JP2000061957A - Eluting method of low melting point metal core and eluting device therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To completely eliminate remnant of a low melting point metal, which forms the low melting point metal core in the hollow part of a plastic molding, onto the inner wall surface of the hollow part of the plastic molding. SOLUTION: The low melting point metal core filled in the hollow parts, each of which has a non-releasable shape, of a plastic molding such as an intake manifold 2 is melted through high frequency induction heating and naturally fallen through the hollow parts of the plastic molding so as to flow out of the molding. After that, an injecting liquid L is injected through an opening part formed at the upper end side of the hollow part so as to flow the liquid along its inner wall surface. Thus, the low melting point metal (a core metal) under the molten state, which is left on the inner wall surface by locally adhering, is eluted through the opening part of the plastic molding 2 together with the injecting liquid L.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of immersing a plastic molded product having a hollow portion having a shape that cannot be released from the mold and having a low melting point metal core filled in the hollow portion in an ethylene glycol solution, A low melting point metal core in the hollow part of the plastic molded product is melted by high frequency induction heating in an ethylene glycol liquid, and a low melting point metal in a molten state is eluted from the opening formed in the plastic molded product. The present invention relates to a melting point metal core elution method and an elution apparatus thereof. In the specification of the present application, the term "hollow part having a non-releasable shape" refers to a low-melting-point metal core filled in the hollow part of a plastic molded product during plastic molding in a solid state after completion of plastic molding. A hollow part having a shape that cannot be separated from the hollow part of the molded product (for example, a meandering shape or a bent shape) is meant.

[0002]

2. Description of the Related Art Conventionally, when melting a low-melting-point metal core filled in a hollow portion of a plastic molded product that cannot be released by high-frequency induction heating and eluting it outside the plastic molded product, Is adopted. That is, conventionally, a high frequency induction heating coil is placed in an ethylene glycol liquid heated to a required temperature, a plastic molded product is immersed in the ethylene glycol liquid, and a plastic molded product is placed in the high frequency induction heating coil. High-frequency induction heating coil melts the low-melting-point metal core in the hollow part of the plastic molded product by high-frequency induction heating to melt it, and the molten metal expands in the hollow part of the plastic molded product. When dropped, it is eluted from the opening formed in the plastic molded product to the outside of the plastic molded product.

An example of this type of plastic molded article is an intake manifold for automobiles. As shown in FIG. 8, an intake manifold 2 for an automobile has a plurality of hollow portions (intake pipe portions or pipe portions) 3 therein, and these hollow portions 3 are made of plastic of the intake manifold 2. At the time of molding, the intake manifold main body 2a is molded at the same time. By the way, the hollow portion 3 is usually bent into a complicated shape as shown in FIGS. 8 and 9, and is a so-called non-separable hollow portion 3. Therefore, when the intake manifold 2 is plastic-molded, the core filled in the hollow part 3 is
Since the hollow portion 3 cannot be separated from the inside, the low melting point metal core 4 is filled into the hollow portion 3 as shown in FIG. By taking out the intake manifold 2 in which the metal core 4 is filled in the hollow portion 3 from the split mold and heating it, only the low-melting metal core 4 is melted to the outside of the hollow portion 3 and thus the intake manifold 2. I try to make it elute. The low melting point metal core 4 is made of a metal having a melting point lower than that of the constituent material (plastic) of the intake manifold.

[0004]

However, the conventional method for eluting a low melting point metal core by high frequency induction heating and the apparatus for carrying out this method have the following problems. First, many plastic molded products having a hollow portion that cannot be released are of complicated shapes. For example, as shown in FIGS. 3 and 4, the inner wall surface 3a of the hollow portion (intake pipe portion) 3 which is in contact with the low-melting metal core 4 such as the intake manifold 2 made of a plastic molding has a cylindrical surface or the like. Many have not a simple shape but a complicated shape such as a meandering shape or a bent shape. In the case of a plastic molded product having a hollow portion with such a complicated shape, there are small-sized corners, etc., in which the molten low-melting metal does not easily flow, and the heating temperature tends to be uneven, so Molten metal does not elute outside the hollow part of the molded product,
A trace amount of molten metal may remain in the hollow part of the plastic molded product. In addition, in order to prevent the core metal (metal constituting the low-melting-point metal core) from remaining, it is the actual situation that high frequency induction heating is continuously performed for a long time. The residual metal is overheated by the high frequency induction heating action, which may cause a problem that material deterioration (heat deterioration) is caused in the inner wall surface of the hollow portion of the plastic molded product.

