Method for regenerating exhaust gas aftertreatment components of an internal combustion engine and exhaust gas aftertreatment device for an internal combustion engine

Abstract

A method for exhaust aftertreatment of a turbocharged, spark-ignition internal combustion engine (10), comprising a fresh air duct (12) and an exhaust duct (20), wherein a compressor (14) driven by a turbine (26) arranged in the exhaust duct (20) for compressing the fresh air is provided in the fresh air duct (12), and a secondary air duct (16) is provided downstream of the compressor (14), which connects the fresh air duct (12) to the exhaust duct (20) and opens into the exhaust duct (20) upstream of the turbine (26), wherein a three-way catalyst (22) is arranged in the exhaust duct (20) and a particulate filter (24) is arranged downstream of the three-way catalyst (22), comprising the following processes: - Determination of the loading status of the particulate filter (24), - if the loading condition requires regeneration of the particulate filter (24), raising the exhaust gas temperature to a regeneration temperature of the particulate filter (24) by at least temporarily adjusting the mixture formation for the combustion engine (10) to a substoichiometric (rich) air-fuel ratio (λ) E <1) and at least temporarily simultaneous introduction of secondary air into the exhaust duct (20) upstream of the turbine (26) and upstream of the three-way catalyst (22), wherein - the unburned components of a combustion mixture of the internal combustion engine (10) are exothermically converted by the secondary air in the exhaust channel (20), and - during a regeneration phase of the particulate filter (24) the secondary air quantity is increased to such an extent that a superstoichiometric air-fuel ratio (λ) is present in the exhaust gas channel (20) before entering the particulate filter (24). M>1) so that soot on the particulate filter (24) is oxidized by the excess oxygen.

Description

[0001] The invention relates to a method for exhaust aftertreatment of a turbocharged, spark-ignition internal combustion engine and to an exhaust aftertreatment device for carrying out such a method according to the independent claims.

[0002] The continuously tightening of emissions legislation places high demands on vehicle manufacturers, which are met through appropriate measures to reduce raw engine emissions and through suitable exhaust aftertreatment. With the introduction of EU6 legislation, a limit for particle number is prescribed for gasoline engines, which in many cases necessitates the use of a gasoline particulate filter (GPF). During driving, such a GPF becomes loaded with soot. To prevent the exhaust backpressure from increasing too much, this GPF must be regenerated continuously or periodically. To carry out thermal oxidation of the soot retained in the GPF with oxygen, a sufficiently high temperature level, combined with the simultaneous presence of oxygen in the exhaust system of the gasoline engine, is required.Since modern gasoline engines are normally operated without excess oxygen at a stoichiometric air-fuel ratio (λ=1), additional measures are required. These measures include, for example, increasing the temperature by adjusting the ignition timing, temporarily leaning out the mixture, injecting secondary air into the exhaust system, or a combination of these measures. Currently, retarding the ignition timing in combination with leaning out the mixture is preferred, as this method requires no additional components and can supply a sufficient amount of oxygen at most operating points of the gasoline engine.

[0003] Such a method is known, for example, from DE 10 2013 220 899 A1. This method employs lambda control for the gasoline engine, whereby the air-fuel ratio for particulate filter regeneration is adjusted from a stoichiometric air-fuel ratio towards a superstoichiometric air-fuel ratio, and the excess oxygen is used to regenerate the particulate filter by oxidizing the soot. However, a disadvantage of this method is that, particularly during low-load cycles of the combustion engine, the temperature required for particulate filter regeneration is not reliably reached.

[0004] From DE 10 2011 118 337 A1, an exhaust aftertreatment device is known in which intake air is compressed by means of a turbocharger and introduced into the exhaust manifold as secondary air downstream of a three-way catalytic converter and upstream of a particulate filter. The combustion engine is operated with a stoichiometric air-fuel ratio, at which exhaust gas purification can take place by the three-way catalytic converter, or with a superstoichiometric, lean air-fuel ratio, at which the NOx emissions not reduced in the three-way catalytic converter are stored in a NOx storage catalyst. A disadvantage is that even with such a solution, the temperatures necessary for the regeneration of the particulate filter are not reliably reached during low-load cycles, particularly when the particulate filter is installed under the vehicle's floor.

