JP3967446B2 - Induction heating cooker - Google Patents

Description

加熱コイル１Ａの入力インピーダンスは、（表皮抵抗）×（加熱コイルの巻数の２乗）に比例する。したがって、入力インピーダンスが定格入力に対して整合するときが効率が良い。表皮抵抗の大きい鉄の場合は、巻数が少なくてよく、５Ｔの第４のコイル５を用い、端子１７ａ，１７ｂ間に高周波電流を流す。次に表皮抵抗の小さい１８−８ステンレス鍋の場合は、端子１７ｂと１７ｃを接続し、合計で６５Ｔとなるように第３のコイル４と第４のコイル５を直列に接続し、端子１７ａ，１７ｄ間に高周波電流を流す。アルミニウムの場合は、合計で７３Ｔとなるように第２のコイル３、第３のコイル４及び第４のコイル５を直列に接続し、端子１７ａ，１７ｆ間に高周波電流を流す。最も表皮抵抗の小さい銅鍋の場合は、合計で８５Ｔとなるように第１から第４のコイル２，３，４，５を直列接続し、端子１７ａ，１７ｈ間に高周波電流を流す。このようにすれば、鍋２０の材質に合った加熱コイル１Ａの巻数で効率良く加熱することができる。ここで、図１に、例えば第４のコイル５をトッププレート１８側に幾分近付けて示したように、複数のコイル２，３，４，５の上面は、同一平面上ではなく凹凸があってもよい。しかし、ターン数の少ない第４のコイル５はトッププレート１８側に近付ける等、各コイル２，３，４，５のターン数に応じてなるべくトッププレート１８側に近付けておいた方が一層効率がよくなる。
【００２２】
次に、図２を用いて、誘導加熱調理器の回路構成及び作用を説明する。２７は商用交流電源、２８はダイオードブリッジ、２９は平滑用のコンデンサであり、ダイオードブリッジ２８及びコンデンサ２９で直流電源回路が構成されている。インバータ駆動回路２３からの駆動信号でスイッチング素子Ｑ₁ ，Ｑ₂ が交互にオン／オフを繰り返し、直流電源回路からの直流電圧を周期的にオン／オフすることで、加熱コイル１Ａに高周波電流を流す。このとき、インバータの制御は、スイッチング素子Ｑ₂ の電圧と共振コンデンサＣ₁ の電圧の位相を位相比較回路２１で検知し、ボルテージコントロールオシレータ２２にそれを入力するＰＬＬフィードバック回路で行われる。これにより、スイッチング素子Ｑ₂ の電圧と共振回路に流れる電流の位相差を一定にすることができ、使用者が入力設定手段で入力設定を行うと位相差設定回路２４により位相差を変えて所望の入力にする。材質検知回路２５は、インバータの電流値をＣＴにより検出し、鍋材質に合った適切な加熱コイル巻数及び鍋材質に合った適切な周波数になるようにコンデンサ容量を切り換える。
【００２３】
まず、動作開始時、第１乃至第４のコイル２，３，４，５及びコンデンサＣ₁ ，Ｃ₂ ，Ｃ₃ ，Ｃ₄ が直列接続になるようにスイッチＳＷ₁ ，ＳＷ₂ ，ＳＷ₃ をそれぞれ１７ｂ−１７ｃ，１７ｄ−１７ｅ，１７ｆ−１７ｇ接続になるように切り換える。このとき、銅鍋を載せたときは、正常なインバータ電流が流れ、効率良く加熱でき動作を続ける。それ以外の鍋（アルミ、鉄、ステンレス）は、表皮抵抗が大きいので、電流が少ない。したがって、動作を止め、加熱コイル１Ａの巻数を減らす必要があり、第２乃至第４のコイル３，４，５及びコンデンサＣ₁ ，Ｃ₂ ，Ｃ₃ が直列接続になるようにスイッチＳＷ₃ を１７ｆ−１７ｋ接続になるように切り換える。このとき、アルミ鍋が載せられていたら、正常なインバータ電流が流れ効率良く加熱でき動作を続ける。それ以外の鍋（鉄、ステンレス）は、表皮抵抗が大きいので、電流が少ない。したがって、動作を止め、加熱コイル１Ａの巻数を減らす必要があり、第３、第４のコイル４，５及びコンデンサＣ₁ ，Ｃ₂ が直列接続になるようにスイッチＳＷ₂ を１７ｄ−１７ｊ接続になるように切り換える。このとき、ステンレス鍋が載せられていたら、正常なインバータ電流が流れ効率良く加熱でき動作を続ける。このとき、鉄鍋は、ステンレスより表皮抵抗が大きいので、電流が少ない。したがって、動作を止め、加熱コイル１Ａの巻数を減らす必要があり、第４のコイル５及びコンデンサＣ₁ が直列接続になるようにスイッチＳＷ₁ を１７ｂ−１７ｉ接続になるように切り換える。このとき鉄鍋が載せられていたら、正常なインバータ電流が流れ効率良く加熱でき動作を続ける。このように、鍋材質に合った加熱コイル巻数を用いることで、どの鍋でも効率良く加熱することができる。図３は、上述のように、加熱コイル１Ａを１段化して占積率を上げた場合において、アルミ鍋を加熱した場合の占積率に対する加熱効率の関係を示している。占積率を４０％以上にすると、ほぼ一定値で高加熱効率とすることができる。占積率が４０％程度以下になると、加熱効率が極端に悪化する。これは、結合係数が小さくなったためである。
【００２４】
図４及び図５には、本発明の第２の実施の形態を示す。図４において、加熱コイル１Ｂは、第１のコイル６の外側に第２のコイル７、第２のコイル７の外側に第３のコイル８、その外側に第４のコイル９が同心的に巻回されて構成されている。各コイル６，７，８，９の直径は、第１のコイル６が１００mm、第２のコイル７が１６０mm、第３のコイル８が２００mm、第４のコイル９が２２０mmとなっている。鍋２０を効率良く加熱するには、鍋２０の直径に合わせた加熱コイルで加熱する必要がある。アルミ鍋の直径が２２０mm以上の場合は、第４のコイル９を用い、端子１７ａ，１７ｂ間に高周波電流を流す。次に小さい直径２００mmから２２０mmのアルミ鍋の場合は、第３のコイル８を用い、１７ｃ，１７ｄ間に高周波電流を流す。直径１６０mmから２００mmのアルミ鍋の場合は、第２のコイル７を用い、直径１６０mm以下のアルミ鍋は、第１のコイル６を用いる。特に、アルミ鍋の場合、加熱コイル１Ｂと鍋２０間の距離が大きく離れると、加熱効率が低下するので、鍋径に合った大きさのコイルを用いると効率良く加熱できる。鍋２０に流れる電流は、ほぼ加熱コイルの形状の内径と外径の中間部を流れる。したがって、鍋径が大きいものは、コイルの寸法の大きいものを用いると、電流の流れる経路長が長く、加熱コイル１Ｂの入力抵抗が上がり、効率が良くなる。即ち、鍋２０を加熱する入力に比例関係がある鍋の入力抵抗Ｒinは、
Ｒin∝Ｒs ・Ｌ …（１）
Ｒs ；表皮抵抗、Ｌ；鍋に流れる電流の経路長
であり、表皮抵抗Ｒs は、
Ｒs ＝√（ｆ・μｒ・ρ） …（２）
ｆ；周波数、μｒ；比透磁率、ρ；抵抗率
となる。加熱コイルの損失が同じなら、入力抵抗Ｒinが大きいものほど、加熱効率は向上する。特に、アルミ又は銅鍋の場合、加熱コイルの巻数、周波数とも上げる必要があり、加熱コイルの損失が大きく、効率を向上させるのが難しいが、鍋の外径付近に電流が流れるような加熱コイルの形状であると大きく効率が向上する。一方、アルミ・銅鍋直径より大きい内径の加熱コイルで加熱すると、非磁性体であるため、加熱コイルの磁束が鍋に入らず著しく効率が悪化する。
【００２５】
次に、図５を用いて、誘導加熱調理器の回路構成及び作用を説明する。鍋径検知回路２６は、インバータの電流値をＣＴにより検出し、鍋径に合った適切な加熱コイル形状に、スイッチＳＷ₅ を切り換える。このとき、大きい径のコイルから順次小さい径のコイルへ切換えていく。まず、動作開始時、第４のコイル９及びコンデンサＣ₅ が直列接続になるように切換えスイッチＳＷ₅ を１７ｊ−１７ａ接続になるように切り換える。このとき、直径２２０mm以上のアルミ鍋を載せたときは、正常なインバータ電流が流れ効率良く加熱でき動作を続ける。これ以下の鍋は、磁束が鍋に入らず入力抵抗が小さく、電流が大きい。したがって、動作を止め、加熱コイル１Ｂを切り換える必要があり、第３のコイル８及びコンデンサＣ₅ が直列接続になるように切換えスイッチＳＷ₅ を１７ｊ−１７ｃ接続になるように切り換える。このとき、直径２００mmから２２０mm以上のアルミ鍋が載せられていたら、正常なインバータ電流が流れ効率良く加熱でき動作を続ける。これ以下の鍋は、磁束が鍋に有効に入らず入力抵抗が小さく、電流が大きい。したがって、動作を止め、加熱コイル１Ｂを切り換える必要があり、第２のコイル７及びコンデンサＣ₅ が直列接続になるように切換えスイッチＳＷ₅ を１７ｊ−１７ｅ接続になるように切り換える。このとき、直径１６０mmから２００mmのアルミ鍋が載せられていたら、正常なインバータ電流が流れ効率良く加熱でき動作を続ける。これ以下の鍋は、磁束が鍋に有効に入らず入力抵抗が小さく、電流が大きい。したがって、動作を止め、加熱コイル１Ｂを切り換える必要があり、第１のコイル６及びコンデンサＣ₅ が直列接続になるように切換えスイッチＳＷ₅ を１７ｊ−１７ｇ接続になるように切り換える。このとき、直径１６０mm以下程度のアルミ鍋が載せられていたら、正常なインバータ電流が流れ効率良く加熱でき動作を続ける。このように、鍋径に合った大きさの加熱コイルを用いて加熱すると、低抵抗、非磁性のアルミ、銅鍋でも効率良く加熱することができる。また、鉄、ステンレスでもこの方法は有効である。
【００２６】
図６には、本発明の第３の実施の形態を示す。アルミ、銅等の低抵抗・非磁性の鍋２０は、第１のコイル１０（例えば６５Ｔ）と第２のコイル１１（例えば２０Ｔ）を直列接続した加熱コイル１Ｃで加熱し、鉄、ステンレス等の高抵抗又は磁性の鍋２０は、外側の第２のコイル１１を用いる。このとき、鉄、ステンレス鍋を加熱する入力抵抗Ｒinは前記式（１）で表され、また、表皮抵抗Ｒs は前記式（２）で表される。したがって、入力抵抗Ｒinはインバータ周波数が同じなら、固定値となる。鉄、ステンレスの高抵抗又は磁性の鍋用コイルを外側に巻くと、電流の流れる経路長が長くなり（図６（ｂ））、入力抵抗Ｒinが大きくなる。したがって、加熱コイル１Ｃのみの損失は、一定なので効率が向上する。よって、鉄、ステンレス加熱は外側の第２のコイル１１を用いる。
【００２７】
図７には、本発明の第４の実施の形態を示す。アルミ、銅等の低抵抗・非磁性の鍋２０は、第１のコイル１２（例えば２０Ｔ）と第２のコイル１３（例えば６５Ｔ）を直列接続した加熱コイル１Ｄで加熱し、鉄、ステンレスの高抵抗又は磁性の鍋２０は、内側の第１のコイル１２を用いる。鉄、ステンレスにおいて小径の鍋２０を加熱するとき、加熱コイル１Ｄの直径が鍋２０に比べて大きすぎると、磁束が有効に鍋２０に入らず、効率良く加熱することができない。そこで、内側に巻いた第１のコイル１２で小径鍋を加熱すると図７（ｂ）のように有効に磁束が鍋２０に鎖交して、効率良く加熱することができる。
【００２８】
本発明の第５の実施の形態を、前記図７を参照して説明する。直径の大きい鍋２０は、第２のコイル１３を用い、直径の小さな鍋２０は内側に巻いた第１のコイル１２を用いる。鍋２０により、加熱コイルの大きさを変えることにより効率良く加熱することができる。
【００２９】
図８には、本発明の第６の実施の形態を示す。アルミ、銅等の低抵抗・非磁性の鍋２０は、第１のコイル１４（例えば３０Ｔ）、第２のコイル１５（例えば２０Ｔ）及び第３のコイル１６（例えば３５Ｔ）を直列接続した加熱コイル１Ｅで加熱し、鉄、ステンレスの高抵抗又は磁性の鍋２０は、中間の第２のコイル１５を用いる。鉄、ステンレス鍋は、アルミ等に比べて熱伝導率が悪い。したがって、標準的な大きさの鍋２０において、鍋底に流れる電流の経路は鍋２０の中心と外周部の中間辺りに流すことが（図８（ｂ））、鍋加熱において、鍋底温度が均一化し調理性能がよくなる。
【００３０】
図９には、本発明の第７の実施の形態を示す。アルミ、銅等の低抵抗・非磁性の鍋は、第１のコイル４１（例えば１０Ｔ）、第２のコイル４２（例えば６５Ｔ）及び第３のコイル４３（例えば１０Ｔ）を直列接続した加熱コイル１Ｇで加熱し、鉄、ステンレスの高抵抗又は磁性の鍋は、第１のコイル４１及び第３のコイル４３を直列接続して用いる。鉄、ステンレス鍋だけでなくアルミ、銅等の鍋も加熱できるようにする１段コイルでは、アルミ、銅等の鍋を加熱する場合に比べ、鉄、ステンレス鍋を加熱する場合のコイル巻数は少ない。さらに、鍋には、加熱コイルに電流を流した上部分で、鍋にも電流が流れ発熱する。したがって、鉄、ステンレス鍋を加熱するとき、１箇所のコイルを使って誘導加熱すると、その部分だけが発熱して加熱むらを起こすおそれがある。特に、被加熱物が加熱中に動かす事の少ないホットケーキ等の場合、電流を流したコイル上面は焼けるが、それ以外は生焼けになってしまう不具合が発生し得る。そこで、内側の第１のコイル４１と外側の第３のコイル４３に電流を流すことで、加熱むらの発生を少なくすることができる。
【００３１】
次に、図１０を用いて、第７の実施の形態に係る加熱コイル１Ｇを用いた誘導加熱調理器の回路構成及び作用を説明する。材質検知回路２５は、インバータの電流値をＣＴにより検出し、鍋の材質に合った適切な加熱コイル巻数及び鍋の材質に合った適切な周波数になるようにコンデンサ容量を、それぞれスイッチＳＷ₆ 及びＳＷ₇ を制御することで、切り換える。
【００３２】
まず、動作開始時、第１乃至第３のコイル４１，４２，４３及びコンデンサＣ₆ ，Ｃ₇ が直列接続になるようにスイッチＳＷ₆ ，ＳＷ₇ をそれぞれ１７ａ−１７ｂ，１７ｄ−１７ｅ接続になるように切り換える。このとき、アルミ、銅等の鍋を載せたときは、正常なインバータ電流が流れ、効率良く加熱でき動作を続ける。それ以外の鍋（鉄、ステンレス）は、動作を止め、第１、第３のコイル４１，４３及びコンデンサＣ₇ を直列接続にすべくスイッチＳＷ₆ を１７ａ−１７ｃ接続になるように、またスイッチＳＷ₇ を１７ｄ−１７ｆ接続になるように切り換える。
【００３３】
図１１は、上記図１０の変形例であり、鍋の材質に合った適切な加熱コイル巻数及び鍋の材質に合った適切な周波数になるようなコンデンサ容量の切り換えを１つのスイッチＳＷ₈ で実現した構成である。すなわち、アルミ、銅等の鍋を加熱するときには、スイッチＳＷ₈ を１７ａ−１７ｂ接続となるようにし、鉄、ステンレスの鍋を加熱するときには、スイッチＳＷ₈ を１７ａ−１７ｃとなるように切り換えるのである。この構成によれば、上記図１０の構成に比べてコストダウンを図ることができる。
【００３４】
図１２には、本発明の第８の実施の形態を示す。アルミ、銅等の低抵抗・非磁性の鍋は、第１のコイル５１（例えば１０Ｔ）及び第２のコイル５２（例えば７５Ｔ）を直列接続した加熱コイル１Ｈで加熱し、鉄、ステンレスの高抵抗又は磁性の鍋は、第１のコイル５１及び第３のコイル５３（例えば１０Ｔ）を直列接続して用いる。これにより、図９に示した実施の形態と同様に加熱むらの発生を少なくすることができる。
【００３５】
次に、図１３を用いて、第８の実施の形態に係る加熱コイル１Ｈを用いた誘導加熱調理器の回路構成及び作用を説明する。材質検知回路２５は、インバータの電流値をＣＴにより検出し、鍋の材質に合った適切な加熱コイル巻数及び鍋の材質に合った適切な周波数になるようにコンデンサ容量を、スイッチＳＷ₉ を制御することで、切り換える。
【００３６】
まず、動作開始時、第１及び第２のコイル５１，５２及びコンデンサＣ₈ ，Ｃ₉ が直列接続になるようにスイッチＳＷ₉ を１７ａ−１７ｂ接続になるように切り換える。このとき、アルミ、銅等の鍋を載せたときは、正常なインバータ電流が流れ、効率良く加熱でき動作を続ける。それ以外の鍋（鉄、ステンレス）は、動作を止め、第１、第３のコイル５１，５３及びコンデンサＣ₉ を直列接続にすべくスイッチＳＷ₉ を１７ａ−１７ｃ接続になるように切り換える。
【００３７】
このような回路構成により、スイッチが１個で済み、コストダウンを図ることができ、また、アルミ、銅等の鍋の加熱時には、スイッチＳＷ₉ の切り換えに伴い、第２のコイル５２の外側で５ｋＶ程度の電圧が発生するが、コイル５２外側でこれに対する絶縁処理を容易に施すことができる。
【００３８】
なお、上記第８の実施の形態では、アルミ、銅等の低抵抗・非磁性の鍋を、第１のコイル５１（例えば１０Ｔ）及び第２のコイル５２（例えば７５Ｔ）を直列接続した加熱コイル１Ｈで加熱し、鉄、ステンレスの高抵抗又は磁性の鍋を、第１のコイル及び第３のコイル５３（例えば１０Ｔ）を直列接続して用いるようにしたが、アルミ、銅等の低抵抗・非磁性の鍋を、第３のコイル５３及び第２のコイル５２を直列接続した加熱コイル１Ｈで加熱し、鉄、ステンレスの高抵抗又は磁性の鍋を、第１のコイル５１及び第３のコイル５３を直列接続して用いるようにしてもよい。これは、鉄鍋等の加熱に使用する内側または外側のコイルの幅が、第２のコイル５２に比べて巻数が少なく、１cm程度で、コイル全体の直径が１９cm程度であるため、アルミ、銅等の加熱時、内側または外側のいずれかのコイルを使用しなくても、加熱むらの影響が小さいことによる。この場合の回路構成としては、図１３において、第１のコイル５１と第３のコイル５３の接続配置位置を逆にすればよい。
【００３９】
図１４には、本発明の第９の実施の形態を示す。アルミ、鉄兼用１段コイルにおいて加熱コイル１Ｆをモールドする。低抵抗、非磁性鍋を加熱するためには、鍋の表皮抵抗が小さいため、加熱コイル巻数を増加させる必要があり、加熱コイル電圧が高くなる。したがって、トッププレート１８にシールド用導電体物３０を配置し、それを低電圧部と接続する必要がある。よって、コイル−シールド間で絶縁破壊防止用にエポキシモールドする必要がある。３１はフェライトである。
【００４０】
図１５乃至図１７には、本発明の第１０の実施の形態を示す。エポキシモールドするとき、１段加熱コイルの場合は、容易にエポキシ型でコイル成形をしモールドする一体成形が可能である。図１５に示すように、アルミ等エポキシを離形できる型３３ａに直接加熱コイルのリッツ線３２を巻き、途中からリッツ線３２を出し、第１のコイルを作り、その後第２のコイルを巻き始める。この型は中心軸を中心に回すことができる。次に、図１６（ａ）に示すように、それをエポキシ樹脂を流し込める型３３ｂにセットし、エポキシ注形を行う。そのとき、コイル上面は、コイルリッツ線３２がむき出しになり、トッププレートのシールド用導電体物と絶縁破壊が起こるおそれがある。そこで、図１７のように再度、コイル上面が開いた型３３ｃに入れ、エポキシ注形を行う。このとき、コイル下面にフェライト３１接着を行う。１段加熱コイルの引き出しリッツ線３２ａや巻き始め、巻き終りのリッツ線３２ｂの部分にエポキシが毛細管現象により、型３３ｂの外へはみ出してくると、その部分が動いたとき折れてしまうおそれがある。そこで、熱収縮チューブ３４をその部分に取り付け、エポキシを固めるためにヒーティングするとき、熱収縮チューブ３４を収縮させてその部分を縮めることで、エポキシの流出を防ぐことができる。このとき、リッツ線３２ａ，３２ｂにシリコン３５を浸み込ませることで（図１６（ｂ））、より確実にエポキシの流出を防ぐことができる。
【００４８】
【発明の効果】
以上説明したように、請求項１記載の発明によれば、被加熱体を誘導加熱する加熱コイルを、第１のコイルと該第１のコイルの外側に同心的に巻回した第２のコイルと該第２のコイルの外側に同心的に巻回した第３のコイルとで構成し、高抵抗又は／及び高透磁率のときは、前記第１のコイル及び第３のコイルを直列接続して用いるようにしたので、第１のコイルまたは第３のコイルを用いて高抵抗又は／及び高透磁率の被加熱体を加熱する場合に比べて、加熱むらの発生を確実に防止することができる。
【００５１】
請求項２記載の発明によれば、前記加熱コイルを構成する各コイルをモールドすると共に、モールド用金型から前記各コイルの接続端子取出し部には、予め熱収縮チューブを被せてモールド材の注形を実行するようにしたため、モールド材の流出がなくなり、モールド材の固化による接続端子取出し部の折損が防止されて歩留まりが向上し、製造性を高めることができる。
【００５２】
請求項３記載の発明によれば、前記各コイルの接続端子取出し部の前記リッツ線には、シリコンを充填させた後に前記熱収縮チューブを被せるようにしたため、より確実にモールド材の流出が防止されて接続端子取出し部の折損がなくなり、一層製造性を高めることができる。
【図面の簡単な説明】
【図１】本発明に係る誘導加熱調理器の第１の実施の形態における加熱コイル部分の断面図である。
【図２】上記第１の実施の形態の回路図である。
【図３】上記第１の実施の形態において占積率と加熱効率の関係を示す特性図である。
【図４】本発明の第２の実施の形態における加熱コイル部分の断面図である。
【図５】上記第２の実施の形態の回路図である。
【図６】本発明の第３の実施の形態における加熱コイル部分を示す図である。
【図７】本発明の第４の実施の形態における加熱コイル部分を示す図である。
【図８】本発明の第６の実施の形態における加熱コイル部分を示す図である。
【図９】本発明の第７の実施の形態における加熱コイル部分の断面図である。
【図１０】上記第７の実施の形態の回路図である。
【図１１】上記第７の実施の形態の他の回路図である。
【図１２】本発明の第８の実施の形態における加熱コイル部分の断面図である。
【図１３】上記第８の実施の形態の回路図である。
【図１４】本発明の第９の実施の形態における加熱コイル部分の断面図である。
【図１５】本発明の第１０の実施の形態において金型に直接リッツ線を巻回してコイル成形を行う工程を説明するための図である。
【図１６】上記第１０の実施の形態において成形後のコイルをエポキシモールドする工程を説明するための図である。
【図１７】上記第１０の実施の形態においてコイル上面に再度エポキシ注形を行う工程を説明するための図である。
【符号の説明】
１Ａ−１Ｈ 加熱コイル
２〜１６ コイル
１８ トッププレート
２０ 鍋（被加熱体）
３２ リッツ線
３３ａ〜３３ｃ 金型
３４ 熱収縮チューブ
３５ シリコン[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an induction heating cooker that induces and heats an object to be heated by supplying a high-frequency current to a heating coil.
[0002]
[Prior art]
As a conventional induction heating cooker, for example, a plurality of coils wound spirally are stacked in multiple stages in the vertical direction with an insulator interposed between each coil, and provided with a heating coil capable of increasing the number of turns. There is one in which the number of turns of the heating coil is switched according to the material of the load such as a low resistance pan or a high resistance pan (Japanese Utility Model Publication No. 3-19192).
[0003]
[Problems to be solved by the invention]
However, in order to further improve the efficiency of the induction heating cooker, it is necessary to consider the electromagnetic coupling between the heating coil and the pan, and the space factor of the wire, that is, the heating, with respect to the overall dimensions of the heating coil. It is necessary to increase the ratio of the wire to the total coil volume. In the multi-stage heating coil as described above, there are irregularities on the coil surface between the coils, there is a gap between them, and an insulator must be inserted between the multiple coils. The rate cannot be improved and it is difficult to increase the efficiency. In addition, since a high voltage is applied between the coils to form the multi-stage coil, it is necessary to bond the insulator after putting it in, so that it is difficult to manufacture and the cost is high.
[0004]
The present invention has been made in view of the above, and an object thereof is to provide an induction heating cooker that has high heating efficiency, is easy to manufacture, and is low in cost.
[0012]
[Means for Solving the Problems]
  To solve the above problem,Claim1The described inventionA heating coil for inductively heating an object to be heated is a first coil, a second coil concentrically wound around the outside of the first coil, and a second coil concentrically wound around the outside of the second coil. When the object to be heated has a low resistance and a low magnetic permeability, the first coil, the second coil, and the third coil are used in series, and a high resistance or / and a high resistance are used. In the case of magnetic permeability, the first coil and the third coil are connected in series and used.Is the gist. With this configuration, it is possible to prevent the occurrence of uneven heating as compared with the case where a heated object having high resistance and / or high magnetic permeability is heated using the first coil or the third coil.
[0015]
  Claim2The invention described is the above claim.1In the induction heating cooker described,Each coil constituting the heating coil is molded, and a molding material is casted by previously covering the connecting terminal extraction portion of each coil from the molding die with a heat shrinkable tube.Is the gist. With this configuration, when heating for solidifying a mold material such as epoxy, the heat-shrinkable tube is contracted to prevent the mold material from flowing out and the mold material is not solidified in the connection terminal extraction portion. As a result, breakage of the connection terminal extraction portion due to solidification of the molding material is prevented.
[0016]
  Claim3The invention described is the above claim.2In the induction heating cooker described above, the gist is that the litz wire of the connection terminal extraction portion of each coil is covered with the heat shrinkable tube after being filled with silicon. With this configuration, by allowing silicon to soak into the litz wire, the mold material can be more reliably prevented from flowing out, and the connecting terminal extraction portion can be prevented from being broken.
[0017]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
[0018]
An induction heating cooker heats a pot by causing a high-frequency current to flow through a spirally wound heating coil to generate magnetic flux, and causing an eddy current to flow through the bottom of the pan, which is the object to be heated. When the electromagnetic coupling between the heating coil and the pan is improved, the heating efficiency is improved. As the method, when the ratio of the volume of the wire (including the insulating layer) to the total volume of the heating coil (space factor) is increased, the wires are first tightly coupled to increase the inductance, Electromagnetic coupling increases. Moreover, the distance between the heating coil and the pan cannot be brought closer than necessary in terms of heat countermeasures as well as the top plate. Therefore, the one-stage coil that can increase the space factor brings the current and the pan closer, increases electromagnetic coupling, and improves efficiency. In particular, when heating an aluminum or copper pan, since it is a non-magnetic material, heating efficiency is improved by reducing the current flowing through the heating coil and the distance between the pans.
[0019]
Below, each embodiment is described in order.
[0020]
1 to 3 are views showing a first embodiment of the present invention. The heating coil 1A will be described with reference to FIG. The heating coil 1A is configured by concentrically winding a second coil 3 on the outside of the first coil 2, a third coil 4 on the outside of the second coil 3, and a fourth coil 5 on the outside thereof. Has been. As an example, the number of turns of each coil is 12T (turn) for the first coil 2, 8T for the second coil 3, 60T for the third coil 4, and 5T for the fourth coil 5. Reference numeral 18 denotes a top plate. In order to efficiently heat the pan 20 that is the object to be heated, as shown in Table 1, since the skin resistance of the pan 20 varies depending on the material, the number of turns of the heating coil 1A can be set to various materials constituting the pan 20. It is necessary to match the skin resistance, and the number of turns of each coil is as described above.
[0021]
[Table 1]

The input impedance of the heating coil 1A is proportional to (skin resistance) × (the square of the number of turns of the heating coil). Therefore, efficiency is good when the input impedance matches the rated input. In the case of iron with a large skin resistance, the number of turns may be small, and a 4T 5T coil is used, and a high-frequency current is passed between the terminals 17a and 17b. Next, in the case of an 18-8 stainless steel pan having a small skin resistance, the terminals 17b and 17c are connected, and the third coil 4 and the fourth coil 5 are connected in series so that the total becomes 65T, and the terminals 17a, 17c, A high-frequency current is passed between 17d. In the case of aluminum, the 2nd coil 3, the 3rd coil 4, and the 4th coil 5 are connected in series so that it may become 73T in total, and a high frequency current is sent between terminals 17a and 17f. In the case of a copper pan with the smallest skin resistance, the first to fourth coils 2, 3, 4, and 5 are connected in series so that the total is 85T, and a high-frequency current is passed between the terminals 17a and 17h. If it does in this way, it can heat efficiently by the number of turns of heating coil 1A suitable for the material of pan 20. Here, for example, as shown in FIG. 1 with the fourth coil 5 slightly closer to the top plate 18 side, the top surfaces of the plurality of coils 2, 3, 4, and 5 are not coplanar but uneven. May be. However, it is more efficient to move the fourth coil 5 having a smaller number of turns closer to the top plate 18 side as much as possible depending on the number of turns of the coils 2, 3, 4, and 5 such as closer to the top plate 18 side. Get better.
[0022]
Next, the circuit configuration and operation of the induction heating cooker will be described with reference to FIG. 27 is a commercial AC power supply, 28 is a diode bridge, 29 is a smoothing capacitor, and the diode bridge 28 and the capacitor 29 constitute a DC power supply circuit. The switching element Q is driven by a drive signal from the inverter drive circuit 23.₁, Q₂Are alternately turned on and off, and the DC voltage from the DC power supply circuit is periodically turned on and off, so that a high-frequency current flows through the heating coil 1A. At this time, the inverter is controlled by the switching element Q.₂Voltage and resonant capacitor C₁This is performed by a PLL feedback circuit that detects the phase of this voltage by the phase comparison circuit 21 and inputs it to the voltage control oscillator 22. Thereby, the switching element Q₂The phase difference between the voltage of the current and the current flowing through the resonance circuit can be made constant, and when the user performs input setting with the input setting means, the phase difference setting circuit 24 changes the phase difference to obtain a desired input. The material detection circuit 25 detects the current value of the inverter by CT, and switches the capacitor capacity so as to obtain an appropriate number of heating coil turns suitable for the pan material and an appropriate frequency suitable for the pan material.
