JP4190057B2 - Overheat prevention device for combustion equipment - Google Patents

Overheat prevention device for combustion equipment Download PDF

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JP4190057B2
JP4190057B2 JP17625498A JP17625498A JP4190057B2 JP 4190057 B2 JP4190057 B2 JP 4190057B2 JP 17625498 A JP17625498 A JP 17625498A JP 17625498 A JP17625498 A JP 17625498A JP 4190057 B2 JP4190057 B2 JP 4190057B2
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conductive pattern
value
resistance value
combustion
overheat prevention
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JP2000018567A (en
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昭仁 鬼頭
公一 光藤
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パロマ工業株式会社
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Description

【０００１】
【発明の属する技術分野】
本発明は、バーナを備えた燃焼室のケーシングの周囲に、導電パターンを形成した感熱シートを配設し、ケーシングに異常過熱によるひび割れ等が生じた際の導電パターンの抵抗値の変化でこれを検知可能とする燃焼器具の過熱防止装置に関する。
【０００２】
【従来の技術】
上記過熱防止装置は、熱溶融性の樹脂シートに導電パターンを印刷した感熱シートを、バーナを備えた燃焼室のケーシングの周囲に配設すると共に、導電パターンを、バーナの燃焼を制御するコントローラに電気的接続して構成される。即ち、異常過熱により燃焼室にひび割れや穴あき等が発生し、そこから燃焼ガスが噴出すると、感熱シートの溶断と共に導電パターンの当該箇所が破断してその抵抗値が急増或は無限大となることから、その抵抗値の変化を検知したコントローラが異常過熱と判断してバーナへの燃料ガスの供給を停止するものである。
【０００３】
【発明が解決しようとする課題】
上記過熱防止装置においては、導電パターンの抵抗値は数Ω程度のものが多く用いられているため、一旦異常過熱により溶断し、燃料の供給が停止されても、その溶断箇所や導電パターンの両端をリード線で短絡することで、導電パターンによる異常過熱の検知状態が解除され、ケーシング側のひび割れ等が手当てされないまま継続使用可能となってしまう。
【０００４】
そこで、請求項１に記載の発明は、異常過熱の検知後は安易に再使用不能として、安全性を高めることができる燃焼器具の過熱防止装置を提供することを目的としたものである。
【０００５】
【課題を解決するための手段】
上記目的を達成するために、請求項１に記載の発明は、導電パターンの抵抗値を所定の判定値と比較する比較手段と、前記導電パターンの抵抗値が前記判定値を超えた場合に前記燃焼室の異常過熱と判断する判断手段とを備えたものにおいて、前記導電パターンの抵抗値を、正常時で前記導電パターンの短絡時より高い値となるように設定すると共に、前記比較手段の判定値を、前記導電パターンの正常時の抵抗値を含んで上限値と下限値とが設定される所定範囲に設定して、前記比較手段は、前記所定範囲の上限値と下限値とを交互に切り換えて前記導電パターンの抵抗値と比較し、前記抵抗値が前記所定範囲内の場合はパルス信号を出力して、前記導電パターンの抵抗値が前記所定範囲を上回る場合と下回る場合とには、前記比較手段からの前記パルス信号が得られなくなることで前記判断手段が異常と判断することを特徴とするものである。
請求項２に記載の発明は、請求項１の目的に加えて、異常の判断後の対処を確実に行うために、判断手段が異常と判断した場合にはバーナの燃焼を停止させる構成としたものである。
請求項３に記載の発明は、請求項１又は２の目的に加えて、判断手段の故障や暴走を考慮して異常過熱への対処を確実に行うために、導電パターンの抵抗値が判定値を超える場合又は下回る場合には、判断手段の判断に拘わらず直接バーナの燃焼を停止させる誤動作防止手段を設けたものである。
【０００６】
【発明の実施の形態】
以下、本発明の実施の形態を図面に基づいて説明する。
