DE102015219122A1 - Method for boost pressure adjustment of a supercharged internal combustion engine with electric machine and internal combustion engine for carrying out such a method - Google Patents

Abstract

The invention relates to a method for adjusting the boost pressure of a supercharged internal combustion engine (1) having an intake system (2) for supplying charge air, an exhaust gas removal system (4) for discharging the exhaust gas, and at least one exhaust gas turbocharger (6) having an exhaust gas discharge system (US Pat. 4) and a compressor (6b) arranged in the intake system (2), wherein the turbine (6a) and the compressor (6b) are arranged on the same rotatable shaft (6c), in which - one with the shaft (6c) of the at least one exhaust gas turbocharger (6) is provided at least drive-connected electric machine (7). It should be shown a method of the type mentioned, with which the efficiency and performance of the exhaust turbocharging and the internal combustion engine (1) can be improved. This is achieved by a method which is characterized in that the electric machine (7) connected to the shaft (6c) is operated as a generator (7a) and absorbs power from the turbine (6a), whereby the power required for driving the compressor ( 6b) power is reduced by the turbine (6a) and the boost pressure downstream of the compressor (6b) is lowered.

Description

• – einem Ansaugsystem zum Zuführen von Ladeluft,
• – einem Abgasabführsystem zum Abführen des Abgases, und
• – mindestens einem Abgasturbolader, der eine im Abgasabführsystem angeordnete Turbine und einen im Ansaugsystem angeordneten Verdichter umfasst, wobei die Turbine und der Verdichter auf derselben drehbaren Welle angeordnet sind, bei der
• – eine mit der Welle des mindestens einen Abgasturboladers zumindest antriebsverbindbare Elektromaschine vorgesehen ist.

The invention relates to a method for boost pressure adjustment of a supercharged internal combustion engine with

• An intake system for supplying charge air,
• An exhaust gas discharge system for discharging the exhaust gas, and
• At least one exhaust-gas turbocharger comprising a turbine arranged in the exhaust-gas discharge system and a compressor arranged in the intake system, the turbine and the compressor being arranged on the same rotatable shaft, in which
• - Is provided with the shaft of the at least one exhaust gas turbocharger at least drive-connected electric machine.

Furthermore, the invention relates to a supercharged internal combustion engine for carrying out such a method.

An internal combustion engine of the type mentioned with turbocharging and electric machine describes the US 2013/0209291 A1 , Wherein the electric machine as an electric auxiliary drive supports the compressor of the second exhaust gas turbocharger serving as a high-pressure stage, ie can drive.

An internal combustion engine of the type mentioned is used as a motor vehicle drive. In the context of the present invention, the term internal combustion engine includes diesel engines and gasoline engines, but also hybrid internal combustion engines, which use a hybrid combustion process, and hybrid drives, which in addition to the internal combustion engine comprise an electric motor which can be electrically connected to the internal combustion engine, which receives power from the internal combustion engine or as switchable auxiliary drive additionally delivers power.

In recent years, there has been a trend toward small, supercharged engines, with supercharging primarily a method of increasing performance by compressing the air needed for the engine combustion process. The economic importance of these engines for the automotive industry continues to increase.

Frequently, an exhaust gas turbocharger is used for charging, in which a compressor and a turbine are arranged on the same shaft. The hot exhaust stream is supplied to the turbine and relaxes with energy release in the turbine, causing the shaft to rotate. 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 a charging of the cylinder is achieved. Advantageously, a charge air cooler is provided downstream of the compressor in the intake system, with which the compressed charge air is cooled before entering the at least one cylinder. The radiator lowers the temperature and thus increases the density of the charge air, so that the cooler to a better filling of the cylinder, d. H. contributes to a larger air mass. There is a compaction by cooling.

The advantage of an exhaust gas turbocharger compared to a mechanical supercharger is that there is no mechanical connection to the power transmission between the supercharger and the internal combustion engine or is required. 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.

The charge is - as already mentioned - the increase in performance. 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. If the displacement is reduced, then the load spectrum can be shifted to higher loads, where the specific fuel consumption is lower. By charging in combination with suitable transmission designs and a so-called downspeeding can be realized, in which also a lower specific fuel consumption can be achieved.

Charging thus supports the constant effort in the development of internal combustion engines to minimize fuel consumption, d. H. to improve the efficiency of the internal combustion engine.

Another fundamental goal is to reduce pollutant emissions. In the solution of this task, the charging can also be effective. With targeted design of the charge namely benefits in efficiency and in the exhaust emissions can be achieved.

