Sewing machine

A sewing machine comprising:

• thread take-up lever formed in a swayable manner, a needle thread control section, a memory section, and a control section, wherein
• the needle thread control section that is disposed at an upstream position in a needle thread path of the thread take-up lever and that controls tension on a needle thread, has
• an upstream grip section including
• an upstream grip section main body which grips a needle thread in a pinching manner and
• an upstream actuation section that performs, with respect to the upstream grip section main body, switching between a closed state in which the needle thread is gripped and an open state in which the needle thread is released from a gripped state,
• a downstream grip section that is disposed at a downstream position in the needle thread path of the upstream grip section and that has
• a downstream grip section main body which grips a needle thread in a pinching manner and
• a downstream actuation section that performs, with respect to the downstream grip section main body, switching between a closed state in which the needle thread is gripped and an open state in which the needle thread is released from a gripped state, and
• a turning section that turns the needle thread between the upstream grip section main body and the downstream grip section main body and that has
• a turning arm which contacts the needle thread and
• a needle thread motor which turns the turning arm;
• the memory section stores torque data and needle thread quantity data, wherein
• the torque data stores a torque value for controlling a needle thread on a per-stitch basis in sewing data,
• the needle thread quantity data has precorrected needle thread requirement data and postcorrected needle thread requirement data,
• the precorrected needle thread requirement data stores a needle thread requirement showing a length of a required needle thread, on a per-stitch basis in the sewing data, and
• the postcorrected needle thread requirement data stores the needle thread requirement of the precorrected needle thread requirement data on a per-stitch basis in the sewing data, in which the needle thread requirement in the postcorrected needle thread requirement data is updated to the postcorrected needle thread requirement for a stitch where the needle thread requirement has been corrected by the control section;
• and
• when performing sewing operation in accordance with sewing data in the control zone for each stitch, the control section,
• in a torque control zone that is a zone including at least a portion from one dead point to the other dead point of the thread take-up lever in which the thread take-up lever pulls the needle thread with respect to a process fabric to be sewn with the needle thread, imparts a rotating force to the turning arm, while closing the upstream grip section main body and while opening the downstream grip body, by controlling the needle thread motor according to the torque value of the torque data so as to impart a tension to the needle thread against a direction in which the thread take-up lever pulls the needle thread;
• in a first position control zone that is at least a portion of a zone other than the torque control zone, turns the turning arm in the same direction as the rotating force is imparted to the turning arm in the torque control zone so as to pull out the needle thread from an upstream position, while opening the upstream grip section main body and while closing the downstream grip body, by controlling the needle thread motor so as to rotate through an angle corresponding to the needle thread requirement in the postcorrected needle thread requirement data for a stitch of an immediately-arriving torque control zone;
• in a second position control zone that is at least a portion of the zone other than the torque control zone and subsequent to the first position control zone, controls the needle thread motor, while closing the upstream grip section main body and while opening the downstream grip body, such that the angle of the needle thread motor returns to an initial position at the angle of the needle thread motor that is the position of the needle thread motor in its rotating direction;
• and
• in relation to a target stitch that is one to be sequentially specified among stitches in the sewing data or a plurality of stitches including the target stitch,
• compares needle thread consumption showing the length of the needle thread used in the torque control zone with the needle thread requirement in the precorrected needle thread requirement data,
• performs a correction to increase the needle thread requirement in the postcorrected needle thread requirement data for the stitch next to the target stitch and subsequent stitches when the needle thread requirement is larger than the needle thread consumption, and
• performs a correction to decrease the needle thread requirement in the postcorrected needle thread requirement data for the stitch next to the target stitch and subsequent stitches when the needle thread requirement is smaller than the needle thread consumption.