GB2509971A

GB2509971A - Stable Speed Control for a vehicle

Info

Publication number: GB2509971A
Application number: GB1301026.9A
Authority: GB
Inventors: Gianmarco Brunetti
Original assignee: GM Global Technology Operations LLC
Current assignee: GM Global Technology Operations LLC
Priority date: 2013-01-21
Filing date: 2013-01-21
Publication date: 2014-07-23
Also published as: GB201301026D0

Abstract

The invention provides a method of operating a motor vehicle equipped with a powertrain, comprising the steps of: detecting if the motor vehicle is requested to move under a stable speed condition 600, and performing an operating strategy, if the request is detected. This operating strategy 625 comprising the steps of deÂtermining a mean value of the motor vehicle speed to be obtained during the stable speed condition, setting an allowable range of speed values around the determined mean value, and repeatedly performing a control cycle that operates the powertrain to accelerate the motor vehicle, until the motor vehicle speed increases to an upper limit of the allowable range of speed values. Then preventing the power-train from providing traction to the motor vehicle by operating a clutch to disengage the engine and allowing the vehicle to freewheel until the speed of the motor vehicle decreases from the upper limit to a lower limit of the alÂlowable range of speed values.

Description

A METHOD OF OPERATING A MOTOR VEHICLE

TECHNICAL FIELD

The present invention relates to a method of operating a motor vehicle.

BACKGROUND

It is known that any motor vehicle is equipped with a powertrain, namely with a group of components and/or devices that are designed for generating mechanical power and for delivering it to the drive wheels of the motor vehicle, in order to produce the traction that allows the motor vehicle to move.

A traditional powertrain includes an internal combustion engine (ICE), such as for exam-ple a compression-ignition engine (Diesel engine) or a spark-ignition engine (gasoline engine), which is couple to rotate a drive axle of the motor vehicle, typically the front drive axle.

The ICE may comprise an engine block defining at least a cylinder which accommodates a reciprocating piston coupled to rotate a crankshaft. The top of the cylinder is closed by a cylinder head, which cooperates with the piston to define a combustion chamber. A fuel-and-air mixture is cyclically supplied into the combustion chamber and ignited, thereby producing hot exhaUst gasses whose expansion causes the movement of the piston and thus the rotation of the crankshaft.

The crankshaft of the ICE is coupled to the drive axle by means of several intermediate components, globally referred as driveline, which include a transmission and a clutch connecting the transmission to the crankshaft.

The transmission, also referred as gearbox, is a mechanical device that includes several gears provided for transferring torque from the crankshaft to the derive axle, each of which defines a different gear ratio. The transmission can be actuated to engage one of these gears or another, thereby changing the gear ratio between the crankshaft and wheels of the drive axle. In some embodiments, the transmission is actuated manually by the driver using a transmission lever. In other embodiments, the transmission is actuated automatically by an electronic control system of the motor vehicle.

The clutch is a mechanical device provided for selectively disengage the crankshaft from the transmission, in order to allow a change of gear. The clutch may be a purely mechan-ical clutch or an electrically actuated clutch (e-clutch).

The e-clutch generally comprises an electrical actuator, which is operated by the elec-tronic control system of the motor vehicle. The e-clutch may be controlled by the driver of the motor vehicle with a clutch pedal, which is movable between a pressed position and a released position, and which is provided with a position sensor connected to the elec-tronic control system. When the clutch pedal is pressed, the electronic control system operates the clutch to disengage the crankshaft from the transmission. When the clutch pedal is released, the clutch returns in a configuration where the crankshaft and the transmission are engaged. In other embodiments, the e-clutch is completely controlled by the electronic control system of the motor vehicle, that automatically disengage the clutch when a change of gear is needed.

In order to reduce the polluting emissions and to increase the fuel economy, some powertrains may be additionally equipped with at least a motor-generator electric unit (MGU), and with an electrical battery suitable to supply the MGU.

In some embodiments (mild hybrid powertrains), the MGU may be a so called Belt Alter-nator Starter (BAS), which is coupled to the crankshaft of the ICE. The BAS is generally provided for starting the ICE, but it is also capable of providing a certain contribution of torque directly to the wheels during acceleration, and of generating a certain quantity of electrical energy during deceleration, working as a regenerative brake.

In other embodiments (full hybrid powertrains), the MGU may be a more powerful electric machine (EM), which is coupled to rotate the wheels of another drive axel of the motor vehicle, typically the rear drive axle. The EM can operate either as an electric motor, for assisting or replacing the ICE in propelling the motor vehicle, or as an electric generator, especially when the motor vehicle is braking, for charging the battery.

In still other embodiments, the powertrain may comprise both the BAS and the EM.

Independently from the kind of powertrain used, the quantity of torque supplied to the drive wheels of the motor vehicle is usually determined by the driver through an accel-erator pedal, which is provided with a position sensor connected to the electronic control system of the motor vehicle. On the basis of the position of the accelerator pedal, which is actuated by the driver, the electronic control system regulates the power supplied by the powertrain and thus the speed of the motor vehicle.

In particular, the driver may press the accelerator pedal to speed up the motor vehicle, he may release the accelerator pedal and possibly press the brake pedal to slow down, or he may keep the accelerator pedal in a stable position to maintain the speed of the motor vehicle at a constant level.

In the first case, the electronic control system generally operates the powertrain to in-crease the torque supplied to the drive wheels. In the second case, the electronic control system prevents the powertrain from supplying torque to the wheels and possibly acti- vates the MGU (BAS and/or EM) to absorb torque from the wheels and charge the bat-tery, thereby performing a regenerative brake. In the third case, the electronic control system generally operates the powertrain to supply a constant torque to the drive wheels, in order to overcome the mechanic and aerodynamic frictions.

From the above it follows that, even when the motor vehicle moves at a constant speed, the powertrain actually consumes a certain quantity of energy, which causes a certain level of fuel consumption and a certain level of polluting emissions.

An object of an embodiment of the invention is to provide a method of operating a motor vehicle, in particular a motor vehicle equipped with a full hybrid powertrain, with a mild hybrid powertrain or with a traditional powertrain adopting an e-clutch, which is able to reduce the energy spent to move the motor vehicle, thereby reducing the fuel consump-tion and the polluting emissions.

Another object is that of reaching that goal with a simple, rational and almost inexpensive solution.

SUMMARY

These and/or other objects are aftained by the features of the embodiments of the inven-tion as reported in the independent claims. The dependent claims recite preferred and/or especially advantageous features of the embodiments of the invention.

