The application of tolerance rings to provide shock overload protection in EPAS systems

摘要

Tolerance Rings have traditionally been used to compensate for component tolerances or differential thermal expansion effects but developments in Tolerance Ring technology are enabling them to be more widely used as simple, low-cost, non-destructive overload protection devices. By following suitable design principles, detailed in this paper, tolerance rings can be designed to operate as shock overload protection devices within existing component space envelopes whilst also allowing reduction in design strength of other components in the drive system. The factors to be considered in selecting between various alternative tolerance ring positions within the EPAS electric drivetrain are explained. The effects of mating component and tolerance ring variation on the performance of the overall system are detailed. Examples of the use of Tolerance Rings in production EPAS systems are outlined.