JP3691905B2 - Combustion monitoring device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a combustion monitoring device, and more particularly to a device for monitoring normality / abnormality of a combustion state in a burner means.
[0002]
[Prior art]
FIG. 8 is an explanatory diagram of a water heater (1) equipped with a conventional combustion monitoring device, and FIG. 9 is a graph showing an electromotive force value (40) of the thermocouple (4) of FIG.
The water heater (1) includes a gas combustion burner (3) and a heat exchanger (1a) heated by combustion exhaust from the burner (3). Cold water supplied from the water supply path (2a) to the heat exchanger (1a) is heated by the heating to become hot water, and a hot water path (2b) connected to the downstream side of the heat exchanger (1a). ) Is discharged.
[0003]
The water heater (1) is provided with a thermocouple (4) provided so as to face the combustion flame in the burner (3) and generating an electromotive force according to the combustion temperature. The electromotive force of the thermocouple (4) is input to the control circuit (5).
The thermocouple (4) is set to generate a negative electromotive force when heated by the combustion, but in the following, for the convenience of explanation, the electromotive force value of the thermocouple (4) The electromotive force value will be described using the absolute value of.
[0004]
In this case, as shown in FIG. 9, when the combustion is started by the burner (3), the flame is in a normal combustion state after that. At this time, the electromotive force value (40) of the thermocouple (4) is stable at a substantially constant value.
Thereafter, when the flame condition becomes abnormal due to incomplete combustion or the like, the electromotive force value (40) decreases. When the electromotive force value (40) exceeds a predetermined limit value (49) (for example, 14 mV) due to this decrease, the control circuit (5) determines that the flame condition is abnormal. Is done. In response to this determination, the water tap (21) of the water supply path (2a) and the gas tap (31) of the gas supply path (3a) to the burner (3) are closed.
[0005]
Thus, in the water heater (1), the abnormality of the combustion state in the burner (3) is automatically determined. In response to the determination, the combustion of the burner (3) is stopped, and the hot water removal from the water heater (1) is stopped.
[0006]
[Problems to be solved by the invention]
In this conventional system, the electromotive force value (40) in a stable state in a normal combustion state differs for each combustion operation of the water heater (1) due to ventilation conditions, deterioration with time, and the like. However, since the limit value (49) for determining the abnormality is a constant value, the limit value (49) is unlikely to be an appropriate value for the normal combustion state.
[0007]
In particular, the limit value (49) is normally set with a sufficient margin for variations in the electromotive force value (40) in the stable state. When the electromotive force value (40) becomes a distant value, the time from occurrence of abnormality in the combustion state to abnormality determination tends to be long.
An object of the invention of claim 1 is to provide a combustion monitoring device that can always set a reference value for determining abnormality of a combustion state appropriately.
[0008]
[Means for Solving the Problems]
The problem-solving means of the invention of claim 1 is “a device for monitoring normality / abnormality of the combustion state in the burner means,
Detecting means for detecting the combustion state;
Detecting means for detecting that the combustion state is normal for each combustion operation in the burner means;
Setting means for setting a reference value for determining an abnormality in the combustion state based on the value of the detection output of the detection means for the normal combustion state detected by the detection means;
A determination unit that compares the value of the detection output of the detection unit with the reference value to determine abnormality in the combustion state;
Second determination means for comparing the value of the detection output of the detection means with a certain limit value to determine an abnormality in the combustion state;
”
[0009]
In this case, the reference value for determining the abnormality of the combustion state is set by the setting means based on the value of the detection output of the detection means for the normal combustion state detected by the detection means. The And the abnormality of the said combustion state is determined by the said determination means which compares the value of the detection output of the said detection means with the said reference value.
[0011]
Further, the apparatus further comprises second determination means for comparing the value of the detection output of the detection means with a certain limit value to determine the abnormality of the combustion state, so that the value of the detection output of the detection means is constant. The abnormality determination of the combustion state is made by the second determination means for comparing with the limit value.
As in the second aspect of the invention, “further comprises a second control means for deactivating the burner means in response to a judgment output of at least one of the judgment means and the second judgment means”. When at least one of the determination means and the second determination means determines that there is an abnormality, the burner means is deactivated by the second determination means.
