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Technical Paper

Application of 980 MPa Grade Advanced High Strength Steel with High Formability

2018-04-03
2018-01-0625
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.
Journal Article

Advanced Technology for Dry Multi-Plate Clutch in FWD HEV Transmission (JATCO CVT8 HYBRID)

2015-04-14
2015-01-1094
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.
Technical Paper

Development of the Aerodynamics of the New Nissan Murano

2015-04-14
2015-01-1542
The new Murano was developed with special emphasis on improving aerodynamics in order to achieve fuel economy superior to that of competitor models. This paper describes the measures developed to attain a drag coefficient (CD) that is overwhelmingly lower than that of other similar models. Special attention was paid to optimizing the rear end shape so as to minimize rear end drag, which contributes markedly to the CD of sport utility vehicles (SUVs). A lower grille shutter was adopted from the early stage of the development process. When open, the shutter allows sufficient inward airflow to ensure satisfactory engine cooling; when closed, the blocked airflow is actively directed upward over the body. The final rear end shape was tuned so as to obtain the maximum aerodynamic benefit from this airflow. In addition, a large front spoiler was adopted to suppress airflow toward the underbody as much as possible.
Technical Paper

DEVELOPMENT OF CRASH SAFETY OF THE NEWLY DEVELOPED ELECTRIC VEHICLE

2011-05-17
2011-39-7232
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.
Technical Paper

Low-cost FC Stack Concept with Increased Power Density and Simplified Configuration: Utilizing an Advanced MEA with Integrated Molded Frame

2011-05-17
2011-39-7260
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.
Journal Article

Low-Cost FC Stack Concept with Increased Power Density and Simplified Configuration Utilizing an Advanced MEA

2011-04-12
2011-01-1344
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.
Technical Paper

Application of CAP to Analyze Mechanisms Producing Dummy Injury Readings under U.S. Side Impact Test Conditions

2011-04-12
2011-01-0014
Evaluations of dummy injury readings obtained in regulatory crash tests and new car assessment program tests provide indices for the development of crash safety performance in the process of developing new vehicles. Based on these indices, vehicle body structures and occupant restraint systems are designed to meet the required occupant injury criteria. There are many types of regulatory tests and new car assessment program tests that are conducted to evaluate vehicle safety performance in side impacts. Factoring all of the multiple test configurations into the development of new vehicles requires advanced design capabilities based on a good understanding of the mechanisms producing dummy injury readings. In recent years, advances in computer-aided engineering (CAE) tools and computer processing power have made it possible to run simulations of occupant restraint systems such as side airbags and seatbelts.
Journal Article

Dissimilar Joining of Aluminum Alloy and Steel by Resistance Spot Welding

2009-04-20
2009-01-0034
This study concerns a dissimilar materials joining technique for aluminum (Al) alloys and steel for the purpose of reducing the vehicle body weight. The tough oxide layer on the Al alloy surface and the ability to control the Fe-Al intermetallic compound (IMC) thickness are issues that have so far complicated the joining of Al alloys and steel. Removing the oxide layer has required a high heat input, resulting in the formation of a thick Fe-Al IMC layer at the joint interface, making it impossible to obtain satisfactory joint strength. To avoid that problem, we propose a unique joining concept that removes the oxide layer at low temperature by using the eutectic reaction between Al in the Al alloy and zinc (Zn) in the coating on galvanized steel (GI) and galvannealed steel (GA). This makes it possible to form a thin, uniform Fe-Al IMC layer at the joint interface. Welded joints of dissimilar materials require anticorrosion performance against electrochemical corrosion.
Technical Paper

Spot-weld Layout Optimization for Body Stiffness by Topology Optimization

2008-04-14
2008-01-0878
In general, the improvement of vehicle body stiffness involves a trade-off with the body weight. The objective of this research is to derive the lightest-weight solution from the original vehicle model by finding the optimized spot-weld layout and body panel thickness, while keeping the body stiffness and number of spot welds constant. As the first step, a method of deriving the optimal layout of spot welds for maximizing body stiffness was developed by applying the topology optimization method. While this method is generally used in shape optimization of continuous solid structures, it was applied to discontinuous spot-weld positions in this work. As a result, the effect of the spot-weld layout on body stiffness was clarified. In the case of the body used for this research, body stiffness was improved by about 10% with respect to torsion and vertical and lateral bending.
Technical Paper

High Throughput Computation of Optical Flow with a High Frame-Rate Camera

2008-04-14
2008-01-0900
This paper presents a new method for calculating optical flow using data from a high frame-rate camera. We focused on a feature of image data captured with a high frame-rate camera in which objects do not move more than one pixel between successive frames. This approach eliminates repetitive processing for object identification among frames taken at different sampling times. High-speed processing hardware architecture was designed with sequential processing only, and the algorithm was implemented in a field programmable gate array. The resultant unit can calculate optical flow for a 640×120 pixel size image with a 480-Hz processing cycle and 0.5-μsec processing latency.
Technical Paper

Feasibility Study of a New Optimization Technique for the Vehicle Body Structure in the Initial Phase of the Design Process

