JP2002054719A - Electric power steering device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain vibration control effect by restraining tooth hammering sound due to backlash from being transmitted through a worm wheel. SOLUTION: The worm wheel 8 has a tooth body 81 made of synthetic resin and meshing with a worm and a holding body 82 made of metal and holding the tooth body 81. A covering body 83 made of synthetic resin and integrated with the tooth body 81 covers the surface of the holding body 83 so that transmission of vibration due to sound is restrained by the covering body 83.

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 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. 8 is a sectional view showing the structure of a conventional electric power steering apparatus, and FIG. 9 is a sectional view showing the structure of a speed reduction mechanism and a motor. As an electric power steering device for an automobile, as shown in FIG. 8, for example, a first steering shaft 101 connected to a steered wheel 100 for steering.
And a second steering shaft 103 whose lower end is coaxially connected to a lower end of the steering shaft 101 via a torsion bar 102 and whose lower end is connected to a steering mechanism connected to wheels, and which rotates the steering wheel 100. The torque sensor 104 detects the torque applied to the first steering shaft 101 by the twist generated in the torsion bar 102, a steering assist motor 105 driven based on the detection result of the torque sensor 104, A speed reduction mechanism having a worm 107 and a worm wheel 108 connected to the output shaft 106 of the motor 105 to reduce the rotation of the output shaft 106 and transmit the reduced speed to the second steering shaft 103; The operation of the steering mechanism is assisted by the rotation of the motor 105 to reduce the burden on the driver for steering. That.

The second steering shaft 103 is connected to a pinion shaft via a universal joint, and the pinion shaft is connected to a steering mechanism such as a rack shaft via a pinion and rack teeth.

[0005] When the speed reduction mechanism is used as described above,
Since backlash occurs at the meshing portion between the worm 107 and the worm wheel 108, an adjusting mechanism for adjusting the distance between the rotation centers of the worm 107 and the worm wheel 108 is provided, and the dimensional accuracy of the teeth of the worm 107 and the worm wheel 108 is adjusted. By reducing the backlash, the initial backlash is reduced, and the rattling noise due to the backlash is reduced.

FIG. 10 is a sectional view showing another configuration of a conventional electric power steering apparatus. Further, as an electric power steering device, as shown in FIG. 10, a synthetic resin tooth body 109 and the tooth body 1 meshing with the worm 107 are provided.
There is known a worm wheel 111 having a metal holding body 110 for holding the worm wheel 09 supported on the steering shaft 103 so as to reduce noise caused by meshing with the worm 107.

[0007]

However, the worm 1
Since it is necessary to provide an appropriate backlash in order to smoothly rotate the worm wheel 07 and the worm wheels 108 and 111, the initial backlash can be reduced by providing an adjustment mechanism as described above or increasing the dimensional accuracy of the teeth. Even if this is the case, the initial backlash cannot be completely eliminated, and the backlash increases due to the increased wear of the teeth of the worm 107 and the worm wheels 108, 111. A rattling sound is generated, and the worm wheels 108 and 111 vibrate due to the rattling noise, and the vibration leaks from the steering shaft 103 supporting the worm wheels 108 and 111 into the cabin of the automobile.

In an electric power steering apparatus using a worm wheel 111 having teeth 109 made of synthetic resin, the holding member 11 holding the teeth 109 is used.
Since 0 is made of metal, abnormal noise generated by the universal joint portion connected to the holding member 110 and abnormal noise generated by the meshing portion of the pinion and the rack connected to the universal joint portion are transmitted to the holding member 110. The transmitted sound is radiated from the holder 110, and the transmitted radiated sound leaks into the cabin of the automobile.

[0009] An object of the present invention is to provide an electric power steering device that can solve the above problems.

[0010]

Means for Solving the Problems and Effects of the Invention An electric power steering apparatus according to a first aspect of the present invention provides a drive gear for outputting the output of a steering assist motor, a synthetic resin tooth body meshed with the drive gear, and In an electric power steering apparatus configured to transmit a steering gear through a driven gear having a metal holding body holding a tooth body to assist steering, the driven gear is made of a synthetic resin integrated with the tooth body. It is characterized in that a coating covers the surface of the holder.

