DE102014216814A1 - Exhaust Turbo-charged internal combustion engine and method for operating such an internal combustion engine - Google Patents

Abstract

Supercharged internal combustion engine (1) having at least two exhaust gas turbochargers (8, 9) and at least one cylinder head (2) with at least two arranged in series along a longitudinal axis of the cylinder head cylinders (3), wherein the at least one cylinder head (2) on a mounting end face can be connected to a cylinder block and each cylinder (3) has at least two outlet openings (4a, 4b), of which at least one is formed as connectable outlet opening (4a), and to each outlet opening (4a, 4b) an exhaust pipe (5a, 5b ), in which - the exhaust pipes (5a) of the switchable outlet openings (4a) of at least two cylinders (3) together to form a first exhaust manifold (6a) to a first total exhaust line (7a), which with the turbine (8a) of a first Exhaust gas turbocharger (8) is connected, and - the exhaust pipes (5b) of the other outlet openings (4b) of the at least two cylinders (3) to form a second exhaust gas merge (6b) to a second total exhaust line (7b) which is connected to the turbine (9a) of a second exhaust gas turbocharger (9), wherein - the exhaust pipes (5a, 5b) of the at least two cylinders (3) within the cylinder head (2 ) to the two total exhaust pipes (7a, 7b) merge, and - the one exhaust gas line (7a, 7b) on the side facing away from the mounting end side of the other exhaust line (7a, 7b) is arranged and the two total exhaust gas lines (7a, 7b) along the longitudinal axis (10a) of the cylinder head (2) are offset with the formation of a distance Δ, wherein the distance Δ between the two total exhaust pipes (7a, 7b) corresponds to the distance of two adjacent outlet openings (4a, 4b) of a cylinder (3).

Description

• – die Abgasleitungen der zuschaltbaren Auslassöffnungen von mindestens zwei Zylindern unter Ausbildung eines ersten Abgaskrümmers zu einer ersten Gesamtabgasleitung zusammenführen, welche mit der Turbine eines ersten Abgasturboladers verbunden ist, und
• – die Abgasleitungen der anderen Auslassöffnungen der mindestens zwei Zylinder 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 two exhaust gas turbochargers and at least one cylinder head with at least two cylinders arranged in series along a longitudinal axis of the cylinder head, wherein the at least one cylinder head is connectable to a cylinder block at a mounting end and each cylinder at least two outlet openings for discharging of the exhaust gases, of which at least one is designed as a switchable outlet opening, and connects to each outlet opening an exhaust pipe, in which

• - Merge the exhaust pipes of the switchable outlet openings of at least two cylinders to form a first exhaust manifold to a first total exhaust gas line, which is connected to the turbine of a first exhaust gas turbocharger, and
• - Merge the exhaust pipes of the other outlet openings of the at least two cylinders to form a second exhaust manifold to a second total exhaust pipe, which is connected to the turbine of a second exhaust gas turbocharger.

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

An internal combustion engine of the type mentioned is, for example, in the German Offenlegungsschrift DE 102 29 116 A1 as well as in the German Offenlegungsschrift DE 10 2007 046 657 A1 described.

In the context of the present invention, the term internal combustion engine includes, in particular gasoline engines, but also diesel engines and hybrid internal combustion engines, which use a hybrid combustion process, 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 an additional auxiliary drive additionally delivers power.

Internal combustion engines have a cylinder block and at least one cylinder head, which are connected together to form the cylinder on a mounting end face. In order to control the charge cycle, an internal combustion engine requires control devices - usually in the form of globe valves - and actuators to operate these controls. The required for the movement of the valves valve actuating mechanism including the valves themselves is referred to as a valve train. Often, the cylinder head serves to accommodate the valve train.

As part of the charge exchange, the exhaust of the combustion gases via the outlet openings of the cylinder and the filling of the combustion chambers, d. H. the intake of the fresh mixture or the charge air via the inlet openings. It is the task of the valve drive to open and close the inlet and outlet openings in good time, with the aim of rapidly releasing as large flow cross sections as possible in order to keep the throttling losses in the inflowing and outflowing gas flows low, and to ensure the best possible filling of the combustion chamber Fresh mixture or an effective, d. H. To ensure complete removal of the exhaust gases. Therefore, according to the prior art, the cylinders are often equipped with two or more inlet and outlet ports. Also, the at least two cylinders of the internal combustion engine, which is the subject of the present invention, are equipped with at least two outlet openings.

