Experimental analyses were conducted on diesel particulate filter under different soot loading conditions. Firstly, pressure drop of DPF loaded under different mean particle diameter loading condition was measured. Secondly, pressure drop of DPF loaded under different exhaust gas flow loading condition was measured. In addition, Hypothesis of mechanism that could be expressed the effect of the soot loading state has been proposed.

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The numerical analytic model that could be expressed the effect of the soot loading condition were developed and validated with experimental data. Firstly, the permeability of soot cake layer was expressed with the function of the total porosity in soot cake layer. Secondly, the total porosity in soot cake layer was expressed with the function of the aggregation diameter of soot secondary particle.

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The authors have been engaged in the research on the combustion noise of an extended expansion linkage engine. First, the authors analyzed the main noise frequency of the combustion noise source using a conventional engine. Thereby, the main noise frequency was 800Hz band radial noise from the flywheel assembled to the crankshaft. Also, the sound pressure of the combustion noise was correlated with the 800Hz frequency band excitation force acting on the crankpin. Next, the authors examined the combustion noise of the extended expansion linkage engine. As a result, the combustion noise of this engine was found to be reduced against a conventional engine because of a lower excitation force and a stronger crankshaft strength created by the linkage mechanism.

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Toward the commercial production of gasoline HCCI engines, it is important to understand the effect of fuel characteristics on HCCI and SI combustion. In this study, the reduced chemical reaction scheme which can simulate the effect of the fuel major components on auto ignition timing has been developed. This reaction scheme was based on the reduced kinetic model for primary reference fuel proposed by Tsurushima et al. with 33 species and 38 reactions, and some pre-exponential factors were modified using Particle Swarm Optimization to fit the ignition delay time calculated by MFC scheme with 2,301 species and 11,116 reactions. The result using this reaction scheme shows good agreements for the effects of EGR, fuel components, and radical species on the ignition timing of HCCI combustion.

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To improve the fuel economy, high EGR combustion stability is improved by the addition of hydrogen with fast burning speed in air-fuel mixture. In order to realize on-board hydrogen gas generation, an engine reformer system assembled with a reformer catalyst and a fuel injector on the external EGR line is explored. Reformed gas is consisted with not only hydrogen but also CO, CH₄ and so on, therefore the effect of reformate gas component except for hydrogen for high EGR combustion performance is one issue of this system. This effect is clarified by the result of single cylinder engine test with simulated reformate gas and real reformate gas.

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The authors have analyzed ignition characteristics of each component of natural gas based on chemical kinetics, and proposed a fuel design concept for HCCI engines to achieve robust ignition. Ethane exhibits following three characteristics, a high heat release rate during the late stage of ignition process, a high anti-knocking property with an HCCI operation, and a low dependence of ignition delay times on O₂ concentration. In this study, effects of these three characteristics of ethane on expanding operating range of HCCI engines were investigated using methane-based blended fuels with EGR. Methane/ethane shows high ignition stability against a high EGR rate caused by the above third characteristic, and a high thermal efficiency with a maximum power caused by the above second characteristic.

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Reducing heat losses is very important to improve thermal efficiency in diesel engines. There are some methods to reduce heat losses, such as adiabatic engines, restricted flow with highly dispersed spray, heat insulation coatings and so on. Multiple injection strategy is one of the most effective approaches to reduce heat losses because it doesn’t need additional engine components. The present study investigated the effects of multiple injection on the heat losses in a passenger’s vehicle diesel engine by using single-cylinder test engine and 3D-CFD code.

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Low-Speed Pre-Ignition (LSPI) has been regarded to be caused by auto-ignition of lubricant which is diluted by fuel impinged on liner wall. This paper shows the results of numerical simulation and experiment for analyzing the LSPI mechanism. Simulation results indicated that flame propagation can be started by auto-ignition of lubricant before spark ignition timing, and then unburned mixture (end gas) cause knock due to compression by flame propagation. Experimental results showed that auto-ignition occurs even if quite small amount of lubricant is included in fuel droplets splashing from piston crevice into cylinder.

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Firstly, this paper studies a Direct Yaw Control (DYC) to reduce spin tendency. To reduce load rate of rear tires, a DYC control law to zero cornering force of rear wheels is formulated. Further vehicle response with this control is obtained. This vehicle response is first order delay system. Its time constant value is similar to the time constant with active rear steer control to zero vehicle slip angle at C.G. Since to zero cornering force of rear wheels is equivalent to zero vehicle slip angle at rear wheels, the relation of the position whose vehicle slip angle is zeroed and vehicles behavior is also considered.

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Reduction of structure-borne sound is an important issue for industry mechanical products. This paper presents a new idea for controlling structural intensity (SI) on panel structure derived from a cancellation of SI due to mode pairs of multiple roots. At first the modal formulation of SI on a flat plate is summarized. Next we discuss the change of SI on a flat plate by attaching a reinforcement beam cross the plate in one direction. It is shown that this attachment give multiple natural frequencies, and their mode pairs and the pairs of modal components of SI are in same phase in the area of half of the plate and in anti-phase in that of the other half. Then the modes and modal components of SI can be said to be canceled by each modal pairs in the area of half on the plate. Based on this cancellation due to modal pairs, a new method for reducing transmitted power to a given area on the plate has been derived and proposed by attaching a beam on the plate for providing partial symmetry on the plate. It is demonstrated that the partial attachment of a beam on the plate based on the proposed method can reduce the transmitted power to the given area by the cancellation due to the pairs of SI modal components.

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The quantitative relationship of the A-weighted sound power of running road vehicles with vehicle category, running condition, and velocity has already been clarified. But its relationship with mass has not been shown. The authors have analyzed the measured values of mass, velocity, and A-weighted sound pressure of 420 heavy vehicles on public roads to calculate an equation in which the A-weighted sound power of a vehicle running constantly is proportional to the 3 power of its velocity and to the 0.5 power of its mass.

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In this paper, optimal control of vehicle motion in obstacle avoidance with both steering and braking is researched. Previous researches have focused on the optimal motion states physically in emergency vehicle control. This research investigates the obstacle avoidance problem in the framework of an optimal control problem, that is, the vehicle is optimally moving at a target point under the minimization of an evaluation function. At first, the maximization problem of the lateral avoidance width is considered, and the area is derived where the vehicle can reach the target point stably. In the following, the minimization problem of the tire workload in the area is resolved. And the minimization problem of the velocity at the side of the obstacle is proposed. The problem is effective for reducing the damage in a collision, if the vehicle cannot avoid the obstacle. Some simulations are performed and the vehicle motion is analyzed in each problem.

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Chest deflection and acceleration of crash dummy have been used as chest injury measures in frontal crash test. In this research, mechanism and relation of the two chest injury measures were investigated. The seat belt path and force limiter load were changed to clarify the effects on the chest injury by Hybrid III dummy and human finite element models. The chest acceleration was derived from external and internal joint force and the effect of seatbelt path was small, whereas the chest deflection was affected by the seatbelt force and the seatbelt path.

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The demand for crashworthiness improvement increases year by year. Weight reduction of automobiles is strongly required from the viewpoint of environmental problems. To achieve both the weight reduction of automobiles and the crashworthiness improvement is difficult. To solve this problem, it is important to enhance collision energy absorption performance efficiently. In this study, the optimization of a cross-sectional shape of crash box was investigated and newly developed collision energy absorption part was proposed.

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Elderly drivers’ performance inspection results for the past 3 times were collected and analyzed in order to grasp the changes by aging of their visual acuity, cognitive reaction time and driving behavior. As a result, elderly drivers with good result of braking response time tended to obtain good scores in the diagnosis of their driving aptitude. In addition, driving characteristics of elderly drivers on a test field were acquired and studied by comparing their self-valuations with the judgments from a driving skill automatic assessment system and by a driving instructor. Elderly drivers showed us un-safe behavior such as insufficient stop at a stop sign, insufficient recognition for safe turning and so on. However, most of these elderly drivers recognized themselves that their driving was safe, rather safe or normal.

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An image analysis technique was applied to evaluation of car body deformations in a side crash test. Target markers on a test car were shot with two high speed cameras. Then, movements of the target markers were analyzed with a triangulation method. The deformation of a center pillar measured by the image analysis was in agreement with that by a conventional measuring instrument. The accuracy of the acceleration calculated from the deformation was confirmed by comparing with the data of accelerometers. Evaluation of crashworthiness of car structures was achieved by combining this technique and conventional measuring techniques in detail.

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The in-situ observation of friction surfaces is conducted under the wet conditions in this report. Three kinds of friction materials removed from the commercial pads are used for the experiment. The friction coefficient and the friction behavior of each pad material are investigated. The difference of friction phenomenon between the cast iron and the glass used as the disc rotor is clarified, and the validity of replacing to the glass rotor for the observation is considered. Moreover, it is speculated that the coefficient of friction varies correspondingly to the mixture of debris and moisture, and its moisture ratio.

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Lightweight connecting rod has generally adopted the special material as a high carbon-steel base. However, it is difficult to improve machinability. So we developed a new material with increased vanadium to get the high yield ratio, adjusted present steel equal ferrite rate, and added calcium to improve machinability. As a result, developed steel achieved good machinability, and 45% higher strength in comparison with the present steel. And new connecting rod’s cross section can be reduced 25%.

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FEM simulation is performed during quenching process to investigate the generation mechanism and control the residual stress distribution for composite rolls. A large number of experimental data of shell and core materials are utilized for the wide range of temperature considering the quenching process. The results verify that initially the tensile stress appears at the roll surface but finally the compressive stress occurs. Furthermore, the effect of shell-core cross sectional ratio on the residual stress is considered. The results show that the residual stress only slightly increases with increasing the shell-core ratio.

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As the automobile control software is becoming larger and more complex, it is increasingly important to improve the efficiency of software development process. In this study, we developed the search based testing technology to increase efficiency of verification process. Search based testing can generate dynamic test data automatically, but it tends to miss generating correct test data to detect the problem when the software has many branch and path. In order to resolve the problem, we devise the method combing the search based testing and static analysis such as model checking, and show the application examples of engine control.

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