JP3606516B2

JP3606516B2 - Exhaust blockage detection device

Info

Publication number: JP3606516B2
Application number: JP2001191193A
Authority: JP
Inventors: 正博太田; 貴裕昆野
Original assignee: パロマ工業株式会社
Priority date: 2001-06-25
Filing date: 2001-06-25
Publication date: 2005-01-05
Anticipated expiration: 2020-01-05
Also published as: JP2002081646A

Description

【０００１】
【発明の属する技術分野】
本発明は排気閉塞検知装置に関し、詳しくは熱電対の起電力レベルに基づいて排気閉塞を検出する排気閉塞検知装置に関する。
【０００２】
【従来の技術】
従来より、燃焼室の側壁に排ガスの一部を流出させる通孔を設け、この通孔に熱電対の温接点を臨ませ、排ガス流路が燃焼生成物等によって閉塞された場合に、通孔から流出する排ガスにより熱電対に起電力を発生し、この起電力レベルに基づいて閉塞傾向を検出し、不完全燃焼を生じる前に燃焼を停止する排気閉塞検知装置が知られている。
このような排気閉塞検知装置で使用される熱電対は、図４に示すように、異なる金属材料からなる温接点支持部５、６（金属線）を溶接することによって作製され、その溶接点が温接点２となる。そして、この温接点支持部５、６の判別を行うために温接点２をずらして設けている。すなわち、溶接前においては、同一の材料を誤って溶接することを防止する目的で、また溶接後においては、起電力のプラス・マイナスの極性を特定する目的で、温接点２をずれた位置に設けて、その形状の違いにより各々の温接点支持部５、６が判別される。
【０００３】
【発明が解決しようとする課題】
しかしながら、上述したような排気閉塞検知装置の熱電対では、温接点２が温接点支持部５の曲げ部３１に近づき、角隅部の溶接作業となって溶接が難しく、また、溶接による溶接代を含むので溶接前後で長さが異なることから、僅かばかりの長さの違いでは溶接後における温接点支持部５と温接点支持部６との判別が不明瞭であるという問題があった。
本発明の排気閉塞検知装置は上記課題を解決し、熱電対の製造を容易にし、かつその極性の判別を確実におこなえるようにすることを目的とする。
【０００４】
【課題を解決するための手段】
上記課題を解決する本発明の請求項１記載の排気閉塞検知装置は、
燃料ガスと空気との混合気を燃焼するバーナと、
上記バーナへのガス流路を開閉する開閉弁と、
上記バーナによる燃焼熱で流水を加熱する熱交換器と、
上記熱交換器と上記バーナ間に形成される燃焼室とを備えた燃焼器に用いられ、
上記燃焼室の側壁に通孔を形成し、
上記熱交換器の排気閉塞時に上記通孔から流出する排ガスによる加熱によって起電力を発生する熱電対を設け、
上記熱電対の起電力レベルに基づいて上記開閉弁を閉弁して燃焼を停止する排気閉塞検知装置において、
上記熱電対は、異種金属の２つの金属線の各先端を左右対称に接続して温接点とし、該２つの金属線の他端を２本の接続線にそれぞれ接続して各接続点を冷接点として、該温接点から各冷接点を水平方向に遠ざけるように横向きに設けられ、一方の金属線を他方の金属線より長くすると共に、長い方の金属線を短い方の金属線より上方位置に設けたことを要旨とする。
【０００５】
上記構成を有する本発明の請求項１記載の排気閉塞検知装置は、長さの異なる異種金属線２本の先端を左右対称に接続して温接点とし、他端を２本の接続線にそれぞれ接続して各接続点を冷接点として熱電対を形成している。すなわち、異種金属線の長さが異なるわけであるから、接続時においては容易に異種金属を判別できる。さらに、接続後においても、それぞれの冷接点の位置がずれるので、容易に異種金属を判別できる。
また、排気閉塞になり始めると、排ガスは通孔の上方ほど多くあふれ出し温度が高くなるが、長い方の金属線を短い方の金属線より上方位置に設けたことにより、温接点と長い方の金属線の冷接点との間に、より大きな温度差が得られ、大きな逆起電力を発生させることができる。
【０００６】
【発明の実施の形態】
以上説明した本発明の構成・作用を一層明らかにするために、以下本発明の排気閉塞検知装置を備えた湯沸器の好適な実施形態について説明する。
【０００７】
湯沸器は、図１に示すように、燃料ガスと一次空気との混合気を燃焼するバーナ２８、燃焼熱を流水へ受け渡す熱交換器２９、熱交換器２９とバーナ２８間に挟まれ燃焼空間を形成する燃焼室１６を備える。
