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In 2006, Nissan began limited leasing of the X-TRAIL FCV equipped with their in-house developed Fuel Cell (FC) stack. Since then, the FC stack has been improved in cost, size, durability and cold start-up capability with the aim of promoting full-scale commercialization of FCVs. However, reduction of cost and size has remained a significant challenge because limited mass transport through the membrane electrode assembly (MEA) has made it difficult to increase the rated current density of the FC. Furthermore, it has been difficult to reduce the variety of FC stack components due to the complex stack configuration. In this study, improvements have been achieved mainly by adopting an advanced MEA to overcome these difficulties. First, the adoption of a new MEA and separators has improved mass transport through the MEA for increased rated current density. Second, an integrated molded frame (IMF) has been adopted as the MEA support.

The ways in which vehicles are used in the field are continually becoming more diverse. In order to provide the optimum solution with respect to performance and weight, it is necessary to be able to assure vehicle endurance reliability with a high degree of accuracy in relation to the manner of use in each market. This situation has increased the importance of accurately quantifying the ways in which vehicles are used in the field and of designing vehicles with sufficient endurance reliability to match the usage requirements. This report presents a “market model” by which the manner of usage in the field can be treated quantitatively using combinations of environmental factors that influence the road load, drive load and corrosion load, representing typical loads vehicles must withstand.

The durability test with road-load input is necessary for evaluating durability of body and chassis structure in automotive applications. This paper shows the method to analyze road-load input to a suspension system for development of a simple component level bench test. This method enables the extraction of the essential inputs to evaluate the durability of suspension parts using the transfer function (frequency response function) measured by Multi-axial Road Simulator and wheel force transducers. These extracted inputs contribute to development of a new realistic component bench test.

This paper describes a newly developed HC-adsorption three-way catalyst and adsorption system that reduce cold-start HC emissions with high efficiency. This system is the first of its kind anywhere in the world to be implemented on production vehicles. An overview is given of the various improvements made to achieve higher cold-start HC conversion efficiency. Improvement of conversion performance was accomplished by (1) increasing the thermal stability of the HC adsorbent, (2) improving desorbed HC conversion efficiency and durability and (3) optimizing the geometric surface area (GSA) of the substrate. Concretely, the thermal stability of the adsorbent was improved by enhancing the high-temperature durability of zeolite. Improvement of desorbed HC conversion efficiency was accomplished by improving the OSC material so as to match the temperature rise characteristic and usage temperature of the catalyst.

Car makers are working hard today to shorten development and production lead times through the use of flexibile manufacturing systems(FMSs)to meet diversified and individualized customer requirements. To achieve this goal, Nissan has been developing many kinds of new technologies and systems such as: (1) the intelligent body assembly system for body assembly processes; (2) a press die stamping simulation method and unified database for press die manufacturing; (3) a robot and facility teaching system using CAD data; (4) an automated assembly line for trim and chassis assembly operations. These new FMS methods have been implemented in many manufacturing areas, including the stamping shop, body assembly shop, painting shop and trim and chassis shop. This paper focuses mainly on the intelligent body assembly system as a typical example of the new production systems and technologies being developed at Nissan.

Eliminating squeal noise generated during braking is an important task for the improvement of vehicle passengers' comfort. Considerable amount of research and development works have been done on the problem to date. In this study, we focused on the analyses of friction self-excited vibration and brake part resonance during high frequency brake squeal. Friction self-excited vibration is caused by the dry friction between pads and rotor, and occurs as a function of their relative sliding velocities. Its vibration frequency can be calculated in relation to the mass and stiffness of the pad sliding surface. Frequency responses of the brake assembly were measured and the vibration modes of the pad, disc and caliper during squeal were identified through modal analysis. Further study led to the development of a computer simulation method for analyzing the vibration modes of brake parts. Analytical results obtained using the method agreed well with the corresponding experimental data.

