The Design of Conjugate Translating Cam Mechanisms with Translating Follower Having an Eccentric Roller

• Main Authors: Lin, Yu Cheng, 林煜晟
• Other Authors: Wu, Long Iong
• Format: Others
• Language: zh-TW
• Published: 2016
• Online Access: http://ndltd.ncl.edu.tw/handle/07362720339560101070

碩士 === 國立清華大學 === 動力機械工程學系 === 104 === Generally the disk cam mechanism needs to equip with a return spring to maintain the contact between the cam and the follower. However, a larger space is required to accommodate the return spring, and the force exerted by the spring may result in a larger contact stress. To avoid the aforementioned disadvantages, the conjugate cam mechanism can be employed instead. The clearance between the conjugate cam and its roller follower can be controlled by means of accurately machined cam profiles and an adequate lubrication at the contact surface. Nevertheless, the accurate cam profile is costly to fabricate. Alternatively, by the application of the adjustable eccentric roller, the clearance can be eliminated efficiently and economically. But when cam works, the contact stress will also create the clearance .Hence, it is the aim of this research to show in ideal situation how to adjust the eccentricity of the eccentric roller to eliminate the clearance caused by contact stress. Firstly, the ideal profiles of the conjugate cams were analytically synthesized by employing the concept of velocity instant centers. Then, the accompanying cam profiles were calculated with considering the adjusted design dimensions caused by the eccentricity of the eccentric roller. The profile differences between the ideal cam and the accompanying cam were regarded as the expected amount of preloading. Next, the force analysis and the contact stress analysis of the conjugate cam mechanism were performed for allocating the suggested range of adjustment of eccentric roller and the conjugate cam arrangement. The obtained results indicated that the conjugate cam mechanism with an adjustable eccentric roller was effective in eliminating the clearance.When the eccentric roller had 0.25 mm eccentricity , the center orientation of the adjustable eccentric roller was suggested to be between 5 and 15 degrees. Meanwhile, the areas of two conjugate cams should be nearly the same so as to avoid undesired vibrations due to non-uniform mass distribution. The arrangement and the roller adjustment of the conjugate cam mechanism presented in this research may be helpful to achieve its expected purpose easily and directly.