KR20220142516A - Particle sensor device with replaceable transparent cover element - Google Patents

Abstract

The present invention relates to a particle sensor device (16) having an inner chamber (36) defined by a housing (40) and a cover element (34), said cover element (34) covering an opening in said housing (40) and It has a central transparent area 34.1 , wherein a laser 18 and a detection device 26 are arranged in the inner chamber 36 . The particle sensor device is designed and arranged so that the laser radiation 10 incident from the laser 18 is focused to the laser spot 22 through the central transparent area 34.1, and the particle sensor device is located at the laser spot 22 . It is designed and arranged to guide the emitted heat radiation through the central transparent area 34.1 to a heat radiation area 29 , which illuminates the detection device 26 . The particle sensor device is characterized in that the cover element 34 can be connected to the housing 40 in a non-destructive and releasable manner so as to cover the inner chamber 36 in an airtight manner.

Description

Particle sensor device with replaceable transparent cover element

The present invention relates to a particle sensor device according to the preamble of claim 1 .

Such a particle sensor device is known, for example, from WO18292433 A1. Particle sensor devices are used in passenger car internal combustion engines for on-board diagnostics of the condition of particle filters.

According to WO 18292433 A1, a very high luminous intensity is achieved for a short time (ns) by heating a particle ensemble using a nanosecond high-power laser. The work is performed on a collimated (parallel run) portion of a beam with a cross-sectional area of several square centimeters or millimeters. That is, thousands of soot particles are heated simultaneously with a single laser pulse, making it impossible to count individual particles. High power lasers cannot be miniaturized and are expensive.

Known particle sensor devices have an inner chamber defined by a housing and a cover element. The cover element covers the opening of the housing and has a transparent area. A laser, a first optical element, a second optical element, and a detection device are disposed in the inner chamber, the first optical element being designed and arranged to focus laser radiation incident from the laser to a laser spot through the transparent area, the second The optical element is designed and arranged to focus the thermal radiation emitted from the laser spot, through the transparent area, to a thermal radiation spot that illuminates the detection device.

The transparent area represents optical access to the exhaust gas required to form the laser spot. This optical access must, on the one hand, be close enough to the exhaust gas to protect the sensor's optical path from contamination and damage that could penetrate from the exhaust pipe. On the other hand, this optical access must be sufficiently transparent for the lifetime of the sensor. There are three main requirements that must be met:

The thermal radiation of the heated particles in the laser spot must not be attenuated to such an extent that it is no longer indistinguishable from the background noise generated, for example, by the hot sensor and its surroundings. The heating laser radiation must not be attenuated so that its intensity is insufficient to sufficiently heat the particles. At the same time, the optical access must maintain the optical quality necessary to focus the light on a sufficiently small laser spot. Laser radiation that may be reflected from the optical access (eg as a result of contamination) must not reach a power that still exceeds an acceptable background radiation level at the detection device.

The requirement for hermeticity is realized, for example, by a transparent area of the cover element which in some forms also performs the optical function of the lens for focusing the laser light. During the lifetime of the sensor, soot or ash may deposit in the transparent area of the optical access. In addition, the surface of the transparent region can be attacked by chemicals carried with the exhaust gas, which results in undesirable changes in the surface structure and associated transparency degradation.

The invention differs from the prior art mentioned at the outset by the features of claim 1 . According to these features, the cover element covers the inner chamber in an airtight manner and can be connected to the housing in a non-destructively releasable manner.

The non-destructive releasability permits cleaning and/or replacement of the cover element realizing optical access. Cleaning or replacement can be performed at regular intervals or when a requirement violation is detected by a self-diagnostic function. Replacing or cleaning the cover element is much less expensive than replacing a particle sensor device that cannot replace the optical access. The present invention also allows shop personnel to replace or clean the optical access at the shop floor, further reducing effort compared to inspection at a manufacturer or specialized shop.

The particle sensor device according to the invention can be used for on-board monitoring of the condition of diesel particle filters and gasoline particle filters. Particle sensor devices have a short response time and can be used almost immediately after activation. Especially in the case of gasoline vehicles, since most of the fine particles (low mass, large number) are generated during cold start, the possibility of measuring the number of particles in gasoline vehicles and the immediate use of the sensor immediately after starting the vehicle is very important.

