Abstract
In contrast to the conventional forced wave generator which consists of cam and flexible bearing in harmonic drive, the novel forced wave generator retains cam but cancels flexible bearing. In this article, the lubrication characteristics of the novel forced wave generator in harmonic drive is studied. First, an elliptical sliding bearing (ESB) model of simplified structure between the novel forced wave generator and the flex spline is established. Further, the computational fluid dynamics (CFD) method is employed to study the effect of some factors on the lubrication characteristics of the ESB model including elliptical gap ratio, width, and rotational speed. According to the analysis, the elliptical gap ratio has a great impact and its optimal value is 3, which is used in the design of the novel forced wave generator. Last, the practical design of the novel forced wave generator in harmonic drive is given, which can provide a basis for design and optimization of a forced wave generator without flexible bearing of the harmonic drive.
Highlights
In the 1950s, the harmonic drive (HD) was invented by C.W
A conventional HD consists of three major components of wave generator (WG), flex spline (FS), and circular spline (CS) and the forced wave generator (FWG) is a common type of wave generator, which is an assembly of a flexible bearing fitted onto the contour of a cam
Xin [5] set up the analysis model of triple wave type harmonic drive and worked out the FS’s radial and tangential deformation expressions under the action of triple disk type wave generator by using the elasticity theory
Summary
In the 1950s, the harmonic drive (HD) was invented by C.W. Musser based on the theory of the thin-walled elastic deformation [1], which has a wide application owing to its significant advantages such as huge reduction ratio and extremely compact structure.A conventional HD consists of three major components of wave generator (WG), flex spline (FS), and circular spline (CS) and the forced wave generator (FWG) is a common type of wave generator, which is an assembly of a flexible bearing fitted onto the contour of a cam. Harmonic drive is a kind of high-precision reducer by means of the periodic controllable elastic deformation generated by the FS and WG to transmit the motion and power. The design parameters of the WG profile directly affect the shape of the FS, and the working stress and the service life of the FS greatly determine the transmission performance of the whole harmonic reducer. In order to improve the meshing performance and extend the service life of harmonic gear transmission, Gravagno [2] discussed and quantitatively evaluated the influence of the wave generator shape on the pure kinematic error and centrodes of harmonic drive. Routh [3] analyzed the coning phenomenon and the lubrication mechanism at flex spline cup and cam interface in conventional harmonic drives using FEM method. Li [6] proposed the wave generator profile for harmonic drive using a closed convex curve generated by the support function and analyzed the stress and deformation using
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