Analysis of the Causes of Burning of the Gearbox Clutch Friction Plate
Main Causes of Burning of the Clutch Friction Plate
(1) Excessive Oil Temperature
Based on the surface condition of the gearbox components and the degree of oxidation of the hydraulic oil, it is judged that the hydraulic system oil temperature is too high. Excessive oil temperature is caused by problems with the hydraulic pump, oil filter, cooler and other components and hydraulic oil in the hydraulic system. Due to excessive oil impurities in the hydraulic system, the oil filter is blocked, the hydraulic system circulation is not smooth, the cooling is poor and the circulation is too fast, which increases the oil temperature; the increase in oil temperature and the aging, deformation and cracking of the rubber seals inside the gearbox clutch reduce the performance and life of the clutch, causing poor engagement of the main and moving parts of the clutch, slippage between the main and moving parts, incomplete clutch separation, increased friction resistance, and accelerated serious wear of the clutch friction plate.
(2) Improper use of hydraulic oil
Based on the degree of oxidation and deterioration of the gearbox residual oil, it can be confirmed that the hydraulic oil is improperly selected. In the hydraulic system, hydraulic oil plays the role of transmitting power, and also plays the role of lubrication and cooling. If the hydraulic oil is used improperly, it will directly affect the working quality of the hydraulic system. Practice has shown that 80% of hydraulic system failures are caused by oxidation and deterioration of hydraulic oil. Valve components in hydraulic systems, such as speed change pumps, control valves, lubrication valves, etc., have very precise clearance requirements. Resistance holes, control valve holes, lubricant holes and hydraulic oil inlets are opened on the components. Once the hydraulic oil is oxidized or mixed with a large amount of impurities, these oil holes will be blocked, the flow of hydraulic oil will be hindered, and these components cannot work normally.
(3) Pressure is too low
If impurities in the hydraulic oil enter the gearbox, it will cause the oil inlet and oil holes to be blocked. If impurities in the oil enter the clutch piston and hydraulic cylinder, the seal ring will be stuck in the hydraulic cylinder and cannot rise outward. Therefore, the seal between the piston seal ring and the hydraulic cylinder body is not tight, causing the pressure oil to leak out, reducing the clutch working oil pressure, causing slippage and poor operation. This in turn causes serious wear of the clutch friction plate, poor meshing, and insufficient lubrication of the clutch master and slave plates, which intensifies the wear of the clutch plate.
2. Preventive measures
In order to extend the service life of the bulldozer gearbox clutch, according to our long-term work experience, the following points must be achieved:
(1) Cleaning system
When installing a new gearbox, the hydraulic pump, oil filter, torque converter, cooler, operating valve, etc. of the main hydraulic system should be strictly cleaned. It is best to use No. 8 hydraulic gearbox oil of the same brand as the torque converter as the cleaning fluid. It is strictly forbidden to use kerosene and diesel for cleaning. When cleaning, the flow rate of the cleaning fluid should be increased as much as possible to flush out the mechanical impurities and oil stains in the hydraulic system pipeline. After cleaning, the cleaning fluid should be discharged in a warm state.
(2) Correct selection of oil
According to the requirements of the instruction manual, the gearbox and chassis hydraulic system use No. 8 hydraulic transmission oil. The selected hydraulic oil should have good low-temperature fluidity, appropriate high-temperature viscosity, good thermal oxidation stability and anti-foaming properties, as well as good friction and corrosion resistance. It is forbidden to use hydraulic oil of different brands. The oil must be strictly filtered before refueling to prevent mechanical impurities, dust, moisture, emulsion, etc. from invading the hydraulic system.
(3) Control system pressure
Before operating the machine, the hydraulic system pressure should be strictly checked, that is, the pressure entering the transmission control valve should be detected with a pressure gauge, and the standard value of the clutch engagement pressure of the transmission II and III gears should be set under the action of the pressure regulating valve (2.5MPa±0.2MPa), the oil pressure of the I gear lock clutch (1.25MPa±0.1MPa), and the oil pressure of the lubrication valve (0.1MPa±0.025MPa). If the measured clutch pressure is lower than the standard value, the speed control valve should be checked first to determine whether the gap between the speed control valve stem and the valve body hole is too large; whether the spring force of the pressure regulating valve and the pressure reducing valve is too weak; whether the O-ring on the speed operating valve stem is damaged. If damaged, it should be replaced and adjusted in time. When the pressure regulating valve pressure reducing spring force is insufficient, a gasket of appropriate thickness can be added to the spring seat to adjust the working oil pressure. Reinstall and test. If the measured pressure is still lower than the standard value, the speed control valve assembly must be replaced.
(4) Reasonable adjustment of meshing clearance
A pair of helical bevel gears is used at the output end of the gearbox to transmit power to the central drive shaft of the rear axle box. Therefore, the correct degree of meshing has a great impact on the noise, service life and working performance of the whole machine. It should be removed before installation. The large bevel gear on the old main engine, install a new pair of large bevel gears on the central drive shaft and fasten them with bolts; adjust the tooth clearance of the bevel gear pair to 0.25-0.33mm through the speed regulating gasket, and keep the meshing indentation; this bevel gear must be used in pairs.
(5) Maintenance
Maintaining good maintenance and care is an important prerequisite for ensuring production safety, giving full play to the performance of the gearbox clutch, and extending its service life. The driver should perform daily maintenance carefully and strictly, and promptly discover and eliminate minor faults to avoid accidents. For newly manufactured bulldozers or bulldozers that have just undergone overhaul, the oil should be cleaned up after trial operation or 100 hours of operation, and No. 8 hydraulic gearbox oil should be refilled. The working oil should be replaced every 1000 hours thereafter. In daily work, the oil pressure and oil temperature of the hydraulic system should be observed at any time to prevent the oil pressure from being too low and the oil temperature from being too high and continuing to work. Check the quality of the hydraulic oil regularly to keep the hydraulic system and hydraulic oil clean. If any abnormal situation is found, the cause should be checked and the fault should be eliminated in time to ensure that the bulldozer gearbox clutch maintains a good working condition.