The particle sensor device according to the invention makes it possible to determine the mass (mg/m3 or mg/mi) and number concentration (particles/m3 or particles/mi) of the emitted particles. It is also possible to measure the particle size distribution. However, the present invention is also relevant if only one of the mentioned measurement parameters is determined. The use of the particle sensor device according to the invention in other scenarios and fields of application is also possible (eg portable emission monitoring systems, inspection exhaust gas analysis devices, indoor air quality measurement, emissions from combustion plants (personal, industrial)).

Where soot particles and exhaust gases are referred to in this application, they are used only as examples for simplification or illustration. The present invention always relates generically to particles/aerosols in fluids, in particular measurement gases.

A preferred embodiment is that the housing has a sensor head, in which an opening in the housing is arranged, the sensor head having a first flange face having an edge surrounding the opening in a closed loop. The cover element, in its shape and size, is designed to lie on the first flange face or on an intermediate element between the first flange face and the cover element.

With this configuration, optical access is exposed by the release of a flange through which the housing connects to a volume carrying the measurement gas (eg exhaust pipe). The cover element can be removed in the exposed state for replacement or cleaning. The intermediate element may be, for example, a seal.

It is also preferred that the particle sensor device has a counter flange with a second flange face, said second flange face being designed to rest on the cover element or on an intermediate element lying between the first flange face and the second flange face.

This flange connection allows the housing to be hermetically connected to the volume carrying the measuring gas, which can be easily opened and closed again.

This flanged connection allows a hermetic closure between the optical component and the measuring gas/exhaust gas and the environment. This prevents penetration of solids such as moisture or soot particles that may condense inside the sensor.

The flange connection also makes it possible to connect the sensor head to the counter flange mechanically sufficiently rigidly.

The particle sensor device preferably has at least one clamping means capable of generating a clamping force which presses the second flange face and the first flange face against each other.

Another preferred embodiment is that the sensor device has a cylindrical protective tube open at two ends, the protective tube having a cylindrical axis coincident with a central beam of laser radiation generating the laser spot, and a jacket face extending around the laser spot. It is characterized by having. A protective tube (or a protective tube arrangement comprising inner and outer protective tubes) branches off a representative portion of the exhaust gas and directs this portion into a directional flow through the laser spot. The protective tube creates a uniform flow through the laser spot, improving the reproducibility of the measurement.

It is also preferred that the end (ie the proximal end) of the protective tube facing the sensor head is designed, in its shape and size, to lie on the cover element or on an intermediate element between the cover element and the proximal end of the protective tube.

Due to this feature, a simple construction is achieved, since the flange is used not only for hermetically clamping the cover element, but also for fixing the protective tube.

The cover element preferably has a central region defined by a transparent region, and the cover element has a peripheral region which surrounds the central region in the form of a closed loop. The central region thus serves as an optical access and the peripheral region serves for the hermetic attachment of the cover element.

The cover element is thus a disk-shaped cover element. The cover element has a circumferential narrow side and two opposing wide sides separated from each other by said narrow side. Since there are no holes on the wide sides, the cover element separates the spaces which lie on the opposite wide sides when the flanges are closed in a hermetic manner from one another.

Another preferred configuration is characterized in that the first flange face has an edge projecting therefrom in the direction normal to the surface of the first flange face, and the cover element is designed in its shape and size to be held in a clamping manner by the edge. . The peripheral area of the cover element is fixed between the two flange faces.

The peripheral region preferably has at least one radially outward projection as viewed from the cylinder axis, the shape and size of the projection being complementary to the recess in the projecting edge so that the projection and the recess together form an anti-torsion means.

The cover element is preferably held by a socket having an external thread that is screwed into an internal thread of the housing.

This solution separates the attachment of the cover element from the attachment of the housing to the part carrying the measurement gas. This has the advantage that replacement or cleaning of the optical access can be temporally and spatially separated from disassembly/assembly of the housing in the part carrying the measurement gas. Thus, replacement and/or cleaning of the optical access may be performed, for example, in a space less susceptible to contamination, while disassembly/assembly may also be performed in a contamination-sensitive workshop environment.

