Title of Invention	METHOD FOR POSITIONING A MEASURING SENSOR IN A HONEYCOMB BODY, CORRESPONDING HONEYCOMB BODY, AND MOTOR VEHICLE
Abstract	Disclosed is a method for positioning a sensor (9) in a honeycomb element (1) which is provided with hollow spaces (3) that can be penetrated at least in part by an exhause gas. Said method is characterized in that the sensor (9) is placed in an area of the honeycomb element (1) in which at least one minimum (10,11) hydrogen concentration (c) occurs when the honeycomb element (1) is operated in the emission system of a motor vehicle. The inventive sensor (9) positioning method advantageously allows a sensor (9) to be placed in a honeycomb element (1) in such a way that systematic errors that occur are kept as small as possible as a result of an inherent transverse sensitivity of the sensor (9) to hydrogen. The applies especially to lambda probes. An inventive honeycomb element (1) comprises a sensor (9) which is placed so as to supply particularly reliable test data whose systematic error is as small as possible.

Title of Invention

METHOD FOR POSITIONING A MEASURING SENSOR IN A HONEYCOMB BODY, CORRESPONDING HONEYCOMB BODY, AND MOTOR VEHICLE

Abstract

Disclosed is a method for positioning a sensor (9) in a honeycomb element (1) which is provided with hollow spaces (3) that can be penetrated at least in part by an exhause gas. Said method is characterized in that the sensor (9) is placed in an area of the honeycomb element (1) in which at least one minimum (10,11) hydrogen concentration (c) occurs when the honeycomb element (1) is operated in the emission system of a motor vehicle. The inventive sensor (9) positioning method advantageously allows a sensor (9) to be placed in a honeycomb element (1) in such a way that systematic errors that occur are kept as small as possible as a result of an inherent transverse sensitivity of the sensor (9) to hydrogen. The applies especially to lambda probes. An inventive honeycomb element (1) comprises a sensor (9) which is placed so as to supply particularly reliable test data whose systematic error is as small as possible.

