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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.

High engine load and over-heated engine cylinder are the main causes of engine knock. When knock occurs in an engine, vibrations composed of several specific resonant frequencies occur. Some of these resonant frequencies are missed stochastically because specific resonant frequencies are caused by different resonant vibration modes in an engine cylinder. However, a conventional knock detector can only measure a fixed resonant frequency using a band-pass filter. This paper presents a multi-spectrum method which greatly improves knock detection accuracy by detecting the knock resonance frequencies from several specific vibration frequencies. Through overcoming the random occurrences of knock resonant frequencies by selecting specific frequencies, knock detection accuracy can be greatly improved. We studied a high precision knock detection method using real-time frequency analysis and a piezoelectric accelerometer on a V-6 engine.

An automatic matching method for engine control parameters is described which can aid efficient development of new engine control systems. In a spark-ignition engine, fuel is fed to a cylinder in proportion to the air mass induced in the cylinder. Air flow meter characteristics and fuel injector characteristics govern fuel control. The control parameters in the electronic controller should be tuned to the physical characteristics of the air flow meter and the fuel injectors during driving. Conventional development of the engine control system requires a lot of experiments for control parameter matching. The new matching method utilizes the deviation of feedback coefficients for stoichiometric combustion. The feedback coefficient reflects errors in control parameters of the air flow meter and fuel injectors. The relationship between the feedback coefficients and control parameters has been derived to provide a way to tune control parameters to their physical characteristics.

A fuel injection control method is developed in which the transient air-fuel ratio is accurately controlled by an internal state estimation method with dynamic characteristics. With conventional methods the air-fuel ratio control precision is limited, because the air measurement system, the air and the fuel dynamic characteristics lack precision. In this development, the factors disturbing the air-fuel ratio under transient conditions are determined by analysis of the control mechanisms. The disturbance factors are found to be (1) the hot wire sensor has a delay time, (2) manifold air charging causes an overshoot phenomenon, (3) there is a dead time between sensing and fuel flow into the cylinder and (4) there is a delay of fuel flow into the cylinder caused by the fuel film. Compensation schemes are constructed for each of these technical problems.

We developed the numerical simulation tool by using OpenFOAM® and in-house simulation codes for Gasoline Direct Injection (GDI) engine in order to carry out the precise investigation of the throughout process from the internal nozzle flow to the fuel/air mixture in engines. For the piston/valve motions, a mapping approach is employed and implemented in this study. In the meantime, the spray atomization including the liquid-columnbreakup region and the secondary-breakup region are simulated by combining the different numerical approaches applied to each region. By connecting the result of liquid-column-breakup simulation to the secondary-breakup simulation, the regions which have different physical phenomena with different length scales are seamlessly jointed; i.e., the velocity and position of droplets predicted by the liquid-column-breakup simulation is used in the secondary breakup simulation so that the initial velocity and position of droplets are transferred.

We have developed an excitation source identification system that can distinguish excitation sources on a sub-assembly level (around 30mm) for vehicle components by combining a measurement and a timing analysis. Therefore, noise and vibration problems can be solved at an early stage of development and the development period can be shortened. This system is composed of measurement, control, modeling, and excitation source identification parts. The measurement and the excitation source identification parts are the main topics of this paper. In the measurement part, multiple physical quantities can be measured in multi-channel (noise and vibration: 48ch, general purpose: 64ch), and these time data can be analyzed by using a high-resolution signal analysis (Instantaneous Frequency Analysis (IFA)) that we developed.

In recent years, improvement of in-use fuel economy is required with tightening of exhaust emission regulation. We assume that one of the most effective solutions is ACC (Adaptive Cruise Control), which can control a powertrain accurately more than a driver. We have been developing a fuel saving ADAS (Advanced Driver Assistance System) application named “Sailing-ACC”. Sailing-ACC system uses sailing stop technology which stops engine fuel injection, and disengages a clutch coupling a transmission when a vehicle does not need acceleration torque. This system has a potential to greatly improve fuel efficiency. In this paper, we present a predictive powertrain state switching algorithm using external information (route information, preceding vehicle information). This algorithm calculates appropriate switching timing between a sailing stop mode and an acceleration mode to generate a “pulse-and-glide” pattern.

A new diagnosis method for an air-fuel ratio cylinder imbalance has been developed. The developed diagnosis method is composed of two parts. The first part detects an occurrence of an air-fuel ratio cylinder imbalance by using a two revolution frequency component of an EGO sensor output signal or an UEGO sensor output signal upstream from a catalyst. The two revolution frequency component is from a cycle where an engine rotates twice. The second part of the diagnosis method detects an increase of emissions by using a low frequency component which is calculated from the output of an EGO sensor downstream from the catalyst. When the two revolution frequency component calculated using the upstream sensor output is larger than a certain level and the low frequency component calculated using the downstream sensor output is shifted to a leaner range, the diagnosis judges that the emissions increase is due to an air-fuel ratio cylinder imbalance.

