JP3558439B2 - Safe combustion device - Google Patents

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a safety combustion device in a gas exhaust device of a forced exhaust type (FE type) or a forced supply / exhaust type (FF type) such as a gas water heater, and more particularly, to a combustion gas exhaust system in these gas combustion devices. A safe combustion in which a carbon monoxide concentration detection sensor (CO sensor) for detecting the concentration of carbon monoxide (CO gas) in the combustion exhaust gas is provided, and the occurrence of incomplete combustion is predicted based on the output signal value of the CO sensor. It concerns the device.
[0002]
[Prior art]
2. Description of the Related Art Conventionally, various types of gas combustion devices of this type have been known. For example, a gas exhaust device of a forced exhaust type (FE type) or a forced supply / exhaust type (FF type) is a type of gas appliance. A method is adopted in which an exhaust pipe through which gas is exhausted passes through a wall in contact with the outside air and is taken out to the outside, and a forced supply / exhaust air supply / exhaust fan is used.
[0003]
In such a gas combustion device, a CO sensor in the combustion exhaust gas by a gas burner is provided in the combustion gas exhaust system, and the output signal value from the CO sensor indicates whether the combustion state is good, whether the combustion is incomplete, etc. Is determined, and if incomplete combustion is detected based on the output signal value from the CO sensor, there is already one that safely stops the gas combustion device.
[0004]
[Problems to be solved by the invention]
However, the detection accuracy of this type of conventionally used CO sensor is poor, and the detection capability of a commonly employed CO sensor is about 1000 ppm ± 400 ppm. However, the limit of CO concentration on whether or not human life is harmed due to carbon monoxide poisoning is at a low level of 300 ppm, and it is said that the detection level of the conventional CO sensor is slow in determining whether or not human life is alive or dead. There are inherent problems.
[0005]
On the other hand, some CO sensors have good detection accuracy. For example, those with good detection accuracy can detect the CO concentration at a low concentration detection level of about 200 to 250 ppm. However, this high-performance CO sensor is generally intended for use in a normal temperature environment, and is used in a high-temperature atmosphere where a high-temperature (about 200 ° C.) combustion gas flows such as a combustion gas exhaust system. It is not intended for use with.
[0006]
Therefore, even if such a high-performance CO sensor is provided in the combustion gas exhaust system to detect the CO concentration, there is a problem that noise is included in the output signal of the CO sensor and the CO concentration cannot be accurately detected.
[0007]
The problem to be solved by the present invention is that the CO concentration detection accuracy is not good, for example, even if a detection level of about 1000 ppm (± 400 ppm) is used, a CO concentration level (300 ppm) lower than a level at which human life is at risk. It is an object of the present invention to provide a safe combustion device that can detect the pressure in the combustion chamber. In this way, the danger of human life due to an increase in the CO concentration in the room is quickly detected, and the safety in using the combustion equipment is not ensured.
[0008]
[Means for Solving the Problems]
In order to solve this problem, a safe combustion apparatus of the present invention is provided with a carbon monoxide concentration detecting means for detecting the concentration of carbon monoxide in the combustion gas flowing through the exhaust gas system of a gas combustion device. A carbon monoxide concentration output comparison for comparing a concentration output value by the carbon monoxide concentration detecting means when the fuel ratio is temporarily reduced by a predetermined amount with a concentration output value by the carbon monoxide concentration detecting means before lowering the air-fuel ratio. Means, and a combustion abnormality judging means for judging a combustion abnormality when a difference or a change rate of the carbon monoxide concentration output value compared by the carbon monoxide concentration output comparing means becomes a predetermined value or more. It is assumed that .
[0009]
According to the safety combustion device configured as described above, the concentration of carbon monoxide in the combustion gas flowing through the exhaust system is detected by the carbon monoxide concentration detection unit provided in the combustion gas exhaust system of the gas combustion device. When the air-fuel ratio is temporarily reduced during use of the gas-fired device, the concentration output value of the carbon monoxide concentration detecting means is lower than the concentration output value of the carbon monoxide concentration detecting means before the air-fuel ratio is reduced. When the difference or the change rate of the carbon monoxide concentration output value compared by the carbon monoxide concentration output comparison means is equal to or more than a predetermined value, the combustion is judged to be abnormal by the combustion over determination means. Is determined.