[0005] German patent DE 10 2011 014 158 A1 describes a compressor bypass for exhaust gas for the regeneration of a particulate filter. In this system, a particulate filter is in fluid communication with an exhaust pipe and periodically takes in heated exhaust gas for the combustion of carbon and particles trapped within it. An air line extends between the intake air compressor and the exhaust pipe, fluidly coupling the intake air compressor to the exhaust pipe. This air line is configured to inject air from the compressor into the exhaust pipe when the particulate filter takes in heated exhaust gas, thus supporting the combustion of the carbon and particles.

[0006] A system for targeted regeneration of a particulate filter is known from DE 10 2011 013 401 A1. The system comprises a particulate filter with an upstream end that receives exhaust gas from an engine. An air pump circuit directs ambient air to a first exhaust line upstream of the particulate filter. A control module determines the current soot load level of the particulate filter. The control module also operates the engine in a richer fuel mixture and / or activates an air pump of the air pump circuit if the current soot load level is greater than a predetermined soot load level.

[0007] German patent DE 10 2013 209 305 A1 discloses a method for exhaust gas afterburning in internal combustion engines with a number of combustion chambers and a turbocharger. In this method, exhaust gases from the combustion chambers of the internal combustion engine are introduced into an exhaust tract. Following fuel injection, the exhaust gases are combusted by an electronically controlled injection device. The amount of fuel supplied is determined based on measurements from at least one lambda sensor, an air mass meter, and an exhaust gas temperature sensor, such that a target lambda value corresponding to a specific engine operating condition is achieved in the mixture cloud consisting of exhaust gas and injected fuel.

[0008] Furthermore, a method and a system for the emission control of an internal combustion engine are known from DE 10 2010 063 444 A1. In this system, an SCR catalyst is arranged downstream of an exhaust turbine in the exhaust system of the internal combustion engine. Additionally, a particulate filter is arranged upstream of the turbine in the exhaust system. The method includes adjusting a turbine wastegate to regulate the catalyst temperature to a desired temperature.

[0009] The invention is based on the objective of providing an exhaust aftertreatment method and an exhaust aftertreatment device in which safe regeneration of the particulate filter is possible even in driving cycles with low load.

[0010] The problem is solved by a method for the exhaust aftertreatment of a turbocharged, spark-ignition internal combustion engine, wherein the internal combustion engine has a fresh air duct and an exhaust duct, wherein a compressor for compressing the fresh air is provided in the fresh air duct, and wherein a secondary air duct is provided downstream of the compressor, connecting the fresh air duct to the exhaust duct, wherein a three-way catalytic converter is arranged in the exhaust duct and a particulate filter is arranged downstream of the three-way catalytic converter. The method comprises the following steps: - Determining the loading status of the particulate filter, - If the loading condition requires regeneration of the particulate filter, the exhaust gas temperature is raised to a regeneration temperature of the particulate filter by at least temporarily adjusting the mixture formation for the combustion engine to a substoichiometric (rich) combustion air ratio and at least temporarily introducing secondary air into the exhaust channel upstream of the three-way catalytic converter, whereby - the unburned components of a combustion mixture in the combustion engine are exothermically converted by the secondary air in the exhaust manifold, and - during a regeneration phase of the particulate filter, the secondary air quantity is increased to such an extent that a superstoichiometric air-mixing ratio is established in the exhaust duct before entering the particulate filter, so that soot on the particulate filter is oxidized by the excess oxygen.

[0011] According to the invention, this method provides that secondary air is injected into the exhaust channel downstream of the exhaust valves of the combustion engine and upstream of the three-way catalytic converter. This allows the unburned components in the exhaust channel to undergo exothermic reactions on the three-way catalytic converter or even upstream of the three-way catalytic converter, for example, already in the exhaust manifold of the combustion engine, thus heating the exhaust gas in the exhaust channel to enable the regeneration of the particulate filter.

[0012] The combustion engine in its normal operation, i.e. before or during the determination of the particulate filter's loading state, is predominantly operated with a stoichiometric combustion air ratio (λ). E =1) operated.

