We propose the new damper concept VZN –Variable Zeta after Necessities, Zeta being the relative damping changing stepwise according piston position, correlated thus with the vehicle load state and the road unevenness amplitude.
VZN main differences comparative to standard dampers are:
It has no valves in piston
Valve body has only filling valve on rebound, no damping valve
Filling on compression is realized with a valve placed at the upper end of the inner cylinder
The damping is realized by many metering orifices (or valves for better damping control) placed in the inner cylinder between both filling valves, giving a progressive damping characteristic on both strokes rebound and compression.
Thus it has small damping coefficients at the strokes beginnings the fluid flows out by a great number of active orifices/valves, medium damping coefficients in the medium position where the number of the active orifices is medium and hard damping coefficients at the stroke end where the numbers of the active orifices/valves are reduced or one. After the last active orifice it works like a hydraulic buffer.

VZN is simplest comparative to the standard dampers and can be realized easy eliminating the valves from piston, eliminating the damping valve in valve body and replacing the filling valve from piston in a cage placed in the upper end on the inner cylinder and machining 10÷20 metering orifices in the inner cylinder between the bottom and upper filling valves. To flooded permanently valves and orifices it uses inner or outer balance chamber placed above the upper valve, or inner or outer balance chambers with floating piston, placed under the valves/orifices level.

Simulation on ¼ and ½ vehicle models show VZN give 30 % and more increased performances comparative to the standard one, similar to the semi-active and magneto rheological shock absorbers, e.g.:
• Increased stability reducing the vehicle vertical body displacement, even SKYHOOK behavior [2]
• Increased comfort, reducing maximal and medium vehicle body accelerations [2]
• Increased passengers, body and axles protection reducing the number and amplitude of the buffer collision at the stroke ends. [2]
• Reduces fuel consumption 4÷8% having reaction perfect according to excitation, no more, no less, reducing thus the unwanted oscillation axle-body, but the same eliminating the exaggerated dissipation [1] specific to the standard one having the same reaction at the same excitation irrespective of the piston position.
VZN progressive characteristic gives best protection at crash [3]

The VZN concept giving organization layouts is granted with European Patent
EP 1190184/2005

The practical solutions for VZN manufacturing are granted with European Patent EP 2078168/2011. It shows solutions with planar and cylindrical filling valves and metering orifices. Variants with cylindrical filling valves eliminates valve body and upper filling cage, the cylindrical plates being placed directly on the inner side of the inner cylinder, solution giving reduced cost comparative to the standard dampers.

VZN performances similar to the semi-active and magneto rheological dampers, but prices 5÷10 times reduced comparative them and similar to the standard one give high marketability.