JP4091805B2 - Mold for casting - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a casting mold used for casting a vehicle wheel. More specifically, the present invention relates to a casting mold capable of suppressing the occurrence of casting defects such as poor hot water, in which the surface of the cavity where the thin wall portion is molded is devised to improve the fluidity of the molten metal.
[0002]
[Prior art]
In order to prevent global warming, which is one of the global environmental problems, reduction of automobile fuel consumption is strongly demanded worldwide. And in order to reduce the fuel consumption, it is said that the weight reduction technology of the automobile is the most important. This is because reducing the weight of the automobile itself reduces the load on the power source, and the amount of fuel used can be reduced regardless of the power source regardless of the gasoline engine.
[0003]
In order to reduce the weight of automobiles, mainly suspension parts can be targets with higher priority. This is because if the weight of the foot is lightened without lowering the mechanical strength, it greatly contributes to the improvement of driving operability and ride comfort of the automobile. And in order to achieve weight reduction, as a technique which is easy to approach, there is a change of the material used for the weight reduction material.
[0004]
From such a background, for example, a lightweight alloy whose main metal is aluminum, magnesium or the like has been adopted as a material for a vehicle wheel that is an automobile underbody part. And as we continue to further reduce weight, carbon materials with lower specific gravity and titanium materials with higher specific strength can be used, but these materials are expensive and workable. However, as a result, the manufacturing cost becomes very high and demand cannot be raised, and there is a limit to the application to mass production parts of automobile undercarriage parts.
[0005]
Therefore, attempts have been made to reduce the thickness while maintaining the mechanical strength by using a light-weight alloy mainly made of aluminum, magnesium or the like, which has been conventionally used, and which is relatively inexpensive. If the thickness is reduced, the automobile suspension parts and the like are naturally reduced in weight.
[0006]
[Problems to be solved by the invention]
However, in the mold for molding the wheel, in the cavity for molding the thin portion of the wheel, the fluidity of the molten metal cannot be denied compared to the cavity for molding the thick portion. Even in the case of casting using a mold having a plurality of gate systems that are more excellent in molten metal filling properties, there is a high probability that defects such as poor hot water will occur in a thin portion of the molded body. That is, when the mechanical strength can be maintained in the thin portion, the thinness naturally has a limit.
[0007]
The present invention has been made to solve such a conventional problem, and the object of the present invention is to reduce the thickness and weight of an undercarriage part for an automobile, particularly a vehicle wheel. It is another object of the present invention to provide a casting mold that is capable of obtaining a casting (product) that has a lower incidence of casting defects such as defective hot water baths and the like and that has excellent mechanical strength.
[0008]
In order to solve the conventional problems, as a result of earnest research on the cause of the poor hot water in the thin wall portion, (1) frictional resistance is generated on the inner wall surface of the cavity. Due to the tension of the oxide film formed in (3), the number of vents for degassing (3) is naturally limited in terms of the mold configuration, and the gas (air) that originally existed in the cavity is poorly blocked, preventing the molten metal from entering. Therefore, it was considered that the flow rate of the molten metal was slowed down and it took time to fill the molten metal. Therefore, if these three factors for lowering the flow rate of molten metal are removed, the experiment can be performed under the policy that the flow rate can be increased even in a cavity for molding a thin wall portion, and the purpose can be achieved. As a result, the present invention was completed. More specifically, the following means are used.
[0009]
[Means for Solving the Problems]
That is, according to the present invention, a vehicle wheel having a thick part and a thin part, comprising a central hub of the design part, a rim constituting the outer periphery, and a spoke connecting the hub and the rim as main constituent parts. And a slit that forms an angle of approximately −60 ° to −30 ° with respect to the traveling direction of the molten metal on a surface that forms a cavity for forming the thin portion, and approximately + 30 ° to There is provided a casting mold characterized in that slits having an angle of + 60 ° are provided in a mesh shape.
[0010]
In the casting mold according to the present invention, it is preferable that one of the thin portions is the rear surface of the spoke, and the mesh-shaped slit is provided on the surface forming the cavity corresponding to the rear surface of the spoke. The casting mold according to the present invention can satisfactorily fill the molten metal even when the shortest distance between the surfaces in the cavity for forming the thin portion is approximately 3.0 to 4.5 mm.
