• Tribology and Lubricants
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• 제20권4호
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• pp.209-217
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• 2004

Lubrication characteristics between a cylinder block and a valve plate for high speed bent-axis type hydraulic pump play an important role in volumetric efficiency and durability of pump. In this paper, a finite element method is presented for the computation of the pressure distribution between a cylinder block and a valve plate for high speed bent-axis type hydraulic pump. Also, a Runge-Kutta method is applied to simulate the cylinder block dynamics of three-degrees of freedom motion. From the results of computation, we can draw two major conclusions. One is related to the fluid film characteristics between a cylinder block and a valve plate and the other is related to the average leakage that is determined by the pressure gradient and the clearance near the discharge port. The numerical results of cylinder block dynamics were compared with the experimental results using eddy-current type gap sensors those are fixed at a pump housing.

• 한국윤활학회:학술대회논문집
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• 한국윤활학회 2004년도 학술대회지
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• pp.99-107
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• 2004

Lubrication characteristics between a cylinder block and a valve plate for high speed bent-axis type hydraulic pump play an important role in volumetric efficiency and durability of pump. In this paper, a finite element method is presented for the computation of the pressure distribution between a cylinder block and a valve plate for high speed bent-axis type hydraulic pump. Also, a Runge-Kutta method is applied to simulate the cylinder block dynamics of three-degrees of freedom motion. From the results of computation, we can draw two major conclusions. One is related to the fluid film characteristics between a cylinder block and a valve plate and the other is related to the average leakage that is determined by the pressure gradient and the clearance near the discharge port. The numerical results of cylinder block dynamics were compared with the experimental results using eddy-current type gap sensors those are fixed at a pump housing.

• Tribology and Lubricants
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• 제14권4호
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• pp.23-28
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• 1998

To increase the efficiency of the hydraulic axial piston pumps, it is need to know the various characteristics in the sliding contact parts of them. Especially, friction characteristics between the cylinder block and the valve plate in the hydraulic axial piston pumps plays an important role to high power density. In this paper, we tried to clarify friction characteristics between the cylinder block and the spherical valve plate in bent-axis-type axial piston pump in experimentally. Results are arranged as follow; (1) friction torque between the cylinder block and the spherical valve plate has a proportional relation to weight or rotational speed, and is strongly affected by temperature. (2) Friction torque strongly depends on force balance ratio in valve plate. (3) In this experiment, lubrication condition between the cylinder block and the spherical valve plate is under hydrodynamic lubrication.

• 한국기계가공학회지
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• 제3권1호
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• pp.90-94
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• 2004

Generally, a hydraulic cylinder block which is one of a vehicle parts that plays Important role in excavator power transmission, has copper alloy separation phenomenon by sliding motion between metals in high pressure condition. In this paper, to solve this problem, the interfacial reaction layer of Fe-Cu With SCM440 and copper alloy is studied through the melting method. As the result of this study, it is found that the interfacial reaction layer of $1{\mu}m$ created in the interface of Fe-Cu which has very strong physical bonding. It has been also confirmed that the melting method can improve life of the hydraulic cylinder block.

• 한국윤활학회:학술대회논문집
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• 한국윤활학회 1998년도 제27회 춘계학술대회
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• pp.249-255
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• 1998

To increase the efficiency of the hydraulic axial piston pumps, we have to know the various characteristics in the sliding parts of them. Especially, friction characteristics between the cylinder block and the valve plate in the hydraulic axial piston pumps plays an important role to high power density. In this paper, we tried to clarify friction characteristics between the cylinder block and the spherical valve plate in bent-axis-type axial piston pump by using of modeling experiment. The main results of this study are these; (1) Friction torque between the cylinder block and the spherical valve plate has a proportional relation to weight or rotational speed, and is strongly affected by temperature. (2) Friction torque strongly depends on force balance ratio. (3) In this experiment, lubrication condition between the cylinder block and the spherical valve plate is under hydrodynamic lubrication.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 2005년도 춘계학술대회 논문집
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• pp.258-261
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• 2005

In this paper, experimental and numerical attempts are made fur application of powder metallurgy forming technology to making the cylinder block of a hydraulic pump of which height reaches nearly 70 mm and is ten times larger than the wall thickness. Leak tests with several compositions are carried out in order to find allowable powder composition to prevent leak under high pressure in service and CAE techniques are applied to finding proper process conditions. Through the research, the possibility of the powder formed cylinder block that is very competitive from the point of both cost and mass production has been shown, even though its thickness exceeds the recommended limit considering heterogeneous density distribution caused by the friction between a powder compact and dies.

• KSTLE International Journal
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• 제8권2호
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• pp.29-34
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• 2007

Recently, requirements relating to performance, environment and noise in the oil hydraulic system of the heavy construction equipment have been reinforced continuously. In order to solve these technical trends, studies on the system compactness, operation under high pressure and great rotating speed, electronic control, substitute oil, and noise reduction have been progressed briskly. Among these recent studies, the system operation under high pressure is quite difficult to carry into effect due to mechanical limitations; that is, for realizing the system operation in the hydraulic pump under high pressure, the improvements or innovations on the design techniques, the manufacturing techniques, and the lubrication performance of the working oil are required. Accordingly, in this study, the stress distribution and optimum design factors under the maximum pressure were discussed by using stress analysis on the cylinder block of the hydraulic axial piston pump, which is one of the most important relative sliding regions.

• Journal of Mechanical Science and Technology
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• 제19권2호
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• pp.655-663
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• 2005

Tribological characteristics in the sliding parts of oil hydraulic piston pumps are very important in increasing overall efficiency. In this study, the fluid film between the valve plate and the cylinder block was measured by using a gap sensor and the mercury-cell slip ring unit under real working conditions. To investigate the effect of the valve shape, we designed three valve plates each having a different shape. One of the valve plates was without bearing pad, another valve plate had bearing pad and the last valve plate was a spherical valve plate. It was noted that these three valve plates observed different aspects of the fluid film characteristics between the cylinder block and the valve plate. The leakage flow rates and the shaft torque were also investigated in order to clarify the performance difference between these three types of valve plates. From the results of this study, we found that the spherical valve plate estimated good fluid film patterns and good performance more than the other valve plates in oil hydraulic axial piston pumps.

• 한국산학기술학회논문지
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• 제16권4호
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• pp.2424-2429
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• 2015

유압 피스톤 펌프에서, 고속 상대운동을 하는 실린더 블록과 밸브 플레이트는 누설 및 마찰 손실의 최적화를 위해 극단적으로 제어되어야 하는 특성을 가지고 있으며, 내압 특성 설계는 고압 성능에 매우 중요하지만 이에 대한 응력 해석에 관한 연구가 활발하게 수행되지는 않았다. 따라서 본 논문에서는 CATIA V5를 사용한 정적 응력 해석을 통하여 사판식 유압 피스톤 펌프의 실린더 블록과 밸브 플레이트의 응력과 변위를 해석하고자 하였으며, 실린더 블록의 최대응력은 실린더 뒷부분 동 재질의 접합 소재에 발생하며, 축방향에 비해 반경방향 작용압력이 응력과 변위에 더 큰 영향을 주고, 응력은 약 66%, 변위는 약 30% 더 크게 나타났다. 밸브 플레이트의 경우 재질 및 형상에 대한 검토가 요구됨을 알 수 있었다.

• 한국윤활학회:학술대회논문집
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• 한국윤활학회 2000년도 제32회 추계학술대회 정기총회
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• pp.221-227
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• 2000

The design of the valve plate is most important to increase efficiency in the oil hydraulic axial piston pump. A theoretical study was carried out to clarify the pressure characteristics at the land of the valve plate in the oil hydraulic axial piston pump. Dynamic pressure acts on the land of the valve plate was computed numerically with discharge pressure, rotational speed and swash plate angle. Pressure distribution between the valve plate and the cylinder block also was obtained with dynamic pressure. The results are applicable to improve the design technique of the valve plate in the oil hydraulic axial piston pump.