HEAT EXCHANGER

Abstract

In a composite-type heat exchanger capable of exchanging heat among three types of fluids, an outside air passage is provided in a periphery of refrigerant tubes and coolant tubes, and the outside air passage includes outer fins that promote heat exchange among a refrigerant, an outside air and a coolant. The outer fins include refrigerant side heat connecting portions configured to thermally connect the refrigerant tubes, and coolant side heat connecting portions configured to thermally connect the refrigerant tubes and the coolant tubes. In a first core portion including most downstream refrigerant tubes which constitute a final path, which is the most downstream side path in a direction of the refrigerant flow, the refrigerant side heat connecting portions is larger in number than the coolant side heat connecting portions.

Description

CROSS REFERENCE TO RELATED APPLICATION

This application is based on and incorporates herein by reference Japanese Patent Application No. 2012-249441 filed on Nov. 13, 2012.

TECHNICAL FIELD

The present disclosure relates to a composite-type heat exchanger configured to be capable of performing heat exchanges among three kinds of fluids.

BACKGROUND ART

Conventionally, a composite-type heat exchanger configured to be capable of performing heat exchanges among three types of fluids is known. For example, disclosed in Patent Document 1 is a composite-type heat exchanger including a refrigerant radiator that performs heat exchange between a refrigerant (a first fluid) discharged from a compressor in a refrigeration cycle and a blown air (a third fluid) such that a heat of the discharged refrigerant is radiated to the blown air, and a radiator that performs heat exchange between a coolant (a second fluid) for cooling an engine and a blown air to radiate heat of the coolant to the blown air combined into one unit as a single heat exchanger.

Specifically, disclosed in Patent Document 1 is a heat exchanger including refrigerant tubes in which the discharged refrigerant flows, coolant tubes in which the coolant flows arranged in a stacked manner, and outer fins arranged in outside air passages configured to allow the outside air to flow therein. Each outer fin is formed between the refrigerant tube and the coolant tube adjacent to each other and configured to allow heat transfer between the refrigerant tubes and the coolant tubes. Accordingly, not only the heat exchange between the refrigerant and the blown air and the heat exchange between the coolant and the blown air, but also the heat exchange between the refrigerant and the coolant are achieved.

PRIOR ART DOCUMENT

Patent Document

Patent Document 1: JP 2012-144245 A

SUMMARY OF THE INVENTION

In the refrigeration cycle, normally, a degree of subcooling of the refrigerant flowing out from the refrigerant radiator is controlled to achieve a maximum coefficient of performance (COP) of the cycle.

According to a study of the inventors of the present application, with the composite-type heat exchanger described in Patent Document 1, in a subcooling portion configured to subcool the condensed refrigerant in the refrigerant radiator, regions of the outer fins arranged between the refrigerant tubes that form the subcooling portion and the coolant tubes adjacent to the refrigerant tubes, which are used for discharging the heat of the coolant to the outside air are excessively increased, and regions thereof used for discharging the heat of the discharged refrigerant to the outside air become small. Therefore, in order to provide the refrigerant on the outlet side of the refrigerant radiator with a desired degree of subcooling, the length of the refrigerant tubes that forms the subcooling portion needs to increase to increase the total surface area of the outer fins connected to the coolant tubes.

However, the subcooling portion in the refrigerant radiator has an extremely low heat transmitting rate on tube wall surfaces in comparison with a condenser (the heat radiating portion in the refrigerant radiator other than the subcooling portion). In contrast, the refrigerant tubes that form the condenser have a high heat transmitting rate on the tube wall surfaces, and have a high heat exchanging performance. Therefore, when the length of the tubes that form the subcooling portion is increased, the length of the refrigerant tubes that form the condenser is reduced, so that the heat exchanging performance of the refrigerant radiator as a whole may be deteriorated.

In view of such points described above, it is an objective of the present disclosure to limit reduction in heat exchanging capacity of a composite-type heat exchanger as a whole while the heat exchanger is configured to be capable of performing heat exchanges among three types of fluids.

According to an aspect of the present disclosure, a heat exchanger includes a plurality of first tubes in which a first fluid flows, a plurality of second tubes in which a second fluid flows, a heat exchange portion including the plurality of first tubes and the plurality of second tubes arranged in a stacked manner and configured to radiate heats of the first fluid and the second fluid to a third fluid, a third fluid channel in which the third fluid flows, the third fluid channel being provided in a periphery of the plurality of first tubes and the plurality of second tubes, and an outer fin arranged in the third fluid channel to promote a heat exchange between the first fluid and the third fluid and a heat exchange between the second fluid and the third fluid. The outer fin includes a first heat connecting portion thermally connecting the plurality of first tubes, and a second heat connecting portion thermally connecting the plurality of first tubes and the plurality of the second tubes. The plurality of first tubes is divided into a plurality of groups, and the plurality of groups of the plurality of first tube are paths through which the first fluids distributed from a same space flow in a same direction. The plurality of first tubes include most downstream first tubes which constitute a part of a final path that is a most downstream path in a flowing direction of the first fluid. The heat exchange portion includes a first core portion including the most downstream first tubes. The first heat connecting portions are larger in number than the second heat connecting portions in the first core portion.

In this configuration, in a heat exchange portion including the most downstream first tubes, since the number of the first heat connecting portions is set to be larger than the number of the second heat connecting portions, an area used for radiating heat of the first fluid to the third fluid is larger than an area used for radiating heat of the second fluid to the third fluid in the outer fins arranged in the heat exchanger including the most downstream first tubes. Therefore, the heat of the first fluid flowing in the most downstream first tubes may be radiated sufficiently to the third fluid.

Therefore, lengths of the most downstream first tubes does not have to be increased in order to achieve a desired temperature as the temperature of the first fluid on the outlet side of the heat exchanger, that is, lengths of first tubes which do not form the final path does not have to be decreased, and hence reduction of the heat exchanging performance as the entire heat exchanger may be limited.

The expression “arrange the first tubes and the second tubes in a stacked manner” means that the first tubes and the second tubes are arranged in a stacked manner in a given order, and does not limit the order of arrangement of the first tubes and the second tubes. The expression “the number of the first heat connecting portions is larger than the number of the second heat connecting portions” includes a case where the number of the second heat connecting portions is zero.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic diagram of a vehicle air conditioning system of a first embodiment of the present disclosure.

FIG. 2 is a perspective view of a composite-type heat exchanger of the first embodiment.

FIG. 3 is an exploded perspective view of the composite-type heat exchanger of the first embodiment.

FIG. 4 is a cross-sectional view taken along a line IV-IV of FIG. 2.

FIG. 5 is a cross-sectional view taken along a line V-V of FIG. 2.

FIG. 6 is a schematic perspective view for explaining a refrigerant flow and a coolant flow in the composite-type heat exchanger of the first embodiment.

FIG. 7 is a characteristic diagram illustrating a relationship between a degree of subcooling and a heat-radiating capacity of a refrigerant.

FIG. 8 is a schematic cross-sectional view taken in a longitudinal direction of a heat exchange portion and illustrating a first core portion of a composite-type heat exchanger according to a second embodiment of the present disclosure.

FIG. 9 is a schematic perspective view for explaining a refrigerant flow and a coolant flow in a composite-type heat exchanger of a third embodiment of the present disclosure.

FIG. 10 is a schematic perspective view for explaining a refrigerant flow and a coolant flow in a composite-type heat exchanger of a fourth embodiment of the present disclosure.

FIG. 11 is a schematic diagram illustrating a heat pump cycle and a flow channel of the coolant circuit at the time of a heating operation of a fifth embodiment of the present disclosure.

FIG. 12 is a schematic diagram illustrating a heat pump cycle and a flow channel of the coolant circuit at the time of a defrosting operation of the fifth embodiment.

FIG. 13 is a schematic diagram illustrating the heat pump cycle and the flow channel of the coolant circuit at the time of a cooling operation of the fifth embodiment.

FIG. 14 is a schematic diagram illustrating a heat pump cycle and a flow channel of the coolant circuit at the time of a heating operation of a sixth embodiment of the present disclosure.

FIG. 15 is a schematic diagram illustrating the heat pump cycle and the flow channel of the coolant circuit at the time of warm-up operation of the sixth embodiment.

FIG. 16 is a schematic diagram illustrating the heat pump cycle and the flow channel of the coolant circuit at the time of a cooling operation of the sixth embodiment.

FIG. 17 is a schematic perspective view for explaining a refrigerant flow and a coolant flow in a composite-type heat exchanger of a modification of the present disclosure.

EMBODIMENTS FOR EXPLOITATION OF THE INVENTION

Hereinafter, multiple embodiments for implementing the present invention will be described referring to drawings. In the respective embodiments, a part that corresponds to a matter described in a preceding embodiment may be assigned 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

A first embodiment of the present disclosure will be described with reference to FIG. 1 to FIG. 7. In the present embodiment, a heat exchange system of the present disclosure is applied to a vehicle air conditioning apparatus 1 for so-called a hybrid vehicle that obtains a drive force for traveling a vehicle from an internal combustion engine (an engine) and a traveling electric motor MG.

The hybrid vehicle is capable of being switched between a traveling state in which the engine is activated or stopped depending on a traveling load of the vehicle and a drive force is obtained both from the engine and the traveling electric motor MG to travel and a traveling state in which the engine is stopped and the drive force is obtained only from the traveling electric motor MG to travel. Accordingly, in the hybrid vehicle, a vehicle fuel efficiency for normal vehicles which obtain the drive force for traveling the vehicle only from the engine can be improved.

The heat exchange system applied to the vehicle air conditioning apparatus 1 of the present embodiment includes a heat pump cycle 10, which is a vapor compression refrigeration cycle, a coolant circulation circuit 40 in which a coolant configured to cool the traveling electric motor MG circulates, and the like.

First of all, the heat pump cycle 10 performs a function of cooling a blown air to be blown into a vehicle interior which is a space to be air-conditioned in the vehicle air conditioning apparatus 1. The heat pump cycle 10 employs a normal fluorocarbon refrigerant as the refrigerant, and constitutes a part of a subcritical refrigeration cycle in which a high pressure side refrigerant pressure does not exceed a critical pressure of the refrigerant. Refrigerant oil for lubricating a compressor 11 is mixed with the refrigerant, and a portion of the refrigerant oil circulates in the cycle together with the refrigerant.

The compressor 11 is an electric compressor arranged in an engine room and sucks, compresses, and discharges the refrigerant in the heat pump cycle 10, is configured to drive a fixed capacity type compressor 11a with a fixed discharge capacity by an electric motor 11b. Specifically, various compression mechanisms such as a scroll-type compression mechanism and a vane-type compression mechanism can be employed as the fixed capacity type compressor 11a.

The operation (a number of rotations) of the electric motor 11b is controlled by a control signal that is output from a control apparatus, which will be described later, and any one of an AC motor and a DC motor may be employed as the electric motor 11b. The refrigerant discharging capacity of the compressor 11 changes according to the number-of-rotations control. Therefore, in the present embodiment, the electric motor 11b constitutes a part of discharge capacity change means of the compressor 11.

A refrigerant inlet side of a refrigerant radiator 12 is connected to a refrigerant discharge port of the compressor 11. The refrigerant radiator 12 is a radiation heat exchanger arranged in the engine room, and configured to cause a discharged refrigerant (a first fluid) discharged from the compressor and outside air as a fluid to be heat exchanged (a third fluid) blown from a blower fan 13 to exchange heat with each other and discharge the heat of the discharged refrigerant to the outside air.

The blower fan 13 is an electric blower of which an operation rate, that is, a number of rotations (an amount of blown air) is controlled by a control voltage output from the control apparatus. The refrigerant radiator 12 of the present embodiment is combined integrally with a radiator (a heat medium radiator) 43 described later configured to cause a coolant (a second fluid) as heat medium for cooling the traveling electric motor MG and the outside air blown from the blower fan 13 to exchange heat with each other.

Therefore, the blower fan 13 of the present embodiment constitutes a part of exterior blowing means configured to blow outside air toward both the refrigerant radiator 12 and the radiator 43. Detailed configuration of the integrated refrigerant radiator 12 and the radiator 43 (hereinafter, referred to as a composite-type heat exchanger 70) will be described later.

A receiver 14 configured to separate gas and liquid of the refrigerant flowing out from the refrigerant radiator 12 and accumulate an excessive liquid-phase refrigerant is arranged on a refrigerant outlet side of the refrigerant radiator 12. In addition, an inlet side of a temperature type expansion valve 15 is connected to an outlet of the liquid-phase refrigerant of the receiver 14, and a refrigerant inlet side of a refrigerant evaporator 16 is connected to an outlet side of the temperature type expansion valve 15.

