JPH0132887B2 - - Google Patents

Description

[Detailed Description of the Invention] Industrial Application Field The present invention detects incomplete combustion of a burner and automatically starts combustion when using a combustion device that burns gas, oil, etc. and performs hot water supply, heating, cooking, etc. This relates to a safety device configured to stop.

Configuration of conventional examples and their problems In recent years, in order to improve the safety of combustion equipment, combustion appliances with built-in mechanisms for detecting burner misfires and incomplete combustion due to lack of air have been commercially available. In particular, stoves and fan heaters that use indoor air for combustion are extremely dangerous as incomplete combustion due to lack of indoor oxygen can lead to fatal accidents. Conventionally, sensors using zirconium dioxide have been widely used as oxygen concentration detection sensors. An example is shown in FIG. Figure 12 shows a cross-sectional view of the sensor. The outer wall is made of cylindrical sintered zirconia (ZrO ₂ ) 1 whose tip is sealed, and the inner wall is made of porous platinum (Pt).
It has a structure covered by 2 and 3. This sensor constitutes an oxygen concentration battery that generates superpower according to the difference in oxygen concentration inside and outside the cylinder.

Next, this operation will be explained using FIG. 13.
The inside 4 of the cylinder is in contact with outside air, and the outside 5 of the cylinder is supplied with oxygen-poor air. At this time, since the electrode and zirconia react electrochemically at the cathode 3, the oxygen ions receive electrons and are incorporated into a portion of the zirconia. The incorporated oxygen ions move through the zirconia electrolyte, release electrons through an oxidation reaction at the anode side 2, and return to oxygen. In other words, if there is a difference in oxygen partial pressure between the inner side 4 and the outer side 5 of the cylinder, an electromotive force is generated in accordance with the difference. This operation is performed stably at high temperatures (400-800°C).

In addition to cylindrical zirconia elements, there are also flat plate types that utilize the difference in oxygen concentration on both sides of the plate.

Figure 3 shows the characteristics when this sensor is inserted into burner exhaust gas. In the figure, the horizontal axis λ indicates the ratio of air to fuel (air-fuel ratio), and the vertical axis ei indicates the sensor electromotive force.
The sensor output ei changes significantly after λ=1. Here, λ = 1 means that the amount of air necessary for combustion of the fuel being used (theoretical air amount) is supplied, and when λ > 1, combustion occurs when more than the theoretical amount of air is supplied. Oxygen remains in the exhaust gas afterwards. Therefore, since there is no large difference in oxygen concentration between the inside and outside of the cylinder shown in FIG. 12, ei is also low. (0.1V or less) λ<1
When this happens, the amount of oxygen becomes insufficient, and almost no oxygen is left in the exhaust gas, generating a large electromotive force (approximately 0.8V).

Combustion equipment is generally used at λ = 1.2 to 1.3. For example, when λ < 1 due to insufficient oxygen concentration, incomplete combustion occurs and carbon monoxide (CO) is produced.
occurs and becomes dangerous. For this reason, combustion was stopped by detecting the point where the sensor electromotive force became large.

FIG. 14 shows a conventional control circuit in block diagram form. Oxygen concentration sensor (hereinafter referred to as _O2 sensor)
The signal of sensor 6 is amplified by an amplifier circuit 7, and compared with a set value 8 by a comparison circuit 9, and when the output of the sensor 6 becomes larger than the set value 8, a signal is outputted to a safety circuit 10. The safety circuit 10 outputs a signal to stop combustion in response to this signal.

As mentioned earlier, combustion is incomplete when λ<1 and oxygen deficiency occurs, but λ≫1
When this happens, that is, when there is an excess of air, a flame list phenomenon occurs, which can lead to misfires. For this reason, a device is required that not only detects oxygen deficiency as in the past, but also stops combustion when oxygen is excessive. Furthermore, since the operation of the zirconia element is greatly affected by the ambient temperature, control of the ambient temperature is also important. Further, FIG. 1 shows a general combustion detection system diagram using a zirconia sensor, and is an example of application to a gas burner 11.
Gas flows in from the inlet 12, passes through the valve 13, and is burned in the burner 11. Reference numeral 6 designates the zirconia _oxygen concentration sensor described in FIG. It is detected that the value is 8 or more.

