It is a well-known fact that limited reserves of petroleum are forcing humankind to develop completely new drive concepts based on hydrogen and renewable energy in the long term. Nevertheless, according to Prof. Dr. P. Tenberge, an expert in hybrid propulsion systems from the University of Chemnitz, Germany, “today’s vehicles still have sufficient development potential for halving fuel consumption. This potential is rooted in their ability to reduce the vehicle’s power input in specific driving situations, to generate power more efficiently, and to manage energy in new ways.” One simple and topical way of reducing power input is to reduce the friction forces at shaft seals. To make this possible, Freudenberg Dichtungs- und Schwingungstechnik has developed a springless radial shaft seal known as the energy-saving Simmerring (ESS for short). In old radial shaft seals, the spring was responsible for creating the necessary contact pressure force that kept the sealing lip on the shaft surface. This ensured a long-term sealing effect. The radial shaft seal acted like a microscopic pump, which was in a position to transport lubricants beneath the sealing lip and back into the oil chamber. This created the necessary lubrication between the shaft and the seal ring. The radial contact pressure force of the sealing lip is of paramount importance for the functioning of the seal, abrasion resistance, and friction. Excessively high radial forces increase wear, overheat the sealing edge, make the oil coke, and result in energy losses and leakages. Insufficient radial forces prevent the sealing lip from sitting securely on the shaft, thereby causing leakages and oil drips.
In order to keep friction forces to a minimum and to simultaneously optimize the function of the seal, Freudenberg developed the ESS. In this seal, the radial force remains stable at a low level over a broad speed range even as the temperature in the joint gap rises. This was made possible by the development of a special elastomer compound and a completely new design. Thanks to this springless radial shaft seal, losses generated by friction can be reduced by up to 50 W for a shaft with a diameter of 45 mm at a speed of 6,000 1/min. This springless radial shaft seal is therefore an easy way of making a sustainable contribution to the reduction of power input in vehicles. It is also the ideal basis for engines in hybrid concepts.