Search Results

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.

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.

Sophisticated product designs enrich people's lives and social demands for creation of good designs are quite strong. In the automobile industry, good design quality is one of the principal factors for determining market competitiveness. In this situation where good design quality is required of every product, the authors have developed a CAD/CAM system which makes it possible to create good and accurate designs by translating designers' ideas directly and quickly into high quality CAD models, a capability that has long been desired. With this high performance system, freely formed curves and surfaces can be easily manipulated with a man-machine interface familiar to industrial designers accutomed to the conventional design process. The system also integrates photo-realistic rendering, stereography and NC milling machines for verifying differences between the realized shape and the image in the designer's mind.

A robotic driver has been designed on the basis of an analysis of a human driver's action in following a given driving schedule. The self-learning algorithm enables the robot to learn the vehicle characteristics without human intervention. Based on learned relationships, the robotic driver can determine an appropriate accelerator position and execute other operations through sophisticated calculations using the future scheduled vehicle speed and vehicle characteristics data. Compensation is also provided to minimize vehicle speed error. The robotic driver can reproduce the same types of exhaust emission and fuel economy data obtained with human drivers with good repeatability. It doesn't require long preparation time. Thereby making it possible to reduce experimentation work in the vehicle development process while providing good accuracy and reliability.

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 possibility of predicting engine bearing durability by elastohydrodynamic lubrication (EHL) calculations was investigated with the aim of being able to improve durability efficiently without conducting numerous confirmation tests. This study focused on the connecting rod big-end bearing of an automotive engine. The mechanisms of wear and fatigue, which determine bearing durability, were estimated by comparing the results of EHL analysis and experimental data. This comparison showed the possibility of predicting the wear amount and the occurrence of fatigue by calculation.

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.

There has been a growing need in recent years to further improve vehicle fuel efficiency and reduce CO2 emissions. JATCO began mass production of a transmission for rear-wheel-drive (RWD) hybrid vehicle with Nissan in 2010, which was followed by the development of a front-wheel-drive (FWD) hybrid system (JATCO CVT8 HYBRID) for use on a midsize SUV in the U.S. market. While various types of hybrid systems have been proposed, the FWD system adopts a one-motor two-clutch parallel hybrid topology which is also used on the RWD hybrid. This high-efficiency system incorporates a clutch for decoupling the transmission of power between the engine and the motor. The hybrid system was substantially downsized from that used on the RWD vehicle in order to mount it on the FWD vehicle. This paper describes various seal technologies developed for housing the dry multi-plate clutch inside the motor, which was a key packaging technology for achieving the FWD hybrid system.

Reduction of interior noise is an important factor in vehicle design and many experimental and theoretical studies have been carried out to find effective noise reduction techniques. Previously, we developed a Structural-Acoustic Uncoupled Program, ACOUST3, as a technique for estimating low-frequency noise in the vehicle interior. In the present work, ACOUST3 has been extended to construct an acoustic coupling analysis system, ASCA, which is used to calculate low-frequency noise, such as boom noise. In order to calculate low-frequency noise accurately, it is necessary to represent the vibration characteristics of the trimmed body as closely as possible. To do this, we built a trimmed body model, incorporating 22 trim parts, based on vibration test results, and found that the calculated results obtained with the model correlated well with experimental data.

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.

An electronically controlled closed-loop carburetor system has been developed for production application in Datsun car models. Providing a means of complying with Japanese Emission Standards, this design features the electronic control of carburetor supplied fuel with significantly improved emission performance and fuel economy. Technological advances include the noteworthy compensation of oxygen sensor output variations and improved transient emission.

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.

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.

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.

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.

There are strong demands for vehicle weight reductions so as to improve fuel economy. At the same time, it is also necessary to ensure crash safety. One effective measure for accomplishing such both requirements conflicting each other is to apply advanced high strength steel (AHSS) of 780 MPa grade or higher to the vehicle body. On the other hand, higher strength steels generally tend to display lower elongation causing formability deterioration. Nissan Motor Corporation have jointly developed with steel manufacturers a new 980 MPa grade AHSS with high formability with the aim of substituting it for the currently used 590 MPa grade high-tensile steel. Several application technologies have been developed through the verifications such as formability, resistance spot weldability, crashworthiness, and delayed fracture.

The use of CAE software in developing plastic components has advanced rapidly in recent years. This progress has been supported by the development of practical analytical tools, based on the finite element and boundary element methods, and on the dramatic improvements seen in computer performance. Following the introduction of a flow analysis program in 1982, Nissan has developed and implemented advanced programs for use in developing plastic components and has integrated the programs into a unified in-house system. This system is being utilized at the design and manufacturing stages of interior and exterior trim parts and has produced concrete results in different phases of component development. Work is now proceeding on the development of a system that can simultaneously analyze both the component performance and the factors that need to be considered in the manufacturing process.

Hydrofrorming is an efficient forming process to produce automotive parts for reducing weight of cars. In order to reduce the period of development of hydrofoming parts, numerical simulation using FEM is applied to evaluate formability. A pipe needs to be bent before hydroforming for forming complicated shape parts. A pipe bending process is also necessary to FEM simulation. In this paper, a highly effective method to create a bent pipe FEM model based on geometrical changing between a pipe before and after bending is proposed. The widely used draw bending process is supposed to be applied. The method can construct the model in a short time. Therefore total computation time can be reduced drastically. The effects of number of integration points and elements to the computed results and springback prediction after bending are also investigated. The proposed method are applied to a actual part, the computed results are in good agreement with the experimental results.

Engines in Japan have higher output versus small displacement (bhp/liter) and require low phosphorus content in the engine oils to meet the most stringent exhaust emission regulation in the world. The market survey of typical API SF oils in Japan showed that the average phosphorus content was approximately 0.07 %. Under such circumstances engine oils provide good performance with the usage of secondary zinc di-alkyldithiophosphates (Zn DTP) for valve train wear protection, addition of friction modifiers for fuel economy, etc.

An electric vehicle (EV) is promising as clean energy powered vehicle, due to increased interest in fuel economy and environment in recent years. However, it requires to meet unique safety performance such as electric safety. Nissan has developed a new electric vehicle which achieves electric safety in addition to maintaining enough cruising distance and cabin space. This was achieved by I he development of an all-new platform for electric vehicles. The electric safety was enhanced by the protection of high-voltage components based on consideration of component layout and body structure, high-voltage shutdown by impact sensing system and prevention of short circuit by fuse in the battery. As an example of the protection of high-voltage components, the battery which locates under the floor was protected by elaborative packaging and multi-layer protection structure.