| 摘要 |
PURPOSE:To safely return rear wheels to a neutral position by interposing an overlap type spool valve for direction selection in an oil passage between a direction selector valve and a power cylinder, and gradually draining the working oil in a power cylinder when the direction selector valve is broken. CONSTITUTION:In the hydraulic system for a rear wheel steering device, the discharge port of a tandem hydraulic pump 1 is connected to a bypass valve 2, hydraulic locking operation valve 3, left and right direction selector valves 11L and 11R of a hydraulic unit 10, direction selector spool valve 12, and a relief valve 4. The direction control spool valve 12 is operated by the direction selector valves 11L and 11R, and the spool valve 12 is made as the overlap type in which a land part 24 formed on the spool and the shoulder part 25 of a groove formed on a housing 20 are overlapped. When the direction selector valve 11L or 11R is broken during the steering with a large steering angle, and the spool valve 12 is returned to a neutral state, the working oil in a power cylinder 31 is gradually drained, and a steering rod is gradually returned to a neutral state. |
