Abstract:
An accumulator/pump housing associated with a motor vehicle hydraulic system that is designed to incorporate a gerotor pump and an accumulator. The accumulator/pump housing comprises a portion of a torque coupling assembly in which a friction clutch selectively engages and disengages a torque coupling case and at least one output shaft. The accumulator/pump housing is located external to a torque coupling housing and at least partially encloses a gerotor pump and a fluid accumulator. The gerotor pump pressurizes the hydraulic fluid and the fluid accumulator selectively stores the pressurized fluid. The hydraulic pump and accumulator supply pressurized fluid to actuate the friction clutch.

Description:
BACKGROUND OF THE INVENTION  
       [0001]     1. Field of the Invention  
         [0002]     The invention generally relates to a hydraulic pressure system associated with a motor vehicle torque coupling. Specifically, the invention relates to an integral housing for a gerotor pump and associated accumulator.  
         [0003]     2. Background of the Invention  
         [0004]     The prior art includes various systems for developing hydraulic pressure to provide power to equipment associated with the hydraulic system of a motor vehicle, such as hydraulically actuated torque coupling assemblies. Vehicle torque coupling assemblies typically include a hydraulic pump and an accumulator. When the hydraulic pump is energized, pressurized fluid is selectively supplied into the vehicle hydraulic system, including the accumulator reservoir. As the hydraulic system is further pressurized, the volume of the accumulator reservoir expands, thereby compressing a gas charge or a resilient member (usually a spring) associated with the accumulator reservoir. When the pump is turned off, the hydraulic pressure within the accumulator reservoir is maintained through pressure applied by the gas charge or resilient member. The fluid within the accumulator reservoir communicates the hydraulic pressure to the other parts of the hydraulic system, thereby ensuring that the hydraulic system is pressurized when the vehicle hydraulic pump is not operating.  
         [0005]     Vehicle hydraulic pumps have a variety of designs including reciprocating piston-type pumps, centrifugal pumps, and gerotor pumps. Hydraulic gerotor pumps are generally preferred in applications associated with torque couplings, including limited slip differentials. Gerotor pumps are typically built into the torque coupling assemblies and housed within the torque coupling housing. The associated accumulator is conventionally mounted to a body or frame member of the motor vehicle. Since the hydraulic pump is the source of hydraulic pressure when the pump is activated, and the accumulator is the source of hydraulic pressure when the pump is inactive, an extensive and redundant system of hydraulic pressure lines is needed to support both sources of hydraulic pressure.  
         [0006]     While known hydraulic couplings, including but not limited to those discussed above, have proven to be acceptable for various vehicular driveline applications, such devices are nevertheless susceptible to improvements that may enhance their performance, cost and simplify both the hydraulic system and the torque coupling design. With this in mind, a need exists to develop improved hydraulic torque-coupling assemblies that advance the art.  
       SUMMARY OF THE INVENTION  
       [0007]     The present invention comprises a torque coupling assembly having a rotatable torque coupling case driven by an outside drive torque. At least one output shaft is drivingly connected to the torque coupling case. A friction clutch pack selectively engages and disengages the torque coupling case and the output shaft. The torque coupling assembly also includes an accumulator/pump housing that is located external to the torque coupling case. The accumulator/pump housing at least partially encloses a fluid pump and a fluid accumulator. The fluid pump includes an internally toothed impeller member and an externally toothed rotor member. The externally toothed rotor member cooperates with the internally toothed impeller member to pressurize a fluid. The fluid accumulator is in fluid communication with an outlet port of the fluid pump and selectively stores the pressurized fluid. The fluid pump and fluid accumulator supply pressurized fluid to the frictional clutch pack. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0008]      FIG. 1  is an isometric view of a torque coupling that includes an accumulator/pump housing according to the preferred embodiment of the present invention.  
         [0009]      FIG. 2  is an isometric view of a gerotor pump drive train.  
         [0010]      FIG. 3  is a sectional view of the drive train of the current invention.  
         [0011]      FIG. 4  is a sectional view of the current invention taken along the line  4 - 4  shown in  FIG. 3 .  
         [0012]      FIG. 5  is a sectional view taken along the line  5 - 5  shown in  FIG. 4 .  
         [0013]      FIG. 6  is a schematic view of a hydraulic circuit according to the preferred embodiment of the present invention. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0014]     The preferred exemplary embodiment of the present invention will now be described with the reference to accompanying drawings.  
