JP3576097B2 - High frequency heating method and apparatus - Google Patents

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a heating method and apparatus for intensively heating only a portion to be heated such as a cylindrical metal body.
[0002]
[Prior art]
FIG. 4 shows a can body 1 of a can (for example, a gallon can including a can body, a can bottom, and a can lid), which is one of cylindrical metal bodies.
In the case where high-frequency heating is partially applied to the welded portion 2 (seam-welded portion along the longitudinal direction) which is the portion to be heated of the can body 1, for example, as shown in FIG. It is conceivable to use a heating coil 3 having a long shape along the length. The can body 1 and the heating coil 3 are both fixedly arranged.
[0003]
When a high frequency power supply is connected to the leads 3a, 3a of the heating coil 3, an induction magnetic field as indicated by an arrow is generated. However, in this case, as shown in FIG. 6, although the portion 1a of the can body 1 close to the heating coil 3 is satisfactorily heated, the portion 1b of the heating coil 3 located on the side of the gap 3b has a passing magnetic flux. Because of the decrease, the problem of difficulty in heating occurs.
Therefore, in the above method, the welded portion 2 is mainly heated by the residual heat from the surroundings. That is, it is difficult to intensively heat only the weld 2.
[0004]
In order to avoid the above-mentioned inconvenience, the interval between the gaps 3b of the heating coil 3 may be reduced as much as possible. However, in order to do so, a high processing accuracy is required for the heating coil 3, so that the manufacturing cost of the coil 3 is increased.
On the other hand, when the heating coil 3 is used, the heating temperature at the central portion in the longitudinal direction of the can body 1 becomes higher than the heating temperature at both sides of the central portion. That is, the heating temperature distribution is biased. This is because the magnetic flux generated by the heating coil 3 tends to concentrate on the lead portion 3a located at the center in the longitudinal direction of the can body 1.
[0005]
In order to eliminate the bias of the heating temperature distribution, a heating coil 3 'having a structure in which the entire length is increased and the lead portion 3a is provided on the end side may be used as shown in FIG. However, when this heating coil 3 'is used, there is a practical problem that the load on the lead portion 3a increases because the length in the longitudinal direction is large. In addition, since the coil 3 'does not match the size of the can body 1, there is a disadvantage that the electric power applied to the load changes.
[0006]
An object of the present invention is to provide a high-frequency heating method and apparatus capable of intensively and uniformly high-frequency heating only a heated portion in view of such a situation.
[0007]
[Means for Solving the Problems]
A first invention is a method for high-frequency heating a heated portion of a metal body, comprising: arranging and fixing a plurality of spirally formed heating coils at a predetermined interval; Transferring the metal body so as to sequentially pass above the heating coil, so that the heated portion is sequentially heated at a high frequency by an induction magnetic field of each of the heating coils.
According to a second aspect, in the first aspect, the heating coils are connected in series with each other so as to be energized.
A third invention is an apparatus for high-frequency heating a heated portion of a metal body, wherein the plurality of heating coils formed in a spiral shape and arranged and fixed at a predetermined interval from each other; Transport means for transporting the metal body so as to sequentially pass above each of the heating coils; and the high frequency heating of the portion to be heated is sequentially performed by an induction magnetic field of each of the heating coils.
In a fourth aspect based on the third aspect, the heating coils are connected in series with each other to energize.
[0008]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of a high-frequency heating method and apparatus according to the present invention will be described with reference to the drawings.
FIG. 1 schematically shows a first embodiment of an apparatus for performing a high-frequency heating method according to the present invention.
[0009]
This high-frequency heating device is for high-frequency heating the welded portion 2 (heated portion) of the can body 1 shown in FIG. 4, and through a high-frequency power supply 10 for outputting high-frequency power of a constant voltage and a transformer 20. A plurality (three in this example) of heating coils 30 connected in series to the high-frequency power supply 10 and a conveyor (not shown) for transporting the can body 1 in the direction of the arrow are provided.
The heating coils 30 are formed in a spiral shape, and are arranged and fixed in the same plane at a predetermined interval from each other.
The conveyor holds the cans 1 so that the welds 2 of the cans 1 are along the transport direction and the welds 2 face downward. Accordingly, with the operation of the conveyor, the welded portion 2 of each can body 1 sequentially passes above each of the heating coils.
[0010]
Each heating coil 30 forms a magnetic field as shown in FIG. 2, that is, a magnetic field in a pattern in which the magnetic flux is concentrated near the center thereof, based on the electric power supplied from the high-frequency power supply 10.
Therefore, when the can body 1 is conveyed by the conveyor, the welded portion 2 of the can body 1 sequentially passes near the center of each heating coil 30 which is the magnetic flux concentrated portion, and as a result, the welded portion 2 is concentrated and uniform. Tends to be heated.
