Importance

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Abstract

A gearbox assembly for an electric power assisted steering apparatus comprises a gearbox housing which houses a worm shaft and a gear wheel, the worm shaft being supported relative to the housing by a main bearing at an end closest to the motor and by a tail bearing at an end furthest from the motor, and the gear wheel being supported by an output shaft having at least one end that provides a take-off from the gearbox assembly, in which the main bearing and tail bearing are free to move relative to the housing through a limited range of motion that enables the worm shaft to pivot away from the wheel gear facilitated by tilting of the main bearing about a pivot that is fixed relative to the housing, characterised in that the gearbox assembly is arranged such that the pivot reacts the axial component of the worm shaft tooth load that arises when a gearwheel torque is applied to the gearwheel in a first direction but not in a second, opposing, direction, and in that a tensioning device is provided that reacts the axial component of the worm shaft tooth load that arises when a gearwheel torque is applied to the gearwheel in the second direction but not in the first direction.

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First Claim