JP2009286228A - Electric power steering device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electric power steering device capable of reducing the rattling sound of a gear and other abnormal sounds with a simple configuration. <P>SOLUTION: The electric power steering device comprising a motor 2 for auxiliary steering force; a rotary shaft 3 supported by two bearings 4a, 4b and spline fitted to a motor shaft; an output shaft 6 for transmitting steering force; and a speed reduction mechanism including a worm 5 integrally formed with the rotary shaft 3 and a worm wheel 7 integrally formed with the output shaft 6 so as to mesh with the worm, transmits the auxiliary steering force of the motor 2 to the output shaft 6 through a worm gear mechanism. In the rotary shaft 3, an O-ring 9 composed of an elastic member is fitted into an annular groove 3b provided around the shaft to which a bearing 4a on the side remote from the motor 2 is journaled so as to be projected from a shaft peripheral surface by a predetermined height. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an electric power steering apparatus in which a worm is provided with a preload mechanism, and more particularly to an electric power steering apparatus that reduces noise generated in this portion.

In the worm wheel speed reduction mechanism of the electric power steering device, the axial distance between the gear housing shaft of the housing and the output shaft of the motor is usually the same distance with respect to the axial distance including the meshing radii of the worm and the worm wheel. Is set.
For this reason, in addition to the set backlash (play), backlash caused by each processing variation also occurs.

  This backlash gives the driver discomfort due to rattling noise when the vehicle travels on a rough road, and damages the commercial value.

  As a countermeasure, the backlash is set as small as possible by increasing the accuracy of the gear, or as shown in Patent Document 1, an elastic body is provided between the worm and its bearing to absorb vibrations. The method was taken.

  In Patent Document 2, the worm shaft is supported by an oval shaft hole (eccentric to the worm wheel side) provided in the worm shaft housing portion via a bearing, and is attached to the inner peripheral surface of the shaft hole. There is disclosed a power transmission device in which an O-ring-shaped elastic member is provided in a concentric circular groove, and a bearing is urged toward the worm wheel by the elastic member to remove backlash.

Furthermore, as a method of preloading the worm in the worm wheel direction and eliminating backlash, for example, a method of generating preload by deforming an elastic body provided between the outer ring of the bearing at the worm shaft end and the gear housing, etc. It has been known.
JP-A-11-43062 Japanese Patent Laid-Open No. 10-281235 No. 2003-047948

  However, among the conventional electric power steering devices described above, in the configuration of Patent Document 2, when the bearing is moved, the worm shaft housing portion is easily worn or when the worm shaft is urged by an elastic member. There is a problem that the worm shaft tends to be misaligned with respect to the motor shaft.

  In addition, for the latter that generates a preload by deforming the elastic body, the deformation amount of the elastic body is determined by the outer diameter of the rolling bearing determined by the inner diameter of the housing and the load load, and is very small due to space constraints. The deformation of the worm must be deformed, and the preload of the worm changes greatly due to minute displacement of the worm end due to variations in housing processing and meshing fluctuations, making it difficult to secure the expected preload. was there. If the preload is too large, the operating force is deteriorated and the feeling at the time of neutral steering is deteriorated. On the other hand, if the preload is too small, a gear hitting sound is generated.

  As described above, in the conventional technology, even when the distance between the worm and the worm wheel shaft center changes due to gear wear or the like, the preload changes due to the minute displacement of the worm, and a stable preload is ensured. Was difficult.

  Therefore, in Patent Document 3, an elastic portion that biases the worm in the meshing direction is provided at the shaft end portion of the rotating shaft that is pivotally supported by the bearing away from the motor, and the bearing is interposed via a buffer member. The structure which loosely fits a rotating shaft is shown. This makes it possible to increase the initial amount of eccentricity that generates preload, which is effective in keeping the worm preload constant even if there is a slight displacement of the worm end due to variations in housing processing or meshing fluctuations. is there.

  However, if the motor's auxiliary steering force is transmitted by spline fitting between the motor shaft and the worm shaft, and if there is a preload mechanism that presses the worm against the worm wheel side, the worm rotation direction, preload direction, and axial direction are combined. There was also a problem that abnormal noise was generated in the spline part due to the dynamic movement.

  Therefore, the present invention solves the above-described conventional problems, eliminates the presence of backlash, and reduces noise generated by the ratchet noise, particularly spline fitting parts, without impairing the transmission performance of the auxiliary steering force. An object of the present invention is to provide an electric power steering device having a simple configuration that can be reduced.

  In order to achieve the above object, according to the present invention, a rotating shaft attached to a housing, supported by a motor for auxiliary steering force, and two bearings disposed in the housing, and spline-fitted to the shaft of the motor. And an output shaft that is pivotally supported at a predetermined position of the housing and transmits a steering force, a worm that is formed integrally with the rotating shaft, and an output shaft that meshes with the worm. An electric power steering device that transmits auxiliary steering force of the motor to the output shaft via the worm gear mechanism. An annular groove is provided around the axis of the portion supported by the bearing, and an O-ring made of an elastic member projects into the annular groove from the outer peripheral surface of the shaft at a predetermined height. It is characterized in that it is written order.

  As described above, since the O-ring is provided in the bearing portion of the rotating shaft on the side away from the motor, the worm is preloaded in the direction of the worm wheel, the backlash is suppressed as much as possible, and the generated rattling noise is reduced. be able to.

  At the same time, the movement of the rotating shaft in the preload direction and the movement in the axial direction are considerably suppressed, so that the noise generated at the spline fitting portion when the motor is driven can be greatly reduced.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  FIG. 1 is a partial sectional view showing an electric power steering apparatus of the present invention, and FIG. 2 is a partially enlarged view showing a portion A of the electric power steering apparatus of FIG.

