SE1950130A1

SE1950130A1 - Method of Controlling a Combustion Engine, Combustion Engine, and Related Devices

Info

Publication number: SE1950130A1
Application number: SE1950130A
Authority: SE
Inventors: Ove Sponton
Original assignee: Scania Cv Ab
Priority date: 2019-02-05
Filing date: 2019-02-05
Publication date: 2020-08-06
Also published as: SE543460C2; DE112020000291T5; WO2020162810A1

Abstract

A method (100) of controlling an internal combustion engine (1) is disclosed. The method (100) comprises determining (110) a knock level (kl) in the at least one cylinder (13) of the engine (1), setting (120) an overlap limit (Olim) based on a current overlap (O) used when the determined knock level (kl) exceeds a threshold value (th), and controlling (130) the overlap (O) based on the overlap limit (Olim). The present disclosure further relates to a computer program, a computer-readable medium (200), a control arrangement (20), a combustion engine (1), and a vehicle (30).

Description

1 Method of Controlling a Combustion Engine, Combustion Engine, and Related Devices TECHNICAL FIELD The present disclosure relates to a method of controlling an internal combustion engine. Thepresent disclosure further relates to a computer program, a computer-readable medium, a control arrangement for controlling an internal combustion engine, a combustion engine, and a vehicle.

BACKGROUND Internal combustion engines, such as four-stroke internal combustion engines operating inthe so called Otto-cycle, comprise one or more cylinders and a piston arranged in eachcylinder. Otto-engines comprise an ignition device arranged to ignite the air/fuel mixture inthe cylinder. The pistons are connected to a crankshaft of the engine and are arranged toreciprocate within the cylinders upon rotation of the crankshaft. The engine usually furthercomprises one or more inlet valves and one or more outlet valves as well as one or more fuelsupply arrangements. The one or more inlet valves and outlet valves are controlled by arespective valve control arrangement usually comprising one or more camshafts rotatablyconnected to a crankshaft of the engine, via a belt, chain, gears, push rods, or similar. A four-stroke internal combustion engine completes four separate strokes while turning a crankshafttvvo revolutions. A stroke refers to the full travel of the piston along the cylinder, in eitherdirection. The uppermost position of the piston in the cylinder is usually referred to as the topdead centre TDC, and the lowermost position of the piston in the cylinder is usually referredto as the bottom dead centre BDC.

The strokes are completed in the following order, inlet stroke, compression stroke, expansionstroke and exhaust stroke. During operation of a conventional four-stroke internalcombustion engine, the inlet valve control arrangement controls inlet valves of a cylinder toan open state during the inlet stroke of a piston within the cylinder, to allow air, or a mixtureof air and fuel, to enter the cylinder. During the compression stroke, all valves should beclosed to allow compression of the air, or the mixture of the air and fuel, in the cylinder. lf theengine is in a power producing state, fuel in the cylinder is ignited, usually towards the end ofthe compression stroke, by the ignition device. The combustion of fuel within the cylindersignificantly increases pressure and temperature in the cylinder. The combustion of the fuelusually continues into a significant portion of the subsequent expansion stroke. Theincreased pressure and temperature in the cylinder obtained by the combustion is partiallyconverted into mechanical work supplied to the crankshaft in the expansion stroke. 2 Obviously, all valves should remain closed during the expansion stroke to allow theincreased pressure and temperature to be converted into mechanical work. The expansionstroke is also usually referred to as the combustion stroke, because usually, the majority ofthe combustion takes place during the expansion stroke. ln the subsequent exhaust stroke,the exhaust valve control arrangement controls exhaust valves of the cylinder to an openstate to allow exhaust gases to be expelled out of the cylinder into an exhaust system. Theexhaust stroke is then followed by an inlet stroke. As is further explained herein, the term“overlap” relates to a time, or a number of crank angle degrees, in which inlet valves andoutlet valves are open simultaneously in a cylinder. The use of overlap provides someadvantages, which is further explained herein, and occurs, if present, in a transition areabetween the exhaust stroke and the inlet stroke. ln general, a high cylinder pressure at, or close to, the top dead centre of the piston of theengine increases the fuel efficiency of the engine. However, a limiting factor for an Ottoengine is engine knock. Engine knock occurs when combustion of some of the air/fuelmixture in the cylinder does not result from propagation of the flame front ignited by theignition device, but one or more pockets of air/fuel mixture explode outside the envelope ofthe normal combustion front. The shock wave creates the characteristic metallic "pinging"sound, and cylinder pressure increases dramatically. Engine knock is harmful for an engineand is to be avoided.

As mentioned above, a high cylinder pressure at, or close to, the top dead centre of thepiston of the engine increases the fuel efficiency of the engine. However, high cylinderpressures increase the tendency of engine knock. High cylinder pressures at, or close to, thetop dead centre of the piston of the engine is achieved by igniting the air/fuel mixture in anearly phase of the piston's stroke towards the top dead centre. Conversely, the maximumcylinder pressure in the cylinder can be reduced by igniting the air/fuel mixture later so as toreduce the tendency of engine knock. The tendency of knocking is also affected by otherfactors, such as the temperature of the engine, the quality of the fuel, the load of the engine,the inlet manifold pressure, weather conditions, altitude, and more. ln order to obtain a high fuel efficiency, modern Otto-engines are usually provided with aknock sensing device arranged to sense the occurrence of knock, and wherein the ignitiondevice is arranged to postpone the ignition in case knock is detected and is arranged toadvance the ignition in case no knock is detected. ln this manner, high maximum cylinderpressures can be achieved given the current operating conditions of the engine and giventhe other factors which affects the tendency of engine knock.

Another challenged faced when designing a combustion engine is to lower emissionsproduced by the engine. The emission of carbon dioxide (C02) is directly correlated with theconsumption of fuel of the engine. However, combustion engines produce many more typesof substances including nitrogen oxide (NO) and nitrogen dioxide (N02), carbon monoxide(C0), particulate matter, hydrocarbons (HC), sulphur dioxide (S02), and formaldehyde.

Three-way catalytic converters are commonly used by 0tto-engines to lower the emissionsfrom the engine. A three-way catalytic converter has three simultaneous tasks, namelyreduction of nitrogen oxide (N0) and nitrogen dioxide (N02) to nitrogen (N2), oxidation ofcarbon monoxide (C0) to carbon dioxide (C02), and oxidation of unburnt hydrocarbons (HC)to carbon dioxide (C02) and water (H20).

Three-way catalytic converters are effective when the engine is operated within a narrowband of air-fuel ratios near the stoichiometric point, such that the exhaust gas compositionoscillates betvveen rich (excess fuel) and lean (excess oxygen). Conversion efficiency fallsrapidly when the engine is operated outside of this band. Under lean engine operation, theexhaust contains excess oxygen, and the reduction of N0x is not favoured. Under richconditions, the excess fuel consumes all of the available oxygen prior to the catalyst, leavingonly oxygen stored in the catalyst available for the oxidation function. Therefore, closed-loopengine control systems are used for effective operation of three-way catalytic convertersbecause of the continuous balancing required for effective N0x reduction and HC oxidation.

