Ordinary Gears Research Articles

Dynamic Analysis of Planetary Gear Reducer

This paper presents dynamic analysis of a three stage planetary gear reducer for operate a tower crane. Ordinary and planetary gears have been designed respecting the coaxial, neighboring and mounting conditions. Harmonic analysis has been processed to identify frequency response for displacements, strains and deformations. The aim of the study was to determine critical frequencies to avoid mechanical resonance phenomenon. The obtained results are based on the superposition method for solving the systems of differential equations resulting from the analysis with finite elements.

Classification and synthesis of three-loop planetary gearboxes

In the transmissions of trucks, agricultural vehicles and tractors, gear boxes with a planetary divider and/or an additional reductor unit which is depending on the traffic conditions of the machine, reduces the speed of rotation or operates on a direct drive are used. The divider and the additional reductor unit are intended for a stepwise changing of the range of the main 3-speed or 4-speed gearbox, consisting of gears with fixed axles, which makes it possible to increase the number of stages realized 4 times. If the planetary train will work in the differential mode, this will allow additionally increase the number of stages in the combined planetary gearboxes and, accordingly, the number of operating modes of the tractor. Consequently, the main gearbox consists of gears with fixed axes of gears can work either separately in a single-flow mode of operation of the planetary train (reductor or in the direct drive mode) or in a two-flow mode - in parallel with other ordinary gears when the planetary train as a differential. When using two planetary trains operating in the differential mode, the number of parallel power flows increases to three, which makes it possible to further improve the functional and power capabilities of multi-flow gearboxes. The purpose of the study is to analyze gearbox schemes consisting of three sets of gears with fixed gearwheel axes and two differential mechanisms forming three parallel power transmission flows. Classification of possible structural schemes of three-flow transmissions is given, a general expression for calculating the number of stages of a three-flow gearbox is obtained. A technique for the synthesis of kinematic schemes of three-flow planetary gearboxes is described, with the using of which new gearbox schemes are obtained for each possible structure, which are characterized by using simple mechanisms, high efficiency and a small number of control elements.

Windage Power Losses of Ordinary Gears: Different CFD Approaches Aimed to the Reduction of the Computational Effort

Efficiency improvement is one of the main challenges in all fields of design. The reduction of power losses is becoming a great concern also in the design of power transmissions. For this reason it is important to have specific models available in order to quantify the power losses during the design stage. The power losses of a gear transmission can be subdivided into bearing losses, seal losses, meshing losses and hydraulic losses. Although literature provides models for the prediction of losses related to bearings or to gear meshing, for the calculations of the losses generated by the interaction with the lubricant, only few and simplified models are available. For this reason the authors recognize that a general purpose method is required in order to overcome this lack of fit and to improve the capability to predict the efficiency of gearboxes. Being able to compare different design solutions means being able to improve the efficiency, reduce the operating temperature and, consequently, improve the reliability of the system. In this paper, the windage losses generated by a single rotating gear have been studied exploiting different numerical approaches. The results obtained have been compared with measurements showing good agreement.

Churning power losses of ordinary gears: a new approach based on the internal fluid dynamics simulations

AbstractThe increasing need of more and more efficient gearboxes implies the need of predictive models in order to compare, during the design stage, different design solutions. The models provided by literature are mostly experimentally derived and not accurate on real applications. A new trend suggests the adoption of computational fluid dynamics (CFD) for the calculation of the no‐load losses of gear transmissions. In this sense, literature provides some works, but most of them involve only one single phase. In this paper, the real operating condition in which the gears are immersed in an oil lubricant mixture is studied. Adopting an open‐source code, OpenFOAM®, the influence of some operating and geometrical parameters on the churning losses has been investigated. The aims are both to provide data that can be effectively used by engineers in the design practice and to prove, once again, CFD to be an effective approach for this kind of investigations. Copyright © 2014 John Wiley & Sons, Ltd.

17 - REMOVED: Mill Gearing

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Influence of lubricant temperature, lubricant level and rotational speed on the churning power loss in an industrial planetary speed reducer: computational and experimental study

Planetary speed reducers are applied in a wide range of applications. Their main advantages are the compact design and high power density. For this reason, the demand for high effi ciency gearboxes is continuously increasing and this is also why models to predict the additional churning loss, characteristic of this kind of gearing, are required. The particular confi guration of the planetary speed reducers, in fact, entails an additional motion with a circular path around the gearbox axis of the planetary gears due to the rotation of the planet carrier on which they are mounted and this induces an additional source of loss. Having effi ciency prediction models allows, in fact, comparison of different solutions during the design step. Literature provides some prediction models for ordinary gears but no models are still available for planetary gears. This report introduces a computational and experimental analysis of this kind of loss. Many simulations have been performed and the infl uence of many operating conditions like lubricant level and temperature and the rotational speed of the planet carrier have been studied. Moreover, the results of an experimental testing campaign on a specially designed gearbox are presented and compared with the computational ones to validate the model. The two approaches give results in good agreement.

The Profile Calculation and the Best Fillet of Powder Metallurgical Gears

this paper researched the profile calculation and the best fillet of powder metallurgical gears. Different from the ordinary gears, we must research the locals of the cutter to make the die of the powder metallurgical gears. And it is possible to revise the fillet in order to increase the bending strength of the powder metallurgical gears.

A Generalized Dynamic Model of Geared System: Establishment and Application

In order to make the dynamic characteristic simulation of the ordinary and planetary gears drive more accurate and more efficient, a generalized dynamic model of geared system is established including internal and external mesh gears in this paper. It is used to build a mathematical model, which achieves the auto judgment of the gear mesh state. We do not need to concern about active or passive gears any more, and the complicated power flow analysis can be avoided. With the numerical integration computation, the axis orbits diagram and dynamic gear mesh force characteristic are acquired and the results show that the dynamic response of translational displacement is greater when contacting line direction change is considered, and with the quickly change of direction of contacting line, the amplitude of mesh force would be increased, which easily causes the damage to the gear tooth. Moreover, compared with ordinary gear, dynamic responses of planetary gear would be affected greater by the gear backlash. Sim...

The FEM Analysis and Torque Calculation of REPM Gear

Permanent magnetic (PM) gears are magneto-mechanical devices that are widely used to replace the ordinary mechanical gears and to transmit torque without any mechanical contact. In this paper, according to the demagnetization curve of REPM material and the relationship between magnetic density and intensity of magnetization with magnetic medium in the magnetic field, the magnetic analysis model of PM external gear is built, and its magnetic field distribution is calculated by the finite element method (FEM). The transmission torque is calculated by the Maxwell stress tensor method and its characteristics are studied theoretically. In the end, the torque curves of PM gear are given. From the curves, the influences of geometry size, magnet number, transmission ratio, height of yoke of the magnet on transmission torque are obtained. It cannot only forecast the field distribution to a certain extent, estimate the transmission performance, calculate the transmission torque, but also can give a quantitative direction to the optical design and related parameters of PM gear.

トルク比一定の歯車に関する研究 (第1報)

Meshing theory of the ordinary gears is based on the condition of constant angular velocity ratio. But it is more important for watches and clocks to get gears of constant torque ratio. Because in order to keep the period of oscillation of pendulums or balance wheels constant, it is preferable to give a constant torque to the axle of the escape-wheel.Unfortunately when a pair of the ordinary gears are in mesh, the transmission torque varies on account of the frictional force between the teeth. From this point of view, the gears of constant torque ratio were investigated.In this paper, the equations of intermeshing of tooth profiles of these gears are introduced with the tangential polar coordinates and some tooth profiles of constant torque ratio are derived using these equations. The results are proved to be reliable by experiments. And the tooth profiles of the racks which are used to generate the gear teeth, are also given.