EP2718917A1

EP2718917A1 - Smoke alarm and method for operating same

Info

Publication number: EP2718917A1
Application number: EP12718918.1A
Authority: EP
Inventors: Gerhard Röpke; Gerhard Niederfeld
Original assignee: Ista International GmbH; Job Lizenz GmbH and Co KG
Current assignee: Ista International GmbH; Job Lizenz GmbH and Co KG
Priority date: 2011-06-09
Filing date: 2012-04-27
Publication date: 2014-04-16
Anticipated expiration: 2032-04-27
Also published as: WO2012167858A1; DE102011105183A1; EP2718917B1

Abstract

The invention relates to a device and a method for operating a smoke alarm having at least one light-transmitting unit (1) and at least one light-receiver unit (6), wherein the light receiver unit (6) receives light (5) which is emitted by the light transmitting unit (1) and is scattered/reflected in at least one light measuring section (R1, R2), wherein the light measuring section (R1, R2) is arranged at least partially outside a housing which accommodates the components of the smoke alarm and in which an intensity-modulated light (2) is emitted with the light-transmitting unit (1) in a measuring step starting from a transmission starting time (T0), wherein the frequency of the intensity modulation changes over time according to a predefined modulation function (8), and the light-receiver unit (6) is tuned to an intensity modulation frequency, which is to be received, of light (5) which is received from the light measuring section (R1, R2), in such a way that starting from an adjustable reception time (TE) the tuned reception frequency changes with the same modulation function (10), and a receiver output signal (11) is detected during the frequency tuning.

Description

Smoke detector and method for its operation

The invention relates to a method for operating a smoke detector with at least one light emitting unit and at least one light receiver unit, wherein the light receiver unit receives from the light emitting unit and emitted in at least one light measuring section scattered / reflected light, wherein the light measuring path at least partially outside of the components of the Smoke alarm receiver receiving housing is arranged.

The invention further relates to a smoke detector with at least one light emitting unit and at least one light receiver unit, wherein the

Light receiver unit is configured to receive from the light emitting unit emitted and scattered in at least one light measuring section / reflected light, wherein the at least one light measuring path at least partially outside of the components of the smoke alarm receiving

Housing is arranged.

Smoke detector of this type and method for operating such

Smoke alarms are basically known in the prior art,

for example from the publication EP 1 191 496 B2.

This publication already describes a smoke detector or a method of the aforementioned generic type, in this publication, the problem is addressed that in the scattering point of such a smoke detector a Scattering of the emitted light can not only be caused by smoke, but also by foreign objects, such as ladders, for

Crafts or boxes stacked high up in the ceiling, as well as by spiders or other insects that are in the

Surrounding area of the scattering point are located.

In order to overcome this problem, the cited publication discloses a method or a smoke detector in which the temporal profile of the received signal of the light receiver is analyzed by means of a processor in order to conclude on the basis of the time course whether smoke or another foreign body is present in the scattering point ,

Thus, it is pointed out that with increasing smoke an increasing intensity of the scattered light signal is to be registered with increasing smoke, whereas when a foreign body penetrates into the scattering point over time a jump function is to be detected in the received signal, which after the jump returns to a fixed signal passes.

The publication also mentions the possibility of additionally using an ultrasonic sensor in such a smoke detector in order to be able to monitor an area around the scattering point in addition to the previously mentioned monitoring of the scattering point.

A disadvantage of this aforementioned prior art that an elaborate, to be implemented with a microprocessor and programmed by a software analysis of the time course of the received signal must be made in order to obtain information about the triggering event of stray light occurring or that for a desired around the scattering point monitoring an additional sensor in the manner of a

Ultrasonic sensor must be used. These measures make the smoke detector of this type as technically complex and costly. It is therefore the object of the invention to provide an alternative method or an alternative smoke detector, with which it is possible, on the one hand to distinguish between different events, the one to

Occurrence of scattered light, in particular to distinguish the occurrence of smoke within a light-measuring distance of objects and also to provide a cost-effective way without additional sensors to monitor the environment of a smoke detector to disturbing objects.

