Patent Publication Number: US-2011061405-A1

Title: Vehicular air conditioner equipped with vehicle shutter device, and failure determining method for vehicle shutter device

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application is based upon and claims the benefit of priority from Japanese Patent Applications No. 2009-214202 filed on Sep. 16, 2009, No. 2009-214203 filed on Sep. 16, 2009, and No. 2009-214207 filed on Sep. 16, 2009, of which the contents are incorporated herein by reference. 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a vehicular air conditioner having both cooling and heating functions, the air conditioner being equipped with a vehicle shutter device for switching an introduction state of external air into an engine room of the vehicle. The present invention also concerns a failure determining method for such a vehicle shutter device. 
     2. Description of the Related Art 
     The present applicants, as disclosed in Japanese Laid-Open Patent Publication No. 2003-170733, have proposed a vehicular air conditioner, which is capable of carrying out a cooling operation for supplying chilled air into a vehicle compartment by switching a flow direction of a coolant, as well as a heating operation for supplying warm air into the vehicle compartment. 
     The vehicular air conditioner is equipped with a shutter, which is capable of switching a communication state between an engine room of the vehicle and the exterior. In the case that the exterior air temperature is low, by blocking access to the engine room through operation of the shutter, escape of air that has been warmed by the engine inside the engine room is prevented, and such warm air can suitably be supplied into the vehicle compartment. Together therewith, in the case that the exterior air temperature is high, the shutter may be set in an opened state, whereby the exterior air can be supplied into the engine room. 
     SUMMARY OF THE INVENTION 
     A general object of the present invention is to provide a vehicular air conditioner equipped with a vehicle shutter device and a failure determining method therefor, in which a heat exchanger can efficiently collect heat generated by the engine, and which can further improve a heating capability of the air conditioner. Together therewith, with a simple structure, opened and closed states of an openable/closable door can reliably be detected, and a failure state of the openable/closable door can reliably be confirmed. 
     A further object of the present invention is to provide a vehicular air conditioner equipped with a vehicle shutter device comprising a heat exchanger, which is capable of reducing pressure losses when a coolant flows through the heat exchanger and heat exchange is performed, and further which enables the coolant to flow through the heat exchanger at a desired pressure for stably carrying out heat exchange. 
     The above and other objects, features, and advantages of the present invention will become more apparent from the following description when taken in conjunction with the accompanying drawings in which a preferred embodiment of the present invention is shown by way of illustrative example. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is an overall schematic view of a vehicular air conditioner equipped with a vehicle shutter device according to an embodiment of the present invention; 
         FIG. 2  is an outline perspective view showing a circulation state of air between a radiator and a cabin-exterior heat exchanger in the vehicular air conditioner of  FIG. 1 ; 
         FIG. 3  is an enlarged side view in the vicinity of shutters in the vehicular air conditioner of  FIG. 1 ; 
         FIG. 4  is an exterior perspective view showing a cabin-exterior heat exchanger in the vehicular air conditioner of  FIG. 1 ; 
         FIG. 5  is a characteristic curve diagram showing a relationship between the flow passage diameter of a second port and pressure loss when a heating operation of the cabin-exterior heat exchanger shown in  FIG. 4  is performed; 
         FIG. 6  is an enlarged perspective view with partial omission showing an opened state of the shutters of  FIG. 3 ; 
         FIG. 7  is an enlarged perspective view with partial omission showing a closed state of the shutters of  FIG. 6 ; 
         FIG. 8  is an enlarged side view showing a closed state of the shutters of  FIG. 3 ; 
         FIG. 9  is an outline plan view showing flow of air during a closed state of the shutters of  FIG. 8 ; 
         FIG. 10  is a structural diagram of an air conditioning circuit showing in outline heating operations of the vehicular air conditioner of  FIG. 1 ; 
         FIG. 11  is a structural diagram of the air conditioning circuit of  FIG. 10 , showing in outline cooling operations thereof; 
         FIG. 12  is an enlarged side view showing a vehicular air conditioner according to a first modified example, in which an upper portion of the radiator extends to a duct; 
         FIG. 13  is an outline plan view showing a vehicular air conditioner according to a second modified example, to which shutters are applied, the width dimension of which is set greater than the width dimension of the radiator; 
         FIG. 14  is an outline plan view showing a vehicular air conditioner according to a third modified example, in which shutters and support shafts supporting the shutters are disposed in a vertical direction; 
         FIG. 15A  is a comparison diagram showing a relationship between pressure loss in a conventional heat exchanger and a heat exchanger of the present invention during a time when heating operations are performed; 
         FIG. 15B  is a comparison diagram showing a relationship between pressure loss in a conventional heat exchanger and a heat exchanger of the present invention during a time when cooling operations are performed; 
         FIG. 16  is a flowchart showing operations when a failure determining process of the vehicle shutter device is carried out; 
         FIG. 17  is a characteristic curve diagram showing a relationship between voltage of a cabin-exterior fan and vehicle velocity; and 
         FIG. 18  is a characteristic curve diagram showing relationships between vehicle velocity, opened and closed states of the vehicle shutter device, voltage of the cabin-exterior fan, and time. 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     A preferred embodiment of a vehicular air conditioner equipped with a vehicle shutter device according to the present invention shall be described below with reference to the drawings. 
     In  FIG. 1 , reference numeral  10  indicates a vehicular air conditioner equipped with a vehicle shutter device according to the present invention. 
     As shown in  FIGS. 1 through 3 , the vehicular air conditioner  10  includes, in an engine room  11 , a compressor  12  that draws in and compresses a coolant, a four-way valve  14  for controlling a supply direction of the coolant, an accumulator  16  disposed in a passage through which the coolant flows from the four-way valve  14  toward the compressor  12 , a cabin-interior heat exchanger  22  disposed inside a unit  20  that communicates with the interior of the vehicle  18 , a cabin-exterior heat exchanger  24  disposed in a front portion of the vehicle  18 , first and second solenoid valves  26   a ,  26   b  arranged between the cabin-interior heat exchanger  22  and the cabin-exterior heat exchanger  24  and which are cable of adjusting a degree of opening therebetween, and a controller  28 , which controls the compressor  12 , the first and second solenoid valves  26   a ,  26   b , etc. 
