JPS643973Y2 - - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to a combustion control device for a forced draft combustion appliance.

In conventional combustion appliances, if the flame goes out for some reason during steady combustion, the flame detection circuit is activated, but even if it is possible to restart the combustion normally by restarting the ignition operation in such a case. ,
The type of abnormality, such as immediately entering safe operation,
This was extremely difficult for users to use, as all devices operated safely and stopped regardless of the condition.

This idea was made in view of the actual situation,
By skillfully linking the pre-purge circuit, flame detection circuit, and gas valve drive circuit, which are essential in forced draft combustion appliances, it not only enables the above-mentioned re-ignition operation, but also has the ability to check for continuity failures in the circuit. It has a simple configuration that also has the following features, and this will be explained below based on the illustrated embodiment.

1 is a heat exchanger for an instantaneous water heater, 2 is the heat exchanger 1
3 is a hot water outlet, and 42 is a hot water supply channel. Reference numeral 4 denotes a burner for heating the heat exchanger 1, and a forced draft combustion method is employed in which air for combustion is supplied by a fan 5. 6 is a gas solenoid valve provided in the gas path to the burner 4, 7 is an igniter placed near the burner 4, and 8 is a flame rod for flame detection. 9 is a water flow switch provided in the inlet channel 2, which detects water flow and closes the water flow. Reference numeral 10 denotes an operating device provided at an arbitrary location, and includes an operation switch 11 and a combustion lamp 12. 13 is a control device. FIG. 2 shows the electric circuit of the above embodiment, in which the fan 5 is connected to the primary side of the power transformer 14 via a first relay contact 15, and the gas solenoid valve 6 is connected to the primary side of the power transformer 14 via a second relay contact 16. are connected. On the secondary side of the power transformer 14, the operation switch 11 and the water flow switch 9 are connected in series to the power line, and the fan drive circuit 17, pre-purge circuit 18, gas solenoid valve drive circuit 19, and flame detection circuit 20 are installed after these. etc. are provided. The fan drive circuit 17 includes a transistor 21 which is turned on when the water flow switch 9 is closed, and a first relay 22 having the first relay contact 15 which is turned on and off by the transistor 21. Prepurge circuit 18
has a comparator 27 whose positive input is the voltage across the capacitor of a CR timer 25 consisting of a resistor 23 and a capacitor 24, and whose negative input is the voltage of a reference resistor 26. Further, the gas solenoid valve drive circuit 19 is
Transistor 2 conductive at the output of the comparator 27
8. PNP transistor 29 provided in the power supply line connected by the transistor 28, the PNP
It consists of a transistor 30 that is conductive when the transistor 29 is conductive, a second relay 31 having the second relay contact 16 provided in the output circuit of the transistor 30, and the like. The flame detection circuit 20 includes a comparator 32 whose output is inverted to high when the flame rod 8 detects the flame, and a transistor 33 whose output is turned off. The collector of the transistor 33 is connected to the base of a PNP transistor 34 that maintains the conduction of the transistor 29 of the gas solenoid valve drive circuit 19 by a line 35, and when a flame is detected, the transistor 29 is kept conductive and the solenoid valve 6 is kept conductive. A self-holding circuit 41 that maintains the open state is activated. Reference numeral 36 is a transistor whose base is connected to the output side of the comparator 32 of the flame detection circuit 20 and which applies positive feedback to the comparator 27 until the flame is detected, and whose collector is connected to the positive terminal of the capacitor 24. be. And the pre-purge circuit 18 and the flame detection circuit 20
And the gas solenoid valve drive circuit 19 means the capacitor 2
4 are connected by lines 37 and 38 which connect the collectors of transistor 30 of circuit 19 and transistor 33 of circuit 20, respectively. The combustion lamp 12 is connected to the line 38 from the downstream side of the water flow switch 9. 39 is a resistor provided on the line 37, 40 is a transistor 36
This is a resistor connected to the output side collector of .

Next, the operation in the above configuration will be explained. When the hot water supply switch 42 is opened after the operation switch 11 is turned on, a water flow is generated in the inlet channel 2 and the water flow switch 9 is closed. As a result, the first relay 22 operates, its contact 15 closes, and the fan 5 is driven. on the other hand,
Current also flows through the CR timer 25, but the comparator 27 does not invert for a certain period of time set by the timer 25, and during this period it becomes a pre-purge circuit in which only air is blown. After this time has elapsed, the comparator 27 is inverted to a high output, and the transistor 28 is turned on, thereby turning on the transistor 29. Therefore, the transistor 30 is turned on, the second relay 31 is operated, its contact 16 is closed, the gas solenoid valve 6 is opened, and gas is supplied to the burner 4. At this time, an ignition circuit (not shown) operates simultaneously to ignite the gas. The flame rod 8 detects this ignition and the comparator 32 is inverted, but until then the comparator 32 is in a low output state. conducts from line 37 to transistor 3
0, the resistors 23, 39, 40
Since the positive input of the comparator 27 is maintained at a potential divided by , the comparator 27 maintains a high output, and therefore the electromagnetic valve 6 is maintained in an open state. When the comparator 32 is inverted due to ignition and the transistor 33 becomes conductive, a base current flows through the line 35, the transistor 34 becomes conductive, and the transistor 29 self-maintains in a conductive state. On the other hand, transistor 36 is turned off, and the positive input potential of comparator 27 falls from transistor 33 to ground via line 38, so that
Although the comparator 27 is reversed to a low output, the gas solenoid valve 6 remains open due to the self-holding operation.
Enters steady combustion. At the same time, the combustion lamp 12 lights up to notify that combustion is in progress.

