Search Results

In this study, a new method is proposed to evaluate the amount of adhered fuel when fuel spray impinges on a wall surface, by considering the normal and tangential droplet impact velocities. To verify this method, how the amount of fuel adhering to a flat plate varies with the spray's angle of incidence is examined. Our experimental results show that less fuel adheres to the wall when spray is oriented obliquely. To verify our method, the concentration of the air-fuel mixture and the fuel film thickness formed in an engine intake port model are also examined. By comparing these experimental results with our calculated results, it is shown that the proposed method can evaluate the behavior of adhered fuel, which conventional methods cannot evaluate.

In recent decades, research and development in the field of autonomous vehicles have rapidly increased throughout the world, and autonomous driving technologies have begun to be applied to mass production vehicles. Especially recently, even affordable mass production vehicles have begun to be equipped with some autonomous driving systems such as a Lane Keeping Assist (LKA) system. In general, mass-produced LKA systems use a lane detection camera as a means of keeping the lane. One of the common limitations of camera-based LKA systems is that the lane keeping performance significantly decreases when the camera cannot detect lane markings for various reasons such as snow coverage or blurred lane markings. To overcome this limitation, we have developed Global Navigation Satellite System (GNSS)-based LKA systems, which are not affected by the surrounding environment such as weather and the condition of lane markings.

A fuel control method to reduce the harmful exhaust gas from SI engines is proposed. As is well known, both the amplitude and the frequency of the limit cycle in a conventional air-fuel ratio control system are determined uniquely by parameters in the system. And this limits our making full use of the oxygen storage effect of TWC. A simple model of TWC reaction revealed the relationship between maximum conversion efficiency and both the amplitude and the frequency in a air fuel control system. It also revealed that TWC conversion efficiency attained to maximum levels when both the amplitude and the frequency of the limit cycle are selected so as to make full use of the oxygen storage effect of TWC. In order to achieve this, it is necessary to vary both the amplitude and the frequency arbitrarily.

An in-vehicle detecting system, which directly monitors the combustion condition in each cylinder by detecting the ionic current generated in the vicinity of combustion flame surface in the internal combustion engine, has been developed for engine control. This system comprises the existing ignition plug employed as an ion probe, an additional ignition coil added with electronic components for the detection, and a detection module to process the ionic current and to provide the engine management system with various information indicating the combustion condition. This system allows the judgment of misfire or normal combustion in the overall engine driving conditions and the detection of knocking level in each cylinder. Furthermore, the development is now under way for practically driving the engine drive with leaner mixture, namely, the control of air fuel ratio in each cylinder through the information based on this ionic current indicating the combustion condition.

In this paper, we suggest a novel algorithm to distinguish semi-steady states from various steering patterns and to estimate the stability factor. The algorithm also estimates each stability factor in left and right turns because there could be a case where they differ based on uneven tire wear and so on. The stability factor, which is the turning characteristic of a vehicle, has been treated as constant for most vehicle control systems. However, in fact, it may change in some situations, for example when a vehicle is overloaded. So there is a chance that a driver may be aware of an unusual sensation when vehicle control is designed based on a constant stability factor. We have succeeded in developing an algorithm to estimate the stability factor accurately enough to be able to compensate for it and have confirmed the effectiveness of the algorithm by simulation and vehicle testing as well.

This paper presents a new motor current control strategy for Electric Power Steering (EPS) to reduce current fluctuation. Such current fluctuation may cause undesirable steering torque ripple and acoustic noise, if an inexpensive microprocessor is used. Using a DC-motor, current fluctuation associated with change in the battery voltage, etc., may occur. We have developed a new current control strategy which effectively alleviates current fluctuations of the motor without using higher performance microprocessors. The new controller is based on the estimation of disturbance voltage and compensation for this disturbance voltage. We have bench-tested the performance of this control strategy and confirmed that current fluctuation is reduced below that using conventional PI controller. The PI gain for the proposed controller is the same as that for the conventional controller.

Experimental investigations of fuel breakup very close to nozzle of practical high-pressure swirl injector, which is used in gasoline direct injection (GDI) engine, were carried out. In GDI engines, fuel is directly injected into cylinder therefore the spray characteristics and mixture formation are of primary importance. In this research, visualizations of primary spray formation process were demonstrated using a high-speed video camera (maximum speed: 1Mfps) with a long-distance microscope. Initial state and development of the spray were discussed under the different injection pressure condition. During the injection period, the length and thickness of the liquid sheet, which is produced from the nozzle exit, were measured using Ar-ion laser sheet and high-speed camera. Primary spray structure and behavior of liquid sheet, especially surface wave of liquid sheet, at nozzle exit were discussed using obtained images.

