GB2557624A

GB2557624A - A method for regenerating a particulate filter of an internal combustion engine

Info

Publication number: GB2557624A
Application number: GB1621133.6A
Authority: GB
Inventors: Frevert Nicolas; Fischer Hartmut; Fritzsche Jan
Original assignee: GM Global Technology Operations LLC
Current assignee: GM Global Technology Operations LLC
Priority date: 2016-12-12
Filing date: 2016-12-12
Publication date: 2018-06-27
Also published as: GB201621133D0

Abstract

A method of regenerating a particulate filter 280 of an internal combustion engine 110 on a motor vehicle 90 which includes monitoring a position of an accelerator 446 and executing a coasting strategy if the accelerator is in a completely released position. The coasting strategy of the motor vehicle comprises decoupling the internal combustion engine from a final drive (550, figure 2), activating an electric supercharger 500 to generate compressed air and delivering the compressed air to the particulate filter 280. The supercharger may be activated provided that a quantity of soot retained in the particulate filter and / or temperature of the particulate filter exceeds a predetermined threshold value. The coasting strategy may comprise turning the internal combustion engine off and / or operating at an idle speed and / or moving a cam phaser (155) in an overlapping position and / or be executed provided that the vehicle exceeds a predetermined speed threshold.

Description

(54) Title of the Invention: A method for regenerating a particulate filter of an internal combustion engine Abstract Title: A method for regenerating a particulate filter of an internal combustion engine (57) A method of regenerating a particulate filter 280 of an internal combustion engine 110 on a motor vehicle 90 which includes monitoring a position of an accelerator 446 and executing a coasting strategy if the accelerator is in a completely released position. The coasting strategy of the motor vehicle comprises decoupling the internal combustion engine from a final drive (550, figure 2), activating an electric supercharger 500 to generate compressed air and delivering the compressed air to the particulate filter 280. The supercharger may be activated provided that a quantity of soot retained in the particulate filter and I or temperature of the particulate filter exceeds a predetermined threshold value. The coasting strategy may comprise turning the internal combustion engine off and / or operating at an idle speed and / or moving a cam phaser (155) in an overlapping position and / or be executed provided that the vehicle exceeds a predetermined speed threshold.

1/3

FIG.2

2/3

515

FIG.3 □·□

3/3

S100

P1OO

FIG.4

A METHOD FOR REGENERATING A PARTICULATE FILTER OF AN INTERNAL COMBUSTION ENGINE

TECHNICAL FIELD

The present invention relates to a method of regenerating a particulate filter of an internal combustion engine on a motor vehicle. In particular, the present invention relates to a method of regenerating a gasoline particulate filter (GPF) of a spark-ignition engine, for example of a gasoline direct injection (GDI) engine.

BACKGROUND

It is known that modern GDI engines generate more particulate matter (soot) than traditional gasoline engines. In order to reduce the polluting emissions, these engines are often equipped with a GPF, which is located in the exhaust pipe to trap the soot before it reaches the atmosphere.

When the quantity of soot trapped inside the GPF exceeds a maximum level, the GPF must be subjected to a regeneration process that basically oxidises the retained soot to carbon dioxides, thereby cleaning up the particulate filter and restoring its original efficiency.

For the regeneration process to be performed, the temperature of the GPF must reach a level able to trigger the combustion of the soot (e.g. 550-600’C) and the oxygen content of the exhaust gas entering the GPF must be high enough to speed up and sustain the oxidation reactions.

These conditions can be obtained during the normal operation of the engine (i.e. when a fuel and air mixture is actually disposed and ignited in the engine combustion chambers) by means of a so-called active regeneration process. The active regeneration process generally provides for operating the engine at lean lambda (i.e. with a fuel and air mixture having a lambda value larger than one), in order to increase the oxygen content in the exhaust gas, while retarding the ignition of the fuel and air mixture and/or performing late fuel injections, in order to increase the exhaust gas temperature and thus the GPF temperature.

The active regeneration process is therefore a process that implies a reduced efficiency of the engine, with a reduction of the engine performance and an increase of the fuel consumption.

