ELECTRIC POWER STEERING APPARATUS

Abstract
An electric power steering apparatus includes a worm interlockedly connected to an output shaft of an electric motor, a first and a second bearing each supporting the respective side of the worm in a housing, and a gear wheel meshed with the worm. The housing includes a fitting bore in which the first bearing supporting a side of the worm closer to the electric motor is to be fitted, and an annular retaining portion located at a position corresponding to the second bearing and eccentrically oriented with respect to the center (axial center) of the fitting bore in a direction that shortens a distance L between the center of rotation of the worm and that of the gear wheel, and the annular retaining portion retains a coil spring around an outer circumference of the second bearing.
Description

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS


FIGS. 1A to 1C are diagrams for explaining an assembly process of the worm according to the prior art (Japanese Patent Application Laid-Open No. 2001-233224);



FIG. 2 is a cross-sectional view showing an important portion of an electric power steering apparatus according to the present invention;



FIG. 3 is an enlarged fragmentary cross-sectional view showing the electric power steering apparatus according to the present invention;



FIG. 4 is a cross-sectional view taken along the line II-II in FIG. 3;



FIG. 5 is a cross-sectional view showing an overall configuration of the electric power steering apparatus according to the present invention;



FIG. 6 is a front view showing a coil spring employed in the electric power steering apparatus according to the present invention;



FIGS. 7A to 7C are diagrams for explaining an assembly process of an important portion of the electric power steering apparatus according to the present invention; and



FIG. 8 is a fragmentary cross-sectional view showing another configuration of the electric power steering apparatus.


Claims
  • 1. An electric power steering apparatus which transmits rotation of an output shaft of an electric motor in a housing to a steering shaft, thereby assisting steering operation, comprising: a pinion interlockedly connected to the output shaft;a first and a second bearing each supporting the pinion at a respective end of a pinion axis in the housing; anda gear wheel meshed with the pinion and concentrically fitted to the steering shaft,wherein the housing includes: a fitting bore in which the first bearing supporting one side of the pinion proximal to the electric motor is to be fitted; anda ring provided at a position corresponding to the second bearing supporting another side of the pinion distal to the electric motor, andwherein the ring retains a coil spring such that an coiling center line of the coil spring is disposed along at least a part of an outer circumference of the second bearing, and a central axis of the ring is eccentrically oriented with respect to a central axis of the fitting bore toward a central axis of rotation of the gear wheel.
  • 2. The electric power steering apparatus according to claim 1, wherein the ring includes a groove which accommodates an outer circumferential portion of the coil spring.
  • 3. The electric power steering apparatus according to claim 1, wherein the housing includes a recessed portion in which at least a part of the bearing is fitted, to thereby allow the second bearing to be displaced closer to or away from a central axis of gear wheel rotation, with respect to a central axis of the fitting bore.
  • 4. The electric power steering apparatus according to claim 1, wherein the coil spring has both end portions connected to each other, and is retained in the groove such that the coiling center line of the coil spring forms a ring-shape around the outer circumference of the second bearing.
  • 5. The electric power steering apparatus according to claim 1, wherein the coil spring is retained in the groove such that the coiling center line of the coil spring is disposed around the outer circumference of the second bearing, and forms a C-shape.
  • 6. The electric power steering apparatus according to claim 2, wherein a plurality of the grooves is provided in the ring.
  • 7. The electric power steering apparatus according to claim 2, wherein the groove is deeper in a radial direction in a region closer to a central axis of gear wheel rotation with respect to a central axis of the fitting bore, than in a region more distant from the central axis of the gear wheel rotation with respect to the central axis of the fitting bore.
Priority Claims (1)
Number Date Country Kind
2006-036871 Feb 2006 JP national