Abstract:
A method for operation of an internal combustion engine, comprising an exhaust treatment device in the exhaust system thereof, with application of a reagent under given operating conditions of the internal combustion engine and/or the exhaust treatment device and a device for carrying out the method are disclosed, wherein a correction parameter is determined for a reagent signal, describing the amount of reagent to be introduced into the exhaust system and the correction parameter is determined by means of a comparison of a measure of the actual amount of the reagent in the exhaust system, which should be introduced based on a measure of a pre-determined set amount and the measure of the set amount. The above method permits a particularly exact maintenance of the amount of reagent introduced into the exhaust system in accordance with the pre-determined measure for the set amount.

Description:
TECHNICAL FIELD 
     The invention is based on the method for the operation of an internal combustion engine, whose exhaust zone, which contains an exhaust gas treating device, is admitted with a reagent at default operating statuses&#39; of the internal combustion engine and/or of the exhaust gas treating device, and on the device for carrying out this method according to the category of independent claims. 
     BACKGROUND 
     Due to DE 199 06 287 A1 a procedure for controlling a combustion engine became known, which has an exhaust gas treating device arranged in its exhaust zone, that contains a particle filter, which retains particles contained in the exhaust gas. For a proper operation of the particle filter a particle loading status has to be known, which can be determined indirectly by the differential pressure present in the particle filter or by model calculations. The regeneration of the particle filter takes place by burning off the particles stored in the particle filter, which happens in the temperature ranges of e.g. 932° F.-1202° F. It is particularly provided that additional fuel is brought into the exhaust zone of the combustion engine, which reacts exothermically as a combustible with the oxygen in the exhaust zone. The fuel is oxidized for example on the catalytically effective surface of a catalyst. On the one hand this increases the temperature of the catalyst, and on the other hand the temperature of the off-gas stream behind the catalyst, which is then admitted to the following particle filter. The catalyst can also be already contained in the particle filter. The fuel arrives for example by at least one fuel injection in the exhaust zone of the combustion engine. 
     Due to DE 101 08 720 A1 a procedure and a device for operating a particle filter, that is arranged in the exhaust zone of a combustion engine became known, which are based on at least one operating parameter, which provides the condition of the combustion engine and/or the condition of the particle filter, and moreover stipulates a parameter, which describes the intensity of the particle burn. The parameter is compared to a threshold. In the case of an exceeding of the threshold arrangements for declining are initiated, which aim on the encroachments to reduce the oxygen content in the exhaust gas. 
     Due to DE 103 33 441 A1 a procedure for operating a particle filter, that is arranged in the exhaust zone of a combustion engine became known, which uses a lambda signal, provided by a lambda sensor, as a dimension of the burning off—speed of the particles during the regeneration of the particle filter. The determined dimension is used to control the particle burning off temperature with the objective of preventing an overheating of the particle filter. A nominal value for the lambda signal or for a change of the lambda signal is given. In case of a noticed deviation between the nominal and the actual value, an intervention takes place for example into the position of the throttle valve, into the charge pressure of an exhaust gas turbocharger or into the determination of a exhaust gas recirculation rate. According to one configuration an actuating element is provided, arranged in the exhaust gas conduit, which brings fuel or another oxidant to the off-gas stream. 
     The invention is based on a procedure for operating a combustion engine, whose exhaust zone, that contains an exhaust gas treating device, is admitted with a reagent at preset operating statuses of the combustion engine and/or of the exhaust gas treating device, and a device for implementing this procedure, which allows the provision of a sufficient amount of the reagent on the one hand, and prevents the damage of the exhaust gas treating device by an overdose on the other hand. 
     This task is solved for the given situation by the specified characteristics of the independent claims. 
     SUMMARY 
     According to the invention for operating a combustion engine, whose exhaust zone, that contains an exhaust gas treating device, is admitted with a reagent at preset operating statuses of the combustion engine and/or of the exhaust gas treating device, an ascertainment of a correction value for the reagent signal is provided, which determines the amount of reagent that has to be put into the exhaust zone. The correction value is ascertained by a comparison of a dimension of the actual value of the reagent in the exhaust zone, which has been introduced according to a dimension for a preset nominal value, and a dimension of the nominal value. 
