Hydraulic damper and elastic-return strut comprising such a damper

A hydraulic damper comprising, in a main body (1;

• 101), two working chambers (8, 9;
• 108, 109) with a volume which is variable in opposite directions, said working chambers (8, 9;
• 108, 109) containing a main viscous fluid intended to pass from one to the other via at least one restricted communication passage (47, 48, 76;
• 147, 148, 176), through the action of the thrust of a damping piston (4;
• 104) being displaced in said body (1;
• 101), an opening cross section of at least one communication passage (47, 48;
• 147, 148) being controlled by the positioning, relative to said passage (47, 48;
• 147, 148), of at least one viscous restriction valve (51, 52;
• 151, 152) on which a control fluid acts, wherein said control fluid is contained in at least one secondary chamber (41, 42;
• 141, 142) delimited in a secondary cylinder (39;
• 139) by a control piston (40 140) mounted slidably in said secondary cylinder (39;
• 139), said secondary chamber (41, 42;
• 141, 142) being associated with a transportation channel (61, 62;
• 161, 162) of the control fluid from said secondary chamber (41, 42;
• 141, 142) as far as the viscous restriction valve (51, 52;
• 151, 152), through the action of the control piston (40;
• 140), said secondary cylinder (39;
• 139) and said control piston (40;
• 140) being integrally attached, one to the main body (1;
• 101), the other to the damping piston (4;
• 104) such that a damping law of said control fluid positioning said viscous restriction valve is linked to the relative dynamic displacements of said main body and said damping piston, said damping dependent upon said relative dynamic displacements of said main body and said damping piston.