GB2560758A

GB2560758A - A method of thermal protecting a particulate filter of an internal combustion engine

Info

Publication number: GB2560758A
Application number: GB1704707.7A
Authority: GB
Inventors: F Hattar Rafat; Michel Alexander; Schiesser Simon
Original assignee: GM Global Technology Operations LLC
Current assignee: GM Global Technology Operations LLC
Priority date: 2017-03-24
Filing date: 2017-03-24
Publication date: 2018-09-26
Also published as: GB2560758A8; GB201704707D0

Abstract

A method of thermal protecting a particulate filter (280, fig.1) of an internal combustion engine, eg from being thermally stressed by uncontrolled soot burning inside the filter during active regeneration, comprises the steps of: determining (step S100) a value of a particulate filter temperature T; determining (step S105) a value of a soot quantity Q trapped inside the particulate filter, and limiting (steps S115/S120) an oxygen quantity that can be supplied to the particulate filter on the basis of the determined value of T and Q. The oxygen quantity may be limited by limiting (step S115) the number of engine cylinders that can be unfuelled, and/or by limiting (step S120) the air/fuel ratio supplied to one or more cylinders. Steps S115/S120 may be preceded by estimation (step S110) of the maximum oxygen mass flow rate through the filter without causing excessive thermal stresses. The filter temperature may be measured; the trapped soot quantity may be estimated.

Description

(54) Title of the Invention: A method of thermal protecting a particulate filter of an internal combustion engine Abstract Title: Thermal protection for the particulate filter of an i.e. engine (57) A method of thermal protecting a particulate filter (280, fig.1) of an internal combustion engine, eg from being thermally stressed by uncontrolled soot burning inside the filter during active regeneration, comprises the steps of: determining (step S100) a value of a particulate filter temperature T; determining (step S105) a value of a soot quantity Q trapped inside the particulate filter, and limiting (steps S115/S120) an oxygen quantity that can be supplied to the particulate filter on the basis of the determined value of T and Q. The oxygen quantity may be limited by limiting (step S115) the number of engine cylinders that can be unfuelled, and/or by limiting (step S120) the air/fuel ratio supplied to one or more cylinders. Steps S115/S120 may be preceded by estimation (step S110) of the maximum oxygen mass flow rate through the filter without causing excessive thermal stresses. The filter temperature may be measured; the trapped soot quantity may be estimated.

1/2

145

2/2

S100 S105

FIG.3

A METHOD OF THERMAL PROTECTING A PARTICULATE FILTER OF AN INTERNAL COMBUSTION ENGINE

TECHNICAL FIELD

The present disclosure generally relates to an internal combustion engine, for example an internal combustion engine of a motor vehicle, which is provided with a particulate filter. In greater details, the present disclosure relates to a method of thermal protecting the particulate filter, particularly from being thermal stressed by uncontrolled soot burning inside the particulate filter.

BACKGROUND

It is known that many internal combustion engines, including spark-ignition engines (e.g. gasoline engines), are commonly provided with a particulate filter for trapping most of the particulate matter (soot) produced by the engine in order to reduce the polluting emissions.

The soot collected inside the particulate filter is removed from time to time by means of a soot combustion process, generally referred to as regeneration process, that takes place when the temperature of the particulate filter is above a certain value (e.g. 500°C) and enough oxygen is present in the exhaust system.

On engines with homogeneous stoichiometric combustion, such as gasoline engines, the regeneration processes can mainly occur during fuel cut off phases, when no fuel is supplied into the engine cylinders and large amounts of oxygen are pumped towards the particulate filter by the engine pistons. Under this conditions, if the temperature of particulate filter reaches the prescribed value, the combustion of the collected soot occurs spontaneously (passive regeneration).

However, during short driving cycles or driving cycles with low load operations, the pas1 sive regeneration could be impossible either because the temperature of the particulate filter is unable to reach the triggering value, or because no fuel cut off phases are performed.

To avoid overloading of the particulate filter under these scenarios, an active regeneration is usually started when the amount of soot collected inside the particulate filter exceeds a predetermined threshold value thereof.

The active regeneration generally provides for changing some of the engine operating parameters, in order to actively increase the temperature and the oxygen concentration inside the particulate filter.

