DE102006025050B4 - Method and device for operating an exhaust aftertreatment system - Google Patents

Abstract

Method for operating a motor vehicle exhaust gas aftertreatment system (1), in which oxygen is supplied and removed from an oxygen store (8) of an exhaust gas aftertreatment component (7) and the oxygen store can have a first and a second part, which are arranged in at least two different exhaust gas aftertreatment components, wherein - at least one parameter, which is determined by the oxygen store and its oxygen content, changes and is used in an operating mode of the motor vehicle exhaust gas aftertreatment system (1), - an oxygen quantity in the oxygen store is calculated by means of an oxygen balance around the oxygen store, a determination of the respective current oxygen content is implemented in an operating strategy in the oxygen store so that a complete emptying of the oxygen store is avoided, and at least one threshold value is adapted as part of a control using the oxygen store st is an aging process, with hysteresis behavior during a cycle change being included in the threshold value adjustment, whereby a measuring probe is used to determine a temperature of the oxygen storage device, with which a direct coupling of the measured temperature is taken into account when calculating the oxygen content of the oxygen storage device and this determined value the temperature is used to check the oxygen content determined via the oxygen balance, the determination of the temperature of the oxygen storage being used to change one or more threshold values for influencing a fat-lean cycle according to the temperature-dependent oxygen storage capacity, and wherein - at least one threshold value (25 , 26) is determined with respect to the determined stored amount of oxygen, if exceeded, a cycle change between lean operation and rich operation is triggered or - a lower (25) and an upper (26) threshold value with respect the amount of oxygen is determined and a cycle change between lean operation and rich operation is triggered when the respective threshold values are exceeded or undershot.

Description

The present invention relates to a method for operating a motor vehicle exhaust aftertreatment system and an exhaust aftertreatment system with a connected internal combustion engine.

Out US 6,843,052 It is known that a rich-lean cycle can be used to utilize the oxygen storage of an exhaust aftertreatment component to oxidize H _s S. The reservoir is filled in a lean phase and at least partially emptied in a fatty phase. To control an O ₂ content, a lambda probe located downstream of the exhaust gas aftertreatment component is used. If a stoichiometric air ratio is detected here, a lean skip is initiated. At a superstoichiometric air ratio, a fat jump is initiated. Also in EP 0 893 154 B1 For example, an oxygen storage downstream of a NOx storage catalyst (NSK) is used to supply oxygen for H ₂ S oxidation.

Out DE 197 47 222 C1 For example, an internal combustion engine plant with NSK and secondary air injection with a process for desulfating the NSK is known. In this system, the desulphation control is controlled by the output of a downstream lambda probe.

Out DE 198 27 195 A1 it is known that in a lean-fat jump initially SO ₂ is formed briefly and a formation of H ₂ S followed with a time delay. An H ₂ S emission can therefore be suppressed by an early fat-lean jump.

In DE 101 26 455 A1 describes a process for the desulfurization of a NSK, which follows the regeneration of a particulate filter, whereby the heating is eliminated or shortened to a Desulfatisierungstemperatur.

Out DE 199 22 962 C2 It is known that the air ratio in the exhaust gas during NSK desulphation can be adjusted by secondary air supply.

Out DE 101 13 382 A1 shows a method for heating a downstream in the flow direction of catalyst in an exhaust system of an internal combustion engine with multiple in the exhaust gas flow direction arranged behind one another catalysts.

In DE 103 41 930 A1 a method is described in which a catalyst temporarily a rich exhaust gas flow is supplied and the unburned exhaust gas components react with an oxygen stored in the oxygen storage of the catalyst and the heat energy released thereby heats the catalyst to regeneration temperature.

The control or control concepts resulting from the above documents relate to a lambda probe signal downstream of an oxygen-storing component in the exhaust gas line. However, especially at high temperatures, the lambda probe will only show unequal one if an oxygen reservoir is completely filled (λ> 1) or completely emptied (λ <1). This can be at z. B. a desulfation fat breaks occur with accompanying H ₂ S emission.

Object of the present invention is to provide an improvement in the performance of an exhaust aftertreatment system, which in particular takes into account the actual conditions in an exhaust aftertreatment system and allows a quick and safe response.

This object is achieved by a method having the features of claim 1 and with an exhaust aftertreatment system having the features of claim 15. Advantageous further embodiments are specified in the respective subclaims.

According to the invention, a method for operating a motor vehicle exhaust aftertreatment system is proposed in which an oxygen storage of an exhaust aftertreatment component oxygen is supplied and removed and the oxygen storage may have a first part and a second part, which are arranged in at least two different exhaust aftertreatment components, wherein at least one through the Oxygen storage and its oxygen content influenced, determined changing parameters and is used in a mode of operation of the motor vehicle exhaust aftertreatment system. Further features will become apparent from the claim 1.

