CN115691032A

CN115691032A - Optical smoke detector and method thereof

Info

Publication number: CN115691032A
Application number: CN202211329581.4A
Authority: CN
Inventors: 侯树春; 托马斯·巴舍尔斯; 徐奂; 黄康; 任利
Original assignee: Siemens Schweiz AG
Current assignee: Siemens Schweiz AG
Priority date: 2016-03-31
Filing date: 2016-03-31
Publication date: 2023-02-03
Also published as: CN105608832A

Abstract

The invention provides a smoke detector and a method thereof. This smoke detector includes: a detection chamber (210), at least one light source (220), at least one light receiver (230), and a controller (240) connected to the light source (220) and the light receiver (230). The controller (240) is configured to issue a FAULT-with-contamination (FAULT) message if it is determined that the optical signal (S) detected by the optical receiver (230) is greater than a predetermined threshold (Th) and that the detected optical signal (S) exhibits minor fluctuations during a predetermined period (P) after power-up. The smoke detector can report pollution fault information in time after being electrified, and can also accurately report fire alarm if a fire occurs during electrification.

Description

Optical smoke detector and method thereof

Technical Field

The invention relates to the field of Fire alarm (Fire alarm), in particular to an optical smoke detector in a Fire system and an alarm method thereof.

Background

The smoke detector is detection equipment commonly used in the field of fire fighting. The smoke detector is divided into a photosensitive mode and a photosensitive and temperature-sensing combined mode. Light-sensitive smoke detectors, also referred to as optical smoke detectors, distinguish between moisture and smoke that may cause a fire based on the degree to which smoke particles scatter light. Such optical smoke detectors typically have a detection chamber, and a light source and light receiver disposed within the detection chamber. The light source emits light into the detection cavity. These rays will be scattered by smoke particles present in the detection chamber. The light receiver senses light scattered by the smoke particles, determines whether a fire exists according to characteristics of the scattered light and reports a fire alarm accordingly.

Because the optical smoke detector is based on the detection of scattered light, the cleanliness of the detection cavity and the cleanliness of the surfaces of the light source and the light receiver directly influence the fire alarm sensitivity of the smoke detector. Under the pollution condition, if the dust particle concentration in the detection cavity reaches a certain value, the smoke detector can falsely report the light scattering caused by the dust as a fire alarm. In other words, for an optical smoke detector, both dust and smoke can result in a sufficiently strong light scattering signal that the smoke detector reports a fire alarm. Therefore, how to distinguish smoke from dust (or pollution) by the optical smoke detector is a problem to be solved.

The existing optical smoke detector periodically monitors and evaluates the degree of dust (or pollution) in the normal operation process of the optical smoke detector, and simultaneously eliminates the adverse effect caused by the dust or the pollution by utilizing a compensation algorithm aiming at the dust so as to eliminate the fire alarm false alarm in the normal operation process. However, at the beginning of the power-up of the smoke detector, the dust compensation algorithm has difficulty achieving the desired effect due to the lack of monitoring data for dust.

For example, if the smoke detector is installed in the field, the fire protection system needs to be shut down for a period of time for reasons such as finishing work. However, during this off time, the smoke detector installed in the field is likely to be required to experience relatively severe air pollution. Thus, the dust enters the detection cavity of the smoke detector. When the fire extinguishing system is powered on again, the optical smoke detector can immediately report dust as a fire alarm due to serious pollution.

In view of the above, a new trend is to test whether the smoke detector can accurately report dust or pollution fault messages when the smoke detector is powered on when the smoke detector passes the national mandatory standard test. One proposed testing method generally includes the following steps. First, the optical smoke detector is placed in a dust test chamber for a period of time (approximately two hours) to achieve a comparable concentration of dust in the chamber. Then, the optical smoke detector is started, and the working state of the smoke detector is detected. If the smoke detector sends a contamination fault message, it indicates a successful pass. If the smoke detector does not report a contamination fault message, its fire sensitivity is detected. If the fire sensitivity is acceptable, it is placed again in the dust test box. If the fire alarm sensitivity is not qualified, the test is failed. This is repeated for about four cycles. The testing method can test whether the smoke detector can accurately report the pollution fault at the beginning of power-on, and the fire alarm sensitivity meets the standard requirement.

To avoid false alarms at the beginning of power-up, one common solution is to report pollution faults preferentially, an exemplary flow of which is shown in fig. 1. As shown in fig. 1, the method flow starts at step S110. In step S110, the smoke detector is powered on, and then initialization is completed in step S120. In step S130, the smoke detector detects the optical signal S detected by its optical receiver within a predetermined time period P after being powered on. Further, in step S140, the optical signal S is determined. If the optical signal S is determined to be greater than the predetermined threshold Th in step S140, step S150 is entered to report a FAULT message, otherwise step S190 is entered to enter normal operation. Here, the threshold Th is a fire alarm threshold. By adopting the method shown in fig. 1, the pollution fault message can be reported successfully at the beginning of power-on, and the recommended dust test can be passed successfully. However, in the event that a fire actually occurs at the beginning of a power-up, the method shown in fig. 1 may result in a fire alarm being missed, which may result in personal or property damage.

