Patent ID: 7364142
Filing Date: 2008-04-29
Classification: B60G,F16F

Abstract:
1. A spring strut unit for a suspension system between a body and a wheel of a motor vehicle, the unit comprising an axially expandible ring-shaped cylinder, a helical spring which can be pretensioned by hydraulic medium in said ring-shaped cylinder, and a vibration damper, the vibration damper comprising: a working cylinder, a damping piston separating the cylinder into an upper working space and a lower working space, the damping piston having damping valves connecting the working spaces, a compensating space connected to one of the working spaces, wherein the compensating space is axially adjacent to said one of the working spaces and separated from said one of said working spaces by a bottom, a piston rod connected to the damping piston and extending from the cylinder, said piston rod having an axial cavity, a hollow pump rod fixed in said cylinder and received in said axial cavity of said piston rod to form a pump space, the hollow pump rod having an axial flow passage connected to the pump space and a drain bore which connects the flow passage to said one of the working spaces when the piston rod is extended from the cylinder by a predetermined amount; a first flow connection connecting said one of the working spaces to the pump space, and a second flow connection connecting the axial flow passage to the ring-shaped cylinder, the second flow connection passing through said bottom, wherein axial movement of the piston rod causes damping medium to be conveyed from said one of the working spaces to the ring-shaped space via the flow connections and the pump space.