With the electrification of automobiles, new tribological challenges have been identified, particularly in the transmission of eAxle. The primary cause lies in the high-speed rotation of motors aimed at downsizing eAxle. Currently, motor speeds in electric vehicles are below 20,000 rpm, but next-generation EVs plan to implement high-speed, compact motors with speeds up to 30,000 rpm. Consequently, transmissions in e-axles must achieve high reduction ratios while ensuring reduced friction losses and durability under high-speed operating conditions. As lubricating oils are being formulated with lower viscosity to reduce churning losses and improve cooling efficiency, addressing low friction and enhanced wear resistance under poor lubrication conditions has become a critical issue for gears and bearings. This paper organizes these new tribological challenges and highlights the authors’ research on the evaluation of pitting wear and the elucidation of its mechanisms, which is particularly significant among these challenges.

A high-speed electric motor with a small reducer and high-power transmission efficiency can be used in a powertrain system that achieves a high power density because the motor can be miniaturized to increase the rotational speed. A traction drive exhibits low vibration noise due to the lack of meshing vibration, making it suitable as a transmission element for high-speed reducers. This paper describes performance measurements for a high-speed traction drive and gears using a test machine capable of operating at 50,000 rpm. In addition, a model was developed to represent the traction characteristics at high rotational speed, and was used to determine the optimal texture for maximizing the traction coefficient. Furthermore, a planetary roller unit was designed and manufactured as a reducer for electric vehicles, and its transmission efficiency at up to 50,000 rpm was evaluated.

In recent years, with the spread of electrified vehicles, it is expected that the demand for ETF, Electrified Transmission Fluid,suitable for these vehicles will increase. ETF needs various performance requirements, such as cooling performance for eMotor, electrical properties, material compatibility such as magnet wires and seals, corrosion prevention, mechanical properties, oxidation stability, and improved efficiency. This paper explains the trends in the performance requirements for ETF and recent development efforts based on those trends.

This paper describes technical topics for seal products in terms of automotive electrification. The trend towards electrification is accelerating, especially in the automobile industry with a view to realizing carbon neutrality in 2050. Seal products used in automobiles are also required to have performance and functionality along with it. For example, they should also maintain sealing performance in case of a motor rotating at high speeds and in both directions. In addition, they should be required to further contribution to energy saving and dealing with safety or new issues because of the use of electricity.

With the increase in the speed of power transmission systems due to the EV shift, gear meshing friction and scuffing have been the focus of much attention. Gear meshing friction is a heat loss that occurs during the power transmission process, and scuffing is damage that occurs when the lubricating oil reaches a critical temperature and oil film formation becomes difficult. Both have a deep historical connection. This paper describes the basics of friction and wear phenomena in gears and presents the results of a study on the effects of gear finishing methods on these friction and wear phenomena.

In this study, a large-scale parallel turbulence computation was conducted to clarify the effect of the rotor or stator grooves on rotating torque and heat transfer of high-speed electric motor. The grooves on rotor side or stator side were either considered. The lattice Boltzmann method was employed for the direct numerical simulation of heat and fluid flow between the gap of rotor and stator. For the computation at higher rotating speed, a large-eddy simulation was additionally conducted. It was found that the power-law of the rotating torque changes at the threshold rotating speed due to the increase of the Reynolds stress induced by grooves. The heat transfer from the stator to rotor correspondingly increases.

The replacement cycle of current collecting materials such as contact wires and contact strips in electric railways is determined mainly by their wear rate. Previous research have clarified that the wear rates of them are greatly affected by wear mode, which transitions by the rise of contact temperature. Therefore, for mechanical wear mode, it is in special important to estimate the contact temperature due to frictional heat. In a previous study, the authors proposed an analytical model for temperature rise of contact point and reported that 60% of the friction work was converted into frictional heat. At that time, however, no theoretical consideration on the heat conversion rate was conducted. In this paper, the authors carried out wear tests using a rotating wear tester to measure the temperature rise of hard-drawn copper plate (contact wire) and iron-sintered alloy contact strip (contact strip) to calculate the heat conversion rate of the friction work by thermal analysis. As a result, it was found that the heat conversion rate of friction work was almost 100% which is different from previous study. The difference between these heat conversion rates could be explained by using two models: the contacts of the one model are fixed and the other model move relatively.

In the construction machinery industry, an ICT service begins in sequence and various machine information is provided. Among them, there is a robust demand for information on lubricant properties. Many lubricants are performed oil analysis every given period. However, it is difficult to detect a characteristic sudden change in the oil that occurred between analysis intervals. To solve this problem, we are investigating the constant monitoring of oil properties using sensors. In this study, we verified the possibility of detecting oil condition monitoring items for hydraulic oil and engine oil using an oil sensor that can be used in construction machinery. Furthermore, we collected the lubrication oil used in the construction machinery and investigated the correlation between the measurement results of the sensor and oil analysis. As a result, qualitative and quantitative indicators of sensor measurement values were obtained for lubricant monitoring items, and a prospect of oil condition monitoring was obtained.