Abstract:
A vehicle air-conditioning device is provided that makes it possible to avoid the occurrence of condensation at a heat exchanger, and to avoid decreases in the heat exchange efficiency of the heat exchanger caused by uneven temperature distribution in the heat exchanger itself. This vehicle air-conditioning device employs a configuration comprising: a heat exchanger that performs heat exchange between air passing through a first flow path and air flowing through a second flow path; and a switching means that alternately switches either the first flow path or the second flow path from a discharge path that discharges the air inside the vehicle toward the outside of the vehicle to an intake path that guides air from outside of the vehicle into the vehicle, and switches the other flow path from the intake path to the discharge path.

Description:
TECHNICAL FIELD 
       [0001]    The present invention relates to a vehicle air-conditioning apparatus. 
       BACKGROUND ART 
       [0002]    Conventionally, as illustrated in  FIG. 20 , there is known sensible heat exchanger  11  that includes two flow paths A and B (respectively indicated by the solid and dashed arrows). Sensible heat exchanger  11  can move heat from one flow path A to the other flow path B when warm air flows through one flow path A and cold air flows through the other flow path B. 
         [0003]    The heat exchanger is installed in a vehicle air-conditioning apparatus, for example, and is used to replace air inside a vehicle interior (referred to as internal air) and air outside a vehicle (referred to as external air) without discharging the heat inside the vehicle interior to the outside of the vehicle when the inside of the vehicle interior is ventilated (for example, see PTL 1). 
         [0004]    In the vehicle air-conditioning apparatus of the related art, the flow path A and flow path B are fixedly used to let external air and internal air to pass through the flow path A and flow path B, respectively. 
       CITATION LIST 
     Patent Literature 
       [0000]    
       
         PTL 1 
       
     
       SUMMARY OF INVENTION 
     Technical Problem 
       [0006]    In the vehicle air-conditioning apparatus of the related art, since one of the flow paths is fixedly used to let the external air passes through in the heat exchanger as described above, condensation sometimes occurs at a position close to an external air inlet when the temperature of the external air is low. When the condensation occurs, the flow path is blocked by the condensation, and hence a problem arises in that the ventilation amount and the heat exchange efficiency of the heat exchanger are reduced. 
         [0007]    Further, in the vehicle air-conditioning apparatus of the related art, since the intake flow path taking the external air and the exhaust flow path discharging the internal air are fixedly used in the heat exchanger, the temperature distribution of the heat exchanger becomes non-uniform when the ventilation is continuously performed. Then, when the non-uniformity of the temperature distribution increases, a problem arises in that the heat exchange efficiency of the heat exchanger is reduced. 
         [0008]    An object of the invention is to provide a vehicle air-conditioning apparatus capable of preventing a reduction of a heat exchange efficiency of a heat exchanger caused by the condensation of the heat exchanger and the non-uniform temperature distribution of the heat exchanger. 
       Solution to Problem 
       [0009]    A vehicle air-conditioning apparatus according to an aspect of the present invention includes: a heat exchanger that performs heat exchange between air passing through a first flow path and air passing through a second flow path; and a switching section that alternatively switches one of the first flow path and the second flow path from an exhaust flow path to an intake flow path and the other one of the first flow path and the second flow path from the intake flow path to the exhaust flow path, internal air from a vehicle interior being discharged to the outside of the vehicle interior through the exhaust flow path and external air from the outside of the vehicle interior being introduced into the vehicle interior through the intake flow path. 
       Advantageous Effects of Invention 
       [0010]    According to the invention, the intake flow path and the exhaust flow path of the heat exchanger are alternately switched by the switching section. Accordingly, it is possible to prevent the inside of the flow path of the heat exchanger from being condensed and to avoid the temperature distribution of the heat exchanger from becoming largely non-uniform. Accordingly, it is possible to prevent a reduction of the heat exchange efficiency of the heat exchanger caused by the occurrence of the condensation or the non-uniformity of the temperature distribution. 
