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Engine oil with viscosity lower than 0W-16 has been needed for improving fuel efficiency in the Japanese market. However, lower viscosity oil generally has negative aspects with regard to oil consumption and anti-wear performance. The technical challenges are to reduce viscosity while keeping anti-wear performance and volatility level the same as 0W-20 oil. They have been solved in developing a new engine oil by focusing on the molybdenum dithiocarbamate friction modifier and base oil properties. This paper describes the new oil that supports good fuel efficiency while reliably maintaining other necessary performance attributes.

The thermal fatigue resistance of engine exhaust system parts has conventionally been evaluated in thermal fatigue tests conducted with a restrained specimen. However, the test results have not always been consistent with data obtained in engine endurance tests. Two new evaluation methods have been developed to overcome this problem. One is a method of predicting thermal fatigue life on the basis of nonlinear elastic and plastic thermal analyses performed with a finite element model and the ABAQUS program. The other is a method of evaluating exhaust system parts using an exhaust system simulator. This paper describes the concepts underlying the two methods and their relative advantages.

Detergent additives in automotive gasoline fuel are mainly designed to reduce deposit formation on intake valves and fuel injectors, but it has been reported that some additives may contribute to CCD formation. Therefore, a standardized bench engine test method for CCDs needs to be developed in response to industry demands. Cooperative research between the Petroleum Association of Japan (PAJ) and the Japan Automobile Manufacturers Association, Inc. (JAMA), has led to the development of a 2.2L Honda engine dynamometer-based CCD test procedure to evaluate CCDs from fuel additives. Ten automobile manufacturers, nine petroleum companies and the Petroleum Energy Center joined the project, which underwent PAJ-JAMA round robin testing. This paper describes the CCD test development activities, which include the selection of an engine and the determination of the optimum test conditions and other test criteria.

A block-on-ring friction and wear testing machine (LFW-1) was used as a test method for making fundamental evaluations of the effect of the Belt-Drive Continuously Variable Transmission(B-CVT) fluid on the friction coefficient between the belt and pulleys. The results confirmed that this method can simulate the friction phenomena between the belt and pulleys of an actual transmission. The mechanism whereby ZDDP and some Ca detergents improve the torque capacity of a B-CVT was also investigated along with the effect of the deterioration of these additives on the friction coefficient. It was found that these additives form a film, 80-90 nm in thickness, on the sliding surface, which is effective in increasing the friction coefficient. The friction coefficient declined with increasing additive deterioration. The results of a 31P-NMR analysis indicated that the decline closely correlated with the amount of ZDDP in the B-CVT fluid.

Many studies have been reported concerning fundamental tribological research aimed at reducing the severe valve train wear that occurs in internal combustion engines. In this paper, cam follower wear was theoretically and experimentally analyzed at the material development stage. Statistical methods have been applied to practical use in determining the material properties quantitatively. Based on the results, a method for predicting cam follower wear has been derived which has made it possible to develop new valve train systems more efficiently. Further, a guideline for developing new wear resistant materials was also clarified. Finally, the precision high chrominum cast iron rocker arm is described, along with its application to a new NISSAN high-performance 4-cylinder DOHC engine, as an example of the use of this method to develop new wear-resistant materials.

Application of microalloyed steel to automobile parts is becoming increasingly common in Japan. However, fatigue properties of actual automotive forged parts with slight notches on their surface have not been fully clarified. In this work, the fatigue properties of microalloyed steel were studied using test specimens and also actual automotive parts. The results indicated that microalloyed steel with an optimal microstructure showed higher notch fatigue resistance than quenched-tempered steel. The improvement of material technology and the application of microalloyed steel have not only served to bring product costs down, but have paved the way for part weight reductions. Lightweight connecting rods for the newly developed Nissan engines have been produced, contributing to improved engine performance.

The life of automotive transmission gears today is often governed by pitting fatigue life. Being able to predict pitting fatigue life accurately is a crucial issue. Pitting fatigue life is substantially influenced by surface hardness and tooth surface geometry. For that reason, this study examined a new method of predicting pitting fatigue life that takes into account changes in these factors over time. This method makes it possible to predict the pitting fatigue life of automotive transmission gears under a wide range of evaluation conditions with markedly better accuracy than conventional methods used previously.

In a previous study, we developed and validated a new driving posture focused on biomechanical loads for physical fatigue reduction in static long-term sitting. In this study, the posture was evaluated in dynamic long-term driving condition by qualitative and quantitative measurements. The results showed physical fatigue of the new posture was halved in comparison with the one of the conventional posture in same car by subjective evaluations. Physiological indices had same tendency with subjective evaluations. From the results, we extracted seven physiological indices as good measures of physical fatigue while driving. Therefore, fatigue reduction of the new posture was qualitatively validated by physiological measurements.

Research is under way on an engine system [1] that achieves a variable compression ratio using a multiple-link mechanism between the crankshaft and pistons for the dual purpose of improving fuel economy and power output. At present, there is no database that allows direct judgment of the feasibility of the specific sliding parts in this mechanism. In this paper, the feasibility was examined by making a comparison with the sliding characteristics and material properties of conventional engine parts, for which databases exist, and using evaluation parameters based on mixed elasto-hydrodynamic (EHD) lubrication calculations. In addition, the innovations made to the mixed EHD calculation method used in this study to facilitate calculations under various lubrication conditions are also explained, including the treatment of surface roughness, wear progress and stiffness around the bearings.

