Variable stiffness hydraulic damper

A hydraulic damper (1), in particular a motor vehicle suspension damper, comprising:

• a tube (3) filed with working liquid;
• a piston assembly (4) disposed slidably within the tube (3) along an axis (A), attached to a piston rod (5) extending outside the hydraulic damper (1) through a sealed piston rod guide (6), defining a rebound chamber (11) adjacent the piston rod (5) and a compression chamber (12) at the opposite side, and including a compression valve assembly (46) and a rebound valve assembly (47) to regulate a flow of the working liquid through the piston assembly (4) during rebound and compression strokes of the hydraulic damper (1) in response to a velocity of the piston assembly (4);
• and
• a controllable solenoid valve (42) configured to control the flow of the working liquid passing through the piston assembly (4) during the rebound and compression strokes of the hydraulic damper (1) in response to a control signal,
• wherein the piston assembly (4) further comprises:
• a housing (41) with the controllable solenoid valve (42) disposed within said housing (41) at a side thereof proximate to the rebound chamber (11);
• a first partition member (43) disposed within said housing (41) and defining a first internal chamber (411) between the controllable solenoid valve (42) and said first partition member (43);
• a second partition member (44) disposed within said housing (41) and defining a second internal chamber (412) between said first partition member (43) and said second partition member (44);
• a third partition member (45) disposed within said housing (41) and defining a third internal chamber (413) between said second partition member (43) and said third partition member (45);
• a first check valve (431) allowing the working liquid to flow through one or more first axial channels (434) in said first partition member (43) from said first internal chamber (411) to said second internal chamber (412), while blocking fluid flow in an opposite direction;
• a second check valve (441) allowing the working liquid to flow through one or more second axial channels (443) in said second partition member (44) from said second internal chamber (412) to said third internal chamber (413), while blocking fluid flow in an opposite direction;
• a third check valve (451) allowing the working liquid to flow through one or more third axial channels (453) in said third partition member (45) from the compression chamber (12) to said third internal chamber (413), while blocking fluid flow in an opposite direction;
• a fourth check valve (417) allowing the working liquid to flow through one or more fourth axial channels (415) disposed within a wall of said housing (41) from said first internal chamber (411) to the compression chamber (12), while blocking fluid flow in an opposite direction;
• and
• one or more radial channels (416) disposed within the wall of said housing (41), non-intersecting said fourth axial channels (415) of said fourth check valve (417), and joining the rebound chamber (11) with said second internal chamber (412),
• wherein said first partition member (43) has a first axial opening (432) and the controllable solenoid valve (42) is provided with at least one inlet (423) in fluid communication with said first axial opening (432), and one or more outlets (424) in fluid communication with said first internal chamber (411), and
• wherein said second partition member (44) has a second axial opening (442);
• wherein said first axial opening (432) and said second axial opening (442) allow the working liquid to flow from said third internal chamber (413) to said at least one inlet (423) of the solenoid valve (42) bypassing said second internal chamber (412).