JPH0442569B2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention provides a combustion control device that detects flame from a combustion means provided in a combustion chamber and controls combustion of the combustion means based on this flame detection signal. It is related to.

[Conventional technology]

Conventionally, in this type of combustion control device, an ultraviolet detection tube for detecting ultraviolet rays of a flame is used as a flame detection means for detecting a flame.

FIGS. 5 and 6 are longitudinal sectional views showing the ultraviolet detection tube. The ultraviolet detection tube shown in FIG. 5 is provided with a cathode 32 and an anode 33 in a glass tube 31 filled with a specific gas, and an external power source (not shown) is provided between the two electrodes.
Apply voltage from

With this voltage applied, when ultraviolet rays generated from a flame are irradiated, photoelectrons are emitted from the cathode 32, and these photoelectrons collide with gas molecules in the glass tube 31 and are ionized repeatedly. A discharge current flows between the anode 33 and the anode 33, and the presence of a flame is detected by this discharge current.

The ultraviolet detection tube shown in FIG. 6 has a cathode 32 and an anode 33 in a glass tube 31 filled with a specific gas.
mesh electrode plates 34 and 35 are provided on each of the cathode 32 and anode 33 so as to face each other, and a voltage is applied between the cathode 32 and anode 33, and the flame detection operation is as shown in FIG. It is the same as the ultraviolet detection tube.

[Problem to be solved by the invention]

Conventional combustion control devices are configured as described above, so if self-discharge is induced due to failure/deterioration of the ultraviolet detection tube, it is possible to detect that a flame exists even if the flame disappears and no ultraviolet light is detected. A signal was issued (simulated flame state), resulting in a malfunctioning mode.

In other words, the ultraviolet detection tube cannot distinguish not only the self-discharge state, but also the state before it becomes a complete pseudo-flame, so the controller determines that it has become a complete pseudo-flame state.
The system is designed to safely shut down the combustion control device, and there was a problem in that it took a long time to restart after detecting a failure.

This invention was made to solve the above-mentioned problems, and aims to provide a combustion control device that can predict failures and improve maintainability.

[Means to solve the problem]

The combustion control device according to the present invention includes a shutter disposed between the combustion means and the flame detection means, a shutter control circuit for controlling opening and closing of the shutter, and a flame detection signal compared with a preset level. a first determination means that makes the comparison result valid only when the shutter is closed; and a second determination circuit that cancels the determination result for a certain period of time from the time the shutter is closed based on the determination result of the first determination circuit. , a third determination circuit that determines that a failure has been predicted when the determination result of the second determination circuit continues for a preset time or more.

Further, the invention according to claim 2 is the combustion control device according to claim 1, in which a fourth determination is made to determine that a failure has been predicted when the determination result of the third determination circuit occurs more than a preset number of determinations. It is equipped with a circuit.

[Effect]

The combustion control device according to the invention according to claim 1 includes:
The flame from the combustion means to the ultraviolet detection tube is continued by opening and closing the shutter, the detection signal of this ultraviolet detection tube is time-integrated and compared with a set level, and the result is valid in the first judgment means only when the shutter is closed. year,
Based on the judgment result, a second judgment circuit cancels the judgment result for a certain period of time after the shutter is closed, and if the judgment result by the second judgment circuit continues for a preset time or more, the judgment result is canceled. By determining a failure using the determination circuit 3, it is possible to accurately determine the self-discharge state of the ultraviolet detector due to failure, and it is possible to improve maintenance.

Further, the invention according to claim 2 is such that the fourth determination circuit determines a failure when the determination result of the third determination circuit occurs more than a preset number of times. To achieve the same effect as the invention with more precision.

〔Example〕

Embodiments of the present invention will be described below with reference to the drawings. In FIG. 1, 1 is a burner as a combustion means, 2 is an ultraviolet detector for detecting the flame 3, 4 is a shutter disposed between the burner 1 and the ultraviolet detector 2, and 5 is the light from the ultraviolet detector 2. This is a flame detection circuit that detects a flame by inputting a detection signal, and this flame detection circuit 5 is composed of a drive circuit 6 for the ultraviolet light detector 2 and a flame current detection circuit 7.

8 is a combustion control means for controlling the burner 1, 9 is a shutter drive circuit for opening and closing the shutter 4, and 10 is a comparison between the output signal V _FL of the flame detection circuit 5 and the judgment level V _ST1 set in advance in the setting device 11. 12 is a first determination circuit that inputs the output signal V ₀ of the comparison circuit 10 to be valid only when the shutter is closed;
Reference numeral 13 denotes a second determination circuit that compares the output signal V ₁ of the first determination circuit 12 with a fixed cancel time T _ST2 from the time of shutter closing set in the setting device 14 .

15 is a third determination circuit that compares the output signal V ₂ of the second determination circuit 13 and the failure duration T _ST3 preset in the setting device 16; 17 is the output signal V of the third determination circuit 15; ₃ output count and the shutter 4
This is a fourth determination circuit that compares the number of times the opening/closing signal V _SH is output.

FIG. 2 is a waveform diagram showing the relationship of the output signal V _FL of the flame detection circuit 5 with respect to the shutter opening/closing operation under normal conditions, and FIG. 3 is the same diagram during abnormal conditions. In Figures 2 and 3, V _FL is the flame detection signal, V _SH is the shutter opening/closing signal, and V ₀ is the comparison circuit 1.
The output signals of 0 and V ₁ to _{V 3} are output signals of the first to third determination circuits 12 , 13 , and 15 .

