Flame detector

Abstract

To reduce an erroneous detection of a flame caused by sunlight.SOLUTION: A flame detector 10 comprises: a first ultraviolet ray sensor 16 that measures a first intensity of ultraviolet rays in a UV-A region; a second ultraviolet ray sensor 17 that measures a second intensity of ultraviolet rays in a short wavelength region, which has a wavelength shorter than the UV-A region; and a flame detection unit 111 that detects a flame using the first intensity measured by the first ultraviolet ray sensor 16 and the second intensity measured by the second ultraviolet ray sensor according to a detection condition for the flame.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a technique for detecting flames. [Background technology]

[0002] Patent Document 1 describes the use of an ultraviolet detector that detects ultraviolet rays in the UVB region and ultraviolet rays in the UVC region as a flame sensor. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent No. 7139203 Summary of the Invention [Problem to be solved by the invention]

[0004] When sunlight enters the sensor of a flame detector, the sunlight may be mistakenly detected as a flame. However, the technology described in Patent Document 1 does not take into consideration the influence of sunlight.

[0005] The present invention aims to reduce false detection of flames due to sunlight. [Means for solving the problem]

[0006] One aspect of the present invention provides a flame detector comprising a first sensor that measures a first intensity of ultraviolet light in the UV-A region, a second sensor that measures a second intensity of ultraviolet light in a wavelength region having a shorter wavelength than the UV-A region, and a flame detection unit that detects a flame using the first intensity measured by the first sensor and the second intensity measured by the second sensor in accordance with flame detection conditions. [Effects of the Invention]

[0007] According to the present invention, it is possible to reduce false detection of flames due to sunlight. [Brief explanation of the drawings]

[0008] [Figure 1] FIG. 2 is a diagram illustrating the configuration of a flame detector. [Figure 2] FIG. 4 is a diagram illustrating the normalized spectral sensitivity of the first ultraviolet sensor. [Figure 3] FIG. 10 is a diagram illustrating the normalized spectral sensitivity of the second ultraviolet sensor. [Figure 4] A diagram illustrating the spectral distribution of a gasoline flame and sunlight. [Figure 5] 5A and 5B are diagrams illustrating output ratios between the first and second ultraviolet sensors according to light sources; [Figure 6] FIG. 4 is a flow diagram illustrating the operation of the flame detector. DETAILED DESCRIPTION OF THE INVENTION

[0009] (composition) 1 is a diagram illustrating an example of the configuration of a flame detector 10. Flame detector 10 detects a flame by utilizing ultraviolet rays emitted from the flame. Flame detector 10 includes a control unit 11, a memory unit 12, a communication unit 13, an operation unit 14, a display unit 15, a first ultraviolet sensor 16, and a second ultraviolet sensor 17.

[0010] The control unit 11 controls and performs calculations for each part of the flame detector 10. The control unit 11 includes a processor such as a CPU. The memory unit 12 stores programs and various data for realizing the functions of the flame detector 10. The memory unit 12 includes memories such as RAM and EEPROM. The communication unit 13 transmits and receives various signals to and from a fire receiver (not shown) connected via a line. The operation unit 14 is used to operate the flame detector 10. The operation unit 14 includes, for example, operation buttons. The display unit 15 displays various information. The display unit 15 includes, for example, an LED.

[0011] The first ultraviolet sensor 16 measures and outputs the intensity of ultraviolet light in the UV-A region (ultraviolet A rays). The first ultraviolet sensor 16 is mainly used to identify sources of false alarms, such as sunlight. The first ultraviolet sensor 16 is an example of a first sensor according to the present invention. The intensity of this ultraviolet light is an example of a first intensity according to the present invention. Generally, the UV-A region is 320 to 400 nm. However, it is practically difficult for the first ultraviolet sensor 16 to be sensitive only to the required wavelength region. Therefore, the first ultraviolet sensor 16 actually has very little sensitivity to wavelengths other than the UV-A region.

