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A very difficult problem exists regarding windshield shape, and that is to create a balance between aerodynamics and optical distortion. To assist in solving this problem, this study, concerning the characteristics of visual perception for the optical distortion when drivers receive visual information through a windshield, was carried out. In this study, the windshield area was divided into 4 zones from the viewpoints of the level of drivers' fixation frequency and types of objects observed. Distortion was defined as the gap angle ( distortion angle ), which crossed the lines of a grid board with and without a windshield, and distortion angles were measured on a total of 4 windshields. Four drivers indicated areas in each windshield in which they felt the area was distorted. As a result, the thresholds of optical distortion were shown as a function of the horizontal and vertical distortion angles by discriminatory analysis.

In the field of automotive body electronic control such as control of door locks, power windows, and wipers, there is a growing need of multiplexing communication to reduce the amount of wire harnesses. To meet this need, we developed a multiplexing communication protocol particularly suited to the body electronic control. Based on the developed protocol, we designed a communication control IC and a simple driver/receiver circuit with a few discrete components. The bus access method of the communication is the CSMA/CD with nondestructive bit arbitration, and its bit rate is 5 kbps. Its transmission media is a single wire. The communication IC has a multiplexing control block and a serial I/O block for an interface with a host CPU. It was fabricated using CMOS technology and has a chip of 2.6mm x 3.0mm in size that contains about 5,000 transistors. The driver/receiver circuit consists of one transistor, one capacitor and several resistors.

Development of a new battery system for Toyota Estima Hybrid, the world's first minivan hybrid vehicle, has been completed. The battery pack that consists of 30 nickel metal hydride battery modules is compactly arranged under the 3rd seat in the cabin along with components such as the battery cooling blower and the ducts. This arrangement was designed in consideration of user's vehicle use, passengers' comfort and efficient battery-cooling performance.

Transmission error is the main cause of gear noise in automobile transmissions, and recently can be estimated by numerical analysis [1]. First, in this report, we establish the accurate numerical analysis of transmission error by using FE analysis and Hertz's contact analysis of gear tooth stiffness. Secondly, on the basis of the established numerical analysis, we develop a new tooth flank form to reduce transmission error. The new tooth flank form aims to ensure the coincidence of meshing stiffness at all meshing positions. Finally, a validation test using an experimental prototype is performed, and we confirm that the estimated effect by the new tooth flank form has been obtained.

To meet the requirements for higher horsepower and torque as well as lower fuel consumption and emissions, we have developed a new “Intelligent Variable Valve Timing (VV-i)” system. It gives continuously variable intake cam phasing by up to 60 degrees crank angle (CA) . This system not only increases WOT output by optimizing intake valve closing timing but also reduces fuel consumption and NOx/ HC emissions under part load by increasing intake and exhaust valve overlap on 4 stroke Spark Ignited engines. VVT-i has been applied to optimize a new 3-liter inline 6 engine for higher torque and at the same time better fuel economy with continuous and wide-range cam phasing.

A new experimental method, that enables to estimate the body and driveline sensitivity to unit transmitting error of a hypoid gear for automotive rear axle gear noise, has been developed. Measurements were made by exciting the tooth of the drive-pinion gear and that of the ring gear separately using the special devices designed with regard to simulation of acceleration and deceleration. The characteristic of this method is to estimate the forces at the contact point of the gears. Estimation of these forces is carried out under the condition that the higher stiffness is provided by the tooth of the drive-pinion gear and that of the ring gear, compared with the stiffness of the driveshafts and that of the propeller shaft etc., and relative angular displacement of the torsional vibration between the teeth of the drive-pinion gear and those of the ring gear is constant.

