JP2003028153A - Electric power steering device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To solve problems in an electric power steering device that the noise sometimes generates due to an internal clearance of a bearing rotatably supporting a worm shaft, when the rotation of an electric motor is decelerated by a worm gear mechanism and transmitted to a steering mechanism, further the preload applied to the bearing by a screw member to eliminate the bearing clearance is instable because of the interlocked rotation of the screw member with a lock nut engaged with the screw member, in fastening the lock nut for locking the screw member, and the steering device is enlarged. SOLUTION: The screw member 45 is engaged in a threaded hole 46 of a housing 7, and an outer ring of the bearing is energized by the screw member 45, whereby the preload to be applied to the bearing is adjusted. Then a pin 47 in parallel to an axis of the screw member 45 is press-fitted into a recessed groove 48 formed on an inner peripheral face of the threaded hole 46. The pin 47 acts as a detent of the screw member 45, and the preload can be stabilized.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electric power steering apparatus using an electric motor as a source of steering assist force.

[0002]

2. Description of the Related Art As an electric steering apparatus for an automobile, a first steering shaft connected to steered wheels and a second steering shaft connected to the first steering shaft via a torsion bar and connected to a steering mechanism. There is a device provided with. In this device, the relative displacement amount of the first and second steering shafts in the rotation direction is detected by the torque sensor, and the rotation of the electric motor is mainly detected by the torque sensor based on the detection result of the torque sensor. By transmitting the steering wheel to the steering shaft, the operation of the steering mechanism according to the rotation of the steered wheels is assisted by the rotation of the electric motor, and the labor load of the driver for steering is reduced.

As the above-mentioned speed reducing mechanism, one having a worm and a worm wheel is provided. The worm shaft provided with the worm is rotatably supported by a pair of bearings at both ends in the axial direction.
However, due to rattling due to the internal clearance of the bearing, abnormal noise may be generated, which may be transmitted to the vehicle interior and become noise. Therefore, the pair of bearings are ball bearings, and a preload is applied in the axial direction in order to remove the internal clearance therebetween.

As the preload-applying member, there is used a screw member which is screwed into a screw hole of the housing to preload the outer ring of the bearing in the axial direction. Further, as a fixing member for fixing the screw member to the screw hole of the housing, a lock nut screw-engaging with the screw member is used.

[0005]

However, the screw member becomes long by the amount of the lock nut that has to be engaged, and the space is taken up. As a result, the electric power steering apparatus becomes large. In addition, the screw member may rotate together with the lock nut in the process of tightening the lock nut after rotating the screw member to adjust it to an appropriate pre-load, and the bending angle and the adjusted pre-load amount may go wrong. . For this reason, it is often necessary to make an adjustment again, and the adjustment work is troublesome.

The present invention has been made in view of the above problems, and it is an object of the present invention to provide an electric power steering apparatus which is small in size and can easily remove a bearing gap.

[0007]

Means for Solving the Problems and Effects of the Invention In order to achieve the above object, the invention according to claim 1 is a steering mechanism for rotating a rotating shaft of an electric motor for steering assist through a worm shaft and a worm wheel. In the electric power steering apparatus, the housing that accommodates the worm shaft and the worm wheel, the bearing that is held in the bearing holding hole of the housing to rotatably support the worm shaft, and screwed into the screw hole of the housing. It is characterized by comprising a screw member for applying a preload to the outer ring of the bearing and a pin which is press-fitted along the screw hole into a fitting portion of the screw member and the screw hole to prevent the screw member from rotating.

In the present invention, the screw member is fixed by driving the pin along the screw hole after adjusting the preload amount by the screw member. Since the screw member does not rotate when the pin is driven in, the adjustment work does not have to be repeated many times, which facilitates the adjustment work. Further, in the conventional locking method using the lock nut, the screw member is elongated by the amount by which the lock nut is engaged, but in the present invention, the screw member can be shortened by the amount by which the lock nut is not used. As a result, space can be reduced, and as a result, miniaturization can be achieved.

According to a second aspect of the present invention, there is provided an electric power steering apparatus for transmitting the rotation of a rotary shaft of an electric motor for assisting steering to a steering mechanism via a worm shaft and a worm wheel. A housing for accommodating, a bearing which is held in a bearing holding hole of the housing to rotatably support the worm shaft, a snap ring which is held in a circumferential groove formed in the housing in the vicinity of the bearing holding hole, and the snap ring And an elastic piece that is integrally formed with the elastic member and urges the outer ring of the bearing in the axial direction.

