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Technical Paper

General Motors 4T65-E Electronic Four-Speed Automatic Transaxle

The 4T65-E transmission produced by General Motors is the third evolution of GM's original 4-speed F.W.D. automatic. This most recent redesign introduced for the 1997 model year meets new corporate goals for fuel economy and reduced noise, along with the ability to adjust shift character to meet the brand image of the various nameplates. Improving fuel economy and cooling at increased engine power levels was enabled by designing a larger diameter torque converter with the aid of 3-D modeling. The new converter has reduced internal leakage and incorporates a controlled slip clutch. Improvements in NVH have been achieved through a revised oil pump design and the use of the new phased drive chain, made affordable by the joint development of powdered metal technology required for the unique sprocket design.
Technical Paper

Modeling, Design and Validation of an Exhaust Muffler for a Commercial Telehandler

This paper describes the design, development and validation of a muffler for reducing exhaust noise from a commercial tele-handler. It also describes the procedure for modeling and optimizing the exhaust muffler along with experimental measurement for correlating the sound transmission loss (STL). The design and tuning of the tele-handler muffler was based on several factors including overall performance, cost, weight, available space, and ease of manufacturing. The analysis for predicting the STL was conducted using the commercial software LMS Virtual Lab (LMS-VL), while the experimental validation was carried out in the laboratory using the two load setup. First, in order to gain confidence in the applicability of LMS-VL, the STL of some simple expansion mufflers with and without extended inlet/outlet and perforations was considered. The STL of these mufflers were predicted using the traditional plane wave transfer matrix approach.
Technical Paper

Calibrating and Protecting Microphones to Allow Acoustic Measurements in Hazardous Environments

Performing acoustic measurements on or near engines, transmissions, as well as in other circumstances where the environment is hazardous and harsh for microphones requires special precautions. Fluids inevitably leak, and the possibility of transducer damage can be very high without proper protection. Properly protecting microphones during testing allows for consistent data quality in these hazardous and difficult environments. While this paper will present the use of a 5 mil Nitrile cover which protects against many fluids within the scope of automotive testing, including water, hydrocarbons, and alcohols, as well as having good heat resistance and high strength, the concepts developed are applicable to other types of microphone protective mechanisms. Acoustic sensitivity was measured and used to calculate the change of the microphone's response after the treatment is applied, as well as after being exposed to various contaminants.
Technical Paper

Sound Power Measurement in a Semi-Reverberant, Volume Deficient Chamber

Sound power can be determined using a variety of methods, but precision methods require the volume of the noise source to be less than 1% of the chamber volume leading to relatively large test chambers. Automotive torque converter performance and noise testing is completed in an enclosed metallic test fixture which inhibits the use of precision methods due to volume and space limitations. This paper describes a new method developed to accurately determine sound power of an automotive torque converter in a relatively small enclosure through characterization of the test environment. The test environment was characterized using two reference noise sources designed to represent torque converter noise output and physical geometry. Sound pressure levels of the sources were measured at multiple microphone locations and at three source amplitude levels to characterize the environment.
Technical Paper

Prospects for Future Non-Manual Transmissions Developments for Vehicle Applications in Brazil

The purpose of this paper is to present the origins and the technology of the different types of non-manual transmissions systems currently available and the wide potential to incorporate such technologies to the vehicles made in Brazil. The Brazilian market is experiencing a huge increase in automated and automatic transmissions vehicles share, and the OEMs are adopting different strategies to offer competitive products with affordable prices to enter in this segment. Many different alternatives are available, and there is no obvious winner. This paper will describe the concepts, the architecture and the operations of such systems and point out the pros and cons of each one.
Technical Paper

Torsional Vibration Analysis of Six Speed MT Transmission and Driveline from Road to Lab

When a manual transmission (MT) powertrain is subjected to high speeds and high torques, the vehicle driveshaft, and other components experience an increase in stored potential energy. When the engine and driveshaft are decoupled during an up or down shift, the potential energy is released causing clunk during the shift event. The customer desires a smooth shift thus reduction of clunk will improve experience and satisfaction. In this study, a six-speed MT, rear-wheel-drive (RWD) passenger vehicle was used to experimentally capture acoustic and vibration data during the clunk event. To replicate the in-situ results, additional data was collected and analyzed for powertrain component roll and pitch. A lumped parameter model of key powertrain components was created to replicate the clunk event and correlate with test data. The lumped parameter model was used to modify clutch tip-out parameters, which resulted in reduced prop shaft oscillations.
Technical Paper

The Algebraic Design of Transmissions & EVTs

This paper describes the creation of novel transmission mechanisms using algebraic design techniques. The objective is to create novel arrangements comprised of one or more planetary gear sets, a pair of motor-generators and several torque-transmitting mechanisms (clutches and brakes). The algebraic design procedure represents the planetary gear sets, fixed interconnections, clutches/brakes, and motor-generator sets as algebraic constraints. Appropriate subsets of constraint equations are solved to identify viable transmission mechanism designs. We have used the above design approach to create several novel candidate multi-speed transmissions as well as EVT concepts. The main benefit of the algebraic design procedure is that it allows the designer to systematically generate and assess novel designs.
Technical Paper

