FOUR-STROKE INTERNAL COMBUSTION ENGINE AND ASSOCIATED VEHICLE AND METHOD

Abstract

Four-stroke internal combustion engine (1), comprising - at least one cylinder (10); - a piston (12) arranged in each cylinder (10); - an inlet system (14); - a crankshaft (16); - at least one intake valve (18) arranged in each cylinder (10), the intake valve (18) being connected to the intake system (14); - an intake valve control arrangement (22) configured to control each intake valve (18) based on a rotational position of the crankshaft (16); - at least one exhaust valve (24) arranged in each cylinder (10), the exhaust valve (24) being connected to an exhaust outlet (26) of the engine (1); - an exhaust valve control arrangement (28) configured to control each exhaust valve (24) based on the rotational position of the crankshaft (16), wherein the exhaust valve control arrangement (28) comprises a device (30) for phase-shifting an exhaust valve, which is configured to phase-shift the control of the at least one exhaust valve (24) into a state in which the at least one exhaust valve (24) is controlled to be opened during the expansion stroke of the engine (1) and closed during the exhaust stroke of the engine (1) in order to achieve engine braking by compression in the cylinders (10) during the exhaust stroke, wherein the intake valve control arrangement (22) is configured to control the at least one intake valve (18) to be open during at least a portion of the expansion stroke of the engine (1), wherein the engine (1) comprises a turbocharger (36) arranged to compress air for the intake system (14) of the engine (1), wherein the engine (1) further comprises a control unit (38) connected to the turbocharger (36), wherein the control unit (38) is configured to regulate the amount of air pumped by the engine (1) during engine braking by regulating the charge air pressure of the turbocharger (36), and wherein the intake valve control arrangement (22) comprises an intake valve phase shifting device (32) configured to phase shift the control of the at least one intake valve (18), wherein the intake valve phase shifting device (32) is configured to regulate the amount of air pumped by the engine (1) during engine braking by regulating the phase shift of the at least one intake valve (18), wherein at least the intake valve phase shifting device (32) is configured to regulate the amount of air as a function of a temperature of a catalyst arranged in fluid communication with the exhaust outlet (26) such that the temperature is maintained above a temperature threshold.

Description

TECHNICAL FIELD

[0001] The present invention relates to a four-stroke internal combustion engine, a vehicle comprising a four-stroke internal combustion engine, a method for controlling a four-stroke internal combustion engine, a computer program for carrying out a method for controlling a four-stroke internal combustion engine and a computer program product for carrying out a method for controlling a four-stroke internal combustion engine. BACKGROUND

[0002] Internal combustion engines, such as four-stroke internal combustion engines, include one or more cylinders and a piston disposed within each cylinder. The pistons are connected to a crankshaft of the engine and are arranged to reciprocate within the cylinders with one revolution of the crankshaft. The engine further typically includes one or more intake valves and exhaust valves, and one or more fuel supply assemblies. The one or more intake valves and exhaust valves are controlled by a respective valve timing assembly, which typically includes one or more camshafts rotatably connected to a crankshaft of the engine via a belt, chain, gears, or the like. A four-stroke internal combustion engine completes four separate strokes while rotating a crankshaft. A stroke refers to the total stroke of the piston along the cylinder in both directions.The top position of the piston in the cylinder is commonly referred to as top dead center (TDC), and the bottom position of the piston in the cylinder is commonly referred to as bottom dead center (BDC).

[0003] The strokes are completed in the following order: intake stroke, compression stroke, expansion stroke, and exhaust stroke. During operation of a conventional four-stroke internal combustion engine, the intake valve control assembly controls a cylinder's intake valves to an open state during the intake stroke of a piston inside the cylinder to allow air or a mixture of air and fuel to enter the cylinder. During the compression stroke, all valves must be closed to allow compression of the air or mixture of air and fuel in the cylinder. If the engine is in a power-generating state, the fuel in the cylinder is usually ignited towards the end of the compression stroke, for example, by a spark plug or by the heat of compression in the cylinder. The combustion of fuel inside the cylinder significantly increases the pressure and temperature in the cylinder.Combustion of the fuel usually continues for a significant portion of the subsequent expansion stroke. The increased pressure and temperature in the cylinder achieved by combustion are partially converted into mechanical work, which is supplied to the crankshaft during the expansion stroke. Obviously, all valves must remain closed during the expansion stroke so that the increased pressure and temperature can be converted into mechanical work. The expansion stroke is also commonly referred to as the combustion stroke because the majority of combustion usually takes place during the expansion stroke. In the subsequent exhaust stroke, the exhaust valve control arrangement controls the cylinder's exhaust valves to an open state to allow exhaust gases to be expelled from the cylinder into an exhaust system.

[0004] During normal engine braking, which occurs, for example, when a vehicle driver releases the accelerator pedal, the engine continues to operate in the strokes described above, except that normally no fuel is supplied to the engine during engine braking, and consequently no combustion occurs towards the end of the compression stroke or during the expansion stroke. In this condition, the engine provides some braking torque due to internal friction and due to the pumping of air from the intake to the exhaust in the respective intake stroke and exhaust stroke. As the piston moves upward during its compression stroke, the gases trapped in the cylinder are compressed. The compressed gases resist the upward movement of the piston. However, almost all of the energy stored in the compressed gases is returned to the crankshaft in the subsequent expansion stroke.As a result, during normal engine braking, the compression stroke together with the subsequent expansion stroke does not contribute to a significant braking torque of the engine.

[0005] A compression release brake, often referred to as a Jake brake or Jacobs brake, is an engine braking mechanism used on certain engines. When activated, it opens the exhaust valves in the cylinders after the compression stroke, releasing the compressed air trapped in the cylinder to the exhaust system. This prevents the energy stored in the compressed gases during the compression stroke from being returned to the crankshaft during the subsequent expansion stroke, increasing the engine's braking torque.

[0006] In some arrangements, the exhaust valves can be deactivated so that they remain closed during the exhaust stroke. Usually, this is achieved using a so-called lost motion arrangement, which, when actuated, is arranged so as not to transmit movement caused by an exhaust cam lobe to the exhaust valve. The air in the cylinders is therefore also compressed during the exhaust stroke. By using a mechanism that opens the exhaust valves towards the end of the exhaust stroke, the compressed air trapped in the cylinders is released to the exhaust system. Such an arrangement almost doubles the braking torque, as compression and release events occur on both the compression and exhaust strokes. Due to environmental considerations, almost all vehicles for sale today include some kind of exhaust aftertreatment system.Examples include catalytic converters, particulate filters, and selective catalytic reduction (SCR) systems. A selective catalytic reduction system is a means of converting nitrogen oxides, also known as NOx, into diatomic nitrogen (N2) and water (H2O) using a catalyst. A gaseous reductant, typically anhydrous ammonia, aqueous ammonia solution, or urea, is added to a stream of exhaust gas and is adsorbed on a catalyst. Carbon dioxide, CO2, is a reaction product when urea is used as a reductant. The operation of these exhaust aftertreatment systems relies on the temperature of the gases passing through the exhaust aftertreatment systems.

[0007] Document WO 2015 / 084 243 A2 relates to a four-stroke internal combustion engine which, instead of deactivating the exhaust valves during the exhaust stroke, performs a phase shift of a camshaft arranged to control the opening of exhaust valves relative to the crankshaft to a state in which the at least one exhaust valve is controlled to be open during the engine's expansion stroke and closed during the engine's exhaust stroke, in order to achieve engine braking by compression in the cylinders during the exhaust stroke. This solution offers several advantages over the conventional engine braking mechanisms used, such as the controllability of the magnitude of the braking torque. However, given the solution proposed in the proposed solution document WO 2015 / 084 243 A2, there is a possibility of improving the achieved braking torque, particularly under certain engine operating conditions.

[0008] DE 696 05 804 T2 discloses a four-stroke engine configured to perform two-stroke decompression engine braking. During engine braking, the exhaust valve is only open in a transitional region between the compression stroke and the expansion stroke, as well as between the exhaust stroke and the intake stroke.

[0009] US 7 565 896 B1 also discloses a two-stroke engine braking operation.

[0010] US 2012 / 0 024 260 A1 discloses a valve actuation system for engine braking operation and drive operation of an engine, wherein the engine may include a variable geometry turbocharger to modify the extent of engine braking.

