JP3693203B2 - Incomplete combustion prevention device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an incomplete combustion preventing device applied to gas combustion equipment such as a forced water supply / exhaust type (FF type) gas water heater, and more particularly, to carbon monoxide (CO) in a combustion exhaust gas system of a gas combustion equipment. The present invention relates to an incomplete combustion prevention apparatus suitable for predicting the incomplete combustion of this gas combustion device by inducing a concentration detection sensor and using a detection signal from the CO concentration detection sensor.
[0002]
[Prior art]
Conventionally, in this type of gas combustion equipment, a CO sensor for detecting the CO concentration in the combustion exhaust gas is provided in the exhaust gas cylinder downstream of the burner in order to avoid an accident of carbon monoxide poisoning caused by fin clogging or the like of the heat exchanger, A safety device is provided for preventing incomplete combustion, such as issuing an alarm in accordance with the output of the CO sensor or stopping gas combustion.
[0003]
For example, a safety device for a gas combustor proposed in Japanese Patent Application Laid-Open No. 5-26440 detects the CO concentration in combustion exhaust gas by a CO sensor, and issues an alarm when this concentration exceeds a first reference concentration. When the CO concentration rises as it is due to exhaust gas recirculation or the like and exceeds the second reference concentration, the gas supply flow path to the burner is closed to stop the fuel gas supply.
[0004]
By the way, it is desirable that the CO sensor for detecting the CO concentration in the combustion exhaust gas has a detection sensitivity at a CO concentration of 300 ppm which may cause harm to the human body, but the combustion exhaust gas system is in a high temperature environment. Even a CO sensor with high detection accuracy at room temperature cannot accurately detect a low CO concentration during combustion. Even if the CO concentration is lower than the reference value, the fuel gas supply is stopped due to misjudgment. There was a problem that even the above CO concentration was erroneously determined to be below the reference value.
[0005]
Therefore, the present applicant has no detection sensitivity at a CO concentration of 300 ppm, which may cause harm to the human body, but a CO sensor having a detection sensitivity at a 1000 ppm level with high CO concentration detection accuracy even in a high-temperature environment such as in combustion exhaust gas. Has been invented and has already filed an application for a combustion apparatus that predicts the occurrence of incomplete combustion.
[0006]
The combustion apparatus according to this earlier application is provided with a CO sensor for detecting the CO concentration in the flue gas in the flue gas system of the gas combustion device, and temporarily reduces the amount of combustion air supplied to the gas burner during steady operation. Or, conversely, increase the gas supply amount of the gas burner without changing the air amount to lower the air-fuel ratio, and the CO concentration in the combustion exhaust gas detected by the detection signal from the CO sensor at that time must not exceed the reference value If it is determined that there is no sign of incomplete combustion, and the CO concentration exceeds the reference value, it is intended to predict that incomplete combustion is occurring due to fin clogging or the like of the heat exchanger.
[0007]
This makes it possible to accurately grasp the increase in CO concentration in the combustion exhaust gas without using a CO sensor with poor detection sensitivity in a high-temperature environment, avoiding the incomplete combustion associated with long-term use. It is intended to ensure safety.
[0008]
[Problems to be solved by the invention]
However, heat exchanger fin clogging 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 viewed from 1 hour to 2 hours.
[0009]
However, even during this CO concentration detection timing (interval), when a top pressure is generated by a gust or the like on the top air supply / exhaust top at the tip of the air supply / exhaust tube, or an obstacle is present on the air supply port side of this gas appliance. The air-fuel ratio may decrease and the combustion of the burner may be worsened due to a load on the blower fan that supplies the combustion air to the burner due to circumstances such as preventing the intake of combustion air. .
[0010]
For example, FIG. 4A is a timing chart showing the relationship between the elapsed combustion time and the CO concentration output value of the incomplete combustion control according to the previous patent application. When a disturbance is added later, during the interval until the next monitoring control, the CO concentration characteristic indicated by the two-dot chain line in the figure shows normal combustion unless the reference output (1000 ppm to 2000 ppm) is exceeded. Can not take long.
[0011]
In such a case, at the CO concentration detection timing at a normal interval, it may be overlooked that incomplete combustion has occurred, and there is a possibility that a response such as stopping combustion of the burner may be delayed.
[0012]
The problem to be solved by the present invention is that it is possible to foresee incomplete combustion due to clogging of fins or the like by detecting the CO concentration in the combustion exhaust gas at a predetermined interval during regular operation of the gas combustion device. Of course, to provide an incomplete combustion prevention device capable of detecting incomplete combustion caused by a top pressure or the like during the CO concentration detection interval and detecting the incomplete combustion thereby promptly responding. It is in.
