Hydraulic control valve for construction machinery

Abstract

Provided is a hydraulic control valve in which a center bypass passage is not blocked, but is unloaded when a swing and an arm are operated at the same time to prevent the pressure in a hydraulic pump from being increased. The hydraulic control valve includes: a hydraulic pump connected to an engine; a swing spool disposed upstream of a center bypass passage communicating with a discharge passage of the hydraulic pump to control the operation and stopping of a swing motor and directional switching of the swing motor when switched; an arm spool disposed downstream of the bypass passage to control the operation and stopping of an arm cylinder and directional switching of the arm cylinder when switched; and a center bypass control valve disposed within the arm spool, the center bypass control valve being switched by a discharge flow pressure of the hydraulic pump which is increased when a multi operation for simultaneously operating the swing and the arm is performed, and unloading the increased swing side pressure to the center bypass passage when switched.

Description

technical field [0001] The invention relates to a hydraulic control valve for construction machinery. More specifically, the present invention relates to a hydraulic control valve for a construction machine in which, without any interruption of a center bypass path, during a combined operation of simultaneously performing a swing manipulation and a manipulation of a work implement such as an arm , the hydraulic fluid discharged from the high-load hydraulic pump is unloaded to the center bypass path, thereby preventing excessive pressure increase of the hydraulic pump. Background technique [0002] Usually, such as figure 1 As shown, hydraulic control valves for construction machines according to the prior art include: [0003] A hydraulic pump 1, the hydraulic pump 1 is connected to an engine (not shown); a rotary spool valve 3, and the rotary spool valve 3 is installed on the upstream side of a central bypass path 5 in fluid communication with the discharge flow path 2 of...

AI Technical Summary

Problems solved by technology

Therefore, since the high load pressure on the swing side has an influence on the control valve system, during performing a combined operation of swing drive or manipulation and manipulation of a hydraulic actuator such as an arm cylinder, since the discharge flow rate varies according to the manipulation of the control valve increases, so the pressure further increases

[0017] For this reason, the use of much higher horsepower than is adequately required for construction machinery results in reduced fuel efficiency and consequent excessive loss of energy

Also, in the positive control system, since the discharge flow rate of the hydraulic pump increases according to the manipulation amount of the control valve, the pressure of the hydraulic pump also increases excessively, resulting in energy loss

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