| 摘要 |
Provided is a hydraulic drive apparatus for working machine capable of preventing an excessive pressure reduction on a meter-in side and moving a load in a lowering direction at a stable speed requiring no counter balance valve. The apparatus includes a hydraulic pump, a hydraulic actuator for lowering the load, an operating device, a hydraulic circuit including a meter-in flow passage, a meter-out flow passage and a regeneration flow passage, a control valve, a meter-in-flow-rate controller for controlling a meter-in flow rate, a meter-out-flow-rate controller for controlling a meter-out flow rate to one not lower than the meter-in flow rate, a back pressure generator located downstream of the regeneration flow passage in the meter-out flow passage, and a meter-out-flow-rate limiter. The meter-out-flow-rate limiter minimizes a flow passage area of the meter-out orifice when a pressure in the meter-in flow passage falls to or below a permissible pressure. |
