DE102021108441A1 - Fastening device for a temperature-stable, transparent element, and particle sensor, comprising the fastening device - Google Patents

Abstract

The present invention generally relates to a fastening device for a temperature-stable element with high transparency, such as a glass, a ceramic or a glass-ceramic. The invention also relates to a particle sensor comprising such a fastening device. A fastening device for holding a temperature-stable element, in particular continuous operation in high-temperature applications above 300°C, preferably above 350°C and particularly preferably above 380°C, is proposed a base body and a temperature-stable element, wherein the base body comprises a continuous opening, which is formed in the region of the holding section for receiving and holding the temperature-stable element, and wherein the temperature-stable element is in operation for electromagnetic radiation in a wavelength spectrum of at least 350 to 1,000 nm Transparency of at least 80%, preferably at least 84% and particularly preferably at least 86%.

Description

The present invention generally relates to a fastening device for a temperature-stable element with high transparency, such as a glass, a ceramic or a glass-ceramic. The invention also relates to a particle sensor comprising such a fastening device.

In the course of increasing environmental awareness, the emissions from internal combustion engines are becoming increasingly important. Of particular interest in this context are often particles, such as soot particles, which can be found in the exhaust gas stream of such internal combustion engines.

That's it U.S. 4,567,750 a soot particle sensor based on a resistance measurement with electrically heatable surfaces is known, one of the surfaces being heated and soot particles being able to deposit on the surfaces.

A further development of this resistive sensor principle is in the DE 103 40 748 shown.

Further developments relate to opto-electronic particle sensors, such as those from DE 10 2017 104 378 A1 are known. These work with an emitting and a detecting opto-electronic semiconductor chip. The disadvantage of this method is the time delay in the measurement.

Recent developments are moving in the direction of optical methods, for example based on laser-induced incandescence to measure or analyze particle flows, for example to determine soot volume fractions.

A good database with regard to the properties of the particle flows, for example an exhaust gas from an internal combustion engine, can be valuable in order to check the functionality of the internal combustion engine or to regulate or optimize the internal combustion engine. This makes it possible, for example, to monitor the functionality of a diesel particulate filter and, if the data obtained is used appropriately, to reduce emissions.

For this it may be necessary to bring optical components or the measuring device or parts thereof close to or even in the particle stream. In these cases, however, it is necessary to protect the associated components from gas or particles in order to avoid abrasion and contamination, and, for example in the case of exhaust gas streams from internal combustion engines, the components also from the heat that occurs, which can be several 100 °C.

A device for accommodating and/or holding components, such as optical components of a measuring device, is therefore desirable, which is tight, preferably fluid-tight or hermetically tight, in order to protect the components, especially if they protrude into the particle flow. On the other hand, this device should also be able to withstand high temperatures and vibrations, such as can occur in an exhaust system of an internal combustion engine.

The device should also have a high level of transparency, at least in one section or area, so that light beams, for example excitation light from a light source, can leave the device or enter it, for example reflected light beams.

Finally, the device should also be able to be mounted easily and flexibly in the vicinity of the particle flow, for example on an exhaust system of an internal combustion engine.

The device should also be durable at the temperatures that occur.

The inventors have taken on this task.

This object is achieved in a surprisingly simple manner by a fastening device for holding a temperature-stable element, in particular for continuous operation in high-temperature applications above 300° C., preferably above 350° C. and particularly preferably above 380° C., and a particle sensor according to one of the preceding claims . Preferred embodiments and developments of the invention can be found in the respective dependent claims.

The temperature-stable element can advantageously have low thermal expansion. In the context of the present invention, this is understood to mean a low coefficient of thermal expansion, which is given here as a linear coefficient of thermal expansion (CTE=Coefficient of Thermal Expansion).

In the context of the invention, low thermal expansion of the temperature-stable element means a thermal expansion coefficient of the temperature-stable element of no greater than 9*10-6/K in a temperature range of 20° C. to 400° C., preferably no greater than 7.5*10 -6/K, further preferably not greater than 7*10-6/K and particularly preferably not greater than 6.5*10-6/K.

• - einen Grundkörper mit zumindest einem Halteabschnitt, einem an diesen Halteabschnitt angrenzenden Rohrabschnitt mit einer umlaufenden Wandung sowie mit einem an diesen Rohrabschnitt angrenzenden Befestigungsabschnitt, und
• - ein temperaturstabiles Element,

wobei der Grundkörper eine durchgehende Öffnung umfasst, welche im Bereich des Halteabschnittes ausgebildet ist zur Aufnahme und Halterung des temperaturstabilen Elementes.In a first embodiment of the invention, the fastening device comprises

• a base body with at least one holding section, a tubular section adjoining this holding section with a peripheral wall and with a fastening section adjoining this tubular section, and
• - a temperature stable element,

wherein the base body comprises a continuous opening which is formed in the area of the holding section for receiving and holding the temperature-stable element.

The temperature-stable element is selected in such a way that it has a transparency of at least 80%, preferably at least 84% and particularly preferably at least 86%.

Transparency means that the temperature-stable element is particularly transmissive for the specified electromagnetic radiation.

• - einen Grundkörper mit zumindest einem Halteabschnitt, einem an diesen Halteabschnitt angrenzenden Rohrabschnitt mit einer umlaufenden Wandung sowie mit einem an diesen Rohrabschnitt angrenzenden Befestigungsabschnitt,
• - ein temperaturstabiles Element, und
• - ein Haltemittel,

wobei der Grundkörper eine durchgehende Öffnung umfasst, welche im Bereich des Halteabschnittes ausgebildet ist zur Aufnahme des temperaturstabilen Elementes, wobei
das temperaturstabile Element vorzugsweise über seine Seitenwand mit dem Haltemittel in der Öffnung gehaltert ist und wobei die Öffnung fluiddicht, vorzugsweise hermetisch dicht, verschlossen ist.In a further embodiment of the invention, the fastening device comprises

• - a base body with at least one holding section, a pipe section adjoining this holding section with a peripheral wall and with a fastening section adjoining this pipe section,
• - a temperature stable element, and
• - a holding device,

wherein the base body comprises a continuous opening, which is formed in the region of the holding section for receiving the temperature-stable element, wherein
the temperature-stable element is preferably held in the opening via its side wall with the holding means, and the opening is closed in a fluid-tight, preferably hermetically-tight manner.

According to this embodiment of the invention, the temperature-stable element is selected in such a way that it has a transparency of at least 80%, preferably at least 84% and particularly preferably at least 86%, both at room temperature and during operation for electromagnetic radiation in a wavelength spectrum of at least 350 to 1000 nm. having.

An improvement in transparency can be achieved if the temperature-stable element comprises a coating, for example a single-layer antireflection coating, on the side facing away from the particle flow.

As a result, the scattering behavior of the temperature-stable element when electromagnetic radiation passes through can be reduced, so that the transparency can be improved by 2% or even 4%, for example. In a preferred embodiment, the temperature-stable element accordingly has a transparency for electromagnetic radiation in a wavelength spectrum of at least 350 to 1000 nm of at least 90%, preferably at least 92% and particularly preferably at least 94%.

The fastening device according to the invention makes it possible to arrange optical components or other components of a measuring device in the vicinity of a particle flow or even to introduce them into a particle flow, whereby they are held in place by the fastening device or the main body of the fastening tion device can be protected. In other words, the fastening device according to the invention can represent a type of interface between a measurement volume and a measurement device.

The particle flow may comprise a flowing fluid, for example an exhaust gas from an internal combustion engine. The attachment section of the base body is provided for simple and flexible installation in the vicinity of the particle flow, via or with which the attachment section can be installed and firmly connected to a unit guiding the particle flow. This can be the exhaust system of an internal combustion engine, for example.

The fastening device according to the invention can thus be permanently connected to the unit guiding the particle flow, for example the exhaust line, by means of welding, for example, with which a tight connection that is permanently operational can be created. The fastening device can thus be attached easily and flexibly in the vicinity of the particle flow. The fastening device according to the invention is designed to also be able to be mounted on an inner side of an exhaust line, which points towards the particle flow, so that at least part of the fastening device protrudes into the particle flow.

A welded joint is favorable in that, in addition to the high temperatures that may occur during operation, it can also withstand vibrations that may occur during operation, such as those that can occur in an exhaust system of an internal combustion engine, and are therefore durable, even in high-temperature applications above 300 °C , preferably above 350 °C and more preferably above 380 °C.

The base body also includes a tubular section with a circumferential wall, which adjoins the fastening section, and a holding section which adjoins the tubular section and is therefore arranged on the side of the tubular section opposite the fastening section. The continuous opening of the base body is advantageously designed in the area of the holding section for receiving and/or holding the temperature-stable element.

In a preferred embodiment, the temperature-stable element is held in the opening, preferably with its side wall, with a holding means. The holding means, which will be discussed in more detail below, is advantageously selected in such a way that the continuous opening of the base body in the area of the holding section can be closed in a fluid-tight, preferably hermetically-tight manner.

In this way, it is possible to protect optical components or other components of the measuring device from the particles if they are arranged on the side of the fastening device opposite the particle stream, and also from the effects of heat, for example in the case of exhaust gas streams from internal combustion engines. The fastening device according to the invention can thus also be arranged in such a way that it protrudes into the particle flow, for example an exhaust gas flow, or is arranged at least in sections in a particle flow.

The transparent design of the temperature-stable element enables electromagnetic radiation in a wavelength spectrum of at least 350 to 1,000 nm, for example visible light, excitation light or scattered or reflected light, or laser light, for example with a wavelength of 820 to 840 nm, to exit the fastening device or can enter the fastening device from the outside through this "window".

In a particularly preferred embodiment, the fastening device is permanently operational in high-temperature applications from at least 400°C, preferably from at least 500°C and particularly preferably from at least 600°C. Such a design of the fastening device enables in particular the arrangement in particle streams such as exhaust gas streams from internal combustion engines, at which temperatures of more than 500° C. or even significantly higher can occur.

A material and/or a component is referred to as high-temperature-resistant or high-temperature-stable if it can be used at the required temperature, i.e. preferably from at least 400 °C, preferably from at least 500 °C and particularly preferably from at least 600 °C and more, in particular more than 100 h or more, preferably 500 h or more and particularly preferably 1000 h or more. In particular, the material and/or the component can be designed to be stable against deformation at these temperatures over the periods of time mentioned.

Long-term operational stability in these temperature ranges also advantageously makes it possible to use pyrolytic cleaning processes during operation, ie thermochemical conversion processes for the decomposition of organic compounds, which generally take place from about 400° C. to 500° C. This is a very great advantage, especially in the case of very warm particle flows such as exhaust gas flows with, for example, soot particles, since otherwise the transparent element would quickly become soiled and the transparency would quickly decrease.

The fastening device according to the invention is therefore durable even at very high operational temperatures of 400° C., 500° C., 600° C. or more. The fastening device is preferably shake and vibration-resistant measured according to ISO 16750-3.

