DE102016120815A1 - Internal combustion engine - Google Patents

Abstract

An internal combustion engine having an internal combustion engine (10), an exhaust system and one or more exhaust gas turbines (20) integrated in the exhaust system, in which the internal combustion engine (10) forms one or more combustion chambers (12) each having at least two exhaust valves (24, 26) in which the exhaust valves (24, 26) can be actuated by means of a valve drive, first exhaust valves (24) assigned to the combustion chambers (12) being connected via a common first exhaust gas flow (28) and second exhaust valves (26) assigned to the combustion chambers (12) ) are in exhaust gas conductively connected via a common second exhaust gas flow (30) of the exhaust line with the exhaust gas or the turbines (20), wherein for the second exhaust gas flow (30) a greater cooling effect is realized than for the first exhaust gas flow (28), characterized in that the minimum and / or the mean flow cross section of the first exhaust gas flow (28) is smaller than the corresponding flow cross section of the second exhaust gas flow (28) LUT (30) is designed. As a result, advantages with regard to the operating behavior of the internal combustion engine can be realized. In particular, the realization of a bump charge is made possible or positively influenced by a relatively strong pulsation of the pressure of the exhaust gas in the first exhaust gas flow (28) is generated with correspondingly pronounced pressure peaks and pressure valleys due to the relatively small dimensions of the first exhaust gas flow (28).

Description

The invention relates to an internal combustion engine with an internal combustion engine, an exhaust system and one or more exhaust gas turbines integrated in the exhaust line, wherein the internal combustion engine forms one or more combustion chambers, each of which at least two exhaust valves are assigned, wherein the exhaust valves are actuated by means of a valve train and wherein the combustion chambers associated first exhaust valves via a common first exhaust gas flow and the combustion chambers associated second exhaust valves via a common second exhaust gas flow of the exhaust line with the exhaust gas or the exhaust gas are in exhaust connection, wherein for the second exhaust gas, a greater cooling effect is realized than for the first exhaust gas flow.

Such an internal combustion engine is from the DE 10 2012 001 199 A1 known. The exhaust gas flows of this internal combustion engine, which are referred to overall as exhaust manifolds, are integrated into a cylinder head of the internal combustion engine, whereby cooling for the exhaust gas flowing through the exhaust gas flows is achieved. Furthermore, in the internal combustion engine according to the DE 10 2012 001 199 A1 provided that each of the exhaust gas flows in exhaust gas conductive connection with each of a separate exhaust gas turbine of an exhaust gas turbocharger. Alternatively, two exhaust gas turbochargers connected in series can also be provided, wherein the exhaust gas flows are first brought together and then supplied to the exhaust gas turbine of a first exhaust gas turbocharger.

An integrated in a cylinder head exhaust manifold is in the DE 10 2012 001 199 A1 referred to as disadvantageous with respect to the cold start behavior and the subsequent warm-up phase of the internal combustion engine and with respect to the response of the exhaust gas turbocharger due to an unwanted cooling of the exhaust gas. To avoid these disadvantages is according to the DE 10 2012 001 199 A1 provided to connect each of the combustion chambers of the internal combustion engine via a respective exhaust valve with a first exhaust gas flow and via each another exhaust valve with a second exhaust gas flow, wherein for the two different exhaust gas flows different cooling effects are realized by, for example, the channels of the first exhaust gas flow shorter and in cross section are dimensioned larger than those of the second exhaust gas flow, whereby a smaller cooling effect is achieved for the exhaust gas flowing through it. For a cooling of the exhaust gas which is as optimal as possible in dependence on the operating point of the internal combustion engine, it is provided either to allow the exhaust gas mass flow to flow completely through one of the exhaust gas flows or to distribute it in a defined ratio to the two exhaust gas flows.

One to the internal combustion engine according to the DE 10 2012 001 199 A1 similar internal combustion engine is from the DE 10 2015 203 157 A1 known. In the internal combustion engine described therein, it is provided to provide a first exhaust pipe including the housing of an exhaust gas turbine integrated in this exhaust pipe of a first exhaust gas turbocharger to an exhaust aftertreatment system disposed downstream of the exhaust gas turbine with an internal, insulating metal structure, while a second exhaust pipe, which is also an exhaust gas turbine integrated a second exhaust gas turbocharger, does not have such an insulating metal structure.

The DE 10 2014 201 433 A1 describes a cylinder head with an integrated coolant jacket for liquid cooling, wherein the coolant jacket limiting walls are at least partially provided with a thermal insulation.

The invention was based on the object, an internal combustion engine, as in principle from the DE 10 2012 001 199 A1 is known to improve in terms of performance, especially in an operation of the internal combustion engine of the internal combustion engine at low speeds and loads.

This object is achieved by means of an internal combustion engine according to the patent claim 1. Advantageous embodiments of the internal combustion engine according to the invention are objects of the other claims and / or will become apparent from the following description of the invention.

According to the invention, an internal combustion engine is provided with an internal combustion engine, an exhaust system and one or more exhaust gas turbines integrated into the exhaust system, which are in particular part of an exhaust gas turbocharger, wherein the internal combustion engine forms one or more combustion chambers to which at least two exhaust valves are respectively assigned. The exhaust valves are actuated by means of a valve drive, wherein the combustion chambers associated first exhaust valves via a common first exhaust gas flow and the combustion chambers associated second exhaust valves via a common second exhaust gas flow of the exhaust system with the exhaust gas or the exhaust gas are in exhaust connection. In this case, a greater cooling effect is realized for the second exhaust gas flow (in at least one operating state of the internal combustion engine and preferably always during operation of the internal combustion engine) than for the first exhaust gas flow.

