Fire alarm system

Abstract

This technology provides an alternative to conventional fire alarms, enabling the detection of LP gas in addition to fire. [Solution] The fire alarm system (1) has a detection unit (11) which integrally includes a fire detection unit (13) and an LP gas detection unit (14). The LP gas detection unit (14) includes a light source (141) that irradiates light into the LP gas detection area and a light receiving unit (142) that receives reflected light from the LP gas detection area, and detects LP gas in the LP gas detection area based on the column density of LP gas obtained from the information of the reflected light.

Description

Technical Field

[0001] The present invention relates to a fire warning system.

Background Art

[0002] The installation location of a fire alarm is determined by law, and from the perspective of detecting smoke, it is installed on the ceiling or a wall surface near the ceiling. Also, a city gas alarm for city gas, which is lighter than air, can be installed in a location close to a fire alarm. Furthermore, an alarm that integrates a fire alarm and a gas alarm capable of detecting city gas has been conventionally known (see, for example, Patent Document 1).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] On the other hand, liquefied petroleum gas (LP gas) such as propane gas used in ordinary households is heavier than air, so an LP gas alarm needs to be installed near the floor surface. Therefore, it cannot be made into a device integrated with a fire alarm, and it is necessary to install both an LP gas alarm and a fire alarm.

[0005] One aspect of the present invention aims to provide a technology that enables detection of LP gas in addition to detection of a fire in a conventional fire alarm.

Means for Solving the Problems

[0006] To solve the above problems, a fire alarm system according to one aspect of the present invention has a detection unit that integrally includes a fire detection unit for detecting a fire and an LP gas detection unit for detecting LP gas, the LP gas detection unit includes a light source that irradiates light into an LP gas detection area below the detection unit and a light receiving unit that receives reflected light from the LP gas detection area, and detects the LP gas in the LP gas detection area based on the column density of LP gas obtained from the information of the reflected light. [Effects of the Invention]

[0007] According to one aspect of the present invention, a technology is provided that enables the detection of LP gas in addition to fire in a conventional fire alarm. [Brief explanation of the drawing]

[0008] [Figure 1] This is a schematic front view showing the configuration of a fire alarm system according to Embodiment 1 of the present invention. [Figure 2] This is a schematic side view showing the configuration of a fire alarm system according to Embodiment 1 of the present invention. [Figure 3] This is a block diagram showing an example of the functional configuration of a fire alarm system according to Embodiment 1 of the present invention. [Figure 4] This is a block diagram showing an example of the functional configuration of the control unit in Embodiment 1 of the present invention. [Figure 5] This figure schematically illustrates one form of use of the fire alarm system according to Embodiment 1 of the present invention. [Figure 6] This figure shows a flowchart illustrating an example of the fire alarm process performed by a fire alarm system according to Embodiment 1 of the present invention. [Figure 7] This figure schematically illustrates one form of use of the fire alarm system according to Embodiment 2 of the present invention. [Figure 8] This is a schematic front view showing the configuration of a fire alarm system according to Embodiment 3 of the present invention. [Figure 9] This is a schematic side view showing the configuration of a fire alarm system according to Embodiment 3 of the present invention. [Figure 10] This figure schematically shows the configuration of the light source and light receiving unit in a fire alarm system according to Embodiment 4 of the present invention. [Figure 11] This figure schematically shows the spectrum of a sensor signal detected by a fire alarm system according to Embodiment 4 of the present invention. [Modes for carrying out the invention]

[0009] [Embodiment 1] The following describes in detail one embodiment of the present invention. The configuration of the fire alarm system according to this embodiment 1 is schematically shown in Figures 1 and 2. The fire alarm system 1 consists of a detection unit 11. The detection unit 11 has a frustoconical main body 12, and the main body 12 integrally includes a fire detection unit 13 for detecting fire and an LP gas detection unit 14 for detecting LP gas.

[0010] The fire detection unit 13 is a detection unit that detects a fire, for example, by detecting smoke. The fire detection unit 13 may be a conventional photoelectric smoke detection unit that detects the diffuse reflection of light from a light-emitting unit due to smoke introduced inside using a light-receiving unit. The fire detection unit 13 has a top plate portion 131 which has a circular shape when viewed from above (planar shape), a support portion 132 which supports the top plate portion 131 on the main body portion 12, and a smoke detection unit 133 which detects smoke entering through the gap between the top plate portion 131 and the main body portion 12.