[0012] FIG. 2 is a diagram illustrating the normalized spectral sensitivity of the first ultraviolet sensor 16. The graph shown in FIG. 2 is a graph showing the normalized spectral sensitivity of an example of a commercially available product, and is created based on information provided by the manufacturer. In FIG. 2, the horizontal axis represents wavelength [nm], and the vertical axis represents relative intensity. The vertical axis on the left side is a logarithmic scale, and the vertical axis on the right side is a linear scale. In this example, the first ultraviolet sensor 16 has sensitivity in the range of approximately 280 to 390 nm.

[0013] The second ultraviolet sensor 17 measures and outputs the intensity of ultraviolet light in the UV-C region (ultraviolet C rays). The second ultraviolet sensor 17 is mainly used to detect flames. The second ultraviolet sensor 17 is an example of a second sensor according to the present invention. This ultraviolet intensity is an example of a second intensity according to the present invention. Generally, the UV-C region is a wavelength region of 200 to 280 nm, which is shorter than the UV-A region. However, it is practically difficult for the second ultraviolet sensor 17 to be sensitive only to the required wavelength region. Therefore, the second ultraviolet sensor 17 actually has very little sensitivity to regions other than the UV-C region.

[0014] FIG. 3 is a diagram illustrating the normalized spectral sensitivity of the second ultraviolet sensor 17. The graph shown in FIG. 3 is a graph showing the normalized spectral sensitivity of an example of a commercially available product, and is created based on information provided by the manufacturer. In FIG. 3, the horizontal axis represents wavelength [nm], and the vertical axis represents relative intensity. The vertical axis on the left side is a logarithmic scale, and the vertical axis on the right side is a linear scale. In this example, the second ultraviolet sensor 17 has sensitivity in the range of approximately 200 to 360 nm.

[0015] Figure 4 is a diagram illustrating the spectral distribution of a gasoline flame and sunlight. In Figure 4, the horizontal axis represents wavelength [nm], and the vertical axis represents relative intensity. As shown in Figure 4, the flame contains ultraviolet rays from the UV-A region to the UV-C region. On the other hand, sunlight at the Earth's surface contains ultraviolet rays in the UV-A region but not in the UV-C region. This is because ultraviolet rays in the UV-C region are absorbed by the ozone layer and do not reach the Earth's surface.

[0016] If the second ultraviolet sensor 17 were sensitive only to ultraviolet light in the UV-C region, the second ultraviolet sensor 17 would not react to sunlight. Therefore, even if the second ultraviolet sensor 17 were used alone to detect a flame without using the first ultraviolet sensor 16, sunlight would not be mistakenly detected as a flame. However, as described above, the second ultraviolet sensor 17 also has a slight sensitivity to light outside the UV-C region. Therefore, when sunlight is incident, the second ultraviolet sensor 17 may react to the sunlight and output the intensity of the ultraviolet light. In this case, if the second ultraviolet sensor 17 were used alone to detect a flame without using the first ultraviolet sensor 16, sunlight may be mistakenly detected as a flame.

[0017] 1, the control unit 11 functions as a flame detection unit 111, a transmission unit 112, and an alarm control unit 113. These functions are realized, for example, by a processor executing a program stored in a memory, causing the control unit 11 to perform calculations or control each unit of the flame detector 10. However, at least some of the functions of the control unit 11 may be realized by a hardware module such as an electronic circuit.

[0018] The flame detection unit 111 detects a flame according to a flame detection condition using the intensity of ultraviolet light measured by the first ultraviolet sensor 16 and the intensity of ultraviolet light measured by the second ultraviolet sensor 17. More specifically, the flame detection unit 111 detects a flame and determines that a fire has occurred when the intensity of ultraviolet light measured by the first ultraviolet sensor 16 and the intensity of ultraviolet light measured by the second ultraviolet sensor 17 satisfy the flame detection condition. On the other hand, the flame detection unit 111 does not detect a flame and determines that no fire has occurred when the intensity of ultraviolet light measured by the first ultraviolet sensor 16 and the intensity of ultraviolet light measured by the second ultraviolet sensor 17 do not satisfy the flame detection condition. The flame detection condition is, for example, a condition in which the intensity of ultraviolet light measured by the second ultraviolet sensor 17 is equal to or greater than an abnormality threshold and the output ratio between the first ultraviolet sensor 16 and the second ultraviolet sensor 17 is greater than a discrimination threshold. The flame detection condition is set in advance and stored in the memory unit 12.

