Patent Publication Number: US-2011076931-A1

Title: Vehicular air conditioning apparatus

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application is based upon and claims the benefit of priority from Japanese Patent Application No. 2009-220729 filed on Sep. 25, 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 conditioning apparatus, which is equipped with a control mechanism for controlling operation of a switching door that switches the communication state of a fluid passage through which air is introduced from the exterior or the interior of a vehicle. 
     2. Description of the Related Art 
     Heretofore, in a vehicular air conditioning apparatus that is mounted in a passenger vehicle, interior and exterior air is drawn into a housing by a blower fan. Cool air, which is cooled by an evaporator that forms a cooling means, and warm air, which is heated by a heater core that forms a heating means, are mixed together at a desired mixing ratio in the housing interior by adjusting the degree of opening of an air mixing damper. The mixed air then is blown selectively by opening and closing outlet doors, which are disposed respectively in each of outlet ports disposed in the vehicle compartment, for adjusting the temperature and humidity inside the vehicle compartment. The air mixing damper and outlet doors include axes, which are supported axially with respect to the housing, such that, by being rotated a predetermined angle about such axes, the mixing ratio of the cool air and the warm air, or the opening condition (degree of opening/closing) of the outlet ports can be switched. 
     With the aforementioned vehicular air conditioning apparatus, for example, as disclosed in Japanese Laid-Open Patent Publication No. 10-250349, a drive source made up from a servo motor or the like is disposed on the exterior of the housing. A driving force of the drive source is transmitted by an output shaft to an arm-shaped first link member, such that by being rotated through a predetermined angle, an arm-shaped second link member, which is axially supported on one end of the first link member, is operated rotatably in a successive fashion. In addition, because a pin, which is inserted through one end of the second link member, is inserted into a groove formed in a switching door constituting an air mixing damper or the like, under a rotary action of the second link member, the air mixing damper or the like is rotated at a predetermined angle. More specifically, a driving force of the drive source is transmitted to the switching door via the first and second link members, whereby an opening/closing operation of the switching door is carried out. 
     However, with the aforementioned vehicular air conditioning apparatus, because the drive section (i.e., the drive source), the first link member, and the second link member are disposed on a side surface of the housing, when the vehicular air conditioning apparatus is mounted inside an engine room of the vehicle, for example, the drive source cannot be arranged in the vicinity of the switching door due to restrictions in the layout of the engine room, and thus, cases occur in which it is problematic and difficult for the driving force of the drive section to be transmitted to the switching door through the first and second link members. 
     SUMMARY OF THE INVENTION 
     A general object of the present invention is to provide a vehicular air conditioning apparatus, in which assembly operations can easily be performed, even in the case that a switching door and a drive section are arranged in a separated fashion from one another, and further, wherein a driving force from the drive section can reliably be transmitted to the switching door. 
     The present invention is characterized by a vehicular air conditioning apparatus for adjusting a temperature of air that is introduced from exterior or interior of a vehicle to a predetermined temperature, and for supplying the air to the vehicle interior, comprising:
         a casing;   a switching damper disposed in interior of the casing for switching a communication state of a flow passage through which the air flows;   a drive section disposed on the casing, which is rotatably driven upon supply of electricity thereto; and   a driving force transmission mechanism including a drive gear connected to a rotary shaft of the drive section, a damper gear disposed on a rotary shaft of the switching damper, a transmission gear disposed between the drive gear and the damper gear and enmeshed mutually therewith, and a holder installed on the casing for rotatably holding the transmission gear.       

     According to the present invention, in the driving force transmission mechanism, which is capable of transmitting a driving force of the drive section to the switching damper accommodated inside the casing, there is provided the transmission gear, which is enmeshed with the drive gear connected to the drive section, as well as with the damper gear that rotates the switching damper. The transmission gear is supported rotatably by the holder, which is installed on the casing. 
     Accordingly, in the casing that makes up the vehicular air conditioning apparatus, even in the case that the drive section and the switching damper are positioned in a separated manner from one another, by means of the transmission gear, which is disposed between the drive gear and the damper gear, the driving force output from the drive gear can reliably and efficiently be transmitted with respect to the damper gear. Together therewith, since the driving force transmission mechanism including the transmission gear can easily be assembled by installing the holder onto the casing, ease of assembly of the driving force transmission mechanism can be improved. 