According to the invention, this object is achieved by a method of the aforementioned generic type, in which further in at least one measuring step, preferably in repetitive measuring steps from a

With the light emitting unit, an intensity modulated light is emitted into the light measuring path, the frequency of the intensity modulation changing with time after a predetermined modulation function, and the light receiving unit changing to a frequency to be received

Intensity modulation of light received from the light measuring path is tuned so that the tuned receiving frequency changes with an adjustable starting time with the same modulation function and during the frequency tuning a receiver output signal is detected or formed.

Accordingly, the object is also achieved by a smoke alarm device of the generic type mentioned in the introduction, in which the light-emitting unit is set up to emit an intensity-modulated light in a measuring step, preferably several measuring steps, starting from a transmission start time

Modulation frequency changes with time after a given time

Modulation function changes and the light receiver unit to one

receiving frequency of an intensity modulation of light received from the light measuring path is tunable so that from an adjustable

Receive the tuned receive frequency with the same

Modulation function changes. An essential core idea of the invention here is that the light receiver unit used is not sensitive to any light signal received from the light measuring path, but is only susceptible to those light signals whose intensity modulation frequency is instantaneous

Receive coincides with the tuned to the light receiver unit receiving frequency.

Thus, a light receiver unit of the type according to the invention generates

Preferably, an output signal which is different from zero only if the currently tuned frequency of the light receiver unit to the

Intensity modulation frequency of a receiving light signal corresponds, otherwise, however, no output signal of the receiver is generated.

Due to the inventive design that a transmission start time is set in the implementation of the method or in the smoke detector according to the invention and is known and the vote of the light receiver unit to a frequency to be received intensity modulation takes place only from an adjustable reception time, by the time period between the transmission start time and the reception time are determined in advance, how long the running time of a receivable light signal between the light emitting unit and

May be light receiver unit or due to the fixed

Propagation speed of the light and the fixed geometry of transmitter and receiver, from which spatial distance between the light emitting unit and the light receiver unit, a detectable scattered light signal can be detected.

Lying in the light measuring path of the path of the light emitting unit

emitted light signal and the path of the scattered by an object / smoke light signal to the light receiver substantially parallel to each other, which can be achieved by the geometric arrangement of light emitting unit and light receiver unit, as well as the emission direction of the transmitting unit, the distance to the light receiver unit results from one scattered light signal is receivable, in a simple way out of the context: distance = speed of light / 2 ^* (reception time - start time)

Only scattered light signals that obey this relationship have a current one at the time of reception at the light receiving unit

Intensity modulation frequency with the currently tuned

Receive frequency match and thus generate a received signal.

Scattered light signals from other distance ranges may, if appropriate, impinge on the light receiver unit, but at this time have no matching to the currently tuned reception frequency intensity modulation and are therefore at least substantially not perceived by the light receiver unit.

As a function of the time duration between the transmission start time and the reception time, it is therefore essentially possible to set any desired interval at which distance from the light receiver unit the monitored scattering point of the smoke alarm device is located.

Thus, the invention of the type described above has the advantage that not only a single scattering point at a certain distance from the light receiver unit can be monitored with this method or such a functioning smoke alarm, but basically any distance can be monitored. Accordingly, for each measurement step to be carried out, it is also possible to individually determine in advance the distance at which scattered light is to be sampled.

Advantageously, therefore, with the aid of the invention, future requirements for smoke detectors may also be met, indicating that during operation of a smoke alarm, it must be ensured that a certain prescribed environment around the smoke alarm is not blocked by objects obstructing safe smoke detection. Depending on the intervals set in such reguiarities, which must be checked, the invention makes it possible to preselect the time difference between the transmission start time and the reception time, and thus in exactly that

desired distance to the smoke detector or its receiver unit to be checked for stray light.

In a particularly preferred embodiment of the invention, it may be provided that the light receiver unit is tuned so that it not only outputs a non-zero receiver output signal when the frequency of the intensity modulation of the receiving light exactly matches the currently tuned frequency of the light receiver unit, but already even if the frequency of the intensity modulation of the

received light within a frequency bandwidth with at the

Light receiver unit matched frequency matched. In this case, it may then be provided in a further particularly preferred embodiment that the frequency bandwidth of the light receiver unit is adjustable.

