A rotor element or a star disk which is designed to be arranged on an electrically excited rotor of an electric machine, includes a base which is designed to be arranged in an insert between the axial end of a laminate stack of the rotor and at least one end winding of the rotor. At least one fin is fastened on the base and is designed to protrude in the insert through the at least one end winding axially out of the at least one end winding.

To provide an actuator in which an unstable movement of a rotor is controlled. An actuator includes a coil, a bobbin around which the coil is wound, a rotor positioned inside the bobbin, a shaft to which the rotor is fixed and which is rotatably supported, a stator including a base portion positioned on one end side of the shaft, outer magnetic pole portions extending from the base portion along the shaft and positioned outside the bobbin and inner magnetic pole portions extending from the base portion along the shaft and positioned between the rotor and the inside of the bobbin, a stator including a base portion positioned on the other end side of the shaft, outer magnetic pole portions extending from the base portion along the shaft and positioned outside the bobbin and inner magnetic pole portions extending from the base portion along the shaft and positioned between the rotor and the inside of the bobbin and a cover positioned between the rotor and the stator and contacting tip portions of the inner magnetic pole portions to regulate the approach of the inner magnetic pole portions to the rotor.

A motor assembly includes a brushless direct current (BLDC) motor; a gear box in which the BLDC motor is installed; and a power transmission part having a plurality of gears installed in the gear box so as to transmit power generated by the BLDC motor to an ice bin. The BLDC motor comprises: a stator and a rotor rotating with respect to the stator, wherein the rotor may be connected to the power transmission part by a shaft and the stator may be coupled to the gear box in a separable manner.

A sintered metal bearing is formed through sintering of a compact obtained through compression molding of raw-material powder. The sintered metal bearing includes chamfered portions that are respectively formed at least along outer rims of both end surfaces of the sintered metal bearing, and a dynamic pressure generating portion formed on an inner peripheral surface of the sintered metal bearing by sizing. An axial dimension of each of the chamfered portions is set larger than a radial dimension of the each of the chamfered portions, and a difference in axial dimension between the chamfered portions on one end side and another end side in an axial direction of the sintered metal bearing is set larger than a difference in radial dimension between the chamfered portions on the one end side and the another end side in the axial direction.

A stepping motor may include a rotor having a rotation shaft and a permanent magnet, a fixed body having a cylindrical stator provided with a plurality of pole teeth so as to face the permanent magnet, an urging member which urges the rotor toward one side in a motor axial line direction, a supported face of the rotor which faces the one side in the motor axial line direction, and a support face of the fixed body which slidably supports the supported face of the rotor on the one side with respect to the supported face. When a first sliding load which is a total sliding load applied to the rotor is “Ta”, a detent torque acted on the rotor is “Td”, and a dynamic torque acted on the rotor by the stator is “Te”, then “Ta”, “Td” and “Te” satisfy the following expression:
“Td”<“Ta”<“Te”.

In one aspect, an improved electric transmission assembly is provided that includes a hydrodynamic bearing. The electric transmission assembly includes a stator arranged inside of an outer housing. A rotor is configured to be rotatably driven by the stator. The rotor can include a rotor shaft having a first gear configured to driveably engage with a differential. A hydrodynamic bearing is arranged between the rotor shaft and the outer housing. The hydrodynamic bearing is formed from a non-conductive material. Specifically, the hydrodynamic bearing can be formed from a polymeric or plastic material. In one aspect, the hydrodynamic bearing is formed from a non-metallic material.

An electric generator 1 includes a shaft 3a (metal rotating body), a ball bearing 4 (metal holding body) configured to hold the shaft 3a, and a resin spacer 5 (resin member) used together with these components. A resin part included in the spacer 5 includes reinforcement fibers F pointing in random directions in a plane orthogonal to the axial direction of the shaft 3a. The linear expansion coefficient of the resin part in a direction orthogonal to the axial direction is the same as the linear expansion coefficient of a metal part included in the shaft 3a or the ball bearing 4. Accordingly, the resin member that achieves a dimensional stability can be provided.

A linear actuator includes: a first tube provided with coils placed there inside, the coils being held by a yoke; a second tube mounted on an outer circumference of the first tube; a rod fixed to an end of the second tube at one end; and permanent magnets held by the rod while being lined up in an axial direction. When the first tube and the second tube are at a fully contracted position, a gap is provided between an end face of an outer tube of the second tube and an opposing face of a base portion of the first tube.

An inner-rotor motor including: an armature assembly including a rotating shaft, an armature unit coupled to the rotating shaft and a pressing unit; a frame assembly including a frame housing the armature unit, a first bearing unit located on one side with respect to the armature unit in an axial direction, and a second bearing unit located on another side with respect to the armature unit in the axial direction; and an urging structure that urges the rotating shaft in a direction away from the second bearing unit and that presses the pressing unit toward the first bearing unit.

Brushless electric motor for an electric handheld power tool, wherein the electric motor has an end plate and a Hall board which is arranged on the end plate, wherein the Hall board is axially fixed to the end plate by an elastic O-ring.