JPH0570912B2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention provides an induction heating device, for example, two sets of iron cores and coils that are spaced apart from each other, and then converts the generated magnetic flux into two sets of induction heating devices. This invention relates to an induction heating device that heats a steel material, such as a steel plate, by concentrating the heat on a part of the gap between the two.

[Conventional technology]

What is shown in FIG. 6 is a sectional view of a conventional induction heating device disclosed, for example, in Japanese Utility Model Application Publication No. 55-2090 filed by the present applicant.

In the figure, reference numeral 1 denotes an iron core that is provided facing each other through a gap 2, 3 a coil wound around the iron core 1, 4 an object to be heated that is inserted into the gap 2, and 5 a coil. 3 is the main magnetic flux generated, and 6 and 7 are other leakage magnetic fluxes that are not involved in heating.

FIG. 7 shows a conventional example in which the above-mentioned induction heating device is arranged, for example, in a steel sheet hot rolling line, where 8 is a conveyance roller made of a magnetic material that supports and conveys the object to be heated 4, and 9 is an induction heating device. It is a heating inductor.

As shown in FIG. 6, in the induction heating device, since the main magnetic flux 5 generated by the coil 3 penetrates the object to be heated 4, an eddy current is generated inside the object to be heated. Heat 4.

However, as shown in FIG. 7, since the induction heating inductor 9 is disposed close to the conveyance roller 8 made of a magnetic material, a part of the leakage magnetic flux 7 passes through the induction heating inductor 9. Let L be the average magnetic path length between the iron core 1 and the conveyance roller 8,
If the area of the transport roller 8 into which the magnetic flux enters is S, then when the transport roller 8 is a magnetic flux, the magnetic flux enters the transport roller 8 as φ ₇ which is inversely proportional to the magnetic resistance determined by the average magnetic path length L and the area S. ,
A voltage corresponding to the magnetic flux φ ₇ is induced within the conveyance roller 8, and an eddy current is generated.

Furthermore, as shown in FIG. 8, eddy currents induced in the conveyance roller 8 and
Due to the contact between the two, a part of the eddy current flows around to the object to be heated 4, and a circulating current I _R is generated in which the eddy current flows from the conveyor roller 8 through the object to be heated 4 and returns to the conveyor roller 8 again. Become.

For this reason, the conveyance roller 8 generates heat by itself, and furthermore, when the object to be heated 4 dances during conveyance or when the tail end of the object to be heated 4 passes through the conveyance roller 8, the object to be heated 4 is heated by the conveyance roller. When leaving the
At that moment, the induced current is interrupted, and therefore an arc discharge occurs between the heated object 4 and the conveying roller 8, causing discharge marks to be generated on the heated object 4 or the conveying roller 8. .

On the other hand, with respect to the leakage magnetic flux 7 of the induction heating inductor 9, a method of fixing a short circuit ring (not shown) to a part of the iron core 1 may be considered to reduce the leakage magnetic flux 7 to the conveying roller 8.

However, when actually operating, the leakage magnetic flux 7
is occurring in all directions, and the transport roller 8
It has been found that it is difficult to completely cancel out the leakage magnetic flux 7 to.

[Problem that the invention seeks to solve]

In the conventional induction heating device, since the magnetic flux 7 leaks to the outside as described above, the conveyance roller 8 made of a magnetic material is disposed in a part of the magnetic path of the leaked magnetic flux 7. An induced current flows through this conveyance roller 8 . As a result, the conveyance roller 8 generates heat by itself, and therefore needs to be cooled.

In addition, arc discharge occurs between the heated object 4 and the conveying roller 8 due to dancing caused by the running of the heated object 4 and eddy current interruption that occurs when the tail end of the heated object 4 passes through the conveying roller 8. generates discharge marks on the heated object 4 or the conveyance roller 8,
As a result, there were problems in that the product value of the heated object 4 decreased and the frequency of maintenance of the conveying roller 8 increased.

