TECHNICAL FIELD

The present disclosure relates to a method performed by a control arrangement for controlling a powertrain of a vehicle, wherein the powertrain comprises an internal combustion engine. The present disclosure further relates to a computer program, a computer-readable medium, a control arrangement, a powertrain for a vehicle, and a vehicle.

BACKGROUND

Internal combustion engines, such as four-stroke internal combustion engines, comprise one or more cylinders and a piston arranged in each cylinder. The pistons are connected to a crankshaft of the engine and are arranged to reciprocate within the cylinders upon rotation of the crankshaft. The engine usually further comprises one or more inlet valves and outlet valves as well as one or more fuel supply arrangements. The one or more inlet valves and outlet valves are controlled by a respective valve control arrangement usually comprising one or more camshafts rotatably connected to a crankshaft of the engine, via a belt, chain, gears, or similar. A four-stroke internal combustion engine completes four separate strokes while turning a crankshaft. A stroke refers to the full travel of the piston along the cylinder, in either direction. The uppermost position of the piston in the cylinder is usually referred to as the top dead centre TDC, and the lowermost position of the piston in the cylinder is usually referred to as the bottom dead centre BDC.

The distance between the top dead centre TDC and the bottom dead centre BDC, measured in a direction coinciding with the moving direction of the piston between the top dead centre TDC and the bottom dead centre BDC, can be referred to as a stroke length of the piston.

The strokes are completed in the following order, inlet stroke, compression stroke, expansion stroke and exhaust stroke. During operation of a conventional four-stroke internal combustion engine, the inlet valve control arrangement controls inlet valves of a cylinder to an open state during the inlet stroke of a piston within the cylinder, to allow air, or a mixture of air and fuel, to enter the cylinder. During the compression stroke, all valves should be closed to allow compression of the air, or the mixture of the air and fuel, in the cylinder. If the engine is in a power producing state, fuel in the cylinder is ignited, usually towards the end of the compression stroke, for example by a spark plug or by compression heat in the cylinder. The combustion of fuel within the cylinder significantly increases pressure and temperature in the cylinder. The combustion of the fuel usually continues into a significant portion of the subsequent expansion stroke. The increased pressure and temperature in the cylinder obtained by the combustion is partially converted into mechanical work supplied to the crank shaft during the expansion stroke. Obviously, all valves should remain closed during the expansion stroke to allow the increased pressure and temperature to be converted into mechanical work. The expansion stroke is also usually referred to as the combustion stroke, since usually, most of the combustion takes place during the expansion stroke. In the subsequent exhaust stroke, the exhaust valve control arrangement controls exhaust valves of the cylinder to an open state to allow exhaust gases to be expelled out of the cylinder into an exhaust system of the combustion engine.

The exhaust stroke and the inlet stroke can each be referred to as a gas exchanging phase of a cylinder because normally, gas is transferred out from and into the cylinder respectively in the exhaust stoke and the inlet stroke. Moreover, the exhaust stroke and the inlet stroke can collectively be referred to as a gas exchanging phase of the cylinder, as well as a transition area between the exhaust stroke and the inlet stroke, because gas is normally transferred out from and into the cylinder in these strokes. As understood from the above, typically, gas is not allowed to flow into or out from the cylinder during the subsequent compression stroke and the expansion stroke of the cylinder.

During normal engine braking, occurring for example when a driver of a vehicle releases an accelerator pedal, the engine will continue to operate in the above described strokes, with the exception that, normally, no fuel is supplied to the engine during engine braking, and consequently, no combustion will take place during the end of the compression stroke or during the expansion stroke. In this condition, the engine will provide some braking torque due to internal friction and due to the pumping of air from the inlet to the exhaust, in the respective inlet stroke and exhaust stroke. As a piston travels upward during its compression stroke, the gases that are trapped in the cylinder are compressed. The compressed gases oppose the upward motion of the piston. However, almost all the energy stored in the compressed gases is returned to the crank shaft on the subsequent expansion stroke.

Thereby, during normal engine braking, the compression stroke together with the subsequent expansion stroke, will not contribute to a significant braking torque of the engine.

Some legislations require heavier vehicles to be provided with an auxiliary braking system in addition to wheel brakes. An efficient means of braking the vehicle is to utilize an engine to provide extra braking force because already existing systems of the vehicle can be utilized to generate the braking force needed and to transport the heat generated during braking to the surroundings. Moreover, the use of an engine to provide extra braking force reduces wear of the wheel brakes.

There are some different types of methods and arrangements for increasing the braking torque of an engine. A compression release engine brake, sometimes referred to a Jake brake or Jacobs brake, is an engine braking mechanism used in some engines. Some compression release brake arrangements comprise a valve actuator assembly which is configured to open exhaust valves in the cylinders after the compression stroke to release the compressed air trapped in the cylinders to the exhaust system. Thereby, the energy stored in the compressed gases during the compression stroke will not be returned to the crank shaft in the subsequent expansion stroke, which increases the braking torque of the engine. Some compression release engine brake arrangements comprise a hydraulic arrangement which actuates the valve actuator assembly by supplying a hydraulic pressure to the valve actuator assembly.

A general problem/concern when designing internal combustion engine is the fuel consumption of the engine. The emission levels of carbon dioxide are directly correlated with the fuel consumption of the engine and environmental concerns and fuel economy have been major concerns for decades. There are many ways of improving the fuel efficiency of an engine but many of these are also provided with drawbacks. Two ways of improving the fuel efficiency of an engine is to reduce the transfer of heat to walls of the combustion chamber and to increase the combustion heat release. Combustion heat release is a measure of burn rate, i.e. the rate at which the fuel is burning, and can be improved by increasing the mixing rate between air and the fuel, the compression ratio, and the like. The transfer of heat to walls of the combustion chamber and combustion heat release are normally conflicting requirements. That is, when increasing the combustion heat release, the transfer of heat to walls of the combustion chamber is normally increased, and vice versa.

Moreover, some ways of improving the fuel efficiency of an engine may have a negative impact on the durability and reliability of an engine. The durability and reliability of an engine are major concerns for vehicle manufacturers.

Furthermore, generally, on today’s consumer market, it is an advantage if products, such as vehicles and associated components, systems, and arrangements, comprise different features and functions while having conditions and/or characteristics suitable for being manufactured and assembled in a cost-efficient manner. SUMMARY

It is an object of the present invention to overcome, or at least alleviate, at least some of the above-mentioned problems and drawbacks.

According to a first aspect of the invention, the object is achieved by a method performed by a control arrangement for controlling a powertrain of a vehicle. The powertrain comprises a combustion engine. The combustion engine comprises a crankshaft, a cylinder, and a piston configured to reciprocate in the cylinder between a top dead centre and a bottom dead centre upon rotation of the crankshaft. The distance between a piston top of the piston and a cylinder head of the cylinder, when the combustion engine is at stand-still and the piston is positioned at the top dead centre, is smaller than 0.5% of a stroke length of the piston. The method comprises the steps of: monitoring a rotational speed of a crankshaft of the combustion engine, and if the rotational speed of the crankshaft exceeds a threshold speed, increasing the cylinder pressure at a gas exchanging phase of the cylinder, and restricting the rotational speed of the crankshaft.

Since the method comprises at least one of the steps of increasing the cylinder pressure at a gas exchanging phase of the cylinder and restricting the rotational speed of the crankshaft if the rotational speed of the crankshaft exceeds the threshold speed, a method is provided allowing for the small distance between the piston top of the piston and a cylinder head of the cylinder without risking damage of the piston/cylinder at higher rotational speeds of the crankshaft.

The distance between the piston top of the piston and the cylinder head of the cylinder, when the combustion engine is at stand-still and the piston is positioned at the top dead centre, is usually referred to as top clearance. Below, this distance between the piston top of the piston and the cylinder head of the cylinder is in some places referred to as “top clearance” for reasons of brevity and clarity.

Due to the small top clearance, the fuel efficiency of the combustion engine can be improved. This is because the transfer of heat to walls of the combustion chamber is reduced as compared to when using a larger top clearance. A further effect is that more freedom is provided in the design of a piston bowl of the piston, which also provides conditions for an improved fuel efficiency of the combustion engine. Moreover, the reduced transfer of heat to walls of the combustion chamber provides conditions for using an increased combustion heat release, which thus also provides conditions for an improved fuel efficiency and an improved performance of the combustion engine. Furthermore, due to the small top clearance, conditions are provided for an increased compression ratio which also provides conditions for an improved fuel efficiency of the combustion engine.

