Research On Variation Design Method Of Rounded-jointed Silent Chain

Silent chain is an important mechanical foundation,which is widely used in the field of mechanical transmission because of its high transmission accuracy and low noise.As an important branch of the silent chain,the rounded-jointed silent chain has a growing demand in the market for its simple structure and multi-type pitch.The individualized demand of different host products is also increasing,which makes the rounded-jointed silent chain present a variable demand.Based on the National Natural Fund project "Variation Theory and Key Design Technology of Silent Chain(51775222)",this paper studied the variation design method of rounded-jointed silent chain.Firstly,the background and significance of the research direction in the selected topic are elaborated,and the classification and application fields of the silent chain are introduced.Subsequently,the research status and problems of Hy-Vo silent chain and rounded-jointed silent chain at home and abroad are introduced in detail,and the necessity and importance of the research content in this paper are explained.In this paper,considering the clearance between pin and pin hole of chain plate,the parameters of inner-outer composite chain plate for rounded-jointed silent chain are calculated and analyzed.Based on the meshing position of chain plate and sprocket,the design calculation of sprocket is carried out.The variation design method of involute sprocket based on the meshing and positioning state of plate is proposed.The method of measuring the involute sprocket twice before and after material removal is put forward,and the solution methods of column diameter and measurement over columns are given.By using the method of mathematical geometry analysis and the principle of solving the tooth profile normal method,the curve equation of the inside outer convex tooth profile of the inner-outer composite chain plate is obtained.According to the meshing relationship between the inner-outer composite chain plate and the involute sprocket,the mathematical relationship between the protrusion of inside outer convex tooth profile and other parameters of the silent chain system is derived.On the premise of considering pin hole clearance,the meshing design system of silent chain-sprocket-cutter is established,and the modification coefficient of involute sprocket is obtained by using a new method.Based on the Recurdyn,a multi-body dynamic analysis software,the dynamic simulation model of the rounded-jointed silent chain is established.The transmission error,chain fluctuation and meshing impact characteristics of the silent chain system are analyzed.The analysis results validate the rationality and accuracy of the previous theoretical calculation,and show the good transmission performance of the rounded-jointed silent chain system with the variation design method.The rigid-flexible coupling model of rounded-jointed silent chain system is established by using the method of joint finite element and dynamic simulation.The stress distribution of chain plate and pin under dynamic loads and the area where the maximum stress occurs are simulated and analyzed.The results show that the maximum stress of chain plate and pin meets the design requirements.The modal and harmonic responses of the rounded-jointed silent chain system are analyzed by using finite element software.The natural vibration characteristics and the dynamic response characteristics under the meshing impact are studied.On the basis of modal and harmonic response analysis,the noise of rounded-jointed silent chain is calculated and simulated.The cloud picture of noise at a specific frequency is obtained and the noise source of the silent chain system is determined.By analyzing the frequency response characteristics of noise in a specific area,the main frequency of noise causing larger decibel noise in this area is determined,which provides a reference for further optimizing the NVH performance of the silent chain system.The variant design method and research results presented in this paper lay a theoretical foundation for the further research on the variant design of rounded-jointed silent chain,and are of great significance for the establishment of the design method system of silent chain with independent intellectual property rights.