JP2004306062A - Method of machining vehicle wheel - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of machining a vehicle wheel by which the thinning and lightening of a disk part and a rim part can be attained. <P>SOLUTION: The preform of a vehicle wheel is subjected to high pressure casting. A cavity 20 for molding having a space 21 for molding a disk part and a space 22 for molding a rim pattern part is formed on a mold 10 used in the high pressure casting stage. The space 21 for molding a disk part is connected with a runner 25. Molten metal under high pressure is filled into the cavity 20 via the runner 25, so that the preform is cast. The preform comprises a disk part and a rim pattern part, and the rim pattern part is subjected to spinning working causing the reduction of thickness, so that a rim part having a final shape or a shape close to the final shape is obtained. Blowholes remaining in the rim pattern part are crushed by the working. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a method for manufacturing a vehicle wheel made of a light alloy such as an aluminum alloy.
[0002]
[Prior art]
Methods of manufacturing aluminum alloy vehicle wheels by casting are well known. The mold used in this method has a lower mold, an upper mold that can move up and down, and one or two pairs of horizontal molds that move horizontally. When the mold is in the clamped state, a molding cavity is formed. This cavity has a shape close to the final shape of the vehicle wheel, and has a space for forming a disk portion and a space for forming a rim portion. A runner connected to the center of the cavity for forming the disc portion of the cavity is formed in the lower die, and a low-pressure molten metal of an aluminum alloy is filled into the cavity from the runner to obtain a vehicle wheel close to the final shape. Thereafter, a vehicle wheel having a final shape is obtained through cutting and the like.
[0003]
In the above-mentioned casting, solidification starts at a portion farthest from the runner, that is, at an edge of the rim portion forming space opposite to the disk forming space, gradually solidifies toward the runner, and finally reaches the center of the disk portion. The neighborhood solidifies. In the space for forming the rim portion, the material is not deteriorated because it is rapidly solidified, but in the space for forming the disk portion, the material is deteriorated because the solidification is delayed. In order to compensate for this material deterioration and obtain the required strength, it is necessary to increase the thickness of the disk portion.
[0004]
The solidification of the molten metal is accompanied by shrinkage. In order to suppress the occurrence of sink marks and nests due to this shrinkage, it is necessary to replenish the molten metal at the site where coagulation has begun. In the casting described above, the flow cross-sectional area of the disc-forming space is widened in order to ensure replenishment of the molten metal, which also causes the disc to be thicker in the casting wheel.
[0005]
A casting method disclosed in WO 00/43153 has been developed in order to avoid the deterioration of the material of the disk portion and to reduce the thickness and weight. In this casting method, the cavity is filled with a high-pressure molten metal via a runner connected to the center of the disk portion forming space. In this high-pressure casting, by applying a high pressure to the molten metal, sufficient riser is possible, and the flow cross-sectional area of the molten metal in the disk portion can be made relatively narrow. Further, since the action of the feeder is high, it is possible to lower the mold temperature of the mold and enhance the cooling capacity of the molten metal, and to quickly solidify not only in the space for forming the rim but also in the space for forming the disk. Since the structure can be made finer by applying high pressure, deterioration of the material of the disk portion can be avoided. As a result, the thickness and weight of the disk portion can be reduced.
[0006]
On the other hand, Japanese Patent Application Laid-Open No. 2000-79801 discloses a method for manufacturing a vehicle wheel in which a rim portion is made thinner and lighter. More specifically, the molding cavity of the mold in the publication has a space for molding the disk portion and a space for shaping the rim prototype. The cross-sectional area of the rim prototype molding space is larger than the final shape rim. The point in which the runner is connected to the center of the disk part forming space is the same as the well-known technique described first. Low pressure casting is performed with this mold to obtain a vehicle wheel preform having a rim prototype that is thicker than the rim of the final or near shape. Thereafter, a spinning process (flow forming process) with a reduced thickness is performed on the rim prototype to obtain a rim close to the final shape. By this spinning, the rim portion is freed from internal defects such as cavities by compression, and the structure is refined, the structure is anisotropic (rolled structure), and work hardening is obtained, and the strength is improved. For this reason, it is possible to make the rim portion of the conventional cast wheel thinner and lighter.
