Automatic Transmission Fluid Research Articles

Effection of calcium phosphate tribofilm on anti-shudder performance in ATFs

Abstract The anti-shudder performance of automatic transmissions (AT) is highly dependent on automatic transmission fluids (ATFs). Additives of ATFs interact with the steel surfaces to form tribofilms to provide AT with the desired properties. Hence, establishing the relationship between the tribofilm and friction characteristics is the key issue for optimizing the anti-shudder performance. This paper evaluates the tribological response of the calcium phosphate tribofilm in a disk-on-disk friction test apparatus (Wazau), which is used to simulate the clutch friction process. The changes of the tribofilm during friction and the variations of the μ-v curves with the tribofilms were discussed. Results showed that the calcium phosphate tribofilm contributed to maintain the anti-shudder property.

TRIBOLOGICAL ANALYSIS ON PALM FATTY ACID DISTILLATE (PFAD) AS ALTERNATIVE TRANSMISSION FLUID FOR CLUTCH APPLICATION

Typically, a mineral based oil from petroleum refining has been widely used as automatic transmission fluid (ATF) in the wet clutch application. However, it has two major disadvantages: (1) It causes pollution to the environment and (2) It is a non-renewable source. Thus, Palm Fatty Acid Distillate (PFAD) is explored as an alternative lubricant for the wet clutch application. In present study, tribological behaviour of PFAD is first sought using a pin on disk tribo-tester and then its behavior will be compared with the behavior obtained in the commercial ATF. It is found in the friction analysis that PFAD has good anti friction ability at low speeds. In addition, PFAD generates almost identical dynamic friction coefficients obtained in the commercial ATF at velocity of 0.4m/s to 0.9 m/s. A slight positive slope in the friction coefficient–velocity graph indicates that PFAD has tendency to have anti-shudder properties, which can improve engaging quality of the wet clutch. However, PFAD has two weaknesses; low viscosity index and less anti wear ability. Some additives should be added into PFAD so that it can give better friction level and less wear rate.

Aging of anhydride‐hardened epoxies in lubricants at elevated temperatures

ABSTRACTIn automotive under‐the‐hood applications, electronics respectively their packaging materials come in contact with automotive fluids. The effect of automatic transmission fluid (ATF) on an anhydride‐cured epoxy was investigated at temperatures up to 180 °C for up to 1000 h. This study has shown that ATF retards the oxidative aging of the epoxy, presumably due to oxygen consumption. Whereas in air the material underwent a thermo‐oxidative aging with a mass loss of up to 4% and a strong broadening of Tg to higher temperatures, in ATF a temperature dependent distinctive drop of Tg from 142 to 126 °C after 1000 h aging at 180 °C, and a mass loss of maximum 1% was observed which might be a thermal decomposition of the epoxy material. A slight broadening of the damping factors might indicate an intrusion of ATF components. A color change of the samples could be observed after aging in air and ATF, with the discoloration in air being more intense. An explanation for the color change might be either a minor amount of oxygen causing an oxidative discoloration reaction or the intrusion of colored ATF degradation products. While the oxidation‐kinetics in air exhibited Arrhenius temperature‐dependence the mechanism in ATF changed above 165 °C. An acceleration of aging tests at temperatures beyond 150 °C is, therefore, not possible. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017, 134, 44877.

Electrical Conductivity of New and Used Automatic Transmission Fluids

Electrical Conductivity of New and Used Automatic Transmission Fluids

Surface chemical characterization of steel clutch plate in ATF

Automatic transmission fluids (ATF) were tested using a new type disc-on-disc simulation tribo-test-rig Wazau triometer with the aim of studying the tribofilm formation on the steel surfaces during the engagement of wet friction clutches. XPS, SIMS, SEM and EDX were used to investigate the chemical composition of this tribofilm. The result confirms that there exist tribochemical reactions between ATF additives and steel rubbing surfaces. P/Ca/O element ratio of the tribofilm is consistent, which has never been reported before in the tribological field of clutch discs. All the results suggest that the chemical composition of this tribofilm is calcium phosphate. Since calcium phosphate ceramics have excellent mechanical and tribological properties, the friction characteristics of wet clutches must have been changed.

Thermal aging of melt-spun NdFeB magnetic powder in hydrogen

High energy product neodymium-iron-boron (NdFeB) magnets are the premier candidate for demanding electrified vehicle traction motor applications. Injection molded (IM) or compression molded (CM) magnets made using NdFeB powders are promising routes to improve motor efficiency, cost, and manufacturability. However, IM and CM NdFeB magnets are susceptible to substantial thermal aging losses at motor operating temperatures when exposed to the automatic transmission fluid (ATF) used as a lubricant and cooling medium. The intrinsic coercivity Hci of NdFeB IM and CM magnets degrades by as much as 18% when aged for 1000h in ATF at 150°C, compared to a 3% loss when aged in air. Here we report aging studies of rapidly quenched NdFeB powder in air, ATF, and H2 gas. Expansion of the NdFeB crystal lattice in both ATF and H2 identified hydrogen dissociated from the ATF during aging and diffused into the primary NdFeB phase as the probable cause of the coercivity loss of IM and CM magnets.

Wet Clutch Friction Interfaces under Water-Contaminated Lubricant Conditions

ABSTRACTThe performance of wet clutches used for automatic transmissions or other applications usually includes the desired positive friction characteristics and a shudder-free torque generation. Changes in the operating variables such as the lubricant conditions influence the formation of a tribofilm, and friction characteristics and can alter the degradation of the friction interfaces. In this work, the friction characteristics and degradation of the paper–steel friction interfaces were monitored when a commercial fully formulated automatic transmission fluid (ATF) was contaminated with water. It was found that water in ATF influenced the clutch stability by increasing the mean coefficient of friction (µ) and the negative friction–velocity slope. Surface studies of the posttest friction interfaces clearly indicated reduced surface porosity and permeability, increased wettability, and changed elemental composition on the contacting surfaces after tested with water-contaminated ATF. Moreover, water-contaminated paper liners' thermal decomposition shifted to a lower temperature compared to an uncontaminated liner during thermal analyses. These results displayed faster degradation and reduced service life of the clutch friction interfaces due to water contamination. The resultant surface condition can be associated with the observed unstable friction and negative friction–velocity slopes.

New Insights on the Impact of Automatic Transmission Fluid (ATF) Additives on Corrosion of Copper

A new method for monitoring the corrosion of copper by automatic transmission fluid additives through the measurement of the electrical resistance of copper wires is presented. The effect of driveline lubricant additive components upon the corrosion rate of copper is discussed. The information on corrosion generated by this method provides details of the corrosion processes that are not obtained from traditional corrosion tests and insight as to how to formulate oils to better protect copper and copper alloys.

Frictional Behavior of a Wet Clutch Using Blends of Automatic Transmission Fluid (ATF) and Biolubricant (Jatropha Oil) in a Pin-on-Disk Tester

Nowadays, biolubricants are being used to replace mineral lubricants totally or partially and it is of great importance due to interest in environmental protection. Jatropha oil is a good alternative as lubricant feedstock and combustible. Its production is cheap in comparison to other vegetable oils. In México, Jatropha curcas L. is widely distributed in more than 15 states, which makes a sustainable supply of this natural resource possible. The aim of this work was to investigate the frictional behavior of blends of automatic transmission fluid with vegetable oil tested in a pin-on-disk rig simulating the wet clutch operation. Two different friction materials were separately tested and used as pins against actual steel disks from a wet clutch. The frictional behavior results demonstrated that the mixtures presented antishudder characteristics. Thus, Jatropha oil could be potentially used as part of automatic transmission fluid (ATF) formulations to enhance their antishudder properties and increase the efficiency of the torque transferred of wet clutches with a controlled lock-up clutch system, which improves the full economy of vehicles.

Surface chemistry of wet clutch influenced by water contamination in automatic transmission fluids

Lubricated friction interfaces used for wet clutches produce different friction behaviours depending on the lubricant conditions. Usually the lubricant conditions vary for water contamination in automatic transmission fluid (ATF). The presence of water retards the ATF performance by increasing the friction and can influence the deterioration of the clutch plates. Water as a polar contaminant can change the absorbability of the surface active additives, which might cause the characteristic friction behaviour. The aim of this paper is to verify the surface chemistry of tribotested standard friction interfaces lubricated with water contaminated commercial ATF (DEXRON® VI). The evidences of the influence of water on ATF performances were shown by surface analyses.

습식 브레이크의 소음 저감에 대한 연구

The wet brakes used on a forklift often produce noise upon engagement. The elimination or reduction of this squeal noise is an important task for the improvement of the comfort of those operating these machines. In this paper, a test rig was developed for the testing of brake noise, and the squeal noise was measured with this apparatus. Automatic transmission fluid and grooves in the material of the friction-plate pad were found to be the main factors causing squeal noise. In order to identify the characteristics of this type of noise, signal analyses of the noise were conducted using different frequency spectra. The experimental results showed that the viscosity of the automatic transmission fluid and the groove pattern on the friction-plate pad largely affected the reduction of the wet brake squeal noise made by an industrial forklift. ( ), Wet Disk Brake(습식 판 브레이크), Friction Plate Pad(마찰판 패드)

Influence of water on the tribological properties of zinc dialkyl-dithiophosphate and over-based calcium sulphonate additives in wet clutch contacts

Usually the wet clutch lubricant properties vary with different formulations of base oil types and additives. The aim of this paper was to evaluate the effect of water on the performance of additives in ATF. Simplified lubricants, ZDDP and over-based Ca-sulfonates detergent additives in an API Group I mineral base oil, were employed to compare with the commercial fully-formulated automatic transmission fluid (DEXRON®VI) during water-contamination. A full-scale wet clutch test rig was used to evaluate the frictional response due to water contamination of the lubricants. Fourier Transform Infrared Spectroscopy was utilized to evaluate the variation in the solubility of these polar organic additives in the water phase and Karl-Fischer titration was utilized to evaluate the post-test water content for different formulations.

Effect of a piston hole under the slip control condition of the lock-up clutch in a torque converter

A torque converter is a fluid coupling that transfers power from an engine to a transmission. To reduce the energy loss of the fluid coupling in conditions of low speed, the torque converter can be adapted to include a lock-up clutch, which directly connects the engine to the transmission at low speeds. To expand the speed range of these lock-up clutches, slip controls for lock-up clutches have been widely researched. However, slip controls can increase the temperature of friction materials on the piston plate of the lock-up clutch system, potentially reducing their durability. For this reason, the piston hole on the piston plate was developed to promote cooling during slip control. In this study, the effects of various slip conditions and the presence or absence of a piston hole on the temperature of the contact frictional surface were investigated experimentally. We confirmed that the inclusion of a piston hole on the piston plate could promote piston cooling by means of forced convection of cold automatic transmission fluid, and also maintained uniform pressure of the friction material under a greater range of automatic transmission fluid pressures.

주행 중 발생한 승용차 화재의 원인 조사분석에 관한 연구

신차 구입 후 14일 만에 시내도로 주행 중에 발생한 승용차 화재에 대해 화재원인을 분석하였다. 이 승용차는 화재로 인해 엔진룸이 큰 피해를 입었을 뿐만 아니라 차체 하부의 변속기 좌우와 변속기 뒤쪽의 배기관 주위도 집중적으로 큰 피해를 입고 있으며, 변속기 부근의 방열판(차열재)이 용융되어 있다. 따라서 발화개소는 변속기 하부 부근이며, 변속기 부근 하부에서 발화된 후 엔진룸 쪽으로 연소확대가 되었으며, 변속기 오일이 누유되어 배기관 위에 뿌려져서 배기관 열에 의해 발화된 것으로 분석된다. 그러므로 화재 발생 원인의 책임은 소유자나 운전자와 관련이 없고 메이커에 있으며, 메이커의 제조결함과 관련이 있는 것으로 분석된다. In this paper, fire cause of an automotive fire was analyzed. The automotive fire broke out while driving in the downtown area 14 days after the purchase. The engine room, the right and left sides of the transmission of lower body parts and an exhaust pipe surrounding behind the transmission were damaged intensively due to the fire. And an insulation plate of the transmission surrounding was melted. It was analyzed that the fire origin was transmission surrounding and the fire spread from transmission of lower part to engine room of upper part. And it was analyzed that the fire cause was automatic transmission fluid leakage that was scattered on the exhaust pipe. Therefore, it was analyzed that an owner or a driver was not responsible for this automotive fire and the automotive fire was associated with automotive maker's manufacturing defect.

Degradation mechanism of automatic transmission fluid by water as a contaminant

The degradation mechanism of water-contaminated automatic transmission fluids (ATF) was experimentally investigated. Water-contaminated ATF was tribotested in a full-scale wet clutch test rig to monitor the friction durability during clutch aging, and was also statically aged in oven to evaluate the interaction of ATF with water. The bulk properties and chemical nature of the ATF were analyzed using viscosity measurements, Fourier transform infrared spectroscopy and thermogravimetric analysis. It was shown that presence of water in the ATF can increase the mean friction coefficient over a short time period, though in the long-term perspective there is a higher loss of mean friction. Phase separation of the water-in-oil emulsion by centrifugation at 20,000 r/min made it possible to examine the water phase using infrared spectroscopy. The spectroscopic analysis revealed the hydrophilic nature of certain ATF constituents, although the impact of water on the bulk properties like lubricant viscosity and thermal stability was insignificant. The analysis of the tribotests showed that the friction increase for water contamination was a short-term effect and likely due to the interaction between polar surface active additives and water. Even though no significant change has been found for thermal degradation or in bulk properties of the lubricant, the initially changed action of the water soluble additives and generation of high friction resulted in a total deterioration of the clutch performance during long-term use.

Matching on Dynamic Characteristics of Automatic Transmission Fluid with Hydraulic Control System

Matching analysis of automatic transmission fluid (ATF) and the hydraulic control system is an essential work for the development of ATFs used in automatic transmissions. Based on the hydrodynamic theory, an ATF model was built. By adopting the modeling concept of combining and establishing models with basic elements, the hydraulic control system model was built, and then complete matching model was built by introducing the ATF model into it. The matching level of the ATF and the hydraulic control system was evaluated, and the key parameters which influence the performance of the hydraulic control system and their proper values were defined, which will be reference for developing optimal ATFs. With the bench test result and vehicle test result on road, the matching method and models for ATFs with the hydraulic control system are confirmed to be effective and feasible, which can significantly shorten the development cycle of ATFs.

차량 운행에 따른 자동변속기유(ATF) 금속분 분석평가 연구

자동변속기유는 자동차의 자동변속기의 성능을 유지시키기 위해 사용되는 유체이다. 최근 자동차 제조사에서는 일반적으로 자동변속기유를 80000~100000 km 주행후 교환 또는 무교환을 보증하고 있지만 국내에서는 많은 운전자들이 50000 km 이하에서도 자동변속기유를 교환하고 있는 것으로 조사되었다. 빈번한 자동변속기유의 교환은 환경오염과 차량유지비용을 상승시키는 원인으로 작용되고 있다. 본 연구에서는 사용하지 않은 신유와 50000 km와 100000 km를 각각 주행한 뒤 회수된 자동변속기유를 대상으로 인화점, 연소점, 유동점, 동점도, 저온겉보기점도, 전산가, 금속분과 같은 물리적 특성을 분석하였다. 연구결과, 신유에 비해 사용유는 전산가, 유동점, 금속분이 증가되는 것을 확인하였지만, 두 종류의 사용유(50000 km, 100000 km)의 물리적 특성과 금속분 함량의 차이는 크지 않음을 알수 있었다. Automatic transmission fluid (ATF) is used for automatic transmissions in the vehicle as the characterized fluid. Recently, the vehicle manufacture usually guarantee for fluid change over 80000~100000 km mileage or no exchange, but most drivers usually change ATF below every 50000 km driving in Republic of Korea. It can cause to raise environmental contamination by used ATF and increase the cost of driving by frequently ATF change. In this study, we investigate the various physical properties such as flash point, fire point, pour point, kinematic viscosity, cold cranking simulator, total acid number, and metal component concentration for fresh and used ATF after driving (50000 km, 100000 km). The result showed that the total acid number, pour point, Fe, Al and Cu component had increased than fresh ATF, but 2 kind of used oil (50000 km and 100000km) had similar physical values and metal component concentration.

Model for Predicting Drag Torque in Open Multi-Disks Wet Clutches

A mathematical model based on continuity and Navier-Stokes equations, considering laminar flow in the gap between the disks, is presented to estimate the drag torque in open multidisks wet clutches. By taking into account the effects of Poiseuille and centrifugal forces, the flow pressure and velocity fields are investigated. The model quantifies the volume fraction of fluids and predicts the evolution of film shape. The drag torque estimated by the model is the sum of drag torque due to shearing of automatic transmission fluid (ATF) and the mist (suspension of ATF in air) film. In order to validate the model, experiments are performed on SAE# 2 test-setup under actual operating conditions of clutches. The model is capable of predicting the drag torque under conditions of variable flow rate and different disks rotational state for higher clutch speed range.

Development of an electric oil pump control algorithm for an automatic-transmission-based hybrid electric vehicle considering the gear shift characteristics

In this paper, an electric oil pump control algorithm for an automatic-transmission-based hybrid electric vehicle was proposed. Dynamic models of the hybrid electric vehicle powertrain and hydraulic control system, including a mechanical oil pump and an electric oil pump, were obtained, and a hybrid electric vehicle performance simulator was developed. Also, a flow consumption model of the hydraulic control system was constructed. To represent the characteristics of the hydraulic control system according to the change in the temperature of the automatic transmission fluid, a viscosity index concept was introduced. Based on the simulation and test results, a viscosity index–line pressure–electric oil pump power map was proposed to describe the power supply requirement according to the viscosity index and the required line pressure. Using the viscosity index–line pressure–electric oil pump power map, an electric oil pump control algorithm was suggested to control the electric oil pump by using multi-stage power for a given viscosity index. The mechanical oil pump speed at which the electric oil pump is turned off was obtained on the basis of the flow consumption model. The electric oil pump control algorithm was evaluated by experiments and simulations. The proposed electric oil pump control algorithm satisfied the target line pressure requirement according to the viscosity index. In addition, an electric oil pump control strategy during an automatic transmission gear shift was suggested for the situation in which the maximum line pressure required for the gear shift cannot be achieved by only the mechanical oil pump. The electric-oil-pump-assisted power was determined from the flow consumption model and the mechanical oil pump speed considering the gear shift. The simulation results confirmed that the electric oil pump control strategy satisfied the maximum line pressure during a gear shift.

Wear Particle Characterization and Severity Evaluation of Perodua Myvi 1.3L Automatic Transmission (AT) Fluid

s. This paper investigates the characteristic and severity level of both wear and wear particles occurred in Perodua MyVi 1300cc automatic transmission (AT) mechanism via wear particle analysis approach. The analyses deployed were based on ferrographic and surface roughness analysis. The work of analysis strictly conducted on automatic transmission fluid (ATF) Perodua original equipment manufacturer (OEM) (ATF-3) series via continuous endurance dynamometer basis at the operating speed of 3000rpm. The operating mileage tested ranged from 0km up to 10,000km maximum operating distance. The wear particle generated at each operating mileage of 1,500km, 3,000km, 4,500km, 7,000km and 10,000km was accordingly analyzed morphologically and qualitatively. Ferrographic analysis is by principal has been recognized as one of the most reliable analysis incorporated with wear particle analysis (WPA) concern [1]. In concern of this study, it is applied to examine the morphology, mode and characteristic of wear particles generated. The surface roughness analysis meanwhile conducted to qualitatively evaluate and predict the wear condition of components within the AT mechanism via qualitative surface texture analysis of the wear particles. The outcome from the investigation done on the wear particles surface characteristics could interpret the wear behaviour and progress (stage/phase) as the surface characteristics of the wear particles do depict the surface characteristics of the wear components [2, 3].