The interpretation of the turbocharger turbocharger is difficult, 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 effect is undesirable. This torque drop becomes understandable if it is taken into account that the boost pressure ratio depends on the turbine pressure ratio. If the engine speed is reduced, this leads to a smaller exhaust gas mass flow and thus to a smaller turbine pressure ratio. Consequently, the boost pressure ratio also decreases toward lower speeds. This is synonymous with a torque drop.

In practice, the relationships described above often result in a small exhaust gas turbocharger, i. H. an exhaust gas turbocharger with a small turbine cross section is used, whereby the turbine pressure ratio can be increased. However, this worsens the charge at higher speeds and shifts the torque drop only towards lower speeds. In addition, this approach, d. H. the reduction of the turbine cross-section limits, since the desired charging and performance increase should be possible without restriction and to the desired extent, even at high speeds.

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, the Abgasabblasung example, by means of boost pressure or by exhaust pressure, but also can be controlled electrically. For this purpose, the turbine is equipped with a blow-off line which branches off from the exhaust-gas removal system upstream of the turbine and in which a shut-off element is arranged. 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 guided past the turbine via the blow-off line as part of the so-called exhaust gas blow-off, d. H. blown off. This approach has the disadvantage that the high-energy blown exhaust gas remains unused and the charging behavior is regularly insufficient at higher speeds.

By opening the blow-off line more or less widely, the amount of exhaust gas passed past the turbine can be adjusted, and by means of the amount of exhaust gas carried past the turbine, in turn, the boost pressure downstream of the compressor can be influenced, ie. H. control, in particular limit.

A turbine with variable turbine geometry allows a further adaptation to the respective operating point of the internal combustion engine by adjusting the turbine geometry or the effective turbine cross-section, to some extent a speed-dependent or load-dependent control of the turbine geometry can be done.

In this case, guide vanes for influencing the flow direction are arranged in the inlet region of the turbine. Unlike the vanes of the rotating impeller, the vanes do not rotate with the shaft of the turbine.

If the turbine has a fixed invariable geometry, the vanes, if present, are not only stationary, but also completely immovable in the entry area, i. H. rigidly fixed. If, on the other hand, a turbine with variable geometry is used, the vanes are indeed arranged stationary, but not completely immobile, but rotatable about their axis, so that the flow of the blades can be influenced.

The internal combustion engine, which is the subject of the present invention, has at least one exhaust-gas turbocharger for charging purposes.

The torque characteristic of a supercharged internal combustion engine may be increased by a plurality of turbochargers arranged in parallel, i. H. be improved by a plurality of parallel turbines of smaller turbine cross-section, with turbines are switched successively with increasing exhaust gas quantity; similar to a register charge.

The torque characteristic can also be advantageously influenced by means of a plurality of exhaust-gas turbochargers connected in series. By switching in series of two exhaust gas turbochargers, one of which is an exhaust gas turbocharger as a high pressure stage and an exhaust gas turbocharger as a low pressure stage, the compressor map can be widened in an advantageous manner, both towards smaller compressor streams as well as towards larger compressor streams.

In particular, in the case of the exhaust gas turbocharger serving as a high-pressure stage, the pumping limit can be shifted toward smaller compressor flows, which means that high boost pressure ratios can be achieved even with small compressor flows and the torque characteristic in the lower rpm range is significantly improved. This is achieved by designing the high-pressure turbine for small exhaust gas mass flows and providing a blow-off line, with which increasing exhaust gas mass flow increasingly exhaust gas is passed to the high-pressure turbine. The blow-off line branches For this purpose, upstream of the high-pressure turbine from the Abgasabführsystem and flows upstream of the low-pressure turbine back into the Abgasabführsystem. In the blow-off line, a shut-off element is arranged in order to control the exhaust gas flow conducted past the high-pressure turbine.

Against the background of the above, it is an object of the present invention to provide a method according to the preamble of claim 1 for boost pressure adjustment of an exhaust gas turbocharged internal combustion engine with which the known from the prior art disadvantages are overcome and with the efficiency and performance the turbocharger and the internal combustion engine can be noticeably improved.

Another object of the present invention is to provide an internal combustion engine for carrying out such a method.