     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 exterior perspective view of a vehicular air conditioning apparatus according to an embodiment of the present invention; 
         FIG. 2  is an overall cross sectional view of the vehicular air conditioning apparatus shown in  FIG. 1 ; 
         FIG. 3  is a perspective view with partial omission showing the relationship between a drive source, a driving force transmission mechanism, and an air mixing damper; 
         FIG. 4  is a perspective view with partial omission showing the features of  FIG. 3 , as seen from a different direction; 
         FIG. 5  is a front view of a driving force transmission unit made up from a driving section and the driving force transmission mechanism; 
         FIG. 6  is a rear view of the driving force transmission unit shown in  FIG. 5 , as seen from a side of the casing; 
         FIG. 7  is a front view showing an enmeshed condition of a first gear, a second gear, and a damper gear that make up the driving force transmission mechanism; 
         FIG. 8  is a plan view of the enmeshed condition of the first gear, the second gear, and the damper gear shown in  FIG. 7  as seen from an opposite side; 
         FIG. 9  is an exterior perspective view of a second gear that constitutes part of a driving force transmission mechanism; and 
         FIG. 10  is an enlarged perspective view showing the vicinity of a damper gear on a damper shaft that constitutes part of the driving force transmission mechanism. 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     In  FIG. 1 , reference numeral  10  indicates a vehicular air conditioning apparatus according to an embodiment of the present invention. 
     As shown in  FIGS. 1 and 2 , the vehicular air conditioning apparatus  10  includes a casing  12  constituted by a plurality of respective air passages therein, an evaporator  14  arranged in the interior of the casing  12  that cools the air, a heater core  16  for heating the air, an air mixing damper (switching damper)  18  that performs heat exchange by means of the evaporator  14  and the heater core  16  on air that is introduced to the interior of the casing  12 , and which mixes at a predetermined mixing ratio cool air and warm air having been adjusted in temperature, thereby producing mixed air, and a driving force transmission mechanism  22  that transmits a driving force of a drive source (drive section)  20 , which is disposed on a side surface of the casing  12 , to the air mixing damper  18  for causing rotary displacement thereof. 
     Further, in the interior of the casing  12 , a plurality of outlet port dampers  24   a  to  24   c  are provided for selectively supplying into the vehicle compartment the mixed air from each of the opened outlet ports. 
     The vehicular air conditioning apparatus  10  is installed such that the right side shown in  FIG. 1  (the direction of the arrow A) forms a front side thereof, and the left side shown in  FIG. 1  (the direction of the arrow B) forms a rear side thereof. Thus, in the explanations given below, the arrow A direction shall be referred to as a forward direction, whereas the arrow B direction shall be referred to as a rearward direction. 
     The casing  12  is made up from substantially symmetrically shaped first and second divided casings  26 ,  28 . In an open portion thereof that opens on a side of the first divided casing  26 , a duct  30  is installed, which is connected to a blower fan, through which air is introduced into the interior of the casing  12 . 
     Further, in the interior of the casing  12 , the evaporator  14  is disposed, which is positioned in the vicinity of an opening portion at the forward side (in the direction of the arrow A) in the vehicular air conditioning apparatus  10 . Also, the heater core  16  is separated a predetermined distance from the evaporator  14  and disposed on the rearward side (in the direction of the arrow B) in the casing  12 . The air mixing damper  18  is disposed between the evaporator  14  and the heater core  16 , for adjusting the flow amount of air, which has been cooled by the evaporator  14 , and which flows to the side of the heater core  16  when flowing toward the downstream side in the casing  12  (see  FIG. 2 ). 
     As shown in  FIGS. 2 to 4 , the air mixing damper  18  comprises a plate, which is arcuate shaped in cross section having a comparatively large radius of curvature, and which is formed with a substantially constant thickness. In addition, the air mixing damper  18  is disposed respectively in the first and second divided casings  26 ,  28 , and is disposed so as to be convexly shaped in a direction away from the evaporator  14 . 
