Developmental Investigation into Low-Noise High-Performance Hybrid Reducers Consisting of Gear and Traction Drives

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Gear drives have been widely used because of their high power transmission efficiency and the compactness of the gear box. However, gear noise causes trouble in many cases when gear drives are operated at high speed. In contrast to this, traction drives hardly cause noise problems because power is transmitted without help of teeth.In order to minimize noise from speed reducers, we designed and made a new hybrid speed-reducer with two reduction stages consisting of gear and traction drives. A traction drive with one driving roller and three following rollers was used in the first (high speed) stage, and a gear drive with one gear and three pinion integrated to the following-roller shafts was used in the second stage.Equations for calculating the theoretical reduction ratio and power transmission efficiency of the hybrid speed reducer were derived, and they were used for the analyses of the experimental results.Two types of the hybrid speed reducers were designed and made to examine the power transmission efficiency and running noise. The trial hybrid reducer with external gears having a total reduction ratio of about 20 was rotated up to 2000 rpm input shaft speed. the total efficiency of the speed reducer reached to about 90 % when a low viscosity mineral oil was used as traction oil. In the case of the reducer with an internal gear, the reduction ratio was increased to about 28 with the same size of reducer box, but the total efficiency did not decrease. Running noise from the speed reducers was extremely low as expected.Effects of kinds of traction oils and contact pressure between rolling elements on the total efficiency and changes in the reduction ratio were clarified by experiments with the help of theory.