JPS5812020Y2 - Combustion control device - Google Patents

Description

[Detailed Description of the Invention] The present invention relates in particular to the construction of a safety circuit of a combustion control device such as a boiler, and will be specifically explained below based on an embodiment shown in the drawings.

1 (/'i With an AC power supply, a burner circuit 4 including an ignition transformer, a fan motor, a fuel valve (all not shown), etc. is connected to the primary side of the transformer 2 via a normally open relay contact 3 of a thermo-relay to be described later. It is connected.

5 is a rectifier placed on the secondary side of the transformer 2, 6 is a smoothing capacitor, and 7 is a resistor.

8 is a thermo circuit, and the circuit 8 includes a thermistor 9,
It has a transistor 10 that becomes conductive when the thermistor 9 has a high resistance (that is, a low water temperature signal), and the collector of the transistor 10 and the base of the first transistor 12 constituting the Schmitt circuit 11 are connected to a Zener diode 13 and in order. The connection is made through a diode 14 which is connected to the diodes 14.

A thermorelay 15 is connected in series with the second transistor 16 of the Schmitt circuit 11.

Reference numeral 17 denotes a lock circuit, in which a transistor 19 is cut off by a non-ignition signal from the combustion determination circuit 18, a timer circuit consisting of a resistor 20 and a capacitor 21 is operated, and a transistor 22 and a transistor 22 are turned on after a set time of this circuit. , the transistor 2 becomes conductive due to conduction of the transistor 22.
3, and the collector of transistor 23 is connected to the base of transistor 22.

The collector of the transistor 23 is connected to the base of the transistor 12 of the Schmitt circuit 11 via a resistor 24 and a diode 25.

Note that 26 is a keep relay connected in series with the transistor 22, and this relay 26 has a normally closed contact 27 in the line between the rectifier 5 and the capacitor 6, and also has a normally closed contact 27 in the line between the rectifier 5 and the capacitor 6.
A diode 28 is connected to the line between them.

29 (ri) This is a reset switch for the keep relay, and the normally open contact of the switch is taken out from the power supply side of the contact 27.

30 is a combustion circuit such as a pre-purge circuit.

The present invention has the above-described configuration. When the power is turned on, first, when the water temperature is low, the thermistor 9 has a high resistance, the transistor 10 is conductive, and the Schmitt circuit 11 operates in a non-inverting manner (that is, the transistor 12 is cut off, and the transistor 16 is turned off). The thermo-relay 15 is driven to close the relay contact 3 and the burner circuit 4 is energized.

Then, by energizing the combustion circuit 30 again, combustion is performed in a sequence such as pre-purge and ignition.

However, if the fire goes out during combustion or a non-ignition situation occurs, first the transistor 19 is cut off by a non-ignition signal from the combustion determination circuit 18.

As a result, a timer circuit consisting of a resistor 20 and a capacitor 21 starts operating, and when the capacitor 21 becomes saturated after a set time, the transistor 22 becomes conductive and the transistor 23 also becomes conductive.

Note that due to the conduction of this transistor 23, current also flows into the base of the transistor 22, so even if the charge of the capacitor 21 is discharged, the current flows into the base of the transistor 22.
This means that conduction between the two is maintained.

When the transistor 23 becomes conductive, the collector voltage becomes high, and this collector voltage becomes the Schmitt circuit 1.
Since the voltage is applied to the base of the transistor 12 of No. 1, the transistor 12 becomes conductive, and the transistor 16 becomes non-conductive, causing the Schmitt circuit 11 to operate in reverse, stopping the driving of the thermorelay 15 and opening the contact 3. , the power to the burner circuit is cut off.

In this embodiment, when the lock circuit 17 is activated, the keep relay 26 is also activated to open the contact 27.

In this device, the lock circuit 17 can be released by turning on the power supply, but the keep relay 26 remains in the kept state even if the power supply is turned on, and to release it, switch the reset switch 29 to the normally open side and switch Relay 26 → Resistor T
This can be done by passing a current through.

As described above, according to the present invention, the changing voltage of the lock circuit 17 operated by the non-ignition signal from the combustion determination circuit is configured to be the inverted output voltage of the Schmitt circuit 11 of the thermo circuit 8. Accordingly, the number of parts such as transistors can be reduced, and in combination with the keep relay 26 as in this embodiment, the safety of the combustion control device can be doubled, and various other effects can be achieved.

[Brief explanation of the drawing]

The drawing is an overall view showing an embodiment of the present invention. 9... Thermistor, 11... Schmitt circuit, 15... Thermorelay 17...
...Lock circuit, 18... Combustion judgment circuit.

Claims (1)

[Scope of utility model registration request] It has a lock circuit that responds to the non-ignition signal from the combustion judgment circuit and maintains its operating state, and a Schmitt circuit that controls the thermorelay in response to the detection signal of the thermistor. A combustion control device that causes a reversal operation to stop driving of a relay based on a detection signal or the operation of the lock circuit.