A computational model is proposed for the prediction of friction-related mechanical efficiency losses of parallel-axis gear pairs. The model incorporates a gear load distribution model, a friction model, and a mechanical efficiency formulation to predict the instantaneous mechanical efficiency of a gear pair under typical operating, surface, and lubrication conditions. The friction model uses a new friction coefficient formula obtained by using a validated non-Newtonian thermal elastohydrodynamic lubrication (EHL) model in conjunction with a multiple linear regression analysis. The load and friction coefficient, distribution predictions are used to compute instantaneous torque/ power losses and the mechanical efficiency of a gear pair at any given rotational position. Efficiency measurements from gear pairs having various gear designs and surface treatments are compared to model predictions. Mechanical efficiency predictions are shown to be within 0.1% of the measured values, indicating that the proposed efficiency model is accurate. Results of a parametric study are presented at the end to highlight the influence of key basic gear geometric parameters, tooth modifications, operating conditions, surface finish, and lubricant properties on mechanical efficiency losses.

Prediction of Mechanical Efficiency of Parallel-Axis Gear Pairs

Survey of nonlinear vibration of gear transmission systems

In this study, a test methodology was developed for measurement of spur gear efficiency under high-speed and variable torque conditions. A power-circulating test machine was designed to operate at speeds to 10,000 rpm and transmitted power levels to 700 kW. A precision torque measurement system was implemented and its accuracy and repeatability in measuring torque loss in the power loop was demonstrated. Tests were conducted on gears with two values of module, and two surface roughness levels, operating in a dry sump jet-lubrication environment with three different gear lubricants. These tests were used to quantify the influence of these parameters on load-dependent (mechanical), load-independent (spin), and total power loss. Trends in mechanical gear mesh efficiency and total gearbox efficiency were discussed in terms of rotational speed and transmitted torque. Finally, recommendations were made for the design of spur gear pairs, surface roughness, and lubricant selection for improved efficiency.Copyright © 2007 by ASME and General Motors

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An Experimental Investigation of Spur Gear Efficiency

A model based upon a finite element procedure is introduced for analyzing the influence of tooth friction on spur and helical gear dynamics. The equations of motion are solved by combining a time-step integration method with several iterative algorithms aimed at satisfying normal and tangential contact conditions. Comparisons between simulated and measured quasi-static bearing forces are satisfactory and largely validate the theoretical developments. Results also reveal the potentially significant contribution of tooth friction to gear vibration and noise. Simulations are then extended to high speeds and the interest of considering both transmission error and tooth friction excitations to achieve silent gears is discussed.

Experimental and Numerical Investigations on the Influence of Tooth Friction in Spur and Helical Gear Dynamics

Development of a generalized mechanical efficiency prediction methodology for gear pairs

By means of the FZG spur gear testing machine the frictional loss of engagement of gears, the temperature rise of tooth, and the limiting load for scoring were investigated using commonly used mineral oils The modules of test gears were changed widely from module 2 to module 6 and the coefficient of addendum modification was also changed widely, ie the position of the path of contact on the line of contact was very widely changed, that is, from an extremely eccentrical position to the standard position The formula for calculation of the limiting load for scoring, the frictional loss, and the temperature rise of tooth was found and the relationships between them was clarified

Studies on Frictional Loss, Temperature Rise and Limiting Load for Scoring of Spur Gear

Nowadays, reducing frictional loss of gears to save energy is a big concern. There are many sources of printed information on this problem for gears, but most of them are practical specialized information and are not developed to give a generalized basic consideration. Since this kind of research has not been brought beyond such, a practical and specialized range, experiments were carried out to study the influences of tooth form, sliding velocity, load, tooth surface roughness, and viscosity of lubricating oils, and kinds of oils on the frictional loss of gears. The frictional loss of spur gears decreases with sliding velocity and the viscosity of lubricating oils, and increases with surface roughness. The frictional loss is very low when using a synthetic oil of the SHF type. The organic molybdenum friction modifier (FM) is also quite effective for reducing frictional loss. Finally, empirical formulas for calculating frictional loss were expressed in terms of tooth form, sliding velocity, tooth surface ...

Study on Frictional Loss of Spur Gears (Concerning the Influence of Tooth Form, Load, Tooth Surface Roughness, and Lubricating Oil)©

Limiting Load for scoring and coefficient of friction, in the case of carburized and hardened steel, under various contact conditions of simultaneous rolling and sliding, were studied. Their characteristics were tested, changing widely the lubricating oils, sliding velocity and specific sliding. We got an approximate formula about the limiting load for scoring as a function of sliding velocity and specific sliding. The critical temperature rise by Blok was also discussed with our experimental results. Moreover we have compared the limiting load for scoring by means of FZG spur gear test and 4 ball test with our experimental results by means of our disk-machine.

Limiting Loads for Scoring and Coefficient of Friction on a Disk-Machine : Effects of Lubricating Oil, Specific Sliding and Sliding Velocity, in the Case of Steel/Steel

For a long time, the tooth surface strength of gears has been investigated under various conditions. At first research concerning tooth surface strength focused mainly on gears of lower hardness. Because the practical usage of gears with high hardness has recently increased considerably, a more fundamental research on tooth surface strength of gears with high hardness is required to increase the load carrying capacity of gears. Recently, many basic studies on the tooth surface strength of gears were carried out in order to improve tooth surface strength. But further research on tooth surface strength is still needed. In view of this present state of research, the authors developed a project to carry out preparatory experiments mainly on the following topics: (1) tooth surface strength using various lubricating oils, (2) tooth surface strength under various effective depths of case-hardening of tooth surfaces, (3) tooth surface strength using test gears with shot peening treatment, (4) tooth surface streng...

Study on Tooth Surface Strength of Spur Gears—Part I: Experimental Procedure and Determination of Tooth Surface Strength©

The limiting load for scoring and frictional loss of the hypoid gears were compared with those of the spur gears and the crossed helical gears. As lubricants were chosen not only the mineral oils but also synthetic oils and a new relationship between limiting load for scoring among these three kinds of gears and the frictional loss of these gears was also investigated. The limiting load for scoring differs depending on whether it is the lubricating oil with Zn-P additive or the mineral oil with EP additive, or synthetic oil. Further the relative defference between the velocities (V1 and V2) of tooth surfaces, which engage each other, is found one of the most important factors for determining the load carrying characteristics.

Limiting Load for Scoring and Frictional Loss of Hypoid Gear : In Comparison with Spur Gear and Crossed Helical Gear, Using Mineral Oil and Synthetic Oil

Shoji Haizuka

Papers

Studies on Frictional Loss, Temperature Rise and Limiting Load for Scoring of Spur Gear

Study on Frictional Loss of Spur Gears (Concerning the Influence of Tooth Form, Load, Tooth Surface Roughness, and Lubricating Oil)©

Limiting Loads for Scoring and Coefficient of Friction on a Disk-Machine : Effects of Lubricating Oil, Specific Sliding and Sliding Velocity, in the Case of Steel/Steel

Study on Tooth Surface Strength of Spur Gears—Part I: Experimental Procedure and Determination of Tooth Surface Strength©

Limiting Load for Scoring and Frictional Loss of Hypoid Gear : In Comparison with Spur Gear and Crossed Helical Gear, Using Mineral Oil and Synthetic Oil