JP3159366B2 - Low pressure casting mold - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

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

[0002]

2. Description of the Related Art In a low-pressure casting method generally used for casting a light alloy, a molten metal is laminar-flow-filled at a low speed into a cavity (mainly a combination of an upper mold, a lower mold, and a horizontal mold) formed in a mold. Entrapment of gas and generation of oxides are suppressed as much as possible in other casting methods. Therefore, it is widely used when manufacturing a cast product having high soundness. However, in order to produce a sound product by the low-pressure casting method, it is necessary to maintain the mold surface temperature to a certain high level in order to secure the flow of molten metal at the time of filling the molten metal. Therefore, it takes time for the mold temperature to drop to the product take-out temperature after solidification of the product is completed after filling the molten metal. Therefore, in order to shorten the casting cycle, the mold is actively cooled by gas, water or the like after filling the molten metal.

[0003]

As shown in the sectional view of FIG. 6, most of the light alloy vehicle wheels have a thick disk portion 4 attached to an axle by bolts and nuts, and a mixture of thick and thin walls. And a thin rim 6 to which a tire is attached. Currently, from the viewpoint of improving the fuel efficiency of vehicles, weight reduction of wheels is required. In order to achieve this reduction in weight, the shape of the disc and rim cannot be changed drastically due to the attachment to the vehicle body and tires. Have been done. The method of changing the shape of the design portion is mainly to increase the number of openings and thin portions in the design portion, and the design portion has a complex shape in which openings, thin portions, and thick portions are mixed.

Normally, when a vehicle wheel is manufactured by low-pressure casting, a method is used in which a molten metal is injected from a disk portion 4 at a central portion, and the molten metal is filled in a design portion 5 and a rim portion 6 in this order. As a solidification form after filling the molten metal, directional solidification is performed in the order of the rim portion, the design portion, and the disk portion in order to sufficiently exert the pushing effect of the gate. As described above, under the current situation in which the shape of the design part in which the thick part and the thin part are mixed is complicated, it is very difficult to achieve the directional solidification from the rim part toward the gate.

When water cooling of a mold is introduced for the purpose of shortening the casting cycle, there is a high-temperature holding furnace for holding the molten metal below the lower mold, and it is difficult to cool naturally. A method of providing a cooling path or embedding a chill provided with a water cooling path in a lower mold has been proposed. However, as described above, there is a thin portion in the design part that is in contact with the lower mold, and when water cooling of the lower mold is performed,
In some cases, the solidification of the design part was completed significantly earlier than the thick disk part on the gate side. If there is a solidified portion that breaks the balance of the directional solidification toward the gate, the effect of pressurizing from the gate becomes insufficient and casting defects occur. Therefore, when water cooling is introduced into the lower mold by a conventional method, casting defects may be induced.

In addition, the introduction of water cooling of the mold lowers the surface temperature of the mold as a whole, so that the temperature of the molten metal in the cavity decreases, and the flow of the molten metal tends to deteriorate. Therefore, in order to improve the temperature drop of the molten metal, it is necessary to increase and maintain the mold surface temperature around the tip of the rim portion farthest from the gate in the thin rim portion when water cooling is applied. is there. If the temperature of this portion falls below the optimum temperature, casting defects may occur at the tip of the thin rim portion. In order to raise the mold surface temperature, a method of reducing the thickness of the mold or keeping the temperature with a heat insulating material is considered. However, in most cases, the upper mold is originally fixed to the movable upper mold platen (upper base) by bolting, and the heat of the upper mold in contact with the periphery of the rim portion, which is liable to cause a defect, is low. However, there is a problem that it is difficult to raise the mold surface temperature in this portion because the heat flows to the upper platen (upper base) side which is bolted for fixing by heat conduction. Therefore, when applying water cooling,
It has been difficult to prevent a defect from being generated around the tip of the thin rim farthest from the gate.

[0007] A vehicle wheel has a design property as one of its functions. For this reason, the design surface facing outward when mounted on a vehicle has a number of complicated shapes such as a spoke type, a fin type, and a disk type in which both thick and thin walls are mixed. Therefore, the surface shape of the lower mold in contact with the design surface has a complicated shape according to the shape of the design surface of each wheel. In order to obtain optimal cooling, it is necessary to change the cooling method of the lower mold in various ways depending on the design of each wheel, but the lower mold with a cooling path or the lower mold with a cooling path embedded Designing a mold for each item was costly. The present invention has been made to solve the above problems, and in a mold for manufacturing a light alloy vehicle wheel by low pressure casting, the cycle time can be reduced without inhibiting directional solidification. It is an object of the present invention to provide a low-pressure casting mold that does not cause casting defects in a rim portion.

