Basic design principle of reducing radiation noise from engine covers was developed. A thin air-film placed between inner and outer cover shells can give damping to the engine cover at its resonant frequencies. The air-film motion along the shells is much greater than the lateral motion of the shells. The damping can be best utilized by adjusting the combination of the resonant frequencies and the mode shapes of the inner and outer shells. The effect was analyzed with FEM and shaker test. Further, a prototype was built and was proved its performance in engine test bench.

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According to the improvement of NVH (Noise, Vibration and Harshness) and the increment of Hybrid vehicle, it is required to reduce aerodynamic noise, especially fluctuating aerodynamic noise. However, it has not been understood in detail because there have been only a few studies. In our previous study, we showed that the velocity fluctuation of relative wind had larger contribution than that of wind direction. In the present paper, we propose a new prediction equation considering both contributions and clarify the influence of the energy balance between aerodynamic noise and other noise on fluctuation level of interior noise qualitatively to develop vehicles with small fluctuating feeling.

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A hybrid SEA modeling method has been developed and applied to obtain an accurate SEA model for a passenger car. However, it is necessary to measure SEA parameters again in order to predict after the trim change. Then, this paper presents the Design Modification (DM) modeling method as the easy and accurate hybrid SEA modeling method after the trim changes. And we performed the acoustic analysis of a passenger car using this method. As a result, the validity of the DM modeling method was shown, and utility of the method was confirmed.

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An experimental study on a reduction of aerodynamic drag and an improvement of fuel economy in platoon driving was conducted to develop an Intelligent Transport System (ITS) with a good fuel economy. The test cars are two sedan cars and a microbus. Two combinations of two-car for platoon driving are tested: microbus - sedan car and sedan car - sedan car. The distance between two cars is varied from 10m to 60m in 25m/s steady driving. The reduction rate of aerodynamic drag on the sedan car was examined by measuring surface pressure on the car body. (1)Results show that the aerodynamic drag is clearly reduced on the following sedan car.(2)hen the sedan car is behind the microbus by 30m, aerodynamic drag of the sedan car is reduced by 30% which corresponds to 5% improvement in fuel economy. Based on these results, the prediction equation is derived by using the similarity power law of the free turbulent circular wake. The aerodynamic drag reduction from the equation has a good agreement with experimental results except for the case of less than 20m vehicle distance.

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We are studying a promising new autonomous control architecture that is a possible solution to difficulties of conventional control architecture way. The conventional control architecture way. The conventional control architecture consists of "Sensing", "Recognition", "Judging" and "Control". Generally "Recognition" process consumes huge computational resource, which might limit range of situations to adapt to. On the other hand, insects can fly quickly and they avoid collision with obstacles despite their small brains. We analyzed insect's collision avoidance behavior to identify a new control model which can avoid obstacles in a coordinated fashion. And we also modify it to adjust to a mobility. We confirmed the effectiveness of this "insect-inspired"model by installing it on an experimental platform Robotic car BR23C.

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Using a driving simulator, we conducted an experiment in which skilled drivers comprehensively evaluated a danger/disturbance level of various lane change behaviors from the viewpoint of the following vehicle driving in the passing lane. Using multiple regression analysis, we specified danger/disturbance factors, quantitatively identified the condition of each factor occurrence, and found some physical quantities that strongly influence the danger/disturbance level. Finally, we obtained an overall index for evaluating danger/disturbance level of lane change behavior.

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The objective of this study is to predict the behaviors of the human body in pre-crash conditions based on the experimental study. In order to simulate the actual pre-crash condition of a car that occurs when the pre-crash braking system is activated in an emergency situation, low speed front impact tests on human volunteers were conducted. From the result of this experiment, pre-crash occupant behavior was predicted. The pelvis motion was strongly influenced by the muscle activity, relating to the driver's posture just before the collision.

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Currently, the introduction of the careful driving support system has been pushed forward for traffic accident number reduction. Therefore, in this study, I am aimed for the development of a traffic simulator judging whether a careful driving support system is effective. I use a universal driver model for this traffic simulator. However, the effectiveness of the universal driver model becomes the problem. I tested it about the recognition region and judgment region to bring a universal driver model close to the driving action of the real driver in this year. I modeled it from this result.