[0019] The abnormality threshold is used to determine whether an abnormality has occurred. The abnormality threshold is set in advance according to at least the reference intensity of ultraviolet light in the UV-C region when a flame has occurred. The discrimination threshold is used to distinguish whether the light source is a flame or a source of a false alarm. The discrimination threshold is set in advance according to at least the reference intensity of ultraviolet light in the UV-A region when sunlight is incident. The reference intensity may be measured in advance by the first ultraviolet sensor 16 and the second ultraviolet sensor 17, or may be measured in advance by another flame detector 10.

[0020] The output ratio between the first ultraviolet sensor 16 and the second ultraviolet sensor 17 is the ratio of the intensity of ultraviolet light measured by the second ultraviolet sensor 17 to the intensity of ultraviolet light measured by the first ultraviolet sensor 16. If the intensity of ultraviolet light measured by the first ultraviolet sensor 16 is ΔUVA and the intensity of ultraviolet light measured by the second ultraviolet sensor 17 is ΔUVC, the output ratio between the first ultraviolet sensor 16 and the second ultraviolet sensor 17 is ΔUVC / ΔUVA. The flame detection unit 111 distinguishes between flames and sources of false alarms, including sunlight, based on the output ratio between the first ultraviolet sensor 16 and the second ultraviolet sensor 17.

[0021] FIG. 5 illustrates the output ratios of the first and second ultraviolet sensors 16 and 17 for various light sources. Light sources include, in addition to flames, fluorescent lamps, incandescent lamps, and sunlight, which can all be sources of false alarms. The flames are generated when heptane burns. The output ratios for a flame are the ratios of the reference intensity of UV-C light to the reference intensity of UV-A light when a flame occurs. Also, in FIG. 5, "heptane_6m," "heptane_10m," "heptane_15m," and "heptane_20m" indicate distances from the flame detector 10 of 6 m, 10 m, 15 m, and 20 m, respectively. As shown in FIG. 5, the greater the distance, the smaller the output ratios for a flame.

[0022] The output ratio corresponding to a fluorescent lamp is the ratio of the reference intensity of UV-C ultraviolet rays to the reference intensity of UV-A ultraviolet rays when fluorescent lamp light is incident. The output ratio corresponding to an incandescent lamp is the ratio of the reference intensity of UV-C ultraviolet rays to the reference intensity of UV-A ultraviolet rays when incandescent lamp light is incident. The output ratio corresponding to sunlight is the ratio of the reference intensity of UV-C ultraviolet rays to the reference intensity of UV-A ultraviolet rays when sunlight is incident.

[0023] As shown in FIG. 5, the output ratio corresponding to sunlight is smaller than the output ratio corresponding to flame. As described above, flame contains ultraviolet rays in the UV-A region and ultraviolet rays in the UV-C region. Therefore, when a flame occurs, there is not much difference between the intensity of ultraviolet rays measured by the first ultraviolet sensor 16 and the intensity of ultraviolet rays measured by the second ultraviolet sensor 17. On the other hand, sunlight on the Earth's surface contains ultraviolet rays in the UV-A region but does not contain ultraviolet rays in the UV-C region. Therefore, when sunlight is incident, the intensity of ultraviolet rays measured by the first ultraviolet sensor 16 is significantly greater than the intensity of ultraviolet rays measured by the second ultraviolet sensor 17. As a result, the output ratio corresponding to sunlight is smaller than the output ratio corresponding to flame.

[0024] Because there is a difference between the output ratio corresponding to sunlight and the output ratio corresponding to flame, by setting a discrimination threshold between the output ratio corresponding to flame and the output ratio corresponding to sunlight, it is possible to distinguish whether the light source is flame or sunlight. In one example, the discrimination threshold is set to a value between the output ratio of "heptane_20m," which is the smallest of the output ratios corresponding to flame, and the output ratio corresponding to sunlight. This discrimination threshold is an example of a first discrimination threshold according to the present invention. The reference intensity of ultraviolet light in the UV-A region included in the output ratio corresponding to sunlight is an example of a first reference intensity according to the present invention.

