JP4716074B2 - Electric power steering device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an electric power steering apparatus using an electric motor as a generation source of steering assist force.
[0002]
[Prior art]
The power steering apparatus for automobiles has many parts that slide or rotate due to its structure, and various abnormal noises are generated. In particular, in recent years, EPS (electric power steering apparatus) that obtains steering assist force with an electric motor has become widespread.
For example, in the column type EPS, the rotational force of the motor is transmitted to the worm, and further transmitted to the worm wheel, thereby decelerating the rotation of the motor and amplifying the output of the motor to assist the steering operation with torque.
[0003]
In this EPS, particularly, rattling noise caused by backlash of a reduction gear mechanism such as a worm gear mechanism propagates into the passenger compartment through the housing of the steering column, resulting in noise that makes the driver feel uncomfortable.
Furthermore, for example, vibration input from the vehicle body side suspension is applied to the steering column through the mounting portion of the steering column, and further transmitted to the reduction gear mechanism to cause resonance and amplification, which causes further noise. ing.
[0004]
[Problems to be solved by the invention]
Therefore, we have improved the meshing accuracy between the worm and worm wheel of the reduction gear mechanism, packed backlash, and adjusted the preload of the worm, but there is also a balance with the rotation resistance of the steering shaft It is difficult to reduce noise by improving the accuracy due to factors such as deterioration in assemblability and cost increase.
This invention is made | formed in view of the said subject, and is providing the electric power steering device which can reduce a noise more.
[0005]
[Means for Solving the Problems and Effects of the Invention]
In order to achieve the above object, an invention according to claim 1 is an electric power steering apparatus for transmitting rotation of an electric motor for assisting steering to a steering mechanism via a reduction gear mechanism. A cylindrical first housing to be accommodated, a cylindrical second housing fitted to an opening edge of one axial end of the first housing, a cylindrical flange formed on a fixed bracket fixed to the vehicle body, An annular elastic body interposed between the cylindrical flange and the second housing. The second housing has a double cylinder structure having an inner cylinder and an outer cylinder, and the outer cylinder is fitted to the first housing. An annular groove that opens in one axial direction is defined between the inner cylinder and the outer cylinder, and a cylindrical flange is inserted into the annular groove, and the elastic body is press-fitted into the cylindrical flange in a state of surrounding the inner cylinder. characterized in that it is It is intended to.
[0006]
In the present invention, by elastically supporting the second housing that may amplify gear rattling vibrations, vibration of the second housing itself can be reduced and high-frequency components of vibration can be removed. Thereby, the noise transmitted to the passenger compartment side can be significantly reduced. Furthermore, since vibration from the vehicle body side can be prevented from being transmitted to the second housing, it is possible to reliably reduce the vibration from the vehicle body side being amplified by the speed reduction mechanism and causing noise.
[0007]
Moreover, the form a double cylinder structure having a second housing inner cylinder and the outer cylinder, the outer cylinder is fitted in the first housing, an annular groove open in the axial direction one end direction between the inner cylinder and the outer cylinder Since the cylindrical flange is inserted into the annular groove and the elastic body is press-fitted into the cylindrical flange in a state of surrounding the circumference of the inner cylinder , the following advantages are obtained. That is , a structure in which the cylindrical flange and the elastic body are sandwiched between the inner cylinder and the outer cylinder of the second housing can increase the vibration reduction effect.
[0008]
According to a second aspect of the present invention, in the first aspect , the inner cylinder includes a main body that holds a bearing for supporting the driven gear, and the elastic body is inserted from the main body in one axial direction. And an extended portion. In the present invention, the second housing, which is the lower end portion of the steering column, is provided with a hollow cylindrical extending portion that opens in one axial end direction, and this portion is elastically supported to reduce vibration most effectively. Like that.
[0009]
DETAILED DESCRIPTION OF THE INVENTION
Preferred embodiments of the present invention will be described with reference to the accompanying drawings.
FIG. 1 is a partially cutaway side view of a main part of an electric power steering apparatus according to an embodiment of the present invention. Referring to FIG. 1, an electric power steering apparatus includes an input shaft 2 connected to a steering wheel 1, an output shaft 3 connected to a steering mechanism such as a rack and pinion mechanism (not shown), an input shaft 2 and an output shaft 3. Mainly based on a torsion bar 4 that is coaxially connected so as to be relatively rotatable, a torque sensor 5 that detects a steering torque based on a relative rotational displacement amount between the input shaft 2 and the output shaft 3, and a torque detected by the torque sensor 5. A steering assisting electric motor 6 to be controlled and a reduction gear mechanism 7 for reducing the rotation of the electric motor 6 and transmitting it to the output shaft 4 are provided. B is a substrate on which a control circuit for controlling the driving of the electric motor 6 is mounted.