The present invention has been made in view of such problems, and an object thereof is to efficiently elute the low-melting-point metal core in the hollow portion of the plastic molded product. The low melting point metal that constitutes the metal core can be completely prevented from remaining on the inner wall surface of the hollow part of the plastic molded product, and the inner wall surface part of the hollow part of the plastic molded product is deteriorated. An object of the present invention is to provide a low melting point metal core elution method and an elution device thereof.

[0006]

[Means for Solving the Problems] A plastic molded product having a hollow portion having a shape that cannot be released from the mold and having a low melting point metal core filled in the hollow portion is dipped in an ethylene glycol liquid to obtain the ethylene glycol. A low-melting-point metal that melts the low-melting-point metal core in the hollow part of the plastic molded product by high-frequency induction heating in a liquid, and dissolves the melted low-melting-point metal from the opening formed in the plastic molded product. In the core elution method, the low-melting-point metal core is melted by high-frequency induction heating and allowed to elute by spontaneously dropping from the hollow part of the plastic molded product, and then an injection liquid consisting of ethylene glycol is added to the plastic molded product. Through the opening formed on the upper end side of the product, it is jetted to the inner wall surface of the hollow part of the plastic molded product, and along this inner wall surface By moving, the molten low melting point metal in the hollow part partially adhered and remaining on the inner wall surface of the hollow part is eluted together with the injection liquid from the opening of the plastic molded product. There is. Further, in the present invention, after sucking the ethylene glycol liquid in which the plastic molded product is dipped by a pump, it is guided to an opening formed at the upper end of the plastic molded product,
The ethylene glycol liquid is injected into the hollow portion of the plastic molded product through the opening.
Further, in the present invention, (a) an ethylene glycol heat bath in which ethylene glycol liquid is stored; (b) a high frequency induction heating coil arranged in the ethylene glycol liquid in the ethylene glycol heat bath; A fixing jig for fixing a plastic molded product having a hollow portion having an unmoldable shape and having a low melting point metal core filled in the hollow portion inside the high frequency induction heating coil;
A pump for sucking the ethylene glycol liquid in the ethylene glycol heat bath, and (e) an upper end side of the plastic molded product fixed with the fixing jig for the ethylene glycol liquid sucked from the heat bath by the pump. And an ethylene glycol liquid ejecting device for ejecting the ethylene glycol liquid into the opening of the plastic molding, so that the ejecting liquid consisting of the ethylene glycol liquid is injected into the hollow portion of the plastic molded product. Further, in the present invention, the ethylene glycol liquid injection device has a plurality of injection holes having an inclined angle with respect to the inner wall surface of the hollow portion of the plastic molded product. Further, in the present invention, the ethylene glycol liquid injection device has an injection pipe arranged at an angle inclined with respect to a direction orthogonal to the axis of the opening on the upper end side of the plastic molded product.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to FIGS. The embodiments of the present invention described below are examples in which a low-melting-point metal core is eluted from a hollow portion of an automotive intake manifold (automatic plastic intake manifold) that is a plastic molded product.

FIG. 1 shows a high-frequency induction heating type elution device 1 according to an embodiment of the present invention. The elution device 1 includes an intake manifold 2 (a plastic having a hollow portion which cannot be released from the mold). A low melting point metal core 4 filled in the hollow portion 3 of the molded product) when molded by plastic.
(See FIG. 9) is a device for eluting from the hollow portion 3 by high-frequency induction heating in an ethylene glycol liquid.

As shown in FIG. 1, the elution device 1 of this embodiment is an ethylene glycol heat bath 6 for storing the ethylene glycol liquid 5 heated to a required temperature, and an ethylene glycol liquid in the ethylene glycol heat bath 6. 5, a high-frequency induction heating coil 7 for high-frequency induction heating the intake manifold 2, a high-frequency power supply 8 for supplying a high-frequency current to the high-frequency induction heating coil 7 immersed in the ethylene glycol liquid 5, and a heating target (workpiece). A work placement fixture 9 for placing and fixing the intake manifold 2 at a predetermined position surrounded by the high-frequency induction heating coil 7 and a work placement fixture 9 for mounting and fixing the intake manifold 2 are moved up and down. The work elevating mechanism (not shown) and the ethylene glycol liquid 5 in the ethylene glycol heat bath 6 are absorbed. A pump 11 to increase, the pump 1
The ethylene glycol liquid 5 sucked up from the ethylene glycol heat bath 6 at 1 is transferred to the upper end opening 3b (see FIGS. 8 and 9) of the hollow portion 3 of the intake manifold 2 fixed by the work placement fixture 9. And an ethylene glycol liquid jetting device 12 for jetting the ethylene glycol liquid 5. Further, although not shown, an ethylene glycol liquid heating heater for heating the ethylene glycol liquid 5 to a required temperature is provided.

The above-mentioned high frequency induction heating coil 7 is composed of a copper pipe through which a cooling liquid is passed inside (hollow portion), and a low melting point metal core filled in the hollow portion 3 of the intake manifold 2. A heating part (main body) 7a having a plurality of windings for heating and melting 4 by a high frequency induction heating action;
a is provided with a lead portion 7b for supplying a high frequency current from a high frequency power source 8.

Further, the ethylene glycol liquid injection device 12
Is a hollow portion 3 of the intake manifold 2 that absorbs the ethylene glycol liquid 5 sucked from the ethylene glycol heat bath 6 through the suction pipe 13 connected to the pump 11.
Ethylene glycol liquid outlet pipe 14 leading to a position near the upper end opening 3b of the
4 is provided with a switching valve 15 and an ethylene glycol liquid injection ring 16 which is connected to the tip of the ethylene glycol liquid outlet pipe 14 and is opposed to the upper opening 3b.

2 and 3 show an example of the ethylene glycol liquid injection ring 16. The ethylene glycol liquid injection ring 16 has a tip wall 16b of an annular body 16a having an elliptical cross section that substantially matches the cross section of the hollow portion 3a.
A plurality of injection holes 17 each having an angle α and a hole diameter R inclined with respect to the inner wall surface 3a of the hollow portion 3 of the intake manifold 2 (see FIG. 3) and corresponding to the inner wall surface 3a are opened. The jet liquid L consisting of the ethylene glycol liquid 5 stored in the ethylene glycol heat bath 6 is caused to flow along the inner wall surface 3a of the hollow portion 3 of the intake manifold 2 to form the inner wall surface 3a. In the above, the dissolved metal existing in the corners where the dissolved metal is likely to remain is efficiently eluted. When the ethylene glycol liquid injection ring 16 is used, the injection liquid L having a required temperature is injected at an angle α with respect to the inner wall surface 3a as shown by an arrow in FIG. As shown in FIG. 5, the inner wall surface 3a is radially injected with a required pressure, a required flow rate, and a required injection angle α.

On the other hand, FIG. 5 and FIG. 6 show another example of the ethylene glycol liquid injection ring 16. The ethylene glycol liquid injection ring 16 is formed by attaching a plurality of injection pipes 18 (hole diameter R) to a tip wall 16d of a low-reduction cylindrical ring body 16c. In this case, the jet liquid L is transferred to the inner wall surface 3
a plurality of injection pipes 18 in order to efficiently elute the molten metal remaining on the inner wall surface 3b of the injection pipes
6, some of the injection holes have an angle α whose angle is inclined with respect to the direction orthogonal to the axis of the upper end opening 3b of the hollow portion 3 of the intake manifold 2 as shown in FIG.
Corresponding to the inner wall surface 3a of the hollow portion 3 and the remaining several pieces are arranged substantially parallel to the axis. When the ethylene glycol liquid injection ring 16 is used, the injection liquid L having the required temperature is injected at an angle α with respect to the inner wall surface 3a as indicated by an arrow in FIG. 6, as in the case described above. In addition, as shown by the arrow in FIG. 7, the inner wall surface 3a is configured to be sprayed at a plurality of locations on the inner wall surface 3a at a required pressure, a flow rate, and a spray angle α, and spirally flow along the inner wall surface 3b. .

Using the elution device 1 having such a structure, the low melting point metal core 4 in the hollow portion 3 of the intake manifold 2 is used.
The operation procedure and action for dissolving and eluting the sol by high-frequency induction heating are as follows.

(1) First, the intake manifold 2 in which the hollow portion 3 is filled with the low-melting-point metal core 4 is placed and fixed on the work placement fixture 9 at a position above the ethylene glycol heat bath 6. (2) Next, by operating a work elevating mechanism (not shown), the intake manifold 2 is moved downward together with the work placement fixture 9, and the ethylene heated to a predetermined heating position, that is, the required temperature is heated. The intake manifold 2 is arranged at a predetermined position (position surrounded by the heating portion 7a of the high frequency induction heating coil 7) in the high frequency induction heating coil 7 which is in the glycol liquid 5 and is immersed in the ethylene glycol liquid 5. . (3) Under this condition, a high-frequency current of a required frequency is supplied from the high-frequency power source 8 to the heating section 7a through the lead section 7b of the high-frequency induction heating coil 7, whereby the high-frequency induction heating of the low melting point metal core 4 is performed. To start. (4) Thus, when the low-melting metal core 4 is subjected to high-frequency induction heating to the required temperature, the low-melting metal core 4 is melted,
The melted metal starts to be eluted from the plurality of openings (not shown) on the lower end side of the intake manifold 2 through the lower end opening 3c (see FIGS. 8 and 9) of the hollow portion 3. Most of the melted core metal is discharged from the hollow portion 3 by the pressure due to expansion and the natural fall due to gravity,
A small amount of molten metal remains (attaches) on the inner wall surface 3a of the hollow portion 3. (5) After that, the switching valve 15 is opened and the pump 1
By activating 1, the ethylene glycol liquid 5 in the ethylene glycol heat bath 6 is sucked up and guided to the ethylene glycol liquid injection ring 16, and the ethylene glycol liquid injection ring 16 has a required temperature, a required pressure, and a required flow rate. The jet liquid L consisting of 5 is jetted from the upper end opening 3b of the hollow portion 3 toward the inner wall surface 3a. As a result, the molten metal remaining in the hollow portion 3 of the intake manifold 2 is rapidly eluted to the outside through the opening (not shown) on the lower end side of the intake manifold 2 by the injection liquid L including the ethylene glycol liquid 5. . (6) After that, the power supply to the high frequency induction heating coil 7 is cut off, and the high frequency induction heating is stopped. (7) Next, the injection of the ethylene glycol liquid 5 from the ethylene glycol liquid injection ring 16 is stopped. (8) After that, the intake manifold 2 is moved up to a predetermined position above the ethylene glycol heat bath 6 together with the workpiece mounting fixture 9 by the lifting mechanism (not shown), and the intake manifold 2 is moved to the predetermined position at the predetermined position. It is removed from the work placement fixing jig 9 and transferred to the next step as an elution completed product.

According to the elution method using the elution device 1 having such a configuration, the intake manifold 2 is melted and eluted by the high frequency induction heating of the low-melting metal core 4 in the hollow portion 3 of the intake manifold 2, or after the intake manifold 2 is completed. A jet of ethylene glycol liquid having a required temperature, pressure and flow rate is introduced from the upper end opening 3b of the hollow portion 3 (opening on the upper end side of the intake manifold 2) to open the lower end side of the intake manifold 2 (not shown). Since the molten metal is eluted together with the ethylene glycol injection liquid L through the above), the molten metal in the hollow portion 3 of the intake manifold 2 can be completely eluted and the molten metal remains in the hollow portion 3. There can be nothing, and the elution work can be performed quickly.

Specific examples according to the present invention will be shown below. Example (1) Workpiece to be eluted: Intake manifold (a) Material of intake manifold; Nylon (PA66GF33) (melting point 265-270
Low melting point metal core material; Sn-Bi alloy (melting start temperature 138.5 ° C) (b) Low melting point metal core weight 70 kg (c) Intake manifold size: 550 x 350 x 260 mm (2) ) High frequency induction heating condition (a) Frequency: 10 kHz (b) Output: 220 kW (c) Heating time: 70 sec (3) Ethylene glycol liquid (a) Type: Lutron (manufactured by BASF) (b) Liquid temperature: 180 ° C ( Heat bath and jet liquid) (4) Injection conditions of ethylene glycol liquid (a) Pressure: 5 Kgf / cm ² (b) Flow rate: 60 l / min

When the low-melting-point metal core 4 was eluted under these conditions in accordance with the above-mentioned elution procedure, the low-melting-point metal core 4 in the hollow portion 3 of the intake manifold 2 was attached to the inner wall surface 3a of the hollow portion 3. It was confirmed that all of them were completely (100%) eluted without any residue and without deterioration of the material due to overheating.

Although the embodiments of the present invention have been described above, the present invention is not limited to these embodiments, and various modifications and changes can be made based on the technical idea of the present invention. For example, in the above-described embodiment, the high frequency induction heating coil 7 having the heating portion 7a in which the winding is wound along the cylindrical surface is used, but the low melting point filled in the hollow portion 3 of the intake manifold 2 is used. A high frequency wave having a heating portion 7a wound in a plurality of turns along the shapes of the intake manifold 2 and the low melting point metal core 4 from the outer surface of the intake manifold 2 so as to uniformly heat and melt the metal core 4. It is also possible to use the induction heating coil 7. Needless to say, the present invention can be applied not only to the intake manifold 2 but also to various plastic molded products having a hollow portion that cannot be released from the mold. Furthermore, the present invention can be applied to a plastic molded product having a hollow portion having a shape that cannot be released from the hollow portion 3 as shown in FIG.

[0020]

According to the method of elution of a low melting metal core according to the present invention as set forth in claim 1, a low melting metal core filled in a hollow portion of a plastic molded product having a shape that cannot be released is subjected to high frequency induction. After dissolving by heating and allowing it to elute by spontaneously dropping from the hollow part of the plastic molded product, the injection liquid consisting of ethylene glycol is passed through the opening formed on the upper end side of the plastic molded product By injecting onto the inner wall surface and causing it to flow along the inner wall surface, the molten low melting point metal partially adhered and remaining on the inner wall surface of the hollow portion remains together with the injection liquid in the plastic molding. Since it is made to elute from the opening of the product, it is possible to eliminate the residual of the molten metal in the hollow part of the plastic molded product and to eliminate the molten metal. It is possible to efficiently elute the scan it is possible to achieve the prevention of material deterioration of the inner wall portion of the molded plastic due to overheating of the molten metal (heat deterioration).

Further, in the method for eluting a low melting point metal core according to the present invention as set forth in claim 2, after the ethylene glycol liquid in which the plastic molded product is immersed is sucked up by a pump,
Guide to the opening formed at the top of the plastic molded product,
Since the ethylene glycol liquid is sprayed through the opening into the hollow part of the plastic molded product, a jet of ethylene glycol liquid at the required temperature, pressure and flow rate is injected into the inner wall surface of the hollow part of the plastic molded product. Therefore, the trace amount of the molten metal that remains on the inner wall surface can be effectively swept away, and it is possible to prevent the molten metal from remaining inside the hollow portion and prevent the deterioration of the material of the inner wall portion.

The device for eluting a low-melting metal core according to a third aspect of the present invention is arranged in an ethylene glycol heat bath in which ethylene glycol liquid is stored, and in the ethylene glycol liquid in the ethylene glycol heat bath. Jig for fixing the molded high frequency induction heating coil and a plastic molded product having a non-separable hollow part and a low melting point metal core filled in the hollow part inside the high frequency induction heating coil And a pump for sucking the ethylene glycol liquid in the ethylene glycol heat bath, and spraying the ethylene glycol liquid sucked from the heat bath by the pump to the opening on the upper end side of the plastic molded product fixed by the fixing jig. And an ethylene glycol liquid injection device for injection of ethylene glycol liquid into the hollow part of the plastic molded product. Since it is obtained so as to inject liquid, after completion dissolution dissolution in or elution of the low-melting-point metal core, can easily supply the required temperature, pressure, flow rate of the ethylene glycol injection fluid into the hollow portion of the plastic molding,
The molten metal can be completely eluted.

According to a fourth aspect of the present invention, there is provided a device for eluting a low-melting-point metal core, wherein the ethylene glycol liquid injection device has a plurality of angles which are inclined with respect to the inner wall surface of the hollow portion of the plastic molded product. Since it has an injection hole, the injection liquid can be effectively flowed along the inner wall surface of the hollow part of the plastic molded product, and can be easily contacted with the inner wall surface to a corner or the like that tends to remain. It is possible to completely elute the existing dissolved metal. Further, by using a plurality of injection holes each having an angle inclined with respect to the inner wall surface of the hollow part of the plastic molded product and a required hole diameter, it is possible to eliminate the residual of the molten metal in the hollow part.

According to a fifth aspect of the present invention, in the low melting point metal core elution device, the ethylene glycol liquid injection device is arranged in a direction orthogonal to the axis of the opening on the upper end side of the plastic molded product. Since it has an injection pipe arranged at an inclined angle, the injection liquid can be made to spirally flow along the inner wall surface of the hollow part of the plastic molded product, and contact with this inner wall surface It is possible to completely elute the dissolved metal existing in the corners and the like where it is likely to remain. Further, by using a plurality of injection pipes each having an angle inclined with respect to the inner wall surface of the hollow part of the plastic molded product and a required hole diameter, it is possible to eliminate the residual of the molten metal in the hollow part.

