JP2001141033A - Worm wheel and its manufacturing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a worm wheel and its manufacturing method that can improve designing freedom of an electric power steering device while securing fixing force between a metal core bar and a resin ring gear. SOLUTION: The worm wheel has any shape and a sufficient strength and can be lightened, because the core bar 31 is casted dish-like and simultaneously can have an outer peripheral projecting/recessed part 31e. The outer peripheral projecting/recessed part 31e is jointed to an inner peripheral projecting/recessed part 32b while an adhesive is interposed between the single ring gear 32 and the single core bar 31, then they are jointed by high frequency welding, and thereby the fixing force between the core bar 31 and the ring gear 32 can be secured.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a worm wheel having a tooth surface made of synthetic resin, for example, a worm wheel of an electric power steering apparatus and a method of manufacturing the worm wheel.

[0002]

2. Description of the Related Art In a steering system for an automobile, a so-called power steering device for performing steering assist based on power from a power source is widely used. In recent years,
2. Description of the Related Art For reasons such as reduction of fuel consumption, an electric power steering apparatus using an electric motor as a power source has been attracting attention, particularly in automobiles having a small displacement.

In general, an electric power steering apparatus uses an electric motor having a relatively high rotation speed and a low torque, so that a deceleration for transmitting torque while decelerating rotation between the electric motor and the steering shaft. Requires a mechanism. As such a reduction mechanism, a worm reduction mechanism including a worm and a worm wheel is often used because a large reduction ratio can be obtained. The worm is connected to a rotating shaft of an electric motor, and a worm wheel meshing with the worm is connected to a steering shaft, and these are disposed in a motor housing also serving as a gear box.

Further, a worm wheel in which a synthetic resin gear ring is fixed to a rim portion of a metal wheel is used in order to reduce driving noise and eliminate the need for supplying a lubricant. is there. According to the worm wheel manufacturing mode of the prior art, in order to improve production efficiency and reduce manufacturing cost, a ring gear layer of synthetic resin is formed on the outer periphery of an elongated metal cylinder, and after manufacturing a cylindrical gear material. A worm wheel composed of a disk-shaped wheel and an annular ring gear is formed by cutting the gear material into a predetermined thickness.

[0005]

However, in order to secure a sufficient fixation between the metal cylinder and the ring gear layer, it is necessary to form irregularities arranged in the circumferential direction such as serrations on the outer periphery of the metal cylinder. However, it is troublesome to form such unevenness over the entire length of the elongated metal cylinder by, for example, cutting.

In some cases, the layout of the electric power steering apparatus requires a deep dish shape in which the inner circumference and the outer circumference of the worm wheel are shifted in the axial direction, but a ring gear made of synthetic resin is provided on the outer circumference of the metal cylinder. After forming the layer, it is possible to form one side of each metal core bar in a deep dish shape, but this causes a large increase in cost.

The present invention has been made in view of the above problems, and a worm wheel capable of improving the degree of freedom in designing an electric power steering apparatus while securing a fixing force between a metal core and a resin ring gear, and manufacturing the worm wheel. The aim is to provide a method.

[0008]

In order to achieve the above object,
The worm wheel of the present invention is a worm wheel having a metal core and a synthetic resin ring gear fixed to the outer periphery of the wheel.
An outer peripheral uneven portion formed in a circumferential direction is formed, and an inner peripheral uneven portion arranged in a circumferential direction corresponding to the outer peripheral uneven portion is formed on an inner periphery of the ring gear, and the worm wheel is a single piece of the ring gear. The outer peripheral uneven portion and the inner peripheral uneven portion are engaged with each other while an adhesive is interposed between the core metal and the single metal core, and then joined by high frequency welding.

Further, in the method of manufacturing a worm wheel according to the present invention, a step of forming an outer peripheral uneven portion arranged in a circumferential direction on an outer periphery of a metal core metal; Forming an inner peripheral uneven portion arranged in the circumferential direction so as to correspond to the portion, and forming the outer peripheral uneven portion and the inner peripheral uneven portion while interposing an adhesive between the ring gear and the core metal. And then joining by high frequency welding.

