JP2003034254A - Electrically driven power steering device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To overcome the problem that noise caused by backlash is spread out in a vehicle room when the revolution of an electric motor is reduced and transmitted to a steering mechanism via a worm shaft and a worm wheel. SOLUTION: Bearing supporting holes 16, 20 covered with resilient films 47, 48 for supporting the worm wheel 12 support outer wheels 15, 19 of first and second bearings 13, 14. In the same way, bearing support holes of the gear housing 7 which is covered with resilient films 47, 48 support outer wheels of bearings which support the worm shaft 11. Vibration caused by tooth hitting is prevented from being transmitted. A resilient member 46 is interposed between the gear housing 7 and a sensor housing 6 for preventing vibration from being transmitted.

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 In an electric steering apparatus for an automobile, for example, a column type EPS, the rotational force of a motor is transmitted to a worm and further transmitted to a worm wheel to decelerate the rotation of the motor to amplify the output of the motor. , The steering operation is torque assisted. Generally, a gear housing that accommodates a reduction gear mechanism such as a worm gear mechanism and a motor housing are connected to each other in such a manner that they intersect each other. A sensor housing for housing a torque sensor that detects the torque applied to the steering shaft is also connected to the gear housing.

[0003]

By the way, a proper backlash is required for the meshing of the worm and the worm wheel as the reduction mechanism, but when the vehicle travels on a bad road such as a stone pavement, the reaction force from the tire is The rattle noise may be generated as a rattling noise due to the above backlash, or the bearing and other components having a clearance may generate a rattle noise. If these sounds are transmitted to the vehicle interior as noise, the driver will feel uncomfortable.

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 capable of reducing noise generated by a reduction mechanism such as backlash.

[0005]

In order to achieve the above object, the invention according to claim 1 transmits the rotation of an electric motor for steering assist to a steering mechanism through a reduction gear mechanism. In the steering device, an elastic film is coated on an inner wall surface of a gear housing that accommodates the reduction gear mechanism.

It is considered that a large factor of noise generation in the vehicle interior is that gear rattling vibrations due to backlash of the reduction gear mechanism are transmitted to the gear housing and the gear housing itself vibrates. In the present invention, by covering the inner wall surface portion of the gear housing with the elastic film, it is possible to suppress propagating tooth rattle vibration to the gear housing, which is very effective in preventing noise in the vehicle interior. Also,
When coating the elastic film, it is not necessary to significantly change the existing mechanism, and therefore, the degree of freedom in design is not reduced, and the increase in manufacturing cost can be minimized.

According to a second aspect of the present invention, in the first aspect, the elastic film includes an elastic film interposed between the bearing supporting the reduction gear mechanism and the gear housing. Since it is possible to suppress the gear rattling vibrations from being transmitted to the gear housing from the drive gears and driven gears of the reduction gear mechanism via the bearings that support them, the vibrations of the gear housings are suppressed, and noise prevention is reliably achieved. be able to. According to a third aspect of the present invention, according to the first or second aspect, an elastic body is interposed between a sensor housing that accommodates a torque sensor for detecting a torque applied to the steering shaft and a connecting portion between the gear housing. It is characterized by being present. In the present invention, it is possible to prevent the vibration of the gear housing due to the tooth striking vibration and the like from being transmitted to the sensor housing closer to the vehicle compartment than the gear housing, so that the propagation of the vibration to the vehicle compartment side can be reliably suppressed. Therefore, noise prevention can be reliably achieved.

According to a fourth aspect of the present invention, in the first, second or third aspect, an elastic body is interposed between a connecting portion between the motor housing and the gear housing of the electric motor. . According to the present invention, it is possible to reliably prevent the generation of noise by preventing the vibration of the gear housing caused by the tooth hammering vibration from being transmitted to the motor housing. According to a fifth aspect of the present invention, in an electric power steering apparatus that transmits the rotation of an electric motor for steering assistance to a steering mechanism via a reduction mechanism that includes a drive gear and a driven gear, a gear that houses the reduction gear mechanism. The housing is filled with a viscous fluid or grease, and the viscous fluid or grease is present inside the gear housing at least between the gear meshing portions.