The soot retained in the GPF may be also removed by means of a so-called passive regeneration process, which happens almost spontaneously when the temperature and the amount of oxygen inside the GPF are very high.

Conventionally, the conditions for a proper passive regeneration of the GPF are met when, upon a complete release of the accelerator, the engine enters a deceleration fuel cut-off (DFCO) phase where the fuel injection is suspended and the crankshaft is still coupled to the final drive of the motor vehicle (e.g. the drive wheels).

In this way the crankshaft is rotated by the final drive and the engine basically operates as a compressor that delivers an oxygen-reach air stream to the GPF. Hence, if the GPF temperature is sufficiently high (e.g. >600°C), the combustion of the retained soot is triggered and sustained.

However, more and more motor vehicles are nowadays implementing coasting strategies that, upon a complete release of the accelerator, prescribe for decoupling the engine from the final drive and then for operating the engine at idle speed or even for turning the engine completely off.

On these motor vehicles, the DFCO phases of the engine are largely reduced and thus also the passive regenerations of the GPF, which therefore requires to be subjected to more frequent active regeneration processes with the related performance loss and fuel consumption.

SUMMARY

An object of the present disclosure is that of providing a solution for triggering and sustaining passive regenerations of the particulate filter even during the above-mentioned coasting strategy of the motor vehicle.

This and other objects are achieved by the embodiments of the solution having the features reported in the independent claims. The dependent claims delineate additional aspects of such embodiments.

In greater details, an embodiment of the solution provides a method of regenerating a particulate filter of an internal combustion engine on a motor vehicle, comprising:

- monitoring a position of an accelerator of the internal combustion engine,

- executing a coasting strategy of the motor vehicle, if the accelerator is in a completely released position, wherein the coasting strategy of the motor vehicle comprises:

- decoupling the internal combustion engine from a final drive of the motor vehicle,

- activating an electric supercharger of the internal combustion engine to generate compressed air, and

- delivering the compressed air to the particulate filter.

Thanks to this solution, even if the engine is decoupled from the final drive during the coasting strategy, the oxygen-reach compressed air generated by the electric supercharger is able to cause and sustain an effective passive regeneration process of the particulate filter.

By restoring the possibility of performing passive regeneration processes during the coasting strategies, the need for active regeneration processes may be significantly reduced as well as the related side effects in terms of performance loss and fuel consumption. According to an aspect of the solution, the electric supercharger may be activated provided that a quantity of soot retained in the particulate filter exceeds a predetermined threshold value thereof.

In this way the electric supercharger is only activated if the need exists for subjecting the particulate filter to a passive regeneration.

According to another aspect of the solution, the electric supercharger may be activated provided that a temperature of the particulate filter exceeds a predetermined threshold value thereof.

In this way the electric supercharger is only activated if the thermal conditions for a passive regeneration process of the particulate filter exists.

In some embodiments, the coasting strategy may further comprise turning the internal combustion engine off.

Thanks to this aspect no fuel is consumed during the coasting strategy ofthe motor vehicle, thereby saving energy and reducing the emissions.

In other embodiments, the coasting strategy may comprise operating the internal combustion engine at idle speed.

This aspect has the effect that all the ancillaries driven by the engine, such as for example oil pump, fuel pump or others, may continue to properly operate during the coasting strategy.

According to a different aspect ofthe solution, the compressed air may be delivered to the particulate filter via the internal combustion engine.

In other words, the compressed air generated by the electric supercharger may flow through an intake valve into a combustion chamber ofthe engine and, from the combustion chamber, through an exhaust valve into an exhaust pipe leading to the particulate filter. Thanks to this aspect, the method may be implemented without modifying the layout ofthe internal combustion engine.

In this context, the coasting strategy may further comprise moving a cam phaser of the internal combustion engine in an overlapping position, for example a maximum overlapping position thereof.

A cam phaser is a device that is able to change the timing of the opening and/or closing events ofthe intake and/or exhaust valves. An overlapping position is a position ofthe cam phaser for which the intake valves open before the closure of the exhaust valves so that, while the engine crankshaft is covering a certain angle of rotation or overlapping angle, both the intake and the exhaust valves are contemporaneously open. The maximum overlapping position is the cam phaser position that corresponds to the maximum value ofthe overlapping angle.

