Patent ID: 7921958

Claim:
An apparatus for driving a steering shaft in a motor-driven power steering system, comprising: a pinion gear having a joining protrusion on a lateral surface thereof facing an electric motor, the pinion gear connected to a front end of a motor shaft of the electric motor and rotating integrally with the motor shaft; a power transmission bearing member slidably coupled to the motor shaft between the electric motor and the pinion gear and provided with a joining groove formed on a lateral surface thereof facing the pinion gear to removably receive the joining protrusion of the pinion gear, wherein the power transmission bearing member rotates integrally with the pinion gear by being joined together when the pinion gear is disengaged from a flywheel ring gear of an engine; a power transmission belt coupling the power transmission bearing member and a wormwheel of the steering shaft and thereby transmitting rotation force of the power transmission bearing member to the wormwheel; and a controller controlling the electric motor by receiving information on a steering angle of a steering wheel from a torque sensor.