JP7527124B2 - Fire detectors and fire detection systems - Google Patents

Description

The present invention relates to a fire detector and a fire detection system that can reduce the effect of environmental noise on fire detection accuracy.

There is a fire detector that judges whether or not a fire has occurred based on the amount of light received by the light-receiving element in the light-receiving unit, which receives the scattered light that is emitted from the light-emitting unit and scattered by smoke particles generated by a fire (see, for example, Patent Document 1).

The light receiving elements used in fire detectors are subject to noise (hereafter referred to as environmental noise) that occurs depending on the installation environment. Therefore, the signal obtained by converting the amount of light received by the light receiving element into a voltage contains environmental noise. If a fire is detected using a signal waveform that contains environmental noise, the peak voltage will fluctuate, which can lead to a deterioration in fire detection accuracy and can also cause the detector to malfunction.

Therefore, in Patent Document 1, the light receiving element is covered with a shielding box to block environmental noise, thereby preventing deterioration of fire detection accuracy.

Japanese Patent Application Publication No. 7-57165

However, the conventional techniques have the following problems.
According to Patent Document 1, the provision of a shielding box can suppress deterioration of fire detection accuracy. However, the need for a shielding box increases the number of parts, which leads to increased costs and labor costs.

The present invention has been made to solve the above-mentioned problems, and aims to provide a fire detector and fire detection system that can reduce the effect of environmental noise on fire detection accuracy without the need for a shielding box.

The fire detector of the present invention is a fire detector comprising: a light-emitting element that emits sinusoidal light having a predetermined frequency; a light-receiving element that receives an optical signal emitted from the light-emitting element, the amount of light of which changes as smoke is generated , converts the optical signal into an electrical signal, and outputs the electrical signal; and a control unit that determines whether or not a fire has occurred based on the signal strength of the electrical signal , and further comprises a narrow-band pass filter unit that outputs a first signal by passing frequencies in a narrow band range of noise components generated in accordance with the installation environment conditions of the fire detector, and is set not to pass signal components indicating the occurrence of a fire and having a predetermined frequency, which are included in the electrical signal output from the light-receiving element; and a wide-band pass filter unit that outputs a second signal by passing frequencies in a wide band range that is set to pass both signal components and noise components, which are included in the electrical signal output from the light-receiving element. The control unit determines whether or not a fire has occurred by comparing a value obtained by subtracting the peak value of the signal strength of the first signal , in which no signal component has passed, from the peak value of the signal strength of the second signal, in which the noise component has been superimposed on the signal component, with a preset threshold value.

In addition, a fire detector according to the present invention is a fire detector comprising: a light-emitting element that emits sinusoidal light having a predetermined frequency; a light-receiving element that receives an optical signal emitted from the light-emitting element, the amount of light of which changes as smoke is generated , converts the optical signal into an electrical signal, and outputs the electrical signal; and a control unit that determines whether or not a fire has occurred based on the signal strength of the electrical signal, and further comprises a narrow-band pass filter unit that outputs a first signal by passing frequencies in a narrow band region of noise components corresponding to environmental conditions in which the fire detector is installed, and that is set not to pass signal components indicative of the occurrence of a fire and having a predetermined frequency, which are included in the electrical signal output from the light-receiving element; and a wide-band pass filter unit that outputs a second signal by passing frequencies in a wide band region that is set to pass both the signal component and the noise component, and the control unit receives the first signal from which the signal component has not passed , and the second signal in which the noise component has been superimposed on the signal component , determines a peak value of the signal strength from the first signal, changes a preset threshold value in accordance with the peak value, and determines whether or not a fire has occurred by comparing the signal strength of the second signal with the changed threshold value.

