JP3939944B2

JP3939944B2 - Electromagnetic induction heating device

Info

Publication number: JP3939944B2
Application number: JP2001261786A
Authority: JP
Inventors: 長次長峯; 喜郎古石; 勝久大蔦; 博田中; 弘司菱山; 渉藤本; 勝雄八代; 隆司須永
Original assignee: Mitsubishi Electric Home Appliance Co Ltd; Mitsubishi Electric Corp
Current assignee: Mitsubishi Electric Home Appliance Co Ltd; Mitsubishi Electric Corp
Priority date: 2001-08-30
Filing date: 2001-08-30
Publication date: 2007-07-04
Anticipated expiration: 2021-08-30
Also published as: JP2003061816A

Description

【０００１】
【発明の属する技術分野】
この発明は、電磁誘導コイルにより磁界を発生させて容器の誘導損により容器を加熱して食品等を調理する電磁誘導加熱装置に関するものである。
【０００２】
【従来の技術】
電磁誘導加熱装置の使用例としては、電磁調理器や炊飯器等が一般に知られており、図１４は例えば特開平６−２５３９７４号公報等により類推される従来の炊飯器の概略構成を示す断面図、図１５は炊飯の各過程における内釜の温度変化を示す図、図１６は炊飯各過程の電磁誘導コイルの動作を示すタイミングチャートである。
【０００３】
図において、１は米、２は水、１１は炊飯器本体、１２は炊飯器本体１１内に配置され、被加熱物を入れる容器である内釜、１３は内釜１２の底部下方および側部外周に間隔を有して配線された電磁誘導コイル、１４は内釜１２の温度を検出する内釜用温度センサ、１５は内釜１２の側部に電極が接触、または接着された超音波振動子、１６は誘導加熱コイル１３に電力を供給する第１インバータ、１７は超音波振動子１５に電力を供給する第２インバータで、超音波振動子１５とともに、超音波発生手段を構成する。１８は炊飯器本体１１の側部に設けられ、炊飯器の運転・停止その他の炊飯メニューをユーザーが選択し、操作する操作パネルである。
【０００４】
次に、動作について説明する。
まず、洗米し、内釜１２内に適量の米１と水２とを共に入れ、炊飯器本体１１にセットする。つぎに、操作パネル１８内の炊飯スイッチ（図示せず）を入れる。炊飯器は、予熱過程に入り、６０℃を越えない程度に誘導加熱コイル１３の通電量を制御しながら米１と水２を加温する（図１５の１）。この際、誘導加熱コイル１３の電流量と温度センサ１４の関係から、大まかに炊飯量を検知する。さらに、この時、第２インバータ１７より超音波振動子１５に超音波振動に必要な電力が供給され、超音波振動子１５自体が振動する。これにより内釜内の米１と水２が微振動し、米の吸水が促進される。
【０００５】
炊飯開始から約１５分後、自動的に炊飯過程に入り（図１５の２）、誘導加熱コイル１３の通電を継続し、釜内温度が１００℃に達すると水が沸騰すると同時に、沸騰状態を継続させるように誘導加熱コイル１３の通電を制御する。炊飯過程に入って約１５分経過後、蒸らし過程（図１５の３）となる。蒸らし過程では釜内温度を約１００℃に維持するように誘導加熱コイル１３の通電を制御する。蒸らし開始から約１５分後、蒸らし過程の終了したことを操作パネル１８の表示と終了報知音（図示せず）によりユーザーに知らせる。
【０００６】
【発明が解決しようとする課題】
上記ような従来の電磁誘導加熱装置では、内釜１２に超音波振動子１５が取り付けられているため、超音波振動子１５の先端部電極が腐食する可能性があるという問題点があり、また、内釜１２の洗浄、洗米等の作業において超音波振動子１５が邪魔になるため、不便であるという問題点があった。
【０００７】
この発明は、上記のような課題を解決するためになされたもので、超音波振動子を使用せずに、内釜等の容器自身を騒音が出ないように超音波振動させることができ、容器内の米の吸水を促進させるようにしても容器の洗浄を容易に行うことができ、美味しい飯を炊飯できる電磁誘導加熱装置を提供することを目的とする。
【０００８】
【課題を解決するための手段】
この発明に係る電磁誘導加熱装置においては、電磁誘導コイルに発生する磁界により内釜を加熱する電磁誘導加熱装置であって、容器底面材料の音速と底面の大きさ・形状よりベッセル関数を用いて算出した容器固有の底面振動数または、その整数倍に合わせて設定した高周波電流の周波数に基づいてインバータ制御するものである。
【０００９】
また、前記算出された容器の固有振動の腹部分に電磁誘導コイルを配置したものである。
【００１０】
さらに、前記算出された容器の固有振動の正、逆どちらかの位相位置にのみ電磁誘導コイルを配置したものである。
【００１１】
また、前記算出された容器の固有振動の位相に対応して、電磁誘導コイルの巻線方向を合わせたものである。
【００１２】
また、容器と電磁誘導コイルの間に強磁性材料、常磁性材料、反磁性材料、およびそれらの含有物質からなる中間材により、容器に伝わる磁界を歪めて容器に発生する振動を増幅させる電磁誘導加熱装置において、中間材を容器振動の腹部分に設けたものである。
【００１３】
また、前記中間材を前記容器の固有振動の位相に応じて、正、逆どちらかの位相位置にのみ用いるものである。
【００１４】
また、容器側面に円盤状の突起を設け、この突起部分に電磁誘導コイルを配置して、前記周波数に基づいてインバータ制御するものである。
【００１５】
また、振動の周波数を２０ｋＨｚ以上の超音波域としたものである。
【００１６】
【発明の実施の形態】
実施の形態１．
図１はこの発明の実施の形態１に係わる電磁誘導加熱装置としての炊飯器を示す断面図、図２は内釜１１を炊飯器本体１０から外し、図１の上方向から見た平面図である。
図において、１は米、２は米１に吸収させる水、１１は炊飯器本体、１２は米１、水２を入れる炊飯容器の内釜、１３は内釜１２を加熱するための電磁誘導コイル、１４は内釜１２に接し、温度を検知するための内釜用温度センサ、２１は炊飯器本体１１に回動自在に設けられた蓋体、２２は蓋体２１に取り付けられた下蓋、２３は内釜１２上部の蓋部分の温度を検知する蓋用温度センサ、２４は電磁誘導コイル１３に高周波電流を供給するインバータである。２５は、操作パネル１８側に設けられた制御回路部で、内釜１２の底部に接触するように取り付けられた内釜用温度センサ１４と蓋用温度センサ２３とからの検出温度に基づいて炊飯状態を認識し、これに基づいてインバータ２４を制御する。
【００１７】
２６は例えば反磁性材の銅、銀、金、黒鉛、ビスマス何れかからなるリング状の磁束変調板で、内釜用温度センサ１４を中心として内釜１２と電磁誘導コイル１３との間に設けられたものである。電磁誘導コイル１３の周囲に発生する磁束を反磁性材の磁束変調板２６が乱すことによって、内釜１２底部の円盤部が振動し、円盤部の固有振動数と一致することによって増幅される。
【００１８】
電磁誘導コイル１３への高周波電流の周波数は、内釜１２底部の円盤部の振動から、以下のように設定されている。
２次元円盤釜底の縦波振動は、ベッセル関数Ｊｎ（ｉ,ｘ）を微分することによって求められる。モード数をｉ、固有値をｎ、無次元半径をｘとすると、ベッセル関数の1階微分値はつぎのようになる。
ｄｉ(x)＝・Ｊｎ（ｉ，ｘ）
ｘ＝ｎ・ｒ/ｒ₀
無次元半径ｘをパラメータとして、振動速度ｄｉ（ｘ）を各モード数ｉについて計算する。
共鳴周波数は、加振点ｒ＝ｒ_ｏで振動速度が最大になるところであり、振動速度の微分値が０となる無次元半径ｘより、固有値ｎｉが求められる。この時の固有値と共鳴周波数ｆ_０の関係は
つぎのようである。
ｆ_０＝ｎｉ・ｃ/２πｒ_０
例えば、モード数０では、振動速度が０になる無次元半径位置ｘを求めると、
ｘ＝1.87、5.33…となる。共鳴周波数ｆ_０は、以下のように計算で求められる。
（ここでは、内釜材の音速ｃを5330ｍ/ｓ、釜底半径を7ｃｍとした。）
ｆ_０＝ｎｉ・ｃ/２πｒ_０＝1.87×5330/（2π×0.07）＝23.5 ｋＨｚ
ｆ_０＝ｎｉ・ｃ/２πｒ_０＝5.33×5330/（2π×0.07）＝67.0 ｋＨｚ
この内釜は、23.5ｋＨｚで共振することがわかり、この場合の振動モードを図５に示す。
【００１９】
ここで、電磁誘導コイル１３の周波数を内釜１２の固有振動と無関係にした場合と上記計算結果に従い、固有振動数と一致させた場合、さらに振動の腹位置とコイル位置を一致させた場合の実験結果を述べる。電磁誘導コイル１３の直径を５ｃｍにして、内釜１２の振動数とは違う２２．０ｋＨｚの電流を流した場合の振動レベルは、-19.8ｄＢ（超音波音圧計（本多電子HUS-5）の出力を画像信号解析装置（RION SA74）を用いて測定）、上記計算結果に合わせた２３．５ｋＨｚの電流を流した場合は-7.3ｄＢ（同）、さらに、電磁誘導コイル１３の直径を７ｃｍにして、図５で示す振動の腹位置に一致させた場合には+2.3ｄＢ（同）であった。
【００２０】
次に実施形態１に係わる炊飯器の動作を図３、図４を用いて説明する。図３は、炊飯各過程の温度を模式的に示した温度変化のグラフ、図４は誘導加熱コイル１３の動作のタイミングチャートである。まず、内釜１２に米と適量の水を入れ、炊飯ＳＷ（図示せず）を入れて炊飯を開始する。すると、誘導加熱コイル１３に電流が流れ、内釜１２には電磁誘導により、熱と機械的な力が発生する。まず、誘電損失による発熱で炊飯する過程を説明する。誘導加熱コイル１３からの磁界では、電流量６０℃を越えない程度に加熱し、約15分間の予熱（吸水促進）過程（図３の１）を経て、炊飯過程（図３の２）に入る。誘導加熱コイル１３への通電によって内釜１２が発熱し続け、内釜１２内がほぼ１００℃に達したことを内釜用温度センサ１４，蓋用温度センサ２３で検知すると、誘導加熱コイル１３の電力供給を制御し、適宜加熱量を調整しながら炊飯を継続する。この時、加熱量が多過ぎても内釜内の水が沸騰するため、この蒸発潜熱によって内釜内の温度は、１００℃を維持する。沸騰を継続した後、内釜１２の水がなくなったことを内釜用温度センサ１４を通して検知すると、インバータ２４の制御を停止し、蒸らし過程（図３の３）に入る。蒸らし過程では、内釜１２の温度を１００℃に保持するため、誘導加熱コイル１３への通電を断続的に約１５分間継続する。
【００２１】
図６は、誘導加熱コイル１３に流れる電流およびこの電流によって発生する磁界、内釜１２内の渦電流によって発生する力の向きと大きさを各部分で計算によって求め、表示したものである。磁束変調板２６は、予熱および炊飯過程において、誘導加熱コイル１３から発生する磁界を乱し、内釜１２に対し図のような加振力を局部的に発生する。内釜１２の振動は、その中の水２を介して、米１に伝わる。本実験例では、超音波音圧計による測定で、磁束変調板２６を用いることにより+5.1ｄＢ（なし条件+2.3ｄＢ）まで増強することができた。このような振動と共に炊飯した飯（図９の超音波振動ありの飯）と、そうでない通常法（-19.8ｄＢ）で炊飯した飯（図９の対象実験の飯）の硬さと粘りを測定した一例を図９に示す。超音波振動中で炊飯した飯の硬さは、対照飯より小さく（柔らかく）、粘りが大きいことから、美味しく炊飯できたものと考えられる。
【００２２】
つぎに、洗米せずに炊飯できる無洗米の吸水率向上の実験例を図７、８を用いて述べる。室温吸水の図７を用いて説明する。通常の米の含水率は、15％程度である（本測定では、１４．５％）。洗米時に約５％の吸水があるため、炊飯開始時の含水率は約２０％である。これに対し、無洗米は、含水率１５％で炊飯を開始するため、通常の米と同一の炊飯条件（温度、維持時間）では、吸水不足状態であり、硬い飯になる。図８の予熱吸水でも同様で、洗米しないことによる吸水不足は修復できていない状態である。これに、超音波吸水を行うことで、かなり改善する効果が見られた。なお、吸水時間を長く設定することで、この無洗米を含め、インディカ米、玄米等吸水しにくい米の美味しさ向上が図れることは周知の通りである。
【００２３】
以上のように、実施の形態１においては、内釜１２の材料の音速と底面の大きさ・形状よりベッセル関数を用いて算出された固有振動数底面振動数または、その整数倍に合わせて設定した高周波電流の周波数に基づいてインバータ制御し、振動の腹位置に合わせて電磁誘導コイル１３と磁束変調板２６を設けてあるため、従来技術のような超音波振動子１５が不要になり、このため、内釜１２の着脱が容易で内釜１２の洗浄や内釜１２での洗米が容易にでき、しかも、美味しい飯ができるという効果が得られる。
【００２４】
実施の形態２．
図１０は本発明の実施の形態２に係わる電磁誘導加熱装置としての炊飯器の構成を模式的に示す断面図である。図において、１２は内釜、１３は電磁誘導コイル、１４は内釜用温度センサ、２８はコイルベース、３０は内釜１２底部の円盤振動の振幅を示したものである。
【００２５】
上記実施の形態１に記述した内釜１２の前記ベッセル関数による固有振動数の計算結果から、電磁誘導コイル１３の周波数を一致させ、その振動の腹部分に電磁誘導コイル１３を設けたため、電磁誘導コイル１３からの磁界による内釜１２の振動が共振周波数と合致し、容易に振動する構造となっている。
【００２６】
以上のように、実施の形態２においては、内釜１２の振動振幅に一致するよう電磁誘導コイル１３を配置しているため、内釜１２の振動が起こりやすい効果があり、内釜１２の着脱が容易で内釜１２の洗浄や内釜１２での洗米が容易にでき、しかも、美味しい飯ができるという効果が得られる。
【００２７】
実施の形態３．
図１１は、本発明の実施の形態３に係わる電磁誘導加熱装置としての炊飯器の構成を模式的に示す断面図である。なお、実施の形態２と同一または相当部分には同じ符号を付し説明を省略する。図において、３０は内釜１２底部の円盤振動の振幅を示したものであり、振幅の方向を＋と―で区別したものである。
【００２８】
上記実施の形態１に記述した前記ベッセル関数による内釜１２の固有振動数の計算結果から、電磁誘導コイル１３の周波数を一致させ、その振動の腹部分で、図に示すように振動の極性が一致するよう電磁誘導コイル１３ａを右巻き、１３ｂを左巻きとして配置している。１３ａの位置と１３ｂの位置では、常に振動の位相が逆となるため、電流の方向を逆にすることで、内釜１２に働くそれぞれの力は、常に逆位相位置で逆方向となるように働く。このため、１３ａ、１３ｂから受ける力が増幅し合い、より強い振動を得ることができる。
【００２９】
以上のように、実施の形態３においては、内釜１２の振動振幅の極性に一致するよう電磁誘導コイル１３を配置しているため、内釜１２の振動が起こりやすい効果があり、内釜１２の着脱が容易で内釜１２の洗浄や内釜１２での洗米が容易にでき、しかも、美味しい飯ができるという効果が得られる。
【００３０】
実施の形態４．
図１２は、本発明の実施の形態４に係わる電磁誘導加熱装置としての炊飯器の構成を模式的に示す断面図である。なお、実施の形態２と同一または相当部分には同じ符号を付し説明を省略する。図において、３０は内釜１２底部の円盤振動の振幅を示したものであり、振幅の方向を＋と―で区別したものである。２６は例えば強磁性材料（鉄、コバルト、ニッケル）、常磁性材料（たとえばアルミ、クロム、チタン）、反磁性材料（たとえば黒鉛、ビスマス、金、銀、銅）およびそれらの含有物質からなるリング状の中間材である磁束変調板で、内釜用温度センサを中心として内釜１２と電磁誘導コイル１３に流れる高周波電流に応じて発生する磁界を歪め、内釜１２の振動を増幅するように作用する。この振動は、電磁誘導コイル１３の周囲に発生する磁束を磁束変調板が乱すことによっておこるものである。
【００３１】
前記ベッセル関数による内釜１２の固有振動数の計算結果から、電磁誘導コイル１３の周波数を一致させ、その振動の腹部分で、図に示すように振動の極性が一致するよう磁束変調板２６を振動振幅が＋位置（２６ａ）または、―位置（２６ｂ）に設けたため、電磁誘導コイル１３からの磁界による内釜１２の振動が共振周波数と合致し、極性も一致するため容易に振動する構造となっている。
【００３２】
以上のように、実施の形態４においては、内釜１２の振動振幅の極性に一致するよう磁束変調板２６を配置しているため、内釜１２の振動が起こりやすい効果があり、内釜１２の着脱が容易で内釜１２の洗浄や内釜１２での洗米が容易にでき、しかも、美味しい飯ができるという効果が得られる。
【００３３】
実施の形態５．
図１３は、本発明の実施の形態５に係わる電磁誘導加熱装置としての炊飯器の構成を模式的に示す断面図である。なお、実施の形態２と同一または相当部分には同じ符号を付し説明を省略する。図において、１２１は内釜１２の側面に設けられた円形の突起部、１３１はこれに対応する加振用の電磁誘導コイルである。
【００３４】
上記実施の形態１に記述した前記ベッセル関数により、内釜１２の突起部１２１の半径から突起部分の固有振動数を計算により求め、対応する電磁誘導コイル１３１の周波数をこの周波数に一致させ、超音波振動を起こさせる構造となっている。
【００３５】
以上のように、実施の形態５においては、内釜１２の側面に超音波振動を起こさせる専用の電磁誘導コイル１３１を設けたため、通常の加熱のための電磁誘導コイルの周波数変更、変調板２６が不要となる効果があり、内釜１２の着脱が容易で内釜１２の洗浄や内釜１２での洗米が容易にでき、しかも、美味しい飯ができるという効果が得られる。
【００３６】
このように、本実施の形態では、内釜１２の固有振動数の整数倍と電磁誘導コイル１３の駆動周波数の整数倍（どちらも1を含む）が一致するよう調整されているため、小さな加振力でも大きな振動が発生させられるという効果がある。
なお、実施の形態１〜５は、炊飯器を示したが、内釜を容器として他の食品の電磁誘導加熱に使用してもよい。
【００３７】
【発明の効果】
この発明は、容器底面材料の音速と底面の大きさ形状よりベッセル関数を用いて算出される容器固有の底面振動数または、その整数倍に合わせて設定した高周波電流の周波数に基づいてインバータ制御するようにしたので、従来技術のような超音波振動子が不要になり、内釜の着脱が容易にでき、内釜を振動させて美味しく炊飯することができる効果がある。
【００３８】
また、前記算出された容器の固有振動の腹部分に電磁誘導コイルを配置するため、振動しやすい腹部分での加振ができ、効率良く振動させることができ、美味しく炊飯することができる効果がある。
【００３９】
さらに、前記算出された容器の固有振動の正、逆どちらかの位相位置にのみ電磁誘導コイルを配置したため、加振力が振動の腹に伝わり、しかも振動位相の違いによる打消し合いがなく、効率良く振動させることができ、美味しく炊飯することができる効果がある。
【００４０】
また、前記算出された容器の固有振動の位相に対応して、電磁誘導コイルの巻線方向を合わせているため、振動位相の違いによる打消し合いがなく、効率良く振動させることができ、美味しく炊飯することができる効果がある。
【００４１】
また、容器と電磁誘導コイルの間に容器に伝わる磁界を歪めて容器に発生する振動を増幅させる中間材を容器振動の腹部分に設けたため、振動しやすい腹部分での加振ができ、効率良く振動させることができ、美味しく炊飯することができる効果がある。
【００４２】
また、容器と電磁誘導コイルの間に設ける中間材を容器振動の腹部分の位相に応じて、正、逆どちらかの位相位置にのみ用いるため、効率良く振動させることができ、美味しく炊飯することができる効果がある。
【００４３】
また、容器側面に円盤状の突起を設け、この突起部分に電磁誘導コイルを配置して、前記周波数に基づいてインバータ制御するため、通常の加熱のための電磁誘導コイルの周波数変更、中間材が不要となる効果があり、美味しく炊飯することができる効果がある。
【００４４】
また、振動の周波数を２０ｋＨｚを超える超音波領域としたので、騒音発生を防止することができる。
【図面の簡単な説明】
【図１】この発明の実施の形態１に係わる電磁誘導加熱装置の構成を示す断面図である。
【図２】図１の蓋体および内釜を外した状態の平面図である。
【図３】電磁誘導加熱装置の炊飯の各過程における内釜の温度変化を示す図である。
【図４】電磁誘導加熱装置の炊飯各過程の電磁誘導コイルの動作を示すタイミングチャートである。
【図５】内釜底部分の振動モード解析した一例である。
【図６】内釜の各部分に発生する力の強さと方向を表示した図である。
【図７】常温吸水した時の米の含水率の変化を示した図である。
【図８】電磁誘導加熱装置による予熱吸水した時の米の含水率の変化を示した図である。
【図９】振動と共に炊飯した飯と、通常法で炊飯した飯の硬さと粘りを測定した一例を示す図である。
【図１０】この発明の実施の形態２に係わる電磁誘導加熱装置の構成を模式的に示す断面図である。
【図１１】この発明の実施の形態３に係わる電磁誘導加熱装置の構成を模式的に示す断面図である。
【図１２】この発明の実施の形態４に係わる電磁誘導加熱装置の構成を模式的に示す断面図である。
【図１３】この発明の実施の形態５に係わる電磁誘導加熱装置の構成を模式的に示す断面図である。
【図１４】従来例として引用した電磁誘導加熱装置を示す断面図である。
【図１５】電磁誘導加熱装置の炊飯の各過程における内釜の温度変化を示す図である。
【図１６】電磁誘導加熱装置の炊飯各過程の電磁誘導コイルの動作を示すタイミングチャートである。
【符号の説明】
１米、２水、１１炊飯器本体、１２内釜、１３誘導加熱コイル、１２１〜１２４発振コイル、１４内釜用温度センサ、１５超音波振動子、１６第１インバータ、１７第２インバータ、１８表示板および操作パネル、２６磁束変調板。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an electromagnetic induction heating device that cooks food by heating a container with an induction loss of the container by generating a magnetic field with an electromagnetic induction coil.
[0002]
[Prior art]
As an example of use of an electromagnetic induction heating device, an electromagnetic cooker, a rice cooker, or the like is generally known, and FIG. 14 is a cross-sectional view showing a schematic configuration of a conventional rice cooker estimated by, for example, Japanese Patent Laid-Open No. 6-253974. FIG. 15 is a diagram showing the temperature change of the inner pot in each process of cooking rice, and FIG. 16 is a timing chart showing the operation of the electromagnetic induction coil in each process of cooking rice.
[0003]
In the figure, 1 is rice, 2 is water, 11 is a rice cooker body, 12 is an inner pot which is placed in the rice cooker body 11 and puts an object to be heated, and 13 is a bottom lower part and a side part of the inner pot 12. Electromagnetic induction coils wired at intervals on the outer periphery, 14 is a temperature sensor for the inner hook that detects the temperature of the inner hook 12, and 15 is an ultrasonic vibration in which an electrode is in contact with or adhered to the side of the inner hook 12. A child, 16 is a first inverter that supplies power to the induction heating coil 13, and 17 is a second inverter that supplies power to the ultrasonic transducer 15, and together with the ultrasonic transducer 15 constitute ultrasonic generating means. Reference numeral 18 denotes an operation panel that is provided on the side of the rice cooker body 11 and that allows the user to select and operate the rice cooker operation / stop and other rice cooking menus.
[0004]
Next, the operation will be described.
First, the rice is washed, and an appropriate amount of rice 1 and water 2 are put together in the inner pot 12 and set in the rice cooker body 11. Next, a rice cooking switch (not shown) in the operation panel 18 is turned on. The rice cooker enters the preheating process and heats the rice 1 and water 2 while controlling the energization amount of the induction heating coil 13 so as not to exceed 60 ° C. (1 in FIG. 15 ). At this time, the amount of cooked rice is roughly detected from the relationship between the current amount of the induction heating coil 13 and the temperature sensor 14. Further, at this time, electric power necessary for ultrasonic vibration is supplied from the second inverter 17 to the ultrasonic vibrator 15, and the ultrasonic vibrator 15 itself vibrates. Thereby, the rice 1 and the water 2 in the inner pot vibrate slightly, and the water absorption of the rice is promoted.
[0005]
About 15 minutes after the start of cooking, the rice cooking process automatically starts (2 in FIG. 15 ). The induction heating coil 13 continues to be energized. When the temperature in the kettle reaches 100 ° C., the water boils at the same time. The energization of the induction heating coil 13 is controlled so as to be continued. After about 15 minutes have passed since the cooking process, the steaming process (3 in FIG. 15 ) is started. In the steaming process, the energization of the induction heating coil 13 is controlled so as to maintain the temperature in the kettle at about 100 ° C. About 15 minutes after the start of steaming, the user is informed by the display on the operation panel 18 and the end notification sound (not shown) that the steaming process has ended.
[0006]
[Problems to be solved by the invention]
In the conventional electromagnetic induction heating apparatus as described above, since the ultrasonic vibrator 15 is attached to the inner pot 12, there is a problem that the tip electrode of the ultrasonic vibrator 15 may corrode. The ultrasonic vibrator 15 becomes an obstacle in operations such as cleaning the inner pot 12 and washing the rice, which is inconvenient.
[0007]
The present invention was made to solve the above-described problems, and without using an ultrasonic vibrator, the container itself such as the inner hook can be ultrasonically vibrated so as not to generate noise. It is an object of the present invention to provide an electromagnetic induction heating apparatus that can easily clean a container even when promoting water absorption of rice in the container and can cook delicious rice.
[0008]
[Means for Solving the Problems]
The electromagnetic induction heating device according to the present invention is an electromagnetic induction heating device that heats the inner pot with a magnetic field generated in an electromagnetic induction coil, and uses a Bessel function from the sound velocity of the container bottom surface material and the size and shape of the bottom surface. The inverter is controlled based on the calculated bottom frequency of the container or the frequency of the high-frequency current set in accordance with an integral multiple thereof.
[0009]
Also, it is obtained by placing the electromagnetic induction coil to the natural vibration antinode portion of the pre-hexane out the container.
[0010]
Moreover, positive intrinsic vibration before hexane issued the container is obtained by placing the electromagnetic induction coil only in the opposite one of the phase position.
[0011]
Further, in response to specific vibration phase prior hexane issued the container, it is a combination of the winding direction of the electromagnetic induction coil.
[0012]
Also, electromagnetic induction that amplifies the vibration generated in the container by distorting the magnetic field transmitted to the container by using an intermediate material composed of a ferromagnetic material, paramagnetic material, diamagnetic material, and those containing substances between the container and the electromagnetic induction coil. In the heating device, the intermediate material is provided on the belly portion of the container vibration.
[0013]
Further, the during material depending on the intrinsic vibration of the phase of the container, positive, those who are for viewing inverse either phase position Nino.
[0014]
Further, a disk-shaped projection provided on the sides of the container, place the electromagnetic induction coil to the protruding portion is for inverter control based on the previous distichum wavenumber.
[0015]
Further, the vibration frequency is an ultrasonic range of 20 kHz or more.
[0016]
DETAILED DESCRIPTION OF THE INVENTION
Embodiment 1 FIG.
1 is a sectional view showing a rice cooker as an electromagnetic induction heating apparatus according to Embodiment 1 of the present invention, and FIG. 2 is a plan view of the rice cooker 11 removed from the rice cooker body 10 and viewed from above in FIG. is there.
In the figure, 1 is rice, 2 is water to be absorbed by rice 1, 11 is a rice cooker body, 12 is an inner pot of a rice container containing rice 1 and water 2, and 13 is an electromagnetic induction coil for heating the inner pot 12 , 14 is a temperature sensor for the inner pot for detecting the temperature in contact with the inner pot 12, 21 is a lid provided rotatably on the rice cooker body 11, 22 is a lower lid attached to the lid 21, Reference numeral 23 denotes a lid temperature sensor for detecting the temperature of the lid portion at the top of the inner hook 12, and 24 denotes an inverter for supplying a high frequency current to the electromagnetic induction coil 13. 25 is a control circuit section provided on the operation panel 18 side, based on the detected temperature from the temperature sensor 14 for the inner pot and the temperature sensor 23 for the lid attached so as to be in contact with the bottom of the inner pot 12. A state is recognized and the inverter 24 is controlled based on this.
[0017]
26 is a ring-shaped magnetic flux modulation plate made of diamagnetic material such as copper, silver, gold, graphite, or bismuth, and is provided between the inner pot 12 and the electromagnetic induction coil 13 with the inner pot temperature sensor 14 as a center. It is what was done. The magnetic flux generated around the electromagnetic induction coil 13 is disturbed by the magnetic flux modulation plate 26 made of a diamagnetic material, so that the disk part at the bottom of the inner hook 12 vibrates and is amplified by matching the natural frequency of the disk part.
[0018]
The frequency of the high-frequency current to the electromagnetic induction coil 13, the vibration of the circular plate portion of the inner hook 12 bottom, are set as follows.
Longitudinal wave vibration at the bottom of the two-dimensional disk pot is obtained by differentiating the Bessel function Jn (i, x). If the number of modes is i, the eigenvalue is n, and the dimensionless radius is x, the first-order differential value of the Bessel function is as follows.
di (x) =. Jn (i, x)
x = n · r / r ₀
The vibration speed di (x) is calculated for each mode number i using the dimensionless radius x as a parameter.
