DE102013206158A1 - Internal combustion engine with deactivatable cylinder and method for operating such an internal combustion engine - Google Patents

Abstract

The invention relates to a BKM (13) with at least two cylinders (1, 2, 3, 4), in which - each cylinder (1, 2, 3, 4) has at least one outlet opening to which an exhaust pipe (7a, 7b ) for removing the exhaust gases via the exhaust gas discharge system (8), - each cylinder (1, 2, 3, 4) has at least one inlet opening, to which an intake duct (5a, 5b) connects for supplying charge air via the intake system (6), and - at least two cylinders (1, 2, 3, 4) are configured in such a way that they form at least two groups, each with at least one cylinder (1, 2, 3, 4), the at least one cylinder (1, 4 ) of a first group is a cylinder (1, 4) that is also in operation when the internal combustion engine (13) is partially switched off and the at least one cylinder (2, 3) of a second group is designed as a load-dependent switchable cylinder (2, 3). A BKM (13) optimized for partial shutdown is to be provided. This object is achieved by a BKM (13), a first shut-off element (9) being provided in the exhaust gas line (7b) of the at least one load-dependent switchable cylinder (2, 3), which connects the exhaust gas line (7b) to discharge the exhaust gases Exhaust gas discharge system (8) releases when the cylinder (2, 3) is switched on and blocks when the cylinder (2, 3) is switched off, and - a return line (10a) is provided which is connected to the exhaust line (7b) of the at least one load-dependent switchable cylinder (2, 3) 3) branches upstream of the first shut-off element (9) and opens into the suction line (5b) of the at least one load-dependent switchable cylinder (2, 3), a second shut-off element (11) being provided in the return line (10a).

Description

• – jeder Zylinder mindestens eine Auslassöffnung aufweist, an die sich eine Abgasleitung zum Abführen der Abgase via Abgasabführsystem anschließt,
• – jeder Zylinder mindestens eine Einlassöffnung aufweist, an die sich eine Ansaugleitung zum Zuführen von Ladeluft via Ansaugsystem anschließt, und
• – mindestens zwei Zylinder in der Art konfiguriert sind, dass sie mindestens zwei Gruppen mit jeweils mindestens einem Zylinder bilden, wobei der mindestens eine Zylinder einer ersten Gruppe ein auch bei Teilabschaltung der Brennkraftmaschine in Betrieb befindlicher Zylinder ist und der mindestens eine Zylinder einer zweiten Gruppe als lastabhängig schaltbarer Zylinder ausgebildet ist.

The invention relates to an internal combustion engine having at least two cylinders, in which

• Each cylinder has at least one outlet opening adjoined by an exhaust pipe for discharging the exhaust gases via the exhaust gas removal system,
• - Each cylinder has at least one inlet opening, which is followed by a suction line for supplying charge air via the intake system, and
• - At least two cylinders are configured in such a way that they form at least two groups each having at least one cylinder, wherein the at least one cylinder of a first group is also in partial shutdown of the internal combustion engine in operation cylinder and the at least one cylinder of a second group as load-dependent switchable cylinder is formed.

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

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 the development of internal combustion engines, it is a fundamental goal to minimize fuel consumption, with an improved overall efficiency in the foreground of the efforts.

The fuel consumption and thus the efficiency, especially in gasoline engines, d. H. in spark-ignition internal combustion engines. The reason for this lies in the basic working method of the gasoline engine. The load control is usually carried out by means of a throttle valve provided in the intake system. By adjusting the throttle, the pressure of the intake air behind the throttle valve can be reduced more or less. The farther the throttle is closed, d. H. the more this obstructs the intake system, the higher the pressure loss of the intake air across the throttle and the lower the pressure of the intake air downstream of the throttle and before the intake into the at least two cylinders, d. H. Combustion chambers. With a constant combustion chamber volume, the air mass, d. H. the quantity will be set. This also explains why the quantity control proves to be disadvantageous especially in part-load operation, because low loads require high throttling and pressure reduction in the intake system, whereby the charge exchange losses increase with decreasing load and increasing throttling.

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

One approach to dethrottling the gasoline engine is, for example, an Otto engine working method with direct injection. The direct injection of the fuel is a suitable means for realizing a stratified combustion chamber charge. The direct injection of the fuel into the combustion chamber thus allows within certain limits a quality control of the gasoline engine. The mixture formation takes place by the direct injection of the fuel in the cylinders or in the air in the cylinders and not by external mixture formation, in which the fuel is introduced into the intake system in the intake air.