Preferably, an amount of oxygen in the oxygen storage is determined and influenced according to a development of a fat-lean cycle as a function of the determined amount of oxygen. For example, an amount of oxygen in the oxygen storage may be included as a size in setting a rich-lean cycle. An exemplary embodiment provides that the amount of oxygen is used as a control or control variable for a rich-lean cycle. A further exemplary embodiment provides that an amount of oxygen in the oxygen storage is regulated by means of at least one fat-lean cycle, preferably by means of different fat-lean cycles. One possible implementation has a motor control that controls or regulates the grease-lean cycles, the Oxygen content in the oxygen storage is controlled or regulated. For this purpose, the engine control, for example, resort to a variety of maps or an oxygen determination that is continuous or discontinuous.

In particular, a degree of filling of the oxygen storage is taken into account. Thus, not only, for example, a lambda probe signal is taken into account in controls or regulations relating to individual components or the overall component exhaust aftertreatment system. Rather, it is lifted to the current state of the oxygen storage and taken into account how it is able to give off oxygen, for example, when operating in a rich portion of the fat-lean cycle or vice versa, in a lean area of the fat-lean cycle yet To be able to absorb oxygen.

In addition, an additional supply of oxygen in the automotive exhaust aftertreatment system depending on the determined oxygen amount of the oxygen storage can be provided. Such an oxygen supply can take place, for example, via an air feed as well as an oxygen feed into the exhaust aftertreatment system. It is also possible, for example, additionally or independently thereof to change the air supply in the exhaust aftertreatment system by a corresponding valve overlap in a connected internal combustion engine.

The amount of oxygen is preferably calculated by means of an oxygen balance around the oxygen storage. This can be done for example by means of a first probe and a second probe. The first probe is preferably arranged in the flow direction in front of the oxygen storage, preferably at least immediately in front of the oxygen storage. The second probe is preferably arranged downstream in the immediate vicinity of the oxygen storage. Furthermore, there is the possibility that at least one of the two probes is arranged directly on an opening of the oxygen storage. There is also the possibility that at least one of the probes is arranged in the oxygen storage. For example, it is then possible to deduce the total storage behavior of the entire oxygen storage unit via a partial behavior of the oxygen storage device.

Preferably, a first probe is used for a continuous measurement of the oxygen content before the oxygen storage. Here, instead of the oxygen content, the air content in front of the oxygen storage can be determined and deduced therefrom on the oxygen content. The second probe preferably determines the oxygen content at least at time intervals after the oxygen storage. It is preferred that a permanent measurement of the oxygen content or the air ratio takes place. For example, it is provided that at least the upstream of the two probes is a broadband lambda probe. The other of the two probes, however, may be a jump probe. However, it is also possible to use two broadband lambda probes. Preferably, at least one of the probes is capable of additionally receiving a temperature.

According to one embodiment, it is provided that the exhaust aftertreatment system is equipped with its own control unit. In the control unit is preferably not only a control or regulation with respect to the oxygen storage stored. Preferably, further components of the exhaust aftertreatment component are also included in the control unit. This can be in addition to the oxygen storage additional catalysts, particulate filters, injectors in the exhaust aftertreatment system, such as ammonia-containing agent or the like. An embodiment provides that such functionality is implemented in an engine control unit. Another embodiment provides that the control unit is arranged separately from the engine control.

According to one embodiment, it is provided that the method is used to achieve a targeted influencing of the rich-lean cycle with the amount of oxygen stored in the oxygen storage. For example, it is possible to be able to change a quantity of heat released per unit of time by a specific filling and emptying of the oxygen storage. This makes it possible, for example, to be able to influence a temperature of the oxygen storage or of a component which has the oxygen storage.

For example, it is provided that a regeneration of an exhaust gas purification component of the motor vehicle has to take place in a specific temperature range. This is the case for example in a regeneration of a diesel particulate filter as well as a desulfation of a nitrogen oxide storage catalyst. For example, if an internal combustion engine is operated in a lean operation in a particulate filter, soot collects. For Rußabbrand a temperature of above 500 ° C is preferably set. If, for example, an uncoated particle filter is used, a temperature above 600 ° C is used. In the case of a catalytically coated filter, for example, a temperature above 550 ° C. exhaust gas temperature is set on the particle filter. According to one embodiment, it is provided that to increase the temperature during regeneration, a grease Lean cycle is used. In this case, an oxygen storage is cyclically at least partially filled and emptied. A successful conversion of the oxygen storage generates heat, which is used to increase the temperature. The temperature increase can for example be done before the actual regeneration, so that preferably only a small enthalpy must be provided to trigger the actual regeneration. For example, the amount of oxygen present in the oxygen storage can be used to at least partially generate a necessary temperature and / or Temepraturererhöhung for regeneration. For this purpose, the oxygen storage takes on oxygen in corresponding phases of oxygen supply, which it can deliver in phases of a regeneration.

