DE102014201685A1 - Exhaust-engine-loaded internal combustion engine with deactivatable cylinder and method for operating such an internal combustion engine - Google Patents

Abstract

The invention relates to a supercharged internal combustion engine (13) having at least two cylinders (1, 2, 3, 4), in which - each cylinder (1, 2, 3, 4) has at least one outlet opening, to which an exhaust pipe (7a, 7b) for discharging the exhaust gases via Abgasabführsystem (8) connects, - each cylinder (1, 2, 3, 4) has at least one inlet opening, to which a suction line (5a, 5b) for supplying charge air via the intake system (6) In that at least two cylinders (1, 2, 3, 4) are configured in such a way that they form at least two groups each having at least one cylinder (1, 2, 3, 4), wherein the at least one cylinder (1, 4 ) of a first group is a cylinder (1, 4) also in partial shutdown of the internal combustion engine (13) in operation and the at least one cylinder (2, 3) of a second group as a load-dependent switchable cylinder (2, 3) is formed, - Exhaust pipes (7a, 7b) of the cylinders (1, 2, 3, 4) of each cylinder group with the formation of an exhaust manifold, in each case merging into an overall exhaust gas line (7A, 7B), and - at least one exhaust gas turbocharger (12) is provided which has a turbine (12a) arranged in the exhaust gas removal system (8) and a compressor (12b) arranged in the intake system (6). wherein at least two exhaust gas turbochargers (12, 14) are provided, wherein the turbine (12a) of a first exhaust gas turbocharger (12) in the first exhaust line (7A) of the first cylinder group and the turbine (14a) of a second exhaust gas turbocharger (14) in the second overall exhaust gas line (7B) of the second cylinder group is arranged and the two associated compressors (12b, 14b) of the at least two exhaust gas turbochargers (12, 14) are arranged in parallel in the intake system (6).

Description

• – jeder Zylinder mindestens eine Auslassöffnung aufweist, an die sich eine Abgasleitung zum Abführen der Abgase via Abgasabführsystem anschließt,
• – jeder Zylinder mindestens eine Einlassöffnung aufweist, an die sich eine Ansaugleitung zum Zuführen von Ladeluft via Ansaugsystem anschließt,
• – mindestens zwei Zylinder in der Art konfiguriert sind, dass diese mindestens zwei Gruppen mit jeweils mindestens einem Zylinder bilden, wobei der mindestens eine Zylinder einer ersten Gruppe ein auch bei Teilabschaltung der Brennkraftmaschine in Betrieb befindlicher Zylinder ist und der mindestens eine Zylinder einer zweiten Gruppe als lastabhängig schaltbarer Zylinder ausgebildet ist,
• – die Abgasleitungen der Zylinder jeder Zylindergruppe unter Ausbildung eines Abgaskrümmers jeweils zu einer Gesamtabgasleitung zusammenführen, und
• – mindestens ein Abgasturbolader vorgesehen ist, der eine im Abgasabführsystem angeordnete Turbine und einen im Ansaugsystem angeordneten Verdichter umfasst.

The invention relates to a supercharged internal combustion engine having at least two cylinders, wherein

• Each cylinder has at least one outlet opening adjoined by an exhaust pipe for discharging the exhaust gases via the exhaust gas removal system,
• Each cylinder has at least one inlet opening adjoined by an intake line for supplying charge air via the intake system,
• - At least two cylinders are configured in such a way that they form at least two groups each having at least one cylinder, wherein the at least one cylinder of a first group is also in partial deactivation of the internal combustion engine in operation cylinder and the at least one cylinder of a second group as Load-dependent switchable cylinder is formed,
• - Combine the exhaust gas lines of the cylinder of each cylinder group to form an exhaust manifold to form an overall exhaust line, and
• - At least one exhaust gas turbocharger is provided which comprises a turbine arranged in the Abgasabführsystem and a compressor arranged in the intake system.

Furthermore, the invention relates to a method for operating such an internal combustion engine.

An internal combustion engine of the type mentioned is used as a motor vehicle drive. In the context of the present invention, the term internal combustion engine includes diesel engines and gasoline engines, but also hybrid internal combustion engines, which use a hybrid combustion process, and 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 switchable auxiliary drive additionally delivers power.

In the development of internal combustion engines, it is a fundamental goal to minimize fuel consumption, with an improved overall efficiency in the foreground of the efforts.

The fuel consumption and thus the efficiency, especially in gasoline engines, d. H. in spark-ignition internal combustion engines. The reason for this lies in the basic working method of the gasoline engine. The load control is usually carried out by means of a throttle valve provided in the intake system. By adjusting the throttle, the pressure of the intake air behind the throttle valve can be reduced more or less. The farther the throttle is closed, d. H. the more this obstructs the intake system, the higher the pressure loss of the intake air across the throttle and the lower the pressure of the intake air downstream of the throttle and before the intake into the at least two cylinders, d. H. Combustion chambers. With a constant combustion chamber volume, the air mass, d. H. the quantity will be set. This also explains why the quantity control proves to be disadvantageous especially in part-load operation, because low loads require high throttling and pressure reduction in the intake system, whereby the charge exchange losses increase with decreasing load and increasing throttling.

To reduce the losses described, various strategies for de-throttling a gasoline engine have been developed.

One approach to dethrottling the gasoline engine is, for example, an Otto engine working method with direct injection. The direct injection of the fuel is a suitable means for realizing a stratified combustion chamber charge. The direct injection of the fuel into the combustion chamber thus allows within certain limits a quality control of the gasoline engine. The mixture formation takes place by the direct injection of the fuel in the cylinders or in the air in the cylinders and not by external mixture formation, in which the fuel is introduced into the intake system in the intake air.