Full Text	WO 2006/084742 PCT/EP2006/001243 Method for positioning a measuring sensor in a honeycomb body, corresponding honeycomb body, and motor vehicle The subject matter of the present invention is a method for positioning a measuring sensor, in particular a lambda probe, in a honeycomb body, a corresponding honeycomb body, and a motor vehicle which comprises a corresponding honeycomb body. Honeycomb bodies are used in particular as catalytic converter support bodies or filter bodies in the exhaust system of motor vehicles such as for example automobiles or motorized two- wheelers . Honeycomb bodies are used as catalytic converter support bodies and/or filter bodies in exhaust systems, in particular of automobiles, motorized two-wheelers, quadbikes, boats or aircraft, and have cavities which can be at least partially traversed by a fluid, in particular an exhaust gas. Said exhaust systems often also have measuring sensors such as lambda probes and/or control probes, which can preferably also be formed in a honeycomb body, as is presented for example in DE 88 16 154 U1. WO 02/075126 A1, for example, discloses a method by means of which, in the case of a honeycomb body which has a honeycomb structure which is constructed from metallic layers and comprises the cavities, a measuring sensor can be inserted such that the least possible surface losses occur for example for a catalytically active coating. In the case of a honeycomb body which comprises a ceramic honeycomb structure, various methods are known for forming a cavity in the honeycomb structure for receiving the measuring sensor, for example boring a hole into the honeycomb structure. WO 2006/084742 PCT/EP2006/001243 - 2 - In all of said methods, however, it was until now unclear where the measuring sensor must be positioned in order to ensure a measurement result of the measuring sensor which is as free as possible from systematic errors. Proceeding from this, the object on which the present invention is based is that of at least partially- alleviating the technical problems known from the prior art and in particular specifying a method for positioning a measuring sensor in a honeycomb body, in which method the measuring sensor is positioned such that possible systematic errors based on the position of the measuring sensor in the honeycomb body are kept as low as possible. It is also intended to propose a corresponding honeycomb body and a motor vehicle having a corresponding honeycomb body. Said objects are achieved by means of a method for positioning a measuring sensor having the features of claim 1, by means of a honeycomb body having the features of claim 7, and by means of a motor vehicle having the features of claim 14. Advantageous refinements are the subject matter of the respective dependent claims. In the method according to the invention for positioning a measuring sensor in a honeycomb body which has cavities which can be at least partially traversed by an exhaust gas, the measuring sensor is positioned in a region of the honeycomb body in which, in operation of the honeycomb body in the exhaust system of a motor vehicle, at least a minimum of the hydrogen concentration is present. It has been proven that in particular lambda probes are sensitive to the surrounding hydrogen concentration, WO 2006/084742 PCT/EP2006/001243 - 3 - that is to say that the measurement result delivered by the probe is highly dependent on the surrounding hydrogen concentration. In order to keep a systematic error of said type as small as possible, and in particular to keep a fluctuation of said systematic error of the measurement result with time as low as possible, it is proposed according to the invention to place the measuring sensor in the region of the hydrogen minimum. The presence of such a minimum is based on the multiplicity of chemical reactions which take place in parallel in particular in a honeycomb body which is used as a catalytic converter support body. In addition to reactions in which hydrogen is consumed, for example in the case of the oxidation of oxygen or in the case of the reduction of nitrogen oxide, reactions also take place as a result of which hydrogen is generated, such as for example the shift reaction in which carbon dioxide (CO) and water (H2O) are converted to form carbon dioxide (CO2) and hydrogen (H2), or also the water vapor reformer reaction. The positioning of the measuring sensor in the minimum of the hydrogen concentration advantageously leads to the systematic error resulting from the cross- sensitivity of the measuring sensor to hydrogen being kept as low as possible. It has surprisingly been shown that even a positioning of the measuring sensor slightly offset with respect to the hydrogen concentration minimum leads to a considerable reduction in said systematic error, so that not only a positioning of the measuring sensor at the minimum but also in a region around the minimum is advantageous and within the spirit of the invention. The position of the minimum is preferably determined while the honeycomb body is subjected to a standard emissions test such as for example the EU Evaporative WO 2006/084742 PCT/EP2006/001243 - 4 — Emissions Test (SHED 2000), the EU Type Approval Test "Type IV" or the US Federal Test Procedure. Predefined in said tests are precise test cycles and details such as for example the temperature of the fuel, the composition of the fuel, vehicle speed and the like. In this application, a motor vehicle is to be understood in particular to mean an automobile, a motorized two-wheeler or quadbike, a boat or an aircraft. The hydrogen concentration is to be understood in particular to mean an axial hydrogen concentration, in which in particular the hydrogen concentration is averaged in a radial direction. The honeycomb body can be in particular a catalytic converter support body and/or a filter body such as an open particle filter or a diesel particle filter, in particular with alternately closed-off ducts. The honeycomb body can encompass a honeycomb structure, which comprises or forms the cavities, in a casing tube. The position of the measuring sensor is to be understood in particular to mean the position of a line of symmetry or of an edge of the measuring sensor. A measuring sensor is to be understood here in particular to mean a lambda probe, a control probe, a temperature sensor and/or a gas concentration sensor, for example for determining the concentration of hydrocarbons or nitrogen oxides. According to one advantageous embodiment of the method according to the invention, the region extends around the position of the minimum in the axial direction in each case by substantially 10% of an axial length of the honeycomb body. WO 2006/084742 PCT/EP2006/001243 - 5 - This means in particular that the measuring sensor is formed both in one partial region with a length of substantially 10% of the axial length of the honeycomb body in one direction, and also in a further partial region with a length of substantially 10% of the length of the honeycomb body in a direction which opposes the first direction. In the case of several minima of the hydrogen concentration, consideration is given in particular to the lowest minimum in said range. According to a further advantageous embodiment of the method according to the invention, the