Excavator boom lowering hydraulic control circuit

Abstract

The invention discloses an excavator boom lowering hydraulic control circuit, the main design points of which are: an electromagnetic reversing valve is arranged between the servo variable mechanism of the variable displacement hydraulic pump and the oil outlet of the boom lowering manual pilot valve ;The connecting pipeline between the rodless chamber of the boom oil cylinder and the two-way hydraulic control reversing valve of the boom is equipped with an electric contact pressure switch controlled by hydraulic force, and the electric contact pressure switch is electrically connected with the electromagnetic reversing valve; the two-way hydraulic control of the boom A compensation channel is arranged on the spool of the reversing valve, and a check valve is arranged in the compensation channel. When the boom is lowered, under the action of the boom and its load gravity, the hydraulic oil that originally flowed back to the oil tank quickly enters the rod chamber through the compensation channel, while the variable displacement hydraulic pump maintains the lowest displacement state, thereby reducing The power consumption is reduced, the oil temperature of the system is reduced, and the energy saving effect is achieved. And when the boom is lowered too fast or the bucket touches the ground, it can prevent the phenomenon of cavitation and keep the boom cylinder under reliable control all the time.

Description

technical field [0001] The invention relates to an excavator hydraulic system, in particular to an excavator boom lowering hydraulic control circuit. Background technique [0002] The positive flow control system has been used more and more in medium and large excavators. The so-called positive flow control system is different from the previous negative flow control system. The positive flow control system refers to the displacement of the hydraulic pump and the pilot operating handle. The output signal pressure is proportional, the main controller judges the flow demand of the actuator and its change trend according to the pilot pressure signal and its change trend, and adjusts the displacement of the hydraulic pump accordingly, and the flow supply of the system can dynamically follow the actuator Real-time matching of system traffic, that is, "what you get is what you need". [0003] According to the principle of positive flow, when the pilot handle is operated to lower t...

AI Technical Summary

Problems solved by technology

If the displacement of the hydraulic pump continues to increase at this time, it will not only cause waste of energy, but also cause adverse phenomena such as system heating.

[0004] If the boom lowering pilot signal is cut off and the hydraulic pump is connected to the oil circuit, the boom can be lowered completely by its own weight adjustment, but this will also encounter the following problems: First, when the boom is lowered too fast, the regenerated oil The amount is far behind the speed of the boom's lowering, which will cause negative pressure in the rod cavity of the boom (that is, the phenomenon of suction), which is not allowed; secondly, when the bucket touches the ground, it will often perform the action of lowering the boom. Realize the working conditions of supporting the car, leveling the ground, etc. However, at this time, the conversion of potential energy and hydraulic energy is no longer performed to achieve the oil supply to the rod cavity of the boom cylinder

However, because the hydraulic pump is disconnected from the oil circuit connected to the boom lowering pilot signal, it cannot receive the command to increase the displacement and supply oil to the rod chamber of the boom cylinder. At this time, although the pilot handle sends out the boom lowering command command, but the boom cylinder will not move

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