[0010]

According to the worm wheel of the present invention, there is provided a worm wheel having a metal core and a synthetic resin ring gear fixed to the outer periphery of the wheel. Peripheral irregularities aligned in the direction are formed,
On the inner periphery of the ring gear, there are formed inner peripheral irregularities arranged in the circumferential direction corresponding to the outer peripheral irregularities, and the worm wheel is provided with an adhesive between the single ring gear and the single core. After the outer peripheral uneven portion and the inner peripheral uneven portion are engaged with each other, they are joined by high-frequency welding. Since the concave and convex portions can be formed, it is possible to achieve weight reduction while forming a desired shape and having sufficient strength. Further, the outer peripheral uneven portion and the inner peripheral uneven portion are engaged with each other while interposing an adhesive between the single ring gear and the single core bar, and then joined by high-frequency welding to thereby form the core. A sufficient fixing force between gold and the ring gear can be secured.

Further, it is preferable that the inner peripheral uneven portion of the ring gear is formed by injection molding, since it can be arbitrarily formed from a mold.

According to the method for manufacturing a worm wheel of the present invention, the step of forming the outer peripheral irregularities arranged in the circumferential direction on the outer periphery of the metal core metal; and the step of forming the outer peripheral irregularities on the inner periphery of the resin ring gear. Forming an inner peripheral uneven portion arranged in the circumferential direction so as to correspond to the portion, and forming the outer peripheral uneven portion and the inner peripheral uneven portion while interposing an adhesive between the ring gear and the core metal. And after joining by high frequency welding, for example, the cored bar can be formed into a deep dish shape by forging and at the same time an outer peripheral uneven portion can be formed. Weight reduction can be achieved while having sufficient strength. Further, the outer peripheral uneven portion and the inner peripheral uneven portion are engaged with each other while interposing an adhesive between the single ring gear and the single core bar, and then joined by high-frequency welding to thereby form the core. A sufficient fixing force between gold and the ring gear can be secured.

[0013]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a side view showing a vehicle interior side portion of a steering system. In FIG. 1, a steering column 1 includes an upper column 4 fixed to a vehicle body 3 indicated by an imaginary line via an adjusting bracket 2, and a vehicle body 3
And a lower column 5 directly fixed to the lower column 5.
The steering system according to the present embodiment includes a steel bellows 1.
Although a shock absorbing mechanism covered by 4 is incorporated, its details are omitted.

An upper shaft 6 is rotatably supported by the upper column 4, and a sensor output shaft 7 is rotatably supported by the lower column 5. A steering wheel 8 is mounted on an upper end of the upper shaft 6, and a lower shaft 10 is connected to a lower end of the sensor output shaft 7 via a universal joint 9.

The housing 11 holds and accommodates an electric motor 12, a torque sensor described later, and the like. By operating the tilt lever 13 attached to the adjusting bracket 2, the column cover 1 is moved.
The upper column 4 covered by 5 can be swung within a predetermined range. It should be noted that a partition 16 for partitioning the vehicle compartment and the engine room is provided.

FIG. 2 is a diagram showing the configuration of FIG. 1 cut along the line II-II, and FIG. 3 is a diagram showing the configuration of FIG. 2 cut along the line III-III. The upper shaft 6 extending inside the outer tube 17 is swingably connected to a synthetic resin ball hub 19 via a joining pin 18. Further, the ball hub 19 is swingably connected to the sensor input shaft 21 via a pair of short pins 20 fitted at positions shifted by 90 ° with respect to the fitting direction of the joining pins 18. Thereby, the upper shaft 6
Is the connecting pin 1 with respect to the sensor input shaft 25.
Since it can swing about the swing point P, which is the intersection of the short pin 8 and the short pin 20, even when the joint angle is within a predetermined range, the torque can be transmitted to the sensor input shaft 25. .

The torque sensor 24 includes a sensor input shaft 25, a slider 26 that moves in the axial direction (left and right in FIG. 2) in accordance with the relative rotation between the sensor input shaft 25 and the sensor output shaft 7, and moves the slider 26 rearward. , A guide ball 28 interposed between the sensor output shaft 7 and the slider 26, a position sensor (not shown) for detecting the movement of the slider 26, and the like.

