JPH0999356A - Metallic mold for casting aluminum wheel - Google Patents

Abstract

PROBLEM TO BE SOLVED: To lower the temp. at a high temp. part, to shorten solidifying time of molten metal, to reduce the difference between the temps. in an inner part and an outer part of a metallic mold and to prevent the development of surface crack caused by thermal stress by arranging an annular passage for coolant on a contact surface between a designing mold and a backup mold and specifying the thickness of a thin part in the designing mold. SOLUTION: A lower metallic mold 1 is divided into the design mold 2 and the backup mold 3 and since the inside passage 16 for coolant can arrange a desirable cooling area while making the distance from a gate part 8, hub surface 13 and feeder part 25 almost the same target value, the surface temp. of the metallic mold can be made to a suitable temp. Further, the thickness (h) at the thin part in the design mold 2 is divided into small molds such thin thickness as <=30mm and the whole temp. difference can be made to small. Further, since an inlet and an outlet holes 19, 20 of the passages 16, 17 for coolant are arranged in the backup mold 3, the concentration of the thermal stress to the outer periphery in the design mold 2 is not developed and there is little probability of cracking from the outer periphery.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention fills a molten metal from a lower central portion of a mold by low pressure casting or die casting,
The present invention relates to a mold for casting an aluminum wheel. Further, according to the present invention, when the mold cavity is filled with the molten metal and casting is performed, a local temperature rise of the mold at a thick portion such as a central gate portion, a hub portion and a rim flange portion is prevented. Therefore, the cooling time of the casting is shortened, the temperature unevenness of the mold is eliminated, the generation of thermal stress is prevented, and the life of the mold is extended.

[0002]

2. Description of the Related Art Generally, in order to prevent a local temperature rise in a casting die or the like, a hole for passing cooling water is formed near a portion of the die where the temperature is high. In some cases, it may be difficult to make a hole for cooling water near the target location.

In the case of an aluminum wheel mold, the gate for filling the cavity with the molten metal is located in the center, and the hub portion of the aluminum wheel has a large wall thickness, so that the amount of heat released from the molten metal during casting is large and the temperature rises. Although it is large, it is difficult to make a hole for cooling water. Especially, in the case where the offset of the mounting surface of the aluminum wheel is small and the central part of the lower mold rises and becomes thick, it is close to the gate exit,
It is difficult to make a hole for cooling water near the surface of the hub, and the amount of heat released by the melt causes the temperature near the surface of the center of the mold to become extremely high.

When the temperature of the central portion of the mold becomes high, circumferential thermal stress acts on the outer periphery of the mold, and the radial drill holes formed as the inlet and outlet passages for the cooling water have the above-mentioned effects. Stress concentration is further superimposed on thermal stress, and cracks are more likely to occur. Moreover, when a mold release agent mixed with water for mold release at the time of casting is sprayed on the high temperature part, the surface is rapidly cooled due to the latent heat of the water, but there is also a time delay in the heat conduction of the mold. Therefore, the temperature inside the mold remains high, and the temperature difference between the mold surface and the inside becomes very large, causing large tensile thermal stress on the surface and causing cracks. On the other hand,
If the mold temperature is too high, the solidification time of the molten metal in the cavity will be long during casting, the casting cycle time will be long, and the productivity will be poor.

FIGS. 5 and 6 show an example of a conventional die for forming an aluminum wheel. In the figures, 1 is a lower die having a vertical melt passage in the center, that is, a fixed die. , 4 is an upper mold, that is, a movable mold, 5 is a slide core mounted on the upper mold 4 so as to be slidable in a horizontal direction, and 6 is mounted in a lower central part of the lower mold 1 with its tip portion inserted. The injection sleeve, 7 is an injection plunger slidably arranged in the injection sleeve 6, 8 is a gate portion, 9 is a gate cutting pin attached to the upper mold 4, 10 is a cavity, and molten metal 11 is contained in the cavity 10. It is a cast product that becomes an aluminum wheel by being cast and molded.