The temperature type expansion valve 15 is decompression means including a temperature sensing unit, which is not illustrated, arranged in a refrigerant passage on the outlet side of the refrigerant evaporator 16, configured to detect a degree of superheat of the refrigerant on the outlet side of the refrigerant evaporator 16 on the basis of a temperature and a pressure of the refrigerant on the outlet side of the refrigerant evaporator 16, and adjust a valve opening (refrigerant flow rate) by a mechanic mechanism so that the degree of superheat of the refrigerant on the outlet side of the refrigerant evaporator 16 falls within a value of a predetermined range set in advance.

The refrigerant evaporator 16 is a cooling heat exchanger arranged in a casing 31 of an indoor air conditioning unit 30, configured to cause a low-pressure refrigerant decompressed and expanded by the temperature type expansion valve 15 and the blown air blown into the vehicle interior to exchange heat with each other, and cool the blown air by evaporating the low-pressure refrigerant. A refrigerant inlet port of the compressor 11 is connected to the refrigerant outlet side of the refrigerant evaporator 16.

Next, the indoor air conditioning unit 30 will be described. The indoor air conditioning unit 30 is arranged inside of a dashboard panel (an instrument panel) in a foremost portion of the vehicle interior, and includes a blower 32, the above described refrigerant evaporator 16, the electric heater 36, and the like accommodated in the casing 31 which forms an outer shell thereof.

The casing 31 forms an air passage for a blown air that is blown into the vehicle interior in the interior thereof, and is made of a resin (for example, polypropylene) that has a certain degree of elasticity and is also excellent in terms of strength. An inside and outside air switching unit 33 configured to switch introduce air between the vehicle interior (inside air) and the outside air is arranged on the most upstream side of the blown airflow in the interior of the casing 31.

The inside and outside air switching unit 33 is provided with inside air inlet port for guiding the inside air into the interior of the casing 31 and the outside air inlet port for guiding the outside air therein. Furthermore, the inside and outside air switching unit 33 includes an inside and outside air switching door configured to adjust opening areas of the inside air inlet port and the outside air inlet port continuously to change an air volume ratio between an air volume of the inside air and an air volume of the outside air arranged in the interior thereof.

The blower 32 that blows the air sucked through the inside and outside air switching unit 33 toward the vehicle interior is arranged on the downstream side of the inside and outside air switching unit 33 in the direction of the airflow. The blower 32 is an electrical blower that drives a centrifugal multiblade fan (a sirocco fan) with an electric motor, and the number of rotations (a blowing rate) thereof is controlled by a control voltage that is output from the control apparatus.

The refrigerant evaporator 16 and the electric heater 36 are arranged on the downstream side of the blower 32 in the direction of the airflow in this order with respect to the flow of the blown air. In other words, the refrigerant evaporator 16 is arranged on the upstream side in the flowing direction of the blown air with respect to the electric heater 36. The electric heater 36 is heating means including a PTC element (positive characteristic thermistor), configured to generate heat by the control apparatus supplying electric power to the PTC element, and heating air after a passage through the refrigerant evaporator 16.

In addition, an air mixture door 34 configured to adjust an air volume proportion of the air that passes through the electric heater 36 to the blown air that has passed through the refrigerant evaporator 16 is arranged on the downstream side of the refrigerant evaporator 16 in the direction of airflow, and on the upstream side of the electric heater 36 in the direction of the airflow. In addition, a mixing space 35 that mixes the blown air heated by the electric heater 36 by the heat exchange with the refrigerant and the blown air which is not heated by bypassing the electric heater 36 is provided on the downstream side of the electric heater 36 in the direction of the airflow.

Outlet port for blowing out an air conditioning wind mixed in the mixing space 35 into the vehicle interior, which is a space to be cooled, is arranged on the most downstream portion of the casing 31 in the direction of the airflow. Specifically, a face outlet port through which the air conditioning wind is blown out toward an upper body of an occupant present in the vehicle interior, a foot outlet port through which the air conditioning wind is blown out toward feet of an occupant, and a defroster outlet port through which the air conditioning wind is blown out toward an inner surface of a windshield of a vehicle (none of which is illustrated) are provided as this outlet port.

Therefore, the air mix door 34 adjusts the proportion of the air volume that passes through the electric heater 36 to adjust a temperature of the air conditioning wind mixed in the mixing space 35, and adjust the temperature of the air conditioning wind blown out from the respective outlet ports. In other words, the air mix door 34 constitutes a part of temperature adjusting means configured to adjust the temperature of the air conditioning wind that is blown into the vehicle interior. The air mix door 34 is driven by a servo motor, which is not illustrated, controlled in operation by the control signal output from the control apparatus.

Furthermore, face doors for adjusting the opening areas of the face outlet ports, foot doors for adjusting the opening areas of the foot outlet ports, and defroster doors for adjusting the opening areas of the defroster outlet ports (none of which are illustrated) are arranged on the upstream sides of the face outlet ports, the foot outlet ports, and the defroster outlet ports in the direction of the airflow, respectively.

The face door, the foot door, and the defroster door constitute a part of outlet port mode switching means configured to switch an outlet port mode, and are driven by the servo motor, which is not illustrated, controlled in operation by the control signal output from the control apparatus via a link mechanism or the like.

Subsequently, the coolant circulation circuit 40 will be described. The coolant circulation circuit 40 is a heat medium circulation circuit configured to flow the coolant (for example, ethylene glycol aqueous solution) as a heat medium in a coolant flow channel formed in the interior of the traveling electric motor MG, which is a vehicle-mounted devices associated with heat generation at the time of operation, to cool the traveling electric motor MG. The coolant circulation circuit 40 includes a coolant pump 41 and the radiator 43 arranged therein.

The coolant pump 41 is an electric water pump configured to pump the coolant into the coolant flow channel formed in the interior of the traveling electric motor MG in the coolant circulation circuit 40, and is controlled in number of rotations (flow rate) by the control signal output from the control apparatus.

When the control apparatus activates the coolant pump 41, the coolant circulates from the coolant pump 41 the traveling electric motor MG→the radiator 43→the coolant pump 41 in this order. Therefore, the coolant pump 41 constitutes a part of heat medium flow rate adjusting means (second fluid flow rate adjusting means) configured to adjust the inflow rate of the coolant flowing into the radiator 43.

The radiator 43 is a radiation heat exchanger arranged in an engine room, and configured to causes a coolant (the second fluid) flowing out from the coolant flow channel formed in the interior of the traveling electric motor MG and the outside air (the third fluid) blown from the blower fan 13 to exchange heat with each other to radiate heat of the coolant to the outside air.

Therefore, in the coolant circulation circuit 40, when the control apparatus activates the coolant pump 41, the coolant absorbs waste heat of the traveling electric motor MG when the coolant passes through the traveling electric motor MG thereby cooling the traveling electric motor MG. In addition, the coolant increased in temperature by absorbing the waste heat of the traveling electric motor MG flows into the radiator 43, radiates heat to the outside air, and is cooled. In other words, the traveling electric motor MG plays a function as an external heat source configured to heat the coolant.

Subsequently, with reference to FIG. 2 to FIG. 6, a detailed configuration of the composite-type heat exchanger 70 will be described. First of all, the composite-type heat exchanger 70 is a composite-type heat exchanger including the refrigerant radiator 12 and the radiator 43 combined into one unit as a single heat exchanger. The refrigerant radiator 12 and the radiator 43 are configured as so-called a tank-and-tube-type heat exchanger having a plurality of tubes 12a, 43a configured to flow the refrigerant or the coolant, respectively, and a pair of collection and distribution tanks 12b, 43b arranged on both end sides of the plurality of tubes and configured to collect or distribute the refrigerant or the coolant flowing in the respective tubes.

The composite-type heat exchanger 70 includes the refrigerant tubes 12a configured to allow the refrigerant as the first fluid to flow therein and the coolant tubes 43a configured to allow the coolant as the second fluid to flow therein in the interior thereof.

Here, the plurality of refrigerant tubes 12a are divided into a plurality of groups, and the plurality of groups of the refrigerant tubes 12a correspond to paths configured to flow the refrigerant distributed from the same space in the same direction, respectively. The refrigerant tubes 12a include a most downstream refrigerant tubes 121a (most downstream first tubes) that form final paths, which are paths on a most downstream side in the refrigerant flow direction.

The composite-type heat exchanger 70 includes a first core portion 701 formed only by the most downstream refrigerant tubes 121a and a second core portion 702 formed by both of the refrigerant tubes 12a and the coolant tubes 43a. In other words, in the composite-type heat exchanger 70, the first core portion 701, which corresponds to a heat exchange portion formed only by the most downstream refrigerant tubes 121a is provided independently from the second core portion 702, which is the other heat exchange portion.

In the present embodiment, the second core portion 702 constitutes a part of a condenser configured to radiate the heat from a high-pressure refrigerant flowing in the refrigerant tubes 12a and condense the high-pressure refrigerant, and the first core portion 701 constitutes a part of a subcooling portion configured to subcool the liquid phase refrigerant flowed out from the second core portion 702 (condenser).

More specifically, the composite-type heat exchanger 70 is provided with an upstream heat exchanging portion 71 formed by arranging the refrigerant tubes 12a and the coolant tubes 43a in an stacked manner. The upstream heat exchanging portion 71 is a heat exchange portion configured to cause the refrigerant flowing in the refrigerant tubes 12a and the air as the third fluid flowing around the refrigerant tubes 12a (the outside air blown from the blower fan 13) to exchange heat with each other and the coolant flowing in the coolant tubes 43a and the air flowing around the coolant tubes 43a (the outside air blown from the blower fan 13) to exchange heat with each other.

A portion of the upstream heat exchanging portion 71 which constitutes a part of the first core portion 701 includes only the most downstream refrigerant tubes 121a arranged in a stacked manner. In contrast, a portion of the upstream heat exchanging portion 71 which constitutes the second core portion 702 includes the refrigerant tubes 12a and the coolant tubes 43a arranged in an alternately stacked manner.

A downstream heat exchanging portion 72 including the refrigerant tubes 12a arranged in a stacked manner is provided on the downstream side of the upstream heat exchanging portion 71 in the direction of the flow of the outside air. In other words, the downstream heat exchanging portion 72 includes only the refrigerant tubes 12a. The downstream heat exchanging portion 72 is the heat exchange portion configured to cause the refrigerant flowing in the refrigerant tubes 12a and the air flowing around the refrigerant tubes 12a (the outside air blown from the blower fan 13) to exchange heat with each other.

As the refrigerant tubes 12a and the coolant tubes 43a, flat tubes having a flat shape in a vertical cross section in the longitudinal direction are employed. More specifically, as the refrigerant tubes 12a, tubes having a flat porous cross section molded by an extrusion processing are employed. As the coolant tubes 43a, tubes having a flat cross section having two holes formed by bending a single plate material are employed.

The refrigerant tubes 12a and the coolant tubes 43a which constitute a part of the second core portion 702 of the upstream heat exchanging portion 71 are arranged at a predetermined distance in an alternately stacked manner with a flat surfaces thereof out of an outer surfaces in parallel to each other and so as to oppose each other. In the same manner, the most downstream refrigerant tubes 121a which constitute a part of the first core portion 701 of the upstream heat exchanging portion 71 and the refrigerant tubes 12a which constitute a part of the downstream heat exchanging portion 72 are arranged at a predetermined distance in a stacked manner, respectively.

The refrigerant tubes 12a which constitute a part of the second core portion 702 of the upstream heat exchanging portion 71 are arranged between the coolant tubes 43a, and the coolant tubes 43a are arranged between the refrigerant tubes 12a. The refrigerant tubes 12a which constitute a part of the downstream heat exchanging portion 72 and the refrigerant tubes 12a or the coolant tubes 43a which constitute a part of the upstream heat exchanging portion 71 are arranged so as to overlap with each other when viewing from a flowing direction of an outside air blown by the blower fan 13.

In the heat exchanger 70, a space formed between the refrigerant tubes 12a and the coolant tubes 43a which constitute a part of the upstream heat exchanging portion 71 and a space formed between the adjacent refrigerant tubes 12a which constitute a part of the downstream heat exchanging portion 72 form an outside air passage 70a (a third fluid channel) in which the outside air blown by the blower fan 13 flows.

In the outside air passage 70a, outer fins 70b configured to promote the heat exchange between the refrigerant and the outside air and the heat exchange between the coolant and the outside air, and allows heat transfer between the refrigerant flowing in the refrigerant tubes 12a which constitute a part of the upstream heat exchanging portion 71 and the coolant flowing in the coolant tubes 43a and heat transfer of the refrigerants flowing in the adjacent refrigerant tubes 12a which constitute a part of the downstream heat exchanging portion 72 are arranged.