[0011] The LP gas detection unit 14 includes a light source 141 that irradiates light into the LP gas detection area below the detection unit 11, and a light receiving unit 142 that receives reflected light from the LP gas detection area. The LP gas detection area is an area that can become a flow path for leaked LP gas and is irradiated by light from the light source 141. Since LP gas is heavier than air, the LP gas detection area may be an area on the floor surface if it is indoors.

[0012] The light source 141 is a light source capable of irradiating light that can detect LP gas in the LP gas detection region, and can be a laser, a light-emitting diode (LED), or a light bulb having a wavelength (for example, 1.6 μm) absorbed by the gas to be measured. In the present embodiment, the light source 141 is, for example, an LED. The light receiving unit 142 is an optical configuration capable of receiving the return light, and is composed of, for example, a condensing optical system that condenses the return light, and a light receiving element (photoelectric conversion element) that detects the light condensed by the condensing optical system.

[0013] An example of the functional configuration in the fire alarm system 1 of Embodiment 1 is shown in the block diagram of FIG. 3. Further, an example of the functional configuration of the control unit in Embodiment 1 is shown in the block diagram of FIG. 4. The fire alarm system 1 includes a control unit 20 and an alarm transmission unit 30. The control unit 20 controls the driving of the light source 141. Further, the control unit 20 acquires warning information according to the detection signals of the light receiving unit 142 and the smoke detection unit 133, respectively. The alarm transmission unit 30 transmits an alarm according to the warning information acquired by the control unit 20. Note that reference numeral 143 indicates a condenser lens as an example of a condenser optical system that condenses the return light. Further, "IL" means the irradiation light from the light source, and "SL" means the return light

[0014] The control unit 20 includes a column density acquisition unit 21, a column density change amount acquisition unit 22, a column density change amount determination unit 23, a smoke density acquisition unit 24, a smoke density determination unit 25, and a warning signal output unit 26.

[0015] The column density acquisition unit 21 acquires the column density of LP gas according to the signal detected by the light receiving unit 142. The light from the light source (LED) is partially absorbed by the LP gas on its optical path and is received by the light receiving unit 142 due to diffuse reflection or the like. The LP gas is measured by the column density (concentration × distance (for example, ppm·m)).

[0016] The column density change amount acquisition unit 22 acquires the column density change amount by referring to the column density of the LP gas acquired by the column density acquisition unit 21. The "column density change amount" is a quantity representing the degree of increase or decrease of the column density over time. Examples of the "column density change amount" include the value of the change amount of the column density of the LP gas per unit time (i.e., the change rate (slope) of the column density), and the time integral value of the column density. When the time is "t" and the column density change amount is "Rco", the former is represented by the ratio of the change amount of the column density (d column density) to the change amount of time (dt), as shown in the following formula (1), and the latter is represented by the following formula (2).

[0017] [Number]

[0018] The column density change amount determination unit determines whether or not the column density change amount acquired by the column density change amount acquisition unit 22 exceeds the reference value by referring to the column density change amount and the reference value. The "reference value" is a value indicating that the column density of the LP gas acquired according to the intensity signal of the return light SL received by the light receiving unit 142 has increased from the normal column density of the LP gas in the LP gas detection region. The "reference value" is a value larger than the normal column density change amount of the LP gas in the LP gas detection region. "Normal" means, for example, when no LP gas is generated from the LP gas generation source in the LP gas detection region or in its vicinity. The normal column density change amount may be a predetermined value, or may be the column density change amount (normal measurement value) acquired by normal measurement, or may be a calculated value obtained by computer simulation.

[0019] The "reference value" can be appropriately determined according to the fire alert level and the type of column density change. For example, when LP gas increases rapidly, the column density increases significantly, and the amount of change in column density becomes even larger. Therefore, the "reference value" may be, for example, the magnitude of the slope at the rising portion during the increase in the column density increase curve. Setting the reference value to the normal state side (smaller value) is preferable from the viewpoint of enabling earlier fire alerts. Setting the reference value to the fire state side (larger value) is preferable from the viewpoint of suppressing the occurrence of false alarms and improving the reliability of the alarm signal. Furthermore, setting the reference value to the value of the change in LP gas column density per unit time is preferable from the viewpoint of achieving earlier fire alerts or from the viewpoint of suppressing false alarms of fire alarm signals.

