Patent Publication Number: US-2013240185-A1

Title: Heat exchanger

Description:
CROSS REFERENCE TO RELATED APPLICATION 
     This application is based on and claims the benefit of priority of Japanese Patent Applications No. 2010-251119 filed on Nov. 9, 2010, and No. 2011-233083 filed on Oct. 24, 2011, the disclosures of which are incorporated herein by reference. 
     TECHNICAL FIELD 
     The present invention relates to a compound heat exchanger that can exchange heat among three kinds of fluids. 
     BACKGROUND ART 
     Conventionally, compound heat exchangers have been conventionally known, which can exchange heat among three kinds of fluids. For example, Patent Document 1 discloses a compound heat exchanger that can exchange heat between outdoor air (outside air) and a refrigerant of a refrigeration cycle device, and between the refrigerant and a coolant for cooling an engine. 
     Specifically, the heat exchanger disclosed in Patent Document 1 includes a plurality of linear refrigerant tubes laminated, each having both ends connected to refrigerant tanks for collecting or distributing the refrigerant. The heat exchanger also includes heat pipes, each having one end connected to a coolant tank for circulation of the coolant, and disposed between the laminated refrigerant tubes in parallel to the refrigerant tubes. And, fins for promoting heat exchange are arranged in outside air passages formed between the refrigerant tubes and the heat pipes. 
     The refrigeration cycle device disclosed in Patent Document 1 employs such a compound heat exchanger as an evaporator for evaporating refrigerant by absorbing heat of the outside air and heat of the coolant (e.g., waste heat of an engine) in the refrigerant. At this time, the waste heat of the engine transferred from the heat pipes can be used to suppress frost formation of the heat exchanger. 
     RELATED ART DOCUMENTS 
     Patent Document 
     
         
         [Patent Document 1] 
         Japanese Unexamined Patent Publication No. 11-157326 
       
    
     In order to achieve the heat exchange between the refrigerant and the outside air, and the heat exchange between the refrigerant and the coolant as mentioned above in the heat exchanger of Patent Document 1, the refrigerant tank and the coolant tank are adjacent to each other in the flow direction of the outside air, and the heat pipes are curved near the coolant tank, so that the heat pipes are arranged between the refrigerant pipes extending linearly. 
     However, the arrangement of the refrigerant tank and the coolant tank adjacent to each other in the flow direction of the outside air leads to an increase in size of the entire heat exchanger in the flow direction of the outside air. Further, the heat exchanger of Patent Document 1 has to use the complicated shaped heat pipes that curve near the coolant tank, thereby resulting in low productivity of the heat exchanger. 
     DISCLOSURE OF THE INVENTION 
     The present invention has been made in view of the above matters, and it is an object of the present invention to improve the productivity of a heat exchanger which can exchange heat among three kinds of fluids. 
     According to a first aspect of the present disclosure, a heat exchanger includes: a first heat exchanging portion including a plurality of first tubes through which a first fluid flows, and a first tank extending in a direction of lamination of the first tubes to collect or distribute the first fluid flowing through the first tubes, the first heat exchanging portion being adapted to exchange heat between the first fluid and a third fluid flowing around the first tubes; and a second heat exchanging portion including a plurality of second tubes through which a second fluid flows, and a second tank extending in a direction of lamination of the second tubes to collect or distribute the second fluid flowing through the second tubes, the second heat exchanging portion being adapted to exchange heat between the second fluid and the third fluid flowing around the second tubes. The first tubes and the second tubes are disposed between the first tank and the second tank, at least one of the first tubes is disposed between the second tubes, at least one of the second tubes is disposed between the first tubes, a space formed between the first tube and the second tube defines a third fluid passage through which the third fluid flows, and an outer fin is disposed in the third fluid passage to promote heat exchange between both the heat exchanging portions while enabling heat transfer between the first fluid flowing through the first tubes and the second fluid flowing through the second tubes. In addition, the first tube is provided with a first turning portion for changing a flow direction of the first fluid, the second tube is provided with a second turning portion for changing a flow direction of the second fluid, the first turning portion is positioned closer to the second tank than the first tank, and the second turning portion is positioned closer to the first tank than the second tank. 
     Thus, the heat can be exchanged between the first fluid and the third fluid via the first tubes and the outer fins. The heat can also be exchanged between the second fluid and the third fluid via the second tubes and the outer fins. The heat can further be exchanged between the first fluid and the second fluid via the outer fins. Accordingly, the heat exchange can be performed among three kinds of fluids. 
     The first and second tubes are disposed between the first and second tanks, and the third fluid passage is formed in a space formed between the first tube and the second tube, so that the first tank and the second tank are not arranged in the flow direction of the third fluid. Thus, the entire heat exchanger can be prevented from increasing in size in the flow direction of the third fluid. 
     The first turning portion of the first tube is positioned closer to the second tank than the first tank, and the second turning portion of the second tube is positioned closer to the first tank than the second tank, so that the connection of the first tube to the first tank can have the same or equivalent shape as the connection of the second tube to the second tank. 
     As a result, the heat exchanger of the present disclosure can improve the productivity of the heat exchanger that can exchange heat among three kinds of fluids without increase in size. The term “three kinds of fluids” as used herein means not only fluids with different properties or compositions, but also fluids which differ in temperature or state, such as a gas phase or a liquid phase, even when those fluids have the same properties or components. Thus, the first to third fluids are not limited to fluids with different properties or compositions. 
     According to a second aspect of the present disclosure, a temperature of the first fluid introduced into the first heat exchanging portion may be different from a temperature of the second fluid introduced into the second heat exchanging portion, and the outer fin may be disposed in a space formed between the first and second tubes and the other first and second tubes adjacent thereto. 
     When the first fluid introduced into the first heat exchanger differs in temperature from the second fluid introduced into the second heat exchanger, the thermal strain (amount of heat expansion) generated in the first tube is different from that generated in the second tube, which might change the size of the first tube and second tube. In such a case, the outer fins promote the heat exchange between the respective fluids, thereby reducing the difference in temperature between the first fluid and the second fluid to relieve (reduce) the difference in thermal strain between the first tube and the second tube. As a result, the breakdown of the heat exchanger can be suppressed. 
     The term “spaces formed between the first and second tubes and the other first and second tubes adjacent thereto” as used herein means spaces formed between a first tube and another first tube or a second tube adjacent to the first tube, and between a second tube and a first tube or another second tube adjacent to the second tube. 
     The term “introduction” or “flow out” as used herein means the movement of the refrigerant in the heat exchanger, and the term “inflow” or “outflow” as used herein means the movement of the refrigerant in each tube. 
     According to a third aspect of the invention disclosed herein, each of the first tube and the second tube may be fixed to both the first tank and the second tank. 
     Since the first tube and the second tube are fixed to both the first and second tanks, the entire heat exchanger can have the mechanical strength increased. Further, the outer fin disposed in the third fluid passage provided between the first tube and the second tube can be easily fixed firmly. 
     According to a fourth aspect of the present disclosure, when one fluid with a higher temperature, of the first fluid introduced into the first heat exchanging portion and the second fluid introduced into the second heat exchanging portion is defined as a high-temperature side fluid, when an upstream side portion of a high-temperature side tube of the first tube and the second tube through which the high-temperature fluid flows with respect to a corresponding one of the first and second turning portions is defined as a high-temperature side tube upstream portion, and when a downstream side portion of the high-temperature side tube of the first tube and the second tube through which the high-temperature fluid flows with respect to the corresponding one of the first and second turning portions is defined as a high-temperature side tube downstream portion, the temperature of the third fluid may be lower than that of the high-temperature side fluid, and the high-temperature side tube upstream portion of at least one of the high-temperature side tubes may be positioned on an upstream side in a flow direction of the third fluid with respect to the high-temperature side tube downstream portion. 
     Thus, the difference in temperature between the high-temperature side fluid and the third fluid can be ensured on the upstream side of the fluid flow in the high-temperature side tube to increase the amount of heat dissipation. As a result, the difference in temperature between the first fluid and the second fluid can be reduced to relieve the difference in thermal strain between the first tubes and the second tubes, and thereby it can suppress the breakdown of the heat exchanger. 
     According to a fifth aspect of the present disclosure, when one fluid having a lower temperature, of the first fluid introduced into the first heat exchanging portion and the second fluid introduced into the second heat exchanging portion is defined as a low-temperature side fluid, when an upstream side portion of a low-temperature side tube of the first tube and the second tube through which the low-temperature side fluid flows with respect to a corresponding one of the first and second turning portions is defined as a low-temperature side tube upstream portion, and when a downstream side portion of the low-temperature side tube of the first tube and the second tube through which the low-temperature fluid flows with respect to the corresponding one of the first and second turning portions is defined as a low-temperature side tube downstream portion, the temperature of the third fluid may be lower than that of the low-temperature side fluid, and the low-temperature side tube upstream portion of at least one of the low-temperature side tubes may be positioned on the upstream side in the flow direction of the third fluid with respect to the low-temperature side tube downstream portion. 
     Thus, on the upstream side of the fluid flow in the low-temperature side tube, the difference in temperature between the low-temperature side fluid and the third fluid can be ensured to increase the amount of heat dissipation. As a result, the difference in temperature between the first fluid and the second fluid can be reduced to relieve the difference in thermal strain between the first tube and the second tube, which can suppress the breakdown of the heat exchanger. 
     According to a sixth aspect of the present disclosure, the temperature of the third fluid may be lower than that of one fluid having a higher temperature, of the first fluid introduced into the first heat exchanging portion and the second fluid introduced into the second heat exchanging portion, and may be higher than that of the other fluid having a lower temperature. 
     Thus, the temperature of a high-temperature side fluid of the first and second fluids in the heat exchanger is decreased while the temperature of a low-temperature side fluid is increased, and thereby it can reduce the difference in temperature between the first fluid and the second fluid. As a result, the difference in thermal strain between the respective tubes can be relieved to effectively suppress the breakdown of the heat exchanger. 
     According to a seventh aspect of the present disclosure, when an upstream side portion of the first tube with respect to the first turning portion is defined as a first tube upstream portion, when a downstream side portion of the first tube with respect to the first turning portion is defined as a first tube downstream portion, when an upstream side portion of the second tube with respect to the second turning portion is defined as a second tube upstream portion, and when a downstream side portion of the second tube with respect to the second turning portion is defined as a second tube downstream portion, the first tube upstream portion and the second tube upstream portion may be arranged in a direction of lamination of the first and second tubes, and the first tube downstream portion and the second tube downstream portion may be arranged in the direction of lamination of the first and second tubes. 
     Thus, the difference in temperature between the first fluid flowing through the first tube and the second fluid flowing through the second tube can be reduced to relieve the difference in thermal strain between the first tube and the second tube. 
     According to an eighth aspect of the present disclosure, the first tube upstream portion and the second tube upstream portion may be positioned on the upstream side in the flow direction of the third fluid with respect to the first tube downstream portion and the second tube downstream portion. 
     When the first fluid introduced into the first heat exchanging portion and the second fluid introduced into the second heat exchanging portion have the temperature higher than that of the third fluid, the difference in temperature between the first and third fluids and the difference in temperature between the second and third fluids can be ensured on the upstream side of the fluid flow of the first tube and on the upstream side of the fluid flow of the second tube to thereby increase the amount of heat dissipation. As a result, the difference in thermal strain between the first tube and the second tube can be relieved to thereby suppress the breakdown of the heat exchanger. 
     According to a ninth aspect of the present disclosure, the first tubes may include an upstream side first tube group in which the first fluid introduced into the first heat exchanging portion flows, and a downstream side first tube group in which the first fluid flowing from the upstream side first tube group flows to cause the first fluid to flow out the first heat exchanging portion, the second tubes may include an upstream side second tube group in which the second fluid introduced into the second heat exchanging portion flows, and a downstream side second tube group in which the second fluid flowing from the upstream side second tube group flows to cause the second fluid to flow out the second heat exchanging portion. In this case, the first tube upstream portion and the second tube upstream portion of the upstream side first tube group and the upstream side second tube group may be positioned on the upstream side in the flow direction of the third fluid with respect to the first tube downstream portion and the second tube downstream portion. 
     When the first fluid introduced into the first heat exchanging portion and the second fluid introduced into the second heat exchanging portion have the temperature higher than that of the third fluid, the difference in temperature between the first and second fluids is reduced, while the differences in temperature between the first and third fluids and between the second and third fluids are ensured on the upstream sides of fluid flows of the upstream side first and second tube groups. Thus, the amount of heat dissipation can be increased. As a result, the difference in thermal strain between the first tube and the second tube can be relieved to thereby suppress the breakdown of the heat exchanger. 
     According to a tenth aspect of the present disclosure, the first tube upstream portion and the second tube upstream portion of the downstream side first tube group and the downstream side second tube group may be positioned on the downstream side in the flow direction of the third fluid with respect to the first tube downstream portion and the second tube downstream portion. 
     When the first fluid introduced into the first heat exchanging portion and the second fluid introduced into the second heat exchanger have the temperature higher than that of the third fluid, the heat contained in the first fluid and the second fluid can be sufficiently dissipated into the third fluid on the downstream sides of fluid flows of the downstream side first and second tube groups. As a result, the performance of the heat exchanger can be improved. 
     According to an eleventh aspect of the present disclosure, the outer fin may be bonded to the first and second tubes, and may be provided with a plurality of slits for locally weakening rigidity of the outer fin. 
     Thus, when the difference in thermal strain between the first tube and the second tube occurs, the slits of the outer fins can absorb the stress acting on each tube. Further, the slits provided in the outer fins can also suppress the breakdown of the heat exchanger within a partial range even with the difference in thermal strain between the respective tubes. 
     According to a twelfth aspect of the present disclosure, an area of a refrigerant passage of an intermediate part of at least one of the first turning portion and the second turning portion may be larger than an area of a fluid passage of each of a fluid inflow portion and a fluid outflow portion of the one turning portion. 
     Thus, when the first fluid passes through the first turning portion, or when the second fluid passes through the second turning portion, the loss in pressure can be reduced. 
     According to a thirteenth aspect of the present disclosure, an inner fin may be disposed within at least one of the first tube and the second tube, to promote the heat exchange between the first fluid or the second fluid, and the third fluid. In this case, the inner fin may have an end protruding into an internal space of the first turning portion or second turning portion. 
     Thus, the end of each inner fin protrudes into the internal space of the first turning portion or second turning portion, thereby preventing the failure of connection between the inner fins and the inner peripheral surfaces of the first tube and the second tube. 