     According to the invention it is possible to adapt the reagent signal, which determines the amount of reagent that has to be brought into the exhaust zone. The preset dimension for the nominal value is corrected by the correction value. The invention considers tolerances and ageing phenomena of a reagent introduction device as well as stream proportions, for example blast waves of the reagent in the reagent introduction device and/or in fuel metering device of the combustion engine, and they can be compensated. The adaptation is based on a comparison of a dimension for the actual value of the reagent in the exhaust zone, which has been introduced according to a dimension for a preset nominal value, and a dimension of the nominal value. 
     The invention prevents an under dose, which would lead to an insufficient exhaust gas treatment, and an overdose, which would lower efficiency and lead to a breakthrough of the reagent. Particularly, an inadmissible burden of the components in the exhaust gas treating device by a possibly occurring over-temperature, due to a too high reagent dose, is prevented. 
     The correction value can be a dimension for the reagent amount or a parameter like for example a time duration for the reagent introduction. 
     Advantageous improvements and configurations of the invention arise from dependent claims. 
     One configuration provides that the dimension for the actual value is determined from a measured lambda signal in the exhaust zone. With this method a sensor signal, that has been supplied by a lambda sensor, for a lambda regulation in the exhaust zone, anyway, can be additionally used for determining the dimension for the actual value. Another possibility provides a calculation of the air lambda occurring in the exhaust zone. 
     Especially advantageous is a combination with a second, already known, soft-ware function, which determines the air lambda of each operation point in a normal driving operation, and which then provides this information as a reference for the present suggested function. If this function also considers the gas duration at least in the exhaust zone of the combustion engine and/or in the combustion engine itself and/or in the exhaust zone, then the present suggested method can be used in a dynamic operation of the combustion engine as well. 
     An exact dimension of the actual value is determined if additionally to the lambda an air signal is used, which is acquired in the exhaust zone of the combustion engine. 
     One configuration provides that the correction value is determined in a periodic learning procedure, which is carried out in default operating statuses of the combustion engine and/or the exhaust gas treating device. 
     The correction value can be determined for example in an operating status of the combustion engine, whose fuel amount, which has been injected into the combustion engine, or a variation of the fuel amount lies within a marginal value. With this procedure it can be checked whether there is at least approximately a stationary operation of the combustion engine. 
     The correction value can furthermore be determined for example by varying fuel amounts, that have been injection to the combustion engine, in order to cover a wide range of different operating statuses of the combustion engine. Particularly, it can be provided that the correction value is determined in an operating status of the combustion engine, which corresponds with the engine idle. 
     Furthermore it can be provided that the correction value is determined by a reagent, which is under pressure, at varying pressures of the reagent. 
     One configuration provides, that the correction value is added to the dimension for the actual value of the reagent or that the nominal value is corrected multiplicatively. 
     According to a configuration it is provided that the reagent is fuel, which is injected at least in one fuel post-injection of the combustion engine. In this case the correction value is determined separately for each fuel post-injection as well as for multiple fuel post-injections. Thereby appearing time-varying conditions at the introduction of the reagent can be considered, particularly by blast waves in the reagent introduction device and/or in the fuel metering device of the combustion engine. 
     According to one configuration it is provided that the reagent is brought directly into the exhaust zone. I this case fuel can be for example the reagent as well. 
     The invention for operating a combustion engine is based at first on a controller, which is customized for the implementation of the procedure. The controller preferably contains at least one electric storage, which stores the steps of the procedure as a computer program. The controller contains preferably a special storage, which stores the different values of the correction value. 
     Further advantageous improvements and configurations of the invention arise from further dependent claims and from the following description. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWING 
       The FIGURE shows function blocks, which are suitable for the implementation of the invention&#39;s procedure for operating a combustion engine. 
     
    
    
     DETAILED DESCRIPTION 
       FIG. 1  shows a combustion engine  10 , which has an air detection  12  in its suction zone  11 , a reagent introduction device  14  in its exhaust zone, a lambda sensor  15  and an exhaust gas treating device  16 . The exhaust gas treating device  16  contains at least on catalyst  17  and/or a particle filter  18 . The exhaust gas treating device  16  is supplied with a pressure sensor  18  and a temperature sensor  20 . 
     The air detection  12  delivers an air signal ms_L, the combustion engine  10  an engine speed n, the lambda sensor a lambda signal lam, the pressure sensor  19  an exhaust gas pressure signal dp and the temperature sensor  20  an exhaust gas temperature signal te_abg to a controller  25 . 