[0020] Furthermore, the column density change may also be the time integral of the column density, in which case the reference value may be the time integral of the LP gas column density which is greater than that under normal conditions. For example, when air convection occurs, LP gas is easily diffused, and its column density may change irregularly. In such cases where the change in LP gas column density is affected by other factors, setting the reference value to a specific integral of the column density is preferable from the viewpoint of achieving early fire warning even when the LP gas detection area is affected by external factors.

[0021] The reference value may be an experimental value obtained through experiments, similar to the column density during normal operation, or it may be a calculated value obtained through computer simulations, etc.

[0022] Thus, the LP gas detection unit 14 is configured to detect LP gas in the LP gas detection region based on the column density of LP gas obtained from the reflected light information.

[0023] The smoke concentration acquisition unit 24 acquires the smoke concentration in accordance with the signal detected by the smoke detection unit 133. The smoke concentration determination unit 25 refers to the smoke concentration acquired by the smoke concentration acquisition unit 24 and determines the fire alert level according to the smoke concentration. This alert level may be determined, for example, by comparing it with a standard value for smoke concentration.

[0024] The warning signal output unit 26 outputs a warning signal indicating a gas warning in response to the column density change determination unit 23's determination that the acquired column density change exceeds the reference value, and outputs a warning signal indicating a fire warning in response to the smoke concentration determination unit 25's determination of the fire warning level according to the smoke concentration. These signals are transmitted to the user, for example, by wireless communication, or notified to the surroundings as a visual or audible alarm.

[0025] [Specific methods of fire prevention] This section provides a more detailed explanation of fire prevention using Fire Warning System 1. Figure 5 schematically shows one form of use of Fire Warning System 1. Figure 5 shows an example of applying Fire Warning System 1 to a kitchen in a typical home.

[0026] Kitchen 100 is equipped with a gas stove 101 and a ventilation fan 102. The gas stove 101 is a gas stove for LP gas. The detection unit 11 of the fire alarm system 1 is fixed to the ceiling 104 with a light source 141 and a light receiver 142 facing the floor 103 of kitchen 100. In other words, the detection unit 11 is mounted on the ceiling 104 so that the light source 141 illuminates the floor 103 with emitted light IL, and the light receiver 142 receives the reflected light SL that has been diffusely reflected by the floor 103.

[0027] In the kitchen 100, if a fire occurs in the gas stove 101, the smoke 105 will mainly spread upwards within the kitchen 100 unless the ventilation fan 102 is operating. The smoke 105 that has spread into the room will reach the smoke detection unit 133 through the gap between the top plate and the main body 12 of the fire detection unit 13, where the smoke detection unit 133 will cause the light from the light-emitting part to be scattered, and this scattered light will be detected by the light-receiving part of the smoke detection unit 133, thereby detecting the fire.

[0028] If LP gas leaks from the gas stove 101, it will flow mainly downwards within the kitchen 100 because LP gas 106 is heavier than air. LP gas flowing over the floor 103 of the room is detected when specific components in the irradiated light are absorbed by gas molecules (propane molecules) through collisions, and the reflected light from which such specific components were absorbed is detected depending on the opportunity for the collision. In the fire alarm system 1, LP gas is detected in column density (ppm·m). Therefore, even low concentrations of LP gas can be detected by the fire alarm system 1.

[0029] Based on the above example, an example of a fire warning method using fire warning system 1 will be explained. An example of the fire warning process by fire warning system 1 is shown in the flowchart in Figure 6.

[0030] In step S101, the control unit 20 starts irradiating with illumination light IL from the light source 141. For example, the control unit 20 irradiates with illumination light IL from the LED.

[0031] Next, in step S102, the light receiving unit 142 receives the reflected light SL (reflected light) that has been diffusely reflected by the floor 103 from the irradiated light IL.

[0032] Next, in step S103, the column density acquisition unit 21 acquires the column density (ppm·m) of the LP gas in the reflected light SL in response to the detection signal of the reflected light SL in the light receiving unit 142.

