EP3874253A1

EP3874253A1 - Optical particle sensor, in particular exhaust gas sensor

Info

Publication number: EP3874253A1
Application number: EP19773078.1A
Authority: EP
Inventors: Enno Baars; Martin Buchholz; Radoslav Rusanov; Johannes Weber
Original assignee: Robert Bosch GmbH
Current assignee: Robert Bosch GmbH
Priority date: 2018-10-31
Filing date: 2019-09-20
Publication date: 2021-09-08
Also published as: JP2022506195A; US20210372886A1; CN113039426A; US11761854B2; JP7137009B2; KR20210083268A; WO2020088843A1; DE102018218734A1

Abstract

The invention relates to a particle sensor for detecting particles in the flow of a measurement gas, in particular in order to detect soot particles in the exhaust gas channel of a burner or an internal combustion engine, comprising means for generating or supplying laser light (10), means for focusing the laser light (10), and means for detecting or transferring thermal radiation, wherein the particle sensor (16) has at least one optical entrance (40) which separates a region (16.1) exposed to the measurement gas from a region (16.2) which faces away from the measurement gas and is not exposed to the measurement gas, and the means for generating or supplying laser light (10) and/or the means for detecting or transferring thermal radiation is arranged in the region (16.2) facing away from the measurement gas. The invention is characterized in that the particle sensor (16) removes a sub-flow (321) from the flow of measurement gas and supplies same to the laser focus (22), and additionally the optical entrance (40) is fluidically shielded from the sub-flow (321).

Description

description

title

Optical particle sensor, in particular exhaust gas sensor

State of the art

The present invention relates to a particle sensor for the detection of particles in a flow of a measurement gas, in particular a sensor for the detection of soot particles in an exhaust duct of a burner or a self-igniting or spark-ignited internal combustion engine, such as the one described

can be used for example for the purpose of on-board diagnosis of a corresponding soot particle filter. Other areas of application are of course also possible, for example portable systems for monitoring emissions and systems for measuring indoor air quality.

For example, the subsequently published DE10 2017 207 402 A1 by the applicant relates to a soot particle sensor with a laser module having a laser and with a detector set up for the detection of temperature radiation. The soot particle sensor presented there is distinguished by the fact that the laser is set up to generate laser light and that the soot particle sensor has an optical element which is arranged in the beam path of the laser and is set up to bundle laser light emanating from the laser module into a spot, and that the detector is arranged in the soot particle sensor so that it detects radiation emanating from the spot.

The sensor presented in the subsequently published DE10 2017 207 402 A1 by the applicant is based on the measurement principle of the laser-induced

Incandescence.

In the subsequently published DE10 2017 207 402 A1 by the applicant, it is also proposed that the soot particle sensor be in a first part, which is set up to be exposed to a measurement gas, and in one

Sample gas not to be exposed second part of the optical components contains the soot particle sensor, is divided, both parts being separated by a partition impermeable to the measurement gas, and that in the

Partition in the beam path of the laser light is a window that is permeable both for the laser light and for radiation emanating from the spot.

Disclosure of the invention

The present invention is based on the observation of the inventors that, in the case of a particle sensor, the optical access of the particle sensor can become dirty over its lifetime. It has been found that, under unfavorable circumstances, the pollution can progress to such an extent that there is sufficient transparency of the optical access for laser light and

Thermal radiation is no longer guaranteed and the particle sensor no longer works properly.

According to the invention it is therefore provided that the particle sensor

Sample gas flow takes a partial flow and feeds it to the laser focus and also fluidically shields the optical access from the partial flow. In this way, the laser focus, i.e. the actual location of the

Particle detection, a partial flow that is representative of the sample gas flow in terms of its particle content. However, the optical access is shielded from the sample gas flow as well as the partial flow, i.e. it is not flowed through by them and any contaminants, for example soot particles, contained in them cannot reach it. Contamination of the optical access therefore no longer occurs, or only to a tolerable extent, over the lifetime, and the lifetime of the

The particle sensor is therefore not restricted or significantly increased.

In the context of the present invention, the detection of particles means in particular a measurement, the result of which is the mass and / or the number of particles and / or the mass and / or the number of particles in a flow per unit of time, in particular at the location of the laser focus , is. The detection of particles can also include the acquisition of information relating to the size and / or the size distribution of the particles. In the context of the present invention, means for generating laser light are understood in particular to be a laser, for example a diode laser, in particular a cw laser, the output power and focusability of which is so high that it is able to excite soot particles to emit thermal radiation, for example in the case of over 3500 K.

In the context of the present invention, means for supplying laser light are understood in particular to mean an optical fiber which is transparent to the laser light in question and / or an optical window which is transparent to the laser light. The laser light can basically be ultraviolet, visible or infrared.

