1. Forms of Failure

A hypoid gear pair is used to match medium truck, medium bus, medium empty cabinet tractor and other vehicles. The average value before optimization is 189,000 times, which can not meet the life requirements. The failure form is bending fatigue of small gear root. The fatigue source is slightly smaller at the middle point of small wheel.

2. Optimizing scheme

According to the initial gear scheme, comprehensive optimization is carried out from three aspects: macro parameters of gear pair, tooth height coefficient and tool modification. The optimization items are shown in Table 4.By increasing working tooth height coefficient and crest height coefficient, the end surface coincidence is increased; by increasing the radius of radius of small wheel tip, crest pitch and optimizing the parameters of small wheel cutter modification, the bearing capacity of gear pair is significantly improved.

The bending stress of the small gear root before and after optimization is reduced by 11.1%.The bending stress of large gear tooth root decreases by 12.3% and the contact stress of tooth surface decreases by 4.47%.The optimization scheme can improve the tooth contact bearing capacity and the tooth root bending bearing capacity to varying degrees, and the optimization effect is obvious.

3. Bench test results

3.1 Optimizing front and rear engagement imprints

As shown in Figure, the loading engagement imprint of front and rear front face of optimized gear is large, the large end has edge contact and the top of the tooth is dislodged; after optimization, the engagement imprint moves slightly to the small end, and the engagement imprint is about 1-2 mm away from the top of the tooth, which makes full use of the tooth surface and avoids edge contact.

3.2 Optimized Fatigue Life

The fatigue life after optimization is 497,000 times, which is more than 2 times higher than that before optimization.After optimization, the first gear pair is tooth contact fatigue pitting, as shown in Figure 2, and the second or third pair is tooth root bending fatigue toothing.It can be seen that the bending fatigue strength of the small gear root has been greatly improved after optimization.