Studies have shown that the piston of an engine risks hitting the cylinder head of the cylinder at higher rotational speeds of the crankshaft if using a small top clearance, such as a top clearance in which the distance between a piston top of the piston and a cylinder head of the cylinder is smaller than 0.5% of a stroke length of the piston. This is due to the increased acceleration and mass forces of the piston at higher rotational speeds of the crankshaft.

Such impacts between the piston top and the cylinder head can cause severe mechanical damage to the combustion engine. The piston is most likely to hit the cylinder head in the transition area between the exhaust stroke and the inlet stroke, i.e. at top dead centre at a gas exchanging phase of the cylinder, because of the lower cylinder pressure at the gas exchanging phase as compared to when the piston is at top dead centre between the compression stroke and the expansion stroke.

However, as pointed out above, since the method comprises at least one of the steps of increasing the cylinder pressure at the gas exchanging phase of the cylinder and restricting the rotational speed of the crankshaft, a method is provided allowing for the small distance between the piston top of the piston and a cylinder head of the cylinder without risking damage of the piston/cylinder at higher rotational speeds of the crankshaft. The increased cylinder pressure at the gas exchanging phase of the cylinder can prevent an impact between the piston top and the cylinder head because the cylinder pressure can act as a damper slowing down the movement of the piston.

Furthermore, due to the features of the method, a cost-efficient method is provided capable of improving the fuel efficiency of the combustion engine in a manner circumventing the need for costly and complex additional arrangements and systems to be added to the combustion engine. In addition, a method is provided capable of utilizing already existing systems and arrangements of the powertrain for avoiding an impact between the piston top and the cylinder head of the combustion engine.

Accordingly, a method is provided overcoming, or at least alleviating, at least some of the above-mentioned problems and drawbacks. As a result, the above-mentioned object is achieved. The cylinder comprises at least one exhaust valve, and the method comprises the step of: increasing the cylinder pressure at the gas exchanging phase of the cylinder by controlling the at least one exhaust valve to assume an at least partially closed state during at least a portion of an exhaust stroke of the cylinder.

Thereby, an impact between the piston top and the cylinder head is avoided in a simple and efficient manner. This is because the controlling of the at least one exhaust valve to the at least partially closed state increases the cylinder pressure in a simple and efficient manner. The increased cylinder pressure thereby acts as a damper slowing down the movement of the piston which reduces the risk of an impact between the piston top and the cylinder head.

The step of increasing the cylinder pressure at the gas exchanging phase of the cylinder by controlling the at least one exhaust valve to assume the at least partially closed state comprises the step of: phase shifting control of the at least one exhaust valve.

Thereby, an impact between the piston top and the cylinder head is avoided in a simple and efficient manner. Moreover, a method is provided having conditions for utilizing already existing systems and arrangements of the combustion engine for avoiding an impact between the piston top and the cylinder head of the combustion engine, such as one or more phase shifting arrangements of the combustion engine.

The step of phase shifting control of the at least one exhaust valve comprises the step of: phase shifting control of the at least one exhaust valve such that the at least one exhaust valve opens during an expansion stroke of the cylinder and closes during an exhaust stroke of the cylinder.

Thereby, an impact between the piston top and the cylinder head is avoided in a simple and efficient manner. Moreover, a method is provided having conditions for utilizing already existing systems and arrangements of the combustion engine in a non-complex manner for avoiding an impact between the piston top and the cylinder head of the combustion engine, such as one or more phase shifting arrangements of the combustion engine.

Optionally, the method comprises the step of: controlling the at least one exhaust valve to an at least partially open state at a region of the top dead centre. Thereby, the energy stored in the compressed gases during the compression stroke will not be returned to the crank shaft in the subsequent expansion stroke, which increases the braking torque of the combustion engine. Furthermore, a phase shift of the control of the at least one exhaust valve can ensure that the movement of the piston towards the top dead centre is braked by an increased cylinder pressure before the at least one exhaust valve is controlled to the at least partially open state at the region of the top dead centre. Thus, a method is provided capable of braking the combustion engine in an efficient manner while reducing the risk of an impact between the piston top and the cylinder head.

Optionally, the cylinder comprises at least one inlet valve, and wherein the method comprises the step of: increasing the cylinder pressure at the gas exchanging phase of the cylinder by phase shifting control of the at least one inlet valve.

Thereby, an impact between the piston top and the cylinder head can be avoided in a simple and efficient manner. Moreover, a method is provided having conditions for utilizing already existing systems and arrangements of the combustion engine for avoiding an impact between the piston top and the cylinder head of the combustion engine, such as one or more phase shifting arrangements of the combustion engine.

Optionally, the step of increasing the cylinder pressure at the gas exchanging phase of the cylinder by phase shifting control of the at least one inlet valve comprises the step of: phase shifting control of the at least one inlet valve such that the at least one inlet valve opens during an inlet stroke of the cylinder and closes during a compression stroke of the cylinder.

Thereby, an impact between the piston top and the cylinder head can be further avoided in a simple and efficient manner. Moreover, a method is provided having conditions for utilizing already existing systems and arrangements of the combustion engine in a non-complex manner for avoiding an impact between the piston top and the cylinder head of the combustion engine, such as one or more phase shifting arrangements of the combustion engine. Moreover, a further increased braking torque can be applied to the crankshaft of the combustion engine while avoiding an impact between the piston top and the cylinder head of the combustion engine. This is because a so called two-stroke compression release braking can be obtained in which a compression of gas is obtained in the expansion stroke as well as in the compression stroke which then is released at the respective top dead centre so as to not return the energy of the compressed gas to the crankshaft of the combustion engine. In this manner, the combustion engine can be braked in an efficient and secure manner.

Optionally, the combustion engine comprises an exhaust conduit, and wherein the method comprises the step of: increasing the cylinder pressure at the gas exchanging phase of the cylinder by increasing the exhaust back pressure in the exhaust conduit.

Thereby, an efficient method is provided for avoiding an impact between the piston top and the cylinder head. This is because the increased exhaust back pressure can act as a damper slowing down the movement of the piston so as to avoid an impact between the piston top and the cylinder head. Moreover, the increased exhaust back pressure can reduce the rotational speed of the crankshaft so as to reduce the risk of an impact between the piston top and the cylinder head. Moreover, a method is provided having conditions for utilizing already existing systems and arrangements of the powertrain for avoiding an impact between the piston top and the cylinder head of the combustion engine, such as one or more of an exhaust throttle, a turbo charger provided with controllable guide vanes, or the like.

Optionally, the method comprises the step of restricting the rotational speed of the crankshaft, and wherein the step of restricting the rotational speed of the crankshaft comprises at least one of the steps of: braking the combustion engine, braking the vehicle comprising the powertrain, and disconnecting the combustion engine from wheels of the vehicle comprising the powertrain.

Thereby, an efficient method is provided for avoiding an impact between the piston top and the cylinder head. This is because the reduced rotational speed of the crankshaft reduces the risk of an impact between the piston top and the cylinder head. Moreover, a method is provided having conditions for utilizing already existing systems and arrangements of the combustion engine for avoiding an impact between the piston top and the cylinder head of the combustion engine, such as for example wheel brakes, one or more retarder arrangements, one or more transmission brakes, one or more clutches, or the like.

Optionally, the powertrain comprises a transmission and wherein the method comprises the step of: restricting the rotational speed of the crankshaft by changing an effective gear ratio of the transmission.

Thereby, an efficient method is provided for avoiding an impact between the piston top and the cylinder head. This is because the reduced rotational speed of the crankshaft reduces the risk of an impact between the piston top and the cylinder head. Moreover, a method is provided having conditions for utilizing already existing systems and arrangements of the powertrain for avoiding an impact between the piston top and the cylinder head of the combustion engine, such as for example a gear selector of the transmission, or the like.

According to a second aspect of the invention, the object is achieved by a computer program comprising instructions which, when the program is executed by a computer, cause the computer to carry out the method according to some embodiments of the present disclosure. Since the computer program comprises instructions which, when the program is executed by a computer, cause the computer to carry out the method according to some embodiments described herein, a computer program is provided which provides conditions for overcoming, or at least alleviating, at least some of the above-mentioned drawbacks. As a result, the above-mentioned object is achieved.

According to a third aspect of the invention, the object is achieved by a computer-readable medium comprising instructions which, when executed by a computer, cause the computer to carry out the method according to some embodiments of the present disclosure. Since the computer-readable medium comprises instructions which, when the program is executed by a computer, cause the computer to carry out the method according to some embodiments described herein, a computer-readable medium is provided which provides conditions for overcoming, or at least alleviating, at least some of the above-mentioned drawbacks. As a result, the above-mentioned object is achieved.

