JP7397934B2 - photoelectric smoke detector - Google Patents

Description

The present invention relates to a photoelectric smoke sensor that identifies and detects the type of smoke caused by a fire by emitting light of two wavelengths so that the light receiving element has different scattering characteristics.

Conventional photoelectric smoke detectors may issue non-fire alarms not only due to smoke from a fire, but also due to cooking smoke, bathroom steam, and the like.

In order to prevent such non-fire alarms due to causes other than fire, the smoke detection space is irradiated with light of two different wavelengths, and the type of smoke is determined by determining the ratio of the light intensity of the different wavelengths of light scattered by the smoke. However, a photoelectric smoke detector has been proposed that increases the accuracy of smoke identification and ensures the prevention of non-fire alarms (Patent Document 1).

In the photoelectric smoke detector of Patent Document 1, two light emitting elements that emit light of different wavelengths have different scattering angles with respect to the light receiving element, thereby creating differences in scattering characteristics depending on the type of smoke. By changing the wavelength of the light emitted from the element, differences in scattering characteristics due to the wavelength are created, and the synergistic effect of the difference in scattering angle and the difference in wavelength produces a remarkable difference in the light intensity of the scattered light depending on the type of smoke. This increases the accuracy of smoke identification, prevents non-fire alarms caused by cooking steam and cigarette smoke, and also enables reliable identification of the types of combustible materials, such as black smoke fires and white smoke fires, for smoke caused by fires. making it possible.

Japanese Patent Application Publication No. 2004-325211 Japanese Unexamined Patent Publication No. 6-109631 Japanese Patent Application Publication No. 7-12724 International Publication No. 2005/048208

However, in such conventional photoelectric smoke detectors, the two light-emitting elements must be made to emit light alternately, so if there is fluctuation in the smoke flowing into the smoke detector, temporal differences may occur. This method involves measuring smoke concentration, and there is a problem in that the simultaneity of measurement is impaired, leading to a decrease in detection accuracy.

Furthermore, since there are two light-emitting elements, which are the components that determine the lifespan of the sensor, the probability of failure increases accordingly, and there is a concern that the product lifespan may be shortened.

The present invention has a structure for detecting smoke that detects the type of smoke by receiving scattered light due to the difference in the scattering characteristics of light of different wavelengths.The present invention improves detection accuracy by ensuring simultaneous measurement and reduces the number of parts. It is an object of the present invention to provide a photoelectric smoke detector that can simplify the structure and improve the reliability.

(Photoelectric smoke detector 1)
The present invention is a photoelectric smoke detector, comprising:
a light emitting element that simultaneously emits light at a first wavelength and light at a second wavelength different from the first wavelength toward a smoke detection space;
a first light-receiving element that is provided at a position that does not directly receive the light emitted from the light-emitting element and is sensitive to light of a first wavelength;
a second light-receiving element that is provided at another position that does not directly receive the light emitted from the light-emitting element and is sensitive to light of a second wavelength;
Equipped with
By comparing the ratio of the first light receiving output from the first light receiving element and the second light receiving output from the second light receiving element with a predetermined threshold value, the type of smoke that has flowed into the smoke detection space or the generation of the smoke is determined. It is characterized in that the type of fire is identified and the threshold value is changed depending on the magnitude of the first light reception output or the second light reception output.

(Photoelectric smoke detector 2)
The present invention is a photoelectric smoke detector, comprising:
a light-emitting element that simultaneously emits light at a first wavelength and light at a second wavelength different from the first wavelength toward a smoke detection space;
a first light receiving element that receives light of a first wavelength emitted from the light emitting element;
a second light receiving element that receives light of a second wavelength emitted from the light emitting element;
Equipped with
By comparing the ratio of the first light receiving output from the first light receiving element and the second light receiving output from the second light receiving element with a predetermined threshold value, the type of smoke that has flowed into the smoke detection space or the generation of the smoke is determined. It is characterized in that the type of fire is identified and the threshold value is increased as the first light reception output or the second light reception output becomes larger.

