SE2250720A1

SE2250720A1 - Method and Control Arrangement for Controlling Four-Stroke Internal Combustion Engine

Info

Publication number: SE2250720A1
Application number: SE2250720A
Authority: SE
Inventors: Andreas Dahl; Eric Lycke; Erik Höckerdal; Joakim Sommansson; Marcus Ahlin; Mikael Nordin; Pontus Johansson
Original assignee: Scania Cv Ab
Priority date: 2022-06-16
Filing date: 2022-06-16
Publication date: 2023-12-17
Also published as: DE102023114379A1; BR102023010151A2

Abstract

The disclosure concerns a method (100) for controlling a four-stroke internal combustion engine (4), and comprises steps of:- setting or determining (102) an initial timing setting of the exhaust camshaft (10) and/or the intake camshaft (12), - providing (104) an alternating control signal for the exhaust camshaft (10) and/or the intake camshaft (12) in order to generate an oscillating change of a timing of the exhaust camshaft (10) and/or the intake camshaft (12), and - controlling (106) the internal combustion engine (4) in accordance with a first mode of operation or a second mode of operation different from the first mode of operation in response to at least one change in the timing of the exhaust camshaft (10) and/or the intake camshaft (12) resulting from the alternating control signal.

Description

Description TECHNICAL FIELD The invention relates to a method for controlling a four-stroke internal combustion engine and to a control arrangement for controlling a four-stroke internal combustion engine. The invention further relates to a computer program and to a computer-readable storage medium.

BACKGROUND Variable valve timing, also referred to as phase shifting or cam phasing, may be provided in an internal combustion engine, ICE, to achieve a number of different effects, properties, engine characteristics, etc.

Commonly, a variable valve timing arrangement is hydraulically powered/actuated, such as by oil from a lubrication oil system of the relevant ICE. The operation of the variable valve timing arrangement is affected by the viscosity of the oil and proper operation of the variable valve timing arrangement can only be expected When the oil is within a certain viscosity range.

During cold starting of an ICE, the oil has a low temperature and accordingly, a high viscosity. Thus, it may be necessary to determine whether the variable valve timing arrangement can be expected to operate as intended. The viscosity is also dependent on oil degradation where degraded oil has a significantly higher viscosity than oil which has not degraded. Hence, both oil that is cold and degraded oil may reduce the performance of a variable valve timing arrangement.

US 2020/256219 discloses a valve timing adjustment device having a phase adjustment unit. A controller is configured to perform a startup phase control when operation of the internal combustion engine is started before a crankshaft of the engine is cranked. The startup phase control includes setting the relative rotation phase to a predetermined initial phase and perform a startup preparation control during a period after the internal combustion engine is stopped and before the startup phase control is performed. The startup preparation control includes a temperature check and changing the relative rotation phase.

US 2010/236227 discloses a hydraulic system control device and a valve timing control device. When a hydraulic pressure generation source begins to generate hydraulic pressure, 2 the hydraulic pressure in an oil supply line connected to a hydraulic actuator is measured and sets a viscosity index value indicating an oil viscosity in accordance with the pace at which the measured hydraulic pressure rises. The viscosity index value is calculated and set so that the slower the pace at which the measured hydraulic pressure rises, the higher the viscosity indicated by the viscosity index value. The viscosity index is utilised for optimising the length of a time period for inhibiting the variable valve timing mechanism operation after engine start.

JP 2004092593 discloses a control device of a variable valve timing mechanism. A responsiveness of the variable valve-timing mechanism, VVT, is improved based on oil viscosity. A control device has a temperature sensor for detecting a temperature of oil for operating the VVT, a response speed detecting means for detecting a response speed of the VVT, a viscosity detecting means for detecting the viscosity of the oil and a learning means for learning the viscosity of the oil detected by the viscosity detecting means. The learning means determines the deterioration in the oil on the basis of the learned viscosity of the oil, calculates target displacement of the VVT and a guard value of the target displacement, and changes the duty ratio by correcting output time and rest time of a driving signal or corrects gain for determining the duty ratio of the driving signal.

SUMMARY lt would be advantageous to achieve an alternative for controlling a variable valve timing arrangement of an internal combustion engine. ln particular, it would be desirable to enable a control of an internal combustion engine that provides conditions to determine current operating conditions of a variable valve timing arrangement. To better address one or more of these concerns, a method, a computer program, a computer-readable storage medium, a control arrangement, an internal combustion engine, and/or a vehicle having the features defined in the independent claims is/are provided.

According to an aspect there is provided a method for controlling a four-stroke internal combustion engine. The internal combustion engine comprises: an exhaust valve and an intake valve, an exhaust camshaft arranged to control the opening and closing of the exhaust valve, an intake camshaft arranged to control the opening and closing of the intake valve, and a variable valve timing arrangement for the exhaust camshaft and/or the intake camshaft. The method comprises steps of: - setting or determining an initial timing setting of the exhaust camshaft and/or the intake camshaft, 3 - providing an alternating control signal for the exhaust camshaft and/or the intake camshaft in order to generate an oscillating change of a timing of the exhaust camshaft and/or the intake camshaft, and - controlling the internal combustion engine in accordance with a first mode of operation or a second mode of operation different from the first mode of operation in response to at least one change in the timing of the exhaust camshaft and/or the intake camshaft resulting from the alternating control signal.

Since the method comprises the step of setting or determining the initial timing setting of the exhaust camshaft and/or the intake camshaft and the step of providing the alternating control signal for the exhaust camshaft and/or the intake camshaft - an oscillating change of the timing of the exhaust camshaft and/or the intake camshaft in relation to the initial timing setting is generated. Moreover, since the method comprises the step of: controlling the internal combustion engine in accordance with the first mode of operation or the second mode of operation in response to at least one change in the timing of the exhaust camshaft and/or the intake camshaft resulting from the alternating control signal - a response to the alternating control signal determines whether the internal combustion engine is operated in the first or second mode of operation.

Namely, a character of the oscillating change of the timing of the exhaust camshaft and/or the intake camshaft i.e., at least one change in the timing of the exhaust and/or intake camshaft, is a result of the character of the variable valve timing arrangement, such as a character of actuators for changing the timing of the exhaust camshaft and/or the intake camshaft, which character for instance may be influenced by the viscosity of the oil supplied to the actuators in the case of hydraulically powered actuators.

For instance, the first mode of operation may be an ordinary mode of operation of the internal combustion engine e.g., without any limitations to the operation of the variable valve timing arrangement. The second mode of operation may be a special mode of operation of the internal combustion engine e.g., with one or more limitations to the operation of the variable valve timing arrangement such as timing changes within a limited range of the initial setting or with the variable valve timing arrangement providing a particular timing setting of the camshaft/s. lf the at least one change in the timing of the exhaust camshaft and/or the intake camshaft resulting from the alternating control signal indicates that the oil is of high viscosity, the second/special mode of operation may not permit engine operating modes that require quick changes in the timing of the exhaust camshaft and/or the intake camshaft.

Alternatively, or additionally, the second/special mode of operation may set the timings of the 4 exhaust and/or intake camshafts to produce a high internal load in the engine, which in turn will heat up the engine and thus, also heat the oil.

