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Viewing 1 to 30 of 2657
Technical Paper
2014-06-30
Joël Perret-Liaudet, Alexandre Carbonelli, Emmanuel Rigaud, Brice Nelain, Pascal Bouvet, C. Jacques Vialonga
Abstract The main source of excitation in gearboxes is generated by the meshing process, which generates vibration transmitted to the casings through shafts and bearings. Casing vibration generates leads to acoustic radiation (whining noise). It is usually assumed that the transmission error and variation of the gear mesh stiffness are the dominant excitation mechanisms. These excitations result from tooth deflection and tooth micro-geometries (voluntary profile modifications and manufacturing errors). For real cases, the prediction of noise induced by the Static Transmission Error (STE) remains a difficult problem. In this work, an original calculation procedure is implemented by using a finite element method and taking into account the parametric excitations and their coupling (Spectral Iterative Method, developed by the Ecole Centrale de Lyon). The procedure is based on a modal approach developed in the frequency domain, particularly efficient to analyze systems having many degrees of freedom.
Technical Paper
2014-05-09
Byeong wook Jeon, Sang-Hwan Kim
This study was conducted to develop and validate a multidimensional measure of shift quality as perceived by drivers during kick-down shift events for automatic transmission vehicles. As part of the first study, a survey was conducted among common drivers to identify primary factors used to describe subjective gear-shifting qualities. A factor analysis on the survey data revealed four semantic subdimensions. These subdimensions include responsiveness, smoothness, unperceivable, and strength. Based on the four descriptive terms, a measure with semantic scales on each subdimension was developed and used in an experiment as the second study. Twelve participants drove and evaluated five vehicles with different gear shifting patterns. Participants were asked to make kick-down events with two different driving intentions (mild vs. sporty) across three different speeds on actual roadway (local streets and highway). After each event, participants were asked to complete the rating of the four descriptive terms as well as a comprehensive rating on the gear-shifting event.
Technical Paper
2014-05-09
John O. Manyala, Todd W. Fritz
Electro-hydraulic actuated systems are widely used in industrial applications due to high torque density, higher speeds and wide bandwidth operation. However, the complexities and the parametric uncertainties of the hydraulic actuated systems pose challenges in establishing analytical mathematical models. Unlike electro-mechanical and pneumatic systems, the nonlinear dynamics due to dead band, hysteresis, nonlinear pressure flow relations, leakages and friction affects the pressure sensitivity and flow gain by altering the system's transient response, which can introduce asymmetric oscillatory behavior and a lag in the system response. The parametric uncertainties make it imperative to have condition monitoring with in-built diagnostics capability. Timely faults detection and isolation can help mitigate catastrophic failures. This paper presents a signal-based fault diagnostic scheme for a gearbox hydraulic actuator leakage detection using the wavelet transform. The novelty of the work is the development of a high fidelity leakage fault detection as low as 0.128 lit/min.
Technical Paper
2014-05-09
John O. Manyala
The emergence of tougher environmental legislations and ever increasing demand for increased ride comfort, fuel efficiency, and low emissions have triggered exploration and advances towards more efficient vehicle gearbox technologies. The growing complexity and spatial distribution of such a mechatronic gearbox demands precise timing and coordination of the embedded electronics, integrated sensors and actuators as well as excellent overall reliability. The increased gearbox distributed systems have seen an increased dependence on sensors for feedback control, predominantly relying on hardware redundancy for faults diagnosis. However, the conventional hardware redundancy has disadvantages due to increased costs, weight, volume, power requirements and failure rates. This paper presents a virtual position sensor-based Fault Detection, Isolation and Accommodation (FDIA), which generates an analytical redundancy for comparison against the actual sensor output. The proposed FDIA scheme has been validated experimentally using an electro-hydraulic test rig and the gearshift simulation model, including the non-linear hydraulic actuator dynamics.
