It consists of two flange half coupling bodies with external teeth and an internal gear ring with an integral structure of front and rear internal teeth. The front and rear internal teeth of the internal gear ring are respectively connected with the flange half coupling body. The outer teeth of the inner gear are engaged, and the front and rear ends of the inner gear ring are provided with annular end caps.The utility model has the advantages of removing the original internal gear ring flange connection form, realizing a gear ring to merge the two internal teeth of the input end and the output end, eliminating the need for coupling flanges and bolts; changing the traditional split The body structure, on the one hand, greatly reduces the material used for the internal gear ring, saves production and manufacturing costs, and is more convenient to install; on the other hand, the structural change makes the outer size of the same specification product smaller, and the structure is simple, compact, and occupies The space is small, so as to meet the narrow working conditions of the working space of some special industry machinery, such as road maintenance engineering vehicles and other special machinery.