Because the micro-design (tooth shape) of helical gears will also affect the vibration and noise, acoustic analysis is also required for each helical gear modification scheme optimized by transmission error, Hertz contact stress, time-varying meshing stiffness and time-varying meshing force. If all the secondary optimal profile modification schemes are directly submitted to the enterprise for production, processing and manufacturing, and then a group of optimal helical gear profile modification schemes with the lowest vibration noise are selected through noise bench test, it is inevitable that the cost is too high and the cycle is too long. Therefore, this chapter carries out acoustic simulation with the help of LMS Virtual Lab Acoustic software to obtain a group of schemes with the lowest noise sound power value, and ultimately reduce the product development cycle, processing and manufacturing costs and test cycle.
Using LMS Virtual Lab Acoustic software and ISO standard sound power level measurement method, the acoustic simulation analysis is carried out for all the modification schemes of helical gear pair of an electric vehicle gearbox after the secondary optimization of time-varying meshing force and time-varying meshing stiffness. The main conclusions are as follows:
(1) At present, many scholars only use the transmission error of helical gears to evaluate the strength of helical gear meshing vibration noise is not rigorous. From the simulation results, the vibration noise of the helical gear will be reduced only if the main dynamic excitation such as transmission error, time-varying meshing force and time-varying meshing stiffness are reduced simultaneously through the modification of the helical gear, and the tooth shape is appropriate.
(2) In all the secondary optimization modification schemes, the drum shape of tooth profile (both big and small gears are modified at the same time) has the best effect of vibration reduction and noise reduction. Because the overall noise reduction effect of the optimization scheme of tooth profile drum (only for large gears) is close to that of the multiple quadratic optimization modification schemes, the optimization modification of tooth profile drum only for large gears can be used in engineering practice due to production cost considerations.
(3) According to the data of transmission error, time-varying meshing force and time-varying meshing stiffness before and after the secondary optimization and modification of the helical gear pair, the vibration noise of the helical gear at high speed (10000r/min) may mainly depend on the time-varying meshing stiffness and transmission error.