According to a fourth aspect of the invention, the object is achieved by a control arrangement for a powertrain of a vehicle. The powertrain comprises a combustion engine. The combustion engine comprises a crankshaft, a cylinder, and a piston configured to reciprocate in the cylinder between a top dead centre and a bottom dead centre upon rotation of the crankshaft. The distance between a piston top of the piston and a cylinder head of the cylinder, when the combustion engine is at stand-still and the piston is positioned at the top dead centre, is smaller than 0.5% of a stroke length of the piston. The control arrangement is configured to: monitor a rotational speed of a crankshaft of the combustion engine, and if the rotational speed of the crankshaft exceeds a threshold speed, increase the cylinder pressure at a gas exchanging phase of the cylinder, and restrict the rotational speed of the crankshaft.

Since the control arrangement is configured to increase the cylinder pressure at a gas exchanging phase of the cylinder, and to restrict the rotational speed of the crankshaft, if the rotational speed of the crankshaft exceeds a threshold speed, a control arrangement is provided allowing for the small distance between the piston top of the piston and a cylinder head of the cylinder without risking damage of the piston/cylinder at higher rotational speeds of the crankshaft.

Due to the small top clearance, the fuel efficiency of the combustion engine can be improved. This is because the transfer of heat to walls of the combustion chamber is reduced as compared to when using a larger top clearance. A further effect is that more freedom is provided in the design of a piston bowl of the piston, which also provides conditions for an improved fuel efficiency of the combustion engine. Moreover, the reduced transfer of heat to walls of the combustion chamber provides conditions for using an increased combustion heat release, which thus also provides conditions for an improved fuel efficiency and an improved performance of the combustion engine. Furthermore, due to the small top clearance, conditions are provided for an increased compression ratio which also provides conditions for an improved fuel efficiency of the combustion engine.

Studies have shown that the piston of an engine risks hitting the cylinder head of the cylinder at higher rotational speeds of the crankshaft if using a small top clearance, such as a top clearance in which the distance between a piston top of the piston and a cylinder head of the cylinder is smaller than 0.5% of a stroke length of the piston. However, as pointed out above, since the control arrangement is configured to increase the cylinder pressure at a gas exchanging phase of the cylinder, and to restrict the rotational speed of the crankshaft, if the rotational speed of the crankshaft exceeds a threshold speed, a control arrangement is provided allowing for the small distance between the piston top of the piston and a cylinder head of the cylinder without risking damage of the piston/cylinder at higher rotational speeds of the crankshaft. The increased cylinder pressure at the gas exchanging phase of the cylinder can prevent an impact between the piston top and the cylinder head because the cylinder pressure can act as a damper slowing down the movement of the piston. Furthermore, a control arrangement is provided capable of improving the fuel efficiency of the combustion engine in a cost-efficient manner circumventing the need for costly and complex additional arrangements and systems to be added to the combustion engine. In addition, a control arrangement is provided capable of utilizing already existing systems and arrangements of the powertrain for avoiding an impact between the piston top and the cylinder head of the combustion engine.

Accordingly, a control arrangement is provided overcoming, or at least alleviating, at least some of the above-mentioned problems and drawbacks. As a result, the above-mentioned object is achieved.

It will be appreciated that the various embodiments described for the method are all combinable with the control arrangement as described herein. That is, the control arrangement according to the fourth aspect of the invention may be configured to perform any one of the method steps of the method according to the first aspect of the invention.

According to a fifth aspect of the invention, the object is achieved by a powertrain for a vehicle. The powertrain comprises a combustion engine. The combustion engine comprises a crankshaft, a cylinder, and a piston configured to reciprocate in the cylinder between a top dead centre and a bottom dead centre upon rotation of the crankshaft. The distance between a piston top of the piston and a cylinder head of the cylinder, when the combustion engine is at stand-still and the piston is positioned at the top dead centre, is smaller than 0.5% of a stroke length of the piston. The powertrain comprises a control arrangement configured to: monitor a rotational speed of a crankshaft of the combustion engine, and if the rotational speed of the crankshaft exceeds a threshold speed, increase the cylinder pressure at a gas exchanging phase of the cylinder, and restrict the rotational speed of the crankshaft.

Since the powertrain comprises a control arrangement configured to increase the cylinder pressure at a gas exchanging phase of the cylinder, and to restrict the rotational speed of the crankshaft, if the rotational speed of the crankshaft exceeds a threshold speed, a powertrain is provided allowing for the small distance between the piston top of the piston and a cylinder head of the cylinder of the combustion engine without risking damage of the piston/cylinder at higher rotational speeds of the crankshaft.

Due to the small top clearance, the fuel efficiency of the combustion engine of the powertrain can be improved. This is because the transfer of heat to walls of the combustion chamber is reduced as compared to when using a larger top clearance. A further effect is that more freedom is provided in the design of a piston bowl of the piston, which also provides conditions for an improved fuel efficiency of the combustion engine. Moreover, the reduced transfer of heat to walls of the combustion chamber provides conditions for using an increased combustion heat release, which thus also provides conditions for an improved fuel efficiency and an improved performance of the combustion engine. Furthermore, due to the small top clearance, conditions are provided for an increased compression ratio which also provides conditions for an improved fuel efficiency of the combustion engine.

Studies have shown that the piston of an engine risks hitting the cylinder head of the cylinder at higher rotational speeds of the crankshaft if using a small top clearance, such as a top clearance in which the distance between a piston top of the piston and a cylinder head of the cylinder is smaller than 0.5% of a stroke length of the piston. However, as pointed out above, since the control arrangement of the powertrain is configured to increase the cylinder pressure at a gas exchanging phase of the cylinder, and to restrict the rotational speed of the crankshaft, if the rotational speed of the crankshaft exceeds a threshold speed, a control arrangement is provided allowing for the small distance between the piston top of the piston and a cylinder head of the cylinder without risking damage of the piston/cylinder at higher rotational speeds of the crankshaft. The increased cylinder pressure at the gas exchanging phase of the cylinder can prevent an impact between the piston top and the cylinder head because the cylinder pressure can act as a damper slowing down the movement of the piston.

Furthermore, a powertrain is provided having conditions for an improved fuel efficiency of the combustion engine in a cost-efficient manner circumventing the need for costly and complex additional arrangements and systems to be added to the powertrain. In addition, a powertrain is provided capable of utilizing already existing systems and arrangements of the powertrain for avoiding an impact between the piston top and the cylinder head of the combustion engine.

Accordingly, a powertrain is provided overcoming, or at least alleviating, at least some of the above-mentioned problems and drawbacks. As a result, the above-mentioned object is achieved.

It will be appreciated that the various embodiments described for the method are all combinable with the control arrangement as described herein. That is, the control arrangement of the powertrain according to the fifth aspect of the invention may be configured to perform any one of the method steps of the method according to the first aspect of the invention.

According to a sixth aspect of the invention, the object is achieved by a vehicle comprising a powertrain according to some embodiments of the present disclosure. Since the vehicle comprises a powertrain according to some embodiments, a vehicle is provided having conditions for overcoming, or at least alleviating, at least some of the above-mentioned drawbacks. As a result, the above-mentioned object is achieved.

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

BRIEF DESCRIPTION OF THE DRAWINGS

Various aspects of the invention, including its particular features and advantages, will be readily understood from the example embodiments discussed in the following detailed description and the accompanying drawings, in which:

Fig. 1 illustrates a vehicle according to some embodiments,

Fig. 2 schematically illustrates a powertrain of the vehicle illustrated in Fig. 1 ,

Fig. 3 schematically illustrates a cross sectional view of a combustion engine of the powertrain illustrated in Fig. 2,

Fig. 4 illustrates a perspective view of a piston of the combustion engine illustrated in Fig. 2 and Fig. 3,

Fig. 5a illustrates valve lift events of at least one inlet valve, and valve lift events of at least one exhaust valve, during operation of the combustion engine illustrated in Fig. 2 and Fig. 3 in a first rotational speed range of a crankshaft of the combustion engine,

Fig. 5b illustrates valve lift events of the at least one inlet valve and valve lift events of the at least one exhaust valve, during operation of the combustion engine illustrated in Fig. 2 and Fig. 3 in a second rotational speed range of the crankshaft of the combustion engine, Fig. 6 illustrates a method of controlling a powertrain of a vehicle, and Fig. 7 illustrates a computer-readable medium.

DETAILED DESCRIPTION

Aspects of the present invention will now be described more fully. Like numbers refer to like elements throughout. Well-known functions or constructions will not necessarily be described in detail for brevity and/or clarity. Fig. 1 illustrates a vehicle 40 according to some embodiments. According to the illustrated embodiments, the vehicle 40 is a truck, i.e. a type of heavy vehicle. According to further embodiments, the vehicle 40, as referred to herein, may be another type of heavy or lighter type of manned or unmanned vehicle for land or water based propulsion such as a lorry, a bus, a construction vehicle, a tractor, a car, a ship, a boat, or the like.

