JPH0331535B2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a worm rolling method, and in particular,
The present invention relates to an improved method for rolling worms having different twist directions in a round bar-shaped material, and relates to a method that is effective for use in, for example, manufacturing worm shafts used in wiper drive devices of automobiles and the like.

[Conventional technology]

As a conventional wiper drive device for automobiles, etc., a wiper drive device as shown in FIG. 6 is sometimes used in order to prevent excessive reaction force from being applied to a bearing or the like.

In FIG. 6, what is driven and rotated by a motor (not shown) is a worm shaft 1 in which a left-handed twisted worm 1a and a right-handed twisted worm 1b are provided adjacent to each other.The left-handed twisted worm 1a and the right-handed twisted worm 1b are respectively The worm wheels 2a and 2b are meshed with each other, and the worm wheels 2a and 2b are respectively linked to the output gear 4 via coaxially fixed pinions 3a and 3b, respectively.

According to this device, the high speed rotation of the motor is efficiently decelerated and the output shaft 5, which is the rotation shaft of the output gear 4, is
transmitted to. Since each part rotates in the direction of the arrow, the reaction forces in the axial direction received by the left-hand twist worm 1a and the right-hand twist worm 1b are in opposite directions and cancel each other out, and the reaction forces in the direction perpendicular to the axis are canceled out. Since the forces are also canceled out in opposite directions via the worm shaft 1, there is an advantage that the load on the bearing etc. is light.

The problem here is the method of forming the worm shaft, and since the worm shaft shown in FIG. You can use all of them.

However, as shown in Fig. 7, the worm rolling method uses a left-handed worm 1a and a right-handed worm 1b, which have regular threads in the center, as well as irregular worms that cannot be used. Screw threads occur on both sides. A partially enlarged view is shown in Fig. 8.

As shown in Fig. 9, the method for rolling the worm is to roll the material C between adjacent dies A and B having teeth with different helixes, and with adjacent dies A and B having teeth with different helixes. having dice
Each die A,
A rolling process is carried out in which the troughs of each worm 1a and 1b are formed with the tooth tips of B, A', and B', and at the same time, the threads of each worm are formed by moving the material along the tooth profile of each die. Ru.

However, each die has a tapered part T at each end, and since this tapered part T has an incomplete tooth, the tip of the tooth of the tapered part T is low, causing the tapered part T to bite into the material C. Since the amount is small and the movement of material is small, the worm that touches the tapered part T has a high tooth bottom and a low tooth tip, and as a result,
The above-mentioned irregular thread portion will occur.

Incidentally, in the rolling process, unless the tapered portions are provided at both ends of the roll die, a considerable load will be applied from the beginning, causing the shaft to bend or break. Therefore, it is essential to provide a tapered portion in the roll die, and therefore, in a worm shaft that has been subjected to a rolling process, the occurrence of the above-mentioned irregular threaded portion is unavoidable. As a result, the total length of the shaft increases by the amount of this irregular threaded portion, and the device inevitably becomes larger.

Therefore, as shown in Fig. 10, by arranging opposing roll dies A, B and A', B' to face each other with axial shifts on the joint surface, the tapered part T can be machined by the other side. A method of rolling a worm has been proposed in which the number of irregular threads is reduced by machining the worm using teeth of the worm (see, for example, Japanese Patent Application No. 107,613/1983).

The worm rolling method shown in FIG. 10 is used to manufacture a worm shaft having left- and right-handed helical worms with double threads (double threads). Rolling is performed by shifting die groups A and B by one pitch P of the thread. According to this method, the irregular thread formed by the taper part T at the right end of die A' is changed into a regular thread part by die A, and the irregular thread formed by the taper part T at the left end of die B is changed to a regular thread part. Irregular threads are removed using dies.
It can be changed to the regular thread part with B′. the result,
Each of the irregular threads becomes shorter by one,
In other words, the regular threaded portion moves one pitch closer to the center. Therefore, the total length of the worm can be shortened by that amount.

FIG. 11 shows a worm shaft with a left-right twisted worm formed by the method shown in FIG. It is formed by crushing the respective worms with a die.

