Study On Tribological Design Of Cup-shaped Flexspline Surface In Harmonic Gear Drive

Harmonic drive has been widely applied in aerospace, precision medicalequipment and robotics fields by its small size, large transmission ratio, high precision,low noise and good coaxiality. In general, the fatigue fracture of flexspline is the mainfailure mode of harmonic drive. However, in special circumstances, the friction andwear is the major failure mode of harmonic drive. To ensure harmonic drive operatewith high efficiency and high precision, it is necessary to analyze its tribologicalproblems systematically.XB1harmonic gear reducer with cup-shaped flexspline is studied in this paper. Theinterference conditions of gear teeth and distribution of gaps between teeth are analyzedusing teeth interference theory. Besides, the movement of flexspline teeth, and thesliding between Inner wall of flexspline and outer wall of flexible bearing are alsoanalyzed.The fatigue strength and teeth wear of cup-shaped flexspline are analyzed. Thenthe number of engaged teeth and load distribution between teeth are analyzed. Thepaper also establishes a simplified model with cosine cam, which considers flexiblebearing radial clearance, then get stress and deformation distribution of cup-shapedflexspline which is assembled with wave generator in no-load and load conditions byfinite element analysis software ANSYS, analyzes stress and deformation distribution offlexspline, cylinder and teeth in different loads and wall thickness of the flexspline.The DLC Lubricate modification is made on surface of flexspline material sample.The special fixture which could test deformation of sample in the friction and wear testis also designed and processed, then UMT Series Multifunction friction and wear testeris used to make pin-plate and ball-plate friction and wear test for simulating the frictionof teeth and flexspline-wave generator. The paper studies friction and wear regularity ofDLC film in different load, speed, sample thickness, surface roughness and lubricatingways, analyzes the wear mechanism under different conditions, and finds the criticalload and speed of DLC film’s lubrication. Based on this, the efficiency of harmonicdrive is also analyzed.