     
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         [0011]      FIG. 1  is a configuration diagram illustrating a heat pump part of an air-conditioning apparatus of an embodiment of the invention; 
           [0012]      FIG. 2  is a configuration diagram illustrating a ventilation facility of an air-conditioning apparatus of Embodiment 1; 
           [0013]      FIG. 3  is a diagram illustrating an operation example of an external air introduction mode of the ventilation facility of Embodiment 1; 
           [0014]      FIG. 4  is a diagram illustrating a first operation example of an internal air introduction mode of the ventilation facility of Embodiment 1; 
           [0015]      FIG. 5  is a diagram illustrating a second operation example of the internal air introduction mode of the ventilation facility of Embodiment 1; 
           [0016]      FIG. 6  is a configuration diagram illustrating a ventilation facility of an air-conditioning apparatus of Embodiment 2; 
           [0017]      FIG. 7  is a diagram illustrating an operation example of the ventilation facility of Embodiment 2; 
           [0018]      FIG. 8  is a configuration diagram illustrating a ventilation facility of an air-conditioning apparatus of Embodiment 3; 
           [0019]      FIG. 9  is a diagram illustrating an operation example of an external air introduction mode of the ventilation facility of Embodiment 3; 
           [0020]      FIG. 10  is a diagram illustrating a first operation example of an internal air circulation mode of the ventilation facility of Embodiment 3; 
           [0021]      FIG. 11  is a diagram illustrating a second operation example of the internal air circulation mode of the ventilation facility of Embodiment 3; 
           [0022]      FIG. 12  is a configuration diagram illustrating a ventilation facility of an air-conditioning apparatus of Embodiment 4; 
           [0023]      FIG. 13  is a diagram illustrating an operation example of an external air introduction mode of the ventilation facility of Embodiment 4; 
           [0024]      FIG. 14  is a diagram illustrating a first operation example of an internal air circulation mode of the ventilation facility of Embodiment 4; 
           [0025]      FIG. 15  is a diagram illustrating a second operation example of the internal air circulation mode of the ventilation facility of Embodiment 4; 
           [0026]      FIG. 16  is a configuration diagram illustrating a ventilation facility of an air-conditioning apparatus of Embodiment 5; 
           [0027]      FIG. 17  is a diagram illustrating an operation example of an external air introduction mode of the ventilation facility of Embodiment 5; 
           [0028]      FIG. 18  is a diagram illustrating a first operation example of an internal air introduction mode of the ventilation facility of Embodiment 5; 
           [0029]      FIG. 19  is a diagram illustrating a second operation example of the internal air introduction mode of the ventilation facility of Embodiment 5; and 
           [0030]      FIG. 20  is a perspective view illustrating a configuration of a heat exchanger. 
       
    
    
     DESCRIPTION OF EMBODIMENTS 
       [0031]    Hereinafter, embodiments of the invention will be described in detail with reference to the drawings. 
       Embodiment 1 
       [0032]      FIG. 1  is a configuration diagram illustrating a heat pump part of an air-conditioning apparatus of an embodiment of the invention, and  FIG. 2  is a configuration diagram illustrating a ventilation facility of an air-conditioning apparatus of Embodiment 1. 
         [0033]    The air-conditioning apparatus of the embodiment includes the heat pump having a configuration illustrated in  FIG. 1  and the ventilation facility illustrated in  FIG. 2 . 
         [0034]    The heat pump is equipped with compressor  8  that compresses a cooling medium, condenser  13  that liquefies the cooling medium, evaporator  2  that evaporates the cooling medium, and expansion valve  4  that depressurizes the cooling medium. Further, the heat pump is equipped with four-way valve  5  that switches the cooling medium flowing direction in order to switch between a cooling operation and a heating operation. 
         [0035]    The ventilation facility includes sensible heat exchanger  11  as a heat exchanger, two internal air flow paths  15  in communication with a vehicle interior, fan  16  that causes air to flow through two internal air flow paths  15 , switching valves  17  and  18 , and opening valves  19  and  20 . 
         [0036]    As illustrated in  FIG. 20  as well, sensible heat exchanger  11  includes therein a first flow path (A) and a second flow path (B), and causes air to flow to each of the flow paths while moving heat from one flow path to the other flow path when warm air flows through one flow path and cold air flows through the other flow path. The first flow path and the second flow path are respectively indicated by the solid line and the dotted line in  FIGS. 2 to 19 . By the above-described action, in a case where the inside of the vehicle interior is warm and the outside of the vehicle interior is cold, the air inside the vehicle interior (referred to as the internal air) can be ventilated by the air outside the vehicle (referred to as the external air) while the heat inside the vehicle interior remains without being discharged to the outside of the vehicle interior significantly. Here, the heat exchange efficiency is about 70%, and the temperature of the exhaust air from sensible heat exchanger  11  is higher than that of the external air. 
