DE102016219041A1 - A method for regenerating an exhaust aftertreatment system, in particular a NOx storage catalyst of an autonomously driving vehicle in conjunction with low-pressure exhaust gas recirculation and control device for an exhaust aftertreatment system and vehicle - Google Patents

Abstract

The subject of the application relates to a method for the regeneration of a NOx storage catalyst during the operation of an autonomously driving vehicle. The method uses the control of a transmission gear, an internal combustion engine and an exhaust gas recirculation loop, as well as the possibilities of autonomous driving, so that there are favorable operating conditions for the regeneration of the NOx storage catalyst. The invention further comprises a device designed to carry out the method and a vehicle which comprises a device designed for carrying out the method.

Description

The invention relates to a method for the regeneration of an exhaust aftertreatment system, in particular a NOx storage catalyst during operation of an autonomously driving vehicle.

Internal combustion engines often generate considerable amounts of nitrogen oxides (NO _x ) during operation. In particular, in diesel and petrol engines used in motor vehicles, the amounts of nitrogen oxide in the raw exhaust gas are generally above the permissible limits, so that an exhaust aftertreatment to reduce NO _x emissions is necessary. In many engines, the reduction of nitrogen oxides by the non-oxidized constituents contained in the exhaust gas, namely by carbon monoxide (CO) and unburned hydrocarbons (HC), using a three-way catalyst. However, this method is not available in particular in the case of diesel and Otto lean-burn engines, since the reduction of NO _x does not or hardly occurs due to the high proportion of oxygen in the exhaust gas. Especially in lean-burn gasoline engines, but also in diesel engines therefore a NOx storage catalyst (also "LNT" of English "lean NOx trap") is used according to a common method, which accumulates the nitrogen oxides contained in the exhaust of the engine. If the capacity of the NOx storage catalyst is exhausted, it is usually regenerated by "rich" operation (operation with excess fuel) of the internal combustion engine. A method for regenerating a nitrogen oxide storage catalyst is, for example, in DE 10 2009 014 360 A1 disclosed.

Another commercial measure for the reduction of nitrogen oxide emissions from internal combustion engines is the exhaust gas recirculation. Exhaust gas recirculation systems are usually designed to divert at least a portion of the exhaust gas from an engine exhaust passage to an engine intake passage. Exhaust gas recirculation can reduce engine pump work and NOx emissions in engines with a throttle device. Thus, the exhaust gas recirculation at partial load operation of the internal combustion engine, the throttle for the same engine load is opened to a greater extent. By reducing the throttling of the motor, pumping losses can be reduced, thereby improving the efficiency. With exhaust gas recirculation, the local flame front temperature can be reduced, which reduces an amount of NOx generated during combustion.

By appropriate arrangement of controllable by a control valve, the proportion of recirculated exhaust gas at the charge supplied to the engine is usually variable. In the course of development of internal combustion engines, the realized maximum proportion of recirculated exhaust gas at the charge supplied to the engine has continued to increase. In commercially available systems, for example for diesel engines are shares of 0% to about 60% recirculated exhaust gas depending on the operating point of the internal combustion engine usual. In special versions, up to 100% of the recirculated exhaust gas is possible at the charge supplied to the engine. The proportion of the recirculated exhaust gas to the charge supplied to the engine is also referred to as exhaust gas recirculation rate.

Modern commercially available internal combustion engines, in particular diesel engines, are equipped with one or more exhaust gas turbochargers. In an exhaust gas turbocharger arrangement, the exhaust gas produced by the internal combustion engine is passed through a turbine. The exhaust gas is extracted from the turbine by expansion enthalpy. Typically, a compressor is connected by a shaft to the turbine. The enthalpy extracted from the exhaust gas thus drives the compressor. The compressor compresses the charge to be supplied to the engine before it is fed into the engine.

Depending on the arrangement of the device for exhaust gas recirculation relative to the exhaust gas turbocharger arrangement is called a low-pressure or high-pressure exhaust gas recirculation. If the removal of the recirculated exhaust gas upstream of the exhaust gas turbocharger turbine, one speaks of high-pressure exhaust gas recirculation. If the removal of the recirculated exhaust gas downstream of the turbocharger turbine, one speaks of low-pressure exhaust gas recirculation.

The operating state of an internal combustion engine determines inter alia the exhaust gas volume flow V. _A , the exhaust gas temperature T _A and the air-fuel ratio λ of the exhaust gas flowing through a NOx storage catalyst. These parameters, in particular the air-fuel ratio λ, have an influence on the regeneration of the NOx storage catalytic converter. For regeneration of the NOx storage catalyst, the internal combustion engine is operated with excess fuel (λ <1), which generates a "rich" exhaust gas with high CO and HC content. In this case, the NOx stored in the NOx storage catalyst is converted into harmless carbon dioxide CO ₂ , water H ₂ O and nitrogen N ₂ with hydrocarbons HC and carbon monoxide CO contained in the exhaust gas.

