JP2004058099A - Metallic mold for casting - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a metallic mold for casting with which the rate of cast defect, such as misrun, is reduced compared with the conventional mold and a casting excellent in mechanical strength can be obtained when a wheel for vehicle having thinner thickness is formed by casting. <P>SOLUTION: The metallic mold for casting has slits having almost -60° to -30° angle and slits having almost +30° to +60° angle to the running direction of molten metal in a network state on the surfaces of a cavity for forming the thinner thickness portion. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
BACKGROUND OF THE INVENTION 1. Field 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 running of a molten metal, in which a surface of the cavity on which a thin portion is formed is devised to improve the fluidity of the molten metal.
[0002]
2. Description of the Related Art In order to prevent global warming, which is one of the global environmental problems, there is a strong demand worldwide for reduction of fuel consumption of automobiles. In order to reduce the fuel consumption, it is said that the technology of reducing the weight of an automobile is the most important. This is because if the vehicle itself is reduced in weight, the load on the power source is reduced, and the fuel consumption can be reduced regardless of the power source regardless of the gasoline engine.
[0003] In order to reduce the weight of an automobile, parts around the feet can be mainly given higher priority. This is because reducing the weight of the foot without reducing the mechanical strength greatly contributes to the improvement of the driving operability and the feeling of riding of the automobile. As a technique which is easy to approach in reducing the weight, there is a change in the material used for the lightweight material.
[0004] From such a background, lightweight alloys containing aluminum, magnesium or the like as a main metal, for example, have been adopted as materials for vehicle wheels, which are vehicle suspension parts. As we further pursue further weight reduction, carbon-based materials with lower specific gravity and titanium-based materials with higher specific strength can be adopted, but these materials themselves are expensive and workability is high. As a result, the production cost becomes extremely high and demand cannot be stimulated, and there is a limit to its application to mass-produced vehicle suspension parts and the like.
Therefore, attempts have been made to reduce the wall thickness while maintaining the mechanical strength by using a relatively inexpensive lightweight alloy mainly composed of aluminum, magnesium or the like, which has been conventionally employed. If the thickness is reduced, the vehicle undercarriage parts and the like are naturally reduced in weight.
[0006]
However, in a mold for molding a wheel, the fluidity of the molten metal is lower in a cavity for molding a thinner portion of the wheel than in a cavity for molding a thicker portion. can not deny. Even in the case of casting using a mold having a plurality of gate systems which are more excellent in melt filling property, the probability of occurrence of defects such as poor running of the melt in the thin portion of the molded body increases. That is, if the mechanical strength can be maintained in the thin portion, the thickness naturally has a limit.
The present invention has been made to solve such a conventional problem, and an object of the present invention is to reduce the thickness and weight of an undercarriage part for an automobile, particularly, a vehicle wheel. Therefore, it is an object of the present invention to provide a casting mold capable of obtaining a casting (product) having an excellent mechanical strength with a lower incidence of casting defects such as poor running of the melt than before.
In order to solve the conventional problems, the inventors of the present invention have made intensive studies on the cause of poor running of the molten metal in the thin portion. As a result, the molten metal as a fluid has (1) frictional resistance generated on the inner wall surface of the cavity. ▼ Because of the tension of the oxide film formed on the surface of the molten metal, the number of venting vents is limited due to the mold configuration, and the gas (air) that originally existed in the cavity is not easily removed. It was thought that the flow rate of the molten metal was slowed down so as to obstruct entry, and it took time to fill the molten metal. Therefore, removing these three factors that lower the flow rate of the molten metal, the flow rate can be increased even in a cavity for forming a thin portion, and the experiment was conducted under the policy of achieving the object. The present invention has been completed. More specifically, the following means is used.
[0009]
That is, according to the present invention, a thick portion having a hub at the center of a design portion and a rim constituting an outer periphery, and a spoke for connecting the hub and the rim are formed as main components. Used for casting a vehicle wheel having a thin portion and an angle of approximately −60 ° to −30 ° with respect to a traveling direction of the molten metal on a surface forming a cavity for forming the thin portion. And a slit forming an angle of approximately + 30 ° to + 60 ° are provided in a mesh form.
In the casting mold according to the present invention, one of the thin portions is the back surface of the spoke, and the mesh-like slit is provided on a surface forming a cavity corresponding to the back surface of the spoke. Is preferred. 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.
Further, according to the present invention, there is provided a vehicle wheel cast by using the above-described casting mold, wherein a rear surface of the spoke is substantially -60 with respect to a traveling direction of the molten metal during casting. A vehicular wheel is provided in which a ridge having an angle of ° to -30 ° and a ridge having an angle of approximately + 30 ° to + 60 ° are provided in a mesh form.
