CN116359080A

CN116359080A - Optical particle sensor, in particular exhaust gas sensor

Info

Publication number: CN116359080A
Application number: CN202211677637.5A
Authority: CN
Inventors: M·布罗齐奥; M·洪贝特; N·文卡特拉曼; S·鲁斯; S·伦奇勒; V·鲁巴什
Original assignee: Robert Bosch GmbH
Current assignee: Robert Bosch GmbH
Priority date: 2021-12-27
Filing date: 2022-12-26
Publication date: 2023-06-30
Also published as: DE102021215037A1

Abstract

A particle sensor for the detection of particles in a gas flow, in particular soot particles in the exhaust gas duct of a burner or an internal combustion engine, has a device for generating a laser light, a device for focusing the laser light onto a laser focus, and a device for detecting temperature radiation. The particle sensor has an optical inlet separating a region exposed to the measurement gas from a region facing away from the measurement gas that is not exposed to the measurement gas. The means for generating laser light and the means for detecting temperature radiation are arranged in a region facing away from the measuring gas. The particle sensor has a housing in which an optical inlet is arranged. The particle sensor has an inlet opening through which the substream can be removed from the measuring gas stream and introduced into the interior of the particle sensor, and an outlet opening for discharging the substream from the particle sensor. The invention expediently relates to the shielding of the environment of the particle sensor, the optical inlet and/or the means for detecting temperature radiation.

Description

Optical particle sensor, in particular exhaust gas sensor

Technical Field

The present invention relates to a particle sensor for detecting particles in a gas flow, for example, a sensor for detecting soot particles in a gas exhaust duct of a burner or a compression-ignition or spark-ignition internal combustion engine, for example, for the on-board diagnosis of a corresponding soot particle filter. Of course, other fields of application are possible, such as portable systems for monitoring emissions and systems for measuring indoor air quality.

Background

The applicant's DE 10 2018 218 734 A1 has disclosed a particle sensor having means for generating a laser light and means for focusing the laser light on a laser light focal point and means for detecting temperature radiation, wherein the particle sensor has at least one optical inlet separating a region exposed to a measuring gas from a region facing away from the measuring gas that is not exposed to the measuring gas, wherein the means for generating a laser light and the means for detecting temperature radiation are arranged in a region facing away from the measuring gas, wherein the particle sensor has a housing in which the optical inlet is arranged and which has at least one inlet opening through which a sub-stream can be extracted from the measuring gas stream and introduced into the interior of the housing, and at least one outlet opening for discharging the sub-stream from the housing.

Disclosure of Invention

The object of the present invention is to further develop the prior art into a high-precision, robust sensor which not only operates more safely but is also suitable for permanent use in harsh environmental conditions, for example in and at the exhaust gas tract of an internal combustion engine.

To this end, it is particularly emphasized that the three aspects of the invention, which independently of one another achieve the desired improvements of the known devices, or can be combined with one another and then cooperate to achieve the above-mentioned objects to an even greater extent.

A first aspect of the invention relates to the configuration of the particle sensor in such a way that it completely optically shields the environment from the laser focus.

In this context, the term optical shielding of the environment with respect to the laser focus is understood to mean in particular: for each point of the environment, the point is connected to an imaginary straight line of the laser focus at least once intersecting the particle sensor at a position where the particle sensor is optically opaque, e.g. made of metal.

The environment is understood in particular to be the entirety of the space not filled or surrounded by the particle sensor, wherein the particle sensor is understood to be, for example, an entire unit, which is not detachably connected to the device having the features of the invention. Other devices that are not or only detachably connected to the device featuring the features of the invention do not belong to the particle sensor, because they already belong to or are located in the environment. For example, this applies to the exhaust gas duct, to which such particle sensor may be screwed or otherwise detachably fastened.

Such shielding ensures that laser radiation (except by scattered radiation) does not escape from the particle sensor into the environment. Thus, this is not dangerous and the particle sensor may operate as a laser device with a low laser protection level (e.g., laser protection level 1).

A second aspect of the invention relates to the configuration of the particle sensor in such a way that the particle sensor completely shields the optical inlet from the environment.

