| 摘要 |
<p>PROBLEM TO BE SOLVED: To inexpensively provide a circuit which quickly checks hunting when hunting occurs with a spool in a directional control valve vibrated during operation of an actuator for a construction machine. SOLUTION: A pressure detecting part 17 is provided at a hydraulic line 8 at the bottom side of a boom cylinder 10. Detection signals from the pressure detecting part 17 are inputted into a control part 3 and changes of pressure PB at the bottom side of the boom cylinder 10 are seized at the control part 3. When a spool of a directional control valve 7 vibrates in the direction (a-b) during operation for lowering the boom, changes of pressure PB at the bottom side of the boom cylinder 10 is detected with the pressure detecting part 17, and the control part 3 makes judgement for the direction of movement for the spool of the directional control valve 7, depending on whether the bottom- side pressure PB is increased or decreased. Then, the control part controls the secondary pressure of a solenoid operated proportional value 4, namely pilot pressure P1 of the directional control valve 7, so that the movement of the spool of the directional control valve 7 can be offsetted.</p> |