[0011] DE 10 2013 019 183 A1, AT 510 527 A1 and US 6 000 374 A disclose further solutions for controlling the engine braking effect of a valve-controlled internal combustion engine.

[0012] In view of the above, there is a need for improved engine braking of a four-stroke internal combustion engine. SUMMARY

[0013] An object of the present invention is to provide engine braking in an improved manner.

[0014] The object of the invention is achieved by a four-stroke internal combustion engine according to claim 1. Furthermore, the object of the invention is achieved by a vehicle according to claim 8. Furthermore, the object of the invention is achieved by a method according to claim 9. Furthermore, the object of the invention is achieved by a computer program according to claim 11 and a computer program product according to claim 12. Advantageous developments of the invention are described in the appended claims.

[0015] According to a first aspect of the invention, the object is achieved by a four-stroke internal combustion engine comprising at least one cylinder, a piston arranged in each cylinder, an intake system, a crankshaft, and at least one intake valve arranged in each cylinder, the intake valve being connected to the intake system. The engine further comprises an intake valve control arrangement configured to control each intake valve based on a rotational position of the crankshaft, and at least one exhaust valve arranged in each cylinder, the exhaust valve being connected to an exhaust outlet of the engine. The engine further comprises an exhaust valve control arrangement configured to control each exhaust valve based on the rotational position of the crankshaft.The exhaust valve control arrangement comprises an exhaust valve phase-shifting device configured to phase-shift the control of the at least one exhaust valve to a state in which the at least one exhaust valve is controlled to be open during the engine's expansion stroke and closed during the engine's exhaust stroke to achieve engine braking by compression in the cylinders during the exhaust stroke. The intake valve control arrangement is configured to control the at least one intake valve to be open during at least a portion of the engine's expansion stroke during engine braking by compression in the cylinders.

[0016] Since the control of the at least one exhaust valve is phase-shifted to a state in which the at least one exhaust valve is controlled to be open during the engine's expansion stroke and closed during the engine's exhaust stroke, engine braking by compression in the cylinders during the exhaust stroke is achieved simply and effectively. Furthermore, since the intake valve control arrangement is configured to control the at least one intake valve to be open during at least part of the engine's expansion stroke, the cylinder also fills with air from the intake system during the expansion stroke. This increases the braking torque because the mass flow through the engine increases during engine braking.

[0017] Furthermore, as the mass flow through the engine increases during engine braking, the temperature of gases leaving the engine decreases, especially at high engine speeds. This allows high braking torque to be achieved without damaging components such as an injector tip, turbine inlet, and / or exhaust aftertreatment system.

[0018] Furthermore, since the mass flow through the engine increases during engine braking, conditions are created to achieve high boost pressures from the engine's turbocharger even at low engine speeds. High boost pressure further increases the achieved braking torque and ensures that high boost pressure is achieved when transitioning to a power-generating engine state.

[0019] This improves engine braking, thus fulfilling the aforementioned task.

[0020] Optionally, the intake valve control arrangement is configured to control the at least one intake valve to be open during substantially the entire expansion stroke of the engine during engine compression braking. This fills the cylinder with a large amount of air from the intake system during the expansion stroke. Consequently, braking torque can be further increased. In addition, the temperature of gases leaving the engine can be further reduced, particularly at high engine speeds, and conditions are provided to achieve even higher boost pressure from an engine turbocharger at low engine speeds, thus further ensuring that high boost pressure can be achieved when transitioning to a power-generating state of the engine.

[0021] Optionally, the exhaust valve control arrangement comprises a decompression device arranged to open and close the at least one exhaust valve in a transition region between the exhaust stroke and the intake stroke of the engine when the piston is at top dead center in the cylinder. This increases the braking torque because the energy stored in the compressed gases during the exhaust stroke is not returned to the crankshaft in the subsequent intake stroke, as the gases are diverted to the exhaust system upon opening and closing of the at least one exhaust valve. Furthermore, the load on the at least one intake valve and its driveline is reduced during the subsequent opening event of the at least one intake valve, namely because the pressure in the cylinder has been reduced by the opening and closing of the at least one exhaust valve.

[0022] Optionally, the decompression device is arranged to open and close the at least one exhaust valve in a transition region between the compression stroke and the expansion stroke of the engine when the piston is at top dead center in the cylinder. This increases the braking torque because the energy stored in the compressed gases during the compression stroke is not returned to the crankshaft in the subsequent expansion stroke, namely because the gases are diverted to the exhaust system when the at least one exhaust valve opens and closes. In addition, the load on the at least one intake valve and its drive train is reduced during the subsequent opening event of the at least one intake valve, namely because the pressure in the cylinder has been reduced by the opening and closing of the at least one exhaust valve.

[0023] Optionally, the exhaust valve phase shifting device is configured to control the magnitude of the braking torque during engine braking by controlling the phase shift of the at least one exhaust valve. This allows the magnitude of the braking torque to be controlled simply and effectively.

[0024] Optionally, the device for phasing an exhaust valve is configured to phase-shift the control of the at least one exhaust valve in a range between 0 degrees of the crankshaft and an end point of the exhaust phase-shift control, wherein the end point of the exhaust phase-shift control is between -40 and -120 degrees of the crankshaft, preferably between -60 and -80 degrees of the crankshaft. This allows the mass flow through the engine during engine braking, the magnitude of the braking torque, and the temperature of gases leaving the engine during engine braking to be largely efficiently controlled.

[0025] The intake valve control arrangement comprises an intake valve phase shifting device configured to phase shift the control of the at least one intake valve. The phase shift of the control of the at least one intake valve affects the mass flow, the load on the valves and their drive trains, and the braking torque. Accordingly, conditions are provided for simple and effective control of the mass flow through the engine and simple and effective control of the braking torque, while ensuring that the maximum loads on the valves and their drive trains are not exceeded.

[0026] The intake valve phase shifting device is configured to regulate the amount of air pumped through the engine during engine braking by controlling the phase shift of at least one intake valve. This allows the temperature of gases leaving the engine during engine braking, the boost air pressure of a turbocharger, and the magnitude of the braking torque to be controlled simply and efficiently. Furthermore, as a result of the improved controllability of the temperature of gases leaving the engine, conditions are provided for maintaining the temperature of an exhaust aftertreatment system within a suitable temperature range during engine braking. This can ensure that, for example, the temperature of a catalyst arranged in fluid communication with the exhaust outlet is maintained above a temperature threshold.Thus, it can be ensured that the catalyst functions even after prolonged engine braking, such as after engine braking during a long downhill stretch. According to some embodiments, the engine is a diesel engine comprising a selective catalytic reduction (SCR) arrangement that uses a reducing agent. In these embodiments, it can be ensured that the temperature of the selective catalytic reduction arrangement remains within a suitable temperature range. Thus, the consumption of the reducing agent can be reduced, since an excessively low temperature of a selective catalytic reduction arrangement leads to increased consumption of reducing agent due to the release of reducing agent in the selective catalytic reduction arrangement, which is harmful to the environment. Thus, as previously shown, conditions are provided for an engine to be more environmentally friendly.

[0027] Optionally, the intake valve phase shifting device is configured to phase shift the control of the at least one intake valve in a range between 0 degrees of the crankshaft and an end point of the intake phase shift control, wherein the end point of the intake phase shift control is between 40 and 120 degrees of the crankshaft, preferably between 60 and 80 degrees of the crankshaft. This allows the mass flow through the engine during engine braking and thus also the temperature of gases leaving the engine during engine braking, as well as the magnitude of the braking torque, to be largely efficiently controlled.

[0028] The engine includes a turbocharger arranged to compress the air to the engine's intake system. Since the mass flow through the engine is increased during engine braking, opening the at least one intake valve during at least a portion of the expansion stroke provides conditions for achieving high turbocharger boost pressure even at low engine speeds, further increasing braking torque and ensuring that high boost pressure can be achieved when transitioning to a power-generating engine state.

[0029] According to a second aspect of the invention, the object is achieved by a vehicle comprising a four-stroke internal combustion engine according to some embodiments. Since the vehicle comprises a four-stroke internal combustion engine capable of performing engine braking in an improved manner, a vehicle is provided capable of performing engine braking in an improved manner. Consequently, the aforementioned object is achieved.

