TECHNICAL FIELD

The invention relates to a method for operating a powertrain of a vehicle. The invention further relates to a vehicle comprising a powertrain and a control system. Also, the invention relates a computer program, and to a computer-readable storage medium comprising instructions.

BACKGROUND

When a land-based vehicle comprising an internal combustion engine (ICE) travels along a path, the drive wheels of the vehicle are driven by the ICE over some stretches of the path. Along other stretches of the path, the ICE does not drive the drive wheels of the vehicle. One example of the latter is when gravity propels the vehicle on a downhill gradient. A further example is when the vehicle has sufficient kinetic energy to propel the vehicle over a certain distance, e.g. as it approaches a road intersection or a portion of the path having a reduced speed limit.

When travelling along the path without the ICE driving the drive wheels of the vehicle, two main travelling modes may be chosen, either coasting or motoring. Coasting means that the vehicle is travelling with an open powertrain, i.e. the drive wheels of the vehicle are disengaged from the ICE e.g. by disengaging the clutch of the powertrain or by setting a transmission of the powertrain into a neutral position. During coasting, the ICE may either run on idle or be switched off. Motoring means that the vehicle is travelling with a closed powertrain, i.e. the drive wheels of the vehicle are engaged with the ICE and the ICE is driven by the kinetic energy of the vehicle via the wheels of the vehicle. Accordingly, the vehicle may be subjected to engine braking during motoring due to e.g. the internal friction of the ICE.

Herein, engine braking is alternatively referred to as running the ICE in a negative torque state. This, as opposed to a positive torque state in which the ICE drives the drive wheels of the vehicle.

Motoring a vehicle may be advantageous under certain circumstances due to the powertrain being closed. For instance, since the powertrain is closed, positive torque may easily be provided to the drive wheels of the vehicle by supplying fuel to the ICE. However, the engine braking of the ICE costs energy and thus, produces undesired energy losses. SUMMARY

It would be advantageous to achieve a method for operating a powertrain of a vehicle and/or a vehicle comprising a powertrain overcoming, or at least alleviating, the above mentioned drawback. In particular, it would be desirable to enable reduced energy losses during motoring of a vehicle. To better address one or more of these concerns, a method for operating a powertrain of a vehicle having the features defined in one of the independent claim is provided and/or a vehicle comprising a powertrain having the features defined in a further independent claim is provided.

According to an aspect of the invention, there is provided a method for operating a powertrain of a vehicle. The powertrain comprises an internal combustion engine, a clutch, and a transmission. The internal combustion engine is a four-stroke internal combustion engine and comprises at least one cylinder arrangement, a crankshaft, a first camshaft, and a second camshaft. The at least one cylinder arrangement comprises a piston connected to the crankshaft, a combustion chamber, an intake valve configured for admitting gas into the combustion chamber, and an exhaust valve configured for admitting gas out of the combustion chamber. The intake valve is controlled by the first camshaft and the exhaust valve is controlled by the second camshaft. At least one of the first and second camshafts is configured to the be shifted in phase. The method comprises steps of:

- selecting a gear in the transmission,

- engaging the clutch,

- running the internal combustion engine in a negative torque state or in a zero torque state, and

- changing a phase of the first camshaft and/or of the second camshaft to provide a first angle of rotation of the crankshaft in a transition between an exhaust stroke of the piston and an intake stroke of the piston, during which first angle of rotation both the intake valve and the exhaust valve are closed.

Since the method comprises the step of running the internal combustion engine (ICE) in a negative torque state or in a zero torque state with a gear selected in the transmission and the clutch engaged, and since the method comprises the step of changing the phase of the first and/or second camshaft to provide the first angle of rotation of the crankshaft, during which both the intake valve and the exhaust valve are closed, the powertrain of the vehicle is operated for motoring the vehicle with lower heat loss and lower gas exchange loss in the ICE than when there is an overlap, during which both the intake valve and the exhaust valve are open. As a result, reduced energy loss during motoring of the vehicle is achieved. More specifically, when an ICE is propelling a vehicle, i.e. when the powertrain is closed and fuel it is injected into the ICE, there is normally an overlap between the intake valve and the exhaust valve. That is, an overlap exists when both the exhaust valve and the intake valve are open at the same time. Due to the overlap a proper gas exchange is achieved in the combustion chamber and residual gas remaining within the combustion chamber between the exhaust stroke and intake stroke of the piston is minimized. In some ICEs there is no overlap. Instead, the intake valve opens at the same angular position of the crankshaft as the exhaust valve closes between the exhaust and intake strokes of the piston.

In accordance with the invention, during motoring, phase shifting of the first and/or second camshaft to provide the first angle of rotation of the crankshaft during which the intake and exhaust valves are both closed, removes the overlap, and produces instead a negative overlap over the first angle of rotation of the crankshaft. Instead of ejecting all gas within the combustion chamber through an exhaust opening at the exhaust valve during the exhaust stroke, an amount of gas is compressed and expanded as the piston passes its top dead centre (TDC). This means that the amount of gas flowing through the combustion chamber is reduced, and thus, gas exchange losses in the ICE are reduced. Similarly, since due to the negative overlap, the intake valve opens after the TDC, less gas will be admitted into the combustion chamber during the intake stroke, which will result in lower cylinder pressure in the following compression stroke of the piston. This leads to reduced heat losses in the ICE.

