JP2008229679A - Vehicular wheel disk and its manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a forming method capable of reducing the weight of a wheel disk without impairing the appearance. <P>SOLUTION: In a first forming step, a center disk part 4, an annular main projecting part 5 which is continuous to an outer circumference of the disk part 4 and projected downwardly, and an annular hat part 12 which is continuous to an outer circumference of the main projecting part 5 and projected upwardly are obtained by forming a flat plate-like work, and a plurality of pairs of sub projecting parts 5a which are formed separately in the circumferential direction and projected upwardly are obtained at a bottom part of the main projecting part 5. In a second forming step, a hub fitting part is obtained by squeezing inner circumferential walls of the disk part 4 and the main projecting part 5, and a material of an annular part located on a boundary between the hub fitting part and the hat part and in a vicinity thereof is increased, and a plurality of pairs of locally material-increased parts separate from each other in the circumferential direction are obtained at the annular part by squeezing the sub projecting parts 5a. In a punching step, hub holes are formed in the hub fitting part, and bolt holes are formed on the reference lines L passing through the center of each hub hole and passing through parts between the pairs of locally material-increased parts. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a wheel disc of a two-piece type vehicle wheel and a method of manufacturing the same.

  As shown in FIG. 1, a two-piece type vehicle wheel in which a wheel disc 10 and a wheel rim 20 are formed from a flat workpiece and welded to each other is well known particularly in a steel wheel.

  The wheel disk 10 includes a disc-shaped hub mounting portion 11, an annular hat portion 12 having a substantially chevron-shaped cross section that is continuous with the outer periphery of the hub mounting portion 11, and an annular design that is continuous with the outer periphery of the hat portion 12. A portion 13 and a cylindrical rim attachment portion 14 connected to the outer periphery of the design portion 13 are provided.

  The boundary between the hat portion 12 and the hub mounting portion 11 and the annular region in the vicinity thereof include a portion having a curved cross section, which will be referred to as a round portion 15 in the following description.

  A hub hole 11a is formed in the center of the hub mounting portion 11, a plurality of nut seats 11x are formed at equal intervals so as to surround the hub hole 11a, and bolt holes 11b are formed in the nut seat 11x. Convex rib portions 11c are formed between the nut seats 11x. A decorative hole 13 a is formed in the design portion 13.

  The vehicle wheel is completed by fitting and welding the rim mounting portion 14 of the wheel disc 10 to the inner periphery of the drop portion 21 of the wheel rim 20.

  The hub mounting portion 11 is fixed to the hub of the vehicle. Since the round portion 15 is adjacent to the outer peripheral edge of the hub, a large load is applied. Therefore, cracks are likely to occur in the rounded portion 15. Therefore, the thickness of the rounded portion 15 is set so as to give sufficient fatigue strength so as not to be a starting point of destruction of the wheel disk 10.

The wheel disc 10 is manufactured in the same manner as FIG. In detail,
A flat workpiece is drawn to obtain a circular recess at the center. The recess bottom wall has a disk shape orthogonal to the central axis of the recess. The disc-shaped concave bottom wall serves as the hub mounting portion 11 as it is.

When the concave portion is drawn, the hub mounting portion 11 and the rounded portion 15 are almost completed. However, the rounded portion 15 is subjected to tensile strain because it is located at the lower edge of the circumferential wall of the concave portion, and the workpiece thickness The thickness is reduced by about 10%. On the other hand, the hub mounting portion 11 is hardly thinned.
The hat part 12, the design part 13, and the rim attachment part 14 are obtained in the next molding step.

According to the result of the stress analysis of the wheel disk having a uniform plate thickness by the inventor, the locations where the stress is concentrated are the hat portion 12 and the round portion 15. Further, it is known from experience that most of the occurrence of cracks is in the vicinity of both sides of the bolt hole in the rounded portion 15, and the rounded portion 15 is required to have a higher strength than other portions.
In the above manufacturing method, the hat portion 12 is drawn and thus does not reduce the thickness. As a result, there are wide portions of the wheel disc having a thickness larger than the thickness corresponding to the required strength, which has been an impediment to promoting weight reduction.

  Therefore, a molding method shown in FIGS. 3 to 7 of Patent Document 1 has been developed. In this molding method as well, a circular recess and a flange extending from the recess are obtained by drawing, and the bottom wall of the recess has a disk shape perpendicular to the central axis of the recess. However, the diameter of the bottom wall of the recess is larger than the diameter of the hub mounting portion finally obtained. In addition, the height of the hat part (height from the bottom wall of the concave part) located at the boundary between the peripheral wall of the concave part and the collar part is higher than the height of the hat part finally obtained (height from the hub mounting part), It is high.

In the next molding step, with the peripheral edge of the bottom wall of the concave portion of the intermediate material hitting the lower mold surface, the hat portion is pushed by the upper die, thereby passing the hillside portion on the inner peripheral side of the hat portion. A compressive load is applied to the vicinity of the peripheral edge of the bottom wall. This molding process provides a hub mounting portion and a rounded portion adjacent to the outer periphery of the hub mounting portion, but the rounded portion is increased in thickness because it receives a compressive load. Therefore, the weight of the wheel disk can be reduced without reducing the strength of the rounded portion.
JP 2004-74248 A

  However, in the molding method shown in FIGS. 3 to 7 of Patent Document 1, compressive strain is applied to the rounded portion via the hillside portion on the inner peripheral side of the hat portion, so that the seat is seated on the hillside portion on the inner peripheral side of the hat portion. Prone to wrinkles due to bending. Since this hat portion is easy to observe from the outside, if there is a wrinkle, the appearance is impaired.

  In the molding method described above, there is room for further improvement with respect to the reinforcement of the rounded portion 15 and the thinning of the wheel disk. That is, in the rounded portion 15, cracks tend to occur near the both sides of the bolt hole, but if the wheel disk is thin, cracks near the both sides of the bolt hole are more likely to occur. The molding method disclosed in Patent Document 1 has not been improved based on such a phenomenon.

  The present invention has been made to solve the above problems, and in the method for manufacturing a vehicle wheel disk, by forming a flat plate-shaped workpiece, the central portion is connected to the outer periphery of the central portion, and is downward from the central portion. An annular main convex portion projecting in the upper direction and an annular hat portion projecting upward connected to the outer periphery of the main convex portion, and a plurality of pairs are formed spaced apart in the circumferential direction at the bottom portion of the main convex portion. And obtaining a disk-shaped hub mounting portion by crushing the inner peripheral wall of the central portion and the main convex portion, and obtaining a boundary between the hub mounting portion and the hat portion. And a second molding step of obtaining a plurality of pairs of locally thickened portions separated in the circumferential direction in the annular portion by increasing the thickness of the annular portion located in the vicinity thereof and crushing the sub-projections. In the hub mounting part A hub hole is formed at the center of the hub hole, and a hole forming step is formed around the base line passing through the center of the hub hole and between the pair of locally thickened portions. Is the gist.

  According to the method of the present invention, the strength can be increased by increasing the thickness of the annular portion (the rounded portion) in the vicinity of the boundary between the hub mounting portion and the hat portion. In addition, since the thickness is locally increased in the vicinity of both sides of the bolt hole, further weight reduction can be achieved while ensuring the strength of the wheel disk. Here, the thickening of the rounded portion includes not only the case of increasing the thickness compared to the workpiece thickness but also the case of increasing the thickness compared to the conventional general method even if the thickness is smaller than the workpiece thickness.

  Further, according to the method of the present invention, since the compressive load is applied to the rounded portion by crushing the central portion, the compressive load is not applied to the hat portion or is light, so that generation of wrinkles in the hat portion can be prevented. .

  Furthermore, the present invention comprises a hub mounting portion and an annular hat portion that is connected to the outer periphery of the hub mounting portion and protrudes from the hub mounting portion, and the hub mounting portion has a hub hole formed in the center thereof, In the vehicle wheel disc in which a plurality of bolt holes are formed around the hub hole, the center of the hub hole and each bolt hole at the annular portion located at and near the boundary between the hub mounting portion and the hat portion. The gist is that a locally thickened portion is formed in the vicinity of both sides of the reference line that connects the center of each.

  As described above, according to the present invention, it is possible to further reduce the weight while securing the strength of the wheel disk. Further, the appearance of the hat portion is not impaired.

  Hereinafter, a method for manufacturing a wheel disk according to an embodiment of the present invention will be described with reference to FIG. The wheel disc 10 finally obtained in the present embodiment is shown in FIG. 2G, but has already been described with reference to FIG.

  As shown in FIG. 2A, a plate-shaped workpiece 1 is prepared. The workpiece 1 is obtained by cutting four corners of a square steel plate material into a circle.

  First, as shown in FIG. 2 (B), the concave portion 2 is formed by drawing the workpiece 1. The planar shape of the recess 2 is circular, and has a bottom wall 2a and a peripheral wall 2b. The outer side of the recess 2 is left as a flat plate-shaped flange 3. The bottom wall 2a and the peripheral wall 2b have a conical shape and gradually become deeper toward the central axis.

  Next, as shown in FIG. 2 (C), the diameter of the recess 2 is reduced by further drawing.

  Next, as shown in FIG. 2 (D), by press molding, a flat disk portion 4 at the center, an annular main convex portion 5 connected to the outer periphery of the disc portion 4, and this main convex An annular hat portion 12 that is continuous with the outer periphery of the portion 5 and is continuous with the inner periphery of the flange portion 3 is obtained.

  The main convex portion 5 protrudes downward from the disk portion 4 and the hat portion 12 protrudes upward. The boundary between the bottom wall of the main convex portion 5 and the hem portion on the inner peripheral side of the hat portion 12 and the vicinity thereof are It is provided as a round portion 15.

  As shown in FIG. 3, by the press molding, at the bottom of the main convex portion 5, each of four (plural) reference lines L extending radially from the center of the work 1 and spaced apart at equal intervals in the circumferential direction, A pair of sub-projections 5a is also obtained. This sub convex part 5a protrudes upward with respect to the other area | region 5b of the other bottom part of the main convex part 5. FIG.

  The reference line L passes through the center of the central hub hole formation planned portion and the center of the bolt hole formation planned portion. The sub-projections 5 a forming the pair are located in the vicinity of both sides of the reference line L and are separated from each other in the circumferential direction of the main projection 5. In other words, the reference line L passes through the middle between the paired sub-projections 5a.

The inner peripheral portion of the disk portion 4, the main convex portion 5, the sub convex portion 5a, and the hat portion 12 is mainly formed by hitting the lower die, and the top portion of the hat portion 12 and the vicinity thereof are hit by the upper die and the lower die. Is formed by.
The steps shown in FIGS. 2B to 2D described above are the first molding step of the present invention.

  Next, as shown in FIG. 2 (E), the upper die is applied to the disk part 4 and pressed so as to mainly crush the inner peripheral walls of the disk part 4 and the main convex part 5, thereby forming the disk-shaped. The hub attachment part 11 is obtained. At this time, since the hat portion 12 is constrained by the lower mold surface, the hat portion 12 is large at the boundary between the bottom portion of the main convex portion 5 and the inner peripheral side hem portion of the hat portion 12 and its vicinity (the above-described round portion 15). A compressive load is applied and the thickness is increased. This thickening region is indicated by the symbol A in FIG.

  In the press molding step of FIG. 2E described above, the sub-projections 5a are also crushed by the upper mold. At this time, a compressive load in a direction orthogonal to the pressing direction is applied to the sub-projection 5a by the resistance of the peripheral portion of the sub-projection 5a in the work 1, and as a result, the rounded portion 15 is applied to the sub-projection 5a. A corresponding local thickened portion 15a (shown only in FIG. 1) is obtained.

In the step of FIG. 2E, the nut seat 11x is formed at the bolt hole formation scheduled portion, and the rib portion 11c is formed.
The process of FIG. 2E is the second molding process of the present invention.

Next, as shown in FIG. 2 (F), the remaining flange 3 is press-molded to be divided into an inner peripheral portion and an outer peripheral portion, and a design portion 13 is obtained by press-molding the inner peripheral portion.
Next, as shown in FIG. 2 (G), the outer peripheral portion of the flange portion 3 is molded to obtain the rim attachment portion 14.

  Finally, a drilling step is performed to form the hub hole 11a, and the bolt hole 11b and the decorative hole 13a (shown only in FIG. 1).

  As shown in FIG. 1, the bolt hole 11b is located on the reference line L. The locally thickened portion 15a is located on both sides of the reference line L in the vicinity of the bolt hole 11b, and is biased radially outward from the bolt hole 11b.

As described above, it is possible to increase the thickness of the rounded portion 15 that is required to have higher fatigue strength than other regions, and to increase the thickness compared to the other regions. Further, the location located on the radially outer side in the vicinity of both sides of the bolt hole 11b is a location where cracks are concentrated and the highest fatigue strength is required, but this location is the locally thickened portion 15b. Even if the workpiece 1 is thinned, the strength of the wheel disk 10 can be secured and the weight can be reduced.
In FIG. 2, the thickness is exaggerated, but the change in thickness is not shown.

The present invention is not limited to the above embodiment, and various forms can be adopted. For example, in the molding process, the name and number corresponding to each part of the final shape have been described, but these parts are not necessarily the same shape as the final shape.
In the above embodiment, there are four bolt holes, but the present invention can also be applied to five holes, six holes, and the like.
In the above embodiment, the flat plate-shaped workpiece 1 has a shape in which the four corners of a square steel plate material are cut into a circle, but the wheel disc may have a shape in which each side of the square is cut out with an arc or a shape in which the four corners are not cut. Applicable.
Moreover, although the said Example fits the wheel disc to the inner periphery of the drop part of a rim | limb, it is applicable also to the wheel disc fitted to the inner periphery of the bead seat part of a rim | limb.

2A and 2B show a conventional two-piece vehicle wheel and FIG. 1A is a longitudinal sectional view and FIG. 1B is a rear view. In one embodiment of the vehicle wheel disk manufacturing method of the present invention, (A) shows a workpiece, and (B) to (G) show the cross-sectional shape of the workpiece obtained in the molding process executed in order. (A) is a principal part top view of the workpiece | work obtained at the process of FIG.2 (D), (B) is sectional drawing in alignment with the BB line in FIG. 3 (A), (C) is FIG. ) Is a cross-sectional view taken along the line CC in FIG. 3, and FIG. 3D is a cross-sectional view taken along the line DD in FIG.

Explanation of symbols

1 Work 4 Disc part (central part)
5 Main convex part 5a Sub convex part 10 Wheel disk 11 Hub attachment part 11a Hub hole 11b Bolt hole 12 Hat part 13 Design part 14 Rim attachment part 15 Round part (annular part)
15a Local thickening part L Reference line

Claims (2)

By forming a flat workpiece, a central part, an annular main convex part that continues to the outer periphery of the central part and protrudes downward from the central part, and an annular part that protrudes upward from the outer periphery of the main convex part A first forming step of obtaining a plurality of pairs of sub-convex parts that are spaced apart in the circumferential direction at the bottom of the main convex part and project upward.
By crushing the inner peripheral walls of the central portion and the main convex portion, a disk-shaped hub mounting portion is obtained, and the annular portion located at and near the boundary between the hub mounting portion and the hat portion is increased, and A second molding step of obtaining a plurality of pairs of locally thickened portions separated in the circumferential direction in the annular portion by crushing the sub-convex portion;
A drilling step of forming a bolt hole on the reference line passing through the center of the hub hole and passing between the pair of locally thickened portions around the hub hole in the hub mounting portion at the center. When,
A vehicle wheel disc manufacturing method comprising: A hub mounting portion and an annular hat portion that is connected to the outer periphery of the hub mounting portion and protrudes from the hub mounting portion. The hub mounting portion has a hub hole formed in the center thereof, and the periphery of the hub hole. In the vehicle wheel disc in which a plurality of bolt holes are formed in
A local thickening portion is formed in the vicinity of both sides of the reference line connecting the center of the hub hole and the center of each bolt hole at the annular portion located at and near the boundary between the hub mounting portion and the hat portion. A wheel disc for a vehicle characterized by comprising:

Images