Patent Description:
The inventive internal combustion engine comprises a set of combustion chambers, each combustion chamber being provided with a controllable intake valve configured for opening and closing an intake port, a controllable exhaust valve configured for opening and closing an exhaust port, a piston displaceable back and forth in said combustion chamber between a top dead center (TDC) and a bottom dead center (BDC), and a fuel injector. The internal combustion engine further comprises an intake manifold connected to the intake port of each combustion chamber of said set of combustion chambers.

The invention also relates to a method of operating such an internal combustion engine.

In internal combustion engines operated in four-stroke cycles, a mixture of air and fuel is provided into a combustion chamber, i.e. cylinder, during an intake stroke. The air-fuel mixture is compressed during a compression stroke, and in connection with the end of the compression stroke the air-fuel mixture is ignited, either by a spark plug or spontaneously due to the compression. The heat and energy released by the burning of the air-fuel mixture causes a further rise in pressure in the combustion chamber which is used to do work against a movable wall of the combustion chamber, i.e. the piston, which work is converted into rotational movement of a crank shaft attached to the piston via a piston rod, during a power stroke. The exhaust gas formed from the burning of the air-fuel mixture is then evacuated from the combustion chamber, during an exhaust stroke, and thereafter a new cycle begins. The cycles of the different combustion chambers of the internal combustion engine are offset in relation to each other.

With rising concerns of the environment and pollution caused by the exhaust gas from internal combustion engines there is a need to lower harmful emissions from internal combustion engines while at the same time maintaining or increasing the efficiency of conversion of the chemical energy in the fuel to kinetic energy of the crankshaft, thereto it is a need to decrease fuel consumption.

In connection with cold starts of an internal combustion engine, i.e. when the catalytic converter of the exhaust discharge arrangement is not warmed up and has not yet reached its working temperature, the catalytic converter cannot fully convert the toxic emissions into less toxic substances. A normal time for igniting a catalytic converter is about <NUM> minutes, and most of the total pollution from the internal combustion engine is emitted during the warm-up period.

One known way to reduce the warm-up period is to use electric heating coils in the catalytic converter or use a smaller catalytic converter arranged upstream the main catalytic converter.

Both these systems requests expensive auxiliary equipment. An example of an engine with an warm-up system is given in <CIT>.

The present invention aims at obviating the disadvantages and failings of previously known internal combustion engines and at providing an improved internal combustion engine. A primary object of the present invention is to provide an improved internal combustion engine of the initially defined type generating less toxic emission during cold starts.

It is another object of the present invention is to provide an improved internal combustion engine having a decreased warm-up period of the catalytic converter.

It is another object of the present invention to provide an improved internal combustion engine having decreased heat losses.

It is yet another object of the invention is to provide an improved internal combustion engine having a more stable ignition from cycle to cycle.

It is another object of the present invention to provide an improved internal combustion engine having internal recirculation of exhaust gas, in order to reduce the amount of unburnt fuel reaching the catalytic converter.

According to the invention at least the primary object is attained by means of the initially defined internal combustion engine and method having the features defined in the independent claims. Preferred embodiments of the present invention are further defined in the dependent claims.

The present invention is a strategy for controlling the operation of an internal combustion engine during a catalytic converter warm-up mode in order to minimize fuel consumption and minimize emissions, during the warm-up period of the catalytic converter.

According to a first aspect of the present invention, there is provided an internal combustion engine of the initially defined type, the internal combustion engine being configured to be operated in a catalytic converter warm-up mode, wherein each combustion chamber is configured to be driven in four-stroke operation comprising a <NUM> crank angle degrees cycle, wherein the internal combustion engine is configured to perform the following activities: open the intake port, the intake port starting to open in the range <NUM> to <NUM> CAD, and close the intake port, the intake port becomes fully closed in the range <NUM> to <NUM> CAD, open the exhaust port during the power stroke, the exhaust port starting to open in the range <NUM> to <NUM> CAD, open the intake port during the exhaust stroke, the intake port starting to open in the range <NUM> to <NUM> CAD, and close the exhaust port during the exhaust stroke, the exhaust port becomees fully closed in the range <NUM> to <NUM> CAD, wherein the exhaust gas is forced into the intake manifold by means of the piston, mix fuel and exhaust gas in the intake manifold, and close the intake port, the intake port becomes fully closed in the range <NUM> to <NUM>+<NUM> CAD.

