습식 DCT의 드래그 토크 저감을 위한 클러치 패드 유로 설계

조정희(Junghee Cho),한준열(Juneyeol Han),김우정(Woo-Jung Kim),장시열(Siyoul Jang) 한국트라이볼로지학회 2017 한국트라이볼로지학회지 (Tribol. Lubr.) Vol.33 No.2

The drag torque in the wet clutch system of a dual clutch transmission system is investigated because it is relatively high, up to 10 of the total output torque of the engine, even when the clutch is in the disengagement state with zero torque transfer. Drag torque results from the shear resistance of the DCTF between the friction pad and separator plate. To reduce the drag torque for ensuring fuel economy, the groove pattern of the wet clutch friction pad is designed to have a high flow rate through the pattern groove. In this study, four types of groove patterns on the friction pad are designed. The volume fraction of the DCTF (VOF) and hydrodynamic pressure developments in the gap between the friction pad and separator plate are computed to correlate with the computation of the drag torque. From the computational results, it is found that a high VOF and hydrodynamics increase the drag torque resulting from the shear resistance of the DCTF. Therefore, a patterned groove design should be used for increasing the flow rate to have more air parts in the gap to reduce the drag torque. In this study, ANSYS FLUENT is used to solve the flow analysis.

초탄성 및 점탄성 물성을 고려한 자동차용 휠 베어링 실의 드래그 토크 예측

이승표 한국트라이볼로지학회 2019 한국윤활학회지(윤활학회지) Vol.35 No.5

Wheel bearings are important automotive parts that bear the vehicle weight and translate rotation motion; in addition, their seals are components that prevent grease leakage and foreign material from entering from the outside of the bearings. Recently, as the need for electric vehicles and eco-friendly vehicles has been emerging, the reduction in fuel consumption and CO2 emissions are becoming the most important issues for automobile manufacturers. In the case of wheel bearings, seals are a key part of drag torque. In this study, we investigate the prediction of the drag torque taking into consideration the hyperelastic and viscoelastic material properties of automotive wheel bearing seals. Numerical analysis based on the finite element method is conducted for the deformation analyses of the seals. To improve the reliability of the rubber seal analysis, three types of rubber material properties are considered, and analysis is conducted using the hyperelastic material properties. Viscoelastic material property tests are also conducted. Deformation analysis considering the hyperelastic and viscoelastic material properties is performed, and the effects of the viscoelastic material properties are compared with the results obtained by the consideration of the hyperelastic material properties. As a result of these analyses, the drag torque is 0.29 Nm when the hyperelastic characteristics are taken into account, and the drag torque is 0.27 Nm when both the hyperelastic and viscoelastic characteristics are taken into account. Therefore, it is determined that the analysis considering both hyperelastic and viscoelastic characteristics must be performed because of its reliability in predicting the drag torque of the rubber seals.

마찰재 그루브에 따른 습식 클러치 드래그 토크 변화 연구

류진석(Jin Seok Ryu),성인하(In-Ha Sung) 한국트라이볼로지학회 2014 한국트라이볼로지학회지 (Tribol. Lubr.) Vol.30 No.2

As the importance of transmission efficiency to reducing fuel consumption and conserving the environment rapidly increases, reducing the drag torque in an automotive wet clutch is emerging as an important issue in the automotive industry. The drag torque in a clutch occurs from viscous drag generated by automatic transmission fluid in the narrow gap between separate friction plates. In this study, the drag torques in an automotive wet clutch are investigated with respect to the angle and density of the grooves between separate friction plate by three-dimensional finite element simulation of a single set of wet clutch disks considering the two-phase flow of air and oil. The simulation results shows that the drag torque generally increases with the rotational speed to a critical point and then decreases at the high-speed regime. The grooves between the plates plays an important role in reducing the drag peak, and the inclined angle of the grooves affects the oil flow. The grooves with an angle of 50° shows the lowest drag torques at both low and high speeds. The flow vectors inside the 50° grooves shows clear evidence that the fluid flows out more easily from the grooves compared with the flow vectors inside grooves with lower angles. The simulation results shows that increasing the number of grooves (density of grooves) decreases the drag torque.

파형 습식클러치의 드래그 토크 저감을 위한 파형내 유로 위치 설정 설계 연구

조정희(Junghee Cho),한준열(Juneyeol Han),김우정(Woojung Kim),장시열(Siyoul Jang) 한국트라이볼로지학회 2017 한국윤활학회지(윤활학회지) Vol.33 No.1

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 aviness 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.

마찰재 편마모 형상에 따른 브레이크 드래그 영향성 분석

유혁진(Hyukjin Ryu),김유호(Yooho Kim),김동선(Dongsun Kim),정영규(Youngkyu Jung),용호균(Hokyun Yong) 한국자동차공학회 2019 한국자동차공학회 학술대회 및 전시회 Vol.2019 No.11

Many vehicle manufactures are constantly trying to reduce brake drag. Brake drags are becoming an important factor in green cars. In order to reduce brake drag values, calipers, discs and rotors must be properly designed. Nevertheless, the brake drag increases with driving. It is estimated that the brake drag will increase as the brake pads wear. In this study, the effects of brake drag on the brake pad shape were analyzed. Six factors for the shape of the friction were selected and the DOE method was conducted. The main effects and interactions for each factor were analyzed.

