Automatic Transmission Fluid Research Articles

Validation of Gear Friction Equation Using Directional Parameter

Abstract In our previous study, the Matsumoto equation was modified by introducing the directivity of machining marks on the tooth surfaces (directional parameter), and it was adapted to estimate the gear friction coefficient with various finishing processes. However, this new estimation equation has been applied only to gear pairs with the same finishing process and under manual transmission fluid (MTF) lubricated conditions. Thus, this study extends its application to a gear pair with different finishing processes and the case under automatic transmission fluid (ATF) lubricated conditions. Herein, efficiency tests were performed using gears with four different finishing processes (grinding, barreling, honing, and small-angle honing), and friction values obtained experimentally were compared with the values estimated from the unmodified and modified Matsumoto equations. Consequently, the correlations between the experimental and estimated friction values were significantly improved.

Tribological behavior of electric vehicle transmission oils using Al2O3 nanoadditives

Antifriction and antiwear performances of Al2O3 nanoparticles (NPs) as additives of an automatic transmission fluid, ATF, are presented in this research. For this purpose, four nanodispersions were formulated: ATF + 0.05 wt% Al2O3 NPs, ATF + 0.10 wt% Al2O3 NPs, ATF + 0.15 wt% Al2O3 NPs and ATF + 0.20 wt% Al2O3 NPs to identify the optimal concentration of additive. Tribological experiments were taken at pure sliding conditions, with the formulated nanolubricants and the ATF, under a working load of 20 N. The four nanolubricants tested resulted in lower friction coefficients than those obtained using ATF, reaching a maximum reduction of 6 % with the ATF + 0.10 wt% Al2O3 nanolubricant. The tribological pairs tested with the Al2O3 nanolubricants show lower wear than those tested with the ATF, having the best wear decrease with the ATF + 0.10 wt% Al2O3 nanolubricant, with reductions of 45, 57 and 78 %, respectively, in diameter, depth and area of the wear scar. Furthermore, by means of confocal Raman microscopy, roughness evaluation and SEM-EDX of the worn tribological specimens, it can be determined that mending, tribo-sintering as well as rolling mechanisms occur.

Preparation and Tribological Properties of Self‐Lubricating Epoxy Resin Composites with Oil‐Containing Carbon‐Based Nanocapsules

Oil‐containing nanocapsules are prepared and used to solve the challenges arising from the low mechanical properties and high coefficient of friction (CoF) of epoxy resin (EP). The shell of the nanocapsules is amorphous carbon and the core is lubricating oil (ATF6, Automatic Transmission Fluid 6). The nanocapsules are uniform hollow spheres with an average particle diameter of 530 nm and a shell thickness of 60 nm. The mass content of the lubricating oil encapsulated in the nanocapsules can reach 64.88% upon vacuum impregnation. Enhancing with the oil‐containing nanocapsules, the tribological properties of EP composites are studied in detail. Compared with those of neat EP, the compressive strength of the EP composite with 7 vol% nanocapsules improves by 9.2%, and the CoF and wear rate reduce by 71.70% and 89.38%, respectively. During the friction process, the oil‐containing nanocapsules are crushed and the oil is released, which contributes to the antifriction property of EP composites. Moreover, the results are expected to open up new ideas for the research and development of self‐lubricating materials.

Tribological evaluation of electric vehicle driveline lubricants in an electrified environment

Electrification continues to permeate the automotive industry, with future projections showing an exponential growth in the market share for both light and heavy-duty applications. Existing test methods for automotive applications were developed to model internal combustion engine vehicles and drivelines and are not appropriate for electric drivelines that experience stray electric currents. Tribometers can be used to evaluate friction and wear on modeled surfaces simulating in-vehicle operation. In this work, a commercially available tribometer was modified to isolate an electrical input into a tribological contact. After necessary modifications to the tribometer, a test matrix was completed for investigating different temperatures, load conditions, speed conditions, voltage input types, frequencies of AC signal, and shapes of AC signal. These parameters were tested on three lubricants—two typical automatic transmission fluid formulations and gear oil used in differential applications. Friction was measured throughout the tests, and wear scar width was measured at the end of each test. Results indicated that temperature, DC voltage, AC frequency, lubricant, and test profile had statistically significant differences in wear scar width. For electrical parameters, AC frequency produced different results from DC voltage when no voltage was applied. This significance applied to only one lubricant, with the other two lubricants having mixed results.

