JPH09283269A - Induction heating apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the current limitation so as to increase the heating variable by winding a heating coil, which is formed by passing a litz wire through inside of a cooling hose, in the direction at a right angle against the progressing direction of the material to be heated so as to be overlapped. SOLUTION: A litz wire 9 formed by twisting an insulated wire is used as a coil conductor, and held by insulating spacers 11, 12 with an appropriate space, and led into a cooling hose 13 made of rubber and the insulating material. A heating coil 3, which is thereby formed of the cooled litz wire, is wound at plural layers, and an iron core 8 and a shield plate 7 are arranged outside of the heating coil 3 so as to improve the efficiency and prevent the leak of magnetic flux to the outside. Furthermore, this heating coil 3 is protected by a coil cement 4. Whole of this heating device is housed in a box 5 made of the insulating material. Heating of the heating coil 3 can be restricted by the use of the litz wire 9 and the water passing through the cooling hoe 13, and heating efficiency is improved. Limitation of current is moderated, and the heating variable can be increased.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an induction heating device for plates, bars and the like.

[0002]

2. Description of the Related Art FIG. 3 shows an example of a conventional induction heating apparatus (Japanese Patent Application No. 6-199862). In an induction heating device that heats the plate material 2 by causing a high-frequency magnetic flux 6 to act on the plate material 2 by causing a high-frequency current to flow through the heating coils 3 arranged in a row along the traveling direction of the plate material 2 that is the material to be heated, By providing the iron core 8 in the magnetic path outside the heating coil 3, the following characteristics are provided. (1) Since the magnetic flux converges on the iron core 8 and the leakage magnetic flux becomes extremely small, it is possible to prevent the surrounding metal such as the metal supporting the roll 1 from being heated. (2) Since the permeance of all magnetic paths can be increased, the heating efficiency is improved. (3) As a result, since the heating power density can be increased, the entire heating length can be shortened.

Another conventional example shown in FIG. 4 is characterized in that the heating coil 3 is wound in multiple layers (5 layers in FIG. 4) in a direction perpendicular to the traveling direction of the material to be heated 2. The heating amount P of the plate material which is the heating material 2 is proportional to the square of the strength H of the magnetic field, and when the current I of the heating coil 3, the number of turns N, and the coil length l are the strength H of the magnetic field. Is H =
It is expressed in NI / l. That is, P∝ (NI / l)
It becomes ² . Therefore, at a constant coil length l, N can be increased by winding the heating coil 3 in multiple layers under the coil current I determined by the allowable variable current density of the heating coil 3, and the heating amount of the plate material 2 can be increased. Can be large.

As a result, by combining the apparatus shown in FIG. 3 for arranging the iron core 8 to concentrate the magnetic flux and the apparatus shown in FIG. 4 for increasing the magnetic field strength H by forming the heating coil 3 in multiple layers, the surroundings can be efficiently produced. There is no heating of metal, and a large amount of heating can be applied to the material to be heated.

[0005]

However, the above-mentioned multilayer heating device shown in FIG. 4 has the following problems. That is, since a high-frequency current is passed through the heating coil 3, a hollow pipe or a hollow square pipe through which cooling water can flow is used. The magnetic flux generated by the current flowing through the coil includes not only the magnetic flux that links with the plate material, which is the original purpose, but also the flux that links the coils of other layers. For example, as shown in the half-cut cross section of FIG. 4 as shown in FIG. 5, the magnetic flux generated by the current 14 in the front direction of the paper flowing through the heating coil 3a of the outermost layer is outside and outside the magnetic flux 6f for heating the plate material 2. To the heating coil 3b of the second layer, the heating coil 3c of the third layer, the heating coil 3d of the fourth layer, the heating coil 3e of the fifth layer, and the magnetic fluxes 6b, 6
c, 6d, 6e will pass. The magnetic fluxes 6b, 6c, 6d and 6e interlinking with these coil conductors heat the coil conductors themselves.