In particular, an embodiment of the invention provides a method of operating a motor ve-hicle equipped with a powertrain, wherein the method comprises the steps of: -detecting if the motor vehicle is requested to move under a stable speed condition, and -performing an operating strategy, if the request is detected, this operating strategy comprising the steps of: -determining a mean value of the motor vehicle speed to be obtained during the stable

S

speed condition, -setting an allowable range of speed values around the determined mean value, -repeatedly performing a control cycle that operates the powerirain to accelerate the mo-tor vehicle, until the motor vehicle speed increases to an upper limit of the allowable range of speed values, and then prevents the powertrain from providing traction to the motor vehicle, until the speed of the motor vehicle decreases from the upper limit to a lower limit of the allowable range of speed values.

As a matter of fact, when the motor vehicle is requested to move under a stable speed condition, that is substantially at a constant speed, the method provides for cyclically in-creasing and decreasing the speed of the motor vehicle between the upper limit and the lower limit around the mean speed value. If the difference between the upper and lower limit is sufficiently small (e.g. 4 km/h), the drivers perception is almost the same as the motor vehicle would move at constant speed, but the energy spent by the powertrain is advantageously reduced. In fact, the deceleration phases are substantially achieved by letting the motor vehicle move by inertia only As a consequence, a lot of energy is saved during these deceleration phases and, even if the following acceleration phases need the powertrain to spend a little more energy, it has been found that the overall results is a sensible reduction of the energy consumption.

According to an aspect of the invention, the operating method may comprise the steps of: -monitoring a speed of the motor vehicle, -monitoring a position of the accelerator pedal operatively connected to the powertrain, and -identifying the request if, over a predetermined time period, the variation of the moni- tored speed of the motor vehicle and the variation of the monitored position of the accel-erator pedal are below respective threshold values.

If the above mentioned threshold values for the vehicle speed variation and for the ac-celerator pedal position variation are sufficiently small (e.g. the threshold value of the speed variation may be 4 km/h), the proposed solution is able to identify when the driver ask for the motor vehicle to move substantially at a constant speed.

In this case, the mean value of the motor vehicle speed (for the stable speed condition) may be calculated as the mean value of the motor vehicle speed monitored during the above mentioned predetermined time period.

As an alternative, another aspect of the invention may provide the step of identifying the request when a cruise control system is activated.

A cruise control system is generally activated by the driver and is provided for automati-cally maintaining the speed of the motor vehicle at a constant speed.

In this case, the mean value of the motor vehicle speed (for the stable speed condition) may be a set-point value, which may be set by the driver through the cruise control sys-tem.

According to an aspect of the invention, the proposed method may be applied to a motor vehicle whose powertrain comprises at least an internal combustion engine coupled to a drive axle by means of an electrically actuated clutch (e.g. traditional or mild hybrid powertrain adopting an e-clutch), which allows to operate the clutch independently from the driver requests. In this case, the control cycle may provide for accelerating the motor vehicle to the upper speed limit by using the internal combustion engine, and for prevent-ing the powertrain from providing traction to the motor vehicle by operating the clutch to disengage the internal combustion engine from the drive axle.

In this way, during every deceleration phase of the motor vehicle, the internal combustion engine is automatically disengaged from the drive axle, thereby advantageously letting the motor vehicle move by inertia.

This phase, in which the motor vehicle move by inertia, may be referred as "sailing" of the motor vehicle.

According to another aspect of the invention, the proposed method may be applied to a motor vehicle whose powertrain comprises an internal combustion engine coupled to a drive axle by means of an electrically actuated clutch and an electric machine coupled to another drive axle (e.g. full hybrid powertrain adopting an e-clutch). In this case, the con- trol cycle may provide for actuating the clutch to disengage the internal combustion en-gine from the first drive axle, for accelerating the motor vehicle to the upper speed limit by using the electric machine, and for preventing the powertrairi from providing traction to the motor vehicle by switching off the electric machine.

In this way, the internal combustion engine is disengaged from the drive axle all the time, while the fluctuation of the motor vehicle speed is advantageously obtained using only the electric machine coupled to the other drive axle.

According to another aspect of the invention, the control cycle may provide for turning off the internal combustion engine when the clutch is operated to disengage the internal combustion engine from the drive axle, and for starting the internal combustion engine as the clutch is operated to engage the internal combustion engine to the drive axle again.

This aspect of the invention has the advantage that, during every deceleration phase, there's no fuel consumption nor polluting emissions at all.

An aspect of this embodiment provides that the internal combustion engine is started by performing injections of fuel into the engine cylinders when the clutch engages the inter-nal combustion engine to the drive axle.

This aspect of the invention has the advantage that the start of the internal combustion engine can be achieved without spending energy, because the engine crankshaft is mi-tially set into rotation by the wheels of the drive axle.

As an alternative, the internal combustion engine may be started by performing injections of fuel into the engine cylinders while an electric starter rotates the engine crankshaft, for example shortly before that the electric actuated clutch engages the internal combustion engine to the drive axle.

This alternative clearly requires to spend a certain amount of energy to start the engine, but has the advantage of reducing the stress which the clutch is subjected to when en-gaging the internal combustion engine to the drive axle.

According to a different aspect of the invention, the control cycle may provide for operat-ing the internal combustion at idle speed when the clutch is operated to disengage the intemalcombustion engine from the drive axle.

In this way, the internal combustion engine is turned on even during the deceleration phases, so that there's no need of activating the electrical starter before the clutch en-gages the internal combustion engine to the drive axle, thereby increasing the life time of the electric starter.

According to an aspect of the invention, the control cycles of the operating strategy may be repeated in continuous, in order to achieve the maximum benefit in terms of energy saving.

According to a different aspect of the invention, the control cycles of the operating strate-gy may be repeated after a predetermined delay between one another, in order to further reduce the stress which the clutch and/or the electric starter are subject to.

Another aspect of the invention provides that the control cycles are performed only if the determined mean value of the motor vehicle speed is below a predetermined threshold value.

This threshold value may be chosen to represent a speed limit below which the motor vehicle is supposed to travel under urban driving conditions, for example 70 km/h. Above this speed limit, the deceleration phases could be so fast that the powertrain could be almost always under an acceleration phase, thereby making the operating strategy fruit-less.

Another aspect of the invention provides for deactivating the operating strategy, if one of the following conditions is met: a position of an accelerator pedal operatively connected to the powertrain varies of a quantity that exceeds a threshold value thereof, a brake pe-dal is pressed, the speed of the motor vehicle exceeds the upper limit, the speed of the motor vehicle decreases below the lower limit.

This solutions has the advantage of allowing the electronic control system to operate the motor vehicle according to the conventional strategies, as soon as the driver requires an acceleration or a deceleration of the motor vehicle.

The method according to the invention can be carried out with the help of a computer program comprising a program-code for carrying out all the steps of the method de-scribed above, and in the form of a computer program product comprising the computer program. The method can be also embodied as an electromagnetic signal, said signal being modulated to carry a sequence of data bits which represent a computer program to carry out all steps of the method.

