JP3573338B2 - Low pressure casting method for vehicle wheels - Google Patents

Description

【００２２】
表１から、３ゲート方式（実施例１〜４及び参考例１、２）の低圧鋳造法によれば、サイドゲート方式（比較例１，２）の方法よりもアルミホイールを１０％以上軽量化することができ、また鋳造サイクルタイムも大幅に短縮できることがわかる。また３ゲート方式でしかも、サイドゲートをフロントフランジ部から離れかつクロス部に隣接する位置に設けた場合（実施例１）は、デザイン面に湯境の発生がなくしかも衝撃テストの結果も良好である。さらにサイドゲートをクロス部よりも上方に設けた場合は（実施例２〜４）、最終製品形状にまで影響を及ぼすサイドゲート除去の際に発生するひずみを極力低減することができる。対して、３ゲート方式でも、サイドゲートをリム端（参考例１）に設けた場合はデザイン面に湯境が発生することがあり、かつ機械的強度が低下することがわかる。
【００２３】
【発明の効果】
以上に記述の如く、本発明によれば、キャビティの特定位置に複数のゲートを設けかつ指向性凝固を促進する金型構造としたので、デザイン面が健全で、高強度でかつ軽量化した車両用ホイールを得ることができる。
【図面の簡単な説明】
【図１】本発明の一実施例に係る鋳造装置の要部を示す断面図である。
【図２】図１のＡ−Ａ矢視図である。
【図３】図２のＢ−Ｂ矢視図である。
【図４】サイドゲートの位置を示す概略図（ａ）、（ｂ）、（ｃ）である。
【図５】サイドゲートとホイールキャビティとの接続部を示す概略図（ａ）、（ｂ）である。
【図６】アルミホイールの断面図（ａ）、同平面図（ｂ）である。
【符号の説明】
１ 金型、２ 下型、３ 上型、４，５ 横型、６ キャビティ
１１ａ，１１ｂ，１１ｃ ゲート、３０ ホイール[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a method for low pressure casting a light alloy vehicle wheel in a mold cavity.
[0002]
[Prior art]
There are various types of road wheels in automobiles, which have various materials and structures.In order to reduce the weight and improve the appearance and design of automobiles, the proportion of light alloy wheels typified by aluminum wheels is increasing. I have. This light alloy wheel is usually manufactured by a low pressure casting method in many cases. That is, in the low-pressure casting method, the molten metal is filled into the mold cavity at a low speed, so that entrainment of gas and generation of oxides are suppressed as much as possible in other casting methods.
[0003]
Generally, as shown in FIG. 6, a light alloy wheel 30 has a thick hub portion 31 attached to an axle by bolts and nuts, a disk portion 33 including a design portion 32 in which a thick portion and a thin portion are mixed, and a tire. It comprises a thin rim 34 to be attached. In FIG. 6A, 35 is a front flange portion, 36 is a rear flange portion, 37 is a cross portion where a rim portion and a disc portion intersect, and 38 is a rim center portion. The design section 32 includes a spoke section 39 and a design hole 39 'as shown in FIG. 6B. From the viewpoint of improving fuel efficiency of vehicles, weight reduction by changing the shape of wheels is being studied. In this case, since the shape of the hub portion and the rim portion cannot be significantly changed from the viewpoint of handling with the vehicle body and the tire, the shape portion of the design portion is changed (for example, the area of the design hole is increased or the spoke portion is made thinner). ), But significant weight reduction is extremely difficult.
[0004]
When the wheel is manufactured by low pressure casting, a gate is provided in the hub portion 31, a molten metal is injected from the gate portion, and the molten metal is injected into the design portion 32 and the rim portion 34 in this order (center gate method) or an end of the rim portion. A method (side gate method) in which a plurality of (usually two) gates are provided in the section (cross section 37) and the molten metal is injected therefrom is adopted.
In the center gate method, as a solidification form after filling the molten metal, directional solidification is performed in the order of the rim portion, the design portion, and the hub portion in order to sufficiently exert the gate pushing effect. However, in this casting method, since the design portion has a complicated shape in which a thick portion and a thin portion are mixed, it is difficult to achieve directional solidification from the rim portion to the disk portion.
On the other hand, in the side gate method, the design portion itself functions as a molten metal supply passage to the hub portion that is easily solidified. Even with this method, it is difficult to significantly reduce the weight of the entire wheel.
[0005]
In order to solve the above-mentioned drawbacks of the conventional method, it has been proposed to provide gates at the center portion (hub portion) of the disk and at the end of the rim, and to pour the metal into the mold from these gates (see, for example, Japanese Unexamined Patent Publication No. Hei 5- 269563 and 6-269923). According to this casting method (three-gate method), directional solidification from the rim toward the disk can be achieved even if the thickness of the design part is reduced, so that the weight of the wheel can be significantly reduced.
