• 한국산학기술학회논문지
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• 제20권12호
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• pp.125-130
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• 2019

가스스프링은 그 사용 목적에 따라 다양한 설계가 가능하여 많은 분야에서 사용되고 있고 그 사용량도 계속하여 증가하고 있다. 본 연구에서는 가스스프링을 압축할 경우 반발력을 감소시키고 피스톤이 복귀할 때 저속으로 복귀할 수 있도록 설계된, 오리피스 홀을 갖는 피스톤의 가스스프링 실린더 내부에서의 거동을 전산유체해석을 이용하여 예측해 보았다. 해석결과 가스스프링 내의 초기 가스압을 일정 수준 이상으로 증가시키면 피스톤의 복귀속도가 시간에 따라 감소하지 않고 일정하게 유지됨을 알 수 있었다. 오리피스 홀 사이즈가 피스톤 복귀속도에 미치는 영향을 해석을 통해 알아보았다. 오리피스 홀 사이즈를 줄이게 되면 피스톤 양단의 압력 차가 증가하여 피스톤 전진속도가 감소하게 되고 보다 등속으로 운동하게 됨을 알 수 있었다. 마지막으로 피스톤의 속도가 일정하다는 가정에서 초기 가스압에 따른 피스톤의 복귀속도를 이론적인 방법으로 도출하였고, 여러 초기 가스압에 대한 해석 결과와 비교하였다. 비교결과 이론적으로 도출한 해와 해석결과로부터 얻어진 결과 값이 거의 일치함을 알 수 있었다.

• 유공압시스템학회:학술대회논문집
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• 유공압시스템학회 2010년도 춘계학술대회
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• pp.99-104
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• 2010

Nonlinear seal friction in pneumatic cylinders can impede the performance of pneumatic systems designed for high precision positioning with favorable high speed actuation. The behaviour of an elastomeric piston seal in high speed pneumatic cylinders is analysed by nonlinear finite element analysis using ABAQUS. The contact pressures, stress and strain distributions and frictional forces of the piston seal are simulated with variation of interference fits, supply pressures, friction coefficients and piston rod velocities. The nonlinear finite element model of the piston seal is used to predict deformation of a seal, friction force and contact pressure distributions.

• KSTLE International Journal
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• 제3권1호
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• pp.1-6
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• 2002

The purpose of this paper is to investigate the effects of design parameters on the friction loss in piston skirt. An analytical model to describe the friction characteristics of piston skirt has been presented, which is based on the secondary motion of piston and mixed lubrication theory, It could be shown that the skirt friction closely depends on the side force acted on the piston pin. The side force is inf1uenced by cylinder pressure at low engine speed, but by inertia force at high engine speed. The usage of extensive skirt area and low weight piston is effective to reduce the friction loss at high speed. The low viscosity oil considerably decreases viscous friction as engine speed increases, but it increases boundary friction at low engine speed. From the parametric study, it is found that the skirt axial profile is the most important design parameter related to the reduction of skirt friction.

• 한국군사과학기술학회지
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• 제3권2호
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• pp.231-243
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• 2000

This paper describes a simulation of secondary motion of piston assemblies using PISDYN by Ricardo. Motions of the piston, pin, rod and skirt are separately calculated, by integrating equations of motion for individual components and dynamic degrees of freedom. The effects of engine speed at full load and pin offsets on the piston assembly secondary motions, forces and friction were investigated in parametric study for 4-cylinder gasoline engine. Results show that lateral displacement and friction loss of the piston increase as a function of engine speed. The lateral motion of the piston is affected by the change in pin offset. The minimum friction loss for the condition of 4800rpm WOT occurs at a pin offset of 1.6mm.

• 대한기계학회논문집
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• 제18권3호
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• pp.793-804
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• 1994

Turbulence intensity caused by piston movement was almost as same tendency as the piston speed. The turbulence intensity was increased from 0.39m/s to 0.79m/s when mean piston speed increased from 2.33m/s to 4.67m/s. In this case the maximum turbulence intensity caused by piston speed was decreased about 82 percent near the top dead center at the end of compression stroke. The maximum turbulence intensity was created from 12m/s to 22m/s when inlet flow velocity was increased from 22m/s to 45m/s. Also turbulence intensity caused by inlet flow velocity was linearly increased from 0.97m/s at top dead center at the end of compression stroke. The ratio of turbulence intensity and mean inlet flow velocity was about 3 percent for inlet flow velocity.