Another preferred embodiment is that the socket is cup-shaped, the cover element forming the bottom of the cup-shaped socket, and the external thread is disposed in the opening of the cup-shaped socket, distal from the bottom, the opening of the cup-shaped socket from the opening of the housing rather than the bottom of the cup-shaped socket. placed further away

These features displace the outer thread further away from the flange into the depth of the housing, reducing the heat resistance of the thread and the need for sealing means such as a sealing ring. This reduction is achieved from the fact that the temperature of the housing decreases with increasing distance from the tube carrying the measuring gas, for example a hot exhaust pipe. The reduction in temperature can be facilitated by the use of cooling fins.

It is also preferred that the cover element is part of the protective tube. In this case, the protective tube can be replaced in order to replace the cover element. This has the advantage of ease of handling since, unlike the transparent area of the cover element, the protective tube is not sensitive to contact, ie to contamination associated with contact.

It is also preferred that the edge of the cover element is arranged in the annular groove in the protective tube in such a way that the cover element is held in a clamping manner.

A further preferred embodiment is characterized in that the cover element is held in a form-fitting manner between two parts of the protective tube which are mechanically rigidly connected to each other after the cover disk has been inserted.

A second transparent cover element is preferably disposed in the housing at a distance from the first flange face, the second transparent cover element having a first side facing the first flange face and a second side opposite the first side , separating the inner chamber into a first partial inner chamber area and a second partial inner chamber area hermetically separated from the first partial inner chamber area. As a result, the optical components (laser, beam forming means, detection device, beam splitter) arranged in the housing are protected from contamination when the first cover element is replaced and/or cleaned.

It is preferred that the second transparent cover element is a plane-parallel cover disk and the transparent area of the first transparent cover element is a converging lens.

Another preferred embodiment is characterized in that the second transparent cover element is a converging lens and the transparent area of the first transparent cover element is a plane-parallel cover disk.

It is also preferred that the second transparent cover element is a converging lens and the transparent area of the first cover element is a converging lens.

It is also preferred that the second transparent cover element is a plane-parallel cover disk and the transparent area of the first cover element is a plane-parallel cover disk.

A further preferred configuration is characterized in that it comprises a first optical element designed and arranged to focus laser radiation incident from the laser through the central transparent region to a laser spot.

It is also preferred that the central transparent region forms the first optical element.

The first optical element is preferably a convex lens.

BRIEF DESCRIPTION OF THE DRAWINGS Embodiments of the invention are illustrated in the drawings and are described in more detail in the description that follows. The same reference numbers in different drawings indicate elements that are identical or at least functionally similar.

1 shows the measuring principle based on laser induced incandescence, used in the present invention.
Figure 2 shows the basic structure of a particle count sensor operating with laser induced incandescence.
3 shows a possible structure of a particle sensor device.
4 shows a cross-sectional view of a sensor head of a particle sensor device according to the invention;
5 shows a detailed view of the clamping fixing elements of the transparent cover element;
6 shows the fixing of the transparent cover element to the sensor head using threads.
7 shows a variant of the solution shown in FIG. 6 .
8 shows the integration of a transparent cover element into a protective tube device.
9 shows a first example of fixing a transparent cover element in a protective tube arrangement.
10 shows a second example of fixing a transparent cover element in a protective tube arrangement.

1 shows a laser-induced incandescent (LII) based measurement principle. High intensity laser radiation 10 collides with particles 12 . Particle 12 is in particular a soot particle. The intensity of the laser radiation 10 is so high that the energy of the laser radiation 10 absorbed by the particles 12 heats the particles 12 to several thousand degrees Celsius. As a result of heating, particles 12 spontaneously and substantially without preferential direction emit significant radiation 14 in the form of thermal radiation (hereinafter also referred to as LII radiation 14 ). Thermal radiation (incandescent or glowing) occurs according to Planck's law of radiation. The thermal radiation serves as a measurement signal and is detected by a detection device. The thermal radiation spectrum is relatively broadband and depends on many factors such as particle temperature and particle material. For soot particles heated to the sublimation temperature, the maximum of the spectrum may be, for example, in the red range (about 650 nm wavelength). A portion of the LII radiation 14 emitted in the form of thermal radiation is emitted opposite to the direction of the incident laser radiation 10 .

