Browse Topic: Automatic transmission clutches

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SAE No. 2 Friction Test Machine 3600 rpm Stepped Power TestJ2487_202507 (Current)7/16/2025
This SAE Recommended Practice is intended as the definition of a standard test, but it may be subject to frequent change to keep pace with experience and technical advances. This should be kept in mind when considering its use. The SAE No. 2 Friction Test Machine is used to evaluate the friction characteristics of automatic transmission plate clutches with automotive transmission fluids. It can also be used to conduct durability tests on wet friction systems. The specific purpose of this document is to define a 3600 rpm stepped power test for the evaluation of wet friction system performance variation as a function of power level. This procedure uses an initial engagement speed of 3600 rpm and is intended as a standard procedure for common use by both suppliers and end users. The only variables selected by the supplier or user of the friction system are: a Friction material b Fluid c Reaction plates These three variables must be clearly identified when reporting the results of using this test. If any of the test parameters or system hardware as described in this document are changed, other than the friction material, test fluid, or reaction plates, the data may not be reported as having been obtained using this document. This procedure is not intended to evaluate the initial coefficient or break-in characteristics. For this information, refer to SAE J2490.
Automatic Transmission and Transaxle Committee
Clutch Torque Optimization for Heavy-Duty Vehicles Starting Based on Intelligent Identification of Driver’s Starting Intention, Vehicle Mass, and Road Grade02-17-03-001810/8/2024
For heavy-duty vehicles equipped with automated mechanical transmission (AMT), the control of automatic clutch torque is crucial during the start-up process. However, the difficulty of controlling clutch torque is exacerbated by differences in driver’s starting intentions, changes in vehicle mass, and road gradient. Therefore, this article proposes the clutch starting torque optimization strategy based on intelligent recognition of driver’s starting intention, vehicle mass, and road gradient. First, an intelligent recognition strategy is proposed based on the combination of data-driven and onboard transmission control unit (TCU) algorithms, which improves the accuracy of recognizing the driver’s intention to start as well as the vehicle mass and road gradient. Based on the vehicle’s historical state data information, the predictive model is trained offline using a long–short-term memory (LSTM) network to obtain predicted parameter identification results, which are then used to calibrate the computed values of the onboard TCU algorithm. Second, the clutch torque optimization strategy is designed based on the driver’s starting intention, while considering the effects of road gradient and vehicle mass on the clutch starting resistance torque. The weight coefficients of the objective performance function are adjusted according to the driver’s starting intention, and the Pontryagin’s minimum principle (PMP) is used to solve the clutch target torque. Finally, offline data training and real-vehicle testing are performed. The results show that the optimization strategy can effectively reduce the friction work and the degree of impact during the starting process, minimize the clutch slipping time, and improve the smoothness of vehicle starting and driving comfort.
Geng, Xiaohu, Liu, Weidong, Lei, Yulong, Fu, Yao, Xue, Maohan
One-Way Clutches - Nomenclature and TerminologyJ1087_202408 (Current)8/12/2024
The definitions and illustrations in this SAE Recommended Practice are intended to establish common nomenclature and terminology for automotive transmission one-way clutches.
Automatic Transmission and Transaxle Committee
SAE No. 2 Friction Test Machine 6000 rpm Stepped Power TestJ2488_201907 (Historical)7/24/2019
This SAE Recommended Practice is intended as the definition of a standard test, but may be subject to frequent change to keep pace with experience and technical advances. This should be kept in mind when considering its use. The SAE No. 2 Friction Test Machine is used to evaluate the friction characteristics of automatic transmission plate clutches with automotive transmission fluids. It can also be used to conduct durability tests on wet friction systems. The specific purpose of this document is to define a 6000 rpm stepped power test for the evaluation of wet friction system performance variation as a function of power level. This procedure uses an initial engagement speed of 6000 rpm and is intended as a standard procedure for common use by both suppliers and end users. The only variables selected by the supplier or user of the friction system are: a Friction material b Fluid c Reaction plates These three variables must be clearly identified when reporting the results of using this test. If any of the test parameters or system hardware as described in this document are changed, other than the friction material, test fluid, or reaction plates, the data may not be reported as having been obtained using this document. This procedure is not intended to evaluate the initial coefficient or break-in characteristics. For this information, refer to SAE J2490 SAE No. 2 Friction Test Machine μPVT test.