Another embodiment of the invention provides an apparatus for operating a motor vehi-cle equipped with a powertrain, wherein the apparatus comprises: -means for detecting if the motor vehicle is requested to move under a stable speed condition, and -means for performing an operating strategy, if the request is detected, the means for performing the operating strategy comprising: -means for determining a mean value of the motor vehicle speed to be obtained during the stable speed condition, -means for setting an allowable range of speed values around the determined mean value, -means for repeatedly performing a control cycle, which is configured to operate the powertrain to accelerate the motor vehicle, until the motor vehicle speed increases to an upper limit of the allowable range of speed values, and then to prevent the powertrain from providing traction to the motor vehicle, until the speed of the motor vehicle decreas-es from the upper limit to a lower limit of the allowable range.

As a matter of fact, this embodiment of the invention has the same advantages of the method described above, in particular that of reducing the fuel consumption and the pol-luting emission when the motor vehicle is requested to travel at substantially constant speed.

According to an aspect of the invention, the apparatus may further comprise: -means for monitoring a speed of the motor vehicle, -means for monitoring a position of the accelerator pedal operatively connected to the powertrain, and -means for identifying the request if, over a predetermined time period, the variation of the monitored speed of the motor vehicle and the variation of the monitored position of the accelerator pedal are below respective threshold values.

This solution can advantageously identify when the driver ask for the motor vehicle to move substantially at a constant speed.

As an alternative, another aspect of the invention may provide that the apparatus com-prises means for identifying the request when a cruise control system is activated.

According to an aspect of the invention, the apparatus may be applied to a motor vehicle whose powertrain comprises at least an internal combustion engine coupled to a drive axle by means of an electrically actuated clutch (e.g. traditional or mild hybrid powertrain adopting an e-clutch), which allows to operate the clutch independently from the driver requests. In this case, the means for performing the control cycle may comprise means for accelerating the motor vehicle to the upper speed limit by using the internal combus-tion engine, and means for preventing the powertrain from providing traction to the motor vehicle by operating the clutch to disengage the internal combustion engine from the drive axle.

According to another aspect of the invention, the apparatus may be applied to a motor vehicle whose powertrain comprises an internal combustion engine coupled to a drive axle by means of an electrically actuated clutch and an electric machine coupled to an-other drive axle (e.g. full hybrid powertrain adopting an e-clutch). In this case, the means for performing the control cycle may comprise means for actuating the clutch to disen-

B

gage the internal combustion engine from the first drive axle all the time! means for ac-celerating the motor vehicle up to the upper speed limit by using the electric machine, and means for preventing the powertrain from providing traction to the motor vehicle by switching off the electric machine.

According to another aspect of the invention, the means for performing the control cycle may comprise means for turning off the intemal combustion engine when the clutch is operated to disengage the internal combustion engine from the drive axle, and means for starting the internal combustion engine as the clutch is operated to engage the internal combustion engine to the drive axle again.

An aspect of thisembodiment provides that the means for starting the internal combus-tion engine comprise means for performing injections of fuel into the engine cylinders when the clutch engages the internal combustion engine to the drive axle.

This aspect of the invention has.the advantage that the start of the internal combustion engine can be achieved without spending energy, because the engine crankshaft is mi-tially set into rotation by the wheels of the drive axle.

As an alternative, the means for starting the intemal combustion engine may comprise an electric starter coupled to rotate an engine crankshaft and means for performing injec- tions of fuel into the engine cylinders while the electric starter rotates the engine crank-shaft, for example shortly before that the electric actuated clutch engages the internal combustion engine to the drive axle.

According to a different aspect of the invention, the means for performing the control cy-cle may comprise means for operating the internal combustion at idle speed when the clutch is operated to disengage the internal combustion engine from the drive axle.

According to an aspect of the invention, the means for performing the control cycles may be configured to repeated the control cycles in continuous, in order to achieve the maxi-mum benefit in terms of energy saving.

According to a different aspect of the invention, the means for performing the control cy- cles may be configured to repeated the control cycles after a predetermined delay be- tween one another, in order to further reduce the stress which the clutch and/or the elec-tric starter are subject to.

Another aspect of the invention provides that the means for performing the control cycle are configured to perform the control cycles only if the determined mean value of the mo-tor vehicle speed is below a predetermined threshold value.

Another aspect of the invention provides that the means for performing the operating strategy are configured to deactivate the operating strategy, if one of the following condi-tions is met: a position of an accelerator pedal operatively connected to the powertrain varies of a quantity that exceeds a threshold value thereof, a brake pedal is pressed, the speed of the motor vehicle exceeds the upper limit, the speed ofthe motor vehicle de-creases below the lower limit.

Still another embodiment of the invention provides a motor vehicle equipped with a powertrain and with an electronic control unit configured to: -detect if the motor vehicle is requested to move under a stable speed condition, and -perform an operating strategy, if the request is detected, this operating strategy comprising the steps of: -determining a mean value of the motor vehicle speed to be obtained during the stable speed condition, -setting an allowable range of speed values around the determined mean value, -repeatedly performing a control cycle that prevents the powertrain from providing trac-tion to the motor vehicle, until the speed of the motor vehicle decreases to a lower limit of the allowable range of speed values, and then operates the powertrain to accelerate the motor vehicle, as long as the motor vehicle increases from the lower limit up to an upper limit of the allowable range of speed values.

As a mailer of fact, this embodiment of the invention has the same advantages of the method described above, in particular that of reducing the fuel consumption and the pol-luting emission when the motor vehicle is requested to move substantially at constant speed According to an aspect of the invention, the control unit may be configured to: -monitor a speed of the motor vehicle, -monitor a position of the accelerator pedal operatively connected to the powertrain, and -identify the request if, over a predetermined time period, the variation of the monitored speed of the motor vehicle and the variation of the monitored position of the accelerator pedal are below respective threshold values.

The proposed solution can advantageously identify when the driver ask for the motor ve-hicle to move substantially at a constant speed.

As an alternative, another aspect of the invention may provide that the electronic control unit is configured to identify the request when a cruise control system is activated.

According to an aspect of the invention, the powertrain of the motor vehicle may com- prise at least an internal combustion engine coupled to a drive axle by means of an elec-trically actuated clutch (e.g. traditional or mild hybrid powertrain adopting an e-clutch), which allows to operate the clutch independently from the driver requests. In this case, the control unit may be configured to perform a control cycle that provides for accelerat-ing the motor vehicle to the upper speed limit by using the internal combustion engine! and for preventing the powertrain from providing traction to the motor vehicle by operat-ing the clutch to disengage the internal combustion engine from the drive axle.

