Sewing machine thread tension apparatus and sewing machine

摘要

Disclosed is a sewing machine thread tension apparatus provided in a sewing machine to adjust a thread tensile force, including: a first thread tension disc; a second thread tension disc facing the first thread tension disc to nip a thread therebetween; a thread tension spring having a resilient force for adjusting the thread tensile force by biasing the second thread tension disc toward the first thread tension disc such that the first and second thread tension discs approaches each other; a movable body movable along a resilient force adjustment direction for adjusting a strength of the resilient force of the thread tensile spring; a rotatable body that is provided rotatably with respect to a rotational center and has a cylindrical portion, a conversion mechanism that moves the movable body along the resilient force adjustment direction in response to rotation, and a plurality of internal teeth formed with a predetermined pitch circle diameter with respect to a rotational center in an inner circumferential wall of the cylindrical portion; and a thread tension dial that is provided rotatably relative to the rotatable body through user's rotation operation, has a plurality of external teeth formed to have a pitch circle diameter Dout smaller than a pitch circle diameter Din of the internal teeth of the rotatable body and capable of meshing with the internal teeth of the rotatable body, and rotates the rotatable body in a common direction by transferring rotation to the rotatable body while a torque is reduced by causing the external teeth and the internal teeth to mesh with each other in response to rotation.