• Tribology and Lubricants
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• 제30권2호
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• pp.92-98
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• 2014

Transmission fluid film behaviors in the gap between the wet clutch pad and separator plate are analyzed using the CFD software ADINA. Three pattern groove designs are selected and are used to validate the fluid film behaviors based on the outlet flow in the gap when the wet clutch pad and separator plate are engaged. The main design goal for pattern grooves is faster engagement. In most cases, much of the outlet flow of transmission fluid in the gap occurs on the outer radius boundary due to the centrifugal force generated by the clutch pad circular motion. Groove patterns are created to ensure faster transmission fluid outlet flow in the direction of the inner radius boundary. Computational results of the selected groove patterns are compared.

• 한국생산제조학회지
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• 제20권6호
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• pp.692-696
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• 2011

A clutch is a very important component when engine starts and gear shifting is needed. The clutch the most commonly used is the dry clutch. This type of clutch has pads, and they are worn after disengagement of clutch little by little. The characteristics of the clutch changes as these pads wear, so wear needs to be measured, and the clutch should be controlled for proper operation. In this study, the clutch contact point estimation algorithm has been developed. From this algorithm, clutch force map changes depending on wear, and the clutch operates properly. We also see the shifting transient of a vehicle for drivability with throttle valve position control and synchronizer movement.

• 한국자동차공학회논문집
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• 제16권5호
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• pp.164-170
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• 2008

A typical clutch system for automotive manual transmissions transfers hydraulic pressure generated by driver's pedal manipulation to the clutch diaphragm spring. The foot effort history during the period of push is different than the period of the clutch pedal's return. The effort or load difference is called clutch foot effort hysteresis. It is known that the hysteresis is caused by friction. The frictional force and moment are produced between various component contact points such as between the rubber seal and the inner wall inside the hydraulic cylinder and between the diaphragm spring and the pressure plate, etc. Understanding the clutch pedal foot effort hysteresis is essential for a clutch release system design and analysis. The dynamic model for a clutch release system is developed for the foot effort hysteresis prediction and a simulation analysis is performed to propose a tool for analysing a clutch system.

• Tribology and Lubricants
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• 제33권3호
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• pp.85-91
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• 2017

This work studies the flow behaviors in the gap between the friction pad and separator in wet-clutch systems. The fluid volume of the lubricant is modeled using the entire system of wet-clutch pack of a dual clutch transmission that has larger outer radius of odd gear shifts and smaller inner radius of even gear shifts. Flow behaviors in the gap of the clutch pad are computed using the gear shift modes that consider the real relative velocities between the friction pad and separator. Flow behaviors in the gap of the disengaged clutch pad are mainly investigated for the wet-clutch system, whereas the engaged clutch pad is modeled with no fluid rate through the contacting surfaces. The developed hydrodynamic fluid pressures and velocity fields in the clutch pad gap are computed to obtain the relevant information for managing flow rates in wet-clutch packs under dual operating conditions during gear shifts. These hydrodynamic pressures and velocity fields are compared on the basis of each gear level and gap location, which is necessary to determine the effects of groove patterns on the friction pad. Shear stresses in the gap locations are also computed on the basis of the gear level for the inner and outer clutch pads. The computed results are compared and used for the design of cooling capacity against frictional heat generation in wet-clutch pack systems.

• 한국기계가공학회지
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• 제20권3호
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• pp.40-46
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• 2021

An automatic transmission of automobiles enables comfortable driving experience with lower transmission shifting jerks. However, the assembly structure is more complicated and requires additional components with lower efficiency than the manual transmission system. Extensive research has been conducted to improve the overall transmission efficiency by optimizing each component of the automatic transmission assembly. This study focuses on enhancing the friction torque of double angular contact ball bearings used in automatic transmission. The friction torque of the bearing varies with the operating conditions such as the operational load and rotating speed. Since reducing the friction torque of the bearing tends to deteriorate the durability of the bearing, it is necessary to design the bearing having a minimum required friction torque by determining the durability life of an automatic transmission assembly, In this study, the theoretical life and friction torque of conventional and newly-developed bearings are calculated. The difference in the friction torque between the new and existing bearings are also evaluated.

• 한국산학기술학회논문지
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• 제20권9호
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• pp.517-524
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• 2019

오버드라이버 허브클러치는 자동차 6단 자동 변속기 미션에 장착되어 엔진의 여유출력을 이용해 연료사용을 절감시켜주는 부품이다. 본 연구에서는 오버드라이버 허브클러치 제품에 대해 피어싱 공정 중 펀치에 가해지는 하중 및 소재 처짐량을 최소화 하고자 한다. 공정 중 펀치의 하중과 처짐량에 영향을 줄 수 있는 다이 클리어런스(die clearance)와 전단각도(shear angle) 그리고 마찰계수(friction coefficient)를 설계 변수로 설정했다. 또한 펀치의 하중과 소재 처짐량에 대해 각 설계 변수들의 영향도를 확인하기 위해 민감도 분석(sensitivity analysis)을 진행했다. 그 결과 전단 각도, 마찰 계수, 다이 클리어런스 순으로 하중 및 처짐량에 대해 민감한 것으로 조사되었다. 이를 통해 펀치의 하중과 소재 처짐량을 목적함수로 설정하고, 반응표면법(Response Surface Method)을 통해 각 설계 변수들과 목적함수의 방정식을 도출했다. 이를 통해 설정된 설계 변수들의 최적 값을 도출해 유한요소해석에 적용한 결과 펀치의 하중 및 소재의 처짐량이 기존대비 22.14% 개선됐다.

• 한국기계가공학회지
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• 제17권5호
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• pp.30-36
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• 2018

Automotive fuel efficiency regulations and air pollution control are hot issues of recent years in the automotive industry. To solve these regulation problems, many studies are continuing to improve the transmission efficiency of transmissions. Tapered roller bearings are useful to improve the transmission efficiency in the recent automobile parts. The frictional losses in the tapered roller bearings are mainly composed of the rolling friction and the sliding friction, and are dependent upon the load, the lubrication, the rotation speed of bearings, and etc. In this paper, the operating conditions of the transmission are defined and then the power losses of each bearing are calculated. In addition, improvement options are suggested after identifying the design factors influenced much by the improvement effect of power loss under the operating conditions of each bearing. We compare the power losses of the entire transmission system due to bearing improvements by comparing the friction losses between the original design and the improved design. Lastly, it is shown that the calculated power losses are valid by comparing the test values and the theoretical values for the frictional torque characteristics of the original and improved bearings.