DE102019113748A1 - Internal combustion engine with variable exhaust valve actuation for the temporary realization of relatively hot exhaust gas and iAGR - Google Patents

Abstract

A method for operating an internal combustion engine provides that during a heating operation of the internal combustion engine in order to achieve a relatively high temperature of the exhaust gas discharged from a combustion chamber of an internal combustion engine of the internal combustion engine, the valve opening of an exhaust valve occurring during an exhaust stroke of the internal combustion engine is set smaller compared to normal operation of the internal combustion engine becomes. Furthermore, it is provided that at least temporarily during the heating operation to achieve internal exhaust gas recirculation (iAGR) by retaining exhaust gas in the combustion chamber, the exhaust valve is closed before the end of the exhaust stroke. In addition or as an alternative, it can be provided that the exhaust valve is additionally opened during the intake stroke to achieve internal exhaust gas recirculation by sucking exhaust gas back into the combustion chamber. By combining the temporary generation of a relatively hot exhaust gas on the one hand with an iAGR on the other hand, particularly low pollutant emissions from the internal combustion engine, in particular after a cold start, can be achieved.

Description

The invention relates to an internal combustion engine with a four-stroke internal combustion engine which forms at least one combustion chamber, with a fresh gas line for supplying fresh gas to the internal combustion engine and with an exhaust gas line for removing exhaust gas from the internal combustion engine, with fresh gas being introduced into the combustion chamber by means of at least one the intake valve assigned to the combustion chamber can be controlled and the discharge of exhaust gas from the combustion chamber and into the exhaust system can be controlled by means of at least one exhaust valve of the combustion chamber, the exhaust valve being operable by means of a valve actuation device which is designed such that the valve opening of the exhaust valve is opened during a The exhaust stroke of the internal combustion engine can be changed.

Such an internal combustion engine is from DE 10 2004 016 386 B4 known. Specifically, a method for operating such an internal combustion engine is disclosed there, in which, after a cold start of the internal combustion engine, an exhaust valve assigned to a combustion chamber of a four-stroke internal combustion engine is actuated with a valve opening that is relatively small compared to normal operation. As a result, the gas exchange work is increased and exhaust gas is thus discharged into an exhaust line at a relatively high temperature via the correspondingly opened exhaust valve, whereby the exhaust gas is intended to cause an exhaust gas aftertreatment device integrated in the exhaust line to be heated as quickly as possible.

A reduction in nitrogen oxide emissions from an internal combustion engine can be achieved on the one hand by means of measures within the engine, in particular by means of exhaust gas recirculation (EGR). Such exhaust gas recirculation can lower the peak temperatures occurring in the combustion chambers during combustion, which leads to the desired reduction in nitrogen oxides (NO _x ) in the exhaust gas. In addition to an "external" EGR, which has so far mainly been used in diesel internal combustion engines and in which exhaust gas is returned by means of an exhaust gas recirculation line connecting the exhaust gas line to the fresh gas line of the internal combustion engine, the implementation of an "internal" EGR is also known, especially in Otto internal combustion engines see. DE 10 2005 053 940 A1 ), in which exhaust gas is returned from the exhaust system into the combustion chambers of the internal combustion engine by influencing the valve timing by means of a variable valve drive to achieve valve overlap between the intake and exhaust valves.

Furthermore, measures outside the engine, in particular so-called SCR procedures, i.e. Method for selective catalytic reduction, to reduce nitrogen oxide emissions can be provided. SCR processes are based on converting the nitrogen oxides contained in the exhaust gas into end products that are not declared as pollutants, such as nitrogen, carbon dioxide and water, using a reducing agent introduced into the exhaust gas, in particular ammonia.

The invention was based on the object of specifying an internal combustion engine which, in particular after a cold start, is characterized by the lowest possible pollutant emissions.

This object is achieved by means of an internal combustion engine according to patent claim 1. A method for operating such an internal combustion engine is the subject matter of patent claim 9. Advantageous embodiments of the internal combustion engine according to the invention and preferred embodiments of the method according to the invention are the subject matter of the further patent claims and / or result from the following description of the invention.

According to the invention, an internal combustion engine, in particular an internal combustion engine for a motor vehicle, is provided. This includes at least one four-stroke internal combustion engine that forms at least one combustion chamber, a fresh gas line for supplying fresh gas to the internal combustion engine and an exhaust line for removing exhaust gas from the internal combustion engine, an exhaust gas aftertreatment device preferably being integrated into the exhaust line. The introduction of fresh gas into the combustion chamber can be controlled by means of at least one inlet valve assigned to the combustion chamber and the discharge of exhaust gas from the combustion chamber and into the exhaust system can be controlled by means of at least one outlet valve assigned to the combustion chamber, the outlet valve being actuatable by means of a valve actuating device designed in this way is that during operation of the internal combustion engine by means of this, the valve opening of the exhaust valve can be changed during the exhaust stroke. In particular, the valve opening can be changed in such a way that at least one relatively large valve opening and one relatively small valve opening (which is greater than zero) can be set. According to the invention, the valve actuation device is additionally designed such that, with a defined valve opening of the outlet valve, the opening period of the outlet valve can be changed (i.e. the period in which the valve opening is performed in relation to, for example, the LW-OT can be changed) and / or the outlet valve can also be changed can be opened during the intake stroke.