2 schematically shows the basic structure of the particle sensor device 16 . The particle sensor device 16 here comprises a laser 18 , the preferably parallel laser radiation 10 of which is at least one first optical element arranged in the beam path of the laser 18 . (20) is focused to a very small laser spot (22).

It is possible for the laser 18 to be modulated or switched on and off (duty cycle < 100%). The laser 18 is preferably a CW laser. This enables the use of inexpensive semiconductor laser devices (laser diodes), making the complete particle count sensor 16 cheaper, and greatly simplifies the control of the laser 18 and the evaluation of the measurement signal. Of course, the use of a pulsed laser is also not excluded.

The first optical element 20 is preferably a first lens 24 , but may also be embodied as a reflector. Only in the volume of the laser spot 22 does the intensity of the laser radiation 10 reach the high value required for LII. The laser 18 may be a continuous wave laser or a laser diode that may be operated in a pulsed fashion. It is desirable to use a continuous working (CW) laser of low power (~50-500 mW, sometimes up to 5000 mW), which is focused into a very small laser spot by an appropriate optical element (eg a lens). Despite the relatively low laser power of the laser diode, the focusing allows the power density to be high enough to reach the required temperature for the LII. Due to the small size of the laser spot, it can be assumed that only a single particle always passes through the laser spot 22 (intrinsic single particle detection) at any given time based on particle concentrations of up to about 10 ¹³ /m ³ .

Since the dimensions of the laser spot 22 are in the range of several micrometers, in particular up to 200 micrometers, the particles 12 traversing the laser spot 22 are excited and emit radiant power that can be evaluated. If the diameter of the laser spot 22 is, for example, 10 μm, there is always at most one particle 12 in the laser spot 22 and the instantaneous measurement signal of the particle number sensor 16 is at most about 10 ¹³ /m ³ Based on the particle concentration of The measurement signal is generated by a detection device 26 arranged in the particle count sensor 16 to detect radiation 14 , in particular thermal radiation, emanating from particles 12 flying through the first spot 22 . For this purpose, the detection device 26 preferably has at least one first face 26.1 which is sensitive to radiation 14 . The detection device 26 may be, for example, a sensitive photodiode or a silicon photomultiplier tube (SiPM) or a multi-pixel photon counter (MPPC).

FIG. 3 shows a schematic arrangement of components of a particle sensor device 16 suitable for use as a soot particle count sensor in an exhaust gas of a combustion process as a measuring gas 32 .

The particle sensor device 16 has a first part 16.1 designed to be exposed to a measuring gas 32 and a second part 16.1 not exposed to the measuring gas 32 and comprising the optical components of the particle sensor device 16 ( 16.2). The two parts are separated by a partition wall 16.3 impermeable to the measuring gas 32 . The bulkhead 16.3 is, for example, a part of an exhaust pipe of an internal combustion engine. In the partition 16.3 , in the beam path of the laser radiation 10 , an optically transparent cover element 34 is attached which is transparent to both the laser radiation 10 and the radiation 14 emitted from the laser spot 22 .

The first part 16.1 of the particle number sensor 16 has a protective tube arrangement consisting of an outer protective tube 28 and an inner protective tube 30 . The two protective tubes 28 , 30 preferably have a general cylindrical or prismatic shape. The cylindrical base is preferably circular, oval or polygonal. The cylinders are preferably arranged coaxially, and the axes of the cylinders are aligned across the flow of exhaust gas 32 . The inner protective tube 30 protrudes into the flowing exhaust gas 32 beyond the outer protective tube 28 in the axial direction of the cylinder. At the ends of the two protective tubes 28 , 30 , away from the flowing exhaust gas 32 , the outer protective tube 28 projects beyond the inner protective tube 30 . The inner width of the outer protective tube 28 is preferably much greater than the outer diameter of the inner protective tube 30 so that a first flow cross-section exists between the two protective tubes 28 , 30 . The inner width of the inner protective tube 30 forms a second flow cross-section.

