Method and apparatus for effecting light-off of a catalytic converter in a hybrid powertrain system

1. Method for operating a powertrain system including a hybrid transmission and an internal combustion engine coupled to an exhaust aftertreatment device, comprising:

operating the hybrid transmission to generate tractive torque responsive to an operator torque request with the internal combustion engine in an engine-off state so long as the tractive torque is less than a threshold;

operating the internal combustion engine in an engine-on state at preferred operating conditions to effect light-off of the exhaust aftertreatment device and coincidentally operating the hybrid transmission to generate tractive torque responsive to the operator torque request when the operator torque request exceeds the threshold; and then

operating the internal combustion engine in the engine-on state to generate tractive torque responsive to the operator torque request.

2. The method of claim 1 , wherein the internal combustion engine is operated in the engine-on state at preferred operating conditions to effect light-off of the exhaust aftertreatment device for a predetermined duration sufficient to effect light-off of the exhaust aftertreatment device.

3. The method of claim 1 , wherein said preferred operating conditions comprise a preferred engine operating point.

4. The method of claim 1 , wherein said preferred operating conditions comprise a preferred engine operating point and a preferred combustion timing.

5. The method of claim 4 , wherein the internal combustion engine is operated in the engine-on state at preferred operating conditions to effect light-off of the exhaust aftertreatment device for a predetermined duration sufficient to effect light-off of the exhaust aftertreatment device.

6. The method of claim 1 , wherein operating the hybrid transmission to generate tractive torque comprises operating the hybrid transmission in a first mode, the method further comprising:

when the tractive torque exceeds the threshold prior to operating the internal combustion engine in the engine-on state at preferred operating conditions to effect light-off of the exhaust aftertreatment device, operating the hybrid transmission in a second mode to generate tractive torque responsive to the operator torque request with the internal combustion engine in a fuel cutoff state.

7. The method of claim 1 , further comprising coincidentally operating the hybrid transmission in one of a first and a second mode when operating the internal combustion engine in the engine-on state to generate tractive torque responsive to the operator torque request.

8. The method of claim 1 , wherein the threshold corresponds to a predetermined limit on hybrid transmission generated tractive torque with the internal combustion engine in the engine-off state.

9. Method for operating a hybrid powertrain system including an internal combustion engine and a plurality of torque machines configured to transfer torque to a transmission, the transmission coupled to a driveline, the method comprising:

operating the internal combustion engine in an engine-on state at preferred operating conditions to effect light-off of an exhaust aftertreatment device and coincidentally operating the torque machines to generate tractive torque responsive to an operator torque request when the operator torque request exceeds a predetermined limit on torque machine generated tractive torque with the internal combustion engine in an engine-off state; and

subsequent to effecting light-off of the exhaust aftertreatment device, operating the internal combustion engine in the engine-on state to generate tractive torque responsive to the operator torque request.

10. The method of claim 9 , further comprising operating the torque machines to generate tractive torque responsive to the operator torque request with the internal combustion engine in the engine-off state so long as the tractive torque is less than said predetermined limit.

11. The method of claim 9 , wherein the internal combustion engine is operated in the engine-on state at preferred operating conditions to effect light-off of the exhaust aftertreatment device for a predetermined duration sufficient to effect light-off of the exhaust aftertreatment device.

12. The method of claim 9 , wherein said preferred operating conditions comprise a preferred engine operating point.

13. The method of claim 9 , wherein said preferred operating conditions comprise a preferred engine operating point and a preferred combustion timing.

14. The method of claim 13 , wherein the internal combustion engine is operated in the engine-on state at preferred operating conditions to effect light-off of the exhaust aftertreatment device for a predetermined duration sufficient to effect light-off of the exhaust aftertreatment device.

15. The method of claim 9 , wherein operating the hybrid transmission to generate tractive torque comprises operating the hybrid transmission in a first mode, the method further comprising:

when the tractive torque exceeds the threshold prior to operating the internal combustion engine in the engine-on state at preferred operating conditions to effect light-off of the exhaust aftertreatment device, operating the hybrid transmission in a second mode to generate tractive torque responsive to the operator torque request with the internal combustion engine in a fuel cutoff state.

16. The method of claim 9 , further comprising coincidentally operating the hybrid transmission in one of a first and a second mode when operating the internal combustion engine in the engine-on state to generate tractive torque responsive to the operator torque request.