JPS5960124A - Incomplete combustion detecting device - Google Patents

Abstract

PURPOSE:To provide the titled device capable of detecting the incomplete combustion state both in an oxygen-lean and-excess cases, by constituting such that the device may stop its burning operation in the event that an oxygen sensor actuating power deviates beyond two preset levels being provided. CONSTITUTION:A fuel gas flows from an inlet 12 via a valve 13 and is burnt by means of a burner 11. A signal outputted from a zirconia oxygen concentration sensor 6 is amplified by an amplifier 7 to compare the signal with a first preset value 8 in a first comparison circuit 9 for thereby detecting the increase of oxygen sensor signal above the first preset value 8. A second comparison circuit 14 functions to detect the decrease of oxygen sensor output below a second preset value 15. A safety circuit 10 functions to output a signal instructive of a valve 13 closure for thereby extingushing a burner 11.

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 and cooking, etc. This relates to a safety device configured to stop.

Conventional configurations 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, fan heaters, etc. 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, which is made of cylindrical sintered zirconia ('Zr○2
) The outer and inner walls of 1 are covered with porous platinum (PT) 2.3. This cell constitutes an oxygen concentration cell that generates an electromotive force 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 6 of the cylinder is supplied with oxygen-poor air. At this time, the cathode 3 electrochemically reacts with the electrode and zirconia, so that the electrons are received and become oxygen ions, which are incorporated into a portion of the zirconia. The absorbed oxygen ions move through the zirconia electrolyte and return to oxygen by an oxidation reaction at the anode side 2. In other words, if there is a difference in oxygen partial pressure between the inside 4 and outside 5 of the cylinder, An electromotive force is generated according to the difference. This operation is performed stably at high temperatures (400 to 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 e4 changes significantly after λ=1. Here, λ = 1 means that the amount of air (theoretical air amount) necessary for the fuel being used to burn is supplied, and λ〉
When the value is 1, oxygen remains in the exhaust gas after combustion when less than the theoretical amount of air is supplied. 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. (o
, 1V or less) When λ becomes 1, the amount of oxygen becomes insufficient, and almost no oxygen exists in the exhaust gas, resulting in a large electromotive force (approximately o, sV)
will occur.

Combustion equipment is generally used at λ = 1.2 to 1.3. For example, when λ becomes 1 due to insufficient oxygen concentration, incomplete combustion occurs and carbon monoxide (Co) is generated, which is dangerous. becomes. 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. The signal from the oxygen concentration sensor (hereinafter referred to as 02 sensor) 6 is amplified by an amplifier circuit 7 and compared with a set value 8 by a comparator circuit 9. When the output of the sensor 6 becomes greater than the set value 8, the safety circuit 10 Outputs a signal to. The safety circuit 10 outputs a signal to stop combustion in response to this signal.

It was mentioned earlier that combustion is incomplete when λ×1 becomes oxygen deficient, but when λ)1,
When there is too much air in the lamp, a flame lift phenomenon occurs, which may cause 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. Since the operation of a single zirconia element is greatly affected by the ambient temperature, control of the ambient temperature was also important.

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. Structure of the Invention In order to achieve this object, the present invention has a structure in which two set levels are provided and combustion is stopped when the 02 sensor electromotive force deviates from these points. .

It was possible to detect any case of excess oxygen. In addition, in order to prevent the electromotive force of the 02 sensor from becoming small and unstable,
The configuration is such that current is passed through the two sensors from an external power source.

Furthermore, by configuring the temperature of the 02 sensor to be simultaneously detected, it is possible to detect incomplete combustion only when the temperature is within the temperature range in which the 02 sensor operates stably.

Similarly, when the 02 sensor temperature is high after combustion has stopped and a re-ignition operation is performed and misfire occurs, the 02 sensor is activated by unburned gas and the combustion level is restored to normal.

The output may be about the same. This can be prevented by cooling the 02 sensor and then re-igniting it.
Based on the temperature detection by the 02 sensor, the burner is ignited only when the temperature of the 02 sensor falls below a certain value.

Additionally, burner ignition and misfire detection can be performed by detecting the temperature of the 02 sensor.

