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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.

Contribution to carbon neutrality is one of the most important challenges for the automotive industry. Though CO2 emission has been reduced through electrification, internal combustion engines equipped in vehicles such as Hybrid Electric Vehicle (HEV) and Plug-in Hybrid Electric Vehicle (PHEV) are still necessary for the foreseeable future, and continuous efforts to improve fuel economy are demanded. To improve powertrain thermal efficiency, direct-injection turbocharged gasoline engines have been widely utilized in recent years. Super lean-burn combustion engine has been being researched as the next generation of turbocharged gasoline engines. It is known that an increase of the boost pressure causes deposit formation, which decrease the turbocharger efficiency, in the turbocharger compressor housing. To avoid the efficiency loss due to deposit, air temperature at compressor outlet has to be limited low.

Carbon Fiber Reinforced Plastic (CFRP) is used for various products in the aerospace and sports industries due to its superior specific tensile strength and specific rigidity. With increasing attention to Carbon Neutrality (CN) in the world, vehicle electrification and lightweighting are expanding. As a result, the application of CFRP to luxury cars, electric cars, and sports cars, is increasing. For example, CFRP is used on Lexus LC and RC-F, and Toyota 86 GRMN. However, there are two technical concerns. The first is its durability, which caused by CFRP resin characteristic. The second is poor appearance, which is caused by CFRP surface pinholes. In order to secure good durability and surface appearance, CFRP must be pre-treated before painting (putty applied as a filler for plastic surface coverage, followed by surface sanding) and needs multiple painting steps. Current painted CFRP is not suitable for mass production due to this long and complicated process.

In recent years, electrically heated catalysts (EHCs) have been developed to achieve lower emissions. In several EHC heating methods, the direct heating method, which an electric current is applied directly to the catalyst substrate, can easily activate the catalyst before engine start-up. The research results reported on the use of the direct heating EHC to achieve significant exhaust gas purification during cold start-up [1]. From the perspective of catalyst loading, ceramics is considered to be a better material for the substrate than metal due to the difference in coefficient of thermal expansion between the catalyst and the substrate, but the EHC made of ceramics has difficulties such as controllability of the current distribution, durability and reliability of the connection between the substrate and the electrodes.

All-solid-state lithium (Li)-ion batteries have attracted significant interest for their enhanced energy density compared with conventional batteries employing an organic liquid electrolyte. However, the interfacial impedance and reaction between electrodes and the electrolyte can hinder the transport of Li-ions, thus degrading the battery performance. This paper presents a systematic screening method to identify coatings to reduce impedance and maintain interface stability during battery operation. Promising coating materials are rapidly selected by evaluating properties for ideal coating materials from computational databases containing a vast collection of Li compounds. Finally, a few candidates are discovered and their battery performances are tested. This approach is demonstrated to be an efficient way to predict and evaluate functional coatings for a high performance all-solid -state battery design.

In Toyota’s 2nd generation FCV, an electric turbo-type air compressor has been adopted for downsizing and cost reduction. Automotive Fuel Cell applications present several challenges for implementing a turbo-type air compressor. When operating a fuel cell in high-temperature or high-altitude locations, the FC stack must be pressurized to prevent dry-up. The flow rate vs pressure conditions that the FC must pass through or in some cases operate at are typically within the surge region of a turbo-type air compressor. Additionally, Toyota requires quick air transient response (< 1 sec) for power generation, energy management, and FC dry-up prevention. If the turbo-type air compressor is not precisely controlled during quick transients, it can easily enter the surge region.

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).

Toyota has developed a new Hybrid (HV) transaxle P810 for Mid-Size SUVs to improve fuel efficiency and power performance. The transaxle was developed based on Toyota's new development strategy - Toyota New Global Architecture (TNGA). By adopting technologies to shorten overall length of the transaxle, installation into the same engine compartment of Mid-Size sedans have been realized while also improving the motor output. This paper will introduce technologies regarding the new mount structure for shortening overall length, and furthermore, noise reduction related to this mount structure.

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.

From the point of global and local environment, internal combustion engine is facing the need for significant improvement of exhaust emission. Especially, important is the reduction of unburned hydrocarbon (HC) from fuel film on liner under cold condition. In this study, at first, quantitative fuel film measurement technique by using Laser Induced Exciplex Fluorescence (LIEF) was developed. For the light source, 4th harmonic pulse yttrium aluminum garnet (YAG) laser (266nm) was used. For the tracer, the combination of N,N-Dimethylaniline (DMA) and naphthalene was used and quantitative concentration was decided by calibration test. With LIEF, the distribution of fuel film can be obtained by measuring the fluorescence only from the liquid phase. In order to evaluate the effect of fuel film on exhaust HC emission from engine, the film distribution was measured using quartz glass liner. For the injector, a prototype 6-hole gasoline injector was used.

