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PERFORMANCE ANALYSIS OF A CVT CLUTCH SYSTEM FOR A HYBRID ELECTRIC VEHICLE
류완식,유인필,송한림,김현수,조남용 한국자동차공학회 2009 International journal of automotive technology Vol.10 No.1
In this study, the performance of a CVT clutch system for a hybrid electric vehicle was investigated. To analyzed the vehicle performance at restart, the restart delay and driveshaft torque was investigated by simulations and experiments. It was found from the simulation results that the vehicle restart response depends on the clutch pressure buildup time to the point where the clutch torque begins to overcome the vehicle road load, and driving comfort at restart is directly related to the rate change of the clutch pressure.
류완식(Wansik Ryu),남주현(Juhyun Nam),이희라(Heera Lee),김현석(Hyunsuk Kim),이진희(Jinhee Lee),이용준(Yongjun Lee),김현수(Hyunsoo Kim) 한국자동차공학회 2002 한국자동차공학회 Symposium Vol.2002 No.11
CVT ratio control can be achieved by either flow control or pressure control. Since the pressure control method is able to control the pulley thrust. it has many advantages such as keeping the belt from slippage. In developing the ratio control valve. steady state and dynamic characteristics of metal belt CVT should be considered. In this paper. 2 types of ratio control valves are developed: type(l) with line pressure area on the ratio control valve spool and type(lI) without line pressure area. In addition. Kpsi line concept is introduced. which can be used to predict shift performance by the pressure margin to the boundary point. Simulation results show that the type(I) gives faster shifting response in downshift compared to that of the type(II), which is due to the residual pressure in the primary actuator. It is found from the simulation and experimental results that the ratio control valve(l) and (II) have advantages and disadvantages in shift speed while satisfying the design specification for the steady state and the dynamic characteristics.
류완식(Wansik Ryu),김현수(Hyunsoo Kim) 한국자동차공학회 2003 한국자동차공학회 춘 추계 학술대회 논문집 Vol.- No.-
In this paper, shin performance for an independent control CYT is investigated. To realize the independent control, pressure control type ratio control valve and secondary valve are proposed. Using the dynamic models of the control valves and CYT dynamic model, shift performances are evaluated and compared with those by the conventional control CYT. It is found from the simulation that independent control CYT shows faster shift speed for the upshift. To improve the downshift shift speed, appropriate selection of the actuator area ratio is required.<br/>
류완식(Wansik Ryu),김현수(Hyunsoo Kim) 한국자동차공학회 2004 한국자동차공학회 춘 추계 학술대회 논문집 Vol.- No.-
In this paper, CVT belt-pulley loss model is proposed. Experiments are performed to measure input and output power of the CVT belt-pulley. It is found from the experiments that the input and output power loss at a steady state depend on the speed and line pressure. In addition, transient loss model is introduced, which depends on the rotational speed, shift speed and inertia torque. Using the CVT belt-pulley loss model, simulation results are compared with the experiments for various speed and line pressure. It is found that the CVT belt-pulley loss model describes closely the actual power loss behavior.
류완식(Wansik Ryu),김현수(Hyunsoo Kim) 한국자동차공학회 2006 한국 자동차공학회논문집 Vol.14 No.4
A modified ratio control algorithm is proposed for the improvement of the fuel economy for a metal belt CVT. In the modified ratio control algorithm, the CVT ratio is controlled to operate the engine on the optimal operation region which provides the best efficiency from the view point of the overall efficiency of the engine-CVT system. In order to construct the modified ratio map, the CVT system loss model is used by assuming that the all the loss is attributed to the torque loss. It is found from the simulation results that the fuel economy by the modified ratio control algorithm is improved by 5.5 percents compared with the existing ratio control.
류완식(Wansik Ryu),김현수(Hyunsoo Kim) 한국자동차공학회 2005 한국자동차공학회 춘 추계 학술대회 논문집 Vol.2005 No.11_2
A modified ratio control algorithm is proposed for the improvement of the fuel economy for a metal belt CVT. In the modified ratio control algorithm, the CVT ratio is controlled to operate the engine on the optimal operation region which provides the best efficiency from the view point of the overall efficiency of the engine-CVT system. In order to construct the modified ratio map, the CVT system loss model is used by assuming that the all the loss is attributed to the torque loss. It is found from the simulation results that the fuel economy by the modified ratio control algorithm is improved by 5.5 percents compared with the existing ratio control.