| 摘要 |
PURPOSE:To ensure stability of a steering wheel operation under high speed car running by stopping hydrailic fluid flow into output driving part by oil locking a spool of a control valve at the neutral position in order to restrict hydraulic assisting for the steering wheel operation. CONSTITUTION:According to a rotating operation of a steering wheel, a spool 17 of a control valve 3 is moved toward the right or left through a planetary gear apparatus 2, hydraulic pressure supplied from a pump is applied into either pressure chamber of an output driving part, then power assistance for steering operation is achieved. The control valve 3 has a valve seat 31 with which a valve port 15 is closed by a flange 28, and which is contacted with surfaces of both ends of a sleeve 16 under neutral position. By the seat 31 and flange 28, chambers 29 and 30 are defined, and a through hole 33 which is interconnecting the chambers 29, 30 and an inner port 18 of the spool is formed on the above seat 31. The through hole 33 is opened or closed by an electromagnetic poppet valve 34, and the valve 34 is caused to the closed position by a solenoid 35 when the car speed exceeds the prescribed value. When the valve 34 is placed to the closed position, the spool 17 is locked at the neutral position. |
