A practical approach to reduce Gear Whine noise through gear Tooth contact analysis in an Agricultural Tractor

Customer demand for comfortable tractors has gone multi-fold in last decade. Transmission gear whine noise as one of the major sources of noise, is an important factor influencing the perceived quality of a vehicle and customer comfort. Investigations were carried out on 57HP tractor reported with high whine noise during deceleration from high speeds to low speeds. The source of whine noise is identified through order analysis as spiral bevel gear. Mitigating spiral bevel gear whine noise is always a challenge because of geometry, tooling and assembly requirements. Tooth contact analysis was performed on the spiral bevel gear for simulating the meshing of gear teeth to determine factors like contact patterns, transmission errors, and load distribution. From tooth contact analysis the root cause for high deceleration noise was identified as the motion transmission was not smooth in entry and exit for both forward and reverse. A practical approach of microgeometry optimization was performed to improve the motion transmission error (MTE) without changing the tool. With these modifications 5-8dBA improvement in transmission whine order observed throughout rpm range and significant improvement in whine noise perception is achieved.