JPS6328703A - Rim mechanism of three-piece type wheel and its manufacture - Google Patents

Abstract

PURPOSE:To improve mass-productivity by forming a recessed well at rear rim and bending its front end inward and forming a sawtooth-shaped connection flange for mounting onto a wheel disc where projections and recesses are formed alternately. CONSTITUTION:A connection flange 20 for mounting onto a wheel disc D is formed at the front end position of a rear rim R2 and a flange 21 for catching a tyre is formed at the rear end position. And a recessed well part 22 is formed at the intermediate section of flanges 20, 21. Further respective connection flanges 19, 20 of the front rim R1 and the rear rim R2 are formed into sawtooth shape or petal shape - viewed from the front or rear direction - where projections a1, a2 and recesses b1, b2 are alternately formed. Further the front rim R1 and the rear R2 are connected by fastening 14 with bolts after connecting connection flanges 19, 20 and engaging it round a cutout 16 for reception. By this constitution, mass-productivity is improved.

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to a rim structure in a three-piece wheel for an automobile and to improvements in its manufacturing method.

<Prior art and its problems> Three-piece automobile wheels are known in which a pair of front rims and rear rims, which have been made separately in advance, and a wheel disk are assembled and integrated using a plurality of bolts and nuts. However, in conventional products, a concave well is usually defined at the boundary between the two rims, so the bottom surface of the well can be used as a caliper in an automobile's disc brake system or other accessory parts. This results in a problem in which there are restrictions on installation and use in front-wheel drive vehicles and the like.

And, as a wheel product that solved this problem, Utility Model Application No. 104302/1983 was published.
In order to make the rear rim removable, it is necessary to either split the core mold or place it eccentrically. It has inferior problems.

<Means for Solving the Problems> The present invention is intended to improve such problems, and for this purpose, as a rim structure, a concave well part is provided in the rear rim, and a well part facing inward from the front end position of the rim is provided. The joint flange portion for attachment to the wheel disc that protrudes in a bent shape is carved into an overall sawtooth shape or petal shape that alternates between convex pieces and concave grooves when viewed from the front and rear directions, and the convex piece is carved into a sawtooth shape or a petal shape. While the bolt insertion holes are opened, the joint flange for attachment to the wheel disc, which extends inwardly from the rear end of the front rim in correspondence with the joint flange mentioned above, also extends from the rear end of the front rim when viewed from the front and rear directions. It is carved into an overall sawtooth shape or petal shape with alternating convex pieces and concave grooves, and a bolt insertion hole is opened in the convex piece to connect the front rim and the rear rim to each other. It is characterized by being integrally welded to each other with the bolt insertion holes of the convex pieces matching each other.

In addition, as a rim manufacturing method for this purpose, a blank made of a light alloy material is press punched to create a disk with a center hole for attachment to a forming die, and the disk is inserted into a forming die using the center hole. While rotating the mold, the disc is spun using a tracing roll to bend the disc into a substantially U-shaped cross section, and at the same time form a tire retaining flange on its circumferential surface. By molding the bead seat part, a front rim spare body is made, and after removing the spare body from the molding die, the center part is press punched to be larger than the center hole mentioned above, and then joined for attachment to the wheel disc. While finishing it as a front rim with a flange formed, it is also made by press punching a blank made of light alloy material.
A disk with a center hole for attachment to the two types of molds was created and was larger than the disk described above, and the disk was first fitted into the rotational center of the primary mold through the center hole. The disc is then spun using a copying roll that rotates the mold, and the disc is bent into a substantially U-shaped cross section to roughly form it into the primary accessory body of the rear rim. 2 with the body in a similar fitted state
Next, it is attached to the center of rotation of the molding mold, and while the mold is rotated, it is spun again using a copying roll to form a tire locking flange part, bead seat part, hump part, and the circumferential surface of the preliminary body. By molding a concave well part, it becomes a secondary fitting body of the rear rim, and after removing the secondary fitting body from the mold, the center part is press punched to be larger than the center hole.
Finish the rear rim with a joint flange for attachment to the wheel disc; weld the joint flange parts of the front rim and rear rim so that the bolt insertion holes opened in each are aligned. The first feature is that it is integrated, and furthermore, a blank made of light alloy material is press punched,
A disk with a center hole for attachment to the mold is created, the disk is fitted into the center of rotation of the mold through the center hole, and the mold is rotated while spinning using a copying roll. Then, by bending the disc into a substantially U-shaped cross section, and at the same time forming a tire locking flange part and a bead seat part on its circumferential surface, a front rim spare body is obtained, and the spare body is molded into a molded metal. After being removed from the mold, the center part is press punched to be larger than the center hole, and the joint is attached to the wheel disk to form an overall sawtooth or petal shape with alternating five pieces and concave grooves. While the front rim is finished with a engraved flange; it is also made by press punching from a light alloy blank.
A disk with a center hole for attachment to the two types of molds was created and was larger than the disk described above, and the disk was first fitted into the rotational center of the primary mold through the center hole. The disc is then spun using a copying roll that rotates the mold, and the disc is bent into a substantially U-shaped cross section to roughly form it into the primary accessory body of the rear rim. 2 with the body in a similar fitted state
Next, it is attached to the center of rotation of the molding mold, and while the mold is rotated, it is spun again using a copying roll to form a tire locking flange part, bead seat part, hump part, and the circumferential surface of the preliminary body. By molding a concave well part, it becomes a secondary fitting body of the rear rim, and after removing the secondary fitting body from the mold, the center part is press punched to be larger than the center hole.
The rear rim is finished with a joint flange portion for attachment to the wheel disc that has an overall sawtooth or petal shape with alternating five pieces and concave grooves; and both joint flanges between the front rim and the rear rim. The second feature is that the parts are welded together in such a manner that the bolt insertion holes opened in each of the five pieces match.

