Title of Invention	A METHOD FOR CONTROLLING A FUEL MIXTURE BY MEANS OF A CONTROL PROBE IN THE EXHAUST SYSTEM OF A MOBILE INTERNAL COMBUSTION ENGINE
Abstract	The invention relates to a method for controlling a fuel mixture by means of a control probe (1) in the waste-gas system (2) of a mobile internal combustion engine (3). The waste-gas system (2) comprises at least one catalytic converter (4) which is disposed in a waste-gas line (5), and control thereof is carried out by means of an individual control probe (1} disposed in the inside of at least one catalytic converter (4). The invention also relates to a waste-gas system (2) which is suitable therefor.

Title of Invention

A METHOD FOR CONTROLLING A FUEL MIXTURE BY MEANS OF A CONTROL PROBE IN THE EXHAUST SYSTEM OF A MOBILE INTERNAL COMBUSTION ENGINE

Abstract

The invention relates to a method for controlling a fuel mixture by means of a control probe (1) in the waste-gas system (2) of a mobile internal combustion engine (3). The waste-gas system (2) comprises at least one catalytic converter (4) which is disposed in a waste-gas line (5), and control thereof is carried out by means of an individual control probe (1} disposed in the inside of at least one catalytic converter (4). The invention also relates to a waste-gas system (2) which is suitable therefor.