[0030] According to a third aspect of the invention, the object is achieved by a method for controlling a four-stroke internal combustion engine, comprising: - at least one cylinder; - a piston arranged in each cylinder; - an inlet system; - a crankshaft; - at least one intake valve arranged in each cylinder, the intake valve being connected to the intake system; - an intake valve control arrangement configured to control each intake valve based on a rotational position of the crankshaft; - at least one exhaust valve arranged in each cylinder, the exhaust valve being connected to an exhaust outlet of the engine; - an exhaust valve control assembly configured to control each exhaust valve based on the rotational position of the crankshaft, the exhaust valve control assembly including a device for phase-shifting an exhaust valve, and the method comprising: - phase-shifting the control of the at least one exhaust valve using the device for phase-shifting an exhaust valve to a state in which the at least one exhaust valve is controlled such that it is opened during the expansion stroke of the engine and closed during the exhaust stroke of the engine in order to achieve engine braking by compression in the cylinders during the exhaust stroke, and - controlling the at least one intake valve to be open during at least a portion of the engine's expansion stroke during engine braking by compression in the cylinders, using the intake valve control arrangement.

[0031] Since the method comprises the step of phase-shifting the control of the at least one exhaust valve to a state in which the at least one exhaust valve is controlled to be open during the engine's expansion stroke and closed during the engine's exhaust stroke, engine braking by compression in the cylinders during the exhaust stroke is achieved simply and effectively. Furthermore, since the method comprises the step of controlling the at least one intake valve to be open during at least part of the engine's expansion stroke, the cylinder fills with air from the intake system even during the expansion stroke. Consequently, the braking torque increases because the mass flow through the engine increases during engine braking.

[0032] Furthermore, because the mass flow through the engine is increased during engine braking, the temperature of gases leaving the engine is reduced, especially at high engine speeds. This allows high braking torque to be achieved without damaging components such as an injector tip, a turbine inlet, and / or an exhaust aftertreatment system.

[0033] Furthermore, since the mass flow through the engine is increased during engine braking, conditions are created to achieve high boost pressure in the engine's turbocharger even at low engine speeds. High boost pressure further increases the achieved braking torque and ensures that high boost pressure is achieved when transitioning to a power-generating engine state.

[0034] This improves engine braking, thus achieving the aforementioned objective.

[0035] Optionally, the procedure also includes: - controlling the at least one intake valve to be open during substantially the entire expansion stroke of the engine during engine braking by compression in the cylinders, using the intake valve control arrangement.

[0036] This allows the cylinder to fill with a large volume of air from the intake system during the expansion stroke. Consequently, braking torque can be further increased. Furthermore, the temperature of gases leaving the engine can be further reduced, especially at high engine speeds, and conditions are created to achieve even higher boost pressure from an engine's turbocharger at low engine speeds, further ensuring that high boost pressure can be achieved when transitioning to a power-generating state of the engine.

[0037] Optionally, the exhaust valve control assembly includes a decompression device, and the method further comprises: - opening and closing the at least one exhaust valve in a transition region between the exhaust stroke and the intake stroke of the engine when the piston is at a top dead center in the cylinders, using the decompression device.

[0038] This increases braking torque because the energy stored in the compressed gases during the exhaust stroke is not returned to the crankshaft during the subsequent intake stroke, as the gases are diverted to the exhaust system during the opening and closing of the at least one exhaust valve. Furthermore, the load on the at least one intake valve and its drivetrain is reduced during the subsequent opening event of the at least one intake valve, because the pressure in the cylinders has been reduced by the opening and closing of the at least one exhaust valve.

[0039] Optionally, the procedure also includes: - Opening and closing the at least one exhaust valve in a transition region between the compression stroke and the expansion stroke of the engine when the piston is at a top dead center in the cylinder, using the decompression device.

[0040] This increases the braking torque because the energy stored in the compressed gases during the compression stroke is not returned to the crankshaft during the subsequent expansion stroke. This is because the gases are diverted to the exhaust system during the opening and closing of the at least one exhaust valve. Furthermore, the load on the at least one intake valve and its drivetrain is reduced during the subsequent opening event of the at least one intake valve, since the pressure in the cylinder has been reduced by the opening and closing of the at least one exhaust valve.

[0041] Optionally, the procedure also includes: - Phase shifting the control of the at least one exhaust valve using the device for phase shifting an exhaust valve in a range between 0 degrees of the crankshaft and an end point of the exhaust phase shift control, wherein the end point of the exhaust phase shift control is between -40 and -120 degrees of the crankshaft, preferably between -60 and -80 degrees of the crankshaft.

[0042] This allows the mass flow through the engine during engine braking, the magnitude of the braking torque, and the temperature of gases leaving the engine during engine braking to be largely efficiently controlled.

[0043] Optionally, the procedure also includes: - Controlling the magnitude of the braking torque during engine braking by controlling the phase shift of at least one exhaust valve.

[0044] This allows the magnitude of the braking torque to be controlled simply and effectively.

[0045] The intake valve control arrangement comprises a device for phase shifting an intake valve, and the method further comprises: - controlling the amount of air pumped through the engine during engine braking by controlling the phase shift of the at least one intake valve using the device for phasing an intake valve.

[0046] This allows the temperature of gases leaving the engine during engine braking, the charge air pressure of a turbocharger, and the magnitude of the braking torque to be controlled simply and efficiently. Furthermore, as a result of the improved controllability of the temperature of gases leaving the engine, conditions are created to maintain the temperature of an exhaust aftertreatment system within a suitable temperature range during engine braking. This can ensure that, for example, the temperature of a catalytic converter arranged in fluid communication with the exhaust outlet remains above a temperature threshold. This can ensure that the catalytic converter functions even after prolonged engine braking, such as after engine braking during a long downhill stretch.According to some embodiments, the engine is a diesel engine comprising a selective catalytic reduction (SCR) arrangement that uses a reducing agent. In these embodiments, it can be ensured that the temperature of the selective catalytic reduction arrangement remains within a correct temperature range. Thus, the consumption of the reducing agent can be reduced, since an excessively low temperature of a selective catalytic reduction arrangement leads to increased consumption of reducing agent due to the release of reducing agent in the selective catalytic reduction arrangement, which is harmful to the environment. Thus, the method for controlling a four-stroke internal combustion engine also provides conditions for an engine to be more environmentally friendly.

[0047] Optionally, the procedure also includes: - Phase shifting the control of the at least one intake valve in a range between 0 degrees of the crankshaft and an end point of the intake phase shift control using the device for phase shifting an intake valve, wherein the end point of the intake phase shift control is between 40 and 120 degrees of the crankshaft, preferably between 60 and 80 degrees of the crankshaft.

[0048] This allows the mass flow through the engine during engine braking and thus also the temperature of gases leaving the engine during engine braking as well as the magnitude of the braking torque to be controlled largely efficiently.

[0049] According to a fourth aspect of the invention, the object is achieved by a computer program for carrying out a method for controlling a four-stroke internal combustion engine, the computer program comprising computer-readable code configured to cause a central unit of a control unit of the engine to carry out the method according to some of the above embodiments.

[0050] Since the computer-readable code of the computer program is configured to cause a central processing unit of the control unit of the engine to execute a method that provides engine braking in an improved manner, the computer program is capable of providing engine braking in an improved manner when loaded onto the processing unit of the control unit.

[0051] Consequently, the previously mentioned task is fulfilled.

[0052] According to a fifth aspect of the invention, the object is achieved by a computer program product for carrying out a method for controlling a four-stroke internal combustion engine, the computer program product comprising computer-readable code configured to cause a central unit of a control unit of the engine to carry out the method according to the method according to some of the above embodiments.

[0053] Since the computer-readable code of the computer program product is configured to cause a central processing unit of a control unit of the engine to execute a method that provides engine braking in an improved manner when loaded onto the processing unit of the control unit, the computer program product is capable of providing engine braking in an improved manner.

[0054] This fulfills the previously mentioned task.

