JPH11192955A - Resin gear with bone - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve a commodity quality by attaining improvement of strength and reduction of tapping and sliding sound when a gear is meshed, in a resin gear with bone suited for use in a transmitting route of steering assist force particularly in an electric motor-driven power steering device. SOLUTION: In a resin gear 16 with bone formed with a boss part 19a, arm part 19b, and a core part 19c of a rim part 19, of a gear 16 by an insert metal fitting 19 to wrap the core part 19c of the rim part with a resin 20 to be formed with a meshing surface of a tooth 20a of the gear 16 in the resin part 20, the insert metal fitting 19 is inserted to a core part of the tooth 20a of the gear 16. The resin gear 16 with bone is used as a worm wheel interposed in a transmitting route of steering assist force in an electric motor-driven power steering device.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a resin gear having a bone, and more particularly to a resin gear having a bone which is suitable for use in a transmission path of a steering assist force in an electric power steering apparatus. Also, the present invention relates to a bone-fitted resin gear with improved merchantability by reducing the hitting sound and sliding sound at the time of gear engagement.

[0002]

2. Description of the Related Art Conventionally, in an electric power steering apparatus, a resin gear with a bone is used as a worm wheel constituting a worm gear reduction mechanism interposed in a power transmission path for transmitting a steering assist force output from an electric motor to wheels. (See JP-A-7-215227).

[0003]

In this case, as shown in FIG. 5, the teeth 020a of the boned resin gear 016 are all formed of resin, and the insert fitting 019 is
The tooth 020a of the gear 016 was weak in strength because it was inserted only slightly inwardly of the tooth bottom of the tooth 020a.
It was not suitable for performing high power assist with an electric motor. 020 is a resin gear with a bone including teeth 020a 01
6 is a resin part.

[0004] In order to improve the strength, if all of the teeth up to the tooth 020a are made of metal, in addition to the cost increase due to the metal, the sound such as the tapping noise and the sliding noise caused by the meshing of the gears. A problem has arisen and the merchantability has been impaired.

An object of the present invention is to provide a resin gear with a bone which has sufficient strength, reduces noise problems such as tapping noise and sliding noise, and is excellent in marketability. I do.

[0006]

SUMMARY OF THE INVENTION The invention of the present application relates to an improvement in a resin gear with a bone which solves the above-mentioned problems, and the invention described in claim 1 relates to a boss portion of a gear and an arm. The part and the core of the rim part are integrally formed by an insert metal fitting, the core part of the rim part is wrapped with resin, and the meshing surfaces of the gear teeth are formed in the resin part. A resin gear with a bone, wherein the insert fitting is inserted up to a core of teeth of the gear.

According to the first aspect of the present invention, as described above, the bone-fitted resin gear has the insert fitting inserted into the core of the gear tooth, and the toothed tooth of the gear is provided. The strength is improved, and the teeth can be prevented from bending when the gears are meshed. Thereby, high power assist by the electric motor becomes possible.

Further, since the meshing surfaces of the gear teeth are formed in the resin portion, noise problems such as a tapping sound and a sliding noise associated with the meshing of the gears are reduced. Further, as described above, the strength of the gear teeth is improved, and the sound problem is reduced. As a result, the commerciality is sufficiently secured.

According to the second aspect of the present invention, the worm wheel includes the resin gear with the bone interposed in the transmission path of the steering assist force in the electric power steering apparatus. So,
Sound problems such as a tapping sound and a sliding sound caused by meshing of the gears in the vehicle are further reduced.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the invention described in claims 1 and 2 of the present application shown in FIGS. 1 to 4 will be described below. In this embodiment, the resin gear with a bone is used as a worm wheel interposed in a transmission path of a steering assist force in an electric power steering device.

In FIG. 1 and FIG. 2, an electric power steering apparatus 1 having a resin gear with a bone according to the present embodiment has a steering wheel (not shown) interlockingly connected to an input shaft 3 which extends from a gear box 2 and extends. The input shaft 3 is connected to an output shaft (pinion shaft) 5 via a torsion bar 4 in the gear box 2. The gear box 2 has two parts, an upper gear box 2a and a lower gear box 2b.