[Problem to be solved by the invention]

However, in the worm rolling method shown in FIG. 10, as shown in FIG.
Since the line a carved by the teeth A' overlaps, the die is damaged and its lifespan is shortened.

An object of the present invention is to provide a worm rolling method that can shorten the total length of a worm shaft having a left-handed worm and a right-handed worm without shortening the life of the die.

[Means to solve the problem]

The worm rolling method according to the present invention includes two sets of roll dies in which a die having a left-handed helical tooth row and a die having a right-handed tooth row are arranged so as to coaxially join each other. , are supported parallel to each other so that their outer circumferential surfaces face each other, and both die joining surfaces in one roll die group and both die joining surfaces in the other roll die group are 1/1/1 of each other in the axial direction. Both die groups are arranged so that they are shifted by 2 pitches, and the arrangement of both die groups is shifted by 1/2 pitch from each other in the circumferential direction, and a round bar-shaped material is placed between both roll die groups. It is characterized by being able to form a left-handed twist worm and a right-handed twist worm on the surface of the material in abutting state, respectively, by sandwiching and pressing the respective dies against each other and rotating the material relatively.

[Effect]

According to the above-mentioned means, the left-handed twist worm and the right-handed twist worm are shifted by 1/2 pitch toward the center because the joint surfaces of both roll die groups are shifted by 1/2 pitch in the axial direction. , the total length becomes shorter. Moreover, the ridge lines of each worm are formed in a state in which the ridge lines of each worm alternately intersect with each other without overlapping each other. Therefore, the teeth of the roll die will not be damaged by the ridge line cut on the material by the other roll die. As a result, the life of each roll die is not shortened.

〔Example〕

FIG. 1 is an enlarged partial front view showing a worm rolling method according to an embodiment of the present invention, and FIGS. 2, 3, and 4 are enlarged partial front views for explaining the operation thereof. .

In this embodiment, the rolling device used in the worm rolling method according to the present invention includes two roll die groups 10 and 20, each of which is arranged so that their axes are parallel to each other. There is. One set of roll die groups (hereinafter referred to as the first die group) 10 has tooth rows 11a with mutually different twists.
and 12a are formed, respectively, and both dice 11 and 12 are provided.
and 12 are on the same axis and have end faces 11b and 1
2b are joined to each other and mounted on an axis so that they rotate together. Tapered portions 11d and 12d are formed on the joint surfaces 11b and 12b of both dies 11 and 12 at the ends of the tooth rows 11a and 12a, respectively. Similarly, the other roll die group (hereinafter referred to as the second die group) 20 includes a pair of dies 21 and 22 each having tooth rows 21a and 22a with different twists. The dies 21 and 22 are mounted coaxially so that they rotate together with end faces 21b and 22b joined to each other. Tapered portions 21d and 22d are formed on the joint surfaces 21b and 22b of both dies 21 and 22 at the ends of the tooth rows 21a and 22a, respectively.

In the first die group 10 and the second die group 20, suppose that the dies each have a tooth row formed to roll a worm in a left-handed helical direction.
The first die 11 for left-handed twist and the second die for left-handed twist
If the dice are 21, then these first dice 1
The first and second dies 21 are arranged so that their outer circumferential surfaces face each other and their tooth rows 11a and 21a are parallel to each other in a developed view. Similarly, in the first die group 10 and the second die group 20, if the dies whose tooth rows are respectively formed to roll a worm in the right-handed helical direction are the right-handed first die 12 and the right-handed worm Assuming that the second die 22 is the second die 22 for use in the
2a are arranged parallel to each other in the developed view.

In this embodiment, the first die group 1
0 and the second die group 20 have a first joint surface 11b-12b between the first die 11 for left-handed twisting and the first die 12 for right-handed twisting, and the second die 2 for left-handed twisting.
1 and the second die 22 for right-hand twisting
1b-22b are arranged so as to be offset by 1/2 of the worm pitch in the axial direction, and so that the end surfaces 11c and 12c and 21c and 22c on the opposite side to the joint surface are aligned, respectively. Therefore, the first die 11 for left-handed twisting and the second die 22 for right-handed twisting are each set to be relatively thinner than the other dies 12 and 21 by the difference in thickness. ing.

