Investigation on The Effects of Tolerancing and Fitting Condition on The Radial Pressure and Stiffness of A Roller Bearing

• Main Authors: Tzu-Ting Chou, 周孜庭
• Other Authors: Jhy-Cherng Tsai
• Format: Others
• Language: zh-TW
• Published: 2019
• Online Access: http://ndltd.ncl.edu.tw/cgi-bin/gs32/gsweb.cgi/login?o=dnclcdr&s=id=%22107NCHU5311059%22.&searchmode=basic

碩士 === 國立中興大學 === 機械工程學系所 === 107 === Tolerance fit is an important feature of mechanical components, it affects the performance of assembled mechanical components. The most typical representative is the fitting condition of shaft and bearing. The state of the fit affects the pressure distribution between the shaft and the hole (radial preload), which in turn affects its radial stiffness. The general bearing fit is selected according to the conditions of use, and is selected through the catalogue or calculation table of the bearing. However, this method does not consider that the shaft and the hole often produce a clearance fit due to machining tolerances, and the radial preload cannot be formed and the radial rigidity cannot be grasped. Therefore, this study is aimed at roller bearings and exploring the distribution of the interference amount when the tolerance is matched, and analyze its radial pressure and stiffness distribution. At the same time, the expected value is analyzed as the basis for designing the bearing fit tolerance. Firstly, the distribution scale distribution corresponding to the tolerance specifications of the shaft and the hole is analyzed by the probability distribution function, and the statistical distribution of the interference of the two is analyzed by convolution method. Then, according to the amount of interference, the interface pressure and stiffness of the shaft hole mating surface are analyzed. Because the interface pressure cannot be directly obtained, this study uses numerical methods to solve. The analysis method is to assume the interface pressure first, and analyze the deformation of the shaft and the hole. The algebraic sum must be equal to the interference amount. If the two are not equal, the interface pressure is adjusted according to the stiffness of the original pressure condition, and the deformation analysis is performed again until the two are equal. At the same time, the radial rigidity of the mating surface is calculated. In this paper, a roller bearing with a diameter of 50 mm is taken as an example. Carry on analysis according to the transition fitting condition H6k5 recommended by the bearing. The results show that the matching distribution part is the gap part interference, and the expected value of interference is gap of 0.5μm, which has a big gap with the original design function. It shows that is not suitable for directly using the recommended values of the bearing catalogue, and should further select the appropriate tolerance fit according to the functional requirements. The main contribution of this research is to find that the selection of tolerances of bearing catalogue cannot meet the requirements of radial stiffness. The tolerance of the bearing should be matched according to the performance requirements.