SE1550267A1

SE1550267A1 - A method for controlling an internal combustion engine, an internal combustion engine controlled by such a method and avehicle comprising such an internal combustion engine.

Info

Publication number: SE1550267A1
Application number: SE1550267A
Authority: SE
Inventors: Ola Stenlåås; Eric Olofsson; Andreas Dahl
Original assignee: Scania Cv Ab
Priority date: 2014-03-07
Filing date: 2015-03-05
Publication date: 2015-09-08
Also published as: DE112015000774T5; WO2015133957A1

Abstract

The invention relates to a method comprises the following steps: a) driving an internal combustion engine (2) at least one cycle of opening and closing of inlet and exhaust valves (18,19,24,25) corresponding to normal operation of the combustion engine (2); b) comparing the exhaust gas properties with a predetermined value for exhaust gas properties, d) supplying fuel to a second cylinder (4) of the internal combustion engine (2), and e) controlling a first inlet valve (18) and a first exhaust valve (24), so that no air is supplied to an exhaust system (26) from the first cylinder when a first piston (P1) moves back and forth in the first cylinder (C1), if the exhaust gas properties deviate from the predetermined exhaust gas properties. The invention also relates to an internal combustion engine (2) which is controlled according to the method and a vehicle (1) which comprises such an internal combustion engine (2). The invention also relates to a computer program (P) and a computer program product for performing the method.(Fig. 5)

Description

The present invention relates to a method for controlling an internal combustion engine according to the preamble of claim 1, an internal combustion engine controlled by such a method according to the preamble of claim 21 and a vehicle comprising such an internal combustion engine according to the preamble of claim 22.

Under certain operating conditions, such as at low load and low speed of internal combustion engines of four-stroke and diesel type, it is desirable to shut off the fuel supply to some cylinders of the internal combustion engine to reduce environmental impact. Shutting off or deactivating the fuel still implies that air is passing the fuel de- activated cylinders without any combustion which means that the exhaust treatment system will be cooled.

The treatment system must reach an operating temperature in the range 200° C - 600° C in order to satisfactory reduce the emissions from the engine.

When one or more cylinder(s) are deactivated through fuel cut off, while the other cylinders undergo normal operation, vibrations will be introduced due to the imbalance between the pressure traces of different cylinders. When cylinder deactivation of for example three of six cylinders of a six-cylinder engine is implemented, vibra- tions of the order of 1,5 are generated, which are perceived as disturbing for the driver and passenger(s) in the vehicle driven by the combustion engine. If only the fuel supply is cut off to the deactivated cylinders no change in mass flow and exhaust temperature is achieved. This applies provided the fuel to the active cylinders is increased, meaning that the load of the engine is held constant. 2 To reduce the mass flow and increase the exhaust temperature, the exhaust and inlet valves of the deactivated cylinders can be closed. The pressure in the deactivated cylinders gives rise to a torque pulse per revolution per cylinder until the pressure, due to leakage, becomes so low in these cylinders that no significant torque is obtained from them. This leads to even greater vibration problems and oil carryover across the piston rings from the crankcase to the combustion chamber during the lower part of the piston stroke in the deactivated cylinders, due to the negative differential pressure across the piston rings. This will occur after a certain period of deactivation.

The vibrations can be reduced if either the exhaust or the intake valves in the deactivated cylinders are kept closed and the active valves do both the exhaust and inlet lift events. Torque pulses will then be obtained from the compression/expansion pressure in the deactivated cylinders. This results in essentially the same vibration level as when the only measure is shutting off the fuel to the deactivated cylinders. More- over, the mass flow to the exhaust treatment is reduced and the exhaust temperature is thereby significantly increased.

By controlling the exhaust or inlet valves of the deactivated cylinders, so that they will remain closed during all strokes, the engine exhaust treatment system will not be cooled because no air is passed to the exhaust treatment system from the deactivated cylinders.

Within the vehicle exhaust emission driving cycle, cylinder deactivation with closed intake and/or exhaust valves might be required to prevent the exhaust temperature to fall below its critical limit. This is done in order to maintain the conversion of the exhaust emissions in the exhaust treatment system.

In order to simultaneously avoid cooling of the exhaust treatment system and reduce vibrations, a zero flow of air through the deactivated cylinders may be created. Thus, air will be prevented from passing through the deactivated cylinders and further to the exhaust treatment system. Consequently, the exhaust treatment system will not be cooled. The zero flow must be achieved in an efficient manner, so that pressure pulses, noise and mechanical stress are reduced or eliminated. 3 Document US 6431154 B1 discloses how the air flow is reduced through the deactivated cylinders in an internal combustion engine in order to avoid that emissions and vibrations occur.

SUMMARY OF THE INVENTION Despite prior art there is a need to further develop a method for controlling an internal combustion engine in which vibrations resulting from a zero flow of air supplied to the exhaust gas system from one or more of the cylinders are reduced. There is also a need to further develop a method for controlling an internal combustion engine which reduces tail pipe exhaust emissions by introducing a zero flow of air to the exhaust gas system from one or more of the cylinders and as a consequence increase the exhaust gas temperature upstream the exhaust treatment system thereby facilitating conversion of emissions.

The object of the present invention is thus to provide a method for controlling an internal combustion engine in which vibrations resulting from a zero flow of air supplied to the exhaust gas system from one or more of the cylinders are reduced.

Another object of the present invention is to provide a method for controlling an internal combustion engine in which the cooling of the exhaust treatment system is reduced.

Another object of the present invention is to provide a method for controlling an inter- nal combustion engine in order to prevent oil from leaking into the combustion chambers due to negative differential pressure in the combustion chambers when a zero flow of air supplied to the exhaust gas system from one or more of the cylinders is implemented.

