JP7413145B2 - combustion device - Google Patents

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JP7413145B2
JP7413145B2 JP2020084932A JP2020084932A JP7413145B2 JP 7413145 B2 JP7413145 B2 JP 7413145B2 JP 2020084932 A JP2020084932 A JP 2020084932A JP 2020084932 A JP2020084932 A JP 2020084932A JP 7413145 B2 JP7413145 B2 JP 7413145B2
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健 竹内
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Rinnai Corp
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Description

本発明は、空気に燃料ガスを混合し、混合気をファンを介してバーナに供給する燃焼装置に関する。 The present invention relates to a combustion device that mixes air with fuel gas and supplies the mixture to a burner via a fan.

従来、この種の燃焼装置として、燃料ガス供給量を調節するガス量調節手段と、バーナから噴出する混合気の燃焼で形成される火炎の電気抵抗値である火炎抵抗値を計測する火炎抵抗計測手段と、制御手段とを備え、制御手段は、混合気の空気過剰率（一次空気量／化学量論的空気量）が所定の適正値であるときの火炎抵抗値と混合気供給量との関係を表す特性線を基準火炎抵抗特性線として記憶し、火炎抵抗計測手段で計測した火炎抵抗値が、ファン回転数から算定された混合気供給量に合致する基準火炎抵抗特性線上の火炎抵抗値になるように、ガス量調節手段により燃料ガス供給量を調節する制御を行うように構成されるものが知られている（例えば、特許文献１参照）。 Conventionally, this type of combustion device has a gas amount adjusting means for adjusting the amount of fuel gas supplied, and a flame resistance measuring means for measuring the flame resistance value, which is the electrical resistance value of the flame formed by combustion of the air-fuel mixture ejected from the burner. and a control means, wherein the control means determines the relationship between the flame resistance value and the mixture supply amount when the excess air ratio (primary air amount/stoichiometric air amount) of the mixture is a predetermined appropriate value. The characteristic line representing the relationship is stored as a standard flame resistance characteristic line, and the flame resistance value measured by the flame resistance measuring means is the flame resistance value on the standard flame resistance characteristic line that matches the air-fuel mixture supply amount calculated from the fan rotation speed. There is known a device configured to perform control to adjust the amount of fuel gas supplied by a gas amount adjusting means so that the amount of fuel gas is supplied (see, for example, Patent Document 1).

ここで、燃料ガスとして同じガス種を使用していても、時間により燃料ガスの発熱量（ウォッベ指数）が変動することがある。上記従来例のものでは、燃料ガスの発熱量が変動しても、基準火炎抵抗特性線に基づく燃料ガス供給量の調節で混合気の空気過剰率は適正値に維持され、燃焼不良の発生を防止できる。 Here, even if the same type of gas is used as the fuel gas, the calorific value (Wobbe index) of the fuel gas may vary depending on time. In the above conventional example, even if the calorific value of the fuel gas fluctuates, the excess air ratio of the mixture is maintained at an appropriate value by adjusting the fuel gas supply amount based on the standard flame resistance characteristic line, thereby preventing the occurrence of combustion defects. It can be prevented.

尚、バーナからの燃焼ガスで加熱する熱交換器のフィン詰まりや排気筒の詰まりといった排気閉塞を生ずると、混合気供給量はファン回転数に対応する基準量よりも減少してしまう。排気閉塞率が高くなると、混合気供給量がファン回転数に対応する基準量に比しより多く減少するようになり、ファン電流（ファンモータへの通電電流）もファン回転数に対応する基準電流に比しより多く減少するようになる。そのため、公知の如く、ファン回転数とファン電流との相関関係から排気閉塞率を算定することができる。従って、ファン回転数と混合気供給量との関係を表すファン特性線として、排気閉塞率に応じた特性線を記憶しておけば、ファン回転数とファン電流との相関関係から算定した排気閉塞率に対応するファン特性線に基づきファン回転数から混合気供給量を算定することができる。そして、このように算定した混合気供給量に合致する基準火炎抵抗特性線上の火炎抵抗値になるように、ガス量調節手段により燃料ガス供給量を調節すれば、排気閉塞率がどのような値になっても、混合気の空気過剰率を適正値に維持できる。 Note that if exhaust gas blockage occurs, such as clogging of the fins of the heat exchanger heated by combustion gas from the burner or clogging of the exhaust pipe, the amount of air-fuel mixture supplied will decrease from the reference amount corresponding to the fan rotation speed. When the exhaust blockage rate increases, the amount of air-fuel mixture supplied decreases more than the reference amount corresponding to the fan rotation speed, and the fan current (current flowing to the fan motor) also decreases to the reference current corresponding to the fan rotation speed. It will decrease more than . Therefore, as is well known, the exhaust air blockage rate can be calculated from the correlation between the fan rotation speed and the fan current. Therefore, if you memorize the characteristic line corresponding to the exhaust blockage rate as the fan characteristic line that represents the relationship between the fan rotation speed and the air-fuel mixture supply amount, you can The air-fuel mixture supply amount can be calculated from the fan rotation speed based on the fan characteristic line corresponding to the ratio. Then, if the fuel gas supply amount is adjusted by the gas amount adjustment means so that the flame resistance value is on the standard flame resistance characteristic line that matches the air-fuel mixture supply amount calculated in this way, what value will the exhaust blockage rate be? The excess air ratio of the mixture can be maintained at an appropriate value even when

ところで、排気筒への風の侵入で排気不良を生じないようにするため、即ち、耐風性能を確保するため、ファンの下限回転数をあまり低く設定することはできない。そして、要求燃焼量がファンの下限回転数に対応する所定の閾値以下になった場合には、要求燃焼量に対応する量の混合気を供給できなくなる。そこで、ファンの上流側の空気供給路の通気抵抗を大小に切換える空気抵抗切換手段を設け、要求燃焼量が所定の閾値以下になったときに、空気抵抗切換手段を空気供給路の通気抵抗を小さくする状態から通気抵抗を大きくする状態に切換えるようにした燃焼装置も従来知られている。これによれば、ファン回転数を下限回転数以下にせずに、閾値以下の要求燃焼量に対応する量の混合気を供給できる。 By the way, in order to prevent poor exhaust from occurring due to wind entering the exhaust stack, that is, to ensure wind resistance performance, the lower limit rotation speed of the fan cannot be set too low. Then, when the required combustion amount becomes less than or equal to a predetermined threshold value corresponding to the lower limit rotation speed of the fan, it becomes impossible to supply an amount of air-fuel mixture corresponding to the required combustion amount. Therefore, an air resistance switching means is provided to change the ventilation resistance of the air supply path on the upstream side of the fan, and when the required combustion amount becomes less than a predetermined threshold, the air resistance switching means changes the ventilation resistance of the air supply path. Combustion devices that switch from a state where the ventilation resistance is reduced to a state where the ventilation resistance is increased are also known. According to this, it is possible to supply an amount of air-fuel mixture corresponding to the required combustion amount below the threshold value without reducing the fan rotation speed below the lower limit rotation speed.