【０００８】
バーナ２８には燃焼炎による加熱によって起電力を発生し燃焼状態を検知する一次熱電対３０が設けられ、排気閉塞を検知する二次熱電対１が燃焼室１６の側壁に設けた通孔３に臨んで設けられ、検出起電力の監視を行うコントローラ２３へ電気的に接続される。コントローラ２３は、一次熱電対３０および二次熱電対１による合成起電力が所定値以下か否かを判定し、異常と判定すれば、コントローラ２３と電気的に接続されるガス流路の開閉弁２４、２５へ閉弁指令を出して燃焼を停止する。
【０００９】
一次熱電対３０は、室内が燃焼排ガスによって酸欠雰囲気となると、一次熱電対３０を加熱している燃焼炎がリフティング（飛火）を起こし始め、発生起電力を低下する。
他方、排気閉塞検知装置である二次熱電対１は、燃焼生成物によって熱交換器２９の排気流路が閉塞してくると、燃焼室１６の側壁に設けた通孔３から排ガスがあふれ始め、このあふれ出た排ガスを感知して起電力を発生する。また、二次熱電対１は、一次熱電対３０に対して逆起電力を発生するように逆極性に接続され、熱交換器２９の排気流路が閉塞する程度につれて発生起電力を上昇し、一次熱電対３０と二次熱電対１との合成起電力を低下する。
従って、燃焼コントローラ２３は、合成起電力値から、酸欠状態の検知、不着火、燃焼炎の消失有無の判定だけでなく、熱交換器２９の閉塞状態の検知を行ない、異常と判定すれば直ちに開閉弁２４、２５を閉弁して、不完全燃焼を防止する。
【００１０】
図２（ニ）に示すように、二次熱電対１を形成する温接点支持部５、６はそれぞれ、クロメル、コンスタンタンの異種金属で形成され、溶接された接続部が温接点２を形成する。他端は、それぞれ被覆された銅線である接続線９、１０が溶接され、この接続部が冷接点７、８を形成する。
温接点支持部５は温接点支持部６より、上方位置に、かつ長く設けられ、この冷接点７は冷接点８より温接点２から離れた位置に設けられる。冷接点７、８部はグラスチューブ１１によって被覆され、電気的に絶縁されている。その外周を、固定金具１２によって温接点支持部５、６が平行に位置するようにカシメて一体化している（図２（イ））。
燃焼室１６の側壁には二次熱電対１を取り付ける取付板１５が設けられ、燃焼室１６に通じて、通孔３より大きな取付孔１７が設けられる。二次熱電対１は温接点２から冷接点７、８を水平方向に遠ざけるように横向きに設けられ、二次熱電対１と取付板１５との間には、ガス種によって通孔３の開口面積を選択して使用する通孔変更板１９の一端が挟み込まれて、取付ビス１４にて固定される。
通孔変更板１９の他端は取付孔１７を塞いで取付孔１７の縁部裏側に引っ掛けられ、この取付孔１７の中心にあたる位置に取付孔１７より小さな通孔３が設けられる。
ガス種に応じて選択される通孔３の大きさは、排気閉塞を検知して良好な燃焼限界内で適正に燃焼停止するように、例えば、ＬＰガスでは縦９ｍｍ×横５ｍｍ、都市ガスの４Ｃガスでは縦５ｍｍ×横４ｍｍの大きさに設けられる。
また、二次熱電対１には、温接点２を包み込むように、通孔３の開口面積に対して通孔３方向への投影面積が１〜１／３の大きさをもつ円柱状の熱容量体４を設ける。熱容量体４の大きさは、通孔３より大き過ぎると、放熱が増して加熱され難くなって二次熱電対１の起電力が発生し難くなると共に、室温の高低によって起電力が影響されやすくなる。また、通孔３の開口面積に対して通孔３方向への投影面積が１／３未満の場合では後述する効果が得られない。
従って、好ましくは直径４ｍｍ×長さ５ｍｍ大きさの熱容量体４を設ける。
また、熱容量体４は、熱容量の大きい黄銅材を用いて温接点２を包み込み、カシメによってずれないように温接点２に固定される。
【００１１】
次に、温接点２に熱容量体４を設けた理由について、以下に詳述する。
第１の理由は、点火初期の誤判定によってガス流路を閉じる立消えを防止するためである。
湯沸器が冷え切った状態での点火（コールドスタートと呼ぶ）の際には、排気閉塞状態でなくても、燃焼排ガスのドラフト力が小さく、しかも熱交換器２９を通過する排ガスの流路抵抗が大きい。従って、コールドスタート時には、燃焼室１６全体が昇温するまで過渡的に通孔３から排ガスが流出する。しかし、熱容量体４は、この過渡的に流出する排ガス熱量を吸収し、温接点２に生じる起電力の上昇を遅らせる。
つまり、二次熱電対１の温接点２がこの過渡的な排ガスを敏感に感知しないので、コールドスタート時に排気閉塞を生じていない場合には、異常と誤判定されることは無く、燃焼は停止しない。即ち、立消えが起こらない。
他方、排気閉塞を生じている場合には、通孔３から排ガスの流出が続いて起電力が上昇し、異常と判定されて燃焼を停止する。
【００１２】
