JP2004063196A

JP2004063196A - Induction cooker

Info

Publication number: JP2004063196A
Application number: JP2002218096A
Authority: JP
Inventors: Masao Morita; 守田　正夫; Kunihiko Kaga; 加賀　邦彦; Koichi Kinoshita; 木下　広一; Yoshihiro Osano; 小佐野　義博
Original assignee: Mitsubishi Electric Home Appliance Co Ltd; Mitsubishi Electric Corp
Current assignee: Mitsubishi Electric Home Appliance Co Ltd; Mitsubishi Electric Corp
Priority date: 2002-07-26
Filing date: 2002-07-26
Publication date: 2004-02-26
Anticipated expiration: 2022-07-26
Also published as: JP3962646B2

Abstract

<P>PROBLEM TO BE SOLVED: To arrange a temperature sensor effectively detecting temperature of a loading pan even in the case where the bottom of the loading pan is bent or a placing position is applied in an induction cooker. <P>SOLUTION: The induction cooker is equipped with a top plate 4 on which the loading pan 16 is placed; a heating coil 10 for induction heating the loading pan 16; a means 12 for applying current to the heating coil 10; and first and second temperature sensors 20a, 20b installed between the top plate 14 and the heating coil 10. As viewed from almost the vertical direction to the top plate 4, the first temperature sensor 20a is arranged in a region of a radius of about 15% to about 50% to the outermost radius of the heating coil 10 and the second temperature sensor 20b is arranged in a region of a radius of about 50% to about 90% to the outermost radius of the heating coil 10. <P>COPYRIGHT: (C)2004,JPO

Description

【０００１】
【発明の属する技術分野】
本発明は電磁調理器に関し、特に負荷鍋の温度を検出するための温度センサを備えた電磁調理器に関する。
【０００２】
【従来の技術】
従来、負荷鍋を載置するトッププレートと、トッププレートの下側に配置され負荷鍋を誘導加熱する電磁誘導コイルまたは加熱コイルとを備えた電磁調理器において、負荷鍋の温度を検出して、負荷鍋の加熱温度を制御したり空焚き等による負荷鍋の過熱を防止したりするために、トッププレートの下面に温度センサを取付けたものが多数知られている。
【０００３】
例えば、特開平４−２４８２９０号公報や特開平１１−８７０４１号公報に開示されている電磁調理器では、トッププレートに略垂直な方向から見て温度センサを加熱コイルの巻回中心またはその近傍に配置している。
【０００４】
【発明が解決しようとする課題】
このような電磁調理器では、空焚き等により負荷鍋の底部が傘状に反り上がる場合がある。このように底部が反り上がった負荷鍋の場合、負荷鍋の底部とトッププレートとの間に隙間（熱伝導率の低い空気層）が生じるため、加熱コイルの巻回中心またはその近傍に配置された温度センサは、負荷鍋の実際の温度よりも低い温度を検出することになり、検出温度に基づいた制御を行うことができず、また、負荷鍋の過熱の危険性がある。これを解決するために、温度センサを加熱コイルの巻回中心またはその近傍以外に配置することが考えられる。
【０００５】
ところで、従来の電磁調理器では、負荷鍋を載置する位置を示すマークとして、トッププレートの上面に加熱コイルの最外半径位置に対応して円が印刷されている。しかしながら、負荷鍋を円に合わせてトッププレートに置かれずに、ずれた状態で置かれる可能性がある。そのため、温度センサを加熱コイルの巻回中心またはその近傍以外に配置した場合であっても、温度センサが負荷鍋の温度を有効に検出できない可能性がある。
【０００６】
本発明者らは、負荷鍋の底部が反った場合や載置位置がずれた場合であっても、負荷鍋の温度を有効に検出することのできる温度センサの配置位置を種々検討し本発明に到った。
【０００７】
【課題を解決するための手段】
本発明に係る電磁調理器の第１の態様は、
負荷鍋を載置するためのトッププレートと、
トッププレートの下方に配設され、負荷鍋を誘導加熱するための加熱コイルと、
加熱コイルに電流を印加する手段と、
トッププレートと加熱コイルとの間に配設された第１及び第２の温度センサとを備えた電磁調理器において、
トッププレートに略垂直な方向から見て、第１の温度センサを加熱コイルの最外半径に対し半径約１５〜約５０％の領域に配置するとともに、第２の温度センサを加熱コイルの最外半径に対し半径約５０〜約９０％の領域に配置することを特徴とする。
【０００８】
