JPH031479A - Induction heating device - Google Patents

Abstract

PURPOSE:To construct an induction heating device in a small size by interposing a conductive shortcircuiting ring between induction heatings, allowing the leak mag. flux at the induction heating coils to flow through this shortcircuiting ring, and reducing the distance between the induction heating coils. CONSTITUTION:A shortcircuiting ring 10 of conductive material has a space which admits passage of an object to be heated 6 and is arranged concentrically in place between the end faces of induction heating coils 4, 4a. When the magnetic flux phi of the coil 4 and that phia of the other 4a interfere with each other, an inducted voltage as expressed by a specific equation is generated in the load circuit of frequency converters 3, 3a, and the load impedance will vary equivalently to generate risk of the converters 3, 3a being incapable of oscillating. However, magnetic flux flows through the ring 10 to produce an induced current, so that the magnetic flux phi on the coil 4 side will no more intersect the coil 4a. This configuration eliminates magnetic interference with each other even though the distance between the coils is reduced.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an induction heating device for induction heating an object to be heated.

[Conventional technology]

FIG. 5 shows an electric circuit of a conventional induction heating device, and FIG. 6 shows a side view of the induction heating device equipped with this electric circuit. In both figures, 1 is a power receiving board that receives the voltage of a three-phase AC power supply at a commercial frequency, 2 is a step-down transformer, and 3 and 3a are frequency converters that send out single-phase AC at a predetermined frequency. 4.4a is an induction heating coil constituting one coil unit, and a capacitor 5.5a is connected in parallel.
and constitute a parallel resonant circuit.

In FIG. 6, 6 is an object to be heated, 7 and 8 are an insertion conveyor and a pinch roller for feeding the object to be heated 6 into the heating space of the induction heating coils 4 and 4a, and 9 is for carrying out the heated object 6. It is a skid rail.

[Problem to be solved by the invention]

In this two-power induction heating device, induction heating coils 4 and 4a are controlled independently by frequency converters 3 and 3.
Since power is supplied from A, as shown in Fig. 4(b), when the distance between both induction heating coils is small,
The magnetic fluxes φ and φa generated from the induction heating coils 4 and 4a interfere with each other, and the frequency converter 3.3a may become unable to oscillate due to a change in the load interferer. Therefore, as shown in FIG. 4(C), However, there was a problem in that the distance between the induction heating coils 4.4a had to be increased, resulting in an increase in size.

This invention was made to solve the above problem.
Compared to the past, the required length of the coil unit has been shortened,
An object of the present invention is to provide an induction heating device that can be downsized.

[Means to solve the problem]

In order to achieve the above object, the present invention interposes a conductive short-circuit ring between the end faces of adjacent induction heating coils, through which the object to be heated can pass.

[Effect]

In this invention, leakage magnetic flux from the induction heating coil is absorbed by the shorting ring, so it does not interfere with adjacent induction heating coils.

〔Example] Hereinafter, one embodiment of the present invention will be described with reference to the drawings.

1 and 2, reference numeral 10 denotes a conductive short-circuit ring, which has a space G through which the object to be heated 6 can pass, as shown in FIG. are arranged concentrically at a predetermined position between the two. The other configurations are the same as those in FIGS. 5 and 6 above.

When the magnetic flux φ of the induction heating coil 4 and the magnetic flux φa of the induction heating coil 4a interfere with each other as shown in FIG. 4(b), the load circuit of the frequency converter 3.3a has v=M−. dφ/dt=2πfMφ・---(1) However, M: Mutual induction impedance f: An induced voltage V expressed in frequency is generated, the load impedance changes equivalently, and the frequency converter 3.3a Although oscillation may become impossible, in this embodiment, magnetic flux flows through the shorting ring 10 and an induced current is generated, so that, for example, the magnetic flux φ on the induction heating coil 4 side does not intersect with the induction heating coil 4a.

As the material of the shorting ring 10, copper or a copper alloy containing copper as a main component, economical aluminum or an aluminum alloy containing aluminum as a main component may be used, or a ring made of an electric wire may be used. If the joule loss caused by the induced current is large, a water-cooled cable may be used. Of course, a highly conductive material such as silver or a superconducting material may also be used.

〔Effect of the invention〕

As explained above, this invention has a structure in which a conductive short-circuiting ring is interposed between the induction heating coils, and the leakage magnetic flux from the induction heating coils flows through the short-circuiting ring, thereby increasing the distance between the induction heating coils. Even if the length of the coil unit is small, mutual magnetic interference can be eliminated, so the length of the coil unit can be reduced and the device can be made more compact than in the past.

[Brief explanation of the drawing]

Fig. 1 is a side view showing an embodiment of the present invention, Fig. 2 is an electric circuit diagram of the above embodiment, Fig. 3 is a perspective view of a shorting ring in the above embodiment, and Fig. 4(a) is a diagram of the above embodiment. Figures 4 (b) and 4 (C) are diagrams showing the magnetic flux relationship between adjacent induction heating coils to explain the effect of the short-circuit ring in the conventional device. FIG. 5 is an electric circuit diagram of a conventional induction heating device, and FIG. 6 is a side view of the conventional device. In the figure, 2 - transformer, 3.3a - frequency converter, 4
．． 4a-induction heating coil, 5.5A-capacitor, 10
- Conductive shorting ring. In addition, in the figures, the same reference numerals indicate the same or corresponding parts.

Claims (1)

[Claims] In an induction heating apparatus that includes a coil unit in which a plurality of induction heating coils are arranged in series, and a frequency converter that individually supplies single-phase AC power of a predetermined frequency to each induction heating coil of this coil unit, An induction heating device characterized in that a conductive short-circuit ring through which a heated object can pass is interposed between end faces of an induction heating coil.