| 摘要 |
PURPOSE:To effectively cool the heat of a coil to realize a high-speed printing hammer drive device with little heat, by providing holes on a part of a yoke corresponding to a coil. CONSTITUTION:A permanent magnet 1 is held between yokes 2 and 3, and the yoke 2 corresponding to a printing hammer 4 is wound with a coil 5 releasing the printing hammer 4. On the yoke 3, holes 6 are disposed corresponding to the coil 5. Usually, the printing hammer 4 is attracted to the yoke 2 with being deflected by the attraction force of the permanent magnet 1. But, if the flux of the permanent magnet 1 is eliminated by passing an electric current through a coil 5 when necessary, the printing hammer 4 is released from the face of the yoke 2, resulting in the conversion of the strain energy stored therein to a kinetic energy, whereby printing is conducted. At this time, the heat caused by the loss in the coil 5 is directly cooled by a cooling air 10 blown through the holes 6 provided on the yoke 3. On the other hand, the holes 6 disposed on the yoke 3 corresponding to the yoke 2 prevent the flux leakage from the yoke 2 to the yoke 3, enabling a small sectional area of the yoke 2 and a compact permanent magnet 1 in size. |