A method according to the invention for operating such an internal combustion engine provides that temporarily, during a heating operation of the internal combustion engine in order to achieve a relatively high temperature of the exhaust gas discharged from the combustion chamber, the valve opening of the exhaust valve occurring during an exhaust stroke of the internal combustion engine is set smaller in comparison to normal operation of the internal combustion engine becomes. Furthermore, it is provided that (at least temporarily) during the heating operation to achieve an internal exhaust gas recirculation (iAGR) by retaining exhaust gas in the combustion chamber, the exhaust valve is closed before the end of the exhaust stroke. The outlet valve can in particular be closed earlier than it is closed during normal operation or at least during normal operation in which no iAGR is carried out. Provision can preferably be made for the outlet valve to be closed at least 5 ° CA, preferably at least 15 ° CA before the LW-OT during heating operation.

In addition or as an alternative, a method according to the invention can provide that the exhaust valve is additionally opened during the intake stroke in order to achieve internal exhaust gas recirculation by sucking exhaust gas back into the combustion chamber. The additional opening of the outlet valve can preferably take place as part of a so-called second event, i.e. the exhaust valve, after it has already been closed during the exhaust stroke, is opened again in the subsequent intake stroke. In principle, however, it is also possible to postpone the closing of the exhaust valve late enough that it is only closed (to a relevant extent) during the intake stroke and the opening process that begins in the exhaust stroke does not end until the subsequent intake stroke. For this purpose, collisions between the still open exhaust valve and a piston delimiting the combustion chamber in its TDC would have to be avoided by, in particular, a corresponding structural design of the internal combustion engine.

For the automated implementation of a method according to the invention, an internal combustion engine according to the invention can have a correspondingly configured control device.

The invention is based on the knowledge that by combining the fundamentally from the DE 10 2004 016 386 B4 known measure for the temporary generation of a relatively hot exhaust gas on the one hand with an iAGR on the other hand particularly low pollutant emissions of the internal combustion engine, in particular after a cold start, can be implemented. The relatively hot exhaust gas, which is generated by a relatively small valve opening during heating operation, is intended in particular to warm up the exhaust gas line and in particular the exhaust gas aftertreatment device preferably integrated into the exhaust line as quickly as possible. This can be done in particular with the aim of making the exhaust gas aftertreatment device effective as quickly as possible after a cold start of the internal combustion engine. The iAGR, on the other hand, can be used in particular to keep the pollutant and especially nitrogen oxide raw emissions, i.e. the quantities of pollutants and especially nitrogen oxides contained in the exhaust gas transferred from the combustion chamber into the exhaust system, as low as possible, which is particularly important after a cold start of the internal combustion engine because then the exhaust gas aftertreatment device integrated in the exhaust system or at least individual components thereof has not yet reached their so-called light-off temperature, from which a sufficiently high level of effectiveness for reducing pollutants can be assumed. The lowest possible raw pollutant emissions are therefore particularly relevant at this point in time for the total quantities of pollutants emitted by the internal combustion engine. The combination according to the invention of the fastest possible warming up of the exhaust gas aftertreatment device and at the same time the lowest possible raw pollutant emissions can accordingly lead to relatively low total pollutant emissions from an internal combustion engine according to the invention.

A “cold start” of an internal combustion engine according to the invention is taken to mean a start-up of the internal combustion engine in which the exhaust gas aftertreatment device as a whole or at least individual components (in particular one or more SCR catalysts) has / have a temperature which is below a limit temperature of 120 ° C and which in particular can correspond essentially (ie ± 5 ° C) to the ambient temperature. In this case, the temperature is at least significantly below the light-off or light-off temperature of one or more SCR catalytic converters of the exhaust gas aftertreatment device, from which the effectiveness of this / these SCR catalytic converters with reduction rates of at least 90, for example % is to be assumed.

The use of an internal combustion engine according to the invention is preferably provided to carry out an iAGR by retaining exhaust gas in the combustion chamber during heating operation. Compared to an iAGR by sucking exhaust gas back into the combustion chamber, this has the additional advantage that the exhaust gas retained in the combustion chamber has a relatively high temperature, which in turn has a positive effect on achieving the highest possible temperature in the Exhaust tract transferred exhaust gas and thus affects the warming up of the exhaust gas aftertreatment device. Exhaust gas that was initially ejected into the exhaust system and then fed back into the combustion chamber as part of an iAGR by sucking back, has already cooled to a relevant extent.

The internal combustion engine of an internal combustion engine according to the invention can in particular be a (self-igniting and quality-controlled) diesel engine. However, there is also the possibility that the internal combustion engine is a gasoline engine (spark ignition and quantity-controlled) or a combination of diesel and gasoline engine, e.g. an internal combustion engine with homogeneous compression ignition. The internal combustion engine can be operated with liquid fuel (i.e. with diesel fuel or gasoline) as well as with a gaseous fuel (in particular with natural gas (CNG), LNG or LPG) or another fuel that mainly consists of hydrogen or hydrocarbons .