The continuous opening of the base body is sealed in a fluid-tight, preferably hermetically sealed manner, by means of the temperature-stable element and/or by means of the temperature-stable element and the holding means.

Such a connection is referred to as fluid-tight, for example a metal-glass connection, if this connection seals, ie is tight against the escape or passage of fluid media and is preferably essentially completely (hermetically) tight. The tightness can be determined by a leak test, usually using a helium leak tester.

Helium leak rates of less than 2 * 10 ^-8 mbar*l/s or 1 * 10 ^-8 mbar*l/s at room temperature indicate that an essentially completely hermetic seal is present. This measurement can preferably be carried out with an application of pressure of one bar.

According to a preferred embodiment, the fastening device has a helium leak rate of at most 5*10 ^-8 mbar*l/s. Particularly low helium leak rates of the fastening device of at most 2 * 10 ^-8 mbar * l / s and particularly preferably at most 1 * 10 ^-8 mbar * l / s can be achieved if a special holding means is introduced between the base body and temperature-stable element according to one embodiment of the invention, an at least partially crystallized glass, which will be discussed in more detail below, is used as the holding means.

Such a configuration is advantageous because in this way sufficient mechanical rigidity is achieved, but such a connection still has a certain elasticity. This is advantageous in the case of thermal cycling and therefore advantageously leads to a particularly temperature-stable connection in the connection zone in which the holding section of the base body is in contact with the temperature-stable element and/or the holding means.

In a preferred embodiment, the opening and/or the base body, in particular the holding section, the tube section and/or the fastening section are circular, preferably cylindrically symmetrical. This leads to a comparatively homogeneous temperature distribution in the base body, especially at high temperatures and thermal cycling loads, so that temperature peaks or areas with greater temperature differences, such as those that can occur around corners or edges, can be avoided and mechanical stresses can be reduced.

The base body can therefore advantageously be sleeve-shaped with a central axis, the opening for receiving and holding the temperature-stable element preferably also being circular, preferably cylindrically symmetrical, and arranged coaxially to the base body.

In principle, other geometries or cross sections are also conceivable, for example square or polygonal, with straight or curved wall sections. However, on the one hand, these are more complex to manufacture and, on the other hand, they are also less favorable with regard to the temperature distribution, as explained above. It goes without saying that the opening, at least in the region of the holding section, is advantageously designed with an exact fit opposite to the temperature-stable element to be accommodated.

Suitable elements that are stable at high temperatures and are transparent or essentially transparent, for example certain glasses or glass ceramics, often have a low or very low coefficient of thermal expansion.

Since the temperature-stable element or the temperature-stable element must be fitted flush with the holding means and permanently sealed during operation in the opening of the base body in order to open the tion to be fluid-tight or hermetically sealed even at the required temperatures, it can therefore be beneficial to also select a material for the base body which has a similar coefficient of thermal expansion as the temperature-stable element.

However, such materials are often not sufficiently thermally stable to be durable at the required high temperatures. With some fundamentally suitable materials, creeping can occur, which can lead to irreversible deformations of the base body and thus impair the tightness. Furthermore, such materials are often expensive to procure and/or complex to process or to assemble.

The inventors have surprisingly found that a specific design of the base body can mean that materials or materials can also be selected for the base body which have a higher or even significantly higher coefficient of thermal expansion than the temperature-stable element, and still also with the required temperatures, the opening can be permanently sealed in a fluid-tight or hermetically sealed manner.

Advantageously, the base body includes compensation means that make it possible to intercept or compensate for forces that can arise during major temperature changes in such a way that they do not fully affect the temperature-stable element or the connection zone. In this way, it is possible to prevent excessive mechanical stresses from occurring in the connection zone, which can lead to cracks or detachments and which, as a consequence, can lead to leaks.

In a particularly preferred embodiment, the basic body according to the invention is therefore characterized in that the tubular section comprises at least a first section which adjoins the fastening section and is designed as a transition section, and a second section which is designed as a compensation section. The compensation section is adjacent to the holding section of the base body. In terms of the invention, the compensation section provides compensation means in order to at least partially compensate for differences in the thermal expansion behavior in the event of temperature changes in the required areas. Accordingly, the transition section and the compensation section together form the tubular section of the base body and each comprise a peripheral wall which adjoins one another.

The compensation section can have an extent in the axial direction which corresponds to at least 30%, preferably at least 50% and particularly preferably at least 70% of the axial extent of the transition section. This enables a correspondingly compact design, since a certain minimum length or extension in the axial direction can be favorable for the transition section for reasons of stability.

The compensation section can also have an axial extent of 100% of the axial extent of the transition section, which means that in this case the axial extent of both sections is the same. In principle, the axial extent of the compensation section can also be greater than the axial extent of the transition section, but care must be taken here that the overall length of the base body does not become too large. In general, it can be sufficient if the axial extent of the compensation section is no more than five times the axial extent of the transition section.

In one embodiment, the compensation section has at least one tapered section as a compensation means with a cross-sectional area that is smaller than the cross-sectional area of the transition section. The result of this is that lever forces, which arise during temperature changes and which can act in the radial direction, cannot be transmitted completely or significantly weakened from the fastening section to the holding section of the base body. In a particularly preferred embodiment, the compensation section with the reduced cross-sectional area is therefore directly adjacent to the holding section.

This significantly reduces the mechanical stresses that can act on the connection zone, as a result of which the risk of detachments or cracks in the connection zone can be minimized and the risk of leaks during operation can be reduced.

This configuration also makes it possible to manufacture the base body inexpensively from several parts, for example the tube section on the one hand and the holding section on the other hand, and then to permanently connect both components to one another, for example by welding or soldering. In this way, also in a likewise preferred embodiment, the holding section can be connected to the temperature-stable element before the pipe section is joined.

It has been shown that even a slight reduction in the cross-sectional area by approximately 1%, better still at least 5%, preferably by at least 10% and particularly preferably by at least 20%, significantly reduces this leverage effect. Too great a reduction in the cross-sectional area, for example by more than 70%, has proven to be unfavorable since the structure of the base body could then be weakened overall or the rigidity could no longer be given.

If the holding section of the base body has the same cross-section as the transition section, the tapering of the cross-sectional area in the compensation section means that the holding section is not flush with the compensation section on the outside, but offset inwards towards the central axis of the base body. As a result, a radially acting force is no longer transmitted from the tubular section of the base body to the outer edges of the holding section, which corresponds to an unfavorable introduction of force similar to a bending beam, but instead the introduction of force takes place inwards, which reduces deflection.

In this way, it is also possible, for example, to attach the attachment device to an exhaust line by means of welding without already causing pre-damage in the connection zone between the temperature-stable element, holding means and holding section as a result of the heat action required for this.

In a further likewise preferred embodiment, the compensation section comprises at least one reduced section as compensation means, in which the thickness of the wall of the compensation section is reduced compared to the thickness of the wall of the transition section.

Even a slight reduction in the wall thickness, for example in a length range of 5-10%, can contribute to the pipe section reacting more elastically overall, especially with the required temperature changes. In this way, too, the introduction of force from the pipe section into the holding section can be reduced, as a result of which undesired mechanical stresses, which can lead to detachments and/or cracks in the connection zone, can also be reduced. Mechanical stresses as a result of different expansion behaviors of the pipe section and the holding section can act as a transverse force in the transition to the holding section and can be unfavorable for a seal that is stable at high temperatures and has a long service life.

This is due to the fact that the holding section with the embedded temperature-stable element can have less thermal expansion in the radial direction than the base body in the other sections. The transverse contraction under thermal stress can therefore be different in the holding section than in the other sections, particularly if the temperature-stable element has a lower coefficient of thermal expansion than the material of the base body.

A slight reduction in the wall thickness has advantages in that the structural stability of the base body is hardly or only slightly impaired. It has been shown that, assuming a corresponding wall thickness in the transition section, a reduction of at least 25%, preferably at least 35% and particularly preferably at least 40%, in particular approximately or exactly 50%, in connection with the required temperatures, the additional loads from vibrations and the rapid temperature changes represents a very good compromise for increasing the elasticity without weakening the structural stability of the base body. This applies, for example, to base bodies with a wall thickness in the tube section or in the transition section of approximately 0.6 mm, although the wall thicknesses can also be between 0.4 mm and 1 mm, for example. In a particularly favorable embodiment, the wall thickness is 0.6 mm in the transition section and 0.3 mm in the compensation section, which corresponds to a reduction of 50%. It is generally favorable not to provide any edges or sharp-edged indentations in the transition between the transition section and the compensation section, but instead to provide radii or transition radii in order to avoid a notch effect.

An excessive reduction in wall thickness, for example by more than 75%, appears unfavorable, since then the transverse contraction and the resulting mechanical stresses in the two sections is too different and the rigidity of the base body as a whole could be endangered. The reduction in wall thickness should therefore be no more than 75%, preferably no more than 65% and particularly preferably no more than 60%.

In a further preferred embodiment, the compensation section comprises at least one projecting section as a compensation means, in which the wall is at an angle α with α>0° to the central axis of the base body. The overhang preferably takes place in the direction of the holding section. In a particularly favorable embodiment, the projecting section is directly adjacent to the holding section. This advantageously means that forces are absorbed by the tubular section of the base body and transverse forces can be better compensated for, since the projecting section provides an additional elastic component with different transverse contractions. The angle α can be between 5° and 75°, preferably between 10° and 70°, and particularly preferably between 15° and 65°, for example 5°, 10°, 15°, 20°, 25°, 30°, 35° °, 40° or 45°.

In a particularly advantageous embodiment, several compensation means can also be combined with one another as described above, for example reducing the wall thickness with the overhang. In other words, the cantilevered pipe section includes the compensation section with the reduced wall thickness. In this way, the projection can be realized in a particularly simple manner, and the elasticity can be increased again.

The base body can be made of a temperature-stable material, preferably a temperature-stable metal from the group of steels, for example normal steels, high-grade steels, stainless steels and high-temperature-stable ferritic or austenitic steels. Preference is given to steels which are readily weldable and remain rust-free when the invention is implemented.

As explained above, the invention makes it possible to select materials for the base body in a particularly advantageous manner, which have a different, also higher, coefficient of thermal expansion than the temperature-stable element. This means that materials can also be selected which can be attached particularly easily to the unit guiding the particle stream and which are permanently operational at the required temperatures.

If the coefficient of thermal expansion of the base body is greater than that of the temperature-stable element, this exerts a tensile or compressive stress that increases with increasing temperature as a result of different transverse contractions on the temperature-stable element. In order to still be able to seal the opening fluid-tight or hermetically tight at the required temperatures, it is favorable if the coefficient of thermal expansion of the material of the base body is not higher than 15 * 10-6/K in a temperature range of 20 °C to 400 °C C, preferably not higher than 14*10-6/K and more preferably not higher than 13*10-6/K.