According to the present invention, the snap ring is simply fitted into the circumferential groove of the housing, and thereafter, the elastic piece integrally provided on the snap ring can apply an appropriate preload to the bearing in the axial direction. To remove the bearing gap,
There is no need to carry out new work and to install members. Further, the size can be reduced. Further, since the one-piece member is sufficient, the manufacturing cost can be reduced by reducing the number of parts.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT A preferred embodiment of the present invention will be described with reference to the accompanying drawings. FIG. 1 is a schematic sectional view of an electric power steering apparatus according to an embodiment of the present invention. With reference to FIG. 1, in this electric power steering apparatus (hereinafter simply referred to as a power steering apparatus), a first steering shaft 2 as an input shaft to which a steering wheel 1 is attached, a rack and pinion mechanism, etc. The second steering shaft 3 as an output shaft connected to the steering mechanism (not shown) is coaxially connected via the torsion bar 4.

The gear housing 5 that supports the first and second steering shafts 2 and 3 is made of, for example, an aluminum alloy,
It is attached to the vehicle body (not shown). The gear housing 5 is composed of an upper housing 6 and a lower housing 7 which are fitted to each other. Specifically, the lower housing 7 has a tubular shape, and the upper end portion 7a thereof has an upper housing 6
Is fitted to the annular step portion 6a on the outer periphery of the lower end of the. The lower housing 7 is a worm gear mechanism 8 as a reduction gear mechanism.
The upper housing 6 houses the torque sensor 9, the control board 10, and the like.

As shown in FIG. 2, the worm gear mechanism 8 has, for example, a spline 3 on the rotary shaft 32 of the electric motor M.
3 and the like are connected to each other via a joint mechanism 33 formed on the inner peripheral portion, and a worm shaft 11 meshes with the worm shaft 11, and as shown in FIG. 1, an axially intermediate portion of the second steering shaft 3. And a worm wheel 12 which is integrally rotatable and whose axial movement is restricted. Although not shown, the worm shaft 11 is rotatably supported in the lower housing 7 via a pair of bearings.

The worm wheel 12 includes an annular core metal 12a that is integrally rotatably coupled to the second steering shaft 3, and a synthetic resin member 12b that is provided around the core metal 12a and has teeth formed on its outer peripheral portion. Is equipped with. The cored bar 12a is, for example, inserted into the mold during resin molding of the synthetic resin member 12b. The second steering shaft 3 is the worm wheel 1
It is rotatably supported by first and second rolling bearings 13 and 14 which are arranged so as to sandwich 2 above and below in the axial direction.

The outer ring 15 of the first rolling bearing 13 has a bearing holding hole 16 in the cylindrical projection 6b at the lower end of the upper housing 6.
It is fitted and retained in. The upper end surface portion of the outer ring 15 is in contact with an annular step portion 17 serving as the bottom of the bearing holding hole 16, and is restricted from moving axially upward with respect to the upper housing 6. On the other hand, the inner ring 18 of the first rolling bearing 13
Are fitted onto the second steering shaft 3 by an interference fit. The lower end surface of the inner ring 18 is in contact with the upper end surface of the core metal 12 a of the worm wheel 12.

The outer ring 19 of the second rolling bearing 14 is fitted and held in the bearing holding hole 20 of the lower housing 7. The lower end surface portion of the outer ring 19 abuts on an annular step portion 21 at the lower end of the lower housing 7, and movement of the lower portion 7 in the axial lower direction is restricted. The inner ring 22 of the second rolling bearing 14 is attached to the second steering shaft 3 such that the inner ring 22 can rotate integrally and its relative movement in the axial direction is restricted.
The inner ring 22 is sandwiched between a step portion 23 of the second steering shaft 3 and a nut 24 that is fastened to the screw portion of the second steering shaft 3.

The torsion bar 4 penetrates the first and second steering shafts 2 and 3. The upper end 4a of the torsion bar 4
Is connected to the first steering shaft 2 by a connecting pin 25 so as to be integrally rotatable, and the lower end portion 4b of the torsion bar 4 is connected to the second steering shaft 3 by a connecting pin 26 so as to be integrally rotatable. The lower end of the second steering shaft 3 is connected to a steering mechanism such as a rack and pinion mechanism via an intermediate shaft (not shown). The connecting pin 25 includes a third steering shaft 27 arranged coaxially with the first steering shaft 2 and a third steering shaft 27.
It is connected so as to be able to rotate integrally with. The third steering shaft 27 penetrates through a tube 28 that forms a steering column.

