Page 62 - Gear Technology Solutions

3. Line contact is maintained in the entire area of engagement if pinion and
ring gear are rotated by angular increments where: (angular pinion
increment) / (angular ring gear increment) = (transmission ratio)

Figure 11: Ease-Offs, motion graphs and contact lines of a real
conjugate hypoid gearset

The Ease-Off is a three-dimensional graphic of the flank deviations from a con-
jugate pair. It is calculated by transformation of a pinion flank “into” the gear
coordinate system according to the first gearing law, resulting in a virtual gear
flank that is conjugate to the actual pinion flank. This conjugate gear flank will
then be compared to the present gear flank, where all differences in arc length
are plotted point by point in ordinate direction into the Ease-Off graphic.

If both mating bevel gears have conjugate manufacturing data, then the Ease-
Off graphic has no deviations in ordinate direction. Also, if the pinion flanks
and the gear flanks have spiral angle and pressure angle errors of equal
amounts, the Ease-Off graphic will not show any deviation. Although the indi-
vidual gears are considered incorrect in this case, they will roll conjugate with
each other, which subsequently leads to an Ease-Off without any ordinate val-
ues. Figure 11 shows the analysis results of a typical conjugate hypoid
gearset. The Ease-Off graphics have zero crowning magnitudes in the ordinate

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