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Technical Paper

Measuring and Comparing Frequency Response Functions of Torque Converter Turbines Submerged in Transmission Fluid

2011-05-17
2011-01-1662
When testing dynamic structures, it is important to note that the dynamic system in question may be submerged into a fluid during operation and to properly test the structure under the same condition in order to understand the true dynamic parameters of the system. In this way, the mass and stiffness coupling to the particular fluid, for the case of this study, automatic transmission fluid, may be taken into account. This is especially important in light structures where the coupling between the fluid mass and the structural mass may be great. A structure was tested with a laser vibrometer using several impact methods in open air to determine which impact method would be most suitable for submerged testing. The structure was then submerged in transmission fluid with an accelerometer attached and subsequently tested and compared to the previous results.
Journal Article

Active Control of Gear Mesh Dynamics

2011-05-17
2011-01-1635
Gears are essential parts of many precision power and torque transmitting machines. However, the radiated intensive tonal noise due to the gear meshing is highly undesirable and annoying. In very severe cases, the gear vibrations can reduce the life and performance of the power transmitting components. Typical gearbox vibration and sound spectra contain several dominant narrowband tonal signals that are mixed in with a lower level broadband response signals. Hence, the control of mesh response of gearbox housing belongs to the problem of the rejection or cancellation of periodical disturbance. The frequencies of these tonal signals are related to the number of teeth and rotation speed, and highly predictable. Thus, a feedforward control system was normally adopted. In most of existed applications, an accurate reference based on the frequency information of tachometer pulse train signal is required for this kind of control system.
Technical Paper

Drive Rattle Elastodynamic Response of Manual Automotive Transmissions

2011-05-17
2011-01-1586
Modern automotive industry is driven by improved fuel efficiency, whilst simultaneously increasing output power and reducing size/weight of vehicle components. This trend has the drawback of inducing various Noise, Vibration and Harshness (NVH) concerns in the drivetrain, since fairly low energy excitation often suffices to excite natural modes of thin walled structures, such as the transmission bell housing. Transmission rattle is one of the many undesired NVH issues, originating from irregularities in engine torque output. The crankshaft speed fluctuations are transferred through the transmission input shaft. Transmission compactness also allows repetitive interaction of conjugate loose gear pairs. The engine fluctuations disturb the otherwise unintended, but orderly meshing of these loose gears. This often leads to radiation of a characteristic air-borne noise from the impact sites.
Journal Article

Nonlinear Characteristics Study and Parameter Optimization of DMF-RS

2011-05-17
2011-01-1550
Dual Mass Flywheel (DMF) has better damping capacity than the conventional Clutch Torsional Damper (CTD), and is more suitable for diesel engine, Dual Clutch Transmission (DCT) and hybrid vehicles. Dual Mass Flywheel-Radial Spring (DMF-RS) is a DMF that has a specific structure. In the light of working principal and static analysis, the hard nonlinear torsional stiffness of DMF-RS is derived in this paper, which is very important to a driveline damper. On this basis, a simulation model is developed to analyze the dynamic response of DMF and CTD excited by idle engine; the comparison of the two dampers reveals that the DMF has better damping capacity, high-frequency filter ability and can reduce crankshaft load.
Technical Paper

6 Speed Automatic Transmission Vibration Magnitude Prediction and Whine Noise Improvement through Transmission System Modeling

2011-05-17
2011-01-1553
Abstract As automotive technology has been developed, gear whine has become a prominent contributor for cabin noise as the masking has been decreased. Whine is not the loudest source, but it is of high tonal noise which is often highly unpleasant. The gear noise originates at gear mesh. Transmission Error acts as an excitation source and these vibrations pass through gears, shafts and bearings to the housing which vibrates to produce noise on surrounding air. As microgeometry optimization target to reduce the fundamental excitation source of the noise, it has been favored method to tackle gear whine noise, especially for manual transmission. However, practicality of microgeometry optimization for the planetary gear system has been still in question, because of complex system structure and interaction among multi mesh gear sets make it hard to predict and even harder to improve. In this paper, successful case of whine noise improvement by microgeometry is presented.
Journal Article

