DE202015102239U1 - Exhaust Turbo-charged internal combustion engine with partial shutdown and parallel turbines - Google Patents

Abstract

A supercharged internal combustion engine (10) having at least three cylinders (1, 2, 3, 4) and an intake system (6) for supplying charge air to the cylinders (1, 2, 3, 4), in which - each cylinder (1, 2 , 3, 4) has at least one outlet opening, to which an exhaust pipe (5a, 5b) for discharging the exhaust gases via Abgasabführsystem (15) connects, - at least two exhaust gas turbochargers (7, 8) are provided, each exhaust gas turbocharger (7, 8 ) comprises a turbine (7a, 8a) arranged in the exhaust gas removal system (15) and a compressor (7b, 8b) arranged in the intake system (6), - at least three cylinders (1, 2, 3, 4) are configured such that they form at least two groups, each with at least one cylinder (1, 2, 3, 4), wherein the at least one cylinder (1, 4) of a first group has a cylinder (1, 4) which is also in operation during partial deactivation of the internal combustion engine (10) ) Is and the at least one cylinder (2, 3) of a second group as a load-dependent switchable Cyl is formed (2, 3), - the exhaust pipes (5a) of the cylinders (1, 4) of the first cylinder group to form a first exhaust manifold (16a) to a first total exhaust line (15a) merge, which with the turbine (7a) of a first exhaust gas turbocharger (7) is connected, and - the exhaust pipes (5b) of the cylinders (2, 3) of the second cylinder group merge to form a second exhaust manifold (16b) to a second total exhaust pipe (15b), which with the turbine (8a) of a second turbocharger (8) is connected, characterized in that - the first compressor (7b) of the first exhaust gas turbocharger (7) downstream of the second compressor (8b) of the second exhaust gas turbocharger (8) in the intake system (6) is arranged, and - the first Exhaust manifold (16a) via a connecting line (9) with the second exhaust manifold (16b) is connected, wherein the connecting line (9) with formation of a first node (9a) from the first exhaust manifold (16a) branches u nd with the formation of a second node (9b) in the second exhaust manifold (16b) opens.

Description

• – jeder Zylinder mindestens eine Auslassöffnung aufweist, an die sich eine Abgasleitung zum Abführen der Abgase via Abgasabführsystem anschließt,
• – mindestens zwei Abgasturbolader vorgesehen sind, wobei jeder Abgasturbolader eine im Abgasabführsystem angeordnete Turbine und einen im Ansaugsystem angeordneten Verdichter umfasst,
• – mindestens drei Zylinder in der Art konfiguriert sind, dass sie 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 der ersten Zylindergruppe unter Ausbildung eines ersten Abgaskrümmers zu einer ersten Gesamtabgasleitung zusammenführen, welche mit der Turbine eines ersten Abgasturboladers verbunden ist, und
• – die Abgasleitungen der Zylinder der zweiten Zylindergruppe unter Ausbildung eines zweiten Abgaskrümmers zu einer zweiten Gesamtabgasleitung zusammenführen, welche mit der Turbine eines zweiten Abgasturboladers verbunden ist.

The invention relates to a supercharged internal combustion engine having at least three cylinders and an intake system for supplying charge air to the 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,
• 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,
• - At least three 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 shutdown 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,
• - Merge the exhaust gas lines of the cylinder of the first cylinder group to form a first exhaust manifold to a first overall exhaust gas line, which is connected to the turbine of a first exhaust gas turbocharger, and
• - Merge the exhaust pipes of the cylinder of the second cylinder group to form a second exhaust manifold to a second total exhaust pipe, which is connected to the turbine of a second exhaust gas turbocharger.

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, but also gasoline engines and hybrid internal combustion engines, d. H. Internal combustion engines, which are operated with a hybrid combustion process, and hybrid drives, which in addition to the internal combustion engine include a drive motor-connectable with the electric motor, which receives power from the internal combustion engine or emits additional power as a switchable auxiliary drive.

The internal combustion engine, which is the subject of the present invention, is an internal combustion engine charged by means of exhaust gas turbocharging. The advantage of an exhaust gas turbocharger, for example in comparison to a mechanical supercharger, is that no mechanical connection is required for transmitting power 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.

Supercharged internal combustion engines are preferably equipped with a charge air cooling, with which the compressed combustion air is cooled before entering the cylinder. As a result, the density of the charge air supplied continues to increase. The cooling also contributes in this way to a compression and better filling of the combustion chambers, d. H. to an improved degree of filling, at. It may be advantageous to equip the intercooler with a bypass line in order to bypass the intercooler if necessary, for example after a cold start.

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.

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 a spark-ignited internal combustion engine. 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 three 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.

