Vibration generator and apparatus for engraving an image

A vibration generator, comprising:

• a stationary permanent magnet;
• a yoke for the permanent magnet;
• a coil fixed to the yoke;
• four springs provided to the yoke;
• and
• a movable piece supported with the yoke through the four springs and configured to vibrate relatively to the yoke according to current applied to the coil in a forward and a backward direction, wherein
• the yoke has a pair of yoke bodies with first ends and second ends, a coil fixing portion and four spring supports for the respective four springs, the first ends connected to respective south and north poles of the permanent magnet, the second ends having symmetric two pairs of proj ections facing each other to form a pair of south and north poles in each pair of the projections, the coil fixing portion into which the coil is accommodated and fixed in the middle between the two pairs of the projections, and springs of the four spring supports, on each side of the coil fixing portion, are symmetrically arranged between the coil fixing portion and a corresponding one of the two pairs of the projections to support respective corresponding springs of the four springs,
• the movable piece has a central portion, end portions and an arm, the end portions symmetrically projecting from the central portion and arranged between the respective two pairs of the projections with first gaps, the central portion arranged in the coil fixing portion, and the arm projecting from one of the end portions to output vibration,
• the springs have a teardrop sectional shape with a pointed end on a first side and an arc-shaped portion on a second side, the pointed ends of the springs supported with the respective spring supports, and the arc-shaped portions of the springs supporting the movable piece on both sides of the central portion, and
• the coil in the coil fixing portion having an outer periphery and an inner periphery, the outer periphery fixed to the yoke through resin, the inner periphery having a through-hole in which the central portion of the movable piece is arranged with second gaps, the second gaps having a size to allow oscillation, which is regulated by the first gaps, of the central portion of the movable piece so that the central portion of the movable piece is oscillated and vibrated with the second gaps when the end portions of the movable piece are vibrated with the first gaps according to the current applied to the coil in the forward and the backward directions, thereby to vibrate the movable piece in seesaw operation.