We investigated the size of fuel spray droplets from nozzles for direct injection gasoline (DIG) engines. Our findings showed that the droplet size can be predicted by referencing the geometry of the nozzle. In a DIG engine, which is used as part of a system to reduce fuel consumption, the injector nozzle causes the fuel to spray directly into the combustion chamber. It is important that this fuel spray avoid adhesion to the chamber wall, so multi-hole injection nozzles are used to obtain spray shape adaptability. It is also important that spray droplets be finely atomized to achieve fast vaporization. We have developed a method to predict the atomization level of nozzles for fine atomization nozzle design. The multi-hole nozzle used in a typical DIG injector has a thin fuel passage upstream of the orifice hole. This thin passage affects the droplet size, and predicting the droplet size is quite difficult if using only the orifice diameter.

A continuously variable valve event and lift (VEL) system, actuated by oscillating cams, can provide optimum lift and event angles matching the engine operating conditions, thereby improving fuel economy, exhaust emission performance and power output. The VEL system allows small lift and event angles even in the engine operating region where the required intake air volume is small and the influence of valvetrain friction is substantial, such as during idling. Therefore, the system can reduce friction to lower levels than conventional valvetrains, which works to improve fuel economy. On the other hand, a distinct feature of oscillating cams is that their sliding velocity is zero at the time of peak lift, which differs from the behavior of conventional rotating cams. For that reason, it is assumed that the friction and lubrication characteristics of oscillating cams may differ from those of conventional cams.

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.

A new numerical simulation system has been developed which predicts flow behavior of fuel film formed on intake port and combustion chamber walls of gasoline engines. The system consists of a film flow model employing film thickness as a dependent variable, an air flow model, and a fuel spray model. The system can analyze fuel film flow formed on any arbitrary three-dimensional configuration. Fuel film flow formed under a condition of continuous intermittent fuel injection and steady-state air flow was calculated, and comparison with experimental data showed the system possessing ability of qualitative prediction.

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 thermodynamic analysis of mixture formation in cylinders that takes into account mixture inhomogeneity and the wall film is presented. Conditions for obtaining low hydrocarbon emission are clarified analytically as a function of the fuel mass of the wall film and inhomogeneity of the mixture. Optimum processes for atomizing and vaporizing fuel are presented to reduce the inhomogeneity and the fuel mass of the film.

This paper presents a single-chip 32bit RISC microcontroller boarding on MY1998 dedicated to highly complicated powertrain management. The high performance 32bit RISC CPU provides the only solution to meet requirements of drastic CPU performance enhancement and integration. Furthermore, a 32bit counter, based on a 20 MHz clock, and a 32bit multiplier make possible misfire detection and precise analysis of the engine management strategy, especially cylinder individual air-fuel ratio control.

We developed a high-pressure fuel pump for a direct injection gasoline engine and used a hydraulic simulator to design it. A single plunger design is the major trend for high-pressure fuel pumps because of its simple structure and small size. However, the single plunger causes large pressure pulsation and an unstable flow rate, especially at high engine speed. Therefore, a fuel-pipe layout that inhibits the pressure pulsation and a flow-rate control that stabilizes the flow are the most important challenges in pump design. Our newly developed hydraulic simulator can evaluate the dynamic characteristics of a total fuel supply system, which consists of pump, pipe, injector, and control logic. Using this simulator, we have improved fuel flow by optimizing the outlet check valve lift and the cam profile, and we reduced pressure pulsation by optimizing the layout of fuel pipes. Our simulation results agreed well with our experimental results.

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.

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.

In order to develop a high-performance turbocharger turbine, compressible turbulent flow analysis is applied to the complicated flow around the nozzle vanes and the spacers. The flow analysis indicates that a combination of a curved nozzle vane and a round spacer causes a low-velocity region at the inner side of the nozzle vane even when the turbine efficiency is highest. As a result of the loss analysis, a teardrop-shaped spacer, which suppresses the low-velocity region and flow separation, is developed, and shown to improve the turbine efficiency. The easiness of the nozzle vane control is also important as well as the high efficiency. The fluid force on the nozzle vane depends on the flow pattern; therefore, the torque about the pivot of the nozzle vane is also numerically calculated.

A recent trend in high-pressure gasoline pumps is increasing the outlet pressure. One of the most important topics for increasing this pressure is improving volumetric efficiency. Therefore, the purpose of this research is to quantify the breakdown of efficiency loss factors and to suggest a new design for improving volumetric efficiency. Authors developed a method of quantifying the efficiency loss breakdown of high-pressure gasoline pumps by using 1D fluid pressure simulation results and conducting evaluation experiments regarding sensitivity. Authors separated pump movement into three phases; suction, compression, and delivery. Authors then investigated the loss factors in each phase. As a result, authors obtained an equation for predicting the final output volume. The equation consists of a limit output volume and other types of leakage volumes.