JPH0477205B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a safety device for a combustor that uses gas or oil as fuel.

Conventional structure and problems With conventional gas stoves, for example, if the user accidentally leaves the cooking area while cooking tempura, etc., the temperature of the tempura oil will rise, and the oil vapor will ignite and cause a fire. There are many cases where this happens.

A number of ideas have been devised to prevent this, but they have not been put into practical use because of the need to ensure safety in the event that the preventive device breaks down, and the cost of such devices increases.

In addition, there is a thermocouple safety device to prevent raw gas from leaking and igniting the leaked gas if the combustion flame blows out due to the influence of wind while using a gas stove, resulting in a fire or explosion. This is a structure in which the thermoelectromotive force is directly used to hold the solenoid valve, and it takes time for the thermocouple to heat up sufficiently, and in order to capture the power of the thermoelectromotive force, its resistance value must be lowered, which increases costs. .

OBJECTS OF THE INVENTION The present invention solves the above-mentioned conventional drawbacks, and aims to provide a safe and inexpensive safety device that ensures safety when overheating of frying pans, etc., and also detects blow-out using the same controller.

Structure of the Invention In order to achieve the above object, the combustion safety device of the present invention uses a thermocouple and a heat-sensitive element as a sensor, feeds back the detection signal to a comparator, and when the comparator determines that the detection signal is in a normal state, generates an oscillator. An oscillation output is output from. This oscillation output and the detection signal from the thermocouple are input to the resistor string and become a reference voltage, and the thermoelectromotive force detection circuit compares the detection signal of the thermocouple with the reference voltage and outputs it when the burner is in normal combustion. . This output and the detection signal of the heat-sensitive element are input to a resistor string, and are compared with the detection signal of the heat-sensitive element as a reference voltage for the overheat detection circuit, and the overheat detection circuit outputs when the heat-sensitive element detects a normal temperature. This output causes the solenoid valve drive circuit to output a drive signal.

With the configuration in which each detection signal is fed back from the thermoelectromotive force detection circuit and the overheating detection circuit to the comparator, each input signal is stopped when both detection circuits detect an abnormality, and both detection circuits, thermocouples, and thermosensor Even when an element malfunctions due to a failure, the input signal is stopped, allowing safe combustion control of the burner. Furthermore, by using a configuration in which the reference voltage for both detection circuits is output from a resistor string connected in series between the power supplies, the influence of disturbance noise on the resistor string can be suppressed, and normal output can be expected from both detection circuits. , burner combustion can be controlled more safely.

DESCRIPTION OF EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings.

In FIG. 1, 1 is a gas tank, 2 is a solenoid valve, 3 is a burner, 4 is a SiC thermistor which is a heat sensitive element, and 5 is a thermocouple.

6 is a power supply, 7 is a switch linked to gas tank 1, 8 is a diode, 9 is an LED, 10 is a resistor,
11 indicates a capacitor. 12, 13, 14,
15 and 16 are resistors, 17 is a capacitor, and 18 is a comparator, which constitute an oscillation circuit. 19 is a comparator; 20, 21, and 22 are resistors connected in series between the power supplies; 23 is a comparator that compares the connection between the thermocouple and the resistors 21 and 22; these constitute a thermoelectromotive force detection circuit. 24 and 25 are resistors connected in series with the heat-sensitive element 4, 26, 27, and 28 are resistors for setting a reference voltage, and 29 is a comparator that compares the connection between the heat-sensitive element 4 and the resistor 24 with the reference voltage. A tempura overheat detector is configured as an overheat detection circuit that detects overheating during cooking. The detection signals from the thermocouple 5 and the heat-sensitive element 4 via both detection circuits are fed back as a reference input voltage to the comparator 19. 30 is a transformer, 31 is a diode, 3
2 is a capacitor, and 33 is a solenoid incorporated in the electromagnetic valve 2.

The operation of the above configuration will be explained below.
First, when the gas stove 1 is turned and held, the solenoid valve 2 is forcibly opened and ignited. (The ignition circuit and the circuit and mechanism for forcibly opening the solenoid valve 2 are not shown.) When the switch 7 linked to the gas tank 1 is closed and energized, the oscillation circuit oscillates. The oscillation output is output from thermocouple 5 by comparator 19.
and the normal value signal from the heat-sensitive element 4, causing the connection portion between the resistor 21 and the resistor 22 connected in series between the power sources to oscillate. Therefore, the connection between the resistors 20 and 21 oscillates at a voltage several mV higher than that. When the thermocouple 5 is not heated, the input terminal of the comparator 23 is always high and the output is L, but when the thermocouple 5 is heated by the flame, the terminal is temporarily lower than the connection between the terminal resistors 21 and 22, and the output is Indicates oscillation. (Even if the output of the comparator 19 oscillates and becomes L, it does not become completely OV.) At this time, even if noise enters between the power supplies, the same resistor series 20, 2
1 and 22, so they are in the same phase and can be ignored as outputs, so they are resistant to noise and can detect several mV without amplification. Also, no matter which resistor 20 to 28 is open shorted, the comparators 18, 19, 2
Even if 3 and 29 fail, the output will not show oscillation.

