Theoretical And Experimental Study On The Dynamics Of Roller Chain Drive System

The roller chain drives, which have the advantages of the high transmission efficiency, the strong bearing capability and the ability to achieve the long distance transmission, are widely used in agriculture, mining, metallurgy, lifting, transportation, petroleum, chemical, automotive, textile, printing and packaging mechanical systems for power transmission. With the development of the roller chain toward the high-speed and high-precision direction in a variety of engineering applications, the research on the dynamics of the high speed roller chain drive systems has become one of the hot topics in this field. The chain drive systems can be divided into the constant and intermittent moving chains. The dissertation studies some basic issues on dynamics of the above two types of chain drive systems under the medium and high speed condition. The following contributions have been made:A parameterized model of the complete roller chain drive system with the tight and slack spans is proposed. Given the basic parameters of the center distance, the two initial position angles of teeth on driving and driven sprockets corresponding to the first seating roller on each side of the tight span, dynamics of roller chain drive systems with any structural parameters can be analyzed by the procedure. In the model, the effect of the clearances on dynamic response of the chain system is taken into account, as well as the flexibility of input shaft, the elastic deformation in the chain, the inertial force, the gravity and the torque on driven shaft. The dynamic behavior of the roller chain can be well simulated by the model, which provides an effective method for the analysis of the dynamic characteristics of the medium and high speed chain drive systems.Based on the parameterized model, the influence of the polygon effect, the engaging impact and the chain links'clearances on the torsional vibration of the sprockets, the vibration of the tight and slack spans, and the dynamic load of the chain are analyzed and summarized. The results show that the higher order harmonic vibration of chain drive system can be excited by the engaging impact. The shock amplitude of the engaging chain link can be strengthened when the clearances are considered. Aiming at the fact that the stability of the high-speed chain drive systems is mainly affected by the transverse vibration, the dynamic model of the transverse vibration of roller chain drive system is proposed. The effect of the parameters, such as the length of chain, the mass of chain, the pitch of link, the transmission velocity, the tension force and the coupling lumped mass, on the modal characteristics of the transverse vibration of the constant moving chain has been analyzed. It is found that the natural frequencies of the transverse vibration present the fluctuating phenomenon when the moving chain is coupled with the lumped mass.Aiming at the working characteristics of the intermittent roller chain drive system with the guide rails, the dynamic model of this kind of mechanical system with multi-clearance is proposed. The influence of the general motion laws, the clearances and the preload on the dynamic characteristics of the intermittent roller chain drive system is analyzed and summarized. The results show that the use of motion laws with small jerk at conversion point can effectively suppress the impact vibration at this point caused by clearances. The use of nonsymmetrical motion laws with small jerk approaching the end of the indexing period can suppress the residual vibration. The conclusions provide a reference for the design of new motion laws for intermittent chain drive systems.A test rig of intermittent roller chain drive system is designed and set up. The longitudinal vibration response of the chain system under the different motion laws and preloads is measured. The experimental results verify the correctness of the theoretical conclusions. It is furter found that the elastic vibration of the chain span at its natural frequency can be excited under the condition of large preload. The proper preload will help to improve the dynamic performance of the intermittent roller chain systems.