JPH0754184B2 - Combustion safety device - Google Patents

Description

Description: TECHNICAL FIELD The present invention constantly monitors the ignition and misfire state in a combustion appliance,
The present invention relates to a safety device configured to automatically stop combustion if there is an abnormality.

2. Description of the Related Art Generally, when a flame detection sensor is a flame rod in a combustion detection circuit of a combustion instrument, a constant level of a flame current flowing due to the rectifying action of the flame (Ignition and misfire detection threshold value. When flame current decreases due to incomplete combustion) It is the same as the incomplete combustion detection threshold value of 1.) The field effect transistor (hereinafter referred to as FET) is turned on by the flame detection signal above and an electric circuit is formed, which is used as a combustion detection signal in the operation control circuit of the combustion appliance. Enter Therefore, when the FET has an open failure, the signal does not electrically transmit and the combustion detection signal does not enter the combustion control circuit even if the instrument is operated, so the operation does not start, and the FET opens while the instrument is operating. Even if a failure occurs, the flame detection signal will not be transmitted as before, so the operation was stopped and safe operation was performed. on the other hand
When the FET is short-circuited, a flame detection signal is generated before ignition when the equipment is operated, so the operation control circuit determines that it is abnormal and does not activate it.

Problems to be Solved by the Invention Generally, in the conventional circuit described above, when the FET is short-circuited while the appliance is operating, the flame detection signal is normally transmitted before and after the FET is short-circuited. The circuit determines that the circuit is normal and will continue to burn. As a result, an incomplete state in which raw gas continues to be released into the room in the unlikely event that the combustion flame blows out or the rubber hose is stomped during a misfire during operation of the appliance. In addition, even if the flame current decreases below the incomplete combustion detection threshold when the CO concentration in the room rises due to incomplete combustion of the equipment due to an unexpected cause.
Since the FET does not turn off, there is a risk that the equipment will continue to operate, resulting in a CO poisoning accident or an oxygen deficiency accident.

In view of the above problems, the present invention provides a combustion safety device capable of automatically stopping the operation of an appliance when a short circuit failure of an FET occurs during the combustion operation.

Means for Solving the Problems In order to solve the above problems, the combustion safety device according to the present invention converts the output signal from the threshold value generating means into a two-level threshold value by a predetermined frequency signal from the microcomputer. Inputting to the microcomputer the threshold conversion means, the ignition detection misfire output generation means for generating the output of a predetermined frequency by comparing the combustion detection output with the two-level threshold, and the signal from the ignition misfire output generation means. A / D conversion means is provided.

Action The present invention, by the above-mentioned configuration, the output signal of the ignition / misfire output generation means is lowered and the A / D conversion means of the next stage is made inoperative when the FET is short-circuited during the combustion operation. When the flame detection signal is not input, the microcomputer judges that there is a misfire and stops the operation of the equipment.

Embodiment One embodiment of the present invention will be described below with reference to the drawings. In FIG. 1, reference numeral 1 is a combustion detection output generating means for outputting a voltage Vg according to a current flowing between a flame rod and a burner due to a rectifying action of a flame. Reference numeral 2 is a D / A conversion means, which converts a signal from the microcomputer 7 according to the combustion amount into an analog signal. 3 is a threshold value generating means, which is the D / A
Based on the signal from the conversion means 2, an ignition / misfire detection threshold value (this value corresponds to an incomplete combustion detection threshold value) corresponding to the combustion amount is created. Reference numeral 4 is a threshold conversion means, which is turned on in synchronization with a predetermined frequency output from the microcomputer 7.
It has a circuit which operates / OFF and outputs a signal from the threshold value generating means 3 (level 1) when it is OFF, and outputs a threshold value (level 2) which is sufficiently higher than the level 1 when it is ON (both are Vs). Reference numeral 5 is an ignition / misfire output generating means, which has a FET inside. The ignition / misfire output generating means 5 receives the signal from the combustion detecting output generating means 1 at the threshold level 1
The FET turns on when it is sufficiently higher, and the FET turns on when the threshold level is 2.
Turns off. As a result, 2 corresponding to ON / OFF operation of FET
The level output is generated in synchronization with the predetermined frequency. Reference numeral 6 denotes an A / D conversion means, which converts the two-level analog value from the ignition / misfire output generation means 5 into an input signal to the microcomputer 7. The inside of the A / D conversion means 6 is a comparator, and the A / D conversion means 6 operates when the FET is normally ON / OFF operated by setting the comparison level near the intermediate value of the two levels. However, when the FET is short-circuited, only the output level when the FET is ON is input to the comparator of the A / D conversion means 6, so that the comparator becomes either HI or LO, and as a result, the microcomputer 7
Works to stop driving.