It was found that pitting resistance of gears is strongly influenced by resistance to temper softening of carburized steel. The investigation about the influence of chemical compositions on hardness after tempering revealed that silicon, chromium and molybdenum are effective elements to improve resistance to temper softening and pitting resistance. Considering the production of gears, molybdenum is unfavorable because it increases hardness of normalized or annealed condition. Developed new steel contains about 0.5 mass% of silicon and 2.7 mass% chromium. The new steel has excellent pitting resistance and wear resistance. Fatigue and impact strength are equivalent to conventional carburized steels. Cold-formability and machinability of the new steel are adequate for manufacturing gears because of its ordinary hardness before carburizing. The new steel has already been put to practical use in automatic transmission gears. Application test results are also reported.

Various prediction methods have been proposed for evaluating the fatigue life of welded joints by combining finite element analysis (FEA) with an experimental database. However, to obtain more universal and accurate fatigue life predictions, it is necessary to have criteria for making integrated evaluations of the fatigue strength of welded joints. This paper presents a study that focuses on the local cyclic plastic zone size (ω*) as the criterion of fatigue strength and investigates its validity. The definition of ω* was given by the relationship between the stress state at the notch tip and the elastic strain which was defined along the strain-life fatigue curve (ε - N diagram) of a base metal. As a result of using ω*, it was found that an integrated fatigue life prediction was possible to a certain extent for notch and arc-welded joint specimens.

This paper presents the results of a strength analysis of a newly developed steel structure featuring a special cross section achieved with the hydroforming process that minimizes the influence of springback. This structure has been developed in pursuit of further weight reductions for the steel body in white. A steel tube with tensile strength of 590 MPa was fabricated in a low-pressure hydroforming operation, resulting in thicker side walls. The results of a three-point bending test showed that the bending strength of the new steel structure with thicker side walls was substantially increased. A finite element crush analysis based on the results of a forming analysis was shown to be effective in predicting the strength of the structure, including the effect of work hardening.

A combined computational fluid dynamics (CFD) and finite element (FE) analysis approach has been developed to simulate in the early stages of design the temperature distribution and estimate the thermal fatigue life of an engine exhaust manifold. To simulate the temperature distribution under actual operating conditions, we considered the external and internal flow fields. Digital mock-ups of the vehicle and engine were used to define the geometry of the engine compartment. External-air-flow simulation using in-house CFD code was used to predict the flow fields in the engine compartment and the heat transfer coefficients between the air and the exhaust manifold wall at various vehicle speeds. Unsteady-gas-flow calculation using the STAR-CD thermal- fluids analysis code was to predict the heat transfer coefficients between the exhaust gas and the manifold wall under various operating conditions.

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.

This paper describes the motor and inverter of Nissan's newly developed parallel hybrid system for rear-wheel-drive hybrid vehicles. The new system incorporates a high-power lithium-ion battery and a one-motor-two-clutch powertrain to achieve both highly responsive acceleration and better fuel economy. As the main components of the hybrid system, both the motor and the inverter have been developed and are manufactured in house to attain high power density for providing responsive acceleration, a quiet EV drive mode and improved fuel economy. Because the motor is located between the engine and the transmission, it had to be shortened to stay within the length allowed for the powertrain. The rotary position sensor and clutch actuator are located inside the rotor to meet the size requirement. High-density winding of square-shaped wire and a small power distribution busbar also contribute to the compact configuration.

Fatigue resulting from long-term driving can be classified into physical and mental fatigue. Physical fatigue seems to be mainly caused by driving posture. The purpose of this study is to develop a new driving posture for reduction of causal factors of physical fatigue, that is, biomechanical loads caused by the posture. In this paper, driving posture was optimized by subjective optimizations of seat contours and biomechanical analysis considering necessary conditions for driving operations and forward view. The new driving posture was tested by subjective evaluations and pelvic movement measurements. It was found that the new posture reduced physical fatigue dramatically.

An analysis was made of wear factors by investigating the effect of engine operating conditions on valve train wear. It was found that cam nose wear increased as larger amounts of combustion products, including nitrogen oxides and unburned gasoline, became intermixed with the engine oil. Based on these results, a valve train wear test procedure has been developed for evaluating cam nose and rocker arm wear under engine firing conditions. It has been confirmed that this test procedure correlates will with ASTM Sequence VE test and CCMC TU-3 test.

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.

The key-points in the diffusion bonding technique of green compacts during sintering, are the material compositions, which should be chosen according to their dimensional change during sintering, and the fitting clearance, which should be maintained in the range of press fit. Applying this technique, we have developed sinter-diffusion bonded idler sprockets for automotive engines by comfirming the bonding strength and torsional fatigue strength. And we also have developed a nondestructive analysis method for assuring the joint strength of idler sprockets in the mass production.

In this study, the functions required of automotive seats were analyzed from the standpoint of occupant posture. The results have been incorporated in the development of the New Generation Ergonomic Seat, which better fits the contours of the human body and prevents a stooped posture that places a greater load on the lumbar region, thereby reducing fatigue during long hours of driving. The new seat adopts the concept of “combined pelvic and lumbar support,” based on an analysis of the muscular and skeletal structure of the human body, sitting posture and body pressure distribution.