Abstract:
An air volume control module for use with a vehicular air conditioning apparatus includes a circuit board including a control circuit for controlling the rotational speed of the blower of the vehicular air conditioning apparatus, a heat sink connected to the circuit board and including a fin for radiating heat generated by the circuit board, and a base housing surrounding the circuit board, the heat sink being inserted in the base housing with the fin projecting from the base housing. The base housing is mounted on the heat sink only by a locking finger. Either one of the base housing and the fin of the heat sink has a protective projection having a heightwise dimension greater than that of the locking finger.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to an air volume control module for controlling the rotational speed of the blower of a vehicular air conditioning apparatus. 
     2. Description of the Related Art 
     Vehicular aid-conditioning systems include a blower unit and a cooling/heating unit. Air delivered from the blower of the blower unit is adjusted in temperature by the evaporator and heater of the cooling/heating unit and introduced as conditioned air from air outlets into the passenger compartment of the vehicle. 
     The blower is rotated by a motor whose rotational speed is controlled by an air volume control module for use with the vehicular air conditioning apparatus, as disclosed in Japanese Laid-Open Patent Publication No. 2005-289243. 
     One known air volume control module of the type described above is shown in  FIGS. 7 and 8  of the accompanying drawings. As shown in  FIGS. 7 and 8 , the air volume control module, generally denoted by  1 , comprises a circuit board  2  including a control circuit, a heat sink  3  on which the circuit board  2  is mounted, and a base housing  5  surrounding a portion  4  of the heat sink  3  on which the circuit board  2  is mounted. The portion  4  will hereinafter be referred to as “board mount  4 ”. 
     The base housing  5  is generally made of a resin material and has an insertion opening  6  defined in one end thereof for the insertion therein of the heat sink  3 . The heat sink  3  has a support base  7  disposed on the board mount  4  and a plurality of fins  8  mounted on the support base  7 . The support base  7  is wider than the insertion opening  6 . When the support base  7  is secured to the base housing  5  with the board mount  4  inserted in the insertion opening  6 , the heat sink  3  is supported on the base housing  5  with the fins  8  projecting therefrom (see  FIG. 8 ). 
     The board mount  4  includes a pair of parallel support plates  9 ,  10  (see  FIG. 7 ) extending parallel to each other away from the support base  7 . The circuit board  2  is firmly mounted on the parallel support plates  9 ,  10 . Four terminals  11  through  14  are joined to the circuit board  2  and extend away from the board mount  4 . When the board mount  4  is housed in the base housing  5 , the terminals  11  through  14  project into a terminal protector  36  of the base housing  5 . In  FIG. 7 , the terminals  12 ,  14  are positioned behind the respective terminals  11 ,  13  and hence concealed from view. 
     A power transistor, not shown, is mounted on the circuit board  2 . The terminals  11 ,  12 , the terminal  13 , and the terminal  14  are electrically connected respectively to the drain, gate, and source electrodes of the power transistor. A capacitor  15  is also mounted on the circuit board  2 . 
     A plurality of resistors, not shown, are also mounted on the circuit board  2 . The power transistor, the capacitor  15 , and the resistors are electrically connected, making up a control circuit for controlling the rotational speed of the motor. 
     The base housing  5  has a pair of through screw holes  16 ,  17  defined therein. The heat sink  3  includes a pair of internally threaded legs  18 ,  19  disposed adjacent to the respective parallel support plates  9 ,  10  and positioned diagonally opposite to each other across the heat sink  3 . Screws  20 ,  21  are inserted respectively through the through screw holes  16 ,  17  and threaded respectively into the internally threaded legs  18 ,  19 , thereby fastening the base housing  5  to the heat sink  3 . 
     The air volume control module  1  thus constructed is installed at a given position in the vehicular air conditioning apparatus, and an electric power source is electrically connected to the terminals  11  through  14 . 
     The base housing  5  has an end flange having a triangular end and a trapezoidal end which are opposite to each other. When an attempt is made to install the base housing  5  in a wrong orientation in the vehicular air conditioning apparatus, the triangular end of the end flange of the base housing  5  physically interferes with a certain surface of the vehicular air conditioning apparatus, preventing the base housing  5  from being installed in the vehicular air conditioning apparatus. Consequently, the base housing  5  can be installed in the vehicular air conditioning apparatus only when the base housing  5  is properly oriented with respect to the vehicular air conditioning apparatus. 
