| Abstract:Face-gear transmission is a new-type gear transmission.It evolves from the transmission with cylindrical gear and bevel gear wheel.Compared with bevel gear drive, it has many advantages, for example, small size, light weight, high bearing capacity, low noise, high reliability, long life.Especially, it used in the main decelerator of armed helicopter, because of its distinctive split-flow characteristic which has been paid close attention. At present, face-gear transmission are taking the place of spiral bevel gears and becoming top-drawer key components in the drive system of armed helicopters.The tooth surface generating and meshing characteristics of face gears were studied for the purpose of designing high-quality face-gear with high strength and low noise. The main contents are as follows:1. The tooth surface generating of face-gear based on generating cutting and the research on the contact traceAccording to the face-gear meshing theory, equations of the working tooth surface and transition curved surface were derived. And the reasons that the outside of tooth appears the tooth top sharpens and the inner side of tooth appears the tooth root undercuts were analyzed.Finally,the change curves of minimum inner radius and maximum external radius’ coefficient which can keep unsharpened tooth top and disundercuted tooth root, which provides convenience for the parameter design of face gear. The equation of contact track on the tooth surface was derived, by which can obtain the distribution map of contact trace. Based on the simulations on tooth surface contact were proceeded under conditions of different modules and tooth number, found that the tooth contact trace is related to the difference of number of teeth, modulus and transmission ratio, and the influence of transmission ratio is larger. And,if the modulus is increased,the height and length of the tooth will increase. While if the number of tooth is increased,width of the tooth will increase,the height of the tooth will decrease.Face-gear transmission coordinate system considering installing deviation is established.The relation among offset deviation, axial deviation and axis shaft deviation that exist during installation is discussed.It was found that controlling the deviation can change the position of the contact area on surface in the meshing process of face-gear drive, and it can adjust the contact trace.2. The research on the geometric method of face-gear tooth surface generating and the physical field of face-gear teeth grindingThe movement was analyzed in process of face-gear grinding by worm grinding wheel, and the geometric model of grinding machine for face-gear tooth surface grinding by worm grinding wheel was built. On the basis of the coordinate system of the worm grinding wheel enveloping process, the coordinate transformation matrix when the tooth surface of shaping cutters enveloped worm grinding wheel tooth surface was derived, and the model of worm grinding wheel was built for face-gear grinding. With the model of worm grinding wheel designed,the surface of face-gear is simulation processed.By comparison of it and theoretical tooth surface, contact and deviation were analyzed in the process of face-gear grinding.Thermo-mechanical coupling and the influence of process parameters on face-gear grinding physical field were analyzed.The distribution diagram of temperature, stress and strain in process of tooth surface grinding were obtained.The results showed that, higher grinding speed and lower grinding depth are beneficial for the tooth surface grinding of face-gear, but the feeding speed’s influence on the tooth surface grinding stress is not obvious. So, it may be appropriate to properly increase the speed of face gear grinding feed.3. Analysis on the temperature field and vibration characteristics of face-gear meshingAbsolute and relative slipping velocity, contact pressure, tooth surface friction coefficient of the meshing points,and the distribution law and the influencing factors of frictional heat flux along meshing surface have been analyzed.And we got conclusions that larger pressure angle is good for the decrease of the frictional heat flux. The analysis on the temperature rise of tooth surface with the variation of meshing position in the meshing process of face-gear drive was conducted. The study found that the highest temperature point is in the region near the top edge.The influences of factors such as tooth number difference, pressure angle, modulus, rotation speed and load on face-gear meshing performance was analyzed. The study found that the main source of surface vibration of face-gear drive is the slave wheel, i.e. face-gear. The vibration of system is the least when the pressure angle is20degree or25degree, the difference of number of teeth is3.Larger modulus is beneficial to the improvement of vibration of system,while larger input speed and load will increase the vibration of the system.4. The research on the experiments on the meshing performance of face-gear driveIn order to verify the correctness of the simulation results of face-gear drive meshing performance, the contact trace and transmission errors of the face-gear drive that a face-gear meshing with three cylindrical gears of1-3tooth difference respectively, were tested on a face-gear tester. The test results showed that the influence of the difference of the number of tooth on contact trace is not obvious, but the transmission ratio’s is large. Larger transmission ratio, within a certain range, can make the contact trace near the middle of tooth. Experimental study on the vibration testing found that the difference of number of teeth is1, least error of face gear drive, but when the difference of number of teeth is2, meshing performance of face-gear drive is better. The influence of rotation on vibration of cylindrical gear and face-gear in the X axis direction are larger than in the Z axis. But the influence of rotation on vibration of face-gear in the Z axis direction is larger than more sensitive than cylindrical gear. |
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