| 摘要 |
A voice coil motor is provided to reduce a size of a housing without a space between a lens holder and a coil to receive an inner wall of the housing by extending the housing to an inner surface of the lens holder. A casing is composed of an upper case(22) and a lower case(21) and receives a magnet housing(33), a permanent magnet unit(31) to generate a magnetic field, a lens holder(29) to support a lens, and a coil fixed to an outer surface of the lens holder. The magnet housing has a circular shape formed by a cylindrical outer wall(38) and a cylindrical inner wall(39), and a lower end thereof is opened. The permanent magnet unit has at least one permanent magnet inserted into an inner surface of the outer wall. The lens holder has a through opening to form an optical axis(70) and a flange(34) located on the radial outer surface toward a lower end and is inserted into the magnet housing so that the inner wall of the magnet housing faces an upper part of a bore of the through opening. An upper cushion(32) is fixed at an inner surface of a top wall(40) of the magnet housing and prevents direct contact between an upper end of the lens holder and the top wall of the magnet housing. Two springs(27), which engage the lower end of the lens holder and the lower case of the casing, elastically support the lens holder to move the lens holder along the optical axis. The coil is placed on an axial upper surface of the flange and arranged within the magnetic field of the permanent magnet unit so that current passing through the coil generates a magnetic field, which reacts with the magnetic field of the permanent magnet unit, to press the coil downward on the flange and move the lens holder against force of the springs.
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