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Downsizing or higher compression ratio of SI engines is an appropriate way to achieve considerable improvements of part load fuel efficiency. As the compression ratio directly impacts the engine cycle thermal efficiency, it is important to increase the compression ratio in order to reduce the specific fuel consumption. However, when operating a highly boosted / downsized SI engine at full load, the actual combustion process deviates strongly from the ideal Otto cycle due to the increased effective loads requiring ignition timing delay to suppress abnormal combustion phenomena such as engine knocking. This means that for an optimal design of an SI engine between balances must be found between part load and full load operation. If the knocking characteristic can be accurately predicted beforehand when designing the combustion chamber, a reduction of design time and /or an increase in development efficiency would be possible.

A second-generation power control unit (PCU) for a two-motor hybrid system is proposed. An optimally designed power module, which is a key component of the PCU, is applied to increase heat-resistant temperature, while the basic structure of the first generation is retained and the power semiconductor chip is directly cooled from the single side. In addition to the optimum design, by decreasing the power loss as well as increasing the heat-resistant temperature of the power semiconductors (IGBT: Insulated Gate Bipolar Transistor and FWD: Free Wheeling Diode), the proposed PCU has attained 25% higher power density and 23% smaller size compared to first-generation units, maintaining PCU efficiency (fuel economy). To achieve a high yield rate in the power module assembly process, a new screening technology is adopted at the initial stage of power module manufacturing.

In recent years, the increased use of electric power steering in vehicles has increased the importance of issues such as making systems more compact and lightweight, and dealing with increased development man-hours. To increase development efficiency, the use of a “Hardware in the loop simulator” (HILS) is being tested to shift from the previous development method that relied on a driver's subjective evaluation in an actual vehicle test to bench-test development. Using HILS enables tasks such as specification studies, performance forecasts, issue identification and countermeasure proposals to be performed at an early stage of development even when there is no prototype vehicle. This report describes a case study of using HILS to solve the issues of reducing the load by adjusting the geometric specifications around the kingpin and eliminating the tradeoff by adding a new EPS control algorithm in order to make the electric power steering (EPS) more compact and lightweight.

Honda announced an independent right and left rear toe control system (first generation) in 2013 and presented it as the world's first. As stated in a previous paper, “Independent Left and Right Rear Toe Control System,” with this system Honda has achieved a balance between an enjoyable driving experience in which handling is performed at the driver's will (“INOMAMA” handling) and stable driving performance.(1) This first generation is optimally designed to the vehicle specifications such as suspension axial force and steering gear ratio of the vehicle to which the system is applied. For more widespread application of independent rear toe control technology, a next generation system (second generation) has been developed, which achieves both cost reduction and flexible system performance which can be adapted to a variety of vehicles. The system development began by setting the required target performance with consideration for adaptation to various car models.

The reduction of fuel consumption is of great importance to automobile manufacturers. As a prospective means to achieve fuel economy, lean burn is being investigated at various research organizations and automobile manufacturers and a number of studies on lean-burn technology have been reported to this date. This paper describes the development of a four-valve lean-burn engine; especially the improvement of the combustion, the development of an engine management system, and the achievement of vehicle test results. Major themes discussed in this paper are (1) the improvement of brake-specific fuel consumption under partial load conditions and the achievement of high output power by adopting an optimized swirl ratio and a variable-swirl system with a specially designed variable valve timing and lift mechanism, (2) the development of an air-fuel ratio control system, (3) the improvement of fuel economy as a vehicle and (4) an approach to satisfy the NOx emission standard.

We had developed Electric Servo Brake System, which can control brake pressure accurately with a DC motor according to brake pedal force. Therefore, the system attains quality brake feeling while reflecting intentions of a driver. By the way, “Build-up” is characteristics that brake effectiveness increases in accordance with the deceleration of the vehicle, which is recognized as brake feeling with a sense of relief as not to elongate an expected braking distance at a downhill road due to large-capacity brake pad such as sports car and large vehicles. Then, we have applied the optical characteristic control to every car with Electric Servo Brake System by means of brake pressure control but not brake pad. Hereby, we confirmed that the control gives a driver the sense of relief and the reduction of pedal load on the further stepping-on of the pedal. In this paper, we describe the development of brake feel based on the control overview.