Full Text	WO 2005/121533 PCT/EP2005/005968 Control system for a mobile internal combustion engine The invention relates to a method for controlling a fuel mixture by means of a control probe in the exhaust system of a mobile internal combustion engine. Furthermore, an exhaust system comprising a mobile internal combustion engine is proposed. The preferred field of use of such exhaust systems or methods is the automobile sector. It is known to use sensors and/or probes in exhaust systems of mobile internal combustion engines in order to obtain detailed information about operating states of the internal combustion engines and/or exhaust gas treatment devices which are integrated in the exhaust system. Thus, it is known, for example, to use an oxygen sensor connected to an electronic device to determine the state of ageing of an exhaust gas catalytic converter. The sensor has an oxygen-sensitive region for measuring the partial pressure of oxygen in the exhaust gas. The state of the ageing of the catalytic converter is determined by the control device by means of this measurement variable since the oxygen load on the catalytic converter can be used as a characteristic variable for its functional capability (referred to as onboard diagnostics). Furthermore it is also known to monitor at least part of the exhaust gas in the exhaust system and thus to influence the supply of fuel to the internal combustion engine. Thus, in internal combustion engines which have warmed up, or after a predefinable exhaust temperature has been reached, oxygen sensors are used to perform lambda control on the internal combustion engine. Lambda (X) , referred to as the excess air factor, describes the ratio of the current air/fuel ratio to WO 20G5/121533 PCT/EP2005/005968 - 2 - the stochiometric air/fuel ratio and is often used as a characteristic value for the combustion processes. In this context, a first oxygen sensor which is arranged upstream of a catalytic converter is used as a control probe, and a second oxygen sensor which is connected downstream of the exhaust gas catalytic converter is used as a trimming probe. The first oxygen sensor is used to determine lambda oscillation with a specific amplitude and frequency, which result from the confoustion processes in the internal combustion engine. These are sensed by means of the first oxygen sensor which ¦ is positioned upstream of the catalytic converter. A person skilled in the art is familiar with the procedure here and does not require any further explanation. The lambda oscillation of the exhaust gas composition which is present at the input end of the catalytic converter is increasingly smoothed as it passes through the catalytic converter owing to its oxygen storage capability. The result is a decrease in amplitude of the lambda oscillations along the catalytic converter. Given a high oxygen storage capability, it is almost impossible to obtain evidence of lambda oscillation anymore at the output end, for example. The amplitude of the lambda oscillation for which evidence can still be obtained after the exhaust gas has run through a partial section or the entire catalytic converter is therefore a measure of the oxygen storage capability of the section of the catalytic converter or of the entire catalytic converter. In this case, the lambda value generally settles to the constant mean value of the lambda oscillation present upstream of the catalytic converter. This mean value is sensed by the second sensor downstream of the catalytic converter, said sensor being the so-called trimming probe. The trimming probe is then used to set a mean WO 2005/121533 PCT/EP200S/005968 - 3 - value of lambda? which cannot be determined or set precisely by means of the oxygen sensor or control sensor which is mounted upstream (of the catalytic converter), Causes for this are, for example, so-called "poisoning11, that Is to say adverse influences due to the high oxygen concentration or other influences of the untreated exhaust gas on. this control sensor which is positioned upstream, As a result, the control sensor which Is positioned upstream changes its measuring behavior so that even though the dynamic oscillating behavior continues to be satisfactorily sensed, without the trimming probe It is not possible to obtain precise Information about the (mean) lambda value over a relatively long period of use of the control sensor which Is mounted upstream. In the chemical balance, the lambda value emerges directly from the partial pressure of the oxygen. For this reason, the lambda value, and thus also the oxygen storage capability of the catalytic converter, can be determined by measuring the partial pressure of the oxygen with the second oxygen sensor {trimming probe) which Is arranged downstream of the catalytic converter, in this way it Is then possible to Install a "slow" correction routine which compensates for the ageing/poisoning of the control sensor which Is mounted upstream. The profile - determined by means of the oxygen sensors - of the partial pressure values of the oxygen or of other parameters which describe the exhaust gas composition also permits conclusions to be drawn about the effectiveness or the scope of the combustion in the individual combustion chambers of the internal combustion engine. The values which are generated therewith can thus also be used to perform lambda control on the internal combustion engine, with, for example, influence being exerted on the composition of WO 2005/121533 PCT/E12005/005968 - 4 - a fuel/air mixture, the ignition time, the pressures prevailing during the combustion, etc. A problem when such oxygen sensors or other control probes are used is also their sensitivity to water. If the sensitive region of the control probe comes into contact with water, the functional capability of the control probe is generally no longer ensured. For this reason, a number of different embodiments of control probes and lambda probes respectively, which are intended to prevent contact of the sensitive area with water have already been proposed. Usually, such oxygen sensors and lambda sensors respectively, are brought to the operating temperature by means of an electric heating conductor structure. It is also known to provide special screening means, grilles or coatings which function as a means of resisting water. Due to the fact that these probes and sensors respectively, are in contact with the exhaust gas line or are guided through it, they generally have a lower temperature than the exhaust gas. It is also necessary to take into account the fact that the temperature of the exhaust gas varies greatly owing to the different operating states of the internal combustion engine. There is thus repeatedly the risk that the sensor or the housing surrounding the sensor will reach temperatures which can result in condensation of water out of the exhaust gas. Taking this as a basis, the object of the invention is to disclose a simplified method for controlling a fuel mixture by means of a control probe in the exhaust system of a mobile internal combustion engine. In particular, the problems described with respect to the prior art are to be at least partially alleviated. Furthermore, an exhaust system which is of cost-effective and simple design is to be proposed. WO 2005/121533 PCT/EP2005/005968 - 5 - These objects are achieved with a method for controlling a fuel mixture having the features of patent claim 1 and an exhaust system having the features of the independently formulated device claim. Further advantageous embodiments of the invention are described in the respective independent patent claims. In addition it is to be noted that the features specified individually in the patent claims can be combined with one another in any desired technically appropriate way and specify further embodiments of the invention. In order to control a fuel mixture of a mobile internal combustion engine a control probe is provided in the exhaust system, the exhaust system comprising at least one catalytic converter in an exhaust line. The method is characterized by the fact that the control is carried out with a single control probe in the interior of the at least one catalytic converter. In the first instance, the invention departs from the preconceptions of the specialists according to which the fuel mixture of the internal combustion engine is controlled with a multiplicity of control probes (one for the dynamic lambda oscillation and one for the slow-acting trimming). As a result, the method can already be carried out at relatively low cost and with relatively little expenditure on electronics, with the susceptibility to faults of this system for controlling the fuel mixture being automatically reduced. In order to protect against condensation water, the aggressive ambient conditions due to the untreated exhaust gas and the large fluctuations of temperature, this one control probe is arranged in the interior of the at least one catalytic converter. This means in particular that parts of the control probe extend into internal regions of the catalytic converter. It is clear that the control probe has to be made to extend out of the WO 2005/121533 PCT/EP2005/005968 - 6 - exhaust system or exhaust line so that the control probe is not arranged completely in the interior of the catalytic converter. The catalytic converter itself represents a type of damping element for the temperatures, pollutant concentrations etc. In particular it is a thermal mass so that here a somewhat sluggish thermal behavior occurs. To this extent, the fluctuations of the exhaust gas temperature as a consequence of different operating states of the internal combustion engine do not affect the control probe to the extent that they would a control probe which projects freely into the exhaust line. The control probe is preferably an oxygen sensor or what is referred to as a lambda probe. Investigations have shown here that the integration of the individual control probe in the catalytic converters surprisingly ensures precise results over a long operating time. It has been found that the influences of the exhaust gas (for example temperature fluctuations, pressure fluctuations, etc.) already decrease considerably over the first millimeters of the catalytic converter so that in this way a significant "protection against ageing and protection against poisoning respectively " of the control probe has been realized. More detailed information will be given on this in the text below. At the same time, there is still sufficient lambda oscillation, which can be used to perform lambda control on the internal combustion engine. In such an embodiment it is advantageously possible to use appropriate types of control probe. For example, in a range up to 50% reduction of the "incoming" lambda oscillation at the catalytic converter it is still possible to use so-called jump probes (for example zircon dioxide probe with a sudden change in the output signal at a lambda value of approximately 1) since these are particularly economical and still sufficiently sensitive. Given WO 2005/121533 PCT/EP2005/005968 - 7 - further reduction of the lambda oscillation amplitudes, for example as far as 5%, so-called linear probes can preferably be used. At this point it is to be noted that this does not mean that no further sensors at all should be provided in the exhaust system. It is thus possible, for example, to connect nitrogen oxygen sensors downstream of the catalytic converter, which sensors determine the nitrogen oxygen concentration in the exhaust gas after contact with the catalytic converter. However, the measured values which are obtained in this way are not used to perform lambda control on the internal combustion engine. According to a further embodiment of the method, the control probe is heated after the internal combustion engine starts, in such a way that it has a temperature of at least 70°C [degree Celsius] before the at least one catalytic converter has reached 95° C. The control probe can be heated passively here (essentially only by means of the temperature of the exhaust gas in contact with it) and/or actively, (for example by means of a heating element, an electric heater etc.) As has already been stated at the beginning, such control probes usually have particular sensitivity to water. It is proposed here that the control probe has a temperature of at least 70°C (at which the phenomenon of condensation no longer occurs to a significant extent owing to the arrangement in the catalytic converter proposed here) before the catalytic converter has reached 95°C. In addition, as well as a thermal mass, the catalytic converter also makes available a large surface which can be used to adsorb water or water vapor. That is to say in other words the catalytic converter or in particular also its coating acts as a sponge for water and binds it for a relatively long time. WO 2005/12i533 PCT/BP2005/005968 — 8 — When the internal combustion engine is (re)started, the exhaust gas flowing the catalytic converter then gradually heats the carrier body of the catalytic converter and the coating. In the process, a temperature profile forms in the direction of flow of the exhaust gas In the catalytic converter so that at first the highest temperatures are present the exhaust gas Inlet side and said temperatures then decrease In the direction of flow. Here, It is then proposed in particular that the control probe already have a temperature of at least TO^C, In particular of at least 90°C [degrees Celsius), before the catalytic converter or the carrier body of the catalytic converter in a plane parallel to the gas Inlet side at a distance of 10 ram. has reached a temperature of 95°C. The accumulated water increasingly vaporizes in a range above average 95°C and propagates in the direction of flow of the catalytic converter, and it condenses again if it arrives at colder regions. In this way, a type of "water vapor front" Is generated through the catalytic converter. By ensuring a certain temperature of the control probe it Is made certain that the control probe does not constitute such a heat sink when in contact with the water vapor front that water condenses. This ensures the functionality of the individual control probe. In particular It Is proposed that the control probe determines at least one