Hybrid HC absorber/EHC PZEV exhaust architecture
View Patent ↗A system may include a hydrocarbon (HC) absorber positioned in an exhaust flow path and an electrically heated catalyst (EHC) positioned in the exhaust flow path downstream of the HC absorber.
1. A method, comprising:
operating a combustion engine in a hybrid vehicle at an air-fuel ratio that is less than a stoichiometric air-fuel ratio during a first time period and at a generally stoichiometric air-fuel ratio during a second time period after the first time period, the hybrid vehicle including the combustion engine, an electric motor, and a battery that powers the electric motor;
trapping hydrocarbons (HC) from an exhaust gas from the combustion engine during the first time period in a HC absorber that is in communication with the exhaust gas and upstream of an electrically heated catalyst (EHC) that is in communication with the exhaust gas;
energizing the EHC with the battery during the first time period; and
oxidizing HC from the exhaust gas within the EHC during the second time period.
2. The method of claim 1 further comprising rotating a crankshaft of the combustion engine using the electric motor when the combustion engine is not in an operating state during a vehicle cold start condition and before operating the combustion engine during the first time period.
3. The method of claim 1 wherein said trapping includes operating the HC absorber at a temperature less than 100 degrees Celsius.
4. The method of claim 1 wherein said energizing occurs simultaneously with or before said operating.
5. The method of claim 1 further comprising determining if the engine is operating at a cold start condition.
6. The method of claim 5 wherein operation of the combustion engine during the first time period corresponds to a cold start condition.
7. The method of claim 1 wherein said oxidizing includes operating the EHC at a temperature greater than 400 degrees Celsius.
8. The method of claim 7 wherein the EHC reaches a temperature of 400 degrees Celsius before the HC absorber reaches a temperature of 100 degrees Celsius.
9. The method of claim 1 further comprising releasing the trapped HC from the HC absorber to the exhaust gas during the second time period.
10. The method of claim 9 wherein said releasing occurs during or after said oxidizing.