JP3171809B2 - Heating equipment - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heating apparatus having a function corresponding to an abnormal heating state or an abnormal state of the apparatus.

[0002]

2. Description of the Related Art Conventionally, in a heating device such as a gas stove, an opening / closing solenoid valve provided in a gas supply path and a container in which a food to be heated is placed in contact with a container, and the temperature of the container is controlled. And a temperature abnormality detecting circuit (high temperature abnormality detecting circuit) for detecting that the temperature detected by the temperature detecting means has exceeded a predetermined temperature. There is an apparatus in which the on-off electromagnetic valve is closed to stop gas supply to the burner to stop combustion.

Further, when the temperature detecting means has a disconnection failure,
Alternatively, in the case where the temperature detecting means is connected to the electronic unit provided in the heating device via a connector, when the connector is disconnected, the temperature cannot be detected, and the high temperature state cannot be detected. Therefore, a disconnection abnormality detection circuit for detecting a disconnection failure of the temperature detection means is provided, and when the temperature detection means has a disconnection failure, the on-off solenoid valve is closed to stop the supply of gas to the burner and inhibit combustion. There is known one that secures safety.

In order to prevent the fuel gas from being continued to be supplied to the burner when the burner is misfired due to spillage or wind of the cooking material during the operation of the heating device, temperature detecting means (for example, a thermocouple) is used. ) To detect the temperature of the combustion flame,
A temperature abnormality detection circuit (misfire abnormality detection circuit) for detecting that the detected temperature of the combustion flame has become equal to or lower than a predetermined value is provided. There is known an apparatus in which supply of water is stopped.

[0005] The high temperature abnormality detection circuit, the disconnection abnormality detection circuit, and the misfire abnormality detection circuit each include a comparator for comparing the output of the temperature detection means with a predetermined reference voltage. When the comparator fails, the output of the comparator is fixed to the same state as when the detected temperature is normal, and the open state of the on-off solenoid valve may be maintained. In this case, since the user does not notice the failure of the comparator, there is an inconvenience that the above-described abnormal state of high temperature or supply of gas at the time of misfire occurs.

[0006] In order to prevent these inconveniences, there has been known one in which two comparators are provided in parallel to improve reliability.
According to this, even if one of the comparators fails, the combustion of the burner can be stopped by the abnormality detecting means by the output of the other comparator, and the supply of gas to the burner is stopped. Can be done.

However, when two ICs each including one comparator are used in one package, there is a disadvantage that the cost of parts increases and the mounting space of the IC package also increases. In addition, when an IC including two comparators in one package is used, there is a high possibility that the two comparators will fail at the same time, so that there is a disadvantage that the effect of improving safety is small.

[0008]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a heating apparatus which solves the above-mentioned inconveniences and which has improved reliability when an abnormal condition occurs.

[0009]

SUMMARY OF THE INVENTION In order to achieve the above object, the present invention provides an on-off solenoid valve provided in a fuel supply passage, abnormality detecting means for outputting a voltage corresponding to an abnormal state, and the abnormality detecting means. And a solenoid valve driving circuit that closes the on-off solenoid valve in response to the abnormality signal, wherein the abnormality detection circuit comprises: An output voltage of the detection means and a predetermined reference voltage are input and compared, and a DC signal is output when the output voltage is in a predetermined relationship with the reference voltage, and an AC signal is output when the output voltage is not in the predetermined relationship. And a DC signal detection circuit connected to the comparison circuit and outputting the abnormal signal only when a DC signal is input from the comparison circuit.

Generally, when a circuit constituted by a semiconductor element is broken, its output is likely to be fixed at a constant voltage level. Therefore, if the comparison circuit is broken,
The output is a constant DC voltage regardless of the input output voltage of the abnormality detecting means. Therefore, a DC signal is output from the comparison circuit to the DC detection circuit, the abnormal signal is output from the DC detection circuit to the electromagnetic drive circuit, and the on-off solenoid valve is closed. That is, when the comparison circuit is broken, the supply of fuel from the fuel supply path to the heating device is stopped, and the heating device becomes unusable. Thus, it is possible to prevent the heating device from being used in a state where the comparison circuit is broken and the abnormal temperature state cannot be detected. Note that the abnormality detection circuit includes:
Any of a high temperature abnormality detection circuit, a misfire abnormality detection circuit, and a disconnection abnormality detection circuit may be used.

The abnormality detecting means includes a series circuit including a temperature detecting element and a voltage dividing resistor connected in series with the temperature detecting element, and a power supply connected to the series circuit. Receives a voltage dividing resistor switching circuit that periodically switches a resistance value of the voltage dividing resistor between high and low values of a first resistance value and a second resistance value, and inputs the reference voltage and an output voltage of the abnormality detection unit. These are compared to determine whether the output voltage of the abnormality detection means has a predetermined relationship with the reference voltage.
A comparator for switching the output voltage level to one of high and low binary levels, when the resistance value of the voltage dividing resistor is the first resistance value of the high resistance value, or the second resistance value of the second resistance is low. The first resistance value or the second resistance value is set so that the output voltage of the abnormality detecting means always has the predetermined relationship with the reference voltage when the resistance value is the resistance value.