A discomforting noise can sometimes be heard in a vehicle passenger compartment during acceleration which can be annoying to passengers. We call this noise a “rumbling noise”. A detailed study of the rumbling noise spectrum has clarified the generating mechanism of the rumbling noise and the relation between the spectral structure and the tone. In order to analyze the rumbling noise, we simulated it with electrically synthesized noise. This method showed that at the times when the noise is heard there are always more than three discrete harmonics which are half an order harmonics of the engine revolution. The sensation of discomfort depends on the phase, frequency and magnitude of each frequency component. To evaluate the noise quantitatively, we also analyzed the shape of the time domain noise envelope. The envelope shape has a good correlation with the feelings of discomfort.

Brake squeal is caused by dynamic instability, which is influenced by its dynamic unstable structure and small disturbance of friction force variation. Recently, FE Analysis of brake squeal is applied for brake design refinements, which is based on dynamic instability theory. As same as the refinement of brake structure is required for brake squeal reduction, the refinement of pad materials is also required for brake effectiveness and brake squeal reduction. It is well known that friction film, which is composed of polymers like phenol formaldehyde resin and so on, influences for friction coefficient. Therefore it is expected that the refinement of polymers in pad materials enable higher brake effectiveness and less brake squeal. In this paper, Molecular Dynamics is applied for the friction force variation of polymers in pad materials. The MD simulation results suggest the reduction method of friction force variation of polymers.

A new method to predict low-frequency brake squeal occurrence was developed and guidelines for its elimination were formulated. First, a characteristic of the phenomenon was investigated using a simplified three-degree-of-freedom system model to obtain guidelines for squeal elimination, such as the natural frequency ratio of the brake rotor and caliper, an equivalent mass ratio of the brake rotor and caliper and the natural frequency and damping coefficient of the dynamic absorber. Then, a practical finite element model of the disk brake system was developed using Substructure Synthesis Method for design stage predictions. Finally, the usefulness of this method was confirmed by experimental validation.

It is well known that disc brake squeal is often caused by high friction coefficient pad materials. Disc brake squeal is caused by dynamic unstable system under small disturbance of friction force variation. Today, disc brake squeal comes to be simulated by FEA, but it is very difficult to put so many dynamic unstable solutions into stable solutions. Therefore it is very important to make it clear the influence of friction force variation. This paper describes a study on trigger of disc brake squeal generation. First, the development of experimental set-up for disc brake squeal basic research and experimental results are described. Second, the equation of motion in disc brake squeal is derived and the vibration induced by small disturbance are analyzed. Furthermore, kinetic energy increase per 1 cycle in minute vibration are calculated, which represents the influence of friction and wear between disc and pad with caliper.

In the field of automobile disk wheels, demands for aluminum wheels have been increasing for the reason of ride comfort and better appearance. And over 90 percent of luxurious passenger cars are equipped with aluminum wheels. This trend is spurred also by the demand for higher fuel efficiency for the cause of environmental protection, which calls for weight reduction of automobiles. This paper reports our research on manufacturing light-weight, high-quality aluminum cast wheels; covering the entire process from basic design to casting, and placing emphasis on the following three points. 1) Determination of optimum wheel configuration through computer simulation 2) Selection of optimum material composition 3) Optimization of the thin plate casting conditions Combination of the above technologies developed for the purpose of weight reduction resulted in the weight reduction of approximately 20% over the conventional aluminum wheels.

The effects of multiple-injection on exhaust emissions and performance in a small HSDI (High Speed Direct Injection) Diesel engine were examined. The causes for the improvement were investigated using both in-cylinder observation and three-dimensional numerical analysis methods. It is possible to increase the maximum torque, which is limited by the exhaust smoke number, while decreasing the combustion noise under low speed and full load conditions by advancing the timing of the pilot injection. Dividing this early-timed pilot injection into two with a small fuel amount is effective for further decreasing the noise while suppressing the increase in HC emission and fuel consumption. This is realized by the reduced amount of adhered fuel to the cylinder wall. At light loads, the amount of pilot injection fuel must be reduced, and the injection must be timed just prior to the main injection in order to suppress a possible increase in smoke and HC.

Porous material is used at the duct wall in order to reduce air resonance in the air intake duct. High frequency component in the intake noise is reduced by escaping of the air through the duct wall. The relation of attached position, the size and air permeability of the porous material to acoustic behaviors was cleared.