[Brief description of drawings]

FIG. 1 is a configuration diagram showing an elution device for a low-melting metal core according to an embodiment of the present invention.

FIG. 2 is a plan view of an ethylene glycol liquid injection ring which constitutes a part of the ethylene glycol liquid injection device.

3 is a cross-sectional view taken along the line AA in FIG.

FIG. 4 is an opening 2 on the upper end side of the intake manifold 2.
It is explanatory drawing which shows the injection direction of the injection liquid injected from the injection hole in a in FIG.

FIG. 5 is a plan view showing another example of an ethylene glycol liquid injection ring which constitutes a part of the ethylene glycol liquid injection device.

6 is a sectional view taken along line BB in FIG.

FIG. 7 is an opening 2 on the upper end side of the intake manifold 2.
It is explanatory drawing which shows the injection direction of the injection liquid injected from the injection pipe in a in FIG.

FIG. 8 is a perspective view of a resin-made automobile intake manifold made of a plastic molded product.

9 is a sectional view taken along line XX in FIG.

[Explanation of symbols]

1 Elution device 2 Intake manifold (molded plastic) 3 Hollow part 3a inner wall surface 3b Top opening 3c Lower end opening 4 Low melting point metal core 5 Ethylene glycol liquid 6 ethylene glycol hot tub 7 High frequency induction heating coil 7a Heating part (main body part) 7b Lead part 8 high frequency power supply 9 Work placement fixture 11 pumps 12 Ethylene glycol liquid injection device 13 Suction tube 14 Ethylene glycol liquid outlet pipe 16 Ethylene glycol liquid injection ring 17 injection holes 18 injection pipes L jet liquid

Continued front page    F-term (reference) 4F202 AG07 AH17 AK11 CA11 CB01                       CK33 CK81 CN20                 4K063 AA12 BA01 BA03 CA00 FA31                       FA43

Claims (5)

[Claims] 1. A plastic molded product having a hollow part having a shape that cannot be released from the mold and a low-melting metal core filled in the hollow part is dipped in an ethylene glycol solution, and a high frequency wave is applied in the ethylene glycol solution. Elution of the low-melting-point metal core by melting the low-melting-point metal core in the hollow part of the plastic molded product by induction heating, and dissolving the low-melting-point metal in the molten state from the opening formed in the plastic molded product. In the method, the low-melting-point metal core is melted by high-frequency induction heating and is allowed to elute by spontaneously dropping from the hollow portion of the plastic molded product, and then an injection liquid composed of ethylene glycol is added to the upper end side of the plastic molded product. Injecting into the inner wall surface of the hollow part of the plastic molded product through the opening formed in Therefore, the molten low melting point metal in the hollow portion partially adhered and remaining on the inner wall surface of the hollow portion is eluted from the opening of the plastic molded product together with the injection liquid. Method for elution of low melting point metal core. 2. An ethylene glycol liquid in which the plastic molded product is dipped is sucked up by a pump, and then introduced into an opening formed at an upper end of the plastic molded product, and the ethylene glycol liquid is passed through the opening to form the plastic molding liquid. The method for eluting a low-melting-point metal core according to claim 1, characterized in that it is injected into the hollow portion of the product. 3. (a) an ethylene glycol heat bath storing ethylene glycol liquid; (b) a high frequency induction heating coil arranged in the ethylene glycol liquid in the ethylene glycol heat bath; and (c) a mold release. A fixing jig for fixing a plastic molded product having a hollow portion having an impossible shape and having a low melting point metal core filled in the hollow portion inside the high frequency induction heating coil, and (d) the ethylene. A pump for sucking up the ethylene glycol liquid in the glycol heat bath, and (e) an opening on the upper end side of the plastic molded product in which the ethylene glycol liquid sucked up from the heat bath by the pump is fixed by the fixing jig. And an ethylene glycol liquid injection device for injecting the ethylene glycol liquid into the hollow part of the plastic molded product. Dissolution apparatus of the low-melting-point metal core, wherein the injection solution was to be injected consisting. 4. The low melting point metal according to claim 3, wherein the ethylene glycol liquid injection device has a plurality of injection holes having an angle inclined with respect to the inner wall surface of the hollow portion of the plastic molded product. Core elution device. 5. The ethylene glycol liquid injection device has an injection pipe arranged at an angle inclined with respect to a direction orthogonal to the axis of the opening on the upper end side of the plastic molded product. Item 4. A device for eluting a low melting point metal core according to Item 3.