The result of this geometry is that the exhaust gas 32 enters the arrangement of the two protection tubes 28 , 30 through the first flow cross-section and then away from the exhaust gas 32 at the ends of the protection tubes 28 , 30 . The direction is changed to flow into the inner protective tube 30 , exit the inner protective tube 30 , and be sucked in by the flowing exhaust gas 32 . This achieves a uniform metering gas flow in the inner protective tube 30 . The arrangement of the protective tubes 28 , 30 together with the rest of the particle sensor arrangement is fixed on or in the exhaust pipe transverse to the exhaust gas flow.

This first part 16.1 of the particle sensor device 16 is a component of the preferred embodiment. However, those features are not essential features of the present invention. An essential feature of the invention is the component of the second part 16.2 of the particle sensor device 16 .

The second part 16.2 of the particle sensor device 16 comprises a laser 18 with a converging lens 19 , a first optical element 20 , a second optical element 23 , a beam splitter 25 , a filter ( 27) and a detection device 26 . The second optical element 23 may be a lens or a reflector. The first optical element 20 is arranged in the beam path of the laser radiation 10 in such a way as to focus the laser radiation 10 incident from the laser 18 to the laser spot 22 , and the second optical element 23 . is arranged in such a way as to focus the radiation 14 emitted from the laser spot 22 to the thermal radiation spot 29 . The beam splitter 25 reflects the incident laser radiation in the direction of the first optical element 20 and is transparent to thermal radiation 14 . The detection device 26 has a first face 26.1 which is sensitive to the radiation 14 , the first face 26.1 being disposed in the beam path of the focused thermal radiation 14 to produce the focused thermal radiation 14 . illuminated The filter 27 is less transparent in the spectral range of the laser radiation 10 than in the rest of the spectral range, thus contributing to that the signal of the detection device is not distorted by the effect of the scattered laser radiation 10 .

An optically transparent cover element 34 is attached between the protective tube device and the optical component (lens, beam splitter, laser, detection device) and protects the sensitive optical elements from the hot, chemically aggressive and "dirty" measuring gas 32 . Insulate.

As an alternative to this, since the first lens 24 performs the above insulation, it is possible to combine the functions as a converging lens and as a transparent cover element in one optical component. An optional filter is placed in front of the detection device 26 and blocks the range of wavelengths the laser 18 emits. This reduces the amount of unwanted scattered light (eg retroreflection of the laser 18 from the optical components) that reaches the detection device 26 . If the detection device 26 has only a small active detection area, the use of a third lens in front of it is possible, which leads to a better capture of the LII radiation 14 .

4 shows a part of a particle sensor device 16 flanged to a partition wall 16.3 impermeable to the measuring gas. The illustration of this part shows the structural details of the part of the particle sensor device 16 close to the exhaust gas. The bulkhead 16.3 is, for example, a part of the exhaust pipe 17 of an internal combustion engine. However, the present invention is not limited to the illustrated structure. 4 is a cross-sectional view in which the central axis 19 of the particle sensor device 16 rests. The part of the particle sensor device 16 shown in FIG. 4 is rotationally symmetric with, for example, the central axis 19 as the axis of symmetry.

The particle sensor device 16 has an inner chamber 36 defined by a housing 40 and a cover element 34 . The cover element 34 covers the opening of the housing 40 and has a central transparent area 34.1 . In particular, the components of the second part 16.2 of the particle sensor device 16 are arranged in the inner chamber 36 .

The cover element 34 gas-tightly covers the inner chamber 36 against the measuring gas 32 , and can be connected to the housing 40 in a non-destructively releasable manner. The housing 40 has a sensor head 42 in which the opening of the housing 40 is disposed. Attached to the end of the sensor head 42 is a front end 44 of a flange having a first flange face. The first flange face has an edge surrounding the opening in the form of a closed loop. The cover element 34, in its shape and size, is designed to lie on the first flange face or optionally on an intermediate element between the first flange face and the cover element. An optional intermediate element is, for example, a seal.