また、第２の理由は、発生起電力のばらつきを小さくするためである。
熱容量体４は、通孔３の面積の１〜１／３の大きさに設けてあり、通孔３との関係寸法位置が少々ずれたとしても、通孔３から流出する全体の排気ガスにさらされる。つまり、ほぼ通孔３全体の排ガス熱量を吸収し、平均化して温接点２へ熱を伝達する。従って、関係寸法位置が少々ずれても起電力がばらつくことはない。
更に、二次熱電対１の温接点支持部５、６について、通孔３の開口方向への投影が通孔３の上下縁にかかるように設けてあるので、二次熱電対１が多少ずれたとしても、実際に通孔３に向かい合う部分の突出し量はほとんど変らない。特に、図３に示すように、温接点支持部５、６を各々通孔３の上下より突出すように設ければ完全に影響が無くなる。
また、通孔３に対する側縁よりの突出し量が変わって排ガスによる加熱面積がたとえ変わったとしても、この温接点支持部の突出し量の増減は、熱容量体４の熱容量に比べてはるかに小さい。従って、温接点支持部の突出し量による起電力への影響は無視できる。
即ち、関係寸法のばらつきが多少あっても、検知性能は安定し、製造上における量産性を高めることができる。
【００１３】
更に、第３の理由は、フロントカバー４０の変色を防止するためである。
排気閉塞を起こすと、通孔３より排ガスが流出してフロントカバー４０の裏面の一部分に集中し、この排ガス温度によってフロントカバー４０の塗装面が変色する場合がある。しかし、熱容量体４を設けることによって、燃焼初期の場合には熱容量体４に排ガス中の熱が吸収され、また、燃焼中の場合には熱容量体４によって排ガス流出方向が分散される。従って、熱容量体４は、高温の排ガスをフロントカバー４０の裏面へ局部的に接触させず、フロントカバー４０の変色を防止する（図２（ロ））。
【００１４】
次に、排気閉塞検知装置のセンサとしての感度向上について、以下に詳述する。
二次熱電対１は、その温接点２と冷接点７、８とを異なった温度に保つと、温度差に応じて熱起電力を発生する。つまり、排気閉塞時には、温接点２と冷接点７、８との温度差が大きいほど大きな逆起電力を発生させることができることになる。
そこで、温度差を大きくするために次のことを行う。
まず第１は、上方の温接点支持部５を下方の温接点支持部６より長くし、温接点２と冷接点７間に距離を設ける。
排ガスは、排気閉塞になり始めると、通孔３の上方ほど多くあふれ出し、しかも温度が高い。従って、上方の温接点支持部５および冷接点７は下方の温接点支持部６および冷接点８より高い温度となり易い。そこで、上方に位置する温接点支持部５を下方に位置する温接点支持部６より長くすることによって（図２（ニ））、温接点２と冷接点７間に、より大きな温度差が得られる。
【００１５】
尚、この長さの違いを設けることによって、別な利点も得られる。
従来においては、図４（ニ）に示すように、材料が異なる各々の温接点支持部５、６における溶接時の判別を行うために、温接点２をずらして設けていた。例えば、溶接前においては同一材料を誤って溶接することを防止する目的で、また溶接後においては、どちらがどの材料で起電力のプラス・マイナス方向なのかを特定する目的で、温接点２はずれた位置に設けられ、この形状の違いによって各々の温接点支持部５、６が判別されていた。
このために、温接点２が温接点支持部５の曲げ部３１に近づき、角隅部の溶接作業となって溶接が難しく、また、溶接による溶解代を含むので溶接前後で長さが異なることから、僅かばかりの長さの違いでは温接点支持部５と温接点支持部６との判別が不明瞭であった。
しかも、温接点部２を包むように熱容量体４を設けるとするなら、溶接後の判別は不可能になってしまうことになる。
しかし、本実施形態では、図２（ニ）に示すように、温接点支持部５、６の各々についての溶接前後における判別は、温接点支持部５を長くし、冷接点７の位置をずらすことによって、冷接点７の位置の違いから容易にできることとなる。また、温接点２は各々の曲げ部３１、３１から遠ざかった中心位置に設けるので、溶接作業が容易となる。
【００１６】
また、温度差を大きくするために、冷接点７、８を燃焼室１６から離して設ける。つまり、排気閉塞になり始めると燃焼室１６が高温となり始め、この際に、冷接点７の温度が高くならないように、冷接点７は燃焼室１６から適切な離隔距離を確保する。
例えば、本実施形態を図２（ハ）に示し、従来例を図４（ハ）に対比させて示すように、冷接点〜温接点間の温接点支持部５、６を燃焼室１６方向に曲げることによって、冷接点７、８と燃焼室１６との離隔距離を温接点２と通孔面との離隔距離より大きくする（Ｈ０寸法）。
つまり、冷接点７、８と燃焼室１６との離隔距離を大きくすることによって、排気閉塞時には大きな温度差が得られて大きな起電力が発生する。
