JP3639948B2 - Electric steering device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an electric steering apparatus using a motor as a generation source of steering assist force.
[0002]
[Prior art]
Automobile steering is performed by turning a steering wheel arranged inside the passenger compartment to a steering mechanism arranged outside the passenger compartment for steering the steering wheel (generally the front wheels). Done.
[0003]
FIG. 6 is a cross-sectional view showing a configuration of a conventional electric steering apparatus.
As shown in FIG. 6, for example, an electric steering apparatus for an automobile includes a first steering shaft 101 coupled to a steering wheel 100 for steering, and a lower end of the steering shaft 101 via a torsion bar 102. A torque applied to the first steering shaft 101 by rotating the steering wheel 100 and a second steering shaft 103 connected to a steering mechanism whose lower end is connected coaxially and whose lower end is connected to a wheel. Torque sensor 104 detected by the twist generated in bar 102, a steering assist motor driven based on the detection result of torque sensor 104, and the output shaft of the motor are connected to decelerate the rotation of the output shaft. A reduction mechanism having a worm 106 and a worm wheel 107 that transmits to the second steering shaft 103, and the operation of the steering mechanism in accordance with the rotation of the steering wheel 100. Assisted by the rotation of the over motor, it is configured to reduce the driver effort burden for steering.
[0004]
The worm 106 constituting the speed reduction mechanism is disposed so as to cross the axis of the second steering shaft 103, is supported by a fitting hole of the housing 108 via a pair of rolling bearings, and a worm wheel 107 is provided. The second steering shaft 103 is supported by a fitting hole of the housing 108 via a pair of rolling bearings 109, 109, and is prevented from moving in the radial direction and the axial direction.
[0005]
When the worm 106 and the worm wheel 107 are used in this way, the distance between the rotational centers of the worm 106 and the worm wheel 107 and the fittings in which the rolling bearings are fitted are fitted in order to reduce the backlash amount of the meshing portion. The worm 106, the worm wheel 107, the rolling bearing, the second steering shaft 103, and the housing 108 which are processed so that the distance between the centers of the joint holes coincides within an allowable range are selected and assembled.
[0006]
[Problems to be solved by the invention]
However, by selecting and assembling as described above, this assembly takes a lot of time, and the backlash amount increases due to increased wear on the teeth of the worm and worm wheel. As a result, the improvement measures were demanded.
[0007]
An object of the present invention is to provide an electric steering apparatus that can solve the above-described problems.
[0008]
[Means for Solving the Problems and Effects of the Invention]
According to a first aspect of the present invention, there is provided an electric steering apparatus in which an output of a steering assist motor is transmitted to a steering mechanism via a worm and a worm wheel meshing with the worm to assist the steering. The apparatus is characterized in that an elastic body and a holding groove for holding the elastic body are provided at a position facing the rotation area of the worm on the outer peripheral side of the worm wheel.
[0009]
In the first invention, the elastic body provided at the position facing the rotation area of the worm can be brought into contact with the tooth tip surface of the worm, and preload can be applied to the meshing portion by this contact. Thus, the backlash amount of the meshing portion can be satisfactorily suppressed without selecting and assembling, and the assembly time can be shortened and the cost can be reduced as compared with the case of selecting and assembling. Even when the wear of the teeth of the worm wheel increases, the backlash amount can be suppressed and the generation of rattling noise can be prevented. In addition, since the ring that fits and holds in the holding groove can be used as the elastic body, the elastic body can be easily and reliably held in the holding groove.
[0012]
The electric steering apparatus according to a second aspect of the invention is characterized in that the holding groove is provided at a position biased in the tooth width direction with respect to at least the central portion of the meshing area meshing with the worm.
[0013]
In the second aspect of the invention, since the meshing area of the worm wheel can be sufficiently secured, it is possible to satisfactorily prevent a decrease in the strength of the worm wheel teeth due to the holding groove.
[0014]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, the present invention will be described in detail with reference to the drawings illustrating embodiments thereof.