Another way to optimize the combustion process of a gasoline engine, is the use of an at least partially variable valve train. In contrast to conventional valve trains, in which both the stroke of the valves and the control times are not variable, these parameters influencing the combustion process and thus the fuel consumption can be varied more or less by means of variable valve trains. Throttle-free and thus lossless load control is already possible if the closing time of the intake valve and the intake valve lift can be varied. The mixture mass or charge air mass flowing into the combustion chamber during the intake process is then not controlled by means of a throttle valve, but via the intake valve stroke and the opening duration of the intake valve. However, variable valve trains are very cost-intensive and therefore often unsuitable for serial installation.

Another solution for dethrottling a gasoline engine offers the cylinder deactivation, ie the shutdown of individual cylinders in certain load ranges. The efficiency of the gasoline engine in part-load operation can be improved by such a partial shutdown, because the shutdown of a cylinder of a multi-cylinder internal combustion engine increases the load of the remaining still operating cylinders at constant engine power, so that the throttle for introducing a larger air mass in This cylinder can be opened further or needs to, which Overall, a Entdrosselung the internal combustion engine is achieved. The continuously operating cylinders operate during partial shutdown in the area of higher loads, where the specific fuel consumption is lower. The load collective is shifted to higher loads.

The further operated during the partial shutdown cylinder also have due to the larger air mass supplied or mixture mass improved mixture formation and tolerate higher exhaust gas recirculation rates.

Further efficiency advantages result from the fact that a deactivated cylinder as a result of the lack of combustion no wall heat losses generated as a result of heat transfer from the combustion gases to the combustion chamber walls.

Although diesel engines, d. H. self-igniting internal combustion engines, due to the applied quality control higher efficiency, d. H. have a lower fuel consumption than gasoline engines, in which the load - as described above - is set by throttling or quantity control on the filling of the cylinder, there is also improvement potential in diesel engines and improvement in fuel consumption and efficiency.

A concept for reducing fuel consumption is also the cylinder deactivation in diesel engines, d. H. the shutdown of individual cylinders in certain load ranges. The efficiency of the diesel engine in part load operation can be improved by a partial shutdown, d. H. be increased, because the shutdown of at least one cylinder of a multi-cylinder internal combustion engine increases at constant engine power even in the diesel engine, the load of the remaining operating cylinders, so that these cylinders operate in areas of higher loads, in which the specific fuel consumption is lower. The load collective in part-load operation of the diesel engine is shifted to higher loads.

The further operated during the partial shutdown cylinders also tolerate due to the larger fuel mass supplied, d. H. due to the richer mixture, higher exhaust gas recirculation rates. With regard to the wall heat losses, the same advantages result as in the gasoline engine, for which reason reference is made to the corresponding explanations.

The partial shutdown in diesel engines should also prevent the fuel-air mixture under the quality scheme with decreasing load by reducing the amount of fuel used too much.

The multi-cylinder internal combustion engines with partial deactivation described in the prior art and the associated methods for operating these internal combustion engines nevertheless have clear potential for improvement, as will be explained briefly and by way of example on the diesel engine below.

Is in a direct-injection diesel engine for the purpose of partial shutdown, the fuel supply to the disabled cylinders prevented, d. H. If the associated valve drive of this cylinder is not deactivated or can not be deactivated, the deactivated cylinders continue to participate in the charge exchange. The thereby generated by the disabled cylinder charge exchange losses reduce the improvements achieved by the partial shutdown in terms of fuel consumption and efficiency and oppose these, so that the benefits of partial shutdown is at least partially lost, d. H. the partial shutdown in the sum actually brings a less significant improvement.

In practice, it is not expedient to remedy the disadvantageous effects described above, characterized in that switchable valve trains are provided because switchable valve trains such as variable valve trains are very costly and are not suitable for mass production.

In addition, switchable valve trains would result in turbocharged supercharged by exhaust gas turbochargers to further problems, since the turbine of an exhaust gas turbocharger is to be interpreted to a certain amount of exhaust gas and thus to a certain number of cylinders. When the valve train of a deactivated cylinder is deactivated, the total mass flow through the cylinders of the internal combustion engine decreases due to the lack of mass flow through the deactivated cylinders. The exhaust gas mass flow guided through the turbine decreases and with it the turbine pressure ratio. This has the consequence that the boost pressure ratio also decreases, d. H. the charge pressure drops, and only a little fresh air or charge air is supplied or can be supplied to the cylinders which are still in operation. The low charge air flow can also cause the compressor to operate beyond the surge line.