On the other hand, the sensor input shaft 25 is
The sensor output shaft 7 is connected to the sensor output shaft 7 via a torsion bar 22 so as to be relatively rotatable. Therefore,
When the driver applies a steering force to the steering wheel 8, the torsion bar 22 is twisted and the sensor input shaft 25 and the sensor output shaft 7 rotate relative to each other, and the steering torque is detected based on the amount of axial movement of the slider 26. It has become.

A worm wheel 30 is fixedly mounted on the outer periphery of the sensor output shaft 7 in the vicinity of the torque sensor 24 by using a retaining ring 37 so as to rotate integrally. The worm wheel 30 meshes with a worm 35 connected to a rotating shaft (not shown) of the electric motor 12 so that the rotation of the electric motor 12 is reduced at a predetermined reduction ratio and transmitted to the sensor output shaft 7. Has become. Sensor output shaft 7
Are rotatably supported by the bearing 36 with respect to the lower column 5.

FIG. 4 is an axial sectional view of the worm wheel 30. The worm wheel 30 includes a ring gear 32 made of a synthetic resin (nylon, polypropylene, or the like) around an outer periphery of a metal core 31 made of a metal (aluminum alloy, cast iron, or the like) as shown in FIG. Is fixed.

The metal core 31 has a deep dish shape in which the outer peripheral surface and the inner peripheral surface are shifted in the axial direction by a predetermined amount L. Therefore, a concave portion 33 is formed in the center of the rear surface of the wheel 31. The core metal 31 includes an inner peripheral hub portion 31a attached to the sensor output shaft 7, an outer peripheral rim portion 31b to which the gear ring 32 is fixed on the outer peripheral surface, and an inner peripheral hub portion 31.
connecting portion 3 that radially connects a to the outer rim portion 31b
1c. Further, in the inner peripheral hub portion 31a,
A shaft hole 31d into which the sensor output shaft 7 is fitted is formed at the center.

In FIG. 2, the upper shaft 6 includes an inner shaft 38 on the sensor output shaft 7 side,
An outer shaft 39 on the steering wheel 8 side is fitted with the outer shaft 39. According to such a configuration, when the driver makes a secondary collision with the steering wheel 8 at the time of a collision of the automobile, the inner shaft 38 enters the outer shaft 39 when the axial load of the predetermined value or more acts on the upper shaft 6. In this way, it functions to collapse (shorten) and absorb the collision energy.

Similarly, the upper column 4 also includes an inner tube 40 on the sensor output shaft 7 side and an outer tube 17 on the steering wheel 8 side that includes the inner tube 40.
And collapses simultaneously with the upper shaft 6. The steel bellows 14 described above is used.
Has one end fixed to the inner tube 40 and the other end fixed to the outer tube 17.

On the right side of the housing 11, a housing-side coupler 41 of a steel sheet press-formed product is bolted. As shown in FIG. 3, the housing-side coupler 41 has a pair of brackets 43 extending rearward (toward the steering wheel 8) from the left and right ends of the rear surface. Moving point P
Pin holes 43a are respectively formed at positions corresponding to. As shown in FIG. 2, a disc-shaped column-side coupler 51 made of a steel plate press-formed product is fixedly attached to one end of the inner tube 40 of the upper column 4 by welding. Further, as shown in FIG. 3, a pair of arms 52 extend from the left and right ends of the column-side coupler 51 to the sensor output shaft 7 side in parallel with each other. A pin hole 52a having the same diameter as the pin hole 43a is formed. The left and right widths of the arm 52 of the column-side coupler 51 are set so as to fit inside the bracket 43 of the housing-side coupler 41.

