| Herringbone gear sets, also known as double helical gear drives, are commonly used in alarge number of automotive, ships and industrial applications in spite of claim for highprecision manufacturing and installation. They posses numerous advantages overparallel-axis gear trains including high bearing capacity, smooth transmission and small axialload. Most common examples of herringbone gear sets can be found in ship transmissions, jetengines, and helicopter drive trains. Because of their growing use in modern industry,dynamic health monitoring and early fault detection has become the subject of intensiveinvestigation and research. Therefore, a reasonable and reliable dynamic transmission modelneeds to be put forward to describe noise and kinetic quality of herringbone gear system inthe design stage.In this paper, with the aid of loaded tooth contact analysis (LTCA), finite element (FEM)and other technologies, excitation sources of gear surface vibration, transmission process ofdynamic load,3-D modification of tooth surface and experimental measurement areconducted in-depth discussion and research. This paper has carried on the following research:(1) Based on the fundamental theory of engagement, related formulas between real teethcontact surfaces are derived considering the tooth surface errors (modification). Loaded toothcontact analysis model of herringbone gear which take into account the axial floating, on thisbasis, calculation method of meshing stiffness is brought out. And variation of tooth meshingstiffness under different loads is discussed. The maximum deviation between classicalcalculation method and LTCA-based method does not exceed15%.(2) As the foundation of meshing impact mechanism, meshing impact starting position,impact velocity, meshing impact force and impact contact time are detail derived. The cornermesh impact model considering contact ratio is presented, and the influences of impact forceand impact time under different loads, wheel speeds and contact ratios are also analyzed.(3) The twelve-dimensional multiple-degrees-of-freedom (d.o.f.s) herringbone gearvibration model is finally established. Considering the different supporting ways betweenpinion and gear shafts, dynamic loads on support bearings are calculated separately. Based onthe rolling bearing dynamic model and internal load distribution on bearings, comprehensiveanalysis of the vibration transmission process from meshing gear pair to rolling bearings, andto internal walls of gearbox bearing holes is conducted. The dynamic contact stress, dynamic bending stress, and the dynamic transmission efficiency are calculated on the basis of thetime-varying dynamic tooth surface load.(4) Finite element model of herringbone gearbox is established by consider of thefluid-solid coupling effect between the gearbox inner wall and lubricating oil. Thefundamental modal shape of gearbox is proposed to verify the box structure design isreasonable. Under the boundary condition with real dynamic load, frequency response andsteady state response of the operating gearbox are obtained correspondingly. And thenvibration acceleration and the corresponding1/3octave structure noise of concerned pointsare obtained. Comparing with full finite element model method, the calculated resultsobtained the maximum deviation of3.29%.(5) Vibration reduction design methods are put forward respectively from vibrationexcitation source of herringbone gear transmission system (tooth meshing quality) andvibration transmission path (box structure). Tooth surface three-dimensional modification ischosen to optimizing the vibration between the herringbone gear meshing teeth undermulti-loads, and the maximum vibration reduction rate reached20.42%. Topologyoptimization is carried out target with static (box deformation) and dynamic (lower naturalfrequency) in order to improve the gearbox dynamics structure, and the optimization resultscan indicate which parts of redundant material and which structure needs to be strengthened.Accordingly, gearbox structural size is optimized to obtaining minimum acceleration ofgearbox feet.(6) To evaluate the proposed model approach, a rolling bearing support herringbone geardrive system is adopted to do the real closed power flow vibration test. The relative vibrationacceleration in meshing line direction is measured through high-precision angle encoders, andvibration acceleration data in gearbox test points are obtained by accelerometers. Simulationand experimental results are in good agreement. |
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