Patent ID: 7857113

Claim:
A hydraulic control system ( 10 ) for a clutch ( 12 ) for a motor vehicle, comprising: an upstream sending cylinder ( 14 ) connected by a conduit ( 16 ) to a downstream receiving cylinder ( 18 ), so as to form a hydraulic control circuit ( 19 ); an assistance cylinder ( 30 ) interposed in the conduit ( 16 ), between the upstream sending cylinder ( 14 ) and the downstream receiving cylinder ( 18 ); and at least one assistance piston ( 32 ) mounted so as to slide axially along a sliding axis (A 1 ) in a body ( 56 ) of the assistance cylinder ( 30 ) between an upstream engagement position and a downstream disengagement position, so as to delimit an upstream hydraulic chamber ( 34 ) and a downstream hydraulic chamber ( 36 ) with variable volumes according to the axial position of the assistance piston ( 32 ); the upstream chamber ( 34 ) being connected to the upstream sending cylinder ( 14 ) by a portion of hydraulic circuit referred to as an upstream circuit ( 40 ) and the downstream hydraulic chamber ( 36 ) being connected to the downstream receiving cylinder ( 18 ) by a portion of the hydraulic circuit referred to as a downstream circuit ( 44 ); each hydraulic circuit portion ( 40 , 44 ) comprising a means ( 52 , 102 , 150 ) of relevelling the volume of fluid connected to at least one fluid reservoir ( 29 ); the assistance cylinder ( 30 ) comprising an assistance device ( 50 ) applying an assistance force (Fa) to the assistance piston ( 32 ) during a disengagement phase of the clutch ( 12 ); the assistance device ( 50 ) comprising a regulation means ( 114 , 115 ) varying the value of the assistance force (Fa) according to the travel (CP) of a clutch control pedal ( 22 ) in accordance with a predetermined assistance law; the assistance device ( 50 ) further comprising an elastic element ( 106 ) storing energy during an engagement phase of the clutch ( 12 ) and restoring the energy during the disengagement phase in order to produce the assistance force (Fa); the elastic element ( 106 ) compressed when the assistance piston ( 32 ) being in the upstream engagement position and expanded when the assistance piston ( 32 ) being in the downstream disengagement position; the regulation means ( 115 ) being a cam mechanism ( 114 ) driven by the axial movement of the piston ( 32 ) for regulating the assistance force (F a ) produced by the elastic element ( 106 ) during the disengagement phase.