DE102015213231A1 - Method for controlling the boost pressure of an internal combustion engine with a parallel switchable turbine - Google Patents

Abstract

Method for controlling a boost pressure of an internal combustion engine, in which - each cylinder (3) has at least two outlet openings (4, 4a, 4b), of which at least one is designed as a switchable outlet opening (4a), - at least two exhaust gas turbochargers (8, 9) are provided, - the exhaust pipes (5a) of the switchable outlet openings (4a) merge to a first total exhaust line (7a) which is connected to the first turbine (8a), - the exhaust pipes (5b) of the other outlet openings (4b) to a second Total exhaust gas line (7b) merge, which is connected to the second turbine (9a), - downstream of the first compressor (8b) a first shut-off element (13a) is arranged, - the second turbine (9a) is designed as a waste gate turbine with a second bypass line (9c) and a second shut-off element (9d), - each cylinder (3) is equipped with at least one further at least partially variable valvetrain in which out by switching off a requested torque, the second shut-off element (9d) in the second bypass line (9c) of the turbine (9a) of the second exhaust gas turbocharger (9) in a predeterminable Scope is closed and further at least partially variable valve trains to adjust a required fresh cylinder charge can be adjusted, and - switched off the outlet openings (4a) for the purpose of activation of the first turbine (8a), wherein a through the second turbine (9a) passed through decreasing exhaust gas by adjustment the cylinder fresh charge is compensated by adjusting further at least partially variable valve trains, to the extent that a requested torque is provided.

Description

• – jeder Zylinder mindestens zwei Auslassöffnungen zum Abführen der Abgase aufweist, von denen mindestens eine als schaltbare Auslassöffnung ausgebildet ist, wobei sich an jede Auslassöffnung eine Abgasleitung zum Abführen der Abgase via Abgasabführsystem anschließt,
• – ein Ansaugsystem zum Zuführen von Ladeluft zu den mindestens zwei Zylindern vorgesehen ist,
• – mindestens zwei Abgasturbolader vorgesehen sind, wobei jeder Abgasturbolader eine im Abgasabführsystem angeordnete Turbine und einen im Ansaugsystem angeordneten Verdichter umfasst,
• – die Verdichter der mindestens zwei Abgasturbolader parallel im Ansaugsystem angeordnet sind, wobei jeder Verdichter in einer separaten Ansaugleitung des Ansaugsystems angeordnet ist und die separaten Ansaugleitungen stromabwärts der Verdichter zu einer Gesamtansaugleitung zusammenführen,
• – die Abgasleitungen der schaltbaren Auslassöffnungen der mindestens zwei Zylinder unter Ausbildung eines ersten Abgaskrümmers zu einer ersten Gesamtabgasleitung zusammenführen, welche mit der Turbine des ersten Abgasturboladers verbunden ist,
• – die Abgasleitungen der anderen Auslassöffnungen der mindestens zwei Zylinder unter Ausbildung eines zweiten Abgaskrümmers zu einer zweiten Gesamtabgasleitung zusammenführen, welche mit der Turbine des zweiten Abgasturboladers verbunden ist,
• – stromabwärts des Verdichters des ersten Abgasturboladers ein erstes Absperrelement in der zugehörigen ersten Ansaugleitung angeordnet ist,
• – die Turbine des zweiten Abgasturboladers als Waste-Gate-Turbine ausgeführt ist, wobei stromaufwärts dieser zweiten Turbine eine zweite Bypassleitung vom Abgasabführsystem abzweigt und ein zweites Absperrelement in der zweiten Bypassleitung vorgesehen ist,
• – jede schaltbare Auslassöffnung mit einem schaltbaren Auslassventil eines zumindest teilweise variablen Ventiltriebs ausgestattet ist, wobei ein abgeschaltetes Auslassventil die zugehörige Auslassöffnung abschaltet und sich ein zugeschaltetes Auslassventil zwischen einer Offenstellung und einer Schließstellung unter Ausbildung eines Ventilhubs ∆h_max bewegt und dabei die zugehörige Auslassöffnung während einer Öffnungsdauer ∆t_max freigibt, und
• – jeder Zylinder zwecks Einstellung der Ladeluft einer Zylinderfrischladung mit mindestens einem weiteren zumindest teilweise variablen Ventiltrieb ausgestattet ist mit einem Ventil, das zwischen einer Ventilschließstellung und einer Ventiloffenstellung unter Vollführung eines Ventilhubs bewegbar ist, um eine ventilzugehörige Öffnung des Zylinders im Rahmen eines Ladungswechsels freizugeben oder zu versperren.

The invention relates to a method for controlling a supercharging pressure of a supercharged internal combustion engine having at least one cylinder head with at least two cylinders, in which

• Each cylinder has at least two outlet openings for discharging the exhaust gases, of which at least one is designed as a switchable outlet opening, wherein an exhaust pipe for discharging the exhaust gases via exhaust gas discharge system adjoins each outlet opening,
• An intake system is provided for supplying charge air to the at least two cylinders,
• At least two exhaust-gas turbochargers are provided, each exhaust-gas turbocharger comprising a turbine arranged in the exhaust-gas removal system and a compressor arranged in the intake system,
• The compressors of the at least two exhaust gas turbochargers are arranged in parallel in the intake system, each compressor being arranged in a separate intake line of the intake system and bringing the separate intake lines downstream of the compressor into an overall intake line,
• To merge the exhaust gas lines of the switchable outlet openings of the at least two cylinders to form a first exhaust gas manifold to form a first overall exhaust gas line which is connected to the turbine of the first exhaust gas turbocharger,
• To merge the exhaust gas lines of the other outlet openings of the at least two cylinders to form a second exhaust gas manifold to form a second overall exhaust line, which is connected to the turbine of the second exhaust gas turbocharger,
• A first shut-off element is arranged in the associated first intake line downstream of the compressor of the first exhaust-gas turbocharger,
• The turbine of the second exhaust-gas turbocharger is designed as a waste-gate turbine, wherein a second bypass line branches off from the exhaust-gas removal system upstream of this second turbine and a second shut-off element is provided in the second bypass line,
• - Each switchable outlet opening is equipped with a switchable exhaust valve of an at least partially variable valve train, wherein a shut-off exhaust valve, the associated outlet opening switches off and a switched exhaust valve between an open position and a closed position to form a valve lift .DELTA.h _max moves while the associated outlet opening during a Opening duration Δt _max releases, and
• - Each cylinder for the purpose of setting the charge air of a cylinder fresh charge with at least one further at least partially variable valve train is equipped with a valve which is movable between a valve closed position and a valve open position under full control of a valve lift to release a valve-related opening of the cylinder as part of a charge cycle or block.

Furthermore, the invention relates to a supercharged internal combustion engine for carrying out such a method.

In the context of the present invention, the term internal combustion engine includes in particular gasoline engines, but also diesel engines and hybrid internal combustion engines, which use a hybrid combustion process, as well as hybrid drives, which in addition to the internal combustion engine comprise an electric motor which can be electrically connected to the internal combustion engine, which receives power from the internal combustion engine or as an additional auxiliary drive additionally delivers power.

Internal combustion engines have a cylinder block and at least one cylinder head, which are connected together to form the cylinder. In order to control the charge cycle, an internal combustion engine requires control devices - usually in the form of globe valves - and actuators to operate these controls. Each lift valve moves under training, d. H. Completing a valve lift between an open position and a closed position, thereby releasing the valve-associated opening during an opening period. The required for the movement of a valve valve actuating mechanism including the valve itself is referred to as a valve train. Often, the cylinder head serves to accommodate the valve train.

As part of the charge cycle, the combustion gases are pushed out via the outlet openings of the cylinders and the combustion chambers are filled with charge air via the inlet openings. It is the task of the valve drive to enable or close the inlet and outlet openings in good time, as a rule a quick release of the largest possible flow cross sections is sought in order to keep the throttle losses in the inflowing and outflowing gas flows low and the best possible filling to ensure the cylinder as well as an effective discharge of the exhaust gases. Therefore, according to the prior art, the cylinders are often equipped with two or more inlet and outlet ports. Also, the at least two cylinders of the internal combustion engine, which is the subject of the present invention, are equipped with at least two outlet openings.