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.

When the air conditioning (A/C) is turned on, the intake air to the HVAC is cooled at the evaporator. This is not only used for cooling the air temperature but also to dehumidify. Therefore, for a typical automatic climate control system, A/C will automatically operate even in winter (cold ambient temperature conditions) in order to prevent the windows from fogging despite its effect on fuel economy. In some applications, a humidity sensor is installed on top of the windshield and when the probability of fogging is low the A/C operation is disabled automatically to prevent unnecessary compressor operation which can increase fuel consumption. However, humidity sensor is not widely adopted as it requires some space to be installed and the cost is relatively expensive compared with other HVAC equipped sensors. In this study, a system was invented that disables the compressor operation when the fogging probability is low without using the conventional humidity sensor.

Further improvements in catalyst performance are required to help protect the atmospheric environment. However, from the viewpoint of resource availability, it is also necessary to decrease the amount of precious metals used at the active sites of the catalyst. Therefore, a high-performance three-way catalyst with an advanced coating layer has been developed to lower the amount of precious metal usage. Fuel efficiency improvement technologies such as high compression ratios and a large-volume exhaust gas recirculation (EGR) generally tend to increase the ratio of hydrocarbons (HC) to nitrogen oxides (NOx) in exhaust gas. This research focused on the palladium (Pd) loading depth in the coating layer with the aim of improving the hydrocarbon (HC) conversion activity of the catalyst.

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.

This paper presents the thermal management of a hybrid vehicle (HV) using a heat pump system in cold weather. One advantage of an HV is the high efficiency of the vehicle system provided by the coupling and optimal control of an electric motor and an engine. However, in a conventional HV, fuel economy degradation is observed in cold weather because delivering heat to the passenger cabin using the engine results in a reduced efficiency of the vehicle system. In this study, a heat pump, combined with an engine, was used for thermal management to decrease fuel economy degradation. The heat pump is equipped with an electrically driven compressor that pumps ambient heat into a water-cooled condenser. The heat generated by the engine and the heat pump is delivered to the engine and the passenger cabin because the engine needs to warm up quickly to reduce emissions and the cabin needs heat to provide thermal comfort.

Vehicle weight reduction is becoming more and more important as increasingly stringent fuel economy regulations are introduced around the world. This development improved the hydraulic gear pump performance of the next-generation Active Height Control (AHC) suspension and achieved significant weight reduction of 5 kg by eliminating the auxiliary pump accumulator. To realize the necessary high-pressure with a high flow rate, the sealing performance of the pump at the tips of the gear teeth is very important. This was achieved by developing “breaking-in” technology that shaves away the aluminum housing using the gear teeth and creates zero clearance between the teeth tips and the housing. To reduce the frictional loss torque of the pump, which was identified as an issue of this technology, it was necessary to completely shave away the initial clearance in the breaking-in process.

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.

This article proposes a rubber suspension bushing model considering amplitude dependence as a useful tool at the initial design phase. The purpose of this study is not to express physical phenomena accurately and in detail and to explore the truth academically, but to provide a useful design method for initial design phase. Experiments were carried out to verify several dynamic characteristics of rubber bushings under vibration up to a frequency of 100 Hz, which is an important frequency range when designing ride comfort performance. When dynamic characteristic theory and the geometrical properties of the force-displacement characteristic curve were considered using these dynamic characteristics as assumptions, an equation was derived that is capable of calculating the dynamic stiffness under an arbitrary amplitude by identifying only two general design parameters (dynamic stiffness and loss factor) under a reference amplitude.

Toyota has developed a new continuously variable transmission (CVT) called "Direct Shift-CVT" which is for 2.0-liter class vehicles. This CVT provided not only power transmission by a metal belt held with a conventional pulley but also additional gear mechanism. This CVT is developed to improve fuel efficiency, acceleration characteristic, and quietness. At this CVT, the startup low gear ratio is achieved by gear mechanism and the power is switched by clutches. Since the belt-pulley portion can be realized to be wide range by using only high gear ratio range, the input load into belt-pulley portion is reduced and unprecedented compact and high efficient belt-pulley portion is established. Consequently, the high efficiency in all fields from startup acceleration to high speed driving is achieved to improve fuel efficiency.

The new P710 hybrid transaxle for a mid-size 2.5-liter class vehicle was developed based on the Toyota New Global Architecture (TNGA) design philosophy to achieve a range of desired performance objects. A smaller and lighter transaxle with low mechanical loss was realized by incorporating a new gear train structure and a downsized motor. The noise of the P710 transaxle was also reduced by adopting a new damper structure.