JP3139394B2 - Combustion control circuit - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a combustion control circuit applied to a boiler or the like.

[0002]

Generally, the opening and closing control of a fuel valve at the time of ignition in a combustion control circuit of a boiler or the like is performed as follows. That is, the microcomputer
After performing pre-purge (scavenging) in the furnace, the fuel valve is opened and a drive signal is sent to the igniter to perform an ignition operation. If the ignition is successful, the flame detection circuit detects the presence of a flame, the microcomputer judges this signal, outputs a signal to the fuel control valve to keep the valve open, and continues combustion. When the presence of a flame is not detected, the microcomputer outputs a close signal to the fuel control valve.

[0003] However, when the microcomputer performs an abnormal operation for some reason, there is no danger that a fuel valve open signal is output even though there is no flame.

[0004]

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and comprises a fuel valve, a fuel valve opening / closing circuit for controlling the opening / closing of the fuel valve, a flame sensor, and an igniter. A microcomputer, a flame detection circuit that inputs an output signal of the flame sensor, and outputs a flame presence signal to the fuel valve opening / closing circuit without passing through the microcomputer, and an OFF signal in the initial state. A timer circuit that starts timing when a timer start signal output from the computer is input and outputs an ON signal to the fuel valve opening / closing circuit during a predetermined time, and an OFF signal after the time has elapsed. The fuel valve opening / closing circuit includes:
The first feature is that the fuel valve is opened when a flame presence signal is output from a flame presence detection circuit or when an ON signal is output from the timer circuit.

According to the first feature, even if the microcomputer performs an unexpected operation due to runaway or the like, and the microcomputer continues to output the timer start signal even though there is no flame, the timer circuit does not operate. Outputs an OFF signal to the fuel valve opening / closing circuit after a predetermined time period, and the flame presence / absence detecting circuit outputs a no-flame signal to the fuel valve opening / closing circuit without going through a microcomputer, so that the fuel valve does not keep opening.

Further, the present invention provides a fuel valve, a fuel valve opening / closing circuit for controlling the opening / closing of the fuel valve, a flame sensor, an igniter, a microcomputer, and an output signal from the flame sensor. A flame presence / absence detection circuit that outputs a flame presence / absence signal to the fuel valve opening / closing circuit without the intervention of a computer, an OFF signal in an initial state, and a timer start signal output from the microcomputer for opening the fuel valve are input. Then, timing is started, an ON signal is output during the first timing time, and an OFF signal is output to the fuel valve opening / closing circuit after the first timing time elapses, and the second timing time is elapsed after the input of the start signal is stopped. A timer circuit for returning to an initial state, wherein the fuel valve opening / closing circuit opens the fuel valve when a flame presence signal is output from the flame presence / absence detection circuit or when the timer circuit outputs an ON signal. A second feature that.

According to a second aspect of the present invention, in the combustion control circuit according to the second aspect, the timer circuit outputs an ON signal when the timer start signal is input, and the second signal is output after the timer start signal is lost . An off-delay timer that keeps the output of the ON time signal and the output signal of this off-delay timer are input, an OFF signal is output in the initial state, an ON signal is output during the first time period, and a first time period is output. O after the lapse
A third feature is that it comprises a differentiating circuit that outputs an FF signal and returns to the initial state by stopping the ON signal of the off-delay timer.

According to the second and third features, the microcomputer performs an unexpected operation due to runaway or the like, and the microcomputer outputs a continuous timer start signal even though there is no flame. Even if a timer start signal having a cycle shorter than the second time is output, the fuel valve opening / closing circuit does not generate a fuel valve open signal, so that safety is ensured.

Further, the present invention relates to the first to third aspects.
A fourth feature is that the timer start signal is used as the igniter drive signal, and the opening and closing of the power supply lines of the fuel valve and the igniter are simultaneously controlled by the outputs of the timer circuit and the flame presence / absence detection circuit.

