JP2001233224A - Electric power steering device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce backlash quantity of an engage part between a worm and a worm wheel by a coil spring urging a rolling bearing and improve durability of the coil spring. SOLUTION: A coil spring 17 is wound around a rolling bearing 12, supporting a worm 71 interlocked with rotation of a motor 6 for assisting the steering in a housing 8, in such a way an axis thereof being circular. The rolling bearing 12 is energized to the radial direction by the coil spring 17. Thus, backlash quantity of an engage part of the worm 71 and a worm wheel 72 can be reduced.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

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

[0002]

2. Description of the Related Art In the steering of a motor vehicle, the steering operation of a steering wheel disposed inside a vehicle compartment is performed by turning the steering wheel (generally, a front wheel) outside the vehicle compartment for steering. This is done by telling the steering mechanism.

FIG. 6 is a sectional view of a conventional electric steering apparatus, and FIG. 7 is a sectional view of a speed reduction mechanism. As an electric steering device for an automobile, for example, as shown in FIG. 6, a first steering shaft 10 connected to a steering wheel 100 for steering is used.
1, a second steering shaft 103 whose upper end is coaxially connected to a lower end of the steering shaft 101 via a torsion bar 102, and a lower end of which is connected to a steering mechanism connected to wheels. By rotating, the first steering shaft 101
A torque sensor 104 for detecting the torque applied to the torsion bar 102 by the torsion generated on the torsion bar 102, a steering assist motor 105 driven based on the detection result of the torque sensor 104, and an output shaft of the motor 105,
A deceleration mechanism having a worm 106 and a worm wheel 107 for decelerating the rotation of the output shaft and transmitting the rotation to the second steering shaft 103, and controlling the operation of the steering mechanism according to the rotation of the steered wheels 100 by the motor 105. Assisted by the rotation of
It is configured to reduce the burden on the driver for steering.

The worm 106 constituting the speed reduction mechanism is supported by a fitting hole of a housing 110 via a pair of rolling bearings 108, 108 as shown in FIG. The shaft 103 is connected to a housing 110 via a pair of rolling bearings 109, 109.
, And is prevented from moving in the radial and axial directions.

When the worm 106 and the worm wheel 107 are used as described above, the distance between the rotation centers of the worm 106 and the worm wheel 107 and the rolling bearings 108 and 109 are fitted to reduce the amount of backlash at the meshing portion. A worm 106 processed so that the center-to-center distance of the mating fitting holes is matched within an allowable range;
Worm wheel 107, rolling bearings 108, 109,
Although the second steering shaft 103 and the housing 110 are selected and assembled, the assembling takes a lot of time, and the amount of backlash due to increased wear of the teeth of the worm 106 and the worm wheel 107 is increased. Increased, and improvement measures were requested.

Further, a rubber ring is provided between the outer peripheral surfaces of the rolling bearings 108, 108 for supporting the worm 106 connected to the output shaft of the motor 105 and the fitting hole of the housing 110, and the rubber ring has an elastic restoring force. 2. Description of the Related Art There is known an electric steering device configured to bias a worm 106 in a radial direction so as to reduce an amount of backlash at a meshing portion of the worm 106 and the worm wheel 107.

[0007]

However, in the conventional electric steering apparatus constructed so as to reduce the amount of backlash by using the rubber ring as described above, the outer periphery of the rolling bearing each time steering is performed. Since a load in the radial direction and a rotational torque are applied to the rubber ring provided on the rubber ring, the rubber ring is liable to be deteriorated, such as set, and the deterioration increases the amount of backlash. Since the elastic restoring force of the ring itself urges the worm, the degree of freedom in setting the preload by this urging is relatively low, and when the rubber ring is assembled by expanding the diameter, the rubber ring may be damaged. There were many. In addition, there is a fear that it may be deteriorated by a lubricant such as grease.

The present invention has been made in view of such circumstances, and has a configuration in which a coil spring is wound around the outer periphery of a rolling bearing so that its axis is annular, so that a backlash is generated by the coil spring. It is an object of the present invention to provide an electric steering device that can reduce the amount of the coil spring, improve the durability of the coil spring, and relatively increase the degree of freedom in setting a preload. I do.

Further, by setting the winding angle of the coil spring at 30 ° to 75 ° with respect to the axis, the amount of change in the elastic restoring force with respect to the amount of bending can be relatively reduced.
An object of the present invention is to provide an electric steering device capable of reducing the resistance of a meshing portion between a small-diameter gear and a large-diameter gear.

[0010]

According to a first aspect of the present invention, an electric steering apparatus includes a small-diameter gear rotatably supported in a housing via a rolling bearing in association with the rotation of a steering assist motor. An electric steering device, comprising: a large-diameter gear meshed with a small-diameter gear, and attached to a steering shaft disposed non-parallel to the rotation center of the small-diameter gear, and assisting steering by rotation of the motor. A coil spring is wound around the outer periphery of the bearing so that its axis becomes annular.

In the first invention, when the small-diameter gear is supported in the housing, the coil spring is inserted into the housing together with the rolling bearing while the coil spring is slightly bent between the inner peripheral portion and the outer peripheral portion. Support and apply a radial preload to the small diameter gear. Due to this preload, the small-diameter gear is urged to the large-diameter gear, and the amount of backlash at the meshing portion between the small-diameter gear and the large-diameter gear can be reduced. In addition, since the coil spring is wound so that its axis becomes annular, the durability of the coil spring can be increased as compared with the conventional one using a rubber ring, and the preload can be set freely. The degree can be relatively increased, and the coil spring can be prevented from being damaged during assembly.

According to a second aspect of the present invention, the winding angle of the coil spring is 30 ° to 75 ° with respect to the axis.
It is characterized by being.

In the second invention, since the coil spring is inclined at an angle of 30 ° to 75 ° between the inner peripheral portion and the outer peripheral portion, the amount of change in the elastic restoring force with respect to the amount of bending is relatively small. Thus, the resistance of the meshing portion between the small-diameter gear and the large-diameter gear can be reduced. Accordingly, the return resistance of the steered wheels after the motor assists the steering can be reduced, and the steered wheels can be returned smoothly.

[0014]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail with reference to the drawings showing the embodiments. FIG. 1 is a sectional view of an electric steering apparatus according to the present invention. The electric steering device has a first steering shaft 2 having one end connected to a steered wheel 1 for steering and a cylindrical portion at the other end, and a first steering shaft 2 inserted into the cylindrical portion and having one end connected to the steering shaft 2. A torsion bar 3 coaxially connected to one end and twisted by the action of steering torque applied to the steering wheel 1, one end of which is inserted around the cylindrical portion, and the other end of which is connected to the other end of the torsion bar 3. A steering torque applied to the steered wheels 1 is detected based on a relative rotational displacement of the second steering shaft 4 coaxially connected and the first and second steering shafts 2 and 4 corresponding to the torsion of the torsion bar 3. Torque sensor 5, a steering assist motor 6 driven based on the torque detected by the torque sensor 5, and the second steering shaft 4 Small-diameter gear (hereinafter referred to as worm) 71 for transmission and The diameter gear (hereinafter referred to as a worm wheel) speed reduction mechanism 7 with 72, and a housing 8 in which the torque sensor 5 and the reduction mechanism 7 is housed, the motor 6 is attached to the housing 8.

The housing 8 has a first housing portion 8a for housing the torque sensor 5 and a second housing portion 8b continuous with the housing portion 8a and housing the worm wheel 72.
And a third accommodating portion 8c which is continuous with the accommodating portion 8b and accommodates the worm 71.

FIG. 2 is a sectional view of the speed reduction mechanism. The accommodation portion 8c is elongated in the axial direction of the worm 71, and a first fitting hole 81 is provided at one longitudinal end of the worm 71, and the holding cylinder 9 is fitted into the fitting hole 81 by press fitting. Further, a second fitting hole 82 and a screw hole 83 continuous with the fitting hole 82 are provided at the other end of the accommodation portion 8c.
Threaded ring 10 is screwed into. Further, a contact portion 84 is provided at the middle of the accommodation portion 8c in the longitudinal direction, with which one end of a second bearing described later contacts via a substantially semicircular seat 11.

Further, the motor 6 having a case communicating with the third housing portion 8c is attached to the housing 8.

The speed reduction mechanism 7 includes an output shaft 60 of the motor 6.
A worm 71 having a shaft portion 71a connected to the
Worm wheel 7 fitted and fixed in the middle of the steering shaft 4
The rotation of the output shaft 60 is reduced by the engagement of the worm 71 and the worm wheel 72, and the second
, And transmitted from the second steering shaft 4 to, for example, a rack-and-pinion type steering mechanism (not shown) via a universal joint.

