JP3308191B2 - Combustion control circuit - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a combustion control circuit which realizes fail-safe control of opening and closing a fuel valve and generates an accurate signal indicating whether or not a combustion state is normal.

2. Description of the Related Art A combustion control device for controlling the combustion of a poiler or the like controls the combustion by controlling the opening and closing of a fuel valve while generating a signal indicating whether or not the combustion is in a normal state. This fuel valve opening / closing control needs to be implemented in a fail-safe manner so as not to cause a dangerous situation, and this signal generates an accurate signal so as not to cause a dangerous situation. There is a need.

[0003]

2. Description of the Related Art When controlling the combustion of a poiler or the like, the most dangerous situation is that fuel is supplied without ignition.

[0004] In order to prevent such a dangerous situation, the combustion control device employs a configuration in which a sensor for detecting ignition is provided, and the fuel valve is opened on condition that the sensor detects ignition. It is structured to go.

However, there is a case where the sensor detects the ignition before the ignition is performed. If such a pseudo flame is detected, the fuel is supplied even though the ignition is not performed. Dangerous situations will occur.

Conventionally, in order to prevent such a dangerous situation from occurring, a method has been adopted in which a sensor that is unlikely to detect a pseudo flame is used. That is, Cds
In a sensor that detects ignition by detecting visible light like this, a pseudo flame is detected by light leakage from the outside world.Therefore, a sensor such as a UV tube that detects only ultraviolet light is prepared. By using a simple sensor to detect ultraviolet rays that are strongly radiated from the flame, a method was adopted in which a pseudo-flame was not detected.

[0007]

However, even a sensor such as a UV tube does not completely detect a simulated flame, and according to the prior art, fuel is supplied even though it is not ignited. There is a problem that it is not possible to completely avoid the dangerous situation of getting lost.

In addition, the pseudo flame may be generated not only by the sensor but also by a failure of the driving circuit of the sensor, and the conventional technique cannot cope with such a case.

The present invention has been made in view of such circumstances, and realizes a fail-safe control of opening and closing of a fuel valve and generates a new signal for generating an accurate signal indicating whether or not a combustion state is normal. It is intended to provide a combustion control circuit.

[0010]

FIG. 1 shows the principle configuration of the present invention. In FIG. 1, reference numeral 1 denotes a combustion control circuit provided with the present invention, which controls the opening and closing of the fuel valve 2 and generates a signal indicating whether or not the combustion is in a normal state.

The combustion control circuit 1 of the present invention comprises an ignition trial circuit 10, a flame detection circuit 11, and a relay driving means 1.
2, capacitor means 13, first control means 14,
A second control unit 15 and a generation unit 16 are provided.

The ignition trial circuit 10 executes an ignition trial by activating an ignition transformer (not shown). The flame detection circuit 11 receives a detection value of a flame sensor (not shown) as an input, and detects whether or not a flame has been established.

The relay driving means 12 is constituted by a series connection of an exciting coil 120 of a relay for opening and closing the fuel valve and a normally open contact 121 of the relay, and opens and closes the fuel valve.
The capacitor means 13 charges via the resistor R1.

The first control means 14 establishes a current path between the capacitor means 13 and the exciting coil 120 when the ignition trial circuit 10 enters the ignition trial, so that the exciting coil 120 And, when a pseudo ignition trial occurs, charging of the capacitor means 13 is suppressed.

The second control means 15 includes a flame detection circuit 11
When a flame is detected, a current path is established between the normally-open contact 121 to be closed and the exciting coil 120, so that a holding current of the relay flows through the exciting coil 120,
Further, when a pseudo flame is generated, the capacitor means 13
Suppress charging.

The generating means 16 generates a signal indicating whether or not the combustion state is normal based on the voltage generated by opening and closing the normally open contact 121 and whether or not a flame is detected. .

In the thus configured combustion control circuit 1 of the present invention, the capacitor means 13 starts charging when the start of combustion control is instructed. On the other hand, ignition trial circuit 1
When the specified time elapses from the combustion control start instruction, the ignition trial starts by starting the ignition transformer for a predetermined time.