According to a further aspect there is provided a control arrangement for controlling a four- stroke internal combustion engine. The internal combustion engine comprises an exhaust valve and an intake valve, an exhaust camshaft arranged to control the opening of the exhaust valve, an intake camshaft arranged to control the opening and closing of the intake valve, and a variable valve timing arrangement for the exhaust camshaft and/or the intake camshaft. The control arrangement is configured to: - set or determine an initial timing setting of the exhaust camshaft and/or the intake camshaft, - provide an alternating control signal for the exhaust camshaft and/or the intake camshaft in order to generate an oscillating change of a timing of the exhaust camshaft and/or the intake camshaft, and - control the internal combustion engine in accordance with a first mode of operation or a second mode of operation different from the first mode of operation in response to at least one change in the timing of the exhaust camshaft and/or the intake camshaft resulting from the alternating control signal.

As discussed above with reference to the method, the control arrangement being configured to set or determine the initial timing setting of the exhaust and/or intake camshaft and to provide the alternating control signal for the exhaust and/or intake camshaft - an oscillating change of the timing of the exhaust camshaft and/or intake camshaft in relation to the initial timing setting is generated. Moreover, since the control arrangement is configured to control the internal combustion engine in accordance with the first or second mode of operation in response to at least one change in the timing of the exhaust and/or intake camshaft resulting from the alternating control signal - a response to the alternating control signal determines whether the internal combustion engine is operated in the first or second mode of operation.

The inventors have realised that overlaying a limited oscillating change of a timing of the exhaust camshaft and/or the intake camshaft over an initial timing setting of the exhaust camshaft and/or the intake camshaft only affects the operation of the internal combustion engine to a minor degree. Further, the inventors have realised that the variable valve timing arrangement as such thus, can be utilised for monitoring operating properties of the variable valve timing arrangement specifically, operating properties related to a viscosity of pressurised oil that powers actuators of a hydraulic variable valve timing arrangement.

The control arrangement may form a part of an engine control unit, ECU, of the internal combustion engine.

The internal combustion engine may form part of a drivetrain of a vehicle, such as a Iand- based vehicle.

The internal combustion engine may alternatively be utilised in or aboard a seaborn vessel or in a stationary installation such as a power source of an electric generator e.g., a so-called gen set.

The four-stroke internal combustion engine, ICE may be a compression ignition ICE, such as a diesel engine. Herein, the four-stroke ICE alternatively may be referred to as the internal combustion engine, the ICE, or simply the engine.

The ICE comprises a crankshaft connected with pistons forming part of a number of cylinder arrangements, such as four, five, six, or eight cylinder arrangements, of the ICE. The piston of each cylinder arrangement reciprocates in a cylinder bore. Each cylinder arrangement comprises one or more exhaust and intake valves. As in any four-stroke ICE, each piston performs an intake stroke, a compression stroke, an expansion stroke also referred to as power stroke or combustion stroke, and an exhaust stroke in the cylinder bore of the cylinder arrangement.

The exhaust camshaft is configured to control the opening and closing of the one or more exhaust valves in a commonly known manner with a cam lobe of the exhaust camshaft controlling the one or more exhaust valve. The intake camshaft is configured to control the opening and closing of the one or more intake valve in a commonly known manner with a cam lobe of the intake camshaft controlling the one or more intake valve. The intake and exhaust valves and the intake and exhaust camshafts form part of a valve train of the ICE.

The rotations of the exhaust and intake camshafts are synchronized with the rotation of the crankshaft. However, the timing of the exhaust and/or intake camshaft is changeable, i.e. the rotational position of the relevant camshaft in relation to the crankshaft is controllable.

Herein, this is referred to as timing change and as variable valve timing. ln practice, this means that the crankshaft angle at which a valve controlled by the relevant camshaft is opened and closed can be changed i.e., the timings of the camshafts can be changed. The changing of the timing of the camshafts may be performed in any known 6 manner. For instance, WO 2017/217908 and US 8714123 disclose suitable hydraulic variable valve timing arrangements to be utilised for changing the timing of the camshafts. lt is to be noted that an angular length of the open period of each of the exhaust and intake valves remains the same when the timings of the camshafts are changed.

As mentioned above, the timings of the exhaust and intake camshafts are controllable by the control arrangement, i.e. the control arrangement is configured to change the rotational position of the camshafts in relation to the crankshaft.

An angle of rotation of a camshaft may be noted as corresponding degrees of rotation of the crankshaft, degrees crankshaft angle, CA. Similarly, rotational positions of the camshaft e.g., for valve opening and valve closing may be presented as degrees CA from a given reference crankshaft angular position such as a top dead centre, TDC, or a bottom dead centre, BDC, of a piston. A timing change angle of the respective camshaft is the angle by which the timing of the camshaft is changed in relation to a rotational reference position of camshaft, such as a starting position of the camshaft before the timing change. Also timing changes of a camshaft may be noted as degrees CA.

Herein, a timing setting, such as the initial timing setting is a setting of an angular relationship between a camshaft and the crankshaft. Accordingly, a change of a timing of a camshaft is a change of a setting of an angular relationship between a camshaft and the crankshaft.

The control arrangement is arranged to control at least the variable valve timing arrangement, but also other functions of the ICE may be controlled by the control arrangement. Accordingly, the control arrangement may form part of an engine control unit, ECU, of the ICE.

The control arrangement may comprise angular sensors for sensing angular positions of one or more of the exhaust camshaft, the intake camshaft, and the crankshaft; an actuator for one or both of the exhaust and intake camshafts such as a hydraulic actuator arranged to change a timing of the relevant camshaft; a calculation unit such as a microcontroller or a central processing unit configured to provide control signals for controlling the actuator/s; optionally, a further calculation unit configured to provide control of operation of the ICE. The calculation unit or calculation units may form part of an ECU. 7 The variable valve timing arrangement may be hydraulically powered. More specifically, actuators of the variable valve timing arrangement may be hydraulically powered, such as by oil from a lubrication oil system of the relevant ICE.

The operation of the variable valve timing arrangement is affected by the viscosity of the oil and proper operation of the variable valve timing arrangement can only be expected when the oil is within a certain viscosity range. Oil of low temperature e.g., below a normal operating temperature range of the ICE, has a high viscosity.

The present method and control arrangement, provide for determining whether the variable valve timing arrangement can be expected to operate as intended. More specifically, one or more of the response, speed, and precision of hydraulically powered actuators are affected by the viscosity of the oil. High viscosity reduces one or more of the response, speed, and precision. However, this may not be acceptable under certain engine operating circumstances or in certain modes of operation of the engine. Accordingly, normal engine operation i.e., the ICE being able to operate with its full spectrum of operating ranges and engine settings, may not be allowed until the oil has an adequate viscosity. ln this context it may be mentioned that the viscosity of oil is also dependent on oil degradation. lf the oil has degraded to such an extent that the at least one change in the timing of the exhaust camshaft and/or the intake camshaft resulting from the alternating control signal even after a longer time period does not indicate that the oil viscosity is adequate for normal engine operation, a notification as to a required engine service such as an oil change may be presented.

As mentioned above, the provision of the alternating control signal for the exhaust and/or intake camshaft is intended to generate an oscillating change of the timing of the relevant camshaft. The oscillating change of the timing of the camshaft results from the alternating control signal and accordingly, the herein discussed at least one change in the timing of the exhaust camshaft and/or the intake camshaft forms at least one portion of these oscillations of the timing/s.

The at least one change in the timing of the exhaust and/or intake camshaft may form e.g., one flank of the oscillating change of the timing of the relevant camshaft, a half oscillation of the change of timing, a full oscillation of the change of timing, or a sequence of oscillating changes of the timing. 8 The oscillating change of the timing of the exhaust camshaft and/or the intake camshaft generated by the alternating control signal will differ when the oil is of high viscosity and when the oil is within a viscosity range required for normal ICE operation. The latter will herein be referred to as ideal viscosity.

