An electric actuator includes: a motor; a first case accommodating the motor; a second case located on one side in an axial direction of the first case; a bearing holder fixed to the first case; and a first bearing held by the bearing holder. The first case has a wall part covering the other side in the axial direction of a stator and having a through hole. The bearing holder has: a holder cylindrical part holding the first bearing and inserted into the through hole; and a holder flange part fixed to the wall part. An inner diameter of the through hole is larger than an outer diameter of the holder cylindrical part. At least a part of a radially outer surface of the holder cylindrical part in a circumferential direction is located in a position radially inside and away from a radially inner surface of the through hole.

A motor includes a rotor including a shaft and a rotor body, a bearing fitted to the shaft and rotatably holding the shaft, a bearing holder arranged on the opposite side to the rotor body so as to hold the bearing, a movement regulation member arranged closer to the rotor body than the bearing and separated to regulate movement of the bearing toward the rotor body, a first engagement part provided at the rotor body to be adjacent to the movement regulation member, a first engagement target part provided at the movement regulation member to be adjacent to the rotor body to be able to be engaged with the first engagement target part, a second engagement part provided at the movement regulation member, a second engagement target part provided at the bearing holder, and a coupling member that couples the bearing holder and the movement regulation member.

A shaft assembly may include two or more Poka-Yoke bearing caps, each Poka-Yoke bearing cap having a pair of reference bores offset from a central axis of the bearing cap by differing offset distances, and each bearing cap defining a semi-circular recess that is positioned so as to align in use a central axis of the semi-cylindrical recess in the bearing cap with an axis of rotation of a shaft rotatably supported by the bearing cap. The differing offsets of the reference bores prevent the bearing cap from being assembled in a reversed orientation. To ensure that each bearing cap can only be fitted in one position, a centre spacing between the first and second reference bores of each bearing cap is different to the centre spacing used for other bearing caps used to support a single shaft.

A shaft assembly may include two or more Poka-Yoke bearing caps, each Poka-Yoke bearing cap having a pair of reference bores offset from a central axis of the bearing cap by differing offset distances, and each bearing cap defining a semi-circular recess that is positioned so as to align in use a central axis of the semi-cylindrical recess in the bearing cap with an axis of rotation of a shaft rotatably supported by the bearing cap. The differing offsets of the reference bores prevent the bearing cap from being assembled in a reversed orientation. To ensure that each bearing cap can only be fitted in one position, a centre spacing between the first and second reference bores of each bearing cap is different to the centre spacing used for other bearing caps used to support a single shaft.

A method for diagnosing an abnormality of rolling bearing includes: measuring a vibration of a rotator; performing a frequency analysis on the vibration to calculate a magnitude of a vibration at each frequency; calculating a characteristic frequency as a frequency of a vibration from a specification of the rolling bearing and a rotation speed of the rotator at a vibration measurement in the measuring; calculating a vibration value from which an effect of the rotation speed is removed by dividing a magnitude of a vibration at the characteristic frequency by a value including a base and an exponent, the base being a predetermined physical quantity in a proportional relation with an angular velocity of the rotator at the vibration measurement in the measuring, the exponent being a positive number; calculating an evaluation index based on the vibration value; and determining an existence of an abnormality based on the evaluation index.

A method for diagnosing an abnormality of rolling bearing includes: measuring a vibration of a rotator; performing a frequency analysis on the vibration to calculate a magnitude of a vibration at each frequency; calculating a characteristic frequency as a frequency of a vibration from a specification of the rolling bearing and a rotation speed of the rotator at a vibration measurement in the measuring; calculating a vibration value from which an effect of the rotation speed is removed by dividing a magnitude of a vibration at the characteristic frequency by a value including a base and an exponent, the base being a predetermined physical quantity in a proportional relation with an angular velocity of the rotator at the vibration measurement in the measuring, the exponent being a positive number; calculating an evaluation index based on the vibration value; and determining an existence of an abnormality based on the evaluation index.

A shaft assembly may include two or more Poka-Yoke bearing caps, each Poka-Yoke bearing cap having a pair of reference bores offset from a central axis of the bearing cap by differing offset distances, and each bearing cap defining a semi-circular recess that is positioned so as to align in use a central axis of the semi-cylindrical recess in the bearing cap with an axis of rotation of a shaft rotatably supported by the bearing cap. The differing offsets of the reference bores prevent the bearing cap from being assembled in a reversed orientation. To ensure that each bearing cap can only be fitted in one position, a center spacing between the first and second reference bores of each bearing cap is different to the center spacing used for other bearing caps used to support a single shaft.

A shaft assembly may include two or more Poka-Yoke bearing caps, each Poka-Yoke bearing cap having a pair of reference bores offset from a central axis of the bearing cap by differing offset distances, and each bearing cap defining a semi-circular recess that is positioned so as to align in use a central axis of the semi-cylindrical recess in the bearing cap with an axis of rotation of a shaft rotatably supported by the bearing cap. The differing offsets of the reference bores prevent the bearing cap from being assembled in a reversed orientation. To ensure that each bearing cap can only be fitted in one position, a center spacing between the first and second reference bores of each bearing cap is different to the center spacing used for other bearing caps used to support a single shaft.

A magnetic fluid seal includes an outer cylinder member with a heat barrier that internally houses a rotating shaft extending from a housing of a fluid machine and includes an attachment portion to be attached to the housing, magnetic pole members that are disposed around the rotating shaft housed in the outer cylinder member and form a magnetic circuit, and sealing films that are magnetically connected to the magnetic circuit, are respectively disposed between the magnetic pole members and the rotating shaft, are made of magnetic fluids, and are formed in an axial direction.

A release unit for a machine tool spindle, in particular motor spindle, for releasing a tool clamp, wherein the release unit comprises at least one adjustment element which can be linearly adjusted along an adjustment path for actuating the tool clamp, which release unit reduces the structural and/or economic complexity. This is achieved according to the invention in that the release unit is constructed as an electric motor which comprises an electromagnetic drive system having a hollow-cylindrical rotor shaft which rotates about a rotation axis, in that the linearly adjustable adjustment element is constructed as a spindle element of a conversion unit for converting the rotation of the electric motor into a linear adjustment and in that the rotor shaft is constructed as a spindle nut of the conversion unit which rotates about the rotation axis.