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A newly developed bearing is a lead-free aluminum alloy bearing with low frictional layer which consists of molybdenum disulfide in thicknesses of sub-micron levels on the bearing surface without required binders such as resin. The new bearing had a 50% lower static friction coefficient compared to the conventional aluminum alloy bearing, and exhibited comparable anti-seizure property and fatigue strength to the conventional bearing by evaluation of rig tests. These rig tests verified that the new bearing showed excellent frictional reduction properties. This paper describes details and performances of this newly developed bearing.

A new environmental friendly method to supply metalworking fluid called Oil on Water Drop is proposed. In this study, the obtained results using this new method are compared to the dry cutting one in the machining of oil grooves in engine bearings. Conventional machining of engine bearings is carried out in the dry cutting condition; however, it was found that using the new Oil on Water Drop method the machining performances were greatly improved. In terms of machining tool life, a twofold increase was obtained, while an improvement in the machining error led to a considerable reduction in the rejection of parts made in the production line.

Recently, the bearing performances have been analyzed by elastohydrodynamic lubrication theory (EHL). However, the oil film temperature is constant within a bearing clearance on this theory. As modern automotive engines are running at high rotational speed, the change of the oil film temperature is remarkable within a bearing clearance. The bearing performances are influenced by the distribution of the oil film temperature. Therefore it is also necessary for the analysis of the bearing performances to consider the effect of the oil film temperature distribution by thermo elastohydrodynamic lubrication theory (TEHL). In this study, the effects of the bearing performances are investigated on connecting rod bearing in general gasoline engine by TEHL. Furthermore, oil film thickness, oil film pressure and oil film temperature of TEHL results are compared with those of EHL.

As the recent engines are designed for higher performance and better efficiency, three layers bearings must endure under heavy dynamic load and higher speed conditions. And it is also expected to develop the bearing without lead due to environmental concerns. In this report, a lead free copper based bearing alloy was studied. At first, in order to keep the anti-seizure property without lead, we studied the effects of bismuth and molybdenum carbide particles addition into the copper based bearing alloy. Secondly, we studied the influence of axial bearing relief to keep a conformability under high load condition.

As the downsizing and lightening of the engine are designed, the compact and lightweight of the housing should be required. Therefore, both the engine bearing and the housing are greatly deformed under the severe condition, and a heat generation due to the friction loss increases in the bearings. In this study, on the connecting rod bearing for the automotive engine, the bearing design factors as the oil inlet temperature, the rotational speed, the bearing clearance and the bearing length, are changed as a parameter. The influences of the design factors for the performance of the connecting rod bearing are investigated by using TEHL analysis (Thermo ElastoHydrodynamic Lubrication theory analysis).

The recent trend toward the compact and light-weight construction of diesel engines with high power output has been imposing higher requirements of fatigue strength and antiseizure characteristics on bearings. In order to meet these requirements, the authors developed a new bearing alloy of higher fatigue strength for use in heavy load engines, through the analysis of the Al-Zn-Si alloy which has high corrosion resistance. Experimental results of this new alloy to study its physical properties and bearing performances indicate that it can be applied to bearings in diesel engines which operate in harsh conditions.

A sintered aluminum-lead alloy of the bimetal type was manufactured in Japan (1977), and has been widely used in main and crankpin bearings for automobile engines. However, the recent trend of automobile engines toward high power output, light-weight and compact construction increases the bearing load. As a result, the margin of fatigue strength of the conventional sintered aluminum-lead alloy has been diminishing. In this paper, a new method of manufacturing bearing material by the hot extrusion process is reported. The new method makes it possible to produce the optimum lead grain distribution and strong adhesion between powder particles. The new manufacturing method produces the aluminum-lead bearing material which has 30% or more increase in fatigue strength over the conventional sintered aluminum-lead bearing material.

As the recent engines are designed for higher performance, piston pin bushing used for small end of connecting rod must endure higher dynamic load and oil temperature conditions. Therefore, the bushing is required higher wear resistance and anti-corrosion. And it is also expected to develop the bushing without lead due to environmental concerns. In this report, lead free copper based bushing alloy was studied. At first, in order to keep the anti-seizure property without lead, we studied the effects of hard particles added into copper based alloy. Second, we evaluated the effect of addition of hard particles on wear resistance and anti-corrosion.

Recent automotive engines for high performance vehicles have been designed for higher speeds and outputs. Not only the combustion load but also the inertia force applied on the connecting rod has been increasing. Automotive engines have also become compact and lighter in weight for needs of lower fuel consumption. For these reasons, the rigidity of the connecting rod has been reduced in comparison with the increasing inertia force. As a result, fretting damage may occur between two surfaces of the connecting rod big end bore and the bearing outer surface, causing breakage of the connecting rod itself. Countermeasures for fretting such as a tighter bearing fit ( interference ) and higher rigidity of the connecting rod big end are generally adopted. But the details for these countermeasures can not be easily predicted at the design stage. Rather they are obtained only by durability tests on the actual engines.

Recent engine bearings are operating under severe conditions to support such engine requirements as lower fuel consumption, longer life and protection of global environment. On Al-Sn-Si alloy bearings, it has some issue that fatigue may occur on the bearing alloy under severe condition such as in automotive diesel engines. Higher strength of alloy, which allows the fatigue resistance, can be obtained by solid solution treatment at higher temperature in general. But at the same time it makes intermetallic compounds with less bonding strength between intermediate layer and steel backing. A new bearing without lead has been developed by applying the heat treatment of bimetal and adequate intermediate layer for the process, consequently concluded to have the higher fatigue strength, with usual property on Al-Sn-Si alloy bearings.

The recent trend toward the compact and light-weight construction of automotive engines with high power output has been imposing higher requirements of fatigue strength, anti-seizure property and conformability on bearings. In order to meet these requirements, the authors analyzed the property of each layer of multi-layer Al-Si-Sn bearings and investigated its influence on bearing performance. Improvement was achieved as to the bearing alloy and the intermediate bonding layer based on the results of the investigation. As a result, this newly improved bearing has been concluded to provide better fatigue strength than conventional bearings. It has thus become possible to apply it as a bearing for the recent engines used under harsh conditions.

Recently, there has been a tendency of high power and high speed in automotive engines. In addition they have been also required high reliability. And engine bearings have been required to be advanced in wear resistance as well as seizure resistance. Therefore, copper-lead alloy bearings with overlay, which have better seizure resistance, have been widely used for high speed engines up to the present. But it becomes very important for them to advance the overlay wear resistance. In this paper, the composite overlay is mainly researched to improve wear resistance regarding kind of hard particles and their amounts in the overlay.

The advent of high-performance, compact, and lightweight engines in recent years brings forth a tendency to increase the load for engine bearings and demands on producing even higher levels of durability and reliability in bearing products against fatigue, seizure, wear, and corrosion. Based on the perspective of extending the bearing life, the authors have studied the problems that are encountered with the current three layer copper-lead alloy bearings after their overlay has worn out. Then, we studied the issues of lowered seizure resistance that results from the exposure of the nickel barrier, and of deficient corrosion resistance that results from the exposure of the bearing alloy. In order to improve upon these areas, we focused on diffusion phenomenon of overlay elements without the nickel barrier and also studied the feasibility of creating engine bearings whose alloy composition has been partially modified.

Heavily-loaded engine bearings in recent years have frequently utilized aluminum-tin-silicon alloy which does not require overlay. It has been found that some special fatigue damage may occur in these aluminum alloys under certain heavy-load application. A microscopic examination of such fatigue revealed a structural change inside the aluminum alloy. In this paper such fatigue phenomenon was studied in detail and reproduction tests were carried out on the bearing test machines. As a result, we have developed a new high-strength aluminum alloy which can prevent such fatigue damage.

The diffusion phenomena of tin and indium which are contained in the lead-base overlay of 3-layer copper-lead alloy bearings were studied. Easier diffusion of tin compared with indium decreases the corrosion resistance of the overlay, and the tin reacts with the underlayer to form brittle Ni-Sn or Cu-Sn intermetallic compound, resulting in weak bonding strength. Addition of copper into Pb-In overlay markedly restrains the diffusion of indium and therefore stabilizes the characteristics of corrosion resistance, bonding strength and mechanical properties for a long period. Cavitation tests, seizure tests and bearing fatigue tests were conducted on Pb-In-Cu overlay to study the feasibility of its application to actual engine bearings.

In recent years, the removal of lead (Pb), which is an environmentally hazardous material often used in bearings for automotive engines, has been continuously promoted. Bismuth (Bi) is attracting attention as a substitute for lead, and it is currently being used mainly for passenger cars and trucks as a lead replacement. However, lead has not been replaced for motorcycles where the bearings are exposed to high temperatures at high rotation speeds, and trucks and generators where high loading capacity, long lifetime and good corrosion resistance are required. It has been difficult to achieve both high load and corrosion resistant for a bearing overlay material. The purpose of this development is to improve the corrosion resistance and fatigue resistance of bismuth overlay by developing a bismuth- antimony alloy overlay in which antimony (Sb) is added to the bismuth matrix.

The possibility of predicting engine bearing durability by elastohydrodynamic lubrication (EHL) calculations was investigated with the aim of being able to improve durability efficiently without conducting numerous confirmation tests. This study focused on the connecting rod big-end bearing of an automotive engine. The mechanisms of wear and fatigue, which determine bearing durability, were estimated by comparing the results of EHL analysis and experimental data. This comparison showed the possibility of predicting the wear amount and the occurrence of fatigue by calculation.

There has been a requirement for automotive bearings materials to be free of the toxic material lead, in accordance with ELV regulations and from the perspective of environmental problems. Currently, bismuth is used as a replacement for lead in copper alloy based main journal bearings and connecting rod bearings for automotive engines. In recent years, there has been changing to lead-free materials for truck engine bearings. Compared with automotive engines, lots of contaminations in the oil and local contact between the shaft and bearings can occur in truck engines. The ability to tolerate contamination and local contact is therefore required for truck engine bearings. In this development, we find that the addition of 8 mass% bismuth and 1.5 mass% molybdenum carbide particles into copper-tin alloy is effective for improving the ability which allow the contamination and local contacts. The development of above mentioned lead-free copper alloy bearing material is described here.

Recent automotive engine developments have made great progress in protecting the global environment and in meeting exhaust gas regulations and fuel economy regulations. As a result, engine bearings tend to be used under severe conditions such as higher specific load onto the bearings and with low viscosity of lubricating oil. Aluminum alloy bearings are widely adopted as main bearings and connecting rod bearings in gasoline and diesel engines for passenger cars, and generally Al-Sn-Si alloy bearings without an additional overlay are used. Although these Al-Sn-Si alloy bearings have good anti-seizure properties and excellent running-in-properties, their material strength under high temperature conditions is not sufficient because of the low melting point of Sn phase contained in the alloy, and they could potentially result in damage to the bearing as seizure and fatigue under these conditions. In such cases, Cu-Pb-Sn alloy bearings with lead-based overlay are usually applied.

Bismuth has been applied successfully as sliding bearing overlay material in internal combustion engines, where a good combination of sliding properties, mechanical strength and corrosion resistance can be attained. However, environmental pressures driving towards lower emission and higher fuel efficiency are set to raise firing loads above the capability of many state-of-the-art bismuth materials in the market. At the same time, in order to meet increasingly stringent environmental regulations modern engines are adapting to more efficient and economic designs which put bearing materials under ever growing pressure to provide enhanced oxidation resistance and robustness to cope with elevated engine operating temperature and tighter oil clearance.