         [0037]    The first flow path and the second flow path of sensible heat exchanger  11  are respectively connected to two internal air flow paths  15 . 
         [0038]    Switching valve  17  is a valve that switches a connection destination of the first flow path of sensible heat exchanger  11  between the intake vent (the external air intake vent or the vehicle interior air intake vent) and the flow path connected to condenser  13 . 
         [0039]    Switching valve  18  is a valve that switches a connection destination of the second flow path of sensible heat exchanger  11  between the intake vent (the external air intake vent or the vehicle interior air intake vent) and the flow path communicating with condenser  13 . 
         [0040]    Opening valve  19  is a valve that switches between the opened state and the closed state of the vehicle interior air intake vent with respect to the intake side of the first flow path of sensible heat exchanger  11 . Opening valve  20  is a valve that switches between the opened state and the closed state of the vehicle interior air intake vent with respect to the intake side of the second flow path of sensible heat exchanger  11 . 
         [0041]    Various valves including switching valves  17  and  18  and opening valves  19  and  20  may be opened and closed by an actuator in an electric control manner or may be opened and closed in a mechanical control manner. Further, a configuration may be employed in which sensors for detecting a temperature, humidity, cloudiness, and the like are provided and a controller determines the state of various valves appropriate for the vehicle environment based on the sensor output. Then, the controller may be configured to control the operation of various valves in an electric control manner. The same applies to various valves of Embodiments 2 to 5. 
         [0042]    Evaporator  2  and an interior condenser (not illustrated) are disposed at the inner end of internal air flow path  15 . The interior condenser has a configuration different from condenser  13 , and is used to heat the air dehumidified by evaporator  2  during the dehumidification and heat operation. This configuration is the same even in the air-conditioning apparatuses of Embodiments 2 to 5 to be described hereinafter. Furthermore, evaporator  2  and the interior condenser may be disposed in a different manner. 
         [0043]    The ventilation facility of Embodiment 1 can be applied to not only a hybrid vehicle in which condenser  13  needs to be disposed at the front side of the vehicle, but also an electric vehicle in which the flexibility in placement of condenser  13  is high. In the hybrid vehicle, since a radiator is disposed at the front side of the vehicle and condenser  13  needs to close to the radiator, condenser  13  needs to be disposed at the front side of the vehicle. 
         [0044]    [Operation of External Air Introduction Mode] 
         [0045]      FIG. 3  is a diagram illustrating an operation example of an external air introduction mode of the ventilation facility of Embodiment 1. 
         [0046]    In the ventilation facility of Embodiment 1, in a case where the heat operation of the heat pump and the ventilation inside the vehicle interior by the external air are performed, the switching of switching valves  17  and  18  and the switching of the blowing direction of fan  16  are intermittently repeated (for example, at a predetermined interval or a timing according to the device or the peripheral environment) as illustrated in  FIGS. 2 and 3 . 
         [0047]    By such an operation, the external air and the internal air are switched through sensible heat exchanger  11  while the intake flow path and the exhaust flow path of sensible heat exchanger  11  are alternately switched. Further, the air discharged through sensible heat exchanger  11  (that is, the exhaust air having a temperature higher than that of the external air) is sent into condenser  13 . 
         [0048]    [Operation of Internal Air Introduction Mode] 
         [0049]      FIGS. 4 and 5  are diagrams illustrating first and second operation examples of an internal air introduction mode of the ventilation facility of Embodiment 1. 
         [0050]    The internal air introduction mode is an operation mode in which opening valves  19  and  20  are opened at an appropriate timing so that the entire air taken into sensible heat exchanger  11  becomes the air inside the vehicle interior or the air inside the vehicle interior is included in the air taken into sensible heat exchanger  11  by a predetermined ratio. 
         [0051]    In the internal air introduction mode, when switching valve  17  connects the first flow path of sensible heat exchanger  11  to the intake vent as illustrated in  FIG. 4 , opening valve  19  is switched to open the vehicle interior air intake vent. 
         [0052]    Further, in the internal air introduction mode, when switching valve  18  connects the second flow path of sensible heat exchanger  11  to the intake vent as illustrated in  FIG. 5 , opening valve  20  is switched to open the vehicle interior air intake vent. 
         [0053]    Then, the state of  FIG. 4  and the state of  FIG. 5  are switched intermittently and repeatedly. 