Further, the second comparison circuit 14 detects when the O ₂ sensor output becomes less than the second set value 15, and the safety circuit 10 is connected to each of the comparison circuits 9 and 14.
When this output occurs, a signal is output to close the valve 13, and the burner 11 is extinguished. That is _O2
When the output of the sensor 6 is between the set values 8 and 15, it is determined that combustion is normal and combustion continues.

FIG. 2 shows an example of this specific circuit. DC power supply 16
divided voltage by resistors 17, 18, 19, 20
es, e8, e15 are obtained. From its operation, the O ₂ sensor 6 is equivalent to a resistor Ri and a power source ei as shown in the figure. An operational amplifier (hereinafter referred to as an operational amplifier) 21 and resistors 22 and 23 constitute an amplifier circuit 7, and the junction of the potential es and the positive terminal of the O ₂ sensor and the negative terminal eO of the O ₂ sensor are connected to the operational amplifier 21. negative,
positive connected to each input terminal. For this reason
When the electromotive force ei=O of the O ₂ sensor, only the resistor Ri exists, and since the input impedance of each input terminal of the operational amplifier 21 is very high, the current flowing through the resistor Ri is almost zero. Therefore, the potential eO
=es, and the output potential ea of the operational amplifier also becomes equal to es. Next, when the electromotive force ei is generated in the O ₂ sensor 6, the potential eO becomes es-ei, and the output ea becomes ea=es-ei (1+R23/R22) according to the general characteristics of operational amplifiers. In other words, the potential ei is multiplied by the ratio of resistors 22 and 23.
will be amplified. The first comparator 9 and the second comparator 14 constitute a window comparator. Although each of the comparators 9 and 14 is constructed of an operational amplifier here, an open collector output comparator may also be used. The first comparator 9 has the first set level e8 connected to its positive input terminal, and the output potential ea of the amplifier circuit 7 connected to its negative input terminal. Further, the comparator 14 has the second set level e15 connected to its negative input terminal, and the potential ea connected to its positive input terminal. The output of each comparator 9, 14 is input to a NOR logic gate circuit 24, the output of which is connected through a resistor 25 to the base of a transistor 26. The emitter of the transistor 26 is connected to the ground of the power supply 16, and the collector is connected to the + potential of the power supply 16 through the valve 13 (here, a solenoid valve is used).

During normal combustion, as shown in Figure 3, λ=1~
Assume that combustion is occurring at 1.3. From the above, if the electromotive force is between ei1 and ei2, it is determined that combustion is normal.

Operational amplifier 2 when the electromotive force is between ei1 and ei2
The output ea of No. 1 is between the potentials e8 and e15 as shown in the X part of FIGS. 4 and 5. Therefore, the comparator 9 outputs a low output, the comparator 14 also outputs a low output, and the output of the NOR gate 24 becomes a high output, so the transistor 26 becomes conductive and the valve 13 is energized to flow gas.

If incomplete combustion occurs due to lack of oxygen or the like, λ becomes smaller than 1 as shown in FIG. 3, and the output ei exceeds ei1. Here, as mentioned above, the potential ea is inversely proportional to ei, so as ei increases,
ea becomes a small value, lower than e8 (Part Y in Figure 4).

From the above, the output of the comparator 9 becomes high, the output of the comparator 14 becomes low, and the output of the NOR gate 24 becomes low, cutting off the transistor 26 and closing the valve 13 to stop combustion. On the other hand, if there is too much air due to some reason, it is dangerous because a flame lift phenomenon may occur. In this case, λ becomes 1.3 or more and enters the Z region in Figure 3, and ei becomes less than ei2. From the above, ea becomes a higher value than e15 (part Z in Fig. 5). As a result, the comparator 14 in FIG. 2 has a high output, the comparator 9 has a low output, the NOR gate has a low output, and the valve 13 is closed.

As described above, by adopting the circuit configuration shown in FIG. 2, it was possible to detect and stop combustion regardless of whether incomplete combustion due to oxygen deficiency or abnormal combustion due to excess air occurred.

Purpose of the Invention The present invention eliminates the above-mentioned conventional drawbacks, and provides an incomplete combustion detection device that automatically stops combustion by detecting incomplete combustion due to lack of oxygen and abnormal combustion due to excess oxygen. The purpose is to

Composition of the Invention To achieve this object, the incomplete combustion detection device of the present invention uses a combustion detection sensor that generates an electromotive force according to the combustion state of a burner to set an output level for determining the combustion state. The configuration includes a safety circuit that stops combustion when the sensor output deviates from these two points, and also supplies current to the sensor from an external power source to detect changes in the internal resistance of the sensor and The temperature of the sensor can be detected based on temperature characteristics, and the safety circuit operates when the temperature is above the temperature at which the sensor operates stably.

