나노구리합금 윤활제의 극압윤활특성과 엔진동특성

Abstract

본 연구에서는 나노구리합금 윤활제가 첨가된 윤활유를 고속마찰마모시험기에 주입하여 일반적인 기계적 윤활 특성을 분석하고, 모터링상태의 실험장치가 설치된 4행정 엔진을 사용하여 윤활유의 윤활특성과 기관에 미치는 영향을 분석하고자 한다.

연구내용은 크게 3가지로 구분된다. 마찰마모시험기에 일반극압제와 나노윤활제를 적용하여 나노윤활특성을 일반극압특성과 비교분석하고, 나노윤활첨가제의 체적 첨가비율을 변화시키면서 하중, 온도 조건에 대한 윤활특성을 분석하며, 나노윤활첨가제를 실엔진에 적용시킬 경우의 윤활과 진동특성을 분석한다. 첫 번째 실험에서는 현재 사용되고 있는 일반극압제를 실질적으로 성분 분석하여, 최적의 성분조합에 의해 샘플을 제조하여, 샘플과 나노구리합금 분말과의 윤활특성 비교를 한다. 두 번째 실험에서는 나노윤활제의 체적첨가율을 0, 0.0075, 0.015, 0.03, 0.06, 0.12로 변화시키고, 하중과 온도 조건을 달리 하면서, 제반특성을 분석한다. 세 번째 실험에서는 실제 디젤엔진에서 피스톤을 제거하고, 밸브계통의 윤활성을 나노구리윤활제의 첨가비율에 따라 실험한다. 엔진을 회전시키는 모터를 로드셀로 고정시켜 엔진회전에 소요되는 토크를 측정하며, 구동축에 x,y방향으로 갭센서를 설치하여 축진동을 측정한다. 로드셀에 의한 토크 측정에 의해서 윤활성능을, 크랭크축과 구동모터사이의 주축에다가 갭센서를 설치하여, 이에 의한 갭(gap)을 측정하여 진동특성을 분석한다.

Lubricant is the material to reduce the friction between two contacting surfaces, which occurs for a moving machinery. Recently the size of machinery becomes reduced without losing performance in order to satisfy the economic requirement. The friction load per area is extremely increased when the performance is increased and the contact area decreased. The traditional lubricant does not meet the severe condition. But, there are many severe conditions, like high temperature , combustion, impact in engine. So, the new development of the improved lubricant is required. The engine lubrication has to satisfy not only the requirement of the high density of the friction load but also the extreme conditions peculiar to the engine.

Many research works for improving a boundary lubrication performance have been studied by using solid lubricants, and have been tried to apply solid lubricants to an engine. However, those general lubricants like MoS2 or PTFE have not been applied on engines due to the extreme conditions such as very high temperature and pressure by combustion process in a cylinder.

Now, nano particles with lubricant additives is developing at many country. Especially, nano particle's volume percentage is important as economy and efficiency. The characteristic of a lubricant is important under severe running condition. On diesel engines, the better lubrication performance is required due to the extreme condition such as high temperature and pressure by combustion process in a combustion chamber.

Recently, the solid lubricant containing a copper nickel alloy has been introduced and studied.

In this thesis, the lubricant containing the alloy particles is applied on a high speed rolling contact wear test machine and a diesel engine. That particle is changed volume percentage. The lubricant is assessed by mechanical characteristic test and by engine performance test. The results by mechanical characteristic test show the decrease of the coefficient of friction and oil temperature. The results by engine test show the decrease of X-axis and Y-axis amplitude which strongly effect on engine vibration and the decrease of torque related strongly to the engine efficiency as well as the improvement of the engine lubrication performance.

It is clear that the lubricant containing the copper nickel alloy nano-powder decreases friction and wear, and it is also expected the increase of the sealing effect between a cylinder and piston rings.