Electric motors are found in anything that has an electrical movement or solenoid function; familiar examples include refrigerators, washing machines and power tools. In the automotive world, car manufacturers are increasingly employing electric motors for powered windows, seat adjusters and mirrors; they are also now being used in electric power steering (EPS) systems and active suspension and brake systems.
Indeed, with the proliferation of electric motors into these wide ranging applications, OEMs are now keeping a close eye on the motor’s reliability, size, weight and noise generation, as well as the overall system costs. This is pushing the motor manufacturers to re-engineer their designs – for example, there have already been novel advances in motor control. Today, however, OEMs are looking to new advances in electric motor design as well as the system itself. Here the innovative use of tolerances rings is already proving invaluable for an impressively wide range of applications.
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. They are, in other words, a special form of frictional fastener. Typically manufactured from high quality spring steel, stainless steel or specialist spring materials, tolerance rings are invariably custom designed to suit a particular application. All types, however, have one essential characteristic in common – a series of protrusions or ‘waves’ around their circumference. Each of these waves acts as an individual radial spring which, when the tolerance ring is in situ, transfers forces between the mating components. This arrangement means that tolerance rings are capable of handling direct torque transfer, torque slip, axial retention, controlled collapse, radial loading and differences in thermal expansion between the mating components.
Tolerance rings have a major role to play in the design and manufacture of safe, dependable electric motors. They have already been successfully designed into appliance and automotive applications, both within the motor itself or part of the overall assembly: typical mounting examples include stator, sensor, gear and bearings.
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