         [0054]    By such an operation, the internal air is circulated through sensible heat exchanger  11  while the intake flow path and the exhaust flow path of sensible heat exchanger  11  are alternately switched. Further, the air discharged through sensible heat exchanger  11  is sent to condenser  13 . 
         [0055]    Furthermore, since the humidity inside the vehicle interior increases when the internal air introduction mode is maintained for a long period of time, the internal air introduction mode may be performed together with the external air introduction mode. 
         [0056]    Further, in the internal air introduction mode, opening valves  19  and  20  may not be entirely opened to the vehicle interior air intake vent, but both the external air intake vent and the vehicle interior air intake vent may be opened to the intake vent of sensible heat exchanger  11  by a predetermined ratio. In this case, the low-temperature external air and the high-temperature internal air may be taken into sensible heat exchanger  11  while being mixed using a predetermined ratio. However, in this case, the external air intake vent and the vehicle interior air intake vent need to be maintained in a negative pressure state so that the external air does not directly flow from the external air intake vent to the vehicle interior air intake vent. 
         [0057]    [Effect] 
         [0058]    According to the air-conditioning apparatus of Embodiment 1, the exhaust air flow path and the intake air flow path of sensible heat exchanger  11  are alternately switched in the external air introduction mode. Accordingly, it is possible to prevent the inside of the flow path of sensible heat exchanger  11  from being condensed and frozen and to prevent the temperature distribution of sensible heat exchanger  11  from becoming largely non-uniform. Accordingly, it is possible to prevent a problem in which the heat exchange efficiency of sensible heat exchanger  11  is reduced due to the occurrence of the condensation or the non-uniformity of the temperature distribution. 
         [0059]    Further, according to the air-conditioning apparatus of Embodiment 1, it is possible to stably send the exhaust air having a remaining heat to condenser  13  by sensible heat exchanger  11  whose heat exchange efficiency is appropriately maintained in the external air introduction mode. That is, it is possible to transmit the heat of the exhaust air of sensible heat exchanger  11 , which is uselessly wasted in the past, to condenser  13 . Thus, in a case where the temperature is not so low because of the heat of the exhaust air, the frost formation of condenser  13  may be prevented or condenser  13  may be defrosted. Further, even in a case where prevention of frost formation of condenser  13  or the defrosting process thereof is performed by the other means such as a heater due to a low temperature, the power consumption may be reduced by the amount of the heat of the exhaust air. 
         [0060]    Further, according to the air-conditioning apparatus of Embodiment 1, since the air which is warmer than the external air may be sent to condenser  13  in the external air introduction mode, a large amount of heat may be supplied to the cooling medium passing through condenser  13 . Accordingly, the heating ability of the heat pump may be improved. 
         [0061]    Further, according to the air-conditioning apparatus of Embodiment 1, only the internal air having a high temperature may flow to sensible heat exchanger  11  in the internal air introduction mode. Thus, it is possible to prevent a situation where sensible heat exchanger  11  is extremely cooled by the external air and hence the heat exchange efficiency is reduced. 
         [0062]    Accordingly, according to the air-conditioning apparatus of Embodiment 1, it is possible to appropriately control the heat exchange between the inside of the vehicle interior and the outside of the vehicle by stably operating sensible heat exchanger  11  and the heat pump. Further, it is also possible to appropriately control the humidity exchange between the inside of the vehicle interior and the outside of the vehicle by stably operating the heat pump. 
       Embodiment 2 
       [0063]      FIG. 6  is a configuration diagram illustrating a ventilation facility of an air-conditioning apparatus of Embodiment 2.  FIG. 7  is a diagram illustrating an operation example of the ventilation facility of Embodiment 2. 
         [0064]    The ventilation facility of Embodiment 2 has a configuration in which sensible heat exchanger  11  and condenser  13  are disposed in a close state so as to be configured as a unit corresponding to heat exchanger unit  12 . 
         [0065]    Heat exchanger unit  12  has a configuration in which the flow path inside condenser  13  is divided into two compartments, the flow path of one compartment is connected to the first flow path of sensible heat exchanger  11 , and the flow path of the other compartment inside condenser  13  is connected to the second flow path of sensible heat exchanger  11 . The flow path of condenser  13  is formed so that the air flowing through the flow paths of two compartments is barely mixed with each other inside condenser  13 . 
         [0066]    The ventilation facility of Embodiment 2 has a configuration in which the first flow path and the second flow path of sensible heat exchanger  11  of heat exchanger unit  12  are respectively connected to two internal air flow paths  15  and one end side of condenser  13  is connected to the external air side flow path passing through the outside of the vehicle. Fan  16  has the same configuration as that of Embodiment 1. 
