Patent ID: 8051961

Claim:
A variable damper, comprising: a cylinder filled with magnetic fluid or magneto-rheological fluid therein and having an end connected to one of a vehicle side member and a wheel side member; a piston slidably received in the cylinder to separate an interior of the cylinder into two chambers and provided with a flow passage communicating the two chambers; and a piston rod extending out of an end of the cylinder remote from the one end thereof, and having an outer end connected to the other of the vehicle side member and the wheel side member and an inner end connected to the piston; the piston comprising a cylindrical outer yoke defining an outer peripheral part of the piston, an inner yoke coaxially received in the outer yoke at a prescribed gap and a coil retained in the inner yoke to provide a magnetic flux extending across the gap, the gap providing at least a part of the flow passage; the piston further comprising a slide member defining a space between an outer circumferential surface of the outer yoke and an inner circumferential surface of the cylinder, wherein the slide member comprises a piston cover that covers an outer circumferential surface of the outer yoke; wherein the piston cover comprises a pair of axial ends crimped onto corresponding axial ends of the piston; and wherein the piston further comprises a pair of end plates disposed on either axial end of the inner yoke, and held in position by the axial ends of the piston cover crimped thereon, each end plate being made of non-magnetic material and provided with openings along an outer periphery thereof so as to form a part of the flow passage.