DE102015210987A1 - Charged spark-ignition internal combustion engine with knock control and method for operating such an internal combustion engine - Google Patents

Abstract

A supercharged spark-ignition internal combustion engine with - at least one cylinder head with at least one cylinder, each cylinder having at least two inlet openings for supplying charge air and at least one outlet opening for discharging the exhaust gases, - at least one throttle valve disposed in the intake system, - at least one exhaust gas turbocharger, and - A knock control, which provides a necessary to avoid knock Zündspätverstellung Δignition as an output signal and provides, in which - at least two at least partially variable valve trains are provided with at least two valves which are movable between a valve closed position and a valve open position to the at least two To open or obstruct inlet openings of the at least one cylinder, with valve spring means to bias the valves in the direction of valve closing position, and with at least two actuators to the valves en open against the biasing force of the valve spring means, each actuator comprises a arranged on a camshaft cam, which is engageable with at least one cam follower element in circumferential cam, whereby the associated valve is actuated, and the cams of the at least two actuators of the at least two at least partially variable valve trains are rotatable relative to each other, and - each cylinder has a geometric compression ratio εgeo ≥ 11.

Description

• – mindestens einem Zylinderkopf mit mindestens einem Zylinder, wobei jeder Zylinder mindestens zwei Einlassöffnungen zum Zuführen von Ladeluft via Ansaugsystem und mindestens eine Auslassöffnung zum Abführen der Abgase via Abgasabführsystem aufweist,
• – mindestens einer Drosselklappe, die im Ansaugsystem angeordnet ist und der Laststeuerung dient,
• – mindestens einem Abgasturbolader, wobei jeder Abgasturbolader eine im Abgasabführsystem angeordnete Turbine und einen im Ansaugsystem angeordneten Verdichter umfasst, und
• – einer Klopfregelung, die eine zur Vermeidung von Klopfen erforderliche Zündspätverstellung ∆_ignition als Ausgangssignal liefert und bereitstellt.

The invention relates to a supercharged spark-ignition internal combustion engine with

• At least one cylinder head with at least one cylinder, each cylinder having at least two inlet openings for supplying charge air via the intake system and at least one outlet opening for discharging the exhaust gases via the exhaust removal system,
• At least one throttle valve, which is arranged in the intake system and serves the load control,
• At least one exhaust gas turbocharger, each exhaust gas turbocharger comprising a turbine arranged in the exhaust gas removal system and a compressor arranged in the intake system, and
• - A knock control, which provides an _ignition delay required to prevent knock Δ _ignition as an output signal and provides.

Furthermore, the invention relates to a method for operating such an internal combustion engine, wherein each cylinder has two inlet openings for supplying charge air via the intake system.

An internal combustion engine of the type mentioned is used as a drive for motor vehicles and, for example, in the German Offenlegungsschrift DE 10 2011 104 837 A1 described. In the context of the present invention, the term internal combustion engine includes 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.

Internal combustion engines have a cylinder block and at least one cylinder head, which are connected to form the at least one cylinder or combustion chamber. The cylinder block has a corresponding number of cylinder bores for receiving the pistons or the cylinder tubes. The cylinder head is usually used to hold the valve train. To control the charge cycle, an internal combustion engine requires controls and actuators to operate the controls. As part of the change of charge, the combustion gases are pushed out via the outlet openings and the combustion chamber is filled with charge air via the inlet openings. To control the charge cycle four-stroke engines almost exclusively lift valves are used as control members that perform an oscillating lifting movement during operation of the internal combustion engine and thus release the inlet and outlet ports and close. The required for the movement of a valve actuator including the valve itself is referred to as a valve train.

An actuating device comprises a camshaft on which at least one cam is arranged. Basically, a distinction is made between an underlying camshaft and an overhead camshaft. In this case, reference is made to the parting line between the cylinder head and cylinder block. If the camshaft is above this parting line, it is an overhead camshaft, otherwise a camshaft underneath.

Overhead camshafts are likewise mounted in the cylinder head, wherein a valve drive with an overhead camshaft as a further valve drive component may have a rocker arm, a rocker arm, a rocker arm and / or a plunger. These cam follower elements are located in the power flow between cam and valve.

It is the task of the valve drive to open or close the inlet openings or outlet openings of a cylinder in good time, with a quick release of the largest possible flow cross sections is sought to keep the throttle losses in the incoming and outflowing gas flows low and the best possible filling of the Cylinder or a complete discharge of the exhaust gases to ensure. In the prior art, therefore, a cylinder is also frequently and increasingly equipped with two or more inlet and outlet ports.

