Method for operating an electrically heatable catalyst
A method for operating an electrically heatable catalytic converter in an exhaust tract of an internal combustion engine having at least one honeycomb body through which an exhaust-gas stream can flow, and having at least one electrically heatable heating conductor positioned upstream of the honeycomb body in a throughflow direction of the exhaust gas includes: applying an electrical current to the heating conductor such that the heating conductor is electrically heated in a manner dependent on an ambient temperature around the heating conductor; and electrically heating the heating conductor such that a dwell time of a temperature of the heating conductor is bounded in a temperature range defined by a first lower limit temperature T G1U and an upper limit temperature T G1O .
1. A method for operating an electrically heatable catalytic converter in an exhaust tract of an internal combustion engine having at least one honeycomb body through which an exhaust-gas stream can flow, and having at least one electrically heatable heating conductor positioned upstream of the honeycomb body in a throughflow direction of the exhaust gas, the method comprising:
applying an electrical current to the heating conductor such that the heating conductor is electrically heated in a manner dependent on an ambient temperature around the heating conductor; and
electrically heating the heating conductor such that a dwell time of a temperature of the heating conductor is bounded in a temperature range defined by a first lower limit temperature T G1U and an upper limit temperature T G1O ,
wherein a temperature transient of the temperature of the heating conductor when passing through the defined temperature range from a higher temperature to a lower temperature does not undershoot a predefined limit value.
2. The method as claimed in claim 1 , wherein the temperature of the heating conductor is, by the electric heating, kept above the upper limit temperature T G1O if the ambient temperature around the heating conductor lies below the upper limit temperature T G1O but lies above a second lower limit temperature T G2U .
3. The method as claimed in claim 2 , wherein the electric heating of the heating conductor is ended if the ambient temperature of the heating conductor has undershot the second lower limit temperature T G2U .
4. The method as claimed in claim 3 , wherein the second lower limit temperature T G2U is lower than the first lower limit temperature T G1U .
5. The method as claimed in claim 2 , further comprising maintaining, by the electric heating, the heating conductor above the upper limit temperature T G1O for a predefinable duration.
6. The method as claimed in claim 5 , further comprising ending the electric heating if the ambient temperature around the heating conductor is below the second lower limit temperature T G2U for a predefined time.
7. The method as claimed in claim 1 , further comprising ending the electric heating of the heating conductor if a temperature difference between surroundings of the heating conductor and a present temperature of the heating conductor exceeds a predefinable value.
8. The method as claimed in claim 2 , further comprising outputting, by a prediction element, a statement regarding a predicted change in the ambient temperature around the heating conductor, and performing the electric heating of the heating conductor in a manner dependent on the predicted change of the ambient temperature around the heating conductor.
9. The method as claimed in claim 8 , further comprising, ending the electric heating of the heating conductor in the event the ambient temperature around the heating conductor is predicted to remain below the second lower limit temperature T G2U .
10. The method as claimed in claim 1 , further comprising defining, by the first lower limit temperature T G1U and the upper limit temperature T G1O , a temperature range in which, due to action of heat, material of the heating conductor undergoes a conversion of material structure that leads to a change in the specific resistance of the heating conductor.