[0013]
The invention of claim 3 is an apparatus for monitoring normality / abnormality of the combustion state in the burner means,
Detecting means for detecting the combustion state;
Detecting means for detecting that the combustion state is normal for each combustion operation in the burner means;
Setting means for setting a reference value for determining an abnormality in the combustion state based on the value of the detection output of the detection means for the normal combustion state detected by the detection means;
A determination unit that compares the value of the detection output of the detection unit with the reference value to determine abnormality in the combustion state;
The detection means includes flame detection means for detecting a flame state in the burner means, and passage detection means for detecting a passage state of the combustion exhaust gas in a heat exchanger heated by the combustion exhaust gas from the burner means. Including,
The detection means includes flame detection means for detecting that the flame condition is normal, and passage detection means for detecting that the passage condition is normal,
The setting means sets a first reference value for determining an abnormality of the flame state based on a detection output value of the flame detection means for a normal flame state detected by the flame detection means. And, based on the value of the detection output of the passage detection means for the normal passage state detected by the passage detection means, a second reference value for determining the abnormality of the passage state is set,
Third determination means for comparing the value of the detection output of the flame detection means with the first reference value to determine an abnormality in the state of the flame, the value of the detection output of the passage detection means and the second reference A fourth determination means for comparing the value and determining the abnormality of the passing state;
A fifth determination means for comparing the value of the detection output of the flame detection means with a constant first limit value to determine an abnormality in the state of the flame, and a value of the detection output of the passage detection means with a constant first And a sixth determination means for comparing the two limit values and determining the abnormality of the passage state ”.
[0014]
In this case, the first reference value is set based on the detection output value of the flame detection means for the normal flame state detected by the flame detection means, and the normal passage detected by the passage detection means. The second reference value is set based on the value of the detection output of the passage detection means for the state.
Then, the abnormality of the flame state is determined by the third determination unit that compares the value of the detection output of the flame detection unit with the first reference value. In addition, the abnormality of the passing state is determined by the fourth determination unit that compares the value of the detection output of the passage detection unit with the second reference value.
[0015]
Furthermore, a fifth determination means for comparing the value of the detection output of the flame detection means with a constant first limit value to determine an abnormality in the state of the flame, and a constant value of the detection output of the passage detection means And a sixth determination means for comparing the second limit value of the flame and determining the abnormality of the passage state, so that the detection output value of the flame detection means is compared with a constant first limit value. The flame determination state abnormality is determined by the fifth determination means. Further, the abnormality of the passing state is determined by the sixth determining means for comparing the value of the detection output of the passage detecting means with a constant second limit value.
[0016]
According to a fourth aspect of the invention, “the setting means includes a value of a detection output of the flame detection means with respect to a normal flame state detected by the flame detection means, and a normal value detected by the passage detection means. Based on the difference value between the detection output value of the passage detection means for the passage state, a third reference value for determining at least one abnormality of the flame state and the passage state is set, and the difference value and It may further comprise a seventh determination means for comparing the third reference value and determining at least one abnormality of the flame state and the passage state.
[0017]
In this case, a third reference value for determining an abnormality in at least one of the flame state and the passage state is set based on the difference value. Then, the seventh determination means for comparing the difference value with the third reference value determines at least one abnormality of the flame state and the passage state.
According to a fifth aspect of the present invention, the apparatus further includes an eighth determination unit that compares the difference value with a constant third limit value to determine abnormality in at least one of the flame state and the passage state. In the above, at least one abnormality of the flame state and the passing state is determined by the eighth determining means that compares the difference value with a constant third limit value.
[0018]
【The invention's effect】
As described above, in the first aspect of the invention, the reference value for determining the abnormality of the combustion state is set based on the value of the detection output of the detection means for the normal combustion state. Even if the value differs for each combustion operation of the burner means, the reference value can be appropriately set for the normal combustion state. Further, it is possible to suppress variation in time from occurrence of abnormality to abnormality determination by the determination means, and the abnormality determination is ensured.
[0019]
In this case, even if the reference value is set to be significantly abnormal due to variations in the detection output value of the detection means with respect to the normal combustion state, the abnormality determination is made when the certain limit value is exceeded. By setting the limit value to a predetermined value in advance, the abnormality determination is further ensured.
[0020]
Even if the combustion state is not good immediately after the start of combustion, the abnormality determination is made based on the certain limit value, so that the abnormality determination is further ensured in this respect.
