Abstract:
The present disclosure relates to electrical component heat dissipation and, more particularly, to a method and apparatus for dissipating heat from a power control module. In one embodiment the invention is a power control module having a housing and an electrical connection. A thermally conductive material is placed between the power control module and a surface of an evaporator core with a first side of the thermally conductive material in contact with the power control module and a second side in contact with the surface of the evaporator core. The thermally conductive material conducts heat from the power control module to the surface of the evaporator core.

Description:
TECHNICAL FIELD 
     The present invention relates to electrical component heat dissipation and, more particularly, to a method and apparatus for dissipating heat from a power control module. 
     BACKGROUND OF THE INVENTION 
     The heating, ventilation and air conditioning (HVAC) systems of a vehicle typically include a blower motor. Often these blower motors are direct current brushed blower motors. Additionally, the system includes a power control module such as a linear power module, a pulse width modulator, or a relay resistor module, all of which provide variable speed control of the blower motor. One difficulty associated with these power control modules is that they typically generate a significant amount of heat, which must be dissipated to preserve the life of the module. The traditional method for dissipating heat has required that a heat sink attached to the power control module be designed individually for each power control module design. In addition, it is typically required that the heat sink be inserted into the airflow of the HVAC system to cool the electronic components inside of the power control module. These specially designed heat sinks have generally been large and cumbersome and typically raise the cost of the power control module by at least 15%. The requirement that the heat sink be located within the airflow of the HVAC system negatively influences the system noise and airflow. 
     Thus, it would be beneficial to design an apparatus and develop a method for dissipating heat from power control modules that is relatively inexpensive, and does not negatively affect system noise or air flow. 
     SUMMARY OF THE INVENTION 
     In one embodiment, the present invention is a power control module comprising: a power control module having a housing and an electrical connection; a thermally conductive material having a first side in contact with the power control module and a second side in contact with a surface of an evaporator core; and the thermally conductive material conducting heat from the power control module to the surface of the evaporator core. 
     In another embodiment the present invention is a power control module comprising: a power control module having a housing and an electrical connection; a thermally conductive material having a first side connected to the power control module and a second side secured to a surface of an evaporator core; and the thermally conductive material conducting heat from the power control module to the surface of the evaporator core. 
     In yet another embodiment the present invention is a method for cooling a power control module comprising the steps of: providing a power control module having a housing and an electrical connection; providing a surface of an evaporator core; positioning a first side of a thermally conductive material against the power control module and positioning a second side of the thermally conductive material against the surface of the evaporator core; and conducting heat from the power control module through the thermally conductive material to the surface of the evaporator core. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a partial view of a heating, ventilation, and air conditioning module of a vehicle designed according to the present invention; 
     FIG. 2 is a partial exploded view of FIG. 1; 
     FIG. 3 is a side view of an evaporator core, mounting bracket, and a power control module designed according to the present invention; 
     FIG. 4 is a cross-sectional view along Line  4 — 4  of FIG. 3; 
     FIG. 5 is a cross-sectional view along Line  5 — 5  of FIG. 3; 
     FIG. 6 is a partial exploded view of an alternative embodiment of a heating, ventilation and air conditioning module designed according to the present invention; 
     FIG. 7 is a view of FIG. 1 showing the post-installation removal of a portion of an outer housing to expose a power control module; 
     FIG. 8 is a partial exploded view of an alternative embodiment of a power control module; and 
     FIG. 9 is a partial view of FIG. 7 after installation of a replacement power control module cover. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Throughout the several views like components are assigned the same reference number. 
     A heating, ventilation, and air conditioning (HVAC) module is shown generally at  20  in FIG.  1 . HVAC module  20  includes an outer housing  22  to which is attached a blower motor mount  24 . Outer housing  22  includes an aperture  26  which provides access to an electrical connection  28  of a power control module  30  (see FIG. 2) and has features that will accept and retain a cover  88  in the event of a replacement operation. 
     FIG. 2 is a partial exploded view of FIG.  1 . Outer housing  22  covers power control module  30 , a mounting bracket  32 , and an evaporator core  34 . Evaporator core  34  is a standard vehicle HVAC evaporator core and includes a plurality of feed lines  36  and a plurality of cooling fins  38 . Evaporator core  34  further includes a first end  40 , which is covered by a surface  42 . Surface  42  includes a first edge  44  opposite a second edge  46 . Evaporator core  34  is known in the art. 
     Bracket  32  includes a pair of engaging surfaces  48  preferably in the shape of channels. Bracket  32  further includes a pair of upper retaining clips  50  and a pair of lower retaining clips  52 . Mounting bracket  32  further includes a central aperture  54  and a stop  56 . Bracket  32  is slidingly received on surface  42  with edges  46  and  44  being received in channels  48 . Stop  56  limits the travel of bracket  32  on surface  42 . As shown in FIG. 4, engaging surfaces  48 , preferably in the shape of channels, receive edges  46  and  44  to retain bracket  32  on surface  42 . Because of the environment that bracket  32  will be exposed to it is important that the bracket  32  be capable of withstanding thermal exposure and corrosive material exposure. In one embodiment bracket  32  is designed using SAE 1050 spring steel in any of a number of tempers that provide sufficient heat treating and that include a corrosion resistant coating. Such coatings are known in the art. Although the bracket  32  preferably includes two engaging surfaces  48  in the shape of channels and two pairs of clips  50  and  52 , bracket  32  could be designed with only one engaging surface  48  and a single clip. 
     Power control module  30  includes a housing  58  that surrounds its internal electronics to protect them from moisture and water susceptibility. In one embodiment the housing  58  is formed from plastic. Housing  58  includes a first end  60  that is received in lower retaining clips  52 . In one embodiment, first end  60  is especially shaped to contour to an interior contour of lower retaining clips  52 . Housing  58  further includes a second end  62  having lips  64  that are received in upper retaining clips  50  (see FIG.  5 ). Power control module  30  further includes a thermally conductive material  66  that is received in a recess  68  in housing  58 . Thermally conductive material  66  includes a first side adjacent to power control module  30  and a second side that is placed against surface  42 . Power control module  30  further includes a seal  70  surrounding electrical connection  28  and being aligned with aperture  26  when the HVAC module  20  is assembled. Seal  70  prevents condensate water from inside the HVAC module  20  from leaking out into an interior area of a vehicle. 
     Thermally conductive material  66  may comprise any material having a high thermal conductivity. Some typical examples include metals such as copper or aluminum. But, thermally conductive material  66  may also comprise thermally conductive non-metallic materials. In one embodiment thermally conductive material  66  comprises a metal plate, preferably an aluminum metal plate. The aluminum metal plate may be anodized-coated for corrosion resistance. Obviously, the size of the thermally conductive material  66  is dependent on the amount of heat that needs to be dissipated, and its thermal conductivity. In one embodiment, the thermally conductive material  66  is a flat anodized-coated aluminum plate having dimensions of approximately 38×55 mm. 
     Seal  70  may be composed of any resilient sealing material. For example, rubber, foam, elastomeric material, and other sealing materials. To compensate for surface irregularities in surface  42  it may be advantageous to include a layer of thermal grease between surface  42  and thermally conductive material  66 . Such thermal greases are well known in the art. 
     As shown in phantom in FIG. 5, when power control module  30  is received in bracket  32  after bracket  32  is mounted on evaporator core  34  thermally conductive material  66  is tightly pressed against surface  42 . This arrangement maximizes transfer of heat from power control module  30  to surface  42 . Thus, evaporator core  34  serves as a large heat sink to cool power control module  30 . 
     Electrical connection  28  can be any of the known electrical connections in the art. In one embodiment, electrical connection  28  comprises a plurality of blades and is shaped for receiving a female plug as is known in the art. 
     FIG. 6 is a partial exploded view of an alternative embodiment of a HVAC module  20  designed in accordance with the present invention. In this embodiment a thermally conductive material in the form of a plate  72  is secured to surface  42  of evaporator core  34 . Plate  72  includes a first side  74  and a second side  76 . In the assembly of this embodiment second side  76  of plate  72  is first secured to surface  42 . Plate  72  can be secured in any of a number of ways; for example, plate  72  can be vacuum brazed to surface  42  during the assembly of evaporator core  34 . Alternatively, plate  72  can be initially spot welded to surface  42  and then brazed to surface  42  during the assembly of evaporator core  34  as is known in the art. In one embodiment, plate  72  includes a series of threaded apertures  78 . Housing  58  further includes a pair of apertures  80  for receiving fasteners  82 . Fasteners  82  are preferably threaded screws that can be inserted through apertures  80  and received in threaded apertures  78  to thereby secure power control module  30  to first side  74  of plate  72 . As would be understood by one of ordinary skill in the art, housing  58  could be secured to plate  72  by many other sorts of fasteners. As discussed above, plate  72  may be formed of any thermally conductive material such as, for example, a metallic material or a synthetic material. In a preferred embodiment, plate  72  comprises an aluminum plate. 
     In FIG. 8 a partial exploded view of an alternative embodiment of power control module  30  is shown. In this embodiment the only change is that electrical connection  28  is replaced by a pigtail connection  84 . Such connections are known in the art. Pigtail connection  84  is sealed at power control module  30  and extends for a distance. Pigtail connection  84  includes a seal  86  that functions to seal aperture  26  as does seal  70 . In FIG. 8 outer housing  22  is shown with a replacement power control module cover  88  discussed below. Pigtail connection  84  further includes a retaining block  90  to maintain the arrangement of the wires. Preferably, cover  88  includes a clip  92  when combined with a pigtail connection  84  to provide a means for holding pigtail connection  84  adjacent cover  88 . 
     In the views shown in FIGS. 1,  2 , and  6  the HVAC module  20  is shown as it would initially be produced. To enable post-production repair of the power control module  30 , it is preferable that HVAC module  20  be provided with a removable portion  94  surrounding aperture  26  as shown in FIG.  7 . In one embodiment, removal portion  94  is defined by score lines on outer housing  22 . Thus, when it becomes necessary to replace power control module  30  a technician may cut along the score lines and thereby remove removable portion  94  and exposed power control module  30 . Following replacement of a power control module  30  the technician would seal outer housing  22  using replacement power control module cover  88  as shown in FIGS. 8 and 9. Cover  88  is sized to fit around the opening left when removable portion  94  is removed. Cover  88  includes an outer seal  96  that surrounds the opening left by removable portion  94  and an aperture  26 ′ for the electrical connection  28  or  84 . In one embodiment, cover  88  includes a hole  98  for receiving a fastener  100  that extends through hole  98  into a corresponding hole  102  in outer housing  22 . As shown in FIGS. 8 and 9 cover  88  can be used with either electrical connection  28  or pigtail connection  84 . Preferably, cover  88  is an injection molded plastic. Preferably outer housing  22  includes a slot  104  for receiving a portion of cover  88 . 
     The foregoing description is exemplary rather than limiting in nature. Variations and modifications to the disclosed embodiment may be come apparent to those skilled in the art and do come within the scope of this invention. Accordingly, the scope of legal protection afforded this invention can only be determined by studying the following claims.