JPS6025689B2 - Combustion control device - Google Patents

Description

[Detailed description of the invention] ｝ Industrial application field The present invention relates to a combustion control device for a gas hot water pot or the like.

'o) Prior Art Conventional small gas burners have almost no safety device to monitor whether there is a flame or not.
In addition, many medium-sized devices use thermocouples to detect flames.

By the way, when detecting flame with this thermocouple, its thermal response is very slow, so it takes about one hour for the flame detection signal to be output at the time of ignition, and it is a hassle to manually open the fuel valve during this time. It takes time and effort,
Furthermore, if ignition does not occur easily, the fuel valve is left open for a long time, and unburned fuel (raw gas, etc.) continues to be released, creating a very dangerous situation.

SUMMARY OF THE INVENTION An object of the present invention is to provide a combustion control device that eliminates the hassle of ignition and improves safety.

Configuration A According to the present invention, the flame detection circuit, the timer circuit, the first relay, the second relay, the pilot valve switch connected in series to the normally open contact of the second relay, and the second a main valve switch connected in series to the normally open contact of the relay via the normally open contact of the first relay; and to the normally open contact of the second relay via the normally closed contact of the first relay. In a combustion control device having an igniter connected in series, the flame detection circuit includes a flame detection element, an operational amplifier to which the flame detection element is connected, and a base thereof connected to an output terminal of the operational amplifier. The timer circuit includes a time constant circuit in which a resistor and a capacitor are connected in series, a switching element that turns on when the voltage across the capacitor reaches a predetermined voltage, and a switching element that turns on when the voltage across the capacitor reaches a predetermined voltage. a second transistor whose base is supplied with the discharge current of the capacitor flowing through the switching element; the first relay is connected to the collector of the first transistor; Connected to one end of the capacitor of the circuit, the second relay is connected to the collector of the second transistor, and the collector and emitter of the third transistor are connected in parallel to the collector and emitter of the second transistor. and the base of the third transistor is connected to the power supply terminal via the other normally open contact of the second relay, and is also connected to the output terminal of the operational amplifier of the flame detection circuit. .

Embodiment As shown in FIG. 1, a combustion control device according to an embodiment of the present invention includes a flame detection circuit (described in detail later), a timer circuit (described in detail later), a first relay XF, Second relay XP and normally open contact X of second relay XP
a pilot valve switch PV connected in series to the PI; a main valve switch MV connected in series to the normally open contact XPI of the second relay XP via the normally open contact XFI of the first relay XF; Normally open contact XPI of the second relay XP mentioned above
and an igniter IG connected in series via the normally open point x F2 of the first relay XF.

The flame detection circuit includes a thermocouple TC which is a flame detection element, an operational amplifier A to which the thermocouple TC is connected, and a transistor Trl whose base is connected to the output terminal of the operational amplifier A.

The timer circuit includes a time constant circuit in which a resistor R9 and a capacitor CI are connected in series, and a PUT (programmer full unity circuit) which is a switching element that turns on when the voltage across the capacitor CI reaches a predetermined voltage. transistor) and a transistor Tr2 whose base is supplied with the discharge current of the capacitor CI flowing through the cathode of the turned-on PUT.

The above predetermined voltage is the resistor R12, R1
This is a voltage given by a voltage dividing circuit made up of three series circuits, and specifically, it is applied to the gate of PUT as shown in the figure. Furthermore, a relay XF is connected to the collector of the transistor Trl, and a capacitor C of the timer circuit is connected via a resistor R8 and a diode DI.
One end of I is connected.

In addition, a second relay XP is connected to the collector of the transistor Tr2.
are connected.

Furthermore, the collector emitter of the third transistor Tr3 is connected in parallel with the collector emitter of the transistor Tr2, and the base of the transistor Tr3 is connected in parallel with the collector emitter of the third transistor Tr3.
It is connected to the power supply terminal via the other normally open contact XP3 of the above-mentioned IJ Ray XP, and is also connected to the output terminal of the operational amplifier A of the above-mentioned flame detection circuit.

The third relay XH has its normally open contacts XHI and IJ relay
It is connected between the power supply terminals through a parallel connection circuit with the normally open contact XP4 of P.

