Comprehensive representation of pitch deviations suitable for engagement evaluation in different types of gears

Tooth flank deviations of gears should be characterized to evaluate the individual gear accuracy which is directly connected to the gear performance during engagement. A comprehensive representation of the pitch deviation is proposed here. The pitch deviation is calculated with multiple surface deviations of a tooth flank as the zeroth order form deviations. According to this new representation, a pitch error should be expressed by a unit of angle, not by a unit of length, and it can be calculated from the measured conventional deviations (profiles and leads) without performing the extra pitch measurement. For spur and helical gears, the pitch deviation can be expressed by single value of a unit of length and also expressed by single value of a unit of angle. On the other hand, for the bevel gear flank, the length representation of the zeroth order form deviation consists of many different values even on single flank evaluation. Nevertheless, by use of the expression with a unit of angle, the form deviation can be described by single parameter exactly. Therefore, it is better to express the pitch deviation by a unit of angle instead of a unit of length. In addition, since multiple measured surface deviations are participating in calculation of the pitch deviation, the comprehensive representation of the pitch deviation proposed here gets rid of disadvantages of the conventional evaluation of the pitch deviation. The proposed representation is also right to the point of evaluation of gear engagement.