Abstract:
An electric motor driven blower assembly provides for a complete air cooling duct running from the inside of the blower housing to the motor at the back of the housing. A vertical cooling tube on the scroll housing is mated to an open, moldable trough in the motor cover across a sealing projection on a vibration gasket. The seal of the vertical tube through the gasket provides a right angle turn in the cooling duct, providing a complete cooling duct while still allowing all parts to be easily molded.

Description:
TECHNICAL FIELD 
   This invention relates to automotive air conditioning system blowers, and particularly to an improved housing for the drive motor that provides an integral cooling duct for the electric drive motor. 
   BACKGROUND OF THE INVENTION 
   Typical automotive heating, ventilation and air conditioning modules (HVAC modules) include an electric driven centrifugal fan that spins within a scroll housing to pull unconditioned air from outside (or inside) the vehicle and blow it toward and through a series of heat exchangers and air flow control valves before introduction into the passenger cabin. While the projecting electric motor shaft turns the centrifugal flower, it&#39;s main body and heat producing coils are encased within a motor holding that is bolted to the back of the scroll housing, and not directly exposed to any cooling air flow. A cooling air flow for the motor is desirable for motor durability. A conventional motor cooling means often seen in production is a simple tube that runs from an air inlet opening at a high air pressure point within the scroll housing, outside of the housing and around to and through the back of the motor cover, so as to feed a constant cooling air stream to the motor. The cooling tube, though effective, represents an extra part and assembly step, with the consequent extra cost. A cooling tube of this basic type may be seen in U.S. Pat. No. 6,034,451, FIG. 2. 
   In order to eliminate the extra part, at least some portion of the cooling tube has been molded integrally into the motor cover itself. An inherent problem with the molding operation, however, at least with a simple mold that has no movable cores, is that any duct so formed will inevitably be left open on one side, and will need to be closed off by some other operation and part. This is especially true at the “elbow” of the duct, that is, that portion of the duct that turns the corner and moves radially inwardly toward the back of the motor cover. A known method of so “closing off” and completing the otherwise open duct, while still maintaining moldability of the motor cover as a whole, is shown in  FIG. 1 . There, a molded motor cover A has an integral, trough shaped duct B, to the end of which is molded an extra flap C, attached by an integral hinge D. Flap C can be folded back over the end of integral duct B, closing off the end thereof while leaving a rectangular window E (in flap C) open. When motor cover A is then bolted to the back of the non illustrated fan scroll, window E can be abutted with another duct formed in the scroll housing to complete a cooling air path from inside the scroll housing, through the window E and ultimately to the motor housing. A drawback of this structure, beyond the extra assembly step of folding over the flap C, is that the abutment of the duct to window E is one of hard plastic to hard plastic, with relatively little tolerance for molding or assembly irregularities at the direct interface. 
   SUMMARY OF THE INVENTION 
   The subject invention provides an alternative structure for providing an integral motor cooling air passage, with better sealing and higher tolerance at the joint. 
   In the preferred embodiment disclosed, a cylindrical air supply tube molded integrally to the outside of the fan scroll housing extends from a lower end exposed to the air stream to an upper end above the back of the scroll fan housing, generally parallel to the blower axis. Fan pressurized air can enter the inlet of the tube and exit the upper end, but needs to turn 90 degrees and move radially inwardly to reach the motor. A motor holding cover adapted to be bolted to the back of the scroll housing has a trough shaped duct integrally molded therein, which extends radially to an outer end beyond the basic perimeter of the motor cover. The cooling tube is located so that its upper end projects into the end of the open trough when the motor cover is bolted to the scroll housing. A separate, elastomer vibration absorbing gasket surrounds the perimeter of the motor cover, to be captured between the cover perimeter and the scroll housing when attached. A projection on the gasket overlies the end of the open trough, with a central window through which the upper end of the air supply tube tightly and sealingly inserts when the motor cover is bolted in place. The extra gasket material provides the transitional corner from the scroll housing cooling tube into the motor cover, and provides a tight, high tolerance seal. No extra parts, and no extra assembly steps are required. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a partial cross sectional view of a prior art design; 
       FIG. 2  is an exploded perspective view of a preferred embodiment of the invention; 
       FIG. 3  is a view of the inside of the motor and cover, without the gasket; 
       FIG. 4  is a view of the inside of the motor and cover with the gasket; 
       FIG. 5  is a cross sectional view of the housing and motor cover showing the air flow path; 
   

   DESCRIPTION OF THE PREFERRED EMBODIMENT 
   Referring first to  FIG. 2 , a preferred embodiment of the invention includes an HVAC case, indicated generally at  10 , an integral part of which is a fan or blower scroll housing  12 , the outside of which is shown. Scroll housing  12  receives a motor holding cover  14  bolted to and through an open side defined by a circular cutout  16 . So mounting motor cover  14  both closes the cutout  16  and locates a blower  44  coaxial to the central axis A of circular cutout  16 , within housing  12 . The blower  44  pulls outside or re circulated inside air into housing  12  and blows it into the rest of HVAC case  10 . At a high air pressure point within housing  12 , a cylindrical cooling tube  18  extends parallel to the central axis A from a non visible inlet end past the plane of the cutout  16  to an upper end  20 . Essentially all the visible features of case  10  and scroll housing  12 , including the cooling tube  18 , are amenable to simple and cost effective by-pass molding, by a single pair of mold elements that part along a line parallel to the central axis A. Cooling tube  18  is inevitably located radially outboard of the scroll housing  12  interior and, being straight and parallel to the central axis A, is not capable of carrying air radially inwardly back to the interior. It cannot “turn the corner,” in effect, and still be moldable by the desired technique. Before motor cover  14  is bolted to and through the scroll cutout  16 , a rubber isolator gasket, indicated generally at  22 , is interposed between the motor cover  14  and the edge of the cutout  16 . Gasket  22  dampens motor and blower vibrations from being translated directly to the scroll housing  12  and the rest of case  10 . In the preferred embodiment of the invention, an additional radial edge projection  24 , with a central, circular window  26  is provided. Projection  24  is unrelated to the basic vibration isolation purpose of gasket  22 . Window  26  is sized to fit tightly over the cooling tube upper end  20 . Surrounding window  26  are three elastic barbs  27  that serve a purpose described below. 
   Referring next to  FIGS. 3 and 4 , the inside of motor cover  14  is illustrated. Cover  14  holds a conventional electric motor  28 , which has a central, blower driving shaft  30  (coaxial to axis A) and an outer sleeve  32  that is ventilated to receive cooling air, if it is available. An inset peripheral rim  34  of motor cover  14 , concentric to and larger in diameter than scroll housing cut out  16 , defines a plane, normal to the central axis. Rim  34  also positions and holds gasket  22  for proper installation location, as shown in  FIG. 4 . As best seen in  FIG. 3 , molded integrally into the body of cover  14  is an open trough  36  that extends from the motor sleeve  32 , generally normal to the axis of the motor shaft  30 , radially past the rim  34  to an outer end bordered by a projecting flange  38  coplanar to rim  34 . Flange  38  contains a circular lead-in  40  that matches the diameter of gasket window  26 . Trough  36  alone, however, being inevitably open on one side, is incapable alone of forming a complete, four sided air duct. Surrounding lead-in  40  are three holes  42  in flange  38  that receive the gasket barbs  27  to help hold gasket  22  in place, flat against the flange  38  with the gasket window  26  aligned with lead-in  40 . As with HVAC case  10 , essentially all the visible features of motor cover  14 , as well, can be by-pass molded. It should be noted that these assembly steps are identical to those that would be carried out simply by mounting a conventional motor cover and gasket. No extra steps, fasteners or components are needed, apart from snapping the barbs  27  through the holes  42 . 
   Referring next to  FIGS. 2 and 5 , when cover  14  is bolted to and through the scroll housing cut out  16  to enclose it, the motor shaft  30  axis is moved generally coaxial to the central axis of cut-out  16 , parallel to the cooling tube  18 . By circumferentially registering the gasket window  26  to the cooling tube upper end  20 , it is assured that the cooling tube upper end  20  simultaneously and automatically is inserted tightly through gasket window  26 , and also enters the trough lead-in  40 . The rest of gasket  22  is compressed between the motor cover rim  34 , surrounding the scroll housing circular cut-out  16 . As shaft mounted blower  44  spins, a portion of the pressurized air stream enters the lower end of cooling tube  18 , leaves the tube upper end  20  and passes through the tight fitting gasket window  26 . Now the air stream can “turn the corner” provided by the gasket projection  24  overlaying the end of trough  36 . Once through the gasket projection  24  and past the boundary of gasket  22 , the air stream has no available path for back flow into cooling tube  18 , and flows to and through the ventilated motor sleeve  32 , exiting in the lower pressure zone beneath blower  44 . In this manner, cooling tube  18 , trough  36  and gasket  22  cooperate to form a cooling duct to supply a continuous stream of cooling air so long as blower  44  is turning. 
   Beyond the advantage of requiring no extra components or significant extra assembly steps, an advantage of the structure disclosed is that the seal provided by the close axial insertion of the cooling tube  18  through the gasket window  26  is both tighter and more tolerance friendly than a hard plastic to hard plastic abutting interface, as noted above. Variations in the preferred embodiment disclosed could be made. Tube  18  need not absolutely be molded in one piece with the scroll housing  12 . Alternatively, for example, a separate round tube of the same size and orientation could be glued or spun welded through a hole in the scroll housing  12 , as a retrofit to an existing design that it was desired not to re tool. Regardless, it will be, in practical effect, an integral part of the scroll housing  12  before assembly of the motor cover  14  The round shape of tube  18  is not strictly necessary, any shape matching a similarly shaped window through the gasket projection  24  would function as well. If desired, the projection  24  could be lengthened so as to overlay the remainder of the open side of trough  36 , closing it off all the way up to the motor sleeve  32 . The gasket barbs  27  may not be absolutely necessary, but help assure that the gasket  22  is not stretched out of place when the cooling tube  18  inserts through window  26 .