A further object of the present invention is to provide a method for controlling an internal combustion engine which reduces tail pipe exhaust emissions when a zero flow of air supplied to the exhaust gas system from one or more of the cylinders is implemented. 4 These objectives are achieved with a method for controlling an internal combustion engine, which is characterized by the features specified in patent claim 1.

According to the method, periodically no air is supplied to the exhaust gas system from one or more of the deactivated cylinders of the internal combustion engine, and the air mass trapped in the cylinders of the combustion engine which supply air to the exhaust system is reduced in relation to the air mass trapped in the respective cylinders which periodically not supply air to the engine exhaust system. This causes the vibrations in the internal combustion engine to be reduced with a simultaneous in- crease of the exhaust gas temperature upstream the exhaust treatment system, thereby facilitating conversion of emissions.

The exhaust gas properties based on a diagnose of oxygen content and/or ternpera- ture of the exhaust gases are compared with predetermined exhaust gas properties. Also, vibrations in the internal combustion engine based on crankshaft torsional vibrations, or other engine vibrations, are compared with a predetermined vibration value of the internal combustion engine.

The internal combustion engine has preferably separate valve control means for the inlet and exhaust valves. At an operating condition of the internal combustion engine corresponding to normal load the control device controls the exhaust valves to open at the bottom dead centre of the termination of the expansion stroke and so that they close at top dead centre for start of the intake stroke, and the inlet valves open at the top dead centre when the intake stroke starts and close at the bottom dead centre when the compression stroke starts.

According to an aspect of the invention, when an operating condition in which the risk of cooling the exhaust treatment system to a critical temperature exists, the intake valves and exhaust valves in one or more of the cylinders are controlled to produce a zero flow of air from the inlet side to the exhaust side of the cylinder when the pistons move back and forth in these cylinders. At the same time, the fuel injection is controlled to supply a first volume of fuel to the cylinders with zero flow of air, and also ensure that a second volume of fuel is supplied to the other cylinders. Preferably, the second fuel volume is greater than the first volume of fuel, which results in a reduction of vibrations of the internal combustion engine. However, under certain operating conditions a different distribution between the first and second fuel volume is advantageous. For example they may be equal, or the first volume of fuel may be greater than the second volume of fuel.

According to another aspect of the invention, one of the first intake valves is controlled to open at a bottom dead centrecentre of the piston in the first cylinder, between an expansion stroke and an exhaust stroke, and to close at a top dead centre of the piston in the first cylinder between an exhaust stroke and an intake stroke. At the same time the other of the first intake valves is controlled to open when one of the first intake valves closes, and to close at bottom dead centre between an inlet stroke and a compression stroke, and the first exhaust valves are controlled so that they remain closed during all strokes of the engine.

According to a further aspect of the invention, one of the first exhaust valves is controlled to open at a bottom dead centre of the piston in the first cylinder, between an expansion stroke and an exhaust stroke, and to close at top dead centre of the piston in the first cylinder between an exhaust stroke and an intake stroke, the other of the first exhaust valves is controlled to open when one of the first exhaust valves closes, and to close at bottom dead centre between an inlet stroke and a compression stroke, and the first intake valves are controlled so that they remain closed during all strokes of the engine.

The above mentioned objectives are also achieved with an internal combustion engine, which is characterized by the features specified in patent claim 21.

Such combustion engine ensures that the vibrations caused by the fact that no air is supplied to the exhaust gas system from one or more of the cylinders, are effectively reduced. Such an internal combustion engine also increases the exhaust gas tem- perature upstream the exhaust treatment system, thereby facilitating conversion of emissions. By controlling the internal combustion engine so that the trapped air mass in the second, active cylinder decreases relative to the trapped air mass of the first deactivated cylinder, the pressure in the active cylinders will reduce and adapt to a 6 pressure level which substantially provide the same torque contribution to the crankshaft vs. crank angle, as the cylinders from which no air is supplied to the exhaust gas system. Thus, the vibrations will be effectively reduced.

When for example 3 out of 6 cylinders are deactivated in an inline six-cylinder en- gine, vibrations of the order 1,5 are created due to loss of torque contribution from the deactivated cylinders. According to the invention the vibrations of order 1,5 are suppressed by maintaining compression and expansion pressure in the deactivated cylinders. By controlling the internal combustion engine so that the trapped air mass in the active cylinders decreases in relation to the trapped air mass in the deactivated cylinders, the suppression of vibrations of order 1,5 is further reduced. The invention is particularly effective for reducing the low-frequency vibrations that arise during idle operation of the engine.

In order to minimize the excitation of vibrations of order 1,5, the sum of torque contri- butions from the pressure in all cylinders should not contain the order of 1,5. This may be achieved by reducing the difference between the torque contributions from the deactivated and the activated cylinders by reducing the air mass trapped in the active cylinders, while trapped air mass in the deactivated cylinders may be in- creased. From the active cylinders air is supplied to the exhaust gas system. How much reduction of the trapped air mass in the active cylinders that is required depends on the load and speed of the engine, and is preferably controlled so that the reduction of vibrations at idle has priority, however exhaust emissions always have top priority. Torque vs. crank angle, produced by the active cylinders is a function of cylinder pressure, cylinder bore and the crank mechanism, i.e. connecting rod length, stroke of the crankshaft, and crankshaft position. The crank mechanism cannot be affected. Therefore, the cylinder pressure is used to optimize the torque contribution. Of particular importance is the crankshaft position approximately 25 degrees before and after top dead centre because the combination of high cylinder pressure and the position of the crank mechanism results in high torque.