Thus, a sensitivity of the light receiver unit within a certain preferably adjustable frequency bandwidth, that a scattered light signal is received not only if it comes from a fixed exactly by the time interval between the transmission start time and reception time spatial distance to the light receiver unit, but also if the

Light scattering occurs in a spatial interval whose length is defined by the frequency bandwidth and the distance to the light receiver unit is given by the time difference between the reception time and the transmission start time.

Thus, a smoke detector or a method of the type according to the invention therefore has the further advantage that not only the monitored distance is adjustable, but also by the adjustable frequency bandwidth

Measuring section can be defined in which a review of scattered light takes place. The invention thus offers the possibility of a virtual outside of the

To provide smoke alarm detector lying measuring chamber whose length extension is defined in the direction of light propagation or backscattering the light receiver unit by the set frequency bandwidth of the receiver and the distance to the light receiver unit is defined by the time interval between the transmission start time and reception time.

For each measurement step to be performed, a reception time can be predetermined in advance by an electronic unit of the smoke alarm, the time difference between the reception time and the transmission start time being the one

Distance to the housing of the smoke alarm is defined, from which the light to be detected in the measuring step should be scattered / reflected. Furthermore, the frequency bandwidth of the light receiving unit can be set around the distance to be checked as a function of a desired interval interval defined by the bandwidth.

For example, there is the ability to perform a measurement in several measuring steps always in the same measuring distance interval in a given distance or between the measuring steps by changing the parameter of the time interval between the transmission start time and the receiving time

Change distance position of the monitored measuring distance interval and / or by changing the frequency bandwidth, the interval length of the monitored

To change the measuring range.

In a particularly simple embodiment of the invention, it may be provided to use such a function for the modulation function in the emission of the intensity-modulated light, according to which the frequency is linearly changed over time, for example linearly increases or decreases. Similarly, the same modulation function is thus also used to set the receivable frequency at the light receiver unit. Of course, it is also possible to use deviating modulation functions without limiting the generality. Preferably, a chosen modulation function ensures that the time derivative of the frequency is not equal to zero at any time of the modulation. A modulation function may preferably be continuous. Furthermore, a light signal is preferably emitted by the light-emitting unit only if an intensity modulation according to the selected function also takes place. The modulation takes place over a predetermined

Modulation time, so that a pulse-like light signal is emitted in the length of the modulation time. For example, at the beginning of the modulation, a light source in the light-emitting unit, e.g. a laser or light emitting diode

switched on and off at the end of the modulation time.

A particularly significant advantage of the method according to the invention is that the light receiver unit always provides an output signal of the same type, namely a zero signal except for noise components if no scattered signal reaches the receiver unit from the measurement interval determined by the time interval (between reception time and transmission start time) and frequency bandwidth but it generates a signal having a first edge, in particular a rising edge, then a

Plateaubereich and a subsequent second edge, in particular a falling edge. If necessary. Here, the height of the plateau region can change, for example, as a function of the intensity of the scattering occurring, which has an effect on the overall intensity of the received light signal.

The method according to the invention or a smoke detector which makes use of this method thus operates essentially with always the same type of received signal, so that in contrast to the prior art of the type described above, no temporal analysis of the course of the

Receive signal is carried out to draw from the received signal conclusions on the events in the scattering point. Rather, in the invention by prior parameter setting of

Scattering point or a measuring distance interval, which is monitored for scattering and defines its distance from the receiver, so that in knowledge of these preselected parameters the occurrence or non-occurrence of a

Receiving signal, in particular of the type described above, is evaluated.

In this case, for example, there is the possibility between the emergence of scattered light due to a solid object or by smoke

metrologically by the preselection of the parameters to be set, ie time interval between the transmission start time and reception time or

Distinguish frequency bandwidth, especially in preselection and

Carrying out the measurement in several measuring steps.

For example, it is typical of the occurrence of smoke that smoke not only occurs singularly at a particular specific location, but in a local area. So, when performing multiple,

successive measuring steps in a monitored measuring distance interval always be detect a received signal when this measuring distance interval is pushed spatially relative to the receiver between several measuring steps, for example, by varying the distance between the start time and reception time. Assuming an even density distribution of smoke within a predetermined interval, if this interval is metrologically checked by varying the time interval between the transmission start time and reception time is always a received signal be detected, possibly with only slightly different altitude.

On the other hand, if there is a solid object in the vicinity of one

Smoke alarm according to the invention, it generates only a light scattering exactly at a very specific distance from the light receiver, in which there is a surface of this object. In spatial areas before or after this concrete distance range, however, no received signal will be detectable, if by appropriate parameter selection of temporal difference between the transmission start time and the time of reception, these areas located in front of and behind the scattering surface are checked for scattered light.

Thus, here a distinction is made between e.g. fixed objects and smoke not based on an evaluation of different temporal characteristics of the received signals caused thereby, as is the case in the prior art, but a distinction between these different ones

Scattering events occur by predetermining the parameter selection at the

Carrying out several measuring steps and measuring always identical reception signals generated thereby.

An electronics, the receiver unit to an inventive

Smoke alarm is followed, thus may have a much simpler structure than is the case in the prior art, since any temporal analysis of a signal waveform can be omitted. For example, a microprocessor initially mentioned in the prior art can either be completely eliminated or, if it is present for the evaluation of the received signal, at least no extensive programming for the purpose of detection is required

different possible time courses in the received signal.

According to the invention, it may accordingly be provided that in one

Smoke alarms of the type according to the invention various measurement scenarios are stored for retrieval, the checks on certain possible

Enable scattering events.

For example, For example, a measurement scenario may be provided which tests in several measuring steps whether or not there is smoke at a specific distance to the receiver unit and in a measuring path interval arranged around this distance. There may be another scenario for performing, if necessary, several measurement steps to determine whether or not there is a measurement step

certain pre-selected distance range to the receiver an interfering object is arranged. According to the invention, it can be provided, for example, that at regular intervals, for example, a sequence of measuring steps for checking for smoke is carried out in order to carry out the actual function of the smoke alarm, wherein in other, eg greater time intervals, a check for the presence of objects in the immediate Environment of the

Smoke detector to make.

In one embodiment of the invention, it may also be provided to carry out a series of measuring steps, in which between two measuring steps

Receiving time is changed relative to the transmission start time, in particular between the measuring steps is changed by an always constant amount of time. In this case, for example, the frequency bandwidth can be kept the same or else also undergo a change between the measuring steps.

Advantageously, the area around the smoke detector is checked successively at different distances to the light receiver for scattered light by this method. From the determination of whether a light receiver signal is generated in one or more measuring steps can be concluded whether in the

predetermined distance smoke is present (if several measurement steps a

Received signal generated) or whether a solid object is present (if only one or very few measuring steps, a received signal was generated).

It can also be provided in another embodiment, to perform a series of measuring steps, in which between the measuring steps

Receive time remains the same relative to the transmission start time, which means that it is always rehearsed for the occurrence of a scattered light event at a predetermined distance to the light receiver. In this case, it may then be provided, for example, over all measurement steps of the aforementioned series

Integrate receiver output signal. This succeeds, the

Resolution of the measuring method or a smoke alarm using this measuring method, for weakly scattering objects or persistent smoke, such as occurs in smoldering fires, compared to To increase the resolution of a single measurement by averaging at least two measurements.

In a preferred embodiment of the invention, it may be provided that with a light receiver unit not only light from a single light measuring path is receivable, but light from at least two different,

optionally even more light measuring paths can be received, in which light, preferably transmitted by the same light-emitting unit.

In this case, it can then be provided in a further preference that the different light measuring sections define different measuring directions, so that a predetermined range, e.g. a predetermined one

Angular environment can be checked by a smoke alarm.

Likewise, it may be provided that a smoke detector the

according to the invention not only a light-emitting unit and a

Photoreceptor unit, but a plurality of such unit pairings. For example, it can be provided for this purpose that a specific light measuring path is defined by each such pairing. For example, For example, a multiplicity of possible measuring paths may extend in a star shape, in particular in a plane around a smoke alarm.

Optionally, it may also be provided to provide a light-emitting unit which emits light in at least one plane by 360 degrees, with different light receivers on scattered light from different

Room areas or directions is checked. This is by a

Set higher-level electronics in the smoke alarm the transmission start time, which is then the same for all recipients, the

Receiving times, from which the modulation of the tuned Receiving frequency at the receiver is carried out for all existing

Light receiver may be the same or different.