According to the present invention, for example, the predetermined relation is that the output voltage of the abnormality detecting means is equal to or lower than the reference voltage, and the output of the comparator is determined by the output voltage of the abnormality detecting means. Low level when voltage is exceeded,
When the voltage is equal to or lower than the reference voltage, the output voltage of the abnormality detecting means is set to be high when the resistance value of the voltage dividing resistor is the first resistance value of the high resistance value. When the first resistance value is set to be as follows, when the resistance value of the voltage dividing resistor is the first resistance value having a high resistance value, regardless of the output voltage of the abnormality detection means, the comparison is performed. Since the output voltage of the abnormality detecting means input to the comparator becomes equal to or lower than the reference voltage, the output of the comparator becomes high level.

On the other hand, when the resistance value of the voltage dividing resistor is the second resistance value having a low resistance value, if the output voltage of the temperature detecting means is lower than the reference voltage, the output of the comparator becomes high level. If the output voltage of the abnormality detecting means exceeds the reference voltage, the output of the comparator goes low.
That is, when the output voltage of the abnormality detecting means exceeds the reference voltage when the resistance value of the voltage dividing resistor is the second resistance value of the low resistance value, the output of the comparator as a whole is high-low binary. When the output of the abnormality detecting means is equal to or lower than the reference voltage when the resistance value of the voltage dividing resistor is the second resistance value which is a low resistance value, the comparison is performed as a whole. The output of the device becomes a DC (constant high level) signal.

As described above, according to the present invention, even in a simple heating device that does not use a microcomputer, the output voltage of the abnormality detecting means can be adjusted to the predetermined value by adding the voltage dividing resistance switching circuit. A comparison circuit that outputs a DC signal when the relationship is established and outputs an AC signal when the relationship is not established can be easily configured. When the comparison circuit breaks down, the comparison operation between the output voltage of the abnormality detection unit and the reference voltage is not performed, so that the output of the comparator does not switch, and a constant level DC signal is output from the comparison circuit. Output to the DC signal detection circuit. Therefore, the abnormality signal is output from the DC signal detection circuit to the electromagnetic valve driving circuit, and the on-off electromagnetic valve is closed, so that use of the device in a state where abnormality cannot be detected can be prohibited.

When the comparator is set to a high level when the output voltage of the abnormality detecting means exceeds the reference voltage and to a low level when the output voltage is equal to or lower than the reference voltage, similarly, When the output voltage of the abnormality detecting means is not in the predetermined relationship with the reference voltage, the output of the comparator becomes a high-low binary level AC (pulse) signal, and the output voltage of the abnormality detecting means is different from the reference voltage. When in the predetermined relationship, the output of the comparator is DC (constant low level)
As a signal, the function of the comparison circuit can be realized. The relationship between the output voltage of the abnormality detecting means and the reference voltage is determined by the configuration of the abnormality detecting means and the type of abnormality to be detected.

Further, the temperature detecting element is a thermistor for detecting a temperature by a change in a resistance value, and the abnormality detecting circuit is configured to output the abnormality signal when the temperature detected by the thermistor is equal to or higher than a predetermined high temperature abnormality judgment value. And a disconnection abnormality detection circuit that outputs the abnormality signal when the resistance value of the thermistor is equal to or greater than a predetermined disconnection abnormality determination value, and the first resistance value of the high resistance value is A value corresponding to the disconnection abnormality determination value, and the second resistance having a low resistance value.
The resistance value is a value corresponding to the resistance value of the thermistor when the detected temperature is the high temperature abnormal temperature.

When a high temperature abnormality and a disconnection abnormality are detected using a thermistor, the resistance value of the thermistor at the time of abnormality detection is
The value is several hundreds Ω for a high temperature abnormality, and several MΩ for a disconnection abnormality, and the values are greatly different. For this reason, if the voltage dividing resistance of the thermistor is a fixed value, it is difficult to accurately detect the entire resistance value range from the high temperature abnormality to the disconnection abnormality. In such a case, the voltage dividing resistance value of the thermistor is periodically switched between a first resistance value corresponding to the disconnection abnormality determination value and a second resistance value corresponding to the high temperature abnormality determination value. The disconnection abnormality is detected when the resistance value is equal to the second resistance value, and the high temperature abnormality is detected when the resistance value is the second resistance value. The amount of change in the output voltage of the means can be increased,
Detection accuracy can be improved.

The resistance value of the voltage dividing resistor is set to the first value.
When the output of the abnormality detecting means is always in the predetermined relationship with the reference voltage when the resistance value is switched to the resistance value, the first resistance value and the second resistance value are cycled by the voltage dividing resistance switching circuit. The two objectives of realizing the function of the comparison circuit and improving the abnormality detection accuracy can be achieved by one switching circuit. Therefore, an increase in component cost can be suppressed, and the installation space for components can be reduced.

Further, the reference voltage input to the comparator of the abnormality detecting circuit is synchronized with a switching period of the voltage dividing resistor by the voltage dividing resistor switching circuit so that the resistance value of the voltage dividing resistor becomes high. A reference voltage switching circuit for switching to a correction reference voltage when the resistance value is the first resistance value; and when the resistance value of the voltage dividing resistor is the first resistance value of a high resistance value, the voltage is input to the comparator. The correction reference voltage is set such that the output voltage of the abnormality detecting means always has the predetermined relationship with the correction reference voltage.