• - bei einem Betrieb des Verbrennungsmotors in einem ersten Betriebskennfeldbereich, der durch relativ niedrige Kombination aus Drehzahl und Last gekennzeichnet ist, die ersten Auslassventile (vorzugsweise im maximalen Ausmaß) betätigt und die zweiten Auslassventile nicht oder in einem relativ kleinen (d.h. nicht maximalen und insbesondere im Vergleich zu den ersten Auslassventilen kleineren) Ausmaß betätigt sowie
• - bei einem Betrieb des Verbrennungsmotors in einem zweiten Betriebskennfeldbereich, der durch relativ hohe Kombination aus Drehzahl und Last gekennzeichnet ist, die zweiten Auslassventile im maximalen Ausmaß betätigt.

The internal combustion engine may further comprise a control device for controlling the valve train based on an operating map of the internal combustion engine, wherein the Control device is designed such that it controls the valve train such that this

• in an operation of the internal combustion engine in a first operating map area, characterized by a relatively low combination of speed and load, the first exhaust valves are operated (preferably to the maximum extent) and the second exhaust valves are not actuated or in a relatively small (ie not maximum and in particular Compared to the first exhaust valves smaller) extent actuated as well
• in an operation of the internal combustion engine in a second operating map area, which is characterized by a relatively high combination of speed and load, the second exhaust valves are actuated to the maximum extent.

In this case, during operation of the internal combustion engine, the first exhaust valves can not be actuated in a relatively small amount or to a maximum extent in accordance with an operating point lying in the second operating characteristic area. There is the possibility that the operating map has, in addition to the defined first and second operating map areas, further operating map areas which are characterized by defined actuations and / or non-actuations of the outlet valves or the defined first and second operating map areas are subdivided into subregions.

An operation of the exhaust valves in terms of "extent" refers to the specific amount of exhaust gas, which can be discharged in the context of an opening event of an exhaust valve due to an opening of the exhaust valve over this from the associated combustion chamber. Preferably, this extent can be influenced, in which the size of the valve lift is variable. This is meant to carry out a zero lift, i. a closed hold, the exhaust valve. Additionally or alternatively, it is also possible to influence this "extent" by changing the opening duration (in ° CA) for the exhaust valves and / or changing the valve lift curves.

By means of such an internal combustion engine, it can be achieved that during operation of the internal combustion engine at low speeds and loads according to an operating point located within the first operating characteristic area, the exhaust gas accumulating in the combustion chambers is realized primarily or exclusively via the first exhaust gas flow, for which a relatively lower cooling effect is realized. dissipated and is guided to the adjoining exhaust gas turbine, which disadvantages, which would result from a cooling of the operation within this operating map area anyway not particularly hot exhaust gas can be avoided, or at least kept low. These disadvantages may be, in particular, a relatively poor response of an exhaust gas turbocharger comprising the exhaust gas turbine as well as a relatively poor low-end torque behavior of the internal combustion engine due to an enthalpy loss of the exhaust gas. Further disadvantages which would result from an unintentional cooling of the operating mode of the internal combustion engine in the first operating characteristic area are a delay in reaching a so-called light-off temperature of, in particular, downstream of or the exhaust gas turbine (s) integrated into the exhaust system of the internal combustion engine Exhaust after-treatment device, an extension of measures for heating such an exhaust aftertreatment device, the risk of cooling the exhaust aftertreatment device and / or increased demands on a cooling system of the internal combustion engine, in particular with regard to the heat dissipation from the cooling system to the environment.

On the other hand, in an operation of the internal combustion engine with relatively high combinations of speed and load in the second operating map area, in which the internal combustion engine generates relatively hot exhaust gas, the exhaust gas is additionally (possibly mainly) or exclusively by the second exhaust gas flow, for which a relatively high cooling effect is realized , dissipated. As a result, a thermal overload of components of the exhaust system and in particular of the exhaust gas turbine (s) can be avoided.

Such an internal combustion engine is inventively characterized in that the minimum and / or the average flow cross section of the first exhaust gas flow is smaller (preferably at least 10%, more preferably at least 30% smaller) than the corresponding flow cross section of the second exhaust gas flow. As a result, further advantages, in particular with regard to the operating behavior of the internal combustion engine, can be realized. In particular, the realization of a bump charge is made possible or positively influenced by a relatively strong pulsation of the pressure of the exhaust gas in the first exhaust gas flow is generated with correspondingly pronounced pressure peaks and pressure valleys due to the relatively small dimensions of the first exhaust gas flow. This results in the range of the charge cycle OT (ie the top dead center in the cyclic back and forth movement of a combustion chamber of the engine limiting piston defining the change between exhaust stroke and intake stroke in a four-stroke internal combustion engine) a pressure gradient (so-called positive Purging gradient) of the pressure of the exhaust gas in the first exhaust gas flow in comparison to the pressure of the fresh gas in a section adjacent to intake valves of the internal combustion engine (eg in an intake manifold) of a fresh gas train of the internal combustion engine. This pressure gradient can be used with a preferably provided for at least one (possibly for each) operating state of an internal combustion engine according to the invention valve overlap, ie a simultaneous opening of at least the first exhaust valve and at least one inlet valve per combustion chamber in a period comprising the change of charge TDC, in the Flue gas contained exhaust gas to flush with fresh gas from the combustion chambers. In this way, an increase in the efficiency of the operation of the internal combustion engine and in particular a better filling of the combustion chambers with fresh gas, a relatively low tendency to knock, by a relatively early ignition and relatively early center of gravity positions are made possible and overall a relatively high specific torque can be realized. Furthermore, an increase in the kinetic energy of the gas flow at the inlet of the exhaust gas turbine and thus an improved response of the exhaust gas turbine can be realized in this way due to the additional fresh gas, which is supplied via the first exhaust gas flow together with the exhaust of the exhaust gas connected to the first exhaust gas. It is particularly advantageous that the advantages that result from the relatively small design of the first exhaust gas flow can be without relevant disadvantages, in particular with regard to the achievable nominal power, because disadvantages in terms of nominal power, in particular increased charge exchange losses and / or a need for enrichment are thereby avoided. that at higher combinations of speed and load, the exhaust gas (or) can be performed on the second, larger-dimensioned exhaust gas flow or will.

