Title of Invention	A HONEYCOMB BODY
Abstract	This invention relates to a honeycomb body (1) having passages (2), through which a fluid can flow and which extend between two end faces (3,4) and having at least one measurement sensor (5,21), which at least partially extends into the honeycomb body (1), a first part-volume (6) of the honeycomb (1) being defined between a first end face (3) and the at least one first measurement sensor (5). The honeycomb body (1) has a lower capacity to take up oxygen in the first part-volume (22,23).

Title of Invention

A HONEYCOMB BODY

Abstract

This invention relates to a honeycomb body (1) having passages (2), through which a fluid can flow and which extend between two end faces (3,4) and having at least one measurement sensor (5,21), which at least partially extends into the honeycomb body (1), a first part-volume (6) of the honeycomb (1) being defined between a first end face (3) and the at least one first measurement sensor (5). The honeycomb body (1) has a lower capacity to take up oxygen in the first part-volume (22,23).

Full Text	The invention relates to a honeycomb body having passages, through which a fluid can flow and which extend between two end faces, and having at least one measurement sensor, which at least partially extends into the honeycomb body. The invention also proposes an exhaust system which includes a honeycomb body of this type. Honeycomb bodies, the basic design of which is known, for example, from EP 0 245 73 7, EP 0 43 0 945 and GB 1,452,982, are used for numerous applications in the automotive industry, in particular as catalyst support bodies in the treatment of exhaust gas. In view of the fact that permitted pollutant concentration limits in exhaust gas from an automobile released to the environment are being constantly reduced by legislation, methods which allow control of an exhaust- gas treatment process are becoming increasingly important. The measurement sensors which such control requires and which make it possible, for example, to determine the exhaust-gas composition or pollutant concentrations in the exhaust gas, are an important part of an exhaust-gas treatment system with controlled operation. Consequently, honeycomb bodies which are able to accommodate one or more measurement sensors and therefore provide data for controlling the catalytic treatment, as are known for example from DE 88 16 154 Ul, are an important element in exhaust- gas treatment systems with controlled operation. Suitable measurement sensors are, for example, sensors which are used to determine the exhaust-gas composition, such as for example lambda sensors and hydrocarbon sensors (HC sensors), which measure the hydrocarbon content of the exhaust gas. Furthermore, it is also possible to use what are known as nitrogen oxide sensors which determine the level of the nitrogen oxides in the exhaust gas. Measurement sensors of this type are used in particular in conjunction with what is known as on-board diagnosis (OBD) . The purpose of OBD is to continuously monitor the components which are of relevance to the exhaust gas in the vehicles, the intention being to immediately recognize and indicate significant increases in emissions over the lifetime of each vehicle. This is intended to ensure permanently low exhaust-gas emissions. When monitoring the functionality of a catalytic converter, it is preferable to determine the oxygen concentration in the exhaust gas upstream and downstream of the catalytic converter. To do this, it is customary for a lambda sensor for determining the oxygen content to be positioned upstream and downstream of a .catalytic converter. With the aid of the lambda sensor arranged upstream of the catalytic converter, it is possible in particular to draw conclusions as to the air/fuel mix fed to the internal combustion engine. The sensor connected downstream of the catalytic converter generates, for example, a comparison value based on the oxygen concentration in the exhaust gas, so that it is possible to draw conclusions as to the functionality of the catalytic converter. The oxygen is at least partially used to convert pollutants contained in the exhaust gas, and therefore a low concentration of oxygen at the exit of the catalytic converter indicates effective conversion. A particular problem with measurement sensors of this type, in addition to the additional space which they take up, is that they react very sensitively to different ambient conditions, as also occur under certain circumstances in exhaust systems. In particular, the sensitivity to water or water vapor needs to be mentioned, as well as the high temperatures prevailing in the aggressive environment, which can lead to undesirably rapid aging of the measurement sensor. However, in particular with a view to OBD, it is necessary for the sensors for controlling the exhaust-gas properties and/or monitoring the components in the exhaust system to remain functional for a prolonged period of time. Working on this basis, it is an object of the present invention to overcome the known technical problems with regard to arranging measurement sensors in exhaust systems. In particular, it is intended to propose a position or form of arrangement of measurement sensors which ensure long-term use of the measurement sensors in the exhaust system of mobile internal combustion engines. The intention is that measured value results which are as precise and accurate as possible and can be used to control the exhaust-gas components should be deliverable. Furthermore, it is intended to propose an exhaust system which has a particularly space-saving and functional arrangement of a honeycomb body with a measurement sensor. These objects are achieved by a honeycomb body having the features of patent claim 1 and by an exhaust system comprising a honeycomb body of this type having the features of patent claim 20. Further advantageous configurations are described in the respective dependent patent claims. At this point, it should be noted that the features disclosed therein can be combined with one another in any technologically appropriate way, in particular even independently of the way in which they are referred back in the patent claims. The honeycomb body according to the invention has passages, through which a fluid can flow and which extend between two end faces, and at least one measurement sensor, which at least partially extends into the honeycomb body. A part-volume of the honeycomb body is defined between a first end face and the at least one first measurement sensor. The honeycomb body is distinguished by the fact that it has a lower capacity to take up oxygen in the first part-volume than in at least one further part-volume. The honeycomb body can in principle be produced from various materials, in particular from ceramic or metallic material. It is preferably to be understood as a body which comprises a multiplicity of passages which are arranged next to one another and extend substantially parallel to one another. The term passage does not necessarily mean a continuous flow passage, but rather also encompasses other forms of flow paths through the honeycomb body. The most important criterion is that the fluid be divided into a multiplicity of partial fluid flows when it comes into contact with an end face of the honeycomb body, with these partial fluid flows being routed separately from one another at least in the vicinity of the end faces, in particular for the first 2 mm to 3 mm. The term fluid in principle encompasses both gaseous and liquid substances, although in this context it is preferably a gas stream, in particular an exhaust-gas stream from a mobile internal combustion engine (spark-ignition engine or diesel engine or the like). The at least one measurement sensor may be any known type of measurement sensor which is used in connection with the control or monitoring of exhaust-gas components of mobile internal combustion engines. This includes in particular lambda sensors, HC measurement sensors, temperature sensors, nitrogen oxide measurement sensors or the like. This at least one measurement sensor at least partially extends into the honeycomb body, in other words the at least one measurement sensor is placed against a lateral surface of the honeycomb body and preferably extends radially inward. For a detailed description of the way in which it is actually arranged, reference is made to the explanations given below. A first part-volume is defined by the first end face, which represents the gas entry side for the use of the honeycomb body in the exhaust system of a mobile internal combustion engine, and the at least one measurement sensor. The part-volume in particular comprises all passages and their walls. It extends from the first end face as far as a cross section through the honeycomb body which is arranged parallel to the first end face and extends through the closest point of the measurement sensor to the first end face. Consequently, the first part-volume is described by the first end face, this cross section which has just been described and the lateral surface of the honeycomb body in between. According to the invention, the honeycomb body has a lower capacity to take up oxygen in this first part- volume than in at least one further part-volume. Therefore, it will firstly be clear that the first measurement sensor is located within the interior of the honeycomb body, i.e. deviates from the known principle of the measurement sensor connected upstream or downstream. The integration of the measurement sensor means that the latter is not directly exposed to the extreme thermal and dynamic stresses in the exhaust system of an internal combustion engine. In this way, it is possible in particular to reduce premature thermal aging and the risk of what is known as "water shocks", since the exhaust gas comes into contact with the honeycomb body first of all and only subsequently with the measurement sensor. With a view to the use of a measurement sensor of this type as part of OBD, it is particularly important for the first measurement sensor, which is, for example, a lambda sensor, to come into contact with a composition of the exhaust-gas stream which still permits conclusions to be drawn as to the underlying air/fuel mix. Therefore, it is proposed here that the honeycomb body have a low capacity to take up oxygen in the part-volume. The result of this is that insufficient oxygen required for virtually 100% conversion of the pollutants contained in the exhaust-gas stream is available in this first part-volume. Consequently, the conversion rates are considerably lower in this first part-volume, for example less than 85%, in particular less than 75% and even less than 5 0%. Therefore, characteristic values of the exhaust gas which provide information as to the fuel/air mix used can still be recorded by the first measurement sensor. According to a further configuration of the honeycomb body, the first part-volume at least in part has a first coating. A coating of this type is preferably applied to the passage walls and itself has a capacity to take up oxygen. The coating may be identical or different over the entire cross section and the entire length of the first part-volume in terms of its coating thickness, the type of coating, the coating surface area or further parameters. It is also possible for regions which do not have any coating to exist in the part-volume. Suitable coatings also include, for example, support layers for catalytically active materials, such as for example washcoat. Furthermore, it is proposed that an exchange of fluid flows between adjacent passages is ensured in the first part-volume. In other words, the partial fluid flows which are formed in the vicinity of the end face of the honeycomb body are at least partially mixed with one another in the first part-volume. For this purpose, it is necessary for the passages arranged adjacent to one another to be provided with means which allow such an exchange of fluid flows. In this context, it is preferably proposed that at least in the first part-volume apertures, in particular with a mean diameter in the range from 2 mm to 10 mm, are provided in the passage walls. The apertures can in principle comprise any conceivable shapes, in particular round, polygonal, oval or similar holes, slots, perforations or the like. In view of the wide range of forms which apertures of this type can take, a mean diameter is to be understood as meaning a mean value for the distance between the opposite edge of the apertures which lies between the maximum extent and the minimum extent. In this context, it should be noted that the apertures do not have to be formed uniformly over the part-volume, but rather it is possible for the apertures to be varied in terms of their form, size or distribution in the first part-volume. To ensure an exchange of fluid flows between adjacent passages, it is also proposed that the apertures, at least in the first part-volume, are provided with microstructures, which are preferably used to divert the fluid in a direction which is transverse to an axis of the honeycomb body. A microstructure is to be understood in particular as meaning structures which, starting from the passage walls, extend into inner regions of the passage or toward adjacent passage walls. These microstructures preferably have a height which is less than the height of the passage itself. Suitable microstructures include studs, stamp formations, guide surfaces, vanes, grooves, bumps or the like. Microstructures of this type are preferably used to generate pressure differences in adjacent passages which cause the partial fluid stream to flow from one passage to the adjacent passage. A suitable arrangement of the microstructures with respect to one another allows uniform mixing of the fluid, with the result that, for example, regions with particularly high concentrations, as may for example also occur individually in exhaust-gas streams, are avoided. Rather, a virtually uniform concentration distribution of a pollutant or a component of the fluid over virtually the entire cross section of the honeycomb body is provided. If a fluid stream which has been mixed in this manner is brought into contact with the downstream measurement sensor, it is possible to