It goes without saying that a lower coefficient of thermal expansion can further reduce the difference to the coefficient of thermal expansion of the temperature-stable element and is therefore fundamentally more favorable if the other material properties are sufficient for the intended use.

The material for the base body can thus be selected from the group comprising the following steels: Thermax, for example Thermax 4016, Thermax4742, or Thermax4762 or Crofer22 APU or CroFer22 H or NiFe-based materials, for example NiFe45, NiFe47, or known under the brand name Inconel , for example Inconel 718 or X-750, or steels, for example known under the designations CF25, Alloy 600, Alloy 625, Alloy 690, SUS310S, SUS430, SUH446 or SUS316, or austenitic steels such as 1.4828 or 1.4841 or ferritic steels such as 1.4762 or Incolloy 909

The temperature-stable element can be disc-shaped and in particular have plane-parallel main surfaces. Furthermore, at least the main surfaces preferably also have an optical polish.

In other embodiments, it is also possible to shape the temperature-stable element in a plano-convex, plano-concave, biconvex, biconcave, convex-concave or concave-convex manner. In this case, the temperature-stable element can also be part of an imaging system assigned to it.

The temperature-stable element can include or consist of glass, glass ceramic or ceramic.

In a particularly preferred embodiment, the temperature-stable element comprises sapphire glass, ie synthetic corundum. The reasons for this are the very good optical properties due to the crystalline structure, the high degree of hardness and the particularly high temperature resistance. For optical reasons, it is favorable if the temperature-stable element is designed to be essentially monocrystalline.

In addition, the thermal expansion coefficient of sapphire glass has also proven to be favorable, which is around 7.5 * 10-6/K (temperature range from 20 °C to 400 °C), since the difference to the thermal expansion coefficient of the base body is not too high.

In another, likewise preferred embodiment, the temperature-stable element comprises quartz glass or quartz glass, which can be produced by melting and resolidifying quartz. Particularly good optical properties can also be achieved here. However, the coefficient of thermal expansion is significantly lower at around 0.5 * 10-6/K, which means that the mechanical stresses during temperature changes between the temperature-stable element and the base body are greater compared to sapphire glass.

In general, it is therefore preferred within the meaning of the invention if the thermal expansion coefficient of the temperature-stable element is not greater than 9*10-6/K in a temperature range from 20° C. to 400° C., preferably not greater than 7.5*10-6/K. K, further preferably not greater than 7*10-6/K and particularly preferably not greater than 6.5*10-6/K.

According to the invention, the amount of the difference in thermal expansion coefficients between the temperature-stable element and the base body can be at least 2.5*10 ^-6 /K, preferably more than 3*10 ^-6 /K and particularly preferably more than 4*10 ^-6 /K . However, this difference should not be too high either, since otherwise even the compensation means described above might not be sufficient to reliably absorb the stresses that occur. The difference in the thermal expansion coefficients between the temperature-stable element and the base body should therefore not be more than 20*10 ^-6 /K, preferably not more than 15*10 ^-6 /K.

A holding means can be provided or included for holding the temperature-stable element in the opening of the base body, preferably for forming a high-temperature-stable and/or mechanically high-strength joint.

In principle, for example, laser welding or metal solders, in particular hard solders, are conceivable. For the production of stable joints that are to be exposed to very high temperatures during operation, for example temperatures of 400 °C or more, certain solder glasses are available which on the one hand withstand these high temperatures and on the other hand can be adapted in their expansion behavior to the materials to be joined . This makes it possible to design the joints to be fluid-tight or hermetically-tight and, at the same time, to be durable.

However, commercially available glass solders with high thermal expansion generally have low melting temperatures, which means that their thermal stability is limited and these glass solders cannot therefore be used at high temperatures.

According to the invention, a crystallizable or at least partially crystallized glass is therefore proposed as the holding means. Such a crystallizable or at least partially crystallized glass is described in the patent application EP 19 181 866.5 proposed by the applicant, which is hereby fully incorporated and made the subject of the present application.

The crystallizable or at least partially crystallized glass according to the embodiments described in this document allows the formation of high-temperature-stable and/or mechanically high-strength joints. With a crystallizable or at least partially crystallized glass, it is possible to form a particularly stable structure in the at least partially crystallized glass, in particular a structure which is stable even at high temperatures above 400° C., preferably above 500° C. and particularly preferably above is mechanically stable from 600 ° C or even up to 1000 ° C or more.

The invention therefore comprises, in a preferred embodiment, a temperature-stable element which is held in an opening of a base body by means of a holding means for forming a joint, comprising an at least partially crystallized glass, the at least partially cris tallized glass comprises a residual glass content of less than 10%, preferably less than 5% by volume. The at least partially crystallized glass includes crystal aggregates. The crystal aggregates are formed from a large number of crystallites. The crystallites are preferably needle-like and/or plate-like. Preferably, the crystallites can be arranged radially, such as spherulitic and/or fan-shaped, and/or rod-shaped and/or flake-shaped, penetrating the at least partially crystallized glass.

Such a design of the joint for holding the temperature-stable element has a number of advantages.

In particular, due to the low residual glass content of less than 10% by volume, preferably even less than 5% by volume, high dimensional stability of the joint is achieved. The high dimensional stability of the joint is furthermore advantageously ensured by the fact that the crystallites comprised by the crystallized glass are aggregated. A needle-like and/or lamellar formation of the crystallites is particularly advantageous. The inventors have found that the needle-like and/or lamellar formation of the crystallites in the crystal aggregates leads to a mechanically stable formation of the at least partially crystallized glass. This is particularly the case when the crystallites, which are preferably needle-shaped and/or platelet-shaped, are arranged, for example, spherulitically and/or fan-shaped and/or rod-shaped or platelet-shaped, penetrating the at least partially crystallized glass.

It is assumed that the preferably needle-like and/or platelet-shaped formation of the crystallites and their arrangement in spherulites, for example, or radially or also rod-shaped-randomly penetrating the at least partially crystallized glass, results in interlocking of the crystallites, which affects the mechanical stability of the at least partially crystallized glass, for example against shearing, compressive or tensile forces, advantageously increased. This interlocking can also take the form of a kind of "house of cards" structure.

The crystallites can also be in the form of flakes, ie penetrate the crystallized glass as small flakes. In the sectional view, such a design also appears as a rod, which is why it is difficult to distinguish in individual cases. In the context of the present disclosure, a platelet is understood to be a geometric shape in which the lateral dimension in one spatial direction of a Cartesian coordinate system (the thickness) is an order of magnitude smaller than the lateral dimensions (length, width) in the other two, to the first direction perpendicular directions.

The glass preferably includes: _{La2O3 _} greater than 0.3 mol% to less than 5 mol%, preferably less than or equal to 4.5 mol%, particularly preferably less than or equal to 4 mol%, _{Nb2O5 _} 0 mole % to 9 mole %, _{Ta2O5 _} 0 mole % to 7 mole %, whereby Σ (A ₂ O ₅ ) greater than 0.2 mol% to 9 mol%, where A is an element which usually has the oxidation number V+ in oxides, and includes or can include, for example, Nb and/or Ta or P and/or mixtures thereof.

It has been shown that a strong joint, for example a high-temperature stable and/or mechanically highly resilient joint, can be achieved by adding the oxides La ₂ O ₃ , Ta ₂ O ₅ and/or Nb ₂ O ₅ and optionally other oxides of the composition A ₂ O ₅ can be achieved.

The oxides La ₂ O ₃ , Nb ₂ O ₅ and Ta ₂ O ₅ and possibly other oxides A ₂ O ₅ comprised by the glass are also referred to as “glass matrix-forming oxides” within the scope of the present disclosure, which is to be understood by this term That such oxides after the thermal treatment of the crystallizable glass, so when the glass is present as at least partially crystallized glass, first in the glass matrix remain. The term “glass matrix-forming oxides” thus differs from the more general term “glass-forming oxides”.

In particular, in the context of the present disclosure, the oxides of MgO and CaO are not oxides that form a glass matrix, even if, for example, CaO is a common component of conventional glasses, for example of soda-lime glasses. In the glasses according to embodiments of the invention, oxides such as CaO and MgO are incorporated into the crystal phases, ie they just do not remain in the glass matrix and are therefore also not glass matrix-forming oxides.

However, it is quite possible that at least some of the oxides forming the glass matrix, for example La ₂ O ₃ , can be incorporated at least partially in crystal phases in the further course of the ceramization. However, a residual content of the glassy phase, albeit a small one, usually remains, which is formed in particular by the oxides forming the glass matrix.

The formation of the joint with the oxides La ₂ O ₃ and Nb ₂ O ₅ and / or Ta ₂ O ₅ and possibly other oxides A ₂ O ₅ within the above limits is advantageous because the at least partially crystallized glass in this way particularly is favorably designed in such a way that glazing takes place during a heat treatment to produce the connection. In this way, a firm connection between the individual parts of the joint is particularly advantageously produced, in particular a firm connection of the at least partially crystallized glass to the joint partner, in this case the base body and the temperature-stable element, is made possible.

However, limiting the oxides forming the glass matrix within the above-mentioned limits advantageously ensures that high temperature stability and/or high mechanical strength of the joint compound is provided at the same time.

Within the scope of the present disclosure, crystallizable glass is understood to mean a glass which is accessible to crystallization, in particular to controlled or at least controllable crystallization. Controlled crystallization is understood here to mean that the crystallizable glass can be converted into a state in which the glass is at least partially crystallized and where the crystallographic composition of the at least partially crystallized glass and/or its structure, i.e. the spatial Arrangement and / or the size of the at least partially crystallized glass comprised crystals and / or crystallites is preferably adjusted in a targeted manner.

Controlled crystallization can preferably be used, for example, to obtain a structure in which the crystallites have an essentially uniform size, for example in the one-digit micrometer range, ie for example all crystallites have an equivalent diameter of about 1 μm to 3 μm. Of course, other structures with larger or smaller crystallites are also possible.

If the at least partially crystallized glass comprises several different crystal phases, it is also possible that the average crystal or crystallite size within a crystal phase is relatively similar, but there may be strong differences between the individual crystal phases in terms of crystallite size.

In contrast to the preferably controlled or controllable crystallization, the spontaneous crystallization of a glass is to be seen in which unexpected crystal phases, frequently also undesired crystal phases, occur and, in particular, complete devitrification can also occur.

In the context of the present disclosure, a crystal aggregate or a crystal association is understood to mean an intergrowth of at least two crystals or crystallites. The crystals or crystallites can, in particular, grow together randomly. This means that the individual crystallites or crystals of an aggregate do not have to grow together along a preferred direction or along a specific crystal plane.