図１は、燃焼器具の一例として強制給気式ガス給湯器（以下単に「給湯器」という）に本発明の過熱防止装置を適用した状態の説明図で、給湯器１において、２は、燃焼室３を内部に形成し、外周面に給水管４を螺旋状に巻回したケーシングとしての内胴で、給水管４は、内胴２の上部に備えられた熱交換器５の吸熱管６に接続されている。一方、内胴２の下方には、ガスバーナ７が設置されており、ガスバーナ７で熱交換器５を加熱することにより、熱交換器５の吸熱管６を通る水を加熱して、吸熱管６の出口側に接続した図示しない出湯管から出湯可能としている。又、燃焼室３の下部に設けた給気室８の下方には、給気ファン９が備えられて、ガスバーナ７へ燃焼用空気を強制給気可能としている。更に、１０はコントローラで、ガスバーナ７の点消火操作時のガス元弁、安全弁の開閉制御や、温度設定時の比例制御弁の開度調整等の他、後述する異常過熱検知を行うものである。
一方、内胴２の外周には、面状の感熱シート１１が配設されている。この感熱シート１１は、２００℃〜３００℃の間に融点を有する樹脂シート（例えばＰＥＴ樹脂製）の表面に、導電性インク等を用いて全面を網羅するように一本線で導電パターンを蛇行状に印刷し、その上面に、被覆層として先の樹脂シートと同じものをラミネート加工して一体化したもので、感熱シート１１に設けたクリップ１２，１２・・で給水管４を挟持させて感熱シート１１の一端を内胴２の前面に装着し、残りは給湯器１のカバーの内面に沿って内胴２の周りを非接触で一周させ、終端をネジ止め等で貼着することで、内胴２の全周を被覆させている。又、導電パターンは、抵抗値が正常時で５０ｋΩ〜１５０ｋΩとなるように設定されており、その両端はコントローラ１０に電気的接続されている。
【０００７】
そして、図２は、コントローラ１０と感熱シート１１とで構成される過熱防止回路２０を示すもので、まず、感熱シート１１の導電パターン１３は分割抵抗２１と直列に接続され、両者間で分圧された電圧としてコンパレータ２２の−入力端子及びコンパレータ２３の＋入力端子に夫々入力される。一方、導電パターン１３及び分割抵抗２１と並設され、直列接続される３つの分割抵抗２４，２５，２６のうち、コンパレータ２２の＋入力端子には、分割抵抗２４，２５間の分圧が上限電圧として、コンパレータ２３の−入力端子には、分割抵抗２５，２６間の分圧が下限電圧として夫々入力され、各コンパレータ２２，２３からの出力が判断手段としてのマイコン２７の入力ポートＩＰに入力可能となっている。
又、マイコン２７の出力ポートＯＰには、ここからの出力によってＯＮ／ＯＦＦされるトランジスタ２８，２９が配置され、その出力側には、ガスバーナ７への安全弁へ電源を供給してこれを開弁させる安全弁駆動回路３０が設けられている。
【０００８】
よって、この過熱防止回路２０によれば、通常では、導電パターン１３の抵抗値が設定された範囲内であれば、基準電圧は、コンパレータ２２への上限電圧及びコンパレータ２３への下限電圧の範囲内にあるため、コンパレータ２２，２３は夫々Ｈｉ出力となり、マイコン２７への入力もＨｉとなる。しかし、異常過熱により内胴２にひび割れや穴あき等が発生し、そこから燃焼ガスが噴出すると、感熱シート１１の導電パターン１３が破断して抵抗値が急増或は無限大になり、コンパレータ２２，２３への入力電圧が下限電圧以下となるため、コンパレータ２３の出力が反転してＬｏとなり、マイコン２７への入力もＬｏとなる。従って、これを検知したマイコン２７は異常過熱が生じたと判断し、トランジスタ２８，２９をＯＦＦさせて安全弁への通電を停止してこれを閉弁させ、ガスバーナ７への燃料ガスの供給を遮断する。又、破断した導電パターン１３が短絡されることがあっても、短絡によるコンパレータ２２，２３への入力電圧は上限電圧を上回る値となるため、この場合もコンパレータ２２の出力がＬｏとなることでマイコン２７への入力がＬｏとなり、マイコン２７は異常過熱と判断して安全弁を閉弁させる。
このように、上記過熱防止回路２０によれば、導電パターン１３の抵抗値を短絡時より高い値としてこれを所定範囲の判定値と比較させることで、導電パターン１３の破断により異常過熱を検知して対処できるのは勿論、導電パターン１３の短絡によっても同様に異常を判断できるため、破断した感熱シート１１の再使用を完全に防止可能となる。よって、過熱防止機能の信頼性が高まる。
【０００９】
尚、図２では、トランジスタ２８，２９をＯＮする出力ポートＯＰを、ダイオード３１を介してコンパレータ２２，２３の出力側に接続する誤動作防止手段を採用している。この場合、過熱防止回路２０が異常過熱を検知すると、コンパレータ２２，２３からの出力がＬｏとなるため、マイコン２７が出力ポートＯＰからトランジスタ２８のＯＮ信号を出力しても、電流はダイオード３１を介してコンパレータ２２，２３側へ流れ、トランジスタ２８，２９をＯＮさせない。よって、マイコン２７に故障や暴走等が生じても、過熱防止回路２０が異常過熱を検知した場合は確実に安全弁駆動回路３０への通電を遮断することができ、安全性の一層の向上が期待できる。
