• 드라이브 ㆍ 컨트롤
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• 제16권3호
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• pp.94-102
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• 2019

• 드라이브 ㆍ 컨트롤
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• 제15권3호
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• pp.14-20
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• 2018

Wet clutches in an automatic transmission enable the transmission of the engine power by the frictional torque experienced and noted between disk and plates. Since the clutch frictional torque considerably affects the shift quality of an automatic transmission as well as the durability of the machinery, its friction characteristics must be carefully examined to meet the design requirements. The SAE No. 2 friction test machine is a well-known standard to evaluate mainly the friction characteristics of plate clutches along with the required automatic transmission fluids. This paper reviews the experimental analysis of the wet clutch friction characteristics by using the exclusively developed clutch test machine which is capable of controlling the clutch test procedure, in accordance with the applicable test standard and processing of the experimental data automatically. As the clutch test machine is designed for the accommodation of dual clutches which is applied to the real transmission, it can evaluate not only the clutch friction characteristics, but also an actuation performance of a measured clutch piston. In respect to friction characteristics involving dynamic friction coefficients, the energy absorbed in a clutch disk and the recorded temperatures of clutch plates during braking actions and procedures are also investigated. Additionally, the change of friction coefficients by the use of the repeated clutch application is also observed with the endurance test functions of an accurately calibrated and dedicated clutch test machine.

• 드라이브 ㆍ 컨트롤
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• 제17권3호
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• pp.47-56
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• 2020

As a shift control of automatic transmission was managed with the electronic control unit (ECU), shift quality which is a measure of shift shock during gear change has markedly improved. However, the initial clutch pressure control of the clutch filling phase should continue to rely on the predetermined control input since the input and output speeds are unchanged until the shifting process attains the inertia phase. It is critical to minimize the clutch response time and control the clutch pressure accurately at the end of clutch fill to achieve quick shift response and smoothness. Advanced transmission companies have adopted an auto calibration method which establishes the databases for the clutch piston fill-up attributes and the frictional characteristics of the disks. In this study, a distinctive auto calibration algorithm for forklift transmission under development is proposed and verified with the real-vehicle test. The experimental calibration results showed consistent turbine dynamics at the initial stage of shifts with the properly calibrated clutch-fill control parameters. By using this technique, it is necessary to finalize the shift control for the various operation conditions.

• 유공압시스템학회논문집
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• 제3권4호
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• pp.21-28
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• 2006

The proportional control solenoid valves as well as the PWM solenoid valves operated by electric signal play an important role in the hydraulic system for automatic transmissions to improve the shift quality. However it is not generally available for the performance data because most of the automotive parts manufacturer don't release the specific test results, especially dynamic performance that is essential to design a shift control algorithm. In this research, a performance test equipment that can be applied to various types of pressure control solenoid valve was developed. It was implemented by 8-bit micro-controller with many useful functions such as adjustable PWM carrier frequency, embedded function generator, current controller, data monitoring and acquisitions, etc. for the test of dynamic performance of solenoid valve as well as the steady-state pressure characteristics. The performance test results for the direct type proportional control solenoid valve show not only the validity of overall functions but also its usefulness as a hydraulic valve tester.

• 한국해양공학회:학술대회논문집
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• 한국해양공학회 2001년도 춘계학술대회 논문집
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• pp.196-201
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• 2001

Electro-Rheological(ER) fluids change their apparent viscosity according to the electric field strength. Therefore, there are many practical applications using the ER fluids. ER effect on the dispersive system of polarizable fine powder/dielectric oil has been investigated. The electrical and rheological properties of starch based ER fluid were reported. Yield stress of the fluids were measured on the couette cell type rheometer as a function of electric fields, particle concetrations, and temperatures. The electric field is applied by high voltage DC power supply, The outer cup is connected to positive electrode(+) and the bob becomes ground(-). And the temperatures the viscosity(or shear stress) versus shear rates were measured. In this experiment shear rates were increased from 0 to 200s$^{-1}$ in 2 minutes. This thesis presents Bingham properties of ER fluids subjected to temperature variations. The temperature dependence of the viscosity was determined for ER fluids consisting of 35 weight % starch particles in automatic transmission oil.