     The controller  25  provides a fuel signal m_K for a fuel metering  26 , in which the first pressure p 1  occurs, and a reagent signal S_Rea for the fuel metering  26  as well as for the reagent introduction device  14 , in which a second pressure p 2  occurs. 
     The controller  25  contains an operating status determination  30 , which is supplied with the fuel signal m_K, the speed engine signal n, a regeneration signal Reg, a temperature signal te, a speed signal v as well as a pressure signal p. The operating status determination  30  delivers a learn-enabling signal S_Lern to a switch  31 . 
     A reagent controlling  32  is provided, which is supplied with the exhaust gas pressure signal dp as well as the exhaust gas temperature te_abg, and which provides the regeneration signal Reg as well as a dimension m_Soll for the nominal value of a reagent. 
     Out of the lambda signal lam and die air signal ms_L an actual value determination  33  determines a dimension m_Ist for the actual value of the reagent that is in the exhaust zone  13 . 
     A comparator  34  compares the dimension m_Soll for the nominal value with the dimension m_Ist for the actual value of the reagent and provides a deviation, which is delivered to a correction value storage  35  by the switch  31 . 
     The correction value storage  35  contains an engine map  36 , which encloses different values of a correction value ti_Korr. The correction value storage  35  is supplied with the deviation dm, the dimension m_Soll for the nominal value, the fuel signal m_K, the first and second pressure p 1 , p 2 , information about at least on fuel post-injection Po_I 1 , Po_I 2  as well as the engine speed n. The correction value storage  35  delivers the correction value ti_Korr, m_Korr to an adder  37 , which adds the correction value ti_Korr, m_Korr to the dimension m_Soll for the nominal value and provides as the result the reagent signal S_Rea. 
     An alternative is listed dash-lined, which converses the dimension m_Soll for the nominal value by a transformation into one value, which illustrates the dimension m_Soll for example in time-units. 
     According to the invention it is proceeded as follows: 
     The exhaust gas, which has been ejected by the combustion engine  10 , is cleaned from at least exhaust gas component by the exhaust gas treating device  16 , which is arranged in the exhaust zone  13 . The exhaust gas treating device  16  contains for example at least one catalyst  17 , for instance an oxidation-catalyst and/or a three-way-catalyst and/or a NOx-storage catalyst and/or a SCR-catalyst and/or a particle filter  18 . The catalyst  17  can a part of the particle filer  18 . 
     The invention is based on the introduction of a reagent in the exhaust zone  13 . An oxidizable reagent like e.g. fuel can be provided for the heating of a component like e.g. the exhaust gas treating device  16  or for heating of the exhaust gas in the exhaust zone. An oxidizable reagent can react exothermically with the present oxygen in the exhaust zone  13 . The exothermic reaction will possibly take place in the catalyst  17 , whereby a heating of the catalyst  17  occurs in addition to a heating of the exhaust. 
     The reagent can furthermore be provided for example for the transformation of exhaust gas components into less harmful components. A SCR-catalyst fro instance requires a reagent for transforming NOx. Ammoniac is for example provided as a reagent, which can be attained from an urea-hydrogen-solution introduced to the exhaust zone  13  or directly introduced into the exhaust zone  13 . Alternatively the reagent can be provided interior power-operated. 
     The reagent can be furthermore provided for the regeneration of e.g. NOx-storage catalysts. 
     The displayed implementation model shows the reagent introduction device  14 , which introduces the reagent directly in the exhaust zone  13 . The reagent introduction device  14  is for instance realized as an injection valve, which injects the reagent, that shows the second pressure p 2 , into the exhaust zone  13 . 
     Alternatively or additionally it can be provided that the reagent is injected interior power-operated into the combustion engine  10 . Therefore the fuel metering device  26  can be used, which injects the fuel, which shows the first pressure p 1 , into the cylinder of the combustion engine  10 . The introduction of the reagent can be carried out for example with at least one fuel post-injection Po_I 1 , Po_I 2 . 
     Firstly a fuel post-injection Po_I 2  can be scheduled, which burns in the combustion engine  10 , but only contributes partially to the production of torque. With this step a heating of the exhaust gas can be achieved in particular. Additionally or alternatively at least one fuel post-injection Po_I 1  can be scheduled, whereby fuel arrives unburnt in the exhaust zone  13 , where it can either react exothermically and/or can be used for chemical conversion processes. 
     The amount of the reagent, that has to be introduced by the fuel metering device  26  and/or the reagent introduction device  14 , is determined by the reagent signal S_Rea, which for example determines an injection duration and where necessary an injection moment of a valve. 