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Finite element simulations of full car oblique side collision with a Hybrid III 3 year old dummy and a child FE model seated in the CRS were conducted. Although the head of the Hybrid III 3year old did not make contact with the door, the head of the child FE model impacted the door. The slack added in the CRS harness made the head of the child FE model impact the door at high velocity, and the HIC was comparable with the acceptance level. It was found that the CRS misuse can be a major factors of the head contact with the door, which observed frequently in accidents.

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Prediction of injured body regions and injury severity from available accident data can lead to more appropriate and hastier emergency care for accident victims. Purpose of this study was to develop a method in order to obtain injury prediction equation by utilizing accident database of numerous computer simulation results. A virtual database of frontal collision accident was constructed from 324 simulation results using occupant multi-body model and a simplified vehicle interior model. Prediction equations for head, thorax and thigh injury probability were derived from ordinal logistic regression analysis of the accident database. Validity of the prediction equations were evaluated by comparing prediction results to real world accident data.

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In this research, by using a driving simulator, we aim to develop an advanced driver assistance system which evaluates the lane change behavior and assists novice drivers to improve their skills in difficult lane change maneuvers. This development is based on a reference model of lane change maneuver extracted from the collected data of experienced drivers and the analytical results of the data collected from the driving simulator and the continuous sensing drive recorder. This paper describes experiment results indicating the validity of the proposed driver assistance system.

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This study proposes an autonomous obstacle avoidance system as one of the active safety technologies. This paper focuses on a scenario where a frontal obstacle suddenly appears during driving in a path with walls in both sides of the vehicle. The system derives an appropriate avoidance trajectory geometrically from the surroundings information obtained by a laser radar. Then, the vehicle is controlled to avoid the obstacle automatically by the cooperative control of braking and steering systems. The validity of the proposed system is verified by numerical simulations and real-time experiments using a micro electric vehicle.

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In this paper, a collision-prevention support alarm at road intersections is used as an example, and a method for analyzing the collision-mitigation ratio is discussed based on the "integrated error of driver and system" that the authors propose. This integrated error refers to not only the system reliability but also to the driver's reliability which will be changed by driver's trust in the system and system dependence during the use of a driving-support system. The investigation regarding the effects of these driver's mental states on collision mitigation considering the integrated error demonstrated that it is important to design an optimal human-machine interface that reduces the driver dependence on the system, while keeping the sense of trust high in order to reduce the number of collisions. However, the study on the trust and dependence found a positive correlation (r= 0.66) between these two factors. This means that it is not easy to satisfy this optimal condition and that developing a method for satisfying this optimal condition in order to reduce the risk-taking behavior of drivers is an important issue.

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Challenging driving situations, such as merge lanes and lane changes, are often a source of traffic jams and accidents. In this paper, a traffic flow improvement strategy is investigated using an autonomous control logic inspired by fish schooling. Fish demonstrates extraordinary "anti-collision" abilities, navigating instinctively and intelligently through challenging terrain by detecting and avoiding obstacles without colliding with each other. With the proposed control logic, it is possible to improve the traffic flow of vehicles by actively adapting their behavior to surrounding vehicles as well as the environment.

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We propose a strategy to estimate the self position and pose of a vehicle by using spherical images. Our method is based on the Perspective-Three-Point (P3P) problem from three pairs of 2D-3D correspondences. Our method introduces a quadratic form of a vector with a 3-rank tensor, which can be solved easily and quickly by using a Newton-Raphson method. A utilization of a spherical image in place of a conventional image overcomes the lack of accuracy for the localization. We present some experimental results that show the practicality and high precision of our method by using real data sets.

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This study focused on time-gap acceptance of elderly drivers when approaching a through street. We measured time-gap acceptance at intersections in straight-travel scenarios. Three types of vehicles, motorcycle, sedan, and truck were used as crossing vehicles at JARI proving ground. Results showed middle-aged drivers relatively accept larger gap than younger and elderly drivers do. We also evaluated elderly drivers' ability to estimate the speed of a crossing vehicle utilizing mechanical shutter device. Results indicated that some drivers whose speed estimation ability are low accept smaller gap and have unsafe tendency regardless of age.