A pinion 5a is formed on the output shaft 5, and the pinion 5a meshes with a rack 7 housed in a rack housing 6 which is integrally connected to the gear box 2 and is oriented in the vehicle width direction. The rack 7 is connected to wheels via a tie rod and a link mechanism (not shown),
When the input shaft 3 is rotated left and right by operating the steering wheel, the rack 7 is moved left and right, and the wheels are turned left and right. The rack 7 has a pinion 5a
Are held down and supported by a rack guide 9 resiliently supported by a spring 8.

A torque sensor core 10 is provided between the input shaft 3 and the output shaft 5 so as to be engaged with the input shaft 3 and the output shaft 5. When actuated, the two shafts 3, 5 are relatively twisted via the torsion bar 4, and the core 10 is displaced in the axial direction of the two shafts 3, 5 according to the amount of the twist.

The displacement of the core 10 in the axial direction is
In this manner, the torque acting between the input shaft 3 and the output shaft 5 and the relative amount of twist between the two shafts 3 and 5 based on the torque are detected as electric amounts. It is supposed to be.

The electric motor 12 is controlled based on the detected value, and the steering assist force output from the electric motor 12 is transmitted to wheels (not shown) via a transmission path as described later. The torque acting between the two shafts 3 and 5 and the relative twist between the two shafts 3 and 5 based on the torque are eliminated so that a light feeling of steering can be obtained.

In the gear box 2, one end (the lower end in FIG. 1) of the output shaft 5 arranged on the same axis as the input shaft 3 is rotatably supported by the rack housing 6 via a needle bearing 13. A substantially central portion thereof is rotatably supported by the rack housing 6 via a ball bearing 14, and the other end (upper end in FIG. 1) is rotatably supported by the lower gear box 2b via a ball bearing 15. I have.

A worm wheel 16 is fitted to a position near the upper end of the output shaft 5 so as to rotate integrally with the output shaft 5 via a key 17, and the worm wheel 16 is connected to an electric motor. It meshes with a worm 18 connected to the output shaft 12 and together with it forms a worm gear reduction mechanism. The worm wheel 16 is vertically positioned by a ball bearing 15 and a stopper ring 21.

When the electric motor 12 is controlled as described above and starts to rotate, the steering assist force output from the electric motor 12 is transmitted to the output shaft 5 via the worm gear reduction mechanisms 18 and 16. The power is transmitted from the output shaft 5 to the wheels via a rack 7, a tie rod (not shown) and a link mechanism.

Here, the worm wheel 16 is configured as follows. 3 and 4, the worm wheel 16 has an insert fitting forming its skeleton.
19, and a resin portion 20 which wraps a rim core portion 19c, which will be described later, of the insert fitting 19 and forms a meshing surface of gear teeth.

[0020] The insert fitting 19 is a worm wheel 16.
Of the boss 19a, the arm 19b, and the core (rim core) 19c of the rim (ring portion on which the teeth are formed).
These are integrally formed of the same metal material,
Teeth 19d are formed by casting on the outer peripheral surface of the rim core 19c. The arm portion 19b may be formed in a plate shape or a disk shape.

The resin portion 20 is a rim core of the insert fitting 19.
The cross-sectional shape formed by molding processing by wrapping a small length of the joint portion between the rim core portion 19c of the arm portion 19c and the arm portion 19b, and cut along a surface along the radial direction after the molding process,
The worm wheel 16 has a rectangular shape that is long in the axial direction (see FIG. 3), and thereafter, teeth 20a are formed on the outer peripheral surface thereof by hobbing. The teeth 20a form the teeth of the worm wheel 16.