Disclosure of Invention

An object of the present invention is to provide a smoke detector and a method thereof in a fire fighting system, by which a pollution fault message can be reported at the beginning of power-on of the smoke detector, and a fire alarm can be reported in time if a fire smoke detector occurs during power-on.

According to one aspect of the invention, there is provided a smoke detector comprising: a detection chamber adapted to receive gas with particles from outside the smoke detector; at least one light source adapted to emit light into the detection chamber; at least one optical receiver that detects optical signals formed by scattering of particles within the detection chamber; a controller connected to the light source and the light receiver and configured to issue a contamination failure message if it is determined that the light signal detected by the light receiver is greater than a predetermined threshold within a predetermined period of time after power up and the detected light signal exhibits minor fluctuations during the predetermined period of time. Preferably, the detected light signal exhibits a minor fluctuation within a first predetermined fluctuation range during the predetermined period. Preferably, the controller is further configured to: and in the preset time period after power-on, if the optical signal detected by the optical receiver is determined to be greater than the preset threshold value and the detected optical signal exceeds the first preset fluctuation range in the preset time period, a fire alarm message is sent out.

The smoke detector not only judges the fire alarm according to whether the detected optical signal is greater than the threshold value, but also can further distinguish the pollution fault and the fire alarm according to whether the optical signal S obviously fluctuates within a preset time period P after electrification. Therefore, the smoke detector can report the pollution fault message in time after being electrified, and can also report the fire alarm in time if a fire occurs during electrification, so that the smoke detector cannot report the pollution fault message in a missing way due to the interference of pollution. Thus, the smoke detector described above may also successfully pass the dust test described earlier.

Preferably, the controller is further configured to: within the predetermined time period after power-up, if the controller determines: the light signal detected by the light receiver is greater than the predetermined threshold and the detected light signal exceeds a second predetermined fluctuation range during the predetermined time period, wherein the second predetermined fluctuation range is greater than the first predetermined fluctuation range, a fire alarm message is issued.

The smoke detector uses dual dynamic range as criterion to distinguish pollution fault and fire alarm. By adopting a dual fluctuation range criterion, a pollution fault is judged only when the fluctuation of the optical signal is small (within a first fluctuation range), and a fire alarm is judged only when the fluctuation of the optical signal is obvious (larger than a second fluctuation range). Therefore, the dual-fluctuation range criterion can distinguish the pollution fault and the fire alarm more accurately, and false alarm and missed fire alarm can be further reduced.

Preferably, the smoke detector further comprises a temperature sensor for detecting a temperature in or near the detection chamber, and the controller is further configured to: within the predetermined time period after power-up, if the controller determines: the light receiver detects a light signal greater than the predetermined threshold, the detected light signal is less than the first predetermined fluctuation range during the predetermined period, and the temperature detected by the temperature sensor increases beyond a predetermined temperature difference threshold, a fire alarm message is issued.

Preferably, the smoke detector further comprises a temperature sensor for detecting a temperature in or near the detection chamber, and the controller is further configured to: within the predetermined time period after power-up, if the controller determines: the light signal detected by the light receiver is greater than the predetermined threshold, the detected light signal is greater than the first predetermined fluctuation range but less than a second predetermined fluctuation range during the predetermined period of time, and a fire alarm message is issued if the temperature increase detected by the temperature sensor exceeds a predetermined temperature difference threshold.

The smoke detection further introduces a temperature gradient criterion. For those fires in which the incipient optical signal fluctuates slightly (e.g., in the case of plastic or other organic combustion), the introduction of a temperature gradient criterion can help to determine the fire early, further reducing the false negative of fire alarms. In addition, since the temperature sensor can be an existing component of the smoke detector, the solution does not increase the hardware cost and complexity of the smoke detector.

Preferably, the threshold is a fire alarm threshold, or the predetermined temperature difference is a fire alarm temperature threshold. More preferably, the first predetermined fluctuation range is equal to or less than ± 8%, preferably equal to or less than ± 5%, and even more preferably equal to 2%; the second predetermined fluctuation range is equal to or greater than ± 8%, preferably equal to or greater than ± 10%; the predetermined temperature difference threshold is greater than or equal to 8 deg.c, preferably greater than or equal to 10 deg.c. It is particularly preferred that the predetermined period of time is substantially between 2s and 180s, preferably between 30s and 180s, more preferably between 50s and 110s, even more preferably 60s or 100s.

