Patent ID: 7694760

Claim:
A hybrid vehicle propulsion system, comprising: an engine having at least one combustion cylinder configured to operate in a first and a second combustion mode, wherein the first combustion mode is a spark ignition mode and the second combustion mode is a compression ignition mode, wherein the engine is configured to supply an engine output, the engine further comprising a lean NOx trap configured to store NOx produced by the engine; a motor configured to selectively supply or absorb a secondary output; an energy storage device configured to selectively store at least a portion of the engine output and selectively supply energy to the vehicle; and a control system configured to control at least the engine, the motor, and the energy storage device, wherein the control system is configured to selectively operate said at least one combustion cylinder in one of the spark ignition mode and the compression ignition mode based on a condition of the energy storage device, and to selectively operate said at least one combustion cylinder in one of the spark ignition mode and the compression ignition mode based on a condition of the lean NOx trap.