JP2018179434A - Flame detector - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a flame detecting device which prevents a stop of burning in an excessive response to a minor error.SOLUTION: In a flame detecting device, a flame-absent judgement value and a flame-present judgement value are set at different values, the flame-absent judgement value being a value for starting a judgement of a flame-absent from a flame-present state, and the flame-present judgement value being a value for starting a judgement of a flame-present from a flame-absent state. CPUs for judging presence/absence of the flame based on the signal value is provided in a double-parallel manner, and a validity of the judgement is confirmed by comparing the judgement results of the two CPUs. While the judgement of the presence/absence of the flame is performed in the two CPUs, the judgement values used in the judgement are the same. When the judgement value used in the judgement of the presence/absence of the flame is changed in either of the CPUs, the change in the judgement value is transferred to the other CPU such that the same judgement value is used for the judgement of the presence/absence of the flame in the other CPU.SELECTED DRAWING: Figure 3

Description

  The present invention relates to a flame detection device that detects the presence or absence of a flame with a boiler or the like.

In a combustion device such as a boiler, it is dangerous to continue supplying fuel without a flame, so monitoring the presence or absence of a flame will immediately stop the fuel supply if there is no flame during combustion operation. It is done. As described in Japanese Utility Model Application Publication No. 2-38214, a flame detection device for detecting the presence or absence of a flame is converting the intensity of light generated by the flame into an electrical signal such as a resistance value, a current value, or a pulse signal. It is widely used to convert and judge the presence or absence of a flame according to the signal value. In the flame detection device, a determination value for determining the presence or absence of a flame is set, and if the detected signal value is in the flame presence region, it is determined that the flame is present, and if the signal value is in the flame absence region, it is not. To do.

The judgment value for judging the presence or absence of the flame is set in the middle of the state where there is no flame and the state where the combustion is stably continued, and the signal value when performing the normal combustion is the area with the flame. When the flame is off, it is in the area without flame. When the signal value without flame is small and the signal value with flame is large, the signal value becomes low until ignition, and when the flame immediately after ignition is small, the signal value increases but is lower than that during normal combustion. When the flame is stabilized and burned after a certain amount of time, the signal value also becomes large. Immediately after the start of combustion and in the process of increasing the signal value, although the signal value is in the flameless region, it passes the judgment value for determining the presence or absence of the flame and enters the flame presence region. Go. It is determined that there is no flame until it passes this determination value, and it is determined that there is a flame after it passes the determination value.

However, the flame has fluctuations, and the strength of light etc. changes due to the fluctuations. In particular, immediately after the start of combustion, the light intensity changes continuously while shaking, so the above signal value also changes while shaking. When the boundary value between the flame presence region and the flame absence region is one value, in the process immediately after the start of combustion and when the signal value changes, in the vicinity of the boundary value between the flame presence region and the flame absence region It is conceivable that the determination of the presence of a flame and the determination of the absence of a flame may be rapidly interchanged with each other only with a slight fluctuation.

Then, as described above, if it is determined that the flame is not present immediately after the determination that the flame is present is started due to a slight fluctuation, it is determined that the flame that was being burned is extinguished in a control manner. Even if there is no abnormality in the control, it is judged as abnormal in control, and the combustion operation will be stopped. As described above, the problem in which the combustion is stopped due to excessive reaction without the need to stop the combustion can be solved by setting a difference between the judgment value of the presence of flame and the judgment value of the absence of flame. The signal value changes from the area with flame to the area without flame when the flame presence judgment value for changing the judgment from flameless to flameless and the flame absence judgment value for changing flame from flame to flameless judgment are shifted. After that, to return to the area with flame, or conversely to change the signal value from the area without flame to the area with flame, and then return to the area without flame, the signal value must change by the difference between the two judgment values. Therefore, it can be prevented that the determination of the presence of flame and no flame is frequently exchanged in a short time.

