US Patent 7358633 Linear vibration motor using resonance frequency

A linear vibration motor comprising a movable unit, a base assembly having a coil assembly, a housing and an elastic member, in which the movable unit has the maximum mass from a fixed housing volume. The elastic member has the outer periphery fixed to the ceiling of the housing and the inner periphery fixed to the top of the movable unit opposed to the outer periphery. The elastic member is deformable to the extent that the outer and inner peripheries are shift to a coplanar position from a parallel position where they are spaced for a predetermined distance from each other. The core assembly is distanced downward from the movable unit or a predetermined gap.