【００１０】
又、過熱防止回路は他の構成でも実現できる。図３はその変更例を示すもので、図２と同じ符号は同じ構成部である。ここに示す過熱防止回路３２では、コンパレータ３３の−入力端子に、導電パターン１３と分割抵抗２１からの電圧を、＋入力端子に分割抵抗３４，３５間の分圧を夫々入力して、コンパレータ３３の出力をマイコン２７の入力ポートＩＰに入力するものとしているが、ここでは、分割抵抗３５の片側に、ベースをマイコン２７の出力ポートＯＰ１に接続したトランジスタ３６を接続しており、マイコン２７は、常態では出力ポートＯＰ１からパルス信号を出力させてトランジスタ３６をＯＮ／ＯＦＦさせ、コンパレータ３３へ判定値をパルス入力している。尚、３７は、分割抵抗３５と並列に接続された抵抗で、トランジスタ３６のＯＦＦ時の上限値を固定するものである。
よって、この過熱防止回路３２によれば、導電パターン１３と分割抵抗２１による基準電圧が、トランジスタ３６のＯＮ／ＯＦＦで設定される上限値及び下限値の範囲内であれば、コンパレータ３３の出力はＬｏとＨｉとを交互に繰り返すパルス信号となる。ここで導電パターン１３が破断すると、抵抗値の急増或は無限大により、コンパレータ３３の出力がＨｉに固定されるため、マイコン２７は異常過熱と判断して出力ポートＯＰ２からの出力でトランジスタ２８，２９をＯＦＦさせ、安全弁を閉弁させる。一方、破断した導電パターン１３を短絡すると、コンパレータ３３の出力はＬｏに固定されるため、ここでもマイコン２７は異常と判断して安全弁を閉弁させる。
【００１１】
このように、上記過熱防止回路３２においても、高い抵抗値を有する導電パターン１３の破断により異常過熱を検知して対処できるのは勿論、導電パターン１３の短絡によっても同様に異常過熱を判断できるため、破断した感熱シート１１の再使用を完全に防止可能となり、過熱防止機能の信頼性が高まる。特にこの形態では、上下限値の設定をパルス信号で得ているため、過熱防止回路３２に回路故障が生じた際には、コンパレータ３３の繰り返しパルスが得られなくなることで、基準電圧側の回路故障も検知可能となる。
【００１２】
【発明の効果】
請求項１に記載の発明によれば、導電パターンの抵抗値を短絡時より高くすると共に、比較手段の判定値をそれに合わせて設定して比較することで、導電パターンの破断により異常過熱と判断して燃焼停止等の対処ができるのは勿論、導電パターンの短絡によっても同様に異常を判断できるため、破断した感熱シートの再使用を完全に防止可能となり、過熱防止機能の信頼性が高まる。
特に、比較手段が前記所定範囲の上限値と下限値とを交互に切り換えて導電パターンの抵抗値と比較することで、正常時の比較結果が上下限の繰り返しパルスで得られるため、過熱防止回路に回路故障が生じた際には、繰り返しパルスが得られなくなることでその回路故障も異常として検知可能となる。
請求項２に記載の発明によれば、請求項１の効果に加えて、判断手段が異常と判断した場合にはバーナの燃焼を停止させることで、異常過熱や回路故障の対処を確実に行うことができる。
請求項３に記載の発明によれば、請求項１又は２の効果に加えて、導電パターンの抵抗値が判定値を超える場合又は下回る場合には、判断手段の判断に拘わらず直接バーナの燃焼を停止させる誤動作防止手段を設けたことで、判断手段に故障や暴走が生じても、比較手段の比較結果に応じた異常過熱の対処が確実に可能となり、安全性の一層の向上が期待できる。
【図面の簡単な説明】
【図１】過熱防止装置を備えた給湯器の説明図である。
【図２】過熱防止回路の回路図である。
【図３】過熱防止回路の変更例を示す回路図である。
【符号の説明】
１・・給湯器、２・・内胴、３・・燃焼室、７・・ガスバーナ、１０・・コントローラ、１１・・感熱シート、１３・・導電パターン、２０，３２・・過熱防止回路、２２，２３，３３・・コンパレータ、２７・・マイコン、２８，２９，３６・・トランジスタ、３０・・安全弁駆動回路、３１・・ダイオード。[0001]
BACKGROUND OF THE INVENTION
In the present invention, a thermal sheet having a conductive pattern is disposed around a casing of a combustion chamber equipped with a burner, and this is detected by a change in the resistance value of the conductive pattern when a crack or the like is caused by abnormal overheating in the casing. The present invention relates to an overheat prevention device for a combustion appliance that can be detected.
[0002]
[Prior art]
The overheat prevention device is provided with a heat-sensitive sheet obtained by printing a conductive pattern on a heat-meltable resin sheet around a casing of a combustion chamber provided with a burner, and the conductive pattern is used as a controller for controlling combustion of the burner. Configured by electrical connection. In other words, cracks and holes are generated in the combustion chamber due to abnormal overheating, and when the combustion gas is ejected from the crack, the portion of the conductive pattern breaks with the fusing of the thermal sheet, and the resistance value increases rapidly or becomes infinite. Therefore, the controller that detects the change in the resistance value determines that the overheating is abnormal and stops the supply of the fuel gas to the burner.
[0003]
[Problems to be solved by the invention]
In the overheat prevention device, a resistance value of the conductive pattern of about several Ω is often used, so even if the fuel supply is stopped due to abnormal overheating once, the fusing point or both ends of the conductive pattern By short-circuiting with the lead wire, the abnormal overheat detection state due to the conductive pattern is released, and the casing can be continuously used without being cracked.
[0004]
SUMMARY OF THE INVENTION An object of the present invention is to provide an overheat prevention device for a combustion appliance that can be easily reused after detection of abnormal overheating and can improve safety.
[0005]
[Means for Solving the Problems]
In order to achieve the above object, the invention according to claim 1 is characterized in that the comparing means for comparing the resistance value of the conductive pattern with a predetermined determination value, and the resistance value of the conductive pattern exceeds the determination value, And a determination means for determining that the combustion chamber is abnormally overheated, wherein the resistance value of the conductive pattern is set to be higher than that at the time of short-circuiting of the conductive pattern in a normal state, and the determination of the comparison means The value is set to a predetermined range in which an upper limit value and a lower limit value are set including a normal resistance value of the conductive pattern, and the comparing means alternately sets the upper limit value and the lower limit value of the predetermined range. Switching and comparing with the resistance value of the conductive pattern, when the resistance value is within the predetermined range, a pulse signal is output, and when the resistance value of the conductive pattern is above and below the predetermined range, The comparison means The pulse signal is possible by the determination unit not obtained in is characterized in that it is determined that the abnormality.
In addition to the object of the first aspect, the invention described in claim 2 is configured to stop the combustion of the burner when the determination means determines that an abnormality has occurred, in order to ensure the countermeasure after the abnormality is determined. Is.
In addition to the object of the first or second aspect, the invention according to claim 3 is characterized in that the resistance value of the conductive pattern is determined as a determination value in order to reliably cope with abnormal overheating in consideration of failure or runaway of the determination means. When it exceeds or falls below, malfunction prevention means for directly stopping combustion of the burner is provided regardless of the judgment of the judgment means.
[0006]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is an explanatory view of a state where an overheating prevention device of the present invention is applied to a forced air supply type gas water heater (hereinafter simply referred to as “hot water heater”) as an example of a combustion appliance. The chamber 3 is formed inside, and an inner cylinder as a casing in which a water supply pipe 4 is spirally wound on the outer peripheral surface. The water supply pipe 4 is an endothermic pipe 6 of a heat exchanger 5 provided on the upper part of the inner cylinder 2. It is connected to the. On the other hand, a gas burner 7 is installed below the inner cylinder 2. By heating the heat exchanger 5 with the gas burner 7, water passing through the heat absorption tube 6 of the heat exchanger 5 is heated, and the heat absorption tube 6. The hot water can be discharged from a hot water pipe (not shown) connected to the outlet side. An air supply fan 9 is provided below an air supply chamber 8 provided at the lower part of the combustion chamber 3 so that combustion air can be forcibly supplied to the gas burner 7. Further, reference numeral 10 denotes a controller for detecting the abnormal overheat described later, in addition to the opening / closing control of the gas source valve and safety valve at the time of the fire extinguishing operation of the gas burner 7 and the opening adjustment of the proportional control valve at the time of temperature setting. .
