Taking into Account the Production Methodology and Estimating the Influence of Manufacturing Quality on NVH Performance when Sizing Gears

摘要

Noise emissions from gear units in electric vehicles are a major problem. It is a well-known fact that if gears with high accuracy are used, their service life is increased and vibrations are reduced, improving the NVH (noise, vibration, and harshness) performance, resulting in less noise. For this reason, many EV (electric vehicle) manufacturers require a high to very high quality according to ISO 1328 (Ref.8) for gear manufacturing. In practice, the profile form deviation, in particular, is greatly restricted. In some cases, requirements are specified that are almost impossible to manufacture. This increases cycle times and therefore manufacturing costs. This begs the question whether the requested high quality actually produces any real improvements or whether, for example, a well-sized profile modification isn't more effective than simply reducing the permitted manufacturing allowances. For this reason, it would be sensible to find a method that can be used to estimate the influence of the manufacturing accuracy. When the gear profile measurement is analyzed, the signal is always statistically scattered and usually overlaid with a certain basic waviness. The size of this waviness directly influences the resulting profile form deviation. This paper describes the basis for, and results from, a project that investigated the influence of quality on the resulting transmission error and the excitation force in the gear meshing. To achieve this, a sinus-shaped waviness is applied to the theoretical ideal tooth flank. The amplitude, length and initial value of the waviness can be modified. This modification can be applied in both the profile or flank line direction, individually, or both at the same time. The changes in transmission error, excitation force and other fundamental influences on the causes of vibration are then evaluated to obtain a result. The amplitude or height of the waviness depends on the maximum permitted profile form deviation f_(fα), according to the selected quality. The waviness length or initial value can however vary during production, without any influence on f_(fα), depending on the situation. For this reason, it is necessary to take into account the result scatter for different forms of waviness. This can be achieved in an automatized process by combining different variants of amplitudes, lengths and phase angles, for the purposes of calculation. The changes in transmission error and other values that occur, can then be displayed and used to forecast the effect of the quality on the NVH performance. The application of this method to some current gear units is shown and discussed.