JP4465642B2 - Low pressure casting method for vehicle wheel - Google Patents

Description

【００２１】
表１から、３ゲート方式（参考例１、実施例２〜４及び比較例１、２）の低圧鋳造法によれば、サイドゲート方式（比較例３、４）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（参考例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が、サイドゲートをクロス部と完全に離別した状態でリム部中央に設けた場合は（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さらに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（比較例１）またはスポークつけ根（比較例２）に設けた場合は、デザイン面に湯境が発生し、またリム端（比較例１）に設けた場合は、機械的強度が低下することがわかる。
【００２２】
【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湯口を設けかつ指向性凝固を促進する金型構造としたので、デザイン面が建全で、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。また、サイドゲートの除去作業の際のホイールにかかる曲げ応力を低減できる金型構造としたので真円度の高い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 湯口、３０ ホイール[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method of low-pressure casting a light alloy vehicle wheel in a mold cavity.
[0002]
[Prior art]
There are various materials and structures for automobile road wheels. For the purpose of reducing the weight and improving the appearance and design of automobiles, the ratio of mounting light alloy wheels such as aluminum wheels has increased. Yes. This light alloy wheel is often manufactured by a low pressure casting method. That is, in the low pressure casting method, the molten metal is filled into the mold cavity at a low speed, so that gas entrainment and oxide generation are suppressed as much as possible as compared with other casting methods.
[0003]
Generally, as shown in FIG. 6, a light alloy wheel 30 includes a thick hub portion 31 attached to an axle by bolts and nuts, a disc portion 33 including a design portion 32 in which a thick portion and a thin portion are mixed, and a tire. It is composed of a thin rim portion 34 to be attached. In FIG. 6A, 35 is a front flange part, 36 is a rear flange part, 37 is a cross part where the rim part and the disk part intersect, and 38 is a rim center part. As shown in FIG. 6B, the design part 32 includes a spoke part 39 and a design hole 39 ′. From the viewpoint of improving the fuel efficiency of vehicles, weight reduction by changing the shape of the wheel has been studied. In this case, the hub part and the rim part cannot be remarkably changed in terms of handling with the vehicle body or the tire, so the shape change of the design part (for example, the area of the design hole is increased or the spoke part is thinned). However, it is extremely difficult to reduce the weight significantly.
[0004]
When the wheel is manufactured by low-pressure casting, a pouring gate is provided in the hub portion 31 and molten metal is poured therefrom, and the design portion 32 and the rim portion 34 and the molten metal are poured in this order (center gate method) or the 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 molten metal is injected therefrom is adopted.
In the center gate method, directional solidification is performed in the order of the rim portion, the design portion, and the hub portion in order to sufficiently exhibit the effect of the hot water pouring as a solidification form after filling the molten metal. However, in this casting method, the design part has a complicated shape in which a thick part and a thin part are mixed, so that it is difficult to achieve directional solidification from the rim part to the disk part.
On the other hand, in the side gate method, the design part itself functions as a molten metal replenishment passage to the hub part that is easily solidified, so that the design part is thick in order to ensure a good hot water flow in the design part. Even with this method, it is difficult to significantly reduce the weight of the entire wheel.
[0005]
In order to eliminate the above-mentioned drawbacks of the conventional method, it has been proposed to provide pouring gates at the center of the disk (hub portion) and the rim, respectively, and to pour molten metal from these pouring gates into the mold (for example, Japanese Patent Laid-Open No. Hei 5- 269563, 6-269923). According to this casting method (3-gate method), directional solidification from the rim portion toward the disc portion can be achieved even if the thickness of the design portion is reduced, so that the weight of the wheel can be significantly reduced.
[0006]
[Problems to be solved by the invention]
Although the weight reduction wheel can be obtained by the above-described three-gate method, there are some problems in practical use. That is, in the above publication, since the gate (side gate) is provided at a portion (cross portion and front flange portion) where the structure must be sufficiently refined from the viewpoint of strength, mechanical strength is insufficient. Therefore, it is necessary to make it thicker than the intended thickness in order to compensate for the lack of strength. Further, in order to achieve directional solidification from the rim portion toward the disk portion, a cooling means is provided in the design portion, but this alone does not necessarily provide good directional solidification, and casting defects are not always achieved. It is easy to generate.