In particular, the oxygen concentration inside the particulate filter can be increased by increasing the ratio of air to fuel which is supplied to the engine cylinders and/or by completely suspending the fuel supply in one or more of them.

During any passive or active regeneration, the soot combustion has the side effect of rising the particulate filter temperature of a quantity that generally depend on the amount of soot trapped inside of the particulate filter, the initial temperature of the particulate filter and the oxygen concentration.

As a consequence, if these parameters reach too high values, the soot combustion may develop uncontrolled and subject the particulate filter to severe thermal stresses that can irremediably damage the component.

SUMMARY

In view of the above, an object of the present disclosure is to protect the particulate filter from excessive thermal stresses, particularly by avoiding uncontrolled soot burning during the regeneration processes.

These 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 present disclosure provides a method of thermal protecting a particulate filter of an internal combustion engine, comprising the steps of:

- determining a value of a particulate filter temperature,

- determining a value of a soot quantity trapped inside the particulate filter, limiting an oxygen quantity that can be supplied to the particulate filter on the ba2 sis of the determined value of the particulate filter temperature and the determined value of the soot quantity trapped inside the particulate filter.

Thanks to this solution, based on the particulate filter temperature and the amount of soot trapped inside the particulate filter, the method avoids the oxygen quantity to reach values that can cause an uncontrolled combustion of the soot and thus excessive thermal stresses.

According to an aspect of the method, the value of the particulate filter temperature may be measured, for example by means of a dedicated sensor, whereas the value of the soot quantity trapped inside the particulate filter may be estimated, for example using a physical model of the particulate filter.

According to another aspect of the method, the oxygen quantity supplied to the particulate filter may be limited by limiting a number of engine cylinders of the internal combustion engine that can be unfueled, namely a number of engine cylinders in which the fuel supply can be suspended.

The effect of this solution is that of limiting the number of cylinders that simply pump air without consuming oxygen for the combustions, so that the amount of oxygen globally supplied to the particulate filter is effectively reduced.

This solution can be used to protect the particulate filter either during passive regenerations or active regenerations.

Under certain conditions, this solution may also lead to limit the number of the unfueled cylinder to zero, thereby actually disabling the fuel cut off phases of the internal combustion engine.

In particular, the limitation of the number of engine cylinders that can be unfueled may comprise the steps of:

- using the determined value of the particulate filter temperature and the determined value of the soot quantity trapped inside the particulate filter for estimating a maximum number of engine cylinders that can be unfueled,

- preventing a number of engine cylinders larger than the estimated maximum number thereof from being unfueled.

This aspect has the effect of providing a simple solution for keeping the number of unfueled cylinder under control.

According to another aspect of the method, the oxygen quantity supplied to the particu3 late filter may be limited by limiting a ratio of air to fuel that can be supplied to one or more engine cylinders of the internal combustion engine.

The effect of this solution is that of preventing the air and fuel mixture supplied to the engine cylinders from becoming too lean, thereby reducing the amount of oxygen that can exit the engine cylinders and reach the particulate filter without having been involved in the fuel combustion.

This solution can be used for protecting the particulate filter during active regenerations, when at least one engine cylinder is supplied with the mixture of air and fuel to generate torque.

In particular, the limitation of the air-to-fuel ratio may comprise the steps of:

- using the determined value of the particulate filter temperature and the determined value of the soot quantity trapped inside the particulate filter for estimating a maximum value of the air-to-fuel ratio,

- regulating a fuel quantity supplied to said one or more engine cylinders so as to not exceed the estimated maximum value of the air-to-fuel ratio.

This aspect has the effect of providing a simple solution for keeping the air-to-fuel ratio under control.

According to another aspect of the method, the air-to-fuel ratio may be only limited if all the engine cylinders of the internal combustion engine are actually supplied with a mixture of air and fuel.

The effect of this solution is that of intervening on the air-to-fuel ratio only when there are no unfueled cylinders.

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 disclosure provides an automotive system comprising an internal combustion engine, a particulate filter and an electronic control unit configured to:

- determine a value of a particulate filter temperature,

- determine a value of a soot quantity trapped inside the particulate filter,

- limit an oxygen quantity that can be supplied to the particulate filter on the basis of the determined value of the particulate filter temperature and the determined value of the soot quantity trapped inside the particulate filter.