According to the present invention, the impact when the gear teeth collide with each other can be softened and the occurrence of gear rattling vibration can be suppressed, so that the generation of noise can be reliably prevented. Further, since the existing mechanism is not largely changed, the degree of freedom in design is not reduced, and the increase in manufacturing cost can be suppressed to the minimum.

[0010]

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 housing 5 supporting the first and second steering shafts 2 and 3 is made of, for example, an aluminum alloy and is attached to a vehicle body (not shown). The housing 5 is
The sensor housing 6 and the gear housing 7 are fitted to each other. Specifically, the gear housing 7 has a tubular shape, and an annular edge portion 7 a at the upper end thereof is fitted to an annular step portion 6 a at the outer periphery of the lower end of the sensor housing 6. An elastic member 46 having a hook-shaped cross section for preventing vibration is interposed between the annular edge portion 7a and the annular step portion 6a to suppress vibration transmission between the sensor housing 6 and the gear housing 7. The gear housing 7 houses a worm gear mechanism 8 as a reduction gear mechanism, and the sensor housing 6 houses a torque sensor 9 and a control board 10.

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.
Worm shaft 11 connected through a joint mechanism such as three joints
And a worm wheel 12 that meshes with the worm shaft 11 and is integrally rotatable with the axially intermediate portion of the second steering shaft 3 and whose axial movement is restricted, as shown in FIG. Although not shown, the worm shaft 11 is rotatably supported in the gear housing 7 via a pair of bearings.

The worm wheel 12 has an annular core metal 12a which is integrally rotatably connected to the second steering shaft 3 and a core metal 1.
Synthetic resin member 12 that surrounds 2a and forms teeth
and b. The core metal 12a is, for example, a synthetic resin member 1
It is to be inserted into the mold during resin molding of 2b. The second steering shaft 3 includes first and second rolling bearings 1 arranged with the worm wheel 12 vertically sandwiched therebetween.
It is rotatably supported by 3 and 14.

The outer ring 15 of the first rolling bearing 13 is fitted and held in a bearing holding hole 16 provided in a cylindrical protrusion 6b at the lower end of the sensor housing 6 and covered with an elastic film 47. The elastic film 47 is the bearing holding hole 16
It is also covered by an annular step portion 17 which is the bottom of the. The upper surface of the outer ring 15 of the first rolling bearing 13 has the elastic coating 4
7 is in contact with the covered annular step portion 17 and is restricted from moving axially upward with respect to the sensor housing 6. On the other hand, the inner ring 18 of the first rolling bearing 13 is fitted to 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.

Further, the outer ring 19 of the second rolling bearing 14
Is fitted and held in the bearing holding hole 20 of the gear housing 7 covered with the elastic film 48. The elastic film 48 is also coated on the annular step portion 21 that serves as the bottom of the bearing holding hole 20, and the lower end surface of the outer ring 19 of the second rolling bearing 14 has an annular step portion to which the elastic film 48 is applied. 21
And is restricted from moving downward in the axial direction with respect to the gear housing 7. Inner ring 22 of the second rolling bearing 14
Is attached to the second steering shaft 3 such that it can rotate integrally with the second steering shaft 3 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 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 connects the third steering shaft 27, which is arranged coaxially with the first steering shaft 2, so as to rotate integrally with the first steering shaft 2. 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 sensor housing 6 via a third rolling bearing 29, which is, for example, a needle roller bearing. First steering shaft 2
The lower diameter reduced portion 30 and the upper hole 31 of the second steering shaft 3 have a predetermined rotation direction so as to restrict the relative rotation of the first and second steering shafts 2 and 3 within a predetermined range. It is fitted with the play of. Next, referring to FIG. 2, the worm shaft 11 is rotatably supported by the fourth and fifth rolling bearings 34 and 35 held by the gear 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,
Outer rings 38 and 39 of 35 are held in bearing holding holes 40 and 41 of the gear housing 7, which are covered with elastic films 49 and 50, respectively. The gear housing 7 includes a portion 7b radially opposed to a part of the peripheral surface of the worm shaft 11, and this portion 7b is also covered with the elastic film 51.

