| 摘要 |
PURPOSE:To reduce the manufacturing cost of hydraulic actuator by sensing a cushion pressure when the hydraulic actuator starts a cushion stroke, and then controlling opening of a controlling spool as to have the sensed pressure coincide with the target cushion value. CONSTITUTION:When a hydraulic actuator starts a cushion stroke, a cushion pressure P2 is sensed. The sensed pressure P2 is sent to an operating pat 38 to compute traveling speed of the controlling spool. A signal related to the speed is then integrated by a primary delay circuit 39 to calculate a displacement of a valve of the controlling spool. The controlling spool is controlled by a signal related to the valve displacement. Since the controlling pressure can be controlled to have a cushion pressure thereof coincide with the target cushion pressure, cushion pressure will be prevented from being increased to an abnormal value. The need for increasing the strength of a cylinder over demanded value will therefore be eliminated, whereby reducing the manufacturing cost. |