The internal combustion engine of an internal combustion engine according to the invention can preferably form a plurality of combustion chambers. Likewise, it can preferably be provided that a plurality of inlet valves and / or outlet valves are assigned to each of these combustion chambers. It can be provided that the valve opening can be changed during the exhaust stroke for all or only individual ones, in particular also for only a single one of the exhaust valves assigned to each combustion chamber.

A change in the valve opening of the exhaust valve in an internal combustion engine according to the invention can preferably be done by shifting the start of opening during the exhaust stroke (preferably in combination with a change in the duration of the opening, ie the end of opening is not shifted or is shifted to a different extent than the start of opening) and / or Variation of the opening stroke (ie the maximum opening travel of the exhaust valve) can be realized.

Advantageously, to vary the valve opening of the outlet valve, a switching device can be used which has at least two and preferably exactly two discrete switching positions which differ with regard to the valve opening of the outlet valve caused by the valve actuating device. Such a switching device can be distinguished by a relatively simple structural design, in particular in comparison to an adjusting device that can also be used, by means of which the valve opening of the outlet valve can be continuously adjusted.

Particularly preferably it can be provided that the valve actuation device comprises a camshaft provided for direct or indirect actuation of the exhaust valve and the switching device comprises a rocker arm that can be switched with regard to the transmission ratio and that transmits a deflection by a cam of the camshaft (to different degrees) to the exhaust valve. Additionally or alternatively, the switching device can also comprise different cams of the camshaft, the different cams alternatively being able to be brought into operative connection with the exhaust valve.

When carrying out a method according to the invention, it can preferably be provided that the exhaust valve is opened between 100 ° CA before LW-OT (KW: crankshaft angle) and 50 ° CA before LW-OT during the heating operation of the internal combustion engine with iAGR by retaining exhaust gas in the combustion chamber and, further preferably between 30 ° CA before LW-OT and 5 ° CA before LW-OT, in particular at 20 ° CA before LW-OT. If, on the other hand, the internal combustion engine is heated without iAGR or with iAGR by sucking exhaust gas back into the combustion chamber, the exhaust valve can preferably be opened between 70 ° CA before LW-OT (KW: crankshaft angle) and 50 ° CA before LW-OT and, furthermore, is preferred between 20 ° CA before LT-OT and 0 ° CA before LT-OT, especially at 10 ° CA before LT-OT. In all cases it can furthermore preferably be provided that the opening stroke of the exhaust valve during the heating operation of the internal combustion engine is between 1 mm and 2 mm. The valve actuation device of an internal combustion engine according to the invention can be brought into corresponding actuation positions for this purpose.

In addition, it can preferably be provided when carrying out a method according to the invention that during normal operation of the internal combustion engine the exhaust valve is opened between 210 ° CA before LW-OT and 190 ° CA before LW-OT, in particular at 200 ° CA before LW-OT, and, furthermore, it is preferred to close between 20 ° CA before LW-TDC and 0 ° CA before LW-TDC, in particular at 10 ° CA before LW-TDC. Furthermore, it can preferably be provided for normal operation that the opening stroke during normal operation of the internal combustion engine is between 8 mm and 10 mm, in particular 9 mm.

These details of the control times can relate to a completely closed position of the exhaust valves or to a lift threshold of 1 mm or 0.5 mm, from the one that is effective Opening of the exhaust valves can be assumed. In particular, a stroke threshold of 1 mm for an opening stroke of at least 2 mm and a stroke threshold of 0.5 mm for an opening stroke of less than 2 mm can be applied.

To set the iAGR during heating operation, i.e. In order to adjust the amount of exhaust gas retained in the combustion chamber or returned to it to a defined extent, a method according to the invention can preferably provide that the closing time of the exhaust valve and / or the valve actuation occurring during the intake stroke (i.e. the valve opening and / or the Opening period) is changed accordingly. For this purpose, an internal combustion engine according to the invention can preferably comprise an exhaust phaser which is set up to adjust the opening period of the exhaust valve.

According to a preferred embodiment of an internal combustion engine according to the invention, it can be provided that at least two or, preferably, exactly two outlet valves are assigned to the combustion chamber, the valve opening of which can be changed by means of the valve actuation device. In such an internal combustion engine, it can preferably be provided that, during the heating operation of the internal combustion engine, the valve opening occurring during an exhaust stroke for (at least) a first of the exhaust valves is set smaller in comparison to normal operation, while (at least) a second of the exhaust valves is set during the heating operation actuated a zero stroke, ie is not opened during the exhaust stroke. Compared to the alternative, which can also be implemented, in which all exhaust valves (per combustion chamber) are actuated with a valve opening that is smaller than in normal operation during heating operation, only part of the basically available exhaust gas can be expelled from the combustion chamber Exhaust valves a particularly high gas exchange work and thus a particularly high temperature of the exhaust gas can be realized.