Two other factors which affect the operation of a combustion engine are residual gasestrapped from a previous combustion cycle and blow through. Blow through is a term used forair blowing the through the cylinder from an open inlet valve to an open exhaust valve. Thesetwo factors are affected by the overlap between inlet valves and outlet valves of the engine.A great overlap reduces residual gases and increases blow through gases. Contrarywise, asmaller overlap increases residual gases and decreases blow through gases. Some enginesoperate with a great overlap, which can be advantageous for combustion aspects and canprovide cooling of outlet valves of the engine. However, the high amount of blow throughgases obtained when using a great overlap increases the amount of oxygen in the exhaustgases. Therefore, in order to preserve function of the three-way catalytic converter, more fuelmust be added which increases the fuel consumption and the emissions of the engine.

Some engines comprise a valve control arrangement capable of controlling the overlapbetween inlet valves and outlet valves of the combustion engine. The amount of blow 4 through, as well as the amount of residual gases, is difficult to measure or estimate. ln a lab-environment, the amount of residual gases and the amount of blow through can bemeasured using expensive, complex, and sensitive sensors and equipment. However, atpresent, there are no means for automotive applications available on the market formeasuring the amount of residual gases and the amount of blow through.

Furthermore, generally, on today's consumer market, it is an advantage if products, such ascombustion engines and their associated arrangements, have conditions and/orcharacteristics suitable for being manufactured and assembled in a cost-efficient manner.

SUMMARYlt is an object of the present invention to overcome, or at least alleviate, at least some of theabove-mentioned problems and drawbacks.

According to a first aspect of the invention, the object is achieved by a method of controllingan internal combustion engine, wherein the combustion engine comprises a valve controlarrangement capable of controlling the overlap between inlet valves and outlet valves of thecombustion engine, and a knock sensing arrangement configured to sense the occurrence ofknock in at least one cylinder of the combustion engine.

The method comprises: - determining a knock level in the at least one cylinder, - setting an overlap limit based on a current overlap used when the determined knock level exceeds a threshold value, and- controlling the overlap based on the overlap limit.

Since the method comprises the step of setting an overlap limit based on a current overlapused when the determined knock level exceeds a threshold value, and the step of controllingthe overlap based on the overlap limit, a method is provided capable of obtaining anadvantageous overlap at different operating conditions of the engine, in a simple and efficientmanner, using input values from a simple and low-cost component, such as a knock sensor, which usually already is comprised in a combustion engine.

Accordingly, a method is provided capable of controlling the combustion engine to operatewith a low amount of residual gases in the cylinder and a low amount of blow through gases,without significantly increasing complexity and cost of the engine. That is, conditions areprovided for obtaining a minimal overlap sufficiently for flushing away heat and residual gases from the cylinder while the amount of blow through gases is kept low, withoutsignificantly increasing complexity and cost of the engine.

Furthermore, conditions are provided for obtaining an advantageous overlap given varyingother factors affecting the combustion in the cylinder, such as the temperature of the engine,the quality of the fuel, the load of the engine, the inlet manifold pressure, weather conditions,altitude, and the like, without significantly increasing complexity and cost of the engine.

Moreover, since a method is provided capable of controlling the combustion engine tooperate with a low amount of blow through gases, the need for adding fuel as a result of ahigh oxygen levels in the exhaust gases is circumvented. As a result thereof, the fuelefficiency of the engine is increased, and the amount of emissions produced by the engine is lowered. ln addition, since a method is provided capable of controlling the combustion engine tooperate with a low amount of heat and residual gases in the cylinder, conditions are providedfor using an early ignition of an air/fuel mixture in the cylinder. This because a low amount ofinitial heat and residual gases in the cylinder reduce the tendency of knock and thereforeallows for a higher maximum cylinder pressure during combustion. As a result thereof, thefuel efficiency of the engine can be increased, and the amount of emissions produced by the engine can be lowered.

Accordingly, a method is provided overcoming, or at least alleviating, at least some of theabove-mentioned problems and drawbacks. As a result, the above-mentioned object isachieved.

Optionally, the step of controlling the overlap comprises the steps of:- setting an overlap target value based on the overlap limit, and- controlling the overlap towards the overlap target value.

Thereby, a method is provided capable of controlling the combustion engine to operate withina narrow window in which the amount of residual gases in the cylinder is low and in whichthe amount of blow through gases is low, without significantly increasing complexity and costof the engine. That is, conditions are provided for operating the combustion engine within anarrow window in which a minimal overlap is obtained sufficiently for flushing away heat andresidual gases from the cylinder while the amount of blow through gases is kept low, withoutsignificantly increasing complexity and cost of the engine.

In addition, further improved conditions are provided for obtaining an advantageous overlapwhen other factors affecting the combustion in the cylinder varies, such as the temperature ofthe engine, the quality of the fuel, the load of the engine, the inlet manifold pressure, weatherconditions, altitude, and the like, without significantly increasing complexity and cost of the engine.

Optionally, the step of setting the overlap target value comprises the step of:- setting the overlap target value to a value being offset from the overlap limit.

Thereby, a simple and efficient method is provided capable of controlling the combustionengine to operate within a narrow window in which the amount of residual gases in thecylinder is low and in which the amount of blow through gases is low, without significantlyincreasing complexity and cost of the engine. That is, further improved conditions areprovided for operating the combustion engine within a narrow window in which a minimaloverlap is obtained sufficiently for flushing away heat and residual gases from the cylinderwhile the amount of blow through gases is kept low, without significantly increasingcomplexity and cost of the engine.

Optionally, the overlap target value involves a greater overlap than at the overlap limit.

Thereby, a simple and efficient method is provided capable of controlling the combustionengine to operate within a narrow window in which the amount of residual gases in thecylinder is low and in which the amount of blow through gases is low, without significantlyincreasing complexity and cost of the engine.

Optionally, the method further comprises:- updating the overlap limit by reducing the overlap.

Thereby, a simple and efficient method is provided capable of controlling the combustion engine to operate within a narrow window in which the amount of residual gases in the 7 cylinder is low and in which the amount of blow through gases is low, also when thecombustion is affected by varying factors, such as the temperature of the engine, the qualityof the fuel, the load of the engine, the inlet manifold pressure, weather conditions, altitude,and the like, without significantly increasing complexity and cost of the engine.

Optionally, the method comprises:- updating the overlap limit periodically.

Thereby, a simple and efficient method is provided capable of controlling the combustionengine to operate within a narrow window in which the amount of residual gases in thecylinder is low and in which the amount of blow through gases is low, also when thecombustion is affected by varying factors, such as the temperature of the engine, the qualityof the fuel, the load of the engine, the inlet manifold pressure, weather conditions, altitude,and the like. This without significantly increasing complexity and cost of the engine.

