Method and apparatus for shift control of an automatic transmission

An apparatus for shift control of an automatic transmission connected to an engine, the apparatus comprising:

• a throttle opening detector for detecting a throttle valve opening of the engine;
• an output shaft rotation speed detector for detecting an output shaft rotation speed of the automatic transmission;
• a turbine speed detector for detecting a turbine speed of the automatic transmission;
• an input torque detector for detecting a input torque to the automatic transmission;
• and
• a transmission control unit for controlling shifting of the automatic transmission on the basis of signals from the detectors,
• wherein the transmission control unit executes instructions for:
• determining whether a 4 to 3 shift condition is satisfied during an execution of a 3 to 4 shifting;
• starting the 4 to 3 shifting before the 3 to 4 shifting is finished, when the 4 to 3 shift condition is satisfied during the execution of the 3 to 4 shifting;
• and
• executing the started 4 to 3 shifting according to a predetermined hydraulic control pattern,
• wherein the executing of the started 4 to 3 shifting comprises:
• controlling off-going and on-coming pressure duties such that the turbine speed rebounds and increases up to a local maximum value exceeding a target speed;
• and
• controlling the off-going and on-coming pressure duties such that the turbine speed reaches the target speed from the local maximum value;
• and
• wherein the controlling of the off-going and on-coming pressure duties such that the turbine speed rebounds and increases up to the local maximum value exceeding the target speed comprises:
• determining whether the turbine speed has increased by a first reference speed after rebounding;
• abruptly increasing the off-going pressure duty by an off-going map duty calculated based on the output shaft rotation speed and the input torque, in the case that the turbine speed has increased by the first reference speed after rebounding;
• determining whether the turbine speed has reached the target speed within a first predetermined deviation;
• abruptly decreasing the off-going pressure duty by a first predetermined rate, in the case that the turbine speed has reached the target speed within the first predetermined deviation;
• determining whether the turbine speed has reached the target speed within a second predetermined deviation;
• abruptly increasing the on-coming pressure duty by an on-coming map duty calculated based on the output shaft rotation speed and the input torque, in the case that the turbine speed has reached the target speed within the second predetermined deviation;
• gradually increasing the on-coming pressure duty at a first predetermined duty-change rate, after the abrupt increasing of the on-coming pressure duty;
• determining whether the turbine speed has reached the target speed within a second reference speed;
• abruptly increasing the on-coming pressure duty by a second predetermined rate, in the case that the turbine speed has reached the target speed within the second reference speed;
• gradually increasing the on-coming pressure duty at a second predetermined duty-change rate, after the abrupt increasing of the on-coming pressure duty by the second predetermined rate;
• and
• gradually increasing the off-going pressure duty at the second predetermined duty-change rate, after the abrupt increasing of the on-coming pressure duty by the second predetermined rate.