JPH0138210B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a combustor using an oxygen concentration cell type sensor for detecting incomplete combustion.

Configuration of Conventional Example and Problems Therein Generally, an oxygen concentration cell type sensor, such as a zirconia sensor, is known as a sensor for detecting incomplete combustion, and has been put into practical use in a combustor using gas as fuel. This zirconia sensor is used in a high-temperature atmosphere as shown in Figure 1.
As shown in FIG. 2, the electromotive force suddenly changes at the point where M≦1 (referred to as the value M≦1), and its internal resistance decreases as the temperature rises. Therefore, conventionally, it has also been used as a sensor that detects ignition by utilizing this temperature characteristic. FIG. 3 shows an example of this detection circuit. 1 is a zirconia sensor, which is equivalent to an electromotive force e _i and an internal resistance R _i . A series resistor 2 is connected in series with the zirconia sensor 1, and is connected to the DC power supply 3. a and b indicate detection output terminals.

Before combustion, the internal resistance R _i is several 100 MΩ, which is sufficiently larger than the series resistance 2, and the output potential is almost the same as that of the DC power supply 3. When the burner burns, the internal resistance R _i decreases as the temperature rises, and becomes a value sufficiently smaller than the series resistance 2.
The divided potential due to R _i drops to almost zero as shown in FIG. 1A. Therefore, by detecting this voltage drop, it is possible to detect that the burner has burned.

As described above, if the oxygen concentration battery type sensor is used, it is possible to detect the ignition of the burner. However, in the past, ignition of this burner was carried out within a normal range where the air-fuel ratio M was greater than or approximately equal to 1 (hereinafter referred to as the normal M value), which often diluted the gas concentration and caused ignition errors. .

This ignition error can be resolved by configuring the engine to ignite in a range where the air-fuel ratio is less than 1 (hereinafter referred to as low M value). However, when ignited at this low M value, the combustion exhaust gas generated contains a large amount of carbon monoxide, which is harmful to the human body, so it is not very preferable, and it is necessary to switch to normal M value combustion at the same time as ignition. This M value switching can be done by detecting ignition with a sensor, but even if ignition occurs at a low M value, it will be in a low M value state, that is, an incomplete combustion state, so the sensor output will be the same as the conventional one. Therefore, it was extremely difficult to detect ignition at a low M value using a sensor for detecting incomplete combustion. In other words, when ignition is performed at a low M value as shown in Figure 4, the output of the sensor tends to drop as in the conventional case as shown by the broken line, but an incomplete combustion state is detected and the sensor's own electromotive force is generated. Initially, as shown by the solid line, there is no change in the output after the burner ignites, which offsets the output drop, making it impossible to detect whether the burner is ignited or misfired. Therefore, it has been difficult to put ignition into practical use at this low M value.

Purpose of the Invention The present invention was made in view of both of the above problems, and aims to improve ignition performance and ensure ignition detection.

Structure of the Invention In order to achieve the above object, the present invention applies a voltage sufficiently larger than the electromotive force of the sensor itself to the oxygen concentration battery sensor that detects the combustion state of the burner, and ignites it at a low M value. It is something. The ignition detection circuit detects that the sensor output reaches a predetermined value, and at the same time detects the ignition of the burner, the low M value is switched to the normal M value.

DESCRIPTION OF EMBODIMENTS One embodiment will be described below with reference to the drawings. Figure 5 shows an example of a combustion device using petroleum as fuel.
11 is a fuel pipe, 12 is a vaporization tube that vaporizes the fuel from this fuel pipe 11, and 13 is this vaporization tube 1.
1 is a heater for preheating 2; 14 is a blower pipe that supplies combustion air into the vaporizing cylinder 13; 15 is a blower;
6 is a fuel pump, 17 is a burner cylinder provided above the vaporizing cylinder, 18 is a through hole formed in this burner cylinder 17,
19 is an exhaust pipe provided so as to surround the outer periphery of the vaporizer pipe 12; 20 is an exhaust port; 21 is a combustion chamber formed between the heat-resistant heat transmitting pipe 21 provided on the exhaust pipe 19 and the burner pipe 17; 23 is a lid that covers the burner cylinder 17 and the heat-resistant heat transmitting cylinder 21, 24 is an igniter attached to the lid 23, and 25 is a sensor for detecting incomplete combustion, which is also attached to the lid 23.