In general, a rich operation of an internal combustion engine produces increased fuel consumption over regular operation. Therefore, as short as possible, rare and efficient regeneration of the NOx storage catalyst are sought.

A "fat" operation of the internal combustion engine at very high speeds and loads for the regeneration of the NOx storage catalyst is unfavorable. Such operating conditions result in very high exhaust gas volume flows and thus flow rates in the NOx storage catalytic converter. At high flow velocities and thus short residence times in the NOx storage catalyst, an incomplete conversion of the HC and CO can occur with the accumulated NOx. The regeneration of the NOx storage catalyst then requires a longer rich engine operation. Usually, therefore, a regeneration of the NOx storage catalyst at low exhaust gas flow rates and thus low speed and load of the internal combustion engine is desired.

Methods are known for the regeneration of NOx storage catalytic converters which use exhaust gas recirculation devices in order to carry out the regeneration of a NOx storage catalytic converter under favorable conditions. These methods are based on the idea of generating a charge with a very rich air-fuel mixture and to pass as many shares of this charge as possible through the NOx storage catalytic converter by using a high exhaust gas recirculation rate. Such methods can be carried out particularly effectively with an exhaust gas recirculation rate of 100%. This accordingly requires a vehicle with exhaust gas recirculation devices that make it possible to completely charge the charge of the internal combustion engine from recirculated exhaust gas.

However, such methods for the regeneration of NOx storage catalysts using a high exhaust gas recirculation rate are subject to restrictions. Operation of an internal combustion engine with delivery of mechanical power at 100% exhaust gas recirculation rate is possible only extremely briefly until the free oxygen O ₂ present in the charge has been used up for combustion. This is at a low air-fuel ratio, as necessary for the regeneration of a NOx storage catalyst, theoretically after a cycle of the internal combustion engine and thus in vehicle engines in operation after a fraction of a second of the case.

Accordingly, in practice, a regeneration of a NOx storage catalyst with rich air-fuel mixture using high exhaust gas recirculation rates only in overrun mode is possible. Push mode means, the internal combustion engine is driven by external mechanical energy supply. Such a pushing operation occurs, for example, when in a conventional vehicle with an internal combustion engine, the driver completely takes the foot of the accelerator pedal while driving and does not actuate a possibly existing clutch. The vehicle then decelerates by the braking action of the internal combustion engine, the internal combustion engine is driven by the kinetic energy of the movement of the vehicle.

A disadvantage for the implementation of such processes for the regeneration of a NOx storage catalyst with a rich air-fuel mixture using high exhaust gas recirculation rates is the previously unknown duration of such a phase of the overrun operation. The regeneration of a NOx storage catalyst usually takes 5-10 seconds. If during the operation of a vehicle by a control device of the internal combustion engine and the exhaust gas recirculation device, both a coasting operation and a regeneration requirement of the NOx storage catalyst is determined, this can initiate a regeneration operation.

To initiate the regeneration operation, a charge with rich air-fuel mixture is generated and the charge of the internal combustion engine is formed by controlling the exhaust gas recirculation device completely from recirculated exhaust gas.

The regeneration of the NOx storage catalyst begins. However, if the driver stops the overrun operation before the completion of a complete regeneration of the NOx storage catalytic converter because, for example, the vehicle is to be accelerated, the regeneration must be aborted with the exhaust gas completely recirculated. The fat charge generated by using fuel "gets lost" and thus increases fuel consumption.

The DE 101 58 480 C1 discloses a method and apparatus for operating an engine of a motor vehicle. In a first step, driving condition parameters of the engine and / or of the motor vehicle are recorded over a predetermined period of time. This is followed by determination of probabilities of parameters for the future operation of the engine as a function of the detected driving state parameters. Finally, setting of operating parameters of the engine takes place as a function of the ascertained probability values for the parameters.

By definition, an autonomously driving vehicle can move in its surroundings without intervention by a driver. A driver or passenger of the vehicle specifies a destination of the ride and must then perform no further actions. The autonomously driving vehicle determines a route from the current location to the destination and drives it off automatically. That means the autonomously driving vehicle chooses its own speed and direction and reacts to traffic events. For this purpose, autonomous vehicles use various sensors, communication means and control devices.

For example, GPS data can be used by an autonomous vehicle to determine a current position and speed of the vehicle. For example, via a mobile network, an autonomously driving vehicle can be provided electronically with local road maps or data on the current traffic situation. Also, an autonomous vehicle may communicate with other vehicles equipped with appropriate facilities to detect traffic events early and to coordinate driving profiles.

Autonomous vehicles typically perceive their environment through various sensors that may be based, for example, on visible light, infrared radiation or radar radiation. By means of appropriate electronic data processing devices and control devices, the available information is processed and the corresponding components of the vehicle such as steering, brakes, internal combustion engine and transmission gear are controlled.

An example of an autonomously driving vehicle is in DE 39 12 353 A1 disclosed.

