Diagnosis and troubleshooting of the failure of th

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Diagnosis and troubleshooting of bulldozer unable to walk fault

1. Fault phenomenon:

bulldozer unable to walk fault has two states: cold car unable to walk refers to that the cold car starts the engine and runs at a medium speed, and then gears up, and the bulldozer cannot start immediately; The failure of the heat engine to walk means that in the normal bulldozing process, as the oil temperature rises (within the normal oil temperature range), the bulldozer becomes weaker and weaker (at this time, the engine works normally), and it is even difficult to walk without load

II. Fault diagnosis method:

when the bulldozer fails to walk, whether it is in the cold or hot engine state, first control the engine throttle at the medium and high speed, then disassemble the left foot pedal in the cab and observe whether the output shaft of the torque converter rotates. If it rotates, check whether the output shaft still rotates after engaging the gear. At the same time, pay attention to distinguish whether the sound of the engine, torque converter and transmission changes before and after engaging the gear. If the output shaft does not rotate after engaging gear, it indicates that the fault is from the torque converter, such as the torque converter is lack of oil; If both the front and rear output shafts can rotate in gear, it is proved that the torque converter has no fault, and the fault may lie in the transmission, steering clutch, brake, etc

in order to distinguish whether it is the fault of the oil circuit system or the fault of the mechanical part, you can loosen the exhaust screw on the secondary filter of the transmission to see whether there is air. If there is air and it cannot be exhausted, it is proved that there is air inlet between the low-pressure oil circuit, that is, the oil suction port and the variable-speed pump. In order to further improve the fuel economy by 5% and determine the air inlet position, you should continue to loosen the exhaust screw on the secondary filter of the steering. If there is air, It proves that the air inlet part is between the oil suction day and the primary filter, because this section of oil circuit is shared by speed change and steering; If there is no air, it is proved that the air intake place should be between the rear of the primary filter and the variable speed pump. If there is no air in the exhaust screw on the secondary variable speed filter and the secondary steering filter, it proves that the fault is not in the variable speed steering oil circuit system, but in the transmission and China's high molecular material industry, we should also move towards intelligent manufacturing, such as steering clutches or brakes

III. examples of fault diagnosis and Troubleshooting:

(1) cold car can't walk:

a bulldozer can't walk immediately in gear after cold car starts engine, and the starting time gradually increases from the initial 5min to about 30min. Loosen the exhaust screw on the secondary transmission filter and check it. It is found that although there is no bubble, there is oil overflow. From the torque converter output shaft can rotate, and everything is normal after hot engine, The reason why it cannot start is the variable speed control valve. Remove the pressure plate on the transmission cover. There is a pressure measuring oil plug screw under the pressure plate. Connect the 0-5mpa pressure gauge. After starting the engine and raising the speed to high speed, shift the speed control lever to forward gears 1, 11 and ill respectively. The measured pressures are 0.23mpa, 0.5MPa and 0.55mpa respectively. The pressure is obviously insufficient (the specified pressures are l.25mpa, 2.5MPa and 2.5MPa respectively). After 10min, the pressure measured again is 1.1MPa, 2.2MPa and 2.3mpa respectively, and then the bulldozer can start. Therefore, it can be concluded that there is leakage in the variable speed control valve

remove the variable speed control room assembly. After inspection, it is found that the O-ring on the control room has been flattened and deformed, and has lost its elasticity, especially the aging of two black O-rings at the five oil inlet holes on the cylinder block is more serious. In order to further identify the fault, use the high-pressure air pipe of the air pump to vent to the five oil inlet holes respectively. Except for the first gear (because there is no planetary carrier, it is completely closed, and the master-slave friction plate is not exposed), the piston can be seen to push the master-slave friction plate to move in the forward, backward, 11, and ill gears, and the sound of the piston in four positions under the action of the spring can be heard when the air is cut off (the wavy spring is used for the return of the first gear, the elasticity is small, and the sound is weak when the piston returns), Thus, it can be inferred that the sealing rings of the transmission are well sealed. After replacing each O-ring on the control valve, the fault that the cold vehicle cannot start is eliminated

the above faults have occurred on three TY220 bulldozers. Three O-rings in the five oil inlet holes on the cylinder block are light red and two are black. The quality of black O-rings was found to be inferior to that of red O-rings in both disassembly and inspection. The problem lies in the two black rubber O-rings. It is recommended that the manufacturer use high-quality ones during assembly to reduce unnecessary faults

(2) the annual sales of hot cars reach 50billion yuan and can't walk:

I have encountered two bulldozers working for about 5000h. The cold start and bulldozing are normal, but after working for 45min, with the gradual increase of oil temperature, the polyether products used in BMW, Mercedes Benz and aviation seats are the same. The bulldozer is becoming weaker and weaker, and it is even difficult to walk under no-load conditions (at this time, the engine throttle has not decreased, and the speed has not decreased, indicating that the bulldozer is weak, which has nothing to do with the engine). If you shut down and rest for about 2H at this time, after the oil temperature decreases, start the engine again, and start and bulldoze again. When the oil temperature rises and the bulldozer is weak, disassemble the foot pedal beside the cab and find that the output shaft of the torque converter is still rotating at this time. Loosen the exhaust screw on the secondary transmission filter and find that there are bubbles in the discharged oil, which cannot be discharged for a long time. If there is air inlet, it is certain that both cold and hot vehicles should be air inlet, and the cold vehicle should also be unable to walk. In fact, the cold vehicle works normally, so it is certain that the low-pressure oil circuit is in good sealing condition; The high-pressure oil circuit of the hot car enters the air and cannot walk because the vacuum of the low-pressure oil circuit is too large. The inspection found that the rubber tube between the oil suction port and the strainer was deflated, and the higher the engine speed, the greater the degree of deflated suction, resulting in poor oil inlet. The reason is: the inner layer of the rubber tube aged and foamed with the increase of service time. With the increase of oil temperature, the bubble became larger, which blocked the oil inlet channel, resulting in excessive vacuum. After replacing the rubber tube, the fault was eliminated

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