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5457results about "Servomotors" patented technology

Method and device for attenuating the motion of hydraulic cylinders of mobile work machinery

The present invention relates to a method for attenuating the motion of hydraulic cylinders of mobile work machinery, in particular of hydraulic excavators, in which prior to the hydraulic cylinder reaching one of the limits of travel, its motion speed is reduced, and the hydraulic cylinder is moved to the respective limit of travel at reduced speed; wherein for the purpose of reducing the speed, the inflow to, and/or the outflow from, the hydraulic cylinder are/is throttled by a flow control device. According to the invention, the method is characterized by, prior to the respective limit of travel being reached, the motion speed of the hydraulic cylinder is registered, and the point in time when throttling commences is changed depending on the registered motion speed. Furthermore, the present invention relates to a device for attenuating the motion of hydraulic cylinders of mobile work machinery, in particular of hydraulic excavators, a position registering device for registering a preliminary limit position of the hydraulic cylinder, a control device for throttling the inflow and/or outflow of the hydraulic cylinder, and a control device for controlling the flow control device when the preliminary limit position is reached. According the invention, the device has a speed registering device for registering the motion speed of the hydraulic cylinder when the preliminary limit position is reached, and the control device has a delay device for delaying driving the flow control device, depending on the recorded motion speed.
Owner:LIEBHERR FRANCE

Flow rate control device in a hydraulic excavator

A flow rate control device in a hydraulic excavator, comprising a hydraulic pump which is driven rotatively by an engine, a hydraulic actuator which is driven by a hydraulic oil discharged from the hydraulic pump, a control valve which controls the supply of the hydraulic oil to the hydraulic actuator, an operating means which operates the control valve so as to change over the valve from one position to another, a relief valve disposed in a discharge oil path extending from the hydraulic pump to limit the maximum pressure in the discharge oil path, an operational condition detecting means for detecting an operational condition of the hydraulic actuator, a pump pressure detecting means for detecting the discharge pressure of the hydraulic oil discharged from the hydraulic pump, a flow rate adjusting means for adjusting the discharge flow rate of the hydraulic oil discharged from the hydraulic pump, and a control means to which are inputted detection signals from both the operational condition detecting means and the pump pressure detecting means. When a specific operational condition of the hydraulic actuator is detected and when the said discharge pressure is held at a predetermined relief cut-off pressure or higher for a predetermined period of time, the control means makes control so that the discharge flow rate of the hydraulic oil discharged from the hydraulic pump is decreased to a relief cut-off pressure by the flow rate adjusting means. According to this construction, the relief cut-off control can be made only where required for each of various works of different conditions which the hydraulic excavator performs, such as excavating work, crushing work and land readjusting work. That is, even when the discharge pressure is held at a predetermined relief cut-off pressure or higher for a predetermined period of time, the relief cut-off control is made if the hydraulic actuator is in the specific operational condition.
Owner:KOBELCO CONSTR MASCH CO LTD
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