Control mechanism for automatic transmission

摘要

Uncomfortable travel of a vehicle due to engine brake actions during the travel of the vehicle in traffic is prevented without using an one-way clutch within a transmission mechanism. An automatic transmission is composed of rotational elements that are braked at the time of establishing low stages, a brake B-3, 32 that brakes the rotational elements, and control systems 5, 6 which control the oil pressure of the hydraulic servo 4 in the brake. A band brake B-3 that creates differences in application forces, using self-energizing and deenergizing actions, serves as the brake, which is set to have an area in which the oil pressure during the drive is lower than the oil pressure during the non-drive, by setting the self-energizing direction as a direction of rotation of the rotational element 31 during the drive and the deenergizing direction as an opposite direction of rotation of the rotational element during the non-drive. The control systems have a supplying mechanism which supplies oil to the hydraulic servo of the band brake at an oil pressure PMD that is lower than the oil pressure PEB during the non-drive and is equal to or higher than the oil pressure PFR during the drive.