In this context, the optical access is to be understood in particular as being shielded from the environment: for each point of the environment, the point intersects an imaginary straight line connection attributable to each location of the optical inlet at least once at a location where the particle sensor does not let gas pass, e.g. is composed of metal.

Herein, the term "environment" may be understood as described above.

By this shielding it is achieved that contaminants from the environment to the particle sensor, at least in a linear movement, do not strike the optical inlet. Thereby protecting the optical inlet and ensuring long-term function of the particle sensor.

A third aspect of the invention relates to a configuration of a particle sensor in that the particle sensor has a protective tube module with at least one inlet opening through which a substream can be taken out of a measuring gas stream and introduced into the interior of the protective tube module, and with at least one outlet opening for discharging the substream from the protective tube module, and the protective tube module has a first protective tube with the at least one inlet opening through which a substream can be taken out of a measuring gas stream and introduced into the interior of the protective tube module, and/or with at least one outlet opening for discharging the substream from the protective tube module, and the protective tube module has a second protective tube which is arranged in a first protective tube and the means for detecting temperature radiation is completely optically shielded relative to the first protective tube.

In this case, the optical shielding of the device for detecting temperature radiation by the second protective tube with respect to the first protective tube is to be understood in particular as meaning that no point on the first protective tube is optically mapped onto the detection device, but rather is interrupted by the presence and design of the (e.g. metallic) second protective tube. In other words, the means for detecting temperature radiation is not able to "see" the first protective tube. In particular, it instead sees the second protective tube.

Since the first protective tube is directly connected to the exhaust gas flow and the second protective tube is arranged in the first protective tube, i.e. in a region shielded from the exhaust gas flow region, it can be assumed that the first protective tube is hotter than the second protective tube and also emits correspondingly strong temperature radiation.

For example, the particle sensor may be operated in a manner such that the temperature of the first protective tube (rather than the second protective tube) exceeds 500 ℃.

Since the means for detecting temperature radiation is optically completely shielded with respect to the first protective tube, it is achieved that the temperature radiation emitted by the first protective tube does not reach the means for detecting temperature radiation. Thus, the actual measurement function suffers less interference.

The above-described aspects of the invention can be further extended by arranging features of the flow rectifier in the second protective tube in the region of the laser focus. However, this feature may also be advantageous independently of these features.

For example, the flow straightener may be composed of a plurality of concentric rings spaced apart from one another, which are connected to one another by radial webs.

For example, the flow rectifier may be pressed into the second protective tube.

Advantageously, it can be provided that the second protective tube radially rests on the first protective tube via a thin-walled tolerance ring. Thereby, the heat flow from the first protection tube to the second protection tube is reduced, and thereby the heat flow to the heat sensitive optical components and/or the electronic components of the particle sensor is reduced.

For example, the tolerance ring has a wall thickness of at most 0.2mm.

In an advantageous development, it is provided that the protective tube module further comprises an outer protective tube having at least one inlet opening through which a partial flow can be removed from the measuring gas flow and introduced into the interior of the protective tube module, wherein the first protective tube is arranged in the outer protective tube such that an annular space is formed between the outer protective tube and the first protective tube, and the first protective tube has at least a first overflow opening through which a partial flow can flow from the annular space into a housing space formed between the housing and the second protective tube, and the second protective tube has at least a second overflow opening through which the partial flow can overflow from the intermediate space into a gas space located inside the second protective tube, the laser focus being located in the gas space, and the second protective tube has at least a third overflow opening through which the partial flow overflows from the gas space into the interior of the first protective tube, from which the partial flow exits the particle sensor through the at least one first protective tube. In this way, a certain cooling of the exhaust gases as they pass through the protective tube module can be achieved, so that heating of the heat-sensitive optical and/or electronic components of the particle sensor is reduced.

It may be provided that the flow cross section of the inlet opening is equal to the flow cross section of the outlet opening and/or to the flow cross section of the first, second and/or third overflow opening. In this way, undesired throttling effects can be prevented during the flow through the particle sensor.