     On the other hand, as shown in  FIGS. 3 and 4 , on an inner wall surface of the air mixing damper  18  facing the evaporator  14 , a rack member  32  is formed, which is enmeshed with a damper shaft (rotary shaft)  50  of the driving force transmission mechanism  22 . The rack member  32  extends from one end portion to the other end portion of the air mixing damper  18  that faces the inner wall surfaces of the first and second divided casings  26 ,  28 . Thus, the rack member  32  extends along the inner wall surfaces of the first and second divided casings  26 ,  28 . 
     Further, the air mixing damper  18  is disposed in a widthwise direction along the casing  12 . Both side ends of the air mixing damper  18  are guided along a pair of guide walls  34   a ,  34   b , the guide walls  34   a ,  34   b  being disposed on inner wall surfaces of the first and second divided casings  26 ,  28 . In the following description, an explanation shall be given only of the air mixing damper  18  disposed on the side of the first divided casing  26 . 
     In the event that the air mixing damper  18  is positioned downward so as to face the heater core  16  in the interior of the casing  12 , air that passes through the evaporator  14  is prevented by the air mixing damper  18  from flowing through to the heater core  16 . On the other hand, in the event that the air mixing damper  18  is moved upwardly away from the heater core  16 , air that passes through the evaporator  14  is allowed to flow to the heater core  16 . Further, if the air mixing damper  18  is disposed in an intermediate position, a portion of the air that passes through the evaporator  14  flows through to the heater core  16 , whereas the remaining air flows into the interior of the casing  12  without flowing to the side of the heater core  16 . 
     As shown in  FIGS. 3 to 6 , the drive source  20  is made up from a servo motor, for example, rotation of which is controlled based on a control signal from a non-illustrated controller, and includes a housing  36 , and a rotary drive shaft (rotary shaft)  38  disposed substantially centrally in the housing  36  (see  FIGS. 4 and 6 ). In addition, the drive source  20 , for example, is fixed with respect to a side surface of the first divided casing  26  via a mounting bracket  40  having a plurality of attachment members. The mounting bracket  40  is formed substantially in a T shape, and is fixed through plural bolts  42  at a position downwardly from the drive source  20  on the first divided casing  26 . In this case, the drive source  20  is fixed such that the drive shaft  38  thereof faces toward a side surface of the first divided casing  26 , in a state of being separated a predetermined distance with respect to the side surface. 
     The driving force transmission mechanism  22 , as shown in  FIGS. 3 to 8 , includes a first gear (drive gear)  44  installed on the drive shaft  38  of the drive source  20 , a second gear (transmission gear)  46  held in mesh with the first gear  44 , a gear holder (holder)  48  connected to the housing  36  of the drive source  20  and which supports the second gear  46 , and a damper shaft  50  enmeshed with the second gear  46  and with the rack member  32  of the air mixing damper  18 . 
     The first gear  44  is formed in a fan-like shape, and is connected to the drive shaft  38  via a hole formed in a central portion thereof. By being fixed to the drive shaft  38 , which is formed with a semicircular shape in cross section, relative rotational displacement between the first gear  44  and the drive shaft  38  is regulated. More specifically, the first gear  44  is rotatably driven in unison (integrally) with drive actions of the drive source  20 . Additionally, the first gear  44  is disposed between the drive source  20  and the side surface of the first divided casing  26 . 
     Further, on the outer circumferential region of the first gear  44 , a plurality of first gear teeth  52  of a radially concave/convex shape are formed along the circumferential direction. In the vicinity of opposite ends thereof on the outer circumferential region, a pair of first locator grooves  54   a ,  54   b , from which the first gear teeth  52  are lacking, are formed respectively. The first locator grooves  54   a ,  54   b  are formed with predetermined widths centrally about the position of a central first gear tooth  52  from among three adjacent first gear teeth  52 , and are formed so as to enable insertion therein respectively of first and second locator parts  56 ,  66  (described later) which make up part of the second gear  46 . 
     The first locator grooves  54   a ,  54   b  are formed with substantially trapezoidal shapes in cross section along the thickness direction of the first gear  44 . First narrow teeth  58  are formed in the first locator grooves  54   a ,  54   b , having a width dimension from a central region of the aforementioned thickness direction to an end surface on the side of the drive source  20 . The first narrow teeth  58  are formed to be narrower than the first gear teeth  52  and at the same pitch as the first gear teeth  52 . Further, the first narrow teeth  58  are formed with the same cross sectional shape. 
