| 摘要 |
PURPOSE:To control a hydraulic work machine at low temperature, by detecting temperature of working oil in the hydraulic work machine, changing a frequency of an alternating carrier signal on the basis of this detection value, pulse width modulating the signal and controlling a solenoid valve for driving the work machine. CONSTITUTION:A temperature detector 8 detects temperature of working oil in a conduit connected to a port of a hydraulic cylinder 2 and outputs a signal ST to be applied to a voltage-frequency converter circuit 9. The circuit 9 outputs a triangular wave signal Sm'. A position signal of the hydraulic cylinder 2 is added to a position instruction signal at an addition point 1, and deviation epsilon is added to a modulator 5, while a triangular signal Sm is pulse width modulated by the deviation epsilon, and a signal Sc is output and applied to a solenoid valve. When a work machine is used under low temperature environment, a frequency of the signal Sm' is decreased, and a duration time of positive and negative polarity parts of the signal Sc is increased, then the urged time of the solenoid valve 7 is increased while sufficient oil is supplied for operating the hydraulic cylinder 2. |
