JP3761328B2

JP3761328B2 - Induction heating coil

Info

Publication number: JP3761328B2
Application number: JP17883898A
Authority: JP
Inventors: 三男東; 樹郎竹本
Original assignee: Neturen Co Ltd
Current assignee: Neturen Co Ltd
Priority date: 1998-06-25
Filing date: 1998-06-25
Publication date: 2006-03-29
Anticipated expiration: 2018-06-25
Also published as: JP2000012205A

Description

【０００１】
【発明の属する技術分野】
本発明は、被加熱物の平面部分を誘導加熱するための誘導加熱コイルに関する。
【０００２】
【従来の技術】
従来から、誘導加熱を利用して鋼製部材などの被加熱物の一部分を加熱し、加熱された一部分を急冷して硬化させる高周波焼入れが広く使用されている。被加熱物には様々な形状のものがあり、また、加熱される一部分にも様々な形状のものがある。このような一例として、被加熱物の平面部分を誘導加熱して急冷し、硬化させる場合がある。
【０００３】
被加熱物の平面部分を誘導加熱する際には、例えば、平面部分とほぼ同じ面積でこの平面部分に向き合う導体部を有する誘導加熱コイルが使用される。平面部分の面積が広い場合は、その広さに応じて導体部の広い誘導加熱コイルが使用される。また、渦巻き状の導体部を有するパンケーキ型コイルと呼ばれる誘導加熱コイルを使用して平面部分を誘導加熱することもある。
【０００４】
【発明が解決しようとする課題】
上述したように平面部分とほぼ同じ面積の導体部を有する誘導加熱コイルやパンケーキ型の誘導加熱コイルを用いて被加熱物の平面部分を誘導加熱して急冷した場合、平面部分の位置によって硬さ分布にむらが生じるおそれがあることが、本発明者によって判明した。このような硬さ分布のむらは、加熱後の冷却法に何らかの問題がある場合があるので、冷却法をいろいろ変えて工夫してみた。しかし、冷却法をいろいろ変えても硬さ分布のむらを解決できなかった。
【０００５】
そこで、本発明者は、被加熱物の平面部分を加熱する誘導加熱方法に問題があると考え、誘導加熱方法について検討した。この結果、被加熱物の平面部分とほぼ同じ面積の導体部を有する誘導加熱コイルを使用した場合、導体部の幅方向両端部に流れる電流の密度が幅方向中央部に流れる電流の密度よりも低く、被加熱物の平面部分を均一に加熱できないおそれがあることが判明した。また、パンケーキ型の誘導加熱コイルを使用した場合も同様に、被加熱物の平面部分を均一に加熱できないおそれがあることが判明した。
【０００６】
本発明は、上記事情に鑑み、被加熱物の平面部分を均一に加熱できる誘導加熱コイルを提供することを目的とする。
【０００７】
【課題を解決するための手段】
上記目的を達成するための本発明の第１の誘導加熱コイルは、被加熱物の平面部分を誘導加熱するための誘導加熱コイルにおいて、
（１）それぞれが上記平面部分に向き合い、それぞれに同一方向の電流が流れる並行な複数の導体部を有することを特徴とするものである。
【０００８】
ここで、
（２）上記複数の導体部は、近接して同一方向に延びる２つの導体部からなるものであってもよい。
【０００９】
また、上記目的を達成するための本発明の第２の誘導加熱コイルは、被加熱物の平面部分を誘導加熱するための誘導加熱コイルにおいて、
（３）所定方向に延びてリードを介して高周波電源に接続される第１導体部
（４）この第１導体部の後端から上記所定方向に交差する方向に延びる第２導体部
（５）上記所定方向とは反対の方向であって上記第１導体部の後端から離れる方向に上記第２導体部の後端から延びる第３導体部
（６）この第３導体部の後端から略直角に折れ曲がって、上記第２導体部の先端から離れる方向に延びる第４導体部
（７）この第４導体部の後端から上記第３導体部に並行に延びる、この第３導体部とほぼ同じ長さの第５導体部
（８）この第５導体部の後端から略直角に折れ曲がって、上記第２導体部の後端から離れる方向に延びる第６導体部
（９）この第６導体部の後端から上記第５導体部に並行に延びる、上記第５導体部とほぼ同じ長さの第７導体部
（１０）この第７導体部の後端から略直角に折れ曲がって、上記第４導体部の後端に近付く方向に延びる、上記第４導体部とほぼ同じ長さの第８導体部
（１１）この第８導体部の後端から、上記第５導体部に近接してこの第５導体部に並行に延びる、この第５導体部とほぼ同じ長さの第９導体部
（１２）この第９導体部の後端から略直交して、上記第１導体部の後端に近付く方向に延びる第１０導体部
（１３）この第１０導体部の後端から上記１導体部に並行に延び、リードを介して上記高周波電源に接続される第１１導体部
を備えたことを特徴とするものである。
【００１０】
ここで、本発明でいう平面部分とは、平らな面のみでなく、多少の凹凸がある平面的な部分や湾曲した面も含む概念である。
【００１１】
【発明の実施の形態】
以下、図面を参照して本発明の実施形態を説明する。
【００１２】
図１、図２を参照して、本発明の誘導加熱コイルの一実施形態を説明する。
【００１３】
図１は、一実施形態の誘導加熱コイルを示す正面図であり、図２は、図１の誘導加熱コイルの側面図である。また、誘導加熱コイルに示された矢印は、電流の流れの一例を表わす。
【００１４】
誘導加熱コイル１０は、矢印Ａ方向（本発明にいう所定方向の一例である）に延びる第１導体部１２を有している。この第１導体部１２は、リード１４を介して高周波電源（図示せず）に接続されている。第１導体部１２の後端１２ａからは、矢印Ａ方向に交差する方向であって、図１の右斜め下方に向かって第２導体部１６が延びている。第２導体部１６の後端１６ａからは、矢印Ａ方向とは反対方向であって第１導体部１２の後端１２ａから離れる方向に第３導体部１８が延びている。第３導体部１８の後端１８ａからは略直角に折れ曲がって、第２導体部１６の先端１６ｂから離れる方向に第４導体部２０が延びている。
【００１５】
第４導体部２０の後端２０ａからは第３導体部１８に並行に第５導体部２２が延びており、この第５導体部２２の長さは第３導体部１８の長さとほぼ同じである。第５導体部２２の後端２２ａからは略直角に折れ曲がって第２導体部１６の後端１６ａから離れる方向に第６導体部２４が延びている。この第６導体部２４の後端２４ａからは第５導体部２２に並行に第７導体部２６が延びており、この第７導体部２６の長さは第５導体部２２の長さとほぼ同じである。第７導体部２６の後端２６ａからは略直角に折れ曲がって、第４導体部２０の後端２０ａに近付く方向に第８導体部２８が延びており、この第８導体部２８の長さは、第４導体部２０の長さとほぼ同じである。
【００１６】
第８導体部２８の後端２８ａからは、第５導体部２２に近接してこの第５導体部２２に並行に第９導体部３０が延びており、この第９導体部３０の長さは第５導体部２２とほぼ同じである。第９導体部３０の後端３０ａから略直交して第１導体部１２の後端１２ａに近付く方向に第１０導体部３２が延びている。この第１０導体部３２の後端３２ａからは第１導体部１２に並行に第１１導体部３４が延びている。第１１導体部３４はリード３６を介して高周波電源（図示せず）に接続されている。
【００１７】
上述した誘導加熱コイル１０を使って被加熱物４０の平面部分４２を誘導加熱する際には、第５導体部２２と第９導体部３０を平面部分４２に対向させる。この状態で誘導加熱コイル１０に高周波電力を投入すると、第５導体部２２と第９導体部３０には同時に同じ方向に電流が流れて交番磁束が発生する。この交番磁束によって平面部分４２には渦電流が誘導されて平面部分４２が加熱されることとなる。
【００１８】
ところで、従来のように平面部分４２の幅とほぼ同じ幅の導体部を有する誘導加熱コイルを用いた場合は、上述したように、導体部の幅方向両端部における電流密度が幅方向中央部における電流密度よりも低くなって、平面部分４２の幅方向両端部が十分に加熱されないことがある。しかし、誘導加熱コイル１０では、図１に示すように第５導体部２２及び第９導体部３０それぞれの幅は、平面部分４２の面積（幅）よりも狭い。従って、第５導体部２２及び第９導体部３０では、それらの幅方向両端部でも幅方向中央部でも電流密度は均一となる。また、第５導体部２２及び第９導体部３０では、同時に同一方向に電流が流れるので、これらの電流によって発生した交番磁束が互いに打ち消し合うことはない。この結果、平面部分４２を均一に加熱できる。
【００１９】
上記した実施形態では、平面部分４２を加熱するための導体部が２本（第５導体部２２及び第９導体部３０）の例を示したが、平面部分４２の面積がさらに広い場合は、平面部分４２を加熱するための導体部を３本以上にすることが好ましい。ただし、各導体部には同時に同一方向に電流が流れるようにする必要がある。
【００２０】
図３、図４を参照して、上述した誘導加熱コイル１０を用いて被加熱物の平面部分を高周波焼入れした実験例を説明する。
【００２１】
図３は、実験に用いた被加熱物の平面部分の硬化層深さを示す模式図であり、図４は、硬化層深さを示すグラフである。図４におけるａ、ｂ、ｃは、図３に示す矢印ａ、ｂ、ｃ方向から測定した硬さ分布を表わす。
【００２２】
この実験で用いた被加熱物４０の材質は、ＦＣＤ６００（ＪＩＳ規格）であり、平面部分４２の幅Ｗは２０ｍｍである。また、第５導体部２２と第９導体部３０の幅ｗは８ｍｍとした。
【００２３】
平面部分４２を誘導加熱するに当っては、誘導加熱コイル１０を用いて４０ｋＷ、８０ｋＨｚで９秒間ほど加熱した。このようにして加熱した後に、平面部分４２に冷却液を７秒間噴出して急冷した。この結果、図４に示すように、平面部分４２の幅方向中央部でも幅方向両端部でも一様な深さの硬化層が得られた。
【００２４】
【発明の効果】
以上説明したように本発明の第１の誘導加熱コイルによれば、被加熱物の平面部分を誘導加熱するに当り、それぞれに同一方向の電流が流れる並行な複数の導体部を平面部分に向き合わせる。このため、各導体部の幅は平面部分の幅よりも狭くて済む。従って、各導体部では、それらの幅方向両端部でも幅方向中央部でも電流密度が均一になる。また、各導体部では同時に同一方向に電流が流れるので、これらの電流によって発生した交番磁束が互いに打ち消し合うことはない。この結果、平面部分を均一に加熱できる。
【００２５】
ここで、複数の導体部が、近接して同一方向に延びる２つの導体部からなるものである場合は、誘導加熱コイルを比較的容易に作製できる。
【００２６】
また、本発明の第２の誘導加熱コイルによれば、第５導体部及び第９導体部それぞれの幅を、平面部分の幅よりも狭くできる。従って、第５導体部及び第９導体部では、それらの幅方向両端部でも幅方向中央部でも電流密度が均一となる。また、第５導体部及び第９導体部では同時に同一方向に電流が流れるので、これらの電流によって発生した交番磁束が互いに打ち消し合うことはない。この結果、平面部分を均一に加熱できる。
【図面の簡単な説明】
【図１】本発明の一実施形態の誘導加熱コイルを示す正面図である。
【図２】図１の誘導加熱コイルの側面図である。
【図３】実験に用いた被加熱物の平面部分の硬化層深さを示す模式図である。
【図４】硬化層深さを示すグラフである。
【符号の説明】
１０誘導加熱コイル
１２第１導体部
１４，３６リード
１６第２導体部
１８第３導体部
２０第４導体部
２２第５導体部
２４第６導体部
２６第７導体部
２８第８導体部
３０第９導体部
３２第１０導体部
３４第１１導体部
４０被加熱物
４２平面部分[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an induction heating coil for induction heating a flat portion of an object to be heated.
[0002]
[Prior art]
Conventionally, induction hardening in which a part of an object to be heated such as a steel member is heated using induction heating, and the heated part is quenched and hardened is widely used. There are various shapes in the object to be heated, and there are various shapes in the part to be heated. As an example of this, there is a case where a planar portion of an object to be heated is induction-heated and rapidly cooled to be cured.
[0003]
When induction heating a flat portion of an object to be heated, for example, an induction heating coil having a conductor portion facing the flat portion with substantially the same area as the flat portion is used. When the area of the plane portion is large, an induction heating coil having a wide conductor portion is used according to the area. In addition, the planar portion may be induction-heated using an induction heating coil called a pancake-type coil having a spiral conductor portion.
[0004]
[Problems to be solved by the invention]
As described above, when an induction heating coil or a pancake type induction heating coil having a conductor portion having substantially the same area as that of the flat portion is used for induction heating and quenching the flat portion of the object to be heated, the hard portion depends on the position of the flat portion. It has been found by the present inventor that unevenness in the thickness distribution may occur. Such unevenness in the hardness distribution may have some problems in the cooling method after heating. However, even if the cooling method was changed variously, the unevenness of hardness distribution could not be solved.
[0005]
Then, this inventor considered that there was a problem in the induction heating method which heats the plane part of to-be-heated material, and examined the induction heating method. As a result, when an induction heating coil having a conductor portion having substantially the same area as the planar portion of the object to be heated is used, the density of current flowing at both ends in the width direction of the conductor portion is higher than the density of current flowing in the center portion in the width direction. It was found that the flat part of the object to be heated could not be heated uniformly. Similarly, it has been found that when a pancake type induction heating coil is used, the planar portion of the object to be heated may not be heated uniformly.
[0006]
An object of this invention is to provide the induction heating coil which can heat the plane part of a to-be-heated object uniformly in view of the said situation.
[0007]
[Means for Solving the Problems]
In order to achieve the above object, a first induction heating coil of the present invention is an induction heating coil for induction heating a flat portion of an object to be heated.
(1) Each has a plurality of parallel conductor portions facing each of the above-described plane portions and each carrying a current in the same direction.
[0008]
here,
(2) The plurality of conductor portions may be composed of two conductor portions that are close to each other and extend in the same direction.
[0009]
Moreover, the second induction heating coil of the present invention for achieving the above object is an induction heating coil for induction heating a flat portion of an object to be heated.
(3) A first conductor portion extending in a predetermined direction and connected to a high-frequency power source via a lead (4) A second conductor portion (5) extending from the rear end of the first conductor portion in a direction intersecting the predetermined direction A third conductor portion (6) extending from the rear end of the second conductor portion in a direction opposite to the predetermined direction and away from the rear end of the first conductor portion. A fourth conductor part (7) bent in a right angle and extending in a direction away from the tip of the second conductor part (7) extends substantially in parallel with the third conductor part from the rear end of the fourth conductor part. Fifth conductor portion (8) having the same length Folded at a substantially right angle from the rear end of the fifth conductor portion, and extended in a direction away from the rear end of the second conductor portion (9) The sixth conductor A seventh conductor portion extending in parallel to the fifth conductor portion from the rear end of the portion and having substantially the same length as the fifth conductor portion 10) An eighth conductor portion (11) which is bent at a substantially right angle from the rear end of the seventh conductor portion and extends in a direction approaching the rear end of the fourth conductor portion. A ninth conductor portion (12) having the same length as the fifth conductor portion, extending in parallel to the fifth conductor portion from the rear end of the eighth conductor portion in the vicinity of the fifth conductor portion. A tenth conductor portion (13) extending in a direction substantially orthogonal to the rear end of the first conductor portion and extending in a direction approaching the rear end of the first conductor portion, extending in parallel to the first conductor portion from the rear end of the tenth conductor portion, And an eleventh conductor portion connected to the high-frequency power source.
[0010]
Here, the plane portion referred to in the present invention is a concept including not only a flat surface but also a flat portion having some unevenness and a curved surface.
[0011]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
[0012]
An embodiment of the induction heating coil according to the present invention will be described with reference to FIGS.
[0013]
FIG. 1 is a front view showing an induction heating coil according to an embodiment, and FIG. 2 is a side view of the induction heating coil of FIG. Moreover, the arrow shown on the induction heating coil represents an example of the flow of current.
[0014]
The induction heating coil 10 has a first conductor portion 12 extending in the direction of arrow A (which is an example of a predetermined direction referred to in the present invention). The first conductor portion 12 is connected to a high frequency power source (not shown) via a lead 14. A second conductor portion 16 extends from the rear end 12a of the first conductor portion 12 in a direction intersecting the arrow A direction and obliquely downward to the right in FIG. A third conductor portion 18 extends from the rear end 16a of the second conductor portion 16 in a direction opposite to the arrow A direction and away from the rear end 12a of the first conductor portion 12. The fourth conductor portion 20 extends from the rear end 18 a of the third conductor portion 18 at a substantially right angle and extends away from the tip 16 b of the second conductor portion 16.
[0015]
A fifth conductor portion 22 extends in parallel with the third conductor portion 18 from the rear end 20a of the fourth conductor portion 20, and the length of the fifth conductor portion 22 is substantially the same as the length of the third conductor portion 18. is there. A sixth conductor portion 24 extends from the rear end 22a of the fifth conductor portion 22 in a direction that is bent at a substantially right angle and away from the rear end 16a of the second conductor portion 16. A seventh conductor portion 26 extends in parallel to the fifth conductor portion 22 from the rear end 24a of the sixth conductor portion 24. The length of the seventh conductor portion 26 is substantially the same as the length of the fifth conductor portion 22. It is. The eighth conductor portion 28 is bent at a substantially right angle from the rear end 26a of the seventh conductor portion 26 and extends in a direction approaching the rear end 20a of the fourth conductor portion 20, and the length of the eighth conductor portion 28 is as follows. The length of the fourth conductor portion 20 is substantially the same.
[0016]
From the rear end 28a of the eighth conductor portion 28, a ninth conductor portion 30 extends in parallel to the fifth conductor portion 22 in proximity to the fifth conductor portion 22, and the length of the ninth conductor portion 30 is as follows. It is almost the same as the fifth conductor portion 22. The tenth conductor portion 32 extends from the rear end 30a of the ninth conductor portion 30 in a direction substantially perpendicular to the rear end 12a of the first conductor portion 12 and approaching the rear end 12a. An eleventh conductor 34 extends from the rear end 32 a of the tenth conductor 32 in parallel to the first conductor 12. The eleventh conductor portion 34 is connected to a high frequency power source (not shown) via a lead 36.
[0017]
When induction heating the flat portion 42 of the article 40 to be heated using the induction heating coil 10 described above, the fifth conductor portion 22 and the ninth conductor portion 30 are opposed to the flat portion 42. When high frequency power is supplied to the induction heating coil 10 in this state, an electric current flows through the fifth conductor portion 22 and the ninth conductor portion 30 simultaneously in the same direction to generate an alternating magnetic flux. Due to this alternating magnetic flux, an eddy current is induced in the flat portion 42 and the flat portion 42 is heated.
[0018]
By the way, when an induction heating coil having a conductor portion having a width substantially the same as the width of the flat portion 42 is used as in the prior art, as described above, the current density at both ends in the width direction of the conductor portion is at the center portion in the width direction. The current density may be lower than the current density, so that both ends in the width direction of the flat portion 42 may not be sufficiently heated. However, in the induction heating coil 10, as shown in FIG. 1, the widths of the fifth conductor portion 22 and the ninth conductor portion 30 are narrower than the area (width) of the planar portion 42. Therefore, in the fifth conductor portion 22 and the ninth conductor portion 30, the current density is uniform at both ends in the width direction and at the center portion in the width direction. In addition, in the fifth conductor portion 22 and the ninth conductor portion 30, currents simultaneously flow in the same direction, so that alternating magnetic fluxes generated by these currents do not cancel each other. As a result, the planar portion 42 can be heated uniformly.
[0019]