Embodiment 1
FIG. 1 is a cross-sectional view showing a configuration of a speed reduction mechanism and a motor portion of an electric steering apparatus according to the present invention, and FIG. 2 is an enlarged cross-sectional view showing a configuration of a speed reduction mechanism portion.
[0015]
Since the basic configuration of the electric steering apparatus is the same as that of the conventional electric steering apparatus shown in FIG. 6, the detailed description and description of the operation of the same configuration will be omitted.
[0016]
A metal worm 3 connected to the output shaft 1a of the steering assisting motor 1 and intersecting with the axis of the second steering shaft 2 and having teeth 30 on the outside, meshed with the worm 3, The worm wheel 4 of the speed reduction mechanism 5 having a worm wheel 4 fitted and fixed in the middle of the second steering shaft 2 is made of a synthetic resin having a plurality of teeth 40 meshing with the worm 3 on the outside. An annular tooth body 41 and a metal fitting body 42 fitted inside the annular tooth body 41 are provided, and a through hole 42a drilled in the center of the fitting body 42 has the second steering shaft. 2 is fitted. Further, by providing the synthetic resin annular tooth body 41, noise due to meshing with the worm 3 is reduced, and the workability of the teeth 40 is improved.
[0017]
FIG. 3 is an enlarged cross-sectional view showing the configuration of the speed reduction mechanism.
The tooth portion of the worm wheel 4 is provided with an annular holding groove 43 at a position biased to one side in the tooth width direction with respect to the meshing area A (shaded portion in FIG. 3) meshing with the worm 3. An elastic body 6 is held in the groove 43 so as to face the rotation region of the worm 3 and to come into contact with the tooth tip surface 30 a of the worm 3.
[0018]
In the meshing area A, the tooth surface 40a of the worm wheel 4 contacts the tooth surface 30b of the worm 3, and the rotation of the output shaft 1a is transmitted from the tooth surface 30b of the worm 3 to the tooth surface 40a of the worm wheel 4. It is inclined with respect to the center line X over both side positions in the tooth width direction with the center line X in the direction of the tooth width H as the center.
[0019]
The holding groove 43 is formed by cutting the tooth portion 40 in the tooth thickness direction from the tooth tip surface 40b to the tooth bottom surface 40c. The holding groove 43 may be deeper than the tooth bottom surface 40c.
[0020]
The elastic body 6 uses an O-ring made of synthetic rubber, and is fitted and held in the holding groove 43 by bending the elastic body 6. Further, the elastic body 6 is bent slightly by contact with the tooth tip surface 30a of the worm 3, and preload is applied to the meshing portion by its elastic restoring force. The elastic body 6 is detachable, but may be fixed by other fixing means such as an adhesive.
[0021]
Further, a fitting portion between the annular tooth body 41 and the fitting body 42, in other words, an outer surface of the fitting body 42 is provided with an uneven strip such as a spline in the middle in the axial direction thereof so as not to rotate relatively. is there.
[0022]
In the electric steering apparatus configured as described above, the elastic body 6 provided in the tooth portion 40 of the worm wheel 4 contacts the tooth tip surface 30a of the worm 3, and preload is applied to the meshing portion by this contact. Therefore, it is possible to satisfactorily suppress the backlash amount of the meshing portion without selecting and assembling as in the past, and it is possible to reduce the assembly time and reduce the cost compared to the case of selecting and assembling, Further, even when the wear of the teeth of the worm 3 and the worm wheel 4 increases, the backlash amount can be suppressed and the occurrence of rattling noise can be prevented.
[0023]
Further, since the elastic body 6 is fitted and held in the holding groove 43 provided in the tooth portion 40 of the worm wheel 4, the elastic body 6 can be easily and reliably held. Further, since the holding groove 43 is biased in the tooth width direction with respect to the meshing area A meshing with the worm 3 and is provided at a position outside the meshing area A, the strength of the teeth 40 of the worm wheel 4 is reduced by the holding groove 43. Can be prevented well.
