• Title/Summary/Keyword: piston effect

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The study on the friction characteristics of spherical hydrostatic bearing for hydraulic piston motor (유압모터 구면 정압베어링의 마찰특성에 관한 연구)

  • 함영복;최영호;김성동
    • Proceedings of the Korean Society of Precision Engineering Conference
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    • 2001.04a
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    • pp.647-650
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    • 2001
  • In case of bent axis type axial piston hydraulic pump or motor, hydrostatic bearing used to achieve the lubrication effect on the mechanical sliding contact areas between the following pairs ; piston shoe and swash plate, valve plate and cylinder block, piston and cylinder block, etc. In this research, we designed two pairs of spherical ball joint in witch connecting rod piston end. The one is not hydrostatic bearing, the other is designed with spherical hydrostatic bearing in point of view minimum pumping power loss. By varying supply pressure on the piston, we can know that it is possible to reduce the friction torque by using hydrostatic bearing designed one. Finally, by comparing the results of driving torque between the two models, it was verified that the spherical hydrostatic bearing is well designed.

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Study of Oil Jet Effect on the Temperature of Piston Head (피스톤 헤드 온도에 오일 제트가 미치는 영향에 대한 연구)

  • Min, Sunki
    • Journal of the Korea Academia-Industrial cooperation Society
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    • v.19 no.11
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    • pp.536-540
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    • 2018
  • As the performance of engines improves, the temperature of engines is increasing, resulting in a high piston temperature. An excessively high piston temperature may result in torque drop or engine failure. An oil jet is used to reduce the piston temperature. In this study, to monitor the effect of oil jet, a templug was used to measure the piston temperature. A templug is a kind of sensor and the hardness of the templug changes according to the piston temperature. Using a templug, the maximum temperature of the piston was measured with and without an oil jet. The piston temperature was lowered using the oil jet. The highest temperature region changed from the center crown to the front/rear area. In addition, the temperature difference between the highest and lowest regions became smaller.

Study of Pressure and Flux Pulsation to Design Optimum Valve-Plate Notch and Pulsation-Variables Analysis of Swash-Plate-Type Piston Pump (가변 사판식 피스톤펌프의 맥동 변수 분석 및 최적 밸브플레이트 노치 설계를 위한 압력 및 유량맥동에 관한 연구)

  • Bae, Jun-Hyeong;Chung, Won-Jee;Jang, Jun-Ho;Yoon, Young-Hwan;Jeon, Ju-Yeol
    • Journal of the Korean Society of Manufacturing Technology Engineers
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    • v.24 no.2
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    • pp.244-250
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    • 2015
  • We propose a simulation technique to estimate the reduction effect of the pressure/flow pulsation by analysis of the pulsation variables and notch shape of the valve plate of a swash-plate-type variable piston pump. First, using SimulationX$^{(R)}$, we perform a theoretical kinematic analysis according to the variable swash-plate angle and rotational velocity in order to design a single-piston pump. In designing the notch shape of the valve plate of the swash-plate-type variable piston pump as one of the pulsation variables, we investigate the effect of the pulsation by comparing two notch types (circular type and V type). Then, we extend our analysis to a nine-piston pump model. This paper not only confirms the effect of the pressure/flow pulsation according to pulsation variables but can also be applied to the development of a SimulationX$^{(R)}$-based simulation technique for notch-shape optimization for a swash-plate-type variable piston pump.

A Study on Pressure Ripple Characteristics in Bent-Axis Type Oil Hydraulic Piston Pump (사축식 유압 피스톤 펌프의 압력 맥동 특성에 관한 연구)

  • Cho, I.S.;Shin, C.G.;Jung, J.Y.
    • Tribology and Lubricants
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    • v.27 no.4
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    • pp.218-223
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    • 2011
  • To improve the performance of a bent-axis type axial piston pump driven by the tapered pistons, it is necessary to know the pressure ripple characteristics. The purpose of this paper is to understand the effect on the pressure ripple characteristics and the prediction by comparing experimental and theoretical results. The simulation model of the bent-axis type axial piston pump is developed in the AMESim environment using the geometrical dimension and the driving mechanism of the piston pump. The results can be obtained to predict the performance characteristics of the bent-axis type axial piston pump.

A Numerical investigation of Oil Jet in an Engine Piston (피스톤 냉각용 Oil Jet 유동 수치해석)

  • Li, Li;Kwon, Ji-Hyuk;Jung, Ho-Yun;Choi, Yoon-Hwan;Lee, Yeon-Won
    • Proceedings of the Korean Society of Marine Engineers Conference
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    • 2005.11a
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    • pp.33-34
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    • 2005
  • The internal state of an automotive engine is very severe. A piston exposes burnt gas of over $2000^{\circ}$ nd is shocked by high pressure at the time of explosion. Furthermore strong friction is caused by high speed motion. A study on the cooling of the piston requires because the cooling and lubrication of the piston has an effect on the life and efficiency of engine directly. The previous system of oil jet cooled only the bottom of the piston. In order to improve the cooling efficiency, the oil gallery is made inside the piston, and oil flows into the oil gallery. The flow rate of oil at the entrance of oil gallery is important because of the cooling efficiency. The purpose of this study is the investigation of fluid flow characteristics of oil jet and flow rate into the oil gallery.

