• 한국윤활학회:학술대회논문집
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• 한국윤활학회 2002년도 proceedings of the second asia international conference on tribology
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• pp.401-402
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• 2002

Diesel engines have many sliding parts with solid body contact. For example, a piston-ring and a cylinder bore, a valve and a valve-seat, a cam and a valve tappet. These parts have a severe wear problem. during engine life times. During these times, the valve tappet has abnormal wear such as scuffing and pitting due to a high hertzian contact stress between the cam and the tappet. Excessive wear problems frequently occur to both the cam and the tappet. To solve these problems, we developed an advanced wear resistant tappet. The developed tappet consisted of a hard-metal wear part and a steel body. To increase a bonding strength, those two parts, were directly bonded to each other. Also to decrease a bonding temperature, we developed the composition of Ni-binder materials in the hard metal. To estimate the wear characteristics of the newly developed tappet, we performed wear tests and engine dynamo tests in order to compare them with a conventional Fe-base tappet. As a result, the newly developed tappet has better wear characteristics than those of the conventional tappet. In addition, we performed a 100,000km field-test, and the newly developed tappet showed much improved wear resistance.

• 한국표면공학회지
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• 제34권5호
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• pp.409-413
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• 2001

In this study, high rate deposition of thick CrNx films was carried out by crossed field unbalanced magnetron sputtering for the special application such as piston ring employed in automobile engine. For the high rate deposition and thick CrNx films formation with thickness of 30$\mu\textrm{m}$, high power density of $35W/cm^2$ in each target was induced and the multi-layer films of Cr/CrN and $\alpha$-Cr/CrN were synthesized by control of $N_2$ flow rate. The dynamic deposition rate of Cr and $\alpha$-CrN film was reached to 0.17$\mu\textrm{m}$/min and 0.12$\mu\textrm{m}$/rnin and the thick CrN$_{x}$. film of 30$\mu\textrm{m}$ could be obtained less than 5 hours. The maximum hardness was obtained above 2200 kg/mm$^2$ and adhesion strength was measured in about 70N, in case of multi-layers films. And the friction coefficient was measured by 0.4, which was similar to the value of CrN single-layer film.m.

• Journal of Advanced Marine Engineering and Technology
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• 제24권1호
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• pp.67-74
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• 2000

Recently, PTFE-polymide composites are being used self-lubricating parts for industrial field. Thus, this study is mainly concerned with friction and wear properties for the piston ring of non-lubricating air compressor which made of PTFE-polymide composites. The friction and wear test was carried out for the different composition ratio under the atomsphere room temperature and constant load of 7.69N and their friction and wear properties were compared with each other at various sliding speed. notable results are summarized as follows. PTFE 100% showed that friction coefficient was almost same values at 0.94 and 1.88m/s but the value was decreased at 2.83m/s because the friction temperature is higher than low speed. PTFE 80%-PI 20% showed the lowest mean friction coefficient at 2.83m/s. PTFE 20-PI 80% showed the highest friction coefficient at 0.94m/s and the value was decreased at high speed but the value is higher than other materials except PTFE 100 %. PI 100% showed the highest friction coefficient at 0.94 and 1.88m/s becuase adhesive wear mainly occurred that speed. PTFE 100% showed highest specific wear rate on the whole. Specific wear rate of PTFE 80%-PI 20% was almost the same value with PTFE 20%-PI80%. PI 100%showed the lowest value at high sliding speed because the friction surface was thicken and carbonated by high friction temperature.

• 한국자동차공학회논문집
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• 제6권5호
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• pp.211-221
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• 1998

Thermal behavior on the cylinder block of a 4-cylinder, 4-stroke 2.0L SOHC gasoline engine was numerically and experimentally analyzed. The numerical calculation was performed using the finite element method. The cylinder block was modelled as a three dimensional finite element by considering its geometry. The physical domain was devided into hexahedron elements. 16 thermocouples were installed at points of 2mm inside from cylinder wall near top ring of piston in cylinder block, which points have suffered major thermal loads and suggested as proper measurement points for engine design by industrial engineers. Under full load and 9$0^{\circ}C$ coolant temperature condition, temperature behavior of cylinder block according to engine speed were analyzed. The results showed that temperature rose gradually to conform to a function of 2nd~4th order of engine speed at intake side, exhaust and siamese side, respectively. As engine load was changed from 100 to 50% by 25% step, temperature curve also conformed to 2nd~7th order function of engine speed. Temperature differences by load condition were similar among 100, 75% and 50%. Under full load and coolant temperature of 11$0^{\circ}C$, temperature behavior were also analyzed and the result also showed conformance to 2n d~7th order function of engine speed. Temperature curve was transferred in parallel upwards corresponding coolant temperature rise.

• 한국정밀공학회지
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• 제25권10호
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• pp.48-57
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• 2008

MR Fluid, one of functional fluids, is developed for the application to automobile products. MR CDC damper using MR fluid has following principles. When ar electric current is applied to the solenoid, apparent viscosity of MR fluid passing through the annular gap which acts as magnetic circuits varies directly as the intensity of the current. These devices have a simple structure and excellent lime response characteristics, emerging as the alternatives of the conventional semi-active suspension systems. In this study, a design procedure of the magnetic circuit through the solenoid fore and the flux ring functioning as a magnetic path is investigated so as to optimize the design and performance of MR CDC dampers for the vehicles. In addition, an operating point on the B-H curve, the magnetization according to the variation in the annular gap, the pole piece width and the density of MR fluid are studied to design the optimal piston head within the restrained dimension range.

• 한국전산유체공학회:학술대회논문집
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• 한국전산유체공학회 2005년도 추계 학술대회논문집
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• pp.223-227
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• 2005

A PCV valve is a part to control the flow rate of Blowby gas in a PCV system. A PCV system re-burns Blowby gas with fuel in a combustion chamber. Some gas enters to a crankcase room through the gap between piston ring and engine cylinder wall. This gas si called 'Blowby gas'. This gas causes many problems. In environmental view, Blowby gas includes about $25\~35\%$ hydrocarbon{HC) of total generated HC in an automobile. Hydrocarbon is a very harmful pollutant element in our life. In mechanical view, Blowby gas has some reaction with lubricant oil of crankcase room. Then, this causes lubricant oil contamination, crankcase corrosion and a decrease fo engine efficiency. Consequently, Blowby gas must be eliminated from a crankcase room. In this study, we simulated internal flow characteristics in a PCV valve according to spool dynamic behavior using local remeshing method And, we programmed our sub routine to simulate a spool dynamic motion. As results, spool dynamic behavior is periodically oscillated by the relationship between fluid force and elastic force of spring. And its magnitude is linearly increased by the differential pressure between inlet and outlet. Also, as spool is largely moved, flow area is suddenly decreased at orifice. For this reason, flow velocity is rapidly decreased by viscous effect.

• Tribology and Lubricants
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• 제30권1호
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• pp.21-28
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• 2014

Damage to the cylinder liner of large ship engines, such as scuffing on the surface, can occur very easily because it is operated in a corrosive environment. This scuffing may be due to oil film destruction and corrosive wear caused by water and sulfur included in the fuel, abrasive impurities, and poor lubricants. Thus, a method for monitoring the condition and diagnosing the failure of the cylinder liner and piston ring is needed. In this study, a reciprocating friction and wear test was carried out with a cast iron specimen, which simulated an engine cylinder in a corrosive atmosphere. The lubricants used were base oil, stirred oil with distilled water, a NaCl solution, and dilute sulfuric acid. The friction coefficient and frequency spectrum were measured using a load cell and acceleration sense in each experimental condition. We then used these results to diagnose the failure of the cylinder liner.

• 한국기계연구소 소보
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• 통권18호
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• pp.75-85
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• 1988

유압 펌프 또는 모터, 특히 레이디얼피스톤형 모터, 용 분배기는 동적인 평형상태를 유지하기 위해 양면이 완전히 똑같이 가공된 회전부재와 이 부재의 양면에 동적평형을 보조할 수 있도록 표면에 가공된 형상이 동일한 2개의 고정부재와 이 2개의 고정부재의 간격유지를 위하여 회전부재주위에 사각의 단면적을 갖는 원형링으로 이루어져 있다. 회전부재는 기본적으로 밸브부를 가지고 있으며 평형상태를 보조하기위해 밸브부의 외주에 정압베어링을 설치할 수도 있다. 2개의 고정 부재중 1개는 몇 개의 단이 있는 부재인데 이는 압력상승에 의한 볼트의 인장을 보상하기 위해 밸브케이싱과 축방향의 이동이 가능하도록 하기 위한 방법이다.

• 한국레이저가공학회지
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• 제13권2호
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• pp.1-5
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• 2010

A high speed laser texturing method that relies on laser scanner conditions, to form pattern shapes with micro-narrow surface detail such as dotted line features is demonstrated and analyzed. For example, this method may be used to piston ring and gear part for automotive. Data on friction characteristics of two laser patterns employed for STD61 steel will be shown. Comparison of pattern depths obtained by repetition overlapping process with laser scanner to the results on friction coefficient will be provide. It will be shown that friction characteristic in dotted line patterns can significantly depend upon interaction with the lubrication and laser pattern conditions. Laser pattern processing into a shallow depth provides only slight improvement in friction, while work into a deep shape indicates a significant improvement.

• 오토저널
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• 제10권5호
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• pp.61-68
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• 1988

This paper reports the basic performance of a naturally aspirated DI diesel engine which is used widely in industry and agriculture when vegetable oils are used as fuel substitutes. In this paper, the properties of vegetable oils as diesel fuel were investigated and the load-performance of diesel engine when vegetable oils were used, as tested compared against diesel fuel. The general objective of this investigation is to realize an efficient, clean, and low carbon deposit combustion of the vegetable oils in diesel engines, showing their feasibility as diesel fuel substitutes. The results of this experiment were as follows; (1) Compared with diesel fuel, the droplet size of vegetable oil is very large. (2) Compared with diesel fuel, rapeseed oil, palm oil, and their blend fuels offered lower smoke, lower NOx, ower engine noise, and high thermal efficiency in a D.I. diesel engine However, there were carbon deposit and piston ring sticking problems with long-term operation. (3) For ethanol-rapeseed oil blends, a 10-20% of ethanol content is recommended to enable lower BSHC and less smoke without a remarkable increase in engine noise compared with pure rapeseed oil. (4) A 10% oxygen content in the vegetable oils is contributed to reduced smoke emission.