The vehicle 40 comprises a powertrain 2. According to the illustrated embodiments, the powertrain 2 is configured to provide motive power to the vehicle 40 via wheels 47 of the vehicle 40.

Fig. 2 schematically illustrates the powertrain 2 of the vehicle 40 illustrated in Fig. 1. The powertrain 2 comprises an internal combustion engine 1. The internal combustion engine 1 is in some places herein referred to as the “combustion engine 1”, or simply “the engine 1”, for reasons of brevity and clarity. Below, simultaneous reference is made to Fig. 1 and Fig. 2, if not indicated otherwise. According to the illustrated embodiments, the powertrain 2 comprises a transmission 4 configured to transmit torque between the combustion engine 1 and wheels 47 of the vehicle 40. Moreover, the powertrain 2 comprises a clutch 46 allowing a disconnection of the combustion engine 1 from the wheels 47 of the vehicle 40.

As understood from the herein described, according to the illustrated embodiments, the internal combustion engine 1 of the powertrain 2 is configured to provide motive power to the vehicle 40 via wheels 47 of the vehicle. The powertrain 2 may comprise one or more electric propulsion motors in addition to the internal combustion engine 1 for providing motive power to the vehicle. Thus, the vehicle 40, as referred to herein, may comprise a so called hybrid electric powertrain comprising one or more electric propulsion motors in addition to the combustion engine 1 for providing motive power to the vehicle 40.

According to the illustrated embodiments, the internal combustion engine 1 comprises six cylinders 10 arranged in one row. The internal combustion engine 1 according to the illustrated embodiments may therefore be referred to an inline-six engine. However, according to further embodiments, the internal combustion engine 1 , as referred to herein, may comprise another number of cylinders 10. Moreover, the cylinders 10 of the internal combustion engine 1 may be arranged in another configuration than in one row, such as in two or more rows.

According to the illustrated embodiments, the combustion engine 1 comprises one fuel injector 31 per cylinder 10 wherein each fuel injector 31 is configured to inject fuel directly into a cylinder 10 of the combustion engine 1. According to further embodiments, the combustion engine 1 may comprise another number of fuel injectors 31 per cylinder 10. Moreover, according to some embodiments, the combustion engine 1 may comprise one or more fuel injectors configured to inject fuel into an air inlet of the combustion engine 1 as an alternative to fuel injectors 31 configured to inject fuel into the cylinders 10 or in addition to the fuel injectors 31 configured to inject fuel into the cylinders 10.

According to embodiments herein, the internal combustion engine 1 is a four-stroke internal combustion engine 1. Moreover, according to the illustrated embodiments, the internal combustion engine 1 is a diesel engine, i.e. a type of compression ignition engine. The internal combustion engine 1 may thus be configured to operate on diesel or a diesel-like fuel, such as biodiesel, biomass to liquid (BTL), or gas to liquid (GTL) diesel. Diesel-like fuels, such as biodiesel, can be obtained from renewable sources such as vegetable oil which mainly comprises fatty acid methyl esters (FAME). Diesel-like fuels can be produced from many types of oils, such as rapeseed oil (rapeseed methyl ester, RME) and soybean oil (soy methyl ester, SME).

According to further embodiments, the internal combustion engine 1 , as referred to herein, may an Otto engine with a spark-ignition device, wherein the Otto engine may be configured to run on petrol, alcohol, similar volatile fuels, or combinations thereof. Alcohol, such as ethanol, can be derived from renewable biomass.

Fig. 3 schematically illustrates a cross sectional view of the internal combustion engine 1 illustrated in Fig. 2. In Fig. 3, the cross section is made in a plane comprising a centre axis of one of the cylinders 10 of the combustion engine 1. The combustion engine 1 comprises at least one cylinder 10 and a piston 12 arranged in each cylinder 10. The piston 12 is connected, via a connecting rod 13 to a crankshaft 16, which at rotation moves the piston 12 forwards and backwards in the cylinder 10, between a top dead centre TDC and a bottom dead centre BDC.

The combustion engine 1 comprises an inlet system 14, which in the illustrated example engine is illustrated as an inlet duct. The inlet system 14 may further comprise an air filter, and according to some embodiments a throttle, a fuel injector, an air flow sensor, and the like. Moreover, the combustion engine 1 may comprise a turbocharger arranged to compress air to the inlet system 14 of the combustion engine 1. Thus, according to such embodiments, the inlet system 14 may be fluidically connected to a compressor of a turbocharger. The compressor may be connected to a shaft which is connected to a turbine of the turbocharger. The turbine may be arranged to be driven by the flow of gases from an exhaust outlet 26 of the combustion engine 1. The combustion engine 1 may comprise more than one turbocharger, wherein the turbochargers may be arranged in parallel or on series.

The combustion engine 1 further comprises at least one inlet valve 18 arranged in each cylinder 10, which at least one inlet valve 18 is connected with the inlet system 14. The combustion engine 1 further comprises an inlet valve control arrangement 22 configured to control each inlet valve 18 on the basis of a rotational position of the crankshaft 16. The combustion engine 1 further comprises at least one exhaust valve 24 arranged in each cylinder 10, which at least one exhaust valve 24 is connected with an exhaust outlet 26 of the combustion engine 1. The combustion engine 1 further comprises an exhaust valve control arrangement 28 configured to control each exhaust valve 24 on the basis of the rotational position of the crankshaft 16. In Fig. 3, the inlet valve 18 and the exhaust valve 24 are illustrated in a respective closed position. In a closed position, each valve 18, 24 abuts against a respective valve seat to close a fluid connection between the cylinder 10 and the respective inlet system 14 and the exhaust outlet 26.

The inlet valve control arrangement 22 is arranged to control the at least one inlet valve 18 between the closed position and an open position by displacing the at least one inlet valve 18 in a direction into the cylinder 10. A fluid connection is thereby opened between the inlet 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 to an open position by displacing the at least one exhaust valve 24 in a direction into the cylinder 10. Thereby, a fluid connection is opened between the cylinder 10 and the exhaust outlet 26. Upon displacement of a valve 18, 24 from the closed position to the open position, the valve 18, 24 is lifted from its valve seat.

The combustion engine 1 further comprises a fuel injector 31 arranged to directly inject fuel into the cylinder 10. As mentioned above, according to the illustrated embodiments, the combustion engine 1 is a diesel engine, i.e. a type of compression ignition engine. According to further embodiments, the combustion engine may be an Otto engine with a spark-ignition device, wherein the Otto engine may be designed to run on gas, petrol, alcohol or similar volatile fuels or combinations thereof. Such fuel may be directly injected into the cylinder 10 using a fuel injector or may be supplied to incoming air prior to entering the cylinder 10, for example by a fuel injector arranged at an inlet duct of the combustion engine. The combustion engine 1 may comprise an exhaust after treatment system. The exhaust after treatment system may comprise one or more of a catalytic converter, a particulate filter, a Selective catalytic reduction (SCR) arrangement, a Diesel Oxidation Catalyst (DOC), a Lean NOx Trap (LNT) and a Three-Way Catalyst (TWC).

The exhaust valve control arrangement 28 and the inlet valve control arrangement 22 may each comprise one or more camshafts 71 , 72 rotatably connected to the crankshaft 16 of the combustion engine 1. Moreover, the exhaust valve control arrangement 28 and the inlet valve control arrangement 22 may each comprise one or more arrangements, such as rocker arms 73, 74, for transferring movement of cam lobes of the camshafts 71 , 72 to valve stems of the valves 18, 24 to an open position upon rotation of the respective camshaft 71, 72. According to further embodiments, the cam lobes of the camshafts 71 , 72 of the combustion engine 1 may be arranged to displace valves 18, 24 to an open position by pressing onto valve stems of the valves 18, 24 upon rotation of the respective camshaft 71 , 72.

The exhaust valve control arrangement 28 and/or the inlet valve control arrangement 22 may according to further embodiments comprise electric, pneumatic, or hydraulic actuators arranged to control valves on the basis of the rotational position of the crankshaft 16. The rotational position of the crankshaft 16 may be obtained using a crank angle sensor 29.

The exhaust valve control arrangement 28 comprises an exhaust valve phase-shifting device 30 configured to phase-shift control of the at least one exhaust valve 24 in relation to the crankshaft 16. Moreover, according to the illustrated embodiments, the inlet valve control arrangement 22 comprises an inlet valve phase-shifting device 32 configured to phase-shift control of the at least one inlet valve 18 in relation to the crankshaft 16.