Accordingly, with oil of ideal viscosity, the oscillating change of the timing of the relevant camshaft will be formed by desired or anticipated changes of the timing. Consequently, also the at least one change in the timing of the relevant camshaft will be formed by at least one desired or anticipated change of the timing.

Conversely, with oil of high viscosity, the oscillating change of the timing of the relevant camshaft will be different from desired or anticipated changes of the timing. Consequently, also the at least one change in the timing of the relevant camshaft will be different from a desired or anticipated change of the timing. That is, with high viscosity oil, the in practice generated changes in the timing of the relevant camshaft are different from desired or anticipated changes in the timing. lt may be noted that in the extreme, with very high viscosity oil, the alternating control signal may not generate an oscillating change of the timing of the relevant camshaft. ln such case, an amplitude of the oscillating change of timing is nil.

The at least one change in the timing of the relevant camshaft may relate to one or more discrete values of parameters related to a timing change, such as an achieved timing change angle and a time derivative of a timing change angle. Alternatively, or additionally, the at least one change in the timing of the relevant camshaft may relate to one or more sequences of values of one or more parameters related to timing changes, such as sequences of timing change angles, sequences of time derivatives of timing change angles. Timestamps may be provided with individual values of a sequence of values.

Even if the timings of both camshafts of an ICE are variable, in order to determine whether the viscosity of the oil is ideal, it may suffice to provide the alternating control signal to only one of the camshafts and/or analyse only the oscillating change of the timing of one of the camshafts.

The method may be performed upon starting the engine. The method may be performed intermittently or continuously until at least one change in the timing of the exhaust camshaft 9 and/or the intake camshaft resulting from the alternating control signal indicates that the oil viscosity is adequate for normal engine operation i.e., that ideal viscosity has been reached.

Additionally, or alternatively, the method may be performed during normal engine operation e.g., as part of a self-test of engine operation by the ECU. This may be done e.g., to determine whether the oil has degraded.

According to embodiments, preceding the step of contro||ing the internal combustion engine, the method may comprise steps of: - determining the at least one change in the timing of the exhaust camshaft and/or the intake camshaft resulting from the alternating control signal, and - comparing the at least one change in the timing of the exhaust camshaft and/or the intake camshaft with one or more timing change parameter reference values, and the step of contro||ing may be based on a result of the step of comparing. ln this manner, the determined at least one change in the timing of the relevant camshaft may be utilized for comparison with one or more timing change parameters and the result of the comparison may be utilized for the decision whether the internal combustion engine is controlled in accordance with the first or second mode of operation.

According to embodiments, the step of comparing may comprise a step of: - determining whether the exhaust camshaft and/or the intake camshaft are/is operating within or outside a nominal range of the one or more timing change parameter reference values based on the at least one change in the timing of the exhaust camshaft and/or the intake camshaft. ln this manner, a nominal range of the one or more timing change parameter reference values may be utilised for the decision whether the internal combustion engine is controlled in accordance with the first or second mode of operation.

The relevant camshaft operating within the nominal range of the one or more timing change parameter reference values may for instance mean, that the timing change parameter equals or is above a minimum threshold value, that the timing change parameter is below or equals a maximum threshold value, or that the timing change parameter is within a permissible value range. Conversely, the relevant camshaft operating outside the nominal range of the one or more timing change parameter reference values may for instance mean, that the timing change parameter is below or equals a minimum threshold value, that the timing change parameter equals or is above a maximum threshold value, or that the timing change parameter is outside a permissible value range.

Accordingly, the nominal range of the one or more timing change parameter reference values may be minimum parameter values, maximum parameter values, and/or limit values of a parameter range reflecting oil having ideal viscosity.

According to embodiments, if in the step of determining whether the exhaust camshaft and/or the intake camshaft are/is operating within or outside a nominal range of the one or more timing change parameter reference values, it is determined that the at least one change in the timing of the exhaust camshaft and/or the intake camshaft is within the nominal range of the one or more timing change parameter reference values, the step of controlling may comprise a step of: - operating the internal combustion engine in accordance With the first mode of operation, and wherein if in the step of determining whether the exhaust camshaft and/or the intake camshaft are/is operating within or outside a nominal range of the one or more timing change parameter reference values, it is determined that the at least one change in the timing of the exhaust camshaft and/or the intake camshaft is outside the nominal range of the one or more timing change parameter reference values, the step of controlling may comprise a step of: - operating the internal combustion engine in accordance with the second mode of operation. ln this manner, the result of the step of determining may decide whether the ICE is operated in accordance with the first or second mode of operation.

According to embodiments, prior to the step of providing an alternating control signal for the exhaust camshaft and/or the intake camshaft, the method may comprise a step of: - starting the internal combustion engine. ln this manner, the method may be performed with the crankshaft of the ICE cranking. The crankshaft may for instance directly or indirectly drive an oil pump of the ICE.

According to embodiments, in conjunction with the step of comparing the at least one change in the timing of the exhaust camshaft and/or the intake camshaft with the one or more timing change parameter reference values, the method may comprise one or more steps of: - measuring a temperature of the internal combustion engine, and/or - determining a time period from a start of the internal combustion engine. ln this manner, it may be determined whether the ICE has reached its normal operating temperature. Such steps of measuring a temperature and/or determining a time period from a start of the ICE may be relevant to determine whether the oil has degraded to such an extent that its viscosity is too high also with the ICE at its normal operating temperature. A change of oil thus, may be required in order to achieve proper operation of the variable valve timing arrangement. 11 According to a further aspect there is provided a four-stroke internal combustion engine comprising a control arrangement according to any one of aspects and/or embodiments discussed herein.

According to a further aspect there is provided a vehicle comprising a four-stroke internal combustion engine according to any one of aspects and/or embodiments discussed herein.

According to a further 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 one of aspects and/or embodiments discussed herein.

According to a further 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 one of aspects and/or embodiments discussed herein.

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

BRIEF DESCRIPTION OF THE DRAWINGS Various aspects and/or embodiments of the invention, including its particular features and advantages, will be readily understood from the example embodiments discussed in the following detailed description and the accompanying drawings, in which: Fig. 1 illustrates embodiments of a vehicle for land-based propulsion, Fig. 2 schematically illustrates embodiments of an ICE, Fig. 3 illustrates a control arrangement, Fig. 4 schematically illustrates a control arrangement and a variable valve timing arrangement, Figs. 5a - 5c schematically illustrate diagrams over example alternating control signals and example generated oscillating changes of the timing of an exhaust camshaft, Figs. 6a - 6c schematically illustrate diagrams over example alternating control signals and example generated oscillating changes of the timing of an intake camshaft, Fig. 7 illustrates embodiments of a method for controlling a four-stroke internal combustion engine, and Fig. 8 illustrates embodiments of a computer-readable storage medium.

DETAILED DESCRIPTION 12 Aspects and/or embodiments of the invention will now be described more fully. Like numbers refer to like elements throughout. Well-known functions or constructions will not necessarily be described in detail for brevity and/or clarity.

Fig. 1 illustrates embodiments of a vehicle 2 configured for land-based propulsion. The vehicle 2 comprises a four-stroke internal combustion engine, ICE, 4 according to aspects and/or embodiments discussed herein, such as e.g. the ICE discussed below with reference to Fig. 2. The ICE 4 comprises a control arrangement, as discussed below with reference to Figs. 2 - 6c. A method as discussed with reference to Fig. 7 may be utilised for controlling the ICE 4.

