Influence of Additives Concentration on the Electrical Properties and the Tribological Behaviour of Three Automatic Transmission Fluids

Abstract

Placing an electric motor (EM) inside the transmission housing of a hybrid electric vehicle (HEV) implies that the automatic transmission fluid (ATF) needs to accomplish additional requirements. Among these requirements, electrical compatibility is of critical significance. This study investigated the influences of the additive concentrations of three commercial ATFs on their electrical compatibilities and tribological performances. Two variations of each ATF with different concentrations of the original additive packages were prepared. The viscosity, electrical conductivity, permittivity, resistivity, dielectric dissipation factor, breakdown voltage, and tribological performance of the nine resulting ATFs were measured. All the ATFs were found to be electrically compatible and showed dissipative performance and sufficiently high breakdown voltage, even at increasing additive concentrations. The tribological performances of the ATFs formulated with the API (American Petroleum Institute) Group III base oils had improved wear reduction at the highest additive concentrations; the better wear performance was related to the formation of iron phosphates and polyphosphates on the worn surface.

Tribo-electrical evaluation of conductive fluid film of Ti3C2Tz MXene-containing lubricant

“…Bridging the gap between electrical properties and tribological performance is essential to solving current triboelectrical challenges such as Electrically Induced Bearing Damages (EIBD). [26][27][28] The root cause of EIBD is current leakage from the stator passing the bearing towards the shaft. This, in turn, can create micro pitting and intense wear on the bearing resulting in bearing failure.…”

Influence of Parasitic Electric Currents on an Exemplary Mineral-Oil-Based Lubricant and the Raceway Surfaces of Thrust Bearings

“…As a result of the interaction between this additional electrical and the mechanical load on the contact, the components can be damaged and their service life reduced [3][4][5]. This affects not only the metallic raceway surfaces of bearings and gears, but the lubricant which separates the contact partners is also affected [6][7][8]. Therefore, the lubricant must also be considered as an electrical component.…”

“…These are shown, for example, by changes in the lubricant at the molecular level [17] (the changes observed here led to an increased occurrence of white etching cracks). Furthermore, the electrical and dielectric properties can also be influenced by the addition of additives [8].…”