• KSTLE International Journal
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• 제10권1_2호
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• pp.37-42
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• 2009

This paper presents the characteristics of volumetric efficiency of an axial type piston pump considering the piston tilting. A numerical analysis is carried out in order to obtain the pressure distribution considering the fluid inertia at the notch of the valve plate. The cylinder pressure variation and the discharge flow rate are measured experimentally according to the operating conditions such as supply pressure, rotational speed, and viscosity of the working fluid by using the cam type test apparatus. Leakage is also measured considering piston tilting. The characteristics of the volumetric efficiency are analyzed with respect to various operating conditions and leakage is also analyzed according to the piston tilting angle. Results are applicable to improve the design of an axial type piston pump.

• 한국산학기술학회논문지
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• 제19권2호
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• pp.9-14
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• 2018

가스스프링은 가스가 압축될 때 가지게 되는 압력을 스프링과 같이 사용하는 형태로, 광범위한 산업분야에 사용되고 있고 그 수요 또한 증가하고 있다. 이 가스스프링은 압축 스프링과 인장 스프링으로 나뉠 수 가 있는데, 압축 스프링과 달리인장 스프링의 경우는 피스톤 속도 제어에 대한 연구가 많이 이루어지지 않았다. 본 연구에서는 2중 실린더 구조를 갖는 인장 가스스프링에서의 압력 손실 계산을 통하여 피스톤 반발압력의 크기를 이론적으로 예측하였고, 피스톤과 실린더 사이의 마찰이 작은 경우와 큰 경우에 대하여 피스톤의 실제 거동을 모사해 보았다. 수치해석을 위해서는 유동해석분야에서 가장 널리 사용되고 있는 FLUENT를 이용하였고, 피스톤의 거동을 모사하기 위하여 FLUENT에서 제공하는 6-DOF 모델과 사용자정의함수(User Defined Function)를 사용하였다. 격자는 Layering 기법만으로도 Dynamic mesh가 성공적으로 구현되도록 피스톤 전후의 유동영역을 따로 분할하여 다른 형태의 격자를 생성하였다. 해석 결과 두 경우 다 최종적으로는 목표로 하는 속도로 피스톤이 복귀하는 결과를 보였으나, 최종 속도에 도달하는 과정에서 다른 차이를 보였다.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 1995년도 추계학술대회 논문집
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• pp.985-990
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• 1995

Recently, the development of high speed and high precision NC-lathe for piston head machining is needed for the complexity and diversity of the piston head shape used in automobile reciprocating engine. THe piston head has many complex shapes in the aspect of fuel economy, such as ovality, profile, double ovality and recess. Among them, for the maching of the over shape of 0.1~1mm the cutting tool should move periodically symchronized with the rotation of piston workpiece. The cutting tool feeed system must have high positioning accuracy for the precise machining, high speed for the fast maching and high dynamic stiffness for the cutting force. The linear brushless DC motor is used for satisfying these coditions. The ballbush guide and supporting guide using turcite is used for the guidance of the feed drive system. Linear encoder, digital servo ampllifer and controller are used for driving the motor. THis paper presents the design and simulation of the new tool feed system for noncircular machining.

• 드라이브 ㆍ 컨트롤
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• 제9권1호
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• pp.18-24
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• 2012

The paper deals with the design of a new low-friction seal for a pneumatic cylinder with high speed actuation. The seal performance with variation of the cross sections in piston seals with elastomeric material was investigated to minimize the friction forces using ABAQUS. The contact stress and strain distributions and frictional forces of the piston seals were investigated with variation of interference fits, supply pressures and friction coefficients. To develop adequate and productive procedures, the finite element models of the piston seals were created and nonlinear analysis of a seal design was conducted in order to build further knowledge and understanding of the seal's performance characteristics.

• 오토저널
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• 제9권3호
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• pp.55-65
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• 1987

This paper presents the method of piston temperature measurement and its data under various engine operating conditions. In case of high speed engine, the thermocouple wires must be guided from moving piston to stationary place with carful attention. for this purpose L_LINK SYSTEM was made and assembled to a passenger car engine on the test bench and then the piston temperature was successfully measured. The tested engine speed ranged from 1,000 to 4,000 rpm with 500 rpm increments. Not only the effects of engine speed and load on the piston temperature but those of spark timing, detonation, coolant temperature and Reynolds number based on inlet air condition were studied form the measurement obtained by this L_LINK SYSTEM.