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Thixomolding® produces net-shape parts from Magnesium alloys in a single step process involving high speed injection molding of semi-solid thixotropic alloys. A description of the process and status of commercial developments will be presented.. The mechanical properties and microstructures of Thixomolded® AZ-91D magnesium materials will be presented. Tensile strengths of semi-solid AZ-91D at both room temperature and elevated temperatures ( 373K, 423K) are compared with die cast AZ-91D. Data on enhanced creep properties of Thixomolded® AZ91-D alloy relative to die cast AZ-91D will be examined with respect to relative changes in microstructural features. Controlling the percent solids in the semi-solid state prior to injection molding can lead to improved creep performance for use in net-shape automotive components.

Thermal effects on three-way catalysts and deterioration characteristics were studied. Aging atmosphere (oxidizing or reducing) and temperature contributed to catalyst performance deterioration. Catalysts sharply lost their activities under oxidizing conditions at an aging temperature of 900°C and above. Thermal degradation was found due mainly to the decrease in the surface area of alumina coated on the substrate and the increase in the size of cerium oxide (CeO2) crystal particle, an oxgen storage component (OSC). Also observed was a close correlation between the alumina surface area loss and the volume loss of micro pores with their radius less than 100 Å. Tests demonstrated that the catalyst thermal degradation can be reduced if the alumina micro pore volume loss and the CeO2 crystal particle size increase are restrained.

A study was performed on a lean NOx trap in which the loading of a ceria-containing mixed oxide in the washcoat was varied. After a mild stabilization of the traps, the time required to purge the NOx trap generally increased with increasing amount of mixed oxide. The purge NOx release also increased with increasing mixed oxide level but was greatly diminished after thermal aging. The sulfur tolerance of the NOx trap improved as the mixed oxide content was increased from 0% to 37%. The sample with 0% mixed oxide was more difficult to desulfate than the other samples due to poor water-gas-shift capability. After thermal aging, the NOx reduction efficiency on a 60 second lean/5 second rich cycle was highest for the samples with 0% to 37% mixed oxide at evaluation temperatures of 400°C to 500°C.

The Complex Cornering Compliance (Complex CC) theory is a method to cascade desired vehicle dynamics characteristics into suspension / steering system applying the Equivalent Cornering Power based on a single track model. Complex CC is used to find front / rear slip angle and time constant after converting the system elements into complex numbers as “slip angle per 1g (gravity) of lateral acceleration and occurrence time”. This enables an analysis of the contribution rate of the slip angle and time constant on the system elements and the impact on lateral force.

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 this report, we proposed an objective evaluation method of the seat lateral support according to the mechanisms to create the performance differences that we reported previously [1]. First, we showed an effect of scrutinizing Seat Pressure Distribution's change during vehicle turn to gain a quantitative index for explaining subjective evaluation results. Second, we showed the examples of the differences of the results according to the subjects and selected the best-correlated subject among them with a market survey result. Then, we contrived a loading condition to SAE manikin to reproduce the subject's Seat Pressure Distribution. Final, by a specific calculation of the Seat Pressure Distribution, the method to indicate the performance rating that had strong correlation with market survey was clarified.

Recently, computational fluid dynamics (CFD) has made great progress. This paper reviews published papers on aerodynamic noise simulated by CFD and studies to what level CFD can predict aerodynamic noise for basic models and for applied models of automobiles. Based on noise generation mechanisms, aerodynamic noise is basically classified into two types, that is, noise induced by two-dimensional flow and by three-dimensional flow. As typical examples of noise generated by two-dimensional flow, wind throb at opened sliding roof, edge tone at the end of liftgate and aeolian tone generated by a cylindrical antenna are simulated by several computational schemes. As typical examples of three-dimensional flow, noise generated by A-pillar longitudinal vortex and noise from a side view mirror are computed by using a wing model and a actual vehicle, respectively.

To investigate NO formation in a combustion flame, PLIF (Planar Laser-Induced-Fluorescence) technique was applied to measure the NO fluorescence distribution in a constant-volume combustion chamber and in a sparkignition engine. The NO fluorescence distribution was taken by an image intensified CCD camera. In the constant-volume combustion chamber, the high NO fluorescence intensity was concentrically observed in the thin flame zone along the flame front. In postflame gas behind the flame zone, the NO fluorescence was widely distributed with weak intensity. In the case of the engine, the fluorescence was distributed in the broad flame zone. The fluorescence intensity had high value near the flame front, and decreased from the flame front to the postflame gas. As the equivalence ratio was changed, the fluorescence intensity reached maximum value at slightly lean condition.

The International Lubricant Standardization and Approval Committee (ILSAC) ATF subcommittee members have compared the two oxidation bench test methods, Aluminum Beaker Oxidation Test (ABOT) and Indiana Stirring Oxidation Stability Test (ISOT), using a number of factory-fill and service-fill ATFs obtained in Japan and in the US. In many cases, the ATFs were more severely oxidized after the ABOT procedure than after the same duration of the ISOT procedure. The relative severity of these two tests was influenced by the composition of the ATFs. The bench test oxidation data were compared with the transmission and the vehicle oxidation test data.

