JP7150497B2 - photoelectric smoke detector - Google Patents

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

However, in such a conventional photoelectric smoke sensor, the two light-emitting elements have two optical axes, which widens the range of light irradiation, and increases the amount of internally reflected light due to dust and condensation. Since a non-fire alarm is output as a result, there is a problem that the processing and structure for suppressing the internally reflected light become complicated.

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 reduces the number of parts, simplifies the structure, and improves the reliability of the structure of the smoke detector 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 detector.

(Photoelectric smoke detector)
The present invention is a photoelectric smoke sensor,
a light emitting element that separately emits light of a first wavelength and light of a second wavelength different from the first wavelength toward the smoke detection space;
It is provided at a position that does not directly receive the light of the first wavelength and the second wavelength emitted from the light emitting element, has sensitivity to both the first wavelength and the second wavelength, and is sensitive to the first wavelength and the second wavelength due to particles present in the smoke detection space. a light receiving element that receives the scattered light of the second wavelength ;
It is arranged at a position facing the light emitting element across the smoke detection space, and reflects light of either one of the light of the first wavelength and the light of the second wavelength toward the smoke detection space, and detects the light of the other wavelength. a reflector that does not reflect toward the smoke space ;
characterized by comprising

(Smoke detector structure 1)
The intersection of the optical axes of the light of the first and second wavelengths emitted from the light-emitting element and the optical axis of the scattered light received by the light-receiving element, and the intersection formed by the three points of the light-emitting element and the light-receiving element have an angle of 30° to 30°. The light- emitting element and the light-receiving element are arranged at a predetermined angle in the range of 70°,
the reflecting mirror reflects the light of the first wavelength toward the smoke detection space and does not reflect the light of the second wavelength toward the smoke detection space;
The light of the first wavelength and the second wavelength emitted from the light emitting element is scattered toward the light receiving element by the particles present in the smoke detection space. The second scattering angle of the light of the first wavelength reflected toward the smoke detection space by is scattered toward the light receiving element by the particles present in the smoke detection space is set within the range of 30° to 70°.

(Smoke type identification by smoke detector structure 1)
In the smoke detection section structure 1, the light of the first wavelength emitted from the light emitting element and received by the light receiving element is scattered by the particles present in the smoke detection space and reflected by the reflecting mirror. The total scattered light amount of the light of the first wavelength scattered by the particles present in the smoke detection space and the scattered light amount of the scattered light , and the light of the second wavelength emitted from the light emitting element scattered by the particles present in the smoke detection space The type of smoke is identified based on the amount of scattered light and the amount of scattered light obtained, and a fire judgment is made according to the identified type of smoke.

(Smoke detector structure 2)
The intersection of the optical axes of the light of the first and second wavelengths emitted from the light-emitting element and the optical axis of the scattered light received by the light-receiving element, and the intersection formed by the three points of the light-emitting element and the light-receiving element form an angle of 110° to 110°. The light- emitting element and the light-receiving element are arranged at a predetermined angle in the range of 150°,
the reflecting mirror reflects the light of the second wavelength toward the smoke detection space and does not reflect the light of the first wavelength toward the smoke detection space;
The light of the first wavelength and the second wavelength emitted from the light emitting element is scattered toward the light receiving element by the particles present in the smoke detection space. The second scattering angle of the light of the first wavelength reflected toward the smoke detection space by scattering toward the light-receiving element by particles present in the smoke detection space is set within the range of 110° to 150°.

(Identification of types of smoke in smoke detector structure 2)
In the smoke detection section structure 2, the light of the first wavelength received by the light receiving element and emitted from the light emitting element is scattered by particles existing in the smoke detection space, and the amount of scattered light emitted from the light emitting element Scattered light amount of the second wavelength light scattered by particles existing in the smoke detection space and scattered light scattered by the second wavelength light reflected by the reflecting mirror Based on the amount of light and the total amount of scattered light, the type of smoke is identified, and a fire judgment is made according to the identified type of smoke.