In the present embodiment, the housing-side coupler 41 and the column-side coupler 51 are connected to the pin holes 43a and 43a.
The rivet pins 61 are connected by two rivet pins 61 that pass right and left. The rivet pin 61 is inserted through the pin hole 43a of the housing-side coupler 41, and
After having passed through the pin hole 52a, the end portion is swaged. In this case, the caulking is performed so that the housing-side coupler 41 and the column-side coupler 51 can be easily rotated relative to each other.
A slight gap is left between the bracket 43 and the arm 52 of the couplers 41 and 51. Accordingly, the column-side coupler 51 can be tilted (swinged) up and down with respect to the housing-side coupler 41 by using the axis of the rivet pin 61 as a tilt pivot. Although the present embodiment is a so-called tilt column, the worm wheel according to the present invention can be used for a non-tilt column.

Next, the procedure for manufacturing the worm wheel 30 will be described. FIG. 5A is a cross-sectional view of the core metal 31 as a single item, and FIG. 5B is a cross-sectional view of the ring gear 32 as a single item. First, forging is performed on a disk-shaped metal material to form a metal core 31 as shown in FIG. More specifically, a deep dish shape is formed by forging, and an outer circumferential uneven portion 31e arranged in the circumferential direction such as a male serration arranged in the circumferential direction is formed on the outer circumferential surface.

At the same time, the ring gear 32 is formed by injection molding. More specifically, an inner circumferential uneven portion 32b arranged in the circumferential direction such as a female serration is formed on the inner circumferential surface so as to correspond to the outer circumferential uneven portion 31e of the core metal 31.

The outer peripheral uneven portion 31a and the inner peripheral uneven portion 32b are engaged while an adhesive is interposed between the ring gear 32 and the cored bar 31 thus formed, and then integrated by high frequency welding. As a result, the worm wheel 30 is formed. By the injection molding, the inner and outer diameters can be formed with high accuracy, and the inner peripheral uneven portion 32b can be arbitrarily formed.

According to the present embodiment, the core metal 31, which has achieved weight reduction while maintaining strength by plastic working, is fitted to the sensor output shaft 7,
Sufficient mounting strength can be secured. Also, the core metal 31 can be easily formed into a relatively arbitrary shape, for example, a deep dish shape by plastic working, and can be adapted according to the layout of the electric power steering device. Furthermore, the core metal 31
The ring gear 32 is connected to the ring gear 32 by engaging the outer peripheral uneven portion 31a and the inner peripheral uneven portion 32b with an adhesive therebetween, and then performing high frequency welding to ensure sufficient fixing strength.

Further, since the ring gear 32 made of resin and the worm 35 made of metal mesh with each other, the meshing noise of the gear can be further reduced as compared with the case where the worm wheel made of metal meshes with the worm. .

Hereinafter, the operation of the electric power steering apparatus according to the present embodiment will be described. When the driver rotates the steering wheel 8, via the upper shaft 6, the sensor output shaft 7, and the lower shaft 10,
The rotational force is transmitted to a steering gear (not shown). In the steering gear, a rack and pinion mechanism etc. that converts rotation input into linear motion is built in,
Steering is performed by changing the steering angle of the wheel via a tie rod (not shown). At this time, the electric motor 12 rotates with a predetermined rotational torque in either the forward or reverse direction based on the detection signal of the torque sensor 24 in the housing 11 or the vehicle speed, and the rotation is transmitted to the sensor output shaft 7 via the reduction gear. The steering assist is realized.

Further, in the present embodiment, a concave portion 33 is formed in the center of the rear surface of the worm wheel 30, and this concave portion 33 is formed.
Since the coil spring 27 and the slider 26 of the torque sensor 24 enter the housing 11, the overall length of the housing 11 is shorter than that of the conventional housing. Thereby, the housing 1
1 can be reduced in size and weight, and the above-described tilt pivot can be arranged closer to the electric motor 12. That is, since the distance between the tilt pivot and the steering wheel 8 can be relatively large, the change in the inclination of the steering wheel 8 during the vertical position adjustment is reduced, and the amount of the inner shaft 38 entering the outer shaft 39 ( (A collapsible amount) can be increased.