In the context of the present invention, means for focusing laser light are understood to mean, in particular, a converging lens which is transparent to the laser light in question. Alternatively, it could also be a concave mirror.

In the context of the present invention, means for forwarding thermal radiation are understood in particular to mean an optical fiber which is transparent to the thermal radiation in question and / or an optical window which is transparent to the thermal radiation in question. In the context of the present invention, temperature radiation is understood in particular to mean: electromagnetic radiation corresponding to the emission of hot bodies, for example incoherent infrared and / or visible radiation.

In the context of the invention, an optical access means in particular an optical fiber or an optical window. The optical access can, in particular, at the same time fulfill the function of the means for focusing laser light; it can be designed, for example, as a converging lens.

The removal of a partial flow from the sample gas flow means in the context of the present invention in particular that part of the sample gas flow, namely the partial flow, is directed into the interior of the particle sensor, while the remaining other part of the sample gas flow flows past the particle sensor without being in it To get inside. The

Partial flow can also be composed of a plurality of individual flows which enter the interior of the particle sensor separately from one another. In the context of the invention, inlet openings and overflow openings can have, for example, diameters of 1-3 mm or, in the case of a non-circular geometry, have corresponding cross-sectional areas.

In the context of the present invention, the fluidic shielding of the optical access from the partial flow is understood to mean, in particular, a fluidic shielding, that is to say understood that the partial flow is deflected in such a way that it does not meet the optical access, or, in other words, before the optical access one of the

Partial flow area not flowed through remains. This can be expressed in particular in the fact that the area through which flow does not flow represents a diffusion-dominated flow area in the sense of the transport phenomena, in contrast to the areas through which flow occurs inside the sensor, which in this respect in particular as convection-dominated flow areas

are to be addressed.

The fluidic shielding of the optical access can take place by means of special constructive measures, which are explained in the following and in the subclaims and in the exemplary embodiments by way of example but not finally.

In a further development it is provided that the particle sensor has, for example, a metallic housing, in or on which the optical access is arranged, and that the housing has at least one inlet opening through which a partial flow can be removed from the flow of the measurement gas and introduced into the interior of the housing and that the case is at least one

Has outlet opening, through which the partial flow leaves the housing, and that a shield is provided in the interior of the housing, which deflects the partial flow in a direction away from the optical access, that is to say, in particular, prevents the optical access from being hit by the partial flow is and / or causes that the optical access is not hit by the partial flow.

The deflection of the partial flow for the purpose of shielding the optical access thus takes place in particular from a direction directed towards the optical access into a direction away from the optical access. the partial flow would have acted on the optical access if the measure effecting the deflection or the shielding had not been provided.

The deflection can take place in particular from a direction directed from the entry opening towards the optical access in a direction directed away from the optical access to the exit opening.

The deflection can take place in particular from a direction directed from an overflow opening (see below) towards the optical access in a direction directed away from the optical access to the outlet opening.

In a further development it can be provided that the housing of the

Particle sensor has a housing body and has a protective tube module attached to the housing body.

The housing body can, for example, be a solid steel part, which has a through-channel in its interior, which in particular has a thread, for example an external thread, and a mounting profile, for example an external hexagon profile. Also a two-part training of

Housing body in which a union nut / union screw having the thread and the mounting profile is pushed onto a housing body sleeve is possible.

The protective tube module can have, for example, a plurality of protective tubes, which are made of sheet steel, for example, and at least one or all of which are attached to the housing body, for example welded and / or inserted into the housing body. The protective tubes can also be welded to one another or plugged into one another, in particular pressed

A one-piece design of the housing body with the protective tube module is also advantageous.

In a further development for the provision of a protective tube module, it is provided that the protective tube module has at least one inlet opening through which a partial flow can be removed from the flow of the measurement gas and into the interior of the Protective tube module is insertable, and has at least one outlet opening through which the partial flow leaves the protective tube module.

The inlet opening or the inlet openings and the outlet opening or the outlet openings and an overflow opening or overflow openings (see below) can be holes in the protective tube module or in the individual

Protective tubes should be formed. In addition, swirl flaps can be added, in particular the rigid formations on the protective tube module or on one

Are protective tube and which guide and / or divert the partial flow in a predetermined direction when flowing through the holes. The combination of a hole with a swirl flap can be produced, for example, by cutting and pressing into the protective tube module or in the individual protective tubes.

In particular, it is provided that a shield is provided in the interior of the protective tube module, by means of which the fluidic shielding of the optical access from the partial flow takes place, in particular as explained above. The fluidic shielding therefore in particular deflects the partial flow in a direction away from the optical access. In the absence of the shielding, the partial flow would have acted on the optical access in particular, and particles contained in the partial flow might have contaminated the optical access in particular.