Accordingly, changing cam phase to prevent overlap between the exhaust valve and the intake valve, i.e. changing cam phase to a negative overlap, is beneficial at motoring since heat transfer and gas exchange is improved. Thus, the negative torque due to gas exchange losses and heat losses in the ICE is reduced during motoring. That is, the negative torque from the ICE during motoring is reduced in accordance with the present invention as compared to motoring with an overlap between the exhaust and intake valves.

Accordingly, due to the method, motoring of the vehicle may be performed in a more energy efficient manner than when motoring is performed with an overlap between the exhaust and intake valves. This may be beneficial since less negative torque is to be overcome when going from motoring to a positive torque state of the ICE. Also, less parasitic torque, i.e. less negative torques, is affecting the vehicle speed during motoring. Further, since the crankshaft of the ICE is rotating, auxiliary components such as e.g. generator, oil pump, water pump are in operation as opposed to when coasting with the ICE shut off. The method may be implemented while the vehicle is driven under the control of a cruise control (CC). The CC may be of an advanced type such as a look ahead cruise control (LACC), which may utilise geographical position of the vehicle and map data related to a travelling path ahead of the vehicle. Also, the method may be implemented while the vehicle is driven entirely under manual control, i.e. under the control of a driver of the vehicle. In both cases, a control system of the vehicle, such as a control system of the ICE, may implement the method during motoring of the vehicle. During manual driving the method can be implemented, e.g. automatically when the driver releases the gas pedal, or by the driver manually pushing a button.

The vehicle may be a heavy load vehicle such as e.g. a truck, a bus, a construction vehicle, a pickup, a van, or other similar motorized manned or unmanned vehicle, designed for land- based propulsion, on or off road.

As in any four-stroke ICE, the piston performs an intake stroke, a compression stroke, a power stroke, and an exhaust stroke in a cylinder bore of the cylinder arrangement. The rotation of the first and second camshafts are synchronized with the crankshaft. The intake valve is configured to open and close an intake opening leading into the combustion chamber, through which intake opening gas is admitted into the combustion chamber. The exhaust valve is configured to open and close an exhaust opening leading out of the combustion chamber, through which exhaust opening gas is admitted out of the combustion chamber.

The powertrain may extend from the ICE to at least one drive wheel of the vehicle. In addition to the ICE, the clutch, and the transmission, the powertrain may comprise e.g. a propeller shaft, an axle gear, a differential gear, a wheel gear, et cetera.

The step of selecting a gear in the transmission relates to the selection of any gear which contributes to forming a closed powertrain. Selecting a gear results in that a gear is engaged in the transmission. Accordingly, a neutral position within the transmission does not form a selected gear.

The step of selecting a gear in the transmission may be performed a longer or shorter timespan before the step of running the ICE in a negative or zero torque state. For instance, the ICE may be operated in a positive torque state with the selected gear prior to the step of running the ICE in a negative or zero torque state. Accordingly, also the step of engaging the clutch may be performed a longer or shorter time span before the step of running the ICE in a negative or zero torque state.

The step of running the internal combustion engine in a negative torque state or in a zero torque state relates to two alternative states of running the ICE. In both of these states, the vehicle will be motoring since the powertrain of the vehicle is closed, i.e. a gear is selected and the clutch is engaged. Motoring the vehicle may be advantageous under certain circumstances. For instance, since the powertrain is closed during motoring, positive torque may easily be provided to the drive wheels of the vehicle by supplying fuel to the ICE without having to first select a gear in the transmission and close the clutch, which would be the case if the vehicle were coasting instead.

In the negative torque state, the ICE is engine braking, i.e. the ICE forms a load on the powertrain which reduces the speed of the vehicle. In the negative torque state, either no fuel is supplied to the ICE, or a limited amount of fuel is supplied to and combusted in the ICE. The limited amount of fuel during the negative torque state is such that the ICE is still engine braking, although with a lesser negative torque than if no fuel is supplied to the ICE. In the zero torque state, fuel is supplied to the ICE at an amount such that the ICE does neither produce negative torque, nor positive torque. Thus, in the zero torque state the ICE does not form a load on the powertrain, i.e. the ICE is not engine braking, but does also not drive the powertrain.

Changing a phase of a camshaft entails that the rotational position of the camshaft in relation to the crankshaft is shifted. This may also be referred to as cam phasing. In practice, this means that the crankshaft angle at which a valve controlled by the camshaft is opened and closed can be changed.

The step of changing a phase of the first camshaft and/or of the second camshaft may be performed in any known manner. For instance, WO 2017/217908 and US 8714123 disclose suitable devices to be utilised for shifting/changing phases of the first and/or second camshafts. Other variable valve timing technology which utilises changing phases of the first and/or second camshafts may alternatively be used.

The first angle of rotation of the crankshaft, during which both the intake and exhaust valves are closed, may be variable to provide different levels of negative torque in the ICE. The transition between an exhaust stroke of the piston and an intake stroke of the piston is around the TDC of the piston in the cylinder bore. The first angle of rotation of the crankshaft in the transition between the exhaust stroke of the piston and the intake stroke of the piston may be at least 5 degrees, such as within a range of 5 - 150 degrees, or within a range of 5 - 200 degrees. The unit of the first angle of rotation may alternatively be referred to as CAD, Crankshaft Angle Degrees.

