WO2025068492A1 - Particle detection unit with integrated air flow sensor, and suction particle detection system - Google Patents

Abstract

The invention relates to a particle detection unit (100) designed to be used with a suction particle detection system (200), said particle detection unit (100) having a housing (110) comprising a detection chamber (120), which is delimited by the housing and which is shielded from ambient light and comprises a flow inlet (121) for introducing a fluid flow (F) into the detection chamber (120) and a flow outlet (122) for discharging the fluid flow (F) out of the detection chamber (120), a light emitter (130) and a light receiver (140) which are aligned relative to each other such that a detection region (DB) is defined within the detection chamber (120) in order to detect particles contained in the fluid flow (F) by superimposing the light emitted from the light emitter (130) on the area of incidence of the light receiver (140), and an air flow sensor (160) which comprises at least one pressure sensor (150) and at least one first section (161), a second section (162), and a cross-sectional constriction, wherein the first section (161) of the air flow sensor (160) has a first cross-sectional surface area (A1), and the second section (162) has a second cross-sectional surface area (A2). The at least one pressure sensor (150, 151, 152) is designed to measure a pressure difference present between the first and second section (161, 162). The aim of the invention is to provide a particle detection unit with a reliable, non-invasive monitoring process of the fluid flow, low pressure losses, long maintenance-free operating times, and a compact design with low production costs. This is achieved in that the air flow sensor (160) is arranged within the detection chamber (120) and downstream of the flow inlet (121) and upstream of the flow outlet (122) in the flow direction of the fluid flow (F).

Description

Particle detection unit with integrated airflow sensor and intake particle detection system

The invention relates to a particle detection unit designed for use with an intake particle detection system. The particle detection unit comprises a housing with a detection chamber delimited therefrom and shielded from ambient light, which comprises a flow inlet for the entry of a fluid flow into the detection chamber and a flow outlet for the exit of the fluid flow from the detection chamber. It also comprises a light transmitter and a light receiver, which are aligned with one another such that a detection region for detecting particles contained in the fluid flow is defined within the detection chamber by superimposing the light emitted by the light transmitter and the incidence region of the light receiver. It also comprises an air flow sensor, which comprises at least one pressure sensor and a first section, a second section, and a cross-sectional constriction, wherein the first section has a first cross-sectional area and the second section has a second cross-sectional area, and wherein the at least one pressure sensor is designed to measure a pressure difference existing between the first and the second section.

The invention also relates to an intake particle detection system, in particular an intake fire detection system for detecting a fire and/or the onset of a fire. The intake particle detection system comprises a fluid line system with at least one pipe and/or hose line, which opens into one or more monitoring areas via one or more intake openings for the respective withdrawal of a fluid sample, a fluid medium which is fluidly connected to the at least one pipe and/or hose line to generate a fluid flow along the at least one pipe and/or hose line, at least one particle detection unit which has a light transmitter and a light receiver for detecting particles contained in the fluid flow, and a detection chamber delimited by a housing with a flow inlet for the fluid flow to enter the detection chamber and a flow outlet for the fluid flow to exit. from the detection chamber, and an air flow sensor comprising at least one pressure sensor and a first section, a second section and a cross-sectional constriction, wherein the first section has a first cross-sectional area and the second section has a second cross-sectional area, and wherein the at least one pressure sensor is designed to measure a pressure difference existing between the first and the second section.

Particle detection units are often used for fire detection, particularly in buildings, vehicles, on ships, etc., whereby particles contained in the ambient air of a monitored area, e.g. smoke particles or aerosols, which indicate a fire or its origin, are detected by the particle detection unit. A monitored area is usually an area to be monitored in which people are present, (valuable) goods are stored, and/or there is an increased fire risk. Monitoring areas can be parts of a building, such as rooms, storage rooms, or server rooms; parts of a vehicle, e.g. a ship, train, bus, or aircraft, such as passenger compartments or engine rooms; but also an area in the immediate vicinity or within an object, such as a machine or a control cabinet.

For the detection of particles, the detection chamber, which is in fluid communication with the ambient air, is located inside the housing of the particle detection unit. The actual detection range, within which particles transported into the detection chamber with the ambient air can be detected, is usually defined by superimposing the light from the light transmitter and the incidence area of the light receiver within the detection chamber. During detection, the particles are illuminated by the light beams emitted by the light transmitter and can be detected by the light receiver either by the transmitted light reduced by the particles (transmitted light detector) or by the scattered light scattered by the particles (scattered light detector). To ensure that only the To ensure that the light emitted by the light transmitter reaches the particles in the detection area, the detection chamber is shielded from ambient light.

A well-known application for the use of particle detection units is aspirating smoke detectors, also known as aspirating particle detection systems or aspirative fire detection systems. Such aspirating particle detection systems comprise at least one pipe and/or hose line, which opens into one or more monitoring areas via one or more suction openings for the respective collection of a fluid sample, in particular an air sample. Multiple monitoring areas can be arranged, for example, in different areas of the same room, such as a (large) warehouse, but also in individual rooms of a building or sections of a vehicle, such as the passenger cabins of a ship. During normal operation of the aspirating particle detection system, a fluid flow is generated along the pipe and/or hose line to collect the fluid samples using a fluid medium, e.g., a blower or a fan. The fluid samples are then transported to the particle detection unit. To ensure the reliable operation of the intake particle detection system, the generated fluid flow must be continuously monitored using an airflow sensor. Changes in the fluid flow volume can be used to detect blockages, clogging, or even leaks.