Optionally, the method comprises: - updating the overlap limit with a first frequency in steady state operatingconditions of the combustion engine, and - updating the overlap limit with a second frequency in transient operatingconditions of the combustion engine, wherein the second frequency is higherthan the first frequency.

Thereby, a method is provided which updates the overlap limit with a lower frequency incases where the factors affecting the combustion is less likely to vary, and which updates theoverlap limit with a higher frequency in cases where the factors affecting the combustion ismore likely to vary. As a result thereof, a simple and efficient method is provided capable ofoperating a combustion engine with improved fuel efficiency and reduced emissions.

According to a second aspect of the invention, the object is achieved by a computer programcomprising instructions which, when the program is executed by a computer, cause thecomputer to carry out the method according to some embodiments of the present disclosure.Since the computer program comprises instructions which, when the program is executed bya computer, cause the computer to carry out the method according to some embodimentsdescribed herein, a computer program is provided which provides conditions for overcoming,or at least alleviating, at least some of the above-mentioned drawbacks. As a result, theabove-mentioned object is achieved. 8 According to a third aspect of the invention, the object is achieved by a computer-readablemedium comprising instructions which, when executed by a computer, cause the computer tocarry out the method according to some embodiments of the present disclosure. Since thecomputer-readable medium comprises instructions which, when the program is executed bya computer, cause the computer to carry out the method according to some embodimentsdescribed herein, a computer-readable medium is provided which provides conditions forovercoming, or at least alleviating, at least some of the above-mentioned drawbacks. As aresult, the above-mentioned object is achieved.

According to a fourth aspect of the invention, the object is achieved by a control arrangementfor controlling an internal combustion engine, wherein the combustion engine comprises avalve control arrangement capable of controlling the overlap between inlet valves and outletvalves of the combustion engine, and a knock sensing arrangement configured to sense theoccurrence of knock in at least one cylinder of the combustion engine. The controlarrangement is arranged to: - determine a knock level in the at least one cylinder, - set an overlap limit based on a current overlap used when the determined knock level exceeds a threshold value, and- control the overlap based on the overlap limit.

Since the control arrangement is arranged to set an overlap limit based on a current overlapused when the determined knock level exceeds a threshold value, and is arranged to controlthe overlap based on the overlap limit, a control arrangement is provided capable ofobtaining an advantageous overlap at different operating conditions of the combustionengine, in a simple and efficient manner, using input values from a simple and low-costcomponent, such as a knock sensor, which usually already is comprised in a combustion engine.

Accordingly, a control arrangement is provided capable of controlling the combustion engineto operate with a low amount of residual gases in the cylinder and a low amount of blowthrough gases, without significantly increasing complexity and cost of the engine. That is,conditions are provided for obtaining a minimal overlap sufficiently for flushing away heat andresidual gases from the cylinder while the amount of blow through gases is kept low, withoutsignificantly increasing complexity and cost of the engine.

Furthermore, conditions are provided for obtaining an advantageous overlap given varyingother factors affecting the combustion in the cylinder, such as the temperature of the engine, 9 the quality of the fuel, the load of the engine, the inlet manifold pressure, weather conditions,altitude, and the like, without significantly increasing complexity and cost of the engine.

Moreover, since a control arrangement is provided capable of controlling the combustionengine to operate with a low amount of blow through gases, the need for adding fuel as aresult of a high oxygen levels in the exhaust gases is circumvented. As a result thereof, thefuel efficiency of the engine is increased, and the amount of emissions produced by the engine is lowered. ln addition, since a control arrangement is provided capable of controlling the combustionengine to operate with a low amount of heat and residual gases in the cylinder, conditionsare provided for using an early ignition of an air/fuel mixture in the cylinder. This because alow amount of initial heat and residual gases in the cylinder reduce the tendency of knockand therefore allows for a higher maximum cylinder pressure during combustion. As a resultthereof, the fuel efficiency of the engine can be increased, and the amount of emissionsproduced by the engine can be lowered.

Accordingly, a control arrangement is provided overcoming, or at least alleviating, at leastsome of the above-mentioned problems and drawbacks. As a result, the above-mentionedobject is achieved.

According to a fifth aspect of the invention, the object is achieved by an internal combustionengine comprising at least one cylinder, a piston arranged in each cylinder, at least one inletvalve at each cylinder, at least one outlet valve at each cylinder, a valve control arrangementcapable of controlling the overlap between the inlet valves and the outlet valves of thecombustion engine, a knock sensing arrangement configured to sense the occurrence ofknock in at least one cylinder of the combustion engine, and a control arrangement. Thecontrol arrangement is arranged to: - determine a knock level in the at least one cylinder, - setting an overlap limit based on a current overlap used when the determined knock level exceeds a threshold value, and- control the overlap based on the overlap limit.

Since the control arrangement of the internal combustion engine is arranged to set anoverlap limit based on a current overlap used when the determined knock level exceeds athreshold value, and is arranged to control the overlap based on the overlap limit, anadvantageous overlap at different operating conditions of the combustion engine can be achieved, in a simple and efficient manner, using input values from a simple and low-cost component, such as a knock sensor.

Accordingly, a combustion engine is provided capable of operating with a low amount ofresidual gases in the cylinder and a low amount of blow through gases, without significantlyincreasing complexity and cost of the engine. That is, conditions are provided for obtaining aminimal overlap sufficiently for flushing away heat and residual gases from the cylinder whilethe amount of blow through gases is kept low, without significantly increasing complexity andcost of the engine.

Moreover, since a combustion engine is provided capable of operating with a low amount ofblow through gases, the need for adding fuel as a result of a high oxygen levels in theexhaust gases is circumvented. As a result thereof, the fuel efficiency of the engine can beincreased, and the amount of emissions produced by the engine can be lowered. ln addition, since a combustion engine is provided capable of operating with a low amount ofheat and residual gases in the cylinder, conditions are provided for using an early ignition ofan air/fuel mixture in the cylinder. This because a low amount of initial heat and residualgases in the cylinder reduce the tendency of knock and therefore allows for a highermaximum cylinder pressure during combustion. As a result thereof, the fuel efficiency of theengine can be increased, and the amount of emissions produced by the engine can be lowered.

Accordingly, a combustion engine is provided overcoming, or at least alleviating, at leastsome of the above-mentioned problems and drawbacks. As a result, the above-mentionedobject is achieved.

Optionally, the valve control arrangement comprises: - an inlet valve phase-shifting device configured to phase-shift control of the atleast one inlet valve, and - an outlet valve phase-shifting device configured to phase-shift control of the atleast one outlet valve. 11 Thereby, conditions are provided for controlling the overlap by phase-shifting control of the atleast one inlet valve and the at least one outlet valve, i.e. with a high degree of control.

Optionally, the valve control arrangement is configured to control the overlap by phase-shifting control of the at least one inlet valve and the at least one outlet valve. Thereby, theoverlap can be controlled with a high degree of control to ensure that the combustion engineis operated within a narrow window in which the amount of residual gases in the cylinder is low and in which the amount of blow through gases is low.

