JPH10103665A - Combustion equipment - Google Patents

Abstract

(57) [Problem] To provide a combustion device for detecting a normal / abnormal combustion state of a burner and capable of improving detection accuracy of abnormal combustion. SOLUTION: When a controller 28 determines whether or not the combustion device is in abnormal combustion, a FR current detection value from a FR current detector 25 and a fan drive current detection circuit 31 according to the amount of combustion of the combustion device. One of the fan drive current detection values is selected. The controller 28 reads only the fan drive current detection value from the fan drive current detection circuit 31 when the combustion amount is large, and determines whether or not the combustion is abnormal. When the combustion amount is small, only the FR current detection value from the current detector 25 is used. Is read to determine whether or not abnormal combustion has occurred.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improvement in a combustion apparatus which detects a combustion state of a burner and determines whether or not the combustion is abnormal. In this specification, a combustion device mainly applied to a water heater for supplying hot water to a bathtub, hot water to a faucet, or the like will be described as an example.

[0002]

2. Description of the Related Art Conventionally, in a combustion device using gas fuel, a device for detecting the flame current of a burner by flame current detection means including a flame rod in order to determine whether or not abnormal combustion has occurred (Japanese Patent Application Laid-Open No. 59-145422). )It has been known. Further, a device for detecting a fan drive current by a fan drive current detection circuit and a fan rotation speed by a rotation speed detector (JP-A-5-196229) is also known.

[0003]

Incidentally, since each of the above-mentioned detecting means has a characteristic that the detection accuracy varies depending on the amount of combustion in each of the above-mentioned combustion devices,
This has the problem that it has an effect when judging the normal / abnormal combustion state of the burner. For example, the flame current detecting means (=
When the flame rod sensor) and the fan drive current detection circuit are used, the detection accuracy of the flame current value by the flame rod sensor when the combustion amount is large and the detection accuracy of the fan drive current value by the current detection circuit when the combustion amount is small are deteriorated. There was a problem. Further, the detected value of the fan drive current has a problem in that the detection accuracy is poor because the fan drive current is easily affected by disturbance due to wind or the like in a small rotation speed region (= small combustion amount region) of the fan.

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a combustion apparatus for detecting the normal / abnormal combustion state of a burner, which can improve the detection accuracy of abnormal combustion.

[0005]

A combustion device according to a first aspect of the present invention supplies fuel and air to a burner and burns the burner. The condition detection means detects a condition of the combustion device. Weighting means for weighting the state detection value output from the state detection means in accordance with the magnitude of the combustion amount of the combustion device; and determining whether or not the combustion is abnormal based on the weighted detection value Determining means for performing the determination.

According to the above configuration, whether or not abnormal combustion is determined is determined based on a state detection value weighted according to the amount of combustion of the combustion device. Improvement can be achieved.

In a preferred embodiment according to the first aspect of the present invention, the state detection values are a frame rod current detection value and a fan drive current detection value. When the combustion amount of the combustion device is relatively small, the weight given to the flame rod current detection value is set large. Conversely, when the combustion amount of the combustion device is relatively large, the weight given to the fan drive current detection value is Set to a large value.

A combustion device according to a second aspect of the present invention supplies fuel and air to a burner and burns the burner. The fan drive current detection means for detecting a fan drive current, and a detected fan drive current value Determining means for determining whether or not abnormal combustion is performed based on the detection result; anda prohibiting means for detecting a fan rotation speed and prohibiting reading of a fan drive current detection value by the determination device when the detected fan rotation speed is equal to or less than a predetermined rotation speed. Is provided.

A combustion device according to a third aspect of the present invention supplies fuel and air to a burner and burns the burner. The flame rod current detection means for detecting a flame rod current, and the detected flame rod current value is abnormal. Threshold variable setting means for variably setting a threshold for determining whether or not the combustion is abnormal combustion based on the detected flame rod current value and the variably set threshold. Determining means for determining whether

[0010] The combustion apparatus according to the second and third aspects of the present invention can provide the same effects as those of the combustion apparatus according to the first aspect of the present invention.

[0011]

Embodiments of the present invention will be described below in detail with reference to the drawings.

FIG. 1 is a block diagram showing the overall configuration of a combustion apparatus according to one embodiment of the present invention.

