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With a goal of contributing to the enrichment of customers’ social lives through adapted vehicles, the authors studied a method for quantitatively expressing the effectiveness of the vehicles in order to understand their effect and communicate their value. Effectiveness was defined as the degree of each customer’s engagement in their individual social activities after continued use of the adapted vehicle, with engagement determined using a scale based on customer responses to 17 5-point questions. The authors then used this scale to statistically verify a predictive value for the degree of involvement in social activities. The questionnaire was given to physically disabled drivers and drivers involved in caregiving services. The results indicated that highly accurate predictions could be made for both groups, with accuracy rates of 0.825 and 0.846, respectively. This confirmed that the scale developed for this study can quantitatively express the effectiveness of adapted vehicles.

Arisa ENDO、Toshihiro KOYAMA、Keiichi SUNAMI、Tetsuya GOMI

To examine the design direction of side mirrors in the early stages of development, a Pix2Pix GAN deep learning model was used to develop an easy-to-operate tool that enables prediction of flow fields with sufficient accuracy in a short period of time and output of the results. In addition to a shorter prediction time with a deep learning model, further time reduction was achieved by omitting the signed distance function for shape recognition that has a high computational load. The tool was also developed to maintain prediction accuracy even with a small amount of training data. Furthermore, output of fluid physical quantities required for verification on the tool operation screen was minimized, allowing performance of the process from input to output solely by button operations, making it easy to use for designers.

Takuro HASHIMOTO、Koji OKABE、Takeshi YAMATODA、Takafusa KIDO

A study of combustion methods was conducted using 3D combustion simulation with the aim of enhancing power at full load and thermal efficiency at partial load for a big-bore spark ignition gasoline engine for large motorcycles. The effect of passive pre-chamber jet combustion on power was confirmed at full load. It was further confirmed that a jet sprayed from the pre-chamber into the main chamber caused an increase in turbulent kinetic energy that sped up combustion, and that increasing the compression ratio from 10.1 to 12.1 resulted in an enhancement of 3.6% in indicated work at full load compared to conventional SI combustion. At partial load, the effect of pre-chamber jet 2plug combustion, achieved by ignition in the pre-chamber after the ignition of the main-chamber side-plug with the aim of enhancing combustion stability, was confirmed. The jet sprayed from the pre-chamber facilitates ignition by coming into contact with the flame surface generated by the earlier ignition of the main-chamber side-plug. It was confirmed that this resulted in an increase in indicated thermal efficiency of 1.7 points at partial load compared to conventional SI combustion.

Hirokazu ANDO、Takumi TANAKA、Kengo TOMIZAWA、Yosuke INOUE

In order to enhance the efficiency of the synthetic methane production process, the authors developed an innovative catalyst that converts synthesis gas (syngas) obtained from the co-electrolysis reaction of water vapor and CO2 into methane, and studied the allowable proportion of water vapor in the source gas, i.e., water resistance. Evaluation of the activity using the continuous-flow method showed that NiAl-LDHs utilizing layered double hydroxides exhibited higher catalytic reactivity for the generation of methane from syngas consisting of CO and H2 at 0.1 MPa and 300°C. In addition, the authors experimented with the methane conversion reaction of syngas containing water vapor, which is an issue in the synthetic methane production process, when combined with a co-electrolysis reactor. The results showed that when up to 20% water vapor was present, CO conversion and CH4 selectivity were equivalent to cases without water vapor, and the catalyst exhibited enhanced performance compared to the conventional metal-supported catalysts.

Hideaki YONEDA、Kazuki YANAGISAWA、Yohei IIJIMA、Junpei YOSHIDA

When producing highly stylized exterior designs for automobiles, conventional manufacturing processes can cause surface distortions on the outer body panels, which require countermeasures in order to meet specifications. To address this issue, we have developed a new development-stage simulation technology. This technology integrates design, manufacturing, and materials factors to predict the potential for a design to be achieved without visible distortions.
We began by proposing a digital development concept that predicts distortions throughout all the plant manufacturing processes (stamp forming, spot welding, and paint curing) based on models made prior to the production of vehicle body design drawings. We then created a simulation technology to analyze the distortions that accumulate throughout all the manufacturing processes, and verified it on actual vehicles.
The technology was then integrated into the development operational rules for new models. This made it possible to reduce reworking due to distortions occurring in plants that had resisted resolution for many years, and thereby enable efficient production of stylized surface designs.

