Patent Grant
7861412
1. Field of the Invention
The present invention relates to a method for molding a vehicular wheel rim made of a metal plate or protruded member.
2. Related Art
Japanese Patent Laid-Open No. 2005-95982 Gazette (US2005091850A1) describes a method for manufacturing a wheel for use in passenger cars, trucks, buggies and the like. It then discloses a method for molding a wheel rim by disposing an electromagnetic molding die whose inner face serves as a molding face at an outer peripheral side of a cylindrical material made of aluminum alloy, disposing an electromagnetic molding coil at an inner peripheral side of the cylindrical material, charging electrical energy to the electromagnetic molding coil in this state to enlarge and press the cylindrical material against the molding face of the molding die to mold a cylindrical body having a drop portion whose outer diameter is small and both side portions whose outer diameter is larger than that of the drop portion and by curling edges of the side portions.
It is noted that the electromagnetic molding refers to a technology of molding a workpiece into a predetermined shape by making use of a phenomenon in which an electromagnetic molding coil produces a strong magnetic field in a very short time when electric energy (electric charge) accumulated at high voltage is instantaneously charged (discharged) into the electromagnetic molding coil and the workpiece placed in the magnetic field is subjected to a strong enlarging force or contraction force caused by a repulsive force (Lorentz force according to Fleming's left-hand rule) of the magnetic field and thereby undergoes fast plastic deformation. In case of this example, the cylindrical material enlarges in a direction of the outer diameter by receiving the strong enlarging force and is pressed against the molding face of the electromagnetic molding die.
Because an extruded member having an equal thickness or a plate member in a cylindrical shape formed by bending and welding edge portions thereof is used as the cylindrical material and the side portions are enlarged more than the drop portion, the above-mentioned method allows the wheel rim having the thicker drop portion (thickness decreases less in enlarging the diameter thereof) and the thinner both side portions (thickness decreases more in enlarging the diameter) to be molded. Therefore, when a disk is fixed to the drop portion, the wheel rim hardly causes welding distortion and can support a large load corresponding to its thickness. Still more, if the thickness of the drop portion is supposed to be equal, weight of the entire wheel rim may be lightened due to the thin both side portions. It should be noted that Japanese Patent Laid-Open No. 2004-224292 Gazette also describes a curling of edges of the wheel rim.
However, there has been a problem in pressing a curling die against the edges of the side portions to bend and curl the edges in an external direction (external curling process) in a curling process after the electromagnetic molding that the drop portion of the cylindrical body buckles due to the pressure in the axial direction of the curling die.
Accordingly, it is an object of the invention to solve the above-mentioned problem in molding the wheel rim from the cylindrical material by applying the electromagnetic molding method and the curling method by pressing.
According to the invention, there is provided a method for molding a vehicular wheel rim by disposing an electromagnetic molding die whose inner face serves as a molding face on the side of an outer periphery of a metallic cylindrical material, disposing an electromagnetic molding coil on the side of an inner periphery of the cylindrical material, charging electrical energy to the electromagnetic molding coil in this state to enlarge and press the cylindrical material against the molding face of the molding die to mold a cylindrical body having a drop portion whose outer diameter is small and both side portions whose outer diameter is larger than that of the drop portion and by externally curling edges of the side portions by pressing by curling dies in the axial direction while restraining the outer periphery of the drop portion of the cylindrical body by a buckling preventing die.
An extruded material having an equal thickness or a plate material in a cylindrical shape obtained by bending and welding end portions thereof may be used as the cylindrical material. It is preferable to use aluminum (including aluminum alloy), copper (including copper alloy) and the like having a high electrical conductivity, and it is particularly preferable to use aluminum (including aluminum alloy).
