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An algorithm for a fuel efficient hybrid drivetrain control system that can attain fewer exhaust emissions and higher fuel economy was investigated. The system integrates a lean burn engine with high supercharging, an exhaust gas recycle system, an electric machine for power assist, and an electronically controlled gear transmission. Smooth switching of the power source, the air-fuel ratio,pressure ratio, exhaust gas ratio as a function of the target torque were analyzed. The estimation of air mass in cylinder by using an air flow meter was investegated to control the air-fuel ratio precisely during transients.

Mixture formation and the ignition process in 4 cycle 4 cylinder spark ignition engines were investigated, using an optical combustion sensor that combines fiber optics with a conventional spark plug. The sensor consists of a 1-mm diameter quartz glass optical fiber cable inserted through the center of a spark plug. The tip of the fiber is machined into a convex shape to provide a 120-degree view of the combustion chamber interior. Light emitted by the spark discharge between spark electrodes and the combustion flames in the cylinder is transmitted by the optical cable to an opto-electric transducer. As a result, the ignition and combustion process which depends on the mixture formation can be easily monitored without installing transparent pistons and cylinders. This sensor can give more accurate information on mixture formation in the cylinders.

The combination of physical models of an advanced engine control system was proposed to obtain sophisticated combustion control in ultra-lean combustion engines, including homogeneous compression-ignition and activated radical combustion. Physical models of intake, combustion (including engine thermodynamics), and transmission were incorporated, in which the effects of residual gas from prior cycles on intake air mass and combustion were taken into consideration. Control of the in-cylinder air/fuel ratio, exhaust temperature and engine speed during start, post-start and gear shifting phases was investigated using simulations.

The combination of physical models of an advanced engine control system was proposed to obtain sophisticated combustion control in ultra-lean combustion engines, including homogeneous compression-ignition and activated radical combustion with variable intake valve timing and a supercharger. Physical models of intake, combustion (including engine thermodynamics), and transmission were incorporated, in which the effects of residual gas from prior cycles on intake air mass and combustion and the effects of ineffective fuel on engine power were taken into consideration. Control of the in-cylinder air/fuel ratio, ignition timing and intake pressure was investigated using simulations.

The combination of physical models, including a combustion model of an advanced engine control system, was proposed to obtain sophisticated air/fuel ratio and residual gas fraction control in lean mixture combustion and high boost engines, including homogeneous charge compression-ignition and activated radical combustion with variable intake valve timing and a turbocharger or supercharger. Physical intake, engine thermodynamic, and combustion models predict air mass and residual gas fraction at the beginning of compression in the cylinder, on the basis of signals from an air flow sensor and an in-pressure sensor. Then, these models determine control variables such as air mass, fuel mass, exhaust gas recycle valve opening, intake valve timing, exhaust valve timing and combustion start crank angle, to attain an optimum air fuel ratio (A/F), optimum residual gas fraction, and highly efficient low nitrogen oxides combustion without power degradation in the above conditions.

The combination of physical models including a combustion model of an advanced engine control system was proposed to obtain sophisticated air/fuel ratio and residual gas fraction control in lean mixture combustion and high boost engines, including homogeneous charge compression-ignition and activated radical combustion with a variable intake valve timing and a turbocharger or supercharger. Physical intake, engine thermodynamic, and combustion models predicted air mass and residual gas fraction at the beginning of compression in the cylinder, on the basis of signals from an air flow sensor and an in-pressure sensor. Then, these models determine control variables such as air mass, fuel mass, exhaust gas recycle valve opening, intake valve timing and combustion start crank angle, to attain an optimum air fuel ratio (A/F), optimum residual gas fraction, and high efficient low nitrogen oxides combustion without power degradation in the above conditions.