The inlet ducts leading to the inlet openings and the exhaust ducts adjoining the outlet openings are upright the technology at least partially integrated in the cylinder head. The exhaust pipes of the cylinders are usually combined to form a common exhaust gas line or - as in the internal combustion engine according to the invention - in groups to two or more total exhaust gas lines. The combination of exhaust pipes to an overall exhaust line is generally and in the context of the present invention referred to as exhaust manifold.

Downstream of the manifold, the exhaust gases in the present case are supplied to the turbines of at least two exhaust-gas turbochargers for charging the internal combustion engine and optionally one or more systems for exhaust-gas aftertreatment.

The advantage of an exhaust gas turbocharger, for example compared to a mechanical supercharger, is that there is no mechanical connection to the power transmission between the supercharger and the internal combustion engine. While a mechanical supercharger obtains the energy required for its drive completely from the internal combustion engine and thus reduces the power provided and thus adversely affects the efficiency, the exhaust gas turbocharger uses the exhaust gas energy of the hot exhaust gases.

An exhaust gas turbocharger includes a compressor and a turbine disposed on the same shaft. The hot exhaust stream is supplied to the turbine and relaxes with energy release in the turbine, causing the shaft to rotate. The energy emitted by the exhaust gas flow to the turbine and finally to the shaft is used to drive the compressor, which is also arranged on the shaft. The compressor conveys and compresses the charge air supplied to it, whereby charging of the at least two cylinders is achieved. Optionally, a charge air cooling is provided, with which the compressed charge air is cooled before entering the cylinder.

The charge is used primarily to increase the performance of the internal combustion engine. The air required for the combustion process is compressed, which allows each cylinder per working cycle, a larger air mass can be supplied. As a result, the fuel mass and thus the medium pressure can be increased. The charge is a suitable means to increase the capacity of an internal combustion engine with unchanged displacement or to reduce the displacement at the same power. In any case, the charging leads to an increase in space performance and a lower power mass. If the cubic capacity is reduced, the load spectrum can be shifted to higher loads at the same vehicle boundary conditions, where the specific fuel consumption is lower.

Basically, it is endeavored to arrange the turbine of an exhaust gas turbocharger as close as possible to the outlet openings of the cylinder in order to be able to optimally use the exhaust gas enthalpy of the hot exhaust gases, which is largely determined by the exhaust gas pressure and the exhaust gas temperature, and a fast response of the turbine and thus of the turbocharger. In this connection, it is also desirable to minimize the thermal inertia and volume of the conduit system between the cylinder and turbine exhaust ports, which can be achieved by reducing the mass and length of the exhaust conduits. The integration of the exhaust manifold in the cylinder head is purposeful.

The design of the exhaust gas turbocharger often causes difficulties, with basically a noticeable increase in performance in all speed ranges is sought. In the prior art, however, a torque drop is observed when falling below a certain speed. This torque drop becomes understandable if it is taken into account that the boost pressure ratio depends on the turbine pressure ratio. For example, if the engine speed is reduced, this leads to a smaller exhaust gas mass flow and thus to a smaller turbine pressure ratio. As a result, the boost pressure ratio and the charge pressure also decrease at lower speeds, which is equivalent to a torque drop.

The torque characteristic of a supercharged internal combustion engine is attempted to be improved by different measures according to the prior art, for example by a small design of the turbine cross-section and simultaneous Abgasabblasung. Such a turbine is also referred to as a waste gate turbine. If the amount of exhaust gas exceeds a critical size, part of the exhaust gas flow is conducted past the turbine via the bypass line as part of the so-called exhaust gas blow-off. This approach has the disadvantage that the charging behavior at higher speeds or larger amounts of exhaust gas is insufficient.

The torque characteristic can also be advantageously influenced by means of a plurality of exhaust-gas turbochargers connected in series. By switching in series of two exhaust gas turbochargers, one of which is an exhaust gas turbocharger as a high pressure stage and an exhaust gas turbocharger as a low pressure stage, the compressor map can be widened in an advantageous manner, both towards smaller compressor streams as well as towards larger compressor streams.

In particular, in the case of the exhaust gas turbocharger serving as a high-pressure stage, the pumping limit can be shifted towards smaller compressor flows, which means that high boost pressure ratios can be achieved even with small compressor flows, which significantly improves the torque characteristic in the lower rpm range. This is achieved by designing the high-pressure turbine for small exhaust gas mass flows and providing a bypass line, with which increasing exhaust gas mass flow increasingly exhaust gas is passed to the high-pressure turbine. For this purpose, the bypass line branches off from the exhaust-gas removal system upstream of the high-pressure turbine and flows back into the exhaust-gas removal system upstream of the low-pressure turbine, wherein a shut-off element is arranged in the bypass line in order to control the exhaust gas flow conducted past the high-pressure turbine. The response of such a supercharged internal combustion engine is significantly improved over a comparable internal combustion engine with single-stage charging, since the smaller high-pressure stage is less sluggish, that is, the running gear of a smaller sized exhaust gas turbocharger accelerate faster.

The torque characteristic of a supercharged internal combustion engine may be further characterized by a plurality of turbochargers arranged in parallel, i. H. can be improved by a plurality of parallel turbines of smaller turbine cross-section, with individual turbine turbines are switched successively with increasing exhaust gas.

A supercharged internal combustion engine with at least two turbines arranged in parallel is also an object of the present invention. At least one turbine is designed as a switchable turbine, which is acted upon only with larger amounts of exhaust gas, d. H. is activated.

In order to further improve the torque characteristic, each cylinder of the internal combustion engine according to the invention is equipped with at least one switchable outlet opening. The exhaust pipes of at least two cylinders are then grouped together in such a way that the exhaust pipes of the switchable exhaust ports and the exhaust pipes of the other exhaust ports are each combined to form an exhaust manifold to form an overall exhaust line.

The exhaust pipes of the switchable exhaust ports lead to the turbine of the first exhaust gas turbocharger and the exhaust pipes of the other exhaust ports to the turbine of the second exhaust gas turbocharger. The switchable outlet openings associated with the first turbine is thus designed as a switchable turbine. According to the prior art, the switchable outlet openings are opened only in the case of larger amounts of exhaust gas in the course of the charge exchange, and thus the exhausted first turbine is exposed to exhaust gas.

Compared to concepts in which a single contiguous exhaust pipe system is provided upstream of the two turbines, the grouping described above, that is to say, increases. H. the use of two separate exhaust manifolds, the operating behavior of the internal combustion engine especially at small amounts of exhaust gas felt; Also, because the line volume upstream of the second turbine continuously flowed through by exhaust gas is reduced by this measure, which at low loads or speeds, d. H. small amounts of exhaust gas, is advantageous and in particular improves the response.

But there are also disadvantages. The speed of the switchable turbine drops sharply when it is deactivated, so that when it is switched on again, the rotor of this turbine must first be accelerated in order to be able to generate and provide the desired boost pressure on the compressor side. The response thus deteriorates.

In order to ensure a minimum speed of the switchable turbine, the switchable turbine could be supplied with a small exhaust gas flow even when the exhaust ports are switched off. For this purpose, a corresponding line would have to connect the second exhaust manifold with the first turbine optionally using at least one additional shut-off, whereby the complexity and space requirements of the exhaust pipe system upstream of the turbines increase unfavorably. In addition, a connection between the two exhaust manifolds would be created by the line and the grouping described above be canceled. The effects achieved by using two separate exhaust manifolds would at least be mitigated.

A further disadvantage with the use of a switchable turbine of the type described above, in which switchable outlet openings are used as a means for switching, is that when connecting the outlet openings for the purpose of switching on the turbine, the exhaust gas flow guided through the second turbine abruptly decreases, since the exhaust gas during the charge exchange now per cylinder another outlet, namely the switched outlet opening, is available. When the first turbine is switched on, the boost pressure generated with the second compressor then decreases abruptly. The associated with the boost pressure drop torque drop is undesirable. In that sense, measures are needed to avoid the transient Behavior of turbocharging to improve when connecting the first turbine.

Against the background of the above, it is a subtask of the present invention to provide a method according to the preamble of claim 1, with which the exhaust gas turbocharging and torque characteristics of the internal combustion engine, in particular the transient behavior, can be further improved.

Another object of the present invention is to provide a supercharged internal combustion engine for performing such a method.

