JP3396258B2 - Removal method of metal core - Google Patents

Description

Description: BACKGROUND OF THE INVENTION A method of removing a metal core according to the present invention comprises, for example, a synthetic resin intake manifold for sending air into a cylinder of an automobile engine. After being manufactured using a metal core, the metal core is heated and melted for use. 2. Description of the Related Art An intake manifold for feeding air into a cylinder of an automobile engine has conventionally been made by die-casting an aluminum alloy.
In order to reduce the weight of automobiles, see, for example,
As disclosed in Japanese Patent Application Laid-Open No. 9-1990, this intake manifold is manufactured by injection molding of a synthetic resin. On the other hand, since the intake manifold is hollow and its outer surface and inner surface are bent three-dimensionally, it cannot be manufactured by an injection molding apparatus having a simple split mold as commonly used. . Therefore, when an intake manifold having a shape bent in a three-dimensional direction is manufactured by injection molding of a synthetic resin, it is performed as follows. That is, prior to injection molding, a core made of a low melting point metal (for example, having a melting point of 150 ° C.) such as an alloy of Bi and Sn or an alloy of Bi, Sn and Pb is prepared. I do. The outer surface shape of this core matches the inner surface shape of the intake manifold made of synthetic resin to be manufactured. [0005] With the core set in a mold having an inner surface shape that matches the outer surface shape of the intake manifold to be produced, a synthetic resin having a higher melting point than the low melting point metal is placed in the mold. For example, nylon 66 (for example, having a melting point of 240 ° C. or more) containing glass fibers is injected and solidified in a space (cavity) between the inner surface of the mold and the outer surface of the core. Although the temperature of the molten synthetic resin injected into the cavity is higher than the melting point of the low melting point metal constituting the core, the molten synthetic resin has a large heat capacity and immediately comes into contact with the core having good heat transfer properties. Since the temperature decreases, part of the core does not melt with the injection of the molten synthetic resin. When the synthetic resin is injected into the mold and solidified, the mold is opened and the intake manifold is taken out. Since the intake manifold is bent in a three-dimensional direction, the core is provided with the intake manifold. It remains in the manifold. Therefore, the core is melted and removed by high-frequency induction heating in high-temperature oil. That is, as shown in FIG. 1, an intake manifold 2 containing a core 1 taken out of a molding die is connected to a coil section 3 of a high-frequency induction heating apparatus as disclosed in Japanese Patent Laid-Open No. 4-282207. Immersed in heated oil while positioned inside. In this state, by passing a high-frequency current through the coil portion 3, an alloy such as Bi-Sn forming the core 1 generates heat, and the core 1 is melted. In addition, the said coil part 3 is comprised by the copper tube 4, and the cooling water can be circulated freely inside. During operation of the high-frequency induction heating device, cooling water is caused to flow in the copper tube 4 constituting the coil unit 3 to prevent the temperature of the coil unit 3 itself from rising. As the oil, polyhydric alcohols such as polyethylene glycol,
Use mineral oil, etc. As described above, the reason why the core is melted and removed using the high-frequency induction heating device in high-temperature oil is as follows. That is, the molten metal is collected and reused, but when the core is melted and removed in the air,
The molten metal is oxidized, and the recovery rate deteriorates.
Further, when the core is melted and removed by high-frequency induction heating, it is inevitable that a residue due to the alloy constituting the core is generated inside the intake manifold made of synthetic resin. Therefore, if the core is melted and removed in oil heated to, for example, 160 to 180 ° C. and the oil is allowed to flow inside the synthetic resin, the residue can be washed away. For these reasons, the core is melted and removed in hot oil. As described above, the core made of the low melting point alloy is melted and removed from the inside of the intake manifold made of synthetic resin. As a result, the outer surface shape matches the inner surface shape of the mold, and the inner surface shape becomes the outer surface of the core. A synthetic resin intake manifold that matches the shape is obtained. Since the oil adheres to the synthetic resin intake manifold taken out of the oil, it is subjected to a cleaning process before moving to the next inspection step. [0011] As described above, when high-frequency induction heating is performed in oil to melt and remove a metal core, there are the following disadvantages. That is, since the oil has a small heat capacity, the time required to completely melt and remove the core increases.
Further, the synthetic resin intake manifold taken out of the oil after the core is melted and removed needs to be cleaned as described above, which is troublesome. Further, when the molten metal is recovered for reuse, the operation of separating the molten metal from the oil must be performed, which is also troublesome. The method for removing a metal core according to the present invention has been invented in order to eliminate any of the above-mentioned disadvantages. A method for removing a metal core according to the present invention is similar to the above-described conventional method for removing a metal core from a metal core made of a low melting point alloy. After injection molding a tubular member made of synthetic resin around the periphery, the tubular member and the metal core are immersed in a high-temperature liquid together with this coil portion while being positioned inside the coil portion of the high-frequency induction heating coil. By energizing the high-frequency induction heating coil, the metal core is melted and removed from the inside of the tubular member. Particularly, in