JP2003290903A - Metallic mold for casting light alloy wheel with low pressure and method for producing light alloy wheel - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain a metallic mold for casting a light alloy wheel with low pressure and a method for producing the light alloy wheel with which the necessary strength can be secured as the wheel without remaining shrinkage hole at the crossing part of a design part and a rim part after processing the wheel blank and the lightening can be obtained by thinning the thickness of the crossing part. <P>SOLUTION: The metallic mold is the one in which a cavity for forming a disk part, the design part and the rim part is provided and the molten light alloy is poured and filled into the cavity from the disk part, and a cooling means is arranged at the outside of the rim part in the crossing part and also, a heat-holding means is arranged at the inside of the rim part in the crossing part. The method for producing the wheel is partially applied to the inside of the rim part in the crossing part of the wheel with a deep following processing after casting the light alloy wheel by using the metallic mold. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a light alloy wheel low pressure casting mold and a method for manufacturing a light alloy wheel.

[0002]

2. Description of the Related Art There are various types of automobile road wheels made of various materials and structures, but light alloy wheels (typically aluminum wheels) are used for the purpose of weight reduction for improved fuel efficiency and improved design. In the following, simply wearing "wheels") is increasing. FIG. 2 is an example of a spoke type wheel, (a) is a wheel material 20.
a sectional view of a, (b) a sectional view of the wheel 20 after processing,
(C) shows the front view which looked at the design part 22 in (b) from the outside. 2 (b) and 2 (c), a wheel 20 includes a disc portion 21 mounted on an axle with bolts and nuts, a design portion 22 which is a design such as a spoke type, a rim portion 23 on which a tire is mounted, and a rim portion thereof. The outer flange portion 24 and the inner flange portion 25, which are a part of the portion 23, are included. In addition to the spoke type, the design section 22 may have various designs such as a mesh type, a fin type, a dish type, and a twin spoke type.

The wheel 20 shown in FIGS. 2 (b) and 2 (c) is
Figure 2 is the result of low-pressure casting using the center gate method.
The material 20a shown in (a) is often manufactured by processing the material 20a thereafter. That is, in order to obtain the wheel material 20a shown in FIG.
A gate (not shown) is provided immediately below the portion to be 1a, and the molten metal in the holding furnace is moved from the stoke to the gate, the disc portion 21a, the design portion 22, the rim portion 23a, the outer flange portion 24.
A and the cavity 11 having the inner flange portion 25a are filled.

By the way, in order to fill the molten metal from the disk portion 21a to the inner flange portion 25a at the end,
It is necessary to keep the surface temperature of the mold forming the cavity high to some extent. On the other hand, however, if the surface temperature of the mold is high, it takes time to complete the solidification of the material 20a after the molten metal is injected, and thus it takes time to remove the material 20a. So, after filling the cavity with molten metal,
The mold is actively cooled with air, water, etc. to promote solidification. Further, when solidification of the thickened portion of the crossing portion 26 of the design portion 22 and the rim portion 23a nears the end, shrinkage cavities are likely to occur in the crossing portion 26 due to solidification contraction. It is also carried out to promote coagulation.

On the other hand, since directional solidification cannot be achieved even if it is excessively cooled, Japanese Patent Laid-Open No. 11-226716 discloses that
In a mold provided with an insert mold on the outer side of the rim portion 23a near the intersection 26 in FIG. 2 (a), a groove is formed on the contact surface between the main mold and the insert mold, and the groove between the main mold and the insert mold is formed. It is described that the contact area is reduced to suppress excessive heat transfer and prevent casting defects such as shrinkage cavities.

The inventor of the present invention will also describe the rim portion 2 by referring to FIG. 2A as Japanese Patent Laid-Open No. 2000-61610.
3a and a mold provided with a cavity forming the design portion 22, a plurality of temperature sensors are installed in a mold forming the outside of the rim portion 23a along a direction in which directional solidification proceeds.
In addition, a plurality of cooling means (not shown) are installed in the mold forming the outside of the rim portion 23a, the values detected by the respective temperature sensors are compared with each other, and the cooling means is selectively operated based on the comparison result. The temperature detected by the temperature sensor to the disk unit 2
A mold cooling method is proposed in which directional solidification is reliably performed by performing feedback control such that the distance becomes lower as the distance from 1a increases.

