A damper valve comprising - a valve housing (111, 112); - a controlled flow channel arranged to provide a fluid connection between a valve inlet side (100.1) and a valve outlet side (100.2) of the damper valve; - a controlled valve provided in the controlled flow channel to allow, in operation, influencing a controlled fluid flow (Fd) in the controlled flow channel in a controlled flow direction (Fd) from the valve inlet side to the valve outlet side; - a movable valve body acting on the controlled valve, the movable valve body being movable with respect to a wall of the controlled flow channel, the wall being associated with the valve housing (111, 112), to change a closing force of the controlled valve; and - a control chamber comprising - - a control chamber inlet in fluid connection with the valve inlet side (100.1) upstream of the controlled valve with reference to the controlled flow direction (Fd), the control chamber inlet comprising a flow restriction (160.1) for a control fluid flow from the valve inlet side to the control chamber; - - a configuration providing a variable volume of the control chamber, a change in volume of the control chamber acting to cause a movement of the movable valve body, an increase of a fluid pressure in the control chamber acting to increase the volume of the control chamber and to move the movable valve body, thereby increasing a closing force of the controlled valve; and - - a first flexible wall allowing a change in volume of the control chamber and allowing movement of the movable valve body upon a change in volume of the control chamber, and providing an effective surface area against which the fluid pressure in the control chamber acts, the effective surface area decreasing upon movement of the movable valve body in a direction outward of the control chamber, the first flexible wall comprising a flex plate bearing against a curved surface (111.1) provided on the valve housing (111, 112) such that the effective surface area decreases upon movement of the flex plate and movable valve body in the direction outward of the control chamber. - a valve housing (111, 112); - a controlled flow channel arranged to provide a fluid connection between a valve inlet side (100.1) and a valve outlet side (100.2) of the damper valve; - a controlled valve provided in the controlled flow channel to allow, in operation, influencing a controlled fluid flow (Fd) in the controlled flow channel in a controlled flow direction (Fd) from the valve inlet side to the valve outlet side; - a movable valve body acting on the controlled valve, the movable valve body being movable with respect to a wall of the controlled flow channel, the wall being associated with the valve housing (111, 112), to change a closing force of the controlled valve; and - a control chamber comprising - - a control chamber inlet in fluid connection with the valve inlet side (100.1) upstream of the controlled valve with reference to the controlled flow direction (Fd), the control chamber inlet comprising a flow restriction (160.1) for a control fluid flow from the valve inlet side to the control chamber; - - a configuration providing a variable volume of the control chamber, a change in volume of the control chamber acting to cause a movement of the movable valve body, an increase of a fluid pressure in the control chamber acting to increase the volume of the control chamber and to move the movable valve body, thereby increasing a closing force of the controlled valve; and - - a first flexible wall allowing a change in volume of the control chamber and allowing movement of the movable valve body upon a change in volume of the control chamber, and providing an effective surface area against which the fluid pressure in the control chamber acts, the effective surface area decreasing upon movement of the movable valve body in a direction outward of the control chamber, the first flexible wall comprising a flex plate bearing against a curved surface (111.1) provided on the valve housing (111, 112) such that the effective surface area decreases upon movement of the flex plate and movable valve body in the direction outward of the control chamber. - - a control chamber inlet in fluid connection with the valve inlet side (100.1) upstream of the controlled valve with reference to the controlled flow direction (Fd), the control chamber inlet comprising a flow restriction (160.1) for a control fluid flow from the valve inlet side to the control chamber; - - a configuration providing a variable volume of the control chamber, a change in volume of the control chamber acting to cause a movement of the movable valve body, an increase of a fluid pressure in the control chamber acting to increase the volume of the control chamber and to move the movable valve body, thereby increasing a closing force of the controlled valve; and - - a first flexible wall allowing a change in volume of the control chamber and allowing movement of the movable valve body upon a change in volume of the control chamber, and providing an effective surface area against which the fluid pressure in the control chamber acts, the effective surface area decreasing upon movement of the movable valve body in a direction outward of the control chamber, the first flexible wall comprising a flex plate bearing against a curved surface (111.1) provided on the valve housing (111, 112) such that the effective surface area decreases upon movement of the flex plate and movable valve body in the direction outward of the control chamber.