An intake particle detection system with a particle detection unit and an airflow sensor is known, for example, from the international patent application WO 2004/034001 A1. The intake particle detection system, implemented as an aspiration fire detection system, comprises several intake pipes with respective intake openings, a detector, and a fan that draws air from the target space and supplies it to the detector. The detector essentially consists of a housing defining the detection chamber with an air inlet duct and an air outlet, the intermediate detection area within which fire parameters entrained in the intake air, such as smoke particles, can be detected, and The smoke sensors, of course. To monitor the volume flow of the intake air, an air flow sensor similar to a hot-wire anemometer is used. A heated wire extends centrally into the air flow, causing it to be cooled by the flowing air. The electrical power required to heat the wire corresponds to the amount of heat dissipated; this allows the volume flow to be calculated. In order to achieve the high measurement accuracy required for the reliable detection of blockages or damage to the intake pipe system, the influence of the temperature and density of the monitored air must be compensated. For this purpose, a temperature sensor, also centrally located, extends into the air flow. The disadvantages of the volume flow measurement described here are, on the one hand, the high energy consumption caused by the constant heating of the wire, and, on the other hand, the sensors must be precisely positioned centrally in the air flow, which increases manufacturing costs. Furthermore, the sensors positioned in the air stream are exposed to contamination and corrosion effects, which are caused in particular by the particles carried in the air stream.

Other measurement techniques for determining volumetric flow, especially for particle-laden flows, are known from the prior art. For example, the German translation of European patent DE 600 05 518 T2 discloses a particle detection system for which the volumetric air flow rate is to be determined using a differential pressure sensor and a pressure sensor for measuring air density. Patent US 4,856,328 B1 describes a differential pressure sensor for determining volumetric flow. Although the pressure sensors are in fluidic contact with different duct sections, they are not directly exposed to the flow to protect against corrosion caused by particles entrained in the flow.

An intake particle detection system with an air flow sensor, in which particles contained in an air flow are detected for fire detection, is also known, for example, from European patent EP 2 278 567 B1. The intake particle detection system comprises several intake pipes with respective sampling openings, which are connected to the Detector housings are connected. Within the detector housing, the following are arranged in sequence in the direction of flow: first, the air flow sensor, the intake device that generates the air flow, a filter for filtering the air flowing into the detection chamber, and finally the detection chamber itself, within which the actual detection of particles contained in the air takes place. Here, too, the air flow sensor can be designed, for example, as a cross-sectional constriction, with the pressure loss across the cross-sectional constriction being measured using a manometer. The disadvantage of the described arrangement is that the air flow sensor for monitoring the flow rate of the air flow is arranged outside the detection chamber, namely directly in front of the intake device. This not only requires more space, but also the flow rate measured by the air flow sensor does not exactly correspond to the actual flow rate in the detection chamber itself. However, the latter is crucial for reliably testing the functionality of an intake particle detection system.

It is the object of the present invention to eliminate the disadvantages of the prior art and to provide a particle detection unit and an intake particle detection system which, in particular, enables reliable, non-invasive monitoring of the fluid flow, the lowest possible pressure loss, long maintenance-free operating times and/or a compact design at low manufacturing costs.

The object is achieved by a particle detection unit according to claim 1 and an intake particle detection system according to claim 14.

A particle detection unit according to the invention, configured for use with an intake particle detection system of the type described in more detail above, is characterized in that the air flow sensor is arranged within the detection chamber and in the flow direction of the fluid flow after the flow inlet of the detection chamber and before its flow outlet. During normal operation of an intake particle detection system, a fluid flow is generated by means of a fluid, starting from intake openings leading into the area to be monitored and along the pipes and/or hoses containing the intake openings. For use with the intake particle detection system, the particle detection unit is fluidically connected to the pipes and/or hoses in such a way that the generated fluid flow enters the detection chamber of the particle detection unit via the flow inlet and exits again via its flow outlet. With regard to this fluid flow generated during normal operation, the air flow sensor is arranged according to the invention within the detection chamber itself, between the flow inlet and the flow outlet, namely downstream of the flow inlet and upstream of the flow outlet in the direction of fluid flow.

By integrating the airflow sensor directly into the detection chamber, precise monitoring of the actual fluid flow through the detection chamber is possible. At the same time, the space requirement is significantly reduced, as an additional airflow sensor implemented outside the detection chamber can be completely dispensed with. Monitoring the fluid flow based on the measured differential pressure also enables a non-invasive measurement method that eliminates the need to position measuring devices within the fluid flow. The detection chamber, with the integrated first and second sections of the airflow sensor, can preferably be manufactured as a one- or two-part component using an injection molding process, thereby increasing production quality, shortening production time, and reducing production costs.

Advantageous embodiments of the particle detection unit according to the invention are claimed in the subclaims and are explained in more detail below.

According to an exemplary embodiment, the air flow sensor can be realized in the form of a measuring orifice, wherein the cross-sectional constriction between the first section and the second section of the air flow sensor is arranged, and wherein the first cross-sectional area has a size identical to the second cross-sectional area.

According to an alternative exemplary embodiment, the cross-sectional constriction can be formed in the first section or in the second section of the air flow sensor, wherein the first cross-sectional area then has a size that differs from the second cross-sectional area.

According to one variant of the invention, the detection chamber of the particle detection unit is preferably divided into several segments or flow sections, and comprises, for example, an inlet channel adjacent to the flow inlet, an outlet channel adjacent to the flow outlet, and the detection region arranged therebetween. The inlet channel and the outlet channel are advantageously aligned or constructed such that the fluid flow entering via the flow inlet is guided through both the detection region and the air flow sensor.