[0007]

However, even if cooling is performed by forming a groove on the contact surface between the main mold and the insert mold to be inserted into the main mold, as described in JP-A No. 11-226716, A shrinkage cavity 29 may occur near the center of the intersection 26 between the design portion 22 and the rim portion 23a of the wheel material 20a, and if this shrinkage cavity 29 remains after processing the wheel material 20a into the wheel 20, Wheel 2
There is concern that the strength may be reduced to 0.

On the other hand, Japanese Patent Laid-Open No. 2000-
According to Japanese Patent No. 61610, the rim portion 23a can be directionally solidified, but if a shrinkage cavity 29 should occur near the center of the intersection portion 26, the shrinkage cavity 29 remains after the material 20a is processed into the wheel 20. Therefore, there is a concern that the strength of the wheel 20 may be reduced.

Now, in order to further improve the fuel economy of automobiles,
There is also a continuous demand for lightweight wheels by changing their shapes. In this weight reduction, FIG.
Since the disk portion 21, the rim portion 23, and the outer flange portion 24 and the inner flange portion 25, which are parts of the rim portion 23 in (c), cannot be significantly changed in shape from the viewpoint of mounting on an axle or tire mounting. The weight of the design portion 22 is reduced by changing the shape of the design portion 22, such as increasing the area of the opening 28 of the design portion 22 or reducing the thickness of the design portion 22. However, even with this, it is extremely difficult to significantly reduce the weight. Therefore, the design section 22 and the rim section 23
Since the crossing portion 26 is relatively thick, it is conceivable to reduce the weight of the wheel by making the crossing portion 26 thin while ensuring strength.

Therefore, the object of the present invention is to prevent the formation of shrinkage cavities at the intersection of the design portion and the rim portion after processing the wheel material, and to secure the strength required for the wheel, and further, to secure the strength required for the design portion and the rim portion. An object of the present invention is to obtain a method for manufacturing a mold and a wheel, which is capable of reducing the weight by making the intersection of the parts thin.

[0011]

A mold of the present invention has a cavity for forming a disc portion, a design portion, and a rim portion, and a wheel for injecting a molten light alloy from the disc portion to fill the cavity. A low-pressure casting mold, characterized in that cooling means is provided outside the rim portion at the intersection of the design portion and the rim portion, and heat retaining means is provided inside the rim portion at the intersection portion. With this configuration, even if a shrinkage cavity is generated in the thick portion at the intersection of the design portion and the rim portion due to solidification shrinkage, the cooling means outside the rim portion causes the solidification to proceed from the outside of the rim portion to reduce the shrinkage. Gradually push the nest toward the inner part of the rim where there is heat insulation. Then, the shrinkage cavity is not left near the center of the intersection, and the inside of the rim portion of the intersection, which will be described later, is partially deep-worked to a certain degree or more to secure the strength of the light alloy wheel.

In the mold of the present invention, it is preferable to use a breathable metal for at least one of the cooling means and the heat retaining means. The breathable metal has fine pores, and the heat insulating effect of the fine pores increases the effect of cooling and heat retention. Further, the gas generated during casting is released from the fine pores inside the air-permeable metal to reduce gas defects in the material. Further, even if the minute gas remains in the material, the minute gas is made to approach the breathable metal side. Then, it is possible to secure the strength of the wheel by preventing a minute gas from remaining in the vicinity of the center of the intersection and by partially performing deep-following processing on the inner side of the rim portion of the intersection, which will be described later, beyond a steady state. In addition,
As a breathable metal, Shinto Kogyo Porcelax 2
[Product type PM20 to PM40, average pore diameter 3 to 7 μm, porosity about 25%, thermal conductivity (room temperature 0.07 to 0.08 W /
(M · K))] or the like is used.

In the mold of the present invention, it is preferable to provide a heat insulating material on the back surface of the air permeable metal to cover the air permeable metal. When only a breathable metal has a small heat capacity and the heat insulating effect is insufficient, a heat insulating material covering the breathable metal enhances the heat retaining effect. In addition, the heat insulation effect is maintained by changing the size of the heat insulating material according to the size and type of the wheel. As the heat insulating material, kao wool or the like is used.