In an expedient development, the protective tube module has at least two protective tubes, namely a first protective tube and a second protective tube.

The first protective tube can have at least one inlet opening, through which a partial flow can be extracted from the flow of the measurement gas and can be introduced into the interior of the protective tube module.

The second protective tube can be arranged inside the first protective tube, so that an annular space is formed between the first and the second protective tube. The first and the second protective tube can have an axial symmetry as the basic shape (that is to say apart from holes, swirl flaps and production-related, slight dimensional deviations) and can therefore be arranged concentrically or coaxially with one another. Furthermore, the second protective tube can have at least one overflow opening through which the partial flow flows from the annular space into a gas space arranged in the interior of the second protective tube.

The outlet opening can be formed on the first or on the second protective tube, in particular on an end face of the particle sensor located on the measurement gas side on the measurement gas side. In particular, it can be a single outlet opening.

In this context, a means is provided in particular that the partial flow during or following the flow through the

Deflected overflow opening in a direction away from the optical access and in particular towards the outlet opening. This means corresponds in particular to the fluidic shielding already mentioned above. Please refer to the corresponding explanations.

Such a means, which redirects the partial flow during or following the flow through the overflow opening in a direction away from the optical access and in particular towards the outlet opening, can be implemented in different ways.

According to one embodiment, this means is implemented by at least one swirl flap which is formed on the overflow opening of the second protective tube and points in a direction away from the optical access and in particular towards the outlet opening. The partial flow thus already enters the gas space with a direction away from the optical access. It therefore does not affect optical access.

According to another embodiment, this means is implemented by a third protective tube which is arranged in the second protective tube. It can be a third protective tube, which tapers conically or stepwise in the direction pointing from the optical access to the outlet opening at the level of the overflow opening. After flowing through the overflow opening, the partial flow meets the third protective tube and because of this

tapering geometry of the protective tube, the partial flow is deflected away from the optical access. According to yet another embodiment, this means is implemented by a front face of the face pointing away from the optical access

Housing body-formed recess, for example groove, which is opposite the overflow opening of the second protective tube. The recess, for example a groove, deflects the partial flow after the partial flow has flowed through the overflow opening, for example by up to 180 °, away from the optical access and in particular towards the outlet opening.

A means can also be qualified to redirect the partial flow during or following the flow through the overflow opening in a direction directed away from the optical access and in particular towards the outlet opening by the fact that it flows from the inlet opening and / or from the overflow opening seen from the visibility of the optical access prevented. In other words, the means is geometric between the entry opening and the optical access or / or between the

Overflow opening and the optical access arranged. This feature can relate to the entire spatial extent of the optical access or can already be fulfilled if it relates to only a part of the spatial extent of the optical access, for example if the optical access is partially visible from the overflow opening and is partially covered by the agent.

Advantageously, it can be provided that the outlet opening is formed on an end face of the protective tube module which faces away from the housing body and that the inlet opening is arranged in front of the outlet opening in the direction facing the optical access to the outlet opening from the optical access. In other words, the outlet opening is arranged at a distal end of the protective tube module or the particle sensor, and the at least one inlet opening is arranged proximal to the outlet opening. When the particle sensor is arranged within a flow channel, such an arrangement has the effect that a measurement gas flow at the location of the outlet opening has a higher speed than at the location of the inlet opening. The static pressure is then higher at the location of the inlet opening than at the location of the outlet opening and the interior of the protective tube module or the particle sensor is flowed through by the partial flow, starting from the inlet opening to the outlet opening. Several inlet openings can also be provided. For example, 6 to 12 entry openings can be provided. Some or all of these can be arranged at the same height in the direction pointing from the optical access to the outlet opening. The statements made for the entry opening apply to several or all of these entry openings. Alternatively, the inlet opening can also be the open mouth of one between the first protective tube and the second protective tube

existing annular gap be formed.

Several overflow openings can also be provided. For example, 4 to 12 overflow openings can be provided. Some or all of these can be arranged at the same height in the direction pointing from the optical access to the outlet opening. This applies to several or all of these overflow openings as part of the registration for the

Overflow opening said to.

It can advantageously be provided that the inlet opening is arranged behind the overflow opening in the direction pointing from the optical access to the outlet opening as seen from the optical access. Such an arrangement has the effect that the partial flow initially flows in the direction of the optical access. After a deflection, it can be aimed at the laser focus and then leave the protective tube module through the outlet opening.

The laser focus is advantageously outside the region that is fluidically shielded from the partial flow. Instead, it lies in particular in an area that is flowed against by the partial flow.

