To reduce the influence of an unintended magnetic flux of a permanent magnet on detection accuracy. An absolute encoder (2) includes a magnet provided at a tip end side of any one of a first worm gear portion (11) and a second worm gear portion (22), and an angle sensor configured to detect a rotation angle of the magnet in response to a change in magnetic flux generated from the magnet. In the magnet, a first magnetic pole portion of a first polarity and a second magnetic pole portion of a second polarity different from the first polarity are formed adjacent to each other as viewed from an axial end surface of the magnet. The first magnetic pole portion and the second magnetic pole portion are formed adjacent to each other in a radial direction with a radial center of the magnet as a boundary, and the first magnetic pole portion and the second magnetic pole portion are formed adjacent to each other in an axial direction with an axial center as a boundary. The absolute encoder (2) is provided with a magnetic interference reduction member formed of a magnetic material on a radially outer peripheral surface of the magnet.

To reduce the influence of backlash in a reduction mechanism on detection accuracy. An absolute encoder includes a first worm gear portion rotating according to rotation of a main shaft and a first worm wheel portion meshing with the first worm gear portion. The absolute encoder is provided coaxially with the first worm wheel portion and includes a second worm gear portion rotating according to rotation of the first worm wheel portion and a second worm wheel portion meshing with the second worm gear portion. The absolute encoder also includes a biasing mechanism biasing the second worm gear portion in the direction of the second worm wheel portion.

Embodiments described herein are for an absolute position sensor system integrated into a steering column assembly. The absolute position sensor system comprises: a sector connected to a rake adjustment mechanism of the steering column assembly and operable to be moved thereby; a gear coupled to the sector and operable to be rotated by the movement thereof; a magnet connected to and retained by the gear such that the magnet rotates responsive to the rotation of the gear; and a sensor device positioned below the magnet and connected to a stationary part of the steering column assembly. The sensor device is configured to: detect an angle of rotation of the magnet, where the angle of rotation of the magnet corresponds to a position of the rake adjustment mechanism.

A sensor apparatus (01) is for determining a rotation angle position of a rotatable shaft (02). The sensor apparatus (01) comprises a main gear wheel (03), which is coaxially coupled to the rotatable shaft (02), and a secondary gear wheel (04), which is arranged so as to be rotatably coupled on the main gear wheel (03). The sensor apparatus (01) furthermore comprises two targets (06, 07), each of which is arranged on a lateral face of the main gear wheel (03) or of the secondary gear wheel (04), and two rotation angle sensors (08, 09), which are arranged in the immediate vicinity of the main gear wheel (03) and the secondary gear wheel (04) on a circuit board (05). The angles of the main gear wheel (03) and of the secondary gear wheel (04) are determined and forwarded as an angular signal to an evaluating unit (10) arranged on the circuit board.

Detection accuracy of a rotation angle of a sub-shaft is to be improved. In an absolute encoder according to an embodiment of the present invention, a second worm wheel part is a second driven gear, has a central axis orthogonal to a central axis of a first worm wheel part, and meshes with a second worm gear part. A support shaft rotatably supports the second worm wheel part. A magnet (Mq) rotates integrally with the support shaft. An angle sensor (Sq) is provided near the magnet (Mq) and detects a change in a magnetic flux generated from the magnet (Mq). A first bearing has an outer ring fixed at the second worm wheel part and an inner ring fixed at the support shaft. A second bearing has an inner ring fixed at the support shaft.

A detection device includes: a sensor that outputs first and second sensor outputs behaving respectively differently according to a change in a rotation angle of an object; a target calculation unit that calculates first and second target angles hat are target values of first and second actual angles corresponding to the first and second sensor outputs; and a selection unit that selects, as a reference destination, one of the first and second sensor outputs for driving the object.

A system includes an encoder magnet, a magnetic field sensor, and a shield structure. The encoder magnet is configured to rotate about an axis of rotation and is configured to produce a measurement magnetic field. The magnetic field sensor is axially displaced away from the encoder magnet and is configured to detect the measurement magnetic field. The shield structure at least partially surrounds both of the encoder magnet and the magnetic field sensor for shielding against stray magnetic fields. The shield structure attaches to a secondary structure. The shield structure and the encoder magnet may be coupled via the secondary structure so that they are commonly rotational. Alternatively, the sensor package and the shield structure are coupled via the secondary structure so that they are nonrotational relative to the encoder magnet.

An absolute steering sensor assembly (10) is provided, comprising a printed circuit board (18), at least one hall sensor (20, 22) being attached to the printed circuit board (18), at least one magnet (34, 36) being rotatably mounted such that the magnet (34, 36) is rotated upon a rotation of a steering column (26), the at least one magnet (34, 36) being placed in proximity of the at least one hall sensor (20, 22) such that the hall sensor (20, 22) can detect the magnetic field emitted by the magnet (34,36), and a protective cover (38, 40) being attached to the printed circuit board (18) such that the protective cover (38, 40) is placed between the magnet (34, 36) and the printed circuit board (18).

The influence of a leakage magnetic flux from a magnet on a magnetic sensor configured to detect a magnetic flux from the permanent magnet is reduced. An absolute encoder includes a first magnet provided at a leading end side of a first worm gear part, a first angle sensor configured to detect a rotation angle of the first worm gear part corresponding to a change in a magnetic flux generated from the first magnet, a second magnet provided at a leading end side of a second worm wheel part, a second angle sensor configured to detect a rotation angle of the second worm wheel part corresponding to a change in a magnetic flux generated from the second magnet, and a gear base part configured to surround at least a part of a periphery of the first angle sensor and the second angle sensor.

A rotation angle detection apparatus capable of reducing the cost and having a small thickness is provided. The rotation angle detection apparatus includes: a housing; a rotating shaft rotatably disposed in the housing; a first internal gear disposed concentrically with the rotating shaft and fixed to the housing; a second internal gear disposed concentrically with the rotating shaft, and rotatably disposed in the housing, the second internal gear having a number of teeth different from a number of teeth of the first internal gear; an external gear rotatably disposed at a position separated from the rotating shaft in rotating body, the external gear meshing with the first internal gear and the second internal gear; and a detection section that detects a rotation angle of the second internal gear.