Depending on the contents of the predetermined relationship, when the resistance value of the voltage dividing resistor is switched to the first resistance value having a high resistance value by the voltage dividing resistance switching circuit, the output voltage of the abnormality detecting means is changed. May not always be in the predetermined relationship with the reference voltage. In this case, when the output voltage of the abnormality detection means and the reference voltage are not in the predetermined relationship,
Even when the resistance value of the voltage dividing resistor is switched between the first resistance value having a high resistance value and the second resistance value having a low resistance value, the output of the comparison circuit is not switched and an AC signal is not output. That is, when the output voltage of the abnormality detecting means does not have a predetermined relationship with the reference voltage, the comparison circuit that outputs an AC signal cannot be realized.

In this case, according to the present invention, the voltage-dividing resistor switching circuit allows the voltage-dividing resistor to have the first resistance having a high resistance value.
When the resistance value is switched, the reference voltage is synchronously switched to the correction reference voltage. The correction reference voltage is set so as to always have the predetermined relationship with the output voltage of the abnormality detecting means. Therefore, when the resistance value of the voltage-dividing resistor is switched to the high resistance value of the first resistance value, the output voltage of the abnormality detection means always has the predetermined relationship with the correction reference voltage. Therefore, when the output voltage of the abnormality detection circuit and the reference voltage are not in the predetermined relationship when the resistance value of the voltage dividing resistor is the second resistance value of a low resistance value, the resistance of the voltage dividing resistor is When the value is switched between the first resistance value having a high resistance value and the second resistance value having a low resistance value, the output of the comparison circuit is switched to a high / low binary level. That is, it is possible to realize the comparison circuit that outputs an AC signal when the output voltage of the abnormality detection unit does not have a predetermined relationship with the reference voltage.

Also, a plurality of the DC signal detection circuits are provided, each DC signal detection circuit receives an output of a comparison circuit of the temperature abnormality detection circuit, and the solenoid valve driving circuit includes at least one DC signal detection circuit. The on / off solenoid valve is closed when the abnormal signal is output from the controller.

According to the present invention, even if some DC signal detection circuits fail, the abnormal signal can be output to the solenoid valve driving circuit by another normal DC signal detection circuit.

[0024]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS First and second embodiments of the present invention will be described with reference to FIGS. FIG. 1 is a configuration diagram of a gas stove, which is a heating device of the first and second embodiments, FIGS. 2A and 2B are characteristic diagrams of a temperature detection element provided in the gas stove of FIG. 1, and FIGS. Circuit configuration diagram of the embodiment,
FIG. 5 is a circuit configuration diagram of the second embodiment.

Referring to FIG. 1, a gas stove according to the present embodiment includes an on-off solenoid valve 3 provided in a gas supply passage 2 serving as a fuel supply passage for supplying a fuel gas to a burner 1 serving as a heating source, and a gas amount adjusting device. The apparatus includes a valve 4, a thermistor 5 for detecting the temperature of the food A to be heated, and an electronic unit 6 for controlling the energization of the on-off electromagnetic valve 3. The opening / closing solenoid valve 3 is operated by an ignition operation (push operation) by an ignition / extinguishing button 7, and a spring 8 is operated.
The valve is opened mechanically, the valve is kept open by energizing the solenoid 9, and the valve is closed by the biasing force of the spring 8 when the energizing of the solenoid 9 is cut off. I have. The opening of the gas amount adjusting valve 4 is adjusted by the user operating the operating element 10 connected thereto, and the supply amount of the fuel gas to the burner 1 is changed.

The thermistor 5 is connected to the electronic unit 6, and is placed at the center of the burner 1 so as to come into contact with the bottom of the cooking container B when the cooking container B containing the food A is placed on the burner 1. It is inserted into the upper end of the support 11 provided. Thereby, the thermistor 5 corresponding to the temperature of the food A
Is detected by the electronic unit 6. Further, a thermocouple 12 provided near the burner 1 and connected to the electronic unit 6 generates an electromotive force according to the temperature of the combustion flame when the burner 1 burns, and the electromotive force is detected by the electronic unit 6. Is done.

The electronic unit 6 includes a high-temperature abnormality detection circuit 13 for outputting an abnormality signal when the resistance of the thermistor 5 detects that the temperature of the food A has reached a high-temperature abnormality exceeding a predetermined value, and a burner 1. That the burner 1 was misfired due to the spillage or wind of the food A during the combustion of the thermocouple 1
2 includes a misfire abnormality detection circuit 14 that outputs an abnormality signal when detected by the electromotive force of 2 and a disconnection abnormality detection circuit 15 that outputs an abnormality signal when disconnection of the thermistor 5 is detected from the resistance value of the thermistor 5. It has a detection circuit 16 and an electromagnetic valve drive circuit 17 that shuts off the power supply to the solenoid 9 when an abnormality signal is output from the abnormality detection circuit 16.

Thus, when the food A is in a high temperature abnormal state, when the burner 1 is misfired, and when the thermistor 5
Is disconnected, the on-off solenoid valve 3 is closed and the burner 1
The supply of gas to is stopped.

Reference numeral 18 denotes a discharge electrode for igniting the burner 1, and 19 denotes a sparker for causing a spark discharge on the discharge electrode 18.