Further, a fire detection system according to the present invention is a fire detection system including a fire detector and a fire receiver, the fire detector including a light emitting element that emits a sine wave light having a predetermined frequency, a light receiving element that receives an optical signal emitted from the light emitting element and whose light quantity changes with the occurrence of smoke, converts the optical signal into an electric signal and outputs the electric signal, a conversion unit that converts the electric signal output from the light receiving element into a signal corresponding to the smoke concentration and outputs the converted electric signal, and a filter that filters a signal component having a predetermined frequency, which is included in the converted electric signal, within a narrow band region of a noise component generated according to the installation environment conditions of the fire detector, and is set not to pass the signal component having the predetermined frequency and which indicates the occurrence of a fire. The fire receiver has a narrow band pass filter section that outputs a first signal by passing a certain wave number, a wide band pass filter section that outputs a second signal by passing frequencies in a wide band range that is set to pass both signal components and noise components contained in the converted electrical signal, and a control section that calculates a value obtained by subtracting the peak signal strength value of the first signal , which does not pass any signal components, from the peak signal strength value of the second signal, which has noise components superimposed on the signal components.The fire receiver has a fire determination section that determines whether or not a fire has occurred by comparing the value obtained by subtracting the peak signal strength value of the first signal from the peak signal strength value of the second signal with a preset threshold value.

The present invention provides a fire detector and fire detection system that can reduce the effect of environmental noise on fire detection accuracy without the need for a shielding box.

FIG. 1 is a functional block diagram of a fire detector according to a first embodiment of the present invention. 5 is an explanatory diagram relating to a signal received by a light receiving element according to the first embodiment of the present invention. FIG. FIG. 4 is an explanatory diagram relating to wide band pass filter processing in the first embodiment of the present invention. 5 is an explanatory diagram relating to narrow band pass filter processing in the first embodiment of the present invention. FIG. 2 is a functional block diagram showing an internal function of an amplifier unit according to the first embodiment of the present invention. FIG. 1 is a functional block diagram of a fire detection system according to a first embodiment of the present invention. FIG. FIG. 11 is a functional block diagram showing internal functions of an amplifier and a controller in a second embodiment of the present invention. FIG. 11 is an explanatory diagram relating to digital signal processing in a second embodiment of the present invention. FIG. 11 is a diagram showing a waveform obtained by connecting digitally sampled data strings by linear interpolation in the second embodiment of the present invention. 13 is a diagram showing a calculation result based on digitally sampled data by the digital filter processing unit according to the second embodiment of the present invention. FIG. 11 is a diagram summarizing the calculation results shown in FIG. 10 by the digital filter processing unit according to the second embodiment of the present invention. FIG. 13 is a diagram showing the results of the variation state of the digital sampling result obtained by the digital filter processing unit according to the second embodiment of the present invention. FIG.

Below, preferred embodiments of the fire detector and fire detection system of the present invention will be described with reference to the drawings. In the description below, both the wide-band pass filter and the low-band pass filter are configured using high-pass filters, but the wide-band pass filter and the low-band pass filter may also be configured using low-pass filters or band-pass filters.

The technical feature of the present invention is to obtain a fire detector and fire detection system that can suppress the effect of environmental noise on fire detection accuracy without the need for a shielding box by performing filtering processing as hardware or digital calculation processing to estimate noise components as software on the signal waveform obtained by the light receiving element.

Embodiment 1.
1 is a functional block diagram of a fire detector according to a first embodiment of the present invention. The fire detector 1 according to the first embodiment is configured to include a light-emitting element 11, a light-receiving element 12, an amplifier section 20, a control section 30, and an alarm section 40.

The light-emitting element 11 emits light with a predetermined wavelength and amount of light as a signal component at a specified timing in order to detect smoke generated by a fire. On the other hand, the light-receiving element 12 is provided in a position where the light emitted by the light-emitting element 11 does not directly enter it. The light-receiving element 12 receives the light emitted from the light-emitting element 11 and scattered by smoke particles, and outputs it as an electrical signal, specifically a voltage value.

One example of a light-emitting element that emits light of a predetermined wavelength and amount of light is an LED that emits a 20 kHz optical signal for fire detection.

The amplifier unit 20 amplifies the voltage value output from the light receiving element 12 and outputs it to the control unit 30.

When smoke detection is performed, the control unit 30 controls the light emitting element 11 to emit light at a predetermined timing. Then, in response to the emission of light from the light emitting element 11, the control unit 30 receives the voltage value received via the light receiving element 12 and the amplifier unit 20 as an electrical signal, and performs smoke detection to determine whether or not a fire has occurred.