Optionally, the combustion engine comprises at least one ignition device in each cylinder ofthe combustion engine. Thereby, conditions are provided for using an early ignition by the at least one ignition device of an air/fuel mixture in the cylinder.

Optionally, the combustion engine is specifically adapted to run on a gaseous fuel. Residualgases have a greater effect on the tendency of knock when operating an engine on agaseous fuel, as compared to when operating an engine on gasoline fuel. This because agaseous fuel is more resistant to high temperatures and pressures than gasoline, and theresidual gases will therefore have a greater effect on the tendency of knock. However, sincethe control arrangement of the combustion engine is capable of operating the combustionengine within a narrow window in which the amount of residual gases in the cylinder is lowand in which the amount of blow through gases is low, the combustion engine can beoperated at high power levels with high fuel efficiency and low emission levels.

Optionally, the combustion engine is specifically adapted to run on an alcohol based fuel.Residual gases obtained when operating an engine on an alcohol based fuel have a greatereffect on the tendency of knock than residual gases obtained when operating an engine ongasoline. Residual gases have a greater effect on the tendency of knock when operating anengine on an alcohol based fuel, as compared to when operating an engine on gasoline fuel.This because an alcohol based fuel is more resistant to high temperatures and pressuresthan gasoline, and the residual gases will therefore have a greater effect on the tendency ofknock. However, since the control arrangement of the combustion engine is capable ofoperating the combustion engine within a narrow window in which the amount of residualgases in the cylinder is low and in which the amount of blow through gases is low, thecombustion engine can be operated at high power levels with high fuel efficiency and low emission levels. 12 According to a sixth aspect of the invention, the object is achieved by a vehicle comprising acombustion engine according to some embodiments of the present disclosure. Since thevehicle comprises a combustion engine according to some embodiments described herein, avehicle is provided which provides conditions for overcoming, or at least alleviating, at leastsome of the above-mentioned drawbacks. As a result, the above-mentioned object isachieved.

Further features of, and advantages with, the present invention will become apparent whenstudying the appended claims and the following detailed description.

BRIEF DESCRIPTION OF THE DRAWINGS Various aspects of the invention, including its particular features and advantages, will bereadily understood from the example embodiments discussed in the following detaileddescription and the accompanying drawings, in which: Fig. 1 schematically illustrates a cross sectional view of an internal combustion engine,according to some embodiments, Fig. 2a and Fig. 2b illustrate opening events of at least one inlet valve and at least oneexhaust valve in two different operational modes of the combustion engine illustrated in Fig.1, Fig. 3 illustrates a diagram illustrating control of overlap performed by a control arrangementof the combustion engine illustrated in Fig. 1, Fig. 4 illustrates vehicle according to some embodiments, Fig. 5 illustrates a method of controlling an internal combustion engine, and Fig. 6 illustrates a computer program product.

DETAILED DESCRIPTION Aspects of the present invention will now be described more fully. Like numbers refer to likeelements throughout. Well-known functions or constructions will not necessarily be describedin detail for brevity and/or clarity.

Fig. 1 schematically illustrates a cross sectional view of an internal combustion engine 1,according to some embodiments. Herein, the internal combustion engine 1 is in some casesreferred to as “the combustion engine 1” and “the engine 1” for the reason of brevity and/orclarity. The engine 1 comprises at least one cylinder 13 and a piston 15 arranged in eachcylinder 13. The piston 15 is connected to a crankshaft 6 via a connecting rod 8. The piston15 moves forwards and backwards in the cylinder 13 upon rotation of the crankshaft 6, 13 between a top dead centre TDC and a bottom dead centre BDC. The engine 1 comprises aninlet system 10, which in the illustrated example embodiments is illustrated as an inlet duct.The inlet system 10 may comprise further components such as an air filter, a throttle, a fuel injector, an air flow sensor, and the like.

The engine 1 further comprises at least one inlet valve 7 arranged in each cylinder 13, whichat least one inlet valve 7 is connected with the inlet system 10. The inlet valve 7 is arrangedto control flow of gas into the cylinder 13. The engine 1 further comprises an inlet valvecontrol arrangement 12 configured to control each inlet valve 7 on the basis of a rotationalposition of the crankshaft 6. The engine 1 further comprises at least one exhaust valve 9arranged in each cylinder 13, which at least one exhaust valve 9 is connected with anexhaust outlet 14 of the engine 1. The exhaust valve 9 is arranged to control flow of gas outof the cylinder 13. The engine 1 further comprises an exhaust valve control arrangement 16configured to control each exhaust valve 9 on the basis of the rotational position of the cran kshaft 6. ln Fig. 1, the at least one inlet valve 7 and the at least one exhaust valve 9 are illustrated in arespective partially open position. ln the partially open position, as well as in a fully openposition, the at least one inlet valve 7 is lifted from valve seat thereof and allows flow of gasfrom the inlet system 10 into the cylinder 13. Likewise, in the partially open position, as wellas in a fully open position, the at least one exhaust valve 9 is lifted from valve seat thereofand allows flow of gas from the cylinder 13 to the exhaust outlet 14. As is further explainedbelow, in Fig. 1, the piston 15 is illustrated in a position corresponding to a transition areabetween an exhaust stroke and an inlet stroke of the engine 1. Since the at least one inletvalve 7 and the at least one exhaust valve 9 are open simultaneously, the engine 1 illustratedin Fig. 1 is operating with a certain amount of overlap. ln a closed position, each valve 7, 9 abuts against a respective valve seat to close fluidconnection between the cylinder 13 and the respective inlet system 10 and the exhaust outlet14. Each valve 7, 9 may be biased towards the closed position, for example by a spring. Theinlet valve control arrangement 12 is arranged to control the at least one inlet valve 7between the closed position and an open position by displacing the at least one inlet valve 7in a direction into the cylinder 13. Likewise, the exhaust valve control arrangement 16 isarranged to control the at least one exhaust valve 9 between the closed position and an openposition by displacing the at least one exhaust valve 9 in a direction into the cylinder 13.According to the illustrated embodiments, the at least one exhaust valve 9, as well as the at 14 least one inlet valve 7, comprises a poppet valve, which also may be referred to as a mushroom valve.

The exhaust valve control arrangement 16 and the inlet valve control arrangement 12 mayeach comprise one or more camshafts rotatably connected to the crankshaft 6, wherein thecamshafts comprises cam lobes arranged to displace valves 7, 9 to an open position bypressing on valve stems of the valves 7, 9 upon rotation of the camshaft. The cam lobes maypress directly onto the valve stems of the valves 7, 9, or may press onto the valve stems ofthe valves 7, 9 via further arrangements such as push rods, rocker arms, hydraulicarrangements, or the like. The exhaust valve control arrangement 16, and/or the inlet valvecontrol arrangement 12, may according to further embodiments comprise electric, pneumatic,or hydraulic actuators arranged to control the valves 7, 9 on the basis of the rotationalposition of the crankshaft 6. The rotational position of the crankshaft 6 may be obtained usinga crank angle sensor 18.

