Failure Analysis of Main Helical Gear Pair of Through-drive Axle for a Three-axle Special Vehicle

For a type of three-axle special vehicle, two identical failures occur continuously, and the driving distance after sale is less than 2000 km. In order to prevent wheel slippage and drive out of muddy road safely when driving on muddy road, the driver opens the differential lock between wheels according to operating regulations and drives on muddy road with low speed and large accelerator.During driving, a sudden chassis noise occurs and the drive shaft is idle and the vehicle cannot continue to drive.After investigation, it was found that something was wrong with the mid-axle (through-drive axle).

Remove the mid-bridge wheel-side reducer and main reducer on site, and find that the wheel-side reducer is in good condition, but most of the main helical gear pairs have broken teeth and broken brittle, the bearing fixing screw rings at both ends of the differential have been loosened and displaced, the right screw ring and locking plate have been withdrawn, and the outer end of the differential housing thread has been withdrawn.1/3. The bearing cover of left screw ring end and the bearing area of differential case show signs of ablation. Other parts have different damages. After main reduction and related damaged parts are replaced on site, the vehicle will operate normally.

It is no longer an accidental problem that two idental faults occur continuously. In order to find the root cause of the faults, we bring back the damaged parts and analyze the faults in many ways.

Inspection basis: Technical requirements provided by axle supplier.During inspection of the damaged parts, it was found that the fixing bolts on the secondary helical teeth were crushed and worn (see Figure 3, where the bolt head was crushed seriously for about 3mm).In order to further eliminate the causes of faults, two axles in the same batch are selected for the inspection of assembly adjustment. The steps are as follows:

(1) Firstly, two mid-axle main reducers selected on-site are decomposed and the installation of left and right screw rings connecting wheel-to-wheel differential to differential housing is observed.The result is that the installation is in place and the locking tabs are qualified.

(2) Check the meshing marks of helical gear pair, and the results basically meet the requirements and are qualified.

(3) Then check the engagement clearance of main and auxiliary umbrellas with dial gauge. The measurement results are 0.30mm (technical requirements of bridge supplier 0.3-0.41mm), 0.01mm (technical requirements of bridge supplier 0.01-0.05) and qualified.

(4) The internal and external threads of the threaded ring are checked with the general (stop) gauge of the threaded ring gauge respectively. The threaded dimensions of the threaded ring meet the processing requirements and are qualified products.