measuring sensor is formed in a region from substantially 20 to 60 mm (millimeter) , preferably 30 to 4 0 mm downstream of an end side, in particular of a gas-inlet-side end side, of the honeycomb body. Many honeycomb bodies have a preferred throughflow direction which is predefined for example by the design of flow-influencing structures in the cavities, so that even in the case of a honeycomb body which is not installed in an exhaust system, it is possible to refer to a gas inlet side. Surprisingly, in the case of a large number of honeycomb bodies, a minimum of the hydrogen concentration is situated in the region from substantially 20 to 60 mm, preferably 30 to 40 mm downstream of a gas-inlet-side end side of the honeycomb body. According to a further advantageous embodiment of the method according to the invention, the position of the minimum is determined in an EU Evaporative Emissions Test (SHED 2000), in an EU Type Approval Test "Type IV" or in a US Federal Test Procedure. Other test methods are however possible and within the spirit of the invention. WO 2006/084742 PCT/EP2006/001243 - 6 - According to a further advantageous embodiment of the method according to the invention, said method serves for positioning at least one of the following measuring sensors: a) lambda probe or b) control probe. A control probe is to be understood to mean a measuring sensor which is part of a closed-loop control circuit. A control probe can encompass the functionality of a lambda probe or can be a lambda probe, with it also being possible for further or other functions to be carried out by the control probe. For example, a control probe can comprise a temperature sensor and/or a gas concentration sensor, for example for determining the concentration of hydrocarbons or nitrogen oxides. According to a further advantageous embodiment of the method according to the invention, the minimum is absolute. It is possible depending on the operating parameters of the honeycomb body for a plurality of minima of the hydrogen concentration to occur, so that the measuring sensor is preferably formed in the region of an absolute hydrogen concentration minimum. According to a further aspect of the concept according to the invention, a honeycomb body having cavities which can be at least partially traversed by an exhaust gas, and comprising a measuring sensor, is proposed, in which the measuring sensor is formed in a region in which, in operation of the honeycomb body in the exhaust system of a motor vehicle, at least one minimum of a hydrogen concentration is present. The formation of the measuring sensor in the region of WO 2006/084742 PCT/EP2006/001243 - 7 - the minimum results in the lowest possible systematic error on account of the cross-sensitivity of the measuring sensor to hydrogen. It is preferable for the measuring sensor to be embodied as a lambda probe or control probe. The minimum is determined using known test methods such as for example the EU Evaporative Emissions Test (SHED 2000), the EU Type Approval Test "Type IV" or the US Federal Test Procedure. The position of the measuring sensor is preferably determined according to one of the above-stated methods. According to a further advantageous embodiment of the honeycomb body according to the invention, the region extends around the position of the minimum in the axial direction in each case by substantially 10% of an axial length of the honeycomb body. According to a further advantageous embodiment of the honeycomb body according to the invention, the measuring sensor is formed in a region from substantially 20 to 60 mm, preferably 30 to 40 mm downstream of an end side, in particular of a gas- inlet-side end side, of the honeycomb body. According to a further advantageous embodiment of the honeycomb body according to the invention, the measuring sensor comprises at least one of the following measuring probes: a) lambda probe or b) control probe. According to a further advantageous embodiment of the honeycomb body according to the invention, the region comprises an absolute minimum of the hydrogen concentration. WO 2006/084742 PCT/EP2006/001243 - 8 - According to a further advantageous embodiment of the honeycomb body according to the invention, the honeycomb body comprises an at least partially ceramic and/or metallic honeycomb structure. Here, the honeycomb structure can be constructed as a ceramic monolith, if appropriate with inserts made from for example metal. The honeycomb structure can also be constructed from at least partially structured and if appropriate substantially smooth layers, by virtue of for example an at least partially structured layer being wound in spiral fashion or for example at least one stack of substantially smooth and at least partially structured layers being wound. Said layers can comprise metal sheet layers, fibrous layers, in particular fibrous layers made from ceramic and/or metallic fibers, other porous layers, in particular metallic and/or ceramic porous layers, and mixtures and/or combinations of the above. The honeycomb structure can for example be extruded, constructed by rapid prototyping techniques or coiled or wound. All coiling, winding and extrusion techniques are possible and within the spirit of the invention. Also proposed is a motor vehicle which comprises at least one honeycomb body according to the invention. A motor vehicle is to be understood in this context to mean in particular an automobile, a motorized two- wheeler or quadbike, a boat or an aircraft. This is to mean in particular a motor vehicle having an exhaust system in which is arranged at least one exhaust gas purification component comprise a honeycomb body of said type. The exhaust system generally comprises an internal combustion engines (for example a diesel or a spark-ignition engine) in which exhaust gases are generated, and an exhaust line through which WO 2006/084742 PCT/EP2006/001243 - 9 - the exhaust gases are conducted in a flow direction and brought into contact with at least one exhaust gas purification component (for example catalytic converter, filter, particle separator, adsorber, etc.), which is arranged in said exhaust line, for converting or separating harmful substances. Here, at least one of the exhaust gas purification components is formed with a honeycomb body of the above-specified type. The arrangement of the at least one measuring sensor is preferably carried out such that the position for the desired exhaust system is determined by means of test procedures and/or by means of calculation (for example with computerized assistance). All of the advantages and details which have been disclosed for the method according to the invention can be transferred and applied to a honeycomb body according to the invention and to a motor vehicle according to the invention, and in each case vice versa. The invention is explained in more detail below on the basis of the drawing, with the invention not being restricted to the particularly preferred exemplary embodiments and advantages shown therein. In the drawing: Figure 1 schematically shows a first exemplary embodiment of a honeycomb body according to the invention; Figure 2 schematically shows a profile of the concentration of hydrogen in a honeycomb body according to the invention; and Figure 3 schematically shows