JPH10137885A - Method for rolling annular rim blank for wheel - Google Patents

Abstract

PROBLEM TO BE SOLVED: To precisely reduce the thickness in a target position in the case of reducing the thickness of an annular rim blank with a rolling by forming the thickness in a drop part, side wall part and bead sheet part of the product rim at thinner than a flange part and corner parts of the product rim in recessing and projecting parts of the rolling rolls. SOLUTION: A lower roll 21 (the roll for arranging at the inner peripheral side of the rim blank) is constituted with the rolling roll applying the recessing and the projecting parts for rolling on the shape for forming. The recessing and the projecting parts of the rolling roll is formed to the thickness in the drop part side wall part and bead sheet parts of the product rim at thinner than the flange part and the corner parts of the product rim. In the roll pair 21, 22, the lower roll 21 is used as the rolling roll and the ruggedness are formed on the rolling roll 21. The shapes of the recessing and the projecting parts in the rolling roll 21 are set so that the drop part, side wall part, bead sheet part and bump part of the product rim are thinner than the flange part and each corner by roll-forming with the rolling roll 21.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of forming a rim material for a vehicle wheel by rolling.

[0002]

2. Description of the Related Art Two-piece disc wheels for automobiles are:
It is made by welding and joining rims and discs that are separately manufactured. In the manufacture of rims, flat plates are rounded and the ends are butt-welded to make a straight cylindrical rim material, which is flared at both ends and passed through a multi-stage roll to form a rim shape, and an annular rim material for wheels Mold into Japanese Patent Application Laid-Open No. 55-33843 discloses a method for preventing a curved portion from being reduced in wall thickness at the rim forming stage to prevent a decrease in strength. The cylindrical rim material is sandwiched and pressed between two grooved, substantially equal diameter forming rolls, and is rolled so as to approach each corner curved at the rim forming stage, and a portion is formed in the width direction of the rim material. It is disclosed that a rolling step for increasing the thickness is provided. Partial thickening is a part other than the part to be thickened,
For example, the thickness is reduced for the flange portion and the rim bead seat portion.

[0003]

However, according to the rim stress analysis using the finite element method, a portion requiring a large thickness in terms of strength and rigidity is located in a drop portion, a sidewall portion, etc. in the rim cross-sectional shape. It has been found that it is a flange and a rim bead seat rather than a curve. Therefore, simply increasing the thickness of the corner portion as disclosed in Japanese Patent Application Laid-Open No. 55-33843 makes it impossible to effectively reduce the thickness and weight of the other portions, and reduces the corner portions such as the drop portion and the side wall portion. It has been found that increasing the thickness unnecessarily increases the weight. Further, when a straight cylindrical rim material is simply rolled with a grooved roll as disclosed in Japanese Patent Application Laid-Open No. 55-33843, the test results show that the material is laterally displaced during the rolling. The cause is that the dimensions of the material are not necessarily symmetrical, the sheet thickness naturally varies, and the required amount of groove processing is not the same for the left and right. Therefore, the elongation of the material becomes non-uniform, and lateral displacement occurs. Furthermore, since the rim shape is formed by multi-stage roll forming after rolling, if the thickened portion is greatly displaced, the thickened portion does not coincide with each rim-shaped corner when the rim shape is formed, and the desired strength, The rigidity is not obtained and only unnecessary weight increase is caused. The object of the present invention is to reduce the thickness of the portion that may be reduced in strength, rigidity, and the amount of the thickness of each portion,
It is another object of the present invention to provide a method of rolling an annular rim material for a wheel, which prevents a lateral displacement at the time of thickness reduction and enables a portion to be reduced in thickness to be accurately reduced in location.

[0004]

