JP3064135B2 - Combustion detection circuit - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a gas stove, a water heater,
The present invention relates to a combustion detection circuit that detects the presence or absence of a flame in various combustion devices such as a bath kettle.

[0002]

2. Description of the Related Art Conventionally, thermocouples have been widely used as means for detecting the presence or absence of a flame in a combustion device. The thermocouple is disposed in the vicinity of a portion where a flame is generated in the combustion device, and the presence or absence of the flame is detected based on a thermoelectromotive force output from the thermocouple. That is, if a flame is generated, the thermoelectromotive force increases. As shown in FIG. 4, the thermoelectromotive force of the thermocouple 1 is compared with the reference voltage generated from the reference voltage generator 9 by the voltage comparator 8. The signal processing unit 4 comprising the microcomputer 6 detects the presence or absence of a flame based on the magnitude relationship between the thermoelectromotive force and the reference voltage. here,
The reference voltage can be adjusted by the reference voltage setting unit 10 so that the relationship of reference voltage ≦ thermo-electromotive force is established when there is a flame, and the relationship of reference voltage> thermo-electromotive force is established when there is no flame. Is done.

[0003]

Since the thermoelectromotive force of the thermocouple 1 is several mV to several tens mV, the voltage comparator 8
It is necessary to make adjustments to satisfy the above conditions with respect to variations in the operating characteristics and variations in the reference voltage. That is, it is necessary to adjust the reference voltage setting unit 10, and there is a problem that such adjustment takes time.

An object of the present invention is to provide a combustion detecting circuit which does not require adjustment of a reference voltage for detecting a flame.

[0005]

According to the first aspect of the present invention, there is provided a flame detecting element comprising a temperature sensor for generating a signal whose output value changes in accordance with the temperature of a flame of a combustion device. , a short circuit and an amplifier for amplifying a signal output from the flame detection device, between the input terminals at the same time the amplification unit when blocking the input to the output of the amplifier of the flame detection device <br/> before detecting the presence or absence of the flame Switching means for selecting a reference state and selecting a detection state in which the output of the flame detection element is input to the amplifier during a period for detecting the presence or absence of a flame, and comparing a difference between an output value of the amplifier between the reference state and the detection state with a threshold value That is, there is provided a discriminating means for discriminating the presence or absence of the flame of the combustion device.

According to the second aspect of the present invention, a monitoring control unit for outputting a control signal for reducing combustion to the combustion device when the output value of the amplifier in the reference state is out of the predetermined range is added. is there. According to the third aspect of the present invention, a monitoring control unit that outputs a control signal in a direction to reduce combustion when the amount of change in the output value of the amplifier between the reference state and the detection state is out of the predetermined range is added. .

[0007]

SUMMARY OF] According to the first aspect, select the reference state to short-circuit the input terminals at the same time amplification unit when blocking the input to the amplifier output of the flame detection device before detecting the presence or absence of the flame,
Switching means for selecting a detection state in which the output of the flame detection element is input to the amplifier during a period of detecting the presence or absence of a flame is provided, and a difference between an output value of the amplifier in the reference state and a detection state in the detection state is compared with a threshold.
The presence or absence of a flame is detected by using the output value of the amplifier in a reference state where no input is made to the amplifier as the reference value, without requiring adjustment of the reference value. Can be determined. Moreover, since the output of the flame detection device in the reference state is short-circuited between the input terminals of the amplifier circuit as well as block the input to the amplifier, the reference state that the external noise from the input terminal to the amplifier input And an accurate reference value can be obtained. In addition, the reference state is only selected before detecting the presence or absence of a flame, and during the detection period of the presence or absence of a flame, the selection by the switching means is unnecessary. Is unnecessary, and the power consumption is also reduced due to the small processing amount of the determination means.

