Hitachi Construction Machinery Co., Ltd.

Hideyo Kato

Masami Ochiai

Ken Ichiryu

Yusaku Nozawa

Takashi Kanai

Gen Yasuda

Sotaro Tanaka

Yuusaku Nozawa

A hydraulic drive system for a supersized hydraulic working machine such as a hydraulic excavator includes hydraulic pumps connected to main lines through a delivery line and a supply line. Branch portions from the main line include flow control valves for allowing a hydraulic fluid to flow from the hydraulic pumps toward hydraulic cylinders. A hydraulic reservoir is connected to the main lines through a reservoir line and a drain line. Other branch portions for the drain line include flow control valves for allowing a hydraulic fluid to flow from the hydraulic cylinders toward the hydraulic reservoir. A line branched for the delivery line includes a bypass valve for supplying the hydraulic fluid delivered from the hydraulic pumps to the supply line at a desired flow rate and returning the remaining hydraulic fluid to the hydraulic reservoir.

Hydraulique drive device

Hydraulic drive system

A flow control system is arranged in a hydraulic circuit provided with a variable displacement hydraulic pump, plural actuators and a pump controller. The pump controller controls the displacement of the pump so that a delivery pressure becomes higher by a predetermined value than a maximum load pressure of the plural actuators, whereby the flow rate of pressure oil to the actuators is controlled. The system includes plural valve units connected between the pump and the actuators. Each valve unit has an operating and correcting variable restrictors. The system also includes pressure compensation valves, which are each arranged on an upstream side of a restrictor group consisting of the operating and correcting variable restrictors. The opening of the pressure compensation valve is independently set by an opening drive force set based on a downstream pressure of the restrictor group, an opening drive force set by a pressure-difference setting device and a closing drive force set based on an upstream pressure of the restrictor group so that the upstream pressure becomes higher by a predetermined pressure than the downstream pressure of the restrictor group.

Flow control system

A flow control valve apparatus includes a housing including a main fluid passage having an inlet port and an outlet port; a main valve disposed between the inlet port and the outlet port for allowing or shutting off communication between the inlet port and the outlet port; a backpressure chamber formed between an inner wall of the housing and a rear portion of a valve member of the main valve, the backpressure chamber communicating with the inlet port through an orifice; an auxiliary passage for placing the backpressure chamber in communication with the outlet port; and a pivot valve for actuating the main valve by controlling the opening and closing of the auxiliary passage and varying the fluid pressure in the backpressure chamber. A differential pressure generating means is disposed in the main fluid passage for generating differential pressures that correspond to the flow rate in the main fluid passage. The differential generating means includes a displacement member disposed for movement in the direction in which a fluid flows in the main fluid passage and spring means for urging the displacement member in the direction opposite to the direction in which the fluid flows, and the displacement member cooperates with a wall surface of the main fluid passage to define a fluid passage having an opening area which increases in accordance with an increase in the stroke of travel of the displacement member.

Flow control valve apparatus

Growing community of inventors

Ibaraki-ken, Japan

Hideyo Kato