Search Results

Exhaust and evaporative emissions systems have been developed to match the characteristics and usage of the Toyota THS II plug-in hybrid electric vehicle (PHEV). Based on the commercially available Prius, the Toyota PHEV features an additional external charging function, which allows it to be driven as an electric vehicle (EV) in urban areas, and as an hybrid electric vehicle (HEV) in high-speed/high-load and long-distance driving situations. To reduce exhaust emissions, the conventional catalyst warm up control has been enhanced to achieve emissions performance that satisfies California's Super Ultra Low Emissions Vehicle (SULEV) standards in every state of battery charge. In addition, a heat insulating fuel vapor containment system (FVS) has been developed using a plastic fuel tank based on the assumption that such a system can reduce the diffusion of vapor inside the fuel tank and the release of fuel vapor in to the atmosphere to the maximum possible extent.

Diesel engines with relatively good fuel economy are known as an effective means of reducing CO₂ emissions. It is expected that diesel engines will continue to expand as efforts to slow global warming are intensified. Diesel particulate and NOx reduction system (DPNR), which was first developed in 2003 for introduction in the Japanese and European markets, shows high purification performance which can meet more stringent regulations in the future. However, it is poisoned by sulfur components in exhaust gas derived from fuel and lubricant. We then developed the sulfur trap DPNR with a sulfur trap catalyst that traps sulfur components in the exhaust gas. High purification performance could be achieved with a small amount of platinum group metal (PGM) due to prevention of sulfur poisoning and thermal deterioration.

At the engine restart, when the temperature of the catalytic converter is low, additional fuel consumption would be required to warm up the catalyst for controlling exhaust emission.The aim of this study is to find a thermally optimal way to reduce fuel consumption for the catalyst warm up at the engine restart, by improving the thermal retention of the catalytic converter in the cool down process after the previous trip. To make analysis of the thermal flow around the catalytic converter, a 2-D thermal flow model was constructed using the thermal network method. This model simulates the following processes: 1) heat conduction between the substrate and the stainless steel case, 2) heat convection between the stainless steel case and the ambient air, 3) heat convection between the substrate and the gas inside the substrate, 4) heat generation due to chemical reactions.

The advantages of gasoline direct-injection are intake air cooling due to fuel vaporization which reduces knocking, additional degrees of freedom in designing a stratified injection mixture, and capability for retarded ignition timing which shortens catalyst light-off time. Stratified mixture combustion designs often require complicated piston shapes which disturb the fluid flow in the cylinder, leading to power reduction, especially in turbocharged gasoline direct-injection engines. Our research replaced the conventional shell-type shallow cavity piston with a dog dish-type curved piston that includes a small lip to facilitate stratification and minimize flow disturbance. As a result, stable stratified combustion and increased power were both achieved.

This paper analyzes low-speed pre-ignition (LSPI), a sudden pre-ignition phenomenon that occurs in downsized boosted gasoline engines in low engine speed high-load operation regions. This research visualized the in-cylinder state before the start of LSPI combustion and observed the behavior of particles, which are thought to be the ignition source. The research also analyzed pre-ignition by injecting deposit flakes and other combustible particulate substances into the combustion chamber. The analysis found that these particles require at least two combustion cycles to reach a glowing state that forms an ignition source. As a result, deposits peeling from combustion chamber walls were identified as a new mechanism causing pre-ignition. Additionally, results also suggested that the well-known phenomenon in which the LSPI frequency rises in accordance with greater oil dilution may also be explained by an increase in deposit generation.

This research developed a new measurement technology for thermal analysis of the heat radiation from a hybrid transaxle case surface to the air and improved the heat radiation performance. This heat flux measurement technology provides the method to measure heat flux without wiring of sensors. The method does not have effects of wiring on the temperature field and the flow field unlike the conventional methods. Therefore, multipoint measurement of heat flux on the case surface was enabled, and the distribution of heat flux was quantified. To measure heat flux, thermal resistances made of plastic plates were attached to the case surface and the infrared thermography was used for the temperature measurement. The preliminary examination was performed to confirm the accuracy of the thermal evaluation through heat flux measurement. The oil in the transaxle was heated and the amount of heat radiation from the case surface was measured.

This paper deals with friction under wet condition in the disk brake system of automobiles. In our previous study, the variation of friction coefficient μ was observed under wet condition. And it was experimentally found that μ becomes high when wear debris contains little moisture. Based on the result, in this paper, we propose a hypothesis that agglomerates composed of the wet wear debris induce the μ variation as the agglomerates are jammed in the gaps between the friction surfaces of a brake pad and a disk rotor. For supporting the hypothesis, firstly, we measure the friction property of the wet wear debris, and confirm that the capillary force under the pendular state is a factor contributing to the μ variation. After that, we simulate the wear debris behavior with or without the capillary force using the particle-based simulation. We prepare the simulation model for the friction surfaces which contribute to the friction force through the wear debris.

