With an increasing number and higher quality of recreational vehicles, user demands for their silence have been growing. One of the methods for improving the silence is gear noise reduction.

In this study, the gear noise and its vibration generating source, the transmission error (the relative rotational delay between a driven and a drive gear) of a three axis gear system are analyzed with the object of a transfer for recreational vehicles. Based on this analysis, the gear noise estimation index is investigated using the transmission error.

The approximate correspondence between the measured and calculated results, proves that transmission errors occurring in the input gear pair and output gear pair of a three axis gear system may be treated by an analytical method of a transmission error for two axis gear pairs. The component considering the interference of the force acting on the idle shaft needs to be added to the transmission errors of two axis gear pairs for the gear noise estimation index of a three axis gear system. Further-more , it is demonstrated that the modified tooth flank of a transfer gear obtained on the basis of this estimation index reduces the gear noise.
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