Study of the tooth contact for high contact ratio spur gears with long tip relief

José I Pedrero,Miguel Pleguezuelos,Miryam B Sánchez,D Karaivanov

doi:10.1051/matecconf/201928701004

José I Pedrero, Miguel Pleguezuelos + Show 2 more

Open Access

https://doi.org/10.1051/matecconf/201928701004

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Abstract

Profile modifications are commonly used to avoid shocks between meshing gear teeth produced by the delay of the driven gear, and the subsequent sooner start of contact, due to the teeth deflections. A suitable tip relief at the driven tooth shifts the start of contact to the proper location at the theoretical inner point of contact. The shape of the relief governs the loading curve of the tooth pair, while the length of relief determines the intervals in which this actual loading curve differs from the theoretical one of unmodified teeth. As at least one tooth pair should be in contact at the unmodified involute profile interval, the length of modification should be smaller than the length of the intervals of two pair tooth contact; otherwise, a shock at the end of contact of the previous pair is unavoidable. However this problem does not occur for high contact ratio spur gears, in which at least two couples of teeth are in contact at any moment. In this work, a study on the load sharing and the quasi-static transmission error for high contact ratio spur gears with long profile modification has been performed, and a model for the tooth contact has been developed.

Highlights

The tooth deflections under load induce a relative rotation between both meshing gears, delaying the driven gear respect to the driving one [1]
As at least one tooth pair should be in contact at the unmodified involute profile interval, the length of modification should be smaller than the length of the intervals of two pair tooth contact; otherwise, a shock at the end of contact of the previous pair is unavoidable
A symmetric tip relief at the driving tooth shifts the end of contact to the theoretical outer point of contact. This profile modification at the upper limit of the contact interval is not as critical as one at the inner limit because the parabolic unloading process induces a sudden disengage of meshing teeth but not a shock

Summary

Introduction

The tooth deflections under load induce a relative rotation between both meshing gears, delaying the driven gear respect to the driving one [1]. A symmetric tip relief at the driving tooth shifts the end of contact to the theoretical outer point of contact This profile modification at the upper limit of the contact interval is not as critical as one at the inner limit because the parabolic unloading process induces a sudden disengage of meshing teeth but not a shock. It is not unusual to modify the profile at the inner limit of the contact interval but not at the outer limit For such a profile modifications, the shape of the tip relief at the driven tooth governs the loading curve of the tooth pair [3,4,5,6], while the unloading curve is described by the mentioned parabola. Though this kind of relieves is not suitable for standard contact ratio spur gears [3], a model for the tooth contact for high contact ratio gears has been developed

Unmodified teeth

Tooth modifications

Long tip relief

Findings

Conclusions