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Owing to the small size of engines and high injection pressures, it is difficult to avoid the fuel spray impingement on the combustion cylinder wall and piston head in Direct Injection Spark Ignition (DISI) engine, which is a possible source of hydrocarbons and soot emission. As a result, the droplets size and distribution are significantly important to evaluate the atomization and predict the impingement behaviors, such as stick, spread or splash. However, the microscopic behaviors of droplets are seldom reported due to the high density of small droplets, especially under high pressure conditions. In order to solve this problem, a “spray slicer” was designed to cut the spray before impingement as a sheet one to observe the droplets clearly. The experiment was performed in a constant volume chamber under non-evaporation condition, and a mini-sac injector with single hole was used.

In previous Life Cycle Assessment (LCA) methods, environmental burden items to be analyzed, prior to a life cycle inventory analysis, were assumed as the main factors of environmental problems regardless of the product category. Next, the life cycle inventory analysis, in which the total amount of environmental burden items emitted during the life cycle of a product was calculated, and an environmental impact assessment were performed. The environmental impact assessment was based on the initially assumed environmental burden items. The process, in other words, was a particular solution based on this assumption. A general solution unconstrained by this assumption was necessary. The purpose of this study was to develop a general method of LCA that did not require such initially assumed environmental burden items, and to make it possible to perform a comprehensive environmental impact assessment and strategically reduce environmental burden of a product.

Spot friction welding (SFW) is a cost-effective spot joining technology for aluminum sheets compared with resistance spot welding (RSW) [1]. In this study, coated mild steel was spot friction welded to 6000 series aluminum using a tool with shoulder diameter of 10 mm and welding conditions of 1500-2000 rpm and time of 5 s. Testing showed that tensile shear strength increased as the solidus temperature of the coating on the steel decreased. Microstructure characterizations of steel/Al joint interfaces showed that zinc from the coatings was incorporated into the stir nuggets and that intermetallic phases may have formed but not in continuous layers. Some Al-Zn oxides that appeared to be amorphous were also found in the joint interfaces.

In recent years, improving fuel efficiency and collision safety are important issue. We have worked on a new construction method to develop body structure which is light weight and strong/stiff. We adopt multi type Tailor-Welded Blanks (TWB) which is formed after welding several steel sheets for ATENZA (MAZDA 6), NEW DEMIO (MAZDA 2), and RX-8. This is a technology to consistently improve of such product properties and to reduce costs. Laser welding is a common TWB welding method, but for further equipment cost reductions and productivity improvements, we have developed a higher welding speed and robust plasma welding and introduced this to mass production. We introduce this activity and results in this report.

Vulcanized rubber hoses are difficult to recycle and have a complicated manufacturing process. Recently, we have developed the vacuum hose for engine control out of thermoplastic elastomers. As a result of this development, scrap material from the manufacturing process can be recycled and, in addition, about a 30 percent weight reduction and a 20 percent cost reduction are achievable by virtue of the lower specific gravity and by the more simplified manufacturing process. In order to assess the feasibility of using thermoplastic elastomers for vacuum hoses, we developed a heat aging simulation test method. This was achieved by first investigating the actual vehicle environmental conditions of currently used vacuum hoses by retrieving and examining these hoses from used vehicles. We then extrapolated what the condition of such hoses would be after being subjected to heat aging for 200,000 km of service in an actual vehicle, and applied this calculation to our newly developed hoses.

Several different steel sheets were tested for energy absorption, using hat square columns and dynamic crash testing. Results indicate that steel sheets containing large volume fraction of retained austenite have relatively high energy absorption. The relationship between retained austenite and energy absorption was analyzed. These special steel sheets have already been successfully used for production body parts, such a front-side-member, without difficulties arising in volume production.

Austempered ductile iron (ADI) is a material having excellent mechanical properties and damping capacity. However practical mass production of ADI gears has not been possible due to ADI's poor machinability and distortion during the austempering heat treatment. With a new process method of carrying out hobbing before austempering when the material is in its soft condition, then austempering it and lastly, conducting the shave finishing process, we have diminished the above defects and developed practical ADI gears. These new gears generate less noise than ordinary nitrocarburized steel gears and are superior in pitting resistance.

When replacing a metal engine part with plastic, it is necessary to regard vibration damping as one of the important factors in terms of noise reduction as well as strength and heat resistance as being characteristics of the material. Plastics are far better for vibration damping than steel or aluminum, but this property is reduced by the addition of glassfiber-reinforced or high heat-resisting resins. We have taken notice of SMC (Sheet Molding Compound) which has the excellent strength and heat resistance properties and studied it in order to increase its vibration damping property. Since organic polymers show the peak value for vibration damping performance in the vicinity of the glass transition temperature (Tg), we studied a method to shift the Tg near the operating temperature region in order to improve the vibration damping property.

Mazda established an original design methodology combining a capacitive coupling technology and transmission line theory, to develop a high performance window antenna for AM/FM radios which construction is very simple to construct and requires no use of any antenna boosters or matching circuits. This paper introduces the design methodology and performance characteristics of the new antenna as well as its application to the production '95 model Mazda 929.

We have developed a tappet with a cam lobe contacting tip made of a hard sintered material whose base material is cobalt, which adheres less to the steel of camshafts, and which also contains fine particles of tungsten carbide and chrome carbide. We have established a new evaluation method to access wear resistance performance of the tappet. It enables us to measure directly the friction force generated between the cam lobe and tappet and to evaluate anti-scuffing performance with high accuracy because we can clarify the time, load and cam angle at which scuffing occures.

An investigation of anti-corrosion steel sheets (non-galvanized) which contain copper for automobile body parts has been conducted. Copper additives accelerate the formation of amorphous substrates. These substrates decrease the rate of corrosion. In order to retain the steel's formability and weldability, the contents of the alloying elements have been optimized. As a result, this newly developed steel sheet can be used for many different applications such as door sashes and door panels of mass produced cars. This paper describes the key properties of the newly developed steel sheet and additionally the mechanism of corrosion prevention, weldability, formability, and so on.

A method was studied for simultaneous zinc phosphating on aluminum and steel surfaces to obtain high corrosion resistance on aluminum surfaces, which conventional phosphatic processing could not provide with sufficient corrosion resistance. Since aluminum is protected by an oxide film on its surface, it has poor processability with zinc phosphating solutions applied to steel. An appropriate quantity of fluoride was therefore added to improve processing, and the coating film, aluminum composition and surface conditions were optimized to suppress filiform corrosion, which is characterized by string-like blisters of paint film starting from a paint defect. In addition, in view of the actual production environment, the corrosion resistance of the ground area made for readjustment after stamping was studied for the optimization of the processing solution.

In order to investigate the corrosion resistance of organic composite-coated steel sheets ( OCS ) in a real automotive environment, many kinds of corrosion tests were performed on test pieces and real automotive doors. Tests with a corrosive solution including iron rust were introduced to simulate the real corrosive environment of automotive doors. The relationship between the components of OCS and the corrosion resistance in the rust-including tests was examined. In addition, electrochemical studies were performed. Results indicate OCS has much better corrosion resistance than plated steel sheets with heavier coating weight in all tests. OCS shows excellent corrosion resistance in rust-free corrosive solution, however, some types of OCS do have corrosion concerns in rust-including tests. It became clear that these OCS types have an organic coating with lower cross-linking.

This paper describes the results of the study and research on ovate wire helical springs which have been jointly conducted by the members of the Japan Society for Spring Research consisting of the engineers from material suppliers, wire and spring producers and automotive manufacturers as well as researchers at Japanese universities. Attention is focused particularly on two types of wire cross sections, typical elliptical shape and Fuchs' egg-shape. Stresses on these two cross sections were analyzed by numerical calculations within the range of practical specification, and then the results have been compared with those of round wire spring. As a result, it has been found that the elliptical wire spring is superior to Fuchs- egg-shaped one for general application. Simple designing methods for the both types of wire helical springs have been developed based on the findings from the stress analysis.

Mitsubishi Motors Corporation uses spiral bevel gears in the transfer system for 4-wheel drive passenger cars modified from the front wheel drive configuration. This transfer gear ratio is near 1:1, and gears have uniform depth teeth cutting by the continuous generating method of OERLIKON cutting machine. In this method, the cutter and the work rotations are timed together to accomplish continuous indexing and cutting in order to enable high productivity. In general, it is difficult to reduce the meshing noise of spiral bevel gears and control its quality. The authors established the tooth surface coordinates, to reduce the meshing noise, by studying the influence of tooth surface coordinates on the meshing transmission error (MTE).

This paper presents several methods for reducing engine weight primarily through substitution with light-weight materials. The efficiency and performance of the engine were reviewed using a light-weight experimental engine (hereinafter called “weight-reduced engine”) constructed by the authors in order to investigate the possibility of practical use of the proposed weight reduction measures. The weight-reduced engine is based on an in-line 4-cylinder, 2.0 liter, gasoline engine with the base engine weight of 162 kg excluding engine oil and coolant and was reduced by 37 kg by applying alternative light-weight materiaLs and new manufacturing techniques. This corresponds to 23 % weight reduction. The materials used in the weight-reduced engine are 53 % steel, 33 % aluminum, 7 % plastics and 7 % other light-weight materials. It was found that by application of light-weight materials, the engine performance of the weight-reduced engine could be improved.

As a demand for vehicles of higher functionality grows, automakers and material suppliers are devoting increasing efforts to develop technologies for greater safety, lighter weight, higher corrosion resistance, and enhanced quietness. The resin-sandwiched vibration damping steel sheet (VDSS), developed as a highly functional material for reducing vehicle vibration and noise, has been used for oil pans1) and compartment partitions2). First applied for a structural dash panel of the new Mazda 929, a Zn-Ni electroplated VDSS which allows direct electric welding has contributed to greater weight reduction as well as improved quietness.

Beta Ti alloy valve spring retainers are newly developed for use in mass produced automobiles for the first time. Ti alloy valve spring retainers vith a weight saving of 42%, compared to steel retainers, have reduced the inertial weight of the valve train components by 6%. And this weight reduction has the benefit of increasing the upper limit of the engine speed, which improves the engine performance. Ti alloy valve spring retainers are cold forged by the conventional fabrication facilities for steel retainers, using Ti-22V-4Al (the beta Ti alloy) which possesses excellent cold workability in a solution treated condition. Oxygen surface hardening is applied to protect Ti alloy valve spring retainers from wear damage. In addition, aging treatment and shot blasting are performed to improve strength and stiffness of valve retainers.

This paper describes a calculating method to predict the quasi-static collapsing behaviors of spot-welded closed-hat section curved beams under axial compression. The overall deformat ions and the local buckling modes of beams were calculated using a geometrical model. Force-displacement relations were predicted by a elastic-plastic structural analysis method using the ‘plastic hinge’ concept. Collapsing tests were made on beams which are differenting section size, rotation angle, and metal sheet thickness. Comparisons between the calculated and experimental results of deformed shapes of beams, the local buckling modes and the force displacement relations are discussed.

The authors developed, for use in diesel engines, ceramic tappets cast in aluminum alloy that drastically improved wear resistance and valve train dynamics. The ceramic tappets consist of two parts: a ceramic head, which contacts the cam and push rod, and a tappet body made of aluminum alloy. Concerning the ceramic, silicon nitride was the best material of the three ceramics evaluated in the tests and the sliding surface, in contact with the cam and push rod, was left unground. As for the aluminum alloy, hyper-eutectic aluminum-silicon alloy with a controlled pro-eutectic silicon size was selected. A reliability analysis using the finite-element method (FEM) was also made on the structure of the ceramic tappet for enhanced durability and reliability. The combination of this tappet and a cam made of hardened ductile cast iron, hardened steel, or chilled cast iron, respectively exhibits excellent wear resistance.