[0013] According to a further development of the method, it is provided that during a heating phase of the particulate filter the combustion engine is operated with a substoichiometric (rich) combustion air ratio λ E <1 is operated and the secondary air quantity is set, in particular regulated, so that a stoichiometric air-mixing ratio λ is achieved upon entry into the three-way catalyst. M The value is set to =1. This ensures the three-way function of the three-way catalytic converter during the heating phase. Therefore, compared to a process where secondary air is only injected into the exhaust manifold downstream of the three-way catalytic converter, faster heating and improved exhaust gas purification can be achieved.

[0014] It is particularly advantageous if the combustion engine operates with a combustion air ratio λ during the heating phase and / or the regeneration phase of the particulate filter. Ein the range of 0.85 to 0.95, preferably of approximately λ E = 0.9. At such an air-fuel ratio, a sufficiently high quantity of reducing agents, especially unburned hydrocarbons, is supplied to the exhaust gas in the exhaust channel. Furthermore, particulate emissions from the combustion engine are not yet significantly increased in this range.

[0015] For the regeneration of the particulate filter, it is advantageous to adjust the air-fuel ratio λ. M (i.e., the mixture of combustion exhaust gas and secondary air) during the regeneration phase in the range of 1.05 to 1.2, preferably at approximately λ MThe value is set to 1.1. In this range, there is a sufficiently large excess of oxygen to oxidize the soot on the particulate filter and regenerate the filter. However, the amount of oxygen is low enough to prevent uncontrolled burning of the soot on the particulate filter and the associated risk of damage to the filter.

[0016] According to the invention, the compressor is driven by a turbine in the exhaust gas duct, and the secondary air line opens into the exhaust gas duct upstream of the turbine. Thus, the secondary air is supplied to the exhaust gas flow upstream of the turbine in the direction of exhaust gas flow. The use of a turbocharger with a turbine located in the exhaust gas duct and a compressor located in the fresh air duct offers the advantage that when secondary air is injected upstream of the turbine into the exhaust gas duct, the energy of the exothermic reaction can be used to drive the turbine. It is particularly advantageous if a bypass is provided on the turbine, bypassing the turbine, which can be closed to increase the compressor's drive power. This allows the power output to be increased at low-load points to ensure a sufficient quantity of secondary air is always available.Furthermore, this method allows the compressor pressure to be increased to achieve a sufficient pressure differential between the fresh air intake and the exhaust duct, enabling the introduction of secondary air against the exhaust backpressure even during periods of low load. It is particularly advantageous if the bypass is closed during the heating phase and / or the regeneration phase of the particulate filter. This allows the compressor output to be increased during the phases when secondary air is required in the exhaust duct, enabling the compressor to supply not only the combustion air but also the volume of air needed for secondary air injection. The bypass can be designed as a wastegate and closed by a suitable valve or flap.

[0017] According to an advantageous further development of the method, it is provided that the superstoichiometric air-mixing ratio λ MThe regeneration phase of the particulate filter is selected for a time interval in the range of 200 to 1000 s, preferably in the range of 300 to 800 s, and particularly preferably in the range of 500 to 600 s. During the regeneration phase of the particulate filter, the three-way catalyst cannot achieve its full effectiveness because a superstoichiometric air-fuel ratio is present at the three-way catalyst during this phase. The proposed time interval makes it possible, on the one hand, to achieve sufficient regeneration of the particulate filter and, on the other hand, to keep the time interval in which the three-way catalyst cannot achieve its full effectiveness as short as possible.

[0018] According to a further advantageous embodiment, the heating phase precedes the regeneration phase and is maintained for a time interval of 50 to 300 seconds, preferably 100 seconds. A separate heating phase allows the particulate filter to be heated while maintaining a stoichiometric air-fuel ratio. Thus, the three-way catalyst can achieve its full effectiveness during the particulate filter heating process without any impairment of its function. By pre-heating the particulate filter separately, the regeneration phase can be shortened compared to a combined heating and regeneration phase, thereby reducing the time interval during which the three-way catalyst operates outside its ideal operating conditions.