The above mentioned objectives are also achieved with a vehicle, which is characterized by the features specified in patent claim 22. 7 A vehicle provided with such an internal combustion engine will avoid cooling of the exhaust treatment system and ensure that vibrations due to the deactivation of the cylinders are effectively reduced. The comfort of the persons travelling in the vehicle increases when the vibrations of the vehicle decrease compared to previously known concept for cylinder deactivation.

The invention also relates to a computer program and a computer program product for performing the method according to the present invention.

BRIEF DESCRIPTION OF THE DRAWINGS Below is a description of, as examples, preferred embodiments of the invention with reference to the enclosed drawings, in which: Fig. 1 shows schematically a vehicle in a side view, with an engine controlled by the method according to the present invention, Fig. 2 shows schematically a view from above of an engine controlled by the method according to the present invention, Fig. 3 shows a sectional view through the line II-II in fig. 2, Fig. 4a-d shows graphs of the crankshaft torque from each cylinder of an engine controlled by the method according to the present invention, Fig. 5 shows graphs of the pressure in a cylinder vs. crank position of an engine controlled by the method according to the present invention, Fig. 6 shows graphs of the pressure in a cylinder vs. volume of an engine controlled by the method according to the present invention, and Fig. 7 shows a flow chart of the method for controlling an engine according to the present invention. 8 DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS OF THE INVENTION Fig. 1 shows schematically a vehicle 1 in a side view, e.g. a truck, which comprises an internal combustion engine 2 controlled by the method according to the present invention. The engine 2, which may be a diesel engine, is connected to a gearbox 4 which is further connected to driving wheels 6 of the vehicle 1 via a propeller shaft 8.

The internal combustion engine controlled by the method according to the invention will now be described with reference to figures 2 and 3. Fig. 2 shows a schematic view from above of an internal combustion engine 2 of a four-stroke type. Preferably, the engine is a diesel engine that is powered by diesel fuel and comprises at least a first and second cylinder Cl, C4. The engine 2 of the embodiment disclosed in fig. 2 comprises six cylinders Cl - C6, which are arranged in a row in which a piston P1 - P6 is arranged in each cylinder Cl - C6 of the engine 2. The invention is applicable to any cylinder configuration and not limited to inline engines only.

At least one first inlet valve 18 is provided in the first cylinder Cl and the first inlet valve 18 is in communication with an intake system 20. At least one first exhaust valve 24 is provided in the first cylinder Cl and the first exhaust valve 24 is in com- munication with an exhaust system 26. At least one second inlet valve 19 is provided in the second cylinder C4 and the second inlet valve 19 is in communication with the intake system 20. At least one second exhaust valve 25 is provided in the second cylinder 04 and the second exhaust valve 25 is in communication with the exhaust system 26. Correspondingly, the inlet and exhaust valves are provided in the remain- ing cylinders 02, 03, 05, 06.

Preferably, two inlet valves 18, 19 and two exhaust valves 24, 25 are arranged in each cylinder Cl - C6 where each inlet valve 18, 19 communicates with the intake system 20 and each exhaust valve 24, 25 communicates with the exhaust system 26.

According to one embodiment, a damper 23 may be arranged in the intake system 20, which damper 23 can be adjusted so that it restricts the air supply to the cylinders 04 - C6 of the engine 2. 9 Fig. 3 shows a cross sectional view of the internal combustion engine 2 through the line II-II in Fig. 2. The piston P1 is via a connecting rod 14 connected to a crankshaft 16, which upon rotation of the crankshaft 16 reciprocates the piston P1 in the cylinder Cl. However, it is possible to replace the crankshaft 16 and use some other force transfer means 16 for transfer force from the piston P1 to the gearbox 4 and to the propeller shaft 8 of the vehicle 1. At least a first valve control means in the form of a first cam shaft 22 is provided to control the first and second inlet valve 18, 19. At least one second valve control means in the form of a second camshaft 28 is arranged to control the first and second exhaust valve 24, 25. According to the illus- trated embodiment the valve control means comprises camshafts 22, 28, but it is however possible to use other types of valve instruments, such as hydraulic, pneumatic or electric valve control means.

The crankshaft 16 is arranged to control each camshaft 22, 28. At least one control device 34 is provided between the crankshaft 16 and each camshaft 22, 28 for controlling the first inlet valve 18 and the first exhaust valve 24, so that no air is supplied to the exhaust system 26 from the first cylinder Cl when the first piston P1 moves back and forth in the first cylinder Cl and when the first cylinder Cl is deactivated. Thus, a zero flow through the first cylinder Cl is created. However, it is possible to replace the crankshaft 16 and use some other force transfer means 16 for controlling each camshaft 22, 28.

The control device 34 is also arranged to control the internal combustion engine 2 so that the intake air mass in the second cylinder C4 decreases relative to the intake air mass in the first cylinder Cl. At one operating condition the combustion engine cor- responding to a normal state the control device 34 is controlled so that the exhaust valves 24, 25 open at the bottom dead centre BDC for the termination of the expansion stroke and so that they close at the top dead centre TDC for start of the inlet stroke, and that the inlet valves 18, 19 open at the top dead centre TDC when the inlet stroke begins, and closes at bottom dead centre BDC when the compression stroke starts.

Depending on the type of internal combustion engine 2, two first and two second cam shafts 22, 28 may be provided in the internal combustion engine 2. This is advantageous if the engine 2 is of a V-type.