In these embodiments, the 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.

Fig. 2 schematically illustrates embodiments of an ICE 4.

The ICE 4 may be configured to form part of a powertrain of a vehicle, such as e.g. the vehicle 2 shown in Fig. 1. The ICE 4 may alternatively be utilised in or aboard a seaborn vessel or in a stationary installation such as a power source of an electric generator.

The ICE 4 is a four-stroke direct injection internal combustion engine, such as a compression ignition ICE 4, e.g. a diesel engine. The ICE 4 comprises at least one cylinder arrangement 6, a crankshaft 8, an exhaust camshaft 10, an intake camshaft 12, an exhaust valve 20, and an intake valve 22.

The cylinder arrangement 6 comprises a combustion chamber 14, a cylinder bore 16, and a piston 18 configured to reciprocate in the cylinder bore 16. The piston 18 is connected to the crankshaft 8 via a connecting rod 24.

The movement 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 movement 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.

The intake valve 22 is configured for admitting charge air into the combustion chamber 14, and the exhaust valve 20 is configured for letting exhaust gas out of the combustion chamber 13 14. The timing of the exhaust camshaft 10 and the intake camshaft 12 is configured to be controlled by a variable valve timing arrangement 30 of the ICE, as indicated by two double arrows. According to alternative embodiments, the variable valve timing arrangement 30 may be configured to control the timing of only one of the exhaust and intake camshafts 10, 12. ln a known manner, the intake valve 22 comprises an intake valve head configured to seal against an intake valve seat extending around an intake opening. The exhaust valve 20 comprises an exhaust valve head configured to seal against an exhaust valve seat extending around an exhaust opening. ln a known manner, the camshafts 10, 12 may rotate at half the rotational speed of the crankshaft 8 and control the movement of the exhaust and intake valves 20, 22 via cam lobes 40, 42 arranged on the camshafts 10, 12. The exhaust camshaft 10 comprises a cam lobe 40. For instance, by abutting against the cam lobe 40, the exhaust valve 20 will follow a contour of the cam lobe 40. The exhaust valve 20 may be biased towards its closed position, e.g. by means of a non-shown spring. The movement of the intake valve 22 is controlled in a corresponding manner by the intake camshaft 12 and its cam lobe 42.

The cylinder arrangement 6 may comprise more than one intake and/or exhaust valve. Also such additional valves may be controlled in the manner discussed herein.

The piston 18 is arranged to reciprocate in the cylinder bore 16 between a bottom dead centre, BDC, and a top dead centre, TDC. 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. ln Fig. 2 the piston 18 is illustrated with continuous lines at its BDC and with broken lines at its TDC. The combustion chamber 14 is formed above the piston 18 inside the cylinder bore 16.

The cylinder arrangement 6 has a total swept volume, VS, in the cylinder bore 16 between the BDC and the TDC. According to some embodiments, the cylinder arrangement 6 may have a total swept volume, VS, of within a range of 0.3 to 4 litres. Mentioned purely as an example, in the lower range of Vs, the cylinder arrangement 6 may form part of an internal combustion engine for a passenger car, and in the middle and higher range of Vs, the cylinder arrangement 6 may form part of an internal combustion engine for a heavy load vehicle such as e.g. a truck, a bus, or a construction vehicle. 14 The ICE 4 comprises a fuel injector 56 configured for injecting fuel into the combustion Chamber 14 when the ICE 4 produces positive torque, e.g. for propelling the vehicle.

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 variable valve timing arrangement 30 of the ICE 4. That is, the control arrangement 38 is configured at least for controlling the timing of the exhaust camshaft 10 and the timing of the intake camshaft 12. The variable valve timing arrangement 30 may form part of the control arrangement 38.

The control arrangement 38 is inter alia configured to: - control the ICE 4 in accordance with a first mode of operation or a second mode of operation different from the first mode of operation in response to at least one change in a timing of the exhaust camshaft 10 and/or the intake camshaft 12 resulting from an alternating control signal.

The control arrangement 38 and the timing changes of the camshafts 10, 12 are further discussed below with reference to Figs. 3 - 6c.

Fig. 3 illustrates a control arrangement 38 to be utilised in connection With different aspects and/or embodiments of the invention. ln particular, the control arrangement 38 is configured for the control of the timing of camshafts 10, 12 of an ICE such as e.g., the ICE 4 discussed in connection with Figs. 1 and 2. The control arrangement 38 is also indicated in Fig. 2.

Accordingly, in the following reference is also made to Fig. 2.

The control arrangement 38 comprises at least one calculation unit 60, which may take the form of substantially any suitable type of processor circuit or microcomputer, e.g. 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 may interpret and execute instructions. The herein utilised expression "calculation unit" may represent a processing circuitry comprising a plurality of processing circuits, such as one or more of the ones mentioned above. The calculation unit 60 may be configured to perform calculations.

The control arrangement 38 comprises a memory unit 62. The calculation unit 60 is connected to the memory unit 62, which provides the calculation unit 60 with, e.g. stored programme code, data tables, and/or other stored data which the calculation unit 60 needs to enable it to do calculations and to control at least some functions of the ICE 4, such as the timing changes of the exhaust and intake camshafts 10, 12. The calculation unit 60 is also adapted to store partial or final results of calculations in the memory unit 62. The memory unit 62 may comprise a physical device utilised to store data or programs, i.e. sequences of instructions on a temporary or permanent basis. According to some embodiments, the memory unit 62 may comprise integrated circuits comprising silicon-based transistors. The memory unit 62 may comprise e.g. a memory card, a flash memory, a USB memory, a hard disc, or another similar volatile or non-volatile storage unit for storing data such as e.g. ROM (Read-Only Memory), PROM (Programmable Read-Only Memory), EPROM (Erasable PROM), EEPROM (Electrically Erasable PROM), etc. in different embodiments. ln the embodiment depicted, only one calculation unit 60 and memory unit 62 are shown, but the control arrangement 38 may alternatively comprise more than one calculation unit and/or memory unit.

The control arrangement 38 is further provided With respective devices 70, 73, 74, 66, 68, for receiving and/or sending input and output signals. These input and output signals may comprise waveforms, pulses or other attributes, which can be detect as information by signal receiving devices, and which can be converted to signals processable by the calculation unit 60. lnput signals are supplied to the calculation unit 60 from the input receiving devices 70, 73, 74. Output signal sending devices 66, 68 are arranged to convert calculation results from the calculation unit 60 to output signals for conveying to 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 may take the form of one or more from among a cable, a data bus, e.g. a CAN (controller area network) bus, a MOST (media orientated systems transport) bus or some other bus configuration, or a wireless connection.

Mentioned as examples, the output signal sending devices 66, 68 may send control signals to the timing control arrangement 30 of the exhaust and intake camshafts 10, 12. The input signal receiving devices 70, 73, 74, may receive signals from the ICE 4, such as e.g. from an angular position sensor 75 of the crankshaft 8 of the ICE 4, an angular position sensor 81 of the exhaust camshaft 10, and an angular position sensor 82 of the intake camshaft 12. The control arrangement 38 may comprise further sensors.

Examples of data tables may be e.g.; - one or more tables containing control data for one or more alternating control signals, - one or more tables containing desired or anticipated changes of the timing of the exhaust and/or intake camshaft 10, 12, 16 - one or more tables containing timing change parameters and/or timing change parameter reference values, and -tables relating to ICE temperature and/or ICE operating time.

