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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.

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 examines the anti-shudder property of automatic transmission fluid (ATF) in terms of evaluation criteria and durability. The anti-shudder property is required for precise slip control around the clutch in that kind of automatic transmission, applications which are currently increasing. To evaluate anti-shudder properties, friction characteristics are measured by modified Low Velocity Friction Apparatus (LVFA), and the data are compared with those from the actual vehicle. The analysis confirms that the occurrence of shudder on the vehicle is closely related to the ratio of the static friction coefficient to the dynamic one measured by modified LVFA.

If a torque converter clutch is allowed to slip to a minimal amount, engine torque can be transmitted through a transmission without torque variation problem, and also low fuel consumption is realized by putting the clutch in operation even at low engine revolution. Oil pressure applied to clutch is electronically feedback-controlled to keep clutch slip to a minimal amount. But this feedback system tends to become unstable by impairment of various factors of the system. This paper relates to the stability analysis of feedback system, and especially to the control method by which feedback system can be made stable even when µ-v characteristic of clutch facing material is impaired.

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.

A high-performance road profile measuring system has developed. The measuring system consists of four laser displacement sensors and an optical speed sensor. It has the advantage of making high-accuracy measurements during a regular run, on a public road, and without any traffic restriction. The measurement is hardly affected by bouncing and pitching motions of the vehicle. The four displacement sensors are arranged at unequal intervals in the direction of vehicle. A road profile is calculated from sensor outputs. This paper describes not only the development of this unique measuring system but also its application to a vehicle behavior. Significant measurements of typical and peculiar public roads in Japan and Northern Europe by the measuring vehicle have been performed for the last few years. The features of these roads are described by the power spectrum densities and the profiles.

In recent year, higher strength for truck and bus transmission gear has become necessary. For the transmission gears, carburized gears have generally been used. We have examined the effects of shot peening and grinding using a CBN grindstone on the pitting strength and the bending fatigue strength of a carburized gear, and further evaluated a material which reduces the structual anomalies produced during carburization. As a result, it has been found that shot peening or CBN grinding is more effective for improving both pitting strength and bending fatigue strength than improving the material composition. Therefore, it is evident that residual compressive stress caused by shot peening or CBN grinding suppresses the propagation of cracks.

This paper describes the method to improve the energy absorption characteristics during the vehicle frontal collision. The method is to control the collapse phases of the members constituting the vehicle body and to increase collapse force of a member. This phase-control can be accomplished by superimposing the crest of the collapse force curve, which one member causes, on the trough of any other members'. The bulkheads installed in the members are useful. to control the phase and to increase the collapse force. Numerical analysis and experiment of a vehicle collision show that the control leads to the improvement of energy absorption characteristics and load transmission efficiency.

During next decade, automotive engineers will take up unprecedented challenges to meet a variety of technical demands on passenger cars. While performance, refinement and reliability will continue to be major technical goals of passenger cars, reducing their impact on the environment not only in urban areas but also on the global basis will become an increasingly urgent issue. In addition, the need for energy and resources saving will necessitate development of more fuel efficient cars, exploitation of alternative energy and recycled materials. In this paper, the authors will review various alternative engines as candidates to satisfy the above demands. The authors will also discuss various alternative transportation energy sources such as alcoholic fuels, natural gas, hydrogen and electricity. Finally the trends of future passenger car engine design will be discussed.

New systems or functionalities have been rapidly introduced for fuel economy improvement. Active vibration suppression has also been introduced. Control algorithm is required to be verified in real time environment to develop controller functionality in a short term. Required frequency domain property concept is proposed for representation of target phenomena with reduced models. It is shown how to select or reduce engine, transmission and vehicle model based on the concept. Engine torque profile which has harmonics of engine rotation is required for engine start, take-off from stand still, noise & vibration suppression and misfire detection for OBD simulation. An engine model which generates torque profile synchronous to crank angle was introduced and modified for real time simulation environment where load changes dynamically. Selected models and control algorithms were modified for real time environment and implemented into two linked universal controllers.

This paper describes a method of predicting cooling performance in order to obtain the optimum design of the cooling system and front-end shape in the early stage of car development. This method consists of four calculation parts: thermal load on the cooling system, air flow through the engine compartment, heat dissipation by the heat exchangers and temperature distribution within the cooling system. It outputs the coolant, engine oil, automatic transmission fluid (A.T.F.) and charge air temperatures in exchange for the input of several car, power plant, drive train, exterior shape and cooling system specifications. For the calculations, in addition to theoretical formulas, several experimental formulas are introduced. This method verification is shown by presenting a few test cases for the respective calculation parts and the final solution.

There have been various predictions made concerning the future profile for automobiles but such predictions have in many cases been based solely on anticipated advances in technology. In presenting a profile for automobiles in the year 2000, the writers predict the evolution and transfiguration of automobiles, taking both phases in the changing social environment and technical trends into account. Interest in automobiles is expected to shift from hardware to software and then to humanware (i.e. more emphasis is placed on the relationship with human beings), and automobiles will evolve and transfigure reflecting these changes.

Improvements of interior and exterior noise are important targets in vehicle engineering. There are many reports concerning the reduction of radiator cooling fan noise. But, most of those reports are associated with studies of air flow noise. A radiator cooling fan connected to a crankshaft occasionally radiates structure-borne noise in addition to air flow noise. This structure-borne noise is caused by fan blade vibration excited by torsional vibration of a crankshaft. In this paper, we surveyed the mechanism of the structure-borne noise and discussed some methods for the noise reduction. And, as a result, we developed one of the noise reduction technique aiming at isolation of crankshaft vibration by modifying viscosity of the oil in a fan clutch.

Optimization of the clutch torsional characteristics is one of the effective methods to reduce the idling rattle noise. Many researches on th.s problem have been reported, but only few of them give sufficient consideration to the drag torque applied to the clutch disc during engine idling. This paper pays attention to the drag torque and discusses the mechanism of idling rattle noise by using vehicle testing, bench test with rotating torsional exciter and computer simulation. Reauction of Idling

Three Japanese automobile manufacturers-Mitsubishi Motors Corp., Nissan Motor Co., Ltd., and Toyo Kogyo Co., Ltd.-have been making efforts over the past three years to design and develop effective thermal reactor-exhaust gas recirculation and catalytic converter systems suitable for small engines. The work is being done by members participating in the IIEC (Inter-Industry Emission Control) Program, and the exhaust emission levels of the concept vehicles developed by these companies have met the goal established by the IIEC Program at low mileage. Each system, however, has a characteristic relationship between exhaust emission level and loss of fuel economy. Much investigation is required, particularly with respect to durability, before any system that will fully satisfy all service requirements can be completed. This paper reports the progress of research and development of the individual concept vehicles.

In previous studies(1)(2), the acceleration performance of vehicles equipped with torque converter has been analysed with the assumption that the converter characteristic was under continued steady-state. However, in case of sharp acceleration of the fluid flow in the converter from inactive flow condition, which would occur at wide-open throttle starting, it is not possible to accurately analyse the vehicle performance at immediately after starting if the converter characteristic is assumed to remain under steady-state condition. In this paper, the transient phenomenon in the converter is verified by applying the theory of angular momentum and the concept of energy balance through the converter elements providing with a dynamic-model for the driveline. The present study has clarified the effect of the transient converter characteristic, at sharp starting, on the acceleration performance.