of the following components of the exhaust gas: hydrocarbon, carbon Rionoxide, oxygen. Furthermore, it Is also possible to measure a partial pressure, a temperature or other physical measuring variables by means of this control probe. According to a further embodiment of the method, the control probe is a lambda probe, said probe being simultaneously used to check the conversion capability WO 2005/121533 PCT/EP2005/005968 - 9 - of the at least one catalytic converter. In particular, this is what is referred to as a broadband lambda probe (lambda probe) which outputs a continuous, for example linear, output signal as a function of the oxygen content in the exhaust gas in the range around lambda = 1 (for example with a tolerance of ± 0.005). This signal is used to control the mixture in accordance with the predefined setpoint values. With the embodiment of the control probe proposed here it is possible to locate said probe relatively far down in the catalytic converter, in particular at a distance of 25 mm to 60 mm. In this region, the lambda oscillations are frequency already reduced or smoothed by more than 50%, in some cases even by more than 90%. The use of such a broadband lambda probe also to the same extent permits a high degree of measuring accuracy, and an extremely low tendency to poisoning occurs by virtue of its position in the catalytic converter so that a mean value for lambda can also be found to occur precisely and over a relatively long time period. The oxygen content determined with the lambda probe can additionally also be used as a measure of the conversion capability of the catalytic converter. With respect to this process, reference is made to the explanations given at the beginning. With such a lambda probe it is possible to carry out onboard diagnostics easily. As a result, a method is specified which has a particularly simple structure and at the same time permits lambda control of the internal combustion engine and onboard diagnostics. Furthermore it is also proposed that the exhaust gas which is generated by the internal combustion engine be mixed in the exhaust line before it reaches the control probe. Owing to the situation or position of the control probe in the exhaust line, only certain peripheral flows of the exhaust gas are always sensed and evaluated. In order to ensure that a result which WO 2005/121533 PCT/EP2005/005968 - 10 - is representative of the entire exhaust gas flow is obtained, the exhaust gas flow is mixed before it reaches the control probe. It is then possible to assume that the position of the individual control probe with respect to the exhaust line does not have a significant adverse effect on the result of the measurement. Separate flow mixers (static or dynamic) and/or particular embodiments of the catalytic converters and/or other exhaust gas treatment devices can also be provided for mixing the exhaust gas. According to a further refinement of the method, the at least one catalytic converter is used to treat at least one of the following components of the exhaust gas: hydrocarbon, carbon monoxide, nitrogen oxide, particles. In particular, there is here a metallic catalytic converter carrier body or a ceramic honeycomb structure which is provided with a coating which acts catalytically on at least one of the abovementioned components and contributes to its conversion. In addition to the catalytic function, the catalytic converter can, for example, also have absorptive functions and/or filtering functions and/or further functions. The coating is advantageously neutral to oxygen here, in order to avoid having an adverse effect on the measurement result. According to a further aspect of the invention, an exhaust system is proposed comprising a mobile internal combustion engine having at least one exhaust line in which at least one catalytic converter is provided as well as a control probe and a control unit which is connected thereto and has the purpose of controlling the fuel mixture for the internal combustion engine. The exhaust system has here just one single control probe in the interior of the at least one catalytic converter. The measurement results of the control probe are evaluated by means of the control unit and WO 2005/121533 PCT/EP2005/005968 - 11 - primarily the composition of the fuel mixture or else also the ignition time, the injection pressures etc. are varied in accordance with predefined setpoint values stored there. As a result, the system of a control probe arranged upstream and a trimming probe arranged downstream is dispensed with and replaced by a system comprising an individual control probe which projects into internal regions of the at least one catalytic converter. This significantly reduces the susceptibility to faults, the technical complexity and the costs. According to one development of the exhaust system, the control probe is arranged at a distance of 10 mm to 80 mm from an exhaust gas inlet side of the at least one catalytic converter. Trials have shown that depending on the internal combustion engine the distance specified here is sufficient to ensure that, when a cold start of the internal combustion engine is performed and there is simultaneous electrical heating of the control probe, the control probe has a temperature above 70°C before it is reached by the water vapor front described above. The control probe is advantageously positioned at a distance of 2 5 mm to 60 mm from the exhaust gas inlet side. Furthermore, it is also proposed that the control probe be a heatable lambda probe. While it is basically possible for the control probe to be heated to the necessary temperature after a cold start simply by the exhaust gas flowing past, here it is advantageously proposed that the lambda probe can be heated, in particular by means of an electric heating conductor structure which is integrated into the lambda probe. When the internal combustion engine is started, this heating conductor structure has current applied to it so that the components of the lambda probe which project into the exhaust line and come into contact WO 2005/121533 PCT/EP2005/005968 - 12 - with the exhaust gas are quickly raised to temperatures above 70°C. In addition it is also proposed that means for reducing a propagation speed of water or water vapor be provided in at least one region of the at least one catalytic converter between an exhaust gas inlet side and the control probe. This means in particular that the water or the water vapor cannot move through the region of the catalytic converter at the same speed as the exhaust gas. Some of these possibilities for reducing the propagation speed of water or water vapor are described in the following paragraph. Accordingly, at least one region of the at least one catalytic converter between a exhaust gas inlet side and the control probe is embodied with passages and at least one of the following features: cell density of 600 to 1200 cpsi [cells per square inch] ; openings in passage walls of the passages; mixer structures; porous surface of the passages; coating with a storage capability for at least water or water vapor; metal passages walls with a thickness in the range from 40 \xm to 110 urn (micrometers) . The embodiment of a catalytic converter with passages is known. These are preferably what are referred to as honeycomb bodies which have a multiplicity of passages which are arranged essentially parallel to one another. The passages can basically be formed by metallic or ceramic passage walls. "Cell density" means the number of passages per unit of cross sectional area of the catalytic converter or of the honeycomb structure. "cpsi" refers to the unit WO 2005/121533 PCT/EP2005/005968 - 13 - "cells per square inch" which is generally used in this technical field. 1 cpsi corresponds here to approximately 6.4516 cells per square centimeter. The range of 600 cpsi to 1200 cpsi indicated here is relatively high and represents a very large surface as" well as a relatively high thermal mass in this region. As a result, both a large contact area for water or water vapor and at the same time also a relatively high thermal capacity are made available so that particularly in the cold start phase of the internal combustion engine the water or the water vapor is satisfactorily bound or held here. Providing openings in the passage walls permits partial gas flows which flow through the individual passages to mix together. As a result the temperature and concentration of the exhaust gas are equalized over the cross section of the catalytic converter so that a characteristic measured value is made possible for the entire exhaust gas flow by means of the control probe, irrespective of the position of said catalytic converter in the exhaust system. In order to promote this mixing effect it is proposed that mixer structures be provided in the at least one region. Mixer structures are to be understood in particular as elevations, baffles etc. which project at least partially into internal regions of the passages or bring about pressure differences or direct flows in some other way. They force the partial gas flows to adjacent passages so that sufficient mixing of the partial gas flows with one another is ensured. A porous surface of the passages provides sufficient accumulation and absorption possibilities for water or water vapor. Here, in particular porous surfaces or materials of the passages walls themselves are meant, for example also of the carrier body of the catalytic WO 2005/121533 PCT/EP2005/005968 - 14 - converter or the honeycomb structure. In addition, the passages or their surface can be provided with a coating which has a storage capability for at least water or water vapor. This means that it is hygroscopic, for example. This delays the propagation of the water vapor front so that again the control probe is provided with the time which it requires to reach the corresponding temperatures. Under certain circumstances it is advantageous if the storage capability in the region mounted in front is greater than in a partial section downstream of the control probe. As a further measure it is also possible for the catalytic converter to be constructed with a metallic catalytic converter carrier body. In this case, metallic passage walls with a thickness in the range from 40 Um to 110 \xm (micrometers) are preferred. These in turn make available the favorable, high thermal capacity which prevents rapid vaporization of adsorbed ¦and absorbed water respectively. Basically it is to be noted that it is advantageous to combine at least two of the abovementioned features with one another. According to one development of the exhaust system, the control probe has a coating with at least one storage capability for at least water and water vapor respectively or a catalytic activity for at least one component of the exhaust gas. In one advantageous embodiment, the coating has both capabilities. A storage capability up to a temperature at which the catalytic activity starts is preferably provided here. In addition it is also proposed that the exhaust system, as described above according to the invention, WO 2005/121533 PCT/EP2005/005968 - 15 - be included in a vehicle. The vehicle is intended here to mean in particular a passenger car, a truck, a motorbike, a motorboat, a motorized aircraft, etc. irrespective of the control probes described up until now, a measuring sensor, in particular the lambda probe, can be provided with a protective cap which advantageously protects the measuring sensor against water impacts. Water impacts are understood to be the impacting of water droplets on the measuring sensor or else the condensing out of water vapor onto it. The function in particular of lambda probes is at least adversely affected by water impacts and the probe can even be made entirely unusable by water impacts. The water impacts can advantageously be prevented if the protective cap heats up more quickly than the honeycomb structure or the honeycomb body into which the measuring sensor is inserted. The protective cap preferably reaches as quickly as possible a temperature at which condensing out of water vapor on the surface of the measuring sensor is reliably avoided. This is achieved, for example, by virtue of the fact that the protective cap is formed from a material which has a significantly lower thermal capacity, in particular specific thermal capacity/ than the material from which the honeycomb body is formed. A material is preferably selected which has a specific thermal capacity such that in the normal operating state it is ensured that if the honeycomb body is at a temperature above the boiling point of water in the direction of flow upstream of the measuring sensor the protective cap is also at a temperature above the boiling point of water, specifically even if the honeycomb body is still at a temperature below the boiling point of water directly adjacent to the measuring sensor downstream of the honeycomb body in the direction of flow. To the same extent, it is advantageous that if the honeycomb body WO 2005/121533 PCT/EP2005/005968 - 16 - is at a temperature above the boiling point of water upstream of the measuring sensor in the direction of flow, the thermal capacity, in particular specific thermal capacity of the protective cap, is selected such that it is at such a temperature that under specific operating conditions the dew point of water on the measuring sensor or the protective cap is reliably avoided, thus effectively avoiding the condensing out of water on the measuring sensor and the protective cap respectively. A further possible way of embodying a corresponding protective cap is to change the heat transfer coefficient a of the protective cap. By adapting this heat transfer coefficient a it is also possible to ensure that the measuring sensor or the protective cap will quickly reach a temperature which effectively prevents the condensing out of water vapor which arises due to vaporization within the honeycomb body. The protective cap can be embodied as a separate component or else embodied integrally on the measuring sensor. The protective cap can also be combined with the control probes according to the invention. The invention and the technical field will be explained in more detail below with reference to the figures. It is to be noted here that