Design and analysis of double-crowned high-contact-ratio cylindrical gears considering the load sharing of the multi-pair contact

Tooth modification is widely used to reduce noise and vibration. However, the traditional middle-convex tooth modification is likely to cause excessive load concentration; therefore, the contact stress sharply increases. In this study, a new method is presented to reduce the amplitude of loaded transmission error and meanwhile significantly less increase of contact stress is caused. First, the pinion is double-crowned through the modified tooth profile of the rack-cutter and a predesigned transmission error. The novelty of the new method is that the transmission error is predesigned based on the theoretical contact ratio of the gears. Second, a multi-objective optimization model is established to minimize the amplitude of loaded transmission error and contact stress. Ultimately, two examples are presented to test the feasibility of this new method. The results show that the new method is more effective in reducing the amplitude of loaded transmission error and that the contact stress of the new method is much smaller than that of the traditional one. Moreover, the advantages of the new method are further confirmed by comparing the amplitudes of loaded transmission errors and contact stresses of the new and traditional method with the misalignment error.