Experimental Study of the Factors Affecting Transfer Case NVH Performance in 4-Lo Operation Mode

2011-05-17
2011-01-1558
In this paper, the results of the experimental study are presented to describe the impact of several gear design and manufacturing related factors on NVH performance of a transfer case operating in 4-Lo mode. The investigated gear design factors include lead crowning and profile crowning of the planet gears. The influence of manufacturing and assembly is investigated by varying carrier pinhole tangential position error and carrier pinhole tangential tilt error. The experimental DOE study is performed on chassis dynamometer by using actual vehicle. The strategically placed accelerometers and microphones are used for data acquisition. The results show that, among the gear design related factors, lead modification has larger influence on the NVH performance than profile modification. The study also shows how manufacturing errors influence NVH performance of the transfer case by causing lead misalignment of gears and unequal planet load sharing.
Journal Article

Full-Toroidal Traction Drive Variator Material and Fluid Durability

2011-04-12
2011-01-1424
Full-toroidal traction drives (IVT, TCVT & TVAD) have demonstrated a significant fuel economy, emissions and cost benefits across a diverse range of applications. However, increasing emphasis is being placed on power density and endurance limits, hence additional demands are being placed on the ability of the variator elements and traction fluid to withstand the heavily loaded rolling contact fatigue conditions within the variator. This paper describes the experimental work done to demonstrate the high temperature durability of traction fluid and variator disc and roller material. In addition, the latest fatigue endurance limit testing results are presented which provide further evidence of traction fluid ‘fill for life’
Technical Paper

ZF EcoLife - The latest Generation of Powershift Automatics for Transit Buses

2011-04-12
2011-01-1423
The megatrends "reduction of emissions" and "fuel consumption reduction" play a predominant role in the development of powertrains. For transit buses this implies both the reduction of emissions and pollutions of the internal combustion engine, and, on the other hand, a further reduction of noise and brake dust. Also very important is the reduction of both fuel consumption and CO₂ emissions. For all these targets the actual developments on the engine side have led to great improvements in the last decades, but what can be mentioned for the other components of the powertrain, especially looking for transmissions? First of all the relevant trends for transit buses have to be considered: A large increase of the torque of the combustion engines during the last years has a big impact on the development of transmissions for buses.
Technical Paper

Gen2 GF6 Transmission Hardware and Controls Updates

2011-04-12
2011-01-1428
In an effort to increase fuel economy and improve shift quality - the GF6 family of General Motors transmissions has been analyzed for potential enhancements. The focus of this analysis was to improve fuel economy, while increasing downshift responsiveness, and manual mode sport delays. This paper describes a variety of the hardware philosophy changes, and control methods which have contributed to the next generation of GM clutch-to-clutch 6-speed transmissions. These changes to hardware and controls have led to a composite fuel economy improvement of 4.5% with no changes to shift or torque-converter scheduling. In addition, the downshift responsiveness has been significantly improved to reduce delay times by approximately 50% while virtually eliminating the dependency on engine torque reductions - ultimately allowing for stacked downshifts to progress with minimal, if any, time between shifts. Additionally, “tap shift” delays have been significantly decreased to levels near 150 ms.
Technical Paper

Study of Effect of CVT Pulleys on Strength and Transmission Efficiency of Metal Pushing V-belts

2011-04-12
2011-01-1426
In designing CVT pulleys, the effect of the fit clearance of the movable pulleys and their stiffness on the transmission efficiency and strength of the metal pushing V-belt is not necessarily clear. The research discussed in this paper introduced a pulley model that defined the pulleys as elastic bodies to a previously developed technology for the prediction of the transmission efficiency of the belts. As a result, it was found that when the fit clearance is reduced, the transmission efficiency of the belt is increased, and the amplitude of stress on the innermost rings and the element neck section is reduced. In addition, it was found that if pulley stiffness was reduced transmission efficiency was also reduced, and the amplitude of stress on the element neck section increased. This indicated that the fit clearance and the pulley stiffness changed the degree of deflection of the pulleys in the axial direction.
Journal Article

