| 摘要 |
PROBLEM TO BE SOLVED: To efficiently detect thread breakage. SOLUTION: A thread advance quantity detecting device 7 detecting the advance quantity of a thread is provided for this thread breakage detecting method for a sewing machine 1. When the advance quantity of the thread detected by the thread advance quantity detecting device 7 while a needle is vertically moved a prescribed number of times is smaller than a reference value based on a detection number table stored in a storage section 32, it is judged that the thread breakage occurs. The prescribed number of times is changed smaller as the swing width of stitches becomes larger based on the detection number table in this thread breakage detecting method.
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