By moving the cam phaser of the internal combustion engine in an overlapping position, the compressed air generated by electric supercharger may thus freely flow through the combustion chamber and reach the particulate filter.

In other embodiments, the compressed air may be delivered to the particulate filter via a conduit that connects the electric supercharger to the particulate filter by-passing the internal combustion engine.

In this way the delivery of the compressed air to the particulate filter may be easier to manage.

According to another aspect of the solution, the coasting strategy may be executed provided that a speed of the motor vehicle exceeds a predetermined threshold value thereof. In this way the coasting strategy is only executed if the motor vehicle is actually moving and the driver wants to slow down.

According to the present disclosure, the method can be carried out with the help of a computer program comprising a program-code for carrying out all the steps of the method described 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 solution provides a motor vehicle comprising an internal combustion engine, a particulate filter and an electronic control unit configured to:

- monitor a position of an accelerator of the internal combustion engine,

- execute a coasting strategy of the motor vehicle, if the accelerator is in a completely released position, wherein the coasting strategy of the motor vehicle provides for the electronic control unit to:

- decouple the internal combustion engine from a final drive of the motor vehicle,

- activate an electric supercharger of the internal combustion engine to generate compressed air, and

- deliver the compressed air to the particulate filter.

This embodiment of the solution achieves basically the same effects of the method above, in particular that allowing an effective passive regeneration of the particulate filter even when the motor vehicle is decoupled from the final drive.

The aspects of the solution described with reference to the method may be applied also to this embodiment. In particular, the electronic control unit may be configured to execute the coasting strategy provided that a speed of the motor vehicle exceeds a predetermined threshold value thereof. The electronic control unit may be configured to activate the electric supercharger provided that a quantity of soot retained in the particulate filter exceeds a predetermined threshold value thereof and/or provided that a temperature of the particulate filter exceeds a predetermined threshold value thereof. The coasting strategy may provide for the electronic control unit to turn the internal combustion engine off or to operate the internal combustion engine at idle speed. The compressed air may be delivered to the particulate filter via the internal combustion engine or via a conduit that connects the electric supercharger to the particulate filter by-passing the internal combustion engine. The coasting strategy may provide for the electronic control unit to move a cam phaser of the internal combustion engine in an overlapping position thereof, for example a maximum overlapping position.

Still another embodiment of the solution provides an apparatus for regenerating a particulate filter of an internal combustion engine on a motor vehicle, comprising:

- means for monitoring a position of an accelerator of the internal combustion engine,

- means for executing a coasting strategy of the motor vehicle, if the accelerator is in a completely released position, wherein the means for executing the coasting strategy of the motor vehicle comprises:

- means for decoupling the internal combustion engine from a final drive of the motor vehicle,

- means for activating an electric supercharger of the internal combustion engine to generate compressed air, and

- means for delivering the compressed air to the particulate filter.

Also this embodiment of the solution achieves basically the same effects of the method above, in particular that allowing an effective passive regeneration of the particulate filter even when the motor vehicle is decoupled from the final drive.

The aspects of the solution described with reference to the method may be applied also to this embodiment, in particular, the electronic control unit may be configured to execute the coasting strategy provided that a speed of the motor vehicle exceeds a predetermined threshold value thereof. The means for activating the electric supercharger may be configured to activate the electric supercharger provided that a quantity of soot retained in the particulate filter exceeds a predetermined threshold value thereof and/or provided that a temperature of the particulate filter exceeds a predetermined threshold value thereof. The means for executing the coasting strategy may include means for turning the internal combustion engine off or means for operating the internal combustion engine at idle speed. The means for delivering the compressed air may be configured to delivered the compressed air to the particulate filter via the internal combustion engine or via a conduit that connects the electric supercharger to the particulate filter by-passing the internal combustion engine. The means for executing the coasting strategy may comprise means for moving a cam phaser of the internal combustion engine in an overlapping position thereof, for example a maximum overlapping position.

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 shows an automotive system.