• 에너지공학
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• 제23권2호
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• pp.28-34
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• 2014

자동변속기유는 자동차의 자동변속기의 성능을 유지시키기 위해 사용되는 유체이다. 최근 자동차 제조사에서는 일반적으로 자동변속기유를 80000~100000 km 주행후 교환 또는 무교환을 보증하고 있지만 국내에서는 많은 운전자들이 50000 km 이하에서도 자동변속기유를 교환하고 있는 것으로 조사되었다. 빈번한 자동변속기유의 교환은 환경오염과 차량유지비용을 상승시키는 원인으로 작용되고 있다. 본 연구에서는 사용하지 않은 신유와 50000 km와 100000 km를 각각 주행한 뒤 회수된 자동변속기유를 대상으로 인화점, 연소점, 유동점, 동점도, 저온겉보기점도, 전산가, 금속분과 같은 물리적 특성을 분석하였다. 연구결과, 신유에 비해 사용유는 전산가, 유동점, 금속분이 증가되는 것을 확인하였지만, 두 종류의 사용유(50000 km, 100000 km)의 물리적 특성과 금속분 함량의 차이는 크지 않음을 알수 있었다.

• Tribology and Lubricants
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• 제30권2호
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• pp.71-76
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• 2014

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 plates 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 $50^{\circ}$ shows the lowest drag torques at both low and high speeds. The flow vectors inside the $50^{\circ}$ 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.

• KSTLE International Journal
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• 제2권2호
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• pp.120-126
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• 2001

Performance requirements for automatic transmission fluids have been changed reflecting the design changes of automatic transmissions. The major purpose of these design changes is concentrated upon improvements of both fuel economy and drivability. In order to formulate such high performance ATFs as satisfy those requirements, it is necessary to use high quality base oils like VHVI base oils and PAOs. In this study, the effect of base oils characteristics on ATF performance is investigated, mainly regarding differences in frictional characteristics with deterioration. Frictional characteristics are determined using the SAE No. 2 machine and ATFs are deteriorated under various controlled conditions. Moreover low-temperature fluidity, oxidation stability, and seal compatibility are also compared for four different ATFs. From the investigation, it was found that the use of Group III and IV base oils in ATFs gives several benefits with respect to low temperature viscosity, oxidation stability and SAE No.2 friction characteristics.

• 한국윤활학회:학술대회논문집
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• 한국윤활학회 2004년도 학술대회지
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• pp.117-122
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• 2004

In order to improve the fuel economy by design change of automatic transmission, various technologies such as increased shift stages, slip control of lock-up clutch and compact and low-weight design have been developed. And also many OEMs have developed their own ATFs as a part of these automatic transmissions. In this study. to investigate the effects of ATF characteristics on fuel economy, we got the worldwide OEM ATFs and made some reference fluids. And physical properties, frictional characteristics and fuel economy using dynamometer test for these fluids were evaluated. From the investigation, it was found that viscosities of ATFs are correlated with fuel economy in dynamometer test and reducing the viscosities made it possible to obtain fuel economy.

• Tribology and Lubricants
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• 제21권3호
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• pp.142-148
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• 2005

In order to improve the fuel economy by design change of automatic transmission, various technologies such as increased shift stages, slip control of lock-up clutch and compact and low-weight design have been developed. And also many OEMs have developed their own ATFs as a part of these automatic transmissions. In this study, to investigate the effects of ATF characteristics on fuel economy, we got the worldwide OEM ATFs and made some reference fluids. And physical properties, frictional characteristics and fuel economy using dynamometer test for these fluids were evaluated. From the investigation, it was found that viscosities of ATFs are correlated with fuel economy in dynamometer test and reducing the viscosities made it possible to obtain fuel economy.