[0033] Next, in step S104, the column density change acquisition unit 22 refers to the column density of the reflected light SL acquired by the column density acquisition unit 21 and acquires the amount of change in the column density of the LP gas in the reflected light SL as, for example, the rate of change of the column density or the time integral of the column density as described above.

[0034] Furthermore, in step S105, the smoke concentration acquisition unit 24 acquires the smoke concentration in accordance with the detection signal from the smoke detection unit 133.

[0035] Next, in step S106, the column density change determination unit 23 refers to the column density change amount of LP gas in the reflected light SL acquired by the column density change acquisition unit 22 and the corresponding reference value, and determines whether the column density change amount of the reflected light SL is greater than the reference value.

[0036] If, in step S106, the change in column density of the reflected light SL is greater than the reference value, then in step S107, the warning signal output unit 26 outputs a gas leak warning signal. The gas leak warning signal is the most preliminary signal among the fire warning information output by the fire warning system 1, and indicates, for example, that there are no signs of fire, but there is a risk of being affected by a gas leak.

[0037] If, in step S106, the amount of change in the column density of the reflected light SL is less than or equal to the reference value, then in step S108, the smoke concentration determination unit 25 refers to the smoke concentration acquired by the smoke concentration acquisition unit 24 and the corresponding reference value to determine whether the smoke concentration is greater than the reference value.

[0038] If the smoke concentration is greater than the standard value in step S108, the warning signal output unit 26 outputs a fire alarm signal in step S109. The fire alarm signal is a signal that indicates the most serious fire situation among the fire warning information output by the fire warning system 1, for example, that a fire is already in progress and that there is a risk of this fire condition spreading further.

[0039] If, in step S108, the smoke concentration is below the reference value, that is, if both the column density change amount of the reflected light SL and the smoke concentration are below their respective reference values, the control unit 20 repeats the steps described above from step S101.

[0040] The alarm transmission unit 30 acquires various signals from the warning signal output unit 26 and transmits the acquired signals in a format corresponding to the acquired signals. For example, the alarm transmission unit 30 outputs audio corresponding to the acquired signals from a speaker built into the detection unit 11. Alternatively, the alarm transmission unit 30 transmits the acquired signals to the outside via a communication device built into the detection unit 11. Alternatively, the alarm transmission unit 30 performs the above audio output and signal transmission simultaneously.

[0041] In this fire alarm system 1, the detection unit 11 integrates a fire detection unit 13 and an LP gas detection unit 14 that detects LP gas in column density by light irradiation and reception. Therefore, since LP gas can be detected from the installation location of the fire detection unit 13, it can be installed in the same location as conventional fire alarms, and it is also possible to detect smaller amounts of LP gas compared to concentration detection. Thus, it is possible to detect LP gas before it reaches a dangerous level, which is advantageous for earlier fire warning.

[0042] Furthermore, in the fire alarm system 1, the light source 141 is a light-emitting diode. Therefore, the light source 141 of the LP gas detection unit 14 can be obtained more cheaply and easily than a laser.

[0043] [Embodiment 2] Other embodiments of the present invention are described below. For the sake of convenience in the following embodiments, components having the same function as those described in the above embodiments will be denoted by the same reference numerals, and their descriptions will not be repeated.

[0044] Figure 7 schematically shows one form of use of the fire alarm system according to Embodiment 2. Fire alarm system 2 is configured similarly to fire alarm system 1 described above, except that it further includes a reflector 50 placed on the floor 103. That is, fire alarm system 2 consists of a detection unit 11 and a reflector 50.

[0045] The reflector 50 is positioned on the optical axis of the light source 141 on the floor 103. The planar shape of the reflector 50 is, for example, circular, and it is desirable that it be about the same size as the light-receiving optical system from the viewpoint of ease of optical axis adjustment during installation and light reception efficiency, for example, its diameter is 50 mm. The reflector 50 is a plate-shaped or sheet-shaped member having a retroreflective surface, and is fixed to the floor 103 by screws or adhesive. Thus, the fire alarm system 2 further has a reflector positioned in the direction of irradiation of the light source 141 and reflecting the light from the light source 141 toward the light-receiving unit 142.

