Research On Discrete Variable Diameter Pulley Continuously Variable Transmission

The using of CVT allows the machine to continuously change the speed of the output shaft within a certain range without changing the input speed,so as to meet the requirements of various working conditions and the production system in operation.In the transmission of mechanical continuously variable transmission,most of the CVT are driven by friction.According to the different contact forms,the current mechanical CVT are mainly in the form of point contact and line contact.Because of the small contact area between the transmission elements and the limited positive pressure per unit volume,the point-contact type and line-contact type continuously variable transmissions cause the current mechanical continuously variable transmission to have a smaller torque and low efficiency.The situation is also a bottleneck restricting the further development of mechanical continuously variable transmissions.Throughout the vast majority of mechanical continuously variable transmission,the different structure types determine the different form of transmission contact,which will directly affect the transmission torque and efficiency.Therefore,it will still have important significance in the research and development of new structure continuously variable transmission.This paper proposes a new type of discrete adjustable radius CVT(AR-CVT).The new structure adopts a belt drive mode in which a combination of discrete pulleys and serpentine belts is used for transmission.The transmission pulley can be arbitrarily changed in diameter,and the surface-contact type friction transmission of the belt and the pulley can be realized.The structure scheme of this new type continuously variable transmission is also given in the article,and its working principle is described in detail.The basic dimensional relationship of the AR-CVT is determined according to the transmission requirements,and a three-dimensional model is established.Through the assembly analysis and interference detection to ensure the correctness of the model and the rationality of the design program,and makes prototypes.This paper combines the basic principles of belt drive and derives the theoretical calculation formula for the critical friction force of the discrete pulley drive.The validity of the formula was verified by MATLAB,which proved that the new continuously variable transmission theoretically has the ability of large torque transmission.Based on the relevant theories of virtual prototyping technology,the dynamic characteristics of the AR-CVT are studied,and a discrete belt drive virtual prototype model is established using ADAMS software.This paper introduces the modeling method of implementing flexible belt drive simulation in ADAMS,and analyzes the speed fluctuation of the AR-CVT at different output speeds.The results show that the AR-CVT can achieve a smooth transmission at high speed,which is consistent with the conditions of the vehicle transmission.Based on the PID control principle,the touch screen integrated PLC is used as the upper computer.The overall design plan of the control system is given,and the design of the new speed control system of the new variable belt pulley CVT is completed.The experiment shows that the control system can achieve fast and accurate speed control.The method of theoretical simulation and experimental analysis is applied to the project.It is proved that using discrete pulley can achieve high speed output,high torque transmission and high efficiency transmission.The speed control system based on PID control principle realizes the characteristics of fast response and high control accuracy in speed control.It laid the foundation for the research and development of a new type of CVT with high efficiency and high torque.