     Stated otherwise, the first narrow teeth  58  are set to have a smaller width dimension than the width of the first gear teeth  52 , and are formed at positions corresponding to each of the first locator grooves  54   a ,  54   b , respectively. 
     The second gear  46  is disposed upwardly of the first gear  44  substantially in the same plane therewith. A shaft member  60 , which is provided on and projects from the center thereof, is supported rotatably by insertion into a hole  62  of the gear holder  48 . Similar to the first gear  44 , on an outer circumferential region of the second gear  46 , a plurality of second gear teeth  64  of a concave/convex shape are formed. The second gear teeth  64  are enmeshed with the first gear teeth  52  of the first gear  44 . A predetermined region along the circumferential direction of the second gear  46  is reduced in diameter in a radial inward direction, and the second gear teeth  64  are not provided on such a reduced diameter region. 
     Further, in an end part of the outer circumferential region on the second gear  46 , the first locator part  56  is formed at a position between the second gear teeth  64 , whereas on a central part on the outer circumferential region, the second locator part  66  is formed at a position between the second gear teeth  64 . 
     The first and second locator parts  56 ,  66  are formed respectively by two adjacent second gear teeth  64 , and wall portions  68   a ,  68   b  that join the second gear teeth  64  to one another. Observed from the outer circumferential direction of the second gear  46 , the first and second locator parts  56 ,  66  are formed with U-shapes in cross section, which open toward the side opposite from the gear holder  48  (see  FIGS. 6 and 9 ). The first and second locator parts  56 ,  66  are formed at substantially the same diameter as the tooth-end diameter of the second gear teeth  64 , and together therewith, at an inside part surrounded by two of the second gear teeth  64  and the wall portions  68   a ,  68   b , the first and second locator parts  56 ,  66  include engagement grooves  70   a ,  70   b  (see  FIG. 8 ), which engage with a first narrow tooth  58  and second narrow tooth  90  (to be described later). 
     When the second gear  46  engages with respect to the first gear  44 , the first gear teeth  52  and the second gear teeth  64  become enmeshed, and together therewith, upon rotation of the first and second gears  44 ,  46 , the first locator part  56  engages within one of the first locator grooves  54   a  on the first gear  44 , whereas the second locator part  66  is engaged with respect to the other first locator groove  54   b.    
     Further, when the first and second locator parts  56 ,  66  are engaged respectively within the first locator grooves  54   a ,  54   b  on the first gear  44 , the first narrow teeth  58  of the first gear  44  become engaged with respect to the engagement grooves  70   a ,  70   b  formed therein, whereupon the driving force from the first gear  44  is transmitted to the second gear  46  via the first narrow teeth  58  and the engagement grooves  70   a ,  70   b.    
     More specifically, when the driving force transmission mechanism  22  including the first and second gears  44 ,  46  is assembled, by insertion of the first locator part  56  into the first locator groove  54   a  of the first gear  44 , such parts function mutually as a positioning means for performing positioning in the direction of rotation. Together therewith, by engagement of the first narrow tooth  58  in the engagement grooves  70   a ,  70   b  formed therein, a driving force transmitting function also is provided, by which the driving force from the first gear  44  can reliably be transmitted to the second gear  46 . 
     The gear holder  48  is formed in a substantially triangular shape and tapers from a lower portion toward an upper portion thereof. The gear holder  48  is connected to the housing  36  of the drive source  20  through a first mounting section  72  formed at the lower portion thereof, and is fixed to a side wall of the first divided casing  26  through a second mounting section  74  formed at the upper portion. 
     More specifically, the first mounting section  72  is fastened together to the upper portion of the housing  36  by two bolts  76 , whereas the second mounting section  74  is fixed by a single bolt  76  while being separated a predetermined distance from the side surface of the first divided casing  26 . 
     Further, at a substantially central portion of the gear holder  48 , the hole  62  is formed through which the shaft member  60  of the second gear  46  is inserted, such that by insertion and fitting of the shaft member  60 , the second gear  46  is retained in a rotatable manner. Moreover, the second gear  46  is arranged between the gear holder  48  and the side wall of the first divided casing  26 . 
