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A new motor has been developed that combines the goals of greater compactness, increased power and a quiet drive. This motor is an interior permanent magnet synchronous motor (IPM motor) that combines an interior permanent magnet rotor and a stator with concentrated windings. In addition, development of the motor focused on the slot combination, the shape of the magnetic circuits and the control method all designed to reduce motor noise and vibration. An 8-pole rotor, 12-slot stator combination was employed, and a gradually enlarged air gap configuration was used in the magnetic circuits. The gradually enlarged air gap brings the centers of the rotor and the stator out of alignment, changing the curvature, and continually changing the amount of air gap as the rotor rotates. The use of the gradually enlarged air gap brings torque degradation to a minimum, and significantly reduces torque fluctuation and iron loss of rotor and stator.

There are strong demands for reduced production costs of ordinary bolts, of which a large number are used throughout automobiles. In addition, there are continued demands for higher performance and lower weight in automobiles. For this reason, there is an increasing trend to develop steel for high strength bolts or to adopt the plastic region tightening method. At present, the principal materials used in high strength bolts of class 10.9 are medium carbon alloy steel. When a low carbon boron steel bolt is used as a class 10.9 bolt under high stress, delayed fracture may occur, so that these cannot always be used for the body and chassis applications. The authors have developed a new low carbon boron steel with increased delayed fracture strength on the same order as that of JIS-SCM435 (equivalent to SAE4135) medium carbon alloy steel. Attention was focused principally on decreasing the amounts of phosphorus and sulfur in the steel.

The moment of inertia of the crankshaft cannot be ignored when analyzing the dynamics of a motorcycle. In this research, the tire friction force (calculated by drag and tire side force) was used as an index of the drive performance. The ratio of roll rate and steering torque (here after referred to as a roll rate gain) was used as an index of the cornering performance, and it was analyzed as the influence of the moment of inertia of a crankshaft on the drive performance as well as cornering performance. As a result, the influence on drive performance and cornering performance by the moment of inertia has been found.

The “Statistical Design Support System” produces a new practical optimal design method. It can be used even on nonlinear behavior. The optimization can be carried out with this system using a small number of calculation results. The authors applied it to the design optimization of the occupant restraint system in order to reduce the injury criteria based on the crash simulation. In line with growing interest and improvements in technology on vehicle safety, it will be necessary to consider some different crash situations simultaneously. The authors made an optimal design taking into account the different collision conditions. This paper describes the effectivity analysis and the optimization.

In a previous study by the authors, austenite (γ phase) formed on the topmost of pulleys after long term operation of continuously variable transmission (CVT) [1]. In general, martensite arising from heat treatment forms on the surface of pulleys and gears. Therefore, the sliding surface has a body-centered cubic (BCC) metal structure, and transformation into and existence of austenite (γ phase) is difficult unless there is a thermal history exceeding the eutectoid point. For the verification of that possibility, it was crucial to obtain temperature variation on the sliding surface. The major problem for such measurements was rotation of parts inside an operating CVT. In this study, uniquely developed measurement system enabled non-contact temperature measurement near the contact portion. Results were substituted to heat conduction equation to predict the temperature at the exact contact portion.

This paper studies various wheel stiffness configurations, with the aim of enhancing driving stability while minimizing the increase in weight associated with an increase in stiffness. Reinforcement was added to the wheel disk and the wheel rim of standard aluminum wheels for passenger vehicles in order to produce four wheels with different stiffness configurations. The effects of disk stiffness and rim stiffness on tire contact patch profiles and driving stability were quantitatively evaluated. From the results of tests with the four wheels, it was observed that disk stiffness and rim stiffness have differing effects on tire contact patch profiles, and on driving stability. Disk stiffness influences especially tire contact patch length, and tire contact patch length influences especially maneuverability in driving stability. Rim stiffness influences especially tire contact patch area, and tire contact patch area influences especially stability in driving stability.

In motorcycles, the mass difference between a vehicle and a rider is small and motions of a rider impose a great influence on the vehicle behaviors as a consequence. Therefore, dynamic properties of motorcycles should be evaluated not merely dealing with a vehicle but considering with a man-machine system. In the studies of a simulation for vehicle dynamics, various types of rider models have been proposed and it has already been reported that rider motions have a significant influence on the dynamic properties. However, the mechanism of the interaction between a rider and a vehicle has not been clarified yet. In our study, we focused on weave motion and constructed a full vehicle simulation model that can reflect the influences of the movements of the rider’s upper body and lower body. To construct the rider model, we first measured the vibrational characteristics of a human body using a vibration test bench.

