Abstract:
A vehicle air conditioner for a passenger compartment includes a power source, a radiator provided outside the passenger compartment, a heat medium passage through which heat medium is circulated between the power source and the radiator, a first peltier module having a first peltier device and a first heat exchanger, and a second peltier module having a second peltier device and a second heat exchanger. The first and second peltier devices each has a first surface and a second surface, one of the first surface and the second surface serves to release heat, the other of the first surface and the second surface serves to absorb heat. The first heat exchanger is thermally coupled to the first surface. The second heat exchanger is thermally coupled to the first surface. The heat medium passage is thermally coupled to the second surfaces of the first and second peltier devices.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    The present invention relates to a vehicle air conditioner. 
         [0002]    Japanese Unexamined Patent Application Publication No. 10-35268 discloses a vehicle air conditioner including a waste heat collector, a radiator, a peltier module, and a heat medium passage through which water as a heat medium is circulated. 
         [0003]    The waste heat collector functions to collect waste heat from a vehicle power source such as an electric motor. The peltier module has a peltier device with a first and a second surface one of which serves as heat releasing surface and the other of which serves as heat absorbing surface, a first heat exchanger thermally coupled to the first surface of the peltier device, and a second heat exchanger thermally coupled to the second surface of the peltier device. The heat medium passage connects the waste heat collector, the radiator, and the second heat exchanger of the peltier module. 
         [0004]    In the air conditioner, air conditioning of vehicle passenger compartment is done by switching the heat releasing and absorbing surfaces of the peltier device and also changing the water flow path in the heat medium passage. 
         [0005]    Specifically, when heating the passenger compartment, the peltier device is operated so that the first surface serves as the heat releasing surface and the second surface serves as the heat absorbing surface. The waste heat collector is connected to the second heat exchanger, while the second heat exchanger and the waste heat collector are disconnected from the radiator. Water flowing in the heat medium passage is heated by the heat in the waste heat collector. Heat of the water is absorbed through the second heat exchanger in the second surface of the peltier device. The heat thus absorbed is radiated from the first heat exchanger into the surrounding air. Then the heated air is supplied to the passenger compartment, so that heating of the passenger compartment is accomplished. 
         [0006]    When cooling the passenger compartment, the peltier device is operated so that the first surface serves as the heat absorbing surface and the second surface serves as the heat releasing surface. The radiator is connected to the second heat exchanger, while the second heat exchanger and the radiator are disconnected from the waste heat collector. Heat is absorbed through the first heat exchanger in the first surface of the peltier device and the air around the first exchanger is cooled. The cooled air is supplied to the passenger compartment, so that cooling of the passenger compartment is accomplished. The water in the heat medium passage is heated by the second heat exchanger to which heat is released from the peltier device, and then cooled in the radiator by heat exchange with the air outside the passenger compartment. 
         [0007]    Another known air conditioner is disclosed in Japanese Unexamined Patent Application Publication No. 2010-195287. The air conditioner includes a radiator, a first peltier module, a second peltier module, and a heat medium passage through which water is circulated. The heat medium passages connects the radiator, the first peltier module and the second peltier module. 
         [0008]    When heating the passenger compartment by the air conditioner, the first peltier module is operated so as to absorb heat from the water flowing in the heat medium passage and also release heat to the surrounding air. The heated air is supplied to the passenger compartment, so that heating of the passenger compartment is accomplished. 
         [0009]    When cooling, the second peltier module and the radiator are operated so that the second peltier module releases heat to the water flowing in the heat medium passage and also absorbs heat from the surrounding air. The cooled air is supplied to the passenger compartment, so that cooling of the passenger compartment is accomplished. 
         [0010]    When dehumidifying, the first and second peltier modules and the radiator are operated. Air is cooled and dehumidified by the second peltier module, and then the cooled air is heated by the first peltier module. The air at appropriately adjusted temperature is supplied to the passenger compartment, so that dehumidifying of the passenger compartment is accomplished. 
         [0011]    The air conditioner disclosed in the publication No. 10-35268 is complex in structure and large in size, which is disadvantageous in the installation in a vehicle. In addition, since the air cooled by the peltier module cannot be re-heated, the dehumidification causes a decrease in the efficiency of heating the compartment. 