Such operation of the oxygen storage in conjunction with a regeneration is supported in different ways, for example via the engine control and / or the separate control unit. For example, the temperature increase can be achieved by raising an exhaust gas temperature at the internal combustion engine or even when operating a turbine at the outlet of the turbine. For example, this can be done in a combustion engine by reducing the air ratio, for example, by a post-injection, by changing a injection angle as well as by throttling the engine or a turbine air supplied. In order to allow an increase in the temperature increase, incomplete or burnt fuel can not be supplied to the oxygen storage. For example, a late post-injection of fuel into an expansion stroke of the internal combustion engine can be used for this purpose. Furthermore, it is possible to provide an injection of fuel into a Ausschiebetakt. In addition, there is the possibility of a direct fuel supply into the exhaust gas flow, for example via an additional injection. There is also the possibility of reforming fuel and feed as synthesis gas. For example, there is also the possibility that in a motor vehicle having a bivalent drive, for example, in addition a liquid gas storage, a natural gas storage or the like is used to allow a corresponding fluid inflow into the exhaust aftertreatment system.

The oxygen to be stored in the oxygen storage is fed, for example, from residual oxygen from the engine combustion. However, it is additionally possible to provide an external air supply into the exhaust gas. For this purpose, for example, a secondary air blower can be used. It is also possible to use a charging device of an internal combustion engine for this purpose. Furthermore, it is possible to use stored oxygen at other locations of the exhaust aftertreatment system for enriching the oxygen emitted by this in the oxygen storage.

A combustible gas component can be converted in the exhaust aftertreatment system by sufficient provision of oxygen, for example by means of exclusively from the oxygen storage, in addition from the oxygen storage, in particular supplementally supplied from the oxygen storage oxygen. When operating the motor vehicle exhaust aftertreatment system is targeted to use the existing oxygen storage controlled use. For example, it is possible to carry out a temperature control or regulation of the particulate filter, in particular if the particulate filter has the option of acting as an oxygen reservoir itself.

According to a further embodiment, it is provided that the determined amount of oxygen of the oxygen storage as a parameter in a desulfation of an oxide memory is preferably received to influence a fat-lean cycle. The oxide store may be, for example, a nitrogen oxide storage catalyst and / or a sulfur oxide storage. In desulfation, an oxygen supply from the oxygen storage is used to oxidize, for example, in substoichiometric operation created H ₂ S in SO ₂ . By determining the respective current oxygen content in the oxygen storage is preferably implemented in the corresponding operating strategy that a complete emptying of the oxygen storage is avoided, especially in rich operation. This prevents a risk of H ₂ S leakage. If, in particular, it is provided as an operating strategy that the oxygen reservoir may never be completely emptied, a jump probe may be provided instead of a lambda probe behind the oxygen reservoir, in particular.

Preferably, not only a determination of an onset of desulfation and / or regeneration can be determined via the considered amount of oxygen. Rather, there is the additional possibility that the determined amount of oxygen is received as a parameter to determine a period of desulfation and / or regeneration.

Preferably, not only a determination of an onset of desulfation and / or regeneration can be determined via the considered amount of oxygen. Rather, there is also the possibility that to determine a Duration of desulfation and / or regeneration received the determined amount of oxygen as a parameter.

The amount of oxygen in the oxygen reservoir necessary for the process is determined according to an embodiment by integration of the oxygen mass flow exchanged with the reservoir. For this purpose, the oxygen mass flow is calculated on the basis of a difference between the probes, in particular the lambda probes and the exhaust gas mass flow. The following formula is used for this:

The result of such or other calculation may be erroneous, for example due to inaccurate lambda signals or an inaccurate exhaust mass flow, such that the calculated oxygen content does not correspond to the actual oxygen content. Also, the integration can make a mistake grow over time. It is then possible that unwanted fat or lean breakthroughs occur. Should such a breakthrough occur, this breakthrough can be used to detect the actual state of the memory and reset the calculation to a specific value. Furthermore, a targeted breakthrough situation can be created in order to achieve a calibration of the measurement. It is also possible to derive a calibration from the operating behavior of the oxygen storage device. For example, a maximum storage state can also be checked by appropriate supply of air or oxygen, and preferably a calibration for the storage capacity and the storage state of the oxygen storage device can be determined therefrom.

A further development provides that within the scope of a control or regulation by using the oxygen storage, preferably also its oxygen storage capacity and in particular the currently determined each stored oxygen amount at least one threshold is set at exceeding a cycle change between lean and rich operation is triggered. The threshold can be fixed. However, there is also the possibility that the threshold value can be adapted to, for example, an aging of the oxygen storage. For example, in a calibration of the oxygen storage capacity or the calculation of the oxygen storage capacity also an increase or decrease of the threshold value can be caused. For example, the threshold is stored in the control unit of the exhaust aftertreatment system. However, it may also be present in the engine control, for example. It is preferably provided that a lower and an upper threshold value with respect to the amount of oxygen is determined and when the threshold value is exceeded, a cycle change between lean and rich operation is triggered. A triggering time for the cycle change can be provided here when the threshold value is reached, as well as after the threshold value has been exceeded. Preferably, a hysteresis behavior is triggered during a cycle change. This means that after reaching the respective threshold value of the oxygen storage either further oxygen additionally slows down receives before a release of the oxygen takes place or in the opposite case, a decrease in the oxygen release is slowed down, again oxygenation takes place in the oxygen storage. It is preferably provided that the threshold value can be exceeded in terms of the amount of oxygen in the oxygen storage, once upon reaching the threshold value and subsequently, after the cycle change has been completed and the operating behavior with respect to the oxygen decrease or absorption of the oxygen storage has reversed.