a detail of a longitudinal section of a honeycomb body WO 2006/084742 PCT/EP2006/001243 - 10 - according to the invention, with the associated longitudinal axis. Figure 1 schematically shows a first exemplary- embodiment of a honeycomb body 1 according to the invention. The latter comprises a honeycomb structure 2 having cavities 3 which can be at least partially traversed by a fluid and which extend in an axial direction 4 of the honeycomb body 1. The cavities 3 are formed by substantially smooth layers 5 and at least partially structured layers 6. The at least partially structured layers 6, which are shown in only a part of the cross section of the honeycomb structure 2 for reasons of clarity, are corrugated. "Substantially smooth" in this context means that the substantially smooth layer 5 can also have structures, whose amplitude is however smaller, preferably significantly smaller, than the structures in the at least partially structured layer 6. In the present exemplary embodiment, the layers 5, 6 have been stacked to form a stack, and this has then been wound about two fixed points 7. The honeycomb structure 2 has a measuring sensor receptacle 8 into which a measuring sensor 9 is inserted. The measuring sensor 9 can be embodied in particular as a lambda probe, a control probe, a temperature sensor and/or a gas concentration sensor, for example for determining the concentration of hydrocarbons or nitrogen oxides. Particularly preferred is a lambda probe which can also be encompassed in a control probe. The measuring sensor 9 is formed at a position which is situated in the region of a minimum of the hydrogen concentration in operation of the honeycomb body 1 in the exhaust system of a motor vehicle. The position of the minimum in the axial WO 2006/084742 PCT/EP2006/001243 - 11 - direction 4 is determined in one of the above-described tests. Figure 2 shows, schematically and by way of example, a profile of the concentration of hydrogen c(H2) in relative units in a honeycomb body 1 according to the invention. The concentration c is plotted against a coordinate x in the axial direction 4. In this exemplary embodiment, the honeycomb body 1 has a length L of 70 mm. The profile of the concentration c has a first minimum 10 at the minimum coordinate xM. A second minimum 11 of the hydrogen concentration c is present at the second minimum coordinate xM2. The minimum coordinate xM is situated in the region of 3 0 to 4 0 mm downstream of an end side 12 of the honeycomb body 1 which, in the concentration profile shown in figure 2, is to be found at a coordinate x of zero. The measuring sensor 9 is formed in the region of the minimum coordinate xM of the first minimum 10. Figure 3 schematically shows a detail from a longitudinal section of a honeycomb structure 2 of a honeycomb body 1 according to the invention. In this example, said honeycomb structure 2 is formed, for example extruded, monolithically from ceramic material, and has a measuring sensor receptacle 8 for holding a measuring sensor 9 (not shown). The measuring sensor receptacle 8 and therefore also the measuring sensor 9 are situated in the region of the minimum coordinate xM, with the region preferably extending around the minimum coordinate xM in the axial direction 4, and in the opposite direction, in each case by 10% of the length L of the honeycomb body. The measuring sensor 9 and the measuring sensor receptacle 8 are therefore situated in a region of xM-L/l0 position of the measuring sensor 9 can refer both to an edge of the measuring sensor 9 and to an axis of WO 2006/084742 PCT/EP2006/001243 - 12 - symmetry of the measuring sensor 9. If the measuring sensor 9 enters into the honeycomb structure 2 not perpendicularly with respect to the axial direction 4 but rather at an angle other than 90°, then the measuring sensor 9 is still formed in the specified preferred regions around the minimum coordinate xM, even if only a part of the measuring sensor 9 is formed in said regions. The method according to the invention for positioning a measuring sensor 9 advantageously makes it possible to position a measuring sensor 9 in a honeycomb body 1 in such a way that occurring systematic errors on account of an existing cross-sensitivity of the measuring sensor 9 to hydrogen are kept as low as possible. This applies in particular to lambda probes. A honeycomb body 1 according to the invention comprises a measuring sensor 9 which is positioned so as to deliver particularly reliable measurement data whose systematic error is as low as possible. WO 2006/084742 PCT/EP2006/001243 - 13 - List of reference symbols 1 Honeycomb body 2 Honeycomb structure 3 Cavity 4 Axial direction 5 Substantially smooth layer 6 At least partially structured layer 7 Fixed point 8 Measuring sensor receptacle 9 Measuring sensor 10 First minimum 11 Second minimum 12 End side L Length of honeycomb body c Hydrogen concentration xM Minimum coordinate xM2 Second minimum coordinate WO 2006/084742 PCT/EP2006/001243 - 14 - Patent claims 1. A method for positioning a measuring sensor (9) in a honeycomb body (1) which has cavities (3) which can be at least partially traversed by an exhaust gas, characterized in that the measuring sensor (9) is positioned in a region of the honeycomb body (1) in which, in operation of the honeycomb body (1) in the exhaust system of a motor vehicle, a minimum (10, 11) of the hydrogen concentration (c) is present. 2. The method as claimed in claim 1, characterized in that the region extends around the position (xM) of the minimum (10, 11) in the axial direction (4) in each case by substantially 10% of an axial length (L) of the honeycomb body (1). 3. The method as claimed in one of the preceding claims, characterized in that the measuring sensor (9) is formed in a region from substantially 20 to 60 mm, preferably 30 to 40 mm downstream of an end side (12) , in particular of a gas-inlet-side end side (12), of the honeycomb body (1). 4. The method as claimed in one of the preceding claims, characterized in that the position (xM, xM2) of the minimum (10, 11) is determined in an EU Evaporative Emissions Test (SHED 2000), in an EU Type Approval Test "Type IV" or in a US Federal Test Procedure. 5. The method as claimed in one of the preceding claims, characterized in that said method serves for positioning at least one of the following measuring sensors (9): a) lambda probe, or Disclosed is a method for positioning a sensor (9) in a honeycomb element (1) which is provided with hollow spaces (3) that can be penetrated at least in part by an exhause gas. Said method is characterized in that the sensor (9) is placed in an area of the honeycomb element (1) in which at least one minimum (10,11) hydrogen concentration (c) occurs when the honeycomb element (1) is operated in the emission system of a motor vehicle. The inventive sensor (9) positioning method advantageously allows a sensor (9) to be placed in a honeycomb element (1) in such a way that systematic errors that occur are kept as small as possible as a result of an inherent transverse sensitivity of the sensor (9) to hydrogen. The applies especially to lambda probes. An inventive honeycomb element (1) comprises a sensor (9) which is placed so as to supply particularly reliable test data whose systematic error is as small as possible.

