HYDRAULIC CIRCUIT IN CLOSED CENTER LOAD SENSING SYSTEM

摘要

PURPOSE:To improve responsiveness and staticity by connecting a change-over valve which changes over interlocking to an operating lever of a change-over valve of a closed center to a piping between a pump and the change-over valve of the closed center. CONSTITUTION:When an operating lever is operated for starting a driving or an operating machine, hydraulic pressure from pilot proportional pressure valves 20a and 21a flows in a two port change-over valve 25 through shuttle valves 20b, 21b and 22 and changes them over, and simultaneously flows in stack type change-over valves 5, 6 of an operated closed center and changes them over. At this time, as the change of an opening area of the two port change-over valve 25 smoothly changes in proportion to the pressure of the stack type pilot proportional pressure valves 20a, 21a, the discharge amount of the pump 2 flowing in a tank 9 gradually decreases and the flow amount to actuators 3, 4 gradually increases. Additionally, as there is no restrictor between the two port change-over valve 25 and the change-over valves 5, 6, the transmission of pressure improves. Consequently, it is possible to improve responsibility and staticity.