Particle sensor

Abstract

The present invention relates to a particle sensor (1) for detection and / or characterization of particulate matter in an aerosol stream (A), comprising a radiation detector (30) that is designed to detect radiation after interaction with particulate matter contained in the aerosol stream (A), the radiation detector (30) being at least partly covered by an EMC shielding (4) that is located in an interior (2a) of a housing of the particle sensor.

Description

[0001] Particle sensor

[0002] Description

[0003] The invention relates to a particle sensor (also called fine dust sensor) for the detection and / or characterization of particulate substances (e.g. fine dust particles) in an aerosol stream that is passed through the particle sensor.

[0004] Such particle sensors are known, for example, from EP3491362B and CN209946101.

[0005] With such sensors, it is often necessary to protect the actual sensor unit—in the case of a particle sensor, for example, a radiation detector—against the excessive influence of electromagnetic fields using what is known as EMC shielding. The electromagnetic compatibility (EMC) requirements for electronic devices, as defined in various standards, specifically require measures to protect such electronic components from external electromagnetic radiation. Therefore, conventional particle sensors typically feature an outer housing that encloses the entire electronics of the particle sensor and shields against the aforementioned electromagnetic radiation.

[0006] The disadvantages of such EMC shielding are their size and relatively high weight.

[0007] Based on this, the invention is based on the object of providing a particle sensor which is improved with regard to the above-mentioned problem.

[0008] This object is achieved by a particle sensor having the features of claim 1. Advantageous embodiments of the invention are specified in the dependent claims and are described below.

[0009] According to claim 1, a particle sensor (also called fine dust sensor) is disclosed for detecting and / or characterizing particulate substances (e.g. fine dust particles) in an aerosol stream passed through the particle sensor, comprising:

[0010] - a housing having an inlet for the aerosol stream and an outlet for the aerosol stream, wherein the housing further surrounds a flow channel communicating with the inlet and the outlet, through which the aerosol stream can be guided in a flow direction, - a radiation source configured to emit radiation into the flow channel such that the radiation interacts with particulate substances of the aerosol stream guided through the flow channel, and

[0011] - a radiation detector arranged in the flow channel, which is designed to detect radiation after interaction with particulate substances in the aerosol stream.

[0012] According to the invention, the radiation detector is at least partially covered by an EMC shield arranged in an interior space surrounded by the housing. The EMC shield can be arranged at least partially in the flow channel or facing it.

[0013] In particular, there is a relatively small EMC shield, which is preferably placed directly around the radiation detector (and in particular also the radiation source, see below).

[0014] According to a preferred embodiment of the invention, the EMC shield is oriented and shaped such that the aerosol or air flow over the radiation detector exhibits less turbulence, thus advantageously reducing the risk of particle deposition and contamination of the radiation detector. The side walls of the EMC shield are preferably beveled and do not form a 90° angle to a carrier or circuit board on which the radiation detector or EMC shield may be mounted.

[0015] Due to the compact EMC shielding, costs are reduced accordingly. This also applies to installation costs. The optimized aerosol flow advantageously reduces the risk of sensor contamination.

[0016] According to one embodiment of the invention, the radiation source is a laser or a light-emitting diode. Furthermore, according to one embodiment of the invention, the radiation detector is a photodiode.

[0017] Furthermore, according to a preferred embodiment of the invention, the EMC shield has a first side wall and a second side wall arranged behind it in the flow direction, wherein the first side wall is preferably continuously rising in the flow direction and the second side wall is preferably continuously falling in the flow direction. According to a preferred embodiment of the invention, the EMC shield has a cover wall that connects the two side walls to one another, preferably in one piece or integrally.

[0018] According to one embodiment, the cover wall preferably has an opening through which radiation can reach the radiation detector or radiation can be emitted from the radiation source.

[0019] According to a preferred embodiment of the invention, the housing surrounds a further flow channel for guiding an additional fluid flow, such that the additional fluid flow flows between the radiation detector and / or between the radiation source and the aerosol flow. The additional fluid flow flows between the aerosol flow and the radiation detector or the radiation source and thus shields the radiation detector / radiation source and protects these components from contamination by particles of the aerosol flow. In particular, the additional fluid flow can be a sheath flow that surrounds the aerosol flow. The further flow channel can in turn communicate with said inlet and / or said outlet. The additional fluid flow can be, for example, an air flow, in particular a filtered air flow.

