JPS6249532B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a combustion control circuit that allows stable combustion to occur in a combustor.

For example, in order to achieve stable combustion in an oil gasification type combustor, the mixing ratio between the amount of oil gas and the combustion air must be maintained at a certain ratio.
For this reason, in the past, the combustion air amount was kept constant by controlling the rotation speed of the blower for blowing combustion air by feedback, and on the other hand, the flame state was detected by a flame sensor and the detected output was The system controlled an electromagnetic pump that supplied oil to the flame, and varied the amount of oil supplied depending on the flame conditions to ensure stable combustion. However, in this case, so-called breathing combustion (pulsation combustion) occurs because the oil is supplied by the pump.

An object of the present invention is to provide a novel combustion control device for maintaining combustion conditions.

Another object of the present invention is to provide a novel combustion control device that prevents the above-mentioned pulsation and does not cause any inconvenience during ignition.

A further object of the invention is to realize the above-described device with a simple circuit.

In short, the present invention is a blower whose rotational speed is stabilized (speed controlled), which is further controlled by the output of a flame sensor, and the amount of combustion air is controlled according to the state of the flame. This is realized by controlling the reference voltage source, which is compared with the detection voltage of the blower rotation speed of the blower rotation speed stabilization control circuit, using the flame sensor output.

That is, the present invention includes a blower rotation speed detector;
A frequency-voltage converter that converts this detection output into a voltage corresponding to the rotation speed, a reference voltage source, a voltage comparison circuit that compares the voltage corresponding to the rotation speed and the reference voltage, and a comparison of the voltage comparison circuit. Combustion air is supplied by the blower, which is controlled so that the rotation speed is stabilized by feedback of the rotation speed of the blower, using a motor control circuit that controls the driving voltage of the blower motor according to the output. A combustor configured to do so includes a flame sensor provided in the combustion section to detect a flame state, a waveform shaping circuit that generates a signal with a duty ratio according to the output of the flame sensor, and an output of the waveform shaping circuit. and an optical coupling element that supplies a signal as a control signal to the reference voltage source, whereby the output of the flame sensor controls the reference voltage of the reference voltage source to control the amount of combustion air according to the flame condition. This is a combustion control device designed to

Hereinafter, the present invention will be explained in detail with reference to embodiments shown in the drawings.

FIG. 1 is a block circuit diagram showing an apparatus according to an embodiment of the present invention, in which a certain amount of oil is continuously supplied from an oil tank 3 to a burner section 2 of a combustor 1 by an electromagnetic pump 4, and a blower 5 provides a constant amount of combustion air to maintain constant combustion.
The blower motor 6 of the blower 5 includes a motor drive circuit 7, a rotation speed detector (for example, a generator) 8,
A frequency-voltage conversion circuit 9 that converts the rotation speed detector output signal frequency into a voltage signal, a reference voltage source 10, a ratio comparison between the output of the frequency-voltage conversion circuit 9 and the reference voltage source 10, and the comparison output drives the motor drive circuit 7. A constant rotation is maintained by the controlling motor speed control system. In addition, to select the combustion state of the combustor,
This is done by synchronously changing the amount of oil fed by the electromagnetic pump 4 and the set voltage of the reference voltage source.

Now, in such a combustor, during combustion,
Combustion may become unstable due to external factors. In order to prevent this, in this embodiment, a flame sensor (for example, a flame rod) 12 for detecting the state of the flame is provided in the burner section 2 of the combustor, and the state of the flame is detected as an electrical signal. This detection output is waveform-shaped and amplified through a waveform shaping circuit 13 and an amplification circuit 14.

FIG. 2 is a diagram showing the relationship between the output of the amplifying circuit 14 and the state of the flame in the burner section. That is, when the combustion in the burner section 2 is in a normal combustion state, when the amount of air increases relative to the fuel gas, the flame becomes blown, causing so-called lift combustion, and at this time, the expansion circuit 14
The output voltage of will be lower. Conversely, when the amount of air decreases relative to the fuel gas, the flame becomes red and incomplete combustion occurs, and at this time the output voltage increases. Now, let V _O be the output voltage during normal combustion, and V O be the specific output voltage when burning with a red flame.
Let _H be the specific voltage during lift combustion and V _L be the specific voltage during lift combustion.

