchanger configured to perform heat exchange between the refrigerant and air outside of a vehicle compartment;

an evaporator, arranged in an air conditioning case, to perform a heat exchange between low-pressure and low-temperature refrigerant and air to be blown into the vehicle compartment;

a radiator disposed to cool a high-pressure and high-temperature refrigerant by performing a heat exchange between the high-pressure and high-temperature refrigerant and air having passed through the evaporator;

a refrigerant flow switching device configured to switch one of refrigerant cycles of a cooling mode, a first heating mode and a second heating mode;

a first decompression device configured to decompress refrigerant at least in the refrigerant cycle of the cooling mode; and

a second decompression device configured to decompress refrigerant at least in the refrigerant cycle of the first heating mode, wherein

the refrigerant cycle of the cooling mode is configured such that the refrigerant discharged from the compressor flows through the exterior heat exchanger, the first decompression device, the evaporator and a refrigerant suction side of the compressor in this order, so that the refrigerant absorbs heat at the evaporator and radiates heat at the exterior heat exchanger,

the refrigerant cycle of the first heating mode is configured such that the refrigerant discharged from the compressor flows through the radiator, the second decompression device and the exterior heat exchanger in this order, and the refrigerant flowing out of the exterior heat exchanger is introduced to the refrigerant suction side of the compressor while bypassing the evaporator, so that the refrigerant absorbs heat at the exterior heat exchanger and radiates heat at the radiator,

the refrigerant cycle of the second heating mode is configured such that the refrigerant discharged from the compressor flows into the radiator, and the refrigerant flowing out of the radiator is introduced to the refrigerant suction side of the compressor while bypassing both the exterior heat exchanger and the evaporator, so that the refrigerant radiates heat at the radiator, and

the refrigerant flow switching device switches the refrigerant cycle from the first heating mode to the second heating mode, when a physical amount having a relation with a heating capacity of the first heating mode becomes a value at which the heating capacity is low in the first heating mode.

2. The air conditioner according to claim 1, further comprising

an air heater disposed in the air conditioning case at a downstream air side of the evaporator to heat air by using a heat source different from the refrigerant cycle, wherein the radiator is disposed in the air conditioning case at a downstream air side of the air heater, to heat air after passing through the air heater by performing heat exchange with refrigerant.

3. The air conditioner according to claim 1, wherein

the refrigerant cycle of the second heating mode is configured such that the refrigerant discharged from the compressor flows into the radiator, and the refrigerant flowing out of the radiator is introduced to the refrigerant suction side of the compressor after being decompressed by the second decompression device.

4. The air conditioner according to claim 1, further comprising

a third decompression device configured to decompress the refrigerant discharged from the compressor, before flowing into the radiator in the second heating mode.

5. The air conditioner according to claim 1, further comprising

an outside air temperature sensor disposed to detect an outside air temperature as the physical amount, wherein the refrigerant flow switching device is configured to switch the refrigerant cycle from the first heating mode to the second heating mode when the outside air temperature detected by the outside air temperature sensor is lower than a predetermined temperature.

6. The air conditioner according to claim 1, further comprising

a pressure detection device disposed to detect a refrigerant pressure at the refrigerant suction side of the compressor, as the physical amount,

wherein the refrigerant flow switching device is configured to switch the refrigerant cycle from the first heating mode to the second heating mode, when the refrigerant pressure detected by the pressure detection device is lower than a predetermined pressure.

7. The air conditioner according to claim 1, further comprising

a temperature detection device disposed to detect a refrigerant temperature at a refrigerant discharge side of the compressor, as the physical amount,

wherein the refrigerant flow switching device is configured to switch the refrigerant cycle from the first heating mode to the second heating mode, when the refrigerant temperature detected by the temperature detection device is higher than a predetermined temperature in the first heating mode.

8. The air conditioner according to claim 1, wherein

the radiator includes a first radiator part disposed in the air conditionig case at a downstream air side of the evaporator, to heat air after passing through the evaporator by using a liquid fluid flowing therein, and a second radiator part disposed to radiate heat from high-pressure and high-temperature refrigerant to the liquid fluid by performing heat exchange between high-pressure and high-temperature refrigerant and the liquid fluid.

9. The air conditioner according to claim 8, further comprising

a liquid heater configured to heat the liquid fluid flowing to the first radiator part.