• Journal of Mechanical Science and Technology
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• 제18권6호
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• pp.1019-1025
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• 2004

Pressure variation is one of the major sources on noise emission in the axial type oil piston pumps. Therefore, it is necessary that the pressure variation characteristics of the oil hydraulic piston pumps be clarified to reduce the pump noise. Pressure variations in a cylinder at the discharge region and the pump noise were simultaneously measured with discharge pressures and rotational speeds during the pump working. To investigate the effects of the pre-compression and the V-notch in the valve plate, we used the three types of valve plates. In this research, it is clear that the pressure variation characteristics of axial type oil piston pumps is deeply related to the pre-compression and to the V-notch design in valve plate. Therefore, we could reduce the pump noise by using the appropriate pre-compression angle and the notch design that are between the suction port and the discharge port in valve plate.

• 드라이브 ㆍ 컨트롤
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• 제13권4호
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• pp.7-13
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• 2016

This paper presents the meter-out and meter-in speed control characteristics of a pneumatic cylinder with relief valve type cushion device. The piston displacement and velocity are measured to investigate high speed driving performance with variation of the pressure setting in relief valve, air supply pressure, load mass, the supply and exhaust flow rate from the cylinder. Also, the internal pressures and temperatures driving pressure and cushion chamber are measured. The piston displacements and velocities of meter-out and meter-in control are compared experimentally determined data. A comparison experimental data meter-out and meter-in control show that a relief valve type cushion device is suitable for high speed pneumatic cylinders. The desired response characteristics of piston displacement and velocity are satisfactory adjust the pressure setting of a relief valve with varying system parameters such as air supply pressure, load mass and controlled flow rate.

• 한국수소및신에너지학회논문집
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• 제21권2호
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• pp.98-103
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• 2010

In order to develop two-stroke free-piston hydrogen engine to obtain high thermal efficiency and low emission, backfire occurrence have to be prevented. In this research, backfire characteristics are analyzed as functions of the intake valve opening timing and compression chamber pressure under piston by using RICEM (Rapid Intake Compression Expansion Machine) that has reverse uni-flow scavenging. As the result, reverse uni-flow scavenging is advantage about back fire. but, it exists suitable intake valve opening timing and its timing become known that equivalence ratio 1 retard until the piston rises. Also, To rise chamber pressure of lower piston, this does not cause backfire occurs in equivalent ratio 0.6 observed back fire. Therefore, 2cycle hydrogen fueled free-piston engine is undesirable scavenging compression by compressing the piston.

• 한국정밀공학회지
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• 제16권12호
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• pp.31-39
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• 1999

Previous researches and experiments have already verified that the primary noise source of high pressure tandem axial thpe piston pump is fluid-borne noise from the process of oil distribution between the kidney-shaped port and valve plate. So, many researchers have improved pressure gradients and reduced sound levels by applying pre-compression and pre-decompression metering grooves to valve plate. In practice however, the sound level of th high pressure tandem axial type piston pump is still undesirable. This paper testified the effect of pumping phase of the piston on vibration and noise of th high pressure tandem axial type piston pump on the best of theoretical research in $this^(1)$. Therefore considering the pumping phase of the piston when assembling the tandem axial type piston pump, it is possible to reduce 1.5~2[dB]of sound level.

• 대한기계학회논문집A
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• 제27권7호
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• pp.1087-1094
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• 2003

The piston slap phenomenon occurs when the piston collides with the internal wall of the cylinder. Impact force caused by piston slap is one of the major mechanical noise sources in reciprocating compressors. In response to public demand, strict regulations are increasingly being imposed on the allowable noise level which is caused mostly by household electric appliances. In this paper, forces acting on piston by considering the dynamic behavior of suction and discharge valves are analytically calculated and the piston slap caused by the piston secondary motion is investigated by the finite element method.

• 드라이브 ㆍ 컨트롤
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• 제13권3호
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• pp.39-46
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• 2016

Flow and pressure ripple in swash plate type piston pumps is largely dependent on the design of notches(silencing grooves) in the valve plate. In uni-directional pumps, the basic design concept for notches in the valve plate could be said to be established. It is easily deduced that the design concept for notches in uni-directional pumps can not be simply applied to bi-directional pumps requested for EHA(electric hydrostatic actuators). To carry out systematic research on technological issues regarding notch applications to bi-directional piston pumps, five notch designs are devised. The effects of the notch designs on the characteristics of the pump are investigated by numerical simulations and experiments. Through this study, basic concepts about notch design for bi-directional piston pumps are suggested.

• 한국수소및신에너지학회논문집
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• 제19권3호
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• pp.182-188
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• 2008

In order to improve scavenging performance of free piston hydrogen fueled engine, this study estimate compatibility of uni-flow scavenging. The scavenging flow characteristics in the cylinder is investigated by flow visualization and PIV method. Consequently it has been found that the scavenging performance decreased with abnormal expansion of piston and delay of the exhaust valve opening timing. And the scavenging performance of exhaust valve located center in cylinder head is better than that of exhaust valve located side in cylinder head.

• 한국정밀공학회지
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• 제18권1호
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• pp.74-81
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• 2001

Dynamic pressure is one of the major sources on noise emission in oil hydraulic piston pump. This paper reports an experimental study of dynamic pressure characteristics in the cylinder bore of oil hydraulic piston pump. We experimently measured dynamic pressure at BDC with delivery pressure, rotational speed and oil temperature. Because the V-grooves at the ends of the kidney ports with three types valve plates. We hope this paper help to design of the valve plate in oil hydraulic piston pump.

• 유공압시스템학회논문집
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• 제1권2호
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• pp.8-14
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• 2004

Abstract: In the oil hydraulic piston pumps the clearance between the valve plate and cylinder block plays an important role for volumetric and overall efficiency. Thus, adequate lubricational fluid film is needed for the interface. In this study, fluid film thickness is measured by a gap sensor and a slip ring under operational conditions to observe the behavior of the lubrication mechanism in detail. To investigate the effect according to the valve plate types in view of the fluid film, three different types were designed. Leakage flow rate and shaft torque were also measured to clarify the effect according to the valve plate types. A broad range of experiments were conducted to provide reasonable data on the effect of fluid film. In this experiments two main parameters were found, of which the one is the discharge pressure and the other is valve plate geometry. As a result, we found that the spherical valve plate could get more stable fluid film thickness, maintain good efficiency for high pressure range than the other types.

• 한국생산제조학회지
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• 제24권2호
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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.