According to a second aspect of the present invention, there is provided a method for controlling such an internal combustion engine.

Thus, the present invention is based on the insight that by minimizing the mechanical efficiency of the internal combustion engine and maximizing the thermal efficiency of the internal combustion engine, i.e. by having less combustion energy to be converted into kinetic energy and the exhaust gas is expelled from the combustion chamber at a higher temperature, and having internal exhaust gas recirculation, the raw emissions during cold start are reduced and the warm-up period of the catalytic converter is reduced.

According to a preferred embodiment of the present invention, the step of starting to open the intake port during the intake stroke takes place in the range <NUM> to <NUM> CAD, even more preferred within the range <NUM> to <NUM> CAD. The longer the intake port is closed during the intake stroke the greater under pressure in the combustion chamber before the intake port is opened, and thereby the engine needs to generate more work and thereby more and warmer exhausted gases are generated.

According to a preferred embodiment of the present invention, during the exhaust stroke, the intake port starts to open in the range <NUM> to <NUM> CAD and the exhaust port becomes fully closed in the range <NUM> to <NUM> CAD. According to a preferred embodiment of the present invention, the method comprises the activity of injecting fuel into the intake manifold, fuel injection taking place in the range that start when the intake port becomes fully closed during the compression stroke, and that stop when the intake port becomes fully closed in connection with the end of the cycle. Preferably, the fuel injection takes place in the range that start when the exhaust port becomes fully closed during the exhaust stroke, and that stop when the intake port becomes fully closed in connection with the end of the cycle. Thereby, the risk of having fuel escaping through the exhaust port is completely eliminated.

According to a preferred embodiment of the present invention, at least two combustion chambers of the set of combustion chambers are activated and at least one combustion chamber of the set of combustion chambers is deactivated when the internal combustion engine is operated in said catalytic converter warm-up mode. Thereby, more exhaust gas having higher temperature is generated in comparison of having all combustion chambers activated.

Further advantages with and features of the invention will be apparent from the other dependent claims as well as from the following detailed description of preferred embodiments.

A more complete understanding of the abovementioned and other features and advantages of the present invention will be apparent from the following detailed description of preferred embodiments in conjunction with the appended drawing, wherein:.

The present invention relates generally to the field of internal combustion engines suitable for powering a vehicle or a machine. The inventive internal combustion engine, generally designated <NUM>, comprises a set of combustion chambers. The set/plurality of combustion chambers comprises at least two separate combustion chambers <NUM>, also known as cylinders. However, the internal combustion engine <NUM> may comprise more combustion chambers, such as <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM> or <NUM>. Each combustion chamber <NUM> is preferably cylindrical.

The internal combustion engine <NUM> is a four-stroke engine, i.e. configured to be driven in four-stroke operation comprising a <NUM> crank angle degrees (CAD) cycle. The four strokes are "intake" during which air/gas and fuel are delivered into the combustion chamber <NUM>, "compression" during which the air-fuel mixture in the combustion chamber <NUM> is compressed, "power/combustion" during which the air-fuel mixture is ignited and combusted, and "exhaust" during which the exhaust gas formed by the combustion of the air-fuel mixture is evacuated, also known as scavenged, from the combustion chamber <NUM>. Preferably the internal combustion engine <NUM> is constituted by a spark-ignition engine, i.e. in which the air-fuel mixture is ignited by a spark from a sparkplug, but may also be constituted by a spontaneous/compression-ignition engine. The internal combustion engine <NUM> is preferably configured to be driven by petrol/gasoline, but may alternatively be configured to be driven by diesel, gas, ethanol, etc. and/or a mixture of said fuels.