Another way to optimize the combustion process of a gasoline engine, is the use of an at least partially variable valve train. In contrast to conventional valve trains, in which both the stroke of the valves and the control times are not variable, these parameters influencing the combustion process and thus the fuel consumption can be varied more or less by means of variable valve trains. Throttle-free and thus lossless load control is already possible if the closing time of the intake valve and the intake valve lift can be varied. The mixture mass or charge air mass flowing into the combustion chamber during the intake process is then not controlled by means of a throttle valve, but via the intake valve stroke and the opening duration of the intake valve. However, variable valve trains are very cost-intensive and therefore often unsuitable for serial installation.

Another solution for dethrottling a gasoline engine offers the cylinder deactivation, ie the shutdown of individual cylinders in certain load ranges. The efficiency of the gasoline engine in partial load operation can by such Teilabschaltung improved, ie increased, because the shutdown of a cylinder of a multi-cylinder internal combustion engine increases the load of the remaining still in-befind cylinder with constant engine power, so that the throttle valve can be opened to introduce a larger air mass in these cylinders on or must, whereby a total Entdrosselung the internal combustion engine is achieved. The continuously operating cylinders operate during partial shutdown in the area of higher loads, where the specific fuel consumption is lower. The load collective is shifted to higher loads.

The further operated during the partial shutdown cylinder also have due to the larger air mass supplied or mixture mass improved mixture formation.

Further efficiency advantages result from the fact that a deactivated cylinder as a result of the lack of combustion no wall heat losses generated as a result of heat transfer from the combustion gases to the combustion chamber walls.

Although diesel engines, d. H. self-igniting internal combustion engines, due to the applied quality control higher efficiency, d. H. have a lower fuel consumption than gasoline engines, in which the load - as described above - is set by throttling or quantity control on the filling of the cylinder, there is room for improvement in diesel engines and improvement in terms of fuel consumption and efficiency.

A concept for reducing fuel consumption is also the cylinder deactivation in diesel engines, d. H. the shutdown of individual cylinders in certain load ranges. The efficiency of the diesel engine in part load operation can be improved by a partial shutdown, d. H. be increased, because the shutdown of at least one cylinder of a multi-cylinder internal combustion engine increases at constant engine power even in the diesel engine, the load of the remaining operating cylinders, so that these cylinders operate in areas of higher loads, in which the specific fuel consumption is lower. The load collective in part-load operation of the diesel engine is shifted to higher loads.

With regard to the wall heat losses, the same advantages result as in the gasoline engine, for which reason reference is made to the corresponding explanations.

The partial shutdown in diesel engines should also prevent the fuel-air mixture under the quality scheme with decreasing load by reducing the amount of fuel used too much.

The internal combustion engine according to the invention is a suitable for partial shutdown internal combustion engine, d. H. an internal combustion engine with at least one deactivatable cylinder.

The multi-cylinder internal combustion engines with partial deactivation described in the prior art and the associated methods for operating these internal combustion engines have a clear potential for improvement, as will be briefly explained below.

If, for the purpose of partial shutdown, the fuel supply to the deactivatable cylinders is prevented, d. H. If the associated valve drive of this cylinder is not deactivated or can not be deactivated, the deactivated cylinders continue to participate in the charge exchange. The charge cycle losses generated thereby by the deactivated cylinders reduce the improvements in fuel consumption and efficiency achieved by the partial shutdown and counteract these, so that the benefit of the partial shutdown is at least partially lost, ie. H. the partial shutdown in the sum actually brings a less significant improvement.

In practice, it is not always expedient to remedy the adverse effects described above, characterized in that switchable valve trains are provided because switchable valve trains such as variable valve trains are very expensive and are only partially suitable for mass production.

In addition, switchable valve trains would result in turbocharged supercharged by exhaust gas turbochargers to further problems, since the turbine of an exhaust gas turbocharger is to be interpreted to a certain amount of exhaust gas and thus to a certain number of cylinders. When the valve train of a deactivated cylinder is deactivated, the total mass flow through the cylinders of the internal combustion engine decreases due to the lack of mass flow through the deactivated cylinders. The exhaust gas mass flow guided through the turbine decreases and with it the turbine pressure ratio. This has the consequence that the boost pressure ratio also decreases, d. H. the charge pressure drops, and only a little fresh air or charge air is supplied or can be supplied to the cylinders which are still in operation. The low charge air flow can also cause the compressor to operate beyond the surge line.

The effects described above lead to a limitation of the applicability of the partial shutdown, namely a limitation of the Load range in which the partial shutdown can be used. The reduced charge air quantity, which is supplied to the operating during the partial shutdown cylinders, also reduces the effectiveness or quality of the combustion and has an adverse effect on fuel consumption and pollutant emissions.

The charge pressure at partial shutdown and thus the still in operation cylinders supplied charge air quantity could be increased, for example, by a small design of the turbine cross-section and simultaneous Abgasabblasung, whereby the relevant for a partial shutdown load range would be extended again. However, this approach has the disadvantage that the charging behavior is insufficient when all cylinders are operated.

The charge pressure at Teilabschaltung and thus the still in operation cylinders supplied charge air quantity could also be increased by the fact that the turbine is equipped with a variable turbine geometry, the adjustment of the effective

Turbine cross-section allows the current exhaust gas mass flow. At the same time, however, the exhaust gas back pressure in the exhaust gas removal system upstream of the turbine would increase, which in turn leads to higher charge exchange losses in the cylinders still in operation.