According to a preferred development of such an internal combustion engine according to the invention with at least or exactly two exhaust valves, the internal combustion engine further comprising an exhaust phaser, it can be provided that the opening periods of the two exhaust valves (or of two of these exhaust valves) can be adjusted relative to one another by means of the exhaust phaser are. Such an internal combustion engine can in particular make it possible to effect an iAGR in an adjustable manner even during normal operation, in that the (preferably the same) opening duration of the exhaust valves is shorter than the exhaust stroke during normal operation and, to achieve normal operation with adjustable iAGR, by retaining exhaust gas in the combustion chamber, the opening periods of the exhaust valves are set offset relative to one another to a variable extent or the exhaust valves are actuated with a variable phase offset.

According to a further preferred embodiment of an internal combustion engine according to the invention, it can be provided that the valve actuation device is designed in such a way that it can be used to change the start of opening of the intake valve during the intake stroke when the internal combustion engine is in operation. This can in particular make it possible to open the inlet valve relatively late during the heating operation compared to normal operation (preferably with an essentially (ie with a deviation of at most ± 5 ° CA) symmetrical difference to the closing of the outlet valve in relation to the LW-OT) which can have a particularly positive effect on the acoustic performance of the internal combustion engine during heating operation. This applies in particular to achieving an iAGR by retaining exhaust gas in the combustion chamber during heating operation, because then the exhaust gas retained in the combustion chamber has already been at least partially released by the intake stroke of the piston that delimits the combustion chamber when the inlet valve (relatively late ) is opened.

Such a procedure can be implemented in a structurally advantageous manner by means of an internal combustion engine according to the invention, in which at least two or, preferably, exactly two intake valves are assigned to the combustion chamber, with an intake phaser also being provided, by means of which the opening periods of the two intake valves (or two these inlet valves) are adjustable relative to each other. This can in particular make it possible to actuate the inlet valves with an (in particular the same) opening duration, which is shorter than the intake stroke in each case, with the opening periods of the two inlet valves being adjusted to a greater extent relative to one another or the inlet valves being actuated with a phase shift during normal operation, than provided during heating operation. In particular, it can be provided that during normal operation (at least) a first of the intake valves is opened at the beginning of the intake stroke and (at least) a second one of the intake valves is closed at the end of the intake stroke, which ensures that a gas-carrying connection between the intake stroke is maintained during the entire intake stroke Combustion chamber and the fresh gas line is present. During the heating operation, however, the at least two inlet valves can preferably be closed at the same time at the end of the intake stroke, which in combination with the each relatively short opening time the relatively late opening of the inlet valves is realized.

Adjustment of the opening periods of two intake or exhaust valves can preferably be implemented by using double camshafts, which are also referred to as cam-in-cam camshafts. These consist of an outer shaft and an inner shaft mounted within the outer shaft, with both the inner and outer shafts being provided with cams for actuating the inlet or outlet valves. The cams of the inner shaft protrude through openings in the outer shaft. The inner and outer shafts can then be rotated independently of one another by means of an exhaust or intake phase adjuster and the opening periods can thereby be adjusted relative to one another if a first of the two intake or exhaust valves has a cam on the inner shaft and a second one of the intake or exhaust valves per combustion chamber A cam of the outer shaft is assigned to each combustion chamber.

The exhaust gas aftertreatment device of an internal combustion engine according to the invention can preferably comprise an NO _x storage catalytic converter and / or an oxidation catalytic converter and / or a particle filter and / or an SCR catalytic converter in order to achieve the most advantageous possible aftertreatment of the exhaust gas or to reduce the pollutants contained in the exhaust gas as comprehensively as possible to be able to realize.

The invention also relates to a motor vehicle, in particular a wheel-based and not rail-bound motor vehicle (preferably a car or a truck), with an internal combustion engine according to the invention. The internal combustion engine or the internal combustion engine thereof can in particular be provided for (direct or indirect) provision of the drive power for the motor vehicle.

The indefinite articles (“a”, “an”, “an” and “an”), in particular in the claims and in the description that generally explains the claims, are to be understood as such and not as numerals. Components specified in this way are therefore to be understood in such a way that they are present at least once and can be present several times.

• 1: in vereinfachter Darstellung eine erfindungsgemäße Brennkraftmaschine;
• 2: in vereinfachter Darstellung eine doppelte Nockenwelle und einen damit zusammenwirkenden Phasensteller für eine erfindungsgemäße Brennkraftmaschine;
• 3: Ventilerhebungskurven für die Einlassventile (gestrichelte Linienführung) und die Auslassventile (durchgehende Linienführung) sowie die Bewegungskurve eines Kolbens (strichpunktierte Linienführung) eines Verbrennungsmotors einer erfindungsgemäßen Brennkraftmaschine während eines Heizbetriebs mit iAGR;
• 4: Ventilerhebungskurven für die Einlassventile (gestrichelte Linienführung) und die Auslassventile (durchgehende Linienführung) sowie die Bewegungskurve eines Kolbens (strichpunktierte Linienführung) eines Verbrennungsmotors einer erfindungsgemäßen Brennkraftmaschine während eines Heizbetriebs ohne iAGR;
• 5a und 5b: Ventilerhebungskurven für die Einlassventile (gestrichelte Linienführung) und die Auslassventile (durchgehende Linienführung) sowie die Bewegungskurve eines Kolbens (strichpunktierte Linienführung) eines Verbrennungsmotors erfindungsgemäßer Brennkraftmaschinen gemäß zwei unterschiedlichen Ausführungsformen während eines Normalbetriebs ohne iAGR; und
• 6: Ventilerhebungskurven für die Einlassventile (gestrichelte Linienführung) und die Auslassventile (durchgehende Linienführung) sowie die Bewegungskurve des Kolbens (strichpunktierte Linienführung) des Verbrennungsmotors der Brennkraftmaschine gemäß der 5b während eines Normalbetriebs mit iAGR.