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A Study on Effects of Piston Pumping Phase on Vibration and Noises of Tandem Swash Plate Type Axial Piston Pump(1) (피스톤 펌핑 위상이 텐덤형 사판식 액셜 피스톤 펌프의 진동 ${\cdot}$ 소음에 미치는 영향에 관한 연구(1))

  • Park, Sung-Hwan;Lee, Jin-Kul
    • Journal of the Korean Society for Precision Engineering
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    • v.16 no.5 s.98
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    • pp.74-82
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    • 1999
  • To meet the needs of the hydraulic excavator of large capacity, tandem axial type piston pump which is high pressure and high speed have been developed. But inevitably we can not help facing the problem of noise at that time. In order to reduce the noise of this pump, many researchers have been studying the problem of oil distribution manner. But they are not interested in the symmetric structure of tandem type pump. So, focusing on the symmetric structure of tandem type pump, this paper analyzed unbalanced force developed in the pump chamber and verified the effect of the pumping phase of the piston on vibration and noise of the tandem axial type piston pump theoretically.

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A measurement of piston surface temperature by using instantaneous temperature measuring probe (순간온도 계측 프로브를 사용한 피스턴 표면 온도측정)

  • 이성열;이영조
    • Journal of the korean Society of Automotive Engineers
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    • v.12 no.6
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    • pp.60-66
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    • 1990
  • In order to measure the piston surface temperature and heat flux, autors have developed the measuring system with an instantaneous temperature probe. Such the instantaneous temperature probes were embodied into the top of piston for measurement and L-link system, designed to fit the test engine, extracts the thermocouple wires from the piston outside of engine employing a mechanical linkage. Then the instantaneous surface temperature was measured to calculate the heat flux flowing into the top surface of piston in a spark ignition engine. As a result, the following phenomena have been obtained through the study. 1) It is found that the time response and durability of temperature probe with a thin film thickness 10um and mechanical linkage with thermocouple wire extraction is sufficient at this experiment. 2) For the quantitative effect of variation in engine speed, the temperature swing and heat flux on the top of piston increase with increasing the engine speed. 3) It is proved that the temperature swing and heat flux decrease with distance from spark plug.

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A Kinematic Analysis on Piston Rod Mechanism in Swashplate Type Hydraulic Axial Piston Motor/Pump Using Constant Velocity Joint (등속조인트를 적용한 사판식 유압 모터/점프의 로드형 피스톤에 대한 운동해석)

  • Kim K.H.;Kim S.D.;Ham Y.B.;Lee J.C.
    • Transactions of The Korea Fluid Power Systems Society
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    • v.2 no.1
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    • pp.1-8
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    • 2005
  • Recently, swash plate type hydraulic axial piston motors/pumps are being extensively used in the world, because of simple design, light weight and effective cost. Structural problem of the swash plate type motor/pump is that tilting angle of swash plate should be limited to relatively small value and lateral farce on pistons has an undesirable effect in reciprocating motion. To solve these problems, piston rod mechanism, which is commonly used in bent axis type motor/pump, is considered to be applied to the swash plate type motor/pump. In this paper, kinematic analysis was done on the piston rod mechanism. A series of formula were derived and numerical calculations were done for a set of motor parameters.

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A Study on Characteristics of a Compensator System for Swash Plate Type Axial Piston Pump (사판식 액시얼 피스톤 펌프의 가변용량 시스템의 특성에 관한 연구)

  • Kim, Shin;Oh, Suk-Hyung;Jung, Jae-Youn
    • Tribology and Lubricants
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    • v.14 no.4
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    • pp.15-22
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    • 1998
  • Recently, the importance of variable displacement piston pump is increasing in industrial world. Especially, most consumers require various range of pressures and flow rates. Pressure compensator is a system controlling flow rate in piston pump at low cost and, therefore, satisfies the need of consumers. However, the system has serious problems, such as response and leakage. The response and leakage are affected by clearance between actuator piston and cylinder, roughness of surface, and spool overlap. In this paper, these effects are investigated experimentally, and optimal clearance and chamfer is obtained. While diameter of cylinder is fixed and diameter of actuator piston is changed in this experiment, response and leakage are measured. Also parameters such as roughness and processing accuracy are changed for piston of fixed clearance. Experimental setup modelled into several parts of actuator piston, cylinder, spool, and swash plate. Input pressure is changed by function generator and proportional valve. The result of this experiment shows that leakage increases very much in proportion to the increase of clearance, and especially leakage occurs enormously when clearance is more than 0.002. The response is not good because as clearance increases leakage increases and as clearance decreases viscous damping effect increases. Accordingly, it is found out that optimal clearance range exists for tile response, within about 0.0012∼0.0014, at this time. Futhermore, the better roughness and geometrical accuracy of actuator piston are, the smaller are leakage and friction. The paper informs that response and leakage are influenced by and geometrical accuracy of actuator piston, roughness of surface, and the clearance between actuator piston and cylinder, and that optimal design of actuator piston in the pressure compensator is possible.

The Investigations of the Characteristics of Unsteady Piston Temperature Using Radiotracers-The Effect of Piston Ring Gap Position and Blow By Gas (방사성 추적자를 이용한 피스톤의 비정상 온도 특성에 관한 연구 -피스톤 링 갭 위치와 블로우 바이 가스의 영향-)

  • 김중수;김승일;민병순;박승일;오대윤;정성희;진준하
    • Transactions of the Korean Society of Automotive Engineers
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    • v.8 no.4
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    • pp.1-9
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    • 2000
  • To understand the thermal characteristics around the piston ring gap ring gap positions and piston temperatures are measured simultaneously. The locations of piston ring gap are measured by the radio-tracer method and piston temperature are measured by a K-type thermocouple and scissors type linkage system. From these experiments following facts are clarified. Piston temperatures fluctuate according to the piston ring rotation. And the temperature fluctuation is mainly affected by top ring gap position irrelevant to the second ring fop position. If the top ring gap position increases and the temperature of top ring groove shows maximum value when top rin gap position coincide with temperature measuring point. The maximum amplitude of temperature fluctuation which is proportional to the blow by gas rate is around 12-15$^{\circ}C$.

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