[0013]
[Means for Solving the Problems]
In order to solve this problem, the present invention is provided with a carbon monoxide concentration detecting means provided in a combustion exhaust gas system of a gas combustion device to detect the carbon monoxide concentration in the combustion exhaust gas, and to the gas burner of the gas combustion device. By lowering the amount of gas to be supplied and the air-fuel ratio of the combustion air at predetermined time intervals, it is confirmed whether or not incomplete combustion is performed based on the detection signal from the carbon monoxide concentration detection means at that time. In the incomplete combustion preventing apparatus, the detection signal by the carbon monoxide concentration detecting means when the air-fuel ratio once lowered is restored during the time interval for lowering the air-fuel ratio is detected, whether incomplete combustion on the basis of the detection signal by again lowered carbon monoxide concentration detection means the air-fuel ratio of the gas burner when the change in the detected output signal value exceeds a predetermined range Providing the monitoring operation control means for monitoring operation of combustion to ensure it is an gist.
[0014]
According to the incomplete combustion preventing apparatus of the present invention having the above-described configuration, the amount of gas supplied to the gas burner and the air-fuel ratio of the combustion air during the steady operation of the gas combustion device are once lowered at predetermined time intervals, The incomplete combustion is confirmed on the basis of the detection signal from the carbon monoxide concentration detection means provided in the combustion exhaust gas system, but it was once lowered during the time interval to lower the air-fuel ratio. A detection signal from the carbon monoxide concentration detection means when the air-fuel ratio is restored is detected, and when the change in the detected output signal value exceeds a predetermined range, the combustion state of the gas burner is monitored operation control means Is monitored by As a result, not only incomplete combustion due to normal fin clogging is foreseen but also incomplete combustion due to top pressure or the like is avoided.
[0015]
The monitoring operation control means lowers the air-fuel ratio and again detects the carbon monoxide concentration by the carbon monoxide concentration detection means, and determines whether or not incomplete combustion is based on the detection signal. Are mentioned as preferred. By doing so, the occurrence of sudden incomplete combustion can be avoided in the routine control of normal incomplete combustion confirmation.
[0016]
The air-fuel ratio can be changed by changing the air volume of the blower fan provided in the gas combustion device or the gas amount of the gas burner provided in the gas combustion device. If the air volume of the blower fan is lowered or the gas amount of the gas burner is increased, the air-fuel ratio is lowered. Conversely, if the air volume of the blower fan is increased or the gas amount of the gas burner is lowered, the air-fuel ratio is raised.
[0017]
DETAILED DESCRIPTION OF THE INVENTION
DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, an exemplary embodiment of the invention will be described in detail with reference to the drawings. FIG. 1 is a schematic configuration diagram of a gas combustion apparatus as an embodiment of the present invention. This gas combustion device is a forced supply / exhaust water heater, a case 10 forming a combustion chamber, a gas burner 11 disposed in a lower portion of the case 10, and a gas supply path 14 for supplying fuel gas to the gas burner 11. And the proportional solenoid valve 13 arrange | positioned in the gas supply path 14, and the original solenoid valve 12 are provided.
[0018]
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 corresponding to the control signal and adjusts to a desired gas supply amount. Further, a fan 15 is provided at the bottom of the case 10, and an amount of combustion air corresponding to the amount of gas supply is supplied into the combustion chamber 24.
[0019]
A heat exchanger 16 is disposed above the gas burner 11, and the water passed through the water supply pipe 17 is heated by the combustion heat in the gas burner 11 and sent out to the hot water supply pipe 18. The upper part of the case 10 above the heat exchanger 16 is connected to the exhaust pipe 20 via the hood 19. The exhaust cylinder 20 is equipped with a CO sensor 21 that detects the CO concentration.
[0020]
Further, 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 constituting a well-known arithmetic logic 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.
[0021]
Based on the signal indicating the CO concentration output value from the CO sensor 21, not only the solenoid valves 12 and 13 are opened and closed, but also hot water temperature control and ignition control are performed. The explanation and illustration of sensors and ignition devices not directly related to are omitted. Further, the combustion exhaust gas is discharged to the outside through the exhaust pipe 25 and the exhaust top 26.
[0022]
FIG. 2 is a graph showing the relationship between the air-fuel ratio λ and the CO concentration in the combustion exhaust gas as general combustion characteristics of this type of gas combustion device shown in FIG. Here, the “air-fuel ratio” refers to the ratio of the actually supplied air amount to the theoretical air amount necessary for complete combustion of the gas.
[0023]
In the figure, point A is the case where normal combustion is performed, the air-fuel ratio λ = 1.8, and the exhaust CO concentration is 300 ppm or less. When normal combustion is performed, even if the air-fuel ratio λ is reduced (decrease width Δλ), the exhaust CO concentration is hardly changed but burned at the point B, but the C point (λ = 1. 45, the exhausted CO concentration is 300 ppm), the exhausted CO concentration reaches the E point of 1000 ppm when the air-fuel ratio λ is decreased (Δλ).
[0024]
Further, at point D (λ = 1.44, exhaust CO concentration of 300 ppm or more), if the air-fuel ratio λ is reduced (Δλ), the exhaust CO concentration exceeds 1000 ppm (F point). That is, when the air-fuel ratio λ is low, the exhaust CO concentration rapidly increases. This is because when the air-fuel ratio λ becomes lower than a certain value, incomplete combustion occurs and the CO concentration rises sharply. Therefore, when it is desired to suppress the CO emission of the instrument at 300 ppm or less, the ratio of the air amount to the supply gas amount can be reduced by Δλ, and 1000 ppm can be set as the detection reference value.
[0025]
Therefore, the present invention temporarily lowers the amount of gas supplied to the gas burner 11 and the air-fuel ratio λ of the combustion air at predetermined intervals during steady operation of the gas combustion device. Then, the incomplete combustion is confirmed based on the CO concentration output value by the CO sensor 21 provided in the combustion exhaust gas system at that time. The CO concentration output value by the CO sensor 21 when the air-fuel ratio λ is returned to the original value is detected, and when the change in the detected CO concentration output value exceeds a predetermined range (Δx), the combustion state of the gas burner 21 is detected. This is monitored by the controller 23.
[0026]
FIG. 3 is a flowchart showing an incomplete combustion prevention control routine applied to the incomplete combustion prevention apparatus according to the embodiment of the present invention. This flow chart shows a case where the air-fuel ratio λ is changed by changing the rotational speed of the fan 15 in order to predict the occurrence of incomplete combustion.
[0027]
In the case where incomplete combustion is expected to occur during steady combustion, first, when the faucet is opened in the forced water supply / exhaust water heater, after the ignition operation inside the water heater, the controller 23 causes the gas burner 21 to flame. Detected (Step 1: “YES”, hereinafter simply expressed as “S1”). Then, the ignition operation by the igniter is finished (S2), and the controller 23 starts the hot water temperature control (S3) and reading of the CO concentration output value detected by the CO sensor 21 (S4). The CO concentration at this time is, for example, the concentration immediately before “monitoring” shown in FIG.
[0028]
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 CO detection timing Combustion control is continued as it is until it comes (S6: “NO”).
[0029]
Next, when the controller 23 determines that the CO detection timing has come after a predetermined time has elapsed (S6: “YES”), the controller 23 performs control to reduce the rotational speed of the fan 15 (S7), and the air-fuel ratio λ. Is reduced by a predetermined ratio or change amount Δλ. Then, the CO concentration rises from the “monitoring” position shown in FIG. 4B and immediately shows the value of the convex portion on the right side. 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).
[0030]
Next, the controller 23 determines again whether or not the CO concentration output value is equal to or less than the reference output A, but it is usually determined that it is equal to or less than the reference output A (S9: “YES”). Here, the CO concentration output value of the convex portion (FIG. 4B) is a concentration in a state where the air-fuel ratio is artificially lowered by the control for lowering the rotational speed of the fan 15, and therefore this concentration is the reference output A. By judging that it does not exceed, it is presumed that the CO concentration is 300 ppm or less. Thereafter, the fan 23 is returned to the original value by the controller 23 (S10), and the CO concentration output value and the air-fuel ratio temporarily increased thereby are restored.
[0031]
Next, the controller 23 reads the CO concentration output value (a) of the CO sensor 21 (S11), stores the value (S12), and then outputs the CO concentration output value (a) for the CO sensor output value read in S4. It is determined whether the output change from is less than or equal to Δx. When there is no disturbance (see FIG. 4B), it is determined that the output change is Δx or less (S13: “YES”), and thereafter, until it is determined that the CO detection timing is reached, S13 to S13 ′. By repeating this process (S13 ′: “NO”), it is constantly monitored whether the output change from the CO concentration output value (a) during the combustion operation is equal to or less than Δx.
[0032]
On the other hand, if there is a condition in which the indoor load increases due to clogging of fins, top pressure, or formation of a sparrow nest while combustion control is being continued, and the occurrence of incomplete combustion is predicted, the CO concentration For example, the output value may show a steep change indicated by a two-dot chain line in FIG. 4B or a change indicated by a broken line.
