Torque transmission device with reduced friction

A turbomachine including a casing (35), a low-pressure shaft (27) mounted in rotation in the casing (35), a fan shaft (32) mounted in rotation relative to the casing (35) and a coupling assembly, the low-pressure shaft (27) being configured to drive the fan shaft (32) in rotation by means of the coupling assembly, the coupling assembly including:

• a first shaft (1) which extends along an axis (X) and [is] integral with one among the low-pressure shaft (27) and the fan shaft (32), the first shaft (1) comprising at least a first portion (5) having an outer face (6) in which are formed a plurality of first axial grooves (7),
• a second shaft (2) coaxial with the first shaft (1) and integral with one among the low-pressure shaft (27) and the fan shaft (32), the second shaft (2) comprising at least one second portion (8) which surrounds the first portion (5) and has an inner face (11) in which are formed a plurality of second axial grooves (12),
• a coupling device (4) including a plurality of rolling elements (13) and an annular cage (14), said cage (14) being positioned between the first shaft (1) and the second shaft (2), a plurality of recesses (15) being formed in the cage (14), each of the rolling elements (13) begin positioned on the one hand in a respective recess (15) and on the other hand between one of the first axial grooves (7) and one of the second axial grooves (12) so as to couple in rotation the first and the second shaft (1, 2), the dimensions of one of the rolling elements (13) and the positioning of one of the second grooves (12) relative to one of the first grooves (7) being configured to supply a radial and tangential clearance to one of the rolling elements (13), and in which each first and second groove (7, 12) has a first (16) and a second (17) substantially planar surface extending along the axis, the first (16) and the second (17) surfaces being inclined relative to one another.