JPH085062B2 - Resin molding core - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial field of application) The present invention relates to resin molding used when resin hollow molding of a two-dimensional or more complicated curved resin hollow molding such as an intake manifold of an automobile is carried out in a mold. Regarding the use core.

(Prior Art) Conventionally, as a resin molding core for an intake manifold, for example, as described in JP-A-58-82059, a low-melting-point alloy is hollow-molded by low-pressure casting that applies gas pressure. A hollow core obtained by doing this is known.

(Problems to be Solved by the Invention) However, in such a conventional resin molding core, since it is only a hollow core, the strength is not enough to withstand injection pressure during injection molding. Is required to have a large core thickness, and particularly in the case of a large hollow molded product, the amount of the low melting point alloy is large, the cost is high, and the weight is heavy, which is not suitable for practical use. There was a problem.

(Means for Solving Problems) The present invention has been made for the purpose of solving the above-mentioned problems, and in order to achieve this object, the present invention proposes water disintegration mainly composed of casting sand. The means has a double structure of a sex inner core and a skin core made of a low melting point alloy coated on the surface of the inner core.

(Function) A method for manufacturing a hollow molded body using the resin molding core of the present invention will be described. First, a resin molding core including an inner core and a skin core is set in a predetermined mold, and then, Thermoplastic resin is injected under pressure from the mold's casting port, then the skin core is heated and melted to remove it after the resin is cured, and then water is injected from the void where the skin core has been removed. Thus, the hollow core is obtained by collapsing and discharging the inner core.

Therefore, in the resin molding core of the present invention, the combination of the water-disintegrating inner core mainly composed of sand and the skin core of the low melting point alloy ensures the ease of core ejection after molding. While the thickness of the skin core is reduced, it is possible to secure the pressure resistance against the pressure during molding by the reinforcing effect of the inner core.

(Example) Hereinafter, the Example of this invention is described based on drawing.

In describing this embodiment, a resin molding core used for molding a resin intake manifold of an automobile will be taken as an example.

 First, the configuration will be described.

As shown in FIGS. 1 to 4, the resin molding core A of the embodiment has a water-disintegratable inner core 1 mainly composed of casting sand, and a low core coated on the surface of the inner core 1. It has a double structure with the skin core 2 made of a melting point alloy.

As the water-disintegratable inner core 1, 70 parts by weight of about 145 mesh casting sand, 30 parts by weight of one or more salts selected from sodium or potassium carbonates, sulfates and silicates, and water-soluble Polyvinyl alcohol (polymerization degree 500) 0 to
A raw material is obtained by kneading 30 parts by weight of water containing 4% with a mixer or a blender.

The skin core 2 is made of a tin-bismuth alloy, etc.
A low melting point alloy that melts at a low temperature of about 0 ° C. is used as a raw material.

 Next, the operation will be described.

The method of manufacturing an intake manifold (hollow molded body) using the resin molding core A of the embodiment will be described with respect to three examples.

(First example) Inner core manufacturing method First, the kneading raw material mainly composed of sand is put into a predetermined inner core mold, and fixed into a predetermined shape in consideration of the thickness of the skin core 2 from the hollow portion of the intake manifold. The inner core 1 is formed by consolidating and then drying at 200 ° C. to 250 ° C. for a predetermined time.

Next, the inner core 1 is set as a temporary core in a predetermined core type, and the core type is kept at about 140 ° C. Then, the melted low melting point alloy is injected from a pouring port provided in the core mold.

Then, the low melting point alloy is solidified by cooling or forced cooling, and the inner core 1 and the outer core 2 are removed by removing the core mold.
A resin molding core A according to is obtained.

Hollow Molded Body Manufacturing Method Next, the resin molding core A is set in a molding die, and then a thermoplastic resin is injected under pressure from a casting port of the molding die.

After the resin is hardened, a temperature higher than the melting temperature of the low melting point alloy and lower than the melting temperature of the thermoplastic resin is applied to heat and melt the skin core 2 to remove it.

Further, by injecting water from the void portion where the skin core 2 is removed, the inner core 1 is collapsed and discharged to obtain an intake manifold as a hollow molded body.

(Second Example) The second example is an example in which the same manufacturing method is used as to and in the first example, but the manufacturing method of the epidermal core is different.

′ The inner core 1 formed by the manufacturing method described in “Surface core manufacturing method” is dipped in a molten low melting point alloy to cool and harden the inner core 1 to form a surface core 2 made of a low melting point alloy. To do.

The thickness of the epidermis core 2 is adjusted by the temperature of the inner core 1 and the immersion time.

(Third Example) In this third example, the surface of the outer skin core 2 formed by the outer skin core manufacturing method by the mold method of the first embodiment or the dipping method of the second embodiment is machined with screws. This is an example in which a step of forming a groove or the like is added.

As described above, the resin molding core A of the embodiment
In that case, the following effects can be obtained.

Since the inner core 1 is provided inside, it is possible to obtain a collapsible core that can withstand the injection pressure during resin injection molding.

Water-disintegrating inner core 1 and low melting point alloy skin core 2
After melting and discharging the epidermis core 2, the contact area between the inner core 1 and water can be increased, and the core can be easily discharged.

As described in the third example, the core itself can be machined differently from the core made of only casting sand. Therefore, a hollow molded body having screws or flanges on the inner surface and high inner surface dimensional accuracy are required. It is possible to manufacture a hollow molded article.

Unlike conventional cores made of low melting point alloys, even if the skin core 2 is made thin, it is reinforced by the inner core 1, so the amount of expensive low melting point alloys used can be reduced. The weight of the child itself can also be reduced.

Since the raw materials for the inner core 1 and the epidermis core 2 can be reused by recovering, the manufacturing cost of the hollow molded body can be kept low.

As described above, the embodiments have been described based on the drawings. However, the specific configuration is not limited to the embodiments, and even if there is a design change or the like without departing from the gist of the present invention, it is included in the present invention. .

For example, in the embodiment, an example of the intake manifold is shown as the hollow molded body, but the hollow molded body is not limited to this, and it is particularly applicable to a resin hollow molded body having a two-dimensional or three-dimensional complicated curved shape.

(Effects of the Invention) As described above, in the resin molding core of the present invention, a water-disintegratable inner core mainly composed of casting sand, and a low-cost core coated on the surface of the inner core. 2 with skin core made of melting point alloy
Since it is composed of a heavy structure, the core can be easily discharged after molding, and the inner core can reinforce the pressure resistance during molding due to the reinforcing effect of the inner core while reducing the thickness of the skin core. The effect that it can be obtained.

[Brief description of drawings]

FIG. 1 is a front view showing a resin molding core of an embodiment of the present invention,
2 is a plan view showing the resin molding core of the embodiment, FIG. 3 is a side view showing the resin molding core of the embodiment, and FIG.
It is sectional drawing of the resin molding core by the line II in FIG. A ... Resin molding core 1 ... Water-disintegrating inner core 2 ... Epidermal core

Claims (1)

[Claims] 1. A double structure consisting of a water-disintegrating inner core mainly composed of casting sand and a skin core made of a low melting point alloy coated on the surface of the inner core. Resin molding core.