Furthermore, if the control unit 30 determines that a fire has occurred, it is capable of reporting the occurrence of a fire to the outside via the alarm unit 40.

The electrical signal received by the control unit 30 contains noise (hereinafter, environmental noise) generated by the installation environment of the fire detector 1. An example of environmental noise is electrical noise emitted from a fluorescent lamp inverter close to the installation location of the fire detector. Therefore, in order to prevent false alarms or non-detection, it is important to suppress the effect of environmental noise on the accuracy of fire detection.

2A to 2C are explanatory diagrams relating to signals received by the light receiving element 12 according to the first embodiment of the present invention, converted into electrical signals, and output. The following waveforms are shown in (a) to (c) of FIG.
FIG. 2(a): Signal waveform S1 that does not contain noise signals and is intended to be received
FIG. 2(b): Noise waveform S2 generated by environmental noise
FIG. 2(c): Signal waveform in which a noise waveform S2 is superimposed on a signal waveform S1

In addition, in all of the signals shown in FIG. 2(a) to FIG. 2(c), the horizontal axis represents time , and the vertical axis represents a voltage value corresponding to the amount of received light.

When the control unit 30 is able to acquire the signal waveform S1 in FIG. 2(a) as an ideal waveform that is not affected by a noise environment, it can determine that a fire has occurred when smoke enters the smoke detector and the peak P1 caused by scattered light exceeds a preset fire determination threshold value.

However, when the signal waveform in FIG. 2(c) is obtained as the signal waveform in which the noise waveform S2 is superimposed on the signal waveform S1, the peak P2 will be greater than the peak P1 shown in FIG. 2(a).

Therefore, when a preset threshold is used, the control unit 30 may erroneously detect that a fire has occurred by comparing the actual peak P1 with peak P2, which is larger than peak P1.

In this manner, in a situation where environmental noise occurs, it is important to suppress the effect of the environmental noise on the accuracy of fire detection.

The fire detector 1 according to the first embodiment therefore performs two types of filtering in the amplifier section 20 and determines whether or not a fire has occurred from the two signals after filtering, thereby suppressing the effect of environmental noise on the accuracy of fire detection.

Specific methods for reducing the impact of environmental noise on fire detection accuracy are explained using Figures 3 to 5.

Figure 3 is an explanatory diagram of wide band pass filter processing in embodiment 1 of the present invention. Also, Figure 4 is an explanatory diagram of narrow band pass filter processing in embodiment 1 of the present invention. Figure 3 (a) is an input signal for performing wide band pass filter processing, and Figure 4 (a) is an input signal for performing narrow band pass filter processing. Both of these input signals are signals in which a noise waveform S2 is superimposed on a signal waveform S1 output from the light receiving element 12.

In the wideband pass filter process shown in FIG. 3(b), a process is performed to pass frequencies in a wideband range that is set to pass both the signal components indicating the occurrence of a fire, which are contained in the optical signal received by the light receiving element 12, and noise components in the installation environment of the fire detector that have frequencies higher than the frequencies of the signal components. Therefore, the wideband pass filter is set to a filter that passes a band higher than the frequencies of the signal components. As a result, as shown in FIG. 3(c), signal waveform S3 is obtained as the signal after wideband pass filter processing.

On the other hand, the narrow band pass filter process shown in Figure 4(b) involves passing frequencies in a narrow band range that is set so as not to pass signal components indicative of the occurrence of a fire, contained in the optical signal received by the light receiving element 12. Here, the width of Figure 4(b) is shown extremely small so that the difference between Figure 3(b) and Figure 4(b) can be seen, but in reality, the filter is set as close as possible to the frequency of the signal components, and does not allow the signal components to pass. This narrow band processing makes it possible to remove the signal components emitted from the light emitting element 11, and pass only the noise components.

As a result, as shown in FIG. 4(c), a signal waveform S4 is obtained as a signal after narrow band pass filter processing. This signal waveform S4 corresponds to a noise signal having a frequency band that can pass through the narrow band.