The effects described above lead to a limitation of the applicability of the partial shutdown, namely to a limitation of the load range in which the partial shutdown can be used. The reduced amount of charge air, which is supplied to the operating during the partial shutdown cylinders reduces the effectiveness or quality of combustion and affects detrimental to fuel consumption and pollutant emissions.

The charge pressure at partial shutdown and thus the still in operation cylinders supplied charge air quantity could be increased, for example, by a small design of the turbine cross-section and simultaneous Abgasabblasung, whereby the relevant for a partial shutdown load range would be extended again. However, this approach has the disadvantage that the charging behavior is insufficient when all cylinders are operated.

The charge pressure at Teilabschaltung and thus the still in operation cylinders supplied charge air quantity could also be increased by the fact that the turbine is equipped with a variable turbine geometry, which allows an adjustment of the effective turbine cross section to the current exhaust gas mass flow. At the same time, however, the exhaust gas back pressure in the exhaust gas removal system upstream of the turbine would increase, which in turn leads to higher charge exchange losses in the cylinders still in operation.

In view of the foregoing, it is an object of the present invention to provide an internal combustion engine according to the preamble of claim 1, which is improved in terms of partial shutdown.

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

• – jeder Zylinder mindestens eine Auslassöffnung aufweist, an die sich eine Abgasleitung zum Abführen der Abgase via Abgasabführsystem anschließt,
• – jeder Zylinder mindestens eine Einlassöffnung aufweist, an die sich eine Ansaugleitung zum Zuführen von Ladeluft via Ansaugsystem anschließt, und
• – mindestens zwei Zylinder in der Art konfiguriert sind, dass sie mindestens zwei Gruppen mit jeweils mindestens einem Zylinder bilden, wobei der mindestens eine Zylinder einer ersten Gruppe ein auch bei Teilabschaltung der Brennkraftmaschine in Betrieb befindlicher Zylinder ist und der mindestens eine Zylinder einer zweiten Gruppe als lastabhängig schaltbarer Zylinder ausgebildet ist, und

die dadurch gekennzeichnet ist, dass

• – in der Abgasleitung des mindestens einen lastabhängig schaltbaren Zylinders ein erstes Absperrelement vorgesehen ist, welches die Abgasleitung zum Abführen der Abgase via Abgasabführsystem bei zugeschaltetem Zylinder freigibt und bei abgeschaltetem Zylinder versperrt, und
• – eine Rückführleitung vorgesehen ist, die von der Abgasleitung des mindestens einen lastabhängig schaltbaren Zylinders stromaufwärts des ersten Absperrelementes abzweigt und in die Ansaugleitung des mindestens einen lastabhängig schaltbaren Zylinders einmündet, wobei ein zweites Absperrelement in der Rückführleitung vorgesehen ist.

The first sub-task is solved by an internal combustion engine with at least two cylinders, in the

• Each cylinder has at least one outlet opening adjoined by an exhaust pipe for discharging the exhaust gases via the exhaust gas removal system,
• - Each cylinder has at least one inlet opening, which is followed by a suction line for supplying charge air via the intake system, and
• - At least two cylinders are configured in such a way that they form at least two groups each having at least one cylinder, wherein the at least one cylinder of a first group is also in partial shutdown of the internal combustion engine in operation cylinder and the at least one cylinder of a second group as load-dependent switchable cylinder is formed, and

which is characterized in that

• - In the exhaust pipe of the at least one load-dependent switchable cylinder, a first shut-off is provided which releases the exhaust pipe for discharging the exhaust gases via Abgasabführsystem with switched cylinder and locked with the cylinder off, and
• - A return line is provided which branches off from the exhaust pipe of the at least one load-dependent switchable cylinder upstream of the first shut-off element and opens into the suction line of the at least one load-dependent switchable cylinder, wherein a second shut-off element is provided in the return line.

In the internal combustion engine according to the invention, the removal of the exhaust gas from the deactivated cylinders via the Abgasabführsystem can be prevented during partial shutdown, without the switchable cylinder with switchable valve drives, which cause high costs must be equipped. For this purpose, a shut-off element is provided in the exhaust pipe of each load-dependent switchable cylinder. This first shut-off element releases the exhaust gas line for the removal of exhaust gas and obstructs it during partial shut-off, ie. H. when switching off the switchable cylinder.