• – jeder Zylinder mindestens zwei Auslassöffnungen zum Abführen der Abgase aufweist, von denen mindestens eine als schaltbare Auslassöffnung ausgebildet ist, wobei sich an jede Auslassöffnung eine Abgasleitung zum Abführen der Abgase via Abgasabführsystem anschließt,
• – ein Ansaugsystem zum Zuführen von Ladeluft zu den mindestens zwei Zylindern vorgesehen ist,
• – mindestens zwei Abgasturbolader vorgesehen sind, wobei jeder Abgasturbolader eine im Abgasabführsystem angeordnete Turbine und einen im Ansaugsystem angeordneten Verdichter umfasst,
• – die Verdichter der mindestens zwei Abgasturbolader parallel im Ansaugsystem angeordnet sind, wobei jeder Verdichter in einer separaten Ansaugleitung des Ansaugsystems angeordnet ist und die separaten Ansaugleitungen stromabwärts der Verdichter zu einer Gesamtansaugleitung zusammenführen,
• – die Abgasleitungen der schaltbaren Auslassöffnungen der mindestens zwei Zylinder unter Ausbildung eines ersten Abgaskrümmers zu einer ersten Gesamtabgasleitung zusammenführen, welche mit der Turbine des ersten Abgasturboladers verbunden ist,
• – die Abgasleitungen der anderen Auslassöffnungen der mindestens zwei Zylinder unter Ausbildung eines zweiten Abgaskrümmers zu einer zweiten Gesamtabgasleitung zusammenführen, welche mit der Turbine des zweiten Abgasturboladers verbunden ist,
• – stromabwärts des Verdichters des ersten Abgasturboladers ein erstes Absperrelement in der zugehörigen ersten Ansaugleitung angeordnet ist,
• – die Turbine des zweiten Abgasturboladers als Waste-Gate-Turbine ausgeführt ist, wobei stromaufwärts dieser zweiten Turbine eine zweite Bypassleitung vom Abgasabführsystem abzweigt und ein zweites Absperrelement in der zweiten Bypassleitung vorgesehen ist,
• – jede schaltbare Auslassöffnung mit einem schaltbaren Auslassventil eines zumindest teilweise variablen Ventiltriebs ausgestattet ist, wobei ein abgeschaltetes Auslassventil die zugehörige Auslassöffnung abschaltet und sich ein zugeschaltetes Auslassventil zwischen einer Offenstellung und einer Schließstellung unter Ausbildung eines Ventilhubs ∆h_max bewegt und dabei die zugehörige Auslassöffnung während einer Öffnungsdauer ∆t_max freigibt, und
• – jeder Zylinder zwecks Einstellung der Ladeluft einer Zylinderfrischladung mit mindestens einem weiteren zumindest teilweise variablen Ventiltrieb ausgestattet ist mit einem Ventil, das zwischen einer Ventilschließstellung und einer Ventiloffenstellung unter Vollführung eines Ventilhubs bewegbar ist, um eine ventilzugehörige Öffnung des Zylinders im Rahmen eines Ladungswechsels freizugeben oder zu versperren,

das dadurch gekennzeichnet ist, dass ausgehend von abgeschalteten Auslassöffnungen die erste Turbine aktiviert wird, indem

• – unter Bereitstellung eines angeforderten Drehmoments das zweite Absperrelement in der zweiten Bypassleitung der Turbine des zweiten Abgasturboladers in einem vorgebbaren Umfang geschlossen wird und weitere zumindest teilweise variable Ventiltriebe zwecks Einstellung einer erforderlichen Zylinderfrischladung verstellt werden, und
• – die abgeschalteten Auslassöffnungen zwecks Aktivierung der ersten Turbine zugeschaltet werden, wobei eine durch die zweite Turbine hindurchgeführte abnehmende Abgasmenge durch Einstellung der Zylinderfrischladung mittels Verstellen weiterer zumindest teilweise variabler Ventiltriebe kompensiert wird, in dem Umfang, dass ein angefordertes Drehmoment bereitgestellt wird.

The first sub-problem is solved by a method for controlling a supercharging pressure of a supercharged internal combustion engine having at least one cylinder head with at least two cylinders, in which

• Each cylinder has at least two outlet openings for discharging the exhaust gases, of which at least one is designed as a switchable outlet opening, wherein an exhaust pipe for discharging the exhaust gases via exhaust gas discharge system adjoins each outlet opening,
• An intake system is provided for supplying charge air to the at least two cylinders,
• At least two exhaust-gas turbochargers are provided, each exhaust-gas turbocharger comprising a turbine arranged in the exhaust-gas removal system and a compressor arranged in the intake system,
• The compressors of the at least two exhaust gas turbochargers are arranged in parallel in the intake system, each compressor being arranged in a separate intake line of the intake system and bringing the separate intake lines downstream of the compressor into an overall intake line,
• To merge the exhaust gas lines of the switchable outlet openings of the at least two cylinders to form a first exhaust gas manifold to form a first overall exhaust gas line which is connected to the turbine of the first exhaust gas turbocharger,
• To merge the exhaust gas lines of the other outlet openings of the at least two cylinders to form a second exhaust gas manifold to form a second overall exhaust line, which is connected to the turbine of the second exhaust gas turbocharger,
• A first shut-off element is arranged in the associated first intake line downstream of the compressor of the first exhaust-gas turbocharger,
• The turbine of the second exhaust-gas turbocharger is designed as a waste-gate turbine, wherein a second bypass line branches off from the exhaust-gas removal system upstream of this second turbine and a second shut-off element is provided in the second bypass line,
• - Each switchable outlet opening is equipped with a switchable exhaust valve of an at least partially variable valve train, wherein a shut-off exhaust valve, the associated outlet opening switches off and a switched exhaust valve between an open position and a closed position to form a valve lift .DELTA.h _max moves while the associated outlet opening during a Opening duration Δt _max releases, and
• - Each cylinder for the purpose of setting the charge air of a cylinder fresh charge with at least one further at least partially variable valve train is equipped with a valve which is movable between a valve closed position and a valve open position under full control of a valve lift to release a valve-related opening of the cylinder as part of a charge cycle or block,

characterized in that, starting from switched off outlet openings, the first turbine is activated by

• - Provided a requested torque, the second shut-off element in the second bypass line of the turbine of the second exhaust gas turbocharger is closed to a predetermined extent and further at least partially variable valve trains are adjusted in order to set a required fresh cylinder charge, and
• The switched-off outlet openings are switched on to activate the first turbine, wherein a decreasing exhaust gas quantity passed through the second turbine is compensated for by adjusting the cylinder fresh charge by adjusting further at least partially variable valve trains, to the extent that a requested torque is provided.

According to the method according to the invention preparatory measures are carried out before switching on the switched-off outlet openings in order to counteract a torque drop when activating the first turbine effectively, preferably without delay.

Thus, the amount of exhaust gas guided past the second turbine is reduced by at least partially closing the second shut-off element or the second bypass line, the power additionally generated at the second turbine, which is available as additional compressor power, increasing or increasing the boost pressure on the inlet side , An increased boost pressure is namely compensated according to the invention in that the cylinder fresh charge, ie in the cylinders after the charge cycle remaining charge air mass, adjusted and dosed, in particular can be kept constant.

The latter is carried out using further at least partially variable valve trains, which are provided on the inlet side and / or outlet side.

An increased or higher charge pressure can be compensated for example by reducing the volumetric air intake. The charge air mass supplied to a cylinder depends on both the boost pressure and the volume supplied. Ie. an increased or higher boost pressure can be compensated by reducing the volumetric efficiency λ _l, where: λ _l = m _z / m _th = V _z · ρ _z / V _th · ρ _th = V _z / V _th

The mass of the supplied fresh cylinder charge is denoted by m _z and the theoretically deliverable fresh cylinder charge with m _th , wherein for the theoretical charge density ρ _th and the charge density ρ _z in the cylinder is approximately: ρ _th = ρ _z . The density ρ is determined in each case by the boost pressure. The theoretical air consumption V _th is made up of the stroke volume and the compression volume.

If the requested torque in maintaining the preparatory measures is to be maintained unchanged, ie maintained, the mass of the cylinder fresh charge must be maintained. At higher boost pressure, the at least partially variable valve trains must then be adjusted in such a way that the volumetric air feed V _z , ie the volumetric fresh cylinder charge is reduced. The second compressor is operated at a significantly higher speed than would actually be required and thus has a momentary speed reserve.

