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Reducing vehicle CO2 emissions is an important measure to help address global warming. To reduce CO2 emissions on a global basis, Toyota Motor Corporation is taking a multi-pathway approach that involves the introduction of the optimal powertrains according to the circumstances of each region, including hybrid electric (HEVs) and plug-in hybrid electric vehicles (PHEVs), as well as battery electric vehicles (BEVs). This report describes the development of a new PHEV system for the Toyota Prius. This system features a traction battery pack structure, transaxle, and power control unit (PCU) with boost converter, which were newly developed based on the 2.0-liter HEV system. As a result, the battery capacity was increased by 1.5 times compared to the previous model with almost the same battery pack size. Transmission efficiency was also improved, extending the distance that the Prius can be driven as an EV by 70%.

Reducing the carbon emissions associated with ICE- containing vehicles is a complimentary step towards carbon neutrality alongside the introduction of vehicles using newer energy vectors. In this study, the authors investigated emissions and efficiency impact of fully renewable E10-grade gasoline fuels blended with sustainable components at both 90 RON and 96 RON in comparison with reference regular E0 and premium certification gasolines across a range of ICE vehicle applications. Both renewable fuels were blended to the Japan JIS K2022 2012 E10 specification. The study shows very low carbon gasolines are technically feasible and potentially have an important role to play in decarbonizing both new advanced technology ICE vehicles and, critically, the existing ICE vehicle parc in the transition towards a zero emissions future.

Internal combustion engines will play an important role in the coming decades, even considering targets of carbon neutrality for a sustainable future. This will be especially true in regions where pure electrified vehicle implementation is not yet practical, or for long-range heavy load transportation purposes, even in regions where BEV infrastructure is well established. HEV/PHEV’s importance and contribution to CO2 emission reduction together with carbon neutral fuels such as hydrogen, e-fuel and biomass fuel etc. will remain crucial regardless of region/transport sectors. In this respect, brake thermal efficiency improvements by friction reduction needs further investigation. This is especially so with the crankshaft bearings’ lubrication system, which can provide as much as 40% of the total mechanical losses in some cases. It is a well-established fact, that plain bearings require a minimum oil flow volume to maintain their real function rather than oil pressure.

HEV and PHEV require an improved aftertreatment system to clean the exhaust gas in various driving situations. The efficiency of aftertreatment system is significantly influenced by the residence time of the gas in a catalyst which gas flow has generally strong pulsation. Simulation showed up to 70% reduction of exhaust gas emission if the pulsation could be completely attenuated. A new concept exhaust manifold was designed to minimize pulsation flow by wall impingement, with slight increase of pressure loss. Experimental results with new concept exhaust manifold showed exhaust gas emission were reduced 16% at cold condition and 40% at high-load condition.

Global focus on CO2 reduction and environmental protection is increasing. To comply with stricter exhaust gas regulations and reduce real world emissions, it is becoming increasingly important to improve the performance of three-way catalysts. Therefore, highly efficient conversion of hydrocarbons (HC), carbon monoxide (CO), and nitrogen oxides (NOx) is required. In general, the more active the precious metals used, the better the conversion performance. However, precious metals have supply risks, such as price fluctuation and the uneven distribution of production areas. Therefore, it is necessary to lower emissions while also lowering the amount of precious metals used. This paper focuses on how catalysts are used and describes the development of a new three-way catalyst for the purpose of strengthening cold conversion and decreasing the usage of precious metals.

To prevent global warming, many countries are making efforts to reduce CO2 emissions toward achieving 2050 carbon neutrality. In order to reduce CO2 concentration quickly, in addition to spread of renewable energy and expansion of BEV, it is also important to reduce CO2 emissions by improving thermal efficiency of ICE (internal combustion engine) and utilizing carbon neutral fuels such as synthetic fuels and biofuels. It is well known that lean burn is an effective technology to increase thermal efficiency of engine highly. However, since NOx emission from lean burn engine cannot be reduced with three-way catalyst, there have been issues such as complicated system configuration due to the addition of NOx reduction catalyst or limiting lean operation to narrow engine speed and load in order to meet emission regulation of each country.

It is necessary for us to reduce CO2 emissions in order to hold down global warming which is advancing year by year. Toyota Motor Corporation believes that not only the introduction of BEVs but also the sale of the hybrid vehicles must spread in order to achieve the necessary CO2 reduction. Therefore, we planned to improve the attractiveness of future hybrid vehicles. Prius has always made full use of hybrid technologies and leading to significant CO2 reduction. Toyota Motor Corporation has developed a 2.0L hybrid system for the new Prius. We built the system which could achieve a comfortable drive along following the customer’s intention while improving the fuel economy more than a conventional system. The engine improves on both output and thermal efficiency. The transaxle decreases mechanical loss by downsizing the differential, and adoption of low viscosity oil.

