| 摘要 |
<p>PROBLEM TO BE SOLVED: To accurately estimate load pressure without using pressure sensor. SOLUTION: A meter-in A2IMU which controls fluid supplied to a hydraulic actuator 2, and a meter-out valve A4IMV which controls fluid discharged from the hydraulic actuator 2, are independently provided for this apparatus. The meter-out valve A4IMV and the meter-in valve A2IMU include main poppets 22, 41 and pilot spools 33, 54 respectively. The tops of pilot 33, 54 are provided with push solenoids 35, 37 which minutely drive the pilot spools in a dead zone close to a neutral position, whereat the flow rates through the non-driven sides of the spools become zero, and displacement sensors 40, 82 which detect displacement of the driven pilot spools 33, 54. The pilot spools 33, 54 comprise load pressure sensing parts 38, 77 that are pressurized by feed back pressure. The force induced by the push solenoids 35, 57, the force produced by pilot spool displacement, and the force produced by load pressure are led to balance, making it possible to accurately compute the load pressure.</p> |
