Common Fault Diagnosis and Elimination of Hydraulic Excavator Drive Axle

Iii. Oil leakage from the drive axle

1. Phenomenon

Oil leakage from the drive axle refers to the leakage of lubricating oil outside the drive axle housing, with obvious oil stains.

2. Cause analysis

Oil leakage is always caused by poor sealing. The main reasons for poor sealing are as follows:

(1) The mating surface of the shell mating parts is uneven, the connecting screws are loose or the sealing gasket is damaged.

(2) Oil seal damage (refer to the transmission description for the cause of damage) or wear of the journal, etc., leads to poor sealing and oil leakage.

(3) Oil leakage from threaded holes is mostly caused by loose screws or damaged threaded threads.

3. Diagnosis and Exclusion

Oil leakage from the drive axle can be directly observed. Based on the analyzed causes, targeted measures can be taken to eliminate the leakage.

Four. The drive axle reducer is overheating

1. Phenomenon

After the excavator has traveled a certain distance, the moving parts inside the drive axle undergo relative sliding friction, thus generating a certain amount of temperature. It should not feel hot when touched by hand; otherwise, it is considered too hot.

2. Cause analysis

The main transmission components in the drive housing mainly include the main reducer, differential and wheel-side reducer, etc. The main reducer and the differential are connected together and centrally distributed in the middle of the drive axle. When this component is in operation, there is a sliding friction phenomenon.

Under normal circumstances, the surfaces of the relatively moving mating parts in the drive axle should have a layer of lubricating oil film as a medium to prevent direct contact and friction between the two parts. This not only delays the wear process of the machine parts, but also reduces the heat generated by friction. Through the flow of lubricating oil, the heat generated by the friction of the machine parts can also be carried away and dissipated, lowering the temperature of the main transmission part in the drive axle to maintain a normal temperature. Otherwise, the two mating parts inside the drive axle will experience semi-dry or dry friction when moving relatively due to the lack of lubricating oil, increasing the coefficient of friction and the corresponding frictional force, as well as raising the temperature. Due to the lack of lubricating oil, heat dissipation is poor, and the temperature of the machine parts cannot be dissipated and accumulates. The higher the speed and the longer the time of the machine parts' movement, the higher the temperature. It can be seen from this that the overheating of the main transmission part of the drive axle is caused by the direct friction between the working surfaces of the two relatively moving parts. The reason why direct friction can occur is that there is no lubricating oil or the lubricating oil is too little. Secondly, although there is sufficient lubricating oil, due to the too small fit clearance, when the gears mesh, the teeth are squeezed too tightly, preventing the formation of an oil film on the tooth surface and causing direct friction. Thirdly, when overloaded, the mating parts press against each other too much, breaking the oil film on the surface of the parts and causing direct friction, which leads to overheating. Fourth, due to the deterioration of the lubricating oil quality, it is difficult to form an oil film on the surface of the parts, and the two components will directly rub against each other and overheat.

3. Diagnosis and Exclusion

(1) If the drive axle overheats during use after maintenance, it is highly likely that the assembly is too tight. It should be inspected and adjusted.

(2) If overheating occurs due to prolonged uphill driving, it is mostly because of excessive driving under heavy load. One should stop and rest.

(3) If the inspection shows that overheating is caused by poor lubrication, the symptoms should be excluded accordingly. For instance, when lubricating oil is lacking, it should be replenished; when it deteriorates, it should be replaced.

V. Other Faults

The other faults mentioned here mainly refer to torsion or breakage of the half shaft and damage to the wheel-side reducer.

The reasons for the torsion or breakage of the half shaft are as follows:

The working site of excavators is rather harsh, often with uneven pits, and the half shafts are frequently subjected to impact loads. When the impact load on the half bearing exceeds the strength of its own material, the half shaft will break.

② Congenital deficiency of the half shaft. When manufacturing half shafts, if there are processing defects or cracks, which cause a decrease in their load-bearing capacity, they are likely to break when overloaded.

③ Due to the prolonged use of the half shaft, fatigue cracks are inevitable. Fatigue cracks tend to extend as the usage time increases until they eventually break.

④ Improper selection of the half shaft material often causes the half shaft to twist into a twisted shape when overloaded.

When the two-wheel side reducer is overloaded, it is prone to damage. When lubrication is poor, it accelerates the wear process of machine parts, leading to premature damage.