Exemplary embodiments of the invention are shown in the drawings and are explained in more detail in the description below. The same reference numerals in different figures designate the same or at least functionally comparable elements. Show it:

1 is an illustration of the measurement principle based on the laser-induced incandescence, which is preferably used in the invention; 2 shows a basic structure to illustrate the functioning of the sensor;

Fig. 3 shows an example of a basic structure of an inventive

Particle sensor;

4 shows three variants of a first exemplary embodiment of the invention;

5 shows three variants of a second exemplary embodiment of the invention;

Fig. 6 shows a third embodiment of the invention.

Figure 1 illustrates the measurement principle based on laser-induced incandescence. High intensity laser light 10 strikes a particle 12, for example a soot particle. The intensity of the laser light 10 is so high that the energy of the laser light 10 absorbed by the particle 12 heats the particle 12 to several thousand degrees Celsius. As a result of the heating, the particle 12 spontaneously emits significant radiation 14 in the form of temperature radiation, essentially without a preferred direction. Part of the radiation 14 emitted in the form of temperature radiation is therefore also emitted in the opposite direction to the direction of the incident laser light 10.

Figure 2 shows schematically a basic structure to illustrate the functioning of the particle sensor 16. The particle sensor 16 here has a laser 18 designed as a CW laser module (CW: continuous wave; continuous wave), whose preferably collimated laser light 10 with at least one in

Beam path of the laser 18 arranged converging lens 20 is focused on a very small focus 22, in which the intensity of the laser light 10 is sufficiently high for laser-induced incandescence. The invention is not restricted to the use of a CW laser. It is also conceivable to use pulsed lasers.

The dimensions of the spot 22 are in the range of a few pm, in particular in the range of at most 200 pm, so that particles 12 passing through the spot 22 are excited to emit evaluable radiation powers, be it through laser-induced incandescence or through chemical reactions (in particular oxidation). As a result, it can usually be assumed that there is always there is at most one particle 12 in the spot 22 and that a current measurement signal from the particle sensor 16 only comes from this at most one particle 12. The measurement signal is generated by a detector 26 which in the

Particle sensor 16 is arranged such that it detects radiation 14, in particular temperature radiation, emanating from particles 12 passing through spot 22. For this purpose, the detector 26 preferably has at least one photodiode 26.1. This enables a single particle measurement, which in principle even involves the extraction of information about the particle 12 such as size and

Speed.

FIG. 3 shows an example of a basic structure of a particle sensor 16 according to the invention.

The particle sensor 16 has an arrangement of a first, outer

Protection tube 210 and a second, inner protection tube 220. The arrangement of the protective tubes is shown here only roughly and schematically, in this respect reference is made to FIGS. 4, 5 and 6.

The particle sensor 16 has a laser 18, which preferably generates collimated laser light 10. A beam splitter 34 is located in the beam path of the laser light 10. A part of the laser light 10 passing through the beam splitter 34 without deflection is focused by the converging lens 20 to a very small focus 22. In this focus 22, the light intensity is high enough to heat the particles 12 transported with the exhaust gas 32 to several thousand degrees Celsius, so that the heated particles 12 emit significant radiation 14 in the form of temperature radiation. This radiation 14 is, for example, in the near infrared and visible spectral range, without the invention being limited to radiation 14 from this spectral range. A part of this radiation 14, which is emitted in the form of non-directional radiation, is detected by the converging lens 20 and directed onto the detector 26 via the beam splitter 34. This construction has the advantage that only one optical access 40 to the exhaust gas 32 is required, since the same optics, in particular the same converging lens 20, are used for the

Generation of the focus 22 and used to detect the radiation 14 emanating from the particle 12. The exhaust gas 32 is an example of a measurement gas. The measuring gas can also be another gas or gas mixture, for example room air. The laser 18 has a laser diode 36 and a second lens 38, which preferably collimates the laser light 10 emanating from the laser diode 36. The use of the laser diode 36 is particularly economical and simple

Manageable possibility of generating laser light 10. The preferably collimated laser light 10 is focused by the converging lens 20.

The optical particle sensor 16 has a first part 16.1 (exhaust 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. Both parts are separated by a partition 16.3 which runs between the protective tubes 210, 220 and the optical elements of the particle sensor 16. The wall 16.3 serves to isolate the sensitive optical elements from the exhaust gas 32. In the partition 16.3, an optical access 40 designed as a window is provided in the beam path of the laser light 10, through which the laser light 10 falls into the exhaust gas 32 and via which the focus is removed 22 outgoing radiation 14 can be incident on the converging lens 20 and from there on the detector 26 via the beam splitter 34.

As an alternative to the exemplary embodiment shown here, the generation of the focus 22 and the detection of those originating from particles in the focus 22 can be carried out

Radiation 14 also take place via separate optical beam paths.

It is also conceivable to focus 22 with other than that only here

To generate embodiment specified lens combinations.

