JP2851235B2 - Combustion equipment - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to ventilation means for ventilating combustion air to a burner and discharging combustion gas to the outside of the room through an exhaust passage, and means for detecting incomplete combustion of the burner. A fuel supply amount adjusting means capable of changing and adjusting a fuel supply amount to the burner; and a control means for controlling the fuel supply amount adjusting means to adjust the fuel supply amount to the burner. In a normal combustion state in which the incomplete combustion detecting means does not detect incomplete combustion, the fuel supply amount is controlled to a target amount for normal combustion, and when the incomplete combustion detecting means detects incomplete combustion, The present invention relates to a combustion device configured to stop fuel supply to a burner.

[0002]

2. Description of the Related Art In a combustion apparatus, for example, when the exhaust passage of a ventilation means is clogged with dust or the like and the amount of ventilation to a burner decreases, the combustion air is insufficient for the fuel supply amount and the combustion of the burner is stopped. Is in an incomplete combustion state, but when such incomplete combustion is detected, the fuel supply to the burner is stopped to prevent the incomplete combustion state from continuing for a long time. When incomplete combustion is detected, if the burner combustion is stopped immediately, the combustion device becomes unusable. To solve such a disadvantage, for example, Japanese Patent Application Laid-Open No. 62-252821 discloses a method. As disclosed, there has been a configuration in which when the incomplete combustion is detected, the amount of ventilation by a fan as ventilation means is controlled to be changed, so that the device can be continuously used.

[0003]

However, according to the above-mentioned conventional configuration, since the incomplete combustion state is avoided by controlling the change in the amount of ventilation, there are the following problems. That is, for example, when the ventilation amount by the ventilation means in the normal combustion state is a ventilation amount close to the maximum value of the ventilation amount change adjustment range, if incomplete combustion is detected, the increase change adjustment of the ventilation means is not performed. This has the disadvantage that the burner combustion must be stopped as a result. In addition, since the configuration is such that the amount of ventilation by the ventilation means is increased and changed, there is a problem that noise such as wind noise is increased due to the large amount of ventilation. Also, considering a water heater as an example of a combustion device, even after an incomplete combustion state is once detected, the combustion state of the burner does not change and the hot water temperature does not change. In this case, the incomplete combustion state can be determined only after the combustion of the burner is stopped, and there is a disadvantage that the maintenance process such as the removal of dust in the exhaust passage is delayed. A first object of the present invention is to provide a combustion device that suppresses an increase in noise when incomplete combustion is detected and enables continuous use of the device. A second object of the present invention is to provide a combustion apparatus that can quickly perform a maintenance process when incomplete combustion is detected.

[0004]

The features of the first invention are as follows.
Ventilation means for ventilating combustion air through the burner and discharging combustion gas to the outside of the room through an exhaust path, incomplete combustion detection means for detecting incomplete combustion of the burner, and changing and adjusting the fuel supply amount to the burner A fuel supply amount adjusting means; and a control means for controlling the fuel supply amount adjusting means so as to adjust the fuel supply amount to the burner. In a normal combustion state in which combustion is not detected, the fuel supply amount is controlled to a target amount for normal combustion, and the fuel supply to the burner is stopped when the incomplete combustion detection means detects incomplete combustion. In the combustion apparatus, the control means reduces and changes the fuel supply amount from the target amount for normal combustion as the incomplete combustion detection means detects incomplete combustion. And the fuel supply to the burner is stopped when the incomplete combustion detection means detects incomplete combustion even after a set time has elapsed after such fuel supply amount decrease change control. In that it is.

[0005] A characteristic feature of the second invention is that the fuel supply amount decreasing change control by the control means is performed a plurality of times by a predetermined amount decreasing control of waiting for a predetermined time after changing the fuel supply amount by a predetermined amount. In that it is configured to

According to a third aspect of the present invention, the control means includes:
The point is that the fuel supply amount decrease change control is performed only in the range on the large supply amount side in the fuel supply amount adjustment allowable range.