         [0015]     As best shown in  FIG. 1 , the preferred embodiment of the current invention comprises a limited slip differential-type torque coupling assembly  10  that includes a torque-distribution device  11  (as shown in  FIG. 2 ) in the form of a limited slip differential disposed in a torque coupling housing  16 , and a combined gerotor pump  12  and hydraulic accumulator  14  both disposed in a common, integral accumulator/pump housing  18 . Preferably, the accumulator/pump housing  18  is manufactured as a single-piece casting. The accumulator/pump housing  18  is secured to the torque coupling housing  16  by any appropriate manner known in the art, such as by threaded fasteners.  
         [0016]     The gerotor pump  12  builds pressure in the hydraulic accumulator  14  that is used to actuate the torque-distributions device  11 . The torque-distributions device  11  of the current invention is well known in the art and includes a multi-disk friction clutch  24  that is hydraulically actuated by a variable pressure piston assembly  25  as shown in  FIG. 6 . More specifically, the hydraulic pressure generated by the gerotor pump  12  and/or stored in the accumulator  14  is used to selectively actuate the friction clutch  24 . The friction clutch  24  is disposed within a torque coupling case  17  (shown in  FIG. 2 ) rotatably supported within the torque coupling housing  16 . The current invention may also be used with any other hydraulic torque coupling known in the art.  
         [0017]     As best shown in  FIG. 1 , the gerotor pump  12  and accumulator  14  are mounted outside of the torque coupling housing  16  in the common accumulator/pump housing  18 . The torque coupling assembly  10  receives an input torque through an input gear shaft  20 . The input torque is communicated to the gerotor pump  12  through a gearing assembly housed in an intermediate portion  22  of the torque coupling housing  16 . The limited slip differential  10  selectively allocates the input torque between first  21  and second  23  output shafts extending from opposite sides of the torque coupling assembly  10 .  
         [0018]     As best shown in  FIG. 2 , the input shaft  20  has an associated pinion-type gear head  26  that drives an intermediate gear  28 . The intermediate gear  28  meshes with teeth  30  of the gerotor pump  12  and drives the gerotor pump  12 . Alternatively, the fluid pump could be driven by a chain drive, or a belt drive mechanism. As best shown in  FIG. 3 , the gerotor pump  12  is comprised of an internally toothed impeller member  32  and a cooperating externally toothed rotor member  34 . As best shown in  FIG. 2 , a stationary port plate  36  is attached to one end of the gerotor pump  12 . The port plate  36  includes inlet apertures  38  through which fluid is drawn into the pump  12 , and outlet apertures  40  through which pressurized fluid is ejected from the pump  12 . Preferably, the port plate  36 , hence the gerotor pump  12 , is considered “reversible” because when the direction of rotation of the drive train is reversed, the port plate  36  rotates 180° to maintain the proper alignment between the port plate  36  and the internal components of the gerotor pump  12 . It would be appreciated that non-reversible pumps are also within the scope of the present invention. As best shown in  FIG. 3 , the gear head  26  and a portion of the intermediate gear  28  are housed in the intermediate portion  22  of the torque coupling housing  16 , and the gerotor pump  12  is disposed in the separate accumulator/pump housing  18 .  
         [0019]      FIG. 4  is a sectional view of the accumulator/pump housing  18 . As shown in  FIG. 4 , the internally toothed impeller member  32  and externally toothed rotor  34  rotate on a gerotor support shaft  42  and bearing sleeves  44 . Hydraulic fluid from a gerotor reservoir  45  is drawn into the gerotor pump  12  through inlet apertures  38  in the port plate  36 . Hydraulic fluid exits the pump  12  through the outlet apertures  40  in the port plate  36  and is directed into a connecting passage  50 .  
         [0020]     As best shown in  FIGS. 4 and 5 , the fluid in the connecting passage  50  is directed through a check valve  52 . The check valve  52  ensures that hydraulic fluid only flows away from the gerotor pump  12  as is not allowed to flow in a reverse direction. In the preferred embodiment, the check valve  52  is spring-driven so that a pre-determined amount of hydraulic pressure must be generated by the gerotor pump  12  to allow fluid to flow through the passage  50 .  
         [0021]     A portion of the fluid in the passage  50  is then directed and into an accumulator reservoir  54  through an accumulator inlet/outlet aperture  48  (best shown in  FIG. 4 ), and a portion of the fluid is directed to a passage  46  (best shown in  FIG. 5 ). In the preferred embodiment, the accumulator  14  has a cylindrical shape and extends parallel and/or perpendicular to the gerotor support shaft  42 . However, in alternate embodiments, the accumulator  14  may be of any form known in the art and may be oriented and configured as required for a specific application.  
