Displacement variable hydraulic pump control device

Abstract

The invention provides a variable displacement hydraulic pump control device. This device is provided with a servo piston for tipping and controlling the variable displacement type hydraulic pump, a regulating valve for performing position control of the servo piston, an electromagnetic proportional pressure reducing valve for controlling a position of the compensation piston for performing power shift control of position of the regulating valve. A first restrictor is provided in a flow passage communicating the electromagnetic proportional pressure reducing valve and the compensation piston, a relief flow passage for branching out of a flow passage between the first restrictor and the compensation piston is provided, a second restrictor and a directional control valve are provided in the relief flow passage. When control fluid output from the electromagnetic proportional pressure reducing valve becomes the maximum pressure, the directional control valve is switched to retain pressure in a flow passage between the first restrictor and the compensation piston at a predetermined pressure by the first restrictor and the second restrictor. Thus, even if control current of a electromagnetic proportional pressure reducing valve is shut off, the late operation is rid of the mode of slow running.

Description

technical field [0001] The present invention relates to a control device of a variable capacity hydraulic pump that can be used in industrial machinery such as hydraulic excavators and hydraulic cranes. Specifically, the present invention relates to a variable capacity type hydraulic pump control device having a hydraulic transmission function. Background technique [0002] Conventionally, industrial machines such as hydraulic excavators and hydraulic cranes are equipped with a plurality of variable displacement hydraulic pumps for supplying pressurized oil having a certain pressure to control valves for shoveling. Control the speed and direction of hydraulic transmission devices such as buckets, booms, and booms. As the variable displacement hydraulic pump, for example, a mode for operating with high power (hereinafter, simply referred to as "H mode"), a mode for operating with emphasis on fuel consumption (hereinafter, simply referred to as "S mode"), and In a mode for l...

AI Technical Summary

Problems solved by technology

But in this way, it is necessary to switch the structure of the pipeline, and the structure required to achieve a certain pressure is more expensive, and the operator must spend time for this switch.

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