A coupling assembly comprising a friction coupling a pressure-generating device comprising a pump body member, an axially-displaceable piston loading the friction coupling, and a pressure chamber formed by the pump body and by the piston and filled with a highly-viscous fluid, and with at least one conveying plate being provided in the pressure chamber; and a shear channel with a control member in the pressure chamber, the control member cooperating with at least one conveying plate. In a first embodiment, the shear channel with a control member forms two circumferential grooves of limited length and each covered by one of the two radial surfaces of the conveying plate, thereby forming two shear channels. Passages through the conveying plate connect the two shear channels. In a second embodiment, the shear channel with a control member forms a circumferential groove of limited length which is covered by one of the two radial surfaces of the conveying plate to form a first shear channel. In the shear channel with a control member, there is a circumferential slot of limited length which is covered by the other one of the two radial surfaces of the conveying plate and by a second conveying plate, the latter being designed to form a second shear channel. The first conveying plate includes fluid passages extending therethrough and connecting both shear channels to one another.