JP2007253230A - High-frequency induction heating device for die casting machine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a high-frequency induction heating device for a die-casting machine which can restrain electric power consumption, evenly maintain the temperature of an object to be heated, and prevent an explosion phenomenon caused by the contact of a molding metal with water. <P>SOLUTION: In the high-frequency induction heating device for the die-casting machine, an object to be heated such as a gooseneck, a nozzle 10 or a die in the die-casting machine is heated by applying a high-frequency electric current to an induction coil 14b connected to a high-frequency alternator 40. The induction coil 14b is composed of a metal wire with high melting point which is either of a nickel wire, a nickel alloy wire or an iron-chromium alloy wire. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a high-frequency induction heating apparatus, and more particularly to a high-frequency induction heating apparatus used to heat a gooseneck, nozzle, or mold of a die casting machine for forming a low melting point metal such as magnesium, zinc, and aluminum.

  In high-frequency induction heating, a high-frequency alternating current generated by an inverter or the like is passed through an induction coil arranged around the object to be heated to induce eddy current loss and hysteresis loss (in the case of a magnetic material) to the object to be heated. As a result, Joule heat is generated in the object to be heated. A high-frequency induction heating device used for high-frequency induction heating is a high-frequency AC power source composed of an inverter and a controller, copper tube induction coils formed in various shapes according to the object to be heated, and induction coils heated to high temperatures And a cooling device for preventing damages such as oxidation and melting.

  Such a high-frequency induction heating apparatus is used in many industrial fields, and has various applications such as heat treatment of metal, brazing, heating of billets, flat heating of metal, melting of casting raw materials, and the like.

  The high-frequency induction heating device has advantages such as the ability to raise the temperature of the object to be heated in a short time and easy control of the heating temperature, so low melting point metal molding such as magnesium, zinc, aluminum, etc. It is also widely used as a preheating or heating device for goosenecks, nozzles, dies, etc. (hereinafter referred to as “objects to be heated”) in a conventional die casting machine. The gooseneck is an apparatus for supplying molten metal for molding melted in a melting furnace from a melting furnace to a nozzle. In die casting, the gooseneck, nozzle, and mold must always be maintained at a constant temperature so that the molten metal does not undergo changes such as temperature drop and solidification during the molding process.

  However, when using a high-frequency induction heating device as a preheating or heating device for gooseneck, nozzle, mold, etc. of a low-melting-point metal forming die casting machine, there are some problems as follows. It is requested.

  In general, in a high-frequency induction heating apparatus, when a forming material is a metal such as magnesium, zinc, or aluminum described above, it is necessary to heat an object to be heated to at least the melting temperature of these metals, that is, 400 ° C. or more. . On the other hand, copper tubes are conventionally used as induction coils for high-frequency induction heating devices, and the reason why copper tubes are used as induction coils is that the specific resistance of copper is so low that power loss is small. This is because there is a need for cooling as described.

  Copper has the fundamental problem of oxidizing at around 400 ° C. The same applies when a copper wire is used instead of the copper tube. In order to solve such problems, when the heating temperature of the forming metal is 400 ° C. or higher, a copper pipe is used as an induction coil, and water or air is allowed to flow inside the copper pipe to thereby induce the induction coil. It is cooled so that it is not overheated above the temperature at which it oxidizes or melts. Therefore, a high-frequency induction heating device that uses a copper tube as an induction coil requires a water-cooled or air-cooled cooling device.

  FIG. 1 is a cross-sectional view illustrating a configuration of a high frequency induction heating device for a nozzle of a conventional die casting machine. Below, with reference to FIG. 1, the problem which the conventional high frequency induction heating apparatus for die-casting machines has is demonstrated in more detail.

  The melting temperature of magnesium and aluminum is around 650 ° C., and the melting temperature of zinc is around 500 ° C. When these low melting point metals are formed by die casting, the nozzle must be heated to around 600 ° C. for magnesium and aluminum and around 450 ° C. for zinc.

  As described above, for example, in order to prevent molten magnesium from dropping or solidifying while passing through the nozzle 10, the nozzle 10 that is an object to be heated must be heated to around 600 ° C. . Therefore, an induction coil 14a made of a copper tube connected through a connecting pipe 16 is disposed around the nozzle 10 that is an object to be heated, and the induction coil 14a has a high-frequency current generated by the high-frequency AC power supply 40. Is applied, and water is supplied from the cooling device 30 to prevent the induction coil 14a from being overheated.

  However, the water supplied from the cooling device 30 not only cools the induction coil 14a, but also lowers the temperature around the nozzle 10 that is the object to be heated, and thus further supplies power necessary to compensate for the temperature drop. Must. Therefore, there is a problem that electric energy for that purpose is required. Further, the heat insulating member 12 is cooled by water flowing inside the induction coil 14a, while the nozzle 10 is maintained at a high temperature by heating, so that the nozzle 10 is thermally expanded and the heat insulating member 12 is contracted. Therefore, cracks and deformation are likely to occur in the nozzle 10 or the heat insulating member 12. These phenomena mean shortening the life of the nozzle.