According to another aspect of the invention, a method of reporting contamination failure by an optical smoke detector is provided. The method comprises the following steps: detecting an optical signal within a predetermined time period after the smoke detector is powered on; and in a preset time period after the power-on, if the detected optical signal is greater than a preset threshold value and the detected optical signal shows small fluctuation in the preset time period, sending a pollution fault message. Preferably, the detected light signal exhibits a minor fluctuation within a first predetermined fluctuation range during the predetermined period.

Preferably, the method further comprises: and in the preset time period after power-on, the detected light signal is larger than the preset threshold value, and the detected light signal exceeds a second preset fluctuation range in the preset time period, a fire alarm message is sent out, wherein the second preset fluctuation range is larger than the first preset fluctuation range.

More preferably, the method further comprises: detecting a temperature in or near a detection cavity of the smoke detector, and if the detected light signal is greater than the predetermined threshold value within the predetermined time period after power-up, the detected light signal is greater than the first predetermined fluctuation range but less than the second predetermined fluctuation range during the predetermined time period, and the detected temperature increases beyond a predetermined temperature difference threshold, then issuing a fire alarm message.

Preferably, the threshold is a fire alarm threshold. Preferably, the predetermined temperature difference is a temperature threshold of a fire alarm. Preferably, the first predetermined fluctuation range is equal to or less than ± 8%, preferably equal to or less than ± 5%, and more preferably equal to or less than 2%. Preferably, the second predetermined fluctuation range is ± 8% or more, preferably ± 10% or more. Preferably, the predetermined temperature difference threshold is greater than or equal to 8 ℃, preferably greater than or equal to 10 ℃.

According to another aspect of the invention, the invention provides a smoke detector comprising: a detection chamber adapted to receive gas with particles from outside the smoke detector; at least one light source adapted to emit light into the detection chamber; at least one optical receiver that detects optical signals formed by scattering of particles within the detection chamber; a controller connected to the light source and the light receiver and configured to: if the optical signal detected by the optical receiver is determined to be less than a predetermined threshold value within a predetermined time period after power-on, entering normal operation; and in the preset time period after power-on, if the optical signal detected by the optical receiver is determined to be larger than the preset threshold value and the detected optical signal shows tiny fluctuation in the preset time period, sending a pollution fault message. Preferably, the detected light signal exhibits a minor fluctuation within a first predetermined fluctuation range during the predetermined period.

According to another aspect of the invention, a method of reporting contamination failure by an optical smoke detector is provided. The method comprises the following steps: detecting an optical signal within a predetermined time period after the smoke detector is powered on; during a preset time period after the power-on, if the optical signal detected by the optical receiver is determined to be less than a preset threshold value, entering the normal operation; and in a preset time period after the power-on, if the detected optical signal is larger than the preset threshold value and the detected optical signal shows small fluctuation in the preset time period, sending a pollution fault message. Preferably, the detected light signal exhibits a minor fluctuation within a first predetermined fluctuation range during the predetermined period.

The above features, technical features, advantages and modes of realisation of the device will be further explained in the following, in a clearly understandable manner, with reference to the accompanying drawings, illustrating preferred embodiments.

Drawings

The following drawings are only schematic illustrations and explanations of the present invention, and do not limit the scope of the present invention.

Fig. 1 shows a flow chart of a conventional method for reporting a pollution fault message.

Fig. 2 shows a block diagram of an optical smoke detector according to an embodiment of the invention.

Fig. 3A and 3B show waveforms of a detected light signal in both a pollution and a fire alarm situation, respectively, and a schematic diagram of a threshold criterion and a fluctuation range criterion according to an embodiment of the present invention.

FIG. 4 illustrates a flow diagram of a method of reporting a pollution fault message, according to one embodiment of the invention.

Fig. 5A and 5B show waveforms of a detected optical signal in both a contamination and a fire alarm, respectively, and a schematic diagram of a threshold criterion and a fluctuation range criterion according to another embodiment of the present invention.

FIG. 6 illustrates a flow diagram of a method of reporting a pollution fault message, according to another embodiment of the invention.

Fig. 7A and 7B show a waveform diagram of a change in an optical signal and a waveform diagram of a change in a temperature signal in case of a fire alarm, respectively, and schematic diagrams of a threshold criterion and a fluctuation range criterion according to still another embodiment of the present invention.

FIG. 8 illustrates a flow diagram of a method of reporting a pollution fault message in accordance with yet another embodiment of the present invention.

Reference numerals

10: particles; 20: a gas;

200: a smoke detector; 210: a probe chamber; 220: a light source; 230: an optical receiver;

240: a controller; 250: a temperature sensor;

th: a threshold value; s: an optical signal; t: (ii) a temperature; r1, R2, R3: a fluctuation range;

t4: threshold temperature difference

Detailed Description

In order to more clearly understand the technical features, objects and effects of the present invention, embodiments of the present invention will now be described with reference to the accompanying drawings, in which the same reference numerals indicate the same or structurally similar but functionally identical elements.