• – einem Ansaugsystem zum Zuführen von Ladeluft,
• – einem Abgasabführsystem zum Abführen des Abgases, und
• – mindestens einem Abgasturbolader, der eine im Abgasabführsystem angeordnete Turbine und einen im Ansaugsystem angeordneten Verdichter umfasst, wobei die Turbine und der Verdichter auf derselben drehbaren Welle angeordnet sind, bei der
• – eine mit der Welle des mindestens einen Abgasturboladers zumindest antriebsverbindbare Elektromaschine vorgesehen ist,

das dadurch gekennzeichnet ist, dass

• – die mit der Welle antriebsverbundene Elektromaschine als Generator betrieben wird und Leistung von der Turbine aufnimmt, wodurch die für den Antrieb des Verdichters von der Turbine zur Verfügung gestellte Leistung vermindert wird und der Ladedruck stromabwärts des Verdichters gesenkt wird.

The first sub-task is solved by a method for boost pressure adjustment of a supercharged internal combustion engine with

• An intake system for supplying charge air,
• An exhaust gas discharge system for discharging the exhaust gas, and
• At least one exhaust-gas turbocharger comprising a turbine arranged in the exhaust-gas discharge system and a compressor arranged in the intake system, the turbine and the compressor being arranged on the same rotatable shaft, in which
• An electric machine, which is at least drive-connected to the shaft of the at least one exhaust-gas turbocharger, is provided,

which is characterized in that

• - The shaft-connected electric machine is operated as a generator and receives power from the turbine, whereby the power provided for driving the compressor from the turbine power is reduced and the boost pressure downstream of the compressor is lowered.

According to the inventive method and in contrast to the prior art, the electric machine of the internal combustion engine according to the invention is initially not used as an electric auxiliary drive for the compressor of the exhaust gas turbocharger, but in case of need, d. H. at least temporarily, used as a generator and operated to recover or recover electrical energy, d. H. Convert exhaust gas energy into electrical energy.

The energy emitted by the exhaust gas flow to the turbine and finally to the shaft is consequently not used exclusively for driving the compressor arranged on the shaft, but is at least partially taken up by the electric machine operated as a generator.

Blowing off exhaust gas for controlling or limiting the boost pressure downstream of the compressor is thus eliminated or is no longer necessary, which is why the turbine of the at least one exhaust gas turbocharger according to the invention basically does not have to be equipped with a blow-off line, whereby the turbocharger is simplified, more compact and less expensive ,

The fact that the electric machine operated as a generator receives power from the turbine, the power provided by the turbine for driving the compressor is reduced. The boost pressure downstream of the compressor can be controlled in this way by the power absorbed by the electric machine, in particular reduce and limit. In this respect, the method according to the invention is a method for adjusting the boost pressure.

With the Abgasabblasung accounts not only the Abblaseleitung, but also the blowing off as such and thus the waste of high-energy exhaust gas due to blow-off. Because the surplus power provided by the turbine on the shaft is no longer disposed of unused by blow-off, d. H. must be reduced, but can be converted into electrical energy by means of a generator operated electric machine, the efficiency of the exhaust gas turbocharger and the internal combustion engine can be significantly improved.

Controlling the boost pressure downstream of the compressor by means of the power consumed by the electric machine has further advantages. Thus, by means of electric machine much faster influence on the boost pressure can be taken as this is possible by means of Abgasabblasung. If the charge pressure is to be lowered rapidly, this can be done faster by activating the electric machine than by opening a blow-off line. A control that engages on the exhaust side to achieve a change in boost pressure on the intake side, in principle, has a worse response than if directly by activating the electric machine, the compressor performance is reduced.

With the ability to reduce the power provided for the drive of the compressor almost instantaneously, the response and thus the Improve performance of the turbocharger and thus the internal combustion engine significantly.

The above-described relationships are important both in terms of limiting the boost pressure as well as in terms of the rapid lowering of the boost pressure during a load change in the context of transient, d. H. Transient operation of the internal combustion engine.

With the method according to the invention, the first object underlying the invention is solved, namely a method according to the claim 1 shown, with which the known from the prior art disadvantages are overcome and with which the efficiency and performance of the turbocharger and the engine noticeably improved become.

Further advantageous embodiments of the method according to the invention are discussed in connection with the subclaims.

Embodiments of the method according to the invention in which the power consumed by the generator is stored in a battery as electrical energy are advantageous.

This variant of the method has the advantage that the power obtained by means of generator operation does not have to be used immediately but can be stored. In an electric machine, which can also be used and operated as a switchable auxiliary drive, the energy stored in the battery is then preferably used to drive the auxiliary drive, without additional energy would have to be provided, which could possibly increase the fuel consumption of the internal combustion engine.