  In particular, in the case of a magnesium molding die casting machine, cooling by the induction coil 14a using water has another problem that there is a possibility of explosion due to a reaction between magnesium and water. When magnesium comes into contact with water, it may explode due to a rapid oxidation reaction. In particular, when cooling water is not supplied smoothly during heating, the induction coil 14a may be oxidized or melted and damaged. In that case, the cooling water is scattered, and the magnesium explosion is likely to occur. Therefore, the high frequency induction heating apparatus cannot be applied to the gooseneck directly connected to the melting furnace. In order to solve such problems, there is a method of supplying air to a tube-type induction coil instead of cooling water. However, since cooling efficiency is remarkably low compared with the case of using water, it is mostly adopted. Absent.

In addition, as a heating apparatus for die casting machines according to the above-described conventional technique, there is an apparatus disclosed in Patent Document 1, for example. The device disclosed in Patent Document 1 is an induction heating device used to heat a mouthpiece part and a nozzle of a casting container. The induction coil is cooled by air, and the induction coil includes, for example, 10 to 15 kHz. A medium wave current is supplied.
US Patent Publication No. 5,960,854

  The present invention has been made to solve the above-described problems of the conventional technology, and an object thereof is to provide a high frequency induction heating device for a die casting machine that does not require a cooling device.

  Another object of the present invention is to provide a high-frequency induction heating device capable of suppressing power consumption and maintaining the temperature of the nozzle uniformly by allowing the heat insulating member to function as a heat insulating layer of the nozzle. There is.

  Still another object of the present invention is to provide a high frequency induction heating apparatus capable of preventing an explosion phenomenon due to contact between magnesium and water in magnesium die casting.

  Still another object of the present invention is to provide a high frequency induction heating apparatus for a die casting machine that can maintain a uniform temperature of each part of a heated object by inducing uniform eddy currents in the entire area of the heated object. It is to provide.

  Still another object of the present invention is to maintain a predetermined distance between the induction coil and the object to be heated and between adjacent windings of the induction coil during filling of the heat insulating member. An object of the present invention is to provide a high frequency induction heating apparatus for a die casting machine that can prevent a short circuit.

  In order to achieve the above object, a high frequency induction heating apparatus for a die casting machine according to the present invention applies a high frequency current to an induction coil connected to a high frequency alternating current power source, so that magnesium such as a gooseneck, nozzle or mold in the die casting machine is used. In a high frequency induction heating apparatus for a die casting machine that heats an object to be heated that transports or accommodates a low melting point metal such as zinc or aluminum, the induction coil is any one of a nickel wire, a nickel alloy wire, and an iron-chromium alloy wire It is characterized by being composed of such a refractory metal wire.

  The nickel alloy wire is preferably one of a nickel-chromium alloy wire, a copper-nickel alloy wire, and an iron-nickel alloy wire.

  The induction coil is spirally disposed at a predetermined distance from the outer peripheral surface of an object to be heated such as a gooseneck, a nozzle, or a mold, and the periphery of the induction coil is covered with a heat insulating member and spirally disposed. A spacer made of an insulating material is provided between the windings of the induction coil that is supported so that a predetermined distance is maintained between each winding and the object to be heated and between adjacent windings. It is desirable that

  It is preferable that the spacer has a quadrangular prism shape, and an inductive coil supporting recess is formed on a contact surface with the winding.

  It is desirable that a connection bar for connecting through the spacer row is provided on the outer peripheral side of the recess for supporting the induction coil of the spacer, and both ends of the connection bar are fastened with nuts.

  According to the high frequency induction heating device for a die casting machine according to the present invention, since a cooling device for the induction coil is unnecessary, the heat loss due to cooling can be remarkably reduced (the heat loss is about 1/2 of the conventional one). In addition, the heat insulating member layer functions as a heat retaining layer for the object to be heated, and not only can maintain the temperature of the entire object to be heated uniformly. There is an effect that it can be prevented. Further, the object to be heated can be uniformly heated in the entire region, and when filling the heat insulating member, a predetermined interval is provided between the induction coil and the object to be heated and between adjacent windings of the induction coil. Therefore, there is an advantage that a short circuit can be prevented.

  Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings.