As the outer fins 70b, corrugate fins formed by bending a metallic thin plate having superior heat transfer properties into a wave shape are employed and, in the present embodiment, the outer fins 70b are joined to both of the refrigerant tubes 12a and the coolant tubes 43a which constitute a part of the upstream heat exchanging portion 71, so that the heat transfer between the refrigerant tubes 12a and the coolant tubes 43a is enabled. Furthermore, the outer fins 70b are joined to the adjacent refrigerant tubes 12a which constitute a part of the downstream heat exchanging portion 72, so that the heat transfer between the adjacent refrigerant tubes 12a is enabled.

The outer fins 70b include refrigerant side heat connecting portions (first heat connecting portions) 71b configured to thermally connect the refrigerant tubes 12a, and coolant side heat connecting portions (second heat connecting portions) 72b configured to thermally connect the refrigerant tubes 12a and the coolant tubes 43a. Specifically, the outer fins 70b arranged between the refrigerant tubes 12a include the refrigerant side heat connecting portions 71b. In contrast, the outer fins 70b arranged between the refrigerant tubes 12a and the coolant tubes 43a include both of the refrigerant side heat connecting portions 71b and the coolant side heat connecting portions 72b.

As described above, the first core portion 701 of the present embodiment includes only the most downstream refrigerant tubes 121a. Therefore, in the first core portion 701, the number of the coolant side heat connecting portions 72b becomes zero. Therefore, in the first core portion 701, the number of the refrigerant side heat connecting portions 71b is larger than the number of the coolant side heat connecting portions 72b.

Dummy tubes 77 in which neither the refrigerant nor the coolant flows are arranged between the most downstream refrigerant tubes 121a which form the first core portion 701 and the coolant tubes 43a which form the second core portion 702. The dummy tubes 77 may have a hollow cylindrical shape, or may have a solid (that is, not hollow) column shape.

Subsequently, upstream side tank units 73 and downstream side tank units 74 will be described. The composite-type heat exchanger 70 includes the upstream side tank units 73 extending in the stacking direction of the refrigerant tubes 12a and the coolant tubes 43a which constitute a part of the upstream heat exchanging portion 71, and the downstream side tank units 74 extending in the stacking direction of the refrigerant tubes 12a which constitute a part of the downstream heat exchanging portion 72.

Each of the upstream side tank units 73 is provided with an upstream side coolant space 731 configured to perform collection or distribution of the coolant flowing in the coolant tubes 43a which constitute a part of the upstream heat exchanging portion 71 formed therein. Each of the downstream side tank units 74 is provided with a downstream side refrigerant space 741 configured to perform collection or distribution of the refrigerant tubes 12a which constitute a part of the downstream heat exchanging portion 72 formed therein.

The upstream side tank unit 73 and the downstream side tank unit 74 are formed integrally. Hereinafter, a configuration in which the upstream side tank unit 73 and the downstream side tank unit 74 are combined into one unit is referred to as a header tank 75.

The header tank 75 includes a header plate 751 to which the refrigerant tubes 12a and the coolant tubes 43a arranged in two rows in flowing direction of the outside air are both fixed, an intermediate plate member 752 fixed to the header plate 751, and a tank forming member 753.

The tank forming member 753 is fixed to the header plate 751 and the intermediate plate member 752 whereby the upstream side coolant space 731 and the downstream side refrigerant space 741 described above are formed in an interior thereof. Specifically, the tank forming member 753 is formed into a double-mountain shape (a W-shape) when viewing from the longitudinal direction thereof by applying press process on a flat metal plate.

A double-mountain shaped center portion 753c of the tank forming member 753 is joined to the intermediate plate member 752, whereby the upstream side coolant space 731 and the downstream side refrigerant space 741 are partitioned.

The intermediate plate member 752 is provided with a plurality of depressed portions 752a that form a plurality of communicating spaces 76 communicating with the coolant tubes 43a formed between the intermediate plate member 752 and the header plate 751 by being fixed to the header plate 751 as illustrated in cross-sectional views in FIG. 4 and FIG. 5.

On the downstream side of the outside airflow in the depressed portions 752a, in other words, in a portion corresponding to the downstream side refrigerant space 741 of each of the downstream side tank units 74, first through holes 752b penetrating therethrough from the front to the back thereof are formed. Accordingly the communicating spaces 76 and the downstream side refrigerant space 741 of each of the downstream side tank units 74 communicate with each other.

Therefore, the refrigerant flowed from the refrigerant tubes 12a which constitute a part of the upstream heat exchanging portion 71 into the communicating spaces 76 flows out from the first through hole 752b to the downstream side refrigerant space 741. Therefore, the communicating spaces 76 have a function as communication paths configured to communicate the refrigerant tubes 12a which constitute a part of the upstream heat exchanging portion 71 and the downstream side refrigerant space 741 of the downstream side tank units 74.

The communicating spaces 76 extend in a direction connecting ends of the refrigerant tubes 12a arranged so as to overlap with each other when viewing in the flowing direction of the outside air out of the refrigerant tubes 12a which constitute a part of the upstream heat exchanging portion 71 and the refrigerant tubes 12a which constitute a part of the downstream heat exchanging portion 72.

More specifically, the communicating spaces 76 extend at the ends of the refrigerant tubes 12a which constitute a part of the upstream heat exchanging portion 71 and of the refrigerant tubes 12a which constitute a part of the downstream heat exchanging portion 72 in the flowing direction of the outside air.

At portions corresponding to the coolant tubes 43a which constitute a part of the upstream heat exchanging portion 71 in the intermediate plate member 752, second through holes 752c penetrating therethrough from the front to the back thereof are formed. The coolant tubes 43a which constitute a part of the upstream heat exchanging portion 71 penetrate through the second through holes 752c. Accordingly, the coolant tubes 43a which constitute a part of the upstream heat exchanging portion 71 communicate with the upstream side coolant space 731 formed in the tank forming member 753.

Furthermore, as illustrated in FIG. 3, at ends of the upstream heat exchanging portion 71 on the header tanks 75 side, the coolant tubes 43a project toward the header tanks 75 more than the refrigerant tubes 12a project. In other words, the ends of the refrigerant tubes 12a on the header tanks 75 side and the ends of the coolant tubes 43a on the header tanks 75 side are arranged irregularly.

In contrast, at portions of the intermediate plate member 752 corresponding to the refrigerant tubes 12a which do not communicate with the communicating spaces 76 out of the refrigerant tubes 12a which constitute a part of the downstream heat exchanging portion 72, third through holes 752d penetrating therethrough from the front to the back thereof are provided. The refrigerant tubes 12a which do not communicate with the communicating spaces 76 out of the refrigerant tubes 12a which constitute a part of the downstream heat exchanging portion 72 penetrates through the third through holes 752d. Accordingly, the refrigerant tubes 12a which do not communicate with the communicating spaces 76 out of the refrigerant tubes 12a which constitute a part of the downstream heat exchanging portion 72 communicate with the downstream side refrigerant space 741 formed in the tank forming member 753.

Furthermore, as illustrated in FIG. 3, at ends of the downstream heat exchanging portion 72 on the header tanks 75 side, the refrigerant tubes 12a which do not communicate with the communicating spaces 76 project toward the header tanks 75 more than the refrigerant tubes 12a that communicate with the communicating spaces 76. In other words, the ends of the adjacent refrigerant tubes 12a are arranged irregularly.

The center portion 753c of each of the tank forming members 753 is formed into a shape matching the depressed portions 752a formed on the intermediate plate member 752 and the upstream side coolant space 731 and the downstream side refrigerant space 741 are partitioned so as to avoid the coolant or the refrigerant in the interior from leaking from joint portions between the header plate 751 and the intermediate plate member 752.

As illustrated in FIG. 2, a coolant outflow pipe 435 configured to flow out the coolant from the upstream side coolant space 731 is connected to one end side in the longitudinal direction (the left side of the paper plane of the drawing) of the upstream side tank units 73 arranged on one end side in the longitudinal direction of the coolant tubes 43a (the upper side of the paper plane of the drawing) (hereinafter referred to as a first upstream side tank unit 730a). A coolant inflow pipe 434 configured to flow the coolant into the upstream side coolant space 731 is connected to the other end side in the longitudinal direction (the right side in the paper plane of the drawing) of the upstream side tank units 73 arranged on the other end side in the longitudinal direction of the coolant tubes 43a (the lower side of the paper plane of the drawing) (hereinafter referred to as a second upstream side tank unit 730b).

A refrigerant outflow pipe 125 configured to flow out the refrigerant from the downstream side refrigerant space 741 is connected to one end side in the longitudinal direction (the left side of the paper plane of the drawing) of the downstream side tank units 74 arranged on one end side in the longitudinal direction of the refrigerant tubes 12a (the upper side of the paper plane of the drawing) (hereinafter referred to as a first downstream side tank unit 740a). A refrigerant inflow pipe 124 configured to flow the refrigerant into the downstream side refrigerant space 741 is connected to the other end side in the longitudinal direction (the right side of the paper plane of the drawing) of the downstream side tank units 74 arranged on the other end side in the longitudinal direction of the refrigerant tubes 12a (the lower side of the paper plane of the drawing) (hereinafter, referred to as a second downstream side tank unit 740b).

As illustrated in a schematic perspective view of FIG. 6, a first downstream side partitioning member 742a configured to partition the downstream side refrigerant space 741 into two parts in the longitudinal direction of the first downstream side tank unit 740a is arranged in the first downstream side tank unit 740a.

Hereinafter, a space communicating with the refrigerant tubes 12a other than the most downstream refrigerant tubes 121a out of the two downstream side refrigerant spaces 741 partitioned by the first downstream side partitioning member 742a is referred to as a first downstream side refrigerant space 741a, and a space communicating directly with the refrigerant outflow pipe 125 and communicating with the most downstream refrigerant tubes 121a is referred to as a second downstream side refrigerant space 741b.

A second downstream side partitioning member 742b configured to partition the downstream side refrigerant space 741 into two parts in the longitudinal direction of the second downstream side tank unit 740b is arranged in the second downstream side tank unit 740b.

Hereinafter, a space communicating directly with the refrigerant inflow pipe 124 out of the two downstream side refrigerant spaces 741 partitioned by the second downstream side partitioning member 742b is referred to as a third downstream side refrigerant space 741c, and a space communicating with both of the most downstream refrigerant tubes 121a and other refrigerant tubes 12a is referred to as a fourth downstream side refrigerant space 741d.

Here, when viewing in an outside air flowing direction X, the first downstream side partitioning member 742a is arranged on a side closer to the refrigerant outflow pipe 125 than the second downstream side partitioning member 742b.

Therefore, in the heat exchanger 70 of the present embodiment, as illustrated in a schematic perspective view of FIG. 6, a part of the refrigerant flowing into the third downstream side refrigerant space 741c of the second downstream side tank unit 740b via the refrigerant inflow pipe 124 flows into the refrigerant tubes 12a which constitute a part of the second core portion 702 of the downstream heat exchanging portion 72, and flows from the lower side toward the upper side of the drawing in the refrigerant tubes 12a. Another part of the refrigerant flowing into the third downstream side refrigerant space 741c of the second downstream side tank unit 740b flows into the refrigerant tubes 12a which constitute a part of the second core portion 702 of the upstream heat exchanging portion 71 via the communicating spaces 76 formed between the header plate 751 and the intermediate plate member 752, and flows from the lower side toward the upper side in the drawing in the refrigerant tubes 12a.

The refrigerant flowing out from the refrigerant tubes 12a which constitute a part of the second core portion 702 of the downstream heat exchanging portion 72 is collected in the first downstream side refrigerant space 741a of the first downstream side tank unit 740a. The refrigerant flowing out from the refrigerant tubes 12a which constitute a part of the second core portion 702 of the upstream heat exchanging portion 71 is collected in the first downstream side refrigerant space 741a of the first downstream side tank unit 740a via the communicating spaces 76 formed between the header plate 751 and the intermediate plate member 752.

The refrigerant collected in the first downstream side refrigerant space 741a of the first downstream side tank unit 740a flows from the right side to the left side of the drawing. Subsequently, a part of the refrigerant collected in the first downstream side refrigerant space 741a of the first downstream side tank unit 740a flows into the refrigerant tubes 12a which constitute a part of the second core portion 702 of the downstream heat exchanging portion 72, and flows from the upper side toward the lower side in the drawing in the refrigerant tubes 12a. Another part of the refrigerant collected in the first downstream side refrigerant space 741a of the first downstream side tank unit 740a flows into the refrigerant tubes 12a which constitute a part of the second core portion 702 of the upstream heat exchanging portion 71 via the communicating spaces 76 formed between the header plate 751 and the intermediate plate member 752, and flows from the upper side toward the lower side in the drawing in the refrigerant tubes 12a.

