Apparatus and method for operating a hybrid drive system during an extended braking condition

A drive train assembly comprising:

• an input shaft adapted to be connected to a source of rotational power;
• an output shaft adapted to be connected to a rotatably driven mechanism;
• and
• a hybrid drive system connected to the input shaft and the output shaft, the hybrid drive system including a control apparatus that operates the hybrid drive system in a normal energy recovery mode in response to a braking request and in an extended braking mode in response to an extended braking request;
• wherein
• deceleration of the output shaft is accomplished in both the normal energy recovery mode and in the extended braking mode without the use of foundation brakes;
• when the hybrid drive system is operated in the normal energy recovery mode, fluid is pumped to an accumulator to consume kinetic energy;
• and
• when the hybrid drive system is operated in the extended braking mode, fluid is pumped through either (1) a pressure relief valve containing a restriction or (2) a pump/motor operating in a motoring mode to consume kinetic energy.

A method comprising the steps of:

• (a) providing a hybrid drive system and a control apparatus;
• (b) operating the control apparatus to operate the hybrid drive system in a normal energy recovery mode in response to a braking request;
• and
• (c) operating the control apparatus to operate the hybrid drive system in an extended braking mode in response to an extended braking request;
• wherein
• deceleration of the hybrid drive system is accomplished in both the normal energy recovery mode and in the extended braking mode without the use of foundation brakes;
• when the hybrid drive system is operated in the normal energy recovery mode, fluid is pumped t an accumulator to consume kinetic energy;
• and
• when the hybrid drive system is operated in the extended braking mode, fluid is pumped through either (1) a pressure relief valve containing a restriction or (2) a pump/motor operating in a motoring mode to consume kinetic energy.