There is still a great need to enhance the thermal efficiency of automobile engines in order to achieve a sustainable society. The Atkinson cycle is an effective method for thermal efficiency enhancement. The Atkinson cycle is more complex than the conventional mechanism, but this complexity leads to a greater degree of freedom in the piston stroke characteristics. The stroke characteristics include the duration of each stroke and the speed of the piston, which affect thermal efficiency, maximum power, and tail pipe emissions. This paper provides a quantitative analysis of these effects and identifies guidelines for designing a new Atkinson cycle engine.

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There is a problem that deposits formed on the air-fuel ratio (A/F) sensor affect A/F control. To solve the problems, the mechanism of deposit formation and reduction method of the deposits are required to be investigated. In this study, the engine experiments for generating the deposits on the A/F sensor were conducted and the formation mechanism of the deposits on the A/F sensor was evaluated. As a result, the amount of the deposit increased with increasing the difference of the exhaust gas temperature and the surface temperature of the A/F sensors, suggesting that the deposit was generated by thermophoresis.

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Both crankshaft and main bearings were optimized to reduce the crank friction by about 50% compared to the conventional engines, aiming for a 1.8% improvement in fuel consumption with the environment-friendly right-sizing concept engine. In this study, an Elasto- Hydrodynamic lubrication (EHD) model that takes into account the roughness contact between the shaft and bearing and a friction coefficient model that depends on the lubrication condition were used. Focusing on the reduction of friction in the fluid lubrication regime as well as the mixed lubrication regime. The calculation result suggests the possibility of achieving significant friction reduction without compromising the reliability of the crank-system. The effect of the optimized crankshaft and bearing for friction reduction and fuel consumption were verified by using the concept engine and it was confirmed that the target was achieved.

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A pattern coating on the piston skirt and an optimization of piston shape are applied to the piston skirt to reduce friction loss on pistons in internal combustion engines. The reduction at skirt friction loss is realized by an increase in the oil film thickness on the skirt due to the wedge action of the oil in the concave area of the pattern coating. In order to reduce skirt friction loss, a numerical method is performed to optimize the skirt profile and the coating pattern positions that affect the wedge action of the oil.

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This paper describes a reduction transmission with a planetary mechanism using a traction drive that operates at an input speed of 50,000 rpm. The planetary mechanism uses a ring output to push the rollers with a constant force. Prototype with two planetary rollers facing each other was designed and manufactured for testing at high speed. The results of experimental tests showed that the system operated normally at 50,000 rpm, with a maximum transmission efficiency of 98%, and that there was little decrease in transmission efficiency even at higher input speed.

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To clarify the transmission characteristics of a traction drive operating at a high rotational speed, the traction coefficient for an actual drive was measured and was found to decrease by 20% at 50000 rpm. Therefore, a traction model was created to design a roller with a higher traction coefficient. Empirical equations were derived to represent the three characteristic values required for the model. By adjusting the coefficients in the equations to match the measured values of the traction coefficient, the traction coefficient could be predicted with a maximum error of 7% regardless of the conditions.

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As a part of efforts to improve the efficiency of powertrain development, highly accurate simulation technology for predicting vehicle fuel economy has been required. The objective of this study is to develop the highly accurate fuel economy prediction technology for changes in driving circumstances. Co-Simulation environment coupled with an engine thermal plant model was developed. The environment can predict EPA 5-Cycle fuel economy that including a wide range of driving circumstances changes with high accuracy.

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Changes due to Vehicle electrification, such as sprung mass inertia specifications, power plant suspension specifications and power train rotational inertia and stiffness, influences vehicle dynamics. In this paper effect of vehicle electrification on each phenomenon of vehicle dynamics such as body control, primary ride and secondary ride is studied and suspension design method including suspension control system is proposed.

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Determining the target characteristics of vehicle components for the road noise requires much development effort because component’s characteristics are set through trial and error utilizing actual vehicles and FEMs. The purpose of this study is to construct a method that can determine the target characteristics without making a vehicle that achieves the target performance, in order to reduce the study time of road noise. This study focuses on drive point inertance. This paper investigates a method of constructing a machine learning model that can determine the target value of the wideband frequency response.

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New vehicles are required to have advanced emergency braking systems. Additionally, collision evasive lateral manoeuvre systems are gaining attention to further reduce traffic accidents. However, there are few studies on driver acceptance of collision evasive lateral manoeuvre systems, this study constructs a system on a driving simulator and examines the interference between the system support and driver operation. As a result, the following conclusions were reached. The avoidance rate with collision evasive lateral manoeuvre systems are higher than without the systems. However, for the type of system in which the system automatically initiates steering avoidance, there were several trials that could not be avoided because the driver restrained the steering wheel. On the other hand, in some trials, the driver's steering operation did not initiate steering avoidance, resulting in unavoidable situations due to delayed start timing.