Although the present invention has been described with reference to the embodiments, it should be understood that the present invention should not be construed as being limited to the above embodiments, and that modifications and improvements can be made as appropriate. is there. For example, the torque sensor according to the present embodiment mechanically detects the steering torque amount. However, as disclosed in, for example, Japanese Patent Application Laid-Open No. H11-248563, a plurality of openings are formed in the circumferential direction. The steering torque may be detected in a magnetostrictive manner using an aluminum sleeve and a coil including the aluminum sleeve.

[0034]

According to the worm wheel of the present invention, there is provided a worm wheel having a metal core and a synthetic resin ring gear fixed to the outer periphery of the wheel.
On the outer periphery of the core metal, an outer peripheral uneven portion formed in the circumferential direction is formed, and on the inner periphery of the ring gear, an inner peripheral uneven portion formed in the circumferential direction corresponding to the outer peripheral uneven portion is formed, The worm wheel engages the outer circumferential uneven portion and the inner circumferential uneven portion while interposing an adhesive between the single ring gear and the single core, and then is joined by high frequency welding. Therefore, for example, the cored bar can be formed into a deep dish shape by forging, and at the same time, the outer peripheral unevenness can be formed, so that it is possible to achieve a light weight while having sufficient strength while forming an arbitrary shape. . Further, after engaging the outer peripheral uneven portion and the inner peripheral uneven portion while interposing an adhesive between the single ring gear and the single core bar,
By bonding by high frequency welding, a sufficient fixing force between the core metal and the ring gear can be secured.

According to the worm wheel manufacturing method of the present invention, the step of forming the outer peripheral irregularities arranged in the circumferential direction on the outer periphery of the metal core metal, the step of forming the outer peripheral irregularities on the inner periphery of the resin ring gear. Forming an inner peripheral uneven portion arranged in the circumferential direction so as to correspond to the portion, and forming the outer peripheral uneven portion and the inner peripheral uneven portion while interposing an adhesive between the ring gear and the core metal. And after joining by high frequency welding, for example, the cored bar can be formed into a deep dish shape by forging and at the same time an outer peripheral uneven portion can be formed. Weight reduction can be achieved while having sufficient strength. Further, the outer peripheral uneven portion and the inner peripheral uneven portion are engaged with each other while interposing an adhesive between the single ring gear and the single core bar, and then joined by high-frequency welding to thereby form the core. A sufficient fixing force between gold and the ring gear can be secured.

[Brief description of the drawings]

FIG. 1 is an explanatory view showing a structure of a steering system according to the present invention on a vehicle cabin side.

FIG. 2 is a view of the configuration of FIG.

FIG. 3 is a view of the configuration of FIG. 2 cut along a line III-III and viewed in a direction of an arrow.

FIG. 4 is an enlarged sectional view of a worm wheel according to the present invention.

FIG. 5A is a cross-sectional view of the core metal 31 as a single item, and FIG. 5B is a cross-sectional view of the ring gear 32 as a single item.

[Explanation of symbols]

 Reference Signs List 1 steering column 7 sensor output shaft 11 housing 12 electric motor 24 torque sensor 30 worm wheel 31 cored bar 32 ring gear 35 worm gear

Claims (3)

[Claims] 1. A worm wheel having a metal core and a synthetic resin ring gear fixed to the outer periphery of the wheel, wherein the outer periphery of the core has an outer peripheral uneven portion arranged in a circumferential direction. Is formed on the inner circumference of the ring gear, and an inner circumferential uneven portion is formed in the circumferential direction corresponding to the outer circumferential uneven portion. The worm wheel is formed of the single ring gear and the single core metal. A worm wheel, wherein the outer peripheral uneven portion and the inner peripheral uneven portion are engaged with each other with an adhesive therebetween, and then joined by high frequency welding. 2. The worm wheel according to claim 1, wherein the inner peripheral uneven portion of the ring gear is formed by injection molding. 3. A step of forming an outer peripheral uneven portion arranged in a circumferential direction on an outer periphery of a metal core, and a circumferential direction on an inner periphery of a resin ring gear so as to correspond to the outer uneven portion. Forming an inner peripheral uneven portion aligned with the, after engaging the outer peripheral uneven portion and the inner peripheral uneven portion while interposing an adhesive between the ring gear and the core metal,
Bonding by high frequency welding.