[0012]
BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, a 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 portion and a thin portion, and is an invention capable of improving the flowability of a molten metal in a thin portion and reducing the incidence rate of molten metal run-out. . It is more preferable to employ a casting mold having a plurality of gates, since the filling property of the molten metal is improved.
The thick portion and the thin portion refer to respective portions of the vehicle wheel having a relatively apparent difference in thickness, and the vehicle wheel including the thick portion and the thin portion refers to the respective portions. This means that the filling rate of the molten metal poured into the cavity for molding the vehicle wheel has a clear difference between the cavity for molding the thick part and the cavity for molding the thin part. As an example, the thick portion has a thickness of about 10 to 50 mm and the thin portion has a thickness of about 3 to 10 mm. However, the present invention is not limited to these thickness values.
In the present invention, the material to be cast is not limited. Typically, aluminum and an aluminum alloy, magnesium and a magnesium alloy can be given, but the material is not limited as long as it can be formed by casting.
In the casting mold according to the present invention, the direction in which the molten metal travels is formed on the surface of the cavity for forming the thin-walled portion, which is the space for forming the vehicle wheel including the thick-walled portion and the thin-walled portion. In contrast, slits that intersect at angles of approximately −60 ° to −30 ° and + 30 ° to + 60 ° are characteristically provided in a mesh shape. FIG. 6 illustrates the angle between the mesh slit and the direction of travel of the molten metal (details will be described later).
This structure is adopted because the oxide film formed on the molten metal, which is a fluid, is broken, the contact resistance between the molten metal and the surface of the mold is reduced, and furthermore, the outgassing in the cavity is improved. This is because the flow rate of the molten metal filled in the cavity is further increased, and the filling is completed more quickly even in a thin cavity.
The molten metal, which is a fluid, is oxidized as soon as it comes into contact with air unless it is under deoxygenation, and an oxide film is formed on its surface. When the molten metal is poured into the cavity from the gate, frictional resistance occurs between the molten metal on which the oxide film is formed and the wall surface of the mold forming the cavity, and the entry of the molten metal into the interior of the cavity is delayed. Therefore, if the oxide film formed on the surface of the molten metal is broken, the molten metal is filled more quickly.
A slit is formed in a mesh shape on the surface forming the cavity for forming the thin portion, which crosses at an angle of approximately −60 ° to −30 ° and + 30 ° to + 60 ° with respect to the traveling direction of the molten metal. As a result, the molten metal enters the mesh-like slits, disturbs the surface tension, and destroys the oxide film by itself. Also, the resistance is reduced because the contact area between the molten metal and the surface forming the cavity is reduced. Further, the gas existing in the cavity passes through the vent provided separately from the mesh slit to the outside of the mold, so that the entry of the molten metal is not hindered.
As a result, the fluidity of the molten metal is improved, the molten metal is easily entered into the thin cavity, and the filling of the molten metal is completed in a short time, thereby reducing the occurrence rate of molten metal run-out. In addition, the angle between the traveling direction of the molten metal and the intersecting mesh-like slit is more preferably approximately −50 ° to −40 ° and + 40 ° to + 50 °.
Referring to the plan view shown in FIG. 6, the inner surface of the cavity forming the thin portion of the casting mold according to the present invention is shown in an enlarged manner, and the intersection angle of the slit will be described. As shown in the figure, a mesh-like slit that intersects at an angle of −60 ° to −30 ° and + 30 ° to + 60 ° with respect to the traveling direction of the molten metal forms an angle θ1 with respect to the traveling direction S of the molten metal. Is a slit 48 formed by intersecting a plurality of slits 49 having an angle θ of + 30 ° to + 60 ° and a plurality of slits 50 having an angle θ2 of −60 ° to −30 °.
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 traveling direction S of the molten metal and the slit 49 formed to the left with respect to the traveling direction S of the molten metal is θ1, the traveling direction S of the molten metal, and the traveling direction S of the molten metal. The angle with the slit 50 formed toward the right side is referred to as θ2.
It is important that the plurality of slits 49 and 50 in at least two directions constituting the slit 48 are formed obliquely at the above-mentioned angle with respect to the traveling direction S of the molten metal. If the slit forms an angle greater than −60 ° or + 60 ° with respect to the traveling direction S of the molten metal, or if the slit forms an angle smaller than −30 ° or + 30 ° with respect to the traveling direction S of the molten metal, the oxide film is formed. Is difficult to break, and the filling speed of the molten metal is not improved. It is also not preferable that only one of the slits 49 and 50 is formed for the same reason.