[0010]
In this case, the air-fuel ratio can be changed by changing the air volume of a blower fan provided in the gas combustion device, or by changing the gas volume of a combustion burner.
When the air-fuel ratio is changed by changing the air flow rate of the blower fan, the change in the air flow rate of the blower fan depends on the fan speed at the time of detecting the carbon monoxide concentration by the carbon monoxide concentration detecting means. When the air-fuel ratio is changed by changing the reduction ratio and changing the gas amount of the combustion burner, the change in the gas amount of the combustion burner depends on the gas amount at the time of detecting the carbon monoxide concentration by the carbon monoxide concentration detecting means. It is preferable to change the ratio of the gas amount.
[0011]
Further, in the safe combustion apparatus according to the present invention, the combustion gas exhaust system of the gas combustion device includes a carbon monoxide concentration detecting means for detecting a carbon monoxide concentration in the combustion gas flowing through the exhaust system. A carbon monoxide concentration output comparing means for comparing a concentration output value by the carbon monoxide concentration detecting means when the air-fuel ratio is temporarily lowered with a reference output value; A combustion abnormality judging means for judging an abnormal combustion when the carbon monoxide concentration output value becomes equal to or higher than the reference output value.
[0012]
According to the safe combustion apparatus of the sixth aspect, the concentration output by the carbon monoxide concentration detecting means when the air-fuel ratio is temporarily lowered is compared with the value reference output value by the carbon monoxide concentration output comparing means, When the carbon monoxide concentration output value compared by the carbon monoxide concentration output comparing means becomes equal to or more than the reference output value, the combustion abnormality determining means determines that the combustion is abnormal.
[0013]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, a preferred embodiment of the present invention will be described in detail with reference to the drawings.
FIG. 1 shows an example in which the safe combustion device of the present invention is applied to a gas water heater. The gas water heater 10 shown in FIG. 1 is of a forced supply / exhaust type (FF type), and is attached to a wall of an indoor kitchen (kitchen).
[0014]
The air for combustion supplied to the gas water heater 10 is introduced indoors through the air supply port 1 provided on the outer wall W, and the combustion gas of the gas water heater 10 is exhausted through the outer wall W. The air is exhausted outside through the pipe 2.
The introduction of the combustion air into the gas water heater 10 and the exhaust of the combustion gas to the outside are forcibly performed by a supply / exhaust blower fan provided in the water heater.
[0015]
A CO sensor 3 for detecting the concentration of carbon monoxide (CO gas) in the combustion gas flowing through the exhaust pipe 2 is provided at a location near the exhaust pipe 2 of the gas water heater 10. Although the details will be described later, it is determined from the output signal from the CO sensor 3 whether or not incomplete combustion is occurring in the gas water heater 10 and the combustion state thereof.
[0016]
FIG. 2 shows a schematic configuration of the gas water heater 10 shown in FIG. In the gas water heater 10, a heat exchanger 16 provided with a water supply pipe 12 and a tapping pipe 14 is provided in a casing 18, and a gas burner 20 for heating the heat exchanger 16 is provided. . The water supply pipe 12 is provided with a water flow switch (flow rate sensor) 22 for detecting the flow and flow rate of water and an inlet water temperature thermistor 24 for detecting the temperature of the water, and the tapping pipe 14 for detecting tap water temperature. A temperature thermistor 28 is provided.
[0017]
On the other hand, the gas line 30 of the gas burner 20 is provided with a main solenoid valve 32, a main solenoid valve 34 and a gas proportional valve 36 for continuously changing the gas amount, and supplies combustion air to the gas burner 20. Fan 38 is provided. The exhaust pipe 2 provided in the casing 18 is provided with the CO sensor 3 for detecting the concentration of CO gas in the combustion gas generated by the combustion of the gas burner 20, as described in the description of FIG.
