Method of forming a cooling structure

Abstract

To provide a method for forming a cooling structure which enables improvement of cooling performance while inhibiting occurrence of an air gap.SOLUTION: In a method for forming a cooling structure according to an embodiment, a bush is provided on an inner peripheral surface of a cooling hole provided at a casting mold. The method includes: a step in which a heatable core pin is installed within the cooling hole; and a step in which the cooling hole is filled with a molten metal with the core pin being heated to cast a casting for forming the bush. In a step in which the casting is cast, a temperature at the core pin side in the molten metal filling the cooling hole is controlled so as to be higher than a temperature at the casing mold side.SELECTED DRAWING: Figure 5

Description

Technical Field

[0001] The present invention relates to a method for forming a cooling structure.

Background Art

[0002] Casting molds such as die-casting molds are provided with a cooling structure including a cooling bush or the like that can cool the casting mold by circulating a refrigerant. Patent Document 1 discloses a technique related to a method for forming a cooling structure, which includes a casting process of filling a molten metal into a cooling hole to form a casting, and a bush forming process of forming a bush from the casting on the inner peripheral surface of the cooling hole.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In order to reduce the machining allowance when forming a bush from a casting, there are cases where a casting pin is provided in the cooling hole to cast the casting. When a casting pin is provided in the molten metal, the molten metal also solidifies from the casting pin side, and due to solidification shrinkage, voids may occur at the interface where the outer peripheral portion of the casting for forming the bush and the inner peripheral portion of the casting mold (the inner peripheral surface of the cooling hole) come into contact. The occurrence of such voids may reduce the thermal conductivity and the cooling performance of the cooling structure.

[0005] The present invention has been made to solve such problems, and an object thereof is to provide a method for forming a cooling structure that can suppress the occurrence of voids and improve the cooling performance.

Means for Solving the Problems

[0006] A method for forming a cooling structure according to one aspect of the present invention is A method for forming a cooling structure, comprising providing a bush on the inner peripheral surface of a cooling hole provided in a casting mold, the step of installing a heatable core pin inside the cooling hole, while heating the core pin, filling the cooling hole with molten metal, and casting a casting for forming the bush, In the step of casting the casting, the temperature on the core pin side in the molten metal filled in the cooling hole is controlled to be higher than the temperature on the casting mold side.

[0007] In the method for forming a cooling structure according to one aspect of the present invention, by heating the core pin provided in the cooling hole, the temperature on the core pin side in the molten metal filled in the cooling hole is controlled to be higher than the temperature on the casting mold side, so that the molten metal can be solidified from the casting mold side. Thereby, the influence of solidification shrinkage of the casting can be reduced, and the generation of voids at the interface between the outer peripheral portion of the casting for forming the bush and the inner peripheral portion of the casting mold can be suppressed. Further, by using a heatable core pin, the molten metal can be gradually solidified compared to the case where no core pin is provided, and the generation of voids at the interface can be suppressed. Therefore, according to the method for forming a cooling structure according to one aspect of the present invention, the generation of voids can be suppressed and the cooling performance in the cooling structure can be improved.

Effect of the Invention

[0008] The present invention can provide a method for forming a cooling structure capable of suppressing the generation of voids and improving the cooling performance.

Brief Description of the Drawings

[0009]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Mode for Carrying Out the Invention

[0010] Hereinafter, specific embodiments to which the present invention is applied will be described in detail with reference to the drawings. However, the present invention is not limited to the following embodiments. Also, for clarity of explanation, the following description and drawings are simplified as appropriate.

[0011] <First Embodiment> First, with reference to FIG. 1, the cooling structure 1 formed by using the method for forming a cooling structure according to the first embodiment will be described. FIG. 1 is a schematic cross-sectional view of a casting mold 2 having the cooling structure 1 according to the first embodiment.

[0012] The cooling structure 1 is provided in the casting mold 2. The cooling structure 1 has cooling holes 2a and a bush 5. The bush 5 has a refrigerant circulation part 5a and a connection part 5b.