The object of the invention is to provide an improved method for the regeneration of an exhaust aftertreatment system of a particularly lean-burned internal combustion engine, which is operable in an autonomously driving vehicle.

A further object of the invention is to provide a corresponding control device for carrying out the method and a vehicle comprising such a control device.

The objects set out above are achieved by a method and by a control device having the features of the independent claims 1 to 16 as well as a vehicle comprising such a control device.

• A: Prüfen eines Regenerationsbedarfs des NOx-Speicherkatalysators; dies kann zum Beispiel durch Vergleich einer rechnerisch ermittelten NOx-Beladung mit einem NOx-Beladungs-Schwellwert erfolgen. Durch diese Prüfung können unnötige Regenerationen vermieden werden.
• B: Wenn ein Regenerationsbedarf des NOx-Speicher-Katalysators festgestellt wurde, Festlegen eines SOLL-Wertfensters für zumindest einen Betriebsparameter des NOx-Speicher-Katalysators. Beispielsweise kann für ein Luft-Kraftstoff-Verhältnis λ des Abgases stromaufwärts des NOx-Speicher-Katalysators und für einen Abgasvolumenstrom (V ._A) durch den NOx-Speicher-Katalysators ein SOLL-Wertfenster festgelegt werden. Aber auch für die Temperatur (T) des NOx-Speicher-Katalysators die Temperatur T_A des Abgases (5), welches durch den NOx-Speicher-Katalysators (1) strömt, kann ein Sollwert-Fenster festgelegt werden.

Disclosed is a method for the regeneration of a NOx storage catalyst of an autonomously driving vehicle. The autonomously driving vehicle comprises an internal combustion engine and an exhaust gas recirculation device. The method comprises the following steps:

• A: checking a regeneration requirement of the NOx storage catalytic converter; This can be done for example by comparing a calculated NOx load with a NOx loading threshold. This test helps to avoid unnecessary regeneration.
• B: When a regeneration demand of the NOx storage catalyst has been determined, setting a target value window for at least one operating parameter of the NOx storage catalyst. For example, for an air-fuel ratio λ of the exhaust gas upstream of the NOx storage catalyst and for a volumetric flow of exhaust gas (V, _A ) through the NOx storage catalyst, a set value window may be set. But also for the temperature (T) of the NOx storage catalyst, the temperature T _{A of} the exhaust gas ( 5 ), which by the NOx storage catalyst ( 1 ), a setpoint window can be set.

By determining these desired value windows, a regeneration of the NOx storage catalyst is ensured in a favorable operating range. This promotes a complete and effective regeneration.

• C: Ermitteln eines Betriebsprofils des Verbrennungsmotors und der Abgasrückführeinrichtung, in dem der IST-Wert des zumindest einen Betriebsparameters des NOx-Speicher-Katalysators das SOLL-Wertfenster des zumindest einen Betriebsparameters des NOx-Speicher-Katalysators durchläuft.

If a desired value window is defined for the exhaust gas volume flow (V _A ) by the NOx storage catalytic converter, this can be limited by an upper threshold value for the exhaust gas volume flow rate (V _A ). This ensures that the residence times of the rich exhaust gas in the NOx storage catalyst are sufficiently long to allow the fullest possible implementation of the CO and HC in the exhaust gas.

• C: Determining an operating profile of the internal combustion engine and of the exhaust gas recirculation device, in which the actual value of the at least one operating parameter of the NOx storage catalytic converter passes through the target value window of the at least one operating parameter of the NOx storage catalytic converter.

For example, the operating profile of the internal combustion engine and the exhaust gas recirculation device may include combinations of a current load (M _D ), a current air-fuel ratio (λ), a current speed (n), and an exhaust gas recirculation rate (EGR%). These are a set of parameters that have a particularly large influence on the operating parameters of the NOx storage catalyst.

In particular, the operating profile of the internal combustion engine and the exhaust gas recirculation device may be an operating profile in which the air-fuel ratio (λ) is a rich air-fuel ratio (λ <1). This is conducive to regeneration of the NOx storage catalyst.

• D: Ermitteln eines von dem Fahrzeug zu durchfahrenden Fahrprofils des autonom fahrenden Fahrzeugs (2), in welchem der Verbrennungsmotor und die Abgasrückführeinrichtung innerhalb des in (C) ermittelten Betriebsprofils betrieben werden. Das von dem Fahrzeug zu durchfahrende Fahrprofil kann beispielsweise eine Geschwindigkeit des autonom fahrenden Fahrzeuges und die aktivierte Gangstufe eines Übersetzungsgetriebes des autonom fahrenden Fahrzeuges umfassen. Wenn das Übersetzungsgetriebe ein stufenloses CVS-Getriebe ist, dann bezeichnet die Gangstufe eine gewählte Übersetzung aus dem Übersetzungsbereich des CVS-Getriebes. Dadurch, dass ein Fahrprofil ermittelt wird, in welchem der Verbrennungsmotor und die Abgasrückführeinrichtung innerhalb des in (C) ermittelten Betriebsprofils betrieben werden, liegen während des Fahrprofils günstige Bedingungen für eine effiziente und vollständige Regeneration des NOx-Speicherkatalysators vor.
• E: Durchfahren des in (D) ermittelten Fahrprofils. Wenn das ermittelte Fahrprofil durchfahren wird, wird eine vollständige und effiziente Regernation des NOx-Speicherkatalysators unterstützt.