Also, in order to further enhance safety, it is also practiced to duplicate the determination circuit in the flame detection device. CPUs for making judgments are provided in parallel, and the judgments are made by the respective CPUs. The results are compared and if they are the same, the judgment is judged to be correct, and if the results are different, some abnormality occurs I judge that it is. By doing this, it is possible to prevent the combustion in the abnormal state when an abnormality occurs in the CPU of the flame detector control circuit.

However, in this case, the signal values at the two CPUs may be slightly different values due to conversion error in the case of analog input and timer error in the case of pulse signal, etc. In the case where the determination is made near the determination value, determination may be made on the presence of a flame in one CPU and determination on the absence of a flame in the other CPU. In this case, even if the error is a slight error that can be ignored in the combustion state, the judgment results will differ if the threshold value is exceeded even in control, so that the two CPUs will make a difference in the judgment. Sometimes. If a contradiction occurs in the determination results of the two CPUs, the difference between the determination results can not be ignored, and the operation control device stops the fuel supply to stop the combustion operation.

Japanese Utility Model Application Publication No. 2-38214

  The problem to be solved by the present invention is that, in the flame detection device, although there is no abnormality in the detection device itself, a slight error that is negligible as a combustion state in the flame such as a conversion error of the CPU It is an object of the present invention to provide a flame detection device capable of preventing excessive stoppage of combustion due to excessive reaction when abnormality occurs due to

The invention converts the intensity of light generated by a flame or the like into an electrical signal such as a resistance value, a current value, or a pulse signal, and determines the presence of a flame if the signal value is in the flame presence region, A flame detection device that performs flameless determination when the signal value is in a flameless region, and the determination value for determining the presence or absence of a flame is a determination for starting the flameless determination from the flame presence state. In the flame detection device in which the flame absence determination value, which is a value, and the flame presence determination value, which is a determination value for starting the flame presence determination from a flame absence state, are set to different values, The effectiveness of the determination is confirmed by duplicating and installing CPUs that determine the presence or absence of in parallel and comparing the determination results of the two CPUs, and the two CPUs independently determine the presence or absence of a flame. But the judgment value used for judgment is the same If one of the CPUs changes the determination value used to determine the presence or absence of a flame, it notifies the other CPU that the determination value has been changed, and the other CPU uses the same determination value. It is characterized in that the determination of the presence or absence of a flame is performed.

The flame detection circuit performs judgment with two CPUs installed in parallel. If an abnormality that can not continue combustion occurs, the combustion is stopped, but the judgment between the two CPUs is broken due to slight deviation of the signal value. For this reason, it is possible to prevent the occurrence of combustion stop although it is not necessary.

Flow chart of the entire boiler implementing the present invention Flow diagram of a flame detector control circuit embodying the invention Determination of the presence or absence of a flame in a flame detection device embodying the present invention

  One embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a flow chart of the entire boiler embodying the present invention, FIG. 2 is a flow chart of a flame detecting circuit embodying the present invention, and FIG. 3 is a flame detecting device of the flame detecting apparatus embodying the present invention FIG.

The boiler 1 of FIG. 1 has a combustion device 2 installed at the top, and generates a flame 3 from the top toward the combustion chamber at the center. A visible light flame detector 4 for detecting light emitted by the flame 3 is installed at the upper part of the boiler, and the visible light flame detector 4 is connected to the flame detector control circuit 5, and the flame detector control circuit 5 Determine the presence or absence of The flame detector control circuit 5 has two CPUs consisting of a CPU 1 and a CPU 2 installed in parallel, and the presence or absence of a flame is determined by each of the two installed CPUs.

The information on the presence or absence of the flame determined by the flame detector control circuit 5 is used in the operation control device 6 that controls the operation of the boiler, and the operation control device 6 performs the presence or absence of the flame when performing the operation control of the boiler 1 Control while checking the information in In the operation control device 6, for example, if the flame disappears in the middle of combustion and fuel supply is continued in that state, uncontrollable combustion may occur in the combustion chamber, so when the flame disappears, the fuel supply is not delayed. The information on the presence or absence of flames is important, and the boiler is operated while monitoring the presence or absence of flames.