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In this study, two injury prediction algorithms for an Advanced Automatic Collision Notification (AACN) system were developed for the road safety benefit of pedestrians and cyclists. The algorithm development data consisted of all car-to-pedestrian and car-to-bicycle accidents that occurred throughout Japan (2014-2019), using macro data from the Institute for Traffic Accident Research and Data Analysis (ITARDA). The injury prediction algorithm for pedestrians was developed by considering the main pedestrian injury risk categories including vehicle travel speed, vehicle type, type of road, pedestrian behavior, pedestrian age and in addition, natural lighting conditions and the main injured body area of the pedestrian. For cyclists, vehicle travel speed, vehicle type and age of cyclist were considered as well as additional injury risk factors which included cyclist behavior, impact direction, helmet usage, natural lighting conditions and the main injured body area of the cyclist. The predicted injury values (objective variables), were used in an ordinal logistic regression for minor injuries, serious injuries and fatalities. In this study, the injury prediction algorithm for pedestrians is referred to as Version 2023P and for cyclists as Version 2023C. In emergency medical care, treatment priorities are determined based on the severity and urgency of the injured patient, known as triage. The priority level differs greatly between a patient with a serious injury requiring urgent treatment and a patient with no signs of life. The injury prediction algorithm developed in this study can represent risk curves for minor injuries, serious injuries and fatalities, and can be applied for triage determination at the time of an accident by incorporating it into an AACN system.

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Accurate reproduction of out-of-plane deformation behavior is essential in automobile crash analysis. Isogeometric analysis has attracted attention for computational simulation procedures because of data compatibility between Isogeometric analysis and CAD. In this study, we validate out-of-plane deformation performance and mathematical consideration of Isogeometric shell structural analysis comparing conventional finite element method in numerical examples.

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It is supposed that more sophisticated automated driving vehicles will have the function to merge or diverge from the main line. For this reason, it is one of the important factors to ensure safety when automated driving vehicles merge and diverge. In this study, an experiment to reproduce a scene where a vehicle driven by a general driver encountered an automated vehicle that merged or diverged was conducted by using a driving simulator.

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The spread of COVID-19 infection has increased the need for a safe and secure cabin air quality. Currently, measures to prevent droplet infection in taxis are physically partitioned or ventilated by opening windows. However, there are problems of applicability to personally owned vehicle and increase in energy consumption due to ventilation heat loss. The purpose of this study is to obtain useful guidelines for preventing droplet infection in a car cabin with airflow from car air conditioner and ceiling circulator using large-scale Large-eddy Simulation (LES) with up to one billion cells. The results show that in the condition with both air conditioner and air curtain, the number of droplets floating in the front area of the cabin is reduced to less than 1/10 compared to the condition without both air conditioner and air curtain.

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The objective of this study is to develop lane-change feasibility judgement algorithm to realize human-like decision making. We propose a lane change feasibility judgement method based on model predictive control. We then demonstrate that the proposed method enables an almost definite determination of infeasibility when skilled drivers judge the lane change as infeasible, and determination of feasibility in a greater number of situations compared to a conventional method when skilled drivers judge them as feasible.

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The test conditions under which whiskers generated from galvanized steel sheets were investigated. Then, it was found that whiskers are generated when a temperature cycle that satisfies certain conditions is given. Based on the results, we estimated the correlation between heat stress and market stress in the test, and devised a method to determine an appropriate test period from the market temperature data.

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In autonomous driving, traversability estimation is a technique for quantifying danger around a vehicle and is used for path planning.Although understanding the environment around the vehicle is essential for traversability estimation, it is impossible to estimate the blind spots of sensors, such as occlusions by obstacles. In this study, we effectively use point clouds measured by LiDAR to restore information on blind spots and realize traversability estimation.

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In communication functional safety, faults are detected by three types of fault detection mechanisms. Among these, it is difficult to obtain an accurate value for DC (Diagnostic Coverage) of CRC. The conventional CRC fault detectability evaluation performs a conservative evaluation that all errors larger than the Hamming distance cannot be detected. However, conservative DC of CRC may not achieve the target value of residual failure probability. Therefore, in this research, Hamming weight is used to evaluate CRC fault detection capability with lower conservativeness than the conventional method. In this evaluation, the proposed method is applied to the CRC arithmetic polynomial of each profile of AUTOSAR E2E. As a result, we were able to improve the failure oversight rate by several digits (nearly 10 digits at maximum).

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Hydrocarbons with higher blending octane number compared to octane number may have a higher antiknock effect for multi components fuel in comparison with the effect predicted from octane number as a single component. In this study, the antiknock effect of isooctane, 4-octyne and 2,3-dimethyl-2-butene for multi components fuels were discussed based on the analysis of reaction products in a flow reactor. As a result, it was suggested that low temperature oxidation reactions of n-heptane promote oxidation reaction of these hydrocarbons. In addition, it was suggested that reaction products from hydrocarbons with high blending octane number such as 4-octyne and 2,3-dimethyl-2-butene inhibit chain reactions by consuming radicals produced from the low temperature oxidation reaction of n-heptane.

