JP2007108133A - Air/fuel ratio detecting method of gas combustor, air/fuel ratio detection sensor thereof, and gas combustor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an air/fuel ratio detecting method of a gas combustor which considers a more safe aspect and is more enhanced in detection capacity, and to provide an air/fuel ratio detection sensor thereof, and the gas combustor. <P>SOLUTION: A fuel cell, which reaches a predetermined high-temperature state to generate electricity, is arranged in the vicinity of the combustion flame of the gas burner of the gas combustor and a combustion gas is brought into contact with the fuel electrode of the fuel cell while the electromotive force of the fuel cell caused by the contact of combustion air with an air electrode is detected and the air/fuel ratio of the gas burner is detected on the basis of the value of the detected electromotive force. Further, the air/fuel ratio detection sensor used therein and the gas combustor equipped with the air/fuel ratio detection sensor are also disclosed. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an air-fuel ratio detection method, an air-fuel ratio detection sensor, and a gas combustion device for a gas combustion device, and more particularly, to an air-fuel ratio detection method and an air-fuel ratio for a gas combustion device using a fuel cell as a sensor for detecting the air-fuel ratio. The present invention relates to a detection sensor and a gas combustion device.

  Conventionally, in a gas combustion device such as a gas water heater, in order to prevent oxygen deficiency and incomplete combustion in the device and maintain a good combustion state, the air-fuel ratio (mixing of air and fuel gas) of the gas combustion device is maintained. Ratio) is required to be detected.

  For example, Patent Literature 1 discloses a gas combustion device using a thermocouple as a sensor for detecting an air-fuel ratio. The structure will be described with reference to FIG. 8. A gas burner 80 that is supplied with a mixed gas X of air and fuel gas and burns the mixed gas X includes a burner plate 82 from which the mixed gas is jetted to form a flame. A combustion cylinder 84 is provided so as to surround the entire circumference of the burner plate 82. Then, a thermocouple 88 is arranged so as to face the combustion flame 86 (indicated by a solid line in the figure), and the heat sensitive portion 88a at the tip of the thermocouple 88 is heated by the combustion flame 86, so that the hot junction and the cold junction are cooled. A potential difference is generated between the contacts and a thermoelectromotive force is generated, and the flame temperature is detected from the value of the electromotive force.

  In such a configuration, since the combustion cylinder 84 surrounds the entire circumference of the burner plate 82, the combustion flame 86 formed on the burner plate 82 does not come into contact with the combustion secondary air. In this case, when the amount of air in the mixed gas X decreases (the air-fuel ratio decreases), the combustion state changes and the combustion speed of the fuel gas becomes slower than the ejection speed.

  As a result, the combustion flame 86 cannot be balanced on the burner plate 82, and the combustion flame 86 is lifted toward the tip opening 84a of the combustion cylinder 84 (indicated by a dotted line in the figure). At this time, since the thermocouple 88 is surrounded by lower temperature unburned gas, the electromotive force is reduced. That is, the combustion flame 86 is lifted according to the change in the air-fuel ratio of the gas burner 80, and the air-fuel ratio of the gas burner 80 is detected by detecting the temperature change at the position of the thermocouple 88 at that time.

JP 2002-162032 A

  Here, the one disclosed in Patent Document 1 ignites the gas burner 80 and detects the combustion flame 86 after the thermocouple 88 is heated to a predetermined temperature by the combustion flame 86. It took a certain time to detect.

  Even with such a configuration, incomplete combustion of the main burner 80 can be prevented at an appropriate timing, but the incomplete combustion can be prevented by detecting the air-fuel ratio of the gas combustion device. Is related to safety. Therefore, further shortening the time for detecting the combustion flame 86 from ignition leads to a gas combustion device pursuing more safety. That is, there is a demand for a higher-performance air-fuel ratio detection sensor that can start detecting a combustion flame in such a short time.

  The problem to be solved by the present invention is to provide an air-fuel ratio detection method, an air-fuel ratio detection sensor, and a gas combustion device for a gas combustion device with higher detection performance in consideration of further safety.

  In order to solve the above problems, an air-fuel ratio detection method for a gas combustion device according to the present invention is provided with a fuel cell that generates power when a predetermined high temperature state is reached in the vicinity of a combustion flame of a gas burner of a gas combustion device, Combustion gas is brought into contact with the fuel electrode of the fuel cell and combustion electromotive force generated by bringing combustion air into contact with the air electrode is detected, and the air-fuel ratio of the gas burner is determined based on the detected electromotive force value. The gist is that it is detected.

