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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.

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.

This paper describes the development of alloy cast iron that can be used for the cutting edges of the trimming die of a press die. Usually, a block of tool steel or steel casting is inserted at the cutting edge of the trimming die of a press die. However, we unified the structure part and the cutting-edge part of a press die with alloy cast iron. As it can''t bear as the cutting edge in this state, the cutting edge is processed by flame-hardening. After the flame- hardening, we developed the alloy cast iron so that enough hardness may be obtained by natural air cooling. Thereby, the machining of the installation seat of the cutting edge decreased and the expense of dies has been reduced.

In Toyota, a robot off-line programming system was developed five years ago for the use at spot welding processes. And it has been effective to reduce and level off the engineering time. This time we have developed the new robot simulation system. It has three newly features so that the system becomes capable of simulating and programming robots from various manufacturers with different functions. As a result, the new system can be applied to a variety of processes in automobile manufacturing. First, a universal robot programming language was developed which includes a variety of commands such as definitions of motion attributes, signals of inputs/outputs, control of program flow, special functions proper to each process, and so on. And the language can be translated to and from any particular programming language using pre / post processor, so the simulation system needs to deal with only one language.

This newly developed helical spring can be used at a stress level up to 1300 MPa. The material is composed of Fe-C-Si-Mn-Ni-Cr-Mo-V alloy. Its strength-toughness balance was greatly superior to that of other spring steels. To improve the fatigue strength at a higher stress level, decarburization at the surface upon austenitizing was severely controlled, applying induction heating. Then, a special shot peening process, introduced for the first time, was applied to obtain a surface residual stress at the surface of over 1000 MPa. The spring was first applied to a 1992 TOYOTA model car. Plans are to increase the use since the spring material achieves a weight reduction of at least 30 % and, possibly, 35 to 40 %.

Since the first robot: was introduced into our factory in 1971, about 1250 playback robots have been operated. But processes in which these robots were installed were limited to particular ones such as spot welding, are welding and painting. In many other processes robots have not been installed. Investing the reasons there is a main factor as follows, As to the application of robot, it is hard to evade the diversity of robot type because robots must be different from each other, if the most suitable robots are chosen in setting space, operating area, load capacity, speed and accurary against applied process and work pieces. If standard robots in the market are fitted to various conditions of processes or work pieces, the types of robots increase and many problems are produced on operation and maintenance.

The EMT (Elastomer Modified Thermoplastics) currently used in passenger car bumper fascia are limited in retaining low CLTE (Coefficient of Linear Thermal Expansion) and impact resistance, although they are highly rigid, which allows a reduction in weight, and also have high flowability during injection molding. We have developed a new bumper material called “Super Olefin Polymer” using a unique theory based upon a reversal of the current concept. The current polymer design concept of the EMT material is to compound and disperse the EPR (Ethylene Propylene Rubber) into the resin matrix such as polypropylene. We reversed the domain and the matrix, and treated the resin phase as the filler and the elastomer phase as the matrix.

In a two-loudspeaker stereophonic reproduction system of a passenger car, the geometrical configuration of the right and left loudspeakers has the disadvantage of being asymmetrical to the listener. For this system, we have made both theoretical and experimental verifications of the effects of strongly reflected sounds on the sound pressure level difference and phase difference between two ears which determine the location of sound image in a small compartment of a passenger car. On the basis of these verifications, we have developed a new sound localization control system. With this system, acoustical effects such as sound expansion and ambience have been greatly improved in a passenger car. In this system, input signals to the loudspeakers are controlled so that the sound image produced by the loudspeaker nearer to the listeners may acoustically move so as to position itself symmetrically with the other loudspeaker with regard to the listeners.

We developed a fastening method to reduce noise levels and fastening work loads. The development was based on research into improved tools and fasteners. This was done in preparation for an increase in elderly worker and female worker population in the Automobile Assembly Shop. The principle of this method is to form female threads inside a straight sleeve by clinching the sleeve around a threaded bolt. We achieved improvements in component material clinching force and a durability for loosening torque compared to conventional bolt and nut methods.

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

The transfer efficiency for painting processes utilizing water-borne materials is low, and the residual paint is disposed of as waste. In this study, we focused on a recycling system to collect and dissolve the paint over-spray in the booth water, and to concentrate and regenerate it by means of an ultra filter (UF). Paint adaptable to the recycling system has been developed by providing compatibility between the high hydrophilicity of liquid paint and the high hydrophobicity of the paint film, in order to ensure the recyclability and the high anti-corrosion performance required of paint on automobile underbody parts. This recycling technology is used in an actual propeller shaft painting process and provides large waste reduction and a decrease in painting cost.

One of the key elements of vehicle safety requires a constantly uninterrupted visible view especially during unexpected weather conditions. Our present development of a light reflection type rain sensor is a key device of our automatic windshield wiper system. The design concept of the sensor is based on the quantification on both detected rainfalls and wiping modes in order to match the wiping mode in an operator's mind by optimizing the optical sensing system and establishing an algorithm for controlling wiping. In addition, auto-initialization of the system has been achieved first in the world.

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.

In preparation for compliance with California's SULEV standard and Euro STAGE 4 standard, which will take effect in 2002 and 2005, respectively, we have developed a laminated planar oxygen sensor. The developed sensor has the following characteristics: high thermal conductivity and superior dielectric characteristic, due to direct joining of the heater element alumina substrate and the sensor element zirconia electrolyte; low heat stress at temperature rise, due to optimized heater design; superior sensor protection from water droplets, and improved sensor response, due to optimized arrangement of intake holes in the sensor cover. With these characteristics, the developed oxygen sensor can be activated in 10 seconds after cold start. This report describes the technologies we used to develop the early-activation oxygen sensor.

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 automotive plastic parts, bumpers are rather bigger parts and easy to be detached. And there is growing need to develop bumpers recycling technology. Now we developed the recycling technology for waste painted Super Olefin Polymer (SOP) bumpers from car dealers in production. This technology consists of discriminating from the repair in market by dyeing, and of melting SOP resin and hydrolysis of the paint film which are carried out simultaneously in a twin-screw extruder Reactive Processing System.

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.

A new, free-cutting steel, hereafter referred to as “non-lead-added free-cutting steel”, has been developed with the intention of replacing currently applied lead containing free cutting steel. The ultimate goal of this project is to provide a new lead-free steel grade that will contribute to the removal of environmentally harmful substances from automobile parts. In this project, we have targeted the development of a material that would demonstrate levels of machinability and other mechanical properties equivalent to those of the conventional free-cutting steel to which sulfur (S), lead (Pb) and calcium (Ca) or combinations, thereof have been added. The fine dispersion of sulfide, modified by adding Mg and Ca, is most effective in enhancing the chip breakability that would otherwise deteriorate due to the absence of lead. The practical application of the non-lead-added free-cutting steel has rendered the goal of total removal of lead from special steel products highly obtainable.

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.