By employing a filter that passes a band slightly wider than the frequency of the electrical signal based on the light emitted from the light-emitting element 11, and a filter that passes a band slightly narrower than the frequency of the electrical signal, the control unit 30 is able to extract, as the signal waveform S4, a signal corresponding to environmental noise from a state in which the noise waveform S2 is superimposed on the signal waveform S1.

Figure 5 is a functional block diagram showing the internal functions of the amplifier unit 20 in the first embodiment of the present invention. The amplifier unit 20 shown in Figure 5 is configured to include a wide band pass filter unit 21 and a narrow band pass filter unit 22 as analog filters.

The wide band pass filter unit 21 performs amplification processing on the signal output from the light receiving element 12, and has the function of executing the wide band pass filter processing described with reference to FIG. 3. On the other hand, the narrow band pass filter unit 22 performs amplification processing on the signal output from the light receiving element 12, and has the function of executing the narrow band pass filter processing described with reference to FIG. 4.

The control unit 30 receives the signal waveform S3 after wide-band pass filter processing from the wide-band pass filter unit 21, and receives the signal waveform S4 after narrow-band pass filter processing from the narrow-band pass filter unit 22.

The control unit 30 executes a judgment process to judge whether or not a fire has occurred based on the signal waveforms S3 and S4. Specific examples of the judgment process include a first judgment process and a second judgment process as described below.

<First Determination Process>
Step 1: The control unit 30 determines the peak value of the signal waveform S3.
Step 2: The control unit 30 determines the peak value of the signal waveform S4 .
Step 3: The control unit 30 obtains a comparison value by subtracting the peak value of the signal waveform S4 from the peak value of the signal waveform S3.
Step 4: The control unit 30 compares the comparison value with a preset threshold value, and if the comparison value is greater than the threshold value, determines that a fire has occurred.

<Second Determination Process>
Step 1: The control unit 30 determines the peak value of the signal waveform S4.
Step 2: The control unit 30 changes the preset threshold value according to the magnitude of the peak value.
Step 3: The control unit 30 determines the peak value of the signal waveform S3.
Step 4: The control unit 30 compares the peak value of the signal waveform S3 with the changed threshold value, and if the peak value is greater than the changed threshold value, determines that a fire has occurred.

In this way, the control unit 30 can determine whether or not a fire has occurred, taking into account the effect of environmental noise on fire detection accuracy, based on the signal waveforms S3 and S4. In other words, the fire detector according to the first embodiment can achieve fire detection that suppresses the effect of environmental noise on fire detection accuracy, without providing a shielding box.

Furthermore, it is also possible to adopt a configuration in which at least one of the wide band-pass filter section 21 and the narrow band-pass filter section 22 is configured as two or more filters having different wide bandwidths and different narrow bandwidths.

For example, the second judgment process described above can be executed using multiple narrow band pass filters having different bandwidths as the narrow band pass filter unit 22. In this case, the control unit 30 selects one of the multiple narrow band pass filters depending on the magnitude of the peak value obtained in step 3. If the peak value obtained in step 3 suddenly exceeds the threshold value for fire judgment, the narrow band pass filter is changed to one with a narrower width. Then, in step 4, the control unit 30 obtains the noise peak value by comparing the peak values before and after the filter change, and can determine whether the sudden increase in peak value is due to noise or a fire.

As a result, more accurate fire detection is possible by using multiple narrow bandpass filters depending on the environmental conditions.

The narrow band pass filter unit 22 may be configured to use multiple narrow band pass filters having different narrow bandwidths corresponding to multiple noise characteristics in the installation environment to execute the first or second judgment process described above. In this case, the control unit 30 may select one narrow band pass filter based on a comparison between the waveform signal S3 and each of the waveform signals S4 that have passed through the multiple narrow band pass filters, and calculate the changed threshold value.

As a result, more accurate fire detection is possible by using multiple narrow bandpass filters depending on the environmental conditions.

Furthermore, multiple combinations of filters may be provided, with the wide band pass filter section 21 and the narrow band pass filter section 22 as one set. When the signal waveform S3 and the signal waveform S4 have the same waveform, there is a possibility that the selection of the signal waveform S1 and the noise waveform S2 has ended up being inadequate. In such a case, the control unit 30 changes to a different combination of filters. When the signal waveform S3 and the signal waveform S4 have different waveforms, the control unit 30 determines that the filtering has been performed correctly and performs a determination process.

As a result, more accurate fire detection is possible by using different combinations of wide-bandpass and narrow-bandpass filters depending on the environmental conditions.

Furthermore, by further providing a temperature sensor that detects the temperature in the installation environment of the fire detector 1 as an installation environment condition, it is possible to improve the accuracy of fire detection according to the installation environment conditions. Since the characteristics of the electrical components used in the filter (described below) change depending on the temperature, it is possible to use a filter that combines different wide-band pass filters and narrow-band pass filters that correspond to the expected temperatures.

The control unit 30 can select one of a plurality of combinations of wide-band pass filters and narrow-band pass filters according to the temperature detected by the temperature sensor, and execute the first or second judgment process described above using the signal waveforms S3 and S4 that have passed through the selected wide-band pass filter and narrow-band pass filter.

As a result, more accurate fire detection is possible by selectively using multiple wide-bandpass and narrow-bandpass filters depending on the environmental conditions identified by the temperature sensor detection results.

In the first embodiment, the wide band pass filter section 21 and the narrow band pass filter section 22 are described as using general high pass filters composed of resistors and capacitors or inductors, but low pass filters, band pass filters, or combinations of these can also be used. In addition, these components can be built into the ASIC, so they can be smaller and less expensive than the shielding box provided for the light receiving element 12.

In the above description of the first embodiment, the first and second judgment processes are described, in which a threshold value is compared with a comparison value within the fire detector 1 to determine whether or not a fire has occurred. However, it is also possible to apply the concept of the first or second judgment process to a fire detection system in which a fire detector and a fire receiver are linked. Therefore, the following description will be given by taking as an example a case in which an analog fire detector is used as the fire detector.

Figure 6 is a functional block diagram of a fire detection system in embodiment 1 of the present invention. The fire detection system 100 shown in Figure 6 is configured with an analog detector 50 and a fire receiver 60.

The analog sensor 50 is configured with a light receiving element 12, a conversion section 13, an amplifier section 20, and a control section 30. The amplifier section 20 includes a wide band pass filter section 21 and a narrow band pass filter section 22. On the other hand, the fire receiver 60 is configured with a fire judgment section 61.

The conversion unit 13 provided in the analog sensor 50 receives the electrical signal output from the light receiving element 12 and converts it into a signal corresponding to the smoke concentration.

The narrow band pass filter section 22 in the amplifier section 20 in the analog sensor 50 outputs a first signal by passing frequencies in a narrow band range that is set not to pass signal components that indicate the occurrence of a fire and are contained in the converted electrical signal received from the converter section 13.

On the other hand, the wideband pass filter section 21 in the amplifier section 20 in the analog sensor 50 outputs a second signal by passing frequencies in a wideband range that is set to pass both the signal components contained in the converted electrical signal received from the converter section 13 and the noise components corresponding to the installation environment conditions of the analog sensor 50.

Then, the control unit 30 in the analog sensor 50 obtains a value obtained by subtracting the peak value of the first signal from the peak value of the second signal, and transmits the obtained value to the fire receiver 60. The fire determination unit 61 in the fire receiver 60 compares the value received from the control unit 30 with a preset threshold value, and determines whether or not a fire has occurred.

In addition, instead of providing the functions of the amplifier unit 20 and the control unit 30 in the analog sensor 50, it is also possible to provide them in the fire receiver 60, and adopt a configuration in which the control unit 30 provided in the fire receiver 60 also executes the processing of the fire judgment unit 61.

In this case, the fire receiver 60 can determine whether or not a fire has occurred by performing the first or second determination process described above on the signal corresponding to the smoke density received from the conversion unit 13 in the analog detector 50.