provide more accurate statements as to the composition of the fluid stream. According to a further configuration, the first part- volume forms in the range of less than 30%, in particular in the range from 10% to 25%, of the total volume of the honeycomb body. In this case, the total volume is to be understood as meaning the volume of the honeycomb body, which is defined by the two end faces and the lateral surface and encompasses both the passages and their walls or coatings, etc. At this point, it should be noted that the honeycomb body does not necessarily have to cylindrical in form. Rather, oval, conical, polygonal or similar shapes of honeycomb bodies are also known. If the honeycomb body has a housing, the housing does not count as part of the total volume of the honeycomb body. Furthermore, it is proposed that the first part-volume has a length of from 10 mm to 40 mm, starting from the first end face. This length may be sufficient on the one hand to provide a sufficient contact area for water vapor contained in the exhaust-gas stream or water entrained therein and at the same time (in particular when providing apertures) to effect sufficient mixing of the exhaust-gas stream. This length detail preferentially relates to honeycomb bodies which have a total length of over 100 mm. It is preferably also proposed that a single measurement sensor is provided, this measurement sensor being a lambda sensor. In other words, in this case the result is a honeycomb body which has only a single measurement sensor, designed as a lambda sensor, which, however, can at the same time also be used to carry out OBD. This single lambda sensor makes it possible, for example, to detect unburnt hydrocarbons, which occur in particular after the mobile internal combustion engine has been started or restarted (known as a "cold start"). According to a further configuration, the honeycomb body, starting from its lateral surface, has a recess, extending radially in the direction of its axis, for accommodating the measurement sensor, this recess preferably having a maximum extent in the range from 15 mm to 35 mm and/or a depth in the range from 15 mm to 40 mm. The term "lateral surface" is to be understood in particular as meaning the envelope of the honeycomb body which is arranged between the two end faces. The "axis" of the honeycomb body relates in particular to a center axis, which preferably extends through the center points of the two end faces. The "recess" or its center axis extends from the lateral surface preferably radially toward the axis. Although at this point it should be noted that this recess may also be arranged skew or obliquely with respect to the axis of the honeycomb body, a radial extent constitutes an embodiment which is preferred here, since in this way a relatively deep penetration of the measurement sensor can be achieved. To ensure that the measurement sensor extends sufficiently far into inner regions of the honeycomb body yet at the same time does not constitute an undesirably major flow resistance, the dimensions indicated should be complied with. In this context, the "maximum extent" is arranged substantially in a cross section of the recess and describes the distance between the opposite points of the recess arranged furthest away from one another. The "depth" extends radially inward from the lateral surface and in this direction describes the dimension of the recess. The number of recesses of this type in the honeycomb body is to be selected taking account of the number of measurement sensors used. Under certain circumstances, however, it is also possible for a plurality of measurement sensors to be arranged in one recess. Moreover, it is also proposed that the shape of the recess is oval-cylindrical, quadrilateral or narrows conically in the direction of the axis. For details as to the production of recesses of this type in honeycomb bodies which comprise a plurality of at least partially structured sheet-metal foils, reference should be made in particular to the content of disclosure of WO 02/075126, the content of which is hereby incorporated in full by reference in the subject matter of the present description, and reference can be made to this content of disclosure in full in particular for a more detailed explanation of the invention. In addition, it is proposed that the recess is at least partially surrounded by a rim which does not permit exchange of adjacent flows, in particular does have any apertures, this rim preferably having a width in the range from 1 mm to 5 mm. The configuration of the recess with a rim of this type means that its external shape is not delimited by especially fissured passage walls. This could lead to particularly fine subregions of the passage walls being freely exposed to the extreme environmental conditions. On account of the ensuing pressure fluctuations, subregions could become detached or cracks could form, which would then propagate through the passage wall. The provision of the rim means that stable passage edge regions are provided in the immediate vicinity of the recess, so as to ensure long-term use of honeycomb bodies of this type. The invention also proposes a honeycomb body, in which there is a second measurement sensor, which is arranged between a first measurement sensor - which is arranged near the first end face and is designed as a lambda sensor - and the second end face, a second part-volume being formed between the second measurement sensor and the first measurement sensor, and a third part-volume being formed between the second measurement sensor and the second end face. In this respect, the honeycomb body has two measurement sensors, which at least in part project into other regions. The measurement sensors, which are preferably each arranged in a cross-sectional plane parallel to at least one end face of the honeycomb body, in this case define different part-volumes of the honeycomb body. The first measurement sensor preferably has the function of generating certain characteristic variables which provide information as to the fluid flowing in. This means that it is possible to ascertain knowledge as to the composition, concentration differences, temperatures, etc. on the basis of the data obtained using the first measurement sensor. The second measurement sensor is used in particular to record the functionality of the honeycomb body or its coating by metrological means. In this case, by way of example, the same parameters which have been recorded using the first measurement sensor are recorded again, and the two recorded parameters are compared with one another. The rise or drop in this characteristic variable accordingly allows conclusions to be drawn as to the for example catalytic activity of the honeycomb body. However, it is also possible for the two measurement sensors to observe different parameters of the fluid or exhaust-gas stream. In this context, it is also proposed that at least in part a coating, which has an increased capacity to take up oxygen compared to the first coating in the first part-volume, is provided in the second part-volume. Accordingly, the second part-volume preferably forms the region of the honeycomb body in which particularly effective conversion of pollutants in an exhaust-gas stream takes place. This preferably achieves an efficiency of over 99%. The higher oxygen uptake capacity of the second oxidizeable coating ensures that the pollutants are brought into contact to a sufficient extent with their reaction partner. Moreover, it is also proposed that the third part- volume at least in part has a third coating, which has a lower catalytic activity than at least the first part-volume and/or the second part-volume. This is to be understood in particular as meaning that a smaller quantity of catalytically active material is provided in this third part-volume. Catalysts of this type used are in particular platinum, rhodium or rare earths (i.e. in particular including weakly basic oxides of the rare earths). According to a further configuration of the honeycomb body, at least the second part-volume and/or the third part-volume ensures an exchange of fluid flows between adjacent passages. Under certain circumstances, it is advantageous not to permit any exchange of fluid flows between adjacent passages in the second part-volume. This is the case, for example, if the first measurement sensor and the second measurement sensor are in each case supposed to generate measured values to be compared with one another. To ensure that the same fluid flows which are routed past the first measurement sensor also flow past the second measurement sensor, cross-mixing between partial fluid flows is to be avoided. If a comparison of this type is not carried out, mixing of partial fluid flows is under certain circumstances also advantageous in the second part- region. According to a refinement of the honeycomb body, the second measurement sensor is positioned at a distance in the range from 10 mm to 3 0 mm from the second end face. The distance described here constitutes a type of minimum distance which should be ensured starting from the second end face, which in the exhaust train of an automobile usually means the gas exit side. This has the advantage that when establishing that a limit value has been exceeded or undershot at the second measurement location, there is still a third part- volume available, which if necessary continues to convert the pollutants until the engine control has effected a change in the fuel/air mix in order to restore the functionality of the honeycomb body. This has its origin, inter alia, in the fact that the functionality of a honeycomb body generally changes with a time delay in different regions. Since the exhaust gas for example always enters from one end face, this region of the honeycomb body is generally impaired first. This may affect, for example, the capacity to store nitrogen oxides, the capacity to trap particulates or similar components. This "malfunctioning" then continues over the course of time into inner regions until ultimately the change can be detected even at the second measurement location. Accordingly, the minimum distance or the size of the third part-volume represents a safety measure to ensure that the emission limits prescribed by legislation are still complied with even in the event of sudden failure of the honeycomb body (for example as a catalyst support body). In particular, it is advantageous if the second measurement sensor is a sensor for monitoring nitrogen oxide levels in the fluid stream. It is already known for an N0x store, which can store the nitrogen oxides produced in operation for a certain period of time, to be provided for example in the exhaust system of a diesel engine or lean-burn engine. Before its storage capacity is exhausted, an N0x store of this type is regenerated by unburnt hydrocarbons being fed to the exhaust system. These hydrocarbons react, if appropriate with the assistance of suitable catalysts, with the stored nitrogen oxides, generally forming the products carbon dioxide, nitrogen and water. Any excess hydrocarbons or hydrocarbons which do not react with the nitrogen oxides are oxidized in the exhaust system or the honeycomb body using the residual oxygen contained in the exhaust gas, so that the result may be just carbon dioxide and water. The catalytic conversion can take place in a catalytically active coating of the N0x store itself or in a downstream oxidation catalytic converter. As has already been mentioned above, the honeycomb body itself may have different coatings, for example an oxidation coating with a high oxygen storage capacity or a coating which is able to store N0x. The monitoring of the ability to store NOX in particular allows statements to be made as to the functioning of the honeycomb body or the combustion of the internal combustion engine at operating temperature. Furthermore, the invention also proposes a honeycomb body which is formed using at least partially structured sheet-metal foils which delimit the passages. In this case, it is preferable for the honeycomb body to have both smooth and structured sheet-metal foils which are stacked on top of one another and wound together. The profiles of the sheet- metal foils may be in a spiral shape, an S shape or a similar intertwined arrangement. These honeycomb bodies have a cell density which is preferably in the range from 200 to 1000 cpsi (cells per square inch) , in particular in the range from 400 to 800 cpsi. The sheet-metal foil thickness is in this case preferably less than 100 m, in particular in a range from 20 to 80 m. Temperature-resistant and corrosion-resistant aluminum/chromium alloys are preferred as material for the sheet-metal foils. According to a further configuration of the honeycomb body, the honeycomb body is surrounded by a housing which has at least one cutout which is used for the gastight fixing of the at least one measurement sensor. The housing substantially ensures the structural integrity of the honeycomb body. The passage walls or sheet-metal foils are preferably nonreleasably connected to the housing; this is to be understood as meaning that they can only be detached from one another again as a result of damage to or destruction of the honeycomb body or the housing. The housing proposed is likewise a metallic tubular casing, in which case the passage walls are preferably welded or soldered to the housing. The cutout is in this case positioned substantially above the recess, so that the at least one measurement sensor can be passed through it from the outside. Special sealing means can be provided to make the cutout gastight. It is also possible for an additional housing or a sleeve to be fitted or welded onto the housing, likewise aligned above the cutout. Moreover, the invention proposes an exhaust system which comprises a pipe section for positioning components for exhaust-gas aftertreatment, in which system at least one honeycomb body in accordance with the statements made above is provided. The pipe section in this case has a longitudinal axis and a base, a secondary axis, which intersects the longitudinal axis and the lowest point of the base being formed, and the at least one measurement sensor being positioned in an angle range of 270° arranged