このように空気抵抗切換手段を設ける場合は、空気抵抗切換手段が空気供給路の通気抵抗を小さくする状態であるときのファン回転数と混合気供給量との関係を表す第１のファン特性線及び空気抵抗切換手段が空気供給路の通気抵抗を大きくする状態であるときのファン回転数と混合気供給量との関係を表す第２のファン特性線として、夫々、排気閉塞率に応じた特性線を記憶しておき、ファン回転数とファン電流との相関関係から算定された排気閉塞率に対応する第１と第２の各ファン特性線に基づいてファン回転数から算定された混合気供給量に合致する基準火炎抵抗特性線上の火炎抵抗値になるように、燃料ガス調節手段により燃料ガス供給量を調節することが考えられる。 When the air resistance switching means is provided in this way, the first fan characteristic line representing the relationship between the fan rotation speed and the air-fuel mixture supply amount when the air resistance switching means is in a state where the air resistance of the air supply path is reduced is and a second fan characteristic line representing the relationship between the fan rotation speed and the air-fuel mixture supply amount when the air resistance switching means is in a state where the ventilation resistance of the air supply path is increased. The air-fuel mixture supply is calculated from the fan rotation speed based on the first and second fan characteristic lines that correspond to the exhaust blockage rate calculated from the correlation between the fan rotation speed and the fan current. It is conceivable that the amount of fuel gas supplied is adjusted by the fuel gas adjusting means so that the flame resistance value is on the reference flame resistance characteristic line that matches the amount of flame resistance.

然し、空気抵抗切換手段が空気供給路の通気抵抗を大きくする状態に切換えられたときは、排気閉塞率に対するファン回転数とファン電流の相関関係の変化が小さくなってしまう。そのため、空気抵抗切換手段が空気供給路の通気抵抗を大きくする状態に切換えられたときは、ファン回転数とファン電流との相関関係から排気閉塞率を正しく算定することが困難になり、その結果、混合気の空気過剰率を適正値に維持することが困難になってしまう。 However, when the air resistance switching means is switched to a state where the ventilation resistance of the air supply path is increased, the change in the correlation between the fan rotation speed and the fan current with respect to the exhaust air blockage rate becomes small. Therefore, when the air resistance switching means is switched to a state that increases the ventilation resistance of the air supply path, it becomes difficult to accurately calculate the exhaust blockage rate from the correlation between the fan rotation speed and the fan current, and as a result, , it becomes difficult to maintain the excess air ratio of the mixture at an appropriate value.

特開２００７－４０６９７号公報Japanese Patent Application Publication No. 2007-40697

本発明は、以上の点に鑑み、空気抵抗切換手段を備える燃焼装置であって、空気抵抗切換手段が空気供給路の通気抵抗を大きくする状態に切換えられたときでも、混合気の空気過剰率を適正値に維持できるようにしたものを提供することをその課題としている。 In view of the above points, the present invention provides a combustion device equipped with an air resistance switching means, wherein even when the air resistance switching means is switched to a state in which the ventilation resistance of the air supply path is increased, the excess air ratio of the air-fuel mixture is reduced. The challenge is to provide something that can maintain the value at an appropriate value.

上記課題を解決するために、本発明は、空気に燃料ガスを混合し、混合気をファンを介してバーナに供給する燃焼装置であって、燃料ガス供給量を調節するガス量調節手段と、バーナから噴出する混合気の燃焼で形成される火炎の電気抵抗値である火炎抵抗値を計測する火炎抵抗計測手段と、制御手段とを備え、制御手段は、ファン回転数から混合気供給量を算定する混合気量算定処理を行うと共に、混合気の空気過剰率が所定の適正値であるときの火炎抵抗値と混合気供給量との関係を表す特性線を基準火炎抵抗特性線として記憶し、火炎抵抗計測手段で計測した火炎抵抗値が、混合気量算定処理で算定された混合気供給量に合致する基準火炎抵抗特性線上の火炎抵抗値になるように、ガス量調節手段により燃料ガス供給量を調節する制御を行うように構成され、更に、ファンの上流側の空気供給路の通気抵抗を大小に切換える、制御手段で制御される空気抵抗切換手段を備え、要求燃焼量が所定の閾値以下になったときに、空気抵抗切換手段を空気供給路の通気抵抗を小さくする状態から通気抵抗を大きくする状態に切換えるようにしたものにおいて、制御手段は、空気抵抗切換手段が空気供給路の通気抵抗を小さくする状態であるときのファン回転数と混合気供給量との関係を表す第１のファン特性線と、空気抵抗切換手段が空気供給路の通気抵抗を大きくする状態であるときのファン回転数と混合気供給量との関係を表す第２のファン特性線として、夫々、バーナから噴出する混合気の燃焼で生ずる燃焼ガスが流れる経路の閉塞率である排気閉塞率に応じた特性線を記憶し、ファン回転数とファン電流との相関関係から排気閉塞率を算定する閉塞率算定処理を行い、この閉塞率算定処理は、空気抵抗切換手段が空気供給路の通気抵抗を小さくする状態であるときにのみ行われ、空気抵抗切換手段が空気供給路の通気抵抗を小さくする状態であるときの混合気量算定処理では、閉塞率算定処理で算定された排気閉塞率に対応する第１のファン特性線に基づきファン回転数から混合気供給量を算定し、空気抵抗切換手段が空気供給路の通気抵抗を大きくする状態であるときの混合気量算定処理では、空気抵抗切換手段が空気供給路の通気抵抗を小さくする状態であるときに行われた閉塞率算定処理で算定された排気閉塞率に対応する第２のファン特性線に基づきファン回転数から混合気供給量を算定するように構成されることを特徴とする。 In order to solve the above problems, the present invention provides a combustion device that mixes fuel gas with air and supplies the mixture to a burner via a fan, comprising: a gas amount adjusting means that adjusts the amount of fuel gas supplied; The control means includes a flame resistance measuring means for measuring a flame resistance value, which is an electrical resistance value of a flame formed by combustion of an air-fuel mixture ejected from a burner, and a control means, and the control means calculates the air-fuel mixture supply amount from the fan rotation speed. At the same time as calculating the amount of mixture to be calculated, a characteristic line representing the relationship between the flame resistance value and the amount of mixture supplied when the excess air ratio of the mixture is at a predetermined appropriate value is stored as a reference flame resistance characteristic line. , the fuel gas is adjusted by the gas amount adjusting means so that the flame resistance value measured by the flame resistance measuring means becomes a flame resistance value on the reference flame resistance characteristic line that matches the air-fuel mixture supply amount calculated in the air-fuel mixture amount calculation process. It is configured to perform control to adjust the supply amount, and further includes air resistance switching means controlled by the control means for switching the ventilation resistance of the air supply path on the upstream side of the fan to large or small, so that the required combustion amount is adjusted to a predetermined value. In the control means, the air resistance switching means is configured to switch the air resistance switching means from a state where the ventilation resistance of the air supply path is reduced to a state where the ventilation resistance is increased when the air resistance becomes equal to or less than a threshold value. A first fan characteristic line representing the relationship between the fan rotation speed and the air-fuel mixture supply amount when the air resistance is in a state where the ventilation resistance of the air supply path is decreased, and when the air resistance switching means is in a state where the ventilation resistance of the air supply path is increased. The second fan characteristic line that represents the relationship between the fan rotation speed and the air-fuel mixture supply amount corresponds to the exhaust blockage rate, which is the blockage rate of the path through which the combustion gas generated by combustion of the air-fuel mixture ejected from the burner flows. The characteristic line is memorized and a blockage rate calculation process is performed to calculate the exhaust blockage rate from the correlation between the fan rotation speed and the fan current. The air-fuel mixture amount calculation process is performed only when the air resistance switching means is in the state of reducing the ventilation resistance of the air supply path, and corresponds to the exhaust air blockage rate calculated in the blockage rate calculation process. The air-fuel mixture supply amount is calculated from the fan rotation speed based on the first fan characteristic line. The air-fuel mixture is supplied based on the fan rotation speed based on the second fan characteristic line corresponding to the exhaust air blockage rate calculated in the blockage rate calculation process performed when the resistance switching means is in a state where the ventilation resistance of the air supply path is reduced. The method is configured to calculate a quantity .