In the configuration shown, the particle sensor device 16 has a counter flange 46 . The counter flange 46 has a second flange face designed to rest on the cover element 34 or on an intermediate element between the first and second flange faces. The counter flange 46 is rigidly connected to the wall 16.3, for example by welding.

The particle sensor device 16 also has at least one clamping means 48 which creates a clamping force which presses the second flange face and the first flange face against each other. The clamping means 48 are, for example, clamps that are tightened with one or more threads and produce a clamping force directed parallel to the central axis 19 .

The sensor head 42 of the particle sensor device 16 is connected to an exhaust pipe to which the two flange halves are connected and fixed together. At the same time, the cover element 34 is clamped between the two flange halves.

As already explained with reference to FIG. 3 , the particle sensor device 16 has a device of cylindrical protective tubes 28 , 30 open at two ends. The protective tubes 28 , 30 preferably have a cylinder axis coincident with the central axis 19 . These axes preferably coincide with the central beam of laser radiation that creates the laser spot 22 . The protective tubes have jacket faces that extend around the laser spot.

The proximal ends of the protective tubes 28 , 30 are preferably flush with the flange connection. The guard tubes 28 , 30 branch off a representative portion of the measuring gas 32 , and guide this measuring gas in a directional flow through the spatial region where the laser spot 22 is located.

A cooling fin 49 is disposed on the exterior of the housing 40 to isolate the sensor head 42 from the high temperature of the measurement gas 32 , which may be a hot exhaust gas of the combustion process. Alternatively or additionally, thermal decoupling may be performed or enhanced using the air gap 50 . The air gap 50 appears as an increase in the inner width of the housing 40 transverse to the direction of the laser beam to the laser spot.

The end of the protective tube 28 , 30 facing the sensor head 42 is, in its shape and size, at the cover element 34 or between the cover element 34 and the proximal end of the protective tube 28 , 30 . It is designed to be placed on an intermediate element. An example of such an intermediate element is a seal.

The cover element 34 has a central region defined by a transparent region 34.1 . The cover element 34 also has a peripheral region 34.2 which surrounds the central region 34.1 in the form of a closed loop.

The first flange face has an edge 52 projecting therefrom in a direction normal to the surface of the first flange face. The cover element 34 is designed in its shape and size to be held in a radially clamping manner by the edge 52 .

The transparent area of the cover element 34 is designed as a lens and fixed to the peripheral area 34.2 . An optionally available inner transparent cover element 51 protects the optical components (laser, lens, beam splitter, detection device) when the cover element 34 is removed. In this case, the protective tube device is rigidly connected to a counter flange 46 fixed to the wall 16.3. When the particle sensor device 16 is connected to the volume carrying the measuring gas 32 by means of the clamping means 48 , the peripheral area 34.2 of the cover element 34 is formed in an airtight manner between the two surfaces of the flange connection. are clamped To facilitate initial assembly and assembly when replacing the cover element 34 , the cover element 34 may be clamped into a groove in the flange of the sensor, for example via a spring structure. Therefore, the insert does not fall off during assembly.

The housing 40 optionally includes an inner transparent cover element 51 disposed within the housing 40 at a distance from the first flange face. The inner transparent cover element 51 has a first side 51.1 facing the first flange side and a second side 51.2 opposite the first side 51.1, and has an inner chamber 36 in the first part. an inner chamber area, and a second partial inner chamber area hermetically separated from the first partial inner chamber area. The inner transparent cover element 51 can be, for example, assembled in a non-destructively releasable manner and optionally used in any of the configurations presented herein.

The non-replaceable and permanently installed inner transparent cover element 51 avoids the risk of ingress of foreign matter when replacing the cover element 34 in the workshop or the risk that the sealability will no longer be guaranteed after replacement. This inner transparent cover element 51 may optionally be used in any configuration of the particle sensor device 16 according to the present invention.

5 shows a detailed view of the clamping manner fastening elements of the transparent cover element 34 . The peripheral region 34.2 has at least one radially outwardly protrusion 54 as viewed from the central axis 19 , the shape and size of the protrusion 54 being a recess in the protruding edge 54 of the front end 44 of the flange. complementary to, so that the projection and the recess together form an anti-torsion means. The protruding edge 54 will also facilitate replacement of the cover element 34 in that the cover element 34 secured by bracing can be more easily released by applying a force to the edge 54 . can

6 shows an embodiment in which the cover element 34 is held by a socket 56 having an external thread that is threaded into an internal thread 58 of a housing 40 . Here too, the protective tube arrangement is rigidly connected to the flange of the exhaust pipe. The replaceable cover element 34 is screwed into the housing via the socket 56 and can be replaced after opening the clamping means 48 .

7 shows an embodiment based on the embodiment according to FIG. 6 . The socket 56 is cup-shaped. The cover element 34 forms the bottom of the cup-shaped socket 56 , and the internal thread 58 (and thus the external thread) is disposed in the opening of the cup-shaped socket remote from the bottom. The opening of the cup-shaped socket 56 is disposed further away from the opening of the housing 40 or the front end 44 of the flange than the bottom of the cup-shaped socket 56 . The thread is displaced further away from the flange in this embodiment into the rear portion of the housing. As a desirable result, the heat resistance requirements for threads and possible sealing structures, such as sealing rings, for example, are significantly relaxed, since the temperature of this part of the housing is already significantly reduced by means of cooling and insulating measures (cooling fins, air gaps). . Because it is placed on the bottom of the cup-shaped shape, the position of the cover element can be maintained in the installation position closer to the flange. This is particularly advantageous when the cover element 34 or its transparent area is designed as a lens. In this case, the high light-converging efficiency of the lens, which varies depending on the position, is maintained.

8 shows an embodiment in which the cover element 34 is a component of a protective tube arrangement consisting of protective tubes 28 , 30 . During assembly, the protective tube device is placed between the two flange parts and clamped via clamping means 48 . The cover element is pre-assembled in the protective tube device. The protective tube arrangement is replaced to replace the cover element 34 . Also in this variant, the protective tube can be connected to the sensor head via a clamping device before assembly, as shown in FIG. 4 , in order to facilitate assembly.

FIG. 9 shows an embodiment of such a device in which the edge of the cover element 34 is disposed in an annular groove in the inner protective tube 30 such that the cover element 34 is held in a clamping manner to the protective tube 30 . The clamping way retention is achieved, for example, by holding the cover element 34 in a form-fitting manner between two parts of the protective tube 30 which are mechanically rigidly connected to each other after the cover element 34 has been inserted.

FIG. 10 also shows an embodiment of such a device wherein the edge of the cover element 34 is disposed in an annular groove in the inner protective tube 30 such that the cover element 34 is held in a clamping manner to the protective tube 30 . The clamping retention is achieved, for example, by holding the cover element 34 in a form-fitting manner between the two sheet metal parts of the protective tube device joined by, for example, spot welding, after the cover element 34 has been inserted.

16: particle sensor device
18: laser
22: laser spot
26: detection device
28, 30: protective tube
29: heat radiation area
34: cover element
40: housing
42: sensor head
46: counter flange
48: clamping means
54: protrusion
56: socket

Claims (18)