the figures indicate to a certain extent particularly preferred embodiments of the invention, but the invention is not restricted thereto. In the drawing: Fig.isa schematic view of a vehicle with an exhaust system; Fig. 2 is a schematic view of a catalytic converter with a control probe; Fig. 3 is a schematic view of a catalytic converter in WO 2005/121533 PCT/EP2005/005968 - 17 - cross section; Fig .4 is a schematic view of a further embodiment of a catalytic converter; Pig. 5 is a detailed view of the catalytic converter from figure 4; Fig .6 is a schematic view of a diagram relating to the measuring quality of the control probe as a function of the position with respect to the catalytic converter; and Pig .7 is a schematic view of the design of a control probe. Fig. 1 is a schematic and perspective view of a vehicle 17 with an internal combustion engine 3 and an associated exhaust system 2. In particular diesel and spark ignition engines can be provided as the internal combustion engine 3. The exhaust gas which is generated by means of the internal combustion engine 3 is output into the surroundings via the exhaust line 5. For this purpose, the exhaust gas is brought into contact with exhaust gas treatment devices such as, for example, catalytic converters, adsorbers, particle traps etc., with pollutants in the exhaust gas being at least partially converted into at least less noxious components. In Fig. 1, the exhaust gas firstly flows through a mixer 2 0 before it is fed to a catalytic converter 4. The catalytic converter 4 is equipped with a control probe 1 for controlling the fuel mixture, respectively for performing onboard diagnostics of the catalytic converter 4, and it protrudes into internal regions of the catalytic converter 4. The control probe 1 is connected to a control unit 6, in particular the engine WO 2005/121533 PCT/EP2005/005968 - 18 - controller. The control unit 6 then varies the composition of the fuel mixture as a function of the parameter sensed by means of the control probe 1 and the predefined values saved there. Fig. 2 is a schematic view of a catalytic converter 4 with a control probe 1. The control 1 is introduced into internal regions of the catalytic converter 4 through the exhaust line 5. The catalytic converter 4 is embodied here with a housing 18 in which a honeycomb structure through which the exhaust gas can flow is provided. The honeycomb structure is formed by a multiplicity of passage walls 12 which make available passages 10 through which the exhaust gas can flow. The exhaust gas flows in the direction 19 of flow and impinges on the exhaust gas inlet side 8. A region 9 which has means for limiting the propagation speed of a water vapor front which propagates through the catalytic converter 4 when the internal combustion engine is (re)started is provided between the exhaust gas inlet side 8 and the control probe 1. In order to ensure that after a cold start the control probe 1 has reached temperatures above 70°C before this water vapor front has reached the control probe 1, the control probe 1 is positioned at a distance 7 of 10 to 80 mm. It is to be noted here that the distance 7 indicated here is illustrated schematically, that is to say the ratio of the entire length of the catalytic converter 4 in the direction 19 of flow is not indicative. Fig. 3 shows a further embodiment of a catalytic converter 4 in cross section. The catalytic converter 4 has in turn a housing 18 and a region 9 which extends from the exhaust gas inlet side 8 over a distance 7. The catalytic converter 4 has here a metallic catalytic converter carrier body so that the passage walls 12 are therefore of metallic origin here. WO 2005/121533 PCT/EP2005/005968 - 19 - Within the region 9, the passages 10 are bounded by passage walls 12 which have a thickness 16 which is larger than other regions of the catalytic converter. At the same time, openings 11 and mixer structures 13 are provided which permit adjacent partial gas flows to mix together. This can ensure that the control probe 1 which is to be inserted into the recess 23 can supply qualified results about the composition of the exhaust gas. The passages are bounded by relatively thin passage walls 12 downstream of the region 9, it being also possible to embody the surface 14 with a coating 15, for example. In the embodiment illustrated here, the passage walls 12 are also provided with openings 11 in the region located downstream. The different regions 9 of the catalytic converter 4 can, if appropriate, also be formed by various separate honeycomb structures and carrier bodies repectively (spaced apart with a gap if appropriate). Fig. 4 and 5 also show a further embodiment of a catalytic converter 4 with a control probe 1. The catalytic converter 4 has in turn a housing 18, the internal honeycomb structure being formed by smooth foils 21 and corrugated foils 22 which are twisted together in the form of an evolvent and brazed together (in particular high-temperature brazed). From the end side view it is apparent that the smooth foils 21 and the corrugated foils 22 respectively form layers 24, it being also possible to mix the adjacent passage 10 within these layers 24. In the detailed view (Fig. 5) it is apparent that the smooth foils 21 and the corrugated foils 22 are positioned so as to alternate with one another and in this way they form passages 10. The catalytically active coating 15 is provided on the surface 14 of the passages 10. WO 2005/121533 PCT/EP2005/005968 - 20 - Fig. 6 is a schematic view of a diagram relating to the measuring quality of the control probe as a function of the position with respect to the catalytic converter. The abscissa shows by way of example the distance 7 between the control probe 1 and the exhaust gas inlet side 8 in mil 1 imeters. The ordinate shows by way of example the reduction in the lambda control oscillation as a percentage. It is apparent from this that even after a few millimeters, for example 10 mm, a significant reduction in the lambda oscillation in particular by at least 50%, has already occurred. Under certain circumstances, reductions of more than 80% can therefore already be present given a distance of 40 mm or even 95% given a distance of 60 mm. The illustrated curve 25 is schematic and is intended to illustrate the profile. In order to obtain a measurement result which is sufficiently precise for the lambda control, it is proposed here under certain circumstances to select different embodiments depending on the position of the control probe. For this purpose, a limiting value 26 has been shown, it being possible for said limiting value 26 to be considered to be a measure of the sensitivity of the control probe. The range identified by "I" is intended to characterize the range of use for a j ump probe, and the range ident i f ied by "II" is intended to characterize that of a broadband linear probe. It is apparent from this, for example, that up to a distance of approximately 20 mm (in other cases also up to 40 mm) a jump probe is advantageous (low costs, sufficiently precise) and in the case of a distance above this the broadband linear probe should be used for control. Figure 7 is a schematic view of the design of a control probe 1 in an installed position, the control probe 1 which is described below representing a particularly preferred embodiment which can, if appropriate, also be used as a single control probe 1, for example WO 2005/121533 PCT/EP2005/005968 - 21 - downstream of a catalytic converter 4. It has a nut 27 and a threaded section 28 for securing it to the housing 18. The sensitive region 29 then projects into a recess 23 in the catalytic converter 4, the passage walls 12 which form in the passages 10. Owing to the protective measures, described above, for the sensitive region 29 by means of the catalytic converter 4 as damping element (for example relating to the temperatures, pollutant concentrations, pressure fluctuations, water content in the exhaust gas) it is possible for the control probe 1 to be exposed directly to the stream of exhaust gas and the protective cap which is usually used can therefore be dispensed with. For reasons of protecting the sensitive region 29 during storage, transportation, assembly etc., it is, however, under certain circumstances necessary nevertheless to provide a cap 30. However, said cap 30 is designed in such a way that it has a particularly low absorptive capacity for heat, in particular less than 1 J/K [Joules per Kelvin] or even less than 0.8 J/K. This can be achieved, for example, by means of a particularly thin-walled cap 30, a porous cap 30, a cap 30 which has a large number of openings 32, a very small cap 30, etc. This cap 3 0 is preferably manufactured from a steel material and is manufactured in particular by means of a shaping fabrication method (for example deep drawing). In addition, baffles 31 can be provided which permit the exhaust gas to flow along to the sensitive region 29 in a suitable manner and, if appropriate, also result in a longer weld time of the exhaust gas in the interior of the cap 30. If the cap 3 0 is at least partially coated, the parameter specified above relates to the cap 3 0 including the coating. Such an embodiment of the control probe 1 can also advantageously be used independently of the control method described here, in particular with an exhaust system in which this control probe 1 is WO 2005/121533 PCT/EP2005/005968 - 22 - arranged downstream of a catalytic converter 4. WO 2005/121533 PCT/EP2005/005968 - 23 -List of reference numerals 1 Control probe 2 Exhaust system 3 Internal combustion engine 4 Catalytic converter 5 Exhaust line 6 Control unit 7 Distance 8 Exhaust gas inlet side 9 Region 10 Passage 11 Opening 12 Duct wall 13 Mixer structure 14 Surface 15 Coating 16 Thickness 17 Vehicle 18 Housing 19 Direction of flow 2 0 Mixer 21 Smooth foil 22 Corrugated foil 23 Recess 24 Position 25 Curve 2 6 Limiting value 27 Nut 2 8 Threaded section 2 9 Region 3 0 Cap 31 Baffle 32 Opening WO 2005/121533 PCT/EP2005/005968 - 24 - Patent claims 1. A method for controlling a fuel mixture by means of a control probe (1) in the exhaust system (2) of a mobile internal combustion engine (3), the exhaust system (2) comprising at least one catalytic converter (4) in an exhaust line (5), characterized in that the control is carried out with an single control probe (1) in the interior of the at least one catalytic converter (4) . 2. The method as claimed in claim 1, characterized in that the control probe (1) is heated after the internal combustion engine (3) starts, in such a way that it has a temperature of at least 70° Celsius before the at least one catalytic converter (4) has reached 95° Celsius. 3. The method as claimed in claim 1 or 2, characterized in that the control probe (1) determines at least one of the following components of the exhaust gas: hydrocarbon, carbon monoxide, nitrogen oxide, oxygen. 4. The method as claimed in one of claims 1 to 3, characterized in that the control probe (1) is a lambda probe, said probe being simultaneously used to check the conversion capability of the at least one catalytic converter (4). 5. The method as claimed in one of claims 1 to 4, characterized in that the exhaust gas which is generated by the internal combustion engine (3) is mixed in the exhaust line (5) before it reaches the control probe (4). 6. The method as claimed in one of claims 1 to 5, characterized in that the at least one catalytic WO 2005/121533 PCT/EP2005/005968 - 25 - converter (4) is used to treat at least one of the following components of the exhaust gas: hydrocarbon, carbon monoxide, nitrogen oxide, particles. 7. An exhaust system (2) comprising a mobile internal combustion engine (3) having at least one exhaust line (5) in which at least one catalytic converter (4) is provided as well as a control probe (1) and a control unit (6) which is connected thereto and has the purpose of controlling the fuel mixture for the internal combustion engine (3), characterized in that an single control probe (1) is arranged in the interior of the at least one catalytic converter (4). 8. The exhaust system (2) as claimed in claim 7, characterized in that the control probe (1) is arranged at a distance (7) of 10 mm to 80 mm [millimeters] from an exhaust inlet side (8) of the at least one catalytic converter (4). 9. The exhaust system (2) as claimed in claim 7 or 8, characterized in that the control probe (1) is a heatable lambda probe. 10 - The exhaust system (2) as claimed in one of claims 7 to 9, characterized in that means for reducing a propagation speed of water or water vapor are provided in at least one region (9) of the at least one catalytic converter (4) between an exhaust gas inlet side (8) and the control probe (1). 11. The exhaust system (2) as claimed in one of claims 7 to 10, characterized in that at least one region (9) of the at least one catalytic converter (4) between an exhaust gas inlet side (8) and the control probe (1) is embodied with passages (10) and at least one of the following features: cell density of 600 to 1200 cpsi (cells per square WO 2005/121533 PCT/EP2005/005968 - 26 - inch); openings (11) in passage walls (12) of the passages (10); mixer structures (13); porous surface (14) of the passages (10); coating (15) with a storage capability for at least water or water vapor; metallic passages walls (12) with a thickness (16) in the range from 40 \xm to 110 (im [micrometers] . 12. The exhaust system (2) as claimed in one of claims 7 to 11, characterized in that the control probe (1) has a coating (15) with at least one storage capability for at least water and water vapor respectively, or a catalytic activity for at least one component of the exhaust gas. 13. A vehicle (17) comprising an exhaust system (2) as claimed in one of claims 7 to 12. The invention relates to a method for controlling a fuel mixture by means of a control probe (1) in the waste-gas system (2) of a mobile internal combustion engine (3). The waste-gas system (2) comprises at least one catalytic converter (4) which is disposed in a waste-gas line (5), and control thereof is carried out by means of an individual control probe (1} disposed in the inside of at least one catalytic converter (4). The invention also relates to a waste-gas system (2) which is suitable therefor.

