A cylindrical friction drive was developed for electric oil pump applications. It was comprised of an outer ring, a sun roller, a loading planet, two supporting planets, and a stationary carrier The sun roller was set eccentric to the outer ring to generate a wedge gap that facilitates a torque actuated loading mechanism for the friction drive. The loading planet was properly assembled in the wedge gal) and elastically supported to the carrier By altering the stiffness ratio of the elastic support to contact, the actual operating function coefficient of the friction drive can be changed regardless of the wedge angle to suit,for performance requirement. This provided a greater freedom for design and performance optimization. Design analysis was presented and a FE model was developed to quantify design parameters. Prototypes of the function drive were fabricated and extensive testing was conducted to evaluate its performance. Results indicated the performance of the friction drive far exceeded the design specifications in speed, torque, and power ratings. The function drive offered a consistent smooth and quiet performance over a wide range of operating conditions. It was capable of operating at an elevated speed of up to 12 000 rpm with adequate thermal characteristics. The friction drive demonstrated a peak efficiency above 97%. Results confirmed that the stiffiness of the elastic support has an important impact on performance. The elastic support stiffness, in conjunction with the contact stiffness, determines the actual operating friction coefficient at the frictional contacts.
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