JP2022165428A - photoelectric smoke detector - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve detection accuracy by securing simultaneity of measurement and also to improve reliability by reducing the number of components so as to simplify a structure, concerning a structure of a smoke detection section for receiving scattered light due to a difference between scattering characteristics of light of different wavelengths, so as to identify the kind of smoke.

SOLUTION: In a photoelectric smoke detector, a smoke detection section 18 includes: a light emitting element 20 using a white light-emitting diode so as to simultaneously emit light of a first wavelength and a second wavelength toward a smoke detection space; and a first light-receiving element 22 having sensitivity to light of the first wavelength and a second light-receiving element 24 having sensitivity to light of the second wavelength, that are arranged at positions of different intersection angles to prevent direct reception of light to be emitted from the light-emitting element. A light reception output of smoke scattered light by a smaller scattering angle by the light of the first wavelength received by the first light-receiving element is compared with a light reception output of smoke scattered light by a larger scattering angle received by the second light-receiving element 24. Then, the kind of smoke is identified so that a fire is determined based on determination reference corresponding to the kind of smoke.

SELECTED DRAWING: Figure 2

COPYRIGHT: (C)2023,JPO&INPIT

Description

The present invention relates to a photoelectric smoke sensor that emits light of two wavelengths with different scattering characteristics for a light receiving element to identify and detect the type of smoke caused by a fire.

A conventional photoelectric smoke sensor may emit a non-fire alarm not only for smoke from a fire, but also for smoke from cooking, steam from a bathroom, 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 types of wavelengths, and the light intensity ratio of different wavelengths of light scattered by smoke is obtained to determine the type of smoke. On the other hand, a photoelectric smoke sensor has been proposed that increases the accuracy of smoke discrimination and ensures the prevention of non-fire alarms (Patent Document 1).

In the photoelectric smoke sensor of Patent Document 1, two light-emitting elements emitting light of different wavelengths are made to have different scattering angles with respect to a light-receiving element to create a difference in scattering characteristics depending on the type of smoke, and emit two lights at the same time. By varying the wavelength of the light emitted from the element, a difference in the scattering characteristics due to the wavelength is created, and the synergistic effect of the difference in the scattering angle and the difference in the wavelength produces a remarkable difference in the light intensity of the scattered light depending on the type of smoke. By increasing the accuracy of smoke identification, it is possible to prevent non-fire alarms due to steam from cooking and cigarette smoke, and to reliably distinguish between black smoke fires and white smoke fires for smoke from fires. making it possible.

Japanese Patent Application Laid-Open No. 2004-325211 JP-A-6-109631 JP-A-7-12724 WO2005/048208

However, in such a conventional photoelectric smoke detector, since the two light emitting elements must alternately emit light, if there is fluctuation in the smoke flowing into the smoke detector, the Since the smoke density is measured, the simultaneity of measurement is lost, resulting in a decrease in detection accuracy.

In addition, since there are two light-emitting elements, which are parts that determine the life of the sensor, the probability of failure increases accordingly, and there is a concern that the life of the product will be shortened.

The present invention relates to the structure of a smoke detection unit that receives scattered light due to differences in the scattering characteristics of light of different wavelengths and identifies the type of smoke. It is an object of the present invention to provide a photoelectric smoke sensor that can be reduced in size, simplified in structure, and improved in reliability.

(Photoelectric smoke sensor 1)
The present invention is a photoelectric smoke sensor,
a light emitting element that simultaneously emits light of a first wavelength and light of a second wavelength different from the first wavelength toward the smoke detection space;
a first light receiving element provided at a position not directly receiving light emitted from the light emitting element and having sensitivity to light of a first wavelength;
a second light-receiving element provided at another position not directly receiving light emitted from the light-emitting element and having sensitivity to light of a second wavelength;
with
By comparing the ratio between 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 flowing into the smoke detection space or the smoke is generated. It is characterized in that the type of fire is identified and the threshold value is changed according to the magnitude of the first received light output or the second received light output.

(Photoelectric smoke sensor 2)
The present invention is a photoelectric smoke sensor,
a light emitting element that simultaneously emits light of a first wavelength and light of a second wavelength different from the first wavelength toward the 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;
with
By comparing the ratio between 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 flowing into the smoke detection space or the smoke is generated. The type of fire is identified, and the threshold value is increased as the first received light output or the second received light output increases.