Also, the operating profile of the internal combustion engine and the exhaust gas recirculation device may be an operating profile in which exhaust gas recirculated to the internal combustion engine is supplied (EGR%> 0). As described above, this is particularly advantageous for an efficient regeneration of the NOx storage catalyst in terms of fuel consumption.

• D: Determining a driving profile of the autonomously driving vehicle to be traversed by the vehicle ( 2 ), in which the internal combustion engine and the exhaust gas recirculation device are operated within the operating profile determined in (C). The driving profile to be traveled by the vehicle can include, for example, a speed of the autonomously driving vehicle and the activated gear stage of a transmission of the autonomously driving vehicle. If the transmission gear is a continuously variable CVS transmission, then the gear stage designates a selected gear ratio from the transmission range of the CVS transmission. By determining a driving profile in which the internal combustion engine and the exhaust gas recirculation device are operated within the operating profile determined in (C), favorable conditions for efficient and complete regeneration of the NOx storage catalytic converter are present during the driving profile.
• E: Passing through the travel profile determined in (D). If the determined driving profile is passed through, a complete and efficient regeneration of the NOx storage catalytic converter is supported.

In the method according to the invention, the operating profile of the internal combustion engine and the exhaust gas recirculation device can be an n-dimensional parameter space which contains only parameter sets whose application describe an operation of the internal combustion engine and the exhaust gas recirculation device, in which the at least one operating parameter of the NOx storage catalyst in the moves to the desired value window selected for this operating parameter.

For example, the operating profile of the internal combustion engine and exhaust gas recirculation means may include combinations of instantaneous load (M _D ), instantaneous air-fuel ratio (λ), instantaneous speed (n), and exhaust gas recirculation rate (EGR%) present in an air-fuel Ratio λ of the exhaust gas upstream of the NOx storage catalyst and an exhaust gas volume flow (V _A ) by the NOx storage catalyst resulting in the target value window set in step (B). This ensures that the internal combustion engine and the exhaust gas recirculation device are operated in such a way that favorable conditions prevail for the regeneration of the NOx storage catalytic converter.

The operating profile of the internal combustion engine and the exhaust gas recirculation device can in particular be an n-dimensional parameter space which exclusively contains parameter sets whose application describe an operation of the internal combustion engine and the exhaust gas recirculation device in which the at least one operating parameter of the NOx storage catalytic converter reaches its destination without interruption a complete regeneration of the NOx storage catalyst moves in the selected for this operating parameter desired value window. Thus, an incomplete regeneration of the NOx storage catalyst is avoided, which is advantageous for the fuel consumption of the vehicle.

In the context of the method according to the invention, a driving profile can be set as the driving profile of the autonomously driving vehicle, in which the internal combustion engine and the exhaust gas recirculation device are operated in the operating profile selected for them in process step (C). In such a driving profile, the regeneration of the NOx storage catalyst is advantageously carried out effectively.

To achieve this, the speed of the vehicle and the gradient of the speed of the vehicle only take on values, the resulting loads M _D and engine speeds within one of combinations of an activated ratio of the vehicle and the n-dimensional parameter space of the selected operating profile of the internal combustion engine and the exhaust gas recirculation parameter space lying. The use of this rule facilitates the determination of a driving profile in which the internal combustion engine and the exhaust gas recirculation device are operated during the driving profile in the operating profile intended for them.

A further embodiment of the method according to the invention uses a distance between the autonomously driving vehicle and a vehicle driving ahead in the road as a variable parameter in order to determine a driving profile. Even in such a driving profile, the speed of the vehicle and the gradient of the speed of the vehicle only take values, the resulting loads M _D and engine speeds within one of combinations of an activated gear ratio of the vehicle and the n-dimensional parameter space of the selected operating profile of the internal combustion engine and the exhaust gas recirculation parameter space lying.

The use of the distance between the autonomously driving vehicle and a road ahead driving vehicle as a variable parameter supports the determination of a driving profile in which the internal combustion engine and the exhaust gas recirculation device are operated during the driving profile in the specific operating profile for them.

The method according to the invention can also be designed so that electronically provided information is taken into account Adjust driving profile. Such information may relate to the traffic situation on possible routes of the autonomously driving vehicle. The use of this information supports the determination of a driving profile in which the internal combustion engine and the exhaust gas recirculation device are operated during the driving profile in the operating profile intended for them.

The information provided electronically to determine the operating profile (C) can therefore comprise at least information transmitted by a traffic control system, for example information about the route and / or information about the traffic situation. The information transmitted by the traffic control system can be transmitted to the vehicle via traffic lights. It is also possible to use for determining the operating profile (C) at least information that has been exchanged with other autonomously driving vehicles.

