WHEEL RIM FORMING METHOD
CROSS-REFERENCE TO PRIOR APPLICATION
Priority is claimed to Japanese Patent Application No. 2011-120091, filed on May 30, 2011, which is hereby incorporated by reference in its entirety herein.
FIELD OF THE INVENTION
The present invention relates to a method for forming a rim which constructs a vehicle wheel, particularly to a method for forming a rim by thinning a desired portion of the rim.
BACKGROUND
For example, as a vehicle wheel, a two-piece wheel formed with a rim and a disc welded together is well known. In such a wheel, the rim is generally formed by curving a rectangular metal plate to form a cylindrical tube material, and subsequently forming it into a desired shape by a rolling process.
Recently, weight reduction of a vehicle wheel is strongly demanded. Therefore, structures have been known in which a portion of a rim having sufficient strength is thinned. Various forming methods have been proposed. An example of the forming method is proposed in JP2008-509005 W("JP '005") , for example. It proposes a method in which a flaring process is performed by which a side wall of the cylindrical tube material is flared outward in the radial direction, the flared side wall is then extended, and its side surface is contoured by a spinning process. This method allows extension of the flared side wall and contouring of the side surface by a one-time spinning process. More specifically, for the contouring, a roller for spinning is pressed onto a prescribed portion from the outside in the radial direction to form a well portion (with substantially the same thickness) . Further, the roller is continuously moved in a front-back direction
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(longitudinal direction) while the roller is pressed onto the portion, thereby thinning and contouring the flared side wall. As described above, the method is proposed in "JP '005" allows the extension and the contouring at the same time by the one-time spinning process, thus providing an effect of reducing time required for rim formation.
SUMMARY
In the conventional method according to the above Patent Document 1, the well portion is first formed by the spinning process in a compact (hereinafter referred to as "flared compact") having the flared side wall formed therein by the flaring process, the flared compact is then thinned and contoured by the spinning process. The method is performed in such a manner for the following reason. The well portion is first formed in the flared compact, and the well portion is fitted into a forming die disposed inside the flared compact, thereby positioning the flared compact to prevent it from moving with respect to the forming die in the front-back direction. The spinning process is thereby performed on a portion to thin and a portion to contour without misaligning these portions and the die. Therefore, the method according to Patent Document 1 has a problem that the spinning process has to be performed for forming the well portions, the thinning, and the contouring, thus resulting in increased time which is required for the spinning process.
Further, the conventional method has difficulty in forming the contour with a complicated shape since the thinning and the contouring are performed by the one-time spinning process and is realistically only capable of contouring into a relatively simple shape. When a relatively simple shape is obtained by the spinning process through thinning and contouring at a time, the obtained compact is more likely to be subjected to a local load in the subsequent rolling process, which often causes wrinkles, sink marks, buckling, or the like on a produced rim.
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The present invention provides a method for forming a rim which allows a reduction in time required for a spinning process for thinning a prescribed portion and allows prevention of wrinkles, sink marks, buckling, or the like during a rolling process.
An aspect of the present invention provides a method for forming a rim in which after a flaring step, a plurality of rolling steps for stepwise contouring a rim into a desired shape are sequentially performed to form a desired rim, in which after performing a first rolling step in which a flared compact which is formed by the flaring step is formed into a rolled compact including a recessed portion which is recessed inward in a radial direction and rolled intermediately-formed portions which are contoured on both front and back sides of the recessed portion, a spinning step is performed in which the rolled compact is positioned in a front-back direction by holding the recessed portion, and all or a part of the rolled intermediately-formed portions are thinned by a spinning process.
In such a method, the rolled compact having the recessed portion formed by the first rolling step is thinned by the spinning process, and no formation of the recessed portion is required in the spinning step, thus allowing a reduction in time required for the spinning step. Furthermore, in the spinning step, the spinning process is performed on the basis of positioning of the recessed portion formed in the first rolling step by holding it-, and the rolled intermediately-formed portions contoured by the first rolling step are thinned. This facilitates specification of a desired portion to be thinned and thus accurately and stably thinning the desired portion. Moreover, since the spinning step for thinning is performed after the first rolling step, the rolling step after the spinning step causes less deformation in the rolled compact. This allows a reduction in local loads applied during the rolling process and also allows prevention of wrinkles, sink marks, buckling, or the like during the rolling process. Accordingly, the method for forming a rim according to the present
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invention allows a reduction in the time required for the spinning step and allows efficient thinning. In addition, when the method is applied to a step of manufacturing the rim, the manufacturing efficiency of the rim in which the desired portion is thinned can be stably improved.