(Photoelectric smoke sensor 3)
The present invention is a photoelectric smoke sensor,
a light emitting element that simultaneously emits light of a first wavelength and light of a second wavelength different from the first wavelength toward the 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;
with
By comparing the ratio between 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 flowed into the smoke detection space or the smoke was generated. By identifying the type of fire and comparing the ratio between the first received light output and the second received light output with a second threshold value, it is possible to identify whether what has flowed into the smoke detection space is smoke or steam. Characterized by

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

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

(basic effect)
In a photoelectric smoke sensor, the present invention provides 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, and light emitted from the light emitting element. A first light-receiving element provided at a position not directly receiving light and having sensitivity to light of the first wavelength, and a second light-receiving element provided at another position not directly receiving light emitted from the light-emitting element and having sensitivity to light having a second wavelength. Since the smoke detection space is irradiated with the light of the first wavelength and the second wavelength from the light emitting element, the first light receiving element and the second light receiving element can receive the scattered light at the same time. There is no deviation in measurement timing due to light of the second wavelength, and even if the concentration of smoke flowing into the smoke detection space fluctuates for a short period of time, it is not affected, and the accuracy of identifying the type of smoke can be improved.

(Effect of changing the threshold)
By comparing the ratio between 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 flowing into the smoke detection space or the smoke is generated. Since the type of fire is identified and the threshold is changed according to the magnitude of the first received light output or the second received light output, if the smoke density becomes extremely high, the threshold may be deviated due to the influence of secondary scattering. Therefore, the threshold value can be changed to compensate for this, and the type of smoke can be determined with high accuracy.

(effect of increasing threshold)
By comparing the ratio between 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 flowing into the smoke detection space or the smoke is generated. Since the type of fire is identified and the threshold is increased as the first received light output or the second received light output increases, it is possible that the threshold will be deviated due to the influence of secondary scattering when the smoke density becomes extremely high. , the threshold can be changed to complement it, and the type of smoke can be determined with high accuracy.

(Effect of distinguishing between smoke and steam)
By comparing the ratio between 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 flowed into the smoke detection space or the smoke was generated. By identifying the type of fire and comparing the ratio of the first received light output and the second received light output with the second threshold value, to identify whether what has flowed into the smoke detection space is smoke or steam, When a non-fire factor such as steam is determined, by transmitting a status signal including non-fire information indicating steam to the receiver, it is possible to cause the receiver to output a caution alarm instead of a fire alarm.

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

1 is a block diagram showing the circuit configuration of a photoelectric smoke sensor according to the present invention; Explanatory drawing showing an embodiment of the smoke detector structure Explanatory diagram showing light receiving outputs of the first light receiving element and the second light receiving element detected by the structure of the smoke detector shown in FIG. Explanatory drawing showing a setting table for changing the ratio threshold for identifying the type of smoke according to the light receiving outputs of the first light receiving element and the second light receiving element. Explanatory drawing showing a setting table of ratio thresholds for identifying types of smoke and non-fire factors according to light receiving outputs of the first light receiving element and the second light receiving element. Flowchart showing an embodiment of fire detection control by the circuit block of FIG. 1 using the smoke detector structure of FIG.

[Circuit Configuration of Photoelectric Smoke Detector]
FIG. 1 is a block diagram showing the circuit configuration of a photoelectric smoke sensor according to the present invention. As shown in FIG. 1, a photoelectric smoke sensor 10 of this embodiment is connected to a control unit 12, which is composed of a computer circuit having a CPU, a memory, and various input/output ports, 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 amplifier circuit sections 26 and 28.

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

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 emits white light by passing the light of the blue LED through the phosphor. The light of λ2=450 nm is included, and the light of the first wavelength λ1 and the light of the second wavelength λ2 can be irradiated into the smoke detector 18 at the same time.

A two-color LED (two-color light emitting diode) can also be used as the light emitting element 20 of the present embodiment. The two-color LED has 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 light of the second wavelength λ2 can be simultaneously irradiated into the smoke detector 18 .