Perbandingan Kinerja 4 Mesin ATF Charger untuk Proses Flashing pada Transmisi Toyota Yaris Matic

ABSTRACT
 This research is an experiment testing several Automatic Transmission Fluid (ATF) charger machines in the Flushing process during oil changes by comparing several ATF machines with the Toyota Yaris automatic transmission hydraulic pump.
 By knowing the performance of each of these tools, we can recommend a better and more efficient use for automatic car maintenance. The purpose of this study was to compare the ATF Charger Lounch Cat-501s, ATF Charger brand X1, ATF Charger brand X2 with a Toyota Yaris automatic transmission hydraulic pump. By knowing the performance of each of these tools, we can recommend a better and more efficient use for automatic car maintenance. besides that it also aims to find out the maintenance of the automatic transmission on the Toyota Yaris automatic transmission hydraulic pump. The method in this study uses experimental methods by conducting literature studies, sample preparation, group division, treatment implementation, measurement and observation and measurement of the speed of oil entering the transmission during flashing, data analysis, data interpretation, and report generation. The data collected includes efficiency, output power, generated pressure, costs incurred including maintenance costs. In addition, testing was also carried out to evaluate the performance of the Toyota Yaris automatic transmission hydraulic pump when using each type of ATF Charger machine during Flushing. The results showed that the ATF Brand X1 engine had the fastest performance in the process of changing the engine oil for the transmission of the Toyota Yaris automatic car, which was able to drain 1000 ml in 17.65 seconds, the speed was around 850 rpm (revolutions per minute), with an electric voltage of 12 Volts, as well as the cost of procuring the lowest equipment, which is IDR 1,807,530
 
 Keywords: ATF Charger, Toyota Yaris, Matic

A brief review of the rapid transformation of driveline lubricants for hybrid electric and electric vehicles

Hybrid electric and electric vehicles have represented a small portion of the automotive market for many years and mainly use current lubricants, typically automatic transmission fluids (ATFs). However, regulatory compliance to limit greenhouse gases and increased consumer demand have resulted in a rapid global transition to electrified vehicles. This has prompted the need for new advances in vehicle technology to improve efficiency and thereby increase range. Enabling and optimizing such advances requires a new generation of driveline lubricants. Incorporating an electric motor in a transmission or axle, where the motor is exposed to the gear box lubricant, creates new challenges that focus attention on lubricant characteristics that were previously not differentiating features, for example, electrical and thermal properties. Additionally, lubricants must now also be compatible with the constituents used in electric motors which include new polymeric materials and, in some cases, exposed copper. Compatibility tests of these polymers vary within the industry and the risk of copper corrosion in these applications is not always properly assessed by current specification tests. In this paper we will begin with a brief history of electric vehicles, highlight how driveline lubricants, specifically ATFs, have evolved over the years to meet new hardware requirements and then describe the performance requirements expected of lubricants specifically designed for vehicles with electric drive units (EDUs). Our primary goal, however, is to summarize the recent literature that illustrates the changing importance of various lubricant performance properties, new proposed test methods and offer some insight into future e-lubricant evolution.

Electrified four-ball testing – A potential alternative for assessing lubricants (E-fluids) for electric vehicles

The increasing worldwide demand for hybrid and electric vehicle technology has brought new challenges for the global lubricant industry. The new lubricants for electric vehicles, also called E-fluids or EV-fluids, are expected to meet a new set of requirements including withstanding the much severe operating conditions of EV powertrains. High starting torques, high RPMs and uncontrollable shaft currents passing through the contact interfaces are some of the most challenging powertrain conditions that can impact the performance of these lubricants. Although there have been some papers already reporting on significant alteration of tribological properties of lubricants under electrification, so far there are no standard test protocols aimed at the fast and reliable screening of base oils, additives and formulated lubricants under such conditions. Thus, this research work focuses on exploring the popular four-ball ASTM-D4172 standard method to evaluate the tribological behavior of lubricants under electrified conditions. Specifically, a conventional four-ball tester was instrumented with a DC power source and a resistance data logger was used to explore the friction and wear performance of various lubricants (including a neat base oil, two automatic transmission fluids (ATF-3 and ATF-5) and a gear oil) with different dielectric strength under the conditions of ASTM-D4172 standard with and without DC currents (0, 1.5 and 3 A). The changes in average wear scar diameter, specific wear modes and mechanisms, friction coefficients, electrical contact resistance and temperature were analyzed and reported. Besides, the chemical changes in oils during the electrified tests were evaluated via IR spectroscopy. The main findings suggest that passing current through the four-ball contact interfaces significantly alters friction, wear and temperature in comparison to the conventional standard method without electrification. Thus, the proposed test method with electrification could be a potential new alternative for testing E-fluids under electrical environments.

Electrification effects on dry and lubricated sliding wear of bearing steel interfaces

In electric vehicles' powertrains, bearings can be susceptible to failure more rapidly than some of the other components mainly because of accelerated fatigue, corrosion and wear. Specifically, due to much severe operating conditions (including high speeds, torques, temperatures) of such vehicles combined with the presence of an electrical environment in which uncontrollable or stray electrical currents discharge through the contact interfaces can further exacerbate the situation and reduce their service lives by triggering much severe adhesive, abrasive and oxidative wear. In this work, we explore the effects of DC current discharges through the contact interfaces of AISI 52100 bearing steel using a novel two-electrode cell-based micro-abrasion tester under electrified dry and boundary lubricated contact conditions. A mineral base oil (as a reference), a gear oil and an automatic transmission fluid (ATF) with different dielectric strengths were tested under unelectrified and DC electrified (1.5 A) conditions. Overall, our test results suggest that passing DC current increases coefficient of friction (CoF) and wear of dry sliding contacts while it slightly reduces CoF but increases wear significantly for lubricated contacts due to accelerated oxidation by electrification. SEM, Raman spectroscopy and non-contact optical profilometry were used for analyzing the physical and chemical nature of worn surfaces and understanding of the specific wear modes and mechanisms.

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

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.

Electrical conductivity and tribological behavior of an automatic transmission fluid additised with a phosphonium-based ionic liquid

There are electric vehicle configurations with the electric motor (EM) inside the transmission housing, putting in contact the automatic transmission fluid (ATF) with the EM. In this case the ATF must fulfil several requirements, such as electrical and material compatibilities, improved cooling performance, etc. The use of ionic liquids (IL) as lubricant additive can impact on electrical conductivity (κ) and tribological behaviour of the ATF. This work analyses the influence of a phosphonium-based ionic liquid ([P6,6,6,14][BEHP]) used as additive at 1 and 3 wt% concentration on the abovementioned properties of a commercial ATF. The addition of the IL increased the κ of the ATF but it continues being dissipative; however, the dielectric strength decreased drastically and further tests about this property should be performed. The IL promotes the formation of a phosphorous-rich tribofilm, which is related to the improved antiwear performance. This formulation including the IL could be used in electric vehicles.

Cooling Performance of Fresh and Aged Automatic Transmission Fluids for Hybrid Electric Vehicles

The cooling performance of automatic transmission fluids (ATFs) plays an important role in hybrid electrical vehicles, in which the electric motor (EM) is placed inside the transmission housing due to their mission of cooling the EM. The cooling performance of the ATFs depends on their thermophysical properties, but these properties change with the oxidation of the ATFs. This work studies the influence of the oxidation of three ATFs (A, B, C) on their thermophysical properties, as well as on some figures-of-merit (FOMs) which are relevant for evaluating the cooling performance. The results indicated that the influence of the molecular structure on thermal conductivity and heat capacity is stronger than on density and viscosity, whereas the molecular structure hardly affects the FOMs of the fresh ATFs; ATFs B and C, formulated with base oils from API Group III, indicated better cooling performance than ATF A which was formulated with base oils from API Group I; the sensitivity to temperature of the variation with oxidation of the studied properties, including the FOMs, was almost null, except for ATF A; therefore, FOMs should be used to compare the cooling performance of ATFs for electric drivetrains instead of a single property, such as thermal conductivity.

Development of Transaxle Fluid for Electrification Vehicles: Design of Novel Additive Formulation

<div class="section abstract"><div class="htmlview paragraph">To achieve carbon neutrality by reducing carbon dioxide (CO<sub>2</sub>) emissions, vehicles with an internal combustion engine have started to be replaced by electrification vehicles such as hybrid electric vehicles (HEVs), plug-in HEVs (PHEVs), and battery EVs (BEVs) worldwide, which have motors in their transaxles (T/As). Reducing transmission torque loss in the transaxles is effective to reduce CO<sub>2</sub> emissions, and lowering the viscosity of lubrication fluids in T/As is a promising method for reducing churning and drag loss. However, lowering viscosity generally leads to thin oil films and makes the lubrication condition severe, resulting in worse anti-fatigue and anti-seizure performance. To deal with these issues, we made improvements on the additive formulation of fluid, such as the addition of an oil-film-forming polymer, chemical structure change of calcium detergents, and an increase of anti-wear additives including phosphorus and sulfur. As a result, we succeeded in developing a novel fluid with greater lubricity than a conventional automatic transmission fluid (ATF), despite the fact that the viscosity of the new fluid was lowered by around 50% compared with that of the ATF. In addition, the electrical insulating and anti-foaming performance of this fluid, which are required for T/A fluid in electrification vehicles, were equal to or greater than those of the ATF. The fuel economy in the Toyota Hybrid System (THS) was improved by 1.0% and more compared with the ATF because of the significant viscosity decrease in the developed fluid. This fluid will be widely used for HEVs, PHEVs, BEVs, and fuel cell electric vehicles (FCEVs) and can contribute to the realization of a carbon-neutral society.</div></div>

Automatic Transmission Fluids in Electrified Transmissions: Compatibility with Elastomers

The location of the electric motor (EM) inside the transmission in an electric vehicle requires the compatibility of the automatic transmission fluids (ATFs) with the materials of the EM and the transmission. This work studies the compatibility of four conventional ATFs with three elastomers: fluoroelastomer (FKM), ethylene-propylene-diene monomer (EPDM), and vinyl-methyl silicone rubber (silicone). Changes in volume, hardness, tensile strength, and elongation at break of the elastomers after aging in the ATFs were measured, and additional Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), and thermogravimetric and derivative thermogravimetric (TGA and DTGA) tests were performed. The four ATFs showed high or medium compatibility with FKM and silicone, and low compatibility with EPDM. This low compatibility was related to changes in the composition and crystalline structure of the elastomer. The non-compatibility of the EPDM with the oils from Group III was also proven.

Effect of ATF temperature on the friction-wear characteristic of a wet multi-disc clutch during the running-in process

PurposeThis paper aims to explore the effect of automatic transmission fluid (ATF) temperature on the dynamic friction-wear properties of the friction component in a wet multi-disc clutch during the running-in process.Design/methodology/approachThe running-in evolution was explored in terms of global friction performance and instantaneous friction characteristics. The variation of friction torque of the initial 300 engagement cycles was obtained by wet-clutch tests. Finally, an optical microscope was used to detect the wear mechanism of friction surfaces.FindingsThe ATF temperature showed a significant effect on the friction-wear performance in the clutch running-in process. The mean coefficient of friction decreased with the increase of the ATF temperature and decreased rapidly in the approximately initial 60 clutch engagements. The higher the ATF temperature was, the thinner the ATF film was, and more asperity summits were cut, thus leading to a smoother surface. Considering the slightly instantaneous friction fluctuation and the wear performance, a proper ATF temperature is necessary.Originality/valueThe results provide theoretical guidance for selecting the optimal ATF temperature during the running-in process.

Preparation and Tribological Properties of Self-Lubricating Epoxy Resins with Oil-Containing Nanocapsules.

The design and development of self-lubricating materials aid in enhancing the tribological performance and prolonging the service life of aero self-lubricating spherical plain bearings. Herein, monodisperse hollow mesoporous carbon nanospheres (HMCNs) with thin shell thickness and uniform particle size were synthesized. Afterward, oil-containing nanocapsules (Oil@HMCNs) were obtained by the impregnation method, which was an innovative approach to prepare nanoscale capsules. The Oil@HMCNs were monodispersed, and the oil content rate could reach 45 wt %. The nanocapsules were applied as additives to achieve the self-lubricating properties of epoxy resin (EP). It was revealed that the coefficient of friction (COF) and the wear rate of EP in dry friction can be decreased from 0.56 to 0.084 and from 50.15 × 10-6 to 0.27 × 10-6 mm3/N/m, respectively. The tribological properties of EP composites in dry friction are better than those of EP with external oil. According to the analysis of friction pairs, the antifriction performance was contributed by the released automatic transmission fluid 6HP (ATF6) from nanocapsules. Meanwhile, the presence of ATF6 effectively could inhibit fatigue wear, and the decrease of compressive strength and surface hardness led to plastic deformation and mechanical polishing. Both resulted in a lower wear rate of EP. In conclusion, this work explored the application possibility of hollow mesoporous materials in lubrication. The prepared EP composites exhibited excellent tribological performances and self-lubricating properties, which were expected to be applied to self-lubricating spherical plain bearings and other mechanical parts.

Compatibility of Automatic Transmission Fluids with Structural Polymers Used in Electrified Transmissions

The use of the electric motor (EM) inside the transmission in electric vehicles (EVs) requires compatibility between the automatic transmission fluids (ATFs) and the materials of the EM and the transmission. The goal of this work is to study the compatibility of four conventional ATFs with three structural polymers (PEEK, PTFE, and PA66) and the feasibility of using them in EVs with the EM located inside the transmission. Changes in volume, hardness, tensile strength, and elongation at break were determined in the polymers after ageing in the ATFs. The polymers were aged in each ATF at 100 °C for periods of time of 168, 336, 504, and 672 h. Complementary tests such as XRD, FT-IR, and DSC were performed to explain the changes found in the measured mechanical properties. PEEK and PTFE showed very low variations in their mechanical properties, while PA66 showed significant changes in elongation at break. The XRD, FT-IR, and DSC tests revealed a change in the crystalline structure of PEEK and PA66. The FT-IR results showed that the polymers were affected more by the time of ageing than by the type of ATF. All of the ATFs showed high compatibility with PEEK and PTFE, and medium compatibility with PA66.

Electrical compatibility of transmission fluids in electric vehicles

The in electrical vehicles, where the electric motor is inside the transmissielectrical compatibility of the automatic transmission fluids (ATFs) is very important on and in contact with the ATF. This work studies the influence of factors like temperature, time, and air exposition on the oxidation of three ATFs and their changes in electrical conductivity. The results showed that the higher content of additive the lower variations of electrical conductivity with the oxidation; the measurements of electrical conductivity are better than FT-IR ones for monitoring oil thermo-oxidative degradation at initial periods; the conventional ATFs could maintain good electrical compatibility in electrified drivelines, although their materials compatibility and copper corrosion protection of electrical components should be also tested.

Effect of Silicon Carbide Nanoparticles on the Friction-Wear Properties of Copper-Based Friction Discs.

To study the influence of nano-additives on the friction-wear characteristics of friction materials, the nano-sized silicon carbide particles which have excellent chemical and physical properties are considered to add in composite to form the modified friction material. The influence of the silicon carbide nanoparticles (SCN) on the friction-wear characteristics of copper-based friction materials (CBFM) is investigated via the SAE#2 (made in Hangzhou, China) clutch bench test with the applied pressure, rotating speed, and automatic transmission fluid (ATF) temperature taken into account. Moreover, the variations of friction torque and temperature are considered to evaluate the friction performance, and the variable coefficient is employed to describe the friction stability. The wear characteristics of friction materials are investigated by the disc changes in thickness and micro-morphology. The results show that the CBFM with SCN can provide a higher friction torque, which increased by 30% to 50% compared with CBFM. The variable coefficient of CBFM with SCN changes from 674 to 52 with the rotating speed raised from 600 rpm to 3000 rpm, which shows that the friction stability is relatively worse. Furthermore, the micromorphology shows that the CBFM with SCN has lower porosity and surface roughness, which increases the microscopic contact area and the coefficient of friction (COF). Simultaneously, the reduction in porosity also leads to a decrease in the cooling quality, bringing about a rapid temperature rise. Thus, the wear amount of CBFM with SCN increases significantly, especially for the friction disc in the axial middle position.

E-Axle用潤滑油下における軸受鋼の転がり摩擦挙動

To extend the cruising range of electric vehicles (EV), it is necessary to improve the power consumption rate. By rotating the motor at high speed, it is possible to reduce the size and the weight of E-Axle, which improves the power consumption rate. However, high-speed rotation increases the number of contacts between gear tooth flanks in E-Axle reduction gears. This promotes the fatigue of the bearings and gears. Additionally, the lubricant has been newly developed for E-Axle, will be used instead of existing automatic transmission fluid. However, the effects of E-Axle lubricants on the fatigue of tooth surfaces have not been elucidated. In addition, on the contact surface of gears, sliding and rolling contact cause stress at the same moment. To evaluate the occurrence factors of fatigue in detail, it is necessary to divide the contact types into sliding and rolling contact and investigate the fatigue on contact surfaces. In this study, we focus on occurrence of pitting by only rolling contact to investigate fatigue factors. In this experiment, ball-on-disk type fatigue tests are conducted to evaluate performances of five different E-Axle lubricants for the occurrence of pitting under pure rolling condition. The results showed that pitting was reduced effectively with the lubricant that has the lowest kinematic viscosity. In addition, the pitting rates increase as the increase of kinematic viscosity. Therefore, the kinematic viscosity is considered to influence the occurrence of pitting fatigue.

Characteristics of Automatic Transmission Fluid for Wet Clutch

Characteristics of Automatic Transmission Fluid for Wet Clutch