The control strategies of auto-ignition for homogeneous charge compression ignition and controlled auto ignition operations were investigated using a simple engine model. The fluctuations of auto-ignition characteristics during transients in variable timing of exhaust and intake valves were analyzed. When the valve timing changed stepwise, the characteristics fluctuated and differed slightly from these in steady state conditions because combustion in the prior cycle affected the gas exchange in the next cycle. To reduce such fluctuations, the control strategies of cylinder air mass, residual gas mass, fuel mass, air/fuel ratio were investigated for a simple engine dynamic model (a 4-cylinder, 4-stroke engine with total cylinder stroke volume of 2000 cm3), which could simulate the dynamics of gas exchange during transient valve timing in a wide dynamic range.

Mixture formation technology for multipoint fuel injection systems in spark ignition engines has been reviewed regarding reduced exhaust emissions, fuel consumption and improved engine performance. In conventional systems, under light load conditions, the mixture of fuel to suction air is not uniform due to a short injection pulse width against a long duration of suction stroke. Under heavy load conditions, fuel spray is apt to be deflected by the air flow through the intake port and the injected fuel clings and remains onesidely on the cylinder wall during the combustion cycle. Under cold start conditions, the fuel on the intake manifolds and ports is not evaporated quickly enough so that it is evaporated in the cylinder after the temperature rises due to the compression stroke. A lot of fuel is injected to compensate for the small evaporation rate.

We have examined a new precise control method of the air fuel ratio during a transient state which provides improved exhaust characteristics of automobile engines. We investigated the measurement method for the mass of fresh air inducted by the cylinder, which is most important for controlling the air fuel ratio. The mass of fresh air must be measured in real time because it changes in each cycle during a transient state. With an conventional systems, it has been difficult to get accurate measurement of this rapidly changing mass of fresh air. The method we studied measures the mass of fresh air by using the intake manifold pressure and air flow sensors. During a transient state, the reverse flow of the residual gas from the cylinder into the intake manifold, which occurs at the first stage of the suction stroke, changes with each cycle. The mass of fresh air changes accordingly.

The relationships between air flow metering and combustion control for spark ignition engines, such as engines with three way catalysts, lean NOx catalysts, two stroke engines and direct fuel injection engines were investigated. The effects of control parameters on combustion were analysed and the relationships between control parameters and air flow metering and roles of the meters in combustion control were clarified. The control strategies adaptable to many types of engines which have a wide control range of the air/fuel mass ratio are classified as (1) air quantity control,(2) fuel quantity control, and (3) exhaust gas recycle quantity control. The control parameters for the three strategies are fuel quantity, air quantity, exhaust gas recycle quantity, exhaust gas temperature, knocking, excess air factor, and mixture quality with additional parameters of swirl ratio, and spark timing for conventional spark ignition engines, two stroke engines and direct injection engines.

A new engine drivetrain control system is described which can provide a higher gear ratio and leaner burning mixture and thus reduce the fuel consumption of spark ignition engines. Simulations were performed to obtain reduced torque fluctuation during changes in the air - fuel ratio and gear ratio, without increasing nitrogen oxide emissions, and with minimum throttle valve control. The results show that the new system does not require the frequent actuation of throttle valves because it uses direct fuel injection, which increases the air - fuel ratio of the lean burning limit. It also achieves a faster response in controlling the air mass in the cylinders. This results in the minimum excursion in the air - fuel ratio which in turn, reduces nitrogen oxide emissions.

A concept for a new engine drivetrain control system that can attain improved exhaust emissions and fuel economy was investigated. The system integrates direct-injection stratified engines with high-pressure charge, a sophisticated continuously variable transmission, and hybrid systems such as electric motor drives. The system is composed of two three-cylinder engines, which are used singly or in combination according to the circumstances. During a traffic jam, the vehicle is driven by the electric motor, at partial load, it is driven by three cylinders, and at full load, by six cylinders with brake energy stored in a battery. The battery is charged at partial and full loads. The system has an expert subsystem that controls the charge and discharge of the battery according to driving data from a car navigation system. Some simulation results of fuel economy gain and exhaust emissions were evaluated using optimum control strategies.

Control strategies for HCCI (Homogeneous Charge Compression Ignition) operation in 4-cylinder, 4-stroke engines were investigated using a simple engine model, which is composed of intake, combustion and gas exchange sub-models. The model can determine, cycle-by-cycle, cylinder-by-cylinder, control variables, such as air mass, residual gas mass, temperature at the beginning of the compression stroke, combustion start timing in a wide range of exhaust valve closing timings and clearance volumes. The calculation results were compared with experimental results which have been presented previously. The model can simulate combustion fluctuation during a operation mode change from spark ignition to HCCI with variable exhaust valve closing timings and clearance volumes. Also, the model can predict the control variables during transient in the compression ratio by clearance volume change and during low temperature combustion reaction, to develop control strategies of transient operations.

Dynamic characteristics of fuel supply system for multi-cylinder gasoline engine was studied analytically and experimentally. We investigaged. (1) The relation between the air flow rate upstream the throttle valve and the air flow rate into the cylinder, when the throttle valve is opened or closed rapidly. (2) The air fuel ratio in the cylinder affected by the above relation. (3) Pmax response affected by the residual fuel in the intake manifold.

A new robust hot wire air flow meter with wire winding probe, to be located in the bypass air passage of the intake air passage, was developed for an electronic engine control system. This bypass type hot wire air flow meter can measure mean air velocity precisely in pulsating flow when the length of the bypass passage and the pressure loss in the bypass are selected appropriately.

Hitachi has recently developed a hot-wire air flow meter which uses a temperature-sensitive resistor of an extremely thin platinum wire wound around a ceramic bobbin and coated with glass. This temperature-sensitive resistor, or a hot wire, is located in a bypass of the intake air passage of an engine and responds exactly for the effective control of engine operation. The flow meter of this construction is sturdy enough to withstand impacts of backfires and vibration and reduces variation in engine output characteristic likely to be caused by dust and dirt present in the intake air. Furthermore, this device requires no cleaning or other maintenance.

Mixture formation technology for gasoline engine multipoint fuel injection systems has been investigated. The fuel injector's spray, the volatility of droplets floating in the air flow, the movement of droplets around the intake valve's upper surface, the volatility of droplets on heated surfaces, and the process of atomizing droplets in the intake valve air flow was analyzed. Droplet diameters and spray patterns for good mixture formation without liquid film in cylinders have been clarified. When sequential injection is used for better responsiveness in fuel injection systems, engine performance may be reduced through increased HC emissions in some conditions. Reducing the diameter of spray droplets and preventing fuel from concentrating in the intake valve promotes vaporization, reduces fuel concentration on cylinder walls, and prevents reductions in engine performance.

The basic structure of a new engine control system for highly accurate air-fuel ratio control is introduced. Improved engine power and decreased fuel consumption are required for today's engines. Better air-fuel ratio control must be attained to set the air-fuel ratio to that of the maximum power and minimum fuel consumption. In order to enhance the accuracy of the air-fuel ratio control, the air flow meter, air-fuel ratio sensor, and fuel supply device are improved in the new system. Accuracy is lost in conventional system owing to the sensors' deterioration over long-term use. So prevention of air flow meter deterioration and compensation of air-fuel ratio sensor deterioration are taken into consideration. Fuel atomization of the fuel supply device is improved in order to reduce the air-fuel ratio fluctuation in the transient operating state. High power and decreased fuel consumption over long-term use are made possible with the new system.

This report outlines the developmental status of the Hitachi hot wire air flow meter. It describes the newly developed hot wire probe and the air flow meter body to realize an improved cost performance ratio. In addition, it covers approaches to improve response time when the air flow rate is changed and to avoid deterioration in measurement accuracy caused by dirt deposits on the hot wire probe.

A totally integrated vehicle electronic control system is described, which optimizes vehicle performance through use of electronics. The system implements efficient coordination of functions of the engine, drive-train, brakes, steering, and suspension control subsystems to give a smoother ride, better handling and greater safety. The principles of the system are based on control and stability augmentation strategies. Each subsystem has two observers which control the force of the actuators according to the vehicle dynamics. The system features a driver support system which allows the average driver to employ the full performance potential of the vehicle in exceptional situations, and an artificial response control system to ensure optimum response and comfort. Application of the system allows the driver to experience a new level of performance and a marked improvement in handling quality and ride comfort.