In a further embodiment, the method according to the invention can be designed so that information exchanged with other autonomously driving vehicles is used to set a driving profile. Thus, on the one hand, information that is available to other vehicles earlier in time than the autonomously driving vehicle executing the process can be taken into account when determining the driving profile.

Also defined by other vehicles driving profiles can be used to determine a separate driving profile. Various autonomously driving vehicles can thus coordinate with each other, for example, to set advantageous fuel-efficient driving profiles. Overall, the consideration of the exchange of information between autonomous vehicles supports the determination of a driving profile in which the internal combustion engine and the exhaust gas recirculation device are operated during the driving profile in the operating profile intended for them.

The process according to the invention can also be designed so that information is exchanged with traffic light systems (colloquially traffic lights). For example, information about impending traffic light phases can be advantageously used to determine driving profiles in which the internal combustion engine and the exhaust gas recirculation device are operated during the driving profile in the operating profile intended for them.

Part of the disclosure is also a control device for operating an autonomously driving vehicle, which is designed for application of the method according to the invention. Among other things, the control device according to the invention can control the internal combustion engine, the transmission gear, and the exhaust gas recirculation device and determine operating parameters.

Another aspect of the invention is an autonomously driving vehicle comprising an internal combustion engine, a NOx storage catalyst, a transmission gear, and an exhaust gas recirculation device comprising a control device according to the invention.

Further features and advantages will be apparent from the following detailed description of an embodiment of the invention. The embodiment will be explained in more detail with reference to the figures. It shows:

1 highly schematic of a vehicle according to the invention; and

2 a method according to the invention

1 shows a highly schematic representation of an inventive autonomously driving vehicle by way of example 2 , which is designed to carry out a method according to the invention. Such an autonomously driving vehicle 2 includes at least one NOx storage catalyst 1 , an internal combustion engine 3 , an exhaust gas recirculation device 8th , a translation gearbox 4 and a control device according to the invention 10 , In this exemplary embodiment, the autonomous vehicle includes 2 also a turbine 7 , and a compressor 9 ,

In the internal combustion engine 3 It can be a commercial diesel or gasoline engine. These can be designed with various combustion and mixture treatment processes and operated with different fuels. For the present invention of particular relevance are internal combustion engines 3 which are at least temporarily operated in lean operation (with excess air) and with fuels from hydrocarbon compounds. Such internal combustion engines 3 encounter exhaust 5 out, which contains NOx. Examples of this are commercially available passenger car and truck diesel engines.

NOx storage catalysts 1 For example, in conjunction with commercially available lean-burn internal combustion engines 3 installed in vehicles. They are in the exhaust system downstream of the internal combustion engine 3 arranged and are accordingly of the exhaust gas 5 that of the internal combustion engine 3 is expelled, flows through. NOx storage catalysts 1 can also be integrated into other components for exhaust aftertreatment, for example particulate filters.

Between internal combustion engine 3 and NOx storage catalyst 1 is the turbine 7 in the exhaust 5 arranged. It extracts the exhaust gas 5 enthalpy through expansion and provides the extracted enthalpy as a mechanical turbo-supercharger energy. With the mechanical turbocharger energy is going through a shaft with the turbine 7 connected compressors 9 driven. The compressor 9 compresses a the internal combustion engine 3 supplied charge 12 ,

This arrangement of turbine 7 and compressors 9 corresponds to a commercial exhaust gas turbocharger, as it belongs in particular to the standard equipment of modern diesel engines. Of course, the method according to the invention can also be used in vehicles without an exhaust gas turbocharger. Between compressors 9 and internal combustion engine 3 can be arranged other components such as heat exchangers or throttle valves. However, this has no direct relevance for the method according to the invention.

The exhaust gas recirculation device 8th is designed so that it has variable proportions of the exhaust gas 5 downstream of the NOx storage catalyst 1 and can redirect these upstream of the compressor 9 in the internal combustion engine 3 supplied charge 12 can initiate. So can the engine 3 supplied charge 12 from variable proportions of fresh air 11 and exhaust 5 be assembled. Exhaust gas recirculation systems are of particular relevance to the process according to the invention 8th that allow the internal combustion engine 3 supplied charge 12 completely made of exhaust gas 5 which corresponds to an exhaust gas recirculation rate (EGR%) of 100%.

The exhaust gas recirculation device 8th is in the in 1 exemplified example designed as low pressure exhaust gas recirculation. Other embodiments are possible as long as the removal of the recirculated portion of the exhaust gas 5 downstream of the NOx storage catalyst 1 takes place and high exhaust gas recirculation rates, ideally 100%, are possible. The exhaust gas recirculation device 8th may include one or more valves and one or more heat exchangers. However, the exact execution is not relevant to the process according to the invention.