According to another aspect of the invention, the powertrain of the motor vehicle may comprise an internal combustion engine coupled to a drive axle by means of an electri- cally actuated clutch and an electric machine coupled to another drive axle (e.g. full hy-brid powertrain adopting an e-clutch). In this case, the control unit may be configured to perform a control cycle that provides for actuating the clutch to disengage the internal combustion engine from the first drive axle, for accelerating the motor vehicle to the up-per speed limit by using the electric machine, and for preventing the powertrain from providing traction to the motor vehicle by switching off the electric machine.

According to another aspect of the invention, the control unit may be configured to per-form a control cycle that provides for turning off the internal combustion engine when the clutch is operated to disengage the internal combustion engine from the drive axle, and for starting the internal combustion engine as the clutch is operated to engage the inter-nal combustion engine to the drive axle again.

An aspect of this embodiment provides that the control unit is configured to start the in-ternal combustion engine by performing injections of fuel into the engine cylinders when the clutch engages the internal combustion engine to the drive axle.

This aspect of the invention has the advantage that the start of the internal combustion engine can be achieved without spending energy, because the engine crankshaft is ini-tially set into rotation by the wheels of the drive axle.

As an alternative, the control unit may be configured to start the internal combustion en- gine by performing injections of fuel into the engine cylinders while an electric starter ro-tates the engine crankshaft, for example shortly before that the electric actuated clutch engages the internal combustion engine to the drive axle.

This altemative clearly requires to spend a certain amount of energy to start the engine, but has the advantage of reducing the stress which the clutch is subjected to when en-gaging the internal combustion engine to the drive axle.

According to a different aspect of the invention, the control unit may be configured to per-form a control cycle that provides for operating the internal combustion at idle speed when the clutch is operated to disengage the internal combustion engine from the drive axle.

According to an aspect of the invention, the control unit may be configured to perform an operating strategy whose control cycles are repeated in continuous, in order to achieve the maximum benefit in terms of energy saving.

According to a different aspect of the invention, the control unit may be configured to per- form an operating strategy whose control cycles are repeated after a predetermined de-lay between one another, in order to further reduce the stress which the clutch and/or the electric starter are subject to.

Another aspect of the invention provides that the control unit is configured to perform the control cycles only if the determined mean value of the motor vehicle speed is below a predetermined threshold value.

Another aspect of the invention provides that the control unit is configured to deactivate the operating strategy, if one of the following conditions is met: a position of an accelera-tor pedal operatively connected to the powerlrain varies of a quantity that exceeds a threshold value thereof, a brake pedal is pressed, the speed of the motor vehicle ex-ceeds the upper limit, the speed of the motor vehicle decreases below the lower limit.

This solutions has the advantage of allowing the electronic control system to operate the motor vehicle according to the conventional strategies, as soon as the driver requires an acceleration or a deceleration of the motor vehicle:

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will now be described, by way of example, with reference to the accompanying drawings.

Figure 1 schematically illustrates a motor vehicle equipped with a full hybrid powertrain.

Figure 2 is a schematic view of an intemal combustion engine belonging to the power-train of figure 1.

Figure 3 is a schematic representation of the section A-A of the internal combustion en-gine of figure 3.

Figure 4 is a flowchart representing a method for operating the motor vehicle of figure 1.

Figure 5 is a flowchart representing a possible strategy to detect a request for the motor vehicle of figure ito move under a stable speed condition.

Figure 6 is a flowchart representing a particular operating strategy which may be includ-ed in the operating method of figure 4.

Figures from 7 to 10 represents the speed and the fuel consumption of the motor vehicle operated according to different alternatives of the operating strategy of figure 6.

Figure 11 is a flowchart representing another operating strategy which may be included in the operating method of figure 4.

DETAILED DESCRIPTION

Some embodiments may include a motor vehicle 100 as shown in figure 1, which com-prises a front drive axle 101 carrying a couple or front wheels 102, a rear drive axle 103 carrying a couple or rear wheels 104, and a powertrain 105 coupled to rotate the front wheels 102 and/or the rear wheels 104.

The powertrain 105 comprises an internal combustion engine (ICE) 110, such as for ex- ample a diesel engine or a gasoline engine. The ICE 110 may comprise, as shown in fig-ures 2 and 3, an engine block 120 defining at least a cylinder 125 having a piston 140 coupled to rotate a crankshaft 145. A cylinder head 130 cooperates with the piston 140 to define a combustion chamber 150. A fuel and air mixture (not shown) is disposed in the combustion chamber 150 and ignited, resulting in hot expanding exhaust gasses causing reciprocal movements of the piston 140. The fuel is provided by at least one fuel injector 160 and the air through at least one intake port 210. The fuel is provided at high pressure to the fuel injector 160 from a fuel rail 170 in fluid communication with a high pressure fuel pump 180 that increases the pressure of the fuel received from a fuel source 190. Each of the cylinders 125 has at least two valves 215, actuated by a cam- shaft 135 rotating in time with the crankshaft 145. The valves 215 selectively allow air in-to the combustion chamber 150 from the port 210 and alternately allow exhaust gases to exit through at least one exhaust port 220.

The air may be distributed to the air intake port(s) 210 through an intake manifold 200.

An air intake pipe 205 may provide air from the ambient environment to the intake mani-fold 200. In other embodiments, a throttle body 330 may be provided to regulate the flow of air into the manifold 200. In still other embodiments, a forced air system such as a tur-bocharger 230, having a compressor 240 rotationally coupled to. a turbine 250, may be provided. Rotation of the compressor 240 increases the pressure and temperature of the air in the intake pipe 205 and manifold 200. An intercooler 260 disposed in the intake pipe 205 may reduce the temperature of the air. The turbine 250 rotates by receiving ex-haust gases from an exhaust manifold 225 that directs exhaust gases from the exhaust ports 220 and through a series of vanes prior to expansion through the turbine 250. This example shows a variable geometry turbine (VGT) with a VGT actuator 290 arranged to move the vanes to alter the flow of the exhaust gases through the turbine 250. In other embodiments, the turbocharger 230 may be fixed geometry and/or include a waste gate.

The exhaust gases exit the turbine 250 and are directed into an exhaust system 270.

The exhaust system 270 may include an exhaust pipe 275 having one or more exhaust aftertreatment devices 280. The aftertreatment devices may be any device configured to change the composition of the exhaust gases. Some examples of aftertreatment devices 280 include1 but are not limited to, catalytic converters (two and three way), oxidation catalysts, lean NO traps, hydrocarbon adsorbers, selective catalytic reduction (8CR) systems, and particulate filters. Other embodiments may include an exhaust gas recircu- lation (EGR) system 300 coupled between the exhaust manifold 225 and the intake man- ifold 200. The EGR system 300 may include an EGR cooler 310 to reduce the tempera-ture of the exhaust gases in the EGR system 300. An EGR valve 320 regulates a flow of exhaust gases in the EGR system 300.

