JPH1126148A - Electromagnetic heating coil - Google Patents

Abstract

PROBLEM TO BE SOLVED: To uniformize the magnetic field strength on the inside of a coil, increase treating amount, and enhance productivity by gradually increasing the radius of each winding part adjacent in the central direction based on the radius of the winding part at both ends of the coil comprising a plurality of winding parts. SOLUTION: High frequency voltage is applied to a solenoid coil comprising a plurality of winding parts Tt1-Tt7 to generate magnetic field, and a heating treatment material loaded in the magnetic field is induction-heated. In the electromagnetic heating coil L1, the diameters of the winding parts T2, T3 adjacent in the central direction are gradually increased based on the diameter D1 of the winding part Tt1 at the upper end part in the direction of coil axis, and the central diameter D2 of the central winding part Tc4 is made largest. Similarly, the diameters of adjacent winding parts T6, T5 are gradually increased based on the diameter of a winding part Tt7 at the lower end. Each winding part is preferable to be wound so as to form a spherical body part. The magnetic field strength within the coil is uniformized, and uniform heating in the axis direction and in the diameter direction is made possible.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electromagnetic heating coil, and more particularly to a high-frequency heating coil having a uniform magnetic field intensity inside the coil.

[0002]

2. Description of the Related Art A high-frequency heating method is widely used as an example of a heat treatment of a component using an electromagnetic wave. As such a component, for example, there is a cathode serving as an electron source of an electron gun incorporated in a CRT, and a cathode serving as an object to be heated is inserted inside a high-frequency coil (RF coil) serving as an electromagnetic heating coil, and A high frequency for heating is applied to the coil, and the high frequency converts an induced current into heat based on an induced current generated in the cathode to be processed by an electromagnetic field generated inside the high frequency coil, thereby increasing the temperature of the cathode itself. Therefore, a configuration in which the cathode is heat-treated is widely used.

FIG. 7 is a front view showing a configuration example of such a conventional electromagnetic heating coil. As shown in the figure,
The conventional electromagnetic heating coil L60 is formed of a solenoid in which seven winding portions T1 to T7 of the same radius are connected to each other, and an electromagnetic field is formed inside the solenoid by extending a high-frequency current to the electromagnetic heating coil L60. The structure is such that the cathode, which is the object to be heated, placed inside is heated.

[0004]

By the way, as described above, the electromagnetic heating coil having the same radius and the number of turns of several turns is used. The characteristic of the electromagnetic heating coil having such a structure is as follows. Since the length in the coil axial direction is finite, there is a problem that the magnetic field intensity distribution in the axial direction inside the coil is not uniform.

That is, in addition to the magnetic field generated by the corresponding winding portion T4, the magnetic field at the central portion in the axial direction includes the magnetic fields generated by the winding portions T3 and T5 adjacent in the axial direction and the winding portions adjacent thereto. A magnetic field generated by T2, T6, and the like is applied, and a combined magnetic field is generated by combining these plurality of magnetic fields, so that the magnetic field strength at the central portion in the axial direction increases.

On the other hand, on the end side of the electromagnetic heating coil L60, there are few winding portions adjacent in the front and rear direction in the axial direction, or there are no adjacent winding portions. For example, winding part T1
(Or T7) is located at the extreme end, so that there is no winding adjacent to the upper part in the axial direction (or the lower part in the axial direction) in the figure.

Therefore, the intensity of the combined magnetic field at the end of the electromagnetic heating coil L60 is weaker than the intensity of the magnetic field at the central portion in the axial direction. As a result, the magnetic field intensity inside the electromagnetic heating coil has a non-uniform magnetic field intensity distribution that is maximized at the axial center and decreases toward both ends of the coil.

FIG. 8 is a graph showing actual measured values showing such changes in the magnetic field strength in the axial direction. The horizontal axis represents the electromagnetic heating coil L60 in a plane orthogonal to the axis when the coil L60 is displayed in cylindrical coordinates. The angle φ and the vertical axis are the normalized magnetic field strength, and the parameters are displayed as the positions inside each winding part. Note that the vertical axis is normalized with the magnetic field intensity at the point P60 (the outermost periphery of the central winding portion T4: see FIG. 7) at which the strongest magnetic field is generated inside the electromagnetic heating coil L60 as 1.00.

In FIG. 7, the magnetic field intensity at a point P61 at a predetermined distance from the axis of the central winding portion T4 is shown by a graph G in FIG.
61, and is a value within the range of 0.935 to 0.915. On the other hand, the magnetic field strength at the point P62 located at the same predetermined distance from the axis of the adjacent winding part T5 is as shown in FIG.
The value is in the range of 0.89 to 0.855, and at the point P62, the magnetic field intensity at the point P61 is reduced by several percent. That is, a non-uniform magnetic field intensity distribution in the longitudinal direction of the coil is observed, which is maximized at the center of the coil and decreases toward both ends of the coil.

As a result of the non-uniform magnetic field intensity distribution as described above, non-uniformity also occurs in the temperature in high-frequency heating, which causes a problem that uniform heating of the object to be heated is not performed.

Further, in addition to the generation of the non-uniform magnetic field strength distribution in the longitudinal direction of the coil, the magnetic field distribution in the radial direction (radial direction) inside the electromagnetic heating coil L60 is also larger at the outer peripheral portion than at the central portion. There was a characteristic that the magnetic field strength at the time was increased.

FIG. 9 shows such a non-uniform magnetic field intensity distribution in the radial direction obtained by simulation. The intensity distribution of the magnetic field H60 on a plane perpendicular to the axis is schematically shown. FIG. 10 is a schematic sectional view illustrating the magnetic field strength distribution in the radial direction. According to the figure, the magnetic field strength distribution 61 is such that the magnetic field strength at the center position is hc60, and the magnetic field strength hc at a position at a distance ri from the center, that is, on the outer peripheral side.
p60 is stronger than the magnetic field strength hc60 at the center position. In addition, the distribution is steep, so that the ratio R60 of the magnetic field strengths is larger than 1 in R60 = hp60 / hc60, and the value is also large.

As a result, uneven heat treatment is performed depending on the position where the object to be heated is placed inside the electromagnetic heating coil L60. Therefore, in the prior art, the object to be heated is loaded. There is a limit on the area to be used. Hereinafter, such a limitation of the loading area will be described.

FIG. 11 is a schematic perspective view showing the configuration of a conventional electromagnetic heating coil L70, in which seven windings of a solenoid shape are continuously connected at the same pitch. That is, the pitches p70 to p75 have the same value. FIG.
Shows a cross section of the electromagnetic heating coil L70. A jig 71 and a plurality of cathodes Ctd inserted into the jig 71 are arranged inside the coil having a radius r70.

The jig 71 has a disk shape, and the cathode Ctd is held in a concave portion provided discretely along the circumference of a distance dt70 from the center of the jig 71. Therefore, the cathodes Ctd are merely arranged in a line on the circumference. Further, the total length of the cathode Ctd is sufficiently shorter than the total length of the electromagnetic heating coil L70, and
The portion of the electromagnetic heating coil L70 that contributes to the heating of the above is limited to the central portion.

In the above configuration, the electromagnetic heating coil L7
Only the center of zero is used because the field strength in this region is more uniform than the field strength at the edges,
That is, since the magnetic field intensity distribution in the longitudinal direction of the coil is not uniform, the usable area in the longitudinal direction of the coil is limited.

The reason why the cathodes Ctd are arranged in only one line on the circumference and are not arranged in multiple lines in the radial direction is that the available area in the coil radial direction is not large because the magnetic field intensity distribution in the coil radial direction is not uniform. Because it is restricted.

As described above, in order to avoid a non-uniform heat treatment due to a non-uniform magnetic field intensity distribution, conventionally, the object to be heated is limited only to a region in the electromagnetic heating coil where the magnetic field intensity distribution is relatively uniform. Since the loading is limited, as a result, the loading amount of the object to be heated is limited. For this reason,
There is a problem that the throughput (throughput) is reduced and the productivity is reduced.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems of the prior art. The present invention has been made to increase the loading amount by making the magnetic field intensity distribution inside the electromagnetic heating coil uniform, and to achieve uniform heat treatment. It is therefore an object of the present invention to provide an electromagnetic heating coil which enables the implementation of the above-described method, thereby increasing the throughput and improving the productivity.

[0020]

The gist of the present invention is that the radius of the winding near the center of the entire length of the electromagnetic heating coil is made larger than the radius of the winding at the end of the coil, and / or the vicinity of the center. The uniformity of the magnetic field strength inside the coil is improved by making the pitch of the winding portion larger than the pitch of the winding portion at the coil end and making the density of the winding portion near the center coarse.

To solve the above problem, an electromagnetic heating coil according to a first aspect of the present invention is an electromagnetic heating coil having a plurality of winding portions, wherein a radius of winding portions at both ends in the coil axial direction is a reference. It is characterized in that the radius of each winding part adjacent to each other in the center direction is gradually increased.

According to the above configuration, the strength of the magnetic field formed on the shaft inside the winding portion having the increased radius decreases, so that the strength of the combined magnetic field inside the winding portion decreases, and thus the axial direction is reduced. And the difference in the magnetic field strength in the radial direction is reduced.

According to a second aspect of the present invention, in the electromagnetic heating coil according to the first aspect, the plurality of winding portions are wound so as to form at least a body of a spherical surface.

According to the above configuration, since the winding portion forms the spherical body portion, the magnetic field strength in the axial direction is further uniformed, and the difference in the magnetic field strength in the radial direction is simultaneously reduced.

An electromagnetic heating coil according to a third aspect of the present invention is an electromagnetic heating coil in which a plurality of winding portions each having the same radius are connected in a cylindrical shape, and the adjacent winding portions of the winding portion located at the center in the axial direction. The pitch between the winding portions at the ends of the coil is larger than the pitch between adjacent winding portions.

According to the above configuration, the magnetic field intensity inside the winding portion having a large pitch is reduced, so that the axial magnetic field intensity distribution is flattened.

In the electromagnetic heating coil according to a fourth aspect of the present invention, the radius of the winding portion of the electromagnetic heating coil having a plurality of winding portions is emitted from both ends in the axial direction of the coil toward the center, and the radius is reduced. It is configured to be gradually increased, and the pitch of the winding portion corresponding to the coil axial direction center, the pitch between adjacent winding portions, the winding portion at the coil end,
The pitch is larger than the pitch between adjacent winding portions.

According to the above configuration, the magnetic field strength distribution in the coil axis direction is flattened and the magnetic field strength difference in the coil radial direction is reduced by increasing the radius of the winding portion on the center side. Further, by increasing the pitch of the winding portion on the center side, the magnetic field strength in the coil axis direction is made uniform.

According to a fifth aspect of the present invention, there is provided an electromagnetic heating coil according to the fourth aspect, wherein the plurality of winding portions are wound while forming at least a body portion of a spherical surface.

According to the above configuration, the effect of reducing the magnetic field strength by increasing the radius of the winding portion on the center side and the effect of reducing the magnetic field intensity by increasing the pitch of the winding portion on the center side are combined. A further flattening of the axial field strength distribution and a further homogenization of the radial field strength are achieved.

[0031]

Embodiments of the present invention will be described below. Note that the following embodiments are preferred examples of the present invention, and various technically preferred limitations have been added.
The scope of the present invention is not limited to these embodiments unless otherwise specified in the following description.

FIG. 1 is a front view of a first embodiment of the electromagnetic heating coil according to the present invention. FIG. 2 is an explanatory diagram of a radial magnetic field intensity distribution in the electromagnetic heating coil shown in FIG. Hereinafter, the configuration of the electromagnetic heating coil according to the first embodiment of the present invention will be described.

