클러치 드래그 토크에 미치는 마찰재 면적 및 클리어런스의 영향
Effects of Friction Plate Area and Clearance on the Drag Torque in a Wet Clutch for an Automatic Transmission
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The reduction of drag torque is an important research issue in terms of improving transmission efficiency. Drag torque in a wet clutch occurs because of the viscous drag generated by the transmission fluid in a narrowgap (clearance) between the friction plate and a separate plate. The objective of this paper is to observe the effects ofthe friction plate area and the clearance on the drag torque using finite element simulation. The two-phase flow of airand oil fluid is considered and modeled for the simulation. The simulation analysis reveals that as the rotational speedincreases, the drag torque generally increases to a critical point and then decreases sharply at a high speed regime. Theclearance between the two plates plays an important role in controlling drag torque peak. An increase in the clearancecauses a decrease in shear stress; thus, the drag torque also decreases according to Newton’s law of viscosity. An observationof the effect of the area of contact between transmission fluid and friction plate shows that the drag torqueincreases with the contact area. The flow vectors inside the flow channel present clear evidence that the velocity of thefluid flows is faster with a larger friction plate, that is, in the case of a larger contact area. Therefore, the optimum sizeof the friction plate should be determined carefully, considering both the clutch performance and drag reduction. It isexpected that the results from this study can be very useful as a database for clutch design and to predict the drag torquefor the initial design with respect to various clutch parameters.
Abstract
The reduction of drag torque is an important research issue in terms of improving transmission efficiency. Drag torque in a wet clutch occurs because of the viscous drag generated by the transmission fluid in a narrowgap (clearance) between the friction plate and a separate plate. The objective of this paper is to observe the effects ofthe friction plate area and the clearance on the drag torque using finite element simulation. The two-phase flow of airand oil fluid is considered and modeled for the simulation. The simulation analysis reveals that as the rotational speedincreases, the drag torque generally increases to a critical point and then decreases sharply at a high speed regime. Theclearance between the two plates plays an important role in controlling drag torque peak. An increase in the clearancecauses a decrease in shear stress; thus, the drag torque also decreases according to Newton’s law of viscosity. An observationof the effect of the area of contact between transmission fluid and friction plate shows that the drag torqueincreases with the contact area. The flow vectors inside the flow channel present clear evidence that the velocity of thefluid flows is faster with a larger friction plate, that is, in the case of a larger contact area. Therefore, the optimum sizeof the friction plate should be determined carefully, considering both the clutch performance and drag reduction. It isexpected that the results from this study can be very useful as a database for clutch design and to predict the drag torquefor the initial design with respect to various clutch parameters.
참고문헌 (13)
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