(Size relationship between the first wavelength and the second wavelength)
The wavelength of the light of the second wavelength is made shorter than the light of the first wavelength emitted from the light emitting element. For example, the center wavelength of the light of the first wavelength emitted from the light emitting element is set to 800 nm or more, and the center wavelength of the light of the second wavelength is set to 600 nm or less.

(dichroic mirror)
A dichroic mirror is used as the reflecting mirror.

(2-color LED)
The light-emitting element is a two-color LED that intermittently emits light of the first and second wavelengths, having a first light-emitting chip that emits light of a first wavelength and a second light-emitting chip that emits light of a second wavelength.

(light emission control)
In a normal monitoring state, the light emitting element is driven to emit light of the first wavelength, and when a predetermined amount of light is received by the light receiving element , the light emitting element is driven to emit light of the second wavelength.

(basic effect)
In a photoelectric smoke sensor, the present invention comprises a light-emitting element that individually emits light of a first wavelength and light of a second wavelength different from the first wavelength toward a smoke detection space; Provided at a position that does not directly receive light of the first and second wavelengths, having sensitivity to both the first and second wavelengths, and scattered light of the first and second wavelengths caused by particles present in the smoke detection space and a light- receiving element that receives the smoke detection space, and is arranged at a position facing the light-emitting element across the smoke detection space, and reflects the light of the first wavelength and the second wavelength toward the smoke detection space, and the light of the other wavelength is the smoke detection space. Since it is equipped with a reflector that does not reflect toward the space, the light axis from the light emitting element to the smoke detection space becomes one, the range of light irradiation is limited, and the internally reflected light due to dust and condensation is reduced and non-existent. Fire alarms can be suppressed and the structure can be simplified, thereby reducing costs.

In addition, since only one light-emitting element, which is a component that determines the life of the sensor, is used, the probability of failure is reduced, the reliability can be improved, and the environmental load can be reduced.

(Effect of smoke detector structure 1)
Further, in the smoke detector structure 1, the intersection of the optical axis of the light of the first wavelength and the second wavelength emitted from the light emitting element and the optical axis of the scattered light received by the light receiving element, the light emitting element and the light receiving element 3 The light- emitting element and the light-receiving element are arranged so that the intersection formed by the points has a predetermined angle in the range of 30° to 70°, and the reflecting mirror reflects the light of the first wavelength toward the smoke detection space. , The light of the second wavelength is not reflected toward the smoke detection space, and the light of the first and second wavelengths emitted from the light emitting element is scattered toward the light receiving element by particles existing in the smoke detection space. The first scattering angle is set in the range of 110° to 150°, and the light of the first wavelength reflected by the reflecting mirror toward the smoke detection space is scattered toward the light receiving element by particles present in the smoke detection space. The second scattering angle of is set in the range of 30 ° to 70 °, and the light of the first wavelength emitted from the light emitting element, which is received by the light receiving element, is scattered by particles present in the smoke detection space. Scattered light The total scattered light amount of the scattered light amount and the scattered light amount of the first wavelength reflected by the reflecting mirror and the scattered light amount scattered by the particles existing in the smoke detection space, and the second wavelength light emitted from the light emitting element Based on the amount of scattered light scattered by particles present in the smoke detection space, the type of smoke is identified, and a fire judgment is made according to the identified type of smoke. Therefore, the first wavelength emitted from the light emitting element For the light of , the scattered light of the first wavelength based on the light emitted from the light emitting element and the scattered light of the first wavelength based on the light reflected toward the smoke detection space by the reflecting mirrors with different scattering angles are scattered. Light is received by the light-receiving element, and for the light of the second wavelength from the light- emitting element, the scattered light of the second wavelength based on the light emitted from the light-emitting element is received by the light-receiving element. By creating a difference and at the same time varying the wavelength of the light emitted from the light emitting element, a difference in scattering characteristics due to the wavelength is created, and the synergistic effect of the difference in scattering angle and the difference in wavelength changes the light intensity of the scattered light depending on the type of smoke. By making a significant difference in the smoke identification accuracy, by distinguishing smoldering and combustion from fire smoke, fire response and control after identification are different, and steam and cigarettes are more important than white smoke. Furthermore, since they are often large particles, by identifying them as non-fire factors, it is possible to reliably prevent non-fire alarms due to steam from cooking or smoke from cigarettes.

