An absolute encoder includes a spindle gear fixed to a motor shaft, a permanent magnet provided on the spindle gear, and a first driven gear having a center axis perpendicular to a center axis of a worm gear portion, and engaging the worm gear portion. The absolute encoder includes a second driving gear provided coaxially with the first driven gear and rotating according to a rotation of the first driven gear, and a second driven gear having a center axis perpendicular to the center axis of the first driven gear, and engaging the second driven gear. The spindle gear includes a magnet holder which is fit onto a tip end of the motor shaft, coaxially with the motor shaft, and a resin gear portion provided with the worm gear portion on an outer side in a radial direction.

An absolute encoder preferable in being made compact is provided. The absolute encoder includes a worm gear (101c) that rotates in accordance with rotation of a main spindle, and a worm wheel (102a) of which a central axis is perpendicular to a central axis of the worm gear (101c), the worm wheel engaging with the worm gear (101c). The worm gear (101c) is formed using a first material, and the worm wheel (102a) is formed using a second material different from the first material.

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.

To correct an error based on a position of a main spindle. An absolute encoder includes a magnet as a permanent magnet provided at a leading end side of a first worm gear part, an angle sensor as an 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 magnet, a microcomputer configured to output angle position information of a first driving gear in a stopped state, wherein the microcomputer outputs angle error information of the first driving gear corresponding to the angle position information.

An apparatus for diagnosing malfunction of a steering angle sensor. A steering angle sensor includes a main gear mounted on a steering shaft, first and second sub-gears meshed with the main gear at a specific gear ratio different from that of the main gear, and position sensors attached to the first and second sub-gears, respectively. A processor receives a signal output with rotation of the corresponding sub-gear from each of the position sensors of the steering angle sensor, detects at least one of the two position sensors which outputs different output signal values that are not designated in correspondence with a value of the same system angle, and determines the detected at least one position sensor as a cause of a malfunction.

An absolute encoder includes a spindle gear fixed to a motor shaft, a permanent magnet provided on the spindle gear, and a first driven gear having a center axis perpendicular to a center axis of a worm gear portion, and engaging the worm gear portion. The absolute encoder includes a second driving gear provided coaxially with the first driven gear and rotating according to a rotation of the first driven gear, and a second driven gear having a center axis perpendicular to the center axis of the first driven gear, and engaging the second driven gear. The spindle gear includes a magnet holder which is fit onto a tip end of the motor shaft, coaxially with the motor shaft, and a resin gear portion provided with the worm gear portion on an outer side in a radial direction.

Disclosed herein are a steering angle sensing device and a torque angle sensor module having the same. The steering angle sensing device includes a main gear rotating at the same angle as a steering shaft, a first sub-gear rotatably engaging with the main gear, a second sub-gear rotatably engaging with the main gear and having a number of teeth different from that of the first sub-gear, a third sub-gear rotatably engaging with the main gear and having a number of teeth different from that of each of the first sub-gear and the second sub-gear, a first magnetic sensor detecting a change in magnetic force of the first sub-gear, a second magnetic sensor detecting a change in magnetic force of the second sub-gear, a third magnetic sensor detecting a change in magnetic force of the third sub-gear, and a control device calculating a steering angle from the change in magnetic force detected by each of the first magnetic sensor, the second magnetic sensor, and the third magnetic sensor.

A method and device for deriving an absolute multiturn rotational angle of a rotating shaft (19), wherein sensors are arranged to sense the absolute rotational angles of wheels (14, 15, 18) or shafts (13, 16, 19) in a power transmission line having an non-integer gear ratio between the wheels/shafts, and wherein the power transmission line includes a gearbox (11) having multiple stages and wherein the rotational angle is sensed on multiple wheels (14, 15, 18) or shafts (13, 16, 19) in different stages, whereby an absolute multiturn rotational angle of the output shaft from the transmission line is derived by sensing the rotational angles of at least three wheels (14, 15, 18) or shafts (13, 16, 19) in different stages, and analyzing the combination of the sensed angles of the wheels or shafts and thereby deriving the absolute multiturn rotational angle based on the rotational angles read by the sensors.

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.

An absolute position sensor includes a first gear having a plurality of teeth, a rotational position sensor operatively coupled to the first gear to be configured to detect a rotational position of the first gear, and a second gear including a spiral tooth engaged with the plurality of teeth of the first gear to rotate with the first gear, and having a first end with a first distance from a center of the second gear, and an opposite second end with a second distance from the center of the second gear, the second distance being less than the first distance.