[0055] Further features and advantages of the present invention will become apparent upon reading the appended claims and the following detailed description. BRIEF DESCRIPTION OF THE DRAWINGS

[0056] Various aspects of the invention, including its particular features and advantages, will be readily understood from the exemplary embodiments discussed in the following detailed description and the accompanying drawings. In the drawings: Fig. 1 a cross-sectional view of a four-stroke internal combustion engine, Fig. 2a Opening events of at least one intake valve and at least one exhaust valve during a normal power-generating operating mode of the engine, Fig. 2b Opening events of the at least one intake valve and the at least one exhaust valve during a first engine braking operating mode, Fig. 2c Opening events of the at least one intake valve and the at least one exhaust valve during a second engine braking operating mode, Fig. 2d Opening events of the at least one intake valve and the at least one exhaust valve during a third engine braking operating mode, Fig. 2e opening events of the at least one intake valve and the at least one exhaust valve during a fourth engine braking operating mode, Fig. 3 a vehicle comprising a four-stroke internal combustion engine, Fig. 4 a method for controlling a four-stroke internal combustion engine, and Fig. 5 a computer program product for carrying out a method for controlling a four-stroke internal combustion engine. DETAILED DESCRIPTION

[0057] Aspects of the present invention will now be described in more detail. Like numerals refer to like elements throughout. Well-known functions or constructions are not necessarily described in detail for the sake of brevity and / or clarity.

[0058] Fig. 1 depicts a cross-sectional view of a four-stroke internal combustion engine 1 according to some embodiments. The engine 1 includes at least one cylinder 10 and a piston 12 disposed within each cylinder 10. The piston 12 is connected to a crankshaft 16 via a connecting rod 13, which, upon one revolution, reciprocates the piston 12 within the cylinder 10 between a top dead center (TDC) and a bottom dead center (BDC). The engine 1 includes an intake system 14, which in the depicted exemplary engine is depicted as an intake manifold. The intake system 14 may further include an air filter and, according to some embodiments, a throttle valve, a fuel injector, an airflow sensor, etc. According to the depicted embodiments, the engine 1 includes a turbocharger 36 disposed to compress the air for the intake system 14 of the engine 1.Thus, according to these embodiments, the intake system 14 is fluidly connected to a compressor of the turbocharger 36. The compressor is connected to a shaft connected to a turbine of the turbocharger 36. The turbine is arranged to be driven by the flow of gases from the exhaust outlet 26 of the engine 1. The engine 1 may include more than one turbocharger 36, wherein the turbochargers may be arranged in parallel or in series.

[0059] The engine 1 further includes at least one intake valve 18 arranged in each cylinder 10, wherein the at least one intake valve 18 is connected to the intake system 14. The engine 1 further includes an intake valve control arrangement 22 configured to control each intake valve 18 based on a rotational position of the crankshaft 16. The engine 1 further includes at least one exhaust valve 24 arranged in each cylinder 10, wherein the at least one exhaust valve 24 is connected to an exhaust outlet 26 of the engine 1. The engine 1 further includes an exhaust valve control arrangement 28 configured to control each exhaust valve 24 based on the rotational position of the crankshaft 16. In Fig. 1, the at least one intake valve 18 and the at least one exhaust valve 24 are depicted in a respective closed position. In the closed position, each valve 18, 24 abuts a respective valve seat to close a fluid connection between the cylinder 10 and the respective intake system 14 and the exhaust outlet 26.

[0060] The intake valve control arrangement 22 is arranged to control the at least one intake valve 18 between the closed position and an open position by displacing the at least one intake valve 18 in a direction into the cylinder 10. This opens a fluid connection between the intake system 14 and the cylinder 10. Likewise, the exhaust valve control arrangement 28 is arranged to control the at least one exhaust valve 24 between the closed position and an open position by displacing the at least one exhaust valve 24 in a direction into the cylinder 10. This opens a fluid connection between the cylinder 10 and the exhaust outlet 26. Upon displacing a valve 18, 24 from the closed position to the open position, the valve 18, 24 is lifted from its valve seat.The engine 1 further comprises a fuel injector 31 arranged to inject fuel directly into the cylinder 10. The engine 1 in the illustrated embodiments is a diesel engine. According to further embodiments, the engine may be a spark ignition engine, which may be designed to run on gas, gasoline, alcohol, or similar volatile fuels, or combinations thereof. Such fuel may be injected directly into the cylinder 10 using a fuel injector or may be added to the incoming air before it enters the cylinder 10, for example, by a fuel injector arranged on an intake manifold of the engine. According to the illustrated embodiments, the engine 1 comprises an exhaust aftertreatment system 39.The exhaust aftertreatment system 39 may include one or more of a catalyst, a particulate filter, a selective catalytic reduction (SCR) assembly, a diesel oxidation catalyst (DOC), a NOx storage catalyst (LNT), and a three-way catalyst (TWC).

[0061] The exhaust valve control assembly 28 and the intake valve control assembly 22 may each include one or more camshafts rotatably connected to the crankshaft 16, the camshaft including cam lobes arranged to shift the valves 18, 24 into an open position by pressing on the valve stems of the valves 18, 24 upon rotation of the camshaft. The exhaust valve control assembly 28 and / or the intake valve control assembly 22 may, according to further embodiments, include electrical, pneumatic, or hydraulic actuators arranged to control the valves based on the rotational position of the crankshaft 16. The rotational position of the crankshaft 16 may be obtained using a crank angle sensor 29.

[0062] The exhaust valve control arrangement 28 includes an exhaust valve phase shifting device 30 configured to phase shift the control of the at least one exhaust valve 24 with respect to the crankshaft 16. The exhaust valve phase shifting device 30 is configured to phase shift the control of the at least one exhaust valve 24 with respect to the crankshaft 16 to a state in which the at least one exhaust valve 24 is controlled to be open during the expansion stroke of the engine 1 and closed during the exhaust stroke of the engine 1. This allows engine braking by compression in the cylinders 10 during the exhaust stroke to be achieved simply and efficiently.Further, according to the depicted embodiments, the intake valve control assembly 22 includes an intake valve phase shifting device 32 configured to phase shift the timing of the at least one intake valve 18 with respect to the crankshaft 16. The exhaust valve phase shifting device 30 and the intake valve phase shifting device 32 may each include a hydraulic assembly using, for example, engine oil as the hydraulic fluid to phase shift the timing of the valve 18, 24 with respect to the crankshaft 16.Such a hydraulic arrangement may be part of a pulley (not shown) arranged to transmit rotation from the crankshaft 16 to a camshaft of the exhaust valve control arrangement 28 and / or the intake valve control arrangement 22, the hydraulic arrangement being arranged to regulate an angular relationship between a first portion of the pulley connected to the crankshaft 16 and a second portion of the pulley connected to the camshaft in order to phase-shift the control of the at least one intake valve 18 and / or the at least one exhaust valve 24. In embodiments in which the exhaust valve control arrangement 28 and / or the intake valve control arrangement 22 comprises electric, pneumatic, or hydraulic actuators.the phase shifting of the control of the at least one intake valve 18 and / or the at least one exhaust valve 24 can be carried out differently, for example by an electronic phase shift of the control.

[0063] The intake valve control arrangement 22 is configured to control the at least one intake valve 18 during engine braking by compression in the cylinders 10 so that it is open during at least part of the expansion stroke of the engine 1. As a result, the cylinder 10 fills with air from the intake system 14 during the expansion stroke. Consequently, the braking torque is increased because the mass flow through the engine 1 increases during engine braking. Furthermore, the temperature of gases leaving the engine is reduced, particularly at high engine speeds, due to the increased mass flow through the engine 1. This allows high braking torques to be achieved without damaging components such as a tip of the injector 31, a turbine inlet of the turbocharger 36, and / or an exhaust aftertreatment system 39.Furthermore, the increased mass flow through the engine 1 during engine braking provides conditions to achieve high charge air pressures of the turbocharger 39 of the engine 1 even at low speeds of the engine 1.

[0064] The opening of the at least one intake valve 18 during the expansion stroke of the engine 1 can be achieved by the intake valve control arrangement 22 comprising a supplementary intake valve opening arrangement 23 which, when actuated, controls the at least one intake valve 18 to an open position during at least part of the expansion stroke of the engine 1. The supplementary intake valve opening arrangement 23 can, as in the illustrated embodiments, comprise an additional cam lobe arranged on a camshaft of the intake valve control arrangement 22. The intake valve control arrangement 22 can comprise a lost motion arrangement which ensures that the displacement of the additional cam lobe is not transmitted to the at least one intake valve 18 when the supplementary intake valve opening arrangement 23 is deactivated, such as during a power-generating mode of the engine 1.Alternatively, according to some embodiments, the additional cam lobe is arranged on the camshaft adjacent to a normal cam lobe in a longitudinal direction of the camshaft, wherein the intake valve control arrangement 22 is arranged to displace the camshaft or a portion of the camshaft comprising the additional cam lobe in the longitudinal direction such that the additional cam lobe displaces the at least one intake valve 18 into an open position during at least a portion of the expansion stroke of the engine 1.In embodiments where the intake valve control arrangement 22 comprises an electric, pneumatic or hydraulic actuator arranged to control the valves based on the rotational position of the crankshaft 16, such an actuator may be used to control the at least one intake valve 18 to an open position during at least part of the expansion stroke of the engine 1 during engine braking.