"exemplary" means "serving as an example, instance, or illustration" herein, and any illustration, embodiment, or steps described as "exemplary" herein should not be construed as a preferred or advantageous alternative.

For the sake of simplicity, the drawings only schematically show the parts relevant to the present invention, and they do not represent the actual structure as a product. In addition, for simplicity and clarity of understanding, only one of the components having the same structure or function is schematically illustrated or labeled in some of the drawings.

In this document, "one" means not only "only one" but also a case of "more than one". In addition, in this document, "first", "second", and the like are used only for distinguishing one from another, and do not indicate the degree of importance, the order, and the like thereof.

Figure 2 schematically illustrates the structure of an optical smoke detector according to one embodiment of the present invention. As shown in fig. 2, the smoke detector 200 includes a detection chamber 210, at least one light source 220, at least one light receiver 230, and a controller 240.

The detection chamber 210 has an opening communicating with the external space. Gas 20 (e.g., air or smoke) outside the detection chamber 210 may diffuse into the detection chamber 210 through these openings. The gas entering the detection chamber 210 may have particles 10, the nature of the particles 10 determining whether they are smoke caused by a fire. For example, if the particles 10 are water vapor, the gas is a mist; the particles 10 are solid particles and when of a certain size and density may be smoke caused by fire.

The light source 220 is arranged to inject light into the detection chamber 210. The light source 220 may be, for example, an LED element. When gas with particles is present in the detection chamber 210, light emitted by the light source 220 is scattered by the particles in the gas. The scattered light formed by the scattering is received and sensed by a light receiver 230 disposed within the detection chamber 210. The light receiver 230 may be a light sensitive element, such as a photodiode. In the example shown in fig. 2, only one light source 220 and one light receiver 230 are shown. In other applications, the smoke detector 200 may have, for example, two or more light sources 220, or two or more light receivers 230. The wavelengths of the light emitted from the light sources 220 may be different from each other, and the light receivers 230 may be sensitive to the scattered light with different wavelengths.

In fig. 2, the light source 220 and the light receiver 230 are both connected to a controller 240. The controller 240 controls the timing or sequence of the light emission of the light source 220 on the one hand, and collects the light signal S detected by the light receiver 230 on the other hand. Typically, if the controller 240 determines that the collected light signal S is greater than a fire threshold Th, a fire ALARM is reported to be present.

As shown in fig. 2, the smoke detector 200 may optionally also have a temperature sensor 250. The temperature sensor 250 is also connected to the controller 240, and the controller 240 collects the temperature T sensed by the temperature sensor 250 and determines whether a fire alarm occurs according to a gradient of the temperature T. For the smoke detector with temperature sensing and light sensing functions, the temperature sensor 250 is used for sensing the temperature T in or near the detection cavity to realize temperature sensing and fire alarm. For a purely light-sensitive smoke detector, the temperature sensor 250 may be disposed in the smoke detector, for example, for sensing the temperature on a printed circuit board, or may be disposed on the surface of the smoke detector for sensing the ambient temperature. If the temperature gradient detected by the temperature sensors is greater than a predetermined temperature difference threshold, a fire is also indicated. The temperature gradient change can be used as an auxiliary criterion together with the optical signal criterion as a fire alarm judgment.

In the smoke detector 200 shown in fig. 2, the controller 240 collects the optical signal S detected by the optical receiver 230. The inventor of the present invention carefully analyzes the characteristics of the optical signal S within a period of time P after the smoke detector is powered on. The time period P described here is substantially between 30s and 180s, preferably 50s to 110s, more preferably 60s or 100s after power-up. Fig. 3A and 3B show waveforms of the optical signal S in the case of pollution and in the case of a fire alarm, respectively. As shown in fig. 3A, in a heavily contaminated situation, such as dust, the optical signal S is above a predetermined threshold Th, which may be the same as the fire threshold, shortly after power-up. Meanwhile, the optical signal S remains substantially stationary during the period P after power-up, i.e., exhibits only a slight fluctuation, the fluctuation range of which is, for example, within the fluctuation range R1 as shown in fig. 3A. Assuming that a fire occurs when the smoke detector 200 is powered on, the waveform of the optical signal S is shown in fig. 3B. As can be seen from fig. 3B, after power-up and initialization, the optical signal S is also greater than the threshold Th quickly, and exhibits a more significant fluctuation state in the time period P, for example, the fluctuation amount Δ S of the optical signal S is greater than the fluctuation range R1. Here, the fluctuation range R1 may be, for example, about ± 8%. Comparing fig. 3A and 3B, the inventors of the present invention propose that it is possible to distinguish between a contamination fault and a fire alarm according to whether the optical signal S fluctuates. For simplicity, the time period P shown in the figure is a predetermined time period after initialization. Since the time from power-on to initialization of the smoke detector is relatively fixed, the time period P in the figure can also be understood as a predetermined time period after power-on.

