JP7548667B2 - Induction heating device for localized heating - Google Patents

Description

The present invention relates to an induction heating device for localized heating.

Induction heating (IH: Induction Heating) is a method for heating conductive objects such as metals, which utilizes electromagnetic induction. Induction heating uses a magnetic field generated around a coil by supplying high-frequency current from a high-frequency power source. In induction heating, the magnetic field supplies magnetic flux to the object to be heated, generating an induced current in the object. The object is directly heated by heat generated by the induced current and the electrical resistance of the object. Therefore, induction heating has the characteristic of being capable of heating the object quickly and efficiently. Taking advantage of these characteristics, induction heating has been widely adopted in various fields in recent years.
For example, Patent Document 1 discloses an induction heating device for a thin plate-shaped heated object in which a magnetic flux is generated approximately perpendicular to the heated object in an approximately rectangular space S1 parallel to the heated object formed by two heating coils shaped approximately in the shape of a root symbol, and the heated object is heated by inducing eddy currents on the surface of the heated object due to the magnetic flux.

Patent No. 5838254

The induction heating device of Patent Document 1 is capable of heating a wide area of the object to be heated by using a heating coil having a space S1 parallel to the object to be heated, but is not capable of locally heating a small area of the object to be heated as is.
In the induction heating device of Patent Document 1, in order to locally heat the object to be heated, it is necessary to reduce the space S1 of the heating coil parallel to the object to be heated. However, if the space S1 is reduced, the magnetic flux supplied from the heating coil to the object to be heated is reduced, and the induced current generated in the object to be heated is reduced. Therefore, in this case, it is difficult to increase the output of the induction heating device.

The object of the present invention is to provide an induction heating device for localized heating that can locally heat an object to be heated with high output.

In order to achieve the above-mentioned object, the invention described in claim 1 comprises a heating coil that inductively heats an object to be heated by supplying a high-frequency current from a high-frequency power source, the heating coil having a first solenoid and a second solenoid, the object to be heated is placed outside the first solenoid and the second solenoid, the central axis of the first solenoid is along the central axis of the second solenoid, the end of the first solenoid facing the object to be heated and the end of the second solenoid facing the object to be heated are adjacent to each other with a gap of 1 mm or more and less than 10 mm , and the first solenoid and the second solenoid generate magnetic fields in opposite directions to each other by the high-frequency current supplied to both of them.
In a second aspect of the present invention , in the above-mentioned configuration, the first solenoid and the second solenoid are formed of a hollow conductor.
In accordance with a third aspect of the present invention , in the above-mentioned configuration, at least one of the first solenoid and the second solenoid is provided in a plurality of units.
In this application, a solenoid refers to a cylindrical coil in which a conducting wire is wound in a spiral shape by one or more turns. Also, "along the central axis" means approximately parallel, and refers to a state in which the central axis of the first solenoid is parallel to the central axis of the second solenoid, or is inclined in a V-shape or letter shape.

The main advantage of the present invention is that it provides an induction heating device for localized heating that is capable of locally heating an object with high output.