In principle, it is conceivable to place the airflow sensor at any position within the detection chamber. However, in a further development of the previously described embodiment, it is advantageous for the airflow sensor to be arranged, according to one design variant, within the inlet channel of the detection chamber, downstream of the flow inlet and upstream of the detection area in the direction of fluid flow, or, according to another design variant, within the outlet channel of the detection chamber, downstream of the detection area and upstream of the flow outlet in the direction of fluid flow. The airflow sensor can, for example, be flush with the flow inlet or the flow outlet and/or, replacing the corresponding sections of the detection chamber, itself form the inlet channel or outlet channel of the detection chamber.

Depending on the design variant, a fluid flow generated during normal operation of an intake particle detection system flows through, after which into the interior of the detection chamber, i.e. first the detection area and preferably immediately adjacent to it the air flow sensor, or the other way around, first the air flow sensor and preferably immediately adjacent to it the detection area.

In order to minimize pressure losses, the air flow sensor can have a third section following the second section in the flow direction of the fluid flow, wherein the second section is designed as a nozzle with a smaller cross-sectional area than the cross-sectional area of the first section and the third section is designed as a diffuser with a continuously increasing cross-sectional area in the flow direction of the fluid flow.

For differential pressure measurement, the air flow sensor comprises at least one pressure sensor. According to an optional variant of the invention, the at least one pressure sensor is a differential pressure sensor that is pressure-transmittingly connected to the first and second sections of the air flow sensor. One possible implementation of differential pressure sensors comprises, for example, two measuring chambers with an intermediate membrane, wherein the measuring chambers are pressure-transmittingly connected to the first and second sections of the air flow sensor via respective connections. Based on the deflection of the membrane, the differential pressure between the two sections can be continuously recorded. The differential pressure sensor can also be designed as a pre-calibrated, so-called "MEMS" (Micro-Electro-Mechanical System) with a control chip and a sensor chip. Such a MEMS enables a compact, space-saving design, more cost-effective production due to the possibility of pre-calibration, and signal processing by the control chip, which simplifies signal processing in a connected microcontroller.

According to an alternative variant of the invention, the air flow sensor can comprise a first pressure sensor connected to the first section in a pressure-transmitting manner, and a second pressure sensor connected to the second section in a pressure-transmitting manner. The first and second pressure sensors are preferably Configured as absolute pressure sensors based on the piezoresistive or capacitive principle. The differential pressure between the first and second sections of the air flow sensor is calculated based on the difference between the pressure measured in the first and second sections.

According to an optional development of the invention, a pressure-transmitting solid barrier, in particular a fluid-permeable filter or a fluid-impermeable membrane, is arranged between the at least one pressure sensor and the first section, as well as between the at least one pressure sensor and the second section of the air flow sensor. The pressure-transmitting solid barrier can act as a diffusion barrier and thus protect the sensors and electronics from chemical influences. The at least one pressure sensor can be connected to the respective section(s) in a pressure-transmitting manner, for example via pipe- or hose-like connecting pieces or corresponding housing recesses. The fluid-permeable filter or the fluid-impermeable membrane is then positioned within the connecting pieces or housing recesses, filling the cross-sections there. In the simplest embodiment, a fine-pored, fluid-permeable foam can be used as a pressure-transmitting solid barrier. In an advantageous further development of the invention, a seal is arranged between the connection pieces or housing recesses that are connected to the detection chamber in a pressure-transmitting manner and the housing that delimits the detection chamber in order to avoid pressure losses.

According to an advantageous embodiment of the invention, the light transmitter, the light receiver, and the at least one pressure sensor are connected to a single, common circuit board, in particular to its front side, for signal transmission. The circuit board connected to the light transmitter and the light receiver represents, for example, a component of the particle detection unit, with the at least one pressure sensor then also being connected to this, the circuit board of the particle detection unit. When using a differential pressure sensor, the differential pressure sensor, the light transmitter, and the light receiver are each connected to connected to the same circuit board. When using a first and a second pressure sensor, the first pressure sensor, the second pressure sensor, the light transmitter, and the light receiver are connected to the same circuit board.

Optionally, the particle detection unit can also have a temperature sensor for measuring the ambient temperature in the detection chamber and/or an air pressure sensor for measuring the ambient pressure in the detection chamber. A thermocouple, a thermistor, or a PTC resistor, for example, can be used as the temperature sensor. Preferably, the temperature sensor, the light transmitter, and the light receiver are connected to the same circuit board, in particular the circuit board of the particle detection unit. The temperature sensor is connected to the detection chamber via an opening penetrating the housing defining the detection chamber. The air pressure sensor can be configured according to the piezoresistive or capacitive principle and can also be connected to the detection chamber via one or the same opening in the housing defining the detection chamber. When two pressure sensors are used to determine the differential pressure, the air pressure sensor can be configured as a first pressure sensor connected to the first section of the detection chamber in a pressure-transmitting manner. According to a particularly advantageous embodiment, the temperature sensor and the air pressure sensor are combined with each other and configured to simultaneously detect the ambient temperature or the ambient pressure present in the detection chamber.