The sensor 25 is made of zirconia and is an oxygen concentration battery type sensor that generates an electromotive force depending on changes in oxygen concentration, and is designed to detect burner ignition and incomplete combustion.

The specific circuit configuration for detecting ignition and incomplete combustion of the burner will be explained below using FIG. 6. Reference numeral 26 is an AC power supply,
The power transformer 29 of the stabilized power supply circuit 28 via
is applied to. The stabilized power supply circuit 28 rectifies the output of the transformer 29 with a diode bridge 30, smoothes it and makes it constant voltage with a resistor 31, a capacitor 32, and a voltage regulator diode 33, and supplies DC power to the sensor 25 and other circuits. There is. The sensor 25 is connected to a power supply circuit 28 through a series resistor 34, and its midpoint potential a outputs a signal to an ignition detection circuit 35 and a combustion state detection circuit 36. The potential a is input to the positive input terminal of the comparator 37 of the ignition detection circuit 35, and the resistor 38, 3 input to the negative input terminal.
9 to obtain an output c. The output c of the comparator 37 is connected to the power supply circuit 28 through the coil 40 of the relay _Ry2 . The combustion state detection circuit 36 compares the output potential a of the sensor 25 with the potentials d and e divided by the resistors 45, 46, and 47 using comparators 43 and 44, respectively, forming a width comparator circuit. The output f of the comparators 43 and 44 is pulled up by a resistor 48 and is also input to an inverter circuit 49 to obtain its output potential g. A resistor 50 represents a pull-up resistor of the inverter circuit 49. Reference numeral 51 indicates a preheating circuit of the heater 13 for preheating the vaporizer cylinder (FIG. 5). The resistor 52 and the divided potential h of the temperature sensor 53 of the vaporizer cylinder 12 (here, a negative temperature sensitive resistance element is used), and the resistors 54 and 55.
A comparator 56 compares the divided potentials i to obtain an output potential j. The output j of the comparator 56 is connected to the power supply circuit 28 through the coil 57 of the relay _Ry3 and is also input to the inverter circuit 58. The output of the inverter circuit 58 is connected to the resistor 60 of the timer circuit 59 and the divided potential k of the capacitor 61, and the timer circuit 59 compares the potential k with the divided potential l of the resistors 62 and 63 using a comparator 64, and outputs m is connected to the coil 65 of the relay R _y1 and to the anode of the diode 66. The cathode of the diode 66 is connected to the output potential g of the combustion state detection circuit 36.

Further, an ignition circuit 67 is connected to the AC power source 26. The ignition circuit 67 includes an operation switch 27, a stop switch 68 connected in parallel with the operation switch 27, and a relay.
Power is supplied by a series circuit of contacts 69 of R _y1 . The igniter 24 is connected to the first contact 70 of the relay _Ry2 .
It is connected to the NC contact, and the NO contact is connected to a motor 71 for driving a hot air blowing fan (not shown). The fuel pump 16 and the combustion blower 15 are connected to the contacts 72 of the relay _Ry3 . Here, the combustion blower 15 changes the air flow rate from Hi (high) to Lo (low).
The switching is enabled by the second contact 70' of the relay _Ry2 . Reference numeral 13 indicates a heater for preheating the vaporizer cylinder 12. Comparator 3 explained here
7, 43, 44, 56, and 64 are generally known input open collector output comparators, and inverter circuits 49 and 58 also use open collector output inverters.

Next, we will explain the operation. When the operation switch 27 is pressed, the heater 13 and the power supply circuit 28 are energized, and power is supplied to the sensor 25, the ignition detection circuit 35, the combustion state detection circuit 36, the preheating circuit 51, and the timer circuit 59.