Examples of data may be measured, monitored, determined, and/or calculated data, such as camshaft timing angle data, timing change angle data, data related to derivatives of timing change angles, timing change time data, and timing change angular speed data. The control arrangement 38 comprises or is connected to various sensors and actuators in order to receive input and provide output for performing the various aspects and embodiments of the method discussed herein. Some of the various sensors are exemplified above. An example of actuators may be actuators configured for changing the timing of the camshafts 10, 12 and forming part of the timing control arrangement 30. See also below with reference to Fig. 4.

The control arrangement 38 may be configured to perform a method 100 according to any one of aspects and/or embodiments discussed herein, see e.g. below with reference to Fig. 7.

Fig. 4 schematically illustrates a control arrangement 38 and a variable valve timing arrangement 30 according to embodiments. The control arrangement 38 and the variable valve timing arrangement 30 may be for an ICE 4 as discussed above with reference to Figs. 2 and 3. Accordingly, in the following reference is also made to Figs. 2 and 3.

The variable valve timing arrangement 30 is shown for one of the exhaust and intake camshafts 10, 12, but the following discussion applies similarly to a second camshaft of the ICE.

The variable valve timing arrangement 30 is a hydraulically powered arrangement and is powered by oil from a Iubrication system of the ICE 4. The Iubrication system of the ICE 4 includes an oil sump 50 from which an oil pump 48 provides pressurised oil to an actuator 44 of the variable valve timing arrangement 30 via a control valve 46 of the variable valve timing arrangement 30. The actuator 44 changes a timing setting of the relevant camshaft 10, 12 by oil being supplied to either of first or second control chambers 52, 54 of the actuator 44.

The herein discussed method 100 and control arrangement 38 are not limited to the illustrated variable valve timing arrangement 30 but may be used in any kind of hydraulically powered variable valve timing arrangement. 17 The control arrangement 38 is configured to control the control valve 46 into one of three positions in order to supply oil to one of the first and second control chambers 52, 54 of the actuator 44 or to none of the control Chambers 52, 54. Thus, the timing setting of the relevant camshaft 10, 12 is changed or maintained in a current position.

As known in the art, the control arrangement 38 comprises sensors 81, 82, 75 for determining angular positions of the exhaust and/or intake camshafts 10, 12 and of the crankshaft 8 of the ICE 4. Such sensors 81, 82, 75 may be arranged to sense marks of respective increment discs (not shown) connect to, and rotationally locked to, the camshafts 10, 12 and the crankshaft 8. As is also known in the art, the control arrangement 38 is configured to determine relative angular positions of one or both camshafts 10, 12 in relation to the crankshaft 8 i.e., to determine timing settings of one or both camshafts 10, 12.

The control arrangement 38 is configured to: - Set or determine an initial timing setting of the exhaust camshaft 10 and/or the intake camshaft 12. The control arrangement 38 may utilise the above-mentioned sensors and increment discs to set one or both of the camshafts 10, 12 in a particular angular relation to the crankshaft 8. Alternatively, the control arrangement 38 may utilise the sensors and increment discs to determine the current angular position of one or both of the camshafts 10, 12 in relation to the crankshaft 8. A further alternative may be for the control arrangement 38 to determine the current angular position of one or both of the camshafts 10, 12 in relation to the crankshaft 8 by accessing stored angular positions of the last used angular positions e.g., angular positions that were used before the ICE 4 was stopped at the immediately preceding crankshaft rotating engine running operation.

- Provide an alternating control signal for the exhaust camshaft 10 and/or the intake camshaft 12 in order to generate an oscillating change of a timing of the exhaust camshaft 10 and/or the intake camshaft 12. The alternating control signal causes the control valve 46 to direct pressurised oil alternatingly to the first chamber 52 and the second chamber 54 of the actuator 44. Accordingly, the oscillating change of the timing of the exhaust camshaft 10 and/or the intake camshaft 12 is generated. The oscillating change of the timing is overlayed over the initial timing setting.

- Control the internal combustion engine in accordance with a first mode of operation or a second mode of operation different from the first mode of operation in response to at least one change in the timing of the exhaust camshaft 10 and/or the intake camshaft 12 resulting from the alternating control signal. Depending on the viscosity of the oil, the oscillating change of the timing will comprise a desired or anticipated change of the timing or a change in the timing different from the desired or anticipated change of the timing. The viscosity of 18 the oil is able to be determined from the at least one change in the timing of the relevant camshaft 10, 12. The viscosity is at least determined in the sense that it is determined whether the oil is suitable to drive the actuator 44 in a manner to achieve timing changes of the relevant camshaft 10, 12 that allow for proper ICE operation. Naturally, the control arrangement 38 may be configured to control the ICE 4 in accordance with the first or second mode of operation in response to more than one change in the timing of the relevant camshaft10, 12. lf the at least one change in the timing of the relevant camshaft corresponds to the desired or anticipated change of the timing, the ICE may be controlled in accordance with the first mode of operation. Depending on how the desired or anticipated change of the timing is defined e.g., if defined by a threshold value, a change in timing different from the desired or anticipated change of the timing may differ to a smaller or lesser degree from the desired or anticipated change of the timing. Depending on a size of the difference in timing from the desired or anticipated change of the timing, the difference may be acceptable or not acceptable. lf the difference is acceptable, the ICE may be controlled in accordance with the first mode of operation. lf the difference is not acceptable, the ICE may be controlled in accordance with the second mode of operation. lt may be noted that the difference may be acceptable for certain ICE operation situations but not for others. Also, such operation of the ICE deviating from the first mode of operation may fall under a second mode of operation. An alternative to a threshold value may be to define the desired or anticipated change of the timing by one or more ranges.

Accordingly, the control arrangement 38 controls the ICE 4 in accordance with the second mode of operation until the viscosity of the oil is such that the desired or anticipated change of the timing is achieved e.g., after the ICE has been operated/running for a period of time or, if the oil has degraded, after the oil has been changed for fresh oil and has reached a viscosity providing the desired or anticipated change of the timing.

According to embodiments, the control arrangement 38 may be configured to: - determine the at least one change in the timing of the exhaust camshaft 10 and/or the intake camshaft 12 resulting from the alternating control signal, and - compare the at least one change in the timing of the exhaust camshaft 10 and/or the intake camshaft 12 with one or more timing change parameter reference values. The control arrangement 38 may be further configured to: - control of the internal combustion engine 4 in accordance with the first mode of operation or the second mode of operation in response to the at least one change in the timing of the 19 exhaust camshaft 10 and/or the intake camshaft 12 based on a result of the comparing of the at least one change in the timing of the exhaust camshaft 10 and/or the intake camshaft 12 with the one or more timing change parameter reference values. ln this manner, the determined at least one change in the timing of the relevant camshaft 10, 12 may be utilized for comparison with one or more timing change parameters and the result of the comparison may be utilized for the decision whether the internal combustion engine 4 is controlled in accordance with the first or second mode of operation.

The one or more timing change parameter reference values may be the above discussed desired or anticipated change of the timing. Accordingly, the one or more timing change parameter reference values may be defined by one or more threshold values and/or by one Ol' mOFG FGfGFGFICG fangeS.

Timing change parameters may be one or more of timing change angular speed, timing change angle, and/or timing change time.

The one or more timing change parameter reference values may relate directly or indirectly to the provided control signal.

According to embodiments, in order to compare the at least one change in the timing of the exhaust camshaft 10 and/or the intake camshaft 12 with the one or more timing change parameter reference values, the control arrangement 38 may be configured to: - determine whether the exhaust camshaft 10 and/or the intake camshaft 12 are/is operating within or outside a nominal range of the one or more timing change parameter reference values based on the at least one change in the timing of the exhaust camshaft 10 and/or the intake camshaft 12. ln this manner, a nominal range of the one or more timing change parameter reference values may be utilised for the decision whether the internal combustion engine 4 is controlled in accordance with the first or second mode of operation.

