Controlling valve actuation of an internal combustion engine

Abstract

The present disclosure relates to a method and a control arrangement (38) for controlling valve actuation of an ICE (4), the ICE comprising an exhaust valve (20), an intake valve (22) and a turbo-compressor (50). The method comprises and the control arrangement (38) is configured to: limit valve actuation changes of the exhaust valve and the intake valve based on compressor data comprising surge limit data of the turbo-compressor and one or both of a current turbo-compressor rotational speed and a current turbo-compressor pressure ratio to maintain a turbo-compressor mass flow above a limit mass flow value.

Description

TECHNICAL FIELD

[0001] The present invention relates to a method for controlling valve actuation and a control arrangement for controlling valve actuation. The invention further relates to an internal combustion engine and a vehicle comprising an internal combustion engine. Furthermore, the invention relates to a computer program and a computer-readable storage medium. BACKGROUND

[0002] Modern internal combustion engines, ICE, often comprise one or more compressors arranged to provide compressed air to be charged into the combustion chambers of the ICE. Often referred to as "boost air" provided by the compressor. The compressor comprises an impeller which can be driven by exhaust gases from the ICE in a so-called turbocharger turbine; by the crankshaft of the ICE, e.g. via a drive belt; or by an electric motor.

[0003] The compressor has an undesirable and / or unstable operating region. These can be noticed as a noise phenomenon and / or unstable ICE behaviour. Compressor surge is a problem associated with the unstable operating region of the compressor which has a negative impact on the ICE and its operation. Compressor surge, also simply referred to as surge, is an instability in the air flow from the compressor to the intake valve of the ICE. During surge, the mass flow of air changes periodically. During so-called "deep surge" or "full surge", the mass flow of air can even flow towards the compressor, i.e. in the opposite direction to the intended flow. Surge can damage and even destroy the compressor.

[0004] A compressor map can be shown as a graph presenting the corrected or reduced mass flow and pressure ratio of the compressor on the x-axis and y-axis, respectively. In the graph, corrected or reduced compressor constant speed lines are shown and a so-called surge line indicates the stable operating range of the compressor. When the mass flow rate drops along the compressor constant speed line, the compressor surge will start at a critical mass flow value. The surge line is usually established by interconnecting critical mass flow values of a plurality of compressor speed lines. The compressor map is usually established by measurements on a compressor running in a test bench, but can also be established by measurements on a compressor on an engine installation.

[0005] Surge in the compressor of the ICE should be avoided since it can damage the compressor and other parts of the ICE.

[0006] JP 2018 / 189060 discloses an engine control system including a variable valve timing mechanism, a supercharger, a state quantity acquisition unit configured to acquire a state quantity of intake air of an engine, a determination unit configured to determine whether the state quantity of intake air is within a predetermined surge region in which a surge phenomenon is likely to occur in the supercharger, and a control unit. The control unit is configured to control the variable valve timing mechanism to prevent the surge phenomenon of the supercharger when it is determined that the state quantity of intake air is within the predetermined surge region. SUMMARY

[0007] It would be advantageous to reduce the risk of operating a compressor of an ICE in an unstable or undesirable operating region. In particular, it would be desirable to provide valve actuation in an ICE while avoiding operation of the compressor of the ICE in an unstable or undesirable region, thereby at least reducing the risk of surge in the compressor. To better address one or more of these concerns, at least one of a method for controlling valve actuation and an arrangement for controlling valve actuation is provided having features as defined herein.

[0008] According to one aspect, a method for controlling valve actuation of an internal combustion engine, ICE, is provided. The ICE comprises an exhaust valve, an intake valve, and a turbo compressor. The method comprises:

[0009] limiting valve actuation changes of the exhaust valve and the intake valve based on compressor data comprising surge limit data of the turbo compressor and one or both of a current turbo compressor speed and a current turbo compressor pressure ratio to maintain the turbo compressor mass flow above a limit mass flow value.

[0010] According to another aspect, a control arrangement for controlling valve actuation of an internal combustion engine, ICE, is provided. The ICE comprises an exhaust valve, an intake valve, and a turbo compressor. The control arrangement is configured to:

[0011] limit valve actuation changes of the exhaust valve and the intake valve based on compressor data comprising surge limit data of the turbo compressor and one or both of a current turbo compressor speed and a current turbo compressor pressure ratio to maintain the turbo compressor mass flow above a limit mass flow value.

[0012] As valve actuation changes of the exhaust valve and the intake valve are limited based on compressor data comprising surge limit data of the turbo compressor and one or both of a current turbo compressor speed and a current turbo compressor pressure ratio to maintain the turbo compressor mass flow above a limit mass flow value, operation of the compressor in an unstable or undesirable operating region of the compressor is avoided or at least largely avoided.

[0013] More specifically, the valve actuation changes of the exhaust valve and the intake valve can lead to unstable or undesired operation of the compressor under certain ICE operating conditions. By limiting the valve actuation changes, the actuation changes that can lead to unstable or undesired operation of the compressor at the final position of the valve actuation changes or in the early stages of the valve actuation changes are prevented from reaching the final position in a way that would otherwise lead to unstable or undesired operation of the compressor, such as surging and / or noise phenomena.

[0014] The inventors have realized that, by utilizing stored compressor data and at least one current compressor operating parameter, it is possible to avoid situations in which unstable or undesired operation of the compressor occurs by limiting the valve actuation changes of the exhaust valve and the intake valve.

[0015] Limiting the valve actuation changes thus means that the valve actuation changes towards the target actuation settings of the exhaust valve and the intake valve, for example calculated in an engine control unit, ECU, are not performed according to the calculations in the ECU, but are limited. The ECU typically determines the target actuation settings of the valve actuation changes of the exhaust valve and the intake valve in order to tune the operation of the ICE. For example, the target actuation settings can maintain the exhaust gas temperature of the ICE above a minimum temperature threshold, can reduce the fuel consumption of the ICE, or can affect the compression release braking of the ICE.

[0016] The target actuation settings are not specifically set for compressor operation, and in particular are not determined in order to avoid unstable or undesired compressor operation. Rather, according to the method and / or control arrangement of the present invention, these measures are taken by limiting the valve actuation changes. Thus, the ECU can provide the basic control of the operation of the ICE, while one feature of the present invention is to intervene only when intervention is needed in order to avoid unstable or undesired compressor operation.

[0017] In different powertrains and different vehicles, the same engine block and cylinders are typically provided in several different ICE configurations, with different power ratings, with different types and numbers of turbo compressors, provided with different transmission types, with different numbers of driven wheels, with different sizes and volumes of charge air conduits including different sizes of charge air coolers, and with other flow paths than the compressor mass flow and the engine intake mass flow, such as EGR, exhaust gas recirculation. Thus, for many different ICE configurations, the basic ICE operation can be provided by the ECU, while the method and control arrangement of the present invention adapts the valve actuation of the ICE to the specific turbo compressor that cooperates with the ICE in the particular powertrain.

[0018] The "limiting" of the valve actuation variation and for "limiting" the valve actuation variation can be achieved by reducing the actual end position reached by the valve actuation variation and / or by increasing the time period used for reaching the end position by the valve actuation variation. In practice, the former can also mean in some ICE operating situations that, if directly executed, the valve actuation variation leading to an end position in which the compressor would operate in an unstable or undesired operating zone can be split into multiple partial valve actuation variations over time to eventually reach the originally intended end position of the valve actuation variation.

[0019] The limit mass flow value is set such that the risk of unstable and / or undesired operation of the compressor is reduced and preferably avoided.

[0020] Maintaining the turbo compressor mass flow above the limit mass flow value requires that stable operation of the turbo compressor can be achieved.