(Effect of smoke detector structure 2)
In the smoke detector structure 2, the intersection of the optical axis of the light of the first and second wavelengths emitted from the light emitting element and the optical axis of the scattered light received by the light receiving element, the light emitting element and the light receiving element The light- emitting element and the light-receiving element are arranged so that the intersection formed by the points has a predetermined angle in the range of 110° to 150°, and the reflecting mirror reflects the light of the second wavelength toward the smoke detection space. , light of the first wavelength is not reflected toward the smoke detection space, and light of the first and second wavelengths emitted from the light emitting element is scattered toward the light receiving element by particles present in the smoke detection space. The first scattering angle is set in the range of 30° to 70°, and the light of the first wavelength reflected by the reflecting mirror toward the smoke detection space is scattered toward the light receiving element by particles present in the smoke detection space. The second scattering angle of is set in the range of 110 ° to 150 °, and the light of the first wavelength emitted from the light emitting element, which is received by the light receiving element, is scattered by particles present in the smoke detection space . The amount of scattered light , the amount of scattered light of the second wavelength light emitted from the light emitting element scattered by the particles present in the smoke detection space, and the second wavelength light reflected by the reflecting mirror exist in the smoke detection space. Based on the scattered light amount of the scattered light scattered by the particles and the total scattered light amount, the type of smoke is identified, and the fire judgment is performed according to the identified smoke type. For the light of , the light receiving element receives the scattered light of the first wavelength based on the light emitted from the light emitting element, and for the light of the second wavelength emitted from the light emitting element, the second wavelength based on the light emitted from the light emitting element By receiving the synthesized scattered light of the scattered light of the second wavelength based on the light reflected toward the smoke detection space by the reflecting mirror and the scattered light of the second wavelength with the light receiving element, a difference in scattering characteristics depending on the type of smoke is created, and at the same time By varying the wavelength of the light emitted from the light-emitting 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. To increase the identification accuracy of smoke, prevent non-fire alarms due to steam from cooking and smoke from cigarettes, and to reliably identify types of burning materials such as black smoke fire and white smoke fire with respect to smoke caused by fire. can be done.

(Effect of size relationship between first wavelength and second wavelength)
Further, the wavelength of the light of the second wavelength is shortened with respect to the light of the first wavelength emitted from the light emitting element, for example, the center wavelength of the light of the first wavelength emitted from the light emitting element is set to 800 nm or more, and the second wavelength is Since the central wavelength of the light is set to 600 nm or less, the wavelength of the light emitted from the light emitting element is sufficiently different to create a difference in the scattering characteristics due to the wavelength, and the light intensity of the scattered light depending on the type of smoke is remarkable. can make a big difference.

(Effect of dichroic mirror)
In addition, since the reflector is a dichroic mirror, by forming a thin film such as a dielectric multilayer film on the mirror surface, the light of the first wavelength or the second wavelength from the light emitting element can be efficiently reflected to form a virtual light emitting element. available as In addition, since the amount of light can be secured by reflection, the amount of light emitted at the wavelength to be reflected can be less than in the conventional case, and power can be saved.

(Effect of two-color LED)
Also, the light-emitting element is a two-color LED that includes a first light-emitting chip that emits light of a first wavelength and a second light-emitting chip that emits light of a second wavelength, and that intermittently emits light of the first and second wavelengths. Therefore, the first light-emitting chip and the second light-emitting chip can be driven separately, thereby intermittently emitting light of the first wavelength and light of the second wavelength. In addition, by using two-color LEDs, it is possible to reduce the number of parts, save space, and save power compared to the case where two LEDs with different wavelengths are arranged.

(Effect of light emission control)
In a normal monitoring state, the light emitting element is driven to emit light of the first wavelength, and when a predetermined amount of light is received by the light receiving element , the light emitting element is driven to emit light of the second wavelength. As a result, power consumption in the normal monitoring state can be reduced.

