Oil-pressure control device of building machine

Abstract

The invention provides a hydraulic control device for construction machine capable of reducing the max. rotation down rate of the engine speed at the time of quick loading, shortening the return time to the engine speed in normal condition, and enhancing the working effectiveness. The hydraulic control device of the construction machine is equipped with a hydraulic pump of variable displacement type driven by an engine and a pump controller to calculate a command to set the absorptive torque T of the pump in accordance with the engine speed N given by an engine speed sensor and control the absorptive torque T in conformity to the command, wherein the pump controller calculates the decremental degree d of the engine speed and emits to a pump controlling means a command to set the absorptive torque T to a value TO specified lower than the currently set torque value when the decremental degree calculated has become over the specified value d1.

Description

technical field [0001] The present invention relates to a hydraulic control device for construction machines such as hydraulic excavators, and more particularly relates to a hydraulic control device for construction machines equipped with a variable displacement hydraulic pump driven by an engine. Background technique [0002] Regarding the oil pressure control device of a construction machine equipped with a variable capacity hydraulic pump driven by an engine and used to drive a transmission of a work machine, the method of controlling the change in the engine speed at the time of a sudden load is given by Figure 6 (a), Figure 6 (b) An example thereof will be described. Figure 6 (a), Figure 6 (b) respectively represent the changes in the rotational speed N of the engine and the absorption torque T of the variable capacity hydraulic pump during this control process. [0003] exist Figure 6 When a heavy load is rapidly applied from a light load state, as the engine speed...

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Problems solved by technology

[0009] In addition, in the technology disclosed in Japanese Patent Application Laid-Open No. 9-195947, in order to return the engine from the automatic slow state to the normal state, it takes 100% of the deviation corresponding to the target rotational speed in the normal state and the target rotational speed in the automatic slow state. Time, so that the target oil discharge volume of the hydraulic pump gradually increases, increasing the absorption torque, so it takes a long time to recover

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