High strength transmission gears have been developed for use in the final gear set of front-wheel-drive vehicles. The steel used as the gear material has a higher molybdenum content, allowing more austenite to be retained following carburizing than is possible with chromium steel. As a result, the steel can be subjected to higher intensity shot peening by using harder peening particles which are projected by an air-nozzle peening system. With this procedure, the fatigue strength of the gears can be increased 1.6 times over that of conventional gears.

Nissan has added ball bearings to its “High-flow Ceramic Turbocharger”(1) (introduced in 1987) to improve acceleration response by reducing friction loss. The following programs were carried out in applying ball bearings to the turbocharger: Optimum bearing size and material were selected to assure long life; lubrication techniques were employed to achieve compatibility between acceleration response and durability; a thrust support system was designed to assure that the ball bearings endure thrust load which varies in direction and magnitude during engine operation; and the squeeze film damper was optimized to keep the turbocharger silent. These innovations have resulted in a practical ball-bearing turbocharger, which has been installed in Nissan's most recent Skyline model(released in May 1989). This is the first time a ball-bearing turbocharger has been applied to a passenger car.

Use of high strength steel (HSS) could be an important consideration in achieving competitive weight and safety performance of the body-in-white (BIW). This study covers key technical issues in the application development. Many aspects were studied such as formability, weldability and impact strength for application of this grade to the BIW. One of the key issues is spot weldability, especially in the assembly of heavy gauge materials for structural parts. The spot weld strength appears not to satisfy the target for some HSS applications, when hardness of the nugget is high. The relation between weld strength and the chemical composition of steel sheets was studied, because hardness can be controlled by chemical composition and welding conditions. It was found that using lower carbon content or carbon equivalent compared to conventional grades could improve weld strength.

This paper presents a new refrigeration lubricant for use with the HFC-134a retrofit refrigerant in automotive air-conditioning systems originally designed to use the CFC-12 refrigerant, one of the regulated CFCs scheduled to be phased out. This new retrofit lubricant provides high lubricity and excellent performance characteristics as a result of adopting a newly developed PAG base oil with a block polymer structure and a new antiwear additive formulation. In retrofit systems, it assures sufficient durability for wobble-plate-type variable displacement compressors, which experience severe lubrication conditions.

The application of both high strength gear steels and shot peening technology has succeeded in strengthening automotive transmission gears. This technology, though, improves mainly the fatigue strength at the tooth root, but not the pitting property at the tooth face. Therefore, demand has moved to the development of new gear steels with good pitting resistance. In order to improve pitting resistance, the authors studied super carburizing which is characterized by carbide dispersion in the case, especially processed with a plasma carburizing furnace. Firstly, the influence of the carburizing temperature and carburizing period on the carbide morphology was investigated and the optimum carburizing conditions were determined. Secondly, the fatigue strength and pitting resistance was evaluated using carbide dispersed specimens.

A study was made of the possibility of using an acoustic emission (AE) technique to estimate the maximum load applied to automotive carburized gears under actual operating conditions. Three-point bending tests done on carburized steel specimens showed that, provided a small crack was induced in the material, AE was not generated until the material was subjected to a higher bending load than the maximum load previously applied. Using this effect, the maximum load applied to gears, in which a crack had been induced during endurance testing, was estimated. Although the estimated maximum load was about 14% higher than the actual load, the AE technique appears to be a promising method for use in the design and durability assurance of carburized parts of automotive powertrains.

Three Japanese automobile manufacturers-Mitsubishi Motors Corp., Nissan Motor Co., Ltd., and Toyo Kogyo Co., Ltd.-have been making efforts over the past three years to design and develop effective thermal reactor-exhaust gas recirculation and catalytic converter systems suitable for small engines. The work is being done by members participating in the IIEC (Inter-Industry Emission Control) Program, and the exhaust emission levels of the concept vehicles developed by these companies have met the goal established by the IIEC Program at low mileage. Each system, however, has a characteristic relationship between exhaust emission level and loss of fuel economy. Much investigation is required, particularly with respect to durability, before any system that will fully satisfy all service requirements can be completed. This paper reports the progress of research and development of the individual concept vehicles.

