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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.

This paper proposes a technology to reduce vehicle surge during towing that utilizes motors and shifting to help ensure comfort in a parallel HEV pickup truck. Hybridization is one way to reduce fuel consumption and help realize carbon neutrality. Parallel HEVs have advantages in the towing, hauling, and high-load operations often carried out by pickup trucks, compared to other HEV systems. Since the engine, motor, torque converter, and transmission are connected in series in a parallel HEV, vehicle surge may occur when the lockup clutch is engaged to enhance fuel efficiency, similar to conventional powertrains. Vehicle surge is a low-frequency vibration phenomenon. In general, the source is torque fluctuation caused by the engine and tires, with amplification provided by first-order torsional driveline resonance, power plant resonance, suspension resonance, and cabin resonance. This vibration is amplified more during towing.

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).

This paper describes an exhaust system using a new air-fuel ratio (hereinafter, A/F) sensor that contributes to low emissions and low fuel consumption of gasoline engines. As the first technical feature, the water splash resistance of the A/F sensor has been substantially improved which allows A/F control to be enabled without delay during engine cold start. To realize this capability, it is important that the sensor characteristics are not affected by the condensed water generated in the exhaust pipe. Therefore, a technique that has the effectiveness of a water splash resistance layer with water repellent function is demonstrated. As the second technical feature, the power consumption of the sensor has been substantially reduced. This is achieved by improving thermal efficiency of the sensor that the element can be activated at a low temperature.

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.

Given a forecast of speed and load demands during a trip, a hybrid powertrain power-split Trajectory Optimization Problem (TOP) can be solved to optimize fuel consumption. This can be done on desktop to set performance benchmarks; however, it has been believed that the TOP could not be solved in real-time and is not a realizable controller. As such, several approximations of the TOP have been made in the interest of obtaining a real-time near-optimal controller, for example, Equivalent Consumption Minimization Strategies (ECMS) and their adaptive counterparts. These strategies decide on the power-split by, at each sampled time instant, minimizing a Horizon-0 (without predicting forward in time) composite function of fuel consumption and equivalent battery energy. The fuel economy that results from these strategies is highly sensitive to the calibration of the associated equivalence factor, and furthermore, must be chosen differently for different drive cycles.

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.

Plugin hybrid electric vehicles (PHEVs) have several attractive features in terms of reduction of greenhouse gas (GHG) emissions. Compared to conventional vehicles (CVs) that only have an internal combustion engine (ICE), PHEVs have better energy efficiency like regular hybrids (HEVs), allow for electrifying an appreciable portion of traveled miles, and have no range anxiety issues like battery-only electric vehicles (BEVs). However, in terms of criteria emissions (e.g., NOx, NMOG, HC), it is unclear if PHEVs are any better than HEVs or CVs. Unlike GHG emissions, criteria emissions are not continuously emitted in proportional quantities to fossil fuel consumption. Rather, the amount and type of criteria emissions is a rather complex function of many factors, including type of fuel, ICE temperature, speed and torque, catalyst temperature, as well as the ICE controls (e.g., fuel-to-air ratio, valve and ignition timing).

Natural gas (NG) is attractive for heavy-duty (HD) engines for reasons of cost stability, emissions, and fuel security. NG cannot be reliably compression-ignited, but conventional gasoline ignition systems are not optimized for NG and are challenged to ignite mixtures that are lean or diluted with exhaust-gas recirculation (EGR). NG ignition is particularly challenging in large-bore engines, where completing combustion in the available time is more difficult. Using two high-speed infrared (IR) cameras with borescopic access to one cylinder of an HD NG engine, the effect of ignition system on the early flame-kernel development and cycle-to-cycle variability (CCV) was investigated. Imaging in the IR yielded strong signals from water emission lines, which located the flame front and burned-gas regions and obviated image intensifiers. A 9.7-liter, six-cylinder engine was modified to enable exhaust-gas recirculation and to provide optical access.

Fuel consumption and CO2 emission regulations for vehicles, such as the Zero Emission Vehicle (ZEV) Regulation, motivate renewable energy technologies in the automotive industry. Therefore, the automotive industry is focused on adopting solar charging systems. Some vehicles have adopted solar energy to power the ventilation system, but these vehicles do not use solar energy to power the drivetrain. One important issue facing the design of solar charging systems is the low power generated by solar panels. Compared to solar panels for residential use, solar panels for vehicles can’t generate as much power because of size and weight limitations. Also, the power generated by solar panels can be extremely affected depending on differences in solar radiation among the cells. Therefore, Toyota has developed a solar charging system that can use solar energy for driving the Prius PHV. This system can efficiently charge the hybrid battery with the low power generated by the solar panel.

In recent years, the automotive manufacturers have been working to reduce fuel consumption in order to cut down on CO2 emissions, promoting weight reduction as one of the fuel saving countermeasures. On the other hand, this trend of weight reduction is well known to reduce vehicle stability in response to disturbances. Thus, automotive aerodynamic development is required not only to reduce aerodynamic drag, which contributes directly to lower fuel consumption, but also to develop technology for controlling unstable vehicle behavior caused by natural wind. In order to control the unstable vehicle motion changed by external contour modification, it is necessary to understand unsteady aerodynamic forces that fluctuating natural wind in real-world environments exerts on vehicles. In the past, some studies have reported the characteristics of unsteady aerodynamic forces induced by natural winds, comparing to steady aerodynamic forces obtained from conventional wind tunnel tests.

