Car underframe draft sill mechanism

Provided is a car underframe draft sill mechanism, comprising a hitch seat, a web, a draw beam upper cover plate and a draw beam lower cover and is characterized in that the web and the draw beam lower cover plate are spliced and tailor-welded; the hitch seat and the web, the hitch seat lower cover plate, a hitch seat reinforcing plate and the draw beam upper cover plate are welded together to form an enclosed cavity structure; the draw beam upper cover plate and a rib plate form a plug welding structure. The car underframe draft sill mechanism employs a steel plate tailor-welding structure, breaks through restriction of folding member thickness, increases a longitudinal force loading sectional area and thereby raises car body bearing longitudinal compression loading capability; the draw beam lower cover plate and the web are spliced; the hitch seat and the web, the hitch seat lower cover plate, the hitch seat reinforcing plate and the draw beam upper cover plate are welded together to form an enclosed cavity