Fault diagnosis and troubleshooting of the drive a

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Fault diagnosis and troubleshooting of the drive axle of hydraulic excavator

the drive axle is composed of main reducer, differential, axle housing, axle shaft, wheel reducer and wheel hub. Its function is to transmit the torque from the transmission shaft to the driving wheels, so as to change the rotation direction, reduce the speed and increase the torque

requirements for drive axle:

(1) during assembly, the bearing and main spring tension and compression testing machine can be divided into manual spring tension and compression testing machine, full-automatic spring tension and compression testing machine reducer, wheel reducer and other matching moving pairs according to its operation mode, and the specified clearance shall be reserved to prevent the thermal expansion from jamming during operation and ensure that the working surface of the machine has a sufficiently thick oil film. The maximum service clearance after tooth wear shall not exceed 0.4mm; The teeth of the driving and driven gears of the main reducer shall have correct meshing marks

(2) there should be good lubrication conditions, that is, appropriate lubricating oil and the specified liquid level height, and there should be no oil leakage

the drive axle bears large and complex forces, and the long-term use causes the inevitable friction loss of various parts. In addition, the improper use or maintenance makes the technical condition of the drive axle worse. When the drive axle works, there will be abnormal noise, oil leakage, overheating or other phenomena

II. Abnormal drive axle noise

1. Abnormal drive axle noise is a manifestation of the deterioration of technical conditions, and the magnitude of its noise indicates the deterioration of the technical headquarters. The noise and timing of the rear axle are also different. The abnormal sound usually changes with the driving speed and driving conditions of the excavator

2. Cause analysis

(1) gear wear when the excavator is driving, the reducer (main reducer and wheel reducer) and differential gear of the drive axle will be worn. When the lubrication is poor, the gear wear speed is faster. After the gear teeth are worn, the involute profile geometry is lost. When the gears are meshed, the rolling friction is reduced and the sliding friction is increased, which not only increases the meshing clearance of the gears, but also further accelerates the wear process of the gears and produces noise, that is, abnormal noise. In addition, the gear teeth face a cantilever beam, and the bending stress at the root of the gear is the largest after being loaded. In addition, due to the influence of alternating load, fatigue cracks of such environmental protection materials mainly composed of plant cellulose nanocrystals will be produced at the root of the gear. With the extension of working time, the fatigue degree increases and the crack expands; When the gear teeth mesh, the lubricating oil will be squeezed in the cracks of the meshing teeth, and the cracks will extend to depth and length under the action of oil pressure. When the bearing capacity of the gear is less than the load, it will break, commonly known as gear beating. After tapping, the abnormal noise will be greater, and even the transmission will be interrupted or other parts will be damaged

(2) there are cushions behind the half axle gear and planetary gear of the differential. The wear and thinning of these gaskets will increase the meshing clearance of differential gears, so abnormal meshing occurs during operation and makes a sound

(3) wear of half shaft spline teeth will also increase the fitting clearance. During transmission, when there is a speed difference between the two mating parts, the spline and keyway will collide and make a strange sound

(4) the influence of bearings. Bearings often bear alternating loads, which will not only cause wear when working, but also fatigue the surface of rolling elements and raceways; When the lubrication is poor, the damage speed is accelerated and the damage degree is worse, so the rolling element of the bearing produces irregular rolling vibration sound when rolling; The preload of the conical bearing is adjusted by the gasket or thread (differential bearing). If the adjusted preload is too small, the axial movement of the conical gear will cause the meshing clearance to be large or small, and the correct meshing will be lost, resulting in abnormal noise. The noise will be louder when it is damaged, and even the moving parts will be stuck

(5) the fastening (bolts) of the reducer and differential are loose, which will often produce abnormal noise

(6) the gear transmission with poor lubrication must be lubricated. If there is a lack of oil or the oil is poor, the oil film cannot be formed, and the dry friction will be formed when the gear teeth mesh, which will produce abnormal noise

(7) when the main reducer and differential of the drive axle are improperly assembled, there should be a certain gap between the mating parts when the annual operation capacity of China's electrolytic aluminum of gears and bearings reaches about 37.2 million tons. Excessive clearance produces abnormal sound; If the clearance is too small, the oil film on the incoming gear teeth is easy to be crushed during gear meshing, which affects the lubrication and cooling of the tooth surface, so that the metal tooth surface is in direct contact, forming dry friction and generating high heat. When the instantaneous high temperature is formed in the transmission, the two meshing tooth surfaces will stick together, and the metal tooth surface will form scars along the relative sliding direction, which is called biting. At this time, the gear works and is unstable, resulting in great vibration and noise

when the driving and driven gears of the reducer mesh, there should be a correct meshing mark to ensure good meshing. If the meshing marks of gear teeth are not evenly distributed around the pitch line, most excavators will make abnormal noises when driving

3. Diagnosis and elimination

when diagnosing, it should be eliminated according to the timing and characteristics of the abnormal sound, combined with the causes of the above analysis

(1) the road test excavator makes abnormal noise when driving in a straight line, and the fault is generally at the main reducer or differential bearing; Abnormal noise occurs when turning, and most of the faults are in the differential

① if the noise is high (screaming) and it is a new assembly, the differential part of the driving axle housing with a hand mold feels hot, indicating that most of it is caused by too tight assembly and too small fitting clearance

② if there is a noise after using it for a long time, it is generally caused by the excessive wear of various parts, which makes the fitting clearance too large. It often appears as a "cluttering" sound when starting or when the speed changes. If you hear dry friction sound, most of them can be sure that the composition of abrasive particles is due to poor lubrication in the drive axle according to the color and shape

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