[0024]
In the embodiment described above, the holding groove 43 is provided at a position displaced in the tooth width direction with respect to the meshing area A. However, the holding groove 43 may be provided at the position of the meshing area A. In this case, in order to reduce the strength reduction of the teeth 40 of the worm wheel 4, it is preferable to provide the holding grooves 43 at positions shifted in the tooth width direction with respect to the central portion of the meshing area A.
[0026]
Embodiment 2
FIG. 4 is an enlarged cross-sectional view showing the configuration of the speed reduction mechanism of the second embodiment.
In the second embodiment, at least the outer portion of the worm wheel 4 is divided at a position deviated to one side in the tooth width direction with respect to the meshing area A (shaded portion in FIG. 3), and the divided bodies 4a and 4b are divided. One side 4a is a transmission side in which the rotation of the output shaft 1a is transmitted from the worm 3 to the steering shaft 2 via the meshing area A, and the other side 4b is a non-transmission side, and the teeth of the divided bodies 4a and 4b are annular. A holding recess 44 (holding groove) is provided, and the elastic body 6 using an O-ring is held in the holding recess 44.
[0027]
The divided bodies 4a and 4b are coupled by a coupling means such as an adhesive or a mounting screw.
[0028]
Since other configurations and operations are the same as those of the first embodiment, a detailed description of the configurations and a description of the operations are omitted.
[0029]
Embodiment 3
FIG. 5 is an enlarged cross-sectional view showing the configuration of the speed reduction mechanism of the third embodiment.
In the third embodiment, a holding plate 7 provided with an annular recess 71 (holding groove) for holding the elastic body 6 on the outer peripheral surface is provided on one surface of the worm wheel 4 with an adhesive, a mounting screw or the like. The elastic body 6 is held in the recess 71 by being connected by a connecting means.
[0030]
In the third embodiment, since the holding plate 7 formed separately from the worm wheel 4 is coupled to the worm wheel 4, the strength of the teeth 40 of the worm wheel 4 due to holding the elastic body 6 is further reduced. Can be prevented.
[0031]
Since other configurations and operations are the same as those of the first embodiment, a detailed description of the configurations and a description of the operations are omitted.
[0032]
In the embodiment described above, the elastic body 6 made of synthetic rubber is used. However, the elastic body 6 may be made of synthetic resin.
[0033]
Further, in the embodiment, the worm wheel 4 is configured by fitting the fitting body 42 to the annular tooth body 41 made of synthetic resin, but the worm wheel 4 is entirely formed of a synthetic resin material or a metal material. It may be what was done.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view showing a configuration of a speed reduction mechanism and a motor portion of an electric steering apparatus according to the present invention.
FIG. 2 is an enlarged cross-sectional view showing a configuration of a speed reduction mechanism portion of the electric steering apparatus according to the present invention.
FIG. 3 is an enlarged sectional view showing a configuration of a speed reduction mechanism of the electric steering apparatus according to the present invention.
FIG. 4 is an enlarged cross-sectional view showing a configuration of a speed reduction mechanism according to a second embodiment of the electric steering apparatus according to the present invention.
FIG. 5 is an enlarged cross-sectional view showing a configuration of a speed reduction mechanism according to a third embodiment of the electric steering apparatus according to the present invention.
FIG. 6 is a cross-sectional view showing a configuration of a conventional electric steering apparatus.
[Explanation of symbols]
1 Motor 3 Worm 4 Worm wheel 43 Holding groove 6 Elastic body A Engagement area

Claims (2)

In the electric steering apparatus, the output of the steering assist motor is transmitted to the steering mechanism via a worm and a worm wheel meshing with the worm to assist the steering, and the worm on the outer peripheral side of the worm wheel An electric steering apparatus characterized in that an elastic body and a holding groove for holding the elastic body are provided at a position facing the rotation region. The retaining groove electric steering apparatus according to claim 1, wherein is provided a position offset to the tooth width direction with respect to at least the central portion of the coupling zone of the worm meshes.

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