Description of examples Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 shows a system diagram to which the present invention is applied, and is an example in which the present invention is applied to a gas burner 11. Gas flows in from the inlet 12, passes through the valve 13, and is burned in the burner 14. Reference numeral 6 designates the zirconia oxygen concentration sensor described in FIG.
It is detected that the signal of the Q2 sensor 6 has become equal to or higher than the first set value 8.

Further, the second comparison circuit 14 detects when the Q2 sensor output becomes less than the second set value 15, and the safety circuit 1
0 outputs a signal to close the valve 13 and extinguishes the burner 11 when the outputs of the respective comparison circuits 9 and 14 are generated. In other words, when the output of the 02 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 and resistor 1
7.18, 19.20, the divided potentials es, e8. e1
I got 5. From its operation, the 02 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 point between the potential es and the + side terminal of the 02 sensor and the one side terminal eO of the o2 sensor are connected to the negative side of the operational amplifier 21, Connected to the correct input terminals. Therefore, when the electromotive force ei=o of the O2 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 02 sensor 6, the potential eO
becomes es-ei, and the output ea amplifies the potential ei by a ratio of 23 according to the general characteristics of operational amplifiers. The first comparator 9 and the second comparator 14 constitute a window comparator. each comparator 9,
14 is constituted by an operational amplifier here, but a comparator with an open collector output may also be used. 1st
The comparator 9 inputs the first set level e8 to the positive input terminal,
The output potential ea of the amplifier circuit 7 is connected to the negative input terminal. The output comparator 14 has the second setting 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 connected to a NOR logic gate circuit 24.
The output is connected to the base of a transistor 26 through a resistor 25. The emitter of the transistor 26 is connected to the ground of the power source 16, and the collector is connected to the potential of the power source 16 through the valve 13 (here, a solenoid valve is used).

Assume that during normal combustion, combustion occurs at λ-1 to 1.3, as shown in FIG. From the above, the electromotive force is ei1~e
If it is i2, it is determined that combustion is normal.

When the electromotive force is between ei1 and ei2, the output ea of the operational amplifier 21 is at potentials e8 and e as shown in the X part of FIGS. 4 and 5.
It is between i5. 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 that the transistor 9 becomes conductive and the valve 13 is energized to flow gas.

If incomplete combustion occurs due to oxygen deficiency, etc., λ becomes smaller than 1 as shown in Figure 3, and the output ei becomes ei.
It exceeds l. Here, as mentioned above, the potential ea is ei
Since it is inversely proportional to , when ei becomes large, ea becomes a small value and becomes lower than ea. (Part Y in Figure 4) From the above, the output of the comparator 9 is NO, the comparator 14 is a low output, the output of the NOR gate 24 is low, the retransistor 26 is cut off, the valve 13 is closed, and combustion is stopped. let On the other hand, if there is too much air due to some reason, it is dangerous because a flame lift phenomenon may occur. At this time, λ becomes 1.3 or more and enters the Z region in Figure 3, where ei is ei2
It becomes below. From the above, ea becomes a higher value than ei5 (Fig. 5, part 2). Accordingly, the comparator 14 in Fig. 2
However, when the output is high, the J1 comparator 9 becomes a low output, becomes a NOROR Gerto output, and closes the valve 13.

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

FIG. 6 shows another embodiment, which solves the problem that the electromotive force e1 of the sensor 6 is as small as 0.8V at the maximum, and becomes unstable at about mV in the Z region of FIG. A current is is supplied from a power source 16 to the sensor 6 via a bias resistor 17 . Also, as in Figure 2, resistance 28.29.31
The reference potential es and the first . second comparison potential e8,
I got ei5.

The positive input terminal of the operational amplifier 21 is inputted with a resistor 27 and the voltage-divided type ('LED') of the sensor 6, and the negative input terminal is inputted with the reference potential es via the resistor 22. The output ea' is ea'=e
O'+(es-eO/) (1+-!-Shoichikuko-) 0222 From the above, eO' and ea' change in proportion. Therefore, as the electromotive force ei increases, ea' also increases, so the second
The figure shows potential e8. The level of e15 is reversed.

Also, due to the current 16, the electromotive force of the sensor 6 is ei+R
i.is, and the configuration is such that a certain level of output potential can be obtained even in the Z region of FIG.