即ち、排気閉塞検知装置としての二次熱電対１のセンサ感度を良くすることができる。
【００１７】
以上、本発明の実施形態について説明したが、本発明はこうした実施形態に何等限定されるものではなく、本発明の趣旨を逸脱しない範囲において、種々なる態様で実施し得ることは勿論である。
例えば、本実施形態では、一次熱電対３０と二次熱電対１とを直列に設けて合成された起電力を監視する構成としたが、各々の熱電対の起電力を別々に監視しても良い。
また、熱電対と直列に接続されるマグネット式安全弁を熱電対の起電力の低下によって閉弁してガス流路を閉じる排気閉塞検出装置であっても良い。
【００１８】
また、熱容量体４は、実施形態による円柱形状に限定されず、球形状でも良く、あるいは通孔の形状を縮小した長方形の形状でも良い。また、板材・線材を温接点に巻き付けた形状であっても良い。
二次熱電対１を形成する金属は実施形態によるクロメルとコンスタンタンとの組合わせに限定されず、クロメルとアルメルとの組合わせ、鉄とコンスタンタンとの組合わせでも、あるいは銅とコンスタンタン等、他の組合わせでも良い。また、熱容量体の材質についても熱容量をもつ材料であれば銅、鉛、鉄、アルミ、亜鉛、またはそれらの合金であっても良い。
また、二次熱電対１は、実施形態（図２（ハ））のように、温接点２と冷接点７、８間に曲げ寸法Ｈ０を設けることに限定されず、二次熱電対１全体を斜めに取り付けることによって、冷接点７、８と燃焼室１６との離隔距離を確保しても良い。
また、本実施形態では、バーナの燃焼炎に臨み起電力を発生する一次熱電対３０と共に、熱交換器２９下部の燃焼室１６に二次熱電対１を設けた湯沸器について説明したが、二次熱電対１だけを設けて一次熱電対３０を設けない他の燃焼器に適用しても良い。
【００１９】
【発明の効果】
以上詳述したように、本発明の請求項１の排気閉塞検知装置によれば、異なる長さの異種金属を用いることにより、冷接点の位置をずらすことができるため、その位置の違いによって容易に熱電対の極性を判別できる。しかも、従来の場合のように金属線を角隅部付近で接続する必要性がなくなるので、熱電対を製造し
やすくなりコストの低減が図れる。
また、長い方の金属線を短い方の金属線より上方位置に設けたことにより、温接点と長い方の金属線の冷接点との間に、より大きな温度差が得られ、大きな逆起電力を発生させることができる。
【図面の簡単な説明】
【図１】湯沸器の概略構成図である。
【図２】本発明の実施形態に係る排気閉塞検出装置の概略図である。
【図３】本発明の他の実施形態を示す排気閉塞検出装置の概略図である。
【図４】従来の実施形態に係る排気閉塞検出装置の概略図である。
【符号の説明】
１…二次熱電対、２…温接点、３…通孔、５…温接点支持部、６…温接点支持部、７…冷接点、８…冷接点、１６…燃焼室、２４…開閉弁、２５…開閉弁、２８…バーナ、２９…熱交換器。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an exhaust blockage detection device, and more particularly to an exhaust blockage detection device that detects exhaust blockage based on an electromotive force level of a thermocouple.
[0002]
[Prior art]
Conventionally, a through hole has been provided in the side wall of the combustion chamber to allow a part of the exhaust gas to flow out. When the exhaust gas passage is blocked by combustion products, etc. 2. Description of the Related Art There is known an exhaust blockage detection device that generates an electromotive force in a thermocouple by exhaust gas flowing out from a gas, detects a blockage tendency based on the electromotive force level, and stops combustion before incomplete combustion occurs.