[0025] Furthermore, as shown in FIG. 5, the output ratio corresponding to a fluorescent lamp is smaller than the output ratio corresponding to a flame, but larger than the output ratio corresponding to an incandescent lamp and the output ratio corresponding to sunlight. Therefore, by setting a discrimination threshold between the output ratio corresponding to a flame and the output ratio corresponding to a fluorescent lamp, it is possible to distinguish whether the light source is a flame or a false alarm source such as a fluorescent lamp, a white light bulb, or sunlight. Therefore, in another example, the discrimination threshold may be set to a value between the output ratio of "heptane_20m," which is the smallest among the output ratios corresponding to a flame, and the output ratio corresponding to a fluorescent lamp. This discrimination threshold is an example of a second discrimination threshold according to the present invention. The reference intensity of ultraviolet light in the UV-A region included in the output ratio corresponding to a fluorescent lamp is an example of a second reference intensity according to the present invention.

[0026] 1, when the flame detection unit 111 detects a flame and determines that a fire has occurred, the transmission unit 112 transmits a fire signal to the fire receiver, which then outputs a fire alarm.

[0027] When ultraviolet rays are detected by at least one of the first ultraviolet sensor 16 and the second ultraviolet sensor 17 and the output ratio between the first ultraviolet sensor 16 and the second ultraviolet sensor 17 is equal to or less than the discrimination threshold, the alarm control unit 113 outputs an abnormality alarm indicating that the first ultraviolet sensor 16 and the second ultraviolet sensor 17 are affected by a false alarm source such as sunlight. The output ratio between the first ultraviolet sensor 16 and the second ultraviolet sensor 17 being equal to or less than the discrimination threshold means that the intensity of ultraviolet rays measured by the first ultraviolet sensor 16 is equal to or greater than a predetermined value. This abnormality alarm may be output, for example, by transmitting an abnormality signal to a fire control receiver via the communication unit 13 or by lighting up an LED on the display unit 15. The communication unit 13 and the display unit 15 are examples of an alarm output unit according to the present invention.

[0028] (operation) FIG. 6 is a flow diagram illustrating the operation of the flame detector 10. This operation is constantly repeated. In step S11, the first ultraviolet sensor 16 and the second ultraviolet sensor 17 measure the intensity of ultraviolet light and output the result to the flame detection unit 111. In step S12, the flame detection unit 111 determines whether or not ultraviolet light has been detected by at least one of the first ultraviolet sensor 16 and the second ultraviolet sensor 17. Here, "detecting ultraviolet light" means that the intensity of ultraviolet light measured by the first ultraviolet sensor 16 is equal to or greater than a predetermined value and the intensity of ultraviolet light measured by the second ultraviolet sensor 17 is equal to or greater than an abnormal threshold. If neither the first ultraviolet sensor 16 nor the second ultraviolet sensor 17 detects ultraviolet light (NO in step S12), this process ends. On the other hand, if ultraviolet light has been detected by at least one of the first ultraviolet sensor 16 and the second ultraviolet sensor 17 (YES in step S12), the process proceeds to step S13.

[0029] In step S13, the flame detection unit 111 determines whether the intensity of ultraviolet light measured by the first ultraviolet sensor 16 and the second ultraviolet sensor 17 satisfies the flame detection condition. For example, if the intensity of ultraviolet light measured by the second ultraviolet sensor 17 is equal to or greater than the abnormal threshold and the output ratio between the first ultraviolet sensor 16 and the second ultraviolet sensor 17 is greater than the discrimination threshold, the flame detection condition is met (the determination in step S13 is YES). In this case, the process proceeds to step S14, where the flame detection unit 111 detects a flame and determines that a fire has occurred. Then, in step S15, the transmission unit 112 transmits a fire signal to the fire receiver.

