PROBLEM TO BE SOLVED: To easily adjust the tension of a bobbin thread without necessity to take out a bobbin case from a rotating hook bobbin case holder after stopping the driving of a sewing machine when adjusting the tension of the bobbin thread during sewing.;SOLUTION: The bobbin thread tension adjusting device includes: a permanent magnet 12 arranged in a rotating hook 8; a coil 13 arranged on a surface opposing to the permanent magnet 12 in the rotating hook bobbin case holder 7; a rotating hook bobbin case holder electrode 15 arranged inside the rotating hook bobbin case holder so as to receive power generated between the permanent magnet 12 and the coil 13 by the rotation of the rotating hook 8 with respect to the rotating hook bobbin case holder 7; a first case electrode 16 arranged in the bobbin case 6 so as to receive the power supplied from the rotating hook bobbin case holder electrode 15; a photo-sensor 22 arranged in the bobbin case 6 so as to receive a control signal by non-contact; a light emitting diode 27 for transmitting the control signal to the photo-sensor 22; and a pulse motor 20 for adjusting the tension to bobbin thread 3 by a bobbin thread adjusting spring 11 through the use of the power supplied from the first case electrode 16 in response to the control signal received by the photo-sensor 22 from the light emitting diode 27.;COPYRIGHT: (C)2009,JPO&INPIT
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