Axial piston pump/motor with clutch and through shaft

Abstract

A hydrostatic pump-motor unit ( 35 ) including a clutch assembly ( 43 ) and a pump-motor portion ( 45 ) disposed within a housing assembly ( 51,55,57 ). An intermediate drive shaft ( 21 ) extends through the entire axial extent of the unit ( 35 ) and is surrounded by a hollow shaft member ( 63 ). The housing assembly ( 51,55,57 ) supports the drive shaft ( 21 ) by means of a pair of bearing sets ( 67,71 ), and the hollow shaft member ( 63 ) is supported relative to the housing assembly by means of a pair of bearing sets ( 75,79 ). The pump-motor portion ( 45 ) includes an axial piston cylinder barrel ( 115 ) surrounding the shaft member ( 63 ) and splined thereto. The clutch assembly ( 43 ) is operable to selectively clutch and de-clutch the drive shaft ( 21 ) and the hollow shaft member ( 63 ). Having the drive line extend through the pump-motor unit ( 35 ) substantially improves the packaging of the overall drive system.

What is claimed is:  
     
         1 . A hydrostatic pump-motor unit adapted for use on a vehicle having a drive system including an engine, a transmission, and a drive-line operable to transmit driving torque from said transmission to a drive axle; said hydrostatic pump-motor unit including a housing defining a fluid inlet port and a fluid outlet port, said housing defining a pumping cavity and disposed therein, a rotatable cylinder barrel defining a plurality of generally axially oriented cylinders, and a piston disposed for reciprocable movement in each cylinder, and a swashplate disposed adjacent said barrel and having said pistons in engagement with said swashplate as said cylinder barrel rotates; characterized by: 
 (a) said hydrostatic pump-motor unit having bearings adapted to fix the location of said housing relative to said driveline;    (b) a hollow, generally cylindrical shaft member adapted to surround said driveline and being surrounded by and non-rotatably fixed relative to said cylinder barrel; and    (c) a clutch assembly disposed adjacent a first end of said shaft member and including a first clutch member adapted to be fixed for rotation with said driveline, and a second clutch member fixed for rotation with said shaft member, said clutch assembly having a first condition in which said first and second clutch members are out of driving engagement, and a second condition in which said first and second clutch members are in driving engagement.    
     
     
         2 . A hydrostatic pump-motor unit as claimed in  claim 1 , characterized by said drive-line including an intermediate driveshaft extending axially through the entire axial extent of said hydrostatic pump-motor unit, and including a forward portion and a rearward portion, said pump-motor unit including said bearings fixing the location of said housing relative to said forward and rearward portions of said intermediate driveshaft.  
     
     
         3 . A hydrostatic pump-motor unit as claimed in  claim 2 , characterized by said hollow shaft member includes a second end, and said pump-motor unit further includes bearings rotatably supporting said first and second ends of said hollow shaft member relative to said housing.  
     
     
         4 . A hydrostatic pump-motor unit as claimed in  claim 1 , characterized by said first clutch member comprises a friction disk and said second clutch member comprises a friction disk, and said clutch assembly further comprises an electromechanical actuator operable to move said friction disks between engaged and disengaged conditions in response to changes in response to an electrical input signal.  
     
     
         5 . A hydrostatic pump-motor unit as claimed in  claim 1 , characterized by said housing enclosing both said cylinder barrel and said clutch assembly.