The rolled intermediately-formed portions subjected to the spinning process are contoured by the first rolling step after the flaring step; therefore, the rolled intermediately-formed portions are different from the portions in the flared compact. In other words, a feature of the present invention is that the rolled intermediately-formed portion contoured by the first rolling step is subjected to the spinning process, thereby providing the above-described effects.
Another aspect of the present invention proposes the method for forming a rim, in which the rolled intermediately-formed portions which are contoured by the first rolling step includes a ledge intermediately-formed portion for forming a ledge portion and bead seat intermediately-formed portions for forming front and back bead seat portions.
In such a method, all or a part of the ledge intermediately-formed portion and the bead seat intermediately-formed portions are thinned by the spinning step. Since the ledge portion and bead seat portions have sufficient strength compared to a flange portion or the like, the thinning facilitates weight reduction of the rim. Further, in the spinning step, the spinning process is performed on the ledge intermediately-formed portion and the bead seat intermediately-formed portions. Accordingly, the ledge portion and the bead seat portions that are the portions to be thinned can be accurately and easily specified and thinned. This allows the efficient spinning process, thus further contributing toward reducing the time for the spinning step.
Another aspect of the present invention proposes the method for
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forming a rim, in which in the spinning step, the recessed portion is positioned in the front-back direction by holding the recessed portion by a first mandrel roll including a first stepped portion which is fitted into the rolled compact from one side of the front and back sides thereof and supports the recessed portion from the one side and a second mandrel roll including a second stepped portion which is fitted into the rolled compact from the other side of the front and back sides thereof and supports the recessed portion from the other side, and the spinning process is performed on all or a part of the rolled intermediately-formed portions by pressing a spinning roll onto the rolled compact from an outside thereof in the radial direction while neither of front and back ends of the rolled compact is held.
In such a method, the first mandrel roll and the second mandrel roll which cooperate with the spinning roll to perform the spinning process are fitted into the rolled compact from both its front and back sides to hold the recessed portion. This allows stable and accurate holding of the recessed portion and contributes toward reducing the time for spinning step by not forming the recessed portion by the spinning process. Since the recessed portion can be stably held, the spinning process can be performed without holding either of the front and back ends of the rolled compact. Accordingly, the spinning process can be preferably performed without limiting movement of both the front and back ends of the rolled compact during the spinning process.
The recessed portion and the first and second stepped portions that support the recessed portion may contact with each other with no gap or with a partial gap, while holding the recessed portion. In other words, the rolled compact may be formed into a shape in which the recessed portion corresponds to the first and second stepped portions or may be formed into a shape not corresponding to those to the extent that the recessed portion can be held by the first and second stepped portions.
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Another aspect of the present invention proposes the method for forming a rim, in which in the spinning step, the spinning roll is moved in a direction away from a portion close to the recessed portion of the rolled compact to perform the spinning process on all or a part of the rolled intermediately-formed portions.
In such a method, the spinning process is performed from the recessed portion held by the first and second mandrel rolls toward an end portion which is not held. The rolled intermediately-formed portion to be subjected to the spinning process can be preferably extended and thinned toward the end portion.
This method is capable of performing the spinning process with the single spinning roll. Further, in the spinning step, the spinning roll may be moved on either one of the front and back sides of the recessed portion or may be sequentially moved on both the front and back sides.
Another aspect of the present invention proposes the method for forming a rim, in which in the spinning step, two spinning rolls are moved in directions away from each other from portions on both front and back sides of the recessed portion of the rolled compact to perform the spinning process on all or a part of the rolled intermediately-formed portions.