The above-described apparatus includes a combustion state monitoring unit 11, an air volume monitoring unit 12, an abnormality determining unit 13, an alarm unit 14, a combustion stopping unit 15, a gas amount limiting unit 16, and an air volume increasing unit 17. Prepare. The combustion state monitoring unit 11 monitors the combustion state of the burner (reference numeral 21 in FIG. 2). The air volume monitoring unit 12 monitors the amount of air supplied to the burner 21. The abnormality determination unit 13
Based on the outputs from the combustion state monitoring unit 11 and the air volume monitoring unit 12, the normal / abnormal combustion state of the burner 21 and the cause of the abnormal combustion state of the burner 21 are determined. Notification unit 1
Reference numeral 4 indicates the determination result by the determination unit 13 in a form (image information or audio information) that can be grasped by the user. The combustion stopping unit 15 determines the burner 21 based on the determination result of the determining unit 13.
To stop the combustion operation. The gas amount limiting unit 16 limits the amount of gas fuel supplied from the gas supply source based on the result of the determination by the determining unit 13. The air volume increasing unit 17 increases the amount of air supplied to the burner 21 based on the determination result of the determining unit 13.

The combustion state monitoring unit 11 includes, for example,
Flame current detecting means for detecting the flame current of the burner 21 (=
A flame rod sensor), a CO concentration sensor for detecting the CO concentration of the burner 21, a combustion temperature sensor for detecting the combustion temperature of the burner 21, or an exhaust gas temperature sensor for detecting the temperature of the exhaust gas from the burner 21. You. The air flow monitoring unit 12 includes a fan drive current detection circuit that detects a fan drive current value when the fan rotation speed is a constant value, and a rotation speed detector that detects a fan rotation speed when the fan drive voltage is a constant value. A hot-wire anemometer type or pressure gauge type wind speed sensor is used.

In the above configuration, the combustion state information from the monitoring unit 11 and the air supply amount information from the monitoring unit 12 are both sent to the determination unit 13. In the determination unit 13, these two
If it is determined based on the type information that the combustion state is abnormal and the air supply amount is normal (that is, the air supply amount detection value is larger than a predetermined first threshold value for determining that the air supply amount is insufficient), the acid The combustion operation of the burner 21 is stopped through the combustion stopping unit 15 by determining that the combustion is abnormal due to lack. Then, the determination result and the content of the processing operation are notified to the user from the determination unit 13 through the notification unit 14 simultaneously with the stop of the combustion operation.

Next, when it is determined that the combustion state is abnormal and the air supply amount is insufficient (that is, the detected air supply amount is smaller than the above-mentioned first threshold value) based on the above two types of information, the determination unit Step 13 checks whether the detected value of the air supply amount is larger than a predetermined second threshold value. Here, the second threshold is for discriminating whether the degree of the air amount shortage is large or small, and is a value smaller than the first threshold. As a result of this check, if it is determined that the air supply amount is larger than the second threshold value, it is determined that the transition to the normal combustion state is possible by increasing the air supply amount, and the determination unit 13
Increases the amount of air supplied to the burner 21 through the air volume increasing unit 17. Also in this case, the determination result and the contents of the processing operation are notified to the user from the determination unit 13 through the notification unit 14 at the same time as the control of increasing the air supply amount is started.

On the other hand, as a result of the check, if it is determined that the detected value of the air supply amount is smaller than the second threshold value, the determining unit 1
3 is to supply gas fuel from the gas supply source to the burner 21 through the gas amount limiting unit 16 in order to judge that it is difficult to shift to the normal combustion state by increasing the air supply amount and to attempt to shift to the normal combustion state by combustion restriction. Let the amount be limited. Also in this case, the determination result and the contents of the processing operation are notified to the user from the determination unit 13 through the notification unit 14 at the same time as the start of the restriction of the gas fuel supply amount.

FIG. 2 is a block diagram showing an example of the configuration of a combustion apparatus when the above-mentioned combustion state monitoring unit 11 employs a flame rod sensor and the air flow monitoring unit 12 employs a fan drive current detection circuit.