[0011]
Further, according to the present invention, there is provided a vehicle wheel that is cast using the casting mold described above, and on the rear surface of the spoke, approximately −60 ° to −− with respect to the molten metal traveling direction during casting. There is provided a vehicle wheel in which ridges having an angle of 30 ° and ridges having an angle of approximately + 30 ° to + 60 ° are provided in a mesh shape.
[0012]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, the casting mold of the present invention will be described in detail. The present invention relates to a mold used for casting a vehicle wheel having a thick part and a thin part, and is an invention that can improve the fluidity of molten metal in the thin part and reduce the occurrence rate of hot water defects. . It is more preferable to use a casting mold having a plurality of gates because the molten metal filling property is improved.
[0013]
The thick-walled portion and the thin-walled portion refer to respective portions of the vehicle wheel having a relatively clear difference in thickness. The vehicle wheel composed of the thick-walled portion and the thin-walled portion is the vehicle wheel. The filling speed of the molten metal poured into the mold cavity is different with a clear difference between the cavity part that molds the thick part and the cavity part that molds the thin part. For example, the thick portion is about 10 to 50 mm and the thin portion is about 3 to 10 mm. However, the present invention is not limited to these thickness values.
[0014]
In the present invention, the material to be cast is not limited. Typical examples include aluminum and aluminum alloys, magnesium and magnesium alloys, but there is no limitation as long as the material can be formed by casting.
[0015]
In the casting mold of the present invention, the surface forming the cavity for forming the thin portion of the cavity, which is the space for forming the vehicle wheel composed of the thick portion and the thin portion, is formed with respect to the traveling direction of the molten metal. The slits intersecting at angles of approximately −60 ° to −30 ° and + 30 ° to + 60 ° are characterized by being provided in a mesh shape. The angle with respect to the mesh slit and the traveling direction of the molten metal is illustrated in FIG. 6 (details will be described later).
[0016]
This structure is used to destroy the oxide film formed on the molten molten metal, reduce the contact resistance between the molten metal and the surface of the mold, and further improve the escape of gas in the cavity. This is because the flow rate of the molten metal to be filled is further increased so that filling can be completed faster even in a thin cavity.
[0017]
If the molten metal is not deoxidized, it is oxidized as soon as it is exposed to air, and an oxide film is formed on the surface. When the molten metal is poured from the gate into the cavity, a frictional resistance is generated between the molten metal on which the oxide film is formed and the wall surface of the mold forming the cavity, thereby delaying the penetration of the molten metal into the interior of the cavity. Therefore, if the oxide film formed on the surface of the molten metal is broken, the molten metal is filled more quickly.
[0018]
By providing, in a mesh shape, slits that intersect at approximately −60 ° to −30 ° and + 30 ° to + 60 ° with respect to the traveling direction of the molten metal on the surface forming the cavity for forming the thin-walled portion. However, it enters the mesh slit, disturbs the surface tension, and destroys the oxide film itself. Further, since the contact area between the molten metal and the surface forming the cavity is reduced, the resistance is also reduced. Furthermore, since the gas existing in the cavity passes through a vent provided separately from the mesh slit to the outside of the mold, the entrance of the molten metal is not hindered.
[0019]
As a result, the fluidity of the molten metal is improved, the inside of the thin cavity is easily entered, the filling of the molten metal is completed in a short time, and the occurrence rate of hot water defects is reduced. In addition, the angle between the traveling direction of the molten metal and the intersecting mesh slits is more preferably approximately −50 ° to −40 ° and + 40 ° to + 50 °.
[0020]
The plan view shown in FIG. 6 shows an enlarged inner surface of the cavity forming the thin portion of the casting mold according to the present invention, and the crossing angle of the slits will be described. The mesh-shaped slits intersecting at an angle of −60 ° to −30 ° and + 30 ° to + 60 ° with respect to the traveling direction of the molten metal are, as shown, an angle θ1 with respect to the traveling direction S of the molten metal. A plurality of slits 49 whose angle is + 30 ° to + 60 ° and a plurality of slits 50 whose angle θ2 is −60 ° to −30 ° are formed by crossing in a mesh shape.
