Multi-body dynamics simulation is carried out for all the modification schemes of helical gear pair of an electric vehicle reduction box optimized by transmission error and Hertz contact stress. By comparing the magnitude of time-varying meshing force and time-varying meshing stiffness of the front and rear gears modified by different optimization modification schemes, the modification schemes with smaller dynamic excitation inside the gears are further selected, and the modification schemes such as spiral angle, backlash between the teeth sides The influence of gear parameters such as pressure angle on time-varying meshing force and time-varying meshing stiffness. The main conclusions are as follows:
(1) The appropriate helix angle can significantly reduce the time-varying meshing force of the gear, make the meshing smooth (the curve is relatively smooth), and reduce the meshing impact, but the larger the helix angle, the greater the time-varying meshing stiffness; Large pressure angle is beneficial to reduce the time-varying meshing stiffness of gears; Therefore, small helix angle and large pressure angle should be selected on the premise of meeting the use requirements and small time-varying meshing force.
(2) The tooth side clearance has no effect on the time-varying meshing stiffness of the gear, but the smaller the tooth side clearance is, the smaller the time-varying meshing force of the helical gear at low speed (2000r/min) is, generally 0.05mm; The tooth width of the helical gear only affects the time-varying meshing force of the gear under the low speed working condition (2000r/min), that is, increasing the tooth width can reduce the time-varying meshing force, but the larger the tooth width is, the greater the time-varying meshing stiffness is. Therefore, if the requirements for the use of the helical gear pair at low speed are not strict, the smaller the tooth width can be selected to obtain better vibration and noise performance of the gear pair at medium and high speed.
(3) From the point of view of reducing the time-varying meshing force and time-varying meshing stiffness of the gear, in all the modification schemes of the helical gear pair of an electric vehicle gearbox optimized by transmission error and Hertz contact stress, the long tooth profile (linear, broken arc), tooth profile drum (only for the pinion) The effect of compound optimization modification of tooth profile and tooth direction of large gear (long tooth profile tooth top involute+tooth direction drum, long tooth profile tooth top arc+tooth direction drum, long tooth profile tooth top broken arc+tooth direction drum) is poor, while the effect of long tooth profile tooth top (arc, involute) and tooth profile drum (large and small gears, only for large gears) is good.
(4) For the drum profile modification, the selection of the modified gear is extremely important. If the main purpose is to reduce the stiffness excitation of the helical gear pair, it is recommended that the large and small gears be modified at the same time; If the objective is to reduce the time-varying meshing force of the helical gear pair, it is recommended that only the large gear or the large and small gears be reshaped at the same time. In addition, as only the driving gear (pinion) can only slightly reduce the stiffness excitation by adopting the tooth profile drum optimization modification, it is not recommended to only modify the pinion.
(5) Because only the compound optimization modification of the large gear of the helical gear pair can only slightly reduce the stiffness excitation, and can not effectively improve the meshing impact between the gear pairs. Therefore, on the premise that the optimization scheme of single modification method can achieve the goal of gear modification, considering the processing cost, it is not recommended to modify the tooth profile and tooth direction.