파형 습식클러치의 드래그 토크 저감을 위한 파형내 유로 위치 설정 설계 연구
A Study on the Flow Path Position Design of Waviness Friction Pad for Drag Torque Reduction in Wet Type DCT
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Drag torque reduction in a wet clutch pack is a key aspect of the design process of the dual clutch transmission (DCT) system. In order to reduce the drag torque caused by lubricant shear resistance, recently developed wet clutch pack systems of DCT, as well as automatic transmission and other four-wheel drive (4WD) couplings, frequently utilize wavy wet clutch pads. Therefore, wavy shape of friction pad are made on the groove patterns like waffle pattern for the reduction of drag torque. Additionally, the groove patterns are designed with larger channels at several locations on the friction pad to facilitate faster outflow of lubricant. However, channel performance is a function of the waviness of the friction pad at the location of the particular channel. This is because the discharge sectional area varies according to the waviness amplitude at the location of the particular channel. The higher location of the additional channel on the friction pad results in a larger cross-sectional area, which allows for a larger flow discharge rate. This results in reduction of the drag torque caused by the shear resistance of DCTF, because of marginal volume fraction of fluid (VOF) in the space between the friction pad and separator. This study computes the VOF in the space between the friction pad and separator, the hydrodynamic pressure developed, and the shear resistance of friction torque, by using CFD software (FLUENT). In addition, the study investigates the dependence of these parameters on the location and waviness amplitude of the channel pattern on the friction pad. The paper presents design guidelines on the proper location of high waviness amplitude on wavy friction pads.
Abstract
Drag torque reduction in a wet clutch pack is a key aspect of the design process of the dual clutch transmission (DCT) system. In order to reduce the drag torque caused by lubricant shear resistance, recently developed wet clutch pack systems of DCT, as well as automatic transmission and other four-wheel drive (4WD) couplings, frequently utilize wavy wet clutch pads. Therefore, wavy shape of friction pad are made on the groove patterns like waffle pattern for the reduction of drag torque. Additionally, the groove patterns are designed with larger channels at several locations on the friction pad to facilitate faster outflow of lubricant. However, channel performance is a function of the waviness of the friction pad at the location of the particular channel. This is because the discharge sectional area varies according to the waviness amplitude at the location of the particular channel. The higher location of the additional channel on the friction pad results in a larger cross-sectional area, which allows for a larger flow discharge rate. This results in reduction of the drag torque caused by the shear resistance of DCTF, because of marginal volume fraction of fluid (VOF) in the space between the friction pad and separator. This study computes the VOF in the space between the friction pad and separator, the hydrodynamic pressure developed, and the shear resistance of friction torque, by using CFD software (FLUENT). In addition, the study investigates the dependence of these parameters on the location and waviness amplitude of the channel pattern on the friction pad. The paper presents design guidelines on the proper location of high waviness amplitude on wavy friction pads.
참고문헌 (5)
- 김해용, "습식클러치 패드의 Groove 패턴에 의한변속기유의 동적 거동", 한국윤활학회지, 30(2), pp.92~98 (2014), 한국윤활학회[DOI]
- Vladimir Ivanović, "Experimental Characterization of Wet Clutch Friction Behaviors Including Thermal Dynamics", SAE International Journal of Engines, 2(1), pp.1211~1220 (2009), SAE International[DOI]
- Shoaib Iqbal, "Mathmatical Model and Experimental Evaluation of Drag Torque in Disengaged Wet Clutches", ISRN Tribology (2013)
- Yiqing Yuan, "An Improved Hydrodynamic Model for Open Wet Transmission Clutches", Journal of Fluids Engineering, 129 (2007)
- Kitabayashi, H., "Analysis of the Various Factors Affecting Drag Torque in Multiple-Plate Wet Clutches", SAE Int. J. Engines (2003)