Figure 2 shows an internal combustion engine ofthe automotive system according to the section A-A of figure 1.

Figure 3 schematically shows an automotive system according to another embodiment of the disclosure.

Figure 4 is a flowchart of a detecting method according to an embodiment of the present disclosure.

DETAILED DESCRIPTION

Some embodiments may include a motor vehicle 90 featuring an automotive system 100, as shown in figures 1 and 2, that includes an internal combustion engine (ICE) 110. In this example, the ICE 110 is a spark-ignition engine (e.g. a gasoline engine), in particular a gasoline direct injection (GDI) engine. In other embodiments, the ICE 110 could be a compression-ignition engine (e.g. Diesel engine). The ICE 110 has an engine block 120 defining at least one 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 gas causing reciprocal movement ofthe piston 140 and the rotation of the crankshaft 145. A spark plug 360 may be coupled to each combustion chamber 150 to provide a spark that ignites the fuel and air mixture.

The fuel is provided by at least one fuel injector 160 coupled directly to the combustion chamber 150 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 increase 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 camshaft 135 rotating in time with the crankshaft 145. The valves 215 include at least one intake valve that selectively allows air into the combustion chamber 150 from the port 210, and at least one exhaust valve that alternately allows exhaust gasses to exit through an exhaust port 220.

The ICE 110 may be further equipped with a cam phaser 155. The cam phaser 155 is a device that can be moved in different positions (or configurations) to selectively vary the timing between the camshaft 135 and the crankshaft 145. In this way, the cam phaser 155 changes the timing of the valves’ opening and/or closing events. In particular, there are positions of the cam phaser 155 (hereinafter referred to as overlapping positions) in which the intake valves open before the closure of the exhaust valves. In this way, while the crankshaft 145 is covering a certain angle of rotation (hereinafter referred to as overlapping angle), both the intake and the exhaust valves are contemporaneously open. The position of the cam phaser 155 that corresponds to the maximum value of the overlapping angle may be generally referred as maximum overlapping position. In the present example, the cam phaser 155 is an electrically driven cam phaser, namely a cam phaser that is moved in the different positions by means of an electric actuator. In other embodiments, the cam phaser 155 could be a more conventional mechanical or hydraulic cam phaser.

The air may be distributed to the air intake port(s) 210 through an intake manifold 200. An air intake duct 205 may provide air from the ambient environment to the intake manifold 200. A throttle body 330 may be provided to regulate the flow of air into the manifold 200. On the other side, the exhaust gas may be directed from the exhaust port(s) 220 into an exhaust system 270 through an exhaust manifold 225.

The exhaust system 270 may include an exhaust pipe 275 having one or more exhaust aftertreatment devices. The aftertreatment devices may be any device configured to change the composition of the exhaust gas. In the present example, the aftertreatment devices include at least one particulate filter 280, in this case a gasoline particulate filter (GPF), which is provided for trapping particulate matter (soot) contained in the exhaust gas. The aftertreatment devices may also include a catalytic converter 285 located in the exhaust pipe 275 upstream of the particulate filter 280, as well as other devices such as lean NOx traps, hydrocarbon adsorbers anc selective catalytic reduction (SCR) systems.

The catalytic converter 285 may be a three-way catalytic converter (TWC), which is generally designed to prompt three different reactions: the reduction of nitrogen oxides to nitrogen and oxygen; the oxidation of carbon monoxide to carbon dioxide; and the oxidation of unburnt hydrocarbons to carbon dioxide and water. In some embodiment, the catalytic converter 285 may be combined with or integrated in the particulate filter 280 (this combination is usually used for gasoline engine and it is referred as to 4-way gasoline particulate filter). A 4-way gasoline particulate filter may be generally obtained by providing the particulate filter 280 with a catalytic coating.

Some embodiments may also include an exhaust gas recirculation (EGR) system 300 coupled between the exhaust manifold 225 and the intake manifold 200. The EGR system 300 may include an EGR cooler 310 to reduce the temperature of the exhaust gasses in the EGR system 300. An EGR valve 320 regulates a flow of exhaust gasses in the EGR system 300.

In some embodiments, a forced air system such as a turbocharger 230, having a compressor 240 rotationally coupled to a turbine 250, may be provided. The turbine 250 is located in the exhaust pipe 275, usually between the exhaust manifold 225 and the catalytic converter 285, and rotates by receiving the exhaust gas from the exhaust ports 220. Prior to the expansion through the turbine 250, the exhaust gas may be directed through a series of vanes, which are movable to alter the flow of the exhaust gas through the turbine 250. This example shows a variable geometry turbine (VGT) with a VGT actuator 290 arranged to move the vanes. In other embodiments, the turbocharger 230 may be fixed geometry and/or include a waste gate. The compressor 230 is located in the intake duct 205, so that the rotation of the compressor 240 (driven by the turbine 250) increases the pressure and temperature of the air in the duct 205 and manifold 200. An intercooler 260 may be disposed in the intake duct 205 downstream of the compressor 240 to reduce the temperature of the air.

The ICE 110 may be also equipped with an electric supercharger 500 disposed in the intake duct 205, for example downstream of the compressor 240. The electric supercharger 500 is an air compressor which is driven by an electric motor to generate compressed air. The compressed air generated by the electric supercharger 500 is conveyed by the intake duct 205 into the intake manifold 200 and the ICE 110. A by-pass conduit 505 may branch from a point of the intake duct 205 between the compressor 240 and the electric supercharger 500 to lead in a point ofthe intake duct between the electric supercharger 500 and the intercooler 260. A valve 510 may be also provided for selectively diverting air directed towards the supercharger 500 into the by-pass conduit 505 and directly into the intake manifold 200.

In some embodiments, as shown in figure 3, an additional conduit 515 may connect the outlet of the electric supercharger 500 directly with a point of the exhaust pipe 275 upstream of the particulate filter 280, for example between the particulate filter 280 and the catalyst converter 285. An additional valve 520 may be provided for selectively allow the compressed air generated by the electric supercharger 500 to flow towards the intake manifold 200 or into the additional conduit 515 towards the particulate filter 280.

In order to move the motor vehicle 90, the crankshaft 145 of the ICE 110 is mechanically coupled to a final drive 550 of the motor vehicle 90 by means of a transmission 555, as very schematically shown in figure 2. The final drive 550 may be any part or device able to transform the torque generated by the ICE into a tractive force that causes to motor vehicle to move, such as for example one or more drive wheels. The transmission 555 may be a manual transmission or an automatic transmission. The transmission generally includes a gearbox coupled to the final drive 550, for example trough a driveline, and a clutch coupled between the gearbox and the crankshaft 145. The clutch may be selectively moved in a closed position, where it actually engages the crankshaft 145 to the gearbox, or in an open position, where the crankshaft 145 is disengaged from the gearbox. The clutch may be an electrically driven clutch, namely a clutch that is moved between the closed and the open position by an electric actuator. The gearbox may be moved in different positions to change the speed ratio between the crankshaft 145 and the final drive 550. These positions usually include also a neutral position in which the crankshaft 145 is disengaged from the final drive 550, irrespective ofthe position ofthe clutch.

The ICE 110 is further equipped with an accelerator 446, for example an accelerator pedal, which can be manually moved by a driver in different positions to regulate the power generated by the ICE 110, for example by regulating the position ofthe throttle valve 330. In particular, the accelerator 446 is designed to generally stay in a released position, for example biased by a spring or other suitable device, and can be moved by the driver in any intermediate position between the released position and a fully depressed position.

The automotive system 100 may further include an electronic control unit (ECU) 450 in communication with one or more sensors and/or devices associated with the ICE 110. The ECU 450 may receive input signals from various sensors configured to generate the signals in proportion to various physical parameters associated with the ICE 110. The sensors include, but are not limited to, a mass airflow and temperature sensor 340, a manifold pressure and temperature sensor 350, coolant and oil temperature and level sensors 380, a fuel rail pressure sensor 400, a cam position sensor 410, a crank position sensor 420, exhaust pressure and temperature sensors 430, a lambda sensor 435, an EGR temperature sensor 440, and an accelerator position sensor 445. Furthermore, the ECU 450 may generate output signals to various control devices that are arranged to control the operation of the ICE 110, including, but not limited to, the fuel injectors 160, the throttle body 330, the EGR Valve 320, the VGT actuator 290, the spark plugs 360, the cam phaser 155, the valves 510 and/or 520 and the electric supercharger 500. Note, dashed lines are used to indicate communication between the ECU 450 and the various sensors and devices, but some are omitted for clarity.

Turning now to the ECU 450, this apparatus may include a digital central processing unit (CPU) in communication with a memory system and an interface bus. The CPU is configured to execute instructions stored as a program in the memory system 460, and send and receive signals to/from the interface bus. The memory system 460 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 and control devices. The program may embody the methods disclosed herein, allowing the CPU to carryout out the steps of such methods and control the ICE 110.

The program stored in the memory system 460 is transmitted from outside via a cable or in a wireless fashion. Outside the automotive system 100 it is normally visible as a computer program product, which is also called computer readable medium or machine readable medium in the art, and which should be understood to be a computer program code residing on a carrier, said carrier being transitory or non-transitory in nature with the consequence that the computer program product can be regarded to be transitory or nontransitory in nature.

An example of a transitory computer program product is a signal, e.g. an electromagnetic signal such as an optical signal, which is a transitory carrier for the computer program code. Carrying such computer program code can be achieved by modulating the signal by a conventional modulation technique such as QPSK for digital data, such that binary data representing said computer program code is impressed on the transitory electromagnetic signal. Such signals are e.g. made use of when transmitting computer program code in a wireless fashion via a wireless connection to a laptop.

In case of a non-transitory computer program product the computer program code is embodied in a tangible storage medium. The storage medium is then the non-transitory carrier mentioned above, such that the computer program code is permanently or non-permanently stored in a retrievable way in or on this storage medium. The storage medium can be of conventional type known in computer technology such as a flash memory, an Asic, a CD or the like.

Instead of an ECU 450, the automotive system 100 may have a different type of processor to provide the electronic logic, e.g. an embedded controller, an on-board computer, or any processing module that might be deployed in the vehicle.

As indicated in the flowchart of figure 4, the ECU 450 may be particularly configured to monitor (e.g. to repeatedly sense) the position a of the accelerator 446 (block S100), for example by means of the position sensor 445.

Based on the sensed position of the accelerator 446 and other engine operating parameters, the ECU 450 may be configured to determine the quantity of fuel to be injected into the combustion chambers 150 and to control the fuel injectors 160 accordingly. In this way, the fuel and air mixture is actually disposed inside the combustion chambers 150 and ignited by the spark plugs 360 (in case of GDI engine) or by the compression (in case of the Diesel engine).

During this operation, the ECU 450 may be also configured to compare (block S105) the accelerator position a with a predetermined value ao thereof, wherein the value ao indicates that the accelerator 446 is in the released position.

If the comparison yields that the accelerator 446 has been brought in the released position (e.g. α=αο), then the ECU 450 may be configured to execute a coasting strategy P100 of the motor vehicle 90.

In some embodiments, the coasting strategy may be executed provided that the accelerator 446 reaches its released position while the motor vehicle 90 is actually moving on the ground, so that the accelerator release is indicative of the fact that the driver wants to slow down.

To do so, the ECU 450 may be configured to sense the speed γ of the motor vehicle 90 on the ground (block S110) and to compare the sensed speed γ with a predetermined threshold value Ymin thereof (block S115), typically a threshold value that represents the minimum speed for the activation of the coasting strategy P100. The threshold value ymin may be a calibration value determined with an experimental activity and stored in the memory system.

If the sensed speed γ is equal to or higher than the minimum value ymin and the accelerator position a corresponds to the released position do, then the coasting strategy P100 is executed.

The coasting strategy P100 may provide for the ECU 450 to disengage the ICE 110 from the final drive 550 (block S115), for example by moving the gearbox of the transmission 555 in the neutral position (especially in case of automatic transmission) or by moving the clutch in the open position (especially in case of manual transmission with electrically driven clutch).