The upper portion of the first steering shaft 2 is rotatably supported by the upper housing 6 via a third rolling bearing 29, which is, for example, a needle roller bearing. The reduced diameter portion 30 on the lower portion of the first steering shaft 2 and the hole 31 on the upper portion of the second steering shaft 3 are
The first and second steering shafts 2 and 3 are fitted with a predetermined play in the rotation direction so as to restrict the relative rotation of the first and second steering shafts 2 and 3 within a predetermined range. Then, referring to FIG. 2, the worm shaft 1
1 is rotatably supported by fourth and fifth rolling bearings 34 and 35 held by the lower housing 7. The fourth and fifth rolling bearings 34 and 35 are, for example, ball bearings.

Inner rings 36 and 37 of the fourth and fifth rolling bearings 34 and 35 are fitted to the corresponding constricted portions of the worm shaft 11. In addition, the fourth and fifth rolling bearings 34,
The outer rings 38 and 39 of 35 are the bearing holding holes 4 of the lower housing 7.
0 and 41 respectively. Further, the outer ring 38 of the fourth rolling bearing 34 that supports the one end 11 a (the end opposite to the joint) of the worm shaft 11 is the step 4 of the lower housing 7.
It is in contact with 2 and is positioned. On the other hand, the inner ring 36 of the fourth rolling bearing 34 has the positioning step portion 4 of the worm shaft 11.
The other end 11 of the worm shaft 11 is brought into contact with the other end 11 of the worm shaft 11.
Movement to side b is restricted.

An inner ring 37 of a fifth rolling bearing 35 that supports the vicinity of the other end 11b (joint side end) of the worm shaft 11.
By contacting the positioning step portion 44 of the worm shaft 11, the movement of the worm shaft 11 toward the one end 11a side is restricted. Further, the outer ring 39 of the fifth rolling bearing 35 is fixed to the fourth rolling bearing 3 by the screw member 45 for adjusting the preload.
It is urged to the 4 side. The screw member 45 is screwed into the screw hole 46 formed in the lower housing 7,
While applying a preload to the pair of rolling bearings 34, 35,
The worm shaft 11 is axially positioned.

In the screw hole 46, one is formed along the screw member 45.
Or a plurality of pins 47 are press-fitted to prevent the screw member 45 from rotating, so that the screw member 45
Is fixed in the axial direction. Specifically, as shown in FIG. 3, a groove 48 for pin press-fitting extending in the depth direction of the screw hole 46 is formed in the inner peripheral surface portion of the screw hole 46 of the lower housing 7 in advance, and this recess is formed. The pin 47 is pressed into the groove 48. The recessed groove 48 for press-fitting the pin 47 may be formed on either the inner peripheral surface of the screw hole 46 or the outer peripheral surface of the screw member 45. Moreover, in FIG.
Reference numeral a is a hexagonal hole for operating the screw member 45. Further, the pin 47 may be a spring pin as shown in FIG. 4 (a) or a serration pin as shown in FIG. 4 (b).

According to this embodiment, after adjusting the preload amount by the screw member 45, the screw member 45 is fixed by driving the pin 47 along the screw hole 46. However, when the pin 47 is driven, Since the screw member 45 does not rotate, it is not necessary to perform adjustment many times, and the adjustment work is facilitated. Further, in the conventional locking method using the lock nut, the screw member is elongated by the amount by which the lock nut is engaged, but in the present embodiment, the screw member 45 is shortened by the amount by which the lock nut is not used. Therefore, the space can be reduced, and as a result, the miniaturization can be achieved.

Next, FIG. 5 is a sectional view of a main part of an electric power steering apparatus according to another embodiment of the present invention. With reference to FIG. 5, the present embodiment is different from the embodiment of FIG.
In the embodiment shown in FIG. 2, the screw member 45 for adjusting the preload and the pin 47 as a fixing member for fixing the screw member 45 are used. However, in the present embodiment, these functions are provided by the bearing of the lower housing 7. The point is that the snap ring 50 alone held by the circumferential groove 49 of the holding hole 41 is made to fulfill.