According to a fourth feature of the present invention, the control means includes:
Controlling the ventilation means to regulate the combustion air; and, in a normal combustion state in which the incomplete combustion detection means does not detect incomplete combustion, combustion air ventilation to the burner by the ventilation means. The incomplete combustion detection means is configured to control the amount to a target amount for normal combustion, and when the fuel supply amount is in a small range where the fuel reduction change control is not performed, the incomplete combustion detection means is incomplete. When combustion is detected, the ventilation amount of the ventilation means is configured to be increased from the target amount for steady combustion.

[0008] A characteristic feature of the fifth invention is that the burner heats a heat exchanger for water for hot water supply.

[0009]

According to the characteristic structure of the first invention, in a normal combustion state in which the incomplete combustion detecting means does not detect incomplete combustion, the fuel supply amount to the burner is controlled to the target amount for normal combustion. A normal combustion state is always maintained.
When the incomplete combustion is detected by the incomplete combustion detection means, the fuel supply amount to the burner is reduced from the target amount for normal combustion. Therefore, incomplete combustion occurs when the amount of combustion air is small relative to the amount of fuel supplied. Therefore, the incomplete combustion state can be eliminated by changing the amount of fuel supply to a reduced value. . In spite of such fuel supply amount decrease change control, incomplete combustion is still detected even after the elapse of the standby time for stabilizing the combustion state of the burner due to the decrease in fuel supply amount. In such a case, the fuel supply is stopped to stop the combustion of the burner, so that the incomplete combustion state can be prevented from continuing for a long time.

According to the characteristic configuration of the second invention, when the incomplete combustion detecting means detects the incomplete combustion, the fuel supply amount to the burner is reduced and changed by a predetermined amount, and after waiting for a set time, the incomplete combustion detecting means. Is detected. Then, such predetermined amount reduction control is repeatedly performed a plurality of times until incomplete combustion is not detected. Then, even after such predetermined amount reduction control is performed a plurality of times, when incomplete combustion is detected, the fuel supply to the burner is stopped. Therefore, by reducing the fuel supply amount by a predetermined amount so that the combustion state of the burner does not significantly change, the combustion state of the burner is sharply reduced by greatly changing the fuel supply amount in accordance with the detection of incomplete combustion. It is possible to prevent the flame from changing and becoming unstable, and the flame from being extinguished due to ventilation during the change.

According to the characteristic configuration of the third invention, the fuel supply amount decrease change control executed in accordance with the detection of the incomplete combustion detecting means is performed in the range of the supply amount larger side in the fuel supply amount adjustment allowable range. Is performed only when the fuel supply to the burner is on the small supply side in the allowable adjustment range.
As compared with the case where the supply amount is large, when the fuel supply amount is reduced, the combustion state of the burner becomes unstable and the flame may go out. It is not executed. As a result, it is possible to prevent the combustion state of the burner from becoming unstable or the flame from going out.

According to the characteristic configuration of the fourth invention, when the fuel supply amount is on the large supply side in the allowable adjustment range, the ventilation air amount to the burner by the ventilation means is controlled to the target amount for normal combustion. , The combustion state of the burner is maintained in a stable state. When the incomplete combustion detection means detects incomplete combustion, the fuel supply amount decrease change control is executed. However, when the fuel supply amount to the burner is on the small supply amount side in the allowable adjustment range, the fuel supply amount is reduced. The incomplete combustion is eliminated by compensating for the insufficient amount of ventilation by increasing / changing the ventilation amount of the ventilation means from the target amount for steady-state combustion without performing the amount decrease / change control. Accordingly, in the range of the small fuel supply amount where the combustion state of the burner is likely to be unstable, the ventilation amount by the ventilation means is increased and changed from the target amount without decreasing the fuel supply amount. It is possible to eliminate incomplete combustion while preventing instability or the flame from going out.