In the invention of claim 2, the deactivation is certain because the burner means is automatically deactivated when at least one of the determination means and the second determination means determines that there is an abnormality. . Further, the operation for deactivation is not necessary.
[0022]
In the third aspect of the invention, as in the first aspect of the invention, the abnormality determination is further ensured by setting the first and second limit values to be predetermined.
In the invention of claim 4, when any one of the above-mentioned flame state and the above-mentioned passing state becomes abnormal, an abnormality determination is made, and this abnormality determination is further ensured.
[0023]
In the fifth aspect of the invention, as in the first aspect of the invention, the abnormality determination is further ensured by setting the third limit value to a predetermined value in advance.
[0024]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
[Embodiment 1]
FIG. 1 is an explanatory diagram of a water heater (1) provided with a combustion monitoring apparatus according to Embodiment 1 of the present invention.
[0025]
[Configuration of each part]
As shown in the figure, the water heater (1) includes a gas combustion burner (3) and a heat exchanger (1a) heated by combustion exhaust from the burner (3). It is the structure to do.
The heat exchanger (1a) includes a water pipe (11) and a large number of fins (12) and (12) extending from the water pipe (11) and arranged parallel to each other. A water supply path (2a) for supplying cold water to the water pipe (11) is connected to the upstream side of the water pipe (11), and a water tap (21) is provided in the water supply path (2a). Yes. Further, a hot water supply path (2b) for taking out hot water heated by the water flow pipe (11) is connected to the downstream side of the water flow pipe (11). Further, the heat exchanger (1a) is disposed in a passage (10) through which combustion exhaust from the burner (3) flows. Incidentally, the constituent wall (13) of the passage (10) is provided with a through hole (14) so as to be located in the vicinity of the upstream side of the heat exchanger (1a) in the direction of the flow of the combustion exhaust gas. .
[0026]
A gas supply path (3a) for supplying gas to the burner (3) is connected to the burner (3), and a gas plug (31) is provided in the gas supply path (3a). An ignition device (33) is provided so as to be positioned on the gas ejection side with respect to the burner (3).
The water heater (1) is provided with first and second thermocouples (4a) and (4b) that generate an electromotive force according to the combustion temperature of the burner (3). One first thermocouple (4a) is arranged so as to face the flame at the time of gas combustion in the burner (3). The other second thermocouple (4b) is arranged facing the above-mentioned through hole (14), and the temperature of the combustion exhaust gas passing through the through hole (14) is reduced by this second thermocouple (4b). Detected. The flow rate of the combustion exhaust gas passing through the through hole (14) increases as the gap between the fins (12) and (12) becomes clogged with dust or the like in the combustion exhaust gas.
[0027]
The first and second thermocouples (4a) and (4b) are connected to a control circuit (5) described later provided in the water heater (1).
The control circuit (5) includes a microcomputer, and the microcomputer monitors the normality / abnormality of the combustion state in the burner (3) and operates the water heater (1) when abnormal. A control program for automatically stopping is stored. An operation switch (51) for instructing operation / stop of the water heater (1) is connected to the control circuit (5).
[0028]
[About control operation]
FIG. 2 is a graph showing the first and second electromotive force values (41) and (42) of the first and second thermocouples (4a) and (4b) in FIG. 3 and 4 are flowcharts showing a control program stored in the microcomputer of the control circuit (5) in FIG. 1, and FIG. 5 is a flowchart showing a combustion monitoring routine of the control program in FIG.
[0029]
Next, the control operation will be described based on these drawings.
In this case, as shown in FIG. 3, when the operation switch (51) is turned on, the faucet (21) is opened (steps (S71) and (S72)), and heat exchange is performed from the water supply path (2a). Cold water is supplied to the vessel (1a). Subsequently, the gas plug (31) is opened, the ignition device (33) is operated for 5 seconds (steps (S73) (S74)), and the burner (3) is in a gas combustion state. Although not shown, when the water flow switch (not shown) detects that the cold water has flowed into the water supply path (2a), a step of executing the steps (S73) and (S74) is provided. ing.
[0030]
Thereafter, the built-in timer of the microcomputer is reset, and time measurement by the built-in timer is started (step (S75)).
When combustion in the burner (3) is started, as shown in FIG. 2, the value of the electromotive force output from the first thermocouple (4a) (first electromotive force value (41), unit: mV), And the value of the electromotive force output from the second thermocouple (4b) (second electromotive force value (42), unit: mV) increases. When the combustion reaches a stable state, the first electromotive force value (41) and the second electromotive force value (42) are also stabilized. The first electromotive force value (41) is higher than the second electromotive force value (42).
