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The purpose of this paper is to present a prediction method for the refrigerator performance of an automotive air conditioner (A/C). In order to predict the refrigerator performance in arbitrary situations, we consider the thermal equilibrium of the refrigeration cycle through A/C components, as the compressor, the evaporator and the condenser. These components are affected by the thermal property of the refrigerant. Influences of circumstantial flow and temperature field in the engine compartment also are reflected upon, because the cooling performance of the condenser is sensitive to that. In this paper, we try to derive algebraic models for the major components with regard to the thermal equilibrium in the refrigeration cycle. Furthermore, we use a Computational Fluid Dynamics analysis (CFD) for the prediction of cooling airflow temperature in the engine compartment, which is another essential factor in determining the state of the refrigeration cycle.

When truck tires have a deformation such as radial runout, flat spot, and abnormal wear as a result of panic braking, they affect vehicle vibration in the form of displacement input whose spectrum involves higher order terms of tire revolution. While a truck has vibration modes of frame bending as well as pitching and unsprung-mass viberation in the input frequency range, the tire displacement input induces vehicle vibration as a combination of these modes. Results of calculations and experiments of a 4x2 medium-duty truck are analyzed and an example of means for improving ride comfort is described in this paper.

Aerodynamic drag reduction is one of the most important aspects of enhancing overall vehicle performance. Many car manufacturers have been working to establish drag reduction techniques. This paper describes the development process of a new small speciality car which achieved coefficient of drag(CD) of 0.25. A description of the test facilities and the systems used for developing the aerodynamic aspect of the car are also introduced briefly.

An analysis of the static behavior of T-shaped joint is presented. Advanced testings by laser holography and infrared ray stress wave analyzers verified the surface deformation and the stress concentration of joint area, which are very important factors of thin-walled joint stiffness. The definition of structural joint stiffness is attempted, and the relationship between structural joint stiffness and sizes(dimension) of the constructing members is obtained in case of a thin-walled T-shaped member with rectangular cross section. The parametric study to accomplish weight reduction, while maintaining the necessary structural joint stiffness, is described in case of Rocker to Center pillar. The numerical analysis of body structure considering the structural joint stiffness shows better accuracy as compared with the analysis with the joint assumed rigid.

We reported, in our first report1), the study of shapes of air deflectors that have strong yawing angle characteristics for the air resistance encountered when vehicles are running at high speed, taking into account the ambient wind. However, it is rarely the case that the optimum shape of air deflector, which was obtained and reported in our first report, is directly adopted for practical use. This paper reports the results of measurement tests on how the air resistance increases (worsens) when an air deflector is mounted on the cab of a vehicle: in the case when the air deflector was slightly changed on the same vehicle; or when the parameters of the vehicle (the height of the rear body) were changed for the same air deflector. We obtained the following results: Considerations and adjustments are required not to allow flows passing over upper and side surfaces of the air deflector to hit the front surface of the rear body.

This paper describes the shape optimization analysis of solid structures such as chassis components of a car, where the shape optimization problems of linearly elastic structures are treated to improve strength or to reduce weight of solid structures. The optimization method used here is the growth-strain method, and the shape optimization system is developed based on this method. The growth-strain method, which modifies a shape by generating bulk strain, was previously proposed for analysis of the uniform-strength shape. The generation law of the bulk strain is given as a function of a distributed parameter to be uniformed, such as von Mises stress. Two improved generation laws are presented. The first law makes the distributed parameter uniform while controlling the structural volume to a target value. The second law makes the distributed parameter uniform while controlling the maximum value of the distributed parameter to a target value.

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

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 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.

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.

Austempered ductile iron (ADI) is a material having excellent mechanical properties and damping capacity. However practical mass production of ADI gears has not been possible due to ADI's poor machinability and distortion during the austempering heat treatment. With a new process method of carrying out hobbing before austempering when the material is in its soft condition, then austempering it and lastly, conducting the shave finishing process, we have diminished the above defects and developed practical ADI gears. These new gears generate less noise than ordinary nitrocarburized steel gears and are superior in pitting resistance.

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.

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.

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 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.

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.

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.