1 is a block diagram showing the circuit configuration of a photoelectric smoke sensor according to the present invention; Explanatory diagram showing the first embodiment of the smoke detector structure in FIG. Explanatory diagram showing the light receiving output detected by the structure of the smoke detection part in FIG. Flowchart showing fire detection control by the circuit block of FIG. 1 using the smoke detector structure of FIG. Explanatory drawing showing the second embodiment of the smoke detector structure in FIG. Explanatory diagram showing the light receiving output detected by the structure of the smoke detection part in 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 a receiver via the transmission lines 11a and 11b, and a power supply unit 15 that converts the power supply voltage supplied via the transmission lines 11a and 11b into a predetermined stabilized voltage and outputs the voltage. , a light emission drive unit 16, a smoke detection unit 18, and an amplifier circuit unit 28.

A light-emitting element 20 is provided in the smoke detector 18 . In this embodiment, a two-color LED (two-color light-emitting diode) is used as the light-emitting element 20. The two-color LED includes a first light-emitting chip 22 that emits light of the first wavelength λ1, A second light emitting chip 24 that emits light of a second wavelength λ2 different from λ1 is provided. Alternatively, it can emit light of the second wavelength λ2.

As the light receiving element 26, a photodiode (PD) having sensitivity to both the light of the first wavelength λ1 and the light of the second wavelength λ2 emitted from the light emitting element 20 is used.

[First embodiment of smoke detector]
FIG. 2 is an explanatory view showing a first embodiment of the structure of the smoke detecting section in FIG. 1, where the crossing angle θ2 between the light emitting element 20 and the light receiving element 26 is 90° or less.

As shown in FIG. 2, a light-emitting element 20, a light-receiving element 26, and a dichroic mirror 30 functioning as a reflecting mirror having wavelength selectivity are arranged in the smoke detector 18 into which smoke from the outside flows.

A light-emitting element 20 using a two-color LED emits light of a first wavelength λ1 from a first light-emitting chip 22 in the direction of an optical axis 20a, and emits light of a second wavelength λ2 from a second light-emitting chip 24 along an optical axis 20a. Irradiate in the direction of 20a.

The light of the first wavelength λ1 emitted by the light emitting element 20 is set to have a center wavelength of 800 nm or more, and in this embodiment, λ1 is set to 900 nm. Further, the light of the second wavelength λ2 emitted by the light emitting element 20 is set to have a center wavelength of 600 nm or less, and in this embodiment, λ2 is set to 500 nm.

The light receiving element 26 is arranged at a position where it does not directly receive the light from the light emitting element 20, and the intersection angle θ2 between the optical axis 20a of the light emitting element 20 and the optical axis 26a of the light receiving element 26 is a predetermined range of 30° to 70°. In this embodiment, the intersection angle θ2 is set to θ2=30°, for example.

The dichroic mirror 30 is arranged on the optical axis 20a from the light emitting element 20 at a position opposite to the smoke detecting point P. In this embodiment, the first light emitting chip 22 of the light emitting element 20 It is configured to reflect only light of one wavelength λ1.

The light receiving element 26 is sensitive to both the light of the first wavelength λ1=900 nm and the light of the second wavelength λ2=500 nm emitted from the light emitting element 20. FIG. When the light emitting element 20 emits light of the first wavelength λ1, the light scattered by the smoke flowing into the smoke detector 18 is received by the light receiving element 26. In this case, the scattering angle θ1 becomes 150°, and the light receiving element 26 is Receive backscattered light.

At the same time, the light of the first wavelength λ1 emitted from the light emitting element 20 is reflected by the dichroic mirror 30 and returns in the direction of the smoke detection point P. The light is received, and the scattering angle θ2 in this case becomes θ2=30°, which is the same as the crossing angle of the light emitting element 20 and the light receiving element 26, and the light receiving element 26 receives the forward scattered light.

Therefore, when the light emitting element 20 emits light of the first wavelength λ1, the light receiving element 26 receives backscattered light at a scattering angle θ1=150° due to direct light from the light emitting element 20 and scattered light due to reflected light from the dichroic mirror 30. Both forward scattered lights at an angle θ2=30° are received, and a received light output A1 corresponding to the combined scattered light amount is obtained.

