GB2490934A - Method of desulphurisation of a Lean NOx Trap - Google Patents

Abstract

A method of operating an exhaust system in an internal combustion engine 110 equipped with a Diesel Particle Filter 282 downstream of a Lean NOx Trap 281, where the method comprises monitoring a sulphur (SOx) level accumulated in the Lean NOx Trap, generating a DeSOx regeneration request if the monitored SOx level is above a first threshold and triggering a DeSOx regeneration phase if a DPF regeneration phase is active. Preferably before triggering the DeSOx regeneration phase the soot level accumulated in the DPF is monitored and if the SOx level is above or equal to a second SOx threshold value, which is greater than the first SOx threshold, and the soot level is below a DPF soot value threshold the regeneration of the DPF is triggered. Also, the DeSOx regeneration phase is only triggered when a high oxygen combustion mode is activated and the percentage that the DPF is regenerated and the temperature of the DPF are above a threshold.

Description

METHW FOR OPERATING A DIESEL EXHNJST SYSTEM IN AN INTERNPI.L CCt4BUS-TIcZ ENGINE TEC@L FlEW Method of operating an exhaust system in an internal corrbustion en-gine equipped with a lean NO trap and a Diesel Particulate Filter.

BAERVND

A diesel engine is normally provided with an exhaust gas after treat-ment system, for degrading and/or removing the pollutants from the exhaust gas emitted by the Diesel engine before discharging it in the environment.

The after treatment system generally comprises an exhaust pipe for leading the exhaust gas from the Diesel engine to the environment; the exhaust pipe comprises a Lean NO Trap (LNT) for trapping nitrogen oxides (NO) and a Diesel Particulate Filter (DPF) located downstream of the Lean NO Trap for capturing and removing diesel particulate matter (soot).

The Lean NO Trap is a catalytic device containing catalysts, such as Rhodium, Pt and Pd, and adsorbents, such as barium based elements, which provide active sites suitable for binding the nitrogen oxides contained in the exhaust gas, in order to trap them within the device itself.

The Lean NO Trap is subjected to periodic regeneration processes, whereby such regeneration processes are generally provided to release and reduce the trapped nitrogen oxides (NO) from the the Lean NO> Trap.

Due to the sulphur contained in the diesel fuel and engine lubricat-ing oil, the exhaust gas produced by the diesel engines generally contains sulphur oxides (SOs), which can be responsible for a progres-sive poisoning of Lean NO, Trap. As a consequence in addition to the regeneration phase above mentioned the Lean NO Trap must be periodi- cally subject to a desulphurization phase, also referred as DeSO re-generation, in order to reduce the SO accumulated and restore its original efficiency.

The DeSO regeneration phase of the LNT is conventionally obtained heating up the Lean NO,( Trap at a temperature, typically up to 600- 650°, which is normally higher than the temperature needed for the regeneration of NOR, and operating the Diesel engine in a rich combus-tion modem i.e. by operating the diesel engine with a fuel mixture having the mass ratio of air to fuel lower than the stoichiometric ration (lambda c 1).

The exhaust gas contains also soot which is trapped during operation of the engine in the Diesel Particulate Filter. The accumulation of trapped soot in the Diesel Particulate Filter over time decreases its storage capacity and therefore, periodically, the Diesel Particulate Filter needs to be regenerated, i.e. the soot needs to be burned off once it has reached a specific soot loading level. This phase, known as DPF regeneration phase, requires a high exhaust temperature suit-able for heating up the trapped soot and burning it off.

Both DPF regeneration phase and DeSOX regeneration phase require tern- peratures which are in the same range of values. The increase in tem-perature needed respectively for the DPF regeneration phase and for the DeSO regeneration are normally obtained by fuel combustion.

Currently the two phases occur independently, two separate combus-tions are carried out with a consequent significant increase in fuel consumption.

An object of an embodiment of the invention disclosed is therefore to define a procedure to coordinate DPF regeneration phase and the the DeSO,< regeneration phase so as to promote a fuel economy optimization.

Another object is to provide a method for coordinating the above men-tioned phases in a rational way without using complex devices and by taking advantage from the computational capabilities of the Electron-ic Control Unit (ECU) of the vehicle.

