Patent ID: 7247126

Claim:
A method for shift control of an automatic transmission comprising: 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 a 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, 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 an output shaft rotation speed and an 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.