  An air-fuel ratio detection sensor according to the present invention is a sensor for detecting an air-fuel ratio of a gas burner of a gas combustion device, and a fuel electrode in which combustion gas of the gas burner is in contact with one surface of a fuel cell that generates power when a predetermined high temperature state is reached. And having the air electrode in contact with the combustion air of the gas burner on the other surface.

  The gist of the gas combustion device according to the present invention is that the air-fuel ratio detection sensor is disposed in proximity to the combustion flame of the gas burner.

  In this case, the gas burner is preferably a monitoring gas burner adjacent to the main gas burner.

  According to the air-fuel ratio detection method for a gas combustion device according to the present invention, the air-fuel ratio of the gas combustion device is determined based on the value of the generated electromotive force of the fuel cell based on the relationship between the electromotive force of the fuel cell and the air-fuel ratio of the supply gas. Can be detected.

  And, since the electrolyte and electrodes constituting this fuel cell have a smaller heat capacity than the thermocouple, the time until the fuel cell can be warmed up to its operating temperature and a combustion flame can be detected, It can be shortened compared with what used the conventional thermocouple as the sensor.

  Moreover, according to the air-fuel ratio detection sensor of the present invention, an electromotive force corresponding to the air-fuel ratio of the gas contained in the combustion flame of the gas burner is generated by disposing it at an appropriate position of the gas burner of the gas combustion device. And since the change of the air-fuel ratio of the gas burner can be regarded as the change of electromotive force generated by the power generation of the fuel cell, this detects the change of the air-fuel ratio, and before the gas combustion device causes incomplete combustion, Can know combustion abnormality.

  According to the gas combustion device of the present invention, since the air-fuel ratio detection sensor is provided inside, the air-fuel ratio of the gas combustion device is detected by the air-fuel ratio detection sensor. Combustion can be stopped by taking measures such as shutting off the supply. Thereby, incomplete combustion of the gas combustion device can be prevented.

  In this case, if a monitoring gas burner is provided adjacent to the main gas burner, and an air-fuel ratio detection sensor is provided on the monitoring gas burner, the initial setting can be changed from that of the main burner, and the change ratio of the air-fuel ratio can be captured more greatly. Can be. Thereby, it is possible to detect that the air-fuel ratio is deteriorated before the combustion state of the main burner is deteriorated.

  An embodiment of the present invention will be described in detail with reference to FIGS.

  An air-fuel ratio detection method for a gas combustion device according to the present invention includes a fuel cell that generates power when a predetermined high temperature is reached in the vicinity of a combustion flame of a gas burner of a gas combustion device, and is disposed at the fuel electrode of the fuel cell. The fuel cell electromotive force generated by bringing the combustion gas into contact with the air electrode and the combustion air is detected, and the air-fuel ratio of the gas burner is detected based on the value of the detected electromotive force. It is characterized by.

  Here, examples of the gas burner include a Bunsen burner and a light and dark burner. Further, examples of the bunsen burner include a flat one and a cylindrical one. These gas burners may be a main gas burner used for supplying combustion heat of the gas burner in a gas combustion device, or a monitor gas burner used for monitoring the oxygen supply state in the gas combustion device. Sometimes it is.

  The arrangement of the fuel cell in the vicinity of the combustion flame of the gas burner means that the fuel cell is brought into contact with the fuel gas contained in the combustion flame of the gas burner so that the fuel cell can generate power. . In this case, a fuel cell may be disposed in the combustion flame. However, in order to efficiently generate power in the fuel cell, it is better to sufficiently supply combustion air to the air electrode.

  More preferably, the fuel cell is arranged along the combustion flame of the gas burner so that only the fuel electrode contacts the combustion flame. That is, a fuel cell is erected near the outer flame of the combustion flame so that the fuel electrode side faces the combustion flame and the air electrode side faces the outside of the combustion flame.