For operating a supercharged internal combustion engine in which the turbine of the at least one exhaust gas turbocharger comprises a blow-off line which branches off from the exhaust gas removal system upstream of the turbine and in which a shut-off element is arranged, embodiments of the method according to the invention in which the blow-off line is opened to exhaust gas are advantageous bypassing the turbine, thereby reducing the power provided by the turbine to the shaft.

Even if the internal combustion engine according to the invention does not have to be equipped a priori with a blow-off line and the method according to the invention makes it possible to dispense with such a line, it may be advantageous to provide an exhaust blow, namely, for example, in the event that a designated battery reaches its maximum state of charge or for any other reason there is no need for generator-generated electrical energy.

Therefore, embodiments of the method according to the invention in which the blow-off line is closed when the electric machine is operated as a generator and receives power from the turbine are also advantageous in this context.

As long as a designated battery has not reached its maximum state of charge or there is a need for generated by generator electrical energy, the blow-off should be closed so as not to waste unnecessarily high-energy exhaust gas, but to use the energy contained in the hot exhaust gas turbine and generator and convert into electrical energy.

Also advantageous in this connection are embodiments of the method according to the invention in which the power consumed by the electric machine as a generator and the amount of exhaust gas carried by the turbine via the blow-off line are controlled in dependence on one another. A one-sided dependency in which the power consumed by the electric machine as a generator is controlled as a function of the amount of exhaust gas blown off or the amount of exhaust gas blown off as a function of the power consumed by the electric machine as the generator is sufficient.

The power provided by the turbine to the shaft can be adjusted by blowing off exhaust gas, i. H. can be controlled, and can be further reduced by means of a generator operated electric machine. The power provided for driving the compressor can thus be adjusted by means of the two control variables mentioned above, ie. H. by electric machine and blow-off line.

For operating a supercharged internal combustion engine in which a throttle valve is arranged in the intake system downstream of the compressor, embodiments of the method according to the invention are advantageous, which are characterized in that the load of the internal combustion engine is controlled and adjusted by means of the throttle valve.

While the injected fuel quantity is used to adjust the air ratio λ, the load or power in the gasoline engine is controlled and adjusted by means of a throttle valve arranged in the intake system. By adjusting the throttle, the pressure of the intake air behind the throttle valve can be reduced more or less. The further the throttle is closed, that is, the more it obstructs the intake system, the higher the pressure loss of the intake air across the throttle and the lower the pressure of the intake air downstream of the throttle and before the inlet into the at least one cylinder, ie combustion chamber. With constant combustion chamber volume can be adjusted in this way on the pressure of the intake air, the air mass, ie the quantity. This is also the reason why the quantity control proves to be disadvantageous, especially in part-load operation, because low loads require high throttling and pressure reduction in the intake system, whereby the charge exchange losses increase with decreasing load and increasing throttling.

Advantageous in this connection are embodiments of the method according to the invention in which the power consumed by the electric machine as a generator and the position of the throttle valve are controlled in dependence on one another. There must be no interdependence. A one-sided dependence in which the power absorbed by the electric machine as a generator is controlled as a function of the position of the throttle valve or the position of the throttle valve as a function of the power consumed by the electric machine as a generator, is sufficient.

The boost pressure downstream of the throttle depends on the boost pressure upstream of the throttle and the position of the throttle itself, wherein the boost pressure upstream of the throttle depends primarily on the drive power provided to the compressor, which depends on the exhaust gas amount and / or the electric machine set the power consumed as a generator, d. H. can control.

As a result, advantageous embodiments of the method according to the invention, in which the boost pressure is controlled and adjusted downstream of the throttle valve by means of the power absorbed by the electric machine as a generator and the position of the throttle valve. The recorded by the electric machine as a generator power and the position of the throttle are controlled in dependence on each other, with a one-sided dependence is sufficient.

To operate a supercharged internal combustion engine in which the turbine of the at least one exhaust gas turbocharger has a variable turbine geometry, embodiments of the method according to the invention are advantageous, which are characterized in that the power absorbed by the electric machine as a generator and the variable geometry of the turbine controlled in dependence become. A one-sided dependency in which the power consumed by the electric machine as a generator is controlled as a function of the geometry of the turbine or the geometry of the turbine as a function of the power consumed by the electric machine as a generator, is sufficient.