Reference is made to <FIG> disclosing a schematic side view of a first embodiment of the inventive internal combustion engine <NUM>, and to <FIG> disclosing a schematic illustration of an internal combustion engine and an exhaust discharge arrangement.

The internal combustion engine <NUM> comprises an engine block <NUM> provided with said set of combustion chambers or cylinders <NUM>. Each combustion chamber <NUM> is defined radially by a stationary cylinder wall, and is defined axially by a stationary cylinder head <NUM> and a displaceable piston <NUM>, respectively. The cylinder head <NUM> may be releasably connected to the engine block <NUM> or may be integral with the engine block <NUM>. The piston <NUM> is configured displaceable back and forth in the axial direction within the combustion chamber <NUM> between a top dead center (TDC) and a bottom dead center (BDC), and is connected to a revolving crankshaft via a piston rod <NUM>, wherein the linear movement of the piston <NUM> is converted into rotational movement of the crankshaft. Thus, the volume of the combustion chamber <NUM> changes cyclically as the piston <NUM> moves up and down in the cylinder.

Each combustion chamber <NUM> is provided with at least one controllable intake valve <NUM> configured for opening and closing an intake port <NUM>, at least one controllable exhaust valve <NUM> configured for opening and closing an exhaust port <NUM>. Preferably, each combustion chamber <NUM> comprises two intake ports and two exhaust ports, each port having a controllable valve that preferably are independently controlled. It shall be pointed out that two intake valves and/or the two exhaust valves, respectively, may be operated jointly. Thus, herein the invention is illustrated using one intake valve <NUM> and one exhaust valve <NUM>, and it shall be realized that in applications having two intake valves and/or exhaust valves these valves can be kept closed or operated jointly with the disclosed valves.

Thereto, in the disclosed embodiment the combustion chamber <NUM> is provided with a spark plug <NUM>. It shall be realized that the intake port <NUM>, the exhaust port <NUM> and the spark plug <NUM> are arranged in the cylinder head <NUM>.

The intake valve <NUM> and the exhaust valve <NUM> are preferably of poppet valve type each having a valve stem and a valve disk attached to the lower end of the valve stem. In the closed position the valve disk abuts the material surrounding the corresponding port to prevent passage of fluid through the port, whereas in the open position the valve disc is displaced vertically down into the combustion chamber <NUM> in order to uncover the port and allow fluid to pass through the port and around the edge of the valve disk. The maximum displacement of the valves is preferably in the range <NUM>-<NUM> millimeters.

Each of the intake valve <NUM> and the exhaust valve <NUM> is preferably operated by means of a corresponding valve actuator. Thus, in the context of the present invention a valve actuator allows the corresponding valve to be freely operated without the operation of the valve being slaved to the operation of the internal combustion engine <NUM>, in particular the angular position of the crankshaft of the internal combustion engine, via a camshaft. A controllable valve operated by means of an actuator is for example described in the patent literature documents <CIT>, <CIT> and <CIT>. A controllable valve can be opened and closed at any time and the degree of lift of the valve is not fixed. Thus, the inventive internal combustion engine <NUM> comprises no camshaft, and is thus camshaft-free. The inventive internal combustion engine <NUM> is preferably also throttle-free. Preferably, the actuator uses both pneumatic and hydraulic for its operation.

The internal combustion engine <NUM> comprises an intake manifold <NUM> for providing air/gas to the combustion chamber <NUM> from an air intake, and an exhaust manifold <NUM> for evacuating exhaust gas from the combustion chamber <NUM> to an exhaust outlet via an exhaust discharge arrangement. Usually at least one muffler (not shown) and/or at least one catalytic converter <NUM> are arranged adjacent the exhaust outlet, for decreasing the noise of operating of the internal combustion engine and/or for treating the exhaust gas, before the exhaust gas is eventually led off to the atmosphere. Thereto, the exhaust discharge arrangement may comprise a pressure booster <NUM>, constituted by a turbocharger, i.e. a pressure booster driven by exhaust gas.

