Method of estimating a variation of a quantity of soot accumulated in a diesel particulate filter

1. A method of estimating a variation of a quantity of soot accumulated in a diesel particulate filter for initiating active regeneration of the diesel particulate filter coupled to an internal combustion engine having an engine control unit, wherein the method comprises:

a passive-regeneration check for checking whether a passive regeneration of the diesel particulate filter is occurring and, when the passive-regeneration check yields that a passive regeneration is actually occurring, the method further comprises the steps of:

storing an initial quantity of soot accumulated in the diesel particulate filter when the passive regeneration began in a memory system;

determining a rough variation of the quantity of soot accumulated in the diesel particulate filter;

determining an engine speed and an engine load of the internal combustion engine;

determining a correction factor to account for passive regeneration using the engine speed, the engine load and the initial quantity of soot, and

calculating with the engine control unit, a variation of the quantity of soot accumulated in the diesel particulate filter as a function of the rough variation and the correction factor;

wherein the variation of the quantity of soot accumulated in the diesel particulate filter is used to compute a current quantity of accumulated soot in the diesel particulate filter for triggering an active regeneration thereof when the current quantity of accumulated soot exceeds a predetermined threshold value.

2. A method according to claim 1 , wherein determining the correction factor comprises:

determining a first correction factor using the engine speed and the engine load;

determining a second correction factor using the initial quantity of soot; and

calculating the correction factor as a function of the first and the second correction factor.

3. A method according to claim 2 , further comprising determining the first correction factor by retrieving, from a first calibration map stored in the memory system, the first correction factor corresponding to the engine speed and the engine load.

4. A method according to claim 3 , further comprising determining the second correction factor by retrieving, from a second calibration map stored in the memory system, the second correction factor corresponding to the initial quantity of soot.

5. A method according to claim 4 , wherein determining the second correction factor is performed by:

calculating a difference between the initial quantity of soot and a predetermined reference value, and

retrieving, from the second calibration map the second correction factor corresponding to this difference.

6. A method according to claim 1 , wherein the passive-regeneration check comprises the steps of:

determining a content of nitrogen oxides in the exhaust gasses at the inlet of the diesel particulate filter;

determining a temperature of the exhaust gasses at the inlet of the diesel particulate filter;

determining a current soot loading level in the diesel particulate filter; and

wherein the regeneration status indicates passive regeneration when following conditions are met:

the content of nitrogen oxides in the exhaust gasses exceeds a predetermined NOX threshold value;

the temperature of the exhaust gasses is within a predetermined temperature range; and

the current soot loading level exceeds a predetermined threshold value.

7. A method according to claim 6 , wherein the predetermined threshold value is determined using parameters comprising the engine speed and the engine load.

8. A method according to claim 7 , wherein the predetermined threshold value is determined using parameters further comprising the initial quantity of soot.

9. A method according to claim 8 , wherein the predetermined threshold value is determined by:

determining a rough threshold value using the engine speed and the engine load;

determining a threshold-value correction using the initial quantity of soot; and

multiplying the rough threshold value by the threshold-value correction.

10. A method according to claim 9 , further comprising determining the rough threshold value by retrieving, from a third calibration map stored in the memory, the rough threshold value corresponding to the engine speed and the engine load.

11. A method according to claim 10 , further comprising determining the threshold-value correction, by retrieving, from a fourth calibration map stored in the memory, the rough threshold value corresponding to the initial quantity of soot.

12. A non-transitory computer readable medium embodying a computer program product, the computer program product comprising:

a computer program, the computer program configured to estimate a variation of a quantity of soot accumulated in a diesel particulate filter for initiating active regeneration of the diesel particulate filter coupled to an internal combustion engine, wherein the computer program comprises a passive-regeneration check for checking whether a passive regeneration of the diesel particulate filter is occurring and, if the passive-regeneration check yields that a passive regeneration is actually occurring, the computer program is configured to:

store an initial quantity of soot accumulated in the diesel particulate filter when the passive regeneration began in a memory system;

determine a rough variation of the quantity of soot accumulated in the diesel particulate filter;

determine an engine speed and an engine load of the internal combustion engine;

determine a correction factor to account for passive regeneration using the engine speed, the engine load and the initial quantity of soot, and

calculate a variation of the quantity of soot accumulated in the diesel particulate filter as a function of the rough variation and the correction factor

wherein the variation of the quantity of soot accumulated in the diesel particulate filter is used to compute a current quantity of accumulated soot in the diesel particulate filter for triggering an active regeneration thereof when the current quantity of accumulated soot exceeds a predetermined threshold value.

13. The non-transitory computer readable medium according to claim 12 , wherein to determine the correction factor the computer program is configured to:

determine a first correction factor using the engine speed and the engine load;

determine a second correction factor using the initial quantity of soot; and

calculate the correction factor as a function of the first and the second correction factor.

14. The non-transitory computer readable medium according to claim 13 , wherein the computer program is configured to determine the first correction factor by retrieving, from a first calibration map from the memory system, the first correction factor corresponding to the engine speed and the engine load.

15. The non-transitory computer readable medium according to claim 14 , wherein the computer program is configured to determine the second correction factor by retrieving, from a second calibration map stored in the memory system, the second correction factor corresponding to the initial quantity of soot.

16. The non-transitory computer readable medium according to claim 15 , wherein the computer program is configured to determine the second correction factor by:

calculating a difference between the initial quantity of soot and a predetermined reference value, and

retrieving, from the second calibration map, the second correction factor corresponding to this difference.

17. The non-transitory computer readable medium according to claim 12 , wherein the computer program is configured to check a regeneration status by:

determining a content of nitrogen oxides in the exhaust gasses at the inlet of the diesel particulate filter;

determining a temperature of the exhaust gasses at the inlet of the diesel particulate filter;

determining a current soot loading level in the diesel particulate filter; and

wherein the regenerations status indicates passive regeneration when the following conditions are met:

the content of nitrogen oxides in the exhaust gasses exceeds a predetermined NOX threshold value;

the temperature of the exhaust gasses is within a predetermined temperature range; and

the current soot loading level exceeds a predetermined threshold value.

18. The non-transitory computer readable medium according to claim 17 , wherein the computer program is configured to determine the predetermined threshold value using parameters comprising the engine speed and the engine load.

19. The non-transitory computer readable medium according to claim 18 , wherein the computer program is configured to determine the predetermined regeneration value using parameters further comprising the initial quantity of soot.

20. The non-transitory computer readable medium according to claim 12 , wherein the computer program is configured to determine the predetermined threshold value by:

determining a rough threshold value using the engine speed and the engine load;

determining a threshold-value correction using the initial quantity of soot; and

multiplying the rough threshold value by the threshold-value correction.

21. The non-transitory computer readable medium according to claim 20 , wherein the computer program is configured to determine the rough threshold value by retrieving, from a third calibration map stored in the memory, the rough threshold value corresponding to the engine speed and the engine load.

22. The non-transitory computer readable medium according to claim 21 , wherein the computer program is configured to determine the threshold-value correction, by retrieving, from a fourth calibration map stored in the memory, the rough threshold value corresponding to the initial quantity of soot.