The combustion engine 1 comprises at least one ignition device 17 in each cylinder 13 of theengine 1. According to the illustrated embodiments, the ignition device 17 is a spark plug.However, according to further embodiments, the combustion engine 1 may comprise one ormore other types of ignition devices in each cylinder 13, such as a plasma or microwaveignition device. The ignition device 17 is arranged to ignite an air/fuel mixture in the cylinder13 so as to initiate combustion in the cylinder 13. According to the illustrated embodiments,the engine is an Otto engine operating with a spark plug. Such an engine may also bereferred to as a spark-ignition engine (SI engine).

The engine 1 further comprises a fuel supply arrangement, such as one or more fuelinjectors. The fuel supply arrangement is not illustrated in Fig. 1 for the reason of brevity andclarity. The fuel may be directly injected into the cylinder 13 using a fuel injector or may beadded to incoming air prior to entering the cylinder 13, for example by a fuel injectorarranged at the inlet system 10 of the engine 1.

The engine 1 further comprises a valve control arrangement 3, 5 capable of controlling theoverlap between the inlet valves 7 and the outlet valves 9 of the combustion engine 1. Thevalve control arrangement 3, 5 is configured to control the overlap by phase-shifting controlof the at least one inlet valve 7 and the at least one outlet valve 9.

According to the illustrated embodiments, the valve control arrangement 3, 5 comprises aninlet valve phase-shifting device 3 configured to phase-shift control of the at least one inlet valve 7. l\/loreover, according to the illustrated embodiments, the valve control arrangement3, 5 comprises an outlet valve phase-shifting device 5 configured to phase-shift control of theat least one outlet valve 9. That is, the inlet valve phase-shifting device 3 is configured tophase-shift control of the at least one inlet valve 7 in relation to the rotational position ofcrankshaft 6. The exhaust valve phase-shifting device 5 is configured to phase-shift controlof the at least one outlet valve 9 in relation to the rotational position of the crankshaft 6.

The exhaust valve phase-shifting device 5 and the inlet valve phase-shifting device 3 mayeach comprise a hydraulic arrangement, for example using engine oil as hydraulic fluid, tophase-shift control of the valves 7, 9 in relation to the crankshaft 6. Such hydraulicarrangement may form part of a belt pulley (not illustrated) arranged to transfer rotation fromthe crankshaft 6 to a camshaft of the exhaust valve control arrangement 16 and/or the inletvalve control arrangement 12, wherein the hydraulic arrangement is arranged to regulate anangular relationship between a first portion of the belt pulley, being connected to thecrankshaft 6, and a second portion of the belt pulley, being connected to the camshaft, inorder to phase-shift control of the at least one inlet valve 7 and/or the at least one exhaustvalve 9. ln embodiments wherein the exhaust valve control arrangement 16 and/or the inletvalve control arrangement 12 comprises electric, pneumatic, or hydraulic actuators, thephase-shift of control of the at least one inlet valve 7 and/or the at least one exhaust valve 9may be performed in other manners, for example by an electronic phase-shift of control.

The engine 1 further comprises a knock sensing arrangement 11 configured to sense theoccurrence of knock in at least one cylinder 13 of the combustion engine 1. According to theillustrated embodiments, the knock sensing arrangement 11 comprises a knock sensor. Theknock sensing arrangement 11 may comprise a vibration sensor, such as a piezo-electricsensor. However, according to further embodiments, the knock sensing arrangement 11 maycomprise another type of device for sensing the occurrence of knock in at least one cylinder13 of the combustion engine 1, such as a microphone, a pressure sensor, an inductiveresonant sensor, and/or a device measuring ionization over at least one ignition device 17 of the engine 1.

The engine 1 further comprises a control arrangement 20 connected to the valve controlarrangement 3, 5 and the knock sensing arrangement 11. The features and functions of thecontrol arrangement are explained in detail below.

According to the illustrated embodiments, the engine 1 comprises a charging device 22arranged to compress air to the inlet system 10. The charging device 22 illustrated is a turbo- 16 charger comprising a turbine arranged to be driven by gases from the exhaust outlet 14. Theturbine is arranged at a shaft connected to a Compressor wheel which is arranged tocompress air to the inlet system 10. The engine 1 may comprise another type of chargingdevice, such as a compressor arranged to be driven by the crankshaft 6 of the engine 1.According to the illustrated embodiments, the control unit 20 is connected to the chargingdevice 22. The control unit 20 is configured to regulate the charge air pressure of thecharging device 22 by regulating a waste gate valve of the charging device 22. According tofurther embodiments, the charging device 22 may be a Variable-geometry turbocharger(VGT). ln such embodiments, the control unit 20 may be configured to regulate the charge airpressure of the charging device 22 by regulating geometry of an inlet portion of the turbine ofthe turbocharger, for example by regulating angular positions of vanes arranged at the inletportion of the turbine.

According to the illustrated embodiments, the engine 1 comprises an exhaust after treatmentsystem 24 in the form of a Three-Way Catalyst (TWC).

Fig. 2a and Fig. 2b illustrate opening events 51, 52 of the at least one inlet valve 7 and theat least one exhaust valve 9 in two different operational modes of the combustion engine 1illustrated in Fig. 1. Therefore, below, simultaneous reference is made to Fig. 1, Fig. 2a, andFig. 2b. The curves illustrated in Fig. 2a and Fig. 2b illustrate opening events performedduring tvvo revolutions of the crank shaft 6, i.e. during all four strokes of the four-strokeinternal combustion engine 1. ln these figures, the strokes are illustrated in the followingorder: compression stroke 41, expansion stroke 42, exhaust stroke 43 and inlet stroke 44.During the compression stroke 41 and the expansion stroke 42, the at least one inlet valve 7and the at least one exhaust valve 9 are closed. When the piston reaches the bottom deadcentre BDC at the end of the expansion stroke 42, the exhaust valve control arrangement 16controls the at least one exhaust valve 9 to an open position to allow exhaust gases to beexpelled from the cylinder 13 to the exhaust outlet 14 during the exhaust stroke 43. When thepiston 15 has passed the top dead centre TDC, the exhaust valve control arrangement 16controls the at least one exhaust valve 9 to the closed position early in the inlet stroke 44.

