For helical gear system, generally, the total coincidence degree is greater than 2, that is, at least two tooth pairs are engaged, and two or more pairs of teeth are engaged alternately in the meshing process. The schematic diagram of contact line and friction force of helical gear system is shown in the figure.
Under the action of input torque TP, the main helical gear rotates clockwise around its axis OP, the torque of the driven gear is TG, and rotates counterclockwise around its axis og. In the direction of the meshing line, points a and B are the tangent points between the meshing line and the base circle of the driving wheel and the driven wheel, and points D and C are the intersection points between the meshing line and the tooth top circle. FFI is the friction force on the contact line. When the helical gear meshes through point P, the direction of the relative sliding speed of the tooth contact point will be reversed, resulting in the change of the friction force direction between the tooth surfaces.
They are in the positive and negative regions of friction respectively. The total friction force of helical gear is the difference between the friction force generated by the two segments. Therefore, the friction force and friction moment on the left and right sides of the pitch line are calculated by the time-varying contact line length and friction force arm on both sides of the pitch line. Specific calculation process.