In order to reduce the losses described, various strategies have been developed for de-throttling a spark-ignited internal combustion engine.

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 flowing into the combustion chamber during the intake process is then controlled not by means of a throttle valve but via the intake valve lift and the opening duration of the intake valve.

Another solution for de-throttling a gasoline engine offers the cylinder deactivation, d. H. the shutdown of individual cylinders in certain load ranges.

The efficiency of the gasoline engine in partial load operation can be improved by a partial shutdown, d. H. be increased, because the shutdown of a cylinder of a multi-cylinder internal combustion engine increases the load of the remaining still in operation cylinder at constant engine power, so that the throttle for introducing a larger air mass in these cylinders can be opened or must, resulting in a total Entdrosselung the internal combustion engine is achieved. The continuously operating cylinders also 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 due to 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 multi-cylinder internal combustion engines with partial deactivation described in the prior art and the associated methods for operating these internal combustion engines nevertheless have clear potential for improvement, as will be explained briefly and by way of example on the diesel engine below.

If, in the case of a direct-injection diesel engine, the fuel supply to the deactivatable cylinders is inhibited, ie adjusted, the deactivated cylinders continue to participate in the charge exchange, if the associated valve drive of this cylinder is not deactivated or can not be deactivated. The charge cycle losses generated thereby reduce the improvements achieved by the partial shutdown in terms of fuel consumption and Efficiency and counter these, so that the benefits of partial shutdown is at least partially lost, ie the partial shutdown in the sum actually brings a less significant improvement.

In order to remedy the disadvantageous effects described above, it may be expedient to provide on the intake side and on the outlet side switchable valve trains with which the deactivated cylinders are kept closed during the partial shutdown and thus do not continue to take part in the charge exchange.

However, switchable valve trains can lead to further problems in internal combustion engines charged by means of exhaust-gas turbocharging, such as the internal combustion engine which is the subject of the present invention, since the turbine of an exhaust-gas turbocharger is designed for a certain amount of exhaust gas and thus also for a specific 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 this, as a rule, also the turbine pressure ratio. A decreasing turbine pressure ratio has the consequence that the boost pressure ratio also decreases, d. H. the charge pressure drops, and the still in operation cylinders only little charge air is supplied or less charge air than intended. It should be noted in particular that significantly more charge air is to be supplied to the cylinders which are still in operation during partial shutdown, since the cylinders in operation replace the missing power of the deactivated cylinders at constant engine power, ie. H. have to compensate. The low charge air flow can also cause the compressor to operate beyond the surge line.

The total mass flow guided during partial shutdown by the cylinders of the internal combustion engine again by the fact that the deactivated cylinders continue to participate in the charge cycle, is not expedient because the guided by the disabled cylinder cooler charge air significantly reduces the enthalpy of the turbine provided exhaust gas flow. It should be noted that the exhaust gas enthalpy of the hot exhaust gases is largely determined by the exhaust gas pressure and the exhaust gas temperature. The exhaust gas mass is therefore not the only relevant aspect when considering the problem in question.

The effects described above lead to a limitation of the applicability of the partial shutdown, namely to a limitation of the load range in which the partial shutdown can be used. A reduced amount of charge air, which is supplied to the cylinders in operation during the partial shutdown, reduces the effectiveness or the 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, which allows an adjustment of the effective turbine cross-section of the current exhaust gas 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.

For the reasons mentioned above, internal combustion engines of the type in question according to the prior art often also equipped with several parallel turbines of smaller turbine cross-section, with increasing load not only cylinders, but with the cylinders and turbines - similar to a register charging - successively switched become. The torque characteristic of the supercharged teilabschaltbaren internal combustion engine can be improved, the use of multiple superchargers or turbines always has the disadvantage of increased friction and multiple turbochargers have a worse overall efficiency than a single exhaust gas turbocharger.

In the present case, each cylinder group is assigned a turbine. The exhaust pipes of the cylinders of the first cylinder group lead together to form a first exhaust manifold to a first exhaust line, which is connected to the turbine of a first exhaust gas turbocharger, and the exhaust pipes of the cylinder of the second cylinder group lead together to form a second exhaust manifold to a second total exhaust gas line is connected to the turbine of a second exhaust gas turbocharger. 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, wherein the Section of the entire exhaust line upstream of a turbine according to the invention is considered as belonging to the manifold.

Against the background of the above, it is the object of the present invention to provide a supercharged internal combustion engine according to the preamble of claim 1, which is further optimized in terms of its torque characteristics and the partial shutdown.

