| In this paper, the author discussed the concept, category, research and application of the high-speed diesel engine's optimizing design in valve train. The focus is on the definition, status quo of research and application of valve train in the overhead camshaft. Meanwhile, the definition and method of finite difference as well as the theory of numerical approximate were further studied. With the emphasis on their application, the finite difference, the theory of numerical approximate and the optimizing design of valve train were harmoniously integrated. According to the characteristics of the overhead camshaft valve train, the author thoroughly analyzed the kinematics and dynamics concerned in the design of valve train cam profile. The results illuminate the influence of valve timing, ample factor as well as the contact stress between cam and tappet on the design of cam profile. On these bases, the author combined the method of analytic function, finite difference and numerical approximate in the optimizing design of valve train cam profile, and developed a special software with the exclusive purpose in the valve train cam profile design. With the aid of this software, the optimizing design was carried out for a valve train cam profile provided by Shanghai Diesel Engine Research Institute. The initial demand of simplification, directness and visualization was realized during the experiment process. In order to enhance the precision and universality of the software, the author provided some improved way of calculation accordingly. The description of arithmetic in the nonsymmetrical valve train cam profile and polynomial dynamic cam profile was stressed. The last part of this paper treated the results with the assistance of spline function and Nth-degree harmonics cam approximate. Thus, the new function of tappet, speed and accelerated speed was gained and the whole designing process was completed. |
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