| 摘要 |
PROBLEM TO BE SOLVED: To solve the problem that hitting force of a printing hammer decreases with time, because the printing hammer is made hard to release, due to an increase in magnetic flux of an attraction part, by reason that an acclimated state of a magnetic attraction surface of the printing hammer is changed depending on the number of hits. SOLUTION: A printer is provided with an electromagnetic coil for release, which imparts deflection to the printing hammer by attracting the printing hammer with a printing pin provided at the tip of the leaf spring, by means of a closed magnetic circuit composed of a magnet, a yoke and the printing hammer itself, so as to cancel out a magnetic field of the closed magnetic circuit. An electric current with an almost rectangular wave is supplied to the electromagnetic coil for release by PWM control etc., depending on a pulse signal, so that the magnetic field can be canceled out. Thus, the printing hammer is released so that a dot can be printed. The number of the driving operations of the printing hammer is counted by a control system, and a waveform of the electric current with the almost rectangular wave, which is supplied to the electromagnetic coil for the release, is controlled in the direction of an increase in current product, in accordance with an increase in the number of the counted driving operations. COPYRIGHT: (C)2005,JPO&NCIPI
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