It is one of the common faults in hydraulic system of hydraulic excavator that the rotary force of hydraulic excavator is weak.
The middle one-way rotation is slow and weak, and there is no brake.
A. Characteristics of swing hydraulic circuit
When the slewing is stopped, the reversing valve returns to the middle position and locks the oil circuit of the slewing motor to form hydraulic braking. The two brake buffer valves not only limit the maximum working pressure (16.7mpa) but also play the role of braking buffer. The two one-way valves play the role of oil replenishment, also known as oil replenishment valve.
B. Causes of weak rotation
The causes of hydraulic failure should be analyzed and checked from the whole system. The causes of the excavator's weak rotation may include: wear of the main pump, motor and reversing valve, excessive oil return resistance, excessive movement resistance of the slewing mechanism and low pilot control pressure. However, the most likely causes are the following two aspects:
1. the damping hole of the brake buffer valve at one end is blocked or the valve core is always open. As the set pressure of the rotary oil circuit is lower than other pressures of the system, it is mainly related to the rated pressure of the hydraulic motor and is far lower than the rated pressure of the main pump, so the brake buffer valve of the rotary oil circuit is often opened. The frequent opening of the brake buffer valve, on the one hand, will cause the wear of the valve core and valve sleeve; on the other hand, the impurities in the oil will cause the blockage of the damping hole of the brake buffer valve core. After the damping hole is blocked, the opening pressure of the brake buffer valve element is completely determined by the preload of the return spring of the main valve element. The pre tightening force can only overcome the friction and hydraulic force of the valve core, and can not drive the rotary motor; b. Impurities are stuck on the sealing surface of the valve element, which keeps the valve element open, and the working pressure oil leaks from the opening of the valve element, which is bound to cause weak rotation. In both cases, the one-way rotation will be slow and weak, and there will always be no braking.
2. the oil make-up valve is worn or always open. A. due to the frequent opening and closing of the oil make-up valve, there will be extrusion deformation and wear between the valve seat and the valve core. Its wear pattern is similar to the valve cone of the engine, and the wear of the valve core cone is the main reason. The worn valve core and valve seat will cause the tightness of the circuit in the non oil make-up state (i.e. the driving state) to decline, and the working pressure oil will leak from the oil make-up valve, resulting in weak rotation or even no rotation.
b. Impurities in the oil make the oil makeup valve element open all the time 3 Anti rebound valve is worn or not closed tightly (yc85, yc135 and yc225 machines) C. troubleshooting A. fault inspection first check the working condition of the main hydraulic pump. Observe the load degree of the engine when the boom is lifted at full speed (or overload the stick cylinder and bucket cylinder), mainly based on the sound of the engine and the exhaust smoke color.
If the load can reach more than 2/3 of the rated power, it indicates that the main pump works normally. If the slewing device is operated again, and the engine load is very low, and the slewing speed is very slow, or even unable to rotate, it can be preliminarily determined that it is the fault of the brake buffer valve and the oil makeup valve.
b. Troubleshooting
(1) Check the brake buffer valve, mainly to see whether the valve core is worn, whether the damping hole is unobstructed, and whether the valve core can be closed tightly.
If the fault still exists, carry out the next inspection.
(2) Disassemble and check whether the oil makeup valve can be closed tightly, and repair or replace the valve core:
(3) Check and disassemble the anti rebound valve.
