| 摘要 |
A rotary member embodying the rotor of a brushless DC motor and having a magnet extending around an axially opening recess is rotatably supported by means of a bearing device on a stationary member which includes a fixed shaft extending into the recess and stator windings arrayed around the fixed shaft on a stator yoke axially confronting the magnet of the rotor to provide a magnetic attraction therebetween constituting at least part of a thrust load; such bearing device comprising first and second ball bearings having outer ring races engaging a cylindrical side wall of the recess in the rotary member and seating against axially spaced first and second annular shoulders, respectively, formed in such side wall and facing axially toward the opening of the recess, while inner ring races of the first and second ball bearings are disposed on the fixed shaft with one of the inner races seating against an additional annular shoulder formed on the shaft and facing axially opposite to the first and second shoulders, and a helical compression spring on the fixed shaft between the inner ring races for axially pre-loading the first and second ball bearing and distributing the thrust load therebetween. |
