The relevance of pinion deflection and twisting for loaded tooth contact analysis of high reduction hypoid gears

Bevel gears are used to transmit power in gear trains between non-parallel axes. In order to better utilize the available space, hypoid gears can be used. These differ from bevel gears primarily in the offset between the axes. This allows larger gear ratios to be achieved in the same installation space, thus increasing the power density. By increasing the hypoid offset, the transmission ratio can be raised. This leads to a reduction of the number of teeth on the pinion while the helix angle increases. Even pinions with only down to one tooth are possible. This makes it possible to generate hypoid gears with ratios of 100[1] and more, so-called high reduction hypoid gears (HRH). Due to increasing demands regarding the power density and efficiency of gearboxes, efforts are being made to promote the use of high reduction hypoid stages. Proven tools for bevel and hypoid gear design shall also be used in the future. These include programs for tooth contact analysis un-der load (LTCA), such as BECAL. Due to the greatly changed geometry of pinions with small numbers of teeth, it must be investigated whether pinion deflection and twisting have a decisive influence on the contact pattern of HRH and whether these must be taken into account in the LTCA. FEA calculations are used to determine the influence of pinion twist and pinion deflection on the contact line. FE models with contact calculations are used. This investigation is used to determine whether these effects must be included in the loaded tooth contact analysis on high reduction hypoid gears. The results are crucial for the further development of LTCA tools like BECAL if load bearing capacities of HRH are to be reliably determined. © 2023 The Authors.