The exhaust valve phase-shifting device 30 and the inlet valve phase-shifting device 32 may each comprise a hydraulic arrangement, for example using engine oil as hydraulic fluid, to phase-shift control of the valves 18, 24 in relation to the crankshaft 16. Such hydraulic arrangement may form part of a belt pulley, gearwheel, sprocket, or the like (not illustrated) arranged to transfer rotation from the crankshaft 16 to a camshaft 71 , 72 of the exhaust valve control arrangement 28 and/or of the inlet valve control arrangement 22. The hydraulic arrangement may be arranged to regulate an angular relationship between a first portion of the belt pulley, gearwheel, sprocket, or the like, being connected to the crankshaft 16, and a second portion of the belt pulley, gearwheel, sprocket, or the like, being connected to the camshaft 71 , 72, in order to phase-shift control of the at least one inlet valve 18 and/or the at least one exhaust valve 24. In embodiments wherein the exhaust valve control arrangement 28 and/or the inlet valve control arrangement 22 comprises electric, pneumatic, or hydraulic actuators, the phase-shift of control of the at least one inlet valve 18 and/or the at least one exhaust valve 24 may be performed in another manner, for example by an electronic phaseshift of control.

The combustion engine 1 is provided with a small top clearance between a piston top 12’ of the piston 12 and a cylinder head 10’ of the cylinder 10. The top clearance can be defined as the distance d between a piston top 12’ of the piston 12 and a cylinder head 10’ of the cylinder 10 when the combustion engine 1 is at stand-still and the piston 12 is positioned at the top dead centre TDC, wherein the distance d is measured in a direction parallel to moving directions d1 , d2 of the piston 12 in the cylinder 12 upon movement of the piston between the top dead centre TDC and the bottom dead centre BDC.

In Fig. 3, the piston 12 is illustrated as positioned in the top dead centre TDC. The distance d between the piston top 12’ of the piston 12 and the cylinder head 10’ of the cylinder 10 at the top dead centre TDC varies with the rotational speed of the crankshaft 16 and is normally reduced with increasing rotational speeds of the crankshaft 16, especially at a gas exchanging phase of the cylinder 10 in which one or both of the inlet and exhaust valve 18, 24 is in an open state. This is because the cylinder pressure, i.e. the pressure in the cylinder 10, is significantly lower in a gas exchanging phase of the cylinder 10 as compared to a nongas exchanging phase, such as an inlet or exhaust stroke of the cylinder 10 or a transition area therebetween. The increased cylinder pressure in such strokes/areas opposes the upward movement of the piston 12 which can ensure that the piston 12 does not hit the cylinder head 10’ of the cylinder 10 in the non-gas exchanging phase.

Fig. 4 illustrates a perspective view of a piston 12 of the combustion engine 1 illustrated in Fig. 2 and Fig. 3. As clearly seen in Fig. 4, the piston 12 comprises a piston bowl 52 at the piston top 12’ of the piston 12. The fuel injector 31 of the cylinder 10, which is schematically illustrated in Fig. 3, may protrude into the piston bowl 52 when the piston 12 is at the top dead centre TDC. Below, simultaneous reference is made to Fig. 1 - Fig. 4, if not indicated otherwise. The cylinder head 10’ of the cylinder 10 may comprise irregularities. However, the distance d between the piston top 12’ of the piston 12 and the cylinder head 10’ of the cylinder 10 may be defined as the smallest distance d between the piston top 12’ of the piston 12 and the cylinder head 10’ of the cylinder 10 when the combustion engine 1 is at stand-still and the piston 12 is positioned at the top dead centre TDC. According to the illustrated example, the smallest distance d is a distance between a surface of the piston top 12’ surrounding the piston bowl 52 of the piston 12 an a substantially flat surface of the cylinder head 10’ of the cylinder 10. The stroke length L of the piston 12 can be defined as the length of the movement of the piston 12 between the top dead centre TDC and the bottom dead centre BDC in an unloaded state of the combustion engine 1. The stroke length L thus corresponds to the distance between a portion of the piston 12, such as the piston top 12’ of the piston 12, when the piston 12 is positioned at the top dead centre TDC and the portion of the piston 12 when the piston 12 is positioned at the bottom dead centre BDC. In Fig. 3, a portion 13’ of the connection rod 13 is schematically illustrated in dashed lines at a position corresponding to when the piston 12 is at the bottom dead centre BDC. The connecting rod 13 is connected to the crankshaft 16 around a rotation axis ax indicated in Fig. 3. As can be seen in Fig. 3, the stroke length L of the piston 12 can also be measured by measuring the distance between the rotation axis ax when the piston 12 is at the top dead centre TDC and the rotation axis ax’ when the piston 12 is at the bottom dead centre BDC.

According to embodiments herein, the distance d between a piston top 12’ of the piston 12 and the cylinder head 10’ of the cylinder 10, when the combustion engine 1 is at stand-still and the piston 12 is positioned at the top dead centre TDC, is smaller than 0.5% of the stroke length L of the piston 12.

This small distance d between the piston top 12’ of the piston 12 and the cylinder head 10’ of the cylinder 10 provides conditions for a fuel efficient combustion engine 1. This is because the transfer of heat to walls of the combustion chamber is reduced as compared to when using a larger top clearance. A further effect is that a relatively small gap is provided between the piston top 12’ of the piston 12 surrounding the piston bowl 52 and the cylinder head 10’ of the cylinder 10 when the piston 12 is at the top dead centre TDC, which provides advantageous combustion properties in the cylinder 10 and a reduced transfer of heat to walls of the combustion chamber. A still further effect is that more freedom is provided in the design of the 52 piston bowl of the piston 12, which also provides conditions for an improved fuel efficiency of the combustion engine 1. Moreover, the reduced transfer of heat to walls of the combustion chamber provides conditions for using an increased combustion heat release, which thus also provides conditions for an improved fuel efficiency and an improved performance of the combustion engine 1. In addition, the small distance d between the piston top 12’ of the piston 12 and the cylinder head 10’ of the cylinder 10 provides conditions for an increased compression ratio which also provides conditions for an improved fuel efficiency of the combustion engine 1.

However, this small distance d between the piston top 12’ of the piston 12 and the cylinder head 10’ of the cylinder 10 may also cause an impact between the piston top 12’ of the piston and the cylinder head 10’ of the cylinder 10, especially in gas exchanging phases of the cylinder 10. The term “combustion chamber”, as used herein, is intended to encompass a chamber delimited by surfaces, in which chamber combustion is occurring in the combustion engine 1, such as surfaces of the cylinder 10, surfaces of the cylinder head 10’, and surfaces of the piston top 12’ of the piston 12.

As indicated in Fig. 2 and Fig. 3, the powertrain 2 comprises a control arrangement 21. In the example embodiments illustrated in Fig. 2, the control arrangement 21 is operably connected to the combustion engine 1, to the clutch 46, to a gear selector unit 54 of the transmission 4, to a retarder arrangement 36, and to wheel brakes 56 of the vehicle 40. According to further embodiments, the control arrangement 21 may be operably connected to one or more of the components/systems illustrated in Fig. 2, and/or to one or more other types of components/systems of the powertrain 2 or of the vehicle 40 comprising the powertrain 2.

In the example embodiments illustrated in Fig. 3, the control arrangement 21 is operably connected to the crank angle sensor 29, the exhaust valve phase-shifting device 30, the inlet valve phase-shifting device 32, and a lost motion arrangement 75 of the combustion engine 1. The lost motion arrangement 75 is explained in more detail below. The control arrangement 21 may be operably connected to one or more further components and systems of the combustion engine 1, such as the inlet valve control arrangement 22 and the exhaust valve control arrangement 28 and may be configured to control operation thereof. Furthermore, the control arrangement 21 may be connected to a number of different sensors to obtain signals therefrom. Examples are sensors arranged to sense exhaust pressure, charge air temperature, mass airflow, throttle position, engine speed, engine load, absolute pressure in an inlet manifold, rotational position of the crank shaft 16, etc.

According to embodiments herein, the control arrangement 21 is configured to: monitor a rotational speed of the crankshaft 16 of the combustion engine 1, and if the rotational speed of the crankshaft 16 exceeds a threshold speed, increase the cylinder pressure at a gas exchanging phase of the cylinder 10, and restrict the rotational speed of the crankshaft 16.

The control arrangement 21 may monitor the rotational speed of the crankshaft 16 of the combustion engine 1 by inputting data from the crank angle sensor 29. Alternatively, the control arrangement 21 may monitor the rotational speed of the crankshaft 16 of the combustion engine 1 in another manner, such as for example by inputting data from another type of device or system, such as an ignition system of the combustion engine 1 , or the like.