     The base housing  5  is fastened to the heat sink  3  by the screws  20 ,  21 . However, the fastening process is tedious and time-consuming to perform because it is necessary to position the screws  20 ,  21  with respect to the through screw holes  16 ,  17  and turn the positioned screws  20 ,  21  to tighten them in the internally threaded legs  18 ,  19 . 
     SUMMARY OF THE INVENTION 
     It is a general object of the present invention to provide an air volume control module for use with a vehicular air conditioning apparatus, which includes a base housing that can easily be installed on a heat sink. 
     A major object of the present invention is to provide an air volume control module for use with a vehicular air conditioning apparatus, which can be assembled according to a highly simple assembling process. 
     According to the present invention, there is provided an air volume control module for controlling the rotational speed of a blower of a vehicular air conditioning apparatus, comprising a circuit board including a control circuit for controlling the rotational speed of the blower, a heat sink connected to the circuit board and including a fin for radiating heat generated by the circuit board, and a base housing surrounding the circuit board, the heat sink being inserted in the base housing with the fin projecting from the base housing, wherein the base housing has an insertion opening for inserting the heat sink therethrough into the base housing, and includes a locking finger disposed adjacent to the insertion opening for locking the heat sink in the base housing, the base housing is mounted on the heat sink only by the locking finger, and either one of the base housing and the fin of the heat sink has a protective projection having a heightwise dimension greater than that of the locking finger. 
     In the present invention, the heat sink is mounted on the base housing by the locking finger. Thus, the heat sink and the base housing do not need to be fastened to each other by screws. In other words, it is not necessary to position screws and turn the positioned screws in securing the heat sink to the base housing. The heat sink may be installed on the base housing simply by inserting a board mount of the heat sink into the base housing. 
     Since no process is required to position screws and no process is required to turn the positioned screws, the air volume control module can be assembled highly efficiently according to a highly simple assembling process. 
     The air volume control module includes the protective projection which has a heightwise dimension greater than that of the locking finger. When the air volume control module is installed on a predetermined position of a structural member of the vehicular air conditioning apparatus, only the protective projection hits the structural member, but the locking finger does not hit the structural member. The locking finger is thus prevented from being broken by the structural member, preventing the heat sink from being dislodged from the base housing. 
     According to the related art, the air volume control module is prevented from being assembled in error in the vehicular air conditioning apparatus because the end surface (flange) of the base housing physically interferes with a certain portion of the vehicular air conditioning apparatus if the air volume control module is wrongly oriented. Therefore, the end flange of the base housing needs to be of a dimension which can physically interfere with the certain portion of the vehicular air conditioning apparatus. According to the present invention, the protective projection should be disposed in a position which physically interferes with the vehicular air conditioning apparatus when an attempt is made to install the air volume control module in a wrong orientation in the vehicular air conditioning apparatus. 
     Because of the protective projection thus positioned, an end flange of the base housing is not required to be of an excessive dimension for physical interference with a certain region of the vehicular air conditioning apparatus. As a result, the amount of a material which the base housing is made of may be reduced. The air volume control module according to the present invention is, therefore, a resource saver and a cost saver. 
     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 preferred embodiments of the present invention are shown by way of illustrative example. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a perspective view of an air volume control module according to a first embodiment of the present invention; 
         FIG. 2  is an enlarged fragmentary cross-sectional view of the air volume control module shown in  FIG. 1 ; 
         FIG. 3  is a plan view, partly in cross section, showing the manner in which the air volume control module shown in  FIG. 1  is installed, with a base housing being directed in a normal orientation, on a structural member of a vehicular air conditioning apparatus; 
         FIG. 4  is a plan view, partly in cross section, showing the manner in which an attempt is made to install the air volume control module shown in  FIG. 1 , with the base housing being directed in a wrong orientation, on the structural member of the vehicular air conditioning apparatus; 
         FIG. 5  is a perspective view of an air volume control module according to a second embodiment of the present invention; 
         FIG. 6  is an enlarged fragmentary cross-sectional view of the air volume control module shown in  FIG. 5 ; 
         FIG. 7  is an exploded plan view of an air volume control module according to the related art; and 
         FIG. 8  is a perspective view of the air volume control module shown in  FIG. 7 . 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Air volume control modules according to preferred embodiments of the present invention will be described in detail below with reference to  FIGS. 1 through 6 . Those parts shown in  FIGS. 1 through 6  which are identical to those shown in  FIGS. 7 and 8  are denoted by identical reference characters, and will not be described in detail below. Furthermore, like or corresponding parts are denoted by like or corresponding reference characters throughout views. 