Once disengaged, the ICE 110 may be turned off or operated at idle speed (block S120). The ICE 110 may be turned off by suspending the fuel injections and the spark generations, whereas it may be operated at idle speed by controlling the fuel injections in order to maintain a minimum rotational speed of the crankshaft 145.

According to the coasting strategy P100, the ECU 450 may be also configured to evaluate a level λ of soot that has been accumulated inside the particulate filter 280 (block S125), and to compare the evaluated level λ with a predetermined threshold value thereof Amax (block S130), typically a threshold value that represents a maximum level of soot that can be retained in the particulate filter 280.

To evaluate the soot level λ, the ECU 450 may implement a strategy based on the pressure differential across the particulate filter 280 and/or based on estimating models that takes into account other engine operating parameters. The threshold value Amax of the soot level may be a calibration value determined with an experimental activity and stored in the memory system 460.

As a matter of fact, if the soot level A is equal to or higher than the threshold value Amax, it means that the particulate filter 280 is full of soot and that a regeneration is needed to prevent an excessive backpressure and for restoring the efficiency of the particulate filter

280.

At the same time, the ECU 450 may be also configured to sense a temperature τ of the particulate filter 280 (block S135), and to compare the evaluated temperature τ with a predetermined threshold value thereof Tmin (block S140), typically a threshold value that represents a minimum temperature that is able to cause the combustion (oxidation) of the soot retained inside the particulate filter 280.

The particulate filter temperature τ may be determined by the ECU 450 using a dedicated sensor (not shown) or estimated on the basis of other parameters, for example on the basis of the temperature of the exhaust gas as measured by the exhaust temperature sensors 430. The threshold value Tmin of the particulate filter temperature may be a calibration value determined with an experimental activity and stored in the memory system 460. In general, the threshold value Tmin of the particulate filter temperature is higher than 550°C, for example equal to 600°C or more.

As a matter of fact, if the particulate filter temperature τ is equal to or higher than the threshold value Tmin, it means that the thermal conditions for a passive regeneration of the particulate filter 280 are met.

However, to perform an efficient passive regeneration, oxygen-reach air should be introduced in the particulate filter to speed up and sustain the soot combustion in an efficient manner.

For this reason, if the soot level λ inside the particulate filter 280 is equal to or higher than the threshold value A_max (regeneration needed) and if the particulate filter temperature τ is equal to or higher than the threshold value T_mm (thermal condition met), the coasting strategy P100 may provide for the ECU 450 to activate the electric supercharger 500 (block S145), in order to generate a stream of compressed air, and to deliver the compressed air into the particulate filter 280 (block S150).

In this way, even if the ICE 110 is decoupled from the final drive 550 during the coasting strategy, the oxygen-reach compressed air generated by the electric supercharger 500 is able to cause and sustain an effective passive regeneration process ofthe particulate filter 280.

In some embodiments, as shown in figure 1, the compressed air generated by the electric supercharger 500 may be delivered to the particulate filter 280 via the ICE 110. In other words, the compressed air may flow through the intake valve(s) 210 into the combustion chamber(s) 150 and, from the combustion chamber(s) 150, through the exhaust valve(s) 220 into the exhaust pipe 275, which directs the compressed air into the particulate filter 280.

To improve the delivery of the compressed air in this case, the ECU 450 may be configured to move the cam phaser 155 in an overlapping position, for example the maximum overlapping position (block S155). In this way, while the intake valve(s) 210 and the exhaust valve(s) 220 are contemporaneously open, the compressed air generated by the electric supercharger 500 can freely flow through the combustion chambers 150 and reach the particulate filter 280.

Should the coasting strategy provide for turning the ICE 110 off, the ECU 450 may be particularly configured to hold the crankshaft 145 in an angular position that guarantees that the intake and exhaust valves 210 and 220 stay contemporaneously open to allow the compressed air to flow through.

In other embodiments, as shown in Figure 3, the compressed air generated by the electric supercharger 500 may be delivered to the particulate filter 280 via the additional conduit 515 that connects the outlet of the supercharger 500 directly with the inlet of the particulate filter 280, for example by opening the valve 520.