The teeth 19d formed on the outer peripheral surface of the rim core portion 19c of the insert metal fitting 19 and the teeth 20a formed on the outer peripheral surface of the resin portion 20 are separated from each other while leaving a thin resin layer having a predetermined thickness t. And the resin portion 20 of the worm wheel 16 is reinforced by a metal material (teeth 19d of the insert metal fitting 19) up to the core of the teeth 20a.
At the time of engagement with the worm, the teeth 20a are prevented from bending.

The teeth 19d of the insert 19 and the resin part
The 20 teeth 20a are formed as spur gears in the illustrated embodiment, but may be formed as helical gears.

Since the present embodiment is configured as described above, the following effects can be obtained. The boned resin gear 16 used as a worm wheel has teeth 19d of an insert 19 inserted into the core of teeth 20a formed on the resin portion 20 of the gear 16, and the teeth 20d of the gear 16 are formed.
The strength of a can be improved and the gear can be prevented from bending when meshing. Thereby, high power assist by the electric motor 12 becomes possible.

The meshing surfaces of the teeth 20a of the gear 16 are
Since it is formed in 20, noise problems such as a tapping sound and a sliding noise caused by meshing of the gears are reduced. Further, as described above, the strength of the teeth 20a of the gear 16 is improved, and the sound problem is reduced. As a result, the commerciality is sufficiently secured.

Further, the resin gear 16 with bone as described above is
Since the worm wheel is used as a worm wheel in a worm gear reduction mechanism having the advantages of quiet rotation and low noise, sound problems such as a tapping sound and a sliding sound caused by meshing of gears in a vehicle are further reduced.

Further, the resin portion 20 of the gear 16 is
The teeth of the insert metal fittings 19 up to the core of the teeth 20a
Since 19d is inserted, the thickness of the resin portion 20 can be made thin, and as a result, the formation of burrs can be prevented when the resin portion 20 is molded.

In the present embodiment, the boned resin gear 16
Has been used as a worm wheel interposed in the transmission path of the steering assist force in the electric power steering apparatus 1, but is not limited thereto, and is used as a component of various gear pairs interposed in the transmission path. can do. Further, the present invention is not limited to the electric power steering device, and can be widely applied as a transmission mechanism element in a field where it is strongly required to ensure both strength of gears and reduction of sound problems.

[Brief description of the drawings]

FIG. 1 is a partial longitudinal sectional view of an electric power steering apparatus provided with a boned resin gear according to an embodiment of the present invention described in claims 1 and 2 of the present application.

FIG. 2 is a partial cross-sectional view taken along line II-II of FIG.

FIG. 3 is a longitudinal sectional view of the worm wheel taken along a line III-III in FIG. 2;

FIG. 4 is a partial cross-sectional view of the worm wheel taken along line IV-IV in FIG. 3;

FIG. 5 is a diagram showing a conventional example, and is a diagram corresponding to FIG. 4;

[Description of References] 1 ... Electric power steering device, 2 ... Gear box, 2a ... Upper gear box, 2b ... Lower gear box, 3 ... Input shaft, 4 ... Torsion bar, 5 ... Output shaft (pinion shaft), 5a ... pinion, 6 ... rack housing,
7 ... rack, 8 ... spring, 9 ... rack guide, 10 ...
Torque sensor core, 11 ... detection coil, 12 ... electric motor, 13
… Needle bearings, 14, 15… ball bearings, 16… worm wheels, 17… keys, 18… worms, 19… insert fittings, 19a… boss parts, 19b… arm parts, 19c… rim core parts, 1
9d ... teeth, 20 ... resin part, 20a ... teeth, 21 ... stopper ring.

Claims (2)

[Claims] 1. A boss portion of a gear, an arm portion, and a core portion of a rim portion are integrally formed by insert metal fittings, and a core portion of the rim portion is wrapped by a resin, and a meshing surface of gear teeth is formed by the resin. A boned resin gear formed in a portion, wherein the insert fitting is inserted up to a core of teeth of the gear. 2. The resin gear with a bone according to claim 1, wherein the resin gear with a bone is a worm wheel interposed in a transmission path of a steering assist force in an electric power steering device.