Returning to FIG. 1, the triangular wave generating circuit 15 is a triangular wave generating circuit whose maximum voltage is the aforementioned voltage V _H and whose minimum voltage is V _L , and its output waveform is shown in FIG.

The output of the amplifying circuit 14 is compared with the output of the triangular wave generating circuit 15 by a voltage comparator 16, and the output is applied to an optical coupling element 17. The output waveform of the optical coupling element 17 is as shown in FIG. That is, when the output of the amplifier circuit 14 is below V _L , the voltage becomes zero as shown in FIG. 4a, and when the output of the amplifier circuit 14 is between V _L and V _H , the voltage becomes zero as shown in FIG. As shown, it becomes a rectangular wave having the same frequency as the triangular wave, and the width of the rectangular wave becomes wider as the output voltage of the amplifier circuit 14 is higher. When the output voltage of the amplification circuit 14 is higher than _VH , it becomes a constant DC voltage signal as shown in FIG. 4c.

The output of the optical coupling element 17 is applied to the reference voltage source 10 to control the set voltage of the reference voltage source 10.

Figure 5 shows a specific circuit of the control system in Figure 1.
Each block in FIG. 1 is indicated by a dotted line block designated by the same reference numeral. In this circuit, the optical coupling element 1
The output side of 7 is connected across the reference voltage setting resistor _R3 , and the capacitor C is for smoothing the rectangular wave. As a result, the output voltage of the amplification circuit 14, that is, the voltage across the resistor _R3 changes according to changes in the flame condition, so the speed of the motor 6 of the blower 5 is controlled, and the combustion The amount of air supplied is controlled.

Now, when the amount of supplied air increases relative to the supplied fuel and lift combustion occurs and the output voltage of the amplifying circuit 14 becomes less than V _L , the triangular wave voltage of the triangular wave generating circuit 15 and
A voltage comparison circuit 16 that compares the voltage of the amplifier circuit 14
The output voltage is a constant high voltage. Therefore, the output side transistor of the optocoupler 17 maintains an on state, thereby controlling the control terminal A of the reference voltage source 10.
-B, that is, the resistor _R3 is short-circuited, and the reference voltage decreases. As a result, the voltage corresponding to the rotation speed obtained by converting the output of the rotation speed detector 8 into a voltage using the frequency-voltage converter 9 and the reference voltage compared with the voltage comparison circuit 11 decreases, so that the output of the voltage comparison circuit 11 decreases. The voltage will drop. Therefore, the drive voltage of the motor drive circuit 7 to the motor 6 decreases, the speed of the motor 6 decreases, the amount of supplied air decreases, and normal combustion returns. On the other hand, when the amount of supplied air decreases relative to the supplied fuel and incomplete combustion occurs, and the output voltage of the amplification circuit 14 exceeds _VH , the voltage applied from the optical coupling element 17 to the reference voltage source 10 remains constant. It becomes a DC voltage,
As a result, the reference voltage of the reference voltage source 10 increases,
The speed of the motor 6 is increased by the motor drive circuit 7, the amount of supplied air is increased, and normal combustion is restored. Further, when the amount of supplied air decreases or increases with respect to the supplied fuel, and the output voltage of the amplifier circuit 14 increases or decreases from V _O in the range of V _L and V _H , the optical coupling element 1
As the pulse width of the square wave applied from 7 to the reference voltage source 10 increases or decreases, the smoothed voltage increases or decreases and thus the reference voltage of the reference voltage source 10 increases or decreases and thus the motor The speed of 6 is increased or decreased, and the amount of supplied air is increased or decreased to maintain normal combustion.

In the circuit shown in FIG. 5, a frame rod is used as the frame sensor, and a DC voltage is applied to the frame rod. Conventionally, alternating current was applied to the flame rod, but by applying direct current, a direct current flame voltage signal with less pulsation can be obtained.