  When detecting the electromotive force of the fuel cell generated by bringing the combustion gas into contact with the fuel electrode of the fuel cell and bringing the combustion air into contact with the air electrode, it is difficult to detect the change in the electromotive force in a no-load state. Therefore, a certain amount of load is usually applied. In this case, in order to increase the detection accuracy of the electromotive force, it is preferable to switch and connect to a plurality of loads having different resistance values by a switching operation or the like so that changes in the electromotive force are captured at the plurality of loads.

  Further, to detect the air-fuel ratio of the gas burner based on the detected electromotive force value, the relationship between the electromotive force value of the fuel cell and the air-fuel ratio value of the fuel gas supplied at that time is examined in advance. By the relationship, it means calculating the air-fuel ratio of the gas burner from the detected electromotive force value.

  In general, this type of fuel cell has a cell temperature, fuel gas supply to the fuel electrode (air-fuel ratio, flow rate, contact method, etc.), and air supply to the air electrode (flow rate, contact method, etc.) ) Etc., the amount of power generation (electromotive force) changes. Then, after examining the relationship between these various conditions and the amount of power generation, the air-fuel ratio of the gas burner can be calculated (detected) by using such characteristics.

  According to such an air-fuel ratio detection method, the air-fuel ratio of the gas combustion device can be detected based on the value of the generated electromotive force of the fuel cell based on the relationship between the electromotive force of the fuel cell and the air-fuel ratio of the supply gas. .

  And, since the electrolyte and electrodes constituting this fuel cell have a smaller heat capacity than the thermocouple, the time until the fuel cell can be warmed up to its operating temperature and a combustion flame can be detected, It can be shortened compared with what used the conventional thermocouple as the sensor.

  Examples of the air-fuel ratio detection sensor that can be suitably used for such an air-fuel ratio detection method for gas combustion equipment include the one shown in FIG.

  As shown in FIG. 1, for example, the air-fuel ratio detection sensor according to the present invention is provided with electrodes (fuel electrode 14a and air electrode 14b) on the surface of a solid electrolyte 12 such as zirconia having oxygen ion conductivity. It consists of a wire (not shown) for taking out electricity from it. This is a fuel cell that generates electricity when it reaches a predetermined high-temperature state, and is disposed in a gas burner of a gas combustion device, by bringing combustion gas into contact with the fuel electrode 14a and bringing combustion air into contact with the air electrode 14b. Generate electromotive force.

  The solid electrolyte 12 is not limited to the illustrated plate shape, and may be, for example, a cylindrical shape in accordance with the shape of the flame opening of the gas burner of the gas combustion device in which the air-fuel ratio detection sensor is provided. . In this case, in order to bring the fuel electrode into contact with the combustion flame ejected from the gas burner, the fuel electrode may be provided inside the cylindrical solid electrolyte and the air electrode may be provided outside.

  The electrode provided on the surface of the solid electrolyte 12 includes a fuel electrode 14a and an air electrode 14b. As shown in the figure, one fuel electrode 14a is provided on one surface and one air electrode 14b is provided on the other surface. It is not limited to the one provided. A fuel electrode and an air electrode may be provided only on one surface. Two or more pairs of fuel electrodes and air electrodes may be used.

  In the air-fuel ratio detection sensor 10, the fuel electrode 14a and the air electrode 14b are not separated by a chamber or the like, and the combustion gas and the combustion air are not supplied separately to the respective electrodes. Therefore, a solid electrolyte or electrode material used in a so-called single-chamber fuel cell that can generate power even with a mixed gas of fuel gas and air may be used.

  Such an air-fuel ratio detection sensor 10 can be disposed at an appropriate position of the gas burner to detect the air-fuel ratio of the gas burner. Examples of the appropriate position at this time include those shown in FIGS.

  For example, the case where the air-fuel ratio detection sensor 10 is disposed on a plurality of flat bunsen burners disposed will be described with reference to FIG. In the gas combustion apparatus, a plurality of flat Bunsen burners 16, 16,... Are arranged, and any one or two or more of the flat Bunsen burners 16, 16,. A sensor provided with the detection sensor 10 may be used. In such a flat Bunsen burner 16, fuel gas from a fuel gas pipe (not shown) and combustion air from an air supply / exhaust fan (not shown) are sent, and fuel is supplied from flow paths A1, A2,. A mixed gas of gas and combustion air is supplied, and combustion air is supplied from the flow paths B1, B2,.