In such a method, the two spinning rolls perform the spinning process on the respective rolled intermediately-formed portions which are contoured on both sides of the recessed portion, thus allowing a further reduction in the time required for the spinning step. Particularly, since the two spinning rolls are almost simultaneously moved, the time can be reduced as much as possible.
Another aspect of the present invention proposes the method for forming a rim, in which in the spinning step, while the recessed portion of the rolled compact is pressed from an outside in the radial direction of the recessed portion by a center guide roll, the spinning process is performed on all or a part of the rolled intermediately-formed
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portions.
In such a method, the recessed portion is held by the first and second mandrel rolls and the center guide roll from the inside and outside of the recessed portion. Accordingly, the rolled compact can be more stably and certainly positioned, thus allowing a further improvement in process accuracy in the spinning process.
In the method for forming a rim according to the present invention, after the flaring step, the first rolling step for contouring the recessed portion and the rolled intermediately-formed portions is performed. The rolled compact formed by the first rolling step is positioned in the front-back direction by holding its recessed portion, and the spinning step for thinning all or a part of the rolled intermediately-formed portions by the spinning process is thereby performed. Accordingly, formation of the recessed portion is not required in the spinning step, and the time required for the spinning step can be thus reduced compared to the above-described conventional method. Furthermore, the spinning process is performed on the rolled intermediately-formed portions on the basis of the positioning by holding the recessed portion. Therefore, the portion to be thinned can be easily specified and can be accurately and stably thinned. Since the spinning step for the thinning is performed after the first rolling step, the rolling step after the spinning step causes less deformation in the rolled compact. Accordingly, loads due to the rolling process after the spinning process can be reduced, thus allowing prevention of wrinkles, sink marks, buckling, or the like. Therefore, the method for forming a rim according to the present invention allows a reduction in the time required for the spinning step and prevention of wrinkles, sink marks, buckling, or the like during the rolling step.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a vertical cross-sectional view of a vehicle wheel 1.
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FIGs. 2A to 2C are explanatory diagrams of forming steps of a rim 2.
FIGs. 3A to 3C are explanatory diagrams of the forming steps of the rim 2, which are continued from FIGs, 2A to 2C.
FIGs. 4A and 4B are explanatory diagrams of a first rolling step according to a first embodiment.
FIGs. 5A and 5B are explanatory diagrams of a spinning step according to the first embodiment.
FIGs. 6A and 6B are explanatory diagrams of the spinning step, which are continued from FIGs. 5A and 5B.
FIGs. 7A and 7B are explanatory diagrams of a spinning step according to a second embodiment.
DETAILED DESCRIPTION
Embodiments of the present invention will be described in detail with reference to the attached drawings. FIG. 1 is a vertical cross-sectional view of a vehicle wheel 1. The vehicle wheel 1 is a so-called two-piece type steel wheel having a rim 2 formed from a steel plate and a disc 3 unitarily fitted and welded together. In this embodiment, the direction from the back side of the disc 3 toward the design surface is referred to as a front direction, and the direction opposite to it is referred to as a back direction. Further, the direction toward a central axial line L of the vehicle wheel 1 along the wheel radial direction is defined as a radially inward direction, and the direction opposite to it is defined as a radially outward direction.
The rim 2 has rim flange portions 11 and 12 on respective opening edges on its front and back sides. The rim flange portions 11 and 12 have front and back bead seat portions 13 and 14 formed continuously therewith. Furthermore, a well portion 15 which is recessed inward in the radial direction is formed between the front and back bead seat portions 13 and 14. A ledge portion 16 is formed continuously between
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the well portion 15 and the back bead seat portion 14. A method for forming the rim 2 relates to an essential element of the present invention and will be described in detail later.
Meanwhile, the disc 3 includes a hub mounting portion 21 having a hub hole 27 at its center, a hat portion 22 projecting in the front direction from an outer edge of the hub mounting portion 21, and a disc flange portion 23 extending in the back direction from an outer edge of the hat portion 22. The hub mounting portion 21 has bolt holes 26 provided at regular intervals in the circumferential direction. The hat portion 22 has a plurality of ornamental holes 28 at regular intervals in the circumferential direction. Such a disc 3 can be formed by pressing a disc-shaped steel plate. Since this forming can be carried out in the same manner as the conventional method, descriptions of its forming steps will be omitted.