A camshaft controller 30 is provided in the internal combustion engine 2. The crank- shaft 16 controls each camshaft 22, 28 via a camshaft transmission 32. At least one control device 34 is provided between the crankshaft 16 and each camshaft 22, 28, so that the valves can be controlled to a position in which the inlet and exhaust valves 18, 19, 24,25 are controlled so that no air is supplied to the exhaust system 26 when the pistons P1 - P3 move back and forth in the cylinders Cl - 03. Prefera- bly, a control device 34 is provided for each camshaft 22, 28. An electronic control unit 36 receives signals from various sensors (not shown) such as the absolute pressure in the intake manifold, the charge air temperature, air mass flow, throttle position, engine speed and engine load. The control unit 36 affects the control device 34, which adjusts the valves 18, 19, 24, 25 opening and closing times relative to the posi- tion of the crankshaft angle (p.

A computer program P controls the internal combustion engine 2, wherein said computer program P comprises program code for making the electronic control unit 36 or another computer 46 connected to the electronic control unit 36 performing the steps of the method according to the present invention. The invention also relates to a computer programme product which is directly storable in an internal memory M into the electronic control unit 36 or the other computer 46.

A fuel pump 41 is connected to injection means 43 arranged in each cylinder Cl - C6. The injection means 43 injecting fuel into the cylinders Cl - C6. Thus, the engine is preferably designed as an Otto engine.

Fig, 4 a - d show graphs of torque versus crankshaft angle cp of an internal combus- Lion engine 2 provided with six cylinders Cl - C6. The Y axis represents torque T from the cylinders Cl - 06. The X axis represents the crankshaft angle cp and thereby the position of piston P1. Each positive torque pulse in Fig. 4a represents an expansion of cylinder Cl - 06, respectively, Every negative torque pulse represents a compression of cylinder Cl - 06, respectively, 11 In Fig. 4b three of the engine's six cylinders Cl - C3 has been deactivated while the remaining three cylinders C4 - 06 are still activated. In a deactivated cylinder no air is supplied to the exhaust gas system. In the embodiment disclosed in fig. 4b no fuel is supplied to the deactivated cylinders Cl - C3. In an activated cylinder fuel and air are supplied to the cylinder corresponding to normal operation conditions of the engine 2. All valves in the three deactivated cylinders Cl - 03 are closed and the cylinders 01 - 03 have gradually deflated. A problem arises when one or more cylinders Cl 03 is deactivated and the other cylinders 04 - 06 are activated. Then vibrations are gener- ated by the combustion engine 2 due to a different frequency spectrum of expansions of the engine 2, since small or no torque pulses are obtained from the pressure in the deactivated cylinders Cl - 03.

In Fig. 4c the vibrations have to some extent been reduced by controlling the corn- bustion engine 2 so that the same amount of gas is trapped in cylinders Cl — C3 as in cylinders 04 — 06, during the inlet stroke. At the same time cylinders Cl — C3 are controlled in such a way that the net flow of gas across these cylinders is zero. The air trapped in the deactivated cylinders Cl - C3 will be compressed and expanded and thereby transfer a torque to the crankshaft. This will change the order of vibra- tions from 1,5 to 3.

Fig. 4c shows however that the positive torque pulse in the active cylinders 04 - C6 is higher than the positive torque pulse which builds up in the deactivated cylinders Cl - C3. This torque difference will cause vibrations in the engine 2, which become especially annoying when the engine 2 is operated at idle speed. The vibrations are generated by the lateral forces between the pistons P1 - P3 and cylinders Cl - C3, and in the bearings for the crankshaft 16.

By reducing the intake air mass to the active cylinders 04 - 06 in relation to the in- take air mass in the deactivated cylinders 01 - C3, ihe torque of the active cylinders C4 - C6 will reduce and adapt to a pressure level substantially corresponding to the torque in the deactivated cylinders Cl - C3, as shown by the graph in Fig. 4d. Thus the vibrations will be effectively reduced. 12 When for example 3 out of 6 of the cylinders C1 — C6 are deactivated in an inline six cylinder engine in the embodiment above, vibrations of order 1,5 arises. However, the method according to the invention changes to the order of vibrations to 3 by maintaining compression and expansion pressure in the deactivated cylinders C1 C3. By controlling the internal combustion engine 2 so that the mass of air trapped in the active cylinders C4 - C6 decreases in relation to the mass of air trapped in the deactivated cylinders Cl - C3 the mass flow of air to the active cylinders 04 - 06 will decrease. According to one embodiment the inlet valves 19 in the active cylinders C4 - 06 are controlled to reduce the intake air mass to the active cylinders 04 - 06. This is achieved by controlling the inlet valves 19 in the active cylinders 04 - 06 to close before or after the closing time of inlet valves 19 during normal operation of the internal combustion engine 2.

According to an embodiment of the invention the inlet and exhaust valves 18, 24 in one or more of the cylinders Cl - C3 are controlled to produce a zero flow of air from the inlet side to the exhaust side of the cylinder when the pistons move back and forth in these cylinders. At the same time, the fuel injector is controlled to supply a first volume of fuel to the cylinders with zero flow of air during these cylinders expansion stroke, and also a second volume of fuel is supplied to the cylinders in which a flow of gas from the inlet side to the exhaust side is executed, during these cylinders expansion. Under these conditions the pressure in the cylinders Cl - 03 will increase and be adapted to a pressure level which substantially corresponds to the pressure in the cylinders C4 - C6, which is shown by the graph in Fig. 4d. Thus vibrations will be effectively reduced. The ratio between the first and second fuel volume can vary depending on the internal combustion engine and vehicle operating conditions. The first and second fuel volume may also be substantially equal.

The graphs in Fig. 4 represent an internal combustion engine 2 of the four-stroke type, where within the crankshaft 16 rotates 70 CA and each piston P1 - P6 travels four strokes to complete a full cycle.