In the flame detector control circuit 5, a judgment value of flame presence and a judgment value of flame absence are set as judgment values for judging presence or absence of flame. In the flame detector control circuit 5, when there is a flame in the combustion chamber, a large amount of current flows in the visible light flame detector 4, and the current that flows when the flame is not present is reduced. Determine the presence or absence.

The judgment value of presence of flame is a set value for changing the judgment of flame to presence of flame when judgment of absence of flame has been made until then, and in the embodiment, it is 60 μA in current value. The judgment value of no flame is a set value for changing the judgment of flame to no flame when the judgment of flame is made until then, and in the embodiment, it is 50 μA in current value.

If the judgment value with flame and the judgment value without flame are set at intervals, it is possible to prevent the judgment value from changing frequently between the presence and absence of flame with only slight fluctuation in the current value. it can. At the beginning, the ones in the flameless region where the current value is low become 60μA or more, which is the flame presence judgment value due to the increase of the current value, and when the judgment changes from flameless to flamed, judgment of flameless next It is from the time when the current value becomes less than 50 μA. Therefore, even if the current value returns to 59 μA after the flame judgment is made to be flame, the judgment is not replaced from flame to no flame at this stage. Similarly, from the state where there is a flame with a high current value, the flame absence judgment value becomes 50 μA or less, and if the judgment changes from flame presence to flame absence, then it is the electric current value for which flame judgment is made next From when it became 60 μA or more. Therefore, even if the current value returns to 51 μA after the flame judgment is no flame, the judgment does not replace the flame from the flame at this stage. Therefore, even if the current value fluctuates around the judgment value, the judgment of the presence of flame and the judgment of no flame do not frequently switch.

In this case, it is determined that there is a flame at one time in a portion sandwiched between two determination values, and it is determined that there is no flame at another time, so two determinations are performed. However, based on which determination value the determination is made depends on the result of the determination of the presence or absence of the flame so far, the case of 50 μA as the determination value and the case of 60 μA as the determination value never occur simultaneously. At the moment of determining the presence or absence of a flame, the threshold value is always one point, and therefore the determination of the presence or absence of a flame does not get lost.

In the flame detector control circuit 5 in which two CPUs are installed in parallel, the value detected by the visible light flame detector 4 is supplied to the CPU 1 and the CPU 2 as an analog input value. The CPU 1 and CPU 2 convert the value input from the visible light flame detector 4 into a signal value for flame presence / absence judgment, and compare the value with the flame presence judgment value or the flame absence judgment value.

The CPU 1 and the CPU 2 independently determine the presence or absence of a flame. The determination by the two CPUs can obtain the same result if they are normal. Therefore, it is confirmed that the two results are the same, and the determination result of the presence or absence of the flame is output. If an abnormality occurs in one of the CPUs, the determination results by the two CPUs will be different, whereby the abnormality in the flame detector control circuit 5 can be detected. Therefore, communication regarding the determination value is performed between the CPU 1 and the CPU 2. In the CPU 1 and the CPU 2, although the determination of the presence or absence of the flame is performed independently, the determination values used for the determination are the same. That is, when either the CPU 1 or the CPU 2 changes the previous determination value, it notifies the other CPU that the determination value has been changed, and the other CPU also changes it to the same determination value.

The determination condition of the flame will be specifically described based on the drawings. FIG. 3 is a time chart of the determination status of the presence or absence of flame in the CPU 1 and the CPU 2. In the figure, the flame presence setting value at which the judgment result switches from no flame to flame presence is 60 μA, and the flame absence setting value at which the judgment result turns from flame to flame absence is 50 μA.

In the time chart, there is no flame, the signal value starts from a low state, and the determination of no flame is made at first. If the signal value becomes not less than 60 μA, which is the determination value of the presence of flame, and the determination of the presence of flame is performed, it is possible to determine that the flame detection device is abnormal in that case. When combustion is started in the boiler, the combustion is started with a small flame at first, and the signal value in the flame detector control circuit rises when the combustion starts. In the figure, the signal values at the CPU 1 and the CPU 2 rise in the same manner, but the CPU 2 has a slightly lower value. At time A, in the CPU 1, the signal value becomes 60 μA or more, and therefore the flame is judged to be flame. When the judgment result changes from no flame to flame, the judgment value for judging the presence or absence of a flame from the moment is set to 50 μA.

