JPH10132274A - Incomplete combustion preventer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To take a quick action for incomplete combustion attributed to rapid worsening of combustion by detecting the concentration of CO in a combustion exhaust gas at a specified interval during normal operation of a gas combustion apparatus to predict the incomplete combustion attributed to the clogging of fins and also by detecting another incomplete combustion attributed to rapid worsening of combustion when this situation occurs owing to a top pressure or the like during the detection interval of the concentration of CO. SOLUTION: The air/fuel ratio of a gas combustion apparatus is lowered once at a specified interval to predict probable incomplete combustion attributed to the clogging of fins or the like and also, the output value of the concentration of CO is detected by a CO sensor when the air/fuel ratio once lowered is returned to the original position during the interval of the prediction (S11). When the change Δx in the output value exceeds a specified range (S13: 'YES'), the air/fuel ratio is lowered again (S7) and the value is read in (S8) to monitor the generation of a sudden incomplete combustion (S9).

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a forced supply / exhaust type (F
More specifically, the present invention relates to a device for preventing incomplete combustion applied to gas-fired equipment such as a gas water heater of type F), and more specifically, a carbon monoxide (CO) concentration detection sensor is provided in a combustion exhaust gas system of gas-fired equipment. The present invention relates to a device for preventing incomplete combustion which is suitable for predicting the occurrence of incomplete combustion of a gas combustion device based on a detection signal from a CO concentration detection sensor.

[0002]

2. Description of the Related Art Conventionally, this type of gas combustion equipment detects CO concentration in flue gas to avoid an accident of carbon monoxide poisoning due to clogging of fins in a heat exchanger.
A safety device for preventing incomplete combustion such as issuing an alarm or stopping gas combustion according to the output of the CO sensor is provided with a sensor provided in the exhaust gas cylinder downstream of the burner.

[0003] For example, a safety device for a gas combustor proposed in Japanese Patent Application Laid-Open No. 5-26440 detects a CO concentration in flue gas by a CO sensor, and issues an alarm when this concentration exceeds a first reference concentration. When the CO concentration rises due to exhaust gas recirculation and exceeds the second reference concentration, the gas supply passage to the burner is closed to stop the supply of the fuel gas.

A CO sensor for detecting the concentration of CO in the combustion exhaust gas is a C sensor that may harm the human body.
Although it is desirable to have a detection sensitivity at the O concentration level of 300 ppm, since the flue gas system is in a high temperature environment, even a CO sensor that can obtain high detection accuracy at room temperature can accurately detect a low CO concentration during combustion. It is not possible, and even if the CO concentration is lower than the reference value, the fuel
Conversely, there is a problem that even if the CO concentration is higher than the reference value, it is erroneously determined to be lower than the reference value.

Therefore, the applicant of the present invention has no detection sensitivity at a CO concentration of 300 ppm which may cause harm to the human body, but has a detection sensitivity of 1000 ppm at which the detection accuracy of the CO concentration is high even in a high temperature environment such as in combustion exhaust gas. A combustion device that predicts the occurrence of incomplete combustion using a CO sensor having the same has been invented and has already been filed.

In the combustion apparatus according to the earlier application, a CO sensor for detecting the CO concentration in the flue gas is provided in a flue gas system of a gas combustion device, and a supply amount of combustion air supplied to a gas burner during a steady operation is temporarily measured. Lower the air-fuel ratio by increasing the gas supply amount of the gas burner without changing the air amount, or conversely, the CO concentration in the combustion exhaust gas detected by the detection signal from the CO sensor at that time is the reference value If it does not exceed, it is judged that there is no sign of incomplete combustion, and CO
If the concentration exceeds the reference value, it is intended to predict that incomplete combustion is occurring due to clogging of the fins of the heat exchanger.

[0007] Thus, even without using a CO sensor having poor detection sensitivity in a high-temperature environment, the rise in the CO concentration in the combustion exhaust gas can be accurately grasped to avoid incomplete combustion associated with long-term use. The safety of use is not guaranteed.

[0008]

However, fin clogging of the heat exchanger does not occur in such a short time. Therefore, the time (interval time) from the detection of the CO concentration in the combustion exhaust gas by the CO sensor to the detection of the next CO concentration may be one to two hours.

However, also during the CO concentration detection timing (interval), when a top pressure is generated due to a gust of wind or the like at the tip of the supply / exhaust cylinder that is exposed outside, or at the supply port side of the gas appliance. The air-fuel ratio is reduced due to obstacles, etc., which impede the suction of combustion air, and the air-fuel ratio is reduced due to the load on the blower fan that supplies the combustion air to the burner. Sometimes.

[0010] For example, FIG. 4A is a timing chart showing the relationship between the elapsed combustion time and the CO concentration output value in the incomplete combustion control according to the earlier patent application. When a disturbance is applied after the monitoring control, during the interval until the next monitoring control, the reference output (1000 ppm to 1000 ppm) in the CO concentration characteristic shown by the two-dot chain line in FIG.
Unless it exceeds 2000 ppm), it usually burns, so that the monitoring interval cannot be long.

In such a case, at the CO concentration detection timing at a normal interval, it is possible that the occurrence of incomplete combustion is overlooked, and the measures such as stopping the combustion of the burner may be delayed.

An object of the present invention is to detect incomplete combustion caused by fin clogging or the like by detecting the CO concentration in flue gas at predetermined intervals during a steady operation of gas combustion equipment. In addition to this, an incomplete combustion prevention device that detects incomplete combustion due to rapid combustion deterioration due to top pressure etc. even during the CO concentration detection interval and can take prompt action To provide.

[0013]

SUMMARY OF THE INVENTION To solve this problem, the present invention provides a carbon monoxide concentration detecting means provided in a flue gas system of a gas combustion device for detecting the concentration of carbon monoxide in the flue gas. By reducing the gas amount supplied to the gas burner of the gas combustion device and the air-fuel ratio of the combustion air at predetermined time intervals, based on the detection signal from the carbon monoxide concentration detecting means at that time. In the incomplete combustion prevention device configured to check whether or not incomplete combustion has occurred, the carbon monoxide concentration when the air-fuel ratio once lowered is returned to the original value even during the time interval for lowering the air-fuel ratio. Monitoring operation control means for detecting a detection signal from the detection means and controlling a monitoring operation of combustion of the gas burner when a change in the detected output signal value exceeds a predetermined range; The one in which the subject matter of the present invention.

According to the apparatus for preventing incomplete combustion of the present invention having the above-described structure, the amount of gas supplied to the gas burner and the air-fuel ratio of the combustion air during a steady operation of the gas-fired equipment are lowered at predetermined time intervals. It is checked whether or not the combustion is incomplete based on the detection signal of the carbon monoxide concentration detection means provided in the flue gas system at that time, but even during the time interval for lowering the air-fuel ratio. A detection signal is detected by the carbon monoxide concentration detecting means when the lowered air-fuel ratio is restored, and when the detected output signal value exceeds a predetermined range, the combustion state of the gas burner is monitored. It is monitored by the operation control means. This not only predicts incomplete combustion due to normal fin clogging and the like, but also avoids incomplete combustion due to top pressure and the like.

The monitoring operation control means includes means for lowering the air-fuel ratio, detecting the carbon monoxide concentration again by the carbon monoxide concentration detection means, and judging whether or not the combustion is incomplete based on the detection signal. Is preferable. In this way, sudden occurrence of incomplete combustion can be avoided during normal incomplete combustion confirmation routine control.

The air-fuel ratio can be changed by changing the air volume of a blower fan provided in the gas combustion device or the gas volume of a gas burner provided in the gas combustion device. The air-fuel ratio decreases when the air volume of the blower fan is decreased or the gas amount of the gas burner is increased, and conversely, the air-fuel ratio increases when the air volume of the blower fan is increased or the gas amount of the gas burner is decreased.