[0021]
The slit 48 is a slit in which a plurality of slits facing at least two directions intersect. In FIG. 6, the angle between the molten metal traveling direction S and the slit 49 formed toward the left side with respect to the molten metal traveling direction S is θ1, and the molten metal traveling direction S and the molten metal traveling direction S are the same. The angle with the slit 50 formed toward the right side is referred to as θ2.
[0022]
It is important that the plurality of slits 49 and 50 that face at least two directions constituting the slit 48 are formed in an oblique direction with the above angle with respect to the traveling direction S of the molten metal. When the slit forms an angle larger than −60 ° or + 60 ° with respect to the molten metal traveling direction S, or the slit forms an angle smaller than −30 ° or + 30 ° with respect to the molten metal traveling direction S, the oxide film Is not preferable because the molten metal filling rate is not improved. It is not preferable for the same reason that the slits 49 and 50 are used alone.
[0023]
As shown in FIG. 6, a plurality of slits (slits 49 or slits 50) facing in two directions are preferably formed in parallel, but the present invention is not limited to this. The slit formation angles θ <b> 1 and θ <b> 2 with respect to the molten metal traveling direction S may not be constant in each of the slit 49 or the slit 50. That is, in FIG. 6, the plurality of slits 49 formed toward the left side at an angle θ1 with respect to the molten metal traveling direction S may not be parallel to each other. The plurality of slits 50 formed toward the right side at an angle θ2 with respect to S may or may not be parallel to each other.
[0024]
FIG. 6 is a plan view showing the inner surface of the cavity of the mold. FIG. 7 shows a BB ′ cross section (cross section of the mold) in FIG. As shown in the drawing, slits 49 and 50 are provided in a mold 72 that forms a cavity 71 that is a molding space for a thin portion. The depth D of the slit can be, for example, about 0.5 to 5 mm, but is not limited to this range. If the depth of the molten metal on which the oxide film is formed is small enough to enter the slit, the oxide film can be destroyed and the slit can be degassed to increase the fluidity of the molten metal. The cross-sectional shape in the depth direction of the slit is not limited. As illustrated, for example, it is possible to employ a V-groove-shaped slit that narrows in the depth direction so that the molten metal can easily enter the slit.
[0025]
The casting mold of the present invention is a mold used for casting a vehicle wheel. For example, in the vehicle wheel, the thin part that is likely to cause a casting defect is the back surface of the hub or the spoke. The back side is mentioned. In the present invention, it is preferable that the above-mentioned slit is provided on a surface forming a cavity for molding at least one of them, and the thin portion of the hub or spoke formed by the casting mold of the present invention. It is possible to reduce the occurrence rate of casting defects.
[0026]
The casting mold of the present invention is a casting mold for molding a vehicle wheel, and preferably has a plurality of gates for pouring molten metal into the cavity. This is because when the molten metal is filled, the moving distance of the molten metal is shorter and filling is easier than in the center gate type mold, and the yield is improved because it is less likely to cause poor hot water.
[0027]
The plurality of gates are preferably provided with one gate leading to a cavity for forming a hub or spoke and a plurality of gates leading to the circumference of a cylindrical cavity for molding a rim at equal intervals. With such a configuration, when the molten metal is filled, the moving distance of the molten metal becomes shorter, and further, poor hot water is less likely to occur, and the time required for filling the molten metal can be shortened.
[0028]
In the vehicle wheel manufactured using the casting mold of the present invention, the thickness of the thin wall portion can be reduced to 3.0 to 4.5 mm, which could not be realized conventionally. Therefore, it can be lighter and more excellent in design, and can have higher competitiveness than competing products.
[0029]
The material constituting the casting mold of the present invention may be a known material, and the present invention does not limit the material used. In general, a material having a higher thermal conductivity, that is, a higher thermal conductivity is used. For example, copper, beryllium copper, or an aluminum alloy can be used.
[0030]
The casting mold of the present invention can be applied to various casting methods, but can be suitably used for a low pressure casting method. The low-pressure casting method generally uses a mold and a holding furnace provided under the mold and containing molten metal, and for example, by injecting nitrogen gas into the holding furnace, about 0.1 to 0.5 kg / cm. Apply a very low pressure of ² or suck in vacuum from the mold side, push the molten metal up into the mold while keeping the temperature constant, solidify with the mold and mold the casting It is a manufacturing method comprising a process of obtaining. Compared to the so-called squeeze casting method and the die casting method, this low pressure casting method has a higher throughput because the molten metal filling speed is faster than the squeeze casting method and is not press-fitted like the die casting method. There is an advantage that the equipment cost including the mold is low.
[0031]
【Example】
Hereinafter, the description of the casting mold of the present invention will be continued with examples. However, the present invention is not limited to these examples.
[0032]
Example 1
[0033]
A vehicle wheel 41 having a shape shown in a perspective view in FIG. 4 was formed. FIG. 5 is a view showing an AA ′ cross section of the vehicle wheel 41 shown in FIG. 4, and the vehicle wheel 41 includes a cylindrical rim and spokes 44 that connect the rim to the hub 51. Further, the rim is composed of an outer rim 43 on the side of the spoke 44 and an inner rim 42 which is a thin part at the opposite end, and the spoke 44 has a concave part formed on the back surface, and a thin part 45 which is the bottom of the dent, It has the thick part 46 which is a dent wall.
[0034]
The slit formation target was the thin portion 45 of the spoke 44, and the thickness of the thin portion 45 was 3.0 mm. The progress of the molten metal is such that a mesh ridge 47 as shown in FIG. 1 is formed on the thin portion 45 of the spoke 44 on the surface forming the cavity for forming the thin portion 45 of the casting mold used. A mesh-like slit intersecting the direction S at angles of approximately −45 ° and + 45 ° was provided. Here, the thin part 45 in which the mesh ridges 47 are formed is referred to as a thin part 45a. In addition, a protruding item | line part means the stripe-like convex part formed by transcribe | transferring a slit.
[0035]
The vehicle wheel 41 is mainly made of an aluminum alloy AC4C defined in Japanese Industrial Standard, and the size is 15 × 6.5 inches. Casting conditions were as follows. The molten metal after the degassing treatment was poured at a temperature of 700 ° C. by pouring, and then cooled and demolded.
[0036]
(Example 2)
[0037]
A vehicle wheel was molded in the same manner as in Example 1 except that the thickness of the thin portion 45 was 4.5 mm.
[0038]
(Comparative Examples 1 and 2)
[0039]
The surface in which the cavity for forming the thin portion 45 of the casting mold is formed is substantially the same as the molten metal traveling direction S so that a plurality of ridges as shown in FIG. 2 are formed in the thin portion 45. A plurality of vertical slits facing the direction were provided to form a vehicle wheel (here, the thin portion 45 to which the plurality of vertical slits were transferred is referred to as a thin portion 45b). The thickness of the thin part 45b was set to 3.0 mm (Comparative Example 1) and 4.5 mm (Comparative Example 2).
[0040]
(Comparative Examples 3 and 4)
[0041]
In the thin wall portion 45, a plurality of protruding strip portions as shown in FIG. 3 are formed. On the surface forming the cavity for forming the thin wall portion 45 of the casting mold, the molten metal traveling direction S is generally the same. A plurality of horizontal slits oriented in the vertical direction were provided to form a vehicle wheel (here, the thin portion 45 to which the plurality of horizontal slits were transferred is referred to as a thin portion 45c). The thickness of the thin part 45c was 3.0 mm (Comparative Example 3) and 4.5 mm (Comparative Example 4).
[0042]
(Comparative Examples 5 and 6)
[0043]
A vehicle wheel was formed without providing a slit on the surface forming the cavity for forming the thin portion 45 of the casting mold (the formed thin portion 45 is called a thin portion 45d (not shown)). The thickness of the thin portion 45d was 3.0 mm (Comparative Example 5) and 4.5 mm (Comparative Example 6).
[0044]
(result)
[0045]
When the yield (non-defective product ratio) of each thin portion of the molded vehicle wheel was measured, the thin portion 45a having a thickness of 3.0 mm was 83%, and the thin portion 45a having a thickness of 4.5 mm was 100% and having a thickness. The thin portion 45b of 3.0mm is 42%, the thin portion 45b of 4.5mm thickness is 70%, the thin portion 45c of 3.0mm thickness is 67%, the thin portion 45c of 4.5mm thickness is 84%, The thin portion 45d having a thickness of 3.0 mm was 10%, and the thin portion 45d having a thickness of 4.5 mm was 48%.
[0046]
As a result, according to the casting mold according to the present invention, slits that intersect the molten metal traveling direction at a predetermined angle are provided in a mesh shape on the surface forming the cavity for forming the thin portion 45. This clearly improved the yield. Good molding of an extremely thin part of 3.0 to 4.5 mm has been difficult with a conventional mold not provided with a slit, but according to the present invention, it is possible to sufficiently improve the yield to withstand practical use. It was.
[0047]
【The invention's effect】
As described above, according to the casting mold of the present invention, it is possible to reduce the thickness of the vehicle wheel while reducing casting defects such as poor hot water and maintaining mechanical strength at least. It is. And, for example, if an aluminum alloy is used and a lighter vehicle wheel having a thin portion with high strength is provided, fuel efficiency of automobiles and the like can be improved, and reduction of exhausted carbon dioxide, which is a global issue, is achieved. Can contribute to environmental measures such as global warming prevention.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view showing an embodiment of a thin portion of a vehicle wheel molded with a casting mold according to the present invention.
FIG. 2 is a cross-sectional view showing an embodiment of a thin portion of a vehicle wheel molded with a casting mold.
FIG. 3 is a cross-sectional view showing an embodiment of a thin portion of a vehicle wheel molded with a casting mold.
FIG. 4 is a perspective view showing an example of a vehicle wheel cast with a casting mold according to the present invention.
5 is a cross-sectional view taken along the line AA ′ of the vehicle wheel shown in FIG. 4. FIG.
FIG. 6 is an enlarged plan view showing an inner surface of a cavity of a thin portion of a casting mold according to the present invention, and is a view for explaining a crossing angle of slits.
7 is a cross-sectional view of a casting mold according to the present invention, and represents a BB ′ cross section shown in FIG. 6;
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 41 ... Wheel for vehicles, 42 ... Inner rim, 43 ... Outer rim, 44 ... Spoke, 45, 45a, 45b, 45c ... Thin part, 46 ... Thick part, 47 ... Mesh convex part, 48, 49, 50 ... Slit, 51 ... hub, 71 ... cavity, 72 ... mold.

Claims (4)

A mold used for casting of a vehicle wheel having a thick part and a thin part, comprising a hub at the center of the design part, a rim constituting the outer periphery, and a spoke connecting the hub and the rim as main constituent parts. Because
The surface forming a cavity for molding the thin portion, the traveling direction of the molten metal, - 60 ° an angle of ~-30 °, depth and V groove-shaped slits in the 0.5 to 5 mm, + A casting mold , wherein an angle of 30 ° to + 60 ° , a depth of 0.5 to 5 mm, and a V-groove slit are provided in a mesh shape.   2. The casting mold according to claim 1, wherein the thin-walled portion is a rear surface of the spoke, and the mesh-shaped slit is provided on a surface forming a cavity corresponding to the rear surface of the spoke. 2. The shortest distance between the surfaces in the cavity for molding the thin portion is 3 . The casting mold according to claim 1, wherein the casting mold is 0 to 4.5 mm. A vehicle wheel cast using the casting mold according to any one of claims 1 to 3,
The rear surface of the spokes, the traveling direction of the molten metal during casting, - 60 ° and convex portion at an angle of ~-30 °, and the convex portion forming an angle of + 30 ° ~ + 60 ° is, reticulated Vehicle wheel provided in

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