A rotating portion includes a hollow shaft extending along a central axis. The hollow shaft includes a through hole passing therethrough in an axial direction. The rotating portion includes an upper screw to close an upper opening that is an opening at an upper end portion of the through hole. The rotating portion includes a lower screw to close a lower opening that is an opening at a lower end portion of the through hole. The hollow shaft includes an upper groove portion into which the upper screw is screwed at the upper opening. The hollow shaft includes a lower groove portion into which the lower screw is screwed at the lower opening. A lubricating oil is in contact with the lower screw. The lower groove portion is shorter in axial length than the upper groove portion, and the lower screw is smaller in axial pitch than the upper screw.

A hollow shaft includes a hollow portion extending in an axial direction from an opening that is open at one end of the hollow shaft in the axial direction. The hollow shaft further includes a first communicating hole establishing radial communication between the hollow portion and an axial space between an upper lubricating oil and a lower lubricating oil. The hollow shaft further includes a second communicating hole establishing radial communication between the hollow portion and an unsealed space inside the motor. The unsealed space is connected to an external space outside the motor. The hollow shaft further includes a sealing member closing the opening. The hollow shaft has, in an inner peripheral surface facing the hollow portion, a recess recessed radially outward. A part of the sealing member is fitted into the recess.

According to one embodiment, linear motor translator assembly for use in an electromagnetic actuator is provided. The linear motor translator assembly comprises: a cylindrical housing having a first end, a second end opposite the first end, a flanged portion at the second end, and a blind hole initiating at the second end and extending into the cylindrical housing to a blind hole base; a tubular body located within the blind hole, the tubular body including a plurality of permanent magnets; and an end cap securely fastened to the flanged portion.

This motor includes a base and a circuit board arranged on a lower surface of the base. The base includes a first annular portion and a second annular portion. The first annular portion is arranged under a stator. The second annular portion is arranged under a flange portion of a hub. A conducting wire drawn out from the stator is arranged to pass through a through hole defined in the first annular portion, and is soldered to a land portion of the circuit board. The second annular portion is arranged to have an axial thickness smaller than that of the first annular portion. The land portion is arranged radially inward of the through hole. The above arrangement makes it easier to achieve a reduced axial dimension of the motor while ensuring a sufficient axial dimension of the hub, which is arranged axially above the second annular portion.

A motor includes a support portion arranged to hold a stator and a bearing. The support portion includes a bearing holding portion arranged to extend upward along a central axis, and arranged to hold the bearing with a radially inner surface thereof; and a stator holding portion being tubular, arranged to project upward from an upper surface of the bearing holding portion, and arranged to hold a radially inner surface of the stator with a radially outer surface thereof. An axially lower portion of the stator holding portion includes a decreased thickness portion where the radial thickness of the stator holding portion is smaller than at another portion of the stator holding portion at another axial position.

An actuator for generating vibration, including a shaft; a middle supporter having a fitting portion fitted into an upper portion of the shaft and a support portion below the fitting portion to form a first space where a lower portion of the shaft is exposed; a circuit board having a driving coil and a hollow formed through the middle supporter; a housing having an inner space that accommodates the middle supporter and the circuit board so the circuit board is fixed thereto; a first yoke plate having a first magnet installed to face an upper surface of the driving coil and coupled to an upper portion of the middle supporter; a second yoke plate having a second magnet installed to face a lower surface of the driving coil and coupled to a lower portion of the middle supporter; and a weight installed to at least one of the yoke plates.

An oil-impregnated sintered bearing (8) includes a copper-iron-based sintered compact containing 40 mass % or more of copper, and has inner pores impregnated with an oil. The sintered compact has: a copper structure derived from copper powder (13) of partially diffusion-alloyed powder (11) in which copper powder (13) having a particle diameter of 20 m or less is diffused on and joined to a surface of iron powder (12) in advance; and a copper structure derived from elemental copper powder (14).

Provided is a fluid dynamic bearing device (1), including: a bearing sleeve (8) made of sintered metal; a rotary member (2) including a shaft portion (21) and a hub portion (23); and first and second thrust bearing portions (T1, T2) that form thrust bearing gaps respectively on an upper end surface (8b) and a lower end surface (8c) of the bearing sleeve (8) along with rotation of the rotary member (2). At least an outer peripheral surface of the bearing sleeve (8) is subjected to pore sealing treatment. A sealing gap (S) for retaining an oil surface of lubricating oil is made along a tapered outer peripheral surface (8d1) of the bearing sleeve (8). A lid member (10) having a bottomed cylindrical shape being fixed to an outer periphery of a lower end of the bearing sleeve (8).

This motor includes a base and a circuit board arranged on a lower surface of the base. The base includes a first annular portion and a second annular portion. The first annular portion is arranged under a stator. The second annular portion is arranged under a flange portion of a hub. A conducting wire drawn out from the stator is arranged to pass through a through hole defined in the first annular portion, and is soldered to a land portion of the circuit board. The second annular portion is arranged to have an axial thickness smaller than that of the first annular portion. The land portion is arranged radially inward of the through hole. The above arrangement makes it easier to achieve a reduced axial dimension of the motor while ensuring a sufficient axial dimension of the hub, which is arranged axially above the second annular portion.

A rotor for an electric motor includes a hub, formed of a plastic material, having a bore and a resilient hub finger; a magnetic ring rotationally connected to the hub; and a fixed axle arranged in the bore for receipt of a radial force applied by the resilient hub finger to facilitate rotation of the hub about the fixed axle.