FIG. 2 is a perspective view illustrating a heating coil and an object to be heated according to the present invention. 2 is an explanatory diagram showing the directions of a current flowing through a heating coil, a magnetic field generated by electromagnetic induction, and an induced current generated on the surface of an object to be heated. FIG. FIG. 1 is an explanatory diagram showing dimensions of models of heating coils in Examples 1 to 4 in a heating simulation. FIG. 4 is an explanatory diagram showing a heating coil of Comparative Example 1. 1A is a central cross-sectional magnetic field strength distribution map, FIG. 1B is a workpiece surface current density distribution map, and FIG. 1C is a workpiece surface heat generation amount distribution map. FIG. 10A is a central cross-sectional magnetic field strength distribution map, FIG. 10B is a workpiece surface current density distribution map, and FIG. 10C is a workpiece surface heat generation amount distribution map. FIG. 10A is a central cross-sectional magnetic field strength distribution map, FIG. 10B is a workpiece surface current density distribution map, and FIG. 10C is a workpiece surface heat generation amount distribution map. FIG. FIG. 13 is a workpiece surface heat generation amount distribution diagram by a heating simulation of Example 4. FIG. 13 is a workpiece surface heat generation amount distribution diagram by a heating simulation of Example 5. FIG. 13 is a workpiece surface heat generation amount distribution diagram by a heating simulation of Example 6. 1A is a diagram illustrating the results of a heating simulation of Comparative Example 1; FIG. 1B is a diagram illustrating the distribution of magnetic field strength at the central cross section; FIG. 1C is a diagram illustrating the distribution of heat generation amount at the work surface; FIG. 4 is a photograph showing the heat generation state of a workpiece caused by induction heating by an actual induction heating device for local heating having the heating coil of Example 1. (a) is an explanatory diagram showing a heating coil with 1 turn, (b) is a photograph showing the heat generation state of a workpiece due to induction heating by an actual induction heating device for local heating having a heating coil with 1 turn, (c) is an explanatory diagram showing a heating coil with 2 turns, and (d) is a photograph showing the heat generation state of a workpiece due to induction heating by an actual induction heating device for local heating having a heating coil with 2 turns. FIG. 2A is an explanatory diagram showing a heating coil capable of linear heating, and FIG. 2B is a workpiece surface heat generation amount distribution diagram obtained by a heating simulation of a heating coil capable of linear heating.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings.
FIG. 1 is a perspective view showing a heating coil and an object to be heated according to the present invention.
As shown in FIG. 1, the induction heating device for local heating includes a heating coil 1 and a high-frequency power source (not shown) connected to both ends 11 and 12 of the heating coil 1 and supplying a high-frequency current to the heating coil 1 .

The heating coil 1 is formed using a hollow conductor wire capable of conducting a cooling fluid (e.g., water) therethrough. As shown in FIG. 1, the heating coil 1 comprises a first solenoid 2, a second solenoid 3 disposed adjacent to the first solenoid 2, and a connecting part 4 connecting these. For ease of explanation, the direction of the heating coil 1 is such that the side closer to the object to be heated is the bottom, the direction in which the first solenoid 2 and the second solenoid 3 are lined up is the left-right direction, and the first solenoid 2 is on the left.

FIG. 2 is an explanatory diagram showing the directions of a current flowing through a heating coil, a magnetic field generated by electromagnetic induction, and an induced current generated on the surface of an object to be heated.
The first solenoid 2 and the second solenoid 3 are both cylindrical solenoids wound in a spiral shape. The central axis C1 of the first solenoid 2 and the central axis C2 of the second solenoid 3 extend vertically and are parallel to each other. The first solenoid 2 and the second solenoid 3 are both wound counterclockwise from top to bottom when viewed from above. The lower end 2a of the first solenoid 2 and the lower end 3a of the second solenoid 3 are adjacent to each other and connected by a connecting portion 4. The lower end 2a of the first solenoid 2 is a portion immediately before it exits the cylindrical portion of the first solenoid 2. The lower end 3a of the second solenoid 3 is a portion immediately before it exits the cylindrical portion of the second solenoid 3. The connecting portion 4 is a portion that connects the lower end 2a of the first solenoid 2 and the lower end 3a of the second solenoid 3 in a direction that intersects with the left-right direction. Further, the lower end 2a of the first solenoid 2, the lower end 3a of the second solenoid 3, and the connecting portion 4 are all located on the same imaginary horizontal plane.
Moreover, the first solenoid 2 and the second solenoid 3 are separated by a distance W so as to prevent short circuit and leakage current between them. The distance W is preferably 1 mm or more and less than 10 mm. More preferably, it is 1 mm or more and 5 mm or less, and most preferably about 1 mm. If the first solenoid 2 and the second solenoid 3 are separated by more than the upper limit of this range, 10 mm, the effect of local heating becomes relatively weak. On the other hand, if the first solenoid 2 and the second solenoid 3 are closer than the lower limit of this range, 1 mm, there is a possibility that a short circuit and leakage current will occur.

The object to be heated is heated as follows: In a state where the object to be heated is placed below the heating coil 1 (for example, at a position 2 mm below the heating coil 1), a high-frequency current is supplied to the heating coil 1 using a high-frequency power source.
When a current is supplied to the heating coil 1 and currents D1 and D2 flow at a certain moment as shown in Fig. 1, a current D3 flows in the first solenoid 2 counterclockwise as viewed from above as shown in Fig. 2, and a current D4 flows in the second solenoid 3 clockwise as viewed from above as shown in Fig. 2. Then, around the first solenoid 2, a magnetic field A is generated inside the first solenoid 2 due to electromagnetic induction, which faces from the back surface of the paper in Fig. 2 to the front surface, i.e., in a direction away from the object to be heated. Meanwhile, around the second solenoid 3, a magnetic field B is generated inside the second solenoid 3, which faces from the front surface of the paper in Fig. 2 to the back surface, i.e., in a direction toward the object to be heated.