Next, the wheel manufacturing method of the present invention is characterized in that after the wheel is cast using the above-mentioned mold, the inside of the rim portion at the intersection of the wheels is partially deep-followed. If shrinkage cavities or minute gas defects occur at the intersection of the design part and the rim part, the inside of the rim part of the wheel intersection is partially deep-tracked to remove the shrinkage cavities and minute gas defects. To be done. Then, the inside of the rim portion at the intersection of the wheels is designed so that the strength can be secured even if a deeper-than-steady deep working is partially performed, and the strength of the light alloy wheel is secured. In addition, in the deep chasing processing,
"Partial" refers to the rim portion where shrinkage cavities are likely to collect, and "deep follow-up" usually means that the material of the rim portion has a turning allowance of approximately 2 to 3 mm in the direction substantially perpendicular to the draft. However, it means to machine deeper than the turning allowance of about 2 to 3 mm.

[0015]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below in detail with reference to the drawings. (Embodiment 1) FIG. 1A is a cross-sectional view of a mold 10 for low-pressure casting a spoke type wheel in Embodiment 1, and FIG. 1B is an enlarged view of part A in FIG. . Figure 1 (a)
In FIG. 2 (b), the mold 10 is mainly composed of a lower mold 12, an upper mold 13, and a movable split mold 14, and a disc portion 21a of a wheel material 20a shown in FIG. 2 (a), a 5-spoke design portion 22, and a rim portion. The cavity 11 is formed as an outer flange portion 24a and an inner flange portion 25a which are a part of the rim portion 23a. Further, the molten aluminum alloy is poured from the sprue 18 facing the disk portion 21a to fill the cavity 11.

The movable split mold 14 of the mold 10 includes
On the outer side of the rim portion 23a at the intersection 26 of the design portion 22 and the rim portion 23a, a cooling block 15b having a cooling pipe 15a is provided in a width substantially equal to the width of each root of the five-spoke design portion 22, and cooling is performed. Pipe 15
Cooling water is circulated (indicated by an arrow) through a to cool the cooling block 15b.

On the other hand, the upper die 13 of the die 10 has a five-spoke design portion 22 and a crossing portion 2 of the rim portion 23a.
As a breathable metal 16a on the inner side of 6, a porcerax 2 [product type PM40, average pore diameter 7 μm, porosity about 25%, thermal conductivity (room temperature 0.07 W / (m.
K))] is provided approximately the same as the width of the root of each spoke. In addition, the upper mold 13 is in contact with the back surface of the air-permeable metal 16a and circulates kao wool as the heat insulating material 16b. Further, hot air is blown from the hot air pipe 16c (indicated by an arrow) to keep the air permeable metal 16a at a constant temperature via the heat insulating material 16b. Insulation material 1
6b keeps the entire upper mold 13 area warm.

Next, the wheel 20 shown in FIGS. 2 (a) (b) (c) using the mold 10 shown in FIGS. 1 (a) (b).
The manufacturing method of will be described. First, FIG. 1 (a) (b)
The lower mold 12, the upper mold 13, and the movable split mold 14 are clamped to form the cavity 11. Next, the inside of the holding furnace (not shown) is pressurized, the molten aluminum alloy stored in the holding furnace is poured toward the gate 18 through the stalk, and the disc portion 21a and the design portion 22 in FIG. The rim portion 23a, and the outer flange portion 24a and the inner flange portion 25a that are part of the rim portion 23a are filled. After confirming that the mold temperature has been filled up to the end of the cavity 11 by detecting the mold temperature with the temperature sensor provided in the mold 10 near the inner flange portion 25a, the pressure inside the holding furnace is maintained for a predetermined time, and the cooling pipe Cooling water is circulated from 15a, and hot air is jetted from the hot air pipe 16c.
As a result, the rim portion 2 at the intersection 26 in the mold 10
The outside of 3a is cooled, and the inside of the rim 23a at the intersection 26 is kept warm. Then, shrinkage may occur as the molten aluminum alloy is directionally solidified, and a minute shrinkage cavity 29 may also occur. However, as shown in FIG. 2A, the shrinkage cavity 29 is located inside the intersection 26. Come together. Then, the pressurization in the holding furnace is stopped, the molten metal is returned to the holding furnace, and the wheel material 20a that has completed the solidification is taken out from the mold.