         [0022]     As best shown in  FIG. 4 , the accumulator  14  includes a piston  56  that is driven by a force-producing means  58 . In the preferred embodiment, the force-producing means  58  is comprised of a gas charge, however, the force-producing means  58  may be comprised of any means known in the art, including a spring or other resilient member. When the force-producing means  58  is compressed (as shown in  FIG. 4 ), the piston  56  applies a pressure to the hydraulic fluid within the accumulator reservoir  54 . The accumulator reservoir  54  has a first end defined by the piston  56  and an oppositely disposed second end  57 , such that the second end  57  is disposed adjacent to the port plate  36 . A removable accumulator cap  60  is positioned opposite the inlet/outlet aperture  48  and allows the force-producing means  58  to be easily adjusted to vary the pressure exerted on the fluid in the hydraulic reservoir  54 . As best shown in  FIG. 5 , the passage  46  connects the gerotor hydraulic system with the remainder of the hydraulic system through an outlet aperture  49 .  
         [0023]     In operation, as best shown in  FIGS. 4-6 , hydraulic fluid from the hydraulic gerotor reservoir  45  is drawn into the gerotor pump  12  through the inlet aperture  38  in the port plate  36 . The fluid passes through the gerotor pump  12  and is ejected into the passage  50 . At least a portion of the fluid is directed through the check valve  52  and into the accumulator reservoir  54 . As the volume of fluid in the reservoir  54  expands, the gas charge  58  is compressed by the piston  56  of the accumulator reservoir  54 . When the accumulator  14  is fully charged, the excess of pressurized hydraulic fluid generated by the pump  12  is returned to the sump  45  through a solenoid valve  66 , a reducer valve  67  and a fluid cooler  68 , as shown in  FIG. 6 .  
         [0024]     When the gerotor pump  12  is turned off, the compressed gas charge  58  applies a force to the fluid in the accumulator reservoir  54 . As best shown in  FIG. 5 , hydraulic pressure from the accumulator reservoir  54  is communicated through the accumulator inlet/outlet  48  to the passage  46 . The hydraulic pressure is then communicated from the passage  46  out the aperture  49  to the remainder of the hydraulic system including the piston assembly  25  through a selectively actuated solenoid valve  64  and a reducer valve  65 , as shown in  FIG. 6 . In turn, the piston assembly  25  actuates the friction clutch  25  if necessary to restrict the speed differential between the first  21  and second  23  output shafts of the torque coupling assembly  10 . More specifically, the hydraulic pressure of the accumulator  14  is used to selectively actuate the friction clutch  24 . The design of the current invention thereby allows the vehicle hydraulic system to be pressurized by either the gerotor pump  12  or the co-located accumulator  14 .  
         [0025]     In an alternate embodiment, as best shown in  FIG. 4 , the gerotor pump  12  and port plate  36  may be driven laterally by a variable pressure piston  62  to create a selectively adjustable seal between the port plate  36  and the inner wall of the accumulator/pump housing  18 . The movement of the piston  62  is controlled by a solenoid valve  70  and a proportional valve  72  which are best shown in  FIGS. 5 and 6 . This embodiment allows an operator to further vary the pressure developed by the gerotor hydraulic system.  
         [0026]     From the foregoing description it is clear that the current invention describes a gerotor pump  12  and accumulator  14  that are co-located in the accumulator/pump housing  18  outside the torque coupling housing  16 . The current invention greatly reduces the length and number of hydraulic lines and valves relative to a conventional system. The current system allows a user to incorporate a larger accumulator and/or gerotor pump into the hydraulic system, and also facilitates removal and adjustment of the gerotor pump and accumulator components.  
         [0027]     It is understood that while various preferred designs have been used to describe this invention, the invention is not limited to the illustrated and described features. For example, although the exemplary embodiment pictured in  FIG. 1  shows a rear wheel drive-type torque coupling, front wheel drive and intermediate torque couplings should also be considered within the scope of the invention. Modifications, usages and/or adaptations following the general principles disclosed herein are included in the present invention, including such departures that come within known or customary practice in the art to which this invention pertains. The present invention is intended to encompass all such departures having the central features set forth above, without departing from the scope and spirit of the invention, and which fall within the scope of the appended claims.