JP2001233225A - 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 energizing a rolling bearing and improve durability of the coil spring. SOLUTION: A sliding bearing 13 supports a worm 71 interlocked with rotation of a motor 6 for assisting the steering in a housing 8. A coil spring 18 is wound around a periphery of the sliding bearing 13 in such a way an axis thereof being circular. The sliding bearing 13 is energized to the radial direction by the coil spring 18. 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 shown in FIG. 6, as an electric steering device for an automobile, for example, a first steering shaft 1 connected to a steered wheel 100 for steering is used.
01 and a torsion bar 102 at the lower end of the steering shaft 101.
A second steering shaft 103 having an upper end coaxially connected thereto and a lower end connected to a steering mechanism connected to wheels.
By rotating the steered wheels 100, the first steering shaft 10
A torque sensor 104 for detecting torque applied to the torsion bar 102 by torsion generated in the torsion bar 102, a steering assist motor 105 driven based on a detection result of the torque sensor 104, and an output shaft of the motor 105, The rotation of the output shaft is reduced and the second steering shaft 103
106 and worm wheel 107 transmitting to
The rotation of the motor 105 assists the operation of the steering mechanism in accordance with the rotation of the steered wheels 100, and reduces the burden on the driver for steering.

A worm 106 constituting a speed reduction mechanism is shown in FIG.
As shown in the figure, the second steering shaft 103, which is supported by the fitting hole of the housing 110 via a pair of rolling bearings 108, 108 and is provided with the worm wheel 107, has 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 made of rubber is provided between the outer peripheral surfaces of the rolling bearings 108, 108 supporting the worm 106 connected to the output shaft of the motor 105 and the fitting hole of the housing 110, or the worm 106 The rubber ring is provided between the inner peripheral surfaces of the rolling bearings 108, 108 that support the worm 106 and the shaft of the worm 106, and the worm 106 is urged in the radial direction by the elastic restoring force of the rubber ring. There is known an electric steering device configured to reduce the amount of backlash of the meshing portion of the 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 a slide bearing supports a small-diameter gear that is interlocked with the rotation of a steering assist motor, and a coil spring is mounted around the outer periphery of the slide bearing. Or the end of the small-diameter gear opposite to the motor is supported by a slide bearing, and the coil spring is wound around the outer periphery of the slide bearing. By adopting a configuration in which a rolling bearing is supported at the motor side end, the amount of backlash can be reduced by the coil spring, and the durability of the coil spring can be improved, and the preload load can be improved. It is an object of the present invention to provide an electric steering device capable of relatively increasing the degree of freedom in setting the steering angle.

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 via a bearing in a housing in conjunction with the rotation of a steering assist motor, and the small-diameter gear. An electric steering device, which includes a large-diameter gear that is engaged with a gear and that is attached to a steering shaft that is arranged non-parallel to the rotation center of the small-diameter gear, and that assists steering by rotation of the motor. A sliding bearing, characterized in that a coil spring is wound around the outer periphery of the sliding bearing so that its axis becomes annular.

In the electric steering apparatus according to a third aspect of the present invention, an end of the small-diameter gear opposite to the motor is supported by the slide bearing, and a motor-side end of the small-diameter gear is supported by a rolling bearing. It is characterized by.

In the first and third inventions, when the small-diameter gear is supported in the housing, the coil spring is slightly bent between the inner peripheral portion and the outer peripheral portion. At the same time, it is inserted and supported in the housing to apply a preload in the radial direction to the small-diameter gear. This preload urges the small-diameter gear to the large-diameter gear, thereby reducing the amount of backlash at the meshing portion between the small-diameter gear and the large-diameter gear, and using a sliding bearing. Since the coil spring is wound so that the axis becomes annular, the circumference of the bearing of the housing can be reduced in size and the weight can be reduced. In addition, since the coil spring is formed by winding the coil spring in a ring shape, the durability of the coil spring can be increased as compared with the conventional one using a rubber ring, and the degree of freedom in setting the preload is increased. It can be made relatively large, and it is possible to prevent the coil spring from being damaged during assembly.

[0013] In the electric steering apparatus according to the second invention, the winding angle of the coil spring is 30 ° to 75 ° with respect to the axis.
It is characterized by being.

According to the second aspect of the present 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 deflection is relatively small. Thus, the resistance of the meshing portion between the small-diameter gear and the large-diameter gear can be reduced. Therefore, the return resistance of the steered wheels after the motor assists the steering can be reduced, and the steered wheels can be returned smoothly.

[0015]

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 mounted on 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. An oilless bush 12 is fitted and fixed to a shaft portion 71a at one end thereof. The sliding bearing 13 is rotatably fitted therein, and the sliding bearing 13 is loosely fitted in the holding cylinder 9, whereby the shaft 71 a at one end is rotatably supported in the first fitting hole 81. , The other end of the shaft portion 71a is
Is rotatably supported in the second fitting hole 82 via
The screw ring 10 screwed into the screw hole 83 is a rolling bearing 1
4, the screw ring 10, the seat body 11, and the contact portion 84 restrain the rolling bearing 14 from moving in the axial direction. Also, the shaft 71a at the other end is
Are connected to the output shaft 60 by spline fitting. In addition, a retaining ring 16 is provided on the shaft portion 71 a at one end, and the retaining ring 16 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 sliding bearing 13 is loosely fitted in the holding cylinder 9 and is movable in the radial direction with respect to the holding cylinder 9 by an amount of the fitting gap, and a plurality of annular grooves 17 and
And coil springs 18, 18 which come into contact with the inner peripheral surface of the holding cylinder 9 in these annular grooves 17, 17.
Are fitted and held so that their axes are annular. Further, pin holes 13a, 9a are provided in a part of the sliding bearing 13 and the holding cylinder 9 in the circumferential direction, respectively. By inserting a detent pin 19 into the pin holes 13a, 9a, the sliding bearing 13 is held. Rotation with respect to the cylinder 9 is prevented, and wear of the coil springs 18, 18 due to the relative rotation is prevented.