the method for removing a metal core of the present invention, the liquid is obtained by melting a low-melting alloy of the same material as the low-melting alloy constituting the metal core. Further, an insulating layer is provided on the surface of the conductor constituting the high frequency induction heating coil. Then, at least when the high-frequency induction heating coil is energized, the liquid is stirred and flown. According to the method for removing a metal core of the present invention, the core is melted in a liquid alloy obtained by melting an alloy having the same composition as the core as described above. Since the heat capacity is large, the speed at which the core is melted is increased, and the melting efficiency of the core is improved. Furthermore, since the separation operation of the oil and the molten metal and the cleaning operation of the synthetic resin tubular member are not required as in the conventional method of melting the core in the oil, the synthesis efficiency is improved in combination with the improvement of the melting efficiency. The production efficiency of the tubular member made of resin is improved. Next, an embodiment shown in the drawings will be described. The method for removing a metal core according to the present invention comprises the steps of: injection-molding, for example, an intake manifold 2 which is a tubular member made of a synthetic resin around a metal core 1 made of a low melting point alloy; 1 is melted away. That is, similarly to the above-mentioned conventional method, the synthetic resin intake manifold 2 containing the core 1 after the injection molding is immersed in a high-temperature liquid while being positioned inside the coil portion 3 of the high-frequency induction heating coil. . Then, by passing a high-frequency current through the copper tube 4 forming the coil part 3, the core 1 is heated and the core 1 is melted. Particularly, in the method for removing a metal core of the present invention, the liquid is a liquid metal 5 obtained by melting a low melting point alloy of the same material as the low melting point alloy forming the core 1.
Then, the core 3 is immersed in the heated high-temperature liquid metal 5 with the coil portion 3 and the intake manifold 2 made of synthetic resin containing the core 1 positioned inside the coil portion 3. 1 is removed by melting. Along with this, an insulating layer such as polytetrafluoroethylene (PTFE) or an alumina sprayed layer is previously provided on the surface of the copper tube 4 constituting the coil portion 3 so that the liquid metal 5 is directly applied to the copper tube 4. Prevent short circuit by touching. In addition, when the core 1 is melted and removed, a stirring (not shown) is performed to prevent the core 1 located in the coil portion 3 from being overheated and to quickly remove the melted core 1 from the inside of the intake manifold 2. The liquid metal 5 is stirred by the device. Further, preferably, in order to prevent the liquid metal 5 from being oxidized, a means for preventing the liquid metal 5 from coming into contact with oxygen is provided. As this means, for example, it is conceivable to cover the surface of the liquid metal 5 with an antioxidant or a lightweight lid member. Further, the core according to the present invention may be melted and removed in an inert gas atmosphere. In the method for removing a metal core of the present invention configured as described above, the liquid in which the core 1 is immersed is made of a low melting point material having a larger heat capacity than oil and the same material as the core 1. Since the liquid metal 5 is obtained by melting the alloy, the time required for melting and removing the core 1 is reduced. Further, since the alloy constituting the melted and removed core 1 has the same composition as the liquid metal 5, the separation operation is not required unlike the conventional method, and the recovery operation for reuse is facilitated. Further, since no oil is used, there is no need to clean the intake manifold 2 taken out of the liquid metal 5, and there is no need to replace the oil deteriorated by repeatedly melting and removing the core 1. As a result, the operation of melting and removing the core 1 can be performed quickly, and the core 1 can be efficiently melted and removed. In this embodiment, an example in which the present invention is applied to a case where a synthetic resin intake manifold is manufactured has been described. However, the present invention is not limited to this.
It can be widely applied to the case where a tubular member made of another synthetic resin is manufactured using a core made of a low melting point alloy. The method of removing a metal core according to the present invention is constructed and operated as described above, so that the core can be efficiently removed by melting, and a synthetic resin such as an intake manifold made of a synthetic resin. Contributes to the improvement of the production efficiency of the tubular member.

[Brief description of the drawings] FIG. 1 is a schematic diagram showing an embodiment of the present invention. [Explanation of symbols] 1 core 2 Intake manifold 3 Coil section 4 Copper tube 5 Liquid metal

Continuation of front page (58) Field surveyed (Int.Cl. ⁷ , DB name) B29C 33 / 52,45 / 44

Claims (1)

(57) [Claim 1] After injection molding a synthetic resin tubular member around a metal core made of a low melting point alloy, the tubular member and the metallic core are In a state where the coil is immersed in a high-temperature liquid together with the coil portion while being positioned inside the coil portion of the high-frequency induction heating coil, and by energizing the high-frequency induction heating coil, the metal core is melted and melted. In the method for removing a metal core, which is removed from the inside of the tubular member, the liquid is obtained by melting a low-melting alloy of the same material as the low-melting alloy constituting the metal core, and A method for removing a metal core, wherein an insulating layer is provided on a surface of a conductor constituting an induction heating coil, and the liquid is stirred and flowed at least when power is supplied to the high-frequency induction heating coil.