Taking the high-speed helical gear transmission of an electric vehicle reducer as the research object, firstly, the time-varying meshing stiffness of the gear is calculated using the improved LTCA method, and the meshing impact curve is calculated using the geometric relationship and mechanical model. Secondly, the bend-torsion-shaft coupling dynamic model of helical gear considering time-varying meshing stiffness and meshing impact is established and solved. Then, the vibration characteristics of single-stage high speed helical gear transmission under three excitation forms, namely, time-varying meshing stiffness, meshing impact and combined excitation, are studied; The main characteristics of the vibration characteristics of the two-stage high-speed helical gear drive and the difference between the vibration characteristics of the two-stage helical gear drive and the single-stage helical gear drive are discussed; Finally, the vibration reduction effect of two kinds of tooth surface modification on high-speed helical gear transmission is analyzed. The research results provide theoretical basis for the design and analysis of high-speed gear transmission, and have guiding significance for its practical application. The main research conclusions are as follows:
(1) Under the excitation of time-varying meshing stiffness alone, obvious superharmonic resonance occurs at 1/3 and 1/2 resonance speed N0; In the non-resonant region, the root mean square value of the relative vibration acceleration of the system does not increase significantly with the increase of the rotational speed; In the over-resonance region, the influence of speed change on the vibration characteristics of the system is not significant; Increasing the mean value of meshing stiffness of gear pair will reduce the vibration of the system and change the resonance speed of the system; Increasing the amplitude of time-varying meshing stiffness fluctuation will aggravate the vibration of the gear pair, but will not change the resonance speed of the system.
(2) Under the separate excitation of meshing impact excitation, the obvious superharmonic resonance occurs at 1/3 and 1/2 resonance speed N0; In the non-resonant region, the root-mean-square value of gear relative vibration acceleration increases significantly with the increase of speed; The vibration response of the system varies greatly with the meshing impact time; The longer the meshing impact time, the greater the vibration response of the system.
(3) Under the combined excitation, in the non-resonant region, the root mean square value of the relative vibration acceleration of the system increases significantly with the increase of the rotational speed, but the amplitude of the system vibration under the combined excitation is smaller than that under the meshing impact alone excitation; In the over-resonance region, the impact of meshing impact on the system is greater than that of time-varying meshing stiffness; The higher the rotational speed, the smaller the influence of time-varying meshing stiffness on the system vibration, and the meshing impact becomes the main excitation component of the system.
(4) In the secondary helical gear transmission, the vibration of two tooth pairs affects each other. In addition to the respective tooth frequency, the vibration response of two tooth pairs also has the tooth frequency of another tooth pair and the superposition of the two frequencies, and the vibration of the input stage tooth pair has a greater impact on the output stage tooth pair, which makes the system vibration response more complex.
(5) Tooth surface modification has a good vibration reduction effect on single-stage high-speed helical gear transmission; In the secondary helical gear transmission, the modified input tooth pair has good vibration reduction effect on itself, and also has obvious vibration reduction effect on the output tooth pair; After modification, the output end tooth pair only has good damping effect on itself, and the damping effect on the input end tooth pair is not obvious; Therefore, in the tooth surface modification design of the secondary gear system and the multistage gear system, the input gear should be focused on.