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

Further, as the first light receiving element 22 and the second light receiving element 24, filter layers for receiving only the wavelength bands of the first wavelength λ1 and the second wavelength λ2 are added to the broadband photodiodes having sensitivity in the visible light wavelength band. It may be provided on the PD molding (transparent cover member), or filters transmitting the respective wavelength bands of the first wavelength λ1 and the second wavelength λ2 may be arranged 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 light reception output A1 to the control section 12 . Further, the amplifying circuit section 28 amplifies the received light signal of the smoke scattered light received by the second light receiving element 24 and provides the control section 12 with the received light output A2.

[Embodiment of smoke detector]
FIG. 2 is an explanatory diagram showing an embodiment of the structure of the smoke detector in FIG. 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 in the smoke detector 18 into which smoke from the outside flows.

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

A 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 The optical axes 22a of the elements 22 are arranged to 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°, and the light emitting element 20 and the second light receiving element 24 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. Further, 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 60°, for example. be.

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 the light of the first wavelength λ1, smoke flowing into the smoke detector 18 causes Scattered light with a scattering angle θ1=30° is received by the first light receiving element 22, and a received light output A1 is obtained. Here, the received light output A1 can be said to be the smoke density detection output detected by the first wavelength λ1 and the first scattering angle θ1.

Further, 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 simultaneously emits the light of the first wavelength λ1 and the light of the second wavelength λ2, , scattered light at the second scattering angle θ2=120° due to the smoke that has flowed into the smoke detector 18 is received by the second light receiving element 24, and a light receiving output A2 is obtained at the same time. Here, the received light output A2 can be said to be the smoke density detection output detected by 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 cycle, thereby emitting white light including the first wavelength λ1 and the second wavelength λ2. Backscattered light with a first scattering angle θ1=30° due to λ1 is received by the first light receiving element 22, and the received light output A1 output from the amplifier circuit section 28 corresponding to this is detected and stored in the memory.

At the same time, the second light receiving element 24 receives the backscattered light of the second wavelength λ2 at the second scattering angle θ2=120°. The received light output A2 output from the unit 26 is detected and stored in the memory.

Subsequently, the control unit 12 compares 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 to identify the type of smoke, and determines the type of smoke. Fire judgment is made based on the judgment criteria.

[Judgment of smoke type by ratio of received light output]
FIG. 3 is an explanatory diagram showing the light receiving output detected by the structure of the smoke detector shown in FIG.

As shown in FIG. 3, the received light output A1 is the scattered light output of the first wavelength λ1=700 nm and the first scattering angle θ1=30°, and the received light output A2 is the second wavelength λ2=450 nm and the first 2 Scattered light with a scattering angle θ2=120° is output.

Taking the ratio R=A1/A2 of the light receiving outputs A1 and A2 measured by burning the cotton lamp wick and kerosene, R=8.0 for the cotton lamp wick and R=2.3 for the kerosene. Therefore, there is a remarkable difference in the ratio R between the cotton lamp wick 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, for example, Rth1=5 as the ratio threshold value Rth1, and determines that white smoke due to smoldering is generated when R>5, and black smoke due to combustion when R<5. is generated, a fire signal including information indicating the type of smoke determined is transmitted to the receiver, and control is performed to output a fire alarm.

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

Also, in FIG. 3, the ratio threshold value Rth is constant, but the level of smoke identification may be changed according to 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 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 setting table of the ratio threshold is based on the received light 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, It 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°. to determine the type of smoke.

When the smoke density becomes extremely high, it is possible that the ratio threshold value Rth1=5 set in FIG. 3 is deviated due to the influence of secondary scattering. To determine 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 factors 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 Rth1=5 to 5.5 for identifying , a ratio threshold Rth2=12 for identifying steam that is a non-fire factor is set.

For example, when steam from a bathroom or the like flows into the photoelectric smoke sensor 10, the conventional smoke sensor misdiagnoses it as smoke from a fire and issues a fire alarm. A ratio threshold value Rth2=12 is selected according to the output A1. If R<12, fire smoke is identified, and if R>12, non-fire factors such as steam are identified. When a non-fire factor such as steam is determined by this, by transmitting a status signal including non-fire information indicating steam to the receiver, it is possible to cause the receiver to output a caution alarm instead of a fire alarm. .

[Embodiment of sensor control]
FIG. 6 is a flow chart showing an embodiment of fire detection control by the circuit block of FIG. 1 using the smoke detector structure of FIG.