[0010]
The reduction gear mechanism 7 includes a worm wheel 8 as a driven gear attached to the output shaft 3 so as to be integrally rotatable, and a worm shaft 9 as a drive gear that meshes with the worm wheel 8 and transmits the driving force of the motor 6 to the worm wheel 8. With. The worm wheel 8 includes an annular cored bar 8a coupled to the output shaft 3 so as to be integrally rotatable, an inner peripheral part fitted to the outer peripheral part of the cored bar 8a, and a synthetic resin member 8b forming teeth. ing.
[0011]
The steering column 10 includes a steering column tube 11 that houses the input shaft 2 and the torque sensor 5, a first housing 12 that is fitted to the lower end of the steering column tube 11 and houses the worm wheel 8, and the first housing 12. A second housing 13 fitted to the lower end of the second housing 13.
On both sides in the axial direction of the worm wheel 8 as a driven gear, first and second bearings 14 and 15 made of, for example, ball bearings are arranged to rotatably support the output shaft 3. The first bearing 14 is interposed between the steering column tube 11 and the output shaft 3, and the second bearing 15 is interposed between the second housing 13 and the output shaft 3.
[0012]
The input shaft 2 has a cylindrical shape, and a torsion bar 4 is inserted into a hole of the input shaft 2, and an upper end portion of the torsion bar 4 and an upper end portion of the input shaft 2 are connected to each other by a dowel pin 16 so as to be integrally rotatable.
The output shaft 3 is provided with a fitting hole 17 at the upper end, and the lower end portion of the input shaft 2 is fitted in the fitting hole 17 so as to be relatively rotatable, and the lower end portion of the torsion bar 4 is connected to the dowel pin 18. Are connected so as to be integrally rotatable.
[0013]
The steering column 10 is attached to a fixed bracket 21 fixed to the vehicle body 19 with screws 20, and the structure thereof will be described with reference to FIGS.
As shown in FIG. 2, the fixing bracket 21 includes a base plate portion 22 that is fixed to the vehicle body 19 with screws 20, and an extended plate portion 23 that extends from the base plate portion 22, and is shown in FIG. 3. As described above, a cylindrical flange 24 that extends toward the steering wheel 1 with an opening defined in the center of the extended plate portion 23 is provided. The extended plate portion 22 has a pair of screw insertion holes 25 formed on both left and right sides of the cylindrical flange 24.
[0014]
Referring to FIG. 3, the second housing 13 includes an annular plate portion 26, an outer cylinder 27 extending from the outer periphery of the annular plate portion 26 toward the anti-steering wheel 1, and the anti-steering wheel 1 from the inner periphery of the annular plate portion 26. And an inner cylinder 28 extending to the side. As described above, the second housing 13 has a double cylinder structure having the outer cylinder 27 and the inner cylinder 28, and opens between the outer cylinder 27 and the inner cylinder 28 toward the side opposite to the steering wheel 1 that is one axial end direction. An annular groove 29 is defined.
[0015]
An annular flange 30 extending radially outward is extended at the distal end of the outer cylinder 27, and this extended flange 30 is connected to the opening edge portion 12 a of the first housing 12 and the extended plate portion 23 of the second housing 13. Is sandwiched between. The screw 31 is inserted into the screw hole 33 of the annular edge portion 12 a of the first housing 12 through the screw insertion hole 25 of the extension plate portion 23 and the screw insertion hole 32 of the extension flange 30.
Further, the opening edge 12 a of the first housing 12 is fitted on the outer peripheral portion of the outer cylinder 27. A cylindrical flange 24 of the fixed bracket 21 is inserted into the annular groove 29 together with an elastic body 34 made of, for example, grommet.
[0016]
Specifically, the outer peripheral portion 24 a of the cylindrical flange 24 is fitted along the inner peripheral portion 27 a of the outer cylinder 27, and the elastic body 34 is attached to the inner peripheral portion 24 b of the cylindrical flange 24 so as to surround the inner cylinder 28. It is press-fitted along. The inner cylinder 28 extends from the main body 35 in one axial direction (on the side opposite to the steering wheel 1) from the main body 35 to hold the second bearing 15 for supporting the worm wheel 8 as the driven gear. And an extending portion 36. An elastic body 34 is inserted into the extended portion 36.
