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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.

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.

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 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 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 inertia 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 and post-start 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, including homogeneous compression-ignition and activated radical combustion with a light load and in stoichiometric mixture combustion with a full load. Physical models of intake, combustion and engine thermodynamics were incorporated, in which the effects of residual gas from prior cycles on intake air mass and combustion were taken into consideration. The combined control of compression ignition at a light load and spark ignition at full load for a high compression ratio engine was investigated using simulations. The control strategies of the variable valve timing and the intake pressure were clarified to keep autoignition at a light load and prevent knock at a full load.

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 and engine thermodynamics were incorporated, in which the effects of residual gas from prior cycles on intake air mass and combustion were taken into consideration. The control of in-cylinder air/fuel ratio, misfire, knocking and auto-ignition was investigated using simulations.

Generalized models of the air/fuel ratio control using estimated air mass in the cylinder were presented to obtain highly accurate control during transient conditions in high supercharged direct injection systems with a complex air induction system. The air mass change was estimated by using upstream models which estimated the pressure of the intake manifold by introducing the output of the air flow meter and the differential of the output into aerodynamic equations of the intake system. The air mass into the cylinders was estimated at the beginning of the intake stroke under a wide range of driving conditions, without compensating for changes in the downstream parameters of the intake system and engine. Therefore, the upstream models required relatively minor calibration changes for each engine modification to be able to estimate the air mass on a cylinder-by-cylinder basis.

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.

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.

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.

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.

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.

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.

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.

Effects of mixture formation of fuel injection systems on gasoline engine performance have been studied. Several fuel injectors which produced various spray diameters and spray patterns were used in engine tests. Spray behavior in an air flow was investigated to clarify the spray distribution through the intake valve. The relationships between the spray distribution near the intake valve and the HC emission or engine response were considered. The amount of HC emissions increased if fuel was injected when the intake valve was open with a heavy load (e.g. an engine speed of 2000 rpm and a manifold pressure of 98 kPa), because fuel would flow into the cylinders one-sidedly, causing a liquid film to form. The amount of HC emissions also increased if fuel was injected when the intake valve was open with a light load (e.g. during idling), because the fuel injection pulse would be short and fuel would flow into the cylinders, but the air-fuel mixing would not be enough to cause a misfire.

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.