Knife sharpener of cloth cutting machine

The invention discloses a knife sharpener of a cloth cutting machine, which comprises a screw, a grinding wheel, a screw cap, a middle shaft mechanism, a first bearing, a second bearing, a bearing seat and a fastening nut, wherein the middle shaft mechanism comprises a clamping ring, a connecting screw rod, a connecting column, a connecting shaft and a transverse positioning hole, one end of the connecting screw rod is connected with the screw through a threaded through hole, and the other end of the connecting screw rod is connected with the screw through a threaded through hole; the other end of the connecting screw rod is connected with a clamping ring, a transverse positioning hole is formed in the clamping ring in the direction perpendicular to the connecting screw rod, one end of the clamping ring is connected with a connecting column, one end of the connecting column is connected with a connecting shaft, and external threads are arranged on the connecting shaft. After a grinding wheel is abraded, a lon