Patent ID: 7632215
Filing Date: 2009-12-15
Classification: F16H,Y10T

Abstract:
1. A method for downshifting an automatic transmission from a first transmission speed ration characterized by engagement of one clutch of a first gearset and one clutch of a second gearset, the one clutch of the second gearset being an overrunning clutch, to a second transmission speed ratio characterized by engagement of another clutch of the first gearset and another clutch of the second gearset, the method comprising, in series, the steps of: (a) partially releasing the one clutch of the gearset until the one clutch of the first gearset carries a slightly greater torque than necessary to couple the input shaft to the output shaft through the selected fears of the first gearset; (b) further releasing the one clutch of the first gearset until the one clutch of the first gearset begins to slip; (c) partially applying the other clutch of the second gearset until the one clutch of the second gearset begins to slip; (d) maintaining the partial application of the other clutch of the second gearset until a target ratio of the second gearset is achieved; (e) fully applying the other clutch of the second gearset; and (f) fully applying the other clutch of the first gearset and fully releasing the one clutch of the first gearset.