Browse Topic: Torque converters
ABSTRACT Thermal management systems (TMS) of armored ground vehicle designs are often incapable of sustained heat rejection during high tractive effort conditions and ambient conditions. The use of a latent heat energy storage system that utilizes Phase Change Materials (PCMs) is an effective way of storing thermal energy and offers key advantages such as high-energy storage density, high heat of fusion values, and greater stability in temperature control. Military vehicles frequently undergo high-transient thermal loads and often do not provide adequate cooling for powertrain subsystems. This work outlines an approach to temporarily store excess heat generated by the transmission during high tractive effort situations through use of a passive PCM retrofit thereby extending the operating time, reducing temperature transients, and limiting overheating. A numerical heat transfer model has been developed based around a conceptual vehicle transmission TMS. The model predicts the
ABSTRACT The following paper describes the new SAPA automatic transmissions for the future military vehicles. The very high mobility requirements, the reclaim of weight, power & space and the actual relevance of the fuel consumption require a rethinking and a new vision of the automatic transmission concept and design. This is what SAPA has been working on for the last 12 years obtaining excellent technical and commercial results, a concept aimed at reducing the power losses of the conventional powershifting transmission eliminating the torque converter, reducing the spin losses -due to hydraulic pumps and friction discs-, and improving vehicle mobility on variable terrain situations as off-road
In torque converters, a lockup clutch is used for direct torque transfer from the engine to the gearbox. Nowadays, earlier lockup engagement is necessary to reduce fuel consumption. It introduces noise and vibration issues in the transmission that are solved by clutch slipping. However, the clutch experiences much heat because of earlier engagement, which needs to be adequately dissipated by ATF oil. To overcome this issue, multi-plate clutches are commonly used for efficient torque transfer and clutch slipping. On the other side, packaging space for torque converters is reducing at the vehicle level, especially in hybrid vehicles, which reduces the efficient cooling of clutches. So, accurate modeling of clutch slipping is necessary to improve the clutch performance and durability of the product. Clutch slipping is a transient phenomenon that involves conjugate heat transfer and rotational flow modeling. There are different ways to model clutch slipping in CFD simulations. One of the
The following listed definitions are intended to establish terminology and criteria for describing the various kinds of automotive transmissions. A specific arrangement may be described by a combination of several of these definitions
Toyota developed a new hybrid unit “L4A0” for the new Tundra, which creates both good drivability and environmental performance. To ensure off-road, towing performance and typical truck driving characteristics, the unit is based on a transmission with a torque converter and a multi-plate lock up clutch, with a motor-generator and K0 clutch installed between the engine and transmission. The motor-generator and K0 clutch are built into a module, making it possible to create new hybrid units by combining the module with various transmissions. The unit features many different motor controls. For example, in the case of step-in acceleration input, in order to achieve the desired output torque, typically a kick-down shift is necessary [1]; however, by utilizing “L4A0” both high response and high power output is achieved even without a kick-down shift. This is accomplished by assisting the engine with the motor-generator even when the engine torque is delayed at low engine speeds
Traditionally, the controls system in production vehicles with automatic transmission interprets the driver’s accelerator pedal position as a demand for transmission input torque. However, with the advent of electrified vehicles, where actuators are located at different positions in the drivetrain, and of autonomous vehicles, which are self-driving, it is more convenient to interpret the demand (either human or virtual) in vehicle acceleration or wheel torque domain. To this end, a Wheel Torque-based longitudinal Control (WTC) framework was developed, wherein demands can be converted accurately between the vehicle acceleration or wheel torque domain and the transmission assembly input torque domain. For powertrains with a step-ratio transmission and a torque converter (TC), a key challenge of this conversion is the determination of the Inertia Compensation Torque (ICT), which is the torque required to accelerate or decelerate the TC’s impeller when the TC operates in the slipping or
A Torque converter is a type of hydro-mechanical device, vastly utilized in the automatic transmission of vehicles and other machines. It is a critical component of the transmission system, having a direct impact on the fuel economy and vehicle´s performance. Computational Fluid Dynamics (CFD) has been employed by many authors and engineers to better understand the complex behavior of fluids inside of torque converters, in a way that it provides design improvements and increases model accuracy. This article presents a methodology that applies CFD as a tool in the design process of automobile torque converters. Therefore, this paper performs an extensive review of CFD associated with torque converters, and the principal concepts are stated and used to have a better understanding of the system’s dynamic behavior. Additionally, this article details some of the work done to develop an automotive torque converter model using the commercial software ANSYS CFX