[0021] The limit mass flow value can be the surge limit mass flow at the current compressor operating conditions as provided by the surge limit data. Alternatively, the limit mass flow value can be set with a margin to the surge limit mass flow to ensure stable operation of the compressor at all or at least most of the ICE operating conditions.

[0022] The turbo compressor can form part of a turbocharger which accordingly comprises a turbine driven by the exhaust gas of the ICE. The turbine drives the impeller of the turbo compressor. Alternatively, the impeller of the turbo compressor can be driven by the crankshaft of the ICE, such as via a drive belt, or the impeller can be driven by an electric motor. In this context, the turbo compressor can alternatively be referred to as compressor. In this context, reference can be made to the compressor rotational speed which accordingly refers to the rotational speed of the compressor impeller.

[0023] The ICE can comprise more than one turbo compressor, such as two, four, six or eight turbo compressors, or for example one turbo compressor for each cylinder of the ICE or for each pair of cylinders. One or more compressors can be arranged to charge separate cylinder groups of the associated ICE. The compressors can be connected in series and / or in a parallel arrangement. The present method and control arrangement for controlling the valve actuation can be applied to each compressor of an ICE comprising multiple compressors in order to avoid unstable or undesired operating zones of each of the compressors.

[0024] The internal combustion engine ICE can be a four-stroke or two-stroke compression ignition ICE, such as a diesel engine, alternatively the ICE can be an Otto engine. In a four-stroke ICE, each piston performs an intake stroke, a compression stroke, a power stroke or expansion stroke and an exhaust stroke during two rotations of the crankshaft. In a two-stroke ICE, each piston performs a compression stroke and an expansion stroke for each rotation of the crankshaft.

[0025] The ICE comprises at least one cylinder, such as four, five, six or eight cylinders. Alternatively, the ICE can comprise more than eight cylinders, such as for example in larger ICEs used on board ships.

[0026] In this context, the term "valve actuation variation" relates to the opening and closing of the exhaust valve and the intake valve in relation to the rotational position of the crankshaft of the ICE. The valve actuation variation comprises a pure timing variation of the opening and closing positions of the exhaust valve and the intake valve, the opening period duration of each valve being maintained constant, as well as a lift height variation of the exhaust valve and the intake valve and combinations thereof. The timing variation and the lift height variation of the exhaust valve and the intake valve affect the amount of air admitted into the cylinder of the ICE and the amount of gas passing through the cylinder to the downstream exhaust system.

[0027] The compressor data can be provided in the form of one or more of a compressor map of the relevant turbo compressor of the ICE, a compressor table containing compressor data of the relevant turbo compressor of the ICE, a mathematical model of the relevant turbo compressor of the ICE, etc.

[0028] In order to perform the valve actuation variation, the ICE comprises a suitable mechanism. Such mechanisms are known. For example, controllable timing of the exhaust camshaft and the intake camshaft requires changing the rotational position of the camshafts in relation to the crankshaft of the ICE and accordingly also the opening and closing of the exhaust valve and the intake valve. This can also be referred to as cam phasing. For example, WO 2017 / 217908 and US 8714123 disclose a timing control arrangement for changing the timing of the camshafts. A different approach is to use so-called variable valve lift, VVL, which provides a variation of how much the exhaust valve and the intake valve are allowed to open, i.e. a variation of the valve lift height. US 2009 / 0151678 discloses a VVL mechanism. A combination of cam phasing and VVL can be referred to as variable valve actuation, VVA. For example, US 2006 / 0174854 discloses such a VVA mechanism. However, there are other ways of implementing VVA, such as by means of the mechanism disclosed in WO 2008 / 149316, which is provided in an ICE without any camshafts or with electromechanically actuated valves provided by the company Freevalve, Sweden. In its broadest aspect, the present invention is not limited to any particular type of mechanism for implementing the valve actuation variation. Sweden. In its broadest aspect, the present invention is not limited to any particular type of mechanism for implementing the valve actuation variation.

[0029] In this context, when discussing timing variation of the camshafts, reference will be made to crank angle, CA, degrees. One complete rotation of the crankshaft is 360 CA degrees. In a four-stroke ICE, the crank angle can for example be measured in relation to top dead center fire, TDCfire, or top dead center gas exchange, TDCge.

[0030] If the cylinder arrangement comprises one or more additional intake valves and / or exhaust valves, these valves can also be controlled with a limited valve actuation variation in the manner discussed above. On the other hand, for example in an ICE comprising a compression release brake, CRB, arrangement, where during CRB only one of e.g. two exhaust valves is actuated, only this valve can be controlled with a limited valve actuation variation in the manner discussed above.

[0031] According to embodiments, the method can further comprise:

[0032] determining target actuation settings for the exhaust valve and the intake valve, and

[0033] initiating a valve actuation variation of the exhaust valve and the intake valve towards the target actuation settings for the exhaust valve and the intake valve, and wherein the step of limiting the valve actuation variation can comprise:

[0034] preventing the initiated valve actuation variation from reaching the target actuation settings for the exhaust valve and the intake valve, or

[0035] increasing a time period required for the valve actuation variation to reach the target actuation settings for the exhaust valve and the intake valve. In this way, unstable or undesired operation of the turbo-compressor can be avoided by either of the steps of preventing or increasing. More specifically, the limiting can be implemented with respect to the target actuation settings for the exhaust valve and the intake valve, and the step of limiting the valve actuation variation can be further defined with respect to these target actuation settings.

[0036] According to embodiments, the method can further comprise:

[0037] determining a target ICE mass flow at the target actuation settings for the exhaust valve and the intake valve, and

[0038] comparing the target ICE mass flow with a limit mass flow value, and wherein

[0039] if the target ICE mass flow reaches said limit mass flow value, the following steps are performed:

[0040] limiting the valve actuation variation of the exhaust valve and the intake valve.

[0041] In this way, unstable or undesired operation of the turbo-compressor can be avoided, since the limiting step prevents the target ICE mass flow from being reached, which otherwise would result in unstable or undesired operation of the turbo-compressor.

[0042] The inventors have recognised that by utilising stored compressor data, such as limit mass flow values, and by calculating the mass flow of air through the ICE at the target actuation settings of the exhaust and intake valves, and comparing them, it is possible to avoid situations where the compressor is unstable or undesirably operated by limiting the valve actuation variation of the exhaust and intake valves.

[0043] According to embodiments, the limit mass flow value can be based on surge limit data, and the method can comprise:

[0044] adapting the limit mass flow value to current ICE operating conditions. In this way, when performing the step of limiting the valve actuation variation of the exhaust and intake valves based on surge limit data, the current operating conditions of the ICE and the mass flow through the ICE during such operating conditions can be further taken into account.

[0045] According to another aspect, there is provided a four-stroke internal combustion engine comprising a control arrangement according to any of the aspects and / or embodiments discussed herein.

[0046] According to another aspect, there is provided a vehicle comprising a four-stroke internal combustion engine according to any of the aspects and / or embodiments discussed herein.

[0047] According to another aspect, there is provided a computer program comprising instructions which, when the program is executed by a computer, cause the computer to carry out the method according to any of the aspects and / or embodiments discussed herein.

[0048] According to another aspect, there is provided a computer-readable storage medium comprising instructions which, when executed by a computer, cause the computer to carry out the method according to any of the aspects and / or embodiments discussed herein.

[0049] Other features and advantages of the present application will become apparent from the detailed description which follows, taken in conjunction with the accompanying drawings. BRIEF DESCRIPTION OF DRAWINGS

[0050] Various aspects and / or embodiments of the present application (including its particular features and advantages) will be readily appreciated by those skilled in the art from the following detailed description, taken in conjunction with the accompanying drawings, from which:

[0051] Figure 1 embodiments of a vehicle are shown,

[0052] Figure 2 embodiments of an ICE are shown schematically,

[0053] Figure 3 a control arrangement is shown,

[0054] Figure 4An example of a compressor characteristic curve diagram is shown.