Air/gas for combustion is supplied to the combustion chamber <NUM> from the intake manifold <NUM> via the intake port <NUM> of each combustion chamber <NUM> of said set of combustion chambers. Each combustion chamber <NUM> is provided with an individual intake pipe/runner that is part of the intake manifold <NUM>. The exhaust manifold <NUM> is connected to the exhaust port <NUM> of each combustion chamber <NUM> of said set of combustion chambers. Each combustion chamber <NUM> is provided with an individual exhaust pipe/runner that is part of the exhaust manifold <NUM>.

The internal combustion engine <NUM> further comprises an electronic control unit (ECU), wherein the ECU is configured to at least control the opening and closing of the intake valve <NUM> and the exhaust valve <NUM>, using the corresponding actuators. The internal combustion engine <NUM> also comprises a sensor for monitoring the rotation of the crankshaft, wherein said sensor is operatively connected to said ECU.

In the disclosed embodiment, a fuel injector <NUM> is provided in the intake runner/pipe (intake manifold <NUM>) for injecting fuel into the intake manifold <NUM> towards the intake port <NUM>. In an alternative embodiment the inventive internal combustion engine is provided with direct injection of the fuel into the combustion chambers <NUM>.

As is known to a person skilled in the art a four-stroke internal combustion engine conventionally proceeds through four strokes in one cycle, namely (<NUM>) Intake <NUM> to <NUM> CAD - this stroke beginning with the piston <NUM> at its highest position, i.e. top dead center closest to the cylinder head <NUM>, and comprising displacement of the piston <NUM> downwards while a mixture of gas and fuel is introduced into the combustion chamber <NUM>, (<NUM>) Compression <NUM> to <NUM> CAD - this stroke beginning with the piston <NUM> at its lowest position, i.e. bottom dead center, and comprising closing the intake valve <NUM> and moving the piston <NUM> upwards towards the cylinder head <NUM> while compressing the gas-fuel mixture, (<NUM>) Power <NUM> to <NUM> CAD - igniting the gas-fuel mixture wherein the resulting pressure caused by the combustion of the fuel will displace the piston <NUM> downwards and away from the cylinder head <NUM>, and (<NUM>) Exhaust <NUM> to <NUM> CAD - opening the exhaust valve <NUM> for allowing the exhaust gas formed by the combustion of the gas-fuel mixture to evacuate from the combustion chamber <NUM> while the piston <NUM> once more is displaced towards the top dead center. The ignition of the gas-fuel mixture takes place in connection with the piston <NUM> being located at the upper dead center between the compression stroke and the power stroke.

The inventive internal combustion engine <NUM> is configured to be operated in at least a catalytic converter warm-up mode, i.e. a cold start mode. According to the inventive method the internal combustion engine <NUM> is operated in the catalytic converter warm-up mode. The output torque [Nm] of the internal combustion engine <NUM> is dependent on engine speed [rpm], and the output torque of the internal combustion engine is in this context equivalent with driver/operator requested output torque via an accelerator pedal. During the catalytic converter warm-up mode, the driver/operator usually requests low or moderate output torque via the accelerator pedal.

The ECU is configured to adjust the filling rate of the combustion chambers <NUM> in view of the engine speed and the requested output torque, i.e. the amount of air/gas going into a combustion chamber <NUM> in relation to the volume of the combustion chamber. The ECU is also configured for varying the amount of fuel injected into each combustion chamber to provide a suitable relationship, or lambda value, between oxygen and fuel.

The internal combustion engine <NUM> is configured to shift from catalytic converter warm-up mode to normal mode (i.e. Low/Part Load mode, High Load mode, Sport mode, Economy mode, etc.) when the catalytic converter <NUM> has reached its working temperature, i.e. when the catalytic converter <NUM> is ignited. Different sensors upstream and downstream the catalytic converter <NUM> are used in a conventional way to determine when the catalytic converter <NUM> is treated as ignited.