Toru FURUSAWA、Yoichi TOYOOKA、Eiichiro YOKOI、Shigeru TAKAMI、Masao UCHIYAMA、Yoshinori TANAKA

A quantitative evaluation method that correlates with human visual inspection is important in helping to predict outer panel surface distortion that may occur in the development phase of the automobile manufacturing process. This study proposes a quantitative evaluation method for distortion using curvature difference, in order to determine specifications through predictive simulations in the development phase. Curvature refers to the rate of change of the slope of a curved surface. The degree of distortion can be quantified by defining the difference in curvature between the standard shape and distorted areas as the curvature difference. The proposed method achieved reliable correlation between outer panel surface distortion and visual evaluation. Therefore, by incorporating curvature difference as one criterion in design phase simulations, it can be utilized as a consistent evaluation index from development to the manufacturing site. This paper reports the details and effectiveness of this evaluation method.

Yoichi TOYOOKA、Toru FURUSAWA、Eiichiro YOKOI、Shigeru TAKAMI、Masao UCHIYAMA、Yoshinori TANAKA

In an attempt to offer a new value of EV in the FUN category such as the motorsports, the electric motocrosser CR ELECTRIC has been developed. The employment of launch control and energy management systems upon the selection and control of battery cells enabled realization of the dynamic performance and the range required for the motocross machine. Developing the L-shape battery pack and optimizing the frame body stiffness, the specification of complete vehicle similar to the CRF450R are achieved. Moreover, the development of high-voltage pack as high as 400 volt along with the redesigning of the cooling system to adjust to the electric motocrosser resulted in the downsizing and weight reduction of various component parts. With these measures taken, the maneuverability and stability such as nimbleness, roadability, and turnability have been accomplished.

Seiji KATO、Hiroyuki AKIYOSHI、Makoto KITAOKA、Masayuki KINOSHITA、Takuya FURUYAMA

A model for predicting lower limit performance including variation terms was constructed to help achieve performance after durability testing of products equipped with lithium-ion batteries. To predict degradation, the model formula includes two types of stochastic variables: random effects multiplied by the battery durability degradation trend term, and a diffusion process in which variation expands proportionally with time. Parameter optimization was conducted by the maximum likelihood method aided by the Markov Chain Monte Carlo method. As a result, the lower limit performance after degradation, which had conventionally been predicted based on 12 months of measured durability data, was successfully computed based on only four months of durability data. It was also demonstrated that prediction of lower limit performance, which previously required the two pieces of information of the predicted typical performance values after durability testing and performance variation during durability, could be achieved with just one piece of information by using the proposed model.