Next, the oscillation output obtained by the generation of thermoelectromotive force is transmitted to the next-stage ceiling-top overheat detectors 24-29. In the case of the SiC thermistor of this example, the heat-sensitive element 4 has a resistance of 700 kΩ at room temperature, and a safe temperature of 250°C at which baking oil ignites.
However, by setting the resistor 24 and the resistors 26, 27, and 28 that create the reference voltage, the comparator 29 transmits oscillation when the temperature exceeds 60 kΩ, that is, below the temperature at which the cooking oil ignites, and It does not transmit oscillation when the temperature is reached. If resistor 26 and resistor 27 and 28 are selected to have the same value, and resistor 24 is 60kΩ, SiC
If the thermistor is 60 kΩ or less, the terminal of the comparator 29 will always be higher than the terminal, and the output will not oscillate. Also, if the value of resistor 25 is 1MΩ,
If the SiC sensor is 1MΩ or more (broken wire), it will not oscillate. Furthermore, if the resistors 26, 27, and 28 that generate the reference voltage of the heat-sensitive element 4 are disconnected or have a soldering defect, the reference input of the comparator 19 becomes the power supply voltage or OV, so its output becomes high or low and does not oscillate. Therefore, since it is composed of resistors in the same row, it is resistant to noise and SiC sensor 4
It is safe because it does not oscillate even when the resistors 24 to 28 open or the comparator 29 fails.

If there is a combustion flame, and the temperature of the frying oil is 250
If the temperature is below ℃, the oscillation output causes the transformer 30 to oscillate and is rectified by the diode 31 and capacitor 32 to keep the solenoid valve 2 open, but in the unlikely event that it blows out or the temperature of the frying pan oil becomes 250℃ or higher. In this case, the transformer 30 does not oscillate and the solenoid valve 2 is not held open.
These accidents can be prevented.

Effects of the Invention As described above, the present invention inputs the feedback signals from the thermoelectromotive force detection circuit and the overheat detection circuit to the comparator that serves as a signal oscillation source for both detection circuits, and only when the comparator determines that the signal is in a normal state. By outputting a signal, in addition to abnormality detection by the thermocouple and heat-sensitive element, an abnormality signal based on circuit abnormality of both of the detection circuits can also be detected and the electromagnetic valve drive signal can be stopped, making it possible to control the appliance more safely.

In addition, the reference voltage with which both of the detection circuits compare the detection signals of the thermocouple and the heat-sensitive element is output from the resistor string connected in series between the power supplies, so that the resistor string effectively eliminates the reception influence of disturbance noise. This allows the output signals of both detection signals to be maintained normally and the instrument to be controlled more safely.

[Brief explanation of drawings]

The figure is a configuration diagram showing a case where a combustion safety device according to an embodiment of the present invention is applied to a gas stove. 4...Thermosensitive element, 5...Thermocouple, 18...Comparator, 20, 21, 22...Resistor.

Claims (1)

[Claims] 1. A thermocouple that detects the combustion flame of the burner of a combustion cooking appliance, a heat-sensitive element that is in close contact with the bottom of the cooking container to detect temperature, a solenoid valve placed in the combustion passage, and a power signal that oscillates to drive the solenoid valve. an oscillator that outputs,
A comparator that receives feedback from the detection signals from the thermocouple and the thermosensitive element to control the oscillation output of the oscillator, and a resistor string that receives feedback between the resistors connected in series between the power supply, the thermocouple detection signal, this detection signal, and the oscillation of the oscillator. A thermo-electromotive force detection circuit that compares and outputs a reference voltage input from a resistor string by output, a detection signal of a thermosensitive element, and a reference voltage input from a resistor string by this detection signal and the output of the thermo-electromotive force detection circuit. A combustion safety device equipped with an overheat detection circuit that compares and outputs an output, and a solenoid valve drive circuit that outputs a solenoid valve drive signal based on input from the overheat detection circuit.