Resonant frequency, the vibration velocity at the excitation point r = r _o is the place where is maximum, from the dimensionless radius x of the differential value of the vibration velocity becomes 0, eigenvalues ni are obtained. Relationship eigenvalues and the resonance frequency f ₀ at this time is as follows.
f ₀ = ni · c / 2πr ₀
For example, when the number of modes is 0 and the dimensionless radial position x at which the vibration speed is 0 is obtained,
x = 1.87, 5.33. Resonance frequency f ₀ is determined by calculation as follows.
(Here, the sound speed c of the inner hook material is 5330 m / s and the bottom radius is 7 cm.)
f ₀ = ni · c / 2πr ₀ = 1.87 × 5330 / (2π × 0.07) = 23.5 kHz
f ₀ = ni · c / 2πr ₀ = 5.33 × 5330 / (2π × 0.07) = 67.0 kHz
This inner hook is found to resonate at 23.5 kHz, and the vibration mode in this case is shown in FIG.
[0019]
Here, when the frequency of the electromagnetic induction coil 13 is irrelevant to the natural vibration of the inner hook 12 and according to the above calculation result, when the frequency is matched with the natural frequency, when the antinode position of the vibration is matched with the coil position. The experimental results are described. When the electromagnetic induction coil 13 has a diameter of 5 cm and a current of 22.0 kHz, which is different from the frequency of the inner pot 12, is passed, the vibration level is -19.8 dB (ultrasonic sound pressure gauge (Honda Electronics HUS-5) Output is measured using an image signal analyzer (RION SA74), -7.3 dB (same as above) when a current of 23.5 kHz is applied to the above calculation result, and the diameter of the electromagnetic induction coil 13 is 7 cm. Thus, when matched with the vibration antinode shown in FIG. 5, it was +2.3 dB (same as above).
[0020]
Next, operation | movement of the rice cooker concerning Embodiment 1 is demonstrated using FIG. 3, FIG. Figure 3 is a graph of the temperature change the temperature of the cooking the process shown schematically, FIG. 4 is a timing chart of the operation of the induction heating coil 13. First, rice and an appropriate amount of water are put into the inner pot 12, rice cooking SW (not shown) is put, and rice cooking is started. Then, a current flows through the induction heating coil 13, and heat and mechanical force are generated in the inner hook 12 by electromagnetic induction. First, the process of cooking rice with heat generated by dielectric loss will be described. In the magnetic field from the induction heating coil 13, the heating is performed so that the current amount does not exceed 60 ° C., and after the preheating (water absorption promotion) process (1 in FIG. 3), the rice cooking process (2 in FIG. 3) is started. . When the induction heating coil 13 is energized, the inner pot 12 continues to generate heat, and when it is detected by the inner pot temperature sensor 14 and the lid temperature sensor 23 that the inner pot 12 has reached approximately 100 ° C., the induction heating coil 13 Rice cooking is continued while controlling the power supply and adjusting the heating amount as appropriate. At this time, since the water in the inner pot boils even if the heating amount is excessive, the temperature in the inner pot is maintained at 100 ° C. by the latent heat of evaporation. After the boiling is continued, if it is detected through the temperature sensor 14 for the inner pot 12 that the water in the inner pot 12 has run out, the control of the inverter 24 is stopped and the steaming process (3 in FIG. 3) is started. In the steaming process, in order to keep the temperature of the inner pot 12 at 100 ° C., the energization of the induction heating coil 13 is intermittently continued for about 15 minutes.
[0021]
FIG. 6 shows the current flowing in the induction heating coil 13, the magnetic field generated by this current, and the direction and magnitude of the force generated by the eddy current in the inner hook 12 by calculation for each part and displayed. Flux modulation plate 26, in the preheating and cooking process, disturbs the magnetic field generated from the induction heating coil 13, it generates a vibration force as Shi pairs inner hook 12 FIG locally. The vibration of the inner pot 12 is transmitted to the rice 1 through the water 2 therein. In the present experimental example, it was possible to increase to +5.1 dB (none condition +2.3 dB) by using the magnetic flux modulation plate 26 by measurement with an ultrasonic sound pressure meter. The hardness and stickiness of the rice cooked with such vibration ( the rice with ultrasonic vibration in FIG. 9) and the rice cooked by the normal method (-19.8 dB) which is not so (the rice of the target experiment in FIG. 9) were measured. An example is shown in FIG . Hardness of rice were cooking in an ultrasonic vibration is smaller than the control rice (soft), since the viscosity is high, presumably made delicious rice.
[0022]
Next, an experimental example of improving the water absorption rate of non-washed rice that can be cooked without washing is described with reference to FIGS. This will be described with reference to FIG. The water content of normal rice is about 15% (14.5% in this measurement). Since there is about 5% water absorption at the time of washing the rice, the water content at the start of cooking is about 20%. On the other hand, unwashed rice starts cooking with a moisture content of 15%, so under the same rice cooking conditions (temperature, maintenance time) as normal rice, it is in a state of insufficient water absorption and becomes hard rice. The same applies to the preheated water absorption in FIG. 8, and the lack of water absorption due to not washing the rice is not repaired. In this, the effect of improving considerably by ultrasonic water absorption was seen. As is well known, by setting the water absorption time long, it is possible to improve the taste of rice that is difficult to absorb water, such as indica rice and brown rice, including this unwashed rice.
[0023]
As described above, in the first embodiment, the natural frequency is calculated using the Bessel function based on the sound speed of the material of the inner hook 12 and the size and shape of the bottom surface, or is set in accordance with an integer multiple thereof. Inverter control is performed based on the frequency of the high-frequency current, and the electromagnetic induction coil 13 and the magnetic flux modulation plate 26 are provided in accordance with the antinode position of the vibration. Therefore, it is easy to attach and detach the inner pot 12, the inner pot 12 can be easily washed and the rice can be washed in the inner pot 12, and delicious rice can be obtained.
[0024]
Embodiment 2. FIG.