The one or more timing change parameter reference values may relate to one or more of a timing change angular speed value, a timing change angle value, and/or a timing change time value. Se further below with reference to the method 100.

The control arrangement 38 may be configured to perform further steps of the method 100 discussed below with reference to Fig. 7.

Figs. 5a - 5c schematically illustrate diagrams over example alternating control signals and example generated oscillating changes of the timing of an exhaust camshaft. Similarly, Figs. 6a - 6c schematically illustrate diagrams over example alternating control signals and example generated oscillating changes of the timing of an intake camshaft. The example alternating control signals and example generated oscillating changes of the timing of relevant camshafts 10, 12 are provided by a control arrangement and, in a method, as discussed herein.

The intake and exhaust camshafts may be camshafts 10, 12 of an ICE 4 as discussed above with reference to Figs. 1 - 4. Accordingly, in the following reference is also made to Figs. 1 - 4.

Each of the diagrams shows a coordinate system representing time, T, along the X-axis and timing change angle, oi, of the relevant camshaft along the Y-axis. The angle a = 0 degrees CA is the angle of the initial timing setting of the relevant camshaft 10, 12 in relation to the crankshaft 8, from which the oscillating changes of the timing commence and to which they revert.

Positive timing change angles related to delaying the opening and closing of a relevant valve and in the discussed examples typically applies to the intake camshaft 12 but may also be applied to the exhaust camshaft 10. Negative timing change angles related to advancing the opening and closing of a relevant valve and in the discussed examples typically applies to the exhaust camshaft 10 but may also be applied to the intake camshaft 12. According to alternative embodiments, the alternating control signal may generate oscillating changes of the timing of the relevant camshaft 10, 12 around the initial timing setting i.e., including both positive and negative timing changes.

The solid line in each of the diagrams indicates the provided alternating control signal and the broken line indicates the generated oscillating changes of the timing of the relevant camshaft 10, 12.

For instance, the amplitude of the timing change angle and/or a derivative of the timing change angle i.e., a timing change angular speed, may form timing change parameters. Timing change parameter reference values may be a threshold amplitude value or a nominal amplitude range and/or a threshold value of the derivative of the timing change angle or a nominal range for the derivative of the timing change angle. 21 The control signal may form a basis for determining Characteristics of the generated oscillating changes of the timing of a camshaft e.g., a point in time of a change in the square wave alternating control signal may form the basis for determining a timing change angular speed of the generated oscillating changes of the timing and an amplitude of the control signal may form the basis for determining an amplitude of the generated oscillating changes of the timing.

Figs. 5a and 6a represent a situation where the oil of the ICE 4 has ideal viscosity and the variable valve timing arrangement 30 responds to the alternating control signal with a generated oscillating change of the timing of the relevant camshaft 10, 12 that quickly reaches the full amplitude of the timing change angle.

As shown in Fig. 5a, for the exhaust camshaft 10, the generated change of the timing oscillates between 0 and -ZoLE degrees CA. The timing change to full -2oiE degrees CA is achieved within a time period of ATEO which is e.g. below a threshold value and/or within a nominal range. The timing change back to 0 degrees CA is achieved within a time period of ATM which is e.g. below a threshold value and/or within a nominal range.

As shown in Fig. 6a, for the intake camshaft 12, the generated change of the timing oscillates between 0 and 2ou degrees CA. The timing change to full Zou degrees CA is achieved within a time period of ATIO which is e.g. below a threshold value and/or within a nominal range. The timing change back to 0 degrees CA is achieved within a time period of ATM which is e.g. below a threshold value and/or within a nominal range.

Figs. 5b and 6b represent a situation where the oil of the ICE 4 has an acceptable viscosity and the variable valve timing arrangement 30 responds to the alternating control signal with a generated oscillating change of the timing of the relevant camshaft 10, 12 that reaches the full amplitude of timing change angle, albeit at a lower speed than in the examples of Figs. 5a and 6a.

As shown in Fig. 5b, for the exhaust camshaft 10, the generated change of the timing still oscillates between 0 and -ZoLE degrees CA. The timing change to full -2oiE degrees CA is achieved within a time period of ATEO which is longer than in the example of Fig. 5a but still below a threshold value and/or within a nominal range. The timing change back to 0 degrees 22 CA is achieved within a time period of ATM which is still below a threshold value and/or within a nominal range.

As shown in Fig. 6b, for the intake camshaft 12, the generated change of the timing still oscillates between 0 and Zon. degrees CA. The timing change to full Zou degrees CA is achieved within a time period of ATIO which is still below a threshold value and/or within a nominal range. The timing change back to 0 degrees CA is achieved within a time period of ATI l which is still below a threshold value and/or within a nominal range.

Figs. 5c and 6c represent a situation where the oil of the ICE 4 has too high a viscosity and the variable valve timing arrangement 30 responds sluggishly to the alternating control signal with a generated oscillating change of the timing of the relevant camshaft 10, 12 that does not reach the full amplitude of timing change angle.

As shown in Fig. 5c, for the exhaust camshaft 10, the generated change of the timing oscillates between 0 degrees CA and a value Aoigo degrees CA that is below the desired or anticipated timing change angle of -ZoLE degrees CA. Moreover, this reduced timing change angle is achieved within a time period of ATEO which is e.g. above a threshold value and/or outside a nominal range. Similarly, the timing change back to 0 degrees CA is achieved within a time period of ATM which is above a threshold value and/or outside a nominal range.

As shown in Fig. 6c, for the intake camshaft 12, the generated change of the timing oscillates between 0 degrees CA and a value Aodo degrees CA that is below the desired or anticipated timing change angle of Zou degrees CA. Also, the timing change angle is achieved within a time period of ATIO which is above a threshold value and/or outside a nominal range. The timing change back to 0 degrees CA is achieved within a time period of ATI 1 which is above a threshold value and/or outside a nominal range. lt may be noted that the timing change angular speed may differ between a rising flank and a falling flank of the oscillating timing changes and accordingly, different threshold values and nominal ranges may apply to the rising and falling flanks. Similarly, the timing change angular speed may differ between the exhaust and intake camshafts 10, 12 and accordingly, different threshold values and nominal ranges may apply to the angular speeds of the exhaust and intake camshafts 10, 12. 23 Fig. 7 illustrates embodiments of a method 100 for controlling a four-stroke internal combustion engine. The ICE may be an ICE 4 comprising a control arrangement 38 as discussed above in connection with Figs. 1 - 6c. Accordingly, in the following reference is also made to Figs. 1 - 6c.

Consequently, the ICE 4 comprises: an exhaust valve 20 and an intake valve 22, an exhaust camshaft 10 arranged to control the opening and closing of the exhaust valve 20, an intake camshaft 12 arranged to control the opening and closing of the intake valve 22, and a variable valve timing arrangement 30 for the exhaust camshaft 10 and/or the intake camshaft 12.

The method 100 comprises steps of: - setting or determining 102 an initial timing setting of the exhaust camshaft 10 and/or the intake camshaft 12, - providing 104 an alternating control signal for the exhaust camshaft 10 and/or the intake camshaft 12 in order to generate an oscillating change of a timing of the exhaust camshaft 10 and/or the intake camshaft 12, and - controlling 106 the internal combustion engine 4 in accordance With a first mode of operation or a second mode of operation different from the first mode of operation in response to at least one change in the timing of the exhaust camshaft 10 and/or the intake camshaft 12 resulting from the alternating control signal.

