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US 4,896,544 AGranted
Magnetoelastic torque transducer
AssigneeMag Dev Inc.
InventorIvan J. Garshelis
Life of this patent
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AssigneeMag Dev Inc.
InventorIvan J. Garshelis
Estimating the term…
A magnetoelastic torque transducer for providing an electrical signal indicative of the torque applied to a member, the member including ferromagnetic, magnetostrictive means affixed to, associated with or forming a part of the surface of the torqued member for altering in magnetic permeability in response to the application of torque to the member. The ferromagnetic, magnetostrictive means is advantageously formed of a thermally hardened or iron-nickel martensite hardenable steel alloy characterized by a substantially isotropic magnetostriction having an absolute value of at least 5 ppm and including from 0.05 to 0.75 percent by weight carbon and sufficient of one or more elements selected from Ni, Cr, Co, Ti, Al, Mn, Mo, Cu and B to raise the alloy magnetostriction to at least 5 ppm absolute. Preferably, the ferromagnetic, magnetostrictive means is formed of nickel maraging steel. The transducer comprises a pair of axially spaced-apart annular bands defined within a region of the ferromagnetic, magnetostrictive means, the bands being endowed with residual stress created, respectively symmetrical right and left hand helically directed magnetic anisotropy of sufficiently large magnitude that the contribution to total magnetic anisotropy of any random anisotropy in the member is negligible. In one aspect of the invention, each said band has at least one circumferential region which is free of residually unstressed areas over at least 50% of its circumferential length. In another aspect of the invention, the alloy is thermally hardened before the bands are endowed with the residual stress-created magnetic anisotropy.
A magnetoelastic torque transducer for providing an electrical signal indicative of the torque applied to a member, said member having a ferromagnetic and magnetostrictive region formed of a thermally hardened steel alloy characterized by a substantially isotropic magnetostriction having an absolute value of at least 5 ppm and including from 0.05 to 0.75 percent by weight carbon and sufficient of an element selected from the group consisting of nickel, chromium, cobalt, titanium, aluminum, manganese, molybdenum, copper, boron, and combinations thereof to raise said alloy magnetostriction value to said at least 5 ppm absolute, said transducer comprising:
A magnetoelastic torque transducer for providing an electrical signal indicative of the torque applied to a member, said member having a ferromagnetic and magnetostrictive region, said transducer comprising:
In a magnetoelastic torque transducer for providing an electrical signal indicative of the torque applied to a member including ferromagnetic, magnetostrictive means associated with said member for altering in magnetic permeability in response to the application of torque to said member, means for applying a magnetic field to said ferromagnetic magnetostrictive means, means for sensing the change in permeability caused by said applied torque, and means for converting said sensed change in permeability to an electrical signal indicative of the magnitude of the torque applied to said member, the improvement comprising forming said ferromagnetic, magnetostrictive means from a thermally hardened steel alloy characterized by a substantially isotropic magnetostriction having an absolute value of at least 5 ppm and including from 0.05 to 0.75 percent by weight carbon and sufficient of an element selected from the group consisting of nickel, chromium, cobalt, titanium, aluminum, manganese, molybdenum, copper, boron, and combinations thereof to raise said alloy magnetostriction value to said at least 5 ppm absolute.
In a method of sensing the torque applied to a member having ferromagnetic, magnetostrictive means associated therewith which includes the steps of applying a magnetic field to said ferromagnetic, magnetostrictive means, sensing the change in permeability caused by said applied torque and converting said sensed change in permeability to an electrical signal indicative of the magnitude of the applied torque, the improvement comprising forming said ferromagnetic, magnetostrictive means of a thermally hardened steel alloy characterized by a substantially isotropic magnetostriction having an absolute value of at least 5 ppm and including from 0.05 to 0.75 percent by weight carbon and sufficient of an element selected from the group consisting of nickel, chromium, cobalt, titanium, aluminum, manganese, molybdenum, copper, boron, and combinations thereof to raise said alloy magnetostriction value to said at least 5 ppm absolute.
In a method of sensing the torque applied to a member having a ferromagnetic and magnetostrictive region including the steps of endowing at least a portion of said region with helically directed residual stress-created magnetic anisotropy, applying a cyclically time varying magnetic field to said portion and to an area of said member not so endowed, and sensing the permeability difference between said portion and said area resulting from the application of torque to said member, the difference being indicative of the magnitude of the applied torque, the improvement comprising forming said region of a thermally hardened steel alloy characterized by a substantially isotropic magnetostriction having an absolute value of at least 5 ppm and including from 0.05 to 0.75 percent by weight carbon and sufficient of an element selected from the group consisting of nickel, chromium, cobalt, titanium, aluminum, manganese, molybdenum, copper, boron, and combinations thereof to raise said alloy magnetostriction value to said at least 5 ppm absolute.
In a method of sensing the torque applied to a member having a ferromagnetic and magnetostrictive region, including the steps of endowing a pair of axially spaced-apart annular bands within said region with respectively symmetrical right and left hand helically directed magnetic anisotropy, applying a cyclically time varying magnetic field to said bands, and sensing the permeability difference between said bands resulting from the application of torque to said member, the difference being indicative of the magnitude of the applied torque, the improvement comprising:
Dependencies are inferred from the claim text.