This embodiment achieves basically the same effects of the method above, in particular that of avoiding that too large quantities of oxygen can reach the particulate filter and cause an uncontrolled combustion of the trapped soot.

The additional aspects that have been previously described with reference to the method may be applied also to this embodiment. In particular, an aspect of the automotive system provide that the electronic control unit may be configured to determine the value of the particulate filter temperature through a measurement, for example by means of a dedicated sensor, whereas the electronic control unit may be configured to determine the value of the soot quantity trapped inside the particulate filter through an estimation, for example using a model or a map. According to another aspect of the automotive system, the electronic control unit may be configured to limit the oxygen quantity supplied to the particulate filter by limiting a number of engine cylinders of the internal combustion engine that can be unfueled. In particular, the electronic control unit may be configured to limit the number of engine cylinders that can be unfueled through the steps of: using the determined value of the particulate filter temperature and the determined value of the soot quantity trapped inside the particulate filter for estimating a maximum number of engine cylinders that can be unfueled, and preventing a number of engine cylinders larger than the estimated maximum number thereof from being unfueled. According to another aspect of the method, the electronic control unit may be configured to limit the oxygen quantity supplied to the particulate filter by limiting a ratio of air to fuel that can be supplied to one or more engine cylinders of the internal combustion engine. In particular, the electronic control unit may be configured to limit the air-to-fuel ratio through the steps of: using the determined value of the particulate filter temperature and the determined value of the soot quantity trapped inside the particulate filter for estimating a maximum value of the air-to-fuel ratio, and regulating a fuel quantity supplied to said one or more engine cylinders so as to not exceed the estimated maximum value of the air-to-fuel ratio. According to a further aspect of the automotive system, the electronic control unit may be configured to only limit the air-to-fuel ratio if all the engine cylinders of the internal combustion engine are actually supplied with a mixture of air and fuel.

Still another embodiment of the solution provides an apparatus for thermal protecting a particulate filter of an internal combustion engine, comprising:

- means for determining a value of a particulate filter temperature,

- means for determining a value of a soot quantity trapped inside the particulate filter,

- means for limiting an oxygen quantity that can be supplied to the particulate filter on the basis of the determined value of the particulate filter temperature and the determined value of the soot quantity trapped inside the particulate filter.

The additional aspects that have been previously described with reference to the method may be applied also to this embodiment. In particular, an aspect of the apparatus provides that the means for determining the value of the particulate filter temperature may include means for measuring such temperature, for example a dedicated sensor, whereas the means for determining the value of the soot quantity trapped inside the particulate filter may include means for estimating such value, for example a model or a map. According to another aspect of the apparatus, the means for limiting the oxygen quantity supplied to the particulate filter may comprise means for limiting a number of engine cylinders of the internal combustion engine that can be unfueled. In particular, the means for limiting the number of engine cylinders that can be unfueled may comprise: means for using the determined value of the particulate filter temperature and the determined value of the soot quantity trapped inside the particulate filter for estimating a maximum number of engine cylinders that can be unfueled, and means for preventing a number of engine cylinders larger than the estimated maximum number thereof from being unfueled. According to another aspect of the apparatus, the means for limiting the oxygen quantity supplied to the particulate filter may comprise means for limiting a ratio of air to fuel that can be supplied to one or more engine cylinders of the internal combustion engine. In particular, the means for limiting the air-to-fuel ratio may comprise: means for using the determined value of the particulate filter temperature and the determined value of the soot quantity trapped inside the particulate filter for estimating a maximum value of the air-to-fuel ratio, and means for regulating a fuel quantity supplied to said one or more en6 gine cylinders so as to not exceed the estimated maximum value of the air-to-fuel ratio. According to a further aspect of the apparatus, the means for limiting the air-to-fuel ratio may be only activated if all the engine cylinders of the internal combustion engine are actually supplied with a mixture of air and fuel.

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 of the automotive system according to the section A-A of figure 1.

Figure 3 is a flowchart representing a method for thermal protecting a particulate filter of the internal combustion engine.

DETAILED DESCRIPTION

Some embodiments may include an automotive system 100, as shown in figures 1 and 2, that includes an internal combustion engine (ICE) 110. The ICE 110 may be a gasoline engine, for example a gasoline direct injection (GDI) 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 gasses causing reciprocal movement 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 camshaft 135 rotating in time with the crankshaft 145. The valves 215 selectively allow air into the combustion chamber 150 from the port 210 and alternately allow exhaust gasses to exit through a port 220. In some examples, a cam phaser 155 may selectively vary the timing between the camshaft 135 and the crankshaft 145.

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. 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 turbocharger 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 duct 205 and manifold 200. An intercooler 260 disposed in the duct 205 may reduce the temperature of the air. The turbine 250 rotates by receiving exhaust gasses from an exhaust manifold 225 that directs exhaust gasses 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 gasses through the turbine 250. In other embodiments, the turbocharger 230 may be fixed geometry and/or include a waste gate.

The exhaust gasses 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. The aftertreatment devices may be any device configured to change the composition of the exhaust gasses. The aftertreatment devices include a particulate filter 280, for example a gasoline particulate filter, configured to trap soot and other particulate matters produced by the fuel combustion and transported by the exhaust gasses. The aftertreatment devices may further include other devices such as, but not limited to, catalytic converters (two and three way), oxidation catalysts, lean NOx traps, hydrocarbon adsorbers and selective catalytic reduction (SCR) systems. Other embodiments may 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.

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, a combustion pressure sensor 360, coolant and oil temperature and level sensors 380, a fuel rail pressure sensor 400, a cam position sensor 410, a crank position sensor 420, a particulate filter temperature sensors 430, other exhaust gas pressure and temperature sensors, an EGR temperature sensor 440, and an accelerator pedal 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, and the cam phaser 155. 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 non-transitory 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 nonpermanently 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 onboard computer, or any processing module that might be deployed in the vehicle.

During normal operation of the ICE 110, the combustion of the air and fuel mixture within the engine cylinder 125 generates a certain amount of soot, which is progressively trapped and collected inside the particulate filter 280.

Any time the driver releases the accelerator pedal, the ECU 450 is generally configured to prevent the fuel from being supplied into the engine cylinders 125, for example by keeping ail the fuel injectors 160 closed.

In this way, the ICE 110 undergoes a so-called fuel cut off phase, during which the reciprocating motion of the pistons 140 in the corresponding cylinders 125 has the only effect of pumping fresh air and thus oxygen from the intake manifold 200 towards the exhaust system 270.

While the ICE 100 undergoes a fuel cut off phase, if the temperature of the particulate filter 280 is high enough (e.g. larger than 500°C), the large amount oxygen coming from the intake manifold 200 has the effect of triggering a spontaneous combustion of the soot trapped inside the particulate filter 280, thereby performing a so-called passive regeneration.

However, if the conditions for the passive regeneration are not met, the soot continues to accumulate inside the particulate filter 280.

To deal with this scenario, when the amount of trapped soot reaches a predetermined maximum value thereof, the ECU 450 is generally configured to activate a so-called active regeneration of the particulate filter 280.

An active regeneration is a procedure which provides for the ECU 450 to change some of the operating parameters of the ICE 110 in order to actively increase the temperature of the particulate filter 280 and/or the amount of oxygen supplied into it, with the aim of provoking the combustion of the trapped soot even if the ICE 110 is not in a fuel cut off phase.

In particular, the ECU 450 may be configured to increase the amount of oxygen supplied to the particulate filter 280 by increasing the air-to-fuel ratio of the air and fuel mixture supplied into the engine cylinders 125 (i.e. making the air and fuel mixture leaner) and/or by interrupting the fuel supply in one or more of the engine cylinder 125, so that these cylinders become unfueled and their effect is solely that of pumping fresh air and oxygen towards the particulate filter 280.

However, during any regeneration of the particulate filter 180, the soot combustion has the side effect of rising the particulate filter temperature of a quantity that generally depends on the amount of soot trapped inside of the particulate filter 180, the initial temperature of the particulate filter 180 and finally the amount of oxygen available inside the particulate filter 180.

If these parameters are not properly controlled, the particulate filter 180 may be subjected to severe thermal stresses that sometimes can irremediably damage the component and require its replacement.

In order to protect the particulate filter 180 from excessive thermal stresses, the ECU 450 may be configured to execute the protective strategy represented in the flowchart of figure 3, which may be periodically and/or cyclically repeated either during the normal operation or during the regenerations of the particulate filter 180.

According to this protective strategy, the ECU 450 may be configured to determine a current value T of the particulate filter temperature (block S100) and a current value Q of the soot quantity trapped inside the particulate filter 180 (block S105).

The current value T of the particulate filter temperature may be measured by means of the temperature sensor 430, whereas the current value Q of the soot quantity may be estimated by means of a dedicated soot level estimating strategy.

The soot level estimating strategy is a strategy for estimating the soot quantity that is trapped inside the particulate filter 280, taking into account both the normal operation of the ICE 110 and the regenerations. This soot level estimating strategy is per se known and may be based on a physical model of the particulate filter 280 that receives as input several operating parameters, such as for example the temperature of the particulate filter 280, the air-to-fuel ratio of the air and fuel mixture supplied to the engine cylinders

125, the temperature of the ICE 110, the time spent in the various conditions and many others.

Based on the current value T of the particulate filter temperature and the current value Q of the soot quantity trapped inside the particulate filter 280, the ECU 450 may be configured to estimate a maximum value F of the oxygen mass flow rate that can flow through the particulate filter 280 without causing excessive thermal stresses (block S110).

The maximum value F of the oxygen mass flow rate may be determined by means of a physical model or a calibration map receiving as input the current value T of the particulate filter temperature and the current value Q of the soot quantity trapped inside the particulate filter 280 and providing as output the corresponding maximum value F of the oxygen mass flow rate.

According to the protective strategy, the ECU 450 may be then configured to operate the ICE 110 so as to limit (i.e. to confine) the oxygen mass flow that actually enters the particulate filter 280 in a range of values that are not larger than the maximum value F. In other words, the ECU 450 may be configured to operate the ICE 110 so as to avoid that the particulate filter 280 receives an oxygen mass flow rate having a value larger than the determined maximum value F.

To do so, the ECU 450 may be particularly configured to use the maximum value F of the oxygen mass flow rate to determine a maximum number N of engine cylinders 125 that can be unfueled (block S115), namely a maximum number of engine cylinders 125 in which the fuel supply can be suspended, and/or a maximum value AFR of the ratio of air to fuel which can be supplied to the engine cylinders 125 (block S120).

The maximum number N of unfueled engine cylinders 125 is an integer which is equal to or smaller than the number of the engine cylinders 125 which are globally present on the ICE 110. By way of example, if the ICE 110 has 4 engine cylinders 125 as depicted in figure 1, the maximum number N of unfueled engine cylinders 125 is an integer comprised between 0 and 4.

The maximum number N of unfueled engine cylinders 125 as well as the maximum value AFR of the air-to-fuel ratio may be determined by means of a physical model or a calibration map receiving as input the maximum value F of the oxygen mass flow rate (and possibly other engine operating parameter such as the engine speed) and providing as output the corresponding maximum number N of unfueled engine cylinders 125 and/or the maximum value AFR of the air-to-fuel ratio.

It should be observed that, in other embodiments, the ECU 450 could be configured to determine the maximum number N of unfueled engine cylinders 125 and/or the maximum value AFR of the air-to-fuel ratio directly on the basis of the current value T of the particulate filter temperature and the current value Q of the soot quantity trapped inside the particulate filter 280, without passing through the estimation of the maximum value F of the oxygen mass flow rate.

A this point, the ECU 450 may be configured to check (block S125) whether all the engine cylinders 125 of the ICE 110 are currently fueled (i.e. supplied with an air and fuel mixture) or whether, at the contrary, one or more of these engine cylinders 125 are currently unfueled.

If all the engine cylinders 125 are currently fueled, for example because the ICE 110 is generating torque, the ECU 450 may be configured to operate the ICE 110 so as to limit (i.e. to confine) the air-to-fuel ratio of the air and fuel mixture which is actually supplied to the engine cylinders 125 in a range of values that are not larger than the maximum value AFR (block S130).

In other words, the ECU 450 may be configured to operate the ICE 110 so as to avoid that the engine cylinders 125 receive an air and fuel mixture having an air-to-fuel ratio larger than the determined maximum value AFR.

To do so, the ECU 450 may be configured to measure the air mass flow rate coming from the intake manifold 200, for example by means of the mass airflow and temperature sensor 340, and to regulate the fuel quantity that is supplied into the engine cylinders 125, in order to not exceed the maximum value AFR of the air-to-fuel ratio.

If conversely at least one of the engine cylinders 125 is currently unfueled, for example because the ICE 110 is undergoing a fuel cut off phase or an active regeneration of the particulate filter 280, the ECU 450 may be configured to limit (i.e. to confine) the number of unfueled engine cylinders 125 in a range of integers that are not larger than the maximum number N (block S135).

In other words, the ECU 450 may be configured to operate the ICE 110 so as to avoid that the fuel supply is suspended in a number of engine cylinders 125 larger than the determined maximum number N.

A particular case arises when the determined maximum number N is equal to zero. In such a case, the ECU 450 is indeed actually configured to disable the fuel cut off phases of the ICE 110.

Even if the example described above the limitation of the air-to-fuel ratio is performed only when the engine cylinders 125 are all supplied with fuel, there may be embodiments which provides for limiting the air-to-fuel ratio even if one or more engine cylinders 125 are currently unfueled.

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

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

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 combustion pressure sensor

380 coolant and oil temperature and level sensors

400 fuel rail pressure sensor

410 cam position sensor

420 crank position sensor

430 particulate filter temperature sensors

440 EGR temperature sensor

445 accelerator pedal position sensor

450 ECU

460 memory system

S100 block

S105 block

S110 block

S115 block

S120 block

S125 block

S130 block

S135 block

Claims

1. A method of thermal protecting a particulate filter (280) of an internal combustion engine (110), comprising the steps of:

- determining a value of a particulate filter temperature,

- determining a value of a soot quantity trapped inside the particulate filter (280),

- limiting an oxygen quantity that can be supplied to the particulate filter (280) on the basis of the determined value of the particulate filter temperature and the determined value of the soot quantity trapped inside the particulate filter (280).

2. A method according to claim 1, wherein the determined value of the particulate filter temperature is measured.

3. A method according to any of the preceding claims, wherein the determined value of the soot quantity trapped inside the particulate filter is estimated.

4. A method according to any of the preceding claims, wherein the oxygen quantity supplied to the particulate filter (280) is limited by limiting a number of engine cylinders (125) of the internal combustion engine that can be unfueled.

5. A method according to claim 4, wherein the limitation of the number of engine cylinders (125) that can be unfueled comprises the steps of:

- using the determined value of the particulate filter temperature and the determined value of the soot quantity trapped inside the particulate filter for estimating a maximum number of engine cylinders (125) that can be unfueied,

- preventing a number of engine cylinders (125) larger than the estimated maximum value thereof from being unfueled.

6. A method according to any of the preceding claims, wherein the oxygen quantity supplied to the particulate filter (280) is limited by limiting a ratio of air to fuel that can be supplied to one or more engine cylinders (125) of the internal combustion engine (110).

7. A method according to claim 6, wherein the limitation of the air-to-fuel ratio comprises the steps of:

- regulating a fuel quantity supplied to said one or more engine cylinders (125) so as to not exceed the estimated maximum value of the air-to-fuel ratio.

8. A method according to claim 6 or 7, wherein the air-to-fuel ration is only limited if all the engine cylinders (125) of the internal combustion engine (110) are actually supplied with a mixture of air and fuel.

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

10. A computer program product comprising the computer program of claim 9.

11. An electromagnetic signal modulated to carry a sequence of data bits which represent the computer program of claim 9.

12. An automotive system (100) comprising an internal combustion engine (110), a particulate filter (280) and an electronic control unit (450) configured to:

- determine a value of a particulate filter temperature (280),

- determine a value of a soot quantity trapped inside the particulate filter (280),

- limit an oxygen quantity that can be supplied to the particulate filter (280) on the basis of the determined value of the particulate filter temperature and the determined value of the soot quantity trapped inside the particulate filter (280).

Intellectual

Property

Office

Application No: GB 1704707.7