Full Text

WO 2005/121533 PCT/EP2005/005968
Control system for a mobile internal combustion engine
The invention relates to a method for controlling a fuel mixture by means of a control probe in the exhaust system of a mobile internal combustion engine. Furthermore, an exhaust system comprising a mobile internal combustion engine is proposed. The preferred field of use of such exhaust systems or methods is the automobile sector.
It is known to use sensors and/or probes in exhaust systems of mobile internal combustion engines in order to obtain detailed information about operating states of the internal combustion engines and/or exhaust gas treatment devices which are integrated in the exhaust system.
Thus, it is known, for example, to use an oxygen sensor connected to an electronic device to determine the state of ageing of an exhaust gas catalytic converter. The sensor has an oxygen-sensitive region for measuring the partial pressure of oxygen in the exhaust gas. The state of the ageing of the catalytic converter is determined by the control device by means of this measurement variable since the oxygen load on the catalytic converter can be used as a characteristic variable for its functional capability (referred to as onboard diagnostics).
Furthermore it is also known to monitor at least part of the exhaust gas in the exhaust system and thus to influence the supply of fuel to the internal combustion engine. Thus, in internal combustion engines which have warmed up, or after a predefinable exhaust temperature has been reached, oxygen sensors are used to perform lambda control on the internal combustion engine. Lambda (X) , referred to as the excess air factor, describes the ratio of the current air/fuel ratio to

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the stochiometric air/fuel ratio and is often used as a characteristic value for the combustion processes. In this context, a first oxygen sensor which is arranged upstream of a catalytic converter is used as a control probe, and a second oxygen sensor which is connected downstream of the exhaust gas catalytic converter is used as a trimming probe. The first oxygen sensor is used to determine lambda oscillation with a specific amplitude and frequency, which result from the confoustion processes in the internal combustion engine. These are sensed by means of the first oxygen sensor which ¦ is positioned upstream of the catalytic converter. A person skilled in the art is familiar with the procedure here and does not require any further explanation.
The lambda oscillation of the exhaust gas composition
which is present at the input end of the catalytic converter is increasingly smoothed as it passes through the catalytic converter owing to its oxygen storage capability. The result is a decrease in amplitude of the lambda oscillations along the catalytic converter. Given a high oxygen storage capability, it is almost impossible to obtain evidence of lambda oscillation anymore at the output end, for example. The amplitude of the lambda oscillation for which evidence can still be obtained after the exhaust gas has run through a partial section or the entire catalytic converter is therefore a measure of the oxygen storage capability of the section of the catalytic converter or of the entire catalytic converter.
In this case, the lambda value generally settles to the constant mean value of the lambda oscillation present upstream of the catalytic converter. This mean value is sensed by the second sensor downstream of the catalytic converter, said sensor being the so-called trimming probe. The trimming probe is then used to set a mean

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value of lambda? which cannot be determined or set precisely by means of the oxygen sensor or control sensor which is mounted upstream (of the catalytic converter), Causes for this are, for example, so-called "poisoning11, that Is to say adverse influences due to the high oxygen concentration or other influences of the untreated exhaust gas on. this control sensor which is positioned upstream, As a result, the control sensor which Is positioned upstream changes its measuring behavior so that even though the dynamic oscillating behavior continues to be satisfactorily sensed, without the trimming probe It is not possible to obtain precise Information about the (mean) lambda value over a relatively long period of use of the control sensor which Is mounted upstream.
In the chemical balance, the lambda value emerges directly from the partial pressure of the oxygen. For this reason, the lambda value, and thus also the oxygen storage capability of the catalytic converter, can be determined by measuring the partial pressure of the oxygen with the second oxygen sensor {trimming probe) which Is arranged downstream of the catalytic converter, in this way it Is then possible to Install a "slow" correction routine which compensates for the ageing/poisoning of the control sensor which Is mounted upstream.
The profile - determined by means of the oxygen sensors - of the partial pressure values of the oxygen or of other parameters which describe the exhaust gas composition also permits conclusions to be drawn about the effectiveness or the scope of the combustion in the individual combustion chambers of the internal combustion engine. The values which are generated therewith can thus also be used to perform lambda control on the internal combustion engine, with, for example, influence being exerted on the composition of

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a fuel/air mixture, the ignition time, the pressures prevailing during the combustion, etc.
A problem when such oxygen sensors or other control probes are used is also their sensitivity to water. If the sensitive region of the control probe comes into contact with water, the functional capability of the control probe is generally no longer ensured. For this reason, a number of different embodiments of control probes and lambda probes respectively, which are intended to prevent contact of the sensitive area with water have already been proposed. Usually, such oxygen sensors and lambda sensors respectively, are brought to the operating temperature by means of an electric heating conductor structure. It is also known to provide special screening means, grilles or coatings which function as a means of resisting water. Due to the fact that these probes and sensors respectively, are in contact with the exhaust gas line or are guided through it, they generally have a lower temperature than the exhaust gas. It is also necessary to take into account the fact that the temperature of the exhaust gas varies greatly owing to the different operating states of the internal combustion engine. There is thus repeatedly the risk that the sensor or the housing surrounding the sensor will reach temperatures which can result in condensation of water out of the exhaust gas.
Taking this as a basis, the object of the invention is to disclose a simplified method for controlling a fuel mixture by means of a control probe in the exhaust system of a mobile internal combustion engine. In particular, the problems described with respect to the prior art are to be at least partially alleviated. Furthermore, an exhaust system which is of cost-effective and simple design is to be proposed.

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These objects are achieved with a method for controlling a fuel mixture having the features of patent claim 1 and an exhaust system having the features of the independently formulated device claim. Further advantageous embodiments of the invention are described in the respective independent patent claims. In addition it is to be noted that the features specified individually in the patent claims can be combined with one another in any desired technically appropriate way and specify further embodiments of the invention.
In order to control a fuel mixture of a mobile internal combustion engine a control probe is provided in the exhaust system, the exhaust system comprising at least one catalytic converter in an exhaust line. The method is characterized by the fact that the control is carried out with a single control probe in the interior of the at least one catalytic converter.
In the first instance, the invention departs from the preconceptions of the specialists according to which the fuel mixture of the internal combustion engine is controlled with a multiplicity of control probes (one for the dynamic lambda oscillation and one for the slow-acting trimming). As a result, the method can already be carried out at relatively low cost and with relatively little expenditure on electronics, with the susceptibility to faults of this system for controlling the fuel mixture being automatically reduced. In order to protect against condensation water, the aggressive ambient conditions due to the untreated exhaust gas and the large fluctuations of temperature, this one control probe is arranged in the interior of the at least one catalytic converter. This means in particular that parts of the control probe extend into internal regions of the catalytic converter. It is clear that the control probe has to be made to extend out of the

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exhaust system or exhaust line so that the control probe is not arranged completely in the interior of the catalytic converter. The catalytic converter itself represents a type of damping element for the temperatures, pollutant concentrations etc. In particular it is a thermal mass so that here a somewhat sluggish thermal behavior occurs. To this extent, the fluctuations of the exhaust gas temperature as a consequence of different operating states of the internal combustion engine do not affect the control probe to the extent that they would a control probe which projects freely into the exhaust line. The control probe is preferably an oxygen sensor or what is referred to as a lambda probe.
Investigations have shown here that the integration of
the individual control probe in the catalytic
converters surprisingly ensures precise results over a
long operating time. It has been found that the
influences of the exhaust gas (for example temperature
fluctuations, pressure fluctuations, etc.) already
decrease considerably over the first millimeters of the
catalytic converter so that in this way a significant
"protection against ageing and protection against
poisoning respectively " of the control probe has been
realized. More detailed information will be given on
this in the text below. At the same time, there is
still sufficient lambda oscillation, which can be used
to perform lambda control on the internal combustion
engine. In such an embodiment it is advantageously
possible to use appropriate types of control probe. For
example, in a range up to 50% reduction of the
"incoming" lambda oscillation at the catalytic
converter it is still possible to use so-called jump
probes (for example zircon dioxide probe with a sudden
change in the output signal at a lambda value of
approximately 1) since these are particularly
economical and still sufficiently sensitive. Given

