A torque transfer mechanism for controlling the magnitude of a clutch
engagement force exerted on a clutch pack that is operably disposed
between a first rotary member and a second rotary member includes an
actuator having an inner sleeve, an outer sleeve, and a plurality of
balls. The inner sleeve is supported for rotation relative to the first
rotary member and each of the inner and outer sleeves includes a spiral
groove aligned with the other. The balls are positioned within the spiral
grooves between the inner and outer sleeves. An electric motor selectively
rotates one of the inner and outer sleeves so as to induce axial movement
of the other of the inner and outer sleeves to engage the clutch.
