As the markets for mobile
phones, videogame machines and other mobile devices grow, the devices
are becoming increasingly compact and lightweight. Most of these
devices are equipped with a vibrating motor for pagers. Restrictions
on the shape and size of magnets and motors stemming from the demand
for further compactness in these devices—particularly in coreless
DC motors—have required increasingly compact and high-performance
magnets and motors. Consequently, these devices are employing neodymium-sintered
magnets as a material to replace more-conventional neodymium bonded
magnets and samarium-cobalt sintered magnets.
Hitachi Metals has created a compact, high-performance neodymium
sintered magnet to respond to such applications.
Features
Figure 1 shows
an external view of representative products, while Chart 1 shows
representative dimensions. Although there exist diametric anisotropic
magnets for standard cylindrical motors as well as radial anisotropic
magnets for compressed motors, these new products realize magnets
of stable quality with little dimensional variation and of minimal
diameter and thickness. Dimensional tolerance of the outer diameter
and height is ±0.05mm.
Chart 1: Representative Dimensions
of Magnet for Vibrating Motors in Mobile Devices
Outer Diameter (mm)
Height (mm)
Surface Treatment
General type
2.0—2.5
4—8±0.05
Nickel-plated or resin-deposed coating
(thickness: 5—25m)
Compressed type
4.0—12±0.05
0.5—1.5±0.05
Nickel-plated or resin-deposed coating
(thickness: 5—25m)
Properties
Chart 2 shows representative
measures of the magnetic properties of the magnet. The use of neodymium
high-performance materials enables selection from a wide range of
magnetic properties, from Br magnesium, which is commonly employed
for general-use devices, to highly coercive magnets for applications
in which thermal reliability is necessary.
Chart 2: Representative Magnetic
Properties of Magnets for Vibrating Motors in Mobile Devices
2.0—2.5
m)