According to the fifth feature of the invention, when the incomplete combustion detecting means detects incomplete combustion, the amount of fuel supplied to the burner is reduced and changed. The amount of heat applied is reduced, and the hot water temperature drops from the desired temperature, so that the user of the water heater can immediately determine that incomplete combustion has been detected, and can quickly perform the maintenance process thereafter. Will be.

[0014]

According to the characteristic configuration of the first invention, while the incomplete combustion can be prevented from continuing for a long time and safety can be ensured, the ventilation of the ventilation means when the incomplete combustion is detected. The incomplete combustion state is effective even when the combustion operation is performed without increasing the noise as in the case of increasing the amount and when the ventilation amount is close to the maximum value of the adjustment range. To provide a combustion device that enables continuous use of the device.

According to the characteristic configuration of the second invention, in addition to the effect of the characteristic configuration of the first invention, the combustion state of the burner is maintained in a stable state in the operation of decreasing the fuel supply amount, so that the flame is reduced. Outflow of fuel can be prevented beforehand.

According to the third aspect of the present invention, in addition to the effects of the first or second aspect of the present invention, the fuel supply amount on the small fuel supply amount side where the combustion of the burner tends to be unstable is increased. By maintaining the combustion state of the burner in a stable state without performing the reduction control, it is possible to prevent the fuel from flowing out due to the extinguishing of the flame.

According to the fourth aspect of the invention, in addition to the effect of the third aspect of the invention, incomplete combustion is detected when the burner is burning with a small amount of fuel supplied. Even in this case, the incomplete combustion state can be effectively avoided by compensating for the shortage of the ventilation volume.

According to the characteristic configuration of the fifth invention, when incomplete combustion is detected by the incomplete combustion detection means, it is possible to immediately determine that incomplete combustion has been detected by lowering the hot water temperature, Subsequent maintenance processing can be promptly performed, and adverse effects such as a long time lapse without being able to determine that the combustion state is incomplete can be prevented.

[0019]

Embodiments will be described below with reference to the drawings. The combustion device (hot water supply device) according to the present invention, as shown in FIG.
The water heater A includes a control unit H as control means for controlling the operation of the water heater A, and an operation unit R. The water heater A is connected to the combustion chamber 1, a burner 2 provided inside the combustion chamber 1, a heat exchanger 3 for water heating, and an upper part of the combustion chamber 1, and supplies the combustion gas in the burner 2 to the combustion chamber 1. An exhaust passage 5 for discharging air to the outside; a fan 4 as ventilation means for supplying combustion air to the burner 2 and for allowing combustion gas in the burner 2 to pass through the exhaust passage 5 to the outside of the room; A hot water supply path 6 for supplying hot water to the heater, a hot water supply path 7 for supplying hot water heated in the heat exchanger 3 to a hot water tap (not shown),
Fuel supply path 8 for supplying fuel (gas) to burner 2
It is composed of In the drawing, reference numeral 30 denotes an igniter for ignition, and reference numeral 31 denotes a frame rod for detecting whether or not the burner 2 is ignited.

The water supply passage 6 has a water supply amount Qi to the heat exchanger 3.
Is provided with a water supply amount sensor 9 for detecting
Hot water temperature sensor 1 for detecting hot water temperature Tx for hot water tap
0 is provided. The fuel supply passage 8 is connected to a general household gas supply pipe.
Proportional valve 11 as a fuel supply amount adjusting means for adjusting the fuel supply amount Ip to the fuel supply, and an intermittent valve 1 for intermittently supplying the fuel
2 is provided.

The operation unit R is connected to the control unit H by wire or wirelessly, and includes an operation switch 13 for instructing start and stop of operation of the hot water supply device, a temperature setting switch 14 for setting a set target hot water supply temperature Ts, LE to display information of
D lamps 15 and 16 are provided. In addition, LED
The lamp 15 is configured to display whether the water heater is operating, and the LED lamp 16 is configured to display whether an incomplete combustion state has occurred.