Automatic Transmission and Transaxle Committee
SAE No. 2 Friction Test Machine μPVT TestJ2490_201905 (Historical)5/31/2019
This SAE Recommended Practice is intended as the definition of a standard test, which may be subject to frequent change to keep pace with experience and technical advances. This should be kept in mind when considering its use. The SAE No. 2 Friction Test Machine is used to evaluate the friction characteristics of automatic transmission plate clutches with automotive transmission fluids. It can also be used to conduct durability tests on wet friction systems. The specific purpose of this document is to define a μPVT Test for the evaluation of the variation of wet friction system performance as a function of speed, temperature, and pressure. This procedure is intended as a standard for both suppliers and end users. The only variables selected by the supplier or user of the friction system are: a Friction material b Fluid c Reaction plates These three variables must be clearly identified when reporting the results of this test. If any of the test parameters or system hardware as described in this document are changed, other than the friction material, test fluid, or reaction plates, the data may not be reported as having been obtained using this document. This procedure is intended to evaluate the endpoint/midpoint ratios, midpoint and breakaway coefficients. The procedure can be used to demonstrate changes that occur between the different levels of engagement speed, sump temperature, and apply pressure. Refer to SAE J2487, SAE J2488, or SAE J2489 for coefficient variations due to changes in power level. The procedure, as described in detail in Table 1, consists of four 50 cycle break-in levels at 3500 rpm with increasing steps of apply pressure, followed by 16 levels consisting of 25 dynamic engagements, and one breakaway following completion of the 25th dynamic cycle. The 16 levels are achieved by varying initial engagement speed, apply pressure, and oil sump temperature while the inertia is kept constant at 0.701 kg/m2.
Automatic Transmission and Transaxle Committee
SAE No. 2 Friction Test Machine 3600 rpm Stepped Power TestJ2487_201905 (Historical)5/23/2019
This SAE Recommended Practice is intended as the definition of a standard test, but may be subject to frequent change to keep pace with experience and technical advances. This should be kept in mind when considering its use. The SAE No. 2 Friction Test Machine is used to evaluate the friction characteristics of automatic transmission plate clutches with automotive transmission fluids. It can also be used to conduct durability tests on wet friction systems. The specific purpose of this document is to define a 3600 rpm Stepped Power Test for the evaluation of wet friction system performance variation as a function of power level. This procedure uses an initial engagement speed of 3600 rpm and is intended as a standard procedure for common use by both suppliers and end users. The only variables selected by the supplier or user of the friction system are: a Friction Material b Fluid c Reaction Plates These three variables must be clearly identified when reporting the results of using this test. If any of the test parameters or system hardware as described in this document are changed, other than the friction material, test fluid, or reaction plates, the data may not be reported as having been obtained using this document. This procedure is not intended to evaluate the initial coefficient or break-in characteristics. For this information, refer to SAE J2490.
Automatic Transmission and Transaxle Committee
Implementation of Torque Hole Filling for Transmission Shift Control2018-01-11694/3/2018
Torque Hole Filling (THF) is a model based approach for controlling the automatic transmission clutches and input torque during a part-pedal upshift or zero-pedal downshift. A desired transmission output torque is first calculated and then the clutches and input torque are controlled to achieve that output torque. This is a system design approach with drivability as one of the direct design objectives. This paper presents the control design and implementation of Torque Hole Filling. First, the paper introduces the topic, defines the terms, and explains the basic operation and intended result. Next, it describes how it works with one instance of implementation and its corresponding dynamics equations, for both torque transfer and ratio change phases. Lastly but most importantly, it covers the various robustness considerations for real-world applications.