         [0067]    The ventilation facility of Embodiment 2 is applied to the electric vehicle having a high flexibility in placement of condenser  13 . The same applies to the ventilation facilities of Embodiments 3 to 5 below. 
         [0068]    [Operation of Ventilation Mode] 
         [0069]    In the ventilation facility of Embodiment 2, in a case where the heat operation of the heat pump and the ventilation inside the vehicle interior by the external air are performed, the blowing direction of fan  16  is switched so as to be intermittently and repeatedly inversed as illustrated in  FIGS. 6 and 7 . 
         [0070]    By such an operation, the external air and the internal air may be replaced through sensible heat exchanger  11  while the intake flow path and the exhaust flow path of sensible heat exchanger  11  are alternately switched. Further, the air that is discharged through sensible heat exchanger  11  (that is, the exhaust air that has a temperature higher than that of the external air) is alternately sent to two compartments of the flow path of condenser  13 . 
         [0071]    Furthermore, in the air-conditioning apparatus of Embodiment 2, the timing of inversing the blowing direction may be, for example, a timing of a predetermined interval or a timing according to the situation of the apparatus through detection of the situation of the apparatus by a sensor or the like. For example, when a temperature sensor is provided in each compartment of condenser  13  and the temperature of one of the compartments decreases based on the temperature detected by the temperature sensor, a control section may switch the blowing direction so that the exhaust air is sent to the compartment. The same applies to Embodiments 3 to 5. 
         [0072]    [Effect] 
         [0073]    Accordingly, according to the air-conditioning apparatus of Embodiment 2, since the exhaust air flow path and the intake air flow path of sensible heat exchanger  11  are alternately switched, it is possible to prevent the inside of the flow path of sensible heat exchanger  11  from being condensed and frozen and to prevent the temperature distribution of sensible heat exchanger  11  from becoming largely non-uniform. Accordingly, it is possible to prevent a situation where the heat exchange efficiency of sensible heat exchanger  11  is reduced due to the occurrence of the condensation or the non-uniformity of the temperature distribution. 
         [0074]    Further, according to the air-conditioning apparatus of Embodiment 2, it is possible to stably send the exhaust air having a remaining heat to condenser  13  by sensible heat exchanger  11  whose heat exchange efficiency is appropriately maintained. That is, it is possible to transmit the heat of the exhaust air of sensible heat exchanger  11 , which is uselessly wasted in the past, to condenser  13 . Thus, in a case where the temperature is not so low because of the heat of the exhaust air, the frost formation of condenser  13  can be prevented or condenser  13  can be defrosted. Further, even in a case where prevention of the frost formation of condenser  13  or the defrosting process thereof is performed by the other means such as a heater due to the low temperature, the power consumption may be reduced by the amount of the heat of the exhaust air. 
         [0075]    Further, according to the air-conditioning apparatus of Embodiment 2, since a long flow path is not interposed between sensible heat exchanger  11  and condenser  13 , the heat of the exhaust air does not escape to the other part, and the heat of the exhaust air may be directly transmitted to condenser  13 . 
       Embodiment 3 
       [0076]      FIG. 8  is a configuration diagram illustrating a ventilation facility of an air-conditioning apparatus of Embodiment 3. 
         [0077]    The ventilation facility of Embodiment 3 has a configuration in which opening-closing valves  21  and  22  are additionally provided in the ventilation facility of Embodiment 2. 
         [0078]    Opening-closing valves  21  and  22  are valves that are provided inside the flow path so as to open and close the flow path extending from condenser  13  to the outside of the vehicle. 
         [0079]    Accordingly, in the ventilation facility of Embodiment 3, when opening-closing valves  21  and  22  are closed, the positions of opening-closing valves  21  and  22  become the boundary between the vehicle interior side and the external air side. 
         [0080]    [Operation of External Air Introduction Mode] 
         [0081]      FIG. 9  is a diagram illustrating an operation example of an external air introduction mode of a ventilation facility of Embodiment 3. 
         [0082]    In the external air introduction mode, opening-closing valves  21  and  22  are normally opened as illustrated in  FIGS. 8 and 9 . The operation and action in this case are the same as those of the ventilation mode of the ventilation facility of Embodiment 2. 