The disc 3 is inserted into the rim 2, and the disc flange portion 23 of the disc 3 and the well portion 15 are welded together, thereby obtaining the vehicle wheel 1 according to this embodiment. The welding steps can be also carried out in the same manner as the conventional method. Descriptions of those will be omitted.
Steps of forming the rim 2, which relates to the essential element of the present invention, will be next described. As shown in FIG. 2 (A) , a generally rectangular steel plate 3 is curved, and its shorter sides are then butted against each other and welded together, thereby obtaining a cylindrical tube material 32.
As shown in FIG. 2 (B) , by a flaring process, truncated-cone-shaped flaring dies 41, 41 are pressed into both end openings of the cylindrical tube material 32, and both the end openings are thereby expanded to form flared end portions 33a, 33a. Accordingly, a flared compact 33 having the flared end portions 33a, 33a is formed. As shown in FIG. 2(C), in a next first rolling step, the flared compact 33 is squeezed from its inside and outside by a first inside die 43 and a first outside die 44, thereby contouring the flared compact 33 into
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an intermediate shape which will be lead into a desired shape. Accordingly, a first rolled compact 51 is formed. As shown in FIG. 3(A), in a next spinning step, a first mandrel roll 91 and a second mandrel roll 92 are fitted into the first rolled compact 51, and spinning rolls 93a and 93b are pressed onto the compact 51 from its outside, thereby partially thinning a desired portion. As shown in FIG. 3(B), in a next second rolling step, a partially-thinned first rolled compact 51' is squeezed from its inside and outside by a second inside die 45 and a second outside die 46, thereby contouring the compact 51' to form a second rolled compact 52. As shown in FIG. 3(C) , in a next third rolling step, the second rolled compact 52 is squeezed from its inside and outside by a third inside die 47 and a third outside die 48. The front and back bead seat portions 13 and 14, the well portion 15, the ledge portion 16, and so forth are contoured, thereby forming the rim 2. In a next expanding step which is not shown, the rim 2 is adjusted into a shape closer to a perfect circle to obtain the rim 2 with a desired shape.
First rolling steps and spinning steps according to first and second embodiments will be each described hereinafter.
FIRST EMBODIMENT
In the first rolling step, as shown in FIG. 4 (A) , the flared compact 33 is loosely fitted to the first inside die 43 which is disposed inside the flared compact 33. As shown in FIG. 4(B), the first outside die 44 is butted to the flared compact 33. At this point, the flared compact 33 is squeezed by rotating the first inside die 43 and the first outside die 44. Accordingly, the flared compact 33 is subjected to a rolling process while being rotated in the circumferential direction.
The first inside die 43 includes an inside recess forming portion 81 which is recessed inward in the radial direction, an inside-front intermediately-formed portion 82 provided on the front side of the
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inside recess forming portion 81, and an inside-back intermediate shape first forming portion 83 and an inside-back intermediate shape second forming portion 84 that are provided on the back side of the inside recess forming portion 81. Meanwhile, the first outside die 44 includes an outside protrusion forming portion 86 facing the inside recess forming portion 81, an outside-front intermediately-formed portion 87 facing the inside-front intermediately-formed portion 82, an outside-back intermediate shape first forming portion 88 facing the inside-back intermediate shape first forming portion 83, and an outside-back intermediate shape second forming portion 89 facing the inside-front intermediate shape second forming portion 84. [0034]
In the first rolling step, an outside protrusion forming portion 86 is pressed into the inside recess forming portion 81, thereby forming a recessed portion 66 which is recessed inward in the radial direction with respect to the flared compact 33. By squeezing by the inside-front intermediately-formed portion 82 and the outside-front intermediately-formed portion 87, a front bead seat intermediately-formed portion 63 for forming the front bead seat portion 13 on the flared compact 33 is contoured. By squeezing by the inside-back intermediate shape first forming portion 83 and the outside-back intermediate shape first forming portion 88, a ledge intermediately-formed portion 67 for forming the ledge portion 17 on the flared compact 33 is contoured. By squeezing by the inside-back intermediate shape second forming portion 84 and the outside-back intermediate shape second forming portion 89, a back bead seat intermediately-formed portion 64 for forming the back bead seat portion 14 on the flared compact 33 is contoured.
As described above, the flared compact 33 is squeezed by the first inside die 43 and the first outside die 44 to form the recessed portion 66, the front bead seat intermediately-formed portion 63, the ledge intermediately-formed portion 67, and the back bead seat
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intermediately-formed portion 64 on the flared compact 33. The first rolled compact 51 including the recessed portion 66, the front bead seat intermediately-formed portion 63, the ledge intermediately-formed portion 67, and the back bead seat intermediately-formed portion 64 is contoured. In other words, since the first rolled compact 51 is contoured by the rolling process on the flared compact 33, the first rolled compact 51 is configured with a shape different from the flared compact 33.
The spinning step is performed following the first rolling step. In the spinning step, as shown in FIGs. 5 (A) and 5(B), the first mandrel roll 91 is fitted into the first rolled compact 51 from its front side, and the second mandrel roll 92 is fitted into the first rolled compact 51 from its back side. The first mandrel roll 91 includes a first stepped portion 95 which contacts with and supports a front inner circumferential surface of the recessed portion 66 of the first rolled compact 51 and a front circumferential portion 96 which contacts with and supports an inner circumferential surface of the front bead seat intermediately-formed portion 63 . Meanwhile, the second mandrel roll 92 includes a second stepped portion 97 which contacts with and supports a back inner circumferential surface of the recessed portion 66, a back first circumferential portion 98 which contacts with and supports an inner circumferential surface of the ledge intermediately-formed portion 67, and a back second circumferential portion 99 which contacts with and supports an inner circumferential surface of the back bead seat intermediately-formed portion 64.
In the first embodiment, as shown in FIG. 5 (B) , by the first mandrel roll 91 and the second mandrel roll 92, the first stepped portion 95 and the second stepped portion 97 contact with and hold the inner circumferential surface of the recessed portion 66 with almost no gap, thereby positioning the first rolled compact 51 in the front-back direction. Further, the front circumferential portion 96, the back first circumferential portion 98, and the back second circumferential
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portion 99 support the front bead seat intermediately-formed portion 63, the ledge intermediately-formed portion 67, and the back bead seat intermediately-formed portion 64 of the first rolled compact 51. In the state of FIG. 5(B), neither of end openings of the first rolled compact 51 is held.
The first mandrel roll 91 and the second mandrel roll 92 fitted into the first rolled compact 51 are rotated in the circumferential direction, thereby rotating the first rolled compact 51 in the circumferential direction. As shown in FIG. 6(A) , while rotating the first rolled compact 51, spinning rolls 93a and 93b are pressed thereto from the outside. The spinning roll 93a on the front side is butted to a back end of the front bead seat intermediately-formed portion 63 of the first rolled compact 51 from the outside in the radial direction, and is moved toward a front end of the front bead seat intermediately-formed portion 63, as shown in FIG. 6(B) . Meanwhile, the spinning roll 93b on the back side is butted to a front end of the ledge intermediately-formed portion 67 from the outside in the radial direction, as shown in FIG. 6(A), and is moved toward a back end of the ledge intermediately-formed portion 67, as shown in FIG. 6(B) . The spinning rolls 93a and 93b on both the sides are controlled and operated to simultaneously start moving.
As described above, the two spinning rolls 93a and 93b are controlled and operated to extend the front bead seat intermediately-formed portion 63 toward the front side to thin it and to extend the ledge intermediately-formed portion 67 toward the back side to thin it. This spinning process provides a first rolled compact 51' which includes thinned front bead seat intermediately-formed portion 63' and thinned ledge intermediately-formed portion 67' . In ' the spinning step, only the spinning process to partially thin the first rolled compact 51 contoured by the first rolling step is performed. However, no contouring is performed.
After the spinning step, the above-described second rolling step,
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third rolling step, and expanding step are sequentially performed, thereby forming the rim 2 having the front bead seat portion 13 and the ledge portion 16 that are thinned.