[0065] The exhaust valve control assembly 28 includes a decompression device 34 arranged to selectively execute auxiliary opening events of the at least one exhaust valve 24 by opening and closing the at least one exhaust valve 24. The decompression device 34 may include one or more decompression cam lobes arranged on a camshaft of the exhaust valve control assembly 28, wherein the decompression cam lobes are arranged, when the decompression device 34 is activated, to execute auxiliary opening events of the at least one exhaust valve 24 by displacing the at least one exhaust valve 24 toward the open position. In such embodiments and in other embodiments described herein, the at least one exhaust valve 24 and the at least one intake valve 18 may be biased toward the closed position, for example, by a spring.

[0066] The engine 1 further includes a control unit 38 connected to the turbocharger 36. The control unit 38 may be configured to further regulate the amount of air pumped through the engine 1 during engine braking by regulating the boost air pressure of the turbocharger 36. This allows the amount of air pumped through the engine 1 during engine braking to be even more effectively regulated. In the illustrated embodiments, the control unit 38 is configured to regulate the boost air pressure of the turbocharger 36 by regulating a wastegate valve of the turbocharger 36. According to further embodiments, the charging device 36 is a variable geometry turbocharger (VGT).In such embodiments, the control unit 38 may be configured to control the charge air pressure of the charging device 36 by controlling the geometry of an inlet portion of the turbine of the turbocharger, for example, by controlling the angular positions of vanes arranged at the inlet portion of the turbine.

[0067] The control unit 38 may further be connected to other components of the engine to control its operation, such as the intake valve control assembly 22, the intake valve phase shifting device 32, the exhaust valve control assembly 28, the exhaust valve phase shifting device 30, the decompression device 34, and / or the supplemental intake valve opening assembly 23. For brevity and clarity, these connections are shown in Fig. 1 not shown. Furthermore, the control unit 38 may be connected to a number of different sensors to obtain signals therefrom. Examples include sensors arranged to detect the absolute pressure in the intake manifold, the exhaust pressure, the charge air temperature, the mass air flow, the throttle position, the engine speed, the engine load, the rotational position of the crankshaft 16, etc.

[0068] Fig. 2a to Fig. 2e form the opening events 51.1 to 54 in different operating modes of the exhaust valve control arrangement 28, the intake valve control arrangement 22 and the decompression device 34, which in Fig. 1. Therefore, reference is made below to Fig. 2a to Fig. 2e and Fig. 1. The curves that are shown in Fig. 2a to Fig. 2e depict opening events that are carried out during two revolutions of the crankshaft 16, i.e. during all four strokes of the four-stroke internal combustion engine 1. In these figures, the strokes are depicted in the following order: compression stroke 41, expansion stroke 42, exhaust stroke 43 and intake stroke 44.

[0069] Fig. 2a depicts the opening events 51.1 of the at least one intake valve 18 and the opening events 52 of the at least one exhaust valve 24 during a normal power-generating operating mode of the engine 1. As indicated, during the compression stroke 41 and the expansion stroke 42, the at least one intake valve 18 and the at least one exhaust valve 24 are closed. When the piston reaches bottom dead center BDC at the end of the expansion stroke 42, the exhaust valve control arrangement 28 controls the at least one exhaust valve 24 to an open position to allow exhaust gases to be expelled from the cylinder 10 to the exhaust outlet 26 during the exhaust stroke 43. In the transition region between the exhaust stroke 43 and the intake stroke 44, the exhaust valve control arrangement 28 controls the at least one exhaust valve 24 to a closed position.Furthermore, in the transition region between the exhaust stroke 43 and the intake stroke 44, the intake valve control arrangement 22 controls the at least one intake valve 18 to an open position so that air or an air / fuel mixture can enter the cylinder 10 during the intake stroke 44. Towards the end of the intake stroke 44, the intake valve control arrangement 22 controls the at least one intake valve 18 to a closed position so that the air or the air / fuel mixture can be compressed in the subsequent compression stroke 41.

[0070] Fig. 2b depicts the opening event 51.1 of the at least one intake valve 18 and the opening events 52 to 54 of the at least one exhaust valve 24 during a first engine braking operating mode of the engine 1. In this mode, the decompression device 34 executes an opening event 53, i.e., it opens and closes the at least one exhaust valve 24 during the intake stroke 44, and executes an opening event 54 during the expansion stroke 42. A small amount of braking torque is achieved in the first engine braking operating mode. The opening event 54 of the at least one exhaust valve 24 during the expansion stroke 42 results in a slightly increased braking torque compared to an operating mode as in Fig. 1, in which no additional opening of the at least one exhaust valve 24 is performed by the decompression device 34. The slightly increased braking is caused by the fact that, as a result of the opening event 54 of the at least one exhaust valve 24 during the expansion stroke 42, a little gas is expelled from the cylinder 10 to the exhaust outlet 26. The compressed gas therefore does not return its energy to the crankshaft in the remaining portion of the expansion stroke 42. The opening event 53 of the at least one exhaust valve 24 during the intake stroke 44 has no significant effect on the braking torque. Even if a small amount of braking torque is achieved in the first engine braking operating mode of the engine 1, as in Fig. 2b, significant cylinder pressures can arise in the transition region between the compression stroke 41 and the expansion stroke 42 when the piston 12 is at top dead center. Namely, the at least one intake valve 18 is open substantially throughout the intake stroke 44 and closed in a transition region between the intake stroke 44 and the compression stroke 41 when the piston is at bottom dead center, thereby allowing a large amount of air into the cylinder during the intake stroke 44. This air is then fully compressed in the subsequent compression stroke 41, since no valves are open during the entire movement of the piston from bottom dead center to top dead center during the compression stroke 41. This can result in significant cylinder pressures in the first engine braking operating mode.

[0071] Fig. 2c depicts the opening events 51.1 of the at least one intake valve 18 and the opening events 52 to 54 of the at least one exhaust valve 24 during a second engine braking operating mode of the engine 1. In the second engine braking operating mode of the engine 1, the device 30 for phase-shifting an exhaust valve phase-shifts the control of the at least one exhaust valve 24 to a state in which the at least one exhaust valve 24 is controlled such that it is open during the expansion stroke 42 and closed during the exhaust stroke 43 of the engine 1. This achieves engine braking by compression in the cylinders 10 during the exhaust stroke 43 simply and efficiently.

[0072] Furthermore, as in Fig. 2c, the additional opening events 53, 54 by the decompression device 34 of the at least one exhaust valve 24 are also phase-shifted due to the phase shift of the control of the at least one exhaust valve 24. In the second engine braking operating mode, which is shown in Fig. 2c, the decompression device 34 performs an opening event 54, ie it opens and closes the at least one exhaust valve 24, in the transition region between the compression stroke 41 and the expansion stroke 42, and performs an opening event 53 in the transition region between the exhaust stroke 43 and the intake stroke 44. This increases the braking torque compared to the second engine braking operating mode of the engine 1, which in Fig. 2b, since gas is exhausted from the cylinder 10 after compression in the compression stroke 1 as well as after compression in the exhaust stroke 41. Thus, according to these embodiments, the device 30 for phase-shifting an exhaust valve is arranged to also phase-shift the control of the decompression device 34 by an amount corresponding to the phase shift of the control of the at least one exhaust valve 24. This can be achieved by phase-shifting a camshaft arranged to control the at least one exhaust valve 24 with respect to the crankshaft 16, wherein the camshaft comprises one or more decompression cam lobes. Thus, in such embodiments, a phase shift of the control of the at least one exhaust valve 24 also results in a corresponding phase shift of the control of the decompression device 34.

