Development of surface strengthening technology for automotive helical gears

The automotive helical gear transmission system under various complex working conditions makes the surface strengthening technology of automotive helical gear constantly appear new topics. For example, the lightweight of automobile transmission system and the working conditions of high speed and high torque of new energy vehicle transmission put forward higher requirements for the strength of automobile helical gear. The working condition of new energy electric vehicle transmission increases from the maximum speed of traditional automobile engine of 6500 R / min to 14000 R / min, the torque increases by about 30%, and the fatigue life of automobile helical gear increases by more than 40%. Single surface strengthening technology is difficult to meet the application requirements of automotive helical gears with high comprehensive performance requirements. The surface strengthening technology with multiple composite surface strengthening technologies will be studied and applied in the field of high-strength automotive helical gears.

The development of surface strengthening technology needs to meet the multi-objective requirements of automotive helical gears with high strength, high precision, high fatigue life and low noise. Because of the non independence and contradiction between the objectives, the composite surface strengthening technology is by no means the superposition of a single strengthening technology. The compound surface strengthening technology of automobile helical gear should establish a multi-objective optimization method for the compound surface strengthening of automobile helical gear. Using the multi-objective optimization design theory, this paper makes a systematic basic research on the relationship between the strengthening mechanism of automobile helical gear surface heat treatment, shot peening strengthening technology, surface conversion coating and the scientific theory of automobile helical gear surface integrity.

The future research focus of automobile helical gear surface heat treatment includes: Mastering the basic parameters and strength characteristics of materials through automobile helical gear material gene analysis and basic performance experiment, research on numerical simulation and control technology for predicting automobile helical gear heat treatment deformation, research and development of new automobile helical gear steel and new heat treatment process; Research on shot peening strengthening technology of automobile helical gear, combined with material mechanics and modern mechanics, the relationship between shot peening parameters and surface integrity of automobile helical gear (residual stress field, roughness, nano scale mechanical properties, etc.); The Tribological Research of various coatings on the tooth surface is one of the important issues in the research of automotive helical gear. Based on the actual working conditions, transient temperature field and lubrication conditions of automotive helical gear, the influence law of the surface integrity of automotive helical gear coating on the contact fatigue life is deeply studied. Another key point is to control the grain size, distribution and grain boundary size in the coating structure, so as to make the coating have higher hardness and toughness. How to further control the grain has become an important link in the research.

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