The invention is explained in more detail below with reference to the exemplary embodiments shown in the drawings. In the drawings shows:

• 1 : an internal combustion engine according to the invention in a simplified representation;
• 2 : in a simplified representation a double camshaft and a phase adjuster interacting therewith for an internal combustion engine according to the invention;
• 3 : Valve lift curves for the inlet valves (dashed lines) and the exhaust valves (continuous lines) and the movement curve of a piston (dash-dotted lines) of an internal combustion engine of an internal combustion engine according to the invention during a heating operation with iAGR;
• 4th : Valve lift curves for the inlet valves (dashed lines) and the exhaust valves (continuous lines) and the movement curve of a piston (dash-dotted lines) of an internal combustion engine of an internal combustion engine according to the invention during a heating operation without iAGR;
• 5a and 5b : Valve lift curves for the inlet valves (dashed lines) and the exhaust valves (continuous lines) and the movement curve of a piston (dash-dotted lines) of an internal combustion engine of internal combustion engines according to the invention according to two different embodiments during normal operation without iAGR; and
• 6th : Valve lift curves for the inlet valves (dashed lines) and the exhaust valves (continuous lines) and the movement curve of the piston (dash-dotted lines) of the internal combustion engine according to FIG 5b during normal operation with iAGR.

The 1 shows a schematic representation of an internal combustion engine according to the invention. This includes a four-stroke internal combustion engine 1 , the example in the form of a reciprocating engine with four cylinders arranged in series 2 is trained. The cylinders 2 limit with piston guided in it 3 and a cylinder head each have a combustion chamber 4th . These combustion chambers 4th is in operation of the internal combustion engine 1 Fresh gas through a fresh gas line 5 fed. This fresh gas is primarily air which is sucked in from the environment and which is then passed through a compressor (not shown). This compressor is part of an exhaust gas turbocharger, which continues to be an exhaust gas turbine 6th includes, which is in an exhaust line 7th the internal combustion engine is integrated. Exhaust gas that is produced during the combustion of mixture quantities that are generated from the fresh gas and from, for example, directly via fuel injectors (not shown) into the combustion chambers 4th injected fuel is created via the exhaust system 7th discharged and flows through the exhaust gas turbine 6th and then an exhaust gas aftertreatment device of the internal combustion engine.

Each of the combustion chambers 4th are in accordance with the 1 illustrated embodiment example two inlet valves 8th and two exhaust valves 9 assigned, via a valve operating device 10 which, for example, each have a double camshaft 11 (see. 2 ) for the inlet valves on the one hand 8th and on the other hand the exhaust valves 9 can include, operated. In operation of the internal combustion engine 1 become the pistons 3 due to the combustion processes in the combustion chambers 4th moves in an oscillating manner between a top dead center (TDC) and a bottom dead center (BDC), whereby the piston 3 alternately perform a gas exchange stroke, which includes an exhaust stroke and an intake stroke, and a power stroke, which includes a compression stroke and an expansion stroke. The pistons 3 are connected to a crankshaft (not shown) via connecting rods (not shown), with the oscillating movements of the pistons 3 cause the crankshaft to rotate. Depending on a crankshaft angle in the gas exchange stroke of the individual pistons 3 become the inlet valves 8th and the exhaust valves 9 by means of the valve operating device 10 opened and closed at defined valve control times, as described in the 3 to 6th is shown. With LW-OT the top dead center of the individual pistons is 3 marked during the respective gas exchange stroke.

According to the 2 can have a double camshaft 11 , as in an internal combustion engine according to the 1 can be used, an outer shaft 12 with several over the length of the outer shaft 12 distributed cams 13 that are used to actuate a first exhaust valve 9 or inlet valve 8th per combustion chamber 4th of the internal combustion engine 1 are provided. Inside the outer shaft 12 is an inner shaft 14th rotatably mounted. Also on the outside of the inner shaft 14th are multiple cams 18th over the length of the inner shaft 14th arranged distributed, each actuating a second exhaust valve 9 or inlet valve 8th per combustion chamber 4th serve. At one end is the camshaft 11 with an inlet or outlet phaser 15th connected. The phaser 15th includes two individual actuators, one of which is the first with the inner shaft 14th and a second with the outer shaft 12 the camshaft 11 is rotatably connected. The individual actuators can rotors in a known manner 16 have with wings that with walls of a housing 17th of the phase adjuster 15th Limit pressure chambers. The sizes of the pressure chambers are determined by a rotation of the respective rotor 16 changeable. This rotation is realized by all or individual, the respective rotors 16 assigned pressure chambers are filled with a hydraulic fluid (under a defined pressure). By turning the two rotors 16 becomes a phase angle with respect to one with the housing 17th connected drive wheel 19th set that of the crankshaft of the internal combustion engine 1 is driven in rotation. This phase angle is created by the rotatable connection of the rotors 16 with the respective interior 14th or outer shaft 12 on the corresponding cams 13 , 18th transmitted, reducing the opening periods of the cams 13 , 18th actuated inlet valves 9 or exhaust valves 8th to be changed.