The above device comprises a burner 21 and an insulating member 23.
, The frame rod 24 and the frame rod current (FR
Current) detector 25, AC power supply 26, amplifier 27,
Controller 28, fan 29, fan drive unit 30
And a fan drive current detection circuit 31. Burner 2
1 burns a mixture of air from the outside air suction fan 29 and gas fuel from a gas supply source (not shown) and blows out the flame 22. The flame rod 24 is supported by the insulating member 23 for detecting a flame current, and faces the flame outlet of the burner 21. The AC power supply 26 forms a closed loop together with the frame rod 24, the burner 21 and the like through the flame 22, and supplies power to the closed loop. FR current detector 25
Constitutes a flame rod sensor (= flame current detecting means) together with the frame rod 24, is connected to this closed loop, and detects and outputs an FR current flowing through this closed loop. In the following description, the description about the frame rod sensor is represented by the FR current detector 25 unless otherwise specified. The amplifier 27 is connected to the detector 25
The output signal from is amplified and output. The fan 29 is driven by the fan drive unit 30. The fan drive current detection circuit 31 detects a fan drive current flowing through the fan drive unit 30 and outputs the same to the controller 28. The controller 28 performs predetermined arithmetic processing operations (each processing operation indicated by reference numerals 13 to 17 in FIG. 1) based on the output from the amplifier 27 and the output from the current detection circuit 31.

The controller 28 compares the output from the amplifier 27 with a threshold value a 'in a table of FR current-CO concentration characteristics stored in advance (see FIG. 3: determined for each number of combustion amounts). Based on the result of the comparison, it is determined whether or not the combustion state is abnormal, and the combustion of the burner 21 is stopped or the combustion amount is limited. This threshold value a 'is the value of C at which abnormal combustion is determined.
This is the FR current value corresponding to the O concentration value a (for example, 1000 ppm).

The FR current-CO concentration characteristic curve shown in FIG. 3 is for judging abnormal combustion caused by an increase in CO concentration (ie, lack of oxygen).

The controller 28 outputs the output from the current detection circuit 31 and a table of the fan drive current-air amount characteristic stored in advance (see FIG. 4: determined for each number of combustion amounts).
Are compared with the threshold values b ′ and c ′. Then, based on the comparison result and the comparison result between the FR current and the threshold value a ′,
The determination of oxygen deficiency, insufficient air amount “medium”, and insufficient air amount “large” is made (see FIG. 6).

FIG. 5 shows the sequence of the processing operation for the above-mentioned determination by the controller 28, and FIG. 6 shows the details of the processing, respectively.

FIG. 4 is a table showing fan driving current-air amount characteristics when the rotation speed of the fan 29 is constant. This table shows not only the relationship between the fan driving current value and the air amount, but also The relationship between these and the CO concentration value is also shown. That is, the table clearly shows that when the fan drive current value (fan rotation speed) increases, the amount of air flowing into the burner 21 increases, and conversely, the CO concentration decreases.

In FIG. 4, a symbol b 'indicates a CO concentration value b (for example, 10%) for judging normal combustion or abnormal combustion.
00 ppm). This value b 'is a threshold value (the above-described first threshold value) for determining whether the air supply amount to the burner 21 is normal or abnormal. The symbol c 'is a CO concentration value c (for example, 2000 ppm) for determining whether the degree of abnormal combustion is large or small.
Is a fan drive current value corresponding to. That is, this value c 'is a threshold value (the above-described second threshold value) for determining whether the degree of the shortage of the air supply amount is large or small.

Next, a first example of the processing operation of the controller 28 will be described with reference to the flowchart of FIG.

First, it is checked whether or not the FR current value detected by the combustion state monitoring unit 11 (ie, the FR current detector 25) is smaller than the threshold value a 'in FIG. (Step S1). At this stage, it is unclear whether the cause of the abnormal combustion is due to lack of oxygen or air shortage for the reasons described above. Next, it is checked whether or not the air amount detected by the air amount monitoring unit 12 is smaller than a first threshold value b '(step S).
2). As a result, if it is determined that it is not small (that is, the air amount is normal), it is determined that the cause of the abnormal combustion is “oxygen deficiency” (the determination result indicated by the symbol in FIG. 6) (step S3), and the safety of the user or the like is secured Immediately, the combustion is stopped (step S4). Then, the user is warned of abnormal combustion due to lack of oxygen in a predetermined manner (image information, audio information, buzzer, or the like) (step S5).

