Automatic Transmission Efficiency Characteristics and Gearbox Torque Loss Data Regression Techniques

<div class="section abstract"><div class="htmlview paragraph">Automatic transmission (AT) is a complex hydroelectromechanical system, since it consists of hydraulic, electrical and mechanical parts.</div><div class="htmlview paragraph">On cars produced by “UzAuto Motors” mainly AT of the 6T family, 6-speed AT family GM: 6T30, 6T40, 6T45, 6T50 “Hydra-Matic” are used.</div><div class="htmlview paragraph">Production of parts of these transmissions is carried out both at American GM plants and at GM plants in China and Korea.</div><div class="htmlview paragraph">The differences between AT 6T30/6T40/6T45/6T50 are in the thickness of the output chain and in the planetary gear, in the sizes of some other units and the housing itself. But the differences are much more influenced by the settings of the transmission unit, which select operating modes with different engines so as not to overload the thinnest places of the automatic transmission.</div><div class="htmlview paragraph">Automatic transmissions 6T30, 6T40, 6T45, 6T50 have the ability to manually shift gears and activate the “kickdown” mode (for quick acceleration of the car, when you sharply press the gas “all the way” it makes the automatic transmission downshift, and sometimes by two steps).</div><div class="htmlview paragraph">The operation of the transmission is controlled by various electronic systems that are responsible for the operability and structural integrity of the gearbox.</div><div class="htmlview paragraph">Failure of the automatic transmission can occur as a result of one or a combination of malfunctions of the following parts: in the torque converter; in the mechanical part of the gearbox; in the hydraulic part of the control system; one or more clutches of the gearbox; in the electrical part of the control system; in the electronic control unit.</div><div class="htmlview paragraph">The authors of the work investigated and determined the occurrence of malfunctions and failures depending on the temperature of the working fluid of the automatic transmission of a passenger car.</div><div class="htmlview paragraph">Also, the dependence of the resource of the automatic transmission on the temperature of the hydraulic fluid was obtained. High-quality diagnostics of the automatic transmission and its control system can in many cases save the car owner from expensive repairs: <ul class="list disc"><li class="list-item"><div class="htmlview paragraph">without thorough diagnostics, the automatic transmission cannot be subjected to routine or major repairs. Only on the basis of diagnostic information can a conclusion be made about the technical maintenance or repair of the automatic transmission;</div></li><li class="list-item"><div class="htmlview paragraph">based on real experience of operating passenger cars equipped with automatic transmission, we recommend changing the oil every 35000 miles under operating conditions in Tashkent. We also recommend conducting diagnostics of the automatic transmission every 12500 miles of the car's mileage.</div></li></ul></div></div>

<div class="htmlview paragraph">This paper introduces mathematical equations for power loss calculations of major automatic transmission components.</div> <div class="htmlview paragraph">It also presents a theoretical investigation on contributions of each component's power loss to transmission total power losses.</div> <div class="htmlview paragraph">A computer program for automatic transmission efficiency calculation has been developed based on mathematical equations.</div> <div class="htmlview paragraph">Efficiency calculations for the Hyundai A4BF1 electronic 4 speed automatic transmission has been executed in order to validate the program.</div> <div class="htmlview paragraph">The calculated efficiency under various input and operating conditions - such as different input torque & RPM, transmission gear state, ATF temperature, torque converter clutch on/off - showed quite good agreement with the test results.</div>

<div class="section abstract"><div class="htmlview paragraph">The worldwide increasing acceptance and success of modern automatic transmissions in passenger cars is based on innovative technology, driving comfort, shifting dynamic and - most important - fuel consumption reduction.</div><div class="htmlview paragraph">New concepts are facing the challenge of further improvements in internal efficiency and very tough future goals on CO2 emissions in connection with more sophisticated gasoline and diesel engine technologies. Based on the competition and current diversity in automatic transmission concepts, high investments in production facilities must be taken also well into account when thinking about follow-up technologies of installed 8-speed and 9-speed technologies. This must also be considered for the different demands in regions and markets.</div><div class="htmlview paragraph">So, how may a successful automatic transmission system look like in 2020 and beyond? Do we have even more gears than the current 8-speed and 9-speed? Does it make sense to increase the total gear ratio any further? Are there measures to improve the overall mechanical efficiency by several percent? What is the prevailing transmission system: torque converter planetary, dual-clutch countershaft or belt-type stepless transmission? How does the electrification and hybridization of the powertrain in the next years effect the system?</div><div class="htmlview paragraph">This article will give some brief answers on how ZF is planning the future of automatic transmissions and how successful systems should look like.</div></div>

<div class="htmlview paragraph">Friction Launch transmissions use a wet multi-plate clutch to replace the torque converter in an automatic transmission. By using one of the range clutches inside the transmission, the benefits of this integrated friction launch technology (IFL), such as reduction in mass, packaging, and cost, can be enhanced. The availability of new automatic transmissions with higher number of speeds and wider ratio spreads makes IFL technology more viable than ever before. The new GM Rear-Wheel-Drive (RWD) six-speed transmission has paved the way for a full implementation of integrated friction launch technology in a GM full size Sport-Utility Vehicle (SUV). This project focuses on both hardware and control issues with the friction launch clutch. The hardware issues include designing the clutch for launch energy, cooling, and durability. The control issues include developing robust control algorithms for launch and creep, and providing damping to the driveline, when required, and ensuring acceptable vehicle drivability. This paper describes in detail the design of the clutch and the cooling system, and the development of the launch and creep control algorithms. Vehicle test data presented in this report show that High-Energy-Capacity Clutch (HECC) design as a friction-launch device can handle a wide-open throttle launch for a full-size truck application. The control strategy developed in this project significantly reduces the gap between the drivability of a starting clutch vehicle and a torque converter equipped vehicle. Also, vehicle fuel economy tests revealed promising fuel economy improvements over production intent 6-speed RWD transmission.</div>

<div class="htmlview paragraph">An automatic transmission for heavy duty trucks and buses has been developed. Automatically controlled dry clutch and synchromeshed gear transmission make driving easier, while maintaining good fuel efficiency of a mechanical transmission.</div> <div class="htmlview paragraph">The system consideration and design philosophies of the electronic controller are described here, as well as the mechanical hardware for conversion of a manual transmission into a fully automatic transmission.</div> <div class="htmlview paragraph">This transmission control system has not only the functions of an automatic transmission but also driveability and efficiency same as that of a skilled driver by incorporating various kinds of control logics.</div> <div class="htmlview paragraph">It is our fair judgement that this transmission can well meet market requirements in new age.</div>

<div class="section abstract"><div class="htmlview paragraph">This paper presents a methodology to represent automatic transmission clutch-to-clutch shift dynamics with a two degree of freedom, lumped inertia model. The method of reducing the automatic transmission to a lumped, two inertia model as a function of shift and input shaft acceleration is detailed using a full kinematic representation of the automatic transmission. For a given clutch-to-clutch shift maneuver there are two dependent equations that utilize the two lumped inertias and represent the response of the transmission system from input to output shaft. Applicability of the method is shown for planetary automatic and layshaft dual clutch transmissions. Typical clutch-to-clutch shift maneuvers are illustrated with the two inertia model for power on upshifts and downshifts. The simplification of automatic transmission shift dynamics using this method enables rapid synthesis of a given transmission powerflow for estimation of shift quality potential, required clutching torques, inertia phase engine torque intervention and output torque through all phases of a shift event.</div></div>

<div class="htmlview paragraph">An electronically controlled five-speed automatic transmission has been developed for use in new 2-liter models. This high-performance gearbox is the world's first five-speed automatic transmission for passenger car use to be equipped with a torque converter. It is designed with an ultra-wide range and close ratio gearing and incorporates a host of outstanding technologies to provide excellent performance and driveability.</div> <div class="htmlview paragraph">This paper describes the major features and performance of this new automatic transmission and some of the studies undertaken concerning multiplication of gear steps.</div>

<div class="htmlview paragraph">The improvement of the torque converter performance necessitates an optimized design of the torque converter stator blade on the basis of a full understanding of the internal flow conditions. However, it is difficult to analyze the flow experimentally or theoretically because the three elements (a pump, a turbine, and a stator) rotate at different speeds and the flow circuit and the blade shapes are complex. Enough explication of the internal flow has not yet been made.</div> <div class="htmlview paragraph">This research has developed a new method of calculating the torque converter performance by taking the stator blade profile into consideration. The internal flow through the torque converter stator can be treated as a two-dimensional flow, and here the flow was analyzed as a potential flow.</div> <div class="htmlview paragraph">The analysis of the torque converter stator blade was made as follows. First, the internal flow through the blade row was numerically analyzed by the boundary element method, and the numerical analysis was introduced into the one-dimensional performance analysis. Next, by this calculation method various stator blades were designed and manufactured by way of experiment. As compared with experimental results, it was verified that the torque converter performance can be calculated with satisfactory accuracy.</div> <div class="htmlview paragraph">This method was applied with success to optimizing the stator blade shape of the torque converter used for a forklift truck.</div>

<div class="htmlview paragraph">Allison Transmission and Castrol Industrial North America have teamed up to offer a new synthetic automatic transmission fluid specially formulated for heavy duty automatic transmissions. The new product is called TRANSYND™<span class="xref"><sup>1</sup></span> and is approved for use in all current transmission models in all current truck and bus applications.</div> <div class="htmlview paragraph">Allison's worldwide customers now have a new option when selecting transmission fluid. Customers may continue to choose from a wide variety of approved DEXRON<sup>®</sup>-III or Allison C4 quality fluids or they may elect to switch to TRANSYND™ and extend drain intervals. TRANSYND™ has been shown to be cost effective by reducing maintenance through extended drain intervals while providing superior performance. Benefits may be optimized in severe vocations such as transit fleets where there are more vehicles and fluid change intervals tend to be more frequent. Similar savings may also be achievable in general (lighter) duty vocations such as school buses, motor homes, etc. Life Cycle Cost analysis software has been developed to evaluate potential savings based on a customer's individual operating conditions and maintenance practices.</div> <div class="htmlview paragraph">Testing at all levels has demonstrated the superior performance of TRANSYND™ in the most severe duty environments. Extended drain intervals have been validated through fleet testing in severe duty applications. This paper discusses the rationale behind the launch of TRANSYND™, reviews the results of various bench, transmission, and fleet validation tests, and discusses the benefits of using this new product in Allison transmissions.</div>

<div class="htmlview paragraph">This paper presents a discussion on manual transmission torque losses and focuses specifically on the relationship between torque loss, input speed and torque. It also includes a discussion on other factors affecting torque loss, such as inclination angle and lube oil temperature.</div> <div class="htmlview paragraph">Manual transmissions used in compact light truck applications have torque losses that are a function of input speed and torque. Efficiency studies done on manual transmissions in the engine-driving mode indicate that torque losses, in other than direct-drive gears, are considerably more dependent on input torque than input speed. It was also observed that efficiency was significantly affected by the inclination angle and lube oil temperature.</div>

<div class="htmlview paragraph">A new automatic transmission called the CEEMAT (Converter Enhanced, Electronically Managed, Automatic Transmission) has been developed to serve the on/off highway truck market. The CEEMAT was also specifically designed to suit military applications.</div> <div class="htmlview paragraph">The CEEMAT is a unique combination of currently available mechanical transmission products and the power and sophistication of electronic control.</div> <div class="htmlview paragraph">The CEEMAT provides ample ratio coverage with proven reliability. Fuel economy can also be improved because of extended torque converter lockup function and the overdrive ratio.</div>

<div class="htmlview paragraph">A wet multi-plate clutch, designated as the “starting clutch”, is used to replace the torque converter in the automatic transmission in order to improve vehicle fuel economy. The transmission ratio spread must be increased to compensate for the torque multiplication of the torque converter and avoid penalizing the 0-60 mph acceleration performance. The main challenge of this concept is the control of the starting clutch to ensure acceptable vehicle drivability. This paper describes the system of a five-speed starting clutch automatic transmission vehicle and shows vehicle test results. Vehicle test data show that (i) the fuel economy benefit of the starting clutch is significant, and (ii) a starting clutch transmission can be designed to equal or better the 0-60 mph acceleration performance of a torque converter transmission by proper selection of the gear ratios.</div>

<div class="section abstract"><div class="htmlview paragraph">The parameters determining shift quality control in automatic transmissions are determined as part of the calibration of the transmission control. The resulting control system typically has three components: feedforward control, where the control output is determined before a gearshift; feedback control, where the control output is determined during the gearshift based on sensed feedback; and learning control (adaptation), where the feedforward or feedback controller parameters are modified after the current gearshift has ended and before the next similar gearshift begins. Gearshifts involving the same ratio change are referred to here as similar gearshifts, though such gearshifts may involve differences in other variables such as vehicle speed or engine torque. In most automatic transmissions, gearshifts are controlled by hydraulic clutches, and operating conditions for these clutches may vary widely, requiring a dedicated transmission controller involving significant calibration effort.</div><div class="htmlview paragraph">In the current work, novel model-based methods are used to accomplish feedforward control of gearshifts, involving offline calibration of fill and torque phase control parameters and learning control of the fill phase. Towards this end, a physics-based model of the oncoming clutch involved in an upshift of a production automatic transmission was developed and experimentally validated against test bench experiments for a wide variety of inputs and operating conditions. The resulting model is used to generate a feedforward controller, offline model-based calibration algorithm, and a learning controller that corrects for clutch under-fill and over-fill. The effectiveness of the resulting controller is validated by simulation studies using the experimentally validated transmission hydraulic system model, in conjunction with a powertrain model. In particular, it is demonstrated that the learning controller corrects for initial under- or over-fill error in two to three gearshifts. Convergence and robustness properties, and transient performance of the learning controller are also discussed.</div></div>

<div class="htmlview paragraph">Most United States vehicle assembly plants produce significantly more automatic transmission equipped vehicles than manual transmission vehicles. Assembling these two vehicles on a common production line can create complexity problems. This paper describes the design and development of a pre-assembled manual transmission clutch and flywheel modular assembly which reduces most of these problems. This assembly is used on the 1993 model year mini-van with a 2.5L four cylinder engine.</div> <div class="htmlview paragraph">This modular clutch system utilizes the same starter ring gear carrier (driveplate) used on automatic transmission equipped vehicles. It pilots into the crankshaft similar to the automatic transmission torque converter. It is balanced as an assembly which results in a lower system imbalance. A significant system piece cost saving, in comparison with today's competitive market, was achieved. The production vehicle assembly technique is common between the automatic transmission torque converter and the manual transmission modular clutch. This assembly also eliminates three parts from the assembly plant and uses the same attaching bolts as the automatic transmission torque converter.</div>

<div class="htmlview paragraph">The performance of a large-volume production torque converter is slightly different from those of development prototype due to the core leakage flow. The sealing gap between the stator crown and pump or turbine core of the production converter is usually larger than that of prototypes because of fabrication method and tolerances. In this work, the core leakage flow of torque converter was investigated using CFD. The core region was modeled and coupled together with other three major components of a converter. Studies show that for a particular converter the core leakage flow could result in a 3.6% stall torque ratio reduction and a 2% peak efficiency decrease. The effects of sealing gap dimensions were also studied.</div> <div class="htmlview paragraph">Computational investigations in this work indicated that the variation of input K factor with input torque level observed in dyno tests is due to the cavitation in the torque converter. Cavitation occurs at high input torque and low speed ratio conditions because of the high volume flow rate and large incidence angle at the stator inlet. The torque converter performances at different input torque levels were predicted by CFD simulations with a cavitation model. A new concept of the maximum input torque of a torque converter, which is limited by cavitation, is presented. The engineering solutions to reduce converter cavitation are also discussed in this paper.</div>