Patent ID: 8539762
Filing Date: 2013-09-24
Classification: E02F,F15B

Abstract:
1. A hydraulic control circuit for a construction machine, the hydraulic control circuit comprising: a hydraulic cylinder that extends and retracts to raise a load through an oil supply to a weight holding-side oil chamber and an oil discharge from an anti-weight holding-side oil chamber and lower the load through an oil supply to the anti-weight holding-side oil chamber and an oil discharge from the weight holding-side oil chamber; a control valve that controls the oil supply and discharge to/from the weight holding-side and anti-weight holding-side oil chambers of the hydraulic cylinder under an operation of a hydraulic cylinder operating unit; a recovery oil passage that connects the weight holding-side oil chamber and the anti-weight holding-side oil chamber; a hydraulic pump that is driven by an engine, the hydraulic pump functioning as a hydraulic supply source for the hydraulic cylinder; an engine rotation speed setting unit that sets a target rotation speed of the engine; a recovery control valve that is in the recovery oil passage, the recovery control valve that supplies the oil discharge from the weight holding-side oil chamber to the anti-weight holding-side oil chamber when the load is lowered; and a controller that: