Electric power steering apparatus

#The present application claims priority under 35 U.S.C. §119 to Japanese Patent Application No. 2002-110811, filed on Apr. 12, 2002. The contents of that application are incorporated herein by reference in their entirety.

#1. Field of the Invention

#The invention relates to an electric power steering apparatus to assist a steering by a force of an electric motor, more particularly relates to a rack and pinion electric power steering apparatus to assist an axial movable rack shaft by the assisted force.

#Various other objects, features and many of the attendant advantages of the present invention will be readily appreciated as the same becomes better understood by reference to the following detailed description of the preferred embodiments when considered in connection with the accompanying drawings, in which:

#FIG. 1 is a rack and pinion power steering device of a related art;

#FIG. 2 is an outline view of an electric power steering apparatus according to an embodiment of a present invention;

#A preferred embodiment of an electric power steering apparatus 10 according to the aforementioned invention will be described referring to FIG. 2 to FIG. 5. Hereinafter, it will be described outline of the electric power steering apparatus 10 first, and then a detailed structure of the electric power steering apparatus 10.

#The outline is shown in FIG. 2 relating to the electric power steering apparatus in a stage fixed on a vehicle body. Referring to FIG. 2, the electric power steering apparatus 10 provides a rack shaft 12 with longitudinal direction in a direction of a transversal width of the vehicle body. The rack shaft 12 is connected to light and left tires 18, which are steered wheel, through a tie rod 14 and a knuckle arm 16. Each tire 18 is steered by a movement of the rack shaft 12 in a longitudinal direction The rack shaft is moved by a rack and pinion mechanism 22 and a ball screw mechanism 26. The rack and pinion mechanism 22 transfers a steering torque at a steering or revolution of a steering wheel 20 and the ball screw mechanism 26 transfer an assisted torque generated by an electric motor 24 of a brushless DC motor.

#The rack and pinion mechanism 22 constructs a rack 28 and a pinion 30. The rack 28 is formed on one axial portion of the rack shaft 12. The pinion 30 is engaged with the rack 28 and is connected to the steering wheel 20 through a steering shaft 32. According to a rotation of the pinion 30 of the rack and pinion mechanism 22 by said steering torque, the rack shaft 12 is axially moved through the rack 28 engaging with the pinion 30. In other words, the rack and pinion mechanism 22 transforms the steering torque to the steering force or a rotating force moving axially the rack shaft 12.