Analysis of the main causes of friction plate burning in variable speed clutch
1, the main reason for the friction plate burning of the transmission clutch
(1) Oil temperature is too high
According to the surface of the transmission parts and the degree of oxidation of hydraulic oil, determine the oil temperature of the hydraulic system is too high, and the oil temperature is too high is affected by the hydraulic system hydraulic pump, oil filter, cooler and other components and hydraulic oil, that is, too much oil impurities in the hydraulic system, resulting in the oil filter blocking, the hydraulic system circulation blocked, poor cooling and circulation too fast, so that the oil temperature rises; The high oil temperature also causes deformation and cracking of the rubber seal in the variable speed clutch due to aging, reducing its performance and life, causing the clutch master and moving slave plate to engage badly, slipping between the master and moving slave plate, the clutch separation is not complete, and the friction resistance increases, thus accelerating the serious friction loss of the clutch friction plate.
(2) Improper selection of hydraulic oil
According to the degree of oxidation deterioration of the residual oil of the transmission, it is confirmed that the hydraulic oil is improperly selected, and the hydraulic oil plays the role of transmitting power in the hydraulic system, and plays the role of lubrication and cooling; If the hydraulic oil is selected improperly, it will directly affect the working quality of the hydraulic system. Practice has proved that 80% of the failure in the hydraulic system is caused by the oxidation deterioration of hydraulic oil, hydraulic system variable speed pump, control valve, lubrication valve and other components in the valve components are required to have a very precise coordination gap, some components are equipped with resistance holes, control valve holes, lubricating oil holes and working oil pressure inlet port, once the hydraulic oil oxidation deterioration or mixed with a large number of impurities, These oil holes will be blocked, blocking the flow of hydraulic oil, so that these components can not work properly.
(3) Too low pressure
If the impurities in the hydraulic oil enter the transmission, it will cause the oil inlet and lubricating oil hole to be blocked; If the impurities in the oil enter the clutch piston and hydraulic cylinder, it will cause the seal ring to be stuck in the hydraulic cylinder and cannot expand outside, resulting in the piston seal ring and hydraulic cylinder block sealing is not strict, resulting in pressure oil leakage and the clutch working oil pressure reduction, and produce slipping phenomenon, weak operation, and then lead to the clutch friction plate serious wear and poor engagement. And the clutch master and slave plate are not sufficiently lubricated and aggravate the burning of the clutch friction plate.
2. Preventive measures
In order to extend the service life of the bulldozer transmission clutch, according to our long-term work experience, we must do the following work:
(1) Cleaning system
When using the new transmission machine, the hydraulic pump, oil filter, hydraulic torque converter, cooler, control valve and other parts of the host hydraulic system should be strictly cleaned. The cleaning fluid is best to use No. 8 hydraulic transmission oil of the same brand as the hydraulic torque converter. It is strictly prohibited to use kerosene or diesel for cleaning. In order to wash out the mechanical impurities and oil in the hydraulic system pipeline. After cleaning, the cleaning liquid should be removed in time under the heat engine state.
(2) Correct selection of oil products
According to the requirements of the instruction manual, the transmission and chassis hydraulic system use No. 8 hydraulic transmission oil. The selected hydraulic oil should have good low temperature fluidity, suitable high temperature viscosity, good thermal oxidation stability and bubble resistance, as well as good anti-friction and anti-corrosion properties. It is strictly prohibited to mix hydraulic oils of different grades. Before refueling, the oil must be strictly filtered to prevent mechanical impurities, dust, water, emulsion and other intrusions into the hydraulic system.
(3) Control system pressure
Before the operation of the machine, the pressure of the hydraulic system should be strictly checked, that is, the pressure of the pressure gauge into the transmission control valve should be tested. Under the action of the pressure regulator, the standard value of the engaging pressure of the transmission II and III clutch should be adjusted (2.5MPa±0.2MPa). I block the oil pressure of the locking clutch (1.25MPa±0.1MPa) and the oil pressure of the lubricating slide valve (0.1MPa±0.025MPa). If the clutch pressure is measured below the standard value, the variable speed control valve is first checked to determine whether the clearance between the valve stem and the valve body hole is too large; Whether the spring spring of the pressure regulating valve and pressure reducing valve is too weak; Whether the O-ring on the variable speed control valve stem is damaged, if damaged, should be replaced and adjusted in time, when the pressure regulator pressure reduction spring force is insufficient in the spring seat to increase the appropriate thickness of the washer to adjust the working oil pressure, and re-installed for testing, if the measured pressure is still lower than the standard value, you must replace the variable speed control valve assembly.
(4) Reasonable adjustment of mesh clearance
Transmission output end through a pair of helical bevel gear to transmit power to the rear axle box central drive shaft, so the correct degree of engagement has a great impact on the noise, service life and performance of the whole machine, before the installation, should be removed on the old main machine, the new pair of large bevel gear installed in the central drive shaft and bolted; By adjusting the speed gasket to adjust the tooth side clearance of the bevel gear pair 0.25-0.33mm, and keep the mesh mark; The helical bevel gears must be used in pairs.
(5) Do maintenance
Maintaining good maintenance and maintenance is an important prerequisite for ensuring production safety, playing the performance of the variable speed clutch and extending its service life, the driver should carefully and strictly carry out daily maintenance, and timely find and eliminate small faults to avoid accidents. For the new factory bulldozer or the bulldozer that has just been overhauled, the oil should be drained while it is hot after test run or 100h of operation, and the No. 8 hydraulic transmission oil should be re-added, and then the working oil should be replaced every 1000h. In daily work, attention should be paid to observing the working oil pressure and oil temperature of the hydraulic system to prevent the oil pressure from being too low and the oil temperature from being too high. Check the quality of hydraulic oil regularly, keep the hydraulic system and hydraulic oil clean, find that there is an abnormal situation should be stopped in time to find out the cause and eliminate the fault, so that the bulldozer speed clutch to maintain a good working condition.