As shown in figure 1, the powertrain 105 may further comprise a Motor Generator electric Unit (MGU) 500, which is connected to a battery 505 through an inverter 510. The MGU 500 is an electro-mechanical energy converter, which is able either to convert electric energy supplied by the battery 505 into mechanical power (i.e., to operate as an electric motor), or to convert mechanical power into electric energy that charges the battery 505 (i.e., to operate as electric generator).

In general, the MGU 500 may comprise a rotor, which is arranged to rotate with respect to a stator, in order to generate or respectively receive the mechanical power. The rotor may comprise means to generate a magnetic field and the stator may comprise electric windings connected to the battery 505, or vice versa. When the MGU 500 operates as electric motor, the battery 505 supplies electric currents to the electric windings, which interact with the magnetic field to set the rotor into rotation. Conversely, when the MGU 500 operates as electric generator, the rotation of the rotor causes a relative movement of the electric windings in the magnetic field1 which generates electrical currents. The MGU 500 can be also switched off, so that it neither generate nor absorb power. The MGU 500 may be of any known type, for example a permanent magnet machine, a brushed machine or an induction machine. The MGU 500 may also be either an asyn-chronous or a synchronous machine.

The rotor of the MGU 500 may comprise a coaxial shaft 515, which is mechanically cou-pled to the crankshaft 145 of the ICE 110. In this way, when the MGU 500 operates as electric motor, the mechanical power generated thereby is transferred to the crankshaft 145, putting it into rotation. Conversely, when the MGU 500 operates as electric genera-tor, the rotation of the crankshaft 145 is transferred to the rotor of the MGU 500 to charge the battery 505. In the present example, the shaft 515 is coupled to the crankshaft 145 through a transmission belt 520, so that the MGU 500 may be alternatively referred as Belt Alternator Starter (BAS).

The powertrain 105 may additionally comprise a second and more powerful Motor Gen-erator electric Unit (MGU) 705, which is coupled to directly rotate the wheels 104 of the rear derive axle 103.

Also this second MGU 705 is an electro-mechanical energy converter, which is connect-ed to the battery 505 through an inverter 710, and which is able either to convert electric energy supplied by the battery 505 into mechanical power delivered to the drive axle 103 (i.e., to operate as an electric motor), or to convert mechanical power from the drive axle 103 into electric energy that charges the battery 505 (i.e., to operate as electric genera-tor). The MGU 705 can be also switched off, so that it neither generate nor absorb power to/from the drive axle 103. As a mailer of fact, the second MGU 705 may be an electric machine of the same kind of the first MGU 500, but it is generally of greater dimensions and power.

The motor vehicle 100 may further include an electronic control system 450 in communi-cation with one or more sensors and/or devices associated with the powertrain 105. The electronic control system 450 may receive input signals from various sensors configured to generate the signals in proportion to various physical parameters associated with the powertrain 105, such as for example a mass airflow and temperature sensor 340, a man-ifold pressure and temperature sensor 350, a combustion pressure sensor 360, coolant and oil temperature and level sensors 380, a fuel rail pressure sensor 400, a camshaft position sensor 410, a crankshaft position sensor 420, exhaust pressure and tempera- ture sensors 430 and an EGR temperature sensor 440. Furthermore, the electronic con-trol system 450 may generate output signals to various control devices that are arranged to control the operation of the powertrain 105, including for example the fuel injectors 160, the throttle body 330, the EGR Valve 320, the VGT actuator 290, and the MGU 500.

In particular, the electronic control system 450 is connected to receive input signals from a position sensor 445 of an accelerator pedal 446, which can be actuated by the driver of the motor vehicle 100 between a completely released position to an completely pressed position. On the basis of the position of the accelerator pedal 446, the electronic control system 450 calculates the power requested by the driver, and operates the powertrain accordingly, for example by regulating the quantity of fuel to be supplied into the en-gine cylinders 125.

The electronic control system 450 may include a one or more digital processing units (CPUs) in communication with a memory system and an interface bus. The memory sys-tem may include various storage types including optical storage, magnetic storage, solid state storage, and other non-volatile memory. The interface bus may be configured to send, receive, and modulate analog and/or digital signals to/from the various sensors tO and control devices. The CPUs are configured to execute instructions stored as a pro-gram in the memory system, and send and receive signals to/from the interface bus.

The ICE 110 is coupled to the front drive axle 101 through a transmission 550, a clutch 555 connecting the transmission 550 to the crankshaft 145, and a differential 560 con-necting the transmission 550 to the drive axle 101. In this way, the rotation of the engine crankshaft 145 can be transferred to wheels 102 of the front drive axle 101, and vice ver-sa.

The transmission 550 (also referred as gearbox) is a mechanical device that include several gears, each of which defines a different gear ratio. The transmission can be ac-tuated to engage one of these gears or another, thereby changing (shifting) the gear ratio between the engine crankshaft 145 and wheels 102. The transmission 550 may be actu- ated manually by the driver using a transmission lever. In other embodiments, the trans- mission 550 may actuated with the aid of an electric actuator. In this case, the transmis-sion 550 may be still controlled by the driver or may be controlled automatically by the electronic control system 450.

The clutch 555 is a mechanical device provided for selectively engaging and disengaging the engine crankshaft 145 to/from the transmission 550. In this example, the clutch 555 is an electrically actuated clutch (e-clutch). In other words, the clutch 555 is operated with the aid of an electric actuator (not shown). When the electric actuator is activated, the clutch 555 is moved in a configuration that disengages the engine crankshaft 145 from the transmission 550. When the electric actuator is deactivated, the clutch 555 au-tomatically moves (usually by means of springs) in a configuration that engages the crankshaft 145 to the transmission 550. The electric actuator of the.clutch 555 may be.

controlled by the electronic control system 450 of the motor vehicle 100 automatically or on the basis of the position of a clutch pedal 565, which can be moved by the driver from a released position to a pressed position. In this latter case, when the driver moves the clutch pedal 565 in the pressed position, the electronic control system 450 activates the electric actuator of the clutch 555, and when the driver release the clutch pedal 565, the electronic control system 450 deactivate the electric actuator of the clutch 555.

The motor vehicle 100 usually comprise also a brake pedal 570, which is connected, di-rectly or through the electronic control system 450, to a braking device (not shown) for braking the front wheels 102 and/or the rear wheels 104. The brake pedal 570 is normal-ly in a released position and can be pressed by the driver to activate the braking device.

While the motor vehicle 100 is travelling, the electronic control system 450 may be con-figured to operate the powertrain 105 according to the method illustrated in figure 4.

This method firstly provides for detecting whether the motor vehicle 100 is requested to travel under a stable speed condition (block 600) A stable speed condition may be de- fined as a travelling condition during which the speed of the motor vehicle 100 is re-quested to remain substantially constant.

According to an embodiment of the invention, the request for a stable speed condition may be detected according to the strategy illustrated by the flowchart of figure 5.