More specifically, the narrow band pass filter section 22 in the amplifier section 20 provided in the fire receiver 60 outputs a first signal by passing frequencies in a narrow band range that is set not to pass signal components that indicate the occurrence of a fire and are included in the converted electrical signal received from the converter section 13.

On the other hand, the wideband pass filter section 21 in the amplifier section 20 provided in the fire receiver 60 outputs a second signal by passing frequencies in a wideband range that is set to pass both the signal components contained in the converted electrical signal received from the converter section 13 and the noise components corresponding to the installation environment conditions of the analog detector.

Then, the control unit 30 in the fire receiver 60 determines whether or not a fire has occurred by comparing the value obtained by subtracting the peak value of the first signal from the peak value of the second signal with a preset threshold value.

As described above, according to the first embodiment, a configuration is provided that can determine whether or not a fire has occurred using a signal that has passed through the wide band pass filter section and a signal that has passed through the narrow band pass filter section. As a result, a fire detector and a fire detection system can be realized that can suppress the effect of environmental noise on fire detection accuracy without providing a shielding box.

Embodiment 2.
In the above-described first embodiment, a case has been described in which an analog filter that suppresses the effect of environmental noise on fire detection accuracy is applied by executing wide-band pass filter processing and narrow-band pass filter processing in the amplifier unit 20. In contrast, in the second embodiment, a case in which a digital filter that suppresses the effect of environmental noise on fire detection accuracy is applied by executing digital filter processing in the control unit 30 will be described below with a specific example.

Figure 7 is a functional block diagram showing the internal functions of the amplifier unit 20 and the control unit 30 in the second embodiment of the present invention. The amplifier unit 20 shown in Figure 7 is configured to include a wide band pass filter unit 21. The control unit 30 shown in Figure 7 is configured to include a digital filter processing unit 31. Note that the digital filter processing unit 31 can also be provided between the amplifier unit 20 and the control unit 30 as a separate component that is not incorporated into the control unit 30.

The control unit 30 receives the signal waveform S3 after the wide band pass filter processing has been performed from the wide band pass filter unit 21. That is, the control unit 30 receives the signal waveform S3 including both a signal component indicating the occurrence of a fire and a noise component according to the installation environment conditions of the fire detector 1, and performs digital signal processing on the signal waveform S3 using the digital filter processing unit 31. Note that in this embodiment 2, the wide band pass filter unit 21 is not necessarily required, and the wide band pass filter unit 21 may be omitted.

Figure 8 is an explanatory diagram relating to digital signal processing in embodiment 2 of the present invention. In Figure 8, the horizontal axis indicates time and the vertical axis indicates signal strength, and three types of time waveforms, signal waveform S1 under normal noise-free conditions, noise waveform S2, and S1+S2, are shown along with the points at which each time waveform is digitally sampled. Points at which signal waveform S1 is digitally sampled are indicated by ● marks, points at which noise waveform S2 is digitally sampled are indicated by × marks, and points at which S1+S2 are digitally sampled are indicated by □ marks.

Figure 9 shows an example of a waveform obtained by connecting digitally sampled data strings in the second embodiment of the present invention by linear interpolation. Specifically, the waveform shows a signal waveform S1 data string (corresponding to the reference data string) and a data string S1+S2 (corresponding to the first data string) connected by linear interpolation. When there is no noise, the digital filter processing unit 31 in the control unit 30 can generate the data string indicated by the ● mark, but in a noisy environment, it will generate the data string indicated by the × mark.

Furthermore, as shown in Figure 9, the digital filter processing unit 31 can set a frame for each half period when the signal waveform S1 changes into a sine wave in a noise-free state. Figure 9 shows an example in which frames 1 to 3 are set and digital sampling is performed at seven points within each frame.

The digital filter processing unit 31 can estimate the noise level from the transition state of the seven points of data acquired for each frame. Figure 10 shows an example of the calculation results based on the digitally sampled data by the digital filter processing unit 31 according to the second embodiment of the present invention.