A particle sensor device (16) having a housing (40) and an inner chamber (36) that covers the opening of the housing (40) and is defined by a cover element (34) having a central transparent area (34.1), comprising: a laser (18); ) and a detection device 26 are arranged in the inner chamber 36 , wherein the particle sensor device transmits the laser radiation 10 incident from the laser 18 through the central transparent area 34.1 to the laser spot 22 . ), wherein the particle sensor device directs the heat radiation emitted from the laser spot 22 through the central transparent area 34.1 to illuminate the detection device 26 . In the particle sensor device (16), designed and arranged to guide
Particle sensor device (16), characterized in that the cover element (34) covers the inner chamber (36) in an airtight manner and can be connected to the housing (40) in a non-destructively releasable manner. 2. The housing (40) according to claim 1, wherein the housing (40) has a sensor head (42) in which an opening of the housing (40) is disposed, the sensor head (42) having an edge surrounding the opening in a closed loop form. having a first flange face, wherein the cover element (34), in its shape and size, is designed to lie on the first flange face or on an intermediate element between the first flange face and the cover element (34) Particle sensor device (16), characterized in that. 3. The particle sensor device (16) according to claim 2, wherein the particle sensor device (16) has a counter flange (46) with a second flange face, the second flange face being on the cover element (34) or on the first flange face and the first flange face. Particle sensor device (16), characterized in that it is designed to rest on an intermediate element between the two flange faces. 4. The particle sensor device (16) according to claim 3, characterized in that it has at least one clamping means (48) for generating a clamping force which presses the second flange face and the first flange face against each other. Particle sensor device (16). 2. The laser radiation according to claim 1, wherein the particle sensor device (16) has a cylindrical protective tube (28, 30) open at two ends, the protective tube (28, 30) generating the laser spot (22). Particle sensor device (16), characterized in that it has a cylinder axis coincident with the central beam of , and the protective tube (28, 30) has a jacket face extending around the laser spot (22). 6. The protective tube (28, 30) according to claim 5, wherein the end of the protective tube (28, 30) facing the sensor head (42) is, in its shape and size, on or on the cover element (34) or with the cover element (34) and the protective tube. Particle sensor device (16), characterized in that it is designed to rest on an intermediate element between the proximal ends of the tube (28, 30). 2. The cover element (34) according to claim 1, wherein the cover element (34) has a central transparent area (34.1), the cover element (34) having a peripheral area (34.2) which surrounds the central transparent area (34.1) in the form of a closed loop. Particle sensor device (16) characterized in that it has. 8. The edge (52) according to claim 7, wherein the first flange face has an edge projecting therefrom in a direction normal to the surface of the first flange face, and the cover element (34) is, in its shape and size, at the edge (52). Particle sensor device (16), characterized in that it is designed to be held in a clamping manner by 9. The perimeter region (34.2) according to claim 5 and 8, wherein the peripheral region (34.2) has at least one radially outward projection (54) when viewed from the cylinder axis, the shape and size of the projection (54) being within the protruding edge (52). Complementary to the recess, the particle sensor device (16) characterized in that the projection (54) and the recess together form an anti-torsion means. 2. Particle sensor device (16) according to claim 1, characterized in that the cover element (34) is held by a socket (56) having an external thread that is screwed into an internal thread of the housing (40). 11. The cup-shaped socket (56) of claim 10, wherein the socket (56) is cup-shaped, and the cover element (34) forms the bottom of the cup-shaped socket (56), and the external thread is in an opening of the cup-shaped socket (56) remote from the bottom. wherein said opening of said cup-shaped socket (56) is disposed further away from the opening of said housing (40) than the bottom of said cup-shaped socket (56). 2. Particle sensor device (16) according to claim 1, characterized in that the cover element (34) is a component of the protective tube (28, 30). 13. Particle sensor device (16) according to claim 12, characterized in that the edge of the cover element (34) is arranged in an annular groove in the protection tube (28, 30) so that the cover element (34) is held in a clamping manner. ). 13. The method according to claim 12, wherein the cover element (34) is maintained in a form-fitting manner between two parts of the protective tube (28, 30) which are mechanically rigidly connected to each other after insertion of the cover element (34). Particle sensor device (16) characterized. 15. A second transparent optical element (51) according to any one of the preceding claims, wherein a second transparent optical element (51) is arranged in the housing (40) at a distance from the first flange face, and the second transparent optical element (51) has a first side (51.1) facing the first flange face, and a second side (51.2) opposite the first side (51.1), wherein the inner chamber (40) comprises a first partial inner chamber region and the Particle sensor device (16) characterized in that it separates from the first partial inner chamber area into a second partial inner chamber area which is hermetically separated. 16. A laser spot (22) according to any one of the preceding claims, wherein the particle sensor device (16) directs the incident laser radiation (10) from the laser (18) through the central transparent region (34.1). A particle sensor device (16) having a first optical element designed and arranged to focus it into 3. Particle sensor device (16) according to claim 2, characterized in that the central transparent region forms the first optical element. 16. Particle sensor device (16) according to any one of the preceding claims, characterized in that the first optical element is a convex lens (24).

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