The first angle of rotation of the crankshaft in a transition between an exhaust stroke of the piston and an intake stroke of the piston, during which first angle of rotation both the intake valve and the exhaust valve are closed - may also be referred to as a negative overlap. This as opposed to an (ordinary) overlap, an angle of rotation of the crankshaft during which both the exhaust and intake valves are open.

If the ICE comprises more than one intake valve and/or more than one exhaust valve, also these valves have to open and close in the manner discussed above in order to provide the negative overlap, which will occur if such additional valves are controlled by the first and/or second camshafts. Accordingly, if the additional valves are controlled by additional camshafts, also the phases of any additional camshafts have to be changed to provide that during the first angle of rotation of the crankshaft all valves are closed.

According to embodiments, the step of selecting a gear in the transmission may comprise a step of selecting a higher gear than appropriate for current driving conditions of the vehicle.

In this manner, the rotational speed of the crankshaft of the ICE may be reduced during the motoring of the vehicle. Such reduction of the rotational speed of the crankshaft of the ICE will further reduce the heat and gas exchange losses and reduce the engine friction and thus, the total losses produced by the ICE.

A higher gear than appropriate for current driving conditions means a gear which is too high for propelling the vehicle with the ICE in a positive torque state. For instance, the selected higher gear could cause stalling of the ICE.

The selecting of a higher gear than appropriate for current driving conditions may be performed as one of the first steps in the method. A further alternative may be to first perform the method with a selected gear appropriate for current driving conditions, and subsequently select the higher gear than appropriate for current driving conditions and continue the method on that higher gear.

For vehicles with a manual transmission, a shift indicator with proposed gear selection when motoring can be provided to indicate to the driver the gear to be selected. According to embodiments, preceding the steps of running the internal combustion engine in a negative torque state or in a zero torque state, and of changing a phase of the first camshaft and/or the second camshaft, the method may comprise steps of:

- determining a geographical position of the vehicle, and

- determining that the vehicle is traveling on a downhill gradient, or that the vehicle approaches a downhill gradient. In this manner, the present travelling conditions of the vehicle may be taken into account when applying the method for operating the powertrain of the vehicle. Thus, motoring of the vehicle may be performed along a stretch of a travelling path which includes a downhill gradient and which is particularly suited for saving energy by motoring of the vehicle. Such steps of determining may be utilised for instance when the vehicle is travelling under control of a cruise control e.g. a look ahead to cruise control.

However, the steps of determining may also be utilised when the vehicle is controlled manually by a driver. In the latter case, a control system of the vehicle may provided an output to the driver to initiate motoring, i.e. releasing the accelerator pedal of the vehicle.

According to embodiments, preceding the steps of running the internal combustion engine in a negative torque state or in a zero torque state, and of changing a phase of the first camshaft and/or the second camshaft, the method may comprise steps of:

- determining a geographical position of the vehicle, and

- determining that the vehicle is approaching a speed reduction section of a road. In this manner, the present travelling conditions of the vehicle may be taken into account when applying the method for operating the powertrain of the vehicle. Thus, motoring of the vehicle may be performed along a stretch of a travelling path which includes a speed reduction section and which is particularly suited for saving energy by motoring of the vehicle. Such steps of determining may be utilised for instance when the vehicle is travelling under control of a cruise control e.g. a look ahead to cruise control.

However, the steps of determining may also be utilised when the vehicle is controlled manually by a driver. In the latter case, a control system of the vehicle may provide an output to the driver to initiate motoring, i.e. releasing the accelerator pedal of the vehicle.

According to a further aspect of the invention, there is provided a vehicle comprising a powertrain and a control system. The powertrain comprises an internal combustion engine, a clutch, and a transmission. The internal combustion engine is a four-stroke internal combustion engine and comprises at least one cylinder arrangement, a crankshaft, a first camshaft, and a second camshaft. The at least one cylinder arrangement comprises a piston connected to the crankshaft, a combustion chamber, an intake valve configured for admitting gas into the combustion chamber, and an exhaust valve configured for admitting gas out of the combustion chamber. The intake valve is controlled by the first camshaft and the exhaust valve is controlled by the second camshaft. At least one of the first and second camshafts is configured to the be shifted in phase. The control system is configured to:

- select a gear in the transmission,

- engage the clutch,

- run the internal combustion engine in a negative torque state or in a zero torque state, and

- change a phase of the first camshaft and/or of the second camshaft to provide a first angle of rotation of the crankshaft in a transition between an exhaust stroke of the piston and an intake stroke of the piston, during which first angle of rotation both the intake valve and the exhaust valve are closed.

As discussed above in relation to the method for operating a powertrain of a vehicle, since the ICE is run in a negative torque state or in a zero torque state with a gear selected in the transmission and the clutch engaged, and since the phase of the first and/or second camshaft is changed to provide the first angle of rotation of the crankshaft, during which both the intake valve and the exhaust valve are closed, the powertrain of the vehicle is operated for motoring the vehicle with lower heat loss and lower gas exchange loss in the ICE than when there is an overlap, during which both the intake valve and the exhaust valve are open. As a result, motoring of the vehicle may be performed in a more energy efficient manner than when motoring is performed with an overlap between the exhaust and intake valves.

