Variable displacement type piston machine of which noise and vibration are reduced by reducing pulsation of discharge fluid

摘要

There is provided a variable displacement type piston machine capable of reducing noise and vibration through reduction of pulsation of discharge fluid by reducing the variation of the rate of operating fluid that is flowing from a high pressure port to a low pressure port and a drain. On a slide surface (1a) of a valve plate (1) is provided an intermittent drain passage (5) in a manner that it directly communicates with neither a high pressure port (3a) nor an oil guide groove (4). When the high pressure port (3a) and a cylinder port (54a) are communicated with each other via the oil guide groove (4) and a back flow from the high pressure port (3a) to the cylinder port (54a) is generated, the intermittent drain passage (5) communicates with neither the high pressure port (3a) nor the cylinder port (54a). When a cylinder block (55) further rotates from the above state, the intermittent drain passage (5) communicates with the high pressure port (3a) via the cylinder port (54a).