HYDRAULIC DRIVING SYSTEM OF CONSTRUCTION MACHINERY

摘要

A hydraulic drive system comprises directional flow control valves (10a-f) for selectively supplying a hydraulic fluid from a first hydraulic pump (1a, 1b), inflow control valves (201-203) disposed respectively in branch lines (150A-C) branched from a supply line (100) for supplying a hydraulic fluid delivered from a second hydraulic pump (3a, 3b) to rod pushing-side chambers (5aA, 5bA, 6A, 7A) of hydraulic cylinders, a bypass flow control valve (204) disposed in a line (104) connecting the supply line (100) and a reservoir (2), and a controller (31) for computing control variables corresponding to operation command signals from control levers (32, 33) and controlling the inflow control valves (201-203) and the bypass flow control valve (204) in accordance with the computed control variables. As a result, the number of flow control valves and the length of piping required for connection of the flow control valves can be further cut, and a total pressure loss can be further reduced. A reduction in the number of flow control valves contributes to simplifying layouts of hydraulic piping between hydraulic sources and actuators receiving hydraulic fluids from the hydraulic sources.