Accordingly, the control system of the vehicle is configured for motoring the vehicle utilising cam phasing to reduce negative torque from the ICE, i.e. to reduce engine braking torque.

The control system may comprise one or more control units. For instance, the control system may comprise a transmission control unit and an engine control unit. According to some embodiments, the control system may further comprise a control unit configured to handle positional data and/or map data, such as a control unit of a cruise control system. Naturally the different control units of the control system are configured to communicate with each other e.g. via a CAN bus.

According to embodiments, the first angle of rotation of the crankshaft in the transition between the exhaust stroke of the piston and the intake stroke of the piston may be at least 5 degrees. In this manner, the crankshaft rotational angle between closing of the exhaust valve and the opening of the intake valve may be at least 5 degrees.

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

According to a further aspect of the invention there is provided a computer-readable storage medium comprising instructions which, when executed by a computer, cause the computer to carry out the method according to any one of aspect and/or embodiments discussed herein.

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

BRIEF DESCRIPTION OF THE DRAWINGS

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

Fig. 1 schematically illustrates a vehicle according to embodiments,

Fig. 2 schematically illustrates embodiments of a powertrain of a vehicle,

Fig. 3 schematically illustrates embodiments of an internal combustion engine,

Fig. 4 illustrates a control system,

Fig. 5 illustrates diagrams over an internal combustion engine,

Fig. 6 illustrates embodiments of a method for operating a powertrain of a vehicle, and Fig. 7 shows a computer-readable storage medium according to embodiments.

DETAILED DESCRIPTION

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

Fig. 1 schematically illustrates a vehicle 2 according to embodiments. The vehicle 2 may be a heavy goods vehicle, designed for land-based propulsion. The vehicle 2 comprises a powertrain. Fig. 2 schematically illustrates embodiments of a powertrain 4 of a vehicle 2, e.g. a vehicle 2 similar to that illustrated in Fig. 1.

The powertrain 4 comprises an internal combustion engine, ICE, 6, a clutch 8, and a transmission 10. The vehicle 2 further comprises a control system 12. The control system 12 is configured for controlling at least part of the powertrain 4 or certain functions of the powertrain 4. Embodiments of the control system 12 are further discussed below with reference to Fig. 4.

The powertrain 4 may be controlled to perform a method according to aspects and/or embodiments discussed herein, see further below with reference to Fig. 6.

The powertrain 4 extends from the ICE 6 to at least one drive wheel 7 of the vehicle 2. The powertrain 4 may further comprise e.g. a propeller shaft 9, a differential gear 1 1 , drive axles 13, wheel gears 15. The powertrain 4 may further comprise a transfer gearbox (not shown).

In a known manner, an actuator (not shown) is provided for opening and closing the clutch 8, and shift actuators (not shown) may be provided for shifting gears in the transmission 10.

The actuator of the clutch 8 and/or the shift actuators may be automatically and/or manually operable. For instance, the transmission 10 may be an automated manual transmission (AMT), which is controlled by a driver of the vehicle 2 and/or by a controls system of the vehicle 2 such as a cruise control, CC, system. The drive wheels 7 are driven by the ICE 6 via the transmission 10. Suitable gears are selected in the transmission 10 during driving of the vehicle 2.

Fig. 3 schematically illustrates embodiments of an ICE 6. The ICE 6 is configured to form part of a powertrain of a vehicle, such as e.g. the powertrain 4 of one of the vehicles 2 shown in Figs. 1 and 2.

The ICE 6 is a four-stroke ICE and comprises at least one cylinder arrangement 14, a crankshaft 16, a first camshaft 18, and a second camshaft 20. The at least one cylinder arrangement comprises a piston 22 connected to the crankshaft 16 via a connecting rod 23, a combustion chamber 24, an intake valve 26 configured for admitting gas into the combustion chamber 24, and an exhaust valve 28 configured for admitting gas out of the combustion chamber 24. The intake valve 26 is controlled by the first camshaft 18 and the exhaust valve 28 is controlled by the second camshaft 20. At least one of the first and second camshafts 26, 28 is configured to the be shifted in phase as indicated by the arrows 30. The cylinder arrangement 14 further comprises a fuel injection arrangement 31 , and/or an ignition device.

In a known manner, the piston 22 is arranged to reciprocate in a cylinder bore 32 of the cylinder arrangement 14. The piston 22 performs four strokes in the cylinder bore 32, corresponding to an intake stroke, a compression stroke, a power stroke, and an exhaust stroke. In Fig. 3 the piston 22 is illustrated with continuous lines at its bottom dead centre, BDC, and with dashed lines at its top dead centre, TDC. The combustion chamber 24 is formed above the piston 22 inside the cylinder bore 32.

In a known manner, the intake valve 26 comprises an intake valve head configured to seal against an intake valve seat extending around an intake opening 34. An inlet conduit 35 for fresh gas, such as air, leads to the intake opening 34. The exhaust valve 28 comprises an exhaust valve head configured to seal against an exhaust valve seat extending around an exhaust opening 36. An exhaust conduit 37 leads from the exhaust opening 36 towards an exhaust system of the ICE 6.