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 are particularly problematic in gasoline engines, ie 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, that is, the more it blocks the intake system, the higher is 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 one cylinder, ie combustion chamber. With constant combustion chamber volume can up This way, the air mass, ie the quantity, can be adjusted via the pressure of the air sucked in. 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.

To reduce the losses described, various strategies for de-throttling a gasoline engine have been developed.

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 direct injection of the fuel into the cylinder or into the air in the cylinder and not by external mixture formation, in which the fuel is introduced in the intake system in the intake air.

Another approach to optimize the combustion process of a gasoline engine is to use 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. A throttle-free and therefore lossless load control is already possible if the valve train is partially variable or switchable and, for example, the closing time of the intake valve and the intake valve 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. Fully variable valve trains are very costly, which is why sometimes variable or switchable valve trains are often used. The switchable valve trains are considered in the context of the present invention as partially variable valve trains.

It should also be considered in this context that the efficiency η of the gasoline engine correlates at least approximately with the compression ratio ε. Ie. the efficiency η increases with the compression ratio ε, is usually higher with a larger compression ratio and generally lower with a smaller compression ratio.

With regard to the efficiency, the cylinders would thus preferably be equipped with the largest possible compression ratio. However, the compression ratio can not be increased arbitrarily, since with increasing compression ratio and the tendency to knock, d. H. the tendency for spontaneous combustion of mixture parts increases. Modern gasoline engines usually have compression ratios of about 8 to 10, with a compression ratio of about 15 promises the best efficiency. As a result, although the efficiency is limited, but also the required security against knocking, especially at high loads guaranteed. According to the prior art, the tendency to knock is also counteracted by the fact that the ignition is delayed if necessary, whereby the focus of combustion moves late and decrease the combustion pressure and the combustion temperature. For this purpose, modern gasoline engines are equipped with a knock control that delivers and provides an ignition retardation required to prevent knocking as an output signal. The ignition retardation, however, has a disadvantageous effect on the efficiency.

The internal combustion engine, which is the subject of the present invention, has such a knock control and moreover at least one exhaust gas turbocharger. 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.

An exhaust gas turbocharger comprises a compressor arranged in the intake system and a turbine arranged in the exhaust gas discharge system, which are arranged on the same shaft. The hot exhaust stream is supplied to the turbine and relaxes with energy release in this 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, as a result of which charging of the at least one cylinder is achieved. Optionally, a charge air cooling is provided, with which the compressed charge air is cooled before entering the cylinder.

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

In light of the above, it is an object of the present invention to provide a supercharged spark-ignition internal combustion engine according to the preamble of claim 1, which is improved in terms of performance, in particular in terms of fuel consumption and efficiency.

A further sub-task is to disclose a method for operating such an internal combustion engine, wherein each cylinder has two intake ports for supplying charge air via the intake system and each piston belonging to a cylinder oscillates between a top dead center and a bottom dead center.

• – mindestens einem Zylinderkopf mit mindestens einem Zylinder, wobei jeder Zylinder mindestens zwei Einlassöffnungen zum Zuführen von Ladeluft via Ansaugsystem und mindestens eine Auslassöffnung zum Abführen der Abgase via Abgasabführsystem aufweist,
• – mindestens einer Drosselklappe, die im Ansaugsystem angeordnet ist und der Laststeuerung dient,
• – mindestens einem Abgasturbolader, wobei jeder Abgasturbolader eine im Abgasabführsystem angeordnete Turbine und einen im Ansaugsystem angeordneten Verdichter umfasst, und
• – einer Klopfregelung, die eine zur Vermeidung von Klopfen erforderliche Zündspätverstellung ∆_ignition als Ausgangssignal liefert und bereitstellt,

die dadurch gekennzeichnet ist, dass

• – mindestens zwei zumindest teilweise variable Ventiltriebe vorgesehen sind mit mindestens zwei Ventilen, die zwischen einer Ventilschließstellung und einer Ventiloffenstellung bewegbar sind, um die mindestens zwei Einlassöffnungen des mindestens einen Zylinders freizugeben bzw. zu versperren, mit Ventilfedermitteln, um die Ventile in Richtung Ventilschließstellung vorzuspannen, und mit mindestens zwei Betätigungseinrichtungen, um die Ventile entgegen der Vorspannkraft der Ventilfedermittel zu öffnen, wobei jede Betätigungseinrichtung einen auf einer Nockenwelle angeordneten Nocken umfasst, der bei umlaufender Nockenwelle mit mindestens einem Nockenfolgeelement in Eingriff bringbar ist, wodurch das zugehörige Ventil betätigbar ist, und die Nocken der mindestens zwei Betätigungseinrichtungen der mindestens zwei zumindest teilweise variablen Ventiltriebe relativ zueinander verdrehbar sind, und
• – jeder Zylinder ein geometrisches Kompressionsverhältnis ε_geo ≥ 11 aufweist.