Embodiments, functions, and configurations of the control arrangement 38 discussed above are applicable in a corresponding manner in the method 100. Similarly, steps of the method 100 are able to be performed in the above-discussed control arrangement 38. Accordingly, embodiments of the control arrangement 38 are configured to perform one or more steps of the method 100.

According to embodiments, preceding the step of controlling 106 the internal combustion engine 4, the method 100 may comprise steps of: - determining 108 the at least one change in the timing of the exhaust camshaft 10 and/or the intake camshaft 12 resulting from the alternating control signal, and - comparing 110 the at least one change in the timing of the exhaust camshaft and/or the intake camshaft with one or more timing change parameter reference values. The step of controlling 106 may be based on a result of the step of comparing 110. 24 Accordingly, the at least one change in the timing of the exhaust and/or intake camshaft 10, 12 determined in the step of determining 108 may be utilized in the step of comparing 110 for comparison with the one or more timing change parameter values, such as threshold values and/or nominal ranges. The result of the step of comparing 110 may be utilized in the step of controlling 106 and whether the internal combustion engine 4 is controlled in accordance With the first or second mode of operation.

According to embodiments, the step of comparing 110 may comprise a step of: - determining 112 whether the exhaust camshaft 10 and/or the intake camshaft 12 are/is operating within or outside a nominal range of the one or more timing change parameter reference values based on the at least one change in the timing of the exhaust camshaft 10 and/or the intake camshaft 12.

Thus, a nominal range of the one or more timing change parameter reference values may be utilized in the step of controlling 106 and whether the internal combustion engine 4 is controlled in accordance with the first or second mode of operation.

According to embodiments, the one or more timing change parameter reference values may relate to one or more of: - a timing change angular speed value, - a timing change angle value, and/or - a timing change time value.

Accordingly, examples of timing change parameters may be with respect to timing change angular speed: a time derivative of a timing change, Au / AT, a maximum time period Tmax for a timing change Aon, or a minimum timing change ocmin during a time period AT; with respect to timing change angle: an amplitude of the angle, Aon; and with respect to timing change time a time period, AT. See also the discussion above relating to Figs. 5a - 6c and the generated oscillating timing changes.

The reference values may be threshold values of the timing change parameters and/or limit values of one or more ranges of the timing change parameters.

According to embodiments, if in the step of determining 112 whether the exhaust camshaft 10 and/or the intake camshaft 12 are/is operating within or outside a nominal range of the one or more timing change parameter reference values, it is determined that the at least one change in the timing of the exhaust camshaft 10 and/or the intake camshaft 12 is within the nominal range of the one or more timing change parameter reference values, the step of controlling 106 may comprise a step of: - operating 114 the internal combustion engine 4 in accordance with the first mode of operation, and wherein if in the step of determining 112 whether the exhaust camshaft 10 and/or the intake camshaft 12 are/is operating within or outside a nominal range of the one or more timing change parameter reference values, it is determined that the at least one change in the timing of the exhaust camshaft 10 and/or the intake camshaft 12 is outside the nominal range of the one or more timing change parameter reference values, the step of controlling 106 may comprise a step of: - operating 116 the internal combustion engine 4 in accordance with the second mode of operation. ln this manner, the result of the step of determining 112 may decide whether the ICE 4 is operated in accordance with the first or second mode of operation.

According to embodiments, the first mode of operation may comprise an ordinary range of available timing settings of the exhaust camshaft 10 and/or the intake camshaft 12, and the second mode of operation may comprise a limited range of available timing settings of the exhaust camshaft 10 and/or the intake camshaft 12.

The ordinary range of available timing settings is a larger range of timing settings than the limited range of available timing settings. The ordinary range of available timing settings may be the full range of available timing settings of the exhaust and/or intake camshaft 10, 12 of the ICE 4. The limited range of available timing settings may be as few as only one available timing setting. For instance, a timing setting which increases the engine temperature by putting the ICE 4 under internal load due to the timing setting of one or both camshafts 10, 12.

According to embodiments, the alternating control signal may be intended to generate an oscillating change of a timing of the exhaust camshaft and/or the intake camshaft within a range of 2 - 20 degrees CA, such as within a range of 5 - 15 degrees CA, such as within a range of 5 - 10 degrees CA. ln this manner, the oscillating change of the timing of the exhaust and/or intake camshaft 10, 12 may be reliably measured while it may have no, or only minor, influence on the operation of the ICE 4 as provided by the initial timing setting of the exhaust and/or intake camshaft 10, 12. The method 100 may, accordingly, only affect the ICE 4 operation in a minor manner, if at all. 26 According to embodiments, the alternating control signal may be intended to generate an oscillating change of a timing of the exhaust camshaft 10 and/or the intake camshaft 12 symmetrically about the initial timing setting.

According to alternative embodiments, the alternating control signal may be intended to generate an oscillating change of a timing of the exhaust camshaft 10 and/or the intake camshaft 12 asymmetrically about the initial timing setting.

According to embodiments, prior to the step of providing 104 an alternating control signal for the exhaust camshaft and/or the intake camshaft, the method 100 may comprise a step of: - starting 118 the internal combustion engine 4. ln this manner, the method 100 may be performed with the ICE 4 operating.

According to embodiments, in conjunction with the step of comparing 110 the at least one change in the timing of the exhaust camshaft 10 and/or the intake camshaft 12 with the one or more timing change parameter reference values, the method 100 may comprises one or more steps of: - measuring 120 a temperature of the internal combustion engine 4, and/or - determining 122 a time period from a start of the internal combustion engine 4.

Thus, it may be determined whether the oil has degraded to such an extent that its viscosity is too high also with the ICE at its normal operating temperature. A change of oil thus, may be required in order to achieve proper operation of the variable valve timing arrangement 30.

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

One skilled in the art will appreciate that the method 100 method for controlling a four-stroke internal combustion engine may be implemented by programmed instructions. These programmed instructions are typically constituted by a computer program, which, when it is executed in a computer or calculation unit 60, ensures that the computer or calculation unit 60 carries out the desired control, such as the method 100, and thereto related steps 102 - 122. The computer program is usually part of a computer-readable storage medium which comprises a suitable digital storage medium on which the computer program is stored. 27 Fig. 8 illustrates embodiments of a computer-readable storage medium 99 comprising instructions which, when executed by a computer or calculation unit 60, cause the computer or calculation unit 60 to carry out the steps of the method 100 according to any one of aspects and/or embodiments discussed herein.

The computer-readable storage medium 99 may be provided for instance in the form of a data carrier carrying computer program code for performing at least some of the steps 102 - 122 according to some embodiments when being loaded into the one or more calculation units 60. The data carrier may be, e.g. a ROM (read-only memory), a PROM (programable read-only memory), an EPROM (erasable PROM), a flash memory, an EEPROM (electrically erasable PROM), a hard disc, a CD ROM disc, a memory stick, an optical storage device, a magnetic storage device or any other appropriate medium such as a disk or tape that may hold machine readable data in a non-transitory manner. The computer-readable storage medium may furthermore be provided as computer program code on a server and may be downloaded to the calculation unit 60 remotely, e.g., over an lnternet or an intranet connection, or via other Wired or wireless communication systems.

The computer-readable storage medium 99 shown in Fig. 8 is a nonlimiting example in the form of a USB memory stick. lt is to be understood that the foregoing is illustrative of various example embodiments and that the invention is defined only by the appended claims. A person skilled in the art will realize that the example embodiments may be modified, and that different features of the example embodiments may be combined to create embodiments other than those described herein, without departing from the scope of the invention, as defined by the appended claims.

Claims

1. A method (100) for controlling a four-stroke internal combustion engine (4), the internal combustion engine (4) comprising: an exhaust valve (20) and an intake valve (22), an exhaust camshaft (10) arranged to control the opening and closing of the exhaust valve (20), an intake camshaft (12) arranged to control the opening and closing of the intake valve (22), and a variable valve timing arrangement (30) for the exhaust camshaft (10) and/or the intake camshaft (12), wherein the method (100) comprises steps of: - setting or determining (102) an initial timing setting of the exhaust camshaft (10) and/or the intake camshaft (12), - providing (104) an alternating control signal for the exhaust camshaft (10) and/or the intake camshaft (12) in order to generate an oscillating change of a timing of the exhaust camshaft (10) and/or the intake camshaft (12), and - controlling (106) the internal combustion engine (4) in accordance with a first mode of operation or a second mode of operation different from the first mode of operation in response to at least one change in the timing of the exhaust camshaft (10) and/or the intake camshaft (12) resulting from the alternating control signal.

2. The method (100) according to claim 1, wherein preceding the step of controlling (106) the internal combustion engine (4), the method (100) comprising steps of: - determining (108) the at least one change in the timing of the exhaust camshaft (10) and/or the intake camshaft (12) resulting from the alternating control signal, and - comparing (110) the at least one change in the timing of the exhaust camshaft (10) and/or the intake camshaft (12) with one or more timing change parameter reference values, and wherein the step of controlling (106) is based on a result of the step of comparing (110).

3. The method (100) according to claim 2, wherein the step of comparing (110) comprises a step of: - determining (112) whetherthe exhaust camshaft (10) and/or the intake camshaft (12) are/is operating within or outside a nominal range of the one or more timing change parameter reference values based on the at least one change in the timing of the exhaust camshaft (10) and/or the intake camshaft (12).

4. The method (100) according to claim 2 or 3, wherein in conjunction with the step of comparing (110) the at least one change in the timing of the exhaust camshaft (10) and/or the intake camshaft (12) with the one or more timing change parameter reference values, the method (100) comprises one or more steps of: - measuring (120) a temperature of the internal combustion engine (4), and/or - determining (122) a time period from a start of the internal combustion engine (4)-

5. The method (100) according to claim 3, wherein if in the step of determining (112) whether the exhaust camshaft and/or the intake camshaft are/is operating within or outside a nominal range of the one or more timing change parameter reference values, it is determined that the at least one change in the timing of the exhaust camshaft (10) and/or the intake camshaft (12) is within the nominal range of the one or more timing change parameter reference values, the step of controlling (106) comprises a step of: - operating (114) the internal combustion engine (4) in accordance with the first mode of operation, and wherein if in the step of determining (112) whetherthe exhaust camshaft and/or the intake camshaft are/is operating Within or outside a nominal range of the one or more timing change parameter reference values, it is determined that the at least one change in the timing of the exhaust camshaft (10) and/or the intake camshaft (12) is outside the nominal range of the one or more timing change parameter reference values, the step of controlling (106) comprises a step of: - operating (116) the internal combustion engine (4) in accordance with the second mode of operation.

6. The method (100) according to any one of claims 2 - 5, wherein the one or more timing change parameter reference values relates to one or more of: - a timing change angular speed value, - a timing change angle value, and/or - a timing change time value.

7. The method (100) according to any one of the preceding claims, wherein the first mode of operation comprises an ordinary range of available timing settings of the exhaust camshaft (10) and/or the intake camshaft (12), and wherein the second mode of operation comprises a limited range of available timing settings of the exhaust camshaft (10) and/or the intake camshaft (12).

8. The method (100) according to any one of the preceding claims, wherein the alternating control signal is intended to generate an oscillating change of a timing of the exhaust camshaft (10) and/or the intake camshaft (12) within a range of 2 - 20 degrees CA, such as within a range of 5 - 15 degrees CA, such as within a range of 5 - 10 degrees CA.

9. The method (100) according to nay one of the preceding claims, wherein the alternating control signal is intended to generate an oscillating change of a timing of the exhaust camshaft (10) and/or the intake camshaft (12) symmetrically about the initial timing setting.

10. The method (100) according to any one of c|aims 1 - 8, wherein, the alternating control signal is intended to generate an oscillating change of a timing of the exhaust camshaft (10) and/or the intake camshaft (12) asymmetrically about the initial timing setting.

11. The method (100) according to ay one of the preceding claims, wherein prior to the step of providing (104) an alternating control signal for the exhaust camshaft (10) and/or the intake camshaft (12), the method (100) comprises a step of: - starting (118) the internal combustion engine (4).

12. A computer program comprising instructions which, when the program is executed by a computer, cause the computer to carry out the steps of the method (100) according to any one of the preceding c|aims.

13. A computer-readable storage medium (99) comprising instructions which, when executed by a computer, cause the computer to carry out the steps of the method (100) according to any one of c|aims 1 -

14. A control arrangement (38) for controlling a four-stroke internal combustion engine (4), the internal combustion engine (4) comprising an exhaust valve (20) and an intake valve (22), an exhaust camshaft (10) arranged to control the opening of the exhaust valve (20), and an intake camshaft (12) arranged to control the opening and closing of the intake valve (22), and a variable valve timing arrangement (30) for the exhaust camshaft (10) and/or the intake camshaft (12), wherein the control arrangement (38) is configured to:- set or determine an initial timing setting of the exhaust camshaft (10) and/or the intake camshaft (12), - provide an alternating control signal for the exhaust camshaft (10) and/or the intake camshaft (12) in order to generate an oscillating change of a timing of the exhaust camshaft (10) and/or the intake camshaft (12), and - control the internal combustion engine (4) in accordance With a first mode of operation or a second mode of operation different from the first mode of operation in response to at least one change in the timing of the exhaust camshaft (10) and/or the intake camshaft (12) resulting from the alternating control signal.

15. The control arrangement (38) according to claim 14, wherein the control arrangement (38) is configured to: - determine the at least one change in the timing of the exhaust camshaft (10) and/or the intake camshaft (12) resulting from the alternating control signal, and - compare the at least one change in the timing of the exhaust camshaft (10) and/or the intake camshaft (12) with one or more timing change parameter reference values, and wherein control arrangement (38) is configured to: - control of the internal combustion engine (4) in accordance with the first mode of operation or the second mode of operation in response to the at least one change in the timing of the exhaust camshaft (10) and/or the intake camshaft (12) based on a result of the comparing of the at least one change in the timing of the exhaust camshaft (10) and/or the intake camshaft (12) with the one or more timing change parameter reference values.

16. The control arrangement (38) according to claim 15, wherein to compare the at least one change in the timing of the exhaust camshaft (10) and/or the intake camshaft (12) with the one or more timing change parameter reference values, the control arrangement (38) is configured to: - determine whether the exhaust camshaft (10) and/or the intake camshaft (12) are/is operating within or outside a nominal range of the one or more timing change parameter reference values based on the at least one change in the timing of the exhaust camshaft (10) and/or the intake camshaft (12).

17. A four-stroke internal combustion engine (4) comprising a control arrangement (38) according to any one of claims 14 -

18. A vehicle (2) comprising a four-stroke internal combustion engine (4) according to the preceding claim.