| 摘要 |
PURPOSE:To prevent a change in internal pressure due to a change in temperature, and obtain a bearing with excellent durability by including a plurality of radial bearing sections, and by providing grooves in a herringbone form for the generation of dynamic force and a vent hole onto the outer circumference of a shaft body and an outer cylinder respectively. CONSTITUTION:A shaft body 1 is formed with a large diameter section 11 having a semispherical recessed bearing surface 31 at its one end, and with a small diameter section 12 having a radial bearing surface 14 including grooves N in a herringbone form. An end plate 5 is fitted on the upper section of an outer cylinder 2, and a projected bearing surface 32 in a spherical form is fixed at an inner end, and a pocket hole 21 is formed to accept the large diameter section 11 of the shaft body 1 for preventing the outer cylinder 2 from being separated from the shaft body 1. In addition, a vent hole 7 is also provided to the outer cylinder 2. An armature and a stator are installed onto the outer cylinder 2 and the shaft body 1 respectively. And at the time of rotation, the outer cylinder 2 is pressed to the bearing surface 31 by magnetic force for preventing floating thereof more than is necessary because of dynamic pressure generated in a bearing surface 4 and for preventing load from being unstable.
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