Abstract With drastically reduction of engine noise, the gear rattle noise generated by the impact between neutral gears inside transmission can be much easily perceived. It is well known that the torsional mode has a direct relationship with the transmission gear rattle noise. This paper establishes a torsional model of a front wheel drive automotive drivetrain, including clutch system, transmission box and equivalent load of a full vehicle, in AMESim software. The experimental engine speed fluctuations at different gears are used to excite the torsional model. The influences of several parameters, including flywheel inertia, clutch stiffness, clutch hysteresis and drive shaft stiffness, on the 2nd order (major engine firing order for a 4-cylinder-4-stroke engine) torsional resonant frequency and the 2nd order torsional resonant peak of the transmission input shaft are analyzed by changing them alternatively.
Abstract This paper describes the development of an analytical method to assess and optimize halfshaft joint angles to avoid excessive 3rd halfshaft order vibrations during wide-open-throttle (WOT) and light drive-away events. The objective was to develop a test-correlated analytical model to assess and optimize driveline working angles during the virtual design phase of a vehicle program when packaging tradeoffs are decided. A twelve degree-of-freedom (12DOF) system model was constructed that comprehends halfshaft dynamic angle change, axle torque, powertrain (P/T) mount rate progression and axial forces generated by tripot type constant velocity (CV) joints. Note: “tripot” and “tripod” are alternate nomenclatures for the same type of joint. Simple lumped parameter models have historically been used for P/T mount optimization; however, this paper describes a method for using a lumped parameter model to also optimize driveline working angles.
Nowadays, the vehicle design is highly ruled by the increasing customer demands and expectations. In addition to ride comfort and vehicle handling, the Noise, Vibration and Harshness (NVH) behavior of the powertrain is also a critical factor that has a big impact on the customer experience. To evaluate the powertrain NVH characteristics, the NVH error states should be studied. A typical NVH event could be decoupled into 3 parts: source, path, and receiver. Take-off shudder, which evaluates the NVH severity level during vehicle take-off, is one of the most important NVH error states. The main sources of Front Wheel Drive (FWD) take-off shudder are the plunging Constant Velocity Joints (CVJ) on the left and right half shafts. This is because a plunging CVJ generates a third order plunging force with half shaft Revolution Per Minute (RPM), which is along the slip of the plunging CVJ.
Abstract Automotive automatic transmissions have multiple axis configurations in which planetary gears transmit torque to a counter gear on another axis. Although general characteristics of a planetary gear (component level) have been studied, no specific investigations are available in literature explaining interactions between planetary and torque-transmitting gears (Full Unit or Sub-System). In this paper, a system FEA model (Using TM3D) of a Ravigneaux and a counter gear pair is introduced, exploring influences of system deflection in pinion load sharing to changes in gear root stress pattern. Additionally, by a series of strain gauge tests under a controlled test jig, reliability of the FEA model is verified. Finally, benefits of system-level FEA are explained by macro/micro-geometry optimization in the early design stage.
Abstract This paper has the objective to present the study made on a front wheel drive passenger car with “3 Points Pendular Mounts System” to minimize the “Power Hop effect” (powertrain forced oscillation) and reduce the loads on Powertrain Mounts System. In this study, we used the Taguchi Method (Design of Experiments) to optimize the number of tests performed to evaluate the influence of powertrain mounts system design characteristics, as well as axle shafts stiffness, and tire/wheels assemblies size. The data acquisition work was all done in a physical hardware (vehicle) on test track used instrumented parts and load cells. Accelerometers were used in previous tests to get qualitative understanding of the behavior of all interface components (mounts and wheels hubs) during the power hop event.
