HYDRAULIC CIRCUIT FOR CONSTRUCTION MACHINE

摘要

A hydraulic circuit for a construction machine, capable of enhancing the effect of reducing a pressure loss due to return oil from a head-side chamber of a hydraulic cylinder, with a simple structure. The circuit includes a hydraulic cylinder, a control valve, a return pipeline, and a tank direct-communication line providing direct communication between the control valve and a tank separately from the return pipeline. The control valve has a flow path leading return oil from a head-side chamber of the hydraulic cylinder to the tank direct-communication line and a flow path leading return oil from a rod-side chamber of the hydraulic cylinder to the return pipeline.

主权项

1. A hydraulic circuit for a construction machine, comprising:
a hydraulic pump that discharges hydraulic oil; a hydraulic cylinder having a head-side chamber and a rod-side chamber and configured to be extended and retracted by hydraulic oil supplied from the hydraulic pump to the head-side chamber and the rod-side chamber; a control valve disposed between the hydraulic pump and the hydraulic cylinder and operated to control supply and discharge of the hydraulic oil to and from the hydraulic cylinder; a head-side pipeline connecting the head-side chamber of the hydraulic cylinder to the control valve; a rod-side pipeline connecting the rod-side chamber of the hydraulic cylinder to the control valve; a return pipeline connecting the control valve to a tank; a back-pressure valve provided to the return pipeline; an oil cooler provided to the return pipeline; and a tank direct-communication line other than the return pipeline, the tank direct-communication line providing direct communication between the control valve and the tank, wherein the control valve has a first return flow path that leads return oil flowed from the head-side chamber of the hydraulic cylinder to the tank direct-communication line and a second return flow path that leads return oil flowed from the rod-side chamber of the hydraulic cylinder to the return pipeline.