JP2001280428A - Worm gear apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a worm gear apparatus wherein gear teeth of worm wheel can be made to shape by die forming means and a backlash adjustment can be carried out on the wheel side. SOLUTION: The worm gear apparatus comprises a worm wheel 1 engaged with a spline 511 arranged around the periphery of an output shaft 51 which constitutes a component of a steering shaft 5, a worm shaft 2 having a worm gear 21 engaged with the worm wheel gear teeth 11, an electric motor 3 which transmits a power to the worm shaft 2, and a spring which acts to press the worm wheel 1 in the direction of the axis thereof. The gear teeth 11 of the worm wheel comprises a helical with constant tooth thickness on one half (11A) thereof and a worm gear on another half thereof which is formed to have a contact with the helical gear and is so shaped that a tooth thickness increases in the direction of a facewidth toward an end-face.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a worm gear device comprising a worm shaft having worm teeth and a worm wheel having hourglass-shaped teeth. BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a worm gear device in which a helical gear is partially formed in a streak direction so that a tooth portion of a worm wheel can be formed by molding means such as sintering molding means.

[0002]

2. Description of the Related Art Generally, as shown in FIG. 5, a worm gear device has a worm shaft 10 having worm teeth, and a drum-shaped tooth portion 210 which meshes with and engages with the worm teeth of the worm shaft 10. 20. In such a worm gear device, the rotational driving force from the worm shaft 10 is transmitted to the worm wheel 20 by the meshing engagement of the teeth.

[0003]

The teeth of the worm wheel 20 of the worm gear device which engages in such a meshing manner basically have a drum-like shape when viewed from the top of the teeth in plan view. The tooth thickness in the tooth trace direction is, for example, as shown in FIG. 6, the tooth thickness (H0) at the center of the tooth width is minimum, and the teeth at both ends in the width direction of the worm wheel 20 are provided. The thickness (H1, H2) has a larger value than that at the center (H0). Therefore, in the worm wheel 20 having such a tooth shape, the formation of the tooth portion has to rely on the cutting process (creation of the tooth surface) by the hob cutter, and it is difficult to perform the molding process by the sintering molding means or the like. . Further, in the worm gear device including the worm wheel 20 having such a tooth profile, at the time of the meshing engagement, for example, when the worm shaft 10 in FIG. Only in the latter half 290 of the meshing engagement movement is there an effective meshing engagement effect. In order to solve such a problem, in the first half of the meshing engagement, a part of the worm wheel teeth which are not substantially involved in the meshing are formed by helical teeth having a constant tooth thickness. SUMMARY OF THE INVENTION It is an object (problem) of the present invention to provide a worm gear device having a tooth portion which can be formed by a mold forming means.

[0004]

Means for Solving the Problems In order to solve the above problems, the present invention takes the following measures. That is, in the invention according to claim 1, a worm gear device including a worm wheel and a worm shaft having a worm tooth portion that meshes with and engages with a tooth portion of the worm wheel. One half corresponding to substantially half of the length is formed of a helical tooth having a constant tooth thickness value, and the other half forming the other half is the helical tooth of the one half. And a worm tooth formed such that the value of the tooth thickness increases as approaching the end face of the worm wheel. By adopting such a configuration, in the present invention, the worm wheel is
The precision of the tooth portion can be obtained more easily than the cutting process, and it can be formed by a sinter molding means or a molding means such as an injection molding means in the case of a synthetic resin gear having high productivity. In other words, when forming the worm wheel tooth portion, the die that contributes to the formation of the tooth portion is removed by sliding in the direction of the tooth trace of the tooth width, in particular, toward the helical tooth portion forming one half. (See FIG. 3). This makes it possible to improve the performance and productivity of the worm wheel, and thus the worm gear device.