[0017]
An annular protrusion 37 is formed on the inner peripheral portion of the main body 35 to contact the end surface of the outer ring of the second bearing 15 and position it in the axial direction. If only the essential function of the second housing 13 for supporting the output shaft 3 via the second bearing 15 is achieved, the inner cylinder 28 may be constituted only by the main body 35 having the annular protrusion 37. However, in the present embodiment, as will be described later, in order to increase the vibration reduction effect, a cylindrical extending portion 36 that is intentionally opened in one axial direction (on the side opposite to the steering wheel 1) is provided. .
[0018]
The elastic body 34 is a cylindrical portion that fills an annular space between the outer peripheral portion 36a of the extending portion 36 of the inner cylinder 28 of the second housing 13 and the inner peripheral portion 24b of the cylindrical flange 24 of the fixing bracket 21 in a compressed state. 38 and first and second annular edges 39 and 40 formed at both ends of the cylindrical portion 38, respectively.
The first annular edge 39 wraps around the side of the extension plate 23 opposite to the steering wheel 1 and the second annular edge 40 wraps around the steering wheel 1 (front end side) of the cylindrical flange 24. The cylindrical flange 24 is elastically sandwiched between the annular edges 39 and 40 in the axial direction.
[0019]
According to the present embodiment, the second housing 13, which may amplify gear rattling vibrations, is elastically supported by the elastic body 34 such as a grommet, thereby reducing the vibration of the second housing 13 itself. Moreover, the high frequency component of vibration can be removed. Thereby, the noise transmitted to the passenger compartment side can be significantly reduced.
Furthermore, for example, the suspension and other vibrations can be prevented from being transmitted from the vehicle body 19 side to the second housing 13 via the fixed bracket 21, so that the vibrations from the vehicle body 19 side are amplified by the reduction gear mechanism 7 and become noise. Can be reliably reduced.
[0020]
Further, the cylindrical flange 24 and the elastic body 34 of the fixed bracket 21 are sandwiched in the annular groove 29 between the outer cylinder 27 and the inner cylinder 28 of the second housing 13 having a double cylinder structure, and the vibration reduction effect is further improved. Can be high.
In addition, the second housing 13 which is the end of the steering column 10 on the side opposite to the steering wheel 1 is provided with a sleeve-like extension 36 that opens to the side opposite to the steering wheel 1 in the axial direction, and this extension 36 is elastically supported. Therefore, vibration can be reduced most effectively.
[0021]
The present invention is not limited to the above embodiment, and various modifications can be made within the scope of the present invention.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view of a main part of an electric power steering apparatus according to an embodiment of the present invention.
FIG. 2 is a schematic view of a steering column as viewed from the side opposite to the steering wheel.
3 is a cross-sectional view taken along line III-III in FIG.
[Explanation of symbols]
1 Steering wheel 2 Input shaft 3 Output shaft 4 Torsion bar 5 Torque sensor 6 Electric motor 7 Reduction gear mechanism 8 Worm wheel (driven gear)
9 Worm shaft 10 Steering column 11 Steering column tube 12 First housing 12a Annular edge 13 Second housing 19 Car body 20 Screw 21 Fixing bracket 22 Base plate part 23 Extension plate part 24 Cylindrical flange 24a Outer peripheral part 24b Inner peripheral part 26 Annular Plate part 27 Outer cylinder 27a Inner peripheral part 28 Inner cylinder 29 Annular groove 30 Annular flange 34 Elastic body 35 Main part 36 Extension part 36a Outer part 38 Cylindrical part 39 First annular edge 40 Second annular edge

Claims (2)

In the electric power steering apparatus that transmits the rotation of the electric motor for assisting steering to the steering mechanism through the reduction gear mechanism,
A cylindrical first housing that houses the driven gear of the reduction gear mechanism;
A cylindrical second housing that is fitted to an opening edge of one axial end of the first housing;
A cylindrical flange formed on a fixed bracket fixed to the vehicle body;
An annular elastic body interposed between the cylindrical flange and the second housing ;
The second housing has a double cylinder structure having an inner cylinder and an outer cylinder,
The outer cylinder is fitted to the first housing,
An annular groove that opens in one axial direction is defined between the inner cylinder and the outer cylinder,
A cylindrical flange is inserted into this annular groove,
An electric power steering apparatus, wherein the elastic body is press-fitted into a cylindrical flange in a state of surrounding the periphery of the inner cylinder . In Claim 1 , the said inner cylinder contains the main part which hold | maintains the bearing for supporting a driven gear, and the extending part extended in the axial direction one end direction from this main part, and the said elastic body was inserted. An electric power steering apparatus that is characterized.

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