Straddle-type monorail traffic is a full-line overhead rail transit system which utilizes a space above ordinary roads, and thus can alleviate the ground traffic congestion problem effectively. And also, a monorail train, due to adopting a special bogie, has a strong adaptability to steep slopes and sharp bends and doesn't have strict requirements on a terrain. Furthermore, the monorail train is drawn by electric power, and there is no exhaust pollution in operation of the train, which is favorable for protection of the urban environment.
A central traction device for the bogie of the monorail train is mainly subjected to a traction force and a braking force, and is subjected to an impact of the bogie against a train body, and the central traction device is further required to satisfy the relative movement between the train body and the bogie. The central traction device mainly includes a frame, a traction pin, a traction beam, a transverse stopper, a damper and so on. In a central traction device of a conventional straddle-type monorail train, the traction beam and the traction pin are connected by a traction pin sleeve for transferring a longitudinal traction force to satisfy the relative rotation between the train body and the bogie. The traction pin sleeve in the conventional technology mostly has a cylindrical structure with equal diameters from top to bottom, and is formed by rubber and a metallic plate being vulcanized together. The traction pin sleeve bears load changes in a horizontal direction by compressive deformation of the rubber in the horizontal direction, thus having damping and buffering effect. However, the traction pin sleeve bears load changes in a vertical direction by torsional dislocation of the rubber, which weakens damping and buffering effect in the vertical direction greatly and further causes a service life of the traction pin sleeve to be reduced greatly.