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Fundamentals of Modern Vehicle Transmissions

2020-10-12
Starting with a look at the transmission's primary function -- to couple the engine to the driveline and provide torque ratios between the two -- this updated and expanded seminar covers the latest transmission systems designed to achieve the most efficient engine operation. Current designs, the components and sub-systems used, their functional modes, how they operate, and the inter-relationships will be discussed. A manual transmission display will be used to explain ratios and how they function within the driveline.
Technical Paper

A Generic Testbody for Low-Frequency Aeroacoustic Buffeting

2020-09-30
2020-01-1515
Raising demands towards lightweight design paired with a loss of originally predominant engine noise pose significant challenges for NVH engineers in the automotive industry. From an aeroacoustic point of view, low frequency buffeting ranks among the most frequently encountered issues. The phenomenon typically arises due to structural transmission of aerodynamic wall pressure fluctuations and/or, as indicated in this work, through rear vent excitation. A possible workflow to simulate structure-excited buffeting contains a strongly coupled vibro-acoustic model for structure and interior cavity excited by a spatial pressure distribution obtained from a CFD simulation. In the case of rear vent buffeting no validated workflow has been published yet. While approaches have been made to simulate the problem for a real-car geometry such attempts suffer from tremendous computation costs, meshing effort and lack of flexibility.
Technical Paper

Innovative Acoustic Material Concept Integration Into Vehicle Design Process

2020-09-30
2020-01-1527
Integration of acoustic material concepts into vehicle design process is an important part of full vehicle design. The ability to assess the acoustic performance of a particular sound package component early in the design process allows designers to test various designs concepts before selecting a final products. This paper describes an innovative acoustic material concept which is easily integrated in a design process through the use of a database of Biot parameters. Biot parameters are widely used in the automotive industry to describe the physical interactions between the acoustics waves travelling through foams, fibers or metamaterials and the solid and fluid phase of these poro-elastic materials. This new acoustic material concept provides a combination of absorption, transmission loss and added damping on the panel it is attached to.
Technical Paper

On Prediction of Automotive Clutch Torsional Vibrations

2020-09-30
2020-01-1508
Automotive clutches are prone to rigid body torsional vibrations during engagement, a phenomenon referred to as take-up judder. This is also accompanied by fore and aft vehicle motions. Aside from driver behaviour in sudden release of clutch pedal (resulting in loss of clamp load), and type and state of friction lining material, the interfacial slip speed and contact temperature can significantly affect the propensity of clutch to judder. The ability to accurately predict the judder phenomenon relies significantly on the determination of operational frictional characteristics of the clutch lining material. This is dependent upon contact pressure, temperature and interfacial slip speed. The current study investigates the ability to predict clutch judder vibration with the degree of complexity of the torsional dynamics model. For this purpose, the results from a four and nine degrees of freedom dynamics models are compared and discussed.
Technical Paper

The In-Depth PHEV Driveline Torsional Vibration Induced Vehicle NVH Response Study by Integrated CAE/Testing Methodology

2020-09-30
2020-01-1507
In this paper,an amesim 1-d refined driveline model, including detailed engine, damper, dual clutch, transmission, differential, motor, halfshaft, wheel, body, suspension, powertrain mounting and powertrain rigid body, was built up, off a p2.5 topology phev,to predict torsional vibration induced vehicle NVH response addressing differing driving scenarios,like WOT rampup,parking engine start/stop,ev driving to tipnin(engine start) then to tipout(engine stop).firstly,the torsional vibration modes were predicted,addressing differing transmission gear steps of hev/ev driving mode,and the critical modes could be detected,as such, caveats/measures could be applied to setup the modal alignment chart/warn other engineering section from the very start of vehicle development; secondly,secondly,the holistic operational testing,which defined plenty measurement points including rpm fluctuation at differing location of engine/transmission,spark angle,crank position,injection angle,valve timing,MAP/MAF,etc, partly for later model calibration,partly for extract mandatory excitation input,like cylinder pressure trace/mount and suspension force,and partly for the reference of next optimization stage, was implemented on vehicle chassis dyno in a hemi-anechoic chamber.as it was merely centered on torsional vibration induced scenarios,the intake system/exhaust system /engine radiation noise contribution was excluded by specific measures,like BAM,etc, during the testing;thirdly,the NTF/VTF from the mount/suspension force exertion points to vehicle response points were measured off trimmed body impact testing, to create structural TPA model,that way,each transfer path contribution to the response point could be predicted and overall response can be synthesized from all paths;fourthly,the above-mentioned driveline model,combined the excitation on each cylinder considering the gas torque/inertia torque and motor average torque,was well calibrated to predict the mount/suspension force/critical rpm fluctuation/vibration;finally,it was validated that CAE results correlate very well to measurement outcome for defined loadcase, and that can be adopted to phev driveline/vehicle NVH development from the very start of vehicle development phase so as to expedite vehicle NVH developing process.
Technical Paper