Next, regarding the first embodiment of the present invention,
This will be described with reference to FIGS. 1, 2a and 3. FIG. 2A is an electromotive force-temperature characteristic diagram of the thermocouple 12, and FIG. 3 is a circuit configuration diagram of the misfire abnormality detection circuit 14 of the electronic unit 6 shown in FIG.

Referring to FIG. 3, misfire abnormality detection circuit 14
Is connected to the temperature detecting means 20 which is an abnormality detecting means for outputting a voltage corresponding to the detected temperature,
A comparison circuit that compares the output voltage with a predetermined reference voltage and outputs a high / low binary level voltage according to the comparison result;
A DC signal detection circuit 22 that is connected to the comparison circuit 21 and outputs a low-level signal when the AC signal is output from the comparison circuit 21 and outputs a high-level signal when the DC signal is output from the comparison circuit 21 And the DC signal detection circuit 2
And a solenoid valve drive circuit 17 that is connected to the solenoid 9 via a timer 23 and that shuts off the power supply to the solenoid 9 when a high-level time-up signal is output from the timer 23.

The temperature detecting means 20 comprises a thermocouple 12 and voltage-dividing resistors 25, 26, 27 connected in series with the thermocouple 12.
And a power supply Vcc (for example, 1.5 V) connected to one end of the voltage dividing resistor 25, and outputs a voltage Vd1 at a connection point between the voltage dividing resistors 26 and 27. As is clear from the graph of FIG. 2A, the electromotive force of the thermocouple 12 increases as the detected temperature increases. Since the positive terminal of the thermocouple 12 is connected to the 0 V point, when the temperature detected by the thermocouple 12 increases, the voltage of Vd1 decreases.

The comparator 21 includes a voltage dividing resistor switching circuit 28 for switching the resistance value of the voltage dividing resistor 25 between high and low values, and a comparator 29. The voltage dividing resistor switching circuit 28 includes a voltage dividing resistor 2
5 includes a transistor 30 connected in parallel with the oscillator 5 and an oscillator 31 that periodically outputs a high-low binary level drive signal to the base of the transistor 30. When a low-level signal is output from the oscillator 31, the transistor 30 is turned on, the emitter-collector conducts, the resistance of the voltage dividing resistor 25 becomes almost 0Ω, and the voltage drop at the voltage dividing resistor 25 becomes almost 0V.
Therefore, the voltage of Vd1 increases. The oscillator 31
When the high level signal is output from the transistor 30, the transistor 30 is turned off and the emitter-collector connection is cut off, so that the resistance value of the voltage dividing resistor 25 increases and a voltage drop occurs.
The voltage of d1 decreases. As described above, the output of the oscillator 31 alternately switches the resistance value of the voltage dividing resistor 25 between the first resistance value having a large resistance value and the second resistance value having a small resistance value.

The comparator 29 compares the voltage input to the positive input terminal and the voltage input to the negative input terminal. If the input voltage at the positive input terminal is equal to or higher than the input voltage at the negative input terminal, a high level signal (Vcc) is output. And outputs a low-level signal (0 V) when the input voltage of the positive input terminal is lower than the input voltage of the negative input terminal.

In the first embodiment, when the detected temperature of the combustion flame of the burner 1 by the thermocouple 12 is equal to or less than the misfire abnormality judgment value which is the electromotive force of the thermocouple 12 when the predetermined misfire abnormality judgment temperature is reached. It is determined that the burner 1 has misfired. As for the resistance values of the voltage dividing resistors 25, 26, and 27, the resistance value of the voltage dividing resistor 25 is the first resistance value (high resistance value), and the electromotive force of the thermocouple is the misfire abnormality determination value. At this time, Vd1 input to the negative input terminal of the comparator 29 is set to be equal to the reference voltage VB1 input to the positive input terminal of the comparator 29. That is, when the electromotive force of the thermocouple 12 is less than the misfire abnormality determination value, Vd1 exceeds VB1,
When the electromotive force of the thermocouple 12 is equal to or higher than the misfire determination voltage, Vd1 is set to be equal to or lower than VB1. When the resistance value of the voltage dividing resistor 25 is the second resistance value (low resistance value, approximately 0Ω), the resistance value of the voltage dividing resistors 25, 26, and 27 is independent of the electromotive force of the thermocouple 12. Vd1 is always V
Set to exceed B1.

Therefore, when the resistance value of the voltage dividing resistor 25 is switched to the second resistance value (low resistance value) by the voltage dividing resistor switching circuit 28, Vd1 always exceeds VB1 and the output of the comparator 29 becomes low. Level. When the voltage dividing resistor 25 is switched to the first resistance value (high resistance value), if the misfiring state occurs, Vd1 exceeds VB1 so that the comparator 2
The output of the comparator 29 is at a high level because Vd1 becomes VB1 or less unless the output of the comparator 9 is in a misfire state. That is, when the output of the comparator 29 is at the second resistance value, it is always low level (low resistance value). When it is at the first resistance value, it is in a misfire state (Vd1> VB1) and at a low level (high resistance value). When Vd1 ≤ VB1), the level becomes high.

Therefore, the resistance value of the voltage dividing resistor 25 is periodically switched by the voltage dividing resistor switching circuit 28 between the first resistance value (high resistance value) and the second resistance value (low resistance value).
When the burner 1 is in the combustion state, the output of the comparator 29 is high or low 2
If the burner 1 is in a misfire state, the output of the comparator 29 is a constant low level DC signal.