According to the second aspect of the present invention, when an output value outside the predetermined range is generated from the amplifier in a state where the output of the flame detecting element is not input to the amplifier, it is determined that there is an abnormality.
The safe control is performed so as to reduce the combustion of the combustion device. According to the configuration of the third aspect, when the amount of change in the output value of the amplifier between the state where the output of the flame detecting element is not input to the amplifier and the state where the output is input is outside the predetermined range, the combustion device is overheated. It is considered that an abnormality such as the occurrence of an abnormality has occurred, and control is performed on the safe side to reduce the combustion of the combustion device.

[0009]

【Example】

(Embodiment 1) In this embodiment, as shown in FIG. 1, a switching means 5 for selecting a state in which the output of a thermocouple 1 as a flame detecting element is input to an amplifier 2 and a state in which the output is not input is provided. is there. The output of the amplifier 2 is converted into a digital signal through an A / D converter 3, and the output of the A / D converter 3 is input to a signal processing unit 4 as a determination unit for determining the presence or absence of a flame. Here, the A / D converter 3 and the signal processor 4 are constituted by a microcomputer 6. The selection state of the switching means 5 is controlled by the signal processing unit 4.

More specifically, as shown in FIG. 2, the switching means 5 includes an analog switch S ₁ connected in series to the thermocouple ₁ and an analog switch S ₂ connected in parallel to the thermocouple 1. The two analog switches S ₁ and S ₂ are controlled so that when one is turned on, the other is turned off. The amplifier 2 is configured by using an operational amplifier OP. By connecting the resistors R ₁ and R ₂ to the operational amplifier OP, the output voltage Vo with respect to the input voltage Vi is given by: Vo = Vi ｛(R ₁ + R ₂ ) / This constitutes a well-known non-inverting amplifying circuit that satisfies R ₁ ｝. Furthermore, the thermoelectromotive force of the thermocouple 1 is input through the non-inverting input terminal of the operational amplifier OP resistor R _3, the resistor R ₄
And bias voltage Vy is inputted through the thermal electromotive force as Vx, if the input voltage to the amplifier 2 and Vi, Vi = (Vy · R 3 + Vx · R 4) / (R 3 + R 4) that the relationship Is established. After all, the amplifier 2 is a non-inverting adder, and the output value of the amplifier 2 is prevented from becoming negative by adding the bias voltage Vy to the thermoelectromotive force Vx. Here, assuming that the output value (noise voltage) of the amplifier 2 in the reference state is Vb, the output value of the amplifier 2 in the detection state is obtained by multiplying the thermoelectromotive force Vx by the amplification α and the noise voltage Vb. If the output value of the amplifier 2 in the detected state is subtracted from the output value of the amplifier 2 in the reference state, the value obtained by multiplying the thermoelectromotive force Vx by the amplification degree α is obtained by subtracting the output value of the amplifier 2 in the detected state from the output value of the amplifier 2 in the reference state. Can be requested. Further, since the thermoelectromotive force Vx (several mV to tens of mV) is generally sufficiently smaller than the bias voltage Vy, the resistance is set so that the input voltage Vi of the operational amplifier OP is sufficiently changed by the change of the thermoelectromotive force Vx. R ₄ is selected to be a sufficiently large value for the resistor R ₃ .

Next, the operation will be described. Before detecting the presence or absence of the flame, by first turning on the analog switch S ₂ as well as turning off the analog switches S _1, as thermal electromotive force Vx thermocouples 1 is not input to the amplifier 2, switching means 5 is set to the reference state. At this time, only the bias voltage Vy is input to the operational amplifier OP, and the output voltage Vo of the amplifier 2 is Vo = {Vy · R ₃ / (R ₃ + R ₄ )} ·｝ (R ₁ + R
₂ ) / R ₁ ｝ The digital value corresponding to the output voltage Vo is taken into the signal processing unit 5, and the output value of the amplifier 2 in the reference state is stored as a reference value.

Next, in order to detect the presence / absence of a flame, the analog switch S ₁ is turned on and the analog switch S ₂ is turned off, and the thermoelectromotive force Vx of the thermocouple 1 is amplified by the amplifier 2.
The switching means 5 is set to the detection state so as to be input to the switch. At this time, the output voltage Vo of the amplifier 2 is as follows: Vo = ｛(Vy · R ₃ + Vx · R ₄ ) / (R ₃ +
R ₄ )｝ · {(R ₁ + R ₂ ) / R ₁ }.

For example, the output voltage of the amplifier 2 in the reference state is 2.399 V and the input value to the signal processing unit 4 is 1
It is assumed to be 7A _{H in} hexadecimal (the subscript H indicates hexadecimal), and the thermoelectromotive force Vx in the detection state is 10 mV
In the output voltage of the amplifier 2 as an input value to the signal processing unit 4 becomes 1.775V was 5A _H in hexadecimal. At this time, the signal processing unit 4 obtains a difference between the input value in the reference state and the input value in the detection state, and when there is a flame when the difference is equal to or more than the threshold value set in the signal processing unit 4 and when the difference is less than the threshold value It is determined that there is no flame. For example, the thermoelectromotive force Vx
Assuming that the output value of the A / D conversion unit 3 is 09 _H in hexadecimal when the value is 3 mV, in the above-described example, the difference between the input value to the signal processing unit 4 in the reference state and the detection state is 7A _H −
Since 5A _H = 20 _H and 20 _H > 09 _H, it is determined that there is a flame.

As described above, the presence or absence of a flame is determined by the difference between the output value of the amplifier 2 in the reference state in which the thermocouple 1 is not connected to the amplifier 2 and the detection state in which the thermocouple 1 is connected to the amplifier 2. Therefore, the reference voltage generator for eliminating the influence of the noise component as in the conventional configuration shown in FIG. 4 becomes unnecessary, and as a result, the adjustment becomes unnecessary. (Embodiment 2) In this embodiment, as shown in FIG. 3, a monitoring control unit 7 is added to the configuration of the embodiment 1. In the reference state where the thermoelectromotive force from the thermocouple 1 is not input to the amplifier 2, the monitoring control unit 7 in this embodiment
It is determined whether or not the input value to is within a predetermined range, and if the input value is outside the predetermined range, a control signal is generated to the combustion apparatus in a direction to reduce combustion. It is desirable that the control signal is such that the combustion is stopped. However, other control signals may be used as long as the control is performed on the safe side so that an accident due to the combustion device can be avoided. In short, in a state where the thermoelectromotive force of the thermocouple 1 is not input to the amplifier 2, the signal processing unit 4
If the input value is outside the specified range, it is considered that a malfunction has occurred in the circuit and normal operation cannot be expected. It prevents that from happening. Other configurations are the same as in the first embodiment.

(Embodiment 3) In this embodiment, a monitoring control unit 7 is provided similarly to the second embodiment. In the monitoring control unit 7, the thermoelectromotive force from the thermocouple 1 is input to the amplifier 2. When the difference between the input value to the signal processing unit 4 in the reference state where the measurement is not performed and the detection state where the thermoelectromotive force from the thermocouple 1 is input to the amplifier 2 is out of the predetermined range, the combustion device may be overheated. It is considered that some abnormality such as abnormality of the circuit or abnormality of the circuit has occurred, and control to the safe side is performed so as to reduce the combustion of the combustion device. That is, in the first embodiment, it is determined that there is a flame when the difference between the input values to the signal processing unit 4 in the reference state and the detection state is equal to or larger than the predetermined threshold, but in the present embodiment, the difference is larger than the threshold. If the threshold value is exceeded (for example, 30 _{H in} hexadecimal), it is determined that an abnormality has occurred. As a result, the lower limit value and the upper limit value are determined by both threshold values. Other configurations are the same as in the first embodiment.