Analytical Rotordynamic Study of a High-Speed Gear Transmission System for Race Applications

2020-09-30
2020-01-1502
In motorsport power transmission systems, high-speed operation can be associated with significant rotordynamic effects. Changes in the natural frequencies of lateral (bending) vibrational modes as a function of spin speed are brought about by gyroscopic action linked to flexible shafts and mounted gear components. In the investigation of high-speed systems, it is important that these effects are included in the analysis in order to accurately predict the critical speeds encountered due to the action of the gear mesh and other sources of excitation. The rotordynamic behaviour of the system can interact with crucial physical parameters of the transmission, such as the stiffnesses of the gear mesh and rolling element-to-raceway contact in the bearings. In addition, the presence of the gear mesh acts to couple the lateral and torsional vibration modes of a dual-shaft transmission through which a torque flows.
Technical Paper

Asian Consumers Challenging the NVH Performance of European Cars – Implications on the Product Development in the 2020ies

2020-09-30
2020-01-1552
Sales of SUV and luxury cars on the largest market of the world – China – are growing at a high rate. The highways in large cities like Beijing or Shanghai are increasingly populated with cars from all over the world like Japan, USA, Europe and Korea and even some refined domestic brands. More than 10 million rich people can afford those cars and are skilled drivers. This huge group of potential consumers is targeted by luxury brand OEMs and by startup companies. It has been understood, that these people have a strong attitude towards comfort. The twistbeam rear axle was replaced by multilink, double clutch transmissions were improved by comfort-mode drive programs, interior trims raised to Western standard performance levels, tyres specially developed for comfort in China, localized insulation materials and packages engineered to a one vehicle class higher level.
Technical Paper

A Diagnostic Technology of Powertrain Parts that Cause Abnormal Noises using Artificial Intelligence

2020-09-30
2020-01-1565
In general, when a problem occurs in a component, various phenomena appear, and abnormal noise is one of them. The service technicians diagnose the noise through the analysis using hearing and equipment. Depending on their experiences, the analysis time and diagnosis accuracy vary widely. The newly developed AI-based diagnostic technology diagnoses parts that cause abnormal noises within seconds when a noise is input to the equipment. To create a learning model for diagnosis, we collected as many abnormal noises as possible from various parts, and selected good and bad data. This process is very important in the development of diagnostic techniques. Artificial intelligence was learned by deep learning with selected good data. This paper is about the technology that can diagnose the abnormal noises generated from the engine, transmission, drivetrain and PE (Power Electric) parts of the eco-friendly vehicle through the diagnosis model composed of various methods of deep learning.
Technical Paper

Root Cause Analysis and Structural Optimization of E-Drive Transmission

2020-09-30
2020-01-1578
We face a growing demand for so-called eAxles (electric axle drive) in vehicle development. An eAxle is a compact electric drive solution for full electric vehicles (and P4 hybrids) with integrated electric machine and transmission. The transmission can be rather simple using fixed gear with cylindrical gear steps but increasing demands on power and speed range as well as efficiency increase its complexity with planetary stages or switchable gear steps. Such an electro-mechanic system has different behavior than the classical ICE-driven powertrains, for example regarding NVH, where high frequency and tonal noise from gear whining and electro-magnetic excitation is an important comfort issue that needs to be understood and controlled.
Technical Paper

Measurement Location Optimization of Component TPA Method for Road Noise

2020-09-30
2020-01-1581
In this paper, an investigation on the application of a non-intrusive on-site component Transfer Path Analysis (TPA) method is presented together with the comparison with a previously performed direct blocked forces method. The latter is the more common method to determine interface forces between active and passive parts of an assembly. Force transducers are placed between the investigated structure and a rigid measurement rig. The presented comparison shows an investigated whether the faster and cheaper TPA method was able to produce relevant results. The TPA method used in this work calculated the force component contributions, without disassembly of the interfaces, through the local stiffness of multiple indicator positions per interface combined with operational measurement. The method is based on the application of an inverse-matrix model. This approach was applied to a vehicle road noise investigation carried out on a roller bench at three different roller speeds.
Technical Paper

On the Effect of Clutch Dynamic Properties on Noise, Vibration and Harshness Phenomena

2020-09-30
2020-01-1510
Noise, vibration and harshness phenomena (NVH) can manifest itself during the engagement and disengagement process of dry friction clutch systems. Such phenomena can have a negative impact on cabin occupants driving experience (as well as others in the immediate vicinity of the vehicle). Typically, unwanted NVH phenomena that pertain to the clutch system include Judder, Chatter, Squeal and Eek. These phenomena are recognised by the quality of the radiated noise, as well as the dynamics occurring during clutch actuation. The aim of the current study is to utilise a numerical clutch system model (fully coupling the main motions of clutch components) to predict clutch dynamics during engagement manoeuvres. The model will be used to assess the effect of various clutch design parameters on mitigating system instability. The clutch model utilises measured coefficient of friction data from a rotary tribometer at representative slip speeds and contact pressures.
Technical Paper

Determination of energy-saving potentials by reducing the rolling bearing friction in the tractor drive train

2020-09-27
2020-24-0024
Increased efficiency and emission reduction have, in recent years, introduced several changes in the architecture of agricultural tractors transmissions. As one of the leading rolling bearing manufacturers for this industry, Schaeffler has explored energy saving potentials related to rolling bearings friction reduction. Starting point of the activity is the actual status of the design of tractor transmission manufactured by one of the key players in the sector.
Technical Paper

INNOVATIVE ELECTRIC OIL PUMPS FOR DIFFERENT AUTOMOTIVE APPLICATIONS

2020-09-27
2020-24-0022
The current request of electrical components is associated to the uncertainty of the market strategy and to the risk of technological recursion during development, due to the high level of innovation. For this reason, the products, which are under development, have to cover the worst-case use scenarios and be modular as much as possible, to be adapted on an evolving context. We developed an innovative electric oil pump, with BLDC motor and integrated electronic for automotive applications. Even if this concept is already consolidated, we upgraded it in order to be able to cover typical automotive temperature ranges and by targeting high power density and reduced packaging, perfect for the new powertrains layouts.
Technical Paper

An Analytical Procedure to Analyse Efficiency, Cooling and Thermal Management of a BEV Sport Car Transmission

2020-09-27
2020-24-0023
The implementation of increasingly stricter regulations on CO2 emissions by the European Community is pushing the automotive industry towards a radical change. In a rush to electrify their model ranges, global carmakers are investing heavily on developing new electrified powertrains. Within this context, this work focuses on the analysis of electric axles drives (eAxles) for a BEV (battery electric vehicle) sport car, with the aim to develop an analytical tool useful to perform predictive analysis in the concept design phase. Through a parametric definition of the procedure, the tool with its 2800 lines of code is able to “adapt” to any drivetrain layout analysed. The tool actually allows to enter more than 100 input values including lubrication conditions (oil viscosity and operating temperature), gears (number, macrogeometry, mesh), bearings (number, type, geometry, mounting layout, angle mesh), shafts, oil seals, external layout and external fluid conditions.
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