Faults and Troubleshooting of Abnormal Noise from the Drive Axle of Hydraulic Excavators

Abnormal noise Faults and troubleshooting methods of Hydraulic Excavator Drive Axle

Abnormal noise from the drive axle is a sign of deteriorating technical condition, and the volume of the noise indicates the extent to which the technical headquarters has deteriorated. The abnormal noise from the rear bridge and the timing are also different. Abnormal noises usually vary with the changes in the traveling speed and conditions of the excavator.

1. Cause analysis

When the excavator is in operation, the gears of the drive axle's reducer (main reducer and wheel-side reducer) and differential will wear out. When the lubrication is poor, the gear wear rate will be even faster. When the teeth of a gear wear out and lose the involute profile geometry, the rolling friction decreases and the sliding friction increases during gear meshing. This not only increases the meshing clearance of the gear but also further accelerates the wear process of the gear, generating noise, that is, abnormal noise. In addition, the gear teeth are directed towards a cantilever beam. After being loaded, the bending stress generated at the tooth root is the greatest. Coupled with the influence of alternating loads, fatigue cracks often occur at the gear root. As the working time increases, the fatigue level rises and cracks expand. When the gear teeth mesh, the lubricating oil will be squeezed into the cracks of the meshing teeth. Under the action of the oil pressure, the cracks extend in depth and length. When the load-bearing capacity of a gear is less than the load, it will break, which is commonly known as "tooth breakage". After teeth grinding, the abnormal noise will be louder, and it may even interrupt the transmission or damage other components.

(2) Gaskets are placed behind the half shaft gears and planetary gears of the differential. When these gaskets wear out and become thinner, the meshing clearance of the differential gears will increase, resulting in abnormal meshing and noise during operation.

(3) Wear of the splined teeth on the half shaft will also increase the fit clearance. When transmission occurs, if there is a speed difference between the two mating parts, the splines and keyways will collide and produce abnormal noises.

(4) The influence of bearings: Bearings are often subjected to alternating loads. During operation, they not only cause wear but also lead to fatigue of the rolling elements and raceway surfaces. When lubrication is poor, the rate of damage accelerates and the degree of damage worsens. As a result, when the rolling elements of the bearing roll, they produce irregular rolling and vibration sounds. The preload of tapered bearings is adjusted by spacers or threads (for differential bearings). If the preload is adjusted too small, it will cause axial movement of the tapered gears, resulting in intermittent meshing clearance, loss of correct meshing and abnormal noise. When damaged, it makes a louder noise and may even jam the moving parts.

(5) Loose fastening (bolts) of the reducer and differential often cause abnormal noises.

(6) Poor lubrication: When gears are in transmission, they must be lubricated. If there is a lack of oil or the oil quality is poor and cannot form an oil film, dry friction will occur when the gear teeth mesh, resulting in 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 of the gears and bearings. Excessive gap causes abnormal noise. If the clearance is too small, the oil film on the feed gear teeth is prone to rupture when the gears mesh, affecting the lubrication and cooling of the tooth surfaces. This causes the metal tooth surfaces to come into direct contact, generating dry friction and high heat. During transmission, an instantaneous high temperature is formed, and the two meshing tooth surfaces will stick together, resulting in scratches along the relative sliding direction on the metal tooth surfaces, which is called biting. At this time, the gears are not working smoothly, generating significant 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 the gear teeth are not evenly distributed around the pitch circle line, the excavator will often make abnormal noises when running.

2. Diagnosis and Exclusion:

When diagnosing, the timing and characteristics of the abnormal noise should be taken into account, and the causes analyzed above should be excluded.

(1) When an excavator is traveling in a straight line during road tests and makes abnormal noises, the fault is usually at the main reducer or differential bearing, etc. Abnormal noises occur when turning, and the fault is mostly in the differential.

If the noise is loud (screaming) and it is newly assembled, and when driving the differential part of the axle housing with a hand mold, there is a burning and unbearable sensation, it indicates that it is mostly caused by overly tight assembly and too small clearance between each fit.

If there is a noise after long-term use, it is generally caused by excessive wear of various components, resulting in excessive fit clearance. It is often manifested as a "clunk" sound when starting or when the speed changes. If a dry friction sound is heard, it is mostly caused by poor lubrication inside the drive axle.

(2) When stopping for inspection, it can be done by hand or with a clearance measuring instrument.

To check the total transmission clearance of the drive axle with a clearance measuring instrument, the method is as follows: place the transmission control lever in neutral position, release the parking brake, brake the wheels, fix the scale of the clearance measuring instrument on the reducer housing, and fix the pointer on the connecting flange of the transmission shaft. Rotate the drive shaft to move it from one limit position to another. The measured Angle value is the total Angle clearance of the drive axle transmission, which is the sum of the meshing clearance of the main reducer gears, the meshing clearance of the differential gears, the fit clearance between the half shafts and the half shaft gears, and the meshing clearance of the wheel side reducer gears, etc. Generally, it should be around 65℃. If the measured Angle is too large, This indicates that the abnormal noise of the drive axle is caused by excessive clearance of its transmission components.

② Check the lubrication condition. Remove the oil level plug and check the height of the oil level. If there is a severe lack of oil or the oil deteriorates, it indicates that the abnormal noise is caused by poor lubrication.

③ Check the temperature. When you hear a high-pitched sound from the drive axle while driving, you can touch the temperature of the main reducer housing, differential housing and wheel-side reducer housing of the drive axle with your hand. If there is an overheating phenomenon, it indicates that the assembly is too tight. Generally, this phenomenon occurs in new or repaired drive axles.

When the drive axle conduction fault is finally confirmed, it should be disassembled for inspection and the symptoms should be eliminated accordingly. For instance, when the bearing is found to be damaged after disassembly, it should be replaced. When the preload is small, adjustments should be made according to the actual situation. If the meshing clearance of the main reducer or differential is too large, or the meshing mark is incorrect, adjustments should be made. When adjusting the meshing marks, refer to the adjustment method of the loader's thrust marks. . Generally, when replacing gears, they should be replaced in pairs. If the gears are not replaced in pairs, not only will abnormal noises still occur after the replacement, but it will also affect the service life of the gears.