The series circuit of resistor R18 and capacitor C4 is relay XP.
The relay XP is connected between the power supply terminals via a normally open contact XP2, and one end of the relay XP is connected to the connection point between the resistor R18 and the capacitor C4. A light emitting diode (LED) LI connected in parallel to the main valve switch MV functions as an indicator light to indicate that the main valve switch MV is energized, the main valve is open, and steady combustion is in progress, and the relay LEDL connected between power terminals via XP's normally closed contact XP5
2 functions as an indicator light indicating that the flame is not ignited.

Next, the operation will be explained with reference to FIG. First, when the power switch SW is turned on, charging of the capacitor CI begins through the normally closed contact XH2 of the IJ relay XH and the resistor R9. When time passes and the voltage of this capacitor CI becomes higher than the voltage determined by resistors R12 and R13, PUT is turned on, and as a result, transistor Tr2 is also turned on, and relay XP is turned on. The time from when the power is turned on until the transistor Tr2 is turned on is the ignition standby time tl (approximately 5 seconds). After the power is turned on and this ignition standby time has elapsed, relay XP operates and closes its normally open contact XPI. As a result, the pilot valve switch PV is energized and the pilot valve opens. At this time, the current that has passed through the normally closed contact XPI flows to the igniter IG via the normally open contact XF2 of the relay XF, so the igniter IG operates and ignition is performed. The time during which this ignition operation is performed is the time during which ignition is attempted, that is, the trial time t2
(approximately 19 sand).

During this trial period, the charge on capacitor CI increases to resistor RI.
0, PUT, is determined as the time required to be discharged through the transistor Tr2 until the transistor Tr2 is turned off. If ignition occurs during this trial time and a flame is detected by the flame detection circuit, the output terminal of operational amplifier A becomes "H". Therefore, the relay
When P is turned on, the current flowing into the output terminal of the operational amplifier A via the normally open contact XP3 and the diode ○2, which are closed, flows to the base of the transistor Tr3, and the transistor Tr3 is turned on. Since this transistor Tr3 is connected in parallel with the transistor Tr2, the ON state of the relay XP is maintained even after the trial time ends and the transistor Tr2 is turned off. By the way, since the flame detection circuit detects a flame and the output terminal of operational amplifier A becomes "H", transistor Trl is turned on, which turns on relay XF, which closes its normally open contact XFI and closes its normally closed contact. XF
Open 2.

As a result, the main valve switch MV is energized to open the main valve, and on the other hand, the operation of the igniter IG is terminated. In this way, steady combustion operation begins. If no flame detection occurs during the trial period, the output terminal of operational amplifier A remains "L".

Therefore, the current flowing through the normally open contact XP3 of the relay XP flows through the diode D2 to the output terminal of the operational amplifier A, so that the transistor Tr3 remains off. As a result, the trial time ends and the transistor T
When r2 is turned off, relay XP returns, its normally open contact XPI opens, power supply to pilot valve switch PV is stopped, pilot valve is closed, and operation of igniter IG is also terminated. Then, normally closed contact XP5 closes, so LE
DL2 lights up to indicate that there is no ignition. Also, at this time, normally open contact XP4 returns to open, but relay XH
When the normally open contact XP4 closes first, it turns on and closes the normally open contact XHI to hold itself, so it continues to be on regardless of this, so the normally closed contact X
H2 remains off. Therefore, when this ignition fails, the capacitor CI will not be charged again.
After the trial period ends, all operations remain stopped. In order to perform the ignition operation again, the power switch SW may be turned off once and then turned on again, and the sequence performed during the above-described ignition standby time and trial time may be repeated.

As mentioned above, if the flame goes out for some reason during steady combustion operation, the output terminal of operational amplifier A becomes "L".
Therefore, the transistor Tr3 is immediately turned off, so the relay XP is turned off, and all operations are stopped as in the case of the ignition failure, and the LED L2 is turned on. At this time, in order to ignite again, it is necessary to turn off the power switch SW and then turn it on again. It should be noted that the circuit of this embodiment is configured to operate safely (fulfill a fail-safe function) against various types of failures of all elements.

