Method of operating an aftertreatment system of an internal combustion engine

1. A method of operating an aftertreatment system of an internal combustion engine having a lean nitrogen-oxides trap and an electric heated catalyst placed upstream of the lean nitrogen-oxide trap, the method comprising:

determining a value of a storage efficiency of the lean nitrogen-oxide trap;

measuring a value of an exhaust gas temperature upstream of the lean nitrogen-oxide trap;

indicating that an electric heated catalyst enabling condition is fulfilled if the determined value of the storage efficiency of the lean nitrogen-oxide trap is smaller than a first predetermined threshold value thereof and the measured value of the exhaust gas temperature upstream of the lean nitrogen-oxide trap is greater than a first predetermined threshold value thereof and less than a second predetermined threshold value thereof;

activating the electric heated catalyst if the electric heated catalyst enabling condition is fulfilled;

identifying that an inhibition enabling condition is fulfilled if the value of storage efficiency is less than a second predetermined threshold value; and

de-activating the electric heated catalyst and starting a denitrification of the lean nitrogen-oxides trap if the inhibition enabling condition is fulfilled.

2. The method according to claim 1 , further comprising:

measuring a value of temperature of an engine coolant;

indicating that the electric heated catalyst enabling condition is fulfilled if the measured value of temperature of the engine coolant is greater than a predetermined threshold value.

3. The method according to claim 2 , further comprising:

determining an actual engine operating point; and

indicating that the inhibition enabling condition is fulfilled if the actual engine operating point is outside from a predetermined inhibition area.

4. The method according to claim 3 , further comprising:

determining the amount of nitrogen-oxides stored in the lean nitrogen-oxides trap; and

stopping the denitrification and activating a time counter to count a lock time when the determined amount of nitrogen-oxides stored in the lean nitrogen-oxides trap gets null.

5. The method according to claim 1 , further comprising:

measuring an amount of energy used by the electric heated catalyst since its last activation; and

indicating the inhibition enabling condition is fulfilled if said measured amount of energy used by the electric heated catalyst is less than a predetermined threshold value.

6. The method according to claim 5 , further comprising:

identifying that the inhibition enabling condition is not fulfilled if said measured amount of energy used by the electric heated catalyst is greater than a predetermined threshold value;

determining the actual engine operating point if said measured amount of energy used by the electric heated catalyst is greater than a predetermined threshold value;

identifying that a tighten inhibition enabling condition is fulfilled if the actual engine operating point is not comprised in a tighten inhibition area and the value of the storage efficiency of the lean nitrogen-oxide trap is less than a predetermined threshold value; and

de-activating the electric heated catalyst and starting a denitrification of the lean nitrogen-oxides trap.

7. The method according to claim 5 , further comprising:

stopping the denitrification of the lean nitrogen-oxides trap; and

activating a time counter to count a lock time if the tighten inhibition enabling condition is not fulfilled.

8. A non-transitory computer readable medium comprising program code, when run on a computer, is configured to perform the method according to claim 1 .

9. An aftertreatment system comprising:

a lean nitrogen oxides trap;

an electric heated catalyst placed upstream of the lean nitrogen-oxide trap;

a temperature sensor configured to measure a value of the exhaust gas temperature upstream of the lean nitrogen oxides trap; and

an electronic control unit configured to:

determine a value of a storage efficiency of the lean nitrogen-oxide trap;

measure a value of an exhaust gas temperature upstream of the lean nitrogen-oxide trap;

indicate that an electric heated catalyst enabling condition is fulfilled if the determined value of the storage efficiency of the lean nitrogen-oxide trap is smaller than a first predetermined threshold value thereof and the measured value of the exhaust gas temperature upstream of the lean nitrogen-oxide trap is greater than a first predetermined threshold value thereof and less than a second predetermined threshold value thereof;

activate the electric heated catalyst if the electric heated catalyst enabling condition is fulfilled;

identify that an inhibition enabling condition is fulfilled if the value of storage efficiency is less than a second predetermined threshold value; and

de-activate the electric heated catalyst and starting a denitrification of the lean nitrogen-oxides trap if the inhibition enabling condition is fulfilled.

10. The aftertreatment system of claim 9 , wherein the electronic control unit is further configured to:

measure a value of temperature of an engine coolant;

indicate that the electric heated catalyst enabling condition is fulfilled if the measured value of temperature of the engine coolant is greater than a predetermined threshold value.

11. The aftertreatment system of claim 10 , wherein the electronic control unit is further configured to:

determine an actual engine operating point; and

indicate that the inhibition enabling condition is fulfilled if the actual engine operating point is outside from a predetermined inhibition area.

12. The aftertreatment system of claim 11 , wherein the electronic control unit is further configured to:

determine the amount of nitrogen-oxides stored in the lean nitrogen-oxides trap; and

stop the denitrification and activating a time counter to count a lock time when the determined amount of nitrogen-oxides stored in the lean nitrogen-oxides trap gets null.

13. The aftertreatment system of claim 9 , wherein the electronic control unit is further configured to:

measure an amount of energy used by the electric heated catalyst since its last activation; and

indicate the inhibition enabling condition is fulfilled if said measured amount of energy used by the electric heated catalyst is less than a predetermined threshold value.

14. The aftertreatment system of claim 13 , wherein the electronic control unit is further configured to:

identify that the inhibition enabling condition is not fulfilled if said measured amount of energy used by the electric heated catalyst is greater than a predetermined threshold value;

determine the actual engine operating point if said measured amount of energy used by the electric heated catalyst is greater than a predetermined threshold value;

identify that a tighten inhibition enabling condition is fulfilled if the actual engine operating point is not comprised in a tighten inhibition area and the value of the storage efficiency of the lean nitrogen-oxide trap is less than a predetermined threshold value; and

de-activate the electric heated catalyst and starting a denitrification of the lean nitrogen-oxides trap.

15. The aftertreatment system of claim 13 , wherein the electronic control unit is further configured to:

stop the denitrification of the lean nitrogen-oxides trap; and

activate a time counter to count a lock time if the tighten inhibition enabling condition is not fulfilled.