A mechanical energy 6 is from the combustion engine 3 generated and to the transmission gear 4 directed. The transmission gear sets those of the internal combustion engine 3 generated mechanical energy to a selectable speed level and passes it to the drive wheels of the vehicle on. The transmission gear can be designed, for example, as a typical automatic transmission with planetary gear sets, as an automated manual transmission or as a CVS transmission.

Between internal combustion engine 3 and transmission gear 4 For example, a clutch or a torque converter can be arranged. For the present invention, the exact design is irrelevant as long as various mechanical translations are provided and the transmission gear 4 by the control device 10 can be controlled.

In the autonomously driving vehicle 2 it can be a car or truck. But training as a watercraft (boat or ship) or as a motorcycle would be theoretically conceivable.

2 shows an example of a method according to the invention. In a step A, it is first checked whether a regeneration requirement for the NOx storage catalyst 1 is present. This can be done, for example, by comparing a calculated NOx load with a threshold value. Regeneration is advantageous only if such a need for regeneration is identified, otherwise unnecessary fuel consumption is caused.

If a regeneration requirement has been determined, in a step B a setpoint value window for at least one operating parameter of the NOx storage catalyst is determined 1 established. For example, a target value window for an exhaust gas volume flow (V _A ) could be provided by the NOx storage catalyst 1 from 100 cubic meters / hour to 180 cubic meters / hour, for an air-fuel ratio λ of 0.85 to 0.9, and a temperature of the exhaust gas of 300 ° Celsius to 400 ° Celsius.

When determining the target value windows, among other things, the structural conditions as well as the chemical properties of the NOx storage catalytic converter must be taken into account. If these are known and taken into account, SOLL value windows can be used for the operating parameters of the NOx storage catalyst 1 that promote efficient and complete regeneration.

For example, with known geometry of the NOx storage catalyst 1 an exhaust gas volumetric flow threshold value can be determined above which the conversion of the HC and CO fractions of the exhaust gas 5 due to a short residence time in the NOx storage catalyst 1 unfavorably incomplete. Thus, for example, an upper limit of the target value window for the exhaust gas volume flow V. _A defines.

A lower limit of the target value window for the exhaust gas volume flow V. _A can for example from fluidic conditions within of the NOx storage catalyst 1 result. Below a threshold value of the exhaust gas volumetric flow V. _A could be some areas of the NOx storage catalyst 1 are not sufficiently flowed through. Also, below a threshold value of the exhaust gas volume flow V. _A results in an impractically long regeneration time of, for example, more than 10 seconds.

In a step C, an operating profile for the internal combustion engine 3 and the exhaust gas recirculation device 8th determined in operating parameters for the NOx storage catalyst 1 result, which lie within the specified in step B setpoint value window. The parameter air-fuel ratio λ can, for example, directly from the specified setpoint value range for the operating parameters of the NOx storage catalyst 1 for the operating profile of the internal combustion engine 3 be taken over.

Since the inventive method to the most effective regeneration of the NOx storage catalyst 1 is aimed primarily at operating profiles for the internal combustion engine 3 and the exhaust gas recirculation device 8th relevant, which have a high exhaust gas recirculation EGR%, preferably 100%, and a rich air-fuel mixture λ. An operating profile for the internal combustion engine 3 and the exhaust gas recirculation device 8th For example, it may include the parameters EGR% = 100% and air-fuel mixture λ = 0.9.

If the charge 12 of the internal combustion engine 3 completely composed of recirculated exhaust gas (EGR% = 100%), the internal combustion engine can 3 do not give off any mechanical energy. The load M _D must therefore be negative, the internal combustion engine 3 must therefore be moved by an external torque. The torque may be from the kinetic energy, or potential energy during downhill driving, of the vehicle 2 be generated. The moment has to be big enough, the friction and the charge cycle of the internal combustion engine 3 to overcome.

The value of the parameter Last M _D therefore depends on the structural design of the internal combustion engine 3 among other things its speed and the design and setting of all charge exchange organs. The charge exchange devices comprise the exhaust gas recirculation device 8th , Compressor 9 and turbine 7 and all connection lines. In the example, the parameter range is between -10Nm and -20Nm.

If EGR% = 100% is set, this results in the parameter speed n of the internal combustion engine 3 upper and lower threshold values mainly from the limits of the target value window for the exhaust gas volume flow V. _A. Other influences on the exhaust gas volume flow V. _A includes the setting of a possibly existing throttle or a variable valve train. For example, the range for the parameter speed n of the internal combustion engine 3 between 1000 1 / min and 2500 1 / min.

Because the load of the internal combustion engine 3 is negative and therefore from the kinetic or potential energy of the vehicle 2 is generated, a constant or increasing speed during the regeneration operation only when driving downhill or strong tailwind for the vehicle 2 possible. This is taken into account when determining the engine operating profile.

Finally, for method step C is one or more plausible operating profiles for the internal combustion engine 3 and the exhaust gas recirculation device 8th determine which in a complete regeneration of the NOx storage catalyst 1 result. Complete regeneration means everything in the NOx storage catalyst 1 accumulated NOx is fully implemented. It would be conceivable, for example, a linear declining speed curve of 2500 1 / min after 1500 1 / min over a period of 10 seconds at EGR% = 100% and an air-fuel ratio λ = 0.9.