  Therefore, in order to bring the combustion gas into contact with the fuel electrode 14a and to bring the combustion air into contact with the air electrode 14b, as shown in the drawing, the air flows in the direction along the combustion flame 18 ejected from the flat Bunsen burner 16. It is preferable that the fuel ratio detection sensor 10 be arranged so that the fuel electrode 14a faces the inside and the air electrode 14b faces the outside. At this time, the reducing flame of the injected combustion flame 18 may be in contact with the fuel electrode 14a. The reducing flame is a flame having a reducing action, and is a flame (inner flame portion) in which fuel gas remains before the mixed gas is completely burned.

  Here, the position at which the air-fuel ratio detection sensor 10 is disposed on the flat bunsen burner 16 is not limited to the illustrated one. For example, it may not be directly attached to the flame opening 16a of the flat Bunsen burner 16, but may be disposed above the flame opening 16a. Further, it may be disposed in the combustion flame 18 so that the fuel electrode 14 a is covered with the combustion flame 18. When disposed in the combustion flame 18, it may be disposed at the upper part of the combustion flame so that the air electrode 14 b is not covered with the combustion flame and combustion air is not supplied.

  The shape of the Bunsen burner is not limited to the illustrated flat shape, and may be a cylindrical shape. In this case, a cylindrical solid electrolyte is used, a fuel electrode is provided inside the cylindrical solid electrolyte, an air electrode is provided outside, and the cylinder is formed in a direction along the combustion flame ejected from the Bunsen burner. The air-fuel ratio detection sensor may be disposed so as to surround the outer periphery of the bunsen burner. When the Bunsen burner is cylindrical, the combustion flame distribution becomes uniform, so that the air-fuel ratio detection sensor arranged so as to surround the outer periphery can obtain a stable output.

  FIG. 3 is a view showing the arrangement in the light and dark burner 20. Fuel gas from a fuel gas pipe (not shown) and combustion air from a supply / exhaust fan (not shown) are sent, and the ratio of the fuel gas is less than the stoichiometric air-fuel ratio of the fuel gas and combustion air from the flow path C. A mixed gas (with a high proportion of combustion air) is supplied, and a mixed gas with a higher fuel gas proportion than the stoichiometric air-fuel ratio (a higher proportion of fuel gas) is supplied from the flow paths D1 and D2.

  And the light flame 22a is formed from the light flame mouth part 20a, and the heavy flame 22b is formed from the fuel flame mouth part 20b. Therefore, in order to bring the rich flame 22b into contact with the fuel electrode 14a and to bring the light flame 22a into contact with the air electrode 14b, as shown in the drawing, the air is discharged in the direction along the combustion flames 22a and 22b ejected from the light and dark burner 20. The fuel ratio detection sensor 10 may be disposed, and the fuel electrode 14a may be disposed outside and the air electrode 14b disposed inside.

  Here, the position at which the air-fuel ratio detection sensor 10 is disposed in the light and dark burner 20 is not limited to that shown in the figure. For example, it may not be directly attached to the flame opening portions 20a and 20b of the light and dark burner 20, but may be arranged above the flame opening portions 20a and 20b. Further, the electrodes 14a and 14b are arranged in the combustion flames 22a and 22b so as to be directed to the flame openings 20a and 20b and orthogonal to the combustion flames 22a and 22b, and are covered with the combustion flames 22a and 22b. It may be.

  FIG. 4 is a diagram showing the arrangement of the gas burner 26 for monitoring adjacent to the main gas burners 24, 24. The gas burner 26 for monitoring can change the initial setting and the change ratio of the air-fuel ratio with the main gas burner 24. When the state of the gas supplied to the main gas burner 24 or the monitor gas burner 26 changes, the state of the combustion flame changes before the main gas burner 24. Thereby, in the gas combustion device, it is possible to detect that the air-fuel ratio has deteriorated before the combustion state of the main gas burner 24 deteriorates.

  In this case, the air-fuel ratio detection sensor 10 may be arranged in a direction along the combustion flame 28 ejected from the gas burner 26 for monitoring, and the fuel electrode 14a is directed to the inside of the combustion flame and the air electrode 14b is directed to the outside. The shape of the gas burner 26 for monitoring can be exemplified by a flat shape or a cylindrical shape as described in the Bunsen burner. Needless to say, the air-fuel ratio detection sensor 10 can appropriately adjust the inner radius, height, and width of the air-fuel ratio detection sensor 10 when attached to the flame opening 26a.