In addition, the particle sensor 16 can also be realized with laser light sources other than the laser diodes 36 specified here for exemplary embodiments.

Figure 4a shows a first embodiment of the invention. The second part 16.2 which is not exposed to the exhaust gas are arranged here

Components in Figure 4a omitted for clarity. In this respect, reference can be made to FIG. 3.

The particle sensor 16 has a housing 100 which is composed of a

Assembles housing body 300 and a protective tube module 200 fixed on the exhaust gas side to housing body 300. The housing body 300 is in turn composed of a cylindrical housing body sleeve 310 and a push-fit onto the housing body sleeve 310

Union screw 320 assembled.

The housing body sleeve 310 has a through-channel 311, which is closed gas-tight on the side facing the exhaust gas by an optical window, which forms the optical access 40. The second part 16.2 of the particle sensor 16 that is not exposed to the exhaust gas thus lies on the side of the optical access 40 that faces away from the exhaust gas.

The housing body sleeve 310 also has at its end facing the exhaust gas a circumferential annular support element 312, the

Exhaust side is provided for planting in a connection piece, for example an exhaust tract. The side of the support element 312 facing away from the exhaust gas is acted upon by the union screw 320. The union screw 320 has an external thread 323 and a hexagonal profile 322 on its outer surface, so that the particle sensor 16, for example, in an exhaust tract

Internal combustion engine is fixable.

On the exhaust gas side of the support element 312, the protective tube module 200 is fixed to the housing body sleeve 310 in the part 16.1 of the particle sensor 16 which is exposed to the exhaust gas. In this example, the protective tube module 200 consists of a first protective tube 210, a second protective tube 220 and a third protective tube 230.

The first protective tube 210 is pot-shaped, with a pot edge 21 1 which is fastened to the support element 312 of the housing body sleeve 310, for example welded on. The first protective tube 210 also has a pot wall 212 forming a lateral surface and a pot base 213. In the pot wall 212, in the vicinity of the pot base 213, a circumferential ring of holes is formed, for example from 12 inlet openings 101 of the particle sensor 16.

The second protective tube 220 has a substantially hat-shaped shape and is arranged essentially inside the first protective tube 210. The second protective tube 220 lies with a circumferential radial flange section 221 axially against the support element 312 of the housing body sleeve 310 and radially against the inside of the cup wall 212 of the first protective tube 210. To the Radial flange section 221 of the second protective tube 220 is followed by an overflow opening portion 223 of the second protective tube 220 tapered via an annular step 222. Provided in the overflow opening section 223 is a perforated ring of 12 overflow openings 103 in the example, which connect an annular space 240 formed between the first protective tube 210 and the second protective tube 220 to a gas space 250 formed in the interior of the second protective tube 220. A conically tapering region 224 adjoins the overflow opening section 223 of the second protective tube 220 and a cup-shaped end region 225 of the second adjoins this

Protective tube 220, which is pressed with its outer surface 225.1 into an opening in the pot bottom 213 of the first protective tube 210. In the end face 225.2 of the end region 225 of the second protective tube 220, the outlet opening 102 of the particle sensor 16 is provided, which in the present example is only slightly smaller than the end face 225.2 itself.

The third protective tube 230 is again arranged in the interior of the second protective tube 220. It has a first, straight cylindrical section 231, with which it is pressed into an opening 312.1 of the support element 312. The straight cylindrical section 231 of the third protective tube 230 is adjoined by a conically tapering section 232, which is on the exhaust gas

facing side 233 of the third protective tube 230 is open.

Along an axial direction 400, which is defined, for example, by the direction pointing from the optical access 40 to the outlet opening 102, the conically tapering section 232 of the third protective tube 230 lies at the same axial height as the overflow openings 103 in the second protective tube 220.

Due to the structure of the particle sensor 16 and in particular the housing 100, a partial flow 321 can be seen from a flow of an exhaust gas 32, which first flows through the inlet openings 101 of the particle sensor 16 arranged in the first protective tube 210 into an annular space arranged between the first protective tube 210 and the second protective tube 220 240, from where it passes through the overflow openings 103 in the second protective tube 220 into the gas space 250 arranged inside the second protective tube 220, where it is deflected by the conically tapering section 232 of the third protective tube 230 and finally the second protective tube 220 and thus the Leaves protective tube module 200 through the outlet opening 102 again.

The deflection at the conically tapering section 232 of the third protective tube 230 has the effect that the partial flow 321 does not reach the optical access 40. In this respect, this lies in an area 500 shielded from the partial flow 321. Particles 12 possibly contained in the exhaust gas 32 can therefore not contaminate the optical access 40.