This detection strategy may firstly provide for checking whether a cruise control system of the motor vehicle 100 is activated (block 601). A cruise control system is generally ac-tivated by the driver and it is conventionally provided for automatically maintaining the speed of the motor vehicle 100 substantially at a constant speed, whose value may be set and possibly adjusted by the driver himself.

If the block 601 yields that the cruise control system is actually activated, then a request for a stable speed condition may be immediately identified (block 621) and thus detected by the block 600 of figure 4.

If the block 601 yields that the cruise control is not activated, the strategy may provide for detecting if the driver himself is actually driving ata stable speed condition.

To do so, the strategy may provide for measuring, over a predetermined time period T during the normal operation of the motor vehicle 100, a plurality of subsequent values V1, 30..., V of the speed of the motor vehicle 100 (block 602) and a plurality of subsequent values A1 A of the position of the accelerator pedal 446 (block 605).

The motor vehicle speed is the speed at which the motor vehicle 100 is moving on the road, and it can be measured by a speedometer (not shown) coupled to the wheels of the motor vehicle 100 and connected to the electronic control unit 450.

The position of the accelerator pedal 446 represents the torque that the driver is request-ing to the powertrain 105, and can be measured through the position sensor 445.

The time period I may be a calibration value memorized in the memory system of the electronic control system 450. By way of example, the time period T may be chosen in a range from 3s to lOs.

Once this monitoring steps have been completed, the strategy may provide for using the measured speed values V1,... V to identify (block 615) whether the variations of the motor vehicle speed, over the predetermined time period T, exceeded a predetermined threshold value AV.

The threshold value AV of the speed variation may be calibration value memorized in the memory system of the electronic control system 450. The threshold values MI is gener-ally quite small, for example a value of about 4 km/h.

In order to perform the identification of the block 615, the strategy may provide for de-termining the maximum and the minimum value among the measured speed values V1 V; for calculating the difference between these maximum and minimum values; and for checking whether the calculated difference exceeds the predetermined threshold value MI.

If the calculated difference exceeds the threshold value V, the identification block 615 2 C yields a positive result and the detection strategy is restarted from the beginning.

If conversely the identification block 615 yields a negative result, the detection strategy provides for using the measured values A1 A to identify (block 620) whether the var-iations of the accelerator pedal position, over the predetermined time period T, exceed a predetermined threshold value M. The threshold value AA may be a calibration value that is memorized in the memory sys-tem of the electronic control system 450. The threshold values APt is generally quite small, in order to be indicative of the fact that the driver is keeping the accelerator pedal 446 almost still.

In order to perform the identification of the block 620, the strategy may provide for de-termining the maximum and the minimum value among the measured values A1 Aof the accelerator pedal position; for calculating the difference between these maximum and minimum values; and for checking whether the difference exceeds the predeter-mined threshold value AA.

If the calculated difference exceeds the threshold value AA, the identification block 620 yields a positive result and the detection strategy is repeated from the beginning.

If conversely the identification block 620 yields a negative result, it globally means that the driver is currently requesting the motor vehicle 100 to move substantially at a con-stant speed, and accordingly the detection strategy provides for identifying this request for a stable speed condition (block 621) which is thus detected by the block 600 of figure 4.

When the block 600 of the flowchart illustrated in figure 4 yields that a request for a sta-ble speed condition has been detected, the operating method provides for activating a special operating strategy (block 625), hereinafter referred as sailing strategy.

As shown in figure 6, the sailing strategy may firstly provide for determining a mean val-ue V (block 630) of the motor vehicle speed to be obtained during the requested stable speed condition.

If the request for a stable speed condition is caused by the activation of the cruise control system, the mean value Vm is the constant speed value pre-set by the cruise control sys-tem itself.

If the request for a stable speed condition is not caused by the activation of the cruise control system, the mean value Vm may be calculated as the mean of the motor vehicle speeds V1 V,, measured during the time period T, which practically represents the constant speed that the driver is requiring the motor vehicle 100 to travel at.

Once the mean value V, has been determined, the sailing strategy may provide for checking whether the mean value Vm is below a predetermined threshold value V there-of (block 631).

The threshold value V(h represents a speed limit below which the motor vehicle 100 is supposed to travel under urban conditions, for example a value of about 70km/h. The threshold value Vtb may be a calibration value that is stored in the memory system of the electronic control system 450.

If the block 631 yields a negative results, the sailing strategy is simply deactivated (block 632).

If conversely the block 631 yields a positive result, the sailing strategy may provide for setting (block 635) an allowable set of speed values, which ranges from a lower limit V10., to an upper limit V including the determined mean value V. By way of example, the lower limit V1 may be calculated by subtracting a predetermined speed quantity AQ from the determined mean value Vm, whereas the upper limit V may be calculated by adding the same predetermined speed quantity AQ to the determined mean value Vm.

The speed quantity AQ may be a calibration value that is stored in the memory system of the electronic control system 450. In general, the speed quantity AQ is chosen quite small, for example of about 2km/h.

Once the lower limit V10, and the upper limit V have been calculated, the sailing strate-gy provides for using them in a control cycle of the powertrain iOS.

This control cycle firstly provides for operating the ICE 110 to gradually accelerate the motor vehicle 100 (block 640).

While the motor vehicle 100 is accelerated by the ICE 110, the control cycle provides for continuously monitoring (block 642) the motor vehicle speed V and for comparing it with the upper limit (block 645): As soon as the motor vehicle speed V reaches the upper limit V,1,, the control cycle pro-vides for operating the clutch 555 to disengage the engine crankshaft 145 from the transmission 550 (block 650), so that the ICE 110 is disconnected from the wheels 102 of the drive axle 101 and the motor vehicle 100 keeps moving by inertia only.

While the ICE 110 is disconnected from the drive axle 101, the control cycle provides for continuously monitoring (block 655) the motor vehicle speed V, which is expected to pro-gressively decrease due to the aerodynamic and mechanic frictions, and for comparing it with the lower limit V10 (block 660).

As soon as the motor vehicle speed V reaches the lower limit V10, the control cycle pro- vides for operating the clutch 555 to engage the engine crankshaft 145 to the transmis-sion 550 (block 665), and for repeating the control cycle from the beginning namely from the block 640.

In this way, the motor vehicle 100 performs a sequence of acceleration phases alternat- ed with deceleration phases, thereby causing the motor vehicle speed to repeatedly fluc-tuate between the lower limit V1, and the upper limit By setting the difference between the lower limit V1 and the upper limit sufficiently small, this fluctuations are not perceived by the driver of the motor vehicle 100.

Taking advantage of this sailing strategy, a first option of the invention may provide that, during each deceleration phase, namely as long as the clutch 555 disengages the ICE from the transmission 550, the control cycle comprises the step of operating the ICE at idle speed.

