Tolerance rings shed weight

Paul Boughton

Thanks to rapidly rising fuel prices, consumer demand is forcing car manufacturers to improve the efficiency of their cars by any means possible – lightweight EPAS Systems are already being adopted, for instance.

To help car manufacturers meet the ever challenging CO2-emission targets, the traditional hydraulic steering system is being replaced by the lighter and more cost-effective electric power assisted steering (EPAS) system.
 
So much so, some analysts predict that a staggering 10.7 million EPAS systems will be fitted to vehicles built in Western Europe by 2013. However, as fuel prices continue to rise, manufacturers are keen to consider each and every technique that can decrease the overall weight of the car, and hence increase efficiency, further. The innovative application of tolerance rings is proving very attractive.

Tolerance rings are already used in the steering column allowing it to slide or collapse longitudinally should the steering wheel be struck by the driver during a collision. Another steering related application for tolerance rings is bearing mounting, where they guard against problematic (noise, vibration and hardness) resonances and ensure good performance over a range of component tolerances and operating temperatures throughout the car’s lifetime. They are now being used as a slipping element in steering column locks, enabling them to withstand the 100Nm force prescribed by EU regulations.

The idea behind tolerance rings is very straightforward – they’re simply radially sprung steel rings that are designed to be press fitted between two mating components, such as a motor shaft and a take-off pulley. Lightweight and simple to use they are, in other words, a special form of spring fastener. In production quantities, these tolerance rings cost a few pence.

The increased adoption rate of EPAS systems has now brought the weight saving benefits of these special steel fasteners into sharp focus. Using tolerance rings for motor mounting, is also becoming widely accepted in EPAS systems. These radially sprung steel fasteners help to absorb shock transmitted from the engine, as well as fixing the stators within the drive motors themselves, where they hold the stator securely in place while reducing the levels of vibration to which it is exposed, allowing considerable savings in both size and weight.

Tolerance Rings are usually purpose-designed for each application, with engineers from Rencol working closely with designers from the early stages of development.


Saint-Gobain Performance Plastics Rencol

Recent Issues