These objects are achieved by a method, by an engine, by a computer program and computer program product, and by an electronagnetic sig-nal and by an automotive system having the features recited in the independent claims.

The dependent claims delineate preferred and/or especially advanta-geous aspects.

DISOSt3RE These and other objects are achieved by the embodiments of the inven- tion having the features contained in the independent claims. The de- pendent claim relates to preferred or particularly advantageous as-pects of the embodiments of the invention.

In particular, an embodiment of the invention provides a method of operating an exhaust system in an internal combustion engine equipped with a lean NO Trap and a Diesel Particulate Filter disposed down- stream of the lean NO trap, the method comprising the step of moni-toring a SO, level accumulated in the Lean NO Trap; generating a DeSO regeneration request if the monitored SO> level is above or equal to a SO First Threshold Value; and triggering a DeSOX regeneration phase if the Diesel Particulate Filter regeneration phase is active.

Thanks to this solution the fuel consumption is optimized since only one warm-up phase is used for both DPF and DeSO regeneration phases.

According to another aspect of an embodiment of the invention the me-thod comprises the steps of monitoring a Diesel Particulate Filter soot level corresponding to an amount of soot accumulated in the Di-esel Particulate Filter; and triggering a Diesel Particulate Filter regeneration phase if the monitored SQ level is above or equal to a SQ Second Threshold Value, greater than the SQ First Threshold Val-ue, and the monitored soot level is below a Diesel Particulate Filter soot Threshold Value.

In this way it is possthle to coordinate the DeSO regeneration phase the DPF regeneration phase so as to further reducing the fuel con-sumption by allowing triggering a DPF regeneration phase, even if it is not needed from a soot point of view, only for urgent DeSQ re-quests.

According to another aspect of the invention the method comprises the additional step of triggering a DeSQ< regeneration phase only if the following conditions are fulfilled: a High-02 DPF combustion mode is activated, a parameter indicative of a percentage of DPF regeneration in the Diesel Particulate Filter is above or equal to a Diesel Parti- culate Filter Percentage Regeneration Threshold, and a parameter in-dicative of the temperature of the exhaust gas entering the Diesel Particulate Filter is equal of above a Regeneration Temperature Thre-shold Value.

Thanks to this solution the DeSO regeneration phase is triggered only in presence of the best combination of working condition, so as to optimize the fuel consumption.

The methods 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 methods described above, and in the form of a computer program product comprising the computer program.

The computer program product can be errbodied as an internal cortus-tion engine provided with a Lean NO Trap and a Diesel Particulate Filter and a ECU in corrmunication with the Lean NO, Trap and the Die-sel Particulate Filter, a memory system associated to the ECU, and the computer program stored in the memory system, so that, when the ECU executes the computer program, all the steps of the method de-scribed above are carried out.

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.

The present invention further provides a control apparatus for an in-ternal combustion engine equipped with a Lean NQ Trap, and a Diesel Particulate Filter disposed downstream of the Lean NO Trap, the con-trol apparatus comprising an Electronic Control Unit in coinnunication with the Lean NO Trap and the Diesel Particulate Filter, a memory system associated to the Electronic Control Unit and a computer pro-gram stored in the memory system.

This embodiment of the invention has the advantage of the method men- tioned above, namely that of reducing the fuel consumption by coordi-nating the DeSO regeneration phase and the DPF regeneration phase.

BRIEF DESCRIPTIC*T OF THE DRAWINGS The present invention will now be described, by way of exarrple, with reference to the accompanying drawing, in which: Figure 1 and 2 are schematic representations of an automotive system comprising an internal combustion engine; Figure 3 is a schematic representation of the internal combustion en- gine of figure 1 and 2 equipped with a Lean NO Trap (LNT) and a Die-sel Particulate Filter (DPF); and Figure 4 is a schematic representation of the steps of an embodiment of the method disclosed.

DEThILED DESIPTIQ1 Preferred embodiments will now be described with reference to the en-closed drawings.

