Abstract
Keywords - smart shock absorber, pitch, roll, metering holes, body protection, comfort
The "VZN" shock absorber concept is a new Romanian concept granted with European Patent EP 1190184, and Romanian Patent 118546 giving high performances at low costs. The VZN acronym is abbreviation for VARIABLE ZETA NECESSARY for well navigation, in all road and load conditions, where ZETA represents the relative damping, which is stepwise changed automatically, according to the piston position.
The energy dissipation system of the self-adjustable shock absorber "VZN" consists of an inner cylinder having sideways damping valves, placed optimally between to the ends. In the cheap solution the damping valves are reduces to metering holes. The inner cylinder is closed at ends with inner head and valve body, either containing or no filling valves. The piston slidably mounted within the inner cylinder, has no filling and damping valves.
Due to this structure the shock absorber assures on both rebound respectively compression strokes small damping coefficients at the beginnings of strokes due to the fact that the liquid is discharged through a high number of damping valves, medium damping coefficients at the medium position due to the fact that the liquid is discharged through a medium number of damping valves, while when the piston approaches by strokes ends the damping coefficients increase due to the reduction of the active damping valves numbers.
The VZN damping coefficient evolution with stroke and the constructive solution confers, relative to standard shock absorbers:
1. Reduced bounce movements, and give skyhook behaviour [1], [3], [4];
2. Reduced vertical body acceleration, so comfort increasing [1], [3], [4];
3. Reduces 75 % the stopper bumpers [2];
4. Eliminate or reduces the stopper bumpers strikes at the stroke end , protecting the axles and body [1], [3], [4];
5. An anti-unbalance torque, progressive with the roll/pitch angle, so increasing roll/pitch stability at unbalancing [1], [3];
6. An anti-redressing torque, regressive with the roll/pitch angle, so favouring roll/pitch stability at redressing [1], [3];
7. Compacter and cheaper solution (variants with cylindrical valves) [3], [4].
The paper presents VZN practical solutions with planar and cylindrical filling valves, evaluates theoretically pitch and roll behaviour and by simulation front and rear car body bounces, vertical accelerations, force in stop bumpers and the pitch behaviour relative to standard shock absorbers.
The high performances and low cost means VZN is a semi active damper at price of standard shock absorber, being a great future automotive opportunity.