This invention was made to solve the above-mentioned problems, and it blocks the leakage magnetic flux, and even if the leakage magnetic flux cannot be blocked locally,
Even if there is a conveyance roller placed near the induction heating inductor, the conveyance roller will not be heated.
Another object of the present invention is to obtain an induction heating device in which arc discharge does not occur between an object to be heated and a conveyance roller.

[Means for solving problems]

The induction heating device according to the present invention is provided with an electromagnetic shield plate having a size that prevents at least the projection of the induction heating inductor onto the transport roller side between the induction heating inductor on the transport roller side and the transport roller. be.

[Effect]

In the induction heating device according to the present invention, an electromagnetic shield plate is interposed between the induction heating inductor and the conveyance roller, so that the leakage magnetic flux generated from the induction heating inductor and not involved in the heating of the object to be heated is absorbed by the electromagnetic shield plate. This reduces the amount of leakage magnetic flux that passes through the conveyance roller, thereby preventing heating of the conveyance roller and preventing arc discharge between the object to be heated and the conveyance roller.

〔Example〕

FIGS. 1 and 2 are explanatory views of an induction heating device according to an embodiment of the present invention. In the figure, numerals 1 to 6, 8, and 9 are the same or corresponding parts as those indicated by the same numerals in the conventional device, and the explanation thereof will be omitted here.

Reference numeral 10 is inserted between the induction heating inductor 9 and the conveyance roller 8, has a surface at least larger than the projection surface of the induction heating inductor 9 on the conveyance roller 8 side, and is made of a non-magnetic material, e.g. This is an electromagnetic shield plate made of copper. Reference numeral 11 denotes leakage magnetic flux that is not involved in heating the object 4 to be heated.

Further, G is the distance between the upper end of the electromagnetic shielding plate 10 and the upper surface level of the conveyance roller 8.

Further, 12 is a center apron that guides the object to be heated 4 in the vertical direction, 13 is a bearing stand for the conveyance roller 8, and 14 is a guide mechanism for vertical movement of the electromagnetic shielding plate 10. The electromagnetic shielding plate 10 has one end The center apron 12 is supported at its other end so as to be movable up and down while being guided by a guide mechanism 14 provided on a bearing pedestal 13 of the conveyance roller 8, respectively.

Next, 15 is a rack attached to the electromagnetic shielding plate 10, 16 is a pinion that meshes with the rack 15, and 17 is a speed reducer that reduces the rotation of the motor 19 via a coupling 18 and transmits it to the pinion 16. , these constitute the elevation adjustment device 20.

Next, what is shown in FIG. 3 is the electromagnetic shielding plate 1.
A line based on actually measured data showing the relationship between the magnitude of the circulating current I _R flowing from the conveying roller 8 through the object to be heated 4 to the conveying roller 8 and the distance G between the upper end of 0 and the upper surface level of the conveying roller 8. It is a diagram.

According to this, the smaller the distance G, the more
The leakage magnetic flux to the transport roller 8 is reduced, and the circulating current I _R
It can be seen that is decreasing.

This will be explained below.

Here, if the average magnetic path length between the iron core 1 and the conveyance roller 8 that constitute the induction heating inductor 9 is L, and the area of the conveyance roller 8 into which the magnetic flux enters is S, it is inversely proportional to the magnetic resistance determined by L and S. The magnetic flux φ ₇ enters the conveyance roller 8, and a voltage corresponding to φ ₇ is induced within the conveyance roller 8, generating an eddy current.

Now, if an electromagnetic shield plate 10 having a surface larger than at least the projection surface of the induction heating inductor ₉ toward the conveyance roller side is provided in a part of the magnetic path of the magnetic flux φ 7, the magnetic flux φ ₇ will penetrate through this electromagnetic shield plate 10. For,
An induced voltage e is generated in a direction that cancels out this leakage magnetic flux φ ₇ , 11. Now, the impedance to the current flowing along the outer periphery of the electromagnetic shielding plate 10 is Z
Then, a current _IS expressed by the following equation [1] flows through the electromagnetic shielding plate 10.

