Abstract: The helicopter power transmission system technology is the key technical area for improving the helicopter performance, reducing the noise/vibration level of helicopters and decreasing the cost of life cycle of helicopters. In this paper, the technical characteristics of the helicopter power transmission system are introduced first. Then, the development history and trend of the transmission configuration, the component and the design and analysis technique of the transmission system are described. The advanced material and process technology applied in the helicopter power transmission system are also described. Finally, the power transmission system technology used in the high speed helicopters is briefly presented.
Abstract: Most transmissions for wind turbines are set up by multiple consecutively arranged planetary gear sets and/or normal gear sets. Therefore these transmissions have a constant ratio. In order to feed the electricity produced by the wind turbines into the grid, an electric conversion to a constant frequency of 50 Hz is necessary. FZG developed a new concept for transmissions of wind turbines based on a planetary gear. By superposition of a small electric engine the transmission ratio is continuously variable. This makes an electric conversion unnecessary and thereby increases the efficiency of the wind turbine.
Abstract: This study presents a numerical model of helical gears to consider the effects of shaft and bearing flexibility. A primary feature of this study is that the time-varying mesh stiffness is not just determined by the geometry of gear pair but also updated for each iteration according to the change of center distance. The effects of shaft and bearing flexibilities are discussed by comparing the dynamic response of gear pairs supported with a rigid and a flexible bearing-shaft system. The results show that the pressure angle and contact ratio are significantly changed due to the center-distance variation of gears and the gear pair with a flexible bearing-shaft system has much larger vibration. Finally, experimental tests are conducted to validate the proposed model. The predicted results show good agreement with the experimental data.
Abstract: This work develops an analytical model of multi-stages planetary gear transmission (PGT) coupled with bearings in housing based on analyzing the displacement relationships of gearing system. The model adopts three planar degree-of-freedom for each of the central components, and the rotational degree-of-freedom for the planets of each stage. Considering the gyroscopic effects, the modified transverse-torsional model is established in the rotating Cartesian coordinates by lumped-parameter method, which is more accurate and may match with the physical model better than the purely torsional model. According to the design parameters of the 3-stage planetary gears of main reducer of shield tunnelling machine, the natural frequencies and vibration modes are investigated by using this transverse-torsional model.
Abstract: Two three-dimensional lumped parameter dynamic models of spiral bevel gears are presented and compared. The first approach is classic and relies on a single averaged mesh stiffness element connecting the gears whereas a time-varying non-linear distribution of discrete stiffness elements over the potential contact area is used in the second model.
Abstract: The generating of face gear with arcuate tooth has been proposed in this paper, and the meshing characteristics are investigated. Based on the concept of imaginary gear cutter, tooth surface equation has been derived, flank modification has also been considered. The transmission errors and bearing contacts of the face gear drive with arcuate tooth under different assembly conditions are investigated by applying the tooth contact analysis. The numerical results reveal that the bearing contacts are not sensitive to the errors of misalignments, and a more favorable type parabolic function of transmission errors with better symmetry and reduced amplitude may be obtained according to the modification of the face gear.
Abstract: A new silk-hat type of harmonic drive device (HDD) with arc flexspline (FS) structure is developed. Loaded gear contact analysis (LGCA) and stress calculations are made for it with three-dimensional, finite element method (3D-FEM). Basic performances and strengths tests are also made. It is found that the new structure almost has the same performances and strength as the old one.
Abstract: In order to minimize the fluctuation of gear transmission error (GTE) about the planetary gear transmission. A method was developed to deciding tooth profile modification curves of planetary transmission. According to the condition of the invariable design load, computing the dynamic characteristics of the planetary transmission system under modified and un-modified gear. At the same time, the compare is carried through of the dynamic characteristics for modified and un-modified gear. The results of the dynamic calculation indicate that the profile modification method can make the amplitudes of gear mesh stiffness change calmness and reduce the amplitudes of gear mesh stiffness by this method in paper. At last, the conclusion can be obtained that the tooth profile modification can reduce the vibration and noise of the planetary transmission system.
Abstract: In a gear box design, it is quite difficult for a designer to quickly find an optimum solution, while the space restriction is given and the weight is to be minimized. Also the manufacturing cost, total power loss and other relevant factors have to be considered. Solving such a problem is very time-consuming, if different variants of reducers have to be evaluated carefully. A new optimization tool, based on KISSsys software, permits to layout automatically a complete gearbox using functions for the layout of gear stages, shaft dimensions and bearings, if the required torque capacity, life time, safety factors and the total ratio are given. This tool is used to generate a complete set of different variants of gear reducers. The main results are displayed in 3D graphics, showing weight, costs and efficiency of the different variants. Another graph shows the casing dimensions of the variants in three dimensions in order to check the compliance with space restriction. The use of this tool in two typical engineering applications gives very good results; the potential for weight reduction is higher than expected, going up to 30%. Manufacturing price reduction is even higher, going up to 50%.