The first partial task is solved by a supercharged spark-ignition internal combustion engine

• At least one cylinder head with at least one cylinder, each cylinder having at least two inlet openings for supplying charge air via the intake system and at least one outlet opening for discharging the exhaust gases via the exhaust removal system,
• At least one throttle valve, which is arranged in the intake system and serves the load control,
• At least one exhaust gas turbocharger, each exhaust gas turbocharger comprising a turbine arranged in the exhaust gas removal system and a compressor arranged in the intake system, and
• - provides a knock control that a required _ignition spark retard for avoiding knocking Δ as the output signal and provides,

which is characterized in that

• At least two at least partially variable valve trains are provided with at least two valves which are movable between a valve closed position and a valve open position to release the at least two inlet openings of the at least one cylinder, with valve spring means to bias the valves towards the valve closing position, and at least two actuators for opening the valves against the biasing force of the valve spring means, each actuator comprising a camshaft cam engageable with at least one cam follower element when the camshaft rotates, whereby the associated valve is actuatable; Cams of the at least two actuators of the at least two at least partially variable valve trains are rotatable relative to each other, and
• - Each cylinder has a geometric compression ratio ε _geo ≥ 11.

According to the invention, the timing of the intake valves of a cylinder can be varied. In the present case, the cams associated with the intake valves of a cylinder of the valve actuators can be rotated relative to each other so that the intake valves associated with a cylinder are not only synchronously actuated, i. H. can be opened and closed at the same time. Instead, the cams belonging to the inlet valves or inlet openings of a cylinder can be rotated relative to each other in such a way that a first inlet valve is actuated earlier than a second inlet valve. The timing of the intake valves then have an offset, which is also referred to below as the control offset Δ. This control offset makes it possible to vary the intake-side opening duration, the opening duration extending from the opening of the first intake valve to the closing of the second intake valve.

The variable valve trains on the inlet side allow an adjustment of the timing of the intake valves to the current operating state of the internal combustion engine, in particular an adaptation to the current load and to the current tendency to knock. In this context, the adaptation of the inlet-side opening period to the respective operating state of the internal combustion engine is of particular interest.

In terms of low fuel consumption is in part-load operation at low loads a large, d. H. as long inlet side opening time, preferably. A high compression ratio in this context additionally contributes to the reduction of fuel consumption.

When the load is increased, a shorter inlet-side opening duration is then sought in the partial load operation towards medium loads in order to ensure the best possible filling of the cylinder. The background of this measure is the increase in torque at medium loads, d. H. the improvement of the torque characteristic of the internal combustion engine.

For higher loads, the operation of the internal combustion engine is increasingly limited by the fact that knock under all circumstances is safe to avoid. In the prior art, knocking is counteracted by shifting the ignition timing late. Impairment losses are accepted.

According to the invention, however, the effective compression ratio ε _eff can be lowered by lengthening the intake-side opening duration or by closing an intake valve, for example the second intake valve, with part of the fresh cylinder charge being pushed back into the intake system while the intake is still open as part of the compression stroke , A high geometric compression ratio ε _geo , which is basically considered to be advantageous and significantly contributes to the efficiency improvement at lower loads, can be mitigated in this way at higher loads. In the internal combustion engine according to the invention geometric compression ratios ε _geo ≥ 11 can be realized.

According to the invention, at least the second intake valve is closed later and after the bottom dead center at a risk of knocking, wherein a Schließzeitspätverstellung .DELTA.t _{intake, closing, knock} , by which the second intake valve is to be closed later, using a current speed n _mot and one of the knock control delivered Zündspätverstellung is determined. The required according to the prior art shift of the ignition point to late deleted and with this the efficiency losses. But at least the required Zündspätverstellung is reduced.

The internal combustion engine according to the invention solves the first object underlying the invention, namely to provide an internal combustion engine that is improved with regard to the operating behavior, in particular with regard to the fuel consumption or efficiency.

According to the invention, the cams of the intake valves of a cylinder are rotatable relative to one another. While maintaining the valve opening duration of each valve, the valve timing can be shifted relative to one another, so that the opening duration of the associated cylinder can be lengthened or shortened on the inlet side. The valve overlap of the valves can be varied.