  According to the air-fuel ratio detection sensor having such a configuration, an electromotive force corresponding to the air-fuel ratio of the gas contained in the combustion flame of the gas burner is generated by disposing it at an appropriate position of the gas burner of the gas combustion device. And since the change of the air-fuel ratio of the gas burner can be regarded as the change of electromotive force generated by the power generation of the fuel cell, this detects the change of the air-fuel ratio, and before the gas combustion device causes incomplete combustion, Can know combustion abnormality.

  Next, an embodiment of a gas combustion device provided with such an air-fuel ratio detection sensor will be described.

  FIG. 5 is an embodiment of a gas combustion device according to the present invention. As shown in FIG. 4, a schematic diagram of a gas water heater 30 in which an air-fuel ratio detection sensor is provided in a monitoring gas burner adjacent to the main gas burner is shown.

  The gas water heater 30 is provided with a heat exchanger 36 in which a water supply pipe 32 and a hot water discharge pipe 34 are arranged in a casing 38 and a plurality of main gas burners 40 for heating the heat exchanger 36. Has been. A gas burner 42 for monitoring is provided adjacent to the main gas burner 40. In the gas burner 42 for monitoring, when the state of the gas supplied to the main gas burner 40 or the gas burner 42 for monitoring occurs (for example, when the oxygen gas becomes deficient), the state of the combustion flame changes before the main gas burner 40. It is like that. Thereby, in the gas combustion apparatus 30, before the combustion state of the main gas burner 40 deteriorates, it detects that the air-fuel ratio has deteriorated.

  The main gas burner 40 and the monitor gas burner 42 are supplied with fuel gas from a gas nozzle 46 provided on a common nozzle base 44. A fuel gas supply pipe 48 is connected to the nozzle base 44.

  The water supply pipe 32 is provided with a water flow switch (water flow sensor) 50 for detecting the flow of water and its flow rate, and an incoming water temperature thermistor 52 for detecting the temperature of the water, and the hot water discharge pipe 34 detects the temperature of the hot water. A hot water temperature thermistor 54 is provided. Further, a hot water tap 56 is provided at the outlet of the outlet pipe 34.

  On the other hand, the gas conduit 48 to the gas burners 40, 42 is provided with an original solenoid valve 58, a main solenoid valve 60, and a gas proportional valve 62 that continuously changes the gas amount. A blower fan 64 is provided below the gas burners 40 and 42 to supply combustion air to the gas burners 40 and 42. An air-fuel ratio detection sensor 10 is disposed in the gas burner 42 for monitoring.

  In the upper part of the casing 38, an exhaust port 66 for exhausting combustion gas from the gas burners 40, 42 to the outside is provided.

  The controller 68 for controlling the operation of the gas water heater 30 receives signals from the water flow switch 50, the incoming water temperature thermistor 52, the outgoing hot water temperature thermistor 54, etc. on the input side. Are also input. On the other hand, a gas proportional valve 62 and a motor (not shown) of the blower fan 64 are connected to the output side of the controller 68.

  In the gas water heater 30 having such a configuration, the water flow switch (water flow sensor) 50 is turned on by opening the hot water tap 56, the signal is received by the controller 68, and the drive circuit (not shown) of the blower fan 64 is received. A command is sent, the blower fan 64 rotates, and combustion air is supplied to the gas burners 40 and 42. In addition, the controller 68 sends commands to the original solenoid valve 58, the main solenoid valve 60, and the gas proportional valve 62, and the fuel gas is supplied to the gas burners 40 and 42 by being sequentially opened, and then the igniter ( The gas burners 40 and 42 are ignited by an ignition operation (not shown).

  In the initial ignition operation stage of the gas burners 40, 42, the temperature of the water flowing through the water supply pipe 32 is grasped by a detection signal from the incoming water temperature thermistor 52 provided in the water supply pipe 32, and the controller 68 flows through the hot water discharge pipe 34. The amount of gas supplied to the gas burners 40 and 42 is adjusted by adjusting the opening of the gas proportional valve 62 so that the hot water discharge temperature approaches the set temperature.