A needle-like formation of a crystal or a crystallite is understood to mean that the crystal or crystallite has a direction in which its dimensions are at least one order of magnitude larger than the dimensions in the other two spatial directions. In other words, a crystal or crystallite with an acicular formation can be acicular or rod-shaped or in the form of a prism, the lateral dimensions of the prismatic basic shape being at least one order of magnitude small ner than the length of the crystal or crystallite. Such crystals or crystallites are also referred to as having a prismatic design.

The crystallites can also be in the form of flakes, ie penetrate the crystallized glass as small flakes. In the sectional view, such a design also appears as a rod, which is why it is difficult to distinguish in individual cases.

In the context of the present disclosure, a radial arrangement of crystals or crystallites is understood to mean that crystals of needle or platelet form, for example needle-shaped or prismatic crystals or crystallites, are arranged around a center so that one end points in the direction of the same point and the respective other end points radially outwards in different spatial directions. For example, the ends pointing toward the center may touch at the central point.

However, this is not necessary. Such a formation of crystal aggregates, which point radially outwards from a center, is present, for example, in the form of a spherulitic formation of a crystal aggregate. Such a spherulitic formation is an approximately spherical or ellipsoidal configuration of the crystal aggregate and can have approximately the shape of a circle in a two-dimensional representation. In practice, however, due to the intergrowth of crystals and crystal aggregates in a structure, there is often a deviation from the ideal spherical or circular shape of a spherulite. In particular, the crystals or crystallites forming the spherulite can have different lengths and/or thicknesses.

A further configuration of a radial arrangement is a fan-shaped design in a two-dimensional section. For example, it is possible that it is not possible for the crystals or crystallites to form in a specific spatial direction in the structure. Here, too, the crystallites or crystals strive outwards from a center, but only within a certain solid angle.

A rod-shaped or platelet-shaped arrangement is understood to mean that the individual crystals or crystallites do not strive outwards from a common center in different spatial directions, but are arranged randomly, for example without a pronounced preferred direction. In particular, the crystallites or crystals can be arranged interlocked with one another. Such a structure can also be compared, for example, to the construction of a "house of cards", in which the individual tiles (like the cards in a house of cards) are arranged opposite one another and form a stable structure.

In the context of the present disclosure, a crystallization nucleus is understood to mean a starting point for crystallization. The crystallization nucleus favors the addition of atoms to build up a crystalline lattice, for example thermodynamically or kinetically. In particular, a crystallization nucleus can be a lattice defect and/or an arrangement of atoms. Frequently, interfaces can be starting points for crystallization or include such starting points for crystallization.

According to one embodiment of the joint, the crystallites at least partially comprise crystallization nuclei at the grain boundaries and/or at least partially enrichments comprising lanthanum, in particular comprising lanthanum compounds, are arranged at the grain boundaries of the crystallites.

Such an embodiment of a joint connection is advantageous in order to enable the formation of a particularly strong connection between at least partially crystallized glass and the joint partner. If the crystallites at least partially include crystallization nuclei at the grain boundaries, this promotes the formation of the structure of the at least partially crystallized glass comprising crystal aggregates with, for example, a radial or rod-shaped or platelet-shaped arrangement, for example in the manner of a house of cards.

This is also the case if at least some enrichments comprising lanthanum, in particular comprising lanthanum compounds, are arranged at the grain boundaries of the crystallites. The inventors suspect that accumulations of lanthanum, for example lanthanum compounds, can act as effective crystallization nuclei.

According to one embodiment, the glass comprises SiO ₂ 30 mol% to 40 mol%, _{Al2O3 _} 3 mole % to 12 mole %, CaO 32 mol% to 46 mol%, MgO 5 mole % to 15 mole %, ZnO 0 mol% to 10 mol%, as well as optional ZrO ₂ 0 mol% to 4 mol%, preferably at most 3 mole %, and/or TiO ₂ 0 mol% to 4 mol%, preferably at most 3 mole %, and/or MnO ₂ 0 mole% to 5 mole%.

According to one embodiment, TiO ₂ , ZrO ₂ and/or MnO ₂ can optionally be included in the glass. However, the content of these components in the glass is limited. In particular, TiO ₂ and ZrO ₂ , which are known nucleating agents, are not required as nucleating agents in the crystallizable glass. In addition, their presence can be disruptive since, in the most unfavorable case, undesired low-expansion crystal phases can form for the present application.

According to a further embodiment, the CaO content of the glass is between at least 35 mol % and at most 46 mol %, preferably between at least 35 mol % and less than 43.5 mol % and/or the glass has an MgO content between 5 mole % and less than 13 mole %.

The limited contents of CaO and/or MgO in the glass according to one embodiment are due to the fact that in this way the stability of the crystallizable glass against spontaneous crystallization is further increased. Thus, CaO and MgO are components that are incorporated into the crystal phases that result from thermal treatment of the crystallizable glass. As explained above, it is of particular importance for the addressed applications that crystal phases with a high thermal expansion coefficient are obtained. In order to promote the fact that predominantly precisely the desired crystal phases with a high thermal expansion coefficient are obtained, the contents of CaO and MgO in the glass are therefore preferably further limited, as explained above. This limitation serves in particular to prevent or even completely prevent the formation of wollastonite, enstatite or diopside or mixed crystals of these crystalline phases at least as far as possible.

According to a further embodiment, the glass is present as a crystallizable glass and has a transformation temperature of more than 720°C.

The transformation temperature of a glass is an important characteristic value that reflects both the processing properties of this glass and its thermal stability. In particular, a high glass transformation temperature is also accompanied by high dimensional stability of the glass.

According to one embodiment, therefore, the crystallizable glass preferably has a particularly high dimensional stability, which is reflected in the indicated high transformation or glass transition temperature T _g of 720° C. or more.

According to one embodiment of the holding means, the thermal expansion coefficient of the crystallizable glass is more than 8*10 ^-6 /K in a temperature range from 20 °C to 300 °C and preferably in a temperature range from 20 °C to 700 °C more than 9*10 ^{- 6} /K In this way, good adaptation of the vitreous material to the coefficient of thermal expansion of the materials of the base body to be joined is advantageously already possible with the crystallizable glass before the end of the thermal treatment for producing the preferably hermetically sealed connection.

The transformation temperature T _g is determined by the point of intersection of the tangents on the two branches of the expansion curve when measured at a heating rate of 5 K/min. This corresponds to a measurement according to ISO 7884-8 or DIN 52324.

According to a further preferred embodiment of the invention, a crystallizable or at least partially crystallized glass is proposed as the holding means, the at least partially crystallized glass having a porosity. This can decrease towards the interface of the at least partially crystallized glass with the joining partner and/or be distributed in a structured manner.

Such a crystallizable or at least partially crystallized glass is described in the patent application WO 2017/220700 proposed by the applicant, which is hereby fully incorporated and made the subject of the present application.

The pores are distributed in a structured manner in the at least partially crystallized glass. If the pores of the at least partially crystallized glass are not already completely created or present in the sintered body, but rather arise for the most part at the same time as or during the crystallization, there can be a complete or almost complete fusion of the glassy phase, which leads to a more homogeneous and solid one Configuration of the composite of glassy phase and in particular later crystallizing and subsequently crystallized portions, which in particular sintered glass ceramics are superior in terms of strength, in particular compressive strength.

The term "pores created or present in the sintered body" or also the expression "pores created or present in a sintered body" refers in the context of this disclosure to the pores formed during sintering, which in particular are caused by the mechanical process of pressing the sintered body or sintered body , but not caused by crystallization. In the method disclosed here, the pores are distributed more homogeneously, and this more homogeneous distribution leads to even better mechanical resistance and even greater thermal shock resistance.

In the case of the preferred at least partially crystallizable glasses, it is also advantageous that they do not have to be subjected to a two-stage thermal process, comprising a nucleation phase and a phase of crystal growth at elevated temperature, since they are already in a one-stage thermal process, as so-called self-crystallizing glasses can be converted into glass-ceramic or ceramic material. In this case, for example, a constant temperature increase can advantageously take place with a defined, in particular almost constant, heating rate. Such temperature-time profiles also offer advantages in terms of process technology, since they are easier to control and can be used with larger thermal tolerances.

Different from crystallization by added nuclei, in these self-crystallizing glasses, the crystallization nucleates on the surface of the powder of the partially crystallizable glass. In the case of the self-crystallizing glasses according to the invention, this occurs at the heating rates mentioned without any further holding time. This enables effective production. This germination occurs at different times and at lower temperatures than the actual crystallization process.

The wetting of the at least one joining partner, for example the temperature-stable element, which is required for hermetic glazing, takes place after germination, but before the actual crystallization process. As a result, a hermetic, high-temperature stable glazing can be achieved.

The porosity according to this embodiment can contribute significantly to mechanical thermal shock resistance. There is a gradient in the pore density in the direction of the interface to the vitrified material, which ensures wetting free of defects and bubbles. The combination of the porosity distribution and homogeneous crystallization leads to a very high mechanical resistance at temperatures up to 900 °C or even higher.

The porosity occurs in the at least partially crystallized glass in a structured distribution, preferably in the form of a controlled porosity. Controlled porosity is characterized in that the porosity, in particular the pores, are not present in the same form everywhere in the volume of the shaped body in question, which is a shaped sintered body or shaped sintered part.

In particular, there is controlled porosity within the meaning of the present invention when the porosity in a border area of the shaped body assumes a very low value of, for example, at most 3%. In particular, the surface of the at least partially crystallized glass with a controlled porosity has essentially no open pores, i.e. pores which open towards the medium surrounding the interface, for example air, which further supports the high hermeticity or fluid tightness.

A controlled porosity and a porosity gradient can be achieved in particular when the actual density of the sintered body or sintered compact is at most 10% lower, advantageously at most 5% lower, than the theoretical density of the glass or the at least partially crystallizing but not yet crystallized glass is. In this case, the degree of sintering is at least 90%, preferably at least 95%. In this case, the pores introduced by the sintered compact or sintered body are generally few in number and can frequently also emerge from the crystallizable or at least partially crystallized glass, so that a structured arrangement of these pores arises from the pores formed during crystallization.

The ratio of the pores already created or present in the sintered body, sintered article or shaped body relative to the pores created according to the invention is, for example, at a degree of sintering of about 99% in the preferred embodiments described here is about at least 1.8 or can also be higher. This means that for every pore remaining in the sintered body there are at least 1.8 pores, which are then additionally present in the at least partially crystallized glass. This value is an extremely cautious statement by the inventors, since it was neglected here that pores already present in the sintered body, sintered compact or molded body can still escape even during the thermal treatment. In addition, these pores, which are formed during or at the same time as crystallization, expand considerably and thus increase the resulting porosity value even more than this ratio corresponds to.

This ratio can be set within a wide range by the maximum sintering temperature and the grinding, in particular also by the degree of grinding of the ground glass, in particular green glass, and can be in a range from at least 1.5 to about 5, for example.