     The displayed implementation model is based on the use of the reagent for heating the particle filter  18 . The heating can be necessary to heat the particle filter  18  to a temperature of e.g. 932° F.-1202° F. in order to induce the regeneration process of the particle filter  18 , which burns the stored particles independently. The heating can for instance take place indirectly per the exhaust gas temperature. Furthermore it can be provided that the reagent reacts exothermically in the catalyst  17 , which is preferably arranged within the particle filter  18 . Thereby the particle filter  18  is heated indirectly as well as directly. 
     The regeneration controller  32  can detect the requirement of a regeneration of the particle filter  18  by e.g. the occurring pressure difference in the particle filter  18 . For this purpose the pressure sensor  19  acquires the exhaust gas pressure dp, which occurs in total at the particle filter  18  or at the exhaust gas treating device  16 . The regeneration controller  32  considers furthermore preferably the exhaust gas temperature te_abg which is at least one dimension for the temperature of the particle filter  18 . 
     One significant function of the regeneration controller  32  is to provide at least the dimension m_Soll for the nominal value of the reagent. The dimension m_Soll for the nominal value has to be determines comparatively accurate. A too low nominal value causes that the required starting temperature for the regeneration of the particle filter cannot be achieved. As long as the reagent is used as a reagent for chemical conversions, the desired transformation would not, or only in an insufficient way, take place, if the dimension m_Soll for the nominal value is too low. A too high nominal value would jeopardize the exhaust gas treating device  18  in respect of an excessive temperature. At this it has to be considered that the starting regeneration of the particle filter  18 , which burns the stored particles, is an exothermic reaction as well, that leads to a significant impact on the temperature. 
     On the basis of experiments it was established that the dimension m_Soll for the nominal value of the reagent can deviate from the actual value m_Ist of the reagent in the exhaust zone  13 . Tolerances in the mechanic components, for example the fuel metering device  26  and/or the reagent introduction device  14 , are responsible for this. Streaming conditions in the reagent introduction device  14  and/or fuel metering device  26  have a significant impact as well. The introduction processes can in particular cause blast waves, which lead to the actual injection of more or less reagent or rather fuel than the dimension m_Soll for the nominal value. 
     According to the invention a provision of the correction value ti_Korr, m_Korr is designated, which is provided for the reagent signal S_Rea, which determines the amount of reagent that has to be introduced into the exhaust zone  13 . The correction value ti_Korr, m_Korr is acquired by a comparison in the comparator  34  of the dimension m_Ist for the actual value of the reagent in the exhaust zone  13  and the dimension m_Soll for the nominal value. 
     The correction value ti_Korr, m_Korr is preferably provided in individual FIGURES, which are deposited in the engine map  36  of the correction value storage  35 . 
     The actual value m_Ist of the reagent in the exhaust zone  13  is acquired preferably by the lambda signal lam, which is provided by the lambda sensor  15 , that is arranged in the exhaust zone  13 . The lambda sensor  15  can be arranged upstream before the exhaust gas treating device  16 , after the exhaust gas treating device  16  or in a specified position in the exhaust gas treating device  16 , which then contains more components than in e.g. the catalyst  17  and the particle filter  18 . 
     Preferably it is a broad band lambda sensor, which can measure a lambda, that can be in a range of e.g. 0.6-4.0. On the basis of experiments it could be established that the lambda sensor  15  can, despite a possible present high oxygen percentage and a simultaneously present fuel percentage and for example the presence of hydrogen, still provide a correct or at least a reproducible lambda signal lam, from which the dimension m_Ist of the reagent in the exhaust zone  13  can be determined reliably and reproducibly. Preferably the air signal ms_L is considered during the determination. 
     The air lambda in the exhaust zone  13  can be calculated by known parameters of the combustion engine  10 , like for example the air signal ms_L and the fuel signal, m_K instead of a measurement with the lambda sensor  15 . 
     Notably advantageous is one configuration, according to which the air lambda, which can be expected during a normal operation, is provided for the suggested function as a reference by another, already known, function. Thereby the change of the air lambda due to the dosage of the reagent can be determined. A precondition is, that the reagent has an impact on the air lambda. This is the case for example, if the reagent is fuel, which is either introduced directly into the exhaust zone  13  or is provided interior power-operated by e.g. at least one fuel post-injection. Thereby an actual lambda is always provided, independent of the gas durations in the suction zone  11  of the combustion engine and/or in the combustion engine  10  itself and/or in the exhaust zone  13 . 