FIG. 4 schematically shows a flow chart of a method of reporting a contamination fault according to one embodiment of the invention. The method illustrated in fig. 4 may be performed by the controller 240 in fig. 2. As shown in fig. 4, the method flow begins at step S110. In step S110, the smoke detector 200 is powered on. In step S120, the controller 240 completes the initialization process. After initialization, in step S130, the controller 240 collects the detected light signal S from the light receiver 230 for a period of time P. Further, in step S140, it is determined whether the optical signal S is greater than a threshold Th. The threshold Th may be a threshold for reporting a fire alarm. If the optical signal S is smaller than the threshold Th, it indicates that the dust in the detection chamber is not serious and there is no fire, and the flow goes to step S190 to enter the normal operation. Regular operation here refers to regular operation of the smoke detector during operation, including for example monitoring dust status, and enabling a dust compensation algorithm.

In fig. 4, if the light signal S is greater than the threshold Th at step S140, it indicates that either a fire alarm or a contamination fault is present. To distinguish between a contamination fault and a fire alarm, the flow proceeds to step S450. In step S450, the controller 240 further determines whether the fluctuation amount Δ S of the optical signal S exceeds a predetermined fluctuation range R1. If the optical signal S exhibits a slight fluctuation, for example, as shown in fig. 3A, the fluctuation amount Δ S thereof falls within the fluctuation range R1 in the time period P, indicating that the optical signal S is greater than the threshold Th due to dust or contamination, the flow proceeds to step S460. In step S460, the controller 240 reports a pollution FAULT message FAULT. On the contrary, if the optical signal S exhibits significant fluctuation, for example, as shown in fig. 3B, the fluctuation amount Δ S exceeds the fluctuation range R1, which indicates that the optical signal S is greater than the threshold Th due to smoke, the flow proceeds to step S480. In step S480, the controller 240 reports a fire ALARM message ALARM. Here, alternatively, step S480 may be omitted, that is, when it is determined in step S450 that Δ S exceeds the fluctuation range R1, step S190 is directly entered for normal operation. At this time, in normal operation, the controller 240 reports the fire ALARM message ALARM because the optical signal S is greater than the fire threshold Th.

In the method flow shown in fig. 4, the controller 240 not only determines a fire alarm according to whether the detected optical signal S is greater than the threshold Th, but also further distinguishes between a pollution fault and a fire alarm according to whether the optical signal S fluctuates significantly within a predetermined time period P after power-up. By using the method shown in fig. 4, the smoke detector 200 can report the pollution fault message in time after being powered on, and can also report the fire alarm in time if a fire occurs during power on, without being interfered by pollution. Thus, the dust test previously described can be successfully passed using the method shown in FIG. 4.

In order to increase the accuracy of the pollution fault judgment, the inventor of the present invention further proposes to adopt a judgment method with a dual-fluctuation-range criterion as shown in fig. 5A and 5B, and a method flowchart thereof is shown in fig. 6. Specifically, fig. 5A and 5B show waveforms of the optical signal S in the case of contamination and in the case of a fire alarm, respectively. As shown in fig. 5A, in a case where dust is seriously contaminated, after the smoke detector is powered on and the initialization is completed, the light signal S is quickly greater than the threshold Th of the fire alarm. Meanwhile, the optical signal S exhibits a slight fluctuation in the period P after the initialization, that is, the fluctuation amount Δ S of the optical signal S falls within the fluctuation range R2. Here, the fluctuation range R2 is preferably less than ± 8%, more preferably equal to or less than ± 5%, and particularly preferably equal to 2%. As shown in fig. 5B, if a fire occurs during power-up, the optical signal S is also rapidly greater than the threshold Th, and the optical signal S exhibits a significant fluctuation in the period P after initialization, for example, the fluctuation amount Δ S is greater than the fluctuation range R3. Here, the fluctuation range R3 is larger than the fluctuation range R2. The fluctuation range R3 may be, for example, greater than. + -. 8%, or even greater than or equal to. + -. 10%.

