Patent ID: 6390227
Filing Date: 2002-05-21
Classification: A01D,B60K,B60Y,Y10S,Y10T

Abstract:
An axle driving unit comprising:a housing eccentrically disposed on a body frame in proximity to a first driving wheel disposed thereon, a first axle having a first longitudinal axis and supported in said housing for mounting thereon the first driving wheel; a second axle having a second longitudinal axis and being longer in length than said first axle for mounting thereon the second driving wheel, said second axle being supported in said housing; a hydraulic stepless speed change transmission disposed in said housing and drivingly connected to said first and second axles, wherein said hydraulic stepless speed change transmission comprises, a hydraulic pump having a substantially vertical input shaft, a hydraulic motor having an output shaft, and a center section for fluidly connecting said hydraulic pump and said hydraulic motor, said center section comprising a pump mounting surface for mounting thereon said hydraulic pump and a motor mounting surface for mounting thereon said hydraulic motor, wherein said motor mounting surface is disposed closer to said first and second axles than is said pump mounting surface; an oil sump formed within said housing; an oil filter disposed within said oil sump; a closed circuit disposed in a distal portion of said center section for circulating oil between said hydraulic pump and said hydraulic motor, said closed circuit including an oil supply port; a charge pump case; a charge pump driven by said input shaft for supplying oil in said oil sump to said oil supply port, said charge pump disposed within said charge pump case and including a suction port fluidly connected to said oil filter, and a discharge port; a charge pump mounting surface formed on a surface of said center section opposite to said pump mounting surface, wherein said oil supply port is open at said charge pump mounting surface and said charge pump is mounted on said charge pump mounting surface so that said discharge port is connected to said oil supply port; and biasing means disposed between said charge pump case and said housing for biasing said charge pump to contact said charge pump mounting surface in a detachable manner, wherein a discharge pressure of said charge pump greater than the biasing force of said biasing means detaches said charge pump from contact with said charge pump mounting surface to adjust said discharge pressure below the biasing force while maintaining fluid communication between said discharge port and said oil supply port.