| 摘要 |
<p>A hydraulic drive system in a civil engineering-construction machine, having anti-rocking back valves (12a, 12b) for preventing rocking back phenomenon of a swingable member (4A) driven by a hydraulic motor (4) by temporarily opening a valve through a throttling action of a small orifice (25) for damping immediately after the stop in operation of the hydraulic motor (4) to allow highly pressurized pressure oil to flow out of a main piping (5 or 8) on the return side of the pressure oil, said drive system being provided with control means (45, 46, 47; 49; 50; 51a; 51b; 60) for selectively restricting the flowout of the pressure oil from the main piping on the return side of the pressure oil via the anti-roccking back valves (12a, 12b) when a direction change-over valve (1) is returned to a neutral position to stop an actuator (4) in operation. With this arrangement, the swingable member can be prevented from rocking back when the civil engineering-construction machine is operated on an inclined ground in a low temperature environment and the actuator can be reliably stopped without an abnormal action, thus avoiding a lowered working efficiency, securing the safety and improving the operability.</p> |
