Hitachi Construction Machinery Co., Ltd.

Akira Tatsumi

Seiji Tamura

Mitsuo Kihara

Toichi Hirata

Kazuhiro Ichimura

Masakazu Haga

Junichi Hosono

Kazuo Asano

Genroku Sugiyama

Hiroshi Watanabe

Osamu Tomikawa

Nobuya Okabe

Masaki Egashira

Hideaki Sayama

Hideaki Tanaka

Eiki Izumi

Tsukasa Toyooka

Hiroshi Onoue

Shigetaka Nakamura

Kuniaki Yoshida

Touichi Hirata

Saburou Yoshio

Saburo Yoshio

The current operational condition is discriminated as being the vehicle propulsion condition or the performing work condition. When the vehicle propulsion operational condition is discriminated, the maximum engine revolution speed is limited to a first revolution speed and the maximum displacement is limited to a first displacement value. When the performing work condition is discriminated, the maximum engine revolution speed is limited to a second revolution speed equal to or lower than the first revolution speed and the maximum displacement is limited to a second displacement value higher than the first displacement value. The first and second revolution speeds and the first and second displacement values are so determined that the first revolution speed multiplied by the first displacement value at least as relating to pressure for vehicle propulsion on level ground is less than the second revolution speed multiplied by the second displacement value as relating to the pressure for below the range of torque limitation control. By this, the pump output flow during vehicle propulsion on level ground is made lower than while performing work and, during vehicle propulsion, reduction of the pressure loss is made possible. Even with the identical pump pressure, the effective motor pressure is increased, so that its output torque can be increased. Because also the maximum displacement of the motor can be reduced according to the reduction of the maximum pump output flow amount, the construction of the hydraulic circuit can be made more compact.

Control device for hydraulically propelled work vehicle

When the pump pressure detected through a pressure detecting line 48 is raised higher than a first predetermined pressure Pd1, a recovery switching valve 44 is shifted to a valve-closed position to cease the recovery function. At this time, the pump delivery pressure detected through a pressure detecting line 51 is higher than a second predetermined pressure Pd1* close to the first predetermined pressure Pd1, and an engine speed increasing device 52 controls an engine controller 11 to increase the rotational speed of an engine 10, thereby increasing the pump delivery rate. Thus, it is possible to make small speed change of an actuator and to increase working efficiency with no deterioration in operability, even when a recovery function is ceased.

Hydraulic control system for construction machines

Apparatus for controlling revolution speed of prime mover for

Hydraulic control apparatus for hydraulic construction machine

Engine revolution speed control device for a hydraulically driven vehicle

Hydraulic drive system for construction machine

Engine remote control system

A controller having an up/down switch for changing the rotational speed of a prime mover such as an engine, an actuator such as an electric motor for driving a governor on the basis of the operation of the up/down switch so as to control the rotational speed of the prime mover. A target speed is calculated on the basis of the operation of the up/down switch, and the prime mover speed is controlled by using the calculated value. Another switch is provided to immediately shift the prime mover speed to a speed previously set as desired. This shift switch is used to control the prime mover so that the prime mover rotates at the set speed, and this speed is adjusted by operating the up/down switch.

Apparatus for controlling rotational speed of prime mover of

Drive control system for hydraulic construction machine

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

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Kashiwa, Japan

Akira Tatsumi