The DC signal detection circuit 22 includes a capacitor 3
2, resistor 33, transistor 34, resistor 35, resistor 3
6 and a capacitor 37. When a high-level signal is output from the comparator 29, a current flows into the base of the transistor 34 until the capacitor 32 is charged, so that the transistor 34 is turned on and the collector and the emitter thereof are in a conductive state. Therefore, the power supply Vcc─resistance 3
Since the current flows through the path of 6─resistance 35─transistor 34─0 V, the capacitor 37 is not charged and the timer 2
The output voltage to 3 goes low. However, when the capacitor 32 is fully charged, no current flows to the base of the transistor 34, so that the transistor 34 is turned off, and the collector-emitter state is cut off. In this case, a current flows through the path of the power supply Vcc─the resistor 36─the capacitor 37, so that the capacitor 37 is charged, and after a predetermined full charge time determined by the resistance value of the resistor 36 and the capacity of the capacitor 37 has elapsed, the timer 23 Becomes high level.

When the output of the comparator 29 is at a low level, no current flows into the base of the transistor 34, the transistor 34 is turned off, and the collector-emitter state is cut off. Also in this case, the power supply Vcc─resistance 3
6. Since a current flows through the path of the capacitor 37, the capacitor 37 is charged, and a high-level signal is output to the timer 23 after the predetermined full charge time has elapsed. That is, when the output of the comparator 29 is a DC signal having a constant high level or a constant low level, the output of the DC signal detection circuit 22 is at a high level.

When the output of the comparator 29 is an AC signal that switches between high and low binary levels in a cycle shorter than the predetermined full charge time determined by the resistance value of the resistor 36 and the capacitance of the capacitor 37, the transistor 34 are turned on and off in the cycle. When the transistor 34 is turned off, the capacitor 37 is charged. However, the transistor is turned on before the capacitor 37 is fully charged, and the electric charge charged in the capacitor 37 is reduced by the resistance 35─the transistor 34─0V point. Is discharged instantaneously in the path of
The capacitor 37 is not fully charged. Therefore, the comparator 2
9 is an AC signal, the DC signal detection circuit 2
2 is low.

When a high level signal is continuously input for a predetermined time (for example, 7 seconds) or more, the timer 23
It outputs a high-level signal. When the output of the temperature detecting means 20 instantaneously becomes the same voltage as that in the misfire state due to the fluctuation of the combustion flame or electric noise, the misfire state is erroneously detected. This is provided so as not to do so.

The solenoid valve drive circuit 17 comprises PNP transistors 38 and 39 and a resistor 40, and the transistor 38 is connected to a power supply Vs. The base terminal of transistor 38 is connected to timer 23, and the base terminal of transistor 39 is connected to timer 41. Therefore, when a high level signal is output from the timer 23, the transistor 3
8 turns off, the emitter-collector is cut off, and when a high level signal is output from the timer 41, the transistor 39 turns off and the emitter-collector is cut off. The energization is cut off and the on-off solenoid valve 3 is closed.

Reference numeral 42 denotes a misfire detection preliminary circuit, which detects a misfire abnormality by comparing the voltage at the connection point of the voltage dividing resistors 44 and 45 connected in series with the thermocouple 12 with the reference voltage VB2. Even when the voltage dividing resistance switching circuit 28 or the DC signal detection circuit 22 fails, the misfire is detected by the misfire detection spare circuit 42, and the transistor 39 of the solenoid valve drive circuit 17 is turned off via the timer 41.

When the comparator 29 provided in the comparison circuit 21 fails, the comparison operation is not performed, so that the output of the comparator 29 is a DC signal of a constant high level or a constant low level. Therefore, the output of the DC signal detecting means 22 becomes high level, and the timer 23 outputs a high level signal (abnormal signal) to the solenoid valve drive circuit 17 when the set time of the timer 23 (for example, 7 seconds) elapses. Then, the transistor 38 is turned off by this high-level signal (abnormal signal), the energization to the solenoid 9 is cut off, and the on-off solenoid valve 3 is closed.

Therefore, when the comparator 29 breaks down, the use of the gas stove becomes impossible, and it is possible to prevent the user from using the gas stove in a state where the misfire cannot be detected.

In the first embodiment, the temperature detecting means 20 uses the thermocouple 12 as the temperature detecting element. However, even if a thermistor is used, a temperature abnormality can be detected by a similar configuration.

Further, a plurality of DC signal detection circuits 22 may be provided in parallel. Thus, the reliability of the DC signal detection circuit 22 against a failure can be improved.

As shown in FIG. 4, the voltage dividing resistors 50 and 51 of the thermocouple 12 are set to fixed values.
The input voltage to the negative input terminal of the comparator 29 is divided by a voltage dividing resistor 50,
It is also possible to switch between the voltage Vd2 at the connection point 51 and Vd3 set to be always equal to or lower than the reference voltage VB3 of the positive input terminal.

Next, a second embodiment of the present invention will be described.
This will be described with reference to FIGS. 1, 2b, and 5. FIG. 2B is a temperature-resistance characteristic diagram of the thermistor 5, and FIG. 5 is a circuit configuration diagram of the high-temperature abnormality detection circuit 13 and the disconnection abnormality detection circuit 15 provided in the abnormality detection circuit 16 of the electronic unit 6 shown in FIG. It is.

Referring to FIG. 5, high-temperature abnormality detecting circuit 13 is connected to temperature detecting means 60, which is an abnormality detecting means for outputting a voltage corresponding to the detected temperature, and its output voltage and reference voltage. Are compared, and high and low 2
A comparison circuit 61 that outputs a voltage of a value level;
DC signal detection circuits 62 and 63, which are connected to the comparator 1 and output a low-level signal when an AC signal is output from the comparison circuit 61 and output a high-level signal when a DC signal is output from the comparison circuit 61; The DC signal detection circuit 62 is connected to the DC signal detection circuit 62 through a timer 71.
The solenoid valve driving circuit 17 is connected to the solenoid valve 9 via a timer 72, and when a high level signal is output from at least one of the timer 71 and the timer 72, the solenoid valve driving circuit 17 and the comparison circuit 61 A reference voltage switching circuit 65 for switching the input reference voltage to a high / low binary level.

The temperature detecting means 60 includes a thermistor 5, voltage dividing resistors 66 and 67 connected in series with the thermistor 5,
The power supply Vcc (for example, 1.
5V), and outputs a voltage Ve at a connection point a between the voltage dividing resistor 67 and the thermistor 5. The resistance value of the thermistor 5 is
As is clear from the graph of FIG. 2B, the temperature decreases as the detected temperature increases. And one end of the thermistor 5 is 0V
Since it is connected to a point, if the temperature detected by the thermistor 5 rises and its resistance value decreases, Ve decreases accordingly.

The comparator 61 includes a voltage dividing resistor switching circuit 68 for switching the resistance value of the voltage dividing resistor 66 between high and low and a comparator 6.
9 The configuration of the voltage dividing resistor switching circuit 68 is the same as that of the voltage dividing resistor switching circuit 28 of the first embodiment, and the transistor 69 is turned on / off by the oscillator 69 to raise or lower the resistance value of the voltage dividing resistor 66. Switch to binary.
The configuration of the comparator 69 is the same as the comparator 29 of the first embodiment.

The configuration of the DC signal detection circuits 62 and 63 is the same as that of the DC signal detection circuit 22 of the first embodiment.
In the second embodiment, by providing the DC signal detection circuits 62 and 63 in parallel, the reliability against failure of the DC signal detection circuit is improved. When the output voltage of the temperature detecting means 60 instantaneously becomes the same voltage as that at the time of high temperature abnormality or at the time of disconnection abnormality due to the fluctuation of the combustion flame of the burner 1 or the electric noise, the timers 71 and 72 erroneously cause the high temperature abnormality. This is to prevent the opening / closing solenoid valve 3 from being closed due to the determination of a disconnection abnormality.

The transistor 73 of the solenoid valve driving circuit 17
74 is actually connected in series with the transistors 38 and 39 of the solenoid valve drive circuit 24 of the first embodiment. Therefore, among the transistors 38, 39, 73 and 74,
When at least one of the solenoids is turned off, the power supply to the solenoid 9 is cut off, and the on-off solenoid valve 3 is closed.

The disconnection abnormality detection circuit 15 comprises a comparator having the same configuration as the comparator 69 of the comparison circuit 61. The reference voltage VB5 is input to the negative input terminal, and the temperature detection means 60 is input to the positive input terminal.
Is input.

As for the resistance values of the voltage dividing resistors 66 and 67 of the temperature detecting means 60, the combined resistance value is determined by the voltage dividing resistance switching circuit 68, and the resistance value of the thermistor 5 is determined by the determination resistance value of disconnection abnormality detection (for example, 1.5 MΩ) , −10 ° C.)) and a fourth resistance value corresponding to a high-temperature abnormality detection determination resistance value (for example, 390Ω, corresponding to 260 ° C.).
It is set so as to switch between a high value and a low value of a resistance value (low resistance value). When the resistance value is the third resistance value (high resistance value), the disconnection abnormality detection circuit 15 determines the disconnection abnormality,
When the high-temperature abnormality is determined by the comparison circuit 61 when the resistance value is the fourth resistance value (low resistance value), the amount of change in the output voltage of the temperature detection means 60 with respect to the change in the resistance value of the thermistor 5 in each case is increased. , The detection accuracy has been improved.

The reference voltage VB5 input to the negative input terminal of the disconnection abnormality detection circuit 15 is such that the combined resistance value of the voltage dividing resistors 67 and 68 is the third resistance value (high resistance value).
Is the output resistance value of the temperature detecting means 60 when the resistance value is the determination resistance value (1.5 MΩ) for disconnection abnormality detection (for example, 1.
2V). When the thermistor 5 is switched to the fourth resistance value (low resistance value), if the thermistor 5 is disconnected, the resistance value of the thermistor 5 (1.5 MΩ or more) is reduced by the voltage dividing resistors 66, 67 The combined resistance value (about 390
.OMEGA.) Is a negligible value, so that the output Ve of the temperature detecting means 60 is substantially at the Vcc level, and is higher than the reference voltage VB5. Therefore, the output of the disconnection abnormality detection circuit 15 becomes a high level. That is, when the output of the disconnection abnormality detection circuit 15 is the third resistance value, the disconnection state (Ve ≧ VB5), the high level (high resistance value), the conduction state (Ve <VB5), and the low level At this time, in a disconnection state (Ve ≧ VB5), and in a high level (low resistance value) conduction state (Ve ≧ VB5 or Ve <VB5), it becomes undefined.