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further reduction of the lambda oscillation amplitudes, for example as far as 5%, so-called linear probes can preferably be used.
At this point it is to be noted that this does not mean that no further sensors at all should be provided in the exhaust system. It is thus possible, for example, to connect nitrogen oxygen sensors downstream of the catalytic converter, which sensors determine the nitrogen oxygen concentration in the exhaust gas after contact with the catalytic converter. However, the measured values which are obtained in this way are not used to perform lambda control on the internal combustion engine.
According to a further embodiment of the method, the
control probe is heated after the internal combustion
engine starts, in such a way that it has a temperature
of at least 70°C [degree Celsius] before the at least
one catalytic converter has reached 95° C. The control
probe can be heated passively here (essentially only by
means of the temperature of the exhaust gas in contact
with it) and/or actively, (for example by means of a
heating element, an electric heater etc.) As has
already been stated at the beginning, such control
probes usually have particular sensitivity to water. It
is proposed here that the control probe has a
temperature of at least 70°C (at which the phenomenon
of condensation no longer occurs to a significant
extent owing to the arrangement in the catalytic
converter proposed here) before the catalytic converter
has reached 95°C. In addition, as well as a thermal
mass, the catalytic converter also makes available a
large surface which can be used to adsorb water or
water vapor. That is to say in other words the
catalytic converter or in particular also its coating
acts as a sponge for water and binds it for a
relatively long time.

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When the internal combustion engine is (re)started, the
exhaust gas flowing the catalytic converter then
gradually heats the carrier body of the catalytic
converter and the coating. In the process, a
temperature profile forms in the direction of flow of
the exhaust gas In the catalytic converter so that at
first the highest temperatures are present the exhaust
gas Inlet side and said temperatures then decrease In
the direction of flow. Here, It is then proposed in
particular that the control probe already have a
temperature of at least TO^C, In particular of at least
90°C [degrees Celsius), before the catalytic converter
or the carrier body of the catalytic converter in a
plane parallel to the gas Inlet side at a distance of
10 ram. has reached a temperature of 95°C. The
accumulated water increasingly vaporizes in a range
above average 95°C and propagates in the direction of
flow of the catalytic converter, and it condenses again
if it arrives at colder regions. In this way, a type of
"water vapor front" Is generated through the catalytic
converter. By ensuring a certain temperature of the
control probe it Is made certain that the control probe
does not constitute such a heat sink when in contact
with the water vapor front that water condenses. This
ensures the functionality of the individual control
probe.
In particular It Is proposed that the control probe determines at least one of the following components of the exhaust gas: hydrocarbon, carbon Rionoxide, oxygen. Furthermore, it Is also possible to measure a partial pressure, a temperature or other physical measuring variables by means of this control probe.
According to a further embodiment of the method, the control probe is a lambda probe, said probe being simultaneously used to check the conversion capability

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of the at least one catalytic converter. In particular,
this is what is referred to as a broadband lambda probe
(lambda probe) which outputs a continuous, for example
linear, output signal as a function of the oxygen
content in the exhaust gas in the range around
lambda = 1 (for example with a tolerance of ± 0.005).
This signal is used to control the mixture in
accordance with the predefined setpoint values. With
the embodiment of the control probe proposed here it is
possible to locate said probe relatively far down in
the catalytic converter, in particular at a distance of
25 mm to 60 mm. In this region, the lambda oscillations
are frequency already reduced or smoothed by more than
50%, in some cases even by more than 90%. The use of
such a broadband lambda probe also to the same extent
permits a high degree of measuring accuracy, and an
extremely low tendency to poisoning occurs by virtue of
its position in the catalytic converter so that a mean
value for lambda can also be found to occur precisely
and over a relatively long time period. The oxygen
content determined with the lambda probe can
additionally also be used as a measure of the
conversion capability of the catalytic converter. With
respect to this process, reference is made to the
explanations given at the beginning. With such a lambda
probe it is possible to carry out onboard diagnostics
easily. As a result, a method is specified which has a
particularly simple structure and at the same time
permits lambda control of the internal combustion
engine and onboard diagnostics.
Furthermore it is also proposed that the exhaust gas which is generated by the internal combustion engine be mixed in the exhaust line before it reaches the control probe. Owing to the situation or position of the control probe in the exhaust line, only certain peripheral flows of the exhaust gas are always sensed and evaluated. In order to ensure that a result which

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is representative of the entire exhaust gas flow is obtained, the exhaust gas flow is mixed before it reaches the control probe. It is then possible to assume that the position of the individual control probe with respect to the exhaust line does not have a significant adverse effect on the result of the measurement. Separate flow mixers (static or dynamic) and/or particular embodiments of the catalytic converters and/or other exhaust gas treatment devices can also be provided for mixing the exhaust gas.
According to a further refinement of the method, the at least one catalytic converter is used to treat at least one of the following components of the exhaust gas: hydrocarbon, carbon monoxide, nitrogen oxide, particles. In particular, there is here a metallic catalytic converter carrier body or a ceramic honeycomb structure which is provided with a coating which acts catalytically on at least one of the abovementioned components and contributes to its conversion. In addition to the catalytic function, the catalytic converter can, for example, also have absorptive functions and/or filtering functions and/or further functions. The coating is advantageously neutral to oxygen here, in order to avoid having an adverse effect on the measurement result.
According to a further aspect of the invention, an exhaust system is proposed comprising a mobile internal combustion engine having at least one exhaust line in which at least one catalytic converter is provided as well as a control probe and a control unit which is connected thereto and has the purpose of controlling the fuel mixture for the internal combustion engine. The exhaust system has here just one single control probe in the interior of the at least one catalytic converter. The measurement results of the control probe are evaluated by means of the control unit and

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primarily the composition of the fuel mixture or else also the ignition time, the injection pressures etc. are varied in accordance with predefined setpoint values stored there. As a result, the system of a control probe arranged upstream and a trimming probe arranged downstream is dispensed with and replaced by a system comprising an individual control probe which projects into internal regions of the at least one catalytic converter. This significantly reduces the susceptibility to faults, the technical complexity and the costs.
According to one development of the exhaust system, the control probe is arranged at a distance of 10 mm to 80 mm from an exhaust gas inlet side of the at least one catalytic converter. Trials have shown that depending on the internal combustion engine the distance specified here is sufficient to ensure that, when a cold start of the internal combustion engine is performed and there is simultaneous electrical heating of the control probe, the control probe has a temperature above 70°C before it is reached by the water vapor front described above. The control probe is advantageously positioned at a distance of 2 5 mm to 60 mm from the exhaust gas inlet side.
Furthermore, it is also proposed that the control probe be a heatable lambda probe. While it is basically possible for the control probe to be heated to the necessary temperature after a cold start simply by the exhaust gas flowing past, here it is advantageously proposed that the lambda probe can be heated, in particular by means of an electric heating conductor structure which is integrated into the lambda probe. When the internal combustion engine is started, this heating conductor structure has current applied to it so that the components of the lambda probe which project into the exhaust line and come into contact

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with the exhaust gas are quickly raised to temperatures above 70°C.
In addition it is also proposed that means for reducing a propagation speed of water or water vapor be provided in at least one region of the at least one catalytic converter between an exhaust gas inlet side and the control probe. This means in particular that the water or the water vapor cannot move through the region of the catalytic converter at the same speed as the exhaust gas. Some of these possibilities for reducing the propagation speed of water or water vapor are described in the following paragraph.
Accordingly, at least one region of the at least one catalytic converter between a exhaust gas inlet side and the control probe is embodied with passages and at least one of the following features:
cell density of 600 to 1200 cpsi [cells per square
inch] ;
openings in passage walls of the passages;
mixer structures;
porous surface of the passages;
coating with a storage capability for at least
water or water vapor;
metal passages walls with a thickness in the range
from 40 \xm to 110 urn (micrometers) .
The embodiment of a catalytic converter with passages is known. These are preferably what are referred to as honeycomb bodies which have a multiplicity of passages which are arranged essentially parallel to one another. The passages can basically be formed by metallic or ceramic passage walls.
"Cell density" means the number of passages per unit of cross sectional area of the catalytic converter or of the honeycomb structure. "cpsi" refers to the unit