However, in the CPU 2, the signal value has not reached 60 μA at time A, and reaching 60 μA is time B, which is slightly delayed. In this case, although the determination of the flame presence / absence at the CPU2 was until then no flame, the determination value of the flame presence / absence at the CPU2 was changed to 50 μA at time A. 50 μA. Then, since the signal value in the CPU 2 is higher than 50 μA, it is in the area with flame, and the judgment result is flame from this moment. Therefore, the determination results of the CPU 1 and the CPU 2 are the same, and it is determined that the combustion is normally performed. It is possible to prevent occurrence of a situation in which it is determined that the combustion is abnormal due to a slight deviation of about the conversion error between the CPU 1 and the CPU 2 and the combustion must be stopped.

In FIG. 3, the flame is extinguished thereafter, and the signal value is decreasing. In this case, at time C, the signal value at CPU 2 is 50 μA or less, which is the judgment value without flame, but at CPU 1 the signal value at time C is larger than 50 μA. The signal value becomes 50 μA or less at time D. Also in this case, if the CPU 2 changes the flame presence / absence determination value to 60 μA at time C, the CPU 1 also changes the flame presence / absence determination value to 60 μA. Then, since the signal value at time C is also within the flameless region even in the CPU 1, the determination of flame presence or absence from the time C is flameless. As a result, the two CPUs perform the determination without flame all at once, and there is no difference in the determination value, so unnecessary stop of combustion can be prevented.

If the CPU 1 does not change the determination value of the CPU 2 at time A when the flame changes from no flame to flame, the CPU 2 determines no flame from time A to time B. Then, in the flame detector control circuit 5, different judgment results can be obtained between the CPU 1 and the CPU 2 during that time. In the operation control device 6, when a contradiction occurs in the determination result in the two CPUs, the flame detector control circuit 5 determines that an abnormality occurs. Therefore, the flame detector control circuit 5 has an abnormality. And the combustion of the boiler 1 was to be stopped. As described above, when the determination values are aligned, if the error is small, the determination results of the two CPUs are aligned, so that combustion can be continued in a normal state.

In the case where an abnormality has actually occurred, for example, the signal value in CPU 1 has changed as described above, but in the case where the signal value in CPU 2 is a much lower value, the judgment value in CPU 1 is Even if the determination value is switched from 60 μA to 50 μA even with the CPU 2 in accordance with the change, it is not erroneously determined as normal. Therefore, in that case, the combustion is stopped as an abnormality.

Further, the present invention is not limited to the embodiments described above, and many modifications can be made by those skilled in the art within the technical concept of the present invention.

1 boiler
2 Combustion device
3 flame 4 visible light flame detector 5 flame detector control circuit 6 operation control device

Claims (1)

The intensity of light generated by a flame is converted into an electrical signal such as a resistance value, a current value, or a pulse signal, and if the signal value is in the flame presence region, it is determined that the flame is present. It is a flame detection device that performs flameless determination when it is in the flameless region, and the determination value for determining the presence or absence of a flame is a determination value for starting the determination of no flame from the state with flame In the flame detection device in which the flame absence determination value and the flame presence determination value, which is a determination value for starting the flame presence determination from the flame absence state, are set to different values, the presence or absence of flame is determined from the above signal value. The CPUs to be judged are installed in parallel in parallel, and the validity of the judgment is confirmed by comparing the judgment results of the two CPUs, and the judgment of the presence or absence of flame is performed independently by the two CPUs, but the judgment The judgment value used for If any of the CPUs changes the determination value used to determine the presence or absence of a flame, it notifies the other CPU that the determination value has been changed, and the other CPU uses the same determination value to determine the flame. A flame detection measure characterized in that the presence or absence is judged.

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