Further, in the above publication, there is no difference between the height of the center gate and the height of the side gate, so 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 poor water boundary occurs on the design surface. Even when the surface temperature of the lower mold is high and no poor boundary occurs, the molten metal joins in the design, so that oxides and gases may be caught in the molten metal. If the design surface is a cutting specification, appearance defects may occur due to this oxide.
[0007]
Further, the above publication does not describe the side gate removal work after casting. In the above publication, a side gate is provided in the front flange portion 35 of FIG. The molten metal cools to form a wheel and the cooled and solidified side gate remains without returning to the stalk. Examples of the processing method for the side gate include plasma processing, cutting processing, shearing processing, buckling processing, and the like. However, in the treatment using plasma, there are problems such as an increase in equipment costs, an increase in maintenance costs, and environmental deterioration due to the generation of ozone, and in the cutting treatment, chips are generated and it is difficult to manufacture. Further, since the shearing process requires a very large shearing force, the equipment becomes large, there are problems such as lack of safety, noise, and the like, which is not practical. When considering the production line configuration, the buckling process is the simplest and there is no chips.
An example of the buckling process of the side gate removing operation is performed as follows. First, the molded body of the wheel is fixed by a predetermined fixing means, and buckled in the vicinity of the joint portion between the side gate and the molded wheel body by a pressing means (not shown) having a protrusion for pushing the side gate to buckle. It is possible to use means such as The fixing means and the pressing means can slide relative to each other. The pressing means can apply a sufficient force to the side gate to buckle, and has a predetermined curved contact surface so as to easily buckle in a predetermined direction.
However, the front flange portion has a complicated and partially thin sectional shape as shown in FIG. Therefore, when the above side gate removal processing operation is performed, the rim portion is chipped when the side gate is removed, which causes a shape defect, and thus a careful operation is necessary. Further, when the side gate is removed, if the rim portion is excessively stressed, there is a problem that the roundness of the wheel is deteriorated during the heat treatment.
[0008]
Accordingly, an object of the present invention is to provide a low pressure casting method capable of obtaining a vehicle wheel with high strength and reduced weight. Still another object of the present invention is to provide a low pressure casting method suitable for manufacturing a vehicle wheel with high roundness in which a side gate can be easily removed.
[0009]
[Means for Solving the Problems]
In order to achieve the above object, according to the first aspect of the present invention, as shown in FIG. 4B, in the method of low-pressure casting a vehicle wheel having a rim portion and a disc portion, the cavity on the front flange side is made of gold. Casting in a state of being placed under the mold, a gate is provided at the center of the cavity forming the disk portion, a gate is also provided in the cavity forming the rim portion, and provided in the cavity forming the rim portion The sprue is spaced apart from the lower end of the sprue that does not include R of the connecting portion with the cavity that forms the rim portion, and the upper end of the cross portion that does not include R provided at the boundary between the cross portion and the rim portion (however, , sprue spaced distance t from the front end of the lower end of the tip and the cross section upper end of the R R) is connected to the rear flange side remote from the cross portion 64, the cavity by injecting molten metal from the sprue Employing the technical means that, for filling. In the present invention, since the gate provided at the center of the cavity forming the disk portion is located lower than the gate provided at the cavity forming the rim portion, it is provided at the center of the cavity forming the disk portion. The molten metal injected from the molten metal pouring gate and the molten metal injected from the pouring gate provided in the cavity forming the rim portion do not merge on the design surface, so that a sound design surface can be obtained. It is also possible to cast a high roundness aluminum wheel.
[0011]
For example, even in the casting method shown in FIG. 4A, it is possible to obtain a highly reliable aluminum wheel having a sound design surface. However, a higher performance wheel can be obtained by applying the present invention. In the casting method of FIG. 4 (a), the side gate is connected to the gate and the wheel cavity in an L shape at the two sides of the center of the rim and the cross as shown in FIG. 5 (a). Therefore, in order to buckle and remove the side gate, a large structural mechanical force is required, and a large bending stress and shearing force are applied to the wheel. When this wheel is heat-treated, the roundness of the wheel may deteriorate due to the influence of the bending stress or the like. By applying the present invention, as shown in FIG. 5B, a connection cross-sectional shape that is a substantially straight shape between the side gate and the center of the rim portion is obtained. As a result, it is possible to reduce the strain applied to the wheel when the side gate is folded and to maintain high roundness. Also, as a further effect, since there is no cross-section and the sprue communicating as 11d in FIG. 5 (a), it suppresses the fluidity of the cavity under the direction to increase the circumferential molten metal of the molten metal Can do. As a result, no hot water boundary is generated on the design side. Further, it is possible to obtain a wheel in which the unevenness of the tissue is reduced in the circumferential direction and the strength is less varied in the circumferential direction.
[0012]
If the distance from the lower end portion of the side gate to the upper end portion of the cross portion is 2 mm or less, there is an uneasy strength on the mold structure. In addition, when the thickness is 40 mm or more, the molten metal from the side gate does not completely reach the cross portion, and casting defects due to sink marks or the like at the cross portion tend to occur frequently. Therefore, the distance t from the lower end of the side gate to the upper end of the cross part is preferably 2 to 40 mm, more preferably about 4 to 20 mm. Usually, an appropriate R (1 to 20 mm) is provided in the vicinity of the connecting portion of the side gate and at the boundary between the cross portion and the rim portion in order to improve the hot water supply property. The side gate lower end portion and the cross portion upper end portion described in the present application indicate the lower end portion of the side gate not including this R and the upper end portion of the cross portion.
[0013]
The width w of the connecting portion between the gate and the rim cavity is preferably 30 mm or less. As described above, the connecting portion is provided with R at the side gate end. In FIG. 5, w is simply described in the connection portion, but the width w of the connection portion indicates the width on the side gate side not including R. When w is 30 mm or more, the stress during the side gate removing operation increases, and defective products frequently occur due to the strain during the heat treatment. On the other hand, if the thickness is 3 mm or less, the amount of molten metal injected into the cavity is limited, resulting in poor hot water. Further, the height of the connecting portion indicated by the hatched portion in FIG. 5 depends on the shape of each wheel, but as described in the present invention, the connecting shape is substantially on a single plane and is linear. Is preferred. For example, if the rim portion having substantially the same outer diameter is long in the rim center portion 38 in FIG. 6, the height of the connection shape can be increased. Even if the rim center part has a slightly stepped outer diameter, there is no problem as long as the difference in the outer diameter in the rim center part is a comparatively gentle step of 10 mm or less. In addition, by providing a diaphragm in the lateral width of the side gate in the vicinity of the connecting portion, it is possible to suppress the occurrence of sink marks at the center of the rim and to have an effect of making it easier to buckle.
[0014]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, the details of the present invention will be described with reference to the drawings.
1 is a cross-sectional view showing the main part of a casting apparatus for carrying out the present invention, FIG. 2 is a view taken along the line AA in FIG. 1, and FIG. 3 is a view taken along the line BB in FIG. It is the figure which looked at the lower mold from the upper part).
In FIG. 1, reference numeral 1 denotes a mold, and a lower mold 2 having various surface shapes corresponding to a wheel design, an upper mold 3 positioned above the lower mold 2, and a lower mold 2 and an upper mold 3 are fitted to the cavity. The horizontal molds 4 and 5 are slidable to the left and right so as to form 6. The lower mold 2 is installed on a lower mold base 8 fixed to the lower mold platen 7. The upper die 3 is fixed to the upper die base 9 with bolts 10. The cavity 6 includes a disk part cavity 60 and a rim part cavity 61. The disk part cavity 60 includes a hub part cavity 62 and a design part cavity 63. The rim part cavity 61 includes a cross part cavity 64 and a central part cavity 65. . The hub portion cavity 62 and the cross portion cavities 64 and 64 are formed with gates 11a, 11b and 11c, respectively, and the gates communicate with the stalks 13a, 13b and 13c via the runners 12a, 12b and 12c. As shown in FIG. 2, the gates 11b and 11c are arranged symmetrically on both sides of the gate 11a as viewed from above, that is, the centers of the gates are located on the same straight line. The lower end portions of these stalks are inserted into a sealed container (not shown) in which the molten metal is accommodated. The lower mold 2 is provided with a lower mold cooling passage 14 at a position corresponding to the design portion cavity 63. Reference numeral 15 denotes a mold breaking surface.
