| Crown gear couplings are commonly applied to transfer rotary motion and torsion from one rotating component to another under a certain misalignment angle.Because of their higher load carrying capacity than other forms of flexible couplings,crown gear couplings are widely used in the power transmission under complex working condition and heavy load,such as marine and wind energy.Huge-scale marine crown gear coupling with maximum diameter of more than 1000mm presented in this dissertation,is a key component of the large warship’s transmission,can transfer torque of more than 10~6N·m and accommodate the effect of ship deformation in all directions under wave’s action.However,the design knowlage of this type of huge-scale crown gear coupling is still blank in our country.The research will not only lay a theoretical foundation for the huge-scale marine crown gear coupling design,but also promote the design and manufacturing level of the novel coupling,even marine transmission.Considering large transmitted torque,large geometry size,small misalignment angle and variable misalignment angle features,this dissertation made a systematic theoretical and experimental study on tooth surface modeling,tooth contact analysis,loaded tooth contact analysis,tooth wear analysis,innovative hub tooth design,and design,manufacture and test of prototype of the huge-scale marine crown gear coupling.The main research works and achievements are as follows:(1)Based on machining simulation technology and gear meshing theory,a high fidelity tooth surface model was built and an analytical tooth contact analysis technique for crown gear coupling with more complex meshing state was proposed.And the accuracy of the analytical method was verified by comparing with the method based on dividing the hub tooth into several nodes proposed by Alfares.In addition,the effects of misalignment angle and displacement circle radius on the tooth contact characteristics were analyzed.The results show that meshing is in line contact and minimum circumferential clearance is always 0μm at any meshing position,when the coupling is aligned;meshing comes into point contact,contact points are all located at the tip and root of the hub tooth,and minimum circumferential clearance reaches the minimum and maximum near the pure tilted area and the pure pivoted area respectively,when the coupling is misaligned;contact points move from middle to end along the tooth width direction,when misalignment angle or displacement circle radius increases;minimum theoretical circumferential backlash is twice the maximum absolute value of the minimum circumferential clearance.(2)A loaded tooth contact analysis model for crown gear coupling with full teeth was established by using self-compiled high precision finite element mesh.Then,the model was employed to investigate the effects of meshing position,torque,misalignment angle,and displacement circle radius on loaded tooth contact characteristics.The results show that maximum stress decreases with the increase of displacement circle radius,when the coupling is aligned;maximum stress changes with displacement circle radius,and reaches the minimum value at a cetrtain displacement circle radius when the coupling is misaligned.Furthermore,the relation between the optimum displacement circle radius with structural parameters and working condition parameters was fitted out based on response surface methodology by considering two boundary conditions of 0°and maximum misalignment angle.Finally,the optimum displacement circle radius values were obtained by the proposed loaded tooth contact analysis model for two sets of parameters,and compared with those obtained by the response surface model.The results show that the response surface model is effective and can be used to design the displacement circle radius of the huge-scale marine crown gear coupling.(3)A fast multi-step discretization and parallelization wear simulation model for marine crown gear coupling considering the influence of variable misalignment angle on dynamic meshing force,load sharing among teeth,load distribution on tooth surface and relative sliding distance was established.Based on the statistical law of offshore ocean waves,analysis of ship’s incline and sway,and dynamic simulation of marine crown gear coupling,the changing rules of misalignment angle and dynamic meshing force were obtained.Using unloaded and loaded tooth contact analysis to obtain the relative sliding distance and contact stress,combined with Archard wear model,a multi-step discretization and parallelization wear model of crown tooth coupling with a constant misalignment angle was proposed and simulation analyses of tooth surface wear of crown gear coupling with different misalignment angles were carried out.Based on these,a fast multi-step discretization and parallelization wear simulation model for marine crown gear coupling with variable misalignment angle was further proposed,and a numerical example was analyzed.It was found that maximum relative sliding distance increases with the increase of misalignment angle,and the relative sliding distance between the teeth near the pure tilted area is larger than that near the pure pivoted area;when the coupling is aligned,the tooth surface doesn’t produce wear;the difference between each tooth surface wear distribution of crown gear coupling with variable misalignment angle is small and the tooth surface wear pattern is symmetrical about the middle of the tooth width.(4)Tooth profile and meshing performance of two traditional hub tooth surface models were analyzed,and an innovative hub tooth profile was further proposed.Two traditional hub tooth surface models were established,and tooth profile and meshing performance of the two models were compared and analyzed.It was found that when the coupling is misaligned,hub tooth tip edge contacts with sleeve tooth root flank and sleeve tooth tip edge contacts with hub tooth root flank for both modelⅠand modelⅡ,which can cause stress concentration.To avoid the occurance of tip edge contact,an innovative hub tooth with profile crowning,longitude crowning,and tip sphere teeth was proposed.Moreover,grinding technology,machining simulation and accurate modeling of the innovative hub tooth surface were studied.By using coordinate transformation,a novel crown gear coupling was assembled by the innovative hub and a spur ring gear according to the given misalignment angle.And then,tooth contact analysis and loaded tooth contact analysis were carried out for novel crown gear coupling with a misalignment angle of 0.2°.The results show that compared with traditional crown gear coupling,novel crown gear coupling needs a much smaller backlash to make the hub and sleeve mesh normally;novel crown gear coupling reduces sensitivity of maximum contact stress to misalignment angle;novel crown gear coupling reduces maximum contact stress by 35%using the example presented in the dissertation,effectively improves load distribution and avoids edge contact along the profile direction in presence of angular misalignment.(5)A dedicated test rig which can adjust misalignment angle of crown gear coupling to measure the meshing performance was designed and set up.According to traditional tooth modification theory and innovative tooth modification theory for the hub,the specimens with the same structure,similar parameters and reduced size for test were designed and processed,and the machining accuracy of tooth surface was tested.On the test rig,the engagement tests under different misalignment angle were conducted.Comparing experimental results and theoretical results,it shows a very good agreement,which means that the theoretical model used to calculate tooth contact analysis is effective.Comparing experimental results obtained by using the novel crown gear coupling and the convention crown gear coupling,it can be found that the novel crown gear coupling effectively avoids edge contact,and its meshing characteristic is much better than the traditional one,which verifies the superiority of the innovative hub tooth profile. |
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