  In FIG. 1, a rotating shaft 3 is spline-fitted to a motor shaft 2 a of a motor 2 fixed to a housing 1. A resin worm (gear portion) 5 is formed integrally with the rotary shaft 3, and both end portions of the shaft are respectively supported by bearings 4a and 4b. The bearings 4 a and 4 b are fitted and fixed to the housing 1. A substantially ring-shaped elastic member 10a is externally disposed adjacent to the axially opposite motor side of the inner ring of the bearing 4a on the motor 2 side, and substantially ring-shaped adjacent to the axial motor side of the inner ring of the bearing 4a. The elastic member 10b is externally disposed on a retaining ring 11 that is externally fixed to the rotary shaft 3. These elastic members 10a and 10b are restricted from spreading by shoulders formed on the rotating shaft 3 and the retaining ring 11, and hold the bearing 4a in the axial direction by elasticity. Therefore, the rotating shaft 3 can be slightly displaced by elasticity in the axial direction with respect to the bearing 4a. On the radially inner side of the inner ring of the bearing 4a, an O-ring is disposed in an annular groove formed in the rotating shaft 3, and the bearing 4a elastically supports the rotating shaft 3 through the O-ring.

  On the other hand, the output shaft 6 is integrally formed with a resin worm wheel 7 and is rotatably supported at a predetermined position of the housing 1 so as to mesh with the worm 5.

  The diameter-reduced end 3a of the rotating shaft 3 opposite to the motor 2 is pivotally supported by a bearing 4b via a cylindrical bearing support member 8 as shown in FIG. The bearing support member 8 is fitted and fixed to the inner ring of the bearing 4b, and the reduced diameter end portion 3a of the rotary shaft 3 is loosely fitted to the bearing support member 8 via an O-ring 9 made of an elastic member. An annular groove 3b is formed in a part of the outer peripheral surface of the rotary shaft 3 that is loosely fitted in the bearing support member 8, and an O-ring 9 is fitted into the annular groove 3b so as to protrude from the outer peripheral surface to a predetermined height. It is. The axial width of the bearing support member 8 is set larger than the axial width of the bearing 4b.

  In the present embodiment, the rotating shaft 3 is arranged eccentrically to the worm wheel side slightly from the motor shaft center. Accordingly, the rotary shaft 3a is elastically loosely fitted to the inner peripheral surface of the bearing support member 8 via the O-ring 9, preloading the worm 5 to the worm wheel 7 side, A slight displacement of the rotating shaft 3 is elastically acceptable. The bearing 4b, the bearing support member 8, the circular groove 3b, and the O-ring 9 constitute a preload mechanism.

  In the above configuration, the driving force of the motor 2 is transmitted to the rotating shaft 3 through spline fitting, and the output shaft 6 rotates due to the meshing of the worm 5 and the worm wheel 7. In this way, the auxiliary steering force of the motor 2 is transmitted to the output shaft, and front wheels (not shown) are steered.

  At this time, since the worm 5 is preloaded against the worm wheel 7 by the elastic force of the O-ring 9, it is possible to reduce backlash, but as shown in FIG. The displaceable amount of B is in a minute range due to the structure of the O-ring 9. For this reason, the movement of the rotating shaft 3 in the preload direction B is suppressed.

  At the same time, the movement of the rotary shaft 3 in the axial direction C is considerably suppressed from the elastic force of the O-ring 9 and the frictional force of the O-ring 9 on the inner peripheral surface of the bearing support member 8.

  For this reason, when the motor is driven, the rattling noise can be reduced, and the combined movements in the preload direction B, the axial direction C, and the rotation direction D that are generated in the spline fitting portion are suppressed. Sound can be reduced.

  In the above embodiment, the end portion 3a of the rotary shaft 3 is pivotally supported by the bearing 4b, and the bearing support member 8 is interposed. This is because of the installation space. It is necessary to use a small bearing 4b on the far side, and by using a bearing support member having an axial width larger than the axial width of the bearing 4b, the stability when the end portion 3a is axially supported is improved. It plays the role of letting.

  However, the present invention is not limited to this configuration, and the bearing 4b may directly support the end 3a of the rotating shaft 3 without the bearing support member 8 interposed therebetween. However, in this case, it is desirable to set the axial width of the bearing 4b slightly larger.

It is a fragmentary sectional view showing the electric power steering device of the present invention. It is the elements on larger scale which show the A section of the electric power steering device of FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Housing 2 Motor 2a Motor shaft 3 Rotating shaft 3a Reduced diameter end 3b Annular groove 4a Bearing (motor side)
4b Bearing (on the non-motor side)
5 Worm 6 Output shaft 7 Worm wheel 8 Bearing support member 9 O-ring 10 Elastic member

Claims (1)

A motor attached to the housing for auxiliary steering force;
A rotating shaft supported by two bearings disposed in the housing and spline-fitted to the shaft of the motor;
An output shaft that is pivotally supported at a predetermined position of the housing and transmits a steering force;
A reduction mechanism including a worm formed integrally with the rotating shaft and a worm wheel formed integrally with the output shaft so as to mesh with the worm,
In the electric power steering device that transmits the auxiliary steering force of the motor to the output shaft via the worm gear mechanism,
The rotating shaft is provided with an annular groove around the shaft supported by the bearing on the side away from the motor, and an O-ring made of an elastic member is provided in the annular groove from the outer peripheral surface of the shaft. An electric power steering device, wherein the electric power steering device is fitted in a protruding shape.

Images