A pump/motor control mechanism.

摘要

To adjust the volumetric displacement of a pump or motor a member 1 is reciprocated as shown by the arrows. For this purpose the control mechanism has a first actuator (4) for shifting the member 1 forward when fluid pressure is introduced into a first cylinder chamber 9 located in the member 1, a second actuator 5 for shifting the member 1 backward when fluid pressure is introduced into a second cylinder chamber 13 located in the member 1, a spool holding hole 14 provided in the member 1 with an axis parallel to the direction of reciprocation and a spool 15 which is slidably fitted in the hole 14. The spool 15 has on its outer periphery a high-pressure groove 16 connected at 19 to a high-pressure fluid source and a low-pressure groove 18 opened to a low-pressure zone at 22. A first pressure introducing path has one end 23 connected to the first cylinder chamber 9 and its other end open to an area 20 which is on the inner periphery of the spool holding hole 14 and connected to the high-pressure groove 16 when the spool is moved forward by actuator 28 and to the low-pressure groove 18 when the spool moves backward, and a second pressure introducing path 24 has one end connected to the second cylinder chamber 13 and its other end open to an area 21 which is on the inner periphery of the spool holding hole 14 and connected to the high-pressure groove 16 when the spool is moved backward by spring 27 and to the low-pressure groove 18 when the spool moves forward.