If the switched-off outlet openings are now activated for the purpose of activating the first turbine, the exhaust gas quantity discharged from the cylinders via the connected outlet openings, ie. H. the exhaust gas flow, which now lacks at the second turbine, compensated by adjusting the cylinder fresh charge by adjusting the further at least partially variable valve trains, to the extent that the requested torque is provided or the existing instantaneous torque is maintained.

Although the exhaust gas flow through the second turbine decreases when the first turbine is switched on. The observed from the prior art torque drop due to a boost pressure loss but remains out of the invention.

A torque drop when activating the first turbine can be counteracted almost without delay, since according to the invention inlet side, d. H. on the side of the intake system, influence on the fresh cylinder charge is taken, namely using at least partially variable valve trains or by changing the timing and / or the valve lift of these valve trains.

This procedure allows a very responsive boost pressure control. Compared to methods in which the charge pressure on the exhaust side by adjusting the second shut-off, d. H. By closing the second bypass line is increased or should be increased, the inventive method for controlling the boost pressure proves to be much faster.

The inventive method solves the first of the invention underlying subtask, namely to show a method according to the preamble of claim 1, with which the exhaust gas turbocharging and torque characteristics of the internal combustion engine, in particular the transient behavior, can be further improved.

An internal combustion engine according to the invention may also have two cylinder heads. There may also be provided three exhaust gas turbochargers.

In the prior art, three-cylinder in-line engines are rarely equipped with two parallel turbines. However, the merging of the exhaust pipes according to the invention makes this possible without problems, although three-cylinder in-line engines of a grouping, in particular a cylinder grouping, are inherently difficult to access.

Also advantageous are embodiments in which the internal combustion engine for carrying out the method according to the invention comprises a cylinder head with three cylinders.

Further advantageous embodiments of the method according to the invention are discussed in connection with the subclaims.

Embodiments of the method are advantageous in which, starting from shut-off outlet openings, the first turbine is activated by closing the second shut-off element while maintaining the torque to a predeterminable extent and further at least partially variable valve trains are adjusted to maintain the fresh cylinder charge to a required extent.

In the present case, the preparatory measures while maintaining the torque performed, ie the internal combustion engine is operated stationary in this phase of the process, at least in terms of torque, ie with substantially unchanged fresh cylinder charge. In the method according to the invention in general, however, the preparatory measures take place while providing a requested torque. The latter formulation therefore also includes dynamic processes, ie a load change during the implementation of the preparatory measures. The torque and the amount of charge air supplied to the cylinders can be maintained unchanged, ie maintained or demand controlled, ie changed.

Embodiments of the method are also advantageous in which, starting from deactivated outlet openings, the first turbine is activated by switching off the switched-off outlet openings in order to activate the first turbine, wherein a decreasing exhaust gas quantity passed through the second turbine is at least partially increased by increasing the volumetric cylinder fresh charge by adjusting further variable valve trains is compensated, to the extent that a requested torque is provided or a momentarily existing torque is maintained unchanged.

In the method according to the invention is generally from an adjustment of the cylinder fresh charge the speech. When activating the first turbine, however, an increase in the volumetric cylinder fresh charge will be required on a regular basis, since the boost pressure decreases when the exhaust gas flow passed through the second turbine decreases.

Nevertheless, dynamic processes are also included in the general method of the invention. Ie. a load change when switching on the switched-off outlet openings is taken into account. Namely, the requested torque may also decrease during the activation of the first turbine, and to an extent which not only brings about a reduction in the fresh cylinder charge, but may also necessitate a reduction in the fresh cylinder volumetric charge, although that supplied to the second turbine Exhaust gas flow decreases and the boost pressure drops.

The advantages described above for the switching on of the switched-off outlet openings or the activation of the first turbine also exist analogously when switching off the switched-on outlet openings or deactivating the first turbine.

• – unter Bereitstellung eines angeforderten Drehmoments das zweite Absperrelement in der zweiten Bypassleitung der Turbine des zweiten Abgasturboladers in einem vorgebbaren Umfang geöffnet wird und weitere zumindest teilweise variable Ventiltriebe zwecks Einstellung einer erforderlichen Zylinderfrischladung verstellt werden, und
• – die zugeschalteten Auslassöffnungen zwecks Deaktivierung der ersten Turbine abgeschaltet werden, wobei eine durch die zweite Turbine hindurchgeführte zunehmende Abgasmenge durch Einstellung der Zylinderfrischladung mittels Verstellen weiterer zumindest teilweise variabler Ventiltriebe kompensiert wird, in dem Umfang, dass ein angefordertes Drehmoment bereitgestellt wird.

Embodiments of the method in which the first turbine is deactivated on the basis of connected outlet openings are also advantageous

• - Provided a requested torque, the second shut-off in the second bypass line of the turbine of the second exhaust gas turbocharger is opened to a predetermined extent and further at least partially variable valve trains are adjusted for the purpose of setting a required fresh cylinder charge, and
• The switched-off outlet openings are switched off in order to deactivate the first turbine, wherein an increasing amount of exhaust gas passed through the second turbine is compensated by adjusting the cylinder fresh charge by adjusting further at least partially variable valve trains, to the extent that a requested torque is provided.

In this context, embodiments of the method are advantageous in which, starting from switched outlet openings, the first turbine is deactivated by opening the second shut-off element while maintaining the torque to a predeterminable extent and adjusting further at least partially variable valve trains to maintain the cylinder fresh charge to a required extent become.

Embodiments of the method in which the first turbine is deactivated on the basis of connected outlet openings are also advantageous in that the switched-on outlet openings are switched off in order to activate the first turbine, an increasing exhaust gas quantity guided through the second turbine being reduced by reducing the volumetric cylinder fresh charge by means of adjustment further at least partially variable valve trains is compensated, to the extent that a requested torque is provided or a momentarily existing torque is maintained unchanged.

With regard to the above variants, a distinction can again be made between method variants in which a requested torque is provided and dynamic processes are taken into account, and those in which the instantaneously present torque is maintained substantially unchanged, ie. H. is maintained.

In the following, in particular the different variants of the connection or disconnection of the switchable outlet openings will be discussed.

In this context, embodiments of the method are advantageous in which, starting from switched off outlet openings first turbine is activated by the switchable to the outlet openings belonging switchable exhaust valves are switched successively.

According to the above embodiment, the switchable outlet ports, i. H. the switchable exhaust valves associated with the switchable exhaust ports are not activated simultaneously upon activation of the first turbine, but gradually.

This procedure is characterized in that the number of connected outlet openings when activating the first turbine is successively increased. In this way, the amount of exhaust gas discharged from the cylinders via the connected outlet openings is likewise successively activated when the first turbine is activated. H. gradually, increased and not - as in the prior art - abruptly in full. As a result, the exhaust gas flow guided through the second turbine also does not decrease abruptly when activating the first turbine, which is why a boost pressure drop or torque drop to be triggered by the method according to the invention is lower.

When switching the switchable outlet openings in order to activate the first turbine, the exhaust gas flow, with which the first turbine is acted upon, gradually increased. The running gear of the connected turbine is accelerated with and with. The compressor of the first exhaust gas turbocharger remains during this start-up enough time to participate in building the boost pressure, d. H. even to generate boost pressure. The transient behavior of the turbocharger when activating the first turbine improves significantly, in particular because the second compressor unabated and undisturbed during this transition phase provides the requested boost pressure. This is achieved with a successive connection of the switchable outlet openings, which allows a successive increase in the exhaust gas flow supplied to the first turbine.

Embodiments of the method in which the first turbine is activated are advantageous in that the exhaust valves belonging to the switchable outlet openings are switched on in cylinders. If, for example, each cylinder has a switchable outlet opening, first the outlet opening of a first cylinder is switched on and this is subsequently repeated successively for the remaining cylinders.

In this context, embodiments of the method in which the first turbine is activated by switching on the outlet valves belonging to the switchable outlet openings in successive working cycles are advantageous. This variant of the method constitutes the fastest possible activation of the first turbine during the successive connection of the switchable exhaust valves.

In this context, embodiments of the method may also be advantageous in which the first turbine is activated by switching on the outlet valves belonging to the switchable outlet openings at intervals of a predeterminable number of working cycles. The exhaust valves belonging to the switchable outlet openings can be switched on, for example, at intervals of two or three working cycles. The distance can also vary with several switchable outlet openings, for example progressively smaller.

