Fluid coupling

A fluid coupling comprising:

• a pump having an annular pump shell with an annular core ring mounted on a pump hub and a plurality of impellers radially arranged in the pump shell;
• a turbine arranged being opposed to the pump and having an annular turbine shell with an annular core ring mounted on a turbine hub capable of rotating relative to the pump hub and a plurality of runners radially arranged in the turbine shell;
• and
• an operation fluid filled in the pump and in the turbine;
• wherein,
• the turbine is so constituted as to slide on the turbine hub in the axial direction thereof, and has centrifugal pushing means for separating the turbine away from the pump side by the action of a centrifugal force produced accompanying the rotation of the turbine;
• and
• the core ring of the pump and the core ring of the turbine are so constituted that the gaps for flowing the operation fluid into the two core rings are increased in a state where the turbine is close to the pump and that the gaps for flowing the operation fluid into the two core rings are decreased as the turbine separates away from the pump shell.