Therefore, when the thermistor 5 is disconnected, the combined resistance value of the voltage dividing resistors 66 and 67 is the third resistance value (high resistance value) or the fourth resistance value (low resistance value).
Irrespective of the above, the output of the disconnection abnormality detection circuit 15 becomes high level, and the high level signal is continuously output to the timer 72 via the 0R element 75. Then, when the set time of the timer 72 (for example, 14 seconds) elapses, a high-level signal is output to the transistor 74 of the solenoid valve driving circuit 15, so that the transistor 74 is turned off and the power supply to the solenoid 9 is cut off.

When the combined resistance value of the voltage dividing resistors 66 and 67 is the fourth resistance value (low resistance value), the thermistor 5
Is low (the resistance value is large), the output voltage Ve of the temperature detecting means 60 becomes higher than the reference voltage VB5,
The output of the disconnection abnormality detection circuit 15 may be high. However, in this case, the voltage dividing resistors 66, 67
Is switched to the third resistance value (high resistance value), the output voltage (almost 0 V) of the temperature detecting means 60 becomes lower than the reference voltage VB5 (1.2 V). The output voltage goes low. And the third
Since the switching period between the resistance value and the fourth resistance value is set shorter than the set time of the timer 72, the high level signal is continuously output from the disconnection abnormality detection circuit 14 beyond the set time of the timer 72 (14 seconds). No high level signal is output from the timer 72.

On the other hand, the voltage VB4 input to the negative input terminal of the comparator 69 of the comparison circuit 61 is switched by the reference voltage switching circuit 65 between the high and low binary levels of the reference voltage VBB and the corrected reference voltage VBD. The reference voltage switching circuit 65 includes voltage dividing resistors 72, 73, 74, a transistor 75, and an inverting element 76.
The transistor 75 is turned on / off by an AC signal output from the oscillator 69 of the voltage dividing resistance switching circuit 68, and the output voltage VB4 is switched. That is, in synchronization with the switching operation of the voltage dividing resistance switching circuit 68, the output voltage VB4 of the reference voltage switching circuit 65 is changed to the corrected reference voltage VBC which is a high voltage.
And the reference voltage VBB which is a low voltage is switched to a high / low binary level.

Transistor 70 of voltage dividing resistance switching circuit 68
Is the third resistance value (high resistance value), which is off, the transistor of the reference voltage switching circuit 65 is turned on,
The voltage VB4 input to the comparator 69 becomes the correction reference voltage VBC (high voltage). When the transistor 70 of the voltage dividing resistance switching circuit 60 has the fourth resistance value (low resistance value) that is on, the transistor 75 of the reference voltage switching circuit 65 turns off and the voltage input to the comparison circuit 69 V
B4 becomes the reference voltage VBB (low voltage).

When the combined resistance value of the voltage dividing resistors 66 and 67 of the temperature detecting means 60 is the third resistance value (high resistance value), the corrected reference voltage VBB is independent of the resistance value of the thermistor 5. The output voltage Ve of the detecting means 60 is set to be lower than the correction reference voltage VBB, and the output of the comparator 69 is set to a low level. When the combined resistance value of the voltage dividing resistors 66 and 67 is the fourth resistance value (low resistance value), the thermistor 5 detects the high temperature abnormality determination temperature (for example, 260 ° C.). Temperature detection means 6
The output voltage is set to 0 (for example, 0.8 V). As a result, when the output of the comparator 69 is the third resistance value, the high-temperature abnormal state (Ve <VBC), the low level (correction reference voltage), the normal state (Ve <VBC), and the low level At this time, in a high temperature abnormal state (Ve ≦ VBB), the level becomes low in a low level (reference voltage) and in a normal state (Ve> VBB).

Therefore, when the abnormal state of high temperature is detected by the thermistor 5, the output of the comparator 69 becomes a constant low level DC signal, and in other normal states, it becomes a high / low binary level AC signal. . Therefore, when a high temperature abnormal state occurs, the DC signal detection circuit 62,
The high-level signal is continuously output from 63 to the timers 71 and 72, and when the set time has elapsed, the solenoid valve driving circuit 15
Transistors 73 and 74 are turned off, and solenoid 9
Is turned off.

By providing the reference voltage switching circuit 65 in this manner, the voltage dividing resistance switching circuit 6 which is a means originally provided for improving the accuracy of the high temperature abnormality detection and the disconnection abnormality detection is provided.
8 can also be used as a voltage dividing resistance switching circuit 28 which is a means for outputting an AC signal from the comparator 29 except when a misfire abnormality is detected in the first embodiment. Then, when the comparator 69 fails and its output becomes a DC signal of a fixed high level or a fixed low level, the DC signal detection circuits 62 and 63 continuously output high level signals to the timers 71 and 72. Therefore, when the set time of the timers 71 and 72 elapses, a high-level signal (abnormal signal) is output to the solenoid valve driving circuit 17, the transistors 72 and 73 are turned off, and the power supply to the solenoid 9 is cut off. As a result, the opening / closing solenoid valve 3 is closed, the heating device becomes unusable, and the use of the gas stove in a state where the abnormal high temperature state cannot be detected can be prevented.