The inlet ducts leading to the inlet openings and the outlet ducts, d. H. Exhaust pipes that connect to the outlet openings are at least partially integrated in the cylinder head according to the prior art. The exhaust pipes of the cylinders are usually combined to form a common exhaust gas line or - as in the internal combustion engine according to the invention - in groups to two or more total exhaust gas lines. The combination of exhaust pipes to an overall exhaust line is generally and in the context of the present invention referred to as the exhaust manifold, wherein the portion of the total exhaust line, which is located upstream of a turbine arranged in the entire exhaust line, according to the invention as belonging to the exhaust manifold.

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

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

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

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

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

In principle, the drop in charge pressure could be counteracted by reducing the size of the turbine cross-section and the associated increase in the turbine pressure ratio. Thus, the torque drop is only shifted towards lower speeds. In addition, this approach, d. H. the reduction of the turbine cross-section limits, since the desired charging and power increase even at high speeds, d. H. large amounts of exhaust gas, should be possible without restriction.

The torque characteristic of a supercharged internal combustion engine is tried to improve in the prior art by various measures.

For example, by a small design of the turbine cross-section and simultaneous Abgasabblasung. Such a turbine is also referred to as a waste gate turbine. If the exhaust gas mass flow exceeds a critical size, part of the exhaust gas flow is conducted past the turbine by means of a bypass line as part of the so-called exhaust gas blow-off. This approach has the disadvantage that the charging behavior at higher speeds or larger amounts of exhaust gas is insufficient.

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

A supercharged internal combustion engine having at least two exhaust gas turbochargers arranged in parallel is also the subject matter of the present invention, wherein a turbine is designed as a switchable turbine, which is exposed to exhaust gas only in the case of relatively large quantities of exhaust gas, d. H. is activated.

It is endeavored to arrange the turbines as close as possible to the exhaust ports of the cylinder, in order to be able to optimally use the exhaust enthalpy of the hot exhaust gases, which is largely determined by the exhaust pressure and the exhaust gas temperature, in this way, and on the other a quick response of the turbocharger to ensure. In this connection, it is therefore also fundamentally desirable to minimize the thermal inertia and the volume of the piping system between the outlet openings of the cylinders and the turbines, which can be achieved by reducing the mass and the length of the exhaust pipes.

In order to improve the torque characteristics of the internal combustion engine according to the invention, the exhaust pipes of at least two cylinders are grouped together in such a way that leads from each of these cylinders at least one exhaust pipe to the turbine of the first exhaust gas turbocharger and at least one exhaust pipe to the turbine of the second exhaust gas turbocharger.

According to the invention, the turbine of the first exhaust-gas turbocharger, ie the first turbine, is constructed as a switchable turbine and the outlet openings of the exhaust-gas pipes leading to this turbine are correspondingly designed as switchable outlet openings. Only with larger amounts of exhaust gas are the switchable Outlet openings opened in the context of the change of charge and thereby activates the first turbine, that is exposed to exhaust gas.

Compared to concepts in which a single contiguous exhaust pipe system is provided upstream of the two turbines, the grouping described above, that is to say, increases. H. the use of two separate exhaust manifold, the performance of the internal combustion engine; in particular with small exhaust gas flows, since the line volume upstream of the second turbine continuously flowed through by exhaust gas is reduced by this measure, which at low loads or rotational speeds, ie. H. small amounts of exhaust gas, is advantageous and in particular also improves the response.

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 having improved exhaust gas turbocharging performance.

A further sub-task of the present invention is to show a method for operating such an internal combustion engine.

• – die Abgasleitungen der zuschaltbaren Auslassöffnungen von mindestens zwei Zylindern unter Ausbildung eines ersten Abgaskrümmers zu einer ersten Gesamtabgasleitung zusammenführen, welche mit der Turbine eines ersten Abgasturboladers verbunden ist, und
• – die Abgasleitungen der anderen Auslassöffnungen der mindestens zwei Zylinder 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

• – die Abgasleitungen der mindestens zwei Zylinder innerhalb des Zylinderkopfes zu den zwei Gesamtabgasleitungen zusammenführen, und
• – die eine Gesamtabgasleitung auf der der Montage-Stirnseite abgewandten Seite der anderen Gesamtabgasleitung angeordnet ist und die beiden Gesamtabgasleitungen entlang der Längsachse des Zylinderkopfes unter Ausbildung eines Abstandes ∆ versetzt angeordnet sind, wobei der Abstand ∆ zwischen den zwei Gesamtabgasleitungen dem Abstand von zwei benachbarten Auslassöffnungen eines Zylinders entspricht.

