| 摘要 |
A seal member is fixed to a predetermined position on an outer peripheral surface of a shaft portion. During rotation of a shaft member, a lower end surface of the seal member is opposed to an upper end surface of a bearing sleeve through an intermediation of a thrust bearing gap to form a second thrust bearing gap. An outer peripheral surface of the seal member defines between itself and an inner peripheral surface of an upper end portion of a housing a seal space having a predetermined volume.
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