     Upwardly of the hole  62 , a shaft groove (support hole)  78  is formed, which extends upwardly in an inclined fashion toward the second mounting section  74 . An end of a later-described damper shaft  50  is supported rotatably with respect to the shaft groove  78 . The shaft groove  78  is formed in a straight shape while tapering gradually in a direction separating away from the hole  62 , the end thereof being formed with a semicircular shape in cross section. 
     In the interior of the casing  12 , a damper shaft  50  is provided that confronts the inner wall surface of the air mixing damper  18 , the damper shaft  50  being disposed along the widthwise direction of the casing  12 . One end of the damper shaft  50  is supported rotatably with respect to a center plate (not shown) sandwiched between the first divided casing  26  and the second divided casing  28 , whereas the other end thereof is inserted into a shaft hole  80  (see  FIG. 1 ) provided in a side of the first divided casing  26 . 
     Further, on the other end of the damper shaft  50 , as shown in  FIG. 10 , a damper gear  82  is formed on the outer side of the first divided casing  26 , which is enmeshed with the second gear  46 . Together therewith, further from the end of the damper gear  82 , a support shaft  84  having a radially inward reduced diameter is formed, which is inserted into and supported rotatably in the shaft groove  78  of the gear holder  48 . In greater detail, the support shaft  84  is axially supported in the end of the shaft groove  78  that is formed with the semicircular shape in cross section. 
     More specifically, opposite ends of the damper shaft  50  are supported by the center plate and the gear holder  48 , such that the damper shaft  50  is supported rotatably in the casing  12 . 
     On the other hand, on the damper shaft  50 , pinion gears  86  are formed respectively at positions facing the rack members  32  of the air mixing damper  18  for being enmeshed respectively with respect to the rack member  32 . More specifically, by rotation of the damper shaft  50 , under engagement of the pinion gear  86  and the rack member  32 , the air mixing damper  18  is moved in upward and downward directions along the guide walls  34   a ,  34   b  of the casing  12 . 
     The damper gear  82  has a predetermined width along the axial direction of the damper shaft  50 , with a plurality of gear teeth being formed along the outer circumferential surface thereof. In addition, a second locator groove  88 , from which one of the gear teeth is removed, is formed on the damper gear  82 . The second locator groove  88  is formed with a predetermined width centrally about the position of a central gear tooth from among three adjacent gear teeth, and is formed so as to enable insertion therein of the second locator part  66  that makes up part of the second gear  46 . 
     The second locator groove  88  is formed along the thickness direction of the damper gear  82 . The second narrow tooth  90  is formed in the second locator groove  88 , having a width dimension that extends from one end side directing one end of the damper shaft  50  to the other end side thereof, and which is roughly half the width of the other gear teeth. The second narrow tooth  90  is formed at the same pitch and with the same cross sectional shape as the other gear teeth. More specifically, the second narrow tooth  90  is constituted with a width dimension roughly half that of one gear tooth. 
     Additionally, when the damper gear  82  and the second gear  46  are enmeshed with each other, the second narrow tooth  90  engages within the engagement groove  70   b  in the second locator part  66  (see  FIG. 8 ). 
     More specifically, when the second gear  46  and the damper gear  82  are assembled, by insertion of the second locator part  66  into the second locator groove  88  of the second gear  46 , such parts function mutually as a positioning means for carrying out positioning in the direction of rotation. Together therewith, by engagement of the second narrow tooth  90  in the engagement groove  70   b  formed therein, a driving force transmitting function also is provided, by which the driving force from the second gear  46  can reliably be transmitted to the damper gear  82 . 
     The vehicular air conditioning apparatus  10  according to the present invention is constructed basically as described above. Next, a situation shall be described by which the driving force transmission mechanism  22  is assembled with respect to the casing  12 , the drive source  20 , and the air mixing damper  18 . 
     Initially, the first gear  44  is mounted on the drive shaft  38  of the drive source  20 , and the first mounting section  72  of the gear holder  48  is fixed by the bolts  76  with respect to the housing  36  of the drive source  20 . Additionally, the first locator part  56  of the second gear  46  is inserted with respect to the first locator groove  54   a  of the first gear  44 , and in a state where the first narrow tooth  58  engages within the engagement groove  70   a , the shaft member  60  of the second gear  46  is inserted and fitted into the hole  62  of the gear holder  48 . 