Tailpipe Emissions and Fuel Economy for 2WD Vehicles and AWD Vehicles Tested on a Double-Axle Chassis Dynamometer: A Comparative Study
Abstract Tailpipe emissions, fuel consumption, and wheel torque data were measured for three pairs of vehicles tested over four drive cycles at the Emissions Research and Measurement Section of Environment and Climate Change Canada in Ottawa, Ontario. Each pair of vehicles included identical vehicle models; one vehicle was equipped with an AWD drivetrain and one vehicle was equipped with a FWD drivetrain. The AWD vehicle was tested on a double-axle chassis dynamometer. The amount of AWD activity was heavily dependent on driving behavior and AWD system design. During periods of torque delivery, the percentage of AWD activity ranged between 32% and 57% for the FTP-75 drive cycle, between 3% and 8% for the HWFCT drive cycle, and between 21% and 29% for the US06 drive cycle. The fourth drive cycle was the FTP-75 driven at -7°C. AWD distributions did not show sensitivity to temperature for the first and second vehicle models.
Abstract Introducing all-new front wheel drive hybrid system installed in the 2016 Toyota Prius. This system was completely re-designed to maximize the potential of THS-II (Toyota Hybrid System-II). This system was designed to be able to minimize the mechanical and electrical losses from the previous generation system, improve environmental performance, and also tried to reduce size and weight. We’d like to take this opportunity to introduce the new technology of each component, and hybrid system performance.
Abstract In order to illustrate the constant development of the automatic transmission controls area, this paper describes how the garage shift calibration works in vehicles with transverse front wheel drive powertrains. A garage shift (GS) is the turbine speed transient commanded by the shift lever movement from Park to Drive or Reverse, from Neutral to Drive or Reverse, from Drive to Reverse, from Reverse to Drive, or from Drive or Reverse to Neutral . A usual metric to verify the garage shift comfort is the data acquisition of the fore-aft acceleration on the seat track, but also the shift time should be considered, as well as the clutch energy and the repeatability of the shift feeling for different temperatures and engine idle speed levels. This paper demonstrates the transmission calibration strategies to determine a sensitive and a non-sensitive garage shift and its interactions with the engine calibration.
Abstract There has been a growing need in recent years to further improve vehicle fuel efficiency and reduce CO2 emissions. JATCO began mass production of a transmission for rear-wheel-drive (RWD) hybrid vehicle with Nissan in 2010, which was followed by the development of a front-wheel-drive (FWD) hybrid system (JATCO CVT8 HYBRID) for use on a midsize SUV in the U.S. market. While various types of hybrid systems have been proposed, the FWD system adopts a one-motor two-clutch parallel hybrid topology which is also used on the RWD hybrid. This high-efficiency system incorporates a clutch for decoupling the transmission of power between the engine and the motor. The hybrid system was substantially downsized from that used on the RWD vehicle in order to mount it on the FWD vehicle. This paper describes various seal technologies developed for housing the dry multi-plate clutch inside the motor, which was a key packaging technology for achieving the FWD hybrid system.
Abstract General Motors has introduced a new front wheel drive seven speed dry dual clutch automatic transmission in 2014. The 250 Nm input torque rated gear box was designed and engineered for a global market in both front wheel drive and all-wheel drive configurations. The transmission has integrated start/stop capability enabled by the use of an electric motor driven pump and a pressurized accumulator. The architecture selected was chosen for optimization of packaging, fuel economy, mass, shift pleasability, and NVH. High mileage durability and world class drivability were the cornerstone deliverables during the engineering and design process Fuel efficiency is estimated to be 3% - 10% improvement over a conventional six speed automatic transmission. FWD variant wet mass of 78.1 kg was achieved through the rigorous engineering processes used to optimize the transmission system.
Creation of Halfshaft Joint Selection Tool in Terms of Strength and Life Calculations for FWD Vehicles
This study is inspired by the calculations and validations required for front wheel drive (FWD)-halfshaft joint selection. To increase design efficiency with decreased response time; a tool is required to validate calculations of strength based on maximum impact torque and endurance life based on corresponding vehicle usage. The tool has been developed to cover both strength and endurance life calculations. It also includes a constant velocity joint (CVJ) size library in order to compare different cases and to be able to see opportunities between different sizes. Validation and correlation has been completed using road load data from actual vehicles and standard load cycle (SLC) rig test results. This study introduces a more efficient methodology that will help the user select a joint that is sized best for strength and cost. After the completion of the study, one can be assured that the joint selected is the proper size-for all kinds of FWD vehicles.