According to the fourth feature, even when the microcomputer operates abnormally, the safety of driving the fuel valve and the igniter is ensured.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the combustion control circuit according to the present invention include a fuel valve, a fuel valve opening / closing circuit for controlling the opening / closing of the fuel valve, a flame sensor, an igniter, a microcomputer, A flame presence / absence detection circuit that inputs an output signal of the flame sensor and outputs a flame presence / absence signal to the fuel valve opening / closing circuit without passing through the microcomputer;
The FF signal, when a timer start signal for opening the fuel valve output from the microcomputer is input, starts timing, outputs an ON signal during a predetermined time, and outputs an OFF signal after the time has elapsed. A timer circuit for outputting to the fuel valve opening / closing circuit, wherein the fuel valve opening / closing circuit opens the fuel valve when a flame presence signal is output from a flame presence / absence detection circuit, or when the timer circuit outputs an ON signal. And

This embodiment will be described below. The combustion control circuit according to the present embodiment is applied to a combustion control circuit such as a boiler. The fuel valve is a valve that is provided in a fuel supply path for supplying gas or oil to the burner and that is electrically driven to open and close.
The fuel valve opening / closing circuit is provided outside of a microcomputer described later, and is a circuit that opens and closes by controlling energization of the fuel valve, and includes a conduction control element such as a transistor, a relay, and a combination thereof. The flame sensor comprises an ultraviolet discharge tube or a semiconductor type flame sensor. The microcomputer is control means such as a fuel valve and an igniter, and outputs a signal for opening the fuel valve as a timer start signal described later. It is preferable to use an igniter drive signal as the timer start signal. The igniter drive signal is a signal (ignition signal) for driving an ignition circuit for igniting the fuel ejected from the fuel valve. At least while the fuel valve is open for ignition, the igniter drive signal is Output continues. If necessary, the igniter drive signal may be output before the fuel valve opens. The igniter drive signal before the fuel valve opens is referred to as a pre-ignition igniter drive signal (preignition signal).

The flame presence / absence detection circuit inputs the output signal of the flame sensor and outputs a flame presence signal or a flame absence signal to the fuel valve opening / closing circuit without passing through a microcomputer. That is, when the output signal of the flame sensor is equal to or more than a predetermined value,
A flame presence signal is output, and when it becomes equal to or less than a predetermined value, a flame absence signal is output.

Further, the timer circuit outputs a signal to the fuel valve opening / closing circuit. This timer circuit outputs an OFF signal in an initial state, outputs an ON signal during the first time period when the timer start signal is input, and outputs an ON signal during the first time period.
Outputs F signal. The return of the timer circuit to the initial state is performed by, for example, automatically returning to the initial state after a lapse of the second time period from the stop of the input of the timer start signal. However, other methods, for example, a method of returning to an initial state by a flameless signal may be used.

After the first time has elapsed, the timer circuit
The output of the N signal is stopped, that is, the OFF signal is output, and this output state is maintained. Then, after the input of the timer start signal is stopped, after the second clocking time is counted, the timer circuit returns to the initial state and outputs the OFF signal. In this initial state, when a timer start signal is input, the first time measurement is started again, and an ON signal is output during that time.

The timer circuit preferably comprises an off-delay timer and a differentiation circuit. The off-delay timer outputs an ON signal when a timer start signal is input,
The second clock time O after the input of the timer start signal is lost
It is assumed that the output of the N signal is maintained. The differentiating circuit receives the output signal of the off-delay timer and outputs
An FF signal is output, an ON signal is output during the first clocking time, an OFF signal is output after the first clocking time has elapsed, and the initial state is restored by stopping the ON signal of the off delay timer. By doing so, the timer circuit configuration can be simplified and the timer circuit can be configured at low cost.

The fuel valve opening / closing circuit is configured to open the fuel valve when a flame presence signal is output from the flame presence / absence detection circuit or when the ignition control timer circuit outputs an ON signal. This fuel valve opening / closing circuit can be configured to be controlled by the output of a flame presence / absence detection circuit and a timer circuit, and separately from the output of a fuel valve opening signal of a microcomputer. In this case, the microcomputer outputs a valve open signal to the fuel valve opening / closing circuit during the ignition operation independently of the output signal of the flame sensor, and after the ignition operation, the output signal of the flame sensor is equal to or more than a predetermined value, that is, The valve opening signal is also output when it is determined that there is a flame. The fuel valve opening / closing circuit is configured to open the fuel valve when an ON signal as a fuel valve opening signal is output from either the flame detection circuit or the timer circuit, and a fuel opening signal is output from the microcomputer. .

When the timer start signal is an igniter drive signal, the fuel valve control circuit is connected to a fuel system feed line in which the igniter and the fuel valve are connected in parallel. And other relay contact opening / closing means controlled by an igniter drive signal, and the fuel valve is controlled by a fuel valve opening signal output from a microcomputer. Open / close means such as another relay contact is connected.