     Owing thereto, in a state where relative positioning in the direction of rotation between the first gear  44  and the second gear  46  is brought about by the first locator part  56  and the first locator groove  54   a , the first and second gears  44 ,  46  are assembled through the gear holder  48 , thus constituting a driving force transmission unit  92 , which is connected integrally to the drive source  20 . 
     Next, the driving force transmission unit  92  is assembled onto a side wall of the first divided casing  26  that constitutes the casing  12 . In this case, the mounting bracket  40  already is installed through plural bolts  42  on a lower part of the drive source  20 , whereas the air mixing damper  18  and the damper shaft  50  are accommodated in the interior of the casing  12 , and the damper gear  82  of the damper shaft  50  is in a state of projecting from the side surface through the shaft hole  80 . 
     In the above-described condition, an operator places the second gear  46  in confronting relation with respect to the first divided casing  26 , and while gripping the driving force transmission unit  92  with the mounting bracket  40  oriented downward and the second mounting section  74  on the gear holder  48  oriented upwardly, causes the driving force transmission unit  92  to approach the side surface of the first divided casing  26 . Additionally, the support shaft  84  of the damper shaft  50  is inserted through the shaft groove  78  of the gear holder  48 , and together therewith, the second gear  46  is made to engage with the damper gear  82  of the damper shaft  50 . At this time, assembly is performed such that the second locator part  66  of the second gear  46  is inserted into the second locator groove  88  of the damper gear  82 , and further, the second narrow tooth  90  of the damper gear  82  engages within the engagement groove  70   b  of the second locator part  66 . 
     Owing thereto, relative positioning between the second gear  46  and the damper gear  82  in the direction of rotation is brought about by the second locator part  66 , and after proper positioning of the second gear  46  and the damper gear  82  has been confirmed, the mounting bracket  40  is fixed to the side surface of the first divided casing  26 , while simultaneously, the second mounting section  74  of the gear holder  48  is fixed to the side surface of the first divided casing  26  by the bolt  76 . 
     As a result, the second gear  46 , which is supported by the gear holder  48 , is assembled onto the side surface of the casing  12  in a state whereby the first gear  44  connected to the drive source  20  and the damper gear  82  of the damper shaft  50  that causes rotary movement (turning) of the air mixing damper  18  are mutually enmeshed respectively with each other. More specifically, the first and second gears  44 ,  46  and the damper gear  82  are assembled together in a condition of mutual positioning therebetween along the direction of rotation. 
     Next, operations and effects of the vehicular air conditioning apparatus  10 , on which the driving force transmission unit  92  has been assembled in the above manner, shall briefly be explained. 
     First, the driver, by operating a non-illustrated operation switch for performing temperature adjustment inside the vehicle compartment, causes a control signal to be output with respect to the drive source  20  through a controller (not shown). 
     For example, in the case that a heating operation is performed in the vehicular air conditioning apparatus  10  sworn in  FIG. 2 , by switching to an operational mode by means of the operation switch, the control signal output to the drive source  20  through the non-illustrated controller is switched, and the drive shaft  38  is rotated under a driving action of the drive source  20 . Owing thereto, the first gear  44  is rotated in a clockwise direction (the direction of arrow C 1  in  FIG. 7 ), and along therewith, the second gear  46  is rotated in a counterclockwise direction (the direction of arrow D 1  in  FIG. 7 ) and the damper gear  82  is rotated in a clockwise direction (the direction of arrow E 1  in  FIG. 7 ). 
     In addition, as a result of the driving force from the drive source  20 , the damper shaft  50  is rotated through a predetermined angle in a counterclockwise direction (the direction of arrow D 1 ), whereupon, due to engagement of the pinion gear  86  and the rack member  32 , the air mixing damper  18  shown in  FIG. 2  is moved upwardly a predetermined distance along the guide walls  34   a ,  34   b  so as to separate from the heater core  16 . 
     Owing thereto, the air mixing damper  18 , which is fitted to close between the evaporator  14  and the heater core  16 , moves, whereupon a portion of the air that has passed through the evaporator  14  flows through the heater core  16 , which is disposed downstream from the evaporator  14 , and passes to the interior. As a result, a portion of the air, after being heated by the heater core  16 , is mixed with air that has passed only through the evaporator  14 , whereby the air is adjusted in temperature in the interior of the casing  12 . Then, the temperature adjusted air, after passing through passages inside the casing  12 , is blown out into the vehicle compartment from outlet ports, for example, in the vicinity of the feet of passengers in the vehicle. 