(Photoelectric smoke detector 3)
The present invention provides a photoelectric smoke detector that includes:
a light-emitting element that simultaneously emits light at a first wavelength and light at a second wavelength different from the first wavelength toward a smoke detection space;
a first light receiving element that receives light of a first wavelength emitted from the light emitting element;
a second light receiving element that receives light of a second wavelength emitted from the light emitting element;
Equipped with
By comparing the ratio of the first light receiving output from the first light receiving element and the second light receiving output from the second light receiving element with the first threshold value, the type of smoke that has flowed into the smoke detection space or the generation of the smoke is determined. By identifying the type of fire and comparing the ratio of the first light receiving output and the second light receiving output with a second threshold value, it is possible to identify whether what has flowed into the smoke detection space is smoke or steam. Features.

When the type of smoke is identified, information indicating the type of smoke, which is the identification result, is transmitted to the fire receiver.

If steam is identified, information indicating that the identification result is steam is transmitted to the fire receiver.

(basic effect)
The present invention provides a photoelectric smoke detector that includes a light emitting element that simultaneously emits light of a first wavelength and light of a second wavelength different from the first wavelength toward a smoke detection space; A first light-receiving element is provided in a position that does not directly receive light and is sensitive to light of a first wavelength, and a second light-receiving element is provided in another position that does not directly receive light emitted from the light-emitting element and is sensitive to light of a second wavelength. Since it is equipped with two light-receiving elements, the light-emitting element illuminates the smoke detection space with light of the first wavelength and the second wavelength, and the first and second light-receiving elements can simultaneously receive the scattered light. There is no deviation in the measurement timing due to the light of the second wavelength, and even if the concentration of smoke flowing into the smoke detection space fluctuates in a short time, it is not affected, and the accuracy of identifying the type of smoke can be improved.

(Effect of changing threshold)
By comparing the ratio of the first light receiving output from the first light receiving element and the second light receiving output from the second light receiving element with a predetermined threshold value, the type of smoke that has flowed into the smoke detection space or the generation of the smoke is determined. Since the type of fire is identified and the threshold value is changed according to the magnitude of the first light reception output or the second light reception output, if the smoke density becomes extremely high, it is possible that the fire will deviate from the threshold value due to the influence of secondary scattering. Therefore, by changing the threshold value to compensate for this, it is possible to judge the type of smoke with high accuracy.

(Effect of increasing threshold)
By comparing the ratio of the first light receiving output from the first light receiving element and the second light receiving output from the second light receiving element with a predetermined threshold value, the type of smoke that has flowed into the smoke detection space or the generation of the smoke is determined. The type of fire is identified and the threshold value is increased as the first light reception output or the second light reception output increases, so if the smoke density becomes extremely high, it may deviate from the threshold value due to the influence of secondary scattering. , by changing the threshold value to complement it, it is possible to judge the type of smoke with high accuracy.

(Effect of distinguishing between smoke and steam)
By comparing the ratio of the first light receiving output from the first light receiving element and the second light receiving output from the second light receiving element with the first threshold value, the type of smoke that has flowed into the smoke detection space or the generation of the smoke is determined. In order to identify whether what has flowed into the smoke detection space is smoke or steam by identifying the type of fire and comparing the ratio of the first light reception output and the second light reception output with a second threshold value, If a non-fire cause such as steam is determined, a status signal including non-fire information indicating steam is sent to the receiver, thereby allowing the receiver to output a caution warning instead of a fire alarm.

(Effect of transmitting identification results to fire receiver)
If the type of smoke is identified, information indicating the type of smoke is sent to the fire receiver, and if steam is identified, information indicating that the identification result is steam is sent to the fire receiver. It is possible to output an alarm according to the information.

A block diagram showing the circuit configuration of a photoelectric smoke detector according to the present invention Explanatory diagram showing an embodiment of the structure of the smoke detection part Explanatory diagram showing the light reception output of the first light receiving element and the second light receiving element and the ratio thereof detected by the smoke detection section structure of Fig. 2 for smoke when cotton wick and kerosene are burned. An explanatory diagram showing a setting table for changing the ratio threshold for identifying the type of smoke according to the light receiving output of the first light receiving element and the second light receiving element. An explanatory diagram showing a setting table of ratio threshold values for identifying types of smoke and non-fire causes according to the light receiving outputs of the first light receiving element and the second light receiving element. A flowchart showing an embodiment of fire detection control using the circuit block of FIG. 1 using the smoke detector structure of FIG. 2.

[Circuit configuration of photoelectric smoke detector]
FIG. 1 is a block diagram showing the circuit configuration of a photoelectric smoke detector according to the present invention. As shown in FIG. 1, the photoelectric smoke detector 10 of this embodiment includes a control unit 12, which is composed of a computer circuit equipped with a CPU, memory, and various input/output ports, and is connected to an S terminal and an SC terminal. A transmission unit 14 that transmits and receives signals to and from the fire receiver via the transmission lines 11a and 11b, and a power supply unit that converts the power supply voltage supplied via the transmission lines 11a and 11b into a predetermined stabilized voltage and outputs it. 15, a light emission drive section 16, a smoke detection section 18, and an amplification circuit section 26, 28.

The smoke detection section 18 is provided with a light emitting element 20 that simultaneously emits light including a first wavelength λ1 and a second wavelength λ2. The center wavelength of the light with the first wavelength λ1 emitted from the light emitting element 20 is determined to be 600 nm or more, and the center wavelength of the light with the second wavelength λ2 is determined to be 500 nm or less. The wavelength λ1 is set to, for example, 700 nm, and the second wavelength λ2 is set to, for example, 450 nm.

In this embodiment, a white LED (white light emitting diode) is used as the light emitting element 20. A white LED, for example, is a combination of a blue LED and a phosphor, and the light of the blue LED is passed through the phosphor to emit white light. Light of λ2=450 nm is included, and the smoke detection section 18 can be irradiated with light of the first wavelength λ1 and the light of the second wavelength λ2 at the same time.

Moreover, as the light emitting element 20 of this embodiment, a two-color LED (two-color light emitting diode) can also be used. The two-color LED includes a first light emitting chip that emits light with a first wavelength λ1 = 700 nm and a second light emitting chip that emits light with a second wavelength λ2 = 450 nm, and by driving both simultaneously, the first wavelength λ1 is emitted. and the second wavelength λ2 can be irradiated into the smoke detection section 18 at the same time.

A photodiode (PD) sensitive to a first wavelength λ1 is used as the first light receiving element 22, and a photodiode (PD) sensitive to a second wavelength λ2 is used as the second light receiving element 24.

The first light receiving element 22 and the second light receiving element 24 are broadband photodiodes sensitive to the visible wavelength band, and filter layers that receive only the first wavelength λ1 and the second wavelength λ2, respectively. It may be provided in the PD molding (transparent cover member), or a filter that transmits the respective wavelength bands of the first wavelength λ1 and the second wavelength λ2 may be placed in front of the broadband photodiode.

The amplifier circuit section 26 amplifies the light reception signal of the smoke scattered light of the first wavelength λ1 received by the first light receiving element 22, and provides the control section 12 with a light reception output A1. Further, the amplifying circuit section 28 amplifies the light reception signal of the smoke scattered light received by the second light receiving element 24, and provides the control section 12 with a light reception output A2.

[Embodiment of smoke detection section]
FIG. 2 is an explanatory diagram showing an embodiment of the structure of the smoke detection section in FIG. 1. As shown in FIG. 2, a light emitting element 20, a first light receiving element 22, and a second light receiving element 24 are arranged within the smoke detection section 18 into which smoke from the outside flows.

For example, the light emitting element 20 using a white LED emits light including a first wavelength λ1 and a second wavelength λ2 in the direction of the optical axis 20a, and as described above, the light with the first wavelength λ1 is set to 700 nm, Further, the light having the second wavelength λ2 is set to 450 nm.

The first scattering angle θ1 formed by the intersection of the optical axis 20a of the light emitting element 20 and the optical axis 22a of the first light receiving element 22 is set in the range of 20° to 70°, and the optical axis 20a of the light emitting element 20 and the first light receiving element 22 are intersected. The elements 22 are arranged so that their optical axes 22a intersect at a predetermined angle in the range of 110° to 160°.

Further, the second scattering angle θ2 formed by the intersection of the optical axis 20a of the light emitting element 20 and the optical axis 24a of the second light receiving element 24 is set in the range of 110° to 150°. are arranged so that their optical axes 24a intersect at a predetermined angle in the range of 30° to 70°.

In this embodiment, since the first scattering angle θ1 is set to 30°, the optical axis 20a of the light emitting element 20 and the optical axis 22a of the first light receiving element 22 are arranged to intersect at an intersection angle of 150°, for example. Furthermore, since the second scattering angle θ2 is set to 120°, the optical axis 20a of the light emitting element 20 and the optical axis 24a of the second light receiving element 24 are arranged to intersect at an intersection angle of, for example, 60°. Ru.

Since the first light receiving element 22 is sensitive to the light of the first wavelength λ1 = 700 nm emitted from the light emitting element 20, when the light emitting element 20 emits light of the first wavelength λ1, the smoke that has entered the smoke detection section 18 Scattered light with a scattering angle θ1=30° is received by the first light receiving element 22, and a light receiving output A1 is obtained. Here, the light reception output A1 can be said to be a smoke density detection output detected using the first wavelength λ1 and the first scattering angle θ1.

Furthermore, since the second light receiving element 24 is sensitive to the light of the second wavelength λ2=450 nm emitted from the light emitting element 20, if the light emitting element 20 emits the light of the second wavelength λ2 at the same time as the light of the first wavelength λ1, , the scattered light at the second scattering angle θ2=120° due to the smoke flowing into the smoke detection section 18 is received by the second light receiving element 24, and the light receiving output A2 is obtained at the same time. Here, the light reception output A2 can be said to be a smoke concentration detection output detected using the second wavelength λ2 and the second scattering angle θ2.

[Smoke identification by control unit]
The control unit 12 shown in FIG. 1 instructs the light emission driving unit 16 to intermittently drive the light emitting element 20 at a predetermined period, thereby emitting white light including a first wavelength λ1 and a second wavelength λ2, and emitting white light having a first wavelength λ1 and a second wavelength λ2. The backscattered light at the first scattering angle θ1=30° due to λ1 is received by the first light receiving element 22, and correspondingly, the light receiving output A1 output from the amplifier circuit section 28 is detected and stored in the memory.

At the same time, the second light receiving element 24 receives the backscattered light with the second scattering angle θ2 = 120° due to the second wavelength λ2. The light reception output A2 outputted from the section 26 is detected and stored in the memory.

Next, the control unit 12 identifies the type of smoke by comparing the light receiving output A1 corresponding to the first light receiving element 22 and the light receiving output A2 corresponding to the second light receiving element 24, and determines the type of smoke according to the type of smoke. A fire judgment will be made based on the criteria.

[Judgment of smoke type based on the ratio of received light output]
FIG. 3 is an explanatory diagram showing the light reception output detected by the smoke detector structure of FIG. 2 and its ratio with respect to smoke when cotton wick and kerosene are burned.

As shown in FIG. 3, the light receiving output A1 is the light receiving output of the scattered light with the first wavelength λ1 = 700 nm and the first scattering angle θ1 = 30°, and the light receiving output A2 is the light receiving output of the scattered light with the first wavelength λ1 = 700 nm and the first scattering angle θ1 = 30°. 2 This is the light reception output of scattered light with a scattering angle θ2=120°.

Taking the ratio R=A1/A2 of the received light outputs A1 and A2 measured in the combustion of such a cotton wick and kerosene, in the case of cotton wick, R=8.0, and in the case of kerosene, R=2.3. Therefore, there is a noticeable difference in the ratio R between cotton wicks and kerosene, and it is possible to identify the type of smoke based on the ratio R.

For this reason, the control unit 12 sets Rth1=5 as the ratio threshold value Rth1, for example, and determines that white smoke is generated due to smoldering when R>5, and black smoke due to combustion when R<5. It determines that smoke is occurring, and controls the receiver to output a fire alarm by transmitting a fire signal containing information indicating the determined type of smoke.

[Change ratio threshold]
The ratio threshold value Rth1 for identifying the type of smoke shown in FIG. The first wavelength λ1 and the second wavelength λ2 emitted from the wavelength can be changed as appropriate.

Further, in FIG. 3, the ratio threshold value Rth is set constant, but the level of smoke discrimination may be changed depending on the magnitude of the received light outputs A1 and A2.

FIG. 4 is an explanatory diagram showing a setting table for changing the ratio threshold value for identifying the type of smoke according to the light receiving outputs of the first light receiving element and the second light receiving element. As shown in FIG. 4, the ratio threshold setting table includes the light receiving output A1 corresponding to the first light receiving element 22 with the first wavelength λ1 = 700 nm and the first scattering angle θ1 = 30°, the second wavelength λ2 = 450 nm, This is a two-dimensional table of the light receiving output A2 corresponding to the second light receiving element 24 with the second scattering angle θ2 = 120°. For example, as the light receiving output A1 increases, the ratio threshold Rth1 is changed from 5.0 to 5.2 to 5.5. to determine the type of smoke.

This is because when the smoke density becomes extremely large, it is possible that the ratio threshold value Rth1 = 5 set in Fig. 3 may deviate from the influence of secondary scattering, so in order to compensate for this, the ratio threshold value Rth1 is changed. To make it possible to judge the type of smoke with high accuracy.

[Identification of non-fire factors]
FIG. 5 is an explanatory diagram showing a setting table of ratio threshold values for identifying types of smoke and non-fire causes according to the light receiving outputs of the first light receiving element and the second light receiving element.

As shown in FIG. 5, the ratio threshold setting table is a two-dimensional table of the light receiving output A1 corresponding to the first light receiving element 22 and the light receiving output A2 corresponding to the second light receiving element 24. In addition to the ratio threshold value Rth1=5 to 5.5 for identifying non-fire causes, a ratio threshold value Rth2=12 is set for identifying steam that is a non-fire cause.

For example, when steam from a bathroom or the like flows into the photoelectric smoke detector 10, conventional smoke detectors misdiagnose this as smoke from a fire and issue a fire alarm. A ratio threshold value Rth2=12 is selected according to the output A1, and if R<12, it is identified as fire smoke, and if R>12, it is identified as a non-fire cause such as steam. If a non-fire cause such as steam is determined, a status signal containing non-fire information indicating steam is sent to the receiver, allowing the receiver to output a caution warning instead of a fire alarm. .

[Embodiment of sensor control]
FIG. 6 is a flowchart showing an embodiment of fire detection control by the circuit block of FIG. 1 using the structure of the smoke detection section of FIG. 2, and is a control operation by the control section 12.

As shown in FIG. 6, in step S1, the control unit 12 instructs the light emission driving unit 16 to drive the light emitting element 20 using a white LED to emit light intermittently at a predetermined period to emit light at a first wavelength λ1 and a second wavelength. λ2 is irradiated into the smoke detection section 18, and in step S2, the light receiving output A1 corresponding to the scattered light of the first wavelength λ1 received by the first light receiving element 22 is detected and stored in the memory in step S3. Then, in step S4, the light receiving output A2 corresponding to the scattered light of the second wavelength λ2 received by the second light receiving element 24 is detected and stored in the memory in step S5.

Subsequently, the control unit 12 calculates the ratio R=A1/A2 of the light reception outputs A1 and A2 in step S6, and compares the ratio R with, for example, a threshold value Rth1=5 in step S7, and determines that the ratio R is equal to or greater than the threshold value Rth1=5. If so, it is compared with the threshold value Rth2=12 for identifying non-fire causes in step S8, but since it is less than the threshold value Rth2, the process proceeds to step S9, where it is determined that the fire is smoldering due to white smoke, and in step S10, the received light output A1 is When it is determined that the fire is equal to or higher than the threshold value Ath1 corresponding to the smoke concentration that requires a caution alarm, the process proceeds to step S11, where a fire signal including white smoke identification information is transmitted to the receiver, and it is determined that the fire is a smoldering fire due to white smoke. Outputs a fire alarm indicating.

