Meshing Theory And Application Of Dual Meshing Silent Chain Drive

Silent chain drive is widely used in the timing mechanism of gasoline engine, such as motorcar and motorcycle engine. However the polygon movement and the meshing contact of silent chain drive are great obstacles in the further development and application of the silent chain mechanism. It is necessary to develop new kind of silent chain drive to improve the transmission performance of silent chain mechanism. The meshing theory and application of the dual meshing silent chain drive are investigated to reduce the polygon movement and the meshing contact.The dual meshing is presented in order to reduce the polygon movement. The characteristic of the presented dual engagement form is that both sides of the silent chain tooth form can engage with the sprocket tooth form. At the beginning of a meshing circle, the inner straight tooth form of the silent chain engages with the sprocket form. At the end of a meshing circle, both sides of the silent chain contact with the sprocket form. The dual meshing silent chain depends on its outer tooth flank to wind around the sprocket. The inner tooth form of link plate is profiled to parallel and project outward of the outer tooth form as the dual meshing silent chain is stretched into a line.The meshing theory of the dual meshing silent chain drive is systematically investigated. The dual meshing silent chain mechanism is designed, which comprises the dual meshing silent chain and new kind of sprockets. First, both forms of silent chain, including the inner form and the outer form, are designed to mesh with the sprocket in order to reduce the amplitude of the polygon movement. According to the envelope principle, the approach to solve the sprocket tooth profile conjugated with the outer tooth form of dual meshing silent chain is presented. The result shows that the sprocket tooth profile is an involute surface with large pressure angle and large negative addendum modification coefficient. Second, in order to acquire the new kind of sprocket, the sprocket tooth profile is modified. Finally, the characteristic of the sprocket tooth profile is studied and the parameter function of the sprocket tooth profile is derived. The analysis results show that the undercut would not generate in the course of sprocket processing as the absolute value of the unique modification coefficient is smaller than that of the minimal modification coefficient.