[0020] According to a further embodiment of the invention, it is provided that the further flow channel is designed to direct the additional fluid flow onto the first rising side wall of the EMC shielding, so that the additional fluid flow can be guided over the EMC shielding.

[0021] Furthermore, according to a preferred embodiment of the invention, the additional flow channel is separated from the flow channel of the aerosol stream by a wall. In the area of ​​the EMC shield, the additional flow channel, according to a preferred embodiment, is in flow communication with the flow channel of the aerosol stream.

[0022] According to one embodiment of the invention, it is very particularly preferably provided that the EMC shield is designed such that the additional fluid flow guided over the EMC shield flows laminarly along the EMC shield. This can be ensured, for example, by the correspondingly rising or falling side wall, which here serve as guide elements for the additional fluid flow. According to a further preferred embodiment of the invention, it is provided that the particle sensor has a filter for cleaning the additional fluid flow upstream of the radiation detector and / or upstream of the radiation source. In other words, the fluid flow is first sucked through a filter so that it is free of particles. In this way, it can effectively prevent the radiation detector or the radiation source from becoming dusty and at the same time shield these components from the aerosol flow containing particles.

[0023] Furthermore, according to a preferred embodiment of the invention, it is provided that the radiation detector and / or the radiation source is / are arranged on a carrier plate.

[0024] According to a preferred embodiment of the invention, the carrier plate is a circuit board, in particular a printed circuit board.

[0025] Furthermore, according to a preferred embodiment of the invention, the radiation source and the radiation detector are integrated into a single sensor unit, which is at least partially covered by the EMC shielding, whereby, in particular, the radiation from the radiation source can now also be emitted through the opening in the cover wall. The radiation can therefore be emitted and detected in a compact manner.

[0026] Furthermore, according to a preferred embodiment, it is provided that the carrier plate together with a housing part of the particle sensor delimits the flow channel at least in sections.

[0027] According to a further embodiment of the invention, it is provided that the carrier plate has a through-opening for the passage of the additional fluid flow.

[0028] Furthermore, according to one embodiment of the invention, it is provided that the side walls and the cover wall of the EMC shield are formed from an electrically conductive material (in particular from a metal or a metallized plastic).

[0029] According to a preferred embodiment of the invention, the EMC shield is attached to the carrier plate. The EMC shield is preferably soldered to the carrier plate, in particular establishing an electrically conductive connection between the EMC shield and the circuit board. According to a preferred embodiment of the invention, the EMC shield further comprises a first base section that is connected to the first side wall and soldered to the carrier plate or circuit board.

[0030] Furthermore, according to a preferred embodiment, it is provided that the EMC shield has a second foot section which is connected to the second side wall and is soldered to the carrier plate or circuit board.

[0031] The particle sensor according to the invention can be designed to detect various particle sizes, in particular PM1.0, PM2.5, PM4, or PM10. For example, PM2.5 refers to particulate matter with a diameter of less than 2.5 micrometers.

[0032] In the following, embodiments of the invention as well as further features and advantages of the invention will be explained with reference to the figures. They show:

[0033] Fig. 1 is a sectional view of an embodiment of a particle sensor according to the invention,

[0034] Fig. 2 a detail of Figure 1,

[0035] Fig. 3 is a perspective view of the particle sensor, in particular a carrier plate of the particle sensor with the EMC shielding arranged thereon,

[0036] Fig. 4 a detail of Fig. 3, and

[0037] Fig. 5 is a plan view of a housing part of the particle sensor, which defines the flow channel and the further flow channel of the particle sensor.

[0038] Fig. 1, in conjunction with Figures 2 to 5, shows an embodiment of a particle sensor 1 according to the invention for detecting and / or characterizing particulate substances in an aerosol stream A that is passed through the particle sensor 1. The particle sensor 1 has a housing 2 having an inlet 20 for the aerosol stream A and an outlet 21 for the aerosol stream A, wherein the housing 2 further forms a flow channel 3 communicating with the inlet 20 and the outlet 21.

[0039] The particle sensor 1 further comprises a radiation source 31 (e.g. in the form of a diode that emits light, in particular a laser diode, e.g. a surface emitter (VC SEL)), which is designed to emit radiation L into the flow channel 3 (cf. Fig. 2), which is e.g. in the wavelength range from 500 nm to 1100 nm, in particular 640 nm to 950 nm, so that the radiation L can interact with particulate substances in the aerosol stream A guided through the flow channel 3 in a flow direction R. Furthermore, a radiation detector 30 (e.g. an optical sensor, in particular a photodiode) is arranged in the flow channel 3 and is designed to detect radiation from the radiation source 31 after it interacts with particulate substances in the aerosol stream A, in order to determine their concentration, for example. For this purpose, the particle sensor 1 can have corresponding evaluation electronics.Particularly preferably, the radiation source 31 and the radiation detector 30, as shown in Figures 1 to 5, are formed by a sensor unit 300 in which both components 30, 31 are integrated.

