| 摘要 |
PROBLEM TO BE SOLVED: To control smoothly the down speed of a hydraulic elevator driven by an inverted motor just before stop when the elevator comes to a down stop. SOLUTION: A hydraulic pilot type pressure reducing valve 31 with variable throttle to actuate pressure between a pilot check valve 7 and a hydraulic pump 1 as pilot pressure during down is provided. The pilot pressure of the hydraulic pilot type pressure reducing valve 31 is turned ON in the case where the frequency of an inverted motor 2 lowers less than about 1 Hz or pressure between the pilot check valve 7 and the hydraulic pump 1 exceeds preset pressure to function through a down stopping solenoid valve 41 acting on the hydraulic pilot type pressure reducing valve 31, and the valve opening pressure of the pilot check valve 7 is slowly reduced through the variable throttle of the hydraulic pilot type pressure reducing valve 31, and after the flow of working oil in the pilot check valve 7 is throttled to the utmost, a down solenoid valve 23 is turned OFF to stop the elevator. |