Incidentally, the internal combustion engine of an internal combustion engine according to the invention may also be only a partial internal combustion engine and, in particular, a so-called cylinder bank in the case of an internal combustion engine having a plurality of cylinder banks, which may be designed, for example, in a so-called V arrangement. It is relevant that the combustion chambers of at least one and preferably each cylinder bank of such an internal combustion engine are connected in the described manner via a first exhaust gas flow and a second exhaust gas flow to at least one exhaust gas turbine.

The different cooling effect for an internal combustion engine according to the invention can be realized in an advantageous manner in that the second exhaust gas flow (active) is cooled; i.e. Measures are provided to actively effect an increased heat removal from the exhaust gas conducted via the second exhaust gas flow at least temporarily. For this purpose, it can be provided, in particular, that the second exhaust gas flow is cooled by means of these associated cooling channels, which are part of a cooling system of the internal combustion engine. The cooling channels may preferably be provided such that they are separated from the second exhaust gas flow only by the smallest possible wall. Such active cooling of the second exhaust gas flow can be realized in an advantageous manner by the second exhaust gas flow is integrated into a cylinder head housing of the engine, since in such a cylinder head housing regularly cooling channels must be integrated to cool other components of the internal combustion engine.

The different cooling effect for an internal combustion engine according to the invention can alternatively or, preferably, also be realized in an advantageous manner that for the first exhaust gas flow thermal insulation, ie a structure whose primary or exclusive function a low heat transfer from the first exhaust gas flowing through the flow Exhaust gas to an environment of the first exhaust gas flow is provided. Such a thermal insulation of the first exhaust gas flow may be particularly useful if, as it is preferably provided, (also) the first exhaust gas flow is integrated into a cylinder head housing of the internal combustion engine, because thereby fundamental advantages, such as in particular a compact design of the internal combustion engine, a short Flow path between the combustion chambers and the exhaust gas or the turbines, a relatively low weight of the internal combustion engine and relatively low manufacturing costs for the internal combustion engine can be realized. By means of the thermal insulation of the first exhaust gas flow, which then by one of the first exhaust gas flow associated (and this preferably as fully surrounds) and integrated into the cylinder crankcase insulation section, which may differ from these adjacent sections of the cylinder head housing in structural and / or material terms, may be formed, therefore, an unwanted cooling of the first exhaust gas flowing through the exhaust gas due to a principle provided for the cylinder head housing cooling can be effectively prevented or at least kept low. Preferably, it may be provided that the insulation portion is formed as an insert of, for example, a ceramic material. This insert can be encapsulated for example in the manufacture of the cylinder head housing with a material provided for the formation of the remaining cylinder head housing material, whereby its integration is associated with only a minor additional manufacturing effort. Also possible is an embodiment of the isolation section as integral, ie of the type the material of the cylinder head housing, which differs from the material of the adjoining sections by a defined porosity and consequently by the formation of a plurality of (vacuum) cavities filled or unfilled, in particular, with air or another gas.

In a preferred embodiment, the valve train of an internal combustion engine according to the invention can be configured such that it can be switched between at least two alternatively usable valve cams with regard to an actuation of the first exhaust valves and / or the second exhaust valves. In this case, the (in each case) at least two different valve cams can, on the one hand, bring about a zero stroke, ie, keeping the corresponding gas exchange valves closed, and, on the other hand, open them to the maximum extent, in particular with a maximum valve lift. In particular, in the embodiment of the valve train with more than two alternatively usable valve cam for the intake and / or exhaust valves and at least one valve cam may be provided by the associated gas exchange valve is opened to an extent that between a zero stroke (no opening) and a Open to the maximum extent. An advantage of such a switchable embodiment of the valve train is the possibility of a relatively simple structural design. In particular, such a switchable valve train according to the in the DE 196 11 641 C1 disclosed embodiment may be provided. However, it is also possible to use alternative valve trains, which offer a variability in terms of the extent of the openings of the gas exchange valves, such as known mechanical, electro-mechanical or hydraulic fully variable valve trains use.

In a further preferred embodiment of an internal combustion engine according to the invention can be provided that the length of the second exhaust gas flow is greater than the length of the first exhaust gas flow. In this case, the term "length" refers to the longitudinal extent of each strand of an exhaust gas flow, which extends from a gas exchange valves associated with this strand to an outlet of the corresponding exhaust gas flow, this outlet preferably in transition to an inlet of an exhaust gas turbine connected to the respective exhaust gas line and / or, in a preferably provided integration of the exhaust gas flow in a cylinder head housing of the internal combustion engine, may be formed as an outlet opening of the cylinder head housing. It should preferably be provided according to the invention that the longitudinal extent (s) of at least one, preferably the plurality and particularly preferably all strands of the second exhaust gas flow is / are greater than the corresponding longitudinal extension (s) of the first exhaust gas flow. In an internal combustion engine according to the invention with an internal combustion engine having an even number of combustion chambers, it follows that also the total length of the second exhaust gas flow is greater than the total length of the first exhaust gas flow. By means of the preferably provided greater length of the second exhaust gas flow in comparison to the length of the first exhaust gas flow, in turn, the realization of an impact charge can be positively influenced.