• – jeder Zylinder mindestens eine Auslassöffnung aufweist, an die sich eine Abgasleitung zum Abführen der Abgase via Abgasabführsystem anschließt,
• – mindestens zwei Abgasturbolader vorgesehen sind, wobei jeder Abgasturbolader eine im Abgasabführsystem angeordnete Turbine und einen im Ansaugsystem angeordneten Verdichter umfasst,
• – mindestens drei Zylinder in der Art konfiguriert sind, dass sie 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 der ersten Zylindergruppe unter Ausbildung eines ersten Abgaskrümmers zu einer ersten Gesamtabgasleitung zusammenführen, welche mit der Turbine eines ersten Abgasturboladers verbunden ist, und
• – die Abgasleitungen der Zylinder der zweiten Zylindergruppe unter Ausbildung eines zweiten Abgaskrümmers zu einer zweiten Gesamtabgasleitung zusammenführen, welche mit der Turbine eines zweiten Abgasturboladers verbunden ist,

und die dadurch gekennzeichnet ist, dass

• – der erste Verdichter des ersten Abgasturboladers stromabwärts des zweiten Verdichters des zweiten Abgasturboladers im Ansaugsystem angeordnet ist, und
• – der erste Abgaskrümmer via Verbindungsleitung mit dem zweiten Abgaskrümmer verbunden ist, wobei die Verbindungsleitung unter Ausbildung eines ersten Knotenpunktes vom ersten Abgaskrümmer abzweigt und unter Ausbildung eines zweiten Knotenpunktes in den zweiten Abgaskrümmer mündet.

This object is achieved by a supercharged internal combustion engine with at least three cylinders and an intake system for supplying charge air to the cylinders, in which

• Each cylinder has at least one outlet opening adjoined by an exhaust pipe for discharging the exhaust gases via the exhaust gas removal system,
• 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,
• - At least three 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 shutdown 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,
• - Merge the exhaust gas lines of the cylinder of the first cylinder group to form a first exhaust manifold to a first overall exhaust gas line, which is connected to the turbine of a first exhaust gas turbocharger, and
• To merge the exhaust lines of the cylinders of the second cylinder group to form a second exhaust manifold to form a second overall exhaust line, which is connected to the turbine of a second exhaust gas turbocharger,

and which is characterized in that

• - The first compressor of the first exhaust gas turbocharger is arranged downstream of the second compressor of the second exhaust gas turbocharger in the intake system, and
• - The first exhaust manifold is connected via a connecting line to the second exhaust manifold, wherein the connecting line branches off to form a first node from the first exhaust manifold and opens to form a second node in the second exhaust manifold.

In the internal combustion engine according to the invention, a connecting line between the first exhaust manifold and the second exhaust manifold is provided. In addition to a single-stage charge at partial shutdown by means of the first exhaust gas turbocharger, this connecting line allows a single-stage supercharging using the second exhaust gas turbocharger in the map areas in which all the cylinders of the internal combustion engine are in operation cylinder. While in internal combustion engines according to the prior art with increasing load of at least one switchable cylinder and the second switchable cylinder associated turbine is switched on, the internal combustion engine according to the invention allows switching to the second turbine and thus a single-stage charge or compression at higher loads and higher speeds at which all cylinders of the internal combustion engine are in operation cylinders. As mentioned above, it is in terms of friction and the overall efficiency more advantageous to use a single exhaust gas turbocharger instead of multiple turbochargers, which is why the internal combustion engine according to the invention over the prior art has advantages in efficiency.

The internal combustion engine according to the invention also allows a connection of the second turbine even with partial shutdown and thus a two-stage supercharging or compression at partial shutdown. The first turbine can therefore be designed for very small amounts of exhaust gas and relatively small dimensions. In contrast to the prior art, the first turbine does not have to be able to cope with the total exhaust gas flow of the first cylinder group under all operating conditions, since exhaust gas of the first group can also be supplied to the second turbine via a connection line past the first turbine. The connecting line acts like a bypass line or blow-off line. Nonetheless, at partial shutdown, single stage supercharging using the first exhaust gas turbocharger is preferred.

Basically, the small-sized first turbine ensures a sufficiently high boost pressure at partial shutdown and very small amounts of exhaust gas, which is why the sufficient charge air can be supplied to the still operating in partial shutdown cylinders. Pumping the first compressor can be prevented. The load range in which the partial shutdown can be used effectively is extended. The torque characteristic of the supercharged internal combustion engine during partial shutdown is significantly improved.

The advantages of a small first turbine described above also come into play when all the cylinders of the internal combustion engine are in operation, in particular at low speeds. Then there is a two-stage supercharging or compression using both exhaust gas turbochargers, with so much exhaust gas at the first turbine can be passed via connecting line as required.