[0055] Figure 5 Showing about Figure 2 The image of the ICE

[0056] Figure 6 An example of a compressor datasheet is shown.

[0057] Figure 7 An embodiment of a method for controlling valve actuation is shown, and

[0058] Figure 8 An embodiment of a computer-readable storage medium is shown. Detailed Implementation

[0059] The aspects and / or embodiments of the invention will now be described more fully. The same numbers always refer to the same elements. For the sake of brevity and / or clarity, well-known functions or constructions need not be described in detail.

[0060] Figure 1 An embodiment of a vehicle 2 configured for land-based propulsion is shown. Vehicle 2 includes a four-stroke internal combustion engine ICE 4 according to the aspects and / or embodiments discussed herein, such as those referenced below. Figure 2 The ICE discussed here. ICE 4 includes control arrangements, as referenced below. Figure 2 and Figure 3 The discussion.

[0061] In these embodiments, vehicle 2 is a heavy-duty vehicle in the form of a truck. However, the invention is not limited to any particular type of vehicle configured for land-based propulsion.

[0062] Figure 2 An embodiment of a four-stroke ICE 4 is schematically illustrated. The ICE 4 can be configured to form a vehicle (such as, for example...) Figure 1 The powertrain system of vehicle 2) shown in the document. The methods discussed herein, especially those referencing... Figure 7 The method described applies to ICE 4. However, the method can alternatively be applied to two-stroke ICEs, such as large two-stroke ICEs used to propel ships.

[0063] The four-stroke ICE 4 is a direct-injection internal combustion engine, such as a compression-ignition ICE 4, like a diesel engine. The ICE 4 includes at least one cylinder arrangement 6 (usually referred to simply as a cylinder) and a crankshaft 8.

[0064] The cylinder arrangement 6 includes a combustion chamber 14, a cylinder bore 16, a piston 18 configured to reciprocate in the cylinder bore 16, an exhaust valve 20, and an intake valve 22. The piston 18 is connected to the crankshaft 8 via a connecting rod 24.

[0065] The intake valve 22 is configured for allowing charge air to enter the combustion chamber 14, and the exhaust valve 20 is configured for allowing exhaust gases to exit the combustion chamber 14. In a known manner, the intake valve 22 comprises an intake valve head configured to seal against an intake valve seat extending around the intake port 26. The exhaust valve 20 comprises an exhaust valve head configured to seal against an exhaust valve seat extending around the exhaust port 28.

[0066] The ICE 4 further comprises a mechanism for controlling the motion of the exhaust valve 20 and the intake valve 22.

[0067] In these embodiments, the mechanism comprises an exhaust camshaft 10 and an intake camshaft 12. The motion of the exhaust valve 20 is controlled by the exhaust camshaft 10, i.e. the exhaust camshaft 10 is configured to control the opening and closing of the exhaust valve 20. The motion of the intake valve 22 is controlled by the intake camshaft 12, i.e. the intake camshaft 12 is configured to control the opening and closing of the intake valve 22.

[0068] However, other mechanical, hydraulic or electro-mechanical mechanisms or combinations thereof can alternatively be used for controlling the motion of the exhaust valve 20 and the intake valve 22.

[0069] In particular, the mechanism for controlling the motion of the exhaust valve 20 and the intake valve 22 provides for valve actuation variation, i.e. the opening and closing of the valves 20, 22 can be varied with respect to the rotational position of the crankshaft 8. For example, the mechanism can be any of the prior art mechanisms mentioned above in the summary section of the description.

[0070] Hence, in order to provide valve actuation variation in these embodiments, the timing of the exhaust camshaft 10 is configured to be controlled by the timing control arrangement 30, as indicated by the double arrow. Similarly, the timing of the intake camshaft 12 is configured to be controlled by the timing control arrangement 32, as indicated by the double arrow.

[0071] The piston 18 is arranged to reciprocate in the cylinder bore 16. The piston 18 performs four strokes in the cylinder bore 16, corresponding to an intake stroke, a compression stroke, an expansion or power stroke, and an exhaust stroke, see also Figure 5 In Figure 2 the piston 18 is shown with a continuous line at its bottom dead centre, BDC, and with a dashed line at its top dead centre, TDC. The combustion chamber 14 is formed above the piston 18 inside the cylinder bore 16.

[0072] The cylinder arrangement 6 has a total displacement V S According to some embodiments, the cylinder arrangement 6 can have a total displacement V SBy way of example only, in a lower range of Vs, the cylinder arrangement 6 can form part of an internal combustion engine for a passenger car, while in an intermediate and higher range of Vs, the cylinder arrangement 6 can form part of an internal combustion engine for a heavy duty vehicle such as a truck, bus or construction vehicle.

[0073] The ICE 4 comprises a turbo-compressor 50. In these embodiments, the turbo-compressor forms part of a turbocharger 44. The turbocharger 44 comprises the turbo-compressor 50 and a turbine 52. The turbo-compressor 50 and the turbine 52 of the turbocharger 44 are connected via a common shaft 54. An inlet conduit 46 for charge air is directed from an outlet of the turbo-compressor 50 to the intake port 26 of the cylinder arrangement 6. For the sake of clarity, the inlet conduit 46 is not shown in its entirety. A charge air cooler (not shown) can be arranged in, or form part of, the inlet conduit 46. An exhaust conduit 48 is directed from the exhaust port 28 of the cylinder arrangement 6 to the turbine 52. The turbo-compressor 50 generates a charge air pressure in the inlet conduit 46 and at the intake valve 22. More specifically, the gases expelled via the exhaust valve 20 drive the turbine 52, which in turn rotates an impeller of the turbo-compressor 50. Thus, the turbo-compressor 50 provides charge air at a charge air pressure to the intake valve 22.

[0074] According to an alternative embodiment, the turbo-compressor 50 can be driven in a different manner than by exhaust gases via the turbine 52, such as by the crankshaft 8 or by a separate electric motor.

[0075] The ICE 4 comprises a fuel injector 56 configured to inject fuel into the combustion chamber 14 when the ICE 4 generates positive torque, e.g. for propelling a vehicle.

[0076] The ICE 4 further comprises a control arrangement 38 according to aspects and / or embodiments discussed herein. The control arrangement 38 is configured for controlling the valve actuation variation of the ICE 4. That is, in these embodiments, the control arrangement 38 is configured for controlling at least the timing of the exhaust camshaft 10 and the timing of the intake camshaft 12. Thus, the timing control arrangements 30, 32 form part of the control arrangement 38.

[0077] According to an alternative embodiment, other or additional mechanisms for controlling the valve actuation variation than the timing control of the exhaust camshaft 10 and the intake camshaft 12 are included, a corresponding control arrangement 38 for implementing the valve actuation variation is provided.

[0078] Irrespective of the mechanisms for controlling the valve actuation variation, the control arrangement 38 is configured to:

[0079] limiting the valve actuation changes of the exhaust valve 20 and the intake valve 22 based on the compressor data including the surge limit data of the turbo-compressor 50 and one or both of the current turbo-compressor speed and the current turbo-compressor pressure ratio to maintain the turbo-compressor mass flow above the limit mass flow value.

[0080] In this way, operation of the turbo-compressor 50 in an unstable or undesired operating region of the turbo-compressor 50 is avoided or at least largely avoided.

