JPH10288334A - Flame current detecting device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve precision on decision of ignition/non-ignition and decision of abnormal combustion by independently arranging an ignition/non-ignition deciding circuit and an oxygen deficiency deciding circuit. SOLUTION: An FR applying source circuit 11 applies an AC source 100V source voltage on an FR. A combination filter and level converting circuit 13 for detecting ignition/fire extinguishment converts a change of the level of a flame current into the voltage of a signal processing source after a source AC component is removed and a signal is fed to a comparing circuit 15 for detecting ignition/fire extinguishment. The comparing circuit 15 for detecting ignition/fire extinguishment compares output signals from a combination filter and the level converting circuit 13 for detecting ignition/fire extinguishment with each other and a logic level signal is fed to a CPU 21. A combination filter and level converting circuit 17 for detecting oxygen deficiency is independently arranged in parallel to the combination filter and level converting circuit 13 for detecting ignition/fire extinguishment and a change of a potential due to a flame potential is converted into the voltage of a signal processing source after a source AC component is removed, and a signal is fed to an A/D converting circuit 19 for detecting oxygen deficiency.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a flame current detecting device for detecting a combustion state by a flame current between a burner and a flame rod sensor.

[0002]

2. Description of the Related Art Conventionally, flame current is detected by a flame current detecting means such as a flame rod sensor inserted into a combustion flame, and when the current value exceeds a reference value, it is determined that abnormal combustion has occurred. It has been known.

[0003]

However, in the above flame current detection device, one flame detection circuit uses two reference values,
For example, it is configured such that when the relative value of the flame current is 0.5 or less, misfire is determined, and when the relative value of the flame current is 7.0 or more, abnormal combustion is determined. Is wide, and the reference value is near the minimum (0.5) and near the maximum (7.0) of the detection range, so that the detection accuracy is poor.

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a flame current detecting device capable of accurately determining ignition / non-ignition and abnormal combustion.

[0005]

In order to achieve the above object, the present invention provides a flame rod sensor inserted into a combustion flame of a burner and a flame rod sensor between the burner and the flame rod sensor. A flame current detection device provided with a detection circuit for detecting a combustion state based on a flame current of said flame current. A power supply circuit for applying an AC power supply to said flame rod sensor, and ignition for igniting / extinguishing a combustion flame according to said flame current. A fire / extinction determination circuit and an oxygen deficiency determination circuit for determining that the combustion state is oxygen deficient, and the ignition / extinction determination circuit and the oxygen deficiency determination circuit are provided independently of each other. The detection range of the flame current for judging fire extinguishing and oxygen deficiency can be set large, and the detection accuracy of each increases.

Further, an ignition / extinguishing conversion circuit for transmitting a signal to the ignition / extinguishing determination circuit after removing the AC component of the AC power supply and converting the AC component into a signal processing voltage, and removing the AC component of the AC power supply. After converting to a signal processing voltage, the apparatus further includes an oxygen deficiency conversion circuit that sends a signal to the oxygen deficiency determination circuit, and the ignition / extinguishing conversion circuit and the oxygen deficiency conversion circuit are provided independently of each other. As described above, the detection range of the flame current for judging ignition / extinguishing and lack of oxygen can be set large, and the detection accuracy of each can be improved.

The ignition / extinguishing determination circuit and the oxygen deficiency determination circuit each include a comparison circuit that compares an input signal with a preset signal, so that processing by the CPU can be reduced.

The ignition / extinguishing determination circuit and the oxygen deficiency determination circuit each include an A / D conversion circuit for converting an input analog signal into a digital signal, so that software processing can be performed and flexible determination processing can be performed. Can be realized.

[0009] Further, since a combustion state judging section for judging the combustion state is provided based on a combination of the judgment result of the ignition / extinction judgment circuit and the judgment result of the oxygen deficiency judgment circuit, more accurate. The combustion state can be determined.

[0010] In addition, there is provided notifying means for notifying the contents of the combustion state by a signal of the combustion state judging section, and the combustion state judging section is provided with a stage for judging that the combustion state is abnormal, and When the state determination unit determines that the combustion state is abnormal, the state determination unit instructs the notification unit to change the notification content according to the combustion state a predetermined time before the abnormal state. Even if the abnormality is the same, it is possible to notify the user depending on the degree of the abnormality, even when the treatment is required immediately.

[0011]

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

FIG. 1 is a block diagram in which a flame current detecting device according to one embodiment of the present invention is applied to a gas water heater.

The gas water heater 10 is connected to a flame rod sensor (hereinafter, FR) 3 and a burner 4 via a flame current detecting device 2 by applying an AC power supply 1. Further, the burner 4 is connected to the earth ground at the time of installation.

FIG. 2 is a control block diagram showing the flame current detector 2.

The flame current detecting device 2 includes an FR applying power supply circuit 11, an ignition / extinguishing detection filter / level conversion circuit 1
3. Ignition / fire extinguishing detection comparison circuit 15, filter / level conversion circuit 17 for oxygen deficiency detection, A / D conversion circuit 1 for oxygen deficiency detection
9 and a CPU 21.

The FR power supply circuit 11 includes an AC power supply 100.
This is a circuit for applying a power supply voltage of V to FR3.

The ignition / extinguishing detection filter / level conversion circuit 13 detects a change in the potential of one end of FR3 due to the flame current.
While removing the AC component, the signal processing system power supply (0
(In the range of ５5 V) and sends a signal to the ignition / extinction detection comparison circuit 15.

The ignition / fire extinguishing detection comparison circuit 15
The output signal of the fire extinguishing detection filter / level conversion circuit 13 is compared with a reference potential. When the comparison result indicates that there is no flame, a Lo level signal is output. When it is determined that there is a flame, a Hi level signal is output. And sends it to the CPU 21 as a logic level signal.

The ignition / extinguishing detection comparison circuit 15
By using the comparison circuit, the processing of the CPU 21 can be reduced.

Oxygen deficiency detection filter / level conversion circuit 17
Is provided independently and in parallel with the ignition / extinguishing detection filter / level conversion circuit 13, similarly to the ignition / extinguishing detection filter / level conversion circuit 13, detects a change in the potential of one end of the FR 3 due to a flame current by a power supply AC. In addition to removing the components, the voltage is converted to a voltage of a signal processing system power supply (in the range of 0 to 5 V), and a signal is sent to the A / D conversion circuit 19 for detecting oxygen deficiency.

The A / D conversion circuit 19 for oxygen deficiency detection converts the output signal of the filter / level conversion circuit 17 for oxygen deficiency detection into impedance by an operational amplifier circuit, and then leads the signal to an A / D conversion circuit built in the CPU 21. This is a circuit that converts digital data that can be processed by the CPU program.

The A / D conversion circuit 19 for detecting oxygen deficiency includes:
Software processing can be realized by an A / D conversion circuit built in the CPU 21, and fine and flexible determination processing such as learning control can be performed.

FIG. 3 shows a signal detected by the oxygen-deficiency detection filter / level conversion circuit 17.

When the gas water heater starts burning, a current flows through FR3. Now, combustion is started and is represented by an equivalent circuit to a circuit in which a resistor Rs connected in series with a diode is connected to FR3. Although the value of the resistance Rs changes depending on the state of the combustion flame, the filter / level conversion circuit 17 for detecting oxygen deficiency can detect the resistance Rs in the range of 0.4 MΩ to 100 MΩ in the range of the oxygen deficiency detection voltage V = 0 to 5 V. It has become. The oxygen deficiency detection voltage V during actual combustion is detected without saturation in a wider range (wide range of the resistance Rs shown in FIG. 3) because of fluctuations due to a load condition and a decrease in the amount of air. There is a need to.

In FIG. 3, the threshold value of oxygen deficiency is 4 V,
When the threshold value of the abnormal combustion is set to 1 V, the CPU 21 determines that V =
If the voltage is 1.0 V or less, it is determined that the combustion is abnormal, if V = 4.0 V or more, it is determined that oxygen is deficient, otherwise, it is normal combustion. The thresholds of oxygen deficiency and abnormal combustion can be varied according to the type of gas and the maximum rated combustion amount.

FIG. 4 is a diagram showing signals input to the ignition / extinguishing detection comparison circuit 15.

FR when combustion flame is generated as in FIG.
3 is measured by an equivalent circuit provided with a resistor Rs connected in series with a diode. For example, if Rs = 30 MΩ is set as an ignition / extinction determination reference value, a voltage V =
1.298 V is the ignition / extinction determination threshold. Therefore,
The value detected by the ignition / extinction detection comparison circuit 15 is V =
Extinguishing (non-ignition) if 1.298V or less, V = 1.298
If V or more, ignition is determined.

As described above, the ignition / extinguishing detection comparison circuit 1
By providing the filter 5 and the oxygen deficiency detection filter / level conversion circuit 17 independently of each other, disturbance elimination or control performance is improved.

The ignition / extinguishing judgment is performed as described above.
It is determined by the fire extinguishing detection comparison circuit 15 whether ignition has been performed or whether fire has been extinguished (non-ignition) based on whether or not the ignition / extinction determination threshold has been exceeded. On the other hand, in the oxygen deficiency determination, the A / D conversion circuit 19 for detecting oxygen deficiency determines whether or not the oxygen deficiency is present based on whether or not the oxygen deficiency threshold value is exceeded. Further, an abnormal combustion threshold is provided, and it is determined whether or not abnormal combustion occurs based on whether or not the abnormal combustion threshold is exceeded.