本発明によれば、空気抵抗切換手段が空気供給路の通気抵抗を大きくする状態であって、排気閉塞率を正しく算定することが困難になっても、空気抵抗切換手段が空気供給路の通気抵抗を小さくする状態であるときに算定された排気閉塞率に対応する第２のファン特性線に基づきファン回転数から混合気供給量を正確に算定できる。そして、このようにして算定した混合気供給量に合致する基準火炎抵抗特性線上の火炎抵抗値になるように、ガス量調節手段により燃料ガス供給量を調節することで、空気抵抗切換手段が空気供給路の通気抵抗を大きくする状態であっても、混合気の空気過剰率を適正値に維持することができる。 According to the present invention, even if the air resistance switching means increases the ventilation resistance of the air supply path and it becomes difficult to accurately calculate the exhaust blockage rate, the air resistance switching means increases the ventilation resistance of the air supply path. The air-fuel mixture supply amount can be accurately calculated from the fan rotation speed based on the second fan characteristic line corresponding to the exhaust gas blockage rate calculated when the resistance is reduced. Then, by adjusting the fuel gas supply amount by the gas amount adjustment means so that the flame resistance value is on the reference flame resistance characteristic line that matches the air-fuel mixture supply amount calculated in this way, the air resistance switching means Even in a state where the ventilation resistance of the supply path is increased, the excess air ratio of the mixture can be maintained at an appropriate value.

また、本発明においては、バーナの燃焼停止後又は燃焼開始前に、空気抵抗切換手段を空気供給路の通気抵抗を小さくする状態にして、閉塞率算定処理を行うことが望ましい。これによれば、バーナ燃焼中、要求燃焼量が閾値以下のままで、空気抵抗切換手段が空気供給路の通気抵抗を大きくする状態のままになって、閉塞率算定処理が実行されなくても、バーナの燃焼停止後又は燃焼開始前の閉塞率算定処理で、排気閉塞率を算定する機会を確保することができる。 Further, in the present invention, it is desirable to perform the blockage rate calculation process by setting the air resistance switching means to a state where the ventilation resistance of the air supply path is reduced after combustion of the burner is stopped or before combustion is started. According to this, during burner combustion, even if the required combustion amount remains below the threshold value, the air resistance switching means remains in the state of increasing the ventilation resistance of the air supply path, and the blockage rate calculation process is not executed. By performing the blockage rate calculation process after the combustion of the burner is stopped or before the combustion starts, an opportunity to calculate the exhaust blockage rate can be secured.

本発明の実施形態の燃焼装置を示す説明図。FIG. 1 is an explanatory diagram showing a combustion device according to an embodiment of the present invention. 基準火炎抵抗特性線と第１と第２の各ファン特性線とを示すグラフ。A graph showing a reference flame resistance characteristic line and first and second fan characteristic lines. 排気閉塞率の変化によるファン電流の低下割合を示すグラフ。Graph showing the rate of decrease in fan current due to changes in exhaust blockage rate. 実施形態の燃焼装置の制御手段による閉塞率算定処理の実行手順を示すフロー図。FIG. 3 is a flowchart showing an execution procedure of a blockage rate calculation process by the control means of the combustion device according to the embodiment.

図１に示す本発明の実施形態の燃焼装置は、全一次燃焼式のバーナ１と、バーナ１の燃焼面１ａから噴出する混合気の燃焼空間を囲う燃焼筐２と、燃焼筐２内に配置した熱交換器３とを備える熱源機である。混合気の燃焼で生ずる燃焼ガスは、熱交換器３を加熱した後に燃焼筐２の端部に接続される排気筒４を介して外部に排出される。 The combustion apparatus according to the embodiment of the present invention shown in FIG. 1 includes an all-primary combustion type burner 1, a combustion case 2 that surrounds a combustion space for an air-fuel mixture ejected from a combustion surface 1a of the burner 1, and a combustion case arranged inside the combustion case 2. This is a heat source device equipped with a heat exchanger 3. Combustion gas generated by combustion of the air-fuel mixture heats the heat exchanger 3 and is then discharged to the outside via the exhaust pipe 4 connected to the end of the combustion case 2.

この燃焼装置では、空気に燃料ガスを混合し、混合気をファン５を介してバーナ１に供給している。そして、燃焼装置は、ファン５の上流側の空気供給路６と、燃料ガスを供給するガス供給路７とを備えている。ガス供給路７の下流端は、空気供給路６に設けられたガス吸引部６１に接続されている。ガス吸引部６１の上流側に隣接する空気供給路６の部分には、後述するバタフライ弁６２を配置した部分よりも小径なベンチュリ部６３が設けられている。ベンチュリ部６３の下流側に隣接する空気供給路６の部分は、ベンチュリ部６３より大径の筒部６４で囲われている。そして、ベンチュリ部６３の下流端部を筒部６４の上流端部に環状の隙間を存して挿入し、この隙間でガス吸引部６１を構成している。ガス供給路７の下流端には、筒部６４を囲うようにして、ガス吸引部６１に連通するガス室７１が設けられている。また、ガス供給路７には、上流側から順に、元弁７２と、二次ガス圧を大気圧に調圧するゼロガバナ７３と、ガス量調節手段たる流量調節弁７４とが介設されている。 In this combustion device, air is mixed with fuel gas, and the mixture is supplied to the burner 1 via the fan 5. The combustion device includes an air supply path 6 upstream of the fan 5 and a gas supply path 7 that supplies fuel gas. The downstream end of the gas supply path 7 is connected to a gas suction section 61 provided in the air supply path 6 . A portion of the air supply path 6 adjacent to the upstream side of the gas suction portion 61 is provided with a venturi portion 63 having a smaller diameter than a portion where a butterfly valve 62 described later is disposed. A portion of the air supply path 6 adjacent to the downstream side of the venturi portion 63 is surrounded by a cylindrical portion 64 having a larger diameter than the venturi portion 63. Then, the downstream end of the venturi section 63 is inserted into the upstream end of the cylindrical section 64 with an annular gap therebetween, and this gap forms the gas suction section 61. A gas chamber 71 is provided at the downstream end of the gas supply path 7 so as to surround the cylindrical portion 64 and communicate with the gas suction portion 61 . Further, the gas supply path 7 is provided with, in order from the upstream side, a main valve 72, a zero governor 73 for regulating the secondary gas pressure to atmospheric pressure, and a flow rate regulating valve 74 serving as a gas amount regulating means.

ガス吸引部６１を介して供給される燃料ガスの量は、二次ガス圧である大気圧と空気供給路６内の負圧との差圧に応じて変化する。ここで、空気供給路６内の負圧は、ファン５の回転数に応じて変化する。そのため、燃料ガスの供給量はファン５の回転数、即ち、空気の供給量に比例して変化する。また、燃料ガスの供給量と空気の供給量との比率は、流量調節弁７４の開度によって変化する。流量調節弁７４の開度を使用するガス種に応じた所定の基準開度にすることで、混合気の空気過剰率が所定の適正値（例えば、１．３）になる。そして、制御手段たるコントローラ８により、要求燃焼量（設定湯温の温水を出湯するために必要な燃焼量）に応じてファン５の回転数を制御し、空気過剰率が適正値で要求燃焼量に応じた量の混合気がバーナ１に供給されるようにしている。 The amount of fuel gas supplied via the gas suction section 61 changes depending on the differential pressure between the atmospheric pressure, which is the secondary gas pressure, and the negative pressure within the air supply path 6. Here, the negative pressure within the air supply path 6 changes depending on the rotation speed of the fan 5. Therefore, the amount of fuel gas supplied changes in proportion to the rotational speed of the fan 5, that is, the amount of air supplied. Further, the ratio between the amount of fuel gas supplied and the amount of air supplied changes depending on the opening degree of the flow rate control valve 74. By setting the opening degree of the flow rate control valve 74 to a predetermined reference opening degree according to the type of gas used, the excess air ratio of the mixture becomes a predetermined appropriate value (for example, 1.3). Then, the controller 8, which is a control means, controls the rotation speed of the fan 5 according to the required combustion amount (the amount of combustion required to dispense hot water at the set hot water temperature), and the required combustion amount when the excess air ratio is at an appropriate value. The amount of air-fuel mixture corresponding to the amount is supplied to the burner 1.

尚、排気筒４への風の侵入で排気不良を生じないようにするため、即ち、耐風性能を確保するため、ファン５の下限回転数をあまり低く設定することはできない。そして、要求燃焼量がファン５の下限回転数に対応する所定の閾値以下になった場合には、要求燃焼量に対応する量の空気を供給できなくなる。 Note that in order to prevent exhaust failure due to wind entering the exhaust pipe 4, that is, to ensure wind resistance, the lower limit rotation speed of the fan 5 cannot be set too low. Then, when the required combustion amount becomes less than or equal to a predetermined threshold value corresponding to the lower limit rotation speed of the fan 5, it becomes impossible to supply the amount of air corresponding to the required combustion amount.

そこで、ガス吸引部６１より上流側の空気供給路６の部分に、当該部分の通気抵抗を大小２段に切換えるために、図外のモータにより図１に実線で示す閉じ姿勢と仮想線で示す開き姿勢とに切換えられる空気抵抗切換手段たるバタフライ弁６２を配置している。そして、コントローラ８により、要求燃焼量が上記閾値以下になった場合には、バタフライ弁６２を閉じ姿勢にして、空気供給路６の通気抵抗を大きくし、ファン５の回転数を下限回転数以下にせずに、閾値以下の要求燃焼量に対応する量の空気を供給できるようにしている。 Therefore, in order to switch the ventilation resistance of the air supply path 6 upstream of the gas suction section 61 into two stages, a motor (not shown) is used to set the closed position shown by the solid line in FIG. 1 and the closed position shown by the imaginary line in FIG. A butterfly valve 62, which serves as an air resistance switching means, is arranged to be switched between an open position and an open position. Then, when the required combustion amount becomes equal to or less than the threshold value, the controller 8 sets the butterfly valve 62 in the closed position, increases the ventilation resistance of the air supply path 6, and lowers the rotation speed of the fan 5 to below the lower limit rotation speed. This makes it possible to supply an amount of air corresponding to the required combustion amount below a threshold value without having to

