Cup shaped magnetic pickoff for use with a variable reluctance motion sensing system
First Claim
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1. A magnetic pickoff comprising:
- a ferromagnetic cup-like outer pole piece having;
a central axis, a hollow walled member having a first and second end and an end member, said end member enclosing said second end of said walled member forming a cylindrical cavity and where said first end is maintained perpendicular to said central axis forming a first pole face;
a cylindrical inner pole piece mounted within said walled member upon said end member, colinear to said central axis, forming a toroidal coil space therebetween;
said inner pole piece having a second pole face opposite said end member;
said inner pole piece further comprising;
source means for causing said inner and said outer pole pieces to achieve opposite magnetic polarities so that magnetic flux flows between said outer and said inner poles forming a first magnetic circuit;
signal generating means responsive to the rate of change of the magnitude of flux flowing within said primary circuit and wherein said outer pole piece, said inner pole piece and said source means cooperate to provide a first means for causing the average flux density per unit area flowing through said second pole face to be greater than the average flux density per unit area flowing through said first pole face wherein the area of said first pole face is determined by the radii r3 -r2 wherein r3 and r2 correspond to the radii defining the thickness of said walled member, andwhere the area of said second pole face is determined by the radius r1 and wherein (r32 -r22) is greater than r12 such that the area of said first pole face is greater than the area of said second pole face, andwherein said first means additionally consists of said end member having a thickness, b, and where the thickness of said end plate and the radius r1, of said inner pole piece, are related so that 2b is greater than r1 therein providing a low flux density path throughout said end plate therein avoiding saturation of said end plate and reducing stray fields.
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Abstract
A crankshaft position sensor having a reluctance sensing magnetic pickoff cooperating with sense features on a nearby, rotating sense wheel. The sense features are filled with a nonmagnetic electrically conductive material to enhance uniform eddy current flow within the sense wheel and where the magnetic pickup contains two coaxial magnetically polarized pole pieces.
52 Citations
1 Claim
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1. A magnetic pickoff comprising:
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a ferromagnetic cup-like outer pole piece having; a central axis, a hollow walled member having a first and second end and an end member, said end member enclosing said second end of said walled member forming a cylindrical cavity and where said first end is maintained perpendicular to said central axis forming a first pole face; a cylindrical inner pole piece mounted within said walled member upon said end member, colinear to said central axis, forming a toroidal coil space therebetween;
said inner pole piece having a second pole face opposite said end member;said inner pole piece further comprising; source means for causing said inner and said outer pole pieces to achieve opposite magnetic polarities so that magnetic flux flows between said outer and said inner poles forming a first magnetic circuit; signal generating means responsive to the rate of change of the magnitude of flux flowing within said primary circuit and wherein said outer pole piece, said inner pole piece and said source means cooperate to provide a first means for causing the average flux density per unit area flowing through said second pole face to be greater than the average flux density per unit area flowing through said first pole face wherein the area of said first pole face is determined by the radii r3 -r2 wherein r3 and r2 correspond to the radii defining the thickness of said walled member, and where the area of said second pole face is determined by the radius r1 and wherein (r32 -r22) is greater than r12 such that the area of said first pole face is greater than the area of said second pole face, and wherein said first means additionally consists of said end member having a thickness, b, and where the thickness of said end plate and the radius r1, of said inner pole piece, are related so that 2b is greater than r1 therein providing a low flux density path throughout said end plate therein avoiding saturation of said end plate and reducing stray fields.
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Specification
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Current AssigneeSiemens-Bendix Automotive Electronics LP
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Original AssigneeThe Bendix Corporation (Honeywell International Inc.)
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InventorsKolter, Roland K.
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Primary Examiner(s)Strecker, Gerard R.
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Assistant Examiner(s)Snow, Walter E.
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Application NumberUS06/038,145Time in Patent Office1,467 DaysField of Search324/166, 324/173, 324/174, 324/207, 324/208, 324/239, 324/228, 310/155, 310/168, 310/169US Class Current324/239CPC Class CodesG01P 3/488 delivered by variable reluc...