The exhaust gas aftertreatment device of the internal combustion engine comprises a first exhaust gas aftertreatment device viewed in the flow direction of the exhaust gas 20th , which can be an oxidation catalyst or a NO _x storage catalyst or a combination of such an oxidation catalyst and such a NO _x storage catalyst.

This first exhaust aftertreatment device 20th a second exhaust gas aftertreatment device in the form of a particulate filter closes 21st at. It can be provided that the particle filter 21st or the filter body forming this has a catalytically active coating, whereby the particle filter 21st simultaneously represents a first SCR catalytic converter of the exhaust gas aftertreatment device. The presence of reducing agent in the exhaust gas, which is required for the catalytic reduction of pollutants contained in the exhaust gas, in particular nitrogen oxides, which filters the particle filter that acts as the first SCR catalytic converter 21st flowed through is by means of an upstream of the particle filter 21st arranged, first metering device 22nd realized for such a reducing agent. The reducing agent can in particular be ammonia or an ammonia-containing solution. Between the first metering device 22nd and the particle filter 21st is a first mixing device 23 arranged, which can be designed for example in the form of flow guide elements that cause turbulence in the flow of the exhaust gas already mixed with the reducing agent.

The exhaust gas aftertreatment device comprises, in an arrangement downstream of the particulate filter 21st , a (further) SCR catalytic converter as a third exhaust gas aftertreatment device 24 . The SCR catalytic converter 24 is a second metering device in an arrangement upstream thereof 25th for a reducing agent and, in an arrangement between this second metering device 25th and the SCR catalytic converter 24 , a second mixing device 26th assigned. This second metering device 25th can be particularly useful or necessary when, as described in the 1 is shown between the particulate filter 21st and this second metering device 25th an exhaust gas recirculation line 27 from the exhaust system 7th goes off, via which, if necessary, part of the exhaust gas in the fresh gas line 5 can be traced back. If such an external exhaust gas recirculation is carried out, it should be avoided that the exhaust gas recirculated in the process contains unconverted reducing agent. Dosing by means of the first dosing device 22nd should therefore take place at least when external exhaust gas recirculation is carried out in such a way that downstream of the particulate filter 21st If possible, no more reducing agent is contained in the exhaust gas. This consequently requires an additional introduction of reducing agent into the exhaust gas upstream of the further SCR catalytic converter 24 in order to be able to achieve a reduction in pollutants through this.

The last component in the flow direction or the fourth exhaust gas aftertreatment device of the exhaust gas aftertreatment device is a blocking catalyst 28 intended. This is an oxidation catalytic converter that converts reducing agents (in particular ammonia into N ₂ and H ₂ O) that is in the SCR catalytic converter 24 has not been implemented in order to avoid release of this reducing agent into the environment.

In order to reach the respective light-off temperature of the exhaust gas aftertreatment devices as quickly as possible after a cold start of the internal combustion engine 20th , 21st , 24 , 28 and in particular the particulate filter which also acts as the first SCR catalytic converter 21st and the (further) SCR catalytic converter 24 and thus to implement the pollutants contained in the exhaust gas as quickly as possible, provision is made for the internal combustion engine to be operated in a heating mode after a cold start by according to the 3 and 4th one or both of each of the combustion chambers 4th associated exhaust valves 9 can be actuated with a significantly smaller valve opening (this corresponds to the area enclosed by the valve lift curve) than is provided for in normal operation (cf. 5 and 6th ). Will only one of the exhaust valves during heating operation 9 per combustion chamber 4th actuated with a relatively small valve opening, it can preferably be provided that the associated second outlet valve 9 is operated with a zero stroke or kept completely closed.

The relatively small valve opening of the individual combustion chambers 4th associated exhaust valves 9 is implemented according to the exemplary embodiment in that on the one hand the opening start is shifted late or closer in the direction of LW-OT compared to normal operation and on the other hand the opening stroke is reduced. As a result of the relatively late start of opening of the opening movements of the exhaust valves 9 takes place in the exhaust stroke initially (with the exhaust valves closed 9 ) a relatively strong compression in the combustion chambers 4th contained exhaust gases, which is already associated with a heating of these exhaust gases. Will the exhaust valves 9 then opened, this relatively strongly compressed exhaust gas flows through the exhaust valves, which are only opened with a relatively small opening stroke 9 This results in high flow velocities that contribute to further heating of the exhaust gas. By opening the exhaust valves 9 with relatively small valve openings, relatively hot exhaust gas will consequently enter the exhaust system 7th and thus the fastest possible heating of the exhaust gas aftertreatment device.