Referring to FIGS. 5 and 6, a plurality of bent elastic pieces 51 are integrally formed on the inner edge portion 50a of the snap ring 50 formed by sheet metal forming. These elastic pieces 5
1 is brought into elastic contact with the end surface of the outer ring 39 of the fifth rolling bearing 35 to apply a preload to both rolling bearings 34, 35. In the present embodiment, the snap ring 50 is attached to the lower housing 7
The elastic piece 51 provided integrally with the snap ring 50 allows the fourth and fifth parts to be fitted.
An appropriate preload can be applied to the rolling bearings 34 and 35. Therefore, it is not necessary to perform any work for removing the bearing gap, and the size can be reduced.

Further, since the snap ring 50 with the elastic piece 51 is a one-piece member, the manufacturing cost can be reduced by reducing the number of parts. In addition,
The present invention is not limited to the above-described embodiment, and for example, the outer ring 38 of the fourth rolling bearing 34 that supports the one end 11a of the worm shaft is biased toward the other end 11b to form both rolling bearings. A preload may be applied to 34 and 35. Besides, various modifications can be made within the scope of the claims of the present invention.

[Brief description of drawings]

FIG. 1 is a sectional view of a main part of an electric power steering apparatus according to an embodiment of the present invention.

FIG. 2 is a sectional view taken along line II-II in FIG.

FIG. 3 is a perspective view for explaining a state in which a pin is press-fitted to fix a preload adjusting screw member screwed into a screw hole of a housing.

4 (a) and 4 (b) are cross-sectional views respectively showing examples of press-fitted pins.

FIG. 5 is a sectional view of a main part of an electric power steering apparatus according to another embodiment of the present invention.

FIG. 6 is a perspective view of a snap ring with an elastic piece used for applying a preload to a bearing.

[Explanation of symbols]

3 Steering shaft (steering shaft) 7 Lower housing 8 Worm gear mechanism 11 Worm axis 12 worm wheel M electric motor 32 rotation axis 34 Fourth Rolling Bearing 35 Fifth Rolling Bearing 36,37 inner ring 38,39 outer ring 40,41 Bearing holding hole 42 steps 43,44 Positioning step 45 screw member 46 screw holes 47 pin 48 groove 49 circumferential groove 50 snap ring 51 elastic piece

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[Procedure amendment]

[Submission date] July 25, 2001 (2001.7.2)
5)

[Procedure Amendment 1]

[Document name to be amended] Statement

[Correction target item name] 0013

[Correction method] Change

[Correction content]

[0013] The worm gear mechanism 8, as shown in FIG. 2, a worm which is connected via a joint mechanism 33 to the rotary shaft 32 for example, spline etc. <br/> is formed on the inner peripheral portion of the electric motor M A shaft 11 and a worm wheel 12 that meshes with the worm shaft 11 and is integrally rotatable with an axially intermediate portion of the second steering shaft 3 and whose axial movement is restricted are provided as shown in FIG. Although not shown, the worm shaft 11 is rotatably supported in the lower housing 7 via a pair of bearings.

   ─────────────────────────────────────────────────── ─── Continued front page    F-term (reference) 3D033 CA02 CA04 CA05 CA28                 3J012 AB03 AB04 AB20 BB03 CB04                       DB14 EB14 FB10 HB02

Claims (2)

[Claims] 1. An electric power steering apparatus for transmitting the rotation of a rotary shaft of an electric motor for assisting steering to a steering mechanism through a worm shaft and a worm wheel, comprising: a housing for housing the worm shaft and the worm wheel; A bearing that is held in the bearing holding hole of the housing to rotatably support the worm shaft, a screw member that is screwed into the screw hole of the housing to apply preload to the outer ring of the bearing, and a fitting portion between the screw member and the screw hole. An electric power steering apparatus, comprising: a pin that is press-fitted along a screw hole to prevent a screw member from rotating. 2. An electric power steering apparatus for transmitting the rotation of a rotary shaft of an electric motor for assisting steering to a steering mechanism through a worm shaft and a worm wheel, and a housing for accommodating the worm shaft and the worm wheel, A bearing which is held in a bearing holding hole of the housing and rotatably supports the worm shaft, a snap ring which is held in a circumferential groove formed in the housing in the vicinity of the bearing holding hole, and a snap ring which is integrally formed with the snap ring. An electric power steering apparatus comprising: an elastic piece for urging an outer ring of a bearing in an axial direction.