但し、バタフライ弁６２を閉じ姿勢にして、空気供給路６の通気抵抗を大きくするだけでは、空気供給路６内の負圧が増加して、燃料ガスの供給量が過大となり、バーナ１に供給される混合気の空気過剰率が適正値を下回ってしまう。そのため、要求燃焼量が閾値以下の場合には、バタフライ弁６２を閉じ姿勢にして、空気供給路６の通気抵抗を大きくすると共に、流量調節弁７４を基準開度から所定開度分だけ絞って、ゼロガバナ７３の下流側のガス供給路７の部分の通気抵抗を大きくした小能力状態として、空気過剰率が適正値で閾値以下の要求燃焼量に対応する量の混合気がバーナ１に供給されるようにし、要求燃焼量が閾値を超える場合には、バタフライ弁６２を開き姿勢にして、空気供給路６の通気抵抗を小さくすると共に、流量調節弁７４を基準開度まで開いて、ゼロガバナ７３の下流側のガス供給路７の部分の通気抵抗を小さくした大能力状態として、空気過剰率が適正値で閾値を超える要求燃焼量に対応する量の混合気がバーナ１に供給されるようにしている。 However, if the butterfly valve 62 is closed and the ventilation resistance of the air supply path 6 is increased, the negative pressure inside the air supply path 6 will increase, and the amount of fuel gas supplied to the burner 1 will become excessive. The excess air ratio of the mixture becomes lower than the appropriate value. Therefore, when the required combustion amount is less than the threshold value, the butterfly valve 62 is placed in the closed position to increase the ventilation resistance of the air supply path 6, and the flow control valve 74 is throttled by a predetermined opening degree from the standard opening degree. , the air-fuel mixture is supplied to the burner 1 in an amount corresponding to the required combustion amount with an appropriate air excess ratio and a threshold value or less. If the required combustion amount exceeds the threshold value, the butterfly valve 62 is opened to reduce the ventilation resistance of the air supply path 6, and the flow rate control valve 74 is opened to the standard opening degree, and the zero governor 73 is opened. The air-fuel mixture is supplied to the burner 1 in an amount corresponding to the required combustion amount in which the excess air ratio exceeds the threshold value at an appropriate value by setting the gas supply path 7 on the downstream side of the gas supply path 7 to a high capacity state where the ventilation resistance is reduced. ing.

ところで、燃料ガスとして同じガス種を使用していても、時間により燃料ガスの発熱量（ウォッベ指数）が変動することがある。この場合、空気供給量に対する燃料ガス供給量の比が一定であると、燃料ガスの発熱量の変動で混合気の空気過剰率が変動して、燃焼不良が発生してしまう。 Incidentally, even if the same type of gas is used as the fuel gas, the calorific value (Wobbe index) of the fuel gas may vary depending on time. In this case, if the ratio of the fuel gas supply amount to the air supply amount is constant, the excess air ratio of the air-fuel mixture will fluctuate due to fluctuations in the calorific value of the fuel gas, resulting in poor combustion.

ここで、バーナ１から噴出する混合気の燃焼で形成される火炎の電気抵抗値である火炎抵抗値は、混合気の空気過剰率と相関関係がある。また、バーナ１への混合気供給量、即ち、燃焼量が増加すると、火炎中のイオン量が増加して、火炎抵抗値が減少する。図２のＲＬは、混合気の空気過剰率が所定の適正値（例えば、１．３）であるときの、火炎抵抗値と混合気供給量との関係を表す基準火炎抵抗特性線を示している。コントローラ８のメモリには、この基準火炎抵抗特性線ＲＬが記憶されている。 Here, the flame resistance value, which is the electrical resistance value of the flame formed by combustion of the air-fuel mixture ejected from the burner 1, has a correlation with the excess air ratio of the air-fuel mixture. Further, when the amount of air-fuel mixture supplied to the burner 1, that is, the amount of combustion increases, the amount of ions in the flame increases, and the flame resistance value decreases. RL in FIG. 2 indicates a reference flame resistance characteristic line representing the relationship between flame resistance value and mixture supply amount when the excess air ratio of the mixture is a predetermined appropriate value (for example, 1.3). There is. The memory of the controller 8 stores this reference flame resistance characteristic line RL.

また、バーナ１の燃焼面１ａに臨むフレームロッドから成る火炎抵抗計測手段９を設け、フレームロッドに流れるフレーム電流とプレームロッドへの印加電圧とから火炎抵抗値を計測するようにしている。また、コントローラ８は、ファン５の回転数（以下、ファン回転数と記す）から混合気供給量を算定する混合気量算定処理を行うと共に、火炎抵抗計測手段９で計測した火炎抵抗値が、混合気量算定処理で算定された混合気供給量に合致する基準火炎抵抗特性線ＲＬ上の火炎抵抗値になるように、流量調節弁７４により燃料ガス供給量を調節するフィードバック制御を行う。 Further, a flame resistance measuring means 9 consisting of a flame rod facing the combustion surface 1a of the burner 1 is provided, and the flame resistance value is measured from the flame current flowing through the flame rod and the voltage applied to the flame rod. Further, the controller 8 performs a mixture amount calculation process that calculates the amount of air-fuel mixture supplied from the rotation speed of the fan 5 (hereinafter referred to as fan rotation speed), and the flame resistance value measured by the flame resistance measuring means 9 is Feedback control is performed to adjust the fuel gas supply amount using the flow control valve 74 so that the flame resistance value on the reference flame resistance characteristic line RL matches the mixture supply amount calculated in the mixture amount calculation process.

ところで、ファン回転数と混合気供給量との関係は、バタフライ弁６２を開き姿勢にした状態（空気供給路６の通気抵抗を小さくした状態）では、図２にＦＬ１で示す第１のファン特性線で示すようになり、バタフライ弁６２を閉じ姿勢にした状態（空気供給路６の通気抵抗を大きくした状態）では、図２にＦＬ２で示す第２のファン特性線で示すようになる。 By the way, the relationship between the fan rotation speed and the amount of air-fuel mixture supplied is as follows with the first fan characteristic indicated by FL1 in FIG. In the state where the butterfly valve 62 is in the closed position (the state where the ventilation resistance of the air supply path 6 is increased), it becomes as shown by the second fan characteristic line indicated by FL2 in FIG.

但し、熱交換器３のフィン詰まりや排気筒４の詰まりといった燃焼ガスが流れる経路の閉塞を生ずると、混合気供給量はファン回転数に対応する基準量よりも減少してしまう。燃焼ガスが流れる経路の閉塞率である排気閉塞率が高くなると、混合気供給量がファン回転数に対応する基準量に比しより多く減少するようになり、ファン電流（ファンモータへの通電電流）もファン回転数に対応する基準電流に比しより多く減少するようになる。そのため、公知の如く、ファン回転数とファン電流との相関関係から排気閉塞率を算定することができる。そこで、コントローラ８のメモリに、第１と第２の各ファン特性線ＦＬ１，ＦＬ２として、排気閉塞率に応じた特性線を記憶しておき、ファン回転数とファン電流との相関関係から排気閉塞率を算定する閉塞率算定処理を行って、混合気量算定処理では、閉塞率算定処理で算定された排気閉塞率に対応する第１と第２の各ファン特性線に基づきファン回転数から混合気供給量を算定するようにした。 However, if a blockage occurs in the path through which combustion gas flows , such as clogging of the fins of the heat exchanger 3 or clogging of the exhaust pipe 4, the amount of air-fuel mixture supplied will decrease from the reference amount corresponding to the fan rotation speed. When the exhaust obstruction rate, which is the obstruction rate of the path through which combustion gas flows , increases, the amount of air-fuel mixture supplied decreases more than the reference amount corresponding to the fan rotation speed, and the fan current (the current flowing to the fan motor) decreases. ) also decreases more than the reference current corresponding to the fan rotation speed. Therefore, as is well known, the exhaust air blockage rate can be calculated from the correlation between the fan rotation speed and the fan current. Therefore, characteristic lines corresponding to the exhaust blockage rate are stored in the memory of the controller 8 as the first and second fan characteristic lines FL1 and FL2, and exhaust blockage is determined based on the correlation between the fan rotation speed and the fan current. In the mixture amount calculation process, the air mixture is calculated from the fan rotation speed based on the first and second fan characteristic lines corresponding to the exhaust air blockage rate calculated in the blockage rate calculation process. The air supply amount is now calculated.

