Hitachi Construction Machinery Co., Ltd.

Mitsuo Kihara

Akira Tatsumi

Seiji Tamura

Junichi Hosono

Kazuhiro Ichimura

Kazuo Asano

Hideaki Sayama

Hiroyuki Adachi

Hiroshi Watanabe

Kazunori Nakamura

Tsuyoshi Nakamura

Masakazu Haga

Hiroyuki Azuma

Hiroshi Onoue

Eiji Egawa

Atsushi Shimazu

Shigetaka Nakamura

Nobuya Okabe

Toshiaki Nishida

Saburo Yoshio

Saburou Yoshio

A hydraulic steering unitgenerates a control pressure corresponding to the rotational quantity and rotational direction of the steering wheelon the basis of pressurized oil of a pilot pump. Signals of pressure sensorsandused to detect the control pressure, and a signal of a front operation detection unit, are inputted into a controller. A controllerand solenoid valvesandcontrol a stroke of a steering valveso that the stroke becomes larger with increase in control pressure detected by each of the pressure sensorsand. In addition, when the operation of a front work device is detected, the controllerand the solenoid valvesandcontrol the stroke of the steering valveso that the stroke becomes larger than that provided when the operation of the front work device is not detected.

Steering system for engineering vehicle

A calculating portion 7a calculates a distance from the tip end of a front device to an interference prevention area, and a detection line 7m detects a moving speed of a boom 1. If the tip end of the front device comes close to the interference prevention area when the boom 1 is moving upward, control is made such that, while continuing to move the boom 1 upward, a control gain calculating portion 7h and a multiplier 7i cooperatively calculate a target speed of an arm in the arm dumping direction (interference avoiding direction) corresponding to the boom-up speed, and an input limit value calculating portion 7c, an adder 7j and a minimum value selecting portion 7f cooperatively control the arm to move in the interference avoiding direction relative to a vehicle body. Interference avoidance control enabling the tip end of the front device to be moved smoothly along the vicinity of a boundary of the interference prevention area is thereby effected and the front device can be prevented from interfering with the vehicle body without reducing the maneuverability and the working efficiency.

Interference preventing system for construction machine

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

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

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

Growing community of inventors

Ibaraki, Japan

Mitsuo Kihara