Embodiments of the method in which a shut-off outlet valve switches off and blocks the associated outlet opening are advantageous, so that no exhaust gas is supplied to the switched-off first turbine. In this case, the deactivated turbine exhaust gas is no longer supplied, d. H. the admission of the first turbine with exhaust gas is completely prevented. In terms of maintaining a minimum speed of the first turbine turned off, this approach is less advantageous.

Also advantageous are embodiments of the method in which a shut-off exhaust valve is operated with a reduced stroke .DELTA.h _low with .DELTA.h _low <Δh _max when opening, so that the amount of exhaust gas supplied to the switched-off first turbine is reduced.

According to the above variant of the method, the valves of the switchable outlet openings are not switched off in the literal sense when the first turbine is deactivated, but continue to be operated and actuated continuously with a reduced stroke Δh _low .

The shut-off first turbine is then supplied with a reduced amount of exhaust gas using the switchable exhaust ports associated switchable exhaust valves, namely by reducing the stroke of the associated exhaust valves.

In this way, the speed of the turned-off first turbine drops less and a minimum speed of the supercharger shaft can be ensured or maintained. The response improves. There is another advantage.

If the exhaust gas supply to the deactivated first turbine is completely prevented, as a result of falling speed of the supercharger shaft leak the seal of the bearing of this oil-lubricated supercharger shaft. Oil leakage has serious disadvantages both on the exhaust side and on the intake side. If oil enters the exhaust system via the switchable first turbine, downstream exhaust aftertreatment systems, ie catalytic converters and particulate filters, are contaminated with oil, which can significantly reduce the conversion rate of these exhaust aftertreatment systems. If necessary, even shorten the life of the exhaust aftertreatment systems, whose functionality can also be endangered in principle. If oil enters the intake system via the associated first compressor, the fresh charge that is contaminated with oil adversely affects the combustion process, which can in particular greatly increase particulate emissions. The oil can also deposit on the inner walls of the intake system and deteriorate the flow conditions in the intake system or in the compressor and contaminate a downstream intercooler.

For operating an internal combustion engine, in which a switchable exhaust valve is an exhaust valve adjustable with respect to the valve lift .DELTA.h, embodiments of the method are advantageous in which a switched-off exhaust valve is switched on by increasing the associated valve lift to the valve lift .DELTA.h _max .

If lift valves are used, which can not only be switched on and off, but are further adjustable with regard to the valve lift .DELTA.h, the valve lift .DELTA.h can be increased successively. In this way, the exhaust port connected via the outlet opening can be successively discharged from a cylinder. H. gradually, be increased and does not need to be fully realized in a flash.

A in the above sense with respect to the valve lift .DELTA.h adjustable exhaust valve may be a lift valve, the at least three different valve lifts .DELTA.h ₁ , .DELTA.h ₂ , .DELTA.h ₃ allows. Such an adjustable in the valve lift .DELTA.h lift valve according to the invention allows next to the disabled state without hub or with reduced stroke .DELTA.h _low and the activated mode with normal stroke .DELTA.h _max at least one further operating mode with reduced stroke or several other modes of operation with different strokes. In this case, the maximum stroke of the valve when passing through the valve lift curve in the respective mode is considered and designated as stroke.

For operating an internal combustion engine, in which a switchable exhaust valve is a two-stage adjustable with respect to the valve lift .DELTA.h outlet valve can be advantageous in this context, which are characterized in that a shut-off exhaust valve is switched by the associated valve in one step is increased to the valve lift Δh _max .

In order to operate an internal combustion engine in which a switchable exhaust valve is a multi-stage adjustable exhaust valve with respect to the valve lift .DELTA.h, process variants may be advantageous in this context, which are characterized in that a switched-off exhaust valve is switched on by the associated valve lift in stages the valve lift Δh _{max is} increased.

Embodiments of the method are advantageous in which a switched-off outlet valve is opened for a shorter opening duration Δt _short with Δt _short <Δt _max and releases the associated outlet opening, so that the quantity of exhaust gas supplied to the switched-off first turbine is reduced. The statements made above in connection with the reduced stroke Δh _low apply analogously.

Embodiments of the method in which a shut-off outlet valve is switched on are advantageous in that the associated opening duration is extended to the opening duration Δt _max ; successive, incremental or two-stage.

The first compressor may be disconnected from the remainder of the intake system with the first turbine disconnected to prevent the second compressor from delivering to the first compressor. For this purpose, a first shut-off element is arranged in the associated intake pipe downstream of the first compressor.

In order that the first compressor then may not promote against the resistance of the closed first shut-off element, it is advantageous to provide a blow-off line, via which the charge air can escape or be removed.

Therefore, embodiments of the method in which a blow-off line is provided which branches off between the first compressor and the first shut-off element from the associated first intake line and in which a third shut-off element is arranged, are advantageous in this connection. This third shut-off element preferably depends on the first shut-off is actuated.

Embodiments of the method are advantageous in which a switched-off outlet valve is actuated intermittently in such a way that the associated exhaust port is kept closed for a first predetermined number of cycles and operated for a second predetermined number of cycles and is opened so that the exhaust gas supplied to the first turbine is reduced by phasing deactivating the switchable exhaust ports. The supply of exhaust gas to the first turbine is then not completely prevented.

The valves of the switchable outlet openings are then not kept closed continuously even when the first turbine is deactivated, but opened in phases for one working cycle or several cycles, so that the turbine is switched off a small amount of exhaust gas is supplied and the speed of the turbine shutdown drops less.

• – jeder Zylinder mindestens zwei Auslassöffnungen zum Abführen der Abgase aufweist, von denen mindestens eine als schaltbare Auslassöffnung ausgebildet ist, wobei sich an jede Auslassöffnung eine Abgasleitung zum Abführen der Abgase via Abgasabführsystem anschließt,
• – ein Ansaugsystem zum Zuführen von Ladeluft zu den mindestens zwei Zylindern vorgesehen ist,
• – mindestens zwei Abgasturbolader vorgesehen sind, wobei jeder Abgasturbolader eine im Abgasabführsystem angeordnete Turbine und einen im Ansaugsystem angeordneten Verdichter umfasst,
• – die Verdichter der mindestens zwei Abgasturbolader parallel im Ansaugsystem angeordnet sind, wobei jeder Verdichter in einer separaten Ansaugleitung des Ansaugsystems angeordnet ist und die separaten Ansaugleitungen stromabwärts der Verdichter zu einer Gesamtansaugleitung zusammenführen,
• – die Abgasleitungen der schaltbaren Auslassöffnungen der mindestens zwei Zylinder unter Ausbildung eines ersten Abgaskrümmers zu einer ersten Gesamtabgasleitung zusammenführen, welche mit der Turbine des ersten Abgasturboladers verbunden ist,
• – die Abgasleitungen der anderen Auslassöffnungen der mindestens zwei Zylinder unter Ausbildung eines zweiten Abgaskrümmers zu einer zweiten Gesamtabgasleitung zusammenführen, welche mit der Turbine des zweiten Abgasturboladers verbunden ist,
• – stromabwärts des Verdichters des ersten Abgasturboladers ein erstes Absperrelement in der zugehörigen ersten Ansaugleitung angeordnet ist,
• – die Turbine des zweiten Abgasturboladers als Waste-Gate-Turbine ausgeführt ist, wobei stromaufwärts dieser zweiten Turbine eine zweite Bypassleitung vom Abgasabführsystem abzweigt und ein zweites Absperrelement in der zweiten Bypassleitung vorgesehen ist, und
• – jede schaltbare Auslassöffnung mit einem schaltbaren Auslassventil eines zumindest teilweise variablen Ventiltriebs ausgestattet ist, wobei ein abgeschaltetes Auslassventil die zugehörige Auslassöffnung abschaltet und sich ein zugeschaltetes Auslassventil zwischen einer Offenstellung und einer Schließstellung unter Ausbildung eines Ventilhubs ∆h_max bewegt und dabei die zugehörige Auslassöffnung während einer Öffnungsdauer ∆t_max freigibt,

und die dadurch gekennzeichnet ist, dass

• – jeder Zylinder zwecks Einstellung der Ladeluft einer Zylinderfrischladung mit mindestens einem weiteren zumindest teilweise variablen Ventiltrieb ausgestattet ist mit einem Ventil, das zwischen einer Ventilschließstellung und einer Ventiloffenstellung unter Vollführung eines Ventilhubs bewegbar ist, um eine ventilzugehörige Öffnung des Zylinders im Rahmen eines Ladungswechsels freizugeben oder zu versperren.