Full Text

WO 2006/084742 PCT/EP2006/001243
Method for positioning a measuring sensor in a
honeycomb body, corresponding honeycomb body, and motor
vehicle
The subject matter of the present invention is a method
for positioning a measuring sensor, in particular a
lambda probe, in a honeycomb body, a corresponding
honeycomb body, and a motor vehicle which comprises a
corresponding honeycomb body. Honeycomb bodies are used
in particular as catalytic converter support bodies or
filter bodies in the exhaust system of motor vehicles
such as for example automobiles or motorized two-
wheelers .
Honeycomb bodies are used as catalytic converter
support bodies and/or filter bodies in exhaust systems,
in particular of automobiles, motorized two-wheelers,
quadbikes, boats or aircraft, and have cavities which
can be at least partially traversed by a fluid, in
particular an exhaust gas. Said exhaust systems often
also have measuring sensors such as lambda probes
and/or control probes, which can preferably also be
formed in a honeycomb body, as is presented for example
in DE 88 16 154 U1. WO 02/075126 A1, for example,
discloses a method by means of which, in the case of a
honeycomb body which has a honeycomb structure which is
constructed from metallic layers and comprises the
cavities, a measuring sensor can be inserted such that
the least possible surface losses occur for example for
a catalytically active coating. In the case of a
honeycomb body which comprises a ceramic honeycomb
structure, various methods are known for forming a
cavity in the honeycomb structure for receiving the
measuring sensor, for example boring a hole into the
honeycomb structure.

WO 2006/084742 PCT/EP2006/001243
- 2 -
In all of said methods, however, it was until now
unclear where the measuring sensor must be positioned
in order to ensure a measurement result of the
measuring sensor which is as free as possible from
systematic errors.
Proceeding from this, the object on which the present
invention is based is that of at least partially-
alleviating the technical problems known from the prior
art and in particular specifying a method for
positioning a measuring sensor in a honeycomb body, in
which method the measuring sensor is positioned such
that possible systematic errors based on the position
of the measuring sensor in the honeycomb body are kept
as low as possible. It is also intended to propose a
corresponding honeycomb body and a motor vehicle having
a corresponding honeycomb body.
Said objects are achieved by means of a method for
positioning a measuring sensor having the features of
claim 1, by means of a honeycomb body having the
features of claim 7, and by means of a motor vehicle
having the features of claim 14. Advantageous
refinements are the subject matter of the respective
dependent claims.
In the method according to the invention for
positioning a measuring sensor in a honeycomb body
which has cavities which can be at least partially
traversed by an exhaust gas, the measuring sensor is
positioned in a region of the honeycomb body in which,
in operation of the honeycomb body in the exhaust
system of a motor vehicle, at least a minimum of the
hydrogen concentration is present.
It has been proven that in particular lambda probes are
sensitive to the surrounding hydrogen concentration,

WO 2006/084742 PCT/EP2006/001243
- 3 -
that is to say that the measurement result delivered by
the probe is highly dependent on the surrounding
hydrogen concentration. In order to keep a systematic
error of said type as small as possible, and in
particular to keep a fluctuation of said systematic
error of the measurement result with time as low as
possible, it is proposed according to the invention to
place the measuring sensor in the region of the
hydrogen minimum. The presence of such a minimum is
based on the multiplicity of chemical reactions which
take place in parallel in particular in a honeycomb
body which is used as a catalytic converter support
body. In addition to reactions in which hydrogen is
consumed, for example in the case of the oxidation of
oxygen or in the case of the reduction of nitrogen
oxide, reactions also take place as a result of which
hydrogen is generated, such as for example the shift
reaction in which carbon dioxide (CO) and water (H2O)
are converted to form carbon dioxide (CO2) and hydrogen
(H2), or also the water vapor reformer reaction.
The positioning of the measuring sensor in the minimum
of the hydrogen concentration advantageously leads to
the systematic error resulting from the cross-
sensitivity of the measuring sensor to hydrogen being
kept as low as possible. It has surprisingly been shown
that even a positioning of the measuring sensor
slightly offset with respect to the hydrogen
concentration minimum leads to a considerable reduction
in said systematic error, so that not only a
positioning of the measuring sensor at the minimum but
also in a region around the minimum is advantageous and
within the spirit of the invention.
The position of the minimum is preferably determined
while the honeycomb body is subjected to a standard
emissions test such as for example the EU Evaporative