[0046] The fire alarm system 2 is used in the same way as the fire alarm system 1 described above and has the same effect as the fire alarm system 1. In addition, because the fire alarm system 2 has a reflector 50, the light receiving sensitivity at the light receiving unit 142 is higher than that of the fire alarm system 1, and the detection accuracy of LP gas is higher. Thus, the fire alarm system 2 is more effective in terms of improving the detection accuracy of LP gas.

[0047] [Embodiment 3] Figures 8 and 9 schematically show one form of use of the fire alarm system according to Embodiment 3. The fire alarm system 3 is substantially configured the same as the fire alarm system 1 described above, except that the light source 141 and the light receiving unit 142 are rotatably attached to the detection unit 31.

[0048] The detection unit 31 of the fire alarm system 3 has a truncated pyramidal main body 32 with a rectangular planar shape. The detection unit 31 has a fire detection unit 13 on one end of the main body 32 in the longitudinal direction, and a rotating support unit 33 and an LP gas detection unit 14 attached to the rotating support unit 33 on the other end.

[0049] The rotating support unit 33 is attached to the detection unit 31 so as to be rotatable along either the long axis or short axis direction of the main body 32, as shown by the double arrows in the figure. The rotating support unit 33 is driven by a motor controlled by the control unit 20 so that, for example, the light emitted from the light source 141 traces a trajectory of a specific shape (for example, a figure eight or a meandering shape that scans the entire floor 103). The rotation of the rotating support unit 33 may be constant, or it may be limited to specific times such as at night.

[0050] The detection unit 31 of the fire alarm system 3 is used in the same way as the fire alarm system 1 described above, except that it is fixed to the upper part of the wall of the kitchen 100, and it has the same effect as the fire alarm system 1. In addition, since the fire alarm system 3 has a rotating support part 33, the range to which the light emitted from the light source 141 reaches can be used as the LP gas detection area, making it more effective than the fire alarm system 1 in terms of achieving LP gas detection over a wider area.

[0051] [Embodiment 4] Embodiment 4 is configured similarly to the fire alarm system described above, except that it includes a light source and a light receiving unit, which are described below. Figure 10 schematically shows the configuration of the light source and light receiving unit in the fire alarm system according to Embodiment 4. As shown in Figure 10, the fire alarm system according to Embodiment 4 has a light source 441 and a light receiving unit 442.

[0052] The light source 441 includes a light source unit 4411 and a power supply 4412. The light source unit 4411, as described above for the light source 141, is configured to irradiate light containing light components of wavelengths absorbed by the gas to be measured, and is, for example, a mid-infrared LED.

[0053] The power supply 4412 is configured to supply a sinusoidal current of a specific frequency (e.g., 1 kHz) to the light source unit 4411. Generally, the amount of light emitted by a light-emitting diode changes in proportion to the amount of current. The amount of light emitted by a light-emitting diode supplied with a current that changes at a specific frequency will change at that specific frequency. Thus, in Embodiment 4, the light source 441 is configured to irradiate the LP gas detection area with light whose amount of light emitted changes at a specific frequency. The power supply 4412 has, for example, a quartz crystal oscillator. A quartz crystal oscillator can stably oscillate at a constant frequency, and it is preferable for the power supply 4412 to have a quartz crystal oscillator from the viewpoint of improving the frequency stability of the irradiated light IL.

[0054] The light-receiving unit 442 further includes an amplifier 4422, a bandpass filter 4423, and a detector 4424, in addition to the light-receiving element 4421. The light-receiving element 4421 can be appropriately determined according to the wavelength of the light emitted from the light source unit 4411. For example, if the light source unit 4411 is a mid-infrared LED, the light-receiving element 4421 may be a mid-infrared PD (photodiode).

[0055] Amplifier 4422 is configured to amplify the electrical signal of the reflected light from the photoelectric conversion in the photodetector 4421.

[0056] The bandpass filter 4423 is configured to allow electrical signals from the photodetector 4421 to pass through a specific frequency band that substantially includes the frequency of the illumination light IL from the light source unit 4411 (e.g., 1 kHz), while attenuating electrical signals in other frequency bands.

[0057] The detector 4424 is configured to detect the amount of an electrical signal with a frequency corresponding to the irradiated light IL. Thus, in Embodiment 4, the light receiving unit 442 is configured to receive light having a specific frequency from a light source and light from the LP gas detection region as reflected light.

[0058] The light source unit 4411 emits illumination light IL by a sinusoidal current of a certain frequency (e.g., 1 kHz). The intensity of the light output from the light source unit 4411 is amplitude-modulated sinusoidally.

[0059] The light-receiving unit 442 receives the return light SL of the amplitude-modulated illumination light IL with a light-receiving element 4421 (mid-infrared photodiode). The electrical signal converted by reception is amplified by amplifier 4422. As a result, both the signal and the noise electrical signals are amplified.

[0060] Figure 11 schematically shows the spectrum of the sensor signal detected by the fire alarm system according to Embodiment 4. Currents in a specific frequency band, including the aforementioned frequencies, of the amplified electrical signal pass through the bandpass filter 4423. For example, currents in the frequency band (Δf) corresponding to the LP gas component to be detected pass through the bandpass filter 4423. Currents in other frequency bands are noise and are attenuated and removed by the bandpass filter 4423.

[0061] The intensity of the electrical signal that has passed through the bandpass filter 4423 is detected by the detector 4424, and the column density of the LP gas corresponding to the detected value is acquired by the column density acquisition unit 21. Thus, in Embodiment 4, the reflected light SL is detected by AC sensing that extracts light of a specific frequency (1 kHz) in the irradiated light IL, and the column density of the LP gas is acquired.

[0062] Generally, LED light sources tend to have shorter optical signal transmission distances compared to laser light sources due to factors such as noise. In Embodiment 4, since the effect of noise that shortens the transmission distance of the LED light source is reduced, it is possible to make the optical signal transmission distance (i.e., the round-trip distance between the fire alarm system and the LP gas detection area) longer when using an LED as the light source compared to when an LED is used alone as the light source. Alternatively, if the optical signal transmission distance is the same, it is possible to further improve the detection accuracy of LP gas compared to when an LED is used alone as the light source.

[0063] In Embodiment 4, the light source 441 may further include a collimating lens. Including a collimating lens is preferable from the viewpoint of improving gas detection accuracy because it prevents divergence of the irradiated light IL from the light source 441.

[0064] Furthermore, the light source 441 may have other oscillating elements such as an LC circuit or a ceramic resonator instead of a quartz crystal oscillator. In Embodiment 4, it is preferable for the light source 441 to have a quartz crystal oscillator as the oscillating element from the viewpoint of excellent frequency accuracy and temperature stability.

[0065] The light-receiving unit 442 may further include a focusing lens that focuses the reflected light SL onto the light-receiving element 4421. Including a focusing lens in the light-receiving unit 442 is preferable from the viewpoint of improving the detection accuracy of LP gas, as it increases the amount of reflected light that can be detected.

[0066] Furthermore, the light-receiving unit 442 may further include an optical filter in the optical path of the reflected light toward the light-receiving element 4421 to cut out light outside the detection wavelength. Including an optical filter in the light-receiving unit 442 is preferable from the viewpoint of improving the detection accuracy of LP gas, as it removes light components that become noise in the reflected light.

[0067] Furthermore, in the light-receiving section 442, it is preferable from the viewpoint of improving the detection accuracy of LP gas, as both the collimating lens and the focusing lens are made of a material that has excellent transmittance of the irradiation light IL emitted from the light source 441, thereby suppressing the loss of irradiation light IL and reflected light SL. For example, if the light source section 4411 is a mid-infrared LED, it is preferable from the above viewpoint that the collimating lens and the focusing lens are made of calcium fluoride.

[0068] In Embodiment 4, the light source 441 is configured to irradiate the LP gas detection area with light whose emission amount changes at a specific frequency, and the light receiving unit 442 is configured to receive light from the LP gas detection area as reflected light, which has a specific frequency from the light source 441. Embodiment 4 is applicable not only to Embodiment 1 described above but also to other embodiments, and is even more effective than when an LED is used alone as the light source in terms of increasing the transmission distance of the optical signal and increasing the detection accuracy of the LP gas.

[0069] [Other Embodiments] In embodiments of the present invention, the change in column density includes not only the increase in column density but also the decrease in column density. In embodiments of the present invention, LP gas may be detected based on such a decrease in column density. For example, the fire alarm system in embodiments of the present invention may be configured to issue an alarm based on a comparison of a first reference value of column density with the change in column density, as well as based on a second reference value of column density lower than the first reference value and the change in column density. Such a configuration is advantageous from the viewpoint of detecting LP gas leaks earlier, because it makes it possible to issue an alarm at a reference value (second reference value) lower than the normal reference value (first reference value) when the amount of LP gas is changing (increasing) rapidly.

[0070] Furthermore, in embodiments of the present invention, the amount of change in column density or smoke concentration may be used as a condition for canceling an issued alarm. For example, the fire alarm system in embodiments of the present invention may be configured to cancel an already issued alarm based on the amount of change in column density or smoke concentration falling below a standard value, or in addition to the above, the amount of change in column density or smoke concentration in the direction of decrease. Such a configuration is preferable from the viewpoint of achieving a smooth return from alarm issuance to normal detection.

[0071] When installing a fire alarm (detection unit in this embodiment), the detection direction of the detector can usually be adjusted by the installer. Therefore, in Embodiments 1 and 2 of the present invention, the orientation of the light source 141 and the light receiving unit 142 may be adjustable when installing the detection unit so that the light is directed toward the source of LP gas (e.g., gas stove 101) and the reflected light is received. Such a configuration is more effective from the viewpoint of improving the LP gas detection efficiency, as it allows the LP gas detection unit to be directed toward a direction advantageous for detecting LP gas, or from the viewpoint of enabling LP gas detection at a location desired by the user.

[0072] Furthermore, in embodiments of the present invention, the LP gas detection unit may have two or more sets of light sources and light receiving units. Such a configuration is more effective from the viewpoint of enabling detection of LP gas in two or more areas, or from the viewpoint of improving the detection accuracy of the LP gas detection unit by referring to the detection result of one of multiple sets.

[0073] Furthermore, in embodiments of the present invention, the LP gas detection unit may further include an optical system for the light source 141. For example, the LP gas detection unit may include a focusing optical system that focuses the light emitted from the light source 141 to a specific position in the direction of illumination, or it may include a collimating optical system that emits the light emitted from the light source 141 as collimated light. Such a configuration is more effective from the viewpoint of improving the detection accuracy of LP gas.

[0074] Furthermore, in embodiments of the present invention, the light-receiving unit 142 may include a light-receiving element having high sensitivity, such as an avalanche photodiode. Such a configuration is also more effective from the viewpoint of improving the detection accuracy of LP gas.

[0075] Furthermore, in embodiments of the present invention, the control unit 20 may also be provided with a function to correct errors in the detected value from the light receiving unit due to external factors such as temperature, ambient light, and dirt on the light receiving optical system. Such a configuration is also more effective from the viewpoint of improving the detection accuracy of LP gas.

[0076] Furthermore, in embodiments of the present invention, the fire detection unit 13 may be a detector that detects fire by detecting heat using a thermal method or by detecting the distance to smoke using a laser method.

[0077] Furthermore, in Embodiment 3 of the present invention, the detection unit may be configured to be attachable to an indoor electrical outlet (such as one for an air conditioner or refrigerator) and to be powered by that outlet. Such a configuration is more effective, for example, in terms of improving the detection accuracy of LP gas, because it allows for the use of detections with fluctuating power consumption.

[0078] Furthermore, in embodiments of the present invention, the control unit may output a warning signal according to the acquired column density value. For example, the control unit 20 may refer to the column density value of the LP gas acquired by the column density acquisition unit 21 and its reference value to determine whether the column density exceeds the reference value, and the warning signal output unit 26 may output a warning signal regarding LP gas leakage according to the information of this determination. Such a configuration is also preferable from the viewpoint of achieving highly accurate detection of LP gas.

[0079] Furthermore, in embodiments of the present invention, the fire alarm system may detect LP gas or fire based on logic including PID control that integrates proportional, differential, and integral components.

[0080] Furthermore, in embodiments of the present invention, the warning signal output unit 26 may output a warning signal indicating fire alert in response to both the determination by the column density change amount determination unit 23 that the acquired column density change amount exceeds the reference value, and the determination by the smoke concentration determination unit 25 regarding the fire alert level according to the smoke concentration.

[0081] For example, in step S106, the smoke concentration determination unit 25 determines whether the smoke concentration is greater than the standard value if the column density change is greater than the standard value. In subsequent steps, if both the column density change and the smoke concentration are greater than the standard value, the warning signal output unit 26 transmits a fire alarm signal. If the column density change is greater than the standard value but the smoke concentration is less than the standard value, the warning signal output unit 26 transmits a gas leak warning signal. If the column density change is less than the standard value but the smoke concentration is greater than the standard value, the warning signal output unit 26 transmits a fire warning signal. In this case, the fire warning signal may be a signal indicating a state between a fire alarm signal and a gas leak warning signal in terms of fire risk. For example, it may be a signal indicating a state in the pre-fire stage among the fire warning information output by the fire warning system 1, indicating that there is a risk of developing into a fire.

[0082] Thus, in the embodiments of the present invention, the fire warning system may be configured to further transmit fire warning information in response to the detection results of both smoke detection and LP gas detection. Since such a configuration can transmit warning information in the preliminary stages of a fire, it is expected to be more effective in preventing fires than conventional fire alarms.

[0083] 〔summary〕 A first aspect of the present invention is a fire alarm system (1) comprising a detection unit (11) integrally equipped with a fire detection unit (13) for detecting fire and an LP gas detection unit (14) for detecting LP gas, wherein the LP gas detection unit comprises a light source (141) that irradiates light into an LP gas detection area below the detection unit and a light receiving unit (142) that receives reflected light from the LP gas detection area, and detects LP gas in the LP gas detection area based on the column density of LP gas obtained from the information of the reflected light. According to the first aspect, in addition to detecting fire, it is possible to detect LP gas in addition to fire in a conventional fire alarm, and earlier warning of fires in LP gas facilities is possible compared to conventional fire alarms.

[0084] A second aspect of the present invention is that, in the first aspect, the light source is a light-emitting diode. The second aspect is even more effective in terms of making the light source of the LP gas detection unit cheaper and easier to configure compared to a laser.

[0085] A third aspect of the present invention is that, in the first or second aspect, the fire alarm system further comprises a reflector (50) positioned in the direction of illumination of the light source and reflecting the light from the light source toward a light receiving unit. The third aspect is even more effective in terms of improving the detection accuracy of LP gas.

[0086] The fire alarm system of the present invention, because its detection unit integrates an LP gas detection unit in addition to a conventional fire detection unit, can be installed in the same way as a conventional fire alarm and is capable of detecting LP gas. Therefore, it enables earlier fire warning compared to conventional fire alarms. The present invention, which has such effects, is expected to contribute to achieving, for example, Goal 9 of the United Nations Sustainable Development Goals (SDGs), "Build resilient infrastructure, promote inclusive and sustainable industrialization and foster innovation."

[0087] The present invention is not limited to the embodiments described above, and various modifications are possible within the scope of the claims. Embodiments obtained by appropriately combining the technical means disclosed in different embodiments are also included in the technical scope of the present invention. [Explanation of Symbols]

[0088] 1-3 Fire alarm system 11, 31 Detection Unit 12, 32 Main body 13 Fire detection unit 14 LP gas detection unit 20 Control Unit 21 Column density acquisition unit 22 Column density change acquisition unit 23 Column density change determination unit 24 Smoke concentration acquisition section 25 Smoke density determination section 26 Warning signal output unit 30 Alarm transmission unit 33 Rotating support section 50 Reflector 100 Kitchen 101 Gas stove 102 Ventilation fan 103 beds 104 Ceiling 105 smoke 106 LP gas 131 Top panel 132 Support part 133 Smoke detection unit 141, 441 light source 142, 442 Light receiving section 143 Focusing lens 4411 Light source section 4412 Power supply 4421 Photodetector 4422 Amplifier 4423 Bandpass Filter 4424 detectors

Claims

1. The detection unit includes a fire detection unit for detecting fire and an LP gas detection unit for detecting LP gas, all integrated into one unit. The LP gas detection unit comprises a light source that irradiates light into an LP gas detection region below the detection unit, and a light receiving unit that receives reflected light from the LP gas detection region. The LP gas in the LP gas detection region is detected based on the column density of the LP gas obtained from the information of the reflected light. Fire alarm system.

2. The fire alarm system according to claim 1, wherein the light source is a light-emitting diode.

3. The fire alarm system according to claim 1, further comprising a reflector plate positioned in the direction of irradiation of the light source and reflecting light from the light source toward the light receiving unit.

Images