Further, in the circuit shown in FIG. 5, the motor drive circuit 7 of the motor control circuit is a circuit that controls the amplitude of the current applied to the motor, but a circuit that controls the phase of the current applied to the motor may also be used.

According to the above-mentioned embodiment, it is possible to maintain a stable combustion state by controlling the amount of supplied air according to the state of the flame during combustion, but the situation at the time of ignition is different from that during combustion, and the ignition Even at times,
If the amount of supplied air is controlled depending on the above-mentioned flame condition, there is a possibility that ignition will not be possible. Therefore, at the time of ignition, it is desirable to suppress control of the amount of supplied air depending on the flame state. That is, at the time of ignition, the output of the comparator 16 may be cut off for a period of time until it completely ignites and enters stable combustion (this varies depending on the combustion method, etc.). A block diagram of such an embodiment is shown in FIG.

Referring to FIG. 6, parts similar to those in FIG. 1 are designated by the same reference numbers as in FIG. 1, and a description thereof will be omitted. The output of the amplifier circuit 14 is supplied to a voltage comparator 18 separate from the voltage comparator 16 and compared with the voltage of a reference voltage source 19. This reference voltage is set to be slightly smaller than the output voltage of the amplifier circuit 14 when ignition is completed. As a result, when ignition is complete, a voltage signal is generated at the output of the voltage comparator. This voltage signal is given to the timer 20, and the timer 20
Start. The timer 20 is an on-delay timer that generates an output signal when a set time has elapsed after being activated. The output of timer 20 is applied to signal discrimination circuit 21. The signal discrimination circuit 21 is supplied with the output of the voltage comparator 16 and the output of the variable duty square wave generation circuit 22, and selects one of the two outputs according to the signal from the timer 20, and selects one of the two outputs according to the signal from the timer 20. Combine to 17. That is, when there is no output signal from the timer 20, the output of the square wave generation circuit 22 is connected to the optical coupling element 17.
and when there is an output signal from the timer 20, the output of the voltage comparator 16 is supplied to the optical coupling element 17.

With such a configuration, the output of the voltage comparator 16 will not be supplied to the reference voltage source of the motor control system until a certain period of time (i.e., the timer set time) has elapsed after ignition. Control of air volume based on flame conditions is suppressed. Note that the timer setting time may be set to a time (for example, 3 minutes) until ignition and a stable combustion state are achieved.

Note that in FIG. 6, the triangular wave generating circuit 15 is realized not as an oscillator but as a waveform converting circuit that converts the output of the square wave generating circuit 22 into a triangular wave.

In this embodiment, the output of the square wave generation circuit 22 is selected by the signal discrimination circuit 21 until the timer 20 starts to generate an output signal, that is, until the set time of the timer has elapsed. The reference voltage source 10 of the motor speed control system is supplied through the reference voltage source 10 in order to maintain the amount of air supplied at the time of ignition at an appropriate value. That is,
If such a configuration is not adopted and the output of the voltage comparator 16 is simply cut off from being supplied to the optical coupling element by controlling the timer 20, in that case, the output of the voltage comparator 16 is not optically coupled to the reference voltage source 10. This is because the voltage input from the element 17 is zero, which is the same as in the lift combustion described above, and the motor rotation speed is low, resulting in too little air supply, which is disadvantageous. If there is no such inconvenience, the square wave generation circuit 22 is not necessary, and the signal discrimination circuit 21 may be simply used as a switching circuit to turn on and off the transmission of the output of the voltage comparator 16.

