Patent ID: 7958979

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; wherein the inner yoke comprises at least two parts that are joined to each other in an axial direction; and the two parts of the inner yoke jointly define an hourglass-shaped profile including a pair of substantially conical surfaces while the outer yoke defines a substantially complementary inner circumferential surface opposing the outer profile of the inner yoke at a prescribed gap.