This adjustment requires at least one rotatable cam. According to a first alternative, an adjustable trained cam is rotated relative to the crankshaft, whereas the at least one other cam is designed as a fixed, static cam. According to a second alternative, the at least two cams are designed as adjustable cams which are rotatable relative to one another and relative to the crankshaft.

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

Embodiments of the internal combustion engine are advantageous in which the cams are arranged on an at least two-part camshaft comprising at least two mutually rotatable camshaft sections, wherein at least one cam is arranged on a first camshaft section and at least one cam is arranged on a second camshaft section. An example of a camshaft of the above type describes the German patent application DE 10 2010 008 958 A1 ,

Embodiments of the internal combustion engine in which the at least two-part camshaft comprises a hollow shaft as the first camshaft section and a shaft which is rotatably arranged in the hollow shaft as the second camshaft section are advantageous.

In internal combustion engines with a crankshaft, which is at least drive-connected with the camshaft, embodiments are also advantageous in which the cams are rotatable relative to the crankshaft, in particular with each other and are rotatable relative to the crankshaft.

The cams can be rotated individually or as in a camshaft adjuster together and in the same way with respect to the crankshaft. According to the last-mentioned variant, the control times of the associated valves are shifted together late or early while maintaining the respective valve opening duration.

Embodiments of the internal combustion engine in which the cams have the same contour are advantageous.

Embodiments of the internal combustion engine in which each cylinder is equipped with a direct injection for the purpose of supplying fuel are advantageous. The direct injection of the fuel into the cylinder is a suitable means for reducing the tendency to knock of the gasoline engine and a measure to improve the efficiency.

Advantageous embodiments of the internal combustion engine, in which each cylinder has a geometric compression ratio ε _geo ≥ 11.5.

Embodiments of the internal combustion engine in which each cylinder has a geometric compression ratio ε _geo ≥ 12 are advantageous.

The higher the compression ratio, the higher the efficiency and the lower the fuel consumption. However, higher geometric compression ratios may require greater variability of the valvetrain in order to more significantly and effectively lower the effective compression ratio.

Embodiments of the internal combustion engine in which the actuators of the inlet valves are hydraulically adjustable actuators are advantageous.

In internal combustion engines having at least two cylinders, embodiments are advantageous in which at least two cylinders are configured in such a way that they form at least two groups, each with at least one cylinder, wherein the at least one cylinder of a first group also in partial shutdown of the internal combustion engine in operation is located cylinder and the at least one cylinder of a second group is designed as a load-dependent switchable cylinder.

The cylinder deactivation, d. H. The shutdown of individual cylinders in certain load ranges, provides another way to dethrottle the gasoline engine. The efficiency of the gasoline engine in partial load operation can be improved by a partial shutdown, d. H. be increased, because the shutdown of a cylinder of a multi-cylinder internal combustion engine increases the load of the remaining still in operation cylinder at constant engine power, so that the throttle for introducing a larger air mass in these cylinders can be opened or must, resulting in a total Entdrosselung the internal combustion engine is achieved. The continuously operating cylinders operate during partial shutdown, i. H. at partial load, more often 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 improved mixture formation. 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.

The second sub-task on which the invention is based, namely to disclose a method for operating an internal combustion engine of the aforementioned type, in which each cylinder has two inlet openings for supplying charge air via the intake system and each piston belonging to a cylinder oscillates between a top dead center and a bottom dead center is achieved by a method which is characterized in that at a risk of knocking at least the second inlet valve is closed later and after the bottom dead center.

The comments made in connection with the internal combustion engine according to the invention also apply to the inventive method.

Advantageous are process variants in which a closing time retard Δt _{intake, closing, knock} , by which the second intake valve is to be closed later, using a current speed n _mot and a Zündspätverstellung Δ _ignition supplied by the knock control is determined.

• – die Drosselklappe weiter geöffnet wird,
• – der Steuerversatz ∆ verringert wird, indem das zweite Einlassventil früher betätigt wird, und
• – der Steuerversatz ∆ in Abhängigkeit von einem mittels Abgasturboaufladung im Ansaugsystem generierten Ladedruck wieder vergrößert wird, indem das zweite Einlassventil später betätigt wird und sobald der mindestens eine Abgasturbolader Ladedruck generiert.