FIG. 6 illustrates a method of reporting a contamination fault according to another embodiment of the present invention, wherein a dual range of motion criterion is utilized as shown in FIGS. 5A and 5B. In fig. 6, the method flow from steps S110 to S140, S190, S460 and S480 are the same as those shown in fig. 4, and are not described again here. Unlike fig. 4, in step S140, if the optical signal S is greater than the threshold Th, the process proceeds to step S650. In step S650, the controller 240 further determines whether the fluctuation amount Δ S of the optical signal S exceeds a smaller predetermined fluctuation range R2. If the optical signal S exhibits a slight fluctuation, for example, the fluctuation amount Δ S is within the fluctuation range R2 as shown in fig. 5A, it indicates that the optical signal S is larger than the threshold Th due to dust or contamination, and the flow proceeds to step S460. In step S460, the controller 240 reports a pollution FAULT message FAULT. On the contrary, if the fluctuation amount Δ S of the optical signal S is larger than the fluctuation range R2, the flow proceeds to step S670. In step S670, the controller 240 further determines whether the fluctuation Δ S of the optical signal exceeds a larger fluctuation range R3, and if so, it indicates that the optical signal S is greater than the threshold Th and is caused by smoke, and the process proceeds to step S480. In step S480, the controller 240 reports a fire ALARM message ALARM. If the fluctuation amount Δ S of the optical signal S happens to fall between the fluctuation range R2 and the fluctuation range R3, an alternative processing manner is to repeat steps S140 to S670 again after a certain time interval. In case of a fire alarm, Δ S will inevitably exceed the fluctuation range R3 after a certain time. In the case of contamination, Δ S inevitably falls within the fluctuation range R2 after a period of stabilization.

In the method flow shown in fig. 6, the controller 240 uses the dual ranges R2 and R3 as criteria to distinguish between a contamination fault and a fire alarm. By adopting a dual-fluctuation range criterion, a pollution fault is judged only when the fluctuation of the optical signal S is small (within a fluctuation range R2), and a fire alarm is judged only when the fluctuation of the optical signal S is obvious (greater than a fluctuation range R3). Therefore, compared with the single fluctuation range R1 criterion, the dual fluctuation range criterion is more accurate in distinguishing the pollution fault and the fire alarm, and false alarm and missed fire alarm can be further reduced.

To further reduce the false alarm of a fire alarm, the inventors of the present invention further propose to use the temperature gradient as an additional criterion to distinguish between a contamination fault and a fire alarm. Fig. 7A and 7B show a waveform diagram of the optical signal S detected by the optical receiver in case of a fire alarm and a waveform diagram of the temperature T sensed by the temperature sensor, respectively. As shown in fig. 7A, for example, in the case of combustion of organic materials such as plastics or combustion of wood, the fluctuation of the optical signal S at the initial stage of a fire may not be significant, and the fluctuation amount Δ S is likely to fall between, for example, the fluctuation range R2 and the fluctuation range R3. A further temperature gradient can then be introduced as an auxiliary criterion. As shown in fig. 7B, in the time period P, the temperature T increases rapidly in the case of a fire, and the temperature increase Δ T is larger than the temperature difference threshold T4. On the other hand, the temperature T hardly changes significantly in the case of contamination. Here, the temperature difference threshold T4 is preferably a fire threshold of the temperature sensitive detector, and is preferably equal to or greater than 8 ℃, and more preferably equal to or greater than 10 ℃.

FIG. 8 illustrates an example pollution fault reporting method incorporating a temperature gradient criterion in accordance with another embodiment of the present invention. Steps S110 to S670, steps S460, 480 and step S190 in fig. 8 are the same as those shown in fig. 6, and are not described again here. Unlike fig. 6, in step S670, if the fluctuation amount Δ S of the optical signal S falls just between the fluctuation range R2 and the fluctuation range R3, the flow proceeds to step S875. In step S875, it is determined whether the temperature difference Δ T detected by the temperature sensor 250 during the time period P exceeds a predetermined temperature difference threshold T4. If the fire is over, as shown in fig. 7B, it indicates that a fire is occurring, and the flow proceeds to step S480. In step S480, the controller 240 reports a fire ALARM message ALARM. In step S875, if the temperature difference Δ T does not exceed the temperature difference T4, step S460 is performed to report a FAULT.

The example shown in fig. 8 combines a dual range criterion with a temperature gradient criterion. Alternatively, the temperature gradient criterion may be combined with the single fluctuation range criterion shown in FIG. 4. That is, when the fluctuation amount Δ S of the optical signal S is smaller than the fluctuation range R1, it may be further determined that the temperature difference Δ T within the period P does not exceed the temperature difference T4. If the ALARM is exceeded, a fire ALARM message ALARM is reported, otherwise, the ALARM is determined to be a pollution fault.

For the fire condition with small fluctuation of the initial optical signal, the introduction of the temperature gradient criterion can further reduce the fire alarm failure. Preferably, the temperature sensor 250 is an existing component of the smoke detector, and thus does not add cost and complexity to the hardware of the smoke detector.

It should be understood that although the specification has been described in terms of various embodiments, not every embodiment includes every single embodiment, and such description is for clarity purposes only, and it will be appreciated by those skilled in the art that the specification as a whole can be combined as appropriate to form additional embodiments as will be apparent to those skilled in the art.

