In monotube dampers, the floating separating piston forms an absolutely leakproof separation between the oil and the gas. The damping valves for rebound and compression are located on the piston. The piston rod and seal are especially important components because the pressurized system must remain perfectly sealed under dynamic loads. The Viton seal is applied to the piston rod by means of mechanical pre-loading and high internal pressure. Both materials and geometry have been optimized to minimize friction.
Twin-tube dampers require lower gas pressure levels; 6 to 8 bar are enough to ensure precision damping as well as low noise levels even at high compression speeds.
A shock absorber’s damping force generally depends on the piston speed. As the piston speed increases, so also does the damping force. The degree to which this takes place is defined by valves. The design, arrangement, and combination of valves allow all the desired and/or optimum damping characteristics (curves) to be attained for different applications. A damper’s characteristic curve can be shown as a force/speed (F-v) diagram. Shock absorbers from ZF can feature degressive or linear characteristic curves as well as combinations thereof.
CDC® is an electronic damping system that noticeably increases driving safety, comfort, and dynamics by adjusting damping forces optimally for each individual wheel. A control unit calculates the requisite damping forces within milliseconds, and adjusts the dampers just as quickly. Vehicle sensors monitor values such as body, wheel, and lateral acceleration, and use them to generate the ideal damping forces for each individual wheel on a continuous basis. The CustomizedLine includes the CDC® actuators; the ActiveLine goes beyond the actuators to offer the entire system consisting of actuators, sensors, hardware, and software.