In step D of the exemplary representation of the method according to the invention, a driving profile is determined that of the autonomously driving vehicle 2 to pass through and in which the internal combustion engine 3 and the exhaust gas recirculation device 8th be operated in the specified in step C operating profile.

The on the vehicle 2 acting acceleration includes the components of the driving resistances including resultant of any downgrade force and wind speeds as well as by the transmission gear 4 translated load M _{D of} the internal combustion engine 3 , In the example shown, the driving profile is the speed of the vehicle 2 and setting the gearbox 4 set so that the resulting acceleration is the speed of the engine 3 at the parameters specified in method step C for internal combustion engine 3 and exhaust gas recirculation device 8th drop from 2500 rpm to 1500 rpm within 10 seconds. Such a determination is based on known driving resistances and driving distance of the vehicle 2 ,

To determine such a driving profile, the distance of the autonomously moving vehicle 2 to be used as a variable parameter to a preceding one. For example, the autonomously driving vehicle can temporarily drive closer to a vehicle in front in order to increase the kinetic energy due to the temporarily increased speed to have a regeneration available. During regeneration, it can then fall back to a greater distance.

In order to support the determination of such a driving profile, in addition to electronically provided information about the geographical conditions of the route of the autonomously driving vehicle 2 With gradients, gradients and possible speeds also more information can be used. For example, electronic information about the traffic situation can be used to ensure the feasibility of the driving profile.

It is also possible to exchange information with other vehicles. When it comes to autonomously driving vehicles, for example, driving profiles of other autonomously driving vehicles can be considered and driving profiles can be synchronized between vehicles. It is also possible to exchange information with traffic lights (traffic lights). For example, pending red or green phases of a traffic light can be taken into account.

Overall, such a driving profile can be determined, which supports a complete and effective regeneration of the NOx storage catalytic converter and in an autonomously driving vehicle 2 surrounding traffic is feasible.

In method step D, the driving profile determined in C is determined by the autonomously driving vehicle 2 passed through. While the determined driving profile is traversed, the NOx storage catalytic converter 1 regenerated.

A control device according to the invention 10 is designed to monitor and perform a method according to the invention. For this purpose, the control device comprises 10 electronic circuits, data carriers and input and output interfaces. The control device 10 is adapted to the internal combustion engine 3 , the transmission gear 4 and steering and braking of the autonomously driving vehicle 2 head for. The control device 10 can also be used with other control devices of the autonomously driving vehicle 2 communicate, be integrated in or include these.

The control device 10 may also be adapted to carry out an electronic exchange of information, for example via mobile networks, with other vehicles or traffic lights.

By the process according to the invention, the regeneration of the NOx storage catalyst 1 by using an exhaust gas recirculation device 8th and the degrees of freedom of an autonomously driving vehicle 2 advantageously carried out effectively, since it is always carried out under advantageous conditions, which are continuously present until a complete regeneration. Thus, the fuel consumption and pollutant emissions of the autonomously driving vehicle 2 be reduced to a vehicle with a normal regeneration process for a NOx storage catalyst.

LIST OF REFERENCE NUMBERS

1

 NOx storage catalyst

2

 Autonomous vehicle

3

 internal combustion engine

4

 up gear

5

 exhaust

6

energy

7

 turbine

8th

 Exhaust gas recirculation device

9

 compressor

10

 control device

11

 fresh air

12

 charge

λ

 Air-fuel ratio

AGR%

 Exhaust gas recirculation rate

M _D

 Load of the internal combustion engine

n

 rotation speed

T

 Temperature of the NOx storage catalyst

V. _A

 Exhaust gas volume flow

T _A

 exhaust gas temperature

A, A ', A ", B, C, D, E, F

 Steps of the procedure

QUOTES INCLUDE IN THE DESCRIPTION

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Cited patent literature

• DE 102009014360 A1 [0002]
• DE 10158480 C1 [0016]
• DE 3912353 A1 [0020]

Claims (19)