[0081] According to some embodiments, the limiting of the valve actuation changes of the exhaust valve 20 and the intake valve 22 can be implemented by the control arrangement 38 being configured to perform one or more of:

[0082] providing the compressor data including the surge limit data of the turbo-compressor 50, which can be stored in a memory of the control arrangement 38,

[0083] providing the current speed of the turbo-compressor 50 and / or the current compressor pressure ratio, as measured by sensors of the control arrangement 38 and, if applicable, calculated in a computing unit of the control arrangement 38, such as the speed sensor 34 of the compressor 50 and the pressure sensors 83, 76 at the inlet side and the outlet side of the compressor 50, and

[0084] limiting the timing changes of the exhaust camshaft 10 and the intake camshaft 12 based on the compressor data including the surge limit data of the turbo-compressor 50 and one or both of the current turbo-compressor speed and the current turbo-compressor pressure ratio to maintain the turbo-compressor mass flow above the limit mass flow value.

[0085] According to some embodiments, the control arrangement 38 can be further configured to:

[0086] determining a target actuation setting of the exhaust valve 20 and the intake valve 22,

[0087] initiating a valve actuation change of the exhaust valve 20 and the intake valve 22 towards the target actuation setting of the exhaust valve 20 and the intake valve 22, and

[0088] preventing the initiated valve actuation change from reaching the target actuation setting of the exhaust valve 20 and the intake valve 22, or

[0089] increasing a time period required for the valve actuation change to reach the target actuation setting of the exhaust valve 20 and the intake valve 22.

[0090] In this way, unstable or undesirable operation of the turbo-compressor 50 can be avoided by preventing the initiated change in valve actuation from reaching the target actuation setting or directly by increasing the period of time required for the change in valve actuation to reach the target actuation setting, for example.

[0091] According to some embodiments, this can be achieved by the control arrangement 38 being configured to perform one or more of:

[0092] determining a target timing setting for the exhaust camshaft 10 and the intake camshaft 12,

[0093] initiating a timing change of the exhaust camshaft 10 and the intake camshaft 12 towards the target timing setting for the exhaust camshaft 10 and the intake camshaft 12,

[0094] preventing the initiated timing change from reaching the target timing setting, and

[0095] increasing a period of time required for the initiated timing change to reach the target timing setting for the exhaust camshaft 10 and the intake camshaft 12.

[0096] According to some embodiments, the control arrangement 38 can be further configured to:

[0097] determine a target ICE mass flow at the target actuation setting, and

[0098] compare the target ICE mass flow to a limit mass flow value, and wherein

[0099] if the target ICE mass flow reaches the limit mass flow value, the control arrangement 38 can be configured to:

[0100] limit the change in valve actuation of the exhaust valve 20 and the intake valve 22.

[0101] In this way, unstable or undesirable operation of the turbo-compressor 50 can be avoided because the limitation prevents the target ICE mass flow from being reached, which otherwise would result in unstable or undesirable operation of the turbo-compressor.

[0102] According to some embodiments, this can be achieved by the control arrangement 38 being configured to perform one or more of:

[0103] determine a target ICE mass flow at the target timing setting for the exhaust camshaft 10 and the intake camshaft 12, and

[0104] limit the initiated timing change of the exhaust camshaft 10 and the intake camshaft 12.

[0105] According to embodiments, the limit mass flow value can be based on surge limit data, and the control arrangement 38 can be configured to:

[0106] Adapt the limit mass flow value to current ICE operating conditions. Further reference is made to the corresponding features of the methods discussed herein.

[0107] According to embodiments, in the context of adapting the limit mass flow to current ICE operating conditions, the control arrangement 38 can be configured to:

[0108] When the degree of change in ICE operation is a sudden reduction in the torque request to the ICE, a greater safety margin is provided for the surge limit data than when the degree of change in ICE operation is a gradual change in the torque request to the ICE. Further reference is made to the corresponding features of the methods discussed herein.

[0109] The torque request is an instruction to provide a certain torque, typically from the ECU of the ICE 4. The torque request can be initiated by an accelerator pedal setting or by a cruise control of the vehicle.

[0110] The control arrangement 38 is further discussed below, as well as the valve actuation changes of the exhaust valve 20 and the intake valve 22. Figure 3 to Figure 6 Further reference is made to the corresponding features of the methods discussed herein.

[0111] The ICE 4 can comprise any suitable or common number of cylinder arrangements 6, such as for example four, five, six or eight cylinder arrangements.

[0112] Figure 3 The control arrangement 38 is shown in connection with different aspects and / or embodiments of the invention. In particular, the control arrangement 38 is configured for controlling the valve actuation changes discussed herein. The control arrangement 38 is also shown in Figure 2 . Thus, reference is also made to Figure 2 .

[0113] The control arrangement 38 comprises at least one computing unit 60, which can take the form of essentially any suitable type of processor circuitry or microcomputer, for example a circuit for digital signal processing (digital signal processor, DSP), a central processing unit (CPU), a processing unit, a processing circuit, a processor, an application-specific integrated circuit (ASIC), a microprocessor, or other processing logic that can interpret and execute instructions. The expression “computing unit” used herein can represent processing circuitry comprising a plurality of processing circuits, such as for example any one, some or all of the processing circuits described above. The computing unit 60 can be configured to perform calculations, such as for example the interpolation and mathematical calculations discussed herein.

[0114] The control arrangement 38 comprises a memory unit 62. The computing unit 60 is connected to the memory unit 62, which provides the computing unit 60 with, for example, stored program code, data tables and / or other stored data, for example related to the turbo compressor 50, which the computing unit 60 needs to enable it to perform calculations and control the valve actuation variation. The computing unit 60 is also adapted to store partial results or final results of calculations in the memory unit 62. The memory unit 62 can comprise a physical device to store data or programs, i.e. sequences of instructions, on a temporary or permanent basis. According to some embodiments, the memory unit 62 can comprise an integrated circuit comprising silicon-based transistors. In different embodiments, the memory unit 62 can comprise, for example, a memory card, a flash memory, a USB memory, a hard disk or another similar volatile or non-volatile storage unit for storing data, such as, for example, a ROM (Read-Only Memory), a PROM (Programmable Read-Only Memory), an EPROM (Erasable PROM), an EEPROM (Electrically Erasable PROM) or the like.

[0115] The control arrangement 38 is also provided with respective devices 66, 67, 68, 69, 70, 72, 73, 74, 77 for receiving and / or sending input and output signals. These input and output signals can comprise waveforms, pulses or other properties that can be detected as information by the signal receiving devices and can be converted into signals that can be processed by the computing unit 60. Input signals are supplied from the input receiving devices 67, 69, 70, 72, 73, 74, 77 to the computing unit 60. The output signal sending devices 66, 68 are arranged to convert the results of calculations from the computing unit 60 into output signals for transmission to the signal receiving devices of other parts of the control arrangement 38. Each of the connections to the respective devices for receiving and sending input and output signals can take the form of one or more from among electrical cables, data buses, for example a CAN (Controller Area Network) bus, a MOST (Media Oriented Systems Transport) bus or some other bus configuration, or wireless connections. In the depicted embodiment, only one computing unit 60 and memory unit 62 are shown, but the control arrangement 38 can instead comprise more than one computing unit and / or memory unit.

[0116] By way of example reference, in the depicted embodiment, the output signal sending devices 66, 68 can send control signals to the timing control arrangements 30, 32 of the exhaust camshaft 10 and the intake camshaft 12. The input signal receiving devices 67, 69, 70, 72, 73, 74, 77 can receive signals from the ICE 4, such as, for example, from the rotational speed sensor 34 of the turbo compressor 50, the rotational speed / position sensor 75 of the crankshaft 8 of the ICE 4, the compressor outlet / boost air pressure sensor 76, the rotational speed / position sensor 81 of the exhaust camshaft 10, the rotational speed / position sensor 82 of the intake camshaft 12, the compressor inlet pressure sensor 83, and the compressor inlet temperature sensor 85.

[0117] An example of a data table can be, for example, a compressor table, a table showing the relationship between turbocharger rotational speed and boost air pressure, a table containing fuel injection amounts, etc. Another example of a data table can be a compressor map relating to the compressor 50.