In the above-described embodiment, the example in which the conductor portions for heating the planar portion 42 are two (the fifth conductor portion 22 and the ninth conductor portion 30) has been shown, but when the area of the planar portion 42 is larger, It is preferable to use three or more conductor portions for heating the flat portion 42. However, it is necessary to allow the current to flow simultaneously in the same direction in each conductor portion.
[0020]
With reference to FIGS. 3 and 4, an experimental example will be described in which the planar portion of the object to be heated is induction-quenched using the induction heating coil 10 described above.
[0021]
FIG. 3 is a schematic diagram showing the hardened layer depth of the planar portion of the object to be heated used in the experiment, and FIG. 4 is a graph showing the hardened layer depth. 4, a, b, and c represent hardness distributions measured from the directions of arrows a, b, and c shown in FIG.
[0022]
The material of the object to be heated 40 used in this experiment is FCD600 (JIS standard), and the width W of the flat portion 42 is 20 mm. The width w of the fifth conductor portion 22 and the ninth conductor portion 30 was 8 mm.
[0023]
In the induction heating of the flat portion 42, the induction heating coil 10 was used for heating for 9 seconds at 40 kW and 80 kHz. After heating in this way, a cooling liquid was jetted onto the flat portion 42 for 7 seconds to quench. As a result, as shown in FIG. 4, a hardened layer having a uniform depth was obtained at the center portion in the width direction of the flat portion 42 and at both end portions in the width direction.
[0024]
【The invention's effect】
As described above, according to the first induction heating coil of the present invention, when induction heating the planar portion of the object to be heated, the parallel conductor portions through which currents in the same direction flow are directed to the planar portion. Match. For this reason, the width | variety of each conductor part may be narrower than the width | variety of a plane part. Accordingly, in each conductor portion, the current density is uniform at both ends in the width direction and at the center portion in the width direction. In addition, since currents simultaneously flow in the same direction in each conductor portion, the alternating magnetic fluxes generated by these currents do not cancel each other. As a result, the planar portion can be heated uniformly.
[0025]
Here, when the plurality of conductor portions are composed of two conductor portions that are close to each other and extend in the same direction, the induction heating coil can be manufactured relatively easily.
[0026]
Moreover, according to the 2nd induction heating coil of this invention, each width | variety of a 5th conductor part and a 9th conductor part can be made narrower than the width | variety of a plane part. Therefore, in the fifth conductor portion and the ninth conductor portion, the current density is uniform at both ends in the width direction and at the center portion in the width direction. In addition, since currents simultaneously flow in the same direction in the fifth conductor portion and the ninth conductor portion, the alternating magnetic fluxes generated by these currents do not cancel each other. As a result, the planar portion can be heated uniformly.
[Brief description of the drawings]
FIG. 1 is a front view showing an induction heating coil according to an embodiment of the present invention.
FIG. 2 is a side view of the induction heating coil of FIG.
FIG. 3 is a schematic diagram showing a hardened layer depth of a planar portion of an object to be heated used in an experiment.
FIG. 4 is a graph showing the depth of a hardened layer.
[Explanation of symbols]
10 induction heating coil 12 first conductor part 14, 36 lead 16 second conductor part 18 third conductor part 20 fourth conductor part 22 fifth conductor part 24 sixth conductor part 26 seventh conductor part 28 eighth conductor part 30 9 conductor portion 32 10th conductor portion 34 11th conductor portion 40 object to be heated 42 plane portion

