Abstract:  The preload of tapered bearing affects the life, efficiency, and noise of gearbox, which were very important indicators to measure the quality of new energy vehicles. In order to obtain the optimum product performance, the design of shafting preload was studied. Firstly, the analysis model of a new energy vehicle reducer with tapered bearing was established, the relevant factors affecting the design of preload were analyzed. Then, the relationship between preload and the life of bearing was determined. Finally,taking the preload of intermediate shaft tapered bearing and differential shaft tapered bearing as bivariate parameters, the influence of preload on the strength, efficiency and noise of gearbox was analyzed. The results show that the efficiency ofreducer assemblyincreases obviously with the increase of the preload of the intermediate shaft, while the transmission error of the primary and secondary gears goes up with the increase of the preload of the intermediate shaft, and the increase of the preload of the differential shaft reduces the transmission error of the secondary gear. The bench test verifies that the order noise of the secondary gear is better than 100 μm when the preload of the intermediate bearing was 50μm, and better than that of the clearance 50 μm, the noise increases after the differential preload is reduced by 50 μm. The effect of the preload on noise is consistent with the analysis results, it verifies that the design of taper bearing preload is feasible.
Key words:  mechanical transmission system; gear strength; bearing life; MASTA; differential shaft; bench test; transmission error of gears; gear misalignment