図２には、第１のファン特性線ＦＬ１として、排気閉塞率が０％であるときに対応する特性線ＦＬ１－０と、排気閉塞率が９０％であるときに対応する特性線ＦＬ１－９０とが図示され、第２のファン特性線ＦＬ２として、排気閉塞率が０％であるときに対応する特性線ＦＬ２－０と、排気閉塞率が９０％であるときに対応する特性線ＦＬ２－９０とが図示されている。例えば、バタフライ弁６２を開き姿勢にした状態であって、ファン回転数がＮｆｘ、排気閉塞率が９０％であれば、混合気量算定処理において、排気閉塞率９０％に対応する第１のファン特性線ＦＬ１－９０上でＮｆｘに合致するＱａを混合気供給量として算定する。そして、火炎抵抗計測手段９で計測した火炎抵抗値が、基準火炎抵抗特性線ＲＬ上でＱａに合致する火炎抵抗値であるＲａになるように流量調節弁７４をフィードバック制御する。また、バタフライ弁６２を閉じ姿勢にした状態であって、ファン回転数がＮｆｘ、排気閉塞率が９０％であれば、混合気量算定処理において、排気閉塞率９０％に対応する第２のファン特性線ＦＬ２－９０上でＮｆｘに合致するＱｂを混合気供給量として算定し、火炎抵抗計測手段９で計測した火炎抵抗値が、基準火炎抵抗特性線ＲＬ上でＱｂに合致する火炎抵抗値であるＲｂになるように流量調節弁７４をフィードバック制御する。 FIG. 2 shows, as the first fan characteristic line FL1, a characteristic line FL1-0 corresponding to when the exhaust air blockage rate is 0%, and a characteristic line FL1-90 corresponding to the case where the exhaust air blockage rate is 90%. are illustrated, and the second fan characteristic line FL2 is a characteristic line FL2-0 corresponding to when the exhaust blockage rate is 0% and a characteristic line FL2-90 corresponding to when the exhaust blockage rate is 90%. is illustrated. For example, if the butterfly valve 62 is in the open position, the fan rotation speed is Nfx, and the exhaust gas blockage rate is 90%, in the mixture amount calculation process, the first fan corresponding to the exhaust gas blockage rate of 90% is selected. Qa that matches Nfx on the characteristic line FL1-90 is calculated as the air-fuel mixture supply amount. Then, the flow control valve 74 is feedback-controlled so that the flame resistance value measured by the flame resistance measuring means 9 becomes Ra, which is a flame resistance value that matches Qa on the reference flame resistance characteristic line RL. Further, if the butterfly valve 62 is in the closed position, the fan rotation speed is Nfx, and the exhaust gas blockage rate is 90%, in the mixture amount calculation process, the second fan corresponding to the exhaust gas blockage rate of 90% is selected. Qb that matches Nfx on the characteristic line FL2-90 is calculated as the air-fuel mixture supply amount, and the flame resistance value measured by the flame resistance measuring means 9 is the flame resistance value that matches Qb on the reference flame resistance characteristic line RL. The flow control valve 74 is feedback-controlled to a certain Rb.

ところで、ファン回転数を一定にした状態で排気閉塞率を変化させると、ファン電流はファン回転数に対応する基準電流に対し図３に示す如く変化する。図３のＡ１は、バタフライ弁６２を開き姿勢にした状態における排気閉塞率の変化によるファン電流の基準電流に対する低下割合の変化を示しており、Ａ２は、バタフライ弁６２を閉じ姿勢にした状態における排気閉塞率の変化によるファン電流の基準電流に対する低下割合の変化を示している。図３から明らかなように、バタフライ弁６２を閉じ姿勢にした状態では、ファン回転数に対応する基準電流に対するファン電流の低下割合の排気閉塞率による変化、即ち、ファン回転数とファン電流の相関関係の排気閉塞率による変化が小さくなってしまう。そのため、バタフライ弁６２を閉じ姿勢にした状態では、ファン回転数とファン電流との相関関係から排気閉塞率を正しく算定することが困難になる。 By the way, when the exhaust air blockage rate is changed while the fan rotation speed is kept constant, the fan current changes as shown in FIG. 3 with respect to the reference current corresponding to the fan rotation speed. A1 in FIG. 3 shows a change in the rate of decrease of the fan current with respect to the reference current due to a change in the exhaust blockage rate when the butterfly valve 62 is in the open position, and A2 shows a change in the rate of decrease in the fan current with respect to the reference current when the butterfly valve 62 is in the closed position. It shows a change in the rate of decrease of the fan current with respect to the reference current due to a change in the exhaust blockage rate. As is clear from FIG. 3, when the butterfly valve 62 is in the closed position, the rate of decrease of the fan current with respect to the reference current corresponding to the fan rotation speed changes depending on the exhaust blockage rate, that is, the correlation between the fan rotation speed and the fan current. The change due to the related exhaust blockage rate becomes small. Therefore, when the butterfly valve 62 is in the closed position, it is difficult to accurately calculate the exhaust air blockage rate from the correlation between the fan rotation speed and the fan current.

そこで、本実施形態では、図４に示す手順で閉塞率算定処理を行うようにした。以下、この手順について詳述する。先ず、ＳＴＥＰ１で熱交換器３に通水されたか否かを判別し、通水が検知されたときに、ＳＴＥＰ２でバタフライ弁６２を開き姿勢すると共に、ＳＴＥＰ３でファン５を規定回転数（例えば、３００Ｈｚ）以上で駆動する。次に、ＳＴＥＰ４に進んで、ファン回転数とファン電流との相関関係から排気閉塞率を算定する閉塞率算定処理を実行して、混合気量算定処理で用いる排気閉塞率を算定した排気閉塞率に更新する。 Therefore, in this embodiment, the blockage rate calculation process is performed in the procedure shown in FIG. This procedure will be explained in detail below. First, in STEP 1, it is determined whether or not water is flowing through the heat exchanger 3. When water passing is detected, the butterfly valve 62 is opened in STEP 2, and the fan 5 is rotated at a specified rotation speed (for example, in STEP 3). 300Hz) or higher. Next, proceed to STEP 4, and execute the exhaust blockage rate calculation process that calculates the exhaust blockage rate from the correlation between the fan rotation speed and the fan current, and calculate the exhaust blockage rate used in the mixture amount calculation process. Update to.