As already described in connection with the prior art, the deactivated cylinders continue to participate in the charge exchange, since the associated valve drive of these cylinders is further actuated, d. H. works, and not shut off together with the cylinders. However, the exhaust removal is inhibited as described above, d. H. modified, wherein the exhaust gas is not discharged, but returned to the inlet side. A deactivated cylinder, no charge air is supplied, but rather exhaust gas from its own exhaust pipe, which is introduced via return line in the intake pipe of the deactivated cylinder to reduce the charge cycle losses of the deactivated cylinder. The return line serves as a short-circuit line and causes a pressure equalization between the inlet side and the outlet side of a deactivated cylinder. This contributes significantly to the reduction of charge exchange losses. The shut-off cylinders pump the recirculated exhaust gas in the manner of a compressor from the inlet side to the outlet side.

By passing hot exhaust gas through the deactivated cylinders during partial shutdown, these cylinders can not cool. This has advantages in particular with regard to the pollutant emissions, in particular with regard to the emissions of unburned hydrocarbons, since the deactivated cylinders again reach or have their operating temperature immediately after termination of the partial shutdown. Strict is taken during the partial shutdown is not permanently returned hot gas via the return line, but at least during the first cycle of partial shutdown the exhaust gas of the previous and thus the hot exhaust gas of the last fired work cycle. During the following cycles of partial shutdown then slowly cooling exhaust gas is introduced with a more or less large amount of cooler charge air in the at least one deactivated cylinder. Nevertheless, in the context of the present invention, the recirculation of hot exhaust gas is mentioned.

Although recirculating hot exhaust gas into the deactivated cylinders does not increase the mass flow through the internal combustion engine. Nevertheless, there are advantages for supercharged internal combustion engines with exhaust gas turbocharger. In contrast to the concepts described in the prior art in which the deactivated cylinders only charge air or as a result of a shut-off valve gear no charge air is supplied during the partial shutdown, with the inventive introduction of hot exhaust gas in the deactivated cylinder, a higher exhaust gas temperature or a higher exhaust pressure generated in the Abgasabführsystem located in the exhaust gas. Both result in a higher exhaust gas enthalpy, which is largely determined by the exhaust gas pressure and the exhaust gas temperature. The higher exhaust gas enthalpy, d. H. the larger exhaust gas energy, which is available at the turbine of an exhaust gas turbocharger, leads to an increase in the boost pressure and thus the charge air quantity. This extends the scope of partial shutdown, namely the load range in which the partial shutdown can be used, and improves the quality of the combustion and thus the fuel consumption and emission behavior of the internal combustion engine. In addition, arranged in Abgasabführsystem exhaust aftertreatment achieve faster due to the hotter exhaust gases their operating temperature or light-off.

With the internal combustion engine according to the invention an internal combustion engine according to the preamble of claim 1 is provided, which is improved in terms of their partial shutdown. Thus, the first object of the invention is solved.

The internal combustion engine according to the invention has at least two cylinders or at least two groups each having at least one cylinder. As such, three-cylinder engines configured in three groups of one cylinder each, or six-cylinder engines configured in three groups of two cylinders, are also internal combustion engines of the present invention. The three cylinder groups can be successively switched on or off as part of a partial shutdown, whereby a two-time switching can be realized. The partial shutdown is thereby further optimized. The cylinder groups may also comprise a different number of cylinders.

The inventive design of the internal combustion engine improves the efficiency of the internal combustion engine in partial load operation, ie at low loads, a low load T _{low is} preferably a load less than 50%, preferably less than 30% of the maximum load T _{max, n} at the moment present speed n is.

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

Embodiments of the internal combustion engine in which the first shut-off element and / or the second shut-off element are infinitely adjustable are advantageous.

In particular, the configuration of the second shut-off element as a continuously variable valve allows the exact dosage of the recirculated into the deactivated cylinder exhaust gas amount; Similar to the setting of the recirculation rate of an exhaust gas recirculation by means of EGR valve. The dimensioning of the recirculated exhaust gas quantity can be specific to the operating point, in particular with regard to the lowest possible charge exchange losses.

On the other hand, the first shut-off element arranged in the exhaust pipe is intended to obstruct only the exhaust pipe of a deactivated cylinder and release it again after completion of the partial shut-off, which is why a shut-off element which can be switched in two stages is basically sufficient.

Therefore, embodiments of the internal combustion engine in which the first shut-off element and / or the second shut-off element can be switched in two stages are also advantageous.

Embodiments of the internal combustion engine in which the first shut-off element and / or the second shut-off element is a valve or a pivotable flap or a throttle flap are advantageous.

The first shut-off element or the second shut-off element can be electrically, hydraulically, pneumatically, mechanically or magnetically controllable, preferably by means of motor control.