[0040] According to the invention, the radiation detector 30 or the sensor unit 300 is at least partially covered by an EMC shield 4, which is arranged in the housing 2 along the flow channel 3. The EMC shield 4 is fixed to a carrier plate 7, on which the sensor unit 300 is also arranged, specifically below the EMC shield 4, so that it extends beyond the sensor unit 300. The carrier plate 7 is designed as a printed circuit board 7, with the sensor unit 300 and the EMC shield 4 each preferably being soldered to the printed circuit board 7.

[0041] The housing 2 surrounds a further flow channel 3a for guiding an additional fluid flow A' such that the additional fluid flow A' flows between the radiation detector 30 or the radiation source 31 and the aerosol flow A. The further flow channel 3a can in turn communicate with the inlet 20 and / or the outlet 21. The further flow channel 3a is designed to guide the additional fluid flow A' such that it flows against the EMC shielding 4. The further flow channel 3a is separated from the flow channel 3 by a wall 60. The carrier plate 7 can have a through-opening 7a for the additional fluid flow A' to pass through, so that it is subsequently guided between the wall 60 and the carrier plate 7 to the EMC shielding 4.As can be seen in particular from Figures 2 and 4, the EMC shield 4 preferably has a first side wall 40 and a second side wall 41 arranged behind it in the flow direction R, wherein the first side wall 40 is designed to rise in the flow direction R and the second side wall 41 is designed to fall in the flow direction R. The two side walls 40, 41 are connected to one another in particular by a cover wall 42 of the EMC shield. The cover wall 42 preferably has an opening 43 through which the radiation source 31 can emit light L into the flow channel 3 and the radiation detector 30 can receive radiation from the flow channel.

[0042] The side walls 40, 41 and the top wall 42, as well as any other components of the EMC shield 4 (e.g., the foot sections 400, 401 described below), are preferably made of a material that is electrically conductive or comprises an electrically conductive material. The electrically conductive material can be, for example, a metal.

[0043] Particularly preferably, the EMC shield 4 is designed such that the fluid flow A', which is guided in the further flow channel 3a to the EMC shield 4 and shields the radiation detector 30 or the radiation source 31 from the aerosol flow A, flows laminarly over the EMC shield 4. This is ensured by the rising and falling side walls 40, 41. The fluid flow A' significantly reduces the risk of contamination of the radiation detector 30 or the radiation source 31. The particle sensor 1 can further comprise a filter (not shown) that serves to clean the additional fluid flow A upstream of the radiation detector 30 or the radiation source 31.

[0044] To secure the EMC shielding to the carrier or circuit board 7, it is preferably provided that the latter has two foot sections 400, 401, wherein the first foot section 400 extends from the first side wall 40 and is soldered to the carrier or circuit board 7. Similarly, the second foot section 401 extends from the second side wall 41 and is also soldered to the carrier or circuit board 7.

[0045] To generate the aerosol stream A or the additional fluid stream A', the particle sensor 1 can further comprise a flow generating means 5, preferably in the form of a fan 5, which is designed to allow the aerosol stream A to flow via the inlet 20 through the flow channel 3 and to output it from the outlet 21, so that the aerosol stream A is guided past the radiation detector 30 or the sensor unit 300. Alternatively, the particle sensor 1 can use a flow generating means 5 of another unit, which feeds the aerosol stream A to the particle sensor 1. The flow generating means 5 therefore does not necessarily have to be a component of the particle sensor 1. The additional fluid stream A' can be sucked via the opening 7a of the carrier plate 7 in the direction of the EMC shielding 4. As can be seen from Fig. 1, the flow channel 3 orthe further flow channel 3a is preferably delimited at least in sections by a housing part 6 and the carrier or circuit board 7. The housing part 6 can have a wall 60 which separates the further flow channel 3a from the flow channel 3. The carrier plate 7 forms a bottom of the further flow channel 3a, wherein the radiation detector 30 and the radiation source 31, preferably in the form of the sensor unit 300, are arranged on the carrier plate 7 so that they lie along the flow channel 3. The radiation L is emitted here normal to the carrier plate 7 into the flow channel 3, and light scattered back by the particulate substances of the aerosol stream A can be detected by the radiation detector 30.

