Hydraulic motor

A hydraulic motor, comprising a stationary housing having two cam tracks spaced from one another;

• a hollow rotor in said housing and rotatable about an axis, said rotor having a plurality of hollow radially extending pistons spaced from one another in a circumferential direction and each having two concentric annular walls forming a first chamber bounded between said annular walls and a second chamber bounded inside an inner wall of said walls, each of said pistons having two separate fluid-conveying passages spaced from one another in an axial direction and each communicating with a respective one of said chambers;
• a plurality of cylinders in said housing spaced from one another in the circumferential direction and arranged to displace said hollow pistons, each of said cylinders having two journals extending oppositely in the axial direction and arranged to cooperate with said cam tracks of said housing, and a radial projection received in said second chamber of a respective one of said pistons;
• and
• a central control member located in said rotor concentric to the latter and displaceable in the axial direction between a plurality of operating positions, said control number having a plurality of further fluid-conveying passages spaced from one another in the axial direction and cooperating with said first-mentioned fluid-conveying passages of said pistons.