Hypoid gears are transmission elements that transfer power and moment between shafts whose axes do not intersect. They are similar in structure to spiral bevel gears. However, there are many differences and advantages compared to spiral bevel gears. For example, the spiral angle in hypoid pinions is higher than spiral bevel gears. This phenomenon increases the load-carrying capacity as it expands the contact area. Since the pinion and gear axes do not intersect, bearings can be used in both shafts. This provides extra rigidity. Hypoid gear pairs are mostly used as powertrain on the rear axles of cars and trucks since it is required higher torque and lower rotational velocity. Hypoid gears are manufactured by two essential methods called face-milling and face-hobbing, and there are mainly two relative kinematic movements (Formate® and Generate), Unlike the Face-hobbing method in the Face-milling method, the workpiece and the cutter head do not rotate synchronously during manufacturing. In the Formate® method, only the cutting head rotates around its axis and opens the slot. In the Generate method, the workpiece rotates synchronously with the cradle, which is holding the cutter head.

In this study, the gears produced with the Face-milling method are discussed. Face milled hypoid gears can be manufactured with both Formate® and Generate, while pinions can only be manufactured with the Generate method. The most crucial factor that determines the performance of hypoid gears during torque transfer is the geometry of gear and the mating pinion. The gear and pinion geometry is directly dependent on the cutting tool geometry, machine manufacturing parameters, and relative motion between the cradle and the workpiece (not valid in Formate®). The resulting gear geometry determines the contact shape, contact pressure, root stress, and transmission error during power transmission.

For this reason, the effects of the tool-machine parameters of the hypoid gears on the gear geometry should be carefully examined. In this study, the mathematical equation of the cutting tool is set. After that, using differential geometry, coordinate transformation, and the gearing theory, the mathematical equation of hypoid gear is obtained. For generate case, the Equation of meshing is given in its open form.

This study is also the first part of a scientific research project (1501) funded by TUBITAK (The Scientific and Technological Research Council of Turkey). In this project, an experimental hypoid test rig will set to observe tool-machine parameters on the performance of hypoid gear under mixed misalignment conditions. The effect of these parameters root stress, and transmission error will be investigated.


An Investigation on the Design of Formate and Generate Face Milled Hypoid Gears

Division / Sponsors: 
Aerospace, Bioengineering, Applied Mechanics, Design Engineering Division, Advanced Energy Systems, Manufacturing Engineering Division, Noise Control and Acoustics, Nondestructive Evaluation, Diagnosis, and Prognosis (NDPD), Nuclear Engineering Division, Process Industries Division, Fluids Engineering, Heat Transfer, Materials, Microelectromechanical Systems, Safety Engineering and Risk Analysis, Computers & Information in Engineering


Paper Proceedings: https://asmedigitalcollection.asme.org/IMECE/IMECE2020/volume/84478

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