Torque control for direct injected engines using a supplemental torque apparatus

A system for torque control for a lean-burn engine, wherein the lean-burn engine includes a fuel-injected, spark-ignition engine having an output shaft, an air intake system mounted having a throttle body for admitting air to the engine, an electronic control unit for controlling the engine including fuel injection and ignition timing, an exhaust manifold system having a catalyst in line with a lean NOx trap apparatus, and sensors operatively connected to the exhaust manifold system for sensing the state of the exhaust gas therein and operatively connected to the electronic control unit, and wherein the engine is operable in a plurality of modes including lean modes characterized by combustion of lean air-fuel mixtures and rich modes characterized by combustion of rich air-fuel mixtures, the system comprising:

• torque control algorithm means located in the electronic control unit for controlling a mode transition of the engine from a first lean mode to a first rich mode and from the first rich mode to a second lean mode, whereby the mode transition is characterized by a purging of the lean NOx trap apparatus;
• a supplemental torque apparatus coupled to the output shaft of the engine, said supplemental torque apparatus including an energy storage device and being operable in response to said torque control algorithm means to drive said output shaft with energy stored in said energy storage device when said lean NOx trap apparatus is not being purged and to charge said energy storage device during the purging of said lean NOx trap apparatus.

A method for torque control for a drive unit, wherein the drive unit includes a fuel-injected, spark-ignited engine having an intake manifold supplying air to at least one cylinder and an exhaust system including a lean NOx trap, and a supplemental torque apparatus operatively connected to the engine, the method including:

• measuring the airflow into the engine;
• controlling the amount of exhaust gases recirculated from the exhaust system to the intake manifold of the engine;
• controlling the spark timing and the fuel charge mixture in the at least one cylinder of the engine;
• determining the output torque of the engine, the load torque being supplied by the engine and the torque being supplied by the supplemental torque apparatus;
• and then
• controlling the charging and absorption of the supplemental torque apparatus to maintain the total torque demand in the system according to the relationship T.sub.e +T.sub.sta =T.sub.d wherein T.sub.e equals engine torque, T.sub.sta equals the torque generated or absorbed by the supplemental torque apparatus and T.sub.d equals total torque demand of the engine system.