A Characteristic Study on a Modified Helical Gear Set

• Main Authors: Yi-Cheng Chen, 陳怡呈
• Other Authors: Chung-Biau Tsay
• Format: Others
• Language: en_US
• Published: 2001
• Online Access: http://ndltd.ncl.edu.tw/handle/74029444522868170089

博士 === 國立交通大學 === 機械工程系 === 89 === This thesis proposes a modified helical gear pair composed of an involute pinion and a modified circular-arc gear. This novel type of modified circular-arc helical gear can be manufactured on hobbing or grinding machines with a curved-template guide in practice. The analyses results reveal that the proposed modified helical gear set possesses a localized bearing contact and a parabolic type of transmission errors (TEs) under an ideal meshing condition. The parabolic TE can absorb the discontinuous TE resulting from the tooth profile errors and assembly errors. In addition, neither TE jump nor edge contact will occur in the case of axial misalignments. Therefore, the proposed modified helical gear set indeed possesses its applicability and superiority. The research subjects of this thesis include the following six major items: (1) The mathematical model of the modified circular-arc helical gear set is developed based on the theory of gearing and the generating mechanism. (2) The sufficient conditions for the existence of a regular tooth surface is derived by considering the relative velocity of the generating tool and the gear blank along with the equation of meshing. These conditions result in the equations for tooth undercutting and provide gear designers with useful information for choosing gear parameters and tool settings to avoid tooth undercutting. (3) The TE and contact patterns of the proposed modified helical gear set are investigated by tooth contact analysis (TCA) and the surface topology method. Additionally, the optimization technique is also adopted to determine the adequate design parameters for the gear set. (4) The influences of design parameters and assembly errors on the TE as well as contact patterns and contact ratio (CR) of the gear set are also studied. (5) Based on the differential geometry and curvature theory, the principal directions and curvatures of the mating gear tooth surfaces are investigated, and the orientations and dimensions of the contact ellipses are also studied. (6) An automatic mesh-generation computer program for the three-dimensional tooth model is developed based on the developed gear geometry. Meanwhile, finite element stress analysis of a pair of contact teeth is performed to investigate the stress distribution on the tooth surface.