<Example> Hereinafter, the present invention will be described in detail based on the drawings.
Figure 4 shows a three-piece automobile wheel according to the present invention, and (D) is a wheel disc integrally cast or forged from a light alloy, with a central part of the mounting surface for the axle. A shaft hole (11) is provided. (
It goes without saying that 12) is a plurality of disc mounting holes opened at the periphery thereof, and is fixed to the hub of the axle by means of bolts and nuts inserted through these holes.

(13) are a plurality of spoke parts that radiate out from the mounting surface, and the adjacent spoke parts form a heat dissipation window (S).
The section has been opened. (14) is each spoke part (
The positioning bolt insertion hole (15) is formed through the protruding tip of each spoke (13), and the positioning reinforcing rib (15) is similarly provided to protrude rearward from the vicinity of the tip of each spoke (13). A notch (16) is formed on the periphery to accommodate the rim receiver, which has a cross-sectional shape. Note that adjacent spoke portions (13) may be separated at their protruding tips.

The rims forming the support members of the tire consist of a pair of separate front rims (R1) and rear rims (R2).

And the front rim (R1) is a relatively narrow band @
(W1), the middle part of which is a bead seat part (17), and from the front end position of the bead seat part (17) there is a tire locking flange part (
18) facing outward, and the disk (
The joint flange portions (19) for attachment to D) are each formed to protrude in an inwardly bent shape.

On the other hand, the rear rim (R2) has a circumferential surface with a considerably wider band width (2) than the front rim (R1), and has a disc (2) at its front end that corresponds to the joining flange (19). D) Joint flange part (20
), but the above locking flange part (18
) The outward tire locking flange portion (21) that is paired with the tire locking flange portion (21) also extends in a bent shape. (22) is a concave well portion recessed at a mutually intermediate position; (23) is a bead seat portion that pairs with the bead seat portion (17) of the front rim (R1); A hump portion (24) is interposed at the boundary position.

The joining flanges (19) and (20) of the front rim (R1) and rear rim (R2) are both convex, especially when viewed from the front and rear directions, as is clear from Figure 7.8.12.13. Piece (a1) (R2) and groove (b1) (b2
) is engraved in an overall sawtooth or petal shape that changes alternately with the biconvex pieces (a1
) (R2), bolt insertion holes (25) that match each other
(26) is formed as an opening. Then, the front rim (R1) and the rear rim (R2) are welded together at their joining flanges (19) (20) in a state where they are joined together, and the rim receiver of the disc (D) is inserted into the notch (16). The bolts (27) are tightly fitted into the bolt holes (14), (25), and (26) of the three bolts, and the fixing nuts (28) are screwed into the bolts (27). will be made into (29
) is a hump formed by the build-up of welding and subsequent milling, and the rear rim (
It forms a pair with the hump part (24) of R2) and locks the tire's end part.

