Method and apparatus for controlling hybrid powertrain system in response to engine temperature

1. Method for controlling a hybrid powertrain system including an internal combustion engine and a non-combustion torque machine, the method comprising controlling operation of the hybrid powertrain system including controlling the internal combustion engine to generate heat to cause the engine coolant temperature to follow a preferred minimum coolant temperature trajectory, wherein the preferred minimum coolant temperature trajectory comprises a vehicle runtime-based trajectory for a minimum coolant temperature during a warm-up period of engine operation and a stabilized period of operation that is selected from one of a plurality of predetermined trajectories in relation to outside air temperature and a vehicle soak time.

2. The method of claim 1 , wherein controlling operation of the hybrid powertrain system comprises executing closed-loop control of the hybrid powertrain system to determine torque commands for the internal combustion engine and the non-combustion torque machine to generate an output torque from the hybrid powertrain system responsive to an operator torque request.

3. The method of claim 2 , wherein executing closed-loop control of the hybrid powertrain system comprises:

adjusting a base engine heat rejection response surface for the engine with a scalar multiplier determined in relation to a difference between the preferred minimum coolant temperature trajectory for the internal combustion engine and the coolant temperature; and

controlling operation of the engine responsive to said adjusted base engine heat rejection response surface to generate heat to cause the coolant temperature to follow the preferred minimum coolant temperature trajectory.

4. The method of claim 3 , wherein the preferred minimum coolant temperature trajectory is within a hysteresis temperature band.

5. The method of claim 4 , wherein said hysteresis temperature band comprises an upper preferred minimum coolant temperature and a lower preferred minimum coolant temperature.

6. The method of claim 5 , wherein the lower preferred minimum coolant temperature is modified in response to vehicle speed.

7. Method for controlling a hybrid powertrain system including an internal combustion engine, the method comprising:

determining a preferred minimum coolant temperature trajectory for the internal combustion engine, wherein the preferred minimum coolant temperature trajectory comprises a vehicle runtime-based trajectory for a minimum coolant temperature during a warm-up period of engine operation and a stabilized period of operation that is selected from one of a plurality of predetermined trajectories in relation to outside air temperature and a vehicle soak time;

executing closed-loop control of the hybrid powertrain system to generate torque commands for the internal combustion engine and a non-combustion torque machine to generate an output torque from the hybrid powertrain system responsive to an operator torque request and in response to the preferred minimum coolant temperature trajectory for the internal combustion engine and an engine coolant temperature; and

controlling operation of the internal combustion engine to generate heat to cause the engine coolant temperature to follow the preferred minimum coolant temperature trajectory.

8. The method of claim 7 , wherein the preferred minimum coolant temperature trajectory is within a hysteresis temperature band.

9. Method for controlling a hybrid powertrain system including an internal combustion engine, the method comprising:

determining a preferred minimum coolant temperature trajectory for the internal combustion engine, the preferred minimum coolant temperature trajectory comprising a vehicle runtime-based trajectory for a minimum coolant temperature during a warm-up period of engine operation and a stabilized period of operation that is selected from one of a plurality of predetermined trajectories in relation to outside air temperature and a vehicle soak time;

controlling the hybrid powertrain system including generating torque commands for the internal combustion engine and a non-combustion torque machine to generate an output torque from the hybrid powertrain system responsive to an operator torque request and in response to the preferred minimum coolant temperature trajectory and engine coolant temperature; and

controlling operation of the internal combustion engine to generate heat to cause the engine coolant temperature to follow the preferred minimum coolant temperature trajectory.

10. The method of claim 9 , wherein the preferred minimum coolant temperature trajectory is within a hysteresis temperature band.

11. The method of claim 10 , wherein the hysteresis temperature band comprises an upper preferred minimum coolant temperature and a lower preferred minimum coolant temperature.

12. The method of claim 11 , wherein the hysteresis temperature band comprises the upper preferred minimum coolant temperature and the lower preferred minimum coolant temperature, wherein the lower preferred minimum coolant temperature is modified in response to vehicle speed.

13. The method of claim 1 , wherein controlling the internal combustion engine in response to a preferred minimum coolant temperature trajectory comprises deactivating engine autostop operation when the coolant temperature is less than the preferred minimum coolant temperature trajectory.

14. The method of claim 3 , wherein controlling operation of the engine responsive to said adjusted base engine heat rejection response surface to generate heat to cause the coolant temperature to follow the preferred minimum coolant temperature trajectory comprises operating the engine at a higher speed/load point with a corresponding higher heat rejection rate when the preferred minimum coolant temperature is greater than the coolant temperature.