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Saint-Gobain Performance Plastics improve design of powertrain components

04 November 2010

Two small components from Saint-Gobain Performance Plastics – Rencol tolerance rings and Norglide self-lubricating plain bearings – are significantly improving the performance of automotive powertrain components. Both can be used in dual mass flywheels while the use of Norglide bearings in decoupled pulleys (shown opposite) has contributed to a change of design.

Originally, pulley decoupling forces were generated by an elastomeric connection between the two components but recent industry demands for higher torque and temperature operation have stretched the durability of such systems. In the latest designs, energised springs initiate mechanical decoupling and a Norglide plain bearing is included in the system to cope with higher temperatures and aging issues pertaining to the elastomeric connection.
 
Norglide bearings have fluoropolymer-based functional layer reinforced by a metal backing. The pulley application uses the product’s full potential, including the ability to specify components with specifically tailored geometries and sliding surface compositions.
 
A dual mass flywheel, or DMF, (see illustration opposite) smoothes engine pulses by transmitting torque to the transmission through two flywheels connected via springs. The oscillating motion between the flywheels is much better suited to the properties of Norglide bearings (which are virtually maintenance free) than it is to roller or ball bearings, which can suffer from a lack of grease take-up due to  high-frequency, small movements of the system. In addition, Norglide bearings are less expensive, require less space, compensate for minor misalignments and reduce NVH (noise, vibration and harshness).
 
Rencol tolerance rings are also used in the DMF. These precision fasteners, manufactured from stainless or hardened carbon steel, have a special geometry that allows them to behave like radial springs. They are press fitted between mating components – in the case of the DMF, a flange and fixing ring.


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