A yarn tension control method includes a bobbin ascending or descending on sliding rails on a yarn carrier module. When the pattern is designed, the ascending or descending speed, time and distance of the fixing frame is calculated directly according to a yarn carrier stop, the quantity of redundant yarn and the speed of the carriage. When the carriage contacts a yarn carrier, a contact sensor feeds a signal back to the carriage, a signal emitter emits an instruction, and when a signal receiver receives the instruction, the fixing frame is controlled to ascend along the sliding rails. When the carriage drives the yarn carrier to enter a knitting area, needles are elected by a needle selection electromagnetic valve, knitting motion information is fed back to the carriage, the signal emitter emits an instruction, and when the signal receiver receives the instruction, the fixing frame is controlled to descend.

This application relates to a yarn carrier device with a yarn tension control function for a flat knitting machine, and a yarn tension control method. At the moment a carriage is connected to a yarn carrier device, a fixing frame carrying a bobbin ascends or descends on sliding rails installed on the yarn carrier device. The ascending or descending speed, time and distance of the fixing frame can be calculated directly according to a yarn carrier stop, the quantity of an unknitted portion of the yarn and the speed of the carriage. When the carriage contacts a yarn carrier, the fixing frame is controlled to ascend along the sliding rails. When the carriage drives the yarn carrier to enter a knitting area, the fixing frame is controlled to descend.