• 한국정밀공학회지
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• 제16권5호통권98호
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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.

• 한국윤활학회:학술대회논문집
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• 한국윤활학회 2000년도 제32회 추계학술대회 정기총회
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• pp.266-272
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• 2000

The importance of variable displacement piston pump is recently increasing in industrial applications, as it is widely used for raising the energy level of the fluid in hydraulic system. The regulator is the device that controls the pump output flow depending on the machine load and engine speed, and that regulates the discharge flow of the piston pump by controlling the swivel angel. This work deals with constant power control of a regulator system in bent-axis type piston pump. In order to use engine power effectively, it is important to keep the horsepower from the engine to the pump constant. Therefore, optimum power usage is obtained by accurately following the power hyperbola. First, the governing equations of the regulator are derived, and analysis is performed by numerical simulation in which significant parameters of regulator are identified. Also, we designed and manufactured the prototype of the constant power control regulator for experiments. The experimental results show the responsibility and pressure-flowrate characteristics and these are compared with the theoretical analysis. As the result, it is confirmed that the characteristics of the designed regulator correspond to the numerical simulation.

• International Journal of Automotive Technology
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• 제6권1호
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• pp.65-70
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• 2005

Pressure ripples, which are inevitably generated by a fluctuation of flow rate caused by a pump mechanism, include noises and vibrations in hydraulic pipeline. These noises and vibration deteriorate the stability and accuracy of hydraulic systems. The accumulator and hydraulic attenuator are normally used to reduce the pressure ripples. In this study, a parallel line is introduced to the hydraulic pipeline for the hydraulic system with a bent-axis piston pump as a method to reduce the pressure ripples. The dynamic characteristics of the hydraulic pipeline with a parallel line are analyzed by a transfer matrix in the frequency domain. The usefulness of the hydraulic pipeline with a parallel line was ascertained by experiment and simulation. The results from the experiment and simulation show that the hydraulic pipeline with a parallel line were effective in reducing the pressure ripples.

• 한국해양공학회지
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• 제24권6호
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• pp.76-80
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• 2010

Oil hydraulic piston pumps are being extensively used around the world, because of their simple design, light weight, effective cost, etc. An oil hydraulic pump is likely to have the serious problems of high leakage, friction, and low energy efficiency after a long period of use. In an oil hydraulic piston pump, the clearance between the valve block and piston plays an important role for volumetric and overall efficiency. In this study, the wear property of the SACM645 material with DLC coating used for a hydraulic piston pump was determined by experimentation with variable heat treatment. To investigate the effect according to the piston surface condition, five different types of specimens were prepared. The maximum tensile strengths of the QT and QT Nitration specimens had similar values of about 800 MPa, but the strains indicated a big difference. In a wear test, the wear characteristic of the DLC coating specimen was shown to be excellent. The QT, QT + IH, QT + Nitration, and matirx specimen showed similar wear characteristics. In the case of a dry condition without oil, the DLC coating specimen had good wear resistance, with no wear shown.

• 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.

• 한국기계가공학회지
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• 제20권4호
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• pp.24-30
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• 2021

In this paper, a structural stability analysis of the swash plate hydraulic piston pump installed on hydraulic supply systems in marine vessels is presented. In order to verify the integrity of the pump design, a standard structural analysis technique based on the finite element method has been applied for various operating and boundary conditions. For the maximum operational torque (223 N·m) at 5°, 10°, and 15° of the swash plate angle, the maximum deformation, equivalent stress and safety factor are evaluated. The analytical results show that under current operating conditions, the structural reliability of the design has been confirmed.

• Journal of Mechanical Science and Technology
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• 제20권3호
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• pp.358-365
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• 2006

The hydraulic pump of an Electro-hydrostatic Actuator 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 through low-speed operation so that the steady state position control error of the actuator can be accurately compensated. Within the scope of axial piston type hydraulic pumps, this paper is focused on the investigation how the surface treatment of their cylinder barrel with TiN plasma coating can contribute to the reduction of the friction and wear rate of valve plate in the low-speed range with mixed lubrication. The results showed that the friction torque of the valve plate mated with a TiN coated cylinder barrel could be reduced to 22% of that with an uncoated original one when load pressure was 300 bar and rotational speed 100 rpm. It means that the torque efficiency of the test pump was expected to increase more than 1.3% under the same working condition. At the same time, the wear rate of the valve plate could be reduced to $40\sim50%$.

• 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.

• 대한기계학회논문집A
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• 제35권5호
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• pp.555-559
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• 2011

본 연구는 유압 피스톤 펌프 재료로 사용되고 있는 SACM645소재를 사용하여 모재, QT(quenching & tempering) 시험편 및 QT 질화시험편의 피로특성을 조사하였다. 피로특성 조사결과는 다음과 같다. QT 질화시험편은 피로한도가 인장강도의 80%로 나타나 아주 높은 값을 나타내었다. 이것은 시험편 표면에 단단한 질화처리를 실시하여 피로균열의 발생을 지연시켰고, 피로균열이 발생하더라고 소재가 단단하여 균열진전속도가 늦었다고 판단된다. 파면 관찰결과 피로균열진전 영역에서는 모두 스트라이에이션이 관찰되었고, 피로균열진전 이외의 영역에서 QT 시험편은 벽개파괴의 양상을, 모재와 Qt 질화시험편은 딤플 파괴의 양상을 나타내었다.

• 유공압시스템학회논문집
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• 제2권4호
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• pp.14-22
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• 2005

The safety factor of hydraulic piston pumps & motors due to high pressurization, high speedization and low weight/volume realization to enhance the output density shows a tendency to decrease. Therefore more effective test methods are necessary to predict the exact life. The failure of hydraulic pumps & motors operating in high pressure and high speed mainly occurs in piston-shoe assemblies, and the major failure mode is wearout of the shoe surface. The sensitive parameters in the endurance life test are speed, pressure and temperature, and the failure production increases in proportion to the operating time. In this research, the authors propose the combined accelerated life test model using the analysis method of the combined accelerated life test results of piston-shoe assemblies by applying simultaneously high speed, high pressure and high temperature in accordance with variation of speed, pressure and temperature to reduce the life test time.