| 摘要 |
PURPOSE:To always carry out rise and fall control of working machine in high accuracy continuously, by controlling addition and reduction of pressure of hydraulic oil to be sent from a hydraulic pump to a rise and fall cylinder for working machine depending upon earth contact pressure of earth contact material. CONSTITUTION:While working, standard value of earth contact pressure is successively obtained from a set value of a setting device 123 of earth contact pressure and a detected value of a surface soil hardness sensor 67, the standard value is compared with the average detected value of practical earth contact pressure sensors 81L and 81R and a pressure control valve 102 is regulated based on the result. For example, when the detected value is smaller than the standard value, inner pressure of a lift cylinder is lowered until the detected value is in accordance with the standard value. When the detected value is larger the standard value, the inner pressure of the light cylinder is raised. The detected values of the left and the right earth contact pressure sensors 81L and 81R are mutually compared and pressure control valves 103 and 104 are regulated in such a way that both the values become equal. The result of the control is used for the next detected values of the earth contact pressure sensors 81L and 81R for feedback.
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