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Carbon neutrality has become a significant target. One essential parameter regarding energy consumption and emissions is the mass of vehicles. Lightweight design improves the result of vehicle life cycle assessment (LCA), increases efficiency, and can be a step towards sustainability and CO2 neutrality. Weight reduction through structural optimization is a challenging task. Typical design development procedures have to be overcome. Instead of just a facelift or the creation of a derivative of the predecessor design, completely alternative design creation methods have to be applied. Automated structural optimization is one tool for exploring completely new design approaches. Different methods are available and weight reduction is the focus of topology optimization. This paper describes a fatigue life homogenization method that enables the weight reduction of vehicle parts. The applied CAE process combines fatigue life prediction and topology optimization.

The concept of the vehicle has changed in accordance with the technological innovations on last decade. Today we can call these changes basically as "CASE" (Connected, Autonomous/Automated, Shared, and Electric). The ease of product access on the user side and the mass production related works have increased worldwide production volumes. This issue has resulted in a greater demand for manpower in the sector. In addition, management, productivity, and profitability related difficulties have occurred. In this project, improvements were made mainly around the productivity through the automation of "vehicle transfer operations in plant operations", which is one of a major problem and a manpower/hour consuming task. This system named as Remote-Control Auto Driving System (RCD). The advance technology used system enabling unmanned, secured operations, were implemented in mass production environment earlier than the rest of the world.

In the 1st generation Toyota "MIRAI" fuel cell stack, carbon protective surface coating is deposited after individual Ti bipolar plate being press-formed into the desired shape. Such a process has relatively low production speed, not ideal for large scale manufacturing. A new coating concept, consisting of a nanostructured composite layer of titanium oxide and carbon particles, was devised to enable the incorporation of both the surface treatment and the press processes into the roll-to-roll production line. The initial coating showed higher than expected contact resistance, of which the root cause was identified as nitrogen contamination during the annealing step that inhibited the formation of the composite film structure. Upon the implementation of a vacuum furnace chamber as the countermeasure, the issue was resolved, and the improved coating could meet all the requirements of productivity, conductivity, and durability for use in the newer generation of fuel cell stacks.

This paper presents a design method for continuous fiber composites in three-dimensional space with locally varying orientation distribution and their fabrication method. The design method is formulated based on topology optimization by augmented tensor field design variables. The fabrication method is based on Tailored Fiber Placement technology, whereby a CNC embroidery machine prepares the preform. The fiber path is generated from an optimized orientation distribution field. The preform is formed with vacuum-assisted resin transfer molding. The fabricated prototype weighs 120 g, a 70% weight reduction, achieving 3.5× mass-specific stiffness improvement.

Since the regulations of CO2 emissions have been tightened in each country recently, each automotive manufacturer has responded by bringing competitive technologies that maximize efficiency while promoting vehicle electrification such as xEV. Not only the efficiency, we need to meet or exceed occupant performance and comfort expectations. The climate control system expends a large amount of energy to keep a comfortable environment, having a significant impact on fuel consumption and EV driving range. Therefore, many manufacturers try to save energy and improve occupant comfort quickly by using not only the conventional convective heating by HVAC but also the conductive heating to heat the human body directly such as seat and steering wheel heater. In this study, a radiative heater, which is more efficient than a convective heating to warm anterior thigh and shin where a conductive heating cannot warm, was applied to vehicle.

The reduction of CO2 emissions is one of the most important challenges for the automotive industry to contribute to address global warming. Reducing friction of internal combustion engines (ICEs) is one effective countermeasure to realize this objective. The improvement of engine oil can contribute to reduce fuel consumption by reducing friction between engine parts. Electrification of ICE powertrains increases the overall efficiency of powertrains and reduces the average engine oil temperature during vehicle operation, due to intermittent engine operation. An effective way of reducing engine friction is to lower the viscosity of the engine oil in the low to medium temperature range. This can be accomplished while maintaining viscosity at high temperatures by reducing the base oil viscosity and increasing the viscosity modifier (VM) content to raise the viscosity index (so-called “flat viscosity” concept).

In recent years, the realization of carbon neutrality has become an activity to be tackled worldwide, and automobile manufacturers are promoting electrification of power train by HEV, PHEV, BEV and FCEV. Although interest in BEV is currently growing, vehicles equipped with internal combustion engines (ICE) including HEV and PHEV will continue to be used in areas where conversion to BEV is not easy due to lack of sufficient infrastructures. For such vehicles, low-viscosity engine oil will be one of the most important means to contribute to further reduction of CO2 emissions. Since HEV requires less work from the engine, the engine oil temperature is lower than that of conventional engine vehicles. Therefore, the reduction of viscous resistance in the mid-to-low temperature range below 80°C is expected to contribute more to fuel economy. On the other hand, the viscosity must be kept above a certain level to ensure the performance of hydraulic devices in the high oil temperature range.

This paper describes the high-pressure hydrogen storage system developed for new FCV. With the aim of further popularizing FCVs, this development succeeded in improving the performance of the system and reducing costs. This new storage system consists of multiple tanks of different sizes, which were optimized to store the necessary amount of hydrogen without sacrificing the interior space of the vehicle. The new tanks achieved one of the highest volume efficiencies in the world by adopting high-strength carbon fiber, developed in conjunction with the carbon fiber manufacturer, and by optimizing the layered construction design which allowed the amount of carbon fiber to be reduced. To increase the amount of available hydrogen, the longer high pressure tanks were mounted under the vehicle floor unlike the previous model. This was accomplished by the following two measures: First, individual design and manufacturing measures for the tanks were adopted.

Since bumper reinforcements are positioned at front/rear ends of vehicles, weight reduction of the bumper reinforcements enhances vehicle dynamic performance by reducing a yaw moment of inertia. CFRP (Carbon Fiber Reinforced Plastic) composites are attractive lightweight materials due to their excellent specific strength and rigidity. However, because of their relatively high cost, applications of CFRP materials to vehicle structural parts are limited. In this study we have developed a lightweight, structural part, which consists of a thin-walled Al (Aluminum) bumper reinforcement with a UD (Unidirectional)-CFRP sheet. The intention is to prevent an increased part cost by reducing the amount of Al and by minimizing the amount of CFRP. Compared to Al, UD-CFRP sheets have even higher tensile strength and modulus. When vehicles crash, bumper reinforcements may be subjected to bending force.

Further fuel economy improvement of the internal combustion engine is indispensable for CO2 reduction in order to cope with serious global environmental problems. Although lowering the viscosity of engine oil is an effective way to improve fuel economy, it may reduce the wear resistance. Therefore, it is important to achieve both improved fuel economy and reliability. We have developed new 0W- 8 engine oil of ultra-low viscosity and achieved an improvement in fuel economy by 0.8% compared to the commercial 0W-16 engine oil. For this new oil, we reduced the friction coefficient under boundary lubrication regime by applying an oil film former and calcium borate detergent. The film former increased the oil film thickness without increasing the oil viscosity. The calcium borate detergent enhanced the friction reduction effect of molybdenum dithiocarbamate (MoDTC).

In order to improve the fuel efficiency of Hybrid Electric Vehicles (HEVs), it is necessary to reduce the size and power loss of the HEV Power Control Units (PCUs). The loss of power devices (IGBTs and FWDs) used in a PCU accounts for approximately 20% of electric power loss of an HEV. Therefore, it is important to reduce the power loss while size reduction of the power devices. In order to achieve the newly developed PCU target for compact-size vehicles, the development targets for the power device were to achieve low power loss equivalent to its previous generation while size reduction by 25%. The size reduction was achieved by developing a new RC-IGBT (Reverse Conducting IGBT) with an IGBT and a FWD integration. As for the power loss aggravation, which was a major issue due to this integration, we optimized some important parameters like the IGBT and FWD surface layout and backside FWD pattern.

Increasingly stringent regulations call for the reduction of emissions at engine startup to purify exhaust gas and reduce the amount of CO2 emitted. Air-fuel ratio (A/F) sensors detect the composition of exhaust gas and provide feedback to control the fuel injection quantity in order to ensure the optimal functioning of the catalytic converter. Reducing the time needed to obtain feedback control and enabling the restriction-free installation of A/F sensors can help meet regulations. Conventional sensors do not activate feedback control immediately after engine startup as the combination of high temperatures and splashes of condensed water in the exhaust pipe can cause thermal shock to the sensor element. Moreover, sensors need to be installed near the engine to increase the catalyst reaction efficiency. This increases the possibility of water splash from the condensed water in the catalyst.

This paper describes the development of a simplified fracture finite element (FE) model for resistance spot welds (RSW) of ultra-high-strength steel (UHSS) that can be incorporated into large-scale vehicle FE model. It is known that the RSW of UHSS generates two types of fracture modes: heat-affected zone (HAZ) and nugget zone fractures. Lap shear and peeling coupon tests using UHSS sheets found that the different RSW fracture modes occurred at different nugget diameters. To analyze this phenomenon, detailed simulated coupon tests were carried out using solid hexahedral elements. The analytical results revealed that RSW fractures are defined by both the application of plastic strain on the elements and the stress triaxiality state of the elements. A detailed model incorporating a new fracture criteria model recreated the different UHSS RSW fracture modes and achieved a close correlation with the coupon test results.

Silver metallic colors with thin and smooth aluminum flake pigments have been introduced for luxury brand OEMs. Regarding the paint formulation for these types of colors, low non-volatile(NV) and high aluminum flake pigment contents are known as technology for high metallic appearance designs. However, there are two technical concerns. First is mottling which is caused by uneven distribution of the aluminum flake pigments in paint film and second is poor film property due to high aluminum pigment concentration in paint film. Therefore, current paint systems have limitation of paint design. As a countermeasure for those two concerns, we had investigated cellulose nanofiber (CNF) dispersion liquid as both the coating binder and rheology control agent in a new type of waterborne paint system. CNF is an effective rheology control agent because it has strong hydrogen bonds with other fiber surfaces in waterborne paint.

In order to achieve the Toyota Environmental Challenge of 2050 (zero CO2 emissions), we have developed an innovative coating system that achieves more than 95% transfer efficiency. In order to reduce paint loss in the painting process, it is necessary to eliminate overdust and bounce dust. The most important point is how to spray (atomization, particle flight, adhesion) without shaping air. We have developed a “super high transfer efficiency system” that eliminates the need for shaping air. We continue to challenge the development of innovative technologies to view the paint shop as clean and eco-friendly environment.

This paper describes a numerical prediction method for fatigue strength of Self Piercing Rivets (SPRs) using fracture mechanics. Recently, high strength steels and non-ferrous metals have been adopted to light weight automotive bodies. Various types of joining are proposed for multi-material bodies. It is important to predict the fatigue life of these joints using numerical simulation. However, the fatigue strength of these joints is related to sheet thickness, base materials, and loading conditions. Therefore, a large number of coupon tests are necessary to determine the S-N curve for the fatigue life prediction of joints in the automotive body. To reduce the amount of coupon testing, numerical simulation will be an efficient method in obtaining the S-N curve of these joints. The fatigue fracture process consists of two stages, crack initiation and crack growth. There are many studies about crack growth estimation methods using stress intensity factor.

Application of SiC power devices is regarded as a promising means of reducing the power loss of power modules mounted in power control units. Due to those high thermostable characteristics, the power module with SiC power devices are required to have higher operating temperature than the conventional power module with Si power devices. However, the limitations of current packaging technology prevent the utilization of the full potential of SiC power devices. To resolve these issues, the development of device bonding technology is very important. Although transient liquid phase (TLP) bonding is a promising technology for enabling high temperature operation because its bonding layer has a high melting point, the characteristics of the TLP bonding layer tend to damage the power devices. This paper describes the development of a bonding technology to achieve high temperature operation using a stress reduction effect.

1 Structural parts, such as the center pillar, are a multi-layer structure. They are a combination of high-strength panels and high-toughness panels, to control the deformation mode during a crash. If we can make this multi-layered structure as one panel, consisting of different hardness within it, we will be able to make a lightweight part. In this study, we have developed a method to fabricate a ‘lightweight center pillar’ with the following processes. First, the whole panel is hardened by quenching within the hot stamp process. Next, certain areas of the panel are softened by partial tempering. We have found that the temperature zone for softening is between A1 and A3, and it is easy to perform a rapid and accurate tempering by utilizing induction heating around the Curie temperature between A1 and A3 transformation temperature.

Wireless Power Transfer (WPT) promises automated and highly efficient charging of electric and plug-in-hybrid vehicles. As commercial development proceeds forward, the technical challenges of efficiency, interoperability, interference and safety are a primary focus for this industry. The SAE Vehicle Wireless Power and Alignment Taskforce published the Recommended Practice J2954 to help harmonize the first phase of high-power WPT technology development. SAE J2954 uses a performance-based approach to standardizing WPT by specifying ground and vehicle assembly coils to be used in a test stand (per Z-class) to validate performance, interoperability and safety. The main goal of this SAE J2954 bench testing campaign was to prove interoperability between WPT systems utilizing different coil magnetic topologies. This type of testing had not been done before on such a scale with real automaker and supplier systems.

To resolve two major problems of conventional CFD-based shape optimization technology: (1) dependence of the outcome on the selection of design parameters, and (2) high computational costs, two types of innovative inverse analysis technologies based on a mathematical theory called the Adjoint Method were developed in previous studies for maximizing an arbitrary hydrodynamic performance aspect as the cost function: surface geometry deformation sensitivity analysis to identify the locations to be modified, and topology optimization to generate an optimal shape. Furthermore, these technologies were extended to transient flows by the application of the transient Adjoint Method theory. However, there are many cases around flow path shapes in vehicles where performance with respect to heat or concentration, such as the total amount of heat transfer or the flow rate of a specific gas component, is very important.