Next, the invention according to claim 2 will be described. This is also basically the same as the first aspect. That is, in the present invention, in the worm gear device according to claim 1, a worm tooth portion forming the other half in the axial direction of the worm wheel and a worm of the worm shaft at a side portion of the worm wheel. A configuration is adopted in which a spring that operates so as to press the worm wheel is provided in a direction in which the teeth are more engaged. By adopting such a configuration, in the present invention, the backlash between the worm tooth portion on the worm shaft side and the worm tooth portion on the worm wheel side is easily adjusted to an optimum state close to almost zero. Will be able to
This makes it possible to keep the tooth contact between the two in an optimal state. Further, in the worm wheel tooth portion, the other half in the tooth trace direction that contributes to the substantial meshing engagement can be positively involved in the meshing engagement. In a more optimal state.

Next, a third aspect of the present invention will be described. The feature of this is that the worm gear device according to claim 1 or 2 is employed in an electric power steering device. That is, in the present invention, with respect to the worm gear device according to claim 1 or 2, the worm wheel is connected to a steering shaft side, and the worm shaft is connected to an output shaft of an electric motor, whereby
An electric power steering device that functions to apply a steering assist force to the steering shaft side by the operation of the electric motor is formed. By adopting such a configuration, according to the present invention, the worm wheel of the worm gear device forming the electric power steering device can be efficiently formed (manufactured) by the molding means. As a result, the manufacturing cost of the worm gear device can be reduced. Further, by slightly moving (finely adjusting) the worm wheel side by the operation of the spring, the backlash in the worm gear device can be adjusted to a state close to substantially zero, and the abnormal noise in the electric power steering device can be adjusted. Can be suppressed.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described with reference to FIGS. As shown in FIG. 2, the structure of the worm wheel 1 and the worm shaft 2 having the worm teeth 21 that mesh with and engage with the teeth 11 of the worm wheel 1, as shown in FIG. It is based on In such a configuration, the worm wheel 1 is connected to a steering shaft 5 forming a steering device as shown in FIGS. 1 and 4 in the present embodiment. is there. The steering shaft 5 has an input shaft 57 and an output shaft 51 which are connected to each other via a torsion bar 56, and the input shaft 57 is finally connected to the steering handle 55. (See FIG. 4). The worm shaft 2
Has one end connected to the output shaft of the electric motor 3, as shown in FIGS. 1 and 4, so that the power from the electric motor 3 is transmitted.

In such a structure, the shape of the tooth portion 11 of the worm wheel 1 is, as shown in FIGS. 1 and 3, one half of the center of the tooth width (OO). Part A and the other half B side,
The tooth profile is made different. Specifically, as shown in FIG. 3, the A side (11A) is made of a helical tooth whose tooth thickness is set to a constant value H0, and the other half B side (11B) is , 11A above
Helical teeth formed in contact with the helical teeth on the side of the worm wheel, and having a semi-drum-shaped worm tooth set such that the value of the tooth thickness increases (the value of HM) increases toward the end face side of the worm wheel. I have to. By adopting such a tooth profile, the tooth portion 11 of the worm wheel 1 is formed.
When molding the worm wheel, the mold (die) 9 for forming the tooth portion can be pulled out (by rotating and sliding) in the direction of the arrow in FIG. Can be formed (manufactured). That is, the worm wheel 1 is formed by sintering molding means mainly composed of powdered metal or the like or injection molding means in the case of a plastic gear.
Can be formed.

In the worm gear device having the above-described configuration, a side portion of the worm wheel 1 is provided.
As shown in FIG. 1, the worm wheel 1 is placed on a spline portion 511 of an output shaft 51 forming a part of a steering shaft 5 to which the worm wheel 1 is attached, in a fixed direction, in particular, the B-side half of the worm wheel 1. And a worm tooth portion 21 provided on the worm shaft 2 are pressed (biased) in a direction in which the half-tooth-shaped tooth portion 11B and the worm tooth portion 21 provided on the worm shaft 2 are in close contact with each other. I have. By the action of the spring 6, the half-hook-shaped tooth portion 11B of the worm wheel 1 and the worm tooth portion 21 of the worm shaft 2 always mesh and engage with the backlash close to zero.

