Suspension damper having piston plate with coined, continuously curved bypass

摘要

A suspension damper or shock absorber for a vehicle suspension system includes a piston assembly across which damping fluid is metered to control relative movement between the vehicle body and chassis. The piston assembly includes a piston plate in which a first set of openings are provided for fluid communication during the rebound stroke of the piston assembly and a second set of openings for communication of damping fluid during the opposite compression stroke. A wall circumscribes the first set of openings to define a recess receiving damping fluid from the first set of openings. A valve disc engages the wall and opens at a predetermined pressure differential. At pressure differentials less than the predetermined pressure differential, highly restricted flow is permitted through a bypass passage formed by a coined depression in the rim of the wall having a continuously curved, preferably semicircular cross section, to provide damping for low level inputs. The curved shape of the bypass passage reduces wear and tear on the coining tooling and also reduces turbulence in fluid flow for greater consistency in flow characteristics.