Integrated hydrostatic transmission for left and right wheel drive

Abstract

A hydrostatic transmission mountable to a frame of a vehicle for driving a left side or right side drive wheel. A motor portion of the transmission can extend outwardly from the frame and a pump portion can extend upwardly from the frame. The motor portion can be configured to be at least partially received within a wheel for direct mounting of the wheel to an output shaft of the motor. The pump portion can include an input shaft extending from a lower side thereof for connection to a prime mover, such as an internal combustion engine.

1 . A vehicle comprising:
 a frame;   a first hydrostatic transmission supported by the frame, the hydrostatic transmission having a housing assembly and a rotatably driven output shaft;   a first wheel mounted to the output shaft of the first hydrostatic transmission for supporting the vehicle for movement over a surface, the first wheel located on a first side of the vehicle;   a second hydrostatic transmission supported by the frame, the hydrostatic transmission having a housing assembly and a rotatably driven output shaft;   a second wheel mounted to the output shaft of the second hydrostatic transmission for supporting the vehicle for movement over a surface, the second wheel located on a second side of the vehicle opposite the first side;   wherein the first and second hydrostatic units are identical.   
   
   
       2 . A vehicle as set forth in  claim 1 , wherein the first and second hydrostatic transmissions have an input shaft extending from the housing assembly perpendicularly to the output shaft. 
   
   
       3 . A vehicle as set forth in  claim 1 , wherein the output shafts of the first and second hydrostatic transmissions extend generally from the housing assembly along a transverse axis of the housing assembly such that the housing assembly extends fore and aft of the output shaft generally the same distance. 
   
   
       4 . A vehicle as set forth in  claim 1 , wherein the housing assembly of the first and second hydrostatic transmissions has a general T-shape with the output shaft forming part of a stem portion of the T-shape. 
   
   
       5 . A vehicle as set forth in  claim 1 , wherein the output shaft of the first and second hydrostatic transmissions is a rotatably driven shaft of a motor, and wherein a distal end of the output shaft is configured to be an axle for supporting the wheel when connected thereto. 
   
   
       6 . A vehicle as set forth in  claim 1 , wherein the housing assembly of the first and second hydrostatic transmissions has a motor portion, and wherein the motor portion is outboard of the frame. 
   
   
       7 . A vehicle as set forth in  claim 1 , wherein the housing assembly of the first and second hydrostatic transmissions has a motor portion, and wherein the motor portion of the housing assembly of each hydrostatic transmission are at least partially received within respective rims of the first and second wheels. 
   
   
       8 . A vehicle as set forth in  claim 1 , wherein the first and second hydrostatic transmissions further include a trunnion arm for controlling speed and direction of rotation of the output shaft, the trunnion arm of each hydrostatic transmission extending from the housing assembly on the same side as the output shaft. 
   
   
       9 . A vehicle as set forth in  claim 1 , wherein the first and second hydrostatic transmissions include a variable flow reversible piston pump. 
   
   
       10 . A vehicle as set forth in  claim 1 , wherein the first and second hydrostatic transmissions include a gerotor motor. 
   
   
       11 . A hydrostatic transmission for driving a drive wheel of a vehicle comprising:
 a housing assembly mountable as a unit to a frame of a vehicle for driving a left side or right side drive wheel;   a pump supported within a pump portion of the housing and configured to be driven by an input shaft of the hydrostatic transmission; and   a motor supported within a motor portion the housing and connected to the pump via supply and return lines, the motor configured to drive an output shaft of the hydrostatic transmission; and   wherein the housing assembly includes a mounting surface for enabling the hydrostatic transmission to be secured to the frame such that:   the output shaft and motor portion of the housing extend outwardly from the frame so that when the output shaft is connected to a drive wheel, the motor portion of the housing can be at least partially received withing the wheel; and   the pump portion of the housing extends upwardly from the mounting surface.   
   
