Loaded TCA of Measured Tooth Flanks for Lapped Hypoid Gears

Usually, the Loaded Tooth Contact Analysis (i.e. LTCA) of hypoid gears uses the nominal tooth flanks described by the machine setting and the cutter specifications. Only a few studies are performed on the LTCA directly using the measured tooth flanks such as carbonize-hardened and lapped hypoid gears. This paper presents an innovative LTCA method directly using the measured tooth flanks at each manufacturing step including not only the milling or hobbing process but also the troublesome heat-treatment, lapping or grinding processes. The proposed new LTCA method is extremely concise. Firstly, the 3-D shape data of the manufactured tooth flanks, which are the original x-y-z coordinates but not the differences against their nominal tooth flanks as before, are obtained on a coordinate-measuring machine. Another important factors the load deflections are measured on the assembled transmission by applying the static transmitting torque. Secondly, the pinion and gear are localized at the nominal mounting position, and the no load TCA can be obtained by calculating the gap between the original tooth flanks at each roll angle. Lastly, since the load deflections can be considered as the movement of mounting position, the Loaded TCA can be obtained by calculating the gap between the moved tooth flanks at new mounting position. As practical applications, the new LTCA method is used to improve the strength of high-torque hypoid gears for an All-Wheel-Drive transmission. As a result, the tooth contact pattern and pitting position observed in endurance test agreed well to the LTCA predictions and the demanding life is achieved by modifying the loaded contact pattern of lapped hypoid gears.