Process for the regeneration of a NOx storage catalyst ( 1 ) of an autonomous vehicle ( 2 ) with an internal combustion engine ( 3 ) and an exhaust gas recirculation device ( 8th ), comprising the following steps: - A: checking a regeneration requirement of the NOx storage catalyst ( 1 ); B: When a regeneration requirement of the NOx storage catalyst ( 1 ), setting a desired value window for at least one operating parameter of the NOx storage catalyst ( 1 ), - C: determining an operating profile of the internal combustion engine ( 3 ) and the exhaust gas recirculation device ( 8th ), in which the actual value of the at least one operating parameter of the NOx storage catalyst ( 1 ) the desired value window of the at least one operating parameter of the NOx storage catalyst ( 1 goes through; D: determining one of the vehicle ( 2 ) to be traveled driving profile of the autonomously driving vehicle ( 2 ), in which the internal combustion engine ( 3 ) and the exhaust gas recirculation device ( 8th ) are operated within the operating profile determined in (C); - E: driving through the driving profile determined in (D). The method of claim 1, wherein the at least one operating parameter of the NOx storage catalyst ( 1 ) at least one parameter of air-fuel ratio λ of the exhaust gas upstream of the NOx storage catalyst (FIG. 1 ), Temperature (T) of the NOx storage catalyst ( 1 ), Exhaust gas volume flow (V _A ) through the NOx storage catalyst ( 1 ) and temperature T _{A of} the exhaust gas ( 5 ), which through the NOx storage catalyst ( 1 ) flows. Method according to one of the preceding claims, in which the parameters of the operating profile of the internal combustion engine ( 3 ) and the exhaust gas recirculation device ( 8th ) comprise a current load (M _D ), a current air-fuel ratio (λ), a current speed (n) and an exhaust gas recirculation rate (EGR%). Method according to one of the preceding claims, in which the driving profile determined in (D) determines the speed of the autonomously driving vehicle ( 2 ) and the activated gear ratio of a transmission ( 4 ). Method according to one of the preceding claims, in which the operating profile of the internal combustion engine ( 3 ) and the exhaust gas recirculation device ( 8th ) is an operating profile in which the air-fuel ratio (λ) is a rich air-fuel ratio (λ <1). Method according to one of the preceding claims, in which the operating profile of the internal combustion engine ( 3 ) and the exhaust gas recirculation device ( 8th ) is an operating profile in which the internal combustion engine ( 3 ) recirculated exhaust gas is supplied (EGR%> 0). Method according to one of claims 2 to 6, wherein the at least one operating parameter of the NOx storage catalyst ( 1 ) at least the exhaust gas volume flow (V, _A ) through the NOx storage catalyst ( 1 ) and the setpoint window defined in method step (C) is a setpoint window which is dependent on an upper threshold value for the exhaust gas volume flow (V _A ) by the NOx storage catalytic converter ( 1 ) is limited. Method according to one of the preceding claims, in which the operating profile of the internal combustion engine ( 3 ) and the exhaust gas recirculation device ( 8th ) is an n-dimensional parameter space containing only parameter sets whose application is an operation of the internal combustion engine ( 3 ) and the exhaust gas recirculation device ( 8th ) in which the at least one operating parameter of the NOx storage catalyst ( 1 ) in the SETPOINT value window selected for this operating parameter. A method according to claim 8, characterized in that the at least one operating parameter of the NOx storage catalyst ( 1 ) without interruption until a complete regeneration of the NOx storage catalyst ( 1 ) in the SETPOINT value window selected for this operating parameter. Method according to one of Claims 8 to 9, in which the internal combustion engine ( 3 ) and the exhaust gas recirculation device ( 8th ) are operated in the operating profile selected for them in method step (C) by using as the driving profile of the autonomously moving vehicle ( 2 ) a driving profile is set, in which the speed of the vehicle ( 2 ) and the gradient of the speed of the vehicle ( 2 ) only assume values whose resulting loads M _D and speeds of the internal combustion engine ( 2 ) within one of combinations of an activated gear ratio of the transmission ( 4 ) and the n-dimensional parameter space of the selected operating profile of the internal combustion engine ( 3 ) and the exhaust gas recirculation device ( 8th ) are located parameter space. A method according to claim 10, characterized in that for setting the driving profile, a distance to a vehicle driving ahead in the vehicle is used as a variable parameter. Method according to one of claims 10 to 11, characterized in that for the Setting the driving profile electronically provided information will be considered. A method according to claim 12, characterized in that the electronically provided information for determining the operating profile (C) comprise at least information transmitted by a traffic control system. A method according to claim 13, characterized in that the information transmitted by the traffic control system information includes at least information about the route. Method according to claim 13 or 14, characterized in that the information transmitted by the traffic control system comprises at least information about the traffic situation. Method according to one of claims 13 to 15, characterized in that the traffic control system transmitted information about traffic lights to the vehicle ( 2 ). Method according to one of claims 12 to 16, characterized in that the electronically provided information for determining the operating profile (C) at least include information that has been exchanged with other autonomously driving vehicles. Control device ( 10 ) for the operation of an autonomous vehicle ( 2 ) including the control of an internal combustion engine ( 3 ), the control of a transmission gear ( 4 ), the control of the exhaust gas recirculation device ( 8th ) and the regeneration of a NOx storage catalyst ( 1 ) during operation of the autonomous vehicle ( 2 ), characterized in that the control device ( 10 ) is designed for carrying out the method according to one of the preceding claims. Autonomous vehicle ( 2 ) comprising an internal combustion engine ( 3 ), a NOx storage catalyst ( 1 ), a transmission gear ( 4 ) and an exhaust gas recirculation device ( 8th ) characterized in that it comprises a control device ( 10 ) according to claim 16.

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