[0013] The casting mold 2 is combined with, for example, a concave outer mold (not shown) and used as a convex inner mold. The gap between the casting mold 2 and the concave outer mold forms the cavity 2b shown in FIG. 1. The cavity 2b formed by the casting mold 2 and the concave outer mold is filled with molten metal. A casting having a shape corresponding to the cavity 2b is formed by the molten metal filled in the cavity 2b.

[0014] The casting mold 2 is formed using a material excellent in high-temperature resistance. Therefore, when the cavity 2b of the casting mold 2 is filled with molten metal, deformation due to the heat of the molten metal hardly occurs. Also, since the cooling structure 1 is provided in the casting mold 2, the molten metal filled in the cavity 2b can be efficiently cooled. Such a casting mold 2 can be suitably used as a die-cast casting mold.

[0015] As shown in Fig. 1, the casting mold 2 is provided with cooling holes 2a. The cooling holes 2a are preferably provided in the vicinity of the cavity 2b. By providing the cooling holes 2a in the vicinity of the cavity 2b, the molten metal filled in the cavity 2b can be efficiently cooled. Further, the cooling holes 2a are preferably provided at positions where the wall thickness from the cavity 2b to the inner peripheral surface of the cooling holes 2a becomes thin. By thinning the wall thickness from the cavity 2b to the inner peripheral surface of the cooling holes 2a, the molten metal filled in the cavity 2b can be cooled more efficiently. Note that the molten metal filled in the cavity 2b can be cooled not only by cooling using the cooling holes 2a but also by air cooling or water cooling from the outside of the casting mold 2 and the outer mold of the concave mold.

[0016] As shown in Fig. 1, a bush 5 is provided on the inner peripheral surface of the cooling hole 2a. The bush 5 is a metal member having a refrigerant circulation part 5a and a connection part 5b, and is used to cool the molten metal filled in the cavity 2b. The bush 5 is preferably formed using a metal material excellent in corrosion resistance and thermal conductivity. The bush 5 is formed using a metal such as copper or aluminum, for example.

[0017] The connection part 5b is connected to a cooling pipe (not shown). Further, the cooling pipe is connected to a pump (not shown). The refrigerant supplied from the cooling pipe is supplied to the refrigerant circulation part 5a via the connection part 5b. By circulating the refrigerant in the refrigerant circulation part 5a, the casting mold 2 is cooled. The refrigerant circulating in the refrigerant circulation part 5a is not particularly limited as long as it is a fluid that can cool the bush 5. The refrigerant circulating in the refrigerant circulation part 5a is water, for example.

[0018] A nozzle (not shown) may be disposed in the bush 5. The nozzle is connected to the cooling pipe and can pass the refrigerant. The tip of the nozzle may be disposed in the vicinity of the tip of the bush 5. In this case, the refrigerant passes through the cooling pipe and the nozzle and circulates in the bush 5 from the vicinity of the tip of the bush 5 toward the connection part 5b. As described above, by providing the cooling structure 1 inside the casting mold 2, the casting mold 2 can be efficiently cooled.

[0019] Hereinafter, with reference to FIGS. 2 to 5, a method for forming the cooling structure according to the present embodiment will be described. FIG. 2 is a flowchart showing a method for forming the cooling structure according to the first embodiment. FIG. 3 is a schematic cross-sectional view of the casting mold 2 in the step of forming the cooling holes 2a. FIG. 4 is a schematic cross-sectional view of the casting mold 2 in the step of installing the heatable punching pin 6 inside the cooling holes 2a. FIG. 5 is a schematic cross-sectional view of the casting mold 2 in the step of casting a casting for forming the bush 5.

[0020] As shown in FIG. 2, the method for forming the cooling structure according to the present embodiment includes a step of forming cooling holes 2a in the casting mold 2 (step S1), a step of installing a heatable punching pin 6 inside the cooling holes 2a (step S2), a step of filling the cooling holes 2a with molten metal 4 while heating the punching pin 6 and casting a casting for forming the bush 5 (step S3), and a step of forming the bush 5 from the casting (step S4).