その後、ＳＴＥＰ５でバタフライ弁６２を閉じ姿勢にしてから、ＳＴＥＰ６でバーナ１の燃焼を開始する。燃焼開始後は、ＳＴＥＰ７でバタフライ弁６２が開き姿勢になったか否かを判別し、開き姿勢になったときに、ＳＴＥＰ８でファン回転数が規定回転数以上であるか否かを判別する。そして、規定回転数以上であるときに、ＳＴＥＰ９で閉塞率算定処理を行って、混合気量算定処理で用いる排気閉塞率を算定した排気閉塞率に更新する。次に、ＳＴＥＰ１０で熱交換器３への通水が停止されたか否かを判別し、通水が停止されるまでは、ＳＴＥＰ７に戻ることを繰り返し、通水が停止されたきに、ＳＴＥＰ１１でバーナ１の燃焼を停止して、ＳＴＥＰ１に戻る。 Thereafter, in STEP 5, the butterfly valve 62 is brought into a closed position, and then, in STEP 6, combustion in the burner 1 is started. After the start of combustion, it is determined in STEP 7 whether the butterfly valve 62 is in the open position, and when the butterfly valve 62 is in the open position, it is determined in STEP 8 whether the fan rotation speed is equal to or higher than the specified rotation speed. Then, when the number of revolutions is equal to or higher than the specified number of rotations, a blockage rate calculation process is performed in STEP 9, and the exhaust blockage rate used in the air-fuel mixture amount calculation process is updated to the calculated exhaust blockage rate. Next, it is determined in STEP 10 whether or not the water flow to the heat exchanger 3 has been stopped, and the process is repeated to return to STEP 7 until the water flow is stopped, and when the water flow is stopped, the burner is Stop the combustion of 1 and return to STEP 1.

以上の手順によれば、閉塞率算定処理は、バタフライ弁６２が開き姿勢であるときにのみ行われる。これによれば、バタフライ弁６２が閉じ姿勢であって、排気閉塞率を正しく算定することが困難になっても、バタフライ弁６２が開き姿勢であるときに算定された排気閉塞率に対応する第２のファン特性線ＦＬ２に基づきファン回転数から混合気供給量を正確に算定できる。そして、このようにして算定した混合気供給量に合致する基準火炎抵抗特性線ＲＬ上の火炎抵抗値になるように、流量調節弁７４により燃料ガス供給量を調節することで、バタフライ弁６２が閉じ姿勢であっても、混合気の空気過剰率を適正値に維持することができる。 According to the above procedure, the blockage rate calculation process is performed only when the butterfly valve 62 is in the open position. According to this, even if the butterfly valve 62 is in the closed position and it is difficult to accurately calculate the exhaust gas blockage rate, the butterfly valve 62 is in the closed position and the exhaust gas blockage rate corresponds to the exhaust gas blockage rate calculated when the butterfly valve 62 is in the open position. The air-fuel mixture supply amount can be accurately calculated from the fan rotation speed based on the fan characteristic line FL2 of No. 2. Then, the butterfly valve 62 is adjusted by adjusting the fuel gas supply amount using the flow control valve 74 so that the flame resistance value is on the reference flame resistance characteristic line RL that matches the air-fuel mixture supply amount calculated in this way. Even in the closed position, the excess air ratio of the mixture can be maintained at an appropriate value.

尚、ファン回転数が低いと、排気閉塞率に対するファン回転数とファン電流の相関関係の変化が小さくなってしまう。そこで、本実施形態では、バタフライ弁６２が開き姿勢であっても、ファン回転数が規定回転数未満である場合は、閉塞率算定処理を実行しないようにしている。 Note that when the fan rotation speed is low, the change in the correlation between the fan rotation speed and the fan current with respect to the exhaust air blockage rate becomes small. Therefore, in this embodiment, even if the butterfly valve 62 is in the open position, if the fan rotation speed is less than the specified rotation speed, the blockage rate calculation process is not executed.

また、本実施形態では、バーナ１の燃焼開始前に、バタフライ弁６２を開き姿勢にして、閉塞率算定処理を行うようにしている。これによれば、バーナ１の燃焼中、要求燃焼量が閾値以下のままで、バタフライ弁６２が閉じ姿勢のままになって、閉塞率算定処理が実行されなくても、バーナ１の燃焼開始前の閉塞率算定処理で、排気閉塞率を算定して更新する機会を確保することができる。尚、バーナ１の燃焼停止後に、バタフライ弁６２を開き姿勢にして、閉塞率算定処理を行うようにしてもよい。 Furthermore, in this embodiment, before the burner 1 starts combustion, the butterfly valve 62 is placed in an open position and the blockage rate calculation process is performed. According to this, even if the required combustion amount remains below the threshold value and the butterfly valve 62 remains in the closed position during combustion of the burner 1, and the blockage rate calculation process is not executed, before the combustion of the burner 1 starts. With the blockage rate calculation process, it is possible to secure an opportunity to calculate and update the exhaust blockage rate. Note that after the combustion of the burner 1 is stopped, the butterfly valve 62 may be placed in an open position and the blockage rate calculation process may be performed.

以上、本発明の実施形態について図面を参照して説明したが、本発明はこれに限定されない。例えば、バタフライ弁６２以外の手段で空気抵抗切換手段を構成することも可能である。また、上記実施形態では、ガス供給路７に、ゼロガバナ７３とその下流側のガス量調節手段たる流量調節弁７４とを介設しているが、ゼロガバナに代えて比例弁を設けることも可能であり、この場合、比例弁をガス量調節手段に兼用してもよい。 Although the embodiments of the present invention have been described above with reference to the drawings, the present invention is not limited thereto. For example, it is also possible to configure the air resistance switching means by means other than the butterfly valve 62. Further, in the above embodiment, the gas supply path 7 is provided with a zero governor 73 and a flow rate control valve 74 which is a gas amount control means downstream thereof, but it is also possible to provide a proportional valve in place of the zero governor. In this case, the proportional valve may also be used as the gas amount adjusting means.