Furthermore, it may be provided that an internal combustion engine is operated in a rich-lean cycle, wherein a temperature of the oxygen storage is determined and an operating parameter influencing the stored amount of oxygen is changed as a function of the determined temperature. In particular, there is the possibility that a temperature control or temperature control of the exhaust gas aftertreatment component having the oxygen storage unit changes an oxygen quantity which is released from the oxygen storage unit per unit time to a temperature adaptation of the exhaust gas aftertreatment component. In the case of a temperature control via the use of the oxygen storage, for example, a PI controller can be used.

In addition, as well as separately from this, an operating mode of the motor vehicle exhaust aftertreatment system can provide that during a desulfurization of an oxide, in particular a nitrogen oxide storage catalyst at least partially driven a fat-lean cycle and added an air ratio behind the oxide, in particular the nitrogen oxide storage catalyst is, wherein the amount of oxygen is determined and used to avoid under- and / or Überstöichometrie the air ratio behind the oxide, in particular the nitrogen oxide storage catalyst. This is in particular to one or more thresholds, which are predetermined in terms of the amount of storage of oxygen in the oxygen storage, resorted to. For example, there is the possibility that not only one threshold, but several thresholds are present. This gives rise to the possibility of being able to operate the oxygen storage with different temperatures or oxygen deliveries or oxygen intakes.

The operation of the oxygen storage is integrated into the exhaust aftertreatment concept of the motor vehicle. Therefore, the oxygen storage may be arranged as a single component in the exhaust aftertreatment system. However, it is preferred that the oxygen storage is part of a component of the exhaust aftertreatment system. This may be a catalyst, particulate filter, or other element in the exhaust after-treatment system.

According to a further aspect of the invention, an exhaust aftertreatment system with a connected internal combustion engine is proposed, wherein the internal combustion engine has an engine controller and the exhaust aftertreatment system at least a regulated catalyst and an oxygen storage, wherein a first probe is disposed in front of the oxygen storage and a second probe is disposed behind the oxygen storage in which the first probe determines a first parameter characterizing an oxygen content, and a signal transmission of the parameters recorded by the first and the second probe to an evaluation unit is provided, and the evaluation unit is coupled with a motor controller to a control or control unit which generates a rich -Mager-cycle based on the determined parameters considered. Further features emerge from claim 15.

By means of such an exhaust aftertreatment system with a connected internal combustion engine, the method described above for operating a motor vehicle exhaust aftertreatment system is preferably carried out.

A further treatment provides that the second probe is a temperature probe whose parameters are included in a control or regulation of a lambda value of the engine control. Preferably, a rich-lean cycle enters as the desired value in a lambda control of the internal combustion engine.

A further refinement of the exhaust aftertreatment system provides that the first and the second probe each determine a first parameter characterizing an oxygen content, and a signal transmission of the first parameter from the first and the second probe to an evaluation unit is provided, and the evaluation unit from the first parameters a determination of a second parameter characterizing an oxygen content of the oxygen storage, and the engine control is coupled to an apparatus for adjusting an air ratio in the exhaust aftertreatment system, wherein an adjustment of the air ratio in dependence on the second parameter is provided via the device.

A further development of the exhaust aftertreatment system provides that the oxygen reservoir has a first part and a second part, which are arranged in at least two different exhaust aftertreatment components. For example, the oxygen storage can be formed from a NOx catalyst as well as from a particulate filter. These may also be present separately from each other. In addition, there is a possibility that a three-way catalyst may also include an oxygen reservoir or a portion thereof. It is preferred if a measuring probe is provided for determining a temperature of the oxygen storage. This allows a direct coupling of the measured temperature in a calculation of the oxygen content of the oxygen storage. For example, this determined value can be used via the temperature for checking the oxygen content determined, for example, via the oxygen balance. Alternatively or additionally, the determination of the temperature of the oxygen storage also allows one or more of the above-mentioned threshold values for influencing the rich-lean cycle to be changed according to the temperature-dependent oxygen storage capacity.

Further advantageous embodiments and further developments are specified in the following drawings. However, the resulting respective features are not limited to the individual embodiments. Rather, individual features can be combined with those of other embodiments of the drawings as well as with features of the above description to further developments. Show it:

1 FIG. 2 is a first schematic view of a first exhaust aftertreatment system. FIG.

2 FIG. 2: a schematic view of a second exhaust aftertreatment system with a temperature control, FIG.

3 in a schematic representation, a change in temperature by changing an operation of an internal combustion engine, taking into account the amount of oxygen submitted per unit time in an oxygen storage at the internal combustion engine connected exhaust gas aftertreatment system,

4 FIG. 2 is a schematic view of a control circuit for adjusting a temperature change by changing a utilization of an oxygen storage. FIG.

5 FIG. 2 is a schematic view of a third exhaust aftertreatment system which, for example, enables a prevention of fat breakdown by calculating a stored amount of oxygen. FIG.

