Tip rounding and tip relief on the pinion

In heavily-loaded gearing (power gearing), meshing interference can occur despite accurate, geometric profiles and theoretically faultless gearing pairing, for example, “excavations” or “chip formation” in the wheel’s root flank, as shown in the picture on the right. This phenomenon is particularly common in pairings with hardened pinions where the tip edges of the pinion act as shavers.

This can be caused by the following:

1) Bending

Dynamic load peaks under high force, acceleration, braking and vibrations cause the elastic deformation of the meshed teeth.

2) Pitch error

The manufacturing tolerance ranges not to be skirted around in any gearing, in the present case, pitch error in particular, can also have a negative impact when combined with the bending.

3) Swivel drive

The pinion shaft turning is unavoidable because of the mostly flying structure of the drive. Simultaneously, elastic deformations between the swivel drive and the companion structure in the bond zone are caused by the high forces introduced. These deformations also facilitate meshing interferences.

4) Lubrication

The three previously mentioned influencing factors result in heavy peak loads on the tip edges of the pinion which can lead to the lubricating film tearing off. As a result of the direct metallic contact which then ensues, chip formation is expedited.

The occasional damages which became apparent in the base could be eliminated, relieving the pinion tip and rounding the tip edges on the pinion.

5) Tip relief

From technical literature, tip reliefs are known for their fast transmissions to reduce vibration effects (noise).

The known investigations prompt us to prescribe pinions with curve radii of 0.1 - 0.15 m, with tip relief and tip edge rounding, for applications with gearing loads subject to extreme conditions.

The radius, ρ_an, must fit in the addendum flank without edges.

A smooth transition from the modified tip flank profile - without edges - to the normal flank profile must be guaranteed.

The tip flank profile should be of a similar shape to involutes.