The refrigerant flowing out from the refrigerant tubes 12a which constitute a part of the second core portion 702 of the downstream heat exchanging portion 72 is collected in the fourth downstream side refrigerant space 741d of the second downstream side tank unit 740b. The refrigerant flowing out from the refrigerant tubes 12a which constitute a part of the second core portion 702 of the upstream heat exchanging portion 71 is collected in the fourth downstream side refrigerant space 741d of the second downstream side tank unit 740b via the communicating spaces 76 formed between the header plate 751 and the intermediate plate member 752.

The refrigerant collected in the fourth downstream side refrigerant space 741d of the second downstream side tank unit 740b flows from the right side to the left side of the drawing. Subsequently, a part of the refrigerant collected in the fourth downstream side refrigerant space 741d of the second downstream side tank unit 740b flows into the most downstream refrigerant tubes 121a which constitute a part of the first core portion 701 of the downstream heat exchanging portion 72, and flows from the lower side toward the upper side in the drawing in the most downstream refrigerant tubes 121a. Another part of the refrigerant collected in the fourth downstream side refrigerant space 741d of the second downstream side tank unit 740b flows into the most downstream refrigerant tubes 121a which constitute a part of the first core portion 701 of the upstream heat exchanging portion 71 via the communicating spaces 76 formed between the header plate 751 and the intermediate plate member 752, and flows from the lower side toward the upper side in the drawing in the most downstream refrigerant tubes 121a.

The refrigerant flowing out from the most downstream refrigerant tubes 121a which constitute a part of the first core portion 701 of the downstream heat exchanging portion 72 is collected in the second downstream side refrigerant space 741b of the first downstream side tank unit 740a. The refrigerant flowing out from the most downstream refrigerant tubes 121a which constitute a part of the first core portion 701 of the upstream heat exchanging portion 71 is collected in the second downstream side refrigerant space 741b of the first downstream side tank unit 740a via the communicating spaces 76 formed between the header plate 751 and the intermediate plate member 752.

The refrigerant collected in the second downstream side refrigerant space 741b of the first downstream side tank unit 740a flows from the right side to the left side of the drawing, and flows out from the refrigerant outflow pipe 125.

In contrast, in the heat exchanger 70 of the present embodiment, as illustrated in the schematic perspective view of FIG. 6, the coolant flowing into the upstream side coolant space 731 of the second upstream side tank unit 730b via the coolant inflow pipe 434 flows into the coolant tubes 43a which constitute a part of the upstream heat exchanging portion 71, and flows from the lower side toward the upper side of the drawing in the coolant tubes 43a.

The coolant flowing out from the coolant tubes 43a which constitute a part of the upstream heat exchanging portion 71 is collected in the upstream side coolant space 731 of the first upstream side tank unit 730a. The coolant collected in the upstream side coolant space 731 of the first upstream side tank unit 730a flows from the right side to the left side of the drawing, and flows out from the coolant outflow pipe 435.

In the present embodiment, a flow channel total cross-sectional area of the plurality of most downstream refrigerant tubes 121a which form a final path (first core portion 701) of the refrigerant flow is smaller than the flow-channel total sectional area of a plurality of second-most downstream refrigerant tubes 122a (second-most downstream first tube) which form a path immediately before the refrigerant flow of the final path. In other words, when viewing the heat exchanger 70 from the outside air flowing direction X, the length of the first core portion 701 in the stacking direction of the tubes 12a shorter than the heat exchange portion (a portion where the plurality of second-most downstream refrigerant tubes 122a are arranged in a stacked manner) which constitute a part of the path immediately before the final path.

In the heat exchanger 70 described above, the refrigerant radiator 12 includes both of the refrigerant tubes 12a which constitute a part of the upstream heat exchanging portion 71 and the refrigerant tubes 12a which constitute a part of the downstream heat exchanging portion 72, and the radiator 43 includes the coolant tubes 43a which constitute a part of the upstream heat exchanging portion

The respective components such as the refrigerant tubes 12a of the heat exchanger 70, the coolant tubes 43a, and the header tank 75 and the outer fins 70b described above are all formed of the same metallic material (aluminum alloy in the present embodiment). The header plate 751 and the tank forming member 753 are fixed by caulking in a state in which the intermediate plate member 752 is interposed therebetween.

In addition, the heat exchanger 70 in a state of being fixed by caulking is loaded entirely into a heating furnace and is heated, a brazing filler metal in which the surface of the respective components are clad in advance is fused and then is cooled until the brazing filler metal is solidified again, so that the respective components are integrally brazed. Accordingly, the refrigerant radiator 12 and the radiator 43 are combined into one unit.

The refrigerant tubes 12a may be used as an example of the first tube in which the first fluid flows, and the coolant tubes 43a may be used as an example of the second tube in which the second fluid flows. In the present embodiment, the refrigerant is used as an example of the first fluid, and the coolant is used as an example of the second fluid.

Subsequently, an electric controller of the present embodiment will be described. The air conditioning control apparatus includes a known microcomputer including a CPU, a ROM, and a RAM and peripheral circuits thereof, and is configured to perform various computations and processes on the basis of an air conditioning control program memorized in the ROM, and control operations of the various air conditioning control devices 11, 13, 41 connected to an output side thereof.

Also, various air conditioning control sensor group, such as an inside air sensor configured to detect a vehicle interior temperature, an outside air sensor configured to detect the outside air temperature, a solar radiation sensor configured to detect the quantity of solar radiation in the vehicle interior, an evaporator-temperature sensor configured to detect the blown out air temperature of the refrigerant evaporator 16 (the temperature of the evaporator), a discharged refrigerant temperature sensor configured to detect the discharged refrigerant temperature from the compressor 11, an outlet refrigerant temperature sensor configured to detect an outlet side refrigerant temperature Te of the refrigerant radiator 12 is connected to an input side of the air conditioning control apparatus.

Furthermore, an operation panel, which is not illustrated, which is arranged near the dashboard panel positioned at the front portion in the vehicle interior, is connected to the input side of the air conditioning control apparatus, so that operation signals output from various air conditioning operation switches provided on the operation panel are input. An operation switch of the vehicle air conditioning apparatus 1, a vehicle interior temperature setting switch configured to set the vehicle interior temperature, an operation mode selecting switch and the like are provided as the various air conditioning operation switches that are mounted on the operation panel.

The air conditioning control apparatus includes control means configured to control the electric motor 11b and the like of the compressor 11 integrally therewith, and is configured to control the operations thereof. However, in the present embodiment, a configuration that controls the operation of the compressor 11 (hardware and software) in the air conditioning control apparatus constitute a part of refrigerant discharging capacity control means.

In addition, the air conditioning control apparatus of the present embodiment has a configuration (frost formation determining means) that determines whether or not frost formation occurs in the refrigerant radiator 12 on the basis of a detection signal from an air conditioning control sensor group described above. Specifically, in the frost formation determining means of the present embodiment, it is determined that the frost formation occurs in the refrigerant radiator 12 when the vehicle speed of the vehicle is not higher than a predetermined reference vehicle speed (20 km/h in the present embodiment) and the outlet side refrigerant temperature Te of the refrigerant radiator 12 is not higher than 0° C.

Subsequently, an operation of the vehicle air conditioning apparatus 1 of the present embodiment having the configuration described above will be descried. When an operation switch of the vehicle air conditioning apparatus 1 of the operation panel is turned on (ON) in a state in which a vehicle activation switch, which is not illustrated, is turned on (ON), the control apparatus executes a program for controlling the air conditioning memorized in a memory circuit in advance. When this program is executed, the control apparatus reads the detection signal from the air conditioning control sensor group described above and the operation signal of the operation panel.

Subsequently, a target blowout temperature TAO that is a target temperature of the air that is blown out into the vehicle interior is calculated on the basis of values of the detection signals and the operation signals. Further, the control device determines operating states of the various air conditioning control devices connected to the output side of the control apparatus on the basis of the calculated target blowout temperature TAO and the detection signals of the sensor group.

For example, the refrigerant discharging capacity of the compressor 11, that is, a control signal to be output to the electric motor of the compressor 11 is determined as described below. First, a target evaporator blowout temperature TEO of the refrigerant evaporator 16 is determined on the basis of the target blowout temperature TAO with reference to a control map that is memorized in the control apparatus in advance.

Subsequently, the control signal to be output to the electric motor of the compressor 11 is determined by using a feedback control method on the basis of a deviation between the target evaporator blowout temperature TEO and an blown out air temperature Te from the refrigerant evaporator 16 detected by a evaporator temperature sensor, so that the blown out air temperature from the refrigerant evaporator 16 gets closer to the target evaporator blowout temperature TEO.

The control signal output to the servo motor of the air mix door 34 is determined by referring the control map memorized in the control apparatus in advance on the basis of the target blowout temperature TAO and the blown out air temperature from the refrigerant evaporator 16, so that the temperature of air blown into the vehicle interior becomes an occupant-desired temperature set by a vehicle interior temperature setting switch.

The control signals determined as described above are output to the various air conditioning control devices. After that, until the stop of the operation of the vehicle air conditioning apparatus 1 is required by the operation panel, a control routine, which includes the reading of the above-mentioned detection signals and the above-mentioned operation signals the calculation of the target blowout temperature TAO the determination of the operating states of the various air conditioning control devices, the output of the control voltages and the control signals, is repeated every predetermined control period.

Therefore, in the heat pump cycle 10, the discharged refrigerant discharged from the compressor 11 flows into the refrigerant radiator 12 and radiates heat by the heat exchange with the outside air blown from the blower fan 13. According to the test and examination performed by the present inventors, in the heat pump cycle 10, the pressure of the discharged refrigerant becomes not lower than a reference refrigerant pressure P1 (specifically, approximately 1.5 MPa), and the surface temperature (the wall surface temperature) of the refrigerant tubes 12a of the refrigerant radiator 12 in this case is known to be increased to a range on the order of 60° C. to 65° C. by a high-temperature refrigerant discharged from the compressor 11.

The refrigerant flowed out from the refrigerant radiator 12 is separated into gas and liquid by the receiver 14. A liquid-phase refrigerant flowed out from the receiver 14 is decompressed and expanded until a low-pressure refrigerant is achieved by the temperature type expansion valve 15. At this time, in the temperature type expansion valve 15, a valve opening is adjusted so that the degree of superheat of the refrigerant on the outlet side of the refrigerant evaporator 16 falls within a predetermined range set in advance.

The low-pressure refrigerant decompressed and expanded by the temperature type expansion valve 15 flows into the refrigerant evaporator 16 and evaporates by absorbing heat from the blown air that is blown by the blower 32. Accordingly, the blown air blown into the vehicle interior is cooled. The refrigerant having flowed out from the refrigerant evaporator 16 is sucked into the compressor 11 and is compressed again.

In contrast, the temperature of the blown air (cold wind) cooled by the refrigerant evaporator 16 is adjusted by heating the blown air (cold wind) of an air volume in accordance with the opening degree of the air mix door 34 with the electric heater 36, and mixing with the blown air flowing in the mixing space 35 so as to bypass the electric heater 36. Subsequently, the air conditioning wind adjusted in temperature is blown out from the mixing space 35 into the vehicle interior via the respective outlets.

In the case where an inside air temperature of the vehicle interior is cooled to a temperature lower than an outside air temperature by the air conditioning wind blown into the vehicle interior, the cooling of the vehicle interior is achieved, while in the case where the inside air temperature is heated to a temperature higher than the outside air temperature, the heating of the vehicle interior is achieved.

As described above, in the present embodiment, the final path of the refrigerant flow is determined to be the first core portion 701 formed only by the most downstream refrigerant tubes 121a, and the first core portion 701 constitutes a part of the subcooling portion. Therefore, the coolant side heat connecting portions 72b is not provided on the outer fins 70b arranged in the first core portion 701, and the number of the refrigerant side heat connecting portions 71b is larger than the number of the coolant side heat connecting portions 72b. Accordingly, the outer fins 70b arranged in the first core portion 701 are used entirely for radiating heat of the discharged refrigerant to the outside air.

Therefore, according to the present embodiment, heat of the discharged refrigerant flowing in the most downstream refrigerant tubes 121a is radiated sufficiently to the outside air in the first core portion 701, so that the refrigerant on the outlet side of the refrigerant radiator 12 has a desired degree of subcooling.

Therefore, the most downstream refrigerant tubes 121a which constitute a part of the subcooling portion (the first core portion 701) having an extremely low heat transmitting rate does not need to be increased in length, that is, the refrigerant tubes 12a which constitute a part of the condenser (second core portion 702) having a high heat transmitting rate does not need to be decreased in length, so that lowering of the heat exchanging performance of the heat exchanger 70 as a whole may be restrained.

Here, the relationship between the degree of subcooling and the heat-radiating capacity of the refrigerant in the composite-type heat exchanger is illustrated in FIG. 7. In FIG. 7, a result of experiment of the composite-type heat exchanger 70 of the present embodiment is shown by a square plot. A result of experiment of a heat exchanger of a comparative example in which the first core portion 701 is not provided and the coolant tubes 43a are arranged over the entire area of the heat exchanger is shown by a triangle plot.

As illustrated in FIG. 7, in the composite-type heat exchanger, when an attempt is made to obtain a predetermined degree of subcooling, since the heat exchanger of the comparative example is affected by heat radiation on the coolant side, so that the heat-radiating capacity of the refrigerant is lowered. In contrast, as in the present embodiment, the heat-radiating capacity of the refrigerant can be improved by providing the first core portion 701.

In the present embodiment, the refrigerant tubes 12a and the coolant tubes 43a which constitute a part of the second core portion 702 are arranged alternately in a stacked manner, and the refrigerant tubes 12a and the coolant tubes 43a are thermally connected by the outer fins 70b. Therefore, in the case where a surface temperature of the coolant tubes 43a and a surface temperature of the refrigerant tubes 12a are different, a range used for radiating heat of the coolant to the outside air and a range for radiating heat of the refrigerant to the outside air in the outer fins 70b are adjusted depending on the temperature difference, and the heat of the coolant and the heat of the discharged refrigerant are radiated adequately to the outside air.

For example, in the case where the heat of the coolant out of the coolant and the discharged refrigerant needs to be radiated, the surface temperature of the coolant tubes 43a is increased, and the temperature difference from the outside air becomes larger in comparison with the refrigerant tubes 12a. At this time, the range used for radiating the heat of the coolant to the outside air becomes larger than the range for radiating the heat of the refrigerant to the outside air in the outer fins 70b, and the heat of the coolant is radiated to the outside air.

Therefore, in the refrigerant radiator 12, the heat of the discharged refrigerant can be radiated to the outside air, and in the radiator 43, the heat of the coolant can be radiated to the outside air. Consequently, an adequate heat exchange is achieved between a plurality of types of fluids.

Here, in the refrigerant tubes 12a and the coolant tubes 43a which constitute a part of the second core portion 702 of the downstream heat exchanging portion 72 out of the upstream heat exchanging portion 71 and the downstream heat exchanging portion 72, the difference between the surface temperature of the both tubes 12a, 43a, and the outside air temperature is reduced, and the adjustment of the range used for radiating the heat of the coolant to the outside air and the range for radiating heat of the refrigerant to the outside air in accordance with the temperature difference in the outer fins 70b becomes less effective.

In contrast, in the present embodiment, the refrigerant tubes 12a and the coolant tubes 43a which constitute at least the second core portion 702 of the upstream heat exchanging portion 71 out of the upstream heat exchanging portion 71 and the downstream heat exchanging portion 72 are arranged alternately in a stacked manner. Accordingly, the range used for radiating the heat of the coolant to the outside air and the range for radiating the heat of the refrigerant to the outside air in the outer fins 70b are adjusted in accordance with the temperature difference, so that the heat of the coolant and the heat of the discharged refrigerant can be radiated adequately to the outside air.

In the present embodiment, the dummy tubes 77 in which neither the refrigerant nor the coolant flows are arranged between the most downstream refrigerant tubes 121a which form the first core portion 701 and the coolant tubes 43a which form the second core portion 702. Therefore, breakage of the tubes 12a, 43a or the header tank 75 by generation of a heat stress in association with a heat distortion of the tubes 12a, 43a or the header tank 75 occurring due to a difference in amount of thermal expansion caused by the temperature difference between the refrigerant flowing in the most downstream refrigerant tubes 121a and the coolant flowing in the coolant tubes 43a can be restrained.

Since the liquid-phase refrigerant flows in the most downstream refrigerant tubes 121a in the first core portion 701 which constitutes a part of the subcooling portion, a pressure loss of the refrigerant is small, but the flow velocity is low and the heat transmitting rate is small.

In contrast, in the present embodiment, the flow channel total cross-sectional area of the plurality of most downstream refrigerant tubes 121a which form the final path (the first core portion 701) of the refrigerant flow is smaller than the flow channel total cross-sectional area of the plurality of second-most downstream refrigerant tubes 122a which form the path immediately before the final path. In this configuration, the flow velocity of the refrigerant in the first core portion 701 can be increased to improve the heat exchanging performance of the first core portion 701. Therefore, the area of the first core portion 701 does not need to be increased for obtaining a desired degree of subcooling, and hence the heat exchanging performance of the heat exchanger 70 as a whole can be improved by increasing the area of the second core portion 702.

Second Embodiment

Subsequently, a second embodiment of the present disclosure will be described with reference to FIG. 8. In comparison with the first embodiment described above, the second embodiment is different in a point that a first core portion 701 includes also a coolant tube 43a. In FIG. 8, refrigerant tubes 12a are illustrated with diagonal hatching and the coolant tube 43a is illustrated by dot hatching for clarifying the drawing.

As illustrated in FIG. 8, the first core portion 701 of a composite-type heat exchanger 70 of the present embodiment is provided with the coolant tube 43a. In the present embodiment, although the number of the refrigerant tubes 12a (nine in this example) is larger than the number of the coolant tube 43a (one in this example) in the first core portion 701. Surfaces of outer fins 70b are provided with a plurality of shutter-like louvers 700 formed along the flowing direction of the outside air by cutting and rising.

In the outer fin 70b between the most downstream refrigerant tube 121a and the coolant tube 43a adjacent thereto in a stacking direction of the tubes 12a, 43a, a first slit hole 70c penetrating through the outer fin 70b from the front to the back and extending in the flowing direction of the outside air is formed. With the first slit hole 70c, heat transfer between the most downstream refrigerant tube 121a and the coolant tube 43a adjacent to each other in the stacking direction of the tubes 12a, 43a is restricted.

A second slit hole 70d extending in the stacking direction of the tubes 12a, 43a is formed at a center portion in the flowing direction of the outside air of the outer fins 70b arranged between the most downstream refrigerant tube 121a and the coolant tube 43a adjacent to each other. With the second slit hole 70d, heat transfer between the most downstream refrigerant tube 121a and the coolant tube 43a adjacent to each other in the flowing direction of the outside air is restricted.

Therefore, the first slit hole 70c and the second slit hole 70d of the present embodiment are used as an example of a heat-shielding portion of the present disclosure. The first slit hole 70c and the second slit hole 70d may be connected to each other.

In the present embodiment, even in the case where the first core portion 701 is provided with the coolant tube 43a, the outer fins 70b arranged between the most downstream refrigerant tube 121a and the coolant tube 43a are provided with the first slit holes 70c and the second slit holes 70d, so that the heat transfer between the most downstream refrigerant tubes 121a and the coolant tube 43a is restricted. In other words, the outer fins 70b arranged on the first core portion 701 is provided only with the refrigerant side heat connecting portions 71b, and the coolant side heat connecting portions 72b is not provided.

Therefore, in the outer fins 70b arranged in the first core portion 701, since the number of the refrigerant side heat connecting portions 71b is larger than the number of the coolant side heat connecting portions 72b, the same effects and advantages as those of the first embodiment described above can be obtained.

Third Embodiment

Subsequently, a third embodiment of the present disclosure will be described with reference to FIG. 9. The third embodiment is different in the flow of the refrigerant of the first core portion 701 in comparison with the first embodiment.

As illustrated in FIG. 9, an upstream side partitioning member 732a configured to partition the upstream side coolant space 731 in the internal space of the second upstream side tank unit 730b into two parts in the longitudinal direction is arranged in the second upstream side tank unit 730b. A space closer to the first core portion 701 (the left side on the paper plane) out of the two internal spaces of the tank partitioned by the upstream side partitioning member 732a (hereinafter, referred to as an upstream side refrigerant space 731a) communicates with the most downstream refrigerant tubes 121a, but not communicate with coolant tube 43a. A refrigerant outflow pipe 125 is connected to the upstream side refrigerant space 731a.

In the present embodiment, the refrigerant collected in the fourth downstream side refrigerant space 741d of the second downstream side tank unit 740b flows into the most downstream refrigerant tubes 121a which constitute a part of the first core portion 701 of a downstream heat exchanging portion 72, and flows from a lower side toward an upper side in the drawing in the most downstream refrigerant tubes 121a. The refrigerant flowing out from the most downstream refrigerant tubes 121a which constitute a part of the first core portion 701 of the downstream heat exchanging portion 72 flows into the most downstream refrigerant tubes 121a which constitute a part of the first core portion 701 of an upstream heat exchanging portion 71 via a communicating spaces 76 formed between a header plate 751 and an intermediate plate member 752, and flows from the upper side toward the lower side in the drawing in the most downstream refrigerant tubes 121a.

The refrigerant flowing out from the most downstream refrigerant tubes 121a which constitute a part of the first core portion 701 of the upstream heat exchanging portion 71 is collected in the upstream side refrigerant space 731a of the second upstream side tank unit 730b. The refrigerant collected in the upstream side refrigerant space 731a of the second upstream side tank unit 730b flows from the right side to the left side of the drawing, and flows out from the refrigerant outflow pipe 125.

As described thus far, in the present embodiment, the refrigerant flowing out from the most downstream refrigerant tubes 121a which constitute a part of the downstream heat exchanging portion 72 in the first core portion 701 flows into the most downstream refrigerant tubes 121a which constitute a part of the upstream heat exchanging portion 71. In other words, a flowing direction of the refrigerant and a flowing direction of the outside air in the first core portion 701 oppose each other. Therefore, heat of the refrigerant flowing in the most downstream refrigerant tubes 121a may be radiated to the outside air with high efficiency in the first core portion 701.

Fourth Embodiment

Subsequently, a fourth embodiment of the present disclosure will be described with reference to FIG. 10. The present embodiment is different in the coolant flow in the heat exchanger 70 in comparison with the first embodiment.

As illustrated in FIG. 10, a coolant outflow pipe 435 configured to allow the coolant to flow out from the upstream side coolant space 731 is connected to one end side (the left side of the paper plane in the drawing) in a longitudinal direction of the second upstream side tank unit 730b. A coolant inflow pipe 434 configured to flow the coolant into the upstream side coolant space 731 is connected to the other end side (the right side of the paper plane in the drawing) in the longitudinal direction of the first upstream side tank unit 730a.

Therefore, in the heat exchanger 70 of the present embodiment, the coolant flowing into the upstream side coolant space 731 of the first upstream side tank unit 730a via the coolant inflow pipe 434 flows into the coolant tubes 43a which constitute a part of the upstream heat exchanging portion 71, and flows from the upper side toward a lower side in the drawing in the coolant tubes 43a.

The coolant flowing out from the coolant tubes 43a which constitute a part of the upstream heat exchanging portion 71 is collected in the upstream side coolant space 731 of the second upstream side tank unit 730b. The coolant collected in the upstream side coolant space 731 of the second upstream side tank unit 730b flows from the right side to the left side in the drawing, and flows out from the coolant outflow pipe 435.

In the present embodiment, a flowing direction of the refrigerant flowing in an second-most downstream refrigerant tubes 122a and a flowing direction of the coolant flowing in the coolant tubes 43a arranged adjacent to the second-most downstream refrigerant tubes 122a become the same direction. In other words, the flowing direction of the refrigerant flowing in the second-most downstream refrigerant tubes 122a and the flowing direction of the coolant flowing in the coolant tubes 43a arranged adjacent to the second-most downstream refrigerant tubes 122a are parallel to each other.

According to the present embodiment, in a path immediately before a final path of the refrigerant flow, the refrigerant flowing in the second-most downstream refrigerant tubes 122a and the coolant flowing in the coolant tubes 43a can be restricted from performing thermal exchange via an outer fins 70b. Therefore, the refrigerant immediately before flowing into a first core portion 701 can be prevented from being heated by heat of the coolant.

Fifth Embodiment

Subsequently, a fifth embodiment of the present disclosure will be described with reference to FIG. 11 to FIG. 13. In the present embodiment, an example in which configurations of a heat pump cycle 10 and a coolant circulation circuit 40 of the first embodiment are modified as illustrated in general configuration drawings in FIG. 11 to FIG. 13 will be described.

The heat pump cycle 10 of the present embodiment is a vapor compression refrigeration cycle having a function of heating or cooling air blown into a vehicle interior, which is a space to be air-conditioned, in a vehicle air conditioning apparatus 1. Therefore, the heat pump cycle 10 is capable of switching the refrigerant flow channel to execute a heating operation (a heat-up operation) for warming the vehicle interior by heating the air blown to the vehicle interior, which is an object fluid of heat exchange, and a cooling operation (refrigerating operation) for cooling the air blown to the vehicle interior to cool the vehicle interior.

In addition, in the heat pump cycle 10, a defrosting operation for melting and removing frost adhered to an outdoor heat exchanger 160 of a composite-type heat exchanger 70, which will be described later, configured to function as a evaporator for evaporating the refrigerant at the time of heating operation can be executed. In the general configuration drawings illustrated in the heat pump cycle 10 of FIG. 11 to FIG. 13, flows of the refrigerant at the time of respective operations are indicated by an arrow of a solid line.

A refrigerant inlet side of an indoor condenser 120 as the using side heat exchanger is connected to a refrigerant discharge port of a compressor 11. The indoor condenser 120 is a heating heat exchanger arranged in the interior of a casing 31 of an indoor air conditioning unit 30 of the vehicle air conditioning apparatus 1 and configured to cause a high-temperature high-pressure refrigerant flowing in the interior thereof and the air blown to the vehicle interior after the passage through an indoor evaporator 20, which will be described later, to change heat with each other. A detailed configuration of the indoor air conditioning unit 30 will be described later.

A warming fixed throttle 130 as decompression means for the heating operation configured to decompress and expand the refrigerant flowing out from the indoor condenser 120 at the time of the heating operation is connected to the refrigerant outlet side of the indoor condenser 120. Examples of the warming fixed throttle 130 which can be employed here include a orifice and a capillary tube. A refrigerant inlet side of the outdoor heat exchanger 160 of the composite-type heat exchanger 70 is connected to an outlet side of the warming fixed throttle 130.

Furthermore, a fixed throttle bypassing passage 140 configured to cause the refrigerant flowing from the indoor condenser 120 to bypass the warming fixed throttle 130 and guide the refrigerant on the outdoor heat exchanger 160 side is connected to the refrigerant outlet side of the indoor condenser 120. The fixed throttle bypassing passage 140 is arranged with an opening-and-closing valve 15a configured to open and close the fixed throttle bypassing passage 140. The opening-and-closing valve 15a is an electromagnetic valve an opening and closing operation of which is controlled by a control voltage output from the air conditioning control apparatus.

A pressure loss generating when the refrigerant passes through the opening-and-closing valve 15a is extremely smaller than a pressure loss generating when the refrigerant passes through the fixed throttle 130. Therefore, the refrigerant flowing out from the indoor condenser 120 flows into the outdoor heat exchanger 160 via the fixed throttle bypassing passage 140 side when the opening-and-closing valve 15a is opened, and flows into the outdoor heat exchanger 160 via the warming fixed throttle 130 when the opening-and-closing valve 15a is closed.

Accordingly, the opening-and-closing valve 15a can switch the refrigerant flow channel of the heat pump cycle 10. Therefore, the opening-and-closing valve 15a of the present embodiment has a function as refrigerant flow channel switching means. Examples of the refrigerant flow channel switching means configured as described above which may be employed here include an electric three-direction valve configured to switch a refrigerant circuit that connects the outlet side of the indoor condenser 120 and the inlet side of the warming fixed throttle 130 and a refrigerant circuit that connects the outlet side of the indoor condenser 120 and the inlet side of the fixed throttle bypassing passage 140.

The outdoor heat exchanger 160 is a heat exchange portion configured to cause the refrigerant flowing in the interior in the heat exchanger 70 and outside air blown from a blower fan 17 to exchange heat with each other. The outdoor heat exchanger 160 is arranged in an engine room and functions as an evaporating heat exchanger (evaporator) configured to evaporate the low-pressure refrigerant to bring out a heat absorbing effect at the time of the heating operation, and functions as a radiation heat exchanger (radiator) configured to radiate heat from a high-pressure refrigerant at the time of the cooling operation.

The blower fan 17 is an electric blower of which an operation rate, that is, a number of rotations (an amount of blown air) is controlled by the control voltage output from the air conditioning control apparatus.

Furthermore, the heat exchanger 70 of the present embodiment integrally includes a radiator 43, which will be described later, configured to cause the coolant for cooling the above-described outdoor heat exchanger 160 and a traveling electric motor MG and the outside air blown from the blower fan 17 to exchange heat with each other.

Therefore, the blower fan 17 of the present embodiment constitutes a part of exterior blowing means configured to blow the outside air toward both of the outdoor heat exchanger 160 and the radiator 43. Since a detailed configuration of the composite-type heat exchanger 70 in which the exterior heat exchanger 160 and the radiator 43 are integrally formed is the same as that of the first embodiment described above, detailed description will be omitted. However, specifically, the refrigerant radiator 12 of the first embodiment out of the composite-type heat exchanger 70 functions as the exterior heat exchanger 160.

An electric three-direction valve 15b is connected to the outlet side of the outdoor heat exchanger 160. The three-direction valve 15b is controlled in operation by a control voltage output from the air conditioning control apparatus and constitutes a part of the refrigerant flow channel switching means together with the above-described opening-and-closing valve 15a. In the air conditioning control apparatus, a configuration configured to control operations of the various devices 15a, 15b which constitute a part of the refrigerant flow channel switching means constitutes a part of the refrigerant flow channel control means and a configuration configured to control an operation of a three-direction valve 42 which constitutes a part of the coolant circuit switching means constitutes a part of coolant circuit control means. An outlet refrigerant temperature sensor 51 configured to detect an outlet side coolant temperature Te of the exterior heat exchanger 160 is provided.

More specifically, the three-direction valve 15b is configured to switch the flow channel to a refrigerant flow channel that connects the outlet side of the outdoor heat exchanger 160 and an inlet side of an accumulator 18, which will be described later, at the time of the heating operation, and to the refrigerant flow channel that connects the outlet side of the outdoor heat exchanger 160 and an inlet side of a cooling fixed throttle 19 at the time of the cooling operation.

The cooling fixed throttle 19 is decompression means for the cooling operation that decompresses and expands the refrigerant flowed out from the outdoor heat exchanger 160 at the time of the cooling operation, and the basic configuration is the same as that of the warming fixed throttle 130. The refrigerant inlet side of the indoor evaporator 20 is connected to the outlet side of the cooling fixed throttle 19.

The indoor evaporator 20 is a heat exchanger for cooling which is arranged on an upstream side of the indoor condenser 120 in the direction of the air flow within the casing 31 of the indoor air conditioning unit 30, and configured to cause the refrigerant flowing in the interior thereof and the air blown to the vehicle interior to exchange heat with each other to cool the air blown to the vehicle interior. The inlet side of the accumulator 18 is connected to the refrigerant outlet side of the indoor evaporator 20.

The accumulator 18 is a gas-liquid separator for the low-pressure side refrigerant that separates gas and liquid in the refrigerant flowing therein and accumulates a surplus refrigerant in the cycle. An intake side of the compressor 11 is connected to a gas-phase refrigerant outlet of the accumulator 18. Therefore, the accumulator 18 has a function of restricting the liquid phase refrigerant from being sucked into the compressor 11, and preventing a liquid compression of the compressor 11.

In the heat pump cycle 10 of the present embodiment, the temperature of the coolant flowing out from the radiator 43 of the heat exchanger 70 at the time of the cooling operation becomes lower than the temperature of the refrigerant flowing out from the outdoor heat exchanger 160 of the heat exchanger 70. Accordingly, at the time of the cooling operation in which the outdoor heat exchanger 160 functions as a heat radiating heat exchange portion configured to radiate heat of the high-pressure refrigerant, the degree of subcooling of the refrigerant flowing out from the outdoor heat exchanger 160 can be increased, so that an improvement of the cycle efficiency is achieved.

In contrast, in the heat pump cycle 10 of the present embodiment, the temperature of the coolant in the interior of the radiator 43 of the heat exchanger 70 at the time of the heating operation becomes higher than the temperature of the refrigerant flowing out from the outdoor heat exchanger 160 of the heat exchanger 70. Accordingly, at the time of the heating operation in which the outdoor heat exchanger 160 functions as the evaporating heat exchanger which brings out the heat absorbing effect by evaporating the low-pressure refrigerant, the heat of the coolant is absorbed and hence the refrigerant is heated, so that the evaporation of the refrigerant is promoted.

Subsequently, the indoor air conditioning unit 30 will be described only on portions different from the first embodiment. The indoor air conditioning unit 30 is arranged inside of a dashboard panel (an instrument panel) in a foremost portion of the vehicle interior, and includes a blower 32, the above-described indoor condenser 120 and the indoor evaporator 20 accommodated in the casing 31 which forms an outer shell thereof.

The indoor evaporator 20 and the indoor condenser 120 are arranged in this order with respect to the flow of air blown to the vehicle interior on the downstream side of the blower 32 in the direction of the air flow. In other words, the indoor evaporator 20 is arranged on the upstream side of the indoor condenser 120 in the flowing direction of the air blown to the vehicle interior.

Further, an air mixture door 34 that adjusts a proportion of the air volume that passes through the indoor condenser 120 to the blown air that has passed through the indoor evaporator 20 is arranged on the downstream side of the indoor evaporator 20 in the direction of the air flow, and on the upstream side of the indoor condenser 120 in the direction of the air flow. Also, a mixing space 35 that mixes the blown air that has been heated by conducting heat exchange with the refrigerant in the indoor condenser 120 with the blown air that has not been heated while bypassing the indoor condenser 120 is provided on the downstream side of the indoor condenser 120 in the direction of the air flow.

Subsequently, the coolant circulation circuit 40 will be described only on portions different from the first embodiment. The coolant circulation circuit 40 includes a coolant pump 41, an electric three-direction valve 42, a radiator 43 of the composite-type heat exchanger 70, and a bypass passage 44 configured to flow the coolant so as to bypass the radiator 43 arranged therein. A coolant temperature sensor 52 configured to detect a coolant temperature is arranged on an outlet side of the coolant pump 41.

The three-direction valve 42 switches the coolant circuit between a coolant circuit that connects an inlet side of the coolant pump 41 and an outlet side of the radiator 43 to cause the coolant to flow into the radiator 43, and a coolant circuit that connects the inlet side of the coolant pump 41 and an outlet side of the bypass passage 44 to cause the coolant to flow while bypassing the radiator 43. The three-direction valve 42 is controlled in operation by a control voltage output from the air conditioning control apparatus and constitutes a part of circuit switching means for the coolant circuit. The three-direction valve 42 also has a function as coolant inflow rate control means configured to control the inflow rate of the coolant into the radiator 43 by switching the coolant circuit.

In other words, in the coolant circulation circuit 40 of the present embodiment, as illustrated by broken line arrows in FIG. 11 so forth, a coolant circuit that circulates the coolant in the order of the coolant pump 41 the traveling electric motor MG the radiator 43 the coolant pump 41, and a coolant circuit that circulates the coolant in the order of the coolant pump 41 the traveling electric motor MG the bypass passage 44 the coolant pump 41 can be switched.

Therefore, when the three-direction valve 42 switches the circuit to the coolant circuit in which the coolant flows so as to bypass the radiator 43 during an operation of the traveling electric motor MG, the coolant does not radiate heat in the radiator 43, and increases in temperature thereof. In other words, when the three-direction valve 42 switches the circuit to the coolant circuit that allows the coolant to bypass the radiator 43, the heat of the traveling electric motor MG (amount of heat generation) is accumulated in the coolant.

In the coolant circulation circuit 40 of the present embodiment, the temperature of the coolant flowing out from the radiator 43 of the heat exchanger 70 is not higher than a predetermined reference temperature (not higher than 65° C. in the present embodiment). Accordingly, an inverter of the traveling electric motor MG can be protected from a high heat.

The outdoor heat exchanger 160 is arranged in the engine room, and functions as the radiation heat exchanger which causes the coolant and the outside air blown from the blower fan 17 to exchange heat with each other. As described above, the radiator 43 constitutes a part of the composite-type heat exchanger 70 together with the outdoor heat exchanger 160.

Subsequently, an operation of the vehicle air conditioning apparatus 1 of the present embodiment having the configuration described above will be descried. The vehicle air conditioning apparatus 1 of the present embodiment is capable of executing the heating operation for heating the vehicle interior and the cooling operation for cooling the vehicle interior, as well as the defrosting operation at the time of the heating operation. Next, the operation of the above-mentioned operations will be described.

(a) Heating Operation

The heating operation starts when a heating mode is selected by a select switch in a state in which an operation switch of the operation panel turns on (ON). In the case where it is determined that frost formation occurs in the outdoor heat exchanger 160 by frost formation determining means at the time of the heating operation, the defrosting operation is executed.

First of all, in the normal heating operation, the air conditioning control apparatus closes the opening-and-closing valve 15a, switches the three-direction valve 15b to the refrigerant flow channel that connects the outlet side of the outdoor heat exchanger 160 and the inlet side of the accumulator 18 and further activate the coolant pump 41 to pump a predetermined flow rate of the coolant, and switches the circuit to the coolant circuit in which the coolant flows through the three-direction valve 42 of the coolant circulation circuit 40 while bypassing the radiator 43.