[0019] According to an advantageous further development of the method, the temperature of the exhaust gas before entering the three-way catalyst is determined, and this temperature is compared with the light-off temperature of the three-way catalyst for the conversion of unburned hydrocarbons. If this light-off temperature is not reached, the ignition timing of the combustion engine is first retarded before the air-fuel ratio λ is adjusted. E is adjusted, in particular to the substoichiometric combustion air ratio λ EThe regeneration phase is set to <1. A so-called light-off temperature is necessary for the exothermic conversion of hydrocarbons to initiate this exothermic reaction. For gasoline engines and the fuels used, this temperature can range from approximately 300°C to 400°C. Below this temperature, further measures are necessary to first bring the exhaust gas into this temperature range, as the proposed method, which involves adjusting the combustion air to create a substoichiometric, rich mixture and initiating the exothermic conversion of the unburned components, can only be effective above the light-off temperature. Below this temperature, the unburned hydrocarbons are not converted, or only to a very limited extent, so that, apart from undesirable HC emissions, there is no significant increase in the exhaust gas temperature.To increase the exhaust gas temperature, especially during low-load phases, it is therefore suggested to additionally adjust the ignition angle of the combustion engine towards "late" and thus increase the exhaust gas temperature.

[0020] According to an advantageous further development of the method, the compressor output is increased for a limited period, particularly during the heating and / or regeneration phases. This allows the compressor's air volume to exceed the volume of air required by the combustion engine for combustion. This additional air volume can then be injected into the exhaust manifold as secondary air.

[0021] The device according to the invention for the exhaust aftertreatment of a turbocharged, spark-ignition combustion engine comprises a fresh air duct and an exhaust duct, wherein a compressor for compressing the fresh air is provided in the fresh air duct, and wherein a secondary air line is provided downstream of the compressor, connecting the fresh air duct to the exhaust duct, and a three-way catalytic converter is arranged in the exhaust duct and a particulate filter is arranged downstream of the three-way catalytic converter, the secondary air line opening into the exhaust duct upstream of the three-way catalytic converter. The device according to the invention makes it possible, with a rich air-fuel ratio in the combustion engine, to set a stoichiometric air-fuel ratio at the three-way catalytic converter by means of the secondary air to raise the exhaust gas temperature, which enables ideal conversion of the pollutants on the three-way catalytic converter.

[0022] The device according to the invention is suitable and configured for carrying out the method according to the invention. In particular, for this purpose, the device comprises a control unit in which a computer-readable control algorithm for carrying out the method is implemented and in which optionally necessary characteristic maps are stored.

[0023] According to an advantageous embodiment, a throttle valve is arranged in the fresh air duct downstream of the compressor, with the secondary air duct branching off from the fresh air duct between the compressor and the throttle valve. Thus, the amount of air supplied to the combustion engine and / or the secondary air duct can be controlled by the throttle valve.

[0024] According to a further advantageous embodiment, the three-way catalytic converter is arranged in a position close to the engine, and the particulate filter in a position farther from the engine, in particular in an underbody position. A position close to the engine is defined as a position in which the inlet opening of the three-way catalytic converter is located less than 50 cm, preferably less than 30 cm, from a cylinder outlet of the internal combustion engine. Typically, the average exhaust gas flow length from a cylinder outlet to the inlet of the particulate filter is at least 100 cm, in particular at least 120 cm. This position is referred to in this application as the position farther from the engine.Positioning the three-way catalytic converter close to the engine allows it to heat up more quickly during the start-up phase, enabling it to reach its light-off temperature more rapidly and effectively convert unburned components of the combustion mixture. Positioning the particulate filter further away from the engine offers the advantage of more space under the floor, making installation easier. Furthermore, underfloor mounting protects the particulate filter from thermal overload and the associated damage or aging.

[0025] According to the invention, the secondary air line opens into the exhaust gas channel upstream of a turbine arranged in the direction of exhaust gas flow upstream of the three-way catalytic converter. This allows unburned components of the combustion mixture to undergo exothermic conversion in the exhaust manifold upstream of the turbine, and the additional energy released during this exothermic conversion can be used to drive the turbine. This enables an increase in engine power, particularly an increase in torque at low-load points where the turbine would otherwise provide little drive power for the compressor.