[0073] The device 30 for phase-shifting an exhaust valve can be configured to phase-shift the control of the at least one exhaust valve 24 in a range between 0 degrees of the crankshaft and an end point of the exhaust phase-shift control. The end point of the exhaust phase-shift control can be between -40 and -120 degrees of the crankshaft, or between -50 and -100 degrees of the crankshaft, or preferably between -60 and -80 degrees of the crankshaft. The device 30 for phase-shifting an exhaust valve can thus phase-shift the control of the at least one exhaust valve 24 and, according to some embodiments, also the decompression device 34 back and forth within such a range. As a result, the mass flow through the engine 1 during engine braking and the magnitude of the braking torque are largely efficiently regulated.Thus, the exhaust valve phase shifting device 30 may be configured to control the magnitude of the braking torque during engine braking by controlling the phase shift of the at least one exhaust valve 24.

[0074] Fig. 2d depicts opening events 51.1, 51.2 of the at least one intake valve 18 and opening events 52 to 54 of the at least one exhaust valve 24 during a third engine braking operating mode of the engine 1. In this third engine braking operating mode of the engine 1, the intake valve control arrangement 22 is configured to control the at least one intake valve 18 to be open during the expansion stroke 42 of the engine 1 during engine braking by compression in the cylinders 10. In the depicted embodiments, the at least one intake valve 18 is open substantially throughout the entire expansion stroke 42 of the engine 1. Due to the opening event 51.2 of the at least one intake valve 18 during the expansion stroke 42, the cylinder 10 fills with air from the intake system 14 during the expansion stroke 42. Consequently, the braking torque increases since the mass flow through the engine 1 is increased during engine braking.In addition, the temperature of gases leaving the engine can be reduced, particularly at high engine speeds. This allows high braking torque to be achieved without damaging components such as the tip of the injector 31, a turbine inlet of the turbocharger 36, and / or an exhaust aftertreatment system 39. Furthermore, the increased mass flow through the engine 1 during engine braking provides conditions for achieving high charge air pressures of the turbocharger 39 of the engine 1 even at low engine speeds.

[0075] As in Fig. 2d, in the third engine braking operating mode of the engine 1, the decompression device 34 further executes the opening event 53 of the at least one exhaust valve 24 before the opening event 51.1 of the at least one intake valve 18 in a region of the transition range between the exhaust stroke 43 and the intake stroke 44. Likewise, the decompression device 34 executes the opening event 54 of the at least one exhaust valve 24 before the opening event 51.2 of the at least one intake valve 18 in the region of the transition range between the compression stroke 41 and the expansion stroke 42. Thus, according to these embodiments, the decompression device 34 significantly reduces the cylinder pressure before the respective opening event 51.1, 52.2 of the at least one intake valve 18.Consequently, the at least one intake valve 18 is opened at a lower cylinder pressure, which reduces the load on the at least one intake valve 18 and the intake valve control arrangement 22 as well as the load on the intake valve control arrangement 22 and the exhaust valve control arrangement 28.

[0076] Fig. 2e depicts the opening events 51.1, 51.2 of the at least one intake valve 18 and the opening events 52 to 54 of the at least one exhaust valve 24 during a fourth engine braking operating mode of the engine 1. In the fourth engine braking operating mode of the engine 1, the device 32 for phase-shifting an intake valve phase-shifts the control of the at least one intake valve 18 to a state in which the at least one intake valve 18 is controlled such that it is open during the intake stroke 44 of the engine 1 and closed during the compression stroke 41 of the engine 1.As a result, the maximum cylinder pressure is reduced and the braking torque is achieved because the at least one intake valve 18 is open during a part of the compression stroke 41, whereby a part of the air that fills the cylinder during the intake stroke 44 can be expelled back into the intake system 14 during the movement of the piston from bottom dead center towards top dead center in the compression stroke 41. In . Fig. 2e, the curve 51.1, which depicts the opening event 51.1 of the at least one intake valve 18, extends into the part of the compression stroke 41, but this is not depicted in this figure for the sake of brevity and clarity.

[0077] Accordingly, the part to the right of the intake stroke 44 in Fig. 2e can be considered as part of the compression stroke 41.

[0078] According to the embodiments described in Fig. 2e, the opening event 51.2 of the one intake valve 18 has been phase-shifted by the intake valve phase-shifting device 32, such that the at least one intake valve 18 opens during the expansion stroke 42 and closes during the exhaust stroke 43 of the engine 1. This is an effect of the intake valve control arrangement 22, which includes a camshaft with two cam lobes that are phase-shifted by a corresponding amount. The phase shift of the opening event 51.2 has no significant effect on the achieved braking torque.

[0079] According to some embodiments, the decompression device 34 is arranged to keep the at least one exhaust valve 24 open during the opening event 53 until the opening event 51.1 of the at least one intake valve 18. Furthermore, the decompression device 34 can be arranged to keep the at least one exhaust valve 24 open during the opening event 54 until the opening event 51.2 of the at least one intake valve 18 is executed by the intake valve control arrangement 22. In this way, the formation of a negative pressure in the cylinder 10 during the intake stroke 44 as well as during the expansion stroke 42 can be avoided.

[0080] The intake valve phasing device 32 may be configured to phase-shift the control of the at least one intake valve 18 in a range between 0 degrees of the crankshaft and an end point of the intake phasing control. The end point of the intake phasing control may be between 40 and 120 degrees of the crankshaft, or between 50 and 100 degrees of the crankshaft, or preferably between 60 and 80 degrees of the crankshaft. The intake valve phasing device 32 may thus phase-shift the control of the at least one intake valve 18 back and forth within such a range to regulate the amount of air pumped through the engine 1 during engine braking.The phase shift of the control of the at least one intake valve 18 further affects the charge mass, the load on the valves 18, 24 and their drive trains, as well as the braking torque, which can thus also be controlled by the phase shift of the control of the at least one intake valve 18. Thus, conditions are provided for efficient control of the amount of air pumped through the engine 1, as well as efficient control of the magnitude of the braking torque and the charge mass, without exceeding the maximum load limits on the valves 18, 24 and their drive trains, and whereby a lower temperature of gases leaving the engine is ensured, especially at high engine speeds, and conditions are also provided for high charge air pressure of a turbocharger of the engine during low engine speeds.

[0081] During an engine braking event, the amount of air pumped through the engine, the charge mass, and the magnitude of the braking torque can be controlled using the previously described engine braking modes. This can be achieved by stepwise or gradual switching between the different engine braking modes.

[0082] For example, in an initial part of an engine braking event, ie when a driver releases the accelerator pedal, the valves 18, 24 are controlled as in Fig. 2a, i.e., without any phase shifts or supplementary opening events of the at least one intake valve 18 or any activation of the decompression device 34 being performed. Subsequently, for example, following a braking request, the engine 1 may enter the first engine braking operating mode, in which the decompression device 34 is activated but provides little or no additional braking torque. The second engine braking operating mode may then be used, in which the control of the at least one exhaust valve 24 is phase-shifted to increase the braking torque.The engine 1 can then enter the third engine braking operating mode in which the intake valve control arrangement 22 controls the at least one intake valve 18 to be open during the expansion stroke 42 in order to further increase the braking torque and / or to reduce the temperature of gases leaving the engine and / or to increase the charge air pressure of the turbocharger 39, for example at low speeds of the engine 1. The fourth engine braking operating mode can then be used in which the device 32 for phasing an intake valve phase-shifts the control of the at least one intake valve 18 to a state in which the at least one intake valve 18 is controlled to be open during the intake stroke 44 of the engine 1 and closed during the compression stroke 41 of the engine 1 in order to reduce the maximum cylinder pressure and / or to reduce the braking torque.

[0083] Instead of performing these steps step by step, the phase shift of the control of the at least one exhaust valve 24 according to the second engine braking operating mode and the supplementary opening 51.2 of the at least one intake valve 18 in the expansion stroke 42 according to the third engine braking operating mode can be performed simultaneously.

[0084] According to some embodiments, the intake valve phase shifting device 32 and the exhaust valve phase shifting device 30 are arranged to perform a simultaneous phase shift of the control of the at least one intake valve 18 and the at least one exhaust valve 24. This provides an engine 1 in which the amount of air pumped through the engine 1, the boost mass, and the braking torque can be controlled even more quickly without exceeding a maximum load on the valves 18, 24 and their drive trains, while ensuring a low temperature of gases leaving the engine, especially at high engine speeds, and thereby ensuring conditions for high boost pressure of a turbocharger of the engine at low engine speeds.