         [0012]    In the air conditioner disclosed in the publication No. 2010-195287, on the other hand, although the dehumidification does not necessarily cause a decrease in the efficiency of cooling the compartment, the air conditioner requires an additional radiator for releasing heat from a vehicle power source. The provision of plural radiators results in an increased size of the air conditioner, which prevents easy installation of the air conditioner in a vehicle. 
         [0013]    The present invention is directed to providing a vehicle air conditioner that allows efficient air conditioning of a passenger compartment and easy installation in a vehicle. 
       SUMMARY OF THE INVENTION 
       [0014]    In accordance with an aspect of the present invention, a vehicle air conditioner for a passenger compartment of a vehicle includes a power source for driving the vehicle, a radiator provided outside the passenger compartment, a heat medium passage through which heat medium is circulated between the power source and the radiator, a first peltier module having a first peltier device and a first heat exchanger, and a second peltier module having a second peltier device and a second heat exchanger. The first peltier device has a first surface and a second surface, one of the first surface and the second surface serves to release heat, the other of the first surface and the second surface serves to absorb heat. The first heat exchanger is thermally coupled to the first surface. The second peltier device has a first surface and a second surface, one of the first surface and the second surface serves to release heat, the other of the first surface and the second surface serves to absorb heat. The second heat exchanger is thermally coupled to the first surface. The heat medium passage is thermally coupled to the second surface of the first peltier device and the second surface of the second peltier device. 
         [0015]    Other aspects and advantages of the invention will become apparent from the following description, taken in conjunction with the accompanying drawings, illustrating by way of example the principles of the invention. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0016]      FIG. 1  is a schematic view of a vehicle air conditioner according to an embodiment of the present invention; 
           [0017]      FIG. 2  is an enlarged fragmentary view of the air conditioner of  FIG. 1 ; 
           [0018]      FIG. 3  is a schematic view explaining the operation of the air conditioner of  FIG. 1  when heating a vehicle passenger compartment; and 
           [0019]      FIG. 4  is similar to  FIG. 3 , but explaining the operation of the air conditioner when dehumidifying the passenger compartment by re-heating the cooled air. 
       
    
    
     DETAILED DESCRIPTION OF THE EMBODIMENTS 
       [0020]    The following will describe the embodiment of the vehicle air conditioner according to the present invention with reference to the accompanying drawings. The air conditioner of the embodiment is intended for use in a vehicle for providing heating, cooling and dehumidifying of a passenger compartment of the vehicle. 
         [0021]    Referring to  FIG. 1 , the air conditioner includes an engine  3 , a radiator  5 , tubes  7 ,  9 , a first peltier module  11 , and a second peltier module  13 . The first and second peltier modules  11 ,  13  are provided in a duct  15  that is in communication with the passenger compartment. 
         [0022]    The engine  3  is the power source for driving the vehicle. Although not shown in the drawing, the engine  3  has a water jacket where engine coolant flows for cooling the engine  3 . The engine  3  has an Inlet  3 A and an outlet  3 B through which engine coolant flows into and out of the water jacket. The engine  3  may be replaced by an electric motor or a driver circuit such as power control unit (PCU). Alternatively, the engine  3  combined with such electric motor or PCU may be used as the power source. 
         [0023]    The radiator  5  is a device where engine coolant flows and is cooled by heat exchange with the surrounding air. The radiator  5  has an Inlet  5 A and an outlet  5 B through which engine coolant flows into and out of the radiator  5 . An electrically operated fan  5 C is provided adjacent to the radiator  5  and electrically connected to a controller (not shown). Engine coolant corresponds to the heat medium of the present invention. 
         [0024]    The engine  3  and the radiator  5  are connected by the tubes  7 ,  9 . Specifically, the tube  7  connects between the outlet  3 B of the engine  3  and the inlet  5 A of the radiator  5 , and the tube  9  connects between the outlet  5 B of the radiator  5  and the inlet  3 A of the engine  3 . Engine coolant is circulated between the engine  3  and the radiator  5 A through the tubes  7 ,  9 . An electrically operated pump P 1  is provided in the tube  7  and electrically connected to the aforementioned controller. The pump P 1  may be provided in the tube  9 . The tubes  7 ,  9  correspond to the heat medium passage of the present invention. 
