Fluid coupling with a predetermined pressure drop in the axial conduction path of the outer periphery of the piston

摘要

The invention relates to a hydrokinetic coupling device ( 10 ) consisting of a case ( 12 ) and a lockup clutch ( 18 ) comprising a piston ( 20 ) which can move axially in relation to the case ( 12 ) between an engaged position, in which the piston is applied against an annular transverse face of the case ( 12 ), and a disengaged position at a distance from the transverse face of the case ( 12 ). According to the invention, the piston ( 20 ) is delimited radially by a convex peripheral face ( 20 e) and the case ( 12 ) comprises an opposing inner concave face, said two faces radially defining an essentially-annular axial conduit ( 30 ). The invention is characterised in that the rotating surfaces ( 20 e , 17 i) of the piston ( 20 ) and the case ( 12 ) are shaped such that the value of the head loss experienced by the fluid circulating in the annular conduit ( 30 ) is pre-determined as a function of the axial position of the piston ( 20 ) in relation to the case ( 12 ).