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The authors used a mass spectrometer to determine an SOF reduction mechanism of a diesel oxidation catalyst. The results indicate that SOF reduction lies in the catalytic conversion of high molecular organic matter to low molecular organic matter. And unregulated emissions are also reduced through this conversion. It is also found that the SOF reduction performance is highly dependent up on the condition of the wash coat. There is some limitation to improving diesel oxidation catalyst performance because of the sulfur content found in diesel fuel. Finally, the authors have determined what we think are the specifications of the presently best catalytic converter.

Optimizing the design of automobile outer panels for weight reductions requires a consideration of stiffness and dent resistance. This paper presents a finite element analysis method for predicting the dent resistance of automobile body panels. The method is based on elastoplasticity analysis and nonlinear contact analysis. The analysis shows that dent resistance is greatly influenced not only by the stress-strain curve of the formed panel but also by the residual stress in the panel. An increase in yield stress improves dent resistance. The computed results obtained with this method compare favorably with experimental data, thereby validating this approach.

This year (1989) Mitsubishi Motors Corp. introduced, on some models, a newly-developed Hydraulic Coupling Uint (HCU), by which 2WD vehicles can be converted into 4WD ones in the same way as done by a viscous coupling (VC). This HCU is similar in the configuration to a vane pump: the oil discharge is returned to the suction chamber through a number of orifices. The rotor and cam ring (housing) are respectively connected to the two shafts; either of the one with the front wheels and the other with the rear wheels. Accordingly, it works as a slip-sensitive differential like a VC while it has a merit of progressive and parabolic torque-response characteristic, which offers stronger traction and acceleration capability and also minimizes tight-corner braking. This paper discusses primarily the configurations, functions and test results of the HCU and also presents an overview on further development possibilities of the 4WD system.

A trap system has been developed that collects particulate using two small filters and regenerates alternately by electric heaters. This system contains a new idea in detection of the amount of particulate accumulation in the filters. The system counts the amount using a particulate accumulation rate map which is a function of the engine load and speed. In vehicle test with this trap system, the particulate collection efficiency and the regeneration efficiency were proved to be high enough for practical use. The test results also showed that the shutdown performance of the route switch valve greatly influenced the regeneration efficiency.

Various parameters for the shift scheduling of an automatic transmission were examined to detect more accurate road conditions, vehicle running conditions, and the driver's intention. The parameters include the vehicle speed, the gradient of a road, an index to curves in the road, and so on. The fuzzy logic was employed to incorporate these parameters into the shift scheduling control. The vehicle running tests have shown that the use of many parameters and the fuzzy logic was effective on reducing the frequencies of the transmission gear shift and the driver's brake operation in such road conditions as usually seen in mountainous areas

It has been over a half century since automatic transmission vehicles were introduced to the market, and many improvements in terms of reliability, performance, and cost have since been made. As a result, over 70 percent of passenger cars in the Japanese market today are equipped with automatic transmissions. Despite these advances, customer demand for quieter operation and reduced vibration in automatic transmission vehicles requires further improvements, particularly in the area of reduced shock and smooth response during shifting. Technological improvements have been in progress to solve this problem by such means as reducing engine output during shifting, adapting feedback control and learning shift control. Consequently, an advanced evaluation method for shift quality, with accuracy matching that of human feeling, is required to help improving the shift quality of automatic transmissions.

A Finite Element Method (FEM) simulation was conducted to predict energy-absorbing characteristics in an impact of a head form against plastic plates. Static and dynamic material tests were conducted in order to determine material properties of the plastics. The properties were applied in an explicit FEM code. The FEM results were validated through the impact tests by the head form against the same plastic plates. It was proved that the FEM could simulate the test result well, when the precise material properties were introduced in the simulation. The method can be expected to be available to predict energy-absorbing characteristics during the impact by the head form against automobile plastic components such as shell portions of instrument panels.

This paper presents a new torque distribution system-“Right/Left Torque Control System”, aimed at improving a vehicle's cornering properties by using yaw moment control. The torque transfer mechanisms of this system have been analyzed. Also, a yaw moment control algorithm using yaw rate feedback control has been designed. Next, vehicle cornering properties were evaluated using numerical simulation developed from data taken from an actual vehicle. As a result, improvements were achieved in the maneuverability and stability of a vehicle during cornering.

Since it is more difficult for truck door panels to realize curvature than passenger car door panels, internal stiffeners are mounted between the outer panel and inner panel through the use of an adhesive for ensuring stiffness. For this reason, a problem occurs as to the proper placement of the stiffeners so as to effectively improve stiffness. By FEM prediction and experimentation, the following have been clarified: (1) Arrangement of stiffeners for effectively improving stiffness (2) Stiffness share of stiffeners and outer panel against stiffness

In order to design a well-balanced truck frame, optimization of not only the stiffness of the entire body and stress of each member, but also the internal force of each member is necessary, including the effect of a rear body mounted on the frame. This paper proposes a new parameter, “torsional stiffness share rate,” that directly correlates the contribution of member torsional stiffness to frame torsional stiffness with the internal force of the members as to torsion of the truck frame. The merits of the torsional stiffness share rate are shown in comparison with the strain energy share rate and the stiffness contribution rate. The results of experimental and FEM analyses of the torsional stiffness share rate are also presented.

Passenger cars with sunroofs sometimes experience a low frequency pulsation noise called “wind throb” when traveling with the roof open. This “wind throb” should be suppressed because it is an unpleasant noise which can adversely affect the acoustic environment inside a car. In this paper, 3-dimensional numerical flow analysis is applied around a car body to investigate the wind throb phenomenon. The computational scheme and the modeling method of the car body is first described. A flow visualization test in a water tunnel was completed for the simple car body shape to compare against the numerical procedure. The numerical and the visualized results compared well and the numerical simulation method employed was considered to be a reliable tool to analyze the wind throb phenomenon. Calculated results of pressure and vorticity distribution in the sunroof opening were analyzed with the spectrum of pressure fluctuation at the sunroof opening with and without a deflector.