[0026] Unless otherwise stated in individual cases, the various embodiments of the invention mentioned in this application can be advantageously combined with one another.

[0027] The invention is explained below using exemplary embodiments with reference to the accompanying drawings. These show: Fig. 1 a first embodiment of a device according to the invention for exhaust gas aftertreatment, Fig. 2 a second embodiment of a device according to the invention for exhaust gas aftertreatment, Fig. 3 a flowchart of a process according to the invention for exhaust gas aftertreatment, Fig. 4 a diagram of a method according to the invention for regenerating a particle filter, and Fig. 5 another diagram of a method according to the invention for regenerating a particle filter.

[0028] Fig. Figure 1 shows a turbocharged, spark-ignition internal combustion engine 10, preferably a turbocharged gasoline engine, with a fresh air duct 12 and an exhaust duct 20. A turbine 26 is arranged in the exhaust duct 20 in the direction of flow of the exhaust gas from the internal combustion engine 10. The turbine 26 is connected via a drive shaft 36 to a compressor 14 in the fresh air duct 12. The turbine 26 and the compressor 14 are part of a turbocharger 40. Downstream of the turbine 26, a preferably close-coupled three-way catalytic converter 22 is arranged in the exhaust duct 20. A bypass channel 38, in particular a so-called wastegate, is formed on the turbine 26, allowing a partial flow of the exhaust gas to bypass the turbine 26. This bypass channel 38 can be closed by a valve or flap (not shown).Downstream of the three-way catalytic converter 22, a particulate filter 24 is arranged in the exhaust duct 20, preferably located in an underbody position far from the engine, i.e., on the underbody of a motor vehicle. The particulate filter 24 can be designed as an uncoated particulate filter 24, but preferably it is designed as a coated wall-flow filter with a catalytic three-way coating. Downstream of the three-way catalytic converter 22, and in particular between the three-way catalytic converter 22 and the particulate filter 24, a lambda sensor 28 is provided for lambda control, in particular for air mass control of the internal combustion engine 10.

[0029] An air filter 32 is arranged at the inlet of the fresh air duct 12. Downstream of the compressor 14, a throttle valve 18 is arranged in the direction of fresh air flow, allowing control of the amount of air supplied to the internal combustion engine 10. Downstream of the throttle valve 18, a charge air cooler 30 is arranged, which cools the compressed air before it enters the combustion chambers of the internal combustion engine 10. A secondary air duct 16 branches off from the fresh air duct 12 between the compressor 14 and the throttle valve 18. This secondary air duct leads into the exhaust duct 20, specifically into an exhaust manifold (not shown), between the exhaust valves of the internal combustion engine 10 and the turbine 26. A secondary air valve 34 is provided at one end of the secondary air duct 16 facing the exhaust duct 20, allowing control of the amount of secondary air supplied to the exhaust duct 20.

[0030] In Fig. Figure 2 shows an embodiment of a device for exhaust gas aftertreatment not belonging to the invention. It has a largely identical structure to that shown in Figure 2. Fig. 1. In the following, only the differences will be discussed. The secondary air line 16 branches off from the fresh air line 12 downstream of the compressor 14 and upstream of the throttle valve 18 and, in this configuration, opens into the exhaust channel 20 between the turbine 26 of the turbocharger 40 and the three-way catalytic converter 22. The turbocharger 40, or rather the turbine 26 of the turbocharger 40, can be operated as described in Fig. 1 have a bypass channel 38, which, however, has not been shown in this embodiment for the sake of clarity.

[0031] In low-load driving cycles, colloquially referred to as "bread-pick-up cycles," the exhaust gas enthalpy can be used by closing the bypass channel 38 to compress an additional fresh air mass flow, not required for the combustion process of the internal combustion engine 10, using the compressor 14. This additional fresh air mass flow can be introduced into the exhaust gas channel 20 via the secondary air line 16.

