| 摘要 |
PURPOSE:To prevent overrun of an engine by providing a specific directional control valve in a pipe line between a hydraulic pump motor and an actuator in a hydraulic controller which conducts the closed-loop circuit drive of the actuator by the hydraulic pump motor. CONSTITUTION:Variable displacement hydraulic pump motors 3-5 of bidirectionally tilting type are connected to actutors 9-11, respectively, through pipe lines 15-20. In this arrangement, there are provided directional control valves 24-29 for communicating the hydraulic pump motors 3-5 with the actuators 9-11 through the pipe lines 15-20 when the valve 24-29 take a first position, but for communicating the hydraulic pump motors 3-5 with a variable displacement pump 22 of bidirectionally tilting type when the valves 24-29 take a second position. The drive shahfts of the hydraulic pump motors 3-5 are coupled to a flywheel 32 through transmission units 2, 33 and the speed of the flywheel 32 is detected by a detector 34. With this arrangement, a throttle lever 21 is set to a minimum position and the valves 24-29 are set in the first position, when a detected value by the detector 34 is larger than a predetermined value. |
