Eccentric Radial Piston Pump and Radial Piston Motor

In an eccentric radial piston pump, a rib 12 protruded in a radial direction is formed on an inner peripheral surface of an end portion on a discharge side of an eccentric cam ring 3 over a prescribed range. In an eccentric radial piston motor, a rib 12 protruded in a radial direction is formed on an inner peripheral surface of an end portion on a high pressure side of an eccentric cam ring 3 over a prescribed range.

By the rib 12 formed in the radial direction, a rigidity of the eccentric cam ring 3 can be improved, and the eccentric cam ring can be prevented from being deformed by a thrust from the piston. Thus, the rigidity of the eccentric cam ring can be increased without increasing the thickness of the eccentric cam ring, and further the eccentric radial piston pump and the eccentric radial piston motor in which outside dimensions in the radial direction are reduced can be provided.

In an eccentric radial piston pump or an eccentric radial piston motor, the center of an eccentric cam ring and the rotation center of the casing in a radial piston pump or an eccentric radial piston motor are made eccentric, and by changing this eccentric amount, the stroke amount of the piston in a cylinder block is changed. By changing the stroke amount of the piston, displacement volume of pressure oil by the piston is changed so that the volume of the eccentric radial piston pump or the eccentric radial piston motor can be variably controlled.

An eccentric radial piston pump having a structure as disclosed in Patent Document 1 has been employed conventionally. In the eccentric radial piston pump disclosed in Patent Document 1, the arrangement relationship of a control piston for driving an eccentric cam ring and a servo control valve is specified, so that the occupancy space in the radial direction is attempted to be reduced.

A cross-sectional shape of the eccentric radial piston pump described in Patent Document 1 is shown in FIG. 13 as a prior art example in the present invention. Respective pistons 41 are disposed in respective cylinder bores of a cylinder block 40. Respective connecting rods 42 having respective piston shoes 42a are rotatably coupled with the respective pistons 41. The piston shoe 42a slides along the inner peripheral surface of an eccentric cam ring 43 disposed in the outer periphery side of the cylinder block 40.

A pintle 44 having an intake port and a discharge port is disposed at the center of the cylinder block 40, and the center of the pintle 44 and the center of the eccentric cam ring 43 can be disposed such that they are eccentric. The eccentric cam ring 43 can eccentrically move while maintaining a parallel condition with respect to the center axis line of the cylinder block 40.

The eccentric amount of the eccentric cam ring 43 is controlled by control pistons 46, 47. The respective ends of the control pistons 46, 47 make contact with the eccentric cam ring 43 and press the eccentric cam ring 43 from the both sides by the urging force of springs 48, 49. The eccentric cam ring 43 can be eccentric with respect to the center axis of the pintle 44 by pressure oil that acts on the control piston 46.

A suitable embodiment of the present invention will be described specifically below with reference to the accompanying drawings. As the structures of an eccentric radial piston pump and an eccentric radial piston motor of the present invention, configurations and arrangement structures through which the problems of the present invention can be solved can also be adopted, other than configurations and arrangement structures described below. Thus, the present invention is not limited to embodiments described below, and various modifications are possible.

Furthermore, by forming the rib on the inner peripheral surface of the end portion on the discharge side of the eccentric cam ring in the eccentric radial piston motor pump, and by forming the rib on the inner peripheral surface of the end portion on the high pressure side of the eccentric cam ring in the eccentric radial piston motor, the eccentric cam ring can be prevented from being deformed by a thrust from the piston.