In the above-described first embodiment, in the spinning step,
the recessed portion 66 formed by the first rolling step is held by
the first mandrel roll 91 and the second mandrel roll 92 to position
the first rolled compact 51 in the front-back direction. Further,
the spinning process is performed to thin the front bead seat
intermediately-formed portion 63 and the ledge intermediately-formed
portion 67 that are contoured in the first rolling step. Accordingly,
only the spinning process for thinning is performed in the spinning
step, thus reducing time required for the spinning step. Furthermore,
using the recessed portion 66 formed in the first rolling step as a
reference facilitates the stable positioning. Therefore, the
spinning rolls are controlled and operated with the recessed portion
66 as a reference. This allows the accurate and stable spinning
process on the front bead seat intermediately-formed portion 63 and
the ledge intermediately-formed portion 67. In addition, in the
spinning step, the spinning rolls 93a and 93b are moved toward the
respective end openings of the first rolled compact 51 without holding
either of the end openings. Accordingly, when the front bead seat
intermediately-formed portion 63 and the ledge intermediately-formed
portion 67 are extended, movement of both the end openings of the first
rolled compact 51 are not limited, thus facilitating preferable
spinning process. Moreover, since the spinning step for thinning is
performed after the first rolling step, the rolling step after the
spinning step causes less deformation in the rolled compact 51' or
52 . This allows a reduction in local loads applied during each rolling
process and also allows prevention of wrinkles, sink marks, buckling,
or the like during the rolling process. As described above, the steps
of forming a rim according to the first embodiment enables a reduction
in the time required for the spinning process and enables efficient
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thinning. When these steps are applied to steps of manufacturing the rim, the manufacturing efficiency in manufacturing the
partially-thinned rim 2 can be stably improved.
In the first embodiment, the first rolled compact 51 constitutes a rolled compact of the present invention. Further, the front bead seat intermediately-formed portion 63, the ledge intermediately-formed portion 67, and the back bead seat intermediately-formed portion 64 constitute rolled intermediately-formed portions of the present invention.
SECOND EMBODIMENT
In the second embodiment, as shown in FIG. 7 (A) , in the spinning step performed following the first rolling step, the first mandrel roll 91 and the second mandrel roll 92 are fitted into the first rolled compact 51. In addition, a center guide roll 94 is brought into contact with the recessed portion 66 from the outside of the first rolled compact 51. Accordingly, the recessed portion 66 can be squeezed and held from its inside and outside. This enables highly effective holding of the recessed portion 66, thus allowing more stable positioning of the first rolled compact 51. While the position of the recessed portion 66 is held in such a manner, the spinning process by the spinning rolls 93a and 93b is performed as shown in FIG. 7 (B) . This allows more stable spinning process and also allows a further improvement in processing accuracy.
Similarly to the above-described first embodiment, the second embodiment allows a reduction in the time required for the spinning step and prevention of wrinkles, sink marks, buckling, or the like during the rolling process. Accordingly, the manufacturing efficiency of the rim 2 can be stably improved.
The second embodiment is the same as the first embodiment except that the recessed portion 66 is held by the center guide roll 94 in the spinning step. Like elements will be thus denoted by like numerals
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and symbols, and descriptions thereof will be omitted.
In the first and second embodiments, the front bead seat intermediately-formed portion and the ledge intermediately-formed portion are thinned by the spinning step. However, in addition to this, the spinning rolls may be controlled and operated to thin the back bead seat intermediately-formed portion. In such a case, the area to be thinned becomes wider, thus further improving weight reduction. The rim may be configured without the ledge portion. In such a configuration, the front bead seat intermediately-formed portion and the back bead seat intermediately-formed portion may be thinned.
As described above, in the spinning step, the spinning process may be performed on one or two arbitrary portions of the front bead seat intermediately-formed portion, the back bead seat intermediately-formed portion, and the ledge intermediately-formed portion. Alternatively, the spinning process may be performed on all the three intermediately-formed portions.