WO 2006/084742 PCT/EP2006/001243
- 4 —
Emissions Test (SHED 2000), the EU Type Approval Test
"Type IV" or the US Federal Test Procedure. Predefined
in said tests are precise test cycles and details such
as for example the temperature of the fuel, the
composition of the fuel, vehicle speed and the like.
In this application, a motor vehicle is to be
understood in particular to mean an automobile, a
motorized two-wheeler or quadbike, a boat or an
aircraft. The hydrogen concentration is to be
understood in particular to mean an axial hydrogen
concentration, in which in particular the hydrogen
concentration is averaged in a radial direction. The
honeycomb body can be in particular a catalytic
converter support body and/or a filter body such as an
open particle filter or a diesel particle filter, in
particular with alternately closed-off ducts. The
honeycomb body can encompass a honeycomb structure,
which comprises or forms the cavities, in a casing
tube.
The position of the measuring sensor is to be
understood in particular to mean the position of a line
of symmetry or of an edge of the measuring sensor. A
measuring sensor is to be understood here in particular
to mean a lambda probe, a control probe, a temperature
sensor and/or a gas concentration sensor, for example
for determining the concentration of hydrocarbons or
nitrogen oxides.
According to one advantageous embodiment of the method
according to the invention, the region extends around
the position of the minimum in the axial direction in
each case by substantially 10% of an axial length of
the honeycomb body.

WO 2006/084742 PCT/EP2006/001243
- 5 -
This means in particular that the measuring sensor is
formed both in one partial region with a length of
substantially 10% of the axial length of the honeycomb
body in one direction, and also in a further partial
region with a length of substantially 10% of the length
of the honeycomb body in a direction which opposes the
first direction. In the case of several minima of the
hydrogen concentration, consideration is given in
particular to the lowest minimum in said range.
According to a further advantageous embodiment of the
method according to the invention, the measuring sensor
is formed in a region from substantially 20 to 60 mm
(millimeter) , preferably 30 to 4 0 mm downstream of an
end side, in particular of a gas-inlet-side end side,
of the honeycomb body.
Many honeycomb bodies have a preferred throughflow
direction which is predefined for example by the design
of flow-influencing structures in the cavities, so that
even in the case of a honeycomb body which is not
installed in an exhaust system, it is possible to refer
to a gas inlet side. Surprisingly, in the case of a
large number of honeycomb bodies, a minimum of the
hydrogen concentration is situated in the region from
substantially 20 to 60 mm, preferably 30 to 40 mm
downstream of a gas-inlet-side end side of the
honeycomb body.
According to a further advantageous embodiment of the
method according to the invention, the position of the
minimum is determined in an EU Evaporative Emissions
Test (SHED 2000), in an EU Type Approval Test "Type IV"
or in a US Federal Test Procedure. Other test methods
are however possible and within the spirit of the
invention.

WO 2006/084742 PCT/EP2006/001243
- 6 -
According to a further advantageous embodiment of the
method according to the invention, said method serves
for positioning at least one of the following measuring
sensors:
a) lambda probe or
b) control probe.
A control probe is to be understood to mean a measuring
sensor which is part of a closed-loop control circuit.
A control probe can encompass the functionality of a
lambda probe or can be a lambda probe, with it also
being possible for further or other functions to be
carried out by the control probe. For example, a
control probe can comprise a temperature sensor and/or
a gas concentration sensor, for example for determining
the concentration of hydrocarbons or nitrogen oxides.
According to a further advantageous embodiment of the
method according to the invention, the minimum is
absolute.
It is possible depending on the operating parameters of
the honeycomb body for a plurality of minima of the
hydrogen concentration to occur, so that the measuring
sensor is preferably formed in the region of an
absolute hydrogen concentration minimum.
According to a further aspect of the concept according
to the invention, a honeycomb body having cavities
which can be at least partially traversed by an exhaust
gas, and comprising a measuring sensor, is proposed, in
which the measuring sensor is formed in a region in
which, in operation of the honeycomb body in the
exhaust system of a motor vehicle, at least one minimum
of a hydrogen concentration is present.
The formation of the measuring sensor in the region of

WO 2006/084742 PCT/EP2006/001243
- 7 -
the minimum results in the lowest possible systematic
error on account of the cross-sensitivity of the
measuring sensor to hydrogen. It is preferable for the
measuring sensor to be embodied as a lambda probe or
control probe. The minimum is determined using known
test methods such as for example the EU Evaporative
Emissions Test (SHED 2000), the EU Type Approval Test
"Type IV" or the US Federal Test Procedure. The
position of the measuring sensor is preferably
determined according to one of the above-stated
methods.
According to a further advantageous embodiment of the
honeycomb body according to the invention, the region
extends around the position of the minimum in the axial
direction in each case by substantially 10% of an axial
length of the honeycomb body.
According to a further advantageous embodiment of the
honeycomb body according to the invention, the
measuring sensor is formed in a region from
substantially 20 to 60 mm, preferably 30 to 40 mm
downstream of an end side, in particular of a gas-
inlet-side end side, of the honeycomb body.
According to a further advantageous embodiment of the
honeycomb body according to the invention, the
measuring sensor comprises at least one of the
following measuring probes:
a) lambda probe or
b) control probe.
According to a further advantageous embodiment of the
honeycomb body according to the invention, the region
comprises an absolute minimum of the hydrogen
concentration.

