Sealed type hydraulic driving adjustable speed cutter of oil pipe string with diameter being phi 73mm or greater

The invention discloses a sealed type hydraulic driving adjustable speed cutter of an oil pipe string with the diameter being phi 73mm or greater and solves the problem of cutting incapability of oil pipes and sleeve pipes in small sizes. The cutter consists of a speed regulating system, a motive power driving system and a spraying system, wherein a motive power pipe in the motive power system consists of two internal reducer pipes wound on a spiral groove of a pipe support body, when cutting liquid flows through the internal reducer pipes, the corresponding piston force is generated, the piston force is resolved in the axial direction and the annular direction, the two internal reducer pipes are in symmetrical arrangement, and the force couple is formed in the annular direction, so the torque is output, and the cutting goal is reached. The tool has the advantages that the pipe string with the minimum inner diameter being 62mm can be cut, in addition, the cutter can be used as a tool for cleaning the inner wall of the pipe string, and the blank of the small-diameter pipe string cutting is filled.