Motor unit

Abstract

Provided is a motor unit which can detect axle rotation in a high-precision manner in a rotation detector through restraining the slot effect. In the rotation detector (1) disposed in the motor unit (210), during the period when a first support fixed with magnets (21, 22) rotates in relative to a second support (12) fixed with magnetic field detectors (31) and along with an axle (213), a magnetic field formed by the magnets (21, 22) is detected through the magnetic field detectors (31), so as to detect the rotation state of the axle (213). In the magnetic field detectors (31),and both ends of the magnetic field detectors (31) are covered by magnetic member (41, 42). Each pair of magnetic members (41-46) face each other with a gap (S1) interposed therebetween in the longitudinal direction of the magnetic field detector (31-33). A dimension (D1) of each of the magnetic field forming units (21, 22, 23, 24) in a tangential direction of a circumference (R) is larger than a dimension (D4) of the corresponding magnetic field forming unit (21, 22, 23, 24) in a radial direction and is larger than the distance of the gap (S1).

Description

technical field [0001] The present invention relates to a motor having a rotation detection device that detects rotation of a shaft using magnetism. Background technique [0002] A rotation detection device that is usually attached to a motor and generates a pulse signal corresponding to the rotation of the shaft of the motor using magnetism has been used. [0003] As a conventional rotation detecting device, there is known a device that is configured to sandwich at least two magnetic elements capable of causing a large Barkhausen jump, a coil wound around each magnetic element, and sandwich the magnetic elements. The element is composed of a pair of permanent magnets whose magnetic pole directions are opposite to each other, and detects the rotation of a gear having a plurality of teeth made of magnetic material (for example, refer to Patent Document 1). [0004] In this rotation detection device, since the pair of permanent magnets are arranged with a space smaller than t...

AI Technical Summary

Problems solved by technology

[0008] There is such a problem that due to the generation of cogging torque, the rotation speed of the gear fluctuates (cogging occurs), and it is transmitted to the rotating shaft of the gear to cause vibration and noise, and it acts like a static torque. Increase the starting torque of the gear

Therefore, in a motor equipped with such a rotation detection device, there is a problem that the rotation of the shaft cannot be detected with high precision by the rotation detection device.

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