If a swirl element is provided at the at least one first overflow opening, which swirl element causes the partial flow to undergo a rotation directed around the longitudinal axis of the protective tube module when the partial flow passes through it, homogenization of the exhaust gas in the protective tube module can be achieved. Furthermore, the exhaust gas is cooled by an improved heat transfer of the exhaust gas into the protective tube. The particle sensor then also works largely independently of the angular position in which it is mounted about its longitudinal axis.

Contamination and heating of the optical inlet can be avoided very effectively if the particle sensor further has an inner protective tube arranged within the second protective tube and fluidly shields the optical inlet from the sub-stream and/or diverts the sub-stream to the laser focus.

It may be provided that the housing comprises a first sub-housing in which the means for generating laser light and the means for detecting temperature radiation are arranged, and that the housing comprises a second sub-housing mounted on the first sub-housing, which is configured tubular and in which the means for focusing laser light onto the laser focus are arranged, and that the housing comprises a third sub-housing mounted on the first sub-housing, which is configured tubular and concentric with the second sub-housing, and which has cooling ribs or cooling fins on its outside. In this way, the heat flow from the exhaust gas to the heat-sensitive optical and/or electronic components of the particle sensor located in the first sub-housing may be reduced.

By retracting the third sub-housing at the level of the cooling ribs and/or from the end of the third sub-housing opposite the first sub-housing in the direction of the first sub-housing in the axial extension of the particle sensor, the temperature of the optical inlet can be reduced. The heat flow to the thermally sensitive optical and/or electronic components of the particle sensor is then reduced.

By providing a mica seal between the sealing surface of the mounting flange of the particle sensor and the corresponding sealing surface of the exhaust gas line in which the particle sensor is mounted, the heat flow along this path can be effectively interrupted. The heat flow to the thermally sensitive optical and/or electronic components of the particle sensor is then reduced. A mica seal is a seal, in particular a sealing ring, made of mica material. Here, it is, for example, muscovite or phlogopite.

In order to optimize the heat dissipation in the particle sensor, it can be provided that the second protective tube consists of a sheet material having a wall thickness greater than the first protective tube and/or that the second protective tube consists of a sheet material having a wall thickness greater than the outer protective tube. It can also be provided that the outer protective tube consists of a sheet material with a wall thickness greater than the first protective tube. For example, the wall thickness may have the following values: the outer protective tube is 0.5mm; the first protective tube is 0.4mm; the second protective tube is 0.6mm.

Drawings

Embodiments of the invention are illustrated in the drawings and explained in more detail in the following description. The same reference numbers in different drawings identify identical or at least functionally comparable elements. In the accompanying drawings:

fig. 1 shows a measurement principle based on laser-induced incandescence, which principle is preferably used in the present invention;

fig. 2 shows a principle structure for explaining a functional manner of the sensor;

FIG. 3 illustrates the principle structure of the particle sensor of the present invention;

FIG. 4 illustrates one embodiment of the present invention;

FIG. 5 shows an enlarged cross-sectional view of the embodiment of FIG. 4;

figure 6 shows the spacer ring in sections a) and b), respectively.

Detailed Description

Fig. 1 shows the principle of measurement based on laser-induced incandescence. The high intensity laser 10 encounters particles 12, such as soot particles. The intensity of the laser 10 is so high that the energy of the laser 10 absorbed by the particles 12 heats the particles 12 to thousands of degrees celsius. As a result of the heating, the particles 12 emit radiation 14 in the form of temperature radiation without a preferred direction. Thus, a portion of the radiation emitted in the form of temperature radiation 14 is also emitted in the opposite direction to the incident laser light 10.

Fig. 2 schematically shows a principle structure for explaining the functional manner of the particle sensor 16. Here, the particle sensor 16 has a laser 18 formed as a CW (continuous wave) laser module, which preferably collimates the laser light 10, is focused by at least one condenser lens 20 arranged in the optical path of the laser 18 onto a very small focal point 22, in which the intensity of the laser light 10 is sufficiently high for laser-induced incandescent degrees. The invention is not limited to the use of CW lasers. The use of pulsed lasers is also conceivable.