On the other hand, a planar heat-sensitive sheet 11 is disposed on the outer periphery of the inner body 2. The heat-sensitive sheet 11 has a conductive pattern in a meandering shape on a single line so as to cover the entire surface using a conductive ink or the like on the surface of a resin sheet (for example, made of PET resin) having a melting point between 200 ° C. and 300 ° C. The same material as the previous resin sheet is laminated and integrated on the upper surface, and the water supply pipe 4 is sandwiched between the clips 12, 12,. One end of the sheet 11 is attached to the front surface of the inner cylinder 2, and the rest is made around the inner cylinder 2 in a non-contact manner along the inner surface of the cover of the water heater 1, and the end is attached by screwing or the like. The entire circumference of the inner cylinder 2 is covered. The conductive pattern is set to have a resistance value of 50 kΩ to 150 kΩ in a normal state, and both ends thereof are electrically connected to the controller 10.
[0007]
FIG. 2 shows an overheat prevention circuit 20 composed of the controller 10 and the heat sensitive sheet 11. First, the conductive pattern 13 of the heat sensitive sheet 11 is connected in series with the dividing resistor 21, and the voltage is divided between the two. The input voltage is input to the negative input terminal of the comparator 22 and the positive input terminal of the comparator 23, respectively. On the other hand, among the three divided resistors 24, 25, and 26 that are arranged in parallel with the conductive pattern 13 and the divided resistor 21, the divided voltage between the divided resistors 24 and 25 is the upper limit at the + input terminal of the comparator 22. As a voltage, the divided voltage between the dividing resistors 25 and 26 is input to the negative input terminal of the comparator 23 as a lower limit voltage, and the output from each comparator 22 and 23 is input to the input port IP of the microcomputer 27 as a determination means. It is possible.
Transistors 28 and 29 that are turned ON / OFF by the output from the microcomputer 27 are arranged at the output port OP of the microcomputer 27. On the output side, power is supplied to the safety valve for the gas burner 7 to open it. A safety valve drive circuit 30 is provided.
[0008]
Therefore, according to the overheat prevention circuit 20, the reference voltage is normally within the range of the upper limit voltage to the comparator 22 and the lower limit voltage to the comparator 23 as long as the resistance value of the conductive pattern 13 is within the set range. Therefore, each of the comparators 22 and 23 becomes Hi output, and the input to the microcomputer 27 becomes Hi. However, when the inner cylinder 2 is cracked or perforated due to abnormal overheating and the combustion gas is ejected from the crack, the conductive pattern 13 of the heat sensitive sheet 11 is broken and the resistance value increases rapidly or becomes infinite. , 23 is lower than the lower limit voltage, the output of the comparator 23 is inverted and becomes Lo, and the input to the microcomputer 27 is also Lo. Accordingly, the microcomputer 27 that has detected this determines that an abnormal overheating has occurred, turns off the transistors 28 and 29, stops energization of the safety valve, closes it, and shuts off the supply of fuel gas to the gas burner 7. . Even if the broken conductive pattern 13 may be short-circuited, the input voltage to the comparators 22 and 23 due to the short-circuit becomes a value exceeding the upper limit voltage. In this case as well, the output of the comparator 22 becomes Lo. The input to the microcomputer 27 becomes Lo, and the microcomputer 27 determines that the overheating is abnormal and closes the safety valve.
As described above, according to the overheat prevention circuit 20, the resistance value of the conductive pattern 13 is set to a value higher than that at the time of the short circuit, and this is compared with a determination value within a predetermined range, thereby detecting abnormal overheating due to the break of the conductive pattern 13. As a matter of course, the abnormality can be similarly determined by a short circuit of the conductive pattern 13, so that the reuse of the broken thermal sheet 11 can be completely prevented. Therefore, the reliability of the overheat prevention function is increased.
[0009]
In FIG. 2, a malfunction preventing means for connecting the output port OP for turning on the transistors 28 and 29 to the output side of the comparators 22 and 23 via the diode 31 is employed. In this case, when the overheat prevention circuit 20 detects an abnormal overheat, the outputs from the comparators 22 and 23 become Lo. Therefore, even if the microcomputer 27 outputs the ON signal of the transistor 28 from the output port OP, the current flows through the diode 31. The transistors 28 and 29 are not turned on. Therefore, even if a failure or runaway occurs in the microcomputer 27, if the overheat prevention circuit 20 detects abnormal overheating, the energization to the safety valve drive circuit 30 can be surely cut off, and further improvement in safety is expected. it can.
[0010]
Further, the overheat prevention circuit can be realized with other configurations. FIG. 3 shows an example of the change, and the same reference numerals as those in FIG. 2 denote the same components. In the overheat prevention circuit 32 shown here, the voltage from the conductive pattern 13 and the dividing resistor 21 is input to the negative input terminal of the comparator 33, and the divided voltage between the dividing resistors 34 and 35 is input to the positive input terminal. Is input to the input port IP of the microcomputer 27. Here, a transistor 36 having a base connected to the output port OP1 of the microcomputer 27 is connected to one side of the dividing resistor 35. In a normal state, a pulse signal is output from the output port OP 1 to turn on / off the transistor 36, and a determination value is pulse input to the comparator 33. Reference numeral 37 denotes a resistor connected in parallel with the dividing resistor 35, which fixes an upper limit value when the transistor 36 is OFF.
Therefore, according to this overheat prevention circuit 32, if the reference voltage by the conductive pattern 13 and the dividing resistor 21 is within the range between the upper limit value and the lower limit value set by ON / OFF of the transistor 36, the output of the comparator 33 is This is a pulse signal that alternately repeats Lo and Hi. Here, when the conductive pattern 13 is broken, the output of the comparator 33 is fixed to Hi due to a sudden increase or infinite resistance value. Therefore, the microcomputer 27 determines that the overheating is abnormal and the transistor 28, 29 is turned OFF and the safety valve is closed. On the other hand, when the broken conductive pattern 13 is short-circuited, the output of the comparator 33 is fixed to Lo, so that the microcomputer 27 also determines that there is an abnormality and closes the safety valve.
[0011]
As described above, the overheat prevention circuit 32 can detect and deal with abnormal overheating by rupturing the conductive pattern 13 having a high resistance value, and can also determine abnormal overheating by a short circuit of the conductive pattern 13 as well. The reuse of the broken heat-sensitive sheet 11 can be completely prevented, and the reliability of the overheat prevention function is increased. In particular, in this embodiment, since the setting of the upper and lower limit values is obtained by a pulse signal, when a circuit failure occurs in the overheat prevention circuit 32, the repetitive pulse of the comparator 33 cannot be obtained, so that the circuit on the reference voltage side Failure can also be detected.
[0012]
【The invention's effect】
According to the first aspect of the present invention, the resistance value of the conductive pattern is made higher than that at the time of the short circuit, and the determination value of the comparison means is set in accordance with the comparison value and compared, thereby determining abnormal overheating due to the breakage of the conductive pattern. As a result, it is possible to determine whether an abnormality is caused by a short circuit of the conductive pattern as well as to cope with stopping the combustion. Therefore, it is possible to completely prevent reuse of the broken heat-sensitive sheet, and the reliability of the overheat prevention function is improved.
In particular, the comparison means alternately switches between the upper limit value and the lower limit value of the predetermined range and compares it with the resistance value of the conductive pattern. When a circuit failure occurs, it becomes possible to detect the circuit failure as an abnormality because the repeated pulse cannot be obtained.
According to the second aspect of the present invention, in addition to the effect of the first aspect, when the determination means determines that an abnormality has occurred, the combustion of the burner is stopped to reliably deal with abnormal overheating and circuit failure. be able to.
According to the third aspect of the invention, in addition to the effect of the first or second aspect, when the resistance value of the conductive pattern exceeds or falls below the judgment value, the burner directly burns regardless of the judgment of the judgment means. By providing a malfunction prevention means that stops operation, even if a failure or runaway occurs in the judgment means, it is possible to reliably handle abnormal overheating according to the comparison result of the comparison means, and further improvement in safety can be expected. .
