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EP-4741476-A1 - LUBRICANT COMPOSITION

EP4741476A1EP 4741476 A1EP4741476 A1EP 4741476A1EP-4741476-A1

Abstract

LUBRICANT COMPOSITION This invention provides a lubricating oil composition suitable for use in an electric vehicle, comprising: a base oil comprising Fischer-Tropsch derived base oils, poly-α-olefin base oils or mixtures thereof; and in the range of from 0.5 to 12wt% of a friction modifier additive, wherein the friction modifier additive is a compound of formula (I) R 1 [(AO) n -R 2 ] m (I) wherein: R 1 is the residue of a group having at least 2 active hydrogen atoms; m is at least 2; AO is an alkylene oxide residue; each n is independently from 0 to 100; and each R 2 is independently H or R 3 , where each R 3 is independently a residue of a polyhydroxyalkyl or polyhydroxyalkenyl carboxylic acid, a residue of a hydroxyalkyl or hydroxyalkenyl carboxylic acid and/or a residue of an oligomer of the hydroxyalkyl or hydroxyalkenyl carboxylic acid; and on average at least 0.5 of R 2 groups are R 3 , wherein the lubricating oil composition has a kinematic viscosity at 100°C in the range of from 2.0 to 5.5 cSt.

Inventors

  • UEDA, Mao

Assignees

  • Shell Internationale Research Maatschappij B.V.

Dates

Publication Date
20260513
Application Date
20241111

Claims (8)

  1. A lubricating oil composition suitable for use in an electric vehicle, comprising: a base oil comprising Fischer-Tropsch derived base oils, poly-α-olefin base oils or mixtures thereof; and in the range of from 0.5 to 12wt% of a friction modifier additive, wherein the friction modifier additive is a compound of formula (I) R 1 [(AO) n -R 2 ] m (I) wherein: R 1 is the residue of a group having at least 2 active hydrogen atoms; m is at least 2; AO is an alkylene oxide residue; each n is independently from 0 to 100; and each R 2 is independently H or R 3 , where each R 3 is independently a residue of a polyhydroxyalkyl or polyhydroxyalkenyl carboxylic acid, a residue of a hydroxyalkyl or hydroxyalkenyl carboxylic acid and/or a residue of an oligomer of the hydroxyalkyl or hydroxyalkenyl carboxylic acid; and on average at least 0.5 of R 2 groups are R 3 , wherein the lubricating oil composition has a kinematic viscosity at 100°C in the range of from 2.0 to 5.5 cSt.
  2. The lubricating oil composition as claimed in Claim 1, wherein the Fischer-Tropsch derived base oil has a kinematic viscosity at 100°C of at least 1.5 cSt and less than 7.0 cSt.
  3. The lubricating oil composition as claimed in Claim 1 or Claim 2, wherein the poly-α-olefin base oil has a kinematic viscosity at 100°C of at least 1.5 cSt and less than 7.0 cSt.
  4. The lubricating oil composition as claimed in any one of Claims 1 to 3, wherein the base oil comprising Fischer Tropsch derived base oil and/or poly-α-olefin base oil contains no less than 75wt% of Fischer-Tropsch derived base oil and/or poly-α-olefin base oil based on the overall amount of base oil.
  5. The lubricating oil composition as claimed in any one of claims 1 to 4, also comprising in the range of from 1.0 to 20wt% of an ester base oil having a kinematic viscosity at 100°C in the range of from 1.5 to 4.0 cSt.
  6. The lubricating oil composition as claimed in any one of claims 1 to 5, wherein the lubricating oil composition has a kinematic viscosity at 100°C in the range of from 2.5 to 5.2 cSt.
  7. The lubricating oil composition as claimed in any one of claims 1 to 6, wherein the lubricating oil composition preferably has a phosphorus content of at least 0.030 wt% based on the overall mass of the lubricating oil composition.
  8. A method for the lubrication of an e-axle said method comprising applying the lubricating oil composition of any one of claims 1 to 7 to an e-axle and operating the e-axle, wherein the e-axle is part of a battery electric vehicle or a hybrid electric vehicle.

Description

Field of the Invention This invention relates to lubricating oil compositions and, in particular, lubricating oil compositions suitable for e-axle applications. Background of the invention The global electric vehicle (EV) market is growing rapidly, in part due to ever increasing CO2 emission requirements. Typically, conventional lubricating fluids, designed for use in internal combustion engine vehicles, have been applied in e-drives. However, the development of dedicated fluids comprising e-transmission and e-axle fluids specifically designed to overcome the challenges specific to vehicles with electric motors, including battery electric vehicles (BEVs) and hybrid vehicles, is an important area of research. Critical fluid performance metrics for lubricating oil compositions suitable for EVs include durability, oxidation control, aeration, heat transfer, material compatibility, electrical conductivity and efficiency. Energy efficiency is a major challenge across the automotive industry. For an e-axle lubricant composition, low friction has generally been required to improve efficiency. The way to reduce friction must be considered for each lubricating regime. For a hydrodynamic regime, one of the ways to lower friction is to reduce lubricant viscosity. However, as viscosity lowers, anti-wear performance becomes poor. For boundary and mixed lubrication regime, friction modifiers (FMs) may be used to reduce friction by forming adsorption films or tribofilms. However, friction modifiers generally contain reactive polar functional groups, which may promote copper corrosion. Lubricating oil compositions for e-axles lubricate both gears and bearings. These are mainly operated in an elastohydrodynamic lubrication regime (EHL). Thus, the technology to reduce friction in an EHL is highly relevant for an e-axle oil. For EHL, low traction base oils are commonly used to reduce friction. A challenge here is that the effect of the base oil to reduce friction is quite limited, so further reduction of EHD friction is required by using a different approach. To solve such challenges, a novel lubricating oil composition must be developed. Summary of the Invention The present invention provides a lubricating oil composition suitable for use in an electric vehicle, comprising: a base oil comprising Fischer-Tropsch derived base oils, poly-α-olefin base oils or mixtures thereof; and in the range of from 0.5 to 12wt% of a friction modifier additive,wherein the friction modifier additive is a compound of formula (I)         R1[(AO)n-R2]m     (I) wherein: R1 is the residue of a group having at least 2 active hydrogen atoms; m is at least 2;AO is an alkylene oxide residue; each n is independently from 0 to 100; and each R2 is independently H or R3, where each R3 is independently a residue of a polyhydroxyalkyl or polyhydroxyalkenyl carboxylic acid, a residue of a hydroxyalkyl or hydroxyalkenyl carboxylic acid and/or a residue of an oligomer of the hydroxyalkyl or hydroxyalkenyl carboxylic acid; and on average at least 0.5 of R2 groups are R3,wherein the lubricating oil composition has a kinematic viscosity at 100°C in the range of from 2.0 to 5.5 cSt. The present invention also provides a method for the lubrication of an e-axle said method comprising applying said lubricating oil composition to an e-axle and operating the e-axle, wherein the e-axle is part of a battery electric vehicle or a hybrid electric vehicle. Detailed Description of the Invention One or more specific embodiments of the present disclosure will be described below. These described embodiments are examples of the presently disclosed techniques. Additionally, in an effort to provide a concise description of these embodiments, not all features of an actual implementation may be described in the specification. When introducing elements of various embodiments of the present disclosure, the articles "a," "an," and "the" are intended to mean that there are one or more of the elements. The terms "comprising," "including," and "having" are intended to be inclusive and mean that there may be additional elements other than the listed elements. Additionally, it should be understood that references to "one embodiment" or "an embodiment" of the present disclosure are not intended to be interpreted as excluding the existence of additional embodiments that also incorporate the recited features. In the context of the present invention, in a case where a composition comprises two or more components, these components are to be selected in an overall amount not to exceed 100 wt%. The present inventors have found that a lubricating oil composition using a certain type of Fischer-Tropsch derived base oil and/or PAO base oil and an ester-based friction modifier, particularly a polymeric ester type friction modifier could overcome the above challenges. The lubricating oil compositions can form adsorption films even under EHL conditions. As well as these characteristics, the compositi