Limited rotation motor
AssigneeGeneral Scanning, Inc.
InventorPierre J. Brosens
Life of this patent
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Abstract
A limited rotation motor has a stator and a rotor mounted for limited rotation relative to the stator. The stator is constructed to conduct bias flux through magnetic circuits that extend across air gaps between the stator and the rotor and a drive system produces drive flux which is conducted through magnetic circuits that extend across air gaps between the stator and rotor to drive the rotor. The stability of radial rotor position in its support bearings is enhanced by an imbalance in the bias flux magnetic circuits which continually produces a resultant radial force on the rotor so that a well defined radial position of the rotor is maintained over the range of limited rotation that the rotor moves in response to the drive system.
Claims22
A limited rotation motor useful in an optical scanner or the like comprising a stator that defines a plurality of axially extensive stator poles,
- an axially extensive rotor mounted for limited rotation relative to said stator and having axially extensive rotor poles for interaction with said stator poles,
- an axially extending rotor shaft at each end of said rotor, a bearing on each said rotor shaft for radially supporting said rotor relative to said stator so that an axially extensive air gap is defined between each rotor pole and adjacent stator poles,
- one of said shafts adapted to carry a device such as a mirror for rotation therewith,
- a restoring force arrangement for locating said rotor in an initial reference position and tending to restore said rotor to said initial reference position when said rotor has been rotated from said reference position,
- drive coil means on said stator for producing drive flux, said stator being constructed to conduct said drive flux through magnetic circuits that extend across air gaps between faces of said stator poles and said rotor poles to interact with bias flux to change the angular position of said rotor,
- said stator including effectively opposed bias flux magnetic circuits that extend across air gaps between faces of said stator poles and said rotor poles which produce radial forces acting upon said rotor effectively in opposite radial directions, a face of a pole in one of said bias flux magnetic circuits having a transversely extending discontinuity of limited axial extent at a selected position along the axial length of said pole face whereby the radial forces produced by said bias flux magnetic circuits are unbalanced to continually produce a resultant radial force of relatively small value compared to the total radial force provided by a given said bias flux, said resultant radial force effective to urge said rotor and its shafts radially in its said bearings to maintain a well defined radial position of said rotor over the range of limited rotation of said rotor while major portions of the applied radial forces produced by said bias flux magnetic circuits are effectively opposed and do not have load effect on said bearings.
A limited rotation motor comprising a stator assembly that defines a plurality of axially extensive stator poles and carries a drive coil,
- an axially extensive rotor defining a plurality of axially extensive rotor poles,
- an axially extending shaft at each end of said rotor, a bearing assembly on each said shaft for radially supporting said rotor relative to said stator assembly so that an axially extensive air gap is defined between each rotor pole and adjacent stator poles,
- said stator assembly including bias flux magnetic circuits that extend across air gaps between faces of said stator poles and said rotor poles which produce radial forces acting upon said rotor effectively in opposite radial directions, each said bias flux magnetic circuit including a permanent magnet, a face of a pole in one of said bias flux magnetic circuits having a transversely extending discontinuity of limited axial extent at a selected position along the axial length of said pole face whereby the radial forces produced by said bias flux magnetic circuits are unbalanced and continually produce a resultant radial force of relatively small value compared to the total radial force provided by a given said bias flux, said resultant radial force being effective to urge said rotor and its shafts radially in its said bearing assemblies to maintain a well defined radial position of said rotor over the range of limited rotation of said rotor while major portions of the applied radial forces produced by said bias flux magnetic circuits are effectively opposed and do not have load effect on said bearing assemblies, said stator assembly being constructed to conduct drive flux produced by said drive coil through magnetic circuits that extend across air gaps between said stator poles and said rotor poles to interact with bias flux to change the angular position of said rotor,
- and a bias arrangement between said rotor and said stator assembly for producing a force tending to restore said rotor to a rest position.
Dependencies are inferred from the claim text.