Without considering the elastic deformation of the tooth surface (assuming that the gear is completely rigid), a pair of local conjugate surfaces, that is, point contact surfaces, are formed between the tooth surfaces of large and small gears. At the same time, in order to ensure the normal operation of the gear pair, it is required to maintain continuous contact during the meshing process. Therefore, this point contact representation is a continuous series of points on the tooth surface, that is, the contact path.
The actual gears are non rigid, so in the actual work process, the gear teeth will inevitably have the problem of loading deformation. According to the elastic contact theory, the contact point will be sunken at a certain time after being loaded, and develop into an instantaneous contact ellipse, and the contact path will eventually form the contact mark of the tooth surface. The design (theoretical) contact ratio of gear pair is defined by formula. The actual coincidence degree is defined as the average of the number of teeth that mesh simultaneously under load.
Tc and Tz=360 ° /N1 are shown in the transmission error curve, as shown in the figure.
