| 摘要 |
PURPOSE: To reduce the pressure loss at the time of elevating operation, and to reduce the power consumption of the electric motor for a hydraulic pump by connecting a flow detector both with an elevating control valve and with a lowering control valve in series. CONSTITUTION: When a hydraulic pump 3 is driven by an electric motor 4, the oil in an oil tank 11 is forcibly fed to a hydraulic jack 2 through a check valve 7. At this time, a part or the entire of the oil discharged from the hydraulic pump 3 is returned to the oil tank 11 through an elevation control valve 5 and a flow detector 10. The flow rate of this return oil is detected by the flow detector 10, and this is compared with the flow-rate command value denoted by the output pattern of an elevating traveling pattern generating circuit 13 by means of a comparator 15, and the deviation thereof is input into a velocity control circuit 16 to calculate a velocity control command value. When the elevation control valve 5 receives an elevating operation command from an elevating operation command circuit 17, the flow rate of the return oil to the oil tank 11 is controlled in accordance with the velocity control command value. Thus, the speed of a car 1 is controlled in accordance with the elevating traveling pattern. |
