Abstract: An output shaft is constituted by a plurality of rotary shafts which are disposed on the same axial line so as to be rotatable relative to each other. A cam ring which fixedly encloses one of said rotary shafts has a cam surface with radial projections and recessions on an inner peripheral surface of the cam ring. A cylinder block which is mounted on said one of the rotary shafts has formed therein a plurality of cylinders for containing in each thereof a piston which is radially moved by sliding contact with the cam surface. A sun gear is mounted on said one of the rotary shafts. Planetary gears are mounted on remaining at least one of the rotary shafts so as to be rotatable in gearing mesh with the sun gear and an internal gear which is fixedly mounted around the sun gear.

Abstract: According to the invention, there is provided a power control system designed to effectively utilize the output power of an engine with the aid of a simple tilt control device, even if any of the pumps are operated under a no load condition. The control system comprises a pressure selector valve with the output pressures of two variable volume pumps of the same capacity being fed thereto, the lower output pressure being selected by the selector valve and introduced to a pilot portion of a tilt control of at least one of the other variable volume pumps, the output pressure of which is fed either directly or through another pressure selector valve to a pilot portion of at least one of the variable volume pumps of the same capacity, thereby controlling the power of the multiple pumps.