• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.31 no.4
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• pp.402-412
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• 1995

A new energy conversion system which converts wind energy directly to heat instead of transforming it to electric power beforehand is suggested in this study. The new energy conversion system is composed of two big parts divided by their functions. One of them is a wind turbine part, and another is the heat energy conversion part. The object of this study is confined only to the heat energy conversion part, so the wind turbine is replaced with an electric motor for the convenience of experiment. In the experimental process, pressure difference at the hydraulic pump, revolution speed of the hydraulic pump, temperature at a few points on the oil circuit and the water circuit are measured at time intervals of five minutes. And integral values of input energy to the system and stored energy in the system is investigated.

• Journal of the Institute of Electronics and Information Engineers
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• v.51 no.2
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• pp.163-167
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• 2014

To prove the vibration and speed error problems caused by the nonlinear friction characteristics and load variation of the hydraulic system, a PID speed controller and a load compensation controller for the hydraulic inverter-fed elevator are proposed. The load compensation controller is composed by the PI controller and the speed controller is composed by the PID controller. The P,I and D gains of the control parameters are obtained by the frequency response of system transfer function. The Effectiveness of the proposed controller are shown by experimental results, which the proposed controller yields robustness with load variations and stable and good speed and acceleration responses with less oscillations.

• Proceedings of the Korean Society for Agricultural Machinery Conference
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• 2017.04a
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• pp.6-6
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• 2017

농용트랙터의 전방차축 현가장치는 노면으로부터 발생하는 진동의 영향을 줄일 수 있기 때문에 트랙터의 대형화, 고속화의 추세에 맞춰서 승차감과 조향감을 향상시키는 데 중요한 역할을 한다. 전방차축의 현가장치는 트랙터의 차체 무게에 의한 부하가 크고, 또한 유압 펌프를 비롯한 유압시스템이 존재하기 때문에 유압식 회로로 구성하는 것이 바람직하다. 하지만, 현가장치의 유압회로를 개발하는데 있어서 실제 시스템을 구성하여 실제 실험을 통한 개발에는 비용과 시간이 많이 필요하다. 본 연구에서는 유압식 전방차축 현가장치에 필요한 유압회로부 개발을 위하여 시뮬레이션 기법과 요인시험 장치를 이용 적정 유압회로를 설계하고자 하였다. 이를 위하여 어큐뮬레이터, 가변 오리피스, 릴리프밸브, 체크밸브 등으로 구성된 유압 현가요인 시험 장치를 설계 제작하였으며, 현가 부품인 실린더 행정, 속도, 전달되는 힘을 측정하고, 유압 해석 프로그램인 SimulationX를 이용 구성된 유압회로 부품에 측정값을 입력하여 실제 조건과 유사한 동특성을 나타내는 전방차축 현가요인 시뮬레이션 모델을 개발하였다. 개발된 시뮬레이션 모델을 이용하여 실제 시험조건과 같은 가진 조건을 부여하여 개발 현가장치의 특성 값 변동에 따른 현가 성능을 구명하였다. 이를 위해 시뮬레이션 상에서 120 마력 트랙터 무게의 50% 수준에 해당하는 2,000 kg의 부하가 존재하는 상태에서 현가장치의 유/무에 따른, 감쇠 계수의 변화에 따른 스프링상 질량의 RMS 가속도를 비교하였다. 입력 가진으로는 1 Hz, 4 Hz, 8 Hz의 진동수에 각각 10 mm, 6.4 mm, 3.2 mm의 진폭을 인가하였다. 시뮬레이션 결과, 1 Hz에서는 현가장치가 있는 경우 최대 55.9% 개선되었고, 4 Hz에서는 최대 3.9 % 개선되었고, 8 Hz에서는 최대 61.4%까지 개선되었다. 이는 4 Hz의 경우에는 2,000 kg의 부하에 해당하는 고유 진동수 대역에 해당하기 때문에 그 감쇠 효과가 없는 것으로 나타났다. 하지만, 다른 주파수 대역에서는 현가장치가 효과적으로 작동하는 것을 나타내었다. 설계한 전방차축 현가 유압회로부를 시뮬레이션을 통하여 분석한 결과, RMS 가속도의 개선이 명확하게 이루어지는 것을 확인하였으며 입력 주파수 변화에 따라 감쇠특성도 나타나는 것을 확인하였다. 추후 연구에는 설계한 유압회로부와 관련 부품을 설계 제작하여 실제 트랙터에 장착 그 성능을 검증할 예정이며, 노면조건에 따라 감쇠성능을 유지하기 위한 반능동형 또는 적응형 현가장치 제어 기술을 적용하여 개선된 현가성능을 확보하기 위한 연구를 수행할 예정이다.