The size of the spot 22 is in the range of a few μm, in particular in the region of a maximum of 200 μm, so that the particles 12 passing through the spot 22 are excited to emit an appreciable radiation power by laser-induced incandescent or by chemical reactions, in particular oxidation. As a result, it can generally be assumed that at most one particle 12 is always present in the spot 22 and that the instantaneous measurement signal of the particle sensor 16 is only from this at most one particle. The measurement signal is generated by a detector 26 which is arranged in the particle sensor 16 such that it detects the radiation 14, in particular the temperature radiation, emitted by the particles 12 flying through the spot 22. For this purpose, the detector 26 preferably has at least one photodiode 26.1. Thus, a single particle measurement is possible, which in principle even allows to extract information about the particles 12, such as size and velocity.

Fig. 3 illustrates the principle structure of the particle sensor 16 of the present invention.

The particle sensor 16 has a protective tube module 200 consisting of a first outer protective tube 210 and a second inner protective tube 220. The arrangement of the protective tube is only schematically shown here in outline, so reference is made to fig. 4.

Particle sensor 16 has a laser 18 that preferably produces collimated laser light 10. In the optical path of the laser light 10 there is a beam splitter 34. A portion of the laser light 10 that passes through the beam splitter 34 without being deflected is focused by the condenser lens 20 to a very small focal point 22. In this focal spot 22, the light intensity is high enough to heat the particles transported with the exhaust gas 32 to thousands of degrees celsius, so that the heated particles 12 significantly emit radiation 14 in the form of temperature radiation. The radiation 14 is for example in the near infrared and visible spectral ranges, and the invention is not limited to radiation 14 from this spectral range. A portion of this undirected radiation emitted in the form of temperature radiation 14 is detected by the collecting lens 20 and directed towards the detector 26 via the beam splitter 34. The advantage of this configuration is that only one optical channel 40 is required to the exhaust gas 32, since the same optics, in particular the same collecting lens 20, are used for the generation of the focal point 22 and for the detection of the radiation 14 emitted from the particles 12. Exhaust gas 32 is an example of a measurement gas. The measuring gas may also be other gases or gas mixtures, such as room air.

The laser 18 has a laser diode 36 and a second lens 38 that preferably collimates the laser light 10 emitted from the laser diode 36. The use of the laser diode 36 represents a particularly cost-effective and easy to handle possibility for generating the laser light 10. Preferably, the collimated laser light 10 is focused by a condenser lens 20.

The optical particle sensor 16 has a first part 16.1 (exhaust gas side) exposed to the exhaust gas and a second part 16.2 (clean gas side) not exposed to the exhaust gas, which contains the optical components of the particle sensor 16. The two parts are separated by a separating wall 16.3 which extends between 210, 220 and the optical element of the particle sensor 16. The wall 16.3 serves to isolate the sensitive optical elements from the exhaust gas 32. In the separating wall 16.3, an optical inlet 40 formed as a window is arranged in the optical path of the laser light 10, through which the laser light 10 enters the exhaust gas 32 and can enter the collecting lens 20 via radiation from the focal point 22 and from there reach the detector 26 via the beam splitter 34.

As an alternative to the embodiment presented here, the generation of the focal spot 22 and the detection of the radiation 14 originating from the particles in the focal spot 22 can also take place via separate light paths.

It is also contemplated that focal point 22 may be created using a combination of lenses other than the combination of lenses specified herein as an example only. Furthermore, particle sensor 16 may also be implemented with other laser light sources other than laser diode 36 as specified herein for the embodiments.

Fig. 4 shows an embodiment of a particle sensor 16 for proving particles 12. It has a first sub-housing 101 in which the laser 18, the photodetector 26 and further electronic components 500, for example for signal acquisition and signal evaluation, are arranged.

The particle sensor 16 also has a second sub-housing 102 which is mounted on the first sub-housing 101 and is formed in a tubular shape. Two planar convex lenses 20 are arranged in the two axial end regions of the second sub-housing 102, thereby forming a telescope.

The particle sensor 16 also has a third sub-housing 103 which is mounted on the first sub-housing 101 and is formed in a tubular shape and is concentric with the second sub-housing 102. An annular space is formed between the second sub-housing and the third sub-housing 103, which can be filled with air or evacuated, for example. The third sub-housing 103 has cooling ribs or cooling fins 103.1 on its outer side.

