NSK has developed an automatic belt tensioning device with viscous
damper, which is claimed to reduce both high frequency tensional
variations and belt noise. Aimed mainly at automotive applications, the
new tensioner requires only a small space envelope, and is easy to
retrofit. Its operation relies on a multi-plate damper, which exploits
the viscous resistance of silicone oil contained between the inner and
outer plates. The damper capacity depends on the number of plates
employed, the gap between the plates and the oil viscosity.