The exhaust passage 5 is provided with a CO sensor S which is an example of an incomplete combustion detecting means for detecting a concentration value CO of an unburned component contained in the combustion gas of the burner 2. FIG.
Shows the configuration of the CO sensor S. CO
The sensor S is mounted on the pedestal 2 inside the protection frame 21 made of stainless steel.
2. Sensor element 23 and temperature-compensating reference element 24
Equipped. The sensor element 23 and the temperature-compensating reference element 24 are each composed of a platinum wire carrying a catalyst, and are heated to about 200 ° C. by the flow of an electric current. The components burn by catalysis. At this time, since the catalyst carried on the sensor element 23 has selectivity for CO, there is a difference between the element temperatures. Since the resistance value of the platinum wire changes depending on the temperature, when the CO concentration in the combustion gas increases, the sensor element 23 and the temperature-compensating reference element 2
4 is large. Therefore, the CO in the combustion gas
It is configured such that the density can be detected as a difference in resistance value (sensor output V). In the figure, reference numeral 25 denotes a connector part for connecting to a lead wire connected to the control part H. FIG. 3 shows the output V of the CO sensor S with respect to the CO concentration in the combustion gas.

The control unit H includes combustion control means 101 for controlling the combustion operation of the water heater A, incomplete combustion discrimination means 102 for discriminating an incomplete combustion state based on the detected concentration value CO of the CO sensor S, During the set time after the start of burner 2 combustion,
A timed restraining means 103 for restraining the operation of the incomplete combustion determining means 102 and an operation locking means 104 for disabling an operation command by the operation unit R after the incomplete combustion state is determined by the incomplete combustion determining means 102 are provided. Have been.

When the water supply amount Qi adjusted by the hot-water tap and detected by the water supply amount sensor 9 reaches the set water amount, the combustion control means 101 executes the following hot water supply operation, and when the water supply amount Qi becomes less than the set water amount, Stop the hot water supply operation. Basically, the hot water supply operation is performed by adjusting the electromagnetic proportional valve 11 so that the hot water supply temperature Tx detected by the hot water supply temperature sensor 10 becomes equal to the set target hot water supply temperature Ts.
Is adjusted to a target amount for the burner 2 to perform normal combustion, and the rotation speed of the fan 4 is
For example, the rotation speed of the fan 4 is controlled such that the target rotation speed F is determined based on a preset characteristic as shown by a characteristic line L1 in FIG. In the following description, the basic control in the hot water supply operation is referred to as proportional control.

When the detected concentration value CO of the CO sensor S is equal to or higher than the set concentration value CO _CHK , the incomplete combustion determination means 102 detects the detected concentration value C of the CO sensor S every unit time.
In accordance with O, as the detected density value CO increases, the detected density value CO is multiplied by a weighting coefficient N, which is larger than the detected density value CO, to obtain a weight value F (F = N × CO). Are integrated, and as the integrated value M becomes equal to or greater than a preset set value M _CHK , it is determined that the combustion is incomplete. The weighting coefficient N is set in advance corresponding to the detected density value CO so that the larger the detected density value CO is, the larger the value becomes.

FIG. 4 shows a change in the output V of the CO sensor S when the combustion of the burner 2 is generally started. In the figure, the combustion start time of the burner 2 is shown at time t1. The sensor output V is initially
In the state where combustion is stopped (before time t1), the output value V1 unique to the sensor S is shown. Immediately after the start of combustion (immediately after time t1), a transient incomplete combustion state occurs in the combustion of the burner 2, and the concentration of unburned components in the exhaust gas (C
O) temporarily becomes very high, so that the output value V once becomes very high. When the combustion of the burner 2 becomes stable, the concentration (CO) of the unburned component decreases, so that the output value V decreases and the output value V2 indicating a steady combustion state.
Converges to

Accordingly, the time limit control means 103 controls the incomplete combustion determination means 102 so that the transient incomplete combustion state immediately after the start of combustion is not determined to be abnormal. After elapse of (sec), the incomplete combustion determination means 102 is operated. That is, the operation of the incomplete combustion determination means 102 is suppressed during the set time T after the start of combustion of the burner 2.

The combustion control means 101 controls the fuel supply amount so as to decrease from the target amount for normal combustion as the incomplete combustion is detected from the detection result of the CO sensor S. If the incomplete combustion is detected even after the set time elapses after the fuel supply amount decrease change control, the fuel supply to the burner 2 is stopped.

Hereinafter, the control operation of the hot water supply apparatus of this embodiment will be described with reference to the flowchart shown in FIG.
First, when the opening of the hot water tap is detected by the water supply amount sensor 9, the sensor power supply 25 is turned on, and the timed restraint means 103 is turned on.
The time timer for timed restraint of the incomplete combustion discriminating means 102 is reset and time counting is started [Step 1].
~ 3]. Then, the blowing (prepurge) of the fan 4 is started, and the combustion of the burner 2 is started [Step 4,
5]. That is, the ignition by the igniter 30 is started, the electromagnetic proportional valve 11 and the intermittent valve 12 are opened, and the combustion is started. Whether or not the fire transfer to the burner 2 has been completed is detected by the frame rod 31.

Next, the hot water supply temperature Tx detected by the hot water supply temperature sensor 10 and the set target hot water supply temperature Ts set in the operation section are read [Step 6], and the hot water supply temperature Tx is set to the set target hot water supply temperature Ts. A target amount of the fuel supply amount Ip is set, and the rotational speed of the fan 4 is set to be different from the fuel supply amount Ip based on a preset characteristic as shown by a characteristic line L1 in FIG. A target rotation speed F of the fan is set [Step 7]. Then, the electromagnetic proportional valve 11 is operated so as to reach the target fuel supply amount, and the fan 4 is operated so as to reach the target rotational speed F [Step 8]. When the set time (about 60 seconds) elapses after the timed timer of the timed restraining means 103 has timed out (step 9), the result of the determination by the incomplete combustion determining means 102 is read. The above proportional control is executed until it is determined from the detection result of the water supply amount sensor 9 that is closed (Steps 6 to 6).
9]. Therefore, during the operation of the timed restraint means 103, the incomplete combustion determination means 102 is not operated.

When the incomplete combustion is detected, the fuel supply amount to the burner 2 is reduced and changed by a predetermined amount ΔIp from the target amount, and the electromagnetic proportional valve 11 is operated to have the changed value [step 11]. -13), if incomplete combustion is detected even after a set time [e.g., 60 seconds] for stabilizing the combustion of the burner 2 has elapsed [step 15], the fuel supply amount as described above is determined. The quantitative reduction control is repeated a plurality of times (N1 times) [steps 14 and 17],
If the incomplete combustion is still detected [Step 18], an abnormal display (the LED lamp 16 flashes) is performed, the operation locking means 104 is operated, and the electromagnetic proportional valve 11 and the intermittent valve 12 are closed. The combustion of the burner 2 is stopped, post-purge is performed, and the sensor power supply 25 is turned off [steps 19 to 23]. In addition, in the combustion control operation during the timed restraint in steps 6 to 9, when the closing of the hot water tap is detected by the water supply amount sensor 9, the operation shifts to the control operation for stopping the combustion and the electromagnetic proportional valve 11 and the intermittent valve 12 Is closed to stop combustion of the burner 2, post-purge is performed, and the sensor power supply 25 is turned off [Step 10, Steps 21 to 21]
23].

During the elapse of the set time in step 15, the proportional control is executed based on the fuel supply target amount reduced and changed by the predetermined amount ΔIp in step 12, and the set time is set. If the hot-water tap is closed during the lapse of time, the operation shifts to the control operation for stopping combustion [step 16, steps 21 to 23].

Next, control for determining incomplete combustion by the incomplete combustion determining means 102 will be described. As shown in FIG. 6, first, the integrated value M is initialized (M = 0), and the counter A is reset to start counting by the counter A (for example, 3 minutes) [Steps 24 and 2
5]. Then, the detected density value CO of the CO sensor S is read, and the detected density value CO at that time is set to the set density value C.
It is determined whether it is O _CHK or more [Step 26,
27].

While the counter A is counting up [Step 28], that is, for three minutes after the counter A starts counting, the detected density value CO of the CO sensor S is read. Concentration value CO
If less than _CHK , the process returns to step 26. When the counter A counts up, the integrated value M is initialized (M = 0), and the process returns to step 25 [step 29].

When the detected density value CO becomes equal to or greater than the set density value CO _CHK , a weight value F is obtained by multiplying the detected density value CO by a preset weighting coefficient N.
Is integrated to obtain an integrated value M. If the integrated value M exceeds the set value M _CHK , it is determined that the combustion is incomplete, and an incomplete combustion determination result is output to the combustion control means 101 [Steps 30 to 30]. 33].

[Another Embodiment] (1) In the above embodiment, the target fuel supply amount after the target amount of the fuel supply amount Ip has been reduced by a predetermined amount ΔIp during the elapse of the set time in step 15. The above-described proportional control is executed based on the above, but when the set target hot water supply temperature Ts is changed during the elapse of the set time, the decrease change target amount is changed accordingly. You may. (2) In the above embodiment, the weighted value of the detection value of the CO sensor is integrated, and when the integrated value exceeds the set value,
Although it is determined that the combustion is incomplete, if the CO concentration by the CO sensor exceeds a set value, the fuel supply amount decrease change control may be executed. (3) As the incomplete combustion detection means, the oxygen sensor detects the oxygen concentration in the exhaust gas instead of the CO sensor.
An incomplete combustion state may be detected from the detection information, and an actual air volume and an actual wind speed with respect to the target air volume are detected by using an air volume sensor and a wind speed sensor that detect an air volume in the exhaust path,
The incomplete combustion state may be detected from the detection information. (4) In the above-described embodiment, the fuel supply amount is reduced and changed in any range of the change adjustment range of the fuel supply amount to the burner 2. However, the supply in the fuel supply amount adjustment allowable range is performed. The fuel supply amount decrease change control may be performed only in the large amount range. That is,
The control shown in FIG. 8 is added to the control flowchart shown in FIG. 5 in the above embodiment, and if it is determined that the combustion is incomplete in step 12 in the control flowchart shown in FIG. the amount is equal to or less than the intermediate setting value Ip _N shown in FIG. 7, it may be configured to perform the abnormal combustion stop control shown in step 19 to 23 in the control flowchart of FIG. (5) In addition, the fuel supply amount decrease change control is performed only in a range where the fuel supply amount to the burner 2 is larger than the supply amount in the allowable adjustment range, and the fuel supply amount decrease change control is performed in a smaller range where the fuel decrease change control is not performed. In a certain state, when incomplete combustion is detected, the ventilation amount of the fan 4 may be increased from the target amount for steady combustion. That is,
When the control shown in FIG. 9 is added to the control flowchart shown in FIG. 5 in the above-described embodiment, and it is determined in step 12 that the combustion is incomplete, the set target amount of the fuel supply amount is changed to that shown in FIG. If the intermediate set value Ip _N is equal to or less than the indicated intermediate set value Ip _N , the target rotation speed of the fan 4 is increased from the current set value by a predetermined amount ΔF as shown by a characteristic line L2 in FIG. , Incomplete combustion determination means 10
If the incomplete combustion is still detected after the determination processing time by the control unit 2 and the set time for stabilizing the combustion of the burner 2, the abnormal combustion shown in steps 19 to 23 in the control flowchart of FIG. Stop control may be performed. (6) In the above embodiment, the fuel supply amount reduction control is performed a plurality of times by a predetermined amount. However, the fuel supply amount may be reduced only once by a reduction amount larger than the predetermined amount. (7) The combustion device according to the present invention is not limited to the application to a water heater provided with a heat exchanger for water for hot water supply, but can be applied to various combustion devices such as stoves and heaters.

