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A high-power photovoltaic (PV) system for an electric vehicle was fabricated. The total rated power of the PV panels was 1150 W. A demonstration test was conducted for a year. The test data showed that the prototype PV system was able to generate energy equivalent to approximately 7,100 km/year in driving distance. It was also found that if the vehicle is used for commuting about 10 km one way, it is mostly not necessary to recharge the vehicle from the grid throughout the year. In addition, the system was able to maintain maximum power point tracking (MPPT) control during driving even when the solar radiation changed frequently.

There are two primary technical issues in the application of position sensorless control to generators for 100% electric-drive hybrid vehicles. The first is the risk of losing control when position sensorless estimation methods are changed in accordance with the generator speed, while. The second is the reduction in the maximum torque if the rate of change in the generator speed is extremely large in a relatively low-rotation-speed area. This study proposes countermeasures for each issue and their effects examines them via simulations and experiments.

In electrified automobiles, wind noise significantly contributes to the overall noise inside the cabin. In particular, underbody airflow is a dominant noise source at low frequencies (less than 500 Hz). However, the wind noise transmission mechanism through a battery electric vehicle (BEV) underbody is complex because the BEV has a battery under the floor panel. Although various types of underbody structures exist for BEVs, in this study, the focus was on an underbody structure with two surfaces as inputs of wind noise sources: the outer surface exposed to the external underbody flow, such as undercover and suspension, and the floor panel, located above the undercover and battery. In this study, aero-vibro-acoustic simulations were performed to clarify the transmission mechanism of the BEV underbody wind noise. The external flow and acoustic fields were simulated using computational fluid dynamics.

The size and weight of the traction inverter needs to be reduced to ensure a sufficient cruising range of an electric vehicle. To this end, one approach involves changing materials of the inverter case from aluminum to resin. However, the resin in use of inverter case causes technical issues in terms of collision performance, electromagnetic compatibility (EMC), and cooling performance because of the difference in the material properties between the resin and the conventionally used aluminum. By solving the abovementioned issues, a resin water jacket case (hereinafter, resin water jacket) was successfully adopted with inverters designed for next-generation electric powertrain in mass production models for the first time. The resin-based structure had advantages to reduce the weight of the inverter case by ~35% and decrease the number of parts to ~3/5, compared to that for the conventional cases.

Nissan’s variable compression turbo (VC-Turbo) engine has a multilink mechanism that continuously adjusts the top and bottom dead centers of the piston to change the compression ratio and achieve both fuel economy and high power performance. Increasing the exhaust gas recirculation (EGR) rate is an effective way to further reduce the fuel consumption, although this increases the exhaust gas condensation in the cylinder bores, causing a more corrosive environment. When the EGR rate is increased in a VC-Turbo engine, the combined effect of piston sliding and exhaust gas condensation at the top dead center accelerates the corrosive wear of the thermal spray coating. Stainless steel coating is used to improve the corrosion resistance, but the adhesion strength between the coating and the cylinder bores is reduced.

The adoption of electric vehicles (EVs) has been announced worldwide with the aim of reducing CO2 emissions. However, a significant increase in electricity demand by EVs might impact the stable operation of the existing power grid. Meanwhile, EV charging is acceptable to most users if it is completed by the time of the next driving event. From the viewpoint of power grid operators, flexibility for shifting the timing of EV charging would be advantageous, including making effective use of renewable energy. In this work, an EV model and simulation tool were developed to make clear how the total charging demand of all EVs in use will be influenced by future EV specifications (e.g., charge power) and installation of charging infrastructure. Among the most influential factors, EV charging behavior according to use cases and regional characteristics were statistically analyzed based on the real-world usage data of over 14, 000 EVs and incorporated in the simulation tool.

There are many production robots used at car manufacturing plants, and each of them is fitted with several reducers. A breakdown of one of these reducers may cause a huge loss due to the stoppage of all production lines. Therefore, condition-based maintenance is currently being used to predict failures by predetermined thresholds for average and standard deviations. However, this method can cause many false alarms or some false negatives. There are some ways of suppressing false alarms, such as detecting a change in the probability density function. However, when false alarms are suppressed using the probability density function in the operational range, some false negatives may occur, leading to a breakdown of a reducer and huge loss. A false negative is caused by overlooking an anomaly with slight changes and it is difficult to detect using only the probability density function.