       FIG. 1  shows in perspective an air volume control module  30  according to a first embodiment of the present invention. As shown in  FIG. 1 , the air volume control module  30  generally comprises a heat sink  32  of metal and a base housing  34  connected to the heat sink  32 . 
     The heat sink  32  is structurally similar to the heat sink  3  shown in  FIGS. 7 and 8  except that the heat sink  32  is free of the internally threaded legs  18 ,  19 . Specifically, the heat sink  32  has a wide support base  7 , a board mount  4  disposed beneath the support base  7 , and a plurality of fins  8  mounted on the support base  7 . The board mount  4  is inserted through an insertion opening  6  defined in an end flange of the base housing  34  and finally placed in the base housing  34 . 
     The board mount  4  includes a pair of parallel support plates  9 ,  10  (see  FIG. 7 ) extending parallel to each other away from the support base  7  as with the heat sink  3 . The circuit board  2  is firmly mounted on the parallel support plates  9 ,  10 . When the board mount  4  is placed in the base housing  34 , terminals that are electrically connected to the drain, gate, and source electrodes of the power transistor mounted on the circuit board  2  project into a terminal protector  36  of the base housing  34 . 
     The fins  8  of the heat sink  32  project from the base housing  34  (see  FIG. 1 ). The fins  8 , which are arranged parallel to each other at spaced intervals in an array, include second fins  8   a ,  8   b  and third fins  8   c ,  8   d  from respective opposite ends of the array. As shown in  FIGS. 1 and 2 , an engaging tooth  38  is mounted on and extends between side edges of the second and third fins  8   a ,  8   c  at their lower ends, and an engaging tooth  40  is also mounted on and extends between side edges of the second and third fins  8   b ,  8   d  at their lower ends. Similarly, an engaging tooth  42  is mounted on and extends between opposite side edges of the second and third fins  8   a ,  8   c  at their lower ends, and an engaging tooth  44  is also mounted on and extends between opposite side edges of the second and third fins  8   b ,  8   d  at their lower ends. The engaging teeth  42 ,  44  are positioned in line-symmetric relationship to the engaging teeth  38 ,  40  with respect to the axis of the array of fins  8 . 
     The base housing  34 , which is made of a resin material, has four locking fingers  46 ,  48 ,  50 ,  52  integrally formed therewith which project from a surface of the base housing  34  that faces away from the board mount  4 . The locking fingers  46 ,  48 ,  50 ,  52 , which are shaped identically to each other, are positioned closely to the insertion opening  6  and held in alignment with the engaging teeth  38 ,  40 ,  42 ,  44 . The locking fingers  50 ,  52  are positioned in line-symmetric relationship to the locking fingers  46 ,  48  with respect to the axis of the array of fins  8 . 
     As shown in  FIG. 2 , the locking fingers  46 ,  48 ,  50 ,  52  have respective hooks  54  projecting toward the fins  8  and engaging the upper end surfaces of the respective engaging teeth  38 ,  40 ,  42 ,  44 . Since the engaging teeth  38 ,  40 ,  42 ,  44  of the heat sink  32  are locked by the respectively hooks  54  of the locking fingers  46 ,  48 ,  50 ,  52 , the heat sink  32  is securely mounted on the base housing  34 . 
     The second fin  8   a  includes a pair of protective projections  56 ,  60  on the respective longitudinal side edges thereof. The protective projections  56 ,  60  have a heightwise dimension greater than the locking fingers  46 ,  50 . Similarly, the second fin  8   b  includes a pair of protective projections  58 ,  62  on the respective longitudinal side edges thereof. The protective projections  58 ,  62  have a heightwise dimension greater than the locking fingers  48 ,  52 . The protective projections  56 ,  58 ,  60 ,  62  are positioned adjacent to the locking fingers  46 ,  48 ,  50 ,  52 , respectively, with small clearances therebetween. 
     The air volume control module  30  according to the first embodiment is basically constructed as described above. A process of assembling the air volume control module  30  and advantages of the air volume control module  30  will be described below. 
     For assembling the air volume control module  30 , the board mount  4  of the heat sink  32  is inserted into the insertion opening  6  of the base housing  34 . At this time, the locking fingers  46 ,  48 ,  50 ,  52 , which are integrally formed with the base housing  34  of resin material, are resiliently flexed away from the insertion opening  6  because the hooks  54  are pressed and laterally displaced by the respective engaging teeth  38 ,  40 ,  42 ,  44 . 
     When the engaging teeth  38 ,  40 ,  42 ,  44  move past the respective hooks  54 , the locking fingers  46 ,  48 ,  50 ,  52  resiliently snap back, bringing the hooks  54  into engagement with the upper end surfaces of the respective engaging teeth  38 ,  40 ,  42 ,  44 . As a result, the engaging teeth  38 ,  40 ,  42 ,  44  are locked by the respective locking fingers  46 ,  48 ,  50 ,  52 , so that the heat sink  32  is securely mounted on the base housing  34 . Therefore, the heat sink  32  does not need to be fastened to the base housing  34  by screws. 
     According to the first embodiment, as described above, the heat sink  32  can easily be installed on the base housing  34  simply by inserting the board mount  4  of the heat sink  32  into the insertion opening  6  of the base housing  34 . It is not necessary to perform a tedious and time-consuming process of positioning and tightening screws in assembling the air volume control module  30 . 
     As shown in  FIG. 3 , the assembled air volume control module  30  is then installed at a given position on a structural member  70  of a vehicular air conditioning apparatus, with the heat sink  32  being placed in a predetermined position in the structural member  70 . 
     If it were not for the protective projections  56 ,  58 ,  60 ,  62 , then the locking fingers  46 ,  48 ,  50 ,  52  would be fully exposed and might possibly be broken when the locking fingers  46 ,  48 ,  50 ,  52  hit the structural member  70  of the vehicular air conditioning apparatus. 
     According to the first embodiment, however, the protective projections  56 ,  58 ,  60 ,  62  which have a heightwise dimension greater than the locking fingers  46 ,  48 ,  50 ,  52  are positioned adjacent to the locking fingers  46 ,  48 ,  50 ,  52 , respectively, as described above. Therefore, only the protective projections  56 ,  58 ,  60 ,  62 , but not the locking fingers  46 ,  48 ,  50 ,  52 , will hit the structural member  70  of the vehicular air conditioning apparatus. Consequently, the locking fingers  46 ,  48 ,  50 ,  52  are protected against being broken, preventing the heat sink  32  from being dislodged from the base housing  34 . 
     In  FIG. 3 , the air volume control module  30  is shown as being installed, with the base housing  34  being directed in a normal orientation, on the structural member  70  of the vehicular air conditioning apparatus. When an attempt is made to install the air volume control module  30 , with the base housing  34  being directed in an opposite orientation, i.e., a wrong orientation, on the structural member  70  of the vehicular air conditioning apparatus, as shown in  FIG. 4 , some of the protective projections  56 ,  58 ,  60 ,  62  physically interfere with the structural member  70 . Accordingly, the air volume control module  30  cannot properly be installed on the structural member  70  of the vehicular air conditioning apparatus, or stated otherwise is prevented from being assembled in error on the vehicular air conditioning apparatus. 
     When an attempt is made to install the air volume control module  30  which is free of the protective projections  56 ,  58 ,  60 ,  62 , with the base housing  34  being directed in the wrong orientation, on the structural member  70  of the vehicular air conditioning apparatus, as shown in  FIG. 4 , some of the locking fingers  46 ,  48 ,  50 ,  52  would possibly hit the structural member  70  and be broken thereby. According to the first embodiment, however, since some of the protective projections  56 ,  58 ,  60 ,  62  physically interfere with the structural member  70 , the heat sink  32  will not be further inserted into the hole in the structural member  70 . The locking fingers  46 ,  48 ,  50 ,  52  will not be brought into hitting engagement with the structural member  70  and hence will not be broken thereby. 
     In addition, the end flange of the base housing  34  is not required to be of such a dimension as to extend to and interfere with a certain region of the structural member  70 , e.g., a rib  72  (see  FIGS. 3 and 4 ), when an attempt is made to install the air volume control module  30  in a wrong orientation on the structural member  70 . As a result, in forming the base housing  34 , the amount of the resin material which the base housing  34  is made of may be reduced. The air volume control module  30  according to the first embodiment is, therefore, a resource saver and a cost saver. 
     The protective projections may be integrally formed with the base housing  34 . Such a modification will be described below. 
       FIG. 5  shows in perspective an air volume control module  80  according to a second embodiment of the present invention. The air volume control module  80  is similar to the air volume control module  30  according to the first embodiment except that the fins  8   a ,  8   b  are free of the protective projections  56 ,  58 ,  60 ,  62  and the base housing  34  has protective projections  82 ,  84 ,  86 ,  88  integrally formed therewith and disposed adjacent to the locking fingers  46 ,  48 ,  50 ,  52 , respectively. Those parts of the air volume control module  80  which are identical to those of the air volume control module  30  according to the first embodiment are denoted by identical reference characters and will not be described in detail below. 
     As shown in  FIGS. 5 and 6 , the protective projections  82 ,  84 ,  86 ,  88  are positioned adjacent to the opposite longitudinal ends of the second fins  8   a ,  8   b  from respective opposite ends of the array of the fins  8 . The protective projections  82 ,  84 ,  86 ,  88  are spaced from the locking fingers  46 ,  48 ,  50 ,  52  with small clearances therebetween to allow the locking fingers  46 ,  48 ,  50 ,  52  to remain resiliently flexible. 
     The protective projections  82 ,  84 ,  86 ,  88  have a heightwise dimension greater than that of the locking fingers  46 ,  48 ,  50 ,  52 . Therefore, when the air volume control module  80  is to be installed on the structural member  70  of the vehicular air conditioning apparatus, only the protective projections  82 ,  84 ,  86 ,  88 , but not the locking fingers  46 ,  48 ,  50 ,  52 , will hit the structural member  70  of the vehicular air conditioning apparatus. Consequently, the locking fingers  46 ,  48 ,  50 ,  52  are protected against being broken, preventing the heat sink  32  from being dislodged from the base housing  34 . 
     When an attempt is made to install the air volume control module  80 , with the base housing  34  being directed in a wrong orientation, on the structural member  70  of the vehicular air conditioning apparatus, some of the protective projections  82 ,  84 ,  86 ,  88  physically interfere with the structural member  70 , as shown in  FIG. 4 . Accordingly, the air volume control module  80  is prevented by the protective projections  82 ,  84 ,  86 ,  88  from being assembled in error on the vehicular air conditioning apparatus. 
     Stated otherwise, if it were not for the protective projections  82 ,  84 ,  86 ,  88 , then when an attempt is made to install the air volume control module  80 , with the base housing  34  being directed in the normal orientation but displaced from a predetermined position or with the base housing  34  being directed in a wrong orientation, on the structural member  70 , some of the locking fingers  46 ,  48 ,  50 ,  52  would possibly hit the structural member  70  and be broken thereby. According to the second embodiment, however, since some of the protective projections  82 ,  84 ,  86 ,  88  physically interfere with the structural member  70 , the heat sink  32  will not be further inserted into the hole in the structural member  70 . The locking fingers  46 ,  48 ,  50 ,  52  will not be brought into hitting engagement with the structural member  70  and hence will not be broken thereby. 
     In the first and second embodiments, as described above, when an attempt is made to install the air volume control module  30  or the air volume control module  80  in a wrong orientation on the structural member  70 , some of the protective projections  56 ,  58 ,  60 ,  62  or the protective projections  82 ,  84 ,  86 ,  88  physically interfere with the structural member  70 , preventing the air volume control module  30  or the air volume control module  80  from being assembled in error on the vehicular air conditioning apparatus. However, the end flange of the base housing  34  may be of such a dimension as to extend to and interfere with a certain region of the structural member  70 , e.g., the rib  72  (see  FIGS. 3 and 4 ), when an attempt is made to install the air volume control module  30  or the air volume control module  80  in a wrong orientation on the structural member  70 . 
     Although certain preferred embodiments of the present invention have been shown and described in detail, it should be understood that various changes and modifications may be made therein without departing from the scope of the appended claims.