[0006]
[Problems to be solved by the invention]
Although a lightweight wheel can be obtained by the above-described three-gate method, there are some problems in practical use. That is, in the above-mentioned publication, since the side gate is provided in a portion (cross portion and front flange portion) where the structure must be sufficiently miniaturized from the viewpoint of strength, mechanical strength becomes insufficient and strength is reduced. It must be thicker than intended to make up for the shortage. Also, in order to achieve directional solidification from the rim to the disk, cooling means is provided in the design part. However, this alone does not always result in good directional solidification, and casting defects are not always achieved. Easy to occur.
[0007]
Further, in the above publication, there is no difference between the height of the center gate and the height of the side gates, so that there is no difference in the filling time of the molten metal, and the molten metal joins at the design part. Therefore, when the lower mold is cooled and the lower mold surface temperature becomes a low temperature of about 350 ° C., a hot boundary failure occurs on the design surface. Even when the surface temperature of the lower mold is high and there is no defect in the molten metal boundary, the molten metal merges on the design surface, so that oxides and gases may be entrained in the molten metal. If the design surface is of a cutting specification, poor appearance may occur due to this oxide.
[0008]
Therefore, an object of the present invention is to provide a low-pressure casting method capable of obtaining a high-strength and lightweight vehicle wheel without casting defects.
[0009]
[Means for Solving the Problems]
In order to achieve the above object, in a method of low-pressure casting a vehicle wheel in a mold having a shape corresponding to a vehicle wheel having a rim portion and a disk portion including a hub portion and a design portion, the disk portion is formed. A center gate is provided at the center of the cavity to be formed, a side gate is provided at the cavity forming the rim, and the cavity opening of the side gate is provided at a position higher than the cavity opening of the center gate. The technical means of injecting and filling the cavity was adopted.
[0010]
In the present invention, since low-pressure casting is performed by the three-gate method, it is possible to achieve a thinner design portion and a finer structure thereof. In particular, in the present invention, since the center gate is located at a position lower than the lower end of the cavity opening of the side gate, the molten metal injected from the center gate and the molten metal injected from the side gate do not merge on the design side, so that the sound is sound. The design aspect is obtained. Naturally, since the hot water boundary is most noticeable on the design surface as described above, it is preferable that the position of the side gate be higher than the rim end or the design surface. The design surface is the surface position of the wheel below the design portion in FIG. Further, it is preferable that the side gate is higher than the entire design part.
[0011]
In addition, as shown in FIG. 4B, by providing the side gate above the cross portion, the side gate is easily broken off in terms of structure. Since the influence of the stress on the vehicle wheel at the time of breaking is reduced, it is possible to cast an aluminum wheel with high roundness. The cross portion indicates a portion where the rim portion and the disk portion intersect.
[0012]
For example, in the casting method shown in FIG. 4A, as shown in FIG. 5A, the gate and the wheel cavity are connected in an L-shape at two sides of the center of the rim portion and the cross portion. Therefore, buckling and removing the side gate requires a large force in terms of structural mechanics, and a large bending stress and shear force are applied to the wheel. When heat treatment is performed on this wheel, the roundness of the wheel may be deteriorated due to the bending stress and the like. As shown in FIG. 5B, a substantially straight connection cross section between the side gate and the center of the rim portion is obtained. As a result, it is possible to reduce distortion applied to the wheel when the side gate is cut off, and to maintain high roundness.
Further, as a further effect, there is no cavity opening communicating with the cross portion like 11d in FIG. 5 (a), so that the flow of molten metal in the downward direction of the cavity can be suppressed, and the molten metal can be more easily run in the circumferential direction. . As a result, since the flow of the molten metal in the downward direction of the cavity is suppressed, the boundary of the molten metal does not occur on the design surface. In addition, it is possible to reduce the deviation of the tissue in the circumferential direction and reduce the variation in strength in the circumferential direction.
[0013]
In the case shown in FIG. 5B, if the distance between the lower end of the side gate and the upper end of the cross portion having the rim center thickness is 2 mm or less, the strength of the mold structure remains uneasy. On the other hand, when the length is 40 mm or more, the molten metal from the side gate does not reach the cross portion, and casting defects due to sink in the cross portion easily occur. Therefore, the distance t from the lower end of the side gate to the upper end of the cross portion is preferably about 2 to 40 mm, more preferably about 4 to 20 mm.
[0014]
Normally, an appropriate radius (1 to 20 mm) is provided in the vicinity of the opening of the side gate and at the boundary between the cross portion and the rim portion in order to improve the hot water flowability. The lower end of the side gate and the upper end of the cross portion described in the present application indicate the lower end of the side gate and the upper end of the cross portion excluding this R.
[0015]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, the present invention will be described in detail with reference to the drawings.
FIG. 1 is a cross-sectional view showing a main part of a casting apparatus for carrying out the present invention, FIG. 2 is a view taken in the direction of arrows AA in FIG. 1 (however, a horizontal type and a lower type are viewed from above), and FIG. FIG. 3 is a view taken in the direction of arrows BB in FIG. 2.
In FIG. 1, reference numeral 1 denotes a mold, a lower mold 2 having various surface shapes corresponding to a wheel design, an upper mold 3 located above the mold, and a cavity fitted with the lower mold 2 and the upper mold 3. 6 which are slidable to the left and right to form 6. The lower die 2 is set on a lower die base 8 fixed to a lower die platen 7. The upper die 3 is fixed to the upper die base 9 with bolts 10. The cavity 6 comprises a disk cavity 60 and a rim cavity 61, the disk cavity 60 comprises a hub cavity 62 and a design cavity 63, and the rim cavity 61 comprises a cross cavity 64 and a central cavity 65. . A center gate 11a is formed in the hub cavity 62, and side gates 11b and 11c are formed in the cross cavity 64, 64. The gates are connected to the stalks 13a, 13b, and 13c via the runners 12a, 12b, and 12c. Communicating. The gates 11b and 11c are arranged symmetrically on both sides of the center gate 11a when viewed from a plane as shown in FIG. 2, that is, the centers of the gates are located on the same straight line. The lower ends of these stalks are inserted into a closed container (not shown) containing a molten metal. The lower die 2 is provided with a lower die cooling passage 14 at a position corresponding to the design part cavity 63. Reference numeral 15 denotes a mold crack surface.
[0016]
The operation of the above configuration will be described. First, by pressurizing the molten metal in the closed container, the molten metal is filled into the cavity 6 from the gates 11a, 11b, and 11c via the stalks 13a, 13b, and 13c, and the runners 12a, 12b, and 12c.
Here, since there is a height difference between the center gate 11a and the side gates 11b and 11c, the molten metal passing through the center gate 11a fills the design portion cavity 63, and the molten metal passing through the side gates 11b and 11c is removed from the rim. The internal cavity 61 is filled. That is, the molten metal joins in the rim cavity 61. After the elapse of a predetermined time, when the pressurization is released, the molten metal in each stalk returns to the closed container, and the molten metal in the cavity 6 solidifies, and the wheel shown in FIG. 6 is obtained.
[0017]
The solidification process of the molten metal in the above casting step will be described in detail below. The molten metal injected into the cavity 6 from the side gates 11b and 11c progresses from the upper end of the rim portion cavity 65 to the lower end thereof. On the other hand, the molten metal injected from the center gate 11a into the disk cavity 60 solidifies from the design cavity 63 to the hub cavity 62. Therefore, it is possible to make the wheel design portion thinner in the casting method without giving the design portion cavity 63 a function of flowing molten metal and a function of supplying molten metal. In addition, since solidification starts from the design part, the structure of the design part becomes fine and high strength can be maintained.
Moreover, in the present invention, since the side gate is provided at a position avoiding the end of the rim, the structure of a portion requiring high strength, such as the front flange or the center of the rim, becomes finer, and thus the design portion of the design portion is viewed from the viewpoint of strength. The thickness can be reduced.
[0018]
If the side gate is provided at the end of the rim cavity 61 [at the position indicated by the solid line in FIG. 4C] or at the side of the cross cavity 64 at the position indicated by the broken line in FIG. May occur. In the present invention, there is a height difference between the center gate and the side gate, as described above, the molten metal can merge at a position avoiding a design portion (rim portion), obtain the total design surface Ken have . Of course, according to the present invention, since the flow length from each gate is shortened and the solidification time is also shortened, there is also an effect of improving productivity such as shortening the casting cycle time.
[0019]
(Example)
Hereinafter, the present invention will be described more specifically with reference to Examples and Comparative Examples.
(Example 1)
Using a casting apparatus shown in FIG. 1, a molten metal (about 450 ° C.) of an Al—Si—Mg-based alloy (JIS AC4CH) is poured into a mold (heated to about 480 ° C.) (at a pressure of 0.5 to 0. 7 kg / cm ² ), and an aluminum wheel having a shape shown in FIG. 6 was cast.