Fig, 5 illustrates cylinder pressure vs, crankshaft position (I) of an internal combustion engine 2. The Y-axis represents the pressure p in the cylinder Cl, and in the cylinder C4. The X-axis represents the crankshaft position co and thus the position of the pis- 13 ton P in the cylinder. Graph A in Fig. 5 illustrates the pressure in the deactivated cylinder Cl vs. crankshaft position cp. Graph B illustrates the pressure in the active cylinder C4 vs. crankshaft position co. The additional pressure increase arising after top dead centre, TDC in the graphs B and C is due to combustion of fuel.

In order to completely eliminate the excitation of vibrations of the order 15, the pressure in all cylinders C1 - CS must be identical. This is almost achieved by reducing the difference between torque pulses from the deactivated and the active cylinders Cl 06, by reducing the air mass trapped in the active cylinders 04 - 06, while the trapped air mass in the deactivated cylinders Cl - 03 may be increased. Graph C shows that the trapped air mass - and hence pressure - in the active cylinder C4 has been reduced and varies with the crankshaft position cp. The required reduction of trapped air in the active cylinders 04 - 06, depends on the load and is preferably controlled so that reduction of vibrations at idle is prioritized. Torque vs. crank angle produced by the active cylinders C4 - CS is a function of cylinder pressure, cylinder bore and the crank mechanism, i.e. connecting rod length, stroke of the crankshaft 16, and crankshaft position, cp. The crank mechanism cannot be influenced, and therefore the cylinder pressure is used to optimize the addition of torque. Of particular importance is the crank position approximately 25 degrees before and after piston top dead centre TDC, since the combination of high in-cylinder pressure, and the crank mechanism position will result in high torque. In an embodiment, the second inlet valves are controlled to reduce the intake air mass to the active cylinders 04 - 06. This is achieved by controlling the inlet valves 19 in the activated cylinders 04 - C6 to close before or after the closing time of inlet valves 19 during normal operation of the internal combustion engine 2.

According to the first embodiment the inlet valves 19 in the cylinders C4 - 06 are controlled to close in the range corresponding to 0 crankshaft angles before bottom dead centre (CA bBDC) to 30° crankshaft angles after bottom dead centre (CA aBDC), preferably at the bottom dead centre (aBDC).

According to the second embodiment the inlet valves 19 in the cylinders C4 - 06 are controlled to close in the range corresponding to 30° CA aBDC to 90° CA aBDC, preferably 60° CA aBDC. According to a third embodiment the damper, e.g. a throttle 14 23 arranged in the intake system 20 is activated. By closing the throttle 23 in order to restrict the air flow to the active cylinders C4 - C6 of engine 2 the trapped mass of air in the active cylinders C4 - 06 will decrease. The throttle 23 can be used in combination with the control of the intake valves 19 to the active cylinders 04 - C6.

In order to control the intake valves 18 and exhaust valves 24 of the deactivated cylinders Cl 03, so that no air enters the exhaust system 26 from the deactivated cylinders Cl - C3 when the pistons P1 - P3 moves back and forth in the deactivated cylinders Cl 03 the intake valves of the deactivated cylinders Cl 03 are con- trolled, according to a first embodiment, to open in the exhaust stroke and in the in- take stroke, while the exhaust valves of the deactivated cylinders Cl - 03 are controlled to a closed position for all strokes.

According to a second embodiment the exhaust valves 24 of the deactivated cylin- ders Cl - C3 are controlled to open in the exhaust stroke and in the intake stroke, while the intake valves of the deactivated cylinders Cl - 03 are controlled to a closed position for all strokes.

Thereby the resulting flow to the exhaust system 26 from the deactivated cylinders CI - C3 will become zero. Since there is no net flow of air through these cylinders of the internal combustion engine 2, cooling and oxygenation of the exhaust treatment system 38 is avoided. Since no sub atmospheric pressure is developed in the cylinders Cl 03, no oil carryover across the piston rings from the crankcase to the combustion chamber takes place. It should be mentioned in this context that it is possible to supply fuel to the deactivated cylinders 01-03, while no net flow of air is generated by these cylinders. Then the cylinder pressure increases in the deactivated cylinders during combustion, which contributes to a reduction of vibrations.

To completely eliminate the excitation of vibrations of the order 1,5, the pressure in all cylinders Cl - C6 must be identical. In order to substantially achieve this the in- take valves and exhaust valves of cylinders Cl - C3 are controlled so that a zero flow of air from the inlet side to the exhaust side is achieved, and so that no air is supplied to the exhaust system from these cylinders, when the pistons move back and forth in the cylinders Cl - C3. Meanwhile, the fuel injectors 43 are controlled to supply a first volume of fuel to the cylinders C1 - 03 at TDCf (Top Dead Centre firing). A second volume of fuel is supplied to the cylinders C4 - C6 at TDCf for these cylinders. As a result, the pressure in the cylinders Cl - C3 will increase and be adapted to a pressure level which substantially corresponds to the pressure in the cylinders C4 - C6.

Thus, the vibrations will be effectively reduced. If the first and second fuel volume are equal an essentially complete elimination of the order of 1,5 is achieved.

According to a further embodiment disclosed in Fig. 6 the inlet valves 18 and 19 and the exhaust valves 24 and 25 in all cylinders Cl — 06 are kept closed so that no air is supplied to the exhaust system 26 from the cylinders Cl —06 when the pistons P1 — P6 move back and forth in the cylinders Cl — C6. The fuel injectors 42 are controlled to supply fuel at TDCf to all of the cylinders Cl — 06, through which a zero flow of air from the inlet side to the exhaust side prevail.

According to this embodiment fuel is supplied during several consecutive expansion strokes in the cylinders Cl — 06. As a result the pressure in the cylinders Cl — 06 will increase in consecutive steps E1 — E3.

When the trapped air within the cylinders has been consumed by the consecutive combustions during the expansion strokes, the inlet valves 18 and 19 and the ex- haust valves 24 and 25 in the cylinders Cl — 06 are controlled to an opening and closing procedure corresponding to a normal operation condition for the engine 2 so that fresh air is supplied to the cylinders Cl — 06. Thereafter, if the exhaust gas properties and/or exhaust temperature deviate from the predetermined exhaust gas properties and/or exhaust temperature the inlet valves 18 and 19 and the exhaust valves 24 and 25 in all cylinders Cl — 06 are kept closed so that no air is supplied to the exhaust system 26, and fuel is supplied during several consecutive expansion strokes in the cylinders Cl — 06.

The method for controlling the internal combustion engine 2 of the present invention will be described along with the flowchart of Fig. 7, comprises the steps of: a) driving the internal combustion engine 2 at least one cycle of opening and closing of the inlet and exhaust valves 18,19,24,25 corresponding to normal operation of the combustion engine 2, 16 b) comparing the exhaust gas properties with a predetermined value for exhaust gas properties, such as exhaust temperature, d) supplying fuel to the second cylinder C4, and e) controlling the first inlet valve 18 and the first exhaust valve 24, so that no air is supplied to the exhaust system 26 from the first cylinder Cl when the first piston P1 moves back and forth in the first cylinder Cl, if the exhaust gas properties deviate from the predetermined exhaust gas properties.

The method comprises the additional step: c) diagnosing vibrations of the internal combustion engine 2 and compare the vibrations with a predetermined value of vibrations of the internal combustion engine 2.

Step b) and step c) are performed in any order or are performed substantially simul15 taneously.

In step b) the exhaust gas properties may for example be the amount of oxygen in the exhaust gases and/or the exhaust temperature of the exhaust gases.

During step a) information about the present air-fuel ratio Apres and present vibrations Vpres of the engine 2 are collected and the collected present air-fuel ratio A -pres is in step b) compared to a predetermined reference value for the air-fuel ratio Aref and the collected present value of vibrations Vpres is in step c) compared to a predetermined reference value for the vibrations Vref. If the exhaust gas properties deviate from the predetermined exhaust gas properties, i.e. A -pres > Aref the first inlet valve 18 and the first exhaust valve 24 are controlled, so that no air is supplied to the exhaust system 26 from the first cylinder Cl when the first piston P1 moves back and forth in the first cylinder Cl. However, X if •• -pres < Aref the first inlet valve 18 and the first exhaust valve 24 are controlled to open and close in accordance to normal engine operation condi30 tions.

The method comprises the additional step: f) reducing the intake air mass to the second cylinder C4 in relation to the intake air mass to the first cylinder Cl, if the vibra- 17 tions in the internal combustion engine 2 are greater than the predetermined value for the vibrations in the internal combustion engine 2.

In step f) if the collected present value of vibrations Vpres in the internal combustion engine 2 is greater than the predetermined reference value for the vibrations Vref in the internal combustion engine 2, i.e. Vpres > Vref the intake air mass to the second cylinder C4 is reduced in relation to the intake air mass to the first cylinder Cl. Thus, the pressure in the second cylinder 04 is reduced and the vibrations in the engine 2 will be effectively reduced.

In step f) the second inlet valve 19 is controlled to reduce the trapped mass of air in the second cylinder 04. This may be achieved by controlling the second inlet valve 19 to close before or after the time of closing of the second inlet valve 19 during normal operation of the combustion engine 2.

According to an embodiment the force transfer means 16 for controlling each valve control means 22, 28 is a crankshaft 16 and the second inlet valve 19 is controlled to close in the range corresponding to 30° CA bBDC to 30° CA aBDC, preferably at BDC.

According to another embodiment the force transfer means 16 for controlling each valve control means 22, 28 is a crankshaft 16 and the second inlet valve 19 is controlled to close in the range corresponding to 30° CA aBDC to 90° CA aBDC, preferably 60° CA aBDC.

According to an embodiment the first inlet valve 18 is in step e) preferably controlled to open during the exhaust stroke and the intake stroke, while the first exhaust valve 24 is controlled to a closed position during all strokes.

According to another embodiment the first exhaust valve 24 is in step e) preferably controlled to open during the exhaust stroke and the intake stroke, while the first inlet valve 18 is controlled to a closed position for all strokes. 18 Preferably, the supplied fuel to the engine 2 is diesel fuel. Since an engine 2 powered by diesel works according to the compression ignition principle, pistons, valves and valve timing are designed with a suitable geometry, so that a functional interaction between the pistons and valves is obtained.

The method comprises the additional step: g) control respective valve 18,19,24,25 by means of two first and two second valve control means 22, 28.

Preferably, the valve control means 22, 28 are camshafts 22, 28. The inlet and ex- haust valves are controlled and driven by a separate valve control device, which is in turn driven by the crankshaft. The respective valve control device has control means which controls the valve and thus the opening and closing times of the valve. The control device is preferably coupled to a control unit which controls the control device to a position which is adapted to the internal combustion engine operating conditions.

The control unit also controls a fuel injection device that supplies fuel to the cylinders.

The method comprises the additional steps: h) supply a first volume of fuel to the first cylinder Cl to be combusted in total or mostly during the expansion stroke of the first cylinder Cl, and i) supply a second volume of fuel to the second cylinder C4 to be combusted in total or mostly during the expansion stroke of the second cylinder C4.

By controlling the inlet valves and exhaust valves of the cylinders where within a zero flow from the inlet side to the exhaust side prevails and consequently no air is sup- plied to the exhaust system from these cylinders when the pistons move back and forth in the cylinders, while the fuel injectors 43 are controlled to supply a first volume of fuel at TDCf to the cylinders through which a zero flow from the inlet side to the exhaust side prevails and also ensure that a second volume of fuel is supplied at TDCf to the cylinders in which a flow of gas from the inlet side to the exhaust side takes place, the pressure in the cylinders Cl - C3 will increase and be adapted to a pressure level substantially corresponding to the pressure in the cylinders C4 - C6. Thus, the vibrations will be effectively reduced. The ratio between the first and second fuel volume can vary depending on the combustion engine and operating conditions of the vehicle. The first and second volume of fuel may be substantially equal, 19 but preferably the second volume of fuel is greater than the first volume of fuel, so that vibrations are effectively reduced.

Preferably, the method comprises the additional step: j) control two inlet valves 18, 19 and two exhaust valves 24, 25 by means of respective valve control means 22, 28. In such an internal combustion engine, the application of the invention may be very efficient, since the number of valves per cylinder affects the air flow and the filling and emptying of the cylinders.

According to an embodiment in step j): control one of the first intake valves 18 to open at a bottom dead centre BDC of the piston P1 in the first cylinder C1 between an expansion stroke and an exhaust stroke, and to close at a top dead centre TDC for the piston P1 in the first cylinder Cl between an exhaust stroke and an intake stroke; -control the other of the first intake valves 18 to open when one of the first intake valves 18 closes, and to close at the bottom dead centre BDC between an intake stroke and a compression stroke, and control the first exhaust valve 24, so that they remain closed during all strokes of the engine 2.

According to another embodiment in step j): control one of the first exhaust valves 24 to open at a bottom dead centre BDC of the piston P1 in the first cylinder Cl between an expansion stroke and an exhaust stroke, and to close at a top dead centre TDC of the piston P1 in the first cylinder Cl between the exhaust stroke and an intake stroke; control the other of the first exhaust valves 24 to open when one of the first exhaust valve 24 closes, and to close at the bottom dead centre BDC between the intake stroke and a compression stroke, and control the first intake valves 18, so that they remain closed during all strokes of the engine 2.

The method comprises the additional step: k) controlling the second inlet valve 19 and the second exhaust valve 25, so that no air is supplied to the exhaust system 26 from the second cylinder C4 when the second piston P4 moves back and forth in the second cylinder C4, if the exhaust gas properties deviate from the predetermined exhaust gas properties.

Preferably, in steps e) and k) fuel is supplied during several consecutive cycles in the first and second cylinders Cl, 04.

If the diagnosed exhaust gas properties comprises information about the present air- fuel ratio A —pres and the predetermined exhaust gas properties comprises information about a predetermined reference value for the air-fuel ratio Aref and if the present air-fuel ratio Apres is less than the air-fuel ratio Aref the inlet and exhaust valves 18, 19, 24, 25 are controlled to open and close in accordance with normal operation of the com- bustion engine 2.

The present invention also relates to a computer programme P (fig. 3) and a computer programme product for performing the steps of the method. The computer program P controls the internal combustion engine, wherein said computer program P comprises program code for making the electronic control unit 36 or another com- puter 46 connected to the electronic control unit 36 performing the steps of the method according to the present invention as mentioned herein, when said computer programme P is run on the electronic control unit 36 or another computer 46 connected to the electronic control unit 36.

The computer programme product comprises a program code stored on a, by an electronic control unit 36 or another computer 46 connected to the electronic control unit 36 readable, media for performing the steps of the method according to the present invention as mentioned herein, when said computer programme P is run on the electronic control unit 36 or another computer 46 connected to the electronic control unit 36. Alternatively, the computer programme product is directly storable in an internal memory M into the electronic control unit 36 or another computer 46 connected to the electronic control unit 36, comprising a computer programme P for performing the steps of the method according to the present invention, when said computer pro- 21 gramme P is run on the electronic control unit 36 or another computer 46 connected to the electronic control unit 36.

The components and features specified above may within the framework of the in-5 vention be combined between the different embodiments specified. 22

Claims

Claims 1. A method for controlling an internal combustion engine, (2) comprising, at least a first and second cylinder (Cl C4); one first piston (P1) arranged in the first cylinder (C1); one second piston (P4) arranged in the second cylinder (04); at least one first inlet valve (18) arranged in the first cylinder (Cl), the first inlet valve (18) communicates with an intake system (20); at least a first exhaust valve (24) arranged in the first cylinder (Cl), the first exhaust valve (24) communicates with an exhaust system (26); at least a second inlet valve (19) arranged in the second cylinder (C4), the second inlet valve (19) communicates with the intake system (20); at least a second exhaust valve (25) arranged in the second cylinder (C4), the second exhaust valve (25) communicates with the exhaust system (26); at least a first valve control means (22) which controls the first and second inlet valve (18, 19); at least a second valve control means (28) which controls the first and second exhaust valve (24, 25); and at least one force transfer means (16) for controlling each valve control means (22, 28), characterized in that the method comprises the following steps:

1. driving the internal combustion engine (2) at least one cycle of opening and closing of the inlet and exhaust valves (18,19,24,25) corresponding to normal operation of the combustion engine (2), 2. comparing the exhaust gas properties with a predetermined value for exhaust gas properties, 4. supplying fuel to the second cylinder (4), and 5. controlling the first inlet valve (18) and the first exhaust valve (24), so that no air is supplied to the exhaust system (26) from the first cylinder (Cl) when the first piston (P1) moves back and forth in the first cylinder (Cl), if the exhaust gas properties de- viate from the predetermined exhaust gas properties. 23

2. The method of claim 1, characterized by the additional step: c) diagnosing vibrations of the internal combustion engine (2) and comparing the vibrations with a predetermined value of vibrations of the internal combustion engine (2).

3. The method of claim 2, characterized in that in step b) and step c) are performed in any order or are performed substantially simultaneously.

4. The method according to any of claim 2 and claim 3, characterized by the additional step: f) reducing the intake air mass to the second cylinder (C4) in relation to the intake air mass to the first cylinder (Cl), if the vibrations in the internal combus- tion engine (2) are greater than the predetermined value for the vibrations in the internal combustion engine (2).

5. The method of claim 4, characterized in that in step f) the second inlet valve (19) is controlled to reduce the trapped mass of air in the second cylinder (C4).

6. The method of claim 5, characterized in that the second inlet valve (19) is controlled to close before or after the time of closing of the second inlet valve (19) during normal operation of the combustion engine (2).

7. The method according to claim 6, characterized in that the force transfer means (16) for controlling each valve control means (22, 28) comprises a crankshaft (16) and in that the second inlet valve (19) is controlled to close in the range corresponding to 0 crank angle before bottom dead centre (CA bBDC) to 0 after bottom dead centre (CA aBDC), preferably at the bottom dead centre (atBDC) .

8. The method of claim 6, characterized in that the force transfer means (16) for controlling each valve control means (22, 28) comprises a crankshaft (16) and in that the second inlet valve (19) is controlled to close in the range corresponding to 0 after bottom dead centre (CA aBDC) to 900 after bottom dead centre (CA aBDC), preferably 60° crank angles after bottom dead centre (CA aBDC). 24

9. The method according to any of the preceding claims, characterized by the additional step: g) control respective valve (18,19,24,25) by means of two first and two second valve control means (22, 28).

10. The method according to any of the preceding claims, characterized in that the valve control means (22, 28) are camshafts (22, 28).

11. The method according to any of the preceding claims, characterized in that the method comprises the further steps of: 8. supply a first volume of fuel to the first cylinder (Cl) to be combusted in total or mostly during the expansion stroke of the first cylinder (Cl), and 9. supply a second volume of fuel to the second cylinder (C4) to be combusted in total or mostly during the expansion stroke of the second cylinder (C4).

12. The method of claim 11, wherein the second volume of fuel is greater than the first volume of fuel.

13. The method according to any of the preceding claims, characterized by the addi- tional step: j) control two inlet valves (18, 19) and two exhaust valves (24, 25) by means of respective valve control means (22, 28).

14. The method of claim 13, characterized in that in step j): -control one of the first intake valves (18) to open at a bottom dead centre (BDC) of the piston (P1) in the first cylinder (Cl) between an expansion stroke and an exhaust stroke, and to close at a top dead centre (TDC) for the piston (P1) in the first cycylinder (Cl) between the exhaust stroke and an intake stroke; 1. control the other of the first intake valves (18) to open when one of the first intake valves (18) closes, and to close at the bottom dead centre (BDC) between the intake stroke and a compression stroke, and 2. control the first exhaust valve (24), so that they remain closed during all strokes of the engine (2).

15. The method of claim 13, characterized in that in step j): 1. control one of the first exhaust valves (24) to open at a bottom dead centre (BDC) of the piston (P1) in the first cylinder (Cl) between an expansion stroke and an exhaust stroke, and to close at a top dead centre (TDC) of the piston (P1) in the first cy- cylinder (Cl) between the exhaust stroke and an intake stroke; 2. control the other of the first exhaust valves (24) to open when one of the first exhaust valve (24) closes, and to close at the bottom dead centre (BDC) between the intake stroke and a compression stroke, and 3. control the first intake valves (18), so that they remain closed during all strokes of the engine (2).

16. The method according to any of the preceding claims, characterized by the additional step: k) controlling the second intake valve (19) and the second exhaust valve (25), so that no air is supplied to the exhaust system (26) from the second cylinder (C4) when the second piston (P4) moves back and forth in the second cylinder (04), if the exhaust gas properties deviate from the predetermined exhaust gas properties.

17. The method of claim 16, characterized in steps e) and k) fuel is supplied during several consecutive cycles in the first and second cylinders (Cl, C4).

18. The method of claim 17, characterized in that the inlet and exhaust valves (18, 19, 24, 25) are controlled to open and close in accordance to normal operation of the combustion engine (2) if the diagnosed exhaust gas properties comprises information about the present air-fuel ratio (A ) and the predetermined exhaust gas properties v -pres, comprises information about a predetermined reference value for the air-fuel ratio (Aref) and if the present air-fuel ratio (Apres, S 1 i less than the air-fuel ratio (Aref). v -

19. The method according to any of claims 1-8, characterized in that in step e) the first inlet valve (18) is controlled to open during the exhaust stroke and the intake stroke, while the first exhaust valve (24) is controlled to a closed position during all strokes. 26

20. The method according to any of claims 1-8, characterized in that in step e), the first exhaust valve (24) is controlled to open during the exhaust stroke and the intake stroke, while the first inlet valve (18) is controlled to a closed position for all strokes.

21. An internal combustion engine (2) characterized in that the engine (2) is con- trolled according to the method of claims 1 - 20.

22. A vehicle (1), characterized in that the vehicle (1) comprises an internal combustion engine (2) according to claim 21.

23. A computer program (P) for controlling an internal combustion engine (2), wherein said computer program (P) comprises program code for making an electronic control unit (36) or another computer (46) connected to the electronic control unit (36) performing the steps according to any of the claims 1 —20.

24. A computer program product comprising a program code stored on a media readable by a computer (36, 46) to perform the steps of the method according to any of the claims 1 — 20, when said program code runs on an electronic control unit (36) or another computer (46) connected to the electronic control unit (36). 1/7 2/7 Li +