On the other hand, when the light emitting element 20 emits light of the second wavelength λ2, scattered light of the second wavelength λ2 due to the smoke flowing into the smoke detector 18 is received by the light receiving element 26, and the scattering angle θ1 in this case is θ1=150°, the light receiving element 26 receives only the backscattered light, and a light receiving output A2 is obtained.

[Smoke identification by control unit]
In a normal monitoring state, the control unit 12 shown in FIG. 1 instructs the light emission driving unit 16 to intermittently drive the first light emitting chip 22 of the light emitting element 20 at a predetermined cycle, thereby emitting light of the first wavelength λ1. Synthetic scattered light, which is the sum of the backward scattered light of the first wavelength λ1 and the forward scattered light reflected by the dichroic mirror 30, is received by the light receiving element 26, and the received light output is output from the amplifier circuit 28 in response to this. A1 is detected, and when it is determined that the received light output A1 has exceeded a predetermined smoke density, for example, a threshold value Ath corresponding to the smoke density requiring a caution alarm, the received light output A1 is stored in the memory.

Subsequently, the controller 12 drives the second light emitting chip 24 of the light emitting element 20 to emit light of the second wavelength λ2 in order to identify the type of smoke. In this case, since the dichroic mirror 30 does not reflect the light of the second wavelength λ2, the light receiving element 26 receives only the backscattered light of the second wavelength λ2 and detects the received light output A2 output from the amplifier circuit 28. Store in memory.

Subsequently, the control unit 12 controls the total scattered light of the smoke backscattered light of the first wavelength λ1 emitted from the light emitting element 20 and the forward scattered light of the first wavelength λ1 reflected by the dichroic mirror 30. By comparing the received light output A1 from the second wavelength λ2 emitted from the light emitting element 20 and the scattered light of the smoke emitted from the light emitting element 20, the type of smoke is identified, and the judgment criteria according to the type of smoke Fire judgment is made by

[Judgment of smoke type by ratio of received light output]
FIG. 3 is an explanatory diagram showing the light receiving output detected by the smoke detector structure of FIG. In order to identify black smoke, cotton lamp wicks and kerosene are selected as representative samples.

As shown in FIG. 3, the received light output A1 is the sum of the backward scattered light with the first wavelength λ1=900 nm and the scattering angle θ1=150° and the forward scattered light with the first wavelength λ1=900 nm and the scattering angle θ2=30°. , and the received light output A2 is backscattered light with a second wavelength λ2=500 nm and a scattering angle θ1=150°.

Taking the ratio R=A1/A2 of the light receiving outputs A1 and A2 measured by burning the cotton lamp wick and kerosene, R=6.1 for the cotton lamp wick and R=1.6 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, Rth=4 as the ratio threshold value Rth. It judges that black smoke is generated, and performs control to output a fire alarm by transmitting a fire signal including identification information indicating the judged type of smoke or the type of fire to the receiver.

When non-fire-causing steam from a bathroom or the like flows into the photoelectric smoke sensor 10, the ratio R becomes a large value, for example, R=10 or more. 12 may be set, and if the ratio R is Rth2 or more, it may be determined as a non-fire factor and a fire signal including identification information of the non-fire factor may be transmitted.

[Detector control]
FIG. 4 is a flow chart showing the fire detection control by the circuit block of FIG. 1 using the smoke detector structure of FIG.

As shown in FIG. 4, in step S1, the control unit 12 instructs the light emission driving unit 16 to intermittently drive the first light emitting chip 22 of the light emitting element 20 to emit light at a predetermined cycle to detect light of the first wavelength λ1. A light receiving output A1 corresponding to the sum of the backward scattered light of the first wavelength λ1 received by the light receiving element 26 and the forward scattered light reflected by the dichroic mirror 30 is detected in step S3. If it is determined that the value is equal to or greater than the predetermined threshold value Ath in step S4, the received light output A1 detected at that time is stored in the memory.

