• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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• 2003.11a
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• pp.235-240
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• 2003

Auto transmission system is composed by torque converter. clutch, brake, planetary goat and valve body controlling oil pressure. In the automatic transmission, the most largest influence elements are torque converter and clutch for oil performance. In this piper I studied failure of tribology causing sealing poor of the acting parts, leakage of the oil pressure and poor of the lubrication.

• Proceedings of the KIEE Conference
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• 2000.07d
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• pp.2561-2563
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• 2000

In this paper, a mathematical vehicle model, the braking force control parameters, the wheel control logic, and vehicle control strategy are presented, in order to analyze the dynamic characteristics of a vehicle equipped with ABS(Antilock Brake System). The full vehicle dynamics model is constructed with sprung mass, brake system, and wheels to verify control algorithms. The valve control algorithms are designed with the wheel accelerations and slip ratio take into consideration. Theses algorithms are applied to the front and rear wheels independently. Simulation is performed under the wet road condition at initial braking speed of 60 [km/h].

• Journal of Aerospace System Engineering
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• v.11 no.3
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• pp.8-15
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• 2017

In this paper, an equivalent brake hydraulic circuit with a piezoelectric hydraulic pump was constructed, and load pressure control for better pressurization/depressurization characteristics was conducted. To understand pressurization/depressurization characteristics of the equivalent hydraulic circuit, the relation between the load pressure and the input voltage was revealed experimentally. Experiments were also conducted to observe effect of the solenoid valve on depressurization characteristics. In the pressurization experiment, it was validated that transient response time required to achieve desired load pressure may be reduced through voltage control to change pressurization gradient. By applying the valve on/off time control and voltage control, it was also possible to reduce response time in the depressurization process. Therefore, transient response time may be improved within 10ms for pressurization and within 30 ms for depressurization using the control technique suggested in this study. The load pressure control method proposed in this study is useful for controlling load pressure of a hydraulic brake system with the piezoelectric hydraulic pump.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.21 no.1
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• pp.61-69
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• 2020

This study examined the braking characteristics of a heavy haul freight train with P4a distribution valves applied to domestic high-speed freight trains. A freight train was composed of 50 cars, which is twice the normal operation. A braking test was performed to confirm the characteristics of the braking of a heavy haul. The brake cylinder pressures were measured for emergency and service braking on the 1st, 10th, 20th, 30th, and 50th cars. Because the brake signal is transmitted to the pressure through the braking tube connected to the end of the train, the rear vehicle is braking later than the vehicle ahead. Therefore, it is necessary to predict the brake pressures in all cars in a train to supplement the results of the limited tests and calculate the braking distance. The pressure in each car was determined using empirical models of linear interpolation, stepwise, and exponential models, which provided reliable information. The predictive results of the empirical models were compared with the measured results, and the exponential model was predicted relatively accurately. These results are expected to contribute to the safe operation of heavy haul freight trains and can be used to predict the braking distance and calculate the level of impact between vehicles during braking.

• 제어로봇시스템학회:학술대회논문집
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• 2001.10a
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• pp.170.3-170
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• 2001

Antilock brake system(ABS) prevent the wheels of road vehicle from locking up and skidding so that the braking force is from static friction instead of kinetic friction. Therefore ABS helps drivers maintain steering control during breaking situation particularly at an emergency stopping situation. So when trying to stop the road vehicle it is best to have the most friction possible for faster deceleration ABS keep the wheels turning which means there is more friction between the tires of vehicles and the road surface. Because of this advantage, ABS are now a commonly installed feature for passenger's safety in road vehicles. In this study, hydraulic system of ABS of vehicle is composed of 3port-2position solenoid valve. In order to minimize ...