[0017]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A preferred embodiment of the present invention will be described below in detail with reference to the drawings. FIG. 1 is a schematic configuration diagram of a gas combustion device as one embodiment of the present invention. This gas combustion device is a forced-supply / exhaust water heater, which includes a case 10 forming a combustion chamber, a gas burner 11 disposed below the case 10, and a gas supply passage 14 for supplying fuel gas to the gas burner 11. , A proportional solenoid valve 13 disposed in the gas supply path 14, and the original solenoid valve 12.

The original solenoid valve 12 is a valve that only opens and closes the gas flow path, and the proportional solenoid valve 13 is a control valve that is set to an opening degree according to a control signal and adjusts to a desired gas supply amount. Further, a fan 15 is provided at the bottom of the case 10 to supply combustion air into the combustion chamber 24 in an amount corresponding to the gas supply amount.

A heat exchanger 16 is provided above the gas burner 11, and the water passed through a water supply pipe 17 is supplied to the gas burner 1.
It is heated by the heat of combustion in 1 and sent out to the hot water supply pipe 18. The upper part of the case 10 above the heat exchanger 16 has a hood 19
Through the exhaust pipe 20. And this exhaust stack 2
A CO sensor 21 for detecting the CO concentration at 0 is mounted.

A controller 23 for controlling the combustion and the like is provided in the main body of the water heater. The controller 23 includes a CPU, a RAM, and a ROM, which constitute a well-known arithmetic and logic operation circuit (not shown), an input interface for inputting signals from various sensors, an output interface for outputting drive signals to various actuators, and the like.

Based on the signal indicating the CO concentration output value from the CO sensor 21, not only the opening and closing of the solenoid valves 12, 13 but also the control of the hot water temperature, the ignition control and the like are performed. Descriptions and illustrations of sensors, ignition devices, and the like that are not directly related to the present invention are omitted. Also,
The combustion exhaust gas is discharged outside through the exhaust pipe 25 and the exhaust top 26.

FIG. 2 shows the air-fuel ratio λ and the C in the combustion exhaust gas as general combustion characteristics of this type of gas-fired equipment shown in FIG.
FIG. 4 is a diagram showing a relationship with an O concentration. Here, the "air-fuel ratio" refers to the ratio of the amount of air actually supplied to the stoichiometric amount of air required for complete combustion of gas.

In FIG. 3, point A is a case where normal combustion is performed, and the air-fuel ratio λ = 1.8 and the exhaust CO concentration is 3
It is not more than 00 ppm. When the normal combustion is performed, even if the air-fuel ratio λ is reduced (decrease width Δλ), the exhaust CO concentration hardly changes and the fuel burns at the point B, but the non-flammable point C (λ = 1. 45, emission CO concentration 300p
pm), reducing the air-fuel ratio λ (Δλ)
O concentration reaches point E of 1000 ppm.

Further, at point D (λ = 1.44, CO concentration of 300 ppm or more), the air-fuel ratio λ is reduced (Δ
λ), the exhausted CO concentration exceeds 1000 ppm (point F). That is, at a low air-fuel ratio λ, the exhaust CO concentration sharply increases. This is because when the air-fuel ratio λ falls below a certain value, incomplete combustion occurs and the CO concentration rises sharply. Therefore, when it is desired to suppress the CO emission of the appliance to 300 ppm or less, the ratio of the air amount to the supply gas amount is reduced by Δλ to 1000 pp.
m can be a detection reference value.

Therefore, according to the present invention, the amount of gas supplied to the gas burner 11 and the air-fuel ratio λ of the combustion air during the steady operation of the gas combustion equipment are gradually reduced at predetermined intervals. Then, whether or not the combustion is incomplete is confirmed based on the CO concentration output value of the CO sensor 21 provided in the flue gas system at that time. The CO concentration output value of the CO sensor 21 when the air-fuel ratio λ is returned to the original value is detected, and when the detected change in the CO concentration output value exceeds a predetermined range (Δx), the combustion state of the gas burner 21 is determined. The monitoring is performed by the controller 23.

FIG. 3 is a flowchart showing an incomplete combustion prevention control routine applied to the incomplete combustion prevention device according to one embodiment of the present invention. This flowchart shows a case where the air-fuel ratio λ is changed by changing the rotation speed of the fan 15 in order to predict the occurrence of incomplete combustion.