According to an optional embodiment of the invention, it is advantageous that the at least one pressure sensor of the air flow sensor is connected to a control module for signal transmission, wherein the control module is configured to determine the volume flow based on the measured pressure difference. For the calculation, in particular the respective sizes of the cross-sectional areas of the first and second sections of the air flow sensor and/or their relationship to one another can be stored on the control module. Preferably, the geometric The conditions of the detection chamber are stored as a standardized transfer curve on the control module. The influence of manufacturing tolerances can be adjusted by specifying the endpoints of the transfer curve. The signal transmission connection can be implemented via lines, particularly cables, or wirelessly, e.g., via a LAN and/or Internet connection.

In a particularly advantageous development of this optional embodiment, the at least one pressure sensor of the air flow sensor is soldered directly to the circuit board of the particle detection unit, wherein the signal-transmitting connection to the control module, in particular a microcontroller soldered to the same circuit board, is then realized via printed circuit board lines. In this development, the light transmitter and the light receiver, the differential pressure sensor or the first and second pressure sensors, and the control module are each connected to the same circuit board, in particular soldered directly to its front side.

Optionally, the temperature and/or air pressure sensor can also be connected to the control module in a signal-transmitting manner, whereby the control module is then configured to determine the volume flow to compensate for the influence of the ambient temperature and/or the influence of the ambient pressure in the detection chamber.

The volume flow is calculated based on the measured pressure difference, depending on the density of the fluid flowing through the detection chamber. In the intended application, i.e. if the particle detection unit is used with an intake particle detection system, the fluid is usually air, the density of which under standard conditions, at an ambient temperature of 20°C and an ambient pressure of 1013.25 mbar, is approximately 1.2 kg/m ^3. With increasing ambient temperature and/or decreasing ambient pressure, the air density decreases; with decreasing ambient temperature and/or increasing ambient pressure, the Air density. The corresponding relationships are known and/or can be determined using appropriate calibration measurements under real conditions at different ambient temperatures and/or ambient pressures and stored, for example, in tabular form on the control module. Based on the values measured by the temperature and/or air pressure sensor and transmitted to the control module, the calculated volume flow can then be compensated. The volume flow measured value is preferably output in standard liters per minute, i.e., based on an ambient temperature of 0°C and an ambient pressure of 1013.25 mbar.

The density and/or viscosity of the fluid being sucked in, and consequently indirectly the ambient temperature and/or pressure, also influence the flow rate of a fluid used to generate the fluid flow, e.g., a fan, which may be part of the intake particle detection system. With constant fan voltage and increasing density and/or viscosity of the pumped fluid, the volume flow decreases, whereas with constant fan voltage and decreasing density and/or viscosity, the volume flow increases.

This indirect influence of ambient temperature and/or ambient pressure on the flow rate of the fluid can also be determined using appropriate calibration measurements under real conditions at different ambient temperatures and/or ambient pressures, e.g. stored in tabular form on the control module, and taken into account for the mathematical determination of the volume flow.

The relationships between ambient temperature and/or ambient pressure described above can therefore be determined in advance and stored on the control module, in particular a memory unit of the control module of the particle detection unit, and used there to compensate for the (actual) volume flow constantly determined by the air flow sensor. In an advantageous further development of the invention, the control module therefore comprises a memory unit which is optionally also provided for storing a predeterminable target volume flow or a predeterminable target volume flow range, wherein the control module is configured to detect deviations of the determined volume flow from the predefined target volume flow or the predefined target volume flow range.

In the intended application, i.e., if the particle detection unit is used with an intake particle detection system, the volume flow generated by the fluid is typically in a range of 20–75 l/min, preferably 30–60 l/min, depending on the fluid line system, in particular the length, diameter, and number of pipes and/or hoses, as well as the diameter and number of intake openings. The volume flow required during normal operation of the intake particle detection system can be stored on the memory unit of the control module either specifically, as a target volume flow value, e.g., 50 l/min, or covering a range, as a target volume flow range, e.g., 40–60 l/min. Alternatively, the percentage of the permitted deviation can be stored on the memory unit, e.g., a value between 10% and 50%, preferably 20%. The control module can be configured, for example, to detect deviations by comparing the actual volume flow determined by the airflow sensor with the stored target volume flow or target volume flow range continuously, periodically, or at one or more specific points in time. This can detect both undershoots and overshoots of the target volume flow or the target volume flow range.

A fall below the target volume flow or the target volume flow range can indicate blockages and/or clogging, and an exceedance of the target volume flow or the target volume flow range can indicate leaks in the fluid line systems connected to the particle detection unit. According to an optional variant of the invention, the control module is therefore designed to output a signal indicating leaks, blockages and/or clogging in the respective pipes and/or hoses or the corresponding intake openings of an intake particle detection system using the particle detection unit, based on a detected deviation from the specified target volume flow or the specified target volume flow range.

Since operational fluctuations in the volume flow always occur during normal operation, even when the intake particle detection system is fully functional, it is advantageous to define respective fault thresholds for the detected undershoot or overshoot of the specified target volume flow. In this case, the message indicating a fault in the fluid line system is only issued if the deviation of the determined actual volume flow from the stored target volume flow falls below or exceeds the respectively defined fault threshold. The fault thresholds must be adapted to the respective fluid line system and can preferably be set independently of one another in a range between 10% and 50%. For fluid line systems with high volume flows, e.g. a target volume flow of 75 l/min, it has proven advantageous to set the upper fault threshold for a reported exceedance of the target volume flow to a maximum of +20%, which in the specific example would correspond to a volume flow of 90 l/min. The lower fault threshold for a reportable undershoot of the target flow rate can be set to -40%, for example, which in this specific example would correspond to a flow rate of 45 l/min. With this example setting, the corresponding fault message is only output if the comparison between the stored target flow rate and the actual flow rate determined by the air flow sensor results in an overshoot of more than 20% or an undershoot of more than 40%, or in other words, if the determined actual flow rate leaves the target flow range specified by the fault thresholds, in this specific example between 45 l/min and 90 l/min.