When starting the ignition trial, the first control means 14 comprises the capacitor means 13 and the exciting coil 12
0, a current path is established, and the relay is excited by flowing an exciting current of the relay through the exciting coil 120, thereby opening the fuel valve.

In response to this operation, when the flame detection circuit 11 detects a flame, the second control means 15 determines whether the normally open contact 121 closed by the excitation of the relay and the exciting coil 120 are connected. Establish a current path to the excitation coil 1
By passing the relay holding current through the relay 20, the excitation of the relay is held, and the opening operation of the fuel valve is held even after the end of the ignition trial.

In the above operation, the first control means 14 establishes a current path between the resistor R1 and the exciting coil 120 when a pseudo ignition trial occurs, thereby charging the capacitor means 13. , Thereby controlling the relay so as not to open the fuel valve by preventing excitation of the relay. Further, the second control means 15 suppresses charging of the capacitor means 13 by establishing a current path between the resistor R1 and the exciting coil 120 when a pseudo flame is generated, thereby exciting the relay. Is controlled to prevent the fuel valve from opening.

At this time, when the normally-open type contact 121 is closed, that is, when the relay is energized (there is a time of the ignition trial and a time of the normal combustion), the generation means 16 has a large value. When a voltage is input and the switch is opened, a voltage corresponding to the opening and closing of the normally open contact 121 is input to the generation unit 16, for example, a small voltage is input to the generation unit 16. The generating means 16 detects whether the relay is energized by comparing the input voltage with a prescribed reference value.

The detection result and the flame detection circuit 11
In response to the detection result, when the excitation of the relay is detected and the flame detection circuit 11 detects the flame, a signal indicating that the combustion state is normal is generated and output.

As described above, according to the combustion control circuit 1 of the present invention, the opening / closing control of the fuel valve can be realized in a fail-safe manner, and an accurate signal indicating whether or not the combustion is in a normal state is generated. become able to.

[0024]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described in detail according to embodiments. FIG. 2 shows an embodiment of the combustion control apparatus 1a provided with the present invention.

As shown in this figure, the combustion control device 1a of the present invention comprises a relay drive circuit 20 / normal combustion detection circuit 21
/ Sequence timer circuit 22 / power supply circuit 23 / lockout memory circuit 24 / frame circuit 25 / start circuit 26
And an internal circuit 30 comprising a reset circuit 27. When the temperature controller 40 is turned on according to the internal circuit 30, an AC power supply 41 is inputted to refer to a detection value of a Cds cell 42 used as a flame sensor. While the fuel valve 4
By controlling 3 / ignition transformer 44 / fan motor 45, combustion is controlled. Here, reference numeral 46 denotes a reset switch.

K3A shown in the figure is a contact point of a relay K3 described later. When the temperature controller 40 is turned on, the AC power supply 41 is connected to the fan motor 45 to start the fan motor 45, and the relay K3 When is excited,
Fuel valve 43 / Ignition transformer 44 / Fan motor 45
To shut off the power supply and activate the alarm.

K2A is a normally open contact of a relay K2 described later. When the relay K2 is excited, the ignition transformer 44 is started by connecting the AC power supply 41 to the ignition transformer 44.

K1A is a contact point of a relay K1 to be described later. When the relay K1 is not excited, the AC power supply 41 is connected to the a side so that the AC power supply 41 is connected to the internal circuit 30, and When K1 is energized, the AC power supply 41 is connected to the b side so that the AC power supply 4 is connected.
1 is connected to the internal circuit 30.

FIG. 3 shows an embodiment of the relay drive circuit 20 / normal combustion detection circuit 21 / power supply circuit 23 constituting the internal circuit 30. FIG. 4 shows a frame circuit 25 / start circuit 26 / FIG. 5 shows an embodiment of the reset circuit 27, and FIG.
2 illustrates one embodiment of the lockout memory circuit 24. Here, points a to o shown in FIGS. 2 to 5 indicate the same points.

Next, referring to FIGS. 2 to 5, a relay drive circuit 20, a normal combustion detection circuit 21, a sequence timer circuit 22, a power supply circuit 23, a lockout memory circuit 24, a frame circuit 25, a start circuit 26, and a reset circuit. 27 will be described in detail.