In the first aspect of the present invention, since the cover made of a synthetic resin integral with the tooth body covers the surface of the holder, when the vibration caused by the above-described rattling noise is transmitted to the holder, The transmission of the vibration can be suppressed by the covering, and a vibration-proof effect can be obtained. Further, the transmission of the vibration due to the transmission sound transmitted from the steering mechanism side to which the worm wheel is connected to the holding body can be suppressed by the covering, and the vibration damping effect can be obtained.

[0012] In the electric power steering apparatus according to a second aspect of the present invention, the holder has a pair of recesses recessed from both side surfaces of the tooth body and a through-hole communicating the recesses. Is provided with the coating.

According to the second aspect of the present invention, since the covering bodies provided on both side surfaces of the holding body are connected via the connecting portions in the through holes, the transmission of vibrations due to rattling noise and the steering mechanism side. Transmission of vibrations from the cover can be further suppressed, and the vibration damping effect of the covering can be further enhanced.

[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 cross-sectional view showing a configuration of an electric power steering device according to the present invention, and FIG. 2 is a cross-sectional view showing a configuration of a speed reduction mechanism and a motor portion. The electric power 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 one end inserted into the cylindrical portion and having one end connected to the other end of the steering shaft 2. A torsion bar 3 coaxially connected to the steering wheel 1 and twisted by the action of a steering torque applied to the steering wheel 1; a second steering shaft 4 coaxially connected at the other end to the other end of the torsion bar 3; The first according to the torsion of the torsion bar 3
And a torque sensor 5 for detecting a steering torque applied to the steered wheels 1 based on a relative rotational displacement of the second steering shafts 2 and 4.
A steering assist motor 6 driven based on the torque detected by the torque sensor 5, and a drive gear that, in conjunction with the rotation of the motor 6, reduces the rotation and transmits the rotation to the second steering shaft 4. The motor includes a reduction mechanism 9 having a worm (hereinafter referred to as a worm) 7 and a driven gear (hereinafter referred to as a worm wheel) 8, and a housing 10 in which the torque sensor 5 and the reduction mechanism 9 are accommodated.

FIG. 3 is an enlarged sectional view showing the structure of the speed reduction mechanism.
FIG. 4 is a front view in which the synthetic resin portion is indicated by oblique lines. The reduction mechanism 9 is disposed so as to intersect with the axis of the second steering shaft 4, and a shaft portion 71 connected to the output shaft 60 of the motor 6.
And a worm wheel 8 which meshes with the worm 7 and is fitted and fixed to the middle of the second steering shaft 4. The meshing of the worm 7 and the worm wheel 8 produces the output. The rotation of the shaft 60 is reduced and transmitted to the second steering shaft 4, and transmitted from the second steering shaft 4 to a rack-and-pinion type steering mechanism (not shown) via a universal joint. .

The worm wheel 8 is made of a synthetic resin tooth body 81 having a plurality of teeth 8a meshing with the worm 7.
And a metal holding body 82 holding the tooth body 81, and a through hole 82 a formed in the center of the holding body 82 is fitted to the second steering shaft 4. The provision of the synthetic resin teeth 81 reduces noise caused by engagement with the worm 7 and improves workability of the teeth 8a.

FIG. 5 is an enlarged sectional view showing the structure of the holder, and FIG. 6 is an enlarged front view showing the structure of the holder. Holder 8
2 is formed in a disk shape by a metal material such as mild steel,
A pair of recesses 82b, 82c recessed with respect to both sides of the tooth body 81 and a through hole 82d communicating the recesses 82b, 82c are provided on both side surfaces thereof, and a spline is formed on the outer peripheral surface. The tooth body 8
It is connected so that relative rotation with respect to 1 and relative movement in the axial direction are not performed.

FIG. 7 is a sectional view showing a method of manufacturing a worm wheel. The tooth body 81 is formed by accommodating the holder 82 as an insert in an injection mold and injecting a synthetic resin such as a molten nylon resin from one side surface 82b of the holder 82 to the outer periphery. It is integrally connected to the body 82. Further, the tooth body 81 includes the tooth 8a and the tooth 8a.
And an annular portion 81a for holding the inner surface of the holding member 82. The inside of the annular portion 81a is fitted to and held by the holding body 82.

Due to the molding of the teeth 81, the synthetic resin fills the concave portions 82b, 82c and the through holes 82d on both side surfaces of the holder 82, and the one side of the holder 82 and the concave portion 82b on the other side are combined with each other. Resin coated. The cover 83 is integral with the tooth body 81.