On the other hand, if the ratio R is less than the threshold value Rth1=5 in step S9, the control unit 12 proceeds to step S12 and determines that the fire is a combustion fire caused by black smoke, and in step S13, the control unit 12 determines that the received light output A2 indicates smoke that requires a warning. If it is determined that the concentration is equal to or higher than the threshold value Ath2, the process proceeds to step S14, where a fire signal including black smoke identification information is transmitted to the receiver, and a fire alarm indicating that it is a combustion fire due to black smoke is output.

Further, if the ratio R is determined to be equal to or higher than the threshold value Rth1=5 in step S7 and equal to or higher than the threshold value Rth2=12 in step S8, the control unit 12 proceeds to step S15 and determines that the non-fire cause is due to steam etc. If it is determined in step S16 that the received light output A1 is equal to or higher than the threshold value Ath1 corresponding to the smoke concentration that requires a caution alarm, the process proceeds to step S17, where a fire signal including identification information of non-fire causes is transmitted to the receiver, and the steam A cautionary warning, etc. is output to indicate that a non-fire alarm has been issued due to a non-fire cause such as.

In addition, in the control shown in FIG. 6, each time the white LED is driven to emit light, the ratio of the light reception outputs A1 and A2 is calculated to determine whether it is white smoke or black smoke. Smoke may be identified by calculating the ratio R when it is equal to or higher than the threshold value Ath1 corresponding to the smoke density that requires . As a result, the processing load on the control unit 12 can be reduced and the current consumption of the photoelectric smoke detector 10 can be reduced by not calculating the ratio based on the detection memory of the light reception outputs A1 and A2 in the normal monitoring state. can.

[Modification of the present invention]
In the above embodiment, a white LED or a two-color LED is provided as a light emitting element, but an LED that emits the first wavelength λ1 and an LED that emits the second wavelength λ2 may be arranged side by side and driven to emit light at the same time. good.

Furthermore, the present invention includes appropriate modifications without impairing its objects and advantages, and is not limited by the numerical values shown in the above embodiments.

10: Photoelectric smoke detector 11a, 11b: Transmission line 12: Control section 14: Transmission section 15: Power supply section 16: Light emitting drive section 18: Smoke detection section 20: Light emitting elements 20a, 22a, 24a: Optical axis 22: No. 1 light receiving element 24: 2nd light receiving element 26, 28: amplifier circuit section

Claims (3)

a light emitting element that simultaneously emits light at a first wavelength and light at a second wavelength different from the first wavelength toward a smoke detection space;
a first light receiving element that receives light of the first wavelength emitted from the light emitting element;
a second light receiving element that receives light of the second wavelength emitted from the light emitting element;
Equipped with
By comparing the ratio of the first light receiving output from the first light receiving element and the second light receiving output from the second light receiving element with a predetermined threshold value, the type of smoke that has flowed into the smoke detection space or the smoke concerned can be determined. A photoelectric smoke detector characterized in that the type of fire that has occurred is identified, and the threshold value is changed according to the magnitude of the first light reception output or the second light reception output.
a light emitting element that simultaneously emits light at a first wavelength and light at a second wavelength different from the first wavelength toward a smoke detection space;
a first light receiving element that receives light of the first wavelength emitted from the light emitting element;
a second light receiving element that receives light of the second wavelength emitted from the light emitting element;
Equipped with
By comparing the ratio of the first light receiving output from the first light receiving element and the second light receiving output from the second light receiving element with a predetermined threshold value, the type of smoke that has flowed into the smoke detection space or the smoke concerned can be determined. A photoelectric smoke detector characterized in that the type of fire that has occurred is identified, and the threshold value is increased as the first light reception output or the second light reception output increases.
The photoelectric smoke detector according to claim 1 or 2 ,
A photoelectric smoke detector characterized in that, when the type of smoke is identified, information indicating the type of smoke, which is the identification result, is transmitted to a fire receiver.

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