Claims

In the induction heating coil arranged only on the one plane portion side, which inductively heats one plane portion of an object to be heated having a plane portion,
Each having a plurality of parallel conductor portions that inductively heat the one plane portion by causing the current in the same direction to flow in each direction facing the one plane portion ,
Each of the plurality of conductor portions has a width smaller than that of the one plane portion and extends in a longitudinal direction perpendicular to the width direction of the one plane portion. Induction heating coil.

2. The induction heating coil according to claim 1, wherein the plurality of conductor portions have a total width that is narrower than a width of the one plane portion.

The induction heating coil according to claim 1 or 2, wherein the plurality of conductor portions are longer than the length in the longitudinal direction of the one plane portion .

4. The induction according to claim 1, wherein one end of the conductor portion in the width direction is located at a center portion in the width direction rather than one end in the width direction of the one plane portion. Heating coil.

In an induction heating coil for induction heating one planar portion of an object to be heated having a planar portion in a state where the object to be heated is fixed ,
A first conductor portion extending in a predetermined direction and connected to a high-frequency power source via a lead;
A second conductor portion extending in a direction intersecting the predetermined direction from the rear end of the first conductor portion;
A third conductor portion extending from the rear end of the second conductor portion in a direction opposite to the predetermined direction and away from the rear end of the first conductor portion;
A fourth conductor part that is bent at a substantially right angle from the rear end of the third conductor part and extends in a direction away from the tip of the second conductor part;
A fifth conductor portion extending in parallel from the rear end of the fourth conductor portion to the third conductor portion and having substantially the same length as the third conductor portion;
A sixth conductor portion that is bent at a substantially right angle from the rear end of the fifth conductor portion and extends in a direction away from the rear end of the second conductor portion;
A seventh conductor portion extending in parallel from the rear end of the sixth conductor portion to the fifth conductor portion and having substantially the same length as the fifth conductor portion;
An eighth conductor portion bent substantially at a right angle from the rear end of the seventh conductor portion and extending in a direction approaching the rear end of the fourth conductor portion;
A ninth conductor portion extending from the rear end of the eighth conductor portion in proximity to the fifth conductor portion and parallel to the fifth conductor portion, and having substantially the same length as the fifth conductor portion;
A tenth conductor portion extending substantially perpendicularly from the rear end of the ninth conductor portion and extending in a direction approaching the rear end of the first conductor portion;
An eleventh conductor portion extending in parallel to the one conductor portion from the rear end of the tenth conductor portion and connected to the high-frequency power source via a lead;
The fifth conductor portion and the ninth conductor portion are
Arranged to face the one plane portion, and
Each width is narrower than the width of the one planar portion, and
Extending in a longitudinal direction perpendicular to the width direction of the one planar portion, and
An induction heating coil, wherein a total width of the fifth conductor portion and the ninth conductor portion is narrower than a width of the one plane portion .