DE102009013040A1 - Internal combustion engine with register charging - Google Patents

Abstract

The invention relates to an internal combustion engine, in particular for a motor vehicle, in particular with an electrified drive train, in particular with a combination of an electric motor and an internal combustion engine (hybrid engine), with at least one first exhaust gas turbocharger (30), which at least one first turbine (28) and at least a first compressor (36), at least one second exhaust gas turbocharger (34) having at least one second turbine (32) and at least one second compressor (38), wherein the first and the second turbine (28, 32) in an exhaust line ( 22) of the internal combustion engine with respect to an exhaust gas mass flow are arranged parallel to each other, wherein the first and the second compressor (36, 38) in a fresh air line (18) of the internal combustion engine with respect to a fresh air mass flow are arranged parallel to each other, wherein in the exhaust line (22) at least one valve device ( 54; 64) is arranged and configured in such a way s this optionally depending on an operating condition of the internal combustion engine, the exhaust gas mass flow through the second turbine (32) reduces and / or interrupts and at the same time the exhaust gas mass flow through the first turbine (28) unrestricted, so that essentially only the first exhaust gas turbocharger (30) a Boost pressure generated. In this case, at least one additional further drive device (58) is arranged next to the second turbine (32) on the second exhaust gas turbocharger (34).

Description

The The invention relates to an internal combustion engine, in particular for a motor vehicle, with at least one first exhaust gas turbocharger, which at least a first turbine and at least a first compressor has, at least a second exhaust gas turbocharger, which at least a second turbine and at least one second compressor, wherein the first and the second turbine in an exhaust line of the Internal combustion engine with respect to an exhaust gas mass flow in parallel are arranged to each other, wherein the first and the second compressor in a fresh air train of the internal combustion engine with respect to a fresh air mass flow are arranged parallel to each other, wherein arranged in the exhaust line at least one valve device such and is designed so that these depend on a Operating state of the internal combustion engine through the exhaust gas mass flow the second turbine optionally reduces and / or interrupts and simultaneously the exhaust gas mass flow through the first turbine unrestricted allows, so a boost pressure essentially only from the first exhaust gas turbocharger is generated according to the The preamble of claim 1. The invention further relates a method of operating an internal combustion engine, wherein fresh air in at least two exhaust gas turbochargers by means of a respective compressor is compressed, wherein the respective compressor of a respective Exhaust gas turbine is driven, depending on an operating point of the internal combustion engine a first exhaust gas turbocharger a second exhaust gas turbocharger is switched on, wherein before the connection accelerates the second exhaust gas turbocharger to a predetermined speed is, according to the preamble of claim 14.

at a so-called register charging an internal combustion engine At least two exhaust gas turbochargers (ATL) are provided by at least one additional switching element on the exhaust gas and / or fresh air side operating point dependent be exposed to exhaust gas or air.

It There are many ways to boot a registry To realize internal combustion engine. These are all characterized the use of at least two ATL's (turbocharger) made by at least one additional switching element on the exhaust gas and / or fresh air side operating point dependent can be acted upon with exhaust gas or air.

specially for the register charging on a gasoline engine are such Register concepts suitable for small engine speeds Apply ATL alone and for the rated power range switch on a second ATL, without focusing on the compaction work of the to forego the first ATL, d. H. the first ATL continues to wear a huge part of the overall charging work. With such a concept, it is possible that in gasoline engines optimally cover very wide air mass flow requirements. Because at one Load requirement in the lower mass air flow of the engine total available exhaust energy only one ATL can be made available very quickly its operating speed can be accelerated and thus also very fast provide a high boost pressure, which is opposite to a conventional mono or twin turbo concept to a superior Responsiveness leads. In a conventional monoturbo concept the ATL must be able to handle the rated horsepower of the engine alone why it should be interpreted as large got to. This inevitably allows only one accordingly slow response at low exhaust gas mass flows, as they are at low engine speeds. In a classic Twin or Biturbokonzept must the available Exhaust gas energy even with small exhaust gas mass flows, which at low engine speed, divided into two ATL's.

A register concept for an internal combustion engine is for example from DE 10 2005 061 649 A1 and has two ATLs that are quite similar or identical in design (pressure ratios, mass / volume throughput, etc.) to a conventional twin-turbine design. Expediently, starting from the optimum ATL design for conventional twin-turbo operation, an ATL is chosen to be slightly smaller and the second ATL slightly larger. The admission of ATL's with exhaust gas takes place in the register concept such that with small exhaust gas mass flows (small engine speeds) via a switchable pipe in the exhaust manifold only the smaller of the two ATL's with the entire available exhaust gas mass flow is applied. If this ATL arrives at its maximum throughput capacity, which is the case for example at medium engine speeds, the connection of the second, somewhat larger ATL takes place and the register system is operated up to the rated power analogous to a conventional twin turbosystem. Depending on the design of the system, the two ATLs share the required mass flow at the nominal point with 50% / 50% or about 40% to 60% or about 45% to 55% in favor of the larger ATL.

In the register system described above, the one-ATL operation, the air mass flow requirements of the engine in the middle and high speed range can not operate, which is why a connection of the second ATL is necessary. A switch to a larger ATL, in which the first small ATL (the so-called high-pressure stage) is switched off and the larger ATL (the low pressure stage) completely takes over the Aufladearbeit is comparatively easy to implement and such concepts are already in series. The connection of a second ATL is however more difficult to master. Switching to the second ATL brings, as already described above, the disadvantage that this second ATL must be very large, so that he can supply the air mass requirement in the rated power point of the engine alone. This leads to corresponding package disadvantages. In addition, the availability of ATL is limited for Otto engine applications, in particular with nominal powers above 200 kW and exhaust gas temperatures> 950 ° C. Against this background, the inclusion of a second ATL for a Otto register concept is more effective. Another disadvantage of such a two-stage regulated charging a gasoline engine is that in the lower speed range both ATL operated in series. Accordingly, the pressure ratios on both turbines multiply and the engine has to work against a very high exhaust backpressure, which leads to a poorer residual gas purging behavior. Since Otto-cycle combustion processes react very critically with respect to their knock limit to remaining residual gas fractions in the combustion chamber, such a two-stage charging process for gasoline engines may be disadvantageous.

As described above, is for use on the gasoline engine Register concept to prefer, in the first only one ATL, which can relax against environment, exposed to exhaust gas and in the speed curve of the engine, a second ATL in parallel is switched, d. H. both ATL relax against environment or against normal pressure loss of the exhaust system. The connection process preferably takes place via a fully variable exhaust valve control, but can also have a thermally highly resilient exhaust flap respectively. The connection process of the second ATL is therefore critical, since the second ATL before the parallel closure to the speed of the first, must be brought in operation first ATL. A connection process can only take place without torque drop when the intake manifold pressure remains constant. With an ATL, the boost pressure is directly dependent from the speed of the ATL. It follows for the same size ATL the condition that the first and the second ATL are identical Must have speed to a torque dip to avoid during the connection process. In case of different sizes ATL has to set the analogue speed for an equal pressure ratio at both ATL before / after the turbine (p2 / p1) can be achieved. For the run-up of the second ATL exhaust gas energy is needed, which is no longer the first ATL is available, d. H. the theoretical boost pressure potential, which consists of a register charge can not be exploited, if without torque dip from a 1-ATL operation to a 2-ATL operation is switched.

From the DE 43 10 148 C2 is an internal combustion engine with register charging known, with a first exhaust gas turbocharger constantly provides charge air and a second exhaust gas turbocharger is optionally switched on. In order to enable a pulsation-free connection of the second exhaust gas turbocharger in the case in which the second exhaust gas turbocharger does not contribute to the charge air supply of the internal combustion engine, a pressure output of a compressor of the second exhaust gas turbocharger is connected to the inlet of a turbine of this second exhaust gas turbocharger. In this way, the second exhaust gas turbocharger is constantly maintained at a speed required for the charge air supply of the internal combustion engine, so that when switching the second exhaust gas turbocharger by disconnecting the pressure output of the compressor of the second exhaust gas turbocharger from the inlet of the turbine of this second exhaust gas turbocharger and connecting the pressure output of the compressor the second exhaust gas turbocharger with the leading to the engine combustion air supply line without pressure jump immediately the required charge air pressure is present.

Of the Invention is based on the object, an internal combustion engine as well a method of o. Type with regard to the connection of a second Turbocharger a register charge to improve.

These The object is achieved by an internal combustion engine the o. g. Art having the features characterized in claim 1 and by a method of o. g. Art with the characterized in claim 14 Characteristics solved. Advantageous embodiments of the invention are described in the further claims.

To it is in an internal combustion engine o. g. Art provided according to the invention, that at the second exhaust gas turbocharger next to the turbine at least arranged an additional additional drive device is.

This has the advantage that before switching on the second exhaust gas turbocharger for raising the speed of this second exhaust gas turbocharger the additional Drive device is provided so that little or no Energy from the exhaust gas mass flow for raising the speed of the second Exhaust gas turbocharger must be removed. This will be on easy Way a connection process without torque drop of the internal combustion engine achieved.

In a preferred embodiment is the additional Drive device an electric motor.

The For example, at least one valve device is upstream and / or upstream arranged downstream of the second turbine of the second exhaust gas turbocharger and includes, for example, an exhaust flap.

In a preferred embodiment has at least one Working cylinder of the internal combustion engine at least two independently mutually controllable exhaust valves, wherein at least one respective first outlet valve of at least one working cylinder flow-conducting connected to the first turbine and with respect to the exhaust gas mass flow is separated from the second turbine, wherein at least one respective second outlet valve of at least one working cylinder flow-conducting connected to the second turbine and with respect to the exhaust gas mass flow is separated from the first turbine, wherein a cyclic operation for selectively opening the second exhaust valves in such a way can be switched off, that the second exhaust valves longer as usual in a working cycle of the internal combustion engine remain closed and the valve means for reducing and / or Forming the exhaust gas mass flow through the second turbine train.

Conveniently, is at least one of the exhaust gas turbochargers as single scroll turbocharger with an inlet spiral or as Twin Scroll turbocharger with two Inlet spirals formed.

In In a preferred embodiment, an input of the first turbine of the first exhaust gas turbocharger and an input of the second Turbine of the second exhaust gas turbocharger via a crosstalk line connected flow-conducting.

Conveniently, the internal combustion engine has at least two working cylinders, wherein an exhaust outlet of at least a first working cylinder exclusively with the first turbine flow-conducting is connected so that the exhaust gas mass flow of at least one first working cylinder exclusively the first turbine acted upon, and an exhaust outlet of at least a second working cylinder exclusively with the second turbine flow-conducting is connected so that the exhaust gas mass flow of at least one second working cylinder exclusively the second turbine applied.

In a preferred embodiment is at the first turbine and / or at the second turbine, a bypass line with valve device, in particular a wastegate, for at least partially bypassing the exhaust gas mass flow at the respective Turbine arranged.

Conveniently, is in the fresh air line downstream of the first compressor and / or arranged at least one pressure control valve of the second compressor.

In a preferred embodiment is in the fresh air line downstream of the first compressor and / or the second compressor arranged at least one throttle.

Conveniently, is a recirculation line provided with a recirculation valve, which optionally with the fresh air line downstream of the second compressor with the flow of fresh air upstream of the second compressor combines.

Further it is in a method of o. g. Art provided according to the invention, that the acceleration of the second exhaust gas turbocharger to the predetermined Speed at least partially by means of a respect to the Exhaust gas turbine of the second exhaust gas turbocharger additional Drive is performed.

This has the advantage that for the acceleration of the second Exhaust gas turbocharger to the desired speed no energy must be removed from an exhaust gas mass flow.

In In a preferred embodiment, the predetermined Speed determined so that a pressure ratio before and after the turbine of the second exhaust gas turbocharger a pressure ratio before and after the turbine of the first exhaust gas turbocharger corresponds.

Conveniently, is used as an additional drive an electric motor.

In In a preferred embodiment, the connection of the second exhaust gas turbocharger by opening a valve device performed in an exhaust line of the internal combustion engine.

Conveniently, is in addition to the connection of the second exhaust gas turbocharger a valve device in a fresh air line of the internal combustion engine open.

In a preferred embodiment, an energy for Drive of the additional drive from an energy store, in particular an accumulator for electrical energy, taken, the energy storage, for example by means of recuperation is fed by braking energy.

The The invention will be explained in more detail below with reference to the drawing explained. This shows in

1 a first preferred embodiment of an internal combustion engine according to the invention in a schematic representation,

2 a second preferred embodiment of an internal combustion engine according to the invention in a schematic representation,

3 A third preferred embodiment of an internal combustion engine according to the invention in a schematic representation,

4 a fourth preferred embodiment of an internal combustion engine according to the invention in a schematic representation and

5 a fifth preferred embodiment of an internal combustion engine according to the invention in a schematic representation.

In the 1 shown, the first preferred embodiment of an internal combustion engine according to the invention comprises four working cylinders 10 . 12 . 14 and 16 that have a fresh air line 18 with a suction pipe 20 be fed with a fresh air mass flow and the exhaust gas mass flow to an exhaust line 22 with catalysts 24 and lambda probes 26 submit. In the exhaust system 22 is a first exhaust gas turbine 28 a first exhaust gas turbocharger 30 and a second exhaust gas turbine 32 a second exhaust gas turbocharger 34 arranged, the two exhaust gas turbines 28 . 32 with respect to the exhaust gas mass flow parallel to each other in the exhaust line 22 are arranged. In the fresh air line 18 is a first compressor 36 of the first exhaust gas turbocharger 30 and a second compressor 38 the second exhaust gas turbocharger 34 arranged, with the two compressors 36 . 38 with respect to the fresh air mass flow parallel to each other in the fresh air line 18 are arranged. The first turbine 28 drives the first compressor 36 on and the second turbine 32 drives the second compressor 38 at. A crosstalk line 40 connects the respective inputs of the two turbines 28 . 32 flow-conducting together. The first turbine 28 has a first bypass line 42 with valve device (wastegate 1 ), which optionally at least a portion of the exhaust gas mass flow at the first turbine 28 passes by. The second turbine 32 has a second bypass line 44 with valve device (wastegate 2 ), which optionally at least a portion of the exhaust gas mass flow at the second turbine 32 passes by. The bypass lines 42 . 44 are, for example, as internal wastegates of the respective turbine 28 . 32 educated. In the fresh air line 18 is downstream of the first compressor 36 a first intercooler 50 and downstream of the second compressor 38 a second intercooler 52 arranged. The second compressor 38 has a recirculation line 46 with a recirculation valve 48 to at least a portion of that of the second compressor 38 compressed air from the outlet of the second compressor 38 downstream of the second intercooler 52 to the input of the second compressor 38 to lead back. In one only the second turbine 32 assigned section of the exhaust tract 22 is an exhaust flap 54 arranged. In the fresh air line 18 is downstream of the two intercoolers 50 . 52 a throttle 56 arranged. Downstream of the second intercooler 52 is in the fresh air line 18 a pressure control valve 60 arranged.

According to the invention, the second exhaust gas turbocharger comprises 34 next to the second turbine 38 another drive device 58 for the second compressor 32 in the form of an electric motor.

At the in 1 shown, the first preferred embodiment of an internal combustion engine according to the invention is the exhaust valve 54 remote engine and with respect to the exhaust gas mass flow downstream of the second turbine 32 arranged. The two turbochargers 30 . 34 are with SS exhaust gas turbines (single-scroll exhaust gas turbines) 28 . 32 with an inlet spiral in the exhaust gas turbine 28 . 32 educated. In the crosstalk line 40 is a control valve (not shown) arranged.

2 shows a second preferred embodiment of an internal combustion engine according to the invention, wherein functionally identical parts with the same reference numerals as in 1 are designated so that their explanation to the above description of 1 is referenced. Unlike the first embodiment according to 1 is the first turbocharger 30 with a TS exhaust gas turbine (twin-scroll exhaust gas turbine) 28 with two inlet spirals in the first exhaust gas turbine 28 formed, whereas the second exhaust gas turbocharger 34 with an SS exhaust turbine 32 is trained.

3 shows a third preferred embodiment of an internal combustion engine according to the invention, wherein functionally identical parts with the same reference numerals as in 1 are designated so that their explanation to the above description of 1 is referenced. Unlike the first embodiment according to 1 is the exhaust flap 54 close to the engine and with respect to the exhaust gas mass flow upstream of the second exhaust gas turbine 32 arranged. Both turbochargers 30 . 34 are with SS exhaust gas turbines 28 . 32 educated.

In all previously explained preferred embodiment according to the 1 to 3 is the exhaust system 22 designed such that the exhaust gas mass flow from first working cylinders 10 . 16 excluding the first turbine 28 is supplied and the exhaust gas mass flow from second working cylinders 12 . 14 excluding the second turbine 32 is supplied.

4 shows a fourth preferred embodiment of a Brennkraftma invention machine, where functionally identical parts with the same reference numerals as in 1 are designated so that their explanation to the above description of 1 is referenced. Unlike the first embodiment according to 1 is the exhaust system 22 double-suction design and the exhaust flap 54 is close to the engine, with respect to the exhaust gas mass flow upstream of the second exhaust gas turbine 32 as well as in the crosstalk line 40 arranged. The first exhaust gas turbocharger 30 and / or the second exhaust gas turbocharger 34 have a TS exhaust gas turbine 28 . 32 on.

5 shows a fifth preferred embodiment of an internal combustion engine according to the invention, wherein functionally identical parts with the same reference numerals as in 1 are designated so that their explanation to the above description of 1 is referenced. Unlike the first embodiment according to 1 is not a crosstalk line 40 intended. Every working cylinder 10 . 12 . 14 . 16 each has a first exhaust valve 62 and a second exhaust valve 64 on. The first exhaust valves 62 are with respect to the exhaust gas mass flow only in flow with the first turbine 28 connected and from the second turbine 32 separated. The second exhaust valves 64 With respect to the exhaust gas mass flow are only in flow with the second turbine 32 connected and from the first turbine 28 separated. In such operating conditions of the internal combustion engine, in which the first exhaust gas turbocharger 30 alone can provide the necessary boost pressure for a desired engine torque, for example, in a low-end torque range, remain the second exhaust valves 64 closed and only the first exhaust valves 62 are cyclically opened and closed according to the working cycle or a crankshaft angle. This is achieved for example by an exhaust camshaft with Hubumschalter. This will only be the first turbine 28 subjected to the exhaust gas mass flow. ATL 30 may be implemented as SS-ATL or TS-ATL (shown here). The first compressor 36 has a recirculation line with a recirculation valve 66 to at least a portion of that of the first compressor 36 compressed air from the outlet of the first compressor 36 downstream of the first intercooler 50 to the entrance of the first compressor 36 to lead back.

In the internal combustion engine according to the invention with register system, the use of an EU ATL (Electrically Assisted ATL) as the second, zuzuschaltender exhaust gas turbocharger 34 proposed. The EU ATL 34 can in addition to the exhaust gas energy supplied to it (bypass mass flow of the first ATL 30 , if this has reached the target boost pressure) additionally accelerated by electrical energy. Thus, on the one hand, the performance of the register network can be increased and, on the other hand, the power peaks during the acceleration of the EU ATL fall 34 in the register network is significantly lower than when using an EU ATL as a mono-ATL concept. The register network must have the second ATL 34 only have reached its target speed (predetermined speed) before it can be switched to 2-ATL operation (connection of the second ATL 34 ), since this is the first ATL accelerated exclusively via exhaust gas energy 30 is decisive for the dynamic feeling.

Ideally, the register system described above is used in an electrified powertrain, with the acceleration energy for the EU ATL 34 is preferably removed from a memory which is fed via recuperated braking energy.

With the second ATL 34 in the form of the EU-ATL an internal combustion engine with a register system is available, in which the second ATL 34 can be accelerated with a mixture of exhaust energy and electrical energy. This is the first ATL 30 In 1-ATL operation more exhaust energy available, whereby higher mid-pressures can be achieved. At the same time the switching process in the 2-ATL mode (connection of the second ATL 34 ) are performed in a simple manner torque neutral. The operating mode of the connection phase of the second ATL which is critical in the case of a register charge 34 is through the use of EU ATL 34 defused. As a result, a higher performance of the register network can be achieved.

QUOTES INCLUDE IN THE DESCRIPTION

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Cited patent literature

• DE 102005061649 A1 [0005]
• - DE 4310148 C2 [0008]

Claims (20)

Internal combustion engine, in particular for a motor vehicle, in particular with an electrified drive train, in particular with a combination of an electric motor and an internal combustion engine (hybrid engine), with at least one first exhaust gas turbocharger ( 30 ), which at least one first turbine ( 28 ) and at least one first compressor ( 36 ), at least one second exhaust gas turbocharger ( 34 ), which at least one second turbine ( 32 ) and at least one second compressor ( 38 ), wherein the first and the second turbine ( 28 . 32 ) in an exhaust gas line ( 22 ) of the internal combustion engine with respect to an exhaust gas mass flow are arranged parallel to each other, wherein the first and the second compressor ( 36 . 38 ) in a fresh air line ( 18 ) of the internal combustion engine with respect to a fresh air mass flow are arranged parallel to each other, wherein in the exhaust line ( 22 ) at least one valve device ( 54 ; 64 ) is arranged and configured in such a way that, as a function of an operating state of the internal combustion engine, the exhaust gas mass flow through the second turbine ( 32 ) optionally reduces and / or interrupts and at the same time the exhaust gas mass flow through the first turbine ( 28 ), so that essentially only the first exhaust gas turbocharger ( 30 ) generates a boost pressure, characterized in that on the second exhaust gas turbocharger ( 34 ) next to the second turbine ( 32 ) at least one additional further drive device ( 58 ) is arranged. Internal combustion engine according to claim 1, characterized in that the additional drive device ( 58 ) is an electric motor. Internal combustion engine according to at least one of the preceding claims, characterized in that the at least one valve device ( 54 ) comprises an exhaust flap. Internal combustion engine according to at least one of the preceding claims, characterized in that at least one valve device ( 54 ) upstream and / or downstream of the second turbine ( 32 ) of the second exhaust gas turbocharger ( 34 ) is arranged. Internal combustion engine according to at least one of the preceding claims, characterized in that at least one working cylinder ( 10 . 12 . 14 . 16 ) of the internal combustion engine at least two independently controllable exhaust valves ( 62 . 64 ), wherein at least one respective first outlet valve ( 62 ) at least one working cylinder ( 10 . 12 . 14 . 16 ) flow-conducting with the first turbine ( 28 ) and with respect to the exhaust gas mass flow from the second turbine ( 32 ) is separated, wherein at least one respective second exhaust valve ( 64 ) at least one working cylinder ( 10 . 12 . 14 . 16 ) flow-conducting with the second turbine ( 32 ) and with respect to the exhaust gas mass flow from the first turbine ( 28 ), wherein a cyclic operation for opening the second exhaust valves ( 64 ) is optionally designed such that it can be switched off so that the second outlet valves ( 64 ) remain closed for a longer time than in a working cycle of the internal combustion engine and the valve device for reducing and / or interrupting the exhaust gas mass flow through the second turbine ( 32 ) train. Internal combustion engine according to at least one of the preceding claims, characterized in that at least one of the exhaust gas turbochargers ( 30 . 34 ) as a single scroll turbocharger with an inlet spiral in the turbine ( 28 . 