The effects of an increasing boost pressure, a high EGR rate and a high injection pressure on exhaust emissions from an HSDI (High Speed Direct Injection) diesel engine were examined. The mechanisms were then investigated with both in-cylinder observations and 3DCFD coupled with ϕT-map analysis. Under a high-load condition, increasing the charging efficiency combined with a high injection pressure and a high EGR rate is an effective way to reduce NOx and soot simultaneously, which realized an ultra low NOx of 16ppm at 1.7MPa of IMEP (Indicated Mean Effective Pressure). The flame temperature with low NOx and low soot emissions is decreased by 260K from that with conventional emissions. Also, the distribution of the fuel-air mixture plot on a ϕT-map is moved away from the NOx and soot formation peninsula, compared to the conventional emissions case.

In this study, we combined a diesel engine with the Toyota Hybrid System (THS). Utilizing the functions of the THS, reducing engine friction, lowering the compression ratio, and adopting a low pressure loop exhaust gas recirculation system (LPL-EGR) were examined to achieve both low fuel consumption and low nitrogen oxides (NOx) emissions over a wide operating range. After applying this system to a test vehicle it was verified that the fuel economy greatly surpassed that of a conventional diesel engine vehicle and that NOx emissions could be reduced below the value specified in the Euro 6 regulations without DeNOx catalysts.

The use of ceramic insulation to reduce engine heat loss and thus improve fuel economy was examined but found to be detrimental rather than advantageous. This paper analyzes the reasons and presents an alternative approach, namely minimizing the heat transfer area. Experiments were conducted to determine the effects of surface smoothness on BSFC, output torque, heat release rate and piston temperature. It was found that with a mirror-finished combustion chamber, heat loss is decreased and consequently engine output is raised, while fuel consumption is lowered. The percentage reduction in heat loss was ascertained by numerically simulating combustion and was confirmed by FEM analysis of piston thermal distribution.

This paper describes the development of one-piece die cast magnesium steering wheel frame for a steering wheel incorporating an air bag system. The light weight magnesium frame was designed to have proper stiffness, strength and characteristics of energy absorption. Magnesium alloys with various aluminum contents were tested, and AM60B alloy was selected because of its favorable properties of strength and elongation. New manufacturing techniques, for example, a vacuum hot chamber die casting system and a surface defect inspection system were developed in order to produce high quality castings. The characteristics of energy absorption were evaluated in the laboratory and on actual vehicle crash test, and the results were satisfactory. The magnesium steering wheel frame is about 45% (550g) lighter than the steel one. It has been in production in Toyota passenger cars with driver side air bags.

The authors, et al. have succeeded in the practical application of the abradable flame spray coating, used in aircraft engines for the prevention of air leakage and the improvement of efficiency, to automobile turbochargers for the first time in the world. Two layers consisting of a bond coated layer and an abradable layer used to be coated by separate spray nozzles under the conventional technique. In this paper, equations of relations between various flame spray coating conditions and the quality of coated film, which were derived from measured results, will be described. Flame spray coating conditions, that allow the double layer coating by the same spray nozzle, have been determined for each layer. Temperatures and speeds of the flame were measured by means of two-color type high-speed cameras, and equations of their relations with the flame spray coating conditions are derived from the measured result.

This paper describes a new plastic coloring and forming system. The system greatly reduces the time and amount of raw materials necessary for color changes, and eliminates the need for manual cleaning during a color change. This system is well-suited for small-lot production with frequent color changes, as well as for automated production systems. The system is being used by auto parts makers, and is practical in a variety of other fields involved with the coloring and forming of plastics.

The effects of high boiling point fuel additives on deposits were investigated in a commercial turbocharged direct injection gasoline engine. It is known that high boiling point substances have a negative effect on deposits. The distillation end points of blended fuels containing these additives may be approximately 15°C higher than the base fuel (end point: 175°C). Three additives with boiling points between 190 and 196°C were examined: 4-tert-Butyltoluene (TBT), N-Methyl Aniline (NMA), and 2-Methyl-1,5-pentanediamine (MPD). Aromatics and anilines, which may be added to gasoline to increase its octane number, might have a negative effect on deposits. TBT has a benzene ring. NMA has a benzene ring and an amino group. MPD, which has no benzene ring and two amino groups, was selected for comparison with the former two additives.

