1. Dirt blocks the small hole of the balance valve of the final drive system, resulting in parking brake force cannot be exempted
When walking in the machine, if the pressure oil cannot pass through the small hole on the balance valve to promote the movement of the balance valve spool, the pressure oil cannot pass through the groove on the balance valve to avoid the parking brake force, resulting in the walking motor not rotating normally. The loader is running away. The cleaning method is: cleaning the balance valve; when disassembling, it is necessary to avoid the entry of dirt.
2. Dirty matter enters the balancing valve in the parking brake oil path on the side of the machine
When the machine is walking, if the dirt blocks the small hole of the balance valve, the parking brake cannot be waived, and then the walking deviation is formed. When the pressure oil cannot pass through the small hole of the balance valve to enter the tension spring chamber of the balance valve to advance the movement of the balance valve spool, the pressure oil cannot enter the hydraulic system through the groove on the balance valve The braking force of the car cannot be exempted, and the resulting walking motor cannot rotate, so it exhibits walking deviation. Sweeping method; cleaning the balance valve; when disassembling, to avoid the entry of dirt; regularly replace the hydraulic oil and filter element that meet the requirements.
3. The center reverse joint sealing ring is damaged
The center reversing joint is composed of a casing and a mandrel. The casing is installed on the upper body and the mandrel is installed on the lower body. The mandrel has an annular groove equal to the number of oil pipes, and the hydraulic oil from the housing flows through these oil grooves from the straight hole on the mandrel to the travel motor, so even if the housing is continuously reversed with the upper body, the mandrel The groove on the top can also keep the oil port on the shell free. The hydraulic oil can enter and exit freely. If the filter element of the hydraulic oil is not replaced in time, the bypass valve on the filter element may be opened, and the impurities in the oil directly enter the sliding surface of the center reversing joint due to the unfiltering, which damages the seal ring on it. When the machine is walking in the machine, the speed of the motor on both sides is different due to the leakage of pressure oil on one side, resulting in the machine running deviation. The cleaning method is: replace the center reverse joint oil seal; replace the hydraulic oil and filter element.
4. Travel motor safety valve oil leakage
If the safety valve leaks oil, it will cause the pressure in the system to be too low, so that the speed of the walking motor will not work, and then it will show walking deviation. The method of cleaning is to replace the damaged safety valve of the walking motor; when judging, the safety valves of the left and right walking motors can be swapped to see if they are deflected when walking in the reverse direction.
5. The output pressure (pressure control) of the walking proportional valve on the deflection side of the machine is too low
This proportional valve can output the corresponding control oil pressure according to the length of the control handle control stroke, so that the main control valve has a corresponding amount of movement, and then control the speed of the working device. If the filter element of the oil filter fails to be changed on time, the filter element may be blocked, causing the oil filter bypass valve to open, and the dirty hydraulic oil directly enters the circuit of the proportional valve without filtering, resulting in a spool in the valve If it is stuck, the control oil cannot flow through the reverse proportional valve on the deflection side of the machine to the reverse main control valve, causing the walk to deviate. When checking, you must check the pressure (3.3MPa) of the walking proportional valve. The cleaning method is: clean the valve body and the front oil circuit, and replace the hydraulic oil and filter element.
6. The movement of the main valve spool on the deflection side of the machine fails
If the tension spring in the walking main valve becomes soft or broken, or the spool is stuck, it may cause the oil pressure to drop, showing a walking deviation. When checking, it is necessary to measure the pressure of the main valve oil circuit, and the normal value is 32.5Mpa. If the walking main valve is damaged, it must be replaced or repaired. The PC200 loader I met had two deviations in walking, both of which were caused by damage to the walking main valve. Therefore, when presenting a walking deviation problem, you should first consider whether the walking main valve is damaged to avoid detours.
7. The walking suction valve on the deflection side of the machine is damaged
The suction valve is installed on the hydraulic cylinder and motor of the working device. Its function is: when the hydraulic cylinder or the motor is subjected to a large external impact force, it can be removed or when the motor is subjected to a large external impact force, the abnormal high pressure in the cylinder or the motor (the set pressure is generally below 36.5Mpa) Protect related oil pipes and cylinders from damage. If the walking suction valve is damaged and the tension spring in the valve becomes soft or broken, the oil pressure in the walking main valve will decrease, resulting in a lack of driving power of the walking motor and causing walking deviation. The cleaning method is to repair or replace the suction valve.
