GB2500925A

GB2500925A - Method of operating a lean NOx trap

Info

Publication number: GB2500925A
Application number: GB1206162.8A
Authority: GB
Inventors: Andrea Dutto; Roberto Argolini; Luca Francesco Mirabella
Original assignee: GM Global Technology Operations LLC
Current assignee: GM Global Technology Operations LLC
Priority date: 2012-04-05
Filing date: 2012-04-05
Publication date: 2013-10-09
Also published as: GB201206162D0

Abstract

Disclosed is a method of operating a lean NOx trap in an exhaust line of an internal combustion engine, the exhaust line being equipped with a diesel particulate filter. The method comprises the steps of starting a DeSOx regeneration event comprising a plurality of rich and lean combustion phases and varying the duration of the DeSOx regeneration event by a time interval that is a function of a parameter indicative of the amount of of SOx storage of the lean NOx trap, K_critical, and of a parameter indicative of a potential desulphation efficiency of the lean NOx trap for a particular engine state or mission profile. An engine system, computer program for calculating the regeneration event duration and engine control unit using the program are also disclosed.

Description

METHOD OF OPERATING A LEAN PgQ TRAP/N AN INTERNAL COMBUSTION

ENGINE

TECHNICAL FIELD

The present disclosure relates to a method of operating a Lean NO Trap in an Internal Combustion Engine.

BACKGROUND

It is known that exhaust gas after-treatment of a Diesel engine may be provided, among other devices, with a Lean NO Trap (LNT) which represents a cost efficient alternative to 5CR (Selective Catalytic Reduction).

A Lean NOx Trap ([NT) traps nitrogen oxides (NOr) contained in the exhaust gas and is located in the exhaust line upstream of a Diesel Particulate Filter (DPF).

In tact, a LNT 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 (NO) contained in the exhaust gas, in order to trap them within the device itself.

Lean NO Traps ([NT) are subjected to periodic regeneration processes or events, whereby such regeneration processes are generally provided to release and reduce the trapped nitrogen oxides (NOt) from the [NT.

For this reason, Lean NO Traps ([NT) are operated cyclically, for example by switching the engine from a lean burn operation to a rich operation, performing a regeneration event also referenced as DeNO regeneration.

Generally speaking, internal combustion engines are currently operated with multi-injection patterns, namely for each engine cycle, a train of injection pulses is performed typically, starting from a pilot injection pulse and following a main injection pulse, eventually terminating with after and post injections.

In particular, fuel after-injections are fuel injections in a cylinder of the engine that occur after the Top Dead Center (TDC) of the piston.

The number of impulses of the train of impulses and their timing is dependent on the combustion mode. After injections may be used, for example but not exclusively, to achieve the needed temperature for LNIT regeneration events. Fuel after-injections are fuel injections in a cylinder of the engine that occur after the iop Dead Center (TOC) of the piston.

Lean NO,, Traps (LNT) may also be subjected to sulphur oxides (SO,,) regeneration events, also referenced as DeSO,, regenerations, because after some thousand kilometers sulphur contained in the diesel fuel poisons the Lean NO,, trap and a desulphurization phase is needed.

More specifically, Lean NO,, Traps are highly vulnerable to deactivation by Sulphur poisoning. The Sulphur contained in the fuel is easily oxidized in lean atmosphere: it is stored as Barium and Aluminum Sulphates in the Trap, that are more stable compounds than the corresponding Nitrates. This process reduces the efficiency of the Trap in terms of NO,, storage capabilities: this efficiency can be restored through a desuiphation process, that requires high temperature and rich atmosphere.

A DeSO,, Regeneration is defined as the process that leads to desuiphation of Lean NO,, Trap. It is critical from the point of view of thermal degradation of the Trap, because of the high temperature that is needed. It is penalizing as well in terms of fuel consumption, because of the additional injected fuel needed to provide a rich atmosphere at the inlet of the Trap.

A DeSO,, regeneration event is performed by means of several rich combustion phases executed at high temperature, where gas temperature in the LNT may be around 650°C, each rich combustion phase being followed by a lean combustion phase, whereby this lean-to-rich-to-lean approach is also referred as wobbling approach.

More specifically, a DeSO,, rich phase is similar to a DeNO,, regeneration, when additional After-injection fuel quantity is injected to provide a rich atmosphere at the inlet of the LNT Trap.

A OeSO Lean phase is basically a Diesel Particulate Filter (DPF) regeneration in which Post-injections are used by means of a closed loop control on temperature to maintain a stable temperature.

The DeSO,, Lean phase has the effect to restore the Oxygen content in the LNT Trap.

The alternation of DeSOx rich and lean phases has also the consequence of burning the Hydrocarbon (HC) accumulated in the LNT Trap during the rich phase and is a fact that must be considered in the control.

Therefore a DeSO Lean regeneration is directly linked to a DPF regeneration the exploit the similarities between the logic and the physical conditions needed by the DPF regeneration and the DeSO Lean phase.

In fact a DeSO Regeneration is linked to a OFF Regeneration, because of the similar physical conditions that are needed for the two processes, namely high temperature in the exhaust line, and in order to guarantee comparable ageing and system performances with systems without LNT.

A problem may arise in the fact is that the OeSO regeneration, when linked to a DPF regeneration, may have to end before reaching acceptable DeSO efficiency targets, even if the driving conditions would allow to perform a more effective regeneration by extending DeSO duration.

In fact, the direct linking of the DeSO regeneration to the DPF regeneration has the consequence that the DeSO regeneration ends when a DPF End Request is activated by the Electronic Control Unit of the engine.

This event may be triggered by the software of the Electronic Control Unit for example by a DPF Deactivation Flag or due to the obtainment of a predetermined OFF regeneration percentage.

In this scenario, there are at least two disadvantages.

The first is that, if the DeSO regeneration is very efficient or the starting Sulphur load is relatively low, the residual Sulphur may reach the desired level before the end of DPF regeneration. In this case, the Sulphur removal efficiency is very low too because Sulphur removed quantity is directly proportional to the Sulphur Load present inside the LNT when performing the DeSO rich phase that, in any case, causes a substantial increase in fuel consumption.

Secondly, if the Sulphur load at the start of the DeSO regeneration is high, at the end of DPF regeneration the Sulphur load may be still critical and a new DeSO regeneration has to be requested at a subsequent opportunity.

It must also be considered that DeSO regenerations are costly, especially but not exclusively, due to the high fuel consumption they require.

An object of an embodiment of the invention is to enhance the performance of the DeSO regenerations and consequently increase the DeSO effectiveness and reduce the DeSO regenerations frequency over a vehicle's lifetime.

A further object of an embodiment of the invention is to provide for a method of operating a Lean NO Trap by performing the DeSO regenerations that allows for significant fuel savings.

Another object of an embodiment of the invention is to provide a method that adapts the DeSOx regeneration to the various conditions encountered during driving by taking advantage from the computational capabilities of the Electronic Control Unit (ECU) of the vehicle.

Another object of the present disclosure is to meet these goals by means of a simple, rational and inexpensive solution.

These objects are achieved by a method, by an engine, by an apparatus, by an automotive system, by a computer program and a computer program product, and by an electromagnetic signal having the features recited in the independent claims.

The dependent claims delineate preferred and/or especially advantageous aspects.

SUMMARY

An embodiment of the disclosure provides for a method of operating a Lean NO Trap in an exhaust line of an Internal Combustion Engine, the exhaust line being equipped with a Diesel Particulate Filter, the method comprising the steps of: -starting a regeneration event of the Diesel Particulate Filter and a DeSO regeneration event of the Lean NO Trap, the DeSO regeneration event being performed by executing a plurality of rich combustion phases, each combustion phase being followed by a lean combustion phase, -monitoring a parameter indicative of a critical condition in terms of SO storage of the Lean NO Trap.

-monitoring a parameter indicative of a potential desulphation efficiency of the 3D Lean NO Trap on a defined mission profile, varying the duration of the DeSO regeneration event by a time interval that is a function of the parameter indicative of a critical condition in terms of SO, storage of the Lean NO Trap and of the parameter indicative of a potential desuiphation efficiency of the Lean NO Trap on a defined mission profile.

An advantage of this embodiment is that it allows to manage the DeSO regenerations on the basis of LNT Sulphur removal efficiency criteria and to adapt the DeSO, regeneration duration and efficiency to the real driving profiles, taking into account fuel consumption and ageing.

Moreover, thanks to this embodiment, a DeSO regeneration can be ended before the end of the Diesel Particulate Filter regeneration event, when the Residual Sulphur Load is so low that can be considered removed; in such a way costs due to fuel consumption needed for the DeSO, regeneration can be saved.

According to another embodiment of the invention, the method further comprises the steps of: -extending the duration of the DeSO, regeneration event after the end of the regeneration event of the Diesel Particulate Filter by a time extension interval that is a function of the parameter indicative of a critical condition in terms of SO, storage of the Lean NO, Trap and of the parameter indicative of a potential desulphation efficiency of the Lean NO, Trap on a defined mission profile, by means of: -starting a counter at the end of Diesel Particulate Filter regeneration event, -updating the time extension interval as a function of the evolution of the parameter indicative of a potential desulphation efficiency of the Lean NO, Trap on a defined mission profile and, -ending the DeSOx regeneration event when the counter reaches the current value of time extension interval.

Advantageously according to this embodiment, it is provided a procedure to extend the OeSO, regeneration duration beyond the end of Diesel Particulate Filter regeneration event, if the Sulphur load of the trap is still critical and a procedure to end the DeSO, regeneration event.

According to an embodiment of the invention, the value of the parameter indicative of a critical condition in terms of SO, storage of the Lean NO, Trap is fixed at the end of the Diesel Particulate Filter regeneration event and kept constant until the end of the DeSO, regeneration event of the Lean NO, Trap.

This embodiment of the invention has the advantage that it takes into account the state of the lean NO trap at the end of the DPF regeneration to calculate the extension of the DeSO, regeneration needed.

According to a further embodiment of the invention the value of the parameter indicative of a critical condition in terms of SO storage of the Lean NO Trap is a function of the residual Sulphur quantity in the Lean NO Trap and of a critical Sulphur threshold.

This embodiment of the invention has the advantage that the extension the DeSO regeneration event can be calculated in such a way that it is ended when the residual Sulphur content is acceptable.

According to an embodiment of the invention, to each defined mission profile a calibratable score is associated that is a function of the expected efficiency of the DeSO regeneration event in the conditions generated by the current mission profile and of the odds of performing sufficiently long rich combustion phases of the DeSO regeneration event.

An advantage of this embodiment is that it allows to take into account the effect of various mission profiles currently performed by the driver on the DeSO regeneration event.

According to still another embodiment of the invention, the value of the parameter indicative of a potential desulphation efficiency of the Lean NO Trap on a defined mission profile is evaluated by taking a low-pass filtered value of the mission profile score corresponding to the instantaneous mission profile.

An advantage of this embodiment is that it allows to stabilize a parameter indicative of the current mission profile considering that the instantaneous mission profile can change very rapidly.

According to a further embodiment of the disclosure, the DeSO regeneration event is ended before the end of the Diesel Particulate Filter regeneration event, if the parameter indicative of a critical condition in terms of SO, storage of the Lean NO, Trap is below a predefined threshold.

An advantage of this embodiment is that it allows to end the DeSOx regeneration before the end of the DPF regeneration if there is no need to continue it until the end of the DPF regeneration substantially improving fuel savings.

S

An embodiment of the invention provides an apparatus for operating a Lean NOx Trap in an exhaust line of an Internal Combustion Engine, the exhaust line being equipped with a Diesel Particulate Filter, the apparatus comprising: -means for starting a regeneration event of the Diesel Particulate Filter and a DeSO regeneration event of the Lean NO Trap, the DeSO regeneration event being performed by executing a plurality of rich combustion phases, each combustion phase being followed by a lean combustion phase, -means for monitoring a parameter indicative of a critical condition in terms of SO storage of the Lean NO Trap, -means for monitoring a parameter indicative of a potential desulphation efficiency of the Lean NO Trap on a defined mission profile, means for varying the duration of the DeSO regeneration event by a time extension interval that is a function of the parameter indicative of a critical condition in terms of SQ storage of the Lean NO Trap and of the parameter indicative of a potential desulphation efficiency of the Lean NQ Trap on a defined mission profile.

According to an aspect of this embodiment, the apparatus further comprises: -means for extending the duration of the DeSO regeneration event after the end of the regeneration event of the Diesel Particulate Filter by a time extension interval that is a function of the parameter indicative of a critical condition in terms of SO storage of the Lean NO Trap and of the parameter indicative of a potential desulphation efficiency of the Lean NiO Trap on a defined mission profile, -means for starting a counter at the end of Diesel Particulate Filter regeneration event, -means for updating the time extension interval as a function of the evolution of the parameter indicative of a potential desulphation efficiency of the Lean NO Trap on a defined mission profile and, -means for ending the DeSOx regeneration event when the counter reaches the current value of time extension interval.

This aspect advantageously extends the DeSO regeneration duration beyond the end of Diesel Particulate Filter regeneration event, if the Sulphur load of the trap is still critical and ends the DeSO regeneration event when appropriate.

Another aspect of the apparatus of the invention provides for means for fixing the value of the parameter indicative of a critical condition in terms of SO, storage of the Lean NO Trap at the end of the Diesel Particulate Filter regeneration event and means to keep said value constant until the end of the DeSO regeneration event of the Lean NC, Trap.

Another aspect of the apparatus of the invention provides means for calculate the value of the parameter indicative of a critical condition in terms of SO storage of the Lean NQ Trap as a function of the residual Sulphur quantity in the Lean NO Trap and of a critical Sulphur threshold.

This embodiment of the invention has the advantage that the extension the DeSO, regeneration event can be calculated in such a way that it is ended when the residual Sulphur content is acceptable.

Still another aspect of the apparatus of the invention provides means to associate a calibratable score to each defined mission profile, the calibratable score being a function of the expected efficiency of the DeSO, regeneration event in the conditions generated by the current mission profile and of the odds of performing sufficiently long rich combustion phases of the DeSO regeneration event An advantage of this embodiment is that it allows to take into account the effect of various mission profiles currently performed by the driver on the DeSO regeneration event.

Still another aspect of the apparatus of the invention provides means to evaluate the value of the parameter indicative of a potential desulphation efficiency of the Lean NO, Trap on a defined mission profile by taking a low-pass filtered value of the mission profile score corresponding to the instantaneous mission profile.

Still another aspect of the apparatus of the invention provides means to end the DeSOx regeneration event before the end of the Diesel Particulate Filter regeneration event, if the parameter indicative of a critical condition in terms of SO storage of the Lean NO Trap is below a predefined threshold.

An advantage of this embodiment is that it allows to end the DeSOx regeneration before the end of the DPF regeneration if there is no need to continue it until the end of the DPE regeneration substantially improving fuel savings.

Another embodiment of the invention provides an automotive system comprising an internal combustion engine, managed by an engine Electronic Control Unit, the engine being equipped with an exhaust line, the exhaust line being equipped with a Lean NO Trap Catalyst and with a Diesel Particulate Filter, wherein the Electronic Control Unit is configured to: -start a regeneration event of the Diesel Particulate Filter and a DeSO regeneration event of the Lean NO Trap, the DeSO, regeneration event being performed by executing a plurality of rich combustion phases, each combustion phase being followed by a lean combustion phase, -monitor a parameter indicative of a critical condition in terms of SO storage of the Lean NO Trap, -monitor a parameter indicative of a potential desuiphation efficiency of the Lean NO Trap on a defined mission profile, -vary the duration of the DeSO regeneration event by a time interval that is a function of the parameter indicative of a critical condition in terms of SO, storage of the Lean NO Trap and of the parameter indicative of a potential desulphation efficiency of the Lean NO, Trap on a defined mission profile.

This last two embodiment has the same advantage of the method disclosed above.

The method according to one of its aspects 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 computer program product comprising the computer program.

The computer program product can be embodied as a control apparatus for an internal combustion engine, comprising an Electronic Control Unit (ECU), a data carrier associated to the ECU, and the computer program stored in a data carrier, so that the control apparatus defines the embodiments described in the same way as the method. In this case, when the control apparatus executes the computer program all the steps of the method described above are carried out.

The method according to a further aspect can be also embodied as an electromagnetic signal, said signal being modulated to carry a sequence of data bits which represents a computer program to carry out all steps of the method.

A still further aspect of the disclosure provides an internal combustion engine controlled by an Electronic Control Unit specially arranged for carrying out the method claimed.

BRIEF DESCRIPTION OF THE DRAWINGS

The various embodiments will now be described, by way of example, with reference to the accompanying drawings, wherein like numerals denote like elements, and in which: Figure 1 shows an automotive system; Figure 2 is a cross-section of an internal combustion engine belonging to the automotive system of figure 1; Figure 3 is a schematic representation of the main components of the automotive system employed in the various embodiment of the invention; Figure 4 shows a schematic representation of the main software modules that manage a DeSO regeneration and its end according to an embodiment of the invention; Figure 5 shows a schematic representation of the main criteria used for implementing an embodiment of the invention; Figure 6 shows a schematic representation of a determination of a mission profile index used in various embodiments of the invention; Figure 7 shows a schematic representation of the main steps needed in an embodiment of the invention; and Figure 8 shows a graph of a Sulphur residual value during a regeneration according to an exemplary embodiment of the invention.

DETAILED DESCRIPTION

Exemplary embodiments will now be described with reference to the enclosed drawings without intent to limit application and uses.

Some embodiments may include an automotive system 1001 as shown in Figures 1 and 2, that includes an internal combustion engine (ICE) 110 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 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 increase the pressure of the fuel received from a fuel source 190. Each of the cylinders 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 gases 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 corripressor 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 gases from an exhaust manifold 225 that directs exhaust gases from the exhaust ports 220 and through a series of vanes prior to expansion through the turbine 250. 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 embodiments, the turbocharger 230 may be fixed geometry and/or include a waste gate.

The exhaust system 270 may include an exhaust line 275 having one or more exhaust aftertreatment devices 280. The aftertreatment devices may be any device configured to change the composition of the exhaust gases. Some examples of aftertreatnient devices 280 include, but are not limited to, catalytic converters (two and three way), oxidation catalysts, lean NO traps, hydrocarbon adsorbers, selective catalytic reduction (3CR) systems, and particulate filters. 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 gases in the EGR system 300. An EGR valve 320 regulates a flow of exhaust gases in the EGR system 300.

In Figure 1, the EGR system is bringing flow from the line before the turbine 250 to the line after the compressor 240. In other enibodimerits, a low pressure EGR could be present.

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, exhaust pressure and temperature sensors 430, 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 liniitedto, 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, or data carrier 460, and an interface bus. The CPU is configured to execute instructions stored as a program in the memory system, and send and receive signals 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.

More specifically, Figure 3 shows a schematic representation of the main components of the automotive system 100 employed in the various embodiment of the invention.

In Figure the engine 110 is represented having the air intake duct 205 and the compressor 240 rotationally coupled to variable geometry turbine 250 having actuator 290.

In the exhaust line 275 an aftertreatment device is provided comprising a Lean No, Trap 285 and a Diesel Particulate Filter 295, A pressure drop sensor 500 is provided across the DPF 295 to measure pressure drop across the DPF 295 and send corresponding signals to the ECU 450.

A temperature sensor 510 upstream of the Lean No Trap 285 and a temperature sensor 520 downstream of it are provided, both being connected to the ECU 450 to send signals therein.

Furthermore, a lambda sensor 530 upstream of the Lean No, Trap 285 and a lambda sensor 540 downstream of it are provided, both being connected to the ECU 450 to send signals therein.

The procedure to start a DeSO regeneration event may be the following.

Sensors information, models or estimations are evaluated inside the ECU 450 to decide whether a change of combustion mode is required. In case there is a request of combustion mode change, the ECU 450 commands the engine actuators, such as EGR valve, Swirl valve, Throttle valve, VGT actuator, Rail Pressure Pump, and as above mentioned fuel injectors 160, in order to move them to dedicated set paints that create an exhaust gas condition that is necessary to promote the chemical reactions in the [NT that are the base of each typical LNT phase, such as NO storage, NO conversion, SO storage, SO,< desorption.

Figure 4 shows a schematic representation of the main software modules or subsystems that manage a DeSO regeneration and its end according to an embodiment of the invention: First a DeSO Request Manager (block 610) is in charge of defining when a DeSO regeneration shall be demanded.

Then a DeSO Release Manager in charge to establish when DeSO shall be released (block 620).

A DeSO Inhibition Manager (block 600) is in charge to interrupt or inhibit DeSOx combustion modes when necessities arise.

A DeSO Wobbling Manager (block 630) is in charge to define when switching between one combustion mode and the other one, namely between a rich combustion mode and a lean one or viceversa.

Finally, according to various embodiment of the invention that will be better explained in the following description, a DeSO End Manager (block 640) is in charge to define when a DeSOx regeneration shall be concluded is provided.

Figure 5 shows a schematic representation of the main criteria used for implementing an embodiment of the invention.

In general, it must be considered that DeSO and OFF regenerations are always performed in parallel since the engine conditions in terms of temperature are the same.

During a DeSQ, phase the status of the DPE 295 is continually monitored by the DeSO Manager.

As it will be better explained hereinafter, a DeSO extension is then calculated when there would not be the need to keep the DPF regeneration on from the soot point of view.

This is done to limit the aging of the component.

The management of the DeSO regeneration is based on a certain efficiency criteria (block 700).

These criteria may give rise to a DeSOx regeneration extension (block 710) in which the DeSOx regeneration is extended beyond the end of the DPF regeneration (block 720). This extension may be based on driving conditions, expressed as mission profile inputs (block 730) suitable evaluated as explained hereinafter (block 740) and on Sulphur load (block 750).

Alternatively, the DeSOx regeneration event can be ended or deactivated (block 760) before the end of the DPF regeneration when the residual Sulphur load is below a threshold.

Generally speaking, the DeSO regeneration can be extended after the end of the DPF regeneration depending on a mission profile of the engine and on a critical factor related to a critical condition in terms of SO storage of the Lean NO Trap 285.

Figure 6 shows a schematic representation of a determination of a mission profile index used in various embodiments of the invention.

Different mission profiles may be defined taking into account the different driving conditions of a vehicle during its use in terms of accelerator position, engine speed and torque, idle, braking1 road and so on.

Each defined mission profile may have a calibratable score Mission Profile Score.

The Mission Profile Score variable may have a value between 0 and 1, and is chosen considering the expected efficiency of DeSO regeneration in those conditions and the odds of performing sufficiently long rich events.

Therefore, first a mission profile is recognized (block 800), examining various parameters of the engine during driving.

Then, having recognized instantaneous mission profile, a Mission Profile Score value is assigned (block 805) and this value is filtered with a low-pass filter (block 810) to calculate a Mission Profile Index. Low-pass filtering o the mission profile score allows to stabilize it considering that the instantaneous mission profile can change very rapidly.

Therefore the Mission Profile Index is defined as the low-pass filtered value of Mission Profile Scora The filter constant Kost can be calibratable.

The Mission Profile Index is therefore indicative of a potential desulphation efficiency of the Lean NO Trap 285 on a defined mission profile.

The Mission Profile Index is then sent to a DeSOx manager block 815.

More specifically, the instantaneous mission profile (block 820) is sent to an array or vector of score assignment (block 833) and a filter constant array or vector (block 825) is used to determine the specific filtering constant Kost, to calculate a filtered mission profile score (block 835).

The Critical Factor K_Critical is a ratio defined considering the sulphur loading that leads to high hydrogen sulphyde (H2S) emission causing bad smell at the tail pipe, reduction of NO storage and regeneration properties decay.

This factor indicates the distance of the current Lean NO Trap 285 conditions a critical Sulphur value SulphurThrs_Critical that should not be trespassed to guarantee the correct functionality of the LNT.

The critical factor K_Critical may be definedby means of the following ratio: K_Critical = Residual Sulphur Quantity! SulphurThrs_Critical Both the K_Critical and the SulphurThrs_Gritical parameter can be calibrated, for example by means of an experimental activity.

Figure 7 shows a schematic representation of the main steps needed in an embodiment of the invention.

In this case the parameter K_Critical indicative of a critical condition in terms of SO storage of the Lean NO Trap 285, is monitored together with the parameter Mission Profile Index that is indicative of a potential desulphation efficiency of the Lean NO Trap 285 on a defined mission profile.

The time duration of the DeSO extension interval is first calculated when the DPF regeneration ends as the output of a map (block 920) that is function of the Mission Profile Index and of the critical ratio K_Critical, The critical ratio K_Critical is calculated and its value is fixed when the DPF regeneration ends (block 910) and kept constant until the end of the DeSO regeneration event of the Lean NO Trap (285).

On the contrary, the Mission Profile Index is continuously calculated (block 900), causing the continuous update, through map of block 920 of DeSO Extension Interval during the extension interval itself.

A time counter variable Time Counter starts at of the Diesel Particulate Filter regeneration event.

And the DeSO regeneration event is terminated when the counter Time Counter reaches the current value of time extension interval DeSo Extension Interval (block 930).

Figure 8 shows a graph of a Sulphur residual value during a regeneration according to an exemplary embodiment of the invention.

In this case, curve A represents a graph of the values of the Sulphur residual in the LNT during a DeSO regeneration process which occurs at the same time of a DPF regeneration.

Due to the fact that, when the DPF regeneration ends (at the 100% point), the residual Sulphur quantity is still higher than the predefined threshold Sulphur Thrs_Demand that would trigger the end also of the DeSO regeneration, the DeSOx regeneration event is continued using the above explained logic reducing the residual Sulphur quantity to a value close or equal to the predefined threshold Sulphur Thrsoemanci.

Curve B represents a graph of the values of the K_c,itfoa! parameter, which at the end of the DPF regeneration is evaluated and its fixed evaluated value is used in map 920 to determine the DeSOx extension interval.

The various embodiments of the invention define a logic suitable to adapt the DeSO regeneration duration and efficiency to the real driving profile, taking into account fuel consumption and ageing.

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

REFERENCE NUMBERS

automotive system internal combustion engine (ICE) 120 engine block cylinder cylinder head camshaft piston 145 crankshaft combustion chamber cam phaser fuel injector fuel rail 180 fuel pump fuel source intake manifold 205 air intake duct 210 intake air port 215 valves of the cylinder 220 exhaust gas port 225 exhaust manifold 230 turbocharger 240 compressor 244 exhaust line portion 250 turbine 260 intercooler 270 exhaust system 275 exhaust line 280 exhaust aftertreatment device 285 LNT trap 290 VGT actuator 295 DFF 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 sensor 434 [NT inlet temperature sensor 436 LNT outlet temperature sensor 445 accelerator pedal position sensor 450 electronic control unit (ECU) 460 data carrier 500 DFF pressure drop sensor 510 temperature sensor upstream LNT 520 temperature sensor downstream LNT 530 lambda sensor upstream LNT 540 lambda sensor downstream LNT 600 DeSO inhibition manager 610 DeSO request manager 620 DeSO release manager 630 wobbling manager 640 DeSO end manager 700 efficiency criteria block 710 DeSOx extension block 720 DPF end request block 730 mission profile block 740 mission profile evaluation block 750 Sulphur load 760 DeSOx deactivation 800 mission profile recognition 805 mission profile score assignment 810 low pass filter 815 DeSOx manager 820 Instantaneous mission profile 825 filter constant array 830 mission profile score assignment array 835 Mission profile score low pass filtering 900 filtered mission profile score 910 K_critical at DPF deactivation 920 DeSOx extension interval map 930 comparison block

Claims

CLAIMS1. A method of operating a Lean NO Trap (285) in an exhaust line (275) of an Internal Combustion Engine (110), the exhaust tine (275) being equipped with a Diesel Particulate Filter (295), the method comprising the steps of: -starting a regeneration event of the Diesel Particulate Filter (295) and a OeSO regeneration event of the Lean NO Trap (285), the DeSO regeneration event being performed by executing a plurality of rich combustion phases, each combustion phase being followed by a lean combustion phase, -monitoring a parameter (k_Critical) indicative of a critical condition in terms of SO storage of the Lean NO, Trap (285), -monitoring a parameter (Mission Profile Index) indicative of a potential desulphation efficiency of the Lean NOK Trap (285) on a defined mission profile, -varying the duration of the DeSO regeneration event by a time interval that is a function of the parameter (K_Critical) indicative of a critical condition in terms of SQ storage of the Lean NO Trap (265) and of the parameter (Mission Profile Index) indicative of a potential desuiphation efficiency of the Lean NO Trap (285) on a defined mission profile.
2. A method as in claim 1, further comprising the steps of: -extending the duration of the DeSO regeneration event after the end of the regeneration event of the Diesel Particulate Filter (295) by a time extension interval (DeSo Extension Interval) that is a function of the parameter (K_Critical) indicative of a critical condition in terms of SO. storage of the Lean NO Trap (285) and of the parameter (MLssion Profile Index) indicative of a potential desulphation efficiency of the Lean NO Trap (285) on a defined mission profile, by means of: -starting a counter (Time Counter) at the end of Diesel Particulate Filter regeneration event, updating the time extension interval (DeSo Extension Inleival) as a function of the evolution of the parameter (Mission Profile Index) indicative of a potential desulphation efficiency of the Lean NO Trap (285) on a defined mission profile and, -ending the DeSOx regeneration event when the counter (Time Counter) reaches the current value of time extension interval (DeSox Extension Interval).
3. A method as in claim 2, in which the value of the parameter (k_Critical) indicative of a critical condition in terms of SO storage of the Lean NO Trap (285) is fixed at the end of the Diesel Particulate Filter (295) regeneration event and kept constant until the end of the DeSO, regeneration event of the Lean NO, Trap (285).
4. A method as in claim 1, in which the value of the parameter (k_Critical) indicative of a critical condition in terms of SO, storage of the Lean NO, Trap (285) is a function of the residual Sulphur quantity in the Lean NO Trap (285) and of a critical Sulphur threshold (Sulphur Thrs_ Critical).
5. A method as in claim 1, in which to each defined mission profile, a calibratable score (Mission Profile Score) is associated that is a function of the expected efficiency of the DeSO, regeneration event in the conditions generated by the current mission profile and of the odds of performing sufficiently long rich combustion phases of the DeSO, regene ration event.
6. A method as in claim 5, in which the value of the parameter (Mission Profile Index) indicative of a potential desulphation efficiency of the Lean NO, Trap (285) on a defined mission profile is evaluated by taking a low-pass filtered value of the mission profile score (Mission Profile Score) corresponding to the instantaneous mission profile.
7. A method as in claim 1, in which the DeSOx regeneration event is ended before the end of the Diesel Particulate Filter regeneration event, if the parameter (K_Critical) indicative of a critical condition in terms of SO,< storage of the Lean NO, Trap (285) is below a predefined threshold (Sulphur Thrs_Demand).
8. An apparatus for operating a Lean NOx Trap (285) in an exhaust line of an Internal Combustion Engine (110), the exhaust line (275) being equipped with a Diesel Particulate Filter (295), the apparatus comprising: -means for starting a regeneration event of the Diesel Particulate Filter (295) and a DeSO, regeneration event of the Lean NO, Trap (285), the DeSO, regeneration event being performed by executing a plurality of rich combustion phases, each combustion phase being followed by a lean combustion phase, -means for monitoring a parameter (K_Critical) indicative of a critical condition in terms of SQ storage of the Lean NO Trap (285), -means for monitoring a parameter (Mission Profile Index) indicative of a potential desulphation efficiency of the Lean NO Trap (285) on a defined mission profile, -means for varying the duration of the DeSO regeneration event by a time extension interval that is a function of the parameter (K_Critical) indicative of a critical condition in terms of SO, storage of the Lean NO Trap (285) and of the parameter (Miss/on Profile Index) indicative of a potential desuiphation efficiency of the Lean NO Trap (285) on a defined mission profile.
9. An automotive system comprising an internal combustion engine (110), managed by an engine Electronic Control Unit (450), the engine (110) being equipped with an exhaust line (275), the exhaust line (275) being equipped with a Lean NOx Trap Catalyst (285) and with a Diesel Particulate Filter (295), wherein the Electronic Control Unit (450) is configured to: -start a regeneration event of the Diesel Particulate Filter (295) and a DeSO regeneration event of the Lean NO Trap (285), the DeSO regeneration event being performed by executing a plurality of rich combustion phases, each combustion phase being followed by a lean combustion phase, -monitor a parameter (K_Critical) indicative of a critical condition in terms of SQ storage of the Lean NO Trap (285), -monitor a parameter (Mission Profile Index) indicative of a potential desulphatiori efficiency of the Lean NO Trap (285) on a defined mission profile, -vary the duration of the DeSO regeneration event by a time interval that is a function of the parameter (K_Critical) indicative of a critical condition in terms of SO, storage of the Lean NO Trap (285) and of the parameter (Mission Profile Index) indicative of a potential desulphation efficiency of the Lean NO Trap (285) on a defined mission profile.
10. An internal combustion engine (110) equipped with an exhaust line (275), the exhaust line (275) being equipped with a Lean NOx Trap Catalyst (285) and with a Diesel Particulate Filter (295), the engine (110) being controlled by an Electronic Control Unit (450) configured for carrying out the method according to any of the claims 1-7.
11. A computer program comprising a computer-code suitable for performing the method according to any of the claims 1-7.
12. Computer program product on which the computer program according to claim 11 is stored.
13. Control apparatus for an internal combustion engine, comprising an Electronic Control Unit, a data carrier associated to the Electronic Control Unit and a computer program according to claim 11 stored in the data carrier.
14. An electromagnetic signal modulated as a carrier for a sequence of data bits representing the computer program according to claim 11.