When high-frequency current is supplied to the heating coil 1, an induced current E1 is generated in a counterclockwise direction as viewed from above in the portion of the surface of the object directly below the first solenoid 2, and an induced current E2 is generated in a clockwise direction as viewed from above in the portion of the surface of the object directly below the second solenoid 3. These induced currents E1 and E2 flow in the same direction in the portion F of the object directly below the lower end 2a of the first solenoid 2 and the lower end 3a of the second solenoid 3 (connection portion 4), and become a large induced current. Therefore, the object directly below the heating coil 1 can be locally heated with high power in portion F.

The induction heating device for localized heating of the above-mentioned form includes a heating coil 1 which inductively heats an object to be heated by supplying a high-frequency current from a high-frequency power source, the heating coil 1 having a first solenoid 2 and a second solenoid 3, the object to be heated is disposed outside the first solenoid 2 and the second solenoid 3, the central axis C1 of the first solenoid 2 is along the central axis C2 of the second solenoid 3, the lower end 2a of the first solenoid 2 on the side of the object to be heated and the lower end 3a of the second solenoid 3 on the side of the object to be heated are adjacent to each other, and the first solenoid 2 and the second solenoid 3 generate magnetic fields A and B in opposite directions to each other due to the high-frequency current supplied to both of them.
In the induction heating device for localized heating configured in this manner, when high-frequency current is supplied to the heating coil 1, an induced current E1 generated on the surface of the heated object by the magnetic field A generated in the first solenoid 2 and an induced current E2 generated on the surface of the heated object by the magnetic field B generated in the second solenoid 3 flow in the same direction in part F, resulting in a stronger induced current in part F, and the heated object can be locally heated with high output.

Below, using a heating simulation model, we will explain Examples 1 to 6 that conform to the above-mentioned configuration, and Comparative Example 1 that does not belong to the present invention. Note that the present invention is not limited to these Examples.

Fig. 3 is an explanatory diagram showing the dimensions of the heating coil models of Examples 1 to 4 in the heating simulation. Fig. 4 is an explanatory diagram showing the heating coil of Comparative Example 1.
The heating simulation was performed using commercially available computer simulation software.
In the first embodiment, the first solenoid 2 and the second solenoid 3 in the above embodiment each have three loops, and the outer diameter of each solenoid is φ17.0 mm. The distance W between them is 1 mm.
Example 2 is similar to Example 1, except that the distance W is set to 5 mm.
Moreover, Examples 3 and 4 are similar to Example 1, except that the distance W in Example 1 is 10 mm. Note that the winding method of each solenoid is the same as in Example 1, but those with a distance W of 10 mm or more will be referred to as "heating coil 1'", "first solenoid 2'", "second solenoid 3'" and "lower ends 2a', 3a'" below.
Examples 5 and 6 are similar to Examples 3 and 4, except that the outer diameter of each solenoid is φ50.0 mm.

As shown in Fig. 4, the heating coil 1a of Comparative Example 1 includes a first solenoid 21 and a second solenoid 31 disposed adjacent to the first solenoid 21. The central axis C3 of the first solenoid 21 and the central axis C4 of the second solenoid 31 both extend vertically and are parallel to each other. The winding direction of the first solenoid 21 is clockwise when viewed from above, and the winding direction of the second solenoid 31 is counterclockwise when viewed from above. The lower end of the first solenoid 21 and the lower end of the second solenoid 31 are connected by a connecting portion 41. The connecting portion 41 is a portion that connects the lower end of the first solenoid 2 and the lower end of the second solenoid 3 in the left-right direction.
4, when currents D5 and D6 are supplied, current flows clockwise in a top view in both the first solenoid 21 and the second solenoid 31. Then, around the first solenoid 21 and the second solenoid 31, magnetic fields A' and B' are generated inside the first solenoid 21 and the second solenoid 31 due to electromagnetic induction, which are oriented in a direction toward the object to be heated.
In the comparative example 1, the distance W between the first solenoid 21 and the second solenoid 31 was set to 1 mm.

The following conditions were set as common conditions for each heating simulation model of the heating coil 1 of Examples 1 to 2, the heating coil 1' of Examples 3 to 6, and the heating coil 1a as Comparative Example 1 in the heating simulation.
The wire forming the solenoid was a solid conductor (cross-sectional dimension φ3.0 mm) made of copper (Cu). The vertical spacing between each loop of the solenoid was 1.0 mm.

In the heating simulations of Examples 1 to 6 and Comparative Example 1, the following conditions were set for the workpiece to be heated.
The material was carbon steel (S45C). The dimensions were 100.0 mm wide x 100.0 mm deep x 10.0 mm thick. The density was 7850.0 kg/m ³ . The relative magnetic permeability was 100. The electrical resistivity was 16.7×10 ⁻⁸ Ω·m.

In addition, when performing the heating simulations of Examples 1 to 3 and 5 and Comparative Example 1, the following conditions were set. The coil-workpiece distance was 2.0 mm. As initial conditions, the workpiece temperature was 25.0° C. and the air temperature was 25° C. As boundary conditions, the current was 600 A and its frequency was 250 kHz.
Examples 4 and 6 are similar to Examples 1 to 3, 5 and Comparative Example 1, except that the current was 1000A.
The analysis was performed as a non-steady analysis for five frequency cycles.

Fig. 5 is an explanatory diagram showing the results of a heating simulation of Example 1 (solenoid outer diameter φ17.0 mm, W=1 mm, solenoids wound in the same direction, current 600 A), where Fig. 5(a) is a magnetic field strength distribution diagram of a cross section (central cross section) in a plane including the central axis of each solenoid, Fig. 5(b) is a current density distribution diagram of the surface (surface) of the workpiece facing the heating coil, and Fig. 5(c) is a heat generation distribution diagram of the workpiece surface. Note that the arrows in Fig. 5(a) indicate the direction of the magnetic field, and the arrows in Fig. 5(b) indicate the direction of the current, and so on below.
As a result of the heating simulation, when the magnetic field strength generated around the heating coil 1 of Example 1 was confirmed, it was confirmed that magnetic fields A and B facing in opposite directions were generated on the central axis C1 of the first solenoid 2 and the central axis C2 of the second solenoid 3 in Example 1, as shown in Figure 5 (a).

Next, when checking the current density on the work surface, as shown in FIG. 5(b), it can be seen that an induced current occurs at a much higher density directly below (part F) between the first solenoid 2 and the second solenoid 3 (connection part 4) on the work surface compared to the surrounding area. This is thought to be because the induced current E1, which is generated on the work surface directly below by the first solenoid 2 and runs counterclockwise when viewed from above, and the induced current E2, which is generated on the work surface directly below by the second solenoid 3 and runs clockwise when viewed from above, are oriented in the same direction directly below between the lower end 2a of the first solenoid 2 and the lower end 3a of the second solenoid 3 (part F), resulting in a large induced current.

Furthermore, when checking the amount of heat generated on the workpiece surface, as shown in Fig. 5(c), it was confirmed that the workpiece was locally heated directly below (part F) between the lower end 2a of the first solenoid 2 and the lower end 3a of the second solenoid 3 of the heating coil 1 in Example 1. The total amount of heat generated on the entire workpiece surface at this time was 3.33 kW.
Therefore, by using an induction heating device for local heating including the heating coil 1 of Example 1, it is possible to locally heat the portion F of the object to be heated.

FIG. 6 is an explanatory diagram showing the results of a heating simulation for Example 2 (solenoid outer diameter φ17.0 mm, W=5 mm, solenoid wound in the same direction, current 600 A), in which FIG. 6(a) is a central cross-section magnetic field strength distribution diagram, FIG. 6(b) is a workpiece surface current density distribution diagram, and FIG. 6(c) is a workpiece surface heat generation amount distribution diagram.
When checking the magnetic field strength generated around the heating coil 1 in Example 2, it can be seen that, as shown in Figure 6 (a), magnetic fields A and B facing in opposite directions are generated on the central axis C1 of the first solenoid 2 and the central axis C2 of the second solenoid 3 in Example 2.

Next, when checking the current density on the work surface, as shown in FIG. 6(b), it can be seen that an induced current occurs at a higher density directly below the area between the lower end 2a of the first solenoid 2 and the lower end 3a of the second solenoid 3 (part F) on the work surface compared to the surrounding area.

Furthermore, when checking the amount of heat generated on the work surface, as shown in Fig. 6(c), it was confirmed that the work surface was locally heated just below (part F) between the lower end 2a of the first solenoid 2 and the lower end 3a of the second solenoid 3. The total amount of heat generated on the entire work surface at this time was 3.38 kW.
Therefore, by using an induction heating device for local heating including the heating coil 1 of Example 2, it is possible to locally heat the portion F of the object to be heated.

FIG. 7 is an explanatory diagram showing the results of a heating simulation for Example 3 (solenoid outer diameter φ17.0 mm, W=10 mm, solenoid wound in the same direction, current 600 A), in which FIG. 7(a) is a central cross-section magnetic field strength distribution diagram, FIG. 7(b) is a workpiece surface current density distribution diagram, and FIG. 7(c) is a workpiece surface heat generation amount distribution diagram.
When checking the magnetic field strength generated around the heating coil 1' in Example 3, it can be seen that, as shown in Figure 7 (a), magnetic fields A and B facing in opposite directions are generated on the central axis C1 of the first solenoid 2' and the central axis C2 of the second solenoid 3' in Example 3.

Next, when checking the current density on the workpiece surface, as shown in FIG. 7(b), it can be confirmed that induced currents are generated at a higher density directly below the first solenoid 2' and the second solenoid 3' of the heating coil 1' on the workpiece surface compared to the surrounding area.

Furthermore, when the amount of heat generated on the work surface was checked, it was confirmed that the work surface was heated in two ring shapes directly below the first solenoid 2' and the second solenoid 3' of the heating coil 1', as shown in Fig. 7(c). However, it was confirmed that the work surface was locally heated directly below the area between the lower end 2a' of the first solenoid 2' and the lower end 3a' of the second solenoid 3' (part F), although the heating was weaker than in Examples 1 and 2. The total amount of heat generated on the entire work surface at this time was 3.34 kW.
Therefore, by using the induction heating device for local heating including the heating coil 1' of the third embodiment, it is possible to locally heat the portion F of the object to be heated.
However, if the distance W between the solenoids is increased to 10 mm or more, although localized heating is possible, it is considered that the effect will be relatively weak.

Based on the above considerations, in Example 4, it was confirmed whether local heating could be effectively achieved by increasing the current supplied to the heating coil 1' of Example 3. In addition, in Example 5, it was confirmed whether local heating could be effectively achieved by providing a heating coil 1' with a larger outer diameter of each solenoid than the heating coil 1' of Example 3. Furthermore, in Example 6, it was confirmed whether local heating could be more effectively achieved by increasing the current supplied to the heating coil 1' of Example 5.

FIG. 8 is a workpiece surface heat generation amount distribution diagram by a heating simulation of Example 4 (solenoid outer diameter φ17.0 mm, W=10 mm, solenoid wound in the same direction, current 1000 A).
When checking the amount of heat generated on the workpiece surface, as shown in Figure 8, it can be confirmed that the workpiece surface is locally heated just below the lower end 2a' of the first solenoid 2' and the lower end 3a' of the second solenoid 3' (part F), as in Example 3, although less strongly than in Examples 1 and 2.
Therefore, by using the induction heating device for local heating including the heating coil 1' of the fourth embodiment, it is possible to locally heat the portion F of the object to be heated.
However, even if the current supplied to the heating coil 1' is increased, the effect of localized heating is considered to be relatively weak because the distance W between the solenoids is large, 10 mm or more.

Fig. 9 is a workpiece surface heat generation amount distribution diagram by a heating simulation of Example 5 (solenoid outer diameter φ50.0 mm, W = 10 mm, solenoid winding in the same direction, current 600 A). However, the scale is different from Figs. 5 to 8, and Fig. 9 is on a smaller scale.
When checking the amount of heat generated on the workpiece surface, as shown in Figure 9, it can be confirmed that the workpiece surface is locally heated just below the lower end 2a' of the first solenoid 2' and the lower end 3a' of the second solenoid 3' (part F), as in Example 3, although less strongly than in Examples 1 and 2.
Therefore, by using the induction heating device for local heating including the heating coil 1' of the fifth embodiment, it is possible to locally heat the portion F of the object to be heated.
However, even if the outer diameter of each solenoid of the heating coil 1' is increased, since the distance W between each solenoid is 10 mm or more, it is considered that the effect of localized heating will be relatively weak.

