• Proceedings of the KSME Conference
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• 2004.11a
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• pp.1335-1340
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• 2004

Due to the distinct advantages of comfort, drive ability and fuel economy standard, the variable displacement swash plate type compressor which can control the compressor displacement by increasing or reducing the swash plate angle has been developed for automotive air-conditioning system. That can be obtained constant temperature of car room on the variation cooling capacities or engine speeds. This paper was carried out the analysis of swash plate behavior to obtain the forces and moments applied to the swash plate and to get the variable controlability on the variation of compressor speeds and swash plate chamber pressures. The results of simuation agree very well with the experimental data.

• Transactions of the Korean Society of Automotive Engineers
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• v.14 no.6
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• pp.160-170
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• 2006

If hydraulic pump controlled by mechanical type regulator has more than one control function, the construction of regulator will be very complicated and control performance falls drastically. It is difficult to have more than one control function for hydraulic pump controlled by electronic type hydraulic valve due to the inconsistency of controllers. This paper proposes a multi-function control technique which controls continuously flow, pressure and power by using EPPR(Electronic Proportional Pressure Reducing) valve in swash plate type axial piston pump. Nonlinear mathematical model is developed from the continuity equation for the pressurized control volume and the torque balance for the swash plate motion. To simplify the model we make the linear state equation by differentiating the nonlinear model. A reaction spring is installed in servo cylinder to secure the stability of the control system. We analyze the stability and disturbance by using the state variable model. Finally, we review the control performances of flow, pressure and power by tests using PID controller.

• Animal Systematics, Evolution and Diversity
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• v.36 no.4
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• pp.285-295
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• 2020

Adults of Prosimulium kiotoense and Twinnia japonensis were collected and reported from Korea for the first time. Since adult black flies are notorious for morphological homogeneity particularly in female, larval and pupal characters have been mainly used to identify them. Adults of P. kiotoense can be identified by the following combination of characteristics: Adult, wing with radial sector (Rs) branched into R²⁺³ and R⁴⁺⁵; hind leg basitarsus without calcipala; first tarsomere without pedisulcus. Female, claw without basal thumblike lobe; hypogenial valve elongate, convex, heavily sclerotized medially, posterior end touching each other, space between valves rhomboid. Male, claw with basal thumblike lobe; ventral plate keel shaped; gonostylus with 2-3 spinules. Adults and pupa of T. japonensis can be identified by the following combination of characteristics: Adult, antenna with 7 flagellomeres. Female, hypogenial valve broad, posterior end of valve not touching each other; cercus elongate, subquadrate; spermatheca slightly wider and long, round. Male, claw with basal thumblike lobe; gonostylus with 1 spinule; ventral plate flat. Pupa, gill of 16 filaments, arising from 3 swollen stalks; abdominal tergites without spine combs except tergites III and IV with small recurved hooks; terminal spine well developed, wavy shaped.

• Transactions of the Korean Society of Automotive Engineers
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• v.5 no.5
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• pp.9-19
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• 1997

In this paper, the modeling and analysis of dynamic characteristics has been carried out for friction clutches and brakes in an automatic transmission. From the operating oil pressure generated by the valve-body, time delay by check valve and the movement of piston has been examined. Also torque capacity and torque transferred at the clutch is studied. Heat capacity and temperature distribution at the reaction plate of clutch are codeled by time-dependent, nonhomogeneous partial differential equation, and brake torque, brake time, and the amount of heat generated are investigated. It is found that the time delay at the check valve is very short but dominant at the spool.

• Journal of the Korean Society for Precision Engineering
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• v.12 no.7
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• pp.148-157
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• 1995

This study deals with controlling the speed of Hydrostatic Transmission (HST) system throuth the control of pumping stroke of positive displacement pump using high-speed solenoid valve controlled by digital closed loop PWM method. The method which was done in this study is as follows: First, we modified original positive displacement pump and designed pumping stroke control system of HST by using the high-speed solenoid valve. Second, after experimenting static and dynamic characteristics on each signal flow, we identified system parameter of approximated model. Finally, to control the speed of HST, we controlled the angle of the swash plate of positive displacement pump by controlling the pressure in the control cylinder chamber. Test which was carried out in the laboratory shows that transient and steady state response could be improved by PID controller.

• The KSFM Journal of Fluid Machinery
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• v.13 no.4
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• pp.11-17
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• 2010

The developed control valves, installed on the hot water distribution manifolds for the floor heating system, consist of the balancing valves and the shut-off valves. The balancing valve was designed to improve the flow control performance and to reduce the noise emitted from the valve by modification of the general V port. The port of the shut-off valve was designed with two ceramic plates, working by rotating upper plate, to improve the duration and to reduce the noise. For the evaluation of the new valves, the flow rate was measured and noise level test was carried out. The test results showed that the error of the flow rate accuracy test for the flow balance of each manifold circuit was less than ${\pm}3%$ and the noise level was less than 35 dB(A).

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2005.10a
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• pp.661-665
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• 2005

The muffler reducing the exhaust noise and vibration from the engine influence on the engine performance. Recently the semi-active muffler was developed and adopted to the actual use in consideration of the cost and technical side for noise and vibration. This study is about the recently developed semi-active muffler. This paper attempt to analyze the dynamic stress field on the gate plate by using the finite element methods. According to the analysis of the Exhaust Variable Valve, its spring has the most influence on its operation compare with effects of other components. The design parameters of the Exhaust Variable Valve such as the spring displacement, diameter, coil number, free angle and so forth were used.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.8 no.2
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• pp.35-43
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• 1999

The paper describes an approach for measuring delivery flow ripple generated by oil hydraulic axial piston pumps. In order to reduce pressure ripple which cause to undesirable noise. vibration and fatigue in hydraulic systems it is indispensible measure a delivery flow ripple from pumps. Since the flow ripple measurement of flow pumps is independent of the dynamic characteristics of the connected hydraulic circuit the measurement of flow ripple is most suitable for pump fluid-borne noise rating. The measurement of flow ripple with high frequencies from axial piston pumps is made by applying the remote instantaneous flow rate measurement method which is based on the dynamic characteristics between pressure and flow rate in hydraulic pipeline. The measured flow ripple waveforms are influenced by the configuration of V-shaped triangular relief groove in the valve plate. It can be seen that the appropriate relief groove in valve plate reduces the pressure and flow ripple amplitude and frequency spectrum for high harmonics.

• Transactions of the Korean Society of Automotive Engineers
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• v.21 no.4
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• pp.188-194
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• 2013

Hydrostatic pumps and motors occupy an important position in hydraulic system. There are a lot of researches on characteristics of hydraulic pumps, but not hydraulic motors. So in order to know the characteristics of hydraulic motors we had this research. The purpose of this study is to derive and analyze the theoretical calculation of hydraulic axial piston motor torque and torque ripples. Then, analyzed the differences between torque ripples with dead place and without dead place on the valve plate, and modeling a hydraulic motor with AMESim software. Finally, theoretical calculation of hydraulic motor torque ripples was verified from the viewpoint of simulation.

• Transactions of the Korean Society of Machine Tool Engineers
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• v.16 no.6
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• pp.117-124
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• 2007

The pressure ripple in most hydraulic systems is the root cause of their noise and vibration. This paper reduced the pressure ripple using side branch hose for an axial piston pump applied to small excavator. First, in calculating open area, a new method using groove area of valve plate is proposed. Simulation model in AMESim environment is developed to verify proposed method, find effective length and diameter of branch hose. Finally, the comparisons with experiment results show that the proposed method is more effective than previous method in reducing the pressure ripple.