It has been shown that the pores of the at least partially crystallized glass are not already fully formed or already present in the sintered compact or sintered body from which the at least partially crystallized glass has emerged, but rather arise for the most part during or at the same time as the crystallization or themselves increase and a volume-related increase in porosity occurs.

In a preferred embodiment, the crystal content of the at least partially crystallized glass is more than 50% by volume, preferably more than 60% by volume. This high proportion of crystal phases also contributes to increasing the viscosity and thus leads to increased mechanical stability at high temperatures. Furthermore, the high level of crystallization and the resulting interlocking of the crystallites leads to a localization of the pores and thus enables controlled porosity to a large extent.

Thus, an at least partially crystallized glass according to this embodiment of the invention comprises at least one crystal phase and pores which are distributed in a structured manner in the at least partially crystallized glass, with the pores of the at least partially crystallized glass preferably not already being in the sintered body from which the at least partially crystallized Glass has emerged, are completely created or already exist, but in particular have largely arisen at the same time or during crystallization.
A sintered body or sintered body is a dimensionally stable sintered body with the crystallizable glass, which is suitable and intended below for entering into a connection with a body that can be a housing material or a sealing element.

The pores or the porosity are preferably distributed in such a way that in the boundary region of the at least partially crystallized glass there is a porosity gradient in the form that from the boundary surface and/or from the surface of the at least partially crystallized glass to its center the pore density increases. The boundary region preferably varies in terms of its extent between a minimum of 5 μm and a maximum of 200 μm in thickness, preferably between 20 μm and 50 μm.

Insofar as porosities occurred in joining materials in the prior art through the use of sintered bodies, in particular sintered bodies that were not highly compressed, these were generally homogeneous and consequently not structured in the sense of the above definition, in particular not arranged in a controlled structured distribution.

A glass, here at least partially crystallizable glass, is referred to as green glass, which is essentially not yet crystallized, which means that it has a volume-related proportion of crystals or proportion of crystal phases of less than 0.1%.

According to a further embodiment, the at least partially crystallized glass is formed in such a way that the pores are at least partially arranged in the vicinity of crystals. This special appearance of the at least partially crystallized glass according to one embodiment is attributed to the fact that the pores arise during crystallization, in particular as a result of crystallization.

According to a further embodiment, the crystal content of the at least partially crystallized glass is at least 25%, based on the total volume of the at least partially crystallized glass, preferably at least 50% and particularly preferably at least 60%.

The porosity is preferably at least 3% based on the total volume of the at least partially crystallized glass, preferably at least 5%, particularly preferably at least 10% or even 20%.

According to a first preferred embodiment of an at least partially crystallized glass with pores, the at least partially crystallized glass comprises the following oxides in % by weight: SiO ₂ : 20 to 60, preferably 25 to 50 _{Al2O3 :} 0.5 to 20, preferably 0.5 to 10 CaO: 10 to 50 MgO: 0.5 to 50, preferably 0.5 to 10 _{Y2O3 :} 0.1 to 20, preferably 3 to 20 ZrO ₂ : 0.1 to 25, preferably 3 to 20 _{B2O3 :} 1 to 15, preferably 3 to 12, where HfO ₂ can optionally be present in amounts of up to 0.25% by weight.

According to a second preferred embodiment of an at least partially crystallized glass with pores, the at least partially crystallized glass comprises the following oxides in % by weight: SiO ₂ : 36 to 54, preferably 40 to 54 _{Al2O3 :} 8 to 16, preferably 8 to 13 CaO: 0 to 35, preferably 5 to 25 MgO: 0 to 17, preferably 3 to 14 RO: 8 to 39, preferably 8 to 35 ZrO ₂ : 0 to 25, preferably 0 to 17 _{B2O3 :} 0 to 3, preferably 0 to 2, especially preferably 0 where the proportion RO designates the oxides BaO, SrO, MgO, ZnO individually or in total or in any mixtures.

Preferably RO is individually or in any combination in % by weight: BaO 0 - 36 MgO 0 - 22 CaO 0 - 25
Y ₂ O ₃ =0 is also preferred. This could be achieved by replacing the Y ₂ O ₃ with MgO and/or CaO, for example in the stabilization of the ZrO ₂ crystal phase.

The crystal content of the at least partially crystallized glass is more than 50% by volume, preferably more than 60% by volume. This high proportion of crystal phases also contributes to increasing the viscosity and thus leads to increased mechanical stability at high temperatures. Furthermore, the high degree of crystallization and the resulting interlocking of the crystallites leads to a localization of the pores and thus enables controlled porosity to a large extent.

This at least partially crystallizable glass achieves its high temperature resistance in particular via a higher viscosity of the residual glass phase.

An important crystal phase of the at least partially crystallizable glass is, for example, Ca- or Mg-stabilized ZrO ₂ at values of ZrO ₂ >0. This is a more thermally stable phase than Y ₂ O ₃ -stabilized ZrO ₂ .

In general, however, ZrO ₂ is difficult to stabilize thermally, because when it is lowered to lower temperatures, a phase transformation into less coordinated phases, for example from tetraclinic to monoclinic, can lead to a jump in volume with an associated reduction in volume, so that cracks can form as a result.

Consequently, in the second preferred embodiment, crystal phases other than ZrO ₂ -based are used in the at least partially crystallizable glass.

The proportion of BaO in the at least partially crystallizable glass is advantageously less than 36% by weight. As a result, less chromate phase is formed at the interface of the at least partially crystallizable glass with Cr-containing steels, for example stainless steels, especially if this interface is part of a connection or a connection and feedthrough element.

In a particularly advantageous version of the second preferred embodiment, the at least partially crystallizable glass is free of B ₂ O ₃ .

The possible B ₂ O ₃ content in the first preferred embodiment is advantageous for use in many applications and temperature ranges. This B ₂ O ₃ content leads to very good wetting of the joining partners even before crystallization at moderate temperatures. This wetting is essential for a hermetically sealed connection, which is required in many applications. If, on the other hand, the composite is to be used at over 1000° C., the B ₂ O ₃ content is not necessarily an advantage, since this can lead to a low viscosity of the residual glass phase at these temperatures, which can lead to greatly reduced mechanical stability .

In the second preferred embodiment, the use of B ₂ O ₃ in the composition of the at least partially crystallizable or crystallized glass is therefore largely dispensed with, resulting in residual glass phases with high viscosities at temperatures above 1000° C. and thus mechanical stability at up to 1200° C or sometimes even more than 1200 °C, in particular up to 1270 °C.

Furthermore, surprisingly, in the second embodiment, Y ₂ O ₃ could even be dispensed with by replacing it with MgO and CaO, which can lead to considerable cost savings in the application.

Normally, B ₂ O ₃ is required for wetting a metal with glasses. Because the at least partially crystallizable glass disclosed here, at least in the second preferred embodiment, can melt at higher temperatures on a metal, which is also referred to as vitrifying or vitrifying, surprisingly in a preferred version of the second preferred embodiment on B ₂ O ₃ even be dispensed with entirely. This temperature, at which the at least partially crystallizable glass melts on a metal, on or in a lead-through or connecting element on its housing, is also referred to as the hemispherical temperature.

The invention also includes a particle sensor, in particular an exhaust gas sensor, for example a soot particle sensor, pressure sensor, temperature sensor, NO _x sensor or oxygen sensor, comprising a fastening device according to the invention for holding a temperature-stable element with low thermal expansion.

The invention also includes an imaging system, comprising a fastening device according to the invention for holding a temperature-stable element with low thermal expansion.

The present invention makes it possible, in connection with a measuring device and/or an imaging system, to provide extensive information regarding the properties of particle flows, such as the soot concentration in an exhaust gas from an internal combustion engine. In this way, for example, a “window” can be provided for the optical analysis of soot particle concentrations in an exhaust system of an internal combustion engine using laser radiation.

The design of the base body and the temperature-stable element also enables a secure seal against penetrating gas, so that optical components or other parts of a measuring device are well protected if they are arranged on the side of the fastening device facing away from the particle flow.

The information obtained in this way can be very valuable in order to check the functionality of the internal combustion engine promptly or in real time or to regulate or optimize the internal combustion engine.

This makes it possible, for example, to monitor the functionality of a diesel particulate filter and, if the information obtained is used appropriately, to reduce emissions.

The invention also includes the use of the aforementioned fastening device according to the invention for holding a temperature-stable element with low thermal expansion in an exhaust gas sensor, a pressure sensor, a particle sensor, such as a soot particle sensor and/or a temperature sensor and/or in a NO _x sensor and/or in an oxygen sensor, or in a feedthrough for a compressor, or in an exhaust element, or in a fuel cell, or in a feedthrough for a chemical reactor, or in an imaging system.

Further details of the invention result from the description of the illustrated exemplary embodiments and the appended claims.

• 1 eine erfindungsgemäße Befestigungsvorrichtung zum Haltern eines temperaturstabilen Elementes in einer Schnittansicht,
• 2 ein Detail der erfindungsgemäßen Befestigungsvorrichtung gemäß Ausschnitt A,
• 3 ein Detail der erfindungsgemäßen Befestigungsvorrichtung gemäß Ausschnitt B,
• 4 eine erfindungsgemäße Befestigungsvorrichtung zum Haltern eines temperaturstabilen Elementes in einer Schnittansicht mit einem verjüngten Abschnitt als Kompensationsmittel,
• 5 eine erfindungsgemäße Befestigungsvorrichtung zum Haltern eines temperaturstabilen Elementes in einer Schnittansicht mit einer reduzierten Wanddicke und einer Auskragung als Kompensationsmittel,
• 6 ein Detail der erfindungsgemäßen Befestigungsvorrichtung gemäß Ausschnitt C,
• 7 eine erfindungsgemäße Befestigungsvorrichtung zum Haltern eines temperaturstabilen Elementes in einer Schnittansicht mit einer reduzierten Wanddicke, einer Auskragung sowie einer Verjüngung der Querschnittsfläche als Kompensationsmittel,
• 8 ein Detail der erfindungsgemäßen Befestigungsvorrichtung gemäß Ausschnitt D, und
• 9 eine erfindungsgemäße Befestigungsvorrichtung zum Haltern eines temperaturstabilen Elementes in einer Schrägansicht.

The drawings show:

• 1 a fastening device according to the invention for holding a temperature-stable element in a sectional view,
• 2 a detail of the fastening device according to the invention according to section A,
• 3 a detail of the fastening device according to the invention according to section B,
• 4 a fastening device according to the invention for holding a temperature-stable element in a sectional view with a tapered section as compensation means,
• 5 a fastening device according to the invention for holding a temperature-stable element in a sectional view with a reduced wall thickness and a projection as compensation means,
• 6 a detail of the fastening device according to the invention according to detail C,
• 7 a fastening device according to the invention for holding a temperature-stable element in a sectional view with a reduced wall thickness, a projection and a narrowing of the cross-sectional area as compensation means,
• 8th a detail of the fastening device according to the invention according to detail D, and
• 9 a fastening device according to the invention for holding a temperature-stable element in an oblique view.

Detailed description of preferred embodiments

In the following detailed description of preferred embodiments, like reference characters designate substantially like parts in or on these embodiments for the sake of clarity. However, in order to better explain the invention, the preferred embodiments shown in the figures are not always drawn to scale.

1 shows a fastening device 10 according to the invention for holding a temperature-stable element 20 with low thermal expansion in a sectional view.

The fastening device 10 is permanently operational in high-temperature applications above 300° C., preferably above 350° C. and particularly preferably above 380° C.

• - einen Grundkörper 40 mit zumindest einem Halteabschnitt 41, einem an diesen Halteabschnitt angrenzenden Rohrabschnitt 42 mit einer umlaufenden Wandung sowie mit einem an diesen Rohrabschnitt angrenzenden Befestigungsabschnitt 43,
• - ein temperaturstabiles Element 20, und
• - ein Haltemittel 30,

wobei der Grundkörper 40 eine durchgehende Öffnung 44 umfasst, welche im Bereich des Halteabschnittes 41 als Öffnung 45 ausgebildet ist zur Aufnahme des temperaturstabilen Elementes 20, wobei
das temperaturstabile Element 20 vorzugsweise über seine Seitenwand 21 mit dem Haltemittel 30 in der Öffnung 45 gehaltert ist und wobei die Öffnung 45 fluiddicht, vorzugsweise hermetisch dicht, verschlossen ist.The fastening device 10 includes

• - a base body 40 with at least one holding section 41, a tubular section 42 adjoining this holding section with a peripheral wall and with a fastening section 43 adjoining this tubular section,
• - a temperature stable element 20, and
• - a holding means 30,

wherein the base body 40 includes a continuous opening 44, which is formed in the region of the holding portion 41 as an opening 45 for receiving the temperature-stable element 20, wherein
the temperature-stable element 20 is preferably held via its side wall 21 with the holding means 30 in the opening 45 and the opening 45 is fluid-tight, preferably hermetically sealed, closed.

in the in 1 The embodiment of the fastening device 10 shown in the drawing already includes a holding means 30, although another embodiment is also conceivable in which this holding means 30 is dispensed with and another type of connection for receiving and holding the temperature-stable element 20 is provided.

The temperature-stable element 20 is selected in such a way that it is transparent to electromagnetic radiation in a wavelength spectrum of at least 350 to 1,000 nm both at room temperature and during operation, i.e. also at high temperatures, as can occur when the device is used as intended of at least 80%, preferably at least 84% and particularly preferably at least 86%.

According to one embodiment, an antireflection coating, for example a single layer, can be applied, for example, to the side 22 facing away from the particle flow.

The fastening device 10 according to the invention makes it possible to mount optical components or other components of a measuring device (not shown) in the vicinity of a particle flow, which is given the reference number 11 in FIG 1 is indicated to be arranged or even to be introduced into a particle stream 11, these being protected by the fastening device 10 or the base body 40 of the fastening device 10. It goes without saying that for this purpose the components to be protected should be arranged on the side of the fastening device 10 facing away from the particle flow 11 .

The particle flow 11 can comprise a flowing fluid, for example an exhaust gas from an internal combustion engine, as assumed in the present exemplary embodiment.

The fastening section 43 of the base body 40 is provided for simple and flexible assembly in the vicinity of the particle stream 11, via or with which the base body 40 can be mounted and firmly connected to a unit (not shown) guiding the particle stream.

3 FIG. 12 shows a detail of the fastening section 43 according to section B, this alone representing an exemplary embodiment. Of course, various other embodiments of the fastening section 43 are conceivable and possible in order to connect the fastening device 10 to another unit, such as an exhaust system. It is advantageously designed in such a way that a tight and permanent connection can be created.

The fastening device 10 can thus be attached easily and flexibly in the vicinity of the particle flow 11, for example on an exhaust system of an internal combustion engine. The fastening device 10 according to the invention is designed to also be arranged on an inner side of an exhaust line, which points to the particle flow, so that at least a part of the fastening device 10 protrudes into the particle flow 11, as in FIG 1 implied.

The base body 40 comprises the tubular section 42 with a peripheral wall, which adjoins the fastening section 43, and a holding section 41 adjoining the tubular section 42, which is therefore arranged on the side of the tubular section 42 opposite the fastening section 43. The continuous opening 44 of the base body is designed as an opening 45 in the area of the holding section 41 for receiving and holding the temperature-stable element 20.

In the illustrated embodiment, the temperature-stable element 20 is held with the side wall 21 with the holding means 30 in the opening of the holding section 41 . The holding means 30 completely surrounds the side wall 21, so that the continuous opening 44 in the region of the holding section 41 is sealed in a fluid-tight, preferably hermetically-tight manner.

2 shows a detail of the fastening device according to the invention according to section A in a section, the connection zone between temperature-stable element 20 and holding section 41 being shown together with a holding means 30 . In a favorable embodiment, the holding means 30 is arranged in such a way that an approximately axial contact surface is formed with the temperature-stable element 20 on the one hand and another approximately axial contact surface with the side of the holding section 41 facing the opening. Accordingly, the holding means has a certain extent in the axial direction parallel to the center axis 12 , which advantageously corresponds to at least half the thickness of the temperature-stable element 20 . As a result, a correspondingly secure joint connection can be implemented.

In this way it is possible to protect optical components or parts of the measuring device (not shown), which can also be arranged in the opening 44 of the fastening device 10, from the particles. Furthermore, protection against the direct effects of heat can also be guaranteed.

The transparent design of the temperature-stable element 20 enables electromagnetic radiation in a wavelength spectrum of at least 350 to 1,000 nm, for example visible light, excitation light or scattered or reflected light, or laser light, to exit the fastening device 10 or enter the fastening device 10 from the outside can enter through this "window". Purely exemplary are in the 1 a beam 13 entering the fastening device 10 and a beam 14 exiting from the fastening device 10 are indicated.

The fastening device 10 according to the illustrated embodiment is durable in high-temperature applications from at least 400° C., preferably from at least 500° C. and particularly preferably from at least 600° C. It is therefore stable against deformation at the required temperatures.

In operation, the fastening device 10 is also suitable for carrying out pyrolytic cleaning processes.

Furthermore, the fastening device 10 shown is stable against shaking and vibrations, measured according to ISO 16750-3.

The fastening device 10 shown has a helium leak rate of at most 5*10 ^-8 mbar*l/s, preferably at most 2*10 ^-8 mbar*l/s and particularly preferably at most 1*10 ^-8 mbar*l/s.

The arrangement and design of the holding means 30 is particularly beneficial for this. Such a design of the fastening device 10 is advantageous because in this way sufficient mechanical rigidity is achieved, but such a connection still has a certain elasticity. This is advantageous in the case of thermal cycling and therefore advantageously leads to a particularly temperature-stable connection in the connection zone.

In the illustrated embodiment, the openings 44, 45 and the base body 40 and accordingly the holding section 41, the tube section 42 and the fastening section 43 are cylindrically symmetrical. This leads, especially at high temperatures and thermal cycling loads, to a comparatively homogeneous change in temperature in the base body 40, so that the temperature peak zen or areas with greater temperature differences, such as those that can occur around corners or edges, are avoided.

As shown, the base body 40 is sleeve-shaped with a center axis 12 , the opening 45 for receiving and holding the temperature-stable element 20 being cylindrically symmetrical and arranged coaxially with the base body 40 .

In principle, other geometries or cross sections of the base body 40 are also conceivable, for example square or polygonal, with straight or curved wall sections. However, on the one hand, these are more complex to manufacture and, on the other hand, they are also less favorable with regard to the temperature distribution, as explained above. It goes without saying that the opening 45 is designed to be exactly the same as the temperature-stable element 20 to be accommodated, with a corresponding space for the holding means 30 obviously having to be provided if a holding means 30 is used.

The invention makes it possible to hold high-temperature-stable and transparent or essentially transparent elements 20, for example certain glasses or glass-ceramics, which also have a low or very low coefficient of thermal expansion. The temperature-stable element 20 or the temperature-stable element 20 with the holding means 30 is permanently fitted into the opening 45 of the holding section 41 in a sealing manner during operation and thus closes the opening 45 in a fluid-tight or hermetically sealed manner even at the required temperatures.

The base body 40 is advantageously designed with compensation means for this purpose, which make it possible to intercept or compensate for forces that can arise with larger temperature changes and/or higher temperatures in such a way that they do not fully affect the temperature-stable element 20 or the affect connection zone. In this way, it is possible to prevent excessive mechanical stresses from occurring in the connection zone, which can lead to cracks or detachments and which, as a consequence, can lead to leaks.

In a particularly preferred embodiment, the basic body 40 according to the invention is therefore characterized in that the tubular section 42 comprises at least a first section which adjoins the fastening section 43 and is designed as a transition section 53, and a second section which is designed as a compensation section 51. The compensation section borders on the holding section 41 of the base body 40 . In terms of the invention, a compensation section 51 provides compensation means in order to at least partially compensate for differences in the thermal expansion behavior of individual sections or parts of the fastening device 10 . The transition section 53 and the compensation section 51 together form the tube section 42 of the base body 40.

The compensation section can have an extent in the axial direction which corresponds to at least 30%, preferably at least 50% and particularly preferably at least 70% of the axial extent of the transition section 53 . This enables a correspondingly compact design, since a certain minimum length or extent in the axial direction for the transition section 53 can be favorable for reasons of stability.

The compensation section 51 can also have an axial extent of 100% of the axial extent of the transition section 53, which means that in this case the axial extent of both sections is the same. In principle, the axial extent of the compensation section 51 can also be greater than the axial extent of the transition section 53, but care must be taken here that the overall length of the base body 40 does not become too large. In general, it can be sufficient if the axial extent of the compensation section 51 is no more than five times the axial extent of the transition section 53 .

A preferred embodiment of a compensation section is shown in FIG 4 , wherein the compensation section 51 shown there has at least one tapered section as a compensation means with a cross-sectional area that is smaller than the cross-sectional area of the transition section 53. This means that lever forces, which can arise during temperature changes and which can act in the radial direction, do not be transferred completely or significantly weakened from the fastening section to the holding section 41 of the base body 40 .

This significantly reduces the mechanical stresses that can act on the connection zone, as a result of which the risk of detachment or cracks in the connection zone is minimized and the risk of leaks, particularly in the region of the connection zone, during operation can be reduced.

This configuration also makes it possible to manufacture the base body 40 inexpensively from several parts, for example the tubular section 42 on the one hand and the holding section 41 on the other hand, and then to permanently connect both components to one another, for example by welding. In this way, in a likewise preferred embodiment, the holding section 41 can first be connected to the temperature-stable element 20 by means of glazing on or in before the tube section 42, preferably with the fastening section 43, is joined.