The power provided by the turbine to the shaft can be adjusted, in particular increased or decreased, by adjusting the turbine geometry, whereby the power provided for driving the compressor is further reduced by means of a generator-operated electric machine, i. H. can be set.

In this context, embodiments of the method according to the invention in which the variable geometry of the turbine is adjusted in an efficiency-optimized manner are advantageous. Preferably, the electric machine is used to record as a switchable generator provided by the turbine power surplus.

If the geometry of the turbine is selected and set with regard to the highest possible efficiency and not with regard to the power provided on the shaft, corrective action can be taken by means of an electric motor.

If more power is provided to the shaft than intended by the efficiency-optimized operation of the turbine, the power provided on the shaft can be reduced by means of the power consumed by the electric machine as a generator. On the other hand, if the variable geometry turbine provides less power to the shaft than required, the electric machine, if possible and provided, can provide additional power to drive the compressor as a switchable auxiliary drive.

Therefore, embodiments of the method according to the invention may also be advantageous in which the electric machine connected to the shaft is operated as a switchable auxiliary drive to support the exhaust gas turbocharger and additionally provides power for the drive of the compressor and delivers it to the compressor.

According to the invention, the electric machine which can be drive-connected to the shaft does not have to be usable a priori as a switchable auxiliary drive to support the exhaust-gas turbocharger, but can be operated as a generator. In this respect, the above embodiment is only an advantageous variant. An electric machine that can only be operated as a generator is completely sufficient for carrying out the method according to the invention.

For operating a supercharged internal combustion engine in which a throttle valve is arranged in the intake system downstream of the compressor, process variants may be advantageous in which the electric machine is operated as a switchable auxiliary drive if necessary, the need as a function of the position of the throttle and the Verstellrate the throttle determined and considered as given. In general, the throttle valve is actuated by means of an accelerator pedal serving as an actuator. The adjustment of the pivotable throttle defines itself as the adjustment angle per unit time.

For operating a supercharged internal combustion engine, in which a throttle valve is arranged downstream of the compressor in the intake system, which is actuated by means of an accelerator pedal serving as an actuator, therefore also process variants may be advantageous in which the electric machine is operated as a switchable auxiliary drive, if necessary, where necessary is determined as a function of the position of the accelerator pedal and the adjustment rate of the accelerator pedal and considered as given. The adjustment of the pivotable accelerator pedal defines itself as adjustment angle per unit time.

The latter two variants of the method depend on an increased load requirement, wherein a high Verstellrate the pivotable throttle or the pivotable accelerator pedal is used as an indication of an increased load request and is used and acted taking into account the current position of the throttle or the accelerator pedal.

If an increased load requirement on the part of the driver is detected, because the adjustment rate exceeds a predefinable adjustment rate, the electric machine, taking into account the current position of the throttle valve or of the accelerator pedal, is optionally operated as a switchable auxiliary drive. The position of the throttle or the accelerator pedal is therefore important because a connection of the electric machine as an auxiliary drive, even at high Verstellrate not under all circumstances, d. H. does not always make sense, for example, when the throttle or the accelerator pedal are already operated or pivoted to 50% or 75% of their maximum adjustment or their maximum adjustment angle.

Advantageous embodiments of the method according to the invention, in which, starting from a powered as a generator electric machine in the operation as a switchable auxiliary drive is changed as soon as there is a need for support of the drive of the compressor and is detected. For the presence of a need, i. H. With regard to the case of need, reference is made to the statements made above.

• – einem Ansaugsystem zum Zuführen von Ladeluft,
• – einem Abgasabführsystem zum Abführen des Abgases, und
• – mindestens einem Abgasturbolader, der eine im Abgasabführsystem angeordnete Turbine und einen im Ansaugsystem angeordneten Verdichter umfasst, wobei die Turbine und der Verdichter auf derselben drehbaren Welle angeordnet sind, bei der
• – eine mit der Welle des mindestens einen Abgasturboladers zumindest antriebsverbindbare Elektromaschine vorgesehen ist,

und die dadurch gekennzeichnet ist, dass

• – die mit der Welle antriebsverbindbare Elektromaschine als Generator betreibbar ist, der Leistung von der Turbine aufnimmt.