[0006] Generally, a metal having a cross section of about twice or more the current penetration depth δ is sufficiently heated by the magnetic flux interlinking with the metal, and the current penetration depth of copper used for the coil conductor is 1 kHz. Is about 2.25 mm, and it is about 0.7 mm at 10 kHz, and the coil conductor with a conductor size of several tens of mm is heated by the coil current of other layers. As a result, a reduction in heating efficiency is unavoidable in the related art, and further, the coil current is limited to prevent heat generation of the coil conductor, and the effect of increasing the plate material heating amount due to the multilayer structure is not sufficient.

It is an object of the present invention to provide an induction heating device which prevents a decrease in heating efficiency due to the leakage magnetic flux and a current limitation for preventing heat generation.

[0008]

The present invention that achieves the above object has the following matters specifying the invention. (1) A litz wire in which a large number of insulated wires are twisted is passed through a cooling hose to form a heating coil. An iron core and a shield plate are provided outside the multi-layer heating coil.

Heating of the coil conductor is suppressed by using a litz wire whose dimensions such as thickness and diameter of one coil conductor are sufficiently smaller than the current penetration depth as the coil conductor and which can be water-cooled to increase the current density. To be

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION Here, referring to FIG. 1 and FIG.
An embodiment of the invention will be described. Figure 2 shows one heating conductor
FIG. For example, about 0.1 to 0.3 mm
The litz wire 9 with the insulated wire having a diameter of 10 degrees is twisted
As a conductor, this litz wire 9 is a spacer made of an insulator.
Spacers held by 11 and 12 at appropriate intervals
Cooling hose made of rubber and insulator together with 11 and 12
Introduced in 13. In this case, the litz wire 9 is 1
Insulated one by one, its diameter is more than the current penetration depth
Small, so it is not heated by the magnetic flux of other layers
Yes. Also, by allowing the litz wire 9 to be water-cooled
Can be increased. As an example, frequency 10kHz
With a conventional water-cooled copper square tube with a conductor width of 30 mm, 100 A / mm ^TwoNo electricity
In terms of flow density, the current penetration depth is about 0.7 mm, so
The coil current is 100 × 30 × 0.7 = 2100A
You. Current when this current is applied to a litz wire with a diameter of 20 mm
Density is about 7A / mm^TwoTherefore, there is no problem under water cooling.

The heating coil 3 composed of such a water-cooled litz wire is wound in five layers in FIG. 1, and an iron core 8 is provided outside the heating coil 3 to improve efficiency and prevent magnetic flux from leaking to the outside.
And the shield plate 7 is arranged. Further, the heating coil and the iron core 8 are protected by the coil cement 4 in order to prevent heat and dust from the plate material 2, and the entire heating device is housed in a box 5 mainly made of an insulator.

[0012]

As described above, according to the present invention, the heating of the heating coil can be suppressed by the use of the litz wire and the water flow through the cooling hose, the heating efficiency can be improved, and the current The restrictions will be relaxed and the amount of heating can be increased.

[Brief description of drawings]

FIG. 1 is a configuration diagram of an example of an embodiment of the present invention.

FIG. 2 is a configuration diagram of a heating coil and a spacer.

FIG. 3 is a configuration diagram of a conventional example.

FIG. 4 is a block diagram of another conventional example.

FIG. 5 is a diagram for explaining a defect of a conventional example.

[Explanation of symbols]

 2 Heated material (plate material) 3, 3a, 3b, 3c, 3d, 3e Heating coil 6, 6b, 6c, 6d, 6e, 6f Magnetic flux 7 Shield plate 8 Iron core 9 Litz wire 11, 12 Spacer 13 Cooling hose

Front Page Continuation (72) Inventor Hironori Fujioka 4-6-22 Kannon Shinmachi, Nishi-ku, Hiroshima-shi, Hiroshima Mitsubishi Heavy Industries Ltd. Hiroshima Works

Claims (1)

[Claims] 1. A heating coil is formed by penetrating a litz wire, in which a large number of insulated wires are twisted, into a cooling hose, and the heating coil is laminated in multiple layers in a direction perpendicular to the direction of travel of the material to be heated. An induction heating device having a winding and a shield plate provided with an iron core on the outside of this multi-layer heating coil.