In the claims, reference numerals are provided for convenience of comparison with the drawings, but the present invention is not limited to the configuration shown in the accompanying drawings.

[Brief description of the drawings]

FIG. 1 is a configuration diagram showing the overall configuration of a combustion device.

FIG. 2 is a schematic diagram showing the overall configuration of a CO sensor.

FIG. 3 is a graph showing a change in an output value of a CO sensor with respect to a CO concentration.

FIG. 4 is a graph showing a time change of an output value of a CO sensor.

FIG. 5 is a flowchart of a control operation.

FIG. 6 is a flowchart of a control operation.

FIG. 7 is a graph showing a change characteristic of a fuel supply amount and a target rotation speed.

FIG. 8 is a diagram showing a part of a flowchart of a control operation according to another embodiment.

FIG. 9 is a diagram showing a part of a flowchart of a control operation according to another embodiment.

[Explanation of symbols]

 2 burner 3 heat exchanger 4 ventilation means 5 exhaust path 11 fuel supply amount adjustment means H control means S incomplete combustion detection means

Continuation of the front page (72) Inventor Hiroshi Kamiya 1-152 Oka, Minami-shi, Minato-ku, Osaka-shi, Osaka Inside Harman Co., Ltd. (58) Field surveyed (Int. Cl. ⁶ , DB name) F23N 5/00 F23N 5 / 24 F23N 5/02 F23N 5/12

Claims (5)

(57) [Claims] A ventilation means (4) for ventilating combustion air to a burner (2) and discharging a combustion gas to the outside through an exhaust path (5), and detects incomplete combustion of the burner (2). An incomplete combustion detecting means (S), a fuel supply amount adjusting means (11) capable of changing and adjusting a fuel supply amount to the burner (2), and controlling the fuel supply amount adjusting means (11). Control means (H) for adjusting the amount of fuel supplied to (2), wherein the control means (H) is configured to: in a normal combustion state in which the incomplete combustion detection means (S) does not detect incomplete combustion; The fuel supply amount is controlled to a target amount for normal combustion, and the fuel supply to the burner (2) is stopped when the incomplete combustion detection means (S) detects incomplete combustion. A combustion device, wherein the control means (H) Is the incomplete combustion detection means (S)
Is controlled to decrease the fuel supply amount from the target amount for normal combustion in accordance with the detection of incomplete combustion, and even after a set time has elapsed after such fuel supply amount decrease change control. A combustion device configured to stop fuel supply to the burner (2) when the incomplete combustion detection means (S) detects incomplete combustion. 2. The fuel supply amount decrease change control by the control means (H) is such that the predetermined amount decrease control of waiting for a predetermined time after changing the fuel supply amount by a predetermined amount is performed a plurality of times. The combustion device according to claim 1, wherein: 3. The control means (H) is configured to perform the fuel supply amount decrease change control only in a range of a large supply amount in the fuel supply amount adjustment allowable range. A combustion device as described. 4. The control means (H) is configured to control the ventilation means (4) to adjust the combustion air, and the incomplete combustion detection means (S) In a normal combustion state in which no fuel is detected, the ventilation means (4) is configured to control the amount of combustion air flowing to the burner (2) to a target amount for normal combustion, and the fuel supply amount is controlled by the fuel supply amount. When the incomplete combustion detection means (S) detects incomplete combustion in a small range where the decrease change control is not performed, the ventilation amount of the ventilation means (4) is changed to the target amount for the steady combustion. The combustion device according to claim 3, wherein the combustion device is configured to increase and change the pressure. 5. The combustion device according to claim 1, wherein the burner (2) heats a heat exchanger (3) for hot water.