     According to a fourteenth aspect of the present disclosure, each of the first tube and the second tube may be made of a plate tube formed by bonding a pair of plates. Alternatively, according to a fifteenth aspect of the present disclosure, each of the first tube and the second tube may be formed by bending a flat tube with a flat section in a direction perpendicular to the longitudinal direction of the tube. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
       The above and other objects, structures, and advantages of the present invention will become apparent from the following detailed description of the invention, when taken in conjunction with the accompanying drawings, which respectively show: 
         FIG. 1  is an entire configuration diagram showing refrigerant flow paths of a heat pump cycle in a heating operation according to a first embodiment; 
         FIG. 2  is an entire configuration diagram showing refrigerant flow paths of the heat pump cycle in a defrosting operation in the first embodiment; 
         FIG. 3  is an entire configuration diagram showing refrigerant flow paths of the heat pump cycle in a waste heat recovering operation in the first embodiment; 
         FIG. 4  is an entire configuration diagram showing refrigerant flow paths of the heat pump cycle in a cooling operation in the first embodiment; 
         FIG. 5  is a perspective view of the contour of a heat exchanger in the first embodiment; 
         FIG. 6(   a ) is a front view of a tube for refrigerant (tube for a cooling medium) in the first embodiment, and  FIG. 6(   b ) is a side view of the tube for refrigerant in  FIG. 6(   a ); 
         FIG. 7  is a cross-sectional view taken along the line VII-VII of  FIG. 6(   a ); 
         FIG. 8  is a cross-sectional view taken along the line VIII-VIII of  FIG. 6(   a ); 
         FIG. 9  is a cross-sectional view taken along the line IX-IX of  FIG. 6(   a ); 
         FIG. 10  is a schematic perspective view for explaining the flows of refrigerant and coolant in the heat exchanger of the first embodiment; 
         FIG. 11  is a schematic partially exploded perspective view of the heat exchanger in the first embodiment; 
         FIG. 12  is a perspective view of the contour of a heat exchanger according to a second embodiment; 
         FIG. 13  is a schematic perspective view for explaining the flows of refrigerant and coolant in the heat exchanger of the second embodiment; 
         FIG. 14  is a schematic partially-exploded perspective view of the heat exchanger in the second embodiment; 
         FIG. 15(   a ) is a front view of a tube for refrigerant (tube for a cooling medium) of the heat exchanger according to a third embodiment, and  FIG. 15(   b ) is a side view of the tube for refrigerant shown in  FIG. 15(   a ); 
         FIG. 16  is an entire configuration diagram showing refrigerant flow paths of the heat pump cycle in a waste heat recovering operation according to a fourth embodiment; 
         FIG. 17  is a perspective view of the contour of a heat exchanger according to a fifth embodiment; 
         FIG. 18  is a schematic appearance perspective view for explaining the flows of refrigerant and coolant in the heat exchanger of the fifth embodiment; 
         FIGS. 19(   a ),  19 ( b ),  19 ( c ), and  19 ( d ) are schematic cross-sectional views of heat exchangers in the longitudinal direction of header tanks according to other embodiments; 
         FIG. 20  is an explanatory diagram for explaining the influences of differences in temperature between the refrigerant and coolant in each tube due to differences in structure between respective heat exchangers; 
         FIG. 21  is a schematic partially perspective view of a heat exchanger according to another embodiment; and 
         FIGS. 22(   a ),  22 ( b ), and  22 ( c ) are explanatory diagrams for explaining outer fins according to another embodiment. 
     
    
    
     EMBODIMENTS FOR CARRYING OUT THE INVENTION 
     Embodiments of the invention will be described below based on the accompanying drawings. The same or equivalent parts through the following embodiments are indicated by the same reference characters in the figures. 
     First Embodiment 
     Referring to  FIGS. 1 to 11 , a first embodiment of the present invention will be described below. In this embodiment, a heat exchanger  16  of the invention is applied to a heat pump cycle  10  for adjusting the temperature of air to be blown into the interior of a vehicle in a vehicle air conditioner  1 .  FIGS. 1 to 4  are entire configuration diagrams of the vehicle air conditioner  1  in this embodiment. The vehicle air conditioner  1  is applied to the so-called hybrid car, which can obtain a driving force for traveling from an internal combustion engine (engine) and an electric motor MG for traveling. 
     The hybrid car can perform switching between a traveling state in which the vehicle travels obtaining the driving force from both engine and electric motor MG for traveling by operating or stopping the engine according to a traveling load on the vehicle or the like, and another traveling state in which the vehicle travels obtaining the driving force only from the electric motor MG for traveling by stopping the engine. Thus, the hybrid car can improve the fuel efficiency as compared to normal cars obtaining a driving force for traveling only from the engine. 
     The heat pump cycle  10  in the vehicle air conditioner  1  is an evaporation compression refrigeration cycle that serves to heat or cool the air in the vehicle compartment to be blown into the vehicle interior as a space of interest for air conditioning. That is, the heat pump cycle  10  can switch between refrigerant flow paths to thereby perform a heating operation (heater operation) and a cooling operation (cooler operation). The heating operation is performed to heat the vehicle interior by heating the air in the vehicle compartment as a fluid of interest for heat exchange. The cooling operation is performed to cool the vehicle interior by cooling the air in the vehicle compartment. 
     Then, the heat pump cycle  10  can also perform a defrosting operation and a waste heat recovering operation. The defrosting operation is performed to melt and remove frost formed at an outdoor heat exchanging portion  60  of the heat exchanger  16  in the heating operation by changing the flow rate of the refrigerant, coolant, or outside air flowing through the heat exchanger  16  as will be described later. The waste heat recovering operation is performed to absorb heat of the electric motor MG for traveling in the refrigerant as the external heat source in the heating operation. In the entire configuration diagrams of the heat pump cycle  10  shown in  FIGS. 1 to 4 , the flows of refrigerant in the respective operations are designated by a solid arrow. 
     The heat pump cycle  10  of this embodiment employs a normal flon-based refrigerant as the refrigerant, and forms a subcritical refrigeration cycle whose high-pressure side refrigerant pressure does not exceed the critical pressure of the refrigerant. Refrigerating machine oil for lubricating a compressor  11  is mixed into the refrigerant, and a part of the refrigerating machine oil circulates through the cycle together with the refrigerant. 
     First, the compressor  11  is positioned in an engine room, and is to suck, compress, and discharge the refrigerant in the heat pump cycle  10 . The compressor is an electric compressor which drives a fixed displacement compressor  11   a  having a fixed discharge capacity by use of an electric motor  11   b . Specifically, various types of compression mechanisms, such as a scroll type compression mechanism, or a vane compression mechanism, can be employed as the fixed displacement compressor  11   a.    
     The electric motor  11   b  is one whose operation (number of revolutions) is controlled by a control signal output from an air conditioning controller to be described later. The motor  11   b  may use either an AC motor or a DC motor. The control of the number of revolutions of the motor changes a refrigerant discharge capacity of the compressor  11 . Thus, in this embodiment, the electric motor  11   b  serves as discharge capacity changing means of the compressor  11 . 
     A refrigerant discharge port of the compressor  11  is coupled to a refrigerant inlet side of an indoor condenser  12  as a user-side heat exchanger. The indoor condenser  12  is disposed in a casing  31  of an indoor air conditioning unit  30  of the air conditioner  1  for the vehicle. The indoor condenser is a heat exchanger for heating that exchanges heat between a high-temperature and high-pressure refrigerant flowing therethrough and the air in the vehicle compartment having passed through an indoor evaporator  20  to be described later. The detailed structure of the indoor air conditioning unit  30  will be described later. 
     A fixed throttle  13  for heating is coupled to a refrigerant outlet side of the indoor condenser  12 . The fixed throttle  13  serves as decompression means for the heating operation that decompresses and expands the refrigerant flowing from the indoor condenser  12  in the heating operation. The fixed throttle  13  for heating can use an orifice, a capillary tube, and the like. The outlet side of the fixed throttle  13  for heating is coupled to the refrigerant inlet side of the outdoor heat exchanging portion  60  of the compound heat exchanger  16 . 
     A bypass passage  14  for the fixed throttle is coupled to the refrigerant outlet side of the indoor condenser  12 . The bypass passage  14  causes a refrigerant flowing from the indoor condenser  12  to bypass the fixed throttle  13  for heating and to guide the refrigerant into the outdoor heat exchanging portion  60  of the heat exchanger  16 . An opening/closing valve  15   a  for opening and closing the bypass passage  14  for the fixed throttle is disposed in the bypass passage  14  for the fixed throttle. The opening/closing valve  15   a  is an electromagnetic valve whose opening and closing operations are controlled by a control voltage output from the air conditioning controller. 
     The loss in pressure caused when the refrigerant passes through the opening/closing valve  15   a  is extremely small as compared to the loss in pressure caused when the refrigerant passes through the fixed throttle  13 . Thus, when the opening/closing valve  15   a  is opened, the refrigerant flowing out of the indoor condenser  12  flows into the outdoor heat exchanging portion  60  of the heat exchanger  16  via the bypass passage  14  for the fixed throttle. In contrast, when the opening/closing valve  15   a  is closed, the refrigerant flows into the outdoor heat exchanging portion  60  of the heat exchanger  16  via the fixed throttle  13  for heating. 
     Thus, the opening/closing valve  15   a  can switch between the refrigerant flow paths of the heat pump cycle  10 . The opening/closing valve  15   a  of this embodiment serves as refrigerant flow path switching means. Alternatively, as such a refrigerant flow path switching means, an electric three-way valve or the like may be provided for switching between a refrigerant circuit for coupling the outlet side of the indoor condenser  12  to the inlet side of the fixed throttle  13  for heating, and another refrigerant circuit for coupling the outlet side of the indoor condenser  12  to the inlet side of the bypass passage  14  for the fixed throttle. 
     The heat exchanger  16  is disposed in an engine room. The outdoor heat exchanging portion  60  of the heat exchanger  16  is a heat exchanging portion for exchanging heat between the low-pressure refrigerant flowing therethrough and an outside air blown from a blower fan  17 . Further, the outdoor heat exchanging portion  60  serves as a heat exchanging portion for evaporation that evaporates the low-pressure refrigerant to exhibit a heat absorption effect in the heating operation, and also as a heat exchanging portion for heat dissipation that dissipates heat from the high-pressure refrigerant in the cooling operation. 
     The blower fan  17  is an electric blower whose operating ratio, that is, whose number of revolutions (volume of air) is controlled by a control voltage output from the air conditioning controller. The heat exchanger  16  of this embodiment is integral with a radiator  70  for exchanging heat between the outside air blown from the blower fan  17  and the coolant circulating through the above outdoor heat exchanging portion  60  and a coolant circulation circuit  40  for cooling the electric motor MG for traveling. 
     The blower fan  17  of this embodiment serves as outdoor blowing means for blowing the outside air toward both the outdoor heat exchanging portion  60  of the heat exchanger  16  and the radiator  70 . The details structures of the compound heat exchanger  16  including the coolant circulation circuit  40 , the outdoor heat exchanging portion  60 , and the radiator  70  which are integral with each other will be described in detail below. 
     The outlet side of the outdoor heat exchanging portion  60  of the heat exchanger  16  is coupled to an electric three-way valve  15   b . The three-way valve  15   b  has its operation controlled by a control voltage output from the air conditioning controller. The three-way valve  15   b  serves as the refrigerant flow path switching means together with the above opening/closing valve  15   a.    
     More specifically, in the heating operation, the three-way valve  15   b  performs switching to the refrigerant flow path for coupling the outlet side of the outdoor heat exchanger  19  to the inlet side of an accumulator  18  to be described later. In contrast, in the cooling operation, the three-way valve  15   b  performs switching to the refrigerant flow path for coupling the outlet side of the outdoor heat exchanging portion  60  of the heat exchanger  16  to the inlet side of a fixed throttle  19  for cooling. The fixed throttle  19  for cooling serves as decompression means for the cooling operation for decompressing and expanding the refrigerant flowing from the outdoor heat exchanging portion  60  in the cooling operation. The fixed throttle  19  has the same basic structure as that of the above fixed throttle  13  for heating. 
     The outlet side of the fixed throttle  19  for cooling is coupled to the refrigerant inlet side of the indoor evaporator  20 . The indoor evaporator  20  is disposed on the upstream side of the air flow with respect to the indoor condenser  12  in the casing  31  of the indoor air conditioning unit  30 . The indoor evaporator  20  is a heat exchanger for cooling that exchanges heat between the air in the vehicle compartment and the refrigerant flowing therethrough to thereby cool the air within the vehicle interior. 
     A refrigerant outlet side of the indoor evaporator  20  is coupled to an inlet side of the accumulator  18 . The accumulator  18  is a gas-liquid separator for the low-pressure side refrigerant that separates the refrigerant flowing thereinto into liquid and gas phases, and which stores therein the excessive refrigerant within the cycle. A vapor-phase refrigerant outlet of the accumulator  18  is coupled to a suction side of the compressor  11 . Thus, the accumulator  18  serves to suppress the suction of the liquid-phase refrigerant into the compressor  11  to thereby prevent the compression of the liquid in the compressor  11 . 
     Next, the indoor air conditioning unit  30  will be described below. The indoor air conditioning unit  30  is disposed inside a gauge board (instrument panel) at the forefront of the vehicle compartment. The unit  30  accommodates in the casing  31  forming an outer envelope, a blower  32 , the above-mentioned indoor condenser  12 , and the indoor evaporator  20 . 
     The casing  31  forms an air passage for flowing the air in the vehicle compartment, blown into the vehicle interior. The casing  31  is formed of resin (for example, polypropylene) having some degree of elasticity, and excellent strength. An inside/outside air switch  33  for switching between the air (inside air) in the vehicle interior and the outside air is disposed on the most upstream side of the vehicle-interior air flow in the casing  31 . 
     The inside/outside air switch  33  is provided with the inside air inlet for introducing the inside air into the casing  31 , and the outside air inlet for introducing the outside air thereinto. An inside/outside air switching door is positioned inside the inside/outside air switch  33  to continuously adjust the opening areas of the inside air inlet and the outside air inlet to thereby change the ratio of volume of the inside air to the outside air. 
     The blower  32  for blowing the air sucked via the inside/outside air switch  33  into the vehicle interior is disposed on the downstream side of the air flow of the inside/outside air switch  33 . The blower  32  is an electric blower which includes a centrifugal multiblade fan (sirocco fan) driven by an electric motor, and whose number of revolutions (volume of air) is controlled by a control voltage output from the air conditioning controller. 
     The indoor evaporator  20  and the indoor condenser  12  are disposed on the downstream side of the air flow of the blower  32  in that order with respect to the flow of the air in the vehicle interior. In short, the indoor evaporator  20  is disposed on the upstream side in the flow direction of the air in the vehicle compartment with respect to the indoor condenser  12 . 
     An air mix door  34  is disposed on the downstream side of the air flow in the indoor evaporator  20  and on the upstream side of the air flow in the indoor condenser  12 . The air mix door  34  adjusts the rate of volume of the air passing through the indoor condenser  12  among the air having passed through the indoor evaporator  20 . A mixing space  35  is provided on the downstream side of the air flow in the indoor condenser  12  so as to mix the air exchanging heat with the refrigerant and heated at the indoor condenser  12 , and the air bypassing the indoor condenser  12  and not heated. 
     Air outlets for blowing the conditioned air mixed in the mixing space  35 , into the vehicle interior as a space of interest to be cooled are disposed on the most downstream side of the air flow in the casing  31 . Specifically, the air outlets (not shown) include a face air outlet for blowing the conditioned air toward the upper body of a passenger in the vehicle compartment, a foot air outlet for blowing the conditioned air toward the foot of the passenger, and a defroster air outlet for blowing the conditioned air toward the inner side of a front glass of the vehicle. 
     The air mix door  34  adjusts the rate of volume of air passing through the indoor condenser  12  to thereby adjust the temperature of conditioned air mixed in the mixing space  35 , thus controlling the temperature of the conditioned air blown from each air outlet. That is, the air mix door  34  serves as temperature adjustment means for adjusting the temperature of the conditioned air blown into the vehicle interior. 