The camshafts 18, 20 rotate at half the rotational speed of the crankshaft 16 and control the movement of the intake and exhaust valves 26, 28 via lobes 38, 40 arranged on the camshafts 18, 20. The first camshaft 18 is arranged for controlling movement of the intake valve 26, and opening and closing of the intake opening 34. The first camshaft 18 comprises a first lobe 38 configured to abut against the intake valve 26. Thus, the intake valve 26 will follow a contour of the first lobe 38. The intake valve 26 may be biased towards its closed position, as known in the art, e.g. by means of a spring. The second camshaft 20 is arranged for controlling movement of the exhaust valve 28, and opening and closing of the exhaust opening 36. The second camshaft 20 comprises a second lobe 40 configured to abut against the exhaust valve 28. Thus, the exhaust valve 28 will follow a contour of the second lobe 40. The exhaust valve 28 may be biased towards its closed position, e.g. by means of a spring.

The cylinder arrangement 4 has a total swept volume, Vs, in the cylinder bore 12 between the BDC and the TDC. According to some embodiments, the cylinder arrangement 4 may have a total swept volume, Vs, in the cylinder bore 12 between the BDC and TDC of the piston 10, wherein 0.3 < Vs < 4 litres. Mentioned purely as an example, in the lower range of Vs, the cylinder arrangement 4 may form part of an internal combustion engine for a passenger car, and in the middle and higher range of Vs, the cylinder arrangement 4 may form part of an internal combustion engine for a heavy load vehicle such as e.g. a truck, a bus, or a construction vehicle. Fig. 4 illustrates a control system 12 to be utilised in connection with the different aspects and/or embodiments of the invention. The control system 12 is also indicated in Fig. 2. The control system 12 comprises at least one calculation unit 50, 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 system 12 comprises a memory unit 52. The calculation unit 50 is connected to the memory unit 52, which provides the calculation unit 50 with, for example, stored programme code, data tables, and/or other stored data which the calculation unit 50 needs to enable it to do calculations and to control components of the vehicle 2. The calculation unit 50 is also adapted to storing partial or final results of calculations in the memory unit 52. The memory unit 52 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 52 may comprise integrated circuits comprising silicon- based transistors. The memory unit 52 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 system 12 is further provided with respective devices 54, 56, 58, 60 for receiving and/or sending input and output signals. These input and output signals may comprise waveforms, pulses or other attributes which input signal receiving devices 58, 60 can detect as information and which can be converted to signals processable by the calculation unit 50. These signals are supplied to the calculation unit 50. Output signal sending devices 54, 56 are arranged to convert calculation results from the calculation unit 50 to output signals for conveying to other parts of the control system 12. Each of the connections to the respective devices for receiving and sending input and output signals may take the form of one or more from among a cable, a data bus, e.g. a CAN (controller area network) bus, a MOST (media orientated systems transport) bus or some other bus configuration, or a wireless connection. In the embodiment depicted, only one calculation unit 50 and memory 52 are shown, but the control system 12 may alternatively comprise more than one control unit and/or memory. Mentioned as examples, the output signal sending devices 54, 56 may send control signals to the clutch 8, to the transmission 10, and to the ICE 6. The input signal receiving devices 58, 60 may receive signals from the ICE 6, such as from a rotation sensor sending signals related to the rotational speed of the crankshaft of the ICE 6, and signals from e.g. the transmission 10 verifying engagement of gears, and/or from the clutch 8 verifying

engagement of the clutch. See also Fig. 2.

An example of a data table may be a table containing the gear ratios of the various gears of the transmission 10. Examples of data may be measured, monitored, and/or calculated data. The control unit 12 is connected to various sensors and actuators in order to receive input and provide output for performing the various aspects and embodiments of the method discussed herein. Examples of sensors may be rotational speed sensors. Examples of actuators are an actuator of the clutch 8, and shift actuators of the transmission 10.

According to some embodiments, the control unit 12 may comprise an engine torque measuring arrangement 62 for monitoring and/or calculating and/or estimating an output torque of the ICE 6. The engine torque measuring arrangement 62 provides engine torque figures. Such engine torque measuring arrangements are known in the art and may e.g. estimate engine torque based on the amount of fuel injected into the ICE 6 and possibly further parameters such as friction losses in the ICE 6 and fuel injection angle. A further example of an engine torque measuring arrangement may estimate engine torque based on measurements from a strain gauge arranged e.g. in an input shaft of the transmission 10. Thus, the control system 12 may establish current torque figures of the ICE 6, such as positive torque figures when the ICE 6 is driving the vehicle, and negative torque figures or zero torques figures when the vehicle is motoring.

Accordingly, the control system 12 may comprise calculation units for controlling the clutch 8, for controlling the transmission 10, and for controlling the ICE 6. The control system 12 may further comprise calculation units, which provide a cruise control function of the vehicle 2, and form part of a navigation system utilising GPS data and map data, such as topographic data, and speed limit data.

The control system 12 is configured to perform a method according to any one aspect and/or embodiment discussed herein, see e.g. below with reference to Fig. 6.