An embodiment of the invention is shown in the following figures

shown. Show it

Figure 1 shows an embodiment with only one measuring section

2 shows an embodiment with several measuring sections

1 shows a schematic representation of only the arrangement of a light emitting unit 1 and a light receiver unit 6 of a smoke detector according to the invention, which is not shown in the figure with respect to its other components.

It is essential here that according to the inventive method the

Transmitted light unit 1 emits a light signal 2, which is modulated in intensity, the modulation frequency is temporally not constant, but a predefined function obeys, here in this embodiment, for example, a linear function that causes the light at the time of the beginning of the transmission first is modulated in intensity with a low frequency and this modulation frequency increases with increasing time. Later emitted light of the light signal 2 thus has a larger

Modulation frequency as light at the beginning of the light signal 2. This functional relationship may e.g. also be the other way round or described by a completely different function.

This light signal 2 then initially propagates over a distance R1 in space until it reaches an assumed obstacle 3, where it is scattered. The light scattering takes place, inter alia, also back towards the light receiver 6, on soft then after bridging the distance R2 between the light receiver 6 and obstacle 3, the scattered light signal 5 hits, which has the same modulation as the originally emitted light signal 2.

According to the invention, it is provided here, the light receiver unit 6 with respect to the possible receivable frequency of the intensity modulation of a

Stray light signal 5 to vote with the same modulation function, as was the case with the transmission of the light signal 2, which means that a

Stray light signal 5 is received regardless of its formation on the obstacle 3 only if the modulation of the receivable frequency of

Receiving unit 6 at a time TE is made at a time interval to the transmission at the time TO of the light signal 2, which corresponds to the time that the light needs to bridge the aforementioned distances R1 and R2.

By selecting this time interval between the transmission start time TO and the time TE of the beginning receiver modulation is thus determined which distance range relative to the light receiver 6 to a

Scatter event is checked.

FIG. 1 shows an amplitude modulation signal 7 with which the

Light transmitter 1 is driven, wherein the frequency of this amplitude signal 7 according to the function 8 changes over time. It will be the same function here as

Function 10 is used to determine the reception frequency of the receiver 6

for which this receiver is sensitive only to or in the vicinity of a frequency bandwidth.

By the time interval between the beginning of the modulation for transmitting the light signal 2, here the start time TO and the reception time TE, to which is started, the light receiving unit 6 with respect to its

To modulate sensitive frequency, therefore, the above-mentioned spatial distance between the receiver unit 6 and obstacle 3 is determined, in which case, when a scattered light signal from the set Distance to the light receiver 6 impinges on the receiver, a signal 11 is generated, as shown in the figure, otherwise not.

The plateau height of the received signal 11 may depend on the one hand on the strength of the scattering by the obstacle 3 and on the degree of

Overlap between the frequency currently set on the receiver and the frequency of the received light signal within the possible range

Frequency bandwidth. The shape of the received signal is otherwise always the same and has over time no characteristics specific to smoke or other objects.

Is the received signal with its currently occurring at the receiver

Modulation frequency exactly centric in the frequency bandwidth with respect to the currently set at the receiver frequency, so the plateau is maximum in height and decreases with increasing deviation, until that outside the frequency bandwidth no signal at the receiver with the illustrated

Signal form is present.

FIG. 2 shows, in a slight modification to FIG. 1, only a situation in which a plurality of objects 14 a, 14 b and 14 c each contribute to a scattering of light emitted here by the light transmitter 12.

Due to the different arrangements of the obstacles 14a-14c to transmitter and receiver 13, different transit times result, so that corresponding scattered light signals 17, starting from the emitted

Light signal 15 arrive at different times on the light receiver 13.

By the relative position between the reception time TE, to which the

Modulation of the reception frequency according to the function 18 begins, based on the time TO, at which the transmission of the signal takes place, can be discriminated, which lead the three signals 17 that arrive at the receiver to an output signal 19 of the receiver 13. It can therefore by temporally pushing the receiving time TE relative to the start time TO in a series of measuring steps, each with

different duration between start time TO and reception time TE also be found to be several at the same time in the environment of a

Smoke Alarms present objects scattered light events arise.

By the choice of parameters, in particular the setting of the duration between the start time and the time of reception, exactly the spatial distance to the receiver unit 12 can be determined.

