| 摘要 |
A sewing machine is provided to change the output torque of a pulse motor according to the thickness of the yarn and to prevent the break of a needle from generating at the falling state of the needle. The sewing machine includes a thread cutting member(1). A pulse output member(41) inputs the command pulse to a pulse motor(2). A command pulse detecting member(42) detects the command pulse inputted to the pulse motor. An output pulse detecting member(3) detects the output pulse from the pulse motor. A load torque calculating member(43) calculates the phase difference between the detected command pulse and the output pulse and then calculates the phase difference as the load torque. A thickness discriminating threshold memorizing member(44) memorizes the threshold of the load torque applied to the pulse motor. A driving control member(45) decreases the driving speed of the pulse motor and increases the output torque simultaneously when the calculated load torque is larger than the threshold of the memorized load torque.
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