Initially, the ambient temperature of the sensor is equal to room temperature, so the internal resistance R _i becomes a large impedance of several 100 MΩ.
This is a sufficiently large value compared to the series resistance 34. Therefore, the divided potential a is almost equal to the potential of the power supply circuit 28 and the reference potential b, so that a>b, and the output c of the comparator 37 becomes a Hi (high) output. Comparator 37
As mentioned above, since it is an open collector output, the output Hi is equal to open, and the coil 40 of the relay _Ry2 is not energized. Therefore, the contacts 70, 70'
Both NC contacts are maintained, and the igniter 24 is energized.

Further, in the preheating circuit 51, since the initial temperature of the vaporization cylinder is low, the resistance value of the temperature sensor 53 is large, the potential h>i, and the output j of the comparator 56 is Hi, and the relay R _y3
57 is also not conductive. Therefore, the pump 16 and the blower 15 do not operate. At the same time, the output of the inverter 58 becomes a Lo output, preventing the capacitor 61 of the timer circuit 59 from being charged. Therefore, the potential k becomes almost zero volts, and since the potential k<l, the comparator 64
The output m becomes the Lo output. This causes relay R _y1
is conductive, and even if the operation switch 27 is released, the contact 69
continues to supply power. That is, initially, the heater 13 and the igniter 24 operate to perform preheating.

As the temperature of the vaporizer cylinder increases and the resistance value of the temperature sensor 53 decreases, the potential h decreases and approaches the potential i. Here, the potential i is designed to be equal to the potential h when the temperature of the vaporization cylinder reaches a temperature at which the fuel can be vaporized, and when the potential h≦i, the comparator 56 outputs Lo. Relay _Ry3 becomes conductive. This causes the fuel pump 16 and the blower 15 to operate. Here, since the relay _Ry2 is not operating, the blower 15 has a low air volume, and the air volume is lower than the amount of air necessary for the fuel supplied from the fuel pump 16. In other words, it has a low M value and supplies a rich mixed gas to improve ignition performance.

When the output j of the comparator 56 becomes a Lo output, the inverter 58 becomes a Hi output (open), and the capacitor 61 of the timer circuit 59 begins to be charged via the resistor 60. If the burner does not ignite for some reason, charge the capacitor 61 to increase the potential k≧
When the voltage reaches 1, the comparator 64 becomes a Hi output, energizing the coil 65 of the relay _Ry1 , cutting off the relay contact 69, and stopping the operation.

This timer circuit 59 is the coil 65 of relay R _y1.
If the burner ignites before turning off the power to the burner, the combustion state detection circuit 36 compares and judges the output from the sensor 25 and sends a relay via the diode 66.
The coil 65 of R _y1 continues to be energized to continue combustion. Here, the output from the sensor 25 changes greatly even in low M value ignition. That is, when the burner is ignited, the temperature of the sensor 25 rises and the internal resistance R _i
decreases, and the divided potential a based on the power supply voltage from the power supply circuit 28 decreases. On the other hand, as the temperature of the sensor 25 rises, the sensor 25 itself generates an electromotive force to prevent the partial voltage potential a from decreasing. However, since the electromotive force of this sensor 25 is about 1V at the maximum, the resistance value of the series resistor 34 is adjusted so that the divided potential a created by the internal resistor R _i and the series resistor 34 is initially sufficiently larger than 1V. Once set, the internal resistance will be reduced as shown in Figure 7.
The partial voltage potential due to the decrease in R _i decreases to the potential A of only the electromotive force of the sensor 25 itself. Therefore, if the potential b divided by the resistors 38 and 39 is set to be larger than the potential due to the electromotive force of the sensor 25 itself, the internal resistance R _i of the sensor 25 can be reduced.
When the electromotive force decreases and becomes only the electromotive force of the sensor itself, a≦b holds, and the ignition detection circuit 35 detects ignition. That is, even if ignition occurs in a low M value state, the output of the sensor 25 can be reliably changed to detect ignition. On the other hand, in this way, the ignition detection circuit 35 can detect ignition. On the other hand, when the ignition detection circuit 35 detects ignition in this way, the output c of the comparator 37 becomes the Lo output and energizes the coil 40 of the relay _Ry2 . As a result, the contact 70 switches to the NO side, stops the operation of the igniter 24, drives the blower fan drive motor 71, and discharges warm air into the room. At the same time, the contact 70' of the relay _Ry2 is also switched to the NO side, and the blower 15 is set to Hi air volume. In other words, a combustion air volume suitable for the fuel supplied by the pump 16 is supplied.
The combustion transitions to normal M value state.