Further, the inlet valve control arrangement 12 controls the at least one inlet valve 7 to anopen position to allow air, or an air/fuel mixture, to enter the cylinder 13 during the inletstroke 44. As can be seen in Fig. 2a and Fig. 2b, the opening event of the at least one inletvalve 7 occurs before the piston 15 has passed the top dead centre TDC in the exhauststroke 43. Accordingly, in Fig. 2a and in Fig. 2b, the engine 1 is operating with an overlap Obetween inlet valves 7 and outlet valves 9 of the combustion engine 1. However, as seen 17 when comparing Fig. 2a and in Fig. 2b, the overlap O is greater in the operational modeillustrated in Fig. 2a than the operational mode illustrated in Fig. 2b. The overlap O may bedefined as a time, or a number of crank angle degrees, in which inlet valves 7 and outletvalves 9 are at least partially open simultaneously. According to the illustrated embodiments,the valve control arrangement 3, 5 has reduced the overlap O in Fig. 2b, as compared to Fig.2a, by advancing control of the at least one outlet valve 9 such that the at least one outletvalve 9 closes earlier, and by retarding control of the at least one inlet valve 7 such that theat least one outlet valve 9 opens later. According to further embodiments, and/or in someoperational conditions of the combustion engine 1, the valve control arrangement 3, 5 mayreduce the overlap O by phase-shifting control of one of the at least one inlet valve 7 and theat least one outlet valve 9.

Similarly, when comparing Fig. 2a with Fig. 2b, the valve control arrangement 3, 5 hasincreased the overlap O in Fig. 2a in relation to Fig. 2b, by retarding control of the at leastone outlet valve 9 such that the at least one outlet valve 9 closes later, and by advancingcontrol of the at least one inlet valve 7 such that the at least one inlet valve 7opens earlier.According to further embodiments, and/or in some operational conditions of the combustionengine 1, the valve control arrangement 3, 5 may increase the overlap O by phase-shiftingcontrol of one of the at least one inlet valve 7 and the at least one outlet valve 9. Towards theend of the inlet stroke 44, the inlet valve control arrangement 12 controls the at least oneinlet valve 7 to a closed position to allow compression of the air, or the air/fuel mixture, in thesubsequent compression stroke 41.

Fig. 3 illustrates a diagram illustrating control of the overlap O performed by the controlarrangement 20 illustrated in Fig. 1. Below, simultaneous reference is made to Fig. 1, Fig.2a, Fig. 2b and Fig. 3. The x-axis of the diagram illustrated in Fig. 3 shows the overlap Obetween inlet valves 7 and outlet valves 9 of the combustion engine 1. The overlap Oincreases along the extension of the x-axis in the diagram illustrated in Fig. 3. The y-axis ofthe diagram illustrated in Fig. 3 shows the amount of residual gases Res trapped in thecylinder 13 from a previous combustion cycle and the amount of blow through gases Bobtained. The amount of blow through gases B obtained can be defined as the amount of airblowing the through the cylinder 13 from an open at least one inlet valve 7 to an open at leastone exhaust valve 9 in the transition area between the exhaust stroke 43 and the inlet stroke44 of the engine 1. The amount of residual gases Res and the amount of blow through gasesB increase along the extension of the y-axis in the diagram illustrated in Fig. 3. 18 The control arrangement 20 is arranged to determine a knock level kl in the at least onecylinder 13 and to set an overlap limit Olim based on a current overlap O used when thedetermined knock level kl exceeds a threshold value th. ln Fig. 3, the determined knock levelkl exceeds the threshold value th at the point indicated with the reference sign “k|=th”. Thecontrol arrangement 20 may determine the knock level kl using input values from the knocksensing arrangement 11. The threshold value th of the knock level kl may be selected to athreshold value in which it is estimated that the knock level kl is not harmful to the engine 1.As is further explained herein, the control arrangement 20 is arranged to control the overlapO based on the overlap limit Olim. According to the illustrated embodiments, this is achievedby the control arrangement 20 being arranged to set an overlap target value Ot based on theoverlap limit Olim and controlling the overlap O towards the overlap target value Ot. As canbe seen in Fig. 3, the overlap target value Otis offset from the overlap limit Olim and involvesa greater overlap O than at the overlap limit Olim. ln this manner, the control arrangement 20 is capable of controlling the overlap O within anarrow window in which the amount of residual gases Res in the cylinder 13 is low and inwhich the amount of blow through gases B is low at different operating conditions of theengine 1. Moreover, this is achieved in a simple and efficient manner, using input valuesfrom a simple and low-cost component, such as a knock sensor 11, which usually already iscomprised in a combustion engine 1. The window, as referred to herein, is delimited in Fig. 3by the overlap limit Olim, in which determined knock level kl exceeds a threshold value th,and an upper overlap limit Olim2, in which the blow through gases B exceeds a thresholdvalue. As understood from the above, due to the control of the overlap O by the controlarrangement 20 based on the overlap limit Olim, there is no need for measuring or detectingwhen the upper overlap limit Olim2 is reached. Thereby, the need for complex and costly sensors is circumvented. l\/loreover, the control arrangement 20 is capable of controlling the overlap O within a narrowwindow in which a minimal overlap O is obtained sufficiently for flushing away heat andresidual gases Res from the cylinder 13 while the amount of blow through gases B is keptlow. As a result thereof, the ignition device 17 can ignite the air/fuel mixture in the cylinder 13earlier than would be the case othenivise. Moreover, a higher charge air pressure by thecharging device 22 is allowed for. As a result thereof, the combustion engine 1 can beoperated at high power levels with high fuel efficiency with a lower tendency of knock.l\/loreover, since the control arrangement 20 is capable of controlling the overlap O within anarrow window in which the amount of blow through gases B is low, the need for addingsupplemental fuel to the cylinder 13 so as to counteract increased oxygen levels in the 19 exhaust gases is circumvented. As a result thereof, the combustion engine 1 can beoperated at high power levels with high fuel efficiency and low emission levels. Furthermore,due to the control of the overlap O by the control arrangement 20, an automatic adaptation ofthe overlap O can be made in cases where other factors affecting the combustion in thecylinder 13 vary.

According to some embodiments, the control arrangement 20 is arranged to update theoverlap limit Olim by reducing the overlap O. According to these embodiments, the controlarrangement 20 may reduce the overlap O when the knock level kl is below the thresholdvalue th. Such a reduction may be performed periodically, incrementally, and/or continuously.When the determined knock level kl exceeds the threshold value th as a result of the reducedoverlap O, the control arrangement 20 set an updated overlap limit Olim based on the currentoverlap O used.

According to some embodiments, the control arrangement 20 may update the overlap limitOlim with a first frequency in steady state operating conditions of the combustion engine 1and update the overlap limit Olim with a second frequency in transient operating conditions ofthe combustion engine 1, wherein the second frequency is higher than the first frequency. Asa result thereof, the control arrangement 20 updates the overlap limit Olim with a lowerfrequency in cases where the factors affecting the combustion is less likely to vary, andwhich updates the overlap limit Olim with a higher frequency in cases where the factorsaffecting the combustion is more likely to vary.

According to some embodiments of the present disclosure, the combustion engine 1, asreferred to herein, is specifically adapted to run on a gaseous fuel. Residual gases have agreater effect on the tendency of knock when operating an engine 1 on a gaseous fuel, ascompared to when operating an engine on gasoline fuel. However, since the controlarrangement 20 of the combustion engine 1 is capable of operating the combustion engine 1within a narrow window in which the amount of residual gases Res in the cylinder 13 is lowand in which the amount of blow through gases B is low, the combustion engine 1 can beoperated at high power levels with high fuel efficiency and low emission levels.