The second sub-task on which the invention is based, namely to provide an internal combustion engine for carrying out a method of the type described above, is solved by an internal combustion engine

• An intake system for supplying charge air,
• An exhaust gas discharge system for discharging the exhaust gas, and
• At least one exhaust-gas turbocharger comprising a turbine arranged in the exhaust-gas discharge system and a compressor arranged in the intake system, the turbine and the compressor being arranged on the same rotatable shaft, in which
• An electric machine, which is at least drive-connected to the shaft of the at least one exhaust-gas turbocharger, is provided,

and which is characterized in that

• - The electric drive machine which can be driven by the shaft can be operated as a generator which receives power from the turbine.

The statements already made for the method according to the invention also apply to the internal combustion engine according to the invention, which is why reference is generally made at this point to the statements made above with regard to the method according to the invention. The different process variants sometimes require different internal combustion engines.

Embodiments of the internal combustion engine in which the electric machine is a generator are advantageous.

Embodiments of the internal combustion engine in which a charge air cooler is arranged in the intake system downstream of the compressor of the at least one exhaust gas turbocharger are advantageous. The intercooler lowers the air temperature and thus increases the density of the air, whereby the radiator to a better filling of the combustion chamber with air, d. H. contributes to a larger air mass.

Embodiments of the supercharged internal combustion engine in which exhaust gas recirculation is provided are advantageous.

In this context, embodiments of the supercharged internal combustion engine in which exhaust gas recirculation is provided, which includes a line which branches off from the exhaust gas removal system upstream of the turbine of the at least one exhaust gas turbocharger and leads into the intake system, are advantageous downstream of the compressor of the at least one exhaust gas turbocharger.

To comply with future limits for nitrogen oxide emissions, an exhaust gas recirculation is increasingly used, ie the return of exhaust gases from the exhaust side to the inlet side, in which the nitrogen oxide emissions can be significantly reduced with increasing exhaust gas recirculation rate. In this case, the exhaust gas recirculation rate x _{AGR is} determined by x _AGR = m _AGR / (m _AGR + m _{fresh air} ), where m _{AGR designates} the mass of recirculated exhaust gas and m _{fresh air} the supplied fresh air or combustion air, possibly guided and compressed by a compressor.

Exhaust gas recirculation is also suitable for reducing emissions of unburned hydrocarbons in the partial load range. In order to achieve a significant reduction in nitrogen oxide emissions, high exhaust gas recirculation rates may be required, which may be on the order of x _AGR ≈ 60% to 70%.

Embodiments in which the line for exhaust gas recirculation leads downstream of a charge air cooler into the intake system are advantageous. In this way, the exhaust gas flow is not passed through the intercooler and consequently can not pollute this radiator by deposits of pollutants contained in the exhaust stream, in particular soot particles and oil.

Embodiments in which an additional cooler is provided in the exhaust gas recirculation line are advantageous. This additional cooler lowers the temperature in the hot exhaust gas flow and thus increases the density of the exhaust gases. The temperature of the cylinder fresh charge, which occurs in the mixture of fresh air with the recirculated exhaust gases, is consequently further reduced, whereby the additional radiator contributes to a better filling of the combustion chamber with charge air.

Embodiments in which a shut-off element is provided in the line for exhaust gas recirculation are advantageous. This shut-off element is used to control the exhaust gas recirculation rate.

Also advantageous are embodiments of the supercharged internal combustion engine, in which an exhaust gas recirculation is provided which comprises a line which branches off from the Abgasabführsystem downstream of the turbine of the at least one exhaust gas turbocharger and opens into the intake system, preferably upstream of the compressor of the at least one exhaust gas turbocharger.

In contrast to the high-pressure EGR already mentioned, which removes exhaust gas from the exhaust gas removal system upstream of the turbine and introduces it into the intake system downstream of the compressor, in a low-pressure EGR exhaust gas is returned to the inlet side, which has already passed through the turbine. For this purpose, the low-pressure EGR comprises a return line, which branches off downstream of the turbine from the Abgasabführsystem and opens upstream of the compressor in the intake system.

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

It is harmless that in the context of low-pressure EGR exhaust gas is passed through the compressor, since exhaust gas is usually used, which downstream of the turbine exhaust after-treatment, in particular in the particulate filter was subjected. Deposits in the compressor, which change the geometry of the compressor, in particular the flow cross-sections, and thus worsen the efficiency of the compressor, are therefore not to be feared.

Embodiments of the internal combustion engine in which a shut-off element used is a valve or a throttle valve are advantageous.

In this case, embodiments in which the shut-off element is electrically, hydraulically, pneumatically, mechanically or magnetically controllable, preferably by means of motor control, are advantageous.