Fig. 5a illustrates valve lift events 51 of the at least one inlet valve 18, and valve lift events 52 of the at least one exhaust valve 24, during normal operation of the combustion engine 1 illustrated in Fig. 2 and Fig. 3 in a first rotational speed range of the crankshaft 16 of the combustion engine 1. Below, simultaneous reference is made to Fig. 1 - Fig. 5a, if not indicated otherwise. Purely as an example, the first rotational speed range may be 500 - 2 800 revolutions per minute. The curves illustrated in Fig. 5a illustrate valve lift events performed during two revolutions of the crank shaft 16, i.e. during all four strokes of the four- stroke internal combustion engine 1. In these figures, the strokes are illustrated in the following order: compression stroke 41, expansion stroke 42, exhaust stroke 43 and inlet stroke 44.

As indicated in Fig. 5a, during the compression stroke 41 and the expansion stroke 42, the at least one inlet valve 18 and the at least one exhaust valve 24 are closed. When the piston reaches the bottom dead centre 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 area between the exhaust stroke 43 and the inlet stroke 44, the exhaust valve control arrangement 28 controls the at least one exhaust valve 24 to a closed position.

Moreover, in the transition area between the exhaust stroke 43 and the inlet stroke 44, the inlet valve control arrangement 22 controls the at least one inlet valve 18 to an open position to allow air, or an air/fuel mixture, to enter the cylinder 10 during the inlet stroke 44. Towards the end of the inlet stroke 44, the inlet valve control arrangement 22 controls the at least one inlet valve 18 to a closed position to allow compression of the air, or the air/fuel mixture, in the subsequent compression stroke 41. The valve lift events 51 of the at least one inlet valve 18 and the valve lift events 52 of the at least one exhaust valve 24 illustrated in Fig. 5a may be maintained during normal engine braking of the combustion engine 1, occurring for example when a driver of a vehicle releases an accelerator pedal and no additional braking torque is requested.

According to some embodiments of the present disclosure, the control arrangement 21 is configured to increase the cylinder pressure at the gas exchanging phase of the cylinder 10 by controlling the at least one exhaust valve 24 to assume an at least partially closed state during at least a portion of an exhaust stroke 43 of the cylinder 10.

Fig. 5b illustrates valve lift events 51 of the at least one inlet valve 18 and valve lift events 52 of the at least one exhaust valve 24, during operation of the combustion engine 1 illustrated in Fig. 2 and Fig. 3 in a second rotational speed range of the crankshaft 16 of the combustion engine 1. Below, simultaneous reference is made to Fig. 1 - Fig. 5a, if not indicated otherwise. The second rotational speed range of the crankshaft 16 is higher than the first rotational speed range. In the illustrated example, the threshold speed of the crankshaft 16, separating the second rotational speed range from the first rotational speed range of the crankshaft 16 of the combustion engine 1 is 2 800 revolutions per minute.

According to the embodiments illustrated in Fig. 5b, the control arrangement 21 is configured to increase the cylinder pressure at the gas exchanging phase of the cylinder 10 by controlling the at least one exhaust valve 24 to assume an at least partially closed state during at least a portion of an exhaust stroke 43 of the cylinder 10 if the rotational speed of the crankshaft 16 exceeds the threshold speed.

In Fig. 5b, a closing event 62’ of the at least one exhaust valve 24 is indicated. The at least one exhaust valve 24 assumes a closed state at the closing event 62’. As can be seen in Fig. 5b, the closing event 62’ occurs in the exhaust stroke 43 of the cylinder 10 before the piston is reaching the top dead centre TDC. In this manner, an increased pressure in the cylinder 10 is obtained which opposes the upward movement of the piston 12 and thereby reduces the risk of an impact between the piston top 12’ of the piston 12 and the cylinder head 10’ of the cylinder 10.

According to the illustrated embodiments, the control arrangement 21 is configured to increase the cylinder pressure at the gas exchanging phase of the cylinder 10 by controlling the at least one exhaust valve 24 to assume the at least partially closed state by phase shifting control of the at least one exhaust valve 24. That is, as indicated in Fig. 3, the control arrangement 21 is operably connected to the exhaust valve phase-shifting device 30 and is configured to control operation thereof. Thus, according to these embodiments, the control arrangement 21 is configured to, if the rotational speed of the crankshaft 16 exceeds the threshold speed, cause the exhaust valve phase-shifting device 30 to increase the cylinder pressure at the gas exchanging phase of the cylinder 10 by controlling the at least one exhaust valve 24 to assume the at least partially closed state by phase shifting control of the at least one exhaust valve 24. Moreover, as seen in Fig. 5b, the control arrangement 21 is configured to phase shifting control of the at least one exhaust valve 24 such that the at least one exhaust valve 24 opens during an expansion stroke 42 of the cylinder 10 and closes during an exhaust stroke 43 of the cylinder 10. In Fig. 5b, the opening event of the at least one exhaust valve 24 in the expansion stroke 42 of the cylinder 10 has been provided with the reference sign “62”.

In the illustrated embodiments, the control arrangement 21 is configured to phase shift control of the at least one exhaust valve 24 such that the control of the at least one exhaust valve 24 is advanced as compared to when the rotational speed of the crankshaft 16 is below the threshold speed. In the illustrated example, the control arrangement 21 is configured to phase shift control of the at least one exhaust valve 24 such that the control of the at least one exhaust valve 24 is advanced approximately 87 crank angle degrees when the rotational speed of the crankshaft 16 exceeds the threshold speed. However, the control arrangement 21 may be configured to phase shift control of the at least one exhaust valve 24 such that the control of the at least one exhaust valve 24 is advanced 7 - 120 crank angle degrees, or 10 - 95 crank angle degrees, when the rotational speed of the crankshaft 16 exceeds the threshold speed.

According to some embodiments, the control arrangement 21 is configured to control the at least one exhaust valve 24 to an at least partially open state at a region of the top dead centre TDC when it is detected that the rotational speed of the crankshaft 16 exceeds the threshold speed. Such valve lift events have been provided with the reference sign “63” in Fig. 5b. As is further explained herein, due to these valve lift events 63, the combustion engine 1 is braked in an efficient manner so as to limit/reduce the rotational speed of the crankshaft 16.

As can be seen in Fig. 3, the camshaft 72 of the exhaust valve control arrangement 28 has been provided with an additional cam lobe 72’. Moreover, as indicated above, the exhaust valve control arrangement 28 comprises a lost motion arrangement 75. The lost motion arrangement 75 is configured such that it does not transfer movement caused by the additional cam lobe 72’ to the at least one exhaust valve 24 when the lost motion arrangement 75 is not activated. However, when activated, the lost motion arrangement 75 is configured to transfer movement caused by the additional cam lobe 72’ to the at least one exhaust valve 24 to thereby cause the valve lift events 63 illustrated in Fig. 5b. The lost motion arrangement 75 may by of hydraulic type and may comprise a hydraulic chamber and at least one valve, wherein the lost motion arrangement 75 is activated by closing the at least one valve and is deactivated by opening the at least one valve. These components are not illustrated in Fig. 3 for reasons of brevity and clarity. Moreover, according to further embodiments, the combustion engine 1 may comprise another type of lost motion arrangement than a hydraulic lost motion arrangement.

Due to the valve lift events 63, the rotational speed of the crankshaft 16 is limited/reduced in an efficient manner because the energy in compressed gasses obtained during an upward movement of the piston 12 is not returned to the crankshaft 16. Still, the increased cylinder pressure obtained by the phase shifting of the control of the at least one exhaust valve 24 and of the at least one inlet valve 18 can oppose the upward movement of the piston 12 before the opening of the at least one exhaust valve 24 caused by the valve lift events 63. Thereby, the risk of an impact between the piston top 12’ of the piston 12 and the cylinder head 10’ of the cylinder 10 is reduced.

According to some embodiments of the present disclosure, the control arrangement 21 is configured to increase the cylinder pressure at the gas exchanging phase of the cylinder 10 by phase shifting control of the at least one inlet valve 18. That is, as indicated in Fig. 3, the control arrangement 21 is operably connected to the inlet valve phase-shifting device 32 and is configured to control operation thereof. Thus, according to these embodiments, the control arrangement 21 is configured to, if the rotational speed of the crankshaft 16 exceeds the threshold speed, cause the inlet valve phase-shifting device 32 to increase the cylinder pressure at the gas exchanging phase of the cylinder 10 by phase shifting control of the at least one inlet valve 18 such that the at least one inlet valve 18 opens during an inlet stroke 44 of the cylinder 10 and closes during a compression stroke 41 of the cylinder 10. In Fig. 5b, the opening event of the at least one inlet valve 18 in the inlet stroke 44 of the cylinder 10 has been provided with the reference sign “61” and the closing event of the at least one inlet valve 18 in the compression stroke 41 of the cylinder 10 has been provided with the reference sign “6T”.

In the illustrated embodiments, the control arrangement 21 is configured to phase shift control of the at least one inlet valve 18 such that the control of the at least one inlet valve 18 is retarded as compared to when the rotational speed of the crankshaft 16 is below the threshold speed. In the illustrated example, the control arrangement 21 is configured to phase shift control of the at least one inlet valve 18 such that the control of the at least one inlet valve 18 is retarded approximately 81 crank angle degrees when the rotational speed of the crankshaft 16 exceeds the threshold speed. However, the control arrangement 21 may be configured to phase shift control of the at least one inlet valve 18 such that the control of the at least one inlet valve 18 is retarded 7 - 120 crank angle degrees, or 10 - 95 crank angle degrees, when the rotational speed of the crankshaft 16 exceeds the threshold speed.

As a result thereof, the at least one inlet valve 18 is not opened before top dead centre TDC, or at a region of the top dead centre TDC, between the exhaust stroke 43 and the inlet stroke 44, as is the case when the combustion engine 1 is operating at a rotational speed below the threshold speed as indicated in Fig. 5a. The cylinder pressure at the gas exchanging phase of the cylinder 10 is increased by the phase shift of the control of the at least one inlet valve 18 because the control of the at least one exhaust valve 24 is advanced as compared to when the rotational speed of the crankshaft 16 is below the threshold speed. Thereby, the cylinder pressure obtained during at least a portion of the exhaust stroke 43 can be maintained in at least a portion of the following inlet stroke 44. As a result, the risk of an impact between the piston top 12’ of the piston 12 and the cylinder head 10’ of the cylinder 10 can be reduced.

Furthermore, by retarding the control of the at least one inlet valve 18 a number of crank angle degrees within one of the above given ranges, it can be ensured that the closing event 6T of the at least one inlet valve 18 occurs in the compression stroke 41 so as to obtain compression of gas in the cylinder 10 during at least a portion of the compression stroke 41.

In addition, when combined with the opening of the at least one exhaust valve 24 at a region of the top dead centre TDC, indicated with the opening events 63 in Fig. 5b, a further increased braking torque can be obtained onto the crankshaft 16 of the combustion engine 1 while avoiding an impact between the piston top 12’ of the piston 12 and the cylinder head 10’ of the cylinder 10 by the phase shifting of the control of the at least one exhaust valve 24 and of the at least one inlet valve 18. The braking torque can be further increased because a so called two-stroke compression release braking can be obtained in which a compression of gas is obtained in the expansion stroke 43 as well as in the compression stroke 41 which then is released at the respective top dead centre TDC so as to not return the energy of the compressed gas to the crankshaft 16 of the combustion engine 1. Moreover, during such two-stroke compression release braking, an impact between the piston top 12’ of the piston 12 and the cylinder head 10’ of the cylinder 10 can be avoided by the increased cylinder pressure obtained by the phase shifting of the control of the at least one exhaust valve 24 and of the at least one inlet valve 18, as explained herein.

According to some embodiments, the control arrangement 21 is configured to, if the rotational speed of the crankshaft 16 exceeds the threshold speed, increase the cylinder pressure at the gas exchanging phase of the cylinder 10 by increasing the exhaust back pressure in the exhaust conduit 30. In Fig. 3, an exhaust conduit 30 of the combustion engine 1 is indicated. According to the illustrated embodiments, the combustion engine 1 comprises an exhaust throttle 34 arranged in the exhaust conduit. In Fig. 3, the exhaust throttle 34 is illustrated in in an open state. According to these embodiments, the control arrangement 21 may be configured to increase the exhaust back pressure in the exhaust conduit 30 by controlling the exhaust throttle 34 to a closed state in which the exhaust throttle 34 at least partially blocks flow of exhaust gas through the exhaust conduit 30. By increasing the exhaust back pressure in the exhaust conduit 30, the cylinder pressure is increased at the gas exchanging phase of the cylinder 10 which thus reduces the risk of an impact between the piston top 12’ of the piston 12 and the cylinder head 10’ of the cylinder 10. Moreover, the rotational speed of the crankshaft 16 can be reduced in an efficient manner which also reduces the risk of an impact between the piston top 12’ of the piston 12 and the cylinder head 10’ of the cylinder 10. The combustion engine 1 may comprise another type of system or arrangement for increasing the exhaust back pressure in the exhaust conduit 30 than an exhaust throttle 34, such as for example a turbo charger provided with controllable guide vanes, or the like.

As indicated above, according to some embodiments, the control arrangement 21 is configured to restrict the rotational speed of the crankshaft 16 if the rotational speed of the crankshaft 16 exceeds a threshold speed so as to avoid an impact between the piston top 12’ of the piston 12 and the cylinder head 10’ of the cylinder 10.

The following is mainly explained with reference to Fig. 1 and Fig. 2. The control arrangement 21 may be configured to restrict the rotational speed of the crankshaft 16 by braking the combustion engine 1. The control arrangement 21 may for example brake the combustion engine 1 by braking the vehicle 40 comprising the powertrain 2. The control arrangement 21 may brake the vehicle 40 by activating wheel brakes 56 of the vehicle 40. Alternatively, or additionally, the control arrangement 21 may be configured to brake the combustion engine 1 or the vehicle 40 comprising the powertrain 2 by activating a retarder arrangement 36 of the vehicle 40. The retarder arrangement 36 may be comprised in the powertrain 2 and may be of hydraulic and/or electric type.

According to some embodiments, the control arrangement 21 may be configured to restrict the rotational speed of the crankshaft 16 by disconnecting the combustion engine 1 from wheels 47 of the vehicle 40 comprising the powertrain 2. The control arrangement 21 may be configured to disconnect the combustion engine 1 from wheels 47 of the vehicle 40 by controlling the clutch 46 to a disengaged state. Alternatively, or additionally, the control arrangement 21 may be configured to disconnect the combustion engine 1 from wheels 47 of the vehicle 40 by controlling the transmission 4 to a neutral state.

According to some embodiments of the present disclosure, the control arrangement 21 may be configured to restrict the rotational speed of the crankshaft 16 by changing an effective gear ratio of the transmission 4. The control arrangement 21 may be configured to change the effective gear ratio of the transmission 4, for example by controlling the gear selector unit 54 illustrated in Fig. 2, such that the crankshaft 16 of the combustion engine 1 obtains a lower rotational speed given a current traveling speed of the vehicle 40 comprising the powertrain 2.

The control arrangement 21 may be configured to perform one or more of the herein described measures of increasing the cylinder pressure at a gas exchanging phase of the cylinder 10 and measures of restricting the rotational speed of the crankshaft 16. In this manner, an impact between the piston top 12’ of the piston 12 and the cylinder head 10’ of the cylinder 10 can be avoided in an efficient manner which allows for the small distance d between the piston top 12’ of the piston 12 and the cylinder head 10’ of the cylinder 10.

The distance d between the piston top 12’ of the piston 12 and the cylinder head 10’ of the cylinder 10, when the combustion engine 1 is at stand-still and the piston 12 is positioned at the top dead centre TDC, may be within the range of 0.2% - 0.495%, or may be within the range of 0.3% - 0.49%, of the stroke length L of the piston 12.

According to some embodiments, the distance d between the piston top 12’ of the piston 12 and the cylinder head 10’ of the cylinder 10, when the combustion engine 1 is at stand-still and the piston 12 is positioned at the top dead centre TDC, may be approximately 0.7 mm and the stroke length L of the piston 12 may be 160 mm. In this example embodiments, the distance d between the piston top 12’ of the piston 12 and the cylinder head 10’ of the cylinder 10, when the combustion engine 1 is at stand-still and the piston 12 is positioned at the top dead centre TDC, is approximately 0.4375% of the stroke length L of the piston 12.

Fig. 6 illustrates a method 100 of controlling a powertrain of a vehicle, wherein the powertrain comprises a combustion engine. The powertrain, the combustion engine, and the vehicle may be a powertrain 2, a combustion engine 1, and a vehicle 40 according to the embodiments explained with reference to Fig. 1 - Fig. 5b. Therefore, in the following, simultaneous reference is made to Fig. 1 - Fig. 6, if not indicated otherwise. The method 100 is a method of controlling a powertrain 2 of a vehicle 40, wherein the powertrain 2 comprises a combustion engine 1, the combustion engine 1 comprising a crankshaft 16, a cylinder 10, and a piston 12 configured to reciprocate in the cylinder 10 between a top dead centre TDC and a bottom dead centre BDC upon rotation of the crankshaft 16. The distance d between a piston top 12’ of the piston 12 and a cylinder head 10’ of the cylinder 10, when the combustion engine 1 is at stand-still and the piston 12 is positioned at the top dead centre TDC, is smaller than 0.5% of a stroke length L of the piston 12. The method 100 comprises the steps of: monitoring 110 a rotational speed of a crankshaft 16 of the combustion engine 1 , and if the rotational speed of the crankshaft 16 exceeds a threshold speed, increasing 120 the cylinder pressure at a gas exchanging phase of the cylinder 10, and restricting 130 the rotational speed of the crankshaft 16.

According to some embodiments, the cylinder 10 comprises at least one exhaust valve 24, and wherein the method 100 comprises the step of: increasing 121 the cylinder pressure at the gas exchanging phase of the cylinder 10 by controlling the at least one exhaust valve 24 to assume an at least partially closed state during at least a portion of an exhaust stroke 43 of the cylinder 10.

According to some embodiments, the step of increasing 121 the cylinder pressure at the gas exchanging phase of the cylinder 10 by controlling the at least one exhaust valve 24 to assume the at least partially closed state comprises the step of: phase shifting 122 control of the at least one exhaust valve 24.

According to some embodiments, the step of phase shifting 122 control of the at least one exhaust valve 24 comprises the step of: phase shifting 123 control of the at least one exhaust valve 24 such that the at least one exhaust valve 24 opens during an expansion stroke 42 of the cylinder 10 and closes during an exhaust stroke 43 of the cylinder 10.

As indicated in Fig. 6, the method 100 may comprise the step of: controlling 125 the at least one exhaust valve 24 to an at least partially open state at a region of the top dead centre TDC. According to some embodiments, the cylinder 10 comprises at least one inlet valve 18, and wherein the method 100 comprises the step of: increasing 126 the cylinder pressure at the gas exchanging phase of the cylinder 10 by phase shifting control of the at least one inlet valve 18.

According to some embodiments, the step of increasing 126 the cylinder pressure at the gas exchanging phase of the cylinder 10 by phase shifting control of the at least one inlet valve 18 comprises the step of: phase shifting 127 control of the at least one inlet valve 18 such that the at least one inlet valve 18 opens during an inlet stroke 44 of the cylinder 10 and closes during a compression stroke 41 of the cylinder 10.

According to some embodiments, the combustion engine 1 comprises an exhaust conduit 30, and wherein the method 100 comprises the step of: increasing 129 the cylinder pressure at the gas exchanging phase of the cylinder 10 by increasing the exhaust back pressure in the exhaust conduit 30.

According to some embodiments, the method 100 comprises the step of restricting 130 the rotational speed of the crankshaft 16, and wherein the step of restricting 130 the rotational speed of the crankshaft 16 comprises at least one of the steps of: braking 131 the combustion engine 1 , braking 133 the vehicle 40 comprising the powertrain 2, and disconnecting 135 the combustion engine 1 from wheels 47 of the vehicle 40 comprising the powertrain 2.

According to some embodiments, the powertrain 2 comprises a transmission 4 and wherein the method 100 comprises the step of: restricting 137 the rotational speed of the crankshaft 16 by changing an effective gear ratio of the transmission 4.

It will be appreciated that the various embodiments described for the method 100 are all combinable with the control arrangement 21 as described herein. That is, the control arrangement 21 may be configured to perform any one of the method steps 110, 120, 121, 122, 123, 125, 126, 127, 129, 130, 131, 133, 135, and 137 of the method 100.

Fig. 7 illustrates a computer-readable medium 200 comprising instructions which, when executed by a computer, cause the computer to carry out the method 100 according to some embodiments of the present disclosure. According to some embodiments, the computer- readable medium 200 comprises a computer program comprising instructions which, when the program is executed by a computer, cause the computer to carry out the method 100 according to some embodiments.

One skilled in the art will appreciate that the method 100 of controlling a powertrain 2 of a vehicle 40 may be implemented by programmed instructions. These programmed instructions are typically constituted by a computer program, which, when it is executed in the control arrangement 21 , ensures that the control arrangement 21 carries out the desired control, such as the method steps 110, 120, 121, 122, 123, 125, 126, 127, 129, 130, 131, 133, 135, and 137 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.

The control arrangement 21 may comprise a calculation unit which may take the form of substantially any suitable type of processor circuit or microcomputer, e.g. a circuit for digital signal processing (digital signal processor, DSP), a Central Processing Unit (CPU), a processing unit, a processing circuit, a processor, an Application Specific Integrated Circuit (ASIC), a microprocessor, or other processing logic that may interpret and execute instructions. The herein utilised expression “calculation unit” may represent a processing circuitry comprising a plurality of processing circuits, such as, e.g., any, some or all of the ones mentioned above.

The control arrangement 21 may further comprise a memory unit, wherein the calculation unit may be connected to the memory unit, which may provide the calculation unit with, for example, stored program code and/or stored data which the calculation unit may need to enable it to do calculations. The calculation unit may also be adapted to store partial or final results of calculations in the memory unit. The memory unit may comprise a physical device utilised to store data or programs, i.e. , sequences of instructions, on a temporary or permanent basis. According to some embodiments, the memory unit may comprise integrated circuits comprising silicon-based transistors. The memory unit may comprise e.g. a memory card, a flash memory, a USB memory, a hard disc, or another similar volatile or non-volatile storage unit for storing data such as e.g. ROM (Read-Only Memory), PROM (Programmable Read-Only Memory), EPROM (Erasable PROM), EEPROM (Electrically Erasable PROM), etc. in different embodiments. The control arrangement 21 is connected to components of the vehicle 40, the powertrain 2, and/or the combustion engine 1 for receiving and/or sending input and output signals. These input and output signals may comprise waveforms, pulses, or other attributes which the input signal receiving devices can detect as information and which can be converted to signals processable by the control arrangement 21. These signals may then be supplied to the calculation unit. One or more output signal sending devices may be arranged to convert calculation results from the calculation unit to output signals for conveying to other parts of the vehicle's control system and/or the component or components for which the signals are intended. Each of the connections to the respective components of the vehicle 40, the powertrain 2, and/or the combustion engine 1 for receiving and sending input and output signals may take the form of one or more from among a cable, a data bus, e.g. a CAN (controller area network) bus, a MOST (media orientated systems transport) bus or some other bus configuration, or a wireless connection.

In the embodiments illustrated, the powertrain 2 comprises a control arrangement 21 but might alternatively be implemented wholly or partly in two or more control arrangements or two or more control units.

Control systems in modern vehicles generally comprise a communication bus system consisting of one or more communication buses for connecting a number of electronic control units (ECUs), or controllers, to various components on board the vehicle. Such a control system may comprise a large number of control units and taking care of a specific function may be shared between two or more of them. Vehicles and engines of the type here concerned are therefore often provided with significantly more control arrangements than depicted in Fig. 2 and 3, as one skilled in the art will surely appreciate.

The computer program product 200 may be provided for instance in the form of a data carrier carrying computer program code for performing at least some of the method steps 110, 120, 121 , 122, 123, 125, 126, 127, 129, 130, 131, 133, 135, and 137 according to some embodiments when being loaded into one or more calculation units of the control arrangement 21. The data carrier may be, e.g. a CD ROM disc, as is illustrated in Fig. 7, or a ROM (read-only memory), a PROM (programable read-only memory), an EPROM (erasable PROM), a flash memory, an EEPROM (electrically erasable PROM), a hard disc, a memory stick, an optical storage device, a magnetic storage device or any other appropriate medium such as a disk or tape that may hold machine readable data in a non-transitory manner. The computer program product may furthermore be provided as computer program code on a server and may be downloaded to the control arrangement 21 remotely, e.g., over an Internet or an intranet connection, or via other wired or wireless communication systems.

The features “advanced” and “advancing”, as used herein means that a control or event referred to is performed earlier regarding crank angle degrees or time, as compared to if the control or event would not be advanced. The features “retarded” and “retarding”, as used herein means that a control or event referred to is performed later regarding crank angle degrees or time, as compared to if the control or event would not be retarded.

It is to be understood that the foregoing is illustrative of various example embodiments and that the invention is defined only by the appended independent claims. A person skilled in the art will realize that the example embodiments may be modified, and that different features of the example embodiments may be combined to create embodiments other than those described herein, without departing from the scope of the present invention, as defined by the appended independent claims.

As used herein, the term "comprising" or "comprises" is open-ended, and includes one or more stated 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.