１…バーナ、５…ファン、６…空気供給路、６２…バタフライ弁（空気抵抗切換手段）、７４…流量調節弁（ガス量調節手段）、８…コントローラ（制御手段）、９…火炎抵抗計測手段、ＲＬ…基準火炎抵抗特性線、ＦＬ１－０…排気閉塞率が０％の場合の第１のファン特性線、ＦＬ１－９０…排気閉塞率が９０％の場合の第１のファン特性線、ＦＬ２－０…排気閉塞率が０％の場合の第２のファン特性線、ＦＬ２－９０…排気閉塞率が９０％の場合の第２のファン特性線。 DESCRIPTION OF SYMBOLS 1... Burner, 5... Fan, 6... Air supply path, 62... Butterfly valve (air resistance switching means), 74... Flow rate adjustment valve (gas amount adjustment means), 8... Controller (control means), 9... Flame resistance measurement Means, RL...Reference flame resistance characteristic line, FL1-0...First fan characteristic line when the exhaust blockage rate is 0%, FL1-90...First fan characteristic line when the exhaust blockage rate is 90%. FL2-0...Second fan characteristic line when the exhaust blockage rate is 0%, FL2-90...Second fan characteristic line when the exhaust blockage rate is 90%.

Claims (2)

空気に燃料ガスを混合し、混合気をファンを介してバーナに供給する燃焼装置であって、燃料ガス供給量を調節するガス量調節手段と、バーナから噴出する混合気の燃焼で形成される火炎の電気抵抗値である火炎抵抗値を計測する火炎抵抗計測手段と、制御手段とを備え、
制御手段は、ファン回転数から混合気供給量を算定する混合気量算定処理を行うと共に、混合気の空気過剰率が所定の適正値であるときの火炎抵抗値と混合気供給量との関係を表す特性線を基準火炎抵抗特性線として記憶し、火炎抵抗計測手段で計測した火炎抵抗値が、混合気量算定処理で算定された混合気供給量に合致する基準火炎抵抗特性線上の火炎抵抗値になるように、ガス量調節手段により燃料ガス供給量を調節する制御を行うように構成され、
更に、ファンの上流側の空気供給路の通気抵抗を大小に切換える、制御手段で制御される空気抵抗切換手段を備え、要求燃焼量が所定の閾値以下になったときに、空気抵抗切換手段を空気供給路の通気抵抗を小さくする状態から通気抵抗を大きくする状態に切換えるようにしたものにおいて、
制御手段は、空気抵抗切換手段が空気供給路の通気抵抗を小さくする状態であるときのファン回転数と混合気供給量との関係を表す第１のファン特性線及び空気抵抗切換手段が空気供給路の通気抵抗を大きくする状態であるときのファン回転数と混合気供給量との関係を表す第２のファン特性線として、夫々、バーナから噴出する混合気の燃焼で生ずる燃焼ガスが流れる経路の閉塞率である排気閉塞率に応じた特性線を記憶し、ファン回転数とファン電流との相関関係から排気閉塞率を算定する閉塞率算定処理を行い、この閉塞率算定処理は、空気抵抗切換手段が空気供給路の通気抵抗を小さくする状態であるときにのみ行われ、
空気抵抗切換手段が空気供給路の通気抵抗を小さくする状態であるときの混合気量算定処理では、閉塞率算定処理で算定された排気閉塞率に対応する第１のファン特性線に基づきファン回転数から混合気供給量を算定し、空気抵抗切換手段が空気供給路の通気抵抗を大きくする状態であるときの混合気量算定処理では、空気抵抗切換手段が空気供給路の通気抵抗を小さくする状態であるときに行われた閉塞率算定処理で算定された排気閉塞率に対応する第２のファン特性線に基づきファン回転数から混合気供給量を算定するように構成されることを特徴とする燃焼装置。 A combustion device that mixes fuel gas with air and supplies the mixture to a burner via a fan, and is formed by a gas amount adjustment means that adjusts the amount of fuel gas supplied, and combustion of the mixture jetted from the burner. A flame resistance measuring means for measuring a flame resistance value, which is an electrical resistance value of the flame, and a control means,
The control means performs a mixture amount calculation process that calculates the amount of mixture supplied from the fan rotation speed, and also calculates the relationship between the flame resistance value and the amount of mixture supplied when the excess air ratio of the mixture is a predetermined appropriate value. The flame resistance value measured by the flame resistance measurement means matches the air-fuel mixture supply amount calculated in the air-fuel mixture amount calculation process. The fuel gas supply amount is controlled by the gas amount adjustment means so that the amount of fuel gas is
The air resistance switching means is further provided with an air resistance switching means controlled by a control means for switching the ventilation resistance of the air supply path on the upstream side of the fan between large and small, and the air resistance switching means is controlled when the required combustion amount becomes less than a predetermined threshold value. In a device that switches from a state where the ventilation resistance of the air supply path is reduced to a state where the ventilation resistance is increased,
The control means includes a first fan characteristic line representing the relationship between the fan rotation speed and the amount of air-fuel mixture supplied when the air resistance switching means is in a state where the ventilation resistance of the air supply path is reduced; The second fan characteristic line represents the relationship between the fan rotation speed and the amount of air-fuel mixture supplied when the ventilation resistance of the air passage is large, and the path through which the combustion gas generated by combustion of the air-fuel mixture ejected from the burner flows. A characteristic line corresponding to the exhaust blockage rate , which is the blockage rate of This is carried out only when the resistance switching means is in a state where the ventilation resistance of the air supply path is reduced,
In the air-fuel mixture amount calculation process when the air resistance switching means is in a state where the ventilation resistance of the air supply path is reduced , the flow rate is calculated based on the first fan characteristic line corresponding to the exhaust air blockage rate calculated in the blockage rate calculation process. The air-fuel mixture supply amount is calculated from the fan rotation speed , and in the air-fuel mixture amount calculation process when the air resistance switching means increases the ventilation resistance of the air supply path, the air resistance switching means increases the ventilation resistance of the air supply path. The air-fuel mixture supply amount is calculated from the fan rotation speed based on the second fan characteristic line corresponding to the exhaust air blockage rate calculated in the blockage rate calculation process performed when the air-fuel mixture is in a state where the air-fuel mixture is reduced . Characteristic combustion device. 前記バーナの燃焼停止後又は燃焼開始前に、前記空気抵抗切換手段を前記空気供給路の通気抵抗を小さくする状態にして、前記閉塞率算定処理を行うことを特徴とする請求項１記載の燃焼装置。 The combustion according to claim 1, wherein the blockage rate calculation process is performed by setting the air resistance switching means to a state where the ventilation resistance of the air supply path is reduced after combustion of the burner is stopped or before combustion is started. Device.
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JP2002089838A (en) 2000-09-14 2002-03-27 Rinnai Corp Combustion device
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JP2007040697A (en) 2005-08-02 2007-02-15 Merloni Termosanitari Spa Combustion control method capable of guiding set point search
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