[0011]
By the way, according to the first embodiment, in addition to the advantage that the welded portion 2 is intensively and uniformly heated, the heating coil 30 can be heated irrespective of the size of the can body 1 that is the metal body to be heated. Another advantage is that only a certain number of values need to be set.
[0012]
That is, in the conventional high-frequency heating method in which the can body 1 is fixedly arranged, when the load on the heating coil fluctuates greatly, the degree of heating greatly changes. For this reason, when the load fluctuates greatly, that is, when a can body having a significantly different size is introduced, the heating coil is replaced with one having a shape adapted to the can body to cope with the load fluctuation. There is no other way than to do it.
[0013]
On the other hand, according to the above-described first embodiment in which the can body 1 is relatively moved with respect to the heating coil 30, the power supplied to the heating coil 30 changes according to the load fluctuation. Thus, it is possible to cope with a load change without replacing the heating coil 30 or the like.
[0014]
The heating temperature and heating rate of the welding portion 2 of the can body 1 are determined by the output of the high-frequency power source 10, the gap between the heating coil 30 and the can body 1, the gap between each heating coil 30 and the number of arranged heating coils 30. It can be adjusted as a function. Further, the width of heating by each heating coil 30 (the width of the welded portion 2) can be changed by changing the size of the coil 30.
[0015]
In the first embodiment, each heating coil 30 is connected in series to the high-frequency power supply 10, but as shown in FIG. 3 showing the second embodiment of the present invention, each heating coil 30 is connected to the high-frequency power supply 10. Are connected in parallel, it is possible to heat the welding portion 2. However, in the case of the second embodiment, since each heating coil 30 is excited independently, a constant magnetic flux is applied to the can body 1 unless the can body 1 as a load is continuously supplied at small intervals. May not be given. In the first embodiment in which the heating coils 30 are connected in series, these coils 30 equivalently have a function as one coil, and therefore, regardless of the input state (input interval) of the can body 1. A constant magnetic flux can always be applied to the can body 1.
[0016]
According to the first and second embodiments, even when the length of the welded portion 2 of the can body 1 is large, the small-sized heating coil 30 is used to cover the entire area of the welded portion 2 of the can body 1. Power can be intensively supplied. In addition, since the heating is performed while moving the can body 1 by the conveyor, the heating can be performed without unevenness.
[0017]
The heating devices according to the first and second embodiments are also effective for heating a heated portion other than the welded portion 2 of the can body 1, for example, for heating a joint portion of a metal flat plate. Can be applied.
[0018]
【The invention's effect】
According to the present invention, a plurality of heating coils formed in a spiral shape are arranged and fixed at predetermined intervals, and the object to be heated is so arranged that the heated portion sequentially passes above each of the heating coils. It is transported. Therefore, the heated portion can be intensively and uniformly heated by the induction magnetic field of each heating coil, and a large-length heated object can be heated using the small-sized heating coil. .
Also, when the heating coils are connected in series, a constant magnetic flux can always be applied to the object to be heated, regardless of the interval between the input of the object to be heated.
[Brief description of the drawings]
FIG. 1 is a schematic diagram showing a first embodiment of the present invention.
FIG. 2 is a schematic diagram showing a magnetic field generated by a spiral heating coil and a heating site.
FIG. 3 is a schematic diagram showing a second embodiment of the present invention.
FIG. 4 is a perspective view showing a can body and a welded portion thereof.
FIG. 5 is a perspective view showing an embodiment of conventional high-frequency heating.
FIG. 6 is a partially enlarged view showing a heating distribution by conventional high-frequency heating.
FIG. 7 is a perspective view showing another embodiment of the conventional high-frequency heating.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Can body 2 Welded part 10 High frequency power supply 20 Transformer 30 Heating coil

Claims (2)

A method for high-frequency heating a weld of a cylindrical can made of metal ,
A plurality of spirally formed heating coils are arranged and fixed at predetermined intervals, and these heating coils are connected in series with each other and energized,
Transporting the can so that the welded portion of the can sequentially passes above each of the heating coils,
And a high-frequency heating method for sequentially heating the welded portion of the can by the induction magnetic field of each of the heating coils. A high-frequency heating device for welding a cylindrical can made of metal ,
A plurality of heating coils that are formed in a spiral shape, are arranged and fixed at predetermined intervals, are connected in series with each other, and are energized,
Conveying means for conveying the can so that the welded portion of the can sequentially passes above each of the heating coils,
And a high-frequency heating device for sequentially heating the welded portion of the can with an induction magnetic field of each of the heating coils.

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