In powertrain systems, combined deflection of loaded gear tooth as well as that of the shafts on which the gears are mounted is responsible for non-ideal meshing conditions. Uneven load distribution along the teeth between mating gears is one such non-ideal condition that can cause significant NVH issues. Lead mismatch, defined as the amount of mismatch along a pair of gear tooth faces, is a critical parameter to maintain uniform load distribution at the gear contact regions. If each of the adjacent shafts is a balance shaft where a counterweight is mounted at an eccentric location, shaft deflection and the resultant lead mismatch is even more. Also, typically, balance shafts are required to rotate at twice the crankshaft speed. At a high engine speed, Coriolis and centrifugal accelerations acting on the balance shafts can be significant resulting in higher shaft deflection and greater lead mismatch. In the present system, a balance shaft mechanism with helical mating gears are considered. Three rotational bodies - crank gear, driving and driven balance shafts are involved where scissors gear are used to reduce backlash and helical gear pairs are used for quieter operation. Two different analytical procedures to predict the lead mismatch of the mating helical gears (Crank gear and fixed gear of the scissors gear) are investigated. These processes involve creating a quasi-static 3D Abaqus model and a multi-body dynamic 3D AVL Excite model to predict the mismatch across the gear face-width. The contact pattern on the gear face shows good correlation with experimental observation. As such, analytical procedures have the capability to be utilized for intentional tooth modifications on the helical gear pair to improve the gear tooth surface wear and aid in quieter operation.


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    Title :

    Lead Mismatch Calculation of a Helical Gear System Mounted on Balance Shafts


    Additional title:

    Sae Technical Papers


    Contributors:

    Conference:

    SAE WCX Digital Summit ; 2021



    Publication date :

    2021-04-06




    Type of media :

    Conference paper


    Type of material :

    Print


    Language :

    English




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