Low damping torque brushless D.C. motor
AssigneeHHK Inc.
InventorEmil S. Mihalko
Life of this patent
Estimating the term…
Abstract
A brushless D.C. motor, suitable for use as a hand-held surgical tool, includes a field of self-supporting coils arranged between a pair of impregnated fiberglass epoxy sheets situated in an air gap formed by a rotatable shaft having an even-number plurality of magnets formed thereon, and a non-electrically conductive housing. The individual magnets abut one another upon the shaft to prevent a magnetic return path from the substantially unidirectional field produced thereby, and are formed in relationship to the coils such that a single rotor pole will never be under a single coil, in order to minimize induced shorted currents.
Claims22
An improved brushless D.C. motor, comprising:
- a rotor including a plurality of permanent magnets radially spaced apart affixed to a rotatable shaft, each said magnet having a coercive force capable of providing a substantially unidirectional field, a longitudinal centerline, an outer arcuate surface, and an inner surface between a pair of corners;
- a plurality of coils formed in a cylindrical array about said rotor each said coil comprising electrical conductors formed in a polygonal array having a predetermined number of turns and including at least two parallel sides with respective centerlines spaced by a predetermined distance approximately equal to said outer arcuate surface, and being substantially perpendicular to said magnetic field, said parallel sides each having a width substantially the same as but no greater than the space between adjacent magnets;
- commutation sensing means mounted contiguously upon preselected ones of said plurality of coils for detecting the magnitude and polarity of said magnetic field produced by said permanent magnets;
- a housing surrounding said plurality of coils with said commutation sensing means and said rotor;
- and
- control means coupled to said plurality of coils and said commutation sensing means for providing power thereto and commutating said rotor.
A hand-held surgical tool, comprising:
- a motor portion including a brushless D.C. motor comprising:
- a rotor including an even plurality of permanent magnets radially spaced apart affixed to a rotatable shaft separated each from the other 360/N mechanical degrees between their respective centerlines where N is the number of magnets, each said magnet having a coercive force capable of producing a substantially unidirectional field;
- a plurality of coils formed in a cylindrical array about said rotor, each said coil comprising electrical conductors formed in a polygonal array having a predetermined number of turns and including at least two sides parallel with said shaft with their respective centerlines spaced by a predetermined distance, and being substantially perpendicular to said magnetic field;
- commutation sensing means mounted contiguously upon preselected ones of said plurality of coils for detecting the magnitude and polarity of a magnetic field produced by said permanent magnets;
- a housing surrounding said plurality of coils with said commutation sensing means and said rotor;
- an adaptor portion coupled to said motor portion for transmitting a torque supplied by said shaft;
- and
- a workpiece coupled to said adaptor portion, said workpiece being adapted to rotate with said torque by said shaft.
Dependencies are inferred from the claim text.