Subsequently, in step S5, the control unit 12 instructs the light emission driving unit 16 to drive the second light emitting chip 24 of the light emitting element 20 to emit light of the second wavelength λ2 into the smoke detection unit 18, and step S6. , the received light output A2 corresponding to the backscattered light of the second wavelength λ2 received by the light receiving element 26 is detected and stored in the memory in step S7.

Subsequently, the control unit 12 calculates the ratio R=A1/A2 of the light receiving outputs A1 and A2 in step S8, compares the ratio R with, for example, a threshold value Rth=4 in step S9, and determines that the ratio R is equal to or greater than the threshold value Rth=4. If so, the process proceeds to step S10 to determine that the fire is smoldering due to white smoke. When it is determined in step S11 that the received light output A1 is equal to or greater than the threshold value Ath1, the process proceeds to step S12 to receive a fire signal including white smoke identification information. and output a fire alarm indicating a smoldering fire caused by white smoke.

On the other hand, if the ratio R is less than the threshold value Rth=4 in step S9 , the control unit 12 proceeds to step S13 to determine that the combustion fire is caused by black smoke. is determined, the process proceeds to step S15, in which a fire signal including black smoke identification information is transmitted to the receiver to output a fire alarm indicating combustion fire due to black smoke.

[Second embodiment of smoke detector structure]
FIG. 5 is an explanatory diagram showing a second embodiment of the structure of the smoke detector in FIG. 1, in which the crossing angle θ2 between the light emitting element 20 and the light receiving element 26 is 90° or more.

As shown in FIG. 5, a light-emitting element 20, a light-receiving element 26, and a dichroic mirror 30 functioning as a reflecting mirror are arranged in the smoke detecting section 18 into which smoke from the outside flows.

A light-emitting element 20 using a two-color LED emits light of a first wavelength λ1 from a first light-emitting chip 22 in the direction of an optical axis 20a, and emits light of a second wavelength λ2 from a second light-emitting chip 24 along an optical axis 20a. Irradiate in the direction of 20a. The light of the first wavelength λ1 emitted by the light emitting element 20 is set to have a center wavelength of 800 nm or more, and in this embodiment, λ1 is set to 900 nm. Further, the light of the second wavelength λ2 emitted by the light emitting element 20 is set to have a center wavelength of 600 nm or less, and in this embodiment, λ2 is set to 500 nm.

The light receiving element 26 is arranged at a position where it does not directly receive the light from the light emitting element 20, and the intersection angle θ2 between the optical axis 20a of the light emitting element 20 and the optical axis 26a of the light receiving element 26 is a predetermined range of 110° to 150°. In this embodiment, the crossing angle θ2 is set to be larger than 90°, for example θ2=150°.

The dichroic mirror 30 is arranged on the optical axis 20a from the light emitting element 20 at a position facing the smoke detection point P. In this embodiment, the second light emitted from the second light emitting chip 24 of the light emitting element 20 It is configured to reflect only light of two wavelengths λ2.

The light receiving element 26 is sensitive to both the light of the first wavelength λ1=900 nm and the light of the second wavelength λ2=500 nm emitted from the light emitting element 20. When the light emitting element 20 emits the light of the first wavelength λ1, Scattered light of the first wavelength λ1 due to smoke flowing into the smoke detector 18 is received by the light receiving element 26. In this case, the scattering angle θ1 is 30°, and the light receiving element 26 receives only forward scattered light. An output A1 is obtained.

On the other hand, when the light emitting element 20 emits light of the second wavelength λ2, the light scattered by the smoke flowing into the smoke detector 18 is received by the light receiving element 26, and the scattering angle θ1 in this case becomes θ1=30°. 26 receives forward scattered light. At the same time, the light of the second wavelength λ2 emitted from the light emitting element 20 is reflected by the dichroic mirror 30 and returns in the direction of the smoke detection point P. The light is received, and the scattering angle θ2 in this case is θ2=150°, which is the same as the intersection angle between the light emitting element 20 and the light receiving element 26, and the light receiving element 26 receives the backscattered light.

