• 한국정밀공학회지
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• 제27권1호
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• pp.105-112
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• 2010

Weldlines are generated during the injection molding process when two or more melt flows are brought into contact. The weldlines are unavoidable in the cases of presence of holes or inserts, multi-gated delivery systems, significant thickness change, etc. At the welded contact region, a 'V'-shaped notch is formed on the surface of the molded part. This 'V'-notch deteriorates not only surface appearance but also mechanical strength of the molded part. To eliminate or reduce weldlines so as to improve the weldline strength, the mold temperature at the corresponding weld locations should be maintained higher than the glass transition temperature of the resin material. The present study implements high-frequency induction heating in order to rapidly raise mold surface temperature without a significant increase in cycle time. This induction heating enables to local mold heating so as to eliminate or reduce weldlines in an injection-molded plastic part. The effect of induction heating conditions on the weldline strength and surface appearance of an injection-molded part is investigated.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2013년도 춘계학술대회 논문집
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• pp.60-64
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• 2013

Water injection pump produced the 1st oil well through the high pressure after the Deep water oil well drilling. After finish the work it is hard to produce only using itself pressure due to low pressure. Therefore it can be increased recovery factor through the injection seawater of high pressure. Is the key equipment used in the marine plant and it is developing at many industries. In this paper, Analyze changes in the natural frequency due to the stiffness of the bearing. Analyze the critical speed of the natural frequency due to the change of operation speed. And evaluate the Stability. And then analyze the displacement and clearance through the unbalance response this way has contributed to the reliability of the developing product. Through a mathematical analysis.

• Elastomers and Composites
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• 제44권4호
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• pp.358-365
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• 2009

고주파 유도가열은 전자기 유도현상을 이용하여 금형표면을 비접촉 형태로 급속 가열할 수 있는 기술이다. 본 연구에서는 고주파 유도가열을 사용하여 사출금형의 표면을 급속으로 가열함으로써 휴대폰 사출성형품의 웰드라인을 제거하기 위한 연구를 수행하였다. 고주파 유도가열 실험을 통해 3초간의 가열로 금형 표면온도를 $143^{\circ}C$까지 가열함으로써 고분자수지의 유리전이온도 이상으로 급속 가열할 수 있음을 확인하였으며, 상기 고주파 유도가열을 적용하여 휴대폰 외장부의 사출성형을 실시하여 기존에 발생되었던 웰드라인을 성공적으로 제거할 수 있었다. 또한 유도가열시 가열조건(고주파 유도가열기 출력 및 가열시간)의 변화에 따른 웰드부 표면특성의 변화를 고찰하였다.

• 한국광학회지
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• 제6권3호
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• pp.222-227
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• 1995

Littman방식의 grating feedback 다이오드 레이저를 주레이저로 사용하여, 100mW 출력의 단일 종모드로 발진하는 고출력 다이오드 레이저를 주입-잠금 하였다. 불완전 주입-잠금 상태에서 종레이저는 두 주파수가 동시에 발진하는 것을 관찰할 수 있었고 두 주파수 성분의 출력비와 주파수이동이 주입광의 세기의 제곱에 비례한다는 것을 알 수 있었다. 완전 주입-잠금 상태에서 (주입된 광의 세기)/(종레이저광의 세기)가 양 $10^{-3}$ 일 때 주입-잠금 대역폭은 약 1.4GHz로 측정되었다. 주입-잠금 대역폭은 주입광세기의 제곱근에 비례하여 증가하는 것을 보여주는데, 이것은 이론과 일치하는 결과이다. 주입-잠금 상태의 선폭은 자유 동작 상태의 선폭 보다 약 5배 좁아져 2.5MHz 이하였다.

• Journal of Power Electronics
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• 제8권1호
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• pp.60-73
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• 2008

In this paper a three-phase ac-to-dc resonant converter with high input power factor and isolated output is proposed. To improve the input power factor of the converter, high frequency current is injected into the input of the three-phase diode bridge rectifier. It is injected through an impedance network consisting of a series of L-C branches from the output of the high frequency three-phase inverter. A narrow switching frequency variation is required to regulate the output voltage. A design example with different design curves is illustrated along with the component ratings. Experimental verification of the converter is performed on a prototype of 3 kW, 1000 V output, operating above 300 kHz. Experimental results confirm the concept of the proposed converter. Narrow switching frequency variation is required to regulate the output voltage.

• 한국분무공학회지
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• 제10권4호
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• pp.8-15
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• 2005

The use of clean gaseous fuels for the purpose of high efficiency and low emission in automotive engines has tendency to increase in order to meet the reinforcing emission regulations and to efficiently utilize limited natural resources. Automotive companies developed and commercialized a LPG liquid injection system, which is mounted on LPLi(Liquid Phase LPG Injection) engines and vehicles based on this research trend. This research examines the biggest problem in LPLi engine, that is, the leakage characteristics of low viscosity LPG fuel according to the injector design variables. This study is also aimed to improve the performance of fuel-leakage in LPLi engine through the addition of a lubrication improver in HFRR(High Frequency Reciprocating Rig) facility. The needle displacement and the spring displacement of an LPLi injector are found to be already optimized. The possibility of a maximum of 70% leakage reduction compared to a conventional case, is verified when 1000ppm of a lubrication improvement material is added and 40% increase of a injector spring constant (K) is applied.

• 한국정보통신학회논문지
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• 제12권1호
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• pp.17-24
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• 2008

서브하모닉파 주입동기에 의한 밀리미터파 대역 고주파원의 고성능화에 대하여 다루었다. MES-FET로 8.7GHz의 발진기를 구성하고 서브하모닉파의 주입동기 방식으로 구동하여 17.4GHz의 고조파를 발생시켰다. 이러한 시스템에서 발진기는 발진과 동시에 체배기의 기능을 수행하여 안정된 고조파 발생시킬 수 있다. 이 기술을 채택하면 자려발진주파수가 비교적 낮은 발진기로도 고안정, 고출력 고주파를 발생시키는 고조파출력 발진기를 실현할 수 있다. 실험의 결과, 주입 동기의 범위 26MHz 내에서 고출력 고조파가 관측되었으며, 서브하모닉파 주입전력에 비례하였다. 스펙트럼 분석기로 고조파 출력의 파형을 관측한 결과, 제2고조파 출력의 위상 안정성이 현저히 향상되었음이 확인되었다.

• International Journal of Automotive Technology
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• 제2권4호
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• pp.165-170
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• 2001

This study is focussed on the investigation of spray characteristics from the high pressure gasoline injector for the application of gasoline direct injection engine. For the analysis of spray structure of high pressure gasoline injector; the laser scattering method with a Nd-Yag laser and the Phase Doppler particle analyzer system were applied to observe the spray development and the measurement of the droplet size and velocity of the spray, respectively. Also spatial velocity distribution of the spray droplet was measured by use of the particle image velocity system. Experimental results show that high pressure gasoline injector shapes the hollow-cone spray, and produce the upward ring shaped vortex on the spray surface region. This upward ring shaped vortex promotes the secondary atomization of fuel droplets and contributes to a uniform distribution of fuel droplets. Most of fuel droplets are distributed under 31$\mu m$ of the mean droplet size (SMD) and the frequency distribution of the droplet size under 25$\mu m$ is over 95% at 7 MPa of injection pressure. According to the experimental results of PIV system, the flow patterns of the droplets velocity distribution in spray region are in good agreement with the spray macroscopic behaviors obtained from the visualization investigation.

• 전력전자학회논문지
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• 제18권3호
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• pp.225-231
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• 2013

This paper presents an improved signal processing technique in the square-wave-type voltage injection method for IPMSM sensorless drives. Since the sensorless method based on the square-wave voltage injection does not use low-pass filters to get an error signal for estimating rotor position and allows the frequency of the injected voltage signal to be high, the sensorless drive system may achieve an enhanced control bandwidth and reduced acoustic noise. However, this sensorless method still requires low-pass and band-pass filters to extract the fundamental component current and the injected frequency component current from the motor current, respectively. In this paper, these filters are replaced by simple arithmetic operations so that the time delay for estimating the rotor position can be effectively reduced to only one current sampling. Hence, the proposed technique can simplify its whole signal process for the IPMSM sensorless control using the square-wave-type voltage injection. The proposed technique is verified by the experiment on the 800W IPMSM drive system.

• 대한기계학회논문집A
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• 제34권5호
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• pp.575-582
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• 2010

최근 박육사출성형이나 마이크로 사출성형에서의 성형성을 높이기 위해 급속 금형가열 기술이 사용되고 있다. 고주파 유도가열은 전자기 유도현상을 이용하여 금형 표면만을 효율적으로 가열할 수 있어 급속 금형가열 기술로서 활용되고 있다. 본 연구에서는 고주파 유도가열 적용 사출성형 과정의 수치적 모사를 위해 전자기장 해석, 열전달 해석, 사출성형 유동해석을 연계한 통합적 전산모사 기법에 관한 연구를 수행하였다. 본 연구에서 제안된 통합적 전산모사 기법을 유도가열 적용 박육 사출성형의 해석에 적용하여 실험결과와 비교하였고, 특히 금형온도 경계조건의 부여방식에 따른 해석의 신뢰성에 대한 고찰이 이루어졌다.