| 摘要 |
The present invention is provided with: a rotatable cylinder block in which are formed a plurality of piston chambers at intervals in the circumferential direction; a plurality of pistons fitted in the piston chambers so as to be capable of moving in the extension and contraction directions, the pistons moving reciprocatingly in the extension and contraction directions; and a valve plate disposed contacting the rear end face of the cylinder block, a first and second port that communicate with the piston chambers being formed in the valve plate. In both the first and second port, a portion on the side near a top dead center switching land formed between the two ports is formed as a narrow part, the opening width thereof becoming narrower in the radial direction of the rotation of the cylinder block, and a subsidiary port is formed in a switching land of the valve plate, the subsidiary port being held at a pressure lower than whichever of the first and second ports has a higher pressure, and the piston chambers and the subsidiary port are caused to communicate with each other when the piston chamber does not communicate with the higher-pressure side of either the first or the second port. |