Further, the outer ring 3 of the fourth rolling bearing 34 that supports one end 11a (the end opposite to the joint) of the worm shaft 11 is supported.
8 is positioned in contact with the step portion 42 covered with the elastic film 52 in the gear housing 7. The elastic film 52, including the step portion 42, is covered on the portion 7c of the gear housing 7 that faces the one end portion 11a of the worm gear 11. On the other hand, the inner ring 3 of the fourth rolling bearing 34
By contacting the positioning step 43 of the worm shaft 11, 6 is restricted from moving toward the other end 11b of the worm shaft 11.

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 gear housing 7 to apply a preload to the pair of rolling bearings 34 and 35 and position the worm shaft 11 in the axial direction. 60
Is a lock nut engaged with the screw member 45 for fixing the screw member 45 after the preload adjustment.

The elastic coatings 49 to 52 are continuously formed. Further, as the elastic coatings 47 to 52, for example, PA (polyamide resin) such as PA11 and PA12, PE
Polyester resin such as T (polyethylene terephthalate) and PBT (polybutylene terephthalate), PPS
(Polyphenylene sulfide), polyolefin resin such as PE (polyethylene) or PP (polypropylene), or an elastic film formed by coating resin powder of other thermoplastic resin by powder coating can be used. Further, it may be an elastic film formed by applying a coating material containing an elastomer such as EPDM (ethylene propylene diene terpolymer). The thickness of the elastic coatings 47 to 52 is preferably in the range of 0.2 to 0.4 mm, for example.

In FIG. 2, an elastic body 55 is interposed between the annular edge portion 53 of the gear housing 7 and the motor housing 54 of the electric motor M to suppress vibration transmission between the housings 7 and 54. . Referring to FIG. 3A, the elastic body 4 interposed between the sensor housing 6 and the gear housing 7
6 is a cored bar 5 made of a cylinder with a flange having a hook-shaped cross section.
3 is joined to both sides of the elastic sheet 57. Similarly, referring to FIG. 3B, the elastic body 55 interposed between the gear housing 7 and the motor housing 54 is a cored bar made of an annular plate. An annular elastic sheet 59 is joined to both surfaces of 58.

The cores 56 and 58 have a thickness of 0.4 to 0.
It is made of a steel plate such as 6 mm SPCC. Each elastic sheet 5
7,59 is, for example, an NBR having a thickness of about 0.2 to 0.3 mm
Made of synthetic rubber such as (nitrile rubber), core metal 56,5
8 is vulcanized and bonded, for example. 0.5m for cores 56 and 58
m, and the elastic sheets 57 and 59 are 0.25 mm,
The elastic bodies 46 and 55 having a total thickness of 1 mm may be used.

As the elastic bodies 46 and 58, the core bar may be omitted and only synthetic resin or synthetic rubber plates may be used. According to the present embodiment, the worm wheel 12
The first and second bearings 13 and 14 that support the gear housing 7 and the third and fourth bearings 34 and 35 that support the worm shaft 11 are mounted on the gear housing 7 via the corresponding elastic films 47, 48, 49 and 50. Since it is supported by the gear housing 7, it is possible to suppress the rattling vibration and the like due to the backlash of the worm gear mechanism 8 from being transmitted to the gear housing 7, and as a result, the noise in the vehicle compartment can be significantly reduced.

Moreover, the elastic body 46 is also interposed between the gear housing 7 and the sensor housing 6 connected to the gear housing 7, so that the sensor housing 6 located closer to the vehicle compartment than the gear housing 7 is provided. Since it is possible to suppress the transmission of vibration, it is possible to reliably achieve noise prevention in the vehicle interior. In addition, the gear housing 7 and the motor housing 54
Since the elastic body 55 between and suppresses the vibration transmission between the housings 7 and 54, the noise prevention effect can be further enhanced.

Further, parts 7b, 7 of the gear housing 7 facing a part of the peripheral surface of the worm shaft 11 and one end 11a.
Since the elastic coatings 51 and 52 are also coated on c, it is possible to suppress the propagation of the radiated sound to these portions 7b and 7c, and it is possible to further enhance the noise prevention effect. Then, FIG.
Shows another embodiment of the present invention. Referring to FIG. 4, in the present embodiment, the viscous fluid F is filled in the gear housing 7, and the viscous fluid F soaks at least the gear meshing portion 61 in the gear housing 7.

