Gear Transmission Error Metric for Use with Gear Inspection Machine

The spur timing gears in Eaton superchargers operate at low torque loads and the supercharger system is especially sensitive to gear whine noise created by minute differences in the spur gear tooth profile quality. This has necessitated the grinding of very high quality profiles on high-contact-ratio spur gears. The manufacturing operation has used subjective evaluation of profile and lead measurements to qualify grinder diamonds and audit gear quality related to noise. They have also relied on supercharger end-of-line-testers to provide a direct measurement of gear noise as the primary quality feedback to the gear manufacturing process. Since the difference in the inspection plots of very high quality profiles is difficult to determine subjectively, the inspection process assessments have been difficult to correlate to the resultant gear noise measurements. The transmission error (TE) calculated from these profile measurements provided and objective assessment that was shown to correlate well with the actual measured gear whine noise. This study resulted in the creation of TE monitoring software that was an add-on to the inspection machine. This software, which uses a version of the LDP code (by The Ohio State Gear Dynamics Laboratory) as the core calculation routine, provides an objective metric of the gear mesh frequency TE and several harmonics calculated from the measured involute profile data. This objective TE metric provides a traceable standard for ensuring low vibration excitation in the gear mesh directly after grinding the gears.