Nitric Oxide (NO) can significantly influence the autoignition reactivity and this can affect knock limits in conventional stoichiometric SI engines. Previous studies also revealed that the role of NO changes with fuel type. Fuels with high RON (Research Octane Number) and high Octane Sensitivity (S = RON - MON (Motor Octane Number)) exhibited monotonically retarding knock-limited combustion phasing (KL-CA50) with increasing NO. In contrast, for a high-RON, low-S fuel, the addition of NO initially resulted in a strongly retarded KL-CA50 but beyond the certain amount of NO, KL-CA50 advanced again. The current study focuses on same high-RON, low-S Alkylate fuel to better understand the mechanisms responsible for the reversal in the effect of NO on KL-CA50 beyond a certain amount of NO.

To achieve carbon neutrality by reducing carbon dioxide (CO2) emissions, vehicles with an internal combustion engine have started to be replaced by electrification vehicles such as hybrid electric vehicles (HEVs), plug-in HEVs (PHEVs), and battery EVs (BEVs) worldwide, which have motors in their transaxles (T/As). Reducing transmission torque loss in the transaxles is effective to reduce CO2 emissions, and lowering the viscosity of lubrication fluids in T/As is a promising method for reducing churning and drag loss. However, lowering viscosity generally leads to thin oil films and makes the lubrication condition severe, resulting in worse anti-fatigue and anti-seizure performance. To deal with these issues, we made improvements on the additive formulation of fluid, such as the addition of an oil-film-forming polymer, chemical structure change of calcium detergents, and an increase of anti-wear additives including phosphorus and sulfur.

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.

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.

The first MIRAI was launched in 2014 as the world’s first commercial fuel cell vehicle (FCV) [1]. Compared to the FC stack used in the first MIRAI, the FC stack in the new MIRAI achieved one of the highest volumetric power densities in the world (5.4 kW/L, excluding end plates, 1.5 times higher than the FC stack in the first MIRAI) by adopting a new flow channel for the bipolar plate and an improved electrode [2]. Enhancing the current density is an important means of increasing power performance and reducing size. The bipolar plate functions to distribute gas and drain water inside the cells to stabilize current generation. However, a conventional straight flow channel tends to cause flooding, which makes it difficult to maintain stable current generation. A partially narrow flow channel was developed to enhance oxygen diffusion without the 3D fine-mesh flow field that was adopted in the previous FC stack.

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).

Combustion of a lean air-fuel mixture diluted with a large amount of air or Exhaust Gas Recirculation (EGR) gas is one of the important technologies that can reduce thermal NOx and improve gasoline engine fuel economy by reducing cooling loss. On the other hand, lean combustion increases unburned Hydro Carbon (HC) and unburned loss compared to stoichiometric combustion. This is because lean combustion reduces the burning rate of the air-fuel mixture and forms a thick quenching layer near the wall surface. In this study, the relationship between the thickness of the unburned HC and the excess air ratio is analyzed using Laser Induced Fluorescence (LIF) method and Computational Fluid Dynamic (CFD) of combustion. The HC distribution near the engine liner when the excess air ratio is increased is investigated by LIF. As a result, it is found that the quenching distance of the flame in the cylinder is larger for lean conditions than the general single-wall quenching relationship.

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.

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.

To correspond to the social requirements such as climate change, air pollution, and energy security, enhancing the engine thermal efficiency is strongly required in these days. As for the specific engine technologies to improve the engine thermal efficiency, Atkinson cycle, cooled EGR (Exhaust Gas Recirculation), and low friction technologies have been developed [1–4]. In regard to combustion technology, lean boosted concept has a potential to reduce CO2 emission because lean boosted concept is expected to enhance the engine thermal efficiency. Although expanding lean combustion limit is important for both increasing the engine thermal efficiency and reducing NOx emission, there is a limitation to realize stable lean combustion with SI (Spark Ignition) gasoline engine. In this study, fuel effects on the combustion characteristics from the viewpoint of chemical reaction capability are focused on.

Numerical modeling of engine combustion products requires detailed chemistry and therefore large computational resources and time. This becomes a constraint when engine optimization at system level is desired. In this paper, a 1D modeling approach is proposed for fast computation to predict emission level at various engine running conditions. A new chemical solver within 1D framework is developed along with suitable reduced chemical mechanism. The reduced reaction scheme is validated against detailed chemistry on 0D and 1D reactors. It is confirmed that the new fast 1D solver achieves more than 100X speed improvement. Now larger mechanisms can be used for better accuracy with reasonable turnaround time. This methodology allows virtual engine emission map generation, with a refined emission map completed within 12 hours of computational time.

The knock-suppression effectiveness of exhaust-gas recirculation (EGR) can vary between implementations that take EGR gases after the three-way catalyst and those that use pre-catalyst EGR gases. A main difference between pre-and post-catalyst EGR gases is the level of trace species like NO, UHC, CO and H2. To quantify the role of NO, this experiment-based study employs NO-seeding in the intake tract for select combinations of fuel types and compression ratios, using simulated post-catalyst EGR gases as the diluent. The four investigated gasoline fuels share a common RON of 98, but vary in octane sensitivity and composition. To enable probing effects of near-zero NO levels, a skip-firing operating strategy is developed whereby the residual gases, which contain trace species like NO, are purged from the combustion chamber. Overall, the effects of NO-seeding on knock are consistent with the differences in knock limits for preand post-catalyst EGR gases.