If it is predicted that incomplete combustion will occur during steady-state combustion, first, when the faucet is opened in the forced water supply / exhaust water heater, the ignition operation inside the water heater is performed, and then the controller 23 starts the gas burner 21. (Step 1: "YES", hereinafter simply referred to as "S1"). Then, the ignition operation by the igniter ends (S2), and the controller 23 controls the hot water temperature (S3).
And reading of the CO concentration output value detected by the CO sensor 21 (S4) is started. The CO concentration at this time is, for example, the concentration immediately before the “monitoring” shown in FIG.

When it is determined that the read CO concentration output value does not exceed the reference output A set to a value within the range of 1000 ppm to 2000 ppm shown in FIG. 4B (S5: "YES"), The combustion control is continued as it is until the CO detection timing comes (S6: "N
O ").

Next, when it is determined by the controller 23 that the predetermined time has elapsed and the CO detection timing has come (S6: "YES"), the controller 23 sets the fan 1
The control for reducing the number of rotations of the motor 5 is performed (S7), and the air-fuel ratio λ is reduced at a predetermined ratio or the change amount Δλ. Then CO
The density rises from the “monitoring” shown in FIG. 4B, and shows the value of the convex portion on the right side. Then, the value of this convex portion is read by the controller 23 as the CO concentration output value of the CO sensor 21 in a state where the air-fuel ratio λ is lowered (S8).

Next, the controller 23 determines again whether or not the CO concentration output value is equal to or lower than the reference output A. Usually, it is determined that the CO concentration output value is equal to or lower than the reference output A (S9:
"YES"). Here, CO of this convex part (FIG. 4B)
Since the concentration output value is a concentration in a state where the air-fuel ratio is artificially lowered by controlling the rotation speed of the fan 15, the CO concentration is determined to be 3 by judging that this concentration does not exceed the reference output A.
It is inferred that it is not more than 00 ppm. Thereafter, the fan speed is returned to the original value by the controller 23 (S10), whereby the CO concentration output value and the air-fuel ratio which have temporarily increased are returned to the original values.

Next, the controller 23 controls the CO sensor 2
After reading the CO concentration output value (a) of No. 1 (S11) and storing the value (S12), the output change from the CO concentration output value (a) with respect to the CO sensor output value read in S4 is not more than Δx. Is determined. If there is no disturbance (see FIG. 4B), it is determined that the output change is equal to or less than Δx (S13: “YES”), and thereafter, S13 to S13 ′ until it is determined that the CO detection timing has come.
(S13 ': "N
O)), whether or not the output change from the CO concentration output value (a) during the combustion operation is equal to or smaller than Δx is constantly monitored.

On the other hand, if there is a state in which the fins are clogged while the combustion control is continuously performed, the indoor load increases due to the top pressure or the formation of a sparrow nest, and the incomplete combustion is foreseen. , CO concentration output value is shown in FIG.
(B) may show a steep change indicated by a two-dot chain line or a change indicated by a broken line.

In such a state, the controller 23
Is determined to be the timing for detecting CO (S1).
3 ′: “YES”) and S7 to S1 in the same manner as described above.
2 and the change from the CO concentration output value (a) is determined to be not less than Δx (S13: “N
O)), the intermittent monitoring shown in the processing of S7 to S13 is performed assuming that there has been some change in the combustion state even at the CO detection timing.

In this case, in the case of a steep change indicated by the two-dot chain line in FIG. 4B, the output value of the CO sensor 21 sharply increases while the processes of S7 to S13 are repeated. Therefore, the controller 23 determines that the output exceeds the reference output A (S9: "NO"), and the combustion control is stopped or an improved operation is performed (S14).
As a result, a prompt response to the occurrence of incomplete combustion is made.

When no flame is detected in the ignition control (S1: "NO") or when the output value of the CO sensor 21 exceeds the reference output A from the beginning even if the ignition control is performed normally (S5). : “NO”), after the original solenoid valve 12 is turned off (S15), an abnormality display for notifying that an abnormality has occurred is made (S16), and the ignition control ends (S17).