A die having molding faces in the shapes corresponding to the drop portion and the side portions of the cylindrical body after molding may be used as the electromagnetic molding die. Beside that, an electromagnetic molding die having no molding face corresponding to part of or an entirety both side portions and having a molding face whose axial length is short as compared to an axial length of the cylindrical body to be molded, i.e., whose inner peripheral face is composed of the molding face in the shape corresponding to the drop portion of the cylindrical body or whose inner peripheral face is composed of the molding face in the shape corresponding to the drop portion and to part of the side portions of the cylindrical body.
The external curling process by pressing is carried out in a manner of pressing curling dies against edges of the side portions. A known arc-like tool (a semi-arc or a quarter-arc tool) or a cone-like tool may be used as the curling die.
The buckling preventing die has an inner peripheral face corresponding at least to the drop portion of the cylindrical body. Still more, the side portions that are subject to the curling process must be exposed out of the die so that the die will not hamper the curling process. Although a dedicated die may be used as the buckling preventing die, the electromagnetic molding die used in the electromagnetic molding step may be used as it is.
A roll-forming process is carried out as necessary after the curling process. The roll-forming process is a processing method carried out by pinching inner and outer sides of the cylindrical body by rollers and is used in finishing a sectional shape of the cylindrical body into a final shape of the wheel rim.
The invention allows the wheel rim to be molded efficiently from the cylindrical material by successively applying the electromagnetic molding step and the curling step and prevents the buckling from occurring at the drop portion of the cylindrical body by restraining the outer periphery of the drop portion by the buckling preventing die in the curling step carried out by pressing. Then, as for the cylindrical material having the equal thickness, while the thickness is kept relatively thick at the drop portion, it is thin at the side portions by the enlargement of the electromagnetic molding step. The thin both side portions may be readily curled by relatively low compression force in the axial direction, allowing the vehicular wheel rim to be manufactured at high precision in combination with the restraint of the outer periphery of the drop portion by the buckling preventing fixture.
Still more, when the electromagnetic molding die is used as the buckling preventing die, it becomes possible to cut the equipment costs and to simplify the molding steps because it is not necessary to replace the electromagnetic molding die with the buckling preventing die.
The wheel rim manufactured by the manufacturing method of the invention has the thick drop portion that junctions with the disk and the relatively thin both side portions, so that it becomes possible to lighten its weight, even though it bears the large load, and to cut the number of processing steps and to improve product performance because the rim has no junction. Further, because the disk is fixed to the drop portion by welding or the like, it becomes possible to design the disk solely and to have an excellent decorative design. Still more, it allows highly accurate products to be obtained.
It is noted that the summary of the invention described above does not necessarily describe all necessary features of the invention. The invention may also be a sub-combination of the features described above.
The invention will be explained below more specifically with reference to
The cylindrical material 1 is an extruded member made of aluminum alloy having a circular section and an equal thickness. An electromagnetic molding die 3 whose inner face serves as a molding face is disposed on the side of an outer periphery of the cylindrical material 1 and an electromagnetic molding coil 4 is disposed on the side of an inner periphery of the cylindrical material 1. Center axes of the cylindrical material 1, the electromagnetic molding die 3 and the electromagnetic molding coil 4 almost coincide from each other. The electromagnetic molding die 3 is composed of three split dies 3a, 3b and 3c split in a longitudinal direction as shown in
In the electromagnetic molding die 3, a center part of the molding face of the split die 3a corresponding to the drop portion 2a of the cylindrical body 2 is cylindrical and has a smallest inner diameter and both sides thereof have an inner diameter that gradually increases toward the outsides (toward the split die 3b and 3c). The molding faces of the split dies 3b and 3c corresponding to the side portions 2b and 2c of the cylindrical body 2 have an inner diameter that gradually increases only at parts close to the split die 3a and is almost cylindrical other than that. There is a slight gap between the outer peripheral face of the cylindrical material 1 and the molding face of the split die 3a at the center part of the molding face of the split die 3a. There is also a gap of adequate size between the inner peripheral face of the cylindrical material 1 and the electromagnetic molding coil 4.