Downsizing the engine would be an effective means of improving fuel economy and reducing CO2 emissions. In this case, low-speed torque generation can be enhanced through the use of impulse charging technology, a subject attracting the attention of many researchers. This paper reports the basic characteristics of impulse charging identified through research using a single-cylinder test engine, aiming for application of the technology to spark ignition (SI) engines. To ensure the maximum level of volumetric efficiency under impulse charging conditions, two requirements are controlling the timing of switching from a negative to a positive pressure wave while turning its direction at the intake chamber, and maximizing the positive pressure wave.

There has been strong public demand for reduced hazardous exhaust gas emissions and improved fuel economy for automobile engines. In recent years, a number of innovative solutions that lead to a reduction in fuel consumption rate have been developed, including in-cylinder direct injection and lean burn combustion technologies, as well as an engine utilizing a large volume of exhaust gas recirculation (EGR). Furthermore, a homogeneous charge compression ignition (HCCI) engine is under development for actual application. However, one of the issues common to these technologies is less stable combustion, which causes difficulty in engine management. Additionally, it is now mandatory to provide an onboard diagnosis (OBD) system. This requires manufacturers to develop a technology that allows onboard monitoring and control of the combustion state. This paper reports on an innovative combustion diagnostic method using an in-cylinder pressure sensor.

In recent years, the contribution of tires on vehicle fuel economy has been garnering attention. Up until now, rolling resistance coefficient (RRC) has been the standard way of measuring the amount of impact the tire has on fuel economy. We devised a new method for evaluating the impact of tires on fuel economy that incorporates the concept of tire “driving transmission efficiency” (hereinafter referred to as “driving stiffness”). In doing so, we have clarified the technology direction for contributing to the improvement of fuel economy while maintaining vehicle maneuverability by reducing RRC and improving tire driving stiffness.

Formula One engines, which are the pursuit of the ultimate in performance, tend to be comparatively vulnerable to durability issues. These engines sometimes run under a state of unstable combustion as compensation for improved fuel economy. To cope with these issues, there have been strong demands in the racing field for a technology that will allow constant monitoring and prompt action to be carried out on system malfunctions and failures, as well as unstable combustion. The research program described in this paper deals with an onboard technology for monitoring combustion under all the operational conditions using ionic current measurement. The technology will possibly be applied to engine management and car-to-pit communications via telemetering. The scope of the control it offers includes; detection of misfire and hesitation, detection and management of detonation, and management of lean-burn combustion.

We have developed a bench test method to assess driver distraction caused by the load of using infotainment systems. In a previous study, we found that this method can be used to assess the task loads of both visual-manual tasks and auditory-vocal tasks. The task loads are assessed using the performances of both pedal tracking task (PT) and detection response task (DRT) while performing secondary tasks. We can perform this method using simple equipment such as game pedals and a PC. The aim of this study is to verify the reproducibility of the PT-DRT. Experiments were conducted in three test environments in which test regions, experimenters and participants differed from each other in the US, and the test procedures were almost the same. We set two types of visual-manual tasks and two types of auditory-vocal tasks as secondary tasks and set two difficulties for each task type to vary the level of task load.

An examination was made on the effect of low-viscosity engine oil on fuel efficiency improvements and engine reliability for the purpose of improving fuel efficiency through the use of select engine oils. Fuel efficiency-improving effects were estimated by measuring friction torque using low-viscosity engine oil. The results show that reducing engine oil viscosity is effective for improving fuel efficiency. In examining engine reliability, attention was paid to the following two aspects which are concerns in practical performance that may arise when engine oil viscosity is reduced. Engine oil consumption Sliding wear at high temperatures Tests and analyses were conducted to develop indexes for engine oil properties that are strongly correlated with each of these two concerns. A strong correlation was found between engine oil consumption and the results of a thermogravimetric analysis, and between high-temperature sliding wear and high-temperature, high-shear viscosity (HTHS).

The use of electric vehicles (EV) is becoming more widespread as a response to global warming. The major issues associated with EV are the annoyance represented by charging the vehicles and their limited cruising range. In an attempt to remove the restrictions on the cruising range of EV, the research discussed in this paper developed a dynamic charging EV and low-cost infrastructure that would make it possible for the vehicles to charge by receiving power directly from infrastructure while in motion. Based on considerations of the effect of electromagnetic waves, charging power, and the amount of power able to be supplied by the system, this development focused on a contact-type charging system. The use of a wireless charging system would produce concerns over danger due to the infiltration of foreign matter into the primary and secondary coils and the health effects of leakage flux.

