Transmission Clutch Stroking Control During an Engine Restart In a Hybrid Electric Vehicle

A method for controlling restart of an engine in a hybrid electric powertrain, comprising the steps of:

• (a) stopping the vehicle and engine;
• (b) initiating the restart using a starter to crank the engine;
• (c) estimating time required to restart the engine after the restart is initiated;
• (d) using an auxiliary pump to fill and stroke launch elements of a transmission when the estimated time substantially equals a second estimated time required to fill and stroke said launch elements;
• (e) using a hydraulic pump in the transmission to provide pressure that increases the torque capacity of the launch elements.

A hybrid electric powertrain, comprising:

• an engine;
• a transmission including launch elements and a hydraulic circuit;
• a source of electric power;
• an auxiliary pump driven from the power source and connected to the hydraulic circuit;
• a starter driven from the power source and connected to the engine;
• and
• a controller configured to stop the engine, use the starter to initiate a restart of the engine, estimate time required to complete the restart after initiating the restart, use the auxiliary pump to stroke launch elements of a transmission when the estimated time substantially equals a second estimated time required to compete the stroking of the launch elements, and increase a torque capacity of the launch elements to accelerate the vehicle.