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Enclosed miniature motor

  • US 4,755,699 A
  • Filed: 09/24/1984
  • Issued: 07/05/1988
  • Est. Priority Date: 09/22/1983
  • Status: Expired due to Term
First Claim
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1. An enclosed, miniature, brushless, cylindrical-air-gap d.c. motor, comprisinga generally cylindrical external housing having two axial ends,interiorly of the external housing a stator,internally of the stator a permanent-magnet rotor having a total of one north and one south pole,a rotor shaft,means mounting the rotor coaxially with the rotor shaft for joint rotation of the two, with the rotor shaft projecting outwardly from one axial end of the external housing and furthermore mounting the stator coaxially with the permanent-magnet rotor, said means including an axial bearing mounted at one of said ends of the external housing, the rotor shaft having an axial end which axially bears against said axial bearing,a three-phase stator winding mounted to cooperate with the stator, the three-phase stator winding consisting of three phases which comprise a plurality of stator coils provided with feed lines for connecting the three phases to a circuit for energizing the three phases, the stator further comprising radially extending pole portions, which include coil carrying portions and circumferentially extending pole shoe portions,the stator, except for the circumferentially extending pole shoe portions, being substantially entirely constituted by a stack of sheet-metal sheets,the stator for the circumferentially extending pole shoe portions being in the form of pole-shoe plates provided at the radially inner end of each coil-carrying portion and extending in the axial direction of the rotor shaft in a first axial direction beyond the stator'"'"'s sheet-metal stack and also extending in the opposite second axial direction beyond the stator'"'"'s sheet-metal stack, the permanent-magnet rotor having two axial ends, andat least one magnetic-field responsive rotor position sensor and means mounting the latter in the region of one of the axial ends of the rotor at a location which is in the region of the axially travelling stray flux emanating from the rotating permanent-magnet rotor,each pole-shoe plate being provided with comb-like parallel slits which extend parallel to the rotation direction and are spaced one from the next in the axial direction of the motor.

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