JPH0424282Y2 - - Google Patents

Description

[Detailed description of the invention] [Field of industrial application] This invention relates to an ignition detection device for gas water heaters that accurately detects whether or not a burner is ignited by an ignition operation within a very short time. It is used in various combustors.

[Conventional technology]

Conventionally, thermocouples are used, and the thermoelectromotive force generated by the thermocouple is applied directly to the coil of an electromagnetic safety valve installed in the gas supply passage, and the thermoelectromotive force is applied to the adsorption voltage level required to open and hold the electromagnetic safety valve. Gas is supplied when the voltage exceeds the withdrawal voltage level, and gas supply is stopped when the voltage drops below the withdrawal voltage level. Combustion is controlled by detecting ignition and flame disappearance using a combination of thermocouple and electromagnetic safety valve. However, it had the drawback that it took a long time to reach the attraction voltage level, and even when it disappeared, it took a long time to drop below the release voltage level and close the electromagnetic safety valve.

Therefore, in order to shorten the above-mentioned time, there is a method of setting a reference voltage lower than the adsorption voltage level and confirming that ignition has occurred when the thermoelectromotive force reaches the reference voltage or higher. One possible method is to detect the rate of change in thermoelectromotive force at a given time and confirm that ignition has occurred when the rate of change exceeds a predetermined rate. When used again, the thermocouple continues to generate thermoelectromotive force due to its thermal inertia and ambient temperature, so in the former method, even if the re-ignition fails, the gas is assumed to have ignited and the gas is supplied and there is a risk of raw gas blowing out. sexual,
In addition, in the latter method, even if the ignition is ignited by the re-ignition operation, the rate of change in the thermoelectromotive force is small, and if the ignition fails, there is a drawback that malfunctions may occur, such as not being able to dispense hot water with the safety valve closed.

[Problem that the invention attempts to solve]

In view of the above-mentioned points, the present invention detects a flame from the magnitude of thermoelectromotive force based on the thermoelectromotive force generated by a thermocouple, and also detects flame from the rate of change of the thermoelectromotive force (rise slope of thermoelectromotive force). Determine whether or not the ignition has occurred or whether there has been a misfire, and based on these detection results, use a logic element to accurately detect whether or not the ignition has occurred within a very short time from the time of the ignition operation,
Moreover, even if the fire is extinguished, the purpose is to be able to detect it within a very short time.

[Means for solving problems]

This idea consists of a thermocouple heated by a burner.
a flame detector 2 that detects the magnitude of thermoelectromotive force generated by the thermocouple 1 and compares it with a flame detection voltage level to determine the presence or absence of a flame; and a rate of change detector that detects the rate of change of the thermoelectromotive force. ignition detection level; An ignition detector 5 is connected in parallel to the change rate detector 3, and the output signal of a NOT circuit 6 which inverts the output signal of the misfire detector 4 and the flame detection signal are connected in parallel to the change rate detector 3. AND circuit 7 which receives the output signal of device 2 as input
and the output signal of the AND circuit 7 and the ignition detector 5
An OR circuit 8 is provided to input the output signal of.

[Effect]

With the above configuration, when the burner is ignited by the ignition operation and the thermocouple 1 is heated, a thermoelectromotive force is generated.
The magnitude of this thermoelectromotive force is detected by the flame detector 2 and compared with the flame detection voltage level for determining the presence or absence of a flame.
When detecting a thermoelectromotive force having a magnitude equal to or higher than the flame detection voltage level, an H level signal is output, and when it is lower than that level, an L level signal is output. In addition, the rate of change detector 3 differentiates the characteristics (curve) of the thermoelectromotive force, detects the rate of change of the thermoelectromotive force (slope of the thermoelectromotive force) at each point, and the subsequent misfire detector 4 detects whether a misfire occurred. When the misfire detection level is below the misfire detection level, an H level signal is output, and when it is above the misfire detection level, an L level signal is output. Furthermore, the ignition detector 5 connected to the rate of change detector 3 compares the ignition detection level to determine whether or not ignition has occurred, and when the ignition detection level is higher than the ignition detection level (when the slope of the thermoelectromotive force is large), the signal becomes H level. is output, and an L level signal is output when the following conditions occur (when the slope is small): Based on the output signal of the NOT circuit 6 which inverts the output signal of the misfire detector 4 mentioned above, the output signal of the ignition detector 5, and the output signal of the flame detector, ignition operation is performed during use via an AND circuit and an OR circuit. The OR circuit 8 outputs an H-level signal only when ignition occurs due to ignition, and when ignition occurs due to a re-ignition operation immediately after stopping use, making it possible to detect ignition at an early stage. If the flame disappears for some reason during use,
An L level signal is output from the OR circuit 8, and this can be detected early.

〔Example〕

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the ignition detection device for a gas water heater according to the present invention will be described below with reference to the drawings.

In the drawing, reference numeral 1 denotes a thermocouple installed to be heated by a burner, and the thermocouple 1 is connected to a flame detector 2 via an amplifier 9 that amplifies the thermoelectromotive force generated.
A misfire detector 4 and an ignition detector 5 are connected in parallel to the output terminal of the rate of change detector 3. Then, the output signal from the misfire detector 4 is inverted on the output side of the misfire detector 4.
The NOT circuit 6 is connected, the output signal of the NOT circuit 6 and the output signal of the flame detector 2 are input to the AND circuit 7, and the output signal of the AND circuit 7 and the output signal of the ignition detector 5 are input to the OR circuit 8. A combustion controller 10 is connected to the output side of the OR circuit 8.
is connected. The combustion controller 10 operates to open the safety valve and supply gas when the output signal from the OR circuit 8 is at the H level, and to close the safety valve and stop the supply of gas when the output signal is at the L level. 1
1 is a thermocouple for detecting incomplete combustion; 13 is the thermocouple 1
An incomplete combustion detector connected to 1 through an amplifier 12 compares it with a set incomplete combustion voltage level, and when it detects a voltage higher than that level, outputs an L level signal and outputs a signal lower than the incomplete combustion voltage level. When the voltage is detected, an H level signal is output and input to the subsequent abnormality safety circuit 14, and when incomplete combustion occurs, a signal to stop combustion is output to the combustion controller 10.

Therefore, when using a gas water heater, if the burner is ignited by the ignition operation, the thermocouple 1 will be heated when the burner is ignited, as shown in Figure 3a.
Generates a thermoelectromotive force with the characteristics shown below. The thermoelectromotive force is amplified by the amplifier 9 and input to the flame detector 2 and rate of change detector 3, and the flame detector 2 determines the flame detection voltage level (E ₁ =
3mV), and when the flame detection voltage level E1 is higher than ₁ , an H level signal is output, and when it is lower, an L level signal is output. Further, the rate of change detector 3 differentiates the thermoelectromotive force at each point in time to detect the rate of change (inclination of the thermoelectromotive force), which is input to the misfire detector 4 and the ignition detector 5 . The misfire detector 4 compares this input rate of change with the misfire detection level (a=-3mV/sec) that determines whether or not a misfire has occurred, and outputs an H level signal when it is below the misfire detection level, and L when it is above the misfire detection level. Outputs a level signal. In addition, the ignition detector 5 uses an ignition detection level (β=1mV/
sec) and when the ignition detection level is higher than β, H
A level signal is output, and an L level signal is output when the following conditions occur. Therefore, in the period from 0 to T ₁ hour immediately after the ignition operation (before reaching point A), the thermoelectromotive force is below the flame detection voltage level E ₁ , and the flame detector 2 outputs an L level signal and AND It is input to circuit 7. On the other hand, since the rate of change of the thermal electromotive force detected by the rate of change detector 3 shows a small positive value from 0, it is higher than the misfire detection level a, so an L level signal is sent from the output detector 4 to the subsequent NOT circuit 6. The signal is inputted, inverted by the NOT circuit 6, and the H level signal is inputted to the AND circuit 7. Therefore, an L level signal is output from the AND circuit and input to the OR circuit 8. Furthermore, since the rate of change input to the ignition detector 5 is below the ignition detection level β, an L level signal is output and input to the OR circuit 8. Therefore, an L level signal is output from the OR circuit 8, which is the same output signal as when ignition fails, and based on this signal, the combustion controller 10
The gas valve remains closed and no gas is supplied.

b After ₁ hour has elapsed since the ignition operation, until T ₂ hours (before reaching point A from point B), the magnitude of the thermoelectromotive force is equal to the flame detection voltage level.
When E is less than ₁ , an L level signal is input to the AND circuit. When the rate of change of the thermoelectromotive force detected by the rate of change detector 3 reaches point A, it becomes the ignition detection level β, and an H level signal is output from the ignition detector and input to the OR circuit 8. Further, since the rate of change is higher than the misfire detection level α, an H level signal is input to the AND circuit 7, and an L level signal is output from the AND circuit 7 and input to the OR circuit 8. Therefore OR
An H-level signal is output from the circuit 8, confirming that ignition has occurred, and based on this signal, the combustion controller 10 operates to open the gas valve and supply gas. During this period of _T1 to _T2 , the magnitude of the thermoelectromotive force does not reach the flame detection voltage level _E1 due to the response delay of the thermocouple 1, but ignition can be detected earlier than the rate of change of the thermoelectromotive force.

FIG. 3b clearly shows this, and shows the relationship between ignition and misfire detected by the ignition detection device and time, corresponding to FIG. 3a.

c After T ₂ hours have passed since the ignition operation (after reaching point B), the magnitude of the thermoelectromotive force becomes equal to or higher than the flame detection voltage level E ₁ , and the flame detector 2
The output signal becomes H level, and the rate of change output from the rate of change detector 3 is the misfire detection level α.
When the misfire detector 4 is larger, a signal at L level is outputted from the misfire detector 4, which is inverted by the NOT circuit 6, and a signal at H level is inputted to the AND circuit 7, which outputs a signal at H level. Therefore, an H level signal is output from the OR circuit 8, confirming that ignition has occurred, and the combustion controller 10
continues to open the gas valve and continue supplying gas.

The table in Figure 4 shows the cases in which the fire ignites due to the ignition operation, the case in which the ignition fails, the case in which the ignition occurs due to the re-ignition operation within a short period of time after suspension of use, the case in which the ignition fails, and the case in which the fire is extinguished. flame detector 2, rate of change detector 3,
Misfire detector 4, ignition detector 5, NOT circuit 6,
It represents the output signals or outputs of the AND circuit 7 and the OR circuit 8. The following explanation will be given with reference to the table shown in FIG.

If the ignition fails despite the ignition operation, the thermocouple 1 does not generate thermoelectromotive force because it is not heated. Therefore, the output of the amplifier 9 becomes 0, and an L level signal is input from the flame detector 2 to the AND circuit 7, and an output with a change rate of ±0 from the change rate detector 3 is sent to the misfire detector 4 and ignition detection. Vessel 5
An L level signal is output from the misfire detector 4, which is inverted by the NOT circuit 6, an H level signal is input to the AND circuit, and an L level signal is output from the AND circuit 7 and input to the OR circuit 8. . Furthermore, since the ignition detector 5 outputs an L level signal, the OR circuit 8 outputs an L level signal, confirming that ignition has failed, and this signal is sent to the combustion controller 10, which sends the safety valve remains closed and no gas is supplied.

If the water heater ignites after it has been stopped and the water heater is re-ignited within a short period of time.
Immediately after the use is stopped (T ₃ hours point E), as shown in Figure 3a, the thermoelectromotive force rapidly decreases to the right due to the thermal inertia of the thermocouple and the temperature of the atmosphere. However, if it does not go to zero immediately and is re-ignited within a short time (T ₅ hours until point D), a thermal electromotive force with a flame detection voltage level of E ₁ or higher is generated, and the ignition is successful. Even if the detection fails, the flame detector 2 outputs an H level signal and inputs it to the AND circuit 7. but,
As for the rate of change in thermoelectromotive force, since residual heat remains at the time of re-ignition, even if thermocouple 1 is heated, the change in temperature is initially small, and therefore the rate of change in thermoelectromotive force generated is small and reaches the ignition detection level ( β=+
1mV/sec) or less. but,
Since the misfire detection level (α=-3mV/sec) does not have a negative rate of change, an L level signal is output from the misfire detector 4 and the NOT circuit 6
The inverted H level signal is input to the AND circuit 7, and the H level output signal from the AND circuit 7 is input to the AND circuit 7.
It is input to the OR circuit 8. and ignition detector 5
A signal of either an H level or an L level is output from the OR circuit 8, and an H level signal is output from the OR circuit to confirm ignition.

If the water heater fails to ignite after it has been stopped and you attempt to re-ignite it within a short period of time to use it again.

Immediately after the use is stopped, thermoelectromotive force is generated as described above, and if the value is equal to or higher than the flame detection voltage level _E1 , an H level signal is output from the flame detector 2 and the AND circuit 7 is input. On the other hand, the output from the rate of change detector 3 shows a large negative value when the rate of change of thermoelectromotive force fails to ignite, and the misfire detection level (α=-3mV/
sec) and the output signal of the misfire detector 4 becomes H.
An L level signal is output from the NOT circuit 6 and input to the AND circuit 7, which outputs an L level signal. Also, since the output of the rate of change detector 3 is a negative value, the output of the ignition detector 4 becomes an L level signal and is input to the OR circuit 8, and the OR circuit 8 outputs an L level signal to prevent ignition. You can confirm that it has failed.

In addition, if the magnitude of the thermoelectromotive force at the time of relighting operation after stopping use has decreased to the flame detection voltage level E ₁ or less (T ₅ hours after point D), a long time has already passed since stopping use. This is the same case as in the above case.

If the flame is accidentally extinguished for some reason during use, the thermocouple 1 has the characteristics shown in FIG. 3a due to its thermal inertia and ambient temperature, and its generated thermoelectromotive force is rapidly reduced. And the flame is T ₃ hours (E
If it disappears at the point ), then the point immediately after the disappearance
At T ₄ hours (point C), the thermal electromotive force is higher than the flame detection voltage level E ₁ , the flame detection voltage outputs an H level signal, and the rate of change detected by the rate of change detection voltage 3 is a large negative value. Therefore, the misfire detector 4 outputs an H level signal, the ignition detector 5 outputs an L level signal, and the AND circuit 7 receives an H level signal and an L level signal. Output signal is OR circuit 8
is input. Also, since the L level signal is input from the ignition detector 5 to the OR circuit 8,
The output of the circuit 8 becomes L level, and it is immediately confirmed that a misfire occurred at _T4 hours, and the combustion controller 10 is actuated by the output signal of the OR circuit 8 to close the safety valve and stop the gas supply.

Next, the embodiment shown in FIG. 2 will be described.