Some embodiments may include an automotive system 100, as shown in Figures 1 and 2, that includes an internal combustion engine (ICE) having 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 cham- ber 150. A fuel and air mixture (not shown) is disposed in the corn-bustion chamber 150 and ignited, resulting in hot expanding exhaust

S

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 corrirnunication with a high pressure fuel purrp 180 that increase the pressure of the fuel received 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 chanter 150 from the port 210 and alternately allow exhaust gases to exit through a port 220. In some exarr1es, 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 re-duce the temperature of the air. The turbine 250 rotates by receiving exhaust gases from an exhaust manifold 225 that directs exhaust gases from the exhaust ports 220 and through a series of vanes prior to ex-pansion through the turbine 250. The exhaust gases exit the turbine 250 and are directed into an exhaust system 270. 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 ertodiments, the turbocharger 230 may be fixed geometry and/or include a waste gate.

The exhaust system 270 may include an exhaust pipe 275 having one or more exhaust after-treatment devices 280. The after-treatment devices may be any device configured to change the composition of the exhaust gases. Some examples of after-treatment devices 280 include, but are not limited to, catalytic converters (two and three way), oxidation catalysts, lean NOx traps, hydrocarbon adsorbers, selective catalytic reduction (SCR) systems, and diesel particulate filters. Other embo-diments 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 tem-perature of the exhaust gases in the EGR system 300. An EGR valve 320 regulates a flow of exhaust gases 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 de- vices associated with the ICE 110. The ECU 450 may receive input sig- nals from various sensors configured to generate the signals in pro-portion to various physical parameters associated with the ICE 110.

The sensors include, but are not limited to, a mass airflow and tem-perature sensor 340, a manifold pressure and temperature sensor 350, a corrbustion 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, exhaust pressure and temper-ature sensors 430, an EGR temperature sensor 440, and an accelerator pedal position sensor 445. Furthermore, the ECU 450 nay generate out-put 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 ac-tuator 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 cen-tral processing unit (CPU) in comminunication with a memory system and an interface bus. The CPU is configured to execute instructions stored as a program in the memory system, and send and receive sig-nals to/from the interface bus. The memory system 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.

Figure 3 shows a schematic view of the internal combustion engine 110 of figure 1, wherein the exhaust after-treatment devices 280 compris- es a Lean NO Trap(LNT) 281 located in the exhaust pipe 275 for trap- ping and reducing the NO,, contained in the exhaust gas and thus pre-venting their environmental release, and a Diesel Particulate Filter (DPF) 282, downstream of the Lean NO,, Trap 281 in close couple po-sition, for capturing and removing diesel particulate matter (soot) from the exhaust gas after it passed through the Lean NO,, Trap 281 and before it is released to the environment.

The Lean NO,, Trap 281 is a catalytic device suitable for trapping ni-trogen oxides (NOx) contained in the exhaust gas. The exhaust gas produced by the diesel engine and passing through the Lean NO,, Trap generally contains sulphur oxides (SO,,) which can be responsible for a progressive poisoning of Lean NO,, Trap. The Lean NO,, Trap 281 may be operated according to the following phases: -a loading phase, in which during normal mode of operation, the LNT 281 acts as trap for NO,, and for oxides such as HC and CO in the exhaust gas, -a DeNO,, regeneration phase in which short periods of rich fuel mixture (with lambda < 1) are used to reduce to N2 the NO,, in the Lean NO,, Trap 281 in order to recover its storage capacity, -a DeSO,, regeneration phase in which a dedicated combustion with rich fuel mixture (lambda < 1) and high tenperature, typically up to 600_6500, is used for recovering the Lean NO, Trap 281 from sulphur deposition. This phase becomes necessary when the level of SO]( in the Lean NO,( Trap 5 exceeds a predetermined SO> First Threshold Value. The SO First Threshold Value is set during a preliminary calibration phase.

Along the exhaust pipe 275, after the the Lean NO Trap 281 the Diesel Particulate Filter 282 is located and it is used to trap soot in the exhaust gas produced by the engine as a residual combustion. Over time the amount of soot trapped in the Diesel Particulate Filter 282 increases and to restore its storage capacity the Diesel Particulate Filter needs to be empty-out, this phase is known as DPF regeneration phase.

The DPF regeneration phase comprises the following steps: (a) Warm-up phase: the exhaust temperature is increased and the soot starts heating up (b) Steady phase: the soot actually burns off.