[0118] Examples of data can be measured, monitored, determined, and / or calculated data, such as rotational speed data, boost air pressure data, timing change angle data, valve actuation change data, surge limit data, such as surge mass flow data, limit mass flow data, compressor inlet pressure, compressor inlet temperature, etc. The control arrangement 38 comprises or is connected to various sensors and actuators in order to receive inputs and provide outputs for performing various aspects and embodiments of the methods and functions of the control arrangement 38 discussed herein. Some of the various sensors are exemplified above. An example of an actuator can be an actuator configured to change valve actuation, such as an actuator for changing the timing of the camshafts 10, 12 forming part of the timing control arrangements 30, 32.

[0119] The control arrangement 38 can be configured to perform the method 100 according to any of the aspects and / or embodiments discussed herein, see, for example, below with reference to Figure 7 . Thus, the discussion relating to the method 100 applies to the corresponding features of the control arrangement 38 and vice versa.

[0120] The computing unit 60 can comprise one single processor, or the computing unit can take the form of a distributed computing unit 60, i.e. comprise more than one processor. Similarly, the computing unit 60 can be dedicated to perform the methods and functions discussed herein, or the computing unit 60 can be configured to perform additional tasks, such as for example an engine control unit ECU forming the ICE 4. In the latter case, the methods and functions discussed herein can be programmed as a separate entity of the ECU, and can be programmed to limit, override, interrupt or interfere with other ICE control operations of the ECU, such as for example intended valve actuation variations, initiated valve actuation variations towards target actuation settings, and initiated timing variations of the camshafts 10, 12.

[0121] The control arrangement 38 is configured to store a representation of the turbo-compressor 50, such as a compressor map, a data table containing compressor data of the turbo-compressor 50 and / or a model of the turbo-compressor 50.

[0122] Figure 4 An example of a compressor map 86 showing parts of a typical compressor 50 of an ICE 4 for a vehicle is shown. The compressor map is a well-known graph showing the operating range of a turbo-compressor. The compressor map 86 can be defined as a field in a coordinate system having axes representing the boost air mass flow m’ and the compressor pressure ratio, i.e. the relation between the boost air pressure after the turbo-compressor and the boost air pressure before the turbo-compressor, P_out:P_in. Typically, the mass flow is the corrected mass flow m’_corr or the reduced mass flow m’_red. Further, constant speed lines of the compressor, i.e. the impeller of the turbo-compressor, are shown in the graph, such as the corrected constant speed line n_corr or the reduced constant speed line n_red. A number of constant speed lines are shown in the graph with dotted lines labelled “n_corr”. A surge line 90 indicates the stable operating range of the turbo-compressor. I.e. the surge line 90 indicates the corrected surge limit mass flow m’_corr_surge for different pressure ratios.

[0123] The corrected mass flow m’_corr is present on the X-axis. The corrected mass flow m’_corr is the mass flow m’ through the compressor 50 corrected to be expressed at a reference temperature T_ref and a reference pressure P_ref, e.g. T_ref = 298 K and P_ref = 100 000 Pa, at a standard temperature and a standard pressure. T_in is the actual air temperature at the compressor inlet and P_in is the actual inlet pressure at the inlet of the compressor. The formula used is:

[0124] m’_corr = m’ * (sqrt(T_in / T_ref)) / (P_in / P_ref)

[0125] If instead a reduced mass flow m'_red is used, the formula for this is:

[0126] m'_red = m' * (sqrt T_in) / P_in

[0127] The pressure ratio is presented on the y-axis, i.e. the ratio between the total outlet pressure P_out at the outlet of the compressor and the total inlet pressure P_in.

[0128] The compressor constant speed line n_corr in the figure is the corrected constant speed line, i.e. the compressor speed in relation to the reference temperature T_ref. The formula used is:

[0129] n_corr = n / sqrt(T_in / T_ref)

[0130] If instead a reduced speed n_red is used, the formula for this is:

[0131] n_corr = n / sqrt T_in

[0132] The difference between the corrected mass flow and the reduced mass flow and between the corrected speed and the reduced speed is thus in the ratio used.

[0133] Generally, to the left of the surge line, the operation of the compressor is unstable - compressor surge occurs. To the right of the surge line, the operation of the compressor is stable, although undesirable phenomena such as noise phenomena can occur. For example, to the right of the surge line, undesirable phenomena such as noise phenomena can also occur under certain ICE operating conditions.

[0134] The present invention thus aims, in a general sense, to maintain the turbo-compressor 50 operating to the right of the surge line 90 by limiting the valve actuation changes that would otherwise cause the compressor 50 to operate to the left of the surge line 90. The safety margin of the surge line 90 can be applied to ensure stable operation of the compressor 50 under all operating conditions of the ICE.

[0135] Figure 4 One example of such a limited valve actuation change is illustrated in Fig. 5. The turbo-compressor 50 operates in the position indicated with x in the compressor characteristic diagram 86. The ECU of the ICE 4 is prepared to perform an expected valve actuation change towards a target actuation setting, which would cause the operating position of the compressor 50 to fall to the left of the surge line 90 in the compressor characteristic diagram 86, indicated with x i . The control arrangement 38 intervenes and limits the valve actuation change so that the operating position of the compressor 50 instead falls to the right of the surge line 90 in the compressor characteristic diagram 86, indicated with x L . The control arrangement 38 intervenes and limits the valve actuation change so that the operating position of the compressor 50 instead falls to the right of the surge line 90 in the compressor characteristic diagram 86, indicated with x

[0136] Figure 5As shown in the reference above Figure 2 to Figure 4 The argument Figure 2 The diagram of ICE 4 and its controls. Therefore, it can also be referenced. Figure 2 to Figure 4 .

[0137] Figure 5 The diagram illustrates the movement of piston 18 during the four strokes of the ICE 4, as well as the movement of exhaust valve 20 (solid line) and intake valve 22 (dotted line). During the four strokes of piston 18, the crankshaft 8 of the ICE 4 rotates 720 CA degrees. For each stroke, crankshaft 8 rotates 180 CA degrees, as shown... Figure 5 As indicated in [the document]. This is purely to illustrate the limitations of valve actuation changes; see [reference]. Figure 5 Lines I and II illustrate examples of this limitation.

[0138] Line I illustrates valve actuation, specifically the opening and closing of exhaust valve 20 and intake valve 22 during normal operation of the ICE 4. Furthermore, the opening and closing of exhaust valve 20 and intake valve 22 at the target actuation setting are shown with dashed lines. In the example shown, the target actuation setting involves advancing the opening and closing of exhaust valve 20 by α_i CA degrees and delaying the opening and closing of intake valve 22 by β_i CA degrees.

[0139] Line II illustrates the actual opening and closing of exhaust valve 20 and intake valve 22, i.e., after a restricted valve actuation change has been performed. The initially anticipated target actuation setting has been restricted, resulting in a reduced valve actuation change in order to maintain the turbo compressor mass flow above the limiting mass flow value and thus reduce the risk of compressor 50 operating in an unstable or undesirable operating range. In the example shown, the initially anticipated target actuation setting has been restricted, resulting in a restricted advance of the αCA degree of opening and closing of exhaust valve 20 and a restricted delay of the βCA degree of opening and closing of intake valve 22, where α < α_i and β < β_i.

[0140] Also refer to Figure 4 The expected valve actuation changes of the exhaust valve 20 (α_i CA degree) and the intake valve 22 (β_i CA degree) will cause the compressor 50 to exhibit the characteristic curve shown in the compressor characteristic curve diagram 86 using x. i Unstable operation at the indicated location. Restricted valve actuation variations of the exhaust valve 20 (αCA degree) and the intake valve 22 (βCA degree) will cause the compressor 50 to exhibit unstable operation as indicated by x in the compressor characteristic curve diagram 86. L Stable operation at the indicated location.