The lower die 1 is formed as an integrated body,
In the lower mold 1, as shown in FIGS. 5 and 6, for several cooling mediums extending straight upward in an oblique direction from the outer peripheral bottom surface to the direction in which the inner upper core is slightly removed. A hole 12 is provided. The cooling medium holes 12 are adjacent to each other and intersect each other on the way, and the outer end portion of the cooling medium hole 12 has an inlet 12
Except for a and the outlet 12b, they are plugged by plugs 12c, respectively, and the cooling medium flowing from the inlet 12a passes through the cooling medium hole 12 in a star shape and flows out from the outlet 12b.

As described above, since the conventional lower mold 1 is an integrated type, the cooling medium hole 12 cannot be formed in a ring shape by a drill hole, and the inner surface of the gate portion 8 or the hub surface 13 portion. It was difficult to get close to, and the temperature was uneven. Therefore, the temperature of the center of the mold becomes high, the temperature difference with the outside is large, and the temperature of the center and the inside of the mold generated when cracks are generated by thermal stress and the mold release agent is sprayed. There were many cracks due to thermal stress due to the difference.

[0008]

[Problems to be solved] In order to reduce the thermal stress, a hole for a cooling medium is brought as close as possible to a high temperature part to cool it, and the temperature of the high temperature part is lowered to spray a release agent. It is necessary to reduce the temperature difference between the inside and the outside, and divide the mold to reduce the temperature difference generated in each mold. However, when the molds are divided, problems occur in the passage of the cooling medium and the entrance / exit of each mold, prevention of leakage of the cooling medium, and heat conduction between the contact surfaces of the two.
If the temperature of the hot part of the mold can be lowered, the solidification time of the molten metal such as aluminum in the cavity during casting can be shortened.

[0009]

In order to solve the above problems, the present invention provides a lower mold of an aluminum wheel casting mold, that is, a fixed mold, with a design mold on the upper surface side having cylindrical holes in the center. It is divided into two disk-shaped molds consisting of the backup mold on the lower surface side, and the central cylindrical protrusion of the design mold on the upper surface side is inserted into the backup mold on the lower surface side to prevent misalignment and By locating the cooling medium passage on the split surface of the mold, it is possible to bring the cooling medium passage closer to the part with a large amount of absorbed heat, lower the temperature of the high temperature part, and In addition to shortening the solidification time of molten metal such as aluminum and improving productivity, the temperature difference between the inside and outside of the mold when spraying the release agent is reduced to prevent the occurrence of surface cracks due to thermal stress.

The thin portion of the design type has a thickness of 30 mm.
By doing the following, this also reduces the temperature difference between the front and back,
Prevents generation of large thermal stress. In the case of a metal mold for an aluminum wheel of an automobile, in view of the size, size, and shape of the aluminum wheel, if the thickness of the design mold is increased, the temperature difference between the front and back becomes large, which causes inconvenience. It was set to 30 mm or less. In addition, on the contact surface between the design type and the backup type, a horizontal portion or a portion near the horizontal portion, which is provided with one or two cooling medium passages on the outer periphery of the concavo-convex fitting circular portion in the central portion, and this horizontal portion. Parts or near-horizontal parts are formed with contact surfaces extending in the vertical direction, and ring-shaped cooling medium passage ports provided on the contact surfaces of the design type and the backup type are provided in the backup type. .

By dividing the lower mold into two disc-shaped molds, a design mold on the upper surface side and a backup mold on the lower surface side,
Generally, the design mold is divided into the high temperature part and the backup mold is divided into the low temperature part, and the temperature difference between the molds is smaller than that of the conventional integrated mold, and the thermal stress generated in the mold is reduced. Mold life is extended. Further, since the backup mold is not provided with the holes for the entrances and exits to the passage for the cooling medium, the design mold having a large temperature difference and high thermal stress does not have a stress concentration portion, and the life of the mold is extended. Since the backup type has low thermal stress, there is no problem even if the inlet and outlet of the cooling medium passage are provided because the stress is low.

[0012]

[Function] The temperature of the mold rises by absorbing and accumulating the solidification heat and sensible heat of the cast aluminum or the like. This heat is absorbed by the cooling medium flowing through the cooling medium passage. Generally, the mold surface temperature is θ ₀ , the passage wall surface temperature is θ ₁ , and the heat passage area is A. Assuming that the distance is 1, the heat quantity Q is Q = λ (θ ₀ −θ ₁ ) A /
Determined by l. Here, λ is the thermal conductivity of the mold material.

In the case of casting, if the casting cycle time is constant, the absorbed heat amount = passing heat amount is constant, so (θ ₀
−θ ₁ ) is proportional to l. That is, in order to keep the mold temperature low, it is necessary to provide cooling medium passages near the gate and hub that require heat absorption and near the thick part at the intersection of the spoke and rim. Can be realized by dividing the mold and providing a cooling medium passage on the split surface, that is, the mating surface, as shown in FIG.

When a cooling medium passage is provided on the mating surface, packing is installed around the passage so as to prevent the cooling medium from leaking, but it is designed so that there is no clearance for the packing due to deformation of both molds. There must be. In general, the design type has a high surface temperature and the inside temperature in contact with the backup type is low, so if the temperature difference increases after repeated casting, the shape changes to medium-high and packing around the cooling medium passage near the center Since there is a possibility that there will be no control margin, it is necessary to suppress the deformation with tightening bolts. However, if the deformation force is large, there is a possibility that the normal bolt tightening force will be insufficient.

The force P required to suppress this deformation is calculated as follows: P∝Q × h ^3, that is, the force P to suppress deformation is the cube of the absorbed heat Q of the mold and the thickness h of the design. Proportional. Here, since Q depends on the shape of the cast product, it is necessary to reduce h in order to reduce P. For this reason, make sure that the die is thin.
The design type is tightened to the backup type with bolts of a size that is less than mm and can be used normally, preventing deformation and preventing leakage of the cooling medium.

[0016]

DETAILED DESCRIPTION OF THE INVENTION An embodiment of the present invention will be described with reference to FIGS. 1 and 2, 1 is a lower mold or a fixed mold, 2 is a design mold on the upper surface side of the lower mold 1, 3 is a backup mold on the lower surface side of the lower mold 1, 4 is an upper mold or movable Mold, 5 is a slide core of the upper mold 4, 6 is an injection sleeve, 7 is an injection plunger, 8 is a gate part, 9 is a gate cutting pin, 10 is a lower mold 1, an upper mold 4 and a slide core 5. The cavities 11 formed in the space between the cavities 11 and 12 are castings which are the molten metal or the solidified product of the aluminum alloy or the like which is cast and filled in the cavities 10 by the injection plunger 7. 26 is a window portion of the design type 2, and 27 is a spoke portion. The thickness h of the thin portion of the design mold 2 was set to 30 mm or less in order to reduce the temperature difference between the front and back and prevent the occurrence of large thermal stress.

The design mold 2 and the backup mold 3 have a cylindrical hole which is a vertical gate portion 8 in the central portion, and the cylindrical protrusion 14 provided on the lower side of the center of the design mold 2 is the backup mold. Designed type 2 that is inserted into the mating part of and sealed
It is designed to prevent misalignment between the backup mold 3 and the backup mold 3. The cylindrical protrusion 14 and the fitting portion form a circular portion that fits in an uneven shape. A horizontal portion 15 or a portion close to the horizontal portion is formed on the outer periphery of the circular portion. The horizontal portion 15 or a portion close to the horizontal portion has a ring-shaped inner passage 16 for the cooling medium and a ring-shaped cooling medium. An outer passageway 17 for the medium is provided. The inner and outer passages 16 and 17 are formed by aligning a ring-shaped groove provided on the lower surface of the design mold 2 with a ring-shaped groove provided on the upper surface of the backup mold 3. The passages 16 and 17 may have one line, but two lines are more efficient.

Vertically extending contact surfaces 18 are provided on both inner and outer sides of the horizontal portion 15 or a portion near the horizontal portion where the ring-shaped inner passage 16 and outer passage 17 are provided. The inner passage 16 and the outer passage 17 are connected to the tips of two holes 19 and 20 obliquely formed in the backup mold 3. In addition, between the portions where the two holes 19 of the inner passage 16 intersect, and
Between the portions where the two holes 20 of the outer passage 17 intersect, as shown in FIG.
Is installed so that the cooling medium does not flow directly between the two holes 19 and 20. A packing 23 such as an O-ring is provided on each of the horizontal portions 15 on both sides of the inner passage 16 and the outer passage 17. Reference numeral 24 is a tightening bolt for attaching the design mold 2 to the backup mold 3.

