Rotary type bending upper die capable of automatically replacing tool bit and tool replacing method

The invention discloses a rotary type bending upper die capable of automatically replacing a tool bit and a tool replacing method. The die head installation body and the limiting body structure are arranged on the upper die body and are distributed in a crossed mode, the limiting body is used for limiting the top of the limiting body structure, and the problems of rotation and upward complete deformation of plates under the reverse action are solved. The limiting body is improved, so that the limiting body structure is hooked while the limiting body limits ascending at the top of the limiting body, and the upper die body can be fixed and prevented from deforming downwards under the influence of gravity through hooking and ascending limitation. By arranging the embracing assembly on the limiting body, the hydraulic damping part can act on the upper die body in cooperation with the embracing assembly in the process of descending to replace the upper die tool bit, and the descending deformation problem is comple