For the dynamics of nonlinear helical gear system, the solid collision method, the finite element transient analysis method and the torsional vibration method are three important methods for calculating the time-varying meshing force of helical gears. Since the torsional vibration method can derive the motion equation according to the helical gear dynamic system, establish the corresponding equivalent vibration model of the meshing helical gear pair, and simulate the helical gear meshing force and the time-varying meshing stiffness of the helical gear respectively through the spring damping system and the spring stiffness along the direction of the meshing line, the torsional vibration method is more efficient and the results are accurate and reliable than the other two methods.
LMS Virtual Lab is an integrated multi-disciplinary 3D simulation software that can perform structural, vibration, acoustic and other analysis. The motion function of the software is a simulation module specially used for multi-body dynamics and theoretical calculation, which can apply various loads and constraints to simulate the actual motion of mechanical system. For nonlinear helical gear drive, the software develops a set of calculation modules specially used for the time-varying meshing force of helical gears on the basis of torsional vibration method. At the same time, Y can be used according to the geometric parameters, material properties, meshing damping, moment of inertia, torsional angle displacement, etc. of the input helical gears The time-varying meshing stiffness of helical gears is calculated by CAI or ISO method.
Taking the helical gear pair of an electric vehicle gearbox as the research object, the dynamic characteristics before and after the helical gear optimal modification are studied on the basis of 10 preliminary optimization modification schemes obtained in the third chapter. Although the tooth profile and tooth direction modification (except the modification of helix angle and pressure angle) will not change the basic parameters of helical gears, it will affect the body reattachment of helical gears. Jia Chao and others believe that the helical gear modification curve is a higher-order parabola, and the basic shape of the modification curve can be reflected by the coincidence of helical gears. Therefore, it is necessary to explain the coincidence degree of the following 10 preliminary optimization modification schemes, as shown in the table.
| Programme | No. 0 | No. 1 | No. 2 | No. 3 | No. 4 | No. 5 | No. 6 | No. 7 | No. 8 | No. 9 | No. 10 |
| End face coincidence | 1.537 | 1.326 | 1.347 | 1.347 | 1.474 | 1.474 | 1.495 | 1.495 | 1.516 | 1.516 | 1.516 |
| The overlap ratio | 2.057 | 2.057 | 2.099 | 2.057 | 2.078 | 2.078 | 2.078 | 2.078 | 1.846 | 1.888 | 1.783 |