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We have developed injection molding technologies consist of a new high-strength long-glass fiber reinforced polypropylene (PPLGF). They are key technologies of new modular design for substantial reductions of weight and cost, offering integrated functionality. The strength of injection molded parts are three times stronger than that of the conventional material. This technology makes it possible to replace parts from steel stamping and press molded glass-mat reinforced polypropylene. The front end and door modules of Atenza / Mazda6, Demio / Mazda2, RX-8 employs the module carriers using this material, resulting in dramatic weight and cost savings. (Fig. 1)

We have developed injection molding technologies consist of a new high-strength long-glass fiber reinforced polypropylene (PPLGF). They are key technologies of new modular design for substantial reductions of weight and cost, offering integrated functionality. The strength of injection molded parts are three times stronger than that of the conventional material. This technology makes it possible to replace parts from steel stamping and press molded glass-mat reinforced polypropylene. The front end and door modules of Mazda 6 employ the module carriers using this material, resulting in dramatic weight and cost savings.

To reduce real world fatal/serious/minor injuries, factors causing such injuries should be investigated in depth from wider perspectives. The aim of this paper is to clarify the factors based on Japanese accident database compiled by ITARDA (Institute for Traffic Accident Research and Data Analysis). ITARDA database has data for injury rates, seatbelt use rate of driver and age of driver involved in crashes, etc. by vehicle model. As a result of an elaborate statistical analysis, the most influential and essential factors on all injuries including fatality were quantitatively found to be seatbelt use rate and vehicle weight. The increase by 1% in seatbelt use rate makes injury rate decrease by 7%. The influence of vehicle weight is 1.7 times higher than seatbelt use rate. Multiple regression analysis on these two parameters was also conducted. The present analysis successfully predicted all injury rates by model per 10,000 units.

The present study investigated the aerodynamic pitching stability of sedan-type vehicles under the influence of A- and C-pillar geometrical configurations. The numerical method used for the investigation is based on the Large Eddy Simulation (LES) method. Whilst, the Arbitrary Lagrangian-Eulerian (ALE) method was employed to realize the prescribed pitching oscillation of vehicles during dynamic pitching and fluid flow coupled simulations. The trailing vortices that shed from the A-pillar and C-pillar edges produced the opposite tendencies on how they affect the aerodynamic pitching stability of vehicles. In particular, the vortex shed from the A-pillar edge tended to enhance the pitching oscillation of vehicle, while the vortex shed from the C-pillar edge tended to suppress it. Hence, the vehicle with rounded A-pillar and angular C-pillar exhibited a higher aerodynamic damping than the vehicle with the opposite A- and C-pillars configurations.

Collision warning systems are expected to be an effective countermeasure to reduce traffic accidents; however there have been relatively few studies on the effects of such warning systems on the driver's collision avoidance behavior. In this study, a driving simulator which had a large motion system was used, and 45 subjects experienced crash imminent situations in which the preceding cars suddenly decelerated while the subject looked off the road. Analyzing the subjects' collision avoidance behaviors, it was found that the braking response time and the number of simulated collisions were substantially decreased with collision warnings. Furthermore, potential reduction of rear-end collisions on the road was estimated by modeling the driver's braking response.

Seat lumbar support is thought to be essential for seating comfort as it plays important role in the driver's fatigue during long term driving. We tried to evaluate the lumbar support performance objectively with Seat Pressure Distribution. First, the tolerance in the measurement was eliminated by application of ASPECT manikin that reproduced a human seating torso posture [1, 2]. Second, an analysis method to visualize the seat support balance on the human back was developed. Third, a hypothesis for the optimal support balance to minimize the fatigue was proposed according to the fatigue growing mechanisms. Examining the deviation of each seat result from the optimal support, the performances were quantitatively evaluated. In addition to that, the effect of the lumbar support adjuster was taken into consideration to predict the market evaluation more precisely.

In order to secure effective occupant protection at vehicle collisions, it is necessary to conduct close examination into vehicle crash characteristics as well as interior parts, etc. This paper analyzes the behavior of a HYBRID III dummy restrained by three point seatbelt using MVMA2D computer simulation program at a 35 mph vehicle frontal barrier crash. As a result, it is found for good agreement between experiment and simulation that the exact input data of successive toeboard intrusion play an important role. As for the parametric study on vehicle crashworthiness, the authors propose the convenient method to represent the actual crash pulse by two simplified trapezoids. Then using these trapezoids, the parametric study clarifies the influence of vehicle deformation characteristics as well as the interior parts on dummy injury.

In the present study, two kinds of simplified vehicle models, which can reproduce flow structures around the two sedan-type vehicles in the previous study, are constructed for the object and the unsteady flow structures are extracted using Large-Eddy Simulation technique. The numerical results are validated in a stationary condition by comparing the results with a wind-tunnel experiment and details of steady and unsteady flow characteristics around the models, especially above the trunk deck, are investigated. In quasi- and non- stationary manner with regard to vehicle pitch motion, unsteady flow characteristics are also investigated and their relations to an aerodynamic stability are discussed.

This study shows an example in which the conventional aerodynamic evaluation method that focuses on “steady” aerodynamic lift coefficient is not necessarily sufficient to evaluate vehicle's straight-ahead stability at high speed, and proposes a new aerodynamic evaluation method for vehicle stability. In vehicle development, it is generally said that vehicle with lower aerodynamic lift coefficient has better straight-ahead stability at high speed. However, in some cases, straight-ahead stability differs between two vehicles with similar low aerodynamic lift coefficient. It is natural to think that this variation is caused by the difference of suspension characteristics or vehicle body rigidity. But from our experiences, different straight-ahead stability was observed between two vehicles having same suspension characteristics, same vehicle body rigidity and almost similar aerodynamic lift coefficient, but different vehicle configurations.