JP2003120761A - Gear, reduction gear mechanism, and electric type power steering device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To easily obtain a desirable hollow without making any special work after a circular member having teeth on its outer circumference is coupled with a core member. SOLUTION: In an engagement part 14 between the circular member 12 of synthetic resin and the core member 13 engaged on the inner side of the circular member 12, a hollow 4 to restrict volume increase in a radial direction by expansion of the circular member 12 is provided, and the circular member 12 is fused with the core member 13. The desirable hollow 4 is thus easily obtained.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a gear in which a core member is fitted inside an annular member made of a synthetic resin having teeth on the outer circumference, a reduction gear mechanism including the gear, and an electric motor including the reduction gear mechanism. Type power steering device.

[0002]

2. Description of the Related Art FIG. 7 is a sectional view showing the structures of a conventional reduction gear mechanism and an electric power steering apparatus. The electric power steering apparatus includes an input shaft 101 connected to steered wheels 100 and a torsion bar 1 attached to the input shaft 101.
Output shaft 103 connected via 02 and steered wheels 100
A torque sensor 104 that detects a rotational torque applied to the input shaft 101 by steering the input shaft 101 by a twist generated in the torsion bar 102, and a steering assist motor (not operated) that is driven based on the steering torque detected by the torque sensor 104. And the output shaft 103 and the output shaft 10 through the reduction gear mechanism 106.
3 is configured to be transmitted to a steering mechanism (not shown) via a transmission means (not shown) connected to 3.

The reduction gear mechanism 106 is provided with a worm 107 that interlocks with the rotation of the motor 105 and a worm wheel 108 that meshes with the worm 107. The worm wheel 108 has an annular member 109 made of synthetic resin having teeth meshing with the worm 107 on the outer circumference, and a metallic core member 110 fitted inside the annular member 109.
The core member 110 is supported by the output shaft 103 to reduce noise caused by meshing with the worm 107. The annular member 109 is formed by accommodating the previously formed core member 110 as an insert in an injection mold and injecting a molten synthetic resin around the outside of the core member 110 to form the core member 110 and integrally connecting the core member 110 with the core member 110. I am doing it.

The worm 107 is arranged so as to intersect with the axes of the input shaft 101 and the output shaft 103, and is supported in a fitting hole of the housing 113 via a pair of rolling bearings (not shown). The output shaft 103 supporting the worm wheel 108 is supported in the housing 113 via a pair of rolling bearings 114 and 115, and the movement of the worm 107 and the worm wheel 108 in the radial direction and the axial direction is prevented.

In the reduction gear mechanism and the electric power steering device using the worm 107 and the worm wheel 108 as described above, an appropriate amount of backlash is provided at the meshing portion of the worm 107 and the worm wheel 108. Also, the worm wheel 108 can be smoothly rotated. When the amount of backlash is large, a rattling sound is generated, and the rattling sound leaks into the interior of the vehicle. When the amount of backlash in the meshing portion is small, the load is large, and the worm 107 and the worm 107 The wheel 108 cannot be smoothly rotated.

[0006]

However, in the conventional electric power steering apparatus, the worm 107 and the worm wheel 108 are prevented from moving in the radial direction, and the distance between the centers of rotation of the worm 107 and the worm wheel 108 is reduced. Since it is fixed, the ambient temperature becomes high, and the temperature of the reduction gear mechanism 106 is, for example, 80 to 14
When the temperature reaches a high temperature of 0 ° C. or when the humidity around the reduction gear mechanism 106 becomes relatively high, meshing clogging occurs, and improvement measures have been demanded.

As a result of investigating the cause of this clogging of meshing, the inventor has made a worm wheel 10 having an annular member 109 and a core member 110 fitted inside the annular member 109.
The annular member 109 of No. 8 is made of synthetic resin, and has a core member 110.
The worm and the worm 107 are made of metal, and although the linear expansion coefficients of the materials are different from each other, the individual parts are processed to have allowable dimensions without considering the linear expansion coefficient. Although the amount of backlash was appropriate at room temperature and humidity, the annular member 109 made of synthetic resin made the metallic core member 110 and the worm 10 due to the temperature increase of the reduction gear mechanism 106 due to the ambient temperature and the like.
It was found that the ring member 109 expanded significantly as compared with No. 7, the volume of the annular member 109 in the radial direction increased, and meshing clogging occurred.

The applicant of the present invention has found on the basis of such knowledge that the outer circumference of the annular member 109 or the core member 110 is
An electric power steering apparatus has been previously proposed (Japanese Patent Application No. 2001-232498), in which a space for suppressing an increase in volume in the radial direction due to expansion of the annular member 109 is provided to prevent clogging of the mesh.

However, in the worm wheel 108, as described above, the core member 110 is accommodated and arranged in the injection mold as an insert, and the molten synthetic resin is used as the core member 110.
Since the annular member 109 is molded by being injected to the outer periphery of and the annular member 109 is integrally connected to the core member 110, in order to obtain the void without performing special processing after the connection, Since the shape and location of the space are restricted, it is difficult to obtain a desired space.

The present invention has been made in view of the above circumstances, and it is possible to easily obtain a desired space without performing special processing after the annular member is joined to the core member. An object of the present invention is to provide a reduction gear mechanism including gears and an electric power steering device.

[0011]

A gear according to the first invention is
In a gear having an annular member made of synthetic resin having teeth on the outer periphery and a core member fitted inside the annular member, a fitting portion of the annular member and the core member, or fitting of the annular member It is characterized in that it has a void near the joint and that the annular member is fused to the core member.

In the first aspect of the invention, the annular member expands due to the temperature increase of the gear and the humidity increase due to the ambient temperature,
When the volume in the radial direction increases, the void becomes narrower, and a part of the volume increase due to expansion can be absorbed by the void. As a result, the increase in volume outward in the radial direction can be suppressed by the void, and clogging due to this increase in volume can be eliminated. Further, if the void does not become so narrow due to the increase in volume, it is possible to bend the portion between the void and the tooth surface in the direction of the void by meshing with another gear. It can eliminate clogging. Further, since the recess to be the void is provided in the annular member and / or the core member before the annular member and the core member are combined, special processing is performed after the annular member is connected to the core member. It is possible to easily obtain a desired empty space without performing the above, and it is possible to easily join the annular member and the core member by fusion bonding.

A gear according to a second aspect of the invention is characterized in that the core member has a recess into which the fused portion of the annular member is inserted into the fitting portion. In the second aspect of the invention, since the fused portion of the annular member is inserted into the concave portion of the core member, it is possible to further increase the bonding strength between the annular member and the core member.

A gear according to a third aspect of the invention is characterized in that the core member has the void in the fitting portion. In the third aspect, the annular member can be easily manufactured.

A gear according to a fourth aspect of the invention is characterized in that the annular member has the void in the fitting portion. According to the fourth aspect of the invention, the thickness from the inner side of the annular member to the tooth bottom can be made relatively small, and the annular member and the core member are fused together without crushing the recess to be the void. Can be easily combined by.

The gear according to the fifth aspect of the invention is characterized in that the fitting portion between the annular member and the core member is tapered so as to be inclined with respect to the center of rotation. In the fifth aspect of the invention, the relative movement of the fitting portion in the axial direction can be restricted, and the surface pressure of the fitting portion can be increased.
The annular member and the core member can be joined by a simple fusion method such as a spin fusion method and a vibration fusion method, as compared with the high frequency induction heating method.

A gear according to a sixth aspect of the invention is characterized in that the core member has a flange at the large diameter end of the taper, which is in contact with one side surface of the annular member. According to the sixth aspect of the invention, since the relative movement of the fitting portion in the axial direction can be restricted even when the annular member is fused, a simple fusion method such as a friction fusion method. Even in the case of coupling with each other, the positional deviation in the axial direction can be reduced.

A reduction gear mechanism according to a seventh aspect of the present invention is a reduction gear mechanism including a large gear having teeth on the outer periphery thereof and a small gear meshing with the large gear, wherein the large gear is defined by claims 1 to 6.
It is a gear described in any of the above.

An electric power steering apparatus according to an eighth aspect of the present invention is a reduction gear mechanism according to a seventh aspect of the present invention, a steering assist motor connected to the small gear, and the large gear that accompanies rotation of the motor. And a transmission means for transmitting the rotational force of the above to the steering mechanism.

The seventh and eighth inventions are the same as any of the first to sixth inventions.

[0021]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be described in detail below with reference to the drawings showing the embodiments thereof. Embodiment 1 FIG. 1 is a partially cutaway front view of Embodiment 1 of a gear according to the present invention, FIG. 2 is an enlarged sectional view taken along the line II-II of FIG. 1, and FIG. 3 is an enlarged view of a part of a core member. It is a side view. This gear 1 is a motor 3
A worm wheel that meshes with the worm 2 that is rotated by the rotation (see FIG. 4), and is an annular member 12 made of synthetic resin having teeth 11 on the outer circumference, and a metal member fitted inside the annular member 12. A core member 13, and the core member 13
The annular member 12 is fused to the above. Further, in the fitting portion 14 between the core member 13 and the annular member 12, the annular member 12
Is provided with an annular space 4 in which an increase in volume in the radial direction due to expansion of the space is to be suppressed.

The core member 13 is formed of a metal material such as mild steel into a disc shape, and circular flanges 13a, 13a are provided on both sides in the widthwise direction of the outer peripheral surface of the flange member 13a, 13a. The void 4 is formed between the two.
The heights of the flanges 13a, 13a are equal, in other words, they are substantially parallel to the center of rotation, and a concave portion 13b made of a twill-shaped lorette is provided on the peripheral surface of the flanges 13a, 13a. . Further, a fitting hole 13c is formed at the center of the core member 13, and the fitting hole 13c is formed.
A rotary shaft (for example, an output shaft 31 described later) is fitted in the.
The fitting portion 14 of the core member 13 is substantially symmetrical in shape on both sides with respect to the center in the width direction.

The annular member 12 is molded by injecting a molten synthetic resin such as nylon resin into a molding die, and the molded annular member 12 is fused to the flanges 13a, 13a of the core member 13. To be done. Inside the annular member 12, the fused portions 12a, 12a on both sides which are fused to the flanges 13a, 13a are substantially parallel to the center of rotation, and the space between the fused portions 12a, 12a is on both sides. It is curved so that the thickness between it and the tooth bottom 11a, which is a concave arc, is substantially equal. Further, the curved portion 12b is capable of bending in the radial direction. This annular member 1
The second tooth 11 is molded by the above-mentioned mold, but after molding the annular element body having no other teeth 11,
It may be formed by gear cutting.

The space 4 is a fusion-bonded portion 12 of the annular member 12.
The fusion-bonded portions 12a and 12a are fusion-bonded to each other in a temporary coupling state in which a and 12a are fitted to the flanges 13a and 13a of the core member 13 so as to be a tight fit, thereby forming a hermetic seal. Further, the space 4 has a width dimension of 1/2 or more, preferably about 2/3 of the width dimension of the annular member 12,
When the annular member 12 expands in the radial direction due to the temperature increase and the humidity increase, a part of the expansion is absorbed in the void 4.

The fusion of the annular member 12 is performed by, for example, a high frequency induction heating method. This high-frequency induction heating method heats the surface of the core member 13 by arranging the temporarily coupled unfinished gear inside an induction coil connected to a high-frequency motor generator and applying a high-frequency current to the induction coil. , The flange portions 13a, by melting the surface portions (contact surface portions with the core member 13) of the fusion-bonded portions 12a, 12a in the annular member 12.
Fused to 13a. In this case, the fused portion enters into the recess 13b provided on the peripheral surfaces of the flanges 13a, 13a, so that the relative rotation between the annular member 12 and the core member 13 and the relative movement in the axial direction are prevented. It

The gear 1 thus constructed is used as a worm wheel of the reduction gear mechanism A, for example. FIG. 4 is a sectional view of the reduction gear mechanism. This reduction gear mechanism A
Is a worm wheel 1 in which a fitting hole 13c of a core member 13 is fitted and fixed to a rotating shaft 5, and teeth 1 of the worm wheel 1.
1, a metal worm 2 that meshes with the bearing 1, bearings 6 and 7 fitted to shaft portions 22 and 23 connected to both ends of a tooth portion 21 of the worm 2, and the worm 2 via the bearings 6 and 7. And a housing 8 made of aluminum rotatably supported. The rotation of the motor 3 connected to one shaft portion 23 is reduced and transmitted to the worm wheel 1 to rotate the rotary shaft 5. ing.

The reduction gear mechanism A thus constructed is
For example, it is used in an electric power steering device. FIG. 5 is a sectional view of the electric power steering apparatus according to the present invention.

The electric power steering apparatus has an upper end connected to a steering wheel 9 for steering and an input shaft 10 having a tubular portion at the lower end, and an upper end of the input shaft 10 inserted into the tubular portion of the input shaft 10. Of the torsion bar 30, a torsion bar 30 that is coaxially connected to the steering wheel 9, and is twisted by the action of steering torque applied to the steered wheels 9, an output shaft 31 whose lower end is coaxially connected to the lower end of the torsion bar 30, and the torsion bar 30. A torque sensor 32 for detecting a steering torque applied to the steered wheels 9 based on a relative rotational displacement amount of the input shaft 10 and the output shaft 31 according to the twist, and a steering assist for driving based on the torque detected by the torque sensor 32. Motor 3 and the rotation of the motor 3 to reduce the rotation of the output shaft 31
To the reduction gear mechanism A that is transmitted to the torque sensor 3
2 and a housing 8 accommodating the reduction gear mechanism A, and the motor 3 is attached to the housing 8. The output shaft 31 constitutes the rotary shaft 5.

The reduction gear mechanism A includes a shaft portion 23 of the worm 2.
Is connected to the drive shaft 3a of the motor 3, and the worm wheel 1 is fitted and fixed in the middle of the output shaft 31. The engagement of the worm 2 and the worm wheel 1 causes the drive shaft 3a to rotate. Decelerate to output shaft 31
To the rack and pinion type steering mechanism (not shown) from the output shaft 31 via the universal joint. The output shaft 31 and the universal joint form a transmission unit that transmits the rotational force of the worm wheel 1 to the steering mechanism.

In the reduction gear mechanism A and the electric power steering apparatus configured as described above, the fitting portion 14 of the core member 13 of the worm wheel 1 to the annular member 12 is provided.
Since there is a space 4 in which the increase in the volume of the annular member 12 in the radial direction due to expansion is to be suppressed, when the annular member 12 expands in the radial direction due to temperature increase and humidity increase, this annular member 12 Expands so that the space 4 becomes narrower, and part of the increase in volume of the annular member 12 is part of the space 4.
Absorbed by As a result, an increase in volume outward in the radial direction can be suppressed, and clogging due to this increase in volume can be eliminated. When the space 4 does not become too narrow due to the increase in volume, the teeth 11 of the annular member 12 having the increased volume are pressed against the tooth surface of the worm 2, and the pressing causes the teeth 11 of the annular member 12 to be closer to the teeth 11 than the space 4. The part flexes into the cavity 4 and a part of the volume increase can be absorbed by the cavity 4, thus eliminating clogging.

Further, since the tooth traces of the worm wheel 1 and the worm 2 constituting the reduction gear mechanism A are twisted in the rotation direction with respect to the rotation center line, the tooth surface of the worm 2 in the electric power steering apparatus is When torque is applied in the rotating direction of the worm wheel 1, a component force is generated in one of the tooth width direction (axial length direction) of the worm wheel 1 and the other, but it is projected on the fitting portion 14 of the core member 13. Since the heights of the formed flanges 13a and 13a are equal to each other, the fused portions 12a and 12a of the annular member 12 can have the same overall strength resistance.

Further, the fused portions 12 are formed on both sides of the annular member 12.
a, 12a, and the vacant space 4 can be hermetically sealed by the fusion-bonded portions 12a, 12a. Further, the steam in the vacant space 4 can be evaporated by the heat generated at the time of the fusion-bonding. The water vapor of No. 4 can be made relatively small. As a result, even when the humidity around the gear increases, the expansion of the annular member 12 due to the humidity can be suppressed.

Second Embodiment FIG. 6 is an enlarged sectional view showing the structure of the second embodiment of the gear. In the gear 1 according to the second embodiment, instead of providing the core member 13 with a recess that should be the void 4, the void 4a is formed around the entire circumference in the central portion between both side surfaces of the annular member 12 in the fitting portion 14. Further, the fitting portion 14 is a tapered surface that is inclined with respect to the center of rotation.

At the large-diameter end of the tapered surface of the core member 13 made of a metal material such as mild steel, there is provided a circular flange 13d that abuts one side surface of the annular member 12. In addition, the core member 13
The taper surface is provided with the concave portion 13b formed of a twill-shaped lowlet.

