Effects of Foaming on Transmission Fluid for Hybrid Vehicles

Shuzo Sonoda (Honda R&D)

In hybrid vehicles, the integration of electric motors within the transmission has become widely adopted, with a single fluid being utilized for both cooling and lubrication.As higher rotational speeds raise concerns regarding shear-induced degradation of the fluid, the present study focuses on foaming behavior under such operating conditions.The differences in surface foam and entrained bubbles, depending on the type of antifoaming agent, as well as their respective effects on lubrication performance, are systematically investigated.

Study on Friction Reduction in Oil-Film Journal Bearings Using Microbubbles
-Application and Evaluation of Novel Oil Grooves-

Shodai Sakabe･Yuki Yoshimura･Yuto Yamazaki･Koki Gonda･Yuki Kawamoto･Akihiko Azetsu･Masayuki Ochiai (Tokai University)

It has been demonstrated that microbubbles reduce friction in oil-film journal bearings, where an increase in the void fraction (the volumetric ratio of the gas phase to the liquid phase) within the bearing clearance enhances the friction reduction effect. Therefore, this study investigated a novel oil groove design aimed at increasing the void fraction, and friction torque measurement experiments were conducted on a bearing incorporating this groove.

A Study on Seizure Prediction of Engine Plain Bearings Using EHL Analysis

Shinichi Sakurai･Akichika Shimizu･Motohiko Koshima (Daido Metal)

In predicting seizure of engine plain bearings, parameters such as PV value, film thickness ratio (Λ), and temperature are typically used. However, by utilizing EHL (elastohydrodynamic lubrication) calculations to evaluate a wider range of physical quantities, further improvements in prediction accuracy are expected. This study presents our research.

Relationship between Electrolytic Corrosion and Lubrication State in e-PT Sliding Components

Tomohiro Sezume･Makoto Maeda･Gou Katou (JATCO)･Shinji Koyama (Gunma University)

Electrolytic corrosion in bearings and similar components is caused by motor leakage current. This phenomenon occurs when current flows through the lubricating oil in sliding interfaces, leading to electrical discharge machining (EDM) and subsequent damage. In this study, we focused on the lubrication state and the properties of the transmission fluid to clarify their influence on electrolytic corrosion through experimental analysis.

Effect of Lubricants on Tooth Surface Damage Behavior of Gears in e-Axle Reduction Units

Takashi Yanagihara (Idemitsu Kosan)

For gears in e-Axle reduction units, where high-speed operation increases the importance of tooth surface damage, the effect of lubricants was evaluated. Based on surface observation, tooth profile measurement, and roughness measurement, differences in wear behavior and fine-scale tooth surface damage caused by different lubricants are reported.

Severity Analysis of m-LSD Differential Durability Test Using the Morrison Surface Fatigue Equation

Hwiun Lee･Daejin Kim･seonghyun Son･seungyong Bae (Hyundai Motor)

This study investigates pitting fatigue life at the cam-ring gear contact in a mechanical limited slip differential (m-LSD) with asymmetric spur gears. Using the Morrison life equation, it quantitatively compares accumulated contact fatigue damage between component-level bench tests and full-vehicle circuit driving. Two representative loading conditions were analyzed: high-load/low-differential-speed and low-load/high-differential-speed. Contact stress factors and fatigue damage were calculated for each case, and equivalent bench test cycles were derived from actual circuit driving distances.