In supercharged internal combustion engines with multi-cylinder internal combustion engines, a common exhaust manifold of the exhaust line, which connects the combustion chambers with the exhaust gas turbine, to a relevant extent lead to a so-called crosstalk of a exhaust stroke of an exhaust gas discharging combustion chamber to the other cylinders. This can lead to an undesirable influence on the operating behavior, since it can come to the backflow of exhaust gas from the exhaust manifold into the combustion chambers. This can be associated with an increased residual gas rate in these combustion chambers and thus for example in gasoline engines with an increased tendency to knock and consequent reduction of the combustion efficiency and the producible torque. The amount of such crosstalk is basically dependent on the speed at which the engine is driven and thus on the frequency of the occurrence of the exhaust surges, with a relatively short opening duration of the exhaust valves being required while keeping crosstalk low at relatively low speeds Opening duration tends to be increased with increasing speed in order to keep crosstalk to a comparable extent low. It can be kept relatively low with a relatively long opening period charge exchange losses and residual gas contents in the combustion chambers in an advantageous manner.

Accordingly, it can advantageously be provided in an internal combustion engine according to the invention that the valve train is designed such that it actuates the first exhaust valves each having an opening duration which is smaller than the firing interval of the combustion chambers or corresponds to this highest. As a result, in particular, crosstalk during operation of the internal combustion engine in the defined first operating map area, which is characterized by rather low rotational speeds, can advantageously be kept low. On the other hand, it may be provided in an advantageous manner that the valve train is designed such that it actuates the second exhaust valves, each with an opening duration (if he operated this), which is greater than the firing interval of the combustion chambers or at least equal. This allows both a relatively low crosstalk than also possible reduced charge exchange losses and residual gas contents can be realized.

According to the invention, the term "opening period" is understood to mean the section of the total opening duration which is situated between the reaching of a valve lift of one millimeter during the opening movement and the subsequent achievement of a valve lift of one millimeter during the closing movement. Accordingly, with regard to the shape of conventional valve lift curves, the very shallow rising or falling sections for the respective beginning and end of the valve lift curves of the "opening period" should not be included, because in these sections of the valve lift curves of the gas exchange valves no relevant opening cross-section is released.

As "firing interval" is the angular range, based on the rotation of an output shaft and in particular a crankshaft of the internal combustion engine understood, which results from the fact that the rotation angle of the output shaft, this principle performs between two desired firing processes in each of the combustion chambers, by the number divided into combustion chambers. In a four-stroke reciprocating engine, in which the invention can be used particularly preferably, the angle of rotation of the crankshaft (output shaft), which this principle performs between two intentional firing processes in each of the combustion chambers, 720 °. In an internal combustion engine having, for example, three combustion chambers (possibly per cylinder bank), the ignition interval is therefore 240 ° CA, in an internal combustion engine with four combustion chambers 180 ° CA, in an internal combustion engine with five combustion chambers 144 ° CA and in an internal combustion engine with six combustion chambers 120 ° CA.

In one embodiment of an internal combustion engine according to the invention can be provided that the first exhaust gas flow and the second exhaust gas flow are in communication with the same exhaust gas turbine. As a result, in particular a simply supercharged embodiment or a configuration with a so-called mono exhaust gas turbocharger can be realized, which can be associated with relatively low production costs. It can be provided in an advantageous manner that the exhaust gas turbine is a segment turbine or a twin-scroll turbine, whereby the individual exhaust gas flows conducted via the exhaust gas flows can be implemented in the exhaust gas turbine energetically advantageous. An embodiment of the exhaust gas turbine as a segment turbine or as a twin-scroll turbine can also have an advantageous effect with regard to crosstalk of exhaust impacts.

Alternatively, there is also the possibility that the first exhaust gas flow and the second exhaust gas flow are in connection with separate exhaust gas turbines, whereby additional design possibilities are provided which can have advantageous effects with regard to the operating behavior of the internal combustion engine.

In particular, it may be provided that a first exhaust gas turbine in communication with the first exhaust gas flow is designed to be smaller than a second exhaust gas turbine that is in communication with the second exhaust gas flow. This allows the best possible response in this exhaust turbine and consequently the best possible low-end torque (LET) can be realized. The relatively large design of the second exhaust gas turbine, however, ensures (possibly in combination with the first exhaust gas applied to the first exhaust gas turbine) at relatively high speeds and loads as complete as possible implementation of the enthalpy of the exhaust gas, which can have a positive effect on the performance and efficiency of the internal combustion engine ,

With regard to the "design" of an exhaust gas turbine while the size of the turbine wheel and, consequently, the size of the exhaust gas mass flow, which can be passed through this, before the stuffing limit of the exhaust gas turbine is reached understood.

Since the first exhaust gas turbine connected to the first exhaust gas flow is to be acted upon primarily at relatively low combinations of speed and load during operation of the internal combustion engine and consequently with relatively cool exhaust gas, it can be provided in an advantageous manner that these are not cooled, ie for these no active Cooling is provided and / or even a thermal insulation is provided for this. It can thereby be achieved that the largest possible proportion of the enthalpy of the exhaust gas can be converted by the exhaust gas turbine. On the other hand, the second exhaust gas turbine connected to the second exhaust gas flow may be cooled in an advantageous manner so as to produce a thermal effect even in the case of operation with relatively high combinations of rotational speed and load in which it is subjected to exhaust gas primarily or exclusively during operation of the internal combustion engine To avoid overloading the second exhaust gas turbine. This can make it possible to design these from relatively low thermal loadable materials and therefore cost. The cooling of the second exhaust gas turbine may relate in particular to the turbine housing and possibly also to a bearing housing. Such a bearing housing accommodates a bearing and a shaft which is non-rotatably connected to a turbine runner of the second exhaust gas turbine and preferably also to a compressor runner of a compressor, which together with the second Exhaust gas turbine forms a (second) exhaust gas turbocharger, is connected.