Advantageous are process variants in which starting from a lower load, in which the cams belonging to the two inlet openings of each cylinder are rotated relative to one another in such a way that a first inlet valve is actuated earlier than a second inlet valve, forming a control offset Δ increased load requirement

• - the throttle is opened further,
• - The control offset Δ is reduced by the second inlet valve is actuated earlier, and
• - The control offset Δ is increased again in response to a boost pressure generated by exhaust gas turbocharging in the intake system by the second inlet valve is actuated later and as soon as the at least one exhaust gas turbocharger generates boost pressure.

If the internal combustion engine is used, for example, as a drive for a motor vehicle, an increased load can be requested by actuating the accelerator pedal. In this case, for example, in the context of an acceleration, the load can also rise sharply, d. H. a load jump can be realized. The subsequent transient operation of the internal combustion engine is significantly determined by the different response of the individual components, which serve to adjust the operating parameters. While the throttle valve at a dramatically increased load request easily, d. H. almost instantaneous, can be opened further, the exhaust gas turbocharger requires a certain amount of time to generate the required boost pressure, d. H. to be able to provide.

In the present case, the throttle valve is opened further and the control offset .DELTA. Of the intake valves at a sudden increased load request is reduced by the second intake valve is actuated earlier than before the load request. It is assumed that before requesting a higher load, ie at lower load, the first inlet valve is actuated earlier than the second inlet valve, ie, there is a control offset Δ for realizing an extended inlet-side opening duration.

This control offset Δ is initially reduced or minimized in the event of a sudden increase in the load requirement, as a result of which the inlet-side opening duration is shortened. A shorter inlet-side opening duration should ensure the best possible filling of the at least one cylinder and thus a high torque supply at the beginning of the acceleration.

In the further course, as soon as the at least one exhaust gas turbocharger responds and generates a boost pressure in the intake system, the control offset Δ is then increased again as a function of this charge pressure, ie, the intake-side opening period is extended again. This approach takes into account the fact that the tendency to knock increases with increasing boost pressure. Knocking is inventively avoided in that the effective compression ratio ε _eff is lowered by an extension of the inlet-side opening period, namely a late closing of the second inlet valve. In this case, part of the fresh cylinder charge, ie charge air, is pushed back into the intake system while the inlet is still open. The higher the boost pressure, the later the second intake valve is closed or the later the second intake valve is to be closed.

Advantageously, process variants in which the throttle valve is fully opened at sudden increased load request.

Advantageous are process variants in which the control offset Δ is minimized within the scope of the reduction.

Process variants in which the control offset Δ is additionally reduced by the fact that the first inlet valve is actuated later are advantageous.

For operating a supercharged spark-ignition internal combustion engine in which each piston belonging to a cylinder oscillates between a top dead center and a bottom dead center, method variants are advantageous, characterized in that at the lower load before the increased load request, the first intake valve before the bottom dead center and the second intake valve is closed after the bottom dead center.

Advantageous in this connection are process variants in which the control offset Δ is reduced by the fact that the second inlet valve is closed before bottom dead center.

• – in einem ersten Verfahrensschritt eine Basisschließzeit t_{intake,closing,base,2} unter Verwendung einer momentanen Drehzahl n_mot und einem momentanen Sollwert für den Druck p_intake,des im Ansaugsystem ermittelt wird,
• – in einem zweiten Verfahrensschritt eine additive Schließzeit ∆t_{intake,closing,2} unter Verwendung einer momentanen Drehzahl n_mot und einem momentanen Istwert für den Druck p_intake im Ansaugsystem ermittelt wird, und
• – in einem dritten Verfahrensschritt die Schließzeit t_{intake,closing,2} berechnet wird, indem die Basisschließzeit und die additive Schließzeit addiert werden mit t_{intake,closing,2} = t_{intake,closing,base,2} + ∆t_{intake,closing,2}.

Advantageous are process _variants in which a closing time t _{intake, closing, 2} , to which the second inlet valve is closed, is calculated by

• In a first method step, a base _{closing time} t _{intake, closing, base, 2} using a current rotational speed n _mot and an instantaneous nominal value for the pressure p _{intake, which is} determined in the intake system,
• - In a second process step, an additive closing time .DELTA.t _{intake, closing, 2} is determined using a current speed n _mot and a current actual value for the pressure p _intake in the intake system, and
• In a third method step, the closing time t _{intake, closing, 2 is} calculated by adding the base closing time and the additive closing time with t _{intake, closing, 2} = t _{intake, closing, base, 2} + Δt _{intake, closing, 2} .

