Theoretical Study On The Teeth Profile Modification Of FA Type Cycloid Transmission

FA cycloid reducer is a high precision transmission, which is based on the conventional cycloid reducer,and the structure and technology has been improved, it has the advantages of small volume, high transmission efficiency, high rotary accuracy, so it has very broad application prospects in the field of construction. When the FA pin-cycloidal gear planetary drive used in robot drive, it has a high requirement of rotating error, and the modification of cycloid gear tooth profile is a key factor to affect the rotation error and capacity, so the paper studies the key technology of modification of the gear profile to meet high capacity and high precision. The research content of this thesis is a part of National Natural Science Fund Project "study on the series of FA transmission based on the theory of optimum gear profile design (No.50875029)", this paper uses the method of the combination of the theoretical analysis and experimental verification to research the key technology of high capacity and high precision FA type cycloid Transmission.Through the research of the generation principle of theoretical cycloid, a reverse modification system of cycloid gear is designed, to get the basic parameters of the model. The generated cycloid curve is in close agreement with the cycloid curve reversed from Japanese prototype profile, which confirms the correctness of the reverse system. According to the cycloidal modification reverse results of the Japanese prototype, confirm that Japanese cycloid gear uses standard profile. But taking into account China’s processing and the limit of installation precision, the cycloid gear profile must be modified. Therefore we need in-depth study of cycloid modification method to seek a kind of cycloid tooth profile which can both to meet actual level of processing installation of our country, and also can satisfy the high precision and high bearing capacity requirements.Based on the analysis and comparison of all kinds of single and composite modification methods, the mathematical model of isometric modification and shift modification cycloid gear and pin gear when the first contact interval computation is build, the calculation formula is derived first contact interval, the left and right boundary points (φTm、φTn). In order to meet the requirement of high capacity and high rotary accuracy, the combining modification methods of "negative offset+positive shift" taken to form the "arch back teeth profile" modification are studied. Establish and deduce the mathematical model of geometric rotation angle of cycloid transmission under the condition of considering the existing gap between the pin gear and pin gear casing, and optimize the optimum modification quantity of "arch back teeth profile "to meet the requirements of the preset minimum geometric rotation angle,and the dynamic stress analysis between the pin gear and cycloid gear surface is taken.High precision drive for "arch back teeth profile" is achieved at the expense of certain capacity, in the transmission of large transmission ratio two teeth difference structure was taken, by increasing the number of meshing gear pairs to improve the meshing condition not only keep the high accuracy but also achieve better bearing capacity, and the theoretical analysis of it have also been carried out, through the programming calculation of theoretical analysis compare with the finite element analysis of the ANSYS to verify. The results show that the two teeth differenced structure "arch back teeth profile" compare the one tooth differenced structure’s can have higher precision and carrying capacity. This paper also proposes the eccentric distance modification method suitable for two teeth difference structure, and make a theory analysis of return difference and stress research for the innovative modification methods to verify the feasibility and application advantages of this modification method.Based on the "inverse arch-shaped teeth profile" of two teeth difference structure the FA45-29prototype was manufactured, and the experimental analysis and comprehensive test plan of return difference,mechanical efficiency, temperature rise, noise and vibration were taken. The test results meet the performance requirements of FA type cycloid transmission of Japan.