[0032] If a defined threshold of soot loading in the particulate filter 24 is detected, which can be done, for example, by differential pressure measurement in the exhaust gas channel 20 before and after the particulate filter 24 or by modeling, a regeneration process is initiated to regenerate the particulate filter 24. A regeneration temperature of approximately 600°C and an excess of oxygen for soot oxidation are necessary for regenerating the particulate filter. To achieve the regeneration temperature in the exhaust gas, the process according to the invention uses the following: Fig. The following steps, as shown in the illustration, were carried out.

[0033] In an initial state <100> The internal combustion engine 10 is operated with a stoichiometric combustion air ratio λ E= 1 operated. In a subsequent process step <110> The system checks whether regeneration of the particulate filter 24 is necessary. For example, it checks whether a pressure difference determined by a differential pressure measurement across the particulate filter 24, or a load level of the particulate filter 24 determined by modulation, exceeds a predetermined threshold. If the query <110> If this is confirmed, a regeneration requirement exists and the regeneration process is initiated.

[0034] In the following step <120> First, a temperature is determined at the three-way catalyst 22, and it is checked whether this temperature is above a light-off temperature of the three-way catalyst 22 of approximately 350 °C, at which a reaction of unburned components of the combustion mixture of the internal combustion engine, in particular unburned hydrocarbons (HC), takes place on the three-way catalyst 22. If the check <120> If the answer is no, meaning the light-off temperature is not present, it will be determined in a subsequent process step. <130> The ignition angle of the combustion engine 10 is adjusted towards a later point in order to increase the combustion temperature and thus the temperature at the inlet of the three-way catalyst 22, thereby enabling an exothermic conversion of the unburned components of the combustion mixture (HC, CO, H2).

[0035] Once the light-off temperature is reached, a further process step is carried out. <140> It checks whether the regeneration temperature of the particulate filter 24 has been reached. This will usually not be the case initially, and the query <140> This can be answered in the negative. In this case, a heating phase follows to heat the particulate filter 24 to its regeneration temperature. For this purpose, a further process step is carried out. <150> the combustion air ratio of engine 10 from a stoichiometric combustion air ratio with k E = 1 to a substoichiometric, rich combustion air ratio λ E < 1, preferably of k E The value is adjusted to 0.9. This allows unburned components (HC, CO, H2) of the combustion mixture to be introduced into the exhaust gas channel 20. The combustion air ratio λ E The combustion engine 10 can be measured via a lambda sensor arranged upstream of the secondary air valve 34 (in the Fig. 1 and Fig. 2 (not shown) are recorded and regulated. Simultaneously, in the procedural step <150> The secondary air compressed by the compressor 14 is fed via the secondary air line 16 to the exhaust gas channel 20 downstream of an outlet of the internal combustion engine 10. This feed can be located either between the outlet of the internal combustion engine 10 and the turbine 26 of the turbocharger 40 ( Fig. 1) or downstream of the turbine 26 of the turbocharger and upstream of the three-way catalyst 22 ( Fig. 2) This occurs. The oxygen introduced into the exhaust channel 20 via the secondary air line 16 and the secondary air valve 34 allows the unburned components of the combustion mixture to react exothermically on the three-way catalyst 22 located downstream of the inlet of the secondary air line 16 or the secondary air valve 34. If the secondary air is injected between the exhaust of the combustion engine 10 and the turbine 26, this exothermic reaction can already take place on an exhaust manifold of the combustion engine 10, and the energy thus released can be used to drive the turbine 26. The air-fuel ratio λ M The combustion air ratio and the secondary air blown into the exhaust channel 20 are detected via the lambda sensor 28 and regulated to lambda = 1, so that the desired target temperature for the regeneration of the particulate filter 24 is set.

[0036] Once the regeneration temperature of the particle filter 24 is reached, the regeneration phase begins, and in a further process step <160> the secondary air supply is increased, resulting in a superstoichiometric air-fuel ratio λ M >1 is set before the particulate filter 24. This allows the soot on the particulate filter 24 to be oxidized and the particulate filter 24 to be regenerated.