[0007]
[Patent Document 1]
WO 00/43153 [Patent Document 2]
Japanese Patent Application Laid-Open No. 2000-79801
[Problems to be solved by the invention]
According to the method disclosed in WO 00/43153, the thickness and weight of the disk portion can be reduced. However, in high-pressure casting, residual blowholes pose a problem. That is, when the cavity is filled with the molten metal, the molten metal blows in air and becomes turbulent, so that a blow hole is generated. Since the mold temperature is low in high pressure casting, the molten metal is rapidly solidified while containing the blowhole. In particular, blow holes are likely to remain at the rim. Since the strength of the rim is reduced by the blow hole, the rim cannot be made thinner and lighter.
In the method disclosed in Japanese Patent Application Laid-Open No. 2000-79801, since the casting is performed at a low pressure, the deterioration of the material of the disk portion cannot be improved similarly to the known technology, and the disk portion cannot be reduced in thickness and weight.
[0009]
[Means for Solving the Problems]
SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems. (A) A molding cavity having a disk part molding space and a rim prototype part molding space in a mold-clamped state is formed, and the disk part molding is performed. By using a mold having a runner connected to the working space and filling the cavity with high-pressure molten metal through the runner, a preform of a vehicle wheel having a disk portion and a rim prototype is cast. A high-pressure casting step; and (b) a step of obtaining a rim portion having a final shape or a shape close to the final shape by subjecting the rim prototype of the preform to spinning with thickness reduction. The gist is a method of manufacturing a vehicle wheel.
[0010]
According to the above method, since the casting pressure is high, the mold temperature of the mold is low and the cooling capacity can be increased, and the molten metal can be rapidly solidified not only in the rim prototype but also in the disk molding space, and the solidification delay This can prevent the material from being deteriorated. Further, since high pressure is applied to the molten metal and the riser is effective, it is not necessary to widen the flow cross-sectional area in order to secure a replenishment path of the molten metal to the rim forming space. As a result, the thickness and weight of the disk portion can be reduced. In addition, although blowholes remain in the rim original part of the preform, the blowholes can be crushed by spinning with thinning, and as a result, the strength of the rim can be improved. In addition, the thickness and weight can be reduced.
[0011]
Preferably, the rim prototype has an annular thick portion from the widthwise middle to the edge on the opposite side of the disc portion, and by spinning this annular thick portion, the opposite side of the rim drop and the disc portion is formed. To obtain a bead seat and flange. According to this, the strength of the rim portion can be reliably improved by spinning a portion far from the gate, where a blow hole is likely to remain.
[0012]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, a method of manufacturing a vehicle wheel according to a first embodiment of the present invention will be described with reference to FIGS. First, a mold used in the casting process will be described. As shown in FIG. 1, the mold 10 includes a base 11, a lower mold 12 fixed on the base 11, an upper mold 13 that moves up and down with respect to the lower mold 12, The horizontal type 14 is provided. The pair of horizontal dies 14 are opposed to each other in a direction perpendicular to the paper surface, and move in the same direction to join and separate. Each of the molds 12 to 14 has a cooling passage through which cooling water passes.
[0013]
When the mold 10 is clamped, the joint surfaces of the pair of horizontal dies 14 bear a large load, for example, 1000 to 1500 tons, and the upper die 13 descends and hits the upper surfaces of these horizontal dies 14, thereby lowering the lower die 12 and the upper die 13. Thus, the pair of horizontal dies 14 is sandwiched with a predetermined load. In this mold clamping state, the lower mold 12, the upper mold 13, and the pair of horizontal molds 14 form a cavity 20 for preform molding.
[0014]
The cavity 20 is formed between the opposing surfaces of the lower die 12 and the upper die 13 and between the outer peripheral surfaces of the lower die 12 and the upper die 13 and the inner peripheral surfaces of the pair of horizontal dies 14. Rim prototype part forming space 22. The rim prototype portion forming space 22 has a lower first portion 22a, an intermediate second portion 22b, and an upper third portion 22c. The first portion 22a has a shape close to a portion corresponding to a rim portion of a vehicle wheel having a final shape. The second portion 22b has a short cylindrical shape, and the third portion 22c has a conical shape expanding toward the tip. The second portion 22b and the third portion 22c have different shapes from the corresponding portions of the rim portion of the vehicle wheel in the final shape, and are thicker than those.
[0015]
Further, a runner 25 is formed in the lower mold 12 and the base 11 of the mold 10, and a gate 25 x at the upper end of the runner 25 is connected to the center of the disk portion forming space 21. A melt filling machine 30 is connected to the lower surface of the base 11, and a cylinder 31 of the melt filling machine 30 is connected to a lower end of the runner 25. The plunger 32 is accommodated in the cylinder 31 so as to advance and retreat.
