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Steinberger M.,LuK United States LLC | Bird N.J.,Ford Motor Company
SAE Technical Papers | Year: 2013

This paper reviews ratcheting one way clutches (OWC). OWC represent a significant cost in a transmission. Optimizing the OWC type helps reduce cost and increase fuel efficiency, and is therefore worth studying. Although the ratcheting OWC design is the primary focus of this paper, some background on roller and sprag type OWC is given. The strengths and weaknesses of ratcheting OWC are discussed. Potential OWC failure modes are reviewed to help engineers perform a thorough design analysis. Formulae and other details useful for the design are also reviewed. Copyright © 2013 SAE International. Source

Swank M.,LuK United States LLC | Lindemann P.,LuK United States LLC
SAE Technical Papers | Year: 2011

This paper describes the use of dynamic vibration absorbers in torque converters to reduce the torsional vibration levels of the vehicle drivetrain. The use of both tuned mass absorbers and centrifugal pendulum absorbers (CPA) are discussed. In the case of the tuned mass absorber, the absorber is tuned near the lugging limit of the torque converter clutch to provide maximum improvement in isolation at low speed where vibration levels generally are the highest. The CPA is tuned for the dominate firing order of the engine, thus tracking the engine excitation at all operating speeds. Vehicle measurements are presented for both absorber types compared to current state of the art torque converter isolator technology. Copyright © 2011 SAE International. Source

Karamavruc A.,LuK United States LLC | Shi Z.,LuK United States LLC | Gunther D.,LuK United States LLC
SAE Technical Papers | Year: 2011

To optimize the performance of continuously slipping wet friction clutches, it is vital to predict the maximum temperature at the friction surface. Prediction necessitates an accurate mathematical model of the heat transfer coefficient in and around the transmission oil grooves of the wet friction facing. All the relevant dimensionless variables in and around the oil grooves with respect to heat transfer coefficients were identified using Buckingham's 'Pi' theorem. Computational fluid dynamics (CFD) was used to create empirical formulas for heat transfer coefficients from relevant dimensionless variables and to study the dynamics of the oil flow through the grooves. Maximum transient temperature at the friction interface was predicted via finite element (FE) code using developed empirical formulas of heat transfer coefficients. Transient temperatures were then measured using thermo-couples for various conditions and groove geometries. An excellent agreement was found between the prediction and the measured data. Copyright © 2011 SAE International. Source

Severyn P.,LuK United States LLC | Hemphill J.,LuK United States LLC | George P.,LuK United States LLC | Sturgin T.,LuK United States LLC
SAE International Journal of Passenger Cars - Mechanical Systems | Year: 2012

The demand for both reduced fuel consumption and increased performance has resulted in the current trend of downsizing and turbo-charging the combustion engine. This started in diesel engines and is being carried over to gasoline direct inject engines. The fuel economy benefit using this strategy is clear, however, the requirements of the launch device are not. One drawback of downsizing and turbo-charging is the effect of lag in boost pressure resulting in a decrease of vehicle performance. This is intensified at increased altitude. One way to reduce turbo lag is by operating the engine at a higher speed. In order to diminish lag, the launch device must allow for faster acceleration of the engine. At the same time, enough engine torque must be transmitted to the wheels to maintain acceptable launch feel. Using a traditional torque converter, the hydrodynamic characteristics can be made looser to allow for faster acceleration of engine speed. This however has a negative impact on fuel consumption. This paper will examine the effects of turbo-charging on launch performance and document the results of different options for launch devices including variable characteristic devices that abate turbo lag while maintaining fuel economy. These options include optimized torque converter characteristics, the Multi-Function Torque Converter, and a new launch device called the Fluid Launch Clutch. These options have been studied both through simulation and hardware testing. © 2012 SAE International. Source

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