Improving vehicle fuel economy is a central part of efforts toward achieving a sustainable society, and an effective way of accomplishing this aim is to enhance the engine thermal efficiency. Measures to mitigate knocking and reduce engine cooling heat loss are important aspects of enhancing the engine thermal efficiency. Cooled exhaust gas recirculation (EGR) is regarded as a key technology because it is capable of achieving both of these objectives. For this reason, it has been adopted in a wide range of both hybrid vehicles and conventional vehicles in recent years. Cooled EGR has the potential to achieve further lower fuel consumption if the EGR ratio can be increased. Fast combustion is an important and effective way for expanding the EGR ratio. The engine combustion enhancement can be categorized into measures to improve ignition characteristics and methods to promote flame propagation.

In recent years, awareness of environmental problems has increased on a global scale, and the development of low fuel consumption technologies has become more and more important in commercial vehicles, as it has been in passenger vehicles. A new 6-speed manual transmission was developed with direct-drive double-overdrive to contribute to the fuel economy performance and engine power of commercial vehicles through gear ratio optimization.

To solve various environmental problems, fuel-efficient vehicles that reduce CO2 emissions as well as exhaust gas emissions have been developed. In such vehicles, a regenerative brake is used to further reduce fuel consumption. Because the market size for such vehicles is expanding, a brake system is required that can be used in a wide range of vehicles extending from internal combustion engine vehicles (ICEVs) to electric vehicles (EVs). In addition, issues such as deceleration fluctuation and brake pedal fluctuation arise because the regenerative brake force is dependent on the vehicle speed. This paper presents a brake system configuration and its element technologies that can replace existing brake systems in different vehicles ranging from ICEVs to EVs. The proposed system can realize a regenerative cooperative brake not only by replacing the brake booster unit but also without replacing the modulator.

To reduce cabin noise and vehicle weight (for lower fuel consumption), a lightweight soundproofing cover was developed as a countermeasure to sources of noise, using the Biot theory (vibration propagation theory in poroelastic materials). This report also presents the results of its application to a metal belt-type continuously variable transmission (CVT) used in Toyota Motor Corporation’s 2.0L vehicles.

It is important to reduce aerodynamic drag for reducing fuel consumption. Conventionally reduction of aerodynamic drag has been carried out by shape optimization of each part of a vehicle based on the investigations of the time-averaged flows around the vehicle. However, the general tendency of drag reduction has been saturated recently and it is required to develop a new flow-control technique to achieve further reduction in aerodynamic drag. We therefore focus on the unsteadiness of the flow around a vehicle to achieve it because the aerodynamic drag of a vehicle fluctuates over time due to repetitions of generation, growth, merging and disappearance of various sizes of vortices around it. These vortices are formed by flow separations, for which the longitudinal coherent vortices inside turbulent boundary layers on vehicle surfaces are presumably playing an important role.

Small bore diesel engines often adopt a two-valve cylinder head and a non-central injector layout to expand the port flow passage area. This non-central injector layout causes asymmetrical gas flow and fuel distribution, resulting in worse heat losses and a less homogenous fuel-air mixture than an equivalent four-valve cylinder head layout with a central injector. This paper describes the improvement of piston bowl geometry to achieve a more homogeneous gas flow and fuel-air mixture. This concept reduced fuel consumption by 2.5% compared to the original piston bowl geometry, while also reducing NOx emissions by 10%.

The Diesel Dual Fuel (DDF) vehicle is one of the technologies to convert diesel vehicles for natural gas usage. The purpose of this research was to study the possibility of a DDF vehicle to meet emission standards for diesel vehicles. This research was done for small passenger vehicles and commercial vehicles. The exhaust emissions compliance of such vehicles in a New European Driving Cycle (NEDC) mode which was composed of Urban Driving Cycles (UDC) and an Extra Urban Driving Cycle (EUDC) was evaluated. (see APPENDIXFigure A1) In this study, the passenger vehicle engine, compliant with the EURO4 standard, was converted to a DDF engine. Engine bench tests under steady state conditions showed similar result to previous papers. Total hydrocarbon (HC) emission was extremely high, compared to diesel engine. The NEDC mode emissions of the DDF vehicle were estimated based on these engine bench test results.

In diesel engines with a straight intake port and a lipless cavity to restrict in-cylinder flow, an injector with numerous small-diameter orifices with a narrow angle can be used to create a highly homogeneous air-fuel mixture that, during PCCI combustion, dramatically reduces the NOX and soot without the addition of expensive new devices. To further improve this new combustion concept, this research focused on cooling losses, which are generally thought to account for 16 to 35% of the total energy of the fuel, and approaches to reducing fuel consumption were explored. First, to clarify the proportions of convective heat transfer and radiation in the cooling losses, a Rapid Compression Machine (RCM) was used to measure the local heat flux and radiation to the combustion chamber wall. The results showed that though larger amounts of injected fuel increased the proportion of heat losses from radiation, the primary factor in cooling losses is convective heat transfer.

In making our products more attractive, it is becoming increasingly important to balance multiple areas of performance, such as fuel economy, emissions and drivability. Customer expectations and government legislations, to protect global environment, strongly increase the work complexity of auto firms in order to release high quality and eco-friendly vehicles. The balancing between several target is becoming a key factor in the car design: respect current (and anticipate future) emission limits optimization of fuel consumption insure high level of drivability maintain acceptable(or increase) performances sustain acceptable cost, reliability, etc. From recent emissions limitations, engine cold start (at the beginning of driving cycle) plays a major role in the total amount of pollutants. Especially, achievements of HC limitations are a big challenge for vehicles with a conventional spark ignition engine.