As the viscous fluid F, a highly viscous lubricating oil can be used. Further, instead of the viscous fluid F, grease having a low consistency can be used. As a lubricating oil,
For example, kinematic viscosity is 100-800 mm ² / s (40 ° C)
Although a lubricating oil in the range of 5 can be used and a synthetic hydrocarbon oil is preferably used, a mineral oil, a silicone oil or the like can be used. In addition, if necessary, as additives, solid lubricants (molybdenum disulfide, graphite, PTFE) for improving wear resistance, extreme pressure additives such as phosphorus-based and sulfur-based compounds, and defoaming properties are improved. For this purpose, an additive such as polymethyl siloxane or an antioxidant such as tributylphenol, trimethylphenol or phenyl-1-naphthylamine for preventing deterioration may be added.

As the grease, for example, the consistency is N
LGI number 00-000, ASTM (JIS)
A grease having a workability of 400 to 500 (25 ° C) is preferably used. As the base oil in the grease, synthetic hydrocarbon oil is preferably used, but in addition,
Mineral oil, silicone oil, etc. can be used. Lithium soap is preferably used as the thickener to be dispersed. In addition, if necessary, solid lubricants (molybdenum disulfide, graphite, PTFE, etc.) can be added as additives.
Extreme pressure additives such as phosphorus compounds and sulfur compounds, additives such as polymethylsiloxane for improving defoaming properties, antioxidants such as tributylphenol, trimethylphenol, phenyl-1-naphthylamine for preventing deterioration. May be added.

When the lubricating oil as the viscous fluid F or the semi-solid lubricant such as grease is filled, the first, second and third parts are prevented from leaking from the gear housing 7.
Sealed bearings are preferably used as the third and fourth rolling bearings 13, 14, 34, and 35. in this case,
It is preferable to dispose a seal on only one side of each bearing 13, 14, 34, 35 and use a lubricant or the like for lubricating the inside of the bearing. That is, as shown in FIG. 4, in the bearings 13 and 14, the seal S is arranged only on one side (outer side). Although not shown, the same applies to the bearings 34 and 35.

According to the present invention, since the impact of the gear teeth of the worm gear mechanism 8 colliding against each other can be softened and the occurrence of rattling vibration can be suppressed, it is possible to reliably prevent the generation of noise. The present invention is not limited to the above-mentioned embodiment, and various modifications can be made within the scope of the claims of the present invention.

[0031]

[Examples] A noise test was conducted on Comparative Examples, which are the current products, and Examples 1 to 6 in which the following vibration countermeasures are applied to the Comparative Examples. Specifications 1) Embodiment 1: Between the bearings 13, 14, 34, 35 and the gear housing 7, an elastic film 47 made of PA12,
48, 49 and 50 are provided with a thickness of 0.3 mm. 2) Example 2: Sensor housing 6 and gear housing 7
An elastic body 46 is interposed between the and. The elastic body 46 is formed by coating both surfaces of a SPCC material having a plate thickness of 0.5 mm with 0.25 mm nitrile rubber, and has a total thickness of 1 mm. 3) Example 3: Gear housing 7 and motor housing 5
An elastic body 55 is interposed between the elastic body 55 and The elastic body 55 is formed by coating both surfaces of a SPCC material having a plate thickness of 0.5 mm with 0.25 mm nitrile rubber, and has an overall thickness of 1 mm. 4) Embodiment 4: The embodiment 2 and the embodiment 3 are combined, and the elastic body 46 is provided between the sensor housing 6 and the gear housing 7.
And the elastic body 55 is interposed between the gear housing 7 and the motor housing 54. Each elastic body 4
Nos. 6,55 are 0.
Made of 25 mm nitrile rubber, the total thickness is 1
mm. 5) Example 5: Kinematic viscosity of 200 mm in the gear housing 7
Fill with ² / s of lubricating oil. The lubricating oil is formed by filling poly-α-olefin oil with polymethylsiloxane. 6) Example 6: Kinematic viscosity of 600 mm in the gear housing 7
Fill with ² / s of lubricating oil. The lubricating oil is formed by filling poly-α-olefin oil with polymethylsiloxane. 7) Comparative Example: A current product that does not take the measures of Examples 1 to 6, and the gear housing 7 is filled with the current grease (concentration NLGI number 2). Test Conditions In the steering unit, the electric motor was rotated in the forward and reverse directions at 5 Hz, and the sound pressure level (dB: decibel) was measured at a position separated by a distance of 0.1 m from the unit. Test Results Comparative Example 1: 70 dB Example 1: 64 dB (6 dB decrease from Comparative Example) Example 2: 68 dB (2 dB decrease from Comparative Example) Example 3: 69 dB (1 dB decrease from Comparative Example) Example 4: 67 dB (Comparison Example: 3 dB reduction Example 5: 64 dB (6 dB reduction from the comparative example) Example 6: 53 dB (17 dB reduction from the comparative example) As described above, it was demonstrated that the noise level was lowered in any of the examples. . In particular, it has been found that by interposing an elastic film between the bearing and the gear housing, a significant reduction in noise level can be achieved. It was also found that the noise level can be remarkably reduced by filling a high-viscosity lubricating oil.

