Brushless motor for electric power tool

摘要

A brushless motor for the electric power tool is configured such that a rotor having a magnet is radially disposed on the inner side of a stator having winding wires, and a bonded magnet is used as the magnet of the rotor.

主权项

1. A brushless motor for an electric power tool configured such that a rotor having a bonded magnet is radially disposed on the inner side of a stator having winding wires, wherein,
the rotor includes a shaft and the bonded magnet that is radially disposed on the outer side of the shaft; a through hole into which the shaft is inserted is axially formed at the center of the bonded magnet; a resin is filled between an inner peripheral surface of the through hole and an outer peripheral surface of the shaft; an inner wall surface of the through hole of the bonded magnet and the outer peripheral surface of the shaft are shaped such that rotation of the shaft with respect to the bonded magnet is prevented through the resin; a plurality of grooves that extend in an axial direction are formed on the inner wall surface of the through hole of the bonded magnet in a circumferential direction; the number of the grooves is configured to be larger than the number of poles of the bonded magnet; a resin block that is integrally formed with the shaft and is provided on the outside of the shaft in the radial direction such that rotation of the resin block with regard to the shaft is prevented; and an axial end surface of the resin block has a plurality of first recesses and a plurality of first protrusions that are arranged in a circumferential direction, the first recesses and the first protrusions being alternately arranged, and further wherein an axial end surface of the bonded magnet has a plurality of second protrusions and a plurality of second recesses that are arranged in a circumferential direction, the second protrusions and the second recesses being alternately arranged, and further wherein by engaging the plurality of the first recesses and the plurality of the first protrusions with the plurality of the second protrusions and the plurality of the second recesses, respectively, the axial end surface of the resin block is configured to be engaged with the axial end surface of the bonded magnet in the circumferential direction.