In this way, during steady combustion, for some reason burner 4
Conventionally, when the flame rod 8 no longer detects the flame due to extinguishing the flame or due to strong wind gusts, the flame rod 8 would immediately operate safely as described above, but in this proposal, when the transistor 33 is turned off, the transistor 34 is turned off. is turned off, the self-holding of the transistor 29 is released, the gas solenoid valve 6 is closed, and the line 38 is cut off to restart the above operation that starts with charging the capacitor 24. In this case, the raw gas is first charged by pre-purge. Since the re-ignition operation begins after the gas is discharged, there is no explosion and ignition, and the re-ignition can be carried out extremely safely, allowing the appliance to continue to be used.

Next, we will explain the case where the transistor 30 for driving the gas solenoid valve has a conduction failure. In this case, the positive input potential of the comparator 27 increases only to the potential divided by the resistor 39 via the line 37 and the transistor 30. Since the comparator 27 is not inverted, the prepurge operation is not completed. Therefore, since the combustion lamp 12 does not turn on forever, the user can know that there is a malfunction. Further, even if the transistor 33 of the flame detection circuit 20 has a conduction failure, the inverting input of the comparator 27 is bypassed from the line 38, so that the failure is similarly notified. This also applies when the flame rod 8 detects a simulated flame from the beginning. By providing the lines 37 and 38 in this manner, any troubles in the transistors 30 and 33 can be detected through safe operation.

In summary, the present invention provides a prepurge circuit that includes a CR timer that starts operating when energized, a comparator that is inverted according to the charging potential of a capacitor that constitutes the timer, and an output of the comparator of the prepurge circuit. a gas solenoid valve drive circuit having a transistor that conducts at a temperature to open the gas solenoid valve; and a flame detection circuit having a transistor that conducts to open the gas solenoid valve by detecting a flame. The positive electrode side of the transistor and the capacitor is connected to the transistor of the flame detection circuit by a line, each line is disconnected by the respective transistor, and the transistor of the gas electromagnetic valve drive circuit is kept conductive or made non-conductive. Since a self-holding circuit is provided and this circuit is controlled by turning on or off the transistor of the flame detection circuit, the appliance does not operate safely by extinguishing the flame once, but by attempting to re-ignite it and continue using the appliance. Furthermore, as the gas is shut off immediately upon detection of extinguishing the flame, pre-purging is performed, and the raw gas is discharged before being re-ignited, it is possible to obtain a safe and convenient appliance without causing explosive ignition. Furthermore, there is no need to construct separate circuits for the function of checking continuity failures in the transistors for driving the gas electromagnetic valve and for detecting the flame, which is advantageous in terms of cost.

[Brief explanation of the drawing]

Figure 1 is an overall configuration diagram of the combustion appliance according to the present invention,
FIG. 2 is an electrical circuit diagram showing an embodiment of the present invention. 6...Gas solenoid valve, 18...Prepurge circuit,
19... Gas solenoid valve drive circuit, 20... Flame detection circuit, 24... Capacitor, 25... CR timer,
27... Comparator, 30, 33... Transistor,
37, 38... line, 41... self-holding circuit.

Claims (1)

[Scope of utility model registration request] A CR timer that starts operating when energized,
A gas solenoid valve drive having a prepurge circuit having a comparator that is inverted in accordance with the charged potential of a capacitor constituting the timer, and a transistor that conducts with the output of the comparator of the prepurge circuit to open the gas solenoid valve. circuit, and a flame detection circuit having a transistor that becomes conductive upon flame detection, the positive electrode side of the capacitor and the transistor of the gas electromagnetic valve drive circuit, and the positive electrode side of the capacitor and the transistor of the flame detection circuit are connected in a line, respectively. A self-holding circuit is provided which connects each line with a transistor and disconnects each line with a respective transistor, and which keeps the transistor of the gas electromagnetic valve drive circuit conductive or non-conductive,
A combustion control device for a forced draft combustion appliance, characterized in that the circuit is controlled by turning on and off a transistor of the flame detection circuit.