         [0083]    [Operation of Internal Air Circulation Mode] 
         [0084]      FIGS. 10 and 11  are diagrams illustrating first and second operation examples of an internal air circulation mode of the ventilation facility of Embodiment 3. 
         [0085]    In the internal air circulation mode, opening-closing valves  21  and  22  may be switched to the closed state as illustrated in  FIGS. 10 and 11 . Further, in a state where opening-closing valves  21  and  22  are normally closed, the blowing direction of fan  16  is switched so as to be intermittently (for example, at every predetermined interval) and repeatedly inversed. 
         [0086]    By such an operation, in the ventilation facility of Embodiment 3, the internal air which is taken from one of two internal air flow paths  15  passes through one flow path of sensible heat exchanger  11  and one compartment of condenser  13 , and changes the direction back to the origin at the front side of opening-closing valves  21  and  22 . Then, the internal air that has changed the direction back to the origin passes through the other compartment of condenser  13  and the other flow path of sensible heat exchanger  11 , and is returned into the vehicle interior through the other of internal air flow paths  15 . 
         [0087]    Further, when the blowing direction of fan  16  is inversed, the flow of the internal air passing through internal air flow path  15 , sensible heat exchanger  11 , and condenser  13  is also inversed. 
         [0088]    Furthermore, since the humidity inside the vehicle interior increases when the internal air circulation mode is maintained for a long period of time, the internal air circulation mode may be performed together with the external air introduction mode. 
         [0089]    [Effect] 
         [0090]    According to the air-conditioning apparatus of Embodiment 3, the same operation and action as those of Embodiment 2 may be obtained by the operation of the external air introduction mode. Further, even when the temperature of the external air is extremely low, the high-temperature internal air may be sent to condenser  13  by the operation of the internal air circulation mode, and hence the frost formation of condenser  13  may be prevented or the defrosting process thereof may be performed. Further, such an internal air circulation mode may be generated by a simple process of closing opening-closing valves  21  and  22 . Moreover, since such an internal air circulation mode may increase the air-tightness inside the vehicle interior, the temperature inside the vehicle interior may be maintained. 
         [0091]    In addition, since the external air is interrupted in the internal air circulation mode, a large amount of heat may be supplied to the cooling medium passing through condenser  13 . Accordingly, the heating ability of the heat pump may be improved. 
       Embodiment 4 
       [0092]      FIG. 12  is a configuration diagram illustrating a ventilation facility of an air-conditioning apparatus of Embodiment 4. 
         [0093]    The ventilation facility of Embodiment 4 has a configuration in which opening-closing valves  23  and  24  and bypass flow path  27  are additionally provided in the ventilation facility of Embodiment 2. 
         [0094]    Opening-closing valves  23  and  24  are valves that switch the closed state and the opened state of internal air flow path  15  between sensible heat exchanger  11  and fan  16 . 
         [0095]    Bypass flow path  27  is a flow path that opens two internal air flow paths  15 , and is installed near fan  16  as compared to opening-closing valves  23  and  24  while opening-closing valves  23  and  24  are closed. 
         [0096]    [Operation of External Air Introduction Mode] 
         [0097]      FIG. 13  is a diagram illustrating an operation example of an external air introduction mode of a ventilation facility of Embodiment 4. 
         [0098]    In the external air introduction mode, opening-closing valves  23  and  24  are always opened as illustrated in  FIGS. 12 and 13 . The operation and action in this case are substantially the same as those of the ventilation mode of the ventilation facility of Embodiment 2. 
         [0099]    Furthermore, in the external air introduction mode, a part of the air of internal air flow path  15  is circulated through bypass flow path  27 . Furthermore, when there is a need to completely stop the circulation, a valve opening and closing bypass flow path  27  may be provided so as to close bypass flow path  27 . 
         [0100]    [Operation of Internal Air Circulation Mode] 
         [0101]      FIGS. 14 and 15  are diagrams illustrating first and second operation examples of an internal air circulation mode of a ventilation facility of Embodiment 4. 
         [0102]    In the internal air circulation mode, opening-closing valves  23  and  24  may be switched to the closed state as illustrated in  FIGS. 14 and 15 . Further, the blowing direction of fan  16  may be switched so as to be intermittently (for example, at every predetermined interval) and repeatedly inversed. 
         [0103]    By such an operation, in the ventilation facility of Embodiment 4, the internal air that is taken from one of two internal air flow paths  15  escapes to the other thereof through bypass flow path  27 , and is returned into the vehicle interior. 
