HYDRAULIC CIRCUIT OF CLOSED CENTER LOAD SENSING SYSTEM

摘要

This invention relates to a hydraulic circuit of a closed center load sensing system. When applied to a construction machine such as a hydraulic excavator, it makes possible to conduct operation with high response and excellent statical determinateness. To accomplish this object, the present invention disposes a two-port change-over valve (25) which is switched in the interlocking arrangement with the levers of change-over valves (5), (6) of a closed center, connects one end of this valve (25) to a piping between a pump (2) and the valves (5), (6) and connects the other end thereof to a piping between the valves (5), (6) and an oil tank (9) so as to constitute a hydraulic circuit.