As shown in FIG. 4, the thermocouple used in such an exhaust blockage detection device is manufactured by welding hot junction support parts 5 and 6 (metal wires) made of different metal materials, and the welding point is It becomes a hot junction 2. And in order to discriminate | determine this hot junction support parts 5 and 6, the hot junction 2 is provided shifting. That is, before welding, in order to prevent the same material from being accidentally welded, and after welding, the hot junction 2 is shifted to a position for the purpose of identifying the positive / negative polarity of the electromotive force. The hot junction support portions 5 and 6 are discriminated by the difference in shape.
[0003]
[Problems to be solved by the invention]
However, in the thermocouple of the exhaust blockage detection apparatus as described above, the hot junction 2 approaches the bent portion 31 of the hot junction support 5 and welding is difficult at the corner corner, and the welding allowance by welding is also difficult. Since the length differs before and after welding, there is a problem that the difference between the warm junction support portion 5 and the warm junction support portion 6 after welding is unclear when there is a slight difference in length.
An object of the present invention is to solve the above-described problems, facilitate manufacture of a thermocouple, and reliably determine the polarity of the thermocouple.
[0004]
[Means for Solving the Problems]
The exhaust blockage detection device according to claim 1 of the present invention for solving the above-described problems is provided.
A burner that burns a mixture of fuel gas and air;
An on-off valve for opening and closing the gas flow path to the burner;
A heat exchanger that heats running water with the combustion heat generated by the burner;
Used in a combustor comprising a combustion chamber formed between the heat exchanger and the burner;
Forming a through hole in the side wall of the combustion chamber;
A thermocouple that generates an electromotive force by heating with exhaust gas flowing out of the through hole when the exhaust of the heat exchanger is closed is provided.
In the exhaust blockage detecting device that closes the on-off valve based on the electromotive force level of the thermocouple and stops combustion,
In the thermocouple, the tips of two metal wires made of different metals are connected symmetrically to form a hot junction, and the other ends of the two metal wires are connected to two connection wires, respectively. and a contact, provided the temperature contacts sideways away each cold junction in the horizontal direction, above the with the longer shorter metal wire metal wire is longer than the other metal wires one metal wire The gist is that it is provided at the position .
[0005]
The exhaust blockage detection device according to claim 1 of the present invention having the above-described configuration is configured so that the tips of two dissimilar metal wires having different lengths are symmetrically connected to form a hot junction, and the other end is connected to two connection wires. A thermocouple is formed by connecting each connection point as a cold junction. That is, since the lengths of the dissimilar metal wires are different, the dissimilar metal can be easily distinguished at the time of connection. Furthermore, even after connection, the positions of the respective cold junctions are shifted, so that different metals can be easily identified.
In addition, when the exhaust gas blockage starts, the exhaust gas overflows and the temperature rises as it goes above the through hole. However, the longer metal wire is located above the shorter metal wire, so that A larger temperature difference is obtained between the metal wire and the cold junction of the metal wire, and a large counter electromotive force can be generated.
[0006]
DETAILED DESCRIPTION OF THE INVENTION
In order to further clarify the configuration and operation of the present invention described above, a preferred embodiment of a water heater provided with an exhaust blockage detection device of the present invention will be described below.
[0007]
As shown in FIG. 1, the water heater is sandwiched between a burner 28 that burns a mixture of fuel gas and primary air, a heat exchanger 29 that transfers combustion heat to running water, and a heat exchanger 29 and a burner 28. A combustion chamber 16 that forms a combustion space is provided.
[0008]
The burner 28 is provided with a primary thermocouple 30 for generating an electromotive force by heating with a combustion flame and detecting a combustion state, and a secondary thermocouple 1 for detecting exhaust blockage is provided in a through hole 3 provided on a side wall of the combustion chamber 16. The controller 23 is provided and is electrically connected to the controller 23 that monitors the detected electromotive force. The controller 23 determines whether or not the combined electromotive force generated by the primary thermocouple 30 and the secondary thermocouple 1 is equal to or less than a predetermined value. If the controller 23 determines an abnormality, the controller 23 opens and closes a gas flow path that is electrically connected to the controller 23. A valve closing command is issued to 24 and 25 to stop combustion.
[0009]
When the interior of the primary thermocouple 30 is in an oxygen-deficient atmosphere due to combustion exhaust gas, the combustion flame heating the primary thermocouple 30 starts to lift, and the generated electromotive force is reduced.
On the other hand, in the secondary thermocouple 1 which is an exhaust blockage detection device, exhaust gas begins to overflow from the through-hole 3 provided in the side wall of the combustion chamber 16 when the exhaust flow path of the heat exchanger 29 is blocked by combustion products. Detects this overflowing exhaust gas and generates electromotive force. Further, the secondary thermocouple 1 is connected in reverse polarity so as to generate a counter electromotive force with respect to the primary thermocouple 30, and the generated electromotive force is increased as the exhaust flow path of the heat exchanger 29 is blocked, The combined electromotive force of the primary thermocouple 30 and the secondary thermocouple 1 is reduced.