On-road turbulences caused by sources such as atmospheric wind and other vehicles influence the flow field and increases the drag in a vehicle. In this study, we focused on a scenario involving a passing vehicle and investigated its effect on the physical mechanism of the drag increase in order to establish a technique for reducing this drag. Firstly, we conducted on-road measurements of two sedan-type vehicles passed by a truck. Their aerodynamic drag estimated from the base pressure measurements showed different increment when passed by the truck. This result raised the possibility of reducing the drag increase by a modification of the local geometry. Then, we conducted wind tunnel measurements of a simplified one-fifth scale vehicle model in quasi-steady state, in order to understand the flow mechanism of the drag increase systematically.

Subjective evaluation tests of “Acceleration Performance Feeling” with a driving simulator have been carried out on a rotary engine sports car. Additionally, although the test condition is limited, a test on an in-line four-cylinder engine sedan has been carried out. Influencing factors were analyzed through the experimental design and the influences of acceleration, gas pedal controllability, engine sound and their interactions were quantified. As the result, it has been found that the interactions must be considered in addition to main effect of each factor to improve users' evaluation especially on a rotary engine sports car. Furthermore, it is concluded that influencing factors are different between a rotary engine sports car and an in-line four-cylinder engine sedan.

Reduction of transmission error by gear tooth profile optimization and tuning of gear resonance modes are known as effective methods for gear noise reduction. This paper concentrates on structuring a process for reducing gear noise using the latter method. The procedure comprises a study of gear noise mechanism from transmission error to radiation noise, an application of Steyer's method in gear frequency analysis and implementation of an invented device called “noise reduction ring”. This inexpensive and practical ring reduces gear noise drastically by 10dB, which is predicted by the simulation and verified by the experiment.

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.

Conventionally, the effort of gear whine reduction has focused on minimizing the transmission error generated in automobile transmission. In mean time, as demands on gear whine reduction increased, the need of controlling noise transfer path was arisen because transmission error turns into interior noise in those paths [1-2]. In this paper, we provide experimental technologies to clarify the noise transfer path which dominants high frequency gear whine from experimental point of view.

Experiment and CFD have been performed to clarify the distribution of wind noise sources and its generation mechanism for a production vehicle. Three noise source identification techniques were applied to measure the wind noise sources from the outside and inside of vehicle. The relation between these noise sources and the interior noise was investigated by modifying the specification of underbody and front-pillar. In addition, CFD was preformed to predict the noise sources and clarify its generation mechanism. The noise sources obtained by simulation show good agreement with experiment in the region of side window and underbody.

Aerodynamic noise generated in production vehicle has been evaluated using experiment and numerical simulation. Finite difference method (FDM) and finite element method (FEM) are applied to analyze the flow field, and Lighthill's analogy is employed to conduct acoustic analysis. The flow fields around front-pillar obtained by numerical simulations agree with those by experiment for two cases with different front-pillar shape. Moreover, the distribution of acoustic source predicted by FEM is consistent with that obtained by experiment. Present study ascertained the feasibility and applicability of FEM with SGS model towards prediction of aerodynamic noise generated in production vehicle.

An all-ceramic swirl chamber has been developed and analyses and evaluations concerning the strength of silicon nitride ceramic (Si3N4) have been performed with a view to using it for the entire internal wall surface of the swirl chamber. The strength characteristics of Si3N4 and their effect and variation have been determined. On the basis of measurements and analyses of thermal stresses, assembling stresses, etc., investigation of the most suitable construction and assembling methods to reduce load stresses on ceramic, and various kinds of duration tests, the swirl chamber has been confirmed to have the required durability. This engine was found to comply with the 1987 U.S. diesel particulate regulation.

A new nitrogen oxide (NOx) reduction concept is suggested. A strong vertical vortex generated within the combustion bowl can mix hot burned gas into the cold excess air at the center of the combustion-bowl. This makes the burned gas cool rapidly. Therefore, it is possible to reduce NOx, which would be produced if the burned gas remained hot. In this paper the effect was verified with a 3D-CFD analysis of spray, air, combustion gas, and thermal efficiency as well as experiments on a 4-cylinder 2.0-liter direct injection diesel engine. The results confirmed that the vertical vortex was able to be strengthened with the change of spray characteristics and the combustion bowl shapes. This strengthened vertical vortex was able to reduce NOx by approximately 20% without making smoke and thermal-efficiency worse. Above results proved the effectiveness of this method.

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.

The reduced chemical reaction scheme which can take the effect of major fuel components on auto ignition timing into account has been developed. This reaction scheme was based on the reduced reaction mechanism for the primary reference fuels (PRF) proposed by Tsurushima [1] with 33 species and 38 reactions. Some pre-exponential factors were modified by using Particle Swarm Optimization to match the ignition delay time versus reciprocal temperature which was calculated by the detailed scheme with 2,301 species and 11,116 elementary chemical reactions. The result using the present reaction scheme shows good agreements with that using the detailed scheme for the effects of EGR, fuel components, and radical species on the ignition timing under homogeneous charge compression ignition combustion (HCCI) conditions.