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Electronics has greatly contributed to the operation of internal combustion engines. This is especially evident in the benefits that it has brought to drivers, such as enhancing the “Fun to Drive” experience and in reducing the cost of fuel. Moreover, this progress has resulted in minimizing environmental degradation, and yet continuing to support improvements in performance. In the diesel engine, which has superb fuel economy, the innovative progress has been achieved by the common rail technology. The common rail system has the features of high injection pressure control in all engine speed range, highly precise injection control and multiple injections per combustion cycle. The latest 2nd generation of the DENSO common rail system features 1800 bar injection pressure, and five times multiple injection with fully electronic control to ensure precise small injection quantities. This technology has been commercialized into passenger car products in the European market.

In this paper, we propose a high voltage brushless AC starter that contributes to improved fuel efficiency and a reduction in the cost of the one-motor two-clutch hybrid system, which we call a 1MG2CL system. We have named it the HV starter, and it is composed of an AC motor, inverter and pinion with a shift mechanism. One of the issues with the 1MG2CL system is the high electrical energy when starting an ICE as it switches over from EV drive to HEV drive. While the ICE is starting, the main motor has to crank the ICE via the clutch; the clutch slips to absorb the main motor power, so the main motor has to output a high power to overcome the loss. Therefore, to contribute to reducing the electrical power by eliminating clutch slip losses, we developed an HV starter as a dedicated ICE starting device. Thanks to the reduction in electrical power, the HV starter is able to improve fuel efficiency and reduce system costs.

Reducing the loss of the power control unit (PCU) in a hybrid vehicle (HV) is an important part of improving HV fuel efficiency. Furthermore the loss of power devices (insulated gate bipolar transistors (IGBTs) and diodes) used in the PCU must be reduced since this amounts to approximately 20% of the total electrical loss in an HV. One of the issues for reducing loss is the trade-off relationship with reducing voltage surge. To restrict voltage surge, it is necessary to slow down the switching speed of the IGBT. In contrast, the loss reduction requires the high speed switching. One widely known method to improve this trade-off relationship is to increase the gate voltage in two stages. However, accurate and high-speed operation of the IGBT gate control circuit is difficult to accomplish. This research clarifies a better condition of the two-stage control and designed a circuit that improves this trade-off relationship by increasing the speed of feedback control.

This study reports on a new generation ECS (Ejector Cycle System) which includes a highly efficient ejector and a novel system configuration. The ejector is working as a fluid jet pump that recovers expansion energy which is wasted in the conventional refrigeration cycle decompression process, and converts the recovered expansion energy into pressure energy and raises the compressor suction pressure. Consequently, the ejector system can reduce power consumption of the compressor by using the above mentioned pressure-rising effect and improve energy efficiency of the refrigeration cycle. The ejector consists of a nozzle, a suction section, a mixing section and a diffuser. The objective of this study is to improve actual fuel economy of all vehicles by ejector technology. The previous generation ECS was reported in 2012 SAE World Congress1. Now, a new generation ECS has been successfully developed and released in the market for Mobile Air Conditioning systems as of 2013.

For the purpose of improving vehicle fuel efficiency, it is necessary to reduce energy loss in the alternator. We have lowered the resistance of the rectifying device and connecting components, and control the rectifying device with an IC to reduce rectification loss. For the package design, we have changed the structure of the part on which the rectifying device is mounted into a high heat dissipation type. The new structure has enabled optimizing the size of the rectifying device, resulting in the reduction of size of the package. In addition, the rectifying device is mounted using a new soldering material and a new process, which has improved the reliability of the connection. Moreover, since the alternator has introduced a new system, the controller IC has a function for preventing malfunction of the rectifying device and a function for detecting abnormalities, in order to ensure safety.

