A torque cam mechanism comprises first and second cam members disposed
relatively rotatably around a common axis and cam balls adapted to fit in
first and second cam grooves formed, respectively, in confronting surfaces
of the first and second cam members. The depth of the first cam grooves is
made larger than the radius of the cam balls, whereas the depth of the
second cam grooves is made smaller than the radius of the cam balls,
whereby even though a centrifugal force is applied to the cam balls which
rotate together with the first and second cam members, the generation of
thrust forces for separating the confronting surfaces of the first and
second cam members can be suppressed by receiving the centrifugal force so
applied to the cam balls by the first cam grooves which are deeper.