The second sub-task on which the invention is based, namely to provide a supercharged internal combustion engine for carrying out a method of the type described above, is achieved by a supercharged internal combustion engine having at least one cylinder head with at least two cylinders, in which

• Each cylinder has at least two outlet openings for discharging the exhaust gases, of which at least one is designed as a switchable outlet opening, wherein an exhaust pipe for discharging the exhaust gases via exhaust gas discharge system adjoins each outlet opening,
• An intake system is provided for supplying charge air to the at least two cylinders,
• At least two exhaust-gas turbochargers are provided, each exhaust-gas turbocharger comprising a turbine arranged in the exhaust-gas removal system and a compressor arranged in the intake system,
• The compressors of the at least two exhaust gas turbochargers are arranged in parallel in the intake system, each compressor being arranged in a separate intake line of the intake system and bringing the separate intake lines downstream of the compressor into an overall intake line,
• To merge the exhaust gas lines of the switchable outlet openings of the at least two cylinders to form a first exhaust gas manifold to form a first overall exhaust gas line which is connected to the turbine of the first exhaust gas turbocharger,
• To merge the exhaust gas lines of the other outlet openings of the at least two cylinders to form a second exhaust gas manifold to form a second overall exhaust line, which is connected to the turbine of the second exhaust gas turbocharger,
• A first shut-off element is arranged in the associated first intake line downstream of the compressor of the first exhaust-gas turbocharger,
• - The turbine of the second exhaust gas turbocharger is designed as a waste-gate turbine, upstream of said second turbine, a second bypass line branches off from the Abgasabführsystem and a second shut-off element is provided in the second bypass line, and
• - Each switchable outlet opening is equipped with a switchable exhaust valve of an at least partially variable valve train, wherein a shut-off exhaust valve, the associated outlet opening switches off and a switched exhaust valve between an open position and a closed position to form a valve lift .DELTA.h _max moves while the associated outlet opening during a Opening period Δt _max releases,

and which is characterized in that

• - Each cylinder for the purpose of setting the charge air of a cylinder fresh charge with at least one further at least partially variable valve train is equipped with a valve which is movable between a valve closed position and a valve open position under full control of a valve lift to release a valve-related opening of the cylinder as part of a charge cycle or block.

The comments made in connection with the method according to the invention also apply to the internal combustion engine according to the invention.

With regard to the adjustability of the further at least partially variable valve trains, what has been said in connection with the switchable outlet openings or what has been said in connection with their at least partially variable valve drives applies.

Downstream of the compressor of the first exhaust gas turbocharger, a first shut-off element is arranged in the associated first intake line, so that the first compressor can be separated from the remainder of the intake system with the first turbine switched off and the second compressor does not feed into the first compressor. The first compressor is not seriously driven when the turbine is off.

So that the first compressor does not promote against the resistance of the closed first shut-off element, a blow-off line is advantageous over which the charge air can escape or be removed.

Therefore, embodiments of the internal combustion engine in which a blow-off line is provided between the first compressor and the first shut-off element from the associated first one are also advantageous in this connection Suction line branches off and in which a second shut-off element is arranged.

Embodiments of the internal combustion engine in which the blow-off line opens into the other intake line upstream of the second compressor are advantageous.

The fact that the blow-off line opens in the present case upstream of the second compressor in the intake system, has advantages, since there is usually negative pressure upstream of the second compressor, whereby a pressure gradient is created, through which the promotion of the charge air compressed by the first compressor is supported.

Also advantageous are embodiments of the internal combustion engine, in which at least one turbine has a variable turbine geometry, which allows a high degree of adaptation to the respective operating point by adjusting the turbine geometry or the effective turbine cross section. In this case, upstream of the impeller of the turbine vanes for influencing the flow direction are arranged. Unlike the blades of the rotating impeller, the vanes do not rotate with the shaft of the turbine, i. H. the impeller. Although the guide vanes are arranged stationary, but not completely immobile, but rotatable about its axis, so that the flow of the blades can be influenced.

On the other hand, if a turbine has a fixed invariable geometry, the vanes are not only stationary but also completely immovable, i. H. rigidly fixed.

Embodiments of the internal combustion engine in which the exhaust pipes of the at least two cylinders merge within the at least one cylinder head to form the overall exhaust gas lines are advantageous.

The cylinder head of a supercharged internal combustion engine is basically a thermally and mechanically highly loaded component. In particular, in the integration of the exhaust manifold, the thermal load of the internal combustion engine or the cylinder head increases again, so that increased demands are placed on the cooling. Therefore, embodiments of the supercharged internal combustion engine in which liquid cooling is provided are advantageous.

Embodiments of the internal combustion engine in which each cylinder is equipped on the inlet side with at least one further at least partially variable valvetrain with an inlet valve that is movable between a valve closed position and a valve open position while performing a valve lift to a valve-associated inlet opening of the invention are advantageous Release or block cylinders as part of a change of charge.

Embodiments of the internal combustion engine in which each cylinder is equipped on the outlet side with at least one further at least partially variable valve drive with an outlet valve that is movable between a valve closed position and a valve open position while performing a valve lift in order to set a valve-related outlet opening of the cylinder are advantageous Release or block cylinders as part of a change of charge.

An altered charge pressure can be compensated according to the invention in that the cylinder fresh charge, d. H. the charge air mass remaining in the cylinders after the charge change is adjusted and metered. Serve for this purpose, at least partially variable valve trains, which are provided on the inlet side and / or outlet side.

In the following the invention with reference to an embodiment and according to 1 described in more detail. Hereby shows:

1 schematically a first embodiment of an internal combustion engine for carrying out the method.

1 schematically shows a first embodiment of the supercharged internal combustion engine 1 that with two exhaust gas turbochargers 8th . 9 Is provided. Every turbocharger 8th . 9 includes a turbine 8a . 9a and a compressor 8b . 9b , The hot exhaust gas relaxes in the turbines 8a . 9a under energy release. The compressors 8b . 9b compress the charge air via the intake system 11 , Intercooler 10 and plenum 12 the cylinders 3 is supplied, whereby a charge of the internal combustion engine 1 is reached.

It is a four-cylinder in-line engine 1 in which the four cylinders 3 along the longitudinal axis of the cylinder head 2 , ie arranged in series. Every cylinder 3 has two outlet openings 4 . 4a . 4b to which are exhaust pipes 5a . 5b for removing the exhaust gases via exhaust gas removal system 5 connect. One outlet each 4 . 4a every cylinder 3 is as a switchable outlet opening 4a formed, which is switched on only when the downstream arranged first turbine 8a to be activated; For example, if the amount of exhaust gas exceeds a predetermined amount of exhaust gas.

The exhaust pipes 5a the switchable outlet openings 4a all cylinders 3 lead to the formation of a first exhaust manifold 6a to a first total exhaust line 7a together, which with the turbine 8a of the first exhaust gas turbocharger 8th connected as a result, which as a switchable turbine 8a acts.

The turbine 8a of the first exhaust gas turbocharger 8th ie the first turbine 8a , is designed as a waste gate · turbine. Ie. upstream of the first turbine 8a A first bypass line, in which a shut-off element is arranged, branches from the associated first overall exhaust gas line 7a from. This first bypass line opens downstream of the first turbine 8a back into the overall exhaust line 7a ,

The exhaust pipes 5b the other outlet openings 4b all cylinders 3 lead to the formation of a second exhaust manifold 6b to a second total exhaust line 7b together, which with the turbine 9a the second exhaust gas turbocharger 9 connected is.

The turbine 9a the second exhaust gas turbocharger 9 ie the second turbine 9a , is designed as a waste · gate turbine. Ie. upstream of the second turbine 9a branches a second bypass line 9c in which a second shut-off element 9d is arranged by the Abgasabführsystem 5 from. The second bypass line 9c opens downstream of the second turbine 9a back into the exhaust system 5 ,

The internal combustion engine 1 has an intake system 11 for supplying the charge air to the cylinders 3 , where the compressors 8b . 9b the turbocharger 8th . 9 parallel in the intake system 11 are arranged. The first compressor 8b is in a first intake pipe 11a arranged and the second compressor 9b in a second suction line 11b , The suction lines 11a . 11b lead downstream of the compressor 8b . 9b to a total suction line together.

Downstream of the first compressor 8b is a first shut-off element 13a in the associated first intake pipe 11a arranged so that the first compressor 8b with deactivated first turbine 8a completely from the rest of the intake system 11 disconnected, ie can be disabled and the second compressor 9b not in the first compressor 8b into it. So that the first compressor 8b not against the resistance of the closed first shut-off element 13a has to promote, is a blow-off line 14 provided between the first compressor 8b and the first shut-off element 13a from the first intake pipe 11a branches off and in the third shut-off 13b is arranged (shown in dotted lines).

Via blow-off line 14 can charge air into the second intake pipe 11b upstream of the second compressor 9b be encouraged, the third shut-off 13b preferably in dependence on the first shut-off element 13a operated, that is controlled.

Each switchable outlet opening 4a is equipped with a switchable lift valve, with a shut off exhaust valve, the associated outlet opening 4a turns off and locks. A switched-off outlet valve moves between an open position and a closed position to form a valve lift .DELTA.h _max and thereby gives the associated outlet opening 4a during an opening period .DELTA.t _max free.

Starting from switched off outlet openings 4a is to activate the first turbine 8a initially while maintaining the torque, the second shut-off 9d in the second bypass line 9c closed to a specifiable extent and exerted influence on the fresh cylinder charge. To maintain the instantaneous torque, the cylinder fresh charge must remain unchanged.

Each cylinder has to be able to adjust the cylinder fresh charge or the charge air of the cylinder fresh charge 3 via at least one further at least partially variable valve drive, which can be provided on the inlet side and / or outlet side. By varying the control times, ie the valve closing time and / or the valve opening time, or the valve lift of the associated valve, influence can be exerted on the cylinder fresh charge, ie the charge air mass, in particular on the volumetric cylinder fresh charge, ie the volumetric air feed V _z .

Closing the second shut-off element 9d in the second bypass line 9c On the inlet side leads to a higher boost pressure, which can be compensated by reducing the volumetric use of air V _z , ie by reducing the degree of delivery λ _l .

The at least partially variable valve trains must therefore be adjusted in such a way that the volumetric air feed V _z , ie the volumetric fresh cylinder charge is reduced.

In a next process step then the shut-off outlet openings 4a to activate the first turbine 8a switched on, one through the second turbine 9a passed decreasing exhaust gas inlet side conditionally lower charge pressure, which is compensated by increasing the volumetric cylinder fresh charge V _z , ie by increasing the degree of delivery λ _l . For this purpose, the further at least partially variable valve trains are adjusted such that the requested torque is provided or the currently present torque can be maintained.

LIST OF REFERENCE NUMBERS

1

 supercharged internal combustion engine, four-cylinder in-line engine

2

 cylinder head

3

 cylinder

4

 outlet

4a

 switchable outlet opening

4b

 other outlet opening

5

 Abgasabführsystem

5a

 Exhaust pipe of a switchable outlet opening

5b

 exhaust pipe

6a

 first exhaust manifold

6b

 second exhaust manifold

7a

 first total exhaust gas line

7b

 second total exhaust line

8th

 first exhaust gas turbocharger

8a

 first turbine, switchable turbine

8b

 first compressor

9

 second exhaust gas turbocharger

9a

 second turbine

9b

 second compressor

9c

 second bypass line, bypass line of the second turbine

9d

 second shut-off element

10

 Intercooler

11

 intake system

11a

 first separate suction line

11b

 second separate suction line

12

 plenum

13a

 first shut-off element

13b

 third shut-off element

14

 blow-off line

.delta.h

 Valve lift of a switchable exhaust valve

m _th

 Mass of theoretically deliverable fresh cylinder charge

m _z

 Mass of fresh cylinder charge supplied

ρ _th

 theoretical charge density

ρ _z

 Charge density in the cylinder

.delta.t

 Opening time of a switchable outlet valve

V _th

 theoretical air deployment

V _z

 volumetric air deployment

Claims (23)

Method for controlling a boost pressure of a supercharged internal combustion engine ( 1 ) with at least one cylinder head ( 2 ) with at least two cylinders ( 3 ), in which - each cylinder ( 3 ) at least two outlet openings ( 4 . 4a . 4b ) for discharging the exhaust gases, of which at least one as a switchable outlet ( 4a ) is formed, wherein at each outlet opening ( 4 . 4a . 4b ) an exhaust pipe ( 5a . 5b ) for discharging the exhaust gases via Abgasabführsystem ( 5 ), - an intake system ( 11 ) for supplying charge air to the at least two cylinders ( 3 ), - at least two exhaust gas turbochargers ( 8th . 9 ) are provided, each exhaust gas turbocharger ( 8th . 9 ) in the exhaust gas removal system ( 5 ) arranged turbine ( 8a . 9a ) and one in the intake system ( 11 ) arranged compressors ( 8b . 9b ), - the compressors ( 8b . 9b ) of the at least two turbocharger ( 8th . 9 ) parallel in the intake system ( 11 ) are arranged, each compressor ( 8b . 9b ) in a separate suction line ( 11a . 11b ) of the intake system ( 11 ) and the separate suction lines ( 11a . 11b ) downstream of the compressors ( 8b . 9b ) to a total intake line, - the exhaust pipes ( 5a ) of the switchable outlet openings ( 4a ) the at least two cylinders ( 3 ) to form a first exhaust manifold ( 6a ) to a first overall exhaust gas line ( 7a ), which with the turbine ( 8a ) of the first exhaust gas turbocharger ( 8th ), - the exhaust pipes ( 5b ) of the other outlet openings ( 4b ) the at least two cylinders ( 3 ) to form a second exhaust manifold ( 6b ) to a second total exhaust line ( 7b ), which with the turbine ( 9a ) of the second exhaust gas turbocharger ( 9 ), - downstream of the compressor ( 8b ) of the first exhaust gas turbocharger ( 8th ) a first shut-off element ( 13a ) in the associated first intake line ( 11a ), - the turbine ( 9a ) of the second exhaust gas turbocharger ( 9 ) is designed as a wastegate turbine, wherein upstream of this second turbine ( 9a ) a second bypass line ( 9c ) from the exhaust gas removal system ( 5 ) branches off and a second shut-off element ( 9d ) in the second bypass line ( 9c ), - each switchable outlet ( 4a ) is equipped with a switchable exhaust valve of an at least partially variable valve train, wherein a shut-off exhaust valve, the associated outlet opening ( 4a ) and a switched-off exhaust valve between an open position and a closed position to form a valve lift .DELTA.h _max moves and thereby the associated outlet opening ( 4a ) releases Δt _max during an opening period, and - each cylinder ( 3 ) is equipped with at least one further at least partially variable valvetrain for adjusting the charge air of a fresh cylinder charge with a valve which is movable between a valve closed position and a valve open position while performing a valve lift to a valve-associated opening of the cylinder ( 3 ) in the Release or blockage of a change of charge, characterized in that, starting from switched-off outlet openings ( 4a ) the first turbine ( 8a ) is activated by - providing the requested shut-off torque - the second shut-off element ( 9d ) in the second bypass line ( 9c ) of the turbine ( 9a ) of the second exhaust gas turbocharger ( 9 ) is closed to a predeterminable extent and further at least partially variable valve trains are adjusted for the purpose of setting a required fresh cylinder charge, and - the exhaust ports ( 4a ) for activation of the first turbine ( 8a ), one through the second turbine ( 9a ) is performed by adjusting the fresh cylinder charge by adjusting further at least partially variable valve trains is compensated, to the extent that a requested torque is provided. Method according to claim 1, characterized in that starting from shut-off outlet openings ( 4a ) the first turbine ( 8a ) is activated by maintaining the second shut-off element while retaining the torque ( 9d ) is closed to a predetermined extent and further at least partially variable valve trains for the purpose of maintaining the fresh cylinder charge are adjusted to a required extent. Method according to claim 1 or 2, characterized in that starting from shut-off outlet openings ( 4a ) the first turbine ( 8a ) is activated by the shut-off outlet openings ( 4a ) for activation of the first turbine ( 8a ), one through the second turbine ( 9a ) decreasing exhaust gas amount is compensated by increasing the volumetric cylinder fresh charge by adjusting further at least partially variable valve trains, to the extent that a requested torque is provided. Method according to one of the preceding claims, characterized in that starting from connected outlet openings ( 4a ) the first turbine ( 8a ) is deactivated by - providing the requested shut-off torque, the second shut-off element ( 9d ) in the second bypass line ( 9c ) of the turbine ( 9a ) of the second exhaust gas turbocharger ( 9 ) is opened to a predeterminable extent and further at least partially variable valve trains are adjusted for the purpose of setting a required fresh cylinder charge, and - the connected outlet openings ( 4a ) for the purpose of deactivating the first turbine ( 8a ), one through the second turbine ( 9a ) guided by adjusting the fresh cylinder charge by adjusting further at least partially variable valve trains is compensated, to the extent that a requested torque is provided. Method according to claim 4, characterized in that starting from connected outlet openings ( 4a ) the first turbine ( 8a ) is deactivated, while retaining the torque, the second shut-off element ( 9d ) is opened to a predetermined extent and further at least partially variable valve trains for the purpose of maintaining the cylinder fresh charge are adjusted to a required extent. Method according to claim 4 or 5, characterized in that starting from connected outlet openings ( 4a ) the first turbine ( 8a ) is deactivated by the connected outlet openings ( 4a ) for activation of the first turbine ( 8a ), one through the second turbine ( 9a ) is compensated by reducing the volumetric cylinder fresh charge by adjusting further at least partially variable valve trains, to the extent that a requested torque is provided. Method according to one of the preceding claims, characterized in that, starting from switched-off outlet openings ( 4a ) the first turbine ( 8a ) is activated by the switchable to the outlet openings ( 4a ) belonging switchable exhaust valves are switched successively. Method according to claim 7, characterized in that the first turbine ( 8a ) is activated by the switchable to the outlet openings ( 4a ) belonging exhaust valves are switched cylinder by cylinder. Method according to claim 7 or 8, characterized in that the first turbine ( 8a ) is activated by the switchable to the outlet openings ( 4a ) associated exhaust valves are connected in successive cycles. Method according to claim 7 or 8, characterized in that the first turbine ( 8a ) is activated by the switchable to the outlet openings ( 4a ) belonging exhaust valves are connected at a distance of a predetermined number of working cycles. Method according to one of the preceding claims, characterized in that a shut-off outlet valve, the associated outlet opening ( 4a ) shuts off and obstructs, leaving the shut off first turbine ( 8a ) no exhaust gas is supplied. Method according to one of claims 1 to 10, characterized in that a shut-off exhaust valve with a reduced stroke Δh _low with Δh _low <Δh _max when opening the associated outlet opening ( 4a ) is actuated, so that the first turbine switched off ( 8a ) supplied amount of exhaust gas is reduced. Method according to one of the preceding claims for operating an internal combustion engine ( 1 ), in which a switchable exhaust valve is an adjustable with respect to the valve lift .DELTA.h outlet valve, characterized in that a switched-off exhaust valve is switched on by the associated valve lift is increasingly increased to the valve lift .DELTA.h _max . Method according to one of claims 1 to 12 for operating an internal combustion engine ( 1 ), in which a switchable exhaust valve is a two-stage adjustable with respect to the valve lift .DELTA.h outlet valve, characterized in that a shut-off exhaust valve is switched on by the associated valve is increased in one step to the valve lift .DELTA.h _max . Method according to one of claims 1 to 13 for operating an internal combustion engine ( 1 ), in which a switchable exhaust valve is a multi-stage adjustable with respect to the valve lift .DELTA.h outlet valve, characterized in that a switched-off exhaust valve is switched on by the associated valve lift is gradually increased to the valve lift .DELTA.h _max . Method according to one of claims 1 to 10 or claim 12, characterized in that a switched-off exhaust valve is opened for a shortened opening duration Δt _short with Δt _short <Δt _max and the associated exhaust port ( 4a ), so that the first turbine switched off ( 8a ) supplied amount of exhaust gas is reduced. Method according to one of the preceding claims, characterized in that a switched-off exhaust valve is switched on by the associated opening period is extended to the opening duration .DELTA.t _max . Method according to one of claims 1 to 10, characterized in that a switched-off exhaust valve is actuated intermittently in such a way that the associated outlet opening ( 4a ) is kept closed for a first predetermined number of working cycles and is operated and opened for a second predetermined number of working cycles, so that the first turbine switched off ( 8a ) supplied by phased deactivation of the switchable outlet openings ( 4a ) is reduced. Charged internal combustion engine ( 1 ) for carrying out a method according to one of the preceding claims with at least one cylinder head ( 2 ) with at least two cylinders ( 3 ), in the - each cylinder ( 3 ) at least two outlet openings ( 4 . 4a . 4b ) for discharging the exhaust gases, of which at least one as a switchable outlet ( 4a ) is formed, wherein at each outlet opening ( 4 . 4a . 4b ) an exhaust pipe ( 5a . 5b ) for discharging the exhaust gases via Abgasabführsystem ( 5 ), - an intake system ( 11 ) for supplying charge air to the at least two cylinders ( 3 ), - at least two exhaust gas turbochargers ( 8th . 9 ) are provided, each exhaust gas turbocharger ( 8th . 9 ) in the exhaust gas removal system ( 5 ) arranged turbine ( 8a . 9a ) and one in the intake system ( 11 ) arranged compressors ( 8b . 9b ), - the compressors ( 8b . 9b ) of the at least two turbocharger ( 8th . 9 ) parallel in the intake system ( 11 ) are arranged, each compressor ( 8b . 9b ) in a separate suction line ( 11a . 11b ) of the intake system ( 11 ) and the separate suction lines ( 11a . 11b ) downstream of the compressors ( 8b . 9b ) to a total intake line, - the exhaust pipes ( 5a ) of the switchable outlet openings ( 4a ) the at least two cylinders ( 3 ) to form a first exhaust manifold ( 6a ) to a first overall exhaust gas line ( 7a ), which with the turbine ( 8a ) of the first exhaust gas turbocharger ( 8th ), - the exhaust pipes ( 5b ) of the other outlet openings ( 4b ) the at least two cylinders ( 3 ) to form a second exhaust manifold ( 6b ) to a second total exhaust line ( 7b ), which with the turbine ( 9a ) of the second exhaust gas turbocharger ( 9 ), - downstream of the compressor ( 8b ) of the first exhaust gas turbocharger ( 8th ) a first shut-off element ( 13a ) in the associated first intake line ( 11a ), - the turbine ( 9a ) of the second exhaust gas turbocharger ( 9 ) is designed as a wastegate turbine, wherein upstream of this second turbine ( 9a ) a second bypass line ( 9c ) from the exhaust gas removal system ( 5 ) branches off and a second shut-off element ( 9d ) in the second bypass line ( 9c ), and - each switchable outlet ( 4a ) is equipped with a switchable exhaust valve of an at least partially variable valve train, wherein a shut-off exhaust valve, the associated outlet opening ( 4a ) and a switched-off exhaust valve between an open position and a closed position to form a valve lift .DELTA.h _max moves and thereby the associated outlet opening ( 4a ) during an opening period Δt _max , characterized in that - each cylinder ( 3 ) is equipped with at least one further at least partially variable valvetrain for adjusting the charge air of a fresh cylinder charge with a valve which is movable between a valve closed position and a valve open position while performing a valve lift to a valve-associated opening of the cylinder ( 3 ) in the context of a change of cargo or block. Charged internal combustion engine ( 1 ) according to claim 19, characterized in that a blow-off line ( 14 ) provided between the first compressor ( 8b ) and the first shut-off element ( 13a ) from the associated first intake line ( 11a ) and in which a second shut-off element ( 13b ) is arranged. Charged internal combustion engine ( 1 ) according to claim 20, characterized in that the blow-off line ( 14 ) upstream of the second compressor ( 9b ) in the other intake line ( 11b ) opens. Charged internal combustion engine ( 1 ) according to one of claims 19 to 21, characterized in that - each cylinder ( 3 ) for adjusting the charge air of a fresh cylinder charge on the inlet side with at least one further at least partially variable valve train is provided with an inlet valve which is movable between a valve closed position and a valve open position to complete a valve lift to a valve-associated inlet opening of the cylinder ( 3 ) in the context of a change of cargo or block. Charged internal combustion engine ( 1 ) according to one of claims 19 to 22, characterized in that - each cylinder ( 3 ) is equipped with at least one further at least partially variable valvetrain for adjusting the charge air of a fresh cylinder charge with an exhaust valve which is movable between a valve closed position and a valve open position under full valve lift to a valve-related outlet opening of the cylinder ( 3 ) in the context of a change of cargo or block.

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