As shown in FIG. 3, the power supply circuit 23 is composed of a general DC smoothing circuit, and the temperature controller 40 is turned on.
By receiving the AC power from the AC power supply 41,
By converting the DC voltage into a DC voltage, a DC voltage Vcc required by the internal circuit 30 is generated.

On the other hand, as shown in FIG. 4, when the DC voltage Vcc is applied, the starting circuit 26 causes a current to flow when the capacitor 260 rises, thereby turning on the transistor 261 to turn on the negative terminal of the comparator 262. , A high level is output. Thereafter, when the steady state is reached and the capacitor 260 stops flowing current, the transistor 26
When 1 is turned off, a high voltage is input to the minus terminal of the comparator 262, and a low level is output.

According to this configuration, when the temperature controller 40 is turned on, the starting circuit 26 operates so as to output a one-pulse high level. On the other hand, the frame circuit 25 includes a Cds cell 42 and a resistor 25 as shown in FIG.
When the Cds cell 42 detects a flame and reduces its resistance value by providing a converter 251 having an input of a voltage determined by resistance division with 0, this comparator 251
Outputs a high level.

Further, the frame circuit 25 has a DC voltage Vcc
Is provided, a transistor 253 that starts charging when the charging is completed, and a transistor 253 that turns on when the charging of the capacitor 252 is completed, and stops supplying the charging current to the capacitor 252 when the transistor 251 outputs a high level. A transistor 254 that discharges the capacitor 252 by causing the capacitor 252 to discharge.

According to this configuration, the frame circuit 25
When the Cds cell 42 detects a flame, it outputs a high level, and when a certain period of time has elapsed since the temperature controller 40 was turned on, the transistor 253 is turned on (as described later, thereby energizing the relay K2 to turn on the ignition transformer). 44 is activated), and when the Cds cell 42 detects a flame thereafter, the transistor 253 is turned off.
It works like it does.

On the other hand, the sequence timer circuit 22
As shown in FIG. 7, a capacitor 220 that starts charging when a DC voltage Vcc is applied, a comparator 221 that outputs a low level when a voltage generated by the capacitor 220 becomes equal to or more than a specified value, and a voltage generated by the capacitor 220 exceeds a specified value Output a low level when the
A comparator 222 for discharging 20 and a comparator 2
A transistor 223 is turned off when the transistor 21 outputs a low level, and a transistor 224 is turned on when the transistor 223 is turned off.

Here, when the comparator 222 switches to the low level output, the state is maintained.
This state is reset when the comparator 262 of the activation circuit 26 outputs a high level.

According to this configuration, the sequence timer circuit 22 turns on the transistor 224 when a certain period of time elapses after the temperature controller 40 is turned on (this causes the relay K1 to be excited and the fuel valve 43 to be turned on, as described later). Open), and after a certain time, the transistor 2
An operation is performed so as to turn off the reference numeral 24.

On the other hand, as shown in FIG. 3, the relay drive circuit 20 starts charging when the DC voltage Vcc is applied, and charges the capacitor 200 when the transistor 224 of the sequence timer circuit 22 is turned on. A relay K1 that is excited by electric charges to switch the relay contact K1, a transistor 201 that holds the relay K1 excited when the comparator 251 of the frame circuit 25 outputs a high level, and a transistor that holds the relay K1 that is excited. A transistor 202 that turns on when the transistor 253 turns on, a relay K2 that is excited when the transistor 202 turns on and switches the relay contact K2A, and a transistor that turns on when the transistor 243 of the lockout memory circuit 24 described later turns on 203 and Tran It is energized when the static 203 turns ON, the and a relay K3 switching the relay contacts K3A.

According to this configuration, the relay drive circuit 20
Starts the ignition transformer 44 by switching the relay contact K2A by the ON operation of the transistor 253 of the frame circuit 25 that operates after a certain time has elapsed since the temperature controller 40 was turned ON. Then, the temperature controller 40 is turned on.
Then, the fuel valve 43 is opened by switching the relay contact K1A by the ON operation of the transistor 224 of the sequence timer circuit 22 which operates after a lapse of a predetermined time.
The opening operation of the fuel valve 43 is limited to a specified short time.