An electric vehicle (EV) has less powertrain energy loss than an internal combustion engine vehicle (ICE), so its aerodynamic accounts have a larger portion of drag contribution of the total energy loss. This means that EV aerodynamic performance has a larger impact on the all-electric range (AER). Therefore, the target set for the aerodynamics development for a new EV hatchback was to improving AER for the customer’s benefit. To achieve lower aerodynamic drag than the previous model’s good aerodynamic performance, an ideal airflow wake structure was initially defined for the new EV hatchback that has a flat underbody with no exhaust system. Several important parameters were specified and proper numerical values for the ideal airflow were defined for them. As a result, the new EV hatchback achieves a 4% reduction in drag coefficient (CD) from the previous model.

During the last decade, fuel economy mandates (CAFE regulations) have driven engine downsizing and down-speeding trends. More recently, downsized turbos are percolating down to heavier SUVs and trucks. Larger/heavier vehicles require high torque engines to provide attractive dynamic performance. While higher torque requirements can be satisfied with new innovations like the variable compression engine, larger and more upscale vehicles also need to deliver higher quietness requirements. For this, the vibration control system for combustion induced forces with high torque engines become very important. To address both dynamic performance and quietness requirements, active engine mounts have been previously adopted, however challenges for light-weighting, downsizing, and costs have still persisted.

This paper describes a study of drag reduction devices for production pick-up trucks with a body-on-frame structure using full-scale wind tunnel testing and Computational Fluid Dynamics (CFD) simulations. First, the flow structure around a pick-up truck was investigated and studied, focusing in particular on the flow structure between the cabin and tailgate. It was found that the flow structure around the tailgate was closely related to aerodynamic drag. A low drag flow structure was found by flow analysis, and the separation angle at the roof end was identified as being important to achieve the flow structure. While proceeding with the development of a new production model, a technical issue of the flow structure involving sensitivity to the vehicle velocity was identified in connection with optimization of the roof end shape. (1)A tailgate spoiler was examined for solving this issue.

The purpose of this work was to gain a fundamental understanding of which fuel property parameters are responsible for particulate emission characteristics, associated with key intermediate behavior in the engine cylinder such as the fuel film and insufficient mixing. Accordingly, engine tests were carried out using various fuels having different volatility and chemical compositions under different coolant temperature conditions. In addition, a fundamental spray and film visualization analysis was also conducted using a constant volume vessel, assuming the engine test conditions. As for the physical effects, the test results showed that a low volatility fuel displayed high particulate number (PN) emissions when the injection timing was advanced. The fundamental test clearly showed that the amount of fuel film on the impingement plate increased under such operating conditions with a low volatility fuel.

This paper presents the technologies incorporated in an electric vehicle (EV)/hybrid electric vehicle (HEV) inverter built with power semiconductors of silicon carbide (SiC) metal-oxide-semiconductor field-effect transistors (MOSFETs) instead of conventional silicon (Si) insulated gate bipolar transistors (IGBTs). A SiC inverter prototype of 2.9 L in size for driving an 80-kW motor was fabricated and evaluated on a motor test bench. The SiC inverter prototype attained average efficiency of 98.5% in the Worldwide harmonized Light-duty Test Cycle (WLTC) driving mode. The two main technologies achieved with this SiC inverter prototype are described. The first one is a new direct-cooled power module with a thick copper (Cu) heat spreader located under the semiconductors that improves thermal resistance by 34% compared with a conventional direct-cooled power module.

With the development of downsized spark ignition (SI) engines, low-speed pre-ignition (LSPI) has been observed more frequently as an abnormal combustion phenomenon, and there is a critical need to solve this issue. It has been acknowledged that LSPI is not directly triggered by autoignition of the fuel, but by some other material with a short ignition delay time. It was previously reported that LSPI can be caused by droplets of lubricant oil intermixed with the fuel. In this work, the ignition behavior of lubricant component containing fuel droplets was experimentally investigated by using a constant volume chamber (CVC) and a rapid compression and expansion machine (RCEM), which enable visualization of the combustion process in the cylinder. Various combinations of fuel compositions for the ambient fuel-air mixture and fractions of base oil/metallic additives/fuel for droplets were tested.

Technologies for improving the fuel economy of gasoline engines have been vigorously developed in recent years for the purpose of reducing CO2 emissions. Increasing the compression ratio is an example of a technology for improving the thermal efficiency of gasoline engines. A significant issue of a high compression ratio engine for improving fuel economy and low-end torque is prevention of knocking under a low engine speed. Knocking is caused by autoignition of the air-fuel mixture in the cylinder and seems to be largely affected by heat transfer from the intake port and combustion chamber walls. In this study, the influence of heat transfer from the walls of each part was analyzed by the following three approaches using computational fluid dynamics (CFD) and experiments conducted with a multi-cooling engine system. First, the temperature rise of the air-fuel mixture by heat transfer from each part was analyzed.