(Example 2)
An aluminum wheel was cast under the same conditions as in Example 1 except that a casting apparatus in which the side gate was provided at the position shown in FIG. 4B (the distance t between the lower end of the side gate and the upper end of the cross portion t = 2 mm) was used.
(Example 3)
An aluminum wheel was cast under the same conditions as in Example 1 except that a casting device in which the side gate was provided at the position shown in FIG.
(Example 4)
Example 2 except that a side gate was provided at the position shown in FIG. 4 (b), a narrowing was provided in the side gate, and the width w of the connection portion was 2/3 (10 mm) of Example 3 and a casting apparatus was used. An aluminum wheel was cast under the same conditions as in No. 3.
[0020]
(Reference Example 1)
An aluminum wheel was cast under the same conditions as in Example 1 except that a casting device in which the side gate was provided at the position shown by the solid line in FIG. 4C was used.
(Reference Example 2)
Casting was performed under the same conditions as in Example 1 except that the side gate was provided at the position indicated by the broken line in FIG.
(Comparative Example 1)
An aluminum wheel was cast under the same conditions as in Example 1 except that the molten metal was injected into the mold only from the side gate [position shown in FIG. 4A] (side gate casting method).
(Comparative Example 2)
An aluminum wheel was cast under the same conditions as in Example 1 except that the molten metal was injected into the mold only from the side gate [position shown in FIG. 4B] (side gate casting method). With respect to the aluminum wheels of each of the above examples, the presence or absence of a hot boundary on the design surface was visually observed, and a sample was cut out from the front flange portion and the rim center portion to perform an impact test. Table 1 shows the results. In addition, the weight of each aluminum wheel, the casting cycle time, and the stress applied to the pressing means when removing the side gate were also measured. The results (however, the ratio when Comparative Example 2 is set to 1) are also shown in Table 1. Shown in
[0021]
[Table 1]

[0022]
From Table 1, according to the low-pressure casting method of the three-gate method (Examples 1 to 4 and Reference Examples 1 and 2), the weight of the aluminum wheel is reduced by 10% or more compared to the method of the side-gate method (Comparative Examples 1 and 2 ). It can be seen that the casting cycle time can be greatly reduced. When the three-gate system is used and the side gate is provided at a position away from the front flange portion and adjacent to the cross portion (Example 1), there is no hot water boundary on the design surface and the result of the impact test is good. is there. Further, when the side gate is provided above the cross portion (Examples 2 to 4), it is possible to reduce as much as possible the distortion generated when removing the side gate, which affects the final product shape. On the other hand, even in the three-gate system, when the side gate is provided at the end of the rim (Reference Example 1), a hot boundary may occur on the design surface, and the mechanical strength is reduced.
[0023]
【The invention's effect】
As above described, according to the present invention, since the mold structures that facilitate providing and directional solidification of the plurality of gates in a specific position of the cavity, the design surface in soundness, and was lightweight high strength A vehicle wheel can be obtained.
[Brief description of the drawings]
FIG. 1 is a sectional view showing a main part of a casting apparatus according to one embodiment of the present invention.
FIG. 2 is a view as viewed in the direction of arrows AA in FIG. 1;
FIG. 3 is a view taken in the direction of arrows BB in FIG. 2;
FIGS. 4A, 4B, and 4C are schematic diagrams showing positions of side gates. FIGS.
FIGS. 5A and 5B are schematic diagrams showing a connection portion between a side gate and a wheel cavity. FIGS.
FIG. 6 is a sectional view (a) and a plan view (b) of an aluminum wheel.
[Explanation of symbols]
1 mold, 2 lower mold, 3 upper mold, 4,5 horizontal mold, 6 cavities 11a, 11b, 11c Gate, 30 wheels

Claims (4)

A method for low pressure casting a vehicle wheel in a mold having a shape corresponding to a vehicle wheel having a rim portion and a disk portion including a hub portion and a design portion, wherein a center gate is provided at the center of a cavity forming the disk portion. A side gate is provided in the cavity forming the rim portion, and the cavity opening of the side gate is provided above the cavity opening of the center gate, and molten metal is injected from each gate to fill the cavity. A low-pressure casting method for a vehicle wheel, characterized in that: 2. The low-pressure casting method for a vehicle wheel according to claim 1, wherein the position of the cavity opening of the side gate is located above the end of the rim of the vehicle wheel on the disk side. The low pressure casting method for a vehicle wheel according to claim 1, wherein the position of the cavity opening of the side gate is located above a design surface of the vehicle wheel. The low-pressure casting method for a vehicle wheel according to claim 1, wherein the position of the cavity opening of the side gate is located above the entire design portion of the vehicle wheel.

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