WO 2006/084742 PCT/EP2006/001243
- 8 -
According to a further advantageous embodiment of the
honeycomb body according to the invention, the
honeycomb body comprises an at least partially ceramic
and/or metallic honeycomb structure.
Here, the honeycomb structure can be constructed as a
ceramic monolith, if appropriate with inserts made from
for example metal. The honeycomb structure can also be
constructed from at least partially structured and if
appropriate substantially smooth layers, by virtue of
for example an at least partially structured layer
being wound in spiral fashion or for example at least
one stack of substantially smooth and at least
partially structured layers being wound. Said layers
can comprise metal sheet layers, fibrous layers, in
particular fibrous layers made from ceramic and/or
metallic fibers, other porous layers, in particular
metallic and/or ceramic porous layers, and mixtures
and/or combinations of the above. The honeycomb
structure can for example be extruded, constructed by
rapid prototyping techniques or coiled or wound. All
coiling, winding and extrusion techniques are possible
and within the spirit of the invention.
Also proposed is a motor vehicle which comprises at
least one honeycomb body according to the invention. A
motor vehicle is to be understood in this context to
mean in particular an automobile, a motorized two-
wheeler or quadbike, a boat or an aircraft.
This is to mean in particular a motor vehicle having an
exhaust system in which is arranged at least one
exhaust gas purification component comprise a honeycomb
body of said type. The exhaust system generally
comprises an internal combustion engines (for example a
diesel or a spark-ignition engine) in which exhaust
gases are generated, and an exhaust line through which

WO 2006/084742 PCT/EP2006/001243
- 9 -
the exhaust gases are conducted in a flow direction and
brought into contact with at least one exhaust gas
purification component (for example catalytic
converter, filter, particle separator, adsorber, etc.),
which is arranged in said exhaust line, for converting
or separating harmful substances. Here, at least one of
the exhaust gas purification components is formed with
a honeycomb body of the above-specified type. The
arrangement of the at least one measuring sensor is
preferably carried out such that the position for the
desired exhaust system is determined by means of test
procedures and/or by means of calculation (for example
with computerized assistance).
All of the advantages and details which have been
disclosed for the method according to the invention can
be transferred and applied to a honeycomb body
according to the invention and to a motor vehicle
according to the invention, and in each case vice
versa.
The invention is explained in more detail below on the
basis of the drawing, with the invention not being
restricted to the particularly preferred exemplary
embodiments and advantages shown therein. In the
drawing:
Figure 1 schematically shows a first exemplary
embodiment of a honeycomb body according to
the invention;
Figure 2 schematically shows a profile of the
concentration of hydrogen in a honeycomb body
according to the invention; and
Figure 3 schematically shows a detail of a
longitudinal section of a honeycomb body

WO 2006/084742 PCT/EP2006/001243
- 10 -
according to the invention, with the
associated longitudinal axis.
Figure 1 schematically shows a first exemplary-
embodiment of a honeycomb body 1 according to the
invention. The latter comprises a honeycomb structure 2
having cavities 3 which can be at least partially
traversed by a fluid and which extend in an axial
direction 4 of the honeycomb body 1. The cavities 3 are
formed by substantially smooth layers 5 and at least
partially structured layers 6. The at least partially
structured layers 6, which are shown in only a part of
the cross section of the honeycomb structure 2 for
reasons of clarity, are corrugated. "Substantially
smooth" in this context means that the substantially
smooth layer 5 can also have structures, whose
amplitude is however smaller, preferably significantly
smaller, than the structures in the at least partially
structured layer 6. In the present exemplary
embodiment, the layers 5, 6 have been stacked to form a
stack, and this has then been wound about two fixed
points 7.
The honeycomb structure 2 has a measuring sensor
receptacle 8 into which a measuring sensor 9 is
inserted. The measuring sensor 9 can be embodied in
particular as a lambda probe, a control probe, a
temperature sensor and/or a gas concentration sensor,
for example for determining the concentration of
hydrocarbons or nitrogen oxides. Particularly preferred
is a lambda probe which can also be encompassed in a
control probe. The measuring sensor 9 is formed at a
position which is situated in the region of a minimum
of the hydrogen concentration in operation of the
honeycomb body 1 in the exhaust system of a motor
vehicle. The position of the minimum in the axial

