Hitachi Construction Machinery Co., Ltd.

Hitachi, Ltd.

Nobuya Okabe

Akira Tatsumi

Genroku Sugiyama

Toichi Hirata

Hideaki Tanaka

Masakazu Haga

Seiji Tamura

Mitsuo Kihara

Kuniaki Yoshida

Fumiki Nakagiri

Hiroshi Mizushima

A control system of hydraulic construction machinery includes a prime mover, at least one variable displacement pump driven by the prime mover, at least one actuator hydraulically driven by the pump, maximum revolution number altering device for the prime mover, maximum displacment volume altering device for the pump and an information provider device for providing information on the operation mode of the actuator, whereby the maximum revolution number altering means and maximum displacement volume altering means are controlled by the information provider device to provide a maximum number of revolutions and a maximum displacement volume which suit the operation mode indicated by the output signal. A product of the maximum displacement volume and the number of revolutions becomes at a constant always at the same time when the maximum displacement volume of the pump is varied in response to an output signal of the information provider device, whereby a change in the quantity of pumped fluid can be avoided when the maximum displacement volume of the pump is altered.

Control system of hydraulic construction machinery

A control system for a hydraulic excavator having a prime mover, revolution number control device for the prime mover, at least one variable displacement hydraulic pump driven by the prime mover, displacement volume control device for the pump, actuators driven by pressurized fluid discharged from the pump and working elements driven by the respective actuators. The control system includes maximum revolution number altering device for the prime mover associated with the revolution number control device, maximum displacement volume altering device for the pump associated with the displacement volume control devices, devices for sensing the operation condition of the actuators, devices for selecting an operation mode for each working element and control devices. The maximum revolution number altering device provides at least one maximum revolution number of the prime mover and the maximum displacement volume altering device provides at least one maximum displacement volume so that maximum revolution numbers of the prime mover and maximum displacement volumes are arranged in a plurality of combinations. The plurality of combinations are set in association with the operation condition of the actuators and the selection of the operation mode. The control means selects a combination of the maximum revolution number of the prime mover and the maximum displacement volume of the pumps on basis of output signals of the sensors and selection devices and drives the maximum revolution number altering device and the maximum displacement volume altering device to set the maximum revolution number of the prime mover and the maximum displacement volume of the hydraulic pump.

Control system for hydraulically-operated construction machinery

A hydraulic drive system for civil engineering and construction machinery in which at least first and second hydraulic circuits having at least first and second hydraulic pumps, respectively, are provided for driving a plurality of actuators such as left and right travelling actuators, a boom actuator and an arm actuator. The first circuit includes a first travelling directional control valve for one of the left and right travelling actuators located downstream of a first boom directional control valve for the boom actuator and a first arm directional control valve for the arm actuator that the latter to receive a hydraulic fluid supply from the first pump by taking priority over the first travelling valve. The second circuit includes a second travelling directional control valve for the other of the left and right travelling actuators upstream of a second boom directional control valve for the boom actuator and/or a second arm directional control valve for the arm actuator so as to be able to receive hydraulic fluid supply from the second pump by taking priority over the second boom and/or arm valves. A bypass circuit extends between the second pump and the one travelling actuator whereby a hydraulic fluid supply from the second pump can be received by the first travelling valve.

Hydraulic drive system for civil engineering and construction machinery

A hydraulic circuit system of a construction machine having first and second hydraulic circuit, and a bypass circuit for connecting the first and second circuits together. The first circuit includes a first hydraulic pump and a first valve group having a plurality of directional control valves for controlling a flow of hydraulic fluid from the first pump, and the second circuit includes a second hydraulic pump and a second valve group having a plurality of directional control valves for controlling a flow of hydraulic fluid from the second pump. A plurality of actuators are driven by the hydraulic fluid supplied from the first and second pumps through the valves. The bypass circuit includes a bypass line for connecting the first travel valve in series with the second travel valve in a position downstream thereof through the selecting valve. The selecting valve has first and second positions and is normally in the first position to communicate the second travel valve with the other valves of the second group to supply the hydraulic fluid from the second travel valve to the other valves. When the first travel valve and at least one of the other valves of the second group are simultaneously actuated, the selecting valve is switched to the second position to bring the second travel valve into communication with the first travel valve through the bypass line thereby to supply the hydraulic fluid from the second travel valve to the first travel valve.

Hydraulic circuit system for construction machine

A universal lever apparatus having a first rod and a second rod each for actuating an operated member, an operation lever connected to the first rod and the second rod and pivotally movable in a first direction for moving the first rod and in a second direction for moving the second rod, and lock mechanism for locking the operation lever. The lock mechanism includes a manually operated device operatively connected to the operation lever for pivotally moving the operation lever to a rearward position in which the operation lever does not interfere with movement of a driver without causing effective movements of the first and second rods, the manually operated device being movable between an unlock position in which the pivotal movement of the operation lever causes the effective movement of the first and second rods and a lock position in which the operation lever is located in the rearward position. The lock mechanism further includes elements operatively associated with the manually operated device for resiliently holding the manually operated device in the unlock position and the lock position, and elements for restraining the operation lever to keep same from pivotally moving in the first and second directions when the manually operated device is in the lock position and the operation lever is in the rearward position.

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Tsuchiura, Japan

Nobuya Okabe