In the present embodiment, a worm gear device having such a structure is provided as shown in FIG.
It is installed in the middle of a steering shaft 5 forming a steering device, whereby an electric power steering device is formed. Therefore, in the present embodiment, when the steering wheel 55 is steered, the electric motor 3 operates in accordance with the steering, and the driving force is transmitted to the worm shaft 2. The transmitted driving force is transmitted to the steering shaft 5 via the worm wheel 1 as shown in FIG. Finally, a steering assist force corresponding to the steering of the steering handle 55 is transmitted from the electric motor 3 to the steering shaft 5. In this way, an electric power steering device is formed (see FIG. 4).

Next, the backlash adjusting method (procedure) of the worm gear device according to the present embodiment having such a configuration will be described. In the present embodiment, as shown in FIG. 2, the worm shaft 2 is fixed at both ends by bearings 88, so that the worm shaft 2 is moved in the axial direction by a small amount to cause the backlash. Can not be adjusted. Therefore, as shown in FIG. 1, the backlash is adjusted by moving the worm wheel 1 in the axial direction. First, in FIG.
The worm wheel 1 is spline-coupled to a spline portion 511 provided on an outer peripheral portion of an output shaft 51 forming a part of the steering shaft 5.
Is engaged with the outer peripheral portion of the output shaft 51 which also forms a part of the steering shaft 5, and based on a spring reaction force of a spring 6 provided at a side surface portion of the worm wheel 1, Move on the spline part 511. Thus, the worm wheel 1
Is adjusted (set) so that the backlash between the teeth 11 provided on the worm shaft 2 and the worm teeth 21 provided on the worm shaft 2 is zero. In such a state, an adjusting screw (nut) screw-coupled to the tip of the output shaft 51 forming a part of the steering shaft 5.
52 is screwed through the inner race 81 of the bearing 8 in a state of resisting the spring reaction force of the disc spring 6. In this way, the pressing force between the tooth portion 11 of the worm wheel 1 and the tooth portion 21 of the worm shaft 2 due to the spring reaction force of the spring 6 is gradually reduced,
When the backlash between the two (between 11 and 21) reaches an appropriate value, the position of the inner race 81 of the bearing 8, that is, the axial position of the nut 52 is fixed.

As a result, an appropriate backlash is secured between the worm wheel 1 and the worm shaft 2. Then, in the state where the backlash between the two is set in this way, the tooth surface between the tooth portion 11 of the worm wheel 1 and the tooth portion 21 of the worm shaft 2 is further adapted by the running-in operation or the like. In this case, or when the tooth surface is worn due to long-time operation, the adjustment screw (nut) 52 is loosened and readjustment is performed. In this way, the backlash between the two (1, 2) is always kept in an optimal state.

[0013]

According to the present invention, a worm wheel,
A worm shaft having worm teeth that mesh with and engage with the teeth of the worm wheel, wherein one half of the worm wheel corresponding to approximately half of the length in the tooth trace direction in the tooth trace direction has a tooth thickness. Is formed of a constant helical tooth, and the other half forming the other half is formed continuously with the helical tooth in the one half. The worm wheel is formed by worm teeth formed so that the thickness value becomes larger as it approaches the end face of the worm wheel, so that the worm wheel is formed by sintering molding means or injection molding in the case of a synthetic resin gear. It can be formed by a mold forming means such as a means. In other words, in forming the worm wheel tooth portion, the die that contributes to the formation of the tooth portion is removed by sliding the die toward the tooth trace of the tooth portion, in particular, toward the helical tooth portion forming one half. This makes it possible to improve the performance and productivity of the worm wheel, and thus the worm gear device.