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"cells per square inch" which is generally used in this technical field. 1 cpsi corresponds here to approximately 6.4516 cells per square centimeter. The range of 600 cpsi to 1200 cpsi indicated here is relatively high and represents a very large surface as" well as a relatively high thermal mass in this region. As a result, both a large contact area for water or water vapor and at the same time also a relatively high thermal capacity are made available so that particularly in the cold start phase of the internal combustion engine the water or the water vapor is satisfactorily bound or held here.
Providing openings in the passage walls permits partial gas flows which flow through the individual passages to mix together. As a result the temperature and concentration of the exhaust gas are equalized over the cross section of the catalytic converter so that a characteristic measured value is made possible for the entire exhaust gas flow by means of the control probe, irrespective of the position of said catalytic converter in the exhaust system.
In order to promote this mixing effect it is proposed that mixer structures be provided in the at least one region. Mixer structures are to be understood in particular as elevations, baffles etc. which project at least partially into internal regions of the passages or bring about pressure differences or direct flows in some other way. They force the partial gas flows to adjacent passages so that sufficient mixing of the partial gas flows with one another is ensured.
A porous surface of the passages provides sufficient accumulation and absorption possibilities for water or water vapor. Here, in particular porous surfaces or materials of the passages walls themselves are meant, for example also of the carrier body of the catalytic

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converter or the honeycomb structure.
In addition, the passages or their surface can be provided with a coating which has a storage capability for at least water or water vapor. This means that it is hygroscopic, for example. This delays the propagation of the water vapor front so that again the control probe is provided with the time which it requires to reach the corresponding temperatures. Under certain circumstances it is advantageous if the storage capability in the region mounted in front is greater than in a partial section downstream of the control probe.
As a further measure it is also possible for the catalytic converter to be constructed with a metallic catalytic converter carrier body. In this case, metallic passage walls with a thickness in the range from 40 Um to 110 \xm (micrometers) are preferred. These in turn make available the favorable, high thermal capacity which prevents rapid vaporization of adsorbed ¦and absorbed water respectively.
Basically it is to be noted that it is advantageous to combine at least two of the abovementioned features with one another.
According to one development of the exhaust system, the control probe has a coating with at least one storage capability for at least water and water vapor respectively or a catalytic activity for at least one component of the exhaust gas. In one advantageous embodiment, the coating has both capabilities. A storage capability up to a temperature at which the catalytic activity starts is preferably provided here.
In addition it is also proposed that the exhaust system, as described above according to the invention,

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be included in a vehicle. The vehicle is intended here to mean in particular a passenger car, a truck, a motorbike, a motorboat, a motorized aircraft, etc.
irrespective of the control probes described up until now, a measuring sensor, in particular the lambda probe, can be provided with a protective cap which advantageously protects the measuring sensor against water impacts. Water impacts are understood to be the impacting of water droplets on the measuring sensor or else the condensing out of water vapor onto it. The function in particular of lambda probes is at least adversely affected by water impacts and the probe can even be made entirely unusable by water impacts.
The water impacts can advantageously be prevented if
the protective cap heats up more quickly than the
honeycomb structure or the honeycomb body into which
the measuring sensor is inserted. The protective cap
preferably reaches as quickly as possible a temperature
at which condensing out of water vapor on the surface
of the measuring sensor is reliably avoided. This is
achieved, for example, by virtue of the fact that the
protective cap is formed from a material which has a
significantly lower thermal capacity, in particular
specific thermal capacity/ than the material from which
the honeycomb body is formed. A material is preferably
selected which has a specific thermal capacity such
that in the normal operating state it is ensured that
if the honeycomb body is at a temperature above the
boiling point of water in the direction of flow
upstream of the measuring sensor the protective cap is
also at a temperature above the boiling point of water,
specifically even if the honeycomb body is still at a
temperature below the boiling point of water directly
adjacent to the measuring sensor downstream of the
honeycomb body in the direction of flow. To the same
extent, it is advantageous that if the honeycomb body

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is at a temperature above the boiling point of water upstream of the measuring sensor in the direction of flow, the thermal capacity, in particular specific thermal capacity of the protective cap, is selected such that it is at such a temperature that under specific operating conditions the dew point of water on the measuring sensor or the protective cap is reliably avoided, thus effectively avoiding the condensing out of water on the measuring sensor and the protective cap respectively.
A further possible way of embodying a corresponding protective cap is to change the heat transfer coefficient a of the protective cap. By adapting this heat transfer coefficient a it is also possible to ensure that the measuring sensor or the protective cap will quickly reach a temperature which effectively prevents the condensing out of water vapor which arises due to vaporization within the honeycomb body. The protective cap can be embodied as a separate component or else embodied integrally on the measuring sensor. The protective cap can also be combined with the control probes according to the invention.
The invention and the technical field will be explained in more detail below with reference to the figures. It is to be noted here that the figures indicate to a certain extent particularly preferred embodiments of the invention, but the invention is not restricted thereto. In the drawing:
Fig.isa schematic view of a vehicle with an exhaust system;
Fig. 2 is a schematic view of a catalytic converter with a control probe;
Fig. 3 is a schematic view of a catalytic converter in

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cross section;
Fig .4 is a schematic view of a further embodiment of a catalytic converter;
Pig. 5 is a detailed view of the catalytic converter from figure 4;
Fig .6 is a schematic view of a diagram relating to the measuring quality of the control probe as a function of the position with respect to the catalytic converter; and
Pig .7 is a schematic view of the design of a control probe.
Fig. 1 is a schematic and perspective view of a vehicle 17 with an internal combustion engine 3 and an associated exhaust system 2. In particular diesel and spark ignition engines can be provided as the internal combustion engine 3. The exhaust gas which is generated by means of the internal combustion engine 3 is output into the surroundings via the exhaust line 5. For this purpose, the exhaust gas is brought into contact with exhaust gas treatment devices such as, for example, catalytic converters, adsorbers, particle traps etc., with pollutants in the exhaust gas being at least partially converted into at least less noxious components.
In Fig. 1, the exhaust gas firstly flows through a mixer 2 0 before it is fed to a catalytic converter 4. The catalytic converter 4 is equipped with a control probe 1 for controlling the fuel mixture, respectively for performing onboard diagnostics of the catalytic converter 4, and it protrudes into internal regions of the catalytic converter 4. The control probe 1 is connected to a control unit 6, in particular the engine

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controller. The control unit 6 then varies the
composition of the fuel mixture as a function of the
parameter sensed by means of the control probe 1 and
the predefined values saved there.
Fig. 2 is a schematic view of a catalytic converter 4 with a control probe 1. The control 1 is introduced into internal regions of the catalytic converter 4 through the exhaust line 5. The catalytic converter 4 is embodied here with a housing 18 in which a honeycomb structure through which the exhaust gas can flow is provided. The honeycomb structure is formed by a multiplicity of passage walls 12 which make available passages 10 through which the exhaust gas can flow. The exhaust gas flows in the direction 19 of flow and impinges on the exhaust gas inlet side 8. A region 9 which has means for limiting the propagation speed of a water vapor front which propagates through the catalytic converter 4 when the internal combustion engine is (re)started is provided between the exhaust gas inlet side 8 and the control probe 1. In order to ensure that after a cold start the control probe 1 has reached temperatures above 70°C before this water vapor front has reached the control probe 1, the control probe 1 is positioned at a distance 7 of 10 to 80 mm. It is to be noted here that the distance 7 indicated here is illustrated schematically, that is to say the ratio of the entire length of the catalytic converter 4 in the direction 19 of flow is not indicative.
Fig. 3 shows a further embodiment of a catalytic converter 4 in cross section. The catalytic converter 4 has in turn a housing 18 and a region 9 which extends from the exhaust gas inlet side 8 over a distance 7. The catalytic converter 4 has here a metallic catalytic converter carrier body so that the passage walls 12 are therefore of metallic origin here.

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Within the region 9, the passages 10 are bounded by passage walls 12 which have a thickness 16 which is larger than other regions of the catalytic converter. At the same time, openings 11 and mixer structures 13 are provided which permit adjacent partial gas flows to mix together. This can ensure that the control probe 1 which is to be inserted into the recess 23 can supply qualified results about the composition of the exhaust gas.
The passages are bounded by relatively thin passage walls 12 downstream of the region 9, it being also possible to embody the surface 14 with a coating 15, for example. In the embodiment illustrated here, the passage walls 12 are also provided with openings 11 in the region located downstream. The different regions 9 of the catalytic converter 4 can, if appropriate, also be formed by various separate honeycomb structures and carrier bodies repectively (spaced apart with a gap if appropriate).
Fig. 4 and 5 also show a further embodiment of a catalytic converter 4 with a control probe 1. The catalytic converter 4 has in turn a housing 18, the internal honeycomb structure being formed by smooth foils 21 and corrugated foils 22 which are twisted together in the form of an evolvent and brazed together (in particular high-temperature brazed). From the end side view it is apparent that the smooth foils 21 and the corrugated foils 22 respectively form layers 24, it being also possible to mix the adjacent passage 10 within these layers 24. In the detailed view (Fig. 5) it is apparent that the smooth foils 21 and the corrugated foils 22 are positioned so as to alternate with one another and in this way they form passages 10. The catalytically active coating 15 is provided on the surface 14 of the passages 10.