一実施形態では、第１及び第２の温度センサは、トッププレートに略垂直な方向から見て、加熱コイルの周方向に関して互いに約１８０度ずらして配置する。
【０００９】
本発明に係る電磁調理器の第２の態様は、
負荷鍋を載置するためのトッププレートと、
トッププレートの下方に配設され、負荷鍋を誘導加熱するための加熱コイルと、
加熱コイルに電流を印加する手段と、
トッププレートと加熱コイルとの間に配設されたｎ個（ｎ：３以上の整数）の温度センサとを備えた電磁調理器において、
ｎ個の温度センサは、トッププレートに略垂直な方向から見て、加熱コイルの最外半径に対し半径約１５〜約９０％の領域に、加熱コイルの周方向に関して略等ピッチで配置されることを特徴とする。
【００１０】
本発明に係る電磁調理器の第３の態様は、
負荷鍋を載置するためのトッププレートと、
トッププレートの下方に配設され、負荷鍋を誘導加熱するための加熱コイルと、
加熱コイルに電流を印加する手段と、
トッププレートと加熱コイルとの間に配設された第１〜第５の温度センサとを備えた電磁調理器において、
トッププレートに略垂直な方向から見て、第１〜第３の温度センサは、加熱コイルの最外半径に対し半径約１５〜約９０％の領域に、加熱コイルの周方向に関して略等ピッチで配置され、第４の温度センサは、加熱コイルの最外半径に対し半径約１５〜約５０％の領域に配置され、第５の温度センサは、加熱コイルの最外半径に対し半径約５０〜約９０％の領域に配置されることを特徴とする。
【００１１】
温度センサはトッププレート下面の温度を検出する。トッププレートとしてはガラスなどが用いられる。
【００１２】
温度センサをトッププレート下面に接して配置し、各温度センサに対し、該センサの周囲を囲むように断熱部材を設けてもよい。
【００１３】
【発明の実施の形態】
以下、添付図面を参照して本発明に係る電磁調理器の実施の形態を説明する。なお、本願明細書では、方向を表す用語（例えば、「上」、「下」、「右」、「左」、およびこれらの用語を含む別の用語）を適宜用いるが、説明に用いる図面中の方向を示すだけのものであって、これらの用語によって本発明が限定的に解釈されるべきでない。
【００１４】
実施の形態１．
図１〜図７を参照して、本発明に係る電磁調理器の実施の形態１について説明する。図１において、全体を符号２で示す電磁調理器は、箱状のハウジング３と、ハウジング３の上部を覆うガラスなどで形成されたトッププレート４とを備える。ハウジング３の外面には、温度調整つまみ６及び温度表示部８が設けてある。
【００１５】
図２に示すように、ハウジング３内部には、概略、トッププレート４の下側に配置された電磁誘導コイルまたは加熱コイル１０と、加熱コイル１０に高周波電流を供給するための電源１２と、電源１２を制御するための制御装置１４とが設けてある。トッププレート４の上面には、負荷鍋１６（図１では図示を省略）を載置するために、加熱コイル１０の最外半径に略一致する半径を有する円１８（図１）が印刷されている。トッププレート４の下面には、トッププレート４に略垂直な方向から見て加熱コイル１０中心から外側に向かう仮想線上の所定の位置に２つの温度センサ（例えばサーミスタ）２０ａ、２０ｂが設置され、トッププレート４を介して負荷鍋１６の温度を検出するようになっている。温度センサ２０ａ、２０ｂの設置位置については後で詳述する。温度センサ２０ａ、２０ｂからの検出信号は制御装置１４に送られ、必要に応じて加熱コイル１０に供給する電流が調整されるようにしてある。
【００１６】
図３（ａ），（ｂ）を参照して、加熱コイル１０の周辺部分をさらに詳しく説明する。加熱コイル１０の中央には中心フェライト２４が配置されるとともに、加熱コイル１０の下側には棒状のフェライト２６が放射状に配置されている。これらフェライト２４、２６は、加熱コイル１０が作る磁束を負荷鍋１６に高効率に導くためのものである。これらフェライト２４、２６の形状や配置位置が変わると、負荷鍋１６の発熱分布も変わる。
【００１７】
図４に示すような加熱コイル１０ａ、底部が平坦の負荷鍋１６、中心フェライト２４（図３参照）、及び棒フェライト２６（図３参照）を備えた電磁調理器モデルを用い、加熱コイル１０ａと負荷鍋１６の中心軸が一致している場合に、中心フェライト２４及び棒フェライト２６の配置や形状を変えた場合に負荷鍋１６の発熱分布がどのように変化するかを、三次元電磁界解析により求めた。すなわち、電磁界解析を行うことにより、加熱コイル１０ａの作る磁束を打ち消そうとして負荷鍋１６に流れる誘導電流に起因するジュール損失を求めた。このジュール損失の半径方向の分布が負荷鍋１６の発熱分布となる。解析に用いた加熱コイル１０ａは、中心側と外径側にそれぞれ一定の割合でコイルが巻回され、中心側のコイル部分と外径側のコイル部分の間に隙間を設けた形状を有するものである。
【００１８】
電磁界解析により得られた、加熱コイル１０ａにより誘導加熱される負荷鍋１６の発熱密度（単位体積当たりの発熱量）の代表数例をまとめて図５に示す。図５は、加熱コイルの最外直径が２００ｍｍ、負荷鍋５の外径が２００ｍｍのものを用いて電磁界解析を行った結果である。図５において、横軸は、加熱コイル１０の最外半径に対する負荷鍋１６の発熱位置の径の比である。例えば、横軸の５０％は、鍋の半径５０ｍｍの部分の径の比を表す。縦軸は、負荷鍋１６の発熱密度比であり、発熱密度が所定の高い値を示す箇所を１００％として示している。
【００１９】
以下では、電磁界解析から求めた発熱密度比の分布に基づいて、温度センサの最適な配置位置を考察する。
【００２０】
図４から明らかなように、負荷鍋１６の中心部と最外周部の発熱密度は実質的にゼロである。仮に発熱密度が実質的にゼロである半径位置に温度センサを設置すると、鍋内で熱が移動した後の温度を温度センサで測定することになるので、温度センサの応答性が良くない。
【００２１】
発熱密度比が高い箇所と見なせ、したがって負荷鍋の温度を有効に検出できるように温度センサを配置できる領域としては、実用的には最大発熱密度の５０％程度より大きい領域と考えられる。５０％程度より小さい領域に温度センサを配置した場合、温度センサの検出温度と負荷鍋１６の最高温度の差が大きいために、制御装置１４による温度制御が的確に行われないこと、及び負荷鍋１６の過熱の危険性があることが実験により確かめられている。図５から発熱密度比が５０％となる加熱コイル１０の最外半径に対する負荷鍋１６の発熱位置の半径の比を求めると、約１５％〜約９０％となる。
【００２２】
以上より、底部が反っていない負荷鍋１６に対しては、温度センサは、加熱コイル１０の最外半径に対し半径約１５〜約９０％の領域に少なくとも１つ配置することで、負荷鍋１６の温度を有効に検出することができる。
【００２３】
一方、負荷鍋１６が反っている場合、特に図６に示すように傘状に反っている場合には、負荷鍋１６とトッププレート４とが接している箇所以外は、熱伝導率が小さい空気の層を介してトッププレート４に熱が伝わるので、特に空気層が厚い箇所に相当するトッププレート４の下面に温度センサを設置した場合応答性が悪くなる。したがって、なるべく空気の層の薄い箇所に相当するトッププレート４の下面に温度センサを設置する必要がある。
【００２４】
例えば、負荷鍋１６が傘状に反っている場合には、最外周（端部）がトッププレート４と接する。負荷鍋１６の中心部の空気層は厚く、端部側になるほど薄くなる。負荷鍋１６の端部はトッププレート４と接しているので、なるべく負荷鍋１６の端部に近い箇所で温度を検知すると、負荷鍋１６の中心部に近い位置（例えば外径２００ｍｍの負荷鍋に対し半径２０ｍｍ付近）で検知した場合に比べて格段に温度センサの応答性がよい。
【００２５】
以上より、温度センサは、加熱コイル１０の最外半径に対し半径約１５〜約９０％の領域であって、特に加熱コイル１０の最外半径位置に近い領域に配置することで、底部が反っている負荷鍋１６及び平坦な負荷鍋１６の両方に対して温度を有効に検出することができる。
【００２６】
以上の考察では、負荷鍋１６が加熱コイル１０の真上に配置された場合を想定していたが、以下では、図７に示すように負荷鍋１６が加熱コイル１０の真上の位置からずれて配置された場合（言い換えれば、負荷鍋１６の中心が載置用の円１８（図１）の中心からずれた場合）であっても、負荷鍋１６の温度を有効に検出できる温度センサの最適な配置位置を考察する。
【００２７】
図７の例は、温度センサ２０ａ、２０ｂを、外径２００ｍｍの加熱コイル１０の半径位置約３０ｍｍと約８０ｍｍにそれぞれ設置したものである。図では、加熱コイル１０、負荷鍋１６、温度センサ２０ａ、２０ｂを上側から透かした図であり、種々の位置に置いた負荷鍋１６を同時に示している。図から明らかなように、一方の温度センサ２０ａを加熱コイル１０の半径の小さな領域に設置するとともに、他方の温度センサ２０ｂを加熱コイル１０の半径の大きな領域に設置することにより、多少負荷鍋１６の位置がずれた場合でも、温度センサ２０ｂは、負荷鍋１６の端部近傍の温度を検出できる。負荷鍋１６の位置が大きくずれた場合、加熱コイル１０の半径の小さな領域に設けた温度センサ２０ａが負荷鍋１６の端部近傍の温度を検出できる場合がある。
【００２８】
なお、負荷鍋１６の外径が加熱コイル１０の最大直径に比べて小さく、例えば、加熱コイル１０の最外直径が２００ｍｍに対し負荷鍋１６の外径が１００ｍｍの場合、加熱コイル１０と負荷鍋１６の中心軸が略一致するように負荷鍋１６をトッププレート上に置いても、加熱コイル１０の外径側に設けた温度センサ２０ｂは、鍋１６の底部から外れてしまうので、加熱コイル１０の半径の小さな領域には必ず温度センサ２０ａが必要となる。
【００２９】
以上より、温度センサは、加熱コイル１０の半径の小さな領域、すなわち加熱コイル１０の最外半径に対し半径約１５〜約５０％の領域と、加熱コイル１０の半径の大きな領域、すなわち加熱コイル１０の最外半径に対し半径約５０〜約９０％の領域にそれぞれ少なくとも１つ配置することで、負荷鍋１６がずれた場合及び負荷鍋１６が反った場合でも負荷鍋１６の温度を有効に検出できる。
【００３０】
実施の形態２．
図８〜１０を参照して、本発明に係る電磁調理器の実施の形態２について説明する。本実施形態に係る電磁調理器は、温度センサの位置が異なる点を除いて実施の形態１と同様の構成を有するので重複する内容については説明を省略する。実施の形態１では、図９に示すように、２つの温度センサ２０ａ、２０ｂは、加熱コイル１０の周方向に関して同一の位置（言い換えれば、トッププレートに略垂直な方向から見てコイル中心から半径方向外側に伸びる一本の仮想線上）に配置している。これに対し、本実施形態に係る電磁調理器は、図１０に示すように、温度センサ２０ａを加熱コイル１０の最外半径に対し半径約１５〜約５０％の領域に、温度センサ２０ｂを加熱コイル１０の最外半径に対し半径約５０〜約９０％の領域に配置するとともに、これら温度センサ２０ａ，２０ｂを加熱コイル１０の周方向に関して約１８０度ずらした位置に配置したものである。
【００３１】
実施の形態１では、図９に示すように、負荷鍋１６が載置位置から大きくずれた場合に、温度センサ２０ａ，２０ｂが負荷鍋１６から外れてしまう場合があるが、実施の形態２では、図１０に示すように、負荷鍋１６が載置位置から大きくずれた場合でも、加熱コイル１０の中心側に位置する温度センサ２０ａが負荷鍋１６の温度を検出できる可能性が高い。
【００３２】
実施の形態３．
本実施形態では、例えば図１１（ａ），（ｂ）に示すように、３つの温度センサ２０ｃ，２０ｄ，２０ｅはそれぞれ、加熱コイル１０の中心から半径方向外側に伸び且つ互いになす角が略１２０度の３つの仮想線３０ｃ，３０ｄ，３０ｅ上に（言い換えれば、加熱コイル１０の周方向に関して略等ピッチに）配置されている。温度センサ２０ｃ，２０ｄ，２０ｅはまた、加熱コイル１０の最外半径に対し半径約１５〜約９０％の領域に配置されている。この場合、負荷鍋が載置位置からどの方向にずれたとしても負荷鍋１６の温度を有効に検出することができる。図１１（ａ）は、加熱コイル１０の最外直径と等しい外径を有する負荷鍋１６がずれて置かれた例を示し、図１１（ｂ）は、加熱コイル１０の最外直径に比べて外径が小さい又は大きい負荷鍋１６がずれて置かれた例を示している。
【００３３】
図１１の例では、３つの温度センサ２０ｃ，２０ｄ，２０ｅは、加熱コイル１０の中心からの距離が等しい位置に配置されているが、異なる位置に配置しても同様の効果を有する。
【００３４】
温度センサは４つ以上配置してもよく、この場合、温度センサの個数と同じ本数であって互いのなす角度が略等しい仮想線上に、各温度センサを配置する。
【００３５】
実施の形態４．
実施の形態３での温度センサの配置位置は、底部が平坦な負荷鍋の場合に鍋の温度を有効に検出できるが、底部が反った負荷鍋をトッププレート上に置く場合に、温度センサの上方に鍋底部とトッププレート間の空気層が比較的厚い部分がくる可能性がある。この場合、負荷鍋の温度を有効に検出することができない。そこで、本実施形態では、例えば図１２に示すように、実施の形態３と同様に温度センサ２０ｃ，２０ｄ，２０ｅを加熱コイル１０の最外半径に対し半径約１５〜約９０％の領域にコイル周方向に関して略等ピッチに配置するとともに、実施の形態１、２と同様に温度センサ２０ａを加熱コイル１０の最外半径に対し半径約１５〜約５０％の領域に、温度センサ２０ｂを加熱コイル１０の最外半径に対し半径約５０〜約９０％の領域に配置する。図１２（ａ）は、加熱コイル１０の最外直径と等しい外径を有する負荷鍋１６がずれて置かれた例を示し、図１２（ｂ）は、加熱コイル１０の最外直径に比べて外径が小さい又は大きい負荷鍋１６がずれて置かれた例を示している。
【００３６】
かかる構成では、底部が反った負荷鍋が載置位置からいずれの方向にずれた場合であっても、負荷鍋の温度を有効に検出できる。
【００３７】
図の例では、温度センサ２０ａ，２０ｂを、温度センサ２０ｃを配置する仮想線３０ｃ上に配置しているが、温度センサ２０ａ，２０ｂを仮想線上に配置する必要はなく、また、温度センサ２０ａ，２０ｂを加熱コイル１０の周方向に関して同一の位置に配置する必要はない。
【００３８】
実施の形態５．
電磁調理器は、一般に、トッププレート及び加熱コイルを冷却するために冷却ファンを備えている。冷却ファンからの冷風は、トッププレートと加熱コイルの間の隙間を通って供給されるため、トッププレート下面に取付けた温度センサ（例えばサーミスタ）に冷風が当たると検知温度に誤差が生じる場合がある。
【００３９】
そこで、本実施形態では、温度センサの周囲を断熱材で囲むことで冷却風が温度センサに直接当たらないようにしている。
【００４０】
より詳しくは、図１３〜１５を参照して、温度センサ（例えばサーミスタ）２０は、例えば断熱ウールなど柔らかくある程度クッション性のある断熱部材３２上に配置されている。断熱部材３２は、例えば加熱コイル１０上に設置された支持台３４上に固定されている。この構成では、温度センサ２０は、トッププレート４の下面に接する部分以外が断熱部材３２で覆われるため、冷却ファンからの冷風３６が温度センサ２０に当たることはない。また、断熱部材３２及び支持台３４は、トッププレート４と加熱コイル１０との隙間の一部を占めているだけであるため、冷風３６は、トッププレート４及び加熱コイル１０の略全体にわたって冷却することができる。
【００４１】
なお、加熱コイルとして、図４に示すように、中心側と外径側にそれぞれ一定の割合でコイルが巻回され、中心側のコイル部分と外径側のコイル部分の間に隙間を設けたものを用いる場合、該隙間に断熱部材を支持するための支持台を配置してもよい。
【００４２】
温度センサの周囲に断熱部材を設けた場合と設けない場合それぞれに対し、加熱コイルに電流を印加して負荷鍋を加熱し、その後冷却ファンを作動させる実験を行った。印加電流の大きさは、断熱部材を設けた場合と設けない場合で異ならせた。図１６は、電流印加開始からの経過時間に対する温度センサの指示温度を示すグラフである。断熱部材を設けない場合には、冷却ファンが作動すると温度センサの指示温度に変曲点が見られたが、断熱部材を設けた場合には、冷却ファンが作動しても変曲点が見られなかった。これは、断熱部材を設けない場合に冷却ファンが作動すると、冷風が温度センサに当たり検出温度誤差が大きくなるが、断熱部材を設けた場合に、温度センサの指示温度は冷風の影響を受けず、負荷鍋の温度を有効に検出していることを示している。
【００４３】
【発明の効果】
本発明に係る電磁調理器によれば、負荷鍋の底部が反った場合や載置位置からずれた場合であっても、負荷鍋の温度を有効に検出できる。
【図面の簡単な説明】
【図１】本発明に係る電磁調理器の実施の形態１を示す概略斜視図。
【図２】図１のＩＩ−ＩＩ線に沿った概略断面図。
【図３】（ａ）図１の加熱コイルの周辺部分の詳細な断面図。（ｂ）図１の加熱コイルの上面図。
【図４】負荷鍋の発熱分布を求めるための電磁調理器モデルを示す概略断面図。
【図５】図４の電磁調理器モデルを用いて求めた負荷鍋の発熱分布を示すグラフ。
【図６】底部が反った負荷鍋を示す図。
【図７】実施の形態１における、加熱コイルと２つの温度センサの位置関係を示す図。
【図８】本発明に係る電磁調理器の実施の形態２を示す、図２に類似した概略断面図。
【図９】実施の形態１に係る電磁調理器において、負荷鍋が載置位置からずれて置かれた状態を示す図。
【図１０】実施の形態２に係る電磁調理器において、負荷鍋が載置位置からずれて置かれた状態を示す図。
【図１１】実施の形態３に係る電磁調理器において、負荷鍋が載置位置からずれて置かれた状態を示す図。
【図１２】実施の形態４に係る電磁調理器において、負荷鍋が載置位置からずれて置かれた状態を示す図。
【図１３】実施の形態５において、温度センサの周辺部分を詳しく示す断面図。
【図１４】実施の形態５において、温度センサを覆うための断熱部材及び該部材を支持するための支持台を示す斜視図。
【図１５】実施の形態５において、温度センサと加熱コイルの位置関係を示す上面図であって、温度センサ及び断熱部材が透視して示してある。
【図１６】温度センサの周囲に断熱部材を設けた場合と設けない場合それぞれについて、加熱コイルに電流を印加したときの温度センサの指示温度を示したグラフ。
【符号の説明】
２：電磁調理器、４：トッププレート、１０：加熱コイル、１２：電源、１４：制御装置、１６：負荷鍋、２０ａ：温度センサ、２０ｂ：温度センサ。[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an electromagnetic cooker, and more particularly to an electromagnetic cooker provided with a temperature sensor for detecting a temperature of a load pan.
[0002]
[Prior art]
Conventionally, in an electromagnetic cooker equipped with a top plate on which a load pan is placed and an electromagnetic induction coil or a heating coil disposed below the top plate and induction heating the load pan, the temperature of the load pan is detected, In order to control the heating temperature of the load pan and to prevent the load pan from overheating due to empty boiling or the like, many types are known in which a temperature sensor is attached to the lower surface of a top plate.
[0003]
For example, in an electromagnetic cooker disclosed in JP-A-4-248290 or JP-A-11-87041, a temperature sensor is placed at or near a winding center of a heating coil when viewed from a direction substantially perpendicular to a top plate. Are placed.
[0004]
[Problems to be solved by the invention]
In such an electromagnetic cooker, the bottom of the load pan may be warped in an umbrella shape due to idle heating or the like. In the case of the load pan having a warped bottom as described above, a gap (air layer having low thermal conductivity) is generated between the bottom of the load pan and the top plate, so that the load pan is disposed at or near the winding center of the heating coil. The temperature sensor detects a temperature lower than the actual temperature of the load pan, and cannot perform control based on the detected temperature, and there is a risk of overheating of the load pan. In order to solve this, it is conceivable to dispose the temperature sensor at a position other than the winding center of the heating coil or in the vicinity thereof.
[0005]
By the way, in the conventional electromagnetic cooker, a circle corresponding to the outermost radius position of the heating coil is printed on the upper surface of the top plate as a mark indicating the position where the load pan is placed. However, there is a possibility that the loading pot is not placed on the top plate in a circle, but is placed in a shifted state. Therefore, even when the temperature sensor is disposed at a position other than the winding center of the heating coil or in the vicinity thereof, there is a possibility that the temperature sensor cannot effectively detect the temperature of the load pan.
[0006]
The present inventors have studied various arrangement positions of a temperature sensor capable of effectively detecting the temperature of the load pan even when the bottom portion of the load pan is warped or the mounting position is shifted. Reached.
[0007]
[Means for Solving the Problems]
A first aspect of the electromagnetic cooker according to the present invention is:
A top plate for placing the loading pan,
A heating coil disposed below the top plate for induction heating the load pan,
Means for applying a current to the heating coil;
An electromagnetic cooker including first and second temperature sensors disposed between a top plate and a heating coil,
When viewed from a direction substantially perpendicular to the top plate, the first temperature sensor is disposed in a region having a radius of about 15 to about 50% of the outermost radius of the heating coil, and the second temperature sensor is disposed at the outermost position of the heating coil. It is characterized in that it is arranged in an area having a radius of about 50 to about 90% of the radius.
[0008]
In one embodiment, the first and second temperature sensors are offset from each other by approximately 180 degrees with respect to the circumferential direction of the heating coil when viewed from a direction substantially perpendicular to the top plate.
[0009]
A second aspect of the electromagnetic cooker according to the present invention is:
A top plate for placing the loading pan,
A heating coil disposed below the top plate for induction heating the load pan,
Means for applying a current to the heating coil;
In an electromagnetic cooker provided with n (n: an integer of 3 or more) temperature sensors disposed between a top plate and a heating coil,
The n temperature sensors are arranged in a region having a radius of about 15 to about 90% with respect to the outermost radius of the heating coil when viewed from a direction substantially perpendicular to the top plate, at a substantially equal pitch in the circumferential direction of the heating coil. It is characterized by the following.
[0010]
A third aspect of the electromagnetic cooker according to the present invention is:
A top plate for placing the loading pan,
A heating coil disposed below the top plate for induction heating the load pan,
Means for applying a current to the heating coil;
In an electromagnetic cooker including first to fifth temperature sensors disposed between a top plate and a heating coil,
When viewed from a direction substantially perpendicular to the top plate, the first to third temperature sensors are arranged in a region having a radius of about 15 to about 90% with respect to the outermost radius of the heating coil at a substantially equal pitch in the circumferential direction of the heating coil. The fourth temperature sensor is disposed in a region having a radius of about 15 to about 50% with respect to the outermost radius of the heating coil, and the fifth temperature sensor is disposed with a radius of about 50 to about 50% with respect to the outermost radius of the heating coil. It is characterized by being arranged in an area of about 90%.
[0011]
The temperature sensor detects the temperature of the lower surface of the top plate. Glass or the like is used as the top plate.
[0012]
A temperature sensor may be arranged in contact with the lower surface of the top plate, and a heat insulating member may be provided for each temperature sensor so as to surround the sensor.
[0013]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, an embodiment of an electromagnetic cooker according to the present invention will be described with reference to the accompanying drawings. In the specification of the present application, terms indicating directions (for example, “up”, “down”, “right”, “left”, and other terms including these terms) are used as appropriate. , And these terms should not be construed as limiting the invention.
[0014]
Embodiment 1 FIG.
The first embodiment of the electromagnetic cooker according to the present invention will be described with reference to FIGS. In FIG. 1, an electromagnetic cooker generally denoted by reference numeral 2 includes a box-shaped housing 3 and a top plate 4 formed of glass or the like that covers an upper portion of the housing 3. A temperature adjustment knob 6 and a temperature display section 8 are provided on an outer surface of the housing 3.
[0015]
As shown in FIG. 2, inside the housing 3, an electromagnetic induction coil or a heating coil 10 arranged generally below the top plate 4, a power supply 12 for supplying a high-frequency current to the heating coil 10, and a power supply There is provided a control device 14 for controlling the power supply 12. On the upper surface of the top plate 4, a circle 18 (FIG. 1) having a radius substantially corresponding to the outermost radius of the heating coil 10 is printed in order to place the load pan 16 (not shown in FIG. 1). I have. On the lower surface of the top plate 4, two temperature sensors (for example, thermistors) 20 a and 20 b are installed at predetermined positions on a virtual line extending outward from the center of the heating coil 10 when viewed from a direction substantially perpendicular to the top plate 4. The temperature of the load pan 16 is detected via the plate 4. The installation positions of the temperature sensors 20a and 20b will be described later in detail. The detection signals from the temperature sensors 20a and 20b are sent to the control device 14, and the current supplied to the heating coil 10 is adjusted as necessary.
[0016]
The peripheral portion of the heating coil 10 will be described in more detail with reference to FIGS. A central ferrite 24 is arranged at the center of the heating coil 10, and a rod-shaped ferrite 26 is radially arranged below the heating coil 10. These ferrites 24 and 26 are for guiding the magnetic flux generated by the heating coil 10 to the load pan 16 with high efficiency. When the shapes and arrangement positions of the ferrites 24 and 26 change, the heat generation distribution of the load pan 16 also changes.
[0017]
Using an electromagnetic cooker model having a heating coil 10a as shown in FIG. 4, a load pan 16 having a flat bottom, a center ferrite 24 (see FIG. 3), and a bar ferrite 26 (see FIG. 3), the heating coil 10a When the center axes of the load pan 16 coincide with each other, a three-dimensional electromagnetic field analysis is performed to determine how the heat distribution of the load pan 16 changes when the arrangement and shape of the center ferrite 24 and the bar ferrite 26 are changed. Determined by That is, by performing an electromagnetic field analysis, a Joule loss caused by an induced current flowing through the load pan 16 in an attempt to cancel the magnetic flux generated by the heating coil 10a was obtained. The radial distribution of the Joule loss is the heat generation distribution of the load pan 16. The heating coil 10a used for the analysis has a shape in which a coil is wound around the center side and the outer diameter side at a fixed ratio, and a gap is provided between the center side coil part and the outer diameter side coil part. It is.
[0018]
FIG. 5 shows several representative examples of the heat generation density (heat generation amount per unit volume) of the load pan 16 that is induction-heated by the heating coil 10a and obtained by the electromagnetic field analysis. FIG. 5 shows the results of an electromagnetic field analysis performed using a heating coil having an outermost diameter of 200 mm and a loading pan 5 having an outer diameter of 200 mm. In FIG. 5, the horizontal axis represents the ratio of the diameter of the heat generating position of the load pan 16 to the outermost radius of the heating coil 10. For example, 50% of the abscissa represents the ratio of the diameter of the pot with a radius of 50 mm. The vertical axis represents the heat generation density ratio of the load pan 16, and a portion where the heat generation density shows a predetermined high value is shown as 100%.
[0019]
In the following, based on the distribution of the heat generation density ratio obtained from the electromagnetic field analysis, the optimum arrangement position of the temperature sensor will be considered.
[0020]
As is clear from FIG. 4, the heat generation density at the center portion and the outermost peripheral portion of the load pan 16 is substantially zero. If the temperature sensor is installed at a radial position where the heat generation density is substantially zero, the temperature after the heat has moved in the pot is measured by the temperature sensor, and the response of the temperature sensor is not good.
[0021]
It can be considered that the heat generation density ratio is high, and therefore, the area where the temperature sensor can be disposed so that the temperature of the load pan can be effectively detected is practically an area larger than about 50% of the maximum heat generation density. When the temperature sensor is arranged in an area smaller than about 50%, the difference between the detected temperature of the temperature sensor and the maximum temperature of the load pan 16 is large, so that the temperature control by the control device 14 is not performed accurately, and Experiments have shown that there is a danger of overheating. The ratio of the radius of the heat generating position of the load pan 16 to the outermost radius of the heating coil 10 at which the heat generation density ratio becomes 50% from FIG. 5 is about 15% to about 90%.
[0022]
As described above, with respect to the load pan 16 whose bottom is not warped, at least one temperature sensor is disposed in an area having a radius of about 15 to about 90% with respect to the outermost radius of the heating coil 10 so that the load pan 16 Can be effectively detected.
[0023]
On the other hand, when the load pan 16 is warped, particularly when it is warped in an umbrella shape as shown in FIG. Since the heat is transmitted to the top plate 4 through the layer of, the responsiveness deteriorates particularly when the temperature sensor is installed on the lower surface of the top plate 4 corresponding to a portion where the air layer is thick. Therefore, it is necessary to install a temperature sensor on the lower surface of the top plate 4 corresponding to a portion where the air layer is as thin as possible.
[0024]
For example, when the load pan 16 is warped in an umbrella shape, the outermost periphery (end) contacts the top plate 4. The air layer at the center of the load pan 16 is thicker, and becomes thinner toward the end. Since the end of the load pan 16 is in contact with the top plate 4, if the temperature is detected as close to the end of the load pan 16 as possible, a position close to the center of the load pan 16 (for example, a load pan having an outer diameter of 200 mm) may be used. The response of the temperature sensor is much better than when the detection is performed at a radius of about 20 mm.
[0025]
As described above, the bottom of the temperature sensor is warped by arranging the temperature sensor in an area having a radius of about 15 to about 90% with respect to the outermost radius of the heating coil 10, particularly near the outermost radius position of the heating coil 10. The temperature can be effectively detected for both the loaded pan 16 and the flat loaded pan 16.
[0026]
In the above discussion, it was assumed that the load pan 16 was disposed directly above the heating coil 10, but in the following, the load pan 16 is shifted from the position directly above the heating coil 10 as shown in FIG. Position (in other words, when the center of the load pan 16 is deviated from the center of the placing circle 18 (FIG. 1)), a temperature sensor capable of effectively detecting the temperature of the load pan 16 is used. Consider the optimal placement position.
[0027]
In the example of FIG. 7, the temperature sensors 20a and 20b are installed at radial positions of about 30 mm and about 80 mm of the heating coil 10 having an outer diameter of 200 mm, respectively. In the figure, the heating coil 10, the load pan 16, and the temperature sensors 20a and 20b are viewed from above, and the load pans 16 placed at various positions are also shown. As is clear from the figure, by placing one of the temperature sensors 20a in a region with a small radius of the heating coil 10 and installing the other temperature sensor 20b in a region with a large radius of the heating coil 10, the load Temperature sensor 20b can detect the temperature in the vicinity of the end of the load pan 16 even if the position is shifted. When the position of the load pan 16 is largely displaced, the temperature sensor 20a provided in an area where the radius of the heating coil 10 is small may detect the temperature near the end of the load pan 16 in some cases.
[0028]
In addition, when the outer diameter of the loading pan 16 is smaller than the maximum diameter of the heating coil 10, for example, when the outer diameter of the heating coil 10 is 200 mm and the outer diameter of the loading pan 16 is 100 mm, the heating coil 10 and the loading pan Even if the load pan 16 is placed on the top plate such that the central axes of the pans 16 are substantially coincident with each other, the temperature sensor 20b provided on the outer diameter side of the heating coil 10 will come off from the bottom of the pan 16 so that the heating coil 10 The temperature sensor 20a is always required in a region with a small radius of.
[0029]
As described above, the temperature sensor has a region with a small radius of the heating coil 10, that is, a region with a radius of about 15 to about 50% of the outermost radius of the heating coil 10, and a region with a large radius of the heating coil 10, that is, the heating coil 10. By arranging at least one in each of the regions having a radius of about 50 to about 90% of the outermost radius of the load pan, the temperature of the load pan 16 can be effectively detected even when the load pan 16 is displaced or the load pan 16 warps. it can.
[0030]
Embodiment 2 FIG.
Embodiment 2 An electromagnetic cooker according to Embodiment 2 of the present invention will be described with reference to FIGS. The electromagnetic cooker according to the present embodiment has the same configuration as that of the first embodiment except that the position of the temperature sensor is different, and the description of the same contents will not be repeated. In the first embodiment, as shown in FIG. 9, the two temperature sensors 20a and 20b are located at the same position in the circumferential direction of the heating coil 10 (in other words, the radius from the coil center when viewed from a direction substantially perpendicular to the top plate). (On one virtual line extending outward in the direction). On the other hand, in the electromagnetic cooker according to the present embodiment, as shown in FIG. 10, the temperature sensor 20a heats the temperature sensor 20b to a region having a radius of about 15 to about 50% of the outermost radius of the heating coil 10. The temperature sensors 20a and 20b are arranged at positions shifted by about 180 degrees with respect to the circumferential direction of the heating coil 10 while being arranged in a region having a radius of about 50 to about 90% of the outermost radius of the coil 10.
[0031]
In the first embodiment, as shown in FIG. 9, when the load pan 16 is greatly displaced from the mounting position, the temperature sensors 20a and 20b may come off the load pan 16, but in the second embodiment, As shown in FIG. 10, even when the load pan 16 is greatly displaced from the mounting position, there is a high possibility that the temperature sensor 20a located at the center side of the heating coil 10 can detect the temperature of the load pan 16.
[0032]
Embodiment 3 FIG.
In the present embodiment, for example, as shown in FIGS. 11A and 11B, each of the three temperature sensors 20c, 20d, and 20e extends radially outward from the center of the heating coil 10 and has an angle of approximately 120 with each other. The three imaginary lines 30c, 30d, and 30e are arranged (in other words, at substantially equal pitches in the circumferential direction of the heating coil 10). The temperature sensors 20c, 20d, and 20e are also arranged in a region having a radius of about 15 to about 90% of the outermost radius of the heating coil 10. In this case, the temperature of the load pan 16 can be effectively detected regardless of the direction in which the load pan deviates from the mounting position. FIG. 11A shows an example in which a load pan 16 having an outer diameter equal to the outermost diameter of the heating coil 10 is shifted, and FIG. An example is shown in which the load pan 16 having a small or large outside diameter is shifted.
[0033]
In the example of FIG. 11, the three temperature sensors 20c, 20d, and 20e are arranged at positions where the distance from the center of the heating coil 10 is equal, but the same effect can be obtained even if they are arranged at different positions.
[0034]
Four or more temperature sensors may be arranged. In this case, each temperature sensor is arranged on an imaginary line having the same number of temperature sensors and substantially equal angles to each other.
[0035]
Embodiment 4 FIG.
The arrangement position of the temperature sensor in the third embodiment can effectively detect the temperature of the pan in the case of a load pan having a flat bottom, but when the load pan with the bent bottom is placed on the top plate, There may be a portion where the air layer between the pot bottom and the top plate is relatively thick upward. In this case, the temperature of the load pan cannot be effectively detected. Therefore, in the present embodiment, as shown in FIG. 12, for example, similarly to the third embodiment, the temperature sensors 20c, 20d, and 20e are placed in a region having a radius of about 15 to about 90% of the outermost radius of the heating coil 10. The temperature sensors 20a are arranged at substantially equal pitches in the circumferential direction, and the temperature sensor 20a is disposed in a region having a radius of about 15 to about 50% of the outermost radius of the heating coil 10 as in the first and second embodiments. It is arranged in a region having a radius of about 50 to about 90% of the outermost radius of 10. FIG. 12A shows an example in which the load pan 16 having an outer diameter equal to the outermost diameter of the heating coil 10 is shifted, and FIG. An example is shown in which the load pan 16 having a small or large outside diameter is shifted.
[0036]
With this configuration, the temperature of the load pan can be effectively detected even when the load pan whose bottom is warped is displaced in any direction from the mounting position.
[0037]
In the illustrated example, the temperature sensors 20a and 20b are arranged on a virtual line 30c on which the temperature sensor 20c is arranged. However, it is not necessary to arrange the temperature sensors 20a and 20b on the virtual line. It is not necessary to arrange the 20b at the same position in the circumferential direction of the heating coil 10.
[0038]
Embodiment 5 FIG.
The electromagnetic cooker generally includes a cooling fan for cooling the top plate and the heating coil. Since the cool air from the cooling fan is supplied through the gap between the top plate and the heating coil, an error may occur in the detected temperature when the cool air hits a temperature sensor (for example, a thermistor) mounted on the lower surface of the top plate. .
[0039]
Therefore, in the present embodiment, by surrounding the temperature sensor with a heat insulating material, the cooling air is prevented from directly hitting the temperature sensor.
[0040]
More specifically, referring to FIGS. 13 to 15, a temperature sensor (for example, a thermistor) 20 is disposed on a soft and somewhat cushioning heat insulating member 32 such as heat insulating wool. The heat insulating member 32 is fixed, for example, on a support table 34 installed on the heating coil 10. In this configuration, since the temperature sensor 20 is covered with the heat insulating member 32 except for the portion in contact with the lower surface of the top plate 4, the cool air 36 from the cooling fan does not hit the temperature sensor 20. Further, since the heat insulating member 32 and the support base 34 occupy only a part of the gap between the top plate 4 and the heating coil 10, the cool air 36 cools substantially the entirety of the top plate 4 and the heating coil 10. be able to.
[0041]
As shown in FIG. 4, as the heating coil, a coil was wound around the center side and the outer diameter side at a fixed ratio, and a gap was provided between the center side coil part and the outer diameter side coil part. When using a support, a support for supporting the heat insulating member may be disposed in the gap.
[0042]
An experiment was conducted in which a current was applied to the heating coil to heat the load pan, and then the cooling fan was operated, in each of the case where the heat insulating member was provided around the temperature sensor and the case where the heat insulating member was not provided. The magnitude of the applied current was made different depending on whether the heat insulating member was provided or not. FIG. 16 is a graph showing the temperature indicated by the temperature sensor with respect to the elapsed time from the start of current application. When the heat insulating member was not provided, an inflection point was observed in the temperature indicated by the temperature sensor when the cooling fan was operated. However, when the heat insulating member was provided, the inflection point was observed even when the cooling fan was operated. I couldn't. This is because, when the cooling fan operates when the heat insulating member is not provided, the cold air hits the temperature sensor and the detected temperature error increases, but when the heat insulating member is provided, the temperature indicated by the temperature sensor is not affected by the cold air, This indicates that the temperature of the loading pan is effectively detected.
[0043]
【The invention's effect】
ADVANTAGE OF THE INVENTION According to the electromagnetic cooker which concerns on this invention, the temperature of a load pan can be detected effectively, even when the bottom part of a load pan warps or deviates from a mounting position.
[Brief description of the drawings]
FIG. 1 is a schematic perspective view showing Embodiment 1 of an electromagnetic cooker according to the present invention.
FIG. 2 is a schematic sectional view taken along the line II-II in FIG.
FIG. 3A is a detailed sectional view of a peripheral portion of a heating coil of FIG. 1; (B) Top view of the heating coil of FIG.
FIG. 4 is a schematic sectional view showing an electromagnetic cooker model for obtaining a heat distribution of a load pan.
FIG. 5 is a graph showing a heat generation distribution of a load pan obtained by using the electromagnetic cooker model of FIG. 4;
FIG. 6 is a view showing a load pan with a warped bottom.
FIG. 7 is a diagram showing a positional relationship between a heating coil and two temperature sensors in the first embodiment.
FIG. 8 is a schematic sectional view similar to FIG. 2, showing a second embodiment of the electromagnetic cooker according to the present invention.
FIG. 9 is a diagram showing a state in which the load pan is shifted from the mounting position in the electromagnetic cooker according to the first embodiment.
FIG. 10 is a diagram showing a state in which the load pan is placed shifted from the placement position in the electromagnetic cooker according to the second embodiment.
FIG. 11 is a diagram showing a state in which the load pan is shifted from the mounting position in the electromagnetic cooker according to the third embodiment.
FIG. 12 is a view showing a state in which the load pan is shifted from the mounting position in the electromagnetic cooker according to the fourth embodiment.
FIG. 13 is a cross-sectional view specifically showing a peripheral portion of a temperature sensor in the fifth embodiment.
FIG. 14 is a perspective view showing a heat insulating member for covering a temperature sensor and a support base for supporting the member in the fifth embodiment.
FIG. 15 is a top view showing a positional relationship between a temperature sensor and a heating coil in the fifth embodiment, in which the temperature sensor and the heat insulating member are shown in a see-through manner.
FIG. 16 is a graph showing the temperature indicated by the temperature sensor when a current is applied to the heating coil in each of the case where a heat insulating member is provided around the temperature sensor and the case where no heat insulating member is provided.
[Explanation of symbols]
2: electromagnetic cooker, 4: top plate, 10: heating coil, 12: power supply, 14: control device, 16: load pan, 20a: temperature sensor, 20b: temperature sensor.

Claims

A top plate for placing the loading pan,
A heating coil disposed below the top plate for induction heating the load pan,
Means for applying a current to the heating coil;
An electromagnetic cooker including first and second temperature sensors disposed between a top plate and a heating coil,
When viewed from a direction substantially perpendicular to the top plate, the first temperature sensor is disposed in a region having a radius of about 15 to about 50% of the outermost radius of the heating coil, and the second temperature sensor is disposed at the outermost position of the heating coil. An electromagnetic cooker, wherein the electromagnetic cooker is arranged in an area having a radius of about 50 to about 90% of the radius.

The electromagnetic cooker according to claim 1, wherein the first and second temperature sensors are arranged to be shifted from each other by about 180 degrees with respect to a circumferential direction of the heating coil when viewed from a direction substantially perpendicular to the top plate.

A top plate for placing the loading pan,
A heating coil disposed below the top plate for induction heating the load pan,
Means for applying a current to the heating coil;
In an electromagnetic cooker provided with n (n: an integer of 3 or more) temperature sensors disposed between a top plate and a heating coil,
The n temperature sensors are arranged in a region having a radius of about 15 to about 90% with respect to the outermost radius of the heating coil when viewed from a direction substantially perpendicular to the top plate, at a substantially equal pitch in the circumferential direction of the heating coil. An electromagnetic cooker characterized by that:

A top plate for placing the loading pan,
A heating coil disposed below the top plate for induction heating the load pan,
Means for applying a current to the heating coil;
In an electromagnetic cooker including first to fifth temperature sensors disposed between a top plate and a heating coil,
When viewed from a direction substantially perpendicular to the top plate, the first to third temperature sensors are arranged in a region having a radius of about 15 to about 90% with respect to the outermost radius of the heating coil at a substantially equal pitch in the circumferential direction of the heating coil. The fourth temperature sensor is disposed in a region having a radius of about 15 to about 50% with respect to the outermost radius of the heating coil, and the fifth temperature sensor is disposed with a radius of about 50 to about 50% with respect to the outermost radius of the heating coil. An electromagnetic cooker, which is arranged in an area of about 90%.

The electromagnetic cooker according to any one of claims 1 to 4, wherein the temperature sensor detects a temperature of a lower surface of the top plate.

The temperature sensor is disposed in contact with the lower surface of the top plate,
The electromagnetic cooker according to any one of claims 1 to 5, wherein a heat insulating member is provided for each temperature sensor so as to surround the periphery of the sensor.