[0141] The above can exemplify a transition between operating points of the ICE 4, such as from a high ICE load to a low ICE load, or from heating of the exhaust system of the ICE to no heating thereof. If the ICE mass flow controlled by the variation of the valve actuation would be allowed to reach the target actuation setting directly, a direct transition from a high load point with a high steady boost air pressure from the compressor 50 to a low load point with a low steady boost air pressure would result in compressor surge. The present invention provides a maximum allowed reduction of the ICE mass flow that the compressor can handle given the current boost air pressure, and limits the variation of the valve actuation of the exhaust valve 20 and the intake valve 22 accordingly.

[0142] Figure 6 An example of a compressor data table showing parts of the compressor characteristic map of a typical turbo compressor 50 forming the ICE 4 of the vehicle 2 is shown. The data table provides corrected mass flow m'_corr values and pressure ratio Pout / Pin at corrected rotational speed n_corr. The surge limit data presented in the data table is the corrected mass flow m'_corr value forming the surge limit mass flow m'_corr_surge value.

[0143] The exemplifying data table is three-dimensional. The data table can be used as a two-dimensional data table by using the current corrected rotational speed n_corr, current pressure ratio Pout:Pin to establish the corrected mass flow m'_corr of the current surge limit mass flow.

[0144] The way of utilizing all three dimensions of the table can be to utilize both the current corrected rotational speed n_corr and the current pressure ratio Pout:Pin to establish the corrected mass flow m'_corr. For example, by averaging between two corrected mass flow m'_corr values established by each of the current corrected rotational speed n_corr and the current pressure ratio Pout:Pin, an alternative is to use the maximum limit of the two corrected mass flows m'_corr, i.e. the maximum value, which corresponds to one of the current corrected rotational speed n_corr and the current pressure ratio Pout:Pin.

[0145] Alternatively, the data table can be a two-dimensional data table by including only one of the columns of pressure ratio Pout / Pin or corrected rotational speed n_corr and the corrected mass flow m'_corr of the current surge limit value.

[0146] Intermediate values not presented in the data table can be established, for example, by interpolation between two close values.

[0147] While the compressor characteristic map and data table surge line representation is easy to visualize, any algorithm that obtains a representative surge line description is sufficient for the applicability of the method and control arrangement presented herein.

[0148] For example, the slope of the straight line through the mass flow corrected by zero compressor and the unit compressor pressure ratio point can be used as a simplified surge line model. The slope can be a least square fit to available surge point data. This would be a single parameter surge model.

[0149] Another example can be to convert the compressor map variables to Phi and Psi variables, which would reduce the compressor speed dependency and can be used to define a single Phi_surge value. Phi and Psi variables are commonly used in the turbocompressor development / research field. This can be used as a single parameter surge model.

[0150] A further alternative can be to utilize 3D computational fluid dynamics (CFD) simulations and / or large eddy simulations (LES) to evaluate the surge mass flow. The resulting simulated surge mass flow can be used in the methods and control arrangements presented herein.

[0151] Hence, exemplary representations of compressor data of a turbocompressor 50 including surge limit data (compressor maps, compressor data tables and compressor / surge models) are known in the art. Other known means for providing compressor surge data can alternatively or additionally be utilized.

[0152] Figure 7 An embodiment of a method 100 for controlling valve actuation of an ICE is shown. The ICE can be an ICE 4 including a control arrangement 38 as discussed above in connection with Figure 1 to Figure 6 . Hence, reference is also made to the above discussion in the following. Figure 1 to Figure 6 .

[0153] The method 100 comprises:

[0154] Limiting 102 a valve actuation change of the exhaust valve 20 and the intake valve 22 based on compressor data including surge limit data of the turbocompressor 50 and one or both of a current turbocompressor speed and a current turbocompressor pressure ratio to maintain the turbocompressor mass flow m’ above a limit mass flow value.

[0155] Maintaining the turbocompressor mass flow above the limit mass flow value entails achieving stable operation of the turbocompressor 50. In this way, operation of the compressor 50 in an unstable or undesired operating region of the compressor 50 is avoided or at least largely avoided.

[0156] Hence, the step of limiting 102 a valve actuation change of the exhaust valve 20 and the intake valve 22 is applied to reduce the risk of unstable or undesired operation of the turbocompressor 50.

[0157] The pressure ratio over the compressor 50 and / or the rotational speed of the compressor 50 and the air temperature T_in at the inlet of the compressor 50 with compressor data provided for example by a compressor map 86, a compressor table or a compressor model provide the mass flow m’, m’_corr, m’_red of the turbo compressor 50.

[0158] The ideal gas law (general gas equation) applied to the one or more cylinder arrangements 6 charged by the compressor 50 provides the mass flow through the relevant cylinder arrangement 6 of the ICE 4. More specifically, the inlet pressure and the inlet temperature at the intake valve 22 provide the physical conditions. The air / gas volume enclosed in the cylinder arrangement 6 depends on the closing positions of both valves 20, 22, i.e. the specific actuation settings of the exhaust valve 20 and the intake valve 22 determine the air / gas volume enclosed and transported through the cylinder arrangement 6. The rotational speed of the ICE 4 then gives the mass flow through the cylinder arrangement 6 of the ICE 4.

[0159] The target mass flow through the cylinder arrangement 6 of the ICE 4 at the target actuation settings (intended end positions) of the exhaust valve 20 and the intake valve 22 is calculated and compared to the limit mass flow value through the compressor 50, such as the surge limit mass flow m’_surge or the surge limit mass flow with a safety margin applied.

[0160] The current operating conditions of the compressor 50 provide a corrected limit mass flow value, such as the corrected surge limit mass flow m’_corr_surge, established according to compressor maps, data tables etc. as discussed above.

[0161] Due to the inherent lag of the operating conditions of the turbo compressor 50 changing and in comparison to the faster changes of the operating conditions of the ICE 4 caused by the valve actuation changes, the current corrected limit mass flow value of the compressor 50 can be compared to the mass flow through the cylinder arrangement 6 of the ICE 4 at the target actuation settings of the exhaust valve 20 and the intake valve 22.

[0162] In order to compare the thus calculated mass flow of the ICE 4 to the current corrected surge limit mass flow m’_corr_surge, the corrected surge limit mass flow m’_corr_surge can be converted to a mass flow m’_surge of the compressor 50. This can be done by reverse calculation with the above mentioned formula for calculating m’_corr, i.e.

[0163] m’_surge = m’_corr_surge * (P_in / P_ref) / (sqrt((T_in / T_ref))

[0164] If a reduced mass flow is applied in the compressor table, data table, etc. instead of the corrected mass flow, the corresponding reverse calculation applies to the reduced mass flow.

[0165] If the compressor outlet pressure sensor 76 is arranged in the vicinity of the outlet of the compressor 50, the outlet pressure P_out of the turbo-compressor 50 can be measured directly by the compressor outlet pressure sensor. If the compressor outlet pressure sensor 76 is arranged further downstream of the compressor outlet, e.g. after an intercooler (not shown) arranged in the inlet conduit 46, the outlet pressure P_out of the turbo-compressor 50 can be calculated with knowledge about the pressure drop between the compressor outlet and the position of the pressure sensor 76.

[0166] The inlet pressure P_in of the turbo-compressor 50 can be measured by a pressure sensor (not shown) arranged at the inlet of the turbo-compressor 50. An alternative to measuring the inlet pressure P_in of the compressor 50 can be to calculate the inlet pressure of the compressor 50 based on a measured ambient air pressure and with knowledge about the pressure drop from the air intake of the ICE 4 to the inlet of the compressor 50.

[0167] The pressure ratio P_out:P_in can be calculated based on the respective established outlet and inlet pressures of the compressor 50.

