A Study on Full Electronic Control of Automatic Transmission: Direct Active Shift Control
Since 1980s, the electronic control units of automatic transmissions have been greatly advanced to make smooth gear shifting and improve fuel economy. Along with it, the solenoid valves as electro-hydraulic actuators have been rapidly developed which have high pressure and large flow capacity. In these days, it is not an expensive solution to adopt more electro-hydraulic actuators to get the better performance of the automatic transmission. This paper introduces a new scheme of full electronic control system, direct active shift control, using the proportional control solenoid valves to control the pressure of each friction element independently and without any passive hydraulic or mechanical component. At first, it reviews the structures of widely used control systems from the old-fashioned to the modern. Next, the concept of the direct active shift control scheme is introduced and the performance of the actuators discussed.