Accordingly, the heat pump cycle 10 is switched to the refrigerant flow channel in which the refrigerant flows as indicated by solid line arrows in FIG. 11, and the coolant circulation circuit 40 is switched to the coolant circuit in which the coolant flows as indicated by dot line arrows in FIG. 11.

In the configurations of the refrigerant flow channel and the coolant circuit, the air conditioning control apparatus reads the detection signals from the above-described air conditioning control sensor group, and the operation signals of the operation panel. Subsequently, a target blowout temperature TAO that is a target temperature of the air that is blown out into the vehicle interior is calculated on the basis of values of the detection signals and the operation signals.

Further, the operating states of the various air conditioning control devices connected to the output side of the air conditioning control apparatus is determined on the basis of the calculated target blowout temperature TAO and the detection signals of the sensor group.

For example, the refrigerant discharging capacity of the compressor 11, that is, a control signal to be output to the electric motor of the compressor 11 is determined as described below. First, a target evaporator blowout temperature TEO of the indoor evaporator 20 is determined on the basis of the target blowout temperature TAO with reference to a control map that is memorized in the air conditioning control apparatus in advance.

Subsequently, the control signal to be output to the electric motor of the compressor 11 is determined by using a feedback control method on the basis of a deviation between the target evaporator blowout temperature TEO and an blown out air temperature from the indoor evaporator 20 detected by an evaporator temperature sensor, so that the blown out air temperature from the indoor evaporator 20 gets closer to the target evaporator blowout temperature TEO.

A control signal output to the servo motor of the air mix door 34 is determined by using the target blowout temperature TAO, an blown out air temperature from the indoor evaporator 20, the discharged refrigerant temperature of the compressor 11 detected by a discharged refrigerant temperature sensor, and the like, so that the temperature of air blown into the vehicle interior becomes an occupant desired temperature set by a vehicle interior temperature setting switch.

At the time of the normal heating operation and the defrosting operation, the opening degree of the air mix door 34 may be controlled so that the total air volume of the air blown to the vehicle interior from the blower 32 passes through the indoor condenser 120.

The control signals determined as described above are output to various air conditioning control devices. After that, until the stop of the operation of the vehicle air conditioning apparatus 1 is required by the operation panel, a control routine, which includes the reading of the above-mentioned detection signals and the above-mentioned operation signals the calculation of the target blowout temperature TAO the determination of the operating states of the various air conditioning control devices, the output of the control voltages and the control signals, is repeated every predetermined control period.

Meanwhile, the repetition of this control routine is also performed basically in the same manner at the time of other operations.

In the heat pump cycle 10 at the time of the normal heating operation, a high-pressure refrigerant discharged from the compressor 11 flows into the indoor condenser 120. The refrigerant flowing into the indoor condenser 120 radiates heat by exchanging heat between itself and the air that has been blown from the blower 32 and passed through the indoor evaporator 20 to the vehicle interior. Accordingly, the air blown to the vehicle interior is heated.

The high-pressure refrigerant flowing out from the indoor condenser 120 flows into the warming fixed throttle 130 and decompressed and expanded since the opening-and-closing valve 15a is closed. The low-pressure refrigerant decompressed and expanded by the warming fixed throttle 130 flows into the outdoor heat exchanger 160. The low-pressure refrigerant flowing into the outdoor heat exchanger 160 absorbs heat from the outside air blown by the blower fan 17, and then evaporates.

At this time, in the coolant circulation circuit 40, since the circuit is switched to the coolant circuit in which the coolant flows while bypassing the radiator 43, the coolant is prevented from radiating heat to the refrigerant flowing in the outdoor heat exchanger 160 and the coolant is prevented from absorbing heat from the refrigerant flowing in the outdoor heat exchanger 160. In other words, the refrigerant flowing in the outdoor heat exchanger 160 is not thermally influenced by the coolant.

The refrigerant flowing out from the outdoor heat exchanger 160 flows into the accumulator 18 and is separated into gas and liquid since the three-direction valve 15b is switched to the refrigerant flow channel which connects the outlet side of the outdoor heat exchanger 160 and the inlet side of the accumulator 18. A gas-phase refrigerant that has been separated by the accumulator 18 is absorbed by the compressor 11, and again compressed.

As described thus far, at the normal heating operation, the air blown to the vehicle interior is heated by the heat of the refrigerant discharged from the compressor 11 by the indoor condenser 120, so that the vehicle interior may be heated.

(b) Defrosting Operation

Subsequently, the defrosting operation will be described. In a refrigeration cycle device configured to cause the refrigerant and the outside air to exchange heat in the outdoor heat exchanger 160 to evaporate the refrigerant as the heat pump cycle 10 of the present embodiment, when the refrigerant evaporation temperature in the outdoor heat exchanger 160 is decreased to the frost formation temperature (0° C., specifically) or below, the frost formation may occur in the outdoor heat exchanger 160.

If such frost formation occurs, an outside air passage 70a of the heat exchanger 70 is clogged by the frost, so that the heat exchange performance of the outdoor heat exchanger 160 is significantly lowered. Therefore, in the heat pump cycle 10 of the present embodiment, in the case where the frost formation determining means determines that frost formation occurs in the outdoor heat exchanger 160 at the time of the heating operation, the defrosting operation is executed.

In this defrosting operation, the air conditioning control apparatus stops the operation of the compressor 11, and stops the operation of the blower fan 17. Therefore, at the time of the defrosting operation, the refrigerant flow rate flowing into the outdoor heat exchanger 160 is reduced and the outside air volume flowing into the outside air passage 70a is reduced with respect to the normal heating operation.

In addition, the air conditioning control apparatus switches the three-direction valve 42 of the coolant circulation circuit 40 into the coolant circuit which allows the coolant to flow into the radiator 43 as indicated by broken line arrows in FIG. 12. Accordingly, the refrigerant does not circulate in the heat pump cycle 10, and the coolant circulation circuit 40 is switched to the coolant circuit in which the refrigerant flows as indicated by broken line arrows in FIG. 12.

Therefore, the heat of the coolant flowing in the coolant tubes 43a of the radiator 43 is transferred to the outdoor heat exchanger 160 via the outer fins 70b, and defrosting of the outdoor heat exchanger 160 is performed. In other words, defrosting which utilizes waste heat of the traveling electric motor MG effectively is achieved.

(c) Cooling Operation

The cooling operation starts when the cooling operation mode is selected by a select switch in a state in which the operation switch of the operation panel turns on. At the time of the cooling operation, the air conditioning control apparatus opens the opening-and-closing valve 15a, and switches the three-direction valve 15b to the refrigerant flow channel that connects the outlet side of the outdoor heat exchanger 160 and the inlet side of the cooling fixed throttle 19. Accordingly, the heat pump cycle 10 is switched to the refrigerant flow channel in which the refrigerant flows as indicated by the solid line arrows in FIG. 13.

At this time, the three-direction valve 42 of the coolant circulation circuit 40 is switched to the coolant circuit which allows the coolant to flow into the radiator 43 when a coolant temperature Tw is increased to a reference temperature or higher, and is switched to the coolant circuit which allows the coolant to flow while bypassing the radiator 43 when the coolant temperature Tw is lowered to a temperature below the predetermined reference temperature. In FIG. 13, a flow of the coolant when the coolant temperature Tw is increased to the reference temperature or higher is indicated by broken line arrows.

In the heat pump cycle 10 at the time of the cooling operation, the high-pressure refrigerant discharged from the compressor 11 flows into the indoor condenser 120 and exchanges heat with the air that has been blown by the blower 32 and passed through the indoor evaporator 20 to the vehicle interior, thereby the refrigerant radiating heat. The high-pressure refrigerant flowed out form the indoor condenser 120 flows into the outdoor heat exchanger 160 via the fixed throttle bypassing passage 140 since the opening-and-closing valve 15a is opened. The low-pressure refrigerant flowing into the outdoor heat exchanger 160 further radiates heat to the outside air blown by the blower fan 17.

The refrigerant flowing out from the outdoor heat exchanger 160 is decompressed and expanded by the cooling fixed throttle 19 since the three-direction valve 15b is switched to the refrigerant flow channel which connects the outlet side of the outdoor heat exchanger 160 and the inlet side of the cooling fixed throttle 19. The refrigerant flowing out from the cooling fixed throttle 19 flows into the indoor evaporator 20, and absorbs heat from the air blown by the blower 32 to the vehicle interior, thereby the refrigerant evaporating. Accordingly, the air blown to the vehicle interior is cooled.

The refrigerant flowing out from the indoor evaporator 20 flows into the accumulator 18 and is separated into gas and liquid. A gas-phase refrigerant that has been separated by the accumulator 18 is absorbed by the compressor 11, and again compressed. As described thus far, at the time of the cooling operation, the air blown to the vehicle interior is cooled by the low-pressure refrigerant absorbing heat from the air blown to the vehicle interior and evaporating in the indoor evaporator 20, so that the vehicle interior may be cooled.

In the vehicle air conditioning apparatus 1 of the present embodiment, various operations can be executed by switching the refrigerant flow channel of the heat pump cycle 10 and the coolant circuit of the coolant circulation circuit 40 as described above. Furthermore, in the present embodiment, since the characteristic heat exchanger 70 described above is employed, the heat exchange amount among three types of fluids, namely, the refrigerant, the coolant, and the outside air may be adjusted adequately.

The heat exchanger 70 described in the second to the fourth embodiments may be applied to the heat pump cycle 10 of the present embodiment.

Sixth Embodiment

Subsequently, a sixth embodiment of the present disclosure will be described with reference to FIG. 14 to FIG. 16. In the present embodiment, an example in which configurations of a heat pump cycle 10 and a coolant circulation circuit 40 of the fifth embodiment are modified will be described. In FIG. 14 to FIG. 16, a flow of a refrigerant in the heat pump cycle 10 is indicated by a solid line, and a flow of a coolant in the coolant circulation circuit 40 is indicated by broken line arrows.

Specifically, the coolant circulation circuit 40 of the present embodiment is a coolant circulation circuit configured to circulate the coolant as a cooling medium (heat medium) to the coolant flow channel formed in the interior of the engine EG, which is one of the vehicle-mounted devices associated with heat generation at the time of operation to cool an engine EG. In other words, in the present embodiment, a traveling electric motor MG of the fifth embodiment is eliminated, and instead, the engine EG is arranged.

In addition, in the present embodiment, an indoor condenser 120 of the fifth embodiment is eliminated, and a composite-type heat exchanger 70 of the fifth embodiment is arranged in a casing 31 of an indoor air conditioning unit 30. An outdoor heat exchanger 160 of the fifth embodiment in this heat exchanger 70 is functioned as the indoor condenser 120.

The radiator 43 of the fifth embodiment in the heat exchanger 70 is functioned as a heat collection heat exchanger 45 for heating the coolant by heat of the refrigerant. Accordingly, in the heat pump cycle 10 of the present embodiment, a warm-up operation for warm-up the engine by heating the coolant by the heat of the refrigerant can be executed. The heat collection heat exchanger 45 is arranged in a bypass passage 44 of the coolant circulation circuit 40.

In contrast, the outdoor heat exchanger 160 is configured as a single heat exchanger configured to cause the refrigerant flowing in an interior and an outside air blown from a blower fan 17 to exchange heat with each other. In the same manner, the radiator 43 is configured as a single heat exchanger configured to cause the coolant flowing in the interior and the outside air blown from a blower fan 46 to exchange heat with each other.

Other structures are the same as those of the fifth embodiment. In the present embodiment, although the warm-up operation is executed instead of a defrosting operation, other operations are the same as those of the fifth embodiment.

Subsequently, the warm-up operation will be described. Here, in order to restrict an overheat of the engine EG, a temperature of the coolant is maintained to be temperatures not higher than a predetermined upper limit temperature, and in order to reduce a friction loss caused by an increase in viscosity of lubricating oil sealed in the interior of the engine EG, the temperature of the coolant is preferably maintained to be a temperature not lower than a lower limit temperature.

Accordingly, in the heat pump cycle 10 of the present embodiment, the warm-up operation is executed when a coolant temperature Tw is decreased to a predetermined reference temperature or below at the time of the heating operation. In this warm-up operation, a three-direction valve 15b of the heat pump cycle 10 is operated in the same manner as the normal heating operation, and a three-direction valve 42 of the coolant circulation circuit 40 is switched to a coolant circuit that causes the coolant to flow while bypassing the radiator 43 as indicated by broken line arrows in FIG. 15, that is, causes the coolant to flow into the heat collection heat exchanger 45.