The detection of deviations of the determined volume flow from the specified target volume flow or the specified target The volume flow range can preferably be determined by the control module of the particle detection unit itself. Alternatively, the determined volume flow values can also be transmitted to a further control module for further processing and evaluation, which is, for example, a component of the intake particle detection system, or to a third, independent device, in particular a mobile device, such as a laptop, a tablet, a mobile phone, or a diagnostic tool specifically configured to evaluate the monitoring data originating from a particle detection unit or an intake particle detection system. Communication between the control module of the particle detection unit and the further control module takes place, for example, via a data cable or wirelessly. In particular, it is also conceivable for the control module of the particle detection unit to communicate with a cloud via a LAN and/or Internet connection, with the function of the further control module then being carried out in the cloud.

The object of the invention stated at the outset is also achieved by an intake particle detection system, in particular a

Aspiration fire detection system for detecting a fire and/or the onset of a fire is solved. The intake particle detection system comprises a fluid line system with at least one pipe and/or hose line, which opens into one or more monitoring areas via one or more intake openings for the respective withdrawal of a fluid sample, a flow medium which is fluidly connected to the at least one pipe and/or hose line to generate a fluid flow along the at least one pipe and/or hose line, at least one particle detection unit, in particular according to one of the previously described embodiments, with a light transmitter and a light receiver for detecting particles contained in the fluid flow, and with a detection chamber delimited by a housing, which has a flow inlet for the entry of the fluid flow into the detection chamber and a flow outlet for the exit of the fluid flow from the detection chamber, and an air flow sensor which comprises at least one pressure sensor and at least a first section and a second section, wherein the first section has a first cross-sectional area and the second section has a second cross-sectional area with a size different from the first cross-sectional area, and wherein the at least one pressure sensor is designed to measure a pressure difference between the first and the second section.

According to the invention, the intake particle detection system is characterized in that the air flow sensor is arranged within the detection chamber and in the flow direction of the fluid flow during normal operation of the intake particle detection system after the flow inlet of the detection chamber and before the flow outlet of the detection chamber.

By integrating the airflow sensor, which is based on the measured differential pressure, directly into the detection chamber, precise, non-invasive monitoring of the actual fluid flow through the detection chamber is possible with significantly reduced space requirements and thus a particularly compact design of the particle detection unit. Furthermore, (additional) airflow sensors positioned elsewhere in the intake particle detection system can be dispensed with.

The compact design of the particle detection unit, each with its own integrated air flow sensor, facilitates a modular design for intake particle detection systems with multiple pipes and/or hoses, so-called “branches”.

According to an advantageous embodiment of the intake particle detection system, each pipe and/or hose line is assigned a respective particle detection unit with an integrated air flow sensor for pipe and/or hose line-specific monitoring of the fluid flow. By guiding the fluid flow within the respective detection chamber through both the detection area and the air flow sensor there, the fluid flows originating from different pipe and/or hose lines can each be specifically monitored for particles contained therein and/or deviations from the specified Volume flow can be monitored. Any faults can then be assigned to the corresponding pipes and/or hoses, which makes it much easier to locate, for example, a fire, the start of a fire and/or a leak, blockage or obstruction. It has proven advantageous to provide for the modular use of two particle detection units in an intake particle detection system, which can be fluidically connected to each pipe and/or hose, the so-called branches, for separate monitoring. If necessary, either one or both particle detection units can then be plugged into a common base unit of the intake particle detection system, which also contains the fluid. The fluid connection to the connected pipes and/or hoses and to the assigned particle detection unit is established via the base unit.

According to an exemplary embodiment, the air flow sensor can be realized in the manner of a measuring orifice, wherein the cross-sectional constriction is arranged between the first section and the second section of the air flow sensor, and wherein the first cross-sectional area has a size identical to the second cross-sectional area.

According to an alternative exemplary embodiment, the cross-sectional constriction can be formed in the first section or in the second section of the air flow sensor, wherein the first cross-sectional area then has a size that differs from the second cross-sectional area.

Preferably, according to a variant of the invention, the respective size of the first and/or the second cross-sectional area of the air flow sensor is designed for the volume flow or volume flow range provided by the fluid with which the fluid flow flows through the detection chamber.

The volume flow to be generated by the fluid depends on the diameter, length and number of pipes and/or hoses as well as the diameter and number of suction openings of the intake particle detection system, and is usually in a range of 20 - 75 l/min. The geometry of the respective sections of the air flow sensor is preferably designed such that the differential pressure can be determined for the entire volume flow range and additionally for additional, operational fluctuations in the volume flow of up to +/- 50% with the required accuracy and the lowest possible pressure loss. In particular, it has proven advantageous if the cross-sectional area of either the first or the second section roughly corresponds to the cross-sectional area of the pipes and/or hoses and the cross-sectional area of the other section is approximately 25 - 30% thereof. The ratio of the first and the second cross-sectional areas to one another is preferably also approximately 25 - 30% and particularly preferably 30%.