6 a schematic representation of the prior art of a conventional control of a catalyst also conventionally with oxygen storage by means of a lambda probe, which is arranged at an outlet of the catalyst, and

7 : one opposite 6 resulting changed operation of the catalyst, which acts taking into account a calculated oxygen content as an oxygen storage, based on a two-point control according to the proposed operating method.

1 shows a schematic view of a first exhaust aftertreatment system 1 in an exemplary embodiment. An internal combustion engine 2 is the exhaust aftertreatment system 1 downstream. This has an exhaust system 3 in which, for example, an additional air supply 4 as well as an additional fuel supply 5 is provided. Both feeds 4 . 5 are in front of a first probe 6 in particular upstream of a lambda probe. The first probe 6 in turn, is an exhaust aftertreatment component 7 upstream in the flow direction. The exhaust aftertreatment component 7 has an oxygen storage 8th on. In addition, the exhaust aftertreatment component 7 a catalyst, in particular a controlled catalyst, a NOx storage catalyst, a particulate trap, a sulfur trap and / or have any other component that is capable of one of the internal combustion engine 2 to change the originating exhaust gas. The oxygen storage 8th has a first part 9 and a second part 10 on. These are, for example, separated from each other in different areas of the exhaust aftertreatment component 7 arranged. For example, the first part of the oxygen storage 8th be arranged in a particulate filter, while the second part 10 of the oxygen storage 8th is arranged in a NOx storage catalyst. The particulate filter and the NOx storage catalyst together form, for example, the exhaust aftertreatment component 7 , This is a second probe 11 downstream, which may for example also be a lambda probe. Behind the second probe 11 When viewed in the flow direction, there may be another exhaust aftertreatment component, which may also have an oxygen storage. For example, the second probe 11 not only when balancing the oxygen content of the exhaust aftertreatment component 7 by determining the corresponding air ratio or the oxygen content behind the exhaust aftertreatment component 7 serve. The second probe 11 At the same time, the same signal can preferably be used as the input parameter for the oxygen content or the air ratio for the subsequent exhaust gas aftertreatment component in the context of a calculation or balancing. For this purpose, a further probe not shown here is preferably arranged behind the subsequent exhaust gas aftertreatment component. Furthermore, there is the possibility that in the exhaust aftertreatment component 7 one or more additional probes are present. For example, one or more of these probes may also replace the second probe 11 if it is possible to deduce the oxygen content of the area outside the balance sheet limits via the calculated balance sheet. Via a motor control 12 In particular, the air ratio in the exhaust line, taking into account the oxygen storage 8th to be changed. The engine control 12 is for example with a separate control unit 13 the first exhaust aftertreatment system 1 connected. The control unit 13 For example, it picks up the readings from the various probes and uses them in its own evaluation unit 14 , By means of this, for example, via an oxygen balance over the oxygen storage 8th the current amount of stored oxygen is detected. For example, this value can be sent to the engine controller 12 be passed on. The control unit 13 In turn, it is able, for example, taking into account the determined current amount of oxygen of an exhaust strategy in conjunction with the engine control 12 to be able to adapt. This may include, for example, that an ammonia-containing agent targeted via the control unit 13 is supplied. In particular, the controller 13 together with the engine control 12 capable of switching between rich operation and lean operation in the first exhaust after-treatment system 1 taking into account the oxygen storage 8th to be able to adjust. A functionality of the control unit shown separately 13 However, according to another embodiment, also in an engine control unit of the engine control 12 implemented.

2 shows a schematic view of a second exhaust aftertreatment system 15 , This is a control unit 16 connected, in turn, with the internal combustion engine 2 is coupled. The control unit 16 is preferably an engine control unit, but may also be a separate from the engine control unit arranged control unit. Between the control unit 16 and the internal combustion engine 2 can drive signals 17 as well as sensor signals 18 be replaced. A lambda probe 19 is between the internal combustion engine 2 and a catalyst 20 who has an oxygen storage 8th contains upstream in the flow direction. About the lambda probe 19 a signal characterizing an oxygen content in front of the catalyst 20 the control unit 16 fed. Via a temperature sensor 21 looking in the flow direction behind the catalyst 20 is arranged, a temperature signal is also the control unit 16 fed. By means of this only schematically the most important components of an exhaust aftertreatment system 15 pointing device, it is possible to control the temperature of the oxygen storage 8th perform. In particular, this device allows second exhaust aftertreatment system 15 and internal combustion engine 2 in that a fat-lean cycle can be run, which is influenced by a change in an air ratio and / or a time, a rich and / or lean phase so that the per unit time from the oxygen storage 8th originating amount of oxygen can be changed and thereby a temperature of the oxygen storage 8th and thus also the catalyst 20 regulated or controlled.

