VOLUME CONTROL VALVE OF VARIABLE DISPLACEMENT HYDRAULIC ROTATING MACHINE

摘要

A volume control valve of a variable displacement hydraulic rotating machine, wherein, while a spool (19) is set at a small volume position, a hydraulic chamber (22) communicates with a tank port (15C) to receive a pilot pressure only on a pressure receiving part (19G) side and reduce a pressure receiving area and, when a motor driving pressure used as a pilot pressure rises over a specified level, the spool (19) is largely displaced slidably against a return spring (24) to be switched to a large volume position, whereby a pilot pressure from a pilot port (15B) is led through a small hole (23) into the hydraulic chamber (22), and the pressure receiving area of the spool (19) is increased by an area of a pressure receiving part (20A) inside the hydraulic chamber (22) and, because the spool (19) receives the pilot pressure by the pressure receiving part (19G) and the pressure receiving part (20A) inside the hydraulic chamber (22), even if the pilot pressure lowers below the specified level, a hunting can be prevented in which, a volume control valve (11) is switched repeatedly between a large volume position and a small volume position.