[0018]
Thus, the input side of the burner controller 40 for controlling the operation of the gas water heater receives signals such as the water flow switch 22, the input water temperature thermistor 24, and the output water temperature thermistor 28, and also the output signal from the CO sensor 3 described above. Is also entered. The output side of the burner controller 40 is connected to a gas proportional valve 36 of the gas burner 20, a fan motor of a blower fan 38, and the like. A hot water tap 42 is provided at a tapping outlet of the tapping pipe 14. An alarm 44 indicating that incomplete combustion has occurred based on a detection signal from the CO sensor 3 is also connected to the burner controller 40.
[0019]
In the gas water heater 10 configured as described above, when the hot water tap 42 is opened, the water flow switch (flow rate sensor) 22 is turned on, the signal is received by the burner controller 40, and the fan drive circuit (see FIG. (Not shown), the blower fan 38 rotates, and combustion air is supplied to the gas burner 20.
In addition, in response to a command from the burner controller 40, the main solenoid valve 32, the main solenoid valve 34, and the gas proportional valve 36 of the gas burner 20 are sequentially opened to supply combustion gas to the gas burner 20, and then the gas burner 20 is ignited by an igniter. You.
[0020]
In the initial operation stage of the ignition of the gas burner 20, the temperature of the water flowing through the water supply pipe 12 is grasped by a detection signal from an incoming water temperature thermistor 22 provided in the water supply pipe 12, and the burner controller 40 outputs the hot water temperature of the hot water flowing through the hot water pipe 14. The opening degree of the gas proportional valve 36 for adjusting the amount of gas supplied to the gas burner 20 is adjusted so that the temperature approaches the set temperature.
[0021]
After the combustion of the gas burner 20 has become stable, the burner controller 40 receives a signal from the tapping temperature thermistor 28 provided in the tapping pipe 14 and the proportional valve current circuit of the gas proportional valve 36 and the fan of the blower fan 38. By sending a signal to the drive circuit and controlling the proportionality of the opening of the gas proportional valve 36 and the fan speed of the blower fan 38, the operation is managed so that the tapping temperature is maintained at the set temperature.
[0022]
In such a gas water heater 10, the CO concentration in the combustion gas discharged from the exhaust pipe 2 is detected by a CO sensor 3 provided in the exhaust pipe 2, and the signal value of the CO sensor 3 is sent to a burner controller 40. Sent. The burner controller 40 determines the CO concentration in the combustion gas based on the output signal value from the CO sensor 3 and determines whether incomplete combustion is currently occurring or incomplete combustion is occurring.
[0023]
FIG. 3A shows the relationship between the air-fuel ratio (λ) and the CO output signal value. The horizontal axis indicates the air-fuel ratio λ, and the vertical axis indicates the CO output signal value. Here, the "air-fuel ratio" refers to the ratio of the amount of air actually supplied to the theoretical amount of air required for complete combustion of gas. As shown in this figure, the CO output signal value sharply increases at a low air-fuel ratio λ. This is because when the air-fuel ratio λ falls below a certain value, incomplete combustion occurs and the CO concentration rises sharply.
[0024]
Therefore, the present invention temporarily reduces the air-fuel ratio λ by temporarily lowering the rotation speed of the blower fan 38 to reduce the amount of air supplied to the gas burner 20 or by increasing the opening of the gas proportional valve 36 to increase the gas amount. Lower. Then, an attempt is made to foresee a combustion abnormality at an early stage based on how much the output signal value from the CO sensor 3 increases during that time.
[0025]
For example, in FIG. 3A, when the air-fuel ratio λ is at a relatively high level (“A” region in FIG. 3), even if the air-fuel ratio λ is temporarily reduced, the output signal value of the CO sensor 3 hardly fluctuates. Absent. Therefore, there is no sign of incomplete combustion in the region where the air-fuel ratio λ is “A”.
[0026]
On the other hand, in FIG. 3A, when the air-fuel ratio λ is relatively low (in the “B” region in FIG. 3), the output signal value of the CO sensor 3 greatly increases when the air-fuel ratio λ is temporarily lowered. The fluctuation range is large. Therefore, it can be said that in the region where the air-fuel ratio λ is “B”, incomplete combustion may be caused.
[0027]
FIG. 3B shows the relationship between the output level of the CO sensor 3 and the CO concentration in the relationship shown in FIG. The horizontal axis indicates the output level of the CO sensor 3, and the vertical axis indicates the CO concentration (ppm). As shown in this figure, the fluctuation range of the output level of the CO sensor 3 and the fluctuation range of the CO concentration when the air-fuel ratio is temporarily lowered are shown in FIG. As can be seen from the example, even if there is some individual difference in the detection sensitivity of each of the sensors (a) to (c), in any case, an increase in the CO concentration is detected in response to a change in the output signal value of the CO sensor. Will be. At this point, there is no significant difference between a CO sensor with good detection accuracy and a CO sensor with poor detection accuracy at a low air-fuel ratio λ.
[0028]
FIG. 4 is a control flowchart of the safe combustion apparatus applied to the gas water heater. This flowchart shows a case where the air-fuel ratio λ is changed by changing the rotation speed of the blower fan 38 in order to predict incomplete combustion.
First, the burner controller 40 determines whether or not the amount of combustion is stable based on the amount of gas from the gas burner 20 and the amount of air from the blower fan 38 (Step 1, hereinafter simply referred to as "S1"). and which (S1, "YES") the output value from the CO sensor 3 when it is determined that the _{(V 1)} is read (S2).
[0029]
Then lowering the fan speed of the blower fan 38 (S3), the timer is started (T ₁₎ at the time of lowering the fan speed (S4). Then, when a predetermined time (T ₁ : for example, 10 seconds) has elapsed (S5, “YES”), the output value (V ₂ ) from the CO sensor 3 is read again (S6).
[0030]
The rate of decrease in the number of revolutions is set smaller as the fan set number of revolutions corresponding to the combustion amount is larger. For example, a reduction rate n = 10% for a fan rotation speed N _max for a large combustion amount, a reduction ratio n = 30% for a fan rotation speed N _mid for a small combustion amount, and a reduction ratio n for a fan rotation speed N _min for a small combustion amount. n = 50%.
[0031]
Therefore, the controller 40 compares the difference (V ₁ −V ₂ ) between the output values V ₁ and V ₂ from the two read CO sensors 3 with the predetermined value Vr, and outputs the output value read by the CO sensor 3. if the difference _V 1 -V ₂ of the determined to be smaller than a predetermined value _{Vr (V 1 -V 2 ≦ Vr} ) (S7, "YES"), it comes to incomplete combustion is not expected.
[0032]
Therefore return the fan speed based on (S8), again the timer _{(T 2)} and to start the (S9), the predetermined time _{(T 2)} after (S10, "YES") is repeated again flowchart. This control flowchart is repeated at intervals of about 10 minutes.
[0033]
On the other hand, in S7 described above, it is determined that the difference (V ₁ −V ₂ ) between the _two output values V ₁ and V ₂ read by the CO sensor 3 is larger than the predetermined value Vr (V ₁ −V ₂ ≧ Vr). (S7, "NO"), it is determined that incomplete combustion is expected to occur soon (S11). In this case, the alarm 44 warns the appliance user that incomplete combustion tends to occur.
[0034]
As described above, when the air-fuel ratio λ is temporarily lowered in the stable combustion state of the gas burner (in this embodiment, the air-fuel ratio is lowered by lowering the rotation speed of the blower fan), the change in the output value from the CO sensor is changed. Incomplete combustion can be expected by observing Since the change in the CO concentration in a short time is captured, the change in the disturbance effect of the CO sensor element is reduced, and the difference in the CO concentration can be accurately detected.
As means for temporarily lowering the air-fuel ratio λ, in addition to lowering the rotation speed of the blower fan 38 as in the above-described embodiment, increasing the opening degree of the gas proportional valve 36 of the gas burner 20 to increase the gas amount It may be.