The results of this first option are illustrated by the graph of figure 7, wherein the line B1 represents the mean speed of the motor vehicle 100 during the sailing strategy, the line E1 represents the actual speed fluctuation due to the sailing strategy, the line F1 repre-sents the instant quantity of fuel that the ICE 110 would consume if the motor vehicle 100 were operated at the constant speed represented by line D1, and line G1 represents the actual quantity of fuel consumed by the ICE 110 thanks to the sailing strategy.

This graph clearly shows that the sailing strategy causes a little more fuel consumption during each acceleration phase, but a sensible reduction during the deceleration phases, so much so that the overall balance over the time yields a global reduction of the fuel consumption and thus of the polluting emissions.

In order to enhance this benefit, an alternative option of the invention may provide that, during each deceleration phase, namely as long as the clutch 555 disengages the ICE from the transmission 550, the control cycle comprises the step of turning the ICE 110 completely off.

In this case, the control cycle also provides for starting the ICE 110 again, as soon as the speed of the motor vehicle 100 reaches the lower limit V1, in order to allow the following acceleration phase to be performed.

The start of the ICE 110 may be achieved with the aid of the MGU 500. In other words, the ICE 110 may be started by performing injections of fuel into the engine cylinders 125, while the MGI) 500 is operated to rotate the engine crankshaft 145, shortly before that the clutch 555 engages the ICE 110 to the transmission 550.

The results of this option are illustrated by the graph of figure 8, wherein the line B2 rep-resents the mean speed of the motor vehicle 100 during the sailing strategy, the line E2 represents the actual speed fluctuation due to the sailing strategy, line F2 represents the instant quantity of fuel that the ICE 110 would consume if the motor vehicle 100 were operated at the constant speed represented by line D2, and line G2 represents the actual quantity of fuel consumed by the ICE 110 thanks to the sailing strategy.

This second graph shows that this option causes a little spike in the fuel consumption during the start of the ICE 110, but it also clearly shows that the overall fuel consumption reduction, and thus the overall reduction of polluting emissions, is greater for this second option than for the first one.

A side effect of this second option is that, due to high frequency of engine starting during the sailing strategy, the durability of the MGU 500 may be reduced.

In order to overcome this' side effect, a third option of the sailing strategy is that of start-ing the ICE 110 with the aid of the clutch 555 only. In other words, the ICE 110 may be started by simply performing injections of fuel into the engine cylinders 125 as soon as the clutch 555 engages the internal combustion engine 110 to the transmission 550.

In this way, the engine crankshaft 145 is advantageously set into rotation by the motion of the wheels 102, without the help of any additional power The results of this third option are illustrated by the graph of figure 9, wherein the line D3 represents the mean speed of the motor vehicle 100 during the sailing strategy, the line E3 represents the actual speed fluctuation due to the sailing strategy, line F3 represents the instant quantity of fuel that the ICE 110 would consume if the motor vehicle were op-erated at the constant speed represented by line D3, and line G3 represents the actual quantity of fuel consumed by the ICE 110 thanks to the sailing strategy.

This third graph shows that the fuel consumption spikes of the second option have been eliminated, so that the overall fuel consumption reduction, and thus the overall reduction of polluting emissions, is further increased.

A side effect of this third option is that, due to the great difference between the rotational speed of the crankshaft 145 and of the gears of the transmission 550 at the time when the clutch 555 engages them one another, the clutch 555, the transmission 550 and the crankshaft bearings are generally subject to great stresses which could reduce the dura-bility of these components.

In order to reduce this side effect, another option is that the control cycles of the sailing strategy are not repeated in continuous as described above, but that they are repeated with a predetermined delay between one another, for example by performing a control cycle every sixty seconds, thereby reducing the frequency with which the ICE 110 must be started.

The results of this fourth option are illustrated by the graph of figure 10, wherein the line D4 represents the mean speed of the motor vehicle 100 during the sailing strategy, the line E4 represents the actual speed fluctuation due to the sailing strategy, line F4 repre-sents the instant quantity of fuel that the ICE 110 would consume if the motor vehicle were operated at the constant speed represented by line D4, and line S. represents the actual quantity of fuel consumed by the ICE 110 thanks to the sailing strategy.

This fourth graph clearly shows that the reduction of fuel consumption (and polluting emissions) is lower under this fourth option than under the third one, but it is still present with respect to the conventional case in which the ICE 110 is operated to maintain the motor vehicle 100 at constant speed.

According to a different embodiment of the invention, the sailing strategy may be per-formed according to the alternative solution illustrated in figure 11.

This alternative sailing strategy involves all the steps of the preceding one at least until the calculation of the lower limit V10 and the upper limit (block 635).

Once the lower limit V, and the upper limit V, have been calculated, the alternative sailing strategy provides for activating the clutch 555 to disengage the engine brankshaft 145 from the transmission 550 (block 715), so that the ICE 110 is disconnected from the drive axle 101, and then for activating a control cycle that uses only the MGU 705 to cy-clically accelerate and decelerate the motor vehicle 100 around the mean value V. In particular, the control cycle firstly provides for operating the MGU 705 to supply torque to the rear drive axle 103 in order to gradually accelerate the motor vehicle 100 (block 715).

While the motor vehicle is accelerating, the control cycle provides for monitoring (block 722) the motor vehicle speed V and for comparing it with the upper limit (block 725).

As soon as the motor vehicle speed V reaches the upper limit the control cycle pro- vides for switching the MGU 705 off (block 730) so that the powertrain 105 does not pro-vide any traction to the motor vehicle 100, which keeps moving by inertia only.

While the MGU 705 is off, the control cycle provides for continuously monitoring (block 735) the motor vehicle speed V, which is expected to progressively decrease due to the aerodynamic and mechanic frictions, and for comparing it with the calculated lower limit V10 (block 740).

As soon as the motor vehicle speed V reaches the lower limit Vi, the control cycle is. re-peated from the beginning, namely from the block 720.

In this way, the motor vehicle lOb performs a sequence of acceleration phases alternat- ed with deceleration phases, thereby causing the motor vehicle speed to repeatedly fluc- tuate between the lower limit V10 and the upper limit while the ICE 110 is disen-gaged from the transmission 550 all the time According to this embodiment, while the clutch 555 disengages the ICE 110 from the transmission 550, namely during the entire sailing strategy, the ICE 110 may be operated at idle speed or possibly turned completely off.

Turning now to figure 4, the operating method provides for keeping the sailing strategy active as long as a deactivating condition is identified (block 670).

When the deactivating condition is identified, the sailing strategy is deactivated (block 675) and the electronic control system 450 restarts to operate the powertrain 105 accord-ing conventional strategies.