In the embodiment shown in FIG. 1, in order to prevent incomplete combustion, an incomplete combustion prevention circuit consisting of an amplifier 12, an incomplete combustion detector 13, and an abnormality safety circuit 14 is provided as a separate system from the ignition detection device. However, in this embodiment, the ignition detection and incomplete combustion prevention are combined into one to simplify the circuit, and the incomplete combustion detection thermocouple 11 and the ignition detection thermocouple 1 are connected are connected in reverse, and when incomplete combustion occurs, the thermoelectromotive force generated in the thermocouple 11 for detecting incomplete combustion cancels out the thermoelectromotive force generated in the thermocouple 1, and the flame described above is generated. An L level signal is output from the OR circuit 8 by the same operation as in the case of disappearance, and the safety valve is closed by the combustion controller 10 to stop the gas supply and prevent incomplete combustion. In this case, the thermoelectromotive force generated in the thermocouple 1 for detecting ignition is canceled by the thermoelectromotive force generated in the thermocouple 11 for preventing incomplete combustion.
The difference in electromotive force is input to the amplifier 9, but if the difference changes slowly, the rate of change is small and it is possible that incomplete combustion cannot be detected early at the misfire detection level α or higher. The difference in thermoelectromotive force gradually decreases and the flame detection voltage level E ₁
When the following occurs, the flame detector 2 outputs an L level signal, the AND circuit 7 outputs an L level signal, and the ignition detector 5 outputs an L level signal, so the OR circuit 8 outputs The signal becomes L level, and the gas supply is stopped in the same way as when the flame is extinguished, thereby preventing incomplete combustion.

[Effect of idea]

As mentioned above, the present invention detects ignition and misfire from both the magnitude and rate of change of the thermoelectromotive force based on the thermoelectromotive force generated by the thermocouple. Since ignition and misfire are determined based on the rate of change in thermoelectromotive force, detection of ignition and ignition failure during ignition operation is extremely quick and accurate.

(b) When the ignition is restarted within a short period of time after stopping use, a thermoelectromotive force is generated due to the thermal inertia of the thermocouple and the ambient temperature (a thermoelectromotive force higher than the flame detection voltage level is generated). It is possible to reliably detect that ignition has failed even if the thermoelectromotive force is small, and it is possible to accurately detect ignition based on the magnitude of the thermoelectromotive force even if the rate of change in the thermoelectromotive force is small.

C. Even if the flame goes out for some reason during use, there is a delay in the response of the thermocouple, but it can be detected much earlier than the rate of change in thermoelectromotive force, and the effect is that the release of raw gas can be minimized. There is.

[Brief explanation of drawings]

Figure 1 is a block diagram of the ignition detection device for a gas water heater according to the present invention, which is also equipped with an incomplete combustion prevention device.
Figure 2 is a block diagram of an ignition detection device for a gas water heater incorporating a thermocouple to prevent incomplete combustion, Figure 3a is a characteristic diagram of the thermoelectromotive force generated by the thermocouple, and Figure 3b is ignition detection. a diagram showing ignition and misfire detected by the device;
FIG. 4 is a table showing the relationship between the ignition and misfire associated with the ignition operation, the output signals of each detector and each logic element, and the ignition detection results. 1... Thermocouple, 2... Flame detector, 3... Rate of change detector, 4... Misfire detector, 5... Ignition detector,
6...NOT circuit, 7...AND circuit, 8...OR
circuit.

Claims (1)

[Scope of utility model registration request] A thermocouple 1 heated by a burner is provided with a flame detector 2 that detects the magnitude of thermoelectromotive force generated by the thermocouple 1 and compares it with a flame detection voltage level to determine the presence or absence of a flame. A misfire system in which a rate of change detector 3 that detects a rate of change is connected in parallel, and the rate of change in thermoelectromotive force detected by the rate of change detector 3 is compared with a misfire detection level to determine whether or not a misfire has occurred. A NOT circuit 6 which connects the detector 4 and an ignition detector 5 in parallel to the change rate detector 3 and inverts the output signal of the misfire detector 4, which compares the ignition detection level with an ignition detector 5 to determine whether or not ignition has occurred. an AND circuit 7 whose inputs are the output signal of the flame detector 2 and the output signal of the flame detector 2;
An ignition detection device for a gas water heater comprising an OR circuit 8 which receives an output signal from the ignition detector 5 and an output signal from the ignition detector 5.