As shown in FIG. 6, it is preferable that a plurality of slits (slits 49 or slits 50) oriented in two directions are formed in parallel, however, the present invention is not limited to this. Not done. The slit forming angles θ1 and θ2 with respect to the traveling direction S of the molten metal do not have to be constant in each of the slit 49 or the slit 50. That is, in FIG. 6, a plurality of slits 49 formed to the left at an angle θ1 with respect to the traveling direction S of the molten metal may or may not be parallel to each other. A plurality of slits 50 formed to the right at an angle θ2 to S may or may not be parallel to each other.
FIG. 6 is a plan view showing the inner surface of the cavity of the mold. FIG. 7 shows a cross section BB ′ (cross section of the mold) in FIG. As shown in the figure, 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 melt on which the oxide film is formed can enter the slits slightly, the oxide film is destroyed and the slits serve as gas vents, so that the fluidity of the melt can be increased. The cross-sectional shape in the depth direction of the slit is not limited. As shown in the drawing, for example, a V-shaped slit narrowing in the depth direction, in which the molten metal easily enters the slit, can be adopted.
The casting mold of the present invention is a mold used for casting a vehicle wheel. For example, in the vehicle wheel, a thin portion where a casting defect is likely to occur includes a rear surface of a hub, , The back of the spokes. 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 these, and a thin portion of a hub or spoke formed by a casting mold of the present invention. Can reduce the incidence of casting defects.
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 filling the molten metal, the moving distance of the molten metal is shorter, the filling is easier, the poor running of the molten metal is less likely to occur, and the yield can be improved as compared with the center gate type mold.
Preferably, the plurality of gates are provided with one gate leading to a cavity for forming a hub or a spoke, and a plurality of gates communicating at equal intervals around the circumference of a cylindrical cavity for forming a rim. . With this configuration, when filling the molten metal, the moving distance of the molten metal becomes shorter, and furthermore, poor running of the molten metal is less likely to occur, and the time required for filling the molten metal becomes shorter.
In the vehicle wheel manufactured by using the casting mold of the present invention, the thickness of the thin-walled portion can be set to 3.0 to 4.5 mm, which cannot be realized conventionally, at the thinnest portion. . Therefore, it can be lighter and more excellent in design, and can have higher competitiveness as compared with competitors.
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. Generally, a material having higher thermal conductivity, that is, a material having high thermal conductivity is used. For example, copper, beryllium copper, or an aluminum alloy is used.
Although the casting mold of the present invention is applicable to various casting methods, it 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 in which a molten metal is placed, and for example, approximately 0.1 to 0.5 kg / cm by injecting nitrogen gas into the holding furnace. ² Apply a very low pressure, or suck in vacuum from the mold side, while keeping the temperature of the molten metal at a constant temperature, push it up into the mold, solidify it with the mold, and mold it. This is a manufacturing method comprising the steps of obtaining This low-pressure casting method has a higher throughput than the so-called squeeze casting method and the die casting method because of a higher filling rate of the molten metal than the squeeze casting method. There is an advantage that the equipment cost including the mold is inexpensive.
[0031]
EXAMPLES The casting mold of the present invention will be described below with reference to examples. However, the present invention is not limited to these examples.
(Example 1)
A vehicle wheel 41 having a shape shown in a perspective view in FIG. 4 was formed. FIG. 5 is a diagram showing a cross section taken along the line AA ′ of the vehicle wheel 41 shown in FIG. 4. The vehicle wheel 41 includes a cylindrical rim and spokes 44 connecting the rim to the hub 51. Further, the rim includes an outer rim 43 on the spoke 44 side and an inner rim 42 as a thin portion at the opposite end, and the spoke 44 has a concave portion formed on the back surface and a thin portion 45 which is the bottom of the concave portion. It has a thick wall portion 46 which is a concave wall.
The slit was formed on the thin portion 45 of the spoke 44, and the thickness of the thin portion 45 was 3.0 mm. On the surface forming the cavity for molding the thin portion 45 of the used casting mold, the progress of the molten metal is performed so that the mesh convex portion 47 as shown in FIG. 1 is formed in the thin portion 45 of the spoke 44. A mesh-like slit that intersects the direction S at an angle of approximately −45 ° and + 45 ° is provided. Here, the thin portion 45 on which the mesh convex portions 47 are formed is referred to as a thin portion 45a. Note that the ridge portion refers to a streak-like convex portion formed by transferring a slit.
The vehicle wheel 41 is mainly made of aluminum alloy AC4C specified by Japanese Industrial Standards and has a size of 15 × 6.5 inches. The casting conditions were such that the molten metal that had been degassed was poured at a temperature of 700 ° C. by low-pressure casting, then cooled and demolded.
