JP2003042264A - Gear, reduction gear mechanism and electric power steering system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a worm wheel that can eliminate meshing extrusion due to a radial volume increase. SOLUTION: A plurality of voids 4 that suppress a radial volume increase due to an expansion under a temperature rise and a humidity rise caused by an atmospheric temperature and the like are defined in a circumferentially spaced arrangement.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a synthetic resin gear having teeth on its outer circumference, a reduction gear mechanism including the gear, and an electric power steering apparatus including the reduction gear mechanism.

[0002]

2. Description of the Related Art The steering of an automobile is arranged outside a vehicle compartment for steering a steering wheel (generally a front wheel) for rotating a steering wheel arranged inside the vehicle compartment. It is performed by telling the steering mechanism.

FIG. 11 is a sectional view showing the structure of a conventional electric power steering apparatus, and FIG. 12 is a sectional view showing the structure of a conventional reduction gear mechanism connected to a motor. As an electric power steering device for an automobile, FIG.
As shown in FIG. 12, for example, a steering wheel 100 for steering.
A first steering shaft 101 connected to the first steering shaft 101, a lower end of the steering shaft 101 is coaxially connected to the lower end of the steering shaft 101 via a torsion bar 102, and a lower end of the second steering shaft is connected to a steering mechanism connected to wheels. A steering shaft 103, a torque sensor 104 for detecting a torque applied to the first steering shaft 101 by rotating the steered wheels 100 by a twist generated in the torsion bar 102, and a detection result of the torque sensor 104,
A motor 105 for steering assistance that is driven based on the vehicle speed, the steering angle of the steered wheels 100, a worm 106 that is interlocked with the rotation of the motor 105, a worm wheel 107 that meshes with the worm 106, the worm 106, The steering shaft 103 is rotatably supported by the housing 108, and the operation of the steering mechanism according to the rotation of the steered wheels 100 is assisted by the rotation of the motor 105 to reduce the labor load of the driver for steering. Is configured.

The worm wheel 107 is an annular member 10 made of synthetic resin having teeth that mesh with the worm 106.
9 and a metallic core member 110 fitted inside the annular member 109, the core member 110 being the steering shaft 10
It is supported by No. 3 to reduce noise caused by meshing with the worm 106.

The worm 106 is arranged so as to intersect with the axis of the steering shaft 103, and a pair of rolling bearings 11 are provided.
The second steering shaft 103 supporting the worm wheel 107 is supported in the fitting hole of the housing 108 via 2, 113, and is supported in the housing 108 via a pair of rolling bearings 114, 115. , Warm 10
6 and the worm wheel 107 are prevented from moving in the radial direction and the axial direction.

In the electric power steering apparatus using the worm 106 and the worm wheel 107 as described above, the worm 106 and the worm wheel 1 are used.
The meshing portion of 07 is provided with an appropriate amount of backlash so that the worm 106 and the worm wheel 107 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 automobile. When the amount of backlash in the meshing portion is small, the load is large, and the worm 106 and the worm It becomes impossible to rotate the wheel 107 smoothly.

[0007]

However, in the conventional electric power steering apparatus configured as described above, the worm 106 and the worm wheel 107 are prevented from moving in the radial direction, and the worm 106 and the worm wheel 107 are prevented. Since the distance between the rotation centers is fixed, the ambient temperature becomes high and the temperature of the reduction gear mechanism becomes high, for example, 80 to 140 ° C., or the humidity around the reduction gear mechanism becomes relatively high. At that time, 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. 7 is made of synthetic resin, and has a core member 110.
The worm 106 and the worm 106 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. When the backlash amount was appropriate at room temperature and humidity, the temperature of the reduction gear mechanism increased due to ambient temperature and the like, and the humidity around the reduction gear mechanism increased. It was also found that the annular member 109 expands more than the worm 106, and the volume of the annular member 109 outward in the radial direction increases, causing meshing clogging.

The present invention has been made on the basis of such knowledge, and its main object is to provide a gear that can suppress meshing clogging due to an increase in volume in the radial direction, a reduction gear mechanism including the gear, and an electric power steering system. To provide a device.

[0010]

A gear according to the first invention is
In a gear with at least outer teeth made of synthetic resin,
It is characterized in that it has a void for suppressing an increase in volume in the radial direction due to expansion.

According to the first aspect of the invention, when the gear is expanded due to temperature increase and humidity increase due to atmospheric temperature and the like, and the volume in the radial direction increases, the void becomes narrower and the volume increases due to expansion. Some 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, when the void does not become so narrow due to the increase in volume, it is possible to bend between the void and the tooth surface in the direction of the void by meshing with another gear. As a result, clogging due to increase in volume can be eliminated.

A gear according to a second aspect of the invention is characterized in that a plurality of the voids are arranged in the circumferential direction with a space therebetween. Second
In the invention, since the voids are dispersed in the circumferential direction,
It is possible to suppress the increase in volume outward in the radial direction while ensuring the desired durability.

A gear according to a third aspect of the present invention is characterized in that the cavity is a long hole elongated in the circumferential direction. In the third invention, since the void is long in the circumferential direction, it is possible to absorb a part of the increase in volume in the radial direction over the entire length of the void,
It is possible to further eliminate clogging.

A gear according to a fourth aspect of the present invention includes an annular member made of synthetic resin having teeth on the outer periphery and a core member fitted inside the annular member. The core member and the annular member are provided. It is characterized in that the fitting portion has the above-mentioned empty space. Fifth
A gear according to the invention has an annular member made of a synthetic resin having teeth on the outer periphery and a core member fitted inside the annular member, and the annular member has the void. It is characterized by

In the fourth and fifth aspects of the invention, the absolute amount of the annular member can be reduced by the core member, the volume increase due to expansion can be reduced, and at the time of molding the annular member, The void can be easily obtained by the molding die.

A gear according to a sixth aspect of the present invention is characterized in that the annular member has the void in the central portion between both side surfaces thereof over the entire circumference. According to the sixth aspect of the present invention, since the void can be hidden, it is possible to surely prevent dust and the like from entering the void.

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 its outer periphery and a small gear that meshes with the large gear, wherein the large gear is defined by any one of 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 assisting motor connected to the small gear, and the large gear accompanying the rotation of the motor. And a transmission means for transmitting the rotational force of the above to the steering mechanism.

In the seventh invention and the eighth invention, when the large gear expands due to temperature increase and humidity increase of the reduction gear mechanism due to atmospheric temperature and the like, and the volume in the radial direction increases, the space becomes narrow. Since a part of the volume increase can be absorbed by the void, the volume increase outward in the radial direction can be suppressed, and the clogging due to this volume increase can be eliminated. In addition, when the void does not become so narrow due to the increase in volume, it is possible to bend between the void and the tooth surface by meshing with the small gear, and therefore, in the radial direction outward in the meshing state with the small gear. It is possible to suppress an increase in the volume of the mesh and eliminate clogging of the mesh.

[0020]

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. 1 is a partially cutaway front view showing a configuration of a first embodiment of a gear according to the present invention, and FIG.
11 is an enlarged cross-sectional view taken along line II-II of FIG. This gear 1 is a motor 3
Is a worm wheel that meshes with the worm 2 rotated by the rotation of, and includes a synthetic resin annular member 12 having teeth 11 on the outer periphery and a metal core member 13 fitted inside the annular member 12. The core member 13 and the annular member 1 are provided.
A plurality of voids 4 in which a volume increase in the radial direction due to the expansion of the annular member 12 is to be suppressed are provided in the fitting portion 14 with the circumferentially spaced apart portions.

The core member 13 is formed of a metal material such as mild steel into a disk shape, and a plurality of protrusions 13a protruding on both side surfaces are integrally provided on the outer peripheral surface so as to be spaced apart from each other in the circumferential direction. Has been done. The protrusions 13a are, for example, 0.01 to 1.0 at a position corresponding to the tooth 11 which is one tooth apart from the tooth 11.
It is projected at a height of 0 mm. A fitting hole 13b is formed in the center of the core member 13, and the fitting hole 13b is formed.
A rotary shaft (for example, a second steering shaft 31 to be described later) is fitted in.

The annular member 12 is formed by placing the core member 13 in an injection molding die as an insert and injecting a molten synthetic resin, and is integrally connected to the core member 13.

When the annular member 12 is molded, the space 4 is formed by the adjacent protrusions 13 on the outer peripheral surface of the core member 13.
After molding with the band-shaped core arranged between a and 13a, the core is extracted to fit the fitting portion 14 of the core member 13 to the annular member 12, in other words, the outer peripheral surface of the core member 13. And the inside of the annular member 12 are formed so as to penetrate through both side surfaces of the annular member 12. The space 4 has a width of 0.01 to 1.00 mm corresponding to the height of the protrusions 13a ...
When 2 expands in the radial direction, a part of this expansion is absorbed in the cavity 4. The annular member 12 is made of polyamide resin, for example.

The gear 1 thus constructed is used, for example, as a worm wheel of the reduction gear mechanism A. FIG. 3 is a sectional view showing the structure of the reduction gear mechanism according to the present invention. The reduction gear mechanism A includes a worm wheel 1 in which a through hole 13b of a core member 13 is fitted and fixed to a rotating shaft 5, a metal worm 2 that meshes with teeth 11 of the worm wheel 1, and teeth of the worm 2. Shaft part 2 connected to both ends of part 21
The bearings 6 and 7 fitted to the bearings 2 and 23 and the aluminum housing 8 that rotatably supports the worm 2 via the bearings 6 and 7 are connected to one shaft portion 23. The worm wheel 1 by decelerating the rotation of the motor 3
And the rotary shaft 5 is rotated.

The reduction gear mechanism A thus constructed is
For example, it is used in an electric power steering device. FIG. 4 is a sectional view showing the configuration of the electric power steering device according to the present invention.

The electric power steering apparatus has an upper end connected to a steering wheel 10 for steering and a first steering shaft 10 having a tubular portion at the lower end, and an upper end inserted into the tubular portion and the steering shaft 10 being at the upper end. A torsion bar 30 which is coaxially connected to the tubular portion of the torsion bar 30 and which is twisted by the action of steering torque applied to the steered wheels 9, and a second steering shaft 31 whose lower end is coaxially connected to the lower end of the torsion bar 30. , The first and second steering shafts 1 according to the twist of the torsion bar 30.
A torque sensor 32 that detects a steering torque applied to the steered wheels 9 based on the relative rotational displacement amounts of 0 and 31, a motor 3 for steering assistance that is driven based on the torque detected by the torque sensor 32, and the motor 3 And a housing 8 accommodating the torque sensor 32 and the speed reduction gear mechanism A. The housing 8 includes the speed reduction gear mechanism A for decelerating the rotation and transmitting the rotation to the second steering shaft 31. The motor 3 is attached to 8. The second steering 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 output shaft 3a of the motor 3, and the worm wheel 1 is fitted and fixed in the middle of the second steering shaft 31, and the output shaft 3a is engaged by the engagement of the worm 2 and the worm wheel 1. Slow down the rotation of the second
Is transmitted to the steering shaft 31 of the second steering shaft 31 via a universal joint, and is transmitted to, for example, a rack and pinion type steering mechanism (not shown). The second
The steering shaft 31 and the universal joint constitute a transmission means for transmitting 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.

Embodiment 2 FIG. 5 is a partially cutaway front view showing the structure of Embodiment 2 of the gear, and FIG. 6 is an enlarged sectional view taken along the line VI-VI of FIG. In the gear 1 of the second embodiment, instead of providing a plurality of cavities 4 in the fitting portion 14 of the core member 13 fitted inside the annular member 12 and the annular member 12 in the circumferential direction, The fitting part 1
4 has a space 4a in the center between both side surfaces of the annular member 12.
Is provided over the entire circumference.

On the outer peripheral surface of the core member 13 made of a metal material such as mild steel, circular flanges 13c, 13 are provided on both sides in the width direction.
c is projected, and the space between the flanges 13c, 13c is the space 4a. The depth of the void 4a is, for example, 0.01 to 1.00 mm.

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 description and the description of the operation will be omitted.

Third Embodiment FIG. 7 is an enlarged cross-sectional view of the essential parts showing the configuration of the third embodiment of the gear according to the present invention. The gear 1 according to the third embodiment is
Instead of providing the cavities 4 and 4a in the fitting portion 14 of the core member 13 fitted inside the annular member 12 and the annular member 12,
A plurality of cavities 4b are provided between the inner circumference of the annular member 12 and the tooth bottom.
Are spaced apart in the circumferential direction. The cavity 4b has a height of, for example, 0.5 to 2.0 mm and is a long hole that is long in the circumferential direction.

8 and 9 are explanatory views showing a state where the volume of the gear according to the third embodiment of the present invention is increased. In the third embodiment, when the annular member 12 expands in the radial direction due to temperature increase and humidity increase, the annular member 1
2 expands so that the space 4b becomes narrower, and part of the increase in volume of the annular member 12 is absorbed by the space 4b. As a result, an increase in volume outward in the radial direction can be suppressed, and clogging of the mesh can be eliminated. Further, when the space 4b does not become so narrow due to the increase in volume, the teeth 11 of the annular member 12 having an 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 4b. The part bends into the cavity 4b and part of the volume increase can be absorbed by the cavity 4b, eliminating clogging.

Since other configurations and operations are the same as those of the first embodiment, like parts are designated by like reference numerals,
The detailed description and the description of the operation will be omitted.

Fourth Embodiment FIG. 10 is an enlarged cross-sectional view of the essential parts showing the structure of the fourth embodiment of the gear according to the present invention. Gear 1 of Embodiment 4
Instead of making the void 4b elongated in the circumferential direction, a plurality of round holes 4c are formed in a row in the region of the elongated hole.

Other configurations and operations are the same as those in the first and third embodiments.
Therefore, the same reference numerals are given to the same parts, and the detailed description and the operation description thereof will be omitted.

In the embodiment described above, the worm wheel 1 in which the metallic core member 13 is fitted inside the annular member 12 made of synthetic resin has been described. Without the core member 13,
The whole may be made of synthetic resin. In this case, the void 4, more specifically, the void 4b, is provided in the middle of the radial direction.

In the embodiment described above, the cavities 4 and 4b are penetrated through both side surfaces of the annular member 12, but in addition, the cavities 4 and 4b are recessed on one side surface of the annular member 12. It may be shaped. Further, the voids 4, 4a, 4b in the embodiment can be bent by the expansion of the worm wheel 1 and the annular member 12 which are made of synthetic resin as a whole, or the voids 4b of the annular member 12 Also, a structure may be used in which a flexible material capable of being bent by the above-described bending of the tooth 11 side portion is filled. Further, the reduction gear mechanism of the embodiment described above 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 including a spur small gear and a large gear. May be

[0040]

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 Can eliminate blockages.

According to the second aspect, since the voids are dispersed in the circumferential direction, it is possible to suppress an increase in volume outward in the radial direction while ensuring desired durability.

According to the third aspect of the invention, since the void is long in the circumferential direction, it is possible to absorb a part of the increase in volume in the radial direction over the entire length of the void, so that the mesh clogging can be further eliminated. .

According to the fourth and fifth aspects of the invention, the absolute amount of the annular member can be reduced by the core member, the volume increase due to expansion can be reduced, and
When molding the annular member, the void can be easily obtained by the molding die.

According to the sixth aspect of the present invention, since the void can be hidden, it is possible to surely prevent dust and the like from entering the void.

According to the seventh invention and the eighth invention, when the large gear expands due to the temperature increase and the humidity increase of the reduction gear mechanism due to the ambient temperature and the volume in the radial direction increases, the void becomes narrow. Since a part of the increase in volume can be absorbed by the void, it is possible to suppress the increase in volume outward in the radial direction and eliminate clogging due to this increase in volume. In addition, when the void does not become so narrow due to the increase in volume, it is possible to bend between the void and the tooth surface by meshing with the small gear, and therefore, in the radial direction outward in the meshing state with the small gear. It is possible to suppress an increase in the volume of the mesh and eliminate clogging of the mesh.

[Brief description of drawings]

FIG. 1 is a partially cutaway front view showing a configuration 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 a sectional view showing a configuration of a reduction gear mechanism according to the present invention.

FIG. 4 is a sectional view showing a configuration of an electric power steering apparatus according to the present invention.

FIG. 5 is a partially cutaway front view showing the configuration of the second embodiment of the gear according to the present invention.

6 is an enlarged cross-sectional view taken along the line VI-VI of FIG.

FIG. 7 is an enlarged cross-sectional view of a main part showing a configuration of a third embodiment of a gear according to the present invention.

FIG. 8 is an explanatory diagram showing a state in which the gear according to the third embodiment of the present invention has increased in volume.

FIG. 9 is an explanatory diagram showing a state in which the gear according to the third embodiment of the present invention has increased in volume.

FIG. 10 is an enlarged cross-sectional view of the main parts showing the configuration of the fourth embodiment of the gear according to the present invention.

FIG. 11 is a cross-sectional view showing a configuration of a conventional electric power steering device.

FIG. 12 is a sectional view showing a configuration of a conventional reduction gear mechanism connected to a motor.

[Explanation of symbols]

1 worm wheel 11 teeth 12 Annular member 13 core member 14 Fitting part 2 warm 3 motor 4, 4a, 4b Vacancy

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Hiroaki Kando             3-5-8 Minamisenba, Chuo-ku, Osaka-shi, Osaka               Koyo Seiko Co., Ltd. F-term (reference) 3D033 CA04 CA16 CA21 CA31                 3J009 DA06 EA04 EA05 EA06 EA11                       EA19 EA23 EA32 EB06 EB14                       FA08 FA14                 3J030 AC10 BA03 BB17 BC01 BC02                       BC08 BD04 CA10

Claims (8)

[Claims] 1. A gear having at least outer teeth made of a synthetic resin, which has a cavity for suppressing an increase in volume in a radial direction due to expansion. 2. The gear according to claim 1, wherein a plurality of the voids are circumferentially spaced from each other. 3. The gear according to claim 1, wherein the cavity is a long hole elongated in the circumferential direction. 4. An annular member made of synthetic resin having teeth on the outer periphery, and a core member fitted inside the annular member, wherein the fitting portion between the core member and the annular member is provided with the above-mentioned member. The gear according to any one of claims 1 to 3, which has a void. 5. An annular member made of synthetic resin having teeth on the outer periphery and a core member fitted inside the annular member, wherein the annular member has the void. Item 1
The gear according to any one of 1 to 3. 6. The gear according to claim 5, wherein the void is provided in the central portion between both side surfaces of the annular member over the entire circumference. 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. Reduction gear mechanism characterized in that. 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. .