HYDRAULIC TRANSMISSION FOR CONSTRUCTION MACHINE

摘要

PROBLEM TO BE SOLVED: To prevent non-required increasing in flow rate of a hydraulic pump under a load sensing control when a lowering operation caused by dead weight dropping of a working element to reduce consumption energy of the hydraulic pump and at the same time to reduce a meter-in loss caused by metering pressure loss not required at a pressure compensation valve related to another actuator when the hydraulic cylinder for driving the working element becomes a high load pressure side when a complex operation is carried out and to promote a high efficiency operation at a hydraulic transmission for a construction machine for performing a load sensing control provided with a regeneration valve.;SOLUTION: There is provided a regeneration circuit 62 and there are provided a first changeover valve 73 and a second changeover valve 74 for shutting off a hydraulic oil feeding passage 105a for feeding hydraulic oil from a main pump 101 to a boom cylinder when a pilot operating pressure a2 is more than a first set value and a pressure at a bottom side of a boom cylinder 3a is more than a second set value and for communicating a load pressure detecting circuit 42a for the boom cylinder 3a with a tank.;SELECTED DRAWING: Figure 1;COPYRIGHT: (C)2018,JPO&INPIT