JP4305798B2 - Aluminum wheel casting method and casting mold - Google Patents

Description

【００２２】
【発明の効果】
以上に記述の如く、本発明によれば、サイドゲートの周方向の位置とスポーク部とリム部の交差部の位置をずらして鋳造を行ったのでガスの巻きこみを低減でき、クロス部およびスポーク部が建全で、高強度でかつ軽量化した車両用ホイールを安定して得ることができる。
【図面の簡単な説明】
【図１】本発明に係るマルチゲートの鋳造に使用する金型キャビティ形状とそのキャビティ内の溶湯の流れを示す模式図である。
【図２】本発明に係るスポーク部とサイドゲートの周方向の位置の関係を示す模式図である。
【図３】本発明の一実施例に係るマルチゲートの鋳造装置の要部を示す断面図である。
【図４】従来のマルチゲートの鋳造に使用する金型キャビティ形状とそのキャビティ内の溶湯の流れを示す模式図である。
【図５】従来のマルチゲートの鋳造に使用する金型キャビティ形状を用いた製品における内部欠陥を示す模式図である。
【図６】アルミホイールの形状を示す図である。
【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 センターゲート、１１ｂ，１１ｃ サイドゲート、
３０ ホイール、３３ ディスク部、３４ リム部、
６３ スポーク部[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for casting a light alloy aluminum wheel in a mold cavity and a casting mold used for the casting.
[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, a light alloy wheel 30 includes a thick hub portion 31 attached to an axle by bolts and nuts as shown in FIG. 6, a disc portion 33 including a spoke 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. 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. There is a design hole between the spoke portions 32. 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 of the spoke part can be changed (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 casting, a gate is provided in the hub portion 31 and molten metal is injected therefrom, and the spoke portion 32 and the rim portion 34 and the molten metal are injected in this order (center gate method) or the end portion of the rim portion. A method (side gate method) in which a plurality of (usually two directions) gates are provided in the (cross portion 37) and molten metal is injected therefrom is employed.
In the center gate method, directional solidification is performed in the order of the rim portion, the spoke portion, and the hub portion in order to sufficiently exhibit the gate hot water effect as a solidification form after filling the molten metal. However, in this casting method, since the spoke part has a complicated shape in which the thick part and the thin part are mixed, 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 spoke part itself functions as a molten metal replenishment passage to the hub part, which is easily solidified, so that the spoke part becomes thick to ensure a good hot water flow in the spoke part. Even with this method, it is difficult to significantly reduce the weight of the entire wheel.
[0005]
In order to eliminate the drawbacks of the conventional methods described above, it has been proposed to provide gates at the center (hub portion) and rim end of the disc, respectively, and to pour molten metal from these gates into the mold (for example, Japanese Patent Laid-Open No. Hei 5- 269563, 6-269923). According to this casting method (hereinafter referred to as a multi-gate method), the directional solidification from the rim portion to the disk portion can be achieved even if the spoke portion is thinned, so that the weight of the wheel can be significantly reduced. .
[0006]
[Problems to be solved by the invention]
A lightweight wheel can be obtained by the multi-gate method described above. However, this multi-gate method has a problem that a gas is entrained when the molten metal injected from the center gate and the molten metal injected from the side gate merge, and defects are likely to occur. Accordingly, an object of the present invention is to provide a casting method and a casting mold capable of efficiently obtaining a vehicle wheel having high strength and light weight.
[0007]
[Means for Solving the Problems]
In order to achieve the above object, a center gate is provided at the center of a cavity for forming a disk portion having a plurality of spoke portions, and molten metal is injected from the center gate to fill the cavity, and a side wall is formed in the cavity for forming a rim portion. In an aluminum wheel casting method in which gates are provided and molten metal is poured into the cavities from each gate, a technical means is adopted in which at least one of the side gates is shifted from the position of the intersection of the spoke part and the rim part.
In the present invention, when casting by the multi-gate method, the position of the circumferential direction in which the side gate is provided in the rim cavity is shifted from the position of the intersection of the spoke and rim as shown in FIG. It has been found that the flow inside can be suppressed and the occurrence of internal defects can be reduced.
[0008]
The position of the side gate in the circumferential direction is preferably shifted by 5 ° or more from the position of the intersection of the spoke part and the rim part. If it is less than 5 °, it is difficult to reduce the occurrence of defects such as blisters. If the minimum width of the spoke portions in the rim portion is 20 mm or more, it is preferable to shift by 10 ° or more. In an aluminum wheel having eight or fewer spoke portions, the deviation angle θ with respect to the number n of spoke portions preferably satisfies the following formula (1).
360 / 8n ≧ θ (1)
In an aluminum wheel having nine or more spoke portions, the deviation angle θ with respect to the number n of spoke portions preferably satisfies the following formula (2).
360 / 12n ≧ θ (2)
[0009]
Here, the circumferential position of the side gate is based on the central portion of the circumferential width where the side gate intersects the outer wall of the rim cavity as shown in FIG. The position of the intersection of the spoke part and the rim part is based on the center part (63 'in the figure) of the circumferential width where the spoke part 63 intersects the inner wall of the rim part cavity. As shown in FIG. 2, the shift angle θ is an angle around the wheel axis between the circumferential position 11 b of the side gate and the spoke position 63 ′ closest thereto. In addition, the position of the spoke part means that the spoke does not extend radially from the wheel axis or the spoke does not extend radially from the wheel axis and the spoke is curved. It is defined as described above. In the figure, reference numeral 40 denotes a design hole 40 between the spoke portions.
[0010]
The flow of the molten metal will be described with reference to the drawings. FIG. 1 schematically shows a wheel that passes through the center of a side gate and a center gate and is divided along the axis of an aluminum wheel. In the figure, 84, 85 and 86 schematically show the flow of the molten metal at the cut surface. First, as shown in FIG. 1, the molten metal flows like a flow 84 from the center gate of the disk portion. Actually, the flow 84 enters and fills the disk portion in a substantially concentric manner from the bottom of the cavity. In addition, the molten metal is injected as a flow 85 from the side gate. Since the molten metal flow 85 is first injected into the cavity of the rim part, the molten metal flow 85 collides with the inner wall 31 part of the rim part cavity formed between the spoke part and the spoke part. Next, the flow of the molten metal is divided along the rim cavity as shown by a flow 86, and moves toward the spoke cavity 63 around the center gate. In this way, the flow rate of the molten metal injected from the side gate is directed to the inner wall of the wheel at one end to reduce the molten metal speed, and then move to the spoke portion. For this reason, when the molten metal from the side gate merges with the molten metal with the center gate, the entrainment of gas can be reduced, so that the occurrence of defects can be suppressed.
[0011]
Even if molten metal is injected from the center gate, the spoke portion is relatively thin, so that it is difficult to fill the molten metal. Therefore, the molten metal is injected from the side gate before the molten metal from the center gate is filled to the lower end of the side gate. Therefore, the molten metal injected from the side gate tends to fall into the rim cavity. Usually, as the upper end portion of the side gate approaches the outer rim side or the lower end portion of the side gate moves away from the inner rim, the falling rate of the molten metal from the side gate increases, so that gas is easily trapped. However, even if the position of the side gate relative to the rim width is too close to the disk surface, the timing of the molten metal injected from the side gate is accelerated, and the molten metal injected from the center gate is near the center of the spoke surface. . Since the design of the spoke surface is very important, it is not preferable that a hot water mark is formed. It is important that the position of the side gate with respect to the rim width is appropriately selected according to the shape of the wheel, for example, the thickness of the disk portion or the rim. Although the effect of the present invention is somewhat affected by the height position and width of the center gate, the basic effect of suppressing the entrainment of gas and the like is effective regardless of the height position and width of the center gate.
[0012]
The present invention is preferably applied to an aluminum wheel having 3 to 36 spoke portions in the disk portion. If the number is less than 3, the balance will deteriorate as an aluminum wheel. If the number is greater than 36, the distance between the spokes is too narrow, and the area of the wheel inner wall is reduced. Since the molten metal from the side gate easily flows into the spoke portion, the effect of the present invention is diminished. It is preferable to apply to an aluminum wheel having 4 to 8 spokes. In particular, it is preferable to apply to an even number of wheels because the molten metal is filled evenly in line symmetry. Further, an appropriate R is provided in the vicinity of the connection portion of the side gate and at the boundary between the cross portion and the rim portion in order to improve the hot water resistance. The optimum value of R is about 1 to 20 mm. If it is 1 mm or less, the hot water resistance is deteriorated. If it is larger than 20 mm, the hot water flow to the spoke portion of the molten metal, which is an effect of the present invention, becomes excessive, and gas entrainment or the like is likely to occur. A casting method suitable for the present invention is preferably low pressure casting in which a molten metal is injected at a pressure of 50 to 100 kPa, but is not particularly limited and can be appropriately selected. Further, although an aluminum alloy is used as the present invention, the wheel can be manufactured even if another light alloy such as an Mg alloy is used.
[0013]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, the details of the present invention will be described with reference to the drawings.
FIG. 3 is a sectional view showing a main part of a casting apparatus for carrying out the present invention. In this embodiment, two side gates are provided on the axis, and they are arranged so that they are symmetrical on both sides of the center gate as viewed from the plane, that is, the centers of the gates are located on the same straight line.
In FIG. 3, reference numeral 1 denotes a mold, which is a cavity formed by fitting the lower mold 2 having various surface shapes corresponding to the wheel design, the upper mold 3 positioned above the lower mold 2, the lower mold 2 and the upper mold 3. 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 spoke part cavity 63, and the rim part cavity 61 includes a cross part cavity 64 and a central part cavity 65. The hub portion cavity 62 is formed with a center gate 11a, and the cross portion cavities 64 and 64 are respectively formed with side gates 11b and 11c. The gates are connected to the stalks 13a, 13b and 13c via the runners 12a, 12b and 12c. Communicate. The side gates 11b and 11c are arranged so that the centers of the gates are located on the same straight line. Moreover, the lower end part of these stalks is inserted in the airtight container (not shown) in which the molten metal was accommodated. The lower mold 2 is provided with a lower mold cooling passage 14 at a position corresponding to the spoke cavity 63.
[0014]
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. The molten metal injected from the side gates 11 b and 11 c fills the spoke cavity 63 while the molten metal that passes through the center gate 11 a fills the rim cavity 61. That is, the molten metal merges at the rim cavity 61 or the spoke cavity 63. When the pressurization is released after the 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.
[0015]
【Example】
Hereinafter, the present invention will be described more specifically with reference to examples and comparative examples.
Example 1
Using the casting apparatus shown in FIG. 1, a molten Al-Si-Mg alloy (JIS AC4CH) (about 450 ° C.) is poured into a mold with 6 spokes (heated to about 480 ° C.) ( The pressure was 50 kPa to 70 kPa), and an aluminum wheel was cast at a low pressure. Further, the side gate is shifted in the circumferential direction by 30 ° from the intersection of the rim portion and the spoke portion, and a mold structure is formed in which the side gate is arranged at an intermediate portion between the spoke portion and the spoke portion. The vertical width of the side gate is the rim portion on the inner flange side from the intersection of the rim portion and the disk portion.
The cast aluminum wheel was taken out from the mold, and after cooling, the aluminum wheel was cut along the axis so as to connect the side gate and the center gate, and the cut surface was observed. As a result of observation, it was confirmed that no defects occurred on the cut surface and a good cast product was obtained.
[0016]
(Comparative Example 1)
An aluminum wheel was cast in the same manner as in Example 1 except that the position of the side gate in the circumferential direction was changed to the position of the spoke part. The cast aluminum wheel was taken out from the mold, and after cooling, the aluminum wheel was cut along the axis so as to connect the side gate and the center gate, and the cut surface was observed. FIG. 5 shows a schematic diagram of the observation surface. It was confirmed that a defect 21 occurred at a location slightly below the portion where the side gate 11b intersects the rim portion. FIG. 4 shows a cavity shape in which the position of the side gate in the circumferential direction and the position of the spoke part are the same. The molten metal 81 from the center gate is the same as in the embodiment. However, the molten metal 82 from the side gate does not rotate along the rim cavity around the center gate as in the embodiment, and the molten metal pressed from the side gate becomes a molten metal flow 83 that flows directly toward the spoke portion. Therefore, it is surmised that the molten metal collided at the above position and a defect occurred because the gas was entrained.
[0017]
(Example 2)
Further, the vertical width of the side gate is continuously provided from the upper end of the outer flange to the rim portion on the inner flange side from the intersection of the rim portion and the disk portion. Otherwise, the aluminum wheel was manufactured in the same manner as in Example 1.
The cast aluminum wheel was taken out from the mold, and after cooling, the aluminum wheel was cut along the axis so as to connect the side gate and the center gate, and the cut surface was observed. As a result, it was confirmed that no defects occurred on the cut surface and a good cast product was obtained.