In addition, the structure is such that the re-ignition operation does not start unless the sensor temperature drops below a certain level after combustion has stopped, which prevents erroneous detection due to reaction between the sensor and unburned gas in a high-temperature atmosphere, and also prevents the sensor temperature during combustion. The structure is such that a misfire of the burner is detected by a decrease in the temperature.

DESCRIPTION OF EMBODIMENTS The basic operation of the structure of the present invention will be explained below using FIGS. 6 and 7, and two embodiments of the present invention will be explained using FIGS. 8 to 11. First, in FIG. 6, the electromotive force ei of the sensor 6 is a small value of 0.8V at most, and in the Z region of FIG. 3 it is about mV, which is a solution to the problem that it becomes unstable. A current is is supplied to the sensor 6 from a power source 16 via a bias resistor 27. Also, as in Fig. 2, resistors 28, 29, 30,
31, the reference potential es and the first and second comparison potentials e
8, e15 is obtained. The resistor 27 and the divided potential e0' of the sensor 6 are input to the positive input terminal of the operational amplifier 21, and the reference potential es is input to the negative input terminal via the resistor 22.
It consists of The output ea′ is ea′=e0′+(es−e0′)
(1+R23/R22). From the above, e0′ and ea′ change proportionally. Therefore, when the electromotive force ei increases,
Since ea' also increases, the potentials e8 and e1 differ from those in Figure 2.
The level of 5 is reversed.

Also, due to the current is, the electromotive force of sensor 6 is ei
+Ri·is, and the configuration is such that a certain level of output potential can be obtained even in the Z region of FIG. Also, since the internal resistance Ri of the sensor has a negative temperature coefficient, if the temperature of the sensor 6 is low before ignition, Ri
= a large value of several 10 to several 100 MΩ, and when the flame ignites and the sensor temperature is heated to 300 to 400℃, Ri
= decreases to several Kz. Therefore, the potential e0' becomes as shown in FIG. The horizontal axis shows time and the vertical axis shows e0'. Before ignition, as mentioned above, the temperature of the sensor 6 is low and Ri is a sufficiently larger value than the resistance 27.
e0' is approximately at the same potential as the power supply 16. time
When ignited at to, Ri decreases and e0′ also decreases accordingly. When the flame burns stably, it stabilizes at the value of the product of Ri and is determined by the temperature at that time and the sum of ei. Here, when ei increases due to a decrease in λ as shown in Fig. 3, e0' increases, and when ei decreases due to an increase in λ, e0' decreases, and the output ea' becomes the potential e8 and e13.
When it deviates from the range, the comparator circuits 9 and 14 are
operates to close the valve 13.

In the embodiment shown in FIG. 8, a temperature detection circuit 32 is provided in the safety circuit 10, and the safety circuit 10 does not operate when the temperature of the sensor 6 is low based on this signal. Furthermore, the temperature signal of the temperature detection circuit 32 is determined by the internal resistance Ri of the sensor 6 explained in FIGS. 6 and 7.
The structure is configured to detect changes in .

FIG. 9 shows an example of this specific circuit. In the figure, the amplifier circuit 7 and comparators 9 and 14 operate in the same manner as in FIGS. 2 and 6, so their explanation will be omitted.

