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When vehicles run on the flooded road, water enters to the engine compartment and sometimes reaches the position of the air intake duct and electrical parts and causes the reliability problems. Numerical simulation is an effective tool for this phenomenon because it can not only evaluate the water level before experiment but also identify the intrusion route. Recently, the gap around the engine cooling modules tends to become smaller and the undercover tends to become bigger than before in order to enhance the vehicle performance (e.g., aerodynamics, exterior noise). Leakage tightness around the engine compartment becomes higher and causes an increase of the buoyancy force from the water. Therefore the vehicle attitude change is causing a greater impact on the water level. This paper describes the development of a water level prediction method in engine compartment while running on the flooded road by using the coupled multibody and fluid dynamics.

Cold weather operation has been a major issue for fuel cell vehicles (FCV). In order to counteract this effect on FCV operation, an approach for rapid warm-up operation based on : concentration overvoltage increase and conversion efficiency decrease by limiting oxygen or hydrogen supply, was adopted in a running fuel cell hybrid vehicle. In order to adjust the output power response of the fuel cell to the target power of the vehicle, -the inherent capacitance characteristics of the fuel cell were measured- based on the oxidation-reduction reaction and an electric double-layer capacitor, and an equivalent electric circuit model of a fuel cell with the capacitance was constructed. This equivalent electric circuit model was used to develop a power control algorithm to manage absorption of the surplus power, or deviation, to the capacitance.

For over a decade and a half, Toyota Motor Corporation has been developing fuel cell vehicles (FCVs) and is continuing various approaches to enable mass production. This study used new methods to quantitatively observe some of the mass transfer phenomena in the reaction field, such as oxygen transport, water drainage, and electronic conductivity. The obtained results are applicable to the design requirements of ideal reaction fields, and have the potential to assist to reduce the size of the fuel cell.

Cold weather operation has been a major issue for fuel cell hybrid vehicles (FCHV). To counteract the effects of low temperatures on FCHV operation, an approach for rapid warm-up operation based on concentration overvoltage increase and conversion efficiency decrease by limiting oxygen or hydrogen supply was adopted. In order to suppress increases in exhaust hydrogen concentration due to pumping hydrogen during rapid warm-up, dilution control using bypass air and reduction of concentration overvoltage by a minimum voltage guard were implemented. These approaches effectively control waste heat generation and suppress exhaust hydrogen concentrations during cold start and warm-up. These developments were incorporated into the 2008 Toyota FCHV-adv and it was confirmed that the rapid warm-up operation strategy allowed the FCHV-adv to be successfully and repeatedly started at -30°C.

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.

For reduction of fuel consumption, a new device “Water Jacket Spacer” which improves temperature distribution of a cylinder block bore wall was developed. In the case of a conventional cylinder block, coolant flow concentrates at the bottom and middle region of the water jacket. While temperature of the upper bore wall is high (due to high-temperature combustion gas) the temperature of the lower bore wall is low, since its only function is to support the piston. When the developed spacer is inserted into a water jacket, the coolant flow concentrates at the upper part of the jacket. As a result, cooling ability to the upper bore wall was improved and temperature of lower bore wall was increased, thereby reducing fuel consumption.

In response to the steadily worsening impact of global warming, greater efforts are being made to achieve carbon neutrality. Toyota Motor Corporation developed an in-vehicle solar charging system that utilizes generated solar energy to drive the vehicle. While the ignition is off, energy generated from a solar panel is used to charge the main battery. Then, while the ignition is on, this energy is supplied to the 12 V system to reduce consumption of the main battery energy, thereby helping to improve the electric driving range. This 1st-generation solar charging system adopted in the Prius PHV in 2017 was the first mass-produced in-vehicle solar charging system in the world. In 2022, the 2nd-generation solar charging system was developed and adopted in the bZ4X, including performance improvements such as a newly designed solar roof and lightweight charging system.