     A cabin-interior fan  30  is disposed adjacent to the cabin-interior heat exchanger  22 . Further, on the cabin-interior side of the unit  20 , there are provided respectively a defroster outlet port  32 , a face outlet port  34  and a foot outlet port  36 , each of the outlet ports  32 ,  34 ,  36  being openable and closable by means of dampers  38 . 
     Further, as shown in  FIG. 4 , the cabin-exterior heat exchanger  24  includes a main body (housing)  40  having passages in the interior thereof through which the coolant flows, a first port (first passage)  42  through which the coolant is introduced into the main body  40 , for example, when a heating operation is carried out, and a second port (second passage)  44  through which the coolant that was introduced from the first port  42  and having passed through the interior of the main body  40  is discharged to the exterior. For example, during a cooling operation, and under a switching action of the four-way valve  14 , the first port  42  may also function as an outlet side port through which the coolant having passed through the interior of the first port  42  is discharged, whereas conversely, the second port  44  may function as an inlet side port through which the coolant is introduced into the main body  40 . 
     The first and second ports  42 ,  44 , for example, are disposed on one side surface of the main body  40 , being separated a predetermined distance from each other, and are formed as pipes that project from the side surface. In addition, pipes or hoses (first passage, second passage)  46   a ,  46   b  through which the coolant flows are connected respectively to the first and second ports  42 ,  44 . 
     The passage diameter (inner diameter) D 2  of the second port  44  is set within a range that exceeds 10 mm and is less than or equal to 14 mm (10 mm&lt;D 2 ≦14 mm), for example, in the case that the passage diameter D 1  of the first port  42  is set at 5 mm. Stated otherwise, the passage diameter D 2  of the second port  44  is set to a size that exceeds roughly two times, and is less than or equal to roughly 2.8 times, the passage diameter (inner diameter) D 1  of the first port  42  (2×D 1 &lt;D 2 ≦2.8×D 1 ). 
     The passage diameter D 2  of the second port  44  is set based on a change in pressure loss that occurs at the second port  44  during a heating operation, details of which shall be explained briefly with reference to  FIG. 5 .  FIG. 5  is a characteristic curve diagram showing changes in pressure loss generated at the second port  44  during a heating operation of the vehicular air conditioner  10 , in the case that the passage diameter D 1  of the first port  42  in the cabin-exterior heat exchanger  24  is set, for example, at 5 mm, and the passage diameter D 2  of the second port  44  varies. 
     As understood from  FIG. 5 , the relationship between pressure loss and the passage diameter D 2  of the second port  44  indicates that, as the passage diameter D 2  of the second port  44  becomes greater, the pressure loss gradually decreases. More specifically, since it can be understood that from a point at which the passage diameter D 2  of the second port  44  exceeds roughly 10 mm, the rate of change in the pressure loss becomes small, preferably, the passage diameter D 2  is set to exceed 10 mm, or more specifically, to exceed roughly two times the passage diameter D 1  of the first port  42 . 
     Stated otherwise, since it can be seen that the pressure loss increases rapidly when the passage diameter D 2  of the second port  44  becomes less than or equal to 10 mm (D 2 ≦10 mm), it is not desirable to set the passage diameter D 2  to reside within such a range. 
     Further, since it also can be understood that, from a point at which the passage diameter D 2  is set in the vicinity of roughly 14 mm, the rate of change in the pressure loss becomes small, preferably, the passage diameter D 2  is set less than or equal to 14 mm, or more specifically, is set to be less than or equal to roughly 2.8 times the passage diameter D 1  of the first port  42 . Even in the case that the passage diameter D 2  exceeds 14 mm, since as shown in  FIG. 5 , the pressure loss as well as the rate of change in the pressure loss remains small, the passage diameter D 2  may be set within this range if desired. 
     The engine  48  of the vehicle  18  is equipped with a water jacket  52  into which cooling water, which flows under operation of a water pump  50 , is supplied. A radiator  54 , which is disposed adjacent to the cabin exterior heat exchanger  24 , is connected via a thermostat  56  to the water jacket  52 . The thermostat  56  and the water pump  50  are interconnected via a bypass passage  58 . 
     As shown in  FIGS. 1 and 2 , a pair of cabin-exterior fans (blower fans)  60   a ,  60   b  is disposed adjacent to the radiator  54 . The cabin-exterior fans  60   a ,  60   b  are connected respectively to the controller  28  via lead lines  62  and are controlled under operation of the controller  28 . Further, in a non-driven state, when control signals from the controller  28  are not input thereto, the cabin-exterior fans  60   a ,  60   b  are disposed in an idle or freely rotatable state (i.e., can be rotated by running wind blowing therethrough). 
     A heater core  64  that is arranged in the unit  20  is connected to the water jacket  52  via a water valve  66 . A damper  68  for blocking the heater core  64  from the cabin-interior heat exchanger  22  is disposed between the cabin-interior heat exchanger  22  and the heater core  64 . 
     On the other hand, a duct  70  is provided to serve as a communication passage that communicates between the cabin-exterior heat exchanger  24  and the radiator  54  and the exterior of the vehicle  18 . A vehicle shutter device  74  having a plurality of shutters (openable/closable doors)  72   a  to  72   h  for opening and closing the duct  70  is disposed in the duct (communication passage)  70 . The shutters  72   a  to  72   h  are disposed in parallel along the height direction of the vehicle  18 . 
     More specifically, in the vehicular air conditioner  10 , the shutters  72   a  to  72   h , the cabin exterior heat exchanger  24  and the radiator  54  are arranged in series from a forward side (in the direction of the arrow A) toward the rearward side (in the direction of the arrow B) of the vehicle  18 , while the engine  48  is disposed rearwardly of the radiator  54 . 
