Isolated Bevel Gear Transmission Dynamic Contact Characteristics

Spiral bevel gears are widely used in the mechanical transmission systems of aviation and motor industry. Their working performances have a vital influence on the whole transmission systems. The working performances of spiral bevel gears are closely related with their tooth contact characterics, including the meshing track, instant transmission ratio and tooth contact pattern. Of the above contact characterics, the meshing track is the most basic one. It decides the instant ratio of the meshing gears and the load spectrum on the gear tooth. It is also the basis of deep research for gear life and heat conduction. Meshing track can be classified into static meshing track and dynamic meshing track, depending on whether the meshing track is related with time or not. So far most researches on the meshing track belong to the static range. Dynamic meshing track is barely touched. This paper takes the dynamic meshing track as the cut-in point and investigates the various kinds of parameters of the spiral bevel gear transmission system to the tooth contact characteristics. To realize these ends, first the tooth surface is formed on the basis of tooth geometry analysis. Second a numerical tooth contact analysis is set up considering the elasticity of the contacting teeth. Third the spiral bevel gear transmission system is taken as the research object and the dynamic meshing track is studied with the changing meshing forces mainly and other parameters of the transmission system considered. The important achievements and creations are in following. 1. Numerical method of Elastic Tooth Contact Analysis (NETCA) of spiral bevel gears is achieved. (a) Conversion coordinate matrix between two random coordinate systems. Conversion coordinate matrix between two coordinate systems is deducted to the requirements of the superposition of the tooth surface base point and the unit vector of the base point when the mating spiral bevel gears are mounted initially. The essence of the deduction is to find the conversion matrix according to the relationship of the same unit vector of a rigid body in the different two coordinate systems. The conversion matrix can be extended to the relationship between two random coordinate systems and then used directly in the Elastic Tooth Contact Analysis in the dynamic analysis of the spiral bevel gear transmission system. (b) Local Coordinate Method for finding the meshing points. Meshing point is just the tangential point of tooth surface, where the tooth gap is zero. Local Coordinate Method can find meshing point. The mechanism of the method is to take one of the mating surfaces as the reference surface or the first surface and build a surface coordinate system on it. Points of the other tooth surface or the second surface should be converted into the above surface coordinate system and the minimum gap between the mating surfaces along some coordiate axis is calculated. By regulating the rotational angle of the second surface gear and assuming the first surface gear stationary, the minimum gap tends to be zero, and the meshing point can be got. (c) Point-Point Search Method for quickly-finding the meshing points and Umbrella Method III for reducing search range. There are several ways of finding the minimum gap between the mating tooth surfaces when Local Coordinate Method tries to find the meshing points. Point-Point Search Method proves to be more quickly. From calculating the gap of some point on one of the mating surfaces, Point-Point...