• Journal of Ocean Engineering and Technology
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• v.23 no.3
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• pp.30-34
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• 2009

Oil hydraulic piston pumps are being extensively used in the world, because of simple design, light weight and effective cost etc. An oil hydraulic pump is likely to have serious problems of high leakage, friction and low energy efficiency according to large time use. In the oil hydraulic piston pumps the clearance between the valve block and piston plays an important role for volumetric and overall efficiency. In this paper, the wear property of the SACM645 material used the hydraulic piston pump has been work out by experimentation with variable heat treatment. To investigate the effect according to the piston surface condition, seven different types specimen were prepared. From the wear test results, induction hardening and nitration were definitely superior to the others. On the whole, nitration was estimated for high strength material to wear resistance.

• Transactions of The Korea Fluid Power Systems Society
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• v.7 no.2
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• pp.13-18
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• 2010

To improve the performance of the bent-axis type axial piston pump driven by the tapered piston, it is necessary to know the driving characteristics and mechanism of the tapered piston and the cylinder block. Since each piston not only rotates on its axis and reciprocates in the cylinder bore, but also revolves around the axis of the driving shaft, it is difficult to analyze the driving mechanism theoretically. The theoretical mechanism for the bent-axis type axial piston pump is studied by using the geometrical method. The driving range of the tapered piston is determined by theoretical equations. The experimental results show that the cylinder block is driven by one tapered piston in a limited range and the core parameters such as driving factor of the piston and the ahead delay angle influenced performance of the bent-axis type axial piston pump.

• Transactions of The Korea Fluid Power Systems Society
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• v.5 no.2
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• pp.1-7
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• 2008

To improve the performance of the bent axis type axial piston pump driven by the tapered piston, it is necessary to know the driving characteristics and mechanism of the tapered piston and the cylinder block. Since each piston not only rotates on its axis and reciprocates in the cylinder bore, but also revolves around the axis of the driving shaft, it is difficult to analyze the driving mechanism theoretically. The theoretical mechanism far the bent axis type axial piston pump is studied by using the geometrical method. The driving range of the tapered piston is determined by theoretical equations. The results show that the cylinder block is driven by one tapered piston in a limited range and the core parameters such as driving factor of the piston and the ahead delay angle influenced performance of the bent axis type axial piston pump.

• Transactions of The Korea Fluid Power Systems Society
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• v.1 no.3
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• pp.7-13
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• 2004

The hydraulic pump for a Electro-hydrostatic Actuator for aircrafts should be able to quickly feed large volume of oil into hydraulic cylinder in order to reduce the response time. On the other hand, it should be also able to precisely dispense small amount of oil by low-speed operation so that the steady state position control error of the EHA can be accurately compensated. This paper is focused on the investigation how the plasma coating surface treatment of cylinder barrel with CrSiN can contribute to the reduction of low-speed friction torque of a bent-axis type piston pump. The results showed that the reduction of the friction torque was not remarkable, but that the anti-wear characteristics of the CrSiN-coated cylinder barrel were much better that those of the original one.

• Journal of Drive and Control
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• v.14 no.2
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• pp.37-44
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• 2017

In this study, in order to prevent cavitation in a variable swash-plate type hydraulic pump, a basic model impeller has been applied to a new pump, and the impeller shape has been optimized through flow analysis. Based on the analysis results, we could propose an impeller shape with high efficiency and low possibility of cavitation in comparison with the basic model. The simplification of the basic shape of the impeller of the hydraulic pump was performed in three parts in the order of hub shape, wing, and curvature, and eight design parameters were defined to satisfy the design requirement. Compared with the initial model of the impeller, when the differential pressure of the optimum model increased, the efficiency was improved. It achieved the goal of design improvement because cavitation did not occur under the rated operating conditions.

• 한국기계연구소 소보
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• s.18
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• pp.75-85
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• 1988

The distributor for hydraulic pumps or motors, particularly radial piston motors, include rotary member which has equally both surface shape for dynamic balance and two fixed members, located in both side of rotary member, which have equal surface shape for dynamic balance and circular ring which use to retain predetermined clearance between two fixed members. Rotary member must have valve part for flow-distribution and can have hydrostatic bearing for excellently dynamic balance. At least two annular steps located on said pressure plate which use in compensation of bolt expansion.

• Proceedings of the KSME Conference
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• 2003.11a
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• pp.1548-1553
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• 2003

The design of a high speed axial piston pump for hydrostatic transmission systems requires specific understanding on where and how much its internal frictional and flow losses are generated. In this study, the frictional loss of a bentaxis type hydraulic piston pump was analyzed in order to find out which design factors influence the mechanical efficiency most significantly. To this end, the friction coefficients of the sliding components were experimentally identified by a specially constructed tribometer. Applying them to the three-dimensional dynamic model of the pump presented by Doh and Hong [1], the friction torques generated by the sliding components such as piston head , bearing and valve plate were theoretically computed. The accuracy of the computed results was confirmed by the comparison with the experimentally measured mechanical efficiency. In this paper, it is shown that the viscous friction on the valve plate and the drive shaft bearing is the primary sources of the frictional losses of the bent-axis type pump, while the friction forces on the piston contribute to them only slightly.