[0018]
(Comparative Example 2)
An aluminum wheel was cast in the same manner as in Example 2 except that the circumferential position of the side gate was changed to the intersection of the rim portion and the spoke portion. The cast aluminum wheel was taken out from the mold, and after cooling, the aluminum wheel was cut along the axis so as to connect the side gate and the center gate, and the cut surface was observed. As a result, it was confirmed that a defect occurred in the vicinity of the rim base portion of the spoke portion.
[0019]
The structure at the intersection of the side gate and the rim in this example was observed, and the DAS value was measured. As a result, the DAS value at the intersection of the side gate and the rim provided between the spoke part and the spoke part was 35 μm or more. Further, the DAS value was measured along the circumferential direction based on the measured vertical position, and it was confirmed that the DAS value is lower than the DAS value at the intersection of the side gate and the rim portion. On the other hand, in the aluminum wheel manufactured by the method according to the comparative example, the portion where the DAS value is the largest is the intersection of the side gate and the rim portion, and a clear difference from the present embodiment appears.
[0020]
(Example 3)
We examined the occurrence of defects due to the shift angle θ between the side gate, rim and spoke. The shift angle θ was examined as 0 °, 3 °, 5 °, 7.5 °, 10 °, and 15 °, respectively.
Using the casting apparatus shown in FIG. 1, an Al-Si-Mg alloy (JIS AC4CH) melt (about 450 ° C.) is poured into a mold (heated to about 480 ° C.) (pressure 50 kPa to 70 kPa). Low pressure cast. The examined aluminum wheel has a shape of 12 spokes, the width of the spokes viewed from the front of the spokes is 11mm at the maximum, 8mm at the minimum, and 5 spokes. The width of the spoke portion viewed from the front of the spoke portion was two types, that is, a spoke type of 62 mm at the position of the spoke portion and a minimum portion of 50 mm. The vertical width of the side gate is the rim portion on the inner flange side from the intersection of the rim portion and the disk portion. The cast aluminum wheel was taken out from the mold, and after cooling, the aluminum wheel was cut along the axis so as to connect the side gate and the center gate, and the cut surface was observed. Table 1 summarizes the observed states.
[0021]
[Table 1]

[0022]
【The invention's effect】
As described above, according to the present invention, since the casting was carried out by shifting the circumferential position of the side gate and the position of the intersection of the spoke part and the rim part, the entrainment of gas can be reduced, and the cross part and the spoke part can be reduced. However, it is possible to stably obtain a vehicle wheel with high strength and light weight.
[Brief description of the drawings]
FIG. 1 is a schematic diagram showing a mold cavity shape used for casting a multigate according to the present invention and the flow of molten metal in the cavity.
FIG. 2 is a schematic diagram showing the relationship between the position of the spoke portion and the side gate in the circumferential direction according to the present invention.
FIG. 3 is a cross-sectional view showing a main part of a multi-gate casting apparatus according to an embodiment of the present invention.
FIG. 4 is a schematic diagram showing a mold cavity shape used in conventional multi-gate casting and a flow of molten metal in the cavity.
FIG. 5 is a schematic diagram showing internal defects in a product using a mold cavity shape used for casting of a conventional multi-gate.
FIG. 6 is a diagram showing the shape of an aluminum wheel.
[Explanation of symbols]
1 mold, 2 lower mold, 3 upper mold, 4,5 horizontal mold, 6 cavity 11a center gate, 11b, 11c side gate,
30 wheel, 33 disc part, 34 rim part,
63 Spoke part

Claims (5)

A center gate is provided at the center of the cavity for forming the disk portion having a plurality of spoke portions, and a molten metal is injected from the center gate to fill the cavity, and a side gate is provided in the cavity for forming the rim portion. In the aluminum wheel casting method, wherein at least one of the side gates is provided at a circumferential position shifted from the position of the intersection of the spoke part and the rim part. Casting method. The aluminum wheel casting method according to claim 1, wherein all of the side gates are provided at positions shifted from the positions of the spoke part and the rim part. The casting method according to claim 1 or 2, wherein a position in a circumferential direction of the side gate and a position of an intersection of the spoke part and the rim part closest to the position are shifted by 5 degrees or more. The casting method according to any one of claims 1 to 3, wherein the number of spokes in the disk portion is 3 to 8. In an aluminum wheel casting mold in which a center gate is provided at the center of a cavity forming a disk part having a plurality of spoke parts, and a side gate is provided in a cavity forming a rim part, at least one of the side gates is A casting mold, wherein the casting mold is provided at a circumferential position shifted from a position of an intersection of the spoke part and the rim part.

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