3 shows a schematic view of an exemplary exploitation of 2 resulting oxygen storage at a setting of a temperature change of the oxygen storage 8th out 1 respectively. 2 , Shown in an upper first illustration of 3 the air ratio lambda plotted on the y-axis versus time plotted on the x-axis. Under this, the course of a stored amount of oxygen in the oxygen storage is indicated, wherein the parallel to the x-axis, the time axis, extending solid line indicates a maximum oxygen storage capacity of the oxygen storage. Below this, a converted amount of oxygen from the oxygen storage is also plotted over time on the x-axis. Below this, a temperature profile of the oxygen storage or of the catalyst, which contains the oxygen storage by way of example, is indicated over time. In the representations of the 3 are facing each other two different fat-lean cycles. A first fat-lean cycle A is indicated by the dashed line in the uppermost illustration of FIG 3 characterized. A second rich-lean cycle B is shown with a dash-and-dot line. A thin line running parallel to the x-axis gives the air ratio lambda = 1 in the uppermost representation of FIG 3 at. The two fat-lean cycles A, B differ in each case by an amplitude of a change in the respective air ratio delta lambda. Both cycles have in common that the oxygen storage is neither completely filled nor completely emptied. This is apparent from the course of the stored oxygen amount in the oxygen storage, which never exceeds the maximum oxygen storage capacity. In a lean phase, a stored amount of oxygen increases. This is in the period I before. In a subsequent fat phase, the oxygen present in the oxygen storage is reacted with combustible exhaust gas constituents. This is shown in the time phase II. By setting a high amplitude, as shown for example in the second rich-lean cycle B, more oxygen is converted in each fat phase II. As a result, there is a higher heat flow, so that sets a higher temperature rise across the oxygen storage. This is in the lowest representation of the 3 played. While a temperature at an inlet of the oxygen storage remains constant, this changes at the outlet depending on the set air ratio or the change in the air ratio, as shown in the uppermost representation of 3 evident. Taking advantage of this relationship, the temperature of the oxygen storage and thus, for example, a catalyst can be controlled or regulated.

4 shows a schematic view of a possibility of implementing a temperature control based on an action plan for the utilization of the oxygen storage. The action plan sees the internal combustion engine 2 which provides a time-varying air ratio lambda as the actual state. The value of the actual state of the air ratio is on the one hand in an oxygen storage 8th one. From this, a temperature T is detected via a corresponding temperature sensor. This can be the temperature of the oxygen storage 8th and / or a temperature of an exhaust stream at an exit from the oxygen storage 8th For example, a catalyst, a particulate trap or other exhaust aftertreatment component, are detected. The temperature value is used as a controlled variable. This allows a temperature value can be specified, which indicates a desired value of the temperature to be set of the oxygen storage or the exhaust gas aftertreatment component. This setpoint value is predetermined, for example, via the engine control or else via a separate control unit. From the comparison of the controlled variable with the setpoint, the control deviation is determined, which is the input variable of a controller 15 is supplied. From this, the regulator generates an amplitude of the air ratio, preferably in the form of an air ratio change. About a corresponding generator, for example by means of a pulse width modulation generator, from the change in the air ratio delta lambda a desired value of the Air ratio are formed. That is, the corresponding rich-lean cycle provides the desired value of the air ratio, which together with the actual value of the air ratio in a lambda controller 16 the internal combustion engine 2 received.

Alternatively to the 4 resulting schematic temperature control in a closed loop with the required temperature measurement is also possible to use a pure control in which a change in the air ratio is stored in a map or a characteristic.

5 shows an exemplary schematic view of a third exhaust aftertreatment system 22 with an internal combustion engine 2 and a control unit 16 , between which control signals 17 and sensor signals 18 can be exchanged. An oxygen storage 8th For example, in the form of a catalyst is a broadband lambda probe 23 upstream. In the flow direction behind the oxygen storage 8th there is a control probe 24 , The control probe 24 may be a broadband lambda probe or a jump probe. By means of the broadband lambda probe 23 is an air ratio or an oxygen content in the exhaust stream based on a characterizing parameter to the control unit 16 to hand over. From the control probe 24 is also an air ratio or an oxygen-characterizing signal value to the control unit 16 passed. This signal can also represent a jump signal based on the probe used. By means of this embodiment, it is possible, on the one hand via a balance over the oxygen storage 8th a determination of the stored amount of oxygen in the oxygen storage 8th to enable. On the other hand, the structure is suitable, a fat break through the oxygen storage 8th and thus, for example, to prevent the associated catalyst with the resulting H ₂ S emissions, especially in a desulfation.

