| 摘要 |
PURPOSE:To secure the stable lowering operation of a loading member by installing an anomaly detecing means for detecting the state where an electric motor can not control the revolution of a hydraulic pump and a selection indicating means for allowing a feedback passage selecting means to select the feedback direction of the returned oil to a drain side on the basis of the result of the above-described detection. CONSTITUTION:When a controller 20 fails, and a drive controlling electric current increases over the standard value of the allowable electric current, an L-signal is outputted from the first comparator 26 of a selection indicating device 24a, and also an AND circuit 28 outputs the L-signal, and a selector valve 8a is deenergized, and held at the (b) position, and the returned oil is recovered into a tank T from a returned oil drain conduit D in the state where the upper limit of the flow rate is restricted by a flow rate control valve 8b. Therefore, if the load of an electric motor 21 is not applied onto a pump 1 because of the defect of the controller 20, the returned oil passes through the inside of the pump 1 at a high speed, and the lowering of a fork in a moment can be suppressed. |