The first sub-task is solved by a supercharged internal combustion engine having at least two exhaust gas turbochargers and at least one cylinder head with at least two cylinders arranged in series along a longitudinal axis of the cylinder head, wherein the at least one cylinder head is connectable to a cylinder block at a mounting end face and each cylinder at least two Having exhaust ports for discharging the exhaust gases, of which at least one is formed as a switchable outlet opening, and connects to each outlet opening an exhaust pipe, in the

• - Merge the exhaust pipes of the switchable outlet openings of at least two cylinders to form a first exhaust manifold to a first total exhaust gas line, which is connected to the turbine of a first exhaust gas turbocharger, and
• To merge the exhaust gas lines of the other outlet openings of the at least two cylinders to form a second exhaust gas manifold to form a second overall exhaust gas line which is connected to the turbine of a second exhaust gas turbocharger,

and which is characterized in that

• - Merge the exhaust pipes of the at least two cylinders within the cylinder head to the two total exhaust pipes, and
• - Is arranged an overall exhaust line on the side facing away from the mounting end side of the other exhaust line and the total two exhaust gas lines along the longitudinal axis of the cylinder head to form a distance Δ offset, wherein the distance Δ between the two exhaust pipes total the distance from two adjacent outlet openings of a Cylinder corresponds.

According to the invention, the exhaust gas lines of both the switchable outlet openings and the other outlet openings are each brought together to form an integrated exhaust manifold within the cylinder head to form an overall exhaust gas line.

As already mentioned, it is fundamentally endeavored to arrange the turbine of an exhaust-gas turbocharger as close as possible to the outlet openings of the cylinders in order to keep the path of the hot exhaust gases to the turbine runner as short as possible and the line volume upstream of the turbine runner small. The most extensive integration of the exhaust pipes and the exhaust manifold in the cylinder head is purposeful.

The length of the exhaust pipes is reduced by integration into the cylinder head. On the one hand thereby the line volume, d. H. reduces the exhaust gas volume of the exhaust pipes upstream of a turbine, so that the response of this turbine is improved. On the other hand, the shortened exhaust pipes also lead to a lower thermal inertia of the exhaust system upstream of the turbine, so that the temperature of the exhaust gases is increased at the turbine inlet, which is why the enthalpy of the exhaust gases at the inlet of the turbine is higher. Optionally provided exhaust aftertreatment systems achieve a required minimum operating temperature faster. The integration of the exhaust pipes according to the invention also allows the densest possible packaging of the drive unit.

According to the invention, the total exhaust gas lines are arranged offset along the longitudinal axis of the cylinder head to form a distance Δ.

The offset allows a compact design of the cylinder head and at the same time ensures a sufficiently large distance of the total exhaust gas lines from each other. In this way, despite a compact design enough space between the exhaust pipes remains compared to embodiments in which the Total exhaust gas lines along the cylinder head longitudinal axis have no offset. This also facilitates the arrangement of coolant channels in the cylinder head between the two exhaust pipes, if a liquid cooling is to be provided.

According to the invention, the two exhaust manifolds are at least partially superimposed, d. H. in the direction of a cylinder longitudinal axis spaced from one another, because the one exhaust line is arranged on the side facing away from the mounting end side of the other total exhaust line.

According to the invention, the distance Δ between the two exhaust gas lines corresponds to the distance between two adjacent outlet openings of a cylinder. This embodiment leads to a certain symmetrical design of the cylinder head and the Abgasabführsysteme and a symmetrical arrangement of the exhaust manifold in the cylinder head, which among other things, the gas dynamics in the Abgasabführsystemen and thus the charge can be improved.

The symmetry ensures and realizes a similarity of the exhaust manifolds and thus a similarity of the sand cores of the exhaust pipes of the two manifolds integrated in the cylinder head. As a result, a sand core of the same shape can be used for both manifolds, wherein the sand core of the one manifold of the two partially stacked manifolds to the outlet openings only needs to be supplemented by extension pieces. The similarity of the sand cores leads to a cost saving in the production by means of casting.