When the resistance value of the voltage dividing resistors 66 and 67 is the third resistance value (high resistance value), the temperature detecting means 60
Under the condition that the output voltage Ve does not exceed the reference voltage VBB, when the resistance values of the voltage dividing resistors 66 and 67 are the third resistance value, the comparator 69
Of the reference voltage switching circuit 6
5 becomes unnecessary, and the reference voltage input to the negative input terminal of the comparator 69 can be fixed to the reference voltage VBB.

[Brief description of the drawings]

FIG. 1 is an apparatus configuration diagram of first and second embodiments of the present invention.

FIG. 2 is a characteristic diagram of a temperature detecting element provided in the heating device of FIG.

FIG. 3 is a circuit configuration diagram according to the first embodiment of the present invention.

FIG. 4 is a circuit configuration diagram according to the first embodiment of the present invention.

FIG. 5 is a circuit configuration diagram according to a second embodiment of the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Burner, 2 ... Fuel supply path, 3 ... Opening / closing solenoid valve, 4 ... Gas amount adjustment valve, 5 ... Thermistor, 6 ... Electronic unit, 7 ...
Ignition / extinguishing button, 8 ... spring, 9 ... solenoid, 10 ...
Operating element, 11 support, 12 thermocouple, 13 high temperature abnormality detection circuit, 14 misfire abnormality detection circuit, 15 disconnection abnormality detection circuit, 16 abnormality detection circuit, 17 solenoid valve driving circuit,
18 discharge electrode, 19 sparker, 20 temperature detection means, 21 comparison circuit, 22 DC signal detection circuit, 28
Voltage dividing resistance switching circuit, 42: misfire detection spare circuit, 60: temperature detecting means, 61: comparison circuit, 62, 63: DC signal detecting circuit, 65: reference voltage switching circuit, 68: voltage dividing resistance switching circuit

────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Norio Miyazaki No. 71 Kannon-do-cho, Kanazawa-shi, Ishikawa Prefecture Inside ARB Controls Co., Ltd. (56) References JP-A-9-60866 (JP, A) JP-A-54-20430 (JP, A) JP-A-58-75624 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) F23N 5/24 F23N 5/14

Claims (5)

(57) [Claims] An open / close solenoid valve provided in a fuel supply path, abnormality detection means for outputting a voltage corresponding to an abnormal state, and abnormality detection for outputting an abnormality signal when the abnormality detection means detects an abnormality. In a heating device comprising a circuit and an electromagnetic valve driving circuit that closes the on-off electromagnetic valve in response to the abnormality signal, the abnormality detection circuit inputs an output voltage of the abnormality detection unit and a predetermined reference voltage. These are compared, and when the output voltage is in a predetermined relationship with the reference voltage, a DC signal is output. When the output voltage is not in the predetermined relationship, an AC signal is output. A heating device comprising: a DC signal detection circuit that outputs the abnormal signal only when a DC signal is input from a circuit. 2. The comparison circuit according to claim 1, wherein the abnormality detecting means includes a series circuit including a temperature detecting element and a voltage dividing resistor connected in series with the temperature detecting element, and a power supply connected to the series circuit. Receives a voltage dividing resistor switching circuit that periodically switches a resistance value of the voltage dividing resistor between high and low values of a first resistance value and a second resistance value, and inputs the reference voltage and an output voltage of the abnormality detection unit. A comparator for switching the output voltage level to one of a high level and a low level depending on whether the output voltage of the abnormality detecting means has a predetermined relationship with the reference voltage. When the resistance value of the voltage dividing resistor is the first resistance value of the high resistance value or the second resistance value of the low resistance value, the output voltage of the abnormality detecting means is always the reference voltage and the predetermined voltage. The first resistance value or the second resistance value The heating device according to claim 1, wherein a resistance value is set. 3. The temperature detecting element is a thermistor for detecting a temperature by a change in a resistance value, and the abnormality detecting circuit is configured to output the abnormality signal when a temperature detected by the thermistor is equal to or higher than a predetermined high temperature abnormality determination value. And a disconnection abnormality detection circuit that outputs the abnormality signal when the resistance value of the thermistor is equal to or greater than a predetermined disconnection abnormality determination value, and the first resistance value of the high resistance value is The second resistance value having a low resistance value is a value corresponding to the resistance value of the thermistor when the detected temperature is the high temperature abnormality temperature. Item 3. The heating device according to Item 2. 4. The method according to claim 1, wherein the reference voltage inputted to the comparator of the abnormality detecting circuit is synchronized with a switching period of the voltage dividing resistor by the voltage dividing resistor switching circuit, so that the resistance value of the voltage dividing resistor becomes high. A reference voltage switching circuit for switching to a correction reference voltage when the resistance value is the first resistance value; and when the resistance value of the voltage dividing resistor is the first resistance value of a high resistance value, the voltage is input to the comparator. 4. The heating apparatus according to claim 3, wherein the correction reference voltage is set such that the output voltage of the abnormality detecting means always has the predetermined relationship with the correction reference voltage. 5. A plurality of said DC signal detection circuits are provided,
The output from the comparison circuit of the abnormality detection circuit is input to each DC signal detection circuit, and the solenoid valve drive circuit is configured to output the abnormality signal when at least one DC signal detection circuit outputs the abnormality signal. The heating device according to claim 1, wherein the valve is closed.