[0019]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A combustion control circuit according to an embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a principle configuration diagram of the embodiment,
2 and 3 are detailed configuration diagrams of the embodiment, FIG. 4 is a voltage waveform diagram of a main part of the embodiment, and FIGS. 5 and 6 are explanatory diagrams of a first time measurement time and a second time measurement time.

In FIG. 1 to FIG. 3, RY1 is a first control relay for controlling the opening / closing of an electromagnetic opening / closing type fuel valve VQ inserted into the fuel supply pipe of the boiler.
It is connected in series with R1 and a second transistor Tr2 composed of an FET to form an AND circuit. First control relay RY
1 is an igniter I connected in parallel to each other as shown in FIG.
It controls a normally open relay contact r11 inserted into a fuel system feed line LV composed of G and a fuel valve VQ. The first transistor Tr1 generates a first signal for exciting the relay RY1, and the second transistor generates a second signal for exciting the relay RY1. S is a flame sensor made of CdS. An analog output from a connection point between the first resistor R1 and the flame sensor S is converted into a digital signal by an A / D converter H and input to the microcomputer MC. The A / D converter H can be formed integrally with the microcomputer MC.
The microcomputer MC outputs a control signal A from the second output port P2 as shown in FIG. This control signal A is output as an H (high) signal regardless of the output signal of the flame sensor S during the igniter operation period (preignition period and ignition try period), and after the igniter operation is completed, the output of the flame sensor is output. When it is determined that the signal is equal to or greater than a predetermined value, that is, equal to or greater than the level of flame, the signal is output as an H signal, and the other signals are output as L (low) signals. The determination of the presence or absence of the flame is performed according to a processing procedure stored in advance by the microcomputer MC.

The flame presence / absence detection circuit SK includes a flame sensor S and a first resistor R1, a second resistor R2 and a third resistor R3, a potential at a connection point between the flame sensor S and the first resistor R1, a second resistor R
A comparison amplifier CP that compares the potential of the connection point of the second and third resistors R3 and outputs a flame signal when the output signal of the flame sensor S exceeds a predetermined value, and outputs a no-flame signal when the output signal falls below the predetermined value. And a fourth resistor R4.

TM denotes a timer circuit, which is a first output port P for outputting an igniter control signal B of the microcomputer MC.
An off-delay timer TM1 connected to the first delay circuit TM1 and a differentiating circuit TM2 that receives an output of the off-delay timer TM1 and outputs a signal to the second transistor Tr2. The H signal of the igniter control signal B becomes a timer start signal of the timer circuit TM. The off-delay timer TM1 includes a series circuit of a diode D1 and a capacitor C1, and a third transistor Tr3 whose base is connected to a connection point of the series circuit via a fifth resistor R5. The igniter control signal B output from the first output port P1 is supplied to an igniter circuit including a transistor and a relay (not shown). This ignition circuit controls so as to close a relay contact r31 described later when the signal B is H. Relay contact r
When 31 is closed, the igniter IG is driven to discharge a spark from a spark plug (not shown).

The differentiating circuit TM2 is mainly composed of a second capacitor C2. One end of the second capacitor C2, which is the input terminal 1 of the differentiating circuit, is connected to the high potential terminal 3 via a sixth resistor R6. The other end, which is the output terminal 2, is connected to the high potential terminal 3 via the seventh resistor R7 and to the high potential terminal 4 via the Zener diode ZD. Tr4
Is a fourth transistor constituting means for synthesizing the output signal of the flame presence / absence detection circuit SK and the output signal of the differentiating circuit TM2, with the collector connected to the output terminal 2 of the differentiating circuit TM2, the emitter connected to the ground terminal, and the base connected to It is connected to the output terminal of the flame detection circuit SK. The eighth resistor R8 is a base resistor of the fourth transistor R4.

In FIG. 3, the igniter IG is connected in series with normally open relay contacts r11, r31, r11. The fuel valve VQ is connected in series with the normally open relay contacts r11, r21, r11. The relay contact r21 is a normally open contact of a relay (not shown) controlled by a control signal C output from the microcomputer MC. When the control signal C is H, the relay contact r21 is closed. The transistor Tr of FIG.
The circuit of 1, the Tr2 and the relay RY1 constitute a safety control circuit for the fuel system feed line LV, and FIG. 3 constitutes a fuel system feed line control circuit, and both circuits constitute the fuel valve opening / closing circuit of the present invention.