Fig. 10 is a workpiece surface heat generation amount distribution diagram by a heating simulation of Example 6 (solenoid outer diameter φ50.0 mm, W = 10 mm, solenoid winding in the same direction, current 1000 A). However, the scale is different from Figs. 5 to 8, and Fig. 10 is on a smaller scale than Fig. 9.
When checking the amount of heat generated on the workpiece surface, as shown in Figure 10, it can be confirmed that the workpiece surface is locally heated just below the lower end 2a' of the first solenoid 2' and the lower end 3a' of the second solenoid 3' (part F), as in Example 3, although less strongly than in Examples 1 and 2.
Therefore, by using the induction heating device for local heating equipped with the heating coil 1 of Comparative Example 4, it is possible to locally heat the portion F of the object to be heated.
However, even if the outer diameter of each solenoid of the heating coil 1' is increased and the current supplied to the heating coil 1' is increased, the distance W between each solenoid is 10 mm or more, so it is considered that the effect of localized heating will be relatively weak.
In addition, when the study examples 1 to 4, which are similar to the examples 3 to 6 except that the distance W was set to 9.9 mm, were simulated, it was confirmed that the workpiece surface was locally heated more effectively in part F than in the examples 3 to 6 (examples 7 to 10).

FIG. 11 is an explanatory diagram showing the results of a heating simulation for comparison example 1 (solenoid outer diameter φ17.0 mm, W=1 mm, solenoid wound in the reverse direction, current 600 A), in which FIG. 11(a) is a central cross-section magnetic field strength distribution diagram, FIG. 11(b) is a workpiece surface current density distribution diagram, and FIG. 11(c) is a workpiece surface heat generation amount distribution diagram.
When checking the magnetic field strength generated around the heating coil 1a, it can be seen that, as shown in Figure 11 (a), magnetic fields A' and B' facing in the same direction are generated on the central axis C3 of the first solenoid 21 and the central axis C4 of the second solenoid 31 in the heating coil 1a.

Next, when checking the current density on the workpiece surface, as shown in FIG. 11(b), it can be seen that induced currents are generated at a higher density directly below the first solenoid 21 and the second solenoid 31 of the heating coil 1a compared to the surrounding areas. However, directly below the lower end of the first solenoid 21 and the lower end of the second solenoid 31 (part F), the induced current E1' (FIG. 4) clockwise as viewed from above generated on the workpiece surface directly below by the first solenoid 21 and the induced current E2' (FIG. 4) clockwise as viewed from above generated on the workpiece surface directly below by the second solenoid 31 are in opposite directions, so it can be seen that the current density is sparse compared to the surrounding areas.

Furthermore, when checking the amount of heat generated on the work surface, it can be seen that the work surface is heated in two ring shapes directly below the first solenoid 21 and the second solenoid 31 of the heating coil 1a, as shown in Fig. 11(c). However, it can be seen that the amount of heat generated directly below the lower end of the first solenoid 2 and the lower end of the second solenoid 3 (part F) on the work surface is lower than the surrounding area, unlike in Examples 1 and 2. The total amount of heat generated on the entire work surface at this time was 3.04 kW.
Therefore, even if an induction heating device for local heating including the heating coil 1a of Comparative Example 1 is used, it is not possible to locally heat an object to be heated.

As described above, the total heat generation amount of the entire work surface induction-heated by the heating coil 1 of Examples 1-2, the heating coil 1' of Example 3, and the heating coil 1a of Comparative Example 1 is 3.33 kW, 3.38 kW, 3.34 kW, and 3.04 kW, respectively, and there is no significant difference. On the other hand, in Examples 1-3, it can be seen that the part F of the work surface is locally heated. This can be seen as the output being concentrated locally. In other words, it can be said that the induction heating device for local heating equipped with the heating coil 1 of Examples 1-2 or the heating coil 1' of Example 3 can locally heat the heated object with high output. Since the effect of local heating is particularly noticeable in Examples 1-2, it can be said that when the end 2a of the first solenoid 2 of the heating coil 1 on the heated object side and the end 3a of the second solenoid 3 on the heated object side are adjacent to each other with an interval of 1 mm or more and 5 mm or less, the heated object can be locally heated with high output. Furthermore, taking into account Examples 3 to 10, it can be said that the first solenoid 2 and the second solenoid 3, which are wound in the same direction, can locally heat the object to be heated. In particular, when the end 2a of the first solenoid 2 of the heating coil 1 that faces the object to be heated and the end 3a of the second solenoid 3 that faces the object to be heated are adjacent to each other with a gap of 1 mm or more but less than 10 mm, it can be said that the object to be heated can be locally heated more effectively with high output.

