JP2004063310A

JP2004063310A - Microwave heating apparatus

Info

Publication number: JP2004063310A
Application number: JP2002220990A
Authority: JP
Inventors: Koji Yoshino; 吉野　浩二; Tomotaka Nobue; 信江　等隆; Susumu Idomoto; 井戸本　晋
Original assignee: Matsushita Electric Industrial Co Ltd
Current assignee: Panasonic Holdings Corp
Priority date: 2002-07-30
Filing date: 2002-07-30
Publication date: 2004-02-26
Anticipated expiration: 2022-07-30
Also published as: JP4036052B2

Abstract

<P>PROBLEM TO BE SOLVED: To generate microwave radiation having asymmetrical directivity with respect to the tube axis of a waveguide by devising the structure of an opening part to resultantly equalize a heating distribution in a heating chamber when the tube axis does not coincide with the center line of a wall surface of the heating chamber. <P>SOLUTION: Since the opening part 5 is formed only on one side when viewed from the tube axis 10 of the waveguide, directivity toward the side having the opening part 5 can be enhanced in relation to the directivity of microwaves radiated into the heating chamber 3 from the opening part 5. In particular, when a linear heating element 13 is disposed at the center of the heating chamber, microwaves having strong directivity can be radiated toward the heating element because the waveguide 2 is disposed on the same wall surface so as to be generally parallel with the heating element 13 and the opening part 5 is formed only on the heating element 13 side when viewed from the tube axis 10. Thereby, heating by the heating element and heating by the microwaves can respectively be equalized. <P>COPYRIGHT: (C)2004,JPO

Description

【０００１】
【発明の属する技術分野】
本発明は、食品などの被加熱物をマイクロ波により加熱するマイクロ波加熱装置に関するものであり、特に導波管から放射されるマイクロ波の向きを開口部により最適化して加熱分布の改良をねらうものである。
【０００２】
【従来の技術】
従来のこの種のマイクロ波加熱装置としては例えば、特開２０００−１６４３４１号公報に記載されているようなものがあった。まず図９は従来のマイクロ波加熱装置の断面構成図、図１０は同斜視図、図１１、図１２は図９のＰ−Ｐ’断面図である。
【０００３】
代表的な放射手段であるマグネトロン１から放射されたマイクロ波は、導波管２により加熱室３内に導かれ、加熱室３内に載置された被加熱物４を加熱するものである。このとき導波管２と加熱室３の結合部には、加熱室３壁面をくりぬいた開口部５を有しており、開口部５は言わばマイクロ波の放射口としての役割をになうものである。導波管２は、幅広のＨ面６と幅の狭いＥ面７により断面がａ×ｂなる箱型に構成され、マグネトロン１の出力アンテナ８から矢印９の方向にマイクロ波を伝送するものである。よって矢印９の方向をマイクロ波の伝送方向と呼ぶことにする。また導波管２の断面（斜線部１０）は、導波管２の対称軸であり、管軸と呼ぶことにする。
【０００４】
導波管２の形状として、一般的には、マイクロ波の波長をλとした場合、Ｈ面の距離ａ（導波管２の幅）をλ／２＜ａ＜λの範囲に、Ｅ面の距離ｂ（導波管２の厚み）をｂ＜λ／２に選ぶことで、ＴＥ１０モードを励振することになる。より具体的には、例えばマイクロ波加熱装置を電子レンジとした場合、λ≒１２２ｍｍ、ａ＝８０〜９０ｍｍ、ｂ＝１５〜４０ｍｍに選ぶことがほとんどである。
【０００５】
図１１の場合、開口部５は導波管幅ａに等しい幅寸法であり、管軸１０に対して対称に配置されているから、図１１の左右方向への指向性も対称となる。また図１２の場合、開口部５、１１ａ、１１ｂを有しているが、やはり管軸１０に対して対称に配置されているから、図１２の左右方向への指向性も対称となる。
【０００６】
また特開平８−１２４６７０号公報には、図１３のような構成が記載されているが、開口部１２ａ、１２ｂは管軸１０に対して対称に配置されているから、図１３の左右方向への指向性も対称となる。
【０００７】
これらの従来のマイクロ波加熱装置は、加熱むらを起こさないようにするために開口部からのマイクロ波をいかに均一に放射させるかを考えた構成であり、管軸に対して対称形状とするのはごく自然な考え方であった。
【０００８】
【発明が解決しようとする課題】
しかしながら前記従来の構成は、管軸が加熱室壁面の中心線と一致する場合に加熱室内を均一に加熱できるということにほかならない。たとえば加熱室が直方体である場合、壁面は長方形となるので対称軸を為す二本の中心線が存在する。このいずれかに導波管の管軸を一致させることができる場合は、管軸に対して対称形状の開口部により加熱室に対しても対称にマイクロ波を放射することができ、均一な分布を期待することができる。
【０００９】
ところがそのような構成にできない場合がある。最近の電子レンジではオーブン機能を有するものが主流であるが、そのためにたとえば図１４のように、天面の中央を管ヒータ１３が横断しているような場合も想定される。この図は電子レンジを上から見た図であり、この時、管ヒータ１３を避けて横に導波管２を平行に配置しようとすると、管軸１０は加熱室３天面の中心線１４、１５のいずれとも一致させることができない。この構成において図１１から図１３に示したような開口部を採用すると、管軸１０に対して対称にマイクロ波が放射されるので、加熱室の後方（図１４の上方）の電界強度が強く、前方（図１４の下方）の電界強度が弱くなり、結果的に被加熱物の後が熱く前が冷たいような加熱むらが起こりやすい。
【００１０】
本発明は前記従来の課題を解決するもので、導波管の管軸と加熱室壁面の中心線が一致しない場合に、開口部構成の工夫によって管軸に対して非対称な指向性を有するマイクロ波放射を引き起こし、結果的に加熱室内における加熱分布を均一化することを目的とするものである。
【００１１】
【課題を解決するための手段】
前記従来の課題を解決するために、本発明のマイクロ波加熱装置は、マイクロ波を放射する放射手段と、管軸から見て片側にのみ構成された開口部を介して前記放射手段を加熱室に結合する導波管とを有するものである。
【００１２】
これによって、管軸に対して開口部のある側への指向性の強いマイクロ波放射を起こすことができ、導波管の管軸と加熱室壁面の中心線が一致しない場合に加熱分布を均一化することができる。
【００１３】
【発明の実施の形態】
請求項１に記載の発明のマイクロ波加熱装置は、マイクロ波を放射する放射手段と、前記放射手段を加熱室に結合する導波管とを備え、前記導波管の管軸から見て片側にのみ開口部を構成したものである。
【００１４】
開口部が導波管の管軸から見て片側にのみ構成されているので、開口部から加熱室内に放射されるマイクロ波の指向性に関しては、開口部のある側への指向性を強くすることができる。
【００１５】
また請求項２に記載の発明のマイクロ波加熱装置は、開口部は、導波管の管軸から見て加熱室壁面の中心側に位置する構成としたものである。
【００１６】
開口部が管軸から見て加熱室天面の中心側に位置するので、加熱室の中心側へのマイクロ波の指向性が強くなる。よって、加熱室の中心が強くて中心から離れるにつれて弱くなるような、加熱室の中心を基準とした対称的なマイクロ波の分布を実現できるので、結果的に被加熱物の加熱分布を均一化することができる。
【００１７】
また請求項３に記載の発明のマイクロ波加熱装置は、開口部、加熱室壁面ともに略長方形状とし、それぞれの長方形状の二本の中心線のうち、一方の中心線は平行でかつ他方の中心線は一致する構成としたものである。
【００１８】
この場合、開口部と加熱室壁面とが平行となり、開口部の二本の中心線の交点から加熱室壁面の二本の中心線の交点に向けて、一致する中心線に沿ってマイクロ波の指向性を強くすることができるとともに、一致する中心線の両側へは対称的にすることができる。よって、加熱室の中心が強くて中心から離れるにつれて弱くなるような、加熱室の中心を基準とした対称的なマイクロ波の分布を容易に実現できるので、結果的に被加熱物の加熱分布を均一化することができる。
【００１９】
また請求項４に記載の発明のマイクロ波加熱装置は、導波管のＨ面で加熱室に結合することで、開口部をＨ面に形成する構成としたものである。
【００２０】
開口部を導波管のＨ面に形成するので、Ｈ面間に発生する電界を利用して、容易に開口部を挟み込むような電界を発生させることができ、この電界の向きに一致する方向を伝搬方向とするような加熱室内の所望の電界強度分布を発生させることができる。よって容易に電界強度分布を制御できる。
【００２１】
また請求項５に記載の発明のマイクロ波加熱装置は、開口部は、導波管の幅方向よりもマイクロ波伝送方向に長い形状としたものである。
【００２２】
開口部は、導波管の幅方向の寸法Ｗよりもマイクロ波伝送方向の寸法Ｌが長いので、導波管内の開口部近傍の電界としては、伝送方向に開口部をまたがる電界よりも幅方向に開口部をまたがる電界が起こりやすく、この電界の向きに一致する方向を伝搬方向とするような加熱室内の所望の電界強度分布を発生させることができる。よって容易に電界強度分布を制御できる。
【００２３】
また請求項６に記載の発明のマイクロ波加熱装置は、開口部の長さは、マイクロ波の導波管内の波長をλｇとしたときに、λｇ／８以上かつ２λｇ以下としたものである。
【００２４】
また請求項７に記載の発明のマイクロ波加熱装置は、開口部の長さは、λｇ／４以上かつλｇ以下としたものである。
【００２５】
開口部の長さＬをλｇ／８以上かつ２λｇ以下とし、中でも特にλｇ／４以上かつλｇ以下としたので、容易に開口部をマイクロ波伝送方向に長い形状とすることができる。特に、長さが短くなりすぎると加熱室にマイクロ波が入りにくくなり、長さが長くなり過ぎると導波管が長くなって部材の量やコストが増えたり、加熱室の強度が弱くなったりする可能性も有る。本発明によれば、適当な長さを選択することができるのでこれらの問題を回避することができる。
【００２６】
また請求項８に記載の発明のマイクロ波加熱装置は、開口部を略長方形状とした時の幅は、１０ｍｍ以上としたものである。
【００２７】
開口部の幅Ｗは導波管の片側つまりａ／２以下で選べるが、１０ｍｍ以上としておけば安全性にも問題が無い。電子レンジなどのように１０００ｋＷ前後の出力の場合は、異常使用時でもスパークなどが起こりにくい構成にすべきであり、１０ｍｍ以上を確保することで、極めて安全に利用できる。
【００２８】
また請求項９に記載の発明のマイクロ波加熱装置は、直状の発熱体を有し、前記発熱体と導波管とを、前記発熱体の長手方向とマイクロ波伝送方向が略平行となるように同一壁面に配置し、開口部は前記導波管の管軸から見て前記発熱体側にのみ構成されたものである。
【００２９】
管軸から見て開口部を発熱体側にのみ構成したので、発熱体側に指向性の強いマイクロ波放射ができる。発熱体が一本の場合、発熱体による輻射加熱分布を均一するためには、できるだけ加熱室中央に配置したいということが想定される。本発明の構成により、発熱体を加熱室中央付近に配置しつつ、マイクロ波放射も発熱体側、即ち加熱室中央に向けることができ、発熱体による加熱とマイクロ波による加熱を、それぞれ均一にすることができる。
【００３０】
また請求項１０に記載の発明のマイクロ波加熱装置は、壁面上に直状のしぼり部を形成し、前記しぼり部と導波管とを、前記しぼり部の長手方向とマイクロ波伝送方向が略平行となるように同一壁面に配置し、開口部は前記導波管の管軸から見て前記しぼり部側にのみ構成されたものである。
【００３１】
開口部を管軸から見てしぼり部側にのみ構成することで、しぼり部側に指向性の強いマイクロ波放射ができる。よって、しぼり部があるために導波管の配置が制限される場合でも、しぼり部側に向けて強いマイクロ波放射が可能となり、しぼり部の有無の影響を受けずに被加熱物を均一に加熱することができる。
【００３２】
また請求項１１に記載の発明のマイクロ波加熱装置は、壁面の中央に導波管配置を妨げる部品を有する時、前記部品側に前記導波管のＥ面を対向させて配置し、開口部は前記導波管の管軸から見て前記部品側に位置する構成としたものである。
【００３３】
開口部を管軸から見て部品側にのみ構成することで、部品側に指向性の強いマイクロ波放射ができる。よって、部品があるために導波管の配置が制限される場合でも、部品側に向けて強いマイクロ波放射が可能となり、部品の有無の影響を受けずに被加熱物を均一に加熱することができる。
【００３４】
また請求項１２に記載の発明のマイクロ波加熱装置は、加熱室内に被加熱物を載置する載置網を有し、載置網の網目を開口部と略平行に構成したものである。
【００３５】
載置網の網目を開口部と平行に配置すると、開口部の幅方向ににかかる向きの電界がそのまま網目の幅方向にもかかりやすく、電界が順次網目間を伝わって載置網上を伝搬することになるので、載置網に沿って均一な電界分布が得やすい。
【００３６】
さらに請求項１３に記載の発明のマイクロ波加熱装置は、開口部の近傍でマイクロ波を攪拌する攪拌手段を有するものである。
【００３７】
攪拌手段でマイクロ波を攪拌することにより、マイクロ波が加熱室内で共振することによる定在波の発生を防ぎ、定在波による加熱むらを抑えてより均一化することができる。
【００３８】
以上によって、管軸に対して開口部のある側への指向性の強いマイクロ波放射を起こすことができ、導波管の管軸と加熱室壁面の中心線が一致しない場合に加熱分布を均一化することができる。
【００３９】
【実施例】
以下、本発明の実施例について図面を参照しながら説明する。
【００４０】
（実施例１）
図１、図２は、本発明の実施例１におけるマイクロ波加熱装置の構成図である。図１は上から見た図、図２は図１の加熱室の第２の中心線１５での断面を右から見た図である。
【００４１】
代表的な放射手段としてのマグネトロン１から放射されたマイクロ波は、導波管２により加熱室３内に導かれ、加熱室３内に載置された被加熱物４を加熱するものである。このとき導波管２と加熱室３の結合部には開口部５を有しており、開口部５は言わばマイクロ波の放射口としての役割をになうものである。導波管２は、幅広のＨ面６と幅の狭いＥ面７により断面がａ×ｂなる箱型に構成されており、Ｈ面６側で加熱室に結合されているため開口部５もＨ面６側に存在する構成である。マイクロ波の伝送方向は、図１で示すとマグネトロン１の出力アンテナ８から管軸１０を左方向に伝送していくものである。このときマイクロ波の自由空間内での波長λ＝１２２ｍｍ、ａ＝８０ｍｍ、ｂ＝１５〜４０ｍｍを選んだ場合、導波管内の伝送方向の波長（管内波長）をλｇとすると、λｇ＝λ／（１−（λ／（２ａ））＾２）＾０．５≒１８９ｍｍとなる。加熱室３の天面にはミラクロンヒータなどの管ヒータに代表される直状の発熱体１３を有し、被加熱物４に焦げ目をつけるなどオーブン調理やトースター調理に使用されるものである。このとき発熱体１３を避けるため導波管２は加熱室の後方（図１の上側、図２の右側）に配置せざるを得ず、開口部も同様の配置となる。１６は加熱室天面のしぼり部であり、開口部５はしぼり部１６の上面のフラットな部位に形成されている。
【００４２】
またこのとき図１から明らかなように、開口部５は長さＬで幅Ｗの細長い長方形状（導波管２の幅方向に狭く伝送方向に長い）であり、開口部５の対称軸を為す二本の中心線１７、１５が、略長方形の加熱室天面の対称軸を為す二本の中心線１４、１５と以下のような関係にある。即ち第１の中心線同志（１４と１７）は平行、第２の中心線同志（いずれも１５）は共通である。この構成では、中心線１４、１５の交点１８を加熱室３天面の中心と考えると、開口部５は管軸１０から見て加熱室の中心１８側に位置する構成である。
【００４３】
また本実施例では、開口部５の形状は、Ｌ＝１２０ｍｍ、Ｗ＝２０ｍｍを選んでいる。また、ドア１９は加熱室３正面に開閉自在に取りつけられたドア、載置網２０は被加熱物４を載置するものである。載置網２０については、図３に上から見た図を示したが、載置網の網目は多数の細長い形状のスリット２１により形成されており、スリット２１と開口部５とは平行な向きに構成されている。また図２にはしぼり部１６の内部に攪拌手段としてのアンテナ２２を配置し、アンテナ軸２３を回転させることで、時間とともにアンテナ２２の向きを変え、マイクロ波を攪拌することで均一化を果たしている。
【００４４】
引き続き開口部５の作用についてシミュレーション結果を用いて補足する。図４、図５は開口部形状による電界強度のシミュレーション結果を示し、図４は従来の開口部２４の場合、図５は本実施例の開口部５の場合である。また図４、図５とも（ａ）は開口の下方２０ｍｍの電界強度、（ｂ）は開口の下方８０ｍｍの電界強度を示しており、図中の線は等電界強度線である。図４、図５とも（ａ）より（ｂ）の方が等電界強度線の目が粗いので、電界強度が弱くなっていることになり、即ち開口部から遠ざかると電界強度が弱くなることがわかる。
【００４５】
まず図４の従来の開口部２４の場合、管軸１０に沿って右側から伝送されてきたマイクロ波に対して、開口は管軸１０に対して対称形状なので図の上方と下方に対称な電界強度分布となる。また一般に導波管内では対向するＨ面間に電界が立っているので、辺ｃからも電界が立とうとしており、今回のようにＨ面上に開口部２４を設けた場合は、開口部２４を挟み込むようにｃからｅ（あるいはｅからｃ）向きの電界が容易に発生する。通常、導波管内ではＴＥ１０モードが起こっており、導波管の中央（管軸１０）での電界が最も強く、導波管の端部での電界は０になることが知られている。
【００４６】
よって辺ｄや辺ｆは電界が０になろうとする位置であるために、ｃあるいはｅからの電界を受け入れられず、ｃ−ｅ間にのみ電界が発生する。そしてこの電界の向きにより、図の左右方向に電界が伝搬しやすくなり、等電界強度線が左右に伸びたような形状となっている。
【００４７】
一方図５の本実施例の場合、まず管軸１０に沿って右側から伝送されてきたマイクロ波に対して、開口部５は管軸１０に対して非対称形状なので図５の上方と下方に非対称な電界強度分布となる。特に開口部５から加熱室にマイクロ波が伝送されるのだから、開口部５での電界強度が強くなる。
【００４８】
また一般に導波管内では対向するＨ面間に電界が立っているので、今回のようにＨ面上に開口部２４を設けた場合は、辺ｃ’と辺ｄ’から電界が立とうとしている。また導波管内のＴＥ１０モードにおいては、導波管の中央（管軸１０）での電界が最も強く、導波管の端部での電界は０になることが知られている。ｃ’は端部寄りにあり、ｄ’は中央部寄りにあるので、結局ｄ’からの電界の方が強くて支配的になるのではないかと考えられる。ここでｄ’から見るとｆ’までの距離が最も近く、ｄ’からｆ’（あるいはｆ’からｄ’）向きの電界が容易に起こる構成である。そしてこの電界の向きにより、図の上下方向に電界が伝搬しやすくなり、等電界強度線が上下に伸びたような形状となる。ただし、この場合は開口形状によって特性が大きく変わってくる。ｄ’−ｆ’間の距離を長くして、たとえばｄ’が管軸１０をまたいで反対側（図の上方向）まで伸びてくるとｃ’の一部も導波管の中央に存在することになってしまうのでｃ’からの電界も強くなってくる。またｃ’−ｅ’間の距離が短くなってくるとｃ’からｅ’に向かう電界が生じやすくなってきて、たとえば図４と図５を平均したような分布も考えられる。
【００４９】
よって本発明の効果を生かすには、導波管の幅方向よりもマイクロ波伝送方向に細長い開口形状が望ましい。具体的には管内波長λｇを用いて、開口部の長さ（図１のＬ）はλｇ／８以上かつ２λｇ以下、できればλｇ／４以上かつλｇ以下が望ましい。ちなみに長さが長くなり過ぎると、導波管が長くなって部材の量やコストが増えたり、加熱室の強度が弱くなったりする可能性も有る。そして特に本実施例ではλｇ＝１８９ｍｍでＬ＝１２０ｍｍとしている。
【００５０】
一方、開口部の幅（図１のＷ）は導波管の片側つまりａ／２以下が望ましいが、電子レンジなどのように１０００ｋＷ前後の出力の場合は、異常使用時でもスパークなどを回避するという安全性を考慮して１０ｍｍ以上にすることが望ましい。特に本実施例ではａ＝８０ｍｍでＷ＝２０ｍｍとしている。
【００５１】
図６は本実施例の特性図であり、被加熱物として４つの紙コップに２００ｃｃずつ水を入れて図のように配置して加熱した場合の温度分布を示している。配置がわかるように導波管２、加熱室３、開口部５についても記している。図中の数字は、７０秒間加熱して、加熱終了後の温度と加熱前の温度との差をとった温度上昇度で示している。温度上昇度は水に入った電力に比例すると考えて良いので、４つの紙コップに加わった電力は極めて近く、電界強度分布が均一であることを示すものである。開口部と紙コップ内の水の距離を考えると、図５（ｂ）の電界強度分布で加熱されたのではないかと考えられるが、図５（ｂ）では開口部よりもやや下側に等電界強度線の中心があるようなので、これが、図６で示すところの加熱室の第１の中心線１４上にほぼ一致し、このために極めて均一に加熱されたのではないかと考えられる。また図６によれば左右方向にも均一であるが、これについても図５の通りである。
【００５２】
最後に、本実施例のマイクロ波加熱装置による効果について記載する。
【００５３】
まず、開口部５が導波管の管軸１０から見て片側にのみ構成されているので、開口部５から加熱室３内に放射されるマイクロ波の指向性に関しては、開口部５のある側への指向性を強くすることができる。
【００５４】
特に、この開口部５が管軸１０から見て加熱室３天面の中心１８側に位置するので、加熱室３の中心１８側へのマイクロ波の指向性が強くなり、結果的に加熱室内における加熱分布を均一化することができる。
【００５５】
また、開口部５、加熱室３天面ともに略長方形状であり、それぞれの二本の中心線のうち、一方の中心線１４、１７が平行でかつ他方の中心線１５は一致する。この時のマイクロ波の指向性は、図１、図５の開口部５の上下方向には下向きに強くなり、かつ開口部５の左右方向へは対称的にすることができる。つまり加熱室に対して均一に放射することができる。
【００５６】
また、開口部５を導波管２のＨ面６に形成するので、Ｈ面間に発生する電界を利用して、容易に開口部５を挟み込むような電界を発生させることができ、この電界の向きに一致する方向を伝搬方向とするような加熱室３内の所望の電界強度分布を発生させることができる。
【００５７】
また、開口部５は、導波管２の幅方向の寸法Ｗよりもマイクロ波伝送方向の寸法Ｌが長いので、導波管２内の開口部５近傍の電界としては、伝送方向に開口部をまたがる電界よりも幅方向に開口部をまたがる電界が起こりやすく、この電界の向きに一致する方向を伝搬方向とするような加熱室３内の所望の電界強度分布を発生させることができる。
【００５８】
また、開口部の長さＬをλｇ／８以上かつ２λｇ以下とし、中でもλｇ／４以上かつλｇ以下としたので、容易に開口部５をマイクロ波伝送方向に長い形状とすることができる。本実施例では、Ｌ＝１２０ｍｍとして示したが、これに限定されるものではない。長さが短くなる（例えば４０ｍｍ未満）と加熱室３にマイクロ波が入りにくくなる場合があり、長さが長くなり過ぎる（たとえば２００ｍｍ超）と導波管が長くなって部材の量やコストが増えたり、加熱室の強度が弱くなったりする可能性も有る。そして特に本実施例ではλｇ＝１８９ｍｍでＬ＝１２０ｍｍとしている。
【００５９】
また、開口部５の幅Ｗは導波管の片側つまりａ／２以下で選べば良いが、電子レンジなどのように１０００ｋＷ前後の出力の場合は、異常使用時でもスパークなどを回避するという安全性を考慮して１０ｍｍ以上にすることが望ましい。特に本実施例ではａ＝８０ｍｍでＷ＝２０ｍｍとしている。
【００６０】
また、直状の発熱体１３と導波管２とを略平行となるように同一壁面に配置し、管軸１０から見て開口部５を発熱体１３側にのみ構成したので、発熱体側に指向性の強いマイクロ波放射ができる。特に図１、図２のような一本の発熱体の場合、発熱体による輻射加熱分布を均一するためには、できるだけ加熱室中央に配置したいということが想定される。本実施例では、発熱体１３を加熱室中央付近に配置しつつ、マイクロ波放射も加熱室中央に向けることができ、発熱体による加熱とマイクロ波による加熱を、それぞれ均一にすることができる。
【００６１】
また、載置網２０のスリット２１を開口部５と平行に配置したので、開口部５の幅方向ににかかる向きの電界がそのままスリット２１の幅方向にもかかりやすく、電界が載置網２０上を伝搬しやすいので、より均一化の効果が見込める。
【００６２】
さらに、開口部５の近傍でマイクロ波を攪拌するアンテナ２２を有するので、マイクロ波の加熱室３内の共振による定在波の発生を防ぎ、定在波による加熱むらを抑えてより均一化することができる。
【００６３】
（実施例２）
図７は、本発明の実施例２のマイクロ波加熱装置の構成図である。
【００６４】
代表的なマイクロ波加熱装置である電子レンジを斜め前から見た構成であり、加熱室３の側壁に導波管２、三角形の開口部２５、開口部をふさぎつつマイクロ波を透過させる材質（マイカやポリプロピレン）からなるカバー２６、直状のしぼり部で構成されたレール２７、被加熱物を載置して回転させるターンテーブル２８などを有している。特にレール２７を壁面のしぼり部で構成する方法は、オーブン機能を有する製品の場合に角皿を乗せるために良く用いられる構成である。
【００６５】
本実施例では、レール２７と導波管２とを略平行に配置し、開口部２５を管軸１０から見てレール２７側にのみ構成することで、レール側に指向性の強いマイクロ波放射ができる。よって図７のようにレール２７があるために導波管２が壁面の上方にしか配置できない場合でも、下向きのマイクロ波放射が実現できるので、被加熱物を均一に加熱することができる。特に被加熱物の形状が平らなものの場合、ターンテーブル２８に置くと随分低い位置に被加熱物があることになるので、より顕著な効果が期待できる。
【００６６】
（実施例３）
図８は、本発明の実施例３のマイクロ波加熱装置の構成図である。
【００６７】
本実施例では、開口部２８がＬ字型であり、加熱室２９の壁面形状が長方形状ではなく五角形となっている。もちろん本発明は開口部、加熱室ともに長方形状のみに限定されるものではない。たとえば本実施例の場合、実際の加熱室２９を３０のように広げて考えても良い。こうすれば加熱室の第１の中心線３１、加熱室の第２の中心線３２、加熱室の中心３３を決めることができ、実施例１で述べた本発明の構成を応用することができる。
【００６８】
また本実施例の開口部２８のような形状の場合、マイクロ波放射の指向性は矢印３４のように、傾向として図８の上から下だけではなく、右から左への指向性も出てくるようである。よってこのような場合は導波管２および開口部２８を加熱室の第２の中心線３２よりも右側に配置することで均一加熱が可能である。
【００６９】
また本実施例では加熱室の中心３３に導波管配置を妨げる部品３５があるが、これはたとえば赤外線センサであるとか湿度センサであるとか、通気用のパンチング孔であるとか庫内灯であるとか、スタラー用のモータであるとか、いろいろな部品が考えられる。もちろんここに記載したものでなくても、導波管配置を妨げるようなものがある場合、本発明の考え方に基づき、開口部の形状と導波管配置を変えることで、加熱室内にマイクロ波を均一に放射することが可能となり、被加熱物を均一に加熱することができる。
【００７０】
【発明の効果】
以上のように、本発明のマイクロ波加熱装置は、マイクロ波を放射する放射手段と、前記放射手段を加熱室に結合する導波管と、前記導波管と前記加熱室の結合部に設けた開口部を有し、前記開口部は前記導波管の管軸から見て片側にのみ構成するものである。
【００７１】
これによって、管軸に対して開口部のある側への指向性の強いマイクロ波放射を起こすことができ、導波管の管軸と加熱室壁面の中心線が一致しない場合に加熱分布を均一化することができる。
【図面の簡単な説明】
【図１】本発明の実施例１におけるマイクロ波加熱装置の構成図
【図２】本発明の実施例１におけるマイクロ波加熱装置の断面構成図
【図３】本発明の実施例１における載置網の構成図
【図４】本発明の実施例１と比較するため、従来例に関してシミュレーションで求めた電界強度分布図
（ａ）開口下２０ｍｍの電界強度分布図
（ｂ）開口下８０ｍｍの電界強度分布図
【図５】本発明の実施例１に関してシミュレーションで求めた電界強度分布図
（ａ）開口下２０ｍｍの電界強度分布図
（ｂ）開口下８０ｍｍの電界強度分布図
【図６】本発明の実施例１における紙コップ内の水の温度分布図
【図７】本発明の実施例２におけるマイクロ波加熱装置の構成図
【図８】本発明の実施例３におけるマイクロ波加熱装置の構成図
【図９】従来のマイクロ波加熱装置の構成図
【図１０】従来のマイクロ波加熱装置のマグネトロンと導波管の斜視構成図
【図１１】従来のマイクロ波加熱装置の開口部の構成図
【図１２】従来のマイクロ波加熱装置の開口部の構成図
【図１３】従来のマイクロ波加熱装置の開口部の構成図
【図１４】発熱体を有するマイクロ波加熱装置の構成図
【符号の説明】
１　マグネトロン（放射手段）
２　導波管
３、２９　加熱室
４　被加熱物
５、２５、２８　開口部
６　Ｈ面
７　Ｅ面
１０　管軸
１３　発熱体
１４、３１　加熱室の第１の中心線
１５　加熱室の第２の中心線、開口部の第２の中心線
１７　開口部の第１の中心線
１８、３３　加熱室の中心
１９　載置網
２１　スリット（網目）
２７　レール（しぼり部）
３２　加熱室の第２の中心線
３５　部品[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a microwave heating apparatus that heats an object to be heated such as food by microwaves, and in particular, aims to improve the heating distribution by optimizing the direction of microwaves radiated from a waveguide with openings. Is.
[0002]
[Prior art]
As a conventional microwave heating apparatus of this type, for example, there is one described in Japanese Patent Laid-Open No. 2000-164341. First, FIG. 9 is a sectional configuration diagram of a conventional microwave heating apparatus, FIG. 10 is a perspective view thereof, and FIGS. 11 and 12 are sectional views taken along the line PP ′ of FIG.
[0003]
The microwave radiated from the magnetron 1 which is a typical radiating means is guided into the heating chamber 3 by the waveguide 2 and heats the object to be heated 4 placed in the heating chamber 3. At this time, the coupling portion between the waveguide 2 and the heating chamber 3 has an opening 5 formed by hollowing out the wall surface of the heating chamber 3, and the opening 5 serves as a microwave radiation port. It is. The waveguide 2 is configured in a box shape having a cross section of a × b by a wide H surface 6 and a narrow E surface 7, and transmits microwaves in the direction of arrow 9 from the output antenna 8 of the magnetron 1. is there. Therefore, the direction of arrow 9 will be referred to as the microwave transmission direction. The cross section (shaded portion 10) of the waveguide 2 is the axis of symmetry of the waveguide 2 and will be referred to as the tube axis.
[0004]
As the shape of the waveguide 2, generally, when the wavelength of the microwave is λ, the distance a of the H surface (the width of the waveguide 2) is in the range of λ / 2 <a <λ, and the E surface. By selecting the distance b (thickness of the waveguide 2) as b <λ / 2, the TE10 mode is excited. More specifically, for example, when the microwave heating apparatus is a microwave oven, λ≈122 mm, a = 80 to 90 mm, and b = 15 to 40 mm are almost always selected.
[0005]
In the case of FIG. 11, the opening 5 has a width dimension equal to the waveguide width a and is arranged symmetrically with respect to the tube axis 10, so the directivity in the left-right direction in FIG. 11 is also symmetric. In the case of FIG. 12, the openings 5, 11 a, and 11 b are provided. However, since they are arranged symmetrically with respect to the tube axis 10, the directivity in the left-right direction in FIG. 12 is also symmetric.
[0006]
Japanese Patent Laid-Open No. 8-124670 discloses a configuration as shown in FIG. 13, but the openings 12a and 12b are arranged symmetrically with respect to the tube axis 10, so that the horizontal direction in FIG. The directivity of is also symmetric.
[0007]
These conventional microwave heating devices have a configuration that considers how to uniformly radiate microwaves from the opening in order to prevent uneven heating, and have a symmetrical shape with respect to the tube axis. Was a very natural way of thinking.
[0008]
[Problems to be solved by the invention]
However, the conventional configuration is nothing but that the heating chamber can be heated uniformly when the tube axis coincides with the center line of the wall surface of the heating chamber. For example, when the heating chamber is a rectangular parallelepiped, the wall surface is rectangular, so there are two center lines that form the axis of symmetry. If the tube axis of the waveguide can coincide with either of these, microwaves can be radiated symmetrically to the heating chamber through openings symmetrical to the tube axis, and the distribution is uniform. Can be expected.
[0009]
However, there are cases where such a configuration is not possible. In recent microwave ovens, those having an oven function are the mainstream. For this reason, for example, as shown in FIG. 14, a case where the tube heater 13 crosses the center of the top surface is assumed. This figure is a view of the microwave oven as viewed from above. At this time, if the waveguide 2 is arranged in parallel to avoid the tube heater 13, the tube axis 10 is aligned with the center line 14 of the top surface of the heating chamber 3. , 15 cannot be matched. If an opening as shown in FIGS. 11 to 13 is employed in this configuration, microwaves are radiated symmetrically with respect to the tube axis 10, so that the electric field strength behind the heating chamber (upper in FIG. 14) is strong. The electric field strength in the front (lower side in FIG. 14) becomes weak, and as a result, heating unevenness is likely to occur such that the object to be heated is hot and the object is cold.
[0010]
The present invention solves the above-described conventional problems. When the tube axis of the waveguide and the center line of the heating chamber wall surface do not coincide with each other, the invention has a directivity that is asymmetric with respect to the tube axis by devising the opening configuration. The object is to cause wave radiation and, as a result, to uniform the heating distribution in the heating chamber.
[0011]
[Means for Solving the Problems]
In order to solve the above-described conventional problems, a microwave heating apparatus according to the present invention includes a radiating unit that radiates microwaves, and a radiating unit that is provided only on one side when viewed from the tube axis. And a waveguide coupled to the.
[0012]
This makes it possible to generate highly directional microwave radiation toward the side with the opening relative to the tube axis, and the heating distribution is uniform when the tube axis of the waveguide does not coincide with the center line of the heating chamber wall surface. Can be
[0013]
DETAILED DESCRIPTION OF THE INVENTION
The microwave heating apparatus according to the first aspect of the present invention includes a radiating unit that radiates microwaves, and a waveguide that couples the radiating unit to a heating chamber, and one side as viewed from the tube axis of the waveguide. The opening is configured only in the case.
[0014]
Since the opening is configured only on one side when viewed from the tube axis of the waveguide, the directivity of the microwave radiated from the opening into the heating chamber is strengthened toward the side where the opening is located. be able to.
[0015]
In the microwave heating apparatus according to the second aspect of the present invention, the opening is positioned on the center side of the wall surface of the heating chamber as viewed from the tube axis of the waveguide.
[0016]
Since the opening is positioned on the center side of the top surface of the heating chamber when viewed from the tube axis, the directivity of the microwave toward the center side of the heating chamber is enhanced. Therefore, it is possible to realize a symmetrical microwave distribution based on the center of the heating chamber, where the center of the heating chamber is strong and weakens as it moves away from the center, resulting in uniform heating distribution of the object to be heated. can do.
[0017]
In the microwave heating apparatus according to the third aspect of the present invention, both the opening and the heating chamber wall surface are substantially rectangular, and one of the two center lines of the rectangular shape is parallel to the other and The center line is configured to match.
[0018]
In this case, the opening and the wall surface of the heating chamber are parallel to each other, and the microwaves pass along the matching center line from the intersection of the two center lines of the opening toward the intersection of the two center lines of the wall of the heating chamber. The directivity can be increased, and both sides of the coincident center line can be symmetrical. Therefore, it is possible to easily realize a symmetrical microwave distribution based on the center of the heating chamber so that the center of the heating chamber is strong and weakens as the distance from the center increases. It can be made uniform.
[0019]
According to a fourth aspect of the present invention, there is provided a microwave heating device having a structure in which an opening is formed in the H plane by coupling to the heating chamber at the H plane of the waveguide.
[0020]
Since the opening is formed in the H plane of the waveguide, an electric field that easily sandwiches the opening can be generated using the electric field generated between the H planes, and the direction matches the direction of the electric field. It is possible to generate a desired electric field intensity distribution in the heating chamber such that the direction of propagation is the propagation direction. Therefore, the electric field strength distribution can be easily controlled.
[0021]
In the microwave heating apparatus according to the fifth aspect of the present invention, the opening has a shape that is longer in the microwave transmission direction than in the width direction of the waveguide.
[0022]
Since the opening has a dimension L in the microwave transmission direction that is longer than the dimension W in the width direction of the waveguide, the electric field near the opening in the waveguide is wider than the electric field across the opening in the transmission direction. It is possible to generate a desired electric field strength distribution in the heating chamber such that the electric field across the opening is likely to occur, and the propagation direction is a direction that coincides with the direction of the electric field. Therefore, the electric field strength distribution can be easily controlled.
[0023]
In the microwave heating apparatus according to the sixth aspect of the invention, the length of the opening is set to λg / 8 or more and 2λg or less when the wavelength in the microwave waveguide is λg.
[0024]
In the microwave heating apparatus according to the seventh aspect of the present invention, the length of the opening is λg / 4 or more and λg or less.
[0025]
Since the length L of the opening is not less than λg / 8 and not more than 2λg, and particularly not less than λg / 4 and not more than λg, the opening can be easily made long in the microwave transmission direction. In particular, if the length is too short, it will be difficult for microwaves to enter the heating chamber, and if the length is too long, the waveguide will become longer, increasing the amount and cost of members, and reducing the strength of the heating chamber. There is also a possibility of doing. According to the present invention, since an appropriate length can be selected, these problems can be avoided.
[0026]
In the microwave heating apparatus according to an eighth aspect of the present invention, the width when the opening is made substantially rectangular is 10 mm or more.
[0027]
The width W of the opening can be selected on one side of the waveguide, that is, a / 2 or less, but if it is 10 mm or more, there is no problem in safety. In the case of an output of about 1000 kW, such as a microwave oven, it should be configured such that no spark or the like occurs even during abnormal use, and can be used extremely safely by securing 10 mm or more.
[0028]
According to a ninth aspect of the present invention, there is provided a microwave heating apparatus having a straight heating element, wherein the heating element and the waveguide are substantially parallel to each other in the longitudinal direction of the heating element and the microwave transmission direction. The openings are arranged only on the heating element side when viewed from the tube axis of the waveguide.
[0029]
Since the opening is configured only on the heating element side as viewed from the tube axis, microwave radiation with strong directivity can be generated on the heating element side. In the case where there is one heating element, it is assumed that it is desired to place the heating element in the center of the heating chamber as much as possible in order to make the radiation heating distribution by the heating element uniform. With the configuration of the present invention, the heating element is arranged near the center of the heating chamber, and the microwave radiation can also be directed to the heating element side, that is, the center of the heating chamber, so that heating by the heating element and heating by the microwave are made uniform. be able to.