Development of iQ with CVT for USA

2011-04-12
2011-01-1425
TOYOTA has developed the iQ with a 1.3L engine for the Scion brand in USA. Due to the importance of fun-to-drive factor for the Scion brand image, a responsive driving performance is required even with compact packaging and a small engine. In addition, because of the recent attention to global-warming and energy issues on a global scale, development of vehicles with high fuel economy is one of the most important issues for a car manufacturer. Therefore, it is necessary for a vehicle to have both high driving performance and fuel economy. TOYOTA has adopted the CVT-i as the transmission for this purpose. The following were achieved by adopting the CVT-i as the transmission for the iQ(1.3L). 1 Responsive driving performance with shift changes without a time lag.2 Compact transmission for efficient vehicle packaging3 Class-leading fuel economy performance. Moreover, it was developed with adjustments for the US market by improving the shift schedule for a linear acceleration feel.
Journal Article

The Fuel Efficiency Improvement through a Six Speed Manual Transmission Application in Passengers Vehicles with Low Displacement Engines

2011-04-12
2011-01-1430
The objective of this paper is to share the benefits regarding a study of fuel economy improvements involving Powertrain technologies. In this case our research was concentrated in vehicles transmissions initiatives like a Six Speed Manual Transmission application in Passengers Vehicles with low displacement engines. During the last 10 years the fuel economy challenges has presented a significant growth mainly due to two simple factors. First of all the fuel price which is the main driver to keep this technological continuous improvement. This fact has a direct influence in customers satisfaction, so all car makers concentrate huge efforts to provide intelligent solutions in order to increase competitiveness, as for example, the flex fuel engines (Figure 1). In parallel, the “green” appeal raises everyday stronger. Therefore the air pollution caused by vehicles gas emissions reinforces this commitment.
Technical Paper

A New Archetype of Automatic Transmission

2011-04-12
2011-01-1429
With the rapid development of the world's automobile industry, china's car sales have increased with each passing day. The automobile industry has become one of china's leading industries, and the market share of the automatic transmission in the Chinese car market is growing rapidly. Based on the actual status of the automatic transmission industry in china, we analyze the present condition and development tendency of the automatic transmission market in china in this thesis. We analyze and discuss some features like structure, design, technology of the AT / AMT / CVT / DCT and their adaptability in Chinese automatic transmission market. On that basis we bring forward a conceptual design of a 8-speed automatic transmission which is for a front-wheel drive vehicles, then we analyze the feature of 8AT's design, introduces the design and engineering development of 8AT.Finally, we discuss the possibility SOP of 8AT in China.
Technical Paper

Study on Wide Ratio Range Toroidal IVT

2011-08-30
2011-01-2032
The author describes a wide ratio range, half-toroidal, continuously variable transmission (CVT) and discusses how this CVT can contribute to improved fuel economy for passenger vehicles. Technologies that have been applied to improve the CVT are first discussed where the author describes how a higher traction coefficient can expand the ratio range of the toroidal variator. Then, improvements to the infinitely variable transmission (IVT) are discussed. Details on how the IVT has two driving modes and an infinite ratio range are discussed; with further details on factors that can improve fuel economy by expanding the over drive ratio. In order to expand the overdrive ratio of the IVT, the author mounted a newly developed, wide ratio range variator and adopted a direct-drive mode for the high-speed driving mode of the IVT.
Technical Paper

Development of Compact Continuously Variable Transmission Engine for Motorcycles

2011-08-30
2011-01-2030
The continuously variable transmission (CVT) with a rubber belt used in scooters is also regarded as a potential automatic transmission mechanism for conventional motorcycles. By making this system more compact and building it into the engine, a motorcycle CVT engine has been developed that is about the same size as a manual transmission (MT) engine. During driving with a CVT, heat is generated by friction at the sheaves, and therefore it was necessary to secure a certain length of belt to ensure that external air flows efficiently to the sheaves. However, making the CVT more compact restricted the belt length, which decreased cooling performance and increased the number of bends in the belt, making it difficult to maintain durability. To address this issue, a plastic resin drive belt and newly designed sheaves were adopted, and durability of more than that of a scooter was achieved.
Technical Paper

