JP2001300716A - Method for casting aluminum wheel and metallic mold for casting - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a casting method and a metallic mold for casting with which a wheel for vehicle having high strength and lightening can efficiently be obtained. SOLUTION: In the casting method of an aluminum wheel with which a center gate is arranged at the center part of a cavity for forming a disk part having plural spoke parts and molten metal is poured into this cavity from this gate and also, side gates are arranged in a cavity for forming a rim part and the molten metal is poured into this cavity from each gate, at least one of the side gates is peculiarly provided at a position in the peripheral direction shifted from the position of crossing part between the spoke part and the rim part.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field 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]

2. Description of the Related Art There are various road wheels of various materials and structures. Light alloy wheels such as aluminum wheels are mounted on the road wheels for the purpose of reducing the weight and improving the appearance and design of the vehicle. The ratio is increasing. 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.

Generally, a light alloy wheel 30 has a thick hub portion 31 attached to an axle by bolts and nuts as shown in FIG. 6, and a spoke portion 3 having a mixture of a thick portion and a thin portion.
2 and a thin rim 34 to which a tire is attached. 35 is a front flange portion, 36 is a rear flange portion, 37 is a cross portion where the rim portion and the disc portion intersect, and 38 is a rim center portion. 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 wheels is being studied. In this case, since the shape of the hub and the rim cannot be significantly changed from the viewpoint of handling with the vehicle body and the tire, the shape of the spoke is changed (for example, the area of the design hole is increased or the spoke is made thinner). ), But significant weight reduction is extremely difficult.

When the wheel is manufactured by casting, a method is provided in which 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 spoke portion 32 and the rim portion 34 in this order (center gate method). A plurality of gates (usually in two directions) are provided at the end (cross section 37), and the molten metal is injected from there (side gate method). 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 spoke portion, and the hub portion in order to sufficiently exert the gate feeding effect of the gate. However, in this casting method, the spokes have a complicated shape in which a thick part and a thin part are mixed, and it is difficult to achieve directional solidification from the rim toward the disk. On the other hand, in the side gate method, the spoke portion itself functions as a molten metal supply passage to the hub portion that is easily solidified.
In order to ensure a good flow of molten metal at the spokes, the spokes are thick, and it is difficult to significantly reduce the weight of the entire wheel even with this casting method.

In order to solve the above-mentioned drawbacks of the conventional method, it has been proposed to provide gates at the center (hub) of the disk and at the end of the rim, respectively, and to pour the molten metal into the mold from these gates (for example, Kaihei 5-269563, 6-2
69923). According to this casting method (hereinafter referred to as a multi-gate method), directional solidification from the rim toward the disk can be achieved even when the thickness of the spokes is reduced, so that the weight of the wheel can be significantly reduced. .

[0006]

By the above-mentioned multi-gate method, it is possible to obtain a lightweight wheel. However, this multi-gate method has a problem that when the molten metal injected from the center gate and the molten metal injected from the side gates merge, the gas is engulfed 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 high-strength and lightweight vehicle wheel.

[0007]

In order to achieve the above object, a center gate is formed at the center of a cavity forming a disk portion having a plurality of spokes, and a molten metal is injected from the center gate to fill the cavity. In a method of casting an aluminum wheel, in which side gates are provided in a cavity forming a rim portion, and molten metal is injected into the cavity from each gate, at least one of the side gates is shifted from a position of an intersection between the spoke portion and the rim portion. , The technical means of adopting. According to the present invention, when casting is performed by the multi-gate method, the position of the side gate in the rim portion cavity in the circumferential direction is shifted from the position of the intersection of the spoke portion and the rim portion as shown in FIG. It has been found that the flow in the inside can be suppressed and the occurrence of internal defects can be reduced.

It is preferable that the position of the side gate in the circumferential direction is shifted by 5 ° or more from the position of the intersection of the spoke portion and the rim portion. If it is less than 5 °, it is difficult to reduce the occurrence of defects such as blisters. If the minimum width of the spokes in the rim is 20 mm or more, it is preferable to shift the spokes by 10 ° or more. In an aluminum wheel having eight or less spokes, the deviation angle θ with respect to the number n of the spokes is expressed by the following equation (1).
Is preferably satisfied. 360 / 8n ≧ θ (1) In the case of an aluminum wheel having nine or more spoke portions, the deviation angle θ with respect to the number n of the spoke portions preferably satisfies the following expression (2). 360 / 12n ≧ θ (2)

Here, the circumferential position of the side gate is based on the center 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 portion and the rim portion is based on the center (63 'in the figure) of the circumferential width at which the spoke portion 63 intersects the inner wall of the rim cavity. The deviation angle θ is, as described in FIG. 2, the angle between the circumferential position 11b of the side gate and the position 63 ′ of the spoke portion closest to the position 11b about the wheel axis. Also, in the case where the spokes do not extend radially from the wheel axis or the spokes do not extend radially from the wheel axis, and the spokes are curved, etc. It is specified as described above. In the drawing, reference numeral 40 denotes a design hole 40 between spoke portions.

The flow of the molten metal will be described with reference to the drawings. FIG. 1 schematically shows a wheel divided through the center of the side gate and the center gate and along the axis of the aluminum wheel. In the figure, 84, 85 and 86 schematically show the flow of the molten metal on the cut surface. First, as shown in FIG. 1, the molten metal flows from the center gate of the disk portion as a flow 84. In practice, the flow 84 fills and fills the disk portion substantially concentrically from below the cavity. Also, the molten metal is injected from the side gate as shown by a flow 85. Since the flow 85 of the molten metal is first injected into the cavity of the rim portion, the molten metal flows into the rim portion cavity inner wall 31 formed between the spoke portions and once collides. Next, the flow of the molten metal is divided along the rim portion cavity like the flow 86, and once moves around the center gate in the direction of the spoke portion cavity 63. By directing the flow of the molten metal injected from the side gate toward the inner wall of the wheel in this manner, the speed of the molten metal is reduced, and thereafter, the molten metal moves to the spokes. For this reason, when the molten metal from the side gate merges with the molten metal with the center gate, it is considered that the entrapment of gas can be reduced, and the occurrence of defects can be suppressed.

[0011] Even if the molten metal is injected from the center gate, the spoke portion is relatively thin and 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 up to the lower end of the side gate. Therefore, the molten metal injected from the side gate tends to fall down the rim cavity. Usually, as the upper end of the side gate approaches the outer rim side or the lower end of the side gate moves away from the inner rim, the falling speed of the molten metal from the side gate increases, so that the gas is easily taken in. However, even if the position of the side gate with respect to the rim width is too close to the disk surface, the timing of the molten metal injected from the side gate is advanced, and the molten metal boundary with 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 to leave a trace of the hot water. 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 and the rim. Although the effect of the present invention is somewhat affected by the height position and width of the center gate, the basic action of suppressing the entrainment of gas and the like is effective regardless of the height position and width of the center gate.