[0015]
The operation of the above configuration will be described. First, by pressurizing the molten metal in the sealed container, the molten metal is filled into the cavity 6 from the gates 11a, 11b and 11c through the runners 12a, 12b and 12c from the stalks 13a, 13b and 13c.
Here, since there is a height difference between the gate 11a and the gates 11b and 11c, the molten metal passing through the gate 11a fills the design portion cavity 63, and the molten metal passing through the gates 11b and 11c passes through the rim portion cavity 61. Fill. That is, the molten metal joins at the rim cavity 61. When the pressurization is released after a lapse of a predetermined time, the molten metal in each stalk returns to the sealed container, and the molten metal in the cavity 6 is solidified to obtain the wheel shown in FIG.
[0016]
It is as follows when the solidification process of the molten metal in said casting process is explained in full detail. The molten metal poured into the cavity 6 from the gates 11b and 11c (side gates) is solidified from the upper end of the rim portion cavity 65 toward the lower end thereof. On the other hand, the molten metal injected from the gate 11a (center gate) into the disk portion cavity 60 is solidified from the design portion cavity 63 toward the hub portion cavity 62. Therefore, it is not necessary to provide the design portion cavity 63 with a hot water flow function or a molten metal replenishment function, and the wheel design portion can be made thinner in terms of the casting method. In addition, since the solidification starts from the design part, the structure of the design part becomes fine and high strength can be maintained.
In addition, in the present invention, the side gates (pouring gates 11b and 11c) are provided at positions avoiding the rim ends, so that the structure of a portion requiring high strength, such as the front flange or the center of the rim, becomes fine, thereby increasing the strength. From the perspective, the design part can be made thinner.
[0017]
In the present invention, since there is a difference in height between the center gate and the side gate as described above, the molten metal can be merged at a position (rim portion) away from the design portion, thereby obtaining a complete design surface. it can. Of course, according to the present invention, since the flow length from each gate is shortened and the solidification time is shortened, there is an effect of improving productivity such as shortening the casting cycle time.
[0018]
In addition, if a predetermined amount of strain is applied during the side gate removal operation, the wheel is affected during heat treatment and the roundness is hindered. However, as in the casting method of the present application, the connecting portion between the side gate and the rim portion is substantially flat and linear, and is easily casted with a weak structural mechanical force. As a result, it is possible to produce a wheel that maintains its roundness even after heat treatment. For example, position contacting the side gate at the upper cross section the cavity 64 than Keru set in FIG. 4 (a)], by providing a position away from the cross-section cavity 64 FIG 4 (b)], the side gate The stress applied to the wheel during removal can be reduced. Further, since the hot water performance in the circumferential direction is improved as compared with the position shown in FIG. 4A and the molten metal is prevented from falling in the cavity, the hot water boundary is less likely to occur in the design portion. When the side gate is provided at the end of the rim cavity 61 [position shown by a solid line in FIG. 4C] or the side surface of the cross cavity 64 [position shown by a broken line in FIG. This is inconvenient.
[0019]
【Example】
Hereinafter, the present invention will be described more specifically with reference to examples and comparative examples.
( Reference Example 1) Using the casting apparatus shown in FIG. 1, a molten Al-Si-Mg alloy (JIS AC4CH) (about 450 ° C) was poured into a mold (heated to about 480 ° C) (pressure 0) 0.5 to 0.7 kg / cm ² ), an aluminum wheel having the shape shown in FIG. 6 was cast.
(Example 2) Aluminum was used under the same conditions as in Reference Example 1 except that a casting apparatus having a side gate provided at the position shown in FIG. 4B (distance t = 2 mm between the lower end of the side gate and the upper end of the cross portion) was used. The wheel was cast.
(Example 3) Aluminum was used under the same conditions as in Reference Example 1 except that a casting apparatus in which the side gate was provided at the position shown in FIG. 4B (distance t = 10 mm between the lower end of the side gate and the upper end of the cross portion) was used. The wheel was cast.
(Example 4) A casting apparatus is used in which a side gate is provided at the position shown in FIG. 4B and a restriction is provided on the side gate so that the width w of the connecting portion is 2/3 (10 mm) of Example 3. An aluminum wheel was cast under the same conditions as in Example 3 except that.