Moreover, the first die 11 for left-handed twisting and the first die 12 for right-handed twisting have a joint surface 11b-1.
2b, the ends of the tooth rows 11a and 12a are arranged so that they butt each other, and similarly, the second die 21 for left-handed twisting and the second die 21 for right-handed twisting
The die 22 is arranged so that the ends of the tooth rows 21a and 22a abut against each other at the joint surfaces 21b-22b. Further, the tooth rows of the first die group 10 and the second die group 20 are 1/1/2 in the circumferential direction.
They are arranged two pitches apart.

Next, the action will be explained.

For example, when rolling the left and right twisted worms on the worm shaft at the same time so that they butt each other,
Worm shaft material 3 formed into the desired round bar shape
0 is sandwiched between the first die group 10 and the second die group 20 so as to circumscribe each die 11, 12 and 21, 22, respectively. 1st
When the raw material 30 is relatively rotated in one direction while the die group 10 and the second die group 20 are pressed in the direction toward each other, the left side is left on the surface of the raw material 30 by each die 11, 12 and 21, 22. The twist worm 31 and the right twist worm 32 are each rolled. At this time, the first die group 10 and the second die group 20 have outer end surfaces 11c and 21
c, 12c, and 22c are arranged in a straight line, so that pressing forces that cancel each other act on the material 30 from both directions.
Therefore, the material 30 is prevented from bending its axis.

In this rolling process, tapered portions 11d, 12d, 21d and 22d are formed on the joint surfaces of each die, so each tooth row 11
Generally, the rolling process of the worms 31 and 32 by the tapered portions a, 12a, 21a and 22a becomes inappropriate.

However, in this embodiment, the first die group 10 and the second die group 20 are arranged so that their joint surfaces 11b and 12b and 21b and 22b are shifted by 1/2 pitch in the axial direction. Therefore, the left-handed twist worm 31 and the right-handed twist worm 32 are rolled approximately properly even in the portions facing the tapered portions 11d, 12d, 21d, and 22d. For example, according to the end of the tooth row 11a formed on the tapered portion 11d of the first die 11 for left-hand twist, the left-hand twist worm 31 is improperly rolled, Due to the deviation, the portion that has been improperly rolled will be corrected using the appropriate area in the tooth row 21a of the second die 21 for left-hand twisting. Similarly, the second die 2 for right-hand twist
Teeth row 2 formed on the tapered portion 22d in 2
According to the terminal 2a, the right-handed twist worm 32 is improperly rolled, but the inappropriately rolled portion is transferred to the other party's right-handed first die 12.
Correct processing is performed using the appropriate area in the tooth row 12a. In other words, by being shifted by 1/2 pitch, the first die group 10 and the second die group 20 compensate for each other.

Here, the joint surface 11b-12b and the joint surface 21b
-22b is off by 1/2 worm pitch, so
As shown in FIG. 2, the tooth line a ₂ in the first right-handed die 12
2 and the tooth line a ₂ ' of the right-handed twist worm 32 formed on the material 30 by the second die 2 for right-handed twist.
The tooth line b ₂ ″ formed on the material 30 by the tooth line b ₂ in 2 must match each other, but the joint surfaces 11b-12b and 21b-22b should be aligned with each other at the 1/2 worm pitch. If left as is, tooth lines a ₂ ′ and b ₂ ″ will not match, and will be shifted by 1/2 worm pitch.

Therefore, as shown in FIG. 3, the dice 21 and 22 of the second die group 20 are rotated about the axis in the E direction. This amount of rotation is
Rotate until b ₂ ′ becomes tooth line b ₂ ″, which coincides with tooth line a′. Then, the amount of rotational movement M on the circumference is determined by the following equation.

Rotational movement amount M=0.5×P/tanθ However, θ represents the twist angle shown in FIG.