Therefore, the combustion controller 23 detects not only an oxygen deficiency state, non-ignition, and whether or not the combustion flame disappears from the resultant electromotive force value, but also detects the closed state of the heat exchanger 29 and determines that it is abnormal. Immediately close the on-off valves 24 and 25 to prevent incomplete combustion.
[0010]
As shown in FIG. 2 (d), the hot junction support portions 5 and 6 forming the secondary thermocouple 1 are formed of dissimilar metals such as chromel and constantan, and the welded connection portion forms the hot junction 2. . The other ends are welded with connecting wires 9 and 10 which are respectively coated copper wires, and this connecting portion forms cold junctions 7 and 8.
The hot junction support part 5 is provided at a position above and longer than the hot junction support part 6, and the cold junction 7 is provided at a position farther from the hot junction 2 than the cold junction 8. The cold junctions 7 and 8 are covered with a glass tube 11 and are electrically insulated. The outer periphery is integrated by caulking so that the hot junction support portions 5 and 6 are positioned in parallel by the fixing metal 12 (FIG. 2 (A)).
An attachment plate 15 for attaching the secondary thermocouple 1 is provided on the side wall of the combustion chamber 16, and an attachment hole 17 larger than the through hole 3 is provided through the combustion chamber 16. The secondary thermocouple 1 is provided sideways so that the cold junctions 7 and 8 are moved away from the hot junction 2 in the horizontal direction, and an opening of the through hole 3 is formed between the secondary thermocouple 1 and the mounting plate 15 depending on the gas type. One end of the through hole changing plate 19 to be used by selecting an area is sandwiched and fixed by the mounting screw 14.
The other end of the through hole changing plate 19 closes the mounting hole 17 and is hooked on the rear side of the edge of the mounting hole 17, and a through hole 3 smaller than the mounting hole 17 is provided at a position corresponding to the center of the mounting hole 17.
The size of the through hole 3 selected according to the gas type is, for example, 9 mm long by 5 mm wide by LP gas so that the combustion can be stopped properly within the good combustion limit by detecting the exhaust blockage. 4C gas is provided in a size of 5 mm long × 4 mm wide.
Further, the secondary thermocouple 1 has a cylindrical heat capacity having a projected area in the direction of the through hole 3 of 1 to 1/3 with respect to the opening area of the through hole 3 so as to wrap the hot junction 2. A body 4 is provided. If the size of the heat capacity body 4 is too larger than the through-hole 3, heat radiation increases and it becomes difficult to be heated, so that it is difficult to generate an electromotive force of the secondary thermocouple 1, and the electromotive force is easily affected by the level of room temperature. Become. Further, when the projected area in the direction of the through hole 3 is less than 1/3 with respect to the opening area of the through hole 3, the effect described later cannot be obtained.
Accordingly, the heat capacity body 4 having a diameter of 4 mm × a length of 5 mm is preferably provided.
Moreover, the heat capacity body 4 wraps the warm contact 2 using a brass material having a large heat capacity, and is fixed to the warm contact 2 so as not to be displaced by caulking.
[0011]
Next, the reason why the heat capacity body 4 is provided in the hot junction 2 will be described in detail below.
The first reason is to prevent extinction that closes the gas flow path due to an erroneous determination at the beginning of ignition.
When ignition is performed in a state where the water heater is completely cooled (referred to as cold start), the exhaust gas flow path through the heat exchanger 29 is small even when the exhaust gas is not closed, and the draft power of the combustion exhaust gas is small. Resistance is great. Therefore, at the cold start, exhaust gas flows out from the through hole 3 transiently until the temperature of the entire combustion chamber 16 rises. However, the heat capacity body 4 absorbs the heat amount of exhaust gas flowing out transiently, and delays the increase in electromotive force generated at the hot junction 2.
In other words, since the hot junction 2 of the secondary thermocouple 1 does not sense this transient exhaust gas sensitively, if there is no exhaust blockage during a cold start, it will not be erroneously determined as abnormal, and combustion will stop. do not do. That is, disappearance does not occur.
On the other hand, if the exhaust gas is blocked, the exhaust gas continues to flow out of the through-hole 3 and the electromotive force rises.
[0012]
The second reason is to reduce variations in generated electromotive force.
The heat capacity body 4 is provided in the size of 1 to 1/3 of the area of the through-hole 3, and even if the dimensional position relative to the through-hole 3 is slightly shifted, the entire exhaust gas flowing out of the through-hole 3 Exposed. That is, the heat quantity of the exhaust gas in the entire through-hole 3 is absorbed, averaged, and heat is transferred to the hot junction 2. Therefore, the electromotive force does not vary even if the relative dimension position is slightly shifted.