In a further preferred embodiment of an internal combustion engine according to the invention can be provided that the operating map has a transition region, so that switching from a control of the valve train according to the first operating map area to a control of the valve train corresponding to the second operating map area at higher combinations of speed and load than a switching from a control of the valve train according to the second operating map area to a control of the valve train according to the first operating map area. As a result, in the case of a dynamic operation of the internal combustion engine in the area of a transition provided in principle for switching, which can be provided in particular approximately in the middle of the transfer area, frequent switching between the operating modes can be avoided.

The internal combustion engine of an internal combustion engine according to the invention may preferably be a gasoline engine or another spark-ignited internal combustion engine, since the exhaust gas of such an internal combustion engine has at least temporarily relatively high temperatures compared to, for example, a diesel engine, whereby the need for at least temporary cooling of the exhaust gas, in particular for reasons of component protection, can result. Also, in a gasoline engine crosstalk between the combustion chambers and / or increased exhaust back pressure can have a particularly negative effect. Of course, however, the internal combustion engine may also be a diesel engine.

• - bei einem Betrieb des Verbrennungsmotors in einem ersten Betriebskennfeldbereich, der durch relativ niedrige Kombinationen aus Drehzahl und Last gekennzeichnet ist, die ersten Auslassventile (vorzugsweise im maximalen Ausmaß) betätigt und die zweiten Auslassventile nicht oder in einem relativ kleinen Ausmaß betätigt werden sowie
• - bei einem Betrieb des Verbrennungsmotors in einem zweiten Betriebskennfeldbereich, der durch relativ hohe Kombinationen aus Drehzahl und Last gekennzeichnet ist, die zweiten Auslassventile im maximalen Ausmaß betätigt werden.

Incidentally, the invention also relates to a method for operating an internal combustion engine according to the defined control of the valve drive by the control device, so that

• when the internal combustion engine is operating in a first operating map area characterized by relatively low combinations of speed and load, the first exhaust valves are actuated (preferably to the maximum extent) and the second exhaust valves are not actuated or operated to a relatively small extent, and
• in an operation of the internal combustion engine in a second operating map area, which is characterized by relatively high combinations of speed and load, the second exhaust valves are actuated to the maximum extent.

The indefinite articles ("a", "an", "an" and "an"), in particular in the patent claims and in the description generally describing the claims, are to be understood as such and not as numerical words. Corresponding to this concretized components are thus to be understood that they are present at least once and may be present more than once.

• 1: eine erfindungsgemäße Brennkraftmaschine gemäß einer ersten Ausgestaltungsform in einer schematischen Darstellung;
• 2: eine erfindungsgemäße Brennkraftmaschine gemäß einer zweiten Ausgestaltungsform in einer schematischen Darstellung;
• 3: ein Betriebskennfeld, gemäß dem ein Verbrennungsmotor einer Brennkraftmaschine gemäß der 1 oder der 2 betrieben werden kann;
• 4: ein weiteres Betriebskennfeld, gemäß dem ein Verbrennungsmotor einer Brennkraftmaschine gemäß der 1 oder der 2 betrieben werden kann; und
• 5: in einem Diagramm beispielhafte Verläufe der Gasdrücke in einer Abgasflut, in einem Brennraum sowie in einem Saugrohr einer Brennkraftmaschine gemäß beispielsweise den 1 und 2.

The present invention will be explained in more detail with reference to embodiments shown in the drawings. In the drawings shows:

• 1 : an internal combustion engine according to the invention according to a first embodiment in a schematic representation;
• 2 a combustion engine according to the invention according to a second embodiment in a schematic representation;
• 3 an operating map according to which an internal combustion engine of an internal combustion engine according to the 1 or the 2 can be operated;
• 4 a further operating map, according to which an internal combustion engine of an internal combustion engine according to the 1 or the 2 can be operated; and
• 5 in a diagram, exemplary curves of the gas pressures in an exhaust gas flow, in a combustion chamber and in a suction pipe of an internal combustion engine according to, for example, the 1 and 2 ,

The 1 shows in a highly simplified representation of a first embodiment of an internal combustion engine according to the invention. This includes an internal combustion engine 10 , which in the present embodiment as a series engine with four cylinders 12 or combustion chambers 12 is trained. The combustion chambers 12 are each of sections of a cylinder wall, from the top of a movable within the associated cylinder 12 guided piston and a cylinder head of the internal combustion engine 10 limited. The combustion chambers 12 Fresh gas, in particular ambient air, can be supplied via a fresh gas train, the introduction of the fresh gas into the combustion chambers by means of inlet valves 14 is controlled. In the fresh gas train is a compressor 16 integrated, which ensures the operation of the internal combustion engine for a variable compression of the fresh gas. A charge air cooler 18 in the charge air route 56 ie in between the compressor 16 and the intake valves 14 arranged portion of the fresh gas line, is integrated, serves to cool the heated as a result of the compression of fresh gas, thereby reducing the filling of the combustion chambers 12 to avoid.

During operation of the internal combustion engine is in the combustion chambers 12 By means not shown fuel injectors directly introduced fuel with the in the combustion chambers 12 introduced fresh gas burned, resulting from the internal combustion engine 10 a drive power is generated. The combustion of the fuel-fresh gas mixture leads to the generation of exhaust gas, which is discharged via an exhaust line of the internal combustion engine. The exhaust gas flowed through an exhaust gas turbine integrated into the exhaust system 20 whereby a turbine runner (not shown) is rotationally driven. This rotation of the turbine runner is via a shaft 22 on a compressor impeller (not shown) of the compressor 16 transferred to produce the compaction performance. The discharge of the exhaust gas from the combustion chambers 12 is by means of exhaust valves 24 . 26 controlled.