[0031]
When the measurement time (61) reaches 50 seconds after the time measurement by the built-in timer is started, the combustion in the burner (3) has reached the stable state, as shown in FIG. In addition, the first electromotive force value (41) at this time is stored as the first stored value (43), and the second electromotive force value (42) at the time is stored as the second stored value (44). (Steps (S77) and (S78)).
[0032]
Thereafter, the combustion monitoring routine described later is repeatedly executed until the operation switch (51) is turned off (steps (S79) (S80)).
In the combustion monitoring routine, as shown in FIG.
(1). Whether the first electromotive force value (41) has reached a value 4 mV lower than the first stored value (43) (first reference value (45), for example, 16 mV) (step (S81)),
(2). Whether the second electromotive force value (42) has reached a value (second reference value (46), for example, 12 mV) 4 mV higher than the second stored value (44) (step (S82)),
(3). Whether the first electromotive force value (41) has reached a predetermined constant first limit value (47) (for example, 14 mV) lower than the first stored value (43) (step (S83)),
(4). Whether the second electromotive force value (42) has reached a predetermined constant second limit value (48) (for example, 14 mV) higher than the second stored value (44) (step (S84)),
Is determined.
[0033]
In this case, when the flame state in the burner (3) becomes abnormal due to incomplete combustion or the like, the first electromotive force value (41) of the first thermocouple (4a) is lowered. Further, when the clogging of the gaps between the fins (12) and (12) of the heat exchanger (1a) proceeds and the flow rate of the combustion exhaust gas passing through the through holes (14) increases, the second thermocouple (4b) The second electromotive force value (42) increases. When the flame condition becomes abnormal, the second electromotive force value (42) slightly increases. When the passing state becomes abnormal, the first electromotive force value (41) slightly decreases.
[0034]
During execution of the combustion monitoring routine, the state of the flame becomes abnormal and the first electromotive force value (41) is set to the first reference value (45) set for each combustion operation or set in advance. When the determined first limit value (47) is exceeded, or when the passing state becomes abnormal, the second electromotive force value (42) is set to the second reference value (46) set for each combustion operation. Alternatively, when a predetermined second limit value (48) set in advance is exceeded, steps (S91) to (S93) are executed, and the operation of the water heater (1) is stopped.
[0035]
Further, when the operation switch (51) is turned off, steps (S91) to (S93) are executed. In these steps, as shown in FIG. 4, first, the gas stopper (31) is closed. As a result, gas combustion in the burner (3) is stopped. Further, after waiting for 1 second, the faucet (21) is closed and the water supply to the heat exchanger (1a) is stopped. For these reasons, hot water removal from the water heater (1) is stopped.
[0036]
Note that if the operation switch (51) is turned off before the measurement time (61) of the built-in timer reaches 50 seconds, the above steps (S91) to ( S93) is executed and the hot water removal is stopped in the same manner as described above.
In this case, the first and second reference values (45) and (46) for the above abnormality determination are set based on the electromotive force value detected in the normal combustion state in the burner (3). Even if the electromotive force value in the normal combustion state is different for each combustion operation of the burner (3), the first and second reference values (45) and (46) can be appropriately set. Further, variation in time from when the abnormality in the combustion state occurs until the abnormality is determined is suppressed, and the abnormality determination is ensured.
[0037]
Even when the first and second reference values (45) and (46) are set to be significantly abnormal due to variations in the normal combustion state, the above-described constant first and second limit values (47) (48) Therefore, the abnormality determination is further ensured by setting the first and second limit values (47) and (48) to a predetermined value.
Even if the combustion state after 50 seconds from ignition is not good, the first and second limit values (47) and (48) are present. Become.
[0038]
Further, when the abnormality determination is made, the burner (3) automatically enters the fire extinguishing state, so that the burner (3) is surely extinguished when an abnormality occurs. Moreover, the operation for the said fire extinguishing is unnecessary.
Moreover, since the combustion state in the burner (3) is detected by the first thermocouple (4a) and the second thermocouple (4b), normal combustion state and abnormal combustion in the burner (3) are detected. The state is captured more accurately.
