| 摘要 |
PURPOSE: To dispense with gain adjustment in closed circuit control by controlling a solenoid proportional pilot valves for ascending/descending by an opening command in closed loop circuit and bleeding off hydraulic fluid from cutouts of both control valve main bodies with small stream line angle. CONSTITUTION: The opening of an electromagnetic proportional pilot valve for an ascending or descending 7 is adjusted by an ascending or descending command, and a cage 5 is made to ascent or and descend by pilot pressure through the ascending control valve 2 or the descending control valve 3 and an actuator 6. In this case, hydraulic fluid is bled off at the small stream line angle from cutouts provided on the control valves 2, 3, a valve element is moved in the closing direction as the difference between pressure of operating oil and operating oil pressure to be bled off is increased, and the supplying amount to an actuator 6 is made to the approximately desired value regardless of pressure from a hydraulic pump 4. Therefore, gain adjustment is dispensed with in feedback control, and the desired accelerating or decelerating speed can be always provided. |