The open operation of the fuel valve 43 is held by the high level output of the comparator 251 of the frame circuit 25 which is output when a flame is detected. Then, by turning on the transistor 245 of the lockout memory circuit 24 described later, the relay contact K3A is switched to operate so as to enter a safe stop.

On the other hand, as shown in FIG. 3, a normal combustion detecting circuit 21 outputs a low level signal when a point of the relay drive circuit 20 becomes higher than a specified voltage.
0, a transistor 211 that is turned on when the comparator 251 of the frame circuit 25 outputs a high level,
A comparator 212 includes a comparator 212 that outputs a high level when the transistor 211 outputs a low level when the transistor 211 is turned on, and a transistor 213 that is turned on when the comparator 212 outputs a high level.

As described above, when the relay K1 is excited, the relay contact K1A is switched, so that the current flows through the route indicated by α in FIG. It will be set to voltage. On the other hand, the transistor 22 of the sequence timer circuit 22
If the short-circuit failure occurs in the relay 4 or the transistor 201 in the relay drive circuit 20 short-circuits (indicating a pseudo flame), the capacitor 200 of the relay drive circuit 20 is not charged, so that the relay K1 is not excited and a large resistance is provided. The current flows through the route indicated by β in FIG. 3, and the point at which the current flows is set to a low voltage. From this, when the relay K1 is excited, the comparator 210 operates to output a low level.

Therefore, according to this configuration, the normal combustion detection circuit 21 can detect whether or not the relay K1 has been excited. Using this detection result, the relay K1 is excited and the comparator 251 of the frame circuit 25 is used. Outputs a high level indicating that there is a flame, that is, when the fuel valve 43 is open and a normal combustion state is detected in which a flame is detected, the transistor 213 is turned ON (as described later, the transistor 213 is locked). (The capacitor 240 of the out-memory circuit 24 is discharged).

On the other hand, as shown in FIG. 5, the lockout memory circuit 24 starts charging when the DC voltage Vcc is applied, and discharges when the transistor 213 of the normal combustion detection circuit 21 is turned on. When a short-circuit fault occurs, a capacitor 240 that turns off the transistor 224 of the sequence timer circuit 22 and a low level output when the voltage generated by the capacitor 240 exceeds a specified value
The capacitor 220 of the sequence timer circuit 22 is discharged, and the transistor 213 of the normal combustion detection circuit 21 is turned off.
F, the output of the comparator 262 of the starting circuit 26 is set to a low level, and the capacitor 252 of the frame circuit 25 is set.
, A comparator 242 that outputs a high level when the voltage generated by the capacitor 240 is equal to or higher than a specified value, and a comparator 242 that is turned on when the comparator 242 outputs a high level. The transistor 2 which turns on and sets the output of the comparator 262 of the starting circuit 26 to a low level
43.

According to this configuration, the lockout memory circuit 24 includes the transistor 213 of the normal combustion detection circuit 21.
When a certain period of time has elapsed without turning ON, the comparator 241 outputs a low level, whereby the capacitor 220 of the sequence timer circuit 22 is discharged, the fuel valve 43 is shut off, and the normal combustion detection circuit 21
Of the transistor 213 is forcibly turned off, the discharge path of the capacitor 240 is cut off, and the transistor 262 of the starting circuit 26 forcibly outputs a low level (this causes the transistor 270 of the reset circuit 27 to be output, as described later). The discharge path of the capacitor 240 is cut off because the discharge path of the capacitor 240 is cut off because the switch is not turned on.
2 discharges, the excitation of the relay K2 for starting the ignition transformer 44 is released.

Then, when the comparator 242 outputs a high level, the transistor 243 is turned on, whereby the transistor 203 of the relay drive circuit 20 is turned on.
N, the relay K3 which enters the safety stop is excited,
When the transistor 262 of the starting circuit 26 forcibly outputs a low level, the discharge path of the capacitor 240 is cut off.

On the other hand, as shown in FIG. 4, the reset circuit 27 is turned on when the comparator 262 of the starting circuit 26 outputs a high level, and is turned on when the reset switch 46 is closed. The capacitor 220 of the circuit 22 and the lockout memory circuit 2
4, the transistor 270 that operates to discharge the capacitor 240 of the frame circuit 25, the capacitor 252 of the frame circuit 25, and the capacitor 200 of the relay drive circuit 20.

