Proceedings of SerbiaTrib '13

2. EFFICIENCY OF CYCLO DRIVEEfficiency of cyclo drive primarily depends onthe resistance due to friction between the elementsof cyclo drive. Two methods for determining ofcyclo drive efficiency are presented in this paper:Malhotra method [11] and Gorla method [12].2.1 Malhotra method for calculating of cyclodrive efficiency, [11]The various sources of power loss in a cyclodrive are:• Rolling friction in the mounting of thecycloid disc on the input shaft,• Rolling friction between output rollers andholes in the cycloid disc,• Rolling friction between housing rollersand the cycloid disc,• Sliding friction in the mounting of theoutput rollers,• Sliding friction in the mounting of thehousing rollers.Design parameters are presented on Figure 2,and loads on Figure 3.W =⎛+ n⎜f+r2⎝+2πn∫ dW =0fs1fr1⋅ d2π⋅ Dm⋅ n n∫ ( θ)dθ +DFr 0 E2π⎞ n q⎟ ∫ ∑ F ( θ)dθ +Kj⎠ 0 j = 12πVK2⎛ ⋅ d ⎞ n q( u + 1) ⎜f+f s2 O ⎟ ∫ ∑ F ( θ)dθ(1)CR ⎜ r3 ⎟⎝2Kj⎠ 0 j = 1where: f r1 , f r2 and f r3 are lever arms of rollingfriction, f s1 and f s2 are sliding friction coefficients,D m is mean diameter of input shaft bearing, D r isinput shaft bearing rollers diameter, F E is bearingreaction, d VK is diameter of outpit mechanism pins,F Kj is force between output roller j and cycloid disc,q is number of output rollers, u CR is cyclo driveratio and d 0 is diameter of housing pins.Figure 3. Loads on cycloid discThe overall efficiency of cyclo drive is then:M a 2π− Wη = (2)M 2πwhere M a is input torque.aFigure 2. Geometry of cyclo driveFor the elemental rotation dθ of the cycloid disc,the rotations of the input shaft, output rollers andhousing rollers are n⋅dθ, n⋅dθ and (n+1)⋅dθ,respectively. The frictional work per rotation of theinput shaft can be determined as:2.2 Gorla method for calculating of cyclo driveefficiency, [12]Power loss due to the bearing friction could becomputed by means of the following equation:WMa M a( ω − ω )= ⋅(3)innerouterwhere: ω inner is bearing inner race speed and ω outeris bearing outer race speed.Power loss due to the friction between the pinsof the output shaft and the holes of the cycloid discis:13 th International Conference on Tribology – Serbiatrib’13 231