According to the present invention, the number of spoke portions of the disk portion is three.
It is desirable to apply to aluminum wheels of up to 36 wheels. If the number is less than 3, the balance will be deteriorated as an aluminum wheel. If the number is more than 36, the distance between the spokes becomes too small, so that the area of the inner wall of the wheel becomes small. Since the molten metal from the side gate easily flows to the spokes, the effect of the present invention is reduced. Preferably, the spoke portion is applied to 4 to 8 aluminum wheels. In particular, it is preferable to apply the present invention to even-numbered wheels because the molten metal is filled evenly and symmetrically. Further, an appropriate radius is provided in the vicinity of the connection part of the side gate and at the boundary between the cross part and the rim part in order to improve the hot water running property. The optimum value of this R is about 1 to 20 mm. If it is 1 mm or less, the hot-water-circulating properties deteriorate. If it is larger than 20 mm, the effect of the present invention on the flow of the molten metal to the spoke portion becomes too remarkable, so that the gas is liable to be entangled. The 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. Although an aluminum alloy is used in the present invention, a wheel can be manufactured by using another light alloy such as an Mg alloy.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The details of the present invention will be described below 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 axially symmetrically, and are arranged on both sides of the center gate when 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 die, a lower die 2 having various surface shapes corresponding to wheel designs, an upper die 3 located above the lower die 2, and a cavity formed by fitting the lower die 2 and the upper die 3 with each other. And horizontal dies 4 and 5 slidable left and right so as 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 an upper die base 9 with bolts 10. The cavity 6 is composed of a disk part cavity 60 and a rim part cavity 61, and the disk part cavity 60 is composed of a hub part cavity 62 and a spoke part cavity 6.
The rim portion cavity 61 includes a cross portion cavity 64 and a center portion cavity 65. The center cavity 11a is provided in the hub cavity 62, and the side gates 11b and 11c are provided in the cross cavity 64, 64, respectively.
Are formed, and each gate is provided with a runner 12a, 12b and 12
c and communicates with the stalks 13a, 13b and 13c. The side gates 11b and 11c are arranged such that the center of each gate is located on the same straight line. Further, the lower ends of these stalks are inserted into a sealed 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 spoke cavity 63.

The operation of the above configuration will be described. First, the molten metal in the closed container is pressurized, so that the molten metal becomes Stoke 1
Runners 12a, 12b and 1 from 3a, 13b and 13c
Via 2c, the cavity 6 is filled from the gates 11a, 11b and 11c. Side gate 11b, 11c
The molten metal that has passed through the center gate 11a fills the spoke cavity 63, and the molten metal that passes through the side gates 11b and 11c is the rim cavity 6.
Fill 1 That is, the molten metal joins in the rim cavity 61 or the spoke cavity 63. 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. 2 and the like is obtained.

[0015]

The present invention will be described more specifically below with reference to examples and comparative examples. (Embodiment 1) Using the casting apparatus shown in FIG.
-Molten alloy (JIS AC4CH) (about 450
C.) was injected into a mold having six spokes (heated to about 480 ° C.) (at a pressure of 50 kPa to 70 kPa) to cast an aluminum wheel at a low pressure. Further, the circumferential position of the side gate was shifted by 30 ° from the intersection of the rim portion and the spoke portion, and a mold structure in which the side gate was disposed at an intermediate portion between the spoke portion and the spoke portion was adopted. The vertical width of the side gate was set to the rim portion on the inner flange side from the intersection of the rim portion and the disc portion. The cast aluminum wheel was taken out of the mold, cooled, 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 the observation, it was confirmed that no defect was generated on the cut surface and a good cast product was obtained.

Comparative Example 1 An aluminum wheel was cast in the same manner as in Example 1 except that the position of the spoke in the circumferential direction of the side gate was used. The cast aluminum wheel was taken out of the mold, cooled, 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 view of the observation surface. It was confirmed that the defect 21 occurred at a location slightly below the portion where the side gate 11b intersects the rim. FIG. 4 shows a cavity shape in which the position of the side gate in the circumferential direction and the position of the spoke portion 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 centering on the center gate as in the embodiment, but becomes a molten metal flow 83 in which the molten metal pressed from the side gate flows directly toward the spoke portion. For,
It is presumed that the melts collided at the above-mentioned positions and the gas was engulfed, thereby causing a defect.

(Embodiment 2) In addition, the vertical width of the side gate is continuously provided from the upper end of the outer flange to the rim on the inner flange side from the intersection of the rim and the disk. Otherwise, an aluminum wheel was manufactured in the same manner as in Example 1. The cast aluminum wheel was taken out of the mold, cooled, cut along the axis so as to connect the side gate and the center gate, and the cut surface was observed. As a result, no defect was found on the cut surface, and it was confirmed that a good cast product was obtained.