With the internal combustion engine according to the invention an internal combustion engine according to the preamble of claim 1 is provided, which is further optimized in terms of their torque characteristics and the partial shutdown. Thus, the object underlying the invention is achieved.

The internal combustion engine according to the invention has at least three 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. 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.

The internal combustion engine according to the invention has at least three cylinders or at least two groups, each with at least one cylinder, each cylinder having at least one outlet opening. In embodiments in which a group comprises only one cylinder having only one outlet opening, the exhaust ducts of this group do not actually converge to form an exhaust manifold. Rather, the one exhaust pipe of an outlet opening forms the manifold and the associated total exhaust gas line.

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

• – die zwischen dem ersten Verdichter und dem zweiten Verdichter vom Ansaugsystem abzweigt,
• – die stromabwärts des ersten Verdichters wieder in das Ansaugsystem einmündet, und
• – in der ein erstes Absperrelement angeordnet ist.

Embodiments of the supercharged internal combustion engine in which a first bypass line is provided are advantageous,

• Which branches off from the intake system between the first compressor and the second compressor,
• - The downstream of the first compressor again opens into the intake system, and
• - In which a first shut-off element is arranged.

The first bypass line is used in particular in the cases in which all the cylinders of the internal combustion engine are in operation cylinders, hardly or no exhaust gas flows through the first turbine and the second, larger turbine performs the compressor work, d. H. a single-stage compression or charging using the second exhaust gas turbocharger takes place. Then, the first compressor is only a flow resistance for the charge air compressed by the second compressor. A first bypass line then allows the bypass of the first compressor and thus a dethrottling of the intake system.

The first bypass line can in principle also serve for charge air blow-off, as a result of which the charge air compressed in the first compressor is blown off and returned. In this case, the first shut-off element in the first bypass line serves to control the blown-off or returned charge air.

• – die stromaufwärts des zweiten Verdichters vom Ansaugsystem abzweigt,
• – die zwischen dem ersten Verdichter und dem zweiten Verdichter wieder in das Ansaugsystem einmündet, und
• – in der ein zweites Absperrelement angeordnet ist.

Embodiments of the supercharged internal combustion engine in which a second bypass line is provided are advantageous,

• Which branches off the intake system upstream of the second compressor,
• - Which re-opens between the first compressor and the second compressor in the intake system, and
• - In which a second shut-off element is arranged.

The second bypass line is used in particular for the intake of fresh air and that in cases where hardly or no exhaust gas flows through the second turbine and the first, smaller turbine performs the compressor work, d. H. a single-stage compression or charging using the first exhaust gas turbocharger takes place. This is especially true during partial shutdown, but also at very low speeds when all the cylinders of the engine are in operation. Then, the second compressor is only a flow resistance for the fresh air sucked by the first compressor. A second bypass line then allows the bypassing of the second compressor and thus a dethrottling of the intake system.

The second bypass line can in principle also serve for charge air blow-off, as a result of which the charge air compressed in the second compressor is returned. In this case, the second shut-off element in the second bypass line serves to control the bleed-off or returned charge air.

Embodiments of the supercharged internal combustion engine in which the first turbine of the first exhaust gas turbocharger has a fixed turbine geometry are advantageous. A fixed turbine geometry is less expensive and may be sufficient in the present case for a satisfactory torque characteristic, since the first turbine is preferably designed for small amounts of exhaust gas and excess exhaust gas can be easily fed via connecting line to the first turbine and the second turbine. In that sense, the first Turbine can also be regarded as an original waste gate turbine.

Also advantageous are embodiments of the supercharged internal combustion engine, in which the first turbine of the first exhaust gas turbocharger has a variable turbine geometry.

A variable turbine geometry increases the flexibility of charging. It allows a stepless adjustment of the turbine geometry to the respective operating point of the internal combustion engine or to the current exhaust gas mass flow. 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, as far as guide vanes or a guide are provided.

In particular, the combination of turbine with variable turbine geometry and a connecting line bypassing this turbine allows the design of the first turbine to very small amounts of exhaust gas. Consequently, at partial shutdown high turbine pressure ratios can be achieved even with very small amounts of exhaust gas.

Embodiments of the supercharged internal combustion engine in which a first turbine-side shutoff element is arranged between the first turbine of the first exhaust gas turbocharger and the first node are advantageous. This shut-off allows by closing the full deactivation of the first turbine, if a single-stage compression or charging to be realized using the second exhaust gas turbocharger. With this first turbine-side shut-off but also the first turbine supplied amount of exhaust gas can be controlled, d. H. set, in particular also limit.