Two different combustion modes for the DPF regeneration phase are possible: -A High Oxygen combustion mode (High-O2) -A Low Oxygen combustion mode (Low-O2) Normally the DPF regeneration phase provides for: -a warm-up phase (a) starting in a High-O2 combustion mode so as to speed up the increase of the exhaust temperature and -a steady phase (b) starting in a Low-02 combustion mode so as to improve the control of the soot burning process in its starting phase.

According to an embodiment of the present invention a method for op-erating an exhaust system in an internal combustion engine 110 equipped with the DPF 282 and LNT 281 is provided, in particular the method provides for a coordination of the DeSO regeneration phase of the LNT 281 and the OFF' regeneration phase of the DPF 282.

The method for coordinating a DeSC regeneration phase a DPF regenera-tion phase will now be described more in details with reference to figure 4.

During normal operation of the engine 110 the level of SQ in the LNT 281 and the level of soot in the OFF 282 are monitored by the ECU 450. For example the level of SQ in the LNT 281 and the level of soot in the DPF 282 are estimated by the ECU using estimation models based on, among other parameters, oil and fuel consumption and driving style.

If, according to the method described in details below, a DeSQ rege-neration phase or a DFF regeneration phase needs to be triggered the ECU 450 actuates a change in the engine combustion mode; this is nor-mally obtained by forcing the engine actuators, like for example, among others, the fuel injectors 160, the common rail high pressure fuel pump, the EGR system 300, the VGT actuator 290 and or the swirl valves, to work in predetermining operating conditions different from the normal operating conditions. In addition the decision to trigger a DPF regeneration phase is taken by the ECU 450 on the basis of sta- tistical and physical models. The level of S0, in the LNT 281 is com-pared to the SO> First Threshold Value, block 1, in order to check if a regeneration might be needed to restore the storage capacity of the LNT 281.

There are two possible cases: a first case wherein the level of SQ< in the LNT 281 is below the SO First Threshold Value and a second case wherein the level of SQ, in the LNT 281 is equal or above the SOX First Threshold Value In the first case the amount of trapped SO, in the LNT 281 is not big enough to require a regeneration. At this point the ECU 450 proceeds with its normal operation and checks if a DPF regeneration is need.

This is accomplished by first comparing the level of soot in the DPF 282 to a DPF soot Threshold Value, block 2. The DPF soot Threshold Value is an amount of soot upon which a DPF regeneration phase is re- quested. The DPF soot Threshold Value varies depending on various pa-rameter including the current driving style (mission profile) of the engine 110. In particular an evaluation model, known as ECU soot evaluation model, is used by the ECU 450 to determine the DPF soot Threshold Value according to, among other parameters, the level of soot in the DPF 282 and the driving style. In particular, according to the ECU soot evaluation model, a DPF regeneration phase can be an-ticipated, and therefore the DPF soot Threshold Value lowered, even if the monitored soot level is not extremely high; or a DPF regenera-tion phase can be delayed, and therefore the DFF soot Threshold Value increased, even if monitored soot level has reached high values. In this way the DPF regeneration is triggered only when the most appro-priate driving conditions are present. If, by monitoring the soot level in the DPF 282, it is established that the level of soot in the DPF 282 is above or equal the DPF soot Threshold Value then a DPF re-generation is activated, block 3.

In the second case, i.e. the level of SO in the LNT 281 is above or equal the SQ First Threshold Value, it is assumed that a 0eSO regene- ration phase is needed and a DeSQ request is generated, i.e. a re-quest for performing a DeSO regeneration phase to empty out the LNT 281 from the SQ, block 4. Upon a DeSC request the level of SO, in the Lean NO Trap 281 is compared to a SQ Second Threshold Value, block 3. The SO Second Threshold Value is set during a calibration phase, is greater than the SQ First Threshold Value and provides an indica-- tion on the maximum level of SO,, in Lean NO,, Trap 281 over which mal-functioning of LNT 281 or damages might occur.

Again two situations are possible: first situation wherein the level of SQ is lower than the SQ Second Threshold Value and second situa-tion wherein the level of SQ is above or equal to the SQ< Second Threshold Value.

In the first situation the DeSQ request is considered "not urgent", i.e. there isn't an immediate critical need to empty out the LNT 281, and the DeSQ regeneration phase can wait until the next cyclical DPF regeneration phase is triggered. At this point the ECU 450 checks if a DPF regeneration phase is already active, block 6, and if this is the case it triggers a DeSO regeneration phase, block 7, so as to ex-ploit the working conditions already set for the DPF regeneration phase. In particular, and this can be explained in more details look-ing at figure 5, before a DeSO regeneration phase can be triggered, according to an embodiment of the present invention, a series of checks on the working conditions is carried out by the ECU 450. In particular the ECU 450 ensures that the combustion mode is a high Oxygen combustion mode, block 8, a DPF Regeneration Percentage, i.e. a weighted average DPF regeneration time spent in each driving style, is greater than a DPE Regeneration Percentage Threshold set in a ca-libration phase, block 16, a parameter indicative of the temperature of the exhaust gas entering the DPF 282 greater than a Regeneration Threshold Temperature Value, block 17, set during a calibration phase and representing the mninimumn exhaust temperature value suitable for a DeSO), regeneration and finally no DeSO,, inhibition flags are active, block 18. If all above conditions are fulfilled the DeSO regeneration phase can be triggered, block 19, otherwise the process starts again from block 14. By fulfilling all the above mentioned working condi- tions a working area for triggering a DeSOX regeneration phase is de-fined which comprises a stable temperature, not too low so as to avoid extra fuel consumption, and an appropriate soot level for the current driving style.

Going back to figure 4, and in particular block 6, if the DPF regene-ration phase is not active the process can start again from block 4.

If the second situation occurs, i.e. if the level of SOD, in the LNT 281 is above or equal to the SO>, Second Threshold Value the DeSOX re-quest is considered "urgent" and a choice can be made by the ECU 450 on whether triggering directly a DPF regeneration phase or either waiting until the next cyclical DPF regeneration phase is autornati-cally triggered. The choice is made according to the level of soot in the OFF 282. The soot level is compared to the DEE' soot Threshold Value, block 8.

If the level of soot is above or equal the DEF soot Threshold Value it means that the level of soot in the DEF 382 is critical and a DEE regeneration phase is planned to happen in the next future, or maybe is already currently happening. The ECU 450 verifies if the DEE' rege-neration phase is currently active, block 9, and if this is the case it triggers a DeSQ regeneration phase, block 10; the DeSO regenera- tion phase will start as soon as all the working conditions are ful-filled as described above. Otherwise, if the DPF regeneration phase is not active, the ECU 450 waits until the next cyclical DPF regene-ration phase and only then it triggers a DeSQ regeneration phase, block 11.

If, on the other hand, from the check on block 8, the level of soot is below the DPF soot Threshold Value, it is clear that there is no immediate need for a DPF regeneration phase, which also means that the next cyclical DPF regeneration phase is not planned to happen in the irediate future. In this case since the amount of SQ in the LNT 281 is such as to require an urgent DeSO regeneration phase ("urgent" DeSQ request) the ECU 450 triggers the DPF regeneration phase even if the DPF regeneration phase is not strictly necessary considered the monitored level of soot, block 12. Once the DPF regeneration phase has been triggered, the DeSQ regeneration phase is also triggered in particular after verifying that all working conditions are ful-filled, as described above.

While at least one exemplary embodiment has been presented in the foregoing sumrariary 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 emrbodiments are only exam- pies, and are not intended to limit the scope, applicability, or con- figuration in any way. Rather, the foregoing surrniary and detailed de-scription 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 ar-rangement of elements described in an exemplary embodiment without departing from the scope as set forth in the appended claims and their legal equivalents.

REFEREMS

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. Intake duct 210. Intake port 215. Valve 220. Exhaust Port 225. Exhaust manifold 230. Turbocharger 240. Compressor 250. Turbine 260. Intercooler 270. Exhaust system 275. Exhaust pipe 280. Exhaust after-treatment device 281. Lean NO Trap 282. Diesel Particulate Filter 290. VGT actuator 300. EGR 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. Exhaust pressure and temperature sensors 440. EGR temperature sensor 445. Accelerator pedal position sensor 450. Electronic Control Unit 451. Memory System cLAD

Claims (13)

1. A Method of operating an exhaust system (270) in an internal corn-bustion engine (110) equipped with a Lean NO Trap (281) and a Diesel Particulate Filter (282) disposed downstream of the Lean NO, Trap (281), the method corrprising the steps of: a) monitoring a SQ level accumulated in the Lean NO Trap (281); b) generating a DeSQ regeneration request if the monitored SQ level is above a SO, First Threshold Value; c) triggering a DeSQ regeneration phase if a Diesel Particulate Filter regeneration phase is active.

2. A method according to claim 1 comprising, before the triggering of the DeSO regeneration phase, the steps of: a) monitoring a Diesel Particulate Filter soot level accurnu-lated in the Diesel Particulate Filter (282); and b) triggering a Diesel Particulate Filter regeneration phase if the monitored SO level is above or equal a SQ Second Thre-shold Value, greater than the SQ First Threshold, and the monitored soot level is below a Diesel Particulate Filter soot Threshold Value.

3. A method according to claim 1 or 2 comprising the steps of trig-gering the DeSO regeneration phase only when: a) a High Oxygen combustion mode is activated; and b) a parameter indicative of a percentage of Diesel Particulate Filter regeneration in the Diesel Particulate Filter (282) is above or equal to a Diesel Particulate Filter Percentage Regeneration Threshold; and c) a parameter indicative of the temperature of the exhaust gas entering the Diesel Particulate Filter (282) is equal of above a Regeneration Temperature Threshold Value.

4. A method according to any of the preceding claims wherein in the step of monitoring the SO,< level accumulated in the Lean N0 Trap (281) comprises the step of estimating the level the SO level accumulated in the Lean NO,< Trap (281) using estimation models.

5. A method according to any of the claims from 2 to 4 wherein in the step of monitoring a Diesel Particulate Filter soot level ac-cumulated in the Diesel Particulate Filter (282) comprises the step of estimating the Diesel Particulate Filter soot level accu-mulated in the Diesel Particulate Filter (282) using estimation models.

6. A method according to any of the preceding claims wherein the step of triggering a DeSO regeneration phase comprises the step of changing the engine corrbustion mode.

7. A method according to any of any of the claims from 2 to 6 where- in the step of triggering a Diesel Particulate Filter regenera-tion phase comprises the step of changing the engine cortustion mode.

8. Internal coithustion engine (110) equipped with a Lean NO Trap (281) and a Diesel Particulate Filter (282) disposed downstream of the Lean NO> Trap (281), the engine (110) comprising an elec-tronic control unit (450) in coriniunication with the Lean NO Trap (281) and the Diesel Particulate Filter (282) and configured for carrying out the method according to any of the preceding claims.

9. A computer program comprising a computer-code suitable for per-forming the method according to any of the claims from 1 to 7.

10. Computer program product on which the computer program according to claim 9 is stored.

11. Control apparatus for an internal combustion engine (110) equipped with a Lean NO Trap (281), and a Diesel Particulate Filter (282) disposed downstream of the Lean NO Trap (281), the control apparatus comprising an Electronic Control Unit (450) in communication with the Lean NO Trap (281) and the Diesel Par-ticulate Filter (282), a memory system (451) associated to the Electronic Control Unit and a computer program according to claim 10 stored in the memory system (451).

12. An electromagnetic signal modulated as a carrier for a sequence of data bits representing the computer program according to claim

13. An automotive system (100) comprising an internal combustion en-gine (110) provided with an exhaust system (270) comprising a Lean NO, Trap (281) and a Diesel Particulate Filter (282) dis-posed downstream of the Lean NO, Trap in the exhaust system (270), the automotive system (100) also comprising an electronic control unit (450) in communication with the Lean NO Trap (281) and the Diesel Particulate Filter (282) and configured to: a) monitor a SO level accumulated in the Lean NQ< Trap (281); b) generate a DeSQ regeneration request if the monitoring SO level is above or equal a SO< First Threshold Value; and c) trigger a DeSQ regeneration phase if the Diesel Particulate Filter regeneration phase is active.