Clutchless Geared Smart Transmission

2011-08-30
2011-01-2031
Most passenger vehicles employ manual or automatic transmission in their power train. Recently, some automated geared transmission including the dual clutch transmission is gaining popularity for its fuel efficiency and smooth driving as well as convenience. In this study, we are proposing a new much simplified clutchless geared transmission which may transmit most powerful torque employing the power-merge planetary gear system to the final drive during gear shift with excellent smoothness in the transmitted torque. This transmission might work for the most kinds of vehicles having internal combustion engine including the hybrid vehicles.
Journal Article

Gear Rattle Noise Prediction from Dynamic Simulation

2011-09-13
2011-01-2242
Gear rattle noise is a common issue in manual gear transmissions and is often difficult to resolve. This paper discusses a methodology involving development of a simulation model for noise prediction and subsequent design of experiments (DOE) analysis to select optimal design parameters to reduce rattle noise. A one-dimensional torsional vibration simulation model for a tractor driveline was developed and was correlated with experimental measurements. This correlated model was used to calculate the torque variation between the gear pairs based on engine excitations. The standard deviation of this mesh torque was used as a metric and was correlated to noise ratings assigned by experts during experimental evaluation. Using this metric as the response variable, a DOE was conducted to determine the contributing factors and their influence on the rattle noise. Optimal design parameters were selected to achieve target value on the rattle metric.
Technical Paper

Gear Shift Fork Stiffness Optimisation

2011-09-13
2011-01-2235
This paper presents a simulation of the stiffness of the shift fork of a manual transmission using contact pattern analysis and optistrut. All the subsystem (i.e. synchronizer and the shift system component) are constrained to optimize the shift fork stiffness. A-5-speed manual transmission is used as an example to illustrate the simulation, co-relation and validation of the optimization of the gear shift fork stiffness. The shift system was modeled in the software to collate the synchronization force, shift system gap etc with the constraint on the shift fork. It is constrained by the synchronizer sleeve and the fork mounting on the gear shift rail. The synchronizer force is then applied on the gear shift fork pads which are translated to the synchronizer sleeve. It has a number of pads which come into contact at different occasion of the synchronization because of the varying stiffness of the fork.
Technical Paper

A Continuously Variable Transmission Controlled by an Electric Motor

2009-06-15
2009-01-1953
A new continuously variable transmission has been developed. The new transmission could convert step transmissions to continuously variable transmissions with an electric motor and two planetary gear sets connected with a worm gear. The output speed of the transmission is determined by the speed of the electric motor instead of the input speed. On the other hand, the output torque comes from the input torque and does not depend on the torque of the electric motor. The output speed could be easily changed by controlling the speed of the electric motor of a small power. The overall structure of the transmission with a step transmission is simple and efficient since a torque converter is not needed for the transmission.
Technical Paper

Optimization of Gear Whine, Efficiency, and Durability of a Manual Transaxle

2009-05-19
2009-01-2064
Development of modern powertrains used in car and truck applications is more competitive than ever before. Powertrains and components previously considered to be advanced technology, such as hybrids and dual-clutch transmission technology, are now commonplace, being designed and manufactured in all worldwide markets. In order to stay competitive, powertrain OEMs must simultaneously optimize attributes such as performance, cost, weight, durability, fuel economy and NVH while producing new, desirable designs with reduced product development timelines. Oftentimes, the ideal solution for optimization of gear whine will result in an unexpected deterioration of durability, and vice versa. An advanced software tool was previously developed for the design of transmissions and transaxles, including analysis of the vibration, efficiency and durability performance under specified speeds and loads.
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