A magnet-based angular displacement measuring system for measuring a rotational movement of a driveshaft. The magnet-based angular displacement measuring system includes a drive shaft comprising a free end. The free end has a coaxial recess so as to form a hollow shaft section. An exciter unit is rotationally coupled to the free end of the drive shaft. A stationary sensor unit functionally cooperates with the exciter unit to measure the rotational movement of the drive shaft.

An encoder includes: a base member; a printed board fixed directly or indirectly to the base member; and a cover member fixed to the base member while the printed board is arranged inside the cover member. A first enclosed space and a second enclosed space are formed inside the cover member. The first enclosed space is space in which the printed board is arranged entirely or partially in an enclosed state. The second enclosed space is formed between the first enclosed space and the cover member.

A rotation angle detection device detects a rotation angle of a motor having a shaft passing through a heat-dissipation plate. The rotation angle detection device includes: a permanent magnet attached to a base end of the shaft; a board that is disposed above the heat-dissipation plate and on which a drive circuit of the motor and a control circuit of the drive circuit are mounted; a magnetic sensor that is provided on the board so as to face the permanent magnet; and a magnetic shielding member that has a tubular shape and is disposed between the heat-dissipation plate and the board to surround the permanent magnet in plan view.

A resolver includes a resolver rotor fixed to a rotating shaft, and a resolver stator disposed around the resolver rotor. The resolver stator includes an annular stator core having a plurality of salient poles which protrudes radially inward and which is disposed at regular intervals in a circumferential direction. The resolver rotor has an outer peripheral surface defined by an outer radius Rm() which is obtained by blending, with respect to a first function Gp() where an air gap between the resolver rotor and the salient poles is proportional to a sine wave (sin ) related to an angle of the resolver rotor, a second function Gip() where the inverse of the air gap is proportional to the sine wave (sin ), at a predetermined ratio .

A motor may include a motor main body having a turning shaft and a motor case; a magnet that turns together with the turning shaft; a magnetism sensing element that faces the magnet; a circuit board on which the magnetism sensing element is mounted, the circuit board having a signal ground that is connected to a ground terminal of the magnetism sensing element; a circuit board holder that covers the circuit board from a side of the magnet; and a first shield member that covers the circuit board from a side opposite to the magnet. The first shield member and the circuit board holder are each made of an electrically-conductive material, and electrically connected to the signal ground.

A magnetism detection device includes a magnetic sensor and a shield member. The magnetic sensor detects variation in magnetism at a detection position that occurs with rotation of a rotating body. The shield member has a pair of plate-like side wall portions opposing each other and a first opening formed by opening the side in a direction intersecting with a direction in which the pair of side wall portions oppose each other. The shield member allows the magnetic sensor to be located in an internal space portion interposed between the pair of side wall portions and allowing the magnetic sensor and the rotating body to oppose each other through the first opening.

An encoder with oil gas prevention structure including a base, a shaft, a bearing, a cover and an encoding device is provided. The base includes a body and a through hole configured on the body. The shaft is disposed within the though hole. The bearing holds the shaft and is disposed within the through hole, and includes an inner ring and an outer ring wherein the inner ring is set against the first section, and the outer ring is set against a circumference of the through hole. The cover holds the shaft and adjacent to the bearing. The encoding device holds the shaft and is disposed on the cover, and includes a code disc rotatably disposed on the shaft wherein the cover is located between the bearing and the code disc. Therefore, the code disc is prevented from being contaminated by the leaking oil gas from the bearing.

An encoder includes: a base member; a printed board fixed directly or indirectly to the base member; and a cover member fixed to the base member while the printed board is arranged inside the cover member. A first enclosed space and a second enclosed space are formed inside the cover member. The first enclosed space is space in which the printed board is arranged entirely or partially in an enclosed state. The second enclosed space is formed between the first enclosed space and the cover member.

Disclosed is a resolver robust against external noise and having a reduced error in the detection of a rotation angle, which includes a stator made of a magnetic material and having a plurality of teeth and a plurality of slots alternately formed at an inner side thereof, insulation covers respectively having a tooth insulating unit formed at an inner side thereof corresponding to the teeth and mounted to the stator at both upper and lower surfaces of the stator, and coils wound on the teeth with the tooth insulating unit being interposed therebetween, wherein regarding winding widths of coils located at an outermost circumference among the wound coils, a ratio of a shortest winding width to a longest winding width is 0.69 or above and 1 or below.

The present invention is intended to provide a protective cover, comprising an inner ring 12 with an inner ring track surface 12A on an outer peripheral surface; an outer ring 13 with an outer ring track surface 13A on an inner peripheral surface; a bearing with rolling elements 14 between the inner ring track surface 12A and the outer ring track surface 13A; a magnetic encoder 8 that is positioned at one axial end portion of the bearing and fixed to the inner ring 12; and a magnetic sensor that is fixed to the outer ring 13, a cup-shaped protective cover 1 press-fitted into the outer ring 13 to cover the magnetic encoder 8 and intervene between the magnetic encoder 8 and the magnetic sensor is formed by performing cold press molding of an austenitic stainless steel plate material with a nickel content of 8.5 to 13 weight %.