System and method for regulating torque transmission in a vehicle powertrain and a vehicle powertrain using same

A method for regulating torque transmitted via a lock-up clutch from a crankshaft of a vehicle engine to an input shaft of a transmission of the vehicle, comprising:

• providing a controller in communication with an engine speed sensor;
• determining an engine acceleration based on data from the engine speed sensor when the controller receives data indicating that engagement of the lock-up clutch is either desired or occurring;
• determining a torque reduction target based on the engine acceleration;
• and
• signaling the engine to output torque substantially equal to the torque reduction target.

A vehicle powertrain comprising:

• an engine including a crankshaft configured to output a variable torque;
• a transmission including an input shaft configured to multiply the torque output by the engine and output the multiplied torque;
• a torque converter assembly including a lock-up clutch, a first input connected to the crankshaft, and a first output connected to the input shaft, wherein the lock-up clutch includes a second input selectively connectable to the first input and a second output connected to the first output, wherein the second input is movable between an engaged position where the second input is connected to the first input and a disengaged position where the second input is disengaged from the first input;
• a position sensor configured to output data indicative of an engaged position of the lock-up clutch and the disengaged position of the lock-up clutch;
• an engine speed sensor configured to output data indicative of the rotational speed of the crankshaft;
• a controller in electrical communication with the engine speed sensor and the position sensor and configured to,
• determine an engine acceleration based on data from the engine speed sensor when the controller determines that actuation of the lock-up clutch is either desired or is occurring;
• determine a torque reduction target based on the engine acceleration;
• and
• signal the engine to output torque substantially equal to the torque reduction target.