Like the above product, the joining flange parts (19) (20) of both rims (R1) (R2) are cut out in the overall sawtooth shape or petal shape, and the convex pieces (a1) (R2
) is inserted into the notch (16) where the rim receiver of the disc CD) is inserted, and the disc (D) and both rims (R1) are assembled together using bolts (27) and nuts (28). It is possible to make the protruding length of the spoke portion (13) look as long as possible within the limited diameter dimension range of the disk CD itself without reducing the assembly strength with (R2) in the slightest. Since the heat dissipation window (S) can also be set as a long opening as much as possible, it is possible to easily change the front design of the wheel and provide an efficient heat dissipation effect for the disc brake device.

However, the joining flange part (1) of both rims (R1) (R2)
9) (20) is not cut out in a special sawtooth shape or petal shape as a whole, and the number 16 corresponding to FIG. 8.13 is not cut out.
As suggested in the partial modification example in the figure, the opening is formed by punching as a simple circular opening, and the flange portion (19)
(20) is the same bolt insertion hole as above (25) (2
6) may of course be provided. This is because there is no difference in that the rear rim (R2) is provided with a concave well portion (22) in advance.

Function> The rims (R1) and (R2) of the above-mentioned wheels are manufactured by the following steps in the present invention. That is, in manufacturing the front rim (R1), first, a blank of light alloy material is press punched to create a disc (30) of the desired size as shown in Fig. 5 (1). At that time, the molding mold (3
The center hole (32) for attachment to 1) is also punched out and opened at the time of early opening.

Then, the disk (30) is arranged such that the plate surface of the disk (30) is perpendicular to the rotation axis (X-X) of the molding die (31).
) into the center of the molding die (31) as shown in FIG. It is processed. In other words, as is clear from FIG. The molding into a front rim preliminary body (34) including a locking flange portion (18) and a bead seat portion (17) is completed.

Thereafter, the preliminary body (34) is removed from the molding die (31), and the center part of the preliminary body (34) is pressed to be larger than the center hole (32). A joint flange portion (19) for attachment to the disk (D) in which the pieces (a1) and the grooves (b1) alternate.
), the bolt insertion hole (25) is also opened in the convex piece (at) at the same time, and the manufacture of the front rim (R1) as shown in Fig. 7.8 is completed. However, as shown in Fig. 5 (■), the bolt insertion hole (25) can be opened in advance at the same time as the press punching of the disk (30), just like the center hole (32). It is.

On the other hand, when manufacturing the rear rim (R2), the ninth
As shown in Figure (1), a disk (35) having a larger diameter than the disk (30) in the front rim (R1) is also created by press punching from a light alloy blank. A center hole (
38) is also punched out at once.

Next, the plate surface of the disk (35) is placed in the primary molding die (36).
) into the center of the cough mold (36) as shown in FIG. ) is rotated and spun with a copying roll (39), and the same figure (■)
At the same time, a primary plastic deformation action is applied along the circumferential surface of the molding die (36) to form the primary fitting structure of the rear rim (R2).40) The material is roughly formed. As is clear from the figure, the circumferential surface of the mold (36) has a flat fIJ inclined surface with an outer edge that intersects the axis of rotation (X-X) at an acute angle (θ). Almost the rear half of the primary organ (4o) is expanded into a smooth trumpet shape.

Subsequently, as shown in FIG. 11 (1), the primary fitting body (40) is replaced with the secondary molding mold (37) in the same fitted state, and the molding mold (37) is also While rotating, it is spun again using a copying roll (41) to form a rear rim (R2) having a tire locking flange portion (21), a bead seat portion (23), a hump portion (24), and a concave well portion (22). ) is transformed into the desired final cross-sectional shape by going through the above two steps. In that case, the well part (22
) is formed at the drawing action starting point (Y
-Y) and press the primary accessory body (40) so to speak, the secondary forming mold (42) does not have to be a special split mold, and its rotational axis (X-X )
Accurate depression molding can be achieved by simply rotating the mold around the center.

After that, the secondary component (42) is placed in the mold (37).
) and insert the center part into the center hole (38
), the convex piece (R
2) and a concave groove (b2) alternate with each other (D)
At the same time as forming the joint flange part (20) for attachment to the convex piece (R2), bolt it! The through holes (26) are also opened at once, and in this way the rear rim (R2) as shown in Fig. 12.13 is completed.

In addition, as shown in FIG. 9(n), the port insertion hole (26) is also punched at the same time as the press punching of the disk (35).
It can be opened in advance.