Embodiments of the supercharged internal combustion engine in which the second turbine of the second exhaust gas turbocharger has a variable turbine geometry are advantageous. The same applies with regard to the variable turbine geometry. An adaptation of the turbine geometry to the current exhaust gas flow becomes possible and thus a satisfactory charge in a wide speed and load range, d. H. with greatly varying amounts of exhaust gas.

Embodiments of the supercharged internal combustion engine in which a second turbine-side shutoff element is arranged between the second turbine of the second exhaust gas turbocharger and the second node point are advantageous. This shut-off allows by closing the full deactivation of the second turbine, if a single-stage compression or charging is to be realized using the first exhaust gas turbocharger, d. H. at partial shutdown.

Alternatively or in addition to a turbine-side shut-off element or both turbine-side shut-off elements, it is also possible to arrange a shut-off element in the connecting line.

Embodiments of the supercharged internal combustion engine in which a charge air cooler is arranged in the intake system downstream of the compressor are advantageous. The intercooling lowers the temperature and increases the density of the compressed charge air and thus contributes to a further compression and better filling of the cylinder. A bypass line for bypassing the intercooler may be advantageous, for example after a cold start.

Embodiments of the supercharged internal combustion engine in which a further charge air cooler is arranged in the intake system between the first compressor and the second compressor are advantageous.

The charge air cooler disposed between the compressors lowers the temperature of the charge air precompressed in the second compressor, thus increasing the charge air density, thereby improving the compression in the first compressor and lowering the discharge temperature from the first compressor at the same total charge ratio of the charge group can. This also provides protection against thermal overload. By means of intercooler but can also increase the total pressure ratio of the compressor group and thus further increase the performance, d. H. to further boost performance.

In this context, embodiments of the supercharged internal combustion engine in which the second bypass line opens into the intake system between the further intercooler and the first compressor are advantageous.

Then the charge air is not cooled in the first compressor before entering the first compressor in a single-stage compression, but only in the first compressor Frame of two-stage compression between the compressors.

Embodiments of the supercharged internal combustion engine in which the first turbine is designed smaller than the second turbine are advantageous. The above dimensioning of the turbines corresponds to the different tasks of the turbines and their preferred use.

Advantageous embodiments of the supercharged internal combustion engine, in which the first compressor is designed smaller than the second compressor. The above dimensioning of the compressor corresponds to the dimensioning of the turbines.

In supercharged 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.

Embodiments of the supercharged internal combustion engine in which each exhaust valve of an at least partially variable valve train of a cylinder of the second group is a switchable exhaust valve are advantageous, wherein a shut-off exhaust valve blocks the associated exhaust port and an activated exhaust valve releases the associated exhaust port during an opening period Δt _{2, ex} and thereby forms a valve lift .DELTA.h _{2, ex} .

Embodiments may also be advantageous in which each outlet valve of an at least partially variable valve drive of a cylinder of the second group is an outlet valve which is adjustable with respect to the opening duration Δt _{2, ex} and / or the valve lift Δh _{2, ex} .

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.

Advantageous embodiments of the supercharged internal combustion engine, in which at least one exhaust gas recirculation is provided, which includes a return line, which branches off from the Abgasabführsystem and opens into the intake system.

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 to be x _AGR = m _AGR / (m _AGR + m _{fresh air} ), where m _{AGR is} the mass of recirculated exhaust gas and m _{fresh air is} the supplied and possibly fresh air guided and compressed by a 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 a valve for adjusting the recirculated exhaust gas quantity is arranged in the return line of the exhaust gas recirculation are advantageous.

In supercharged internal combustion engines with at least one exhaust gas turbocharger and exhaust gas recirculation embodiments are advantageous in which the return line of exhaust gas recirculation upstream of a turbine of the at least one exhaust gas turbocharger branches off from Abgasabführsystem and opens downstream of a compressor in the intake system. 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, since a contamination of the 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 the turbine. For this purpose, the low-pressure EGR has a return line, which branches off downstream of the turbine from the Abgasabführsystem and preferably opens upstream of the compressor in the intake system.

The exhaust gas recirculated to the inlet side by means of low-pressure EGR is mixed with fresh air. 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 frequently passed through the compressor as part of the low-pressure EGR, it must first be subjected to exhaust gas aftertreatment, in particular in a particle 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.

For the above-mentioned reasons, embodiments of the internal combustion engine are advantageous in which the return line of the exhaust gas recirculation branches off from the exhaust gas removal system downstream of a turbine and opens into the intake system upstream of the compressor.

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.

For operating an internal combustion engine of a type described above, the at least one switchable cylinder of the second group is switched as a function of the load T of the internal combustion engine in such a way that this at least one switchable cylinder is switched off when falling below a predetermined load T _down and when exceeded a predefinable load T _{up is} switched on.

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.

It may be advantageous if the predefinable load T _down and / or T _up is dependent on the rotational speed n of the internal combustion engine. 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 variants in which the at least one cylinder of the second group is switched off as soon as the predetermined load T _{down is} undershot and the instantaneous load for a predefinable period of time is lower than this predetermined load T _down .

The introduction of an additional condition for the shutdown of the cylinders of the second group, ie the partial shutdown, is to prevent too frequent switching on and off, in particular a partial shutdown when the load only temporarily _falls below the predetermined load T _down and then rises again or to the predetermined value for the load T _down fluctuates, without the falling below would justify or require a partial shutdown.

For these reasons, variants are likewise advantageous in which the at least one cylinder of the second group is switched on as soon as the predetermined load T _{up is} exceeded and the instantaneous load is higher than this predefined load T _up for a predefinable period of time.

It is advantageous if only the turbine of the first exhaust gas turbocharger is used during the partial shutdown to generate a boost pressure in the context of a one-stage compression.

It may be advantageous, starting from an operation of the internal combustion engine in which the at least two cylinders of the at least two groups are in operation, both the turbine of the first exhaust gas turbocharger and the turbine of the second exhaust gas turbocharger for generating a boost pressure in the context of a two-stage compression to be used as long as the Speed n _{mot is} less than a predefinable speed n _{limit, 1} .

However, it may also be advantageous, starting from an operation of the internal combustion engine in which the at least two cylinders of the at least two groups are in operation, to use only the turbine of the first exhaust gas turbocharger for generating a boost pressure in the context of a one-stage compression, as long as the rotational speed n _{mot is} less than a predefinable speed n _{limit, 1} . Then, if necessary, open a second bypass line on the second compressor, ie to release.

It is advantageous in particular, starting from an operation of the internal combustion engine in which the at least two cylinders of the at least two groups are in operation, only the turbine of the second exhaust gas turbocharger for generating a boost pressure in the context of a one-stage compression, as long as the speed n _mot is greater than a predefinable speed n _{limit, 2} .

For the purpose of partial deactivation, it is advantageous to first deactivate a fuel supply of the at least one switchable cylinder. There are advantages in terms of fuel consumption and pollutant emissions, which supports the goal of partial shutdown, namely to reduce fuel consumption and improve efficiency. In self-igniting internal combustion engines, it may even be necessary to deactivate the fuel supply in order to reliably prevent ignition of the mixture in the cylinder.

In the following, the invention is based on an embodiment of a supercharged internal combustion engine and according to the 1 and 2 explained in more detail. Hereby shows:

1 schematically a first embodiment of the internal combustion engine, and

2 schematically the engine map of the first embodiment.

1 schematically shows a first embodiment of the supercharged internal combustion engine 10 that with two exhaust gas turbochargers 7 . 8th Is provided. Every turbocharger 7 . 8th includes one in the exhaust system 15 arranged turbine 7a . 8a and one in the intake system 6 arranged compressor 7b . 8b , The hot exhaust gas relaxes in the turbines 7a . 8a under energy release. The compressors 8b . 9b compress the charge air via the intake system 6 , Intercooler 13 and plenum the cylinders 1 . 2 . 3 . 4 is supplied, whereby a charge of the internal combustion engine 10 is reached.

It is a four-cylinder in-line engine 10 in which the four cylinders 1 . 2 . 3 . 4 along the longitudinal axis of the cylinder head, that are arranged in series. The four cylinders 1 . 2 . 3 . 4 are configured and form two groups with two cylinders each 1 . 2 . 3 . 4 , where 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, and the two outer cylinder 1 . 4 form a first group whose cylinder 1 . 4 are also in partial shutdown in operation.

Every cylinder 1 . 2 . 3 . 4 has two outlet ports, to which exhaust pipes 5a . 5b for removing the exhaust gases via exhaust gas removal system 15 connect, with the sake of simplicity, only one outlet opening per cylinder 1 . 2 . 3 . 4 is shown. The exhaust pipes 5a . 5b the cylinder 1 . 2 . 3 . 4 Each cylinder group lead to the formation of an exhaust manifold 16a . 16b each to a total exhaust line 15a . 15b together. These total exhaust pipes 15a . 15b in turn lead to a common exhaust pipe 14 together. The first exhaust manifold 16a is via connection line 9 with the second exhaust manifold 16b connected, the connecting line 9 forming a first node 9a from the first exhaust manifold 16a branches off and forming a second node 9b in the second exhaust manifold 16b empties.

The turbine 7a of the first exhaust gas turbocharger 7 is in the first total exhaust line 15a the first cylinder group and the turbine 8a the second exhaust gas turbocharger 8th in the second total exhaust line 15b arranged the second cylinder group, so that in this case the first turbine 7a the turbine 7a is, which is activated at Teilabschaltung or remains and ensures the required boost pressure. The first turbine 7a of the first exhaust gas turbocharger 7 in the present case has a fixed and the turbine 8a the second exhaust gas turbocharger 8th a variable turbine geometry.

The first compressor 7b of the first exhaust gas turbocharger 7 is downstream of the second compressor 8b the second exhaust gas turbocharger 8th in the intake system 6 arranged, the intercooler 13 downstream of the compressor 7b . 8b is arranged. Between the first compressor 7b and the second compressor 8b branches a first bypass line 7c from the intake system 6 off, downstream of the first compressor 7b back into the intake system 6 opens and in the first shut-off 7d is arranged. Upstream of the second compressor 8b branches a second bypass line 8c from the intake system 6 starting between the first compressor 7b and the second compressor 8b back into the intake system 6 opens and in the second shut-off 8d is arranged.

The first bypass line 7c is used when all cylinders 1 . 2 . 3 . 4 the internal combustion engine 10 in operation cylinders 1 . 2 . 3 . 4 are and the second, larger turbine 8a performs the compressor work, ie a single-stage compression or charging using the second exhaust gas turbocharger 8th he follows. Then put the first compressor 7b a flow resistance for the second compressor 8b compressed charge air. The first bypass line 7c then allows the bypass of the first compressor 7b and thus a dethrottling of the intake system 6 , That between the first turbine 7a and the first node 9a arranged first turbine-side shut-off 11 is preferably closed, whereby the first turbine 7a is deactivated.

The second bypass line 8c is used to suck in fresh air in cases where the first, smaller turbine 7a performs the compressor work, ie a single-stage compression or charging using the first exhaust gas turbocharger 7 takes place, namely during partial shutdown. Then put the second compressor 8b only a flow resistance for the first compressor 7b sucked fresh air. A second bypass line 8c then allows the bypass of the second compressor 7b and thus a dethrottling of the intake system 6 , One between the second turbine 8a and the second node 9b arranged second turbine-side shut-off 12 is preferably closed during partial shutdown.

2 schematically shows the engine map of the first embodiment according to 1 ,

When operating the internal combustion engine 10 become the two switchable cylinders 2 . 3 the second group as a function of the load T of the internal combustion engine 10 switched, with the switchable cylinder 2 . 3 switched off below a predetermined load T _down and switched on when a predetermined load T _{up is} exceeded. The prescribed for falling below or exceeding limit loads T _down and T _up are the same size here. The operation mode C indicates the map area of the partial shutdown.

Are all cylinders 1 . 2 . 3 . 4 the internal combustion engine 10 in operation cylinders 1 . 2 . 3 . 4 , be both the turbine 7a of the first exhaust gas turbocharger 7 as well as the turbine 8a the second exhaust gas turbocharger 8th used for generating the boost pressure in the context of a two-stage compression, as long as the speed n _{mot of} the internal combustion engine 10 is smaller than a predefinable speed n _{limit, 1} . The operating mode A identifies this map area.

Is the speed n _{mot of} the internal combustion engine 10 on the other hand, greater than a predefinable speed n _{limit, 2} , becomes the first turbine 7a disabled and only the turbine 8a the second exhaust gas turbocharger 8th used in accordance with the operating mode B for generating the boost pressure in the context of a single-stage compression.

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

 Exhaust pipe of a cylinder of the first group

5b

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

6

 intake system

7

 first exhaust gas turbocharger

7a

 Turbine of the first exhaust gas turbocharger

7b

 Compressor of the first exhaust gas turbocharger

7c

 Bypass line of the first compressor

7d

 first shut-off element

8th

 second exhaust gas turbocharger

8a

 Turbine of the second exhaust gas turbocharger

8b

 Compressor of the second exhaust gas turbocharger

8c

 Bypass line of the second compressor

8d

 second shut-off element

9

 connecting line

9a

 first node

9b

 second node

10

 Internal combustion engine, four-cylinder in-line engine

11

 first turbine-related shut-off element

12

 second turbine-related shut-off

13

 Intercooler

14

 common exhaust pipe

15

 Abgasabführsystem

15a

 first total exhaust gas line

15b

 second total exhaust line

16a

 first exhaust manifold

16b

 second exhaust manifold

n _mot

 Speed of the internal combustion engine

n _{limit, 1}

 predefinable speed

n _{limit, 2}

 predefinable speed

Claims (14)

Charged internal combustion engine ( 10 ) with at least three cylinders ( 1 . 2 . 3 . 4 ) and an intake system ( 6 ) for supplying charge air to the cylinders ( 1 . 2 . 3 . 4 ), in which - each cylinder ( 1 . 2 . 3 . 4 ) has at least one outlet opening, to which an exhaust pipe ( 5a . 5b ) for discharging the exhaust gases via Abgasabführsystem ( 15 ), - at least two turbochargers ( 7 . 8th ) are provided, each exhaust gas turbocharger ( 7 . 8th ) in the exhaust gas removal system ( 15 ) arranged turbine ( 7a . 8a ) and one in the intake system ( 6 ) arranged compressors ( 7b . 8b ), - at least three cylinders ( 1 . 2 . 3 . 4 ) are configured in such a way that they have 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 ( 10 ) 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 ( 5a ) the cylinder ( 1 . 4 ) of the first cylinder group to form a first exhaust manifold ( 16a ) to a first overall exhaust gas line ( 15a ), which with the turbine ( 7a ) of a first exhaust gas turbocharger ( 7 ), and - the exhaust pipes ( 5b ) the cylinder ( 2 . 3 ) of the second cylinder group to form a second exhaust manifold ( 16b ) to a second total exhaust line ( 15b ), which with the turbine ( 8a ) of a second exhaust gas turbocharger ( 8th ), characterized in that - the first compressor ( 7b ) of the first exhaust gas turbocharger ( 7 ) downstream of the second compressor ( 8b ) of the second exhaust gas turbocharger ( 8th ) in the intake system ( 6 ), and - the first exhaust manifold ( 16a ) via connection line ( 9 ) with the second exhaust manifold ( 16b ), the connecting line ( 9 ) forming a first node ( 9a ) from the first exhaust manifold ( 16a ) branches off and forming a second node ( 9b ) in the second exhaust manifold ( 16b ) opens. Charged internal combustion engine ( 10 ) according to claim 1, characterized in that a first bypass line ( 7c ) is provided, - between the first compressor ( 7b ) and the second compressor ( 8b ) from the intake system ( 6 ), - the downstream of the first compressor ( 7b ) back into the intake system ( 6 ), and - in which a first shut-off element ( 7d ) is arranged. Charged internal combustion engine ( 10 ) according to claim 1 or 2, characterized in that a second bypass line ( 8c ) is provided, - the upstream of the second compressor ( 8b ) from the intake system ( 6 ), - between the first compressor ( 7b ) and the second compressor ( 8b ) back into the intake system ( 6 ), and - in which a second shut-off element ( 8d ) is arranged. Charged internal combustion engine ( 10 ) according to one of the preceding claims, characterized in that the first turbine ( 7a ) of the first exhaust gas turbocharger ( 7 ) has a fixed turbine geometry. Charged internal combustion engine ( 10 ) according to one of claims 1 to 3, characterized in that the first turbine ( 7a ) of the first exhaust gas turbocharger ( 7 ) has a variable turbine geometry. Charged internal combustion engine ( 10 ) according to one of the preceding claims, characterized in that between the first turbine ( 7a ) of the first exhaust gas turbocharger ( 7 ) and the first node ( 9a ) a first turbine-side shut-off element ( 11 ) is arranged. Charged internal combustion engine ( 10 ) according to one of the preceding claims, characterized in that the second turbine ( 8a ) of the second exhaust gas turbocharger ( 8th ) has a variable turbine geometry. Charged internal combustion engine ( 10 ) according to one of the preceding claims, characterized in that between the second turbine ( 8a ) of the second exhaust gas turbocharger ( 8th ) and the second node ( 9b ) a second turbine-side shut-off element ( 12 ) is arranged. Charged internal combustion engine ( 10 ) according to one of the preceding claims, characterized in that downstream of the compressor ( 7b . 8b ) a charge air cooler ( 13 ) in the intake system ( 6 ) is arranged. Charged internal combustion engine ( 10 ) according to one of the preceding claims, characterized in that between the first compressor ( 7b ) and the second compressor ( 8b ) another intercooler in the intake system ( 6 ) is arranged. Charged internal combustion engine ( 10 ) according to claim 10, characterized in that the second bypass line ( 8c ) between the further intercooler and the first compressor ( 7b ) into the intake system ( 6 ). Charged internal combustion engine ( 10 ) according to one of the preceding claims, characterized in that the first compressor ( 7b ) is designed smaller than the second compressor ( 8b ). Charged internal combustion engine ( 10 ) according to one of the preceding claims, characterized characterized in that the first turbine ( 7a ) is smaller than the second turbine ( 8a ). Charged internal combustion engine ( 10 ) 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.

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