         [0025]    Referring to  FIG. 2 , the first peltier module  11  has a first peltier device  17  and a first fin  19 . The first peltier device  17  has a first insulated substrate  21 , a second insulated substrate  23 , and plural thermoelectric transducers  25  held between the first and second insulated substrates  21 ,  23 . In the first peltier device  17 , the first insulated substrate  21  forms a first surface  17 A from which heat is released, and the second insulated substrate  23  forms a second surface  17 B in which heat is absorbed. The first peltier device  17  is electrically connected to the controller. The first peltier device  17  is fixed at the first surface  17 A to the first fin  19  in a thermally coupled manner, and disposed in contact at the second surface  17 B with the tube  9  so that the first peltier module  11  is thermally coupled to the tube  9 . 
         [0026]    The first fin  19  is formed by a plurality of heat radiation plates extending along the direction of air flow in the duct  15  so as to provide a large surface area exposed to the air, specifically, to the outdoor air and the indoor air flowing through the duct  15 , while lowering the air flow resistance. In the duct  15 , heat exchange occurs between the heat radiation plates of the first fin  19  and outdoor or indoor air. The first fin  19  is provided, for example, by a corrugated fin. 
         [0027]    The second peltier module  13  has a second peltier device  27  and a second fin  29 . As with the first peltier device  17 , the second peltier device  27  has a first insulated substrate  21 , a second insulated substrate  23 , and plural thermoelectric transducers  25  held between the first and second insulated substrates  21 ,  23 . In the second peltier device  27 , the first insulated substrate  21  forms a first surface  27 A in which heat is absorbed, and the second insulated substrate  23  forms a second surface  27 B from which heat is released. The second peltier device  27  is electrically connected to the controller. The second pettier device  27  is fixed at the first surface  27 A to the second fin  29  in a thermally coupled manner, and disposed in contact at the second surface  27 B with the tube  9  so that the second peltier module  13  is thermally coupled to the tube  9 . 
         [0028]    The second fin  29  has a structure similar to that of the first fin  19  and also may be provided by a corrugated fin. The first and second fins  19 ,  29  correspond to the first and second heat exchangers, respectively, of the present invention. 
         [0029]    The duct  15  has a cylindrical main portion  31  and two cylindrical branch portions  33 ,  35  branched from the main portion  31  at the upstream end thereof as seen in the air flow direction in the duct  15 . The end of the branch portion  33  remote from the branch forms an indoor air inlet  33 A that is opened to the passenger compartment of the vehicle, and the end of the branch portion  35  remote from the branch forms an outdoor air inlet  35 A that is opened to the outdoor air outside the vehicle. An electrically operated flapper  37  is provided in the part of the duct  15  where the branch portions  33 ,  35  are joined. The main portion  31  is provided therein with an electrically operated fan  31 A and in communication at the downstream side thereof with the passenger compartment. The fan  31 A and the flapper  37  are electrically connected to the controller. The flapper  37 , which corresponds to the selector of the present invention, may be replaced by any suitable valves that are operable to open and close the respective indoor and outdoor air inlets  33 A,  35 A with respect to the main portion  31  of the duct  15 . 
         [0030]    The first and second peltier modules  11 ,  13  are provided in the main portion  31  of the duct  15  in a manner that the first and second peltier modules  11 ,  13  are thermally coupled to the tube  9 . The second peltier module  13  is provided downstream of the first peltier module  11  as seen in the engine coolant flowing direction in the tube  9 . The main portion  31  of the duct  15  has holes  15 A,  15 B through which the tube  9  is inserted. 
         [0031]    In the above-described vehicle air conditioner, while the engine  3  is operating, the pump P 1  and the fan  5 C are operated by the controller so that engine coolant is circulated through the tubes  7 ,  9  in the direction indicated by arrows in  FIG. 3 . Engine coolant heated by the waste heat of the engine  3  flows from the outlet  3 B of the engine  3 , flowing through the tube  7  and then into the inlet  5 A of the radiator  5 . Heat exchange occurs between the engine coolant flowing in the radiator  5  and the air around the radiator  5 , so that the heat of the engine coolant is radiated by the aid of the fan  5 C into the air outside the passenger compartment. The engine coolant thus cooled in the radiator  5  then flows from the outlet  5 B of the radiator  5  through the tube  9  and into the inlet  3 A of the engine  3 , cooling the engine  3 . While the engine  3  is operating, the air conditioner of the present embodiment provide heating, cooling and dehumidifying of the passenger compartment of the vehicle as described below. 
