Search Results

Sintered silicon nitride, particularly in structural ceramics, has superior properties such as low weight, heat resistance, wear resistance, etc. It is already being applied to automobile engine parts such as the swirl chamber and the turbine rotor. In recent years, the strength of silicon nitride has shown to be above 1000MPa. This has been achieved through advances in manufacturing technology such as materials powder, forming, sintering and so on. But the silicon nitride is easily damaged during grinding because it has less fracture toughness than metal. Consequently, the inherent strength of the material is not demonstrated in the actual products presently produced. It is assumed that the main cause of strength reduction is microcrack. In ordinary grinding methods, the length of microcrack has been estimated at approximately twenty micrometers by fracture mechanics analysis.

The recent growth of available computational resources has enabled the automotive industry to utilize unsteady Computational Fluid Dynamics (CFD) for their product development on a regular basis. Over the past years, it has been confirmed that unsteady CFD can accurately simulate the transient flow field around complex geometries. Concerning the aerodynamic properties of road vehicles, the detailed analysis of the transient flow field can help to improve the driving stability. Until now, however, there haven’t been many investigations that successfully identified a specific transient phenomenon from a simulated flow field corresponding to driving stability. This is because the unsteady flow field around a vehicle consists of various time and length scales and is therefore too complex to be analyzed with the same strategies as for steady state results.

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.

Filiform corrosion phenomenon and its prevention method for 5000 series aluminum alloy sheet have been investigated. The painted aluminum alloy sheets were subject significantly to filiform corrosion caused by formation of a mottled and coarse zinc phosphate film during chemical conversion process. On the other hand, galvanized aluminum alloy sheet showed an uniform and fine phosphate film in a brief time and the filiform corrosion resistance was improved markedly. The test results of press-forming and corrosion for the prototype engine hoods made of this newly developed galvanized sheets have revealed a good formability and an excellent filiform corrosion resistance.

The wheel torque measuring system (abbr. WTMS) has been developed for evaluating the torque applied to each wheel of automotive vehicles under actual running conditions. WTMS is a novel type system in which the torque signal is transmitted by a high-performance and compact photo-telemetric coupling system. Within the torque measurement range of ±2.94 kN·m, the resolution of torque output is ±1 N·m so that torque can be measured with an extremely high degree of accuracy. Therefore, measurements can be taken from the high torque applied in the case of a quick accelerating test or a sudden braking test to the measurement of a low amount of torque such as running resistance of a vehicle.

Toyota Hybrid System (THS), that combines a gasoline engine and an electric motor was installed in the Prius, which was introduced in 1997 as the world's first mass-produced hybrid passenger car, and was vastly improved in 2003. The new Prius gained a status of highly innovative and practical vehicle. In 2005, combined with a V6 engine, THS had a further evolution as a Hybrid System for SUV, which was installed in the RX400h and Highlander Hybrid to be introduced into the world. This report will explain “new THS” which achieved both V8 engine power performance and compact class fuel economy, while securing the most stringent emission standard, SULEV.

A new method to measure in-cylinder flame propagation and mixture distribution has been developed. The distribution is derived from analyzing the temporal history of flame spectra of CH* and C2*, which are detected by a spark plug type sensor with multi-optical fibers. The validity of this method was confirmed by verifying that the measurement results corresponded with the results of high speed flame visualization and laser induced fluorescence (LIF) measurement. This method was also applied to analysis of cyclic combustion fluctuation on start-up in a direct injection spark ignition (DISI) engine, and its applicability was confirmed.

In the field of automotive gasoline engines, new products aiming at greater fuel economy and cleaner exhaust gases are under development with the aim of preventing environmental destruction. Severe ignition environments such as lean combustion, stronger charge motion, and large quantities of EGR require ever greater combustion stability. In an effort to meet these requirements, an iridium plug has been developed that achieves high ignitability and long service life through reduction of its diameter, using a highly wear-resistant iridium alloy as the center electrode.(1)(2) Recently, direct injection engines have attracted attention. In stratified combustion, a feature of the direct injection engine, the introduction of rich air-fuel mixtures in the vicinity of the plug ignition region tends to cause carbon fouling. This necessitates plug carbon fouling resistance.

In October 1998, a new mass-produced car with titanium engine-valves was released from TOYOTA Motor Corporation. Both intake and exhaust valves were manufactured via a newly developed cost-effective P/M forging process. Furthermore, the material which was specially designed for the exhaust one is a unique titanium metal matrix composite (MMC). This paper discusses the materials and manufacturing methods used. The tensile, fatigue strength and creep resistance of the MMC are always superior to those for the typical heat-resistant steel of 21-4N. Both valves have achieved sufficient durability and reliability with a manufacturing cost acceptable for mass-produced automobile parts.

Newly designed gears are subject to higher loads that demand a steel that is capable of greater pitting resistance. The application of shot peening to gears has been increasing to improve tooth root strength, but pitting resistance had not been necessarily high. This study examines the effect of alloying additions mainly on tempering resistance and the formation of a non-martensitic layer. The developed high Si-Mo type steel shows excellent pitting resistance, even in shot peened gears, as compared to that of conventional steels due to high tempering resistance and the thin, uniform non-martensitic layer. This new steel is of practical use in some multi-speed automatic transmission gears.

In the present social environment, automobile demands further reduction of fuel consumption and light weight. Now that the reduction of vehicle weight is being pursued, even a slight looseness in each element of an automobile may become a source of vibration and noise due to the lowered rigidity of such an automobile. The quietness of vehicles is urged, spline backlash in the spline mechanism exhibits a problem in some cases. A propeller shaft, a part of the automobile driving system, also has a sliding spline mechanism as shown in Fig. 1. Such a propeller shaft is required to have functions of transmitting high torque driving forces, and absorbing the variation of the vehicle driveline overall length at the same time. Vibration and noise are apt to occur if when torque is applied, there is a significant balance fluctuation or great sliding resistance due to spline backlash.

The camshaft for an automobile engine is generally made of chilled cast iron. Due to increasing demand for higher performance, lawer maintenance and better fuel economy, it is difficult to make the cast iron camshaft lighter and/or more durable. In order to overcome these problems, development of an integral camshaft comprised of a sintered alloy cam piece for better wear resistance and steel tube for weight saving has been accomplished. In 1981 Toyota Motor Corporation successively started the mass-production of the sintered intergral camshaft for the new 1.8 liter ls engine. The significant advantages are as follows; (1) Weight saving (2) Excellent wear resistance (3) Improvement of lubrication system (4) Saving machining cost

A camshaft for an automobile engine is generally made of chilled cast iron. But, because of increased demand for higher performance engines, a camshaft with many camshaft has been expected. The cam intervals were necessarily narrow. So it was difficult to manufacture the conventional chilled cast iron camshaft at a moderate price. In the case of a rocker-arm type valve mechanism, higher wear resistance was necessary. After due consideration to solve these problems, development of surface remelted chilled layer camshafts by Toyota's unique manufacturing method has been accomplished. In 1984 Toyota Motor Corporation started the mass-production of this camshaft, first for the new 1.0 liter 1E engine, and then for the 1.3 liter 2E engine. In this paper, the excellent wear resistance, the low manufacturing cost and the characteristic manufacturing method are described.

A new partial strengthening method, TIG (Tungsten Inert Gas) remelting process, for automobile aluminum alloy castings is described. The preferable operating variables to strengthen, and metallurgical-mechanical properties of remelted alloys formed under selected conditions have been investigated. As a result, the mechanical properties such as strength and toughness, and thermal crack resistance of the remelted alloys were improved markedly due to the effects of microstructure refining and cast defects decrement by remelting. So, the application studies for automobile parts to meet the characteristics of this process have been carried out. Consequently, TIG remelting process has been practically used as an available strengthening method for the portion between valve ports of high performance diesel engine cylinder head.

To reduse crosswind sensitivity, the yaw moment should be decreased under both transient and steady conditions. The transient condition is when a vehicle comes out immediately from a tunnel into a crosswind while the steady condition is when driving straight along the coastline. After studying the pressure distribution and the flow pattern around the body, we have reached the ideal air flow at the front-side corner that reduces the yaw moment under both conditions. And we have devised an entirely new method to achieve this better air flow. The method uses an internal flow generated by a pressure difference in the flow feeld to create a jet effect and by using only a duct for internal flow to control the outside air flow. It is done without any change to the exterior styling, except at the flow exit. We call it “Aero Slit”. This “Aero Slit” is effective only under crosswind conditions, and does not increase aerodynamic drag when a crosswind is not blowing.

Previous studies and recent practical aerodynamic evaluations have shown that aerodynamic drag of passenger vehicles with “ground simulation” with moving ground and rotating wheels may increase in some cases and decrease in other cases relative to the fixed ground and stationary wheel conditions. Accordingly, the effects of the ground simulation on the aerodynamic drag should be deeply understood for further drag reduction. Although the previous studies demonstrated what is changed by the ground simulation, the reason for the change has not been fully understood. In this article, the effects of wheels and wheel houses attachment and those by the ground simulation with ground movement and wheel rotation on the aerodynamic drag were investigated by quantification of the underfloor flow that plays a crucially important role on the formation of vortical structure around vehicles.

Engine friction reduction is an effective means to improve fuel consumption. Fluid friction reduction of main bearing is examined for engine friction reduction in cold condition. As one of the examinations, it was focused on low temperature of lubricating oil in the early stage during engine cold start. In hydrodynamic lubrication, the oil film temperature is maintained by balance between heat generation and heat transfer. The heat generation is generated by shear of lubricating oil. The factors of the heat transfer, the following elements are considered as follows, A) The heat transfer to a crank shaft, B) The heat transfer to a bearing, C) The heat transfer by convection. If the heat generation is constant, oil film temperature is increased by reduction of heat transfer. It is considered that the reduction of oil leakage and reduction of the heat transfer by convection is equivalent.

This paper provides an overview of the automotive technology and its future trends mainly focussing on Japan. The future automotive technology will basically be on the projection of current technology, although it is expected more progress to be made in advanced and precision control systems. The application of electronics and development of new materials will play a very important role in this area.

The authors developed a high-reliability low-cost gold-plated connector for automobiles. The connector is covered with three plated layers, nickel, palladium-nickel alloy, and gold. The three-layer plating helps to reduce the required thickness of gold. This paper describes the reasons why palladium-nickel plating was adopted and compares the corrosion resistance, oxidation resistance and wear resistance of three-layer-plated materials with those of conventional gold-plated materials. In addition, the characterisitics of three-layer-plated connectors were compared with those of conventional gold-plated connectors. It was found that the reliability of three-layer-plated connectors was as high as that of conventional gold-plated connectors.

Conventionally, sound insulation materials have been applied to control interior noise above 500 Hz, and damping materials to control interior noise below 500 Hz. In this paper, the noise control component for vehicle panels, which consists of damping material and sound insulation material, is investigated by using a two-degrees-of-freedom system. The investigation shows that sound insulation material can be effective in reducing interior noise below 500 Hz if its stiffness is reduced. This stiffness depends not only on the spring of the material itself but also on its pneumatic spring which is determined by air-flow resistance. This paper concludes with applications of techniques to reduce interior noise below 500 Hz by improving sound insulation materials.