In port fuel injection (PFI) gasoline engines, combustion fluctuations are caused by the interaction of various factors during ignition. Variations in the fuel deposition on the intake port walls cause fluctuations in the fuel supply to the combustion chamber and in the fuel concentration distribution, which causes knocking. In addition, when a large amount of fuel deposition occurs, it flows into the cylinder in liquid form without vaporizing, generating unburned hydrocarbons. In the previous report, we confirmed that the fuel adhesion amount on the port wall can be reduced by increasing the fuel injection pressure. In this paper, we investigated fuel atomization under even higher injection pressure conditions than the injection pressure range commonly used in intake port injection, with the aim of further reducing the amount of adhesion.
In this paper, shadowgraph photography and Super High Spatial Resolution Photography were used to visualize and measure the free-spray jet morphology and atomization characteristics. The effect of high injection pressure to like direct injection, which on the Jet configuration and atomization characteristics of the spray. The results showed that the droplet diameter changed significantly from 1 to 3 MPa (Wavy region) to 4 MPa (Spray region), but no significant change was observed after 8 MPa (Spray region, Spray region with secondary breakup), and that the droplet diameter did not decrease after 8 MPa.

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Ash formation in post-injection is considered to be caused by the splashing of lubricant oil due to the impingement of the spray on the lubricant oil film. In this paper, the mixing ratio of diesel fuel and lubricating oil in droplets splashed from the oil crown was measured using the laser-induced fluorescence method. By measuring the droplet diameter and the number of droplets, the experimental equation to predict the amount of lubricant dispersed is calculated. As a result, it was shown that the amount of lubricant splashed from the oil crown decreased as the K-factor increased, and the amount of lubricant splashed increased as the non-dimensional film thickness 𝛿𝑛𝑜𝑛 increased.

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We propose a combustion concept for significant NOx reduction by stratifying water within the engine cylinder. Through 3D-CFD analysis, we found that stratifying water around the upper region of the piston cavity results in much higher NOx reduction compared to homogeneously distributing water in the cylinder. To achieve this stratified water distribution, we developed a multi-hole fan spray nozzle and installed it on the engine head to establish a system for direct water injection into the cylinder. Experimental results at an IMEP of 0.8 MPa showed that under conditions where the mass of water injection accounted for 50% of the fuel mass, optimizing the timing of water injection led to an approximately 40% reduction in NOx. Furthermore, dividing the water injection into two stages resulted in a 50% reduction in soot. When applying Exhausted Gas Recirculation (EGR) under these conditions with equivalent soot concentrations, we observed up to a 75% reduction in NOx compared to not using water injection.

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CO₂ capture performance from engine exhaust using adsorption method was investigated. Zeolite 13X and NaY were used as adsorbents. When NaY is used, CO₂ capture performance was 34% lower than that of 13X. However, zeolite regeneration performance was improved 75% compared to use of 13X. This could be because lower CO₂ and water adsorption in low-pressure atmosphere, and desorption of water in a lower temperature range than those of 13X. These characteristics are due to the higher Si/Al ratio (Si/Al (13X) = 1.23, Si/Al (NaY) = 2.75). It was also demonstrated that when reducing humidity and removing pollutants from raw engine exhaust in the use of NaY, regeneration performance was farther improved.

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A method for directly measuring the voltage and impedance of EV traction batteries through the rapid (DC) charging port is reported. The principles and verification results of this approach are presented. A methodology for assessing and managing battery state, based on physical quantities obtained through this method, is proposed with the aim of ensuring secure long-term EV usage and maximizing the value of the batteries, thereby contributing to the realization of a sustainable circular society.

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The authors have developed and built a new system which could achieve carbon neutral of all energy to use at a home including the privately-owned car economically using Photovoltaic Power Generation and Electric Vehicle. The built energy system is managed by an automatic control completely. The effect of the system has been verified the demonstration experiment through real life for more than one year. As the result, CO₂ emissions from home was reduced more than 90%.