[0023]
First, at the start of operation, the first to fourth coils 2, 3, 4, 5 and the capacitor C₁, C₂, C_Three, C_FourSwitch SW so that is connected in series₁, SW₂, SW_ThreeAre switched to 17b-17c, 17d-17e, and 17f-17g connections, respectively. At this time, when a copper pan is placed, a normal inverter current flows, and heating can be performed efficiently and operation continues. Other pans (aluminum, iron, stainless steel) have a large skin resistance, so there is little current. Therefore, it is necessary to stop the operation and reduce the number of turns of the heating coil 1A, and the second to fourth coils 3, 4, 5 and the capacitor C₁, C₂, C_ThreeSwitch SW so that is connected in series_ThreeSwitch to a 17f-17k connection. At this time, if an aluminum pan is placed, normal inverter current flows and heating can be performed efficiently, and the operation continues. Other pans (iron, stainless steel) have high skin resistance, so there is little current. Therefore, it is necessary to stop the operation and reduce the number of turns of the heating coil 1A, and the third and fourth coils 4, 5 and the capacitor C₁, C₂Switch SW so that is connected in series₂Is switched to 17d-17j connection. At this time, if a stainless steel pan is placed, normal inverter current flows and heating can be performed efficiently, and the operation continues. At this time, the iron pan has a smaller skin resistance than stainless steel, and therefore has a lower current. Therefore, it is necessary to stop the operation and reduce the number of turns of the heating coil 1A, the fourth coil 5 and the capacitor C.₁Switch SW so that is connected in series₁Switch to 17b-17i connection. If an iron pan is placed at this time, a normal inverter current flows and heating can be performed efficiently, and the operation continues. Thus, any pan can be efficiently heated by using the number of turns of the heating coil suitable for the pan material. FIG. 3 shows the relationship of the heating efficiency to the space factor when the aluminum pan is heated in the case where the heating coil 1A is made one stage and the space factor is increased as described above. When the space factor is 40% or more, high heating efficiency can be achieved with a substantially constant value. When the space factor is about 40% or less, the heating efficiency is extremely deteriorated. This is because the coupling coefficient is reduced.
[0024]
4 and 5 show a second embodiment of the present invention. In FIG. 4, the heating coil 1B has a second coil 7 outside the first coil 6, a third coil 8 outside the second coil 7, and a fourth coil 9 concentrically wound outside. It is configured to be turned. The diameters of the coils 6, 7, 8, 9 are 100 mm for the first coil 6, 160 mm for the second coil 7, 200 mm for the third coil 8, and 220 mm for the fourth coil 9. In order to heat the pot 20 efficiently, it is necessary to heat with the heating coil matched to the diameter of the pot 20. When the diameter of the aluminum pan is 220 mm or more, the fourth coil 9 is used and a high frequency current is passed between the terminals 17a and 17b. In the case of an aluminum pan having the next smallest diameter of 200 mm to 220 mm, the third coil 8 is used and a high frequency current is passed between 17c and 17d. In the case of an aluminum pan having a diameter of 160 mm to 200 mm, the second coil 7 is used, and in the aluminum pan having a diameter of 160 mm or less, the first coil 6 is used. In particular, in the case of an aluminum pan, if the distance between the heating coil 1B and the pan 20 is greatly separated, the heating efficiency is lowered. Therefore, when a coil having a size that matches the pan diameter is used, the heating can be efficiently performed. The electric current flowing through the pan 20 flows through an intermediate portion between the inner and outer diameters of the shape of the heating coil. Therefore, when the one having a large pan diameter is used, the one having a large coil size has a long path length through which the current flows, the input resistance of the heating coil 1B is increased, and the efficiency is improved. That is, the input resistance Rin of the pan that is proportional to the input to heat the pan 20 is
Rin∝Rs · L (1)
Rs: skin resistance, L: path length of current flowing in the pan
And the skin resistance Rs is
Rs = √ (f · μr · ρ) (2)
f: frequency, μr: relative permeability, ρ: resistivity
It becomes. If the loss of the heating coil is the same, the heating efficiency improves as the input resistance Rin increases. In particular, in the case of aluminum or copper pans, it is necessary to increase both the number of turns and the frequency of the heating coil. The efficiency is greatly improved with this shape. On the other hand, when heated with a heating coil having an inner diameter larger than the diameter of the aluminum / copper pan, since it is a non-magnetic material, the magnetic flux of the heating coil does not enter the pan and the efficiency is significantly deteriorated.
[0025]
Next, the circuit configuration and operation of the induction heating cooker will be described with reference to FIG. The pot diameter detection circuit 26 detects the current value of the inverter by CT, and switches the switch SW into an appropriate heating coil shape suitable for the pot diameter._FiveSwitch. At this time, the coil having a smaller diameter is sequentially switched from the coil having the larger diameter. First, at the start of operation, the fourth coil 9 and the capacitor C_FiveSwitch SW so that is connected in series_FiveIs switched to 17j-17a connection. At this time, when an aluminum pan having a diameter of 220 mm or more is placed, a normal inverter current flows and heating can be performed efficiently, and the operation continues. A pan below this has a low input resistance and a large current because the magnetic flux does not enter the pan. Therefore, it is necessary to stop the operation and switch the heating coil 1B, and the third coil 8 and the capacitor C_FiveSwitch SW so that is connected in series_FiveAre switched to 17j-17c connection. At this time, if an aluminum pan having a diameter of 200 mm to 220 mm or more is placed, a normal inverter current flows and heating can be performed efficiently, and the operation continues. A pan below this has a low input resistance and a large current because the magnetic flux does not enter the pan effectively. Therefore, it is necessary to stop the operation and switch the heating coil 1B, and the second coil 7 and the capacitor C_FiveSwitch SW so that is connected in series_FiveIs switched to 17j-17e connection. At this time, if an aluminum pan having a diameter of 160 mm to 200 mm is placed, a normal inverter current flows and heating can be performed efficiently, and the operation continues. A pan below this has a low input resistance and a large current because the magnetic flux does not enter the pan effectively. Therefore, it is necessary to stop the operation and switch the heating coil 1B, and the first coil 6 and the capacitor C_FiveSwitch SW so that is connected in series_FiveIs switched to 17j-17g connection. At this time, if an aluminum pan having a diameter of about 160 mm or less is placed, a normal inverter current flows and heating can be performed efficiently, and the operation continues. Thus, if it heats using the heating coil of the magnitude | size suitable for the pan diameter, even low resistance, nonmagnetic aluminum, and a copper pan can be heated efficiently. This method is also effective for iron and stainless steel.