The internal combustion engine is provided at least temporarily during heating operation 1 with iAGR by retaining exhaust gas in the combustion chambers 4th operate, reducing the raw nitrogen oxide emissions of the internal combustion engine 1 can be kept relatively low. This is achieved by means of an outlet phaser 15th the opening period of the exhaust valve or valves to be opened 9 is set so that this (s) are closed well before the end of the exhaust cycle (cf. 3 ). In comparison, the 4th a heating operation of the internal combustion engine without implementing an iAGR, wherein the one or more exhaust valves 9 is / are essentially closed exactly at the end of the exhaust stroke.

According to the 3 intended closing of the outlet valve or valves 9 well before the end of the exhaust stroke, some of the exhaust gas is in the combustion chamber 4th held back. The 3 shows only one of a large number of possible positions of the outlet phase adjuster 15th . Through different settings of the outlet phaser 15th and consequently by closing the exhaust valve or valves 9 at different times before the end of the exhaust stroke, the amount of in the combustion chamber 4th retained exhaust gas and consequently the iAGR can be specifically adjusted.

To achieve an advantageous or inconspicuous noise behavior of the combustion engine during heating operation with iAGR 1 to realize it is intended that the two inlet valves 8th per combustion chamber 4th are each operated with an opening period that is shorter than the intake stroke, the intake valves then being opened at the same time 8th be opened well after the start of the intake stroke (cf. 3 and also 6th ). This achieves that in the combustion chamber 4th remaining exhaust gas due to the piston already performing the intake stroke 3 was relaxed when the intake valves 8th be opened. Will the internal combustion engine 1 on the other hand operated without iAGR (cf. 4th and 5 ), if possible, the entire intake stroke should be used to introduce fresh gas into the combustion chamber. This is achieved by reducing the opening periods by means of a double camshaft 11 actuated inlet valves so relatively are adjusted to each other that a first inlet valve 8th per combustion chamber 4th opened right at the beginning of the intake stroke and a second intake valve 8th per combustion chamber 4th is opened later in such a way that it is not closed again until the end of the intake stroke.

The 5a , 5b and 6th show valve lift curves of the intake valves 8th and the exhaust valves 9 internal combustion engines according to the invention during normal operation. Such normal operation is provided as soon as there is sufficient heating of at least one, several or all of the exhaust gas aftertreatment devices 20th , 21st , 24 , 28 the exhaust gas aftertreatment device has been reached. In normal operation, the valve opening is the outlet valves 9 significantly larger than in the heating mode of the internal combustion engine. This serves to minimize the gas exchange work of the internal combustion engine as much as possible, which has an advantageous effect on the efficiency and thus the fuel consumption of the internal combustion engine 1 affects. In the internal combustion engine according to 5a become both exhaust valves 9 actuated with identical valve lift curves, with the opening duration extending over the entire exhaust stroke. With such an internal combustion engine, no iAGR is possible during normal operation. Such an iAGR during normal operation, on the other hand, can be implemented with an internal combustion engine in which according to FIGS 5b and 6th the two exhaust valves 9 per combustion chamber 4th are each operated with an opening duration that is shorter than the exhaust stroke, with the exhaust valves that are then open at the same time being closed well before the end of the exhaust stroke in order to achieve an iAGR (as large as possible) (cf. 6th ). If, on the other hand, the combustion engine is operated without iAGR (cf. 5b) , are the opening periods of the means of a double camshaft 11 actuated exhaust valves 9 so set offset relative to each other that a first outlet valve 9 per combustion chamber 4th opened right at the beginning of the exhaust stroke and a second exhaust valve 9 per combustion chamber 4th is opened later in such a way that it is only closed again at the end of the exhaust stroke. The 5b and 6th do not show the end of operations for the realization of any iAGR (cf. 5b) or a maximum iAGR (cf. 6th ). Using the exhaust phaser 15th In principle, any operating position between these operating end positions can be set and thereby the iAGR or the amount of in the combustion chambers 4th retained exhaust gas can be adjusted.

The actuation of the inlet valves 8th in normal operation of the internal combustion engine without (cf. 5b) or with iAGR (cf. 6th ) corresponds to the strategy already described for a heating operation of the internal combustion engine without iAGR (cf. 4th ) or with iAGR (cf. 3 ).

Switching between heating operation and normal operation of the internal combustion engine can preferably take place by means of switchable rocker arms (not shown), which advantageously have a double camshaft 15th can be combined.

List of reference symbols

1

(Four-stroke) combustion engine

2

cylinder

3

piston

4th

Combustion chamber

5

Fresh gas line

6

Exhaust gas turbine

7th

Exhaust system

8th

Inlet valve

9

outlet valve

10

Valve actuation device

11

(double) camshaft

12

Outer shaft of the camshaft

13

Outer shaft cams

14th

Inner shaft of the camshaft

15th

(Inlet or outlet) phaser

16

Phaser rotor

17th

Housing of the phase adjuster

18th

Inner shaft cams

19th

Drive wheel of the phaser

20th

first exhaust gas aftertreatment device / oxidation catalytic converter / NO _x storage catalytic converter

21st

second exhaust aftertreatment device / particulate filter / first SCR catalyst

22nd

first dosing device

23

first mixing device

24

third exhaust gas aftertreatment device / (further) SCR catalytic converter

25th

second dosing device

26th

second mixing device

27

Exhaust gas recirculation line

28

fourth exhaust aftertreatment device / slip catalyst

QUOTES INCLUDED IN THE DESCRIPTION

This list of the documents listed by the applicant was 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.