Furthermore, since the internal resistance Ri of the sensor has a negative temperature coefficient, if the temperature of the sensor 6 is low before ignition, R1-1a1
It becomes a large value of 0 to several 100 MQ, and when the flame is ignited and the sensor temperature is 300 to 400'CK, it becomes 1(i
-Decreases to several Kz. Therefore, the potential eO' becomes as shown in FIG. The horizontal axis shows time and the vertical axis shows e O/. Before ignition, as mentioned above, the temperature of sensor 6 is low and Hi means resistance 27.
Since the voltage is also a sufficiently large value, its eo' is approximately at the same potential as the power supply 16. When ignited at time to, Ri
decreases, and eO' also decreases accordingly. When the flame burns stably, Ri is determined by the temperature at that time.
It becomes stable at the value of the product of IS and the sum of ei. Here, when ei increases due to a decrease in λ as shown in FIG. 3, eo' increases, and when ei decreases due to an increase in λ, eO' decreases and the output ea
When ' is removed from the potentials e8 and 01, the comparator circuits 9 and 14 operate as in FIG. 2, and the valve 13 is closed.

FIG. 8 is a system diagram showing another embodiment, in which a temperature detection circuit 31 is included in the safety circuit 10, and the safety circuit 10 is configured not to operate when the temperature of the sensor 6 is low based on this signal. Further, the temperature signal of the temperature detection circuit 32 is
The configuration is such that a change in the internal resistance Ri of the sensor 6 explained in FIGS. 7 and 7 is detected.

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 eO' of the resistor 27 and the sensor 6 is determined by the operational amplifier 21.
At the same time, it is input to the positive input terminal of the comparator 33 (consisting of an operational amplifier) of the temperature detection circuit 32. Further, the negative input terminal of the comparator 33 is connected to the divided voltage e of the resistor 34.35.
T1 (first temperature setting value) is input. The output is connected to the base of the transistor 26 through a diode 36 and a resistor 37. As mentioned above, in the circuit shown in FIG. 6, the potential eO' remains high until the temperature of the sensor 6 rises after ignition, as shown in the characteristics shown in FIG. Something happened. For this reason, there is a method of operating a timer after ignition to kill the operation of the mmJ safety circuit for a certain period of time. However, in this method, variations in the temperature rise time of the sensor 6 are a problem, so it is necessary to set a long timer time for safety.

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.

(Note that e8' and ei5 in Fig. 7 are values obtained by converting e8°ei5 in Fig. 6 to correspond to the input potential eQ' with the gain of the amplifier circuit 7.) In order to solve the above problems, the sensor 6 internal resistance Ri
The safety circuit 1o is configured to be operable after the temperature of the sensor 6 reaches a certain temperature or higher by utilizing the temperature characteristics of the sensor. The partial voltage 'magnetic potential e O/ 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 eT10' and the output becomes high level. For this reason, the diode 36. Since the base potential is supplied to the transistor 26 through 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 rises, Ri decreases and eO/ also decreases as shown in FIG. As a result, when the potential eT1≦Ro', the output of the comparator 33 becomes low level, and the diode 36 becomes reverse biased and is turned on and off according to the output level of the transistor ViNOR gate 24. As described above, since the temperature of the sensor 6 itself is measured, the sensor 6 operates at the optimal timing even if there are variations in the heating time. In addition, in Fig. 9, the signal of the temperature detection circuit can be detected by e □ /, but it is also possible to detect it by ea' as shown by the broken line, and it is also possible to provide another temperature sensor. .

Although omitted in Fig. 9, in addition to this configuration, a timer circuit that operates dry after the ignition operation is installed, and if the temperature of the sensor 6 does not rise after a certain period of time, a circuit is added that deems the ignition to be non-ignition and stops the valve 13. is also publicly known.

FIG. 10 is a system diagram showing another embodiment, which includes 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 even if the burner 11 is not ignited, a normal level of electromotive force ei will be generated, 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 and screen for driving the ignition signal circuit 38 shown in FIG. 10, a third set temperature for detecting misfire of the burner 11 and closing the valve 13 is also provided.