Kaoru OMICHI、Kotone SUZUKI、Hideki NAGATSUKA、Michihiro YASUDA

In recent years, a probabilistic approach is increasingly needed as mechanical products are expected to provide higher functionality. This is not unrelated to the fact that, as mechanical products provide higher functionality, the consequences of any accident tend to be more serious. A typical example would be an on-board composite hydrogen tank stored under high pressure. In his examination of standards development, for example, G. W. Mair proposes to introduce a probabilistic approach to the consideration of safety margins(1). The present author introduces the concept of a probabilistic approach, which is often discussed in terms of GTR and other standards, as an approach to safety standards for composite hydrogen tanks for fuel cell vehicles(2). The current paper provides an overview from the perspective of reliability design that the author has experienced outside the automotive field. This paper has mentioned the historical background, details of the method, advantages and disadvantages, examples of use in other fields, and the possibility of use in fuel cell vehicles. Following this, an important action would be to start an evidence-based discussion of safety margins for bursting strength, with specific application of a probabilistic approach to the current situation in Japan. An essential part of this process is the organization of statistical data. The basic statistics involved include the mean value and variance of the bursting pressure of hydrogen tanks. However, obtaining basic statistics of hydrogen tank bursting strength experimentally is not easy in terms of cost and labor. Moreover, considering the severity of the results, the need for a higher degree of safety performance means that the probability of bursting is extremely small, which also makes it a challenge to take a large sample size. If a very large amount of data could be obtained, it might not such a challenge to evaluate the basic statistics of the population with a high degree of accuracy based on so-called sample statistics. However, in the case of composite hydrogen tanks, if large sample sizes are not expected, then the application of sample statistics is generally a challenge. In such cases, there is an approach called Bayesian statistics that is effective for evaluating small-sample statistics. For example, Bayes’ theorem is used for the statistical processing of maintenance data in risk-based inspections of plant pressure equipment(3), (4). This is related to the fact that one cannot obtain large samples of maintenance data. This paper summarizes the basic ideas of Bayes’ theorem as well as examples, applications, and precautions related to applying the theorem.

Shinsuke SAKAI

The coloring of motorcycles is an important element that conveys the concept and appeal of the model to customers and greatly influences their purchasing motivation. During the author’s assignment in Vietnam, I devised a “coloring strategy” to highlight the individuality of each model by reviewing the coloring of all models from a comprehensive perspective. Based on this strategy, the upper-grade models set the trend in coloring, and the entry models followed. This enabled us to provide customers with high-satisfaction products. Building on the example in Vietnam, we applied the “coloring strategy” to 50 cc scooters in Japan and reviewed the coloring for each model. This provided each different customer for each model with high-satisfaction color options, while also achieving a product lineup with high business contribution. Although conditions vary by region and market, such as differences in market background and production facility capabilities, the “coloring strategy”, which aims to optimize the product lineup by highlighting the character of each model from the “color” perspective, can be applied to the development of various models.

Masaharu YOSHIMURA

A time filtering method was constructed as a means of decomposing the turbulent component that contributes to promoting engine combustion. This time filtering method used the frequency at which the frequency characteristic of the in-cylinder flow changes as the cut-off frequency, and this frequency was confirmed to correspond to the time scale of the relatively large in-cylinder flow induced by the combustion chamber, intake port, and piston shapes. It was also clarified that the cut-off frequency can be uniquely determined by using the inverse of the integral time scale of in-cylinder flow as the cut-off frequency. The time filtering method was applied to a flow field equipped with a tumble control valve, which is an intake switching device. The obtained turbulence was highly correlated with the combustion duration of a metal engine, which confirmed the reliability of the decomposition method. The time filtering method was implemented in commercial analysis software and applied to hybrid engine development. Turbulence was enhanced by the in-cylinder flow enhancement specification that changed the intake port and piston shape from the early development specification and verified the in-cylinder flow enhancement concept for achieving rapid combustion.

Yasuhiro OKURA、Makoto SEGAWA、Hiromi ONIMARU、Seisuke SATO、Yasuhiro URATA

In order to reduce emissions immediately after engine cold-start, which is a challenge for conventional three-way catalyst systems, an HC trap catalyst was developed that combines new HC trap materials and an HC purification catalyst for efficiently purifying the trapped HC. Ag-CHA and Cu-FAU were developed as zeolite HC trap materials that have pore sizes close to the HC molecular sizes and can adsorb HC up to higher temperatures by increasing the stability of the exchanged ions that promote chemisorption. It was also clarified that arranging the HC purification catalyst layer in the upper layer of the HC trap materials is key to effectively purifying the desorbed HC, and that adding an oxygen absorbing and releasing material consisting of CeO2 and ZrO2 in a 1:1 ratio to the HC purification catalyst enables purification of the desorbed HC even under stoichiometric conditions. A V6 engine with this HC trap catalyst in an underfloor arrangement was able to reduce HC emissions during engine cold-start by approximately 50% in the LA#4 mode emission test.

Hiroki TAKEORI、Koji NEMOTO、Yuki OKU、Ryohei IKUTOMO、Keita NAKAO、Toyohiro USUI

In this paper, the authors propose a method of customizing automatic speech recognition models using editable term lists to increase recognition accuracy for phrases registered at the discretion of the user. The proposed method adds a text encoder and cross-attention layer to the conventional Connectionist Temporal Classification/Attention-based automatic speech recognition model to detect registered terms in speech signals. To increase registered term recognition accuracy, the authors propose an inference algorithm that integrates the probability of detected registered words and Connectionist Temporal Classification. Results of their evaluation using the in-house Japanese-language dataset and the English-language Librispeech corpus showed that using the proposed method lowered the character error rate and the word error rate for registered terms.

Yui SUDO、Shakeel MUHAMMAD、Naoaki SUMIDA

We have developed the Honda E-Clutch system, which allows starting, gear shifting, and stopping without manually engaging or disengaging the clutch while permitting manual clutch operations when necessary. The clutch actuator added to the existing engine enables controlling the clutch automatically. With the three-split construction employed in the engine-side clutch lever and by the appropriate detection of rider’s manual clutch operation, the system permits smooth change over from automatic to manual and vice versa. Equipped with the automatic clutch, the rider can now enjoy sportier and easier riding than before while maintaining an option of manual clutch operations. The system is configured to minimize restrictive factors in mounting the new system to the vehicle so that it is applicable to various types of motorcycles.

Junya ONO、Tatsuya RYUZAKI、Masazumi NAITO

Development is proceeding on a circulative renewable energy system for lunar night power supply. For proof of principle of the circulative renewable energy system, a system with approximately 1/10 the power of the expected launch unit was constructed, and a cycle test with 39 cycles was conducted, which is equivalent to three years of lunar use.
In the fuel cell stack, the membrane electrode assembly was designed in consideration of changes in the electrolyte membrane properties due to pure oxygen supply. In the electrolysis cell stack, component materials were selected that have reliable flame-retardant properties and oxidation resistance under high-pressure oxygen. In the electrochemical hydrogen compressor stack, discharge of stagnant water on the reaction surface was enhanced by optimizing the flow path structure. In addition, controls and systems were constructed to establish stable water circulation.
Through these initiatives, a cycle test was achieved and demonstrated the feasibility of continuous power generation through water circulation, which is the concept of the circulative renewable energy system and completed the proof of principle.

Ryosuke INANISHI、Hayato DAIMON、Kazunori FUKUMA、Takumi KAWANO、Toru HONDA

The researchers developed a transmission mechanism that combines one-way clutches capable of rotating in both directions and can change speeds by switching the connection state of the clutch.
This makes the clutch smaller and lighter than an electromagnetic clutch and makes it possible to transmit driving force for both forward and reverse rotation. Other features of the mechanism are that it consumes power only for switching, not for maintaining the rotational state, and there is no limit to the number of speed ratio levels that can be set.
When this technology is applied to motor-driven prosthetic legs, the walking speed is independent of motor performance, which means that the motor can be made smaller and the prosthetic leg can be made lighter due to the power savings. In addition, the swinging of the leg while walking can be made quieter, which expands the life possibilities for users of prosthetic legs.

Hiromi ONO、Kei SHIMADA、Yutaka HIKI、Seiji ONOZAWA、Fumihito GOTO

The authors conducted a demonstration experiment of a small electric outboard motor system that utilizes an electric scooter power unit and swappable batteries. As the use case, the experiment took place on the “Horikawa Meguri” sightseeing tour in Matsue City, Shimane Prefecture, in which a small boat is used to tour a moat.
The braking distance when berthing was reduced by 30% by using a switch that changes propeller rotation direction and a speed adjustment function that enables control even at very low speeds. In terms of operability, the authors verified how operators used the equipment and tuned the relationship between the throttle position and tour boat speed for an electric outboard motor. Furthermore, the use of swappable batteries enabled quick battery replacement on board. As a result, the performance and feeling of the outboard motor were better than those of internal combustion engine outboard motors.

Takamasa TAKESHIGE、Kenta KATO、Shohma HIGANO