  FIG. 2 is a cross-sectional view schematically showing a configuration of a high frequency induction heating device for a die casting machine (hereinafter sometimes simply referred to as “high frequency induction heating device”) according to an embodiment of the present invention, and FIG. Sectional drawing which shows schematically the structure of the high frequency induction heating apparatus for die-casting machines concerning another embodiment of this invention, FIG. 4A is arrangement | positioning of the induction coil in the high frequency induction heating apparatus for die-casting machines shown in FIG. 4B is a side view showing the arrangement of the induction coil shown in FIG. 4A, and FIG. 4C is a cross-sectional view taken along the line IVC-IVC ′ shown in FIG. 4B.

  2 to 4C, the case where the object to be heated is the nozzle 10 will be described as an example. However, the following description can be applied as it is to other heated objects such as gooseneck and mold.

  As shown in FIG. 2, in the high frequency induction heating apparatus for nozzles according to the embodiment, one thick high melting point metal wire is used as the induction coil 14b. The feature of this device is that any high-melting point metal wire of nickel wire, nickel alloy wire and iron-chromium alloy wire is used as the induction coil 14b. The induction coil 14b is connected via a connector 18. Thus, when the high melting point metal wire is used as the induction coil 14b, the induction coil cooling device is not required unlike the case of the induction heating device shown in FIG. Become. Therefore, it is possible to prevent heat loss due to the heat generated in the nozzle 10 being cooled by water and the occurrence of an explosion phenomenon due to contact between water and a molding metal such as magnesium. Further, since a certain amount of Joule heat generated in the induction coil 14 b is stored in the heat insulating member 12, the heat insulating member 12 functions as a heat insulating layer of the nozzle 10. Therefore, the temperature difference between the nozzle 10 and the heat insulating member 12 is reduced, and cracks and deformation in the nozzle 10 or the heat insulating member 12 are prevented.

  Refractory metal wires such as the nickel wire, nickel alloy wire, and iron-chromium alloy wire have the following characteristics.

  First, the melting temperature of the refractory metal wire is at least higher than the melting temperature of a forming metal such as magnesium, aluminum, or zinc. For example, the melting temperature of the nickel wire is around 1453 ° C., the melting temperature of the nickel alloy wire is 900 to 1200 ° C., and the melting temperature of the iron-chromium alloy wire is around 1300 ° C., depending on the composition of the alloy. Therefore, the induction coil 14b is not oxidized or melted near the melting temperature of the forming metal. Thus, the nickel wire, the nickel alloy wire, and the iron-chromium alloy wire are very suitable for the nozzle high frequency induction heating apparatus according to the embodiment from the viewpoint of the oxidation temperature and the melting temperature thereof.

  Further, the resistance value of the refractory metal wire is the value shown in Table 1 when the wire diameter is 5 mm.

ここで、表１に示した抵抗値の単位はΩ／ｍであり、それぞれ平均値を示している。なお、同じ線径の銅の抵抗値は、０．００１１Ω／ｍである。

Here, the unit of the resistance value shown in Table 1 is Ω / m, and each shows an average value. The resistance value of copper having the same wire diameter is 0.0011 Ω / m.

  Therefore, in the present invention, the refractory metal wire can be defined as a metal wire having a melting temperature of 900 ° C. or higher and a resistance value of a wire diameter of 5 mm less than 0.1 Ω / m.

  The metal wire having the resistance value not only has no hindrance to high-frequency current conduction, but the Joule heat that increases as the resistance value increases is used as it is for heating the nozzle 10.

  Moreover, since the oxidation temperature and melting temperature of the induction coil 14b are significantly higher than the heating temperature of the nozzle 10 that is the object to be heated, there is no need to cool the induction coil 14b during die casting. Therefore, only the high-frequency AC power supply 40 is connected to the induction coil 14b, and no cooling device is connected. Therefore, heat loss due to cooling with water or air is prevented, and the object to be heated can be heated uniformly. In particular, explosions that may occur due to contact with water when forming magnesium. There is an advantage that the phenomenon can be prevented beforehand.

  FIG. 3 does not use a single thick refractory metal wire as in the example shown in FIG. 2, but collects a plurality of thin wires whose surfaces are covered with an electrically insulating material as the induction coil 14c. This shows a case where a twisted high melting point metal wire is used. When using such a thin stranded wire, the surface area of the coil is increased, and the effective area through which high-frequency current that flows only near the surface can be increased by the skin effect, so the entire refractory metal wire There is an advantage that the resistance value can be lowered.

  As shown in FIGS. 4A to 4C, the induction coil 14 b is spirally wound and disposed at a predetermined distance from the outer peripheral surface of the nozzle 10, and both ends thereof are connected to the high-frequency AC power supply 40. . Further, the periphery and the outside of the induction coil 14 b are covered with the heat insulating member 12, and the induction coil 14 b is configured to be embedded in the heat insulating member 12. Although not shown in FIGS. 4A to 4C, it is desirable to further provide a casing formed of a ferrous metal material such as stainless steel and a non-ferrous metal material such as aluminum outside the heat insulating member 12. Damage to the heat insulating member 12 due to external impact or the like is prevented, and damage to the heat insulating member 12 or the induction coil 14b due to the scattered molten metal penetrating into the heat insulating member 12 is prevented.