When the sensor 25 is further heated in this state, the internal resistance R _i further decreases and becomes a sufficiently small value with respect to the series resistance 34 . As a result, the divided potential a becomes almost zero volts, and only the output of the electromotive force e _i of the sensor 25 remains. At this time, combustion is normal M
Since the state has shifted to the value state, the electromotive force of the sensor 25 is extremely small, that is, it has dropped beyond the above-mentioned point A and is extremely small. The comparators 43 and 44 compare the a potential equal to this electromotive force e _i with the potentials d and e, and the combustion state detection circuit 36 monitors the combustion and stops the combustion if incomplete combustion occurs. Since this is not the gist of the present invention, the explanation will be omitted.

Although the above embodiments are explained using electronic circuits, these combustion sequences can also be easily realized by using programs on a microcomputer, etc. In this case, the circuit configuration is simplified and further Highly accurate control and complex control sequences can also be easily realized. Further, although the blower 15 switches between Hi and Lo air volume depending on the rotational speed of the motor, it is also easy to switch the air volume by using an air path switching method using a damper or the like. Further, although the burner has been described using petroleum as fuel, the same effect can be obtained even if the burner uses gas as fuel.

Effects of the Invention As described above, the combustion device of the present invention has the following effects.

(1) Since the ignition circuit is configured to ignite at a low air-fuel ratio when igniting the burner, it is possible to ignite with a rich air-fuel mixture. Therefore, even under adverse conditions such as low outside air temperature, ignition can be ensured.

(2) When an oxygen concentration battery type sensor ignites, the change in electromotive force is small and it is difficult to detect ignition. However, by providing a power supply circuit that applies voltage from the outside to the sensor, ignition can be detected by temperature changes in the internal resistance of the sensor. becomes detectable.

(3) Additionally, an ignition detection circuit is provided that returns the air-fuel ratio to normal when the burner is ignited, so that normal combustion is restored as soon as the sensor detects ignition, instantly suppressing incomplete combustion due to a low air-fuel ratio. If the burner burns abnormally after this, the abnormal combustion can be detected by the electromotive force of the sensor.

(4) Since the configuration uses changes in the temperature characteristics of the internal resistance and changes in the electromotive force of one sensor for ignition detection and abnormal combustion detection, and uses only the advantageous characteristics of each, each detection is reliable and safe. Highly sexual.
Furthermore, since only one sensor is required, the configuration is simple and reliability is improved.

[Brief explanation of drawings]

Figure 1 is an output characteristic diagram of a conventional oxygen concentration battery type sensor that detects incomplete combustion, Figure 2 is a temperature characteristic diagram of the same sensor, and Figure 3 is a circuit diagram of a conventional incomplete combustion detection and ignition detection device. , FIG. 4 is a characteristic diagram of the sensor output when igniting with a low M value, FIG. 5 is a sectional view of a combustion device in an embodiment of the present invention, FIG. 6 is a circuit diagram of the same, and FIG. 7 is a diagram of the same sensor. FIG. 17... Burner, 25... Sensor, 28... Power supply circuit, 34... Resistor, 36... Ignition detection circuit,
67...Ignition circuit.

Claims (1)

[Claims] 1. A burner that mixes and burns air and fuel, an oxygen concentration cell type sensor using zirconia or the like that detects the combustion state of the burner and generates an electromotive force, and a a power supply circuit that applies a large voltage from the outside; an ignition circuit that ignites the burner at a low air-fuel ratio; and when the output of a sensor obtained by igniting the burner reaches a predetermined value, this is detected as an ignition signal. A combustion device including an ignition detection circuit that switches an air-fuel ratio from a low air-fuel ratio state to a normal air-fuel ratio state.