Vehicular collision avoidance radar systems using millimeter-wave have been developed in recent years. Because of their simple structures, a microstrip antenna or a lens antenna is often used as the radar antenna. However, the antenna efficiencies of these antennas are low, in general. Therefore, the types of antenna that have small antenna aperture are difficult to obtain high antenna gains. In addition, it is difficult to radiate many beams at narrow beam intervals with a lens antenna. We developed an offset paraboloidal reflector antenna (the OP antenna) for the vehicular collision avoidance radar. This antenna consists of one pyramidal horn antenna and one offset paraboloidal reflector. They pyramidal horn and the radio frequency unit (the RF unit) of the radar are fixed in the radar head. To scan the beam, only the reflector is rotated. Using a reflector-rotating mechanism, the OP antenna can radiate many beams toward different directions.

In a gasoline-direct injection (DI) engine, the formation of the air-fuel mixture, which is governed by the fuel spray geometry, the air motion, and the interaction among the spray, air motion, and wall, directly influences the engine performance. The fuel injected into the cylinder involves air and evaporates to form the air-fuel mixture. The mixture is forced near a spark plug by the spray penetration, air motion, and/or wall reflection. In this paper, we investigated the spray wall impingement and the interaction between the spray, air motion, and wall using an experiment and a numerical simulation. A high-pressure swirl injector simulation model was developed and applied to calculate the spray characteristics and spray wall impingement. The simulation results of the spray shapes under atmospheric and pressurized ambient pressure agreed with the experimental results.

A small. low-cost piezoresistive acceleration sensor suitable for automotive applications such as advanced breaking control and suspension control systems has been developed. A piezoresistive semiconductor sensor has such advantages as high output linearity, long-term output repeatability and DC response a piezoelectric sensor doesn't feature. One drawback. however, is that piezoresistive characteristics are quite temperature sensitive: Such that temperature dependence of DC offset and span have to be compensated with a certain electrical circuit. With 1 mV/Vs/G, the low sensitivity of the acceleration sensor [Vs:bridge voltage. G:gravitational acceleration], the temperature shift of DC offset represented in terms of the sensitivity, becomes relatively high.

Recently, development of vehicle control system targeting Full Driving Automation (autonomous driving level 5) has advanced. Some applications of autonomous driving systems like the Lane Keeping Assist system (LKA) and Auto Lane Change system (ALC) (autonomous driving level 1-3) have been put on the market. However, the conventional system using information from front camera, it is difficult to operate in some situations. For example the road that no line, large curvature and number of lane increases or decreases. We propose an autonomous driving system using high accuracy vehicle position estimation technology and a high definition map. An LKA system calculates the target steering wheel angle based on both vehicle position information from the Global Navigation Satellite System (GNSS) and the target lane of high the definition map, according to the method of front gaze driver model. Then, the system controls steering the wheel angle by Electric Power Steering (EPS).

In recent years, the fuel consumption improvement of automobiles is indispensable due to the global move to reduce CO₂ emissions. Downsizing of engines by turbocharger obtains the output equal to a large engine, and improves the fuel consumption. However, turbocharger has the response delay called turbo lag. In order to improve a transient response, we developed a high-speed motor. The electric supercharger consists of high-speed motor and compressor, and drives compressor by high-speed motor instead of an exhaust gas turbine. By combining conventional turbocharger and electric supercharger, we developed two-stage turbocharger system. In this paper, we explained development of high-speed motor and inverter. And, as application example, we explained electric two-stage turbocharger system. The high-speed motor and inverter are connected without harness, and assembled in one single unit. The motor is driven at high efficiency by vector control.

In order to achieve NOx reduction by modification of the combustor and/or the combustor arrangement in Stirling engine, the effect of several parameters on NOx emission was investigated experimentally. The combination of appropriate “distance”, swirl intensity and burner throat configuration reduces the NOx emission without EGR(Exhaust Gas Recirculation) or any other countermeasures. The NOx and CO emissions obtained are within the Japanese exhaust gas regulation code (NOx<150ppmV, CO<100ppmV at residual Oxygen 5%) for 20kW class gas boiler. In addition, the effect of the parameters on the distributions of the chemical species, burned gas temperature and ion current in the combustion chamber of the model combustor was studied experimentally to grasp the combustion process.