FIG. 4b shows a variant in which the inlet openings 101 of the

Particle sensor 16 are not designed as simple holes, but as holes provided with swirl flaps 101.1. Swirl flaps 101.1 are like this

aligned so that they impart a flow direction to the partial flow 321 entering the annular space 240, which has a portion that is tangential to the lateral surface 212 of the first protective tube 210 and also has a portion that is directed toward the housing body 300, that is to say downward in FIG. is directed.

The inlet opening 101 as a combination of a hole with the associated swirl flap 101.1 can be cut in and out, for example

Pressing in the first protective tube 210.

FIG. 4c shows another variant of the particle sensor 16 shown in FIG. 4a. The difference is that the inlet openings 101 are not formed in the pot wall 212 of the first protective tube 210, but rather are formed on a perforated rim in the pot base 213 of the first protective tube 210 are.

Figure 5a shows a second embodiment of the invention. The second part 16.2 which is not exposed to the exhaust gas are arranged here

Components in Figure 5a omitted for clarity. In this respect, reference can be made to FIG. 3.

The particle sensor 16 has a housing 100 which is composed of a

Assembles housing body 300 and a protective tube module 200 fixed on the exhaust gas side to housing body 300.

The housing body 300 is in turn composed of a cylindrical housing body sleeve 310 and a push-fit onto the housing body sleeve 310 Union screw 320 assembled.

The housing body sleeve 310 also has at its end facing the exhaust gas an annular encircling support element 312, the exhaust side of which is provided for abutment in a connecting piece, for example of an exhaust tract. The side of the support element 312 facing away from the exhaust gas is acted upon by the cap screw 320. The cap screw 320 has an external thread 323 and a hexagonal profile 322 on its outer surface, so that the particle sensor 16 can be fixed, for example, in an exhaust tract of an internal combustion engine.

On the exhaust gas side of the support element 312, the protective tube module 200 is fixed to the housing body sleeve 310 in the part 16.1 of the particle sensor 16 which is exposed to the exhaust gas. In this example, the protective tube module 200 consists of a first protective tube 210 and a second protective tube 220.

The first protective tube 210 is pot-shaped with a pot edge 21 1 which is fastened to the support element 312 of the housing body sleeve 310, for example welded on. The first protective tube 210 also has a cup wall 212 forming a lateral surface. The pot wall 212 tapers in a step-like manner over an annular shoulder surface 216. A subsequent, conically tapering section 217 has a central opening on the end face, which represents the outlet opening 102 of the particle sensor 16.

The second protective tube 220 essentially has the shape of a stepped sleeve that is open on both sides. It is arranged inside the first protective tube 210. The second protective tube 220 is circumferential

Radial flange section 221 axially on the support element 312 of the

Housing body sleeve 310 and radially on the inside of the pot wall 212 of the first protective tube 210. Connected to the radial flange section 221 of the second protective tube 220 is a tapered via an annular step 222 and in the Substantially cylindrical overflow opening section 223 of the second

Protection tube 220 on. Provided in the overflow opening section 223 is a perforated ring of overflow openings 103 in the example 8, which connect an annular space 240 formed between the first protective tube 210 and the second protective tube 220 to a gas space 250 formed in the interior of the second protective tube 220.

The overflow openings 103 are designed as holes with swirl flaps 103.1, the swirl flaps 103 impressing the partial flow 321 entering the gas space 250 from the annular space 240 in a direction away from the optical access and towards the outlet opening 102.

An overflow opening 103 as a combination of a hole with associated

Swirl flap 103.1 can be produced, for example, by cutting and pressing in the second protective tube 220 in certain areas,

In this example, the second protective tube 220 comes with the end portion 223.1 of its overflow opening portion 223 facing the exhaust gas in the tapered portion of the cup wall 212 of the first protective tube 210 to form a sealing and flat system 223.2.

Due to the structure of the particle sensor 16 and in particular the housing 100, a partial flow 321 can be derived from a flow of an exhaust gas 32, which first flows through the inlet openings 101 of the particle sensor 16 arranged in the first protective tube 210 into an annular space arranged between the first protective tube 210 and the second protective tube 220 240, from where it passes through the overflow openings 103 in the second protective tube 220 into the gas space 250 arranged in the interior of the second protective tube 220. At the

Passing through the overflow openings 103, a direction is impressed on it which is directed away from the optical access 40, upwards in FIG. 5a. In this respect, the optical access 40 lies in an area 500 shielded from the partial flow 321. Particles 12 which may be present in the exhaust gas 32 can therefore not contaminate the optical access 40.

FIG. 5b shows a variant in which the inlet openings 101 of the

Particle sensor 16 are not designed as simple holes, but as holes provided with swirl flaps 101.1. Swirl flaps 101.1 are like this aligned so that they impose a flow direction on the partial flow 321 entering the annular space 240, which has a portion that is tangential to the lateral surface 212 of the first protective tube 210 and also has a portion that is directed toward the housing body 300, ie downwards in FIG. 5b is.

