The phenomenon of sluggishness of hydraulic excavator is one of the common faults of hydraulic system of excavator.
One-way rotation is slow and weak, and there is no brake in the other direction.
A. Characteristics of rotary hydraulic circuit
As shown in the working principle diagram of the slewing motor of the excavator, when the operation of the slewing is stopped, the directional valve returns to the neutral position, the oil circuit of the slewing motor is blocked, and a hydraulic brake is formed. The two brake buffer valves both limit the maximum working pressure (16.7MPa) It also acts as a brake buffer, and the two one-way valves act as a replenisher, also known as a replenisher.
B. Reasons for sluggishness
The cause of hydraulic failure should be analyzed and checked from the entire system. The reasons for the weak rotation of the excavator may include: wear of the main pump, motor and directional valve, excessive oil return resistance, excessive resistance to movement of the slewing mechanism and pilot operation The pressure is too low, etc. However, the most likely causes are the following two aspects:
1. The damping hole of one end of the brake buffer valve is blocked or the valve core is always open. Because the setting pressure of the rotary oil circuit is lower than the other pressures of the system, it is mainly related to the rated pressure of the hydraulic motor and is also much lower than the rated pressure of the main pump The road's brake buffer valve is often open. Frequent opening of the brake buffer valve will cause wear on the spool and sleeve. On the other hand, impurities in the oil will cause a. Blockage of the damping hole of the brake buffer spool. After the damping hole is blocked, the opening pressure of the brake buffer spool valve is completely determined by the preload of the main spool return spring. The preload force can only overcome the friction force and hydrodynamic force of the spool and cannot drive the rotary motor; b. Impurities are stuck on the sealing surface of the spool, so that the spool is always open, and the working pressure oil leaks from the spool opening Cause sluggishness. In both cases, one-way slewing will be slow and weak, and the other will have no brakes.
2. The charge valve wears or keeps opening a. Because the charge valve is often opened and closed, the valve seat and the valve core will produce squeezing deformation and wear, and its wear form is similar to the valve cone surface of the engine, and the valve core cone Surface wear is the main cause. The worn valve core and valve seat will cause the leakage of the circuit in the non-refueling state (that is, the driving state) to decrease, and the working pressure oil leaks from the replenishing valve, resulting in weak or even unable to rotate.
B. Impurities in the oil keep the charge valve spool open. 3. Anti-rebound valve is worn or not closed tightly. C. Trouble shooting a. Fault inspection First check the working condition of the hydraulic main pump Observe the load level of the engine when the boom is at full speed (or overloading the arm cylinder and bucket cylinder), mainly based on the sound of the engine and the color of the exhaust smoke.
If the load level can reach more than 2/3 of the rated power, the main pump is working normally. Then operate the swing device, if the engine load is very low, and the swing speed is very slow, or even unable to turn, it can be preliminarily determined that it is a failure of the brake buffer valve and the charge valve.
B. Troubleshooting
(1) Check the brake buffer valve, mainly to see whether the valve core is worn, whether the damping hole is smooth, and whether the valve core can be closed tightly.
If the fault persists, check for the next step.
(2) Check whether the charge valve can be closed tightly, repair or replace the valve core:
(3) Check and remove the anti-bounce valve.