(Comparative Example 1) An aluminum wheel was cast under the same conditions as in Reference Example 1 except that a casting apparatus having a side gate provided at the position indicated by the solid line in FIG.
Comparative Example 2 Casting was performed under the same conditions as in Reference Example 1 except that the side gate was provided at the position indicated by the broken line in FIG.
Comparative Example 3 An aluminum wheel was cast under the same conditions as in Reference Example 1 except that the molten metal was injected into the mold only from the side gate [position shown in FIG. 4 (a)].
(Comparative Example 4) 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. 4 (b)]. About the aluminum wheel of each said example, the presence or absence of the hot water boundary of a design surface was observed visually, the sample was cut out from the front flange part and the rim center part, and the impact test was done. The results are shown in Table 1. Also, the weight of each aluminum wheel, the casting cycle time, and the stress applied to the pressing means at the time of removing the side gate were measured, and the results (however, the ratio is shown by the ratio when Comparative Example 4 is 1) are also shown in Table 1. Shown in
[0020]
[Table 1]

[0021]
According to Table 1, according to the low-pressure casting method of the three-gate method ( Reference Example 1, Examples 2 to 4 and Comparative Examples 1 and 2), 10 aluminum wheels are used as compared with the side-gate method (Comparative Examples 3 and 4). It can be seen that the weight can be reduced by more than%, and the casting cycle time can be greatly shortened. In addition, when the 3-gate method is used and the side gate is provided at a position that is separated from the front flange portion and adjacent to the cross portion ( Reference Example 1), there is no generation of a hot water boundary on the design surface and the result of the impact test is also good. However, when the side gate is provided in the center of the rim part in a state of being completely separated from the cross part (Examples 2 to 4), the strain generated when removing the side gate that affects the final product shape is further increased. It can be reduced as much as possible. On the other hand, even in the case of the 3-gate method, when the side gate is provided at the rim end (Comparative Example 1) or at the base of the spoke (Comparative Example 2), a hot water boundary is generated on the design surface and the rim end (Comparative Example 1). When provided, it can be seen that the mechanical strength decreases.
[0022]
【The invention's effect】
As described above, according to the present invention, a mold structure that provides a plurality of gates at a specific position of the cavity and promotes directional solidification, the design surface is complete, high strength and light weight. A vehicle wheel can be obtained. In addition, since the mold structure can reduce the bending stress applied to the wheel during the side gate removing operation, a vehicle wheel with high roundness can be obtained.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view showing a main part of a casting apparatus according to an embodiment of the present invention.
FIG. 2 is a view taken in the direction of arrows AA in FIG.
FIG. 3 is a view taken along arrow BB in FIG. 2;
FIGS. 4A and 4B are schematic views (a), (b), and (c) showing positions of side gates.
FIGS. 5A and 5B are schematic views (a) and (b) showing a connection portion between a side gate and a wheel cavity. FIGS.
FIG. 6 is a cross-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 cavity 11a, 11b, 11c gate, 30 wheel

Claims (3)

In a method for low-pressure casting of a vehicle wheel having a rim portion and a disc portion, casting is performed in a state where a cavity on the front flange side is arranged on the lower side of a mold, and a gate is provided at the center of the cavity forming the disc portion. The gate that forms the rim portion is also provided with a gate, and the gate formed in the cavity that forms the rim portion includes the lower end portion of the gate and the cross portion 64 that does not include R of the connection portion with the cavity that forms the rim portion. The cross provided at the boundary with the rim part is separated from the upper end of the cross part 64 not including R (however, the tip of R at the lower end of the gate and the tip of R at the upper end of the cross part are separated by a distance t) A low-pressure casting method for a vehicle wheel, characterized in that it is connected to a rear flange side away from the portion 64 and injects molten metal from each gate to fill the cavity.   2. The low-pressure casting method for a vehicle wheel according to claim 1, wherein the gate provided in the cavity forming the rim portion is opened to the cavity surface below the rear flange.   The low pressure casting method for a vehicle wheel according to claim 1 or 2, wherein a gate provided in a cavity forming the rim portion is opened at a position 2 to 40 mm away from the cross portion.

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