JPH0433379B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application This invention relates to a flame detector that detects infrared rays generated by a flame and generates a signal.

BACKGROUND OF THE INVENTION Flame detectors that detect infrared rays emitted by flames and generate signals are already known. This type of detector utilizes the fact that in the spectral distribution of radiant energy generated by a flame, there is a peak of radiant energy at a wavelength of 4.3 μm, and detects infrared rays at this wavelength. Its advantages include (1) good sensitivity to flame; (2) In the spectral distribution of artificial light such as illumination light, the component at the wavelength of 4.3 μm is extremely small, so there is no malfunction due to the artificial light itself. (3) For the same reason, there should be no malfunction due to spark discharge, lightning, etc. can be given.

Furthermore, among the detected infrared output signals, 3
By detecting the alternating current component of ~30Hz and detecting the fluctuation of the flame, it is possible to distinguish the flame from a noise source with steady radiant energy.

However, even if flames are detected by detecting infrared rays of 4.3 μm, which is the peak value of the radiation spectrum distribution unique to flames, direct light such as sunlight or reflection from objects with high reflectance such as metal If the light enters the detector as light that vibrates at approximately the same frequency as the flame fluctuations, it may cause a malfunction, which is problematic when used outdoors.

A solution to this problem is to detect the radiant energy at a wavelength around 4.3 μm, where flames are generated, and to detect the radiant energy of non-fire light such as sunlight, which has a peak value at a shorter wavelength than this, and to combine both. Comparative error-free flame detection means have been proposed.
(For example, JP-A-49-128782, JP-A-54-
(See Publication No. 146596).

To explain this below, FIG. 2 shows the radiant energy distribution between flame and sunlight, and in the figure, A shows the relative energy distribution of the flame and B shows the relative energy distribution of sunlight.

Figure 3 shows the principle of detecting flame by detecting the radiant energy of flame and sunlight. In the figure, 31 is an infrared sensor that detects the infrared wavelength peculiar to flame,
is a sensor that detects visible light such as sunlight, and the output electric signals of both are compared by a comparator 33 to obtain an input.

Figure 4 shows the flame and visible light output electrical signal waveforms detected by each sensor. When the signal source is flame, the infrared sensor 3
Although waveform a appears at 1, no output electrical signal is output to the visible light sensor 32. When the signal source is interference light such as sunlight, similar waveforms c and d appear on both sensors 31 and 32. If the interfering light fluctuates as if it were a flame, it cannot be distinguished from the flame only by the output electric signal of the infrared sensor 31, causing malfunction. When the signal sources include flame and interference light, the output electrical signals from both sensors 31 and 32 exhibit waveforms e and f that are independent of each other. At this time, if the phase shift of each output electric signal is detected, the black part in the figure will be detected, and the presence of flame can be detected while also eliminating false alarms regarding interference light.

Problems to be Solved by the Invention However, in such a detection means, it is an essential condition that interference light is simultaneously incident on both the infrared sensor and the visible light sensor together with the flame. If the interfering light is from a non-beam radiation source such as a heat source, the interfering light can be made to enter both sensors at the same time by arranging both sensors close to each other. In the case of interference light in the form of a beam, such as when it is reflected by a beam and incident on the sensor, it may not be incident at the same time even if both sensors are placed close to each other.
There was a possibility of malfunction.

Means for Solving the Problems This invention solves the above problems, and includes a first light receiving element that is sensitive to a wavelength range specific to flames, and a first light receiving element that is sensitive to a specific wavelength range of visible light. a second light-receiving element having a second light-receiving element, a phase comparator that compares the phases of output signals of the first and second light-receiving elements, and a determining means that determines the occurrence of flame based on the output signal of the phase comparator. In the flame detector, a light diffusing plate is disposed in an annular shape around the first light receiving element, and the second light receiving element is arranged to receive light passing through the light diffusing plate. It is characterized by:

Function The second light-receiving element receives sufficiently diffused light after passing through a light diffusion plate arranged in an annular shape around the first light-receiving element. In contrast, the eleventh light receiving element and the second light receiving element can simultaneously receive light and reduce the phase difference between their output signals.