[0039]
In this case, the first thermocouple (4a) is the “flame detection means” described in the claims, and the second thermocouple (4b) is the “passage detection means”. The first and second thermocouples (4a) and (4b) are "temperature detecting means" and "detecting means".
The above step (S77) is “flame detection means”, “passage detection means”, and “detection means” described in the claims.
[0040]
The above steps (S78), (S81), and (S82) are the “setting means” described in the claims, the first reference value (45) is the “first reference value”, and the second reference value ( 46) is a “second reference value”, and the first and second reference values (45) and (46) are “reference values”.
The step (S81) is the “third determination means” described in the claims, the step (S82) is the “fourth determination means”, and these steps (S81) (S82) Is the “determination means”.
[0041]
The first limit value (47) is the “first limit value” described in the claims, and the second limit value (48) is the “second limit value”. The limit values (47) and (48) are “limit values”.
The step (S83) is the “fifth determination means” described in the claims, the step (S84) is the “sixth determination means”, and these steps (S83) (S84) are “ Second determination means ”.
[0042]
The step (S91) and the gas plug (31) are “second control means” and “control means” described in the claims.
In the first embodiment described above, a pair of thermocouples is shown, but only one of them may be provided.
Further, the electromotive force value of the thermocouple at the time when 50 seconds have elapsed from the start of combustion is set as the electromotive force value in a normal combustion state, and this is the electromotive force value after the thermocouple value has increased after the start of combustion. It is also possible to directly detect that has become a stable state, and the electromotive force value at this time may be the electromotive force value in the normal combustion state.
[Embodiment 2]
FIG. 6 is a graph showing the first and second electromotive force values (41) and (42) of the first and second thermocouples (4a) and (4b) according to the second embodiment of the present invention. 6 is a flowchart illustrating a combustion monitoring routine of a control program according to a second embodiment.
[0043]
In the second embodiment, the combustion monitoring routine in the control program of the first embodiment is changed to that shown in FIG. Other configurations are the same as those in the first embodiment.
In the combustion monitoring routine, the difference value (400) obtained by subtracting the second electromotive force value (42) from the first electromotive force value (41) subtracts the second stored value (44) from the first stored value (43). The difference value (third reference value (401)) has reached a value 5 mV lower or the difference value (400) is equal to a predetermined third limit value (402) (for example, 4 mV). ) Is reached (steps (S86) (S87)).
[0044]
In this case, as in the first embodiment, when the flame condition in the burner (3) becomes abnormal, the first electromotive force value (41) is lowered and the combustion exhaust gas passing through the heat exchanger (1a) is reduced. When the passage state of becomes abnormal, the second electromotive force value (42) increases. Therefore, the difference value (400) decreases in any abnormality.
Then, during the execution of the combustion monitoring routine, due to the abnormality, the difference value (400) is set to a third reference value (401) set for each combustion operation or a predetermined third limit value (402 ), The steps (S91) to (S93) are executed as in the first embodiment, and the operation of the water heater (1) is stopped.
[0045]
This is based on the difference between the electromotive force value detected in the normal flame state in the burner (3) and the electromotive force value detected in the normal passage state in the heat exchanger (1a). Since the above abnormality is determined by the third reference value (401) set in this way, this abnormality determination is reliable.
Even if the third reference value (401) is set to be significantly abnormal, there is a third limit value (402), which makes the abnormality determination even more reliable.
[0046]
Further, even when the combustion state is not good from the start of combustion, since the third limit value (402) exists, the abnormality determination is further ensured in this respect.
In this, steps (S78) and (S86) are “setting means” described in the claims, the third reference value (401) is “third reference value”, and step (S86) is “Seventh determination means”. The third limit value (402) is the “third limit value”, and step (S87) is the “eighth determination means”.
[0047]
In Embodiment 1 or 2, the thermocouple is shown as the “detecting means”, but this may be a frame rod.