     On the other hand, in the case that a cooling operation is performed in the vehicular air conditioning apparatus  10 , by switching to an operational mode by means of the operation switch, the drive shaft  38  is rotated in an opposite direction under a driving action of the drive source  20 , and the first gear  44  is rotated together with the drive shaft  38  in a counterclockwise direction (the direction of arrow C 2  in  FIG. 7 ). As a result, the second gear  46 , through engagement with the first gear  44 , is rotated in a clockwise direction (the direction of arrow D 2  in  FIG. 7 ), and the damper gear  82 , through engagement with the second gear  46 , is rotated in a counterclockwise direction (the direction of arrow E 2  in  FIG. 7 ). 
     Owing thereto, the damper shaft  50  is rotated counterclockwise (the direction of arrow E 2 ) by the driving force from the drive source  20 , and the air mixing damper  18 , which is engaged with the pinion gear  86  through the rack member  32 , is moved along the guide walls  34   a ,  34   b  to the downward side facing the heater core  16 . 
     As a result, since the flow of air that has passed between the evaporator  14  and the heater core  16  is blocked by the air mixing damper  18 , air (cooled air) supplied from the blower fan and which has passed through the evaporator  14  does not flow through to the side of the heater core  16 , but flows directly to the outlet ports through passages inside the casing  12 , and is blown out into the vehicle compartment from outlet ports, for example, which are capable of blowing air in the vicinity of faces of passengers in the vehicle. 
     In the foregoing manner, with the present embodiment, in the driving force transmission mechanism  22 , which is capable of transmitting a driving force from the drive source  20  to the air mixing damper  18  accommodated in the casing  12 , a structure is provided comprising the second gear  46 , which is enmeshed with the first gear  44  connected to the drive source  20 , and further is enmeshed with the damper shaft  50  that causes the air mixing damper  18  to turn, and the second gear  46  is rotatably supported with respect to the gear holder  48 . 
     As a result of the aforementioned structure, even in the case that, in the casing  12 , the drive source  20  and the air mixing damper  18 , which is turned by the driving force from the drive source  20 , are arranged at positions separated from each other, the driving force output from the first gear  44  can be transmitted reliably and efficiently to the damper shaft  50  through the second gear  46 . Together therewith, since the gear holder  48  in which the second gear  46  is supported can easily be fixed with respect to the first divided casing  26  and the drive source  20 , ease of assembly of the vehicular air conditioning apparatus  10  including the driving force transmission mechanism  22  can be improved. 
     Further, because the driving force of the drive source  20  is transmitted efficiently to the air mixing damper  18  via a gear mechanism defined by the first and second gears  44 ,  46  and the damper shaft  50  that constitute the driving force transmission mechanism  22 , the air mixing damper  18  is capable of undergoing switching movements with high precision, and along therewith, the mixing ratio of cool air and warm air can be controlled highly precisely by the air mixing damper  18 . 
     Furthermore, because, by insertion of the damper shaft  50  through the shaft groove  78  of the gear holder  48 , a constant distance is maintained between the damper shaft  50  and the second gear  46  supported in the gear holder  48 , mutual separation of the damper shaft  50  and the second gear  46  away from each other can be avoided. More specifically, a problem in which the driving force of the second gear  46  does not get transmitted to the damper shaft  50 , due to the damper shaft  50  and the second gear  46  moving in directions away from each other and resulting in release of the enmeshed state therebetween, can be avoided. Stated otherwise, changes in the enmeshed condition between the second gear  46  and the damper shaft  50  are avoided. 
     As a result, the driving force, which is transmitted from the drive source  20  to the second gear  46  via the first gear  44 , can be reliably transmitted to the damper shaft  50 , thus enabling driving of the air mixing damper  18  to be controlled. 
     The vehicular air conditioning apparatus according to the present invention is not limited to the aforementioned embodiment. It should be understood that various changes and modifications may be made thereto without departing from the scope of the invention as set forth in the appended claims.