Because the geometry of the airflow sensor is designed for use across the entire volume flow range typical for intake particle detection systems, including operational fluctuations (approx. 20 l/min - 95 l/min), identical particle detection units with identical airflow sensor geometry can be assigned to the respective pipe and/or hose lines of the intake particle detection system, even if their line lengths and number of intake openings differ. To detect any deviations between the measured actual volume flow and the target volume flow or target volume flow range, respective target values, specifically adapted to the line length and number of intake openings of the corresponding pipe and/or hose line, can be stored on the respective control modules of the particle detection unit.

Further details, features, feature (sub)combinations, advantages and effects based on the invention will become apparent from the following description of a preferred embodiment of the invention and the drawings. These show in Fig. 1 is a schematic representation of a

Intake particle detection system with a branched pipe and/or hose line,

Fig. 2 shows an exemplary, two-part embodiment of a particle detection unit according to the invention with air flow sensor and circuit board in a perspective exploded view,

Fig. 3 is a perspective partial view of the particle detection unit from Figure 2 from above,

Fig. 4 is a section of the partial view of Figure 3 showing several sections of the air flow sensor, and

Fig. 5 shows a schematic representation of the geometry of the air flow sensor.

The figures are merely exemplary and serve only to clarify the invention. The same elements are designated by the same reference numerals.

Figure 1 shows a schematic representation of an intake particle detection system 200 with a pipe and/or hose line 210 and a base unit 220. The pipe and/or hose line 210, which is branched in the case shown here, comprises a plurality of intake openings 211 that open into one or more monitoring areas. The base unit 220 has a fluid 230, e.g., a fan, and two line connections 221. To take respective fluid samples from the monitoring areas, the fluid 230 generates a fluid flow F directed toward the base unit 220 along the pipe and/or hose line 210. For this purpose, the pipe and/or hose line is fluidically connected to one of the line connections 221. If necessary, a second pipe and/or hose line 210 (not shown here) can be connected to the other line connection 221. For each connected pipe and/or hose line 210, the basic device 220 can further comprise a respective particle detection unit 100, which is fluidically connected to the correspondingly assigned pipe and/or hose line 210. In the example shown here, only one pipe and/or Hose line 210 is connected to the basic unit and consequently only one particle detection unit 100 is shown.

Figure 2 shows an exemplary embodiment of a particle detection unit 100 according to the invention with an air flow sensor 160 and a circuit board 170 in a perspective exploded view. In the embodiment shown here, the particle detection unit 100 is manufactured in two parts using an injection molding process, with both parts together forming the housing 110 delimiting the detection chamber 120. The detection chamber 120, shielded from ambient light by the housing 110, extends approximately U-shaped from the flow inlet 121 to the flow outlet 122, with the detection area DB defined by the superposition of the light emitted by the light transmitter 130 and the incidence area of the light receiver 140 being located in the central U-segment. The two U-shaped legs form the inlet channel, which is directly flush with the flow inlet 121, and the outlet channel, which is directly flush with the flow outlet 122. In the present embodiment, the outlet channel has the air flow sensor 160, or the outlet channel is formed by the air flow sensor 160 itself.

The light transmitter 130 and light receiver 140, not shown in Figure 2, are mounted as so-called "surface-mount" LEDs directly on the surface or front of the circuit board 170. The mounting location provided for the light receiver 140 can be seen. Also directly connected to the front of the circuit board 170 are a pressure sensor 150 configured as a differential pressure sensor and a control module 180, e.g., a microcontroller, only indicated schematically here. The differential pressure sensor 150, as a component of the air flow sensor 160, is arranged directly below the outlet channel of the detection chamber 120 adjacent to the flow outlet 122 and is configured to measure a pressure difference present in the air flow sensor 160. Based on the measured pressure difference, the volume flow of the fluid flow F flowing through the detection chamber 120 is calculated using the control module 180. Figure 3 shows a perspective partial view of the particle detection unit 100 from Figure 2 from above, with the circuit board 170 (see also Figure 2) arranged directly below. The positioning of the light transmitter 130 and the light receiver 140, diagonally to one another, is clearly visible from the respective mounting locations on the circuit board 170. In the middle segment of the U-shaped detection chamber 120, the detection area DB is defined between the light transmitter 130 and the light receiver 140, in their overlapping area. The flow direction of the fluid flow F generated by the fluid 230 of the intake particle detection system 200 (see Figure 1) during normal operation is illustrated by an arrow. The fluid flow F enters the detection chamber 120 via the flow inlet 121, first flows through the subsequent detection area DB and then the air flow sensor 160, before exiting the detection chamber 120 via the flow outlet 122. Also formed in the middle segment of the U-shaped detection chamber 120, immediately in front of the light transmitter 130, is a recess penetrating the housing 110, via which a temperature and air pressure sensor 151 mounted on the circuit board 170 is connected to the detection chamber 120 for measuring the ambient temperature and pressure present in the detection chamber 120, transmitting temperature and pressure. The values measured by the temperature and air pressure sensor 151 can be used to compensate for the temperature and pressure influence on the calculation of the volume flow based on the pressure difference measured by the differential pressure sensor 150. Alternatively, and not shown in Figure 3, the differential pressure can be determined by calculating the difference between the measured pressure values of two absolute pressure sensors. In this case, the temperature and air pressure sensor 151 functions as the first pressure sensor, and a second pressure sensor 152 is then arranged in place of the differential pressure sensor 150 in the area of the outlet duct or air flow sensor.