The fitting portion 14 of the injection-molded annular member 12
Then, circular flanges 12c and 12d are provided so as to project on both sides in the width direction, and the space 4a is formed between the flanges 12c and 12d. The flanges 12c and 12d have different heights, and the peripheral surfaces of the flanges 12c and 12d are tapered surfaces. Further, the flanges 12c and 12d are curved so that the thickness between the flanges 12c and 12d and the tooth bottom 11a, which is a concave arc, is substantially equal over both side surfaces. Further, the curved portion 12b is capable of bending in the radial direction.

The space 4a is the flange 1 of the annular member 12.
The peripheral surface portions of the flanges 12c and 12d are fusion-bonded to each other in a sealed state in which the taper surfaces 2c and 12d are fitted to the tapered surface of the core member 13 to form a hermetic seal. Also, this vacant space 4
The width a is not less than ½ of the width of the annular member 12, preferably about ⅔, and when the annular member 12 expands in the radial direction due to temperature increase and humidity increase, a part of the expansion is taken. The absorption is made in the void 4a.

The fusion of the annular member 12 is performed by a friction fusion method, a spin fusion method, or a vibration fusion method in addition to the high frequency induction heating method. For example, in the friction welding method, a vibration transmitting member (not shown) is fitted into the fitting hole 13c from the flange 13d side of the core member 13 in a state where the other side surface of the annular member 12 is brought into contact with the pedestal. The vibrating member is vibrated in the axial direction of the core member 13 while pressing the tapered surfaces of the joint portion 14 together to generate frictional heat between the tapered surface of the core member 13 and the flanges 12c and 12d. The peripheral surface portions of the flanges 12c and 12d are melted by frictional heat and fused to the core member 13. In this case, the fused portion enters into the concave portion provided on the peripheral surfaces of the flanges 13a, 13a, so that relative rotation and relative movement in the axial direction are prevented. Further, since the fitting portion 14 has a tapered surface, the surface pressure at the fitting portion 14 can be increased by vibration in the axial direction. Further, since the flange 13d is provided on the large-diameter end of the tapered surface of the core member 13, even when the peripheral surface portions of the flanges 13a, 13a are fused, the flange portion 13d is moved in the axial direction of the fitting portion 14. The flange 13d regulates the relative movement of the fitting portion 14d.
It is possible to reduce the positional deviation in the axial direction.

In the second embodiment, when the annular member 12 expands in the radial direction due to temperature increase and humidity increase, the annular member 12 expands so that the space 4a becomes narrower and the volume of the annular member 12 increases. Is partially absorbed by the void 4a. As a result, an increase in volume outward in the radial direction can be suppressed, and clogging of the mesh can be eliminated. Also,
When the space 4a does not become too narrow due to the increase in volume, the teeth 11 of the annular member 12 having the increased volume are replaced by the worm 2
Is pressed against the tooth surface of the annular member 12 by this pressing.
The portion of the tooth 11 side closer to the cavity 4a of the above is bent into the cavity 4a, and a part of the volume increase can be absorbed by the cavity 4a.
It can eliminate clogging.

Since other configurations and operations are the same as those of the first embodiment, the same parts are designated by the same reference numerals,
The detailed explanation and the explanation of the action and effect are omitted.

In the embodiment described above, the voids 4 and 4a are filled with dry air, a gas containing no water vapor, or an elastic body having a Young's modulus smaller than that of the material of the annular member 12. It is also possible to eliminate the water vapor in the voids 4 and 4a. In this case, since there is no water vapor in the cavities 4 and 4a or there is relatively little water vapor, expansion of the annular member 12 due to water vapor in the cavities 4 and 4a can be suppressed. When the space 4, 4a is filled or accommodated with the elastic body, the elastic body can adjust the amount of bending of the annular member 12 toward the space 4, 4a side due to the engagement with the worm 2. Therefore, the bending amount of the annular member 12 can be easily set.

Further, in the embodiment described above, the cavities 4 and 4a are formed over the entire circumference, but one or a plurality of elongated holes that are long in the circumferential direction may be used. Also,
The cavities 4 and 4a may be open to one side surface or both side surfaces of the annular member 12 and may be arranged in a plurality in a circumferentially spaced manner. Further, the voids 4 and 4a are annular members 12.
It may be formed so as to be spaced apart in the circumferential direction between the inner side of and the bottom 11a.

