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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.

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.

Resin-based overlays as lead-free bearing materials for automobile engines are experimentally studied using tribology testing apparatus and an engine bench test rig. A resin overlay newly proposed is composed of Polybenzimidazole (PBI) as the base resin and solid lubricant Molybdenum disulfide (MoS2) as an additive. PBI has high temperature performance and good adhesion and physical strength under higher temperatures. Consequently, a PBI-based overlay has good sliding properties in terms of wear resistance and fatigue resistance. The resin overlay shows applicability to automobile engine bearings which are used under high loads.

Properties of engine bearings were investigated with different bearing materials and different HTHS viscosity oils by means of both an engine test and a rig test. The rig test well simulated the bearing wear which occurred in the engine test. Lead-bronze bearings with lead-tin-indium overlay gave the least amount of wear in operating under high speed and heavy load conditions even with low HTHS viscosity oil. Aluminum bearings without overlay gave good wear resistance in the case of no seizure occurrence. The wear amount of bearings were well correlated with HTHS viscosity, not with kinematic viscosity.

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).

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.

Friction loss of bearings under dynamic load is often measured by motoring on an actual engine. Motoring, however, is not capable of reproducing the bearing load during the firing. The authors developed a dynamic load simulating machine, which applies variable load corresponding to one engine load cycle by means of a hydraulic pressure controlled with servo valves. Friction loss and the shaft center locus were measured under the static load and the dynamic load simulating to the main bearing load of V-engine. The variation was studied while changing various dimensions of a bearing such as clearance, bearing length, revolution speed, shaft diameter, and presence of a circumferential groove. By comparing the test results with theoretical values, good agreement in the basic tendency was obtained.

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.

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.

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.

This study focuses on the oil flow, supplied from the oil hole in plain bearings; the oil flow in bearings that were statically loaded was measured precisely using a test rig. In the case that oil was supplied through an oil hole, experimental results showed that the bearing oil flow depended largely on the circumferential angle of the oil feed hole in relation to the loading direction. When compared with the results of conventional theoretical analysis, it became obvious that the conventional analysis method could not make an exact prediction. The authors have assumed that such difference would come from the oil film extent. Using a transparent bearing so that the behavior of the oil film within the bearing clearance could be visible, the oil film extent for different circumferential positions of the oil feed hole were observed. The bearing oil flow was calculated based on the actually measured oil film extent. The calculated result was compared with the experimental one.

In order to determine the seizure limit of the main bearings of passenger vehicles under actual operating conditions, evaluations were conducted in environments containing noise factors (Various factors which designer cannot adjust and which make function vary were defined as noise factors in this paper.) [1,2] It was shown that noise factors have an effect on seizure limit performance in relation to performance under ideal test conditions (test conditions in which no noise is present). In relation to oil properties, the results showed that a reduction in viscosity as a result of dilution affected seizure limit performance. In relation to the shape of the sliding sections of the test shaft, seizure limit performance declined in a shaft in which the central section was swollen (“convex shaft” below).

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.

As the recent automotive engines are designed for higher performance, the rotating speed of the engines have been increased drastically. Therefore the engine bearings should be further improved to have better anti-seizure and wear properties under the high temperature at the high rotating speed. The authors have analyzed the necessary functions of the three layers copper-lead bearings at such operating conditions, and then improved and developed the overlay and the copper based bearing alloy with steel back. Physical and chemical properties for this new bearing were studied. Then the bearing performance tests were carried out including the high speed seizure tests and engine tests. From these test results, it was confirmed that this new bearing could be applied for the recent very high speed automotive engines.

The number of vehicles with engines using idling stop systems and hybrid systems to improve fuel consumption has recently been increasing. However, with such systems the frequent starts and stops of the engine, where the oil film between the bearings and shaft is squeezed out and direct contact between the components is more likely, can result in increased wear of the engine bearings, particularly in the main bearing. Bearings with resin overlays have been shown to display superior resistance to wear from such start-stop cycles. Moreover, cast iron shafts without quenching treatment have also been used in engines for cost reduction. Because the cast shaft has low hardness and unstable surface graphite after abrasive finishing, increase in the wear amount cannot be suppressed by conventional resin overlay in comparison with steel shaft. Therefore, the resin overlay with improved wear resistance achieved by adding hard particles was developed.

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.

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.

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.

Emission control and other restrictions prescribed in the EU's recent EUROIV regulations require automobile manufacturers to decrease NOX and PM (Particulate Matter) in exhaust emissions. Diesel engines in recent years tend to have higher cylinder pressure in pursuit of higher performance and meeting emission regulations. At the same time, under the ELV (End-of-Life Vehicles) regulation, use of lead, which is an environmental pollutant, in automobile parts has become increasingly difficult in recent years. Accordingly, we have developed lead-free overlay for tri-metal copper bearings for applications of highly specific load. We chose a dual-layer structure, bismuth and silver overlay. This type of structure can create fatigue resistance without compromising the two advantages of lead overlay: conformability and anti-seizure property.

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.