• Title/Summary/Keyword: Variable-Pressure

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High-Precision Direct-Operated Relief Valve with a Variable Elasticity Spring (변탄성 스프링을 이용한 고정밀 직동형 릴리프 밸브)

  • Kim, SungDong
    • Journal of Drive and Control
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    • v.17 no.4
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    • pp.87-96
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    • 2020
  • In this study, a variable elasticity spring was applied to improve the pressure control precision of conventional relief valves. The equilibrium equation of the forces acting on the valve poppet was derived; it is demonstrated that matching the elastic rate of the pressure-adjusting coil spring to the equivalent elastic rate of the flow force improved the pressure override. The procedures that were used to design the variable elasticity spring are presented, and some applications of the variable elasticity spring are also introduced. Computer simulations were used to analyze three cases: a poppet-closed flow force structure, a poppet-open flow force structure with a constant elasticity spring, and a structure containing a variable elasticity spring. It is confirmed that the pressure control precision of the relief valve can be significantly improved upon by applying a variable elasticity spring to the poppet-open flow force structure.

Dynamics Analysis of Pressure Control Characteristics in a Variable Pressure Solenoid Valve (비례제어방식 솔레노이드 밸브 압력제어특성에 관한 동적해석)

  • 김형만;태혁준;이현우;이창훈
    • Transactions of the Korean Society of Automotive Engineers
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    • v.11 no.6
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    • pp.80-85
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    • 2003
  • In the present paper, dynamics analyses of pressure control characteristics have been performed in a variable pressure solenoid valve. A number of solenoid valves have been used in the electronic control system, especially automatic transmission of an automobile. Variable pressure solenoid valve is intended to produce spatial movement by the electrical signal. Dynamics analyses of pressure control characteristics have been practiced by the Finite Difference Method, which show the pressure distribution in the solenoid valve. The results of numerical analyses show the dependence of pressure distribution on the displacement of the spool in the solenoid valve, and then, are compared with the experimental results.

A Study on the Discharge Pressure Ripple Characteristics of Variable Displacement Vane Pump (가변용량형 유압 베인펌프의 토출압력맥동 특성 연구)

  • 장주섭;김경훈
    • Transactions of the Korean Society of Automotive Engineers
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    • v.11 no.3
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    • pp.106-114
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    • 2003
  • The pressure ripple in the delivery port is caused by flow ripple, which is induced by variation of pumping chamber volume. The other reason is the reverse flow from the outlet volume produced by pressure difference between pumping chamber and outlet volume, when the pumping chamber is connected with the outlet volume. In this study, a mathematical model is presented for analyzing discharge pressure ripple, which includes vane detachment, cam ring movement , and fluid inertia effects in V-groove in the side plate. From the analysis and experiment, it was found that V-groove on the side plate, coefficient of spring supporting the cam ring, and average discharge pressure are the main factors of discharge pressure ripple in variable displacement vane pump. The theoretical results, provided in this study, were well agreed with experimental results. The analytical model to estimate the magnitude of pressure ripple in this study is expected to be used f3r the optimal design of the variable displacement vane pump.

A Basic Study on the Application of a Variable Preload Device using Rubber Pressure for High Speed Spindle Systems (고속스핀들의 고무압을 이용한 가변예압장치 실용화를 위한 기초연구)

  • Choi, Chi Hyuk;Sim, Min Seop;Lee, Choon Man
    • Journal of the Korean Society for Precision Engineering
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    • v.31 no.8
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    • pp.677-682
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    • 2014
  • One of the most important element technologies for achieving high-precision in machine tool spindle systems is preload technology for the bearing of spindle systems. Fixed position preload, constant pressure preload, conversion preload and variable preload methods have been applied for the spindle systems. In this study, a new variable preload method using centrifugal force and rubber pressure is used for reducing installation costs through simplifying its structure. The main objective of the work is the verification of the operability in a preload device using the rubber pressure by the finite element analysis. It is shown that the variable preload device proposed in this study is applicable to high speed machine tool spindles.

Reduction of Power Consumption for Constant Pressure Control of Variable Swash Plate-type Piston Pump by Varying the Pump Speed (가변 용적형 사판식 피스톤 펌프의 회전 속도 조절에 의한 정압 제어 소비 동력 절감)

  • Kim, J.H.;Hong, Y.S.
    • Journal of Drive and Control
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    • v.11 no.4
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    • pp.53-60
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    • 2014
  • This paper proposes a control scheme to reduce the power consumption of a variable displacement swash-plate type piston pump supplying oil to a valve-controlled hydraulic cylinder at constant pressure. Whenever flow rate demand was absent, the swash plate angle and the pump speed were changed to the minimum values required to compensate for the internal leakage flow. In response to command signals, the pump speed was changed in proportion to the absolute mean value of the speed component for position commands. At the same time, a pressure regulator was activated to maintain constant system pressure by precisely adjusting the pump speed with the swash plate angle fixed at the maximum. The conventional system consisting of a pressure-compensated variable displacement type pump is driven at a constant speed of 1,800rpm. By comparison, computer simulation and experimental results showed that idling power at stand-by status could be reduced by up to 70% by reducing the pump speed from 1,800rpm to 300rpm and the swash plate angle to the minimum.

Development of Efficient Plate Element Considering Variable Thickness and Nonuniform Pressure (단면과 압력변화를 고려한 효율적인 평판 요소의 개발)

  • 이성우;심규점
    • Proceedings of the Computational Structural Engineering Institute Conference
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    • 1993.10a
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    • pp.1-7
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    • 1993
  • Most of wall or plate structures subjected to nonuniform earth or water pressure has variable thickness. These problems were generally solved by models with uniform thickness and pressure. To obtain more accurate and economic solution for this type of problem. efficient isoparametric plate element considering variable thickness and nonuniform pressure were developed. Some example problems demonstrated efficiency of the proposed element.

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Study on Synchronization Characteristics of a Variable Nozzle in Environment of Simulated Combustion Pressure (연소압 모사 환경 상태의 가변노즐 동기화 특성 연구)

  • Park, Dong-Chang;Lee, Sang-Youn;Lee, Ju-Young;Cho, Sung-Won;Yun, Su-Jin;Yoon, Hyun-Gull;Lim, Jin-Shik
    • Proceedings of the Korean Society of Propulsion Engineers Conference
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    • 2011.11a
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    • pp.919-921
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    • 2011
  • Variable nozzles are used to enhance the effectiveness of aircraft engines at various altitudes. Unsynchronized movements of variable nozzle flaps affect the direction of thrust in case the variable nozzle consists of many flaps. A synchronization test system was developed to verify the synchronization characteristics of variable nozzle mechanism including flaps. The test system has a capability to simulate combustion pressure in variable nozzle space. The test system was used to qualify the synchronization characteristics of a variable nozzle flaps affected by magnitude and uniformity of simulated combustion pressure, and time delay of each nozzle actuators.

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Pressure Control of Electro-Hydraulic Variable Displacement Pump Using Genetic Algorithms (GA를 이용한 전기유압식 가변펌프의 압력제어)

  • 안경관;현장환;조용래;오범승
    • Journal of the Korean Society for Precision Engineering
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    • v.21 no.9
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    • pp.48-55
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    • 2004
  • This study presents a genetic algorithm-based method fur optimizing control parameters in the pressure control of electro-hydraulic pump with variable displacement. Genetic algorithms are general-purpose optimization methods based on natural evolution and genetics and search the optimal control parameters maximizing a measure that evaluates the performance of a system. Four control gains of the PI-PD cascade controller for an electro-hydraulic pressure control system are optimized using a genetic algorithm in the experiment. Optimized gains are confirmed by inspecting the fitness distribution which represents system performance in gain spaces. It is shown that genetic algorithm is an efficient scheme in optimizing control parameters of the pressure control of electro-hydraulic pump with variable displacement.

The Discriminant Analysis of Blood Pressure - Including the Risk Factors - (혈압 판별 분석 -위험요인을 중심으로-)

  • 오현수;서화숙
    • Journal of Korean Academy of Nursing
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    • v.28 no.2
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    • pp.256-269
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    • 1998
  • The purpose of this study was to evaluate the usefulness of variables which were known to be related to blood pressure for discriminating between hypertensive and normotensive groups. Variables were obesity, serum lipids, life style-related variables such as smoking, alcohol, exercise, and stress, and demographic variables such as age, economical status, and education. The data were collected from 400 male clients who visited one university hospital located in Incheon, Republic of Korea, from May 1996 to December 1996 for a regular physical examination. Variables which showed significance for discriminating systolic blood pressure in this study were age, serum lipids, education, HDL, exercise, total cholesterol, body fat percent, alcohol, stress, and smoking(in order of significance). By using the combination of these variables, the possibility of proper prediction for a high-systolic pressure group was 2%, predicting a normal-systolic pressure group was 70.3%, and total Hit Ratio was 70%. Variables which showed significance for discriminating diastolic blood pressure were exercise, triglyceride, alcohol, smoking, economical status, age, and BMI (in order of significance). By using the combination of these variables, the possibility of proper prediction for a high-diastolic pressure group was 71.2%, predicting a normal-diastolic pressure group was 71.3%, and total Hit Ratio was 71.3%. Multiple regression analysis was performed to examine the association of systolic blood pressure with life style-related variables after adjustment for obesity, serum lipids, and demographic variables. First, the effect of demographic variable alone on the systolic blood pressure was statistically significant (p=.000) and adjusted $R^2$was 0.09. Adding the variable obesity on demographic variables resulted in raising adjusted $R^2$to 0.11 (p=.000) : therefore, the contribution rate of obesity on the systolic blood pressure was 2.0%. On the next step, adding the variable serum lipids on the obesity and demographic variables resulted in raising adjusted R2 to 0.12(P=.000) : therefore, the contribution rate of serum lipid on the systolic pressure was 1.0%. Finally, adding life style-related variables on all other variables resulted in raising the adjusted $R^2$to 0.18(p=.000) ; therefore, the contribution rate of life style-related variables on the systolic blood pressure after adjustment for obesity, serum lipids, and demographic variables was 6.0%. Multiple regression analysis was also performed to examine the association of diastolic blood pressure with life style-related variables after adjustment for obesity, serum lipids, and demographic variables. First, the effect of demographic variable alone on the diastolic blood pressure was statistically significant (p=.01) and adjusted $R^2$was 0.03. Adding the variable obesity on demographic variables resulted in raising adjusted $R^2$to 0.06 (p=.000) ; therefore, the contribution rate of obesity on the diastolic blood pressure was 3.0%. On the next step, adding the variable serum lipids on the obesity and demographic variables resulted in raising the adjusted $R^2$ to 0.09(p=.000) ; therefore, the contribution rate of serum lipid on the diastolic pressure was 3.0%. Finally, adding life style-related variables on all other variables resulted in raising the adjusted $R^2$ to 0.12 (p=.000) : therefore, the contribution rate of life style-related variables on the systolic blood pressure after adjustment for obesity, serum lipids, and demographic variables was 3.0%.

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A Fundamental Study on the Development of a Variable Preload Device Using Toggle Joint Mechanism (토글 조인트장치를 이용한 가변예압장치 개발을 위한 기초 연구)

  • Choi, Chi Hyuk;Cha, Na Hyeon;Lee, Choon Man
    • Journal of the Korean Society for Precision Engineering
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    • v.30 no.3
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    • pp.260-265
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    • 2013
  • To increase the machine accuracy by improving the stiffness of spindle bearings, preload was applied to the spindle bearings. The methods of fixed position preload, convertible preload, constant pressure preload, and variable preload are used to apply the preload to the spindle bearing. The previous studies performed by the author of this study were variable preload methods using rubber pressure and centrifugal force based on mechanical systems. This study proposed a toggle joint mechanism that could be applied to variable preload method using centrifugal force and rubber pressure to increase the preload. Also, a finite element analysis was conducted to predict the deformation of the rubber and change of the preload. And the analysis results showed that the preload by the device using rubber pressure only was increased by the toggle joint mechanism using rubber pressure.