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In order to meet the requirements of variable transmission ratios and improve the bearing capacity of gear teeth, a new type of double-circular-arc tooth profile elliptical gear is proposed based on the meshing theory and the structural parameter characteristics of the double-circular-arc tooth circular profile curve. The design method of its pitch curve is described. A three-dimensional model of the double-circular-arc tooth circular profile elliptical gear is established using SolidWorks software. Adams software is used to simulate the kinematics of the elliptical gear pair model with double-circular-arc tooth profiles, and the influence of different eccentricities on the variation rule of the double-circular-arc gear pair transmission ratio is analyzed; compared with the theoretical transmission ratio curve, the influencing factors of the fluctuation error of the simulation transmission ratio curve are analyzed. In order to reduce the vibration pulse of the gear pair, the appropriate value range of eccentricities is given. The design method and analysis results in this study have theoretical reference value for parametric design of non-circular gears with double-circular-arc tooth profiles, and can provide a basis for NC manufacturing and application of elliptic gear pairs with double-circular-arc tooth profiles.

Based on the hypothesis of stretch small distortion and distortion congruity,the model and algorithm of meshing force analysis under theoretical conditions are given.According to the Hertz theory and geometric relation of meshing pair,the meshing rigidity models of the meshing pair are established,and the calculation formulas of the meshing rigidity and the principal curvature of the contact point are deduced.The presented methods is illustrated through an example,and the distributing characteristic of meshing forces,sum of principal curvature and meshing rigidity of this type of transmission device is acquired.The acquired result can be adopted as the analytical base for structure design,vibration analysis.

In view of the problem that the conventional analysis method cannot directly solve reliability problem of the complex cylinder sine oscillating tooth transmission system,a simulation method based on minimal cut sets of fault tree is proposed,which can solves system reliability.According to the structural characteristics of cylinder sine oscillating tooth transmission,the function block diagram of the system is given and the fault tree of the system is built.The minimal cut sets of the fault tree are acquired,and the cumulative failure probability and the probability density are calculated.Different types life distribution function of the system are fitted out.The life distribution function is determined preliminarily based on the principle of minimum residual sum of squared,and the K-S hypothesis testing is carried out for the life distribution function,which ultimately determine life distribution function of cylinder sine oscillating tooth transmission is Weibull distribution.The weak links of cylinder sine oscillating tooth transmission system are determined by analysis of model importance.

A statically designed derrick of deep oil well drilling rig may have poor dynamic characteristics, which can cause earlier structure failure of the drilling rig and harsh working condition. One such designed derrick is found to vibrate severely in operation while the rotation speed of rotary table is about 120 r/min with the working frequency of 2.0 Hz. To solve this problem, an experimental modal test of the derrick is conducted and the modal frequencies and vibration shapes are obtained. Through comparison of modal frequencies with that of exciting devices, it is found that the severe vibration of the drilling rig is caused by the resonance of second modal frequency (1.96 Hz) and the working frequency of rotary table. Based on principles of sensitivity analysis and structural dynamics modification method, the frequency sensitivities of all nodes on the derrick are calculated and compared, and then seven nodes with high-frequency sensitivity are selected on which corresponding mass are added to vary the modal frequency. Result shows that the second modal frequency of the derrick is reduced to 1.42 Hz and is out of the normal working frequency range of rotary table, which demonstrates that the dynamic characteristics of the derrick is improved and severe vibration can be avoided.