opposite the lowest point of the base. The term exhaust system is to be understood in particular as meaning an exhaust system of mobile internal combustion engines, i.e. of automobiles, motorcycles, trucks or similar vehicles. The exhaust system is usually connected to the internal combustion engine and has an opening to the environment, from which the exhaust gas produced, which has first been treated, flows out. If appropriate a plurality of different components for exhaust-gas aftertreatment, such as for example filter elements, adsorbers, heating elements, particulate separators, catalytic converters, etc., are arranged in a pipe section, which is preferably of widened design. If appropriate, this exhaust system may be equipped with additional nozzles, sensors or feed lines for reducing agents or oxidizing agents. The arrangement of the at least one measurement sensor will now be described with reference to the longitudinal axis and the lowest point of the base of the pipe section. The invention here proposes a particularly wide angle range, namely of 270°. Hitherto, measurement sensors of this type have only- been arranged in a very limited angle range opposite the lowest point of the base. This was done in particular with a view to the condensation water which may form in the pipe section in the vicinity of the base, which has an adverse effect on the measurement result acquired using the at least one measurement sensor. However, this risk of accumulation of liquids is considerably reduced on account of the configuration of the recess and the provision of apertures. Therefore, it is possible to vary the arrangement within a particularly wide angle range. It is in this context very particularly advantageous if the at least one measurement sensor is positioned in an angle range of 45° which extends from a tertiary axis extending perpendicular to the secondary axis and through the longitudinal axis toward the lowest point of the base. This is to be understood as meaning in particular that the at least one measurement sensor is arranged below a horizontal through the longitudinal axis of the pipe section. More detailed explanations as to this arrangement of the at least one measurement sensor will be provided with reference to the figures. The invention will now be explained in more detail with reference to the figures, which show particularly preferred embodiments, without the invention being restricted to these embodiments. In the drawing Fig. 1 diagrammatically depicts a longitudinal section through a first embodiment of the honeycomb body; Fig. 2 diagrammatically depicts a detail view of a further embodiment of the honeycomb body in cross section; and Fig. 3 diagranunatically depicts the arrangement of an embodiment of the honeycomb body in an exhaust system. Fig. 1 diagrammatically depicts a cross section through a first embodiment of the honeycomb body 1 according to the invention with passages 2 through which a fluid can flow and which extend between two end faces 3, 4. The honeycomb body 1 comprises a housing 28, through which two measurement sensors 5, 21 extend, via cutouts 29, into inner regions of the honeycomb body 1. Both measurement sensors 5, 21 are connected to a measurement data recording means 38, which preferably interacts with the engine control or an internal combustion engine (not shown). The honeycomb body 1 has a total volume 13, which is divided into a first part-volume 6, a centrally arranged, second part-volume 22 and a third part-volume 23. The part-volumes 6, 22, 23 are substantially defined by the position of the measurement sensors 5, 21 and the two end faces 3, 4. The first part-volume 6 has a length 14 extending from the first end face 3 as far as a cross-sectional plane through the honeycomb body 1, which is substantially defined by the position of the first measurement sensor 5. The second part- volume 22 is arranged between the first measurement sensor 5 and the second measurement sensor 21 and is once again defined by the position of these measurement sensors. The third part-volume 23 is defined by the position of the second measurement sensor and the second end face 4, so as to form a distance 26. The honeycomb body 1 in each case has different coatings in the part-volumes 6, 22, 23. In the first part-volume 6 there is a first coating 7, which has a low oxygen storage capacity. In the second part-volume 22 there is a second coating 24, which has a higher oxygen storage capacity than the coating 7 in the first part-volume 6. In the third part-volume 23 there is a third coating 25, which is distinguished by a reduced catalytic activity compared to the coating 24. The honeycomb body 1 has a multiplicity of passages 2 which are arranged substantially parallel to one another and in this case preferably continue parallel to an axis 12 of the honeycomb body 1 through the interior of the latter. In the embodiment illustrated, the passages 2 in the first part-volume 6 are formed in such a way that they ensure an exchange of fluid flows between adjacent passages 2. For this purpose, apertures 8 and microstructures 11 are provided in the passage walls 9. Fig. 2 shows a diagrammatic, sectional illustration of a further embodiment of the honeycomb body 1, which is formed using smooth and structured sheet-metal foils 27. The sheet-metal foils 27 are equipped with apertures 8 which have a mean diameter 10 in the range from 2 mm to 10 mm. The at least partially structured sheet-metal foils 27 in turn delimit the passages 2. Starting from its lateral surface 15, the honeycomb body 1 has a recess 16 extending radially in the direction of its axis 12 for accommodating the measurement sensor 5, this recess having a maximum extent 17 and a depth 18. The measurement sensor 5 is arranged in such a way as to ensure a distance from the boundary of the recess 16 which is preferably in the range from 3 to 2 0 mm. A rim 19 which has a width 2 0 of preferably between 1 mm and 5 mm is provided around the recess 16. No exchange of adjacent flows is possible within this rim 19, since in this section or rim 19 the sheet-metal foils 27 do not have any apertures 8 and/or microstructures 11. Fig. 3 diagrammatically depicts the arrangement of an exhaust system 3 0 secured to a bearing surface 40, as may be provided for example on an automobile. The exhaust system 3 0 comprises a pipe section 31 for positioning components for exhaust-gas aftertreatment, with a honeycomb body 1 being indicated here. The pipe section 31 has a longitudinal axis 32 and a base 33, with a secondary axis 35 which intersects the longitudinal axis 32 and the lowest point 34 of the base 33 being formed. The measurement sensor 5 is positioned in an angle range 36 of 270° arranged opposite the lowest point 34 of the base 33. In the embodiment illustrated here, the measurement sensor 5 is even positioned in an angle range of 45° which extends from a tertiary axis 37, extending perpendicular to the secondary axis 35 and through the longitudinal axis 32, toward the lowest point 34 of the base 33. Arranging the measurement sensor 5 in the angle range 36 means that it does not come into contact with a liquid 41 which collects in the vicinity of the lowest point 34 of the base 33. At the same time, however, it is possible for the pipe section 31 to be positioned close to the bearing surface 40, since the region lying precisely opposite the lowest point 34 does not necessarily have to be used to position the measurement sensor 5. List of designations 1 Honeycomb body 2 Passage 3 First end face 4 Second end face 5 First measurement sensor 6 First part-volume 7 First coating 8 Aperture 9 Passage wall 10 Diameter 11 Microstructure 12 Axis 13 Total volume 14 Length 15 Lateral surface 16 Recess 17 Extent 18 Depth 19 Rim 2 0 Width 21 Second measurement sensor 22 Second part-volume 23 Third part-volume 24 Second coating 25 Third coating 26 Distance 27 Sheet-metal foil 28 Housing 29 Cutout 3 0 Exhaust system 31 Pipe section 32 Longitudinal axis 3 3 Base 34 Lowest point 35 Secondary axis 3 6 Angle range 3 7 Tertiary axis 3 8 Measurement data recording means 3 9 Distance 4 0 Bearing surface 41 Liquid WE CLAIM 1. A honeycomb body (1) having passages (2), through which a fluid can flow and which extend between two end faces (3,4) and having at least one measurement sensor (5,21), which at least partially extends into the honeycomb body (1), a first part-volume (6) of the honeycomb (1) being defined between a first end face (3) and the at least one first measurement sensor (5), characterized in that the honeycomb body (1) has a lower capacity to take up oxygen in the first part-volume (6), than atleast in a further part-volume (22-23). 2. The honeycomb body (1) as claimed in claim 1, wherein the first part- volume (6) at least in part has a first coating (7). 3. The honeycomb body (1) as claimed in claim 1 or 2, wherein an exchange of fluid flows between adjacent passages (2) is ensured in the first part- volume (6). 4. The honeycomb body (1) as claimed in claim 3, wherein at least in the first part-volume (6) apertures (8) in particular with a mean diameter (10) in the range from 2 mm to 10mm, are provided in the passage walls (9). 5. The honeycomb body (1) as claimed in claim 3 or 4, wherein the apertures (2), at least in the first part-volume (6), are provided with microstructures (11), which are preferably used to divert the fluid in a direction which is transverse to an axis (12) of the honeycomb body (1). 6. The honeycomb body (1) as claimed in one of the preceding claims, wherein the first part volume (6) forms in the range of less than 30% , in particular in the range from 10% to 25%, of the total volume (13) of the honeycomb body (1). 7. The honeycomb body (1) as claimed in one of the preceding claims, wherein the first part-volume (6) has a length (14) of from 10 mm to 40 mm, starting from the first end face (3). 8. The honeycomb body (1) as claimed in one of the preceding claims, wherein a single measurement sensor (5) is provided, this measurement sensor being a lambda sensor. 9. The honeycomb body (1) as claimed in one of the preceding claims, wherein the honeycomb body (1), starting from its lateral surface (15), has a recess (16), extending radially in the direction of its axis (12), for accommodating the measurement sensor (5, 21), this recess preferably having a maximum extent (17) in the range from 15 mm to 35 mm and/or a depth (18) in the range from 15 mm to 40 mm. lO.the honeycomb body (1) as claimed in claim 9, wherein the shape of the recess (16) is oval-cylindrical, quadrilateral or narrows conically in the direction of the axis (12). 11.The honeycomb body (1) as claimed in claim 9 or 10, wherein the recess (16) is at least partially surrounded by a rim (19) which does not permit exchange of adjacent flows, in particular does not have any apertures (8), this rim (19) preferably having a width (20) in the range from 1 mm to 5 mm. 12.The honeycomb body (1) as claimed in one of the preceding claims, wherein there is a second measurement sensor (21) which is arranged between the first measurement sensor (5) - which is arranged near the first end face (3) and is designed as a lambda sensor - and the second end face (4), a second part-volume (22) being formed between the second measurement sensor (21) and the first measurement sensor (5), and a third part-volume (23) being formed between the second measurement sensor (21) and the second end face (4). 13.The honeycomb body (1) as claimed in claim 12, wherein at least in part a second coating (24) which has an increased capacity to take up oxygen compared to a first coating (7) in the first part-volume (22). 14.The honeycomb body (1) as claimed in claim 12 or 13, wherein the third part-volume (23) at least in part has a third coating (25), which has a lower catalytic activity than at least the first part-volume (22). 15. The honeycomb body (1) as claimed in one of the preceding claims 12 to 14, wherein at least the second part-volume (22) and/or the third part- volume (23) ensures an exchange of fluid flows between adjacent passages (2). 16.The honeycomb body (1) as claimed in one of claims 12 to 15, wherein the second measurement sensor (21) is positioned at a distance (26) in the range from 10 mm to 30 mm from the second end face (4). 17.The honeycomb body (1) as claimed in one of preceding claims 12 to 16, wherein the second measurement sensor (21) is a sensor for monitoring nitrogen oxide levels in the fluid stream. 18.The honeycomb body (1) as claimed in one of the preceding claims, wherein the honeycomb body is formed using at least partially structured sheet-metal foils (27) which delimit the passages (2). 19.The honeycomb body (1) as claimed in one of the preceding claims, wherein the honeycomb body is surrounded by a housing (28) which has at least one cutout (29) which is used for the gastight fixing of the at least one measurement sensor (5,21). 2O.An exhaust system (30) comprising a pipe section (31) for positioning components for exhaust-gas after treatment; and at least one honey- comb body (1) as claimed in one of the preceding claims, characterized in that the pipe section (31) has a longitudinal axis (32) and a base (33), a secondary axis (35), which intersects the longitudinal axis (32) and the lowest point (34) of the base (33) being formed, and the at leart measurement sensor (5,21) being positioned in an angle range (36) of 270° arranged opposite the lowest point (34) of the base (33). 21.The exhaust system (30) as claimed in claim 20, wherein the at least one* measurement sensor (5,21) is positioned in an angle range (36) of 45° which extends from a tertiary axis (37) extending perpendicular to eth secondary axis (35) and through the longitudinal axis (32) toward the lowest point (34) of the base (33). This invention relates to a honeycomb body (1) having passages (2), through which a fluid can flow and which extend between two end faces (3,4) and having at least one measurement sensor (5,21), which at least partially extends into the honeycomb body (1), a first part-volume (6) of the honeycomb (1) being defined between a first end face (3) and the at least one first measurement sensor (5). The honeycomb body (1) has a lower capacity to take up oxygen in the first part-volume (22,23).