         [0104]    This internal air circulation mode is an operation mode that is employed when the operation of the heat pump is stopped. 
         [0105]    [Effect] 
         [0106]    According to the air-conditioning apparatus of Embodiment 4, the same operation and action as those of Embodiment 2 may be obtained by the operation of the external air introduction mode. Further, when the operation of the heat pump is stopped, no useless heat exchange occurs between the internal air streams by the operation of the internal air circulation mode, and hence the internal air may be circulated while the air-tightness inside the vehicle interior is highly maintained and the temperature inside the vehicle interior is maintained. Further, such an internal air circulation mode may be generated by a simple process of closing opening-closing valves  23  and  24 . Further, in the internal air circulation mode, since the internal air is circulated without passing through sensible heat exchanger  11  and condenser  13  having a high resistance with respect to the air, the power consumption of fan  16  may be reduced. 
       Embodiment 5 
       [0107]      FIG. 16  is a configuration diagram illustrating a ventilation facility of an air-conditioning apparatus of Embodiment 5. 
         [0108]    The ventilation facility of Embodiment 5 has a configuration in which opening valves  25  and  26  and the flow path connected to the vehicle interior air intake vent are additionally provided in the ventilation facility of Embodiment 3. 
         [0109]    Opening valves  25  and  26  are valves that respectively switch the opened state and the closed state of the vehicle interior air intake vent with respect to the flow paths of two compartments of condenser  13 . 
         [0110]    [Operation of External Air Introduction Mode] 
         [0111]      FIG. 17  is a diagram illustrating an operation example of an external air introduction mode of a ventilation facility of Embodiment 5. 
         [0112]    In the external air introduction mode, opening valves  25  and  26  close the vehicle interior air intake vent as illustrated in  FIGS. 16 and 17 . The operation and action in this case are the same as those of the ventilation mode of the ventilation facility of Embodiment 2. 
         [0113]    [Operation of Internal Air Introduction Mode] 
         [0114]      FIGS. 18 and 19  are diagrams illustrating first and second operation examples of an internal air introduction mode of a ventilation facility of Embodiment 5. 
         [0115]    The internal air introduction mode is an operation mode in which the air inside the vehicle interior is included in the air taken to sensible heat exchanger  11  through condenser  13  when opening valves  25  and  26  are opened at an appropriate timing. 
         [0116]    In the internal air introduction mode, opening valve  25  closes the vehicle interior air intake vent and opening valve  26  opens the vehicle interior air intake vent in a period for which the blowing direction of fan  16  is the direction in which air is taken from the second flow path of sensible heat exchanger  11  as illustrated in  FIG. 18 . When opening valve  26  is opened, the entire part of one compartment of the flow path of condenser  13  is connected to the flow path of the vehicle interior air intake vent, and hence the internal air is suctioned into the second flow path of sensible heat exchanger  11 . 
         [0117]    Further, in the internal air introduction mode, opening valve  26  closes the vehicle interior air intake vent and opening valve  25  opens the vehicle interior air intake vent in a period for which the blowing direction of fan  16  is the direction in which air is taken from the first flow path of sensible heat exchanger  11  as illustrated in  FIG. 19 . When opening valve  25  is opened, the entire part of the other compartment of the flow path of condenser  13  is connected to the flow path of the vehicle interior air intake vent, and hence the internal air is taken into the first flow path of the sensible heat exchanger. 
         [0118]    Then, the state of  FIG. 18  and the state of  FIG. 19  are intermittently and repeatedly switched. 
         [0119]    According to the operation of such an internal air introduction mode, the high-temperature air may be directly sent to condenser  13  without passing through sensible heat exchanger  11  compared to the operation of the internal air circulation mode of the ventilation facility of Embodiment 3. Thus, it is possible to improve an effect of preventing the frost formation of condenser  13  and the defrosting process thereof. Here, in the internal air introduction mode, the heat efficiency is not good in that the air having a temperature substantially equal to the temperature inside the vehicle interior is discharged. 
         [0120]    [Effect] 
         [0121]    Accordingly, according to the air-conditioning apparatus of Embodiment 5, the same operation and action as those of Embodiment 2 may be obtained by the operation of the external air introduction mode. Further, the operation of the internal air introduction mode makes it possible to promptly improve the heating efficiency by preferentially performing the defrosting process of condenser  13  when the air-conditioning operation is started in an extremely cold region. 