In FIG. 10, the values of seven digital sampling data points in each of frames 1, 2, and 3 are shown, corresponding to No. 1 to No. 7 from the earliest acquisition time. Based on these values, the digital filter processing unit 31 performs digital signal processing to obtain statistical values such as the average value, median value, moving average value 1, and moving average value 2 as index values, as shown in FIG. 10. Note that FIG. 10 also shows an ideal signal in a noise-free state, along with various statistical values.

These index values refer to values calculated by the digital filter processing unit 31 in the following manner.
Average: For each No., the average of the three values in boxes 1 to 3 is calculated. Median: For each No., the median of the three values in boxes 1 to 3 is calculated. Moving average 1: Using the average calculation results, the moving average of two consecutive averages is calculated. Moving average 2: Using the average calculation results, the moving average of three consecutive averages is calculated.

Figure 11 is a diagram summarizing the calculation results shown in Figure 10 by the digital filter processing unit 31 according to the second embodiment of the present invention. The control unit 30 generates multiple index data strings corresponding to the first data string based on the calculation results of the digital filter processing unit 31 that calculates multiple index values indicating the transition state of the first data string.

The control unit 30 then selects, from among the multiple index values, an index data sequence that is closest to a reference data sequence that corresponds to an ideal (noise-free) signal waveform. Furthermore, the control unit 30 can determine whether or not a fire has occurred by comparing the selected index data sequence with a preset threshold value. Note that it is possible to set an appropriate threshold value individually for each index data sequence. As a result, more accurate fire detection is possible by using different index values and threshold values for fire determination depending on environmental conditions.

Figure 12 is a diagram showing the results of determining the state of variation in the digital sampling results by the digital filter processing unit 31 according to the second embodiment of the present invention. The horizontal axis in Figure 12 corresponds to No. 1 to No. 7 in Figure 10, and the vertical axis corresponds to the variance of the three values in frames 1 to 3, which were determined as the index value of variation.

When an ideal noise-free waveform is obtained, there is no variation, so the variance value is 0. However, when the three values in boxes 1 to 3 vary due to the influence of noise, the variance value shown in Figure 12 is obtained.

The control unit 30 can quantitatively evaluate the degree of influence of environmental noise from the state of the variance value based on the calculation results of the digital filter processing unit 31. Therefore, the control unit 30 can update the threshold by selecting a threshold that matches the environmental noise based on the quantitative evaluation results, and determine whether a fire has occurred. As a result, more accurate fire detection is possible by using different thresholds depending on the environmental conditions. At this time, the maximum value of the variation may be added to the threshold, or a table of thresholds according to the value of the variation may be prepared.

As described above, according to the second embodiment, a configuration is provided in which digital filter processing (digital calculation processing) is performed on the signal that has passed through the amplifier section, and the environmental noise is quantitatively evaluated, after which it is possible to determine whether or not a fire has occurred. As a result, a fire detector that can suppress the effect of environmental noise on fire detection accuracy can be realized without providing a shielding box.

In the above-mentioned first and second embodiments, the light receiving element is provided at a position where the light emitted by the light emitting element does not directly enter, and the light receiving element receives the light emitted from the light emitting element and scattered by smoke particles. However, the present invention is not limited to such a configuration.

A similar judgment method can also be applied to fire detectors that have a configuration in which the light-emitting element and the light-receiving element are arranged opposite each other, such as separate detectors, and the amount of light received by the light-receiving element decreases when smoke is generated.

1 Fire detector, 11 Light emitting element, 12 Light receiving element, 13 Conversion section, 20 Amplification section, 21 Wide band pass filter section, 22 Narrow band pass filter section, 30 Control section, 31 Digital filter processing section, 40 Alarm section, 50 Analog detector, 60 Fire receiver, 100 Fire detection system.