The above-listed detailed description is only a specific description of a possible embodiment of the present invention, and they are not intended to limit the scope of the present invention, and equivalent embodiments or modifications such as combinations, divisions or repetitions of features, which do not depart from the technical spirit of the present invention, should be included in the scope of the present invention.

Claims

1. A smoke detector, comprising:

a detection chamber (210) adapted to receive gas with particles (10) from outside the smoke detector;

at least one light source (220) adapted to emit light into the detection chamber (210);

at least one light receiver (230) that detects a light signal (S) formed by scattering of particles (10) within the detection cavity (210);

a controller (240) coupled to said light source (220) and said light receiver (230) and configured to:

entering normal operation if it is determined that the optical signal (S) detected by said optical receiver (230) is less than a predetermined Threshold (TH) within a predetermined time period (P) after power-up; and

-issuing a contamination Failure (FAULT) message if it is determined that the light signal (S) detected by the light receiver (230) is greater than the predetermined threshold value (Th) and that the detected light signal (S) exhibits minor fluctuations during the predetermined period of time (P) after power-up during the predetermined period of time (P).

2. The smoke detector according to claim 1, wherein said detected light signal (S) exhibits a minor fluctuation within a first predetermined fluctuation range (R1, R2) during said predetermined time period (P) after power-up.

3. The smoke detector of any one of claims 1-2 wherein the controller (240) is further configured to: within a predetermined time period (P) after power-up, if it is determined:

the optical signal (S) detected by the optical receiver (230) is greater than the predetermined threshold value (Th), and

said detected light signal (S) exceeding said first predetermined fluctuation range (R1) within said predetermined period of time (P) after power-up,

a fire ALARM (ALARM) message is issued.

4. The smoke detector according to any one of claims 1-2, wherein the controller (240) is further configured to determine, within a predetermined time period (P) after power up, if:

said detected light signal (S) exceeding a second predetermined fluctuation range (R3) during said predetermined time period (P) after power-up,

a fire ALARM (ALARM) message is issued,

wherein the second predetermined fluctuation range (R3) is larger than the first predetermined fluctuation range (R2).

5. The smoke detector according to any one of claims 1-2, further comprising a temperature sensor (250) detecting a temperature (T) within said detection chamber (210) or in the vicinity of said detection chamber (210), and,

the controller (240) is further configured to, within a predetermined time period (P) after power-up, if it is determined:

the light signal (S) detected by the light receiver (230) is greater than the predetermined threshold value (Th),

said detected light signal (S) being smaller than said first predetermined fluctuation range (R1) within a predetermined time period (P) after said power-up, and,

-the temperature increase of said temperature sensor (250) within a predetermined time period (P) after said power-up exceeds a predetermined temperature difference threshold (T4),

a fire ALARM (ALARM) message is issued.

6. The smoke detector according to any one of claims 1-2, further comprising a temperature sensor (250) detecting a temperature within said detection chamber (210) or in the vicinity of said detection chamber (210), and,

the controller (240) is further configured to, if determined within a predetermined time period (P) after power-up:

said detected light signal (S) being greater than said first predetermined fluctuation range (R2) but less than a second predetermined fluctuation range (R3) during said predetermined period (P), and,

-the temperature increase of the temperature sensor (250) within the predetermined period of time (P) exceeds a predetermined temperature difference threshold (T4),

a fire ALARM (ALARM) message is issued.

7. A smoke detector according to any one of the claims 1-6, wherein said threshold value (Th) is a fire alarm threshold value or said predetermined temperature difference threshold value (T4) is a fire alarm temperature threshold value.

8. The smoke detector of any one of claims 1-7,

-said first predetermined fluctuation range (R1, R2) is equal to or less than ± 8%, preferably equal to or less than ± 5%, and more preferably equal to 2%;

the second predetermined fluctuation range (R3) is ± 8% or more, preferably ± 10% or more;

the predetermined temperature difference threshold (T4) is greater than or equal to 8 ℃, preferably greater than or equal to 10 ℃.

9. A smoke detector according to any one of the claims 1-8, wherein said predetermined period of time (P) is substantially between 2s and 180s, preferably 50s to 110s, more preferably 60s or 100s.

10. A method of reporting contamination failure by an optical smoke detector, comprising:

detecting an optical signal (S) for a predetermined period of time (P) after said smoke detector is powered on;

entering normal operation if said detected light signal (S) is determined to be less than a predetermined Threshold (TH) within a predetermined time period (P) after said powering up; -issuing a FAULT of contamination (FAULT) message if it is determined that said detected light signal (S) is greater than said predetermined threshold value (Th) and said detected light signal (S) exhibits minor fluctuations during said predetermined period of time (P) within a predetermined period of time (P) after said powering up.

11. The method according to claim 10, wherein the detected light signal (S) exhibits a minor fluctuation within a first predetermined fluctuation range (R1, R2) during the predetermined period of time (P).