Next, a description will be given of the case where the determination is made based on a combination of the output of the ignition / extinction detection comparison circuit 15 and the output of the A / D conversion circuit 19 for detecting oxygen deficiency with reference to FIG.

When it is determined that the fire is extinguished by the ignition / extinguishing determination, and when it is determined that the oxygen is lacking by the oxygen deficiency determination, the fire is determined to be extinguished.
Further, when it is determined that the fire is extinguished by the ignition / extinguishing determination, and when it is determined that the detection is normal or abnormal by the oxygen deficiency determination, it is determined that the detection device is out of order.

When it is determined that ignition has occurred by the ignition / extinguishing determination, and when it is determined that oxygen is lacking by the oxygen deficiency determination, it is determined that oxygen is lacking.
In addition, it is determined that ignition has occurred by the ignition / extinguishing determination, and normal combustion is determined when the oxygen deficiency determination is normal, and abnormal combustion is determined when the oxygen deficiency determination determines that the combustion is abnormal.

Further, the countermeasures to be taken thereafter are made different depending on the timing of the judgment based on the combination of the ignition / extinction judgment and the oxygen deficiency judgment.

For example, as shown in FIG. 6, when the initial oxygen deficiency a is not in a normal combustion state and remains in an oxygen deficient state even when ignited, only a failure display is performed. ,
An alarm is issued by the alarm means to urge the user to take urgent action. Further, in the case of a failure c determined to be abnormal combustion or normal combustion from the time of extinguishing, only a failure display is performed. An alarm is issued by the alarm means to prompt the user to take urgent action.

[Brief description of the drawings]

FIG. 1 is a block diagram of a gas water heater as one embodiment of a flame current detection device of the present invention.

FIG. 2 is a control block diagram of the flame current detection device.

FIG. 3 is a diagram showing a signal detected by an oxygen deficiency detection filter and level conversion circuit.

FIG. 4 is a diagram showing signals input to an ignition / extinction detection comparison circuit.

FIG. 5 is a diagram showing a determination process of a combustion state determination unit.

FIG. 6 is a diagram showing a determination process of a combustion state determination unit.

[Explanation of symbols]

 2: Flame current detection device 3: Flame rod 4: Burner 11: FR application power supply circuit 13: Ignition / fire extinguishing detection filter / level conversion circuit 15: Ignition / extinguishing detection comparison circuit 17: Oxygen deficiency detection filter / level conversion Circuit 19: A / D conversion circuit for detecting oxygen deficiency

Claims (6)

[Claims] 1. A flame current detection device comprising: a flame rod sensor inserted into a combustion flame of a burner; and a detection circuit for detecting a combustion state by a flame current between the burner and the flame rod sensor. A power supply circuit that applies the flame current to the flame rod sensor; an ignition / extinguishing determination circuit that determines ignition / extinction of the combustion flame according to the flame current; and an oxygen deficiency determination circuit that determines that the combustion state is oxygen deficient. The flame current detecting device, wherein the ignition / extinguishing determination circuit and the oxygen deficiency determination circuit are provided independently of each other. 2. The ignition / extinguishing conversion circuit according to claim 1, wherein an AC component of the AC power is removed and converted to a signal processing voltage, and then a signal is transmitted to the ignition / extinguishing determination circuit. And an oxygen deficiency conversion circuit that removes the AC component of the AC power supply and converts the signal into a signal processing voltage and then sends a signal to the oxygen deficiency determination circuit, and the ignition / extinguishing conversion circuit and the oxygen deficiency conversion circuit , A flame current detecting device provided independently. 3. The flame current detection device according to claim 1, wherein the ignition / extinguishing determination circuit and the oxygen deficiency determination circuit include a comparison circuit that compares an input signal with a preset signal. Flame current detector. 4. The flame current detection device according to claim 1, wherein the ignition / extinguishing determination circuit and the oxygen deficiency determination circuit include an A / D conversion circuit that converts an input analog signal into a digital signal. Characteristic flame current detector. 5. The flame current detection device according to claim 1, wherein the combustion state is determined based on a combination of the determination result of the ignition / extinction determination circuit and the determination result of the oxygen deficiency determination circuit. And a flame current detection device. 6. The flame current detecting device according to claim 5, further comprising: a notifying unit for notifying a content of the combustion state by a signal of the combustion state determination unit, wherein the combustion state determination unit determines that the combustion state is abnormal. A flame current detecting device, wherein when it is determined that there is, a flame current detecting device is instructed to change the content of the notification in accordance with the combustion state a predetermined time before becoming abnormal.