Abstract
Harmonic gear reducer is widely used in industrial robots, aerospace, optics, and other high-end fields. The failure of harmonic gear reducer is mainly caused by the damage of flexible bearing and flexspline of thin-walled vulnerable components. To study the contact mechanical characteristics of flexible components such as flexible bearing and flexspline in harmonic gear reducer, the contact mechanical model of flexible bearing, vibration differential equation of flexspline, and finite element model of each component in harmonic gear reducer were established. Based on the established model of harmonic gear reducer, the influence of the length of flexspline cylinder and the thickness of cylinder bottom on the stress of flexspline is discussed, respectively, and the motion characteristics of flexible bearing are studied. At the same time, the spatial distribution of the displacement of the flexspline and the axial vibration response of the flexspline are studied. The correctness of the model established in this paper is verified by experiments. The results show that the increase of cylinder length can improve the stress of flexspline in harmonic gear reducer; the wall thickness of cylinder bottom mainly affects the stress at the bottom of flexspline but has little effect on the stress of gear ring and smooth cylinder. Along the axis direction of the flexspline, the radial displacement, circumferential displacement, and angular displacement increase linearly with the increase of the axial distance between the cylinder and the bottom. When the excitation frequency is high, the vibration mode of flexspline shell is mainly axial vibration. The research results will provide a theoretical reference for the optimal design of harmonic gear reducer and improving the service life of flexible parts.
Highlights
Gear transmission has the advantages of high transmission accuracy and compact structure, which has been widely used in the field of mechanical transmission [1, 2]
To verify the correctness of the finite element model of harmonic gear reducer established in this paper, the strain gauge tester is used as the data collector to study the deformation characteristics of flexspline of harmonic gear reducer
In the range of L 70∼85 mm, the decrease trend of the maximum equivalent stress tends to be gentle, from 514 MPa to 488 MPa, 406 MPa to 303 MPa, and 98.1 MPa to 79.2 MPa. It shows that the stress concentration of flexspline decreases with the increase of cylinder length
Summary
Gear transmission has the advantages of high transmission accuracy and compact structure, which has been widely used in the field of mechanical transmission [1, 2]. Folega [7] used the boundary element method to calculate the strength of the teeth of the flexible gear ring in the process of harmonic gear transmission and analyzed the design characteristics of the flexible gear and the influence of different tooth shapes on the stress value of the bottom surface of the ring gear. It indicates that many models of harmonic gear reducer are established and analyzed, but the comprehensive analysis of the contact mechanical properties of the flexible bearing and the flexspline with thin-wall vulnerable components is rare. Based on the established contact mechanics model and finite element model, the motion characteristics of the flexible bearing and the dynamic response of the flexspline are analyzed.
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