As shown in FIG. 6, in step S1, the control unit 12 instructs the light emission driving unit 16 to intermittently drive the light emitting element 20 using a white LED to emit light at a predetermined cycle to obtain a first wavelength λ1 and a second wavelength λ1. A white light containing λ2 is irradiated into the smoke detector 18, and a received light output A1 corresponding to the scattered light of the first wavelength λ1 received by the first light receiving element 22 is detected in step S2 and stored in the memory in step S3. Subsequently, in step S4, the received light 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 receiving outputs A1 and A2 in step S6, compares the ratio R with, for example, the 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, in step S8, it is compared with the threshold value Rth2=12 for identifying non-fire factors, 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 equal to or greater than the threshold value Ath1 corresponding to the smoke density requiring a caution alarm, the process proceeds to step S11, a fire signal including white smoke identification information is transmitted to the receiver, and a smoldering fire caused by white smoke is detected. to output 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 to determine that the combustion fire is caused by black smoke. If it is determined that the concentration is equal to or greater than the threshold value Ath2 corresponding to the concentration, the process proceeds to step S14, in which a fire signal including black smoke identification information is transmitted to the receiver to output a fire alarm indicating combustion due to black smoke.

Further, when the ratio R is determined to be the threshold value Rth1=5 or more in step S7 and the threshold value Rth2=12 or more in step S8, the control unit 12 proceeds to step S15 to determine that the non-fire factor is due to steam or the like. When it is determined in step S16 that the received light output A1 is equal to or greater than the threshold value Ath1 corresponding to the smoke density requiring a caution alarm, the process proceeds to step S17, in which a fire signal including identification information of non-fire factors is transmitted to the receiver, and steam is generated. A caution alarm or the like indicating that the non-fire alarm is triggered by a non-fire factor such as is output.

In the control of FIG. 6, each time the white LED is driven to emit light, the ratio of the light receiving outputs A1 and A2 is calculated to determine whether white smoke or black smoke. Smoke identification may be performed by calculating the ratio R when the threshold value Ath1 corresponding to the smoke density requiring . As a result, the processing load of the control unit 12 can be reduced and the current consumption of the photoelectric smoke sensor 10 can be reduced by not performing the ratio calculation by detecting and storing the received light outputs A1 and A2 in the normal monitoring state. can.

[Modification of the present invention]
In the above embodiment, white LEDs or two-color LEDs are provided as light emitting elements, but an LED emitting the first wavelength λ1 and an LED emitting the second wavelength λ2 may be arranged side by side and simultaneously driven to emit light. good.

Moreover, the present invention includes appropriate modifications that do not impair its purpose and advantages, and is not limited by the numerical values shown in the above embodiments.

10: Photoelectric smoke detectors 11a, 11b: Transmission line 12: Control unit 14: Transmission unit 15: Power supply unit 16: Light emission drive unit 18: Smoke detection unit 20: Light emitting elements 20a, 22a, 24a: Optical axis 22: Third 1 light receiving element 24: second light receiving elements 26, 28: amplifier circuit section

Claims (5)

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 that receives the 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;
with
By comparing the ratio between 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 flowing into the smoke detection space or the smoke concerned is determined. A photoelectric smoke sensor, wherein the type of fire that has occurred is identified, and the threshold value is changed according to the magnitude of the first light receiving output or the second light receiving output.
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 that receives the 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;
with
By comparing the ratio between 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 flowing into the smoke detection space or the smoke concerned is determined. A photoelectric smoke sensor, wherein the type of fire that has occurred is identified, and the threshold value is increased as the first received light output or the second received light output increases.
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 that receives the 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;
with
By comparing the ratio between 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 first threshold value, the type of smoke flowing into the smoke detection space or the smoke concerned is determined. By identifying the type of fire that has occurred and comparing the ratio between the first received light output and the second received light output with a second threshold value, it is determined whether what has flowed into the smoke detection space is smoke or steam. A photoelectric smoke detector characterized by identifying whether
The photoelectric smoke sensor according to any one of claims 1 to 3,
A photoelectric smoke sensor characterized in that, when the type of smoke is identified, information indicating the type of smoke as a result of identification is transmitted to a fire receiver.
The photoelectric smoke sensor according to claim 3,
A photoelectric smoke detector characterized in that, when steam is identified, information indicating that the result of identification is steam is transmitted to a fire receiver.

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