Rearch On Design And NC Machining Technology For High-speed Involute Cylindrical Gears

In view of spur gears, helical gears and herringbone gears emploied in the gearbox of marine and aircraft, a tooth contact analysis(TCA), loaded tooth contact analysis(LTC A), calculation of stress, modified optimization with different target, multi-axis linkage nc processing modified tooth surface, design of gears with a higher order transmission error and systematic experiments and theory are studied based on the gear meshing theory and the finite element method(FEM), which aim at developing a set of software of engineering application value, improving the transmission system stability and reducing the vibration and noise of gear box.The important achievements are listed as follows:(1) A LTCA model considering the pitch errors is investigated, and the results prove that pitch errors lead to rising amplitude of loaded transmission error(ALTE) and uneven loads distribution of the tooth. Besides, a precise FEM and assembled model is proposed for modified herringbone gears, and some programming data files are loaded into Abaqus software to execute analysis, then the key performances parameters are obtained,which show that LTCA method is higher efficiency and more accuracy than method of abaqus software.(2) A model of real tooth surfaces represented with a sum of two vector functions that determine the theoretical tooth surface and the deviation based on data from three-coordinate measuring machine(CMM) are developed. Besides, a model of TCA including tooth contact, edge tooth contact are developed, which show a higher efficiency and more concise model of TCA than directly representing the actual tooth surface with the fitting technique of complex curved surfaces.(3) Firstly, methods of double crown and diagonal modification for cylindrical gears are developed. The former contributs to reducing vibration and increasing strength of gears due to constant length of instantaneous contact line, and the latter reflect the real tooth surface shapes. Secondly, the optimization design of modified gears is based on TCA and LTCA technology. Thirdly, optimal aims are minimum the ALTE, minimum vibration, loads sharing, minimum flash temperature and multi-objective of above to improve performances of gears. Finally, the result shows that: there are minimum flash temperat ure with profile modified gears due to sufficient lubrication. Besides, the flash temperature has little changes in the one tooth meshing zone of spur gear. Axial moving of herringbone gears is about mutual compensation of the tooth gap for the double helical gears, in short, considering both modification and axial motion, then the loads tend to be uniform totally. The corner meshing impact increases with increasing loads and rotating speeds, and the system vibration are more sensitive to the latter than the former, so the resonance sensibility is dulled. ALTE under multi- loads reflects the varying trend of vibration for modified gear. Torsional vibration mainly result from corner meshing impact and meshing stiffness excitation which have little effect on axial vibration, and the axia l motions excitation contribute to both axial and swing vibration for herringbone gears. In brief, the vibration decrease greatly because of smaller excitations with modified gears.(4) Some CNC machine models of multi-axis and multi-degree of freedom are established. Error correction models based on sensitivity analysis are determined, and the topographic flank errors are developed by estimating whether the wheel contact with the gear. With minimum squared error as the objective function, the corrections were solved using optimization algorithm. The result are as follows: Firstly, the topologically modified tooth can then be efficiently ground by slightly adjusting five-axis movement of the forming grinding machine according to the solved corrections. Secondly, slight variations in pressure angle, helix angle and generating angle produces some specific diagonal modified tooth respectively. Besides, diagonal modified helical gear with big size and helix angle can then be efficiently ground with a smaller flat wheel translating along axis. Thirdly, an accurate tangential feed of the hob with longitudinal correction can attain an anti-twist helical gear tooth flank with longitudinal tooth crowning, because continuous changes in profile along longitudinal of hobber contributes to reduce distortion of profile; Besides, adjusting hobber profile and coefficients of the polynomials based on their sensitivity, double-crown tooth are produced. Finally, two kinds of different methods of grinding gear with cone wheel are simulating. One is the grinding wheel reciprocating along the axial of the gear. In this case, the radial position of the wheel and the number of stroke are determined based the theoretical surface roughness, which can reduce surface roughness and shorte n grinding time remarkably. Besides, an error correction model based on a sensitivity analysis of machine tool motion is developed, and the kinematic relations of each axis are determined, and the validity of the method are numerically demonstrated using the CNC gear machines, which effectively reduce the machining errors, and grind complex modification of tooth surface. The other is the grinding wheel reciprocating along longitudinal of the gear. In this case, grinding wheel just moves along the contact line, which contributes to simplifying the machine movement and the numerical control programming. The key technology are accurate alignment of meshing starting point between the gear and the cone wheel. Further more, the grinding experimental results show the validity of the case, which effectively reduce machining errors.(5) An design of tooth surface modifications for cylindrical gears that are provided with a controllable higher order polynomial function of transmission error(H- TE) are proposed to further reduce vibration and noise. The polynomial coefficients of H-TE curve as well as processing parameters for rack generating pinion tooth surface can be individually determined based on TC A and LTCA by optimizing the aim of minimum the ALTE of drive gears. The result are as follows: Firstly, the ALTE increases with increasing loads due to a const actual contact ratio for unmodified gears, and the ALTE decreases with increasing loads due to more and more pair of tooth contacts with each other, which contributed to a increasing contact ratio for modified gears. Secondly, the loads increases to a certain value, then the contact ratio attain maximum value, and the ALTE increases with increasing loads due to a const actual contact ratio. Thirdly, gears with H-TE has the lowest ALTE, because the slope of H-TE is the most flexibility than of second order or forth order polynomial function of transmission error, and decrease the fluctuation of tooth stiffness caused by the regions of different pair meshing. Finaly, curvature analysis of tooth surface shows that it is feasible to process the tooth with plane grinding wheel. Besides, taking into account the contact pattern, another modified gears with H-TE are presented to demonstrate the advantages over a smaller ALTE. The results shows the parameters of concave depends on loads, and the parameters value increases with loads increasing.(6) An experiment of vibration for the gears shows that modification tooth have better dynamic performances than standard tooth. ALTE and vibration decreases by 30% or more under the design loads, The experiment verified the methed of according to the magnitude of load optiming quantity in profile modification is basic right, thus the theory and method of the project can be used in engineering practice.