The worm 71 is disposed so as to intersect with the axis of the second steering shaft 4. The inner race of the first rolling bearing 12 is fitted to a shaft portion 71 a at one end of the worm 71. When the outer ring is loosely fitted into the holding cylinder 9, the shaft portion 71 a at one end is rotatably supported by the first fitting hole 81, and the shaft portion 71 a at the other end is connected via the second rolling bearing 13. The screw ring 10 rotatably supported by the second fitting hole 82 and screwed into the screw hole 83 comes into contact with the outer ring of the second rolling bearing 13, and the screw ring 10, the seat body 1
The first and contact portions 84 restrict the movement of the second rolling bearing 13 in the axial direction. Also, the shaft portion 71a at the other end
Are spline-fitted to the inner surface of the connecting cylinder 14 so that the output shaft 6
Connected to 0. The retaining ring 15 is provided on the shaft 71a at one end, and the retaining ring 15 restricts the worm 71 from moving in the opposite direction to the motor 6.

FIG. 3 is an enlarged sectional view taken along line III-III of FIG. The first rolling bearing 12 is capable of moving in the radial direction with respect to the holding cylinder 9 by an amount of a fitting gap by loose fitting into the holding cylinder 9, and the holding cylinder 9 has a plurality of annular grooves 16 on its inner peripheral surface. , 16 are provided apart from each other, and these annular grooves 1 are provided.
Coil springs 17, 17 that come into contact with the outer peripheral surface of the first rolling bearing 12 are fitted and held in the first and second rolling bearings 6, 16 so that their axial centers are annular.

FIG. 4 is a front view of the coil spring, and FIG. 5 is a diagram showing the relationship between the amount of deflection of the coil spring and the elastic restoring force. The coil springs 17, 17 are formed by winding a metal wire having a wire diameter of 0.1 to 0.2 mm in a coil shape. The coil springs 17, 17 are wound such that their axes are annular. Both ends are connected. The outer peripheral portions of these coil springs 17 are held in the annular grooves 16, the inner peripheral portion contacts the outer peripheral surface of the rolling bearing 12, and the rolling bearing 12 is bent by bending between the inner peripheral portion and the outer peripheral portion. Is urged in the radial direction, and the worm 71 is urged toward the meshing portion with the worm wheel 72. Further, the coil spring 17 is inclined such that the winding angle is 30 ° to 75 ° with respect to the axis, and when the preload is applied as shown in FIG. 5, the change amount of the elastic restoring force with respect to the bending amount is relatively small. I have less.

In the embodiment, when the worm 71 is incorporated, for example, the coil spring 17 is fitted and held in the annular grooves 16, 16 so that the axial center thereof is annular, and a first rolling bearing is provided on the inner peripheral surface thereof. The worm 71 is inserted from the second fitting hole 82 into the third accommodating portion 8c in a state where the holding cylinder 9 having the loosely fitted 12 is press-fitted into the first fitting hole 81 of the housing 8 and attached. , One end side shaft portion 71 of the worm 71
a to the inner ring of the first rolling bearing 12, and the second fitting hole 82 and the other end side shaft portion 7 of the worm 71.
1a, the second rolling bearing 13 is fitted, and the screw ring 10 is screwed into the screw hole 83, whereby the outer ring of the second rolling bearing 13 is sandwiched between the seat body 11 and the screw ring 10 and the worm 7
1 is restricted from moving in the axial direction.

The inner peripheral portion of the coil spring 17 for urging the built-in worm 71 abuts on the first rolling bearing 12, and radially urges the rolling bearing 12 from the entire circumferential position to thereby provide the worm 71. To the meshing portion with the worm wheel 72, the amount of backlash between the meshing portion of the worm 71 and the worm wheel 72 can be reduced, and the amount of wear of the teeth of the worm 71 and the worm wheel 72 increases. The backlash amount can be reduced even when the meshing state changes over time due to the worm wheel 72 made of synthetic resin contracting due to a low temperature in winter or the like. Further, since the coil spring 17 is wound so that its axis becomes annular,
The durability of the coil spring 17 can be increased as compared with a conventional one using a rubber ring. Further, in the state where the preload is applied, since the amount of change in the elastic restoring force with respect to the amount of deflection of the coil spring 17 is relatively small, the meshing resistance of the worm 71 and the worm wheel 72 can be reduced, and the motor 6 assists the steering. The return resistance of the rear steered wheels can be reduced.