   
       12 . A hydrostatic transmission for driving a drive wheel of a vehicle as set forth in  claim 11 , further comprising an input drive wheel connected to the input shaft for rotatably driving the input shaft, the input drive wheel mounted to the input shaft on a lower side of the pump portion of the housing. 
   
   
       13 . A hydrostatic transmission for driving a drive wheel of a vehicle as set forth in  claim 11 , wherein the output shaft extends generally from the housing assembly along a central transverse axis of the housing assembly such that the housing assembly extends fore and aft of the output shaft generally the same distance. 
   
   
       14 . A hydrostatic transmission for driving a wheel of a vehicle as set forth in  claim 11 , wherein the housing assembly has a general T-shape with the output shaft forming a stem portion of the T-shape. 
   
   
       15 . A hydrostatic transmission for driving a wheel of a vehicle as set forth in  claim 11 , wherein the output shaft is a rotatably driven shaft of the motor, and wherein a distal end of the output shaft is configured to be an axle for supporting the wheel when connected thereto. 
   
   
       16 . A hydrostatic transmission for driving a wheel of a vehicle as set forth in  claim 11 , wherein a trunnion arm for controlling the pump extends from a side of the housing assembly transversely opposite the output shaft. 
   
   
       17 . A hydrostatic transmission for driving a wheel of a vehicle as set forth in  claim 11 , wherein the pump is a variable flow reversible piston pump. 
   
   
       18 . A hydrostatic transmission for driving a wheel of a vehicle as set forth in  claim 11 , wherein the motor is a gerotor motor. 
   
   
       19 . A vehicle comprising a frame, a first hydrostatic transmission as set forth in  claim 11  mounted to a first side of the frame for driving a first drive wheel configured to support the vehicle for movement over a surface, and a second hydrostatic transmission as set forth in  claim 11  mounted to a second side of the frame opposite the first side for driving a second drive wheel configured to support the vehicle for movement over a surface. 
   
   
       20 . A vehicle comprising:
 a frame;   a first hydrostatic transmission supported by the frame and configured to drive a first drive wheel mounted on a first side of the vehicle;   a second hydrostatic transmission supported by the frame and configured to drive a second drive wheel mounted on a second side of the vehicle opposite the first side;   wherein the first and second hydrostatic units comprise:
 a housing assembly mountable as a unit to a frame of the vehicle; 
 a pump supported within a pump portion of the housing and configured to be driven by an input shaft of the hydrostatic transmission; and 
 a motor supported within a motor portion of the housing and connected to the pump via supply and return lines, the motor configured to drive the output shaft of the hydrostatic transmission; 
 wherein the housing assembly includes a mounting surface for securing the hydrostatic transmission to the frame such that: 
 the output shaft and motor portion of the housing extend outwardly from the frame and are at least partially received within the wheel, and 
 the pump portion of the housing extends upwardly from the motor portion. 
   
   
   
       21 . A vehicle as set forth in  claim 20 , wherein the first and second transmissions further comprise an input drive wheel connected to the input shaft for rotatably driving the input shaft, the input shaft extending from the lower surface of the pump portion of the housing, and the input drive wheel mounted to the input shaft on the lower side of the pump portion of the housing. 
   
   
       22 . A vehicle as set forth in  claim 20 , wherein the output shafts of the first and second transmissions extends from the housing assembly generally along a central transverse axis of the housing assembly such that the housing assembly extends for and aft of the output shaft generally the same distance. 
   
   
       23 . A vehicle as set forth in  claim 20 , wherein the first and second transmissions have a trunnion arm for controlling the pump, wherein the trunnion arm extends from an outboard side of the housing assembly for connection to a control member of the vehicle. 
   
   
       24 . A vehicle as set forth in  claim 20 , wherein the pump of the first and second transmissions is a variable flow reversible piston pump. 
   
   
       25 . A vehicle as set forth in  claim 20 , wherein the motor of the first and second transmissions is a gerotor motor.