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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 new prototype oxygen storage componented oxygen sensor has been developed which shows significant emission reductions of a 3-way catalyst system. This sensor is composed of ceria, as an oxygen storage component and supported pellets as a buffer layer surrounding the protective coating of the sensor element. This sensor offers a more rapid response than conventional ones under lean and rich fuel mixture excursions, which is caused by CO or O2 electrode poisoning.

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.

This paper presents the results of acoustic analyses of light duty truck cabs by actual vehicle testing and by numerical analysis utilizing the boundary element method (BEM). In the resonance mode analysis using BEM, by taking into account the vibration characteristics of cab panels, the presence of the modes other than the purely acoustic cavity resonance modes were confirmed. The contribution of the panel vibrations to booming noise that occurs in actual light duty trucks was analyzed. BEM analysis showed that some of the panel vibration had a negative contribution to booming noise. In other words, decreasing vibration in such a section was shown to increase sound pressure. The results of the BEM analysis match well with actual test results. It has thus been demonstrated that BEM is an effective method for analyzing truck interior noise reduction.

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.

In the diesel engine industry, the growing trends are toward wider use of electronically controlled high pressure fuel injection equipment to provide better engine performance, while conforming to the stringent exhaust emission standards. Although there have been some recent announcements of a diesel engine that applies an electronically controlled common rail type fuel injection system, there is little literature published about any attempt to reduce both exhaust emissions and noise and to improve engine performance by varying injection pressure and injection timing independently and introducing pilot injection in combination. This paper describes the details of a study made on the parameters associated with injection timing, injection pressure and pilot injection and the procedures for their optimization, with an electronically controlled common rail type fuel injection system installed in an in-line 6-cylinder 6.9 liter turbocharged and intercooled DI diesel engine.

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.

This paper describes the results of the study and research on ovate wire helical springs which have been jointly conducted by the members of the Japan Society for Spring Research consisting of the engineers from material suppliers, wire and spring producers and automotive manufacturers as well as researchers at Japanese universities. Attention is focused particularly on two types of wire cross sections, typical elliptical shape and Fuchs' egg-shape. Stresses on these two cross sections were analyzed by numerical calculations within the range of practical specification, and then the results have been compared with those of round wire spring. As a result, it has been found that the elliptical wire spring is superior to Fuchs- egg-shaped one for general application. Simple designing methods for the both types of wire helical springs have been developed based on the findings from the stress analysis.

This is to introduce a development history of Doubles-Combinations in Japan and a several important technological points briefly. We understand that our wide promotion of these development activities are strongly supported by the General/Technical Committee members. And totally 10 - million kirometers practical operation data included by 3 - famous Japanese fleet owners, these must be very much useful and valuable for anyone interesting those of Trailer-Combination technologies.

When replacing a metal engine part with plastic, it is necessary to regard vibration damping as one of the important factors in terms of noise reduction as well as strength and heat resistance as being characteristics of the material. Plastics are far better for vibration damping than steel or aluminum, but this property is reduced by the addition of glassfiber-reinforced or high heat-resisting resins. We have taken notice of SMC (Sheet Molding Compound) which has the excellent strength and heat resistance properties and studied it in order to increase its vibration damping property. Since organic polymers show the peak value for vibration damping performance in the vicinity of the glass transition temperature (Tg), we studied a method to shift the Tg near the operating temperature region in order to improve the vibration damping property.

This paper concerns driver's burden for visual information processing in which his central vision is coupled with his peripheral one. A visual driving simulator was applied to the first step of the study, where driver's responses to both central and peripheral tasks were simultaneously investigated. The series of test indicate that the driver's responsiveness to the central and peripheral tasks could define the whole burden for visual information processing. Therefore, it appears that the responsiveness to the peripheral vision could be more or less compromised to support the central one.

Three zone mixture preparation model, assuming that fuel and air are distributed in three separate zones, fuel air and mixture zone, was proposed. Air Utilization Efficiency derived from the model was used to evaluate the mixing nonuniformity. Effect of the large scale nonisotropic turbulence downstream of the dimple or edge in the intake port of MPI engine on the convective mass transfer from fuel film was clarified by the proposed nondimensional index, Local Sherwood Number. It was found that when the fuel is injected toward the wall where large scale turbulence exists, almost all of the fuel is seeded in the air passing the region at the beginning of the intake process, resulting in the time-resolved nonuniformity of the mixture strength at the intake valve. Using the Air Utilization Efficiency, it was elucidated that time-resolved mixing nonuniformity at intake valves induces spatially nonuniform fuel/air distribution in the cylinder.