It should be noted that preferably the electromagnetic molding die 3 is made of a metal having a low electrical conductivity such as stainless steel. If it is not used as a buckling preventing die as described later, a material other than the metal such as a structural material having no electrical conductivity such as fiber reinforced plastic and bakelite for example may be used for the electromagnetic molding die 3. The electromagnetic molding coil 4 is what a molding coil is embedded within an electrical insulator.
A moldable material having a high electrical conductivity such as O material (modification: annealing) of aluminum alloy of JIS 6000 such as 6063, 6061 and 6N01 is preferable as the material of the cylindrical material 1. When the cylindrical material 1 is placed within the electromagnetic molding die 3 and the electromagnetic molding coil 4 is inserted into the cylindrical material 1 as indicated by the imaginary lines in
After the electromagnetic molding, the split dies 3b and 3c are split and are removed, the electromagnetic molding coil 4 is pulled out and an external curling process by pressing is carried out on edges of the side portions 2b and 2c of the cylindrical body 2 (curling step).
When curling dies 5 that are well-known per se are advanced in the same time and pressed against the edges of the side portions 2b and 2c of the cylindrical body 2, the edges cause external curling deformation along almost semi-circular grooves 5a as shown in
After the curling process, it becomes possible to obtain a cylindrical body (wheel rim) 6 by moving back the curling dies 5 and splitting and removing the split die 3a as shown in
It should be noted that although the electromagnetic molding die 3 (3a through 3c) that covers the entire length of the cylindrical material 1 has been used in the electromagnetic molding step in the example described above, it is also possible to adopt a method of disposing only the electromagnetic molding die (i.e., the split die 3a) that covers not the entire length but a range corresponding to the drop portion 2a of the cylindrical body 2 for example around the cylindrical material 1 to mold the drop portion 2a into the shape corresponding to the molding face of the die and of freely deforming the side portions corresponding to the electromagnetic molding force.
Still more, although the split die 3a composing the electromagnetic molding die 3 is used as the buckling preventing die in the curling step in the example described above, it is also possible to use a dedicated buckling preventing die separately.
(1) Standard Name: Wheel Rim specified by JATMA (Japan Automobile Tyre Manufacturers Association)
(2) Nominal Size of Rim: 10×5.5 AT
(3) Material: A6063-O material
(4) Workpiece: Cylindrical material molded by extrusion molding
Outer Diameter: (φ198.8 [mm]
Thickness (plate thickness): 2.5 [mm]
(5) State of Cylindrical Body caused by Electromagnetic Molding Step
Diameter of Edge of Enlarged Tube (both side portions): (φ250 [mm]
Thickness of Edge of Enlarged Tube: 2.1 [mm]
Rate of Enlargement of Tube: about 25%
(6) Processing Conditions in Curling Step
Example 1: Maximum Load 95 [KN]
Machining Speed 20 [mm/min.]
Example 2: Maximum Load 100 [KN]
Machining Speed 10 [mm/min.]
<Comparison with Other Manufacturing Method>
(a) Present Invention
Composition of Parts: 2 pieces (cylindrical body+disk)
Thickness of Plate Member (drop portion): about 2.5 [mm]
Weight of Wheel: about 1450 [g]
(b) Spinning
Composition of Parts: 2 pieces
Thickness of Plate Member: about 3.0 [mm]
Weight of Wheel: about 1850 [g]
(c) Pressing
Composition of Parts: 3 pieces (two cup-like members+disk)
Thickness of Plate Member: about 2.5 [mm]
Weight of Wheel: about 1550 [g]
Although the invention has been described by way of the exemplary embodiment, it should be understood that those skilled in the art might make many changes and substitutions without departing from the spirit and scope of the invention. It is obvious from the definition of the appended claims that the embodiments with such modifications also belong to the scope of the invention.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2005-376441 | Dec 2005 | JP | national |
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| Number | Date | Country | |
|---|---|---|---|
| 20070143988 A1 | Jun 2007 | US |