An optical inlet 40 is mounted in the half of the third sub-housing 103 facing away from the first sub-housing 101 in the form of a window 42 mounted in a window holder 41.

A flange-shaped heat protection cover 44 is also mounted on the side of the third sub-housing 103 facing away from the first housing 101. For example, it consists of two metal sheets and a gap formed between them, which can be filled with air or evacuated, for example.

A mounting flange 46 for mounting the particle sensor 16 on the measuring gas line is also provided on the side of the third sub-housing 103 facing away from the first sub-housing 101. The mounting flange is supported, for example, flat on the welded joint 50 of the exhaust gas line 300 and is detachably fastened by means of a V-shaped band 52 known per se.

Furthermore, a protective tube module 200 is also fastened to the third sub-housing on the side facing away from the first sub-housing.

In this example, the protection pipe module 200 includes an outer protection pipe 210, a first protection pipe 220, a second protection pipe 225, and an inner protection pipe 230.

The outer protective tube 210 is embodied in the form of a pot having a pot wall and a pot bottom, which form side faces. In the tank wall, a circumferential ring of, for example, twelve inlet openings 301 of particle sensor 16 is formed near the bottom of the tank. At the rim of the tank, the outer protective tube 210 is fastened circumferentially to the exhaust gas-facing, radially inward flange 46.1 of the mounting flange 46.

The first protective tube 220 has a substantially cap-shaped form and is arranged substantially inside the outer protective tube 210, so that an annular space 240 extending in the longitudinal direction, through which flow can take place, is formed between the outer protective tube 210 and the first protective tube 220, which extends radially inwards from the flange 46.1 into the mounting flange 46. The first protection tube 220 is pressed into the inner side of the outer protection tube 210, for example, on the exhaust gas side. Alternatively or additionally, it may also penetrate a central opening in the bottom of the outer protective tube 210 on the exhaust gas side and thus protrude from the outer protective tube 210 on the exhaust gas side. On the side of the first protective tube 220 facing away from the exhaust gas, in the region of the radially projecting cap peak, the first protective tube 22 is fastened to a radially inner projection 46.2 of the mounting flange 46, which projection is arranged on the radially inner side of the flange 46.1.

In the region of the cap peak of the first protective tube 220, a plurality of first overflow openings 303 are provided, which connect the annular space 240 with a housing space 255 formed between the housing 100 or the mounting flange 46 and the second protective tube 225.

At each first overflow 303, a swirl element 303' may be provided which converts the gas flow into a rotation about the longitudinal axis 400 of the protection pipe module 200 when passing through the overflow, see also fig. 5.

The second protective tube 225 is arranged in its exhaust-gas side portion 225.1, which is formed in a substantially cylindrical shape, in the first protective tube 220. On its left side as viewed in fig. 4, the second protective tube 225 widens conically and merges into its likewise approximately cylindrically embodied exhaust gas outlet portion 225.2, with which it is fastened to the inner side of the third partial housing 103.

In the exhaust gas-facing away portion 225.2, the second protective tube 225 has a plurality of second overflow openings 304 arranged on the surrounding ring, which connect the housing space 255 with the gas space 250 located inside the second protective tube.

In addition, the second protective tube 225 has a plurality of third overflow openings 305 in the exhaust-gas side portion 225.1, which connect the gas space 250 with the interior of the first protective tube 220.

The second protective tube has a convex bottom in the exhaust-gas side part 225.1. The laser radiation reaching the ground after passing through the focal point is therefore additionally scattered here, so that its intensity decreases during further propagation.

The third overflow opening 305 is directed radially outwards but not in the axial direction 400. This, together with the other

protective tubes

210, 220, helps to prevent leakage of laser radiation from the particle sensor 16.

An inner protection tube 230 is disposed inside the second protection tube 225. It has a straight cylindrical first section. A conically tapering section, which is open on the exhaust-gas-facing side of the third protective tube 230, engages in a straight cylindrical section of the third protective tube 230.

Along an axial direction 400 (which is defined, for example, by the direction from the optical inlet 40 to the outlet 302), the conically tapering section of the third protection tube 230 is located at the same axial height as the overflow opening 303 in the second protection tube 225.

