In the process of gear transmission design, especially the closed transmission, if the hardness of gear is not fully considered in the design, it will have a great influence on the performance of the transmission system. Such as common gear failure: tooth surface depression, tooth root fatigue crack. Related to gear hardness and gear quality. According to the tooth surface meshing, gear reducer gear is divided into soft tooth surface and hard tooth surface, reflected in the following applications:
1: soft tooth surface gear transmission (tooth surface hardness ≤350HBs), at least one of a pair of gears is soft tooth surface, usually used for general low and medium speed gear transmission, accuracy requirements are not high.
2: hard tooth surface gear transmission (tooth surface hardness > 350 HBS), the two gears are hard tooth surface. It is usually used for gear transmission with strong bearing capacity and small volume.
In some equipment, such as winches, soft tooth surfaces are usually used, while hoists now mainly use hard tooth surfaces.
The following three points are usually considered in design:
1. Close soft tooth surface gear transmission under general working conditions. Soft tooth surface steel gear transmission (≤350HBs): mainly based on the tooth surface contact strength, according to the tooth surface contact fatigue strength design; Then the bending fatigue strength of the root was checked.
2: suitable for hard tooth surface closed gear transmission device. Hard tooth surface (> 350 HBS) steel gear and cast iron gear transmission: the tooth root is mainly based on the bending strength of the tooth root, according to the bending fatigue strength design; Then the contact fatigue strength of tooth surface is checked.
3: used for open gear transmission. The main failure modes are tooth surface wear and tooth fracture. The design standard is: only according to the bending fatigue strength of the tooth root design calculation, determine the modulus, on the basis of the design modulus increase 10%-20% to consider the impact of wear.