Reducing vehicle fuel consumption has become one of the most important issues in recent years in connection with environmental concerns such as global warming. Therefore, in the vehicle development process, attention has been focused on reducing aerodynamic drag as a way of improving fuel economy. When considering environmental issues, the development of vehicle aerodynamics must take into account real-world driving conditions. A crosswind is one of the representative conditions. It is well known that drag changes in a crosswind compared with a condition without a crosswind, and that the change depends on the vehicle shape. It is generally considered that the influence of a crosswind is relatively small since drag accounts for a small proportion of the total running resistance. However, for electric vehicles, the energy loss of the drive train is smaller than that of an internal combustion engine (ICE) vehicle.

Technologies for improving the fuel economy of gasoline engines have been vigorously developed in recent years for the purpose of reducing CO2 emissions. Increasing the compression ratio for improving thermal efficiency and downsizing the engine based on fuel-efficient operating conditions are good examples of technologies for enhancing gasoline engine fuel economy. A direct-injection system is adopted for most of these engines. Direct injection can prevent knocking by lowering the in-cylinder temperature through fuel evaporation in the cylinder. Therefore, direct injection is highly compatible with downsized engines that frequently operate under severe supercharging conditions for improving fuel economy as well as with high compression ratio engines for which susceptibility to knocking is a disadvantage.

There has been a growing need in recent years to further improve vehicle fuel efficiency and reduce CO2 emissions. JATCO began mass production of a transmission for rear-wheel-drive (RWD) hybrid vehicle with Nissan in 2010, which was followed by the development of a front-wheel-drive (FWD) hybrid system (JATCO CVT8 HYBRID) for use on a midsize SUV in the U.S. market. While various types of hybrid systems have been proposed, the FWD system adopts a one-motor two-clutch parallel hybrid topology which is also used on the RWD hybrid. This high-efficiency system incorporates a clutch for decoupling the transmission of power between the engine and the motor. The hybrid system was substantially downsized from that used on the RWD vehicle in order to mount it on the FWD vehicle. This paper describes various seal technologies developed for housing the dry multi-plate clutch inside the motor, which was a key packaging technology for achieving the FWD hybrid system.

In a direct injection gasoline engine, the impingement of injected fuel on the oil film, i.e. cylinder liner gives rise to various problems such as abnormal combustion, oil dilution and particulate matter emission. Therefore, in order to solve these problems, it is necessary to have a clear understanding of the impingement behavior of the fuel spray onto the oil film. However, there is little information on the impingement behavior of the fuel droplet onto the oil film, whereas many investigations on the impingement behavior of the fuel droplet onto the fuel film are reported. In this study, fundamental investigations were performed for the purpose of clarifying the impingement behavior of the fuel spray onto the oil film. A single fuel droplet mixed with fluorescence dye was dripped on the oil film. To separately measure the fuel and the oil after impingement, simultaneous Mie scattering and laser-induced fluorescence (LIF) methods were performed.

HEV and EV markets are in a rapid expansion tendency. Development of low-cost regenerative cooperation brake system is needed in order to respond to the consumers needs for HEV and EV. Regenerative cooperation brake system which HEV and EV are generally equipped with has stroke simulator. We developed simple composition brake system based on the conventional ESC unit without the stroke simulator, and our system realized a low-cost regenerative cooperation brake. The key technologies are the quiet pressurization control which can be used in the service application, which is to make brake force depending on brake travel, by gear pump and the master cylinder with idle stroke to realize regenerative cooperation brake. Thanks to the key technologies, both the high regenerative efficiency and the good service brake feeling were achieved.

This paper describes the development of the drive motor adopted on the newly developed 2013 Model Year (MY) electric vehicle (EV). Based on the 2011MY EV that was specifically designed and engineered for mass-production, the 2013MY powertrain integrates the electric motor, inverter and charging system into one unit in order to achieve downsizing and weight saving, unlike previous 2011 model which had these components segregated. In general, integration of all components into one unit causes deterioration of the noise and vibration performance of vehicles due to an increase in weight and the number of resonance parts. In order to overcome such problems associated with this integration, each component in the 2013 model has been optimized to reduce noise and vibration resulting in high degree of vehicle quietness.