FIG. 4 is a front view of the coil spring, and FIG. 5 is a view showing the relationship between the amount of deflection of the coil spring and the elastic restoring force. The coil spring 18 is formed by winding a metal wire having a wire diameter of 0.1 to 0.2 mm in a coil shape.
18 is wound so that its axis becomes annular, and its both ends are connected. These coil springs 18, 18 have their inner peripheral portions held by the annular groove 17 and their outer peripheral portions held by the holding cylinder 9.
Contacting the inner peripheral surface of the worm 7 to urge the sliding bearing 13 in the radial direction by bending between the inner peripheral portion and the outer peripheral portion.
1 is urged toward a meshing portion with the worm wheel 72.
The coil spring 18 has a winding angle of 30 ° with respect to the axis.
The angle of inclination is set to be between 75 ° and 75 °, and the amount of change in the elastic restoring force with respect to the amount of deflection is relatively small.

In the embodiment, when the worm 71 is incorporated, for example, a holding cylinder 9 in which a sliding bearing 13 in which a coil spring 18 is fitted and held in an annular groove 17 is loosely fitted.
Is pressed into the first fitting hole 81 of the housing 8 and the worm 71 is inserted into the third housing portion 8c from the second fitting hole 82, and one end side shaft portion 71a of the worm 71 is inserted.
The bush 12 fitted to and fixed to the sliding bearing 13 is fitted and supported, and the rolling bearing 14 is fitted to the second fitting hole 82 and the other end side shaft portion 71a of the worm 71, and the screw ring 10 is By being screwed into the screw hole 83, the outer ring of the rolling bearing 14 is sandwiched between the seat body 11 and the screw ring 10 to restrict the movement of the worm 71 in the axial direction.

The coil spring 18 that urges the built-in worm 71 has an inner peripheral portion that abuts against the sliding bearing 13 and urges the sliding bearing 13 from all circumferential positions. The amount of backlash at the meshing portion can be reduced. In addition, even when the meshing state changes over time due to an increase in the amount of wear of the teeth of the worm 71 and the worm wheel 72 and a contraction of the synthetic resin worm wheel 72 due to a low temperature in winter, etc., the backlash amount is reduced. Can be reduced.

Further, since the coil spring 18 is wound so that its axis becomes annular, the durability of the coil spring 18 can be increased as compared with the conventional one using a rubber ring, , The degree of freedom in setting the preload can be relatively increased, and the coil spring can be prevented from being damaged during assembly. Further, since the coil spring 18 is provided around the outer periphery of the slide bearing 13, the size of the housing 8 around the bearing can be reduced, and the weight can be reduced. 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 18 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 18 is held on the slide bearing 13 that is loosely fitted to the holding cylinder 9. Instead of providing the annular groove 17, the annular groove 17 is provided on the inner peripheral surface of the holding cylinder 9, and the coil spring 18 is provided.
May be held in the holding cylinder 9, or the holding cylinder 9 may be eliminated, and at least one annular groove 17 may be provided in the first fitting hole 81 of the housing 8 or the outer periphery of the slide bearing 13. The coil spring 18 may be held in the groove 17. However, by providing the holding cylinder 9 as in the embodiment, the coil spring 18 and the slide bearing 13 can be easily incorporated into the housing 8. In addition, the bush 12 is eliminated, and the one end side shaft portion 71a of the worm 71 is mounted on the sliding bearing 1.
3 may be directly fitted.

The coil spring 18 is formed in a ring shape by connecting both ends thereof. However, the coil spring is not connected to the both ends so that the axis of the coil spring becomes substantially C-shaped in the annular groove 17, for example. It may be formed into an annular shape by winding. Further, the number of the coil springs 18 may be one in addition to the plurality.

The speed reduction mechanism 7 of the embodiment described above is a worm gear having 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.

[0029]

According to the first and third aspects of the invention, the coil spring is wound so that its axis becomes annular, and the coil spring urges the slide bearing in the radial direction. The amount of backlash at the meshing portion of the radial gear can be reduced favorably, and a sliding bearing is used, and a coil spring is provided around the outer periphery of the sliding bearing. Can be achieved.

Further, since the coil spring is wound so that its axis is annular, the durability of the coil spring can be increased as compared with the conventional one using a rubber ring, and the backlash can be extended over a long period of time. Can be prevented from leaking into the cabin of the automobile, the degree of freedom in setting the preload can be relatively increased, and the coil spring can be prevented from being damaged during assembly.

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 made relatively small. 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 13 sliding bearing 18 coil spring

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

Claims (3)

[Claims] 1. A small-diameter gear rotatably supported via a bearing in a housing in conjunction with the rotation of a steering assist motor and meshed with the small-diameter gear, and are arranged non-parallel to the rotation center of the small-diameter gear. In a motor-driven steering device comprising a large-diameter gear attached to a steering shaft to be driven and assisting steering by rotation of the motor, the bearing is a slide bearing, and a coil spring is provided around the outer periphery of the slide bearing. An electric steering device, wherein the shaft is wound so as to be annular. 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. 3. The electric type according to claim 1, wherein an end of the small-diameter gear opposite to the motor is supported by the slide bearing, and a motor-side end of the small-diameter gear is supported by a rolling bearing. Steering gear.