Abstract Front end accessory drive (FEAD) system explained in this paper is a sub-system of an engine. In FEAD system, a poly-v belt is used to drive the alternator and water pump by transmitting power from crankshaft pulley. In a new vehicle development program, durability targets of FEAD system are based on required life of poly-v belt, its static tension readjustment interval and replacement frequency. To meet these durability targets following methodology is applied in design stage:- 1 Simulation of FEAD system to calculate the theoretical life of belt2 Part level testing of belt as per SAE J2432 These methods give sufficient information on belt durability. However in actual usage, certain failures are prone to happen and enormous difference is always observed between theoretical and actual life of belt. This paper describes the traditional stair-case approach followed to optimize the FEAD system based on the outcome of durability tests.
The new General Motors 2-mode hybrid transmission for front-wheel-drive vehicles has been incorporated into a 2009 Saturn Vue by the West Virginia University EcoCAR team. The 2-mode hybrid transmission can operate in either one of two electrically variable transmission modes or four fixed gear modes although only the electrically variable modes were explored in this paper. Other major power train components include a GM 1.3L SDE turbo diesel engine fueled with B20 biodiesel and an A123 Systems 12.9 kWh lithium-ion battery system. Two additional vehicle controllers were integrated for tailpipe emission control, CAN message integration, and power train hybridization control. Control laws for producing maximum fuel efficiency were implemented and include such features as engine auto-stop, regenerative braking and optimized engine operation. The engine operating range is confined to a high efficiency area that improves the overall combined engine and electric motor efficiency.
The open (standard) differential provides an important function in vehicle dynamics and handling by splitting the applied driveline torque and allowing each wheel or axle to spin at different speeds. This function is necessary to eliminate axle bind-up while negotiating turns. However, it inherently impedes optimal traction and mobility performance by allowing the available torque to be limited by the wheel or axle having the least amount of traction. Loss of traction could result in loss of driveline torque control and a resulting loss of vehicle control. This loss of control could be catastrophic in the case of higher speed maneuvers. The proposed electronically controlled hydraulic limited slip differential solution corrects this problem, seamless to the driver, while maintaining the fundamental open differential function. Furthermore, this system maintains efficient forward motion compared to other solutions that slow the vehicle down while expending valuable energy.
A Design for Six Sigma Approach to Optimize a Front-Wheel-Drive Transmission for Improved Efficiency and Robustness
Environmental concerns and government regulations are factors that have led to an increased focus on fuel economy in the automotive industry. This paper identifies a method used to improve the efficiency of a front-wheel-drive (FWD) automatic transmission. In order to create improvements in large complex systems, it is key to have a large scope, to include as much of the system as possible. The approach taken in this work was to use Design for Six Sigma (DFSS) methodology. This was done to optimize as many of the front-wheel-drive transmission components as possible to increase robustness and efficiency. A focus of robustness, or consistency in torque transformation, is as important as the value of efficiency itself, because of the huge range of usage conditions. Therefore, it was necessary to find a solution of the best transmission component settings that would not depend on specific usage conditions such as temperatures, system pressures, or gear ratio.
Kinematic Study of the GM Front-Wheel Drive Two-Mode Transmission and the Toyota Hybrid System THS-II Transmission
General Motors has recently developed a front-wheel drive version of its two planetary two-mode transmission (2-MT) for a hybrid-electric vehicle powertrain . This newer transmission includes two planetary gears with two transfer clutches and two braking clutches. With activation of designated pairs of these four clutches, four fixed-gear ratios between the transmission's input shaft and output shaft are obtained. In addition, activation of specific individual clutches gives two modes of operation whereby the IC engine speed is decoupled from the vehicle velocity thus providing an electrical continuously variable transmission (ECVT). This present paper extends the power-split analysis in  by deriving a safe-operating region (SOR) in the plane of IC engine speed vs. vehicle velocity for the four fixed-gear and two ECVT modes. This SOR is bounded by the speed limitations of the 2-MT components. Similar results are presented for the Toyota Hybrid System II (THS-II) transmission.