Thus, the first object of the invention is achieved, namely to provide a supercharged internal combustion engine, which has an improved performance with respect to the exhaust gas turbocharging.

The integration of the exhaust manifold in the cylinder head also has the advantage that can be participated in an optionally provided in the cylinder head liquid cooling, in the way that the manifold does not have to be made of thermally highly resilient and thus costly materials.

The integration of the exhaust manifold in the cylinder head also leads to a smaller number of components and thus to a reduction in costs, in particular the installation and deployment costs.

An internal combustion engine according to the invention may also have two cylinder heads. According to the invention, the exhaust pipes of all the cylinders of a cylinder head need not merge into two total exhaust pipes, but only the exhaust pipes of at least two cylinders are connected in the manner described.

However, embodiments in which the exhaust gas lines of all the cylinders of the at least one cylinder head merge to form two total exhaust gas lines are particularly advantageous.

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

Embodiments of the supercharged internal combustion engine in which the following applies to the distance Δ between the two total exhaust gas lines are advantageous: 3 mm ≦ Δ ≦ 45 mm.

Embodiments of the supercharged internal combustion engine in which the following applies to the distance Δ between the two total exhaust gas lines are also advantageous: 5 mm ≦ Δ ≦ 40 mm.

Embodiments of the supercharged internal combustion engine in which the following applies to the distance Δ between the two exhaust gas lines are particularly advantageous: 20 mm ≦ Δ ≦ 35 mm

The cylinder head of an internal combustion engine is basically a thermally and mechanically highly loaded component. The requirements for the cylinder head according to the invention are particularly high. It should be noted in this context that supercharged internal combustion engines are subject to particularly high thermal loads. Due to the integration of the exhaust manifold, the thermal load of the internal combustion engine or the cylinder head increases again, so that increased demands are placed on the cooling.

Therefore, embodiments of the supercharged internal combustion engine in which liquid cooling is provided are advantageous.

Embodiments of the supercharged internal combustion engine in which the at least one cylinder head is equipped with at least one integrated coolant jacket are advantageous. The cylinder block which can be connected to the at least one cylinder head can likewise be equipped with at least one integrated coolant jacket.

In principle, it is possible to carry out the cooling in the form of air cooling or liquid cooling. In the air cooling, the internal combustion engine is provided with a fan, wherein the heat dissipation takes place by means of a guided over the surface of the cylinder head air flow.

Due to the higher heat capacity of liquids compared to air can be dissipated with the liquid cooling much larger amounts of heat than is possible with air cooling. Therefore, it is advantageous to equip thermally highly loaded internal combustion engines with a liquid cooling.

Liquid cooling requires the equipment of the cylinder head with at least one coolant jacket, d. H. the arrangement of the coolant through the cylinder head leading coolant channels, which causes a complex structure of the cylinder head construction. In this case, the heat need not be directed to the cylinder head surface, as in the case of air cooling, in order to be dissipated. The heat is already released inside the cylinder head to the coolant, usually a water-glycol mixture. The coolant is conveyed by means of a pump arranged in the cooling circuit, so that it circulates in the coolant jacket. The heat emitted to the coolant heat is dissipated in this way from the interior of the cylinder head and removed from the coolant in a heat exchanger again. The heat exchanger is this often and preferably arranged in the front-end region of the vehicle, where a sufficiently large air flow ensures the required heat exchange between the coolant and air.

Embodiments of the supercharged internal combustion engine in which the at least one coolant jacket also extends between the two overall exhaust gas lines are advantageous. In particular, this includes embodiments in which the at least one coolant jacket has an imaginary envelope placed around the two overall exhaust lines, i. H. Envelope passes, d. H. cuts.

In the area of the total exhaust gas lines, the cylinder head is subjected to particularly high thermal loads, since the two exhaust gas lines are exposed to larger quantities of exhaust gas, in contrast to a single exhaust gas line. H. the absolute amount of exhaust gas that gives off heat to the cylinder head is comparatively large. On the other hand, the total exhaust gas lines are almost continuously exposed to hot exhaust gases, whereas an exhaust pipe of a cylinder is only flowed through during the change of charge of the respective cylinder of hot exhaust gas.

In supercharged internal combustion engines with at least one cylinder head, which is equipped with at least one integrated coolant jacket, embodiments are advantageous, which is characterized in that the at least one integrated coolant jacket has a lower coolant jacket, which is arranged between the exhaust pipes and the mounting end face of the cylinder head, and an upper coolant jacket disposed on the side of the exhaust pipes opposite to the lower coolant jacket.

In this context, embodiments of the supercharged internal combustion engine are advantageous in which at least one connection between the lower coolant jacket and the upper coolant jacket, which serves for the passage of coolant, is provided at a distance to the exhaust gas lines in an outer wall of the cylinder head from which the total exhaust gas lines emerge.

Coolant can flow out of the lower coolant jacket into the upper coolant jacket via the at least one connection in the outer wall of the cylinder head, and vice versa. This is arranged in the cylinder head at least one compound on the side facing away from the at least two cylinders of the integrated exhaust manifold. The at least one connection is thus so to speak outside the integrated exhaust manifold.

In the present case, the connection is a breakthrough or flow channel which connects the lower coolant jacket to the upper coolant jacket and enables and realizes an exchange of coolant between the two coolant jackets.

On the one hand, cooling basically also takes place in the region of the outer wall of the cylinder head. On the other hand, the conventional longitudinal flow of the coolant, d. H. the coolant flow in the direction of the longitudinal axis of the cylinder head, supplemented by a coolant transverse flow, which runs transversely to the longitudinal flow and preferably approximately in the direction of the cylinder longitudinal axes. The coolant flow passed through the at least one connection contributes significantly to the heat dissipation. In particular, a suitable dimensioning of the cross section of the at least one connection can specifically influence the flow velocity of the coolant in the connection and thus the heat dissipation in the region of this at least one connection.

In this context, embodiments of the cylinder head in which the lower and the upper coolant jacket are not connected to one another over the entire area of the outer wall are advantageous, but the at least one connection only extends over a partial area of the outer wall. Thereby, the flow velocity can be increased in the at least one compound, which the heat transfer through Convection increased. This also offers advantages in terms of the mechanical strength of the cylinder head.

The cooling of the cylinder head can additionally and advantageously be improved by generating a pressure gradient between the upper and lower coolant jacket, which in turn increases the speed in the at least one connection, which leads to increased heat transfer due to convection.

Preferably, the at least one connection is arranged adjacent to the total exhaust gas lines, since the area around the total exhaust gas lines is subjected to particularly high thermal loads, as has already been explained in detail above.

Advantageously, embodiments of the supercharged internal combustion engine, which are equipped to actuate the valves of the switchable outlet openings with a switchable valve train, for example, serving as a cam follower and located in the power flow plunger is designed as a switchable plunger.

Embodiments of the supercharged internal combustion engine in which the one exhaust gas turbocharger is arranged laterally and adjacent to the cylinder head and the other exhaust gas turbocharger laterally and adjacent to the cylinder block are advantageous. This configuration ensures a close-to-motor arrangement of the two turbines in the direction of the cylinder longitudinal axis and a dense packaging of the entire drive unit.

The turbines used can be equipped with a variable turbine geometry, which is adjusted by adjusting to the respective operating point of the internal combustion engine.

In particular, the second turbine can also be designed as a waste-gate turbine, in which exhaust gas is bypassed via bypass line to the turbine as soon as the exhaust gas mass flow exceeds a critical size. For this purpose, a shut-off is to be provided in the bypass line.

The bypass line can open downstream of the turbines in one of the two exhaust pipes total or, according to a preferred embodiment, in the first exhaust manifold upstream of the first turbine.

In embodiments of the latter type, the bypass line can then be used advantageously to accelerate the impeller of the first switchable turbine shortly before activation by opening the bypass line.

The second sub-task on which the invention is based, namely to disclose a method for operating an internal combustion engine of the type described above, is achieved by a method in which the switchable exhaust ports deactivated at a low exhaust gas quantity are activated as soon as the exhaust gas quantity exceeds a predefinable exhaust gas quantity.

The comments made in connection with the internal combustion engine according to the invention also apply to the inventive method. The activation of the outlet openings is equivalent to the connection of the first turbine. A previous acceleration of the switchable turbine via an optionally provided bypass line designed as a waste-gate turbine second turbine remains unaffected.

In a non-supercharged internal combustion engine, the amount of exhaust gas corresponds approximately to the speed and / or the load of the internal combustion engine, depending on the load control used in the individual case. In a traditional gasoline engine with a quantity control system, the exhaust gas quantity increases with increasing load even at constant speed, whereas the exhaust gas quantity in traditional quality controlled diesel engines only depends on the engine speed, because the load composition and constant speed will vary the mixture composition but not the mixture quantity.

If the internal combustion engine according to the invention is based on a quantity control in which the load is controlled by the amount of fresh mixture, the amount of exhaust gas can determine the relevant, d. H. exceed the predetermined amount of exhaust gas even at a constant speed when the load of the internal combustion engine exceeds a predetermined load, since the amount of exhaust gas correlates with the load, the amount of exhaust gas increases with increasing load and decreases with decreasing load.

On the other hand, if the internal combustion engine is based on a quality control in which the load is controlled by the composition of the fresh mixture and the amount of exhaust gas changes almost exclusively with the rotational speed, d. H. is proportional to the speed, the amount of exhaust gas, regardless of the load exceeds the predetermined amount of exhaust gas when the speed of the internal combustion engine exceeds a predetermined speed.

The internal combustion engine according to the invention is a supercharged internal combustion engine, so that in addition the charge pressure on the intake side is to be considered, which can change with the load and / or the speed and has an influence on the exhaust gas quantity. The above Consequences relating to the amount of exhaust gas and the load or speed therefore apply only conditionally in this general form. Therefore, the method according to the invention is generally based on the amount of exhaust gas and not on the load or speed.

If the amount of exhaust gas falls below a predefinable amount of exhaust gas again, the switchable outlet openings are deactivated again and with these the switchable turbine.

Advantageous are process variants in which the switchable outlet openings are activated as soon as the amount of exhaust gas exceeds a predefinable amount of exhaust gas and for a predeterminable period Δt _{1 is} greater than this predetermined amount of exhaust gas.

The introduction of an additional condition for the connection of the first turbine is to prevent too frequent switching, in particular an activation of the switchable exhaust ports, if the exhaust gas only briefly exceeds the predetermined amount of exhaust gas and then falls again or fluctuates by the predetermined value for the amount of exhaust gas, without that exceeding would justify a connection of the first turbine.

For the aforementioned reasons, process variants are also advantageous in which the switchable outlet openings are deactivated as soon as the exhaust gas quantity falls below a predefinable exhaust gas quantity and is smaller than this predetermined exhaust gas quantity for a predefinable time interval Δt ₂ .

If the second turbine is a wastegate turbine whose bypass line opens into the first exhaust manifold upstream of the first turbine, embodiments of the method are advantageous in which the first switchable turbine is accelerated shortly before activation by opening a shut-off element arranged in the bypass line.

For the reasons mentioned above, method variants are advantageous in which the switchable outlet openings which are deactivated when the exhaust gas quantity is low are activated as soon as the rotational speed of the internal combustion engine exceeds a specifiable rotational speed n _mot .

In the following the invention is based on two embodiments according to the 1 and 2 described in more detail. Hereby shows:

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

2 in a perspective view of the sand cores integrated in the cylinder head exhaust pipes according to a second embodiment of the internal combustion engine.

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

At the in 1 illustrated internal combustion engine 1 it is a four-cylinder in-line engine in which the cylinders 3 along the longitudinal axis 10a of the cylinder head 2 , ie in series, are arranged. Every cylinder 3 has two outlet openings 4a . 4b on, being attached to each outlet opening 4a . 4b an exhaust pipe 5a . 5b for removing the exhaust gases from the cylinder 3 followed.

One outlet each 4a every cylinder 3 is as a switchable outlet opening 4a formed, which is opened in the context of the charge change only when the amount of exhaust gas exceeds a predetermined amount of exhaust gas. This turns the downstream turbine into the first turbine 8a activated, ie subjected to exhaust gas. The exhaust pipes 5a the switchable outlet openings 4a all cylinders 3 lead to the formation of a first exhaust manifold 6a inside the cylinder head 2 to a first total exhaust line 7a together, which with the turbine 8a of the first exhaust gas turbocharger 8th connected (dashed lines).

The exhaust pipes 5b the other outlet openings 4b all cylinders 3 lead to the formation of a second exhaust manifold 6b inside the cylinder head 2 to a second total exhaust line 7b together, which with the turbine 9a the second exhaust gas turbocharger 9 is connected (solid lines).

How out 1 can be seen, are the first exhaust manifold 6a and the second exhaust manifold 6b upstream of the turbines 8a . 9a separated from each other. The second turbine 9a but can also be designed as a waste-gate turbine, the bypass line upstream of the first turbine 8a in the first exhaust manifold 6a empties. Then the exhaust manifolds 6a . 6b at least connectable via bypass line.

In the present case lead the exhaust pipes 5a . 5b inside the cylinder head 2 to two total exhaust pipes 7a . 7b together, the two total exhaust pipes 7a . 7b along the longitudinal axis 10a of the cylinder head 2 are arranged offset by forming a distance .DELTA.

2 shows a perspective view of the sand cores to form the integrated in the cylinder head exhaust pipes 5a . 5b . 7a . 7b according to a second embodiment of the internal combustion engine.

2 thus shows the system of integrated in the cylinder head exhaust pipes 5a . 5b . 7a . 7b or exhaust manifolds 6a . 6b , which is why the reference numbers for the exhaust pipes 5a . 5b . 7a . 7b and the exhaust manifold 6a . 6b are registered.

At the in 2 shown sand cores or exhaust manifolds 6a . 6b it is the exhaust pipes 4a . 4b . 7a . 7b the four cylinders 3 a four-cylinder in-line engine, in which the cylinders 3 are arranged along the longitudinal axis of the cylinder head. Each of the four cylinders 3 is with two outlet openings 4a . 4b fitted to each outlet 4a . 4b an exhaust pipe 5a . 5b followed.

The exhaust pipes 5a the switchable outlet openings 4a lead to the formation of a first integrated exhaust manifold 6a within the cylinder head to a first overall exhaust line 7a and the exhaust pipes 5b the other outlet openings 4b lead to the formation of a second integrated exhaust manifold 6b within the cylinder head to a second total exhaust line 7b together.

How out 2 As can be seen, the two total exhaust pipes 7a . 7b the integrated exhaust manifold 6a . 6b along the longitudinal axis of the cylinder head, ie also along a parallel 10 arranged offset to the longitudinal axis of the cylinder head to form a distance Δ, wherein the total exhaust gas line 7a of the first integrated exhaust manifold 6a on the side facing away from the mounting end side of the entire exhaust line 7b of the second integrated exhaust manifold 6b lies. Ie. the total exhaust pipes 7a . 7b lie one above the other, with the second total exhaust line 7b between the mounting end face and the first overall exhaust gas line 7a is arranged.

LIST OF REFERENCE NUMBERS

1

 charged internal combustion engine

2

 cylinder head

3

 cylinder

4a

 switchable outlet opening

4b

 outlet

5a

 exhaust pipe

5b

 exhaust pipe

6a

 first exhaust manifold

6b

 second exhaust manifold

7a

 first total exhaust gas line

7b

 second total exhaust line

8th

 first exhaust gas turbocharger

8a

 first turbine, switchable turbine

8b

 first compressor

9

 second exhaust gas turbocharger

9a

 second turbine

9b

 second compressor

10

 Parallel to the longitudinal axis of the cylinder head

10a

 Longitudinal axis of the cylinder head

11a

 first suction line

11b

 second intake pipe

12

 plenum

n _mot

 Speed of the internal combustion engine

Δ

 Distance of the total exhaust gas lines along the longitudinal axis of the cylinder head

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• DE 10229116 A1 [0003]
• DE 102007046657 A1 [0003]

Claims (16)

Charged internal combustion engine ( 1 ) with at least two exhaust gas turbochargers ( 8th . 9 ) and at least one cylinder head ( 2 ) having at least two cylinders arranged in series along a longitudinal axis of the cylinder head ( 3 ), wherein the at least one cylinder head ( 2 ) is connectable to a cylinder block at a mounting end face and each cylinder ( 3 ) at least two outlet openings ( 4a . 4b ) for discharging the exhaust gases, of which at least one as switchable outlet ( 4a ) is formed, and to each outlet opening ( 4a . 4b ) an exhaust pipe ( 5a . 5b ), in which - the exhaust pipes ( 5a ) of the switchable outlet openings ( 4a ) of at least two cylinders ( 3 ) to form a first exhaust manifold ( 6a ) to a first overall exhaust gas line ( 7a ), which with the turbine ( 8a ) of a first exhaust gas turbocharger ( 8th ), and - the exhaust pipes ( 5b ) of the other outlet openings ( 4b ) the at least two cylinders ( 3 ) to form a second exhaust manifold ( 6b ) to a second total exhaust line ( 7b ), which with the turbine ( 9a ) of a second exhaust gas turbocharger ( 9 ), characterized in that - the exhaust pipes ( 5a . 5b ) the at least two cylinders ( 3 ) within the cylinder head ( 2 ) to the two total exhaust pipes ( 7a . 7b ), and - the one total exhaust gas line ( 7a . 7b ) on the side facing away from the mounting end side of the other exhaust line ( 7a . 7b ) is arranged and the two total exhaust gas lines ( 7a . 7b ) along the longitudinal axis ( 10a ) of the cylinder head ( 2 ) are arranged offset by forming a distance Δ, wherein the distance Δ between the two exhaust gas lines ( 7a . 7b ) the distance from two adjacent outlet openings ( 4a . 4b ) of a cylinder ( 3 ) corresponds. Charged internal combustion engine ( 1 ) according to claim 1, characterized in that for the distance Δ between the two total exhaust gas lines ( 7a . 7b ): 3mm ≤ Δ ≤ 45mm. Charged internal combustion engine ( 1 ) according to claim 1 or 2, characterized in that for the distance Δ between the two total exhaust gas lines ( 7a . 7b ): 5mm ≤ Δ ≤ 40mm. Charged internal combustion engine ( 1 ) according to one of the preceding claims, characterized in that for the distance Δ between the two exhaust gas lines ( 7a . 7b ): 20mm ≤ Δ ≤ 35mm. Charged internal combustion engine ( 1 ) according to one of the preceding claims, characterized in that a liquid cooling is provided. Charged internal combustion engine ( 1 ) according to claim 5, characterized in that the at least one cylinder head ( 2 ) is equipped with at least one integrated coolant jacket. Charged internal combustion engine ( 1 ) according to claim 6, characterized in that the at least one coolant jacket also between the two total exhaust gas lines ( 7a . 7b ). Charged internal combustion engine ( 1 ) according to claim 6 or 7, characterized in that the at least one coolant jacket a lower coolant jacket, which between the exhaust pipes ( 5a . 5b ) and the mounting end face ( 9 ) of the cylinder head ( 2 ) is arranged, and an upper coolant jacket, which on the opposite side of the lower coolant jacket exhaust pipes ( 5a . 5b ) is arranged. Charged internal combustion engine ( 1 ) according to claim 8, characterized in that spaced from the exhaust pipes ( 5a . 5b ) in an outer wall of the cylinder head ( 2 ) from which the total exhaust pipes ( 7a . 7b ), at least one connection between the lower coolant jacket and the upper coolant jacket is provided, which serves for the passage of coolant. Charged internal combustion engine ( 1 ) according to claim 9, characterized in that the at least one connection adjacent to the total exhaust gas lines ( 7a . 7b ) is arranged. Charged internal combustion engine ( 1 ) according to one of the preceding claims, characterized in that the second turbine ( 9a ) is designed as a waste-gate turbine, wherein upstream of the second turbine ( 9a ) a bypass line from the second exhaust manifold ( 6b ) branches off and a shut-off element is provided in the bypass line. Charged internal combustion engine ( 1 ) according to claim 11, characterized in that the bypass line downstream of the turbines ( 8a . 9a ) into one of the two exhaust pipes ( 7a . 7b ) opens. Charged internal combustion engine ( 1 ) according to claim 11, characterized in that the bypass line upstream of the first turbine ( 8a ) in the first exhaust manifold ( 6a ) opens. Charged internal combustion engine ( 1 ) according to one of the preceding claims, characterized in that the one exhaust gas turbocharger ( 8th . 9 ) laterally and adjacent to the cylinder head ( 2 ) and the other exhaust gas turbocharger ( 8th . 9 ) is arranged laterally and adjacent to the cylinder block. Method for operating a supercharged internal combustion engine ( 1 ) according to one of the preceding claims, characterized in that the deactivatable with a small amount of exhaust gas switchable outlet openings ( 4a ) are activated as soon as the amount of exhaust gas exceeds a predefinable amount of exhaust gas. A method according to claim 15, characterized in that the deactivatable at a small amount of exhaust gas switchable outlet openings ( 4a ) are activated when the speed of the internal combustion engine exceeds a predetermined speed n _mot .

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