Variable displacement hydraulic motor

A variable displacement hydraulic motor comprising:

• an end cover fixedly mounted on an end surface of a substantially cylindrical main casing;
• a drive shaft rotatably mounted in said main casing;
• a center shaft a plurality of pistons, an end portion of each of which shaft and pistons is swingably engaged with a flange portion of said drive shaft, the flange portion being formed in a rear-end portion of said drive shaft;
• a cylinder block for slidably receiving the other end portion of each of said pistons therein, said cylinder block being provided with a through-hole through which said center shaft passes, the through-hole being formed in a central portion of said cylinder block;
• a valve plate fixedly mounted on a base-end portion of said cylinder block, said valve plate being provided with a central portion in which the other end portion of said center shaft is rotatably mounted;
• guide means for swingably guiding said valve plate, said guide means being provided in opposite sides of an inner portion of said end cover;
• a swinging means for moving said valve plate in a swinging manner, said swinging means being provided with a piston lever slidably mounted in a substantially central portion of said end cover and extending in a direction perpendicular to an axis of said drive shaft;
• and a pin for connecting said swinging means with said valve plate, said pin being mounted in a small bore at its base portion, and has a ball-like form at its front end portion slidably in a substantially circular hole, said small bore being formed in an axial substantially central portion of said piston lever, said substantially circular hole being formed in an end portion of said valve plate at a position near an axis of said drive shaft and offset from an axis of said center shaft.