     The duct  70 , for example, is formed from plates having a fixed thickness, and comprises an opening  76  with a rectangle-shaped cross section in the center thereof in which shafts are arranged. On an upper portion of the opening  76 , an upper end wall  78  is formed that extends in a vertical upward direction. The duct  70  is bent from an edge of the upper end wall  78  toward the rearward side (in the direction of the arrow B) of the vehicle  18 , thereby forming a cover  80  that extends substantially horizontally for a predetermined length. In greater detail, on the upper portion of the duct  70 , the cover  80  extends from the upper part of the shutter  72   a  in a rearward direction (the direction of the arrow B) of the vehicle  18 , the cover  80  being formed so as to cover the region above the radiator  54 . 
     In other words, the upper end wall  78  of the duct  70  is arranged in the vicinity of the uppermost disposed shutter  72   a , such that when the shutters  72   a  to  72   h  are in an opened condition, one end portion of the shutter  72   a  abuts against the upper end wall  78 . 
     Further, the upper portion of the duct  70  is separated a predetermined distance from the top of the cabin-exterior heat exchanger  24  and the radiator  54 , thereby forming a gap S between the duct  70  and both the cabin-exterior heat exchanger  24  and the radiator  54 . 
     The cover  80  is not limited to a case of extending over the upper region of the radiator  54 , and for example, may extend to a position that covers a portion of the engine  48 , which is disposed more rearwardly than the radiator  54 . 
     On the other hand, at the lower portion of the opening  76  in the duct  70 , a lower end wall  82  is formed that extends vertically downward, at which point the duct  70  is bent perpendicularly in a rearward direction (the direction of the arrow B) of the vehicle  18  from the end portion of the lower end wall  82 , and extends to a position in abutment with the side surface of the cabin-exterior heat exchanger  24 . More specifically, because the lower portion of the duct  70  abuts against the side wall of the cabin-exterior heat exchanger  24  via the lower end wall  82 , leakage of air is prevented from occurring between the lower end wall  82  and the cabin-exterior heat exchanger  24 . 
     Stated otherwise, the lower end wall  82  of the duct  70  functions as a seal, which is cable of preventing leakage of air from occurring between the lower portion of the duct  70  and the cabin-exterior heat exchanger  24 . 
     As shown in  FIGS. 6 and 7 , the shutters  72   a  to  72   h  are rotatably disposed in the duct  70  via support shafts  84  on opposite sides thereof, and further, are supported substantially in parallel with each other while being separated mutually by predetermined distances. 
     Additionally, shafts  86 , which are formed at end portions of the shutters  72   a  to  72   h  offset from the substantially horizontally disposed support shafts  84 , are supported axially on displacement members  88 , which are arranged at opposite sides of the duct  70 . 
     Additionally, as shown in  FIGS. 3 and 6 , in an opened condition (OPEN) when the shutters  72   a  to  72   h  are disposed substantially horizontally about the support shafts  84 , one end of the uppermost shutter  72   a  on the forward side (the direction of the arrow A) of the vehicle  18  is disposed in abutment against the upper end wall  78  of the duct, whereas one end of the lower most shutter  72   h  on the forward side (the direction of the arrow A) of the vehicle  18  is disposed out of contact with the lower end wall  82  of the duct  70 . 
     Further, when the shutters  72   a  to  72   h  are in an opened state, the other ends of the shutters  72   a  to  72   h  facing the rearward side (in the direction of the arrow B) of the vehicle  18  are disposed in close proximity to a side surface of the cabin-exterior heat exchanger  24 . 
     The displacement members  88  are disposed so as to be displaceable upwardly and downwardly (in the vertical direction) by driving units  90 , which are connected to lower ends thereof. For example, in a heating mode region when the outside temperature is equal to or less than 10° C., as shown in  FIGS. 7 and 8 , based on a driving signal from the controller  28 , the displacement members  88  are displaced downwardly to switch the shutters  72   a  to  72   h  to a closed state (CLOSE), whereas, in a cooling mode region when the outside temperature is greater than 10° C., as shown in  FIGS. 3 and 6 , the displacement members  88  are displaced upwardly to switch the shutters  72   a  to  72   h  into an opened state (OPEN). The driving units  90 , for example, may comprise actuators having stepping motors, which are driven by supplying electricity thereto. 
     In the aforementioned cabin-exterior heat exchanger  24 , a case has been explained in which the passage diameter D 1  of the first port  42  and the passage diameter D 2  of the second port  44  are set respectively at substantially constant diameters. However, the invention is not limited by this feature and, for example, when the first and second ports  42 ,  44  are connected by crimping or caulking with respect to non-illustrated pipes or the like, it is foreseen that the diameters D 1  and D 2  may become partially smaller at such areas. Stated otherwise, at such portions thereof, the first and second ports  42 ,  44  may be reduced in diameter in the radial direction thereof. 
     Generally, because an increase in pressure loss is caused at regions (smallest diameter regions) where the flow passage diameter through which the fluid flows is smallest, in the case described above, the passage diameters D 1 , D 2  that cause pressure loss of the fluid are set at such regions, which are compressed radially inward and result in the minimum passage diameter of the passages. 
     Further, for example, in the case that the inner diameters of the pipes  46   a ,  46   b , which are connected to the first and second ports  42 ,  44 , are set smaller than the passage diameters D 1 , D 2  of the first and second ports  42 ,  44 , then with respect to the inner diameter of one pipe  46   a  that is connected to the first port  42 , the inner diameter of the other pipe  46   b , which is connected to the second port  44 , may be formed so as to exceed roughly two times the inner diameter of the one pipe  46   a.    
     The vehicular air conditioner  10  including a vehicle shutter device  74  according to the embodiment of the present invention is constructed basically as described above. Next, operations and advantages of the vehicular air conditioner  10  and the vehicle shutter device  74  shall be explained. First, operations shall be described when a heating operation is carried out in the vehicular air conditioner  10 . 
     For example, in the case of a heating mode region when the temperature outside the vehicle  18  is equal to or less than 10° C., when the driver D (see  FIG. 1 ) performs an action on an operating panel (not shown) of the vehicular air conditioner  10  and selects a heating drive mode, based on a drive signal from the controller  28 , the driving units  90  are driven, whereupon the displacement members  88  are displaced upwardly by the driving units  90 , and the shutters  72   a  to  72   h  are rotated into a closed condition (CLOSE), thereby blocking the duct  70  (see  FIGS. 7 and 8 ). 
