Variable volume hydraulic pump control - has shuttle valve moved against spring load by electric signal controlled fluid pressure

摘要

The control system (56) is intended for a variable hydraulic pump (10) or motor using hydraulic systems (46, 28, 30) to alter the swept volume of of the pump or motor and comprises a source of pressurised fluid (20) and a drain (38). It comprises a housing with bore (58, 60) having a first connection (64) to the means (46, 28, 30), a second (62) to the source (20), and a third (66) to drain (38). A shuttle valve (68, 72) in the bore has a first position connecting the first (64) to the second connection (62) and a second position connecting the first (64) to the third connection (66). The shuttle is spring-loaded (76) towards the first position and fluid pressure-loaded (82, 74) towards the second position and means are provided which respond to a signal to alter the pressure in the chamber (82).