The divided potential e0' of the resistor 27 and the sensor 6 is input to the operational amplifier 21 and simultaneously input to the positive input terminal of the comparator 33 (consisting of an operational amplifier) of the temperature detection circuit 32. Also, the negative input terminal of the comparator 33 is connected to the divided potential e _T1 (first temperature setting value) of the resistors 34 and 35.
is entered. Output is 36 diodes and 3 resistors
7 to the base of transistor 26. As mentioned above, in the circuit shown in Fig. 6, as shown in the characteristics shown in Fig. 7, the potential e0' remains high until the temperature of the sensor 6 rises after ignition, and the valve is closed when detected at a potential e8' or higher. I had to put it away. For this reason, there is a method of operating a timer after ignition to disable the safety circuit for a certain period of time. However, in this method, the temperature rise time of the sensor 6 varies widely, and for safety reasons, it is necessary to set the timer time long.
However, if the timer time is long, there is a problem in that if incomplete combustion occurs during the timer operation, it will not be detected and is dangerous. (In addition, e8' and e15 in Fig. 7 are the input potentials of e8 and e15 in Fig. 6 with the gain of the amplifier circuit 7.
This is the value converted to correspond to e0′. ) In order to solve the above problems, the temperature characteristics of the internal resistance Ri of the sensor 6 are utilized to enable the safety circuit 10 to operate after the temperature of the sensor 6 reaches a certain temperature or higher. The divided potential e0' of the resistor 27 and the sensor 6 is almost the voltage of the power supply 16 when the temperature of the sensor 6 is low. At this time, the input potential of the comparator becomes e _T1 ≪ e0′, and the output becomes high level. Therefore, since the base potential is supplied to the transistor 26 through the diode 36 and the resistor 37, the transistor 26 is not cut off even if the output of the NOR gate 24 becomes low level. Next, as the temperature of the sensor 6 increases, Ri decreases, and e0' also decreases as shown in FIG. As a result, the potential e _T1 ≦
When Ro' is reached, the output of the comparator 33 becomes low level, the diode 36 becomes reverse biased, and the transistor is turned on and off according to the output level of the NOR gate 24. As described above, since the temperature of the sensor 6 itself is measured, the sensor 6 operates at the optimum timing even if there are variations in the heating time. Further, in FIG. 9, the signal of the temperature detection circuit is configured to be detected at e0', but it is also possible to detect it at ea' as shown by the broken line, and it is also possible to provide another temperature sensor.

Although not shown in FIG. 9, it is also known that in addition to this configuration, a timer circuit that operates after the ignition operation is added, and if the temperature of the sensor 6 does not rise after a certain period of time, it is assumed that there is no ignition and the valve 13 is stopped. It is.

The embodiment shown in FIG. 10 has an ignition signal circuit 38 driven by a temperature detection circuit 32. This is because if the ignition operation is performed again while the temperature of the sensor 6 is high after the burner has been extinguished, catalytic combustion will occur within the sensor 6, and a normal level of electromotive force ei will be generated even if the burner 11 is not ignited, resulting in false detection. This is to prevent the re-ignition operation from occurring until the temperature of the sensor 6 falls below a certain temperature (second set temperature).

FIG. 11 shows an example of this specific circuit. Here, in addition to the second set temperature that drives the ignition signal circuit 38 shown in FIG.
3 is also provided with a third set temperature.

The second set temperature is set by resistors 39, 40, and 41.
e _T2 and a third temperature set value e _T3 are provided. e _T2
and e _T3 are connected to the negative input terminal of the comparison circuit 42 and the positive input terminal of the comparison circuit 43, respectively.
Also, the temperature signal e0' is sent to the comparators 42 and 43 as shown in the figure.
The comparator 43 constitutes a misfire detection circuit, the output of which is connected to the base potential of the transistor 26 through a diode 44, and the emitter of the transistor 26 is connected to one terminal of the power supply 16 through a diode 45. Similarly, the output of comparator 42 provides a drive signal to ignition signal circuit 38.

Now, during normal combustion, the temperature of sensor 6 is high and the potential is high.
Since e0'<e _T3 <e _T2 , the output of the comparator 43 becomes high and the diode 44 is reverse biased.
Transistor 26 operates in response to the output of NOR gate 24. Further, the comparator 42 outputs a low output, and the ignition signal circuit 38 is also not driven. If the burner 11 misfires for some reason, the temperature of the sensor 6 decreases and the potential e0' increases. As a result, the potential e _T3 <e0'< e _T2 and the comparator 43 becomes a low output. From the above, the base potential of the transistor 26 is grounded to the power supply 16 through the diode 44, so that it is cut off and the valve 13 is closed. However, at this time, the comparator 42 still has a low output and no ignition operation is performed.

The temperature of sensor 6 further decreases and the potential e _T3 < e _T2
When <e0', the comparator 42 becomes a high output and drives the ignition signal circuit. As a result, an igniter (not shown) operates to reignite the burner 11. The ignition signal circuit also has a built-in structure that resets the comparator 43 circuit at the same time as the valve 13 is opened.

In addition to the configuration shown in FIG. 11, it is also possible to add the configuration explained in FIG. 9, and it is also easy to put the comparators 42 and 43 in FIG. 11 into practical use individually.

