Patent ID: 7980981
Filing Date: 2011-07-19
Classification: F16H

Abstract:
1. An automatic transmission of a motor vehicle, comprising: a plurality of planetary gear units; a plurality of frictional elements, the frictional elements assuming engaged/disengaged condition upon receiving a ratio change instruction thereby to establish a desired speed of the transmission with the aid of the planetary gear units; a deceleration detecting means that detects a deceleration of the motor vehicle; a gear ratio detecting means that detects an actual gear ratio that is actually established in the transmission; and an interlock judgment means that judges whether or not the transmission is subjected to an interlock, the interlock being a condition wherein upon receiving the ratio change instruction, at least one of the frictional elements is brought into unintended engagement, the interlock judgment means being configured to carry out judgment of the interlock by analyzing the deceleration of the vehicle and a relation between a gear ratio intended by the ratio change instruction and the actual gear ratio actually established by the transmission while the transmission is not under a ratio change, and the interlock judgment means being configured to judge occurrence of the interlock when the deceleration of the vehicle is higher than a predetermined deceleration and the actual gear ratio relative to the intended gear ratio exceeds a predetermined range.