[0021] In the method for forming the cooling structure according to the present embodiment, first, as shown in FIG. 3, cooling holes 2a are formed in the casting mold 2 (step S1). Specifically, for example, the casting mold 2 is cut to form the cooling holes 2a. Note that the method for forming the cooling holes 2a in the casting mold 2 is not particularly limited. For example, when casting the casting mold 2, a core having a shape corresponding to the cooling holes 2a may be arranged at a predetermined position, and after the molten metal is solidified, the core may be removed to form the cooling holes 2a.

[0022] Next, as shown in FIG. 4, a heatable punching pin 6 is installed inside the cooling holes 2a (step S2). For example, a heater 7 is provided inside the punching pin 6. Thereby, the punching pin 6 can be heated using the heater 7 provided inside the punching pin 6. The heater 7 is connected to an external control device (not shown).

[0023] Further, a circulation section (not shown) for a heat medium may be provided inside the punching pin 6, and the punching pin 6 may be heated by circulating the heat medium through the circulation section. The heat medium circulating through the circulation section is not particularly limited as long as it is a fluid capable of heating the punching pin 6. The heat medium is, for example, oil.

[0024] Next, as shown in FIG. 5, while heating the punching pin 6, the molten metal 4 is filled into the cooling hole 2a, and a casting for forming the bush 5 is cast (step S3). In the step of casting the casting in step S3, the temperature on the punching pin 6 side in the molten metal 4 filled in the cooling hole 2a is controlled to be higher than the temperature on the casting mold 2 side for casting.

[0025] In this way, by generating a temperature gradient between the casting mold 2 and the punching pin 6, the molten metal 4 can be gradually solidified from the casting mold 2 side. Thereby, the influence of solidification shrinkage of the casting can be reduced, and the generation of voids at the interface between the outer peripheral portion of the casting for forming the bush 5 and the inner peripheral portion of the casting mold 2 can be suppressed. Further, by using the heatable punching pin 6, the molten metal can be gradually cooled and solidified as compared with the case where no punching pin is provided, so that the generation of voids at the interface can be further suppressed. By suppressing the generation of voids at the interface between the outer peripheral portion of the casting for forming the bush 5 and the inner peripheral portion of the casting mold 2, the thermal conductivity between the casting mold 2 and the bush 5 can be increased, and the cooling performance in the cooling structure 1 can be improved.

[0026] Thereafter, the punching pin 6 is removed, the casting formed by solidifying the molten metal 4 is cut, and the bush 5 is formed on the inner peripheral surface of the cooling hole 2a (step S4). In this way, as shown in FIG. 1, the cooling structure 1 including the bush 5 can be formed.

[0027] As described above, according to the method for forming the cooling structure according to the present embodiment, the generation of voids can be suppressed and the cooling performance in the cooling structure can be improved.

[0028] Note that the present invention is not limited to the above-described embodiments and can be appropriately modified without departing from the spirit thereof.

Explanation of Reference Numerals

[0029] 1 Cooling structure 2 Casting mold 2a Cooling hole 2b Cavity 4 Molten metal 5 Bush 5a Refrigerant circulation section 5b Connection section 6 Punching pin 7 Heater

Claims

1. A method for forming a cooling structure, comprising providing a bush on the inner peripheral surface of a cooling hole provided in a casting mold, the method comprising: installing a heatable knockout pin inside the cooling hole; casting a casting for forming the bush while filling the cooling hole with molten metal while heating the knockout pin; in the step of casting the casting, controlling the temperature on the knockout pin side in the molten metal filled in the cooling hole to be higher than the temperature on the casting mold side; heating the knockout pin by circulating heat transfer oil through a circulation part provided inside the knockout pin; A method for forming a cooling structure.

2. The method for forming a cooling structure according to claim 1, further comprising a step of cutting the casting to form the bush on the inner peripheral surface of the cooling hole. The method for forming a cooling structure according to claim 1.

3. heating the knockout pin using a heater provided inside the knockout pin; The method for forming a cooling structure according to claim 1 or 2.

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