Hydraulic motors and vehicle hydrostatic transmission system of wheel motor type

A vehicle hydrostatic transmission system of a wheel motor type, which comprises an engine, an oil pump driven by said engine, oil pipe lines including a high pressure line and a low pressure line, an oil tank connected to the oil pump by a charge pump circuit, and at least one wheel motor receiving oil output from the oil pump and driven thereby, wherein the wheel motor is a variable displacement hydraulic motor with a rotating casing and fixed shaft having:

• (a) a casing having a plurality of planar surfaces on the inner surface;
• (b) a cover therefor;
• (c) bearings fitted in the central part of said casing and cover;
• (d) an eccentric shaft with an eccentric supported between said bearings, said eccentric shaft having two separated groups of fluid passages disposed therein and fluid distributing means communicating therewith for conducting a fluid, one group of said fluid passages being connected to a high pressure fluid system and the other group of fluid passages to a low pressure fluid system;
• (e) a cylinder block rotatably mounted on the outer periphery of the eccentric of said eccentric shaft, said cylinder block having a plurality of cylinders corresponding to said plurality of the planar surface in said casing, radially arranged in a plane perpendicular to the axis of said eccentric and eccentric shaft;
• (f) a sliding piston fitted in each said cylindres, each piston having an outer flat end contacting with a planar surface in said casing, whereby when said casing is provided with rotary movement relative to said eccentric shaft, said eccentric urges said pistons to reciprocatingly slide in said cylinders in turn;
• and
• wherein the eccentric of the eccentric shaft and eccentric sleeve with a bore and two separate arcuate fluid distributing grooves communicating respectively with said two separate groups of fluid passages in said eccentric shaft and with said cylinders in said cylinder block in turn to work as a distributing valve, said eccentric sleeve being rotatably mounted on said eccentric shaft through its bore and with said cylinder block mounted on the outer periphery thereof, the dimension of said combined eccentric being adjustable continuously by a controlling means to control the relative angular position of said eccentric sleeve to said eccentric shaft to adjust the displacement of said hydraulic motor or pump continuously.