| 摘要 |
PURPOSE:To enhance the operability and workability of a construction machine by making a degree of manipulation of a control lever for a hydraulic actuator upon initial movement thereof in a low engine rotational speed range, substantially equal to a degree of manipulation thereof upon initial movement thereof in an engine idle rotational speed range. CONSTITUTION:A pump characteristic curve with which the discharge volume of a variable displacement pump is determined in accordance with a displacement of a control lever 7 is stored in a controller 25. The controller 25 calculates the ratio between a high idle rotation speed and a present desired rotational speed of an engine 1 for driving the pump 2, and the controller multiplies a pump tilt angle which is obtained at the time when the movement of the manipulating lever 7 is initiated during operation at the high rotational speed, with the above-mentioned ratio. With the result of the multiplication, a pump tilt angle increasing instruction signal is delivered to a regulator 9' through an electromagnetic proportional pressure reducing valve 27. Thereby it is possible to make the manipulation degree of the control lever upon initial movement during operation at a low engine rotational speed, equal to that during operation at an idle rotational speed. |