In this embodiment, as can be understood from the explanation regarding FIGS. 1 to 5, the set voltage of the reference voltage source 10 of the motor control system is low, and the rotation of the motor 6 based on that voltage is normal. A sufficient amount of air for combustion cannot be supplied, and during normal combustion, the output rectangular wave of the voltage comparator 16 is added, resulting in a high reference voltage. Therefore, the set voltage of the reference voltage source 10 is selected to a value corresponding to the motor rotation speed that provides the amount of air necessary for normal combustion, and the way in which the output of the voltage comparator circuit 16 is applied to the reference voltage is determined by the amplifier circuit 10. When the output is greater than _VO , a voltage corresponding to the difference may be added to the set voltage, and when the output is smaller than _VO , the voltage corresponding to the difference may be subtracted from the set voltage. In this case, the amount of air for normal combustion will be supplied by simply cutting off the output of the comparison circuit 16 at the time of ignition.

The reason why the square wave generation circuit is of a variable duty type is that it is possible to adjust the appropriate amount of air at the time of ignition for each combustor.

The signal discrimination circuit 21 may be any circuit as long as it selects either the output of the voltage comparison circuit 16 or the output of the square wave generation circuit 22 according to the output from the timer 20. , here, an example configured with gate circuits 23 and 24 is shown. The gate circuit 23 receives the output of the timer 20 via an inverter 25 and receives the square wave 2.
2 is input, and when the output signal from the inverter 25 is on, a square wave 22 is output. On the other hand, the gate circuit 24 receives the output of the timer 20 and the output of the voltage comparator 16, and outputs the output of the voltage comparator 16 when the output of the timer 20 is on. It is easily understood that the inverter 25 can be omitted if the timer 20 has two output terminals that generate opposite ON and OFF signals.

Although the invention has been described with reference to specific embodiments, it will be obvious that various designs and modifications may be made within the scope of the invention. The present invention is applicable not only to oil gasification type combustors but also to combustion control devices for various combustors such as pot oil combustors.

According to the present invention, a reference voltage to be compared with a detected rotation speed signal of a blower motor in a blower motor speed control device for feeding back the rotation speed of the blower motor to stably control the rotation speed is applied to the combustion section. Since it is controlled by the output of the installed flame sensor, the amount of combustion air supplied by the blower can be controlled according to the combustion state, and the amount of combustion air supplied can be maintained unchanged in stable combustion conditions. There are advantages. Furthermore, by disconnecting the output of the flame sensor from the reference voltage source for a certain period of time during ignition, it is possible to supply sufficient air for ignition.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing an apparatus according to an embodiment of the present invention, FIG. 2 is a diagram showing the relationship between the output voltage of the amplifier circuit 14 of FIG. 1 and the state of the flame in the combustor, and FIG. 4 is a diagram showing the output waveform of the triangular wave generation circuit 15 in FIG. 1, FIG. 4 is a diagram showing the output waveform of the optical coupling element 17 in FIG. A specific example circuit diagram of the control system of the device shown in Figure 1, No. 6
The figure is a block diagram showing another embodiment of the invention. DESCRIPTION OF SYMBOLS 1... Combustor, 2... Burner part, 3... Oil tank, 4... Electromagnetic pump, 5... Blower, 6... Motor, 7... Motor drive circuit, 8... Rotation speed detector, 9
...Frequency voltage converter, 10... Reference voltage source, 11...
Voltage comparison circuit, 12... Frame sensor, 13... Waveform shaping circuit, 14... Amplification circuit, 15... Triangular wave generation circuit, 16... Voltage comparison circuit, 17... Optical coupling element,
18... Voltage comparison circuit, 19... Reference voltage source, 20...
Timer, 21...Signal discrimination circuit, 22...Square wave generation circuit, 23, 24...Gate circuit, 25...Inverter.