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In the case of hybrid cars with both an internal combustion engine and a battery-powered electric motor, less space in the engine room is available. Then, we need the aftertreatment system of a gasoline particulate filter (GPF) combined with a three-way catalyst (TWC). However, deposited soot inside the filter may degrade catalytic activity. In this study, by using a lattice Boltzmann method (LBM), we conducted numerical simulations of catalyzed GPF to discuss the effect of soot layer on the conversion rate of TWC. We investigated the effects of the deposited soot mass, the exhaust gas component and the filter length on the catalyst performance. Results show that as the deposited mass is increased, the conversion rates of CO, HC and NO are generally decreased. The concentrations of CO, HC and NO largely affect these conversion rates. When the filter length is larger, these conversion rates do not change much.

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Precious metal catalysts such as platinum are used for automotive exhaust gas aftertreatment, but there is concern about the depletion of precious metals due to political conditions in the producing countries. We have focused on titanium dioxide with different crystal structures with thermal excitation activity as an alternative catalyst. Previously, it has been reported that titanium dioxide could oxidize particulate matter (PM) as well as CO and hydrocarbons by thermal excitation. In this study, we focused on the thermally excited catalytic activity of titanium dioxide, which is used in photocatalysts as an alternative material for catalysts. We investigated the catalytic effects of titanium dioxides with different crystal structures experimentally by changing the oxidation temperature and the oxygen concentration.

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The formation of ash and NOx by post-injection is considered to be caused by fuel spray impingement on the lubricant film. In this study, the impingement behavior between fuel spray and lubricant film was measured using the TIR-LIF method. The results showed that the amount of fuel adhered was larger than that to the dry wall at the end of spraying, but the amounts were equal after 5ms, and 40% of the amount of fuel adhered on the wall. It was also found that lubricant film spreads in a circular pattern starting from the point of spray impingement and disappears.

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The purpose of this study is to understand evaporation and ignition phenomena and the mixture formation process of the diesel spray near the ignition position at the ignition timing. In this study, we measured the ignition region and ignition delay of diesel spray from OH radical emission and analyzed the quantitative distribution of mixture concentration by the laser induced exciplex fluorescence (LIEF) method. It seems that ignition occurs near the tip of the spray, where there is no liquid phase and the air-fuel mixture becomes homogeneous due to entrainment of the ambient air.

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In diesel engines, the interaction between evaporative sprays and combustion wall is unavoidable phenomena. The fields with large temperature gradient should be occurred near the wall against high temperature ambient gas as well as evaporative vapor fuel. Thus, this paper is focusing on the quantitative measurement of fuel vapor concentration in nonreacting field near the wall, where large temperature gradient is existing, by applying exciplex fluorescence method. Two – wavelength exciplex system is originally developed to detect the quantitative vapor concentration fields inside the wall impinged evaporative spray, by accessed with the signal ratio of two wavelength, based on the predetermined calibration experiments. By applying this method, quantitative fuel vapor concentration could be obtained with a variation of, fuel injection pressure and wall – nozzle distance.

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In the previous report, we proposed a soot particle size distribution prediction model applicable for design calculations of internal combustion engines. The model was validated for experimental results measured by using burner stabilized stagnation flames for iso-octane/n-heptane/toluene blended fuels. In this study, we performed numerical calculations of soot emissions from a DISI engine under cold-start conditions by using the proposed model. The model calculation results were validated for experimental results of the soot mass emission and the particle size distribution. As a result, it was shown that the proposed model can reproduce the particle formation characteristics with changes in the fuel injection timing. However, there is room for improvement in the formation, behavior, and evaporation process of the liquid fuel film.

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Kumamoto University carried out EV school bus verification project as project of the Ministry of the Environment on FY2021-2023. In this project, we have operated EV school bus and evaluated its performance, and measured its data in driving, charging, and discharging, to confirm advantage of our unique EV school bus concept which utilize renewable energy in region, and which includes emergency power supply in region. As a results, we have confirmed the effects on CO2 reduction, fuel economy reduction, and energy localization. In this paper, we report details of this project.

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Most of off-road performance has been evaluated by subjective method in the development of tire. It has become more difficult to achieve both on-road and off-road performance only by subjective evaluation. One of the aspects to establish objective evaluation difficult is today’s off-road subjective evaluation has been done by experienced evaluators depend on their tacit knowledge and driving maneuver has not been clear. So, we start classifying driving methods and set measurement conditions on Mud off-road. Proposed objective evaluation method explains subjective results. It became possible to evaluate the performance objectively.

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The weave mode of a motorcycle is greatly affected by the frame flexibility of the body. In this paper, the analysis is performed using a 10-degree-of-freedom model with a new coordinate system. Vehicle specifications are used in which the weave mode is greatly destabilized in the high-speed range for the analysis. As a result, it is shown that instability occurs through the front tire lateral force due to the steering angle phase delay. This phase delay is caused by the gyro torque generated by the bending velocity of the front frame.

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Recently, the development of electric vehicles is active. For battery cases of electric vehicles, deep rectangular cup shape is required, it is necessary to improve the formability of press forming. Multistep forming is one way to improve formability. In previous studies, it was shown that there exists an optimum shape for the preform in cylindrical stretch forming, and the formability is improved by forming the target shape through the preformed shape. In this report, the effect of preform and blank shape on formability in multistep forming of rectangular cup deep drawing was examined by FEM and verified by trial.

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