The present invention to achieve the above object is as follows. (1) A first forming step of forming a straight cylindrical rim material into a first intermediate rim material having a drop portion shape using a first-stage roll pair, and forming a flange portion using a second-stage roll pair of the first intermediate rim material. A second forming step of forming the second intermediate rim material into a rim having a flange portion shape folded back by a third-stage roll pair;
Any one of the second forming step and the third forming step is a forming / rolling step of performing rim forming and locally rolling the rim material to locally change the thickness. At least one roll of the roll pair in the rolling step is formed from a rolling roller having a compacting shape provided with compacting irregularities, and the irregularities of the compacting roll, a drop portion of a product rim,
A method of rolling an annular rim material for a wheel, in which a sidewall portion and a bead seat portion are formed to be thinner than a flange portion and a corner portion of a product rim. (2) A first forming step of forming a straight cylindrical rim material into a first intermediate rim material having a drop portion shape using a first-stage roll pair, and forming a flange portion using a second-stage roll pair of the first intermediate rim material. A second forming step of forming the second intermediate rim material into a rim having a flange portion shape folded back by a third-stage roll pair;
Between the second forming step and the third forming step or after the third forming step, the rim material is rolled by a roll pair different from the first, second, and third roll pairs. A pressing step for locally changing the thickness by pressing is provided, and at least one of the roll pairs of the pressing step is formed by forming one of the roll pairs in the forming step immediately preceding the pressing step. It is composed of a compacting roll having rolling compaction formed on the same forming shape as the forming shape, and the unevenness of the compacting roll is a drop portion of the product rim, a side wall portion, a bead seat portion, a flange portion of the product rim and A method of rolling an annular rim material for a wheel, which is made thinner than the corners.

In the method (1) and the method (2), the thickness of the rim material is changed by rolling the rim material after the flange portion is formed on the rim material. Grooves and flanges interfere with the roll in the axial direction, preventing lateral displacement of the rim material during rolling, making it possible to accurately reduce the thickness of the target position, and It is possible to reduce the weight while ensuring a sufficient thickness.

[0006]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS As shown in FIG. 1, in a rim forming step, in a method according to the present invention and in a conventional method, a straight cylindrical rim material 1A is formed into a drop shape by first-stage roll pairs 11 and 12. Forming the first intermediate rim material 1B having
Forming step, the first intermediate rim material 1B is transferred to the second-stage roll pair 2
Second intermediate rim material 1C having a flange portion shape at 1, 22
And a third forming step of forming the second intermediate rim material 1C into a rim 1D having a flange shape folded back by the third pair of rolls 31 and 32.
The upper rolls 12, 22, 32 may be pressed by the backup roll from the side opposite to the lower rolls 11, 21, 31. In the method for rolling an annular rim material for a wheel according to the embodiment of the present invention, the first or second rim forming step is performed as a forming / rolling step in which a rolling is performed in the same step as the forming.
The present invention includes an embodiment and a second embodiment in which rolling is performed after the second rim forming step or the third rim forming step by a rolling-specific step different from the first to third rim forming steps.

In the method for rolling an annular rim material for a wheel according to the first embodiment of the present invention, either the second forming step or the third forming step is performed by performing rim forming and rolling the rim material to increase the thickness. This is a forming / rolling step in which the thickness is locally changed. FIG.
Shows the case where the second forming step is a forming / rolling step, but the third forming step may be a forming / rolling step.
The lower roll 21 (a roll disposed on the inner peripheral side of the rim material) of the pair of rolls in the forming / rolling step is configured by a rolling roller having a rolling shape on a forming shape.
The unevenness of the compacting roll is formed in a shape such that the drop portion, the sidewall portion, and the bead seat portion of the product rim are thinner than the flange portion and the corner portion of the product rim.

In the example shown in FIG. 2, the lower roll 21 of the pair of rolls 21 and 22 is a rolling roll, and the rolling roll 21 is provided with irregularities. 22 indicates an upper roll, and 23 indicates a backup roll. As shown in FIG. 3, the concavo-convex shape of the rolling roller 21 is such that the drop portion 1e, the side wall portion 1d, the bead seat portion 1b, and the hump portion 1c of the product rim are formed by the rolling by the rolling roller 21 as shown in FIG. It is set so as to be thinner than the section 1a and the corner sections 1f, 1g, 1h. The hatched portions in FIG. 4 are the thinned portions.

In the method for rolling an annular rim material for a wheel according to the second embodiment of the present invention, as shown in FIG. 2, between the second forming step and the third forming step or after the third forming step. A roll pair 4 different from the first, second and third roll pairs.
In steps 1 and 42, a step dedicated to rolling is provided to locally change the thickness by rolling the rim material. Of the pair of rolls 41, 42, the lower roll (the roll disposed on the inner peripheral side of the rim material) 41 is used for forming the same shape as the lower roll of the pair of rolls in the forming step immediately before the step of exclusively rolling. As shown in FIG. 3, the concavities and convexities of the rolling roller 41 are formed by dropping portions 1e, side wall portions 1d, bead seat portions 1b, and hump portions of a product rim. 1c
To the product rim flange 1a and corners 1f, 1f
g and 1h. In the second embodiment of the present invention, the thickness non-uniformity is performed in a step dedicated to rolling. FIG. 3 shows the thickness distribution after compaction, and the hatched portion is the portion thinned in the compaction step.

The following description is based on the first embodiment of the present invention and the second embodiment.
Applicable to both embodiments. In the uneven thickness forming step by the compaction, the flange 1a requiring rigidity and the corner 1 which shifts from the flange 1a to the rim bead seat 1b.
Each corner portion including f is not reduced in the rolling compaction. Since the drop portion 1e, the side wall portion 1d, and the bead seat portion 1b have sufficient strength and rigidity, the drop portion 1e, the side wall portion 1d, and the bead seat portion 1b are thinned during rolling. . The thickness of the thinned portion is brought to each of the corners 1f, 1g, and 1h, and the thickness of the portion is made thicker than that of the thinned portion.

In the rolling step, a greater pressing force is required than in the rim shape forming step in order to plastically deform the wall of the rim material in the thickness direction to make it thinner. In order to obtain a large amount of compaction with a relatively small pressing force, the diameter of the lower roll arranged inside the rim material is increased, and the diameter of the upper roll arranged outside the rim material is decreased. The upper roll arranged on the outside is held down by backup rolls 23 and 43 from the side opposite to the lower roll arranged on the inside of the rim material 1.

[0012] More specifically, for example, as shown in FIG. 2, the lower roll (compaction roll) 21 outer diameter d ₁ close to D by using the inner diameter D of the annular rim material 1 full (however, d ₁
<D) Roll. The rim diameter for the wheel is 10 inches at the minimum, and the minimum inner diameter of the material is about 250 mm. Since the rolling pressure P decreases as the diameter of the upper roll 22 decreases, as described later, the diameter d ₂ of the upper roll 22 decreases.
Is much smaller than the diameter d ₁ of. However, too small slip occurs in the balance between the coefficient of friction between the rolls 22 and the material 1, since the processing becomes impossible, desirably about 90mm the minimum value of the diameter d ₂ of the upper roll 22 (90
± 10 mm, although it is possible to make the diameter smaller than this, but the limitation of the amount of rolling per rotation is increased), and both the rolls 21 and 22 are driven. The backup roll 23 contacts the upper roll 22. The backup roll 23 has a larger diameter than the upper roll 22 and has substantially the same diameter as the lower roll 1.

A description will be given of the reduction of the rolling pressure P due to the small diameter of the upper roll 22. FIG. 4 shows a conventional straight cylindrical material 1 using two conventional rolls 21 'and 22' having substantially the same diameter.
'Is being roll compacted. in this case,
The pressing force P when machining a groove in a cylindrical material by rolling is obtained by the following equation. P = k · B · L · K (1) However, k = rolling resistance B = rolling pressure width (axial direction) L = material and roll contact width (circumferential ^{direction) K = {e m · L} / (h-1 )｝ / {M · L / h} In order to reduce P, k, B,
L and K may be reduced, but k cannot be changed in order to secure the strength of the rim, and B cannot be reduced from the original purpose of reducing the weight of the rim.

In order to reduce L, the amount of compaction is reduced,
Either the contact width between the material and the roll must be reduced or the roll diameter must be reduced. Among them, the former (reducing the amount of compaction) means reducing the amount of pressurization, and mass-produced products such as wheel rims pose a problem in terms of productivity. In the latter case (reducing the contact width between the material and the roll), there is no bearing for receiving the roll, so that the rolling equipment cannot be realized.

However, in the method of the present invention, the diameter of the upper roll 22 is reduced, and L in equation (1) is reduced to reduce the rolling pressure P as compared with the conventional method (however, the formability does not change).
This solves the problem from the bearing by reducing the bearing load of all rolls. With regard to the upper roll 22 and the backup roll 23, the rolling pressure P is distributed to the respective rolls, and the bearing becomes more comfortable. Also, regarding the bending of the upper roll 22 having a small diameter, there is no problem because the upper roll 22 is backed up by the backup roll 23 having high rigidity, and the upper roll 22 escapes from the material 1 and hinders thin-wall forming. No. According to the method of the embodiment of the present invention, an arbitrary portion of the rim material 1 can be freely thinned, and the rim can be reduced in weight by as much as 30% which cannot be achieved by the conventional method.

