Thread breakage detection device for sewing machine

A stitch balancing thread tension comprising:

• a stationary member;
• a shaft relatively rotatable with respect to the stationary member;
• a rotary disk that applies a tension to a thread, the rotary disk being mounted on the shaft and having a surface that extends perpendicular to an axial direction of the shaft;
• a permanent magnet member attached to the surface of the rotary disk;
• and
• a hole element mounted on the stationary member, the hole element detecting a magnetic field generated in the permanent magnet member, wherein
• the hole element is disposed on one side of the permanent magnet member and the rotary disk is disposed on an opposite side of the permanent magnet member.

A sewing machine comprising;

• a stationary member;
• a shaft relatively rotatable with respect to the stationary member;
• a rotary disk that applies a tension to a thread, the rotary disk being mounted on the shaft and having a surface that extends perpendicular to an axial direction of the shaft;
• a permanent magnet member attached to the surface of the rotary disk;
• a hole element mounted on the stationary member, the hole element detecting a magnetic field generated in the permanent magnet member and outputting a detection signal based on the detected magnetic field;
• a measuring unit that measures a time duration during an embroidery operation;
• a counting unit that counts a number of times the detection signal changes during the embroidery operation;
• and
• a detector that detects a thread breakage of the thread when the counting unit does not count a predetermined number within a predetermined time duration during the embroidery operation, wherein
• the hole element is disposed on one side of the permanent magnet member and the rotary disk is disposed on an opposite side of the permanent magnet member.