I _S = e/Z ... [1] Here, if the number of turns on one side of the coil 3 is N and the coil current is I _C , the magnetomotive force that determines the magnitude of the magnetic flux φ ₇ is N × I _C. When I _S flows through the electromagnetic shielding plate 10, the magnetomotive force becomes [N×I _C −I _S ], so
The leakage magnetic flux φ ₇ and the magnetic flux 11 entering the conveyance roller 8 are reduced at the rate of (N・I _C −I _S )/N・I _C , and therefore, the eddy current flowing through the conveyance roller 8 is proportional to that value. and reduce
Further, the amount of heat generated decreases in proportion to the square of the value.

Here, since the electromagnetic shielding plate 10 is made of a non-magnetic material, for example, a copper plate, the impedance Z is made small and the current flowing through the electromagnetic shielding plate 10 is
By increasing _IS , the eddy current flowing through the conveyance roller 8 can be further reduced, and self-heating of the electromagnetic shielding plate 10 can also be suppressed.

However, depending on the size of the distance G between the upper end of the electromagnetic shielding plate 10 and the upper surface level of the conveying roller 8, the leakage magnetic flux 11 is
It enters the conveying roller 8 through the gap between the upper end and the upper surface level of the conveying roller 8, that is, the lower surface of the object to be heated 4. Therefore, as shown in FIG. 3, an induced voltage is generated in the conveying roller 8 depending on the size of the distance G, resulting in an eddy current flowing.

Of course, ideally, the electromagnetic shield plate 10 should be arranged so that the distance G is 0, but in reality, the tail end of the object to be heated 4 hangs below the level of the upper surface of the conveyance roller 8. It's going down. Therefore, the electromagnetic shielding plate 10 must be installed within a range where the object to be heated 4 does not collide with the electromagnetic shielding plate 10.

Further, the shape of the object to be heated 4 is usually different at the tip, center, and tail. Therefore, the electromagnetic shielding plate 10 can be adjusted vertically depending on the position through which the heated object 4 passes, for example, as shown in FIGS. 1 and 2, by driving the rack 15, pinion 16, and motor 19. By doing so, it becomes possible to move the electromagnetic shielding plate 10 to a mechanically permissible position, and the maximum shielding effect within the permissible range shown in FIG. 3 can be expected.

Further, although the shape of the heated object 4 differs depending on the material, a shielding effect can be expected up to the permissible limit in that case as well.

Furthermore, according to what was confirmed using an actual machine, the effect of sparks generated between the conveyance roller 8 and the object to be heated 4 is approximately 60% or less of the effect of the circulating current when the electromagnetic shield plate 10 is not provided. It was also found that there was no actual harm if the amount was reduced.

In this way, the electromagnetic shielding plate 10 is placed between the induction heating inductor 9 and the conveying roller 8, and the distance G between the upper end of the electromagnetic shielding plate 10 and the upper surface level of the conveying roller 8 is set from the conveying roller 8 of the object to be heated 4. By adjusting and inserting it so that it does not hit the hanging part of the conveyor roller 8, the penetration of leakage magnetic flux 11 into the conveyor roller 8 can be reduced according to the mechanically allowed limit gap, and the self-heating of the conveyor roller 8 and the conveyor roller 8 can be reduced. Arc discharge between the roller 8 and the object to be heated 4 can be reduced to the limit possible.

Further, as described above, if the electromagnetic shielding plate 10 cannot sufficiently block the leakage magnetic flux 11 and a part of the leakage magnetic flux 11 penetrates the conveyance roller 8, the conveyance roller 8 is made of a non-magnetic material, As a result, even if leakage magnetic flux 11 that cannot be blocked by electromagnetic shielding plate 10 occurs locally, the amount of leakage magnetic flux passing through conveyance roller 8 is reduced compared to when conveyance roller 8 is made of a magnetic material. By inserting the electromagnetic shield plate 10 between the induction heating inductor 9 and the conveyance roller 8, the eddy current generated in the conveyance roller 8 can be significantly reduced. This combined effect can prevent self-heating of the transport roller 8 and arc discharge between the transport roller 8 and the object to be heated 4.