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A pre-feasibility study was conducted to detect increased risk of thermal runaway for single cell by the Charging curve analysis. Cycled cells with lithium plating were prepared as samples with increased risk of thermal runaway. The increased risk of thermal runaway was evaluated experimentally with thermal runaway tests using laser irradiation. The Charging curve analysis is one of the non-destructive diagnostic methods based on electrochemistry. The Charging curve analysis detected the lithium plating in the cycled cells, demonstrating its potential as a non-destructive diagnostic method for increased risk of thermal runaway.

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One of the causes of brake actuator operating noise is the amplification of pressure pulsation in the actuator due to fluid column resonance. By identifying the characteristics from experiments of a gear pump and valves in the actuator with compound pipeline connecting the left and right brake calipers, we have developed a computational model that can reproduce peak level and frequency of pressure pulsation in the actual system. This model can predict the pressure pulsation of an existing actuator when combined with any brake pipe, and can be used to study the gear pump speed to achieve both braking performance and brake actuator operating noise.

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We developed the outboard motor (OM) equipped with a new V8 type engine with a V-bank angle of 60 degrees. In OMs, the low vibration performance is important to provide the comfortable cruising. However, in this type of engine, the conventional crankshaft cannot cancel the inertial couples. Additionally, because high rpm range mainly used in OMs, the inertial couples contribute to the engine vibrations. In this paper, we proposed the new crankshaft which can cancel them with no additional parts such as balancers. In the examination of the structure, we performed the parametric study of the crankpin offset angle and the counterweight balance ratio. Finally, adopting the new crankshaft to the OM, we achieved the low vibration performance.

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In this study, we focus on reducing training time of disparity networks.We use kernel re-parameterization to build an under-parameterized model to reduce operations required for training. Experiments have shown that we can reduce the time by 13.7% without decreasing accuracy.

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Combined heat transfer coefficient hcal of naked thermal manikin in standard environment was investigated for evaluation of equivalent temperature Teq defined in ISO14505 through the measurement in climate chamber with displacement ventilation. Calculating the value of the reference temperature from the local air temperature and the local wall temperature derived the more uniform value of the hcal than that from the average air temperature. The sensitivity of hcal to Teq was derived and evaluated. It could be larger with the naked part under the air-cooling condition than the clothed under the air-heating condition. 1-W/m2K difference on Teq could affect on the actual human sensation.

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Improving the thermal efficiency of gasoline automobile engines is a very important issue as a measure against global warming. For that purpose, we need to optimize the gasoline fuel so that the high engine performance can be fully exhibited. In the present study, the ignition delay times of new gasoline candidates containing light olefins were measured using a high-pressure shock tube, and both their knock resistance and lean-limit expansion were evaluated. The fuel performances of oxygenated hydrocarbons such as ethanol and ETBE for biofuels were also examined and their chemical effects in new gasoline candidates were discussed.

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This study proposes a technique to predict the catalytic activity of the CO-NO-O₂ reaction using the first principle calculations without any experiments. The proposed method consists of four parts. (1) Assuming the detailed chemical reactions based on the Langmuir-Hinshelwood mechanism. (2) Estimating the activation energy (Ea) for each detailed chemical reaction by the first principle (e.g. DFT: Density Functional Theory) calculations. (3) Defining frequency factors (A) theoretically. (4) Inputting the estimated Ea and A values into simulation software for chemical kinetics (e.g. exothermia suite) and running the simulation. The validity of the proposed method was evaluated. This study predicted the catalytic activity of Rh (111) surface. The predicted results reproduced well the experimental results of the Rh thin-film catalyst, which was prepared by the "arc plasma method".

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Chips caught in the shank during automatic tool change on a machining center can cause runout of the tool and affect machining accuracy. To accurately measure the runout amount, the center position of the tool was calculated using the least-squares method and filter processing, taking into account the measurement error of the sensor, the runout amount of the spindle itself, and the variation in the individual dimensions of each tool. As a result, the runout of the tool was detected with high speed and accuracy, enabling automatic operation to be stopped before the start of the next machining process.

