Tolerance Rings

Tolerance Rings are radially sprung rings that are press fitted between two mating components to act as frictional fasteners. They are flexible shims designed to fix two cylindrical parts together. The wavelike protrusions that run around the circumference of the ring generate a retention force to provide an optimal fit between the two mating components without the need for adhesive or excessive assembly force, simplifying the process for manufacturers. They allow for any misalignment caused by thermal expansion or excessive vibration. Tolerance rings can be used as bearing mounts and as a means of dealing with torque transfer, torque overload protection and axial slip between mating components. They are often used to isolate undesirable vibration in engines and electric motors, for noise-free mechanism operation in passenger vehicles and domestic appliances, where noise reduction has become a major trend in recent years. Modifications to tolerance rings can be made to tune the dynamic stiffness and, therefore, the frequencies that can be isolated.

Tolerance rings can be used to eliminate noise completely, simply by taking up clearance between mating components, which could otherwise lead to rattling in the system as the parts are not completely constrained.

Tolerance rings are used in a number of mechanisms throughout the automotive powertrain and steering systems, as well as the car interior and exterior. Their torque limiting and overload capabilities allow them to be used as simple clutch devices in several applications, such as the automatic tailgate motor and the collapsible steering column. They are also used by automotive manufacturers to mount bearings in hinges and gears in the power train.

Their lightweight properties have also made tolerance rings attractive to automotive manufacturers as they seek to enhance car performance while complying with government requirements for reductions in carbon emissions. In the European Union, regulations on car emissions have been introduced by the European Commission, restricting the amount of carbon dioxide (CO₂) emissions that a car can emit. Since 2015, EU law requires that new cars do not emit more than 130 grams per kilometer of carbon dioxide (CO₂). If that limit is breached then manufacturers can face fines. From 2021 the new mandatory emission target will be a fleet average of 95 grams per kilometer.China is beginning to introduce legislation to create a National Standard, based on carbon emission reduction regulations already in effect in Europe. The U.S. Environmental Protection Agency (EPA) requires automotive companies to average carbon dioxide (CO₂) tailpipe emissions at 101 grams per kilometer (163 grams/mile) by model year 2025. These regulations require car manufacturers to reduce the weight of their engines and vehicles to enhance fuel efficiency. According to the EPA estimations, every 10 per cent drop in car mass decreases fuel use between 5 and 10 per cent.

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