[0030]
In the microwave heating apparatus of the invention described in claim 10, a straight squeezing part is formed on a wall surface, and the squeezing part and the waveguide are arranged so that the longitudinal direction of the squeezing part and the microwave transmission direction are substantially the same. It arrange | positions on the same wall surface so that it may become parallel, and an opening part is comprised only in the said narrowing part side seeing from the tube axis | shaft of the said waveguide.
[0031]
By configuring the opening only on the narrowed portion side when viewed from the tube axis, microwave radiation with strong directivity can be generated on the narrowed portion side. Therefore, even when the placement of the waveguide is limited due to the presence of the squeezed part, strong microwave radiation toward the squeezed part side is possible, and the object to be heated is made uniform without being affected by the presence or absence of the squeezed part Can be heated.
[0032]
The microwave heating device according to the invention of claim 11 is provided with an opening portion, when a component that obstructs the waveguide arrangement is provided at the center of the wall surface, with the E surface of the waveguide facing the component side. Is configured to be positioned on the component side when viewed from the tube axis of the waveguide.
[0033]
By configuring the opening only on the component side when viewed from the tube axis, microwave radiation with strong directivity can be generated on the component side. Therefore, even if the placement of the waveguide is limited due to the presence of components, strong microwave radiation toward the component side is possible, and the object to be heated is uniformly heated without being affected by the presence or absence of the component. Can do.
[0034]
A microwave heating apparatus according to a twelfth aspect of the present invention has a placing net for placing an object to be heated in a heating chamber, and the mesh of the placing net is configured substantially parallel to the opening.
[0035]
If the mesh of the placement network is arranged in parallel with the opening, the electric field in the direction of the width of the opening is likely to be applied to the width of the mesh as it is, and the electric field propagates through the placement network sequentially between the meshes. Therefore, it is easy to obtain a uniform electric field distribution along the placement network.
[0036]
Furthermore, the microwave heating device of the invention described in claim 13 has a stirring means for stirring the microwave in the vicinity of the opening.
[0037]
By stirring the microwave with the stirring means, it is possible to prevent the standing wave from being generated due to the resonance of the microwave in the heating chamber, and to make the heating uneven by the standing wave more uniform.
[0038]
By the above, microwave radiation with strong directivity to the side with the opening with respect to the tube axis can be generated, and the heating distribution is uniform when the tube axis of the waveguide does not coincide with the center line of the heating chamber wall surface. Can be
[0039]
【Example】
Embodiments of the present invention will be described below with reference to the drawings.
[0040]
Example 1
1 and 2 are configuration diagrams of a microwave heating apparatus according to Embodiment 1 of the present invention. FIG. 1 is a view seen from above, and FIG. 2 is a view seen from the right of a cross section taken along the second center line 15 of the heating chamber of FIG.
[0041]
The microwave radiated from the magnetron 1 as a typical radiating means is guided into the heating chamber 3 by the waveguide 2 and heats the object to be heated 4 placed in the heating chamber 3. At this time, the coupling portion between the waveguide 2 and the heating chamber 3 has an opening 5, and the opening 5 serves as a microwave emission port. The waveguide 2 is formed in a box shape having a cross section of a × b by a wide H surface 6 and a narrow E surface 7. Since the waveguide 2 is coupled to the heating chamber on the H surface 6 side, the opening 5 is also formed. This is a configuration existing on the H surface 6 side. As shown in FIG. 1, the transmission direction of the microwave is such that the tube shaft 10 is transmitted leftward from the output antenna 8 of the magnetron 1. At this time, when wavelengths λ = 122 mm, a = 80 mm, and b = 15 to 40 mm in the free space of the microwave are selected, assuming that the wavelength in the transmission direction (in-tube wavelength) in the waveguide is λg, λg = λ / (1- (λ / (2a)) ^ 2) ^ 0.5≈189 mm. The top surface of the heating chamber 3 has a straight heating element 13 typified by a tube heater such as a miraclon heater, and is used for oven cooking and toaster cooking such as scorching the object 4 to be heated. . At this time, in order to avoid the heating element 13, the waveguide 2 has to be arranged behind the heating chamber (upper side in FIG. 1, right side in FIG. 2), and the opening is similarly arranged. Reference numeral 16 denotes a squeezed portion on the top surface of the heating chamber, and the opening 5 is formed in a flat portion on the upper surface of the squeezed portion 16.
[0042]
At this time, as is clear from FIG. 1, the opening 5 has an elongated rectangular shape with a length L and a width W (narrow in the width direction of the waveguide 2 and long in the transmission direction). The two center lines 17 and 15 have the following relationship with the two center lines 14 and 15 that form the symmetry axis of the substantially rectangular heating chamber top surface. That is, the first center lines (14 and 17) are parallel, and the second center lines (15 are both). In this configuration, when the intersection 18 of the center lines 14 and 15 is considered as the center of the top surface of the heating chamber 3, the opening 5 is positioned on the center 18 side of the heating chamber as viewed from the tube axis 10.
[0043]
In the present embodiment, L = 120 mm and W = 20 mm are selected as the shape of the opening 5. The door 19 is a door that can be freely opened and closed in front of the heating chamber 3, and the placement net 20 is for placing the article to be heated 4. FIG. 3 shows the placement net 20 as viewed from above. The mesh of the placement net is formed by a number of elongated slits 21, and the slit 21 and the opening 5 are oriented in parallel. It is configured. Also, in FIG. 2, an antenna 22 as an agitating means is arranged inside the squeezing portion 16, and the antenna shaft 23 is rotated to change the direction of the antenna 22 with time and to achieve uniformity by agitating the microwave. Yes.
[0044]
Subsequently, the operation of the opening 5 will be supplemented using simulation results. 4 and 5 show the simulation results of the electric field strength by the shape of the opening, FIG. 4 shows the case of the conventional opening 24, and FIG. 5 shows the case of the opening 5 of the present embodiment. 4A and 5B, (a) shows the electric field intensity 20 mm below the opening, and (b) shows the electric field intensity 80 mm below the opening, and the lines in the figure are equal electric field intensity lines. 4 and 5, the equal electric field strength lines are coarser in (b) than in (a), so that the electric field strength is weak, that is, the electric field strength is weakened when moving away from the opening. Recognize.
[0045]
First, in the case of the conventional opening 24 shown in FIG. 4, with respect to the microwave transmitted from the right side along the tube axis 10, the opening is symmetrical with respect to the tube axis 10. Intensity distribution. In general, since an electric field stands between the H planes facing each other in the waveguide, the electric field tends to stand from the side c. When the opening 24 is provided on the H plane as in this case, the opening 24 is provided. An electric field in the direction from c to e (or from e to c) is easily generated so as to sandwich the gap. It is known that the TE10 mode usually occurs in the waveguide, the electric field at the center of the waveguide (tube axis 10) is the strongest, and the electric field at the end of the waveguide is zero.
[0046]
Therefore, since the side d and the side f are positions where the electric field is about to be zero, the electric field from c or e cannot be accepted, and an electric field is generated only between c and e. The direction of the electric field makes it easier for the electric field to propagate in the left-right direction in the figure, and the shape of the electric field strength line extends to the left and right.
[0047]
On the other hand, in the case of the present embodiment of FIG. 5, the opening 5 is asymmetric with respect to the tube axis 10 with respect to the microwave transmitted from the right side along the tube axis 10. Electric field strength distribution. In particular, since microwaves are transmitted from the opening 5 to the heating chamber, the electric field strength at the opening 5 is increased.
[0048]
In general, since an electric field stands between the H planes facing each other in the waveguide, when the opening 24 is provided on the H plane as in this case, the electric field tends to rise from the side c ′ and the side d ′. . In the TE10 mode in the waveguide, it is known that the electric field at the center of the waveguide (tube axis 10) is the strongest and the electric field at the end of the waveguide is zero. Since c ′ is closer to the end and d ′ is closer to the center, it is considered that the electric field from d ′ is stronger and dominant. Here, when viewed from d ′, the distance from f ′ is the shortest, and an electric field in the direction from d ′ to f ′ (or from f ′ to d ′) easily occurs. Then, depending on the direction of the electric field, the electric field easily propagates in the vertical direction in the figure, and the shape of the electric field strength line extends vertically. In this case, however, the characteristics vary greatly depending on the opening shape. When the distance between d ′ and f ′ is increased, for example, d ′ extends across the tube axis 10 to the opposite side (upward in the figure), part of c ′ is also present at the center of the waveguide. As a result, the electric field from c ′ also becomes stronger. Further, as the distance between c ′ and e ′ becomes shorter, an electric field from c ′ to e ′ is likely to be generated, and for example, a distribution that averages FIGS. 4 and 5 can be considered.
[0049]
Therefore, in order to take advantage of the effect of the present invention, an opening shape that is elongated in the microwave transmission direction rather than the width direction of the waveguide is desirable. Specifically, using the in-tube wavelength λg, the length of the opening (L in FIG. 1) is preferably λg / 8 or more and 2λg or less, preferably λg / 4 or more and λg or less. Incidentally, if the length becomes too long, there is a possibility that the waveguide becomes longer and the amount and cost of members increase, and the strength of the heating chamber becomes weak. Particularly in this embodiment, λg = 189 mm and L = 120 mm.
[0050]
On the other hand, the width of the opening (W in FIG. 1) is desirably one side of the waveguide, that is, a / 2 or less. However, in the case of an output of about 1000 kW such as a microwave oven, a spark is avoided even during abnormal use. In view of the safety, it is desirable to set it to 10 mm or more. Particularly, in this embodiment, a = 80 mm and W = 20 mm.
[0051]
FIG. 6 is a characteristic diagram of the present example, and shows a temperature distribution when 200 cc of water is placed in four paper cups as objects to be heated and arranged and heated as shown in the figure. The waveguide 2, the heating chamber 3, and the opening 5 are also shown so that the arrangement can be understood. The numbers in the figure indicate the degree of temperature increase obtained by heating for 70 seconds and taking the difference between the temperature after heating and the temperature before heating. Since it can be considered that the temperature rise is proportional to the power in the water, the power applied to the four paper cups is very close, indicating that the electric field strength distribution is uniform. Considering the distance between the opening and the water in the paper cup, it can be considered that the heating was performed with the electric field intensity distribution of FIG. 5B, but in FIG. Since there seems to be a center of the electric field strength line, this almost coincides with the first center line 14 of the heating chamber as shown in FIG. 6, and it is considered that it was heated extremely uniformly for this reason. Moreover, although it is uniform also in the left-right direction according to FIG. 6, this is also as FIG.
[0052]
Finally, the effect of the microwave heating apparatus of this example will be described.
[0053]
First, since the opening 5 is formed only on one side when viewed from the tube axis 10 of the waveguide, the directivity of the microwave radiated from the opening 5 into the heating chamber 3 exists. The directivity to the side can be strengthened.
[0054]
In particular, since the opening 5 is located on the center 18 side of the top surface of the heating chamber 3 as viewed from the tube axis 10, the directivity of the microwave toward the center 18 side of the heating chamber 3 is increased, and as a result, the heating chamber 3 The heating distribution in can be made uniform.
[0055]
Further, both the opening 5 and the top surface of the heating chamber 3 have a substantially rectangular shape, and of the two center lines, one center lines 14 and 17 are parallel and the other center line 15 coincides. At this time, the directivity of the microwave becomes stronger downward in the vertical direction of the opening 5 in FIGS. 1 and 5 and can be made symmetrical in the left-right direction of the opening 5. That is, it can radiate | emit uniformly with respect to a heating chamber.
[0056]
In addition, since the opening 5 is formed in the H surface 6 of the waveguide 2, an electric field that easily sandwiches the opening 5 can be generated using the electric field generated between the H surfaces. It is possible to generate a desired electric field strength distribution in the heating chamber 3 such that the direction coincident with the direction of the propagation is the propagation direction.
[0057]
Further, since the opening 5 has a dimension L in the microwave transmission direction that is longer than the dimension W in the width direction of the waveguide 2, the electric field in the vicinity of the opening 5 in the waveguide 2 has an opening in the transmission direction. An electric field that crosses the opening in the width direction is more likely to occur than an electric field that crosses the electric field, and a desired electric field strength distribution in the heating chamber 3 can be generated such that the direction corresponding to the direction of the electric field is the propagation direction.
[0058]
Further, since the length L of the opening is λg / 8 or more and 2λg or less, and particularly λg / 4 or more and λg or less, the opening 5 can be easily made long in the microwave transmission direction. In this embodiment, L = 120 mm is shown, but the present invention is not limited to this. When the length is shortened (for example, less than 40 mm), it may be difficult for microwaves to enter the heating chamber 3, and when the length is too long (for example, more than 200 mm), the waveguide becomes long and the amount and cost of members are increased. There is also the possibility that the strength of the heating chamber will be weakened. Particularly in this embodiment, λg = 189 mm and L = 120 mm.
[0059]
Further, the width W of the opening 5 may be selected on one side of the waveguide, that is, a / 2 or less. However, in the case of an output of about 1000 kW such as a microwave oven, it is safe to avoid sparks even during abnormal use. It is desirable to make it 10 mm or more in consideration of the properties. Particularly, in this embodiment, a = 80 mm and W = 20 mm.
