• Journal of Advanced Marine Engineering and Technology
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• 제37권6호
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• pp.631-637
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• 2013

기어 끝단과 하우징 사이의 간극이 회전방향으로 편심된 인벌류트펌프에서 체적유량과 유량효율을 검토하였다. 해석은 k-e 모델을 이용하여 FLUENT/R-13을 사용하여 기어의 회전속도, 간극의 거리 및 출구압력이 주어져 있을 경우 난류유동을 해석하였다. 동심축과 편심축의 경우 체적유량을 비롯한 유동특성에 대해 독립변수들의 영향은 지속되었으나 회전방향에 대한 압력 분포는 서로 달라 편심의 경우 상류부에서 대부분의 압력이 상승하고 하류부의 압력은 거의 일정한 특성을 보였으며 편심의 영향이 클수록 이러한 현상은 심하게 나타났다. 편심펌프에서 유동특성은 최소 간극에 의존하며 체적유량 혹은 체적효율은 편심되기 전 동심축보다 크나 최소간극과 같은 크기의 동심펌프보다는 작다. 펌프에서 기어축의 편심에 의한 간극 축소는 펌프성능에 긍정적인 영향을 미칠 수 있다.

• Journal of Advanced Marine Engineering and Technology
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• 제38권3호
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• pp.253-261
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• 2014

본 연구에서는 스퍼 유성기어시스템 2단, 헬리컬기어 시스템 1단으로 구성되어 있고, 메인 축과 증속기가 플랜지 결합되어 있는 동력분기식 2.5MW 풍력발전기에 대해 진동해석을 수행하였다. 유성기어시스템, 헬리컬기어시스템, 메인 축 등은 MASTA 상용프로그램으로 모델링하고, 기어박스 케이스, 토크암, 유성캐리어, 플랜지 등은 유한요소법으로 모델링하였으며, 부분구조합성법으로 조합하여 진동해석을 수행하였다. 2.5MW 동력분기식 풍력발전기 기어트레인의 고유진동 특성 해석을 수행하였고, 블레이드 풍하중에 의한 가진, 질량불평형, 축 어긋남 등에 발생하는 가진원에 대해 위험속도 분석을 하였다.

• 한국정밀공학회지
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• 제23권5호
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• pp.37-43
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• 2006

Fitting process carried out in automobile transmission assembly line is classified into three classes; heat fitting, press fitting, and their combined fitting. Heat fitting is a method that heats gear to a suitable range under the tempering temperature and squeezes it toward the outer diameter of shaft. Its stress depends on the yield strength of gear. Press fitting is a method that generally squeezes gear toward that of shaft at room temperature by press. Another method heats warmly gear and safely squeezes it toward that of shaft. Warm shrink fitting process for automobile transmission part is now gradually increased, but the parts (shaft/gear) assembled by this process produced dimensional change in both outer diameter and profile of the gear. So that it may cause noise and vibration between gears. In order to solve these problems, we need an analysis of warm shrink fitting process, in which design parameters are involved; contact pressure according to fitting interference between outer diameter of shaft and inner diameter of gear, fitting temperature, and profile tolerance of gear. In this study, an closed form equation to predict contact pressure and fitting load was proposed in order to develop optimization technique of warm shrink fitting process and verified its reliability through the experimental results measured in the field and FEM, that is, thermal-structural coupled field analysis. Actual loads measured in the field have a good agreement with the results obtained by theoretical and finite element analysis and also the expanded amounts of the outer diameters of the gears have a good agreement with results.

• 한국분말재료학회지
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• 제17권6호
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• pp.456-463
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• 2010

This paper describes the results of the application of Cr-Diamond-like carbon (DLC) films for efficiency improvement through surface modification of spur gear parts in the hydraulic gear pump. Cr-DLC films were successfully deposited on SCM 415 substrates by a hybrid coating process using linear ion source (LIS) and magnetron sputtering method. The characteristics of the films were systematically investigated using FE-SEM, nano-indentation, sliding tester and AFM instrument. The microstructure of Cr-DLC films turned into the dense and fine grains with relatively preferred orientation. The thickness formed in our Cr buffer layer and DLC coating layer were obtained the 487 nm and $1.14\;{\mu}m$. The average friction coefficient of Cr-DLC films considerably decreased to 0.15 for 0.50 of uncoated SCM415 material. The hardness and surface roughness of Cr-DLC films were measured 20 GPa and 10.76 nm, respectively. And then, efficiency tests were performed on the hydraulic gear pump to investigate the efficiency performance of the Cr-DLC coated spur gear. The experimental results show that the volumetric and mechanical efficiency of hydraulic gear pump using the Cr-DLC spur gear were improved up to 2~5% and better efficiency improvement could be attributed to its excellent microstructure, higher hardness, and lower friction coefficient. This conclusion proves the feasibility in the efficiency improvement of hydraulic gear pump for industrial applications.

• 한국정밀공학회지
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• 제25권6호
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• pp.47-54
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• 2008

Fitting process carried out in the automobile transmission assembly line is classified into three classes; heat fitting, press fitting, and their combined fitting. Heat fitting is a method that heats gear to a suitable range under the tempering temperature and squeezes it toward the outer diameter of shaft. Its stress depends on the yield strength of gear. Press fitting is a method that generally squeezes gear toward that of shaft at room temperature by a press. Another method heats warmly gear and safely squeezes it toward that of shaft. Warm shrink fitting process for the automobile transmission part is now gradually increased, but the parts (shaft/gear) assembled by this process produced dimensional changes in both the outer diameter and profile of the gear. So that it may cause noise and vibration between gears. In order to solve these problems, we need an analysis of warm shrink fitting process, in which design parameters are involved; contact pressure according to fitting interference between outer diameter of shaft and inner diameter of gear, fitting temperature, and profile tolerance of gear. In this study, an closed form equation to predict contact pressure and fitting load was proposed in order to develop an optimization technique of the warm shrink fitting process and verified its reliability through the experimental results measured in the field and FEM, that is, thermal-structural coupled field analysis. Actual loads measured in the field was in good agreements with the results obtained by the theoretical and finite element analysis.

• Tribology and Lubricants
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• 제37권2호
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• pp.48-53
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• 2021

Wind energy is considered as the most competitive energy source in terms of power generation cost and efficiency. The power train of the pitch drive for a wind turbine uses a 3-stage complex planetary gear system in being developed locally. A gear train of the pitch drive consists of an electric or hydraulic motor and a planetary decelerator, which optimizes the pitch angle of the blade for wind generators in response to the change in wind speed. However, it is prone to many problems, such as excessive repair costs in case of failure. Complex planetary gears are very important parts of a pitch drive system because of strength problem. When gears are designed for the power train of a pitch drive, it is necessary to analyze the fatigue strength of gears. While calculating the specifications of the complex planetary gears along with the bending and compressive stresses of the gears, it is necessary to analyze the fatigue strength of gears to obtain an optimal design of the complex planetary gears in terms of cost and reliability. In this study, the specifications of planetary gears are calculated using a self-developed gear design program. The actual gear bending and compressive stresses of the planetary gear system were analyzed using the Lewes and Hertz equation. Additionally, the calculated specifications of the complex planetary gears were verified by evaluating the results from the Stress - No. of cycles curves of gears.

• 농업과학연구
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• 제46권3호
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• pp.613-627
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• 2019

The purpose of this study was to design a powertrain for a 78 kW AWD (all wheel drive) electric tractor by analyzing the combination of various reduction gear ratios on a commercial motor using data from actual agricultural work and driving conditions. A load measurement system was constructed to collect data using wheel torque meters, proximity sensors, and a data acquisition system. Field experiments for measuring load data were performed for two environmental driving conditions (on asphalt and soil) and four agricultural operations (plow tillage, rotary tillage, loader operation, and baler operation). The attached implements and gear stages were selected through farmer surveys. The range of the reduction ratio was determined by selecting the minimum reduction ratio needed to satisfy the torque condition required for agricultural operations and the maximum reduction gear ratio to satisfy the maximum travel speed. The minimum reduction gear ratio selected was 57 in consideration of the working load condition and the maximum reduction gear ratio selected was 62 considering the maximum running speed. In the range of the reduction gear ratio 57 - 62, the selected motor satisfied all working torque conditions. As a result, the combination of the selected motor and reduction gear ratio was applicable for satisfying the loads required during agricultural operation and driving operation.

• 한국전자통신학회논문지
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• 제19권1호
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• pp.77-84
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• 2024

기어비 변환을 목적으로 설계한 전자석 마그네틱 기어는 영구자석을 이용한 마그네틱 기어와 비교해 낮은 토크 밀도를 가져 토크 밀도의 개선이 필요하다. 이를 보완하고자 기어비 변환 시 각각의 회전자의 자화 방향이 일정한 치를 확인하여 이에 영구자석을 부착해 부족한 토크 밀도를 높이는 연구를 진행했다. 하지만 영구자석이 고르게 부착되지 않으면서 발생한 자속밀도의 불균일로 인해 토크 리플이 증가하는 현상이 문제점으로 발생 되었다. 따라서 전자석 마그네틱 기어의 토크 리플을 감소시키고자 진행된 선행연구를 토대로 폴피스 브릿지, 필레 방식을 적용하여 기어비 변환을 하더라도 각각의 토크 리플을 개선할 수 있는 최적의 방법을 모색하고자 한다.

• 한국기계가공학회지
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• 제14권2호
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• pp.7-13
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• 2015

In this study, we developed a gear-type vane damper which replaces the link type through a proper gear design by means of a finite element analysis. We analyzed the fluid flow according to the amount of angular displacement. torque and backlash problems were addressed in conjunction with the pinion as a structural improvement of the forced draft fan (FD FAN). Through an environmental test. Also, results nearly identical to those in the test could be drawn when using a numerical method. Finally, we compared the gear driving result with simulation results. objective of the present study is to identify a nonlinear flow rate control method for a gear-type vane damper and to propose a damper shape which offers linear flow rate control. This study is related to the development of a gear-type vane damper of the change-link type in a forced draft fan.

• 한국기계가공학회지
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• 제13권5호
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• pp.8-14
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• 2014

A slewing reducer consists of two planetary gearsets which require a good load distribution over the gear tooth flank for enhanced durability. This work investigates how the bearing characteristics influence the load distribution over the gear tooth flank. A complete system model is developed to analyze a slewing reducer, including the non-linear mesh stiffness of the gears and the non-linear stiffness of bearings. The results indicate that the type, arrangement and preload of the output shaft bearings greatly influence the gear mesh misalignment, contact pattern, face load factor, gear safety factor and lifetimes of the parts.