Patent literature cited

• DE 102004016386 B4 [0002, 0011]
• DE 102005053940 A1 [0003]

Claims (13)

Internal combustion engine with a four-stroke internal combustion engine (1) which forms at least one combustion chamber (4), with a fresh gas line (5) for supplying fresh gas to the internal combustion engine (1) and with an exhaust gas line (7) for removing exhaust gas from the internal combustion engine ( 1), whereby the introduction of fresh gas into the combustion chamber (4) can be controlled by means of at least one inlet valve (9) assigned to the combustion chamber (4) and the discharge of exhaust gas from the combustion chamber (4) by means of at least one outlet valve assigned to the combustion chamber (4) (9) is controllable, wherein the outlet valve (9) can be actuated by means of a valve actuation device (10) which is designed such that the valve opening of the outlet valve (9) can be changed during the exhaust stroke during operation of the internal combustion engine (1), thereby characterized in that the valve actuation device (10) is additionally designed such that, with a defined valve opening of the outlet valve (9), the opening The duration of the exhaust valve (9) is adjustable and / or the exhaust valve (9) can also be opened during the intake stroke. Internal combustion engine according to Claim 1 , characterized by an outlet phaser (15) for adjusting the opening period of the outlet valve (9). Internal combustion engine according to Claim 1 or 2 , characterized in that the valve actuating device (10) comprises a switching device which has at least two or exactly two discrete switching positions which differ with regard to the valve opening of the outlet valve (9) caused by the switching device. Internal combustion engine according to Claim 3 , characterized in that - the valve actuation device (10) comprises a camshaft (15) provided for direct or indirect actuation of the exhaust valve and - the switching device - a rocker arm which can be switched with regard to the transmission ratio and which deflects a cam of the camshaft onto the exhaust valve (9 ) transmits, and / or comprises different cams of the camshaft, the different cams alternatively being able to be brought into operative connection with the outlet valve (9). Internal combustion engine according to one of the preceding claims, characterized in that at least two outlet valves (9) are assigned to the combustion chamber (4), the valve openings of which can be changed by means of the valve actuation device (10). Internal combustion engine according to Claim 2 or one of the from Claim 2 dependent claims and according to Claim 5 , characterized in that the opening times of the two exhaust valves (9) can be adjusted relative to one another by means of the exhaust phaser (15). Internal combustion engine according to one of the preceding claims, characterized in that the valve actuation device (10) is designed in such a way that the opening time of the intake valve (8) during the intake stroke can be changed by means of it during operation of the internal combustion engine (1). Internal combustion engine according to one of the preceding claims, characterized in that the combustion chamber (4) is assigned at least two inlet valves (8), the opening periods of these two inlet valves (8) being adjustable relative to one another by means of an inlet phase adjuster (15). Method for operating an internal combustion engine according to one of the preceding claims, characterized in that during a heating operation of the internal combustion engine - to achieve a relatively high temperature of the exhaust gas discharged from the combustion chamber (4), the valve opening of the exhaust valve (1) occurring during an exhaust cycle of the internal combustion engine (1) 9) is set smaller compared to normal operation of the internal combustion engine and - to achieve internal exhaust gas recirculation (iAGR) by retaining exhaust gas in the combustion chamber (4), the outlet valve (9) is closed before the end of the exhaust stroke and / or - to achieve this an iAGR by sucking exhaust gas back into the combustion chamber (4), the exhaust valve (9) is additionally opened during the intake stroke. Procedure according to Claim 9 , characterized in that the closing time of the exhaust valve (9) and / or the valve actuation taking place during the intake stroke is changed during the heating operation to adjust the iAGR. Procedure according to Claim 9 or 10 for operating an internal combustion engine according to Claim 7 or one of the from Claim 7 The dependent claims, characterized in that the inlet valve (8) is opened relatively late during the heating operation compared to the normal operation. Method according to one of the Claims 9 to 11 for operating an internal combustion engine according to Claim 8 , characterized in that the inlet valves (8) are each actuated with an opening duration which is shorter than the intake stroke, with the during normal operation Opening periods of the inlet valves (8) are set offset relative to one another to a greater extent than is provided during the heating operation. Method according to one of the Claims 9 to 12 for operating an internal combustion engine according to Claim 6 or one of the from Claim 6 dependent claims, characterized in that the exhaust valves (9) are actuated during normal operation each with an opening period that is shorter than the exhaust stroke, whereby to achieve normal operation with adjustable iAGR by retaining exhaust gas in the combustion chamber (4) the opening periods of the Outlet valves can be set offset relative to one another to a variable extent.

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