[0030] On the other hand, in step S13 described above, even if the intensity of ultraviolet light measured by the second ultraviolet sensor 17 is equal to or greater than the abnormality threshold, if the output ratio between the first ultraviolet sensor 16 and the second ultraviolet sensor 17 is equal to or less than the discrimination threshold, this indicates that the intensity of ultraviolet light from a false alarm source, such as sunlight, has been measured. In these cases, the flame detection condition is not met (NO in step S13), so the process proceeds to step S16, where the flame detection unit 111 does not detect a flame and determines that no fire has occurred. Then, in step S17, the alarm control unit 113 outputs an abnormality alarm. For example, the alarm control unit 113 may send an abnormality signal from the communication unit 13 to the fire receiver or may light up an LED on the display unit 15. The output of this abnormality alarm notifies the user that the first ultraviolet sensor 16 and the second ultraviolet sensor 17 have been affected by a false alarm source, such as sunlight.

[0031] According to the above-described embodiment, flames and sunlight are distinguished based on the output ratio between the first and second ultraviolet sensors 16 and 17. Therefore, flames are not detected when sunlight is detected, thereby reducing false detection of flames due to sunlight. Furthermore, by setting a discrimination threshold based on the output ratio corresponding to fluorescent light, false detection of flames due to not only sunlight but also fluorescent light can be reduced. Furthermore, if the intensity of ultraviolet light measured by the first ultraviolet sensor 16 exceeds a predetermined value, an abnormality alarm is output, thereby notifying the user of the influence of a false alarm source such as sunlight. Furthermore, because the first ultraviolet sensor 16 is sensitive to the UV-A region and the second ultraviolet sensor 17 is sensitive to the UV-C region, the difference between the output ratio corresponding to sunlight and the output ratio corresponding to flame becomes significant, improving the accuracy of distinguishing between flames and sunlight. Furthermore, because the flame detector 10 does not use UVTron®, it is more resistant to vibration and more durable than a device using UVTron®.

[0032] (Variation) The present invention is not limited to the above-described embodiment, and may be implemented by modifying it as in the following modifications. The following modifications may be used alone or in combination of two or more.

[0033] (Variation 1) The flame detection condition is not limited to the example described in the above embodiment. In one example, the flame detection condition may be a condition that the output ratio between the first ultraviolet sensor 16 and the second ultraviolet sensor 17 is equal to or greater than a threshold value. The threshold value in this modification is set in advance according to, for example, the ratio of the reference intensity of ultraviolet light in the UV-C region to the reference intensity of ultraviolet light in the UV-A region when a flame occurs. When this flame detection condition is adopted, a flame is detected when the output ratio between the first ultraviolet sensor 16 and the second ultraviolet sensor 17 is equal to or greater than the threshold value, and a flame is not detected when the output ratio is less than the threshold value.

[0034] In another example, the flame detection condition may be that the intensity of ultraviolet light measured by the second ultraviolet sensor 17 is equal to or greater than the abnormal threshold and the intensity of ultraviolet light measured by the first ultraviolet sensor 16 is equal to or less than the discrimination threshold. The discrimination threshold in this modification is set in advance between, for example, a reference intensity of ultraviolet light in the UV-A region when a flame occurs and a reference intensity of ultraviolet light in the UV-A region when sunlight is incident. When this flame detection condition is adopted, even if the intensity of ultraviolet light measured by the second ultraviolet sensor 17 is equal to or greater than the abnormal threshold, a flame will not be detected if the intensity of ultraviolet light measured by the first ultraviolet sensor 16 is greater than the discrimination threshold.

[0035] In yet another example, instead of the output ratio between the first ultraviolet sensor 16 and the second ultraviolet sensor 17, the difference between the intensity of ultraviolet light measured by the first ultraviolet sensor 16 and the intensity of ultraviolet light measured by the second ultraviolet sensor 17 may be used. The discrimination threshold used in this modification is set in advance according to, for example, the difference between the reference intensity of ultraviolet light in the UV-A region and the reference intensity of ultraviolet light in the UV-C region when sunlight is incident. The configuration according to modification 1 can also reduce false detection of flames due to sunlight.