[0035]
When the air-fuel ratio is changed by changing the air flow of the blower fan, the change in the air flow of the blower fan changes the reduction rate of the fan speed according to the fan speed at the time of detecting the CO concentration by the CO sensor 3. It is good to do. Further, when the air-fuel ratio is changed by changing the gas amount of the gas burner, the change in the gas amount of the gas burner may be changed by changing the ratio of the gas amount according to the gas amount when the CO concentration is detected by the CO sensor 3. .
[0036]
The present invention is not limited to the above embodiment at all, and various modifications can be made without departing from the spirit of the present invention. For example, in the above embodiment, the combustion abnormality is determined based on the difference in the CO concentration output value when the air-fuel ratio is temporarily reduced. However, the combustion abnormality is determined based on the rate of change in the CO concentration output value. Is also good. Further, when the CO concentration output value of the CO sensor when the air-fuel ratio is temporarily lowered becomes higher than the reference output value by comparison with the reference output value, it may be determined that the combustion is abnormal.
[0037]
【The invention's effect】
The safe combustion device of the present invention detects a change in the CO concentration in the combustion gas by temporarily lowering the air-fuel ratio in a state where combustion is stable, and may cause a combustion abnormality such as incomplete combustion in the near future. It is foreseeable that there is. And even if a general CO sensor is used, the determination can be easily made at a low CO concentration of, for example, 300 ppm. Therefore, applying this device to gas-fired equipment such as gas water heaters can avoid the danger to human life due to incomplete combustion and guarantee safe driving. It is.
[Brief description of the drawings]
FIG. 1 is an overall configuration diagram of a state in which a gas combustion device (a gas water heater as an example thereof) to which a safe combustion device according to an embodiment of the present invention is applied is installed indoors.
FIG. 2 is a schematic configuration diagram of the gas water heater shown in FIG.
3A is a diagram showing a relationship between an air-fuel ratio and a CO output signal value, and FIG. 3B is a diagram showing a relationship between the CO output signal value and a CO concentration.
FIG. 4 is a control flowchart of the safe combustion device.
[Explanation of symbols]
2 Exhaust pipe 3 Carbon monoxide (CO gas) concentration sensor 10 Gas water heater 20 Gas burner 38 Blower fan 40 Burner controller

Claims (6)

A combustion gas exhaust system of a gas combustion device is provided with carbon monoxide concentration detecting means for detecting a carbon monoxide concentration in combustion gas flowing through the exhaust system, and the carbon monoxide concentration detection when the air-fuel ratio is temporarily lowered Means for comparing the concentration output value by the means and the concentration output value by the carbon monoxide concentration detection means before lowering the air-fuel ratio; and the monoxide concentration compared by the carbon monoxide concentration output comparison means. A safe combustion device comprising: combustion abnormality determining means for determining a combustion abnormality when a difference or a change rate of a carbon concentration output value becomes a predetermined value or more. 2. The safe 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. 3. 3. The method according to claim 2, wherein the change in the air volume of the blower fan changes a reduction ratio of the fan rotation speed according to the fan rotation speed when the carbon monoxide concentration detection unit detects the carbon monoxide concentration. A safe combustion device as described. The safe combustion device according to claim 1, wherein the air-fuel ratio is changed by changing a gas amount of a combustion burner provided in the gas combustion device. 5. The method according to claim 4, wherein the change in the gas amount of the combustion burner changes a ratio of the gas amount according to the gas amount when the carbon monoxide concentration detecting unit detects the carbon monoxide concentration. Safe combustion device. A combustion gas exhaust system of a gas combustion device is provided with carbon monoxide concentration detecting means for detecting a carbon monoxide concentration in combustion gas flowing through the exhaust system, and the carbon monoxide concentration detection when the air-fuel ratio is temporarily lowered A carbon monoxide concentration output comparing means for comparing the concentration output value by the means with a reference output value, and a carbon monoxide concentration output value compared by the carbon monoxide concentration output comparing means becomes equal to or more than the reference output value. A safe combustion device comprising: combustion abnormality determination means for determining combustion abnormality.

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