JPH0527693B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an induction heating device, and more particularly to an induction heating device for metal wires that can efficiently and continuously heat a metal wire.

[Conventional technology and its problems]

Induction heating devices are widely known that inductively heat a metal wire that passes continuously through the coil along the coil axis by passing a high-frequency current through the induction heating coil. In induction heating, tightly wound solenoid coils were used.

However, in this conventional induction heating, heating efficiency is poor, and in particular, heating of non-magnetic metal wires and heating of magnetic metal wires above the Curie temperature is very inefficient.

In addition, the induction coil of this type of device is a pipe or
This method has been carried out using wires with a large diameter such as a bar with a diameter of 7 m/mφ or more, but the heating efficiency is poor and it has not been applied to heating wires with a smaller diameter than this.

Furthermore, as disclosed in Japanese Patent Publication No. 56-52978, for example, there is a method of forming a secondary short circuit by running a metal wire in the secondary circuit of a transformer and short-circuiting it. An iron core was required due to the inability to run in a straight line and the efficiency of the transformer, and when the frequency was raised, the iron core's self-loss caused problems with its material.

[Problem that the invention seeks to solve]

The purpose of this invention is to solve the above-mentioned problems regarding induction heating of metal wires,
It is an object of the present invention to provide a novel induction heating device for metal wires, which can efficiently heat non-magnetic metal wires and heating at temperatures higher than the Curie temperature.

[Technical means to solve problems]

The above object is to provide an induction heating device that inductively heats a metal wire that passes continuously through the coil along the coil axis by passing a high-frequency current through the induction heating coil. The induction heating coil is wound with a large coil pitch so as to generate an alternating magnetic flux having a sufficiently large component in the direction perpendicular to the coil, and the metal wire is short-circuited at the inlet side and the outlet side of the induction heating coil. This is achieved by an induction heating device for metal wire, which is characterized by being provided with a short-circuiting member.

[Effect]

When a high-frequency current is applied to an induction heating coil, an alternating magnetic field is generated in the direction perpendicular to the coil axis due to the current component in the coil axis direction, and a high-frequency voltage is generated in the axial direction of the metal wire that continuously passes through the coil axis. occurs. Since this metal wire is short-circuited at the inlet and outlet sides of the induction heating coil, a high-frequency current flows through the metal wire, generating heat due to ohmic loss.

Note that the heating in this case is different from the ohmic loss caused by the eddy current perpendicular to the coil axis when using a conventional solenoid coil, and is caused by the ohmic loss caused by the short current in the metal wire loop, so it is caused by the high frequency current. The penetration depth into the metal wire that is the object to be heated has little effect, and good heating efficiency can be maintained up to low frequencies.

〔Example〕

FIG. 1 is a schematic diagram of an embodiment of a metal wire heating device according to the present invention. The metal wire 3 is supported so that it can continuously pass through the axis of the induction heating coil 1.

The coil pitch of this induction heating coil 1 is formed larger than the radius of the coil 1, and as shown in FIG. 1, when the angle between the direction perpendicular to the coil axis and the tangent to the induction heating coil 1 is θ. , abbreviates θ
It is set at 30° or more.

Furthermore, 4 is a short-circuiting member made of a conductor, and contacts 5a and 5b made of a conductor are placed on the inlet and outlet sides of the induction heating coil 1, respectively, and the metal wire 3, which is the object to be heated, is connected to the induction heating coil 1. It is designed to be short-circuited at the front and back and supported slidably.

Next, to explain the operation of this embodiment, when a high frequency current is passed from the high frequency oscillator 2 to the induction heating coil 1, an alternating magnetic field is generated in a direction perpendicular to the coil axis due to the current component in the coil axis direction, and this alternating magnetic field is generated in a direction perpendicular to the coil axis. A high frequency voltage is generated in the axial direction of the metal wire 3 passing through the coil shaft due to the magnetic field. This metal wire 3 is connected to short-circuiting members 4 before and after the induction heating coil 1.
Since the contactors 5a and 5b are short-circuited, a high-frequency current flows through the short-circuited portion, that is, the wire 3 between the contacts 5a and 5b, and heat is generated due to ohmic loss. In addition, the second
The figure is an equivalent circuit diagram of this induction heating device. Since the coil current I is in the direction of angle θ, the axial component current is approximately Isinθ, and the radial component current is approximately Icosθ.
Good results were obtained experimentally when θ was set to approximately 30°C or higher.

Next, with reference to FIGS. 3, 4, and 5, the results of a comparative experiment between a conventional example of a closely wound coil, a case where a loosely wound coil is not short-circuited, and the present invention will be described.

When heating an iron wire with a single point, μ = 100
(μ: magnetic permeability) up to the single point (740℃) using a coarsely wound coil, the heating efficiency is good due to the ohmic loss caused by the eddy current that does not short-circuit the metal wire 3, and FIG. 4, which shows the effect of the present invention, shows that the heating efficiency is The copper wire (non-magnetic metal μ=
This is more than six times the case in case 1). Also, as shown in Figure 3, the heating efficiency is 50
Even better at ~60%. Next, when heating to more than one point with μ = 1, there is no data on heating efficiency, but it can be inferred from the data for copper wire (μ = 1) that it is more efficient to use a coarsely wound coil and short-circuit the metal wire 3. It was good. As shown in the lower part of Figure 4, the heating efficiency is
This is around 10%, which is twice as much as when there is no short circuit. Further, as shown in FIG. 3, unlike the present invention, close winding had almost no short-circuiting effect.