Pressing in the first protective tube 210.

FIG. 5c shows another variant of the particle sensor 16 shown in FIG. 5a. The difference is that the inlet openings 101 are not formed in the pot wall 212 of the first protective tube 210, but rather are formed on a ring of holes in the pot base 213 of the first protective tube 210 are.

Figure 6 shows a third embodiment of the invention. The second part 16.2 which is not exposed to the exhaust gas are arranged here

Components in Figure 6 omitted for clarity. In this respect, reference can be made to FIG. 3.

The particle sensor 16 has a housing 100 which is composed of a

The housing body 300 has a through-channel 311, which is sealed gas-tight on the side facing the exhaust gas by an optical window which forms the optical access 40. The second part 16.2 of the particle sensor 16 that is not exposed to the exhaust gas thus lies on the side of the optical access 40 that faces away from the exhaust gas.

The housing body 300 has, for example, on its outer surface

External thread 323 and a hexagonal profile 322, so that the particle sensor 16 can be fixed, for example, in an exhaust tract of an internal combustion engine.

On the exhaust gas side, the protective tube module 200 is fixed on the housing body 300 in the part 16.1 of the particle sensor 16 which is exposed to the exhaust gas. The Protective tube module 200 consists, in this example, of a first protective tube 210 and a second protective tube 220.

The first protective tube 210 is pot-shaped, with a pot rim 211 which is fastened to the housing body 300, for example welded on. The first protective tube 210 also has a cup wall 212 forming a lateral surface.

The second protective tube 220 has a substantially hat-shaped shape and is arranged radially in the interior of the first protective tube 210. The second protective tube 220 lies axially with a circumferential hat brim section 221 ′

Housing body 300 and radially on the inside of the pot wall 212 of the first protective tube 210. A hat ring of overflow openings 103 in the example 8 is also arranged in the hat brim section 22T. The overflow openings 103 thus point in the direction of the housing body 300 and thus enable gas exchange between the annular space 240 formed between the first protective tube 210 and the second protective tube 220 and a gas space 250 formed in the interior of the second protective tube 220.

A radially closed and axially open hat jacket section 222 'adjoins the hat brim section 22T of the second protective tube 220.

The open end of the hat jacket section 222 ′ facing the exhaust gas forms the outlet opening 102 of the particle sensor 16

facing open end of the annular space 240 forms the inlet opening 101 of the particle sensor 16.

At least one recess 305 is formed opposite the overflow openings 103 in the end face of the housing body 300 facing the exhaust gas. This recess 305 directs one through one

Partial flow 321 passing overflow opening 103, in the example by almost 180 °, away from the optical access 40 and towards the outlet opening 102.

It can be provided that each overflow opening 103 is provided with an individual recess 305 on the end face of the housing body 300, for example a cup-shaped recess 305, for example with a round cross section when viewed from above. However, it can also be provided that a single recess 305 in the form of a single recess in the end face of the housing body 300 circumferential groove is provided, which is opposite to all overflow openings 103 together.

Due to the structure of the particle sensor 16 and in particular the housing 100, a partial flow 321 can be seen from a flow of an exhaust gas 32, which first flows through the inlet opening 101 of the particle sensor 16 arranged in the first protective tube 210 into an annular space arranged between the first protective tube 210 and the second protective tube 220 240, from where it passes through the overflow openings 103 in the second protective tube 220 into the gas space 250 arranged in the interior of the second protective tube 220.

The deflection at the recess 305 in the housing body 300 has the effect that the partial flow 321 does not reach the optical access 40. In this respect, the optical access 40 lies in an area 500 shielded from the partial flow 321. Particles 12 which may be present in the exhaust gas 32 can therefore not contaminate the optical access 40.

Claims

Expectations

1. Particle sensor for the detection of particles (12) in a flow of a measuring gas, in particular for the detection of soot particles in one

Exhaust gas duct of a burner or an internal combustion engine, with means for generating or supplying laser light (10) and with means for focusing laser light (10) and with means for detecting or transmitting thermal radiation, the particle sensor (16) having at least one optical access (40), which separates an area (16.1) exposed to the measurement gas from an area (16.2) facing away from the measurement gas, which is not exposed to the measurement gas, the means for generating or supplying laser light (10) and / or the Means for the detection or for the transmission of temperature radiation are arranged in the area (16.2) facing away from the measurement gas

Particle sensor (16) takes a partial flow (321) from the measuring gas flow and feeds it to the laser focus (22) and also fluidically shields the optical access (40) from the partial flow (321).

