Patent ID: 8131436
Filing Date: 2012-03-06
Classification: F16H,Y10T

Abstract:
1. A speed change control system of an automatic transmission mounted on a motor vehicle, the transmission having a first frictional element that changes its operation condition from a disengaged condition to an engaged condition upon issuance of a speed change instruction, a second frictional element that changes its operation condition from an engaged condition to a disengaged condition upon issuance of the speed change instruction, a vehicle speed sensor that detects a speed of the vehicle and a control device that controls a hydraulic pressure applied to the first frictional element based on information on a target gear ratio, the speed change control system comprising: a judge section that judges whether or not the vehicle speed detected by the vehicle speed sensor is equal to or lower than a predetermined very low value; a very low vehicle speed pre-charge control section that, when, upon issuance of the speed change instruction, the judge section judges that the vehicle speed detected by the vehicle speed sensor is equal to or lower than the predetermined very low value, sharply increases the hydraulic pressure applied to the first frictional element, sharply reduces the hydraulic pressure and then holds the hydraulic pressure higher than a given value capable of effecting a piston stroke of a corresponding piston unit for the first frictional element until a time when the piston stroke is completed; and a very low vehicle speed phase control section that, upon completion of the piston stroke, increases the hydraulic pressure to a maximum level in a time that is shorter than that set when the vehicle speed detected by the vehicle speed sensor is higher than the predetermined very low value.