Further, in the first embodiment, the annular member 12 is fused to the core member 13 by the high frequency induction heating method, but in addition, as in the second embodiment, the friction welding method, the spin welding method, and the vibration fusion method are used. It may be fused by a bonding method. Further, in the second embodiment, fusion may be performed by a high frequency induction heating method,
The fusion method is not particularly limited. Further, the reduction gear mechanism A of the above-described embodiment is a worm gear including a small gear that is the worm 2 and a large gear that is the worm wheel 1, as well as a spur gear that includes a spur small gear and a large gear. It may be a gear.

[0043]

As described above in detail, according to the first invention,
When the volume of the gear in the radial direction increases due to the temperature rise and humidity increase around the gear, a part of the volume increase can be absorbed by the void, so that the volume increase outward in the radial direction can be suppressed, and the meshing It is possible to eliminate clogging, and further, it is possible to easily obtain a desired empty space without performing special processing after the annular member is joined to the core member,
Moreover, the annular member and the core member can be easily joined by fusion.

According to the second invention, it is possible to further increase the coupling strength between the annular member and the core member.

According to the third invention, it is easy to manufacture the annular member.

According to the fourth invention, the thickness from the inner side of the annular member to the tooth bottom can be made relatively small, and moreover,
The annular member and the core member can be easily joined by fusion without crushing the recess to be the void.

According to the fifth aspect of the present invention, the annular member and the core member can be joined by a simple fusion method such as a friction fusion method, a spin fusion method, a vibration fusion method and the like, as compared with the high frequency induction heating method. it can.

According to the sixth aspect of the present invention, it is possible to reduce the positional deviation in the axial direction even when joining by a simple fusion method such as a friction fusion method.

According to the seventh and eighth inventions, the same effect as that of any one of the first to sixth inventions can be obtained.

[Brief description of drawings]

FIG. 1 is a partially cutaway front view of a first embodiment of a gear according to the present invention.

FIG. 2 is an enlarged sectional view taken along line II-II of FIG.

FIG. 3 is an enlarged side view of a part of the core member of the gear according to the present invention.

FIG. 4 is a sectional view of a reduction gear mechanism according to the present invention.

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

FIG. 6 is an enlarged cross-sectional view showing the configuration of the second embodiment of the gear according to the present invention.

FIG. 7 is a cross-sectional view showing a configuration of a conventional reduction gear mechanism and an electric power steering device.

[Explanation of symbols]

1 Worm wheel (large gear) 11 teeth 12 Annular member 13 core member 13b recess 13d Tsuba 14 Fitting part 2 worm (small gear) 3 motor 4, 4a void A reduction gear mechanism

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Mitsuharu Minami             3-5-8 Minamisenba, Chuo-ku, Osaka-shi, Osaka               Koyo Seiko Co., Ltd. (72) Inventor Masashi Kuze             3-5-8 Minamisenba, Chuo-ku, Osaka-shi, Osaka               Koyo Seiko Co., Ltd. F-term (reference) 3D033 CA04                 3J009 DA06 DA16 DA18 EA06 EA19                       EA23 EA32 EB06 EB14 FA06                 3J030 AB03 BA03 BB02 BC01 BC10                       BD06 CA10

Claims (8)

[Claims] 1. A gear having an annular member made of a synthetic resin having teeth on the outer periphery and a core member fitted inside the annular member, wherein a fitting portion between the annular member and the core member, or A gear having a space in the vicinity of the fitting portion of the annular member, wherein the annular member is fused to the core member. 2. The gear according to claim 1, wherein the core member has a recess into which the fused portion of the annular member is inserted into the fitting portion. 3. The gear according to claim 1, wherein the core member has the void in a fitting portion. 4. The gear according to claim 1, wherein the annular member has the void in a fitting portion. 5. The fitting portion between the annular member and the core member is tapered to incline with respect to the center of rotation.
The gear according to any one of 1. 6. The gear according to claim 5, wherein the core member has a flange at the large-diameter end of the taper, which comes into contact with one side surface of the annular member. 7. A reduction gear mechanism comprising a large gear having teeth on its outer periphery and a small gear meshing with the large gear, wherein the large gear is the gear according to any one of claims 1 to 6. A reduction gear mechanism characterized by the above. 8. A reduction gear mechanism according to claim 7,
An electric power steering device comprising: a steering assisting motor connected to the small gear; and a transmission means for transmitting the rotational force of the large gear accompanying the rotation of the motor to a steering mechanism. .