Therefore, when the light emitting element 20 emits light of the second wavelength λ2, the light receiving element 26 receives forward scattered light at a scattering angle θ1=30° due to direct light from the light emitting element 20 and scattered light due to reflected light from the dichroic mirror 30. Both of the backscattered lights at the angle θ2=150° are received, and a received light output A2 corresponding to the combined scattered light amount is obtained.

[Smoke identification by control unit]
FIG. 6 is an explanatory diagram showing the light receiving output detected by the structure of the smoke detector shown in FIG.

As shown in FIG. 6, the received light output A1 is forward scattered light with a first wavelength λ1=900 nm and a scattering angle θ1=30°, and the received light output A2 is forward scattered light with a second wavelength λ2=500 nm and a scattering angle θ1=30°. It is the sum of the forward scattered light and the backward scattered light with the second wavelength λ2=500 nm and the scattering angle θ2=150°.

Taking the ratio R=A1/A2 of the light receiving outputs A1 and A2 measured by burning the cotton lamp wick and kerosene, R=2.7 for the cotton lamp wick and R=0.4 for the kerosene. Thus, a difference appears in the ratio R between the cotton lamp wick and kerosene, and the type of smoke based on the ratio R can be identified.

For this reason, the control unit 12 sets, for example, Rth=1.5 as the ratio threshold value Rth. determines that black smoke is generated due to combustion, and controls to transmit a fire signal including information indicating the type of smoke determined to the receiver to output a fire alarm.

Further, the sensor control by the control unit 12 in FIG. 1 targeting the smoke detector structure in FIG. 6 is basically the same as the control shown in the flow chart in FIG.

[Modification of the present invention]
(Drive control of light emitting element)
In the above embodiment, the light emitting element 20 intermittently emits light of the first wavelength λ1 to detect the received light output A1, and when the received light output A1 is equal to or greater than the threshold, emits the second wavelength λ2 to detect the received light output A2. The light of the first wavelength λ1 and the light of the second wavelength λ2 are emitted from the light emitting element 20 with a time lag at each predetermined cycle, and the received light outputs A1 and A2 are detected. You may make it identify the kind of smoke.

(Scattering angle)
In the above embodiment, the scattering angle θ1 is set to 150° or 30°, but the scattering angle θ1 can be appropriately selected according to the required specifications of the photoelectric smoke sensor. For example, if it is desired to reduce the size of the sensor, the width of the smoke detector 18 can be narrowed by reducing the scattering angle .theta.1. However, as the scattering angle θ1 decreases, the light beam from the light emitting element 20 may directly enter the light receiving element 26, or the reflected light from the wall surface of the smoke detector 18 may enter the light receiving element 26. Measures against internally reflected light from the smoke detector 18 are required.

Conversely, in order to efficiently process the internally reflected light of the smoke detector 18, it is desirable to set the scattering angle θ1 to be close to 90° and to be relatively large. Thus, the scattering angle .theta.1 can be appropriately selected according to the specifications required for the photoelectric smoke sensor.

(others)
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, 26a: optical axis 22: first light emission Chip 24: Second light emitting chip 26: Light receiving element 28: Amplifier circuit section 30: Dichroic mirror

Claims (10)

