Importance

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Abstract

To provide a protective bearing, a bearing unit, and a vacuum pump that are configured to prevent a touchdown bearing from co-rotating with the rotation of a rotor that is supported in a levitated state and a non-contact state. Slits are formed in the radial direction at four sections on the inner side of a securing member. A pair of permanent magnets of the same polarity is fixed to the upper surface of each of the four regions partitioned by the slits. The inner rim of the securing member has projections that are formed circumferentially downward. An attractive force is generated between an outer ring and an inner ring. An attractive force is also generated between the projections projecting toward the inner end of the securing member and the inner ring. Due to this configuration, even when a rotational torque is applied to the inner ring of the touchdown bearing as a result the rotation of the rotating body, co-rotation of the inner ring does not occur due to a large holding torque.

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First Claim