According to this configuration, reset circuit 27
When the activation circuit 26 outputs a one-pulse high level in response to the ON operation of the temperature controller 40 and when the reset switch 46 is closed in response to a manual operation, the capacitor 220 of the sequence timer circuit 22 , The capacitor 240 of the lockout memory circuit 24, the capacitor 252 of the frame circuit 25, and the capacitor 200 of the relay drive circuit 20.

In the combustion control apparatus 1a according to the present invention thus configured, when a combustion request is issued by turning on the temperature controller 40, the fan motor 45 is started to enter the pre-purge and the power supply circuit 23 Generates the DC voltage Vcc required by the internal circuit 30.

In response to the generation of the DC voltage Vcc, the start-up circuit 26 outputs a high level in the form of one pulse, and in response, the transistor 270 of the reset circuit 27 is turned on.
By doing so, the capacitor 2 of the sequence timer circuit 22
20 and the capacitor 24 of the lockout memory circuit 24
0, the capacitor 252 of the frame circuit 25, and the capacitor 200 of the relay drive circuit 20 are discharged, and the comparator 222 of the sequence timer circuit 22 is reset to output a high level.

After this initialization processing, the capacitor 220 of the sequence timer circuit 22, the capacitor 240 of the lockout memory circuit 24, the capacitor 252 of the frame circuit 25, and the capacitor 200 of the relay drive circuit 20
Starts charging.

In response to the charging process, the frame circuit 25
Turns on the transistor 253 after a lapse of a predetermined time defined by the completion of charging of the capacitor 252, and in response, turns on the transistor 202 of the relay drive circuit 20 to excite the relay K2 and turn on the ignition transformer 44. Is started.

Further, in response to the charging process, the sequence timer circuit 22 outputs a low level to the comparator 221 after a certain period of time defined by the completion of charging of the capacitor 220, thereby turning on the transistor 224.
In response, the capacitor 200 of the relay drive circuit 20
Flows through the relay K1, the relay K1 is excited, and the fuel valve 43 is opened. Thereafter, the sequence timer circuit 22 turns off the transistor 224 by discharging the capacitor 220 in response to the low level output of the comparator 222, and releases the excitation of the relay K1 by its own circuit.

According to the processing of the frame circuit 25 / sequence timer circuit 22, the ignition transformer 44 is started and the fuel valve 45 is opened to attempt ignition after a lapse of a predetermined time from the start of the pre-purge.

When a flame is established by this ignition operation, the frame circuit 25 outputs a high level to the comparator 251 and, in response to this, turns on the transistor 201 of the relay drive circuit 20 to hold the excitation in the relay K1. The current flows, the excitation of the relay K1 is maintained, and the opening operation of the fuel valve 43 is maintained. Then, the frame circuit 25 turns on the transistor 254 in accordance with the high level output of the comparator 251, thereby turning on the capacitor 2
The ignition transformer 44 is stopped by discharging the 52, thereby releasing the excitation of the relay K2.

The excitation of the relay K1 and the frame circuit 2
In response to the processing of No. 5, the normal combustion detection circuit 21 detects that the flame has been detected while the relay K1 has been excited.
When the comparator 251 of the frame circuit 25 outputs a high level, it is determined that the combustion state is normal, and the transistor 213 is turned on.

On the other hand, the lockout memory circuit 24 continues the discharging process by the starting
Start charging. This charging is performed by the normal combustion detection circuit 21.
When the transistor 213 is turned on, it stops. That is, when it is detected that the combustion state is normal, the operation is stopped.

Here, when the capacitor 240 is short-circuited, the transistor 224 of the sequence timer circuit 22 is forcibly turned off.
The fuel valve 43 does not open.

The lockout memory circuit 24
When the transistor 213 of the normal combustion detection circuit 21 is not turned on, the charging of the capacitor 240 is continued. When the charged amount reaches a specified value, a low level is output to the comparator 241.

