| 摘要 |
PURPOSE:To prevent a hydraulic pump and a hydraulic motor from damaging, by providing a charge signal valve which can be switched through charge pressure so that a pilot pressure operating part of a brake control valve is drained when charge pressure is decreased. CONSTITUTION:When charge pressure is decreased, pilot pressure applying to a pilot pressure operating part 25 of a charge signal valve 21 is decreased and the signal valve 21 is returned to a No.1 position (a). Pilot pressure of a brake control valve 17 is drained through the signal valve 21 and a brake 13 is operated. Signal pressure to servo-controllers 15 and 16 of a hydraulic pump 1 and a hydraulic motor 3 is drained through the No.1 port (a) of the brake control valve 17, which becomes powerless and does not operate a car speed control valve 29, and a car body is stopped automatically due to decrease of the charge pressure. With this, the damage resulting from cavitation of the hydraulic pump and the hydraulic motor is prevented from occurring. |