[0033]
In such a state, if it is determined by the controller 23 that the CO detection timing has come (S13 ′: “YES”), the processing of S7 to S12 is performed in the same manner as described above, and from the CO concentration output value (a). If it is determined that the change in the pressure is not less than or equal to Δx (S13: “NO”), even if it is not the CO detection timing, the intermittent monitoring shown in the processing of S7 to S13 is performed assuming that there is some change in the combustion state. .
[0034]
In this case, in the case of the steep change indicated by the two-dot chain line in FIG. 4B, the output value of the CO sensor 21 rises rapidly while the processing of S7 to S13 is repeated, so the controller 23 Accordingly, it is determined that the reference output A is exceeded (S9: “NO”), and the combustion control is stopped or the improvement operation is performed (S14). As a result, a prompt response is made to the incomplete combustion.
[0035]
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 when the ignition control is normal (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 is terminated (S17).
[0036]
Thus, according to the above-described embodiment, incomplete combustion caused by heat exchanger fin clogging or the like associated with long-term use of a gas appliance causes the air-fuel ratio at a predetermined interval to be performed each time the gas appliance is used. Is monitored by detecting the CO concentration output value by lowering (S6 to S9), but in addition to that, the detection of the CO concentration output value when the air-fuel ratio is restored (S10 to S13 ′) Sudden incomplete combustion due to top pressure or the like is also monitored. Therefore, avoidance of incomplete combustion is further strengthened.
[0037]
The present invention is not limited to the embodiments described above, and various modifications can be made without departing from the spirit of the present invention. For example, in the above embodiment, the air-fuel ratio is temporarily lowered by lowering the fan speed, but the air-fuel ratio may be temporarily lowered by increasing the amount of combustion gas. Further, in a state where intermittent monitoring is repeated, the user may be made aware by changing the LED display. If it does so, measures, such as improving indoor ventilation, can also be taken and safety | security is ensured more.
[0038]
【The invention's effect】
According to the incomplete combustion preventing apparatus according to the present invention, the detection signal by the carbon monoxide concentration detecting means when the air-fuel ratio once lowered during the time interval for lowering the air-fuel ratio is restored is detected, When the detected change in the output signal value exceeds a predetermined range, the combustion state of the gas burner is monitored by the monitoring operation control means. This not only predicts incomplete combustion due to normal fin clogging, etc., but also detects incomplete combustion due to top pressure etc. and can take prompt measures such as combustion stop and improved operation Become. Applying this to gas combustion equipment is extremely beneficial in the industry because it improves its safety.
[Brief description of the drawings]
FIG. 1 is a schematic configuration diagram of a gas combustion apparatus as an embodiment of the present invention.
2 is a graph showing the relationship between the air-fuel ratio λ and the CO concentration in the combustion exhaust gas as the general combustion characteristics of this type of gas combustion device shown in FIG.
FIG. 3 is a flowchart showing an incomplete combustion prevention control routine as an 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. 5 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 by applying the control routine of the present invention.
[Explanation of symbols]
10 Case 11 Gas burner 12 Original solenoid valve 13 Proportional solenoid valve 14 Gas supply path 20 Exhaust cylinder 21 CO sensor 23 Controller 24 Combustion chamber

Claims (3)

Provided in a flue gas system of a gas combustion device and having a carbon monoxide concentration detection means for detecting the carbon monoxide concentration in the flue gas, the amount of gas supplied to the gas burner of the gas combustion device and the air-fuel ratio of the combustion air In the incomplete combustion preventing apparatus for confirming whether or not incomplete combustion is performed based on a detection signal from the carbon monoxide concentration detection means at that time by lowering the value once at a predetermined time interval, The detection signal by the carbon monoxide concentration detecting means when the air-fuel ratio once lowered is restored during the time interval for lowering the air-fuel ratio is detected, and the change of the detected output signal value is predetermined. audit to monitor operation of combustion for confirming whether incomplete combustion on the basis of the detection signal by again lowered carbon monoxide concentration detection means the air-fuel ratio of the gas burner when exceeding the range of Incomplete combustion prevention device, characterized in that it comprises the operation control means. The incomplete combustion apparatus according to claim 1 , wherein the air-fuel ratio is changed by changing an air volume of a blower fan provided in the gas combustion device. 2. The incomplete combustion preventing apparatus according to claim 1 , wherein the air-fuel ratio is changed by changing a gas amount of a gas burner provided in a gas combustion device.

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