In both figures, the electromagnetic heating coil L1 is an electromagnetic heating coil having seven winding portions Tt1 to Tt7, and is adjacent to the center direction with reference to the diameter D1 of the winding portion Tt1 at the upper end in the coil axial direction. The diameter of each winding part T2, T3 is gradually increased, and the winding part Tc located at the center is gradually increased.
4 (center diameter) D2 is configured to be larger than the radius of the winding portion T3.

Similarly, the winding portion Tt at the lower end in the coil axial direction
7, each winding part T adjacent in the center direction.
6, the diameter of T5 is gradually increased in order, and the diameter of the winding part Tc4 located at the center is larger than the diameter of the winding part T5. That is, the diameter of each winding part adjacent in the center direction is gradually increased based on the diameter of the winding parts Tt1 and Tt7 at both ends in the coil axial direction.

An electromagnetic heating coil L configured as shown in FIG.
1 is that, by gradually increasing the diameter of the winding portion to the diameter of the winding portion located on the center side in the longitudinal direction of the coil, the effect of reducing the magnetic field intensity generated by each winding portion is obtained. The magnetic field strength distribution in the coil longitudinal direction can be made uniform.

By the way, when the diameter of the winding portion is increased,
The radial magnetic field strength ratio can be reduced and this ratio can be made closer to one. FIG. 2 explains this radial magnetic field strength distribution, and is a schematic diagram of the radial magnetic field strength distribution of the winding part Tc4 located at the center. Hereinafter, this principle will be described with reference to FIG.

According to the figure, when the magnetic field intensity at the center position is hc1 and the inner peripheral radius of the winding portion Tc4 is D2 ', the magnetic field intensity distribution 11 is at the distance D2' from the center. The magnetic field strength hp1 becomes stronger than the magnetic field strength hc1 at the center position. However, the magnetic field strength hm1 at the position at the distance ri from the center is a magnetic field strength weaker than the magnetic field strength hp1.

Therefore, when the diameter of the winding portion is increased, the increase in the magnetic field strength from the magnetic field strength hc1 at the center position is gradual, so that the magnetic field strength hm1 at the distance ri from the center at the center position is small. The increase from the magnetic field strength hc1 becomes very small. This effect is evident in comparison with the magnetic field strength hp60 at the position of the distance ri from the center in the configuration of the prior art in FIG. 10 described above. (See Fig. 10)

As a result, the ratio R1 of the magnetic field strength becomes R1 = hm1 / hc1, which is a value closer to 1, and the effect of reducing the magnetic field strength ratio in the radial direction is obtained. Is effectively alleviated.

As a result, the area in the electromagnetic heating coil L1 where heat treatment can be performed can be expanded not only in the axial direction but also in the radial direction. Due to the remarkable expansion of the heat-processable area, the amount of the object to be heated can be significantly increased, and the throughput can be greatly improved.

FIG. 3 is a front sectional view of a second embodiment of the electromagnetic heating coil according to the present invention, in a state where an object to be heated is loaded. As shown in the drawing, the electromagnetic heating coil L2 is an electromagnetic heating coil having a plurality of winding portions Tt2 to Tt2 ', and each winding portion has a diameter of winding portions Tt2 and Tt2' at both upper and lower ends in the coil axis direction. , The diameter of each winding portion adjacent in the center direction is gradually increased, so that the diameter of the winding portion Tc2 located at the center is maximized.

In the electromagnetic heating coil L2, jigs 5 and 6 stacked in two stages in the axial direction and a plurality of cathodes Ctd2 to Ctd5 fitted to the jigs 5 and 6 are arranged. I have.

Each of the jigs 5 and 6 has the same disk-shaped configuration. For example, when the jig 5 is described, it is provided discretely along the circumference of a plurality of concentric circles having a plurality of predetermined radii from the center. The cathodes Ctd2 and Ctd3 are gripped by the recesses formed of the plurality of rows so as to form the plurality of rows.

That is, in this configuration, the plurality of cathodes Ctd3 are arranged in a row on the circumference of the smaller side, and the plurality of cathodes Ctd3 are further arranged on the outer circumference of the larger side.
d2 are arranged in a single row, and consequently the cathodes are arranged in two rows. Further, the cathode Ctd5 and the cathode C
The same applies to td4. This utilizes the fact that, as described above, the configuration in which the magnetic field intensity difference in the radial direction in the electromagnetic heating coil L2 is reduced, the heat treatment region is expanded in the radial direction, and thus the amount of loading increases. I do.

Further, as described above, the configuration for reducing the axial magnetic field strength difference in the electromagnetic heating coil L2,
Utilizing the fact that the heat treatment region is expanded in the axial direction, the cathodes Ctd are loaded in a two-tiered manner, so that the loading amount increases.

As described above, the electromagnetic heating coil L2 can effectively use the space in the coil by increasing the available area in the coil longitudinal direction and the radial direction, thereby improving the productivity and improving the uniform magnetic field strength. It is possible to perform more uniform heating by distribution, which is effective for quality control.

FIG. 4 is a front view of a third embodiment of the electromagnetic heating coil according to the present invention. As shown in the figure, the electromagnetic heating coil L3 of the fourth embodiment includes a plurality of winding portions Tt.
A pitch p32 between the winding portions T32 to T33 adjacent in the center direction and a winding portion T33 to the center direction with reference to a pitch p31 between the winding portion Tt31 at the upper end of the coil axis direction and the adjacent winding portion T32. Pitch p between Tc34
33 is gradually increased.

Similarly, based on the pitch p36 between the winding portion Tt37 at the lower end in the coil axial direction and the adjacent winding portion T36, the pitch p35 between the winding portions T36 to T35 adjacent in the center direction and the winding portions T35 to Tc34. Pitch p between
34 are sequentially increased. That is, the configuration is such that p31 <p32 <p33 and p36 <p35 <p34.

An electromagnetic heating coil L configured as shown in FIG.
3 is that the pitch between the winding portions is gradually increased to the winding portion on the center side in the longitudinal direction of the coil, so that the effect of reducing the magnetic field intensity by reducing the density of the winding portion is obtained. The magnetic field strength distribution in the coil longitudinal direction in L3 can be made uniform.

As a result, the area in the electromagnetic heating coil L3 where the heat treatment can be performed is expanded, so that the load of the object to be heated can be increased and the throughput can be improved.

FIG. 5 is a front view of a fourth embodiment of the electromagnetic heating coil according to the present invention. As shown in the figure, the electromagnetic heating coil L4 of the fourth embodiment includes a plurality of winding portions Tt.
41 to Tt47, the radius of each winding part T42, T43 adjacent in the center direction is gradually increased with reference to the radius of the winding part Tt41 at the upper end in the coil axis direction, and the winding positioned at the center is gradually increased. Winding part T4
3 is configured to be larger than the radius.

Similarly, the winding portion Tt at the lower end in the coil axial direction
The radius of each of the winding portions T46 and T45 adjacent in the center direction is gradually increased based on the radius of the winding portion T47, and the radius of the winding portion Tc44 located at the center is larger than the radius of the winding portion T45. To be configured.

Further, the pitches p43 and p44 of the winding portion Tc44 located at the center in the coil axis direction with the adjacent winding portions T43 and T45 are determined by the winding portion Tt4 at the coil end.
1 (or Tt47) is larger than the pitch p41 (or p46) between adjacent winding portions T42 (or T46).

Further, it is preferable that the pitch is gradually increased in order from the pitch at the winding portion at the end in the coil axis direction to the pitch at the winding portion located at the center in the coil axis direction. That is, the pitch between the adjacent winding portions in the winding portions Tt41 to Tt47 is p41 as shown in the drawing.
It is configured such that p41 <p42 <p43 and that p46 <p45 <p44.