2007-05-15
2007-01-2344
This paper proposes a new hierarchical optimization technique for the vehicle body structure, by combining topology optimization and shape optimization based on the traction method. With the proposed approach, topology optimization is first performed on the overall allowable design domain in 3D. The surface is extracted from the optimization result and converted to a thin shell structure. Shape optimization based on the traction method is then applied to obtain an overall optimal body shape. In the shape optimization process, iterative calculations are performed in the course of consolidating parts by deleting those whose contribution is small. The result obtained by applying this method to the front frame structure of a vehicle is explained. The resultant optimal shape has stiffness greater than or equal to the original structure and is 35% lighter. This confirms the validity of the proposed technique. It was found, however, that some issues remain to be addressed.
Technical Paper

A Study of Car Body Structure to Reduce Environmental Burdens

2003-10-27
2003-01-2833
In the initial design stage, it is important to discuss what kind of body concept is effective from a viewpoint of environment burden reduction. This paper describes the importance of both weight reduction and recycling through conducting LCA (Life Cycle Assessment) for four kinds of body structures. In addition, using each software, DFMA (Design for Manufacture and Assembly), DFE (Design for Environment) and LCA to parts unit, each effectiveness was discussed through the assessment of the material-hybrid body.
Technical Paper

Evaluation and Improvement of Vehicle Roll Behavior

1997-02-24
970093
Vehicle roll behavior has a large influence on how drivers evaluate handling performance. This paper describes an approach to quantifying roll behavior experimentally and presents a method for designing suspension properties to improve the sensation of roll. In this study, it was found that using pitch motion as an evaluation index results in good correspondence with subjective evaluations. To obtain acceptable roll behavior, it is important to control pitch motion during roll to a lower mode at the front end relative to the rear. This desirable behavior can be achieved by designing suitable roll center characteristics, nonlinear load changes and damping force coefficients.
Technical Paper

Numerical Analysis of Vehicle Frontal Crash Phenomena

1992-02-01
920357
Recent years have seen remarkable advances in the development and diffusion of numerical analysis techniques using the finite element method for examining vehicle crashworthiness. The importance of numerical analysis in vehicle development work has also increased. One reason for this is that the use of numerical analysis makes it possible to study crash phenomena in detail based on calculated data which can not be obtained experimentally. In this study, the non-linear dynamic finite element program PAM-CRASH was applied to a vehicle frontal crash simulation to calculate the body deformation modes, the force transmitted at different sections of the body structure and the internal energy accumulation of each component. The results obtained provide a quantitative explanation of the deformation mechanism of the body structure.
Technical Paper

A Lightweight, Multifunctional Plastic Reinforcement for Body Panels

1990-02-01
900292
A light weight,multifunctional plastic reinforcement has been developed for the outer body panels of vehicles. This new plastic reinforcement,composed mainly of polyvinylchloride resin, epoxy resin and an organic foaming agent, provides a 63% weight reduction over conventional plastic reinforcements, while adding the damping function to outer body panels. This paper introduces the process followed in developing the new plastic reinforcement and describes its characteristics. This new plastic reinforcement is already employed in the Nissan S-Cargo model, and it will be adopted in other passenger car models to be released in the near future.
Technical Paper

Development of Practical Multiplexed Wiring System

1988-02-01
880589
This paper describes a new approach to solving various problems inherent in conventional multiplexed wiring systems. These problems include the fact that the quantity of cut leads, which determines the cost, is not reduced even though the bulk of the wire harness is decreased. Another problem is that the communications system has a very complex configuration. With the approach proposed here it has been found that the number of cut leads can be reduced by housing the communications circuits individually in each piece of electrical equipment. This can be accomplished by grouping together the wiring in which the signals activating electrical load units all flow in the same direction. Custom LSI circuits have been developed to simplify the communications circuits. All of these developments have been combined into practical multiplexed wiring systems for controlling the power Windows, automatic door locks and power seats.
Technical Paper

On-Line Painted Thermal Plastic Exterior Body Panels for Nissan Be-1 and Application to CAE

1988-02-01
880034
This paper describes the plastic body panels developed for the Nissan Be-1 which was released and put on sale in Japan in January 1987. The panels include four body parts: left and right front fenders, front apron and rear apron. They are made of a thermoplastic resin and are produced by injection molding. The top paint coat can be sprayed on all four panels simultaneously with other steel body panels. The panels provide a high-quality appearance that is in no way inferior to the paint quality of steel panels. This is true during initial use as well as over long periods of time. Besides providing weight reductions, they also deliver improved resistance to impacts. CAE process was applied to develop these panels and proved to be quite effective.
Technical Paper

An Automatic Sealing Robot System for Cars

1987-11-08
871258
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.
Technical Paper

Positioning System with Vision Sensor for Automatic Arc Welding

1986-02-01
860607
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.
Technical Paper

Research Concentrated on An Experimental Method for Protecting Pedestrians

1985-01-01
856115
This paper describes a test procedure in which a dummy and a sled impact tester are used to simulate vehicle-pedestrian accidents for the purpose of investigating pedestrian protection. In the series of tests conducted, the bumper height, hood-edge height, bumper lead, front-end compliance of the vehicle, impact velocity, and other factors were varied in an effort to clarify to what extent modifications to the vehicle front end would contribute to enhanced pedestrian protection. Preliminary test findings obtained with this test procedure are also presented regarding the effects of the front-end shape of the vehicle and the stance of the dummy at the moment of impact.
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