Further, since the hot junction support portions 5 and 6 of the secondary thermocouple 1 are provided so that the projection in the opening direction of the through hole 3 is applied to the upper and lower edges of the through hole 3, the secondary thermocouple 1 is slightly shifted. Even if this is the case, the amount of protrusion of the portion that actually faces the through hole 3 hardly changes. In particular, as shown in FIG. 3, if the hot junction support portions 5 and 6 are provided so as to protrude from the upper and lower sides of the through holes 3 respectively, the influence is completely eliminated.
Further, even if the amount of protrusion from the side edge with respect to the through hole 3 changes and the heating area by the exhaust gas changes, the increase and decrease in the amount of protrusion of the hot junction support part is much smaller than the heat capacity of the heat capacity body 4. Therefore, the influence on the electromotive force due to the protruding amount of the hot junction support portion can be ignored.
That is, even if there is some variation in the related dimensions, the detection performance is stable, and mass productivity in manufacturing can be improved.
[0013]
Furthermore, the third reason is to prevent discoloration of the front cover 40.
When exhaust blockage occurs, the exhaust gas flows out from the through hole 3 and concentrates on a part of the back surface of the front cover 40, and the painted surface of the front cover 40 may be discolored by the exhaust gas temperature. However, by providing the heat capacity body 4, the heat capacity body 4 absorbs the heat in the exhaust gas in the early stage of combustion, and the heat capacity body 4 disperses the exhaust gas outflow direction in the case of combustion. Therefore, the heat capacity body 4 does not cause high temperature exhaust gas to contact the back surface of the front cover 40 locally, and prevents discoloration of the front cover 40 (FIG. 2 (B)).
[0014]
Next, the sensitivity improvement as a sensor of the exhaust blockage detection device will be described in detail below.
The secondary thermocouple 1 generates a thermoelectromotive force according to the temperature difference when the hot junction 2 and the cold junctions 7 and 8 are kept at different temperatures. That is, when the exhaust is closed, the larger the temperature difference between the hot junction 2 and the cold junctions 7 and 8, the larger the back electromotive force can be generated.
Therefore, the following is performed to increase the temperature difference.
First, the upper hot junction support 5 is made longer than the lower hot junction support 6 and a distance is provided between the hot junction 2 and the cold junction 7.
When the exhaust gas begins to become exhausted, the amount of exhaust gas overflows upward from the through-hole 3 and the temperature is high. Therefore, the upper hot junction support portion 5 and the cold junction 7 are likely to have a higher temperature than the lower hot junction support portion 6 and the cold junction 8. Therefore, a larger temperature difference is obtained between the hot junction 2 and the cold junction 7 by making the hot junction support portion 5 located above the longer hot junction support portion 6 located below (FIG. 2 (d)). It is done.
[0015]
In addition, another advantage is acquired by providing this difference in length.
Conventionally, as shown in FIG. 4 (d), the hot junction 2 is provided in a shifted manner in order to make a discrimination at the time of welding in the hot junction support portions 5 and 6 of different materials. For example, in order to prevent the same material from being mistakenly welded before welding, and after welding, the hot junction 2 has shifted in order to identify which material is in the positive or negative direction of the electromotive force. The hot junction support portions 5 and 6 are discriminated by the difference in the shape.
For this reason, the hot junction 2 approaches the bent portion 31 of the hot junction support portion 5 and is difficult to be welded as a corner corner welding operation. Also, since the melting allowance by welding is included, the length differs before and after welding. Therefore, the difference between the warm junction support portion 5 and the warm junction support portion 6 is unclear with a slight difference in length.
In addition, if the heat capacity body 4 is provided so as to wrap the hot junction 2, discrimination after welding becomes impossible.
However, in the present embodiment, as shown in FIG. 2 (d), before and after welding for each of the hot junction support portions 5 and 6, the hot junction support portion 5 is lengthened and the position of the cold junction 7 is shifted. Thus, it can be easily done from the difference in the position of the cold junction 7. Moreover, since the hot junction 2 is provided at the center position away from the bent portions 31, 31, the welding operation is facilitated.
[0016]
Further, the cold junctions 7 and 8 are provided away from the combustion chamber 16 in order to increase the temperature difference. In other words, the combustion chamber 16 starts to become hot when the exhaust blockage starts, and at this time, the cold junction 7 secures an appropriate separation distance from the combustion chamber 16 so that the temperature of the cold junction 7 does not increase.
