JPH08323447A - Resin core for casting - Google Patents

Abstract

PURPOSE: To prevent generation of shrinkage of the surface wall of a cavity part due to a thickness part in a casting. CONSTITUTION: A resin core 15 consists of a cylindrical resin part 20 and a copper pipe 21 inserted into the axial direction of the resin part. A supply block 22, which supplies cooling water as a cooling medium into the pipe 21, is connected to one side of the pipe 21. The pipe 21 devides its pipe passage into a outgoing route 24 and a return route 25. A water supply route 26 and a drain route 27 are formed corresponding to the outgoing route 24 and the return route 25. A heat transfer quantity of the resin part 20 is substantially increased by the pipe 21, roughly on equal heat transfer is executed to both a die 17 and a resin core from a thickness part 17, thus, generation of shrinkage is prevented.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a casting resin core for use in a molding apparatus using a resin core, which prevents the occurrence of sink marks on the surface wall of the hollow portion caused by the thick portion of the cast product. .

[0002]

2. Description of the Related Art Casting products having a hollow portion such as a cylinder are
It is cast by a molding device using a core. The core is generally made of synthetic sand, but a resin core is used when the shape of the hollow portion is required.

[0003]

However, in the conventional molding apparatus using the resin core, when the casting 1 has the thick portion 2 such as the flange and the protrusion as shown in FIG.
There is a problem in that the sink mark 4 is generated on the surface wall of the hollow portion inside the thick portion in the cast product 1 and the shape of the hollow portion 3 cannot be obtained.

That is, a cast product, a resin core, and a mold (not shown)
Have different thermal conductivity (when the casting is aluminum and the mold is made of alloy, the ratio of the thermal conductivity of aluminum, resin, and mold is 1840: 1: 360). Since it is remarkably small, as shown in FIG. 5 (B), when the resin core 5 is not removed, the temperature of the thick portion 2 is higher than the surroundings and the thick portion 2 shrinks at the end, The inner wall of the hollow portion inside the thick portion recedes from the resin core 5, and a gap 4'which becomes the sink mark 4 is formed.

In view of the above-mentioned problems of the prior art, the present invention has a technical problem to be solved to ensure the shape of the surface wall of the hollow portion in the cast product regardless of the presence of the thick portion.

[0006]

[Means for Solving the Problems] The cause of the sink mark is that the thermal conductivity of the resin core, that is, the amount of heat flowing through the resin core when the temperature gradient is constant is extremely smaller than that of the mold. I thought it would be better to increase the amount of heat transfer of the child. That is, the invention of claim 1 which has solved the above-mentioned problems is a resin core for casting for forming a hollow portion in a casting formed in a cavity of a mold, wherein the resin portion of the resin core is It is characterized in that a good thermal conductor is fitted in the.

In a preferred embodiment, the thickness ratio between the resin portion and the good thermal conductor in the longitudinal cross-sectional direction of the resin core is preferably larger than that of the resin portion. Further, it is preferable that the good heat conductor fitted in the resin portion is provided with an outer portion protruding from the resin portion, and the outer portion serves as a heat radiation portion. The invention of claim 2 is characterized in that the good heat conductor is a pipe capable of circulating a fluid cooling medium, and the cooling medium supply block is attached to an opening end portion of the pipe.

Here, as the good heat conductor, copper, nickel, silver or the like can be used. In short, it is sufficient if it has a higher thermal conductivity than the material used for the mold and a higher melting point than the cast product.

[0009]

In the resin core according to the first aspect of the present invention, the heat of the molten cast product is transferred to the good heat conductor inside through the resin portion. That is, the good heat conductor can increase the substantial amount of heat transfer in the resin portion of the resin core. Therefore, when the thick portion cools and shrinks, heat is transferred to the thick portion substantially evenly in both the mold and the resin core.
Therefore, when the thick portion cools and shrinks, the thick portion shrinks almost uniformly in both the mold and the resin core, preventing the occurrence of sink marks on the surface wall of the hollow portion inside the thick portion. be able to.

According to the second aspect of the invention, since the cooling medium can be circulated in the pipe made of a good heat conductor, the amount of heat for moving the resin portion to be transferred to the pipe can be increased. In other words, the transfer of heat to the pipe made of a good heat conductor becomes efficient. Therefore, for example, even if the ratio of the thermal conductivity of the mold to the thermal conductivity of the resin core is large or the resin core has a large wall thickness, it is possible to prevent the occurrence of the sink mark.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A casting resin core according to an embodiment of the present invention will be specifically described below with reference to the drawings. The cast product of the molding apparatus shown in FIG. 1 is an example of a master cylinder for brakes and clutches, and shows a cross section at the stage of cooling the cast product. In FIG. 1, reference numeral 11 is, for example, a lower die in which a recess 13 having an outer shape approximately half that of the cast product 12 is formed. In the recess 13 of the lower die 11, a hollow part 14 of the cast product 12 is formed. A resin core (hereinafter abbreviated as “resin core”) 15 is fitted therein.

