Study On The Principle And Characteristics Of Cosine Gear Drive

It is well known that the tooth profile is a fundamental element to determine transmission performances of a gear drive.With development of modem scientific teclmology,the characteristics of gear transmission is being improved increasingly, especially in the area of high speed,heavy load and miniaturization.For gear drive,the key factor afecting its dynamic property is the tooth profile.So many tooth profiles(including modification of standard involute tooth profile) are being developed and used to satisfiy different applications.However,in practical production,the tooth profiles should satisfiy the needs of a certain transmission ratio,as well as the needs of the design,manufacture, installation,application and so on.Considering the difficulty of manufacture,the initial tooth profiles are simple curves,such as the involute and circular arc.With the development of computerized numerical control(CNC) technology,the manufacture of complicated curve and surface can be realized.Therefore,new tooth profiles can be applied to improve the transmission performance.Moreover,a number of significant advances in this area were achieved in the recent decades.The mathematical models,including the equation of the cosine tooth profile,the equation of the conjugate tooth profile and the equation of the line of action,are established based on the meshing theory.A few characteristics,such as contact and bending stresses,sliding coefficient and contact ratio,of this new drive are analyzed.A comparison study of these characteristics with the involute gear drive was also carried out in this work.The proposed gear drive demonstrated a number of advantages,such as low sliding coefficient and high strength.The results show thatâ…°) the cosine gear take the zero line of cosine curve as the pitch circle,a period of the curve as a teeth space,and the amplitude of the curve as the tooth addendum,â…±) There is no meshing interference during the meshing process.Moreover,the cosine gear drive is line contact,â…²) Near the pitch circle of the cosine profile,the change of the curvature is stable,and the value is small,so it is advantageous to increase the contact strength.â…³) The contact ratio of the cosine gear drive is about 1.1 to 1.4.which is smaller than that of the involute gear drive.It decreases with the increase of the teeth number and the pressure angle,and increases with the increase of the addendum coefficient.â…´) The slide coefficient of cosine-gear drive is smaller than that of involute gear drive and it changes stable.The results are good to reduce the wear,improve the meshing performance and prolong the life-span,â…µ) The contact and the bending stresses of the cosine gear drive are higher than that of the involute gear drive.