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A computer-implemented method for detecting and reducing the amount of urea crystals in an exhaust aftertreatment system including at least one NOx sensor upstream of a urea injector is provided, The method includes: acquiring measurement values from the NOx-sensor; determining lambda values associated with the measurement values, wherein a lambda value being indicative of a ratio between an amount of air and an amount of fuel in a combustion chamber of an engine connected to the exhaust aftertreatment system; determining at least one ratio between the measurement values and the inverse of the determined lambda values, when the ratio between the measurement values and an inverse of the determined lambda values is equal to or exceeds a threshold, using a NOx engine emissions model for urea dosing control in the exhaust aftertreatment system.

Titel:	UREA CRYSTAL DETECTION BY MONITORING A RATIO BETWEEN A NOx SENSOR SIGNAL AND A EQUIVALENCE RATIO
Link:	Zum Volltext
Veröffentlichung:	2024
Medientyp:	Patent
Sonstiges:	Nachgewiesen in: USPTO Patent Applications Sprachen: English Document Number: 20240003284 Publication Date: January 4, 2024 Appl. No: 18/341878 Application Filed: June 27, 2023 Assignees: VOLVO TRUCK CORPORATION (Göteborg, SE) Claim: 1. A computer-implemented method for detecting and reducing the amount of urea crystals in an exhaust aftertreatment system comprising at least one NOx sensor upstream of a urea injector, the method comprises: acquiring measurement values from the NOx-sensor; determining lambda values associated with the measurement values, wherein a lambda value being indicative of a ratio between an amount of air and an amount of fuel in a combustion chamber of an engine connected to the exhaust aftertreatment system; determining at least one ratio between the measurement values and an inverse of the determined lambda values, and, when the ratio between the measurement values and the inverse of the determined lambda values is equal to or exceeds a threshold, using a NOx engine emissions model for urea dosing control in the exhaust aftertreatment system. Claim: 2. The method according to claim 1, comprising: if one of the determined ratios is below the threshold, using a measurement value from the NOx sensor for urea dosing control in the exhaust aftertreatment system. Claim: 3. The method according to claim 1, comprising: if one of the determined ratios is equal to or exceeds the threshold, switching from using the NOx sensor for urea dosing control in the exhaust aftertreatment system to using the NOx engine emissions model for urea dosing control in the exhaust aftertreatment system. Claim: 4. The method according to claim 1, comprising: if one of the determined ratios is below the threshold, switching from using the NOx engine emissions model for urea dosing control in the exhaust aftertreatment system to using the NOx sensor for urea dosing control in the exhaust aftertreatment system. Claim: 5. The method according to claim 1, further comprising: if one of the determined ratios is equal to or exceeds a second threshold, calculating an integral of the determined ratios over the period of time, wherein, if the integral is equal to or exceeds a predetermined level, increasing the temperature of exhaust gas to sublime urea crystals in the exhaust aftertreatment system. Claim: 6. The method according to claim 1, wherein the method steps are continuously repeated for the time period after a cold start. Claim: 7. The method according to claim 1, wherein the acquired measurement values from the NOx-sensor are indicative of NH3 molecules released by the urea crystals and NOx levels in the exhaust gas. Claim: 8. The method according to claim 1, wherein the threshold is set by an on-board diagnostics model. Claim: 9. The method according to claim 1, wherein the NOx sensor is arranged upstream of a catalytic conversion unit of the exhaust aftertreatment system. Claim: 10. The method according to claim 1, wherein the measurements are continuously acquired, and ratios are continuously determined while the method is operative, wherein, once a ratio is equal to or exceeds the threshold, using a NOx engine emissions model for urea dosing control in the exhaust aftertreatment system, and once a ratio is determined to be below the threshold, using a measurement from the NOx sensor for urea dosing control in the exhaust aftertreatment system. Claim: 11. An exhaust aftertreatment system of a vehicle, comprising: at least one NOx sensor upstream of a urea injector; and a control unit configured to: acquire measurement values from the NOx-sensor; determine lambda values associated with the measurement values, wherein a lambda value being indicative of a ratio between an amount of air and an amount of fuel in a combustion chamber of an engine connected to the exhaust aftertreatment system; determine at least one ratio between the measurement values and the inverse of the determined lambda values, if one of the determined ratios between the measurement values and the inverse of the determined lambda values is equal to or exceeds a threshold, use a NOx engine emissions model for urea dosing control in the exhaust aftertreatment system. Claim: 12. A vehicle comprising an exhaust aftertreatment system according to claim 11. Claim: 13. A computer program comprising program code for performing the steps of claim 1 when said program is run on a computer. Claim: 14. A non-transitory computer readable medium carrying a computer program comprising program code for performing the steps of claim 1 when said program code is run on a computer. Claim: 15. A control unit, the control unit being configured to perform the steps of the method according to claim 1. Current International Class: 01; 01

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UREA CRYSTAL DETECTION BY MONITORING A RATIO BETWEEN A NOx SENSOR SIGNAL AND A EQUIVALENCE RATIO