JP2003065422A - Gear, reduction gear mechanism and electric power steering device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method capable of retaining a lubricant between tooth flanks to reduce frictions between tooth flanks when tooth flanks are made to forcibly contact with each other and capable of reducing a rotational resistance when a gear engagement malfunctions. SOLUTION: A recess 12 is provided to hold a lubricant in a gear 11a to increase a lubricity between gears.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a gear, a reduction gear mechanism including the gear, and an electric power steering apparatus including the reduction gear mechanism and using a motor as a source of a steering assist force.

[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. 5 is a sectional view showing the structure of a conventional electric power steering apparatus, and FIG. 6 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, as shown in FIGS. 5 and 6, for example, a first steering shaft 101 connected to steering wheels 100 for steering, and a torsion bar 102 at the lower end of the steering shaft 101. The lower end of which is coaxially connected via the second end of which is connected to a steering mechanism which is connected to wheels.
Steering shaft 103, a torque sensor 104 for detecting the torque applied to the first steering shaft 101 by rotating the steered wheels 100 by the torsion generated in the torsion bar 102, the detection result of the torque sensor 104, the vehicle speed, the steering A worm 10 which is connected to an output shaft of a motor 105 for assisting steering which is driven based on the steering angle of the wheels 100, reduces the rotation of the output shaft, and transmits the decelerated rotation to the second steering shaft 103.
6 and a reduction gear mechanism having a worm wheel 107, the operation of the steering mechanism according to the rotation of the steered wheels 100 is assisted by the rotation of the motor 105, and the labor load of the driver for steering is reduced. Is configured.

The worm wheel 107 constituting the reduction gear mechanism is provided with a synthetic resin annular member 108 having teeth meshing with the worm 106, and a metal core member 109 fitted inside the annular member 108. And the core member 109 is supported by the steering shaft 103, and the worm 1
The noise due to the meshing with 06 is reduced.

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 steering shaft 103, which is supported in the housing 113 via the bearings 1 and 112, supports the worm wheel 107, and the housing 1 via the pair of rolling bearings 114 and 115.
It is supported in 13 to prevent the worm 106 and the worm wheel 107 from moving in the radial direction and the axial direction.

When the motor 105 is used as the source of the steering assist force, the rotation of the motor 105 is mechanically transmitted from the worm 106 of the reduction gear mechanism to the worm wheel 107, so that as the output of the motor 105 increases, The load on the reduction gear mechanism increases, and as a result, the worm 1
06, the wear of the tooth surface of the worm wheel 107 increases.

In order to suppress the increase in the wear of the tooth surface, a lubricant such as grease having high viscosity is applied to the teeth of the worm 106 and the worm wheel 107.

[0008]

However, the motor 10
5 rotations from worm 106 to worm wheel 107
When it is transmitted to the tooth surface of the worm 106 and the tooth surface of the worm wheel 107, the lubricant is scraped outward from the tooth surface by this pressure contact, and there is almost no lubricant between the tooth surfaces. Since the tooth surfaces are pressed against each other in this state, the tooth surfaces are likely to be worn, and improvement measures have been demanded.

The annular member 108 of the worm wheel 107 is made of synthetic resin, and has a core member 109 and the worm 1.
No. 06 is made of metal, and although each has a different linear expansion coefficient, 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 temperature of the reduction gear mechanism rises due to the ambient temperature and the like, and the humidity around the reduction gear mechanism rises, so that the synthetic resin annular member 108 becomes a metal core member 109 and a worm. Compared with No. 106, it expands greatly, the pressure contact force between the tooth surfaces increases, meshing clogging occurs, and the rotation resistance increases.

The present invention has been made in view of such circumstances, and a main object thereof is to be able to hold a lubricant between tooth surfaces when the tooth surfaces are pressed against each other, and to prevent wear of the tooth surfaces. It is an object of the present invention to provide a gear, a reduction gear mechanism, and an electric power steering device that can reduce the rotational resistance when the meshing is clogged.

[0011]

A gear according to the first invention is
The tooth surface has a recess for holding a lubricant.