In the electric power steering apparatus configured as described above, the rotation of the steering assist motor 6 is controlled by the worm 7.
Is transmitted to the second steering shaft 4 via a worm wheel 8 having a tooth body 81 meshing with the worm 7 and a holding body 82 holding the tooth body 81. Further, an appropriate initial backlash is provided at the meshing portion of the worm 7 and the worm wheel 8 so that the worm 7 and the worm wheel 8 can be smoothly rotated. Accordingly, rattling noise due to the backlash is generated, and the worm wheel 8 vibrates due to the rattling noise. However, since the worm wheel 8 is made of a synthetic resin, the tooth body 81 meshing with the worm 7 is formed. The rattle can be reduced,
Moreover, since the cover 83 made of a synthetic resin that is integral with the tooth body 81 covers the surface of the holder 82, transmission of vibration due to the rattling noise can be suppressed by the cover 83, and the vibration damping effect is improved. can get.

The noise generated by the universal joint connected to the worm wheel 8 via the second steering shaft 4 and the noise generated by the meshing portion of the pinion and the rack connected to the universal joint are determined by the worm wheel. 8 is transmitted to the holding member 82, but since the surface of the holding member 82 is covered with the cover 83, the transmission of the vibration due to the transmission sound transmitted to the holder 82 is suppressed by the cover 83. And an anti-vibration effect can be obtained.

In the embodiment described above, the teeth 8
1 and the holding body 82 are formed with a ridge 82 such as a spline.
However, the tooth shape may be similar to the tooth 8a, and the structure is not particularly limited.

The speed reduction mechanism 9 of the embodiment described above is a worm gear having a drive gear 7 as a worm and a driven gear 8 as a worm wheel, and a drive gear and a hypoid wheel as a hypoid pinion. It may be a hypoid gear provided with a certain driven gear. Further, the reduction mechanism may be a bevel gear.

[Brief description of the drawings]

FIG. 1 is a sectional view showing a configuration of an electric power steering device according to the present invention.

FIG. 2 is a cross-sectional view showing a configuration of a speed reduction mechanism and a motor portion of the electric power steering device according to the present invention.

FIG. 3 is an enlarged sectional view showing a configuration of a speed reduction mechanism of the electric power steering device according to the present invention.

FIG. 4 is a front view of a synthetic resin portion of a worm wheel of the electric power steering device according to the present invention, which is indicated by oblique lines.

FIG. 5 is an enlarged sectional view showing a configuration of a holder of the electric power steering device according to the present invention.

FIG. 6 is an enlarged front view showing a configuration of a holder of the electric power steering device according to the present invention.

FIG. 7 is a cross-sectional view illustrating a method of manufacturing a worm wheel of the electric power steering device according to the present invention.

FIG. 8 is a cross-sectional view showing a configuration of a conventional electric power steering device.

FIG. 9 is a cross-sectional view showing a configuration of a speed reduction mechanism and a motor portion of a conventional electric power steering device.

FIG. 10 is a sectional view showing another configuration of a conventional electric power steering device.

[Explanation of symbols]

 Reference Signs List 6 motor 7 drive gear (worm) 8 driven gear (worm wheel) 81 tooth body 82 holder 83 covering body 82b, 82c recess 82d through hole

Continued on the front page F term (reference) 3D033 CA04 3J030 AA11 BA03 BB17 BC01 CA10 5H605 AA04 AA05 BB05 CC05 CC08 CC10 EA09 EB10 EB18 FF06 5H607 AA04 BB01 CC03 CC09 DD03 DD07 DD17 EE21 EE32 EE36 FF24 GG08 KK24

Claims (2)

[Claims] An output of a steering assist motor is steered through a driving gear, a synthetic resin tooth body meshed with the driving gear, and a driven gear having a metal holding body holding the tooth body. In the electric power steering apparatus configured to transmit steering to a steering mechanism, the driven gear has a synthetic resin covering body integral with the tooth body covering a surface of the holding body. Power steering device. 2. The holding body has a pair of recesses recessed from both side surfaces of the tooth body and a through hole communicating the recess, and the cover is provided in the through hole and the recess. Item 2. The electric power steering device according to Item 1.