a light emitting element that individually emits light of a first wavelength and light of a second wavelength different from the first wavelength toward the smoke detection space;
provided at a position not directly receiving light of the first wavelength and the second wavelength emitted from the light emitting element, having sensitivity to both the first wavelength and the second wavelength, and present in the smoke detection space a light-receiving element that receives scattered light of the first wavelength and the second wavelength by particles ;
arranged at a position facing the light emitting element with the smoke detection space interposed therebetween, and reflects light of either one of the first wavelength and the second wavelength toward the smoke detection space , a reflecting mirror that does not reflect light of the wavelength toward the smoke detection space ;
A photoelectric smoke sensor comprising:
The photoelectric smoke sensor according to claim 1,
It is formed by three points: the intersection of the optical axis of the light of the first wavelength and the second wavelength emitted from the light emitting element and the optical axis of the scattered light received by the light receiving element, the light emitting element and the light receiving element The light- emitting element and the light-receiving element are arranged such that the angle of the intersection is a predetermined angle in the range of 30° to 70°,
the reflecting mirror reflects the light of the first wavelength toward the smoke detection space and does not reflect the light of the second wavelength toward the smoke detection space;
The light of the first wavelength and the light of the second wavelength emitted from the light emitting element is scattered toward the light receiving element by particles existing in the smoke detection space, and the first scattering angle of the scattered light is in the range of 110° to 150°. and the light of the first wavelength reflected by the reflecting mirror toward the smoke detection space is scattered toward the light receiving element by particles existing in the smoke detection space, and the second scattering angle of the scattered light is 30 A photoelectric smoke detector characterized in that the range is set between degrees and 70 degrees.
The photoelectric smoke sensor according to claim 2,
Scattered light amount of light of the first wavelength emitted from the light-emitting element and scattered by particles present in the smoke detection space and the first wavelength reflected by the reflecting mirror, which is received by the light-receiving element The total scattered light amount of the scattered light scattered by the particles present in the smoke detection space, and the light of the second wavelength emitted from the light emitting element by the particles present in the smoke detection space 1. A photoelectric smoke detector, wherein the type of smoke is identified based on the amount of scattered scattered light and the amount of scattered light, and a fire judgment is made according to the identified type of smoke.
The photoelectric smoke sensor according to claim 1,
It is formed by three points: the intersection of the optical axis of the light of the first wavelength and the second wavelength emitted from the light emitting element and the optical axis of the scattered light received by the light receiving element, the light emitting element and the light receiving element The light- emitting element and the light-receiving element are arranged such that the intersection angle is a predetermined angle in the range of 110° to 150°,
the reflecting mirror reflects the light of the second wavelength toward the smoke detection space and does not reflect the light of the first wavelength toward the smoke detection space;
The light of the first wavelength and the light of the second wavelength emitted from the light emitting element is scattered toward the light receiving element by particles existing in the smoke detection space, and the first scattering angle of the scattered light is in the range of 30° to 70°. and the light of the second wavelength reflected by the reflecting mirror toward the smoke detection space is scattered toward the light receiving element by particles existing in the smoke detection space, and the second scattering angle of the scattered light is 110 A photoelectric smoke detector characterized in that the range is set between ° and 150°.
The photoelectric smoke sensor according to claim 4,
The scattered light amount of the light of the first wavelength emitted from the light-emitting element, which is received by the light-receiving element, is scattered by particles present in the smoke detection space ; Scattered light amount of light of the wavelength scattered by particles present in the smoke detection space and scattering of scattered light of the light of the second wavelength reflected by the reflecting mirror and scattered by particles present in the smoke detection space 1. A photoelectric smoke sensor that identifies the type of smoke based on the amount of light and the total amount of scattered light, and makes a fire judgment according to the identified type of smoke.
The photoelectric smoke sensor according to any one of claims 1 to 5,
A photoelectric smoke detector, wherein the wavelength of the light of the second wavelength is shorter than the light of the first wavelength emitted from the light emitting element.
The photoelectric smoke sensor according to claim 6,
A photoelectric smoke sensor, wherein the central wavelength of the light of the first wavelength emitted from the light emitting element is set to 800 nm or more, and the central wavelength of the light of the second wavelength is set to 600 nm or less.
The photoelectric smoke sensor according to any one of claims 1 to 7,
A photoelectric smoke detector, wherein the reflecting mirror is a dichroic mirror.
The photoelectric smoke sensor according to any one of claims 1 to 8,
The light emitting element includes a first light emitting chip that emits light of the first wavelength and a second light emitting chip that emits light of the second wavelength, and intermittently emits light of the first wavelength and the light of the second wavelength. A photoelectric smoke detector characterized by using color light emitting diodes.
The photoelectric smoke sensor according to any one of claims 1 to 9,
In a normal monitoring state, the light-emitting element is driven to emit light of the first wavelength, and when a predetermined amount of light is received by the light-receiving element , the light-emitting element emits light of the second wavelength. A photoelectric smoke detector characterized by driving as follows.

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