This research sought to develop a dynamic charging system, achieving an unlimited EV cruising range by charging the EV at high power during cruising. This system would help make it possible to finish battery charging in a short time by contact with the EV while cruising and enable drivers to freely cruise their intended routes after charging. A simulation of dynamic charging conditions was conducted for ordinary autonomous cruising (i.e., ordinary EV cruising) when dynamically charging at a high power of 450-kW (DC 750 V, 600 A). This report discusses the study results of a method of building the infrastructure, as well as looking at the cruise test results and future outlook. In particular, the research clarified the conditions for achieving an unlimited vehicle cruising range with a 450-kW dynamic charging system. It also demonstrated that this system would allow battery capacities to be greatly reduced and make it possible to secure the battery supply volume and resources.

When a vehicle drives over road seams or a bumpy surface, low-frequency noise called drumming is generated, causing driver discomfort. The generation of drumming noise is closely related to the vibration characteristics of the suspension, body frame, and body panels, as well as the acoustic characteristics of the vehicle interior. It is therefore difficult to take measures to get rid of drumming after the basic vehicle construction has been finalized. Aiming to ensure drumming performance in the drawing review phase, we applied the Finite Element Method (FEM) to obtain acoustical transfer functions of the body, and Multi Body Simulation to get suspension load characteristics. This paper presents the results of the study of drumming prediction technology using this hybrid approach.

Simulation was employed to estimate the fuel economy enhancement from the application of an exhaust heat recovery system using a thermoelectric generator (TEG) in a series hybrid. The properties of the thermoelectric elements were obtained by self-assessment and set as the conditions for estimating the fuel economy. It was concluded that applying exhaust system insulation and forming the appropriate combination of elements with differing temperature properties inside the TEG could yield an enhancement of about 3% in fuel economy. An actual vehicle was also used to verify the calculation elements in the fuel economy simulation, and their reliability was confirmed.

In an attempt for further improvement of exhaust gas purification and fuel economy, an electronically controlled fuel injection (FI) system has been applied to small size motorcycles. As compared to a similar system for cars, FI systems for small two wheeled vehicles are required to be small, lightweight and low cost. In order to meet these requirements, authors developed a new control method of determining the required quantity of fuel. This system removes the intake pressure sensor of the intake pipe that exists in the conventional FI system. From correlating the peak intake pressure in the intake pipe with the quantity of intake air closely, the peak intake pressure is estimated by using rotation change of the crankshaft. The required quantity of fuel is injected into the engine intake pipe determined by the map set up in the peak intake pressure and the fuel injection period.

High viscosity index(HVI) petroleum base stock, with excellent temperature-viscosity characteristics, oxidation resistance, and low-evaporation properties, offers advantages as the base stock for high fuel economy engine oils, particularly because of its low-friction properties in the boundary and/or “E.H.L (Elastohydrodynamic Lubrication)” area due to its rheological characteristics. This research evaluated HVI base stock's low-friction properties. Upgrading the oil from 5W-30 to 5W-20 was also investigated. The friction properties of the HVI base stock were measured by a unit friction platform. The results show a 28% reduction in friction coefficient compared with the conventional, solvent refined oil, which is attributable to the high-pressure viscosity of the base oil.

A theoretical evaluation technology for timing chain systems in single-cylinder engine has been established. Hitherto, there have been almost no theoretical evaluation reports published about drive loss and slapping noise in cam drive systems including timing chains. Thus, tensioner lifter and tensioner guide specifications to satisfy requirements related to slapping noise and friction loss have been determined only by tests with actual engines. In this research, a highly accurate mechanism-simulation model has been constructed that takes into account factors such as dynamic characteristics along with crank sprocket and timing chain contact stiffness and friction coefficient in addition to static characteristics of the timing chain and tensioner guide. Our results have confirmed a high correlation with actual engine tests at an absolute value level.

Lane departure prevention systems are able to detect imminent departure from the road, allowing the driver to apply control to prevent lane departure. These systems possess enormous potential to reduce the number of accidents resulting from road departure, but their effectiveness is highly reliant on their level of acceptance by drivers. The effectiveness of the systems will depend on when they are providing driving assistance, what level of laxness in terms of maintaining contact with the steering wheel is allowed on the part of the driver, and what level of assistance the system provides. This paper will discuss research on the minimum necessary contact and contact strength with the steering wheel on the part of the driver when a lane departure prevention system is in operation.