To comply with increasing fuel efficiency regulations, a low temperature radiator (LT radiator) is required to cool the charge-air system of a turbocharged engine. These engines are important to use for environmentally-friendly cars. Since heavy-duty and high-performance cars demand high cooling performance, the main radiator alone is typically insufficient in meeting the vehicle’s cooling requirements. An additional radiator installed in the front of the wheel-well is required to meet the extra cooling demand. In order to install this radiator in the front of the wheel-well, guaranteed performance in the limited packaging space and impact resistance of the leading tube edge are required. We developed the Supplementary Inner-Fin Radiator (SIR) which achieves the compact, high-performance, and durability requirements by use of an inner-fin tube (I/F tube). The purpose of this paper is to report our design approach and product specifications of the SIR.

Toyota Motor Corporation has developed the new compact-class hybrid vehicle (HV). This vehicle incorporates a new hybrid system for the improvement of fuel efficiency. For this system, a new Power Control Unit (PCU) is developed. The feature of the PCU is downsizing, lightweight, and high efficiency. In expectation of rapid popularization of HV, the aptitude for mass production is also improved. The PCU, which plays an important role in the new system, is our main focus in this paper. Its development is described.

In recent years, from a viewpoint of global warming and energy issues, the need to improve vehicle fuel economy to reduce CO2 emission has become apparent. One of the ways to improve this is to enhance engine thermal efficiency, and for that, automakers have been developing the technologies of high compression ratio and dilute combustion such as exhaust gas recirculation (EGR), and lean combustion. Since excessive dilute combustion causes the failure of flame propagation, combustion promotion by intensifying in-cylinder turbulence has been indispensable. However, instability of flame kernel formation by gas flow fluctuation between combustion cycles is becoming an issue. Therefore, achieving stable flame kernel formation and propagation under a high dilute condition is important technology.

Alternator, which supplies electric energy to a battery and electrical loads when it is rotated by engine via belt, is one of key components to improve vehicle fuel efficiency. We have reduced rectification loss from AC to DC with a MOSFET instead of a rectifier diode. It is important to turn on the MOSFET and off during a rectification period, called synchronous control, to avoid a current flow in the reverse direction from the battery. We turn it off so as to remain a certain conduction period through a body diode of the MOSFET before the rectification end. It is controlled by making a feedback process to coincide with an internal target conduction period based on the rotational speed of the alternator. We reduced a voltage surge risk at turn-off by changing the feedback gain depending on the sign of the time difference between the measured period and the target.

In automobiles, Integrated Starter Generators (ISGs) are important components since they ensure significant fuel economy improvements. With motors that operate at high voltage such as ISGs, it is important to accurately know partial discharge inception voltages (PDIVs) for the assured insulation reliability of the motors. However, the PDIVs vary due to various factors including the environment (temperature, atmospheric pressure and humidity), materials (water absorption and degradation) and voltage waveforms. Consequently, it is not easy either empirically or analytically to ascertain the PDIVs in a complex environment (involving, for example, high temperature, low atmospheric pressure and high humidity) in which many factors vary simultaneously, as with invehicle environments. As a well-known method, PDIVs can be analyzed in terms of two voltage values, which are the breakdown voltage of the air (called “Paschen curve”) and the shared voltage of the air layer.

Exhaust Gas Recirculation (EGR) systems reduce exhaust emissions and improve fuel efficiency. Recently, the number of EGR system installed vehicles has been increasing, especially for gasoline engine systems. One of the major causes of decreasing EGR function is deposit accumulation on a gas passage. The deposit consists mainly of hydrocarbons which are degradation products of fuel, thus the amount of deposit seems to be strongly affected by fuel compositions. Unfortunately there are not as many studies on EGR deposits with gasoline fuel as there are with diesel fuel. In this study, the influence of gasoline fuel compositions, especially aromatics which are major components of EGR gas, on chemical structures of the deposit were investigated. To clarify the accumulation mechanism of EGR deposits, a thermal oxidative degradation test with an autoclave unit and an actual gasoline engine test were employed.