It has been shown that even a slight reduction in the cross-sectional area by approximately 1%, better still at least 5%, preferably by at least 10% and particularly preferably by at least 20%, significantly reduces this leverage effect. Too great a reduction in the cross-sectional area, for example by more than 70%, has proven to be unfavorable since the structure of the base body could then be weakened overall or the rigidity could no longer be given.

In the illustrated embodiment, the inner diameter is reduced from about 30 mm to about 27 mm in the compensation section 51, which corresponds to a reduction in cross-sectional area of about 15%. Such a reduction has proven to be favorable for the wall thickness of the tube section 42, which is 0.6 mm in the exemplary embodiment.

With larger wall thicknesses, the reduction in cross-sectional area can also be greater, since the wall thickness offers sufficient stability. At lower wall thicknesses, a smaller reduction in cross-sectional area will be more beneficial.

In the exemplary embodiment shown, the holding section 41 has the same cross-section as the transition section 53, so that the narrowing of the cross-sectional area in the compensation section 51 means that the holding section 41 is not flush with the compensation section 51 on the outside, but is instead offset inward towards the central axis 12 . This results in a circumferential open area 45. In a preferred embodiment, the extension of this open area 45 in the radial direction corresponds to at least half the wall thickness of the tube section 42, particularly preferably at least to the simple wall thickness.

A radially acting force is thus no longer transmitted from the tubular section 42 of the base body 40 to the outer edges of the holding section 41, which corresponds to an unfavorable introduction of force similar to a bending beam, but the introduction of force takes place inwardly, which reduces the deflection.

In a further likewise preferred embodiment, a compensation section 54 is provided with at least one reduced section as a compensation means, in which the thickness of the wall of the compensation section 54 is reduced compared to the thickness of the wall of the transition section 53 .

Even a small reduction in the wall thickness, for example in a range of 5-10%, can contribute to the pipe section 42 reacting more elastically overall, in particular with the required temperature changes. In this way, too, the introduction of force into the holding section 41 can be reduced, as a result of which undesired mechanical stresses, which can lead to detachments and/or cracks in the connection zone, can also be reduced.

A slight reduction in the wall thickness has advantages in that the structural stability of the base body 40 is hardly or only slightly impaired as a result. It has been shown that, assuming a corresponding wall thickness in the transition section 53, a reduction of at least 25%, preferably at least 35% and particularly preferably at least 40%, in particular approximately or exactly 50%, in connection with the required temperatures, the additional stresses caused by vibrations and the rapid changes in temperature represent a very good compromise for increasing the elasticity without weakening the structural stability of the base body 40.

This applies, for example, to a base body 40 as in 5 shown with a wall thickness of about 0.6 mm, but wall thicknesses can also be between 0.4 mm and 1 mm, for example. In a particularly favorable embodiment, the wall thickness in the transition section 53 is 0.6 mm and in the compensation section 54 is 0.3 mm. It is generally favorable not to provide any edges or sharp-edged indentations in the transition between the transition section 53 and the compensation section, but instead to provide radii or transition radii 55 in order to reduce a notch effect.

Too great a reduction in the wall thickness, for example by more than 75%, appears unfavorable since the transverse contraction and the resulting mechanical stresses in the two sections are too different and the rigidity of the base body 40 as a whole could be endangered. The reduction in wall thickness should therefore be no more than 75%, preferably no more than 65% and particularly preferably no more than 60%.

in the in 5 In the embodiment shown, the compensation section 54 is not only designed with a reduced wall thickness, but also includes a further compensation means in the form of a projection of the wall. In other words, the compensation section 54 is designed with a reduced wall thickness and a projecting section as a compensation means and thus combines two compensation means according to the invention in a particularly favorable manner, which of course can also be used individually.

In the case of the overhang, the wall is aligned at an angle α with α>0° to the central axis 12 of the base body 40 . The overhang is in the direction of the holding section 41. This advantageously means that axial forces are absorbed by the pipe section 42 and the resulting transverse forces can be better compensated, since the overhanging section provides an additional elastic component with different transverse contractions. The angle α can be between 5° and 75°, preferably between 10° and 70°, and particularly preferably between 15° and 60°. In the exemplary embodiment, the angle is approximately α=15°.

6 shows a detail of the fastening device 10 according to the invention according to detail C, wherein the overhang and the wall thickness reduction as well as the transition radii 55 and the angle α are shown.

In a particularly preferred embodiment, several compensation means can be combined with one another, for example reducing the wall thickness with the overhang as in 5 shown embodiment.

7 shows another example of an embodiment of the fastening device 10 according to the invention, in which several compensation means are also combined with one another. In the example shown, these are the taper of the cross-sectional area, the reduction in wall thickness and the overhang. The compensation section 56 shown accordingly comprises a section 57 with a narrowing of the cross section, which in turn comprises a section 58 with a reduction in wall thickness and a projection. Wall thickness reduction and projection are formed as in the embodiment 5 explained, of course, other training and possible combinations are given.

This design of the compensation section 56 showed the highest elasticity in tests. It is therefore particularly well suited for fastening devices 10 in which there are particularly large differences in the thermal expansion behavior between the temperature-stable element 20 and the base body 40 .

8th shows a detail of the fastening device 10 according to the invention according to section D, wherein the overhang and the wall thickness reduction as well as the transition radii 55 are shown.

9 finally shows a fastening device 10 according to the invention for holding a temperature-stable element 20 in an oblique view.

The base body 40 comprises a temperature-stable material, preferably a temperature-stable metal from the group of steels, for example normal steels, high-grade steels, stainless steels and high-temperature-stable ferritic or austenitic steels. Preference is given to steels which are readily weldable and remain rust-free when the invention is implemented.

The invention makes it possible to select materials for the base body 40 in a particularly advantageous manner, which have a higher coefficient of thermal expansion than the temperature-stable element 20 .

Since the coefficient of thermal expansion of the base body 40 is greater than that of the temperature-stable element 20 in these cases, this exerts a tensile or compressive stress that increases with increasing temperature as a result of different transverse contractions on the temperature-stable element 20 . In order to still be able to seal the opening fluid-tight or hermetically tight at the required temperatures, it is favorable if the coefficient of thermal expansion of the material of the base body 40 is not higher than 15 * 10-6/K in a temperature range of 20 °C to 400 °C, preferably not higher than 14*10-6/K and particularly preferably not higher than 13*10-6/K.

The material for the base body 40 can thus be selected from the group comprising the following steels: Thermax, for example Thermax 4016, Thermax4742, or Thermax4762 or Crofer22 APU or CroFer22 H or NiFe-based materials, for example NiFe45, NiFe47, or known by the brand name Inconel, for example Inconel 718 or X-750, or steels, for example known under the names CF25, Alloy 600, Alloy 625, Alloy 690, SUS310S, SUS430, SUH446 or SUS316, or austenitic steels such as 1.4828 or 1.4841 or ferritic steels such as 1.4762 or Incolloy 909.

In the exemplary embodiments shown, ferritic steel 1.4762 and Alloy 600 with coefficients of thermal expansion between 11*10-6/K and 14.5*10-6/K in a temperature range of 20°C to 400°C were used with good success as the material for the base body used.

With these materials, the base body 40 could be made sufficiently dimensionally stable with a wall thickness of about 0.6 mm in the area of the transition section 53 and a diameter of about 30 mm in the area of the holding section 41 . Of course, other dimensions are also possible and conceivable.

The temperature-stable element 20 is disc-shaped with plane-parallel main surfaces and has an optical polish, for example of quality P3, on at least the main surfaces.

In the exemplary embodiments, the outside diameter of the temperature-stable element 20 is approximately 23 mm with a thickness of approximately 1.5 mm. Of course, other dimensions are also possible and conceivable.

In other embodiments, it is also possible, for example, to shape the temperature-stable element 20 in a plano-convex, plano-concave, biconvex, biconcave, convex-concave or concave-convex manner.

The temperature-stable element 20 can also be part of an imaging system assigned to it.

The temperature-stable element 20 can comprise or consist of glass, glass-ceramic or ceramic.

In the exemplary embodiments, good experiences have been made with the material sapphire glass or synthetic corundum for the temperature-stable element 20, which offers very good optical properties due to the crystalline structure and has a high level of hardness and particularly high temperature resistance.

In addition, the coefficient of thermal expansion of sapphire glass has also proven to be favorable, which is approximately 7.5*10-6/K (temperature range from 20° C. to 400° C.), since the difference to the coefficient of thermal expansion of the base body 40 is not too high as a result.

In the exemplary embodiments, good experiences were also made with the material quartz glass or silica glass for the temperature-stable element 20, which also has particularly good optical properties.

However, the coefficient of thermal expansion is significantly lower at around 0.5 * 10-6/K, which means that the mechanical stresses during temperature changes between the temperature-stable element and the base body are greater compared to sapphire glass.

According to the invention, it is generally preferred if the coefficient of thermal expansion of the temperature-stable element 20 is no greater than 9*10-6/K in a temperature range of 20° C. to 400° C., preferably no greater than 7.5*10-6 /K, further preferably not greater than 7*10-6/K and particularly preferably not greater than 6.5*10-6/K.

In the aforementioned exemplary embodiments, the amount of the difference in the thermal expansion coefficients between the temperature-stable element 20 and the base body 40 is at least 2.5*10 ^-6 /K, preferably more than 3*10 ^-6 /K and particularly preferably more than 4*10 ^-6 /K

This makes it possible to design both the base body 40 with regard to its intended properties and the temperature-stable element 20 accordingly.

However, this difference should not be too high either, since otherwise even the compensation means described above would not be sufficient to reliably absorb the stresses that occur. The difference in the thermal expansion coefficients between the temperature-stable element 20 and the base body 40 should therefore not be more than 20*10 ^-6 /K, preferably not more than 15*10 ^-6 /K and particularly preferably not more than 13*10 ^-6 /K. amount to K.

To hold the temperature-stable element 20 in the opening 45 of the base body 40, a holding means 30 is provided in the exemplary embodiments shown, in order to produce a high-temperature-stable and/or mechanically high-strength joint.

Particularly good experiences have been made with a holding means 30 which comprises a crystallizable or at least partially crystallizable glass, as is described in the patent application EP 19 181 866.5 the applicant is proposed.

Good experiences have also been made with a holding means 30 which comprises a crystallizable or at least partially crystallized glass, the at least partially crystallized glass having a porosity. This can decrease towards the interface of the at least partially crystallized glass with the joining partner and/or be distributed in a structured manner.

Such a crystallizable or at least partially crystallized glass is described in the patent application WO 2017/220700 proposed by the applicant.