[0026]
FIG. 6 shows a third embodiment of the present invention. A low-resistance nonmagnetic pan 20 such as aluminum or copper is heated by a heating coil 1C in which a first coil 10 (for example, 65T) and a second coil 11 (for example, 20T) are connected in series, such as iron or stainless steel. The high resistance or magnetic pot 20 uses the outer second coil 11. At this time, the input resistance Rin for heating the iron and stainless steel pan is expressed by the above formula (1), and the skin resistance Rs is expressed by the above formula (2). Therefore, the input resistance Rin has a fixed value if the inverter frequency is the same. When a high-resistance or magnetic pot coil made of iron or stainless steel is wound outwardly, the path length through which the current flows is increased (FIG. 6B), and the input resistance Rin is increased. Therefore, since the loss of only the heating coil 1C is constant, the efficiency is improved. Therefore, the outer second coil 11 is used for heating the iron and stainless steel.
[0027]
FIG. 7 shows a fourth embodiment of the present invention. A low resistance / nonmagnetic pan 20 such as aluminum or copper is heated by a heating coil 1D in which a first coil 12 (for example, 20T) and a second coil 13 (for example, 65T) are connected in series. The resistance or magnetic pan 20 uses the inner first coil 12. When heating a small-diameter pan 20 in iron or stainless steel, if the diameter of the heating coil 1D is too large compared to the pan 20, the magnetic flux does not effectively enter the pan 20 and cannot be efficiently heated. Therefore, when the small-diameter pan is heated by the first coil 12 wound inside, the magnetic flux is effectively linked to the pan 20 as shown in FIG.
[0028]
A fifth embodiment of the present invention will be described with reference to FIG. The pot 20 with a large diameter uses the second coil 13, and the pot 20 with a small diameter uses the first coil 12 wound inside. The pot 20 can be efficiently heated by changing the size of the heating coil.
[0029]
FIG. 8 shows a sixth embodiment of the present invention. A low-resistance nonmagnetic pan 20 such as aluminum or copper is a heating coil in which a first coil 14 (for example, 30T), a second coil 15 (for example, 20T), and a third coil 16 (for example, 35T) are connected in series. Heated with 1E, the iron or stainless steel high resistance or magnetic pot 20 uses the second coil 15 in the middle. Iron and stainless steel pans have lower thermal conductivity than aluminum. Therefore, in the pan 20 having a standard size, the path of the current flowing through the pan bottom should flow around the center and the outer periphery of the pan 20 (FIG. 8 (b)). Cooking performance is improved.
[0030]
FIG. 9 shows a seventh embodiment of the present invention. A low-resistance nonmagnetic pan such as aluminum or copper is a heating coil 1G in which a first coil 41 (for example, 10T), a second coil 42 (for example, 65T), and a third coil 43 (for example, 10T) are connected in series. The first coil 41 and the third coil 43 are connected in series and used in a high-resistance or magnetic pot of iron or stainless steel. A one-stage coil that can heat not only iron and stainless steel pans but also aluminum and copper pans has fewer coil turns when heating iron and stainless steel pans than when heating aluminum and copper pans. . Furthermore, in the pan, the current flows through the pan and heat is generated at the upper portion where the current is passed through the heating coil. Therefore, when heating an iron or stainless steel pan, if induction heating is performed using one coil, only that portion may generate heat and cause uneven heating. In particular, in the case of a hot cake or the like in which the object to be heated is less likely to move during heating, the upper surface of the coil through which an electric current is passed is burned, but otherwise, there is a problem that it becomes burnt. Therefore, by causing a current to flow through the inner first coil 41 and the outer third coil 43, the occurrence of uneven heating can be reduced.
[0031]
Next, the circuit configuration and operation of the induction heating cooker using the heating coil 1G according to the seventh embodiment will be described with reference to FIG. The material detection circuit 25 detects the current value of the inverter by CT, and sets the capacitor capacity so as to obtain an appropriate number of heating coil turns suitable for the material of the pan and an appropriate frequency suitable for the material of the pan.₆And SW₇It is switched by controlling.
[0032]
First, at the start of operation, the first to third coils 41, 42, 43 and the capacitor C₆, C₇Switch SW so that is connected in series₆, SW₇Are switched to 17a-17b and 17d-17e, respectively. At this time, when a pan made of aluminum, copper or the like is placed, a normal inverter current flows, and heating can be performed efficiently and operation continues. Other pans (iron, stainless steel) stop operating, the first and third coils 41 and 43 and the capacitor C₇Switch SW to make serial connection₆Switch 17a-17c and switch SW₇Switch to 17d-17f connection.
[0033]
FIG. 11 is a modification of FIG. 10 described above, and switches the capacitor capacity so that the appropriate number of heating coil turns suitable for the material of the pan and the appropriate frequency suitable for the material of the pan are obtained.₈This is the configuration realized in That is, when heating pans such as aluminum and copper, switch SW₈Switch 17a-17b, and when heating an iron or stainless steel pan, switch SW₈Is switched to 17a-17c. According to this configuration, the cost can be reduced as compared with the configuration of FIG.
[0034]
FIG. 12 shows an eighth embodiment of the present invention. Low resistance and non-magnetic pans such as aluminum and copper are heated by a heating coil 1H in which a first coil 51 (for example, 10T) and a second coil 52 (for example, 75T) are connected in series, and high resistance of iron and stainless steel. Alternatively, the magnetic pan is used by connecting the first coil 51 and the third coil 53 (for example, 10T) in series. As a result, the occurrence of uneven heating can be reduced as in the embodiment shown in FIG.
[0035]
Next, the circuit configuration and operation of the induction heating cooker using the heating coil 1H according to the eighth embodiment will be described with reference to FIG. The material detection circuit 25 detects the current value of the inverter by CT and sets the capacitor capacity so as to obtain an appropriate number of heating coil turns suitable for the material of the pan and an appropriate frequency suitable for the material of the pan.₉It is switched by controlling.
[0036]
First, at the start of operation, the first and second coils 51 and 52 and the capacitor C₈, C₉Switch SW so that is connected in series₉Is switched to 17a-17b connection. At this time, when a pan made of aluminum, copper or the like is placed, a normal inverter current flows, and heating can be performed efficiently and operation continues. Other pans (iron, stainless steel) stop operating, the first and third coils 51, 53 and the capacitor C₉Switch SW to make serial connection₉Switch to 17a-17c connection.
[0037]
With such a circuit configuration, only one switch is required, and the cost can be reduced. When a pan such as aluminum or copper is heated, the switch SW₉As a result of the switching, a voltage of about 5 kV is generated outside the second coil 52, but the insulation treatment can be easily performed outside the coil 52.
