Improved ride comfort and constantly high stability of the vehicle body are not mutually exclusive. ZF Friedrichshafen AG has proven this with the hydraulic damping system Premium Comfort Valve (PCV) which leads to great benefits for buses and trucks. After all, the newly designed piston valve enables a differentiated, gradual adjustment of the damping characteristic curve to the properties of the respective vehicle. In addition, calmed oil flows inside the valve reduce the functional hydraulic noise and thus increase the comfort for the driver and the passengers.
At the UITP World Congress which will take place in Milan from June 8-10, 2015, ZF will show exhibition visitors how chassis design can combine ride comfort and driving stability offering a noise-optimized and cost-effective solution. In fact, PCV is a purely hydraulic vibration damper that does without any electronic or pneumatic additional systems.
PCV is a smart redesigned version of bus damper piston valves. This means that the damper characteristic curves can be adapted even better to the respective vehicle requirements. An innovative oil feed system makes this possible: The flow characteristics change depending on the speed with which the damper piston extends or retracts. The heart of PCV technology is the newly developed oil feed system at the piston dog point. "Thanks to the different spring washers, valves, and bores, PCV provides us with considerably more parameters for the characteristic curve design than standard dampers," Georg Memmel, Head of Development, explains."As a result, the damper characteristics can be defined in a much more differentiated way to match customer requirements and the vehicle's field of application."
A significant increase in the damping force in the low speed range reduces rolling and pitching motions to a minimum. Above all, this increases the safety of bus drivers and passengers during braking and starting maneuvers. At medium speeds, the PCV with a modified oil feed system provides a slower rise in the damping force. The development of the characteristic curve is flatter, which is expressed in a softer, more comfortable suspension response. To keep the vehicle uniformly stable and to prevent the vehicle body from pitching and subsequently rocking, PCV adjusts the oil flow at high speeds. Higher flow resistance leads to a further increase in the damping force. The vehicle body remains stable. This ensures safe vehicle handling.
PCV offers yet another plus in terms of ride comfort: Thanks to the new valve geometry, the oil flow in the bypasses is much calmer compared to traditional twin-tube dampers. "This way, we managed to considerably reduce the functional hydraulic flow noise of dampers with PCV – an aspect which has gained increasing importance for the attractiveness of buses and coaches with alternative, silent drives," Mr. Memmel explains. For buses with alternative drives, which are naturally more silent. "As a result, PCV is also beneficial to the new, pleasant feel when traveling along, as we have it in electric buses, for example."