Such crystallizable or at least partially crystallized glasses allow the formation of high-temperature-stable and/or mechanically high-strength joints. With a crystallizable or at least partially crystallized glass, it is possible to form a particularly stable structure in the at least partially crystallized glass, in particular a structure which is stable even at high temperatures above 400° C., preferably above 500° C. and particularly preferably above is mechanically stable from 600 ° C or even up to 1000 ° C or more.

With the invention, a particle sensor, in particular an exhaust gas sensor, for example a soot particle sensor, pressure sensor, temperature sensor, NO _x sensor or oxygen sensor, can be made available in which the optical components of a measuring device can be arranged in the vicinity of a hot particle flow, whereby they can be Fastening device 10 are protected from heat and penetrating gas.

In this way, for example, a “window” can be provided for the optical analysis of soot particle concentrations in an exhaust system of an internal combustion engine using laser radiation.

With the invention, for example, an imaging system can also be made available which, by means of the fastening device 10, includes a temperature-stable “window” as an interface between the measuring device and the measuring volume and can therefore be used in the vicinity of or in particle streams 11 or fluids.

The invention also includes the use of the fastening device 10 for holding a temperature-stable element 20 with low thermal expansion in an exhaust gas sensor, a pressure sensor, a particle sensor, such as a soot particle sensor and/or a temperature sensor and/or in a NO _x sensor and /or in an oxygen sensor, or in a feedthrough for a compressor, or in an exhaust element, or in a fuel cell, or in a feedthrough for a chemical reactor, or in an imaging system.

QUOTES INCLUDED IN DESCRIPTION

This list of documents cited by the applicant was generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Patent Literature Cited

• US4567750 [0003]
• DE 10340748 [0004]
• DE 102017104378 A1 [0005]
• EP19181866 [0081, 0235]
• WO 2017/220700 [0120, 0237]

Claims (25)

Fastening device for holding a temperature-stable element, in particular permanently operational in high-temperature applications above 300° C., preferably above 350° C. and particularly preferably above 380° C., comprising a base body with at least one holding section, a tubular section adjoining this holding section with a peripheral wall and with a fastening section adjoining this tubular section, and - a temperature stable element, wherein the base body comprises a continuous opening which is formed in the region of the holding section for receiving and holding the temperature-stable element, and wherein the temperature-stable element has a transparency of at least 80%, preferably at least 84% and particularly preferably at least 86%, during operation for electromagnetic radiation in a wavelength spectrum of at least 350 to 1000 nm. Fastening device for holding a temperature-stable element, in particular permanently operational in high-temperature applications above 300° C., preferably above 350° C. and particularly preferably above 380° C., in particular according to the preceding claim, comprising - a base body with at least one holding section, a pipe section adjoining this holding section with a peripheral wall and with a fastening section adjoining this pipe section, - a temperature stable element, and - A holding means, wherein the base body comprises a continuous opening, which is formed in the region of the holding portion for receiving the temperature-stable element, wherein the temperature-stable element is held in the opening by the holding means and the opening is closed in a fluid-tight, preferably hermetically-tight manner, and wherein the temperature-stable element has a transparency of at least 80%, preferably at least 84% and particularly preferably at least 86%, during operation for electromagnetic radiation in a wavelength spectrum of at least 350 to 1000 nm. Fastening device according to one of the two preceding claims, characterized in that the fastening device is permanently operational in high-temperature applications from at least 400 °C, preferably from at least 500 °C and particularly preferably from at least 600 °C. Fastening device according to one of the preceding claims, characterized in that the opening of the fastening device is tightly closed, the helium leak rate being at most 5 * 10 ^-8 mbar*l/s, preferably at most 2 * 10 ^-8 mbar*l/s and in particular preferably at most 1*10 ^-8 mbar*l/s. Fastening device according to one of the preceding claims, characterized in that the opening and/or the base body, in particular the holding section, the tube section and/or the fastening section are of cylindrically symmetrical design. Fastening device according to one of the preceding claims, characterized in that the tubular section comprises at least a first section which adjoins the fastening section and is designed as a transition section, and a second section which is designed as a compensation section, the compensation section having an extent in the axial direction , which corresponds to at least 30%, preferably at least 50% and particularly preferably at least 70% of the axial extent of the transition section. Fastening device according to the preceding claim, characterized in that the compensation section has at least one tapered section with a cross-sectional area which is smaller than the cross-sectional area of the transition section, the cross-sectional area being at least 5%, preferably at least 10% and particularly preferably at least 20% smaller is. Fastening device according to one of the two preceding claims, characterized in that the compensation section comprises at least one reduced section, in which the thickness of the wall is reduced compared to the thickness of the wall of the transition section by at least 25%, preferably by at least 35% and particularly preferably by at least 40%, and by no more than 75%, preferably by no more than 65% and most preferably by no more than 60%. Fastening device according to one of the two preceding claims, characterized in that the compensation section comprises at least one projecting section in which the wall is at an angle α to the central axis of the base body and the projection preferably takes place in the direction of the holding section. Fastening device according to the preceding claim, characterized in that angle α is between 5° and 75°, preferably between 10° and 70°, and particularly preferably between 15° and 60°. Fastening device according to one of the preceding claims, characterized in that the base body is made of a temperature-stable material, preferably a temperature-stable metal from the group of steels, for example normal steels, stainless steels, stainless steels and high-temperature-stable steels, with the thermal expansion coefficient CTE of the material not being higher is than 15 * 10-6/K, preferably not higher than 14 * 10-6/K and more preferably not higher than 13 * 10-6/K, and preferably at least 10 * 10-6/K. Fastening device according to one of the preceding claims, characterized in that the material of the base body is selected from the group comprising the following steels: Thermax, for example Thermax 4016, Thermax4742, or Thermax4762 or Crofer22 APU or CroFer22 H or NiFe-based materials, for example NiFe45, NiFe47, or known by the brand name Inconel, for example Inconel 718 or X-750, or steels, known for example by the names CF25, Alloy 600, Alloy 625, Alloy 690, SUS310S, SUS430, SUH446 or SUS316, or austenitic steels such as 1.4828 or 1.4841, or ferritic steels such as 1.4762 or Incolloy 909. Fastening device according to one of the preceding claims, characterized in that the temperature-stable element is disc-shaped and in particular has plane-parallel main surfaces. Fastening device according to one of the preceding claims, characterized in that the temperature-stable element comprises or consists of glass, glass ceramic or ceramic, in particular sapphire glass or quartz glass. Fastening device according to one of the preceding claims, characterized in that the temperature-stable element is essentially monocrystalline. Fastening device according to one of the preceding claims, characterized in that the temperature-stable element has a thermal expansion coefficient of no greater than 9 * 10-6/K, preferably no greater than 7.5 * 10-6/K, further preferably no greater than 7 * 10 -6/K and particularly preferably not greater than 6.5*10-6/K. Fastening device according to one of the preceding claims, characterized in that the amount of the difference in thermal expansion coefficients between the temperature-stable element and the base body is at least 2.5 * 10 ^-6 /K, preferably more than 3 * 10 ^-6 /K and particularly preferred more than 4 * 10 ^-6 /K. Fastening device according to one of the preceding claims, characterized in that the holding means comprises a glass solder, preferably comprising a crystallizable or at least partially crystallizable glass, or consists of this. Fastening device according to the preceding claim, characterized in that (*** P5041) the at least partially crystallized glass comprises a residual glass content of less than 10%, preferably less than 5%, by volume, the at least partially crystallized glass comprising crystal aggregates , wherein the crystal aggregates are formed from a large number of crystallites, wherein the crystallites are preferably needle-like and/or plate-shaped, the crystallites particularly preferably radially, such as spherulitic and/or fan-shaped, and/or rod-shaped and/or plate-shaped the at least partially crystallized Glass are arranged penetrating. Fastening device according to the preceding claim, characterized in that the glass comprises La ₂ O ₃ greater than 0.3 mol% to less than 5 mol%, preferably less than or equal to 4.5 mol%, particularly preferably less than or equal to 4 mol%, _{Nb2O5 _} 0 mole % to 9 mole %, _{Ta2O5 _} 0 mole % to 7 mole %, whereby Σ (A ₂ O ₅ ) greater than 0.2 mol% to 9 mol%, where A is an element which usually has the oxidation number V+ in oxides, and may comprise Nb and/or Ta or P and/or mixtures thereof. Fastening device according to the preceding claim, characterized in that the glass comprises SiO ₂ 30 mol% to 40 mol%, _{Al2O3 _} 3 mole % to 12 mole %, CaO 32 mol% to 46 mol%, MgO 5 mole % to 15 mole %, ZnO 0 mol% to 10 mol%, as well as optional ZrO ₂ 0 mole % to 4 mole %, preferably at most 3 mol%, and/or TiO ₂ 0 mole % to 4 mole %, preferably at most 3 mol%, and/or MnO ₂ 0 mole% to 5 mole%. Fastening device according to any of the preceding claims 18 - 21 , characterized in that the at least partially crystallized glass comprises a porosity and has the following composition, in % by weight: SiO ₂ : 20 to 60, preferably 25 to 50 _{Al2O3 :} 0.5 to 20, preferably 0.5 to 10 CaO: 10 to 50 MgO: 0.5 to 50, preferably 0.5 to 10 _{Y2O3 :} 0.1 to 20, preferably 3 to 20 ZrO ₂ : 0.1 to 25, preferably 3 to 20 _{B2O3 :} 1 to 15, preferably 3 to 12, where HfO ₂ can optionally be present in amounts of up to 0.25% by weight. Fastening device according to any of the preceding claims 18 - 22 , characterized in that the at least partially crystallized glass comprises a porosity and has the following composition, in % by weight: SiO ₂ : 36 to 54, preferably 40 to 54 _{Al2O3 :} 8 to 16, preferably 8 to 13 CaO: 0 to 35, preferably 5 to 25 MgO: 0 to 17, preferably 3 to 14 RO: 8 bis 39, preferably 8 to 35 ZrO ₂ : 0 to 25, preferably 0 to 17 B ₂ O ₃ : 0 to 3, preferably 0 to 2, especially preferably 0 where the proportion RO denotes the oxides BaO, SrO, MgO, ZnO individually or in total or in any mixtures and preferably RO individually or in any combination in % by weight: BaO 0 - 36 MgO 0 - 22 CaO 0 amounts to. Particle sensor, in particular exhaust gas sensor, for example soot particle sensor, pressure sensor, temperature sensor, NO _x sensor or oxygen sensor, comprising a fastening device for holding a temperature-stable element according to one of the preceding claims. Use of a fastening device for holding a temperature-stable element according to any one of the preceding claims according to any one of the preceding claims Claims 1 until 23 or a particle sensor according to the preceding claim in an exhaust gas sensor, a pressure sensor, a particle sensor, such as a soot particle sensor and/or a temperature sensor and/or in a NO _x sensor and/or in an oxygen sensor, or in a passage for a compressor or in an exhaust element, or in a fuel cell, or in a feedthrough for a chemical reactor, or in an imaging system.

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