The intake valves 14 and the exhaust valves 24 . 26 of the internal combustion engine 10 are actuated by means of a valve drive, not shown, which may comprise two camshafts, in particular in a known manner, of a driven or crankshaft of the internal combustion engine 10 be driven with a translation of ½ rotating. The camshafts form for each gas exchange valve (intake valve 14 or exhaust valve 24 . 26 ) At least one cam track with at least one cam lobe, wherein the cam tracks directly or indirectly with the gas exchange valves, which are each acted upon spring loaded in a closed position, contact. In the case of a contact in the region of the cam elevation, the respective gas exchange valve is first opened in accordance with a valve lift curve defined by the shape of the cam elevation and subsequently closed again.

Each of the combustion chambers 12 is a first exhaust valve 24 and a second exhaust valve 26 assigned. The first exhaust valves 24 are about a common first exhaust gas flow 28 with the exhaust gas turbine 20 (inlet side) in exhaust gas conducting connection, while the second exhaust valves 26 via a common second exhaust gas flow 30 also with the exhaust gas turbine 20 (inlet side) are in exhaust gas conductive connection. Both exhaust fumes 28 . 30 are in a cylinder head housing 32 of the internal combustion engine 10 integrated and each include four outlet channels 34 , each one of the exhaust valves 24 . 26 with a collection section 36 the corresponding exhaust gas flow 28 . 30 connect. An outlet section 38 every flood of exhaust 28 . 30 connects the associated collection section 38 with a (separate or common) outlet opening, which in turn is directly connected in fluid communication with an inlet formed by a housing of the exhaust gas turbine. A housing of the exhaust gas turbine 20 is therefore directly to the cylinder head housing 32 flanged.

In the cylinder head housing 32 are cooling channels 40 integrated, which are part of a fundamentally known cooling system of the internal combustion engine and which can be flowed through for the purpose of cooling by means of a cooling liquid. The arrangement of the cooling channels 40 within the cylinder head housing is such that targeted also active cooling for exhaust gas, the second exhaust gas flow 30 flows through, is reached. This can be provided in particular, the cooling channels 40 at least in sections close to the second exhaust gas flow 30 or only by relatively small wall thicknesses separated from the second exhaust gas flow 30 to let go. On the other hand, for exhaust, that the first exhaust gas flow 28 flows through, if possible, no cooling effect can be realized. For this it is provided that for the first exhaust gas flow 28 at least in sections a thermal insulation 42 is provided, for example, by inserts of a thermally well insulating, for example ceramic material, are integrated into the Zylinderkopfgehäuse32 so that this is the first exhaust gas flow 28 from a cooling effect through the cooling channels 40 Shield as well as possible

The valve drive is designed such that it is at least the second exhaust valves with respect to an actuation 26 and preferably also the first exhaust valves 24 between at least two alternatively usable valve cam per gas exchange valve is switchable, wherein one of these at least two valve cams is designed as a zero cam and this has a cylindrical cam tracks without cam lobe. On the other hand, another of these at least two valve cams is designed as an actuation cam whose cam lobe leads to an opening of the gas exchange valve assigned thereto (with a maximum valve lift). One or more additional valve cams may include cam lobes that result in differential actuation of the gas exchange valve, particularly with respect to the magnitude of the maximum valve lift, the shape of the valve lift curve, and / or the control time, ie, the occurrence of the opening event relative to the rotational orientation of the crankshaft lead to an actuation by means of the actuating cam. A preferred embodiment of such a valve train is in the DE 196 11 641 C1 or the DE 10 2015 105 735 C1 (there in divergent use for actuating a high pressure fuel pump) disclosed.

An operation of the internal combustion engine according to the 1 can use one of the in the 3 and 4 carried out simplified operating maps. The show 3 and 4 each the so-called full load line 44 that limits the operating map upwards (ie with respect to the achievable torque M). Points within such an operating map define an operating condition for the internal combustion engine and specifically the internal combustion engine 10 , Such an operating condition by the amount of the combustion engine 10 generated dependent on the load with which it operates, dependent torque M (vertical axis) and the rotational speed n (horizontal axis), with which the internal combustion engine 10 is driven, is defined.

The operating map according to 3 is by means of a dividing line 46 into a first operating map area 48 and a second operating map area 50 divided. The first operating map area 48 is, in each case in comparison to the second operating map area 50 , characterized by relatively low combinations of speed n and load (corresponding to the torque M), although in the first operating map area 48 can operate at full load, but only at lower speeds than in the second operating map area 50 , Similarly, when operating in the first operating map area 48 Even relatively high speeds n be provided, but only in combination with relatively low (ie compared to an operation with correspondingly high speeds n in the second operating map area 50 lower) loads (M).

Due to the relatively low combinations of speed n and load (M) during operation of the internal combustion engine 10 in the first operating map area 48 shows this from the combustion chambers 12 discharged exhaust gas to a relatively low temperature. Also, the size of the entire exhaust gas mass flow can then be relatively small. The in the exhaust gas turbine 20 enthalpy and / or kinetic energy of the exhaust gas stream which can be converted into mechanical power is therefore correspondingly low. To avoid this enthalpy by cooling the exhaust gas while flowing through the overall cooled cylinder head housing 32 is further lowered, it is provided that during operation of the internal combustion engine 10 in the first operating map area 48 excluding the first exhaust valves 24 be actuated so that the exhaust gas produced completely on the thermally insulated first exhaust gas flow 28 to the exhaust gas turbine 20 to be led. Will the internal combustion engine 10 in contrast, according to one within the second operating map area 50 operated operating point, are additionally or exclusively the second exhaust valves 26 operated by the valve train, so that the exhaust then exclusively or additionally via the second, cooled exhaust gas flow 30 from the combustion chambers 12 Off and the exhaust gas turbine 20 is supplied. By cooling the (proportion of) through the second exhaust gas flow 30 guided exhaust gas, the temperature of the exhaust gas turbine 20 flowing exhaust gases are kept relatively low, creating a thermal overload of the exhaust gas turbine 20 can be avoided.

The 4 shows the possibility of replacing one by a single dividing line 46 defined transition between the operating map areas 48 . 50 a transition area 52 to be defined by two dividing lines 46 is limited, at each of which a switching between the modes ((1.) operation of the internal combustion engine 10 with a guiding of the exhaust gas exclusively via the first exhaust gas flow 28 or (2.) additionally / exclusively via the second exhaust gas flow 30 ), depending on whether the operation of the internal combustion engine 10 prior to switching to operating points that occurred in the first operating map area 48 or the second operating map area 50 lay. Previously, an operation with a guidance of the exhaust gas took place exclusively via the first exhaust gas flow 28 , so switching to the other mode takes place only when in the operating map according to the 4 higher and further right dividing line 46 and thus at (compared to the other dividing line 46 ) relatively high combinations of speed n and load (M). On the other hand, an operation with a guidance of the exhaust gas took place exclusively or additionally via the second exhaust gas flow 30 , so switching to the other mode takes place only at the lower in the operating map and further to the left dividing line 46 and thus at relatively low combinations of speed n and load (M). By means of the transition region, a frequent switching of the modes of operation which could occur when defining only a dividing line according to the 3 a longer-lasting dynamic operation of the internal combustion engine 10 near this dividing line 46 is provided.

According to the invention, it is provided that the minimum and / or the mean flow cross section of the first exhaust gas flow 28 smaller than the corresponding flow cross section of the second exhaust gas flow 30 is designed. This is intended in particular for the operation of the internal combustion engine 10 positive benefits of a so-called shock charging in an operation of the internal combustion engine 10 according to one within the first operating map area 48 operating point as optimally as possible. Due to the relatively small design of the first exhaust gas flow 28 can be a relatively strong pulsation of pressure p _A be realized in the first exhaust gas flow, as exemplified in the 5 is shown. There is over the duration of two turns (rotation angle φ ) of the crankshaft next to the course of the pressure p _A in the first exhaust gas flow also the pressure p _L in the charge air path as well as the pressure p _Z1 in a first combustion chamber 12 shown. Furthermore, it is the opening time t _EZ1 . t _AZ1 for this or that combustion chamber 12 associated intake valves 14 ( t _EZ1 : extends from an opening time E _O until a closing time ( E _C )) and for this combustion chamber 12 associated first outlet valve 24 ( t _AZ1 : extends from an opening time _AO until a closing time A _C ). A pronounced pressure peak for the pressure p _A in the first exhaust gas flow, one of the first exhaust valves results shortly after an incipient opening 24 , this pressure p _A falls relatively quickly and sharply after reaching a maximum, so that until reaching a further pressure peak, which is characterized by the subsequent opening of a combustion chamber associated with another first exhaust valve 24 results, a pressure valley is formed, in which the pressure p _A in the first flood of the exhaust 28 well below the boost pressure p _L is located. Simultaneous with the passage of such a pressure valley is a valve overlap φ _U between the opening time of the inlet valve or valves 14 and the opening time of the first exhaust valve 24 a combustion chamber 12 intended. Inside this through the valve overlap φ _U Defined period therefore there is a pressure gradient of the charge air route 56 to the first exhaust gas flow 28 , which in conjunction with the simultaneous opening of the inlet valve or valves 14 and the first exhaust valve 24 a combustion chamber 12 to rinse this combustion chamber 12 through directly from the charge air route 56 into the first exhaust gas flow 28 overflowing fresh gas leads. The size of this as a positive flushing gradient 54 designated effect is in the 5 for the first combustion chamber 12 on the basis of the marked area, on the one hand by the courses for the pressure p _A in the first exhaust gas flow and the pressure p _L in the charge air route 56 and on the other hand by the period of valve overlap φ _U the one or the first combustion chamber 12 associated intake valves 14 and the associated first exhaust valve 24 is limited.

In an internal combustion engine according to the invention is a relatively small, a shock charging positively influencing interpretation of the first exhaust gas flow 28 easily possible, because in an operation of the internal combustion engine 10 at the nominal point, which is at the upper edge of the second operating map area 50 is located and in which the largest possible exhaust gas mass flow in the combustion chambers 12 is generated, this exhaust gas mass flow not (exclusively) on the first exhaust gas flow 28 but (also) about the relatively large second exhaust gas flow 30 is dissipated.

The in the 2 illustrated internal combustion engine differs from that according to the 1 in that instead of a single exhaust gas turbine 20 , which is part of a single exhaust gas turbocharger and whose inlet both with the first exhaust gas flow 28 as well as with the second exhaust gas flow 30 is in exhaust gas conducting connection, two exhaust gas turbines 20a . 20b are provided, which are each part of a separate exhaust gas turbocharger. It is provided that a relatively small dimensioned and with a Rigid geometry (with or without wastegate) or a variable geometry (VTG) trained first exhaust gas turbine 20a exclusively with the first exhaust gas flow 28 in exhaust gas conducting connection, while a relatively large-sized, optionally cooled and formed, for example, with a rigid geometry with wastegate or with a variable geometry (VTG) second exhaust gas turbine 20b exclusively with the second exhaust gas flow 30 in exhaust gas conductive connection.

As a result of the two exhaust gas turbochargers 20a . 20b results in sections, a two-flow design of the charge air passage 56 , these two floods the charge air route 56 in the intercooler 18 be merged again.

