Abstract
The crankshaft bearing is the key component of a rotate vector (RV) reducer. However, owing to the harsh working load and restricted available space, the bearing often suffers from fatigue failure. Therefore, this study proposes a novel optimization method for RV reducer crankshaft bearings. A nonlinear constraint optimization model for the design of the bearing considering the crowned roller profile is formulated and is solved by using a crow search algorithm. The goal of the optimization is to maximize the fatigue life of the bearing. The design variables corresponding to the bearing geometry and crowned roller profile are considered. The load working conditions of the bearing and structure of the RV reducer are analyzed. Various constraints, including geometry, lubrication, strength of the bearing, and structure of the RV reducer, are established. Through the optimization design, the optimum crowned roller profile suitable for the working load of the bearing is obtained, and the stress concentration between the roller and raceway is eliminated. Taking the crankshaft bearing of RV-20E and RV-110E type reducers as examples, the bearings were optimized by the proposed method. After optimization, the bearing life of the RV-20E type reducer is increased by 196%, and the bearing life of the RV-110E type reducer is increased by 168%.
Highlights
The rotate vector (RV) reducer is widely used in industrial robots because of its compact structure, small size, high torsional rigidity, large transmission ratio, and great load capacity [1,2]
For an RV reducer, the service life mainly depends on the rated life of crankshaft bearings [4,5]
Both the RV reducer sample manuals of Nabtesco and standard GB/T37718 take the rated life of the crankshaft bearing as the service life of the reducer
Summary
The rotate vector (RV) reducer is widely used in industrial robots because of its compact structure, small size, high torsional rigidity, large transmission ratio, and great load capacity [1,2]. Wang [12] proposed a new contact model of cycloidal meshing pair and analyzed the transmission accuracy of RV reducer. The above review shows that most of the published works focus on the meshing characteristics of the cycloidal pair, tooth profile modification, and performance characteristics of the RV reducer. Studies [16,18] have optimized the fatigue life of cycloidal reducers by using a multi-objective optimization method, the geometric parameters and roller profile of the bearing have not been comprehensively considered during the optimization design. An optimization method for RV reducer crankshaft bearings considering the bearing geometry and crowned roller profile is presented. The fatigue life of the crankshaft bearing considering the clearance and crowned roller profile is evaluated
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