6 shows a schematic representation of a conventional control of a catalyst of the prior art, which uses a lambda probe disposed at an exit. In the upper illustration of the 6 Again, the air ratio is shown, in the lower part of the 6 the stored amount of oxygen in the catalyst is reproduced. The values are plotted over time. If it is determined via the lambda probe that the air ratio behind the catalyst is greater than 1, a switching point is set by jumping from lean operation to rich operation. If, on the other hand, it is determined via the lambda probe that there is an air ratio of less than 1 behind the catalytic converter, the system switches from rich operation to lean operation. From the lower illustration, the respective switching points are drawn down in dashed lines from the upper illustration. The substoichiometric or superstoichiometric air ratios are preferably set by the fact that the respective stored amount of oxygen in the oxygen storage has been completely removed from the oxygen storage or the storage capacity of the oxygen storage was exceeded. From the upper illustration of the 6 goes to this as a solid line c, the target value of the air ratio in front of the catalyst. In dotted representation a, the actual value of the air ratio is shown in front of the catalyst, while dashed lines, the air ratio after the catalyst b is also registered. This results in the following relationship with respect to the rich-lean cycle, which is controlled by the lambda signal behind the catalyst: In the lean phase I with lambda greater than 1 in front of the catalyst, this and thus the oxygen storage is filled. If oxygen storage is not controlled in this phase, oxygen will not pass through the reservoir and the lambda signal received as oxygen storage after the catalyst will remain at the value of 1. Only when the oxygen reservoir is completely filled can an oxygen breakthrough be detected on the basis of the lambda signal and a fat jump be initiated. In this fat phase II, the memory empties. If a sufficiently high temperature is present here, almost all the reducing agent is converted so that the lambda signal remains at 1 again. After a complete emptying of the oxygen storage, however, there is a reductant breakthrough, which is indicated by the probe. Only when this has been detected by the lambda probe, a lean jump can take place again. By existing in the control system and in the respective actuators inertia occurs here for a certain time reducing agent. In a desulfation this may mean that H ₂ S emerges. With the out 5 On the other hand, it is possible to prevent such an outlet and, in particular, to allow a different type of regulation.

7 shows the opposite 6 resulting catalyst control possible embodiment of a 2-point control of the oxygen storage. Here, the fat-lean cycle is controlled by the stored amount of oxygen, for example, in the catalyst. This allows to prevent fat as well as lean breakthroughs. For this purpose, it is preferable for example to use a 2-point control with a hysteresis. If a certain oxygen threshold is exceeded, a fat jump is initiated. When falling below another threshold, a lean jump occurs. In the case of desulfurization, sufficient oxygen is thus present at all times, which can serve for the oxidation of H ₂ S. From 7 in the lower illustration drawn upper threshold 25 and lower threshold can thus ensure a safe operation in all operating points of the exhaust aftertreatment system with sufficient spacing to a maximum oxygen uptake capacity of the oxygen storage or a depleted state of the oxygen storage. From the upper illustration of the 7 It can be seen that in turn the target value before the catalyst, shown as a dashed line c, as well as the actual value of the air ratio before the catalyst, shown as a dotted line a, to an air ratio of lambda = 1 after the catalyst, taking into account the amount of oxygen in the oxygen storage and thus may result in the exhaust aftertreatment component. In particular, this makes it possible to reliably set a constant air ratio b of lambda = 1 after the catalyst or the exhaust gas aftertreatment component.

Claims (26)