[Brief description of the drawings]
FIG. 1 is an explanatory diagram of a water heater provided with an overheat prevention device.
FIG. 2 is a circuit diagram of an overheat prevention circuit.
FIG. 3 is a circuit diagram showing a modification example of the overheat prevention circuit.
[Explanation of symbols]
1 .. Hot water heater, 2 .... Inner shell, 3 .... Combustion chamber, 7 .... Gas burner, 10 .... Controller, 11 .... Thermal sheet, 13 .... Conductive pattern, 20, 32 ... Overheat prevention circuit, 22 , 23, 33... Comparator, 27 .. Microcomputer, 28, 29, 36 .. Transistor, 30... Safety valve drive circuit, 31.

Claims (3)

バーナを備えた燃焼室のケーシングの周囲に配設され、導電パターンを形成した感熱シートと、前記導電パターンに電気的接続され、前記導電パターンの抵抗値を所定の判定値と比較する比較手段と、前記導電パターンの抵抗値が前記判定値を超えた場合に前記燃焼室の異常過熱と判断する判断手段とを備えた燃焼器具の過熱防止装置であって、
前記導電パターンの抵抗値を、正常時で前記導電パターンの短絡時より高い値となるように設定すると共に、前記比較手段の判定値を、前記導電パターンの正常時の抵抗値を含んで上限値と下限値とが設定される所定範囲に設定して、前記比較手段は、前記所定範囲の上限値と下限値とを交互に切り換えて前記導電パターンの抵抗値と比較し、前記抵抗値が前記所定範囲内の場合はパルス信号を出力して、前記導電パターンの抵抗値が前記所定範囲を上回る場合と下回る場合とには、前記比較手段からの前記パルス信号が得られなくなることで前記判断手段が異常と判断することを特徴とする燃焼器具の過熱防止装置。A thermal sheet disposed around a casing of a combustion chamber provided with a burner and formed with a conductive pattern; and a comparison means that is electrically connected to the conductive pattern and compares the resistance value of the conductive pattern with a predetermined determination value; An overheat prevention device for a combustion appliance, comprising: a determination unit that determines that the combustion chamber is abnormally overheated when a resistance value of the conductive pattern exceeds the determination value;
The resistance value of the conductive pattern is set to be higher than normal when the conductive pattern is short-circuited, and the determination value of the comparing means includes an upper limit value including the resistance value when the conductive pattern is normal. It is set to a predetermined range and the lower limit value is set and, the comparison means, the upper limit of the predetermined range and the lower limit value is switched alternately compared with the resistance value of the conductive pattern, wherein the resistance value of the A pulse signal is output when the value is within the predetermined range, and the determination unit is configured such that the pulse signal from the comparison unit cannot be obtained when the resistance value of the conductive pattern exceeds or falls below the predetermined range. The overheat prevention device for a combustion appliance is characterized in that it is determined as abnormal. 判断手段が異常と判断した場合にはバーナの燃焼を停止させる請求項１に記載の燃焼器具の過熱防止装置。  The overheat prevention device for a combustion appliance according to claim 1, wherein the burner combustion is stopped when the determination means determines that there is an abnormality. 導電パターンの抵抗値が判定値を超える場合又は下回る場合には、判断手段の判断に拘わらず直接バーナの燃焼を停止させる誤動作防止手段を設けた請求項１又は２に記載の燃焼器具の過熱防止装置。  The overheating prevention of the combustion appliance according to claim 1 or 2, further comprising a malfunction prevention means for directly stopping the combustion of the burner regardless of the judgment of the judgment means when the resistance value of the conductive pattern exceeds or falls below the judgment value. apparatus.
JP17625498A 1998-06-23 1998-06-23 Overheat prevention device for combustion equipment Expired - Fee Related JP4190057B2 (en)

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JP2515049Y2 (en) * 1990-07-14 1996-10-23 パロマ工業株式会社 Overheat prevention device for combustion equipment
JPH04198616A (en) * 1990-11-28 1992-07-20 Sanyo Electric Co Ltd Safety device of combustion apparatus
JPH062845A (en) * 1992-06-22 1994-01-11 Noritz Corp Safety device for burner
JP2738805B2 (en) * 1993-05-28 1998-04-08 リンナイ株式会社 Combustion equipment
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