| 摘要 |
PURPOSE:To prevent the fluctuation of a lifting low speed even when an error occurs in the amount of oil supply to a hydraulic actuator by providing a check valve having the predetermined characteristics, a stroke sensor and a feedback correction control means. CONSTITUTION:A control unit CU detects the stroke of the valve body of a check valve 50 to shift depending upon a supply flowrate via a stroke sensor 55, when a supply oil flowrate changes due to a drop in the volume ratio of a hydraulic pump and the fluctuation of an oil temperature, a load on an actuator 4 and the like during the slow speed lifting of a cage 2 after deceleration in a lifting stroke. Furthermore, an actual supply flowrate is detected on the basis of the detected stroke and a pilot control valve 33 is feedback controlled so that the flowrate can be so set as the correspond to the predetermined slow speed operation. The supply flowrate is thereby corrected. According to the aforesaid construction, the fluctuation of a lifting slow speed operation can be prevented and the accuracy of a cage stop position can be ensured. |
