The problem of uncontrollably dropping the loading arm

The automatic fall of the boom is a shortcoming often encountered in the use of wheeled loaders.

The loader often works under the condition of automatic fall of the boom, which will not only make the loader work with low power, the hydraulic oil temperature rise is too high, and the service life is reduced, but also constitute an increase in fuel consumption of the loader starter.

The reasons for the automatic fall of the boom are explained: under normal circumstances, when the piston rod of the boom cylinder reaches the limit position, the boom cylinder no longer moves, the hydraulic oil is compressed, and the pressure of the hydraulic system continues to rise.

When the pressure of the hydraulic system reaches the pressure setting value of the working equipment of the loader (that is, the calibration value of the main safety valve), the main safety valve opens, and the high pressure oil output from the gear pump will be relieved from the main safety valve to the hydraulic tank.

According to the above principles, the reasons for the automatic fall of the boom are analyzed in the following four points:

(1) Hydraulic hose leakage Assuming that the sealing ring of the hydraulic pipe joint is damaged, the crimping is not solid, or the pipe body itself is damaged, the hydraulic oil in the high pressure chamber of the boom cylinder will spray hydraulic oil from the damaged and gap, and then the boom will automatically fall.

(2) The spool of the boom reversing valve can not return to the middle position, the spool is seriously worn and the seal is not strict, which will cause the hydraulic oil in the high pressure chamber of the boom cylinder to flow back to the hydraulic tank, resulting in the boom falling automatically.

(3) Main safety valve shortcomings When the main pressure of the hydraulic system exceeds the set value, the hydraulic oil in the main oil supply pipeline of the hydraulic system will be relieved by the main safety valve.

If the main safety valve is stuck or damaged, it will constitute abnormal pressure relief of the hydraulic system here, and then cause the boom to fall automatically.

(4) The leakage defect in the boom cylinder during the rapid movement of the piston rod of the boom cylinder, the air in the boom cylinder will suffer from a sharp contraction and a moment of high temperature and high pressure. If the high temperature and high pressure exceed the bearing limit of the boom cylinder seal ring, the seal ring will fail.

After the piston seal ring of boom cylinder fails, the hydraulic oil in its rodless cavity will leak to the rod-bearing cavity, and then the boom will fall automatically

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