| 摘要 |
PROBLEM TO BE SOLVED: To suppress the useless energy consumption of a pump when the required operating oil pressure is low in the nonoperating state of an actuator by composing a spool valve of an inner spool and an outer spool of bottomed cylinder shape, and making the bottom part of the outer spool face a pressure chamber. SOLUTION: A spool valve 50 of a power steering is composed of an inner spool 51 and an outer spool 52 and disposed in such a way that a cylindrical part 52a of the outer spool 52 faces a pressure chamber 15 and that a bottom part 52b of the outer spool 52 faces a pressure chamber 16. In the nonoperating state of an actuator, the operating pressure of a discharge passage 8 is lowered. In order to keep the longitudinal differential pressure of a control orifice 9 constant, the spool valve 50 moves onto the pressure chamber 16 side against the spring force of a control spring 17 in the pressure chamber 16 to enlarge the opening area of a drain passage 19. Much of operating oil led into the pressure chamber 15 from a lead-in passage 20 thereby flows into the drain passage 19 so as to reduce the workload of a pump. |