Stirling engine and Stirling engine driven heat pump system (SEHP) has been developing in four years project assisted by Ministry of International Trade and Industry (MITI). In this development, 6 kW output displacer type engine and 5HP class SEHP installing with that engine were designed and manufactured Several component technologies such as combustor, heat exchanger, crank mechanism, mechanical seal etc. were also investigated in order to ensure the engine reliability. For the performance of SEHP, a capacity of 12,500 kcal/hr for cooling and 15,000 kcal/hr for heating, respectively, was achieved. Approximately 20,000 hours of accumulative operation time in total of 9 units and 7,000 hours of the one unit longest time were recorded in the field test, which demonstrated durability of SEHP.

A robust cruise control system using a disturbance observer is proposed. A control design method based on the two-degree-of-freedom (2-DOF) control including a disturbance observer is introduced. The proposed controller provides that: (1) input command responses are not affected by driving condition, such as vehicle speed, and road gradient (2) input command response and disturbance suppression performance can be designed independently (3) choice of an appropriate parameter value in the disturbance observer depending on the throttle opening gives a proper trade-off between the robust performance and the robust stability over a wide driving range. Simulation and experimental results show that the proposed system is robust against both parameter variations and disturbances.

An SOI type pressure sensor has been developed which can measure pressure at high temperature environments above 150°C. SOI stands for Silicon On Insulator. A single-crystalline silicon layer is located on an insulating layer formed on a silicon substrate. The piezoresistors of the SOI type pressure sensor are made from the single-crystalline silicon layer which is isolated from the silicon substrate by the insulating layer. There is no leakage current from the piezoresistors. The SOI structure is made by the laser-recrystallization-method. The properties of the SOI type pressure senor are as good as conventional semiconductor pressure sensors.

We have developed an effective secondary air-injection system that reduces harmful substances such as HC and CO. The secondary air in this system is heated to 300°C and injected into the exhaust pipe. Though the temperature of the secondary air is relatively low, it can activate a three way catalyst more rapidly than conventional secondary air injection systems. Thus, in our system (a “Heated-Air-Injection System”) is expected to be very effective in reducing harmful substances in the cold transient phase of the US Federal Test Procedure. For designing the system and analyzing its performance, we developed a simulation model including the design parameters of the system, such as flow rate of heated air, heater power, and so on. Besides these design parameters, the model takes into account of heat transfer from exhaust gas to exhaust pipe, gas-conversion reactions in a three way catalyst, and heat transfer efficiency of the electric heater.

A new automotive Mini Disc (MD) changer mechanism has been developed which fits a 1 DIN size chassis. This mechanism, mainly consisting of a disc change mechanism and an anti-vibration mechanism employing a floating disc drive unit system, offers a high vibration resistance, quick disc change capability and a size small enough to set a unit in an instrumental panel (I/P).

In this paper, an application of variable structure systems (VSS)(1) to electromagnetic-clutch (EMC) control for starting vehicles is studied. Using a conventional open-loop controller, there is the case that changes in EMC dynamics lead to undesirable vehicle vibration though it may be rare. First, to overcome the above problem, we developed a control strategy based on VSS. The VSS control is robust with respect to changes in EMC dynamics. Second, we discussed the chattering problem of this controller in application to actual vehicle control. Finally, we confirmed the validity of the proposed control strategy and the appropriateness of the conditions for reduced chattering derived by simulation. The validity of this control strategy was also confirmed experimentally.

An in-vehicle detecting apparatus has been developed which detects an ion current to monitor the combustion condition of each cylinder of the spark ignition internal combustion engine. This apparatus uses the spark plug electrode as an ion probe, and applies, as bias power, a very low ignition energy accumulated in the ignition coil. Thus it has the feature of requiring no particular modification on the engine side except a minor revision of the ignition system and addition of a detection module. This paper presents the construction and operation of this detection apparatus; in-engine evaluation and consideration on misfire and knocking level detecting performance; and consideration on effects of various factors on ion current values detected. In addition, data on the possibility of detecting an air-fuel ratio is reported.