Patent ID: 7127337

Claim:
A method of providing a silent mode of operation for a hybrid electric vehicle having a rechargeable energy storage system (ESS), comprising the steps of: (1) transmitting a silent mode initiation request to a silent mode controller; (2) comparing an actual value of at least one state parameter of the ESS that is indicative of the availability of the ESS for implementing the silent mode to at least one silent mode initiation limit value associated with the actual value, wherein if the actual value of the at least one state parameter compared to the associated at least one mode initiation limit value indicates that the silent mode is allowed, the method proceeds to step (3), and wherein if the actual value of the at least one state parameter indicates that the silent mode is not allowed, step (2) is repeated so long as the silent mode initiation request is being transmitted; (3) transmitting a silent mode activation request to the silent mode controller; (4) operating the vehicle in the silent mode using the silent mode controller, comprising designating an electric drive motor as a primary source of propulsion energy for the vehicle and designating an engine as a secondary source of the propulsion energy for the vehicle, wherein a modal quantity of energy in the ESS is allocated for use by the electric drive motor during the silent mode and the engine is used to make up the difference between the modal quantity of energy and a total vehicle propulsion energy requirement during the silent mode; (4A) limiting an output power of the engine while the vehicle is in the silent mode to a silent mode output power limit that is less than a maximum output power of the engine, and, (5) terminating the silent mode in response to the occurrence of a mode termination event.