In view of the foregoing, it is an object of the present invention to provide a supercharged internal combustion engine according to the preamble of claim 1, which is improved in terms of partial shutdown and turbocharging.

It is another object of the present invention to provide a method of operating such a supercharged internal combustion engine.

• – jeder Zylinder mindestens eine Auslassöffnung aufweist, an die sich eine Abgasleitung zum Abführen der Abgase via Abgasabführsystem anschließt,
• – jeder Zylinder mindestens eine Einlassöffnung aufweist, an die sich eine Ansaugleitung zum Zuführen von Ladeluft via Ansaugsystem anschließt,
• – mindestens zwei Zylinder in der Art konfiguriert sind, dass diese mindestens zwei Gruppen mit jeweils mindestens einem Zylinder bilden, wobei der mindestens eine Zylinder einer ersten Gruppe ein auch bei Teilabschaltung der Brennkraftmaschine in Betrieb befindlicher Zylinder ist und der mindestens eine Zylinder einer zweiten Gruppe als lastabhängig schaltbarer Zylinder ausgebildet ist,
• – die Abgasleitungen der Zylinder jeder Zylindergruppe unter Ausbildung eines Abgaskrümmers jeweils zu einer Gesamtabgasleitung zusammenführen, und
• – mindestens ein Abgasturbolader vorgesehen ist, der eine im Abgasabführsystem angeordnete Turbine und einen im Ansaugsystem angeordneten Verdichter umfasst, und die dadurch gekennzeichnet ist, dass
• – mindestens zwei Abgasturbolader vorgesehen sind, wobei die Turbine eines ersten Abgasturboladers in der ersten Gesamtabgasleitung der ersten Zylindergruppe und die Turbine eines zweiten Abgasturboladers in der zweiten Gesamtabgasleitung der zweiten Zylindergruppe angeordnet ist und die zwei dazugehörigen Verdichter der mindestens zwei Abgasturbolader parallel im Ansaugsystem angeordnet sind.

The first sub-task is solved by a supercharged internal combustion engine with at least two cylinders, in the

• Each cylinder has at least one outlet opening adjoined by an exhaust pipe for discharging the exhaust gases via the exhaust gas removal system,
• Each cylinder has at least one inlet opening adjoined by an intake line for supplying charge air via the intake system,
• - At least two cylinders are configured in such a way that they form at least two groups each having at least one cylinder, wherein the at least one cylinder of a first group is also in partial deactivation of the internal combustion engine in operation cylinder and the at least one cylinder of a second group as Load-dependent switchable cylinder is formed,
• - Combine the exhaust gas lines of the cylinder of each cylinder group to form an exhaust manifold to form an overall exhaust line, and
• At least one exhaust-gas turbocharger is provided which comprises a turbine arranged in the exhaust-gas removal system and a compressor arranged in the intake system, and which is characterized in that
• - At least two exhaust gas turbochargers are provided, wherein the turbine of a first exhaust gas turbocharger in the first exhaust line of the first cylinder group and the turbine of a second exhaust gas turbocharger in the second exhaust line of the second cylinder group is arranged and the two associated compressor of the at least two turbochargers are arranged in parallel in the intake system.

The internal combustion engine according to the invention is equipped with at least two exhaust gas turbochargers and consequently with more than one turbine in the exhaust gas removal system. The turbines of the at least two exhaust-gas turbochargers are arranged in parallel in the exhaust-gas removal system, each cylinder group being assigned a turbine. This improves the charging behavior, d. H. the torque characteristic of the internal combustion engine, clearly, especially during partial shutdown.

Each turbine can be designed for the exhaust gas quantity of the associated cylinder group, i. H. on the number of cylinders of each group. If the at least one deactivatable cylinder of the second group is then deactivated during partial deactivation, this no longer necessarily has an influence on the exhaust gas quantity passed through the turbine of the first group, for which reason the turbine pressure ratio of this first turbine does not necessarily decrease. The boost pressure ratio does not drop and sufficient cylinders are supplied with charge air.

Preferably, the charge air supply to the deactivated cylinders is prevented or reduced and deactivated the compressor of the second exhaust gas turbocharger, for example by means of shut-off from the rest of the intake system.

In contrast to the prior art, according to which a single larger turbine is provided in the Abgasabführsystem, the turbines of the invention are at least two exhaust gas turbochargers smaller dimensions, since each turbine has not all cylinders, but only the cylinders of a group to supply with charge air. The smaller turbine runner results in less inertia, which improves in particular the response of the associated exhaust gas turbocharger and ultimately the internal combustion engine. This offers advantages, in particular, when the turbine assigned to the second cylinder group has to be accelerated again after completion of the partial shutdown.

With the internal combustion engine according to the invention, a supercharged internal combustion engine according to the preamble of claim 1 is provided, which is improved in terms of partial shutdown and turbocharging. Thus, the first object of the invention is solved.

The internal combustion engine according to the invention has at least two cylinders or at least two groups each having at least one cylinder. As such, three-cylinder engines configured in three groups of one cylinder each, or six-cylinder engines configured in three groups of two cylinders, are also internal combustion engines of the present invention. Then, the exhaust pipes of the cylinder together to form three exhaust manifolds to three total exhaust pipes together, with three exhaust gas turbochargers are provided and a turbine of an exhaust gas turbocharger is arranged in an overall exhaust line of a cylinder group.

The three cylinder groups can be successively switched on or off as part of a partial shutdown, whereby a two-time switching can be realized. The partial shutdown is thereby further optimized. The cylinder groups may also comprise a different number of cylinders, for example, in a three-cylinder engine, forming a one-cylinder group and a two-cylinder group.

The embodiment of the invention improves the efficiency of the internal combustion engine in partial load operation, d. H. at low and medium loads, respectively, such a load preferably being a load which is less than 50%, preferably less than 30%, of the maximum load at the instantaneous speed n.

Further advantageous embodiments of the supercharged internal combustion engine are discussed in connection with the subclaims.

Advantageous embodiments of the supercharged internal combustion engine, in which the intake system comprises at least two Gesamtansaugleitungen, wherein the compressor of the first exhaust gas turbocharger in a first Gesamtansaugleitung and the compressor of the second exhaust gas turbocharger is arranged in a second Gesamtansaugleitung.

Like the turbines in the present case, the compressors are arranged in parallel. This embodiment of the intake system allows the compressor of the second exhaust gas turbocharger, d. H. the second cylinder group to deactivate in a partial shutdown in an advantageous manner.

For this purpose, a shut-off can be arranged downstream of the compressor, with which this second compressor is separated by closing the shut-off element from the rest of the intake system.

In this context, embodiments of the supercharged internal combustion engine in which the at least two total intake lines can be connected to each other at least downstream of the compressor are advantageous. This embodiment allows a modification of the intake system, in particular depending on the operating condition of the cylinders of the second group. Depending on whether the second cylinder group is switched on or off, the at least two total intake lines downstream of the compressors may be interconnected or disconnected.

In separate Gesamtansaugleitungen each compressor supplies only its assigned cylinder group with charge air, so that when partial shutdown and deactivated second compressor, the deactivated cylinders of the second group are no longer supplied with charge air without additional measures are taken.

In interconnected intake manifolds, each compressor supplies all the cylinders with charge air, so that at partial shutdown - even with deactivated second compressor - and the deactivated cylinders of the second group are supplied with charge air from the first compressor, if in the intake system or the intake pipes of the deactivated cylinders no shut-off elements are provided with which the charge air supply can be prevented or reduced.

Also advantageous in this context are embodiments of the supercharged internal combustion engine in which the at least two total intake lines merge downstream of the compressor to form an intake manifold.

In the present case, the at least two total suction lines downstream of the compressor are permanently connected to each other, d. H. not separable from each other. Reference is made to the previous embodiment and the notes relating to the interconnected Gesamtansaugleitungen.

Also advantageous in this connection are embodiments of the supercharged internal combustion engine in which the at least two total intake lines open into a plenum upstream of the inlet openings. The plenum as a collection container serves to calm the charge air before entering the cylinder.

In this context, further advantageous embodiments of the supercharged internal combustion engine, in which in the second Gesamtansaugleitung downstream of the compressor of the second exhaust gas turbocharger, a first shut-off element is arranged. The first shut-off serves, as already mentioned, the deactivation of the second compressor during partial shutdown. When the second cylinder group is switched off, this compressor is no longer or only limitedly driven by the associated second turbine and indeed dependent on the control of the charge air supply to the deactivated cylinders. The closing of the first shut-off prevents both a charge air conveyance by means of the second compressor to the cylinders as well as a promotion of charge air by means of the first compressor in the second compressor.

In this context, embodiments of the supercharged internal combustion engine in which a bypass line is provided, which branches off from the second Gesamtansaugleitung upstream of the compressor of the second exhaust gas turbocharger and opens into the second Gesamtansaugleitung downstream of the compressor of the second exhaust gas turbocharger are advantageous. Thus, the second compressor does not promote or promote partial disconnection against the resistance of a sealed first shut-off, it is advantageous to provide a bypass line of the type described, which is opened at partial shutdown and the charge air bleed serves.

Therefore, embodiments of the supercharged internal combustion engine in which a second shut-off element is arranged in the bypass line are also advantageous.

Embodiments of the supercharged internal combustion engine in which means are provided with which a charge air supply to the at least one deactivated cylinder of the second group can be controlled during partial shutdown of the internal combustion engine are advantageous.

The charge air supply to the at least one cylinder which is also in operation during partial shutdown on the one hand and the at least one deactivated cylinder during partial shutdown on the other hand can in the present case be carried out and controlled independently of one another.

It opens the possibility to control the charge air supply to the deactivated cylinders, d. H. to reduce the amount of charge air supplied to these cylinders at partial shutdown or completely prevent. Either the charge air is no longer supplied to the at least one deactivated cylinder or the charge air quantity, which is supplied to the at least one deactivated cylinder during the partial shutdown, is set selectively, d. H. dosed.

The deactivated cylinders basically continue to participate in the charge cycle if the associated valvetrain of these cylinders is not shut down together with the cylinders. But the charge air can be reduced or prevented for example by means of shut-off. In this case, less or no charge air is supplied in order to reduce the charge cycle losses of the deactivated cylinders.

The reduced or completely missing charge air flow through the at least one deactivated cylinder leads to a reduced heat transfer due to convection, so that the deactivated cylinders do not cool or less during the partial shutdown. This has advantages in particular with regard to the pollutant emissions, in particular with regard to the emissions of unburned hydrocarbons, since the deactivated cylinders again reach or have their operating temperature immediately after termination of the partial shutdown.

Reducing the charge air flow may have advantages over completely suppressing the charge air flow. With a reduction of the charge air supply, the mass flow through the internal combustion engine is higher than when the supply of charge air is completely prevented. When charged by means of exhaust gas turbocharger internal combustion engine as the internal combustion engine according to the invention, the second turbine is also flowed through during partial shutdown, namely of charge air, which flows through the deactivated cylinder. Consequently, the second turbine is maintained at a certain minimum speed, so that the acceleration of this turbine at the completion of the partial shutdown can be significantly shortened.

In this context, embodiments of the supercharged internal combustion engine in which a third shut-off element is provided in the at least one intake line of the at least one load-dependent switch are advantageous, which releases the intake line for supplying charge air when the cylinder is switched on and blocks or narrows when the cylinder is switched off.

Embodiments of the supercharged internal combustion engine in which the third shut-off element is infinitely adjustable are advantageous. Then it is not only a prohibition of the charge air supply possible, but a targeted setting, ie dosing the charge air to the deactivated cylinders.

In this context, embodiments of the supercharged internal combustion engine may also be advantageous in which the intake lines of the cylinders of the second cylinder group merge to form a conduit to form an intake manifold and the intake manifold or line is equipped with a shut-off element with which - in partial shutdown of the internal combustion engine - the amount of charge air supplied to the at least one deactivated cylinder is adjustable.

Despite higher costs, embodiments of the supercharged internal combustion engine may be advantageous in which the cylinders of the second cylinder group are equipped with a switchable or variable valve train to control the charge air supply to the deactivated cylinders and / or to prevent.

Embodiments of the supercharged internal combustion engine in which at least one exhaust aftertreatment system is provided in the exhaust gas removal system are advantageous; For example, an oxidation catalyst, a three-way catalyst, a storage catalyst, a selective catalyst and / or a particulate filter.

Embodiments of the supercharged internal combustion engine in which the total exhaust gas lines of the at least two exhaust-gas turbochargers downstream of the turbines combine to form a common overall exhaust-gas line are advantageous. This embodiment brings advantages in the exhaust aftertreatment with it, since a common exhaust aftertreatment system can be provided in the common exhaust gas line for the entire exhaust gas.

In internal combustion engines with four cylinders arranged in series, embodiments are advantageous in which the two outer cylinders and the two inner cylinders each form a group.

The cylinders are presently grouped in such a way that the cylinders of a group influence each other as little as possible. In a cylinder head with four cylinders arranged in series, it is advantageous to combine two cylinders, which have a firing interval of 360 ° KW, in each case to form a cylinder group. If, for example, the ignition in the cylinders is initiated according to the ignition sequence 1-2-4-3 or according to the ignition sequence 1-3-4-2, it is advantageous for the outer cylinders to be a first group and the inner cylinders to be a second group to get together. This also assists in maintaining and utilizing the pressure pulses of the pre-discharge joints for the purpose of supercharging, in particular the pressure pulses of the continuously operating cylinders during partial shut-down.

Embodiments of the internal combustion engine in which the first shut-off element and / or the second shut-off element and / or the third shut-off element is a valve or a pivotable flap or a throttle flap are advantageous. The shut-off elements can be controlled electrically, hydraulically, pneumatically, mechanically or magnetically, preferably by means of motor control.

Embodiments of the supercharged internal combustion engine in which at least one exhaust gas recirculation is provided, which comprises at least one line which branches off from the exhaust gas removal system and opens into the intake system, are advantageous.

The exhaust gas recirculation, ie the recirculation of combustion gases, is a suitable means to reduce the nitrogen oxide emissions, with the exhaust gas recirculation rate can be significantly reduced with increasing exhaust gas recirculation rate. In this case, the exhaust gas recirculation rate x _{AGR is} determined as x _AGR = m _AGR / (m _AGR + m _{fresh air} ), where m _{AGR denotes} the mass of recirculated exhaust gas and m _{fresh air} the supplied and compressed fresh air through the compressor. In order to achieve a significant reduction in nitrogen oxide emissions, high exhaust gas recirculation rates are required, which can be on the order of x _EGR ≈ 60% to 70%.

Embodiments of the supercharged internal combustion engine in which at least one valve for adjusting the recirculated exhaust gas quantity is arranged in the at least one line of the exhaust gas recirculation are advantageous.

Embodiments of the supercharged internal combustion engine are advantageous in which the at least one line of the exhaust gas recirculation branches off from the exhaust gas removal system upstream of a turbine and opens into the intake system downstream of a compressor.

In this so-called high-pressure EGR, the exhaust gas is taken upstream of a turbine from the Abgasabführsystem and fed downstream of a compressor in the intake system, which is why the exhaust before recirculation subjected no exhaust aftertreatment, in particular no particle filter must be supplied because contamination of a compressor is not to be feared ,

When operating an internal combustion engine with exhaust gas turbocharging and simultaneous use of a high-pressure EGR, however, a conflict may arise because the recirculated exhaust gas is no longer available for driving the turbine. With an increase in the exhaust gas recirculation rate, the exhaust gas flow introduced into the turbine decreases. The reduced exhaust gas mass flow through the turbine causes a smaller turbine pressure ratio, whereby the charge pressure ratio also decreases, which is equivalent to a smaller charge air flow. One solution to this problem is the so-called low-pressure EGR. In contrast to the high-pressure EGR, exhaust gas is introduced into the intake system in the low-pressure EGR, which has already passed through a turbine. For this purpose, the low-pressure EGR has a return line, which branches off downstream of a turbine from the Abgasabführsystem and opens upstream of a compressor in the intake system.

The exhaust gas recirculated to the intake side by means of low-pressure EGR is mixed with fresh air upstream of a compressor. The mixture of fresh air and recirculated exhaust gas produced in this way forms the charge air, which is supplied to the compressor and compressed.

Since exhaust gas is passed through the compressor as part of the low-pressure EGR, it must first be subjected to exhaust gas aftertreatment, in particular in the particulate filter. Deposits in the compressor, which change the geometry of the compressor, in particular the flow cross-sections, and in this way deteriorate the efficiency of the compressor are to be avoided.

Advantageous embodiments of the supercharged internal combustion engine, in which each cylinder is equipped for introducing fuel with a direct injection.

Embodiments in which each cylinder is equipped with an injection nozzle for the purpose of direct injection are advantageous.

The fuel supply can be deactivated faster and more reliable for the purpose of partial shutdown in direct-injection internal combustion engines as in internal combustion engines with intake manifold injection, in which fuel residues in the intake manifold can lead to unwanted burns in the deactivated cylinder.

Nevertheless, embodiments of the internal combustion engine may be advantageous in which for the purpose of a fuel supply, a port injection is provided.

The second sub-task on which the invention is based, namely to disclose a method for operating a supercharged internal combustion engine of the type described above, is achieved by a method which is characterized in that the at least one switchable cylinder of the second group is dependent on the load T of the internal combustion engine is switched, in such a way that this at least one switchable cylinder is switched off when falling below a predetermined load T _{down and is} switched on when a predetermined load T _up is exceeded.

What has already been said for the internal combustion engine according to the invention also applies to the method according to the invention, which is why at this point in general reference is made to the statements made above with regard to the supercharged internal combustion engine. The various internal combustion engines sometimes require different process variants.

The prescribed for falling below or exceeding limit loads T _down and T _up can be the same size, but also different sizes. When the internal combustion engine is in operation, the cylinders of the first cylinder group are constantly in operation. There is a switching of the second cylinder group, ie a connection or disconnection of this second group.

Advantageous are process variants in which the fuel supply of the at least one switchable cylinder is deactivated when switched off.

Advantageous are process variants in which the at least one cylinder in operation is ignited by means of autoignition.

The above process variant relates to methods in which the combustion is initiated by means of auto-ignition, and thus also on working methods, such as are commonly used in diesel engines.

It is also possible to use a hybrid combustion process with auto-ignition for operating a gasoline engine, for example the so-called HCCI process, which is also referred to as a space ignition process or as a CAI process. This method is based on a controlled auto-ignition of the fuel supplied to the cylinder. Here, the fuel - as in a diesel engine - under excess air, ie more than stoichiometric, burned. The lean-burn gasoline engine has comparatively low nitrogen oxide emissions due to the low combustion temperatures and also no soot emissions due to the lean mixture. In addition, leads the HCCI process to a high thermal efficiency. The fuel can be introduced both directly into the cylinder and into the intake manifold.

Embodiments of the method in which the predefinable load T _down and / or T _up is dependent on the rotational speed n of the internal combustion engine are advantageous. Then there is not just a concrete load whose falling below or exceeding is switched independent of the speed n. Rather, speed-dependent procedure and an area defined in the map, is switched off in the part.

In principle, further operating parameters of the internal combustion engine can be used as a criterion for a partial shutdown, for example the engine temperature or the coolant temperature after a cold start of the internal combustion engine.

Advantageous are process variants in which each cylinder is equipped to initiate a spark ignition with an ignition device, wherein the ignition device of the at least one switchable cylinder is deactivated at shutdown.

The above method variant relates to the application of the method in a spark-ignited internal combustion engine, for example a direct-injection spark-ignition engine, the cylinders of which are each equipped with an ignition device for initiating spark ignition.

For operating a supercharged internal combustion engine in which the intake system comprises at least two Gesamtansaugleitungen and in the second Gesamtansaugleitung downstream of the compressor of the second exhaust gas turbocharger a first shut-off is arranged, are advantageous variants of the method, which are characterized in that the first shut-off element is closed in the context of partial shutdown ,

In the following, the invention is based on an embodiment of the supercharged internal combustion engine according to the 1 explained in more detail. Hereby shows:

1 schematically a first embodiment of the supercharged internal combustion engine.

1 schematically shows a first embodiment of the supercharged internal combustion engine 13 , It is a four-cylinder in-line engine 13 in which the four cylinders 1 . 2 . 3 . 4 along the longitudinal axis of the cylinder head, ie in series, are arranged.

The four cylinders 1 . 2 . 3 . 4 are configured and form two groups with two cylinders each 1 . 2 . 3 . 4 , where the two outer cylinders 1 . 4 form a first group whose cylinder 1 . 4 even with partial shutdown of the internal combustion engine 13 are in operation, and the two inner cylinders 2 . 3 form a second group whose cylinder 2 . 3 as a load-dependent switchable cylinder 2 . 3 are formed, which are turned off in the context of a partial shutdown.

Every cylinder 1 . 2 . 3 . 4 has a suction line 5a . 5b for supplying charge air via intake system 6 and an exhaust pipe 7a . 7b for removing the exhaust gases via exhaust gas removal system 8th ,

In the intake pipes 5b the two inner cylinders 2 . 3 are as third shut-off elements 9 serving flaps 9 provided, which the suction lines 5b for supplying charge air via intake system 6 release when the inner cylinder 2 . 3 are switched on, and obstruct or narrow, if the two inner cylinder 2 . 3 for the purpose of partial shutdown of the internal combustion engine 13 are switched off or are.

The exhaust pipes 7a . 7b the cylinder 1 . 2 . 3 . 4 each cylinder group lead to the formation of an exhaust manifold each to an overall exhaust line 7A . 7B together. These total exhaust pipes 7A . 7B in turn lead to a common overall exhaust gas line 7C together, in which an exhaust aftertreatment system 16 is provided.

The internal combustion engine 13 is for the purpose of charging with two turbochargers 12 . 14 equipped, each exhaust gas turbocharger 12 . 14 one in the exhaust system 8th arranged turbine 12a . 14a and one in the intake system 6 arranged compressor 12b . 14b includes. The two turbines 12a . 14a each have a variable turbine geometry (arrow).

The turbine 12a of the first exhaust gas turbocharger 12 is in the first total exhaust line 7A the first cylinder group and the turbine 14a the second exhaust gas turbocharger 14 in the second total exhaust line 7B arranged the second cylinder group, the two associated compressor 12b . 14b the two turbochargers 12 . 14 parallel in the intake system 6 are arranged.

The intake system 6 includes two total intake lines 6a . 6b , The first compressor 12b of the first exhaust gas turbocharger 12 is in a first overall intake line 6a and the second compressor 14b the second exhaust gas turbocharger 14 in a second total suction line 6b arranged.

In the present case lead the two total intake lines 6a . 6b downstream of the compressor 12b . 14b under formation of an intake manifold 10 together and open upstream of the inlet openings of the cylinder 1 . 2 . 3 . 4 in a plenum 10a ,

In the second total suction line 6b is downstream of the second compressor 14b a first shut-off element 14b' arranged, which is the deactivation of the second compressor 14b when partial shutdown is used. The compressor 14b When the second cylinder group is switched off, it is no longer or only restrictedly by the associated second turbine 14a driven. Closing the first shut-off element 14b' prevents charge air conveyance by means of a second compressor 14b to the cylinders 1 . 2 . 3 . 4 and a promotion of charge air by means of first compressor 12b in the second compressor 14b into it.

So that the second compressor 14b at Teilabschaltung not against the resistance of the closed first shut-off 14b' has to promote, is a bypass line 14c provided upstream of the compressor 14b the second exhaust gas turbocharger 14 from the second Gesamtansaugleitung 6b branches off and downstream of the compressor 14b again in the second Gesamtansaugleitung 6b opens and the partial shutdown and closed first shut-off 14b' is opened for the purpose of charge air recirculation. This is in the bypass line 14c a second shut-off element 14c' arranged.

The internal combustion engine 13 is also with an exhaust gas recirculation 15 equipped and in the present case with a low-pressure EGR. For this branch lines 15a to recirculate exhaust gas downstream of the turbines 12a . 14a and downstream of the exhaust aftertreatment system 16 from the common total exhaust gas line 7C from. A first return line opens upstream of the first compressor 12b into the first total exhaust gas line 7A , A second return line opens upstream of the second compressor 14b in the second total exhaust line 7B , In every line 15a the exhaust gas recirculation 15 is a valve 15b ₁ , 15b _{2 arranged} to adjust the amount of recirculated exhaust gas.

The valve 15b ₂ in the pipe 15a that is upstream of the second compressor 14b in the second total exhaust line 7B leads, is at Teilabschaltung the internal combustion engine 13 preferably closed.

LIST OF REFERENCE NUMBERS

1

 first cylinder, outboard cylinder

2

 second cylinder, internal cylinder, switchable cylinder

3

 third cylinder, internal cylinder, switchable cylinder

4

 fourth cylinder, outboard cylinder

5a

 Intake line of a cylinder of the first group

5b

 Intake line of a cylinder of the second group

6

 Intake system, inlet side

6a

 first total suction line

6b

 second total suction line

7a

 Exhaust pipe of a cylinder of the first group

7A

 Total exhaust line of the first cylinder group

7b

 Exhaust pipe of a cylinder of the second group, d. H. a switchable cylinder

7B

 Total exhaust gas line of the second cylinder group

7C

 common total exhaust gas line

8th

 Exhaust system, exhaust side

9

 third shut-off element, flap

10

 intake manifold

10a

 plenum

11

 second shut-off element, valve

12

 first exhaust gas turbocharger

12a

 Turbine of the first turbocharger, first turbine

12b

 Compressor of the first exhaust gas turbocharger, first compressor

13

 Internal combustion engine, four-cylinder in-line engine

14

 second exhaust gas turbocharger

14a

 Turbine of the second turbocharger, second turbine

14b

 Compressor of the second exhaust gas turbocharger, second compressor

14b'

 first shut-off element

14c

 bypass line

14c'

 second shut-off element

15

 Exhaust gas recirculation

15a

 Line, return line

15b ₁

 AGR valve

15b ₂

 AGR valve

16

 aftertreatment system

n

 Speed of the internal combustion engine

T

 load

T _down

 predefinable load for falling below a load

T _{max, n}

 maximum load at a given speed n

T _up

 predefinable load for exceeding a load

Claims (16)

Charged internal combustion engine ( 13 ) with at least two cylinders ( 1 . 2 . 3 . 4 ), in the - each cylinder ( 1 . 2 . 3 . 4 ) has at least one outlet opening, to which an exhaust pipe ( 7a . 7b ) for discharging the exhaust gases via Abgasabführsystem ( 8th ), - each cylinder ( 1 . 2 . 3 . 4 ) has at least one inlet opening, to which a suction line ( 5a . 5b ) for supplying charge air via intake system ( 6 ), - at least two cylinders ( 1 . 2 . 3 . 4 ) are configured in such a way that these at least two groups each having at least one cylinder ( 1 . 2 . 3 . 4 ), wherein the at least one cylinder ( 1 . 4 ) a first group also at partial shutdown of the internal combustion engine ( 13 ) operating cylinder ( 1 . 4 ) and the at least one cylinder ( 2 . 3 ) of a second group as a load-dependent switchable cylinder ( 2 . 3 ), - the exhaust pipes ( 7a . 7b ) the cylinder ( 1 . 2 . 3 . 4 ) each cylinder group with the formation of an exhaust manifold each to a total exhaust gas line ( 7A . 7B ), and - at least one exhaust gas turbocharger ( 12 . 14 ) is provided, the one in Abgasabführsystem ( 8th ) arranged turbine ( 12a . 14a ) and one in the intake system ( 6 ) arranged compressors ( 12b . 14b ), characterized in that - at least two exhaust gas turbochargers ( 12 . 14 ) are provided, wherein the turbine ( 12a ) of a first exhaust gas turbocharger ( 12 ) in the first exhaust line ( 7A ) of the first cylinder group and the turbine ( 14a ) of a second exhaust gas turbocharger ( 14 ) in the second total exhaust line ( 7B ) of the second cylinder group and the two associated compressors ( 12b . 14b ) of the at least two turbocharger ( 12 . 14 ) parallel in the intake system ( 6 ) are arranged. Charged internal combustion engine ( 13 ) according to claim 1, characterized in that the intake system ( 6 ) at least two total intake lines ( 6a . 6b ), wherein the compressor ( 12b ) of the first exhaust gas turbocharger ( 12 ) in a first total intake line ( 6a ) and the compressor ( 14b ) of the second exhaust gas turbocharger ( 14 ) in a second total intake line ( 6b ) is arranged. Charged internal combustion engine ( 13 ) according to claim 2, characterized in that the at least two total intake lines ( 6a . 6b ) downstream of the compressors ( 12b . 14b ) are at least connectable to each other. Charged internal combustion engine ( 13 ) according to claim 2, characterized in that the at least two total intake lines ( 6a . 6b ) downstream of the compressors ( 12b . 14b ) while forming an intake manifold ( 10 ) merge. Charged internal combustion engine ( 13 ) according to one of claims 2 to 4, characterized in that the at least two Gesamtansaugleitungen ( 6a . 6b ) in a plenary session ( 10a ) open upstream of the inlet openings. Charged internal combustion engine ( 13 ) according to one of claims 2 to 5, characterized in that in the second Gesamtansaugleitung ( 6b ) downstream of the compressor ( 14b ) of the second exhaust gas turbocharger ( 14 ) a first shut-off element ( 14b' ) is arranged. Charged internal combustion engine ( 13 ) according to one of claims 2 to 6, characterized in that a bypass line ( 14c ) provided upstream of the compressor ( 14b ) of the second exhaust gas turbocharger ( 14 ) from the second total intake line ( 6b ) branches off and downstream of the compressor ( 14b ) of the second exhaust gas turbocharger ( 14 ) into the second total intake line ( 6b ). Charged internal combustion engine ( 13 ) according to claim 7, characterized in that in the bypass line ( 14c ) a second shut-off element ( 14c' ) is arranged. Charged internal combustion engine ( 13 ) according to one of the preceding claims, characterized in that means ( 9 ) are provided with which at partial shutdown of the internal combustion engine ( 13 ) a charge air supply to the at least one deactivated cylinder ( 2 . 3 ) of the second group is controllable. Charged internal combustion engine ( 13 ) according to claim 9, characterized in that in the suction line ( 5b ) of the at least one load-dependent switchable cylinder ( 2 . 3 ) a third shut-off element ( 9 ) is provided, which the suction line ( 5b ) for supplying charge air with the cylinder switched on ( 2 . 3 ) and with deactivated cylinder ( 2 . 3 ) blocked or narrowed. Charged internal combustion engine ( 13 ) according to claim 10, characterized in that the third shut-off element ( 9 ) is infinitely adjustable. Charged internal combustion engine ( 13 ) according to one of the preceding claims, characterized in that at least one exhaust aftertreatment system ( 16 ) in the exhaust gas removal system ( 8th ) is provided. Charged internal combustion engine ( 13 ) according to one of the preceding claims, characterized in that the total exhaust gas lines ( 7A . 7B ) of the at least two cylinder groups downstream of the turbines ( 12a . 14a ) to a common overall exhaust gas line ( 7C ) merge. Charged internal combustion engine ( 13 ) according to one of the preceding claims with four cylinders arranged in series ( 1 . 2 . 3 . 4 ), characterized in that the two outer cylinders ( 1 . 4 ) and the two inner cylinders ( 2 . 3 ) each form a group. Method for operating a supercharged internal combustion engine ( 13 ) according to one of the preceding claims, characterized in that the at least one switchable cylinder ( 2 . 3 ) of the second group as a function of the load T of the internal combustion engine ( 13 ) is switched in such a way that this at least one switchable cylinder ( 2 . 3 ) Is switched off on falling below a predeterminable load and T _down is activated on exceeding a predetermined load T _up. Method according to claim 15 for operating a supercharged internal combustion engine ( 13 ), in which the intake system ( 6 ) at least two total intake lines ( 6a . 6b ) and in the second total intake line ( 6b ) downstream of the compressor ( 14b ) of the second exhaust gas turbocharger ( 14 ) a first shut-off element ( 14b' ), characterized in that the first shut-off element ( 14b' ) is closed during a partial shutdown.

Images