The particle sensor 16 is designed such that the laser focus 22 is located in the exhaust-gas side portion 225.1 of the second protective tube 225 close to the conically widening of the second protective tube 225. Thus, in order to orient and rectify the flow in the longitudinal direction in the region of the laser focus 22, a flow rectifier 228 is provided here, for example pressed into a second protective tube 225.

In this example, the flow straightener 228 is comprised of a plurality of concentric rings 228.1 spaced apart from one another, connected to one another by radial webs 228.2, see FIG. 5.

The second protective tube 225 is pressed into the interior of the first protective tube 220 in its exhaust-gas side portion 225.1 by means of a spacer ring 229, see fig. 5. By using a spacer ring 229, a mechanically stable connection with low heat conduction can be achieved, so that the second protective tube remains relatively cool.

Figure 6a shows a spacer ring 229 with radial protrusions. Figure 6b shows a spacer ring 229 having a c-shaped cross section.

For example, the mica seal 260 is provided in the form of a mica seal ring for sealing between the sealing surface of the mounting flange 46 and the corresponding sealing surface of the exhaust gas line.

For example, as shown in FIG. 4, the environment of particle sensor 16 is completely optically shielded from laser focus 22 by protective tube module 200 and housing 100 and mounting flange 46. Laser radiation (except scattered radiation) cannot leave the particle sensor 16.

For example, as shown in FIG. 4, window 42 is completely shielded from the environment of particle sensor 16 by protective tube module 200 and housing 100 and mounting flange 46, thereby protecting it from contamination.

For example, as shown in fig. 4, the photodetector 26 is completely optically shielded from the first protective tube 220 by the second protective tube 225. Since the second protective tube 225 is much hotter than the first protective tube 220 when the particle sensor 16 is operated as an exhaust gas sensor in the exhaust gas line of an internal combustion engine, the radiation of heat incident on the detector 26 is reduced. Thus, the signal to be verified by the light detector, i.e. the temperature radiation 14 emitted from the particle 12 to be verified, is less disturbed and the particle sensor 16 can be measured more accurately.

Claims

1. Particle sensor for the detection of particles (12) in a measuring gas flow, in particular for the detection of soot particles in a waste gas duct of a burner or an internal combustion engine, having means for generating laser light (10), means for focusing the laser light (10) onto a laser focal point (22) and means for detecting temperature radiation, wherein the particle sensor (16) has at least one optical inlet (40) separating a region (16.1) exposed to measuring gas from a region (16.2) facing away from measuring gas, which region is not exposed to measuring gas, wherein the means for generating laser light (10) and the means for detecting temperature radiation are arranged in the region (16.2) facing away from measuring gas, wherein the particle sensor (16) has a housing (100), in which the optical inlet (40) is arranged, and the particle sensor (16) has at least one inlet opening (301) and at least one outlet opening (302) through which a sub-flow (321) can be conducted from the measuring gas flow into the particle sensor (16) and out of the particle sensor (16) can be taken out of the sensor, the particle sensor (16) completely optically shields the environment of the particle sensor from the laser focus (22).

2. The particle sensor according to the preamble of claim 1 or according to claim 1, characterized in that the particle sensor (16) completely optically shields the optical inlet (40) from the environment of the particle detector (16).

3. Particle sensor according to claim 1 or 2, characterized in that the particle sensor (16) has a protective tube module (200) with at least one inlet opening (301) through which a substream (321) can be taken out of the measuring gas flow and introduced into the interior of the protective tube module (200), and at least one outlet opening (302) for discharging the substream from the protective tube module (200), and the protective tube module (200) has a first protective tube (220), and the protective tube module (200) has a second protective tube (225) which is arranged in part in the first protective tube (220).

4. Particle sensor according to the preamble of claim 1 or according to claim 1, characterized in that the particle sensor (16) has a protective tube module (200) with at least one inlet opening (301) through which a substream (321) can be taken out of the measuring gas flow and introduced into the interior of the protective tube module (200), and at least one outlet opening (302) for discharging the substream from the protective tube module (200), and the protective tube module (200) has a first protective tube (220) and the protective tube module (200) has a second protective tube (225) which is arranged in the first protective tube (220) and which completely optically shields the means for detecting temperature radiation with respect to the first protective tube.

