Voice coil motors and magnetic circuits therefor

Abstract

A magnet of rectangular prism of parallelepiped prism shape is disposed on a yoke having a triangle shape or a frusto-triangular shape to construct a magnetic circuit for a voice coil motor. The magnetic circuits facilitate positioning and holding of a moving coil, and the voice coil motor is improved in positioning precision of a magnetic head.

1 . A magnetic circuit for a voice coil motor, comprising a magnetic material yoke and magnet means disposed thereon,
 wherein the magnetic material yoke is configured to a triangular shape, a frusto-triangular shape in which the apex of a triangle is truncated or rounded, or an arcuate, crescent or semi-circular ring shape in which the bottom of a triangle at its center is recessed or cut-off in a semi-circular, triangular or apex-rounded triangular form,   the magnet means on said yoke consists of two magnet pieces of rectangular prism or parallelepiped prism shape which are serially arranged thereon so that the magnet pieces produce alternate magnetic poles while their end faces are in abutment or spaced apart, and   the two magnet pieces are arranged in series such that the longitudinal direction of the magnet pieces is parallel to the bottom of said yoke or a straight line connecting the lower ends of two oblique sides of said yoke.   
     
     
         2 . A magnetic circuit for a voice coil motor, comprising
 a pair of opposed magnetic material yokes; and   the magnet means disposed on at least one of the pair of yokes so that the magnet faces the other yoke,   wherein the magnetic material yoke is configured to a triangular shape, a frusto-triangular shape in which the apex of a triangle is truncated or rounded, or an arcuate, crescent or semi-circular ring shape in which the bottom of a triangle at its center is recessed or cut-off in a semi-circular, triangular or apex-rounded triangular form,   said magnet means disposed on a said yoke consists of two magnet pieces of rectangular prism or parallelepiped prism shape, which are serially arranged on the yoke so that the magnet pieces produce alternate magnetic poles while their end faces are in abutment or spaced apart, and   the two magnet pieces are arranged in series such that the longitudinal direction of said magnet pieces is parallel to the bottom of said yoke or a straight line connecting the lower ends of two oblique sides of said yoke.   
     
     
         3 . The magnetic circuit of  claim 2 , wherein the magnet means is disposed on each of the pair of yokes so that the magnet means face each other,
 each said magnet consists of two magnet pieces of rectangular prism or parallelepiped prism shape, which are serially arranged on the yoke so that the magnet pieces produce alternate magnetic poles while their end faces are in abutment or spaced apart, and   each two magnet pieces are disposed on said yoke such that the longitudinal direction of said magnet piece is parallel to the bottom of said yoke or a straight line connecting the lower ends of two oblique sides of said yoke.   
     
     
         4 . A voice coil motor comprising the magnetic circuit of  claim 2  and
 a moving coil located between the magnet means on one yoke and the other yoke. 
 
     
     
         5 . The voice coil motor of  claim 4 , wherein the magnetic circuit comprises:
 a pair of opposed magnetic material yokes; and   the magnet means disposed on at least one of the pair of yokes so that the magnet means faces the other yoke, wherein   the magnetic material yoke is configured to a triangular shape, a frusto-triangular shape in which the apex of a triangle is truncated or rounded, or an arcuate, crescent or semi-circular ring shape in which the bottom of a triangle at its center is recessed or cut-off in a semi-circular, triangular or apex-rounded triangular form,   the magnet means is disposed on each of the pair of yokes so that the magnet means magnets face each other,   each said magnet means disposed on said yoke consists of two magnet pieces of rectangular prism or parallelepiped prism shape, which are serially arranged on the yoke so that the magnet pieces produce alternate magnetic poles while their end faces are in abutment or spaced apart, and   each two magnet pieces are disposed on said yoke such that the longitudinal direction of said magnet piece is parallel to the bottom of said yoke or a straight line connecting the lower ends of two oblique sides of said yoke.