Patent ID: 7159689
Filing Date: 2007-01-09
Classification: B62D

Abstract:
1. An electric power steering apparatus for a vehicle comprising: a pinion provided on a shaft co-rotatable with a steering member; a steering shaft including a rack meshed with the pinion, the steering shaft being movable in an axial direction thereof; a steering shaft guiding device comprising a guide which guides the steering shaft for movement in the axial direction, and a biasing member which biases the steering shaft toward the pinion by biasing the guide; and a motion converting mechanism comprising a rotary cylinder surrounding the steering shaft and driven by a steering assist electric motor, the motion converting mechanism being capable of converting rotation of the rotary cylinder into the axial movement of the steering shaft; wherein the steering shaft is supported by the rotary cylinder, the pinion and the guide; wherein the pinion is located between the rotary cylinder and the guide axially of the steering shaft; wherein a distance between a middle position of the rotary cylinder and a middle position of the pinion as measured in the axial direction of the steering shaft is 20 to 45 times a distance between the middle position of the pinion and a middle position of the guide as measured in the axial direction of the steering shaft, and wherein the steering shaft, pinion and rotatable cylinder are configured in relation such that a bending moment applied to warp the steering shaft, in a manner that both ends of the steering shaft are displaced in a single direction either forwardly or rearwardly with respect to the vehicle, will press the steering shaft against the rotatable cylinder pivotally about a point where the pinion meshes with the steering shaft.