FIG. 12 is a photograph showing the heat generation state of a workpiece due to induction heating by an actual induction heating device for local heating including the heating coil 1 of Example 1.
Based on the results of the heating simulation, an induction heating device for local heating including the heating coil 1 of Example 1 was actually created, induction heating was performed on a workpiece made of CFRP material, and heat generation from the workpiece was observed.
When a high-frequency current of 282 kHz and 350 A was supplied to the heating coil 1, localized heat generation of 200° C. or more was observed directly below the connecting portion 4 of the heating coil 1 (portion F), as shown in FIG.
That is, the induction heating device for local heating equipped with the heating coil 1 is capable of locally heating an object to be heated with high output.

The present invention has been described above based on the illustrated examples, and the technical scope of the present invention is not limited to these. For example, the material of the heating coil is not limited to copper, and can be selected from any material. In addition, the inner diameter, outer diameter, and cross-sectional shape of the wire forming the heating coil can also be selected arbitrarily.
In addition, the number of turns of each of the first solenoid 2 and the second solenoid 3 is not limited to 3, and each may have 1 turn as shown in FIG. 13(a), or may have 2 turns as shown in FIG. 13(c). When an induction heating device for local heating having heating coils with 1 or 2 turns was actually created and a CFRP workpiece was induction heated, local heat generation on the workpiece surface was confirmed in both the cases of 1 and 2 turns as shown in FIG. 13(b) and (d). On the other hand, each number of turns may be more than 3 and can be set arbitrarily. In addition, the number of turns of the first solenoid 2 and the number of turns of the second solenoid 3 may be different. Furthermore, as long as the magnetic field directions of adjacent solenoids are opposite, the winding direction of the solenoids may be clockwise or counterclockwise when viewed from above.
Further, the first solenoid and the second solenoid may have a shape other than a circle when viewed from above, such as a square when viewed from above. Furthermore, the inner diameter and the outer diameter of the solenoid can be set arbitrarily.
In addition, the heating coil may have three or more solenoids as long as the adjacent solenoids generate magnetic fields in opposite directions. That is, at least one of the first solenoid and the second solenoid may be provided in multiple numbers. For example, as shown in FIG. 14(a) in the heating coil 101, solenoids 102 and 103 that generate magnetic fields in opposite directions and solenoids 104 and 105 that generate magnetic fields in opposite directions can be arranged adjacent to each other. As a result, as shown in FIG. 14(b), the portions F1 and F2 of the heated object can be locally heated, and the linear range passing through the portions F1 and F2 can be heated with high output.
Moreover, the first solenoid and the second solenoid may each have a core.
Furthermore, the magnitude and frequency of the high-frequency current supplied to the heating coil 1 may be changed as necessary.
Furthermore, if the periods of the high frequency currents in the first solenoid and the second solenoid are completely the same, different high frequency power sources may be connected to the first solenoid and the second solenoid, respectively.

1, 1': heating coil, 2, 2': first solenoid, 2a, 2a': lower end (end), 3, 3': second solenoid, 3a, 3a': lower end (end on the heated object side), A, B: magnetic field, C1, C2: central axis, W: spacing.

Claims (3)

The device is equipped with a heating coil that inductively heats an object to be heated by supplying high-frequency current from a high-frequency power source.
The heating coil includes a first solenoid and a second solenoid.
the object to be heated is disposed outside the first solenoid and the second solenoid,
The central axis of the first solenoid is aligned with the central axis of the second solenoid,
The end of the first solenoid on the side of the object to be heated and the end of the second solenoid on the side of the object to be heated are adjacent to each other with a gap of 1 mm or more and less than 10 mm ,
The induction heating device for localized heating, wherein the first solenoid and the second solenoid generate magnetic fields in opposite directions due to the high frequency current supplied to both of them. 2. The induction heating device for local heating according to claim 1 , wherein the first solenoid and the second solenoid are formed of hollow conductors. 3. The induction heating device for local heating according to claim 1 , wherein at least one of the first solenoid and the second solenoid is provided in plurality.

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