In the above-described embodiment, the holding cylinder 9 fixed to the housing 8 is provided, and the coil spring 17 is held in the holding cylinder 9. However, the annular groove of the holding cylinder 9 is eliminated and the rolling bearing is provided. The coil spring 17 may be held on the rolling bearing 12 by providing the annular groove 16 on the outer peripheral surface of the housing 12.
At least one annular groove 16 may be provided in the first fitting hole 81 or the outer periphery of the first rolling shaft 12, and the coil spring 17 may be held in the annular groove 16. However, by providing the holding cylinder 9 as in the embodiment, the coil spring 17 and the first rolling bearing 12 can be easily incorporated into the housing 8.

The coil spring 17 is formed by joining both ends of the coil spring to form an annular shape. However, without joining both ends of the coil spring, the coil spring becomes substantially C-shaped in the annular groove 16, for example. It may be formed into an annular shape by winding as described above. In addition to a plurality of coil springs 17,
It may be one.

The speed reduction mechanism 7 of the embodiment described above is a worm gear provided with a small gear 71 as a worm and a large gear 72 as a worm wheel, and a small gear 71 as a hypoid pinion and a hypoid wheel. May be a hypoid gear provided with the large gear 72.

[0027]

According to the first aspect of the present invention, the coil spring is wound so that its axis becomes annular, and the rolling bearing is urged in the radial direction. Therefore, the backlash of the meshing portion between the small diameter gear and the large diameter gear is achieved. The amount can be reduced favorably, and the coil spring is wound so that its axis is annular, so that the durability of the coil spring is increased as compared with the conventional one using a rubber ring. It is possible to prevent the noise caused by the backlash from leaking into the cabin of the automobile over a long period of time, and it is possible to relatively increase the degree of freedom of setting the preload, and the coil spring is damaged during assembly. Can be prevented.

According to the second aspect, the coil spring is inclined at an angle of 30 ° to 75 ° between the inner peripheral portion and the outer peripheral portion, so that the amount of change in the elastic restoring force with respect to the amount of bending can be relatively reduced. Therefore, the meshing resistance of the small-diameter gear and the large-diameter gear can be reduced, the return resistance of the steered wheels after the motor assists the steering can be reduced, and the steered wheels can be returned smoothly.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of an electric steering device according to the present invention.

FIG. 2 is a sectional view of a speed reduction mechanism of the electric steering apparatus according to the present invention.

FIG. 3 is an enlarged sectional view taken along line III-III of FIG. 2;

FIG. 4 is a front view of a coil spring of the electric steering device according to the present invention.

FIG. 5 is a diagram showing the relationship between the amount of deflection of a coil spring and the elastic restoring force of the electric steering device according to the present invention.

FIG. 6 is a sectional view of a conventional electric steering device.

FIG. 7 is a cross-sectional view of a speed reduction mechanism of a conventional electric steering device.

[Explanation of symbols]

 Reference Signs List 4 steering shaft 6 motor 7 reduction mechanism 71 small diameter gear (worm) 72 large diameter gear (worm wheel) 8 housing 12 first rolling bearing 17 coil spring

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Kunihiro Oka 3-5-8 Minamisenba, Chuo-ku, Osaka City, Osaka Prefecture Inside Koyo Seiko Co., Ltd. (72) Kazutoshi Yamamoto 3-5-Minamisenba, Chuo-ku, Osaka City, Osaka No. 8 Koyo Seiko Co., Ltd. F-term (reference) 3D033 CA02 CA04 CA22

Claims (2)

[Claims] 1. A small-diameter gear rotatably supported in a housing via a rolling bearing in conjunction with the rotation of a steering assist motor, meshes with the small-diameter gear, and is non-parallel to the rotation center of the small-diameter gear. In a motor-driven steering device having a large-diameter gear attached to a steering shaft provided, and assisting steering by rotation of the motor, a coil spring is provided around the outer periphery of the rolling bearing so that the axis of the coil spring is annular. An electric steering device characterized by being wound around. 2. The electric steering apparatus according to claim 1, wherein a winding angle of the coil spring is 30 ° to 75 ° with respect to an axis.