Applying micro-alloyed steel as a cost-effective method of forging engine parts eliminates quench and temper processes and saves energy. We have expanded this application to timing gears and crankshafts by changing the connecting rod material to carbon steel and vanadium, applied at the outset. Then, micro-alloyed steel treated with a soft nitriding process was used. Our recent studies have been focused on materials which exhibit both higher tensile strength and better machinability. This paper describes the results of applying different types of micro-alloyed steel to those engine parts.

Several different steel sheets were tested for energy absorption, using hat square columns and dynamic crash testing. Results indicate that steel sheets containing large volume fraction of retained austenite have relatively high energy absorption. The relationship between retained austenite and energy absorption was analyzed. These special steel sheets have already been successfully used for production body parts, such a front-side-member, without difficulties arising in volume production.

The need of lightweight vehicle design is motivated by the recent global trend of less fuel consumption and lower emission in vehicle. However in NVH development of vehicle, it becomes more difficult for the lightweight vehicle to reach low vibro-acoustic sensitivity than, for the heavy weight one to do so. Inthis environment, this paper describes about the practical finite element (FE) modeling of vehicle structure and acoustics, in order to predict "boom" response to powertrain excitation. The FE modeling process through validation and updating with experimental mode makes, the accumulation of considerable expertise for improving prediction accuracy, possible. FE analysis based on this modeling process is so useful for predicting "boom" levels up to 200 Hz. Using the result of FE analysis, structural optimization is executed in order to improve "boom" level of 80 Hz.

The authors developed, for use in diesel engines, ceramic tappets cast in aluminum alloy that drastically improved wear resistance and valve train dynamics. The ceramic tappets consist of two parts: a ceramic head, which contacts the cam and push rod, and a tappet body made of aluminum alloy. Concerning the ceramic, silicon nitride was the best material of the three ceramics evaluated in the tests and the sliding surface, in contact with the cam and push rod, was left unground. As for the aluminum alloy, hyper-eutectic aluminum-silicon alloy with a controlled pro-eutectic silicon size was selected. A reliability analysis using the finite-element method (FEM) was also made on the structure of the ceramic tappet for enhanced durability and reliability. The combination of this tappet and a cam made of hardened ductile cast iron, hardened steel, or chilled cast iron, respectively exhibits excellent wear resistance.

This paper describes a calculating method to predict the quasi-static collapsing behaviors of spot-welded closed-hat section curved beams under axial compression. The overall deformat ions and the local buckling modes of beams were calculated using a geometrical model. Force-displacement relations were predicted by a elastic-plastic structural analysis method using the ‘plastic hinge’ concept. Collapsing tests were made on beams which are differenting section size, rotation angle, and metal sheet thickness. Comparisons between the calculated and experimental results of deformed shapes of beams, the local buckling modes and the force displacement relations are discussed.

Auto-regeneration of diesel particulate traps, particularly combustion mode of soot in a wall flow filter with fuel additives, was investigated using a diesel engine of a light duty truck and truck itself. Soot burning in the trap and regeneration were observed under any engine operating condition including prolonged idling and stop-and-go driving at 0.18g metal/1 dosage of a mixture of copper and lead in the fuels. However, trap life was limited by ash clogging due to the metallic compounds. Although the influence of metallic additives on the environment was debatable, test results of the trap durability and calculations of soot burning based on the thermal ignition theory indicated that dosage and kind of fuel additives should be optimized in view of both trap life and reliability of soot burning.

With the intention of improving engine performance and emissions, the authors examined the influence of the method of initial fuel injection quantity reduction and of the injector configuration of a common rail fuel injection system on engine performance and exhaust emissions. Results showed that decreasing the nozzle hole diameter was an effective way to reduce the initial injection quantity without increasing black smoke. Compared to a three-way type injector, it was found that a two-way type injector can greatly reduce the amount of fuel leakage from the electromagnetic injector control valve and fuel consumption could be further improved by reduction of the driving loss. Furthermore, the increase of driving losses with higher injection pressure was small, and as a result, higher pressure injection was possible.

As the global environmental protection becomes the world consensus recently, the regulations of the fuel consumption and the exhaust gas have large effects on the performance and the fundamental structure of commercial vehicles. Especially the technology concerning "fluid" and "heat" has a close relationship with those issues. Owing to above circumstances, commercial vehicles such as large trucks and buses are forced to be designed near the limit of allowance. Furthermore, a rapid design is another requirement. However, though significant number of variations, i.e., cab configuration, wheel base, rear body configuration, engine specification, etc., are prepared, it is impossible to improve the performance of all those combinations by experiments which cost a lot. Accordingly, the quantitative prediction using computer will become indispensable at the beginning term of new car development.

Periodic oscillations of the speed of SI engine with MPI system at idle observed in the steady state and in the converging process after the inditial increase of load were investigated. These non-steady phenomena are the self-excitations of the closed-loop system induced by the lag factors inherent to the system such as the manifold charging delay and the fuel metering and transport lag and by the nonlinear factors such as the sensitivity of the torque to the equivalence ratio. But, even in the cases where the lags and the nonlinearity are insufficient, continuous oscillations with large amplitude are observed in the actual engine. They can be explained by introducing the concept of external perturbation induced by the combustion fluctuation. Disturbance prevents the phase lag in the system from converging, resulting in the continuation of oscillation.