Advantageous embodiments of the internal combustion engine, in which at least one exhaust gas turbocharger is provided which has a in the Exhaust gas removal system arranged turbine and arranged in the intake compressor.

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

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

The charge is a suitable means to increase the capacity of an internal combustion engine with unchanged displacement, or to reduce the displacement at the same power. In any case, the charging leads to an increase in space performance and a lower power mass. At the same vehicle boundary conditions, the load collective can thus be shifted to higher loads in which the specific fuel consumption is lower.

The interpretation of the turbocharger turbocharger is difficult, with basically a noticeable increase in performance in all speed ranges is sought. In the prior art, a strong torque drop is often observed when falling below a certain speed. The torque characteristic of a supercharged internal combustion engine can be improved by different measures, for example, the fact that a plurality of superchargers - exhaust gas turbocharger and / or mechanical supercharger - are arranged in parallel and / or arranged in series in the Abgasabführsystem.

Embodiments of the internal combustion engine in which at least one exhaust aftertreatment system is provided in the exhaust gas removal system are advantageous; For example, an oxidation catalyst, a three-way catalyst, a storage catalyst, a selective catalyst and / or a particulate filter.

In internal combustion engines with four cylinders in series, embodiments are advantageous, which are characterized in that the two outer cylinders and the two inner cylinders each form a group.

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

The exhaust gas recirculation, ie the recirculation of combustion gases, is a suitable means to reduce the nitrogen oxide emissions, and with increasing exhaust gas recirculation rate, the nitrogen oxide emissions can be significantly reduced. In this case, the exhaust gas recirculation rate x _{AGR is} determined to be x _AGR = m _AGR / (m _AGR + m _{fresh air} ), where m _{AGR is} the mass of recirculated exhaust gas and m _{fresh air is} the supplied and possibly fresh air guided and compressed by a compressor. In order to achieve a significant reduction in nitrogen oxide emissions, high exhaust gas recirculation rates are required, which can be on the order of x _EGR ≈ 60% to 70%.

Embodiments of the internal combustion engine in which a valve for adjusting the recirculated exhaust gas quantity is arranged in the line of the additional exhaust gas recirculation are advantageous.

In internal combustion engines having at least one exhaust gas turbocharger and exhaust gas recirculation, embodiments are advantageous in which the line of the additional exhaust gas recirculation branches off from the exhaust gas removal system upstream of the turbine of the at least one exhaust gas turbocharger and opens into the intake system downstream of the compressor. In this so-called high-pressure EGR, the exhaust gas is taken from the Abgasabführsystem upstream of the turbine and fed downstream of the compressor in the intake system, which is why the exhaust before recirculation subjected no exhaust aftertreatment, in particular no particle filter must be supplied, since contamination of the compressor is not to be feared ,

When operating an internal combustion engine with exhaust gas turbocharging and simultaneous use of a high-pressure EGR, however, a conflict may arise because the recirculated exhaust gas is no longer available for driving the turbine. With an increase in the exhaust gas recirculation rate, the exhaust gas flow introduced into the turbine decreases. The reduced exhaust gas mass flow through the turbine causes a smaller turbine pressure ratio, whereby the charge pressure ratio also decreases, which is equivalent to a smaller charge air flow.

One solution to this problem is the so-called low-pressure EGR. In contrast to the high-pressure EGR, exhaust gas is introduced into the intake system in the low-pressure EGR, which has already passed through the turbine. For this purpose, the low-pressure EGR has a return line, which branches off downstream of the turbine from the Abgasabführsystem and opens upstream of the compressor in the intake system.

The exhaust gas recirculated to the inlet side by means of low-pressure EGR is mixed with fresh air 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.

Since exhaust gas is passed through the compressor as part of the low-pressure EGR, it must first be subjected to exhaust gas aftertreatment, in particular in the particulate filter. Deposits in the compressor, which change the geometry of the compressor, in particular the flow cross-sections, and in this way deteriorate the efficiency of the compressor are to be avoided.

Advantageous embodiments of the internal combustion engine, in which each cylinder is equipped for introducing fuel with a direct injection.

Embodiments in which each cylinder is equipped with an injection nozzle for the purpose of direct injection are advantageous.

The fuel supply can be deactivated faster and more reliable for the purpose of partial shutdown in direct-injection internal combustion engines as in internal combustion engines with intake manifold injection, in which fuel residues in the intake manifold can lead to unwanted burns in the deactivated cylinder.

Nevertheless, embodiments of the internal combustion engine may be advantageous in which for the purpose of a fuel supply, a port injection is provided.

• – zur Abschaltung die Abgasleitung des mindestens einen schaltbaren Zylinders mittels erstem Absperrelement versperrt wird, und
• – Abgas aus der Abgasleitung des mindestens einen abgeschalteten Zylinders via Rückführleitung in den mindestens einen abgeschalteten Zylinder eingeleitet wird.

The second sub-task on which the invention is based, namely to disclose a method for operating an internal combustion engine of the type described above, is achieved by a method which is characterized in that the at least one switchable cylinder of the second group is switched as a function of the load T of the internal combustion engine is, in the way that this at least one switchable cylinder is switched off when falling below a predetermined load T _{down and is} switched on when a predetermined load T _up is exceeded, wherein

• - To shut off the exhaust pipe of the at least one switchable cylinder is blocked by means of the first shut-off, and
• - Exhaust gas is introduced from the exhaust pipe of the at least one deactivated cylinder via the return line in the at least one deactivated cylinder.

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

The prescribed for falling below or exceeding limit loads T _down and T _up can be the same size, but also different sizes. When the internal combustion engine is in operation, the cylinders of the first cylinder group are constantly in operation. There is a switching of the second cylinder group, ie a connection or disconnection of this second group.

Advantageous are process variants in which the at least one cylinder of the second group is switched off as soon as the predetermined load T _{down is} undershot and the instantaneous load for a predefinable time interval Δt _{1 is} lower than this predetermined load T _down .

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

For these reasons, method variants are also advantageous in which the at least one cylinder of the second group is switched on as soon as the predetermined load T _{up is} exceeded and the instantaneous load is higher for a predefinable time interval Δt ₂ than this predetermined load T _up .

Advantageous are process variants in which the fuel supply of the at least one switchable cylinder is deactivated when switched off. There are advantages in terms of fuel consumption and pollutant emissions, which supports the goal of partial shutdown, namely to reduce fuel consumption and improve efficiency. In self-igniting internal combustion engines, it may even be necessary to supply the fuel to prevent ignition of the mixture in the cylinder.

Advantageous are process variants in which the at least one cylinder in operation is ignited by means of autoignition.

The above process variant relates to methods in which the combustion is initiated by means of auto-ignition, and thus also on working methods, such as are commonly used in diesel engines.

Also advantageous are process variants in which each cylinder is equipped with an ignition device for initiating spark ignition, wherein the ignition device of the at least one switchable cylinder is preferably deactivated when switched off.

The above method variant relates to the application of the method in a spark-ignited internal combustion engine, for example a direct-injection spark-ignition engine, the cylinders of which are each equipped with an ignition device for initiating spark ignition.

However, it is also possible to use a hybrid combustion process with auto-ignition for operating a gasoline engine, for example the so-called HCCI process, which is also referred to as a space ignition process or as a CAI process. This method is based on a controlled auto-ignition of the fuel supplied to the cylinder. Here, the fuel - as in a diesel engine - under excess air, so superstoichiometric, burned. The lean-burn gasoline engine has comparatively low nitrogen oxide emissions due to the low combustion temperatures and also no soot emissions due to the lean mixture. In addition, the HCCI process leads to a high thermal efficiency. The fuel can be introduced both directly into the cylinder and into the intake manifold.

Embodiments of the method in which the predefinable load T _down and / or T _up is dependent on the rotational speed n of the internal combustion engine are advantageous. Then there is not just a concrete load whose falling below or exceeding is switched independent of the speed n. Rather, speed-dependent procedure and an area defined in the map, is switched off in the part.

In principle, further operating parameters of the internal combustion engine can be used as a criterion for a partial shutdown, for example the engine temperature or the coolant temperature after a cold start of the internal combustion engine.

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

1 schematically a first embodiment of a self-igniting internal combustion engine.

1 schematically shows a first embodiment of a self-igniting internal combustion engine 13 ,

It is a four-cylinder in-line engine 13 with direct injection, in which the four cylinders 1 . 2 . 3 . 4 along the longitudinal axis of the cylinder head, ie arranged in series, and each equipped with an injector for injecting fuel, the injected amount of fuel used to adjust the air ratio λ (not shown).

Every cylinder 1 . 2 . 3 . 4 has a suction line 5a . 5b for supplying charge air via intake system 6 and an exhaust pipe 7a . 7b for removing the exhaust gases via exhaust gas removal system 8th ,

The internal combustion engine 13 is for the purpose of charging with an exhaust gas turbocharger 12 equipped, being in an overall exhaust line 18 the exhaust system 8th the turbine 12a and in a total intake line 16 of the intake system 6 the compressor 12b are arranged. That of the internal combustion engine 13 supplied fresh air is in the compressor 12b compressed, including the enthalpy of the exhaust gas flow in the turbine 12a is being used.

The internal combustion engine 13 is also with an exhaust gas recirculation 15 equipped with a high-pressure EGR. For this purpose, a line branches 17 to recirculate exhaust gas upstream of the turbine 12a from the exhaust system 8th and discharges downstream of the compressor 12b into the intake system 6 one. In the line 17 the additional exhaust gas recirculation 15 is a valve 14 arranged to adjust the amount of recirculated exhaust gas.

The four cylinders 1 . 2 . 3 . 4 are configured and form two groups with two cylinders each 1 . 2 . 3 . 4 , where the two outer cylinders 1 . 4 form a first group whose cylinder 1 . 4 even with partial shutdown of the internal combustion engine 13 are in operation, and the two inner cylinders 2 . 3 form a second group whose cylinder as a load-dependent switchable cylinder 2 . 3 are formed, which are turned off in the context of a partial shutdown.

In the exhaust pipes 7b the two inner cylinders 2 . 3 are the first shut-off elements 9 serving flaps 9 provided, which the exhaust pipes 7b for discharging exhaust gas via exhaust gas removal system 8th release when the inner cylinder 2 . 3 are switched on, or block if the two inner cylinder 2 . 3 for the purpose of partial shutdown of the internal combustion engine 13 are switched off or are.

Return lines 10a coming from the exhaust pipes 7b the two switchable cylinders 2 . 3 upstream of the shut-off elements 9 branch off and into the suction lines 5b the two cylinders 2 . 3 serve, during the partial shutdown exhaust into the deactivated cylinder 2 . 3 initiate. One in the exhaust gas recirculation system 10 provided second shut-off 11 is used for dosing the introduced amount of exhaust gas.

The return lines 10a During partial shutdown, pressure equalization is provided between the inlet side and the outlet side of the deactivated cylinders 2 . 3 , whereby the charge cycle losses of these cylinders 2 . 3 be reduced during partial shutdown.

The cylinders 2 . 3 The second group are present as switchable cylinder 2 . 3 trained, which are switched off in partial load operation falls below a predetermined load and indeed by blocking their exhaust pipes 7b by means of flaps 9 and deactivating the fuel injection. This increases the load requirement on the cylinders which are still in operation 1 . 4 the first group, who then work at higher loads with lower specific fuel consumption. An improvement in the efficiency is the result.

LIST OF REFERENCE NUMBERS

1

first cylinder, outboard cylinder

2

second cylinder, internal cylinder, switchable cylinder

3

third cylinder, internal cylinder, switchable cylinder

4

fourth cylinder, outboard cylinder

5a

Intake line of a cylinder of the first group

5b

Intake line of a cylinder of the second group, d. H. a switchable cylinder

6

intake system

7a

Exhaust pipe of a cylinder of the first group

7b

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

8th

Abgasabführsystem

9

first shut-off element, flap

10

Exhaust gas recirculation system

10a

Return line

11

second shut-off element, valve

12

turbocharger

12a

turbine

12b

compressor

13

Internal combustion engine, four-cylinder in-line engine

14

AGR valve

15

Exhaust gas recirculation

16

Gesamtansaugleitung

17

management

18

Total exhaust pipe

n

Speed of the internal combustion engine

T

load

T _down

predefinable load for falling below a load

T _low

Load in the lower part load range

T _{max, n}

maximum load at a given speed n

T _up

predefinable load for exceeding a load

Δt ₁

predefinable time span

Δt ₂

predefinable time span

Claims (15)

Internal combustion engine ( 13 ) with at least two cylinders ( 1 . 2 . 3 . 4 ), in which - each cylinder ( 1 . 2 . 3 . 4 ) has at least one outlet opening, to which an exhaust pipe ( 7a . 7b ) for discharging the exhaust gases via Abgasabführsystem ( 8th ), - each cylinder ( 1 . 2 . 3 . 4 ) has at least one inlet opening, to which a suction line ( 5a . 5b ) for supplying charge air via intake system ( 6 ), and - at least two cylinders ( 1 . 2 . 3 . 4 ) are configured in such a way that these at least two groups each having at least one cylinder ( 1 . 2 . 3 . 4 ), wherein the at least one cylinder ( 1 . 4 ) a first group also at partial shutdown of the internal combustion engine ( 13 ) operating cylinder ( 1 . 4 ) and the at least one cylinder ( 2 . 3 ) of a second group as a load-dependent switchable cylinder ( 2 . 3 ) is formed, characterized in that - in the exhaust pipe ( 7b ) of the at least one load-dependent switchable cylinder ( 2 . 3 ) a first shut-off element ( 9 ) is provided, which the exhaust pipe ( 7b ) for discharging the exhaust gases via Abgasabführsystem ( 8th ) with the cylinder switched on ( 2 . 3 ) and with deactivated cylinder ( 2 . 3 ), and - a return line ( 10a ) provided by the exhaust pipe ( 7b ) of the at least one load-dependent switchable cylinder ( 2 . 3 ) upstream of the first shut-off element ( 9 ) branches off and into the Intake pipe ( 5b ) of the at least one load-dependent switchable cylinder ( 2 . 3 ), wherein a second shut-off element ( 11 ) in the return line ( 10a ) is provided. Internal combustion engine ( 13 ) according to claim 1, characterized in that the first shut-off element ( 9 ) and / or the second shut-off element ( 11 ) is infinitely adjustable. Internal combustion engine ( 13 ) according to claim 1, characterized in that the first shut-off element ( 9 ) and / or the second shut-off element ( 11 ) is switchable in two stages. Internal combustion engine ( 13 ) according to one of the preceding claims, characterized in that at least one exhaust gas turbocharger ( 12 ) is provided, the one in Abgasabführsystem ( 8th ) arranged turbine ( 12a ) and one in the intake system ( 6 ) arranged compressors ( 12b ). Internal combustion engine ( 13 ) according to one of the preceding claims, characterized in that at least one exhaust aftertreatment system in Abgasabführsystem ( 8th ) is provided. Internal combustion engine ( 13 ) according to one of the preceding claims with four cylinders arranged in series ( 1 . 2 . 3 . 4 ), characterized in that the two outer cylinders ( 1 . 4 ) and the two inner cylinders ( 2 . 3 ) each form a group. Internal combustion engine ( 13 ) according to one of the preceding claims, characterized in that at least one additional exhaust gas recirculation ( 15 ), which is a line ( 17 ), which from the Abgasabführsystem ( 8th ) branches off and into the intake system ( 6 ). Internal combustion engine ( 13 ) according to claim 7, characterized in that in the line ( 17 ) of the additional exhaust gas recirculation ( 15 ) a valve ( 14 ) is arranged to adjust the amount of recirculated exhaust gas. Internal combustion engine ( 13 ) according to claim 7 or 8 with at least one exhaust gas turbocharger ( 12 ), characterized in that the line ( 17 ) of the additional exhaust gas recirculation ( 15 ) upstream of the turbine ( 12a ) of the at least one exhaust gas turbocharger ( 12 ) from the exhaust gas removal system ( 8th ) branches off. Internal combustion engine ( 13 ) according to claim 9, characterized in that the line ( 17 ) of the additional exhaust gas recirculation ( 15 ) downstream of the compressor ( 12b ) of the at least one exhaust gas turbocharger ( 12 ) into the intake system ( 6 ). Internal combustion engine ( 13 ) according to one of the preceding claims, characterized in that each cylinder ( 1 . 2 . 3 . 4 ) is equipped for introducing fuel with a direct injection. Method for operating an internal combustion engine ( 13 ) according to one of the preceding claims, characterized in that the at least one switchable cylinder ( 2 . 3 ) of the second group as a function of the load T of the internal combustion engine ( 13 ) is switched in such a way that this at least one switchable cylinder ( 2 . 3 ) is switched off when falling below a predefinable load T _{down and is} switched on when a predetermined load T _up is exceeded, wherein - for switching off the exhaust pipe ( 7b ) of the at least one switchable cylinder ( 2 . 3 ) by means of the first shut-off element ( 9 ), and - exhaust gas from the exhaust pipe ( 7b ) of the at least one deactivated cylinder ( 2 . 3 ) via return line ( 10 ) in the at least one deactivated cylinder ( 2 . 3 ) is initiated. A method according to claim 12, characterized in that the fuel supply of the at least one switchable cylinder ( 2 . 3 ) is deactivated at shutdown. A method according to claim 12 or 13, characterized in that the at least one operating cylinder ( 1 . 2 . 3 . 4 ) is ignited by auto-ignition. Method according to claim 12 or 13, characterized in that each cylinder ( 1 . 2 . 3 . 4 ) is provided with an ignition device for initiating a spark ignition, wherein the ignition device of the at least one switchable cylinder ( 2 . 3 ) is deactivated at shutdown.

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