New Method of Joining a Polygon Mirror Using a Shrink Fitter : Static and Dynamic Properties of Assemblies and Effect of Size on the Flatness of End Surfaces

A conventionally shrink-fitted assembly of an aluminum polygon mirror and a SiC self-acting air bearing becomes loosened at temperatures as low as 60℃ because of the great difference in the thermal expansions of these two components, although it exhibits sufficient strength at room temperature. Temperature rise and centrifugal force in operation deform the mirror end surfaces by the order of hundreds of nano Meters or more. The distorted mirror end surfaces adversely affect the quality of devices such as photocopiers and laser printers. This problem has been solved by using a shrink fitter, which is a new machine element developed in previous work. The shrink fitter is ring-shaped and has several slits in the radial direction. Its material needs to have a higher coefficient of thermal expansion than aluminum. Thus, polyimide was used for the material of the shrink fitter. Dynamic properties, such as jitter and tracking accuracy, of the assembly fabricated using the shrink fitter were one-fifth to one-tenth of those of the conventional assembly. This new joining method eliminates the need for maintenance. The shrink fitter made it easier to attach the polygon mirror to the air bearing. The omission of final cutting of the polygon mirror after fabrication was discussed