In the present invention, as shown in FIGS. 1 and 2, the lower mold 1 is divided into a design mold 2 and a backup mold 3, and the inner passage 16 for the cooling medium is connected to the gate portion 8 Since the distance from the hub surface 13 and the riser portion 25 can be set close to the target numerical value 1 and the cooling area can be set in a desired cooling area, the mold surface temperature can be set to an appropriate temperature. Therefore, the thermal stress generated on the surface of the mold when the mold release agent is sprayed is not so large, cracks are less likely to occur, and the life is extended. On the other hand, the outer passage 17 can also be designed with an appropriate distance and area to absorb the amount of heat radiated from the cavity 10.

In the design mold 2, the thickness h of the thin portion is 30
Since it is divided into thin and small parts of less than mm, the temperature difference of the whole can be reduced, and moreover, the cooling medium passages 16 and 1
Since the holes 19 and 20 for the entrance and exit to 7 are provided in the backup mold 3, there is no stress concentration of thermal stress on the outer periphery of the design mold 2, and there is almost no probability of cracking from the outer periphery. Since the backup mold 3 has a small portion in contact with the molten metal 11, the temperature rise is small, the thermal stress is small, and the passages 16 and 17 for the heat medium are formed.
Even if the holes 19 and 20 for the entrance and exit are provided, it will not be destroyed.

Around the inner passage 16 and the outer passage 17 for the cooling medium provided between the design mold 2 and the backup mold 3, as described above, in order to prevent the leakage of the cooling medium, a packing such as an O-ring is provided. Install 23. However,
When the design mold 2 is deformed due to the temperature difference between the front surface and the back surface of the design mold 2, a gap is generated between the design mold 2 and the backup mold 3, and there is no space to hold the packing 23, and the cooling medium may leak. Therefore, in the present invention, in order to prevent this, as described in the section of action, etc., the design mold 2 is thinned to reduce the temperature difference between the front and back sides to reduce the deformation amount and the thickness. The deformation force of the design mold 2 is reduced by making the mold thin, and the deformation is prevented by tightening with the tightening bolts 24 having a size that can be normally used. The thin mold portion h is set to 30 mm or less.

In order to secure the tightening force, although not shown, a tightening bolt 24 having a hole at the center is used, and when tightening, an electric heater is inserted into this hole for heating. By tightening the tightening bolts 24 at a constant temperature, it is possible to easily prevent the generation of a gap between the design mold 2 and the backup mold 3 due to the deformation of the design mold 2.

[0023]

1 and 2 show an embodiment of the present invention. Reference numeral 2 is a design type of the lower die 1, and 3 is a backup type, which are connected by tightening bolts 24 and are attached to a lower die holder and a fixed platen, which are not shown. 4 is the upper mold, 5
Is a slide core of the upper mold 4, and is attached to the upper mold holder and the movable platen. This figure shows the state of being closed by the mold clamping device.
0 is formed. The molten metal 11 such as an aluminum alloy is pushed up in the injection sleeve 6 by the injection plunger 7 and filled in the cavity 10 to cast a cast product 11 which is an aluminum wheel material. Casting 11 is lower mold 1
It is cut by the gate cutting pin 9 at the gate portion 8 and is taken out from the molds 1 and 4.

When the molten metal 11 is solidified, heat of solidification and sensible heat are released. In particular, since the amount of heat released from the gate portion 8 and the hub portion is large, it is necessary to bring the inner passage 16 for the cooling medium as close as possible for cooling, but in the present invention, the amount of cooling heat of each of the design type 2 and the backup type 3 is reduced. Since a groove having an area corresponding to is processed and aligned, it is possible to make a structure with a value close to the desired value. Both types 2,
3 are connected by a tightening bolt 24, but the amount of deformation can be reduced by reducing the thickness h of the thin portion of the design mold 2, so that the packing 23 around the inner passage 16 shown in FIG. Without overloading
The cooling medium can be prevented from leaking.

