Supercharger torsion damping mechanism with friction damping

Abstract

An intake manifold (18) for an engine (10) includes a Roots-type supercharger (26) having a torsion damping mechanism (54) for reducing audible gear tooth rattle of timing gears (72,74) which prevent contact of meshed lobes (28c,29a) of the supercharger rotors (28,29). The damping mechanism includes a drive member (90) having an annular band portion (90d) banded about an annular member (100) formed of relatively soft elastomeric material which is fixed for rotation with the drive member via lugs (90e). The member (100) includes three arcuate slots (100d) each defining forward and reverse direction stops (100e,100f) for limiting movement of pins (94) slidably disposed at one end in the slots and fixed at the other end to the gear (74). A torsion spring (96) of low rate resiliently connects the annular member to the pins for reducing the audible gear tooth rattle. Member (100) is snugly constrained against deformation by the annular band (90 d) and audible impacts of the stops (100e,100f) are mitigated by the soft material of the annular member (100). A second spring (98) resiliently opposes negative torque spikes to further mitigate audible impacts of stops (100f), a friction damper (99) is operative in response to negative torque effecting flexing of the second spring for further mitigating audible impacts of stops (100f).