An electromagnetic heating coil L configured as shown in FIG.
4 is to gradually increase the radius of the winding portion to the radius of the winding portion on the center side in the coil longitudinal direction, thereby reducing the magnetic field intensity generated by each winding portion and reducing the magnetic field intensity ratio in the radial direction. Both are obtained, whereby the magnetic field strength distribution in the coil longitudinal direction in the electromagnetic heating coil L4 can be made uniform, and the difference in the magnetic field strength distribution in the radial direction can be reduced.

Further, in addition to the above, the flattening of the magnetic field intensity distribution in the axial direction can be more effectively achieved in combination with the effect of decreasing the magnetic field intensity by increasing the pitch of the winding portion on the center side.

As a result, the area in the electromagnetic heating coil L4 where the heat treatment can be performed is greatly expanded, so that the amount of the object to be heated can be significantly increased, and the throughput can be greatly improved.

FIG. 6 is a perspective view of a fifth embodiment of the electromagnetic heating coil according to the present invention. As shown in the figure, the electromagnetic heating coil L5 of the fifth embodiment is wound so that a plurality of winding portions form a virtual spherical surface Sph, and as a result, forms at least a body portion Bd of the virtual spherical surface Sph. It is characterized by being wound.

Here, the number of turns is N turns, and the virtual spherical surface Sp is
When the radius of h is a and the center of the sphere is O, an arbitrary position on the center axis Cz in the z-axis direction is a distance b from the center O.
Is a point P, and a magnetic field generated by a minute portion (on the virtual spherical surface) of the winding portion of the electromagnetic heating coil L5 at the point P is ΔH, and each portion of each winding portion of the electromagnetic heating coil L5 is generated at the point P. The synthetic magnetic field H of the magnetic field is obtained by integrating along the central axis Cz as shown in Expression 1 based on the Biot-Savart law.

[0060]

(Equation 1)

As described above, the composite magnetic field H of the magnetic field formed at the point P, which is an arbitrary position on the central axis Cz, is H = 4πNI / 3a, and is uniquely determined by the radius, the number of turns, and the current value. It is constant regardless of the position. Therefore, according to the electromagnetic heating coil L5 of the present embodiment, the area where the heat treatment operation can be performed can be further expanded in the axial direction.

Further, in the configuration shown in FIG. 6, the pitch of the winding portion positioned at the center in the coil axis direction with the adjacent winding portion is made larger than the pitch of the winding portion at the coil end portion with the adjacent winding portion. It is also possible to adopt a configuration that has been adopted.

[0063]

As described in detail above, claim 1 of the present invention
The electromagnetic heating coil according to the present invention has a configuration in which the radius of the winding portion of the electromagnetic heating coil having a plurality of winding portions is emitted from both ends in the coil axial direction toward the center and gradually increases, so that the radius is increased. The intensity of the magnetic field formed on the axis inside the increased winding portion decreases, thereby reducing the combined magnetic field intensity inside the winding portion to equalize the magnetic field intensity in the axial direction and the magnetic field intensity in the radial direction. Is also uniformed.
As a result, the loading area of the object to be heated can be expanded, so that the processing amount can be increased, and the quality of the heat treatment can be improved by making the magnetic field intensity uniform.

According to a second aspect of the present invention, in the electromagnetic heating coil according to the first aspect, the plurality of winding portions are formed by forming at least a body portion of a spherical surface and wound. Further uniformity of the axial magnetic field strength can be realized.

In the electromagnetic heating coil according to the third aspect of the present invention, the plurality of winding portions form a cylindrical shape, and the pitch between the winding portion located at the center position in the coil longitudinal (axial) direction and the adjacent winding portion. Is configured to be larger than the pitch between the winding part at the coil end and the adjacent winding part.
The magnetic field strength in the coil longitudinal (axial) direction can be made uniform, and the loading area can be expanded in the coil longitudinal (axial) direction.