Influence of the Piston Inter-ring Pressure on the Ring Pack Behaviour in a Medium Speed Diesel Engine

The present work aims to determine the gas pressure acting in the ring pack area in a medium-speed four stroke diesel engine. The experimental part of the study was carried out as firing engine tests, with an instrumented piston, with telemetric data transmission, and an instrumented cylinder liner in a 6-cylinder test engine. The results, in terms of inter-ring gas pressure are compared with the results of computer simulations. Moreover, the computer simulations were carried out to predict and compare the effects of the piston running clearance and the ring face wear on the inter-ring pressures. The study comprises aspects on inter-ring pressures under a set of loads. The measured inter-ring gas pressures indicate steady ring operation. The simulation results show good agreement with measurement results.
Technical Paper

Characterizing the Effect of Automotive Torque Converter Design Parameters on the Onset of Cavitation at Stall

This paper details a study of the effects of multiple torque converter design and operating point parameters on the resistance of the converter to cavitation during vehicle launch. The onset of cavitation is determined by an identifiable change in the noise radiating from the converter during operation, when the collapse of cavitation bubbles becomes detectable by nearfield acoustical measurement instrumentation. An automated torque converter dynamometer test cell was developed to perform these studies, and special converter test fixturing is utilized to isolate the test unit from outside disturbances. A standard speed sweep test schedule is utilized, and an analytical technique for identifying the onset of cavitation from acoustical measurement is derived. Effects of torque converter diameter, torus dimensions, and pump and stator blade designs are determined.
Technical Paper

Development of the MTU Automatic Shifting Manual Six Speed Transmission

The purpose of this report is to describe the process for the development of the automatically shifting manual transmission control system hardware and software to be used in the MTU Challenge X Equinox, a through-the-road parallel hybrid electric vehicle. The automatically shifting manual transmission was chosen for development, as it combines the ease of use of an automatic transmission with the fuel efficiency of a manual, while eliminating the parasitic losses in the torque converter and the transmission hydraulic pump. This report illustrates the process used to develop the software-in-the loop modeling that was developed for the initial proof of concept. In addition, it describes the development of the control strategy and hardware build for the prototype transmission. To begin the design process research was preformed on existing automatically shifting manuals and manual transmissions in general. From there vehicle subsystems were assembled using Simulink block diagrams.
Technical Paper

Adaptation of Four-Stroke Motorcycle Engine to Continuously Variable Transmission for Snowmobile Application

The successful implementation of a clean, quiet, high-performance four-stroke motorcycle engine into an existing snowmobile chassis has been achieved. The snowmobile is easy to start, easy to drive, and environmentally friendly. The following paper describes the conversion process in detail with actual dynamometer and field test data. The vehicle meets the proposed 2010 EPA snowmobile emissions regulations and is quieter than a stock snowmobile. The snowmobile not only addresses environmental concerns, it is economical as well, with an approximate cost of $5874.
Technical Paper

Cavitation Detection in Automotive Torque Converters Using Nearfield Acoustical Measurements

As automotive torque converters decrease in both diameter and axial length, the effects of cavitation in the torque converter becomes increasingly important on noise, efficiency, and performance goals. Cavitation is the formation and collapse of vapor bubbles in a working fluid when local static pressure falls below the vapor pressure of the working fluid. A technique to detect cavitation in automotive torque converters using nearfield acoustical measurements is presented. The technique concentrates on high frequency noise that is associated with the collapse of vapor bubbles. The nearfield acoustical technique is compared to two other techniques using static pressure measurements inside the torque converter; one on the torque converter stator blades and the other on the torque converter pump blades. A microwave telemetry transmitter was used to obtain data from inside the torque converter in both previous investigations.
Technical Paper

Cavitation Prediction in Automotive Torque Converters

As automotive torque converters decrease in both diameter and axial length, the effects of cavitation in the torque converter becomes increasingly important on noise, efficiency, and performance goals. Therefore, a cavitation prediction technique is developed in this investigation. In a previous investigation it was shown that cavitation is effected by inlet temperature, charge pressure, and K-factor. The prediction technique is devolved to encompass these variables. A dimensional analysis using the power product method is performed with all relevant variables. The nearfield acoustical cavitation detection technique, discussed in the previous investigation, is used to obtain experimental results from a torque converter test lab. The test matrix for the experimental results was constructed to include effects from inlet temperature, charge pressure, and K-factor. The data obtained experimentally is used to curve fit the results found through the power product method.
Technical Paper

General Motors “VTi” Electronic Continuously Variable Transaxle

The VT25-E transmission introduced by General Motors for the 2002 model year is the first variant of GM VTi variable transmission family. The VTi is an electronically controlled Continuously Variable Transaxle (CVT). It is the first North American, high volume production CVT. This CVT enables fuel economy improvements over traditional step gear transmissions, with an improved packaging, wider ratio spread, neutral idle and complete absence of shifts for driver comfort. The VT25-E utilizes a controlled slip converter clutch in conjunction with electronically scheduled ratios and an integrated electronic throttle control to operate the powertrain at its most efficient level. A dual-lobed fixed displacement vane pump and jet nozzle filter arrangement provide the source pressure to a multi-tiered hydraulic control system. The multi-tiered hydraulic control system helps to achieve the precise control necessary to meet the durability requirements of this demanding market.
Technical Paper

Modeling and Drivability Assessment of a Single-Motor Strong Hybrid at Engine Start

Using a clutch to disconnect and shut-off the engine when engine power is not required, the single-motor strong hybrid has the potential for significant fuel economy improvement with reduced costs and less system complexity. However, it is a challenge for the single-motor strong hybrid to maintain acceptable drivability at engine start since it requires diverting motor torque through a slipping clutch to start the engine. In this study, dynamic simulations of the hybrid transmission driveline with hydraulic and motor controls have been employed to assess the feasibility of the single-motor strong hybrid, to address drivability issues specific to this hybrid architecture at engine start, and to develop control methods to manage driveline disturbances to an acceptable level.
Journal Article

Truck Utility & Functionality in the GM 2-Mode Hybrid

The present production General Motors 2-Mode Hybrid system for full-size SUVs and pickup trucks integrates truck utility functions with a full hybrid system. The 2-mode hybrid system incorporates two electro-mechanical power-split operating modes with four fixed-gear ratios. The combination provides fuel savings from electric assist, regenerative braking and low-speed electric vehicle operation. The combination of two power-split modes reduces the amount of mechanical power that is converted to electric power for continuously variable transmission operation, meeting the utility required for SUVs and trucks. This paper describes how fuel economy functionality was blended with full-size truck utility functions. Truck functions described include: Manual Range Select, Cruise Control, 4WD-Low and continuous high load operation.
Journal Article

Characterizing the Onset of Manual Transmission Gear Rattle Part I: Experimental Results

The objective of this investigation is to characterize the ability of loose gears to resist rattle in a manual transmission driven by an internal combustion engine. A hemi-anechoic transmission dynamometer test cell with the capability to produce torsional oscillations is utilized to initiate gear rattle in a front wheel drive (FWD) manual transmission, for a matrix of operating loads and selected gear states. A signal processing technique is derived herein to identify onset of gear rattle resulting from a standardized set of measurements. Gear rattle was identified by a distinct change in noise and vibration measures, and correlated to gear oscillations by a computed quantity referred to as percent deviation in normalized gear speed. An angular acceleration rattle threshold is defined based upon loose gear inertia and drag torque. The effects of mean speed, mean and dynamic torque, and gear state on the occurrence of loose gear rattle are reported.
Journal Article

Characterizing the Onset of Manual Transmission Gear Rattle Part II: Analytical Results

Lumped parameter analysis is a simple and commonly used technique for performing torsional analysis or design parameter sensitivity studies on automotive powertrains and drivelines. The purpose of this paper is to demonstrate the application of lumped parameter analysis to manual transmission gear rattle. A representative model is developed for a FWD manual transmission, as operated in a dynamometer test cell. Once validated by experimental data, the model is used to investigate the influence on gear rattle of parameters not readily modified or controlled during hardware evaluations. A sinusoidal torque is used to excite the system, and a signal processing technique similar to that derived in Part I of this two part paper is used to identify the inception of gear rattle. Functional relations for torque losses associated with shafts, gears, seals, lubricating oil flow and bearing clearances as a function of basic design parameters are included within the model.
Technical Paper

Control-Oriented Modeling of a Vehicle Drivetrain for Shuffle and Clunk Mitigation

Flexibility and backlash of vehicle drivelines typically cause unwanted oscillations and noise, known as shuffle and clunk, during tip-in and tip-out events. Computationally efficient and accurate driveline models are necessary for the design and evaluation of torque shaping strategies to mitigate this shuffle and clunk. To accomplish these goals, this paper develops a full-order physics-based model and uses this model to develop a reduced-order model (ROM), which captures the main dynamics that influence the shuffle and clunk phenomena. The full-order model (FOM) comprises several components, including the engine as a torque generator, backlash elements as discontinuities, and propeller and axle shafts as compliant elements. This model is experimentally validated using the data collected from a Ford vehicle. The validation results indicate less than 1% error between the model and measured shuffle oscillation frequencies.
Technical Paper

Control Strategy and Energy Recovery Potential for P2 Parallel Hybrid Step Gear Automatic Transmissions

The purpose of this investigation is to present a control strategy and energy recovery potential for P2 parallel hybrid step gear automatic transmissions. The automatic transmission types considered for the investigation are rear wheel drive 8 speed dual clutch transmission and 8 speed planetary automatic equipped each equipped with an electric motor between the engine and transmission. The governing equations of clutch-to-clutch upshift controls are presented and are identical for each transmission type. Various strategies are explored for executing the upshift under a range of input torques, shift times and engine torque management approaches. The differences in energy recovery potential based upon control strategy is explored piecewise as well as through a DFSS study. On a comprehensive drive cycle consisting of FTP 75, US06 and HWFET test cycles, it is shown that upshift regen torque management can be equivalent to approximately 0.8% of the total fuel energy used.