Electronically controlled automatic transmission and method of controlling the same

摘要

An electronically controlled automatic transmission in which the transmission gear stage and engaging or disengaging operations of a lock-up clutch in a torque converter are determined on the basis of the number of transmission output revolutions and the throttle opening and in which a shifting solenoid and a lock-up solenoid incorporated in the transmission are controlled in. The transmission has a sensor for detecting an input rotational speed. The number of transmission input revolutions output from this sensor and the number of transmission output revolutions are compared with each other, thereby detecting malfunction of a transmission output speed sensor. If the transmission output speed sensor malfunctions, gearshift and lock-up control are performed on the basis of the number of transmission output revolutions calculated from the number of transmission input revolutions and the corresponding gear ratio. The transmission also has an malfunction alarm device for issuing an alarm indicating malfunction of the transmission output speed sensor in response to a signal output from an electronic control device. When both the transmission output speed sensor and the transmission input speed sensor operate normally, the number of revolutions output from the transmission output speed sensor and the number of transmission output revolutions calculated by the electronic control device from the number of transmission input revolutions and the gear ratio are compared, thereby detecting malfunction such as slip failure of a friction member in the transmission or shift failure.