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.
Hypoid gear machining is a critical process in automobile industries. Many studies have discussed the gear machining in the geometrical model for manufacturing and design of the gears. In terms of the cutting process, the accuracies of the gears largely depend on the cutting forces. Therefore, the cutting force should be estimated to perform the high accurate gear cutting. However, few studies have been done on prediction of the cutting force. Analytical predictions of the cutting forces are required for manufacturing of gears with high qualities. This study presents an analytical model to predict cutting force in the hypoid gear cutting, in which the gear grooves are machined by sets of inner and outer cutting blades. Both of the blades finish the side and the end faces in the gear grooves. Different chip flows occurs on the end and the side edges of the blades. The chip flows are modeled by piling up orthogonal cuttings containing the cutting and the chip flow directions, where the chip flow direction is determined to minimize the cutting energy. The cutting forces loaded on the inner and the outer blades are predicted in the chip flow models. The presented model is validated in the cutting tests with measuring the cutting forces.
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