Fig. 5 illustrates diagrams over the ICE 6 of Figs. 2 and 3. Fig. 5 illustrates the four strokes of a piston and the movements of the exhaust valve (full line) and of the intake valve (dash- dotted line) during ordinary operation of the ICE as well as during motoring in accordance with the present invention.

The crankshaft of the ICE rotates 720° as the four strokes of the piston are performed. For each stroke, the crankshaft rotates 180° as indicated in Fig. 5.

Along line I. the opening and closing of the exhaust and intake valves during ordinary operation of the ICE are shown. There exists an overlap between the exhaust valve and the intake valve, i.e. both the exhaust valve and the intake valve are open over a rotational angle b of the crankshaft.

Along line II. the opening and closing of the exhaust and intake valves during motoring in accordance with the present invention are shown. A negative overlap is provided between the exhaust valve and the intake valve, i.e. both the exhaust valve and the intake valve are closed over a rotational angle a of the crankshaft. Put differently, a first angle a of rotation of the crankshaft in a transition between an exhaust stroke of the piston and an intake stroke of the piston is provided, during which first angle a of rotation both the intake valve and the exhaust valve are closed.

The first angle a of rotation of the crankshaft in the transition between the exhaust stroke of the piston and the intake stroke of the piston may be at least 5 degrees. That is, the negative overlap may be at least 5 degrees, i.e. at least 5 CAD, Crankshaft Angle Degrees .

According to some embodiments, the first angle a of rotation of the crankshaft in the transition between the exhaust stroke of the piston and the intake stroke of the piston is within a range of 5 - 200 degrees. That is, the negative overlap may be within a range of 5 - 200 CAD. In general, a small negative overlap provides a small reduction of the losses within the ICE during motoring, whereas a large negative overlap provides a large reduction of losses within the ICE during motoring.

According to some embodiments, the negative overlap may be variable. Thus, the reduction of losses within the ICE may be adapted, e.g. to current driving conditions of the vehicle, upcoming changes in driving conditions of the vehicle, and/or future driving conditions of the vehicle.

In the following reference is made to Figs. 2 - 5. The control system 12 is configured to: - select a gear in the transmission 10, - engage the clutch 8,

- run the ICE 6 in a negative torque state or in a zero torque state, and

- change a phase of the first camshaft 18 and/or of the second camshaft 20 to provide a first angle a of rotation of the crankshaft 16 in a transition between an exhaust stroke of the piston 22 and an intake stroke of the piston 22, during which first angle a of rotation both the intake valve 26 and the exhaust valve 28 are closed.

In this manner, the control system 12 is configured for motoring the vehicle 2. In particular, the vehicle is motored with a negative overlap between the exhaust and intake valves 26, 28. The negative overlap achieved by cam phasing reduces negative torque from the ICE acting on the powertrain 4 during motoring. Accordingly, provisions are made for reduced losses in the powertrain 4 and in particular in the ICE 6. Thus, fuel may be saved during traveling with the vehicle 2.

According to embodiments, the control system 12 may be further configured to:

- select a higher gear than appropriate for current driving conditions of the vehicle 2. In this manner, the rotational speed of the crankshaft 16 of the ICE 6 may be reduced during the motoring of the vehicle. Thus, the losses produced by the ICE 6 are reduced in comparison with if the appropriate gear for current driving conditions remained selected. The higher gear is suitably selected in the transmission. For instance, the higher gear may be a higher gear in split section of the transmission 10, in main section of the transmission 10, or in a range section of the transmission 10.

According to embodiments, the control system 12 may be configured to:

- determine a geographical position of the vehicle 2, and

- determine that the vehicle 2 is traveling on a downhill gradient, or that the vehicle 2 approaches a downhill gradient. In this manner, the vehicle 2 may be motored in response to the determined geographical position and the path the vehicle 2 is currently traveling on. Namely, when the vehicle 2 is travelling on a downhill gradient or approaching a downhill gradient, the vehicle 2 may be motored. When motoring is performed with a negative overlap between the exhaust and inlet valves 26, 28, losses may be reduced, and energy may be saved.

According to embodiments, the control system 12 may be configured to:

- determining a geographical position of the vehicle 2, and

- determining that the vehicle 2 is approaching a speed reduction section of a road. In this manner, the vehicle 2 may be motored in response to the determined geographical position and the path the vehicle 2 is currently traveling on. Namely, when the vehicle 2 is

approaching a speed reduction section of a road, the vehicle 2 may be motored while its speed is reduced to match that of the speed reduction section. When motoring is performed with a negative overlap between the exhaust and inlet valves 26, 28, losses may be reduced, and energy may be saved.

According to the last two embodiments, e.g. an LACC having access to a geographical position of the vehicle 2, e.g. via use of a GPS system, and map data including topographic information and/or speed limit data for different road sections, may by utilising to motor the vehicle with the negative overlap as discussed herein.

Fig. 6 illustrates embodiments of a method 100 for operating a powertrain of a vehicle. The vehicle and the powertrain may be a vehicle 2 and a powertrain 4 as discussed above in connection with Figs. 1 - 5. Accordingly, in the following reference is also made to Figs. 1 - 5.

