Patent ID: 6133664
Filing Date: 2000-10-17
Classification: H02K

Abstract:
A self-starting brushless electric motor, comprisinga first motor part (11) including a plurality of pole units arranged in a first spaced-apart relation in a first pole row,a second motor part (16) including a plurality of poles arranged in a second spaced-apart relation in a second pole row,bearing means supporting the first motor part and the second motor part for relative movement with the first pool row confronting the second pole row across an air gap,the first and second pole rows comprising pole types including reluctance poles and permanent-magnet poles which are polarized transversely to the air gap, anda polyphase winding system (15) on the first motor part comprising winding coils respectively arranged in association with each pole unit to produce a magnetic field linking poles of the second pole row to poles of the first pole row through the pole unit upon energization of the coil,at least one of the first pole row and the second pole row exhibiting a magnetic asymmetry providing a preferential relative direction of movement of the motor parts upon energization of the winding system,wherein:the winding system winding coils comprise at least one first-phase coil (15U) forming part of a first-phase winding and at least one additional-phase coil (15V) forming part of an additional-phase winding andone of the pole types comprises common-type poles associated with each of the phase windings of the winding system, the common-type poles being common to all phase windings and included in at least one pole unit in each of the phase windings, andthe common-type poles of the pole units of the first pole row are spaced apart such that the relative movement of the first motor part and the second motor part includes a relative position in whichone of the common-type poles, belonging to a pole unit associated with a winding coil of one of the phase windings, is in an attracted position with respect to one of the poles of the second pole row, andall poles of the second pole row are in non-attracted positions with respect to the common-type poles of the first pole row associated with a winding coil or coils belonging to a different one of the windings;the common-type poles of the first pole row are reluctance poles,the poles of the second row are substantially evenly spaced reluctance poles, andeach pole unit of the first pole row comprises a reluctance pole and a permanent-magnet pole spaced from the reluctance pole along the pole row by a distance corresponding to one-half of a spacing of poles along the second pole row;the second pole row includes reluctance poles including an auxiliary pole part projecting from a main pole part in the preferential direction of relative movement; andwherein the pole units of the first pole row include one of reluctance and permanent-magnet poles comprising an auxiliary pole part projecting from a main pole part in the preferential direction of relative movement.