| 摘要 |
<p>PURPOSE:To obtain a high precision gap and hence to effectively improve seal effect by utilizing an outer race of a ball bearing supporting a rotor hub and providing a labyrinth gap between the outer circumferential surface of this outer race and the inner circumferential surface of a base supporting cylinder. CONSTITUTION:A base 1 to be a fixed member is formed with an annular recessed part 2 in an appropriate place, and a boss part 3 is provided to be projected in the center of this part 2, and a fixed shaft 5 is forcibly fitted and fixed in this center hole 4, and then the rotor hub 8 is freely rotatably supported via the upper and lower ball bearings 6 and 7 by the shaft 5. A short supporting cylinder 13 is projectingly provided on the upper surface of the boss part 3, and this outer circumference is fitted into a stator 14, to which a rotary magnet 12 fixed via a slight gap to the hub 8 is opposed. The inner circumference of the supporting cylinder 13 is made to be a some small diameter and this is regared as a labyrinth gap surface 13a, which is opposed to the outer race of the ball bearing 7 via a gap G1 so as to make the labyrinth effect sufficient. Then, the level of the lower end of an inner circumferential part of the hub 8 supported by the ball bearings 6 and 7 is raised to be positioned in the middle part of the ball bearing 7, so that the seal length is secured enough.</p> |