Next, the operation will be explained. When the shutter 4 opens during steady combustion, a flame detection signal is sent from the flame detection circuit 5 based on the detection signal from the ultraviolet detection tube 2.
V _FL is output, and this flame detection signal controls the burner 1 via the combustion control means 8 and also operates the shutter drive circuit 9.

When this shutter drive circuit 9 is activated, the shutter 4 closes, so the detection signal from the ultraviolet detection tube 2 disappears, and the input to the combustion control means 8 and the shutter drive circuit 9 also disappears, and the shutter 4 opens again, and the following occurs. , this series of shutter opening and closing operations is repeated at regular intervals. In this case, the opening/closing cycle of the shutter 4 is approximately several seconds.

The comparison circuit 12 compares the output signal V _FL of the flame detection circuit 5 when the shutter 4 is open and the judgment level V _ST1 of the setting device 11, and outputs the output signal V ₀ of the comparison circuit 12 only when the shutter 4 is closed. valid and first
The determination circuit 12 makes the determination.

Then, the output signal V _{FL '} between the output signal V ₁ of the first determination circuit 12 and the cancel time V _ST2 set in the setting device 14 (shaded area in FIGS. 2 and 3)
is canceled by the second determination circuit 13, and this second
When the output signal V ₂ of the determination circuit 13 continues for the failure duration time T _ST3 set in the setting device 16 or more, the third determination circuit 15 outputs the output signal V ₃ .

In other words, as shown in Figure 2, if combustion is normal, the output signal V _FL of the flame detection circuit 5 maintains a voltage above a certain level when the shutter 4 is open, and flame is detected when the shutter 4 is closed. It stops working and the voltage drops.

However, when the ultraviolet detector 2 malfunctions and starts self-discharging, the output signal V _FL rises to exceed the judgment level V _ST1 even when the shutter 4 is closed, and the output signal V ₁ from the first judgment circuit 12 Output.

Next, in the second determination circuit 13, a cancel time T _ST2 is determined after the shutter 4 changes from open to closed.
The output signal between them is canceled and the determination result is output as the output signal _V2 . The third determination circuit 15 outputs an output signal V ₃ when the output signal V ₂ exceeds the failure duration T _ST3 .

Although it is possible to notify the occurrence of a failure using this output signal V ₃ , if a direct judgment is made only based on this output signal V ₃ , there is a possibility that a failure has occurred even if the failure has not yet occurred.

Therefore, in the combustion control device of claim 2, when the number of outputs of the output signal V ₃ of the third determination circuit 15 exceeds the set number of times the shutter is opened and closed, the fourth determination circuit is activated as shown in FIG. Output signal from 17 V ₄
This configuration is configured to output a (failure detection signal), which allows for more accurate failure determination.

〔Effect of the invention〕

As described above, according to the invention set forth in claim 1,
A shutter is provided between the combustion means and the ultraviolet detection tube,
Based on the output signal of the ultraviolet detection tube only when the shutter is closed, the output signal for a certain period of time after the shutter is closed is canceled, and based on the output signal after this cancellation, it is determined whether or not a failure has occurred. With this configuration, the self-discharge state of the ultraviolet detection tube can be detected early, and maintenance can be improved.

Further, according to the second aspect of the invention, when the number of occurrences of the output signal exceeds a preset number of opening and closing times of the shutter, a signal indicating the occurrence of a failure is output, so that the failure can be detected. This has the effect of ensuring that the process is carried out accurately.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing a combustion control device according to an embodiment of the present invention, FIG. 2 is a waveform diagram showing the relationship between the output signal of the flame detection circuit and the shutter opening/closing operation in normal conditions, and FIG. 3 is a waveform diagram in abnormal conditions. The same figure and FIG. 4 are timing diagrams showing the occurrence of a defective signal, and FIGS. 5 and 6 are longitudinal sectional views of the ultraviolet detection tube. 1 is a combustion means (burner), 2 is an ultraviolet detection tube,
4 is a shutter, 5 is a flame detection circuit, 8 is a combustion control means, 9 is a shutter drive circuit, 12 is a first judgment circuit, 13 is a second judgment circuit, 15 is a third judgment circuit, 17 is a fourth judgment circuit. judgment circuit.

Claims (1)

[Claims] 1. A combustion means provided in a combustion chamber, an ultraviolet detection tube for detecting flame generated from the combustion means,
A combustion control device comprising a combustion control means for controlling combustion of the combustion means based on a flame detection signal from the ultraviolet detection tube, comprising: a shutter for opening and closing between the combustion means and the ultraviolet detection tube; and a shutter for opening and closing the shutter. a shutter control circuit that controls the flame detection signal; a first determination circuit that compares the flame detection signal with a preset level and makes the comparison result valid only when the shutter is closed; and a determination result by the first determination circuit. Accordingly, a second determination circuit cancels the determination result for a certain period of time after the shutter is closed, and a failure is determined if the determination result of the second determination circuit continues for a preset time or more. A combustion control device characterized by comprising a third determination circuit that performs the following steps. 2. The combustion control device according to claim 1, wherein the third
A combustion control device comprising a fourth determination circuit that determines a failure when the determination result of the determination circuit occurs a predetermined number of times or more.