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 foregoing 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 their legal equivalents.

REFERENCES motor vehicle

100 automotive system

110 internal combustion engine

120 engine block

125 cylinder

130 cylinder head

135 camshaft

140 piston

145 crankshaft

150 combustion chamber

155 cam phaser

160 fuel injector

170 fuel rail

180 fuel pump

190 fuel source

200 intake manifold

205 air intake duct

210 intake port

215 valves

220 exhaust port

225 exhaust manifold

230 turbocharger

240 compressor

250 turbine

260 intercooler

270 exhaust system

275 exhaust pipe

280 particulate filter

285 oxidization catalyst

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 spark plug

380 coolant and oil temperature and level sensors

400 fuel rail pressure sensor

410 cam position sensor

420 crank position sensor

430 exhaust pressure and temperature sensors

435 first oxygen sensor

440 EGR temperature sensor

445 accelerator position sensor

446 accelerator

450 ECU

460 memory system

465 oxygen sensor

500 electric supercharger

505 by-pass conduit

510 valve

515 additional conduit

520 valve

550 final drive

555 transmission

S100 block

S105 block

S110 block

S115	block
S120	block
S125	block
S130	block
S135	Block
S140	Block
S145	Block
S150	Block
S155	Block
P100	coasting strategy

Claims

1. A method of regenerating a particulate filter (280) of an internal combustion engine (110) on a motor vehicle (90), comprising:

- monitoring a position of an accelerator (446) of the internal combustion engine (110),

- executing a coasting strategy of the motor vehicle (90), if the accelerator (446) is in a completely released position, wherein the coasting strategy of the motor vehicle (90) comprises:

- decoupling the internal combustion engine (110) from a final drive (550) ofthe motor vehicle (90),

- activating an electric supercharger (500) of the internal combustion engine (110) to generate compressed air, and

- delivering the compressed air to the particulate filter (280).

2. A method according to claim 1, wherein the electric supercharger (500) is activated provided that a quantity of soot retained in the particulate filter (280) exceeds a predetermined threshold value thereof.

3. A method according to claim 1 or 2, wherein the electric supercharger (500) is activated provided that a temperature ofthe particulate filter (280) exceeds a predetermined threshold value thereof.

4. A method according to any of the preceding claims, wherein the coasting strategy comprises turning the internal combustion engine (110) off.

5. A method according to any claims from 1 to 3, wherein the coasting strategy comprises operating the internal combustion engine (110) at idle speed.

6. A method according to any of the preceding claims, wherein the compressed air is delivered to the particulate filter (280) via the internal combustion engine (110).

7. A method according to claim 6, wherein the coasting strategy comprises moving a cam phaser (155) of the internal combustion engine (110) in an overlapping position thereof.

8. A method according to any of the preceding claims, wherein the compressed air is delivered to the particulate filter (280) via a conduit (515) that connects the electric supercharger (550) to the particulate filter (280) by-passing the internal combustion engine (110).

9. A method according to any of the preceding claims, wherein the coasting strategy is executed provided that a speed of the motor vehicle (90) exceeds a predetermined threshold value thereof.

10. A computer program comprising a program-code for carrying out the method according to any of the preceding claims.

11. A computer program product comprising the computer program according to claim

10.

12. An electromagnetic signal modulated to carry a sequence of data bits which represent a computer program according to claim 10.

13. A motor vehicle (90) comprising an internal combustion engine (110), a particulate filter (280) and an electronic control unit (450) configured to:

- monitor a position of an accelerator (446) of the internal combustion engine (110),

- execute a coasting strategy of the motor vehicle (90), if the accelerator (446) is in a completely released position, wherein the coasting strategy of the motor vehicle (90) provides for the electronic control unit to:

- decouple the internal combustion engine (110) from a final drive (550) of the motor vehicle (90),

- activate an electric supercharger (500) of the internal combustion engine (110) to generate compressed air, and deliver the compressed air to the particulate filter (280).

Go?

Intellectual

Property

Office

Application No: GB1621133.6 Examiner: Mr Mat Smith