In motorcycles traveling at medium to high speed, roll stability is usually maintained by restoration forces generated by a self-steering effect. However, when the vehicle is stationary or traveling in low speed, sufficient restoring force does not occur because some of the forces, such as centrifugal force, become small. In our study, we aimed at prototyping a motorcycle having roll stability when the vehicle is stationary or at low speed with a steering control for self-standing assist, while maintaining stability properties in medium to high speed. A model was built to represent dynamics of roll motion, which is composed of a fixed point mass located above the vehicle’s center of gravity and another movable point mass below that gravity center. According to the model, when steered, the roll moment direction generated by the shift of the movable point mass becomes the same as the direction generated by the ground contact point shift of the front tire.

In order to reveal the shifting mechanisms for CVT using a metal pushing V-belt, three shifting rates were introduced. The belt motion in the pulley groove was also characterized using mean coefficients of friction as parameters, which identify the slippage condition of the belt in the pulley groove. The experimental results showed that one of shifting rates, dR/ds was almost constant in the narrowing pulley regardless of both rotational speed and transmitted torque. Here, R is the belt pitch radius in the pulley and s is the length measured along the belt pitch line. This fact indicates that the shifting is primarily governed by elastic deformation of blocks of the belt. Power transmitting states were also evaluated using a different type of lubricating oil whose nominal coefficient of friction was higher than that for the conventional AT oil. The observed mean coefficients of friction vary due to oil although the basic response of the CVT unchanged.

At present, measurements of running resistance are conducted outdoors as a matter of course. Because of this, the ambient temperature at the time of the measurements has a considerable impact on the measurement data. The research discussed in this paper focused on the temperature characteristic of the tires and developed a new correction technique using a special rolling test apparatus. Specifically, using a tire rolling test apparatus that made it possible to vary the ambient temperature, measurements were conducted while varying the levels of factors other than temperature that affect rolling resistance (load, inflation pressure, and speed). Next, a regression analysis was applied to the data for each factor, and coefficients for a relational expression were derived, making it possible to derive a quadratic equation for the tire rolling resistance correction formula.

1 A new surface modification heat treatment technology called Wonder Process Craft which is different from plating and coating, was applied to the skirt section, which is the sliding surface of the piston in an internal combustion engine. This was intended to improve fuel economy and mechanical characteristics by reducing sliding resistance. In the application of solid lubrication, this treatment does not require the usage of binder, which was necessary for conventional coating, leading to the highest level achievable for the low sliding resistance effect inherent of solid lubrication. Since this treatment does not involve any change in significant dimensions, shapes, surface roughness, and so on, applying this treatment is easy. The persistence of the effect, productivity and recyclability of waste and emissions during treatment were also taken into account.

The effects of aerodynamic coefficients on handling response and flat ride were quantified. For handling response, the aerodynamic effect was quantified by analysis with linear representation and a two-wheel simulation model, using aerodynamic coefficients obtained from a full scale car wind tunnel. The correlation of aerodynamic coefficients and handling response with driving feel was also ascertained. Aerodynamic yaw moment and side-force were also converted to equivalent front and rear lift to standardize aerodynamic indexes and improve aerodynamic development efficiency. For flat ride, steady and unsteady aerodynamic effects were quantified by analysis with a two-degree-of-freedom mass-spring-damper simulation model and aerodynamic coefficients obtained from a 35% scale model wind tunnel and towing tank test. Unsteady aerodynamic force occurrence mechanism was ascertained by unsteady CFD using dynamic mesh.

When fluctuations in the speed of rotation of the drive pulley are transmitted to the driven pulley via the metal V-belt, the transmitted fluctuations become attenuated as friction force approaches a state of saturation. The research discussed in this paper focused on these fluctuations in the speed of rotation and developed an index for the slip state between the belt and the pulleys. The drive and driven pulleys were regarded as a one-dimensional vibrating system connected by elastic bodies, and changes in the state matrix of the system were focused on. It was determined that when all of the eigenvalues in this state matrix become real numbers, slip speed between the belt and the pulleys increases sharply. A method was proposed of estimating this behavior of the eigenvalues from changes in the speed of rotation of the drive and driven pulleys, and indexing the current slip state.