2. Particle sensor according to claim 1, characterized in that the

Particle sensor (16) has a housing (100) in or on which the optical access (40) is arranged, and that the housing (100) has at least one inlet opening (101) through which the flow of the measurement gas has a partial flow (321) can be removed and inserted into the interior of the housing (100), and has at least one outlet opening (102) through which the partial flow (321) leaves the housing (100), and a shield is provided in the interior of the housing (100), which redirects the partial flow (321) in a direction away from the optical access (40).

3. Particle sensor according to claim 2, characterized in that the

Shield deflects the partial flow (321) from a direction directed towards the optical access (40) in a direction away from the optical access (40).

4. Particle sensor according to claim 3, characterized in that the

Shielding the partial flow (321) from a direction from the inlet opening (101) towards the optical access (40) in a direction away from the optical access (40) to the outlet opening (102)

Redirected direction.

5. Particle sensor according to one of the preceding claims, characterized

characterized in that the housing (100) has a housing body (300) in or on which the optical access (40) is arranged, and that the housing (100) further has a protective tube module (200) which is attached to the housing body (300) is fastened or is integral with the housing body (300) and has at least one inlet opening (101) through which a partial flow (321) can be removed from the flow of the measuring gas and can be introduced into the interior of the protective tube module (200) and at least one outlet opening (102 ), through which the partial flow (321) leaves the protective tube module (200), and a shield is provided inside the protective tube module (200) which deflects the partial flow (321) in a direction away from the optical access (40).

6. Particle sensor according to claim 5, characterized in that the

Protection tube module (200) has a first protection tube (210), which has at least one inlet opening (101) through which a partial flow (321) can be removed from the flow of the measurement gas and into the interior of the

Protective tube module (200) is insertable, and that the protective tube module (200) has a second protective tube (220) which is arranged in the first protective tube (210), so that an annular space between the first protective tube (210) and the second protective tube (220) (240) and that the second protective tube (220) has at least one overflow opening (103) through which the partial flow (321) from the annular space (240) into a gas space (250) arranged in the interior of the second protective tube (220) flows, and that the outlet opening (102) is formed on the first protective tube (210) or on the second protective tube (220) and that a means is provided that the partial flow (321) during or following the flow through the overflow opening (103) deflected in a direction directed away from the optical access (40) to the outlet opening (102).

7. Particle sensor according to claim 6, characterized in that the means that the partial flow (321) during or subsequent to the flow through the overflow opening (103) in a directed away from the optical access (40) to the outlet opening (102) Direction is deflected, either at least one swirl flap (103 ') formed on the overflow opening (103) of the second protective tube (220), which points in a direction directed away from the optical access (40) to the outlet opening (102) and / or one is a third protective tube (230), which is arranged in the second protective tube (220) and tapers in the direction from the optical access (40) to the outlet opening (102) at the level of the overflow opening (103) or tapers in is a recess (305), for example a groove, formed on the end face of the housing body (300) facing away from the optical access (40), which faces the overflow opening (103) of the second protective tube (220) overlaps.

8. Particle sensor according to claim 6 or 7, characterized in that the means that the partial flow (321) at or following the

Flow through the overflow opening (103) is deflected in a direction directed away from the optical access (40) to the outlet opening (102), viewed from the inlet opening (101) and / or from the overflow opening (103) the visibility of the optical access ( 40) prevented in whole or in part.

9. Particle sensor according to one of claims 5 to 8, characterized in that the outlet opening (102) is formed on an end face of the protective tube module (200) pointing away from the housing body (300) and the inlet opening (101) in that of the optical access ( 40) to the direction of the outlet opening (102) as seen from the optical access (40) in front of the outlet hole (102).

10. Particle sensor according to one of claims 2 to 9, characterized in that a plurality, in particular 6-12, of inlet openings (101) are provided, all in the same direction from the optical access (40) to the outlet opening (102) Height are arranged.

1 1. Particle sensor according to one of claims 6 to 10, characterized in that the second protective tube (220) at least several, in particular 4-12, Has overflow openings (103) which are all arranged at the same height in the direction pointing from the optical access (40) to the outlet opening (102).

12. Particle sensor according to claim 9 and 1 1, characterized in that the inlet openings (101) all in the direction from the optical access (40) to the outlet opening (102) pointing from the optical access (40) seen behind the overflow openings ( 103) are arranged.

13. Particle sensor according to one of the preceding claims, characterized

characterized in that the laser focus (22) lies outside the fluidically shielded area (500).

14. Particle sensor according to one of the preceding claims, characterized

characterized in that the means for generating laser light (10) is a laser (18) and / or that the means for supplying laser light (10) is an optical fiber and / or that the means for focusing is a lens, in particular as Lens designed optical access (40), and / or that the means for detecting thermal radiation is a photodetector (26) and / or that the means for transmitting thermal radiation is an optical fiber and / or that the optical access (40) Window or an optical fiber.