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We propose a robust self-localization method against seasonal environmental changes. In environments where plants are widespread, high-precision maps used for self-localization with scan matching using LiDAR can become outdated due to seasonal variations of plants, resulting in deterioration of the accuracy of self-localization. In this study, we propose a method of creating a high-precision map containing artificial structures that do not change with seasons and self-localization algorithm using the map. The experimental results show that the accuracy of self-localization is maintained through different seasons by the proposed method.

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To achieve the high efficiency of power unit development through the application of MBD, 1D system model that can flexibly respond to the refinement of model granularity and domain extension is necessary. The refinement of model granularity requires 1D sub-system models, and domain extension requires models with expanded behavioral representations. This paper presents an initiative for standardizing the 1D system model and discusses the evolution of the development process by applying a virtual development environment that integrates the 1D sub-system models and the expanded behavioral models to power unit development.

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In compression ignition engines, the urea selective catalytic reduction system is used to reduce NOX in the exhaust gas. However, under low exhaust gas temperature conditions, the urea water solution (UWS) film forms on the wall where the spray impinges and changes chemically to the solid deposit. Since this solid deposit prevents the NH3 formation and its homogeneous dispersion, it is necessary to understand the detailed chemical reaction process under actual engine conditions. In this study, the chemical reaction process of the UWS film was measured by Raman spectroscopy in an experimental system simulating the actual exhaust system. As a result, the UWS film evaporated and decomposed at all gas temperatures, and finally solid deposits remained on the wall, with different mass and composition at each gas temperature. Immediately after the UWS was put in, the urea mass decreased, and the wall surface temperature also decreased due to the vaporization latent heat. Thereafter, the rate of decrease of urea mass becomes smaller as the surface temperature of the wall surface decreases.

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Methane is one of the main components of automobile exhaust and has 25 times higher greenhouse effect than CO2. Methane is difficult to be purified by three-way catalyst (TWC) because of its stable chemical property. However lean / rich lambda oscillation improves methane purification rate. In this study we clarified CO, NO, and H2O in the exhaust and CeZr oxide in catalyst play a crucial role in improving the methane purification rate under lambda oscillation.

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In compression ignition engines, the urea selective catalytic reduction (SCR) system is used to reduce NOX in the exhaust gas. However, under low exhaust gas temperature conditions, the urea is not decomposed completely, leading to a decreased NOx purification rate. In this study, the temperature of the urea water solution (UWS) was controlled to promote atomization, evaporation, and the chemical reaction of the UWS spray. To understand the effect of the degree of superheat on UWS spray characteristics, the urea SCR nozzle tip was electrically heated, and the UWS spray was optically measured at different temperatures. The Super High Spatial Resolution Photography (SHSRP) method, which allows for whole spray imaging while maintaining the spatial resolution of small droplets, was applied, and the UWS droplet size distribution in quiescent conditions was analyzed. By applying a phase change model of flash boiling with energy balance, the vapor mass fraction at the nozzle outlet of the heated UWS spray was analyzed. Assuming a low-temperature exhaust gas flow field, the mass fraction of UWS spray droplets following the gas flow, the adhesion mass on the wall, and the location of water evaporation were estimated. The efficiency of UWS heating in urea SCR systems was discussed.

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Improving fuel economy of gasoline-powered vehicles is of great importance for achieving carbon neutrality of the society. The present paper deals with a concept study of a series hybrid powertrain to reduce CO2 emissions as much as possible, considering both engine and vehicle key performances. The study utilized model-based research using 0D/1D/3D-CAE and DOE optimization techniques. The ICE simulation shows >47% break thermal efficiency under restrictions from combustion noise level and tail pipe emissions. In terms of series hybrid powertrain vehicle fuel economy, ICE power in generation for best fuel economy shall be optimized according to the given battery capacity. Also, short-term future driving power demands information may help reasonable ICE activation through the transient driving cycle.