[0016]
A high-pressure casting process of a preform for a vehicle wheel using the mold 10 will be described. When the plunger 32 is advanced at a relatively low speed in a state in which the cylinder 31 of the melt filling machine 30 is filled with the melt, the melt reaches the disk portion forming space 21 in which the gate 25x is located via the runner 25, From here, the space is filled into the disc portion forming space 21 and also into the rim prototype shape forming space 22. In addition, the filling of the molten metal can be performed at a relatively low speed because the rim shape of the preform is narrow and thick and is significantly different from the wide and thin rim shape of a normal wheel. Generation itself can be reduced. By applying a high pressure to the molten metal via the plunger 32 after filling, the riser is forcibly applied. Here, the high pressure means a much higher pressure than in the case of low-pressure casting (less than ^{1Kg / cm 2) (100Kg /} cm 2 or higher). In this embodiment, it is about 1000 kg / cm ² .
[0017]
The solidification of the molten metal starts at a portion of the runner 25 farthest from the gate 25x, that is, at a tip end portion of the rim portion forming space 22 (an edge portion on the opposite side of the disk portion forming space 21) and moves toward the gate portion 25x. The solidification proceeds and reaches the gate 25x. Thereafter, the plunger 32 is retracted, and a casting is obtained after the mold is opened. Compared with a wheel having a normal shape, the path on which solidification proceeds is shorter, so that directional solidification to the gate 25x can be easily performed.
[0018]
By the above casting, a vehicle wheel preform 50 shown in FIG. 2A is obtained. The preform 50 has a disk part 51 formed by solidification of the molten metal in the disk part molding space 21 and a rim original part 52 formed by solidification of the molten metal in the rim original part molding space 22. are doing. The rim prototype 52 has a disk-side flange 52a and a disk-side bead seat 52b corresponding to the first portion 22a of the rim prototype-formation space 22. These parts have a shape close to the final shape of the vehicle wheel. Further, the rim prototype 52 has annular thick portions 52x and 52y corresponding to the second portion 22b and the third portion 22c of the rim prototype molding space 22, respectively. In the center of the disk portion 21, a projection is formed near the gate 25x of the runner 25 due to solidification of the molten metal.
[0019]
In the high-pressure casting step, since the mold temperature is low and the cooling capacity of the molten metal is high, rapid solidification is performed not only in the space 22 for molding the rim prototype but also in the space 21 for molding the disk. Material deterioration does not occur not only in the rim original shape portion 52 but also in the disk portion 51. Therefore, the disk portion 51 does not need to be thick in order to compensate for the material deterioration due to casting. In addition, since a sufficient riser is effective by applying a high pressure, it is not necessary to secure a wide molten metal path to the rim portion forming space 22, and the flow cross-sectional area of the disk portion forming space 21 can be minimized. As a result, the weight and thickness of the disk portion 51 can be reduced.
[0020]
In the high-pressure casting step, since the rim prototype portion forming space 22 has a large flow cross-sectional area, the replenishment of the molten metal to the portion where the solidification has occurred in combination with the application of the high pressure of the molten metal is favorably performed. And the occurrence of sink marks and nests can be reliably suppressed. However, residual blowholes pose a problem. That is, when the cavity is filled with the molten metal, the molten metal blows in air and becomes turbulent, so that a blow hole is generated. Since the mold temperature is low in high pressure casting, the molten metal is rapidly solidified while containing the blowhole. Particularly in the rim prototype 52 far from the runner 25, many blow holes remain due to rapid solidification.
[0021]
Next to the casting step, a pre-processing step is performed. In this pre-processing step, deburring is performed. In addition, a protrusion formed by solidification of the molten metal near the gate 25x of the runner 25 is cut, and a hub hole 51a is formed in the center of the disk portion 51.
[0022]
Next, the main processing step is performed. In this processing step, after the preform 50 is heated, spinning processing (flow forming processing) is performed. When the main processing step is performed in a short time from the casting step, heating before the spinning processing can be omitted. In the spinning process, as shown in FIG. 2 (A), a preform 50 is attached to a mandrel 41 having an outer peripheral shape close to the final shape of the vehicle wheel, and the mandrel 41 is rotated to press the roller 42 against the preform 50 while the mandrel 41 is pressed. The mandrel 41 is moved in the axial direction along the peripheral surface shape of the mandrel 41.