A new method for measuring friction has been developed in order to analyze piston and piston ring assembly friction force during engine operation. While this method does not require extensive modification to the piston or cylinder, two extra compression and expansion strokes each are added at the end of the conventional four-stroke cycle. In these measuring strokes, the gas pressure and temperature are maintained at firing levels, and friction force characteristics of the piston and piston ring assembly are measured continuously while the burned gas is compressed and expanded.

Development of a high strength valve spring for automotive engines achieves higher power output and better fuel economy. New material which consists of finely structure and subjected to advanced shot peening, has been developed. Stress analysis of the valve spring moving edge, using the finite element method, has been done for effective application. The merits of this new spring have been confirmed by engine experiments.

A compact, high-performance and durable metal-supported catalyst has been developed by using the properties of the metal support effectively. The advantages of the metal-surpported catalyst against the ceramic-supported one are higher geometrical surface area, higher heat conductivity and thinner wall thickness. Higher geometlical surface area and higher heat conductivity lead to higher conversion efficiency after durability test and it allows reduction in catalyst volume. And the thinner wall thickness lowers gas flow resistance. But also, the metal-supported catalyst has the disadvantage of larger heat expansion and it requires special structure and material.

Excellent fuel economy and high performance have been urgent in Japanese automobile industries. With increasing engine power, many of the power train components have to withstand higher loads. Differential pinion gear being one of those highly stressed parts, excellent fatigue and shock resistance have been demanded. At first the fundamental study on the fatigue and impact crack behavior of carburized components was studied and the new grade composed of 0.18%C-0.7%Mn-1.0%Cr-0.4%Mo was alloy designed. Furthermore, Si and P is reduced less than 0.15 and 0.015%, respectively aiming at the reduction of intergranular oxidation and improved case toughness. The differential gear assembly test has proved that the new grade shows three times as high impact strength as that of conventional steel, SCM418, and almost the same as that of SNCM420 containing 1.8%Ni.

Methods to evaluate the light degradation environment of automotive interior materials in the market have been studied. The aim for this study was calculating the light degradation environment quantitatively on the basis of meteorologically observed value. For the quantitative light degradation factor, Equivalent Total Sunshing Energy (ESE) was used. ESE was a value presented by the authors in 1982. Although ESE correlates closely with the degradation, it takes more than one year to determine at a given resion. With this new method, a monthly average daily ESE at the gien resion was estimated numetically based on the meteorologically observed monthly average solar radiation and monthly maximum air temperature at the resion. The calculated value in relation to actual measured value were accurate to within 10%.

In 2006, Nissan began limited leasing of the X-TRAIL FCV equipped with their in-house developed Fuel Cell (FC) stack. Since then, the FC stack has been improved in durability, cold start-up capability, cost and size with the aim of promoting full-scale commercialization of FCVs. However, reduction of cost and size has remained a significant challenge because limited mass transport through the membrane electrode assembly (MEA) has made it difficult to increase the rated current density of the FC. Furthermore, it has been difficult to reduce the variety of FC stack components due to the complex stack configuration. In this study, improvements have been achieved mainly by adopting an advanced MEA to overcome these difficulties. First, the adoption of a new MEA and separators has improved mass transport through the MEA for increased rated current density. Second, an integrated molded frame (IMF) has been adopted as the MEA support.

Wireless Power Transfer (WPT) promises automated and highly efficient charging of electric and plug-in-hybrid vehicles. As commercial development proceeds forward, the technical challenges of efficiency, interoperability, interference and safety are a primary focus for this industry. The SAE Vehicle Wireless Power and Alignment Taskforce published the Recommended Practice J2954 to help harmonize the first phase of high-power WPT technology development. SAE J2954 uses a performance-based approach to standardizing WPT by specifying ground and vehicle assembly coils to be used in a test stand (per Z-class) to validate performance, interoperability and safety. The main goal of this SAE J2954 bench testing campaign was to prove interoperability between WPT systems utilizing different coil magnetic topologies. This type of testing had not been done before on such a scale with real automaker and supplier systems.