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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.

This paper describes the HMI, navigation and telematics systems developed specifically for the Nissan LEAF electric vehicle to dispel drivers' anxieties about operating an EV. Drivers of EVs will need to understand various new kinds of information about the vehicle's operational status that differ from conventional gasoline-engine vehicles. Additionally, owing to the current driving range of EVs and limited availability of charging stations, drivers will want to know acccurate the remaining driving range, amount of power and the latest information about charging station locations. It will also be important to ensure that people unfamiliar with EVs will be able to operate them easily as rental cars or in car-sharing systems without experiencing any inconvenience.

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.

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.

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.

Maintaining reliability of the connecting rod bearing is a very important subject, and the following is a problem that needs to be overcome. Predicting reliability has generally depended on minimum oil film thickness (M.O.F.T), but recently, the engines of passenger cars which have greater power and speed potential than conventional ones are sometimes run beyond their M.O.F.T. limit (a degree of roughness around the crank shaft's axis.) In such a case, it is so difficult to predict reliability according to M.O.F.T., that we need a new index which directly shows seizure and wear. For this purpose, we found that the crank shaft pin temperature can be a key cause of seizure and wear according to an analysis of the relationship between its temperature and the seizure and wear caused intentionally. Using this method, we confirmed that the combination of bearing and crank shaft materials is very important for preventing seizure and wear.

Nissan has developed a second generation ceramic turbocharger rotor which provides greater reliability and higher performance than a conventional ceramic rotor. The new rotor is made of silicon nitride, which has demonstrated sufficient strength in vehicle applications. The bonding technique for joining the ceramic rotor to the metal shaft has been confirmed through experimentation to have sufficient reliability. The second generation rotor is featured by the low stress design and higher dynamic strength, and two factors contribute to its higher reliability. The rotor shape was optimized on the basis of results obtained in two analyses of particle impact resistance and applied combined stress. Test results show that the reliability of the second generation rotor have been substantially improved over those of the conventional rotor now being used on production vehicles.

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.

This report describes an arc-welding robot system with a vision sensor which Nissan Motor Co., Ltd. has introduced to automate the arc welding line for truck frames. Developed in-house, this system is now in operation on the arc welding line for Nissan Truck frames at Nissan's Kyushu plant. In developing the system, primary emphasis was placed on assuring practicality and high reliability. Included among the prominent features of the system is the capability to detect the welding line of thin panels with a high degree of accuracy and to calculate corrections when needed. To assure the high speed and reliability needed for the production line, the robot and sensor are separated, and the vision sensors are placed at fixed positions. Detection of the welding line and transmission of data to the robots to correct their positions are completed just prior to welding, so as to avoid the effects of noise and the arc flash during welding.

Car rust has been a big problem. To improve the effectiveness of rustproofing, car materials and some methods are being developed. Sealing the seams of body panels is one important method. But the sealing operation is a difficult process and it is not easy to maintain quality standards for workmen and automatized systems. To overcome this problem, we developed an automatic robot sealing system with following features: 1. The system can be easily installed on an existing conveyor and follows the line conveyor in synchronization during sealing operation. 2. Small robots can cover wide area inside the vihecle. 3. New sealant supply controllers can regurate the supply rate in response to speed and motion of robots with a high accuracy. This system has already been installed in the Murayma plant and has proved successful in achieving a high quality sealing result.

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 contrast to the conventional two-stage cam drive system with a 9.52- mm pitch roller chain, a newly developed silent chain with a 6.35-mm pitch has made it possible to achieve a single-stage system. One traditional drawback of silent chains has been wear elongation. In developing the new chain, reliability was substantially improved by identifying the factors causing wear elongation and their effects and also by optimizing the characteristics of the chain components. The application of this single-stage cam drive system to the new QG engine series has resulted in reduced chain noise, a more compact cylinder head and significant weight savings due to the smaller part count and other improvements.