Examples Examples of the present invention will be described below. First, the configuration and operation of a flame detector to which the present invention is applied will be explained.

FIG. 1 shows the circuit configuration of a flame detector to which the present invention is applied. In the figure, 1 is an infrared sensor that is sensitive to a wavelength of 4.3μ, 2 is a visible light sensor that is arranged in a ring around the infrared sensor 1 and is sensitive to visible light, and 3 is an increase in the output electric signal of sensor 1. 4 is an output electric signal amplifier of sensor 2; 5 is a
The phase comparator compares the phases of the output electrical signals from the sensors 1 and 2 amplified by the amplifiers 3 and 4, and the output electrical signals are taken out as a flame detection signal through the signal processor 6. be done.

Next, its operation will be explained based on FIGS. 5 and 6.

In FIG. 5, light from the sun S is reflected by a reflector M and enters sensors 1 and 2, but the reflector M
When the sensor vibrates in the direction shown by the arrow, the reflected light incident on the sensor also vibrates in the direction shown.

The output electric signal waveforms of the sensor at this time are as shown in FIGS. 6A, 6B, and 6C, and the arrangement of the infrared sensor 1 and the visible light sensor 2 according to the present invention is shown in FIG. 6A. In addition, for comparison, an infrared sensor 1 and a visible light sensor 2 were arranged independently in parallel,
Figure 6B shows the case where the moving direction of the reflected light and the sensor array direction are perpendicular, and Figure 6 shows the case where both sensors are arranged independently and in parallel, and the moving direction of the reflected light and the sensor array direction are parallel. Shown in c.

That is, according to the sensor arrangement according to the present invention, the output signal waveform of the infrared sensor 1 has a trapezoidal shape a, and the output signal waveform of the visible light sensor 2 has a trapezoidal waveform b, which is approximately the same shape as the output waveform of the infrared sensor. On the other hand, when the sensor arrangement is shown in FIG. 6B, the output signal waveforms of the infrared sensor 1 and the visible light sensor 2 become trapezoidal waveforms a and b, which rise and disappear simultaneously. Furthermore, in the case where the sensor arrangement is shown in FIG. It becomes shape b. When these output signal waveforms are processed by a phase comparator, in the case of the sensor arrangement for the incident light shown in FIG. 6C, the phase difference signal waveform c
appears.

In addition, when a selective amplification circuit is used as an output amplification circuit for the sensor signal shown in FIG. 1, the output signal and phase difference detection signal are a', b' in FIG. , c′ is similar to the differential waveform shown in FIG.

In this way, when reflected light from the sun etc. enters the sensor while vibrating, the difference between the output signals of both sensors may vary depending on the relationship between the arrangement of the infrared sensor and visible light sensor and the direction of movement of the incident light. However, with the arrangement of the infrared sensor and visible light sensor according to the present invention, the output of both sensors will be the same regardless of the incident light from any direction. There is no phase difference between signals, and there is no risk of malfunction.

FIG. 7 shows an embodiment of the detection portion of the flame detector of the present invention. The figure shows a cross section of the flame detection part, where 9 is a cylindrical light shielding member with a light incidence part 1 in the center of the top surface.
There is 1. Reference numeral 1 denotes an infrared sensor arranged directly below the light incidence section 11 . A conical light diffusing plate 8 is arranged between the light incidence section 11 and the infrared sensor 1.
A visible light sensor 2 is arranged in an annular shape at the bottom of the cylindrical light shielding member 9. In order to reduce sensitivity unevenness, it is preferable to use a plurality of elements and use the sum of their output signals. 10 is a heat insulating member that thermally blocks and protects the infrared sensor 2; 7 is a light shielding member 9;
This space is formed by the inner wall of the heat insulating member 10 and the outer wall of the heat insulating member 10, and is an integral part that further diffuses the incident light that has passed through the diffuser plate 8 and guides it to the visible light sensor.