First, in case a failure occurs in which the transistor Trl operates in the on direction in the flame detection circuit, a series circuit consisting of a resistor R8 and a diode DI is connected between the collector of the transistor Trl and the positive end of the capacitor CI. The resistance value of the resistor R8 in parentheses is set to be sufficiently smaller than the resistance value of the resistor R9. As a result, if the transistor Trl fails in the direction of turning on, the charging level of the capacitor CI is set to almost zero volts, so that the timer circuit does not time out no matter how long it takes, so that the relay XP is not turned off and the ignition operation etc. Safety is ensured by not moving on to the next sequence. Further, if a failure occurs in the flame detection circuit in the direction in which the transistor Trl is turned off, the same operation as when no flame is detected is performed, so it is safe. Transistor Tr of timer circuit
2 and a failure in which the holding transistor Tr3 operates in the on direction at the time of ignition, safety is ensured as follows.

The ratio of the resistance value of resistor R14 to the resistance value of the coil of relay XP is determined as Vmin>VccX{resistance value of XP/(R14
resistance value + resistance value of XP)} (Vmin is the maximum operating voltage of relay (Resistance value of R18 + resistance value of XP)} (Vmax is the maximum reset voltage of relay XP).

Therefore, in the relay XP, the discharge current of the capacitor C4 can be turned on only when the transistor Tr2 is turned on in a state where the voltage of the capacitor C4 is sufficiently high due to the charging performed through the resistor R14. If there is a failure and transistors Tr2 and Tr3 are turned on from the beginning, the charging voltage of capacitor C4 will not reach the minimum operating voltage of relay XP, and therefore will not turn on. Additionally, once the relay XP operates, its normally open contact XP2 turns on, so a voltage higher than the maximum reset voltage is applied to both ends of the relay coil via the resistor R18, and the relay XP maintains its operating state. Become. In the above embodiment, the flame detection circuit is composed of a thermocouple TC and an operational amplifier A, but it is also possible to use other heat-sensitive elements, for example, a flame detection element such as a flame rod, or a photoelectric sensor such as CdS. It is also possible to use a flame detection element of the formula.

In addition, in the above embodiment, only the pilot valve switch PV, main valve switch MV, igniter IG, and flame detection element TC are installed near the combustion device, and other control circuits are placed in a control box located at a remote location. It is also possible to configure it so that it can be stored and remotely controlled. H effect In the combustion control device according to the present invention, when the first transistor of the flame detection circuit is short-circuited, the capacitor forming the time constant circuit of the timer circuit is short-circuited via the resistor by the short-circuited first transistor. As a result, the voltage across this capacitor does not rise and the switching element does not turn on, and as a result, the second transistor does not turn on, so the second relay never turns on, and its constant state Since the opening point is not turned on, none of the pilot valve switch, main valve switch, and igniter are energized, and various fail-safe functions such as ensuring safety can be realized.

Further, even when flame is detected using an element with a slow thermal response such as a thermocouple, the ignition operation can be performed automatically, and it is also possible to prevent unburned fuel from continuing to be released for a long time.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram showing an embodiment of the present invention, and FIG. 2 is a circuit diagram showing an embodiment of the present invention.
3 is a time chart for explaining the operation shown in the figure. PV...Pilot valve switch, MV...Main valve switch, IG...Igniter, Trl...
- Output transistor of flame detection circuit, Tr2...output transistor of timer circuit, Tr3...transistor for holding during ignition, XP, XF, XH...relay. Figure ＾ Sphere Diagram N

Claims (1)

[Claims] 1. A flame detection circuit, a timer circuit, a first relay, a second relay, a pilot valve switch connected in series to a normally open contact of the second relay, and a normally open contact of the second relay. a main valve switch connected in series through a normally open contact of the first relay, and an ignition connected in series to a normally open contact of the second relay through a normally open contact of the first relay. The flame detection circuit includes a flame detection element, an operational amplifier to which the flame detection element is connected, and a first transistor whose base is connected to the output terminal of the operational amplifier. The above timer circuit consists of a time constant circuit in which a resistor and a capacitor are connected in series, a switching element that turns on when the voltage across the capacitor reaches a predetermined voltage, and a current flowing through this switching element that is turned on. a second transistor to whose base the discharge current of the capacitor is applied;
The first relay is connected to the collector of the first transistor, and one end of the capacitor of the timer circuit is connected via a resistor, and the second relay is connected to the collector of the second transistor. , Furthermore, a third transistor is connected to the collector-emitter of this second transistor.
The collectors and emitters of the transistors are connected in parallel, and the base of this third transistor is connected to the power supply terminal via the other normally open contact of the second relay, and the output of the operational amplifier of the flame detection circuit is connected in parallel. A combustion control device characterized in that it is connected to a terminal.