Adjustable hydraulic vibration damper for motor vehicles

An adjustable vibration damper for motor vehicles, said adjustable vibration damper comprising:

• a first cylinder, said first cylinder defining a chamber therein;
• first piston means disposed within said chamber of said first cylinder, said first piston means for damping vibrations transmitted to said first cylinder, said first piston means dividing said chamber into a first chamber portion and a second chamber portion;
• said first piston means comprising:
• first fluid passage means disposed therethrough and fluidly connecting said first chamber portion to said second chamber portion;
• and
• bi-directional valve means disposed within said first fluid passage means for generating a first damping force and allowing fluid flow from each of said first chamber portion and said second chamber portion to the other of said first chamber portion and said second chamber portion through said first fluid passage means;
• at least a second fluid passage by-passing said piston means for allowing damping fluid to flow between said first and said second chamber portions around said piston means;
• at least one additional valve means for controlling said flow of damping fluid through said second fluid passage, said at least one additional valve means for generating a secondary damping force, and said at least one additional valve means comprising:
• valve body means disposed adjacent said second fluid passage, said valve body means having a first end for blocking at least a portion of said second fluid passage to control said flow of damping fluid through said second fluid passage, and a second end opposite said first end;
• said damping fluid for applying a first pressure to said first end of said valve body means to open said second fluid passage;
• second piston means disposed adjacent said second end of said valve body means;
• said second end of said valve body means having a first surface disposed towards said second piston means;
• said second piston means having a first surface disposed towards said valve body means;
• means for introducing a pressure medium between said first surface of said valve body means and said first surface of said second piston means to apply a second pressure to said first surface of said valve body means and said first surface of said second piston means;
• and
• said second pressure being independent from said first pressure to oppose said first pressure and close said second fluid passage to control said flow of damping fluid through said second fluid passage.