Gear Design and Development

This is due to a high sliding to rolling ratio In these types of gears.

In this paper, a study on measuring of surface flash of both ring gear and pinion will be presented. Moreover, the effects of lapping and superintending on surface finish will be discussed. Using an accurate form-measuring machine, surface finish measurements were done on several experimentally produced hybrid gear pairs.Despite the fact that lapping is expected to improve the surface finish, measurement exults show that ring gear's 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 (SIFT) 60TH it will be shown experimentally that transmission errors up to the second harmonics for both sides will be decreased.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 finish and transmission errors, this paper will also present the effects of the superintending process on hybrid gears surface finish and transmission errors. This study shows the result of measurements taken before and after supervising, although supervising improves surface finish drastically it will be shown that surface finish quality will be decreased when gear sets are rolled together. Hybrid gears are widely used in automotive industries to transfer rotation between non-intersecting axes in rear wheel drive and ADD vehicles.

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 ELL 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 supervising and lapping will change surface finish of hybrid gear sets.The aim of this study is to investigate the effects of supervising 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 supervising and lapping may change transmission errors (up to first two harmonics for lapping and first harmonic for supervising). Manager, Gear Design & Development, American Axle and Manufacturing Inc. , Email: massetJ@aam.

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.In this study, supervising effects on surface finish and transmission errors will be explained as a complement of previous study by the authors of this paper. This study will not cover theoretical issues related to this phenomenon (effects of supervising and lapping on surface finish and transmission errors) at this step; the goal here is to discuss the issue experimentally and more experiments and theoretical studies in true will help investigating the supervising and lapping effects in more details.

SURFACE FINISH MEASUREMENT PROCEDURE -or experimentally see the effects of lapping or supervising on surface finish of hybrid gears; surface finish measurements were performed on nine hybrid gear sets before and after lapping. All gear sets were the same and had 1 1. 5 in outer diameter and their geometric parameters are as mentioned in table . To measure surface finish a CNN form- measuring machines (figure 1), equipped with software called Performance was used to analyze measured data to extract surface finish.

Table 2 shows an example of Ra, Ray, 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. Table 1 . Hybrid gear set geometric parameters Geometric parameters Number of teeth Diametrical Pitch Face width Pinion offset Shaft AngleOuter cone distance Pitch diameter Pitch angle Mean spiral angle Hand of spiral Generation type Depths tooth taper Figure 1. Form measuring machine setup Table 2.

A sample of measurement parameters Parameter Ra Ray Results 1. 24255 um 6. 54780 um Parameter RPR Razed Results 3. 49220 urn 6. 54780 urn Evaluate Condition List Standard OLDIE Kind of Profile R Small Length (LLC) 0. 8 mm No of Small(Nile) 1 LLC 0.

8 mm Kind of Filter Gaussian Velvet Length(elm) 0. 8 mm Pre- Travel 0. 4 mm Post-Travel 0. 4 mm Smooth Connection Off Mean Line Compensation Off Measurement Condition Measurement Length Column Escape Auto-Leveling SpeedOver Range Pitch Machine Detector Polar Reversal Arm Compensation Auto-Notch(+) Compensation Method 1.

6 mm 5. 0 mm Off 0. 0 m's Abort 0. 5 um Off Off Off Off Pinion 11 --2. 13"2. 00" 905.

36" --ADD MM ADD MM LA Generated IF Gear 41 3. 57" 1. 78" 6. 46" 1 1. 50" ADD MM ADD MM RE Non-Generated In order to check surface finish variation on pinion flank a pinion surface was divided into 9 regions (three divisions from toe to heel and three divisions from top to root) and surface finish was measured in the middle of each region.

The results shows that surface finish improves from top to middle and then get worse continuing ND heel toward center (in lengthwise direction). Although it may not be a general rule, it is consistent result for most of measured pinions. 3 LAPPING EFFECTS ON SURFACE FINISH AND TRANSMISSION ERRORS Lapping one of the processes used for gear finishing. While for many types of gears grinding may also be (sometimes) economical, for bevel and hybrid gears still lapping is the - Immunity Scoop 2 most applicable process and is used as an economically applicable procedure (except for some case in aerospace applications).It is also the aim of lapping to make reface smoother through increasing conjugal between pinion and gear and hence reduction in level of noise [3, 4].

As for hybrid gears in automotive industries, due to large production volume, grinding with currently available technology of machines and procedures is hard to be used instead of lapping. The main advantage of lapping over grinding in large volume production lines is that lapping needs cheaper machines and shorter processing time [8]. Depending on hybrid gear geometry (specially the amount of offset), the sliding velocity and contact pressure will be changed during mesh cycle.As a result, sliding distance caused by the combination of sliding velocity and contact pressure on every contact point (or spot) results in surface wear. Therefore the complex physical quantity of sliding distance on each surface point forms a surface wear distribution over the gear flank. To experimentally measure how much lapping will effect on surface finish, some sets of experiments have been performed.

In order to check lapping effects on surface finish, a set of measurements were performed to evaluate surface finish (namely Ra and Razed) on both gears and pinions.All measurements were done on same location in all gears ND pinions (at the center of lengthwise and profile directions). For all gear sets the same lapping settings for lapping machine were used and all were lapped with a same abrasive (silicon carbide) lapping compound. Also lapping procedure was conducted under light brake load with about 10 N. M torque on gear shaft and pinion speed was kept at 2300 RPM.

For all gears and pinions, measurements were performed on both drive and coast sides before and after lapping.