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Dynamic wireless transfer (D-WPT) of electric vehicles (EVs) will free EV users from limited cruising range, thus increasing the potential for electrification of passenger cars. For convenient usage in real world, D-WPT systems must be light, affordable, and accessible by mixed traffic. The authors' study group have proposed 150kW D-WPT system installable to passenger cars. In this study, we propose inverter control algorithm of SS circuit 150kW D-WPT system which controls power under safe level, and transfers power at high efficiency only. The system is verified through dynamic experiment.

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We verified battery capacity estimation and lithium precipitation detection using charging curve analysis for application to SOH/SOS diagnosis of EV batteries. In this presentation, as a detailed principle verification of non-destructive diagnosis, we compared and contrasted the results of cycle deterioration tests for single cells, the results of decomposition analysis of cells after deterioration, and the internal state estimation based on charging curve analysis, and considered the validity of the estimation.

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Virtual Point Transformation is a method for estimating vibration characteristics (vibration acceleration, transfer function along 6 degree of freedom) where direct measurement is hard by using directly measured vibration characteristics at the other points and the position. On the other hand, the method is known to be applicable at a frequency band where the target structure vibrates rigidly. Hence estimating the vibration characteristics and obtaining correct contribution at wide frequency band is generally hard. In this study, we considered a combined method of virtual point and operational TPA to estimate the force contribution at wide frequency band. In the method, the blocked force at a virtual point was estimated and the transfer function to the response point was calculated using the blocked force and the vibration in operation. The method was then applied to a simple plate model and the accuracy of the obtained contribution was verified.

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In 2023, a socio-acoustic survey on community response to road traffic noise was conducted in residential areas along arterial roads in Kanagawa Prefecture. The survey targeted residents living in detached houses and apartment buildings. The questionnaire used for the survey was designed based on new findings from a survey conducted in 2021. This paper developed the relationship between noise exposure and the following community responses due to noise: annoyance, listening disturbance, economic burden, negative effect on family members. In addition, we discussed the difference in exposure-response function and importance of measures reducing road traffic noise between housing categories.

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The present research focuses on a motorcycle rider assistance system that uses a camera to inform the rider when the preceding vehicle is approaching. The behavior of motorcycles differs from that of four-wheeled vehicles, and must be taken into account when developing functions. In this paper, we propose both ego vehicle and other vehicles path prediction algorithms, which is necessary for the system to select objects to watch, considering the characteristics of motorcycles.

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A method was developed to automatically calculate sensor layouts that eliminate blind spots at intersections based on operation design domain (ODD) conditions and the road network. The purpose of the method is to reduce the man-hours required to design an automatic driving system (ADS) that cooperates with infrastructure support sensors in the ODD. As a result of evaluation using a driving simulator, it was confirmed that the method can calculate sensor layouts that eliminate blind spots from the perspective of the ADS while taking into account the degradation of recognition performance due to weather conditions.

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Currently, distance detection systems using millimeter-wave radar are widely used to assist safe driving of automobiles. Although millimeter waves are not susceptible to fog, rain, or snowfall, it is known that the detection capability of millimeter-wave radar is severely hampered by snow accretion on the radar dome during cold weather. However, there are very few previous studies on the capability reduction of the radar due to wet snow deposition. Therefore, in this study, we experimentally investigated the effect of snow accretion on radar at 79 GHz wavelengths changing the thickness and the liquid water content of snow with using artificially formed snow particles. The results quantitatively show the relationship between the thickness and the liquid water content of snow and the attenuation of the radar received signal strength.

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We propose computational procedures for treating fracture problems in Isogeometric Analysis (IGA). In this study, we introduce an algorithm for analyzing ductile crack propagation. The proposed algorithm determines the propagation direction and simulates the propagation process. We validate the effectiveness of our method by comparing crack propagation analyses to tensile experiments using thin high-tensile steel specimens.