[0046] Preferably, the particle sensor 1 further comprises a temperature sensor 32 which is arranged at the inlet 20 of the flow channel 3.

[0047] For electrical contacting of the particle sensor 1, electrical contacts 70 are provided on the carrier or circuit board 7, e.g. for establishing a connection to the evaluation electronics of the particle sensor, so that an output signal of the particle sensor can be read out via the contacts 70.

Claims

Claims 1. A particle sensor (1) for detecting and / or characterizing particulate substances in an aerosol stream (A) that is passed through the particle sensor (1), comprising: a housing (2) having an inlet (20) for the aerosol stream (A) and an outlet (21) for the aerosol stream (A), wherein the housing (2) further surrounds a flow channel (3) communicating with the inlet (20) and the outlet (21), through which the aerosol stream (A) can be guided in a flow direction (R), a radiation source (31) configured to emit radiation into the flow channel (3) such that the radiation interacts with particulate substances of the aerosol stream (A) passed through the flow channel (3), and a radiation detector (30) configured to detect radiation after interaction with particulate substances of the aerosol stream (A), characterized in thatthat the radiation detector (30) is at least partially covered by an EMC shield (4) which is arranged in an interior space (2a) surrounded by the housing (2).

2. Particle sensor according to claim 1, characterized in that the EMC shield (4) has a first side wall (40) and a second side wall (41) arranged behind it in the flow direction (R), wherein the first side wall (40) is designed to rise in the flow direction (R) and the second side wall (41) is designed to fall in the flow direction (R).

3. Particle sensor according to claim 2, characterized in that the EMC shield (4) has a cover wall (42) which connects the two side walls (40, 41) to one another.

4. Particle sensor according to claim 3, characterized in that the cover wall (42) has an opening (43) through which radiation can reach the radiation detector (30). Particle sensor according to one of the preceding claims, characterized in that the housing (2) surrounds a further flow channel (3a) for guiding an additional fluid flow (A'), such that the additional fluid flow (A') flows between the radiation detector (30) and / or the radiation source (31) and the aerosol flow (A). Particle sensor according to claim 5, characterized in that the further flow channel (3a) is designed to direct the additional fluid flow (A') onto the first side wall (40) of the EMC shield (4). Particle sensor according to claim 5 or 6, characterized in that the further flow channel (3a) is separated from the flow channel (3) by a wall (60). Particle sensor according to one of the preceding claims, characterized in that the EMC shield (4) is designed such that the additional fluid flow (A') guided over the EMC shield (4) flows laminarly along the EMC shield (4).Particle sensor according to one of claims 5 to 8, characterized in that the particle sensor (1) has a filter for cleaning the additional fluid flow (A') upstream of the radiation detector (30) and / or upstream of the radiation source (31). Particle sensor according to one of the preceding claims, characterized in that the radiation detector (30) and / or the radiation source (31) is arranged on a carrier plate (7). Particle sensor according to claim 10, characterized in that the carrier plate (7) is a printed circuit board (7). Particle sensor according to 10 or 11, characterized in that the carrier plate (7), together with a housing part (6) of the particle sensor (1), delimits the flow channel (3) at least in sections. Particle sensor according to claim 5 and one of claims 10 to 12, characterized in that the carrier plate (7) has a through-opening (7a) for conducting the additional fluid flow (A'). Particle sensor according to one of the preceding claims, characterized in that the radiation source (31) and the radiation detector (30) are integrated into a sensor unit (300) which is at least partially covered by the EMC shield (4). Particle sensor according to claim 2 or 3 or according to one of claims 4 to 14 as far as dependent on claim 2 or 3, characterized in that the side walls (40, 41) and the cover wall (42) of the EMC shield (4) are formed from an electrically conductive material. Particle sensor according to one of claims 10 to 15, characterized in that the EMC shield (4) is fixed to the carrier plate (7).Particle sensor according to one of claims 10 to 15 or claim 16, characterized in that the EMC shield (4) is soldered to the carrier plate (7). Particle sensor according to claim 2 and one of claims 10 to 17, characterized in that the EMC shield (4) has a first base section (400) which is connected to the first side wall (40) and is soldered to the carrier plate (7). Particle sensor according to claim 2 and one of claims 10 to 18, characterized in that the EMC shield (4) has a second base section (401) which is connected to the second side wall (41) and is soldered to the carrier plate (7). *****

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