From the standpoint of safety, the demands are growing in recent years for better controllability and stability of automobiles and in particular in trucks. The truck, however, when compared with the passenger car, is subject to larger changes in gross vehicle mass and center of gravity depending on its load placement. In addition, since the cornering power generated by the truck tire per load is smaller than that generated by the passenger car tire, it is difficult to introduce significant improvements in controllability and stability simply by use of passive techniques like suspension characteristic tuning. Therefore, studies were performed on the applicability of the 4WS system, an active vehicle dynamic characteristic control technique, to a Truck as a means for solving these problems.

This paper describes an experimental analysis of frictional heat generated between the pads and rotors of disc brakes, to determine the paths and amounts of heat flow. The brakes were applied repeatedly at a constant initial speed, deceleration and interval until brake temperature became saturated. Under these conditions we measured an unsteady temperature distribution state during a single application of the brakes, and also a saturated (quasi-stationary) temperature distribution during repeated braking. Heat flow was studied in six paths: heat conduction to the pad; heat convection to the air from the friction areas of the inner and outer disc, from the ventilating parts and from the tube section of the rotor; and heat conduction to the rotor flange section.

Global environment protection, Co2 emission reduction and so on, is an important problem in automotive industry. An Electric Vehicle (EV) production is one of policies. Co2 emission of EV is lower than Internal Combustion Engine (ICE), petrol and diesel engine. On the other hand, customer's needs for the comfort on driving increase year after year. So it's an important factor for new car performance. Generally speaking, it's thought that the noise and vibration performance of EV have the better of ICE performance. However the aerodynamic noise and road noise contribution for interior noise in EV rise in comparison with ICE, and moreover the sound quality change by new noise component of the motor noise. Therefore new sound evaluation method is needed for EV. So this paper demonstrates each noise component contribution in EV by new noise separation technology, and show the comparison result with EV and ICE.

Structural attenuation of a running diesel engine measured by a new technique showed a constant value regardless of engine speeds. It was verified by this result that structural attenuation is a physical quantity unique to the structure of each engine and, therefore, a good indicator for evaluation of low noise engine structure. In addition, a hydraulic excitation test rig was devised to measure structural attenuation directly and to make effective use of it for noise reduction. Based on the accurate measurements by the excitation test rig, modal analysis and system simulation were conducted for implementation of countermeasures against noise.

The 4M5 series of four-cylinder, in-line, direct-injection diesel engines has been released by Mitsubishi Motors Corporation for light and medium-duty trucks and buses. Featuring an updated structure and reflecting the employment of state-of-the-art technology in the design of every component, the new engine series offers high reliability and compact dimensions. Moreover, the new series well meets contemporary demands for high performance, low noise, and clean combustion.

In the heavy-duty commercial vehicle market in Japan, particularly in the segment of dump trucks and tractors, naturally aspirated engines maintain a dominant market share because of their superior torque characteristics in the low speed range. In order to meet the ever increasing needs for higher speeds of transportation, better fuel economy and higher reliability, and the needs for increasingly strict exhaust emission regulations, Mitsubishi Motors Corporation (MMC) has developed the 8M20, a 20 liter V8 diesel engine. The '92 model series of “THE GREAT”, MMC's main heavy-duty trucks, has featured this new and powerful engine and has been in the market place since October, 1991. The 8M20 is a naturally aspirated engine that provides an output of 294kW/2200rpm, complying with the current Japanese exhaust emission regulations.

Flow and flame structure visualization and modeling were performed to clarify the characteristics of bulk flow, turbulence and mixing in a four-valve engine to adopt the lean combustion concept named “Barrel-Stratification” to the larger displacement center-spark four-valve engine. It was found that the partitions provided in the intake port and the tumble-control piston with a curved-top configuration were effective to enhance the lean combustion of such an engine. By these methods, the fuel distribution in the intake port and the in-cylinder bulk flow structure are optimized, so that the relatively rich mixture zone is arranged around the spark plug. The tumble-control piston also contributes to optimize the flow field structure after the distortion of tumble and to enable stable lean combustion.