In particular, the operating method may provide for continuously monitoring, during the sailing strategy, the position of the brake pedal 570, as welt as the position of the accel-erator pedal 446 and the speed of the motor vehicle 100, and for deactivating the sailing control mode as soon as one of the following conditions is met: the accelerator pedal po-sition varies of a quantity that exceeds the threshold value A, the brake pedal 570 is pressed, the speed of the motor vehicle exceeds the upper limit or the speed of the motor vehicle decreases below the lower limit V10.

As a mafter of fact, the two first conditions are indicative of the fact that the driver doesn't want to travel at constant speed anymore, while the two last conditions are security con-ditions that may occur for example if the slope of the road changes so that the sailing strategy is unable to maintain the motor vehicle speed in the allowable range.

While at least one exemplary embodiment has been presented in the foregoing summary and detailed description, it should be appreciated that a vast number of variations exist. It should, also be appreciated that the exemplary embodiment or exemplary embodiments are only examples! and are not intended to limit the scope, applicability, or configuration in any way. Rather, the forgoing summary and detailed description will provide those skilled in the art with a convenient road map for implementing at least one exemplary embodiment, it being understood that various changes may be made in the function and arrangement of elements described in an exemplary embodiment without departing from the scope as set forth in the appended claims and in their legal equivalents.

REFERENCES

motor vehicle 101 front drive axle 102 front wheels 103 rear drive axle 104 rearwheels powertrain 110 internal combustion engine engine block cylinder cylinder head camshaft 140 piston crankshaft combustion chamber fuel injector fuelrail 180 fuel pump fuelsource intake manifold 205 air intake pipe 210 intake port 215 valves 220 exhaust pod 225 exhaust manifold 230 turbocharger 240 compressor 250 turbine 260 intercooler 270 exhaust system 275 exhaust pipe 280 afteitreatnient devices 290 VGT actuator 300 exhaust gas recirculation system 310 EGR cooler 320 EGR valve 330 throttle body 340 mass airflow and temperature sensor 350 manifold pressure and temperature sensor 360 in-cylinder pressure sensor 380 coolant and oil temperature and level sensors 400 fuel rail pressure sensor 410 camshaft position sensor 420 crankshaft position sensor 430 exhaust pressure and temperature sensors 440 EGR temperature sensor 445 accelerator pedal position sensor 446 accelerator pedal 450 electronic control system 500 MGU 505 battery 510 inverter 515 coaxial shaft 520 transmission belt 550 transmission 555 clutch 560 differential 565 clutch pedal 570 brake pedal 600 block 601 block 602 block 605 block 615 block 620 block 621 block 625 block 630 block 631 block 632 block 635 block 640 block 642 block 645 block 650 block 655 block 660 block 665 block 670 block 675 blockS 705 MGU 710 inverter 715 block 720 block 722 block 725 block 730 block 735 block 740 block

Claims

CLAIMS1. A method of operating a motor vehicle (100) equipped with a powertrain (105), comprising the steps of: -detecting if the motor vehicle (110) is requested to move under a stable speed condi-tion, and -performing an operating strategy, if the request is detected, this operating strategy comprising the steps of: -determining a mean value (Vm) of the motor vehicle speed to be obtained during the stable speed condition, -setting an allowable range of speed values around the determined mean value (V4, -repeatedly performing a control cycle that operates the powertrain (105) to accelerate the motor vehicle (100), until the motor vehicle speed (V) increases to an upper limit (V) of the allowable range of speed values, and then prevents the powertrain (105) from providing traction to the motor vehicle (100), until the speed (V) of the motor vehicle (100) decreases from the upper limit (V) to a lower limit (V1) of the allowable range of speed values.
2. A method according to claim I comprising the steps of: -monitoring a speed of the motor vehicle (100), -monitoring a position of the accelerator pedal (446) operatively connected to the power-train (105), and -identifying the request if, over a predetermined time period (D1 the variation of the mon-itored speed of the moto! vehicle (100) and the variation of the monitored position of the accelerator pedal (446) are below respective threshold values.
3. A method according to claim 1, comprising the step of identifying the request when a cruise control system is activated.
4. A method according to any of the preceding claims, wherein the powertrain (105) comprises an internal combustion engine (110) coupled to a drive axle (101) by means of an electrically actuated clutch (555), and wherein the control cycle provides for accelerat- ing the motor vehicle (100) to the upper speed limit (V) by using the internal combus-tion engine (110), and for preventing the powertrain (105) from providing traction to the motor vehicle (100) by operating the clutch (555) to disengage the internal combustion engine (110) from the drive axle (101).
5. A method according to any of the claims from Ito 3, wherein the powertrain (105) comprises an internal combustion engine (110) coupled to a drive axle (101) by means of an electrically actuated clutch (555) and an electric machine (705) coupled to another drive axle (103), and wherein the control cycle provides for actuating the clutch (555) to disengage the internal combustion engine (110) from the first drive axle (101), for accel- erating the motor vehicle (100) to the upper speed limit (V) by using the electric ma-chine (705), and for preventing the powertrain (105) from providing traction to the motor vehicle (100) by switching off the electric machine (705).
6. A method according to claim 4 or 5, wherein the control cycle provides for turning off the internal combustion engine (110) when the clutch (555) is operated to disengage the internal combustion engine from the drive axle (101), and for starling the internal combustion engine (110) as the clutch (555) is operated to engage the internal combus-tion engine to the drive axle (101) again.
7. A method according to claim 6, wherein the internal combustion engine (110) is started by performing injections of fuel into the engine cylinders (125) when the clutch (555) engages the internal combustion engine (110) to the drive axle (101).
8. A method according to claim 6, wherein the internal combustion engine (110) is started by performing injections of fuel into the engine cylinders (125) while an electric starter (500) rotates an engine crankshaft (145).
9. A method according to claim 4 or 5, wherein the control cycle provides for operat-ing the internal combustion engine (110) at idle speed when the clutch (555) is operated to disengage the intemal combustion engine (110) from.the drive axle (101).
10. A method according to any of the preceding claims, wherein the control cycles of the operating strategy are repeated in continuous.
11. A method according to any of the claims from ito 7, wherein the control cycles of the operating strategy are repeated after a predetermined delay between one another.
12. A method according to any of the preceding claims, wherein the control cycles are performed only if the determined mean value (Vm) of the motor vehicle speed is below a predetermined threshold value (V).
13. A method according to any of the preceding claims, comprising the step of deac-tivating the operating strategy if one of the following conditions is met: a position ol an accelerator pedal (446) operatively connected to the powertrain varies of a quantity that exceeds a threshold value thereof, a brake pedal (570) is pressed, the speed of the mo-tor vehicle (100) exceeds the upper limit, the speed of the motor vehicle (100) decreases below the Lower limit.
14. A computer program comprising a computer code suitable for performing the method according to any of the preceding claims.
15. A computer program product on which the computer program of claim 14 is stored.