(Example 2)
A vehicle wheel was formed in the same manner as in Example 1 except that the thickness of the thin portion 45 was 4.5 mm.
(Comparative Examples 1 and 2)
In order to form a plurality of ridges as shown in FIG. 2 on the thin portion 45, a surface forming a cavity for forming the thin portion 45 of the casting mold is provided with a moving direction S of the molten metal. A plurality of vertical slits oriented substantially in the same direction were provided, and a vehicle wheel was formed (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 portion 45b was 3.0 mm (Comparative Example 1) and 4.5 mm (Comparative Example 2).
(Comparative Examples 3 and 4)
In order to form a plurality of ridges as shown in FIG. 3 on the thin portion 45, a surface forming a cavity for forming the thin portion 45 of the casting mold is provided with a moving direction S of the molten metal. A plurality of lateral slits oriented in a direction substantially perpendicular to the vertical direction are provided to form a vehicle wheel (here, the thin portion 45 to which the plurality of horizontal slits are transferred is referred to as a thin portion 45c). The thickness of the thin portion 45c was 3.0 mm (Comparative Example 3) and 4.5 mm (Comparative Example 4).
(Comparative Examples 5 and 6)
A vehicle wheel was formed without forming a slit on a surface of a cavity for forming the thin portion 45 of the casting mold (the formed thin portion 45 is referred to as 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).
(Result)
The yield (yield rate) of each thin portion of the formed vehicle wheel was measured, and 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%. The thin portion 45b with a thickness of 3.0 mm is 42%, the thin portion 45b with a thickness of 4.5 mm is 70%, the thin portion 45c with a thickness of 3.0 mm is 67%, and the thin portion 45c with a thickness of 4.5 mm 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%.
From these results, it is found that a casting metal having a mesh formed with a slit intersecting at a predetermined angle with respect to the traveling direction of the molten metal is provided on the surface forming the cavity for forming the thin portion 45 according to the present invention. According to the mold, the yield was clearly improved. Good molding of an extremely thin portion of 3.0 to 4.5 mm has been difficult with a conventional mold having no slit. However, according to the present invention, it is possible to sufficiently increase the yield to practical use. Was.
[0047]
As described above, according to the casting mold of the present invention, in a vehicle wheel, casting defects such as poor running of the molten metal are reduced, and at least mechanical strength is maintained, while the thickness is reduced. It is possible to achieve. For example, if an aluminum alloy is used to provide a lighter vehicle wheel having a strong thin portion, the fuel efficiency of automobiles and the like can be improved, and the reduction of carbon dioxide emissions, which is a global issue, can be achieved. And contribute to environmental measures such as prevention of global warming.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view showing one embodiment of a thin portion of a vehicle wheel formed by a casting mold according to the present invention.
FIG. 2 is a cross-sectional view showing one embodiment of a thin portion of a vehicle wheel formed by a casting mold.
FIG. 3 is a cross-sectional view showing one embodiment of a thin portion of a vehicle wheel formed by a casting mold.
FIG. 4 is a perspective view showing an example of a vehicle wheel cast by a casting mold according to the present invention.
5 is a sectional view of the vehicle wheel shown in FIG. 4 taken along the line AA '.
FIG. 6 is an enlarged plan view showing an inner surface of a cavity of a thin portion of the casting mold according to the present invention, and is a view for explaining an intersection angle of a slit.
FIG. 7 is a cross-sectional view of the casting mold according to the present invention, showing a BB ′ cross section shown in FIG. 6;
[Explanation of symbols]
41: Wheel for vehicle, 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 a vehicle wheel having a thick portion and a thin portion, wherein a main hub and a rim forming an outer periphery of the design portion and a spoke connecting the hub and the rim are main constituent portions. And
A slit forming an angle of approximately −60 ° to −30 ° and a slit forming an angle of approximately + 30 ° to + 60 ° with respect to the direction of travel of the molten metal on a surface forming a cavity for forming the thin portion, A casting mold, which is provided in a mesh shape. The casting mold according to claim 1, wherein the thin portion is a back surface of the spoke, and the mesh-shaped slit is provided on a surface forming a cavity corresponding to the back surface of the spoke. The casting mold according to claim 1, wherein a shortest distance between surfaces in the cavity for forming the thin portion is approximately 3.0 to 4.5 mm. A vehicle wheel cast using the casting mold according to any one of claims 1 to 3,
On the back surface of the spoke, a ridge having an angle of approximately −60 ° to −30 ° and a ridge having an angle of approximately + 30 ° to + 60 ° with respect to the direction of travel of the molten metal during casting are meshed. A vehicle wheel provided in a shape.

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