A hybrid transmission with more than 10 times speed ratio is introduced in this paper. The transmission consists of a electric torque converter module (eTC) and a dual input-shaft gearbox (DIG). The configuration structure and operation mode of the hybrid system based on eTC-DIG are analyzed in detail. The hybrid module comprises a motor, a planetary gear set (PGS), and a clutch. The rotating elements of the PGS are connected to engine shaft, motor shaft, and two input shafts of DIG, respectively, in such a way, that a new speed ratio is created between each odd-numbered gearset and an adjacent even-numbered gearset. The transmission has twice as many speed ratios for the engine as the number of the speed-changing gear sets. The hybrid system can realize a variety of working modes and eliminate the dual clutch of DCT, which greatly reduces the cost and risk. The economic simulation of the hybrid system is carried out for a Pickup truck. The results show that multi-gear is conducive to
The emission norms around the world are continuously changing and getting stringent with every revision. India is on its way to make its emission norms at par with that prevailing in the developed nations. The cold-start condition is an important factor affecting vehicle emissions from gasoline direct injection (GDI) and port fuel injection (PFI) vehicles. In this paper, the effects of change in torque converter losses on emissions are experimentally investigated in a TGDI AT vehicle. The instant engagement of the torque converter puts a sudden load on the engine and thus affects its stability. Thus, to overcome the stability issue, Engine Torque has to be simultaneously increased for smooth engagement. As a result, the likelihood of the slightly leaner air-fuel mixture in the cylinder, which results in higher NOx formation, is much greater in an AT vehicle than that of a similar MT vehicle. Additionally, the temporary ineffectiveness of motor vehicle emission controls at startup
Dynamic Skip Fire (DSF) is an advanced cylinder deactivation technology to reduce fuel consumption and emissions of internal combustion engines. The firing sequence may vary dynamically depending on driver demanded torque with all cylinders capable of deactivation. This creates a challenge for managing noise vibration and harshness (NVH) caused by the low frequency excitation in the engine’s torque profile, especially in smaller engines with 3 or 4 cylinders. Due to the varying nature of firing sequences, the excitation is not limited to one or two engine orders and can vary with time, requiring broadband mitigation of the driveline. This work proposes the optimization of flywheel inertia combined with careful control of torque converter slip to overcome this challenge. Four different flywheel configurations and varying levels of torque converter slip were tested on a VW Jetta fitted with a 1.8L 4-cylinder engine with DSF control capability. For each configuration, DSF flyzone maps
A torque converter is a type of fluid coupling device used to transfer engine power to the gearbox and driveline. A bypass clutch equipped in a torque converter assembly is a friction element which when fully engaged, can directly connect the engine to the gearbox. The torque converter is an important launch device in an automatic transmission which decouples engine speed from gearbox input speed while providing torque multiplication to drive the vehicle. During partial pedal launch, it is desired to engage the bypass clutch early and reduce the converter slippage in order to reduce power loss and achieve better fuel economy. However, engaging the bypass clutch early and aggressively may disturb the wheel torque and cause unpleasant driving experiences. This paper describes a multi-input multi-output (MIMO) control method to coordinate both engine and converter bypass clutch to simultaneously deliver desired wheel torque and reduce converter slippage. The proposed control method
Mobility performance prediction models for tracked vehicles are well established as seen from the literature reviews. However, these simulation models are more suitable for commercial vehicle applications than for military vehicles which operate under a wide range of terrain conditions and hostile environment. Most of the models do not take into account the effect of cooling fans, soft ground rolling resistance, and torque converter to predict mobility, and therefore using them for military vehicles would pose vital problems and not yield the expected results. This paper attempts to address these problems by using a MATLAB/SIMULINK model, which takes into account these factors for a 65 ton Main Battle Tank (MBT) as a case study. A simulation model for the above vehicle was developed incorporating effects of cooling fan and torque converter. The results were validated with published trial data for an in-service Main Battle Tank of the same weight class. The results revealed that the
This Aerospace Information Report (AIR) is intended to be concerned with fleet programs rather than programs for individual units. Technical and administrative considerations in developing an approach to a program will be suggested. Organization of material possibly wanted in the form of a detailed specification for airline rebuilder communication is reviewed
Determining an amount of clutch clearance for the lockup device in a torque converter is important for its being operating precisely in the intended mode. Challenges may exist for the torque converters whose nominal clearances are on purpose very small. Any potential changes in the clutch lockup system (e.g., due to the deformation of components) may make such a small clearance instantaneously diminish during the mode of open-clutch, thus leading to unwanted drag in the clutch and unnecessary loss of energy. In the open-clutch mode, the actual clutch clearance may be different from the nominal clearance anticipated, primarily because of deformation caused by the internal load acting on clutch members. It has been found that the pressure distribution in a clutch chamber also depends on the very clutch gap through which the fluid flows. This interdependence between the fluid pressure load and structural deformation is typical of two-way coupling in simulation. As an alternative approach