The inventive internal combustion engine <NUM> is configured to perform the inventive method comprising several essential activities/steps. It shall be pointed out that the mutual order of the activities listed in the claims is not entirely delimiting for the invention. The essential activities/steps of the invention are constituted by:.

It shall be realized that in addition to the essential activities/steps mentioned above, the operation of the internal combustion engine also comprises suitable/conventional activities/steps, i.e. compression stroke and beginning of power stroke.

Thus, according to the invention the exhaust port <NUM> becomes fully closed and the intake port <NUM> starts to open before the piston <NUM> reaches top dead center during the exhaust stroke. Irrespective of the fuel is added/injected into the intake manifold <NUM> or into the combustion chamber <NUM>, the substantial mixing of the fuel and gas takes place in the intake manifold <NUM>. During the mixing of the exhaust gas and fuel in the intake manifold, the fuel is evaporated and the exhaust gas is cooled down. Preferably substantially all fuel is injected when the exhaust port <NUM> is closed, the intake port <NUM> is open and exhaust gas is pressed into the intake manifold <NUM> by means of the piston <NUM>. Preferably the fuel injection takes place within <NUM> CAD, preferably within <NUM> CAD. Best mixing of the exhaust gas and fuel is achieved if the fuel is injected directly into the flow of exhaust gas that is pressed into the intake manifold <NUM>.

According to the disclosed embodiment the fuel is added/injected into the intake manifold <NUM> by means of the fuel injector <NUM>, and the fuel injection preferably takes place in the range that start when the intake port <NUM> becomes fully closed during the compression stroke, and that stop when the intake port <NUM> becomes fully closed in connection with the end of the cycle. Thus, the fuel can be added/injected after the intake valve <NUM> has become closed after the intake stroke of the present cycle, either when the intake valve <NUM> is still closed and/or when the intake port <NUM> is opened during the exhaust stroke. According to the alternative embodiment the fuel is injected into the combustion chamber <NUM> by means of the fuel injector <NUM> when the intake valve <NUM> is open, the exhaust valve <NUM> is closed and all the exhaust gas is forced/pressed into the intake manifold <NUM>.

In one embodiment the fuel injection takes place in the range that start when the exhaust port <NUM> becomes fully closed during the exhaust stroke, and that stop when the intake port <NUM> becomes fully closed in connection with the end of the cycle. Preferably the fuel injection starts in the range <NUM> to <NUM> CAD. Thus, it is preferred to inject the fuel when the intake valve <NUM> is open during the exhaust stroke and the exhaust gas flow into the intake manifold <NUM>. According to another embodiment the fuel injection takes place in the range that start at <NUM> and that stop when the intake port <NUM> starts to open during the exhaust stroke, i.e. all fuel is injected when the intake valve <NUM> is closed such that all fuel is ready to mix with (be added to) the exhaust gas when the intake valve <NUM> is opened and the exhaust gas is pressed into the intake manifold <NUM> by means of the piston <NUM>.

During the power stroke, the exhaust port <NUM> shall start to open as soon as possible after ignition/combustion of the gas-fuel-mixture in order to evacuate as warm exhaust gases as possible via the exhaust manifold <NUM> to the catalytic converter <NUM>. However, enough chemical energy of the fuel has to be converted to kinetic energy to be able to turn the crankshaft of the internal combustion engine <NUM>, before the exhaust port <NUM> starts to open during the power stroke. The internal combustion engine <NUM> has a predetermined cold start rpm, usually in the range <NUM>-<NUM> rpm and for instance <NUM> rpm. Upon start of the internal combustion engine <NUM>, the exhaust port <NUM> is preferably default to open at a predetermined CAD, for instance <NUM> CAD. Thereafter the ECU determine the actual rpm and if there is a difference between the actual rpm and the predetermined cold start rpm, the moment the exhaust port <NUM> starts to open is revised. When the actual rpm is too low the exhaust port <NUM> is kept closed a longer period, and when the actual rpm is too high the exhaust port <NUM> is kept closed a shorter period. The moment the exhaust port <NUM> starts to open is preferably altered in steps of <NUM> CAD. Preferably, this procedure takes place during the entire cold start period. Preferably the exhaust port <NUM> starts to open in the range <NUM> to <NUM> CAD, most preferably in the range <NUM> to <NUM> CAD.

According to a preferred embodiment the moment the exhaust port <NUM> becomes fully closed and the moment the intake port <NUM> starts to open, takes place within <NUM> CAD, preferably within <NUM> CAD. Thus, the valve overlap period shall be as short as possible, but long enough for the exhaust gas to be continuously evacuated from the combustion chamber also during the shift from open exhaust valve <NUM> to open intake valve <NUM>. Preferably the exhaust port <NUM> becomes fully closed in the range <NUM> to <NUM> CAD, and preferably the intake port <NUM> starts to open in the range <NUM> to <NUM> CAD. Preferably the intake valve <NUM> starts to open before the exhaust valve <NUM> is fully closed. Alternatively, it is preferred that the intake port <NUM> starts to open in the range <NUM> to <NUM> CAD, and that the exhaust port <NUM> becomes fully closed in the range <NUM> to <NUM> CAD. It is most preferred that the intake port <NUM> starts to open in the range <NUM> to <NUM> CAD. It is most preferred that the exhaust port <NUM> becomes fully closed in the range <NUM> to <NUM>. In order to prevent knocking at the same time as enough internal EGR is achieved during warm-up.

It shall be pointed out that according to a preferred embodiment the volume of the individual intake runner should be big enough to ensure that the exhaust gas pressed into the intake manifold <NUM> by means of the piston <NUM> does not slip over into an intake runner of a neighboring combustion chamber <NUM>. Thus, the mixing of the fuel and exhaust gas takes place in the individual intake runner and is sucked into the same combustion chamber during the intake stroke of the following cycle.

In some applications the intake valve <NUM> can be open or fully open when the piston <NUM> reaches top dead center, especially gasoline engines, and in some applications the intake valve <NUM> has to be closed when the piston <NUM> reaches top dead center in order not to become damaged by the piston <NUM>, especially diesel engines. In the first type applications the intake valve <NUM> may be kept open past <NUM> CAD, at most until <NUM>+<NUM> CAD and preferably at most until <NUM>+<NUM> CAD. According the second type application the intake valve <NUM> has to be fully closed at <NUM> CAD, and it shall be pointed out that this may also be applied to the first type application. According to the inventive method the intake port <NUM> is kept closed until at least <NUM> CAD, preferably until at least <NUM> CAD and most preferably until at least <NUM> CAD, in order to create under pressure in the combustion chamber <NUM>, in order for the other combustion chambers to create more work and thereby more and warmer exhaust gas are generated. Thereto, due to the high speed of the gas-fuel mixture when the intake port <NUM> is open, the combustion chamber <NUM> is overfilled and thereby more and warmer exhaust gas are generated. Since the exhaust gas and fuel is mixed in the intake manifold, a better and more efficient combustion is obtained generating less emission, and a more stable combustion from cycle to cycle resulting in decreased fuel consumption. Preferably the intake port <NUM> becomes fully closed in the range <NUM> to <NUM> CAD, most preferably in the range <NUM> to <NUM> CAD. The earlier the intake port <NUM> is closed during the compression stroke the higher over pressure is generated, i.e. the engine needs to perform more work.

Preferably not all combustion chambers of the set of combustion chambers of the internal combustion engine <NUM> are active during the catalytic converter warm-up mode. By having some combustion chambers <NUM> deactivated, the activated combustion chambers <NUM> need to perform more work and thereby produces more and warmer exhaust gas. Preferably, at least two combustion chambers <NUM> of the set of combustion chambers are activated and at least one combustion chamber <NUM> of the set of combustion chambers is deactivated when the internal combustion engine <NUM> is operated in said catalytic converter warm-up mode. When a combustion chamber is deactivated it is provided with any fuel. In one embodiment the intake port and the exhaust port of the deactivated combustion chamber are closed the entire cycle.

According to another embodiment the intake port of the deactivated combustion chamber may be operated to be closed during the intake stroke to create under pressure, open shortly in connection with <NUM> CAD, closed during the compression stroke to create over pressure, open shortly in connection with <NUM> CAD, closed during the power stroke to create under pressure, open shortly in connection with <NUM> CAD, closed during the exhaust stroke to create over pressure, open shortly in connection with <NUM> CAD. Thereby the activated combustion chambers has to perform more work and thereby produces more and warmer exhaust gas.

In the disclosed embodiment the internal combustion engine <NUM> comprises a pressure booster <NUM> constituted by a turbocharger, and it is preferred that the exhaust gas evacuated from the combustion chamber <NUM> via the exhaust port <NUM> bypass the pressure booster <NUM>, via a bypass <NUM>.

The ECU or similar computer readable medium having stored thereon a computer program product comprises instructions to cause the inventive internal combustion engine <NUM> to execute the steps of the inventive method.

The invention is not limited only to the embodiments described above and shown in the drawings, which primarily have an illustrative and exemplifying purpose. This patent application is intended to cover all adjustments and variants of the preferred embodiments described herein, thus the present invention is defined by the wording of the appended claims and thus, the equipment may be modified in all kinds of ways within the scope of the appended claims.

It shall be pointed out that controlling the opening is also to be understood as controlling the closing. Controlling the opening is further to be understood as controlling any of the valve lift, the duration of opening, and when in the operation/cycle of the internal combustion engine the valve is opened.

Claim 1:
An internal combustion engine (<NUM>) comprising a set of combustion chambers (<NUM>), each combustion chamber (<NUM>) being provided with:
- a controllable intake valve (<NUM>) configured for opening and closing an intake port (<NUM>),
- a controllable exhaust valve (<NUM>) configured for opening and closing an exhaust port (<NUM>),
- a piston (<NUM>) displaceable back and forth in said combustion chamber (<NUM>) between a top dead center (TDC) and a bottom dead center (BDC), and
- a fuel injector (<NUM>),
the internal combustion engine (<NUM>) further comprising an intake manifold (<NUM>) connected to the intake port (<NUM>) of each combustion chamber of said set of combustion chambers (<NUM>),
and where the internal combustion engine (<NUM>) is configured to be operated in a catalytic converter warm-up mode, wherein each combustion chamber (<NUM>) is configured to be driven in four-stroke operation comprising a <NUM> crank angle degrees cycle, wherein the internal combustion engine (<NUM>) is configured to perform the following activities:
- open the intake port (<NUM>), the intake port (<NUM>) starting to open in the range <NUM> to <NUM> CAD, and close the intake port (<NUM>), the intake port (<NUM>) becomes fully closed in the range <NUM> to <NUM> CAD,
- open the exhaust port (<NUM>) (<NUM>) during the power stroke, the exhaust port (<NUM>) starting to open in the range <NUM> to <NUM> CAD,
- open the intake port (<NUM>) during the exhaust stroke, the intake port (<NUM>) starting to open in the range <NUM> to <NUM> CAD, and close the exhaust port (<NUM>) during the exhaust stroke, the exhaust port (<NUM>) becomes fully closed in the range <NUM> to <NUM> CAD, wherein the exhaust gas is forced into the intake manifold (<NUM>) by means of the piston (<NUM>),
- mix fuel and exhaust gas in the intake manifold (<NUM>), and
- close the intake port (<NUM>), the intake port (<NUM>) becomes fully closed in the range <NUM> to <NUM>+<NUM> CAD.