     In short, the air mix door  34  serves as heat exchanging amount adjustment means for adjusting the amount of heat to be exchanged between the air in the vehicle interior and the refrigerant discharged from the compressor  11  in the indoor condenser  12  serving as the user-side heat exchanger. The air mix door  34  is driven by a servo motor (not shown) whose operation is controlled based on the control signal output from the air conditioning controller. 
     The face air outlet, foot air outlet, and defroster air outlet have, at the respective upstream sides of the air flows thereof, a face door for adjusting an opening area of the face air outlet, a foot door for adjusting an opening area of the foot air outlet, and a defroster door for adjusting an opening area of the defroster air outlet, respectively (all doors being not shown). 
     The face door, foot door, and defroster door serve as air outlet mode switching means for switching among air outlet modes. The doors are driven by a servo motor (not shown) whose operation is controlled based on a control signal output from the air conditioning controller via a link mechanism or the like. 
     Next, the coolant circulation circuit  40  will be described below. The coolant circulation circuit  40  is a cooling medium circulation circuit for cooling the electric motor MG for traveling by allowing the coolant (for example, ethylene glycol aqueous solution) as a cooling medium (heat medium) to circulate through a coolant passage formed in the above electric motor MG for traveling, which is one of the vehicle-mounted devices generating heat in operation. 
     The coolant circulation circuit  40  is provided with a coolant pump  41 , an electric three-way valve  42 , the radiator  70  of the compound heat exchanger  16 , and a bypass passage  44  for allowing the coolant to flow bypassing the radiator  70 . 
     The coolant pump  41  is an electric pump for squeezing the coolant into a coolant passage formed within the electric motor MG for traveling in the coolant circulation circuit  40 , and whose number of revolutions (flow rate) is controlled by a control signal output from the air conditioning controller. Thus, the coolant pump  41  serves as cooling capacity adjustment means for adjusting the cooling capacity by changing the flow rate of the coolant for cooling the electric motor MG for traveling. 
     The three-way valve  42  switches between a cooling medium circuit for flowing the coolant into a radiator  70  by connecting the inlet side of the coolant pump  41  to the outlet side of the radiator  70 , and another cooling medium circuit for flowing the coolant to bypass the radiator  70  by connecting the inlet side of the coolant pump  41  to the outlet side of the bypass passage  44 . The three-way valve  42  whose operation is controlled by a control voltage output from the air conditioning controller serves as circuit switching means for switching between the cooling medium circuits. 
     That is, the coolant circulation circuit  40  of this embodiment can perform switching between one cooling medium circuit for circulation of the coolant from the coolant pump  41 , to the electric motor MG for travelling, the bypass passage  44 , and the coolant pump  41  in that order as illustrated by a dashed arrow of  FIG. 1  or the like, and another cooling medium circuit for circulation of the coolant from the coolant pump  41 , to the electric motor MG for traveling, the radiator  70 , and the coolant pump  41  in that order as illustrated by a dashed arrow of  FIG. 2  or the like. 
     Thus, when the three-way valve  42  performs switching to the cooling medium circuit for allowing the coolant to bypass the radiator  70  during the operation of the electric motor MG for traveling, the coolant has its temperature increased without dissipating its heat into the radiator  70 . That is, when the three-way valve  42  performs switching to the cooling medium circuit for allowing the coolant to bypass the radiator  70 , the heat (heat generated) contained in the electric motor MG for traveling is stored in the coolant. 
     In contrast, when the three-way valve  42  performs switching to the cooling medium circuit for allowing the coolant to pass through the radiator  70  during the operation of the electric motor MG for traveling, the coolant flows into the radiator  70  and then exchanges heat with the outside air blown from the blower fan  17 . The heat exchanger  16  of this embodiment allows the coolant flowing into the radiator  70  to exchange heat with not only the outside air, but also the refrigerant flowing through the outdoor heat exchanging portion  60 . 
     Next, the compound heat exchanger  16  of this embodiment will be described in detail using  FIGS. 5 to 11 .  FIG. 5  shows a perspective view of the contour of the heat exchanger  16  of this embodiment.  FIG. 6(   a ) shows a front view of a tube  61  for refrigerant (tube  71  for a cooling medium) of the outdoor heat exchanging portion  60  (radiator  70 ) in the first embodiment.  FIG. 6(   b ) shows a side view of the tube of  FIG. 6(   a ).  FIG. 7  shows an enlarged cross-sectional view taken along the line VII-VII of  FIG. 6(   a ).  FIG. 8  shows a cross-sectional view taken along the line VIII-VIII of  FIG. 6(   a ).  FIG. 9  shows an enlarged cross-sectional view taken along the line IX-IX of  FIG. 6(   a ).  FIG. 10  shows a schematic perspective view for explaining the flows of refrigerant and coolant in the heat exchanger  16 . 
     As shown in  FIG. 5 , the outdoor heat exchanging portion  60  and the radiator  70  of the heat exchanger  16  includes a plurality of tubes ( 61  and  71 ) for flowing the refrigerant or coolant therethrough, and tanks ( 62  and  72 ) for collection and distribution disposed on the end side of each of the tubes in the longitudinal direction and adapted to collect and distribute the refrigerant or coolant flowing through the tubes, which forms the so-called tank and tube heat exchanger structure. 
     Specifically, the outdoor heat exchanging portion  60  includes a plurality of refrigerant tubes  61  for allowing the refrigerant as a first fluid to flow therethrough, and a refrigerant side header tank  62  extending in the lamination direction of the tubes  61  to collect or distribute the refrigerant flowing through the refrigerant tubes  61 . The outdoor heat exchanging portion  60  is a heat exchanging portion for exchanging heat between the refrigerant flowing through the tubes  61  and air (outside air blown from the blower fan  17 ) as a third fluid flowing through around the refrigerant tubes  61 . 
     In contrast, the radiator  70  includes a plurality of cooling medium tubes  71  for allowing the coolant as a second fluid to flow therethrough, and a cooling medium side header tank  72  extending in the lamination direction of the tubes  71  to collect or distribute the coolant flowing through the tubes  71 . The radiator  70  is a heat exchanging portion for exchanging heat between the coolant flowing through the tubes  71  and air (outside air blown from the blower fan  17 ) flowing around the tubes  71 . 
     In this embodiment as shown in  FIGS. 6(   a ) and  6 ( b ), each of the refrigerant tube  61  and the cooling medium tube  71  employs the so-called plate tube which is formed by bonding a pair of plates  61   a  and  61   b  ( 71   a  and  71   b ) with concave and convex portions on one surface of each plate so as to align the center of one plate with that of the other. The plates  61   a  and  61   b  ( 71   a  and  71   b ) are formed of metal with excellent heat conductivity (aluminum alloy in this embodiment). 
     The refrigerant tubes  61  and the cooling medium tubes  71  in this embodiment have the same basic structure.  FIGS. 6(   a ) and  6 ( b ) illustrate the refrigerant tube  61  while components of the cooling medium tube  71  corresponding to components of the refrigerant tube  61  are indicated by respective reference numerals within parentheses. 
     As shown in  FIG. 5 , the refrigerant tubes  61  and the cooling medium tubes  71  extend in the direction that connect the refrigerant side header tank  62  with the cooling medium side header tank  72  to be described later, and are disposed between the refrigerant side header tank  62  and the cooling medium side header tank  72 . In short, the refrigerant side header tank  62  is positioned on one end side of each of the refrigerant tube  61  and the cooling medium tube  71  in the longitudinal direction. The cooling medium side header tank  72  is positioned on the other end side of each of the refrigerant tube  61  and the cooling medium tube  71  in the longitudinal direction. 
     Each of the refrigerant tube  61  and the cooling medium tube  71  has one end in the longitudinal direction fixed to the refrigerant side header tank  62 , and the other end in the longitudinal direction fixed to the cooling medium side header tank  72 . 
     As shown in  FIGS. 6(   a ) and  6 ( b ), the refrigerant tube  61  extends in the longitudinal direction of the refrigerant tube  61  (in the direction perpendicular to the flow direction of outside air blown from the blower fan  17 ). As shown in the cross-sectional view of  FIG. 7 , refrigerant flow paths  61   c  with a flat section are arranged in two lines in the flow direction A of the outside air blown from the blower fan  17 . Thus, the outer surface of a part forming the refrigerant flow path  61   c  of the refrigerant tubes  61  is a flat surface  61   d  expanding in parallel to the flow direction of the outside air blown from the blower fan  17 . 
     As shown in the cross-sectional view of  FIG. 8 , the end of each of both refrigerant flow paths  61   c  arranged in two lines on the refrigerant side header tank  62  side is externally opened at the end of the refrigerant tube  61 . In this embodiment, the refrigerant side header tank  62  is placed on the opened end of the refrigerant flow path  61   c , so that both the refrigerant flow paths  61   c  are in communication with the internal space of the refrigerant side header tank  62 . 
     In contrast, as shown in the cross-sectional view of  FIG. 9 , the other end of each of both refrigerant flow paths  61   c  arranged in two lines on the cool medium side header tank  72  side is not externally opened to the outside of the refrigerant tube  61 , and the refrigerant flow paths  61   c  in two lines are connected together by a refrigerant side turning portion  61   e . In this way, the internal space of the cooling medium side header tank  72  is not in communication with the refrigerant tube  61 , so that the two-lined refrigerant flow paths  61   c  are in communication with each other. 
     Thus, in the refrigerant tube  61  of this embodiment, the refrigerant side turning portion  61   e  is positioned closer to the cooling medium side header tank  72  than the refrigerant side header tank  62 . As indicated by the solid arrow of  FIG. 10 , the refrigerant flowing into one of the refrigerant flow paths  61   c  arranged in two lines from the refrigerant side header tank  62  has its flow direction reversed at the refrigerant side turning portion  61   e , and flows into the other refrigerant flow path  61   c  to return to the refrigerant side header tank  62 . 
     An area of a refrigerant passage of the refrigerant side turning point  61   e  is larger than that of a refrigerant passage of the refrigerant flow path  61   c . That is, the area of the refrigerant passage of an intermediate part of the refrigerant side turning portion  61   e  is larger than that of each of a refrigerant inflow part and a refrigerant outflow part of the refrigerant side turning portion  61   e  connected to the refrigerant flow path  61   c . The refrigerant passage area is defined as a sectional area perpendicular to the flow direction of the refrigerant. 
     An enlarging portion  61   f  is provided for enlarging the refrigerant passage area of the refrigerant flow path  61   c , on the other end of the refrigerant flow path  61   c  of the refrigerant tube  61  opposite to the refrigerant side turning point  61   e . Both refrigerant flow paths  61   c  are in communication with the internal space of the refrigerant side header tank  62  via the enlarging portion  61   f . The enlarging portion  61   f  is formed to enlarge a surface area of the inside of the refrigerant tube  61  to thereby improve the pressure resistance. 
     An inner fin  65  for promoting the heat exchange between the refrigerant and the outside air blown from the blow fan  17  is disposed within the refrigerant flow path  61   c  of the refrigerant tube  61 . The inner fin  65  is formed by bending a thin metal plate in a wave shape. As shown in  FIGS. 8 and 9 , the inner fin  65  has both ends in the longitudinal direction protruding into the internal space of the enlarging portion  61   f  and the refrigerant side turning portion  61   e , respectively. 
     In the cooling medium tube  71 , like the refrigerant tube  61 , cooling medium flow paths  71   c  with a flat section are arranged in two lines in the flow direction A of the outside air blown from the blower fan  17 . Thus, the outer surface of a part forming the cooling medium flow path  71   c  of the cooling medium tube  71  is a flat surface  71   d  expanding in parallel to the flow direction of the outside air blown from the blower fan  17 . 
     Each cooling medium flow path  71   c  of the cooling medium tube  71  has one end on the cooling medium side header tank  72  side in communication with the internal space of the cooling medium side header tank  72 . The other ends of both cooling medium flow paths  71   c  on the refrigerant header tank  62  side are connected to the cooling medium side turning portion  71   e  having the same structure as that of the refrigerant side turning portion  61   e.    
     Thus, in the cooling medium tube  71 , the cooling medium side turning portion  71   e  is positioned closer to the refrigerant side header tank  62  than the cooling medium side header tank  72 . As indicated by the dashed arrow of  FIG. 10 , the refrigerant flowing into one of the cooling medium flow paths  71   c  arranged in two lines from the cooling medium side header tank  72  has its flow direction reversed at the cooling medium side turning portion  71   e , and flows into the other refrigerant flow path  71   c  to return to the cooling medium side header tank  72 . 
     An inner fin  75  for promoting the heat exchange between the coolant and the outside air blown from the blow fan  17  is disposed within the cool medium flow path  71   c  of the cool medium tube  71 . The inner fin  75  has the same structure as that of the inner fin  65  disposed in the refrigerant flow path  61   c . The inner fin  75  has both ends in the longitudinal direction protruding into the internal space of the enlarging portion  71   f  and the cooling medium side turning portion  71   e , respectively. 
     In the refrigerant tube  61  and the cooling medium tube  71 , the flat surfaces  61   d  and  71   d  of the outer surfaces of the tubes are laminated in parallel with a predetermined distance therebetween. That is, the refrigerant tube  61  is disposed between the cooling medium tubes  71 . Conversely, the cooling medium tube  71  is disposed between the refrigerant tubes  61 . 
     A space formed between the refrigerant tube  61  and the cooling medium tube  71  forms an outside air passage  16   a  (third fluid passage) for allowing the outside air blown from the blower fan  17  to flow therethrough. 
     In the outside air passage  16   a , an outer fin  50  is disposed in connection with the flat surface  61   d  of the refrigerant tube  61  and the flat surface  71   d  of the cooling medium tube  71  which are opposed to each other. The outer fin  50  can promote the heat exchange between the outside air and the refrigerant in the outdoor heat exchanging portion  60 , and the heat exchange between the outside air and the coolant in the radiator  70 . Further, the outer fins  50  enable heat transfer between the refrigerant flowing through the refrigerant tube  61  and the coolant flowing through the cooling medium tube  71 . 
     The outer fin  50  for use is a corrugated fin formed by bending a thin metal plate in a wave shape. In this embodiment, the outer fin  50  is coupled to both the refrigerant tube  61  and the cooling medium tube  71 , which enables the heat transfer between the refrigerant tube  61  and the cooling medium tube  71 . 
     Next, the detailed structures of the refrigerant tube  61 , the cooling medium tube  71 , the refrigerant side header tank  62 , and the cooling medium side header tank  72  will be described below with reference to  FIG. 11 .  FIG. 11  shows a schematic partially exploded perspective view of the heat exchanger  16 . For easy understanding,  FIG. 11  omits the illustration of the outer fin  50 . 
     As shown in  FIG. 11 , each refrigerant tube  61  includes a refrigerant tube upstream portion  611  located on the upstream side of the refrigerant side turning portion  61   e , and a refrigerant tube downstream portion  612  located on the downstream side of the refrigerant side turning portion  61   e . That is, the refrigerant tube  61  of this embodiment is composed of the refrigerant tube upstream portion  611 , the refrigerant side turning portion  61   e , and the refrigerant tube downstream portion  612 . In the refrigerant tube  61  of this embodiment, the refrigerant tube upstream portion  611  is disposed on the downstream side in the flow direction A of the outside air with respect to the refrigerant tube downstream portion  612 . 