Method for operating a motor vehicle exhaust aftertreatment system ( 1 ), in which an oxygen storage ( 8th ) an exhaust aftertreatment component ( 7 ) Oxygen is supplied and removed and the oxygen storage may have a first and a second part, which are arranged in at least two different exhaust aftertreatment components, wherein - at least one determined by the oxygen storage and its oxygen content determined changing parameters and in a mode of operation of the motor vehicle Exhaust after-treatment system ( 1 ), an oxygen amount in the oxygen storage is calculated by means of an oxygen balance around the oxygen storage, wherein a determination of the respective current oxygen content in the oxygen storage is implemented in an operating strategy, so that a complete emptying of the oxygen storage is avoided, and in the context of a control under use At least one threshold value is adapted to aging, wherein a hysteresis behavior during a cycle change in the Threshold adjustment, wherein a probe is used to determine a temperature of the oxygen storage, whereby a direct coupling of the measured temperature is received in a calculation of the oxygen content of the oxygen storage and this determined value is used over the temperature for checking the oxygen content determined via the oxygen balance, wherein the determination of the temperature of the oxygen storage s is used to change one or more threshold values for influencing a fat-lean cycle according to the temperature-dependent oxygen storage capacity, and wherein - at least one threshold value ( 25 . 26 ) is determined with respect to the determined amount of stored oxygen, at the exceeding of which a cycle change between lean operation and rich operation is triggered or - a lower ( 25 ) and an upper ( 26 ) Threshold value is set with respect to the amount of oxygen and when exceeding or falling short of the respective threshold values, a cycle change between lean operation and rich operation is triggered. A method according to claim 1, characterized in that a ammonia-containing agent specifically via a control unit ( 13 ) is supplied. A method according to claim 1 or 2, characterized in that a cyclical change of a stored amount of oxygen is used for the defined influencing a temperature of an exhaust gas or the oxygen storage. Method according to one of the preceding claims, characterized in that an additional oxygen supply in the motor vehicle exhaust aftertreatment system ( 1 ) takes place as a function of the determined amount of oxygen. Method according to one of the preceding claims, characterized in that a first probe ( 6 ) a continuous measurement of an oxygen content in front of the oxygen storage ( 8th ), while a second probe ( 11 ), in particular a jump probe, determines whether an exhaust gas is rich or lean. Method according to one of the preceding claims, characterized in that received in a regeneration of a particulate filter and / or a NOx storage catalyst, the determined amount of oxygen as a parameter. Method according to one of the preceding claims, characterized in that in a desulfation of an oxide storage, in particular a nitrogen oxide storage, the determined amount of oxygen is received as a parameter. A method according to claim 6 or 7, characterized in that for determining a start of the desulfating and / or the regeneration, the determined amount of oxygen enters as a parameter. A method according to claim 6, 7 or 8, characterized in that the determined amount of oxygen is received as a parameter for determining a period of desulfurization and / or regeneration. Method according to one of the preceding claims, characterized in that a cyclical use of the oxygen storage is used to increase the temperature before a diesel particulate filter regeneration. Method according to one of the preceding claims, characterized in that an internal combustion engine is operated in a rich-lean cycle, wherein a temperature of the oxygen storage ( 8th ) is determined and an operating parameter influencing a speed of an oxygen storage and / or an oxygen removal is changed as a function of the determined temperature. Method according to one of the preceding claims, characterized in that an internal combustion engine is operated in a rich-lean cycle, wherein a temperature of the oxygen storage ( 8th ) is determined and an operating parameter influencing the stored amount of oxygen is changed as a function of the determined temperature. Method according to one of the preceding claims, characterized in that a temperature control or temperature control with respect to the oxygen storage ( 8th ) exhaust aftertreatment component ( 7 ) one per unit of time from the oxygen storage ( 8th ) releasing or receiving oxygen quantity to a temperature adjustment of the exhaust aftertreatment component ( 7 ) changes. Method according to one of the preceding claims, characterized in that during a desulfurization of an oxide storage catalyst at least partially driven a fat-lean cycle and an air ratio in front of and behind the oxide storage catalyst is taken, the oxygen amount is determined and the oxygen storage ( 8th ) is used to avoid a lower and / or superstoichiometry of the air ratio behind the oxide storage catalyst. Exhaust after-treatment system ( 1 ) with an attached internal combustion engine ( 2 ), wherein the internal combustion engine ( 2 ) an engine control ( 12 ) and the exhaust aftertreatment system ( 1 ) at least one regulated catalyst and an oxygen storage ( 8th ), wherein a first probe ( 6 ) in front of the oxygen storage ( 8th ) and a second probe ( 11 ) behind the oxygen storage ( 8th ), wherein at least the first probe ( 6 ) determines an oxygen content characterizing first parameter, and a signal transmission of the first ( 6 ) and the second ( 11 ) Probe recorded parameters to an evaluation unit ( 14 ), and the evaluation unit ( 14 ) with a motor control ( 12 ) is coupled to a control or control unit, which takes into account a fat-lean cycle on the basis of the determined parameters, wherein an amount of oxygen is represented by means of an oxygen balance of the parameters and wherein in a control unit, a threshold value relative to one in the oxygen storage ( 8th ) stored amount of oxygen is present, wherein the internal combustion engine has a method according to one of claims 1 to 14 implemented. Exhaust treatment plant according to claim 15, characterized in that the second probe ( 11 ) is a temperature probe whose parameters are in a control or regulation of a lambda value of the engine control ( 12 ) received. Exhaust treatment plant according to claim 16, characterized in that a rich-lean cycle as a setpoint in a lambda control of the internal combustion engine ( 2 ) received. Exhaust after-treatment system ( 1 ) according to one of the preceding claims, characterized in that the first ( 6 ) and the second ( 11 ) Probe each determine a oxygen content characterizing first parameter, and a signal transmission of the first parameter of the first ( 6 ) and the second ( 11 ) Probe to an evaluation unit ( 14 ), and the evaluation unit ( 14 ) from the first parameters a determination of an oxygen content of the oxygen storage ( 8th ) characterizing second parameter, and the engine control ( 12 ) with an apparatus for adjusting an air ratio in the exhaust aftertreatment system ( 1 ), wherein an adjustment of the air ratio is provided in dependence on the second parameter via the device. Exhaust after-treatment system ( 1 ) according to one of the preceding claims, characterized in that the first probe ( 6 ) is a broadband lambda probe and the second probe ( 11 ) is a jump probe. Exhaust after-treatment system ( 1 ) according to one of the preceding claims, characterized in that the oxygen storage ( 8th ) a first part ( 9 ) and a second part ( 10 ) in one or at least two different exhaust aftertreatment components ( 7 ) are arranged. Exhaust after-treatment system ( 1 ) according to one of the preceding claims, characterized in that the oxygen storage ( 8th ) Is part of a NOx catalyst. Exhaust after-treatment system ( 1 ) according to one of the preceding claims, characterized in that the oxygen storage ( 8th ) Is part of a particulate filter. Exhaust after-treatment system ( 1 ) according to any one of the preceding claims, characterized in that a measuring probe for determining a temperature of the oxygen storage ( 8th ) is provided. Exhaust after-treatment system ( 1 ) according to one of claims 18 to 23, characterized in that at least one control is deposited, which adjusts to the second parameter to trigger a change between rich and lean operation. Exhaust after-treatment system ( 1 ) according to claim 24, characterized in that a control is deposited, which adjusts to the second parameter. Exhaust after-treatment plant according to one of the preceding claims with a motor control ( 12 ), with a control of a fat-lean cycle by controlling an oxygen content of an oxygen storage.

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