US 5,947,238 A · Passive magnetorheological fluid device with excursion dependent characteristic

Abstract

A magnetorheological fluid device which exhibits excursion (stroke or rotation) dependent resistance (force or torque) which is obtained passively. Linear and rotary embodiments are described. The devices described herein include various ways for passively varying magnetic circuit reluctance to accomplish the stroke or rotation dependent characteristic. The devices include a first component with an internal cavity, a second component received in the cavity and moveable relative to the first component, a working zone created between the first and second component, a magnetorheological fluid contained therein, at least one permanent magnet for producing a magnetic field, a magnetic circuit for directing a magnetic flux created by the permanent magnet toward the magnetorheological fluid in the working zone, and passively varying a magnetic circuit reluctance (such as by changing a thickness of a magnetic return, by changing a gap thickness, by changing the material reluctance, by interacting multiple magnetic fields, or combinations thereof) as a function of excursion. This changes the magnetic field strength acting upon the MR fluid in the working zone and produces a force/torque which varies as a function of excursion (x or .theta.).

Claims21

Dependent claims

A linear magnetorheological fluid device, comprising:

(a) a housing having an internal cavity,
(b) a piston slidably received within said internal cavity and subdividing said internal cavity into a first chamber and second chamber, said piston moveable throughout a linear excursion,
(c) a passageway interconnecting said first and second chambers,
(d) a magnetorheological fluid contained within said first chamber, said second chamber, and said passageway,
(e) at least one permanent magnet for producing a magnetic flux included within at least one of:
(i) said piston, and
(ii) said housing,
(f) a magnetic circuit for directing said magnetic flux created by said at least one permanent magnet through said magnetorheological fluid contained within said passageway,
(g) means for passively varying a reluctance of said magnetic circuit as a function of said linear excursion thereby resultantly changing a density of said magnetic flux acting upon said magnetorheological fluid contained within said passageway and, thereby, passively producing a force which varies as a function of said linear excursion of said device.

6 more elements

Dependencies are inferred from the claim text.

Passive magnetorheological fluid device with excursion dependent characteristic

Life of this patent

Passive magnetorheological fluid device with excursion dependent characteristic

Life of this patent

Abstract

Claims21