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This paper describes the calculative verification of the effect of the right-and-left torque vectoring system in various types of drivetrain, namely, the front wheels only, the rear wheels only, and both front and rear wheels in FWD, RWD, and AWD vehicles. The effect is evaluated by calculating the vehicle dynamics limit; maximum acceleration and cornering ability. The right-and-left vectoring torque, which is needed for expanding the vehicle dynamics limit, is also calculated. And finally, the paper evaluates the suitable wheels for which the system should be applied in each drivetrain. The application to the front wheels is more effective for FWD vehicles. On the other hand, the application to the rear wheels is more effective for RWD and AWD vehicles.

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.

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 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.

It is well-known that double-mass torsional rubber dampers which have two masses and springs in parallel are effective for controlling torsional vibration characteristics over a wide range of engine speed. On the occasion of reliability estimation of the rubber dampers, it is important to consider generation of heat in the rubber due to torsional vibration. By predicting generation of heat at the designing stage, optimum design of the torsional rubber dampers can be achieved. By development and application of this prediction method, a new type double-mass damper was developed. It provided higher vibration control characteristics and reliability than conventional viscous dampers, and also it provided advantages in terms of noise, productivity and weight.

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.

Beta Ti alloy valve spring retainers are newly developed for use in mass produced automobiles for the first time. Ti alloy valve spring retainers vith a weight saving of 42%, compared to steel retainers, have reduced the inertial weight of the valve train components by 6%. And this weight reduction has the benefit of increasing the upper limit of the engine speed, which improves the engine performance. Ti alloy valve spring retainers are cold forged by the conventional fabrication facilities for steel retainers, using Ti-22V-4Al (the beta Ti alloy) which possesses excellent cold workability in a solution treated condition. Oxygen surface hardening is applied to protect Ti alloy valve spring retainers from wear damage. In addition, aging treatment and shot blasting are performed to improve strength and stiffness of valve retainers.