[0023]
By the spinning process, the annular thick portions 52x and 52y are reduced in thickness (thinned) while being squeezed by the rollers 42 and spread in the width direction along the peripheral surface shape of the mandrel 41, as shown in FIG. Thus, a vehicle wheel 50 'having a rim portion 52' close to the final shape is obtained. In the rim part 52 ', the flange 52a and the bead seat 52b on the disk part 51 side are already in a shape close to the final shape by the casting described above. The rim drop 52c of the rim portion 52 'is mainly formed by the spinning of the annular thick portion 52x, and the bead sheet 52d and the flange 52e on the opposite side of the disk portion 51 are mainly formed by the spinning of the annular thick portion 52y. You.
[0024]
The spinning process involves a large flow of the material of the annular thick portions 52x and 52y of the rim prototype 52, and the compression of the nest, the refinement of the structure (dynamic recrystallization), the anisotropy of the structure (rolled structure), Work hardening can be realized. Also, blow holes generated in the rim prototype 52 during the high-pressure casting can be crushed. As a result, the rim portion 52 'does not have to be made thick to compensate for the deterioration of the material, and the thickness and the weight can be reduced.
[0025]
After the above spinning process, heat treatment is performed, and if necessary, the surface of the design surface of the disc portion 51 is subjected to surface treatment by shot blasting, and the outer peripheral surface of the rim portion 52 'is cut and painted to complete the vehicle wheel. I do. At the time of cutting, the rim portion 52 'is slightly reduced in thickness to have a final shape. When cutting is not performed, the shape after spinning is the final shape of the vehicle wheel.
[0026]
In the high-pressure casting, the molten metal is rapidly solidified, so that the productivity is good. One preform 50 is formed in three minutes. Since one spinning process can be performed in one minute, a vehicle wheel can be efficiently produced by combining three molds 10 and one spinning device.
As described above, since the clamping force of the horizontal die 14 is large, the preform 50 can be cast in a state close to a perfect circle, and the workability of the subsequent spinning process is good.
In high pressure casting, it is necessary to apply a lubricant to the inner surface of the cavity 20. For example, graphite powder is dissolved in water and sprayed onto the inner surface of the mold in a mold-open state. Therefore, the lubricant adheres to the inner and outer peripheral surfaces of the preform 50 that has been cast at high pressure. Generally, during spinning, a lubricant is applied to the outer peripheral surface of the mandrel 41 to prevent seizure of the material. However, in the present embodiment, the inner peripheral surface of the preform 50 is already lubricated as described above. Since the agent is attached, the application of the lubricant to the outer peripheral surface of the mandrel 41 can be omitted.
[0027]
The present invention is not limited to the above embodiment, and various modes are possible. For example, in the above embodiment, the horizontal type may be divided into four parts. In the flow forming process, the mandrel can be formed in a desired shape by moving the mandrel in the axial direction while fixing the roller side.
[0028]
【The invention's effect】
As described above, according to the present invention, it is possible to reduce the thickness and weight while maintaining high strength in both the disk portion and the rim portion.
[Brief description of the drawings]
FIG. 1 is a longitudinal sectional view showing a mold for casting a preform of a vehicle wheel in a first embodiment of the method of the present invention.
FIGS. 2A and 2B are cross-sectional views showing a step of spinning a preform cast by the mold, wherein FIG. 2A shows a preform and a spinning apparatus before processing, and FIG. 2B shows a final shape after processing. Shows the near vehicle wheel.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 10 Mold 11 Lower mold 12 Upper mold 13 Horizontal mold 20 Cavity 21 Disk part molding space 22 Rim prototype molding space 25 Runner 25x Gate 40 Spinning device 50 Preform 51 Disk part 52 Rim prototype 52x, 52y Thick annular Part 52 'rim

Claims (2)

(A) A mold is used in which a molding cavity having a disk portion molding space and a rim prototype shape molding space is formed in a mold-clamped state, and a runner connected to the disk portion molding space is formed. A high-pressure casting step of casting a preform of a vehicle wheel having a disk portion and a rim prototype by filling a cavity with high-pressure molten metal through the runner;
(B) a step of obtaining a rim portion having a final shape or a shape close to the final shape by subjecting the rim prototype portion of the preform to spinning with thickness reduction;
A method for manufacturing a vehicle wheel, comprising: The rim prototype has an annular thick portion from the widthwise middle to the edge on the opposite side of the disk portion. By spinning the annular thick portion, the bead sheet on the opposite side of the rim drop and the disk portion is formed. The method for manufacturing a vehicle wheel according to claim 1, wherein a flange and a flange are obtained.

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