The behavior knowledge of the vehicle on uphill maneuvers - startability on grade, is an important metric for sizing powertrain components, such as the engine torque, clutch, first and reverse gear ratios, final drive and tire sizes. During the uphill maneuver, all components of the powertrain are subject to efforts that determine the vehicle performance in this condition. The analysis of this maneuver, for a front-wheel-drive vehicle, is evaluated in this article, through a correlation of a computer program developed in Matlab-Simulink, with experimental measurements performed on the vehicle at the track, becoming an important tool for analysis of passenger vehicles subject to these conditions present on Brazilian streets.
General Motors introduced a family of small front wheel drive six speed automatic transmissions for the 2008 model year. The family currently has two variants: 6T40 and 6T45, which cover a range of vehicles from small & compact cars to small SUVs and handle engines torque capacities up to 240 Nm Gas(280 Nm Diesel) & 315 Nm Gas (380 Nm Diesel) respectively. The 6T40/45 transmissions replace GM traditional four speed automatic wrap around transmissions 4T40/45. The wrap around transmissions have Torque Converter, Pump & Controls on the engine axis and the rest of the transmission content on the output axis. The 6T40/45 have an on-axis architecture with majority of the transmission content on the engine axis and final drive & differential on the output axis. The 4T40/45 have input chain transfer whereas the 6T40/45 have an output chain transfer.
Employment of Magneto-Rheological Semi-Active Differential in a Front Wheel Drive Vehicle: Device Modelling and Software Simulations
This paper presents a semi-active differential, denoted by MRF LSD (Magneto-Rheological Fluid Limited Slip Differential) that allows to bias torque between the driving wheels. It is based on the Magneto-Rheological (MR) fluid employment, by which it is possible to change, in controlled manner, the internal friction torque and, consequently, the torque bias ratio. The device is an adaptive one and allows to obtain an asymmetric torque distribution in order to improve vehicle handling. The device modelling and the control algorithm, realized for this activity, are described. The illustrated results highlight the advantages that are attainable regarding directional behaviour, stability and traction for a front wheel drive (FWD) vehicle. A comparison with a traditional passive limited slip differential has been conducted.
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.
General Motors has developed a two-mode hybrid transmission for transverse front wheel drive vehicles. Mechanical components for this system were packaged into the basic space constraints of a conventional automatic transmission by using a space-saving arrangement of two planetary gear sets and four clutches extending through two electric motors with large internal diameters. This full-function hybrid system delivers electric propulsion for low-speed urban driving, regenerative braking, electric acceleration assist, two continuously variable engine-to-wheels speed ranges, and four fixed gear ratios. This electrically-variable transmission is based on a scalable architecture for applications ranging from small vehicles and engines to full-size vehicles with large engines and towing capacity.
The production of vehicles with low noise and vibration level at low costs has been one of the main targets of the automobilist industry. The noise level heard by the passengers inside the vehicle influences directly on the perception they have about the car. On the other hand, low prices are extremely necessary to keep the projects competitive on the sales market. This job analyses the impact caused over the noise heard inside the vehicle when a change was applied on the design of the halfshaft: the substitution of a tubular shaft by a barshaft. The main goal of this design change is the cost reduction.
The mini block rear spring is used in several FWD vehicles around the world and the main reason is the great characteristics for suspension packaging, wheel travel and Ride & Handling compromise for driver load up to full load condition. The rear suspension rate for driver or driver plus passenger load condition is tuned usually without major penalties, being necessary to perform the correct balance between front and rear axle vibration / grip. While the vehicle is loaded at the rear seat and trunk, the rear suspension rate changes, which is great for lower vehicle pitch angle, resulting also in smaller jounce suspension travel. The critical point is the how to achieve the optimum suspension rate as the vehicle goes heavier for a good Ride and Handling compromise. It's important to remember that this higher suspension rate for jounce motions will influence the vehicle for driver load condition when the vehicle rolls with lateral acceleration or passes through a speed bump.
Study on Transient Vibration Response Characteristics of Front Transverse Power Train at the Key On/Off
The purpose of this study is to reduce driver's seat vibration during an engine start or stop. In general, this is an important research item for NVH performance in the vehicle development stage. However, it has been difficult to improve this vibration performance since the testing group evaluates this item using the trial and error method at the very last development period. Thus, the present study is meant to overcome the current issues by: 1 Performing the overall study investigating the key on/off characteristics through excitation force, transfer system and response system to define the mechanism and to validate the findings experimentally and with CAE analysis. 2 Developing the CAE analysis technique to predict the key on/off performance quantitatively. This method can be applied earlier in the vehicle development stage, allowing more time to improve and optimize the design.