A second set temperature eT2 and a third set temperature eT3 are provided by resistors 39, 40.41.0eT2 and eT3 are connected to the negative input terminal of the comparator circuit 42 and the positive input terminal of the comparator circuit 43, respectively. . Also, the temperature signal e
O/ is input to comparators 42 and 43 as shown in the figure, comparator 43 constitutes a misfire detection circuit, and its output is connected to diode 44.
The emitter of the transistor 26 is connected to the power source 1 through the diode 45.
It is grounded to one terminal of 6. 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 eO'
Since eT3<eT2, the output of the comparator 43 is
・The diode 44 is reversely biased, and the transistor 26 operates according to the output of the NOR gate 24. The output comparator 42 has 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 eO' increases.

As a result, the stain level e·r3 becomes eO'<eT2, and the comparator 43 becomes a low output. From the above, the base potential of the transistor 260 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.

When the temperature of the sensor 6 further decreases and the potential becomes higher than rs, the comparator 42 becomes a high output and drives the ignition signal circuit.As a result, although not shown, the igniter operates and the burner is turned on. 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.

It is also possible to add the configuration explained in FIG. 9 in addition to the configuration in FIG. 11, and the comparators 42 and 43 in FIG.
It is also easy to put each of them into practical use independently.

Although the present embodiment has been described using a gas burner as an example, the same thing can be said 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.

As described in detail, 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 using the above-mentioned configuration to flow the bias current, 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 Malfunctions can be prevented by starting the operation after the temperature rises to 1 minute.

Similarly, by configuring the engine to restart the re-ignition operation after the sensor temperature has cooled down to 7 minutes, reliability has been improved by eliminating the possibility of erroneous detection due to catalytic combustion of unburned gas in 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 the drawing]

Fig. 1 is a control system diagram showing one embodiment of the present invention;
The figure is a specific circuit diagram of the same, Figure 3 is a characteristic diagram of the zirconia oxygen concentration sensor, Figures 4 and 5 are diagrams explaining the operation of the circuit in Figure 2, and Figure 6 is a circuit diagram showing another example of a specific circuit. , FIG. 7 is an explanatory diagram of its operation, FIG. 8 is a system diagram showing another embodiment, FIG. 9 is a specific circuit diagram thereof, FIG. 10 is a system diagram showing still another embodiment, and FIG. 11 is a system diagram showing another embodiment. Its specific circuit diagram, FIG. 12, is a sectional view showing an example of a zirconia oxygen concentration sensor.
FIG. 3 is an explanatory diagram of its operation, and FIG. 14 is a block diagram showing a conventional control system. 6... Combustion detection sensor, 8. e8...
First setting level, 9...First comparison circuit, 1
o...Safety circuit, 14...Second comparison circuit, 15, e15...Second setting level control 16...External power supply, 27... ...Nokuias resistance (bias circuit), 32...Temperature detection circuit,
38...Ignition signal circuit, 43...Comparator (misfire detection circuit), "TI...First set temperature,
eT2...Second set temperature, eT3...
・Third setting salinity. Name of agent: Patent attorney Toshio Nakao and 1 other person No. 1
Figure 〆/ Figure 3 with Figure 4 Figure 5 Figure 6 Figure 7 Figure 0 ime

Claims (5)

[Claims] (1) A combustion detection sensor that detects the combustion state of the burner and generates an electromotive force, and a first comparison that detects that the output of the combustion detection sensor has exceeded a predetermined/ζ first setting level. circuit, and a second comparison circuit that detects that the level has become below a second set level, and detects the output of either of the first and second comparison circuits and generates a signal to stop combustion. Incomplete combustion detection device with a safety circuit that outputs. (2) The incomplete combustion detection device according to claim 1, wherein the combustion detection sensor has a bias circuit for supplying a stain current from an external power source. (3) The safety circuit has a temperature detection circuit that detects the temperature of the combustion detection sensor, and is configured to operate when the temperature of the combustion detection sensor is equal to or higher than a first set temperature according to the output of the temperature detection circuit. An incomplete combustion detection device according to claim 2. (4) The safety circuit has a temperature detection circuit that detects the temperature of the combustion detection sensor, and starts combustion of the burner when the temperature of the combustion detection sensor is below a second set temperature based on the output of the temperature detection circuit. The incomplete combustion detection device according to claim 2, wherein the incomplete combustion detection device is configured to include an ignition signal circuit that outputs a signal. (5) The safety circuit includes a temperature detection circuit that detects the temperature of the combustion detection sensor, and stops 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. An incomplete combustion detection device according to claim 2, 3, or 4, which is configured to include a misfire detection circuit that outputs a signal.