     Further, accompanying an operation from the driver D, the dampers  38  are actuated, so that opened/closed states of the defroster outlet port  32 , the face outlet port  34  and the foot outlet port  36  are set appropriately. In this manner, when the heating drive mode is selected, the four-way valve  14  is switched to the condition shown in  FIG. 10 , so that the coolant from the compressor  12  is supplied to the side of the cabin-interior heat exchanger  22 . 
     Next, the cabin-interior fan  30  is driven rotatably, such that air inside the cabin of the vehicle  18  is supplied, via the cabin interior heat exchanger  22  and the heater core  64 , to the selected defroster outlet port  32 , the face outlet port  34 , or the foot outlet port  36 . Together therewith, because the shutters  72   a  to  72   h  are closed, the two cabin-exterior fans  60   a ,  60   b  arranged adjacent to the radiator  54  are driven rotatably in a positive direction of rotation (i.e., a direction such that air from the exterior is drawn into the vehicle). 
     In this case, as a result of the cabin-exterior fans  60   a ,  60   b  being driven in a positive direction of rotation, air on the side of the engine  48 , after flowing toward the forward side (in the direction of the arrow A) of the vehicle  18  while passing through the gap S between the cover  80  of the duct  70  and both the radiator  54  and the cabin exterior heat exchanger  24 , is drawn in toward the side of the engine  48  from the inner side of the shutters  72   a  to  72   h , which are in a closed condition (CLOSE), via the cabin-exterior heat exchanger  24  and the radiator  54 . 
     Upon completion of the aforementioned preparatory operations, the compressor  12  is driven and the heating drive mode is initiated. 
     Consequently, the coolant that is discharged from the compressor  12  is supplied via the four-way valve  14  to the cabin interior heat exchanger  22 , whereupon the coolant undergoes condensation. At this time, under a driving action of the cabin-exterior fans  60   a ,  60   b , air (warm air) that has been heated by heat generated from the engine  48  flows to the forward side of the vehicle  18  (in the direction of the arrow A) passing through the gap S between the cover  80  of the duct  70  and both the radiator  54  and the cabin exterior heat exchanger  24 . In addition, after flowing between the shutters  72   a  to  72   h , which are in a closed condition, and the cabin-exterior heat exchanger  24 , the air is drawn in while passing over surfaces of the cabin-exterior heat exchanger  24  and the radiator  54 , whereupon heat exchange is carried out, and the air passes through the radiator  54  and is taken in toward the side of the engine  48 . 
     Additionally, the air having undergone heat exchange is supplied by the cabin-interior fan  30  to the cabin-interior heat exchanger  22 , and after being raised in temperature at the cabin-interior heat exchanger  22 , passes through the heater core  64  and is supplied into the vehicle cabin from the selected defroster outlet port  32 , the face outlet port  34 , or the foot outlet port  36 . 
     Further, the water pump  50  supplies cooling water, which has been heated by the engine  48 , from the water jacket  52  to the heater core  64  through the water valve  66 . Accordingly, heated air (warm air), which is supplied to the cabin-interior heat exchanger  22  by the cabin-interior fan  30 , is further heated by passing through the heater core  64 , and then is supplied into the cabin interior. 
     Next, operations shall be described when a cooling operation is carried out in the vehicular air conditioner  10 . 
     For example, in the case of a cooling mode region, when the temperature outside the vehicle  18  is of a generally high temperature, the shutters  72   a  to  72   h  are set to place the duct  70  in an open condition. More specifically, the driving units  90  are driven, whereupon the shutters  72   a  to  72   h  are rotated about the support shafts  84  and the duct  70  is opened. Next, when the driver D (see  FIG. 1 ) performs an action on an operating panel (not shown) of the vehicular air conditioner  10  and selects a cooling drive mode, based on a drive signal from the controller  28 , the driving units  90  are driven, whereupon the displacement members  88  are displaced downward by the driving units  90 , and the shutters  72   a  to  72   h  are rotated into an opened condition (OPEN), thereby opening the duct  70  (see  FIGS. 3 and 6 ). Further, simultaneously, the dampers  38  are actuated, so that opened/closed states of the defroster outlet port  32 , the face outlet port  34  and the foot outlet port  36  are set appropriately. Together therewith, the four-way valve  14  is switched to the condition shown in  FIG. 11 , so that the coolant discharged from the compressor  12  is supplied to the side of the cabin-exterior heat exchanger  24 . Further, the water valve  66  is closed, so that supply of cooling water to the heater core  64  is stopped. 
     In this case, as shown in  FIGS. 3 and 6 , the shutters  72   a  to  72   h  are placed in a substantially horizontal condition through the support shafts  84 , and one end of the uppermost shutter  72   a  abuts against the upper end wall  78  of the duct  70 , whereas the other end portions of the shutters  72   a  to  72   h  are arranged in close proximity to the side surface of the cabin-exterior heat exchanger  24 , which is disposed rearwardly of the shutters  72   a  to  72   h.    
     Next, the cabin-interior fan  30  is driven so as to supply external air into the cabin through the cabin-interior heat exchanger  22 , while the cabin-exterior fans  60   a ,  60   b  are driven in a positive direction in order to take in external air and cool the cabin-exterior heat exchanger  24  and the radiator  54 . 
     As a result of these actions, by means of the cabin-exterior fans  60   a ,  60   b , which are rotated in a positive direction, air on the side of the engine  48  flows toward the forward side of the vehicle  18  (in the direction of the arrow A) while passing through the gap S between the cover  80  of the duct  70  and both the radiator  54  and the cabin-exterior heat exchanger  24 . At this time, the shutters  72   a  to  72   h  are opened (OPEN) and in a horizontal condition, and in addition, the one end portion of the uppermost shutter  72   a  abuts against and seals the upper end wall  78  of the duct  70 . Furthermore, because the other ends of the shutters  72   a  to  72   h  are arranged in close proximity to the side surface of the cabin-exterior heat exchanger  24 , heated air is prevented from flowing to the forward side (in the direction of the arrow A) of the vehicle  18  while passing between the upper end wall  78  of the duct  70  and the shutters  72   a  to  72   h . Additionally, air is prevented from passing between the shutters  72   a  to  72   h  and the cabin-exterior heat exchanger  24  and flowing in a downward direction. Owing thereto, air (warm air) that is heated by the engine  48  does not pass through the cabin-exterior heat exchanger  24  and is not drawn into the cabin interior. 