  After the combustion of the gas burners 40 and 42 becomes stable, the controller 68 receives a signal from the hot water temperature thermistor 54 provided in the hot water pipe 34, and the controller 68 receives a proportional valve current circuit (not shown) of the gas proportional valve 62. ) And a drive circuit (not shown) of the blower fan 64, and the operation management is performed so that the tapping temperature is maintained at the set temperature by adjusting the opening degree of the gas proportional valve 62 and the rotation speed of the blower fan 64. Made.

  Next, an embodiment of a control flow during operation of such a gas water heater 30 will be described with reference to FIGS. 6 and 7.

  First, the control flow shown in FIG. 6 will be described. When the operation switch is turned on, the gas burner is ignited and combustion (operation) is started. After the air-fuel ratio detection sensor (shown as DFFC in the figure) is warmed to its operating temperature by the combustion heat due to this combustion, flame is detected (in step 1, in the figure and below, S1, S2,... write).

  After waiting for a certain period of time from the detection of the flame until the air-fuel ratio detection sensor is stabilized (S2, “YES”), the output side of this air-fuel ratio detection sensor is connected to the detection load (resistance load) A ( S3). An output signal is sent from the air-fuel ratio detection sensor to the controller in accordance with the combustion state of the monitoring gas burner. When the detected output value (electromotive force value) is not equal to or greater than a predetermined reference value A (S4, “NO”), it is determined that the air-fuel ratio is not within a predetermined range, and combustion abnormality is determined. The combustion (operation) of the gas burner is stopped (extinguishes) (S8). In this case, an error code is displayed on the operation panel (not shown) of the gas water heater (S9). The user turns off the operation switch, removes the cause of the error, and then restarts the operation.

  On the other hand, when the detected output value is equal to or greater than a predetermined reference value A, it is determined that the combustion of the gas burner is normally performed based on the normal air-fuel ratio (S4, “YES”).

  After the detection load A determines that the output value from the air-fuel ratio detection sensor is greater than or equal to the reference value A, the detection load B is connected to the detection load B having a higher reference value than the detection load A (S5). In this detected load B, when the output value detected by the air-fuel ratio detection sensor is lower than the reference value B (S6, “NO”), as in S4, it is determined that the air-fuel ratio is not within the predetermined range and combustion abnormality occurs. And the combustion (operation) of the gas burner is stopped (extinguishes) (S8).

  On the other hand, when the output value from the air-fuel ratio detection sensor also exceeds the reference value B at the detection load B (S6, “YES”), it is determined as normal operation (S7). The air-fuel ratio detection sensor is connected to the detection load A again. Such an operation is repeated and continued at regular time intervals.

  The detection load may be switched at the time of detection using a semiconductor switch such as a transistor or FET (field effect transistor).

  Next, the control flow shown in FIG. 7 will be described.

  From the ON operation of the operation switch to the flame detection and detection load A connection, the control flow is the same as that shown in FIG. After connection to the detection load A (S3), an output signal is sent from the air-fuel ratio detection sensor to the controller in accordance with the combustion state of the monitoring gas burner. When the detected output value is not equal to or greater than the predetermined reference value A (S4, “NO”), an operation for increasing the supply amount of combustion air to the gas burner is performed in order to change the air-fuel ratio. (S10). This operation can be performed by increasing the rotational speed of the blower fan or reducing the amount of fuel gas supplied.

  When the supply amount of combustion air to the gas burner is increased by the operation of S10 and the output of the air-fuel ratio detection sensor is increased (S11, “YES”), the process proceeds to S4, and the output value is equal to or higher than the reference value A again. It is judged whether or not. On the other hand, when the output is not increased by the operation of S10 (S11, “NO”), on the contrary, an operation of decreasing the supply amount of the combustion air to the gas burner is performed (S12). This operation can be performed by reducing the rotational speed of the blower fan or increasing the supply amount of the fuel gas.

  When the air-fuel ratio becomes an appropriate air-fuel ratio by the operation of S12 and the output of the air-fuel ratio detection sensor rises (S13, “YES”), the process proceeds to S4, and it is determined again whether the output value is equal to or greater than the reference value A. On the other hand, when the output does not increase even after the operation of S12 (S13, “NO”), it is considered that there is a problem other than the amount of combustion air. Is stopped (operation) (S8).