     A change of lambda caused by the introduction of reagent can be acquired by the relation:
 
delta (1/lambda)=(14.5 ×m   —   Ist )/ ms   —   L  
 
whereby a multiplicative correction factor KF can be considered if necessary, which can be achieved by the development of a thermodynamic balance at the lambda sensor  15 , that is not always complete. If an accuracy of measurement of the lambda sensor  15  of 4% regarding the oxygen concentration, a lambda of 2 and an exactness of the air detection  12  of e.g. 5% is assumed, the dimension m_Ist for the actual value of the reagent in the exhaust zone  13  can be acquired with an accuracy of approximately 6.5%.
 
     The deviation dm, which has been established in the comparator  34 , is used to determine the individual factors in the engine map  36 . The determination preferably takes place for different fuel signals m_K and/or different pressures p 1 , p 2  of the reagent and/or depending on at least one fuel post-injection P 0 _I 1 , Po_I 2 . 
     Practically different factors are deposited depending on whether the first or the second or further fuel post-injections Po_I 1 , Po_I 2  are scheduled as separate or multiple fuel post-injections Po_I 1 , Po_I 2  in one cycle. Generally the deviations dm do not match due to the blast waves that develop different during different configurations of fuel post-injections Po_I 1 , Po_I 2 . Additionally or alternatively the separate factors are deposited depending on the angle signal w, which indicates the angle location of leastwise one fuel post-injection Po_I 1 , Po_I 2  in relation to the position of the crankshaft. 
     The individual factors of the engine map  36  of the correction value ti_Korr, m_Korr are preferably studied and stored only in preset operating statuses of the combustion engine  10  and/or the exhaust gas treating device  16 . For determining the preset operating statuses, the operating status-determination  30  is designated, which provides the learn-enabling signal S_Lern, which closes the switch  31 . The switch  31  symbolizes an enabling for the listing of the individual factors in the engine map  36 . 
     The operating status-determination  30  delivers the learn-enabling signal S_Lern for example depending on the fuel signal m_K. For instance it is checked, whether the fuel signal m_K and/or a change of the fuel signal m_K lies at least within one marginal value. A lower and/or an upper boundary can be stipulated for example. Furthermore for example the regeneration signal Reg is preferably considered, which indicates that the exhaust gas treating device  16  is being regenerated at this moment. Preferably the learn-enabling signal S_Lern is suppressed in the presence of the regeneration signal Reg. Furthermore the learn-enabling signal S_Lern can be released depending on the temperature signal T. The temperature signal T can be for example the temperature of the combustion engine  10  and/or the temperature of the exhaust zone  13  and/or the temperature of the lambda sensor  15 . 
     Furthermore the operating status determination  30  can provide the learn-enabling signal S_Lern depending on the driving speed v of a not further displayed motor vehicle, that is powered by the combustion engine  10 . It can be observed for instance, whether the driving speed equals zero, so that an idling of the combustion engine  10  can be assumed. 
     Furthermore the pressure signal p can be considered, whereby the first and/or second pressure p 1 , p 2  of the reagent for instance is meant. Alternatively or additionally the speed engine signal n can be considered. Particularly the fuel signal m_K and/or the pressure signal p and/or the engine speed signal n can provide a dimension for the deviation of the of the combustion engine  10 , depending on which the learn-enabling signal S_Lern is displayed. 
     The correction value ti_Korr, m_Korr is preferably added in the adder  37  to the dimension m_Soll for the nominal value of the reagent. Compared to a multiplicative connection, the addition shows the significant advantage, that the mistake is significantly lower in a faulty correction value ti_Korr, m_Korr, than it would be in a multiplicative connection. 
     The reagent signal S_Rea can directly be a dimension for the amount of the reagent. The reagent signal S_Rea is preferably already a control value, which is suitable for controlling the reagent introduction device  14  and/or the exhaust gas metering device  26 . In that case the reagent signal S_Rea is preferably a time duration, which mirrors for example the opening time of a valve. In this case before the adder  37  a conversion  38  is designated, which transforms the dimension m_Soll for the nominal value of the reagent from an amount into a time duration. Accordingly the corresponding dimension for an allocated time of a valve-opening is added to the correction value storage  35  instead of the dimension m_Soll for the nominal value. The connection is shown dash-lined in the FIGURE.