Embodiments of the internal combustion engine in which the turbine of the at least one exhaust-gas turbocharger is not equipped with a blow-off line or a variable turbine geometry may be advantageous. This results in particular advantages in terms of costs and packaging and the control of the internal combustion engine.

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 schematically a second embodiment of the internal combustion engine.

1 shows a first embodiment of the supercharged internal combustion engine 1 the example of a four-cylinder in-line engine 1 ,

For discharging the hot exhaust gases have the four cylinders arranged in series 3 via an exhaust gas removal system 4 , Furthermore, the cylinders have 3 via an intake system 2 for supplying charge air.

The internal combustion engine 1 is with an exhaust gas turbocharger 6 equipped, the one in the exhaust system 4 arranged turbine 6a and one in the intake system 2 arranged compressor 6b includes, the turbine 6a and the compressor 6b on the same rotatable shaft 6c are arranged.

Downstream of the compressor 6b is a charge air cooler 5 in the intake system 2 arranged. The intercooler 5 lowers the charge air temperature and thus increases the density of the air, which is why the radiator 5 to a better filling of the cylinder 3 contributes with charge air. Furthermore, in the intake system 2 downstream of the compressor 6b and the intercooler 5 a throttle 10 arranged, the control and adjustment of the load of the internal combustion engine 1 serves.

The internal combustion engine 1 may further be provided with an exhaust gas recirculation, which includes a line upstream and downstream of the turbine 6a , from the exhaust gas removal system 4 branches off and downstream or upstream of the compressor 6b into the intake system 2 flows (not shown).

The turbine 6a is with a blow-off line 8th equipped, the upstream of the turbine 6a from the exhaust system 4 branches off and downstream of the turbine 6a back into the exhaust system 4 opens and in the a shut-off 8a is arranged. This is the turbine 6a designed as a so-called waste gate turbine.

By a more or less wide opening of the blow-off line 8th can the at the turbine 6a be adjusted exhaust gas amount, wherein the boost pressure downstream of the compressor 6b by means of the turbine 6a influence the amount of exhaust gas passed, ie control, in particular limits.

One with the wave 6c the exhaust gas turbocharger 6 drive-connected electric machine 7 can be used as a generator 7a operate. The generator 7a takes power from the turbine 6a on, causing the turbine 6a for driving the compressor 6b provided service is reduced. The boost pressure downstream of the compressor 6b will be reduced. The generator 7a Recorded power is called electrical energy in a battery 9 saved.

2 shows a second embodiment of the supercharged internal combustion engine 1 , It should only the differences to the in 1 Otherwise, reference will be made to FIG 1 , The same reference numerals have been used for the same components.

Unlike the in 1 embodiment shown is in the in 2 illustrated internal combustion engine 1 the turbine 6a not equipped with a blow-off line. The advantages are those already mentioned.

LIST OF REFERENCE NUMBERS

1

 supercharged internal combustion engine, four-cylinder in-line engine

2

 intake system

3

 cylinder

4

 Abgasabführsystem

5

 Intercooler

6

 turbocharger

6a

 turbine

6b

 compressor

6c

 wave

7

 electric machine

7a

 generator

8th

 blow-off line

8a

 shut-off

9

 battery

10

 throttle

QUOTES INCLUDE IN THE DESCRIPTION

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Cited patent literature

• US 2013/0209291 A1 [0003]

Claims (16)