WO 2006/084742 PCT/EP2006/001243
- 11 -
direction 4 is determined in one of the above-described
tests.
Figure 2 shows, schematically and by way of example, a
profile of the concentration of hydrogen c(H2) in
relative units in a honeycomb body 1 according to the
invention. The concentration c is plotted against a
coordinate x in the axial direction 4. In this
exemplary embodiment, the honeycomb body 1 has a length
L of 70 mm. The profile of the concentration c has a
first minimum 10 at the minimum coordinate xM. A second
minimum 11 of the hydrogen concentration c is present
at the second minimum coordinate xM2. The minimum
coordinate xM is situated in the region of 3 0 to 4 0 mm
downstream of an end side 12 of the honeycomb body 1
which, in the concentration profile shown in figure 2,
is to be found at a coordinate x of zero. The measuring
sensor 9 is formed in the region of the minimum
coordinate xM of the first minimum 10.
Figure 3 schematically shows a detail from a
longitudinal section of a honeycomb structure 2 of a
honeycomb body 1 according to the invention. In this
example, said honeycomb structure 2 is formed, for
example extruded, monolithically from ceramic material,
and has a measuring sensor receptacle 8 for holding a
measuring sensor 9 (not shown). The measuring sensor
receptacle 8 and therefore also the measuring sensor 9
are situated in the region of the minimum coordinate
xM, with the region preferably extending around the
minimum coordinate xM in the axial direction 4, and in
the opposite direction, in each case by 10% of the
length L of the honeycomb body. The measuring sensor 9
and the measuring sensor receptacle 8 are therefore
situated in a region of xM-L/l0 position of the measuring sensor 9 can refer both to an
edge of the measuring sensor 9 and to an axis of

WO 2006/084742 PCT/EP2006/001243
- 12 -
symmetry of the measuring sensor 9. If the measuring
sensor 9 enters into the honeycomb structure 2 not
perpendicularly with respect to the axial direction 4
but rather at an angle other than 90°, then the
measuring sensor 9 is still formed in the specified
preferred regions around the minimum coordinate xM,
even if only a part of the measuring sensor 9 is formed
in said regions.
The method according to the invention for positioning a
measuring sensor 9 advantageously makes it possible to
position a measuring sensor 9 in a honeycomb body 1 in
such a way that occurring systematic errors on account
of an existing cross-sensitivity of the measuring
sensor 9 to hydrogen are kept as low as possible. This
applies in particular to lambda probes. A honeycomb
body 1 according to the invention comprises a measuring
sensor 9 which is positioned so as to deliver
particularly reliable measurement data whose systematic
error is as low as possible.

WO 2006/084742 PCT/EP2006/001243
- 13 -
List of reference symbols
1 Honeycomb body
2 Honeycomb structure
3 Cavity
4 Axial direction
5 Substantially smooth layer
6 At least partially structured layer
7 Fixed point
8 Measuring sensor receptacle
9 Measuring sensor
10 First minimum
11 Second minimum
12 End side
L Length of honeycomb body
c Hydrogen concentration
xM Minimum coordinate
xM2 Second minimum coordinate

WO 2006/084742 PCT/EP2006/001243
- 14 -
Patent claims
1. A method for positioning a measuring sensor (9) in
a honeycomb body (1) which has cavities (3) which
can be at least partially traversed by an exhaust
gas, characterized in that the measuring sensor
(9) is positioned in a region of the honeycomb
body (1) in which, in operation of the honeycomb
body (1) in the exhaust system of a motor vehicle,
a minimum (10, 11) of the hydrogen concentration
(c) is present.
2. The method as claimed in claim 1, characterized in
that the region extends around the position (xM)
of the minimum (10, 11) in the axial direction (4)
in each case by substantially 10% of an axial
length (L) of the honeycomb body (1).
3. The method as claimed in one of the preceding
claims, characterized in that the measuring sensor
(9) is formed in a region from substantially 20 to
60 mm, preferably 30 to 40 mm downstream of an end
side (12) , in particular of a gas-inlet-side end
side (12), of the honeycomb body (1).
4. The method as claimed in one of the preceding
claims, characterized in that the position (xM,
xM2) of the minimum (10, 11) is determined in an
EU Evaporative Emissions Test (SHED 2000), in an
EU Type Approval Test "Type IV" or in a US Federal
Test Procedure.
5. The method as claimed in one of the preceding
claims, characterized in that said method serves
for positioning at least one of the following
measuring sensors (9):
a) lambda probe, or

Disclosed is a method for positioning a sensor (9) in a honeycomb element (1)
which is provided with hollow spaces (3) that can be penetrated at least in part
by an exhause gas. Said method is characterized in that the sensor (9) is placed
in an area of the honeycomb element (1) in which at least one minimum (10,11)
hydrogen concentration (c) occurs when the honeycomb element (1) is operated
in the emission system of a motor vehicle. The inventive sensor (9) positioning
method advantageously allows a sensor (9) to be placed in a honeycomb
element (1) in such a way that systematic errors that occur are kept as small as
possible as a result of an inherent transverse sensitivity of the sensor (9) to
hydrogen. The applies especially to lambda probes. An inventive honeycomb
element (1) comprises a sensor (9) which is placed so as to supply particularly
reliable test data whose systematic error is as small as possible.

METHOD FOR POSITIONING A MEASURING SENSOR IN A HONEYCOMB BODY, CORRESPONDING HONEYCOMB BODY, AND MOTOR VEHICLE

Documents:

Inventors:

PCT Conventions: