GB2557690A

GB2557690A - A method of detecting that a particulate filter is clean from soot

Info

Publication number: GB2557690A
Application number: GB1621424.9A
Authority: GB
Inventors: Fritzsche Jan; A Ramappan Vijay
Original assignee: GM Global Technology Operations LLC
Current assignee: GM Global Technology Operations LLC
Priority date: 2016-12-15
Filing date: 2016-12-15
Publication date: 2018-06-27
Also published as: GB201621424D0

Abstract

A method of detecting that a particulate filter (PF) 280 of an internal combustion engine 100 is clean from soot comprises determining a value of a temperature of the particulate filter 280, and determining first and second values of an oxygen content in the exhaust gas upstream and downstream of the particulate filter 280. The PF 280 is determined to be clean of soot when the temperature is above a threshold, and the upstream oxygen content is above a threshold, and the difference between the first and second values is below a threshold. The temperature threshold represents a minimum temperature for regeneration, and the upstream oxygen threshold is a value sufficient for regeneration, so if the difference between upstream and downstream oxygen levels is below the threshold, it is determined that minimal combustion of trapped particulate matter is taking place, and therefore minimal or zero soot is present in the filter.

Description

(54) Title of the Invention: A method of detecting that a particulate filter is clean from soot

Abstract Title: Determining that a particulate filter is clean of soot using oxygen measurements (57) A method of detecting that a particulate filter (PF) 280 of an internal combustion engine 100 is clean from soot comprises determining a value of a temperature of the particulate filter 280, and determining first and second values of an oxygen content in the exhaust gas upstream and downstream of the particulate filter 280. The PF 280 is determined to be clean of soot when the temperature is above a threshold, and the upstream oxygen content is above a threshold, and the difference between the first and second values is below a threshold. The temperature threshold represents a minimum temperature for regeneration, and the upstream oxygen threshold is a value sufficient for regeneration, so if the difference between upstream and downstream oxygen levels is below the threshold, it is determined that minimal combustion of trapped particulate matter is taking place, and therefore minimal or zero soot is present in the filter.

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S130

A METHOD OF DETECTING THAT A PARTICULATE FILTER IS CLEAN FROM SOOT

TECHNICAL FIELD

The present disclosure generally relates to a particulate filter of an internal combustion engine, for example an internal combustion engine of a motor vehicle. More particularly, the present disclosure relates to a method of detecting whether the particulate filter is clean from particulate matter (soot).

BACKGROUND

It is known that an internal combustion engine, such as a diesel engine or a gasoline engine, may be provided with a particulate filter for trapping soot (e.g. impure carbon particles) that may be contained in the exhaust gas.

When the amount of soot trapped inside the particulate filter exceeds a maximum admissible level, the particulate filter is cleaned up by means of a so-called regeneration process.

The regeneration process usually provides for increasing the oxygen content of the exhaust gas and the temperature of the particulate filter up to values that trigger the combustion of the trapped soot.

In order to properly manage the activation and the deactivation of the regeneration processes, the amount of soot which is trapped inside the particulate filter (i.e. the so-called soot load) must be constantly monitored.

The known strategies for monitoring the soot load are based on measurements of the pressure differential across the particulate filter and/or on mathematical models configured to yield an estimation of the soot load on the basis of several different operating parameters.

However, in order to improve the soot load estimation, these strategies must be able to accurately determine when the particulate filter is completely clean from soot, for example at the end of a regeneration process.

SUMMARY

In view of the above, one of the objects of the present invention is that of providing a method that allows to accurately identify when the particulate filter is completely or almost completely clean from soot.

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

More particularly, an embodiment of the invention provides a method of detecting that a particulate filter of an internal combustion engine is clean from soot, comprising:

- determining a value of a temperature of the particulate filter,

- determining a first value of an oxygen content in an exhaust gas flowing towards the particulate filter,

- determining a second value of the oxygen concentration in the exhaust gas discharged from the particulate filter,

- identifying that the particulate filter is clean from soot, if the following conditions are met:

the particulate filter temperature value is equal to or larger than a predetermined threshold value thereof (e.g. a minimum value of the particulate filter temperature that is able to trigger a soot combustion), the first value of the oxygen content is equal to or larger than a predetermined threshold value thereof (e.g. a minimum value of the oxygen content that indicates that the engine is operating “lean, namely with an air-to-fuel ratio which is higher than the stoichiometric ratio), and a difference between the first value and the second value of the oxygen content is equal to or smaller than a predetermined threshold value thereof (e.g. a maximum difference value that indicates that no soot combustion has occurred inside the particulate filter).

Thanks to this solution, the method is able to accurately identify when the particulate fil2 ter is clean from soot.

In particular, this method can be reliably performed any time the engine is operating under lean conditions, both during fuel cut-off engine operations and during normal engine operations (i.e. when the fuel and air mixture is actually disposed and ignited inside the combustion chambers).

The method may be favorably implemented in conjunction with the known strategies for monitoring the soot load in the particulate filter (e.g. those based on the pressure differential across the particulate filter and/or on estimating models), for example in order to precisely determine a “starting condition” (i.e. clean filter) from which these strategies can start to calculate the soot load.

As a consequence, the strategies for monitoring the soot load may become more accurate as well as the entire management of the regeneration processes, which imply the possibility of reducing fuel consumption and/or the risk of failures or excessive backpressures due to an overloaded particulate filter.

According to an aspect of the method, the particulate filter may be identified to be clean from soot provided that the above-mentioned conditions are fulfilled for longer than a predetermined period of time.

This aspect has the effect of improving the robustness of the method by reducing the risk of false “clean filter” identifications.

According to another aspect of the method, the second value of the oxygen content may be determined by means of an oxygen sensor (also referred as to lambda sensor) located in an exhaust pipe downstream of the particulate filter.

This aspect provides a very reliable solution for determining the oxygen content in the exhaust gas discharged from the particulate filter.

According to another aspect of the method, the first value of the oxygen content may be determined by means of an additional oxygen sensor located in an exhaust pipe upstream of the particulate filter.

This aspect provides a very reliable solution for determining the oxygen content in the exhaust gas flowing towards the particulate filter.

In some embodiments, the additional oxygen sensor may be particularly located between a catalytic converter and the particulate filter.

In this way, the difference between the first and the second value of the oxygen content is only affected by the oxidation reactions that may occur inside the particulate filter, so that it represents a direct indication of whether the particulate filter still contain soot or not.

In other embodiments, the additional oxygen sensor may be located upstream of the catalytic converter.

In this case, the difference between the first and the second value of the oxygen content can also be affected by the oxygen which is stored inside the catalytic converter. Nevertheless, it is still possible to reliably identify the absence of soot within the particulate filter, for example by means of a proper calibration of the threshold value of the difference between the first and the second oxygen content value and/or by calculating said difference a certain time after the first value of the oxygen content and the temperature value have exceeded their threshold values, typically after the catalytic converter has reached its full oxygen storage capacity.

The oxygen sensors may be any sensor suitable to provide an indication of the oxygen content in the exhaust gas, including wide range air-fuel (WRAF) sensors or switching (two-state) oxygen sensors.

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 invention provides an internal combustion engine comprising a particulate filter and an electronic control unit configured to:

- determine a value of a temperature of the particulate filter,

- determine a first value of an oxygen content in an exhaust gas flowing towards the particulate filter,

- determine a second value of the oxygen content in the exhaust gas discharged from the particulate filter,

- identify that the particulate filter is clean from soot, if all the following conditions are met:

the temperature value is equal to or larger than a predetermined threshold value thereof, the first value of the oxygen content is equal to or larger than a predetermined threshold value thereof, and a difference between the first value and the second value of the oxygen content is equal to or smaller than a predetermined threshold value thereof.

This embodiment of the invention achieves basically the same effects of the method above, in particular the effect of accurately identifying when the particulate filter is completely or almost completely clean from soot.

The electronic control may further implement any of the additional aspects of the invention that have been described with reference to the method, in order to achieve the related effects. In particular, the electronic control unit may be configured to identify that the particulate filter is clean from soot provided that the conditions are fulfilled for longer than a predetermined time period. In addition, the electronic control unit may be configured to determine the second value of the oxygen content by means of an oxygen sensor (also referred as to lambda sensor) located in an exhaust pipe downstream of the particulate filter, for example a wide range air fuel (WRAF) sensor or a switching sensor. The electronic control unit may be further configured to determine the first value of the oxygen content by means of an additional oxygen sensor located in an exhaust pipe upstream of the particulate filter, for example another wide range air fuel (WRAF) sensor or switching sensor. This additional oxygen sensor may be located either between the particulate filter and a catalytic converter or upstream of the catalytic converter.

Still another embodiment of the invention provides an apparatus for detecting that a particulate filter of an internal combustion engine is clean from soot, comprising:

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

- means for determining a first value of an oxygen content in an exhaust gas flowing towards the particulate filter,

- means for determining a second value of the oxygen concentration in the exhaust gas discharged from the particulate filter,

- means for identifying that the particulate filter is clean from soot, if the following conditions are met:

The apparatus may further implement any of the additional aspects of the invention that have been described with reference to the method, in order to achieve the related effects. In particular, the means for identifying that the particulate filter is clean from soot may be configured to identify that the particulate filter is clean from soot provided that the above-mentioned conditions are fulfilled for longer than a predetermined period of time. According to another aspect of the method, the means for determining the second value of the oxygen content may include an oxygen sensor (also referred as to lambda sensor) located in an exhaust pipe downstream of the particulate filter, for example a wide range air fuel (WRAF) sensor or a switching sensor. According to another aspect of the method, the means for determining the first value of an oxygen content may include an additional oxygen sensor located in an exhaust pipe upstream of the particulate filter, for example another wide range air fuel (WRAF) sensor or switching sensor. This additional oxygen sensor may be located either between the particulate filter and a catalytic converter or upstream of the catalytic converter.

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 of a detecting method according to an embodiment of the present disclosure.

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. In the instant example, the ICE 110 is a spark-ignition engine (e.g. a gasoline engine), in particular a direct-injection gasoline engine. In other embodiments, the ICE 110 could be a compression-ignition engine (e.g. Diesel engine). The ICE 110 has an engine block 120 defining at least one cylinder 125 having a piston 140 coupled to rotate a crankshaft 145. A cylinder head 130 cooperates with the piston 140 to define a combustion chamber 150. A fuel and air mixture (not shown) is disposed in the combustion chamber 150 and ignited, resulting in hot expanding exhaust gas causing reciprocal movement of the piston 140. A spark plug 360 may be coupled to each combustion chamber 150 to provide the spark that ignites the fuel and air mixture.

The fuel is provided by at least one fuel injector 160 coupled directly to the combustion chamber 150 and the air through at least one intake port 210. The fuel is provided at high pressure to the fuel injector 160 from a fuel rail 170 in fluid communication with a high pressure fuel pump 180 that increase the pressure of the fuel received from a fuel source 190. Each of the cylinders 125 has at least two valves 215, actuated by a camshaft 135 rotating in time with the crankshaft 145. The valves 215 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 gas exits the turbine 250 and is 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 gas. In the present example, the aftertreatment devices include at least one particulate filter 280, in this case a gasoline particulate filter (GPF), which is provided for trapping particulate matter (soot) contained in the exhaust gas. The aftertreatment devices may also include a catalytic converter 285 located in the exhaust pipe 275 upstream of the particulate filter 280, as well as other devices such as catalytic converters (two and three way), lean NOx traps, hydrocarbon adsorbers and selective catalytic reduction (SCR) systems.

The catalytic converter 285 may be a three-way catalytic converter (TWC), which is generally designed to prompt three different reactions: the reduction of nitrogen oxides to nitrogen and oxygen; the oxidation of carbon monoxide to carbon dioxide; and the oxidation of unburnt hydrocarbons to carbon dioxide and water. A three-way catalytic converter can store oxygen from the exhaust gas, usually when the air-fuel ratio of the fuel and air mixture is lean (i.e. when the value of the air-fuel ratio is larger than the stoichiometric ratio). When the exhaust gas does not contain enough oxygen to prompt the reactions, the stored oxygen is released and consumed. In some embodiment, the catalytic converter 285 may be combined with or integrated in the particulate filter 280 (this combination is usually used for gasoline engine and it is referred as to 4-way gasoline particulate filter). A 4-way gasoline particulate filter may be generally obtained by providing the particulate filter 280 with a catalytic coating.

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

EGR system 300.

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. Furthermore, the ECU 450 may generate output signals to various control devices that are arranged to control the operation of the ICE 110, including, but not limited to, the fuel injectors 160, the throttle body 330, the EGR Valve 320, the VGT actuator 290, the spark plugs 360 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.

The sensors include, but are not limited to, a mass airflow and temperature sensor 340, a manifold pressure and temperature sensor 350, coolant and oil temperature and level sensors 380, a fuel rail pressure sensor 400, a cam position sensor 410, a crank position sensor 420, exhaust pressure and temperature sensors 430, an EGR temperature sensor 440, and an accelerator pedal position sensor 445. The sensors may also include two oxygen sensors (also referred to as lambda sensors), including a first oxygen sensor 435 located in the exhaust pipe 275 downstream of the particulate filter 280 to measure the oxygen content (or equivalently a so-called lambda” parameter) in the exhaust gas that exits the particulate filter 280, and a second oxygen sensor 465 located in the exhaust pipe 275 upstream of the particulate filter 280 to measure the oxygen content (or equivalently a so-called “lambda” parameter) in the exhaust gas that flows towards the particulate filter 280. The terms “upstream” and “downstream” are here intended with reference to the flowing direction of the exhaust gas. In particular, the oxygen sensor 465 may be located either between the catalytic converter 285 and the particulate filter 280 (as illustrated in solid line in figure 1) or upstream of the catalytic converter 285, for example between the catalytic converter 285 and the turbine 250 of the turbocharger 230 (as illustrate in dotted line in figure 1). The oxygen sensors 435 and 465 may be any sensor suitable to provide an indication of the oxygen content in the exhaust gas. By way of example, the oxygen sensors 435 and 465 may be two wide range air-fuel (WRAF) sensors, whose output is usually proportional to the oxygen content in a linearized manner, or they may be two switching oxygen sensors, whose output may be a two-state output: lean or rich depending on whether the oxygen content exceeds a predetermined level or not.

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 proces10 sor 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 the operation of the ICE 110, the soot produced by the combustion of the fuel and air mixture inside the combustion chamber 150 is discharged with the exhaust gas and progressively accumulated inside the particulate filter 280, thereby lowering the polluting emissions.

When the amount of soot trapped inside the particulate filter 280 exceeds a maximum admissible level, the ECU 450 may activate a so-called regeneration process, which generally causes the oxidization of the retained soot to produce CO2.

The regeneration process may be performed by increasing the amount of oxygen entering the particulate filter 280 and, at the same time, by increasing the temperature of the particulate filter 280 up to a value that triggers the combustion of the trapped soot (e.g. 600°C and above).

The amount of oxygen entering the particulate filter 280 may be increased by running the internal combustion “lean, namely by controlling the fuel injectors 160 so that the air-fuel ratio of the fuel and air mixture in the combustion chambers 150 is larger than the stoichiometric ratio.

On the other hand, the particulate filter temperature may be increased by retarding the spark timing of the spark plugs 360, so that the combustion occurs near or during the exhaust valve opening, with the result that a relevant part of the heat generated by the combustion is transferred from the combustion chambers 150 directly to the exhaust system 270.

In order to properly manage the activation and the deactivation of the regeneration process, the ECU 450 may be configured to monitor the amount of soot which is trapped inside the particulate filter (i.e. the soot load).

Known strategies to monitor the soot load are based on a measurement of the pressure differential across the particulate filter and/or on a mathematical model configured to yield an estimation of the soot load based on several different engine operating parameters.

However, in order to guarantee that these strategies provide accurate results, the ECU 450 should be able to precisely determine when the particulate filter 280 is completely or almost completely clean from soot, for example at the end of any regeneration process11 es.

To perform this task, the ECU 450 may use the oxygen sensors 435 and 465 which are located in the exhaust pipe 275 downstream and upstream of the particulate filter 280. More particularly, the ECU may carry out the detecting method represented in the flow chart of figure 3.

This method firstly provides for the ECU 450 to determine (block S100) a current value T of a temperature of the particulate filter 280.

This temperature value T may be determined by the ECU 450 using a dedicated sensor (not shown) or estimated on the basis of other parameters, for example on the basis of the temperature of the exhaust gas as measured by the exhaust temperature sensors 430.

The method further provides for the ECU 450 to determine (block S105) a current value 01 of the oxygen content in the exhaust gas that flows towards the particulate filter 280, for example by means of the oxygen sensor 465.

The oxygen content may be expressed in term of a volumetric percentage of oxygen in the exhaust gas or in term of any other parameter (for example a lambda parameter) that represents the oxygen content.

At this point, the ECU 450 may be configured to check (block S110) if two preliminary conditions are fulfilled at the same time.

A first preliminary condition is that the temperature value T of the particulate filter 280 is equal to or larger than a predetermined threshold value thereof, typically a minimum value Tmm of the temperature that is able to trigger a soot combustion inside the particulate filter 280.

The minimum value T_m,_n of the particulate filter temperature may be a calibration value which is pre-determined by means of an experimental activity and then stored in the memory system 460 connected to the ECU 450. Generally speaking, the minimum value Tmin of the particulate filter temperature may be of about 550-600°C.

A second preliminary condition is that the oxygen content 01 in the exhaust gas flowing towards the particulate filter 280 is equal to or larger than a predetermined threshold value thereof, typically a minimum value 01 min of the oxygen content that indicates that the internal combustion engine is operating “lean” (i.e. with an air-to-fuel ratio of the fuel and air mixture which is higher than the stoichiometric ratio).

Also the minimum value 01 min of the oxygen content may be a calibration value which is pre-determined by means of an experimental activity and then stored in the memory system 460 connected to the ECU 450.

If both the above-mentioned preliminary conditions are met at the same time, it means that the oxygen level and the temperature inside the particulate filter 280 are high enough to cause the combustion of the trapped soot (if any), thereby performing a regeneration process.

At this point, the detecting method may prescribe for the ECU 450 to determine (block S115) a current value 02 of the oxygen content in the exhaust gas discharged from the particulate filter 280, for example by means of the oxygen sensor 435, and to calculate (block S120) a difference ΔΟ between the first value 01 and the second value 02 of the oxygen content.

The ECU 450 may now check a third conditions (block S125), namely if the calculated difference ΔΟ is equal to or smaller than a predetermined threshold value, typically a maximum value AOmax of such difference that indicates that no soot combustion is occurring inside the particulate filter 280.

In some embodiments, for example where the oxygen sensor 465 is located between the three-way catalyst 285 and the particulate filter 280, the maximum value AOmax may be zero or anyway a small value that indicates that the oxygen content values 01 and 02 are equal or substantially equal.

In other embodiments, for example where the oxygen sensor 465 is located upstream of the three-way catalyst 285, the maximum value AO_max may be a value that takes into account other phenomena which are able to change the oxygen content in the exhaust gas and which may occur in the exhaust pipe 275 between the oxygen sensor 465 and the inlet of the particulate filter 280 (e.g. in the three-way catalyst 285).

In any case, the maximum value AO_max may be a calibration value which is predetermined by means of an experimental activity and then stored in the memory system 460 connected to the ECU 450.

If all the three conditions mentioned above are fulfilled at the same time, then the ECU 450 may be finally configured to identify (block S130) that the particulate filter 280 is clean from soot.

This detecting method can be understood considering that the oxygen content of the ex13 haust gas exiting the particulate filter 280 generally corresponds to the oxygen content of exhaust gas entering the particulate filter 280 minus the oxygen quantity spent for the soot combustion inside the particulate filter 280.

As a consequence, when the conditions for causing the soot combustion are fulfilled (preliminary conditions), the fact that the oxygen content of the exhaust gas discharged from the particulate filter 280 is equal or substantially equal to the oxygen content of the exhaust gas entering the particulate filter 280 (third condition) implies that no soot combustion is actually occurring in the particulate filter 280 and thus that no soot is present inside the particulate filter 280.

In order to improve the robustness of the detecting method and prevent false “clean filter” identifications, the three conditions may be repeatedly checked over time and the ECU 450 may be configured to identify that the particulate filter 280 is clean from soot, only if the three conditions are continuatively fulfilled for longer than a predetermined time period, for example for longer than 5 seconds.

Other embodiments, for example where the oxygen sensor 465 is located upstream of the three-way catalyst 285, may prescribe to start calculating the difference between the oxygen content values O1 an 02 (and thus checking the third condition), once the preliminary conditions (related to the temperature and the oxygen level inside the particulate filter 280) have been fulfilled for longer than a predetermined waiting period, for example for longer than several seconds.

This waiting period may be useful for allowing the three-way catalyst 285 to reach its full oxygen storage capacity, so that the difference between the oxygen content values 01 an 02 is not affected by this phenomenon.

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 automotive system internal combustion engine engine block cylinder cylinder head camshaft piston crankshaft combustion chamber cam phaser fuel injector fuel rail fuel pump fuel source intake manifold air intake duct intake port valves exhaust port exhaust manifold turbocharger compressor turbine intercooler exhaust system exhaust pipe particulate filter

	285	oxidization catalyst
	290	VGT actuator
	300	exhaust gas recirculation system
	310	EGR cooler
5	320	EGR valve
	330	throttle body
	340	mass airflow and temperature sensor
	350	manifold pressure and temperature sensor
	360	spark plug
10	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
15	435	first oxygen sensor
	440	EGR temperature sensor
	445	accelerator pedal position sensor
	450	ECU
	460	memory system
20	465	oxygen sensor
	S100	block
	SI 05	block
	S110	block
	S115	block
25	S120	block
	S125	block
	S130	block

Claims

1. A method of detecting that a particulate filter (280) of an internal combustion engine (100) is clean from soot, comprising:

- determining a value of a temperature of the particulate filter (280),

- determining a first value of an oxygen content in an exhaust gas flowing towards the particulate filter (280),

- determining a second value of the oxygen concentration in the exhaust gas discharged from the particulate filter (280),

- identifying that the particulate filter (280) is clean from soot, if the following conditions are met:

2. A method according to claim 1, wherein the particulate filter (280) is identified to be clean from soot provided that the conditions are fulfilled for longer than a predetermined time period.

3. A method according to any of the preceding claims, wherein the second value of the oxygen content is determined by means of an oxygen sensor (435) located in an exhaust pipe (275) downstream of the particulate filter (280).

4. A method according to any of the preceding claims, wherein the first value of the oxygen content is determined by means of an oxygen sensor (265) located in an exhaust pipe (275) upstream of the particulate filter (280).

5. A method according to claim 4, wherein the oxygen sensor (465) is located be17 tween a catalytic converter (285) and the particulate filter (280).

6. A method according to claim 4, wherein the oxygen sensor (435) is located upstream of a catalytic converter (285).

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

8. A computer program product comprising the computer program according to claim 7.

9. An electromagnetic signal modulated to carry a sequence of data bits which represent a computer program according to claim 7.

10. An internal combustion engine (110) comprising a particulate filter (280) and an electronic control unit (450) configured to:

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

- determine a first value of an oxygen content in an exhaust gas flowing towards the particulate filter (280),

- determine a second value of the oxygen concentration in the exhaust gas discharged from the particulate filter (280),

- identify that the particulate filter (280) is clean from soot, if the following conditions are met:

Intellectual

Property

Office

Application No: GB 1621424.9 Examiner: Mr Peter Middleton