Method for boost pressure adjustment of a supercharged internal combustion engine ( 1 ) with an intake system ( 2 ) for supplying charge air, - an exhaust gas removal system ( 4 ) for discharging the exhaust gas, and - at least one exhaust gas turbocharger ( 6 ), one in the exhaust system ( 4 ) arranged turbine ( 6a ) and one in the intake system ( 2 ) arranged compressors ( 6b ), wherein the turbine ( 6a ) and the compressor ( 6b ) on the same rotatable shaft ( 6c ) are arranged, in which - one with the shaft ( 6c ) of the at least one exhaust gas turbocharger ( 6 ) at least drive-connected electric machine ( 7 ), characterized in that - with the shaft ( 6c ) drive-connected electric machine ( 7 ) as a generator ( 7a ) and power from the turbine ( 6a ), whereby the for the drive of the compressor ( 6b ) from the turbine ( 6a ) and the charge pressure downstream of the compressor ( 6b ) is lowered. A method according to claim 1, characterized in that the from the generator ( 7a ) recorded power as electrical energy in a battery ( 9 ) is stored. Method according to Claim 1 or 2 for operating a supercharged internal combustion engine ( 1 ), in which the turbine ( 6a ) of the at least one exhaust gas turbocharger ( 6 ) a blow-off line ( 8th ), which upstream of the turbine ( 6a ) from the exhaust gas removal system ( 4 ) and in which a shut-off element ( 8a ), characterized in that the blow-off line ( 8th ) is opened to exhaust gas on the turbine ( 6a ), whereby the turbine ( 6a ) on the shaft ( 6c ) is reduced. A method according to claim 3, characterized in that the blow-off line ( 8th ) is closed when the electric machine ( 7 ) as a generator ( 7a ) and power from the turbine ( 6a ). Method according to claim 3, characterized in that that of the electric machine ( 7 ) as a generator ( 7a ) and at the turbine ( 6a ) via blow-off line ( 8th ) Passed amount of exhaust gas are controlled in dependence on each other. Method according to one of the preceding claims for operating a supercharged internal combustion engine ( 1 ), in the intake system ( 2 ) downstream of the compressor ( 6b ) a throttle valve ( 10 ), characterized in that the load of the internal combustion engine ( 1 ) by means of the throttle valve ( 10 ) is controlled and adjusted. Method according to claim 6, characterized in that that of the electric machine ( 7 ) as a generator ( 7a ) and the position of the throttle valve ( 10 ) are controlled in dependence on each other. A method according to claim 6 or 7, characterized in that the boost pressure downstream of the throttle valve ( 10 ) by means of the electric machine ( 7 ) as a generator ( 7a ) and the position of the throttle valve ( 10 ) is controlled and adjusted. Method according to one of the preceding claims for operating a supercharged internal combustion engine ( 1 ), in which the turbine ( 6a ) of the at least one exhaust gas turbocharger ( 6 ) has a variable turbine geometry, characterized in that the of the electric machine ( 7 ) as a generator ( 7a ) and the variable geometry of the turbine ( 6a ) are controlled in dependence on each other. Method according to claim 9, characterized in that the variable geometry of the turbine ( 6a ) is set to optimize efficiency. Method according to one of the preceding claims, characterized in that the with the shaft ( 6c ) drive-connected electric machine ( 7 ) as a switchable auxiliary drive to support the exhaust gas turbocharger ( 6 ) and additional power for the drive of the compressor ( 6b ) and to the compressor ( 6b ). Method according to one of the preceding claims for operating a supercharged internal combustion engine ( 1 ), in the intake system ( 2 ) downstream of the compressor ( 6b ) a throttle valve ( 10 ), characterized in that the electric machine ( 7 ) is operated as a switchable auxiliary drive in case of need, the need, depending on the position of the throttle valve ( 10 ) and the adjustment rate of the throttle valve ( 10 ) and considered as given. Method according to one of the preceding claims for operating a supercharged internal combustion engine ( 1 ), in the intake system ( 2 ) downstream of the compressor ( 6b ) a throttle valve ( 10 ) is actuated, which is actuated by means of an accelerator pedal serving as an actuator, characterized in that the electric machine ( 7 ) If necessary, operated as a switchable auxiliary drive, the case of need depending on the position of Accelerators and the rate of adjustment of the accelerator pedal is detected and considered to be given. Method according to one of the preceding claims, characterized in that starting from a generator ( 7a ) operated electric machine ( 7 ) is switched into operation as a switchable auxiliary drive, as soon as need for support of the drive of the compressor ( 6b ) and is found. Charged internal combustion engine ( 1 ) for carrying out a method according to one of the preceding claims, comprising - an intake system ( 2 ) for supplying charge air, - an exhaust gas removal system ( 4 ) for discharging the exhaust gas, and - at least one exhaust gas turbocharger ( 6 ), one in the exhaust system ( 4 ) arranged turbine ( 6a ) and one in the intake system ( 2 ) arranged compressors ( 6b ), wherein the turbine ( 6a ) and the compressor ( 6b ) on the same rotatable shaft ( 6c ) are arranged, in which - one with the shaft ( 6c ) of the at least one exhaust gas turbocharger ( 6 ) at least drive-connected electric machine ( 7 ), characterized in that - with the shaft ( 6c ) drive-connected electric machine ( 7 ) as a generator ( 7a ), the power from the turbine ( 6a ). Charged internal combustion engine ( 1 ) according to claim 15 for carrying out a method according to one of claims 1 to 10, characterized in that the electric machine ( 7 ) a generator ( 7a ).

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