Full Text

The invention relates to a honeycomb body having
passages, through which a fluid can flow and which
extend between two end faces, and having at least one
measurement sensor, which at least partially extends
into the honeycomb body. The invention also proposes an
exhaust system which includes a honeycomb body of this
type.
Honeycomb bodies, the basic design of which is known,
for example, from EP 0 245 73 7, EP 0 43 0 945 and
GB 1,452,982, are used for numerous applications in the
automotive industry, in particular as catalyst support
bodies in the treatment of exhaust gas. In view of the
fact that permitted pollutant concentration limits in
exhaust gas from an automobile released to the
environment are being constantly reduced by
legislation, methods which allow control of an exhaust-
gas treatment process are becoming increasingly
important. The measurement sensors which such control
requires and which make it possible, for example, to
determine the exhaust-gas composition or pollutant
concentrations in the exhaust gas, are an important
part of an exhaust-gas treatment system with controlled
operation. Consequently, honeycomb bodies which are
able to accommodate one or more measurement sensors and
therefore provide data for controlling the catalytic
treatment, as are known for example from
DE 88 16 154 Ul, are an important element in exhaust-
gas treatment systems with controlled operation.
Suitable measurement sensors are, for example, sensors
which are used to determine the exhaust-gas
composition, such as for example lambda sensors and
hydrocarbon sensors (HC sensors), which measure the
hydrocarbon content of the exhaust gas. Furthermore, it
is also possible to use what are known as nitrogen

oxide sensors which determine the level of the nitrogen
oxides in the exhaust gas.
Measurement sensors of this type are used in particular
in conjunction with what is known as on-board diagnosis
(OBD) . The purpose of OBD is to continuously monitor
the components which are of relevance to the exhaust
gas in the vehicles, the intention being to immediately
recognize and indicate significant increases in
emissions over the lifetime of each vehicle. This is
intended to ensure permanently low exhaust-gas
emissions.
When monitoring the functionality of a catalytic
converter, it is preferable to determine the oxygen
concentration in the exhaust gas upstream and
downstream of the catalytic converter. To do this, it
is customary for a lambda sensor for determining the
oxygen content to be positioned upstream and downstream
of a .catalytic converter. With the aid of the lambda
sensor arranged upstream of the catalytic converter, it
is possible in particular to draw conclusions as to the
air/fuel mix fed to the internal combustion engine. The
sensor connected downstream of the catalytic converter
generates, for example, a comparison value based on the
oxygen concentration in the exhaust gas, so that it is
possible to draw conclusions as to the functionality of
the catalytic converter. The oxygen is at least
partially used to convert pollutants contained in the
exhaust gas, and therefore a low concentration of
oxygen at the exit of the catalytic converter indicates
effective conversion.
A particular problem with measurement sensors of this
type, in addition to the additional space which they
take up, is that they react very sensitively to
different ambient conditions, as also occur under
certain circumstances in exhaust systems. In

particular, the sensitivity to water or water vapor
needs to be mentioned, as well as the high temperatures
prevailing in the aggressive environment, which can
lead to undesirably rapid aging of the measurement
sensor. However, in particular with a view to OBD, it
is necessary for the sensors for controlling the
exhaust-gas properties and/or monitoring the components
in the exhaust system to remain functional for a
prolonged period of time.
Working on this basis, it is an object of the present
invention to overcome the known technical problems with
regard to arranging measurement sensors in exhaust
systems. In particular, it is intended to propose a
position or form of arrangement of measurement sensors
which ensure long-term use of the measurement sensors
in the exhaust system of mobile internal combustion
engines. The intention is that measured value results
which are as precise and accurate as possible and can
be used to control the exhaust-gas components should be
deliverable. Furthermore, it is intended to propose an
exhaust system which has a particularly space-saving
and functional arrangement of a honeycomb body with a
measurement sensor.
These objects are achieved by a honeycomb body having
the features of patent claim 1 and by an exhaust system
comprising a honeycomb body of this type having the
features of patent claim 20. Further advantageous
configurations are described in the respective
dependent patent claims. At this point, it should be
noted that the features disclosed therein can be
combined with one another in any technologically
appropriate way, in particular even independently of
the way in which they are referred back in the patent
claims.

The honeycomb body according to the invention has
passages, through which a fluid can flow and which
extend between two end faces, and at least one
measurement sensor, which at least partially extends
into the honeycomb body. A part-volume of the honeycomb
body is defined between a first end face and the at
least one first measurement sensor. The honeycomb body
is distinguished by the fact that it has a lower
capacity to take up oxygen in the first part-volume
than in at least one further part-volume.
The honeycomb body can in principle be produced from
various materials, in particular from ceramic or
metallic material. It is preferably to be understood as
a body which comprises a multiplicity of passages which
are arranged next to one another and extend
substantially parallel to one another. The term passage
does not necessarily mean a continuous flow passage,
but rather also encompasses other forms of flow paths
through the honeycomb body. The most important
criterion is that the fluid be divided into a
multiplicity of partial fluid flows when it comes into
contact with an end face of the honeycomb body, with
these partial fluid flows being routed separately from
one another at least in the vicinity of the end faces,
in particular for the first 2 mm to 3 mm. The term
fluid in principle encompasses both gaseous and liquid
substances, although in this context it is preferably a
gas stream, in particular an exhaust-gas stream from a
mobile internal combustion engine (spark-ignition
engine or diesel engine or the like).
The at least one measurement sensor may be any known
type of measurement sensor which is used in connection
with the control or monitoring of exhaust-gas
components of mobile internal combustion engines. This
includes in particular lambda sensors, HC measurement
sensors, temperature sensors, nitrogen oxide

measurement sensors or the like. This at least one
measurement sensor at least partially extends into the
honeycomb body, in other words the at least one
measurement sensor is placed against a lateral surface
of the honeycomb body and preferably extends radially
inward. For a detailed description of the way in which
it is actually arranged, reference is made to the
explanations given below.
A first part-volume is defined by the first end face,
which represents the gas entry side for the use of the
honeycomb body in the exhaust system of a mobile
internal combustion engine, and the at least one
measurement sensor. The part-volume in particular
comprises all passages and their walls. It extends from
the first end face as far as a cross section through
the honeycomb body which is arranged parallel to the
first end face and extends through the closest point of
the measurement sensor to the first end face.
Consequently, the first part-volume is described by the
first end face, this cross section which has just been
described and the lateral surface of the honeycomb body
in between.
According to the invention, the honeycomb body has a
lower capacity to take up oxygen in this first part-
volume than in at least one further part-volume.
Therefore, it will firstly be clear that the first
measurement sensor is located within the interior of
the honeycomb body, i.e. deviates from the known
principle of the measurement sensor connected upstream
or downstream. The integration of the measurement
sensor means that the latter is not directly exposed to
the extreme thermal and dynamic stresses in the exhaust
system of an internal combustion engine. In this way,
it is possible in particular to reduce premature
thermal aging and the risk of what is known as "water
shocks", since the exhaust gas comes into contact with

the honeycomb body first of all and only subsequently
with the measurement sensor. With a view to the use of
a measurement sensor of this type as part of OBD, it is
particularly important for the first measurement
sensor, which is, for example, a lambda sensor, to come
into contact with a composition of the exhaust-gas
stream which still permits conclusions to be drawn as
to the underlying air/fuel mix. Therefore, it is
proposed here that the honeycomb body have a low
capacity to take up oxygen in the part-volume. The
result of this is that insufficient oxygen required for
virtually 100% conversion of the pollutants contained
in the exhaust-gas stream is available in this first
part-volume. Consequently, the conversion rates are
considerably lower in this first part-volume, for
example less than 85%, in particular less than 75% and
even less than 5 0%. Therefore, characteristic values of
the exhaust gas which provide information as to the
fuel/air mix used can still be recorded by the first
measurement sensor.
According to a further configuration of the honeycomb
body, the first part-volume at least in part has a
first coating. A coating of this type is preferably
applied to the passage walls and itself has a capacity
to take up oxygen. The coating may be identical or
different over the entire cross section and the entire
length of the first part-volume in terms of its coating
thickness, the type of coating, the coating surface
area or further parameters. It is also possible for
regions which do not have any coating to exist in the
part-volume. Suitable coatings also include, for
example, support layers for catalytically active
materials, such as for example washcoat.
Furthermore, it is proposed that an exchange of fluid
flows between adjacent passages is ensured in the first
part-volume. In other words, the partial fluid flows

which are formed in the vicinity of the end face of the
honeycomb body are at least partially mixed with one
another in the first part-volume. For this purpose, it
is necessary for the passages arranged adjacent to one
another to be provided with means which allow such an
exchange of fluid flows.
In this context, it is preferably proposed that at
least in the first part-volume apertures, in particular
with a mean diameter in the range from 2 mm to 10 mm,
are provided in the passage walls. The apertures can in
principle comprise any conceivable shapes, in
particular round, polygonal, oval or similar holes,
slots, perforations or the like. In view of the wide
range of forms which apertures of this type can take, a
mean diameter is to be understood as meaning a mean
value for the distance between the opposite edge of the
apertures which lies between the maximum extent and the
minimum extent. In this context, it should be noted
that the apertures do not have to be formed uniformly
over the part-volume, but rather it is possible for the
apertures to be varied in terms of their form, size or
distribution in the first part-volume.
To ensure an exchange of fluid flows between adjacent
passages, it is also proposed that the apertures, at
least in the first part-volume, are provided with
microstructures, which are preferably used to divert
the fluid in a direction which is transverse to an axis
of the honeycomb body. A microstructure is to be
understood in particular as meaning structures which,
starting from the passage walls, extend into inner
regions of the passage or toward adjacent passage
walls. These microstructures preferably have a height
which is less than the height of the passage itself.
Suitable microstructures include studs, stamp
formations, guide surfaces, vanes, grooves, bumps or
the like.

Microstructures of this type are preferably used to
generate pressure differences in adjacent passages
which cause the partial fluid stream to flow from one
passage to the adjacent passage. A suitable arrangement
of the microstructures with respect to one another
allows uniform mixing of the fluid, with the result
that, for example, regions with particularly high
concentrations, as may for example also occur
individually in exhaust-gas streams, are avoided.
Rather, a virtually uniform concentration distribution
of a pollutant or a component of the fluid over
virtually the entire cross section of the honeycomb
body is provided. If a fluid stream which has been
mixed in this manner is brought into contact with the
downstream measurement sensor, it is possible to
provide more accurate statements as to the composition
of the fluid stream.
According to a further configuration, the first part-
volume forms in the range of less than 30%, in
particular in the range from 10% to 25%, of the total
volume of the honeycomb body. In this case, the total
volume is to be understood as meaning the volume of the
honeycomb body, which is defined by the two end faces
and the lateral surface and encompasses both the
passages and their walls or coatings, etc. At this
point, it should be noted that the honeycomb body does
not necessarily have to cylindrical in form. Rather,
oval, conical, polygonal or similar shapes of honeycomb
bodies are also known. If the honeycomb body has a
housing, the housing does not count as part of the
total volume of the honeycomb body.
Furthermore, it is proposed that the first part-volume
has a length of from 10 mm to 40 mm, starting from the
first end face. This length may be sufficient on the
one hand to provide a sufficient contact area for water

vapor contained in the exhaust-gas stream or water
entrained therein and at the same time (in particular
when providing apertures) to effect sufficient mixing
of the exhaust-gas stream. This length detail
preferentially relates to honeycomb bodies which have a
total length of over 100 mm.
It is preferably also proposed that a single
measurement sensor is provided, this measurement sensor
being a lambda sensor. In other words, in this case the
result is a honeycomb body which has only a single
measurement sensor, designed as a lambda sensor, which,
however, can at the same time also be used to carry out
OBD. This single lambda sensor makes it possible, for
example, to detect unburnt hydrocarbons, which occur in
particular after the mobile internal combustion engine
has been started or restarted (known as a "cold
start").
According to a further configuration, the honeycomb
body, starting from its lateral surface, has a recess,
extending radially in the direction of its axis, for
accommodating the measurement sensor, this recess
preferably having a maximum extent in the range from
15 mm to 35 mm and/or a depth in the range from 15 mm
to 40 mm.
The term "lateral surface" is to be understood in
particular as meaning the envelope of the honeycomb
body which is arranged between the two end faces. The
"axis" of the honeycomb body relates in particular to a
center axis, which preferably extends through the
center points of the two end faces. The "recess" or its
center axis extends from the lateral surface preferably
radially toward the axis. Although at this point it
should be noted that this recess may also be arranged
skew or obliquely with respect to the axis of the
honeycomb body, a radial extent constitutes an

embodiment which is preferred here, since in this way a
relatively deep penetration of the measurement sensor
can be achieved.
To ensure that the measurement sensor extends
sufficiently far into inner regions of the honeycomb
body yet at the same time does not constitute an
undesirably major flow resistance, the dimensions
indicated should be complied with. In this context, the
"maximum extent" is arranged substantially in a cross
section of the recess and describes the distance
between the opposite points of the recess arranged
furthest away from one another. The "depth" extends
radially inward from the lateral surface and in this
direction describes the dimension of the recess. The
number of recesses of this type in the honeycomb body
is to be selected taking account of the number of
measurement sensors used. Under certain circumstances,
however, it is also possible for a plurality of
measurement sensors to be arranged in one recess.
Moreover, it is also proposed that the shape of the
recess is oval-cylindrical, quadrilateral or narrows
conically in the direction of the axis. For details as
to the production of recesses of this type in honeycomb
bodies which comprise a plurality of at least partially
structured sheet-metal foils, reference should be made
in particular to the content of disclosure of
WO 02/075126, the content of which is hereby
incorporated in full by reference in the subject matter
of the present description, and reference can be made
to this content of disclosure in full in particular for
a more detailed explanation of the invention.
In addition, it is proposed that the recess is at least
partially surrounded by a rim which does not permit
exchange of adjacent flows, in particular does have any
apertures, this rim preferably having a width in the

range from 1 mm to 5 mm. The configuration of the
recess with a rim of this type means that its external
shape is not delimited by especially fissured passage
walls. This could lead to particularly fine subregions
of the passage walls being freely exposed to the
extreme environmental conditions. On account of the
ensuing pressure fluctuations, subregions could become
detached or cracks could form, which would then
propagate through the passage wall. The provision of
the rim means that stable passage edge regions are
provided in the immediate vicinity of the recess, so as
to ensure long-term use of honeycomb bodies of this
type.
The invention also proposes a honeycomb body, in which
there is a second measurement sensor, which is arranged
between a first measurement sensor - which is arranged
near the first end face and is designed as a lambda
sensor - and the second end face, a second part-volume
being formed between the second measurement sensor and
the first measurement sensor, and a third part-volume
being formed between the second measurement sensor and
the second end face.
In this respect, the honeycomb body has two measurement
sensors, which at least in part project into other
regions. The measurement sensors, which are preferably
each arranged in a cross-sectional plane parallel to at
least one end face of the honeycomb body, in this case
define different part-volumes of the honeycomb body.
The first measurement sensor preferably has the
function of generating certain characteristic variables
which provide information as to the fluid flowing in.
This means that it is possible to ascertain knowledge
as to the composition, concentration differences,
temperatures, etc. on the basis of the data obtained
using the first measurement sensor. The second
measurement sensor is used in particular to record the

functionality of the honeycomb body or its coating by
metrological means. In this case, by way of example,
the same parameters which have been recorded using the
first measurement sensor are recorded again, and the
two recorded parameters are compared with one another.
The rise or drop in this characteristic variable
accordingly allows conclusions to be drawn as to the
for example catalytic activity of the honeycomb body.
However, it is also possible for the two measurement
sensors to observe different parameters of the fluid or
exhaust-gas stream.
In this context, it is also proposed that at least in
part a coating, which has an increased capacity to take
up oxygen compared to the first coating in the first
part-volume, is provided in the second part-volume.
Accordingly, the second part-volume preferably forms
the region of the honeycomb body in which particularly
effective conversion of pollutants in an exhaust-gas
stream takes place. This preferably achieves an
efficiency of over 99%. The higher oxygen uptake
capacity of the second oxidizeable coating ensures that
the pollutants are brought into contact to a sufficient
extent with their reaction partner.
Moreover, it is also proposed that the third part-
volume at least in part has a third coating, which has
a lower catalytic activity than at least the first
part-volume and/or the second part-volume. This is to
be understood in particular as meaning that a smaller
quantity of catalytically active material is provided
in this third part-volume. Catalysts of this type used
are in particular platinum, rhodium or rare earths
(i.e. in particular including weakly basic oxides of
the rare earths).
According to a further configuration of the honeycomb
body, at least the second part-volume and/or the third

part-volume ensures an exchange of fluid flows between
adjacent passages. Under certain circumstances, it is
advantageous not to permit any exchange of fluid flows
between adjacent passages in the second part-volume.
This is the case, for example, if the first measurement
sensor and the second measurement sensor are in each
case supposed to generate measured values to be
compared with one another. To ensure that the same
fluid flows which are routed past the first measurement
sensor also flow past the second measurement sensor,
cross-mixing between partial fluid flows is to be
avoided. If a comparison of this type is not carried
out, mixing of partial fluid flows is under certain
circumstances also advantageous in the second part-
region.
According to a refinement of the honeycomb body, the
second measurement sensor is positioned at a distance
in the range from 10 mm to 3 0 mm from the second end
face. The distance described here constitutes a type of
minimum distance which should be ensured starting from
the second end face, which in the exhaust train of an
automobile usually means the gas exit side. This has
the advantage that when establishing that a limit value
has been exceeded or undershot at the second
measurement location, there is still a third part-
volume available, which if necessary continues to
convert the pollutants until the engine control has
effected a change in the fuel/air mix in order to
restore the functionality of the honeycomb body. This
has its origin, inter alia, in the fact that the
functionality of a honeycomb body generally changes
with a time delay in different regions. Since the
exhaust gas for example always enters from one end
face, this region of the honeycomb body is generally
impaired first. This may affect, for example, the
capacity to store nitrogen oxides, the capacity to trap
particulates or similar components. This

