Abstract:
A seal for use between the housing of an automatic transmission and the housing (can) of a transmission drive motor is disposed at each end of the drive motor housing. The seal includes a preferably metal annulus having inner and outer elastomeric ribbed seals secured thereto. The annulus, which defines a non-hardened “S” shape in cross section, maintains the shape and strength of the seal and the ribbed inner seal provides a fluid tight seal with the motor housing while the ribbed outer seal provides a fluid tight seal with the transmission housing.

Description:
FIELD 
     The present disclosure relates to fluid tight seal structures and more particularly to fluid tight seals for installation between a drive motor housing and a housing of an automatic transmission. 
     BACKGROUND 
     The statements in this section merely provide background information related to the present disclosure and may or may not constitute prior art. 
     Modern passenger car and truck hybrid automatic transmissions frequently employ high torque electric motors to act as the sole energy source in certain operational modes and to operate in conjunction with a gasoline, Diesel or flexible fuel engine in other operational modes. Because these electric motors generate significant mechanical power for lengthy periods of time while consuming corresponding quantities of electrical power, they generate significant amounts of heat. In order to maintain a suitable, low operating temperature, it is necessary to remove such heat, typically by circulation of a heat transfer medium around the motor housing. Given the availability of transmission fluid, its system for circulation and heat rejection and its acknowledged heat transfer function, it is the obvious general solution to this requirement. 
     Because of the presence of pressurized or unpressurized moving fluid nearly everywhere within an automatic transmission, a first solution might appear to be simply exposing the motors to fluid circulating in the transmission. In reality, such fluid circulation at any given location within the transmission may vary widely depending upon the current operating state of the transmission and compromise cooling of the motor under certain conditions. It is thus apparent that a controlled, dedicated flow of transmission fluid to cool the motor is desirable. 
     However, due to the importance of maintaining relatively cool motor temperatures under all operating conditions with large motors occupying much or all of the transmission cross section, and the need to both positively provide fluid flow and control the volume of fluid flow, the choice to utilize a dedicated flow of transmission fluid for cooling creates a new array of engineering challenges. A first challenge relates to the fact that the motors may occupy all or a significant portion of the cross section of the transmission. This creates difficulties relating to fluid distribution to and within the motor. One solution to this challenge is to provide pressurized fluid to an annular passageway disposed between the motor housing and the inside of the transmission housing. Radial ports in the motor housing direct fluid to motor components such as the windings to absorb and carry away heat. A related challenge involves providing a secure, fluid tight seal between the transmission housing and motor housing so that a consistent, controlled flow of transmission fluid through the motor and its windings can be achieved. 
     One prior art approach to achieving a seal between a transmission and a drive motor housing utilizes O-rings disposed in channels extending about the circumference of the motor housing that engage complementarily located and configured circular shoulders or surfaces in the transmission housing. While this arrangement provides an acceptable seal, it is subject to assembly variations. For example, since the O-rings are installed on the outside of the motor housing, they are subject to being accidentally dislodged before or during mounting of the motor. Additionally, if an O-ring comes in contact with, for example, a sharp edge of the transmission housing during mounting of the motor, minor and possibly undetected damage to the O-ring can occur, resulting in initial or premature seal failure. Additionally, verification that the O-ring is assembled is very difficult due to its small size relative to the motor assembly. This precludes use of a vision system to ensure the O-ring is in place prior to assembly into the main housing. 
     From the foregoing brief review of the prior art of drive motor/transmission seal technology, it is apparent that improvements to this art are desirable. 
     SUMMARY 
     The present invention provides an improved seal between the housing of an automatic transmission and the housing (can) of a transmission drive motor. The seal, one of which is disposed at each end of the drive motor housing, includes a metal annulus having inner and outer elastomeric ribbed seals bonded thereto. The metal annulus, which defines a non-hardened “S” shape in cross section, maintains the shape and strength of the seal and the ribbed inner seal provides a fluid tight seal against the motor housing while the ribbed outer seal provides a fluid tight seal against the transmission housing. In pre-assembly configuration, rather than being installed on the outside of the motor housing, the motor seals according to the present invention are installed into the transmission housing where they are protected against damage and the drive motor is then installed into the transmission. The motor housing seal according to the present invention provides improved ease and certainty of correct installation as well as reduced likelihood of damage to the seal during installation, thereby reducing subsequent failures and service. 
     Thus it is an object of the present invention to provide a seal for disposition between the housing of an electric motor and the housing of an automatic transmission. 
     It is a further object of the present invention to provide a seal for disposition between the outside of a housing of an electric motor and the inside of a housing of an automatic transmission. 
     It is a still further object of the present invention to provide an annular seal for disposition between the housing of an electric motor and the housing of an automatic transmission having a metal ring and resilient sealing portions bonded to the ring. 
     It is a still further object of the present invention to provide a seal for disposition between the housing of an electric motor and the housing of an automatic transmission having a metal ring and resilient ribbed portions bonded to the ring. 
     It is a still further object of the present invention to provide an annular seal for disposition between the outside of a housing of an electric motor and the inside of a housing of an automatic transmission having a metal ring and resilient ribbed portions bonded to the ring. 
     Further objects, advantages and areas of applicability will become apparent from the description provided herein. It should be understood that the description and specific examples are intended for purposes of illustration only and are not intended to limit the scope of the present disclosure. 
    