[Brief description of the drawings]
FIG. 1 is an explanatory diagram of a water heater (1) provided with a combustion monitoring apparatus according to Embodiment 1 of the present invention. FIG. 2 is a first diagram of first and second thermocouples (4a) and (4b) in FIG. A graph showing the second electromotive force values (41) and (42) [FIG. 3] A flowchart showing a control program stored in the microcomputer of the control circuit (5) of FIG. 1 [FIG. 4] Same as above [FIG. 5] FIG. FIG. 6 is a flowchart showing a combustion monitoring routine of the control program of FIG. 6. First and second electromotive force values (41) and (42) of first and second thermocouples (4a) and (4b) according to the second embodiment of the present invention. FIG. 7 is a flowchart showing a combustion monitoring routine of the control program of the second embodiment. FIG. 8 is an explanatory diagram of a water heater (1) provided with a conventional combustion monitoring device. Graph showing electromotive force (40) of pair (4) [Explanation of symbols]
(3) ... Burner
(1a) ・ ・ ・ Heat exchanger
(4a) ・ ・ ・ First thermocouple
(4b) ... Second thermocouple
(31) ・ ・ ・ Gas stopper

Claims (5)

A device for monitoring the normality / abnormality of the combustion state in the burner means,
Detecting means for detecting the combustion state;
Detecting means for detecting that the combustion state is normal for each combustion operation in the burner means;
Setting means for setting a reference value for determining an abnormality in the combustion state based on the value of the detection output of the detection means for the normal combustion state detected by the detection means;
A determination unit that compares the value of the detection output of the detection unit with the reference value to determine abnormality in the combustion state;
Second determination means for comparing the value of the detection output of the detection means with a certain limit value to determine an abnormality in the combustion state;
A combustion monitoring apparatus comprising:   2. The combustion monitoring apparatus according to claim 1, further comprising a second control unit that deactivates the burner unit in response to a determination output of at least one of the determination unit and the second determination unit. A device for monitoring the normality / abnormality of the combustion state in the burner means,
Detecting means for detecting the combustion state;
Detecting means for detecting that the combustion state is normal for each combustion operation in the burner means;
Setting means for setting a reference value for determining an abnormality in the combustion state based on the value of the detection output of the detection means for the normal combustion state detected by the detection means;
A determination unit that compares the value of the detection output of the detection unit with the reference value to determine abnormality in the combustion state;
The detection means includes flame detection means for detecting a flame state in the burner means, and passage detection means for detecting a passage state of the combustion exhaust gas in a heat exchanger heated by the combustion exhaust gas from the burner means. Including,
The detection means includes flame detection means for detecting that the flame condition is normal, and passage detection means for detecting that the passage condition is normal,
The setting means sets a first reference value for determining an abnormality of the flame state based on a detection output value of the flame detection means for a normal flame state detected by the flame detection means. And, based on the value of the detection output of the passage detection means for the normal passage state detected by the passage detection means, a second reference value for determining the abnormality of the passage state is set,
Third determination means for comparing the value of the detection output of the flame detection means with the first reference value to determine an abnormality in the state of the flame, the value of the detection output of the passage detection means and the second reference A fourth determination means for comparing the value and determining the abnormality of the passing state;
A fifth determination means for comparing the value of the detection output of the flame detection means with a constant first limit value to determine an abnormality in the state of the flame, and a value of the detection output of the passage detection means with a constant first A combustion monitoring apparatus further comprising: sixth determination means for comparing the two limit values to determine abnormality in the passing state. A device for monitoring the normality / abnormality of the combustion state in the burner means,
Detecting means for detecting the combustion state;
Detecting means for detecting that the combustion state is normal for each combustion operation in the burner means;
Setting means for setting a reference value for determining an abnormality in the combustion state based on the value of the detection output of the detection means for the normal combustion state detected by the detection means;
A determination unit that compares the value of the detection output of the detection unit with the reference value to determine abnormality in the combustion state;
The detection means includes flame detection means for detecting a flame state in the burner means, and passage detection means for detecting a passage state of the combustion exhaust gas in a heat exchanger heated by the combustion exhaust gas from the burner means. Including,
The detection means includes flame detection means for detecting that the flame condition is normal, and passage detection means for detecting that the passage condition is normal,
The setting means includes a detection output value of the flame detection means for a normal flame state detected by the flame detection means, and a detection output of the passage detection means for a normal passage state detected by the passage detection means. A third reference value for determining an abnormality in at least one of the flame state and the passing state is set based on a difference value between the difference value and the difference value and the third reference value; A combustion monitoring apparatus further comprising seventh determination means for determining an abnormality in at least one of the flame state and the passage state.   The combustion monitoring apparatus according to claim 4, further comprising an eighth determination unit that compares the difference value with a constant third limit value to determine an abnormality in at least one of the flame state and the passage state.

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