Upon receiving the low level output of the comparator 241, the capacitor 22 of the sequence timer circuit 22
0 is forcibly discharged, whereby the fuel valve 43 is forcibly closed. Further, the transistor 213 of the normal combustion detection circuit 21 is forcibly turned off, whereby the discharge path of the capacitor 240 is forcibly cut off. Also,
The comparator 262 of the starting circuit 26 is set to forcibly output a low level.
Is forcedly stopped, and the discharge path is forcibly cut off. Further, the capacitor 252 of the frame circuit 25 is forcibly discharged, whereby the activation of the ignition transformer 44 is forcibly stopped.

Further, when the charge amount of the capacitor 240 reaches a specified value because the transistor 213 of the normal combustion detection circuit 21 does not turn on, the lockout memory circuit 24 outputs a high level to the comparator 242 so that the transistor 243 Turn ON.

In response to the ON operation of the transistor 243, the transistor K3 of the relay drive circuit 20 is turned ON to excite the relay K3, thereby supplying power to the fuel valve 43 / ignition transformer 44 / fan motor 45. At the same time, the alarm device is activated. In addition, the comparator 262 of the starting circuit 26 is set to forcibly output a low level, whereby the discharging process of the capacitor 240 by the starting circuit 26 is forcibly stopped, and the discharging path is forcibly cut off.

As described above, the combustion control device 1 of the present invention
As shown in FIG. 6, when the temperature controller 40 is turned on, a pre-purge is performed by activating the fan motor 45, and after a lapse of a specified time, the ignition transformer 44 is started to enter an ignition trial, thereby setting the ignition trial. The ignition is attempted by opening the fuel valve 43 after performing the preignition of time. When the ignition is confirmed by the Cds cell 42, the opening operation of the fuel valve 43 is maintained, the post-ignition is performed for a specified time, and then the ignition transformer 44 is stopped.

In this combustion control sequence, even if an ignition trial is performed for a specified time, the Cds cell 4
2 does not detect the flame, the lockout memory circuit 24 operates and, as shown in FIG.
/ Ignition transformer 44 / Fan motor 45 is stopped to activate the alarm device. Then, when the reset switch 46 is operated, the normal combustion control sequence is executed again.

At the time of this combustion control sequence,
When a pseudo flame is generated, the charging of the capacitor 252 is stopped by turning on the transistor 254 of the frame circuit 25, thereby preventing the ignition transformer from being activated, and turning on the transistor 201 of the relay driving circuit 20 to turn on the capacitor. By discharging 200, the excitation of the relay K1 is stopped so that the fuel valve 43 is not opened. Then, as shown in FIG. 8, when the specified time elapses in this state, the lockout memory circuit 24 operates, the fan motor 45 also stops, and the alarm device is activated. Then, when the reset switch 46 is operated, the normal combustion control sequence is executed again.

As described above, the combustion control device 1 of the present invention
In the case of a, when it does not ignite or when a pseudo flame occurs,
Fuel valve 43 / Ignition transformer 44 / Fan motor 45
By stopping the power supply to the system, the vehicle will be safely stopped.

Next, the relay drive circuit 20 and the normal combustion detection circuit 21, which are the gist of the present invention, will be described in further detail. The normal combustion detection circuit 21, as shown in FIG.
A configuration is employed in which a potential at a point of the relay drive circuit 20 is input. FIG. 9 shows an arrangement of circuits around the point of the relay drive circuit 20.

More specifically, the circuit includes a series connection circuit of a resistor r1 and a capacitor 200, and a series connection circuit of a resistor r2, an exciting coil 100 of a relay K1, a resistor r3, and a transistor 201. As shown in the figure, the former series connection circuit receives power supply from point a, and receives the power supply from point b of the latter series connection circuit. And relay K
The collector of the transistor 224 of the sequence timer circuit 22 is connected to the connection point between the one excitation coil 100 and the resistor r3.

The start process of relay K1 will be described with reference to this circuit diagram. Capacitor 200 starts discharging after discharging in response to the ON operation of transistor 270 of reset circuit 27.

At this time, when the transistor 201 has a short-circuit failure (indicating a pseudo flame) or the transistor 224 of the sequence timer circuit 22 has a short-circuit failure, the route of β is applied to the exciting coil 100 of the relay K1. Does not flow, and the capacitor 200 is not charged. Further, since this current is limited by the resistor r1, the relay K1 is not excited.