"malfunctioning" then continues over the course of time
into inner regions until ultimately the change can be
detected even at the second measurement location.
Accordingly, the minimum distance or the size of the
third part-volume represents a safety measure to ensure
that the emission limits prescribed by legislation are
still complied with even in the event of sudden failure
of the honeycomb body (for example as a catalyst
support body).
In particular, it is advantageous if the second
measurement sensor is a sensor for monitoring nitrogen
oxide levels in the fluid stream. It is already known
for an N0x store, which can store the nitrogen oxides
produced in operation for a certain period of time, to
be provided for example in the exhaust system of a
diesel engine or lean-burn engine. Before its storage
capacity is exhausted, an N0x store of this type is
regenerated by unburnt hydrocarbons being fed to the
exhaust system. These hydrocarbons react, if
appropriate with the assistance of suitable catalysts,
with the stored nitrogen oxides, generally forming the
products carbon dioxide, nitrogen and water. Any excess
hydrocarbons or hydrocarbons which do not react with
the nitrogen oxides are oxidized in the exhaust system
or the honeycomb body using the residual oxygen
contained in the exhaust gas, so that the result may be
just carbon dioxide and water.
The catalytic conversion can take place in a
catalytically active coating of the N0x store itself or
in a downstream oxidation catalytic converter. As has
already been mentioned above, the honeycomb body itself
may have different coatings, for example an oxidation
coating with a high oxygen storage capacity or a
coating which is able to store N0x. The monitoring of
the ability to store NOX in particular allows
statements to be made as to the functioning of the

honeycomb body or the combustion of the internal
combustion engine at operating temperature.
Furthermore, the invention also proposes a honeycomb
body which is formed using at least partially
structured sheet-metal foils which delimit the
passages. In this case, it is preferable for the
honeycomb body to have both smooth and structured
sheet-metal foils which are stacked on top of one
another and wound together. The profiles of the sheet-
metal foils may be in a spiral shape, an S shape or a
similar intertwined arrangement. These honeycomb bodies
have a cell density which is preferably in the range
from 200 to 1000 cpsi (cells per square inch) , in
particular in the range from 400 to 800 cpsi. The
sheet-metal foil thickness is in this case preferably
less than 100 m, in particular in a range from 20 to
80 m. Temperature-resistant and corrosion-resistant
aluminum/chromium alloys are preferred as material for
the sheet-metal foils.
According to a further configuration of the honeycomb
body, the honeycomb body is surrounded by a housing
which has at least one cutout which is used for the
gastight fixing of the at least one measurement sensor.
The housing substantially ensures the structural
integrity of the honeycomb body. The passage walls or
sheet-metal foils are preferably nonreleasably
connected to the housing; this is to be understood as
meaning that they can only be detached from one another
again as a result of damage to or destruction of the
honeycomb body or the housing. The housing proposed is
likewise a metallic tubular casing, in which case the
passage walls are preferably welded or soldered to the
housing. The cutout is in this case positioned
substantially above the recess, so that the at least
one measurement sensor can be passed through it from
the outside. Special sealing means can be provided to

make the cutout gastight. It is also possible for an
additional housing or a sleeve to be fitted or welded
onto the housing, likewise aligned above the cutout.
Moreover, the invention proposes an exhaust system
which comprises a pipe section for positioning
components for exhaust-gas aftertreatment, in which
system at least one honeycomb body in accordance with
the statements made above is provided. The pipe section
in this case has a longitudinal axis and a base, a
secondary axis, which intersects the longitudinal axis
and the lowest point of the base being formed, and the
at least one measurement sensor being positioned in an
angle range of 270° arranged opposite the lowest point
of the base.
The term exhaust system is to be understood in
particular as meaning an exhaust system of mobile
internal combustion engines, i.e. of automobiles,
motorcycles, trucks or similar vehicles. The exhaust
system is usually connected to the internal combustion
engine and has an opening to the environment, from
which the exhaust gas produced, which has first been
treated, flows out. If appropriate a plurality of
different components for exhaust-gas aftertreatment,
such as for example filter elements, adsorbers, heating
elements, particulate separators, catalytic converters,
etc., are arranged in a pipe section, which is
preferably of widened design. If appropriate, this
exhaust system may be equipped with additional nozzles,
sensors or feed lines for reducing agents or oxidizing
agents.
The arrangement of the at least one measurement sensor
will now be described with reference to the
longitudinal axis and the lowest point of the base of
the pipe section. The invention here proposes a
particularly wide angle range, namely of 270°.

Hitherto, measurement sensors of this type have only-
been arranged in a very limited angle range opposite
the lowest point of the base. This was done in
particular with a view to the condensation water which
may form in the pipe section in the vicinity of the
base, which has an adverse effect on the measurement
result acquired using the at least one measurement
sensor. However, this risk of accumulation of liquids
is considerably reduced on account of the configuration
of the recess and the provision of apertures.
Therefore, it is possible to vary the arrangement
within a particularly wide angle range.
It is in this context very particularly advantageous if
the at least one measurement sensor is positioned in an
angle range of 45° which extends from a tertiary axis
extending perpendicular to the secondary axis and
through the longitudinal axis toward the lowest point
of the base. This is to be understood as meaning in
particular that the at least one measurement sensor is
arranged below a horizontal through the longitudinal
axis of the pipe section. More detailed explanations as
to this arrangement of the at least one measurement
sensor will be provided with reference to the figures.
The invention will now be explained in more detail with
reference to the figures, which show particularly
preferred embodiments, without the invention being
restricted to these embodiments. In the drawing
Fig. 1 diagrammatically depicts a longitudinal section
through a first embodiment of the honeycomb
body;
Fig. 2 diagrammatically depicts a detail view of a
further embodiment of the honeycomb body in
cross section; and

Fig. 3 diagranunatically depicts the arrangement of an
embodiment of the honeycomb body in an exhaust
system.
Fig. 1 diagrammatically depicts a cross section through
a first embodiment of the honeycomb body 1 according to
the invention with passages 2 through which a fluid can
flow and which extend between two end faces 3, 4. The
honeycomb body 1 comprises a housing 28, through which
two measurement sensors 5, 21 extend, via cutouts 29,
into inner regions of the honeycomb body 1. Both
measurement sensors 5, 21 are connected to a
measurement data recording means 38, which preferably
interacts with the engine control or an internal
combustion engine (not shown).
The honeycomb body 1 has a total volume 13, which is
divided into a first part-volume 6, a centrally
arranged, second part-volume 22 and a third part-volume
23. The part-volumes 6, 22, 23 are substantially
defined by the position of the measurement sensors 5,
21 and the two end faces 3, 4. The first part-volume 6
has a length 14 extending from the first end face 3 as
far as a cross-sectional plane through the honeycomb
body 1, which is substantially defined by the position
of the first measurement sensor 5. The second part-
volume 22 is arranged between the first measurement
sensor 5 and the second measurement sensor 21 and is
once again defined by the position of these measurement
sensors. The third part-volume 23 is defined by the
position of the second measurement sensor and the
second end face 4, so as to form a distance 26.
The honeycomb body 1 in each case has different
coatings in the part-volumes 6, 22, 23. In the first
part-volume 6 there is a first coating 7, which has a
low oxygen storage capacity. In the second part-volume
22 there is a second coating 24, which has a higher

oxygen storage capacity than the coating 7 in the first
part-volume 6. In the third part-volume 23 there is a
third coating 25, which is distinguished by a reduced
catalytic activity compared to the coating 24.
The honeycomb body 1 has a multiplicity of passages 2
which are arranged substantially parallel to one
another and in this case preferably continue parallel
to an axis 12 of the honeycomb body 1 through the
interior of the latter. In the embodiment illustrated,
the passages 2 in the first part-volume 6 are formed in
such a way that they ensure an exchange of fluid flows
between adjacent passages 2. For this purpose,
apertures 8 and microstructures 11 are provided in the
passage walls 9.
Fig. 2 shows a diagrammatic, sectional illustration of
a further embodiment of the honeycomb body 1, which is
formed using smooth and structured sheet-metal foils
27. The sheet-metal foils 27 are equipped with
apertures 8 which have a mean diameter 10 in the range
from 2 mm to 10 mm. The at least partially structured
sheet-metal foils 27 in turn delimit the passages 2.
Starting from its lateral surface 15, the honeycomb
body 1 has a recess 16 extending radially in the
direction of its axis 12 for accommodating the
measurement sensor 5, this recess having a maximum
extent 17 and a depth 18. The measurement sensor 5 is
arranged in such a way as to ensure a distance from the
boundary of the recess 16 which is preferably in the
range from 3 to 2 0 mm. A rim 19 which has a width 2 0 of
preferably between 1 mm and 5 mm is provided around the
recess 16. No exchange of adjacent flows is possible
within this rim 19, since in this section or rim 19 the
sheet-metal foils 27 do not have any apertures 8 and/or
microstructures 11.

Fig. 3 diagrammatically depicts the arrangement of an
exhaust system 3 0 secured to a bearing surface 40, as
may be provided for example on an automobile. The
exhaust system 3 0 comprises a pipe section 31 for
positioning components for exhaust-gas aftertreatment,
with a honeycomb body 1 being indicated here. The pipe
section 31 has a longitudinal axis 32 and a base 33,
with a secondary axis 35 which intersects the
longitudinal axis 32 and the lowest point 34 of the
base 33 being formed. The measurement sensor 5 is
positioned in an angle range 36 of 270° arranged
opposite the lowest point 34 of the base 33. In the
embodiment illustrated here, the measurement sensor 5
is even positioned in an angle range of 45° which
extends from a tertiary axis 37, extending
perpendicular to the secondary axis 35 and through the
longitudinal axis 32, toward the lowest point 34 of the
base 33. Arranging the measurement sensor 5 in the
angle range 36 means that it does not come into contact
with a liquid 41 which collects in the vicinity of the
lowest point 34 of the base 33. At the same time,
however, it is possible for the pipe section 31 to be
positioned close to the bearing surface 40, since the
region lying precisely opposite the lowest point 34
does not necessarily have to be used to position the
measurement sensor 5.

