Anisotropy ferrite magnet and motor

Abstract

The present invention provides a dry-formed anisotropic ferrite magnet capable of reducing cogging torque and torque ripple. The anisotropic ferrite magnet has an inner peripheral surface and an outer peripheral surface opposite to the inner peripheral surface, has an arc-shaped cross section, and has magnetic anisotropy in its radial direction and is formed by dry molding, and is characterized in that , in the Bd distribution curve with the measurement region length in the circumferential direction of the inner peripheral surface or the outer peripheral surface as the abscissa and the surface magnetic flux density Bd as the vertical axis, the maximum value and the minimum value of the above-mentioned Bd in the above-mentioned inner peripheral surface are set Respectively Bdi(max), Bdi(min), when the maximum value and minimum value of the above-mentioned Bd in the above-mentioned outer peripheral surface are respectively Bdo(max), Bdo(min), satisfy Ro=Bdo(min)/Bdo(max )≥0.5, and Ri/Ro={Bdi(min)/Bdi(max)}/{Bdo(min)/Bdo(max)}<1.0.

Description

technical field [0001] The present invention relates to an arc-shaped ferrite magnet with anisotropy in the radial direction and a motor using the ferrite magnet produced by a dry forming method. Background technique [0002] High performance, small size, and light weight are required for motors used in home appliances, automotive electrical installations, and the like. Such a motor is a DC motor, and arc-shaped anisotropic ferrite magnets are used as magnets. These motors use magnets that are anisotropic with the radial direction being the easy axis. For these magnets, the surface magnetic flux density Bd on the inner peripheral surface side is required to be large and the distribution of the surface magnetic flux density Bd on the inner peripheral surface side to be uniform in the circumferential direction. If the fluctuation of the magnetic flux density Bd on the inner peripheral surface is large from the circumference to the upper surface, the cogging torque and torque...

AI Technical Summary

Problems solved by technology

[0006] According to Patent Document 1, it is possible to provide an anisotropic ferrite magnet capable o

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