The method 100 comprises steps of:

- selecting 102 a gear in the transmission 10,

- engaging 104 the clutch 8,

- running 106 the ICE 6 in a negative torque state or in a zero torque state, and

- changing 108 a phase of the first camshaft 18, and/or of the second camshaft 20 to provide a first angle a of rotation of the crankshaft 16 in a transition between an exhaust stroke of the piston 22 and an intake stroke of the piston 22, during which first angle a of rotation both the intake valve 26 and the exhaust valve 28 are closed.

The steps of selecting 102 a gear in the transmission 10 and engaging 104 the clutch 8 entails that the powertrain 4 is set for motoring when the step of running 106 the ICE 6 in the negative torque state or in the zero torque state is performed. The step of phase shifting of the first and/or second camshaft 18, 20 provides a negative overlap between the exhaust and intake valves 26, 28. Thus, the method 100 provides for energy savings during motoring of the vehicle 2.

In the negative torque state, the ICE 6 produces negative torque, i.e. the ICE 6 forms a load on the powertrain 4. The amount of negative torque provided during negative torques states may be varied by the amount of negative overlap between the exhaust and intake valves 26, 28. Further, the amount of negative torque may be varied by either supplying no fuel to the ICE 6, or by supplying varied limited amounts of fuel to the ICE 6. The various limited amounts of fuel are so low that the ICE 6 is engine braking, although with a lesser negative torque than if no fuel is supplied to the ICE 6.

In the zero torque state, the ICE 6 does not form a load on the powertrain 4. The zero torque state is provided by using the negative overlap between the exhaust and intake valves 26, 28. and by suppling fuel to the ICE 6 at an amount such that the ICE 6 does neither produce negative torque, nor positive torque. Depending e.g. on the amount of negative overlap, the amount of fuel required for producing zero torque may vary.

The engine torque measuring arrangement 62 discussed above with reference to Fig. 4 may be utilised for controlling the amount of negative overlap between the exhaust and intake valves 26, 28, and/or for providing an adequate amount of fuel to be injected into the ICE 6, during any negative torque state as well as during the zero torque state.

The amount of fuel supplied to the ICE 6 may be gradually decreased from a positive torque state as the control system 12 is controlling the ICE 6 to reach the step of running 106 the ICE 6 in the negative torque state or in the zero torque state.

Similarly, in order to end the method 100, the amount of fuel supplied to the ICE 6 may be gradually increased by the control system 12 to reach a positive torque state of the ICE 6.

According to embodiments of the method 100, the step of changing 108 a phase of the first camshaft 18 and/or of the second camshaft 20 may comprise a step of:

- changing 1 16 the phase of the first camshaft 18 and/or of the second camshaft 20, such that the first angle a of rotation of the crankshaft 16 in the transition between the exhaust stroke of the piston 22 and the intake stroke of the piston 22 is at least 5 degrees. In this manner, a negative overlap may be provided.

According to embodiments of the method 100, the step of changing 108 a phase of the first camshaft 18 and/or of the second camshaft 20 comprises a step of:

- changing 1 18 the phase of the first camshaft 18 and/or of the second camshaft 20, such that the first angle a of rotation of the crankshaft 1 6 in the transition between the exhaust stroke of the piston 22 and the intake stroke of the piston 22 is within a range of

5 - 200 degrees. In this manner, a negative overlap may be provided. Within the range 5 - 200 degrees the produced negative torque by the ICE 6 may vary. Thus, according to some embodiments, a negative overlap suitable for particular motoring conditions of the vehicle 2 may be selected by selecting the first angle a of rotation of the crankshaft 16. According to embodiments, the step of selecting 102 a gear in the transmission 10 may comprise a step of selecting 109 a higher gear than appropriate for current driving conditions of the vehicle 2. This results in a reduction of the rotational speed of the crankshaft 16 during the motoring of the vehicle 2. Thus, the ICE 6 lower heat and gas exchange losses than on a gear appropriate for current driving conditions. Thus, the vehicle 2 may be motored over a longer period.

Depending on how the first and second camshafts 18, 20 are set when the ICE 6 produces positive torque to drive the vehicle 2, the step of changing 108 a phase of the first camshaft 18 and/or of the second camshaft 20, may include one of:

- Reduction from an overlap between the exhaust and intake valves 26, 28 when the ICE is producing positive torque, to a negative overlap between the exhaust and intake valves 26,

28 when the ICE 6 is operated for motoring the vehicle 2. That is, the herein defined first angle a of rotation of the crankshaft 16 goes from a negative value, during which an overlap exists, to a positive value during which a negative overlap exists.

- Increase a low negative overlap between the exhaust and intake valves 26, 28 when the ICE 6 produces positive torque to a larger negative overlap when the ICE 6 is operated for motoring the vehicle 2. That is, the herein defined first angle a of rotation of the crankshaft 16 goes from 0 degrees, or a small positive value, to a larger positive value.

The method 100 may be implemented while the vehicle 2 is driven under manual control by a driver of the vehicle 2.

Alternatively, the method 100 may be implemented while the vehicle 2 is driven under the control of a cruise control (CC), such as a look ahead cruise control (LACC), which may utilise geographical position of the vehicle and map data related to a travelling path ahead of the vehicle. Thus, e.g. an itinerary of the vehicle 2, topographic data, road section lengths, and/or speed limits, may be utilised for motoring the vehicle 2, and to utilise the benefits of the method 100.

Accordingly, particularly in the case of the method 100 being implemented during CC, preceding the steps of running 106 the ICE 6 in the negative torque state or in the zero torque state, and of changing 108 a phase of the first camshaft 18 and/or the second camshaft 20, the method 100 may comprise steps of:

- determining 1 10 a geographical position of the vehicle 2, and - determining 1 12 that the vehicle 2 is traveling on a downhill gradient, or that the vehicle 2 approaches a downhill gradient. In this manner, once it has been determined that the vehicle 2 is in a geographical position, in which it either is traveling on a downhill gradient or approaching a downhill gradient, the powertrain 4 of the vehicle 2 may be operated in accordance with the steps 102 - 108 of the method 100. The lower heat and gas exchange losses of the ICE 6 due to the negative overlap between the exhaust and intake valves 26,

28 provides for the vehicle 2 to be motored over a longer distance. This in turn saves energy.

Further, particularly in the case of the method 100 being implemented during CC, preceding the steps of running 106 the internal combustion engine in the negative torque state or in the zero torque state, and of changing 108 a phase of the first camshaft 18 and/or the second camshaft 20, the method 100 may comprise steps of:

- determining 1 10 a geographical position of the vehicle, and

- determining 1 14 that the vehicle is approaching a speed reduction section of a road. In this manner, once it has been determined that the vehicle 2 is in a geographical position, in which it is approaching a speed reduction section of a road, the powertrain 4 of the vehicle 2 may be operated in accordance with the steps 102 - 108 of the method 100. The lower heat and gas exchange losses of the ICE 6 due to the negative overlap between the exhaust and intake valves 26, 28 provides for the vehicle 2 to be motored over a longer distance, i.e. a longer distance before the speed reduction section of the road starts than if motoring without the negative overlap were performed. This in turn saves energy.

The speed reduction section of the road may be e.g. an upcoming reduction of the speed limit on the road the vehicle 2 is traveling on or a section of road leading up to an intersection and/or up to a traffic light.

In Fig. 6 the steps 1 10, 1 12, 1 14 have been indicated after the steps 102 and 104.

Alternatively one or more of the steps 1 10;1 12, 1 14 may be performed before one or both of the steps 102, 104.

The basic operation of a CC is known and will not be elaborated on herein. A driver of a vehicle sets a desired target speed for the vehicle. The CC determines a reference speed and demands the reference speed from the control system which controls the vehicle’s powertrain. The reference speed may vary within an interval around the target speed. With knowledge of the road ahead of the vehicle, an LACC may vary the vehicle’s speed according to variations of the road along which the vehicle travels, either within the reference speed interval as the vehicle travels on downhill and uphill gradients, or outside the reference speed interval e.g. when a speed reduction section of a road is upcoming.

Two non-limiting examples of implementation of the method 100 may be:

- In order to stay within the reference speed interval of the LACC, the control system 12 of the powertrain 4 may implement an embodiment of the method 100 according to the present invention thus, reducing the heat and gas exchange losses of the ICE 6 when the vehicle 2 is traveling on, or approaching, a shallow downhill gradient, in comparison with ordinary motoring with overlap between the exhaust and intake valves.

- As the vehicle 2 is approaching a speed reduction section of a road, the LACC may order the control system 12 of the powertrain 4 to implement an embodiment of the method 100 according to the present invention thus, reducing the heat and gas exchange losses of the ICE 6 to achieve a longer distance, over which the vehicle 2 is motored before reaching the speed reduction section of the road, in comparison with ordinary motoring with overlap between the exhaust and intake valves.

According to an aspect there is provided a computer program comprising instructions which, when the program is executed by a computer, cause the computer to carry out the method 100 according to any one of aspect and/or embodiments discussed herein, in particular with reference to Fig. 6. One skilled in the art will appreciate that the method 100 for operating a powertrain of a vehicle may be implemented by programmed instructions. These

programmed instructions are typically constituted by a computer program, which, when it is executed in a computer or control system, ensures that the computer or control system carries out the desired control, such as the method steps 102 - 1 18 according to the invention. The computer program is usually part of a computer programme product which comprises a suitable digital storage medium on which the computer program is stored.

Fig. 7 shows a computer-readable storage medium 90 according to embodiments. The computer-readable storage medium 90 comprises instructions which, when executed by a computer or other control system 12, causes the computer or other control system 12 to carry out the method 100 according to any one of aspect and/or embodiments discussed herein. The computer-readable storage medium 90 may be provided for instance in the form of a data carrier carrying computer program code for performing at least some of the steps 102 - 1 18 according to some embodiments when being loaded into the one or more calculation units 50 of the control system 12. The data carrier may be, e.g. a ROM (read-only memory), a PROM (programable read-only memory), an EPROM (erasable PROM), a flash memory, an EEPROM (electrically erasable PROM), a hard disc, a CD ROM disc, a memory stick, an optical storage device, a magnetic storage device or any other appropriate medium such as a disk or tape that may hold machine readable data in a non-transitory manner. The computer-readable storage medium may furthermore be provided as computer program code on a server and may be downloaded to the control system 12 remotely, e.g., over an Internet or an intranet connection, or via other wired or wireless communication systems.

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