Self-sealed joint

The invention discloses a self-sealed joint. An upper installation boss located at the upper end of a lower casing is fixedly connected with a halving cover plate through studs. A rubber core assembly is installed in the lower casing, an outer curved edge arranged on the upper portion of a rubber sleeve is supported on a limit step located at the upper end on the inner wall of the lower casing, and a pressing sleeve is clamped between the outer curved edge and the halving cover plate. A rubber sleeve outer wall located below the outer curved surface is a combined surface, the hole wall of a central hole of the rubber sleeve is a combined surface, and a steel sheet is embedded in the rubber sleeve. The outer diameter of the upper portion of a bushing is larger than that of the lower portion of the bushing, a stepped surface is formed between a large-diameter section and a small-diameter section, the large-diameter section of the bushing attaches to the hole wall of a central hole of the halving cover plate and a third cylindrical surface of the rubber sleeve, the stepped surface attaches to the plane where the rubber sleeve is located, and the small-diameter section of the bushing is inserted into a notch located on the upper portion of a second conical surface of the rubber sleeve. The self-sealed joint can not only reliably seal harmful gases in a well to prevent blowout caused by overflow of the harmful gases, but also ascend and descend a drill flexibly, and accordingly can ascend and descend the drill under pressure.