[0037] In a further procedural step <170> After the regeneration of the particulate filter 24 is complete, the supply of secondary air is stopped and the combustion engine 10 is restarted with a stoichiometric combustion air ratio λ. E = 1 operated.

[0038] The curves of the particulate filter temperature, the engine air-fuel ratio k E of the internal combustion engine 10 and the air-fuel ratio λ M during the according to Fig. The 3 executed procedures show Fig. 4. As in Fig. As shown in Figure 4, the combustion air ratio λ is changed during a heating phase of the particulate filter 24. E of the internal combustion engine 1 on λ E < 1 pre-controlled and the mixing ratio set to λ M = 1. The heating phase is maintained for a time interval of 50 to 300 s, preferably 100 s. This ensures the three-way function of the three-way catalyst 22 during the heating phase and allows all pollutants to be effectively converted.

[0039] Once the regeneration temperature for regenerating the particulate filter 24 is reached, the engine control unit switches to the regeneration phase. For this purpose, the combustion engine 10 continues to operate with a substoichiometric, rich air-fuel ratio λ. E< 1 operated. However, in order to provide the oxygen for the regeneration of the particulate filter 24, the amount of secondary air that is blown into the exhaust duct 20 via the secondary air line 16 and the secondary air valve 34 is increased such that a superstoichiometric air-mixing ratio λ is present at the inlet of the particulate filter 24. M >1, preferably λ M between 1.05 and 1.2, particularly preferably λ M The value is set to 1.1. This ensures that the soot conversion rate does not become too high and that the particulate filter 24 is not thermally damaged. This process is maintained until the particulate filter 24 can be considered regenerated. A typical regeneration time interval for the particulate filter 24 is chosen to be between 200 and 1000 seconds, preferably between 300 and 800 seconds, and particularly preferably between 500 and 600 seconds.

[0040] Alternatively, as in Fig. Figure 5 shows that the heating phase and the regeneration phase of the particulate filter 24 are carried out in parallel. The combustion engine 10 is operated with a substoichiometric, rich air-fuel ratio λ. E < 1 operated and simultaneously secondary air blown into the exhaust gas channel 20, so that a superstoichiometric air-mixing ratio λ is achieved during the heating phase and during the parallel regeneration phase. M >1 is set. Thus, the unburned components of the combustion mixture are simultaneously converted exothermically, and sufficient oxygen is available to convert the stored soot in the particulate filter 24.

[0041] Both described methods can be carried out with either of the proposed devices, regardless of whether the secondary air line leads into the exhaust channel 20 between the exhaust of the combustion engine 10 and turbine 26 of the turbocharger 40 or between turbine 26 of the turbocharger 40 and the three-way catalytic converter 22. The described methods result in NOx slip during the regeneration phase. In the Fig. However, in the 4 illustrated and preferred methods, this phase is shortened with the existing NOx slip, since the heating phase of the particulate filter 24 with a stoichiometric combustion air ratio λ E = 1 and is carried out under full effectiveness of the three-way catalyst 22. Reference symbol list 10 Internal combustion engine 12 Fresh air duct 14 compressors 16 Secondary air line 18 Throttle valve 20 Exhaust duct 22 Three-way catalytic converter 24 particulate filters 26 Turbine 28 Lambda sensor 30 intercoolers 32 air filters 34 Secondary air valve 36 Drive shaft 38 Bypass channel 40 turbochargers λ E combustion air ratio λ M air-mixture ratio