A partition plug 21 is attached to a part of the inner passage 16 for the cooling medium, holes 19 for the inlet and outlet of the cooling medium are formed on both sides of the partition plug 21, and the cooling medium is flowed to cool the mold. The entrance hole 19 is a backup type 3
Since it is provided on the
Thermal stress can be reduced and life can be extended. The same applies to the outside passage 17 for the cooling medium.

[0026]

According to the present invention, the lower die of the die for casting the aluminum wheel having the casting port in the center is divided into a disc shape into a design type and a backup type as described in the claims. However, by providing the passage for the cooling medium on the divided surface, it is possible to dispose the passage in the high temperature portion of the mold, and it is possible to prevent an unnecessary temperature rise of the mold. As a result, it is possible to reduce the temperature difference between the surface and the inside of the lower mold, which occurs when the mold release agent is sprayed, and the thermal stress is reduced, so that the occurrence of hair cracks on the surface can be prevented. Of course, the cooling time for casting can be shortened.

Further, by thinning the divided design type, the temperature difference between the front and back is reduced, the deformation amount of the design type is reduced, and the rigidity is reduced. Also, it is possible to suppress the deformation amount so that the cooling medium does not leak from the dividing surface. further,
By reducing the temperature difference of the entire design mold and moving the inlet and outlet of the cooling medium passage to the backup mold, the tensile stress generated on the outer periphery of the design mold is reduced, stress concentration is prevented and the mold life is extended. You can

In addition, when the mold surface temperature is set to an appropriate temperature, the adhesion efficiency of the mold release agent becomes very good, and it is possible to reduce casting defects and consumption of the mold release agent.

[Brief description of drawings]

FIG. 1 is a vertical sectional view showing an embodiment of the present invention.

FIG. 2 is a plan view of a lower mold shown in FIG.

FIG. 3 is an enlarged view of the periphery of the cooling medium passage shown in FIG.

FIG. 4 is a sectional view taken along line AA of FIG. 3;

FIG. 5 is a vertical sectional view showing an example of a conventional mold similar to the present invention.

FIG. 6 is a plan view of a lower mold in FIG. 5;

[Explanation of symbols]

 1 Lower mold (fixed mold) 2 Design mold 3 Backup mold 4 Upper mold (movable mold) 5 Slide core 6 Injection sleeve 7 Injection plunger 8 Gate part 9 Gate cutting pin 10 Cavity 11 Molten metal (cast product) 12 Cooling Medium hole 14 Cylindrical protrusion (circular part) 15 Horizontal part 16 Inner passage 17 Outer passage 18 Vertical contact surface 19,20 Hole 21,22 Partition plug 23 Packing 24 Tightening bolt

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Claims (4)

[Claims] 1. An aluminum wheel casting die comprising an upper die and a lower die having a casting port and a gate portion in a central portion, and a lower die is divided into upper and lower halves to obtain a design die on the upper surface side. An aluminum wheel casting mold in which the backup mold on the lower surface side is fixed with a fixing member, a ring-shaped cooling medium passage is provided on the contact surface between the design mold and the backup mold, and the thin portion of the design mold has a thickness of 30 mm or less. 2. The contact surface between the design type and the backup type is formed with a circular portion fitted in a concavo-convex shape in the central portion and a horizontal portion or a portion near the horizontal portion of the outer periphery of the circular portion. The mold for casting an aluminum wheel according to claim 1, wherein one or two inner and outer cooling medium passages are provided in the horizontal portion or a portion close to horizontal. 3. A contact surface between the design type and the backup type, and a horizontal portion or a portion close to horizontal on the outer periphery of the circular portion,
The mold for casting an aluminum wheel according to claim 1 or 2, wherein a contact surface extending in the vertical direction is formed on each of both sides of the horizontal portion or a portion close to the horizontal portion. 4. A mold for casting an aluminum wheel according to claim 1, wherein the inlet and outlet of the ring-shaped cooling medium passage provided on the contact surface between the design type and the backup type are provided in the backup type. .