[0038]
In the eighth embodiment, a low resistance / nonmagnetic pan such as aluminum or copper is connected to a heating coil in which a first coil 51 (for example, 10T) and a second coil 52 (for example, 75T) are connected in series. Heated at 1H and used a high-resistance or magnetic pot of iron or stainless steel with a first coil and a third coil 53 (for example, 10T) connected in series. A non-magnetic pan is heated by a heating coil 1H in which a third coil 53 and a second coil 52 are connected in series, and a high-resistance or magnetic pan of iron or stainless steel is heated to the first coil 51 and the third coil. 53 may be used in series connection. This is because the width of the inner or outer coil used for heating the iron pan or the like is less than that of the second coil 52 and is about 1 cm, and the overall coil diameter is about 19 cm. This is because the influence of the heating unevenness is small without using either the inner or outer coil during heating. As a circuit configuration in this case, the connection arrangement positions of the first coil 51 and the third coil 53 may be reversed in FIG.
[0039]
FIG. 14 shows a ninth embodiment of the present invention. The heating coil 1F is molded in the aluminum and iron combined one-stage coil. In order to heat a low resistance, non-magnetic pan, since the skin resistance of the pan is small, it is necessary to increase the number of turns of the heating coil, which increases the heating coil voltage. Therefore, it is necessary to arrange the shield conductor 30 on the top plate 18 and connect it to the low voltage portion. Therefore, it is necessary to perform epoxy molding for preventing dielectric breakdown between the coil and the shield. 31 is a ferrite.
[0040]
15 to 17 show a tenth embodiment of the present invention. In the case of epoxy molding, in the case of a one-stage heating coil, it is possible to easily perform integral molding by forming a coil with an epoxy mold. As shown in FIG. 15, a litz wire 32 of a heating coil is directly wound around a mold 33a capable of releasing an epoxy such as aluminum, a litz wire 32 is drawn out halfway, a first coil is formed, and then a second coil is started to be wound. . This mold can be rotated around the central axis. Next, as shown in FIG. 16A, it is set in a mold 33b into which an epoxy resin can be poured, and epoxy casting is performed. At that time, the coil litz wire 32 is exposed on the upper surface of the coil, and there is a possibility that dielectric breakdown may occur with the shielding conductor of the top plate. Then, as shown in FIG. 17, it is again put into the mold 33c with the coil upper surface opened, and epoxy casting is performed. At this time, the ferrite 31 is bonded to the lower surface of the coil. If epoxy protrudes out of the mold 33b due to capillary action on the litz wire 32a of the first stage heating coil or the litz wire 32b at the beginning or end of winding, there is a risk of breakage when that portion moves. . Therefore, when the heat-shrinkable tube 34 is attached to the part and heated to harden the epoxy, the heat-shrinkable tube 34 is contracted to shrink the part, thereby preventing the epoxy from flowing out. At this time, the silicon 35 is immersed in the litz wires 32a and 32b (FIG. 16B), so that the outflow of epoxy can be prevented more reliably.
[0048]
【The invention's effect】
  As explained above,Claim1According to the described invention, the heating coil for induction heating the object to be heated is provided on the outside of the first coil, the second coil concentrically wound around the outside of the first coil, and the outside of the second coil. Since the first coil and the third coil are connected in series when the resistance is high and / or high magnetic permeability, the first coil and the third coil are connected in series. As compared with the case where a heated object having a high resistance or / and a high magnetic permeability is heated using this coil or the third coil, the occurrence of uneven heating can be reliably prevented.
[0051]
  Claim2According to the described invention,While molding each coil constituting the heating coil,Since the molding material is cast by covering the connecting terminal extraction part of each coil from the mold for molding with a heat-shrink tube in advance, there is no outflow of the molding material, and the connection terminal is extracted by solidifying the molding material. The breakage of the portion is prevented, the yield is improved, and the productivity can be improved.
[0052]
  Claim3According to the invention described above, since the Litz wire of the connection terminal extraction portion of each coil is covered with the heat shrinkable tube after being filled with silicon, the molding material is prevented from flowing out more reliably. The breakage of the terminal lead-out portion is eliminated, and the productivity can be further improved.
[Brief description of the drawings]
FIG. 1 is a sectional view of a heating coil portion in a first embodiment of an induction heating cooker according to the present invention.
FIG. 2 is a circuit diagram of the first embodiment.
FIG. 3 is a characteristic diagram showing a relationship between a space factor and heating efficiency in the first embodiment.
FIG. 4 is a sectional view of a heating coil portion in a second embodiment of the present invention.
FIG. 5 is a circuit diagram of the second embodiment.
FIG. 6 is a diagram showing a heating coil portion in a third embodiment of the present invention.
FIG. 7 is a diagram showing a heating coil portion in a fourth embodiment of the present invention.
FIG. 8 is a diagram showing a heating coil portion in a sixth embodiment of the present invention.
FIG. 9 is a sectional view of a heating coil portion according to a seventh embodiment of the present invention.
FIG. 10 is a circuit diagram of the seventh embodiment.
FIG. 11 is another circuit diagram of the seventh embodiment.
FIG. 12 is a sectional view of a heating coil portion according to an eighth embodiment of the present invention.
FIG. 13 is a circuit diagram of the eighth embodiment.
FIG. 14 is a sectional view of a heating coil portion according to a ninth embodiment of the present invention.
FIG. 15 is a diagram for explaining a process of forming a coil by winding a litz wire directly around a mold in the tenth embodiment of the present invention.
FIG. 16 is a diagram for explaining a process of epoxy molding a coil after molding in the tenth embodiment;
FIG. 17 is a diagram for explaining a process of performing epoxy casting again on the coil upper surface in the tenth embodiment;
[Explanation of symbols]
1A-1H Heating coil
2-16 coils
18 Top plate
20 pans (objects to be heated)
32 litz wire
33a-33c Mold
34 Heat Shrink Tube
35 silicon

Claims (3)

  A heating coil for inductively heating an object to be heated is a first coil, a second coil concentrically wound around the outside of the first coil, and a second coil concentrically wound around the outside of the second coil. When the object to be heated has a low resistance and a low magnetic permeability, the first coil, the second coil, and the third coil are used in series connection, and a high resistance or / and a high resistance are used. In the case of magnetic permeability, the induction heating cooker is configured to use the first coil and the third coil connected in series. It is characterized by molding each coil constituting the heating coil and casting a molding material by covering the connecting terminal extraction portion of each coil from a molding die with a heat shrink tube in advance. The induction heating cooker according to claim 1 . The induction heating cooker according to claim 2 , wherein the Litz wire of the connection terminal extraction portion of each coil is covered with the heat shrinkable tube after being filled with silicon.

Images