The shrinkage cavities 29 gathered inside the intersecting portion 26 of the wheel material 20a are partially subjected to a deep-cutting processing 27 to, for example, 3 mm or more, so that the shrinkage cavities 29 which become the starting points of the destruction of the wheel 20 are removed. It The strength of the wheel 20 can be ensured by eliminating the shrinkage cavity 29 after the processing by designing the wheel 20 so that the strength is secured even if the wheel 20 is partially deep-cut. Further, the weight can be reduced by partially deep-processing 27 the wheel.

(Embodiment 2) FIG.
It is a deformation | transformation enlarged view of the A section in the metal mold | die 10 of (a). Figure 1
In FIG. 1C, the mold 10 is shown in FIG.
The cavity 11 is formed in the same manner as in (b), and the molten aluminum alloy is injected from the spout facing the disk portion.
I am trying to fill it.

Then, the design portion 22 and the rim portion 23
On the back surface of the movable split mold 14 of the mold 10 at the intersection 26 of a, as a breathable metal 15e, a porcerax 2 made by Shinto Kogyo [Product type PM40, average pore diameter 7 μm, porosity about 25%, thermal conductivity] The ratio (room temperature 0.07 W / (m · K))] is set to be approximately the same as the width of each root of the five-spoke that is the design part 22. Further, cold air is blown from the cold air pipe 15c (indicated by an arrow) to cool the breathable metal 15e.

On the other hand, in the upper mold 13 of the mold 10, a heat insulating block 16d having a recessed back surface is provided inside the intersecting portion 26 of the design portion 22 and the rim portion 23a. It is provided in the upper mold 13 to have substantially the same width, and hot air is ejected (indicated by an arrow) from the tip of the curved pipe of the warm air pipe 16e toward the concave portion of the heat retaining block 12d.
The heat insulating block 16d is kept warm.

Even if the wheel is cast by the low pressure casting method using the mold 10 having the structure shown in FIG.
Similarly, the outside of the rim portion 23a at the intersection 26 is cooled and the inside of the rim portion 23a at the intersection 26 is kept warm. Then, as the molten aluminum alloy is directionally solidified, shrinkage may occur, and minute shrinkage cavities 29 may also occur. However, as shown in FIG.
9 gather inside the intersection 26.

The shrinkage cavities 2 gathered inside the intersection 26.
9 is partially deep-cut to 27 mm or more, for example, so that the shrinkage cavity 29 that becomes the starting point of the destruction of the wheel 20 is removed. Then, by designing the wheel 20 so that the strength is secured even when the wheel 20 is partially deep-processed 27, the shrinkage cavity 29 is eliminated after the processing and the wheel 20 is removed.
The strength of can be secured. Further, the weight can be reduced by partially deep-processing 27 the wheel.

[0025]

EXAMPLES Next, examples and comparative examples will be described. (Example) Using the mold 10 of the first embodiment described above, the inside of the holding furnace was pressurized to 50 to 70 kPa, and Al-Si-Mg was used.
The cavity 11 is filled with a molten alloy (JIS AC4CH equivalent) at about 450 ° C., and has five spokes shown in FIG. 2 (c). The total height H in FIG. 2 (a) is about 250 mm and the rim portion 23a. Has an outer diameter D of about 410 mm and a wall thickness t of about 5 to 1
0 mm, the maximum thickness S of the intersection 26 is about 30 mm, and several castings were performed.
0a. Then, several pieces of the material 20a were taken out again and cut in the axial direction, and the cut surface of the intersecting portion 26 was observed. As a result of the observation, the material 20 in which a small shrinkage cavity 29 has occurred
There was also a, but they were gathered inside the intersection 26.

Next, the material 20a which is not cut in the axial direction was attached to the lathe, and the laminating process including the rim portion 23a was performed.
Here, a deep-following processing 27 generation was given to the inner side of the rim portion 23a of the intersection portion 26, and in the turning processing, the deep-following processing 27 was partially performed by 5 mm. After deep follow-up processing 27, rim portion 2 of intersection 26
Inside the 3a, there was no casting defect such as shrinkage cavity 29, and the aluminum wheel 20 was sound. Further, the aluminum wheel 20 has been reduced in weight by performing the follow-up processing 27 of 5 mm.