The individual sections 161, 162, 163 of the air flow sensor 160 are highlighted in Figure 3 by means of a circular marking and are shown enlarged in a corresponding section in Figure 4. In the embodiment shown here, the air flow sensor 160 comprises a total of three sections, the first section 161 with a first cross-sectional area A1, the second section 162 with a second cross-sectional area A2 and the third section 163 with a third cross-sectional area A3, which follow one another in the stated order in the flow direction of the fluid flow F. To accelerate the fluid flow F, the second section 162 is designed as a nozzle, with a cross-sectional area A2 that is smaller than the cross-sectional area A1 of the first section 161. The pressure difference correspondingly present between the first section 161 and the second section 162 is measured by means of the differential pressure sensor 150. For this purpose, the differential pressure sensor 150 is connected in a pressure-transmitting manner to both the first section 161 and the second section 162 via a respective connection (see also Figure 2) and complementary recesses penetrating the housing 110 of the particle detection unit 100. With this non-invasive measurement method for determining the differential pressure, positioning the sensor directly within the fluid flow F is not necessary. To protect the sensor from potential chemical influences, pressure-transmitting solid barriers, such as a membrane or a fine-pored foam, can optionally be inserted into the recesses penetrating the housing 110 (not shown here). In the embodiment shown here, with respect to the flow direction of the fluid flow F, the second section 162 is followed by an optional third section 163 designed as a diffuser, the cross-sectional area A3 of which continuously increases in the flow direction for the controlled deceleration of the fluid flow F.

For use with an intake particle detection system 200, the geometry and dimensions of the air flow sensor 160 are designed to specifically match the operating parameters there, such as the total length and diameter of the pipes and/or hoses 210, the number and diameter of the intake openings 211 and the volume flow of the fluid flow F.

In Figure 5, the geometry and approximate size ratios of the individual sections 161, 162, 163 of the air flow sensor 160 are schematically indicated. For the design of the air flow sensor 160, the highest possible Measurement accuracy, a broad application range for different volume flows and the lowest possible pressure loss at the air flow sensor 160 must be taken into account. Based on test series it has been shown that for a volume flow range of 20 l/min to 95 l/min, a pressure difference of 250/270 Pa and a distance L between the pressure take-off points of the differential pressure sensor 150 of approximately 6 - 8 mm, an optimal compromise between measurement accuracy and pressure loss could be achieved for a ratio of the cross-sectional areas A2/A1 of the first and second sections 161, 162 of approximately 30%. The exact distance L between the two pressure take-off points depends on the sensor model used and is specified by it. The cross-sectional area A2 of the second section 162 or the nozzle is circular. The total length L2 of the nozzle is approximately 1.3 times the nozzle diameter. To further reduce pressure losses, the inlet of the nozzle is rounded. At the outlet of the nozzle, i.e. following the second section 162 in the flow direction of the fluid flow F, there is immediately adjacent the third section 163 or the diffuser, whose likewise circular cross-sectional area A3 continuously increases from the cross-sectional area A2 of the second section 162 over the average length L3 of the diffuser. The average length L3 of the diffuser corresponds approximately to 1.7 times the nozzle diameter. The dimensions and ratios mentioned are specifically designed for use with an intake particle detection system. In principle, however, other applications are also conceivable for the particle detection unit 100 according to the invention, in which case the geometry and dimensions can then be adapted accordingly.

List of reference symbols

100 particle detection unit

110 housings

120 detection chamber

121 Flow inlet

122 Flow outlet

130 light transmitters

140 light receivers

150 Pressure sensor, especially differential pressure sensor

151 first pressure sensor, in particular temperature and

Air pressure sensor

152 second pressure sensor

160 Airflow sensor

161 first section

162 second section

163 third section

170 circuit board

180 control module

200 intake particle detection system

210 Pipe and/or hose line

211 Intake opening

220 basic unit

221 line connection

230 fluids

A1 first cross-sectional area of the first section

A2 second cross-sectional area of the second section

A3 third cross-sectional area of the third section

DB detection range

F Fluid flow

L Distance between the pressure sampling points of the differential pressure sensor