In the present case, a base _{closing time} t _{intake, closing, base, 2 is first} determined, the charge pressure and thus the charge being neglected, ie not considered. The boost pressure and thus the charge is only accounted for by a second additive component .DELTA.t _{intake, closing, 2} .

A closing time retardation Δt _{intake, closing, knock} by which the second inlet valve is to be closed later, if necessary, is then additionally taken into account in the calculation of the closing time t _{intake, closing, 2} , ie added.

• – für den ersten Verfahrensschritt ein Umgebungsdruck p_atm vorgegeben wird, der als maximal zulässiger Sollwert für den Druck p_intake,des im Ansaugsystem verwendet wird und durch den der Sollwert für den Druck p_intake,des im Ansaugsystem bei der Ermittlung der Basisschließzeit begrenzt wird.

Advantageous in this context are process variants in which

• - For the first step, an ambient pressure p _{atm is} given, which is used as the maximum allowable setpoint for the pressure p _intake, which is used in the intake system and by the setpoint for the pressure p _intake, in the intake system in determining the base closing time.

In order to ensure that the charge pressure and thus the charge actually remain unconsidered within the scope of the first method step, a maximum permissible set value is specified, namely the ambient pressure p _atm , which may amount to 1013 hPa, for example. The supercharged internal combustion engine is considered as a naturally aspirated engine.

• – für den zweiten Verfahrensschritt ein Umgebungsdruck p_atm vorgegeben wird, der zur Ermittlung einer Ladedruckdifferenz ∆p_charge von dem momentanen Istwert für den Druck p_intake im Ansaugsystem subtrahiert wird, wobei die additive Schließzeit ∆t_{intake,closing,2} unter Verwendung dieser Ladedruckdifferenz ∆p_charge ermittelt wird, falls ∆p_charge > 0.

Also advantageous in this context are process variants in which

• - For the second step, an ambient pressure p _{atm is} given, which is subtracted from the current actual value for the pressure p _intake in the intake system to determine a _charge pressure difference Δp _charge , wherein the additive closing time .DELTA.t _{intake, closing, 2} using this _charge pressure difference _.DELTA p _{charge is} determined if Δp _charge > 0.

In order to ensure that in the second method step only the effect generated by the charge or the charge pressure is taken into account, the ambient pressure p _{atm is} subtracted from the actual pressure p _intake in the intake system and a _charge pressure difference Δp _{charge is} formed. The second method step only supplies an additive closing time Δt _{intake, closing, 2} if Δp _charge > 0, ie if the at least one exhaust gas turbocharger responds and generates a boost pressure in the intake system.

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

1 schematically in a diagram operating parameters of the internal combustion engine at a load step, and

2 schematically in a diagram, the determination of the closing time of the second inlet valve.

1 schematically shows in a diagram operating parameters of the internal combustion engine at a load step. The internal combustion engine is used here as a drive for a motor vehicle and has two inlet openings per cylinder.

Shown are the left ordinate the position of the accelerator pedal [%] as curve A, the position of the throttle valve [%] as curve B, the torque [%] as curve C and the closing time t _{closing, 1} or t _{closing, 2} of first or the second intake valve in degrees crank angle after the bottom dead center of the charge cycle [° KWn.uT] as a curve E1 or E2. The pressure p _intake in the intake system or the _charge pressure p _charge is plotted on the right ordinate in [hPa] as curve D. The time t in seconds is plotted on the abscissa.

By pressing the accelerator pedal, the load requirement is increased suddenly. The throttle valve is opened almost instantaneously and that completely.

Triggered by the sudden increase in load demand, the control offset Δ of the intake valves is reduced by closing the second intake valve earlier. As 1 can be seen, the first intake valve is closed before the load increase at low load earlier than the second intake valve. The closing times have at this time t a large control offset Δ to realize a long inlet-side opening period. This has advantages at low load.

The control offset Δ is minimized in the present case with increased load requirement, whereby the inlet-side opening duration is shortened. A shorter inlet-side opening duration should ensure the best possible filling of the at least one cylinder and thus a high torque supply at the beginning of the acceleration.

As soon as the exhaust gas turbocharger responds and generates boost pressure p _charge , the control offset Δ is then increased again as a function of this boost pressure p _charge , ie, the intake-side opening period is extended again, by closing the second intake valve later. This reduces the effective compression ratio ε _eff and prevents knocking. Part of the charge air is pushed back into the intake system with the second intake valve open. The higher the boost pressure, the later the second intake valve is closed.

The timing of the intake valves of a cylinder can be varied. 2 schematically shows in a diagram the determination of the closing time t _{intake, closing, 2 of} the second inlet valve.

In a first method step, using the engine speed n _mot and a setpoint value for the pressure p _intake, a base _{closing time} t _{intake, closing, base, 2} determined in the intake system (middle branch). In this case, the ambient pressure p _{atm is set} as the maximum permissible setpoint for the pressure p _{intake, that} in the intake system. Charge effects, if any, are therefore not taken into account.

In a second method step, using the rotational speed n _mot and the actual pressure p _intake in the intake system, an additive closing time Δt _{intake, closing, 2 is} determined and thus the charge is taken into account (lower branch).

In this case, a boost pressure difference Δp _{charge is} determined by subtracting the ambient pressure p _atm from the actual pressure p _intake in the intake system. The additive closing time Δt _{intake, closing, 2} is then determined using this _charge pressure difference Δp _charge , but only if Δp _charge > 0 applies. The second method step delivers an additive closing time Δt _{intake, closing, 2} only if the exhaust gas turbocharging generates a _charge pressure p _charge > p _atm in the intake system.

If there is a risk of knocking, the knock control of the internal combustion engine provides a Ignition retard Δ _ignition , by which the ignition must be retarded so that knocking combustion can be safely avoided.

Using the current rotational speed n _mot and the spark retard Δ supplied by the knock control is _ignition then a closing timing retard .DELTA.t _{intake, closing, knock} detected to the second intake valve is to be for the purpose of lowering the effective compression ratio later closed (upper arm). In this case, the _ignition retard Δ ref is used as an input signal through a low-pass filter 1 and a delay element 2 (1 / z) directed. This takes into account the different response of a spark timing and a variable valve train. There should be enough time to adjust the valve train in order to adjust the closing time of the second intake valve. The delay ensures that the knock control due to the adjustment of the closing time of the second intake valve, the originally envisaged ignition timing Δ _ignition for no longer considered necessary. A higher efficiency is the result.

A closing time retardation Δt _{intake, closing, knock} , by which the second intake valve is to be closed later, is then additionally taken into account in the calculation of the closing time t _{intake, closing, 2} , ie added (upper arm).

The closing time t _{intake, closing, 2} is calculated by adding the base closing time, the additive closing time and the closing time retard with t _{intake, closing, 2} = tintake, closing, base, 2 ^{+ Δt} intake, closing, 2 ^{+ Δt} intake , closing, knock ^.

LIST OF REFERENCE NUMBERS

1

 Low Pass Filter

2

 delay

Δ

 tax offset

Δ _ignition

 spark retard

ε _eff

 effective compression ratio

_geo

 geometric compression ratio

° KWn.u.T

 Degree crank angle after the bottom dead center of the charge cycle

n _mot

 Speed of the internal combustion engine

p _atm

 ambient pressure

p _charge

 boost pressure

Δp _charge

 Boost pressure difference

p _intake

 Pressure in the intake system, actual value

p _{intake, of}

 Setpoint for the pressure in the intake system

t _{intake, closing, 2}

 Closing time of the second inlet valve

t _{closing, 2}

 Closing time of the second inlet valve

t _{closing, 1}

 Closing time of the first inlet valve

t _{intake, closing, base, 2}

 Base closing time

Δt _{intake, closing, 2}

 additive closing time

Δt _{intake, closing, knock}

 Closing time retard

QUOTES INCLUDE IN THE DESCRIPTION

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

Cited patent literature

• DE 102011104837 A1 [0003]
• DE 102010008958 A1 [0032]

Claims (19)

A supercharged spark-ignition internal combustion engine with - at least one cylinder head with at least one cylinder, each cylinder having at least two inlet openings for supplying charge air via the intake system and at least one outlet opening for discharging the exhaust via Abgasabführsystem, - at least one throttle valve, which is arranged in the intake system and the load control serves, - at least one exhaust gas turbocharger, each exhaust gas turbocharger comprising a arranged in Abgasabführsystem turbine and a compressor disposed in the intake compressor, and - a knock control, which provides a necessary to avoid knock spark retard Δ _ignition as an output signal and provides, characterized in that - at least two at least partially variable valve trains are provided with at least two valves which are movable between a valve closed position and a valve open position to the at least two inlet openings with at least two actuators to open the valves against the biasing force of the valve spring means, each actuator comprising a cam disposed on a camshaft, with at least two actuators to unlock the at least one cylinder, with valve spring means for biasing the valves towards the valve closing position; which can be brought into engagement with at least one cam follower element when the camshaft rotates, whereby the associated valve can be actuated, and the cams of the at least two actuators of the at least two at least partially variable valve trains are rotatable relative to each other, and - each cylinder has a geometric compression ratio ε _geo ≥ 11 having. Supercharged spark-ignition internal combustion engine according to claim 1, characterized in that the cams are arranged on an at least two-part camshaft comprising at least two mutually rotatable camshaft sections, wherein at least one cam is arranged on a first camshaft section and at least one cam is arranged on a second camshaft section. Supercharged spark-ignition internal combustion engine according to claim 2, characterized in that the at least two-part camshaft as the first camshaft section comprises a hollow shaft and the second camshaft section comprises a shaft rotatably arranged in the hollow shaft. Charged spark-ignition internal combustion engine according to one of the preceding claims with a crankshaft, which is at least drive-connected to the camshaft, characterized in that the cams are rotatable relative to the crankshaft. Supercharged spark-ignition internal combustion engine according to one of the preceding claims, characterized in that the cams have the same contour. Supercharged spark-ignition internal combustion engine according to one of the preceding claims, characterized in that each cylinder is equipped with a direct injection for the purpose of supplying fuel. Supercharged spark-ignition internal combustion engine according to one of the preceding claims, characterized in that each cylinder has a geometric compression ratio ε _geo ≥ 11.5. Supercharged spark-ignition internal combustion engine according to one of the preceding claims, characterized in that each cylinder has a geometric compression ratio ε _geo ≥ 12. A method of operating a supercharged spark-ignition internal combustion engine according to any one of the preceding claims, wherein each cylinder has two intake ports for supplying charge air via intake system and each piston belonging to a cylinder oscillates between a top dead center and a bottom dead center, characterized in that at a risk of knocking at least the second inlet valve is closed later and after the bottom dead center. A method according to claim 9, characterized in that a closing timing _retardation Δt _{intake, closing, knock} , by which the second intake valve is to be closed later, using a current speed n _mot and a Zündspätverstellung Δ _ignition supplied by the knock control is determined. A method according to claim 9 or 10, characterized in that, starting from a lower load in which the cams belonging to the two intake ports of each cylinder are rotated against each other in such a way that a first intake valve is actuated earlier than a second one to form a control offset Δ Intake valve, in the event of an abrupt increase in load demand - the throttle valve is opened further, - the control offset Δ is reduced by the second intake valve being actuated earlier, and - the control offset Δ as a function of exhaust gas turbocharging in the intake system generated boost pressure is increased again by the second intake valve is actuated later and as soon as the at least one exhaust gas turbocharger generates boost pressure. A method according to claim 11, characterized in that the throttle valve is fully opened at sudden increased load request. A method according to claim 11 or 12, characterized in that the control offset Δ is minimized as part of the reduction. Method according to one of claims 11 to 13, characterized in that the control offset Δ is additionally reduced by the fact that the first inlet valve is actuated later. Method according to one of claims 11 to 14, characterized in that at the lower load before the increased load request, the first intake valve is closed before the bottom dead center and the second intake valve after the bottom dead center. Method according to one of claims 11 to 15, characterized in that the control offset Δ is reduced by the fact that the second inlet valve is closed before the bottom dead center. Method according to one of claims 9 to 16, characterized in that a closing time t _{intake, closing, 2} , to which the second inlet valve is closed, is calculated by - in a first method step, a base _{closing time} t _{intake, closing, base, 2} below Using a current speed n _mot and a current setpoint for the pressure p _{intake, which is} determined in the intake system, - in a second method step, an additive closing time .DELTA.t _{intake, closing, 2} using a current speed n _mot and a current actual value for the Pressure p _intake in the intake system is determined, and - in a third method step, the closing time t _{intake, closing, 2 is} calculated by adding the base closing time and the additive closing time with t _{intake, closing, 2} = t _{intake, closing, base, 2} + Δt _{intake, closing, 2} . A method according to claim 17, characterized in that - for the first method step, an ambient pressure p _atm is set, which is used as the maximum permissible setpoint for the pressure p _intake, which is used in the intake system and by the setpoint for the pressure p _{intake of the} im Intake system is limited in determining the base closing time. A method according to claim 17 or 18, characterized in that - for the second method step, an ambient pressure p _{atm is} given, which is subtracted to determine a _charge pressure difference Δp _charge from the instantaneous actual value for the pressure p _intake in the intake system, wherein the additive closing time Δ t _{intake, closing, 2} is determined using this _charge pressure difference Δp _charge , if Δp _charge > 0.

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