(Comparative Example) Mold 10 of FIGS. 1 (a) and 1 (b)
At the intersection 26 of the design portion 22 and the rim portion 23a, a cooling block 15b having a cooling pipe 15a is provided outside the rim portion 23a so as to have a width substantially the same as that of the root of the spoke which is the design portion 22. The cooling water was circulated through (shown by an arrow). On the other hand, the rim portion 2 at the intersection 26
No heat-retaining means was provided inside 3a, and the structure was the same as the conventional one. Then, as in the embodiment, the inside of the holding furnace is 50 to 70 k.
Pressurized to Pa, Al-Si-Mg based alloy (JIS AC
A molten metal (corresponding to 4CH) was filled in the cavity 11 at about 450 ° C., several pieces were cast with the same dimensions as those in the example, and unnecessary parts such as a sprue were removed to obtain a material 20a. Then, several more pieces are taken out of this material 20a and cut in the axial direction,
The cross section of the intersection 26 was observed. As a result of observation, shrinkage nest 2
Some 9 were gathered near the center of the intersection 26.

On the other hand, the material 20a which is not cut in the axial direction was attached to the lathe, and the turning process including the rim portion 23a was performed.
Here, a deep-following processing 27 generation was given to the inner side of the rim portion 23a of the intersection portion 26, and in the turning processing, the deep-following processing 27 was partially performed by 5 mm. After deep follow-up processing 27, rim portion 2 of intersection 26
Some of the inside 3a has a shrinkage cavity 29 exposed,
There was still a need to improve casting quality.

The present invention is not limited to the embodiments and examples, but can be variously modified within the scope of the technical idea of the present invention. For example, the wheels may be magnesium wheels instead of aluminum holes. In addition, the design section is not only a spoke type, but also a mesh type, a fin type,
Dish type, twin spoke type, etc. may be used. Further, the breathable metal may be provided not only on the outer side or the inner side of the rim portion at the intersection of the design portion and the rim portion but also on both of them.

[0030]

As described above in detail, according to the mold and wheel manufacturing method of the present invention, it is possible to eliminate shrinkage cavities at the intersection of the design portion and the rim portion after processing the wheel material. As a result, the strength required for the wheel can be secured, and the weight can be reduced by thinning the intersection of the design part and the rim part.

[Brief description of drawings]

FIG. 1A is a cross-sectional view of a mold 10 for low-pressure casting a spoke type wheel according to the first embodiment, and FIG. 1B is an enlarged view of part A in FIG. 1A. (A) is a sectional view of the mold 10 according to the first embodiment, and (c) is a mold 10 of (a).
FIG. 7 is an enlarged view of a portion A in FIG.

FIG. 2 is an example of a spoke type wheel,
(A) is sectional drawing of the wheel raw material 20a, (b) is sectional drawing of the wheel 20 after processing, (c) shows the front view which looked at the design part 22 in (b) from the outer side.

[Explanation of symbols]

10: Light alloy wheel low pressure casting mold (mold) 11: Cavity 12: Lower mold 13: Upper mold 14: Movable split type 15a: cooling pipe 15b: cooling block 15c: Cold air pipe 15e, 16a: Breathable metal 16b: heat insulating material 16c: Hot air pipe 16d: Heat insulation block 16e: Hot air pipe 18: Yukata 20: Light alloy wheels (aluminum wheels, wheels) 20a: Wheel material 21, 21a: disk part 22: Design department (spokes) 23, 23a: rim part 24, 24a: Outer flange part 25, 25a: Inner flange part 26: intersection 27: Deep chasing 28: opening 29: Shrinkage nest D: Outer diameter H: Total height S: Thickness t: wall thickness

Claims (4)

[Claims] 1. A light alloy wheel low-pressure casting mold having a cavity for forming a disc portion, a design portion, and a rim portion, and injecting a molten light alloy from the disc portion to fill the cavity. A light alloy wheel low-pressure casting mold characterized in that cooling means is provided outside the rim portion at the intersection of the design portion and the rim portion, and heat retaining means is provided inside the rim portion at the intersection portion. 2. A permeable metal is used for at least one of the cooling means and the heat retaining means.
Light alloy wheel low pressure casting mold described in. 3. The light alloy wheel low pressure casting mold according to claim 2, wherein a heat insulating material covering the breathable metal is provided on the back surface of the breathable metal. 4. A light alloy wheel according to claim 1, wherein a light alloy wheel is cast using the low pressure casting mold, and then the inner side of the rim portion of the intersection of the light alloy wheel is partially A method for manufacturing a light alloy wheel, which is characterized by performing deep follow processing.