Claims

[1] A method for the exhaust aftertreatment of a turbocharged, spark-ignition internal combustion engine (10), comprising a fresh air duct (12) and an exhaust duct (20), wherein a compressor (14) driven by a turbine (26) arranged in the exhaust duct (20) for compressing the fresh air is provided in the fresh air duct (12), and a secondary air duct (16) is provided downstream of the compressor (14), which connects the fresh air duct (12) to the exhaust duct (20) and opens into the exhaust duct (20) upstream of the turbine (26), wherein a three-way catalyst (22) is arranged in the exhaust duct (20) and a particulate filter (24) is arranged downstream of the three-way catalyst (22), comprising the following processes: - Determination of the loading status of the particulate filter (24), - if the loading condition requires regeneration of the particulate filter (24), raising the exhaust gas temperature to a regeneration temperature of the particulate filter (24) by at least temporarily adjusting the mixture formation for the combustion engine (10) to a substoichiometric (rich) air-fuel ratio (λ) E <1) and at least temporarily simultaneous introduction of secondary air into the exhaust duct (20) upstream of the turbine (26) and upstream of the three-way catalyst (22), wherein - the unburned components of a combustion mixture of the internal combustion engine (10) are exothermically converted by the secondary air in the exhaust channel (20), and - during a regeneration phase of the particulate filter (24) the secondary air quantity is increased to such an extent that a superstoichiometric air-fuel ratio (λ) is present in the exhaust gas channel (20) before entering the particulate filter (24). M>1) so that soot on the particulate filter (24) is oxidized by the excess oxygen. [2] Method for exhaust gas aftertreatment according to claim 1, characterized by , that during a heating phase of the particulate filter (24) the combustion engine (10) operates with a substoichiometric (rich) air-fuel ratio (λ) E <1) is operated and the secondary air quantity is adjusted so that a stoichiometric air-mixing ratio (λ) is present upon entry into the three-way catalyst (22). M =1). [3] Method for exhaust gas aftertreatment according to claim 1 or 2, characterized by , that the internal combustion engine (10) with a combustion air ratio (λ E ) is operated in the range of 0.85 to 0.

95. [4] Method for exhaust gas aftertreatment according to any one of claims 1 to 3, characterized by , that the air-fuel ratio (λ M) is set in the regeneration phase of the particulate filter (24) in the range of 1.05 to 1.

2. [5] Method for exhaust aftertreatment according to any one of claims 1 to 4, characterized by , that a bypass (38) is formed on the turbine (26) which bypasses the turbine and is closed to increase the drive power of the compressor (14). [6] Method for exhaust gas aftertreatment according to claim 5, characterized by , that the bypass (38) is closed during the heating phase and / or the regeneration phase of the particulate filter (24). [7] Method for exhaust gas aftertreatment according to any one of claims 1 to 6, characterized by , that the superstoichiometric air-mixing ratio λ M for the regeneration phase of the particulate filter (24) for a time interval in the range of 200 to 1000 s is selected. [8] Method for exhaust gas aftertreatment according to any one of claims 1 to 7, characterized bythat a heating phase precedes the regeneration phase and is maintained for a time interval in the range of 50 to 300s. [9] Method according to any one of claims 1 to 8, characterized by , that a temperature of the exhaust gas before entering the three-way catalyst (22) is determined, this temperature is compared with a light-off temperature of the three-way catalyst (22) and if this light-off temperature is not reached, the ignition angle of the combustion engine (10) is first adjusted towards a late setting before the air-fuel ratio λ E will be adjusted. [10] Exhaust gas aftertreatment method according to any one of claims 1 to 9, characterized by , that the power of the compressor (14) is increased for a limited period of time, in particular for the heating phase and / or the regeneration phase. [11] Device for exhaust aftertreatment of a turbocharged, spark-ignition internal combustion engine (10), comprising a fresh air duct (12) and an exhaust duct (20), wherein a compressor (14) for compressing the fresh air is provided in the fresh air duct (12) and a secondary air duct (16) is provided downstream of the compressor (14), which connects the fresh air duct (12) to the exhaust duct (20), wherein a three-way catalyst (22) is arranged in the exhaust duct (20) and a particulate filter (24) is arranged downstream of the three-way catalyst (22), characterized by , that the secondary air line (16) leads into the exhaust gas channel (20) upstream of a turbine (26) arranged in the direction of exhaust gas flow in front of the three-way catalyst (22). [12] Exhaust gas aftertreatment device according to claim 11, characterized by, that a throttle valve (18) is arranged in the fresh air duct downstream of the compressor (14), wherein the secondary air duct (16) branches off from the fresh air duct (12) between the compressor (14) and the throttle valve (18). [13] Exhaust gas aftertreatment device according to one of claims 11 or 12, characterized by , that the three-way catalyst (22) is located in a position close to the engine and the particulate filter (24) is located in an underfloor position.

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