    
     
       DRAWINGS 
       The drawings described herein are for illustration purposes only and are not intended to limit the scope of the present disclosure in any way. 
         FIG. 1  is a fragmentary, side elevational view of an automatic transmission incorporating the present invention, 
         FIG. 2  is a perspective view of an electric motor housing having front and rear seals according to the present invention; 
         FIG. 3  is an enlarged, side elevational view of a electric drive motor housing for an automatic transmission having front and rear seals according to the present invention; and 
         FIG. 4  is an enlarged perspective view of a control motor housing and seal according to the present invention. 
     
    
    
     DETAILED DESCRIPTION 
     The following description is merely exemplary in nature and is not intended to limit the present disclosure, application, or uses. 
     With reference to  FIG. 1 , a portion of an automatic vehicular transmission is illustrated and designated by the reference number  10 . The automatic transmission  10  includes a typically cast, metal housing  12  having an inner cylindrical surface  13 . A shoulder  15  representing a sloped or angled portion of the inner cylindrical surface  13  of the housing  12  is also situated along the inner cylindrical surface  13 . The housing  12  supports, positions and protects various internal components such as an input shaft (not illustrated), a main output shaft  14 , one or more planetary gear assemblies  16  (one of which is illustrated), a plurality of electrical feed-throughs or connectors  18  (one of which is illustrated), an electric motor assembly  20  and a hydraulic vane or gerotor pump (not illustrated). It will be appreciated that although only one electric motor assembly  20  is illustrated in the automatic transmission  10 , more than one may be incorporated therein and the present invention is equally suitable for use with additional electric motor assemblies. 
     Referring now to  FIGS. 1 and 2 , the electric motor assembly  20  includes a generally tubular or cylindrical housing  22  which encircles a stator  24  having electrical field windings  26 . The housing  22  includes an outer cylindrical surface  27 . The inner cylindrical surface  13  of the housing  12  of the transmission  10  surrounds the outer cylindrical surface  27  of the housing  22 . Rotatably disposed within the housing  22  and the stator  24  is a rotor  28  which is supported upon a pair of anti-friction support devices such as ball bearing assemblies  30 . The ball bearing assemblies are, in turn, supported on a tubular member or bearing support  32  which is connected with a welded joint to the cylindrical motor housing  22 . The rotor  28  is coupled to the main shaft  14  by an internally and externally splined hub  34  or similar component. 
     The cylindrical motor housing  22  includes a plurality of radially oriented lubrication passageways or apertures  36  arranged in front and rear circumferential arrays at the upper portion of the housing  22 . The cylindrical motor housing  22  also includes two or more locating tabs or projections  38  that engage complementarily arranged slots or recesses (not illustrated) within the automatic transmission  10 . The slots and projections  38  are dimensionally related to ensure that the cylindrical motor housing  22  is oriented properly, that is, with the lubrication passageways or apertures  36  at the top of the automatic transmission  10  when it is installed therein. 
     Referring now to  FIGS. 1 ,  2  and  3 , about the outer surface  27  of the motor housing  22  are disposed a pair of seals  40  according to the present invention. A front or first seal  40 A is located along a front or first edge of the cylindrical motor housing  22  outside the lubrication passageways  36  and a second or rear seal  40 B is located along a second or rear edge of the cylindrical motor housing  22  also outside the lubrication passageways  36 . Stated somewhat differently, the lubrication passageways or apertures  36  reside in an (axial) region between the front seal  40 A and the rear seal  40 B. 
     Referring now to  FIGS. 3 and 4 , it should be appreciated that but for their distinct diameters, the front seal  40 A and the rear seal  40 B have an identical cross-section. Thus, in  FIG. 4 , only the front seal  40 A is illustrated as the description applies with equal accuracy to the rear seal  40 B. The front seal  40 A includes a center metal band or annulus  42  that is formed into a non-hardened “S” shape having a first end  44  that is curved or formed inwardly at a right angle (90°) such that the first end face  46  of the annulus  42  is parallel to the axis of the cylindrical housing  22  and extends inwardly from the inner surface  48  of the annulus  42 . Referring now to  FIG. 1 , the inwardly curved portion of the annulus  42  corresponds with the shoulder  15  of the housing  12  and seats the first end face  46  of the annulus parallel to the outer cylindrical surface  27  of the housing  22 . The other or second end  50  of the annulus  42  is curved or formed outwardly such that the second end face  52  is also parallel to the axis of the cylindrical housing  22  but is substantially flush or co-planar with the outer surface  54  of the annulus  42 . The shape of the metal band or annulus  42  in the seal  40 A provides rigidity and dimensional stability to the seal  40 A. 
     Molded in-situ or bonded to the inner surface  48  of the annulus  42  by any suitable bonding or fastening technique is a first resilient internal seal  62  of, for example, an elastomeric material having two or more ribs  64  which contact and seal against the outside of the cylindrical motor housing  22 . Molded in-situ or bonded to the outer surface  54  of the annulus  42  by any suitable bonding or fastening technique is a second resilient internal seal  66  also of, for example, an elastomeric material having three or more ribs  68  which contact and seal against the inside surface of the transmission housing  12 . 
     Inspection of  FIG. 3  reveals that the seals  40 A and  40 B are oriented with the first end surfaces  46  and the first end faces  46  of the metal bands  42  remote from the open end of the cylindrical motor housing  22  and the second end surfaces  52  of the metal bands  42  nearer the open end of the cylindrical motor housing  22 . Inspection of  FIG. 4  reveals that the first end face  46  of the annulus  42  is preferably exposed because the bonding process requires a non-sealed portion of the metal band  42  for gating processes during fabrication and will assist properly locating the motor housing  22  whereas the second end face  52  of the annulus  42  is preferably covered or encased by a thin layer of the elastomeric material to ensure proper bonding of the elastomeric material to the metal band  42 . 
     Returning to  FIG. 1 , It will be appreciated that the front seal  40 A and the rear seal  40 B define an annular cavity or region  70  that extends circumferentially about the motor housing  22  between it and the inside surface of the transmission housing  12 . This circumferential region  70  is pressurized by the hydraulic pump of the automatic transmission  10  and hydraulic fluid flows into the circumferential region  70  at low pressure, through the lubrication passageways or apertures  36  and is directed by the apertures  36  and contacts the motor windings  26 . Heat generated in the motor windings  26  is carried away by the hydraulic fluid and rejected to the atmosphere through a transmission fluid cooler (not illustrated). 
     The description of the invention is merely exemplary in nature and variations that do not depart from the gist of the invention are intended to be within the scope of the invention. Such variations are not to be regarded as a departure from the spirit and scope of the invention or the following claims.