In vehicles using a typical heating, ventilating, and air conditioning (HVAC) unit, ventilation loss through the cabin accounts for more than 60% of the heating load. This fact has increasingly important because of the low heat source characteristics of today's increasingly efficient engines. In response to this trend, a new type of air conditioning system, a “Two layer flow HVAC unit”, has been developed. This unit sends low humidity fresh intake air to the window neighborhood in order to promote good demist performance and warm recirculated air to the occupant foot area for increased efficiency. With this system, it is possible to reduce the ventilation loss by half and to raise the cabin temperature by 5°C.

Generally, pass-by noise levels measured outdoors vary according to the influence of weather conditions, background noise and the driver’s skill. Manufactures, therefore, are trying to reproduce proving ground driving conditions on a chassis dynamometer. The tire noise that occurs on actual road surfaces, however, is difficult to reproduce in indoor tests. In 2016, new pass-by noise regulations (UN R51-03) will take effect in Europe, Japan and other countries. Furthermore, stricter regulations (2dB) will take effect in 2020. In addition to the acceleration runs required under current regulations, UN R51-03 will require constant speed runs. Therefore, an efficient measurement methods are necessary for vehicle development. To solve the above mentioned issues, an indoor evaluation system capable of reproducing the tire noise that occurs on road surfaces has been developed.

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.

As part of efforts to address climate change and improve energy security, researchers have improved the thermal efficiency of engines by expanding the lean combustion limit. To further expand the lean combustion limit, the authors focused not only on engine technology but the chemical reactivity of various fuel molecules. Furan and anisole were among the fuel molecules selected, based on the idea that promising candidates should enhance the flame propagation speed and have good knocking resistance. Engine testing showed that the lean limit can be expanded by using fuels with the right molecular structures, resulting in higher thermal efficiency.

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.

Since 1992, Toyota Motor Corporation (TMC) has been working on the development of fuel cell system technology. TMC is designing principal components in-house, including fuel cell stacks, high-pressure hydrogen storage tank systems, and hybrid systems. TMC developed the '02 model TOYOTA FCHV, the world-first market-ready fuel cell vehicle, and started limited lease of the vehicles in 2002. In 2005, TMC developed a new model of TOYOTA FCHV which obtained vehicle type certification in Japan, and is currently available for leasing. TMC has improved the cruising range and cold start/drive capability of the TOYOTA FCHV, and conducted public road tests to evaluate the performance. The improved TOYOTA FCHV successfully traveled from Osaka to Tokyo (approximately 560km, 350 miles) on a single fueling of hydrogen. In addition, the cold weather tests carried out in Hokkaido and North America have verified its starting/driving capability at subfreezing temperatures including -37°C.

Toyota Motor Corporation (TMC) has been developing fuel cell vehicles (FCVs) since 1992. As part of a demonstration program, TMC launched the FCHV-adv in 2008, which established major technical improvements in key performance areas such as efficiency, driving range, durability, and operation in sub-zero conditions. However, to encourage commercialization and widespread adoption of FCVs, further improvements in performance were required. During sub-zero operating conditions, the FC system output power was lower than under normal operating conditions. The FC stack in the FCHV-adv needed to dry the electrolyte membrane to remove unneeded water from the stack. This increased the stack resistance and caused low output power. In December 2014, TMC launched the world’s first commercially available FCV named the Mirai, which greatly improved output power even after start-up in sub-zero conditions.

As a result of recent improvements in engine efficiency, vehicle heating performance has decreased and the demand for auxiliary heat sources is increasing. To help meet this need, we have developed an auxiliary heat system known as the “Hot Gas Heater”. The Hot Gas Heater uses components common to the vehicle air-conditioning system that are not used during winter. However, there are some concerns with this system. In this paper we describe our solutions to these problems. We reduced gas flow noise through multi-stage pressure reduction, and prevented fogging by adding “water retention memory” and “evaporator outlet air temperature control” functions to the system. As a further benefit, we developed a New Accumulator Cycle that moves the cooling cycle accumulator tank to the high-pressure side.