Technical Paper
2014-05-05
Jean-Baptiste Gallo
Several drive cycles have been developed to describe heavy-duty class 8 truck tractor operations. However, regional delivery operations, consisting of a mix of urban and over-the-road driving using highways to access several delivery/pick-up sites in dense urban areas, have not been well described. With funding from the U.S. Army National Automotive Center, the High-efficiency Truck Users Forum (HTUF) developed two drive cycles in an effort to better describe the full range of Class 8 truck tractor operations, which in total consumed about 30 billion gallons of diesel in the United States in 2010. This paper describes the rational for and the process to develop two regional delivery drive cycles: HTUF Regional Delivery #1 and HTUF Regional Delivery #2. These cycles were developed from more than eight months of cumulative data collected on six diesel Class 8 truck tractors operating across North America and representing several types of truck vocations. The HTUF Regional Delivery drive cycles fill an important gap in understanding and describing the full range of Class 8 truck tractor operations.
Technical Paper
2014-04-01
Sandeep Mahadev Jadhav
Abstract Objective of this research is to reduce gear rattle and whine noise. Study includes measurement of noise, vibration on transmission for source identification in order to eliminate rattle, whine through optimization of gear design and clutch damper performance. In order to optimize, we measured transmission torsional vibration and analyzed for proper selection of clutch dampers to reduce engine vibration transfer function to transmission. Through Noise & Vibration FFT, order and color map analysis we identified noise sources and further scope for specific gears design improvement. Hence test methodology adopted for development of gears and clutch damper successfully eliminated noise.
Technical Paper
2014-04-01
Matija Hoic, Nenad Kranjcevic, Zvonko Herold, Josko Deur, Vladimir Ivanovic
Clutch wear is dominantly manifested as the reduction of friction plate thickness. For dry dual clutch with position-controlled electromechanical actuators this affects the accuracy of normal force control because of the increased clutch clearance. In order to compensate for the wear, dry dual clutch is equipped with wear compensation mechanism. The paper presents results of experimental characterization and mathematical modeling of two clutch wear related effects. The first one is the decrease of clutch friction plate thickness (i.e. increase of clutch clearance) which is described using friction material wear rate experimentally characterized using a pin-on-disc type tribometer test rig. The second wear related effect, namely the influence of the clutch wear compensation mechanism activation at various stages of clutch wear on main clutch characteristics, was experimentally characterized using a clutch test rig which incorporates entire clutch with related bell housing. Finally, the previously proposed and experimentally validated physical clutch model, which was focused on the clutch actuator and axial dynamics, is extended to capture both wear related effects as a further step towards a more comprehensive overall clutch dynamics model.
Technical Paper
2014-04-01
Darrell Robinette
This investigation utilizes a DFSS analysis approach to determine automatic transmission gear content required to minimize fuel consumption for various powertrain - vehicle systems. L18 and L27 inner arrays with automatic transmission design and shift pattern constraint parameters were varied to determine their relative influence on fuel consumption. An outer noise array consisting of two vehicles with various engines, final drive ratios and legislated emissions test cycles was used to make a robust transmission selection based on minimizing fuel consumption. The full details of the DFSS analysis method and assumptions are presented along with a detailed examination of the results. With respect to transmission design parameters, parasitic spinloss and gear mesh efficiency were found to be most important followed by the number of gears. The DFSS analysis further revealed that unique transmission design formulations are potentially required for widely varying engines. The shift pattern constraint of minimum operating speed in gear that establishes the downshift line was found to be most significant while all other shift parameters proved to be negligible.
Technical Paper
2014-04-01
Namdoo Kim, Aymeric Rousseau, Henning Lohse-Busch
Abstract As a result of increasingly stringent regulations and higher customer expectations, auto manufacturers have been considering numerous technology options to improve vehicle fuel economy. Transmissions have been shown to be one of the most cost-effective technologies for improving fuel economy. Over the past couple of years, transmissions have significantly evolved and impacted both performance and fuel efficiency. This study validates the shifting control of advanced automatic transmission technologies in vehicle systems by using Argonne National Laboratory's model-based vehicle simulation tool, Autonomie. Different midsize vehicles, including several with automatic transmission (6-speeds, 7-speeds, and 8-speeds), were tested at Argonne's Advanced Powertrain Research Facility (APRF). For the vehicles, a novel process was used to import test data. In addition to importing measured test signals into the Autonomie environment, the process also calculated some of the critical missing signals, such as gear ratio and torque converter lockup.