(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 set to the intersection of the rim portion and the spoke portion. The cast aluminum wheel was taken out of the mold, cooled, 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 near the base of the rim of the spoke.

In this embodiment, the structure at the intersection between the side gate and the rim was observed, and the DAS value was measured. As a result, the DAS value at the intersection of the rim and the side gate provided between the spokes was 35 μm or more. The DAS value was measured along the circumferential direction based on the measured vertical position, and it was confirmed that the DAS value was lower than the DAS value at the intersection of the side gate and the rim.
On the other hand, in the aluminum wheel manufactured by the method according to the comparative example, the place where the DAS value was the largest was the intersection between the side gate and the rim, and a clear difference from the present example appeared.

(Embodiment 3) The occurrence of defects due to the deviation angle θ at the intersection of the side gate, the rim and the spoke was examined. Shift angle θ is 0 °, 3 °, 5 °, 7.5 °, 10 °
° and 15 °, respectively. An Al-Si-Mg based alloy (JIS AC4C) was used using the casting apparatus shown in FIG.
H) molten metal (about 450 ° C) in mold (heated to about 480 ° C)
(Pressure: 50 kPa to 70 kPa) to cast an aluminum wheel at a low pressure. The aluminum wheels examined were of the fin type with 12 spokes and a spoke width of 11 mm at the maximum and 8 mm at the minimum when viewed from the front of the spokes, and 5 spokes. When viewed from the front of the spoke portion, the spoke portion had a width of 62 mm at the position of the spoke portion and a spoke type having a minimum portion of 50 mm. The vertical width of the side gate was set to the rim portion on the inner flange side from the intersection of the rim portion and the disc portion. The cast aluminum wheel was taken out of the mold, cooled, 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]

As described above, according to the present invention, since the casting is performed by shifting the position of the side gate in the circumferential direction and the position of the intersection of the spoke portion and the rim portion, the entrainment of gas can be reduced. Since the cross portion and the spoke portion are completely constructed, a high-strength and lightweight vehicle wheel can be stably obtained.

[Brief description of the drawings]

FIG. 1 is a schematic view showing the shape of a mold cavity used for casting a multi-gate according to the present invention and the flow of molten metal in the cavity.

FIG. 2 is a schematic diagram showing a relationship between circumferential positions of a spoke portion and a side gate according to the present invention.

FIG. 3 is a sectional view showing a main part of a multi-gate casting apparatus according to one embodiment of the present invention.

FIG. 4 is a schematic diagram showing the shape of a mold cavity used for casting a conventional multi-gate and the flow of molten metal in the cavity.

FIG. 5 is a schematic view showing internal defects in a product using a mold cavity shape used for conventional multi-gate casting.

FIG. 6 is a view 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)

[Claims] 1. A center gate is provided at the center of a cavity forming a disk having a plurality of spokes, a molten metal is injected from the center to fill the cavity, and a side gate is provided at a cavity forming a rim. A method for casting an aluminum wheel in which a molten metal is injected from each gate into the cavity, wherein at least one of the side gates is provided at a circumferential position shifted from a position of an intersection of the spoke portion and the rim portion. Aluminum wheel casting method. 2. The aluminum wheel casting method according to claim 1, wherein all of the side gates are provided at positions shifted from positions of the spoke portion and the rim portion. 3. The casting method according to claim 1, wherein a position of the side gate in a circumferential direction and a position of an intersection of the spoke portion and the rim portion closest to the position are shifted by 5 degrees or more. 4. The casting method according to claim 1, wherein the number of spokes in the disk portion is 3 to 8. 5. A casting mold for an aluminum wheel, wherein a center gate is provided at a center of a cavity forming a disk portion having a plurality of spokes, and a side gate is provided at a cavity forming a rim portion. A casting mold, wherein the two side gates are provided at circumferential positions shifted from the positions of intersections of the spoke portions and the rim portions.