Weft insertion mechanism and weft insertion device and method capable of automatically adjusting along with breadth

The invention relates to a weft insertion mechanism and a weft insertion device and method capable of automatically adjusting along with breadth. The weft insertion mechanism comprises a double-layer rapier pneumatic auxiliary mechanism (comprising a first rapier and a second rapier), a double-layer rapier transmission mechanism (comprising a double-layer rapier transmission motor used for driving the first rapier and the second rapier to integrally move in the left-right direction), and an automatic breadth adjusting mechanism (comprising a double-layer rapier transmission motor used for driving the first rapier and the second rapier). Comprising a horizontal servo motor used for driving the double-layer rapier transmission mechanism and the double-layer rapier pneumatic auxiliary mechanism to integrally move in the left-right direction. The weft insertion device comprises a weft insertion mechanism A located on the left side and a weft insertion mechanism B (namely the weft insertion mechanism) located on t