Patent ID: 8651250
Filing Date: 2014-02-18
Classification: F16F

Abstract:
1. A magnetorheological device comprising: a piston having a high magnetic permeability and extending along an axis from a first end to a second end axially spaced from said first end; a rod having a high magnetic permeability connected to and extending from said first end of said piston along said axis; a case element surrounding at least a portion of said piston to define a passage between said piston and said case element; a first magnetic flux generator including a permanent magnet to generate bias magnetic flux between said piston and said case element; a second magnetic flux generator including an electromagnet for providing controllable magnetic flux between said piston and said case element; wherein said first magnetic flux generator is disposed radially outwardly of said second magnetic flux generator; said second magnetic flux generator surrounding a portion of said piston and said first magnetic flux generator surrounding at least a portion of said second magnetic flux generator and disposed adjacent said passage; a first magnetic gap having a low magnetic permeability being less than said high magnetic permeability of said piston and said rod and interconnecting said rod and said piston in an arrangement where said rod is devoid of contact with said piston for reducing magnetic influence of said magnetic flux generators on said rod and influencing the bias magnetic flux of said permanent magnet and the controllable magnetic flux of said coil to substantially cancel each other along said passage; said piston including a second magnetic gap having a low magnetic permeability being less than said high magnetic permeability of said piston disposed radially inwardly of at least one of said magnetic flux generators to define a cylindrical shape extending annularly within said piston with respect to said axis and longitudinally from one of said magnetic flux generators to a position flush with at least one of said ends of said piston for reducing leakage of the bias magnetic flux from said permanent magnet and influencing the bias magnetic flux of said permanent magnet and the controllable magnetic flux of said coil to substantially cancel each other along said passage; and said first magnetic gap and said second magnetic gap each made of aluminum or non-magnetic stainless steel.