[0060]
Further, the straight heating element 13 and the waveguide 2 are arranged on the same wall so as to be substantially parallel, and the opening 5 is configured only on the heating element 13 side when viewed from the tube axis 10. Highly directional microwave radiation is possible. In particular, in the case of a single heating element as shown in FIGS. 1 and 2, it is assumed that it is desired to place the heating element in the center of the heating chamber as much as possible in order to make the radiation heating distribution by the heating element uniform. In this embodiment, the heating element 13 is disposed near the center of the heating chamber, and the microwave radiation can be directed toward the center of the heating chamber, so that heating by the heating element and heating by the microwave can be made uniform.
[0061]
In addition, since the slit 21 of the placement net 20 is arranged in parallel with the opening 5, the electric field directed in the width direction of the opening 5 is easily applied to the width direction of the slit 21 as it is, and the electric field is applied to the placement net 20. Since it is easy to propagate above, more uniform effect can be expected.
[0062]
Further, since the antenna 22 for stirring the microwave is provided in the vicinity of the opening 5, the generation of the standing wave due to the resonance in the microwave heating chamber 3 is prevented, and the heating unevenness due to the standing wave is suppressed to make it more uniform. be able to.
[0063]
(Example 2)
FIG. 7 is a configuration diagram of the microwave heating apparatus according to the second embodiment of the present invention.
[0064]
A microwave oven, which is a typical microwave heating device, is viewed obliquely from the front, and the side wall of the heating chamber 3 is made of a waveguide 2, a triangular opening 25, and a material that transmits microwaves while blocking the opening ( A cover 26 made of mica or polypropylene), a rail 27 composed of a straight squeezed portion, a turntable 28 on which an object to be heated is placed and rotated. In particular, the method of constructing the rail 27 with the narrowed portion of the wall surface is a configuration often used for placing a square dish in the case of a product having an oven function.
[0065]
In the present embodiment, the rail 27 and the waveguide 2 are arranged substantially in parallel, and the opening 25 is configured only on the rail 27 side as viewed from the tube axis 10, so that microwave radiation having strong directivity is provided on the rail side. Can do. Therefore, even when the waveguide 2 can be disposed only above the wall surface due to the rails 27 as shown in FIG. 7, the downward microwave radiation can be realized, so that the object to be heated can be heated uniformly. In particular, when the shape of the object to be heated is flat, the object to be heated is located at a considerably lower position when placed on the turntable 28, so that a more remarkable effect can be expected.
[0066]
(Example 3)
FIG. 8 is a configuration diagram of the microwave heating apparatus according to the third embodiment of the present invention.
[0067]
In this embodiment, the opening 28 is L-shaped, and the wall surface shape of the heating chamber 29 is not a rectangular shape but a pentagon. Of course, the present invention is not limited to the rectangular shape of both the opening and the heating chamber. For example, in the case of the present embodiment, the actual heating chamber 29 may be expanded as 30. In this way, the first center line 31 of the heating chamber, the second center line 32 of the heating chamber, and the center 33 of the heating chamber can be determined, and the configuration of the present invention described in the first embodiment can be applied. .
[0068]
In the case of the shape of the opening 28 of the present embodiment, the directivity of the microwave radiation tends not only from the top to the bottom of FIG. 8 but also from the right to the left as shown by the arrow 34. It seems to come. Therefore, in such a case, uniform heating is possible by arranging the waveguide 2 and the opening 28 on the right side of the second center line 32 of the heating chamber.
[0069]
Further, in this embodiment, there is a part 35 that obstructs the waveguide arrangement at the center 33 of the heating chamber, which is, for example, an infrared sensor, a humidity sensor, a punching hole for ventilation, or an interior lamp. Various parts such as a motor for a stirrer can be considered. Of course, even if there is something that is not described here, it may interfere with the waveguide arrangement, and based on the idea of the present invention, by changing the shape of the opening and the waveguide arrangement, Can be emitted uniformly, and the object to be heated can be heated uniformly.
[0070]
【The invention's effect】
As described above, the microwave heating apparatus according to the present invention includes a radiating unit that radiates microwaves, a waveguide that couples the radiating unit to the heating chamber, and a coupling portion between the waveguide and the heating chamber. The opening is configured only on one side when viewed from the tube axis of the waveguide.
[0071]
This makes it possible to generate highly directional microwave radiation toward the side with the opening relative to the tube axis, and the heating distribution is uniform when the tube axis of the waveguide does not coincide with the center line of the heating chamber wall surface. Can be
[Brief description of the drawings]
FIG. 1 is a configuration diagram of a microwave heating apparatus according to a first embodiment of the present invention.
FIG. 2 is a cross-sectional configuration diagram of the microwave heating apparatus according to the first embodiment of the present invention.
FIG. 3 is a configuration diagram of a placement network according to the first embodiment of the present invention.
FIG. 4 is an electric field intensity distribution diagram obtained by simulation for a conventional example for comparison with Example 1 of the present invention.
(A) Electric field intensity distribution diagram 20 mm below the opening
(B) Electric field intensity distribution diagram 80 mm below the opening
FIG. 5 is an electric field intensity distribution diagram obtained by simulation with respect to Example 1 of the present invention.
(A) Electric field intensity distribution diagram 20 mm below the opening
(B) Electric field intensity distribution diagram 80 mm below the opening
FIG. 6 is a temperature distribution diagram of water in a paper cup in Embodiment 1 of the present invention.
FIG. 7 is a configuration diagram of a microwave heating apparatus according to a second embodiment of the present invention.
FIG. 8 is a configuration diagram of a microwave heating device according to a third embodiment of the present invention.
FIG. 9 is a configuration diagram of a conventional microwave heating apparatus.
FIG. 10 is a perspective configuration diagram of a magnetron and a waveguide of a conventional microwave heating apparatus.
FIG. 11 is a configuration diagram of an opening of a conventional microwave heating apparatus.
FIG. 12 is a configuration diagram of an opening of a conventional microwave heating apparatus.
FIG. 13 is a configuration diagram of an opening of a conventional microwave heating apparatus.
FIG. 14 is a configuration diagram of a microwave heating apparatus having a heating element.
[Explanation of symbols]
1 Magnetron (radiation means)
2 Waveguide
3, 29 Heating chamber
4 Object to be heated
5, 25, 28 opening
6 H side
7 E side
10 pipe shaft
13 Heating element
14, 31 First center line of heating chamber
15 Second center line of heating chamber, second center line of opening
17 First centerline of opening
18, 33 Center of heating chamber
19 Placement network
21 Slit (mesh)
27 Rail (squeezed part)
32 Second centerline of heating chamber
35 parts