Based on the above experimental results, the present invention balances the ratio of ohmic loss due to eddy current and ohmic loss due to short circuit current of the metal wire 3, and rapidly heats a metal wire such as iron with a single point beyond the single point. You can see that this has made this possible industrially.

In other words, as shown in Figure 5, even at linear speeds of 100 m/min or higher, which can be carried out on an industrial scale, there is no change in the temperature rise curve near the Kyuri point, and the temperature rises in proportion to the input power. It was possible.

Also, as is clear from the lower graph in Figure 4, when heating non-magnetic metals such as copper wire (μ = 1), it is natural that the heating efficiency is good due to the ohmic loss of the short-circuit current of the metal wire, but The good region extends to low frequencies (5KHz).

In Fig. 5, the range of a single point in the mild steel is shown by a hatched band C. If the metal wire (mild steel) is heated to this area, no more power can be input in the conventional example in which the metal wire is not short-circuited. . That is, even if the voltage is increased, the current decreases, and the temperature will eventually stagnate around this region C.

Next, FIG. 6 shows another embodiment of the induction heating device for metal wire according to the present invention, in which two induction heating coils 1 and 1' are arranged in series, and the metal wire 3 is It is designed so that it can pass through the axes of the induction heating coils 1 and 1'.

Note that high frequency oscillators 2 and 2' having the same output are connected to the two induction heating coils 1 and 1', respectively.

Furthermore, the shorting member 4 has three contacts 5a, 5b,
5c, and the contact 5a is the induction heating coil 1.
The contactor 5b is located between the outlet side of the induction heating coil 1 and the inlet side of the induction heating coil 1', and the contactor 5c is located at the outlet side of the induction heating coil 1'. It seems to be short circuiting. The distance between the contacts 5b and 5c is larger than the distance between the contacts 5a and 5b.

In this embodiment, the metal wire 3 is heated by the induction heating coil 1, and kept warm or slowly cooled by the induction heating coil 1'.

In this way, by appropriately selecting the distance between the contacts 5b and 5c, the metal wire 3 can be kept warm and slowly cooled freely.

In this example, two induction heating coils were used, but three or more induction heating coils may be used to provide each step of heating, heat retention, and slow cooling, or only heat retention and cooling may be performed. Of course it's a good thing.

In the embodiment shown in FIG. 6, the high frequency oscillator 2,
2′ with the same output was used, but of course,
Different ones may be used, and in this case, instead of changing the distance between the contacts 5b and 5c, the output is changed at these frequencies or voltages, even if they are different in frequency or voltage. Good too.

Further, in the embodiments shown in FIGS. 1 and 6, a roller was used at the contact portion between the metal wire 3 and the shorting member 4, but as shown in the embodiments shown in FIGS. 3 and 4, a roller was used instead. A strip made of a conductor bent in a U-shape may be used, and both ends thereof may be simply brought into sliding contact with the metal wire 3.

Further, in the Examples and Experimental Examples, the coil pitch was constant over the entire length of the coil, but it does not have to be constant; for example, the coil pitch may be wound densely at the center and loosely wound at both ends. Alternatively, a coarsely wound coil with a fixed pitch and a closely wound coil with a fixed pitch may be electrically connected in series.

〔Effect of the invention〕

The induction heating device for metal wire according to the present invention utilizes heat generation due to ohmic loss caused by shot current in the metal wire loop, and unlike conventional devices, a high frequency voltage is generated in the axial direction of the metal wire, and the high frequency current is generated. The penetration depth into the metal wire has little effect, and it can heat efficiently even at low frequencies, and can extremely efficiently heat non-magnetic metal wires and metal wires to temperatures above one temperature, which conventional devices were not good at. It has excellent effects.

[Brief explanation of the drawing]

Fig. 1 is a schematic diagram of an induction heating device for metal wire according to an embodiment of the present invention, Fig. 2 is an equivalent circuit diagram of the same device, and Fig. 3 is a close-wound coil of a conventional example for comparison with the present invention. Fig. 4 is a graph showing the experimental results obtained using the coarsely wound coil according to the present invention as an induction heating coil, and a schematic diagram showing the dimensional relationships. FIG. 5 is a graph showing the relationship between input power and heating temperature when the coarsely wound coil according to the present invention is used as an induction heating coil and the metal wire is short-circuited, and FIG. 6 is a graph according to another embodiment of the present invention. FIG. 1 is a schematic diagram of an induction heating device for metal wire. In the figure, 1...induction heating coil, 2...
...High frequency oscillator, 3... Metal wire, 4... Short circuit member, 5a, 5b... Contactor.

Claims (1)

[Scope of Claims] 1. An induction heating device that inductively heats a metal wire that passes continuously through the coil along the coil axis of the coil by passing a high-frequency current through the induction heating coil, The induction heating coil is wound with a large coil pitch so as to generate an alternating magnetic flux having a sufficiently large component in the direction perpendicular to the coil axis, and the metal wire is short-circuited at the inlet side and the outlet side of the induction heating coil. 1. An induction heating device for metal wire, characterized in that a short-circuiting member is provided to allow the metal wire to be heated. 2. The induction heating device for metal wire according to item 1, wherein the coil pitch is larger than the diameter of the induction heating coil.