| 摘要 |
PURPOSE:To prevent overslew of a slewing table, by a method wherein an unloader valve is mounted between a hydraulic motor for turning the slewing table and a pump, and when the table is turned in an arc of wider than a set angle, the unload valve is changed over to an unload state. CONSTITUTION:A working vehicle is provided with a hydraulic motor 5 for turning a slewing table, valves V1 and 14 for controlling forward and reverse driving and stop of the hydraulic motor 5, a detector 21 for detecting an angle theta of the slewing table with a vehicle body, a setter 22 for setting the slewing table to vehicle body position thetaf where the slewing table is to stop, a device 18 for detecting the control conditions of the control valves V1 and 14, and a controller 19 which causes the slewing table to be brought to an automatic stop on the position thetaf according to information from the detector 21 and the device 18. An unloader valve 23 is located between the motor 5 and a pump 11, and when the slewing table is turned in an arc of wider than a set angle alpha from the position thetaf, the valve 23 is automatically changed over to an unload state by a safety device 24 according to information from the detector 21 and the setter 22. |