With the above configuration, the light incident from the light incidence part is incident on the infrared sensor 1 and the visible light sensor 2 over a wide range of incident angles and detected, but the light incident on the annular visible light sensor 2 is Since the light is sufficiently diffused by the diffuser plate 8 and the integrating portion 7, and the visible light sensor 2 is composed of a plurality of elements,
Sensitivity unevenness based on the magnitude of the incident angle, the direction of incidence, etc. can be reduced.

Next, the phase discrimination circuit of the phase comparator used in the present invention will be explained with reference to FIG. CP ₁ is a comparator that outputs "H" when the output signal a of amplifier 3 is positive and "L" when it is negative, and CP ₂ is amplifier 4.
“L” when output signal b is positive, negative or 0
_CP3 is a comparator that outputs "H" when the output signal b of the amplifier 4 is positive or 0, and outputs "L" when it is negative. The output signals of the comparators CP ₁ and CP ₂ are input to the OR circuit OR via the AND circuit AN ₁ . On the other hand, the output of the comparator CP ₁ is input to the AND circuit AN ₂ via the inverter IV, and the output of the comparator CP ₃ is input as is to the AND circuit AN ₂ . The output of AND circuit AN ₂ is an OR circuit
Entered into OR.

With this configuration, the output of the phase discrimination circuit (that is, the output c of the OR circuit OR) is "H" only when the sensor output signal b is smaller than the output when only flame exists, and the sensor output signal b is larger than when only flame exists, but the sensor output signal a
It becomes "H" only when the signs of and b are opposite, and becomes "L" in other cases. i.e. comparator
The determination levels of CP ₂ and CP ₃ are slightly offset to the positive or negative side depending on the magnitude of the sensor output signal b when only flame is present, as described above.

Effects of the Invention As explained above, according to the present invention, the second light receiving element receives sufficiently diffused light that has passed through the light diffusing plate arranged in an annular shape around the first light receiving element. Therefore, the first and second light receiving elements simultaneously receive light incident from any direction, and not only can the phase difference between the output signals be reduced, but also the light diffusing plate By using this, it is possible to reduce sensitivity unevenness based on the magnitude and direction of the incident angle of light.

Furthermore, by using a light diffusing plate, the second light receiving element only needs to be arranged in an appropriate shape around the first light receiving element. For example, placing it coaxially with the light receiving element of 1.
Since a light receiving element with a special structure is not required, and there are no restrictions on the arrangement position or number of second light receiving elements, manufacturing is facilitated.

[Brief explanation of drawings]

FIG. 1 is a diagram showing the circuit configuration of a flame detector to which the present invention is applied. Figure 2 is a diagram showing the relationship between the wavelength of flame and sunlight and the intensity of radiant energy. FIG. 3 is a basic configuration diagram of a known flame detector. FIG. 4 is a diagram showing the output electric signal waveform when flame or interference light enters the sensor. Fifth
The figure is an explanatory diagram when sunlight is reflected and enters the sensor. FIG. 6 is a diagram showing waveforms of output electrical signals that vary depending on the direction of incident light and the arrangement of sensors. FIG. 7 is a sectional view of an embodiment showing the configuration of the detection portion of the flame detector of the present invention. FIG. 8 shows an example of a phase discrimination circuit of a phase comparator used in the present invention. 1...Infrared sensor, 2...Visible light sensor,
3, 4...Amplifier, 5...Phase comparator, 6...Signal processor, 7...Integrator part, 8...Diffusion plate, 9...
... Light shielding member, 10 ... Heat insulation member, 11 ... Light incidence part.

Claims (1)

[Claims] 1. A first device that is sensitive to a wavelength range specific to flame.
a second photodetector that is sensitive to a specific wavelength range of visible light.
a light-receiving element, a phase comparator that compares the phases of output signals of the first and second light-receiving elements, and a determining means that determines the occurrence of a flame based on the output signal of the phase comparator. The detector is characterized in that a light diffusing plate is arranged in an annular shape around the first light receiving element, and the second light receiving element is arranged to receive the light that has passed through the light diffusing plate. flame detector.