According to the first aspect of the present invention, a part of the lubricant applied to the teeth in advance enters the concave portion of the tooth surface, and the lubricant is retained in the concave portion. When pressed, the lubricity between the tooth surfaces can be improved, and the wear of the tooth surfaces can be reduced. Further, even when the pressure contact force between the tooth surfaces increases due to the expansion of the gears and the meshing clogging occurs, the lubricity between the tooth surfaces can be improved by the lubricant in the recesses, and the rotation resistance can be reduced.

A gear according to a second aspect of the invention is characterized in that the recess is formed by shot peening. According to the second aspect of the invention, since the recesses are easily formed by spraying the steel particles on the tooth surface of the gear body that has been processed similarly to the existing gear, it is possible to easily obtain a plurality of recesses. Further, the cost can be reduced despite the fact that the concave portion is provided.

A reduction gear mechanism according to a third aspect of the present invention is the first aspect of the present invention.
Alternatively, it is provided with the gear described in 2. In the third aspect of the invention, a part of the lubricant applied to the teeth in advance enters the concave portion of the tooth surface and the lubricant is held in the concave portion, so that the tooth surfaces are pressed against each other by the meshing of the gears. At this time, the lubricity between the tooth surfaces can be improved, and the wear of the tooth surfaces can be reduced.

A reduction gear mechanism according to a fourth aspect of the present invention is a driven gear having an annular member made of synthetic resin having teeth on the outer periphery and a core member fitted inside the annular member, and a drive gear meshing with the driven gear. In a reduction gear mechanism including a gear, at least one tooth surface of the driven gear and the drive gear has a recess for holding a lubricant.

According to the fourth aspect of the present invention, a part of the lubricant applied to the teeth in advance enters the concave portion of the tooth surface, and the lubricant can be retained in the concave portion, so that the tooth surface is expanded by the expansion of the annular member. Even when the pressure contact force between them increases and clogging of the mesh occurs, the lubricant of the recess can improve the lubricity between the tooth surfaces and reduce the rotation resistance.

An electric power steering device according to a fifth aspect of the present invention includes a reduction gear mechanism according to claim 3 or 4,
A steering assisting motor connected to a drive gear of the reduction gear mechanism, and a transmission means for transmitting a rotational force of a driven gear resulting from the rotation of the motor to the steering mechanism.

According to the fifth aspect of the invention, when the rotation of the motor is transmitted from the drive gear to the driven gear and the tooth flanks of the gears are pressed against each other, there is a recess between the tooth flanks that holds the lubricant. Therefore, the lubricity between the tooth surfaces can be improved, and even when the pressure contact force between the tooth surfaces increases due to the expansion of the driven gear and the meshing clogging occurs, the lubricant in the recessed portion causes The lubricity can be improved, and the rotation resistance can be reduced.

[0019]

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 front view showing a configuration of Embodiment 1 of a gear according to the present invention, FIG. 2 is an enlarged view of a main part of the gear according to the present invention, (a) is a sectional view of teeth, (b) is a cross-sectional view of the concave portion of the tooth surface. The gear is a worm 1 in which a tooth portion 1a having a plurality of teeth 11 is formed by hobbing the outer periphery of a right circular cylinder member with, for example, a hob, and has shaft portions 1b and 1c at both ends. The tooth surface 11a of the tooth 11 of the worm 1 is provided with a plurality of recesses 12 for holding a lubricant.

After the teeth 11 are formed by the hob, the recesses 12 are formed randomly by subjecting the surfaces of the teeth 11, that is, the tooth surfaces 11a, the tooth top surfaces 11b and the tooth bottom surfaces 11c to shot peening. There is. The shot peening process is to dent the surface of the tooth 11 by hitting small steel particles on the surface of the tooth 11, and the recess 12 has a diameter of the opening edge of about 0.05 to 0.5 mm.
The depth is about 0.05 to 0.5 mm.

The gear configured as described above is used as a worm of the reduction gear mechanism A. FIG. 3 is a sectional view showing the structure of the reduction gear mechanism. The reduction gear mechanism A meshes with a metal worm 1 and teeth 11 of the worm 1,
A worm wheel 2 having a fitting hole 2a at its center fitted and fixed to a rotary shaft 3, and bearings 4 and 5 fitted to shaft portions 1b and 1c connected to both ends of the tooth portion 1a of the worm 1, An aluminum housing 6 rotatably supporting the worm 1 via the bearings 4 and 5 is provided, and the rotation of a motor 8 joined to one shaft portion 1c via a shaft coupling 7 is reduced. Then, the worm wheel 2 is transmitted to the worm wheel 2 to rotate the rotating shaft 3.