List of designations
1 Honeycomb body
2 Passage
3 First end face
4 Second end face
5 First measurement sensor
6 First part-volume
7 First coating
8 Aperture
9 Passage wall
10 Diameter
11 Microstructure
12 Axis
13 Total volume
14 Length
15 Lateral surface
16 Recess
17 Extent
18 Depth
19 Rim
2 0 Width
21 Second measurement sensor
22 Second part-volume
23 Third part-volume
24 Second coating
25 Third coating
26 Distance
27 Sheet-metal foil
28 Housing
29 Cutout
3 0 Exhaust system
31 Pipe section
32 Longitudinal axis
3 3 Base
34 Lowest point
35 Secondary axis
3 6 Angle range

3 7 Tertiary axis
3 8 Measurement data recording means
3 9 Distance
4 0 Bearing surface
41 Liquid

WE CLAIM
1. A honeycomb body (1) having passages (2), through which a fluid can
flow and which extend between two end faces (3,4) and having at least
one measurement sensor (5,21), which at least partially extends into the
honeycomb body (1), a first part-volume (6) of the honeycomb (1) being
defined between a first end face (3) and the at least one first
measurement sensor (5), characterized in that the honeycomb body (1)
has a lower capacity to take up oxygen in the first part-volume (6), than
atleast in a further part-volume (22-23).
2. The honeycomb body (1) as claimed in claim 1, wherein the first part-
volume (6) at least in part has a first coating (7).
3. The honeycomb body (1) as claimed in claim 1 or 2, wherein an exchange
of fluid flows between adjacent passages (2) is ensured in the first part-
volume (6).
4. The honeycomb body (1) as claimed in claim 3, wherein at least in the
first part-volume (6) apertures (8) in particular with a mean diameter (10)
in the range from 2 mm to 10mm, are provided in the passage walls (9).
5. The honeycomb body (1) as claimed in claim 3 or 4, wherein the
apertures (2), at least in the first part-volume (6), are provided with
microstructures (11), which are preferably used to divert the fluid in a
direction which is transverse to an axis (12) of the honeycomb body (1).

6. The honeycomb body (1) as claimed in one of the preceding claims,
wherein the first part volume (6) forms in the range of less than 30% , in
particular in the range from 10% to 25%, of the total volume (13) of the
honeycomb body (1).
7. The honeycomb body (1) as claimed in one of the preceding claims,
wherein the first part-volume (6) has a length (14) of from 10 mm to 40
mm, starting from the first end face (3).
8. The honeycomb body (1) as claimed in one of the preceding claims,
wherein a single measurement sensor (5) is provided, this measurement
sensor being a lambda sensor.
9. The honeycomb body (1) as claimed in one of the preceding claims,
wherein the honeycomb body (1), starting from its lateral surface (15),
has a recess (16), extending radially in the direction of its axis (12), for
accommodating the measurement sensor (5, 21), this recess preferably
having a maximum extent (17) in the range from 15 mm to 35 mm and/or
a depth (18) in the range from 15 mm to 40 mm.
lO.the honeycomb body (1) as claimed in claim 9, wherein the shape of the
recess (16) is oval-cylindrical, quadrilateral or narrows conically in the
direction of the axis (12).

11.The honeycomb body (1) as claimed in claim 9 or 10, wherein the recess
(16) is at least partially surrounded by a rim (19) which does not permit
exchange of adjacent flows, in particular does not have any apertures (8),
this rim (19) preferably having a width (20) in the range from 1 mm to 5
mm.
12.The honeycomb body (1) as claimed in one of the preceding claims,
wherein there is a second measurement sensor (21) which is arranged
between the first measurement sensor (5) - which is arranged near the
first end face (3) and is designed as a lambda sensor - and the second
end face (4), a second part-volume (22) being formed between the
second measurement sensor (21) and the first measurement sensor (5),
and a third part-volume (23) being formed between the second
measurement sensor (21) and the second end face (4).
13.The honeycomb body (1) as claimed in claim 12, wherein at least in part
a second coating (24) which has an increased capacity to take up oxygen
compared to a first coating (7) in the first part-volume (22).
14.The honeycomb body (1) as claimed in claim 12 or 13, wherein the third
part-volume (23) at least in part has a third coating (25), which has a
lower catalytic activity than at least the first part-volume (22).

15. The honeycomb body (1) as claimed in one of the preceding claims 12 to
14, wherein at least the second part-volume (22) and/or the third part-
volume (23) ensures an exchange of fluid flows between adjacent
passages (2).
16.The honeycomb body (1) as claimed in one of claims 12 to 15, wherein
the second measurement sensor (21) is positioned at a distance (26) in
the range from 10 mm to 30 mm from the second end face (4).
17.The honeycomb body (1) as claimed in one of preceding claims 12 to 16,
wherein the second measurement sensor (21) is a sensor for monitoring
nitrogen oxide levels in the fluid stream.
18.The honeycomb body (1) as claimed in one of the preceding claims,
wherein the honeycomb body is formed using at least partially structured
sheet-metal foils (27) which delimit the passages (2).
19.The honeycomb body (1) as claimed in one of the preceding claims,
wherein the honeycomb body is surrounded by a housing (28) which has
at least one cutout (29) which is used for the gastight fixing of the at least
one measurement sensor (5,21).
2O.An exhaust system (30) comprising a pipe section (31) for positioning
components for exhaust-gas after treatment; and at least one honey-
comb body (1) as claimed in one of the preceding claims, characterized in
that the pipe section (31) has a longitudinal axis (32) and a base (33), a

secondary axis (35), which intersects the longitudinal axis (32) and the
lowest point (34) of the base (33) being formed, and the at leart
measurement sensor (5,21) being positioned in an angle range (36) of
270° arranged opposite the lowest point (34) of the base (33).
21.The exhaust system (30) as claimed in claim 20, wherein the at least one*
measurement sensor (5,21) is positioned in an angle range (36) of 45°
which extends from a tertiary axis (37) extending perpendicular to eth
secondary axis (35) and through the longitudinal axis (32) toward the
lowest point (34) of the base (33).

This invention relates to a honeycomb body (1) having passages (2), through
which a fluid can flow and which extend between two end faces (3,4) and having
at least one measurement sensor (5,21), which at least partially extends into the
honeycomb body (1), a first part-volume (6) of the honeycomb (1) being defined
between a first end face (3) and the at least one first measurement sensor (5).
The honeycomb body (1) has a lower capacity to take up oxygen in the first
part-volume (22,23).

Documents:

727-KOLNP-2006-FORM 27.pdf

727-KOLNP-2006-FORM-27.pdf

727-kolnp-2006-granted-abstract.pdf

727-kolnp-2006-granted-claims.pdf

727-kolnp-2006-granted-correspondence.pdf

727-kolnp-2006-granted-description (complete).pdf

727-kolnp-2006-granted-drawings.pdf

727-kolnp-2006-granted-examination report.pdf

727-kolnp-2006-granted-form 1.pdf

727-kolnp-2006-granted-form 18.pdf

727-kolnp-2006-granted-form 2.pdf

727-kolnp-2006-granted-form 3.pdf

727-kolnp-2006-granted-form 5.pdf

727-kolnp-2006-granted-gpa.pdf

727-kolnp-2006-granted-reply to examination report.pdf

727-kolnp-2006-granted-specification.pdf

727-kolnp-2006-granted-translated copy of priority document.pdf

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Patent Number

228770

Indian Patent Application Number

727/KOLNP/2006

PG Journal Number

07/2009

Publication Date

13-Feb-2009

Grant Date

10-Feb-2009

Date of Filing

27-Mar-2006

Name of Patentee

EMITEC GESELLLSCHAFT FUR EMISSIONSTECHNOLOGIE MBH

Applicant Address

HAUPTSTRASSE 150, 53797 LOHMAR

Inventors:

#	Inventor's Name	Inventor's Address
1	BRUCK, ROLF	FROBELSTRASSE 12, 51429 BERGISCH GLADBACH
2	HIRTH, PETER	FORSTSTRASSE 10 51107 KOLN
3	KONIECHZNY, JORG-ROMAN	AM TANNENHOF 40 53721 SIEGBURG

PCT International Classification Number

F01N 11/00

PCT International Application Number

PCT/EP2004/010452

PCT International Filing date

2004-09-17

PCT Conventions:

#	PCT Application Number	Date of Convention	Priority Country
1	103 45 896.4	2003-09-30	Germany