Study On New Profile High Speed Roller Chain Sprocket

The roller chain drive is one of the most important mechanical foundation parts and widely used in vehicle engine, petrochemical industry, auto assembly line etc. It has been the first choice of many industries especially under the condition of heavy haul and great center distance, However, as drive speed continuously improves, the traditional roller chain sprocket tooth profile is difficult to meet the conditions of high speed, low noise etc. Besides, owning to the deficiency of necessary theoretical and technical support, domestic research of new sprocket tooth profile is still at initial stage and has not cast off its passive situation of depending on the foreign imported high value chain. Therefore, it is an urgent research subject at present to improve the transmission performance of roller chain mechanism by studying on new tooth profile sprocket.First of all, the formation mechanism of chordal action and meshing impact which cause vibration and noise in roller chain transmission process is analyzed; and the research of new tooth profile sprocket is carried out in order to decrease the meshing impact and fluctuation of chain under high speed condition. As the trochoidal curve has no singular point, no intersection point with basic circle and smooth transmission, therefore, the trochoidal curve is used as the tooth profile of new roller chain sprocket.Secondly, according to the formation mechanism of trochoidal curve, the equation of curtate epicycloid is deduced by the premise that the moving circle rolls without slipping on basic circle, and the equation of new tooth profile sprocket is obtained by the method of seeking equidistant curve using parameter equation. What's more, the three-dimensional models of curtate epicycloid sprocket, involute curve sprocket, epicycloid sprocket and two kinds of standard sprocket are established by means of 3-D modeling technique, and the data of each sprocket tooth profile is calculated using MATLAB. Finally, according to the actual working condition, establish multi-body dynamics model of the timing chain transmission mechanism by using simulation software, and all the sprocket profile data calculated by MATLAB are inputted into the model. Simulation experiments are performed with every tooth profile as the speed range from 1000-8000r/min, and under the condition of various rotating speeds, the tension of chain, friction between chain and other transmission parts, fluctuation of chain, meshing impact between sprocket and roller and the nonuniformity coefficient of driven sprocket angular velocity are comparatively analyzed when using different tooth profile sprocket. The simulation results show that the meshing impact between sprocket and roller, tension of chain and friction between chain and transmission parts are efficiently reduced using curtate epicycloid sprocket compared with involute curve sprocket and epicycloid sprocket; and using curtate epicycloid sprocket could improve the stability and dynamic performance of chain at all kinds of speeds compared with standard sprocket.