In the above embodiment, the material of the electromagnetic shield plate is copper, but the material is not limited to this, and the electromagnetic shield plate may be made of a non-magnetic material such as aluminum. In that case, the same effect as in the above embodiment can be obtained. Needless to say, you can get it.

Further, it is generally considered that stainless steel is suitable for the conveyance roller 8 made of non-magnetic material, but it goes without saying that the same effect can be obtained by using any non-magnetic material. .

Furthermore, in the above embodiment, an electromagnetic shield plate was attached to the bearing frame of the conveyance roller and the center apron, but an electromagnetic shield plate was attached to the induction heating device body under the same conditions so as to be placed between the induction heating inductor and the conveyance roller. It goes without saying that the same effect can be obtained by installing the .

Further, although the electromagnetic shielding plate elevation adjustment device is constructed of a rack, pinion, motor, etc., a certain effect can be expected even if it is moved by a simple manual handle, air cylinder, etc.

Furthermore, as shown in FIGS. 4 and 5, the electromagnetic shield plate may be fixed to the bearing frame and the center apron after adjusting its vertical position in advance; in this case, the configuration is simple. become.

〔Effect of the invention〕

As described above, according to the present invention, an electromagnetic shielding plate having a size that at least prevents the induction heating inductor from projecting onto the transport roller is inserted between the induction heating inductor on the transport roller side and the transport roller. By doing so, it is possible to reduce the penetration of leakage magnetic flux into the conveyance roller, thereby reducing the heating of the conveyance roller, and also to reduce the degree of occurrence of arc discharge between the object to be heated and the conveyance roller. As a result, it is possible to obtain an induction heating apparatus that can improve the quality of the heated object and reduce the frequency of maintenance of the conveying roller.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram of a vertical cross-sectional configuration of an induction heating device according to an embodiment of the present invention, FIG. 2 is a plan view of FIG. 1, and FIG. A relationship diagram of the induced voltage induced in the conveying roller with respect to the distance, FIG. 4 is a longitudinal cross-sectional configuration explanatory diagram of another embodiment, FIG. 5 is a plan view of FIG. 4, and FIG. 6 is a conventional induction heating device. FIG. 7 is a diagram showing the arrangement of FIG. 6, and FIG. 8 is a model diagram of an eddy current generated in a conventional conveyance roller. In the figure, 1... Iron core, 2... Gap, 3... Coil, 4... Heated object, 5... Main magnetic flux, 6... Leakage magnetic flux, 8... Conveyance roller, 9... Induction heating inductor, 10... Electromagnetic shield plate, 11... Leakage magnetic flux, 20... Elevation adjustment device. In each figure, the same reference numerals indicate the same or equivalent parts.

Claims (1)

[Claims] 1. It has two sets of iron cores that are arranged opposite to each other with an air space in between, and a coil wound around each of these iron cores, and heats an object to be heated that is inserted into the air space. an induction heating inductor that supports and conveys the object to be heated; and a large size provided between the induction heating inductor and the conveyance roller to prevent the induction heating inductor from projecting toward the conveyance roller. An induction heating device characterized by comprising an electromagnetic shielding plate having a 2. The induction heating device according to claim 1, wherein the conveyance roller is made of a non-magnetic material. 3. The induction heating device according to claim 1 or 2, wherein the electromagnetic shield plate is made of a non-magnetic material. 4. The induction heating device according to claim 3, wherein the non-magnetic material constituting the electromagnetic shield plate is copper, aluminum, or stainless steel. 5. The induction heating device according to any one of claims 1 to 4, wherein the electromagnetic shield plate is configured to be adjustable in the vertical direction by an elevation adjustment device. 6. The distance between the upper end of the electromagnetic shielding plate and the upper surface level of the conveying roller is within the range of 100 mm to the minimum value at which the upper end of the electromagnetic shielding plate does not touch the object to be heated on the conveying roller. Claim 1 The induction heating device according to any one of items 5 to 6.