According to some further embodiments of the present disclosure, the combustion engine 1,as referred to herein, is specifically adapted to run on an alcohol based fuel. Residual gasesobtained when operating an engine 1 on an alcohol based fuel have a greater effect on thetendency of knock than residual gases obtained when operating an engine on gasoline.However, since the control arrangement 20 of the combustion engine 1 is capable of operating the combustion engine 1 within a narrow window in which the amount of residualgases Res in the cylinder 13 is low and in which the amount of blow through gases B is low,the combustion engine1 can be operated at high power levels with high fuel efficiency and low emission levels.

Fig. 4 illustrates vehicle 30 according to some embodiments. The vehicle 30 comprises acombustion engine 1 according to the embodiments illustrated in Fig. 1. The combustion engine 30 is arranged to provide motive power to the vehicle 30 via wheels 32 of the vehicle.

The vehicle 30 illustrated in Fig. 4 is a truck. However, the combustion engine 1, as referredto herein, may be comprised in another type of manned or unmanned vehicle for land basedpropulsion such as a lorry, a bus, a construction vehicle, a tractor, a car, or the like.

Fig. 5 illustrates a method 100 of controlling an internal combustion engine 1. The engine 1may be a combustion engine 1 according to the embodiments illustrated in Fig. 1, and somefeatures, functions and advantages are explained with reference to Fig. 2a, Fig. 2b, and Fig.3. Therefore, below, simultaneous reference is made to Fig. 1, Fig. 2a, Fig. 2b, and Fig. 3.The method 100 is a method 100 of controlling an internal combustion engine 1, wherein thecombustion engine 1 comprises a valve control arrangement 3, 5 capable of controlling theoverlap O between inlet valves 7 and outlet valves 9 of the combustion engine 1, and aknock sensing arrangement 11 configured to sense the occurrence of knock in at least onecylinder 13 of the combustion engine 1. The method 100 comprises: - determining 110 a knock level kl in the at least one cylinder 13, - setting 120 an overlap limit Olim based on a current overlap O used when the determined knock level kl exceeds a threshold value th, and- controlling 130 the overlap O based on the overlap limit Olim.

As illustrated in Fig. 5, the step of controlling 130 the overlap O may comprise the steps of:- setting 132 an overlap target value Ot based on the overlap limit Olim, and- controlling 134 the overlap O towards the overlap target value Ot.

Moreover, as illustrated in Fig. 5, the step of setting 132 the overlap target value Otcomprises the step of:- setting 133 the overlap target value Otto a value being offset from the overlap limit Olim.

As illustrated in Fig. 5, the method 100 may further comprise:- updating 140 the overlap limit Olim by reducing the overlap O. 21 Moreover, as illustrated in Fig. 5, the method 100 may further comprise:- updating 142 the overlap limit Olim periodically.

Furthermore, as illustrated in Fig. 5, the method 100 may further comprise: - updating 143 the overlap limit Olim with a first frequency in steady stateoperating conditions of the combustion engine 1, and - updating 144 the overlap limit Olim with a second frequency in transientoperating conditions of the combustion engine 1, wherein the second frequencyis higher than the first frequency. lt will be appreciated that the various embodiments described for the method 100 are allcombinable with the control arrangement 20 as described herein. That is, the controlarrangement 20 may be configured to perform any one of the method steps 110, 120, 130,132, 133, 134, 140, 142, 143, and 144 of the method 100.

Fig. 6 illustrates a computer program product 200 for performing a method 100 of controllingan internal combustion engine 1, as illustrated in Fig. 1, wherein the computer programproduct 200 comprises computer readable code configured to cause a central processingunit of a control arrangement 20 of the engine 1 to perform the method 100 as illustrated inFig. 5.

Further, the computer program product 200 comprises a computer program for performing amethod 100 of controlling an internal combustion engine 1, as illustrated in Fig. 1,whereinthe computer program comprises computer readable code configured to cause a centralprocessing unit of a control arrangement 20 of the engine 1 to perform the method 100 asillustrated in Fig. 5.

One skilled in the art will appreciate that the method of controlling an internal combustionengine 1 may be implemented by programmed instructions. These programmed instructionsare typically constituted by a computer program, which, when it is executed in controlarrangement 20, ensures that the control arrangement 20 carries out the desired control,such as the method steps 110, 120, 130, 132, 133, 134, 140, 142, 143, and 144 describedherein. The computer program is usually part of a computer program product 200 whichcomprises a suitable digital storage medium on which the computer program is stored. 22 The control arrangement 20 may comprise a calculation unit which may take the form ofsubstantially any suitable type of processor circuit or microcomputer, e.g. a circuit for digitalsignal processing (digital signal processor, DSP), a Central Processing Unit (CPU), aprocessing unit, a processing circuit, a processor, an Application Specific Integrated Circuit(ASIC), a microprocessor, or other processing logic that may interpret and executeinstructions. The herein utilised expression “calculation unit” may represent a processingcircuitry comprising a plurality of processing circuits, such as, e.g., any, some or all of the ones mentioned above.

The control arrangement 20 may further comprise a memory unit, wherein the calculationunit may be connected to the memory unit, which may provide the calculation unit with, forexample, stored program code and/or stored data which the calculation unit may need toenable it to do calculations. The calculation unit may also be adapted to store partial or finalresults of calculations in the memory unit. The memory unit may comprise a physical deviceutilised to store data or programs, i.e., sequences of instructions, on a temporary orpermanent basis. According to some embodiments, the memory unit may compriseintegrated circuits comprising silicon-based transistors. The memory unit may comprise e.g.a memory card, a flash memory, a USB memory, a hard disc, or another similar volatile ornon-volatile storage unit for storing data such as e.g. ROIVI (Read-Only l\/lemory), PROIVI(Programmable Read-Only Memory), EPROIVI (Erasable PROM), EEPROIVI (ElectricallyErasable PRONI), etc. in different embodiments.

The control arrangement 20 is connected to components of the internal combustion engine 1for receiving and/or sending input and output signals. These input and output signals maycomprise waveforms, pulses, or other attributes which the input signal receiving devices candetect as information and which can be converted to signals processable by the controlarrangement 20. These signals may then be supplied to the calculation unit. One or moreoutput signal sending devices may be arranged to convert calculation results from thecalculation unit to output signals for conveying to other parts of the vehicle's control systemand/or the component or components for which the signals are intended. Each of theconnections to the respective components of the internal combustion engine 1 for receivingand sending input and output signals may take the form of one or more from among a cable,a data bus, e.g. a CAN (controller area network) bus, a l\/IOST (media orientated systems transport) bus or some other bus configuration, or a wireless connection. 23 ln the embodiments illustrated, the internal combustion engine 1 comprises a controlarrangement 20 but might alternatively be implemented wholly or partly in two or more control arrangements or control units.

