Cylindrical gears have the advantages of strong bearing capacity, stable meshing, convenient processing and adjustment, and are widely used in aviation, automobile and other industries. The dynamic performance of cylindrical gears is very important to the reliability and stable operation of the system, so it has attracted much attention. The meshing stiffness, meshing impact and backlash of cylindrical gear pair are the main factors affecting the dynamic characteristics of cylindrical gears. In early studies, the time-varying meshing stiffness was not considered. With the deepening of research work, the importance of time-varying meshing stiffness is highlighted, and researchers have also used different methods to calculate the time-varying meshing stiffness. In addition, there are many researches on the theoretical calculation and influence of cylindrical gear meshing impact force. For low and medium speed cylindrical gear transmission, the development of modern industry has increased the demand for high-speed cylindrical gear transmission. For example, in order to improve the power density ratio of pure electric vehicles, the motor output speed is often higher, even more than 10000r / min. At this time, it is not clear whether the action law of time-varying meshing stiffness and meshing impact excitation is consistent with that under low speed conditions, and whether the influence proportion of the two changes. Therefore, studying the influence of time-varying meshing stiffness and meshing impact on the vibration of cylindrical gear transmission system at high speed and exploring the corresponding vibration reduction and noise reduction methods are of great significance to the design and application of high-speed cylindrical gear transmission system.
(1) Under the excitation of time-varying meshing stiffness, in the non resonant region, the influence of speed change on system vibration is not significant, and the root mean square value of acceleration does not increase significantly with the increase of speed.
(2) Under the meshing impact excitation of cylindrical gears, the root mean square value of the applied speed, excluding the formant, increases significantly with the increase of speed, and the meshing impact area is mainly characterized by the sudden change of vibration acceleration.
(3) Under the condition of comprehensive excitation, the root mean square value of the applied velocity excluding the formant increases significantly with the increase of the rotating speed, but the increase of the system vibration is slower than that under the single excitation of the meshing impact.
(4) In the over resonance region, the meshing impact of cylindrical gears becomes the main excitation component, which should be paid attention to in the design of vibration and noise reduction such as tooth surface modification.
Taking the two-stage high-speed cylindrical gear transmission of a pure electric vehicle as the research object, firstly, a six degree of freedom bending torsion axis dynamic model of the transmission system is established; Then, the time-varying meshing stiffness of the gear is calculated based on the load-bearing contact analysis, and the impact time and impact force amplitude are calculated by using the meshing impact theoretical model; Finally, the vibration characteristics of the system under the three conditions of time-varying meshing stiffness excitation, meshing impact excitation and their combined excitation are analyzed through the results of the time domain, frequency domain and vibration speed diagram of the relative vibration acceleration in the meshing line direction of the cylindrical gear pair, which provides a reference for the design and application of high-speed cylindrical gear transmission.