| 摘要 |
PURPOSE:To maintain generated thrust constant regardless of the fluctuation of a current level, by providing a mechanism for automatically regulating a gap between fixed side magnetic circuit and movable side magnetic circuit in linear motor according to the temperature variation of a line printer. CONSTITUTION:A pair of gap regulation mechnisms 52 comprising a bracket 52a, a thermally extendable/shrinkable member 52b and a resilient member 52c and supporting a holding member 54 slidably up and down are fixed upright on a base plate 32. Upon inner temperature rise due to the heating of a coil 23 during an operation, the thermally extendable/shrinkable member 52b in the gap regulation mechanism 52 extends to reduce the gap between a fixed side magnetic circuit 22 and a movable side magnetic circuit 24 so as to increase magnetic flux in the gap. Consequently, even if current level drops due to inner temperature rise, thrust does not decrease but maintained constant. On the contrary, temperature drop causes enlargement of gap through the recovery force of the resilient member 52c so as to return to the original condition. Consequently, the constant rolling speed of a hammer bank is achieved, and drop in printing speed due to a temperature rise can be prevented. |