12. The method of claim 10 or 11, further comprising: -said detected light signal (S) is greater than said predetermined threshold value (Th) during said predetermined period of time (P) after power-up, and said detected light signal (S) exceeds a second predetermined fluctuation range (R3) during said predetermined period of time (P), a fire ALARM (ALARM) message is issued, wherein said second predetermined fluctuation range (R3) is greater than said first predetermined fluctuation range (R2).

13. The method of any of claims 10-11, further comprising:

detecting a temperature in a detection chamber (210) of the smoke detector or in the vicinity of the detection chamber (210), an

-issuing a fire ALARM (ALARM) message if, during said predetermined period of time (P) after power-up, the detected light signal (S) is greater than said predetermined threshold value (Th), said detected light signal (S) is greater than said first predetermined fluctuation range (R2) but less than said second predetermined fluctuation range (R3) during said predetermined period of time (P), and the temperature increase during said predetermined period of time (P) exceeds a predetermined temperature difference threshold value (T4).

14. The method of any one of claims 10-13,

the first threshold is a fire alarm threshold;

the predetermined temperature difference threshold (T4) is a temperature threshold for a fire alarm;

the second predetermined fluctuation range (R3) is ± 8% or more, preferably ± 10% or more; or

15. A smoke detector, comprising:

-issuing a FAULT of contamination (FAULT) message if it is determined, within a predetermined time period (P) after said smoke detector has been powered up, that the light signal (S) detected by said light receiver (230) is greater than a predetermined threshold value (Th) and that said detected light signal (S) exhibits a minor fluctuation within a first predetermined fluctuation range (R1, R2) during said predetermined time period (P); and

-if it is determined that the light signal (S) detected by the light receiver (230) is above the predetermined threshold value (Th) and that the detected light signal (S) exceeds the first predetermined fluctuation range (R1, R2) within the predetermined time period (P) within a predetermined time period (P) after the smoke detector is powered on, issuing a fire ALARM (ALARM) message without issuing the contamination Failure (FAULT) message.

16. The smoke detector of claim 15, wherein the controller (240) is further configured to determine, within a predetermined time period (P) after power up, if:

a fire ALARM (ALARM) message is issued,

17. The smoke detector of claim 15, further comprising a temperature sensor (250) that detects a temperature (T) within said detection chamber (210) or in the vicinity of said detection chamber (210), and,

a fire ALARM (ALARM) message is issued.

18. The smoke detector of claim 15, further comprising a temperature sensor (250) that detects a temperature within the detection chamber (210) or in the vicinity of the detection chamber (210), and,

the temperature increase of the temperature sensor (250) within the predetermined period of time (P) exceeds a predetermined temperature difference threshold (T4),

a fire ALARM (ALARM) message is issued.

19. A smoke detector according to any one of the claims 15-18, wherein said threshold value (Th) is a fire alarm threshold value or said predetermined temperature difference threshold value (T4) is a fire alarm temperature threshold value.

20. A smoke detector according to any one of the claims 15-19,

the first predetermined fluctuation range (R1, R2) is equal to or less than ± 8%, preferably equal to or less than ± 5%, and more preferably equal to 2%;

21. A smoke detector according to any one of the claims 15-20, wherein said predetermined period of time (P) is substantially between 2s and 180s, preferably 50s to 110s, more preferably 60s or 100s.

22. A method of reporting contamination failure by an optical smoke detector, comprising:

-issuing a FAULT of contamination (FAULT) message if, within a predetermined period of time (P) after said powering up, said detected light signal (S) is greater than a predetermined threshold value (Th) and said detected light signal (S) exhibits minor fluctuations during said predetermined period of time (P); -not issuing said pollution Failure (FAULT) message but issuing a fire ALARM (ALARM) message if said detected light signal (S) is greater than said predetermined threshold (Th) within said predetermined period of time (P) after said power-up and exceeds said first predetermined fluctuation range (R1) within said predetermined period of time (P) after power-up.

23. The method of claim 22, further comprising: -said detected light signal (S) is greater than said predetermined threshold value (Th) during said predetermined period of time (P) after power-up, and said detected light signal (S) exceeds a second predetermined fluctuation range (R3) during said predetermined period of time (P), a fire ALARM (ALARM) message is issued, wherein said second predetermined fluctuation range (R3) is greater than said first predetermined fluctuation range (R2).

24. The method of claim 22, further comprising:

-issuing a fire ALARM (ALARM) message if the detected light signal (S) is greater than the predetermined threshold value (Th), said detected light signal (S) is greater than the first predetermined fluctuation range (R2) but less than the second predetermined fluctuation range (R3) during the predetermined period (P), and the temperature increase in the predetermined period (P) exceeds a predetermined temperature difference threshold value (T4), during the predetermined period (P) after power-up.

25. The method of any one of claims 22-24,

the first threshold is a fire alarm threshold;