The worm wheel 2 is provided with a synthetic resin annular member 21 having teeth 2b on the outer periphery thereof, and a metal core member 22 fitted inside the annular member 21.

The annular member 21 is formed by placing the core member 22 formed of a metal material such as mild steel in a disc shape as an insert in an injection molding die and injecting a molten synthetic resin material. Yes, it is integrally connected to the core member 22. A fitting hole 2a is formed in the center of the core member 22.
The rotary shaft 3 (for example, a second steering shaft 31 described later) is fitted into the fitting hole 2a.

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 9 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 so that the steering shaft 10 has 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 a 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 10 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 a relative rotational displacement amount of the steering wheel 31, and a steering assist that is driven based on the torque detected by the torque sensor 32, the vehicle speed, the steering angle of the steered wheels 9, and the like. Motor 8 and the motor 8
The speed reduction gear mechanism A that reduces the speed of the rotation and transmits the rotation to the second steering shaft 31, and the torque sensor 32.
And a housing 6 accommodating the reduction gear mechanism A, and the motor 8 is attached to the housing 6. The second steering shaft 31 constitutes the rotary shaft 3.

The reduction gear mechanism A includes a shaft portion 1c of the worm 1.
Is connected to the output shaft 8a of the motor 8, and the worm wheel 2 is fitted and fixed in the middle of the second steering shaft 31, and the output shaft 8a is meshed with the worm 1 and the worm wheel 2. 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 2 to the steering mechanism.

In the reduction gear mechanism A and the electric power steering apparatus configured as described above, since the tooth surface 11a of the worm 1 is provided with the recess 12 for holding the lubricant, the worm 1 and the worm wheel 2 are provided. Tooth 1
A lubricant such as grease applied in advance to the first and second b is held in the recess 12. As a result, the tooth surface 11a of the worm 1 and the tooth surface of the worm wheel 2 are brought into pressure contact with each other by the rotation of the motor 8, and the applied lubricant is scraped outward from the tooth surface 11a by the pressure contact between the tooth surfaces. When this is done, most of the lubricant retained in the recess 12 of the tooth surface 11a is maintained in a retained state without being scratched out from the tooth surface 11a, and the lubricant in the recess 12 allows the lubricity of the tooth surface 11a to be improved. And the wear of the tooth surface 11a can be reduced. In addition, when the tooth surface in the pressure contact state becomes the non-pressure contact state due to the change in the meshing relationship between the teeth 11 and 2b, the lubricant that has been scraped out from the tooth surface due to the pressure contact between the tooth surfaces is changed due to its viscosity. Since it returns to the tooth surface, the returned lubricant is replenished in the recess 12.

Further, the backlash amount of the reduction gear mechanism A was proper at room temperature and humidity at the time of assembly, but it was synthesized by the temperature increase of the reduction gear mechanism A due to the ambient temperature and the humidity around the reduction gear mechanism A. When the resin annular member 21 expands more than the metal core member 22 and the worm 1 and the pressure contact force between the tooth surfaces increases to cause meshing clogging, the recess 12 provided in the tooth surface 11a. The internal lubricant can enhance the lubricity of the tooth surface 11a and reduce the wear of the tooth surface 11a.

Embodiment 2 In the gear of Embodiment 2, instead of forming the recess 12 by shot peening, a worm 1 having a plurality of recesses 12 on its surface is formed by sintering a sintered material such as iron. It was done. The recessed portion 12 is formed by a sintered body having a surface roughness, and a lubricant is impregnated and held in the recessed portion 12.

In the second embodiment, it is not necessary to form the recess 12 by shot peening or the like, and the recess 12 can be obtained by sintering, so that the processing steps can be reduced and the cost can be reduced. obtain.

Since the other structure and operation are similar to those of the first embodiment, detailed description of the structure and operation will be omitted.