After the charging of the capacitor 200 has expired, the transistor 224 of the sequence timer circuit 22 is turned on.
As a result, the electric charge of the capacitor 200 is transferred to the relay K1.
, The relay K1 is excited.

When the flame is detected by the Cds cell 42, the transistor 201 is turned on to turn off the transistor 224 of the sequence timer circuit 22. Is supplied, the excitation of the relay K1 is maintained.

From this point, the point of the relay drive circuit 20 is that, when the relay K1 is excited, a current flows according to the route of α having a small resistance r2, so that a high potential is shown. When a failure (indicating a pseudo flame) or a short-circuit failure of the transistor 224 of the sequence timer circuit 22, the relay K1 is not excited and a current flows according to the route of β having a large resistance r1. so,
It will show a smaller potential.

Upon receiving the potential at the point of the relay drive circuit 20, the normal combustion detection circuit 21
Is used to determine whether the point of the relay drive circuit 20 is equal to or higher than a specified voltage, thereby detecting whether the relay K1 is excited and detecting that the relay K1 is excited. In some cases, a low level is output to the comparator 210.

On the other hand, it is notified from the frame circuit 25 whether or not a flame has been detected (however, a pseudo flame may occur).
When a high level indicating flame detection is notified from the comparator 251 of the frame circuit 25, the transistor 211 is turned on.

In response to the operation of the comparator 210 and the operation of the transistor 211, the normal combustion detection circuit 21
The comparator 212 outputs a high level when the comparator 210 outputs a low level and the transistor 211 is turned on. That is, when the relay K1 is energized, the fuel valve 43 is opened and the flame circuit 25 detects the presence of a flame. Is output.

With such a configuration, the relay drive circuit 20 can control the short-circuit failure of the transistor 201 (which indicates a pseudo flame) or the sequence timer circuit 2
The opening operation of the fuel valve 43 can be realized in a fail-safe manner without being affected by the short-circuit failure of the second transistor 224. Then, the normal combustion detection circuit 21 can accurately generate a signal indicating that it is in a normal combustion state without being affected by the pseudo flame.

[0079]

As described above, according to the present invention,
The open / close control of the fuel valve can be realized in a fail-safe manner, and an accurate signal indicating whether or not the combustion state is normal can be generated.

[Brief description of the drawings]

FIG. 1 is a principle configuration diagram of the present invention.

FIG. 2 is an embodiment of the present invention.

FIG. 3 is an embodiment of an internal circuit.

FIG. 4 is an embodiment of an internal circuit.

FIG. 5 is an embodiment of an internal circuit.

FIG. 6 is a time chart of the present invention.

FIG. 7 is a time chart of the present invention.

FIG. 8 is a time chart of the present invention.

FIG. 9 is an explanatory diagram of a relay drive circuit.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Combustion control circuit 2 Fuel valve 10 Ignition trial circuit 11 Flame detection circuit 12 Relay drive means 13 Capacitor means 14 First control means 15 Second control means 16 Generation means

Claims (2)

(57) [Claims] 1. A relay comprising an exciting coil for opening and closing a fuel valve, and a normally open contact of the relay, which is connected in series,
Relay driving means for opening and closing a fuel valve, capacitor means for charging electric charge in response to a combustion control start instruction, and establishing a current path between the capacitor means and the exciting coil when entering an ignition trial. A first control means for supplying an exciting current of the relay to the exciting coil and for suppressing charging of the capacitor means when a pseudo ignition trial occurs; and a contact means for detecting a flame when a flame is detected. Establishing a current path between the exciting coil and the exciting coil, so that the holding current of the relay flows through the exciting coil, and further, when a pseudo flame occurs, a second control for suppressing charging of the capacitor means. Means for generating a signal indicating whether or not a normal combustion state is present, based on a voltage generated by opening and closing of the contact and whether or not a flame is detected. A combustion control circuit comprising: 2. The combustion control circuit according to claim 1, wherein the generation unit detects whether the relay is energized by comparing a voltage generated by opening and closing the contact with a predetermined reference value, A combustion control circuit, which, when excitation of a relay is detected and a flame is detected, generates a signal indicating a normal combustion state.