US Patent 7249608 Flow control for power steering

The flow control device comprises a supply passage (2) for supplying hydraulic fluid discharged by a pump (1) to a power steering output section (8); a variable throttle section (3) situated at an intermediate position of the supply passage (2); and a flow control valve (4) for returning the hydraulic fluid in the supply passage (2) to the pump inlet side, in accordance with a pressure differential between upstream and downstream of the variable throttle section (3). When the pump (1) is halted, the flow control valve (4) is impelled by a spring (13) and closes the variable throttle section (3). A throttle passage (51) is provided for connecting the upstream side and the downstream side of the variable throttle section with the supply passage (2).