         [0122]    Furthermore, in the hybrid vehicle, when the hybrid vehicle runs only by an electric motor for a long period of time, no heat is supplied from the internal-combustion engine to the hybrid vehicle. Electric vehicles have no internal-combustion engine in the first place. For that reason, in the hybrid vehicle or the electric vehicle, frost is generated in condenser  13  when the heat pump is driven. Further, frost is easily generated even in sensible heat exchanger  11  in a cold period. For example, in the heat pump type vehicle air-conditioning apparatus, the temperature of the external air is lower than the temperature (for example, −20° C. or less) of the cooling medium passing through condenser  13 , and hence heat is not easily supplied to the cooling medium. 
         [0123]    Accordingly, in the hybrid vehicle or the electric vehicle, the effects of the air-conditioning apparatuses of Embodiments 1 to 5 are particularly useful. 
         [0124]    Generally, some vehicle air-conditioning apparatuses require the ventilation to be performed by opening a window and others are configured to send a warm wind into the vehicle during a heat operation but to discharge internal air through leakage of the internal air from the window or the like. Thus, in these air-conditioning apparatuses, the heat inside the vehicle interior is uselessly discharged to the outside of the vehicle. On the contrary, according to the air-conditioning apparatuses of Embodiments 1 to 5, the heat inside the vehicle interior is prevented from being uselessly discharged to the outside of the vehicle by sensible heat exchanger  11 , and the heat which may not be collected by sensible heat exchanger  11  is sent to condenser  13  and used. Accordingly, the air-conditioning operation inside the vehicle interior may be realized with high efficiency. 
         [0125]    The embodiments of the invention have been described above. 
         [0126]    Furthermore, in the embodiments, a configuration has been described in which sensible heat exchanger  11  returning only the heat from the exhaust air to the intake air is used as the heat exchanger, but the total heat exchanger that returns the heat and the humidity from the exhaust air to the intake air may be used. 
         [0127]    Further, the air-conditioning apparatus of the embodiment of the invention may have a configuration in which the configuration of realizing the internal air introduction mode, that is, the configuration of opening valves  19  and  20  is omitted from the ventilation facility of Embodiment 1. 
         [0128]    Further, the air-conditioning apparatus of the embodiment of the invention may employ a configuration including any two sets or the full sets of opening-closing valves  21  and  22  of Embodiment 3, opening-closing valves  23  and  24  of Embodiment 4, and opening valves  25  and  26  of Embodiment 5. In such a configuration, it is possible to selectively perform any two or the entirety of the operation of the internal air circulation mode of Embodiment 3, the operation of the internal air circulation mode of Embodiment 4, and the operation of the internal air introduction mode of Embodiment 5. 
         [0129]    Further, as long as the switching valve, the opening-closing valve, and the opening valve of an embodiment can adjust the air flow amount (interrupting and passing the air, and increasing or decreasing the air flow amount), they are not limited to one type. The valves may have, for example, an opening and closing type door shape, a slide door shape, or a circular shutter shape. 
         [0130]    Further, in the embodiments, the valves each configured to open and close one flow path has been described as examples of the switching valve, the opening-closing valve, and the opening valve, but valves configured to simultaneously open and close a plurality of flow paths by an integrated valve body may be employed. 
         [0131]    In addition, the details of elements illustrated in the embodiments such as the type of fan, the type of flow paths, and the like may be modified within a range not departing from the spirit of the invention. 
         [0132]    The disclosure of Japanese Patent Application No. 2011-266205, filed on Dec. 5, 2011, including the specification, drawings and abstract, is incorporated herein by reference in its entirety. 
       INDUSTRIAL APPLICABILITY 
       [0133]    The invention is useful for a vehicle air-conditioning apparatus that is mounted on a hybrid vehicle or electric vehicle. 
       REFERENCE SIGNS LIST 
       [0000]    
       
           2  Evaporator 
           4  Expansion valve 
           8  Compressor 
           11  Sensible heat exchanger 
           12  Heat exchanger unit 
           13  Condenser 
           15  Internal air flow path 
           16  Fan 
           17  Switching valve (first switching valve) 
           18  Switching valve (second switching valve) 
           19  Opening valve (first opening valve) 
           20  Opening valve (second opening valve) 
           21 ,  22 ,  23 ,  24  Opening-closing valve 
           25  Opening valve (third opening valve) 
           26  Opening valve (fourth opening valve) 
           27  Bypass flow path