L2 Length of the second section

L3 Length of the third section

Claims

Patent claims: 1. Particle detection unit (100) designed for use with an intake particle detection system (200), wherein the particle detection unit (100) has a housing (110) with a detection chamber (120) delimited therefrom and shielded from ambient light, which comprises a flow inlet (121) for the entry of a fluid flow (F) into the detection chamber (120) and a flow outlet (122) for the exit of the fluid flow (F) from the detection chamber (120), a light transmitter (130) and a light receiver (140) which are aligned with one another in such a way that a detection area (DB) for detecting particles contained in the fluid flow (F) is defined by superimposing the light emitted by the light transmitter (130) and the incidence area of the light receiver (140) within the detection chamber (120), and a Air flow sensor (160) comprising at least one pressure sensor (150, 151, 152) and at least one first section (161), a second section (162), and a cross-sectional constriction, wherein the first section (161) of the air flow sensor (160) has a first cross-sectional area (A1) and the second section (162) has a second cross-sectional area (A2), and wherein the at least one pressure sensor (150, 151, 152) is designed to measure a pressure difference existing between the first and the second section (161, 162), characterized in that the air flow sensor (160) is arranged within the detection chamber (120) and, in the flow direction of the fluid flow (F), downstream of the flow inlet (121) of the detection chamber (120) and upstream of the flow outlet (122) thereof. 2. Particle detection unit (100) according to claim 1, characterized in that the cross-sectional constriction is formed in the first section (161) or in the second section (162) of the air flow sensor (160), wherein the first cross-sectional area (A1) has a size different from the second cross-sectional area (A2). 3. Particle detection unit (100) according to claim 1 or 2, characterized in that the detection chamber (120) comprises an inlet channel adjacent to the flow inlet (121), an outlet channel adjacent to the flow outlet (122) and the detection region (DB) arranged therebetween. 4. Particle detection unit (100) according to claim 3, characterized in that the air flow sensor (160) is arranged within the inlet channel of the detection chamber (120), in the flow direction of the fluid flow (F) after the flow inlet (121 ) and in front of the detection area (DB) or within the outlet channel of the detection chamber (120), in the flow direction of the fluid flow (F) after the detection area (DB) and in front of the flow outlet (122). 5. Particle detection unit (100) according to one of the preceding claims, characterized in that the air flow sensor (160) comprises a third section (163) following the second section (162) in the flow direction of the fluid flow (F), wherein the second section (162) is designed as a nozzle with a cross-sectional area (A2) that is smaller than the cross-sectional area (A1) of the first section (161) and the third section (163) is designed as a diffuser with a cross-sectional area (A3) that continuously increases in the flow direction of the fluid flow (F). 6. Particle detection unit (100) according to one of the preceding claims, characterized in that the at least one pressure sensor (150) is a differential pressure sensor which is connected to the first section (161) and the second section (162) of the air flow sensor (160) in a pressure-transmitting manner. 7. Particle detection unit (100) according to claim 6, characterized in that a pressure-transmitting solid barrier, in particular a fluid-permeable filter or a fluid-impermeable membrane, is arranged between the at least one pressure sensor (150, 151, 152) and the first section (161) and/or the at least one pressure sensor (150, 151, 152) and the second section (162) of the air flow sensor (160). 8. Particle detection unit (100) according to one of the preceding claims, characterized in that the particle detection unit (100) comprises a circuit board (170) connected to the light transmitter (130) and the light receiver (140), wherein the at least one pressure sensor (150, 151, 152) is also connected to this circuit board (170). 9. Particle detection unit (100) according to one of the preceding claims, characterized in that the particle detection unit (100) has a temperature sensor for measuring the ambient temperature present in the detection chamber (120) and/or an air pressure sensor (151) for measuring the ambient pressure present in the detection chamber (120). 10. Particle detection unit (100) according to one of the preceding claims, characterized in that the at least one pressure sensor (150, 151, 152) of the air flow sensor (160) is connected to a control module (180) in a signal-transmitting manner, wherein the control module (180) is configured to determine the volume flow of the fluid flow (F) on the basis of the measured pressure difference. 11. Particle detection unit (100) according to one of claims 9 or 10, characterized in that the temperature sensor and/or the air pressure sensor (151) is connected to the control module (180) in a signal-transmitting manner, wherein the control module (180) is used to determine the volume flow of the fluid flow (F) to compensate for the influence of the air pressure present in the detection chamber (120). Ambient temperature and/or the influence of the ambient pressure there. 12. Particle detection unit (100) according to one of claims 10 or 11, characterized in that the control module (180) comprises a memory unit for storing a predeterminable target volume flow or a predeterminable target volume flow range and is configured to detect deviations of the determined volume flow from the predefined target volume flow or the predefined target volume flow range. 13. Particle detection unit (100) according to claim 12, characterized in that the control module (180) is configured to output a signal indicating leaks and/or blockages of respective pipe and/or hose lines (210) of a device using the particle detection unit (100). Intake particle detection system (200) indicating message based on a detected deviation from the specified target volume flow or the specified target volume flow range. 14. Intake particle detection system (200), in particular Suction fire detection system for detecting a fire and/or the occurrence of a fire, comprising at least one pipe and/or hose line (210) which opens into one or more monitoring areas via one or more suction openings (211) for the respective removal of a fluid sample, - a flow means (230) which is fluidically connected to the at least one pipe and/or hose line (210) for generating a fluid flow (F) along the latter, at least one particle detection unit (100) with a light transmitter (130) and a light receiver (140) for detecting particles contained in the fluid flow (F) and with a detection chamber (120) delimited by a housing (110) which has a flow inlet (121) for the entry of the fluid flow (F) into the detection chamber (120) and a flow outlet (122) for the outlet of the fluid flow (F) from the detection chamber (120), and an air flow sensor (160) which comprises at least one pressure sensor (150, 151, 152) and at least one first section (161), a second section (162) and a cross-sectional constriction, wherein the first section (161) has a first cross-sectional area (A1) and the second section (162) has a second cross-sectional area (A2), and wherein the at least one pressure sensor (150, 151, 152) is designed to measure a pressure difference existing between the first and the second section (161, 162), characterized in that the air flow sensor (160) is arranged within the detection chamber (120) and in the flow direction of the fluid flow (F) downstream of the flow inlet (121) of the detection chamber (120) and upstream of the flow outlet (122) is arranged. 15. Intake particle detection system (200) according to claim 14, characterized in that each pipe and/or hose line (220) of the intake particle detection system (200) is assigned a respective particle detection unit (100) with an integrated air flow sensor (160) for pipe and/or hose line-specific monitoring of the fluid flow (F). 16. Intake particle detection system (200) according to one of claims 14 or 15, characterized in that the cross-sectional constriction is formed in the first section (161) or in the second section (162) of the air flow sensor (160), wherein the first cross-sectional area (A1) has a size that differs from the second cross-sectional area (A2), and the respective size of the first and/or the second cross-sectional area (A1, A2) of the air flow sensor (160) is adapted to the volume flow or volume flow range generated by the flow medium (230) with which the fluid flow (F) flows through the detection chamber (120).