Although the above embodiments have been explained using a gas burner as an example, the same applies even if the burner is an oil burner. Further, in the case of petroleum, the valve 13 may be a fuel pump without any problem. Furthermore, the combustion method can also be applied to various types of things.

Effects of the Invention As explained above, the incomplete combustion detection device of the present invention has the following effects.

1 The combustion detection sensor has two detection levels, and the sensor output is within these two levels under normal conditions, so it is possible to detect both incomplete combustion due to lack of oxygen and abnormal combustion due to excess oxygen, and to stop combustion. Therefore, it is highly safe.

2. By configuring the sensor to flow a bias current from the outside, the stability of the sensor output can be improved and false detections and detection errors can be prevented.

3. By configuring the bias current as described above to flow, the sensor temperature can also be measured, and by providing a circuit that prohibits the operation of the safety circuit that stops the burner due to incomplete combustion during unstable initial combustion, the sensor temperature can be sufficiently measured. This prevents malfunctions since it starts operating after the temperature rises to .

4. Also, by adopting a configuration that includes an ignition signal circuit that shifts to re-ignition operation after the temperature has cooled sufficiently, reliability is improved by eliminating the possibility of erroneous detection due to catalytic combustion of unburned gas by the high-temperature sensor.

5. Furthermore, it is possible to detect burner misfire based on the sensor temperature, and there is no need to add another flame sensor, resulting in a simple configuration.

[Brief explanation of drawings]

Fig. 1 is a control system diagram showing one embodiment of the present invention, Fig. 2 is a specific circuit diagram of the same, Fig. 3 is a characteristic diagram of a zirconia oxygen concentration sensor, and Figs.
6 is a circuit diagram showing another specific example of the circuit, FIG. 7 is a diagram explaining its operation, FIG. 8 is a system diagram showing another embodiment, and FIG. 9 is a specific example of the circuit. A circuit diagram, FIG. 10 is a system diagram showing another embodiment, FIG. 11 is a specific circuit diagram thereof, FIG. 12 is a sectional view showing an example of a zirconia oxygen concentration sensor, and FIG. 13 is an explanatory diagram of its operation. FIG. 14 is a block diagram showing a conventional control system. 6... Combustion detection sensor, 8, e8... First setting level, 9... First comparison circuit, 10... Safety circuit, 14... Second comparison circuit, 15, e15...
...Second setting level, 16...External power supply, 27...
... Bias resistor (bias circuit), 32 ... Temperature detection circuit, 38 ... Ignition signal circuit, 43 ... Comparator (misfire detection circuit), e _T1 ... First set temperature,
e _T2 ...Second set temperature, e _T3 ...Third set temperature.

Claims (1)

[Claims] 1. A combustion detection sensor that detects the combustion state of the burner and generates an electromotive force, and a combustion detection sensor that detects that the output of the combustion detection sensor has exceeded a predetermined first setting level. The combustion engine has a first comparison circuit and a second comparison circuit that detects that the level has fallen below a second set level, and stops combustion by detecting the output of either the first or second comparison circuit. The combustion detection sensor has a safety circuit that outputs a signal to
The safety circuit includes a bias circuit that supplies current from an external power source, and the safety circuit includes a temperature detection circuit that detects the temperature of the combustion detection sensor, and the temperature of the combustion detection sensor is determined by the output of the temperature detection circuit. An incomplete combustion detection device configured to operate when the temperature is higher than a set temperature. 2. A combustion detection sensor that detects the combustion state of the burner and generates an electromotive force, and a first comparison circuit that detects that the output of the combustion detection sensor has exceeded a predetermined first setting level; and a second comparison circuit that detects that the temperature has fallen below a second set level, and detects the output of either of the first and second comparison circuits and outputs a signal to stop combustion. The combustion detection sensor has a circuit, and the combustion detection sensor includes:
The safety circuit includes a bias circuit that supplies current from an external power source, and the safety circuit includes a temperature detection circuit that detects the temperature of the combustion detection sensor, and the temperature of the combustion detection sensor is determined by the output of the temperature detection circuit. an ignition signal circuit that outputs a signal to start combustion of the burner when the temperature is below the set temperature of No. 2;
An incomplete combustion detection device configured to include a misfire detection circuit that outputs a signal to stop combustion when the temperature of the combustion detection sensor becomes equal to or lower than a third set temperature based on the output of the temperature detection circuit.