In the first and second embodiments, the two spinning rolls are used to perform the spinning process in the spinning step. However, the single spinning roll can be alternatively used to perform the spinning process. For example, in a case that the front bead seat intermediately-formed portion and the ledge intermediately-formed portion are thinned similarly to the first embodiment, the spinning roll is controlled and operated to first move from the back end to the front end of the front bead seat intermediately-formed portion to thin it and subsequently to move from the front end to the back end of the ledge intermediately-formed portion to thin it.
Furthermore, in the first and second embodiments, in the spinning step, the first stepped portion of the first mandrel roll and the second stepped portion of the second mandrel roll contact with the recessed portion with almost no gap for positioning the recessed portion. However, alternatively, the positioning may be conducted with a gap
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between the recessed portion and the first and second stepped portions . In other words, as long as the recessed portion can be positioned, there may be a gap between the recessed portion and the first and second stepped portions.
In the first and second embodiments, only the thinning of the front bead seat intermediately-formed portion and the ledge intermediately-formed portion is performed in the spinning step. However, simultaneously with the spinning process, a process for changing the shape of each of the intermediately-formed portions may be performed.
The present invention is not limited to the above-described embodiments, but configurations other than the embodiments may be appropriately carried out within the scope of the gist of the present invention.
DESCRIPITION OF REFERENCE NUMERALS AND SYMBOLS
2: rim
13: front bead seat portion
14: back bead seat portion
16: ledge portion
33: flared compact
51: first rolled compact (rolled compact)
63: front bead seat intermediately-formed portion (rolled
intermediately-formed portion)
64: back bead seat intermediately-formed portion (rolled
intermediately-formed portion)
66: recessed portion
67: ledge intermediately-formed portion (rolled
intermediately-formed portion)
91: first mandrel roll
92: second mandrel roll
93a: front spinning roll
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93b: back spinning roll 94: center guide roll 95: first stepped portion 96: second stepped portion
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CLAIMS
1. A method for forming a rim in which after a flaring step, a
plurality of rolling steps for stepwise contouring a rim into a desired
shape are sequentially performed to form a desired rim.
Wherein after performing a first rolling step in which a flared compact which is formed by the flaring step is formed into a rolled compact including a recessed portion which is recessed inward in a radial direction and rolled intermediately-formed portions which are contoured on both front and back sides of the recessed portion, a spinning step is performed in which the rolled compact is positioned in a front-back direction by holding the recessed portion, and all or a part of the rolled intermediately-formed portions are thinned by a spinning process.
2. The method for forming a rim according to claim 1,
wherein the rolled intermediately-formed portions which are
contoured by the first rolling step includes a ledge intermediately-formed portion for forming a ledge portion and bead seat intermediately-formed portions for forming front and back bead seat portions.
3. The method for forming a rim according to claim 1 or 2,
wherein in the spinning step, the recessed portion is
positioned in the front-back direction by holding the recessed portion by a first mandrel roll including a first stepped portion which is fitted into the rolled compact from one side of the front and back sides thereof and supports the recessed portion from the one side and a second mandrel roll including a second stepped portion which is fitted into the rolled compact from the other side of the front and back sides thereof and supports the recessed portion from the other side, and
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the spinning process is performed on all or a part of the rolled intermediately-formed portions by pressing a spinning roll onto the rolled compact from an outside thereof in the radial direction while neither of front and back ends of the rolled compact is held.
4. The method for forming a rim according to claim 3,
wherein in- the spinning step, the spinning roll is moved in
a direction away from a portion close to the recessed portion of the rolled compact to perform the spinning process on all or a part of the rolled intermediately-formed portions.
5. ■ The method for forming a rim according to claim 3 or 4,
wherein in the spinning step, two spinning rolls are moved in directions away from each other from portions on both front and back sides of the recessed portion of the rolled compact to perform the spinning process on all or a part of the rolled intermediately-formed portions.
6. The method for forming a rim according to any one of claims
3 to 5,
wherein in the spinning step, while the recessed portion of the rolled compact is pressed from an outside in the radial direction of the recessed portion by a center guide roll, the spinning process is performed on all or a part of the rolled intermediately-formed portions.
7 . A method for forming a rim, substantially as herein described with reference to accompanying drawings.
Dated this 15"^ day of March 2012
Of Anand atid Anand, Adv^ocates * Agents for the Applicants
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