Therefore, as illustrated by arrows of the solid line in FIG. 15, a high-pressure high-temperature refrigerant discharged from a compressor 11 flows into the indoor condenser 120 in the same manner as in the normal heating operation. A heat of the high-temperature high-pressure refrigerant flowing into the indoor condenser 120 is transferred to an air blown by a blower 32 and is transferred to the coolant via outer fins 70b since the circuit is switched to the coolant circuit which allows the three-direction valve 42 to flow the coolant to the heat collection heat exchanger 45. Other operations are the same as those at the normal heating operation.

As described thus far, at the time of warm-up operation, an air blown to a vehicle interior is heated by the heat of the refrigerant discharged from the compressor 11 by the indoor condenser 120, so that the vehicle interior may be heated. The heat of the refrigerant discharged from the compressor 11 in the indoor condenser 120 is also transferred to the coolant via the outer fins 70b, so that the temperature of the coolant increases. Therefore, by using the heat of the refrigerant, the warm-up of the engine EG is achieved.

The heat exchanger 70 described in the second to the fourth embodiments may be applied to the heat pump cycle 10 of the present embodiment.

The present disclosure is not limited to the above-mentioned embodiments, and may have various modifications as described below without departing from the gist of the present disclosure.

(1) In the above-described embodiments, an example in which a first core portion 701 including refrigerant tubes 12a is arranged on the downstream side of a second core portion 702 including both the refrigerant tubes 12a and the coolant tubes 43a in the direction of the refrigerant flow in the heat exchanger 70 has been described. However, the plurality of first core portions may be provided.

For example, as illustrated in FIG. 17, a first core portion 703 including the refrigerant tubes 12a may be provided on the upstream side of the second core portion 702 in the direction of the refrigerant flow (specifically, a path on the most upstream side in the direction of the refrigerant flow).

(2) In the embodiments described above, an example in which one each of the refrigerant tubes 12a and the coolant tubes 43a is arranged alternately in the second core portion 702 of the upstream heat exchanging portion 71 has been described. However, the arrangement of the refrigerant tubes 12a and the coolant tubes 43a are not limited thereto.

For example, in the second core portion 702 of the upstream heat exchanging portion 71, a coolant tubes 43a may be arranged after every two of the refrigerant tubes 12a. In other words, in the upstream heat exchanging portion 71, the two refrigerant tubes 12a may be arranged between the adjacent coolant tubes 43a.

(3) In the first embodiment described above, an example in which the refrigerant of the heat pump cycle 10 is employed as a first fluid and the coolant of the coolant circulation circuit 40 is employed as a second fluid, and the outside air blown by the blower fan 17 is employed as a third fluid has been described. However, the first to the third fluid are not limited thereto. For example, in the same manner as the sixth embodiment, the air blown to the vehicle interior may be employed as the third fluid. The third fluid may also be a coolant.

For example, the first fluid may be a high-pressure side refrigerant or may be a low-pressure side refrigerant of the heat pump cycle 10.

For example, a coolant for cooling electric device such as an inverter configured to supply power to the engine, the traveling electric motor MG may be employed as the second fluid. Oil for cooling may be employed as the second fluid to cause the second heat exchange portion to function as an oil cooler or a heat storage agent, a cooling storage agent or the like may be employed as the second fluid.

In addition, in the case where the heat pump cycle 10 to which the heat exchanger 70 of the present disclosure is applied is applied to a stationary air conditioning apparatus, a cool temperature storage, or an automatic vending machine, a coolant for cooling an engine, an electric motor, and other electric devices as a drive source of the compressor of the heat pump cycle 10 may be employed as the second fluid.

In addition, in the above embodiment, an example in which the heat exchanger 70 of the present disclosure is applied to the heat pump cycle (the refrigeration cycle). However, the application of the heat exchanger 70 according to the present disclosure is not limited thereto. In other words, the heat exchanger 70 may be applied widely to apparatuses which perform heat exchange between three types of fluids.

For example, the heat exchanger 70 may be applied as a heat exchanger applied to a vehicle cooling system. A configuration in which the first fluid is a heat medium which has absorbed a heat of first vehicle-mounted devices associated with heat generation at the time of operation, the second fluid is a heat medium which has absorbed a heat of a second vehicle-mounted device associated with heat generation at the time of operation, and the third fluid is outdoor air is also applicable.

More specifically, in the case of being applied to a hybrid vehicle, a configuration in which the first vehicle-mounted device is an engine EG, the first fluid is a coolant of the engine EG, the second vehicle-mounted device is a traveling electric motor, and the second fluid is a coolant of the traveling electric motor is also applicable.

Amounts of heat generation of these vehicle-mounted devices vary respectively in accordance with a traveling state (traveling load) of the vehicle, so that the temperature of the coolant of the engine EG and the temperature of the coolant of the traveling electric motor vary in accordance with the traveling state of the vehicle as well. Therefore, according to this example, the heat generated by the vehicle-mounted devices which generate a large amount of heat may be radiated not only to air, but also to vehicle-mounted devices which generate heat by a small amount.

As the first vehicle-mounted device or the second vehicle-mounted device, an exhaust air reflux apparatus (EGR), a supercharger, a power steering apparatus, a battery, and the like may be employed. The heat exchange portion may be functioned as an EGR cooler, an inter cooler, or an oil cooler for cooling power steering oil.

(4) In the embodiment described above, an example in which the electric three-direction valve 42 is employed as circuit switching means configured to switch the cooling medium circuit of the coolant circulation circuit 40 has been described. However, the circuit switching means is not limited thereto. For example, a thermostat valve may be employed. The thermostat valve is a cooling medium temperature reaction valve including a mechanic mechanism for opening and closing a cooling medium path by displacing a valve body by a thermo wax (temperature sensing member) which is changed in volume in accordance with the temperature. Therefore, by employing the thermostat valve, a coolant temperature sensor 52 may be eliminated.

(5) In the above embodiment, an example in which a normal fluorocarbon refrigerant is used as the refrigerant has been described. However, the type of the refrigerant is not limited thereto. A natural refrigerant such as carbon dioxide or a hydrocarbon system refrigerant may be employed. Furthermore, the heat pump cycle 10 may constitute a part of a supercritical refrigeration cycle in which the discharged refrigerant of the compressor 11 has a critical pressure of the refrigerant or higher.

(6) In the fifth embodiment described above, an example in which the blown air is heated by causing the high-pressure refrigerant and the blown air to exchange heat in the indoor condenser 120 has been described. However, instead of the indoor condenser 120, for example, a configuration in which a heat medium circulation circuit which circulates the heat medium is provided, and a water-refrigerant heat exchanger configured to exchange heat between the high-pressure refrigerant and the heat medium and a heating heat exchanger configured to heat the blown air by causing the heat medium heated by the water-refrigerant exchanger and the blown air to exchange heat with each other may be arranged in the heat medium circulation circuit is also applicable.

In other words, a configuration in which the high-pressure refrigerant is used as a heat source, and the blown air is heated indirectly via the heat medium is also applicable. In addition, in the case of being applied to a vehicle having an internal combustion engine, the coolant of the internal combustion engine is used as the heat medium so as to flow through the heat medium circulation circuit. In an electric vehicle, a coolant for cooling the battery or the electric devices may be flowed in the heat medium circulation circuit as the heat medium.

(7) In the second embodiment described above, an example in which a first slit holes 70c and a second slit holes 70d are provided as a heat-shielding portion on the outer fins 70b arranged between most downstream refrigerant tubes 121a and the coolant tubes 43a in the case where the coolant tubes 43a is provided in the first core portion 701 has been described. However, the present disclosure is not limited thereto, and the heat-shielding portion may not be provided.

In the case where the heat-shielding portion is not provided, the outer fins 70b of the first core portion 701 includes a coolant side heat connecting portions 72b. However, since the number of the coolant side heat connecting portions 72b is smaller than the number of the refrigerant side heat connecting portions 71b, the area used for radiating heat of the discharged refrigerant to the outside air in the outer fins 70b arranged in the first core portion 701 becomes larger than an area used for radiating the heat of the coolant to the outside air. Therefore, the heat of the refrigerant flowing in the most downstream refrigerant tubes 121a may be radiated sufficiently to the outside air.

(8) In the second embodiment, an example in which the slit holes 70c, 70d are employed as the heat-shielding portions has been described. However, the heat-shielding portion is not limited thereto. For example, the louvers may be formed instead of the slit holes 70c, 70d, or the outer fins 70b may be cut.

Alternatively, the most downstream refrigerant tubes 121a may constitute a part of the downstream heat exchanging portion 72, and the refrigerant tubes 12a and the coolant tubes 43a which constitute a part of the upstream heat exchanging portion 71 may be arranged alternately in a stacked manner with each other.

Claims

1. A heat exchanger including:

a plurality of first tubes in which a first fluid flows;

a plurality of second tubes in which a second fluid flows;

a heat exchange portion including the plurality of first tubes and the plurality of second tubes arranged in a stacked manner and configured to radiate heats of the first fluid and the second fluid to a third fluid;

a third fluid channel in which the third fluid flows, the third fluid channel being provided in a periphery of the plurality of first tubes and the plurality of second tubes; and

an outer fin arranged in the third fluid channel to promote a heat exchange between the first fluid and the third fluid and a heat exchange between the second fluid and the third fluid, wherein

the outer fin includes first heat connecting portions thermally connecting the plurality of first tubes, and second heat connecting portions thermally connecting the plurality of first tubes and the plurality of the second tubes,

the plurality of first tubes is divided into a plurality of groups,

the plurality of groups of the plurality of first tube are paths through which the first fluids distributed from a same space flow in a same direction,

the plurality of first tubes include most downstream first tubes which constitute a part of a final path that is a most downstream path in a flowing direction of the first fluid,

the heat exchange portion includes a first core portion including the most downstream first tubes, and

the first heat connecting portions are larger in number than the second heat connecting portions in the first core portion.

2. The heat exchanger according to claim 1, wherein

the first core portion includes the most downstream first tubes and at least one of the plurality of second tubes, and

the first core portion is provided with a heat-shielding portion located at a position corresponding to the second heat connecting portion of the outer fin the heat-shielding portion limiting heat transfer between the first fluid flowing in the most downstream first tubes and the second fluid flowing in the plurality of second tubes.

3. The heat exchanger according to claim 2, wherein the heat-shielding portion includes a slit hole penetrating through the outer fin.

4. The heat exchanger according to claim 1, wherein

the first fluid is a refrigerant for a vapor compression refrigeration cycle, and

the heat exchange portion causes the refrigerant to concentrate.

5. The heat exchanger according to claim 1, wherein

the plurality of first tubes include second-most downstream first tubes that constitute a part of a path immediately before the final path in the flowing direction of the first fluid, and

the second-most downstream first tubes, through which the first fluid flows, and the plurality of second tubes, through which the second fluid flows, are arranged adjacent to each other such that the first fluid and the second fluid are same in flowing direction.

6. The heat exchanger according to claim 1, wherein the plurality of first tubes and the plurality of second tubes are arranged alternately in a stacked manner except for the final path.

7. The heat exchanger according to claim 1, wherein

the heat exchange portion includes an upstream heat exchanging portion and a downstream heat exchanging portion arranged on a downstream side of the upstream heat exchanging portion in a flowing direction of the third fluid,

the most downstream first tubes constitute a part of the downstream heat exchanging portion, and

the first tubes and the second tubes in the upstream heat exchanging portion are arranged alternately in a stacked manner.

8. The heat exchanger according to claim 1, wherein

the heat exchange portion further includes a second core portion having the plurality of second tubes and the plurality of first tubes other than the most downstream first tubes, and

the plurality of first tubes and the plurality of second tubes in the second core portion are arranged alternately in a stacked manner.

9. The heat exchanger according to claim 1, further comprising a dummy tube in which both the first fluid and the second fluid do not flow, the dummy tube being arranged between the most downstream first tubes and the plurality of second tubes.

10. The heat exchanger according to claim 1, wherein

the plurality of first tubes include second-most downstream first tubes which constitute a part of a path immediately before the final path in the flowing direction of the first fluid, and

a flow-channel total sectional area of the most downstream first tubes constituting the part of the final path is smaller than a flow-channel total sectional area of the second-most downstream first tubes.

11. The heat exchanger according to claim 1, wherein

the heat exchange portion includes an upstream heat exchanging portion and a downstream heat exchanging portion arranged on the downstream side of the upstream heat exchanging portion in the flowing direction of the third fluid,

the upstream heat exchanging portion includes a part of the most downstream first tubes of the first core portion,

the downstream heat exchanging portion includes a part of the most downstream first tubes of the first core portion), and

the part of the most downstream first tubes of the downstream heat exchanging portion is connected to the part of the most downstream first tubes of the upstream heat exchanging portion such that the first fluid flows from the downstream heat exchanging portion to the upstream heat exchanging portion in the most downstream first tubes.

12. The heat exchanger according to claim 1, wherein

the number of the second heat connecting portion is zero in the first core portion, and

the first core portion includes only the most downstream first tubes.