[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. 3A is a sectional view of an essential part of an elastic body interposed between the sensor housing and the gear housing, and FIG. 3B is a main part of the elastic body interposed between the gear housing and the motor housing. FIG.

FIG. 4 is a sectional view of a main part of an electric power steering apparatus according to another embodiment of the present invention.

[Explanation of symbols]

3 Steering shaft (steering shaft) 6 sensor housing 7 Gear housing 8 Worm gear mechanism 11 Worm axis 12 worm wheel 13 First rolling bearing 14 Second rolling bearing 15,19 outer ring 16,20 Bearing holding hole 17,21 steps M electric motor 34 Fourth Rolling Bearing 35 Fifth Rolling Bearing 38,39 outer ring 40,41 Bearing holding hole 42 steps 46,55 elastic body 47, 48, 49, 50, 51, 52 Elastic film 54 motor housing 56,58 core 57,59 Elastic sheet

[Procedure amendment]

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

[Procedure Amendment 1]

[Document name to be amended] Statement

[Correction target item name] 0012

[Correction method] Change

[Correction content]

The worm gear mechanism 8 is, for example, a spline joint to the rotary shaft 32 of the electric motor M, as shown in FIG.
Worm shaft 11 connected through a joint mechanism such as hand 33
And a worm wheel 12 that meshes with the worm shaft 11 and is integrally rotatable with the axially intermediate portion of the second steering shaft 3 and whose axial movement is restricted, as shown in FIG. Although not shown, the worm shaft 11 is rotatably supported in the gear housing 7 via a pair of bearings.

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Kazutoshi Yamamoto             3-5-8 Minamisenba, Chuo-ku, Osaka Koyo             Within Seiko Co., Ltd. (72) Inventor Kenji Yamamoto             3-5-8 Minamisenba, Chuo-ku, Osaka Koyo             Within Seiko Co., Ltd. F-term (reference) 3D033 CA04

Claims (5)

[Claims] 1. An electric power steering apparatus for transmitting the rotation of an electric motor for assisting steering to a steering mechanism through a reduction gear mechanism, wherein an inner wall surface of a gear housing for accommodating the reduction gear mechanism is coated with an elastic film. An electric power steering device characterized by being provided. 2. The electric power steering apparatus according to claim 1, wherein the elastic film includes an elastic film interposed between a bearing supporting the reduction gear mechanism and a gear housing. 3. An elastic body is interposed between a sensor housing for accommodating a torque sensor for detecting a torque applied to a steering shaft and a connecting portion between the gear housing and the gear housing. An electric power steering device. 4. The electric power steering apparatus according to claim 1, wherein an elastic body is interposed between a connecting portion between the motor housing and the gear housing of the electric motor. 5. An electric power steering apparatus that transmits the rotation of an electric motor for steering assistance to a steering mechanism via a reduction mechanism including a drive gear and a driven gear, and an inside of a gear housing that accommodates the reduction gear mechanism. An electric power steering apparatus characterized in that a viscous fluid or grease is filled in, and the viscous fluid or grease is present at least between gear engagement portions inside a gear housing.