FIG. 10: is sectional drawing which shows typically the structure of the rice cooker as an electromagnetic induction heating apparatus concerning Embodiment 2 of this invention. In the figure, 12 is an inner hook, 13 is an electromagnetic induction coil, 14 is an inner hook temperature sensor, 28 is a coil base, and 30 is an amplitude of disk vibration at the bottom of the inner hook 12.
[0025]
The frequency of the electromagnetic induction coil 13 is matched from the calculation result of the natural frequency by the Bessel function of the inner pot 12 described in the first embodiment, and the electromagnetic induction coil 13 is provided at the antinode portion of the vibration. The structure of the inner hook 12 caused by the magnetic field from the coil 13 matches the resonance frequency and easily vibrates.
[0026]
As described above, in the form state 2 of implementation, since the arrangement of electromagnetic induction coil 13 to match the vibration amplitude of the inner hook 12, there is prone effect vibration of the bobbin 12, the bobbin 12 Can be easily attached and detached, the inner pot 12 can be easily washed and the inner pot 12 can be washed with rice, and delicious rice can be produced.
[0027]
Embodiment 3 FIG.
FIG. 11: is sectional drawing which shows typically the structure of the rice cooker as an electromagnetic induction heating apparatus concerning Embodiment 3 of this invention. In addition, the same code | symbol is attached | subjected to the part which is the same as that of Embodiment 2, or an equivalent, and description is abbreviate | omitted. In the figure, 30 indicates the amplitude of the disc vibration at the bottom of the inner hook 12 and the direction of the amplitude is distinguished by + and-.
[0028]
From the calculation result of the natural frequency of the inner hook 12 by the Bessel function described in the first embodiment, the frequency of the electromagnetic induction coil 13 is matched and the vibration polarity is shown at the antinode portion of the vibration as shown in the figure. The electromagnetic induction coil 13a is arranged in a right-handed manner and 13b is arranged in a left-handed manner so as to match. Since the vibration phase is always reversed at the positions 13a and 13b, by reversing the direction of the current, each force acting on the inner hook 12 is always reversed at the opposite phase position. work. For this reason, the forces received from 13a and 13b are amplified and stronger vibrations can be obtained.
[0029]
As described above, in the form state 3 of implementation, since the arrangement of electromagnetic induction coil 13 to match the polarity of the oscillation amplitude of the inner hook 12, there is prone effect vibration of the bobbin 12, the inner The hook 12 can be easily attached and detached, the inner pot 12 can be easily washed and the rice in the inner pot 12 can be washed easily, and delicious rice can be produced.
[0030]
Embodiment 4 FIG.
FIG. 12: is sectional drawing which shows typically the structure of the rice cooker as an electromagnetic induction heating apparatus concerning Embodiment 4 of this invention. In addition, the same code | symbol is attached | subjected to the part which is the same as that of Embodiment 2, or an equivalent, and description is abbreviate | omitted. In the figure, 30 indicates the amplitude of the disc vibration at the bottom of the inner hook 12 and the direction of the amplitude is distinguished by + and-. 26 is a ring shape made of, for example, a ferromagnetic material (iron, cobalt, nickel), a paramagnetic material (for example, aluminum, chromium, titanium), a diamagnetic material (for example, graphite, bismuth, gold, silver, copper) and their containing substances. The magnetic flux modulation plate, which is an intermediate material, distorts the magnetic field generated according to the high-frequency current flowing through the inner hook 12 and the electromagnetic induction coil 13 around the temperature sensor for the inner hook, and amplifies the vibration of the inner hook 12. To do. This vibration is caused by the magnetic flux modulation plate disturbing the magnetic flux generated around the electromagnetic induction coil 13.
[0031]
From the calculation result of the natural frequency of the inner hook 12 by the Bessel function, the frequency of the electromagnetic induction coil 13 is matched, and the magnetic flux modulation plate 26 is adjusted so that the vibration polarity is matched at the antinode portion of the vibration as shown in the figure. vibration amplitude + position (26a) or, - since provided to position (26b), consistent with the resonance frequency vibrations of the bobbin 12 by the magnetic field from an electromagnetic induction coil 13, to easily vibrate for polarity matching structure It has become.
[0032]
As described above, in the form state 4 of implementation, since the arranged magnetic flux modulation plate 26 to match the polarity of the oscillation amplitude of the inner hook 12, there is prone effect vibration of the bobbin 12, the inner The hook 12 can be easily attached and detached, the inner pot 12 can be easily washed and the rice in the inner pot 12 can be washed easily, and delicious rice can be produced.
[0033]
Embodiment 5 FIG.
FIG. 13: is sectional drawing which shows typically the structure of the rice cooker as an electromagnetic induction heating apparatus concerning Embodiment 5 of this invention. In addition, the same code | symbol is attached | subjected to the part which is the same as that of Embodiment 2, or an equivalent, and description is abbreviate | omitted. In the figure, 121 is a circular protrusion provided on the side surface of the inner hook 12, and 131 is an electromagnetic induction coil for vibration corresponding thereto.
[0034]
Using the Bessel function described in the first embodiment, the natural frequency of the protruding portion is calculated from the radius of the protruding portion 121 of the inner hook 12, and the frequency of the corresponding electromagnetic induction coil 131 is matched with this frequency. It has a structure that causes sonic vibration.
[0035]
As described above, in the form state 5 of implementation, due to the special electromagnetic induction coil 131 to cause ultrasonic vibration to the side surface of the inner hook 12 provided, the frequency change of the electromagnetic induction coil for conventional heating, the modulation There is an effect that the plate 26 is not required, the inner hook 12 can be easily attached and detached, the inner pot 12 can be easily washed, the rice can be washed in the inner pot 12, and a delicious rice can be obtained.
[0036]
As described above, in this embodiment, since an integral multiple of the natural frequency of the inner hook 12 and an integral multiple of the drive frequency of the electromagnetic induction coil 13 (both include 1) are adjusted, a small addition There is an effect that a large vibration can be generated even by a vibration force.
In addition, although Embodiment 1-5 showed the rice cooker, you may use it for the electromagnetic induction heating of another foodstuff by using an inner pot as a container.
[0037]
【The invention's effect】
This invention performs inverter control based on the vessel-specific bottom frequency calculated from the sound velocity of the vessel bottom surface material and the size of the bottom surface using a Bessel function, or the frequency of a high-frequency current set in accordance with an integer multiple thereof. Since it did in this way, the ultrasonic vibrator like the prior art becomes unnecessary, and the inner pot can be easily attached and detached, and there is an effect that the inner pot is vibrated and can be cooked deliciously.
[0038]
Also, before to place the electromagnetic induction coil on the ventral part of the inherent vibration of hexane issued the container, it is vibrated in the vibration easily belly portion, it can be efficiently vibrated, to delicious rice There is an effect that can.
[0039]
Furthermore, before positive intrinsic vibration of hexane issued the container, because of arranging the electromagnetic induction coil only in the opposite one of the phase position, the excitation force is transmitted to antinodes, moreover cancellation due to the difference of the vibration phase There is no match, it can vibrate efficiently, and there is an effect that can be cooked deliciously.
[0040]
Further, in response to specific vibration phase prior hexane issued the container, since the combined winding direction of the electromagnetic induction coil, no cancel due to the difference of the oscillation phase, thereby efficiently vibrate Can be cooked deliciously.
[0041]
In addition, an intermediate material that distorts the magnetic field transmitted to the container and amplifies the vibration generated in the container between the container and the electromagnetic induction coil is provided in the container's vibration anti-vibration part. It can be vibrated well and has the effect of cooking deliciously.
[0042]
Also, depending on the phase of the abdominal portion of the container oscillates between material in provided between the container and the electromagnetic induction coil, positive, since there for seen opposite either phase position Nino, can be efficiently vibrate, delicious There is an effect that can cook rice.
[0043]
Further, a disk-shaped projection provided on the sides of the container, place the electromagnetic induction coil to the protrusion, prior to inverter control based on distichum wavenumber, frequency change of the electromagnetic induction coil for conventional heating, the intermediate There is an effect that the material becomes unnecessary, and there is an effect that the rice can be cooked deliciously.
[0044]
Further, since the vibration frequency is in the ultrasonic region exceeding 20 kHz, noise generation can be prevented.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view showing a configuration of an electromagnetic induction heating device according to Embodiment 1 of the present invention.
FIG. 2 is a plan view showing a state in which a lid body and an inner hook in FIG. 1 are removed.
FIG. 3 is a diagram showing a temperature change of the inner pot in each process of rice cooking by the electromagnetic induction heating device.
FIG. 4 is a timing chart showing the operation of the electromagnetic induction coil during each rice cooking process of the electromagnetic induction heating device.
FIG. 5 is an example of a vibration mode analysis of an inner pot bottom portion.
FIG. 6 is a diagram showing the strength and direction of the force generated in each part of the inner hook.
FIG. 7 is a graph showing changes in the moisture content of rice when water is absorbed at room temperature.
FIG. 8 is a graph showing changes in the moisture content of rice when preheated water is absorbed by an electromagnetic induction heating device.
FIG. 9 is a diagram showing an example of measuring the hardness and stickiness of cooked rice with vibration and cooked rice by a normal method.
FIG. 10 is a cross-sectional view schematically showing a configuration of an electromagnetic induction heating device according to Embodiment 2 of the present invention.
FIG. 11 is a cross-sectional view schematically showing a configuration of an electromagnetic induction heating device according to Embodiment 3 of the present invention.
FIG. 12 is a cross-sectional view schematically showing a configuration of an electromagnetic induction heating device according to Embodiment 4 of the present invention.
FIG. 13 is a cross-sectional view schematically showing a configuration of an electromagnetic induction heating device according to Embodiment 5 of the present invention.
FIG. 14 is a cross-sectional view showing an electromagnetic induction heating device cited as a conventional example.
FIG. 15 is a diagram showing a temperature change of the inner pot in each process of rice cooking by the electromagnetic induction heating device.
FIG. 16 is a timing chart showing the operation of the electromagnetic induction coil in each rice cooking process of the electromagnetic induction heating device.
[Explanation of symbols]
1 rice, 2 water, 11 rice cooker body, 12 inner pot, 13 induction heating coil, 121-124 oscillation coil, 14 inner pot temperature sensor, 15 ultrasonic vibrator, 16 first inverter, 17 second inverter, 18 Display board and operation panel, 26 magnetic flux modulation board.

Claims

In an electromagnetic induction heating apparatus provided with a container for storing an object to be heated, an electromagnetic induction coil for electromagnetically inducing the container, an inverter for supplying a high-frequency current flowing through the electromagnetic induction coil, and a control means for controlling the inverter , the container of sound velocity and bottom surfaces of the material size and shape than the number vessel-specific bottom vibration calculated using the Bessel function or, to inverter control based on the frequency of the high frequency current which is set in accordance with an integral multiple thereof An electromagnetic induction heating device.

Electromagnetic induction heating device according to claim 1, wherein placing an electromagnetic induction coil to the natural vibration antinode portion of the pre-hexane out the container.

Specific vibration positive, the electromagnetic induction heating device according to claim 1 Symbol placement arranged an electromagnetic induction coil only in the opposite one of the phase position of the front hexane issued the container.

Before corresponding to specific vibration phase of hexane issued the container, according to claim 1 Symbol mounting an electromagnetic induction heating device characterized by aligning the winding direction of the electromagnetic induction coil.

Ferromagnetic material between the container and the electromagnetic induction coil, paramagnetic materials, diamagnetic materials, and by an intermediate member consisting of containing material to amplify the vibration generated in the container distort the magnetic field transmitted in said container in the electromagnetic induction heating device, an electromagnetic induction heating device according to claim 1, wherein the providing the during material to the natural frequency belly portion of said container.

Depending said during material inherent vibration of the phase of the container, the positive, the electromagnetic induction heating device according to claim 5 wherein, wherein the are for viewing inverse either phase position Nino.

A disk-shaped projection provided on the sides of the container, place the electromagnetic induction coil to the protrusion portion, an electromagnetic induction heating device according to claim 1, characterized in that the inverter control based on the previous distichum wavenumber.

The electromagnetic induction heating device according to any one of claims 1 to 7, wherein the vibration frequency is an ultrasonic region of 20 kHz or more.