The operation of the embodiment having the above configuration will be described below with reference to FIGS. The fuel valve control signal A shown in FIG. 4 is output from the second output port P2, and becomes an H signal from the start time t2 of the preignition period to turn on the first transistor Tr1. Further, the capacitor C1 of the timer TM1 is instantaneously charged by the igniter drive signal (H signal) from the first output port P1, and the third transistor TR3 is turned on to output an ON signal. By this output signal, the input terminal 1 of the differentiating circuit TM2 becomes the ground potential, and the output terminal 2 outputs a differential signal which rises in a sawtooth form from the ground potential as shown in FIG. The second transistor Tr2 conducts when the base potential is equal to or lower than the predetermined potential V10, and becomes non-conductive when the base potential is lower than V10. Therefore, the differentiating circuit TM2 performs the predetermined time (first time counting) from the time t1 when the igniter control signal B becomes H. Time T1)
During the period, the conduction signal (ON signal) of the second transistor Tr2 is continuously output. As a result, the second transistor Tr
2 becomes conductive from the preignition period start time t1 as shown in FIG. The first transistors Tr1 and Tr2 are both turned on from the start time t1 of the preignition period, and the conduction turns on the relay RY1 to close the relay contact r11.
On the other hand, since the relay contact r31 is closed from the preignition period start time t1 by the control signal B, the igniter IG
Starts the ignition operation from time t1. Then, at time t
At 2, the relay contact r21 closes, the fuel valve VQ opens, and the ignition operation starts.

If the ignition succeeds at time t3, an H signal is output from the flame presence / absence detection circuit SK and the fourth transistor Tr4 is turned on. At this point, the output terminal potential of the differentiation circuit TM2 becomes the ground potential, The conduction of the two transistors Tr2 is maintained. When the potential at the output terminal 2 of the differentiating circuit TM2 becomes the ground potential, the charge of the capacitor C2 is instantaneously discharged. During the combustion period starting from the time point t4, the microcomputer MC determines that there is a flame from the second output port P2 of the microcomputer MC based on the output signal of the flame sensor S, and continuously outputs the H signal. One transistor TR1 continues to conduct. Then, since the second transistor TR2 continues to be turned on by the H signal (flame presence signal) of the flame presence / absence detection circuit SK, the excitation of the relay RY1 is continued. On the other hand, since the closing of the relay contact r21 is also continued, the combustion is continuously performed.

Here, the operation of the timer circuit TM will be described in detail. The off-delay timer TM1 instantaneously responds to the H signal (igniter drive signal) of the igniter control signal B by using the transistor T
By conducting r3, an ON signal is output to the differentiating circuit TM2. Thereby, the differentiating circuit TM2 starts measuring the above-described first time counting time T1. The differentiating circuit TM2 outputs an ON signal during the first clocking time T1, and outputs an OFF signal after the clocking ends. Then, when the H signal of the igniter control signal B becomes an L (low) signal, the off-delay timer TM1 operates for a predetermined time (second time T2) until the potential of the capacitor C1 decreases to the predetermined value V20. The conduction of the transistor TR3 is maintained. When the second time T2 elapses, the charge of the capacitor C2 of the differentiating circuit TM2 is discharged instantaneously mainly through the Zener diode ZD, and the differentiating circuit TM2 returns to the initial state. In this initial state, the transistor Tr3 is non-conductive and the output of the differentiating circuit TM2 is in the H OFF output state.

Next, the microcomputer M during the ignition operation
The operation when C is abnormal will be described. First, when the H signal continues to be output from the second output port P2 despite the absence of flame during the ignition operation, the flame presence / absence detection circuit SK outputs an L signal and does not conduct the fourth transistor Tt4. on the other hand,
As indicated by the dashed line of the signal E in FIG. 4, the differentiating circuit TM2 sets the second transistor Tr2 at the time t4 when the first time T1 ends (when the potential of the output terminal 2 exceeds the potential V10).
Are made non-conductive, and this non-conductive state is maintained. Therefore, the relay RY1 is de-energized, the relay contact r11 is opened, and the fuel valve VQ is closed, so that safety is maintained. In this embodiment, the timing end time of the first clock time is substantially coincident with the end time t4 of the ignition try period, which is preferable, but not necessarily.

The case where the H signal is output from the second output ports P2 and P3 and the H signal is continuously output from the first output port P1 of the microcomputer MC even though there is no flame during the ignition operation will be described. I do. In this case, since the third transistor Tr3 continues to conduct, the differentiation circuit T
M2 turns off the second transistor Tt2, de-energizes the relay RY1, opens the relay contact r11, and controls the fuel valve VQ to a safe side after the end of the first clocking time T1.