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In this paper, the cyclists' decision making behavior is measured and analyzed. The cyclists' decision state are considered to be expressed by operations of pedal and brake. In order to discriminate the pedaling state, a special force sensor was attached on the pedal of the cycling simulator. Then, the cyclists' decision making model was constructed by logistic regression model using the data measured by the cycling simulator. Finally, the accuracy of the model was analyzed and verified. It was found that the proposed model is useful for virtual simulation and/or design of autonomous vehicle, which need interactive behavior model of cyclists.

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To precisely analyze residual stress in arc welded lap joints of high strength steel sheets, a method to measure material properties on both heating and cooling processes was developed. Then welding residual stresses in arc welded lap joints were analyzed by thermal elastic-plastic finite element method (FEM) using measured material properties on heating or cooling or both, respectively, for investigation of their effect on accuracy. The maximum temperature distribution on the surface of heat affected zone (HAZ) was measured and well predicted by welding thermal conduction analysis. When the material properties measured on heating only or cooling only or both were, respectively, used in thermal elastic-plastic FEM, the analyzed results showed that the distribution characteristics of welding residual stresses in arc welded joints of 780MPa high strength steel sheets are similar and their magnitude is different. The analyzed residual stress using material properties measured on cooling is closer to that using those measured on both heating and cooling. It was also confirmed by both analysis and measurement that the maximum longitudinal tensile residual stress in an arc welded original lap joint was released about 60% in the cut specimen for tensile-shear strength test and the transverse residual stress changed greatly in its distribution characteristics.

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In this study, we investigated reducing the VUV irradiation dose required for modification of a silicone hard coat in plastic glazing for automobile windows by utilizing xenon excimer lamps. We assessed the effects of heating temperature on the surface composition and surface hardness in the modification of the hard coat using Fourier transform infrared spectroscopy and nanoindentation, respectively. We revealed that the higher the heating temperature during VUV irradiation, the greater the degree of modification and hardness of the surface layer at the same VUV irradiation dose, indicating that heating accelerates the modification and reduces the necessary VUV irradiation dose.

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Methanation, which synthesizes methane from CO₂ and hydrogen, is one of the most promising CO₂ recycling technologies. Our group are developing a noble-metal-free Ni catalyst aiming to high CO₂ conversion. The reaction mechanism was estimated by clarifying the effect of the catalyst support. By improving the Ni catalyst based on the reaction mechanism, the CO₂ conversion of the Ni catalyst was increased.

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We propose an efficient method for implementing decision-making functions in automated buses at specific locations. Based on our experience operating an automated shuttle bus, we recognize that the automated bus must make judgments at various points along its route. For instance, it needs to determine whether the traffic signal is green or not, whether passengers are waiting at a bus stop or not, and whether pedestrians will cross the road at a crosswalk or not. Some of these judgments become evident to be necessary after the automated bus begins its operation. To achieve efficient decision-making at specific locations, we propose a method where the automated bus switches simple inference models. These models are trained using thousands of image files captured and stored during the bus's travels near the judgment points. Our approach effectively enhances the driving decision capabilities of an automated bus following a fixed route.

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Depth can be estimated with high accuracy by using deep learning. However, for camera pairs with long baseline, the accuracy of disparity is reduced because of the visual difference between left and right images. In this paper, we propose disparity estimation method based on feature map correlation using contrastive learning. By taking into account visual difference between the left and right images, we improve the accuracy of disparity estimation. Experimental results show that the proposed method improves accuracy within 20 m.

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For highly efficient power unit development, it is important to construct a detailed 1D system model and predict vehicle performance in the performance design phase, considering market usage conditions. Market load forecasting technology using market data, which has been increasingly utilized in the automotive industry in recent years, is indispensable for highly accurate performance prediction. In this study, we developed a simulation technology that can analyze market driving strength by using a 1D system model and market data. Furthermore, we describe how the representative data extracted from the driving strength analysis results can be used to predict vehicle performance.

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