WO 2005/121533 PCT/EP2005/005968
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Fig. 6 is a schematic view of a diagram relating to the measuring quality of the control probe as a function of the position with respect to the catalytic converter. The abscissa shows by way of example the distance 7 between the control probe 1 and the exhaust gas inlet side 8 in mil 1 imeters. The ordinate shows by way of example the reduction in the lambda control oscillation as a percentage. It is apparent from this that even after a few millimeters, for example 10 mm, a significant reduction in the lambda oscillation in particular by at least 50%, has already occurred. Under certain circumstances, reductions of more than 80% can therefore already be present given a distance of 40 mm or even 95% given a distance of 60 mm. The illustrated curve 25 is schematic and is intended to illustrate the profile. In order to obtain a measurement result which is sufficiently precise for the lambda control, it is proposed here under certain circumstances to select different embodiments depending on the position of the control probe. For this purpose, a limiting value 26 has been shown, it being possible for said limiting value 26 to be considered to be a measure of the sensitivity of the control probe. The range identified by "I" is intended to characterize the range of use for a j ump probe, and the range ident i f ied by "II" is intended to characterize that of a broadband linear probe. It is apparent from this, for example, that up to a distance of approximately 20 mm (in other cases also up to 40 mm) a jump probe is advantageous (low costs, sufficiently precise) and in the case of a distance above this the broadband linear probe should be used for control.
Figure 7 is a schematic view of the design of a control probe 1 in an installed position, the control probe 1 which is described below representing a particularly preferred embodiment which can, if appropriate, also be used as a single control probe 1, for example

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downstream of a catalytic converter 4. It has a nut 27 and a threaded section 28 for securing it to the housing 18. The sensitive region 29 then projects into a recess 23 in the catalytic converter 4, the passage walls 12 which form in the passages 10.
Owing to the protective measures, described above, for the sensitive region 29 by means of the catalytic converter 4 as damping element (for example relating to the temperatures, pollutant concentrations, pressure fluctuations, water content in the exhaust gas) it is possible for the control probe 1 to be exposed directly to the stream of exhaust gas and the protective cap which is usually used can therefore be dispensed with. For reasons of protecting the sensitive region 29 during storage, transportation, assembly etc., it is, however, under certain circumstances necessary nevertheless to provide a cap 30. However, said cap 30 is designed in such a way that it has a particularly low absorptive capacity for heat, in particular less than 1 J/K [Joules per Kelvin] or even less than 0.8 J/K. This can be achieved, for example, by means of a particularly thin-walled cap 30, a porous cap 30, a cap 30 which has a large number of openings 32, a very small cap 30, etc. This cap 3 0 is preferably manufactured from a steel material and is manufactured in particular by means of a shaping fabrication method (for example deep drawing). In addition, baffles 31 can be provided which permit the exhaust gas to flow along to the sensitive region 29 in a suitable manner and, if appropriate, also result in a longer weld time of the exhaust gas in the interior of the cap 30. If the cap 3 0 is at least partially coated, the parameter specified above relates to the cap 3 0 including the coating. Such an embodiment of the control probe 1 can also advantageously be used independently of the control method described here, in particular with an exhaust system in which this control probe 1 is

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arranged downstream of a catalytic converter 4.

WO 2005/121533 PCT/EP2005/005968
- 23 -List of reference numerals
1 Control probe
2 Exhaust system
3 Internal combustion engine
4 Catalytic converter
5 Exhaust line
6 Control unit
7 Distance
8 Exhaust gas inlet side
9 Region
10 Passage
11 Opening
12 Duct wall
13 Mixer structure
14 Surface
15 Coating
16 Thickness
17 Vehicle
18 Housing
19 Direction of flow
2 0 Mixer
21 Smooth foil
22 Corrugated foil
23 Recess
24 Position
25 Curve
2 6 Limiting value
27 Nut
2 8 Threaded section
2 9 Region
3 0 Cap

31 Baffle
32 Opening

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Patent claims
1. A method for controlling a fuel mixture by means
of a control probe (1) in the exhaust system (2) of a
mobile internal combustion engine (3), the exhaust
system (2) comprising at least one catalytic converter
(4) in an exhaust line (5), characterized in that the control is carried out with an single control probe (1) in the interior of the at least one catalytic converter
(4) .
2. The method as claimed in claim 1, characterized in
that the control probe (1) is heated after the internal
combustion engine (3) starts, in such a way that it has
a temperature of at least 70° Celsius before the at
least one catalytic converter (4) has reached
95° Celsius.
3. The method as claimed in claim 1 or 2,
characterized in that the control probe (1) determines
at least one of the following components of the exhaust
gas: hydrocarbon, carbon monoxide, nitrogen oxide,
oxygen.
4. The method as claimed in one of claims 1 to 3,
characterized in that the control probe (1) is a lambda
probe, said probe being simultaneously used to check
the conversion capability of the at least one catalytic
converter (4).
5. The method as claimed in one of claims 1 to 4,
characterized in that the exhaust gas which is
generated by the internal combustion engine (3) is
mixed in the exhaust line (5) before it reaches the
control probe (4).
6. The method as claimed in one of claims 1 to 5,
characterized in that the at least one catalytic

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converter (4) is used to treat at least one of the following components of the exhaust gas: hydrocarbon, carbon monoxide, nitrogen oxide, particles.
7. An exhaust system (2) comprising a mobile internal
combustion engine (3) having at least one exhaust line
(5) in which at least one catalytic converter (4) is
provided as well as a control probe (1) and a control unit (6) which is connected thereto and has the purpose of controlling the fuel mixture for the internal combustion engine (3), characterized in that an single control probe (1) is arranged in the interior of the at least one catalytic converter (4).
8. The exhaust system (2) as claimed in claim 7,
characterized in that the control probe (1) is arranged
at a distance (7) of 10 mm to 80 mm [millimeters] from
an exhaust inlet side (8) of the at least one catalytic
converter (4).
9. The exhaust system (2) as claimed in claim 7 or 8,
characterized in that the control probe (1) is a
heatable lambda probe.
10 - The exhaust system (2) as claimed in one of claims 7 to 9, characterized in that means for reducing a propagation speed of water or water vapor are provided in at least one region (9) of the at least one catalytic converter (4) between an exhaust gas inlet side (8) and the control probe (1).
11. The exhaust system (2) as claimed in one of claims 7 to 10, characterized in that at least one region (9) of the at least one catalytic converter (4) between an exhaust gas inlet side (8) and the control probe (1) is embodied with passages (10) and at least one of the following features:
cell density of 600 to 1200 cpsi (cells per square

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inch);
openings (11) in passage walls (12) of the passages (10); mixer structures (13);
porous surface (14) of the passages (10); coating (15) with a storage capability for at least water or water vapor;
metallic passages walls (12) with a thickness (16) in the range from 40 \xm to 110 (im [micrometers] .
12. The exhaust system (2) as claimed in one of
claims 7 to 11, characterized in that the control probe
(1) has a coating (15) with at least one storage
capability for at least water and water vapor respectively, or a catalytic activity for at least one component of the exhaust gas.
13. A vehicle (17) comprising an exhaust system (2) as
claimed in one of claims 7 to 12.
The invention relates to a method for controlling a fuel mixture by means of a control probe (1) in the waste-gas system (2) of a mobile internal combustion engine (3). The waste-gas system (2) comprises at least one catalytic converter (4) which is disposed in a waste-gas line (5), and control thereof is carried out by means of an individual control probe (1} disposed in the inside of at least one catalytic converter (4). The invention also relates to a waste-gas system (2) which is suitable therefor.

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Patent Number

252244

Indian Patent Application Number

3635/KOLNP/2006

PG Journal Number

18/2012

Publication Date

04-May-2012

Grant Date

02-May-2012

Date of Filing

05-Dec-2006

Name of Patentee

EMITEC GESELLSCHAFT FUR EMISSIONS-TECHNOLOGIE MBH

Applicant Address

HAUPTSTRASSE 128, 53797 LOHMAR, GERMANY

Inventors:

#	Inventor's Name	Inventor's Address
1	BRUCK, ROLF	FROBELSTRASSE 12, 51429 BERGISCH GLADBACH, GERMANY

PCT International Classification Number

F02D41/14;F01N3/28

PCT International Application Number

PCT/EP2005/005968

PCT International Filing date

2005-06-03

PCT Conventions:

#	PCT Application Number	Date of Convention	Priority Country
1	10 2004 027 907.1	2004-06-09	Germany