Then, the front rim (R1
) and the joint flange part (20) of the rear rim (R2) with its double convex piece (a1) (
The R2 port insertion holes (25) and (26) are joined so that they match and are welded to each other as shown in FIG. 14, thereby assembling and integrating them as a rim. At the same time, as shown in FIG. 15, the rim receiver of the disk (D) is tightly fitted into the notch (16), and the two joining flanges (19) and (20) are tightly fitted into the notch (16) of the disk (D). The disc (D)
Needless to say, they are combined and integrated into a complete wheel.

Both the joining flange parts (19) and (20) of the front rim (R1) and the rear rim (R2) are connected to the convex pieces (a1) (R2) and the concave grooves (b1), as shown in the modified example of FIG.
(b2) If the overall petal shape or sawtooth shape is not specified, the bolt insertion holes (25) and (26) to be opened therein are shown in FIGS. 5(II) and 9. As shown in the figure (■), at the initial stage of creating the disks (30) (35), the center hole (32) (38
) and - Press punching can be performed during early opening. However, the remaining manufacturing steps are the same as those illustrated in FIGS. 5-15.

When using either of these manufacturing methods, the front rim (R
1) and the rear rim (R2).
) When welding (20), the welded part forms a pair with the hump part (24) of the rear rim (R2).
29) can be bulged. Also, as shown in Figure 17? It is also possible to bulge the hump portion (29) by performing a cutting process using a milling cutter. Other symbols (43) and (44) are mounting holes for air valves, and (45) is a cutter.

<Effects of the Invention> As described above, according to the method for manufacturing a rim of a three-piece wheel according to the present invention, a blank of a light alloy material is press punched, and a center hole for attachment to a molding die (31) is formed. (
32) is opened, the disc (30) is fitted into the rotational center of the molding die (31) through the center hole (32), and the mold (31) is rotated. At the same time, spinning is performed using a copying roll (33) to bend the disc (30) into a substantially U-shaped cross section, and at the same time, a tire locking flange part (18) is formed on the circumferential surface of the disc (30).
) and the bead seat part (17) to form a front rim spare body (34), and after removing the preliminary body (34) from the molding die (31), insert the center part into the center hole (32). ) to form a front rim (R1) with a joining flange (19) for attachment to the wheel disc (D); , create a circle Fi (35) which has a center hole (38) for attachment to the two types of molding molds (36) and (37) and is larger than the disk (30), and the disk (35). ) through the center hole (38), first 1
Next, the disc (35) is fitted into the rotational center of the mold (36), and while the mold (36) is rotated, spinning is performed using a copying roll (39), so that the disc (35) has a substantially U-shaped cross section. Fold it to the primary auxiliary body of the rear rim (R2) (40)
Then, the primary fitting body (40) is placed in the same fitted state and replaced at the rotation center of the secondary molding die (37),
The mold (37) is rotated and spun again using a copying roll (41) to form a tire retaining flange part (21) and a bead seat part (23) on the circumferential surface of the preliminary body (40). , a hump part (24) and a concave well part (
22) of the rear rim (R2).
After removing the secondary fitting body (42) from the mold (37), the center part is press punched to be larger than the center hole (38), and the wheel disc is made into a secondary fitting body (42). (D) Finished as a rear rim (R2) on which the attachment layer joining flange part (20) was formed; and the front rim (
R1) and the rear rim (R2) and the joint flange part (1
9) Since (20) are set to be welded together under the condition that the bolt insertion holes (25) and (26) opened in each of them match, the conventional technology mentioned at the beginning is not possible. The problem can be solved and the rear rim (R2
), the concave well portion (22) can be molded with high efficiency while using a simple molding die as a whole, and is extremely suitable for mass production.

In particular, the rim manufacturing method involves press punching a light alloy blank to create a disk (3o) with a center hole (32) for attachment to a molding die (31). The plate (30) is fitted into the rotation center of the molding die (31) through the center hole (32), and while the die (31) is rotated, spinning is performed using the copying roll (33) to form the disc. (30) into a substantially U-shaped cross section, and at the same time attach the tire locking flange 65 (1) to its circumferential surface.
8) and the bead seat part (17),
Front rim spare body (34) To L, its spare body (34)
) is removed from the molding die (31), and then its center is press punched to be larger than the center hole (32) to form a whole with alternating convex pieces (a1) and concave grooves (b1). A wheel disc with a serrated or petal shape (
While the front rim (R1) is finished with a engraved joint flange (19) for attachment to D);
The disk (30) is provided with a center hole (38) for attachment to the two types of molding molds (36) (37), and
Create a disk (35) larger than the disk (35)
First, the primary molding die (36) is inserted through the center hole (38).
), and while the mold (36) is rotated, spinning is performed using a copying roll (39).
The above-mentioned disk (35) is bent into a substantially U-shaped cross section and roughly formed into a primary fitting body (40) of the rear rim (R2), and then the primary fitting body (40) is fitted in a similar manner. As a state, replace it with the rotation center of the secondary mold (37),
While rotating the mold 37), the copying roll (41) is spun again, and a tire locking flange part (21) and a bead seat part (23) are formed on the circumferential surface of the preliminary body (40). , a hump part (24) and a concave well part (
22) of the rear rim (R2).
After removing the secondary fitting body (42) from the mold (37), the center part is press punched to be larger than the center hole (38), and the mouth piece is formed into a secondary fitting body (42). (R2) and groove (b2)
) and a joint flange for attachment to the wheel disc (D) having an overall sawtooth or petal shape alternating with (
20) is engraved as a rear rim (R2); and the joining flange portions (19) and (20) of the front rim (R1) and rear rim (R2) are finished with each mouth piece (a
1) Bolt insertion hole (25) opened in (R2) (
26) If it is determined that the parts are welded and integrated under the condition that the above conditions are met, in addition to the above effects, the rim and the entire wheel including the rim can be shaped with interesting changes in design, which increases the manufacturing process. (In addition, as a rim product, when used on a front-wheel drive vehicle, sufficient space is secured to accommodate the disc brake device, and the rim center and wheel disc (
D) The distance (offset amount) from the mounting surface can also be freely maintained large.

[Brief explanation of the drawing]

1 to 4 relate to a wheel equipped with the rim structure of the present invention, in which FIG. 1 is a front view, FIG. 2 is a rear view, and FIG.
Figure 4 is a front view of the extracted wheel disc, Figures 5 to 8 show the manufacturing process of the front rim, and Figure 5 (1) (■) shows the disc. Front views showing two types of processing conditions, Figure 6 (+) (11>) is an explanatory diagram showing the working process of the spinning process, Figure 7.8 is a front view and rear view showing the front rim after processing is completed, Figures 9 to 13 relate to the manufacturing process of the rear rim, Figure 9 (■) (■) is a front view showing two types of processing states of the disc, and Figure 10 (1) (I
I) is an explanatory diagram showing the process of the primary spinning process, Figure 11 (+) (II) is an explanatory diagram showing the process of the secondary spinning process, and Figures 12 and 13 are the process Front and rear views showing the completed rear rim, 1st
4.15 is an explanatory diagram showing the assembly process of the front rim and rear rim and the completed state, and FIG.
FIG. 13 is a rear view showing a modified rim corresponding to FIG. 13, and FIG. 17 is an explanatory view showing the process of milling. (D) ...Wheel disc (R1) ・
・・・Front rim (R2) ・ ・ ・ ・Rear rim (17) (2
3) ・Bead seat part (18) (21)
・ ・Tire locking flange part (19) (20)
...Joining flange part (22)...Well part (24) (29)...Hump part (14) (2
5) (26) ・Bolt insertion hole (27)...
Bolt (28)...Nut (30) (35)...Disc (31) (36) (37) Molding mold (32)
(38) ...Center hole (33) (39) (
41) - Copy roll (34)...Front rim spare body (40)...Primary subsidiary body of rear rim (
42)...Secondary auxiliary body of Riyarim (a1) (
R2) ... Mouth piece (b1) (b2) ... Concave l & Patent applicant Enryo Aluminum Wheel Co., Ltd. Fig. 1 Fig. 3 Fig. 4 Fig. 6 Fig. 7 bl Fig. 11 (1)
(II) Figure 9 (II)

Claims (1)

[Claims] 1. A concave well portion (22) is provided in the rear rim (R2), and a joint for attachment to the wheel disc (D) that protrudes inwardly from the front end position of the rim (R2). When looking at the flange portion (20) from the front and back direction, the convex piece (a2
) and concave grooves (b2) are carved in an overall sawtooth or petal shape, and a bolt insertion hole (26) is opened in the convex piece (a2), while the joining flange part ( 20
), the wheel disc (
The joint flange part (19) for attachment to D) is also carved in the overall sawtooth shape or petal shape with alternating convex pieces (a1) and concave grooves (b1) when viewed from the front and back directions, A bolt insertion hole (25) is opened in the convex piece (a1), and both the joining flange parts (19) and (20) of the front rim (R1) and rear rim (R2) are connected to the convex piece (a1) ( a2
A three-piece wheel rim structure characterized in that the bolt insertion holes (25) and (26) of the parts (25) and (26) are integrally welded to each other so that they match. 2. Press punch a blank of light alloy material to create a disc (30) with a center hole (32) for attachment to the molding die (31), and place the disc (30) at the center. The disc (30) is fitted into the rotational center of the molding die (31) through the hole (32), and while the mold (31) is rotated, spinning is performed using the copying roll (33), so that the disc (30) has an approximately cross-sectional shape. At the same time as bending it into a U-shape, the tire locking flange part (18
) and the bead seat part (17) to form a front rim spare body (34), and after removing the preliminary body (34) from the molding die (31), insert the center part into the center hole (32). ) to create a front rim (R1) with a joining flange (19) for attachment to the wheel disc (D); ,
A disk (35), which has a center hole (38) for attachment to the two types of molding molds (36) and (37), and is larger than the disk (30) above is created, and the disk (35) First, the primary molding mold (36) is inserted through the center hole (38).
While rotating the mold (36), the disc (35) is spun using a copying roll (39), and the disc (35) is bent into a substantially U-shaped cross section to form a rear rim (R2). The primary fitting body (40) is roughly formed into a primary fitting body (40), and then the primary fitting body (40) is placed in the same fitted state at the rotation center of the secondary molding die (37),
The mold (37) is rotated and spun again using a copying roll (41) to form a tire retaining flange part (21) and a bead seat part (23) on the circumferential surface of the preliminary body (40). , a hump part (24) and a concave well part (
22) of the rear rim (R2).
After removing the secondary abutment body (42) from the mold (37), the center part is press punched to be larger than the center hole (38) to form a wheel disc. (D) Joint flange part (20
) is formed as a rear rim (R2); and bolt insertion holes (25) are formed in both the joining flange portions (19) and (20) of the front rim (R1) and rear rim (R2). (26) A method for manufacturing a rim of a three-piece wheel, characterized in that the rims are welded and integrated under a condition in which (26) coincides with each other. 3. Press punch a blank of light alloy material to create a disk (30) with a center hole (32) for attachment to the molding die (31), and place the disk (30) at the center. The disc (30) is fitted into the rotational center of the molding die (31) through the hole (32), and while the mold (31) is rotated, spinning is performed using the copying roll (33), so that the disc (30) has an approximately cross-sectional shape. At the same time as bending it into a U-shape, the tire locking flange part (18
) and the bead seat part (17) to form a front rim spare body (34), and after removing the preliminary body (34) from the molding die (31), insert the center part into the center hole (32). ) A wheel disk (D) which is press-cutted to a size larger than that of 1.0 mm and has an overall sawtooth or petal shape with alternating convex pieces (a1) and concave grooves (b1).
The front rim (R1) is finished with a engraved joint flange (19) for attachment to the front rim (R1);
A disk (35), which has a center hole (38) for attachment to the two types of molding molds (36) and (37), and is larger than the disk (30) above is created, and the disk (35) First, the primary molding mold (36) is inserted through the center hole (38).
While rotating the mold (36), the disc (35) is spun using a copying roll (39), and the disc (35) is bent into a substantially U-shaped cross section to form a rear rim (R2). The primary fitting body (40) is then roughly formed into a primary fitting body (40), and then the primary fitting body (40) is placed in a similar fitted state to the rotation center of the secondary molding die (37),
The mold (37) is rotated and spun again using a tracing roll (41) to form a tire retaining flange part (21) and a bead seat part (23) on the circumferential surface of the preliminary body (40). , a hump part (24) and a concave well part (
22) of the rear rim (R2).
After removing the secondary abutment body (42) from the mold (37), the center part is press punched to be larger than the center hole (38), and a convex piece is formed. The rear rim (20) is carved with a joint flange (20) for attachment to the wheel disc (D), which has an overall sawtooth or petal shape with alternating grooves (a2) and grooves (b2).
R2) and finish the joint flange portions (19) and (20) of the front rim (R1) and rear rim (R2) with their respective convex pieces (a1).
) (a2) bolt insertion holes (25) (26)
A method for manufacturing a rim of a three-piece wheel, characterized in that the rim is welded and integrated under conditions in which the rims match. 4. When welding both joint flange parts (19) and (20), weld the hump that pairs with the hump part (24) of the rear rim (R2) itself by overlay welding or by welding and subsequent milling. A method for manufacturing a rim of a three-piece wheel according to claim 2 or 3, characterized in that the portion (29) is bulge-molded.