JPS6362800B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a flame detection device using infrared pulses.

Conventional flame detection devices include those that detect the ultraviolet component of the flame and those that detect the infrared component of the flame.In the latter case, the infrared component of the flame is directly detected by a light receiving element, for example as shown in Figure 1. Most of the conventional optical signal amplification circuits 1 using amplifier A and photodiode 2 directly amplify the infrared component of the flame, but signal processing is very difficult in such a configuration. Not only was it difficult to use, but it also had the disadvantage of not being able to check the amplification function.

The present invention has been made in order to eliminate the drawbacks of the conventional ones as described above, and is made by emitting an infrared pulse in advance from a light emitting element placed near a light receiving element, and causing the light receiving element to receive the infrared pulse. By configuring the circuit so that when the light-receiving element detects the infrared component of flame, the amplitude of the received pulse changes accordingly, subsequent signal processing is extremely easy and simple, and flame is reliably detected. The purpose of this invention is to provide a flame detection device that can detect flames.

An embodiment of the present invention will be described below with reference to FIGS. 2 to 5.

FIG. 2 shows an embodiment of the present invention, which has a circuit configuration in which a capacitor C is inserted in series with a photodiode 2 in the conventional optical signal amplification circuit shown in FIG.

FIG. 3 shows a light-receiving section of a flame detection device according to an embodiment of the present invention, in which 2 is a light-receiving element consisting of a photodiode, 3 is a light-emitting element, for example, an infrared LED; The light receiving element 2 is disposed perpendicularly to the optical axis between the light receiving element 2 and the light from the flame, and at a predetermined intermediate position between the light receiving element 2 and the lens 4.

FIG. 4 is a circuit diagram showing an embodiment of the present invention equipped with a flame detection device as shown in FIG.
In the figure, 5 is an amplifier, and 6 is a pulse oscillator, which generates a sharp pulse with a duty cycle of 1% or less, causes the light emitting element 3 to emit an infrared pulse 3a through the amplifier 5, and the infrared pulse 3a is applied to the light receiving element 2. It is configured to hold. Reference numeral 7 denotes a synchronization circuit connected to the amplifier 1 and the pulse oscillator 6 for synchronizing with the pulse oscillator 6 and eliminating unnecessary signals. 8 is a comparator that compares the output of the synchronization circuit 7 with a preset threshold level, and 9 is a timer circuit using a one-shot multivibrator that can be retriggered. The configuration is such that the output remains in the "H" state of the logic circuit, and when a flame is detected and the pulse train is disturbed, the output becomes "L" at that point. 1
0 is a counter that counts the output pulses of the timer circuit 9 and outputs a detection signal 10a when a predetermined count is reached within a certain period of time, and 11 is a timer that indicates when the output of the timer circuit 9 is in the "L" state. It is configured to measure time and output an abnormality signal 11a if the "L" state is maintained for longer than a preset time. A comparator 12 is connected to the synchronization circuit 7 and in parallel with the comparator 8 for detecting received light pulses, and together with the following timer circuit 13, monitors the received light pulses during normal operation. That is, the timer circuit 13 operates in the same manner as the timer circuit 9, and is configured to output an "L" state and output a failure signal 13a when the pulse is not normal.

Based on the above configuration, the operation of an embodiment of the present invention will be explained with reference to FIG. In addition, FIG. 5 is an operation waveform diagram of each main part in FIG.
1 shows the relationship between the preset threshold level V _1c and the output pulse 7a of the synchronization circuit 7, FIG. 2C shows the output pulse 8a of the comparator 8, and FIG.

First, by turning on the pulse oscillator 6, a constant cycle infrared pulse 3 as shown in FIG. 5a is generated.
A is received by the light emitting element 3, and the light is received by the light receiving element 2. The light-receiving element 2 can catch the infrared component of the flame in front of it through the lens 4 disposed in front, and if an amplifier circuit 1 as shown in FIG. 2 is used, when flame is detected, Amplifier A
attenuates and oscillates the amplitude of the output pulse of.
If this is applied to the comparator 8 and compared with the preset threshold level V _1c as shown in FIG. Outputs below the tsusjord level V _1c are selected, resulting in a state where the teeth of a comb have fallen off (Figure 5c).
The output 9a of the timer circuit 9 inputting the output 8a of the comparator 8 is in the "H" state while periodically receiving pulses, and becomes "L" at that point when a flame is detected and the pulse train is disrupted. Thereafter, as shown in FIG. 5d, a rectangular pulse 9a repeats "H" and "L". This rectangular pulse 9a is counted by a counter 10, and when a predetermined number of counts is reached within a certain period of time, a detection signal 10a is generated.
is output from the counter 10. Further, the timer 11 measures the time during which the output of the timer circuit 8 is in the "L" state, and if the output remains in the "L" state for longer than a preset time, an abnormality signal 11a is output. Furthermore, when the pulse is not normal, the output pulse 7a of the synchronization circuit 7 is passed through a comparator 12 that compares it with a preset threshold level _V2c , and then a timer circuit 13 that operates in the same manner as the timer circuit 9 is activated. If it is determined that the output state is "L", a failure signal 13a is output.

As explained above, according to the present invention, instead of directly amplifying the infrared component of the flame as in conventional devices, the light-receiving element is made to receive an infrared pulse in advance, and the amplitude of the received pulse is adjusted to the infrared component of the flame. By configuring the circuit so as to change according to the value, signal processing can be performed digitally, which has the great practical effect of simplifying the process and making it possible to detect flames reliably.

[Brief explanation of drawings]

FIG. 1 shows an optical signal amplification circuit used in a conventional flame detection device, and FIG. 2 shows an optical signal amplification circuit according to an embodiment of the present invention.
3 is a light receiving section of a flame detection device according to an embodiment of the present invention, FIG. 4 is a circuit diagram of a flame detection device according to an embodiment of the present invention, and FIG. FIG. 3 is an operational waveform diagram of main parts. 1, 5... Amplification circuit, 2... Light receiving element, 3...
Light emitting element, 4...lens, 6...pulse oscillator,
7... Synchronous circuit, 8, 12... Comparator,
9, 13...timer circuit, 10...counter, 11...timer. In addition, in the figures, the same reference numerals indicate the same or equivalent parts.

Claims (1)

[Claims] 1. A pulse oscillator, a light-emitting element that emits light with an amplified output pulse of the pulse oscillator, and a light-emitting element that is placed near the light-emitting element and directly or indirectly receives an infrared pulse emitted from the light-emitting element to generate a received light pulse signal. A flame detection device having a light-emitting element that emits light, characterized in that, when the light-emitting element detects an infrared component of the flame, a circuit is configured to convert this into an amplitude change of the light-receiving pulse signal as a reception signal. flame detection device.