Claims (1)

[Claims] 1. A blower rotation speed detector, a frequency-voltage converter that converts the detected output into a voltage corresponding to the rotation speed, a reference voltage source, a voltage corresponding to the rotation speed, and a reference voltage. and a motor control circuit configured to control the drive voltage of the blower motor according to the comparison output of the voltage comparison circuit, feedback the rotation speed of the blower to increase the rotation speed. In a combustor that supplies combustion air using a blower that is controlled to be stable, a flame sensor is provided in the combustion section to detect the flame state, and a duty ratio is adjusted according to the output of the flame sensor. comprising a waveform shaping circuit that generates a signal, and an optical coupling element that supplies an output signal of the waveform shaping circuit to the reference voltage source as a control signal,
Thereby, the combustion control device controls the reference voltage of the reference voltage source based on the output of the flame sensor to control the amount of combustion air according to the flame condition. 2. In the combustion control device according to claim 1, the waveform shaping circuit includes a waveform shaping amplification circuit that amplifies the flame sensor output, and a triangular wave generation circuit that generates triangular waves of predetermined positive maximum and minimum voltages. A combustion control device comprising: a voltage comparison circuit that compares voltages between the output of the waveform shaping amplifier circuit and the output of the triangular wave generation circuit. 3. The combustion control device according to claim 1, wherein the flame sensor comprises a flame rod, and a direct current is applied to the flame rod to obtain a direct current signal from the flame rod. 4. A blower rotation speed detector, a frequency-voltage converter that converts this detection output into a voltage corresponding to the rotation speed, a reference voltage source, and a voltage comparison that compares the voltage corresponding to the rotation speed with the reference voltage. and a motor control circuit configured to control the drive voltage of the blower motor according to the comparison output of the voltage comparison circuit, the rotation speed of the blower is controlled so as to feed back and stabilize the rotation speed. In a combustor that supplies combustion air with a blower, there is a flame sensor installed in the combustion section to detect the flame state, and a waveform shaping device that generates a signal with a duty ratio according to the output of the flame sensor. a timer activated by the generation of the output of the flame sensor; a gate circuit that closes during the set time of the timer; and a gate circuit that connects the output signal of the waveform shaping circuit to the reference voltage source while the gate circuit is open. and an optical coupling element that supplies the control signal to the
Thereby, the combustion control device controls the reference voltage of the reference voltage source by the output of the flame sensor after the elapse of the set time of the timer immediately after ignition, and controls the amount of air for combustion according to the flame state. 5. The combustion control device according to claim 4, wherein the flame sensor comprises a flame rod, and a direct current is applied to the flame rod to obtain a direct current signal from the flame rod. 6 A blower rotation speed detector, a frequency-voltage converter that converts this detection output into a voltage corresponding to the rotation speed, a reference voltage source, and a voltage comparison that compares the voltage corresponding to the rotation speed with the reference voltage. and a motor control circuit configured to control the drive voltage of the blower motor in accordance with the comparison output of the voltage comparison circuit, the rotation speed of the blower is controlled to feed back and stabilize the rotation speed. In a combustor that supplies combustion air with a blower, there is a flame sensor installed in the combustion section to detect the flame state, and a waveform shaping device that generates a signal with a duty ratio according to the output of the flame sensor. a circuit, a timer activated by the generation of the output of the flame sensor, a first gate that is closed during a set time of the timer, a second gate that is open during a set time of the timer, and an adjustable reference signal source. and a light source that supplies the output of the waveform shaping circuit as a control signal to the reference voltage source while the first gate is open, and the output of the reference signal source as a control signal while the second gate is open. The coupling element controls the reference voltage of the reference voltage source using the output of the flame sensor to control the amount of combustion air according to the flame condition, and also controls the amount of combustion air for a certain period of time during ignition. A combustion control device that provides constant control. 7. In the combustion control device according to claim 6, the waveform shaping circuit includes a waveform shaping amplifier circuit that amplifies the output of the flame sensor, a variable duty square wave generation circuit, and a predetermined positive maximum and minimum voltage generator. a triangular wave generation circuit that generates a triangular wave; a voltage comparison circuit that compares voltages between the output of the waveform shaping amplifier circuit and the output of the triangular wave generation circuit; the timer; and the first voltage comparison circuit that receives the output of the voltage comparison circuit as input.
A combustion control device comprising: a gate; and a second gate which receives the square wave generating circuit as an input. 8. The combustion control device according to claim 6, wherein the flame sensor comprises a flame rod, and a direct current is applied to the flame rod to obtain a direct current signal from the flame rod.