Control systems in modern vehicles generally comprise a communication bus systemconsisting of one or more communication buses for connecting a number of electronic controlunits (ECUs), or controllers, to various components on board the vehicle. Such a controlsystem may comprise a large number of control units and taking care of a specific functionmay be shared between two or more of them. Vehicles of the type here concerned aretherefore often provided with significantly more control units than depicted in Fig. 1, as oneskilled in the art will surely appreciate.

The computer program product 200 may be provided for instance in the form of a data carriercarrying computer program code for performing at least some of the method steps 110, 120,130, 132, 133, 134, 140, 142, 143, and 144 according to some embodiments when beingloaded into one or more calculation units of the control arrangement 20. The data carrier maybe, e.g. a CD ROIVI disc, as is illustrated in Fig. 6, or a ROIVI (read-only memory), a PROIVI(programable read-only memory), an EPROIVI (erasable PROM), a flash memory, anEEPROIVI (electrically erasable PRONI), a hard disc, a memory stick, an optical storagedevice, a magnetic storage device or any other appropriate medium such as a disk or tapethat may hold machine readable data in a non-transitory manner. The computer programproduct may furthermore be provided as computer program code on a server and may bedownloaded to the control arrangement 20 remotely, e.g., over an Internet or an intranet connection, or via other wired or wireless communication systems. lt is to be understood that the foregoing is illustrative of various example embodiments andthat the invention is defined only by the appended claims. A person skilled in the art willrealize that the example embodiments may be modified, and that different features of theexample embodiments may be combined to create embodiments other than those describedherein, without departing from the scope of the present invention, as defined by theappended claims. For instance, the term “air” as used herein may comprise a mixture of air,fuel, and/or recirculated exhaust gases. Further, the terms compression stroke 41, expansionstroke 42, exhaust stroke 43 and inlet stroke 44 may be replaced by the terms compressionphase 41, expansion phase 42, exhaust phase 43 and inlet phase 44.

As used herein, the term "comprising" or "comprises" is open-ended, and includes one ormore stated features, elements, steps, components, or functions but does not preclude the 24 presence or addition of one or more other features, elements, steps, components, functionsor groups thereof.

Claims

CLA|I\/IS

1.

2. A method (100) of controlling an internal combustion engine (1), wherein the combustion engine (1) comprises: - a valve control arrangement (3, 5) capable of controlling the overlap (O) betweeninlet valves (7) and outlet valves (9) of the combustion engine (1), and - a knock sensing arrangement (11) configured to sense the occurrence of knock in atleast one cylinder (13) of the combustion engine (1), wherein the method (100) comprises: - determining (110) a knock level (kl) in the at least one cylinder (13), - setting (120) an overlap limit (Olim) based on a current overlap (O) used when thedetermined knock level (kl) exceeds a threshold value (th), and - controlling (130) the overlap (O) based on the overlap limit (Olim).

3. . The method (100) according to claim 1, wherein the step of controlling (130) the overlap

4. (O) comprises the steps of:- setting (132) an overlap target value (Ot) based on the overlap limit (Olim), and- controlling (134) the overlap (O) towards the overlap target value (Ot).

5. The method (100) according to claim 2, wherein the step of setting (132) the overlap target value (Ot) comprises the step of: - setting (133) the overlap target value (Ot) to a value being offset from the overlaplimit (Olim).

6. The method (100) according to claim 2 or 3, wherein the overlap target value (Ot)involves a greater overlap (O) than at the overlap limit (Olim).

7. The method (100) according to any one of the preceding claims, wherein the method(100) further comprises:- updating (140) the overlap limit (Olim) by reducing the overlap (O).

8. The method (100) according to claim 5, wherein the method (100) comprises:- updating (142) the overlap limit (Olim) periodically.

9. The method (100) according to claim 6, wherein the method (100) comprises:- updating (143) the overlap limit (Olim) with a first frequency in steady state operatingconditions of the combustion engine (1 ), and

10.

11. 26 - updating (144) the overlap limit (Olim) with a second frequency in transient operatingconditions of the combustion engine (1 ),wherein the second frequency is higher than the first frequency. A computer program comprising instructions which, when the program is executed by acomputer, cause the computer to carry out the method (100) according to any one of theclaims 1 - 7. A computer-readable medium (200) comprising instructions which, when executed by acomputer, cause the computer to carry out the method (100) according to any one of theclaims 1 - 7. A control arrangement (20) for contro||ing an internal combustion engine (1), wherein the combustion engine (1) comprises: - a valve control arrangement (3, 5) capable of contro||ing the overlap (O) betweeninlet valves (7) and outlet valves (9) of the combustion engine (1), and - a knock sensing arrangement (11) configured to sense the occurrence of knock in atleast one cylinder (13) of the combustion engine (1), wherein the control arrangement (20) is arranged to: - determine a knock level (kl) in the at least one cylinder (13), - set an overlap limit (Olim) based on a current overlap (O) used when the determined knock level (kl) exceeds a threshold value (th), and- control the overlap (O) based on the overlap limit (Olim). An internal combustion engine (1) comprising: - at least one cylinder (13), - a piston (15) arranged in each cylinder (13), - at least one inlet valve (7) at each cylinder (13), - at least one outlet valve (9) at each cylinder (13), - a valve control arrangement (3, 5) capable of contro||ing the overlap (O) between theinlet valves (7) and the outlet valves (9) of the combustion engine (1), - a knock sensing arrangement (11) configured to sense the occurrence of knock in atleast one cylinder (13) of the combustion engine (1), and - a control arrangement (20), wherein the control arrangement (20) is arranged to:- determine a knock level (kl) in the at least one cylinder (13), 5

12.

13.

14.

15.

16.

17. 27 - setting an overlap limit (Olim) based on a current overlap (O) used when thedetermined knock level (kl) exceeds a threshold value (th), and- control the overlap (O) based on the overlap limit (Olim). The combustion engine (1) according to claim 11, wherein the valve control arrangement (3, 5) comprises: - an inlet valve phase-shifting device (3) configured to phase-shift control of the atleast one inlet valve (7), and - an outlet valve phase-shifting device (5) configured to phase-shift control of the atleast one outlet valve (9). The combustion engine (1) according to claim 12, wherein the valve control arrangement(3, 5) is configured to control the overlap (O) by phase-shifting control of the at least oneinlet valve (7) and the at least one outlet valve (9). The combustion engine (1) according to any one of the claims 11 - 13, wherein thecombustion engine (1) comprises at least one ignition device (17) in each cylinder (13) ofthe combustion engine (1). The combustion engine (1) according to any one of the claims 11 - 14, wherein thecombustion engine (1) is specifically adapted to run on a gaseous fuel. The combustion engine (1) according to any one of the claims 11 - 14, wherein thecombustion engine (1) is specifically adapted to run on an alcohol based fuel. A vehicle (30) comprising a combustion engine (1) according to any one of the claims 11- 16.