5. Particle sensor according to claim 3 or 4, characterized in that a flow rectifier (228) is arranged in the second protective tube (200) in the region of the laser focus (22).

6. The particle sensor of claim 5, wherein the flow rectifier (228) is comprised of a plurality of concentric rings (228.1) spaced apart from each other, the concentric rings being connected to each other by radial webs (228.2).

7. The particle sensor of any one of claims 3 to 6, characterized in that the second protective tube (225) radially abuts against the first protective tube (220) via a thin-walled tolerance ring (229).

8. The particle sensor as claimed in any one of claims 3 to 7, characterized in that the protective tube module (200) further comprises an outer protective tube (210) having at least one inlet opening (301) through which a substream (321) can be taken out of the measuring gas flow and introduced into the interior of the protective tube module (200), wherein the first protective tube (220) is arranged in the outer protective tube (210) such that an annular space (240) is formed between the outer protective tube (210) and the first protective tube (220), and the first protective tube (220) has at least one first overflow opening (303) through which the substream (321) flows from the annular space (240) into a housing space (255) formed between the housing (100) and the second protective tube (225), and the second protective tube (225) has at least one second overflow opening (304) through which the substream (321) is situated in the focal space (250) from the housing (225) to the third protective tube (250), the substream (321) overflows from the gas space (250) into the interior of the first protective tube (220), from where it exits the particle sensor through at least one outlet opening (302) of the first protective tube (220) and/or the outer protective tube (210).

9. Particle sensor according to claim 8, characterized in that a swirl element (303') is arranged at the at least one first overflow opening (303), which swirl element causes the substream (321) to rotate in the direction of the longitudinal axis (400) of the protective tube module (200) when passing.

10. Particle sensor according to claim 8 or 9, characterized in that the particle sensor (16) further has an inner protection tube (230) which is arranged inside the second protection tube (225) and which fluidly shields the optical inlet (40) from the substream (321) and/or diverts the substream (321) to the laser focus (20).

11. Particle sensor according to any one of claims 3 to 10, characterized in that the housing (100) comprises a first sub-housing (101) in which the means for generating laser light (10) and the means for detecting temperature radiation are arranged, and in that the housing (100) comprises a second sub-housing (102) which is mounted on the first sub-housing (101) and is constructed in a tubular manner, and in which the means for focusing the laser light (10) onto the laser focus (22) are arranged, and in that the housing (100) comprises a third sub-housing (103) which is mounted on the first sub-housing (101) and is constructed in a tubular manner, and which is concentric with the second sub-housing (102), and in that the third sub-housing (103) has cooling ribs (103.1) on its outer side.

12. Particle sensor according to claim 11, characterized in that the optical inlet (40) is recessed in the axial extension of the particle sensor (16) at the level of the cooling ribs (103.1) of the third sub-housing (103) and/or from the end of the third sub-housing (103) opposite the first sub-housing (101) in the direction of the first sub-housing (101).

13. Particle sensor according to claim 11 or 12, characterized in that a sleeve-shaped mounting flange (46) is fastened to the third sub-housing (103), in particular to a side of the third sub-housing (103) facing away from the first sub-housing (101), for mounting the particle sensor (16) on a measuring gas line, in particular a waste gas duct (300).

14. The particle sensor of any one of claims 8 to 10 and 13, characterized in that the first protective tube (220) is fixed in the mounting flange (46) and the housing space (255) is at least partially configured inside the mounting flange (46).

15. Particle sensor according to claim 13 or 14, characterized in that a mica seal (260), in particular a mica seal ring, is provided for sealing between the sealing surface of the mounting flange (46) and the corresponding sealing surface of the exhaust gas line.

16. Particle sensor according to any one of the preceding claims, characterized in that the means for generating laser light (10) is a laser (18) and/or the means for focusing comprises a lens (20), in particular an optical inlet (40) configured as a lens (40), and/or the means for detecting temperature radiation is a photodetector (26), such as a single photon avalanche diode, and/or the optical inlet (40) is a window (42).