| 摘要 |
<p>PURPOSE:To protect a front member from damage, by restricting the pressurized oil for a bucket cylinder depending on a signal of detection of relative position of a boom and an arm to limit the load upon the front member. CONSTITUTION:A directional control valve 11 is shifted by operating a control lever 14, to connect a hydraulic pump 12 and an oil tank 13 to a hydraulic circuit to supply cylinders with pressurized oil to drive a front section. The maximum pressure of the pressurized oil for the cylinders is limited by overload relief valves 23. A signal from a signal generator 19 is applied through a switch 18 to an overload relief valve 20 at the bottom side of a bucket cylinder 6 to set relief pressure. When an arm cylinder 4 is driven to the most contracted state, the switch 18 is shifted by the output of an arm angle detector 21 so that the relief pressure for the overload relief valve 20 is set by the output of a function generator 16.</p> |