5 belt wind tunnels are the most common facility to conduct the experimental aerodynamics development for production cars. Among aerodynamic properties, usually drag is the most important development target, but lift force and its front/rear balance is also important for vehicle dynamics. Related to the lift measurement, it is known that the “pad correction”, the correction in the lift measurement values for the undesirable aerodynamic force acting on wheel belt surface around the tire contact patch, must be accounted. Due to the pad correction measurement difficulties, it is common to simply subtract a fixed amount of lift values from measured lift force. However, this method is obviously not perfect as the pad corrections are different for differing vehicle body shapes, aerodynamic configurations, tire sizes and shapes.

This paper describes the oil-film bearing analysis simulation was utilized for the optimization of pin boss form which reduces a piston-pin noise. It is clear from the mechanism analysis of the piston-pin noise which is the last research that an oil-film flow inside a pin boss is an important factor for pin noise reduction. So, in this research, the oil-film simulation of the piston-pin-boss bearing part was performed using oil-film bearing analysis tool. After setting up the simulation conditions of the oil-film bearing part so that actual pin behavior and high correlativity might be shown, a parameter, effective hydrodynamic angular velocity, and an oil flow rate of change suitable for evaluation of a pin noise were found out. The pin noise in semi floating piston was reduced to the same level as full floating type by applying pin boss form to which each evaluation parameter becomes the optimal to a piston.

Designing a lightweight and durable engine is universally important from the standpoints of fuel economy, vehicle dynamics and cost. However, it is challenging to theoretically find an optimal solution which meets both requirements in products such as the cylinder head, to which various thermal loads and mechanical loads are simultaneously applied. In our research, we focused on “non-parametric optimization” and attempted to establish a new design approach derived from the weight reduction of a cylinder head. Our optimization process consists of topology optimization and shape optimization. In the topology optimization process, we explored an optimal structure with the theoretically-highest stiffness in the given design space. This is to provide an efficient structure for pursuing both lightweight and durable characteristics in the subsequent shape optimization process.

Currently, car bodies require further weight reduction in order to support increasing fuel economy requirements. An efficient way for light weight body design is to include body member size as a design variable in addition to part thickness. However it is currently difficult for finite element (FE) models to change member size even using current morphing techniques. To break through this challenge, a hybrid modeling approach was developed which combines shell and beam element representations of body structural members. The original member shell element thickness was decreased by 40%. Then the stiffness reduction caused by this change is offset by beam elements incorporated inside these members. These beams can represent the stiffness change due to new cross sectional dimensions or orientations without changing the original shell elements, thus avoiding modeling instabilities that can occur from morphing.

A multi-objective optimization model using a piston behavior simulation for the prediction of NV, friction and scuffing was created. This model was used to optimize the piston skirt form, helping to enable well-balanced forms to be sought. Optimization calculations, involving extended analyses and numerous design variables, conventionally necessitate long calculation times in order to achieve adequate outcomes. Because of this, in the present project data was converted into functions in order to help enable the complex piston skirt form to be expressed using a small amount of coefficients. Using the limit values for manufacturability and the degree of contribution to the target functions, the scope of design variables was restricted, and the time necessary for the analysis was significantly reduced. This has helped to enable optimal solutions to be determined within a practical time frame.

Since the operation of the powertrain system and the engine speed and torque are determined in the ECU in hybrid vehicles, control parameters in these vehicles are more sensitive to a variety of performance factors than those employed in conventional vehicles. The three performance factors acceleration performance, NVH and fuel consumption in particular are in a tradeoff relationship, the calibration of control parameters in order to satisfy these performance targets entail considerable development costs. Given this, it is possible to increase the efficiency of hybrid vehicle development by determining Pareto design solutions for the three performance factors via multi-objective optimization using CAE, and selecting target performance and control parameters based on these Pareto design solutions.

A technique was created to separate the contributions of combustion noise and mechanical noise to engine noise in the time domain in order to achieve efficient measures for enhancing the sound quality of combustion noise. There is an existing technique based on 1/3 octave band analysis that is known as a method for separating the contributions to engine radiation noise, but this technique cannot provide time-domain data. Therefore, the author has proposed a technique that separates engine radiation noise into combustion noise and mechanical noise in the time domain by finding the combustion noise for each cylinder and calculating its structural response function by considering its real and imaginary components. Results of analysis of actual engine radiation noise with this technique confirmed that combustion noise, which is characterized by strong pulsation, and irregular mechanical noise can be separated in the time domain with good precision.