Automatic engine stop and restart mode for reducing emissions of a hybrid electric vehicle

A method of providing an engine stop and restart mode of operation for a hybrid electric vehicle having an engine that is operatively and selectively coupled to an electric drive motor and transmission, comprising the steps of:

• (1) defueling the engine and maintaining rotation of the engine by rotation of the electric drive motor at a vehicle speed that is less than a vehicle stop threshold value;
• (2) decoupling the engine and transmission in response to a first predetermined vehicle operating condition and stopping the rotation of the engine using the electric drive motor to apply a torque to oppose the rotation of the engine;
• (3) restarting rotation of the engine in response to a second predetermined vehicle operating condition using the electric drive motor;
• and
• (4) recoupling the engine and transmission.

A method of providing an engine stop mode of operation for a hybrid electric vehicle having an engine that is operatively and selectively coupled to an electric drive motor and transmission, comprising the steps of:

• (1) defueling the engine and maintaining a rotational speed of the engine by rotation of the electric drive motor at a vehicle speed that is less than a vehicle stop threshold value;
• (2) initiating a motor off request in response to a first predetermined vehicle operating condition;
• (3) commanding a neutral state of the engine and transmission, whereby the neutral state comprises selecting the operative decoupling of the engine from the transmission;
• (4) confirming that the neutral state has been attained;
• (5) stopping the rotation of the engine using the electric drive motor to apply a torque to oppose the rotation of the engine;
• (6) initiating a motor on request in response to a second predetermined vehicle operating condition;
• (7) restarting the rotation of the engine without fuel using the electric drive motor to apply a torque to the engine;
• (8) commanding a range state of the engine and transmission, whereby the range state comprises selecting the operative coupling of the engine and transmission;
• (9) commanding a vehicle speed to the electric drive motor, whereby if the vehicle speed command is greater than a vehicle restart threshold value, proceeding to step 10, and whereby if the vehicle speed is less than or equal to the vehicle restart threshold, returning to step 2;
• (10) refueling the engine.