[0168] If the pressure drop from the compressor outlet pressure sensor 76 to the intake valve 22 is known, the inlet pressure at the intake valve 22 can be calculated based on the outlet pressure P_out of the turbo-compressor 50 as measured by the compressor outlet pressure sensor 76. Otherwise, a pressure sensor can be provided in the vicinity of the intake valve 22. Similarly, the temperature at the intake valve 22 can be calculated from the known inlet temperature T_in of the compressor 50, or a temperature sensor can be provided in the vicinity of the intake valve 22.

[0169] The mass flow through the cylinder arrangement 6 of the ICE 4 is decisive for the turbo-compressor ICE combination. In other words, the turbo-compressor 50 cannot force a mass flow through the cylinder arrangement 6 of the ICE 4 higher than the mass flow drawn through the cylinder arrangement 6 of the ICE 4. Therefore, a reduction of the mass flow through the cylinder arrangement 6 of the ICE 4 due to a valve actuation variation of the valves 20, 22 will affect the mass flow m’ of the turbo-compressor 50. Too large valve actuation variations can force the compressor 50 into an unstable operation.

[0170] Hence, the mass flow through the cylinder arrangement 6 of the ICE 4 is controlled by the step of limiting 102 the valve actuation of the valves 20, 22 to maintain the mass flow m’ of the turbo-compressor 50 above the limit mass flow value of the turbo-compressor 50. That is, the mass flow through the cylinder arrangement 6 of the ICE 4 does not force a mass flow onto the compressor 50 that would result in unstable or undesired operation of the compressor 50.

[0171] The limit mass flow value of the compressor 50 depends on operating parameters of the compressor 50 and is related to the surge line 90 as provided in, for example, a compressor characteristic map 86, a compressor table or a compressor model.

[0172] Prior to the step of limiting 102, the method 100 can comprise:

[0173] providing 101 compressor data comprising surge limit data of the turbo-compressor 50,

[0174] providing 103 a current turbo-compressor speed and / or a current turbo-compressor pressure ratio, and

[0175] initiating 105 a valve actuation change.

[0176] In embodiments of the ICE 4 where a change in timing of the camshafts 10, 12 provides the valve actuation change, the step of initiating 105 the valve actuation change can comprise initiating a change in timing of the exhaust camshaft 10 and the intake camshaft 12.

[0177] According to embodiments, the method 100 can further comprise:

[0178] determining 104 target actuation settings of the exhaust valves 20 and the intake valves 22, and

[0179] initiating 106 a valve actuation change of the exhaust valves 20 and the intake valves 22 towards the target actuation settings of the exhaust valves 20 and the intake valves 22, and wherein the step of limiting 102 the valve actuation change can comprise:

[0180] preventing 108 the initiated valve actuation change from reaching the target actuation settings of the exhaust valves 20 and the intake valves 22, or

[0181] increasing 109 a time period required for the valve actuation change to reach the target actuation settings of the exhaust valves 20 and the intake valves 22.

[0182] In this way, unstable or undesired operation of the turbo-compressor 50 can be avoided by the step of limiting 102 the valve actuation change applying one of the steps of preventing 108 the initiated valve actuation change from reaching the target actuation settings of the exhaust valves 20 and the intake valves 22, or increasing 109 a time period required for the valve actuation change to reach the target actuation settings of the exhaust valves 20 and the intake valves 22.

[0183] The mass flow through the cylinder arrangement 6 of the ICE 4 at the target actuation settings of the valves 20, 22 can be calculated in the above-described manner. Thus, it can be determined in the step of limiting 102 the valve actuation variation whether the initiated valve actuation variation will require limiting to avoid unstable or undesired operation of the turbo-compressor 50.

[0184] Preventing 108 the initiated valve actuation variation from reaching the target actuation settings means that the intended valve actuation variation, e.g. determined by the ECU of the ICE, is not executed to the maximum, i.e. does not reach the target actuation settings. Thus, unstable operation of e.g. the turbo-compressor 50 at the target actuation settings can be avoided.

[0185] Increasing 109 the time period required for the valve actuation variation to reach the target actuation settings means that it will take longer to execute the intended valve actuation variation. For example, when the ECU of the ICE would simply execute the initiated valve actuation variation in as short time as possible, causing a sudden change in the mass flow through the cylinder arrangement 6 of the ICE 4, increasing the time period to reach the target actuation settings allows for a gradual change in the charge air supply mass flow through the cylinder arrangement 6, which can prevent unstable or undesired operation of the turbo-compressor 50.

[0186] According to embodiments, the method 100 can further comprise:

[0187] determining 110 a target ICE mass flow at the target actuation settings of the valves 20, 22, and

[0188] comparing 112 the target ICE mass flow to a limit mass flow value, and wherein

[0189] if the target ICE mass flow reaches the limit mass flow value of the turbo-compressor 50, the following steps are executed:

[0190] limiting 102 the valve actuation variation of the exhaust valve 20 and the intake valve 22.

[0191] By executing the step of comparing 112 the target ICE mass flow, i.e. the mass flow of air through the cylinder arrangement 6 of the ICE 4 at the target actuation settings of the exhaust valve 20 and the intake valve 22, and the step of limiting 102 if necessary, it can be avoided that a situation occurs in which unstable or undesired operation of the compressor would occur.

[0192] According to some embodiments, in the step of determining 104 the target actuation settings, the target actuation settings of the exhaust valve 20 and the intake valve 22 can be determined based on the ICE load and the ICE rotational speed for controlling the exhaust valve 20 and the intake valve 22 towards a certain fuel consumption level and / or towards a certain exhaust gas temperature.

[0193] Hence, the target actuation setting can be a setting of the valves 20, 22 forming part of normal ICE operation, where changing the valve actuation is one component of achieving optimal or desired ICE operation.

[0194] According to embodiments, the limit mass flow value can be based on surge limit data, and the method 100 can comprise:

[0195] Adapting 114 the limit mass flow value to current ICE operation conditions.

[0196] Hence, when setting the limit mass flow value, the current operation conditions of the ICE 4 and the mass flow through the cylinder arrangement 6 of the ICE 4 can be taken into account. For example, the surge limit mass flow m'_surge or the corresponding corrected surge limit mass flow m'_corr_surge through the compressor 50 can form the basis for the adapted limit mass flow value.

[0197] For example, according to some embodiments, the degree of change in ICE operation can be related to a sudden change in torque request to the ICE 4.

[0198] In this way, when adapting the limit mass flow value, the degree of change in ICE operation can be taken into account, above which the mass flow through the compressor 50 will be maintained. The limit mass flow value can be greater for a dynamic ICE operation or when performing a sudden change in ICE operation than when performing a gradual change in ICE operation.

[0199] According to some embodiments, the step of adapting 114 the limit mass flow value can comprise:

[0200] When the degree of change in ICE operation is a sudden decrease in torque request to the ICE 4, a greater safety margin is provided 116 for the surge limit data than when the degree of change in ICE operation is a gradual change in torque request to the ICE 4.

[0201] In this way, unstable or undesirable turbo-compressor operation 50 can be avoided while taking different operation conditions of the ICE into account. Hence, the step of limiting 102 the valve actuation change of the exhaust valve 20 and the intake valve 22 can be performed closer to the surge limit mass flow through the compressor 50 for less dynamic ICE operation than when operating the ICE 4 dynamically. Hence, a greater operating range of the turbo-compressor 50 and a greater operating range of the ICE 4 can be available without limiting the actuation change of the starting valve compared to when the limit mass flow value would be prescribed for the most dynamic ICE operation.

[0202] As an example reference; sudden changes / dynamic operation of the ICE 4 can occur when performing so-called kick-down (~0% -> ~100% torque request) or kick-up (~100% -> ~0% torque request) of the accelerator pedal and during gear shift operations in a transmission connected to the ICE 4. Gradual changes of the ICE 4 can occur when the cruise control controls the vehicle speed over a stretch of road with small slopes, or when the vehicle is decelerated or accelerated with a fixed torque request.

