Torque transmission device with reduced friction

A turbomachine including a casing, a low-pressure shaft mounted in rotation in the casing, a fan shaft mounted in rotation relative to the casing and a coupling assembly, the low-pressure shaft being configured to drive the fan shaft in rotation by means of the coupling assembly, the coupling assembly including:

• a first shaft which extends along an axis and integral with one among the low-pressure shaft and the fan shaft, the first shaft comprising at least a first portion having an outer face in which are formed a plurality of first axial grooves,
• a second shaft coaxial with the first shaft and integral with one among the low-pressure shaft and the fan shaft, the second shaft comprising at least one second portion which surrounds the first portion and has an inner face in which are formed a plurality of second axial grooves,
• a coupling device including a plurality of rolling elements and a cage that is annular, said cage being positioned between the first shaft and the second shaft, a plurality of recesses being formed in the cage, each of the rolling elements being positioned in a respective recess and between one of the first axial grooves and one of the second axial grooves so as to couple in rotation the first and the second shaft, dimensions of one of the rolling elements and the positioning of one of the second axial grooves relative to one of the first axial grooves being configured to supply a radial and tangential clearance to one of the rolling elements, and in which each first and second groove has a first and a second substantially planar surface extending along the axis,
• wherein, within each of the first and second groove, the first and the second surfaces are inclined relative to one another.