Technical Paper
2014-04-01
Daiki Saegusa, Shinji Kawai
Abstract An analytic technology able to rapidly and accurately predict oil flows and churning torque in a transmission has been developed. The new method uses the finite difference method for analysis; with regard to wall boundaries it reproduces the shapes of physical objects by imparting boundary information to cells. This has made it a simple matter to treat the rotation and meshing of the gears, which form oil flows, and has also reduced the calculation cost. Tests of single-phase and multi-phase flows and churning torque were conducted in order to verify the accuracy of the new method. Calculation results for the flow velocity fields produced by rotating bodies, the trajectory of oil, and the behavior of the surface of the fluid displayed a good correlation with test results. Considering air entrainment in the oil, the ability of the method to reproduce these phenomena at high speeds of rotation was also increased. The method also displayed good reproduction of changes in churning torque produced by differences in the speed of rotation of the gears.
Technical Paper
2014-04-01
Chengwu Duan
A dog clutch, if successfully implemented in an automatic transmission, provides better packaging and the potential for improved fuel economy. The technical requirements for this concept are examined through modeling and simulation. As a first step, a physics-based component level model is developed that provides an understanding of the basic contact and impact dynamics. The model is compared to a built-in AMESim block to establish confidence. This component level model is then integrated into a powertrain system model within the AMESim environment. As a test bed, the powertrain model is exercised to simulate a friction plate to dog clutch shift in a 6-speed automatic transmission. The analysis helps to define the slip speed target at the onset of the dog clutch engagement while ensuring shift requirements are met. Finally, the model is validated by comparing the simulated results with measured dynamometer data.
Technical Paper
2014-04-01
Darrell Robinette
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.
Technical Paper
2014-04-01
Soovadeep Bakshi, Parveen Dhillon, Teja Maruvada
This paper presents the method of designing an optimized light weight, cost effective planetary gearbox for a Formula Student vehicle. The gearbox has a high speed functioning capability, in addition to the compact size and light weight. The iterative optimization procedure used provides a technique for selecting the best possible configuration of the gearbox. Conventional gearboxes used for this purpose are generally two step reduction gearboxes, which are bulkier in terms of weight and volume. Also, a review of the existing market reveals that the planetary gearboxes manufactured in India are not capable of handling high speeds, thus rendering them futile for racing applications. The target reduction ratio for the gearbox is a fixed parameter. The method involves design and optimization of the gear-train with the calculated ratio. A detailed algorithm has been used, which involves developing a mathematically modelled code for deciding gear characteristics, physical modelling using CAD, and structural testing of the same through simulation, with repeated iterations with a target to reduce both weight and volume.
Technical Paper
2014-04-01
Tatsuya Osone, Terauchi Seiji, Takeshi Yamamoto, Fumihito Konagaya
Abstract Conflicting customer demands for reduction of CO2 emissions (fuel economy improvement) and enhancement of driving pleasure are continuing to become more rigorous all the time. Against this backdrop, JATCO launched the transmission for hybrid system with Nissan in 2010, followed by the development of a hybrid system for use on a front-wheel-drive midsize SUV in the North American market. Among the various types of hybrid systems proposed to date, this one-motor two-clutch (1M2CL) parallel hybrid system achieves high efficiency with no engine friction loss during the EV mode and energy regeneration. This paper describes the new Jatco CVT8 HYBRID (CVT8 HYBRID), it is newly developed packaging technologies for compactly mounting the 1M2CL parallel hybrid system on front-wheel-drive vehicles.
Technical Paper
2014-04-01
Chen Wang, Zhiguo Zhao, Tong Zhang, Xianjun Dai, Xiyue Yuan
Abstract Several types of power-split hybrid transmissions are outlined and the strengths and weaknesses of typical compound power-split prototype designs are summarized in this paper. Based on an modified Ravigneaux gear set, a novel compound power-split hybrid transmission with compact mechanical structure is presented, its dynamic and kinematic characteristics in equations and operating modes are described, and then equivalent lever diagrams are used to investigate the proposed compound power-split device. Control strategies in different operating modes are discussed with the simplified combined lever diagram, and a global optimization method is implemented to find the optimum operation point for the hybrid powertrain. To evaluate the fuel economy of a hybrid car equipped with this hybrid transmission, a forward powertrain simulation model is developed and real vehicle performance tests are conducted in the chassis dynamometer. Simulations and test results show that the proposed hybrid transmission can improve the efficiency of the powertrain and demonstrate lower fuel consumptions than the corresponding conventional vehicle.
