| 摘要 |
PROBLEM TO BE SOLVED: To correct the rotational phase of a shuttle driving motor so as to time the encounter of a needle point with the encounter of a sewing needle, prevent breakage of a needle thread or skippping stitches, improve sewing efficiency and form beautiful stitches at any sewing speed. SOLUTION: In high-speed sewing, the inertia of a needle bar vertically driven at a high speed by a sewing machine spindle with a sewing machine motor through a needle driving mechanism or a needle jumping mechanism increases, causing a delay in the vertical movement phase of the needle bar in the timing of encounter of a needle thread loop of a needle point. However, in shuttle shaft synchronization control, on the basis of a phase difference command pulse P obtained in accordance with the rotation speed of the sewing machine spindle and a current phase difference pulse Q (S33: Q<P), as the rotation phase of the shuttle driving motor in relation to the sewing machine spindle is delayed and a phase delay in the rotation phase of the shuttle driving motor is increased in accordance with an increase in the rotation speed of the sewing machine motor (S34 to S36), irrespective of a sewing speed, a phase delay of the sewing needle in relation to shuttle for capturing a bobbin can be eliminated reliably.
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