         [0032]    When heating the passenger compartment, the first peltier device  17  of the first peltier module  11  is operated by the controller. The flapper  37  and the fan  31 A are also operated by the controller so that the main portion  31  of the duct  15  is connected to the branch portion  33  but disconnected from the branch portion  35 , as shown in  FIG. 3 , and indoor air is introduced into the main portion  31 . In this case, the second surface  17 B or heat absorbing surface of the first peltier device  17  absorbs heat from the engine coolant flowing in the tube  9 , while the first surface  17 A or heat releasing surface of the first peltier device  17  releases heat to the first fin  19 . As a result, the first fin  19  is heated, and the indoor air in contact with the heated first fin  19  in the main portion  31  is heated, accordingly. The indoor air existing in the passenger compartment has a higher temperature than the outdoor air, and the indoor air is efficiently heated by the first fin  19 . Heated indoor air is supplied by the fan  31 A through the duct  15  to the passenger compartment. In this way, heating of the passenger compartment is done. 
         [0033]    The engine coolant flowing in the tube  9  and cooled by the first peltier device  17  flows into the engine  3  through its inlet  3 A to be used to cool the engine  3 . In the air conditioner of the present embodiment wherein the engine  3  is located downstream of the first peltier module  11  as seen in the engine coolant flowing direction in the tubes  7 ,  9 , the engine  3  can be cooled by the engine coolant cooled by the first peltier device  17  as well as by the radiator  5 . In other word, the engine  3  can be efficiently cooled by utilizing the waste heat of the first peltier module  11  during the heating operation of the air conditioner. 
         [0034]    When cooling the passenger compartment, the second peltier device  27  of the second peltier module  13  is operated, and the flapper  37  and the fan  31 A are operated as in the case of the above heating operation so that indoor air is introduced into the main portion  31  of the duct  15 . In this case, the second surface  27 B of the second peltier device  27  releases heat to the engine coolant flowing in the tube  9 , while the first surface  27 A of the second peltier device  27  absorbs heat from the second fin  29 . As a result, the second fin  29  is cooled, and the indoor air in contact with the second fin  29  in the main portion  31  is cooled. The indoor air existing in the passenger compartment has a lower temperature than the outdoor air, and the indoor air is efficiently cooled by the second fin  29 . Cooled indoor air is supplied to the passenger compartment, so that cooling of the passenger compartment is done. The engine coolant flowing in the tube  9  and receiving heat from the second peltier device  27  is used to cool the engine  3  and then cooled by the radiator  5 . That is, the waste heat of the second peltier module  13  during the cooling operation is released along with the waste heat of the engine  3  into the air outside the passenger compartment. 
         [0035]    When dehumidifying the passenger compartment, both of the first and second peltier modules  11 ,  13  are operated by the controller, as shown in  FIG. 4 . The flapper  37  and the fan  31 A are also operated so that the main portion  31  is connected to the branch portion  35  but disconnected from the branch portion  33  and the outdoor air is introduced into the main portion  31 . In this case, the outdoor air cooled by the second fin  29  and dehumidified is in turn heated by the first fin  19  to an appropriate temperature. The outdoor air which has a lower humidity than the indoor air is efficiently cooled and dehumidified by the second fin  29 . The outdoor air adjusted at an appropriate temperature is supplied to the passenger compartment for dehumidifying of the passenger compartment, as well as for appropriate air-conditioning of the passenger compartment. The engine coolant releasing heat to the first peltier device  17  and receiving heat from the second peltier device  27  while flowing in the tube  9  is introduced into the engine  3  through its inlet  3 A and used to cool the engine  3 . When there is no need to heat the dehumidified outdoor air, no operation of the first pettier module  11  is performed. 