[0008]

Means for Solving the Problems The present inventors have conducted intensive studies on the heat flow of a low-pressure casting mold in order to solve the above problems. As a result, the lower mold is not cooled directly using a water-cooling route, etc., but is cooled indirectly, so that the temperature gradient of the lower mold due to cooling becomes gentler, and the directional solidification toward the gate is obstructed. And found the present invention. That is, the present invention relates to a low-pressure casting mold used in a low-pressure casting method for filling a molten metal from near the center of a lower mold into a vehicle wheel cavity formed of an upper mold, a lower mold, and a horizontal mold, wherein the lower mold is cooled. A lower mold base fixed to an outer peripheral portion with at least one mold component cooled by a medium , wherein the mold component fixes a lower mold;
Alternatively, it is a lower platen. Also on
For light alloy vehicle wheels composed of mold, lower mold and horizontal mold
Low pressure to fill the cavity with molten metal from near the center of the lower mold
A low-pressure casting mold used for a casting method, wherein the lower mold
At least one mold arrangement in which is cooled by a cooling medium
It is characterized in that it is fastened to the component only at the outer periphery.
Further, it is preferable to fasten the lower mold and the mold components with bolts.

The low-pressure casting mold according to the present invention is a low-pressure casting mold used in a low-pressure casting method in which a molten metal is filled into a vehicle wheel cavity constituted by an upper mold, a lower mold, and a horizontal mold from near the center of the lower mold. In the mold, the lower mold is fastened at the outer periphery with mold components such as a lower mold base and a lower mold platen that fixes the lower mold cooled by the cooling medium. It can be cooled and shorten the casting cycle while promoting directional solidification towards the gate. Normally, when cooling the mold, a method of directly cooling a portion having a high temperature, that is, in the case of such a lower mold, near a center gate portion is employed. However, such cooling not only hinders directional solidification, but also makes the temperature distribution in the lower mold non-uniform, which may cause casting defects. On the other hand, since the low-pressure casting mold of the present invention cools indirectly, it is inferior to direct cooling in terms of cooling efficiency as compared with direct cooling, but does not hinder directional solidification. Since the uniformity of distribution is maintained,
A sound casting can be manufactured. Further, since the contact area of the contact portion between the outer periphery of the lower mold and the lower mold base or the lower mold platen can be arbitrarily changed, the cooling amount can be controlled in proportion to the contact area. In addition, the lower mold, the lower mold base and the lower mold platen are fastened with bolts, so that the lower mold and the lower mold base and the lower mold platen can be easily removed, adhere to each other, and improve thermal conductivity. .

[0010] Further, among the lower mold parts which are in contact with a design surface facing outward when mounted on a vehicle, a lower mold base or a lower mold platen provided with a water cooling path is provided in each lower mold having various designs. It is common to the above, and it is possible to deal with vehicle wheels of different designs by replacing only the lower mold. Therefore, there is no need to provide a water cooling path in the lower mold for each item or to embed a chill having a water cooling path, so that the cost of the mold can be reduced. In addition, a heat insulating material with high compressive strength is inserted between the upper mold and the mold component parts, and the heat insulation effect is increased by tightening bolts. By not lowering the surface temperature of the upper die in contact with the tip of the thin rim, it is possible to prevent defects from occurring at the tip of the rim.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A preferred mold structure of a vehicle wheel according to the present invention will be described below with reference to the drawings. (Embodiment 1) FIG. 1 shows a first embodiment. The first embodiment shows a case where the lower mold is fixed to a lower mold base as a mold part by bolting. The cavity of FIG. 1 has a lower mold 7 having various surface shapes depending on wheel design, an upper mold 8 above the horizontal mold, and a horizontal mold sliding to the left and right arranged to fit the lower mold 7 and the upper mold 8. 9 and 10 are basically configured. The molten metal stored in the holding furnace 1 is pressurized with a pressurized gas, and ascends the stalk 2 and the sprue insert 3 to fill the cavity. The cavity is composed of a thick disk portion 4, a thin and thick mixed design portion 5, and a thin rim portion 6 in this order from the gate side. The design portion of the wheel facing outward when mounted on the vehicle has various shapes, and these are formed by the lower mold 7. This lower mold 7
It is fastened by bolts 12 to a lower mold base 11 fixed on a lower platen 16 of the casting machine by clamps (not shown) or the like. The lower mold base 11 is provided with a cooling water passage 13 through which cooling water flows. The effect of the water cooling is transmitted to the lower mold 7 only through the contact surface 14 between the lower mold 7 and the lower mold base 11 by bolting. You. There is a gap 15 between the side surface of the lower mold 7 and the lower mold base 11, and there is no heat conduction therefrom. The cooling amount can be controlled by arbitrarily changing the area of the contact surface 14 between the lower die 7 and the lower die base 11. FIG. 5 shows an example in which the temperature distribution of the lower mold surface of this embodiment and the conventional example are measured. FIG. 5 shows that the present embodiment has a temperature gradient toward the gate on the surface of the mold and promotes directional solidification as compared with the conventional example.