When the dies 11, 12, 21 and 22 are set in the above-described state, the limit point of the incomplete tooth is formed at point _S2 by the first die 12 for right-hand twisting, as shown in FIG. However, the limit point of incomplete toothing due to the second right-handed twisting die 22 facing the first die 12 is formed at point _S4 . on the other hand,
Rolling is performed while rotating the material 30, so there are no points.
S ₄ moves to point T ₁ and point S ₂ is included in the complete tooth. Similarly, the limit point of an incomplete tooth is formed by the first die 11 for left-handed twisting at the limit point _S1 , and the limit point of an incomplete tooth by the second die 21 is formed at the point _T2 ,
Since point S ₃ moves to point T ₂ and point S ₁ is included in the complete tooth, the incomplete tooth falls within the range of points S ₁ to _{T 1} and T ₂ to _{S 4} .

As a result, the length of points T ₁ to _{T 2} is smaller than the length of points S ₃ to S ₄ (or S ₁ to _{S 2} )=2×k by 0.5×P.
It will be less. This means that there are fewer incomplete teeth. Here, k corresponds to the width of the tapered portion.

In this state, as shown in FIG.
At the boundary between the right-handed worm and the right-handed worm 32, the ridge lines of the teeth are formed so as to intersect with each other. Further, as shown in FIG. 1, the tooth line 32a formed by the tooth row 12a of the first die 12 for right-handed twist and the second die 2 for left-handed twist
Tooth line 31a formed by one tooth row 21a
Since there is no possibility of polymerization, each die can be prevented from being damaged.

According to this embodiment, since the total length of the worm shaft can be shortened, it is possible to reduce manufacturing costs and contribute to miniaturization of the speed reduction mechanism. Furthermore, since the width of each die can be made narrower, the manufacturing cost of the die can be reduced.

〔Effect of the invention〕

As explained above, according to the present invention, the two roll die groups are 1/1/2 of each other in the axial direction and the circumferential direction.
Since the left-handed worm and the right-handed worm are rolled on the material with two worm pitches shifted, the total length of the worm shaft can be shortened, and the life of the die can be extended. Furthermore, by arranging both end surfaces of the die on the same straight line, bending of the material in the axial direction can be prevented.

[Brief explanation of the drawing]

FIG. 1 is an enlarged partial front view showing a worm rolling method according to an embodiment of the present invention; FIGS. 2, 3, and 4 are enlarged partial front views for explaining the operation thereof; Fig. 5 is a front view showing the main parts of the manufactured worm, Fig. 6 is a partially omitted front view showing the main parts of the wiper drive device, Fig. 7 is a front view showing the worm shaft of the conventional example, and Fig. 8 is a front view showing the main parts of the manufactured worm. The figure is also an enlarged partial front view, Fig. 9 is a front view showing a conventional worm rolling method, Fig. 10 is a front view showing another conventional worm rolling method, and Fig. 11 is the same as Fig. 10. FIG. 12 is a front view showing a worm shaft manufactured by the worm rolling method shown in FIG. 10, and is a schematic diagram for explaining the operation of the worm rolling method shown in FIG. DESCRIPTION OF SYMBOLS 10...First roll die group, 11...First die for left-handed twist, 12...Second die for right-handed twist, 20...Second roll die group, 21...Second die for left-handed twist, 22... ...Second die for right-hand twist, 30...Material, 31...Left-hand twist worm,
32...Right twist worm.

Claims (1)

[Claims] 1 Two sets of roll dies are arranged such that a die having a left-handed helical tooth row and a die having a right-handed tooth row are coaxially joined to each other,
They are supported parallel to each other so that their outer circumferential surfaces face each other, and both die joint surfaces in one roll die group and both die joint surfaces in the other roll die group are 1/1/2 of each other in the axial direction.
Both die groups are arranged so that they are shifted by 2 pitches, and the arrangement of both die groups is shifted by 1/2 pitch from each other in the circumferential direction, and a round bar-shaped material is placed between both roll die groups. A worm rolling method characterized in that a left-handed helical worm and a right-handed worm are abutted against each other and can be formed on the surface of a raw material by sandwiching the dies, pressing each die against each other, and rotating the raw material relative to each other. Method.