• Journal of Advanced Marine Engineering and Technology
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• v.24 no.5
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• pp.86-96
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• 2000

This study is to consider that the helical intake port flow and fuel injection system have effects on the characteristics of engine performance and emissions in a turbocharged DI diesel engine of the displacement 9.4L. The swirl ratio for ports was modified by hand-working and measured by impulse torque swirl meter, For the effects on performance and emission, the brake torque, BSFC were measured by engine dynamometer and NOx, smoke were by gas analyzer and smoke meter. As a result of steady flow test, when the valve eccentricity ratio are closed to cylinder wall, the flow coefficient and swirl intensity are increased, And as the swirl is increased, the mean flow coefficient is decreasing, whereas the gulf factor is increasing. Also, through engine test its can be expected to meet performance and emission by the following applied parameter; the swirl ratio is 2.43, injection timing is BTDC $13^{\circ}$CA and compression is 15.5.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2010.05a
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• pp.833-834
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• 2010

• Transactions of the Korean Society of Mechanical Engineers B
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• v.24 no.9
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• pp.1185-1194
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• 2000

The characteristics of intake port flow and engine performance with swirl ratio variance in a turbocharged D.I. diesel engine were studied in this paper. The intake port flow is important factor which have influence on the engine performance and exhaust emission because the properties in the injected fuel depend on the combustion characteristics. Through these experiments it can be expected to satisfy performance and emission by optimizing the main parameters; the swirl ratio of intake port, injection timing and compression ratio. The swirl ratio for ports was modified by hand-working and measured by impulse swirl meter. For the effects on performance and emission, the brake torque and brake specific fuel consumption were measured by engine dynamometer, NOx and smoke were measured by gas analyzer and smoke meter. The results of steady flow test are as follows; as the valve eccentricity ratio are closed to cylinder wall, the flow coefficient and swirl intensity are increased. Also we realized that there is a trade-off that the increase of swirl ratio decreases mean flow coefficient and increases the Gulf factor. And the optimum parameters to meet performance and emission through engine test are as follows; the swirl ratio 2.43, injection timing BTDC 13oCA and compression ratio 15.5.

• Journal of Advanced Marine Engineering and Technology
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• v.37 no.4
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• pp.378-383
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• 2013

A butterfly throttle valve has been used to control the brake power of an SI engine by controlling the mass flow-rate of intake air in the induction system. However, the valve has a serious effect on the volumetric efficiency of the engine due to the pressure resistance in the induction system. In this study, a new intake air controlling valve named "Variable Geometry Throttle Valve(VGTV)" is proposed to minimize the pressure resistance in the intake system of an SI engine. The design concept of VGTV is on the application of a venturi nozzle in the air flow path. Instead of change of the butterfly valve angle in the airflow field, the throat width of the VGTV valve is varied with the operating condition of an SI engine. In this numerical study, CFD(computational fluid dynamics) simulation technique was incorporated to have an aerodynamics performance analysis of the two air flow controlling systems; butterfly valve and VGTV and compared the results to know which system has lower pressure resistance in the air intake system. From the result, it was found that VGTV has lower pressure resistance than the butterfly valve. Especially VGTV is effective on the low and medium load operating condition of an SI engine. The averaged pressure resistance of VGTV is about 49.0% lower than the value of the conventional butterfly throttle valve.

• Transactions of the Korean Society of Automotive Engineers
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• v.18 no.6
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• pp.70-75
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• 2010

Compressed air represents an energy source and an force-transmission medium for brake systems on medium-heavy and heavy-duty commercial vehicles. However, one disadvantage is the tendency of air to absorb moisture in the form of water vapor. This water vapor condenses once the air, which is heated during compression, cools back to ambient temperature upon emerging from the air compressor. The resulting condensation assumes the form of moisture in pneumatic lines, air tanks, cylinders and valve assemblies and can have negative consequences for the brake system and vehicle safety. The pneumatic systems on today's vehicles are equipped with air dryers, in which the supplied air is dried according to the adsorption principle. In the systems, the compressed air flows through a granular desiccant with molecular sieves which captures the water molecules.