Next, the contact surface 14 between the lower mold 7 and the lower mold base 11
FIGS. 3 and 4 show an embodiment in which the area is changed arbitrarily. These are obtained by changing the shape of the contact surface with the lower mold base 11 of the lower mold 7 to change the area of the contact surface 14 (the hatched portion in the figure), and it is possible to obtain a cooling effect proportional to the contact area. I understand. The upper die 8 is fastened to a vertically movable upper platen (upper base) 17 by a bolt 19 via a heat insulating material 18 having a high compressive strength in a high temperature range. With this configuration, the temperature of the rim portion can be raised by 20 to 30 ° C. as compared with the case without the heat insulating material, and no casting defects occurred.

(Embodiment 2) The second embodiment shows a case where the lower die is fixed to a lower die platen as a part of a casting machine by bolting. In FIG. 2, the lower mold 7 is directly fixed to the lower platen 16 of the casting machine by the bolts 12.
The lower mold platen 16 is provided with a cooling water path 13, and this water cooling effect is transmitted to the lower mold 7 only by the bolted contact surface 14. Others are exactly the same as the first embodiment.

[0014]

According to the present invention, the lower mold is indirectly cooled.
This reduces the temperature gradient of the lower mold due to cooling.
Low pressure that does not hinder directional solidification towards the gate
A casting mold was obtained. Also, the lower mold is a mold configuration
Because the part and the outer periphery are fastened only,
Thus, a cycle time can be reduced while performing directional solidification for indirectly and uniformly cooling, and a low-pressure casting mold having no casting defects in the rim portion can be obtained.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of a vehicle wheel mold structure according to a first embodiment of the present invention.

FIG. 2 is a cross-sectional view of a vehicle wheel mold structure according to a second embodiment of the present invention.

FIG. 3 is a plan view of a lower mold base of the vehicle wheel mold according to the first embodiment of the present invention.

FIG. 4 is a plan view of a lower die base of the vehicle wheel mold according to the first embodiment of the present invention.

FIG. 5 is a surface temperature distribution of the lower mold before and after the first embodiment of the present invention is performed.

FIG. 6 shows a sectional view of a vehicle wheel.

[Explanation of symbols]

1 holding furnace, 4 disk section, 5 design section,
6 rim, 7 lower die, 8 upper die, 9, 10 horizontal type, 11 lower die base, 13 cooling water path, 14 contact surface, 16 lower die platen, 17 upper die base, 1
8 Insulation

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) B22D 18/04 B22C 9/06

Claims (6)

(57) [Claims] 1. A light alloy comprising an upper mold, a lower mold, and a horizontal mold.
From the center of the lower mold into the cavity for the vehicle wheel
For low-pressure casting molds used in low-pressure casting method for filling hot water
The lower mold is cooled by a cooling medium at least.
Is also fastened to the outer periphery of one mold component,
The component is a lower mold base that fixes the lower mold.
Mold for low pressure casting. 2. A light alloy comprising an upper die, a lower die, and a horizontal die.
From the center of the lower mold into the cavity for the vehicle wheel
For low-pressure casting molds used in low-pressure casting method for filling hot water
The lower mold is cooled by a cooling medium at least.
Is also fastened to the outer periphery of one mold component,
Low pressure casting characterized in that the component is a lower platen
Mold. 3. A low-pressure casting mold used in a low-pressure casting method for filling a molten metal into a light alloy vehicle wheel cavity formed of an upper die, a lower die, and a horizontal die from near the center of the lower die. A low-pressure casting mold, wherein the lower mold is fastened to at least one mold component cooled by a cooling medium only at an outer peripheral portion. 4. The low-pressure casting mold according to claim 3, wherein the mold component is a lower mold base for fixing a lower mold. 5. The low pressure casting mold according to claim 3, wherein the mold component is a lower mold platen. 6. An upper rim end cavity through an insulating material.
The low pressure casting mold according to any one of claims 1 to 5 , wherein the vicinity of the mold is fastened to a mold component.