The impact of fatty acid methyl ester (FAME) blended diesel fuel on engine/vehicle systems was comprehensively investigated by vehicle, laboratory and engine tests. In this study, 20% FAME blended fuel (B20) was mainly used and soy bean oil methyl ester (SME) was primarily selected as the FAME. Vehicle testing with long-term fuel storage in vehicle fuel tanks was conducted, considering the most severe conditions in market use. Laboratory and engine tests were also conducted to better understand the vehicle test results. In the vehicle test, engine startability, idle roughness and fuel injection control were evaluated using nine vehicles with plastic or metal fuel tanks. All vehicles showed no problems up to 7 months. While five vehicles with plastic fuel tank did not show any problems throughout the test period up to 18 months, four vehicles with metal fuel tanks experienced malfunctions in engine start or fuel injection control following 8, 13, 13 and 18 months respectively.

The hole diameter of injection nozzles in diesel engines has become smaller and the nozzle coking could potentially cause injection characteristics and emissions to deteriorate. In this research, engine tests with zinc-added fuels, deposit analyses, laboratory tests and numerical calculations were carried out to clarify the deposit formation mechanisms. In the initial phase of deposit formation, lower zinc carboxylate formed close to the nozzle hole outlet by reactions between zinc in the fuel and lower carboxylic acid in the combustion gas. In the subsequent growth phase, the main component changed to zinc carbonate close to nozzle hole inlet by reactions with CO₂ in the combustion gas. Metal components and combustion gases are essential elements in the composition of these deposits. One way of removing these deposits is to utilize cavitations inside the nozzle holes.

An unprecedented phenomenon that achieves high NOx conversion was found over an NSR catalyst. This phenomenon occurs when continuous short cycle injections of hydrocarbons (HCs) are supplied at a predetermined concentration in lean conditions. Furthermore, this phenomenon has a wider range of applicability for different catalyst temperatures (up to 800 degrees Celsius) and SVs, and for extending thermal and sulfur durability than a conventional NOx storage and reduction system. This paper analyzes the reaction mechanism and concludes it to be highly active HC-deNOx by intermediates generated from adsorbed NOx over the base catalysts and HCs partially oxidized by oscillated HC injection. Subsequently, a high performance deNOx system named Di-Air (diesel NOx aftertreatment by adsorbed intermediate reductants) was demonstrated that applies this concept to high speed driving cycles.

An on-board particulate matter (PM) sensor, consisting of a gas-permeable electrochemical cell with a porous yttria-stabilized zirconia solid oxide electrolyte, was developed to assist the on-board diagnostics (OBD) system of a vehicle. Exhaust is pumped from the anode side to the cathode side and PM deposited on the anode is instantly oxidized by the catalytic effects of the metal component of the electrode at temperatures higher than 350°C. The PM oxidation reaction occurs at the three-phase boundary between the anode, electrolyte and gas phase, and causes a slight change in the bulk average oxygen concentration, which produces electrochemical polarization by the difference in oxygen partial pressures between the anode and cathode. The developed PM sensor has a detection limit of 2 mg/m₃, at which level will enable PM detection in the OBD system according to the EURO VI regulation.

The stability of Diesel/Biodiesel blends can play an important role in deposits formation inside the fuel injection system (FIS). The impact of the stability of FAME/Diesel fuel blends on lacquer deposits formation and on the behavior and reliability of the FIS was investigated using blends of Rapeseed and Soybean methyl esters (RME, SME) and conventional Diesel fuel (volume fractions of RME and SME range from 0 to 20%v/v). Fuels were aged under accelerated conditions and tested on an injection test rig according to an operating cycle developed to provoke injector needle blocking. The soaking duration was found to affect injector fouling. A relationship between the injector fouling tendency and the fuel stability was established. Under current test condition, injectors fouling increased with fuel oxidation measured with Total-Acid-Number.

A slip-controlled lock-up clutch system Is very efficient in improving the fuel economy of automatic transmission (AT) equipped vehicles. However, a special automatic transmission fluid (ATF) which combines an anti-shudder property with high torque capacity is required for this system. In this study, we established additive technology for ATF having a sufficient anti-shudder property and high torque capacity. Based on the technology, new ATF: ATF-T4 was developed. It was confirmed in actual AT tests that ATF-T4 has excellent anti-shudder durability and high torque capacity. Furthermore, ATF-T4 has good SAE No. 2 friction characteristics, oxidation stability, compatibility with materials (elastomers, nylons, etc.) and viscosity at low temperatures.