It is common that angular velocities can be different from time to time between an engine output and transmission input, because both are connected by a damper in torque converter with flexible elements in it. When this difference occurs abruptly for some reasons, an internal impact could start between the engine-attached members (also known as driving members) and the transmission-attached members (or driven members). The resulting impact load could be several times the torque an engine’s combustion force can generate, depending on the impact energy. An impact load can be very devastating to a torque converter and other power-train members, just as to all other mechanical systems. This work presents a comprehensive and interesting study to help understand the rotational impact behavior for a system where none of bodies is stationary at the onset of impact. Using an explicit finite-element solver for case studies, the author will assess what role a friction-based clutch, placed between
As part of the U.S. Environmental Protection Agency’s (EPA’s) continuing assessment of advanced light-duty automotive technologies in support of regulatory and compliance programs, a 2018 Toyota Camry front wheel drive eight-speed automatic transmission was benchmarked. The benchmarking data were used as inputs to EPA’s Advanced Light-duty Powertrain and Hybrid Analysis (ALPHA) vehicle simulation model to estimate GHG emissions from light-duty vehicles. ALPHA requires both detailed engine fuel consumption maps and transmission torque loss maps. EPA’s National Vehicle and Fuels Emissions Laboratory has developed a streamlined, cost-effective in-house method of transmission testing, capable of gathering a dataset sufficient to characterize transmissions within ALPHA. This testing methodology targets the range of transmission operation observed during vehicle testing over EPA’s city and highway drive cycles. With this method, the transmission is tested as a complete system, as opposed to
The wet clutch system (WCS) is a complex combination of friction plates, separator plates and fluid (lubricant). The basic function of the WCS is to transfer torque under various operating conditions such as slipping, shifting, start/launch and/or torque converter clutch (TCC) operation. Under these conditions the slope of the coefficient of friction (μ or COF) versus slip speed (μ-v) curve must be positive to prevent shudder of the WCS, a highly undesirable condition in the lubricated friction system. An extended durability duty cycle test procedure is required to evaluate the WCS during which the μ-v curve is monitored for a negative slope, a condition indicating the potential for shudder. The friction plates, separator plates, and lubricant must be tested together and remain together during the test to be properly evaluated as a WCS. This paper describes a new test procedure which builds on the basics of the SAE J2964 - Low Speed Continuous Slip μPVT Procedure [1] by adding a
This SAE Recommended Practice establishes the test procedures, performance requirements, and criteria necessary to evaluate minimum safety and reliability requirements of a children's snowmobile as identified in 1.2
The constant growth of the automotive market demands for comfort to the user and energy efficiency have caused the intensification of the industry researches and development of the automatic transmissions (AT). However, vehicles equipped with these gearboxes entails in higher fuel consumption levels than the one required by vehicles equipped with manual transmission. In the automotive industry due to the advantages offered using computer simulations, such as fast evaluation an optimization, many researchers are using virtual models for optimization of dynamic behavior of systems and fuel consumption. Aiming to study the dynamic behavior of an AT and the influence of its components on that behavior, this paper presents an AT dynamic model developed in MATLAB® / Simulink®. The AT model has three main subsystems: a torque converter model, which includes the dynamic of both the forward flow mode and the reverse flow mode; a Lepelletier gearbox model, composed by a set of three planetary
Since the torque converter and fluid coupling are commonly used components of automatic transmissions in industry, the SAE appointed a committee to standardize terminology, test procedure, data recording, design symbols, and so forth, in this field. The following committee recommendations will facilitate a clear understanding for engineering discussions, comparisons, and the preparation of technical papers. The recommended usages represent the predominant practice or the acceptable practice. Where agreement is not complete, alternates have been included for clarification. EXAMPLE: Two systems of blade angle designations are described. Consequently, when a blade angle is specified, the system should be designated. This SAE Recommended Practice deals only with the physical parts and dimensions and does not attempt to standardize the design considerations, such as the actual fluid flow angle resulting from the physical blade shape
The automobile manufacturers are currently facing a double challenge. While they must meet tight vehicle emission regulations established by the authorities, they also have to achieve the current market demands, which look towards fuel efficient vehicles for city driving, but still delivering high performance for unproblematic highway cycles. The purpose of this study is to evaluate the influence of different axle ratios in the conflicting fuel economy versus acceleration performance trade-off. The article will present the modeling and simulation of a four-wheel-drive light-duty vehicle with six-speed automatic transmission subjected to three drive cycles: the FTP-72 (Federal Test Procedure) cycle, the Highway Fuel Economy Test (HWFET) cycle, and the 0-100 km/h acceleration cycle. The simulations were performed in MATLAB/Simulink® environment by using system modeling that incorporates powertrain components such as engine, transmission, torque converter, axle ratio, wheels, driveshaft
The scope of this SAE Draft Technical Report is to establish dimensional standards for high-performance domestic torque converter manufacturers. Many torque converter manufacturers build converters to their own standards. Some of these standards may be outside of the specifications that define a quality performance torque converter
This document outlines the functional and design requirements for baggage/cargo tow tractors used for airline services
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