Figures 1 and 2 show that the output signal 11 and 19 always has the same waveform, regardless of the distance at which a scattered light event takes place or by what type of event, the scattering takes place, so for example by an obstacle 3 or by diffuse smoke.

As described in the general part, a discrimination between solid objects and smoke is preferably made by the type of measurement series and the parameter selection made in a measurement series, in particular that for each

Measuring step individually defined time intervals between the start of the transmission and the reception time and the frequency bandwidth.

Claims

claims

1. A method for operating a smoke detector with at least one

Light emitting unit (1) and at least one light receiver unit (6), wherein the light receiver unit (6) receives light (5) emitted by the light emitting unit (1) and scattered / reflected in at least one light measuring section (R1, R2); Measuring section (R1, R2) is arranged at least partially outside of the components of the smoke detector receiving housing, characterized in that in one

Measuring step from a transmission start time (TO) with the light emitting unit (1) an intensity modulated light (2) is emitted, wherein the frequency of the intensity modulation with time after a predetermined

Modulation function (8) changes and of an electronics of the

Smoke alarm for a measuring step to be carried out

Receiving time (TE) is given, being defined by the time difference between the reception time (TE) and the transmission start time (TO) the distance to the housing of the smoke alarm from which the light to be detected in the measuring step (5) should be scattered / reflected and Then, the light receiver unit (6) is tuned to a frequency to be received an intensity modulation of the light measuring section (R1, R2) received light (5) that changes from the set reception time (TE) the tuned reception frequency with the same modulation function (10) and during frequency tuning

Receiver output signal (11) is detected.

2. The method according to claim 1, characterized in that the

Light receiver unit (6) is tuned so that it only outputs a non-zero receiver output signal (11) when the frequency the intensity modulation of the received light (5) within an adjustable frequency bandwidth of the light receiver unit (6) coincides with the tuned frequency.

3. The method according to any one of the preceding claims, characterized in that with the modulation function (8, 10) the frequency is changed linearly over time.

4. The method according to any one of the preceding claims, characterized in that the frequency bandwidth of the light receiving unit (6) is set in response to a desired distance interval defined by the bandwidth around the distance to be tested around.

5. The method according to any one of the preceding claims, characterized in that a series of measuring steps is carried out in which between two measuring steps, the reception time (TE) is changed relative to the transmission start time (TO), in particular between the measuring steps changed by an always constant amount of time becomes.

6. The method according to any one of the preceding claims, characterized in that a series of measuring steps is performed in which between the measuring steps, the reception time (TE) relative to the transmission start time (TO) remains the same and the receiver output signal (11) is integrated over all measuring steps.

7. The method according to any one of the preceding claims, characterized in that light from at least two different light measuring sections is received with a light receiver unit (6), in which light from the same

Light transmitting unit (1) is sent, in particular wherein the different light measuring paths are assigned to different measuring directions.

8. smoke detector with at least one light emitting unit (1) and at least at least one light receiver unit (6), wherein the light receiver unit (6) is arranged to receive from the light emitting unit (1) and scattered in at least one light measuring section (R1, R2) scattered / reflected light (5), wherein the light measuring section (R1, R2) at least partially outside of a Components of the smoke detector receiving housing is arranged, characterized in that the

Lichtsendeeinheit (1) is further set up in a measuring step from a transmission start time (TO) emit an intensity-modulated light (2), the modulation frequency with time after a predetermined

Modulation function (8) changes and of an electronics of the

Smoke alarm for a measuring step to be carried out

Receiving time (TE) can be specified, which on the time difference between the reception time (TE) and the transmission start time (TO) that distance to the housing of the smoke alarm is definable, from which the light to be detected in the measuring step (5) should be scattered / reflected and then the light receiver unit (6) is tuned to a frequency to be received intensity modulation of light received from the light path (5) that changes from the set reception time (TE) the tuned reception frequency with the same modulation function (10).

9. smoke detector according to claim 8, characterized in that the

Light receiver unit (6) is tunable so that it only outputs a non-zero receiver output signal (11) when the frequency of the intensity modulation of the received light (5) within an adjustable frequency bandwidth of the light receiver unit (6) coincides with the tuned frequency.