LIST OF REFERENCE NUMBERS

10

internal combustion engine

12

Cylinder / combustion chamber

14

intake valve

16

compressor

18

Intercooler

20

exhaust turbine

20a

first exhaust gas turbine

20b

second exhaust gas turbine

22

wave

24

first exhaust valve

26

second exhaust valve

28

first exhaust gas flow

30

second exhaust gas flow

32

Cylinder head housing

34

exhaust port

36

Collection section of an exhaust gas flow

38

Outlet section of an exhaust gas flow

40

cooling channel

42

thermal insulation

44

Full load line

46

parting line

48

first operating map area

50

second operating map area

52

Transition area

54

positive flushing gradient

56

Charge-air duct

p _A

Pressure in the first exhaust gas flow

φ

Angle of rotation of the crankshaft

p _L

Pressure in the charge air path

p _Z1

Pressure in a first combustion chamber

t _EZ1

Opening duration for the intake valve associated with the first combustion chamber

t _AZ1

Opening duration for the first exhaust valve associated with the first combustion chamber

E _O

Opening time for the inlet valve associated with the first combustion chamber

E _C

Closing time for the inlet valve associated with the first combustion chamber

_AO

Opening time for the first exhaust chamber associated with the first exhaust valve

A _C

Closing time for the first exhaust chamber associated with the first exhaust valve

φ _U

valve overlap

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 102012001199 A1 [0002, 0003, 0004, 0006]
• DE 102015203157 A1 [0004]
• DE 102014201433 A1 [0005]
• DE 19611641 C1 [0018, 0039]
• DE 102015105735 C1 [0039]

Claims (15)

Internal combustion engine having an internal combustion engine (10), an exhaust system and one or more exhaust gas turbines integrated in the exhaust line, wherein the internal combustion engine (10) one or more combustion chambers (12), each associated with at least two exhaust valves (24, 26) , and wherein the exhaust valves (24, 26) are actuated by means of a valve drive, the first exhaust valves (24) assigned to the combustion chambers (12) via a common first exhaust gas flow (28) and second exhaust valves (26) associated with the combustion chambers (12) common second exhaust gas flow (30) of the exhaust line with the exhaust or the exhaust gas turbine (20) are in exhaust gas conducting connection, wherein for the second exhaust gas flow (30) a greater cooling effect is realized than for the first exhaust gas flow (28), characterized in that the minimum and / or the mean flow cross section of the first exhaust gas flow (28) is smaller than the corresponding flow cross section of the second exhaust gas flow (30) is laid. Internal combustion engine according to Claim 1 , characterized in that the valve train is designed such that it causes a valve overlap (φ _U ) in at least one operating state of the internal combustion engine. Internal combustion engine according to Claim 1 or 2 , characterized in that the second exhaust gas flow (30) is cooled and / or for the first exhaust gas flow (28), a thermal insulation (42) is provided. Internal combustion engine according to Claim 3 , characterized in that the first exhaust gas flow (28) and / or the second exhaust gas flow (30) in a cylinder head housing (32) of the internal combustion engine (10) is integrated, wherein the second exhaust gas flow (30) by means of these associated cooling channels (40) Are part of a cooling system of the internal combustion engine, is coolable and / or that the first exhaust gas flow (28) by means of in the cylinder head housing (32) integrated insulation sections is isolated. Internal combustion engine according to Claim 4 , characterized in that the insulating portion is formed as a preferably ceramic insert or as an integral porous portion. Internal combustion engine according to one of the preceding claims, characterized in that the valve drive with respect to an actuation of the first exhaust valves (24) and / or the second exhaust valves (26) by at least two alternatively usable valve cam is switchable. Internal combustion engine according to one of the preceding claims, characterized in that the length of the second exhaust gas flow (30) is greater than the length of the first exhaust gas flow (28). Internal combustion engine according to one of the preceding claims, characterized in that the valve train is designed such that it - the first exhaust valves (24) each operated with an opening duration which is smaller than the firing interval of the combustion chambers (12) or at most equal to, and / or - the second exhaust valves (26) each actuated with an opening duration which is greater than the firing interval of the combustion chambers (12) or at least equal thereto. Internal combustion engine according to one of the preceding claims, characterized in that the first exhaust gas flow (28) and the second exhaust gas flow (30) are in communication with the same exhaust gas turbine (20). Internal combustion engine according to one of Claims 1 to 8th , characterized in that the first exhaust gas flow (28) and the second exhaust gas flow (30) communicate with separate exhaust gas turbines (20a, 20b). Internal combustion engine according to Claim 10 , characterized in that a first exhaust gas turbine (20a) which is in communication with the first exhaust gas flow (28) is designed to be smaller than a second exhaust gas turbine (20b) which is in communication with the second exhaust gas flow (30). Internal combustion engine according to Claim 10 or 11 , characterized in that one or the first exhaust gas flow (28) in connection first exhaust gas turbine (20a) is uncooled and / or provided for this thermal insulation. Internal combustion engine according to one of Claims 10 to 12 , characterized in that one or the second exhaust gas turbine (20b) communicating with the second exhaust gas flow (30) is cooled. Internal combustion engine according to one of the preceding claims, characterized by a control device for controlling the valve train based on an operating map of the internal combustion engine (10), wherein the control device (10) is designed such that it drives the valve train such that this - during operation of the internal combustion engine (10) in a first operating map area (48) characterized by relatively low combinations of speed and load, the first exhaust valves (24) actuated and the second exhaust valves are not operated or to a relatively small extent and - in an operation of the internal combustion engine ( 10) in a second operating map area (50), the is characterized by a relatively high combination of speed and load, the second exhaust valves (26) operated to the maximum extent. Internal combustion engine according to Claim 14 , characterized in that the operating map has a transition region (52), so that switching from a control of the valve train according to the first operating map area (48) to a control of the valve train corresponding to the second operating map area (50) at higher combination of speed and load as switching from driving the valve train according to the second operation map area (50) to driving the valve train corresponding to the first operation map area (48).

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