FIG. 2 shows a detailed circuit diagram of the above embodiment. 10 is power supply, 11
Is an insulating transformer, and one side of the secondary side is connected to the burner 13. Reference numeral 12 is a frame rod, which is set at a position facing the burner 13 to detect a combustion flame. 14, 16, 18, and 19 are resistors, and 15 and 17 are capacitors. 20, 21, 22, and 23 are resistors, and 24 and 25 are high resistors, and have the same value, and the intersection is an intermediate value between the voltage of the resistor 21 and the voltage of the resistor 23. 26 is a transistor,
27, 28 and 29 are resistors, 30 is an operational amplifier, and 31 and 32 are resistors, which determine the amplification gain of the operational amplifier 30. 33 is a field effect transistor (called FET), 34, 35, 36, 37 are resistors, 38
Is a comparator, 39 is a resistor, 40 is a DC voltage Va, and 41 is a DC voltage Vb. Reference numeral 7 is a microcomputer that controls the equipment.

Next, the operation will be described. When a combustion flame is formed on the burner 13, an insulation transformer is applied between the burner 13 and the frame rod 12.
Frame rod 12, burner 13, resistance by the secondary voltage of 11
A flame current flows through 14, 16 and 18 to output a voltage Vg to the resistor 18. The output of the D / A conversion means 2 is an output proportional to the combustion amount, and is O (V) when the combustion is minimum and Va (V) when the combustion is maximum. Therefore, by appropriately setting the values of the resistors 21 and 23, a voltage proportional to the combustion amount is output at the intersection of the resistors 24 and 25 (output waveform is shown in FIG. 3), and then the operational amplifier 30, resistor 31, and
The source voltage Vs of the FET 33 is amplified by the non-inverting amplifier 32. FET33 has a gate voltage Vg lower than the source voltage Vs −
It has the characteristic of turning on when the voltage changes from 0.2 to -0.6V. That is, the source voltage − (0.2 to 0.6 V) is the ignition / misfire detection threshold value. On the other hand, the HI of a predetermined frequency from the microcomputer 7
When the transistor 26 is turned on / off by the / LO signal and the transistor 26 is turned on, the voltage at the intersection of the resistors 24 and 25 is raised by the resistor 27, and as a result, the voltage input to the + input of the operational amplifier 30 is the operational amplifier 30 and the resistor 31. , And the source voltage Vs of the FET 33 is sufficiently higher than the gate voltage Vg (value of 0.2 to 0.6 or more) by being amplified by the non-inverting amplifier of 32, and the FET 33 is turned off. When the transistor 26 is off, the output voltage of the resistance 18 of the combustion detection output generating means 1 is the gate voltage Vg of the FET 33 in the FET 33.
And Vg-Vs =-(0.2 to 0.6) V so that resistance 2
FET33 is turned on by setting the values of 1, 23 and resistors 31, 32 in advance.
(The output waveform is shown in FIG. 4). A two-level voltage is generated at the intersection of the resistance 34 and the resistance 35 when the FET 33 is turned ON / OFF. resistance
Since the intersection of 36 and 37 is set to an approximately intermediate value of the two-level voltage, the comparator 38 outputs a digital value of a predetermined frequency. Now when the FET33 is short-circuited while burning,
Since the voltage when the FET 33 is ON is continuously output to the intersection of the resistors 34 and 35, the comparator 38 becomes an HI output and the microcomputer 7 judges that there is an abnormality and stops the operation of the equipment (the output waveform is shown in FIG. 5). Shown).

The microcomputer 7 which is a component of the present invention
Is a so-called one-chip microcomputer having a CPU, ROM, RAM, and an input / output unit.

EFFECTS OF THE INVENTION As is apparent from the embodiments described above, the present invention comprises threshold conversion means for converting an output signal from the threshold generation means into a two-level threshold value by a predetermined frequency signal from a microcomputer, An ignition / misfire output generating means for comparing the combustion detection output with a two-level threshold value to generate an output of a predetermined frequency and an A / D conversion means for inputting a signal from the ignition / misfire output generating means to a microcomputer are provided. As a result, when the FET is short-circuited during combustion operation, the output signal of the ignition / misfire output generation means drops and the A / D conversion means in the next stage becomes inoperative, resulting in no flame detection signal being input to the microcomputer. The microcomputer determines that a misfire has occurred and stops the operation of the equipment to ensure the safety of the user.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of the present invention, FIG. 2 is a detailed circuit diagram showing an embodiment of the present invention, and FIGS. 3 to 5 are output waveform diagrams of respective portions of FIG. . 1 ... Combustion detection output generation means, 2 ... D / A conversion means, 3
...... Threshold value generating means, 4 ... Threshold value converting means, 5 ...
… Ignition and misfire output generation means, 6 …… A / D conversion means, 7 ……
Microcomputer, 33 ... Field effect transistor (FET).

Claims (1)

[Claims] 1. A combustion detection output generating means for detecting a combustion flame by a flame rod to generate an output, a D / A converter for converting a signal from a microcomputer according to a combustion amount, and the D / A conversion. A threshold value generating means for determining the ignition and misfire detection level from the signal of the pressure vessel, and a predetermined frequency signal from the microcomputer for converting the output signal from the threshold value generating means into a two-level threshold value (Vs). Threshold value conversion means, ignition detection misfire output generation means for comparing the combustion detection output (Vg) with the two-level threshold value (Vs) converted by the threshold value conversion means to generate an output of a predetermined frequency, and the ignition. A combustion safety device comprising A / D conversion means for inputting a signal from a misfire output generation means to a microcomputer.