Automatic transmission system for a vehicle

Abstract

The invention relates to an automatic speed transmission system for a vehicle comprising an engine capable of rotating an input shaft (1), said system comprising a first low-ratio clutch device and a second high-ratio clutch device depending on the speed of the output shaft (1), the clutch devices comprising a common hub (9), or separate means, which is mechanically linked to the output shaft (1) and which comprises: - drive means for transmitting the motion from the input shaft to the output shaft, - disengageable coupling means, which couple the drive means to the output shaft, - at least one control device capable of controlling the engagement and disengagement of the clutch devices, to change from one ratio to another, - a unidirectional coupling means (6) between the drive means of the first low-ratio clutch device and the output shaft (1).Figure for the abridged version: Fig 1.