[0203] According to embodiments, the compressor data can comprise pressure ratio, mass flow and turbo compressor speed provided in a data table.

[0204] The data table can be a data table as shown in Figure 6 or a corresponding data table. Alternatively, the compressor data can be provided in a compressor characteristic map 86 as shown in Figure 4 or a similar characteristic map, or by a mathematical compressor model as described above.

[0205] According to another aspect, there is provided a computer program comprising instructions which, when the program is executed by a computer, cause the computer to carry out the method 100 according to any of the aspects and / or embodiments discussed herein.

[0206] The skilled person will appreciate that the method 100 for controlling valve actuation can be implemented by programmed instructions. These programmed instructions are typically constituted by a computer program which, when executed in the computer or computing unit 60, ensures that the computer or computing unit 60 carries out the required control, such as the method 100 and at least some of the steps 102-116 related thereto. The computer program is typically part of a computer-readable storage medium comprising a suitable digital storage medium on which the computer program is stored.

[0207] Figure 8 An embodiment of a computer-readable storage medium 99 comprising instructions which, when executed by the computer or computing unit 60, cause the computer or computing unit 60 to carry out the steps of the method 100 according to any of the aspects and / or embodiments discussed herein is shown.

[0208] The computer-readable storage medium 99 can for example be provided in the form of a data carrier carrying computer program code for performing at least some of the steps 102-116 according to some embodiments when loaded into the computing unit(s) 60. The data carrier can be for example a ROM (Read-Only Memory), a PROM (Programmable Read-Only memory), an EPROM (Erasable PROM), a Flash memory, an EEPROM (Electrically Erasable PROM), a hard disk, a CD-ROM optical disk, a memory stick, an optical storage device, a magnetic storage device, or any other appropriate medium such as a diskette or tape which can hold machine readable data in a non-transitory manner, which can be coupled to the computing unit 60. The computer-readable storage medium can also be provided as computer program code on a server and can be downloaded remotely, e.g. over the Internet or an intranet connection, or via other wired or wireless communication systems, to the computing unit 60.

[0209] Figure 8 The computer-readable storage medium 99 illustrated in the middle is a non-limiting example in the form of a USB memory stick.

[0210] It is to be understood that the above description is by way of example only, and that the present application is defined by the text herein. Those skilled in the art will realize that modifications can be made to the example embodiments described without departing from the scope of the present application as defined by the text herein, and that different features of the example embodiments can be combined to form further embodiments.

Claims

1. A method (100) for controlling valve actuation of an internal combustion engine (4), the internal combustion engine (4) comprising an exhaust valve (20), an intake valve (22), a turbo-compressor (50), and an electronic control unit for controlling operation of the internal combustion engine, wherein the method is performed by a control arrangement (38), and wherein the method (100) comprises: limiting and / or preventing a valve actuation change of the exhaust valve and the intake valve (20, 22) determined by the electronic control unit to be implemented or being implemented, wherein the limitation of the determined valve actuation change is based on compressor data comprising one or both of a current turbo-compressor speed and a current turbo-compressor pressure ratio and surge limit data of the turbo-compressor (50) in order to maintain a turbo-compressor mass flow above a limit mass flow value and to prevent or limit a compressor surge event, wherein the limit mass flow value is based on the surge limit data, and the method (100) further comprises: adapting the limit mass flow value to current internal combustion engine operating conditions.

2. The method (100) according to claim 1, further comprising: determining a target actuation setting of the exhaust valve and the intake valve (20, 22), and initiating a valve actuation change of the exhaust valve and the intake valve (20, 22) towards the target actuation setting of the exhaust valve and the intake valve (20, 22), and wherein the step of limiting the valve actuation change comprises one of: preventing the initiated valve actuation change from reaching the target actuation setting of the exhaust valve and the intake valve (20, 22), or increasing a time period required for the valve actuation change to reach the target actuation setting of the exhaust valve and the intake valve (20, 22).

3. The method (100) according to claim 2, further comprising: determining a target internal combustion engine mass flow at the target actuation setting of the exhaust valve and the intake valve (20, 22), and comparing the target internal combustion engine mass flow to the limit mass flow value, and wherein if the target internal combustion engine mass flow reaches the limit mass flow value, the following step is performed: limiting the valve actuation change of the exhaust valve and the intake valve (20, 22).

4. The method (100) according to claim 2 or 3, wherein in the step of determining the target actuation setting, the target actuation setting of the exhaust valve and the intake valve (20, 22) is determined based on an internal combustion engine load and an internal combustion engine speed for controlling the exhaust valve and the intake valve (20, 22) towards a specific fuel consumption level and / or towards a specific exhaust gas temperature.

5. The method (100) according to claim 1, wherein the current internal combustion engine operating conditions relate to a degree of change in internal combustion engine operation.

6. The method (100) according to claim 5, the step of adapting the limit mass flow value to current internal combustion engine operating conditions comprises: determining a degree of change in internal combustion engine operation, and adapting the limit mass flow value to the determined degree of change in internal combustion engine operation. A greater safety margin is provided for the surge limit data when the degree of change in the operation of the internal combustion engine is a sudden decrease in the torque request to the internal combustion engine (4) compared to when the degree of change in the operation of the internal combustion engine is a gradual change in the torque request to the internal combustion engine (4).

7. The method (100) of claim 1, wherein the compressor data comprises pressure ratio, mass flow, and turbo-compressor speed provided in a data table.

8. A computer program product comprising instructions which, when executed by a computer, cause the computer to carry out the method (100) of any one of claims 1 to 7.

9. A computer-readable storage medium (99) comprising instructions which, when executed by a computer, cause the computer to carry out the method (100) of any one of claims 1 to 7.

10. A control arrangement (38) for controlling valve actuation of a compression-ignited internal combustion engine (4), the internal combustion engine (4) comprising an exhaust valve (20), an intake valve (22), a turbo-compressor (50), and an electronic control unit for controlling operation of the internal combustion engine, wherein the control arrangement (38) is configured to: limit and / or prevent a valve actuation change of the exhaust and intake valves (20, 22) determined by the electronic control unit to be implemented or being implemented, wherein the limitation of the determined valve actuation change is based on compressor data comprising one or both of a current turbo-compressor speed and a current turbo-compressor pressure ratio and surge limit data of the turbo-compressor (50) in order to maintain a turbo-compressor mass flow above a limit mass flow value and to prevent or limit a compressor surge event, wherein the limit mass flow value is based on the surge limit data, and the control arrangement (38) is further configured to: adapt the limit mass flow value to current internal combustion engine operating conditions, the control arrangement (38) is further configured to: determine a target actuation setting of the exhaust and intake valves (20, 22), and initiate a valve actuation change of the exhaust and intake valves (20, 22) towards the target actuation setting of the exhaust and intake valves (20, 22), and one of prevent the initiated valve actuation change from reaching the target actuation setting of the exhaust and intake valves (20, 22), or increase a time period required for the valve actuation change to reach the target actuation setting of the exhaust and intake valves (20, 22).

11. The control arrangement (38) of claim 10, further configured to: determine a target internal combustion engine mass flow at the target actuation setting of the exhaust and intake valves (20, 22), and compare the target internal combustion engine mass flow to the limit mass flow value, and wherein if the target internal combustion engine mass flow reaches the limit mass flow value, the control arrangement is configured to: limit the valve actuation change of the exhaust and intake valves (20, 22).

12. A compression-ignited internal combustion engine (4) comprising a control arrangement (38) according to claim 10 or 11.

13. A vehicle (2) comprising a compression-ignited internal combustion engine (4) according to claim 12.

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