Gear Design and Development

Despite the fact that lapping Is expected to Improve the surface finish, measurement exults show that ring gears surface finish becomes worse (roughness increased) after lapping while no consistent results for pinion surface finish were observed. However, it will be shown that lapping decreases transmission errors for both sides (drive and coast). Utilizing a Gleason single flank tester (SOFT) 60TH It will be shown experimentally that transmission errors up to the second harmonics for both sides will be decreased.

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In addition, it can be seen that lapping decreases surface finish variation among gear sets. As an expansion of the previous study [1] by the authors n lapping effects on surface flash and transmission errors, this paper will also present the effects of the superhumanly process on hybrid gears surface finish and transmission errors. This study shows the result of measurements taken before and after superintending, although superintending improves surface finish drastically it will be shown that surface finish quality will be decreased when gear sets are rolled together. Compared to other options for gear types (such as straight and spiral bevel gears), that geometrically are capable of transferring power between Mosses Sullivan Ph. D. Student, Gear Dynamics and Gear Noise Research Laboratory, Ohio State university perpendicular axes, hybrid gears have more advantages which allows this type of bevel gear to dominate in automotive axle applications.

In general two basic different cutting processes are used to generate hybrid gears namely face- milling (FM, also called single Indexing) and face-hobbling (IF, also called continuous indexing which have their own advantages and disadvantages over each other. Costly because they need shorter cutting time compared to face-milling method [2-4]. In hybrid gears due to having intersecting axes, a higher sliding velocity between contact surfaces exists; as a result, sliding friction is one of the main power loss sources in addition to rolling friction.

Therefore, hybrid gears have considerably more mechanical power loss during gear mesh than intersecting types of bevel gears and as a result are less efficient than other types of bevel gears. In a study on gears surface finish effects on friction [5] by comparing frictional losses of conventionally ground (Ra =0. Um) with superfluities um) teeth, it was shown that with the same load and speed this surface finish improvement will decrease friction around 30 percent in addition to decreasing tooth surface temperature.

Moreover, based on Ex.’s proposed model for hybrid gear efficiency prediction [6, 7] which uses an EEL model with contact data provided by a FEE based modeling software (9), (depending on lubricant temperature at inlet) a change in surface finish from Ra=O. 2 um to Ra=O. 6 um may decrease hybrid gear efficiency around 0. 5 percent. As a result, improving surface finish can be one way to increase efficiency. In this study a set of measurements were done to see how superintending and lapping will change surface finish of hybrid gear sets.

The aim of this study is to investigate the effects of superintending and lapping on surface finish of hybrid gears for to have an insight of effects of these processes on surface finish. Moreover, it will be experimentally shown how superintending and lapping may change transmission errors (up to first two harmonics for lapping and first harmonic for superintending). Manager, Gear Design & Development, American Axle and Manufacturing Inc. , Email: [email protected] Com. Upright 2007 by SAME First, surface finish measurement procedure will be explained and then the results of measurements with more details of measuring procedure will be provided.

Table 2 shows an example of Ra, Rye, Razed, etc) and settings. There are several measuring parameters which need to be set before beginning measurement that are mentioned in table 2. Machine is equipped with both pinion and gear fixtures (holders) in order to keep parts securely in place while measurements is being performed. The software on the machine is capable to remove surface curvature from data and calculate pure surface finish for curved surfaces. It should be mentioned here that all measurements were done with 0. 8 mm sample length (length of taking data “cut-off).

Measuring surface finish quality in different location on gear and pinion shows that surface finish considerably varies in both lengthwise and profile directions. Therefore in order to have consistent surface finish data to compare results before and after lapping process; data should be taken from same location on flank meaning that lengthwise (from toe to heel) and profile (from top to root) location of measuring spot should be consistent for all measurements.