Claims (5)

A light emitting element that emits a sinusoidal light having a predetermined frequency;
a light receiving element that receives an optical signal emitted from the light emitting element, the amount of light of which changes with the generation of smoke , converts the optical signal into an electrical signal, and outputs the electrical signal;
a control unit that determines whether or not a fire has occurred based on the signal strength of the electrical signal ;
A fire detector comprising:
a narrow band pass filter unit configured to not pass a signal component indicating the occurrence of a fire having the predetermined frequency included in the electrical signal output from the light receiving element, the narrow band pass filter unit passing a frequency in a narrow band range of a noise component generated according to an installation environment condition of the fire detector, thereby outputting a first signal;
a wide band pass filter unit that outputs a second signal by passing frequencies in a wide band range that is set to pass both the signal component and the noise component included in the electrical signal output from the light receiving element,
The control unit determines whether or not a fire has occurred by comparing a value obtained by subtracting a peak value of the signal strength of the first signal without passing the signal component from a peak value of the signal strength of the second signal in a state in which the noise component is superimposed on the signal component, with a preset threshold value. A light emitting element that emits a sinusoidal light having a predetermined frequency;
a light receiving element that receives an optical signal emitted from the light emitting element, the amount of light of which changes with the generation of smoke , converts the optical signal into an electrical signal, and outputs the electrical signal;
a control unit that determines whether or not a fire has occurred based on the signal strength of the electrical signal ;
A fire detector comprising:
a narrow band pass filter unit configured to not pass a signal component indicating the occurrence of a fire having the predetermined frequency included in the electrical signal output from the light receiving element, the narrow band pass filter unit passing a frequency in a narrow band range of a noise component corresponding to an installation environment condition of the fire detector, thereby outputting a first signal;
a wide band pass filter unit that outputs a second signal by passing frequencies in a wide band range that is set to pass both the signal component and the noise component included in the electrical signal output from the light receiving element,
The control unit is
receiving the first signal , through which the signal component has not passed , and the second signal , in which the noise component has been superimposed on the signal component ;
determining a peak value of a signal strength from the first signal;
A preset threshold value is changed according to the peak value;
A fire detector that determines whether or not a fire has occurred by comparing the signal strength of the second signal with the changed threshold value. A temperature sensor is further provided to detect a temperature in the installation environment as the installation environment condition,
the narrow band pass filter unit is composed of a plurality of narrow band pass filters having different narrow bandwidths corresponding to temperatures in the installation environment,
The control unit is
selecting one of the plurality of narrow band pass filters in response to a temperature detected by the temperature sensor;
The fire detector according to claim 1 or 2 , wherein a signal that has passed through a selected narrow band pass filter is received as the first signal. the narrow band pass filter unit is composed of a plurality of narrow band pass filters having different narrow bandwidths corresponding to a plurality of noise characteristics in an installation environment,
The control unit is
receiving the signals that have passed through the narrow band pass filters as the first signals, and calculating a changed threshold value from the first signals;
The fire detector according to claim 1 or 2, wherein whether or not a fire has occurred is determined by comparing the second signal with the changed threshold value. A fire detection system including a fire detector and a fire receiver,
The fire detector comprises:
A light emitting element that emits a sinusoidal light having a predetermined frequency;
a light receiving element that receives an optical signal emitted from the light emitting element, the amount of light of which changes with the generation of smoke , converts the optical signal into an electrical signal, and outputs the electrical signal;
A conversion unit that converts the electrical signal output from the light receiving element into a signal corresponding to a smoke concentration and outputs the converted electrical signal;
a narrow band pass filter unit configured to not pass a signal component indicating the occurrence of a fire having the predetermined frequency included in the converted electrical signal, the narrow band pass filter unit passing a frequency in a narrow band range of a noise component generated in accordance with an installation environment condition of the fire detector, thereby outputting a first signal;
a wideband pass filter unit that outputs a second signal by passing frequencies in a wideband range that is set to pass both the signal component and the noise component contained in the converted electrical signal;
a control unit that calculates a value obtained by subtracting a peak value of a signal strength of the first signal that does not pass through the signal component from a peak value of a signal strength of the second signal in a state in which the noise component is superimposed on the signal component,
The fire receiver has a fire detection system having a fire determination unit that determines whether or not a fire has occurred by comparing the value obtained by subtracting the peak signal strength of the first signal from the peak signal strength of the second signal with a preset threshold value.

Images