  In S4, when the detected output value is equal to or greater than the predetermined reference value A, the combustion of the gas burner is normally performed based on the normal air-fuel ratio, as in the control flow shown in FIG. Determination is made (S4, “YES”). Then, it is repeatedly determined whether the output of the air-fuel ratio detection sensor is equal to or higher than the reference value A at regular time intervals.

  Unlike the method shown in FIG. 6, the control method shown in FIG. 7 not only determines whether the operation is normal based on whether the output exceeds the reference value, but also if the detected value deviates from the target value. Control is performed such as changing the air-fuel ratio so as to approach the target value and feeding back the output. In this case, the change of the air-fuel ratio may be performed, for example, by changing the open / close state of the gas proportional valve or changing the rotation speed of the blower fan by a signal from the controller.

  These are one embodiment of the control flow, and various other types of control can be performed.

  According to the gas combustion device having such a configuration, since the air-fuel ratio detection sensor is provided inside, measures such as detecting the air-fuel ratio of the gas combustion device by the air-fuel ratio detection sensor and shutting off the supply of fuel gas, etc. Can be used to stop the combustion. Thereby, incomplete combustion of the gas combustion device can be prevented.

  When a monitoring gas burner is provided next to the main gas burner and an air-fuel ratio detection sensor is provided on the monitoring gas burner, the initial setting is changed from that of the main burner so that the rate of change of the air-fuel ratio is increased. Can be. Thereby, it is possible to detect that the air-fuel ratio is deteriorated before the combustion state of the main burner is deteriorated.

  Although the embodiments of the present invention have been described in detail above, the present invention is not limited to the above-described embodiments, and various modifications can be made without departing from the gist of the present invention.

  For example, in the above-described embodiment, the gas combustion apparatus shows a gas water heater in which an air-fuel ratio detection sensor is provided in a monitor gas burner, but an air-fuel ratio detection sensor is provided in a main gas burner. Of course, it is also good. Further, the gas combustion device is not limited to the hot water heater, and may be a gas stove or the like.

  The air-fuel ratio detection sensor according to the present invention can be used as a device for preventing incomplete combustion in gas combustion equipment such as a water heater or a gas stove.

It is a figure showing one Embodiment of the air fuel ratio detection sensor which concerns on this invention. It is a figure explaining what has arrange | positioned the air-fuel-ratio detection sensor which concerns on this invention to the flat bunsen burner. It is a figure explaining what has arrange | positioned the air-fuel ratio detection sensor which concerns on this invention to the light / dark burner. It is a figure explaining what has arrange | positioned the air fuel ratio detection sensor which concerns on this invention to the gas burner for monitoring. It is a figure showing the gas water heater which is one Embodiment of the gas combustion apparatus which concerns on this invention. It is a figure which shows one Embodiment of the control flow in the driving | operation of a gas water heater. It is a figure which shows one Embodiment of the control flow in the driving | operation of a gas water heater. It is the figure which expanded and represented the gas burner part of the conventional gas combustion apparatus using a thermocouple as an air fuel ratio detection sensor.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Air-fuel-ratio detection sensor 12 Solid electrolyte 14a Fuel electrode 14b Air electrode 16 Flat bunsen burner 18, 28 Combustion flame 20 Concentration burner 22a Light flame 22b Concentration flame 26, 42 Gas burner 30 for monitoring Gas water heater

Claims (4)

  In the vicinity of the combustion flame of the gas burner of the gas combustion equipment, a fuel cell that generates power when a predetermined high temperature state is reached is disposed, the combustion gas is brought into contact with the fuel electrode of the fuel cell, and the combustion air is brought into contact with the air electrode An air-fuel ratio detection method for a gas combustion device, characterized in that an electromotive force of a fuel cell generated by the detection is detected, and an air-fuel ratio of the gas burner is detected based on a value of the detected electromotive force. A sensor for detecting an air-fuel ratio of a gas burner of a gas combustion device,
An air electrode having a fuel electrode in contact with combustion gas of a gas burner on one surface of a fuel cell that generates electricity when a predetermined high temperature state is reached, and an air electrode in contact with combustion air of the gas burner on the other surface Fuel ratio detection sensor.   A gas combustion apparatus, wherein the air-fuel ratio detection sensor according to claim 2 is disposed in proximity to a combustion flame of a gas burner.   The gas burner according to claim 3, wherein the gas burner is a gas burner for monitoring adjacent to the main gas burner.

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