International Colloquium Tribology
ict
expert verlag Tübingen
125
2022
231
Novel Transmission Lubricants for New Generation Vehicles
125
2022
Ratnadeep Joshi
Lakshmi Katta
Sarita Seth
Pankaj Bhatnagar
Deepak Saxena
SSV Ramakumar
ict2310073
23rd International Colloquium Tribology - January 2022 73 Novel Transmission Lubricants for New Generation Vehicles Ratnadeep Joshi Research & Development Centre, Indian Oil Corporation Ltd, Sector-13, Faridabad, India-121007 Corresponding author: Email: joshir2@indianoil.in Lakshmi Katta, Sarita Seth, Pankaj Bhatnagar, Deepak Saxena, SSV Ramakumar Research & Development Centre, Indian Oil Corporation Ltd, Sector-13, Faridabad, India-121007 1. Introduction Electrification or e-mobility is witnessed as one of the prominent routes towards meeting the ever-tightening emission targets being implemented worldwide. The current and future developments of EV lubricants have a common goal to minimize friction loss, enhance durability, boost efficiency, and strengthen other performance aspects. Satisfying these salient goals for EVs would pave the way towards a greener future [1, 2]. Transmission lubricants will play an important role in e-mobility. However, development of transmission lubricants for EVs is dependent on various aspects set by OEMs due to their own unique transmission technology and type of e-motor system (wet or dry), utilizing lots of copper windings and new materials(elastomers, plastic and other materials). Hence, customised EV lubricants are required for smooth & trouble free operations meeting various OEM needs suiting to their hardware. Technical requirements for EV transmission lubricants are additional and specific compared to conventional transmission oils as indicated in Figure 1. Figure 1: Comparative Performance of EV Tranmission Oil w.r.t Conventional tranmission oils In view of the specific require, development of a high performance Electrical vehicle transmission oils, there are many parameters to be carefully selected and measured. Selection of base oils, viscosity modifier and suitable additive components play an important role in development of EV transmission lubricants. The critical parameters are conventional transmission oil properties likeantirust, anti corrosion, anti wear/ EP and special properties for electric vehicle applications are seal compatibility / plastic material/ other materials compatibility and electrical properties. In this paper, author’s have aimed for development of a robust transmission oil with extended drain potential which can be used in wet and dry both type of e-motor applications interval. Three candidate oils (A, B & C) were developed in the author’s laboratory. Performance assessment methodology included series of lab-screening tests. Detailed comparative evaluation of the candidate oils was done w.r.t. different performance parameters including low temperature fluidity (Table 1), tribological tests like Extreme Pressure(EP)/ Antiwear(AW) characterisitcs, shear stability test, film forming properties & FZG scuffing load test. Candidate oils were also evaluated for electrical properties like electrical conductivity and brake down voltage (BDV) measured at ambient condition (Figure 2). Copper resistivity test was done to assess the electrical resistivity (also known as specific electrical resistance) and to check electric current effect on copper wire. This test is important for the fluids, which are in direct contact with new components of the electric motor (wet type e-motor) transmissions. Test was conducted at 120 °C with 1mA current source and by using specific copper wire. The copper wire degradation was measured by plotting resistance (Ω) vs time duration in Figure 3. Further, vehicle level Noise, vibration, and harshness (NVH) testing was carried out by mounting the test vehicle on a chassis dynamometer and measuring the noise & vibration with the help of a digital signal processing Fast Fourier Transform (FFT) analyzer in Figure 4. 74 23rd International Colloquium Tribology - January 2022 Novel Transmission Lubricants for New Generation Vehicles Table 1: Physicochemical & performance data of Candidate oils Oil Category Test Methods OIL A OIL B OIL C Base oil Category Mineral Synthetic Synthetic Viscosity Grade SAE J 306 SAE 80W90 SAE 75W90 SAE 75W90 Kinematic Viscosity @ 100 ºC, cSt D-445 15.72 15.22 16.18 Aniline point , ºC D-611 113 119.2 121 Viscosity Index D-2270 143 178 181 BF viscosity @-40 ºC, cP D-2983 >150000 34394 40091 Sulphur, % D-2622 2.11 1.82 0.12 Weld Load, kgf IP 239 400 400 200 Load Wear Index, kgf D-2783 55.89 55.89 29.93 KRL shear stability @20hrs CEC- L-45-A-99 7.0 8.40 8.80 FZG gear test rig, scuffing load stage A10/ 16.6R/ 90 ºC 14 14 10 Figure 2: Conductivity and BDV results of candidate oils Figure 3: Copper resistivity test on candidate oils Figure 4: FFT Analysis of Candidate oils in electrical vehicles 23rd International Colloquium Tribology - January 2022 75 Novel Transmission Lubricants for New Generation Vehicles 2. Results and discussion: It can be seen from the comparative Physico-chemical & performance data (Table 1) that Oil B & C are superior in low temperature performance properties w.r.t. Oil A as measured by Brookfield viscosity test (ASTM D 2983). Oil A & Oil B found to be superior in tribological performance, i.e., EP/ AW tests, KRL Shear stability test and in FZG Scuffing load stage test (IP239, D2783, CE- CL-45-A-99 FZG and A10/ 16.6R/ 90 °C), are w.r.t Oil C. Interestingly, Oil C has shown superior performance w.r.t Oil A & Oil B (Figure 5 & 6) in extended copper corrosion test and vapour phase copper corrosion test. Similarly, in copper resistivity test, Oil C has performed better w.r.t Oil A & Oil B. All the three candidate oils were also tested for vehicle level NVH testing to assess vehicle level transmission noise and fluid’s dampening effect for reduction of cabin noise. Fast Fourier Transform Analysis shows that at low and at high-speed conditions Oil B & C are superior w.r.t. Oil A. Figure 5: Vapor phase copper corrosion-120 deg c 72 h Figure 6: Copper corrosion by ASTM D 130- 120 degc, 100 h 3. Conclusion Electrical vehicles require customised transmission oils and the requirements vary from OEM to OEM. These oils should be compatible with all the materials in contact with the oil in an electric vehicle transmission system. The present study shows, that a candidate oil with excellent properties for EV transmission lubricants has been developed; however, there is still a need to generate more data and explore new test methods for evaluation of EV transmission lubricants in line with OEM specific needs. References [1] Khurana A. Ravi Kumar V. V. and Sidhpuria M. A Study on the Adoption of Electric Vehicles in India: The Mediating Role of Attitude Vision, 24(1) 23-34, 2020 [2] https: / / www.electrichybridvehicletechnology.com/ features/ the-new-age-of-lubricants-for-electric-vehicles.html