Thus, according to the above-described embodiment, incomplete combustion due to clogging of the fins of the heat exchanger accompanying long-term use of the gas appliance occurs at predetermined intervals performed each time the gas appliance is used. C by lowering the air-fuel ratio of
It is monitored by the detection of the O concentration output value (S6 to S9). In addition, by detecting the CO concentration output value when the air-fuel ratio is restored (S10 to S13 '), the top pressure of the air supply / exhaust port is monitored. The resulting sudden incomplete combustion is also monitored. Therefore, avoidance of incomplete combustion is further enhanced.

The present invention is not limited to the above-described embodiment, and various modifications can be made without departing from the spirit of the present invention. For example, in the above-described embodiment, the air-fuel ratio is temporarily reduced by reducing the fan rotation speed. However, the air-fuel ratio may be temporarily reduced by increasing the amount of combustion gas. Also,
LED when intermittent monitoring is repeated
The display may be changed so that the user can understand. Then, measures such as improving indoor ventilation can be taken, and safety is further ensured.

[0038]

According to the apparatus for preventing incomplete combustion according to the present invention, even when the air-fuel ratio is lowered during the time interval for lowering the air-fuel ratio, the detection by the carbon monoxide concentration detecting means can be performed. When the signal is detected and the change in the detected output signal value exceeds a predetermined range, the combustion state of the gas burner is monitored by the monitoring operation control means. As a result, not only incomplete combustion due to normal fin clogging and the like can be predicted, but also incomplete combustion due to top pressure and the like can be detected and prompt measures such as stopping combustion and improving operation can be taken. Become. Applying this to gas-fired equipment is extremely useful industrially because it improves its safety.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of a gas combustion device as one embodiment of the present invention.

FIG. 2 is a diagram showing a relationship between an air-fuel ratio λ and a CO concentration in combustion exhaust gas as general combustion characteristics of the gas combustion device of this type shown in FIG.

FIG. 3 is a flowchart illustrating an incomplete combustion prevention control routine as one embodiment of the present invention.

FIG. 4A is a timing chart showing the relationship between the elapsed combustion time and the CO concentration output value based on the incomplete combustion prevention control routine before the control routine of the present invention is applied, and FIG. 4 is a timing chart showing the relationship between the elapsed combustion time and the CO concentration output value based on the incomplete combustion prevention control routine resulting from the application of the control routine of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Case 11 Gas burner 12 Primary solenoid valve 13 Proportional solenoid valve 14 Gas supply path 20 Exhaust cylinder 21 CO sensor 23 Controller 24 Combustion chamber

Claims (4)

[Claims] 1. A method for detecting the concentration of carbon monoxide in a flue gas system of a gas-fired device, comprising: means for detecting the concentration of carbon monoxide in the flue gas. The air-fuel ratio of the working air is gradually lowered at predetermined time intervals, thereby confirming whether or not the combustion is incomplete based on the detection signal from the carbon monoxide concentration detecting means at that time. In the prevention device, the detection signal by the carbon monoxide concentration detecting means when the lowered air-fuel ratio is returned to the original value even during the time interval for lowering the air-fuel ratio is detected, and the detected output signal is detected. An incomplete combustion prevention device comprising monitoring operation control means for controlling a monitoring operation of combustion of the gas burner when a change in the value exceeds a predetermined range. 2. The monitoring operation control means lowers the air-fuel ratio, detects the carbon monoxide concentration again by the carbon monoxide concentration detection means, and determines whether or not the combustion is incomplete based on the detection signal. The incomplete combustion prevention device according to claim 1, wherein the device is a device for preventing incomplete combustion. 3. The incomplete combustion prevention device according to claim 1, wherein the air-fuel ratio is changed by changing a flow rate of a blower fan provided in the gas combustion device. 4. The incomplete combustion prevention device according to claim 1, wherein the air-fuel ratio is changed by changing a gas amount of a gas burner provided in the gas combustion device.