[0036] (Variation 2) In the above-described embodiment, the second ultraviolet sensor 17 may measure the intensity of ultraviolet rays in the UV-B region (ultraviolet-B rays) instead of the intensity of ultraviolet rays in the UV-C region. Sunlight at the Earth's surface contains ultraviolet rays in the UV-A region and ultraviolet rays in the UV-B region, but there is a difference in intensity between them. Therefore, even in a configuration in which the second ultraviolet sensor 17 measures the intensity of ultraviolet rays in the UV-B region, false detection of a flame due to sunlight can be reduced by detecting a flame based on the output ratio between the first ultraviolet sensor 16 and the second ultraviolet sensor 17.

[0037] (Variation 3) In the above-described embodiment, the output ratio between the first ultraviolet sensor 16 and the second ultraviolet sensor 17 may be used to select the installation location of the flame detector 10. The flame detector 10 is preferably installed in a location that is less susceptible to sources of false alarms, such as sunlight. However, if the output ratio between the first ultraviolet sensor 16 and the second ultraviolet sensor 17 is equal to or less than the discrimination threshold, this indicates that the current installation location of the flame detector 10 is affected by sources of false alarms, such as sunlight. Therefore, the alarm control unit 113 may output information recommending a change in installation location if the frequency at which the output ratio between the first ultraviolet sensor 16 and the second ultraviolet sensor 17 is equal to or less than the discrimination threshold is equal to or greater than a predetermined frequency. This information may be output by transmitting a signal from the communication unit 13 or by lighting an LED on the display unit 15.

[0038] (Variation 4) In the above-described embodiment, the flames detected by the flame detector 10 may include various flames such as a flame generated when heptane is burned, a gasoline flame, a hydrogen flame, a methane flame, a spark, and the like.

[0039] (Variation 5) In the above-described embodiment, the configuration of the flame detector 10 is not limited to the above-described example. The flame detector 10 may be configured to include one or more of the above-described components, or may be configured to exclude some of the components.

[0040] (Variation 6) In the above-described embodiment, the operation of the flame detector 10 is not limited to the above-described example. The order of the operational steps of the flame detector 10 may be changed or some operational steps may be omitted, as long as there is no contradiction. Another aspect of the present invention may provide a method having operational steps performed in the flame detector 10.

[0041] (Variation 7) Another aspect of the present invention may provide a program for realizing the functions of the flame detector 10. This program may be provided by being stored in a computer-readable recording medium, or may be provided by being downloaded via the Internet or the like. [Explanation of symbols]

[0042] 10: Flame detector, 11: Control unit, 12: Memory unit, 13: Communication unit, 14: Operation unit, 15: Display unit, 16: First ultraviolet sensor, 17: Second ultraviolet sensor, 111: Flame detection unit, 112: Transmission unit, 113: Alarm control unit

Claims

1. a first sensor for measuring a first intensity of ultraviolet light in the UV-A region; a second sensor that measures a second intensity of ultraviolet light in a wavelength range shorter than the UV-A range; a flame detection unit that detects a flame using the first intensity measured by the first sensor and the second intensity measured by the second sensor in accordance with a flame detection condition; A flame detector comprising:

2. The flame detection condition is set according to a first reference intensity of ultraviolet light in the UV-A region contained in sunlight.

10. The flame detector of claim 1.

3. the flame detection condition includes a first discrimination threshold set according to the first reference intensity, The flame detection unit does not detect the flame when the ratio of the second intensity to the first intensity is equal to or less than the first discrimination threshold.

3. The flame detector of claim 2.

4. the flame detection condition includes a second discrimination threshold set according to a second reference intensity of ultraviolet rays in the UV-A region contained in the light of a fluorescent lamp; The flame detection unit does not detect the flame when the ratio is equal to or less than the second discrimination threshold.

4. The flame detector of claim 3.

5. The apparatus further includes an alarm output unit that outputs an alarm when the first intensity measured by the first sensor is equal to or greater than a predetermined value.

10. The flame detector of claim 1.

6. The wavelength region having a shorter wavelength than the UV-A region is the UV-C region.

2. The flame detector of claim 1.

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