[0085] The various engine braking operating modes can thus be used stepwise to gradually increase the braking torque. Alternatively or additionally, the selection of and / or transition between the various engine braking operating modes can be carried out depending on a desired braking torque level, a desired air flow through the engine 1, a desired charge air mass, a desired charge air pressure, and / or a desired temperature of the exhaust aftertreatment system 39. Furthermore, as is apparent from the above, a gradual transition between various engine braking operating modes can be carried out, for example, by a gradual phase shift of the control of the at least one intake valve 18 and / or the at least one exhaust valve 24.

[0086] Fig. 3 depicts a vehicle 40 including a four-stroke internal combustion engine 1 according to some embodiments for propulsion of the vehicle 40. The Fig. The vehicle 40 depicted in Figure 3 is a truck. However, the four-stroke internal combustion engine 1 may be incorporated into another type of manned or unmanned land-based vehicle, such as a truck, bus, construction vehicle, tractor, car, etc.

[0087] Fig. 4 depicts a method 100 for controlling a four-stroke internal combustion engine 1. The engine 1 may be a four-stroke internal combustion engine 1 according to the Fig. 1 illustrated embodiments. Therefore, the following will refer to Fig. 4 and on Fig. 1. The method 100 is a method 100 for controlling a four-stroke internal combustion engine 1, which comprises - at least one cylinder 10; - a piston 12 arranged in each cylinder 10; - an inlet system 14; - a crankshaft 16; - at least one intake valve 18 arranged in each cylinder 10, the intake valve 18 being connected to the intake system 14; - an intake valve control assembly 22 configured to control each intake valve 18 based on a rotational position of the crankshaft 16; - at least one exhaust valve 24 arranged in each cylinder 10, the exhaust valve 24 being connected to an exhaust outlet 26 of the engine 1; - an exhaust valve control assembly 28 configured to control each exhaust valve 24 based on the rotational position of the crankshaft 16, wherein the exhaust valve control assembly 28 includes a device 30 for phasing an exhaust valve, and wherein the method 100 comprises: - phase shifting 110 of the control of the at least one exhaust valve 24 using the device 30 for phase shifting an exhaust valve into a state in which the at least one exhaust valve 24 is controlled such that it is opened during the expansion stroke of the engine 1 and closed during the exhaust stroke of the engine 1 in order to achieve engine braking by compression in the cylinders 10 during the exhaust stroke, and - controlling 120 the at least one intake valve 18 to be open during at least part of the expansion stroke of the engine 1 during engine braking by compression in the cylinders 10, using the intake valve control arrangement 22.

[0088] As in Fig. 4, the method 100 may further include: - controlling 121 the at least one intake valve 18 to be open substantially throughout the expansion stroke of the engine 1 during engine braking by compression in the cylinders 10, using the intake valve control arrangement 22.

[0089] According to some embodiments, the exhaust valve control assembly 28 includes a decompression device 34, and the method 100 further includes: - Opening and closing 130 of the at least one exhaust valve 24 in a transition region between the exhaust stroke and the intake stroke of the engine 1, when the piston 12 is at a top dead center in the cylinder 10, using the decompression device 34.

[0090] As in Fig. 4, the method 100 may further include: - Opening and closing 131 of the at least one exhaust valve 24 in a transition region between the compression stroke and the expansion stroke of the engine 1, when the piston 12 is at a top dead center in the cylinder 10, using the decompression device 34.

[0091] As in Fig. 4, the method 100 may further include: - Phase shifting 111 of the control of the at least one exhaust valve 24 using the device 30 for phase shifting an exhaust valve in a range between 0 degrees of the crankshaft and an end point of the exhaust phase shift control, wherein the end point of the exhaust phase shift control is between -40 and -120 degrees of the crankshaft, preferably between -60 and -80 degrees of the crankshaft.

[0092] As in Fig. 4, the method 100 may further include: - Controlling 112 the magnitude of the braking torque during engine braking by controlling the phase shift of at least one exhaust valve 24.

[0093] According to some embodiments, the intake valve control assembly 22 includes a device 32 for phasing an intake valve, and the method 100 further includes: - Controlling 140 the amount of air pumped through the engine 1 during engine braking by controlling the phase shift of the at least one intake valve 18 using the device 32 for phasing an intake valve.

[0094] As in Fig. 4, the method 100 may further include: - Phase shifting 141 of the control of the at least one intake valve 18 in a range between 0 degrees of the crankshaft and an end point of the intake phase shift control using the device 32 for phase shifting an intake valve, wherein the end point of the intake phase shift control is between 40 and 120 degrees of the crankshaft, preferably between 60 and 80 degrees of the crankshaft.

[0095] Fig. 5 forms a computer program product 200 for executing a method 100 for controlling a four-stroke internal combustion engine 1, as in Fig. 1, wherein the computer program product 200 comprises a computer-readable code configured to cause a central unit of a control unit 38 of the engine 1 to execute the method 100 as shown in Fig. 4 shown.

[0096] Furthermore, the computer program product 200 comprises a computer program for executing a method 100 for controlling a four-stroke internal combustion engine 1, as in Fig. 1, wherein the computer program comprises a computer-readable code configured to cause a central unit of a control unit 38 of the engine 1 to execute the method 100 as shown in Fig. 4 shown.

[0097] The control unit 38 may be connected to the intake valve control assembly 22, the intake valve phase shifting device 32, the supplementary intake valve opening assembly 23, the exhaust valve control assembly 28, the exhaust valve phase shifting device 30, and the decompression device 34 to control the operation of these components to achieve the Fig. 4 to carry out the procedure 100 shown.

[0098] Those skilled in the art will understand that the method for controlling a four-stroke internal combustion engine 1 can be implemented by programmed instructions. These programmed instructions typically consist of a computer program that, when executed in the control unit 38, ensures that the control unit 38 performs the desired control, such as the method steps 110 to 112, 120, 121, 130, 131, 140, 141 described herein. The computer program is usually part of a computer program product 200, which comprises a suitable digital storage medium on which the computer program is stored.

[0099] The control unit 38 may include a computing unit, which may take the form of essentially any suitable type of processor circuit or microcomputer, e.g., a digital signal processing circuit (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 capable of interpreting and executing instructions. As used herein, the term "computing unit" may represent processing circuitry that includes a plurality of processing circuits, such as one, some, or all of the aforementioned.

[0100] The control unit 38 may further comprise a memory unit, wherein the computing unit may be connected to the memory unit, which may provide the computing unit, for example, with stored program code and / or stored data that the computing unit may need to perform the calculations. The computing unit may also be adapted to store incomplete or final results of the calculations in the memory unit. The memory unit may comprise a spatial device used to store data or programs, i.e., sequences of instructions, on a temporary or permanent basis. According to some embodiments, the memory unit may comprise integrated circuits comprising silicon-based transistors.The storage unit may, in various embodiments, comprise, for example, a memory card, a flash memory, a USB memory, a hard disk, or other similar volatile or non-volatile storage unit for storing data, such as a ROM (read-only memory), PROM (programmable read-only memory), EPROM (erasable PROM), EEPROM (electrically erasable PROM), etc.

[0101] The control unit 38 is connected to components of the four-stroke internal combustion engine 1 to receive and / or transmit input and output signals. These input and output signals may comprise waveforms, pulses, or other attributes that the input signal receiving devices can detect as information and that can be converted into signals that can be processed by the control unit 38. These signals can then be fed to the computing unit. One or more output signal transmitting devices can be arranged to convert calculation results from the computing unit into output signals for transmission to other parts of the vehicle's control system and / or the component(s) for which the signals are intended.Each of the connections to the respective components of the four-stroke internal combustion engine 1 for receiving and transmitting input and output signals may take the form of one or more of a cable, a data bus, e.g., a CAN (control unit network) bus, a MOST (media oriented system transport) bus, or another bus configuration, or a wireless connection.

[0102] In the illustrated embodiments, the four-stroke internal combustion engine 1 comprises one control unit 38, but could alternatively be implemented entirely or partially in two or more control units.

[0103] Control systems in modern vehicles generally include a communication bus system consisting of one or more communication buses to connect a number of electronic control units (ECUs) or controllers to various components on board the vehicle. Such a control system may include a large number of control units, and the performance of a specific function may be shared between two or more of them. Vehicles of the type in question are therefore often equipped with considerably more control units than in Fig. 1, as the expert will certainly understand.

[0104] The computer program product 200 may, for example, be provided in the form of a data carrier carrying computer program code for executing at least some of the method steps 110 to 112, 120, 121, 130, 131, 140, 141 according to some embodiments when loaded onto one or more computing units of the control unit 38. The data carrier may, for example, be a CD-ROM, as in Fig.5, or a ROM (read-only memory), a PROM (programmable read-only memory), an EPROM (erasable PROM), a flash memory, an EEPROM (electrically erasable PROM), a hard disk, a memory stick, an optical storage device, a magnetic storage device, or any other suitable medium, such as a disk or tape, capable of containing machine-readable data in a non-transitory manner. The computer program product may further be provided as computer program code on a server and may be remotely downloaded to the control unit 38, e.g., via an Internet or intranet connection or via other wired or wireless communication systems.

[0105] It is to be understood that the foregoing illustrates various embodiments and that the invention is defined only by the appended claims. Those skilled in the art will recognize that the embodiments may be modified and that various features of the embodiments may be combined to create embodiments other than those described herein without departing from the scope of the present invention as defined by the appended claims. For example, the term braking torque as used herein may also be referred to as braking effect, deceleration power, or the like. The term "air" as used herein may include a mixture of air, fuel, and / or recirculated exhaust gases. Furthermore, the terms compression stroke 41, expansion stroke 42, exhaust stroke 43, and intake stroke 44 may be replaced by the terms compression phase 41, expansion phase 42, exhaust phase 43, and intake phase 44.

[0106] As used herein, the term "comprising" or "comprises" is open-ended and includes one or more specified features, elements, steps, components, or functions, but does not preclude the presence or addition of one or more other features, elements, steps, components, functions, or groups thereof.

Claims

[1] Four-stroke internal combustion engine (1), comprising - at least one cylinder (10); - a piston (12) arranged in each cylinder (10); - an inlet system (14); - a crankshaft (16); - at least one intake valve (18) arranged in each cylinder (10), the intake valve (18) being connected to the intake system (14); - an intake valve control arrangement (22) configured to control each intake valve (18) based on a rotational position of the crankshaft (16); - at least one exhaust valve (24) arranged in each cylinder (10), the exhaust valve (24) being connected to an exhaust outlet (26) of the engine (1); - an exhaust valve control arrangement (28) configured to control each exhaust valve (24) based on the rotational position of the crankshaft (16), wherein the exhaust valve control arrangement (28) comprises a device (30) for phase-shifting an exhaust valve, which is configured to phase-shift the control of the at least one exhaust valve (24) into a state in which the at least one exhaust valve (24) is controlled to be opened during the expansion stroke of the engine (1) and closed during the exhaust stroke of the engine (1) in order to achieve engine braking by compression in the cylinders (10) during the exhaust stroke, wherein the intake valve control arrangement (22) is configured to control the at least one intake valve (18) to be open during at least a portion of the expansion stroke of the engine (1), wherein the engine (1) comprises a turbocharger (36) arranged to compress air for the intake system (14) of the engine (1), wherein the engine (1) further comprises a control unit (38) connected to the turbocharger (36), wherein the control unit (38) is configured to regulate the amount of air pumped by the engine (1) during engine braking by regulating the charge air pressure of the turbocharger (36), and wherein the intake valve control arrangement (22) comprises an intake valve phase shifting device (32) configured to phase shift the control of the at least one intake valve (18), wherein the intake valve phase shifting device (32) is configured to regulate the amount of air pumped by the engine (1) during engine braking by regulating the phase shift of the at least one intake valve (18), wherein at least the intake valve phase shifting device (32) is configured to regulate the amount of air as a function of a temperature of a catalyst arranged in fluid communication with the exhaust outlet (26) such that the temperature is maintained above a temperature threshold. [2] Engine (1) according to claim 1, wherein the intake valve control arrangement (22) is configured to control the at least one intake valve (18) to be open during substantially the entire expansion stroke of the engine (1) during engine braking by compression in the cylinders (10). [3] Engine (1) according to claim 1 or 2, wherein the exhaust valve control arrangement (28) comprises a decompression device (34) arranged to open and close the at least one exhaust valve (24) in a transition region between the exhaust stroke and the intake stroke of the engine (1) when the piston (12) is at a top dead center in the cylinder (10). [4] Engine (1) according to claim 3, wherein the decompression device (34) is arranged to open and close the at least one exhaust valve (24) in a transition region between the compression stroke and the expansion stroke of the engine (1) when the piston (12) is at a top dead center in the cylinder (10). [5] Engine (1) according to one of the preceding claims, wherein the device (30) for phase-shifting an exhaust valve is configured to phase-shift the control of the at least one exhaust valve (24) in a range between 0 degrees of the crankshaft and an end point of the exhaust phase-shift control, wherein the end point of the exhaust phase-shift control is between -40 and -120 degrees of the crankshaft, preferably between -60 and -80 degrees of the crankshaft. [6] Engine (1) according to one of the preceding claims, wherein the device (30) for phase shifting an exhaust valve is configured to control the magnitude of the braking torque during engine braking by controlling the phase shift of the at least one exhaust valve (24). [7] Engine (1) according to one of the preceding claims, wherein the device (32) for phase-shifting an intake valve is configured to phase-shift the control of the at least one intake valve (18) in a range between 0 degrees of the crankshaft and an end point of the intake phase-shift control, wherein the end point of the intake phase-shift control is between 40 and 120 degrees of the crankshaft, preferably between 60 and 80 degrees of the crankshaft. [8] Vehicle (40) comprising a four-stroke internal combustion engine (1) according to any one of the preceding claims. [9] Method (100) for controlling a four-stroke internal combustion engine (1), comprising - at least one cylinder (10); - a piston (12) arranged in each cylinder (10); - an inlet system (14); - a crankshaft (16); - at least one intake valve (18) arranged in each cylinder (10), the intake valve (18) being connected to the intake system (14); - an intake valve control arrangement (22) configured to control each intake valve (18) based on a rotational position of the crankshaft (16), the intake valve control arrangement (22) comprising a device (32) for phase-shifting the at least one intake valve (18); - at least one exhaust valve (24) arranged in each cylinder (10), the exhaust valve (24) being connected to an exhaust outlet (26) of the engine (1); - an exhaust valve control arrangement (28) configured to control each exhaust valve (24) based on the rotational position of the crankshaft (16), wherein the exhaust valve control arrangement (28) comprises a device (30) for phase-shifting an exhaust valve, wherein the engine (1) comprises a turbocharger (36) arranged to compress air for the intake system (14) of the engine (1), wherein the engine (1) further comprises a control unit (38) connected to the turbocharger (36), and wherein the method (100) comprises: - phase-shifting (110) the control of the at least one exhaust valve (24) using the device (30) for phase-shifting an exhaust valve into a state in which the at least one exhaust valve (24) is controlled such that it is opened during the expansion stroke of the engine (1) and closed during the exhaust stroke of the engine (1) in order to achieve engine braking by compression in the cylinders (10) during the exhaust stroke, and - controlling (120) the at least one intake valve (18) to be open during at least part of the expansion stroke of the engine (1) during engine braking by compression in the cylinders (10), using the intake valve control arrangement (22) and - Control of the amount of air pumped by the engine (1) during engine braking by the control unit (38) by regulating the charge air pressure of the turbocharger (36), - Controlling the amount of air pumped through the engine (1) during engine braking by at least controlling the phase shift of the at least one intake valve (18) using the device (32) for phase shifting an intake valve, wherein the amount of air is controlled as a function of a temperature of a catalyst arranged in fluid communication with the exhaust outlet (26) such that the temperature is maintained above a temperature threshold. [10] The method (100) of claim 9, wherein the exhaust valve control assembly (28) includes a decompression device (34), and wherein the method (100) further comprises: - opening and closing (130) the at least one exhaust valve (24) in a transition region between the exhaust stroke and the intake stroke of the engine (1) when the piston (12) is at a top dead center in the cylinder (10), using the decompression device (34). [11] Computer program for carrying out a method (100) for controlling a four-stroke internal combustion engine (1), the computer program comprising computer-readable code configured to cause a central unit of a control unit (38) of the engine (1) to carry out the method (100) according to claim 9 or 10. [12] Computer program product (200) for carrying out a method (100) for controlling a four-stroke internal combustion engine (1), the computer program product (200) comprising computer-readable code configured to cause a central unit of a control unit (38) of the engine (1) to carry out the method (100) according to claim 9 or 10.

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