Method for determining a corrected nitrogen oxide value and ammonia value in an internal combustion engine
A method for acquiring a corrected nitrogen oxide and/or corrected ammonia value in an internal combustion engine by determining that the engine is in an overrun cut-off phase, interrupting an injection of urea, acquiring a nitrogen oxide reference value from a nitrogen oxide reference signal generated by a nitrogen oxide sensor and acquiring an ammonia reference value from an ammonia reference signal generated by an ammonia sensor, and acquiring a corrected nitrogen oxide value from a nitrogen oxide signal generated by the nitrogen oxide sensor during normal operation of the engine, taking into account the nitrogen oxide reference value, and acquiring a corrected ammonia value from an ammonia signal generated by the ammonia sensor during normal operation of the engine, taking into account the ammonia reference value.
1. A method for acquiring a corrected nitrogen oxide value in an internal combustion engine which has an SCR catalytic converter, a nitrogen oxide sensor arranged downstream of the SCR catalytic converter, and a urea injection device arranged upstream of the SCR catalytic converter, comprising:
determining that the internal combustion engine is in an overrun cut-off phase;
interrupting an injection of urea by the urea injection device during the overrun cut-off phase;
acquiring a nitrogen oxide reference value from a nitrogen oxide reference signal generated by the nitrogen oxide sensor during the overrun cut-off phase; and
acquiring a corrected nitrogen oxide value from a nitrogen oxide signal generated by the nitrogen oxide sensor during normal operation of the internal combustion engine, based at least in part on the nitrogen oxide reference value,
wherein at least one of:
the acquisition of a nitrogen oxide reference value or an acquisition of an ammonia reference value does not take place until a corrected ammonia value absolute change gradient of the reference signal of the nitrogen oxide sensor is lower than a predetermined change threshold value of nitrogen oxide or if an absolute change gradient of a reference signal of an ammonia sensor is less than a predetermined ammonia change threshold value and
the acquisition of the nitrogen oxide reference value or an acquisition of an ammonia reference value does not take place until an absolute change gradient of the reference signal of the nitrogen oxide sensor is lower than a predetermined change threshold value of nitrogen oxide or if an absolute change gradient of a reference signal of an ammonia sensor is less than a predetermined ammonia change threshold value.
2. The method as claimed in claim 1 , wherein the acquisition of the nitrogen oxide reference value or the acquisition of the ammonia reference value does not take place until a nitrogen oxide value is lower than a predetermined nitrogen oxide threshold value and/or an ammonia value is lower than a predetermined ammonia threshold value.
3. The method as claimed in claim 1 , further comprising:
acquiring a difference in ammonia between an ammonia value acquired from an ammonia signal generated by an ammonia sensor during a normal operation of the internal combustion engine, and a further ammonia value acquired from the nitrogen oxide signal generated by the nitrogen oxide sensor during the normal operation of the internal combustion engine,
executing, during a subsequent overrun cut-off phase if the difference in ammonia acquired during the normal operation of the internal combustion engine is higher than a predetermined ammonia difference threshold value:
activating the urea injection device to inject a predetermined quantity of urea during a predetermined time period;
acquiring at least one first ammonia value from ammonia signals generated by the ammonia sensor;
determining that a change gradient of the at least one first ammonia value is less than a predetermined first change threshold value,
acquiring at least one second ammonia value from signals generated by the nitrogen oxide sensor;
determining that a change gradient of the at least one second ammonia value is less than a predetermined second change threshold value; and
adapting a slope of a characteristic curve of the ammonia sensor based at least in part on the second ammonia values if the change gradient of the at least one first or second ammonia value is lower than the predetermined first or second change threshold value.
4. The method as claimed in claim 1 , wherein the nitrogen oxide reference value is acquired as follows:
NO X Ref,neu =NO X Ref,alt −K 1 (T t1-t2 )·NO X
where:
NO X Ref,neu nitrogen oxide reference value for a correction,
NO X Ref,alt nitrogen oxide reference value of a preceding correction,
K 1 (T t1-t2 ) weighting factor between 0 and 1 depending on an operating time of the internal combustion engine between two corrections, and
NO X currently acquired nitrogen oxide value (acquired during the overrun cut-off phase of the internal combustion engine, from a nitrogen oxide signal generated by the nitrogen oxide sensor;
and/or wherein a new ammonia reference value is determined as follows:
NH 3 Ref,neu =NH 3 Ref,alt −K 2 (T t1-t2 )·NH 3
where:
NH 3 Ref,neu ammonia reference value for a correction,
NH 3 Ref,alt ammonia reference value of a preceding correction,
K 2 (T t1-t2 ) weighting factor between 0 and 1 depending on an operating time of the internal combustion engine between two corrections, and
NH 3 currently acquired ammonia value (acquired during the overrun cut-off phase of the internal combustion engine, from an ammonia signal generated by an ammonia sensor.
5. The method as claimed in claim 1 , wherein the internal combustion engine has a further nitrogen oxide sensor arranged upstream of the SCR catalytic converter, wherein the method further comprises:
acquiring a further nitrogen oxide value from a nitrogen oxide reference signal generated by the further nitrogen oxide sensor during the overrun cut-off phase; and
acquiring a corrected further nitrogen oxide value from a nitrogen oxide signal generated by the further nitrogen oxide sensor during normal operation of the internal combustion engine, based at least in part on the nitrogen oxide reference value.
6. The method as claimed in claim 1 , wherein the corrected nitrogen oxide value which is acquired from a nitrogen oxide signal generated by the nitrogen oxide sensor is corrected as follows with an ammonia value which from an ammonia signal generated by an ammonia sensor:
NO X netto =NO X −NH 3
where:
NO X netto nitrogen oxide value which has been corrected and cleaned of ammonia,
NO X nitrogen oxide value which has been acquired from a nitrogen oxide signal generated by the nitrogen oxide sensor, and
NH 3 ammonia value which has been acquired from an ammonia signal generated by an ammonia sensor.
7. A method for acquiring a corrected ammonia value in an internal combustion engine which has an SCR catalytic converter, a urea injection device arranged upstream of the SCR catalytic converter, and an ammonia sensor arranged downstream of the SCR catalytic converter, comprising:
determining that the internal combustion engine is in an overrun cut-off phase;
interrupting an injection of urea by the urea injection device during the overrun cut-off phase;
acquiring an ammonia reference value from an ammonia reference signal generated by the ammonia sensor during the overrun cut-off phase; and
acquiring a corrected ammonia value from an ammonia signal generated by the ammonia sensor during normal operation of the internal combustion engine, based at least in part on the ammonia reference value,
wherein an acquisition of a nitrogen oxide reference value or the acquisition of the ammonia reference value does not take place until a corrected ammonia value absolute change gradient of a reference signal of a nitrogen oxide sensor is lower than a predetermined change threshold value of nitrogen oxide or if an absolute change gradient of the reference signal of the ammonia sensor is less than a predetermined ammonia change threshold value.
8. The method as claimed in claim 7 , wherein the acquisition of the nitrogen oxide reference value or the acquisition of the ammonia reference value does not take place until a nitrogen oxide value is lower than a predetermined nitrogen oxide threshold value and/or the ammonia value is lower than a predetermined ammonia threshold value.
9. The method as claimed in claim 7 , further comprising:
acquiring a difference in ammonia between an ammonia value acquired from the ammonia signal generated by the ammonia sensor during a normal operation of the internal combustion engine, and a further ammonia value acquired from the nitrogen oxide signal generated by a nitrogen oxide sensor during the normal operation of the internal combustion engine,
executing, during a subsequent overrun cut-off phase if a difference in ammonia acquired during the normal operation of the internal combustion engine is higher than a predetermined ammonia difference threshold value:
activating the urea injection device to inject a predetermined quantity of urea during a predetermined time period;
acquiring at least one first ammonia value from ammonia signals generated by the ammonia sensor;
determining that a change gradient of the at least one first ammonia value is less than a predetermined first change threshold value;
acquiring at least one second ammonia value from signals generated by a nitrogen oxide sensor;
determining that a change gradient of the at least one second ammonia value is less than a predetermined second change threshold value; and
adapting a slope of a characteristic curve of the ammonia sensor by the second ammonia values if the change gradient of the at least one first or second ammonia value is lower than the predetermined first or second change threshold value.
10. The method as claimed in claim 7 , wherein a nitrogen oxide reference value is acquired as follows:
NO X Ref,neu =NO X Ref,alt −K 1 (T t1-t2 )·NO X
where:
NO X Ref,neu nitrogen oxide reference value for a correction,
NO X Ref,alt nitrogen oxide reference value of a preceding correction,
K 1 (T t1-t2 ) weighting factor between 0 and 1 depending on an operating time of the internal combustion engine between two corrections, and
NO X currently acquired nitrogen oxide value (acquired during the overrun cut-off phase of the internal combustion engine, from a nitrogen oxide signal generated by a nitrogen oxide sensor;
and/or wherein the new ammonia reference value is determined as follows:
NH 3 Ref,neu =NH 3 Ref,alt −K 2 (T t1-t2 )·NH 3
where:
NH 3 Ref,neu ammonia reference value for a correction,
NH 3 Ref,alt ammonia reference value of a preceding correction,
K 2 (T t1-t2 ) weighting factor between 0 and 1 depending on an operating time of the internal combustion engine between two corrections, and
NH 3 currently acquired ammonia value (acquired during the overrun cut-off phase of the internal combustion engine, from an ammonia signal generated by the ammonia sensor.
11. The method as claimed in claim 7 , wherein the internal combustion engine has a nitrogen oxide sensor arranged upstream of the SCR catalytic converter, wherein the method further comprises:
acquiring a further nitrogen oxide value from a nitrogen oxide reference signal generated by the nitrogen oxide sensor during the overrun cut-off phase, and
acquiring a corrected further nitrogen oxide value from a nitrogen oxide signal generated by the nitrogen oxide sensor during normal operation of the internal combustion engine, based at least in part on the nitrogen oxide reference value.
12. The method as claimed in claim 7 , wherein a corrected nitrogen oxide value which is acquired from a nitrogen oxide signal generated by a nitrogen oxide sensor is corrected as follows with the ammonia value which from the ammonia signal generated by the ammonia sensor:
NO X netto =NO X −NH 3
where:
NO X netto nitrogen oxide value which has been corrected and cleaned of ammonia,
NO X nitrogen oxide value which has been acquired from a nitrogen oxide signal generated by the nitrogen oxide sensor, and
NH 3 ammonia value which has been acquired from an ammonia signal generated by the ammonia sensor.
13. An exhaust section for an internal combustion engine, having:
an SCR catalytic converter;
a nitrogen oxide sensor arranged downstream of the SCR catalytic converter and configured to generate a nitrogen oxide signal that indicates a nitrogen oxide value downstream of the SCR catalytic converter;
a urea injection device arranged upstream of the SCR catalytic converter and configured to inject a predetermined quantity of urea;
an ammonia sensor arranged downstream of the SCR catalytic converter and configured to generate an ammonia signal that indicates an ammonia value downstream of the SCR catalytic converter; and
a control unit configured to receive the nitrogen oxide signal and the ammonia signal and execute a method comprising:
determine that the internal combustion engine is in an overrun cut-off phase;
interrupt an injection of urea by the urea injection device during the overrun cut-off phase; and
at least one of:
acquire a nitrogen oxide reference value from a nitrogen oxide reference signal generated by the nitrogen oxide sensor during the overrun cut-off phase and acquire a corrected nitrogen oxide value from a nitrogen oxide signal generated by the nitrogen oxide sensor during normal operation of the internal combustion engine, based at least in part on the nitrogen oxide reference value; and
acquire an ammonia reference value from an ammonia reference signal generated by the ammonia sensor during the overrun cut-off phase and acquire a corrected ammonia value from an ammonia signal generated by the ammonia sensor during normal operation of the internal combustion engine, based at least in part on the ammonia reference value,
wherein the acquisition of the nitrogen oxide reference value or the acquisition of the ammonia reference value does not take place until a corrected ammonia value absolute change gradient of the reference signal of the nitrogen oxide sensor is lower than a predetermined change threshold value of nitrogen oxide or if an absolute change gradient of the reference signal of the ammonia sensor is less than a predetermined ammonia change threshold value.
14. The exhaust section as claimed in claim 13 , further comprising:
a further nitrogen oxide sensor arranged upstream of the SCR catalytic converter and configured to generate a further nitrogen oxide signal that indicates the quantity of nitrogen oxide upstream of the SCR catalytic converter.