Next, the operation of the method according to the embodiment of the present invention (first example)
The operation common to the embodiment and the second embodiment) will be described. Since the rim material 1 is unevenly thickened after the formation of the groove portion corresponding to the drop portion 1e of the rim material and the formation of the flange portion 1a, the rim material 4 is displaced laterally (in the rim axial direction) at the time of uneven thickness. The rim material 1 and the rolls 21 and 22 or 31 and 32 interfere with each other at the drop portion and the flange portion, so that the rim material 1 does not cause a lateral displacement and the thickness is reduced. It is possible to accurately reduce the thickness of a desired portion without displacement, and to reduce the weight without causing problems in strength and rigidity.

The upper rolls 22 and 32 are connected to the lower roll 2.
Since a roll smaller in diameter than 1, 31 is used, the rolling pressure in the annular rim material thickness reduction forming is smaller than in the conventional case where the roll is formed by the same diameter roll. As a result, the load applied to the roll bearing is reduced, and no problem occurs in the life of the bearing. In addition, since the small-diameter upper rolls 22 and 32 are backed up by the backup rolls, the upper rolls 22 and 32 can be prevented from bending in the direction of escaping from the material during rolling, and any part of the rim material can be moved in any axial direction. Can be reduced in thickness over distance.
In this thickness reduction, the rim weight can be reduced by about 30% as compared with the conventional one by reducing the excess thickness of the rim material, which becomes the drop portion, the sidewall portion, and the hump portion after the rim shape molding. It can contribute to the weight reduction of vehicles and improvement of fuel efficiency.

[0018]

According to both the method of claim 1 and the method of claim 2, since the rim material is rolled after the drop portion groove and the flange portion are formed in the rim material, the drop portion groove of the rim material is formed. The flange part interferes with the roll in the axial direction, preventing lateral displacement of the rim material during rolling, making it possible to accurately reduce the thickness of the target position. It is possible to reduce the weight while securing the required thickness.

[Brief description of the drawings]

FIG. 1 is a process chart of forming a rim shape applicable to the present invention.

FIG. 2 is a cross-sectional view of an apparatus that implements a method for rolling an annular rim material for a wheel according to a first embodiment and a second embodiment of the present invention.

FIG. 3 is a cross-sectional view of the rim material after being compacted by the method according to the first and second embodiments of the present invention.

FIG. 4 is a front view of a conventional case in which an annular rim material is roll-formed using rolls of the same diameter.

[Explanation of symbols]

 1, 1A, 1B, 1C, 1D Rim material 21, 31 Lower roll 22, 32 Upper roll

Claims (2)

[Claims] 1. A first cylindrical rim material is formed into a first intermediate rim material having a drop portion shape by a first-stage roll pair.
A forming step; a second forming step of forming the first intermediate rim material into a second intermediate rim material having a flange portion shape by a second-stage roll pair; and a second intermediate rim material folded back by the third-stage roll pair. A third forming step of forming the flange into a rim having a flange shape. In the second forming step or the third forming step, the rim is formed and the rim material is rolled to obtain a thickness. And forming at least one roll of a pair of rolls in the forming / rolling step is formed from a rolling roller having a rolling shape with concavities and convexities formed on a forming shape. A method of rolling an annular rim material for a wheel, in which the unevenness of a roll is formed such that a drop portion, a sidewall portion, and a bead seat portion of a product rim are thinner than a flange portion and a corner portion of the product rim. 2. A first cylindrical rim material formed by a first-stage roll pair into a first intermediate rim material having a drop portion shape.
A forming step; a second forming step of forming the first intermediate rim material into a second intermediate rim material having a flange portion shape by a second-stage roll pair; and a second intermediate rim material folded back by the third-stage roll pair. A third forming step of forming the rim having a flange shape, between the second forming step and the third forming step or after the third forming step. And a roll-specific step of locally changing the thickness by rolling the rim material with a roll pair different from the roll pair of No. 3; It is composed of a compacting roll having a compacting roll formed on the same compacting shape as one of the pair of rolls in the immediately preceding compacting process of the dedicated process. , Side wall and bead seat are flanged on the product rim A method of rolling an annular rim material for a wheel, wherein the shape is made thinner than a portion and a corner portion.