The need for improved axle NVH integration has increased significantly in recent years with industry trends toward full-time and automatic four wheel drive (4wd) systems. Along with seamless 4wd operation, quiet performance has become a universal expectation. Axle gear-mesh noise can be transmitted to the vehicle passenger compartment through airborne paths (not discussed in this paper) and structure-borne paths (the focus of this paper.) A variety of mounting configurations are used in an attempt to provide improved axle isolation and reduce structure-borne transmission of gear-mesh noise. The configuration discussed in this paper is a 4-point vertical mount design for an Independent Front Drive Axle (IFDA). A significant benefit of this configuration is improved isolation in the range of drive torques where axle-related NVH issues typically exist.
Development of Water Level Predicting Method around the Air Intake Duct by using Multivariate Analysis
This paper describes a water-level prediction method for the air intake duct using multivariate analysis. When a vehicle runs on a submerged proving ground, in some cases the water level around the air intake duct rises. Although the rise in water level can be measured experimentally in actual vehicles, the design factors that determine the water level are not yet fully understood. The first step in understanding the factors for determining the water level on front-engine and front-drive (FF) -type vehicles is to establish a water level prediction technique. This is accomplished by the development of an original Computational Fluid Dynamics (CFD) analysis method capable of accurately simulating a free surface. The next step is to conduct multivariate analysis based on the results of parametric studies using this CFD analysis method that leads to the factors determining the water level at the air intake duct.
The Hydra-Matic 6T70 is General Motors first model of a new, two-variant front wheel drive (FWD) six speed automatic transmission family. The second variant is a higher capacity model, the 6T75. The transmission was co-developed with Ford Motor Company. The 6F50 is the Ford variant that aligns with the GM 6T70 transmission. Approximately eighty five percent of the hardware is shared or common between the GM and Ford transmission variants. Ford will also have a higher capacity variant the 6F55 to align with the GM 6T75. The first GM application is the Saturn Aura for the 2007 Model Year. The Ford Edge and Lincoln MKX in MY 2007 will be the first applications for the 6F50. While the Hydra-Matic and Ford FWD six-speed family was designed with two variants in mind, the designed in modularity requires only changes to the second and third axis and case housings depending on specific torque requirements. This modular design enables a tremendous amount of part sharing.
JATCO has launched its new belt-type continuously variable transmission (CVT) for 2 - 2.5L class cars in November 2004. JATCO has been planning to deploy this continuously variable transmission, as the new CVT2 model replacing the existing Hyper-CVT, for 2 - 2.5L front-wheel-drive cars around the world, starting in Japan. This paper describes the engineering contents of the oil pump, which has been developed to improve the principal concepts of CVT2: fuel economy improvement, shift performance improvement, and size and weight reduction.
Toyota Motor Corporation has developed a new super-flat torque converter for the Flex Start System. It is installed in a new six-speed automatic transaxle (U660E) for front engine, front wheel drive vehicles. The Flex Start System is the first technology in the world that can start smoothly and reduce torque converter slipping loss by using a lock-up clutch at start. The newly developed super-flat torus achieves a high torque capacity and a maximum efficiency of 90%. Fuel economy is increased further by adding an efficient damper for low-speed lock-up in the free space provided by utilizing the super-flat torus. Toyota also developed a simple and super-flat structure at the one-way clutch (O.W.C.) area. This paper describes the structure, features, and performance of this new torque converter and the Flex Start System.
Toyota Motor Corporation has developed a new six-speed automatic transaxle (U660E) for Front Wheel Drive (FWD) vehicles. Component parts of U660E are completely redesigned. By combining an innovative gear train which Toyota originally invented and newer technologies, U660E has achieved outstanding fuel economy, smooth and quick shift performance and quietness in a lightweight package among Automatic Transaxles (AT) with similar torque capacity.