         [0036]    In the vehicle air conditioner of the present embodiment, heating and cooling of the passenger compartment can also be accomplished by using heated outdoor air and cooled outdoor air, respectively, which makes it easy to keep the humidity of the passenger compartment during the heating and cooling operation when the outdoor air has a lower humidity than the indoor air. Dehumidifying of the passenger compartment can also be accomplished by using the dehumidified indoor air. In a weather condition that the outdoor air has a higher humidity than the indoor air, the use of such dehumidified indoor air allows efficient dehumidifying of the passenger compartment and makes it easy to keep the humidity of the passenger compartment by circulating the indoor air between the main portion  31  of the duct  15  and the passenger compartment. The flapper  37  may be positioned so that both of the branch portions  33 ,  35  are connected to the main portion  31  of the duct  15 , which allows air conditioning of the passenger compartment using the outdoor air and the indoor air mixed together in a desired mixing ratio. 
         [0037]    As described above, according to the vehicle air conditioner of the present embodiment, there is no need to change the flow path of the engine coolant flowing in the tubes  7 ,  9  depending on the operating modes, including heating, cooling or dehumidifying of the passenger compartment. In the air conditioner wherein the engine  3  is connected to the tubes  7 ,  9  and cooled by the engine coolant flowing in the tubes  7 ,  9 , not only the waste heat of the first and second peltier modules  11 ,  13  during the air conditioning, but also the waste heat of the engine  3  are transferred by the engine coolant and radiated from the radiator  5  into the air outside the passenger compartment. Thus, the air conditioner of the embodiment requires no additional radiator to cool the engine  3 , which results in a smaller size of the air conditioner. 
         [0038]    Thus, the vehicle air conditioner of the present embodiment allows efficient air conditioning of the passenger compartment and easy installation of the air conditioner in a vehicle. 
         [0039]    Particularly in the air conditioner of the present embodiment wherein second peltier module  13  is provided downstream of the first peltier module  11  as seen in the engine coolant flowing direction in the tube  9 , since the second peltier device  27  releases heat to the engine coolant that has been cooled by the first peltier device  17  when dehumidifying the vehicle passenger compartment, a larger amount of heat is absorbed in the heat absorbing surface of the second peltier device  27  and hence the second fin  29  is sufficiently cooled. The outdoor air is cooled efficiently and dehumidified sufficiently by such cooled second fin  29 , resulting in efficient dehumidification of the passenger compartment. The cooled outdoor air can be re-heated by the first fin  19 , which does not cause a decrease in the efficiency of air conditioning of the passenger compartment. 
         [0040]    In the air conditioner of the present embodiment, the first and second peltier modules  11 ,  13  are provided in the duct  15  that is in communication with the passenger compartment. The duct  15  is provided with the flapper  37  which allows selective supply of the outdoor air or the indoor air to the passenger compartment. Efficient air conditioning of the passenger compartment is accomplished by heating, cooling or dehumidifying the outdoor or the indoor air selected as required. 
         [0041]    It is to be understood that the present invention is not limited to the above-described embodiments, but it may be modified in various ways without departing from the scope of the invention. 
         [0042]    For example, the engine coolant flowing through the tubes  7 ,  9  may be used not only to cool the engine  3  but also to cool any other component such as a battery provided in a vehicle and thermally coupled to the tubes  7 ,  9 . 
         [0043]    The number of the first peltier modules  11  and of the second peltier modules  13  may be two or more. The number of the first peltier module  11  and the number of the second peltier module  13  need not necessarily be the same, but they may be different from each other. 
         [0044]    The first fin  19  and the second fin  29  may be replaced by a first heat exchanger and a second heat exchanger, respectively, through which water circulates. In such a case, the water flowing in the first heat exchanger receives heat from the first peltier device  17  and hence is heated. Outdoor air or indoor air in the main portion  31  of the duct  15  is heated by heat exchange with such heated water. Similarly, the water flowing in the second heat exchanger releases heat to the second peltier device  27  and is cooled. Outdoor air or indoor air in the main portion  31  of the duct  15  is cooled by heat exchange with such cooled water. 
         [0045]    The present invention is applicable to an air conditioner for use in an engine powered vehicle, a hybrid vehicle driven by an engine and an electric motor, and an electric vehicle driven by an electric motor.