An electromagnetic heating coil according to a fourth aspect of the present invention is configured such that the radius of each of the plurality of winding portions is emitted from both ends in the axial direction of the coil toward the center, and the radius is gradually increased. The pitch of the winding portion corresponding to the center in the direction is set to be larger than the pitch of the winding portion at the coil end to the adjacent winding portion.

Accordingly, the effect of flattening the magnetic field intensity distribution in the longitudinal direction of the coil (axial) due to the decrease in the magnetic field intensity due to the increase in the radius of the winding portion on the center side and the effect of reducing the difference in the magnetic field intensity in the radial direction are realized. it can. Moreover, coupled with the effect of decreasing the magnetic field intensity by increasing the pitch of the winding portion on the center side,
Flattening of the magnetic field intensity distribution in the coil longitudinal (axial) direction can be realized more effectively.

According to a fifth aspect of the present invention, in the electromagnetic heating coil according to the fourth aspect, the plurality of winding portions are wound by forming at least a body portion of a spherical surface.
Further uniformity of the axial magnetic field strength can be realized.

[Brief description of the drawings]

FIG. 1 is a front view of a first embodiment of an electromagnetic heating coil according to the present invention.

FIG. 2 is an explanatory diagram of a radial magnetic field strength distribution in the electromagnetic heating coil shown in FIG.

FIG. 3 is a front sectional view of a second embodiment of the electromagnetic heating coil according to the present invention, in a state where an object to be heated is loaded.

FIG. 4 is a front view of a third embodiment of the electromagnetic heating coil according to the present invention.

FIG. 5 is a front view of a fourth embodiment of the electromagnetic heating coil according to the present invention.

FIG. 6 is a perspective view of a fifth embodiment of the electromagnetic heating coil according to the present invention.

FIG. 7 is a front view showing a configuration example of a conventional electromagnetic heating coil.

8 is a diagram showing a change in magnetic field strength in the axial direction of the electromagnetic heating coil shown in FIG. 7;

FIG. 9 is a schematic diagram showing a simulation result of a magnetic field intensity distribution on a plane orthogonal to an axis of a conventional electromagnetic heating coil.

10 is a schematic cross-sectional view illustrating a magnetic field strength distribution in a radial direction shown in FIG.

FIG. 11 is a schematic perspective view showing another configuration example of a conventional electromagnetic heating coil.

FIG. 12 is a sectional view of the electromagnetic heating coil of FIG. 11 loaded with an object to be heated;

[Explanation of symbols]

L1 ... electromagnetic heating coil, D1 ... end diameter, D2 ... center diameter, Tt1 ... end winding part, T2 ... winding part, T3 ...
... winding part, Tc4 ... center winding part, T5 ... winding part, T
6 ... winding part, Tt7 ... end winding part

Claims (5)

[Claims] 1. An electromagnetic heating coil having a plurality of winding portions, wherein a radius of each winding portion adjacent in the center direction is gradually increased with reference to a radius of a winding portion at both ends in the coil axial direction. An electromagnetic heating coil characterized in that: 2. The electromagnetic heating coil according to claim 1, wherein the plurality of winding portions are wound while forming at least a body portion of a spherical surface. 3. An electromagnetic heating coil in which a plurality of winding portions each having the same radius are connected in a cylindrical shape, wherein the pitch of the winding portion located at the center in the axial direction with the adjacent winding portion is determined by the winding at the coil end. An electromagnetic heating coil characterized in that the pitch is larger than the pitch between adjacent winding portions. 4. An electromagnetic heating coil having a plurality of windings, wherein the radius of each winding adjacent in the center direction is gradually increased based on the radius of the winding at both ends in the coil axial direction. And, the pitch of the winding portion located at the center of the coil axial direction with the adjacent winding portion is configured to be larger than the pitch of the winding portion at the coil end portion with the adjacent winding portion. Electromagnetic heating coil. 5. The electromagnetic heating coil according to claim 4, wherein the plurality of winding portions are wound while forming at least a body portion of a spherical surface.