32 ) is trained. Internal combustion engine according to at least one of the preceding claims, characterized in that at least one of the exhaust gas turbochargers ( 30 . 34 ) as Twin Scroll turbocharger with two inlet spirals in the turbine ( 28 . 32 ) is trained. Internal combustion engine according to at least one of the preceding claims, characterized in that an input of the first turbine ( 28 ) of the first exhaust gas turbocharger ( 30 ) and an input of the second turbine ( 32 ) of the second exhaust gas turbocharger ( 34 ) via a crosstalk line ( 40 ) are conductively connected to each other. Internal combustion engine according to at least one of the preceding claims, characterized in that this internal combustion engine has at least two working cylinders ( 10 . 12 . 14 . 16 ), wherein an exhaust gas outlet of at least one first working cylinder ( 10 . 16 ) exclusively with the first turbine ( 28 ) is conductively connected, so that the exhaust gas mass flow from at least one first working cylinder ( 10 . 16 ) only the first turbine ( 28 ), and an exhaust gas outlet of at least one second working cylinder ( 12 . 14 ) exclusively with the second turbine ( 32 ) is conductively connected, so that the exhaust gas mass flow from at least one second working cylinder ( 12 . 14 ) exclusively the second turbine ( 32 ). Internal combustion engine according to at least one of the preceding claims, characterized in that on the first turbine ( 28 ) and / or at the second turbine ( 32 ) a bridging line ( 42 . 44 ) with valve device, in particular a wastegate, for at least partially bypassing the exhaust gas mass flow at the respective turbine ( 28 . 32 ) is arranged. Internal combustion engine according to at least one of the preceding claims, characterized in that in the fresh air line ( 18 ) downstream of the first compressor ( 36 ) and / or the second compressor ( 38 ) at least one pressure regulating valve ( 60 ) is arranged. Internal combustion engine according to at least one of the preceding claims, characterized in that in the fresh air line ( 18 ) downstream of the first compressor ( 36 ) and / or the second compressor ( 38 ) at least one throttle valve ( 56 ) is arranged. Internal combustion engine according to at least one of the preceding claims, characterized in that a recirculating air line ( 46 ) with a recirculation valve ( 48 ) is provided, which optionally the fresh air line ( 18 ) downstream of the second compressor ( 38 ) with the fresh air line ( 18 ) upstream of the second compressor ( 38 ) connects in a flow-conducting manner. Method for operating an internal combustion engine, wherein fresh air in at least two exhaust gas turbochargers by means of a each compressor is compressed, wherein the respective compressor is driven by a respective exhaust gas turbine, depending on from an operating point of the internal combustion engine to a first exhaust gas turbocharger a second exhaust gas turbocharger is switched on, whereby before connecting accelerates the second exhaust gas turbocharger to a predetermined speed is characterized in that the acceleration of the second Exhaust gas turbocharger at the predetermined speed at least partially by means of a with respect to the exhaust gas turbine of the second exhaust gas turbocharger additional Drive is performed. Method according to claim 14, characterized in that that the predetermined speed is determined such that a pressure ratio before and after the turbine of the second exhaust gas turbocharger a pressure ratio before and after the turbine of the first exhaust gas turbocharger corresponds. Method according to claim 14 or 15, characterized that uses as an additional drive an electric motor becomes. Method according to at least one of the claims 14 to 16, characterized in that the connection of the second Exhaust gas turbocharger by opening a valve device performed in an exhaust line of the internal combustion engine becomes. Method according to at least one of the claims 14 to 17, characterized in that when connecting the second Exhaust gas turbocharger additionally a valve device in one Fresh air train of the internal combustion engine is opened. Method according to at least one of the claims 14 to 18, characterized in that an energy for driving the additional drive from an energy store, in particular an accumulator for electrical energy is taken. Method according to claim 19, characterized that the energy storage powered by recuperation of braking energy becomes.