On the other hand, if it is determined that the detected air amount is smaller than the first threshold value b '(that is, the air amount is insufficient) (steps S2 and S6), then it is determined whether the air amount is smaller than the second threshold value c'. Is checked (step S7). As a result,
When it is determined that the air amount is not small (that is, the air amount is insufficient, the result of determination is indicated by the reference numeral in FIG. 6), it is determined that the transition to normal combustion is possible by eliminating the air amount insufficiency, and the fan drive unit 30 is activated. By controlling, the air supply amount to the burner 21 is increased (step S8).

If it is determined that the detected air amount is smaller than the second threshold value c '(the determination result indicated by the reference numeral in FIG. 6) (step S7), the air supply filter is clogged or the soot of the heat exchanger is removed. It is supposed that the air introduction part is extremely blocked, such as clogging, and the degree of air shortage has increased. Therefore, it is determined that it is difficult to solve the shortage of the air amount due to the increase in the number of rotations of the fan.
The amount of gas fuel supplied to the burner 21 is controlled so that the amount of combustion of the burner 21 matches the amount of air supplied (step S).
9). Then, the amount of combustion is limited (for example, the number of combustion is 20
That the burning operation of the burner 21 is continued in a state where the number is reduced from No. 10 to No. 10 in a form such as image information or audio information that can be grasped by the user (step S1).
0).

If it is determined in step S1 that the FR current value is larger than the threshold value a 'in FIG. 3, there is no problem since it is "normal combustion" (determination result indicated by reference numeral in FIG. 6).

As described above, according to one embodiment of the present invention, it is possible to determine whether the cause of abnormal combustion is due to lack of oxygen or due to an insufficient amount of air. Then, the combustion is immediately stopped, so that sufficient safety for the user can be ensured. Also,
When it is determined that the abnormal combustion is due to the shortage of the air amount, it is possible to grasp whether the degree of the shortage of the air amount is large or small, and when the degree of the shortage of the air amount is small, the normal combustion is performed by increasing the air supply amount to the burner 21. Is possible,
Usability is improved. On the other hand, when the degree of the shortage of the air amount is large, the supply amount of the gas fuel to the burner 21 is limited, and the combustion amount of the burner 21 is controlled so as to match the air supply amount. Since the combustion operation of the above can be continued, the usability is also improved. When the combustion is stopped due to lack of oxygen, a warning is issued to the user, and the combustion operation of the burner 21 is continued in a state where the amount of combustion is restricted due to a large degree of insufficient air amount. In such a case, the user is notified to that effect, so that the user can easily grasp the cause of the stop of combustion and the restriction of combustion.

Incidentally, as described above, the FR current detector 25 has the characteristic that the detection accuracy is reduced when the combustion device has a large amount of combustion, and the fan drive current detection circuit 31
Is known to have a characteristic that detection accuracy is reduced when the combustion amount of the combustion device is small.

Therefore, in another embodiment of the present invention described below, the detected value of the FR current output from the FR current detector 25 according to the amount of combustion of the combustion device and the output of the current detection circuit 31 The detection accuracy of abnormal combustion is improved by weighting each of the detected fan drive current values.

FIG. 7 shows an FR according to another embodiment of the present invention.
FIG. 8 is a diagram illustrating a relationship between a detected current value and weighting, and FIG. 8 is a diagram illustrating a relationship between a detected fan driving current value and weighting according to another embodiment of the present invention.

In FIG. 7, the abscissa indicates the combustion amount F, and the ordinate indicates the weight by which the FR current detection value f (F) is multiplied. In FIG. 8, the abscissa indicates the weight. Combustion amount F
On the vertical axis, weights by which the fan drive current detection value f (F) is multiplied are shown.

As shown in FIG. 7, when the combustion amount F increases to reach the large combustion amount region, the FR current detector 25
Since the detection accuracy of the current value is deteriorated, the weight f (F) is reduced. When the combustion amount F decreases and reaches the small combustion amount region, F
The weight f (F) is increased to improve the detection accuracy of the R current value. On the other hand, the fan drive current detection circuit 31
As shown in the figure, when the combustion amount F increases and reaches the large combustion amount region, the detection accuracy of the fan drive current value is improved.
When the weight f (F) is increased and the combustion amount F decreases to reach the small combustion amount region, the detection accuracy of the fan drive current value deteriorates, so the weight f (F) is decreased.

Next, an embodiment of a method for weighting the detected FR current value and the detected fan drive current value will be described.

The first embodiment is a method of selecting one of the FR current detector 25 and the fan drive current detection circuit 31 according to the amount of combustion.

That is, when the amount of combustion is large, only the detected value of the fan drive current from the current detection circuit 31 is read to determine whether or not the combustion is abnormal, and when the amount of combustion is small, only the FR current detection value from the current detector 25 is used. The reading is performed to determine whether or not the combustion is abnormal.

It is known that the number of revolutions of the fan 29 is proportional to the amount of combustion of the combustion device. If the amount of combustion decreases, the number of revolutions of the fan 29 decreases accordingly. When the number is equal to or less than a predetermined value (for example, 2500 rpm or less as shown in FIG. 9), the fan drive current detection value is easily affected by disturbance such as wind. For this reason, the detection accuracy of the fan drive current detection value becomes a problem.
When the number of revolutions is equal to or less than 2500 rpm, the fan drive current detection value is not read, and only the FR current detection value from the detector 25 is read to determine whether or not abnormal combustion has occurred.

In the second embodiment, the set point of the threshold value for determining whether or not the detected value of the FR current and the detected value of the fan drive current indicate abnormal combustion is determined by the magnitude of the combustion amount of the combustion device. It is a method of changing according to.

FIG. 10 is an explanatory diagram showing the setting points of the above-described threshold values of the FR current detection value and the fan drive current detection value.

In FIG. 10, the numerical value (%) indicates the rate of decrease in the amount of air. That is, this numerical value (%) is 0% during normal combustion of the combustion device, and increases as the combustion state deteriorates.

In the case of the FR current detector 25, since the accuracy of the detected value of the FR current is high at the time of a small combustion amount, the threshold value of the FR current is set so that the rate of decrease of the air amount is 10% and the abnormal combustion is determined. Since the accuracy of the FR current detection value decreases as the amount of combustion increases, the rate of decrease in the amount of air is determined to be 20% for a medium amount of combustion, and 30% for a large amount of combustion so that the FR current is determined to be abnormal combustion. Change the threshold setting point. Thus, even if the accuracy of the FR current detection value deteriorates with an increase in the amount of combustion, it is possible to prevent a problem that the combustion is not erroneously determined to be abnormal combustion even though the combustion is not abnormal.

On the other hand, in the case of the fan drive current detection circuit 31, since the detection accuracy is good at the time of a large combustion amount, the threshold value of the fan drive current is set so as to detect the abnormal combustion at the rate of air amount decrease of 10%. Since the accuracy of the fan drive current detection value deteriorates as the combustion amount decreases, the air amount decrease rate is 20% for the medium combustion amount and 3% for the small combustion amount.
The set point of the threshold value of the fan drive current is varied so that 0% is determined as abnormal combustion. As a result, even if the accuracy of the detected value of the fan drive current deteriorates with the decrease in the combustion amount, it is possible to prevent a problem that the combustion is not erroneously determined as abnormal combustion even though the combustion is not abnormal.

The third embodiment is a method of varying the weight in a calculation formula for determining whether or not abnormal combustion occurs depending on the amount of combustion.

That is, based on the addition result Z (= integrated state value) of the FR current state value X obtained from the detected FR current value and the fan drive current state value Y obtained from the fan drive current detected value, the abnormal combustion is determined. If the determination is made in an integrated manner, the respective state values X, Y according to the magnitude of the combustion amount
Is a method of varying the coefficient by which the term representing is multiplied.

For example, when the combustion amount is small, the accuracy of the FR current detection value is good and the accuracy of the fan drive current detection value is poor. Therefore, the coefficient for multiplying the FR current state value X is 2 and the coefficient for multiplying the fan drive current state value Y is 2. Is 0.5, the integrated state value Z is represented by Z = 2X + 0.5Y. Next, when the combustion amount is large, the accuracy of the detected value of the fan drive current is good and the accuracy of the detected value of the FR current is poor. If the multiplication coefficient is 0.5, the integrated state value Z is Z = 0.
It is represented by 5X + 2Y. In addition, since the accuracy of each detection value is substantially the same at the time of the medium combustion amount, both the coefficients for multiplying the terms representing the state values X and Y are set to 1. As a result, the integrated state value Z at the time of the medium combustion amount is represented by Z = 1X + 1Y.

The FR current state value X is a value representing the degree of abnormal combustion by a numerical value from 0 to 10 based on the detected FR current value.
Is a value representing the degree of abnormal combustion by a numerical value from 0 to 10 based on the detected value of the fan drive current. If the integrated state value Z is Z> 10, it is determined that abnormal combustion has occurred.

As described above, according to another embodiment of the present invention, the abnormal current is detected by weighting the FR current detection value and the fan drive current detection value according to the amount of combustion of the combustion device. The detection accuracy of combustion can be further improved.

The above description relates only to each embodiment of the present invention, and does not mean that the present invention is limited to only the above content.

[0052]

As described above, according to the present invention,
In a combustion device for detecting a normal / abnormal combustion state of a burner, it is possible to provide a combustion device capable of improving detection accuracy of abnormal combustion.

[Brief description of the drawings]

FIG. 1 is a block diagram of a combustion device according to an embodiment of the present invention.

FIG. 2 is a block diagram when an FR current detector and a fan drive current detection circuit are employed in the apparatus of FIG. 1;

FIG. 3 is a diagram showing an FR current-CO concentration characteristic of a frame rod.

FIG. 4 is a diagram showing a fan drive current-air amount characteristic of the fan drive current detection circuit.

FIG. 5 is a flowchart showing a processing flow by a controller (abnormality determining unit).

FIG. 6 is an explanatory diagram of decision logic obtained as a result of the processing flow of FIG. 5;

FIG. 7 is a diagram showing a relationship between a combustion amount and weighting in a detected FR current value according to another embodiment.

FIG. 8 is a diagram showing a relationship between a combustion amount and a weight in a fan drive current detection value according to another embodiment.

FIG. 9 is a diagram showing a relationship between a fan rotation speed and a fan drive current detection value-abnormal combustion detection accuracy characteristic according to another embodiment.

FIG. 10 is an explanatory diagram showing setting points of threshold values of an FR current detection value and a fan drive current detection value according to another embodiment.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 11 Combustion state monitoring part 12 Air volume monitoring part 13 Abnormality judgment part 14 Notification part 15 Combustion stopping part 16 Gas amount restriction part 17 Air volume increasing part 21 Burner 23 Insulation member 24 Frame rod 25 FR current detector 26 AC power supply 27 Amplifier 28 Controller 29 Fan 30 Fan drive unit 31 Fan drive current detection circuit

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Yasuaki Baba 43-1, Uozakihama-cho, Higashinada-ku, Kobe, Hyogo Prefecture Within Nihon Yupro Corporation (72) Inventor Hiroshi Munemura 43, Uozakihama-cho, Higashinada-ku, Kobe-shi, Hyogo No. 1 Inside Nippon Yupro Co., Ltd. (72) Inventor Shigeo Yoshida 43-1, Uozakihama-cho, Higashinada-ku, Kobe City, Hyogo Prefecture Inside Nippon Yupro Co., Ltd.

Claims (5)

[Claims] 1. A combustion device for supplying fuel and air to a burner and burning the burner, wherein a condition detecting means for detecting a condition of the combustion device, and the condition according to the amount of combustion of the combustion device Weighting means for weighting the state detection value output from the detection means, and determination means for determining whether or not abnormal combustion is to be performed based on the weighted detection value, Burning device. 2. The combustion apparatus according to claim 1, wherein the state detection value is a flame rod current detection value and a fan drive current detection value. 3. The combustion device according to claim 2, wherein when the combustion amount of the combustion device is relatively small, the weight given to the flame rod current detection value is increased, and the combustion amount of the combustion device is relatively large. In some cases, the weight given to the fan drive current detection value is increased. 4. A combustion device for supplying fuel and air to a burner for combustion, wherein a fan drive current detecting means for detecting a fan drive current, and whether or not abnormal combustion is detected based on the detected fan drive current value. And a prohibition unit for detecting the fan rotation speed and prohibiting reading of the fan drive current detection value by the determination unit when the detected fan rotation speed is equal to or less than a predetermined rotation speed. Burning device. 5. A combustion apparatus for supplying fuel and air to a burner and burning the burner, wherein a flame rod current detecting means for detecting a flame rod current, and for judging whether or not the flame rod current detected value is abnormal. Threshold variable setting means for variably setting a threshold value according to the magnitude of the combustion amount; determining whether abnormal combustion is to be performed based on the detected flame rod current value and the variably set threshold value Means, and a combustion device comprising: