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This paper presents an improvement in the accuracy of NOx sensors at high NOx concentration regions by optimizing the manufacturing process, sensor electrode materials and structure, in order to suppress the deterioration mechanism of sensor electrodes. Though NOx sensors generally consist of Pt/Au alloy based oxygen pump electrodes and Pt/Rh alloy based sensor electrodes, detailed experimental analysis of aged NOx sensors showed changes in the surface composition and morphology of the sensor electrode. The surface of the sensor electrode was covered with Au, which is not originally contained in the electrode, resulting in a diminished active site for NOx detection on the sensor electrode and a decrease in sensor output. Theoretical analysis using CAE with molecular dynamics supported that Au tends to be concentrated on the surface of the sensor electrode.

We have developed a new torsional damper spring which lowers the torsional rigidity of the clutch disc while retaining its conventional size. The following two items have been adopted in the newly developed spring: 1) A new steel wire which suppresses any core-softening of the element wire through nitriding. 2) A dual-stage shot peening method which uses harder steel shots (rather than conventional shots) in order to obtain an optimal residual stress profile. As a result of evaluating the fatigue characteristics of this spring, it was discovered that its fatigue strength is approximately 35% higher than that of the conventional spring. A clutch disc using this spring was able to absorb rattling noises which conventional clutch discs could not.

In conventional gasoline engine vehicles, three-way catalysts are used to simultaneously remove HC, CO and NOx from the exhaust gas. The effectiveness of the catalyst to remove these harmful species depends strongly on the oxygen concentration in the exhaust gas. Deterioration of three-way catalyst results in a reduction in its purification activity and OSC (oxygen storage capacity). In this investigation, additive elements were used to enhance the durability and OSC of the catalyst support material. An optimized formulation of a CeO2-ZrO2 and a ZrO2 material was developed to have excellent durability, improved OSC, enhanced interaction between precious metals and support materials, and increase thermal stability. Using these newly developed support materials, catalysts with increased performance was designed.

A high strength and high toughness new bainitic steel has been developed which shows comparable mechanical properties, fatigue property, and machinability to those of quenched and tempered SAE 5140. The heat treatment of the bainitic steel is aging after hot forging in order to improve ratio of 0.2% proof stress and tensile strength (i.e. yield ratio) and to avoid warpage associated with quenching. The new bainitic steel has been applied to the slender and lightweight lower arms for automotive suspension. As a result, the total production costs in the lower arms have been reduced by nearly 15 percent.

The new Toyota FCV “Mirai” has reduced the weight, size, and cost of the high-pressure hydrogen storage system while improving fueling performance. The four 70 MPa tanks used on the 2008 Toyota FCHV-adv were reduced to two new larger diameter tanks. The laminated structure of the tanks was optimized to reduce weight, and a high-strength low-cost carbon fiber material was newly developed and adopted. The size of the high-pressure valve was reduced by improving its structure and a high-pressure sensor from a conventional vehicle was modified for use in a high-pressure hydrogen atmosphere. These innovations helped to improve the weight of the whole storage system by approximately 15% in comparison with Toyota FCHV-adv, while reducing the number of component parts by half and substantially reducing cost. The time required to fuel the FCV was greatly reduced by chilling the filling gas temperature at the hydrogen filling station to −40°C (as per SAE J2601).

Mass reduction of parts is growing in importance as a means for reducing CO2 emissions from vehicles.The aim of the present research was to contribute to further mass reduction of pistons by developing a new aluminum casting material with highest level of fatigue strength. This goal was achieved using a development concept of creating a homogeneous structure in which Ti was added to create a fine structure and appropriate quantities of Fe and Mn were added to form a compound that is stable at high temperatures. Stand-alone tests of prototype pistons fabricated using the developed material show that the material is 14% stronger than the conventional material, thereby enabling increases in power and mass reduction.

This paper describes the development of one-piece die cast magnesium steering wheel frame for a steering wheel incorporating an air bag system. The light weight magnesium frame was designed to have proper stiffness, strength and characteristics of energy absorption. Magnesium alloys with various aluminum contents were tested, and AM60B alloy was selected because of its favorable properties of strength and elongation. New manufacturing techniques, for example, a vacuum hot chamber die casting system and a surface defect inspection system were developed in order to produce high quality castings. The characteristics of energy absorption were evaluated in the laboratory and on actual vehicle crash test, and the results were satisfactory. The magnesium steering wheel frame is about 45% (550g) lighter than the steel one. It has been in production in Toyota passenger cars with driver side air bags.

Toyota Motor Corporation has mass-produced turbochager with sillicon nitride ceramic rotors. A moment of inertia was reduced by 60% using ceramic rotor which improved turbochager response. The ceramic rotor was joined to metal shaft by new method which compensated problems in both shrink fitting and active brazing methods. They are generals for mechanical and chemical techniques, respectively. There still exist the following disadvantages. It is quite severe to controll the clearance of shrink fitting to obtain the reliability of the joint. The shaft may be loosened at high temperature with a small shrink-fit interference. The large shrink-fit interference could result in a failure of ceramic shaft due to large stress. Those may require a machinig accuracy with micron meter order of surface roughness which, leads to high cost.

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.

A new 3-way catalyst with NOx conversion performance for lean-burn engines has been developed. The catalyst oxidizes NOx and stores the resulting nitrate, which is then reduced by HC and CO during engine operation around the stoichiometric air/fuel ratio. Both the composition of the storage component and the particle sizes of the noble metal were optimized. In addition, a special air fuel mixture control has been developed to make the best of the NOx storage-reduction function. The present catalyst showed 90% conversion efficiency and improved fuel economy by 4% in the Japanese 10-15 mode test cycle. The efficiency remained at 60% or more after durability test.

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 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.

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 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.

Concerning the road load of the vehicle, there are many discussions about how to measure and how to simulate it on the chassis dynamometer. Also many studies have been done in our laboratory to find out the best solution in aspects of logic, instruments, procedure and reliability. Our solution resulted in “Simplified Coastdown Method (SCD)” which is featured by the concept of force-based measurement and setting of chassis dynamometer. This method was proposed to ISO as a candidate for the standard procedure under the support of Society of Automotive Engineers Japan. In this paper, the method is evaluated by comparing with current coastdown method and wheel torque method. From a practical point of view such as easiness of instruments handling, applicability of the facilities, simplicity of installation and procedure, we have come to a conclusion that the SCD method is the most suitable procedure

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

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 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 succession to the world-first introduction of a mass production gasoline hybrid passenger car into the Japanese market in 1997, Toyota also has introduced an enhanced version of the above to the US and European markets in 2000. Upon introduction of Toyota Hybrid System (THS) into the US market, a drastic reduction of gasoline vapor evaporation from the fuel tank was necessary, in order to meet the most stringent exhaust emission (SULEV) and evaporative emission standards in the world. In order to meet this requirement, a fuel tank system named “Vapor Reducing Fuel Tank System” was developed. This is the first commercial application in the world to use a variable tank volume to drastically reduce gasoline vapor generation.