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The reduction of the friction loss in the automotive engine is one of the important topics. There are many factors to affect the friction between the piston and the cylinder. In this papaer, the lubricant oil behavior is observed by using visualization techniques. Laser induced fluorescence (LIF) method is applied for the evaluation of the oil film behavior. The effect of the profiles at the piston skirt is discussed with experimental results. It shows that the thick oil film is introduced from the oval clearance to under the oil ring on the piston skirt at BDC. It is more clearly seen in changing the piston profiles. Contacting areas between piston and cylinder are also evaluated from results of oil film thickness distributions.

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A visualization experiment of flow pattern in a piston cooling channel was performed for the investigation of an oil behavior in the cooling channel. Two- and three-dimensional acrylic-resin channel substitutes simulating the piston cooling channel of the engine were prepared for the experiments, and distilled water was used instead of cooling oil. In addition, the flow pattern was observed by a high-speed camera and rapid motion of liquid phase in the channel was visualized. The results showed that the visualized flow pattern was obtained and they indicated that the energy of the cooling oil jet was lost at the inlet branching point because of collision against the wall inside the channel. This caused the decrease of the total flow rate of the cooling oil.

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In order to detect the combustion quality in a production SI engine, the ion sensor of gasket type was used. The relationship between the ion current and the rate of heat release was discussed. Under the operating conditions that the equivalence ratio, intake pressure and engine speed were varied, the averaged timing of rise of ion current for gasket ion sensor corresponds with the timing of 50% MFB. The ion current fraction accumulated, ICFA, was defined from the summation waveforms of ion current for gasket ion sensor. It was found that the timing of 5% ICFA corresponds with that of 50% MFB and the timing of 50% ICFA corresponds with that of 90% MFB. Therefore, the circular type gasket ion sensor can obtain the information of rate of heat release for individual cycle.

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A possibility of thermal ignition promotion by an interaction between low-temperature oxidation and spark discharge was investigated. A homogeneous-charge compression and expansion machine fueled with n-C7H16 was operated at equivalence ratio of 0.33 so that low-temperature oxidation appeared but thermal ignition didn't in it. A spark discharge was done at the center of a combustion chamber, synchronized with LTO preparation, LTO (low-temperature oxidation) or thermal ignition preparation of a fuel oxidation process. With the discharge at LTO, a rise of pressure was observed, showing that thermal ignition was induced by the discharge. In the atmosphere of LTO to thermal ignition preparation, a propagating flame was formed by the discharge even under the lean condition beyond the general flame propagation limit. The flame compressed the end gas in the atmosphere of thermal ignition preparation, resulting in the thermal ignition in an end gas zone. It is considered that activation of H₂O₂ loop reactions by the compression promoted the thermal ignition.

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The basic characteristics of a spark plug washer type piezoelectric force sensor are investigated for measuring the indicated mean effective pressure. The sensitivity and the natural frequency of the sensor are revealed, and some constants in the charge amplifier are be able to set, then the experiments with the facility are became possible. As the results, seeming sensitivity of the sensor was changed with the time constant of the measuring system and the configurations of the pressure wave generated with the calibration facility.

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The equivalent indicated mean effective pressure (Equivalent IMEP) of an engine calculated from the values based on the spark plug washer type piezoelectric force sensor were compared with the indicated mean effective pressure getting from ordinary cylinder pressure diagram. The correction coefficient was about 0.941, and then the correlation coefficient was improved to 0.990 by changing of the setting in calculation gate and charge amplifier.

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NOx and NO₂ emission characteristics of heavy duty diesel vehicles that have aftertreatment devices for emission reduction such as Diesel Particulate Filter (DPF) or urea SCR to meet the Japanese '05 emission regulation are investigated. Most of urea SCR vehicles increased NOx by increase of total driving distance, due to HC poisoning of the SCR catalyst and deterioration of NO₂ formation for pre-DOC, though both NOx and NO₂ emission of DPF vehicles little changed. NO₂ emission in urea SCR vehicles decrease in most cases by catalyst deteriorations, but NO₂ increased in some cases if only SCR catalyst is poisoned.

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It has been studied to promote the high boost and wide range high rate of EGR combustion in transient operation and improve dynamic performance, fuel consumption and emissions in a multi cylinder diesel engine equipped with both a high pressure loop EGR and a low pressure loop EGR. The combination of the low pressure loop EGR which increase turbine work and the high pressure loop EGR which has quick response of EGR increases both boost pressure and EGR rate simultaneously in transient operation by controlling the fractions of each EGR and total EGR rate.

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Particulate matter (PM) has harmful effects on human health. Ccharacteristics of PM and its compositions inside and outside of flame were required to develop reduction technologies for combustion origin PM. In this paper, relationship between PM size distribution and compositions such as soot and soluble organic fraction (SOF) of filter sampled PM were investigated. A laser induced incandescence (LII) method was used to obtain spatial distribution of soot in a laminar diffusion benzene flame. PM at the LII region in the flame and exhaust PM from the flame tip were directly sampled on a glass fiber filter. Compositions of PM sampled from inside and outside of the flame were characterized using a combustion type PM analyser (MEXA-1370PM). In addition, size distributions of PM were measured using an ELPI (Electrical Low Pressure Impactor). It was confirmed that main composition of PM in the flame (In-flame PM) was nuclei or aggregation mode particle (particle diameter is 150nm) with SOF of low boiling point, but PM emitted from the flame tip (Out-flame PM) was aggregation mode particle (about 400nm) with SOF of high boiling point.

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Biodiesel fuel (BDF) has high viscosity and poor volatility. In this study, it aims at the reformulation of physical properties of BDF by mixing with ethanol. In this paper, the influence that the change in the atmosphere temperature and mixture ratio of BDF and ethanol give to the spray and combustion characteristic are evaluated by using constant volume combustion vessel. In the spray experiment, the spray characteristics were measured by shadowgraph photography and Mie-scattered light photography. In the combustion experiment, the soot formation characteristics were investigated by taking direct photograph in addition to the grasp the apparent heat release rate.

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The new approach of developing the simplified chemical kinetic model, which was proposed in our previous paper, has the possibility to be applicable to the wide range of conditions, such as temperature, pressure, equivalence ratio and fuel molecule. This simplified model contains two reaction parts; fuel specific RO₂ chemistry reaction part, and small fragments reaction part which is common to all fuels. In this study, the lumped or reduced reactions and their rate constants of alkene, methyl radical and formaldehyde, were established. And, these reactions were verified as a common small fragments reaction part to linear and branched alkanes.

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A new clean diesel combustion concept has been proposed, which achieves very low NOx emission level less than a half of Euro6 standards without DeNOx catalysts. The combustion concept features promoted fuel-air mixture with a highly dispersed sprays and drastically restricted in-cylinder flows with near-zero swirl ports and with lip-less shallow dish piston cavity. The concept realizes a high thermal efficiency caused by considerably lowered heat-loss, while offering very low NOx and soot emissions. In the first report, the basic ideas of the concept are introduced and such emissions reduction and improved fuel economy were demonstrated using a single cylinder diesel engine.

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In order to improve the pour point of palm oil biodiesel, varying the types of alcohol used at transesterification, blending alcohol, adding pour point depressant and combining these three methods are examined. The pour point of palm oil biodiesel decreases as the carbon number of alcohol used at transesterification increases to 4. Palm oil buty1 ester/1-butanol/pour point depressant (68/30/2 mass%, PBE-B30-A2) has the pour point of -5 °C. which is lower than it of palm oil isobutyl ester, 0 °C. PBE-B30-A2 has lower smoke emission from DI diesel engine compared to palm oil butyl and methyl esters.

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Of emissions of diesel vehicle, nitrogen dioxide is considered to be accumulated by roadsides so-called “Hot-spot”, and result in harmful influence to pedestrians and residents. The mechanism of Hot-spot consists of more than one contributing factors; exhaust gas dynamics, vehicle dynamics, engine dynamics, drivers' operation and road environment. In this research, it was investigated influences of these contributing factors to Hot-spot by road test using on-board measurement system. And it was also confirmed that adopting for New Long Term Regulation is effective to restraining taking place of Hot-spot by comparing to the results of Vehicle adopted for Long Term Regulation.

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In NV performance development of new rear suspension and new drivetrain for FR vehicle. It becomes possible to solve the trade off problems between roadnoise and handling performance by new rear suspension. And booming noise is grealy decreased by New rear suspension and drivetrain without spoiling weight and fuel economy under the large torque.

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To know the surface strain of a rotating tire at high speed has been requested from the former, not only to design the tire construction or tire material but also to verify FEM analysis results. We adopted Sampling Moire Method to measure the rotating tire sidewall strain when cornering and braking. This method, taken by two separate cameras at the same time the portion attached with grid sheet and analyzed the images can be gained the 3D shape. With this method, we can measure the tire deformed shape and surface strain with practical accuracy.

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CO2 reduction, energy security, and emission reduction are the critical issues in the current automotive industry. As one of the solution to these issues, Plug-in Hybrid Vehicles (PHVs), which will share both advantages with Hybrid Vehicles (HVs) and Electric Vehicles (EVs), are attracting attention recently. The authors have newly developed BLENDED type PHV which achieves 20km EV range without sacrificing base vehicle package or performance, 75% of fuel economy improvement, and also meets severest emission regulations in the world. PHVs have the potential to become popular as a realistic solution for renewable electricity usage.

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A measurement technique using the new digital telemeter which measures the piston secondary motion as ensuring high accuracy while under the operation have been developed. The telemeter has an original signal processing circuit and a self-contained power generator, and its compact and lightweight design enables measurements giving only small impact on the motion.
The authors applied the telemeter to measure the piston secondary motion and clarified what may be the effects of the center of gravity of the piston, the pressure in the crankcase, and the amount of lubricating oil supplied on the cylinder bore.

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In recent years, circumstance for prime mover of automobile has been severer. Reliability or durability also is requested for more long running time. DOHC mechanism for intake or exhaust system must be refined for these requirements. Particularly, jump phenomena on high speed operation cause noise which give offensive to the ear and fracture this system. However, research on this field has not treated direct visibility. Therefore, this study describes that jump phenomena find out running with soft valve spring. Also, it is reported that comparison between test results using strain gage and laser displacement meter, and calculation results of five mass model which has developed for valve mechanism of direct attack type.

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Performance of the dimethly ether (DME) engine with the developed common rail type DME injection system was investigateed. The commom rail pressure and the injection timing of the DME engine were optimized to reduce fuel consumption and exhaust gas emissions. The unburned gas emissions from the DME engine was much lower than the value of the previous developed the DME engine with jerk type injection system. Especially at higher speed and load condition, the emissions of CO and THC ware reduced by 95 % and 93 % respectively. The Combustion efficiency at this condition was improved by 2.0% and the fuel consumption also was improved.

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Lock-up clutch (LC) control reported in this paper finely controls the degree of slip in the LC in response to operationg conditions including vehicle speed, engine speed, and degree of throttle opening, in order to expand the range of operation of LC control by increasing the accuracy of torque transmission control using torque converter (TC).To realize this, a multi-plate LC TC and a newly developed LC direct hydraulic control circuit have been employed, aiming at expanding the range of LC control by finely controlling the target slip ratio for actual vehicles.

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The driver support system (DSS) ECU is the computer responsible for controlling multiple systems such as adaptive cruise control (ACC), pre-crash safety (PCS), and lane-keeping assist (LKA). The DSS ECU makes requests to various actuators based on information from peripheral sensors such as radars and cameras. To enable such systems to share parts and operate simultaneously, it is important to make sure that the systems do not interfere with each other. This article describes the logical mediation structures applied in the design of diagnostics, controls, and human-machine interfaces (HMI) to prevent such interference.

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An acoustic field model for reproducing the acoustic characteristics of the car interior has been developed by treating the space on the inside of the interior trim as a Helmholtz resonator. This acoustic field model can make clear the noise generation mechanism at frequencies where it has not been fully understood heretofore. It thus facilitates detailed studies of the acoustic characteristics of vehicle body structures.

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The driving support systems using road or vehicle communication are studied. The HMI (Human Machine Interface) to inform the driver is very important for these driving support systems. In this paper, we examined a display position and method experimentally assuming some driving support systems with vehicle communication. As a result, we understood that oversight of display on navigation position and meter position increased while the driver is waiting to right turn. In addition, we clarified reaction time for a display position and subjectivity evaluation such as happiness for display. And we suggested the evaluation method to estimate an appropriate display position and method from reaction time and subjectivity evaluation.

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