2-Pisotn Brake Caliper의 Piston seal죄임량에 따른 제동 드래그 영향성 분석

김유호(Yooho Kim),권택상(TaikSang Kwon),이순욱(Soonwook Lee),유상협(SangHyup Ryu),용호균(Hokyun Yong) 한국자동차공학회 2021 한국자동차공학회 부문종합 학술대회 Vol.2021 No.6

Reducing brake drag has always been one of the most important goals among brake system engineers and its importance is getting higher than ever with a historic ramp-up in global fuel economy and carbon emission standard. Although many studies have been done with regard to the improvement of brake drag, previous papers have focused mainly on studying the shape optimization of the piston seal groove where the piston seal is to be located. The present work attempts to illuminate the interaction between brake drag and piston seal clamping force of the floating type 2-piston caliper. Data from bench tests and CAE are presented and discussed to get a better understanding the effects of piston seal clamping force on brake drag.

MODIFIED GENERALISED MAXWELL SLIP BASED ELECTRO-HYDRAULIC TRANSFER CASE MODELING FOR ALL-WHEEL DRIVE VEHICLE SIMULATION

정호진,최세범 한국자동차공학회 2023 International journal of automotive technology Vol.24 No.1

This paper describes the modeling of a torque-on-demand transfer case and an all-wheel drive (AWD) vehicle simulation through model integration. To develop the AWD vehicle controller, reliable and robust mathematical modeling of transfer case for AWD vehicle simulation should be proceeded. However, conventional wet clutch model cannot be applied for simulating the AWD vehicle especially when clutch is fully lock up state because of the chattering response of torque followed by the change of external factors. By replacing a slip-regulation equation of lock-up state with a degree of freedom (DOF) reduction equation in the generalized maxwell slip (GMS) model, the chattering and instability issue of original GMS model for AWD vehicle simulation was solved in this study. For parameter verification of the wet clutch, the simulation of the transfer case module and validation with the experimental data were conducted first. Then, the simulation of an AWD vehicle was conducted through the integration of the developed one in CarSim software. Through the comparison of the modified GMS model with the original GMS model, the former is verified to be superior to the latter for stable simulation.

Analysis of vibro-impacts in a torsional system under both wide open throttle and coast conditions with focus on the multi-staged clutch damper

윤종윤,김병일 대한기계학회 2015 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.29 No.12

Vibro-impacts of gear pairs in a torsion system inherently occur under the steady state torque input condition since clearance type nonlinearitiesare related to the torsional vibration induced by the firing stroke of an engine. In order to investigate the dynamic characteristicsof gear rattle, front engine and front wheel drive configuration of the manual transmission is investigated under both wide open throttleand coast conditions. This configuration is examined using 6 degree-of-freedom system model, embedded by the relevant nonlinearitiessuch as multi-staged clutch dampers, gear backlash and drag torques. This article focuses on the relationship of vibro-impacts withkey parameters of clutch dampers, where the gear rattle phenomena are defined by “sing-sided”, “double-sided” and “no-impact” alongwith different clutch dampers. Thus, the mathematical model of the multi-staged clutch dampers is developed by including the asymmetrictransition angles and pre-load effect. Based upon this nonlinear model, three real-life clutch dampers are employed and simulatedresults are compared with limited experimental measurements conducted on a vehicle. Also, the dynamic characteristics of gear motionsunder the coast condition are investigated. This coast condition is explained corresponding to different input torque conditions and itssimulations show the main reasons of vibro-impacts induced by the clutch stopper well. Finally, modified clutch damper concepts forrattle-free transmission are proposed along with dynamic clutch design guidelines.

습식 클러치 시스템의 작동환경 조건별 드래그토크 특성 연구

오영택(Youngtaek Oh),장시열(Siyoul Jang) 한국자동차공학회 2021 한국 자동차공학회논문집 Vol.29 No.1

In general, the wet clutch system is used for automatic transmissions in automobiles. These wet clutch systems operate under the automatic transmission fluid(ATF) environment and their performance is greatly influenced by the ATF. Various conditions, such as oil flow rate, temperature, and clutch pad pattern, which are the main operating factors, have a significant effect on the power transmission performance by the friction mechanism either in engagement or in disengagement status. Drag torque is another factor that is greatly influenced by the ATF flow behaviors on automatic transmission efficiency, and it can be significantly reduced through a properly designed clutch pad pattern. In this study, the drag torques generated under various operating conditions of the ATF supply environment were measured in order to verify the differences of friction pad structures. Comparative experiments of various groove designs were conducted according to the SAE J2863 test modes with the SAE No #2 test machine. This study provides useful information of clutch pad design with respect to less drag torque.

선형적 요소 예측을 통한 비선형 시스템 동적 특성 연구

안민주(Min-ju Ahn),류성기(Sung-ki Lyu),윤종윤(Jong-yun Yoon),장기(Zhang-Qi),안인효(In-hyo Ahn) 한국기계가공학회 2010 한국기계가공학회지 Vol.9 No.2

The characteristics of the torsional systems are generally examined with the nonlinearities such as the several staged clutch damper springs, gear backlashes and drag torques. Generally speaking, the system's characteristics can be found out by the eigensolutions which can show the system natural frequencies and the mode shapes. However, these factors can not give the complete solutions to avoid the noise and vibration problems related to the nonlinear effects. Therefore, several assumptions should be made for solving the real physical system problems under the linear analysis which can reflect the nonlinear effects in the torsional system. This means that the several modified linear factors such as the modified clutch damper spring constants can be used to examine and avoid the natural frequency zones related to the noise and vibration problems. Under the linear analysis with the assumed and modified values, the system can be investigated with the more reliable ways for the realistic phenomena.