Technical Paper
2014-04-01
Xingxing Zhou, Paul Walker, Nong Zhang, Bo Zhu, Jiageng Ruan
Abstract This paper mainly studies the power losses in a refined two-speed dual clutch transmission which is equipped in a electric vehicle test rig. Both numerical and experimental investigations are carried out. After theoretical analysis of the power losses original sources, the developed model is implemented into simulation code to predict the power losses. In order to validate the effectiveness of the proposed model, results from experimental test are used to compare the difference the simulation and test. The simulation and test result agree well with each other. Results show that the power losses in the two-speed are mainly generated by multi-plate wet clutch drag torque and gear churning loss.
Technical Paper
2014-04-01
Gabriela Achtenova
The target of the work is to find out the algorithm of definition of the ratios of mechanical part of complex powersplit CVT/IVT system with regard to the highest achievable efficiency. The presented synthesis is focused on powersplit systems, which will consist of a CVT part, differential and eventually by-pass gear. The algorithm will be programmed and become an integral part of the program Sungear developed on Czech Technical University in Prague for analyses and synthesis of planetary stepped transmissions and CVT/IVT powersplit systems. The article will mainly present the algorithm of definition of efficient powersplit system. For the search of the efficient powersplit system we assume that the following parameters are given: a Spread and efficiency of used CVT system.b Total spread of the whole powersplit CVT/IVT mechanism.c Optional: Ratios of the used CVT system.d Optional: Ratios of the whole powersplit CVT/IVT system. The more kinematic parameters will be given, the more constraints of mechanism are defined and the less optimization capabilities will remain.
Technical Paper
2014-04-01
James Gramling
Abstract It is very important to note that most present-day CVT's drive with a friction element. Unlike gears that can be produced with any size necessary for the torque load they must transfer, CVT's are limited in torque capacity and are only marginally suitable for small vehicle applications. A system is described using two variable-inertia flywheels to not only supply the heavy torque requirements during acceleration of a vehicle but also operate in reverse capturing the otherwise wasted decelerating torque (I.E. braking torque). This system (called Kinetic Energy Power Transmission System or KEPTS) provides all of the documented benefits of the use of an IVT for motor vehicle acceleration and also incorporates regenerative braking. The significance of the system is that besides providing a complete KERS (kinetic energy recovery and storage) system, all accelerating and braking torque is provided by the two variable-inertia flywheels, thus allowing the main motive engine (ICE, electric traction motor, gas turbine, etc.) to operate at a fixed angular velocity (rpm) isolated from large torque variances, and the CVT elements can be minimized in size (I.E. low-torque).
Technical Paper
2014-04-01
Chao Jiang, Wenhua Huang, Weirong Fang, Jun Xin
To meet the requirements of low fuel consumption, good driving performance, vehicle packaging constraint, and manufacturing feasibility, a new wet dual clutch transmission family has been developed by SAIC Motor. This paper will provide a design overview of the transmission architecture, main characteristics, key subsystems and control strategies. The paper will also provide an overview of the development process, and the fuel economy benefit to the vehicle. The transmission family adopts compact layout of gears and shafts, wet dual clutch, hydraulic system for actuation of clutch and forks, integrated parking system, integrated fork and synchronizer system, etc. To achieve compact package target, a coaxial dual clutch with integrated damper system, two countershafts system, and optimized layout of gear system are adopted. The technical features for low fuel consumption include waved clutch plates, targeted cooling of wet clutch, optimized gear ratios, optimized control strategies. The technical features for high driving performance include optimized control on clutch pre-filling and clutch swap, close loop control on gear engagement, optimized control on different driving mode.
Technical Paper
2014-04-01
James Michael Hart
General Motors shall introduce a new rear wheel drive eight speed automatic transmission, known as the 8L90, in the 2015 Chevrolet Corvette. The rated turbine torque capacity is 1000 Nm. This transmission replaces the venerable 6L80 six speed automatic. The objectives behind creation of this transmission are improved fuel economy, performance, and NVH. Packaging in the existing vehicle architecture and high mileage dependability are the givens. The architecture is required to offer low cost for a rear drive eight speed transmission while meeting the givens and objectives. An eight speed powerflow, invented by General Motors, was selected. This powerflow yields a 7.0 overall ratio spread, enabling improved launch capability because of a deeper first gear ratio and better fuel economy due to lower top gear N/V capability, relative to the 6L80. The eight speed ratios are generated using four simple planetary gearsets, two brake clutches, and three rotating clutches. The resultant on-axis transmission architecture utilizes a squashed torque converter, an off-axis pump and four close coupled gearsets.
Technical Paper
2014-04-01
Amit Sandooja
Abstract In a transmission for Automobiles, the driver's comfort of smooth shifting and selection of gears is a major concern for the transmission designer. To achieve this comfort, lot of work and improvement has been done in the past few years and still some more improvements are in continuation by the automobile manufacturer. Apart from the smooth shifting and selection of gears while driving, the safety of the driver is also a major concern for the vehicle manufacturer. This paper relates to a safety Interlock mechanism of vehicle gear shifter selector lever to a drive position, until a predetermined condition is satisfied. There are various gear shift pattern exists in the vehicles, which depends upon the number of gears in the gearbox. Generally, two types of gear shift pattern are commonly used in commercial vehicles. 1st-2nd, 3rd- 4th, 5th-6th, Rev and Rev-1st, 2nd-3rd, 4th-5th, 6th. In the first type of gear shift pattern, neutral gear is placed in between 3rd-4th gear and reverse gear is separate.
Technical Paper
2014-04-01
Abhijeet Pingale
Advancements in engine technology have increased overall torque rating of engine and demanded further improvement in transmissions to sustain higher input torque. Conventional brass synchronizers have proved inadequate for these torque and gear inertia. It becomes necessary to use advanced material science and enhanced technology to synchronizer capabilities. Multi-cone compact synchronizer with carbon composite friction material technology has been tested successfully for these more demanding applications. This paper will focus on some of the key challenges in modern synchronized transmission, and way forward to address those. Some of the key areas delivering highest impact are being discussed. A combination of various techniques has enabled a significant reduction in overall transmission length along with enhancement in shift effort, life and overall performance.
Technical Paper
2014-04-01
Robert Lloyd
Abstract A hydro-mechanical transmission is described that approximates the “gearing” performance of a continuously variable transmission and incorporates all functions required for hydraulic regenerative braking. Other characteristics such as efficiency, noise, and responsiveness, match or exceed that of present day conventional automatic transmissions. Performance and physical sizing are shown for passenger vehicle, bus and truck transmissions.
Technical Paper
2014-04-01
Kenji Matsumoto, Hideharu Koga, Satoru Suzuki, Yuji Mihara
In order to reduce friction and predict wear of the sliding part, it is important to determine the oil film thickness of particular area. A sensor or similar device must be attached to the sliding surface to detect the oil film thickness. However, a sensor could not be attached, due to the lack of space on contact surface, and moreover there was no method to secure the sensor on contact surface at that time. A several-micrometer-thin-film sensor was installed on a sliding surface to attempt measurement, but since the sensor was attached on a contact surface, wear occurred immediately and data was unable to be obtained. To accomplish above issue, we developed a protective layer with excellent wear-resistance that successfully extended the measurement time by protecting the thin-film sensor. In order to measure pressure during driving, we provided a PVD (Physical Vapor Deposition) thin-film sensor of several micrometers on the drive transmission surface of a CVT (Continuously Variable Transmission) pulley.
Technical Paper
2014-04-01
Sergei Aliukov, Vladimir Gorshenin
Abstract The inertial continuously variable transmission is a mechanical transmission which is based on the principle of inertia. This transmission has a lot of advantages, namely: compactness, minimum friction losses and high efficiency as a result of the relatively small number of rotating components, a wide range of transformation of the torque. It does not need any conventional friction clutches. This transmission protects the engine from overload when the output shaft is braked. This drive guarantees optimum conditions of work for the engine regardless of the changing of load, and smoothly changes output speed according to the load. Mostly, design of this transmission consists of a pulsed mechanism with unbalanced inertial units and two one-way clutches. The pulsed mechanism is well developed and possesses high reliability. However, the one-way clutches are the most unreliable parts of the transmission and restrain wide use of the transmission. In this paper a new design of the inertial transmission with the only one-way clutch is considered.
Technical Paper
2014-04-01
HoYoung Lee, TaeHee Cho, Chan-Hee Won, Byoungkee Kim
Abstract In CVT, it is essential to optimize Clamping Force in Pulley to improve fuel efficiency. Clamping force in pulley is shaft force to control primary pulley and secondary pulley. It is determined by pulley ratio, input engine torque in CVT and safety factor for protecting belt slip. It is difficult to calculate correct clamping force and detect belt slip. Generally speaking, CVT has a tendency to have excessive Safety factor to prevent belt slip. This excessive safety factor in clamping force leads to lower fuel efficiency. In order to find an optimal clamping force, ‘the minimum clamping force’ which will not induce belt slip should be determined even during decreasing clamping force. Furthermore, clamping force should be maintained near the ‘minimum clamping force’. For this, following logics was developed First, the logic to calculate first safety ratio of belt, Second, the logic to detect belt slip state, Third, the logic to calculate the optimal clamping force. This logic was verified and validated on each SILS, HILS and Vehicle.
Technical Paper
2014-04-01
Francisco J. Morales, Francisco G. Benitez
Abstract Currently, continuously variable transmission (CVT) is a topic of special interest as it allows the vehicle to have the engine working at its optimum regime (either minimum or maximum power consumption as required) remaining unaltered despite the changes in speed and the torque required on the drive wheels during operation. There is a particular group of CVTs with special characteristics: dynamic type CVTs. In these, in addition to acting on a control element, as in the rest of the kinematic type transmissions, the gear ratio also depends on the external conditions to which the transmission is subjected, that is, the transmission ratio is also determined by other variables such as the angular velocity of the input shaft and the load torque exerted on the output shaft. This paper reviews the most representative dynamic CVTs and torque converters (TCs) stating the basics of their functioning. The transmissions analyzed correspond to different patents, from one of the first [1] to the most recent [2,3] In addition, a brief description of each mechanism is given based on analytical and computational studies of the most interesting items, analyzing the advantages, disadvantages and deficiencies in the operation.
Technical Paper
2014-04-01
Toshihiro Aoyama, Hideaki Takahara, Shinya Kuwabara, Hideki Miyata, Makoto Nakayashiki, Shinji Kasuga
Abstract In response to global demands for environmental conservation, the automotive industry is placing greater focus on the development of fuel-efficient technologies to help reduce global CO2 emissions. With the aim of simultaneously improving fuel economy and driveability, TOYOTA has developed a new continuously variable transmission (CVT) vehicles in North America equipped with a 1.8-liter engine [1]. This new CVT features various technologies for improving fuel economy, including: the world's first coaxial 2-discharge port oil pump system, wider ratio coverage, a flex start system, low-viscosity CVT fluid, and a higher final gear ratio. This paper outlines the configuration, characteristics, performance, and new technologies of this CVT.
Technical Paper
2014-04-01
Hiromu Soya, Makoto Yoshida, Kazutaka Imai, Yoshitaka Miura, Yuuki Matsushita
Abstract The new Jatco CVT8 High Torque (CVT8 HT) was developed for use on front-wheel-drive vehicles fitted with a large displacement engine. The development objectives set for this new CVT with a high torque capacity were outstanding fuel economy, size and weight reductions. To achieve those targets, a high torque capacity CVT chain was newly developed in cooperation with LuK GmbH & Co. KG. This article describes the efforts undertaken to develop increasing torque capacity.
Technical Paper
2014-04-01
Masahiro Tawara, Andrew Sata, Naoyuki Sakamoto, Toshiya Oishi, Shun Minaki, Motonori Kimura, Koshiro Kosaka
Abstract Toyota Motor Corporation developed a continuously variable transmission (CVT), unit K313, to satisfy the rising demand for improved fuel economy. This transmission was installed in the North American market Corolla for the 2014 model year. In this market, the driveability demands for automatic transmissions (AT) are very high. Additionally, the market is dominated by conventional AT with fixed gear ratios, leaving CVTs in the minority. In order to increase the volume and acceptance of CVTs in North America, excellent driveability had to be ensured. The key driveability advantage of CVTs is the ability to change gear ratio continuously without engaging or disengaging clutches. This allows for smooth driving without any shocks or gaps in drive force; however, it can also feel strange to drivers of conventional AT. To achieve the required driveability performance for the CVT in North America, the following technologies were introduced: A new drive force design method was developed to better utilize the continuously variable gear ratio, which results in better, more proportional acceleration feelings for the driver.
Viewing 1 to 30 of 2657