Teslak, Christopher, Tseng, Eric, Cicala, Stephen, Riedle, Bradley D., Fujii, Yuji, Zhang, Jianping, Griffin, Chad, Slayton, Joseph, O'Neil, Brian
SAE No. 2 Friction Test Machine µPVT TestJ2490_201208 (Historical)8/6/2012
This SAE Recommended Practice is intended as the definition of a standard test, which may be subject to frequent change to keep pace with experience and technical advances. This should be kept in mind when considering its use. The SAE No. 2 Friction Test Machine is used to evaluate the friction characteristics of automatic transmission plate clutches with automotive transmission fluids. It can also be used to conduct durability tests on wet friction systems. The specific purpose of this document is to define a µPVT Test for the evaluation of the variation of wet friction system performance as a function of speed, temperature, and pressure. This procedure is intended as a standard for both suppliers and end users. The only variables selected by the supplier or user of the friction system are: a Friction Material b Fluid c Reaction Plates These three variables must be clearly identified when reporting the results of this test. If any of the test parameters or system hardware as described in this document are changed, other than the friction material, test fluid, or reaction plates, the data may not be reported as having been obtained using this document. This procedure is intended to evaluate the endpoint/midpoint ratios, midpoint and breakaway coefficients. The procedure can be used to demonstrate changes that occur between the different levels of engagement speed, sump temperature and apply pressure. Refer to SAE J2487, SAE J2488, or SAE J2489 for coefficient variations due to changes in power level. The procedure, as described in detail in Table 1, consists of four 50 cycle break-in levels at 3500 r/min with increasing steps of apply pressure, followed by 16 levels consisting of 25 dynamic engagements and one breakaway following completion of the 25th dynamic cycle. The 16 levels are achieved by varying initial engagement speed, apply pressure and oil sump temperature while the inertia is kept constant at 0.701 kg-m2.
Automatic Transmission and Transaxle Committee
Glossary of Terms - Lubricated Friction SystemsJ1646_201203 (Current)3/19/2012
This SAE Recommended Practice defines the principal terms and equations pertaining to automotive automatic transmission clutch plate, band, or other wet-friction systems. The terms apply directly to friction-system testing as is typically conducted on inertia-stop test equipment. Some terms can be directly applied to the analysis of friction in the transmission or brake assembly and other friction-test equipment. The glossary presents terms used to describe the set-up, testing, and results of tests as shown in Figure 1, which were taken on a clutch SAE No. 2 machine. The glossary is intended to provide a collection of definitions in the hope of eliminating confusion in development and their application to passenger cars and trucks. This document focuses on the terminology of friction-system testing. References for this type of testing are shown in Section 2.
Automatic Transmission and Transaxle Committee
Spin Loss Computation for Open Clutch Using CFD2011-01-12384/12/2011
Open clutch spin loss computation is of interest for new clutch designs. It is desirable to minimize open clutch spin loss. Spin loss in automatic transmission clutches is mainly due to the viscous shear of the transmission fluid. Depending on the relative rotational speed of the plates the spin loss varies. At low rotational speeds the gap between the plates is filled with ATF (Automatic Transmission Fluid) and spin loss increases linearly with the rotational speed. At higher speeds the ATF layer, which is held together primarily by surface tension, begins to breakdown due to higher centrifugal forces and air pockets form at outward radial locations of the clutch plates. This results in a decrease in spin loss for the open clutch. CFD (computational fluid dynamics) modeling is an attractive option in calculating the spin loss for an open clutch. Not only can a CFD model give an accurate estimation of the magnitude and trend of spin loss variation but it can also compare various groove designs. This is a significant advantage compared to some existing analytical methods for spin loss estimation of open clutches, as they are limited to either groove-less designs or designs with radial grooves. This work describes a 3D CFD modeling procedure that yields spin loss computations of sufficiently high accuracy by improvements made to some stated procedures in literature. Effect of variation of design parameters such as number of grooves, flow rates, etc, is studied.
Jammulamadaka, Anand K., Gaokar, Prajal
Glossary of Terms—Lubricated Friction SystemsJ1646_200608 (Historical)8/25/2006
This SAE Recommended Practice defines the principal terms and equations pertaining to automotive automatic transmission clutch plate, band, or other wet-friction systems. The terms apply directly to friction-system testing as is typically conducted on inertia-stop test equipment. Some terms can be directly applied to the analysis of friction in the transmission or brake assembly and other friction-test equipment. The glossary presents terms used to describe the set-up, testing, and results of tests as shown in Figure 1, which were taken on a clutch SAE No. 2 machine. The glossary is intended to provide a collection of definitions in the hope of eliminating confusion in development and their application to passenger cars and trucks. This document focuses on the terminology of friction-system testing. References for this type of testing are shown in Section 2.
Automatic Transmission Friction Standards Committee
SAE No.2 Friction Test Machine 6000 r/min Stepped Power TestJ2488_200608 (Historical)8/16/2006
This SAE Recommended Practice is intended as the definition of a standard test, but may be subject to frequent change to keep pace with experience and technical advances. This should be kept in mind when considering its use. The SAE No. 2 Friction Test Machine is used to evaluate the friction characteristics of automatic transmission plate clutches with automotive transmission fluids. It can also be used to conduct durability tests on wet friction systems. The specific purpose of this document is to define a 6000 r/min Stepped Power Test for the evaluation of wet friction system performance variation as a function of power level. This procedure uses an initial engagement speed of 6000 r/min and is intended as a standard procedure for common use by both suppliers and end users. The only variables selected by the supplier or user of the friction system are: a Friction Material b Fluid c Reaction Plates These three variables must be clearly identified when reporting the results of using this test. If any of the test parameters or system hardware as described in this document are changed, other than the friction material, test fluid, or reaction plates, the data may not be reported as having been obtained using this document. This procedure is not intended to evaluate the initial coefficient or break-in characteristics. For this information, refer to SAE J2490 SAE No. 2 Friction Test Machine μPVT Test.
Automatic Transmission Friction Standards Committee
Testing and engineering servicesAUTOJUL06_047/1/2006
This special edition of Testing & Simulation focuses on the latest technology for vehicle development and validation. The use of mechatronic systems continues to increase in all types of ground vehicles. From electronic stability control and automated manual transmissions to active dampers and active steering systems, the growing complexity, integration, and need to directly characterize the mechanical, software, and electronic interactions of such systems is creating demand for physical test systems that provide a more efficient means of mechatronics development and validation. By providing engineers with the tools to move mechatronics testing from the proving ground to the test lab, OEMs and suppliers will have a much more precise, safe, affordable, and repeatable means of evaluating component and vehicle performance.
Monaghan, Matthew
Fluid for Passenger Car Type Automatic TransmissionsJ311_200002 (Historical)2/22/2000
This SAE Information Report details some of the equipment and procedures used to measure critical characteristics of automatic transmission fluid (ATF) used in current automatic transmissions. It is intended to assist those concerned with the design of transmission components, and with the selection and marketing of automatic transmission fluids for the use in passenger car and light-duty truck automatic transmissions. The information contained herein will be helpful in understanding the terms related to properties, designations, and service applications of automatic transmission fluids.
Fuels and Lubricants TC 3 Driveline and Chassis Lubrication
Fundamental Studies on ATF Friction I.9716215/1/1997
Automatic transmission clutches are complex tribological systems. Frictional performance is controlled by the interaction of base fluids, additive components, composition clutches, and steel reaction plates with varying energy inputs and thermal stresses in an oxidizing environment. This paper, rather than addressing fully formulated fluid performance in such a system, takes a more fundamental approach where the number of system variables is reduced and the relative effects of formulation variables on system performance can be better examined. Relationships among observed friction performance, system oxidation, friction member condition, and representative performance additives are explored using a synthetic base fluid and a conventionally refined mineral base fluid.
Tipton, C. D., Schiferl, E. A.
The Effects of Water on Cellulose-Based Frictional Surfaces in Automatic Transmission Clutch Plates96191710/1/1996
A bench scale apparatus and accelerated test protocol were developed to evaluate the effect of contamination of automatic transmsission fluid by mg/kg levels of water on cellulose frictional clutch surfaces. The testing indicated that water added at levels as low as 600 mg/kg migrated to the surface of untreated paper frictionals and contributed to loss of the paper coating and erratic torque transfer properties. Treated, “high performance” paper frictional surfaces showed less physical damage but the same torque transfer effects from water contaminated ATF. A mechanism of the water coating, swelling and weakening the hydrophillic cellulose fibers, with subsequent destruction due to hydrodynamic shear was proposed.
Williamson, Will, RhodILLEGIBLE, Blaine
SAE NO. 2 CLUTCH FRICTION TEST MACHINE GUIDELINESJ286_199609 (Historical)9/1/1996
This SAE Recommended Practice is intended as a guide toward implementation of a standard practice but may be subject to frequent change to keep pace with experience and technical advances. This should be kept in mind when considering its use. The SAE No. 2 Friction Test Machine is used to evaluate the friction characteristics of automatic transmission plate clutch with automotive transmission fluids. It can also be used to conduct durability tests on wet friction systems.
Automatic Transmission Friction Standards Committee
GLOSSARY OF TERMS—LUBRICATED FRICTION SYSTEMSJ1646_199607 (Historical)7/1/1996
This SAE Recommended Practice defines the principal terms and equations pertaining to automotive automatic transmission clutch plate, band, or other wet-friction systems. The terms apply directly to friction-system testing as is typically conducted on inertia-stop test equipment. Some terms can be directly applied to the analysis of friction in the transmission or brake assembly and other friction-test equipment. The glossary presents terms used to describe the set-up, testing, and results of tests as shown in Figure 1, which were taken on a clutch SAE No. 2 machine. The glossary is intended to provide a collection of definitions in the hope of eliminating confusion in terminology and a common set of terms for improving the state-of-the-art of friction-system development and their application to passenger cars and trucks. This document focuses on the terminology of friction-system testing. References for this type of testing are shown in Section 2.
Automatic Transmission and Transaxle Committee
FLUID FOR PASSENGER CAR TYPE AUTOMATIC TRANSMISSIONSJ311_199402 (Historical)2/1/1994
This SAE Information Report details some of the equipment and procedures used to measure critical characteristics of automatic transmission fluid (ATF) used in current automatic transmissions. It is intended to assist those concerned with the design of transmission components, and with the selection and marketing of automatic transmission fluids for the use in passenger car and light-duty truck automatic transmissions. The information contained herein will be helpful in understanding the terms related to properties, designations, and service applications of automatic transmission fluids.
Fuels and Lubricants TC 3 Driveline and Chassis Lubrication
The Effect of Separator Flatness on the Performance and Durability of Wet Friction Clutches9309153/1/1993
The automatic transmission clutch represents a complex system involving critical interactions between the separator plates, fluid, operating conditions and friction material. This paper focuses on the effect of separator plate flatness on the performance and durability of two friction materials on an SAE #2 machine. The data from this study shows that flat separator plates yield higher dynamic coefficients and lower wear when compared to non-flat plates. These effects were obtained for separator plates with peak-to-peak departure from flatness values between approximately .08mm and .25mm. In addition, other variables such as material elastic modulus, separator plate thickness, and material operating pressure were studied. The use of soft friction materials to improve performance with non-flat reaction plates was quantified.
Barker, Keith
Control of Band/Drum Interface Temperature in Automatic Transmissions and the Impact Upon Friction System Durability90214710/1/1990
The importance of controlling band/drum interface temperature to maintain friction system durability in an automatic transmission clutch is investigated in this paper. Frictional durability is extremely important to assure smooth, consistent shifts and long transmission life. A statistically designed series of experiments was run in a SAE No. 2 band test machine to determine the parameters which impact interface temperature. Sump level, sump temperature, engagement speed, system inertia, direct lubrication of the drum surface, and engagement time were all examined. The analysis reveals each of these parameters, with the exception of engagement time, directly influences interface temperature under the tested conditions. Interface temperature was then linked to frictional system stability. This was accomplished through a second series of experiments where interface temperature was varied by changing only one of the previously identified parameters. Based upon these results, a graph is presented relating interface temperature to system durability. This graph may be used in transmission design to ensure consistent shifts and increased durability of band friction systems.
Castanien, Christian J.
Optimizing Automatic Transmission Clutch Lining Load Distribution Using Finite Element Analysis9005592/1/1990
A Finite Element Analysis technique was used to predict the clutch lining load distribution in automatic transmissions. This technique is explained and demonstrated on several clutch designs. The analysis shows the importance of rigid backing plates and optimum piston apply points. The benefit of tapered apply plates is also discussed. The importance of having a uniform clutch lining load distribution is described as it relates to clutch torque and energy capacity. THE PURPOSE of this paper is to discuss the importance of clutch lining load distribution for automatic transmissions as it relates to torque and clutch energy capacity. The design variables that affect these will be presented. Clutch pack compliance versus rigidity will also be addressed. A finite element technique for calculating the clutch lining load distribution will be discussed. This technique will be demonstrated on several clutch designs. Based on the finite element analysis, recommendations for designing higher torque and energy density clutches will be made.
Solt, Michael B.
FLUID FOR PASSENGER CAR TYPE AUTOMATIC TRANSMISSIONSJ311_198604 (Historical)4/1/1986
Fuels and Lubricants TC 3 Driveline and Chassis Lubrication
An Analysis of Automatic Transmission Clutch-Plate Temperatures7202872/1/1972
Automatic transmission clutch failures and rapid oxidation of the transmission fluid have sometimes been attributed to high temperatures in the clutch pack. For the purpose of estimating these temperatures, an analysis was made of the clutch system, and a solution was developed from the partial differential equations of heat conduction with appropriate boundary conditions. The solution thus obtained was verified experimentally. There were several important conclusions to this study. The maximum temperature rise occurs somewhat earlier than the end of the lockup time. The interface temperature rise increases as the lockup time decreases for a fixed amount of energy input. The ratio of heat flux entering the reaction plate to that entering the composite plate is not constant, as has been assumed by others. The heat absorbed by the fluid outside the clutch pack is negligible during the short lockup time. Temperature rises for some typical cases are computed.
Tataiah, K.
SAE NO. 2 CLUTCH FRICTION TEST MACHINE TEST PROCEDUREJ286_197201 (Historical)1/1/1972
The SAE No. 2 clutch friction test machine is used to evaluate the dynamic and static friction coefficients of automatic transmission clutch friction materials when submerged in various working fluids. It can also be used to conduct life tests on friction materials and working fluids.
Automatic Transmission Friction Standards Committee
Putting Automatic Transmission Clutch Friction Researchers on Speaking Terms6700512/1/1967
With the object of improving the technique of testing and specifying friction materials, a new type of friction material test fixture has been developed by the SAE Friction Subcommittee. This is a completely self-contained machine especially designed for cyclic testing and quality control work. This does not replace, but rather supplements, the steady state type friction test fixture (SAE No. 1) previously developed by the committee. This fixture, known as the SAE No. 2 test fixture, is designed to test clutch packs in an environment which is as close as possible to that of the friction elements in an automatic transmission. Both friction material manufacturers and users are employing this machine for quality control, component selection, and evaluation of friction materials and lubricants.
Smith, G. R., Ross, W. D., Silbert, P. L., Herndon, W. B.
A NEW BENCH TEST FOR EVALUATING CLUTCH PLATE LUBRICATION6300291/1/1963
A new, low cost, simple and compact bench type machine has been developed for investigating automatic transmission clutch plate lubrication. The energy absorbed per unit of clutch facing area during clutch engagement is comparable to that absorbed by the clutch during a full-throttle upshift in a car. The machine uses full-size clutch plates and requires a 13-ounce sample of fluid. Condition of the clutch plates after running under cycling conditions correlates with that found in an engine-transmission-dynamometer cycling test.
Davison, E. D.
Influence of Lubricant Breakdown on Frictional Performance6300271/1/1963
The influence of lubricant breakdown and additives on the frictional performance of wet automatic transmission clutch linings was studied with a low velocity friction apparatus. Base oil degradation products were shown to reduce static friction. Type A fluids were degraded in the friction machine to evaluate initial effects and in a bench oxidizing apparatus to evaluate extensive degradation effects. These methods rated the fluids in the same order and showed they varied widely in sludge formation, frictional and chemical stability. On frictional degradation, the friction level of two fluids increased with paper-based linings and decreased with sintered copper powder linings. The copper linings accelerated lubricant degradation and caused a different type of degradation.
Albertson, C. E., Okubo, H. S.
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