     In contrast, each cooling medium tube  71  includes a cooling medium tube upstream portion  711  located on the upstream side of the cooling medium side turning portion  71   e , and a cooling medium tube downstream portion  712  located on the downstream side of the cooling medium side turning portion  71   e . That is, the cooling medium tube  71  of this embodiment is composed of the cooling medium tube upstream portion  711 , the cooling medium side turning portion  71   e , and the cooling medium tube downstream portion  712 . In the cooling medium tube  71  of this embodiment, the cooling medium tube upstream portion  711  is disposed on the upstream side in the flow direction A of the outside air with respect to the cooling medium tube downstream portion  712 . 
     The refrigerant tubes  61  and the cooling medium tubes  71  in this embodiment are disposed such that the refrigerant tube upstream portions  611  and the cooling medium tube downstream portions  712  are arranged in the lamination direction of the tubes  61  and  71 , and such that the refrigerant tube downstream portions  612  and the cooling medium tube upstream portions  711  are arranged in the lamination direction of the tubes  61  and  71 . 
     With this arrangement, the refrigerant flowing through the refrigerant tube  61  flows from the downstream side in the flow direction of the outside air to the upstream side thereof, and the coolant flowing through the cooling medium tube  71  flows from the upstream side in the flow direction of the outside air to the downstream side thereof. Thus, in the refrigerant tubes  61  and the cooling medium tubes  71 , the flow direction of refrigerant flowing through the refrigerant tube  61  is opposite to that of the coolant flowing through the cooling medium tube  71  with respect to the flow direction A of the outside air. 
     Next, the refrigerant side header tank  62  and the cooling medium side header tank  72  will be described later. The refrigerant side header tank  62  has the same basic structure as that of the cooling medium side header tank  72 . The refrigerant side header tank  62  includes a refrigerant side plate  63  to which both the refrigerant tubes  61  and the cooling medium tubes  71  are fixed, and a refrigerant side tank  64  fixed to the refrigerant side plate  63 . 
     A part of the refrigerant side plate  63  corresponding to each refrigerant tube  61  is provided with a communication hole penetrating the plate. The refrigerant tube  61  passes through the communication hole. Thus, the refrigerant flow path  61   c  of each refrigerant tube  61  is in communication with the internal space of the refrigerant side header tank  62 . The width of the part of the refrigerant tube  61  inserted into the communication hole in the flow direction of the outside air is shorter than that of the refrigerant flow path  61   c.    
     Similarly, a part of the refrigerant side plate  63  corresponding to each cooling medium tube  71  is provided with a communication hole penetrating the plate. The refrigerant tube  71  is inserted into the communication hole, so that the hole is closed. The width of the part of the cooling medium tube  71  inserted into the communication hole in the flow direction of the outside air is shorter than that of the cooling medium flow path  71   c.    
     The refrigerant side plate  63  is fixed to the refrigerant side tank  64  to thereby form a concave portion  63   a  for partitioning a space formed between the plate  63  and tank  64 . The concave portion  63   a  is provided over the entire area of the refrigerant side plate  63  in the longitudinal direction. 
     The refrigerant side tank  64  is fixed to the refrigerant side plate  63  to thereby form a collection space  62   a  for collecting the refrigerants therein, and a distribution space  62   b  for distributing the refrigerant. Specifically, the refrigerant side tank  64  is formed by pressing a flat metal plate into a double mountain (W-like) shape as viewed in the longitudinal direction. 
     A center portion  64   a  of the double mountain shape of the refrigerant side tank  64  is coupled to the concave portion  63   a  of the refrigerant side plate  63 , which partitions the internal space into the collection space  62   a  and the distribution space  62   b . In this embodiment, the collection space  62   a  is disposed on the windward side in the flow direction A of the outside air, and the distribution space  62   b  is disposed on the leeward side in the flow direction A of the outside air. 
     As mentioned above, the refrigerant tube  61  passes through the communication hole of the refrigerant side plate  63 , so that the refrigerant flow paths  61   c  (refrigerant tube downstream portion  612 ) disposed on the windward side in the flow direction A of the outside air are brought into communication with the collection space  62   a , while the refrigerant flow paths  61   c  (refrigerant tube upstream portion  611 ) disposed on the leeward side in the flow direction A of the outside air are brought into communication with the distribution space  62   b.    
     As shown in  FIG. 5 , one end of the refrigerant side tank  64  in the longitudinal direction is connected to a refrigerant introduction pipe  64   b  for introducing the refrigerant into the distribution space  62   b , and a refrigerant guiding pipe  64   c  for guiding the refrigerant from the collection space  62   a . The other end of the refrigerant side tank  64  in the longitudinal direction is closed by a closing member. 
     Also, as shown in  FIG. 11 , the cooling medium side header tank  72  also includes a cooling medium side plate  73  and a cooling medium side tank  74 . The cooling medium tube  71  passes through a communication hole provided at the part of the cooling medium plate  73  corresponding to the cooling medium tube  71 . The refrigerant tube  61  is inserted into another communication hole provided at the part of the cooling medium plate  73  corresponding to the refrigerant tube  61 . 
     The cooling medium side tank  74  is fixed to the cooling medium side plate  73 , causing a concave portion  73   a  of the cooling medium side plate  73  to be coupled to a center portion  74   a  in the double mountain shape of the cooling medium side tank  74 , which partitions the internal space into a collection space  72   a  for collecting the refrigerants therein, and a distribution space  72   b  for distributing the refrigerant. In this embodiment, the distribution space  72   b  is disposed on the windward side in the flow direction A of the outside air, and the collection space  72   a  is disposed on the leeward side in the flow direction A of the outside air. 
     As mentioned above, the cooling medium tube  71  passes through the communication hole of the cooling medium side plate  73 , so that the cooling medium flow paths  71   c  (cooling medium tube upstream portion  711 ) disposed on the windward side in the flow direction A of the outside air are brought into communication with the distribution space  72   b , while the cooling medium flow paths  71   c  (cooling medium tube downstream portion  712 ) disposed on the leeward side in the flow direction A of the outside air are brought into communication with the collection space  72   a.    
     As shown in  FIG. 5 , one end of the cooling medium side tank  74  in the longitudinal direction is connected to a cooling medium introduction pipe  74   b  for introducing the cooling medium into the distribution space  72   b , and a cooling medium guiding pipe  74   c  for guiding and deriving the cooling medium from the collection space  72   a . The other end of the cooling medium side header tank  72  in the longitudinal direction is closed by a closing member. 
     Thus, in the heat exchanger  16  of this embodiment, as shown in the schematic perspective view of  FIG. 10 , the refrigerant introduced into the distribution space  62   b  of the refrigerant side header tank  62  via the refrigerant introduction pipe  64   b  flows into each refrigerant flow path  61   c  (refrigerant tube upstream portion  611 ) of one of the refrigerant tubes  61  in two lines disposed on the leeward side in the flow direction A of the outside air. 
     Then, the refrigerant flowing from each refrigerant flow path  61   c  disposed on the leeward side (refrigerant tube upstream portion  611 ) flows into the other refrigerant flow path  61  disposed on the windward side (refrigerant tube downstream portion  612 ) via the refrigerant side turning portion  61   e . Further, the refrigerants flowing from the refrigerant flow paths  61   c  (refrigerant tube downstream portion  612 ) disposed on the windward side are collected into the collection space  62   a  of the refrigerant side header tank  62 , and then derived from the refrigerant guiding pipe  64   c.    
     That is, in the heat exchanger  16  of this embodiment, the refrigerant flows and turns around from the refrigerant flow path  61   c  on the leeward side of the refrigerant tube  61  (refrigerant tube upstream portion  611 ) to the refrigerant side turning portion  61   e , and the refrigerant flow path  61   c  on the windward side of the refrigerant tube  61  (refrigerant tube downstream portion  612 ) in that order. 
     Likewise, the coolant flows and turns around from the cooling medium flow path  71   c  on the windward side of the cooling medium tube  71  (cooling medium tube upstream portion  711 ) to the cooling medium side turning portion  71   e , and the cooling medium flow path  71   c  on the leeward side of the cooling medium tube  71  (cooling medium tube downstream portion  712 ) in that order. Thus, the refrigerants flowing through the adjacent refrigerant tubes  61  have the flow direction opposite to that of the coolants flowing through the adjacent cooling medium tubes  71  in the longitudinal direction of the tubes  61  and  71  and in the flow direction of the outside air (which is referred to as an “opposite flow structure”). 
     Components of the above inner fins  65  and  72 , the refrigerant side header tank  62 , the cooling medium side header tank  72 , and the outer fin  50  are formed of the same metal as that of the plates  61   a ,  61   b ,  71   a , and  71   b  forming the refrigerant tube  61  and the cooling medium tube  71 . 
     Now, a manufacturing method of the heat exchanger  16  will be described below. First, the refrigerant tubes  61 , the cooling medium tubes  71 , the refrigerant side header tank  62 , and the cooling medium header tank  72  are temporarily fixed (which is referred to as a “tube-tank temporary fixing step”). 
     Specifically, in the refrigerant tube  61 , the plates  61   a  and  61   b  are assembled such that the center of the one plate is aligned with that of the other with the inner fin  65  fitted to the refrigerant flow path  61   c . A claw portion is formed in at least one of the upstream side and the downstream side of the plate  61  in the flow direction of the outside air (in this embodiment, the entire area in the vertical direction). The claw portion is bent toward the plate  61   b.    
     In this embodiment, the plate  61   a  includes claw portions  61   g  formed between the refrigerant flow paths  61   c  arranged in two lines, and the claw portions are bent into through holes formed in the plate  61   b , so that the plate  61   a  is temporarily fixed to the plate  61   b . Likewise, in the cooling medium tube  71 , the plates  71   a  and  71   b  and the inner fin  75  are temporarily fixed together. 
     In the refrigerant side header tank  62 , the refrigerant side plate  63  and the refrigerant tank  64  are combined by bending the claw portions formed at the outer peripheral ends of the refrigerant side tank  64  over the refrigerant plate  63 , so that the plates  63  and  64  are temporarily fixed. Also, in the cooling medium header tank  72 , the cooling medium side plate  73  and the cooling medium tank  74  are temporarily fixed. 
     The order of the temporary fixing of the refrigerant tube  61 , the cooling medium tube  71 , the refrigerant side header tank  62 , and the cooling medium side header tank  72  is not limited to the above. 
     Then, the refrigerant tube  61  and the cooling medium tube  71  are inserted into the communication holes provided in the refrigerant side plate  63  of the refrigerant header tank  62  and in the cooling medium side plate  73  of the cooling medium side header tank  72 , respectively. At this time, in this embodiment, the tubes are inserted such that the distance between the edge of an opening of the corresponding communication hole and each of the turning portions  61   e  and  71   e  and the enlarging portions  61   f  and  71   f  is 3 mm or less. 
     The outer fins  50  are inserted and temporarily fixed to the outside air passages  16   a  formed in the refrigerant tubes  61  and the cooling medium tubes  71 , and then the respective introduction/guiding pipes  64   b ,  64   c ,  74   b , and  74   c  are temporarily fixed (which is referred to as a “heat exchanger temporary fixing step”). 
     After fixing the heat exchanger  16  temporarily assembled with a wire jig or the like, the entire heat exchanger  16  is put and heated in a heating furnace. At this time, solder previously cladded to the surface of each component is melted, and the heat exchanger  16  is cooled until the solder is solidified again. As a result, the respective components are integrally soldered (which is referred to as a “heat exchanger bonding step”). The above method can produce the heat exchanger including the outdoor heat exchanging portion  60  and the radiator  70  which are integral with each other. 
     As can be seen from the above description, the outdoor heat exchanging portion  60  of this embodiment corresponds to a first heat exchanging portion; the refrigerant tube  61  corresponds to a first tube; the refrigerant side header tank  62  corresponds to a first tank; and the refrigerant side turning portion  61   e  corresponds to a first turning portion, for example. 
     The refrigerant tube upstream portion  611  of the cooling medium tube  61  corresponds to a first tube upstream portion; and the refrigerant tube downstream portion  612  corresponds to a first tube downstream portion, for example. 
     In contrast, the radiator  70  corresponds to a second heat exchanger; the cooling medium tube  71  corresponds to a second tube; the cooling medium side header tank  72  corresponds to a second tank; and the cooling medium side turning portion  71   e  corresponds to a second turning portion, for example. 
     The cooling medium tube upstream portion  711  of the cooling medium tube  71  corresponds to a second tube upstream portion; and the cooling medium tube downstream portion  712  corresponds to a second tube downstream portion, for example. 
     Now, an electric control unit of this embodiment will be described below. The air conditioning controller is comprised of the known microcomputer including a CPU, an ROM, and an RAM, and peripheral circuits thereof. The control unit controls the operation of each of various types of air conditioning controller  11 ,  15   a ,  15   b ,  17 ,  41 , and  42  connected to its output by executing various operations and processing based on air conditioning control programs stored in the ROM. 
     A group of various sensors for control of air conditioning is coupled to the input side of the air conditioning controller. The sensors include an inside air sensor for detecting a temperature of the vehicle interior, an outside air sensor for detecting a temperature of the outside air, a solar radiation sensor for detecting an amount of solar radiation in the vehicle interior, and an evaporator temperature sensor for detecting a temperature of blown air from the indoor evaporator  20  (evaporator temperature). And, the sensors also include a discharged refrigerant temperature sensor for detecting a temperature of the refrigerant discharged from the compressor  11 , an outlet refrigerant temperature sensor  51  for detecting a refrigerant temperature Te on the outlet side of the outdoor heat exchanging portion  60 , and a coolant temperature sensor  52  serving as coolant temperature detection means for detecting a coolant temperature Tw of the coolant flowing into the electric motor MG for traveling. 
     In this embodiment, the coolant temperature sensor  52  detects the coolant temperature Tw of the coolant squeezed from the coolant pump  41 . Alternatively, the coolant temperature Tw of the coolant sucked into the coolant pump  41  may be detected. 
     An operation panel (not shown) disposed near an instrument board at the front of the vehicle compartment is connected to the input side of the air conditioning controller. Operation signals are input from various types of air conditioning operation switches provided on the operation panel. Various air conditioning operation switches provided on the panel include an operation switch for the air conditioner for the vehicle, a vehicle-interior temperature setting switch for setting the temperature of the vehicle interior, and a selection switch for selecting an operation mode. 
     The air conditioning controller includes control means for controlling the electric motor  11   b  for the compressor  11 , and the opening/closing valve  15   a  and the like which are integral with each other, and is designed to control the operations of these components. In the air conditioning controller of this embodiment, the structure (hardware and software) for controlling the operation of the compressor  11  serves as refrigerant discharge capacity control means. The structure for controlling the operations of the respective devices  15   a  and  15   b  forming the refrigerant flow path switching means serves as refrigerant flow path control means. The structure for controlling the operation of the three-way valve  42  forming the cooling medium circuit switching means for coolant serves as cooling medium circuit control means. 
     The air conditioning controller of this embodiment includes the structure (frost formation determination means) for determining whether or not the frost is formed at the outdoor heat exchanger  60 , based on a detection signal from the above sensor group for the air conditioning control. Specifically, when the speed of a travelling vehicle is equal to or less than a predetermined reference value (in this embodiment, 20 km/h), and the refrigerant temperature Te on the outlet side of the outdoor heat exchanger  60  is equal to or less than 0° C., the frost formation determination means of this embodiment determines that the frost formation is caused at the outdoor heat exchanger  60 . 
     Next, the operation of the vehicle air conditioner  1  with the above arrangement in this embodiment will be described below. The vehicle air conditioner  1  of this embodiment can execute a heating operation for heating the vehicle interior, and a cooling operation for cooling the vehicle interior. In the heating operation, a defrosting operation and a waste heat recovering operation can also be carried out. Now, each operation will be explained in the following. 
     (a) Heating Operation 
     The heating operation is started when the heating operation mode is selected by the selection switch with the operation switch of the operation panel turned on (ON). Then, in the heating operation, when the frost formation determination means determines that the frost is formed at the outdoor heat exchanger  60 , the defrosting operation is performed. When the coolant temperature Tw detected by the coolant temperature sensor  52  is equal to or more than the predetermined reference temperature (in this embodiment, 60° C.), the waste heat recovering operation is performed. 
     In the normal heating operation, the air conditioning controller closes the opening/closing valve  15   a , and switches the three-way valve  15   b  to the refrigerant flow path for coupling the outlet side of the outdoor heat exchanging portion  60  to the inlet side of the accumulator  18 . Further, the controller actuates the coolant pump  41  to squeeze the coolant in a predetermined flow rate, and switches the three-way valve  42  of the coolant circulation circuit  40  to the cooling medium circuit for allowing the coolant to bypass the radiator  70 . 
     In this way, the heat pump cycle  10  is switched to the refrigerant flow path for allowing the refrigerant to flow as illustrated by the solid arrow in  FIG. 1 . The coolant circulation circuit  40  is also switched to the cooling medium circuit for allowing the refrigerant to flow as illustrated by the dashed arrow in  FIG. 1 . 
     The air conditioning controller with the above refrigerant flow path and cooling medium circuit reads a detection signal from the above sensor group for the air conditioning control and an operation signal from the operation panel. Based on the detection signal and the operation signal, a target outlet air temperature TAO is calculated as the target temperature of the air to be blown into the vehicle interior. Further, the operating states of various air conditioning control components connected to the output side of the air conditioning controller are determined based on the calculated target outlet air temperature TAO and the detection signal from the sensor group. 
     For example, the refrigerant discharge capacity of the compressor  11 , that is, a control signal output to the electric motor of the compressor  11  is determined as follows. First, a target evaporator outlet air temperature TEO of the indoor evaporator  20  is determined based on the target outlet air temperature TAO with reference to a control map previously stored in the air conditioning controller. 
     Based on a deviation between the target evaporator outlet air temperature TEO and the blown air temperature from the indoor evaporator  20  detected by the evaporator temperature sensor, the control signal to be output to the electrode motor of the compressor  11  is determined such that the blown air temperature of the air blown from the indoor evaporator  20  approaches the target evaporator outlet air temperature TEO by use of a feedback control method. 
     The control signal to be output to the servo motor of the air mix door  34  is determined based on the target outlet air temperature TAO, the blown air temperature of the indoor evaporator  20 , and the temperature of the refrigerant discharged from the compressor  11  detected by the discharge refrigerant temperature sensor such that the temperature of air blown into the vehicle interior becomes a desired temperature set by the passenger using the vehicle interior temperature setting switch. 
     During the normal heating operation, the defrosting operation, and the waste heat recovering operation, the opening degree of the air mix door  34  may be controlled such that the whole volume of air in the vehicle interior blown from the blower  32  passes through the indoor condenser  12 . 
     Then, the control signals determined as described above are output to various air conditioning control components. Thereafter, until the stopping of the vehicle air conditioner is requested by the operation panel, a control routine is repeated at every predetermined control cycle. The control routine includes a series of processes: reading of the detection signal and the operation signal, calculation of the target outlet air temperature TAO, determination of the operating states of various air conditioning control components, and output of the control voltage and the control signal in that order. Such repetition of the control routine is basically performed in other operation modes in the same way. 
     In the heat pump cycle  10  during the normal heating operation, the high-pressure refrigerant discharged from the compressor  11  flows into the indoor condenser  12 . The refrigerant flowing into the indoor condenser  12  exchanges heat with the vehicle interior air blown by the blower  32  through the indoor evaporator  20  to dissipate the heat therefrom, so that the air in the vehicle compartment is heated. 
     The high-pressure refrigerant flowing from the indoor condenser  12  flows into the fixed throttle  13  for heating to be decompressed and expanded by the throttle  13  because the opening/closing valve  15   a  is closed. The low-pressure refrigerant decompressed and expanded by the fixed throttle  13  for heating flows into an outdoor heat exchanging portion  60 . The low-pressure refrigerant flowing into the outdoor heat exchanging portion  60  absorbs heat from the outside air blown by the blower fan  17 , and is evaporated. 
     At this time, the coolant circulation circuit  40  is switched to the cooling medium circuit for allowing the coolant to bypass the radiator  70 , which prevents the coolant from dissipating heat to the refrigerant flowing through the outdoor heat exchanging portion  60 , and also prevents the coolant from absorbing heat from the refrigerant flowing through the outdoor heat exchanging portion  60 . That is, the coolant never has a thermal influence on the refrigerant flowing through the outdoor heat exchanging portion  60 . 
     Since the three-way valve  15   b  is switched to the refrigerant flow path connecting the outlet side of the outdoor heat exchanging portion  60  to the inlet side of the accumulator  18 , the refrigerant flowing from the outdoor heat exchanging portion  60  flows into the accumulator  18  and is separated into liquid and gas phases. The gas-phase refrigerant separated by the accumulator  18  is sucked by the compressor  11  and compressed again. 
     As mentioned above, in the normal heating operation, the air in the vehicle interior is heated by the indoor condenser  12  with the heat contained in the refrigerant discharged from the compressor  11 , which can perform the heating operation of the vehicle interior. 
     (b) Defrosting Operation 
     Next, the defrosting operation will be described below. In the refrigeration cycle device for evaporating the refrigerant by exchanging heat between the refrigerant and outside air in the outdoor heat exchanging portion  60 , like the heat pump cycle  10  of this embodiment, when a refrigerant evaporation temperature of the outdoor heat exchanging portion  60  becomes equal to or less than a frost formation temperature (specifically, 0° C.), the frost might be formed at the outdoor heat exchanging portion  60 . 
     Such formation of the frost closes the outside air passage  16   a  of the heat exchanger  16  with the frost, which drastically reduces the heat exchange capacity of the outdoor heat exchanging portion  60 . In the heat pump cycle  10  of this embodiment, when the frost formation is determined to be caused at the outdoor heat exchanging portion  60  by the frost formation determination means in the heating operation, the defrosting operation is started. 
     In the defrosting operation, the air conditioning controller stops the operation of the compressor  11 , and also stops the operation of the blower fan  17 . Thus, during the defrosting operation, the flow rate of refrigerant flowing into the outdoor heat exchanging portion  60  is decreased to thereby decrease the volume of outside air flowing into the outside air passage  16   a , as compared to the normal heating operation. 
     The air conditioning controller switches the three-way valve  42  of the coolant circulation circuit  40  to the cooling medium circuit for allowing the coolant to flow into the radiator  70  as indicated by the dashed arrow in  FIG. 2 . Thus, the coolant circulation circuit  40  is switched to the cooling medium circuit for flowing the refrigerant as indicated by the dashed arrow in  FIG. 2  without circulation of the refrigerant through the heat pump cycle  10 . 
     Thus, the heat contained in the coolant flowing through the cooling medium tubes  71  of the radiator  70  is transferred to the outdoor heat exchanging portion  60  via the outer fins  50 , which performs the defrosting operation of the outdoor heat exchanging portion  60 . That is, the flow rates of the refrigerant and outside air flowing through the heat exchanger  16  are changed (specifically, reduced) to achieve the defrosting operation effectively using the waste heat of the electric motor MG for traveling. 
     (c) Waste Heat Recovering Operation 
     Next, the waste heat recovering operation will be described below. Preferably, in order to suppress overheat of the electric motor MG for traveling, the temperature of the coolant is maintained at a predetermined upper limit temperature or less. Further, in order to reduce the friction loss due to an increase in viscosity of oil for lubrication sealed into the electric motor MG for traveling, preferably, the temperature of the coolant is maintained at a predetermined lower limit temperature or more. 
     In the heat pump cycle  10  of this embodiment, when the coolant temperature Tw is equal to or more than the predetermined reference temperature (60° C. in this embodiment) during the heating operation, the waste heat recovering operation is performed. In the defrosting operation, the three-way valve  15   b  of the heat pump cycle  10  is performed in the same way as in the normal heating operation, but the three-way valve  42  of the coolant circulation circuit  40  is switched to the cooling medium circuit for flowing the coolant into the radiator  70  as indicated by the dashed arrow in  FIG. 3  in the same way as in the defrosting operation. 
     Thus, as illustrated by the solid arrow in  FIG. 3 , the high-pressure and high-temperature refrigerant discharged from the compressor  11  heats the air in the vehicle interior at the indoor condenser  12 , and is then decompressed and expanded by the fixed throttle  13  for heating to flow into the outdoor heat exchanging portion  60  in the same way as in the normal heating operation. 
     Since the three-way valve  42  performs switching to the cooling medium circuit for flowing the coolant into the radiator  70 , the low-pressure refrigerant flowing into the outdoor heat exchanging portion  60  absorbs both the heat contained in the outside air blown by the blower fan  17  and the heat contained in the coolant and transmitted thereto via the outer fins  50 , thereby to be evaporated. Other operations are the same as those in the normal heating operation. 
     As described above, in the waste heat recovering operation, the air in the vehicle interior is heated at the indoor condenser  12  with the heat of the refrigerant discharged from the compressor  11 , which can perform heating of the vehicle interior. At this time, the refrigerant absorbs not only the heat contained in the outside air, but also the heat contained in the coolant and transmitted thereto via the outer fins  50 , which can achieve the heating of the vehicle interior effectively using the waste heat of the electric motor MG for traveling. 
     (d) Cooling Operation 
     The cooling operation is started when the cooling operation mode is selected by the selection switch with the operation switch of the operation panel turned on (ON). In the cooling operation, the air conditioning controller opens the opening/closing valve  15   a , and switches the three-way valve  15   b  to the refrigerant flow path for connecting the outlet side of the outdoor heat exchanging portion  60  to the inlet side of the fixed throttle  19  for cooling. Thus, the heat pump cycle  10  is switched to the refrigerant flow path for flowing the refrigerant as indicated by the solid arrow in  FIG. 4 . 
     At this time, when the coolant temperature Tw is equal to or more than the reference temperature, the three-way valve  42  of the coolant circulation circuit  40  is switched to the cooling medium circuit for flowing the coolant into the radiator  70 . In contrast, when the coolant temperature Tw is less than the predetermined reference temperature, the three-way valve  42  is switched to the cooling medium circuit for allowing the coolant to bypass the radiator  70 . The flow of the coolant obtained when the coolant temperature Tw is equal to or more than the reference temperature is indicated by the dashed arrow in  FIG. 4 . 
     In the heat pump cycle  10  during the cooling operation, the high-pressure refrigerant discharged from the compressor  11  flows into the indoor condenser  12 , and exchanges heat with the air in the vehicle interior blown by the blower  32  and having passed through the indoor evaporator  20  to dissipate heat therefrom. The high-pressure refrigerant flowing from the indoor condenser  12  flows into the outdoor heat exchanging portion  60  via the bypass passage  14  for the fixed throttle because the opening/closing valve  15   a  is opened. The low-pressure refrigerant flowing into the outdoor heat exchanging portion  60  further radiates heat toward the outside air blown by the blower fan  17 . 
     Since the three-way valve  15   b  is switched to the refrigerant flow path for connecting the outlet side of the outdoor heat exchanging portion  60  to the inlet side of the fixed throttle  19  for cooling, the refrigerant flowing from the outdoor heat exchanging portion  60  is decompressed and expanded by the fixed throttle  19  for cooling. The refrigerant flowing from the fixed throttle  19  for cooling flows into the indoor evaporator  20 , and absorbs heat from the air in the vehicle interior blown by the blower  32  to be evaporated. In this way, the air in the vehicle interior can be cooled. 
     The refrigerant flowing from the indoor evaporator  20  flows into the accumulator  18 , and is then separated into liquid and gas phases by the accumulator  18 . The gas-phase refrigerant separated by the accumulator  18  is sucked into and compressed by the compressor  11  again. As mentioned above, during the cooling operation, the low-pressure refrigerant absorbs heat from the air in the vehicle interior and evaporates itself at the indoor evaporator  20  to thereby cool the air in the vehicle compartment, which can perform cooling of the vehicle interior. 
     As described above, the air conditioner  1  for the vehicle in this embodiment can perform switching among the refrigerant flow paths of the heat pump cycle  10 , and among the cooling medium circuits of the coolant circulation circuit  40  to thereby carry out various operations. Further, in this embodiment, the above specific heat exchanger  16  can be used to perform appropriate heat exchange among three kinds of fluids, namely, refrigerant, coolant, and outside air in each operation. 
     More specifically, the heat exchanger  16  of this embodiment includes outer fins  50  each disposed in the outside air passage  16   a  formed between the refrigerant tube  61  of the outdoor heat exchanging portion  60  and the cooling medium tube  71  of the radiator  70 . Such outer fins  50  enable heat transfer between the refrigerant tubes  61  and the cooling medium tubes  71 . 
     Thus, during the defrosting operation, the heat contained in the coolant can be transferred to the outdoor heat exchanging portion  60  via the outer fins  50 , which can effectively use the waste heat of the electric motor MG for traveling to defrost the outdoor heat exchanging portion  60 . 
     Further, in this embodiment, during the defrosting operation, the operation of the compressor  11  is stopped to reduce the flow rate of refrigerant flowing into the outdoor heat exchanging portion  60 , which can prevent the heat transferred to the outdoor heat exchanging portion  60  from absorbing in the refrigerant flowing through the refrigerant tubes  61  via the outer fins  50  and the refrigerant tubes  61 . That is, unnecessary heat exchange between the coolant and the refrigerant can be suppressed. 
     During the defrosting operation, the operation of the blower fan  17  is stopped to decrease the volume of outside air flowing into the outside air passages  16   a , which can prevent the heat transmitted to the outdoor heat exchanging portion  60  via the outer fins  50  from being absorbed in the outside air flowing through the outside air passages  16   a . That is, the unnecessary heat exchange between the coolant and outside air can be suppressed. 
     During the waste heat recovering operation, the heat exchanger exchanges heat between the coolant and the refrigerant via the refrigerant tubes  61 , the cooling medium tubes  71 , and the outer fins  50 , so that the waste heat of the electric motor MG for traveling can be absorbed in the refrigerant. And the heat exchanger also exchanges heat between the coolant and the outside air via the cooling medium tubes  71  and the outer fins  50 , so that the unnecessary waste heat of the electric motor MG for traveling can be dissipated to the outside air. 
     During the normal heat operation, the heat exchanger exchanges heat between the refrigerant and the outside air via the refrigerant tubes  61  and the outer fins  50 , so that the heat of the outside air can be absorbed in the refrigerant. And during the normal heat operation, the three-way valve  42  of the coolant circulation circuit  40  is switched to the cooling medium circuit for allowing the coolant to bypass the radiator  70 , which can suppress the unnecessary heat exchange between the coolant and outside air to store the waste heat of the electric motor MG for traveling in the coolant, thus promoting the warming of the electric motor MG for traveling. 
     In the heat exchanger  16  of this embodiment, the refrigerant tubes  61  and the cooling medium tubes  71  are disposed between the refrigerant side header tank  62  and the cooling medium side header tank  72 , so that each outside air passage  16   a  is formed of a space between the refrigerant tube  61  and the cooling medium tube  71 . The refrigerant side header tank  62  and the cooling medium side header tank  72  are not arranged in the flow direction of the outside air. Thus, the entire heat exchanger  16  can be prevented from increasing in size in the flow direction of the outside air. 
     Additionally, the refrigerant side turning portion  61   e  of the refrigerant tube  61  is positioned closer to the cooling medium side header tank  72  than the refrigerant side header tank  62 . And the cooling medium side turning portion  71   e  of the cooling medium tube  71  is positioned closer to the refrigerant header tank  62  than the cooling medium side header tank  72 . The structure with the refrigerant side header tank  62  connected to the refrigerant tubes  61  can have the same shape as that of the structure with the cooling medium side header tank  72  connected to the cooling medium tube  71 . 
     In this embodiment, the refrigerant side plate  63  of the refrigerant side header tank  62  and the cooling medium side plate  73  of the cooling medium side header tank  72  are provided with communication holes in communication with the refrigerant flow path  61   c  and the cooling medium flow path  71   c , respectively, and other closed communication holes. The structure for connecting the refrigerant tubes  61  to the refrigerant side header tank  62  can have the same shape as that for connecting the cooling medium tubes  71  to the cooling medium side header tank  72 , which can improve the productivity of the heat exchanger. 
     As a result, the heat exchanger  16  of this embodiment can improve the productivity of the heat exchanger that can exchange heat among three kinds of fluids without increase in size. 
     In the heat exchanger  16  of this embodiment, the refrigerant tube  61  and the cooling medium tube  71  are fixed to both the refrigerant side header tank  62  and the cooling medium side header tank  72 , which can increase the mechanical strength of the entire heat exchanger  16 . Further, in a temporary process of the outer fin  50  to be disposed in the outside air passage  16   a , the outer fin  50  can be easily fixed temporarily, and then can be strongly fixed after the temporary bonding. 
     The refrigerant passage area of an intermediate part of each of the refrigerant side turning portion  61   e  and the cooling medium side turning portion  71   e  is larger than a fluid passage area of each of a fluid inflow portion and a fluid outflow portion of the corresponding turning portion. When the refrigerant passes through the refrigerant side turning portion  61   e , or when the coolant passes through the cooling medium side turning portion  71   e , the loss in pressure can be reduced. 
     The ends of the inner fins  65  and  75  disposed inside the refrigerant tube  61  and the cooling medium tube  71  protrude into the internal spaces of the enlarging portions  61   f  and  71   f  of the respective turning portions  61   e  and  71   e . Thus, the parts of the inner fins  65  and  75  where the cladded solder is apt to be peeled off, such as the ends of the inner fins  65  and  75 , do not serve as a surface of interest to be soldered, which tends to suppress the bonding defect between each of the inner fins  65  and  75  and the inner peripheral surface of each of the refrigerant tube  61  and the cooling medium tube  71 . 
     Like this embodiment, in the heat exchanger  16  that can exchange heat among three kinds of fluids, the temperature of refrigerant introduced into the outdoor heat exchanging portion  60  sometimes differs from that of coolant introduced into the radiator  70 , depending on the operation condition. In this case, the amount of thermal strain (heat expansion amount) generated in the refrigerant tube  61  differs from that generated in the cooling medium tube  71 , which might lead to a breakdown of the heat exchanger  16 . 
     In contrast, the heat exchanger  16  of this embodiment includes the outer fins  50  disposed between the refrigerant tubes  61  and the cooling medium tubes  71 , which are alternately laminated or stacked at predetermined intervals. Each outer fin  50  promotes the heat exchange among the outside air, the refrigerant, and the coolant to thereby relieve the difference in thermal strain between the tubes  61  and  71 . Thus, the heat exchanger  16  of this embodiment can suppress the breakdown of the refrigerant tube  61  and the cooling medium tube  71  due to the difference in thermal strain (heat expansion amount) generated between the refrigerant tubes  61  and the cooling medium tubes  71 . 
     In the heat exchanger  16  of this embodiment, the cooling medium tube upstream portion  711  of the cooling medium tube  71  is located on the upstream side in the flow direction A of the outside air with respect to the cooling medium tube downstream portion  712 . Thus, in an operating state where the temperature of the cooling medium flowing into the cooling medium tube  71  is higher than the temperature of each of the refrigerant and outside air, the difference in temperature between the coolant and the outside air can be ensured on the upstream side of the coolant flow of the cooling medium tube  71  to thereby increase the amount of heat dissipation. As a result, the difference in temperature between the coolant and the refrigerant can be reduced to relieve the difference in thermal strain between the refrigerant tube  61  and the cooling medium tube  71 . In this example, the coolant corresponds to the “high-temperature side fluid”; the cooling medium tube  71  to the “high-temperature side tube”; the cooling medium tube upstream portion  711  of the cooling medium tube  71  to the “high-temperature side tube upstream portion”; and the cooling medium tube downstream portion  712  of the cooling medium tube  71  to the “high-temperature side tube downstream portion”. The refrigerant corresponds to the “low-temperature side fluid”; the refrigerant tube  61  to the “low-temperature side tube”; the refrigerant tube upstream portion  611  of the refrigerant tube  61  to the “low-temperature side tube upstream portion”; and the refrigerant tube downstream portion  612  of the refrigerant tube  61  to the “low-temperature side tube downstream portion”. 
     Second Embodiment 
     In this embodiment, some changes are made to the structure of the heat exchanger  16  of the first embodiment. The detailed structure of a heat exchanger  16  of this embodiment will be described below using  FIGS. 12 to 14 . 
       FIG. 12  shows a perspective view of the contour of the heat exchanger  16  in the first embodiment.  FIG. 13  shows a schematic perspective view for explaining the flows of refrigerant and coolant in the heat exchanger  16 .  FIG. 14  shows a schematic partially exploded perspective view of the heat exchanger  16 .  FIGS. 12 ,  13 , and  14  correspond to  FIGS. 5 ,  10 , and  11  of the first embodiment, respectively. In  FIGS. 12 to 14 , the same or equivalent parts as those in the first embodiment are indicated by the same reference characters. The same goes for all the following drawings. 
     As shown in  FIGS. 12 and 14 , each of the refrigerant tube  61  and the cooling medium tube  71  of this embodiment is formed by bending a flat tube with a flat section in the direction perpendicular to the longitudinal direction. More specifically, the refrigerant tube  61  is bent such that the flat surfaces thereof are opposed to each other, and the cooling medium tube  71  is also bent such that the flat surfaces thereof are opposed to each other. 
     Thus, the refrigerant side turning portion  61   e  of the refrigerant tube  61  and the cooling medium side turning portion  71   e  of the cooling medium tube  71  in this embodiment are formed of the bent portions of the tubes  61  and  71 , respectively. The outside air passages  16   a  in this embodiment are formed not only between the flat surface of the refrigerant tube  61  and the flat surface of the cooling medium tube  71  opposed thereto, but also between the flat surfaces of the opposed refrigerant tubes  61 , and between the flat surfaces of the opposed cooling medium tubes  71 . 
     The outside air passages  16   a  are provided with the outer fins  50  which are the same as in the first embodiment.  FIG. 14  omits the illustration of the outer fins  50  for easy understanding, like  FIG. 11 . 
     As shown in  FIG. 14 , the refrigerant tubes  61  are arranged in two lines along the flow direction A of the outside air. An opening end of one refrigerant tube  61  disposed on the leeward side is in communication with the distribution space  62   b  of the refrigerant side header tank  62 , while an opening end of the other tube  61  disposed on the windward side is in communication with the collection space  62   a  of the refrigerant side header tank  62 . 
     A partition member (not shown) is disposed inside the refrigerant side header tank  62 . The partition member causes the other opening end of the one refrigerant tube  61  disposed on the leeward side to be brought into communication with the other opening end of the other tube  61  disposed on the windward side without communicating with the collection space  62   a  and the distribution space  62   b  inside the refrigerant side header tank  62 . 
     As shown in  FIG. 14 , the cooling medium tubes  71  are arranged in two lines along the flow direction A of the outside air. An opening end of one cooling medium tube  71  disposed on the windward side is in communication with the distribution space  72   b  of the cooling medium side header tank  72 , while an opening end of the other tube  71  disposed on the leeward is in communication with the collection space  72   a  of the cooling medium side header tank  72 . 
     A partition member (not shown) is also disposed inside the cooling medium side header tank  72 . The partition member causes the other opening end of the one cooling medium tube  71  disposed on the windward side to be brought into communication with the other opening end of the other tube  71  disposed on the leeward side without communicating with the collection space  72   a  and the distribution space  72   b  inside the cooling medium side header tank  72 . 
     Thus, as shown in  FIG. 13 , in the heat exchanger  16  of this embodiment, the refrigerant introduced into the distribution space  62   b  of the refrigerant side header tank  62  flows into the refrigerant tube  61  disposed on the leeward side to pass through the refrigerant side turning portion  61   e  of the refrigerant tube  61  disposed on the leeward side, and then returns to the refrigerant side header tank  62 . Then, the refrigerant flows into the refrigerant tube  61  disposed on the windward side to pass through the refrigerant side turning portion  61   e  of the refrigerant side tube  61  disposed on the windward side, and is derived from the collection space  62   a  of the refrigerant side header tank  62 . 
     In contrast, the refrigerant introduced into the distribution space  72   b  of the cooling medium side header tank  72  flows into the cooling medium tube  71  disposed on the windward side to pass through the cooling medium side turning portion  71   e  of the cooling medium tube  71  disposed on the windward side, and then returns to the cooling medium side header tank  72 . Then, the refrigerant flows into the cooling medium tube  71  disposed on the leeward side to pass through the cooling medium side turning portion  71   e  of the cooling medium side tube  71  disposed on the leeward side, and is derived from the collection space  72   a  of the cooling medium side header tank  72 . 
     The structures and operations of other components of the heat pump cycle  10  including the heat exchanger  16  are the same as those of the first embodiment. Thus, like the first embodiment, the heat exchanger  16  of this embodiment can also perform the appropriate heat exchange among three kinds of fluids, refrigerant, coolant, and outside air in each operation of the heat pump cycle  10 . This embodiment can also improve the productivity of the heat exchanger that can exchange heat among the three kinds of fluids without increase in size. 
     Further, the heat exchanger  16  of this embodiment uses as the refrigerant tube  61  and the cooling medium tube  71 , the flat tube that can be formed at low cost by an extrusion process or drawing process. Therefore, this embodiment can further improve the productivity. 
     Third Embodiment 
     The second embodiment uses the flat tube bent with the flat surface parts opposed to each other, as the refrigerant tube  61  and the cooling medium tube  71 , by way of example. In this embodiment, as shown in  FIG. 15 , each tube is bent such that a flat surface on the upstream side of each of the turning portions  61   e  and  71   e  and a flat surface on the downstream side thereof are arranged in two lines on the same plane in the flow direction A of the outside air. 
     In  FIG. 15 , (a) is a front view of the refrigerant tube  61  of this embodiment (cooling medium tube  71 ), and (b) is a side view of the tube for refrigerant.  FIGS. 15(   a ) and  15 ( b ) correspond to  FIGS. 6(   a ) and  6 ( b ) of the first embodiment.  FIGS. 15(   a ) and  15 ( b ) shows the refrigerant tube  61 , while components of the cooling medium tube  71  corresponding to the components of the refrigerant tube  61  are indicated by respective reference numerals within parentheses. 
     The structures and operations of other components of the heat pump cycle  10  including the heat exchanger  16  are the same as those of the first embodiment. Thus, like the first embodiment, the heat exchanger  16  of this embodiment can also perform the appropriate heat exchange among three kinds of fluids, refrigerant, coolant, and outside air in each operation of the heat pump cycle  10 . This embodiment can also improve the productivity of the heat exchanger that can exchange heat among the three kinds of fluids without increase in size. 
     Like the second embodiment, this embodiment can also manufacture the refrigerant tube  61  and the cooling medium tube  71  at low cost, and thus can further improve the productivity. 
     Fourth Embodiment 
     In this embodiment, as shown in the entire configuration diagram of  FIG. 16 , some changes are made to the structure of the heat pump cycle  10  of the first embodiment.  FIG. 16  shows the entire configuration diagram of refrigerant flow paths in the waste heat recovering operation in this embodiment. In the figure, the flow of refrigerant in the heat pump cycle  10  is indicated by a solid line, and the flow of coolant in the coolant circulation circuit  40  is indicated by a dashed arrow. 
     Specifically, in this embodiment, the indoor condenser  12  of the first embodiment is removed, and the compound heat exchanger  16  of the first embodiment is disposed in the casing  31  of the indoor air conditioning unit  30 . The outdoor heat exchanging portion  60  of the first embodiment in the compound heat exchanger  16  serves as the indoor condenser  12 . In the following, a portion of the heat exchanger  16  serving as the indoor condenser  12  is referred to as an “indoor condenser”. 
     In contrast, the outdoor heat exchanging portion  60  is composed of a single heat exchanger for exchanging heat between the refrigerant flowing therethrough and the outside air blown by the blower fan  17 . The structures of other components in this embodiment are the same as those of the first embodiment. In this embodiment, the defrosting operation is not performed, but other operations are performed in the same way as the first embodiment. 
     Thus, during the waste heat recovering operation in this embodiment, the air in the vehicle interior is heated by exchanging heat with the refrigerant discharged from the compressor  11  in the indoor evaporator of the heat exchanger  16 . Further, the air in the vehicle interior heated by the indoor condenser can be heated by exchanging heat with coolant in the radiator  70  of the heat exchanger  16 . 
     The structure of the heat pump cycle  10  of this embodiment can exchange heat between the air in the vehicle interior and the coolant. Even when the operation of the heat pump cycle  10  (specifically, compressor  11 ) is stopped, the heating of the vehicle interior can be achieved. Even when the temperature of the refrigerant discharged from the compressor  11  is low and the heating capacity of the heat pump cycle  10  is low, the heating of the vehicle interior can be achieved. 
     Obviously, the heat exchanger  16  disclosed in the second and third embodiments may be applied to the heat pump cycle  10  of this embodiment. 
     Fifth Embodiment 
     In this embodiment, some changes are made to the structure of the heat exchanger  16  of the first embodiment. The detailed structure of a heat exchanger  16  of this embodiment will be described below using  FIGS. 17 and 18 . 
       FIG. 18  shows a perspective view of the contour of the heat exchanger  16  in this embodiment.  FIG. 18  is a schematic perspective view for explaining the flows of refrigerant and coolant in the heat exchanger  16 .  FIGS. 17 and 18  correspond to  FIGS. 5 and 10  of the first embodiment. For convenience of the description,  FIG. 17  omits the illustration of the tubes  61  and  71  and the outer fins  50  of the heat exchanger  16 . 
     The outdoor heat exchanging portion  60  of the heat exchanger  16  in this embodiment includes a refrigerant side header tank  62  composed of tanks  621  and  622  arranged in two lines along the flow direction A of the outside air. The first refrigerant tank  621  disposed on the upstream side in the flow direction of the outside air of the tanks  621  and  622  in two lines is provided with a partition member  621   c  disposed in the center in the longitudinal direction for partitioning the internal space into two spaces  621   a  and  621   b.    
     The first refrigerant tank  621  is connected to tubes disposed on the windward side in the flow direction A of the outside air among a plurality of refrigerant tube upstream portions  611  and refrigerant tube downstream portions  612 . The tank  621  serves as a collection and distribution tank for collecting and/or distributing the refrigerants flowing through the tubes. 
     One end of the first refrigerant tank  621  in the longitudinal direction is connected to the refrigerant introduction pipe  64   b  for introducing the refrigerant, and the other end of the refrigerant side tank  64  in the longitudinal direction is connected to the refrigerant guiding pipe  64   c  for deriving and guiding the refrigerant. The refrigerant introduction pipe  64   b  is in communication with the distribution space  621   a  of the two spaces  621   a  and  621   b  formed in the first refrigerant tank  621 . The refrigerant guiding pipe  64   c  is in communication with the collection space  621   b  of the two spaces  621   a  and  621   b  formed in the first refrigerant tank  621 . 
     Among the tanks  621  and  622  arranged in two lines and included in the refrigerant side header tank  62 , the second refrigerant tank  622  disposed on the downstream side in the flow direction A of the outside air is connected to the tubes disposed on the leeward side in the flow direction A of the outside air among the plurality of refrigerant tube upstream portions  611  and the refrigerant tube downstream portions  612 . The second refrigerant tank  622  serves as a collection and distribution tank for collecting and/or distributing the refrigerants flowing through the tubes. Both ends of the second refrigerant tank  622  in the longitudinal direction are closed by closing members. 
     A group of the refrigerant tubes  61  for flowing therethrough the refrigerant introduced into the outdoor heat exchanging portion  60  via the refrigerant introduction pipe  64   b  forms an upstream side refrigerant tube group  60   a . Another group of the refrigerant tubes  61  for flowing therethrough the refrigerant from the upstream side refrigerant tube group  60   a  to derive the refrigerant from the refrigerant guiding pipe  64   c  forms a downstream side refrigerant tube group  60   b.    
     In the refrigerant tubes  61  forming the upstream side refrigerant tube group  60   a , the refrigerant tube upstream portion  611  is disposed on the upstream side in the flow direction A of the outside air with respect to the refrigerant tube downstream portion  612 . In the refrigerant tubes  61  forming the downstream side refrigerant tube group  60   b , the refrigerant tube upstream portion  611  is disposed on the downstream side in the flow direction A of the outside air with respect to the refrigerant tube downstream portion  612 . 
     In the outdoor heat exchanging portion  60  of this embodiment, as indicated by a solid arrow in the schematic perspective view of  FIG. 18 , the refrigerant introduced into the distribution space  621   a  of the first refrigerant tank  621  of the header tank  62  via the refrigerant introduction pipe  64   b  flows from the refrigerant tube upstream portion  611  on the windward side in the outside air flow direction A in the upstream side refrigerant tube group  60   a  to the refrigerant side turning portion  61   e . The refrigerant then flows and turns around to the refrigerant tube downstream portion  612  on the leeward side in the outside air flow direction A in the upstream side refrigerant tube group  60   a . The refrigerant flowing from the refrigerant tube downstream portion  612  into the second refrigerant tank  622  flows and turns around from the refrigerant tube upstream portion  611  on the leeward side in the flow direction A of the outside air in the downstream side refrigerant tube group  60   b  to the refrigerant side turning portion  61   e , and the refrigerant tube downstream portion  612  on the windword side in the outside air flow direction A in the downstream side refrigerant tube group  60   b  in that order. 
     Turning back to  FIG. 17 , the radiator  70  of the heat exchanger  16  of this embodiment includes the cooling medium side header tank  72  composed of tanks  721  and  722  arranged in two lines along the flow direction A of the outside air. The first cooling medium tank  721  disposed on the upstream side in the flow direction of the outside air of the tanks  721  and  722  in two lines is provided with a partition member  721   c  disposed in the center in the longitudinal direction for partitioning the internal space into two spaces. 
     The first cooling medium tank  721  is connected to tubes disposed on the windward side in the flow direction A of the outside air among a plurality of the cooling medium tube upstream portions  711  and the cooling medium tube downstream portions  712 . The tank  721  serves as a collection and distribution tank for collecting and/or distributing the refrigerants flowing through the tubes. 
     One end of the first cooling medium tank  721  in the longitudinal direction is connected to the cooling medium introduction pipe  74   b  for introducing the cooling medium, and the other end of the cooling medium side tank  74  in the longitudinal direction is connected to the cooling medium guiding pipe  74   c  for deriving and guiding the cooling medium. The cooling medium introduction pipe  74   b  is in communication with the distribution space  721   a  of the two spaces  721   a  and  721   b  formed in the first cooling medium tank  721 . The cooling medium guiding pipe  74   c  is in communication with the collection space  721   b  of the two spaces  721   a  and  721   b  formed in the first cooling medium tank  721 . 
     Among the tanks  721  and  722  arranged in two lines and included in the cooling medium side header tank  72 , the second cooling medium tank  722  disposed on the downstream side in the flow direction A of the outside air is connected to the tubes disposed on the leeward side in the flow direction A of the outside air among the cooling medium tube upstream portions  711  and the cooling medium tube downstream portions  712 . The second cooling medium tank serves as a collection and distribution tank for collecting and/or distributing the cooling medium flowing through the tubes. Both ends of the second cooling medium tank  722  in the longitudinal direction are closed by closing members. 
     A group of the cooling medium tubes  71  for flowing therethrough the coolant introduced into the radiator  70  via the cooling medium introduction pipe  74   b  forms an upstream side cooling medium tube group  70   a . Another group of the cooling medium tubes  71  for flowing therethrough the coolant from the upstream side cooling medium tube group  70   a  to derive the coolant from the cooling medium guiding pipe  74   c  forms a downstream side cooling medium tube group  70   b.    
     In the cooling medium tubes  71  forming the upstream side cooling medium tube group  70   a , the cooling medium tube upstream portion  711  is placed on the upstream side in the flow direction A of the outside air with respect to the cooling medium tube downstream portion  712 . In the cooling medium tubes  71  forming the downstream side cooling medium tube group  70   b , the cooling medium tube upstream portion  711  is placed on the downstream side in the flow direction A of the outside air with respect to the cooling medium tube downstream portion  712 . 
     In the radiator  70  of this embodiment, as indicated by a chain arrow in the schematic perspective view of  FIG. 18 , the refrigerant introduced into the distribution space  721   a  of the first cooling medium tank  721  of the cooling medium side header tank  72  via the refrigerant  64   b  flows from the cooling medium tube upstream portion  711  on the windward side in the flow direction A of the outside air in the upstream side cooling medium tube group  70   a  to the cooling medium side turning portion  71   e . Then, the refrigerant flows and turns around to the cooling medium tube downstream side  712  on the leeward side in the outside air flow direction in the upstream side cooling medium tube group  70   a . The refrigerant flowing from the cooling medium tube downstream portion  712  into the second cooling medium tank portion  722  flows from the cooling medium tube upstream portion  711  on the leeward side in the outside air flow direction A in the downstream side cooling medium tube group  70   b  to the cooling medium side turning portion  71   e . Then, the refrigerant flows and turns around to the cooling medium tube downstream portion  712  on the windward side in the flow direction A of the outside air in the downstream side cooling medium tube group  70   b.    
     In the heat exchanger  16  of this embodiment, the refrigerant tube upstream portion  611  of the upstream side refrigerant tube group  60   a  and the cooling medium tube upstream portion  711  of the upstream side cooling medium tube group  70   a  are arranged in parallel in the lamination direction of the tubes  61  and  71 . And, the refrigerant tube downstream portion  612  of the upstream side refrigerant tube group  60   a  and the cooling medium tube downstream portion  712  of the upstream side cooling medium tube group  70   a  are arranged in parallel in the lamination direction of the tubes  61  and  71 . 
     In the heat exchanger  16  of this embodiment, the refrigerant tube upstream portion  611  of the downstream side refrigerant tube group  60   b  and the cooling medium tube upstream portion  711  of the downstream side cooling medium tube group  70   b  are arranged in parallel in the lamination direction of the tubes  61  and  71 . And, the refrigerant tube downstream portion  612  of the downstream side refrigerant tube group  60   b  and the cooling medium tube downstream portion  712  of the downstream side cooling medium tube group  70   b  are arranged in parallel in the lamination direction of the tubes  61  and  71 . 
     In the outdoor heat exchanging portion  60 , the refrigerant flows from the downstream side to the upstream side in the flow direction of the outside air in the upstream side refrigerant tube group  60   a , and the refrigerant flows from the downstream side to the upstream side in the flow direction of the outside air in the downstream side refrigerant tube group  60   b . Likewise, in the radiator  70 , the coolant flows from the upstream side to the downstream side in the flow direction of the outside air in the upstream side cooling medium tube group  70   a , and flows from the downstream side to the upstream side in the flow direction of the outside air in the downstream side cooling medium tube group  70   b.    
     Thus, the refrigerant tubes  61  and the cooling medium tubes  71  forming the upstream side refrigerant tube group  60   a  and the upstream side cooling medium tube group  70   a  are designed to allow the refrigerants to flow in the same direction from the windward side to the leeward side along the flow direction A of the outside air. The refrigerant tubes  61  and the cooling medium tubes  71  forming the downstream side refrigerant tube group  60   b  and the downstream side cooling medium tube  70   b , respectively, are designed to allow the refrigerant and the coolant to flow in the same direction from the leeward side to the windward side in the flow direction A of the outside air. 
     The structures and operations of other components of the heat pump cycle  10  including the heat exchanger  16  are the same as those of the first embodiment. Like the first embodiment, the heat exchanger  16  of this embodiment can also perform appropriate heat exchange among three kinds of fluids, including refrigerant, coolant, and outside air in each operation of the heat pump cycle  10 . This embodiment can also improve the productivity of the heat exchanger that can exchange heat among the three kinds of fluids without increase in size. 
     Additionally, in the heat exchanger  16  of this embodiment, the refrigerant tube upstream portion  611  of each refrigerant tube  61  forming the upstream side refrigerant tube group  60   a  is disposed on the upstream side in the flow direction A of the outside air with respect to the refrigerant tube downstream portion  612 . And, the cooling medium tube upstream portion  711  of each cooling medium tube  71  forming the upstream side cooling medium tube group  70   a  is disposed on the upstream side in the flow direction A of the outside air with respect to the cooling medium tube downstream portion  712 . 
     In the operating state in which the refrigerant introduced into the outdoor heat exchanging portion  60  and the cooling medium introduced into the radiator  70  have the temperature higher than that of the outside air, a difference in temperature between the refrigerant and coolant is reduced on the refrigerant upstream side of the upstream side refrigerant tube group  60   a  and on the coolant upstream side of the upstream side cooling medium tube group  70   a . And differences in temperature between the refrigerant and outside air and between the cooling medium and outside air can be ensured, which can increase the amount of heat dissipation. As a result, a difference in thermal strain between the refrigerant tube  61  and the cooling medium tube  71  can be relieved. 
     In the heat exchanger  16  of this embodiment, the refrigerant tube upstream portion  611  of each refrigerant tube  61  forming the downstream side refrigerant tube group  60   b  is disposed on the downstream side in the flow direction A of the outside air with respect to the refrigerant tube downstream portion  612 . And, the cooling medium tube upstream portion  711  of each cooling medium tube  71  forming the downstream side cooling medium tube group  70   b  is disposed on the downstream side in the flow direction A of the outside air with respect to the cooling medium tube downstream portion  712 . 
     In the operating state in which the refrigerant introduced into the outdoor heat exchanging portion  60  and the cooling medium introduced into the radiator  70  have the temperature higher than that of the outside air, the heat contained in the refrigerant and the coolant can be sufficiently dissipated into outside air on the refrigerant downstream side of the downstream side refrigerant tube group  60   b  and on the coolant downstream side of the downstream side cooling medium tube group  70   b . As a result, the performance of the heat exchanger  16  can be improved. 
     As can be seen from the above description, the upstream side refrigerant tube group  60   a  of this embodiment corresponds to an upstream side first tube group described in the accompanying claims. The downstream side refrigerant tube  60   b  of this embodiment corresponds to a downstream side first tube group. The upstream side cooling medium tube group  70   a  of this embodiment corresponds to an upstream side second tube group described in the claims. The downstream side cooling medium tube  70   b  of this embodiment corresponds to a downstream side second tube group. 
     Other Embodiments 
     The present invention is not limited to the above embodiments, and various modifications and changes can be made to the disclosed embodiments without departing from the scope of the invention. 
     (1) In the above embodiments, the heat exchanger  16  has the tank and tube heat exchanger structure including two heat exchanging portions  60  and  70  with the tubes ( 61 ,  71 ) and the collection and distribution tanks ( 62 ,  72 ), by way of example. The structure of each of the heat exchanging portions  60  and  70  is not limited thereto. 
     Alternatively, for example, the heat exchanger may employ a so-called drawn cup heat exchanger structure including lamination of a plurality of sheets of plates via the outer fins  50 . Each plate includes a tube and a tank in communication with the tube which are formed by bonding a pair of plate members with the respective centers aligned with each other. 
     In such a drawn cup heat exchanger structure, the plates are laminated to communicate the tanks of the plates with each other, which can form the structure corresponding to each of the refrigerant side header tank  62  and the cooling medium side header tank  72  described in the above embodiments. 
     (2) In the above embodiments, the plates  63  and  73  are coupled to the tanks  64  and  74 , respectively, which partitions the internal spaces into the collection spaces  62   a  and  72   a , and the distribution spaces  62   b  and  72   b  to thereby form the refrigerant side header tank  62  and the cooling medium side header tank  72 , by way of example. The structures of the header tanks  62  and  72  are not limited thereto. 
     For example, the header tank may be composed of two pipes, and the internal space of each pipe may be a collection space or a distribution space. This can improve the resistance to pressure of each header tank. 
     (3) In the above embodiments, the refrigerant tubes  61  and the cooling medium tubes  71  are alternately laminated or stacked, by way of example. However, the arrangement of the refrigerant tubes  61  and the cooling medium tubes  71  is not limited thereto. 
     For example, in the heat exchanger  16  of the first and third embodiments, as shown in  FIG. 19(   a ), a plurality of (N pieces of) refrigerant tubes  61  may be continuously laminated, and then a plurality of (M pieces of) cooling medium tubes  71  may be continuously laminated. At this time, the number of the cooling tubes  61  may be equal or different to that of the cooling medium tubes  71  continuously laminated thereon. 
     For example, in the heat exchanger  16  of the second embodiment, as shown in  FIGS. 19(   b ) to  19 ( d ), the refrigerant tubes  61  may be positioned on the upstream side with respect to the flow direction A of the outside air, while the cooling medium tubes  71  may be positioned on the downstream side. 
       FIGS. 19(   a ) to  19 ( d ) schematically show the cross-sectional views of the header tank of the heat exchanger  16  in the longitudinal direction. In  FIGS. 19(   a ) to  19 ( d ), for easy understanding, the refrigerant tubes  61  are indicated by hatching with shaded areas, and the cooling medium tubes  71  are indicated by dotted hatching. 
     In the arrangement including the refrigerant tubes  61  placed adjacent to each other, or the cooling medium tubes  71  placed adjacent to each other as shown in  FIGS. 19(   a ) to  19 ( d ), the outer fins  50  may be desirably disposed in a space between the adjacent refrigerant tubes  61 , and between the adjacent cooling medium tubes  71 . 
     In this way, the outer fins  50  are disposed in all spaces formed between each of the tubes  61  and  71 , and the adjacent refrigerant tube  61  or cooling medium tube  71 . Thus, the outer fins  50  promote the heat exchange between the outside air and the fluid (refrigerant or coolant) flowing through the tubes  61  and  71 , and can relieve (reduce) a difference in thermal strain between the refrigerant tube  61  and the cooling medium tube  71 . As a result, the breakdown of the heat exchanger  16  can be suppressed. 
     (4) In the above first embodiment, the cooling medium tube upstream portion  711  of the cooling medium tube  71  among the refrigerant tubes  61  and the cooling medium tubes  71  is positioned on the upstream side in the flow direction A of the outside air with respect to the cooling medium tube downstream portion  712 , by way of example, which does not limit the invention. 
     For example, the refrigerant tube upstream portion  611  of the refrigerant tubes  61  among the refrigerant tubes  61  and the cooling medium tubes  71  may be positioned on the upstream side in the flow direction A of the outside air with respect to the refrigerant tube downstream portion  612 . 
     In the operating state in which the refrigerant introduced into the outdoor heat exchanging portion  60  has the temperature higher than that of each of the cooling medium and the outside air, a difference in temperature between the refrigerant and the outside air can be ensured on the upstream side of the refrigerant flow of the refrigerant tubes  61  to increase the amount of heat dissipation. Thus, the difference in temperature between the refrigerant and coolant can be reduced, which can release the difference in thermal strain between the refrigerant tubes  61  and the cooling medium tubes  71 . In this example, the refrigerant corresponds to a “high-temperature side fluid”; the refrigerant tube  61  to a “high-temperature side tube”; the refrigerant tube upstream portion  611  of the refrigerant tube  61  to a “high-temperature side tube upstream portion”; and the refrigerant tube downstream portion  12  of the refrigerant tube  61  to a “high-temperature side tube downstream portion”. The coolant corresponds to a “low-temperature side fluid”; the cooling medium tube  71  to a “low-temperature side tube”; the cooling medium tube upstream portion  711  of the cooling medium tube  71  to a “low-temperature side tube upstream portion”; and the cooling medium tube downstream portion  712  of the cooling medium tube  71  to a “low-temperature side tube downstream portion”. 
     (5) In the above first embodiment, the refrigerant tube upstream portions  611  of the refrigerant tubes  61  and the cooling medium tube downstream portions  712  of the cooling medium tubes  71  are arranged in the lamination direction of the tubes  61  and  71 . And the refrigerant tube downstream portions  612  and the cooling medium tube upstream portions  711  are arranged in the lamination direction of the tubes  61  and  71 , by way of example. The invention is not limited to the above arrangement. 
     For example, the refrigerant tube upstream portions  611  of the refrigerant tubes  61  and the cooling medium tube upstream portions  711  of the cooling medium tubes  71  may be arranged in the lamination direction of the tubes  61  and  71 , and the refrigerant tube downstream portions  612  and the cooling medium tube downstream portions  712  may be arranged in the lamination direction of the tubes  61  and  71 . 
     In such a structure, the refrigerant flowing through the refrigerant tube  61  and the coolant flowing through the cooling medium tube  71  have the flow directions opposed to each other in the longitudinal direction of the respective tubes  61  and  71 , and the same flow direction in the flow direction of outside air (for example, from the windward side to the leeward side, or the leeward side to the windward side) (which is a partially parallel flow structure). 
     The heat exchanger  16  with such a structure reduces the heat exchanging capacity as compared to the heat exchanger  16  of the first embodiment, but can decrease the difference in temperature between the refrigerant flowing through the refrigerant tubes  61  and the cooling medium flowing through the cooling medium tubes  71  as a whole. 
     Referring to  FIG. 20 , the following will be the reason why the difference in temperature between the refrigerant flowing through the refrigerant tube  61  and the cooling medium flowing through the cooling medium tube  71  can be reduced in the heat exchanger  16  with the partially parallel flow structure.  FIG. 20  is an explanatory diagram for explaining how the difference in structure between various types of heat exchangers affects the difference in temperature between the refrigerant and coolant in each tube. In  FIG. 20 , a solid line schematically indicates a change in temperature of a high-temperature fluid (high-temperature side fluid) of the refrigerant and the coolant (indicating an inflow portion by a black circle and an outflow portion by a black diamond). An alternate long and short dash line schematically indicates a change in temperature of a low-temperature fluid (low-temperature side fluid) in the heat exchanger  16  with a partially parallel flow structure. An alternate long and two short dashes line schematically indicates a change in temperature of a low-temperature fluid in the opposite flow structure (heat exchanger  16  described in the first embodiment). The alternate long and short dash line and the alternate long and two short dashes line respectively show the change in temperature on the following conditions. In the operating state in which the temperature of the outside air is lower than that of each of the refrigerant and the coolant, an outflow temperature Tl 2  of the low-temperature side fluid flowing from the tube using the heat exchanger  16  with the partially parallel flow structure is identical to an outflow temperature Tl 2 ′ of the low-temperature side fluid flowing from the tube using the heat exchanger  16  with the opposite flow structure. 
     As mentioned above, the heat exchanger  16  with the partially parallel flow structure has the heat exchanging capacity reduced as compared to the heat exchanger  16  described in the first embodiment. As indicated by the alternate long and short dash line and the alternate long and two short dashes line in  FIG. 20 , in the heat exchanger  16  with the partially parallel flow structure, the inflow temperature Tl 1  of the low-temperature side fluid flowing into the tubes becomes higher than the inflow temperature Tl 1 ′ of the low-temperature side fluid flowing into the heat exchanger  16  of the first embodiment. 
     That is, the difference in temperature ΔT between the inflow temperature Th 1  of the high-temperature side fluid and the inflow temperature Tl 1  of the low-temperature side fluid flowing into the heat exchanger  16  with the partially parallel flow structure is small as compared to the difference in temperature ΔT′ between the inflow temperature Tl 1  of the high-temperature side fluid and the inflow temperature Tl 1 ′ of the low-temperature side fluid flowing into the heat exchanger  16  of the first embodiment. 
     Thus, the heat exchanger  16  with the partially parallel flow structure can reduce the difference in temperature between the refrigerant flowing through the refrigerant tube  61  and the cooling medium flowing through the cooling medium tube  71  as a whole, as compared to the heat exchanger  16  of the first embodiment. As a result, the heat exchanger can relieve the difference in thermal strain between the refrigerant tube  61  and the cooling medium tube  71 . This embodiment is applied to the operating state in which the temperature of the outside air is lower than that of each of the refrigerant and coolant, but the heat exchanger  16  with the partially parallel flow structure can have the following effect regardless of the relationship between the temperature of outside air and that of refrigerant and coolant. That is, the heat exchanger  16  with the partially parallel flow structure can reduce the difference in temperature between the refrigerant flowing through the refrigerant tube  61  and the cooling medium flowing through the cooking medium tube  71  as a whole as compared to the heat exchanger  16  of the first embodiment. 
     Further, in the heat exchanger  16  with the partially parallel flow structure, the refrigerant tube upstream portion  611  and the cooling medium tube upstream portion  711  are desirably positioned on the upstream side in the flow direction of the outside air with respect to the refrigerant tube downstream portion  612  and the cooling medium tube downstream portion  712 . 
     In the operating state in which the refrigerant introduced into the outdoor heat exchanging portion  60  and the cooling medium introduced into the radiator  70  have the temperature higher than that of the outside air, the heat exchanger can ensure the differences in temperature between the refrigerant and the outside air, and between the coolant and the outside air to thereby increase the amount of heat dissipation. As a result, the difference in thermal strain between the refrigerant tube  61  and the cooling medium tube  71  can be relieved to suppress the breakdown of the heat exchanger  16 . 
     (6) In the above first embodiment, the refrigerant of the heat pump cycle  10  is used as the first fluid, the coolant of the coolant circulation circuit  40  is used as the second fluid, and the outside air blown by the blower fan  17  is used as the third fluid, but the first to third fluids are not limited thereto. For example, like the third embodiment, the air in the vehicle interior may be used as the third fluid. 
     For example, the first fluid may be a high-pressure side refrigerant or a low-pressure side refrigerant in the heat pump cycle  10 . 
     For example, the second fluid may be a coolant for cooling electric devices, such as an engine or an inverter for supplying electric power to an electric motor MG for traveling. Alternatively, the second fluid may be oil for cooling, the second heat exchanging portion may serve as an oil cooler, and the second fluid for use may be a heat storage agent, a cooling storage agent, or the like. 
     The first to third fluids are not limited to fluids whose properties or components are different from each other. The first to third fluids may be fluids which differ in temperature or state, such as a gas phase or a liquid phase even when those fluids have the same properties or components. For example, the first fluid for use may be a high-pressure side refrigerant in the heat pump cycle  10 , and the second fluid for use may be a low-pressure side refrigerant in the heat pump cycle  10 . For example, when the heat exchanger is provided with different circuits adapted for circulating the coolant for cooling the engine and for circulating the coolant for cooling the invertor, the first fluid for use is a coolant for the engine, and the second fluid for use is a coolant for the inverter. 
     The relationship between the temperatures of the first to third fluids is desirably as follows: the temperature of the third fluid is lower than that of one of the first and second fluids having a higher temperature (high-temperature side fluid), and higher than that of the other having a lower temperature (low-temperature side fluid). Such a temperature relationship decreases the temperature of the high-temperature side fluid and increases the temperature of the low-temperature side fluid in the heat exchanger  16 , which can decrease the difference in temperature between the first fluid and the second fluid. As a result, the difference in thermal strain between the tubes  61  and  71  can be relieved to thereby effectively suppress the breakdown of the heat exchanger  16 . 
     When the heat pump cycle  10  to which the heat exchanger  16  of the invention is applied is used in a stationary air conditioner, a cooling storage cabinet, a cooling and heating device for a vending machine, or the like, the second fluid may be a coolant for cooling the engine and electric motor which serve as a driving source of the compressor of the heat pump cycle  10 , as well as other electric devices. 
     In the above embodiments, the heat exchanger  16  of the invention is applied to the heat pump cycle (refrigeration cycle), by way of example. The applications of the heat exchanger  16  of the invention are not limited thereto. That is, the heat exchanger  16  of the invention can be widely applied to any devices for exchanging heat among three kinds of fluids and the like. 
     (7) In the above embodiments, the refrigerant tubes  61  of the outdoor heat exchanging portion  60 , the cooling medium tubes  71  of the radiator  70 , and the outer fins  50  are formed of an aluminum alloy (metal) and brazed together, by way of example. The outer fin  50  may be formed of material with excellent heat conductivity (for example, carbon nanotube, or the like), and may be bonded by any bonding means, such as adhesive or the like. 
       FIG. 21  schematically shows a partial perspective view of a heat exchanger  16  according to another embodiment.  FIGS. 22(   a ),  22 ( b ), and  22 ( c ) are explanatory diagrams for explaining an outer fin  50  in another embodiment.  FIG. 22(   a ) is a partial front view of the outer fin  50 ,  FIG. 22(   b ) is a cross-sectional view taken along the line XXIIB-XXIIB of  FIG. 22(   a ), and  FIG. 22(   c ) is an enlarged view of an XXIIC part of  FIG. 22(   a ). 
     When the outer fin  50  is bonded with the tubes  61  and  71  like the above respective embodiments, as shown in  FIGS. 21 ,  22 ( a ),  22 ( b ), and  22 ( c ), the outer fin  50  is desirably provided with a plurality of slits  50   a  for locally weakening the rigidity of the outer fin  50 . The slit  50   a  can be formed of a through hole penetrating the outer fin  50 , or a cutout formed at the peripheral edge of the outer fin  50 . 
     Thus, each slit  50   a  of the outer fin  50  can absorb the stress acting on the tubes  61  and  71  when there is the difference in thermal strain between the tubes  61  and  71 . Further, the outer fins  50  with the slits  50   a  can suppress the breakdown of the heat exchanger  16  within a partial range when the difference in thermal strain between the tubes  61  and  71  occurs. 
     (8) In the above first embodiment, in the tube and tank temporary fixing step, the refrigerant tubes  61  and the cooling medium tubes  71  are temporarily fixed together with the inner fins  65  and  75  stuck in the plates  61   a ,  61   b ,  71   a , and  71   b , by way of example. Alternatively, the plates  61   a ,  61   b ,  71   a , and  71   b  may be provided with positioning portions for the inner fins  65  and  75 . 
     Such positioning portions may be formed of protrusions that protrude inward, for example, from the refrigerant flow path  61   c , the cooling medium flow path  71   c , the turning portions  61   e  and  71   e , and the enlarging portions  61   f  and  71   f.    
     (9) The above second and third embodiments do not describe the inner fins  65  and  75  disposed inside the refrigerant tubes  61  and the cooling medium tubes  71 . However, when the inner fins  65  and  75  are intended to be employed, the flat tubes are bent, and then the fins are desirably inserted into fluid flow paths on the upstream side and the downstream side of each of the turning portions  61   e  and  71   e . Thus, the inner fins can be prevented from being deformed upon bending the flat tube. 
     (10) In the above embodiments, the electric three-way valve  42  is employed as circuit switching means for switching among the cooling medium circuits of the coolant circulation circuit  40 , by way of example. However, the circuit switching means is not limited thereto. For example, a thermostatic valve may be employed. The thermostatic valve is a cooling medium temperature responsive valve composed of a mechanical system that is designed to open and close a cooling medium passage by displacing a valve body by use of a thermowax (temperature sensing member) whose volume is changed depending on the temperature. Thus, the thermostatic valve can be used to remove the coolant temperature sensor  52 . 
     (11) Although in the above embodiments, the refrigerant for use is the normal flon-based refrigerant by way of example, the kind of the refrigerant is not limited thereto. The refrigerant for use may be natural refrigerant, such as carbon dioxide, or a hydrocarbon-based refrigerant. Further, the heat pump cycle  10  may be a supercritical refrigeration cycle in which the pressure of refrigerant discharged from the compressor  11  is equal to or higher than the critical pressure of the refrigerant. 
     The present invention has been disclosed with reference to the preferred embodiments. However, it is to be understood that the present invention is not limited to the above preferred embodiments and the structures described above. 
     The present invention is intended to cover various modified examples and equivalent arrangements thereto. In addition, other preferred embodiments which includes one additional element or which loses one element with respect to the disclosed embodiments, or various other combinations of the embodiments also fall within the scope and spirit of the present invention.