Further, a worm tooth portion forming the other half in the axial direction of the worm wheel and a worm tooth portion of the worm shaft are provided at a side portion of the worm wheel forming the worm gear device. In the present invention, the worm wheel is provided with a spring that operates to press the worm wheel in a direction in which the worm wheel is more engaged. The backlash between the side worm teeth can be adjusted to a state close to zero, and the tooth contact between the two can be maintained in an optimum state. Further, in the worm wheel tooth portion, the other half in the tooth trace direction that contributes to the substantial meshing engagement can be positively involved in the meshing engagement. Can be kept more optimal.

In the present invention, since the worm gear device is provided in the middle of the steering shaft of the electric power steering device, the worm wheel of the worm gear device forming the electric power steering device is formed by molding. By means of high accuracy, and
The worm gear device can be formed (manufactured) efficiently, and the performance of the worm gear device can be improved and the manufacturing cost can be reduced. Further, by slightly moving (finely adjusting) the worm wheel side by the operation of the spring, the backlash in the worm gear device can be adjusted to an optimum state close to zero, and the electric power steering device can be adjusted. The generation of abnormal noise can be suppressed.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view showing the overall configuration of the present invention.

FIG. 2 is a cross-sectional view showing the overall configuration of the present invention.

FIG. 3 is a view showing the shape of a tooth portion in the worm wheel according to the present invention.

FIG. 4 is a perspective view showing the overall configuration of an electric power steering device using the worm gear device according to the present invention.

FIG. 5 is a diagram showing an entire configuration of a general worm gear mechanism.

FIG. 6 is a perspective view showing a structure of a drum-shaped worm tooth portion in a general worm wheel.

[Explanation of symbols]

 Reference Signs List 1 worm wheel 11 tooth portion 11A one half portion 11B other half portion 2 worm shaft 21 tooth portion (worm tooth portion) 3 electric motor 5 steering shaft 51 output shaft 511 spline portion 52 adjusting screw (nut) 55 steering handle 56 torsion Bar 57 Input shaft 6 Spring 8 Bearing 81 Inner race 88 Bearing 9 Mold

 ──────────────────────────────────────────────────続 き Continuing from the front page (72) Inventor Yoshiharu Inakuma 1-1-1, Asahi-cho, Kariya-shi, Aichi Toyota Machine Works Co., Ltd. (72) Inventor Susumu Honaga 1-1-1, Asahi-cho, Kariya-shi, Aichi Toyota (72) Inventor Tetsuya Murakami 3-5-8 Minamisenba, Chuo-ku, Osaka City, Osaka Prefecture Inside Koyo Seiko Co., Ltd. (72) Osamu Ogawa 1 Toyota Town, Toyota City, Aichi Prefecture Toyota Motor Corporation F term (reference) 3D033 CA04 CA05 3J009 DA03 DA12 DA18 EA06 EA19 EA23 EA32 EB02 EC04 FA08 5H607 AA12 BB01 CC05 DD03 DD19 EE32 FF01

Claims (3)

[Claims] 1. A worm gear device comprising: a worm wheel; and a worm shaft having a worm tooth portion that meshes with and engages with a tooth portion of the worm wheel. One corresponding half is formed of a helical tooth having a constant tooth thickness value, and the other half forming the other half is formed continuously with the helical tooth in the one half. A worm gear device comprising worm teeth formed such that the value of the tooth thickness increases as approaching the end surface of the worm wheel. 2. The worm gear device according to claim 1, wherein a worm tooth portion forming the other half in the axial direction of the worm wheel and a worm tooth portion of the worm shaft at a side portion of the worm wheel. A worm gear device provided with a spring operable to press the worm wheel in a direction in which the worm wheel is more engaged. 3. The worm gear device according to claim 1, wherein the worm wheel is connected to a steering shaft side, and the worm shaft is connected to an output shaft of an electric motor. A worm gear device, wherein an electric power steering device that functions to apply a steering assisting force to the steering shaft side by operation is formed.