[0016]

[0017]

According to the present invention as described above, and select the reference state to short-circuit the input terminals at the same time amplification unit when blocking the input to the output of the amplifier of the flame detection device before detecting the presence or absence of the flame, Switching means for selecting a detection state in which the output of the flame detection element is input to the amplifier during a period of detecting the presence or absence of a flame is provided, and a difference between an output value of the amplifier between the reference state and the detection state is set as a threshold.
Since the presence or absence of a flame is detected by comparison, the thermoelectromotive force of the thermocouple is amplified based on the state where no input is made to the amplifier, so that the output value of the amplifier in the reference state where no input is made to the amplifier is obtained. The use of the reference value has the advantage that the presence or absence of a flame can be determined by the output of the thermocouple without the need for adjustment. Moreover, since the output of the flame detection device in the reference state is short-circuited between the input terminals of the amplifier circuit as well as block the input to the amplifier, the reference state that the external noise from the input terminal to the amplifier input Therefore, there is an advantage that an accurate reference value can be obtained. In addition, the reference state is only selected before detecting the presence or absence of a flame, and during the detection period of the presence or absence of a flame, the selection by the switching means is unnecessary. There is an advantage that the selection process is unnecessary and the power consumption is reduced due to the small processing amount of the determination means.

Further, a control signal for reducing the combustion of the combustion device when an output value outside the predetermined range is generated from the amplifier in a state where the output of the flame detecting element is not input to the amplifier, Even if the output of the flame detection element is not input to the amplifier, when an abnormal signal is input, it is considered that there is something abnormal, and control is performed on the safe side to reduce the combustion of the combustion device. Therefore, there is an advantage that an accident due to the combustion device can be prevented beforehand.

Further, when the output value of the amplifier is out of a predetermined range between the state where the output of the flame detecting element is not input to the amplifier and the state where the output of the flame detection element is input, the combustion of the combustion device is reduced. For generating a control signal to control, the difference between the output value of the amplifier in the reference state and the output value of the amplifier in the detection state
It is possible to detect abnormalities such as the overheating of the combustion device, and to control the safety to reduce the combustion of the combustion device when such an abnormality occurs, and to prevent accidents. There is an advantage that it can be prevented.

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating a first embodiment;

FIG. 2 is a circuit diagram showing a first embodiment;

FIG. 3 is a block diagram showing a second embodiment and a third embodiment.

FIG. 4 is a block diagram showing a conventional example.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Thermocouple 2 Amplifier 3 A / D conversion part 4 Signal processing part 5 Switching means 6 Microcomputer 7 Monitoring control part

──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Akihito Hayano 1-152 Oka, Minami-shi, Minato-ku, Osaka-shi Harman Co., Ltd. (56) References JP-A-5-33933 (JP, A) (58) Survey Field (Int.Cl. ⁷ , DB name) F23N 5/10

Claims (3)

(57) [Claims] 1. A flame detecting element comprising a temperature sensor for generating a signal whose output value changes according to the temperature of a flame of a combustion device, an amplifier for amplifying a signal output from the flame detecting element, select the reference state to short-circuit the input terminals at the same time amplification unit when blocking the input to the output of the amplifier of the flame detection device prior to detecting an input the output of the flame detection device to the amplifier in the period for detecting the presence or absence of flame Switching means for selecting a detection state to be performed, and determination means for determining the presence or absence of a flame of the combustion device by comparing a difference between the output value of the amplifier in the reference state and the output value of the amplifier with a threshold value. Combustion detection circuit. 2. A monitoring control unit for outputting a control signal for reducing combustion to a combustion device when an output value of an amplifier in a reference state is out of a predetermined range. Item 2. The combustion detection circuit according to Item 1. 3. A monitoring control unit for outputting a control signal for reducing combustion when an amount of change in an output value of an amplifier between a reference state and a detection state is out of a predetermined range. The combustion detection circuit according to claim 1, wherein