A safe and comfortable trip

The internal combustion engine in a vehicle provides the driving force – but the oscillating pistons and rotating crankshaft along with the drive train connected to them are a constant source of vibration. If these movements were not damped and isolated to a large degree from the chassis and the body, a comfortable journey by car, bus or truck would be unthinkable.

To isolate the vibration from the rest of the vehicle and its occupants, the engine and gearbox unit is fitted with powerful dampers known as unit bearings. They secure the engine block and gearbox to the vehicle body. These inconspicuous components perform a multitude of tasks. They have to prevent the low-frequency natural vibration of the engine – in neutral for example – from being transferred to the body in the form of noise and vibration.

They also have to isolate the highfrequency vibrations that occur at full speed. What’s more, the bearings also have to absorb the shock arising from uneven road surfaces to ensure that the engine/gearbox unit does not make the vehicle start to judder. There is a conflict of objectives here, which the vehicle manufacturer has to try to resolve by means of a trade-off – depending on the vehicle class – between comfort and driving dynamics, using rubber-to-metal bearings or hydraulic bearings, depending on preference and vehicle type. The choice is either to increase comfort by reducing noise, particularly in neutral, or to focus on driving dynamics by eliminating road-induced movement of major assemblies.

In mid-range and high-end vehicles in particular, car manufacturers tend to opt for hydraulic-damping engine bearings, which form an adjustable connection between the drive and chassis, offering more effective damping of strong vibrations – caused by load changes and juddering, for example – than rubber-tometal bearings.

Hydraulic bearings have been used in automotive construction since 1977. Since these bearings have to operate in a hot environment, engine bearing manufacturers often use the high-performance rubber Therban®. Hydraulic bearings in modern commercial vehicles also deliver greater comfort in the driver’s cab by absorbing shock and vibration and at the same time by isolating the cab from engine noise and road noise.