  In the case of the high-frequency induction heating device according to the present embodiment, a predetermined gap is provided between each winding and the object to be heated and between adjacent windings with respect to each winding of the spirally wound induction coil. A spacer 20 made of an insulating material that supports the gap so as to be maintained is inserted. The spacer 20 can be of various shapes. As shown in FIG. 4A, the spacer 20 has a substantially quadrangular prism shape, and a coil support recess is formed on the contact surface with the winding of the induction coil 14b. 26 is preferably formed. With this configuration, during the filling of the heat insulating member 12, a predetermined interval is maintained between the induction coil 14b and the nozzle 10 that is the object to be heated and between adjacent windings of the induction coil 14b. It is possible to prevent a short circuit of the winding. Further, since the eddy current and the induction heat can be generated uniformly over the entire nozzle 10, there is an advantage that the forming metal can be flown in a uniform molten state.

  In addition, it is desirable that a connecting bar 22 is provided on the outer peripheral side of the spacer 20 inserted between the windings so as to penetrate and connect the row of the spacers 20. It is preferable that male screws are formed at both ends of the connecting bar 22 and the spacers 20 are fastened and fixed by using the male screws and nuts 24.

  4A and 4B show an example in which three rows of spacers 20 are arranged on the outer peripheral surface of the nozzle 10, but one row, two rows, four rows to ten rows, or more rows are provided as necessary. It can be.

  As shown in FIG. 4C, by adopting the above configuration, the gaps between the windings of the induction coil 14b and between the windings and the outer peripheral surface of the nozzle 10 are maintained at predetermined intervals. Heat generation at the position becomes uniform, and as a result, the molten state of the forming metal passing through the nozzle is maintained uniformly.

  As mentioned above, although preferred embodiment of this invention was described with reference to drawings, it cannot be overemphasized that this invention is not limited to the said embodiment. It will be apparent to those skilled in the art that various modifications and improvements can be made within the scope of the claims, and these are also within the technical scope of the present invention.

  The high frequency induction heating device for a die casting machine according to the present invention is suitable as a high frequency induction heating device for heating a gooseneck, a nozzle, a mold, or the like of a low melting point metal forming die casting machine.

It is sectional drawing which shows schematically the structure of the high frequency induction heating apparatus for nozzles of the die-casting machine concerning a prior art. It is sectional drawing which shows roughly the structure of the high frequency induction heating apparatus for die-casting machines concerning one embodiment of this invention. It is sectional drawing which shows schematically the structure of the high frequency induction heating apparatus for die-casting machines concerning another embodiment of this invention. It is a perspective view which shows the arrangement | positioning state of the induction coil in the high frequency induction heating apparatus for die-casting machines shown in FIG. It is a side view which shows the induction coil arrangement | positioning state shown to FIG. 4A. FIG. 4B is a cross-sectional view taken along the line IVC-IVC ′ shown in FIG. 4B.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Nozzle 12 Heat insulation member 14a, 14b, 14c Induction coil 16 Connection pipe 18 Connector 20 Spacer 22 Connection bar 24 Nut 26 Coil support recessed part 30 Cooling device 40 High frequency alternating current power supply

Claims (5)

In a high frequency induction heating apparatus for a die casting machine that heats an object to be heated that transports or accommodates a low melting point metal in a die casting machine by applying a high frequency current to an induction coil connected to a high frequency AC power source.
A high frequency induction heating apparatus for a die casting machine, wherein the induction coil is made of a refractory metal wire of any one of a nickel wire, a nickel alloy wire, and an iron-chromium alloy wire.   2. The high frequency induction heating apparatus for die casting machine according to claim 1, wherein the nickel alloy wire is any one of a nickel-chromium alloy wire, a copper-nickel alloy wire, and an iron-nickel alloy wire.   The induction coil is spirally disposed at a predetermined distance from the outer peripheral surface of the object to be heated, the periphery of the induction coil is covered with a heat insulating member, and each winding of the induction coil disposed spirally It is characterized in that a spacer made of an insulating material is provided between the wires so as to support each winding and the object to be heated and between adjacent windings so as to be maintained at a predetermined distance. The high frequency induction heating apparatus for die-casting machines according to claim 1 or 2.   4. The high frequency induction heating apparatus for a die casting machine according to claim 3, wherein the spacer has a quadrangular prism shape, and a concave portion for supporting an induction coil is formed on a contact surface with the winding. 5. The high frequency induction heating apparatus for a die casting machine according to claim 4, further comprising a connection bar that penetrates and connects the row of the spacers on an outer peripheral side of the recess for supporting the induction coil of the spacer.

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