Patent ID: 8554401
Filing Date: 2013-10-08
Classification: E02F,F15B

Abstract:
1. A safety device for hydraulic working machine, comprising: a hydraulic source; at least first and second hydraulic actuators that are driven by pressure oil from the hydraulic source; first and second control valves that control flow of pressure oil from the hydraulic source to the first and second hydraulic actuators; first and second electric lever devices that output first and second electrical operation signals, which are drive instructions for the first hydraulic actuator and second hydraulic actuator respectively, in correspondence to lever operation; first and second electromagnetic proportional valves through which control pressures for controlling the first control valve are output; third and fourth electromagnetic proportional valves through which control pressures for controlling the second control valve are output; a pressure calculating unit that calculates first and second control pressures in correspondence to a first operation signal that is output from the first electric lever device, and calculates third and fourth control pressures in correspondence to a second operation signal that is output from the second electric lever device; a control unit that controls the first and second electromagnetic proportional valves so that control pressures to be output from the first and second electromagnetic proportional valves become the first and second control pressures that have been calculated by the pressure calculating unit, and controls the third and fourth electromagnetic proportional valves so that control pressures to be output from the third and fourth electromagnetic proportional valves become the third and fourth control pressures that have been calculated by the pressure calculating unit; a high-pressure selection circuit that selects a maximum control pressure from among control pressures that have been output from the first to fourth electromagnetic proportional valves; a pressure detector that detects a control pressure selected by the high-pressure selection circuit; an abnormality determination unit that determines an abnormality in the first to fourth electromagnetic proportional valves based upon the control pressure detected by the pressure detector and the first to fourth control pressures calculated by the pressure calculating unit; and an inhibiting device that prohibits the first to fourth electromagnetic proportional valves from controlling the first and second control valves when the abnormality determination unit determines that an abnormality has occurred in the first to fourth electromagnetic proportional valves, wherein: said control unit determines whether the first operation signal output from the first electric lever device and the second operation signal output from the second electric lever device are abnormal, and when said control unit determines that the first operation signal output from the first electric lever device or the second operation signal output from the second electric lever device is abnormal, the pressure calculating unit calculates the first and second control pressures or the third and fourth control pressures to be smaller than the first and second control pressures or the third and fourth control pressures calculated when the first operation signal or the second operation signal is normal.