In addition, the H signal is output from the second output ports P2 and P3 even though there is no flame during the ignition operation, and the H signal having a cycle shorter than the set time T2 of the off-delay timer TM1 is output from the first output port P1. The case where the repetition signal of -L is output will be described. Also in this case, the third transistor Tr3 continues to conduct, and the differentiation circuit TM2 turns off the second transistor Tr2 when the first clocking time T1 ends, so that the first output port P1 of the microcomputer MC described above. , H signal is continuously output, similarly to the case where the H signal is continuously output. Further, since the set time T2 of the off-delay timer TM1 is set to be sufficiently long, the fuel valve VQ will not be continuously turned on even if the HL repetitive signal is output in a cycle longer than T2.

[0031]

Effects of the Invention According to the present invention that will be configured as described above,
Even if the microcomputer performs an unexpected operation due to runaway or the like and there is no flame, even if the microcomputer continues to output the timer start signal for opening the fuel valve at the time of ignition, the timer circuit keeps the specified time. After a time, an OFF signal is output to the fuel valve opening / closing circuit, and the flame presence / absence detection circuit outputs a flameless signal to the fuel valve opening / closing circuit without going through a microcomputer. Control can be realized. Also, the timer start signal
Is output at a cycle shorter than the second time measured by the timer circuit.
The timer circuit fires the OFF signal after the first time has elapsed.
Outputs to the fuel valve opening / closing circuit, so the fuel valve is on the safe side
It can be controlled. Thus, the present invention provides a microphone
Safe ignition and combustion control against computer malfunction
Can be realized.

[0032]

[0033]

[Brief description of the drawings]

FIG. 1 is a diagram showing a basic configuration of an embodiment of the present invention.

FIG. 2 is a diagram showing a specific circuit configuration of the embodiment.

FIG. 3 is a diagram showing a specific circuit configuration of another portion of the embodiment.

FIG. 4 is an output signal waveform diagram of the embodiment.

FIG. 5 is an output signal waveform diagram of a main part of the embodiment.

FIG. 6 is an output signal waveform diagram of another main part of the embodiment.

[Explanation of symbols]

MC microcomputer TM timer circuit S flame sensor SK flame presence detection circuit VQ control relay

──────────────────────────────────────────────────続 き Continuing from the front page (72) Inventor Yoshihide Kubo 7-cho, Horie-cho, Matsuyama-shi, Ehime Pref. Hei 4-143514 (JP, A) Actually open Hei 6-22751 (JP, U) (58) Fields investigated (Int. Cl. ⁷ , DB name) F23N 5/20 F23N 5/24

Claims (3)

(57) [Claims] 1. A fuel valve, a fuel valve opening / closing circuit for controlling opening / closing of a fuel valve, a flame sensor, an igniter, a microcomputer, and an output signal of the flame sensor being input and passed through the microcomputer. A flame detection circuit that outputs a flame presence / absence signal to the fuel valve opening / closing circuit, an OFF signal in an initial state, and a timer start signal for opening the fuel valve that is output from the microcomputer are timed. the start and oN signal during a first measurement time, the after first <br/> counting time and outputs the OFF signals to each of the fuel valves open and close circuit, the activation signal when the second time counting from the input stop
A timer circuit that returns to the initial state after a lapse of time , wherein the fuel valve opening / closing circuit opens the fuel valve when a flame presence signal is output from a flame presence / absence detection circuit or when an ON signal is output from the timer circuit. A combustion control circuit. 2. A timer circuit according to claim 1 , wherein said timer start signal is inputted.
When it is input, an ON signal is output, and the input of the timer start signal is
Maintains the output of the ON signal for the second time period after it has run out
Off-delay timer and output of this off-delay timer
Signal, and output an OFF signal in the initial state.
An ON signal is output during the time, and O is output after the first time has elapsed.
The FF signal is output, and the ON signal of the off-delay timer is output.
From the differentiation circuit that returns to the initial state when the output stops
The combustion control circuit according to claim 1 , wherein: 3. The igniter drive signal is a timer start signal,
The output of the timer circuit and flame presence / absence detection circuit
And the simultaneous control of the opening and closing of the power supply line of the igniter.
The combustion control circuit according to claim 1 or 2 , wherein: