| 摘要 |
<p>A hydraulic drive device having target compensation pressure differences for pressure compensating valves (21a, 21b) set by a pressure difference between a pump delivery pressure and the maximum load pressure and a target LS pressure difference set as a variable value dependent upon the number of rotations of an engine (1), wherein a fixed throttle (32) and a signal pressure variable relief valve (33) are disposed in a maximum load pressure line (35), and a relief set pressure PLMAX' is set to be PLMAX'=PR - PGR + α (α is a value smaller than PGR) where the target LS pressure difference is RGR and the set pressure of a main relief valve (30) is PR, whereby, in the combined operation where a plurality of actuators are driven simultaneously, even if a load pressure of any one of the actuators reaches the set pressure of the main relief valve, the pressure compensating valves will not close, the other actuators do not increase their speeds, and thus an excellent combined controllability can be obtained.</p> |