For example, this embodiment is shown in FIG. 2 (c), and the hot junction support portions 5 and 6 between the cold junction and the hot junction are arranged in the direction of the combustion chamber 16 as shown in FIG. By bending, the separation distance between the cold junctions 7 and 8 and the combustion chamber 16 is made larger than the separation distance between the hot junction 2 and the through hole surface (H0 dimension).
That is, by increasing the separation distance between the cold junctions 7 and 8 and the combustion chamber 16, a large temperature difference is obtained when the exhaust is closed, and a large electromotive force is generated.
That is, the sensor sensitivity of the secondary thermocouple 1 as the exhaust blockage detection device can be improved.
[0017]
As mentioned above, although embodiment of this invention was described, this invention is not limited to such embodiment at all, Of course, it can implement in a various aspect in the range which does not deviate from the meaning of this invention.
For example, in the present embodiment, the primary thermocouple 30 and the secondary thermocouple 1 are provided in series to monitor the combined electromotive force, but the electromotive force of each thermocouple can be monitored separately. good.
Further, an exhaust blockage detection device that closes a gas flow path by closing a magnet-type safety valve connected in series with a thermocouple by lowering the electromotive force of the thermocouple may be used.
[0018]
Further, the heat capacity body 4 is not limited to the cylindrical shape according to the embodiment, and may be a spherical shape or a rectangular shape obtained by reducing the shape of the through hole. Moreover, the shape which wound the board | plate material and the wire around the hot junction may be sufficient.
The metal forming the secondary thermocouple 1 is not limited to the combination of chromel and constantan according to the embodiment, and may be a combination of chromel and alumel, a combination of iron and constantan, or other combinations such as copper and constantan. A combination may be used. Further, the material of the heat capacity body may be copper, lead, iron, aluminum, zinc, or an alloy thereof as long as it has a heat capacity.
Moreover, the secondary thermocouple 1 is not limited to providing the bending dimension H0 between the hot junction 2 and the cold junctions 7 and 8 as in the embodiment (FIG. 2 (C)), and the secondary thermocouple 1 as a whole. May be secured diagonally to ensure a separation distance between the cold junctions 7 and 8 and the combustion chamber 16.
In the present embodiment, the water heater has been described in which the secondary thermocouple 1 is provided in the combustion chamber 16 below the heat exchanger 29 together with the primary thermocouple 30 that generates an electromotive force in the combustion flame of the burner. You may apply to the other combustor which provides only the secondary thermocouple 1 and does not provide the primary thermocouple 30.
[0019]
【The invention's effect】
As described above in detail, according to the exhaust blockage detection device of claim 1 of the present invention, the position of the cold junction can be shifted by using different lengths of dissimilar metals. The polarity of the thermocouple can be discriminated. In addition, since there is no need to connect the metal wires near the corners as in the conventional case, it is easy to manufacture the thermocouple and the cost can be reduced.
In addition, by providing the longer metal wire above the shorter metal wire, a larger temperature difference can be obtained between the hot junction and the cold junction of the longer metal wire, resulting in a large back electromotive force. Can be generated.
[Brief description of the drawings]
FIG. 1 is a schematic configuration diagram of a water heater.
FIG. 2 is a schematic view of an exhaust blockage detection device according to an embodiment of the present invention.
FIG. 3 is a schematic view of an exhaust blockage detection device showing another embodiment of the present invention.
FIG. 4 is a schematic view of an exhaust blockage detection device according to a conventional embodiment.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Secondary thermocouple, 2 ... Hot junction, 3 ... Through-hole, 5 ... Hot junction support part, 6 ... Hot junction support part, 7 ... Cold junction, 8 ... Cold junction, 16 ... Combustion chamber, 24 ... Open / close valve 25 ... Open / close valve, 28 ... Burner, 29 ... Heat exchanger.

Claims

A burner that burns a mixture of fuel gas and air;
An on-off valve for opening and closing the gas flow path to the burner;
A heat exchanger that heats running water with the combustion heat generated by the burner;
Used in a combustor comprising a combustion chamber formed between the heat exchanger and the burner;
Forming a through hole in the side wall of the combustion chamber;
A thermocouple that generates an electromotive force by heating with exhaust gas flowing out of the through hole when the exhaust of the heat exchanger is closed is provided.
In the exhaust blockage detecting device that closes the on-off valve based on the electromotive force level of the thermocouple and stops combustion,
In the thermocouple, the tips of two metal wires made of different metals are connected symmetrically to form a hot junction, and the other ends of the two metal wires are connected to two connection wires, respectively. and a contact, provided the temperature contacts sideways away each cold junction in the horizontal direction, above the with the longer shorter metal wire metal wire is longer than the other metal wires one metal wire An exhaust blockage detecting device provided at a position .