Although the recess 12 is provided on the tooth surface 11a of the worm 1 in the above-described embodiment, the recess 12 may be provided on the tooth surface of the worm wheel 2, or the worm 1 may be provided. It may be provided on the tooth surface of the worm wheel 2. Further, the recess 12 is the tooth surface 11 of the tooth 11.
a, the tooth crest surface 11b and the tooth bottom surface 11c, and may be provided only on the tooth surface 11a or may be provided on the entire surface.

Further, in the embodiment described above, the worm wheel 2 in which the core member 22 is fitted to the annular member 21 made of synthetic resin is used, but in addition, the worm wheel 2 is entirely made of synthetic resin material. Alternatively, it may be formed of a metal material.

The speed reduction mechanism A of the above-described embodiment is a worm gear including a drive gear that is a worm 1 and a driven gear that is a worm wheel 2, and a drive gear and a hypoid wheel that are hypoid pinions. It may be a hypoid gear equipped with a driven gear. Further, the reduction gear mechanism may be a bevel gear.

[0035]

According to the first aspect of the present invention, when the tooth surfaces are brought into pressure contact with each other by the meshing of the gears, the lubricity between the tooth surfaces can be improved and the wear of the tooth surfaces can be reduced. Further, even when the pressure contact force between the tooth surfaces increases due to the expansion of the gears and the meshing clogging occurs, the lubricity between the tooth surfaces can be improved by the lubricant in the recesses, and the rotation resistance can be reduced.

According to the second invention, it is possible to easily obtain a plurality of recesses, and it is possible to reduce the cost because the recesses are provided.

According to the third aspect, when the tooth surfaces are brought into pressure contact with each other by the meshing of the gears, the lubricity between the tooth surfaces can be improved and the wear of the tooth surfaces can be reduced.

According to the fourth aspect of the present invention, even when the pressure contact force between the tooth surfaces increases due to the expansion of the annular member, and the meshing clogging occurs, the lubricant in the recessed portion improves the lubricity between the tooth surfaces. Therefore, rotation resistance can be reduced.

According to the fifth aspect of the invention, when the rotation of the motor is transmitted from the drive gear to the driven gear and the tooth surfaces of the gears are pressed against each other, the lubricity between the tooth surfaces can be improved, and the driven gear can be made. Even when the pressure contact force between the tooth surfaces increases due to the expansion of No. 1 and the meshing clogging occurs, the lubricant of the recessed portions can improve the lubricity between the tooth surfaces and reduce the rotation resistance.

[Brief description of drawings]

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

FIG. 2 is an enlarged view of a main part of a gear according to the present invention,
(a) is a cross-sectional view of a tooth, and (b) is a cross-sectional view of a recess on a tooth surface.

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

FIG. 6 is a sectional view showing a configuration of a conventional reduction gear mechanism connected to a motor.

[Explanation of symbols]

1 worm (gear) 11 teeth 11a tooth surface 12 recess 2 Worm wheel (gear) 21 annular member 22 Core member 8 motor

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Masayoshi Sakuta             3-5-8 Minamisenba, Chuo-ku, Osaka-shi, Osaka               Koyo Seiko Co., Ltd. (72) Inventor, Kajuya Yoshioka             3-5-8 Minamisenba, Chuo-ku, Osaka-shi, Osaka               Koyo Seiko Co., Ltd. F-term (reference) 3D033 CA04                 3J030 AC01 BA03 BB06 BC01 BC02                       BC03

Claims (5)

[Claims] 1. A gear having a tooth surface having a recess for holding a lubricant. 2. The gear according to claim 1, wherein the recess is formed by shot peening. 3. A reduction gear mechanism comprising the gear according to claim 1 or 2. 4. A reduction gear mechanism including a driven gear having an annular member made of synthetic resin having teeth on the outer periphery and a core member fitted inside the annular member, and a drive gear meshing with the driven gear. 2. The reduction gear mechanism according to claim 1, wherein at least one tooth surface of the driven gear and the drive gear has a recess for holding a lubricant. 5. The reduction gear mechanism according to claim 3, a steering assisting motor connected to a drive gear of the reduction gear mechanism, and a steering force of a driven gear accompanying rotation of the motor. An electric power steering apparatus, comprising: a transmission unit that transmits the power to the take-up mechanism.