Claims

A microwave heating apparatus comprising a radiating means for radiating microwaves and a waveguide for coupling the radiating means to a heating chamber, wherein an opening is formed only on one side when viewed from the tube axis of the waveguide.

The microwave heating device according to claim 1, wherein the opening is configured to be positioned on a center side of the heating chamber wall surface as viewed from the tube axis.

2. The micro of claim 1, wherein both the opening and the heating chamber wall surface have a substantially rectangular shape, and one of the two center lines of the rectangular shape is parallel and the other center line coincides. Wave heating device.

2. The microwave heating apparatus according to claim 1, wherein the opening is formed in the H plane by coupling to the heating chamber at the H plane of the waveguide.

The microwave heating apparatus according to claim 1, wherein the opening has a shape that is longer in the microwave transmission direction than in the width direction of the waveguide.

6. The microwave heating apparatus according to claim 5, wherein the length of the opening is λg / 8 or more and 2λg or less when the wavelength in the microwave waveguide is λg.

The microwave heating device according to claim 6, wherein the length of the opening is λg / 4 or more and λg or less.

The microwave heating device according to claim 5, wherein the width when the opening is substantially rectangular is 10 mm or more.

A straight heating element, and the heating element and the waveguide are disposed on the same wall so that the longitudinal direction of the heating element and the microwave transmission direction are substantially parallel to each other, and the opening is formed in the waveguide The microwave heating device according to claim 1, wherein the microwave heating device is configured only on the heating element side when viewed from the tube axis.

A straight-line squeezing part is formed on the wall surface, the squeezing part and the waveguide are arranged on the same wall surface so that the longitudinal direction of the squeezing part and the microwave transmission direction are substantially parallel, and the opening part is The microwave heating device according to claim 1, wherein the microwave heating device is configured only on the side of the narrowed portion when viewed from the tube axis of the waveguide.

When having a component that obstructs the waveguide arrangement at the center of the wall surface, the E side of the waveguide is arranged opposite to the component side, and the opening is on the component side when viewed from the tube axis of the waveguide. The microwave heating device according to claim 1, wherein the microwave heating device is positioned.

The microwave heating apparatus according to claim 1, further comprising a placement net for placing an object to be heated in the heating chamber, wherein the mesh of the placement net is configured substantially parallel to the opening.

The microwave heating apparatus according to claim 1, wherein the microwave heating apparatus includes a stirring unit that stirs the microwave in the vicinity of the opening.