     Upon completion of the aforementioned preparatory operations, the coolant, which is compressed and discharged from the compressor  12 , is directed via the four-way valve  14  to the second port  44  of the cabin-exterior heat exchanger  24 , is evaporated in the main body  40  of the cabin-exterior heat exchanger  24 , and further is cooled by external air that is taken in by the cabin-exterior fans  60   a ,  60   b.    
     Subsequently, the coolant is supplied to the first solenoid valve  26   a  via the second solenoid valve  26   b , and after being nebulized, and as a result of being evaporated in the cabin-interior heat exchanger  22 , the exterior air supplied from the cabin-interior fan  30  is chilled and cools the interior of the vehicle cabin. After the evaporated coolant is supplied from the four-way valve  14  to the accumulator  16 , the gaseous part of the coolant is sucked in by the compressor  12 , and the cooling operation (refrigeration cycle) is continued. 
     In the forgoing manner, in the present embodiment, as a result of forming the cover  80  at an upper portion of the duct  70 , which extends toward the rearward side (the direction of the arrow B) of the vehicle  18  while covering at least the upper portion of the cabin-exterior heat exchanger  24 , when the shutters  72   a  to  72   h  are closed and a heating operation is carried out, air (warm air), the temperature of which is raised by heat generated from the engine  48 , passes through the gap S between the cover  80  and the cabin-exterior heat exchanger  24 , and can be guided suitably toward the forward side (in the direction of the arrow A) of the vehicle  18 . Owing thereto, by rotation of the cabin-exterior fans  60   a ,  60   b , heated air (warm air) can be drawn in from the upper side of the shutters  72   a  to  72   h  while passing over the entire surface of the cabin-exterior heat exchanger  24 , and heat exchange can be performed efficiently. 
     As a result, in the cabin-exterior heat exchanger  24 , heat can be recovered efficiently from air (warm air) that has been heated by heat from the engine  48 , and along therewith, the heating capability in the vehicular air conditioner  10  can be improved, and the comfort of passengers in the vehicle cabin can be enhanced. 
     Further, during a cooling operation when the shutters  72   a  to  72   h  are opened and air external to the vehicle  18  is capable of being introduced into the engine room  11 , because the other ends of the shutters  72   a  to  72   h  are positioned in close proximity to the side surface of the cabin-exterior heat exchanger  24 , when air (warm air) that has been raised in temperature from the heat generated by the engine  48  flows toward the forward side of the vehicle  18  (in the direction of the arrow A) passing through the upper portion of the duct  70 , flow of such air between the shutters  72   a  to  72   h  and the cabin-exterior heat exchanger  24  is stopped. As a result, heated air (warm air) is prevented from being drawn into the cabin-exterior heat exchanger  24 , and during the cooling operation, deterioration in the cooling capability caused by such heated air (warm air) being supplied to the cabin-exterior heat exchanger  24  can be prevented. In addition, a desired cooling capability can be brought about as a result of external air passing through the opened shutters  72   a  to  72   h  and being taken in from the forward end of the vehicle  18 , thereby enhancing the comfort of vehicle passengers. 
     Stated otherwise, since the heated air (warm air) that flows through the gap S disposed above the cabin-exterior heat exchanger  24  is prevented, by the uppermost shutter  72   a , from wrapping around and flowing back toward the forward side (in the direction of the arrow A) of the cabin-exterior heat exchanger  24 , deterioration of cooling efficiency, which would be of concern if such air were taken in, can be avoided. 
     Furthermore, because lowering of the intake pressure in the compressor  12  can be prevented, deterioration in the durability of the compressor  12  caused by a decline in the intake pressure thereof can also be prevented. 
     The aforementioned cover  80  that makes up the duct  70  is not limited to a case of extending over the upper portion of the radiator  54 . For example, the cover  80  may also extend to a position covering a portion of the engine  48 , which is disposed more rearwardly than the radiator  54 . In this case, as a result of the cover  80  that extends to the vicinity of the engine  48 , air that is heated by heat generated at the engine  48  can be guided appropriately to the forward side of the vehicle  18 , thus enabling heat exchange to be performed more efficiently by the cabin-exterior heat exchanger  24 . Owing thereto, the heating capability of the vehicular air conditioner  10  can be enhanced. 
     Further, as in the first modified example shown in  FIG. 12 , by setting the height of the upper portion of the radiator  54   a  at the same height as the upper portion of the duct  70 , because air that flows along the upper portion of the duct  70  upon driving of the cabin-exterior fans  60   a ,  60   b  is made to flow through the radiator  54   a  toward the forward side of the vehicle  18  (in the direction of the arrow A), such air is cable of recovering heat generated by the engine  48  added together with heat in the radiator  54   a , so that air (warm air) more greatly elevated in temperature can be blown into the cabin interior via the cabin-interior fan  30 . That is, the heating capability of the vehicular air conditioner  10  can be further improved, and the comfort of passengers in the vehicle cabin can be enhanced. 
     Furthermore, as in the second modified example shown in  FIG. 13 , the widthwise dimension of the shutters  92  may be widened, such that opposite ends thereof project at a fixed width in the lateral direction (the direction of arrows C and D) with respect to opposite end portions of the cabin-exterior heat exchanger  24  and the radiator  54 . In this case, corresponding to widening of the shutters  92 , the widthwise dimension of the duct  70   a  also is widened. 
     Owing thereto, for example, even if a V-type engine  48   a  providing a heat source in a lateral direction which lies in the widthwise direction of the vehicle  18  is mounted lengthwise in the vehicle  18 , when air (warm air) that has been raised in temperature by heat generated respectively on left and right sides with respect to the center of the engine room  11  is made to flow toward the forward side (in the direction of the arrow A) of the vehicle  18 , such air can be collected efficiently by the widened duct  70   a  and guided to the forward side of the vehicle  18 . 
     More specifically, heat that is generated at left and right sides (i.e., in the widthwise direction) of the engine room  11  in the vehicle  18  can be suitably recovered, and by making use of such heated air (warm air), the heating capability of the vehicular air conditioner  10  can be improved. 
     Further, in the vehicular air conditioner  10  shown in  FIG. 1 , the plurality of support shafts  84  and shutters  72   a  to  72   h , which are disposed horizontally, may, as in the third modified example shown in  FIG. 14 , be arranged perpendicularly thereto so as to extend in a vertical direction, the shutters  72   a  to  72   h  being supported rotatably with respect to the duct  70 . 
     By adopting such a structure, as shown in  FIG. 14 , in a vehicle having the aforementioned V-type engine  48   a  mounted therein, when a cooling operation is carried out, the shutters (openable/closable doors)  94   a  to  94   p  are rotated into an opened state under a driving action of the driving units  90 . At this time, one end of the shutter  94   a , which is disposed at the most outside position, abuts against an end surface of the opening  76  in the duct  96 , while other ends of the shutters  94   a  to  94   p  are positioned in close proximity to a side surface of the cabin-exterior heat exchanger  24 . In addition, heated air (warm air) flowing toward the front side of the vehicle  18  (in the direction of the arrow A) from left and right sides of the V-type engine  48   a  can be stopped and prevented, by the opened shutters  94   a  to  94   p , from being supplied to the side of the cabin-exterior heat exchanger  24 . Accordingly, even in the case of a heat source in left and right directions, such as the V-type engine  48   a , in the engine room  11 , during the cooling operation, supply of heated air (warm air) to the cabin-exterior heat exchanger  24  can be avoided, and a deterioration in the cooling capability due to supplying such heated air to the cabin-exterior heat exchanger  24  can be prevented. 
     Stated otherwise, since wrapping around of the heated air (warm air) from left and right directions with respect to the cabin-exterior heat exchanger  24 , and such heated air being drawn into the cabin-exterior heat exchanger  24  can be prevented, deterioration of the cooling capability can be avoided. 
     Further, for example, when a heating operation is performed, the first port  42  through which the coolant is introduced in to the main body  40 , and the second port  44  through which the coolant having been introduced from the first port  42  and passed through the interior of the main body  40  is discharged to the exterior, are both disposed on the same side surface of the main body  40  that makes up the cabin-exterior heat exchanger  24 . Further, concerning the first and second ports  42 ,  44 , which are tubular shaped, the passage diameter (interior diameter) D 2  of the second port  44  is set within a range that exceeds roughly two times, and is equal to or less than roughly 2.8 times, the passage diameter (interior diameter) D 1  of the first port  42 . 
     Generally speaking, in a conventional heat exchanger used in a vehicular air conditioner  10  equipped with both cooling and heating functions, the passage diameters D 1 , D 2  of the first and second ports  42 ,  44  are set considering only the cooling operation of the vehicular air conditioner, and the ratio of the passage diameter D 1  of the first port  42  to the passage diameter D 2  of the second port  44  is set at 1 to 1.5 (1:1.5). In this case, although problems do not occur during the cooling operation, during the heating operation, pressure losses on the side of the second port  44  through which the coolant is discharged become large, and because lowering of the flow rate of the coolant caused by the increase in pressure loss occurs, the heating capability tends to be deteriorated, and there is a concern that the durability of the compressor  12  will suffer accompanying a decline in the flow rate of the coolant. 
     In contrast thereto, with the present invention, the ratio of the passage diameter D 2  of the second port  44  with respect to the passage diameter D 1  of the first port  42  to which the coolant is introduced during a heating operation is set large, whereby the heating capability during the heating mode can be improved, together with reducing pressure losses (see  FIG. 15A ). Further, lowering of the coolant flow rate, which is feared when pressure losses occur, can be avoided, and a decline in durability of the compressor  12  can be prevented. 
     Further, even during cooling operations, the cooling capability can be maintained while pressure losses of the coolant can be decreased slightly (see  FIG. 15B ). 
     More specifically, in the cabin-exterior heat exchanger  24 , by setting the passage diameter D 2  of the second port  44  to exceed roughly two times, and to be equal to or less than 2.8 times, the passage diameter D 1  of the first port  42 , the heating capability during heating operations can be increased along with decreasing pressure losses, and in addition, pressure losses during cooling operations can also be decreased slightly. 
     Next, in accordance with the flowchart shown in  FIG. 16 , explanations shall be given of a case of carrying out failure determination of the vehicle shutter device  74 . 
     First, based on drive signals imposed with respect to the driving units  90 , the opened or closed condition of the shutters  72   a  to  72   h  in the vehicle shutter device  74  is confirmed (step S 1 ). More specifically, in the case that drive signals are imposed with respect to the driving units  90  to cause the displacement members  88  to be displaced in a downward direction, the shutters  72   a  to  72   h  are in an opened state (OPEN), while conversely, in the case that drive signals are imposed with respect to the driving units  90  to cause the displacement members  88  to be displaced in an upward direction, the shutters  72   a  to  72   h  are in a closed state (CLOSE). 
     Additionally, if the shutters  72   a  to  72   h  are in an opened condition, in step S 2 , it is determined whether or not the vehicle velocity C of the vehicle  18  is equal to or greater than a predetermined velocity Cs (e.g. 50 km/h), which has been set beforehand. The vehicle velocity C is confirmed, for example, based on a velocity signal that is output to the controller  28  from a velocity sensor mounted in the vehicle  18 . On the other hand, if it is confirmed that the shutters  72   a  to  72   h  are in a closed condition, the sequence proceeds directly to step S 5  (described later) without going through step S 2 . 
     In this case, because the shutters  72   a  to  72   h  are in an opened condition, running wind (air) is introduced into the engine room  11  through the vehicle shutter device  74  from the forward side of the vehicle  18 . The running wind impinges upon the cabin-exterior fans  60   a ,  60   b , whereupon the cabin-exterior fans  60   a ,  60   b  are made to rotate at a given rotational speed (RPM) by means of the running wind. 
     The aforementioned predetermined velocity Cs is set to a velocity that generates a predetermined voltage (e.g., about 1 volt) from the rotating cabin-exterior fans  60   a ,  60   b , the cabin-exterior fans  60   a ,  60   b  being forcibly rotated during running of the vehicle  18  by means of the running wind, which is introduced into the engine room  11  from the front side of the vehicle  18 . 
     Based on the relationship shown in  FIG. 17  between vehicle velocity C and the voltage E generated by the cabin-exterior fans  60   a ,  60   b , a case shall briefly be explained concerning setting of the predetermined velocity Cs. The solid line in  FIG. 17  is a characteristic curve L 1  indicative of a relationship between vehicle velocity C and the voltage E generated by the cabin-exterior fans  60   a ,  60   b  in a case when the shutters  72   a  to  72   h  in the vehicle shutter device  74  are opened (OPEN). The broken line is a characteristic curve L 2  indicative of a relationship between vehicle velocity C and the voltage E generated by the cabin-exterior fans  60   a ,  60   b  in a case when the shutters  72   a  to  72   h  are closed (CLOSE). 
     As shown in  FIG. 17 , for example, at a point around where the vehicle velocity C of the vehicle  18  reaches about 40 km/h, the cabin-exterior fans  60   a ,  60   b  begin to be rotated by the running wind that impinges upon the cabin-exterior fans  60   a ,  60   b , and accompanying such rotation, a voltage E starts to be generated. Additionally, at a point where the vehicle velocity C reaches about 50 km/h, compared to the point at about 40 km/h, it can be understood that the voltage E increases further and reaches the predetermined value. Owing thereto, in this case, roughly 50 km/h at which the predetermined voltage E (e.g., 1V) is obtained, is set as the predetermined velocity Cs. Moreover, in the case that the shutters  72   a  to  72   h  are closed, as understood from the broken line L 2  in  FIG. 17 , since running wind does not impinge upon the cabin-exterior fans  60   a ,  60   b , and the cabin-exterior fans  60   a ,  60   b  are not rotated, no voltage E whatsoever is generated. 
     Additionally, in the flowchart of  FIG. 16 , in the case that the vehicle velocity C of the vehicle  18  is greater than or equal to the predetermined velocity Cs (C≧Cs), then the sequence progresses to step S 3 , at which the voltage E generated by the rotating cabin-exterior fans  60   a ,  60   b  is output to the controller  28  via the lead lines  62 , and the voltage value thereof is detected in the controller  28 . In the controller  28 , the generated voltage E is compared with a predetermined voltage Es set beforehand, and a determination is made as to whether or not the voltage E is greater than or equal to the predetermined voltage Es (step S 3 ). The predetermined voltage Es is set at a size (e.g., about 1V) at which generation of the voltage E in the cabin-exterior fans  60   a ,  60   b  can clearly be confirmed. 
     In addition, in the case that the voltage E of the cabin-exterior fans  60   a ,  60   b  is smaller than the predetermined voltage Es (E&lt;Es), it is judged that the cabin-exterior fans  60   a ,  60   b  are not rotating despite the fact that the shutters  72   a  to  72   h  should be in an opened condition (OPEN). More specifically, it is assumed that the cabin-exterior fans  60   a ,  60   b  are not rotating because, for some reason, the shutters  72   a  to  72   h  are closed and not opened, and hence running wind is not being introduced into the engine room  11 . 
     Consequently, it is judged that a failure condition has occurred in the vehicle shutter device  74 , whereupon, for example, a warning signal is output from the controller  28  to a non-illustrated warning lamp or the like inside the vehicle compartment, thereby causing the warning lamp or the like to become illuminated and display the failure state (step S 4 ). 
     Further, in step S 3 , in the case that the voltage E at the cabin-exterior fans  60   a ,  60   b  is greater than or equal to the predetermined voltage Es (E≧Es), since it is confirmed that the shutters  72   a  to  72   h  are opened to the preset opening degree, and that running wind is being introduced into the engine room  11  at a desired flow rate whereby the cabin-exterior fans  60   a ,  60   b  are rotated by the running wind, it is understood that the vehicle shutter device  74  is in an opened condition and is being driven normally. Thus, the sequence returns again to step S 1 , and failure determination of the vehicle shutter device  74  continues to be carried out in succession. 
     On the other hand, in step S 1 , in the event it is confirmed that the shutters  72   a  to  72   h  are in a closed state (CLOSE) based on the driving signal output from the controller  28  with respect to the driving units  90 , then in the controller  28 , it is determined whether or not the vehicle velocity C of the vehicle  18  is greater than or equal to the predetermined velocity Cs (e.g., 50 km/h) set beforehand (step S 5 ). When the shutters  72   a  to  72   h  are in a closed condition, running wind (air) is not introduced into the engine room  11  from the exterior of the vehicle  18 , and thus such running wind does not impinge upon the cabin-exterior fans  60   a ,  60   b  and does not forcibly cause the cabin-exterior fans  60   a ,  60   b  to rotate. 
     Next, in step S 5 , if the vehicle velocity C of the vehicle  18  is greater than or equal to the predetermined velocity Cs set beforehand (C≧Cs), then the voltage E generated by the cabin-exterior fans  60   a ,  60   b  is detected and is output as an output signal to the controller  28 , and in the controller  28  a comparison is performed with the predetermined voltage Es (step S 6 ). In step S 5 , in the case that the vehicle velocity C of the vehicle  18  is less than the predetermined velocity Cs set beforehand (C&lt;Cs), the sequence returns to step S 1 , and determination of the opened/closed state of the shutters  72   a  to  72   h  is carried out again. 
     In addition, in step S 6 , if the fan voltage E is greater than or equal to the predetermined voltage Es (E≧Es) although the shutters  72   a  to  72   h  are indicated to be in a closed condition (CLOSE), it is determined that the cabin-exterior fans  60   a ,  60   b  are in a rotating state (step S 4 ). More specifically, it is assumed that, due to some reason, the shutters  72   a  to  72   h  have experienced a failure and are in an opened state (OPEN) without properly closing. 
     Consequently, it is judged that a failure condition has occurred in the vehicle shutter device  74 , whereupon, for example, a warning signal is output from the controller  28  to a non-illustrated warning lamp or the like inside the vehicle compartment, thereby causing the warning lamp or the like to become illuminated and display the failure state (step S 4 ). 
     Further, in the case that the voltage E at the cabin-exterior fans  60   a ,  60   b  is less than the predetermined voltage Es (E&lt;Es), it is understood that the vehicle shutters  72   a  to  72   h  have reliably closed, that running wind is not impinging upon the cabin-exterior fans  60   a ,  60   b  and the fans are in a non-rotating state. Additionally, while the vehicle  18  continues running, the sequence returns again to step S 1 , and failure determination of the vehicle shutter device  74  continues to be carried out in succession. 
     In the case that the vehicle shutter device  74  is not faulty and opening/closing operations thereon are performed properly, as understood from the characteristic curve diagram shown in  FIG. 18 , which shows relationships between the vehicle velocity C of the vehicle  18 , the voltage E generated by the cabin-exterior fans  60   a ,  60   b  which are rotated by running wind, and opened and closed states of the shutters  72   a  to  72   h , if the shutters  72   a  to  72   h  are in an opened condition (OPEN) and the vehicle velocity C is greater than or equal to the predetermined velocity Cs (C≧Cs), then the voltage E generated at the cabin-exterior fans  60   a ,  60   b  becomes equal to or greater than the predetermined voltage Es (E≧Es), whereas by closing the shutters  72   a  to  72   h  while the vehicle velocity C is maintained, the voltage E becomes less than the predetermined voltage Es (E&lt;Es). Further, in the case that the vehicle velocity C is less than the predetermined velocity Cs (C&lt;Cs) as well, the voltage E becomes less than the predetermined voltage Es (E&lt;Es). 
     On the other hand, when a cooling operation is carried out, based on driving signals output from the controller  28  to the driving units  90 , the displacement members  88  are displaced downwardly, and the plural shutters  72   a  to  72   h  are rotated about the support shafts  84  into a substantially horizontal condition. As a result thereof, the shutters  72   a  to  72   h  place the duct  70  in an opened state, and by putting the exterior of the vehicle  18  in communication with the engine room  11 , running wind during running of the vehicle  18  is directed into the engine room  11 . Since they have already been discussed above, detailed explanations concerning features that occur during the cooling operation have been omitted. 
     In this case as well, failure determination of the vehicle shutter device  74  is carried out according to the flowchart shown in  FIG. 16 . 
     In the foregoing manner, with the present embodiment, when the vehicle  18  is running, by detecting the voltage E generated by the cabin-exterior fans  60   a ,  60   b , malfunctioning of the vehicle shutter device  74 , which is capable of switching an introduction state of external air into the engine room  11 , can easily and reliably be detected. More specifically, without separately providing a dedicated failure detection means for detecting malfunctions of the vehicle shutter device  74 , and with a simple structure using only the cabin-exterior fans  60   a ,  60   b , malfunctioning of the vehicle shutter device  74  during running of the vehicle  18  can be confirmed. 
     Stated otherwise, utilizing forced rotation of the cabin-exterior fans  60   a ,  60   b , which is caused when running wind during running of the vehicle  18  impinges against the cabin-exterior fans  60   a ,  60   b , malfunctioning of the vehicle shutter device  74  can easily be detected. 
     Further, for example, by placing the shutters  72   a  to  72   h  of the vehicle shutter device  74  in a closed condition (CLOSE), and supplying, into the cabin, air that has been heated using heat generated by the engine  48  inside the engine room  11 , heating of the cabin interior is carried out. However, in this case, if the shutters  72   a  to  72   h , as a result of the aforementioned malfunctioning, are placed in an opened state (OPEN), then a problem results in that the heat inside the engine room  11  escapes to the exterior, and the heating efficiency, particularly at times of low temperature, becomes deteriorated. In contrast thereto, in the present invention, since malfunctioning of the shutters  72   a  to  72   h  can reliably be detected from the voltage E generated by the cabin-exterior fans  60   a ,  60   b , escape of heat from the engine room  11  at times of low temperature, can reliably be avoided. As a result, deterioration of the heating efficiency at times of low temperature can be prevented, and a desired heating capability can suitably be obtained. 
     Furthermore, for example, in the case that the shutters  72   a  to  72   h  are placed in a closed condition, whereby the cooling water temperature of the engine  48  inside the engine room  11  to which exterior air is not introduced becomes raised, lowering of the water temperature, which would be feared in the case that the shutters  72   a  to  72   h  were mistakenly placed in an opened state (OPEN), can be avoided, and the cooling water can efficiently be heated, and the temperature of the water can be raised. 
     Still further, for example, in a high load condition of the engine  48 , during high speed running or acceleration, etc., of the vehicle  18 , in the case that the amount of heat generated by the engine  48  is increased compared to normal running conditions, it is necessary for the shutters  72   a  to  72   h  to be placed in an opened condition (OPEN), for running wind to impinge against the radiator  54  to cool the engine  48 , and for the temperature of the cooling liquid to be lowered. However, in such a high load condition, in the case that the shutters  72   a  to  72   h  malfunction and are mistakenly placed in a closed condition (CLOSE), the temperature of the cooling water is raised, and since the engine  48  cannot be cooled, a condition of overheating occurs, and it can be presumed that a trouble during running of the vehicle  18  may result. In the present invention, even in the case of such a high load condition, since malfunctioning of the vehicle shutter device  74  can reliably be detected from the voltage E generated by the cabin-exterior fans  60   a ,  60   b , raising of the cooling water temperature due to failure of the vehicle shutter device  74 , and the occurrence of overheating, etc., can reliably be prevented. 
     The vehicular air conditioner according to the present invention is not limited to the embodiments and examples described above. It is a matter of course that various modified or additional structures could be adopted without deviated from the essence and scope of the present invention as set forth in the appended claims.