The cast product 12 has a cylindrical shape in which the molten aluminum 16 is filled in the outer space of the recess 13 which is removed by the resin core 15, and a thick portion is formed by forming a protrusion on one side of the cylindrical shape. 17 and a cylindrical portion 19 in which a rod 18 is inserted in parallel with the thick portion 17. Resin core 15
As shown in FIG. 2, it comprises a tubular resin portion 20 and a copper pipe 21 fitted in the axial direction of the resin portion 20 by molding, press fitting or the like. Here, the pipe 21 penetrates the resin portion 20, and a supply block 22 for supplying cooling water as a cooling medium into the pipe 21 is connected to one end side thereof. As shown in FIG. 3, the pipe 21 is divided into a forward path 24 and a return path 25 by a partition plate 23, and the supply block 22 has a water supply path 26 and a drainage path corresponding to the forward path 24 and the return path 25. A path 27 is formed. The water supply passage 26 and the drainage passage 27 are connected to connecting portions 28 and 29 for connecting to a hose of a cooling water facility (not shown).

As shown in FIG. 4, the molding apparatus using the resin core 15 having the above structure has a recess 13 of the lower mold 11, as shown in FIG.
Then, the resin core 15 having the supply block 22 attached thereto is loaded, the bar 18 is set in the space 19 ′ for forming the tubular portion 19, and the upper mold 30 having the injection port 31 is set to the lower mold 11. Mating. Then, before or immediately after the molten metal is poured, the cooling water is circulated from the supply block 22 to the pipe 21.

By such a procedure, after cooling time,
In the space 17 ′ for forming the thick portion 17, the thick portion 17
It is possible to mold the cast product 12 having the rod member 18 inserted in the space portion 19 '. Cast product 12 after molding
Removes the resin core 15 and takes it out. As described above, according to the molding apparatus using the resin core 15 in which the copper pipe 21 is fitted inside and the cooling water is circulated in the pipe 21, the resin portion 20 is formed by the pipe 21.
The amount of heat transferred to the mold is substantially increased, and the amount of heat transferred to the lower mold 11 and the upper mold 30 can be balanced. Therefore,
When the thick portion 17 cools and contracts, heat is transferred to the thick portion 17 substantially evenly in both the mold and the resin core. Therefore, when the thick portion 17 cools and shrinks, the thick portion 17
It is possible to prevent both the lower mold 11 and the upper mold 30 and the resin core 15 from contracting substantially evenly, and to prevent sink marks from being generated on the surface wall of the hollow portion inside the thick portion.

As another embodiment, if a good heat conductor such as solid copper is fitted in the resin portion 20 instead of the pipe 21,
The same effect as that of the above embodiment is obtained. In this case, it is preferable to provide a heat radiating portion on the outer portion of the good thermal conductor protruding from the resin portion 20. Further, in each of the above embodiments, the resin portion 20 may be thin.

[0016]

As described above, according to the invention of claim 1, the good heat conductor fitted in the resin core can increase the substantial amount of heat transfer of the resin core. So
It is possible to prevent the occurrence of meat sink regardless of the presence of the thick portion. According to the invention of claim 2, the heat is efficiently transferred to the pipe made of the good heat conductor, and the effect of preventing the occurrence of the sink mark is enhanced.

[Brief description of drawings]

FIG. 1 is a sectional view showing a molding apparatus using a casting resin core according to an embodiment of the present invention.

FIG. 2 is a transverse sectional view showing the casting resin core.

FIG. 3 is a vertical sectional view showing the casting resin core in more detail.

FIG. 4 is a perspective view for explaining a work procedure of the molding apparatus.

5A and 5B are a horizontal cross-sectional view and a vertical cross-sectional view for explaining the problems of the conventional resin core.

[Explanation of symbols]

12 is a cast product, 15 is a resin core for casting, 20 is a resin portion, 21 is a pipe, 22 is a supply block, 23 is a partition plate, 24 is an outward path, 25 is a return path, 26 is a water supply path, and 27 is a drainage path. The same elements will be denoted by the same reference numerals.

 ─────────────────────────────────────────────────── ─── Continued Front Page (72) Inventor Tadahiko Obama 2-1-1 Asahi-cho, Kariya City, Aichi Aisin Seiki Co., Ltd.

Claims (2)

[Claims] 1. A casting resin core for forming a hollow portion in a casting formed in a cavity of a mold, wherein a good heat conductor is fitted in the resin portion of the resin core. A resin core for casting, characterized in that 2. The good heat conductor is a pipe capable of circulating a fluid cooling medium, and the cooling medium supply block is attached to an open end of the pipe. The casting resin core described.