An active engine mount using a piezo actuator for a large vibrational amplitude is discussed. As a piezo actuator has a small displacement, the active mount requires a mechanism to increase the displacement of the piezo actuator to sufficiently counteract vibration. This paper describes in detail the construction of the prototype and the background theory from which the increase in displacement was achieved. Secondary, it describes a proving test performed on an experimental device that simulates the transfer of vibration from the engine to the chassis through the piezo active mounts. Finally it reports the decrease in floor vibration achieved when a piezo active mount was installed on an experimental vehicle.

It is well known and a common experience among drivers that controllability and stability of a car-trailer combination is affected when an articulated Heavy Goods Vehicle overtakes. In this paper, aerodynamic effects to a car-trailer combination when it is overtaken by an articulated HGV, have been analyzed experimentally using 1/20 scale models in wind tunnel, and a method to suppress this phenomenon has been investigated. The dynamic behaivor of a car-trailer combination is simulated by a simple mathematical model. The result shows that a car-trailer combination can be stable following the addittion of aerodynamic devices to each side of the vehicle. This simulated result is verified by the on-read test.

In recent years, a number of different Blind Spot Monitor (BSM) systems have become more and more popular in North American automotive market. The BSM system advises the driver of vehicles travelling in adjacent lanes when these vehicles are also in the driver's outside rearview mirror blind spots. Similarly, when the vehicle is backing up from a parking spot, cross-traffic vehicles can be in the driver's outside mirror blind spots. In this situation, the Rear Cross Traffic Alert (RCTA) system alerts the driver when the driver shifts the vehicle in the reverse gear and there are approaching cross-traffic vehicles. The benefits of RCTA system was presented by [1]. The RCTA alert studied in this paper is given by playing an audible sound and by flashing the outside mirror indicators. The RCTA and BSM systems share the same vehicle sensors and most of their vehicle components.

Technologies of 4WD chassis dynamometers (CHDY hereinafter) have advanced dramatically over the past several years, enabling 4WD vehicles to be tested without modifying their drive-train into 2WD. These advances have opened the use of 4WD-CHDY in all fuel economy and emission evaluation tests. In this paper, factors that influence the accuracy of fuel economy tests on 4WD CHDY are discussed. Fuel economy tests were conducted on 4WD CHDY and we found that most of the vehicle mechanical loss is the tire loss and that stabilizing the tire loss of the test vehicle is essential for the test reproducibility.

This paper presents a new method of predicting judder occurrence. In this method, the friction characteristics of the clutch, that is, the relationship between the slip speed and the friction coefficient, and torsional vibration characteristics of the drive line are both considered. Judder occurrence is judged by calculating complex eigen values of a torsional vibration model of the drive line considering the clutch friction characteristics. This method is applied to judder phenomena of automatic transmissions. Comparisons between calculations and experiments are shown. Studies of the influence of viscous damping coefficients of drive line units are also described.

The present paper describes an application of non-parametric shape optimization to disc brake squeal phenomena. A main problem is defined as complex eigenvalue problem in which the real part of the complex eigenvalue causing the brake squeal is chosen as an objective cost function. The Fre´chet derivative of the objective cost function with respect to the domain variation, named as the shape derivative of the objective cost function, is evaluated using the solution of the main problem and the adjoint problem. A selection criterion of the adoptive mode number in component mode synthesis (CMS), which is used in the main problem, is presented in order to reduce the computational error in complex eigenvalue pairs. A scheme to solve the shape optimization problem is presented using an iterative algorithm based on the H1 gradient method for reshaping. For an application of the optimization method, a numerical example of a practical disc brake model is presented.

Recently engine sound quality is becoming more noticeable as noise level in a vehicle passenger compartment has been decreasing. It is necessary to reduce such discomforting noise as rumbling noise in order to improve engine sound quality. This paper describes the experimental study to find out causes of rumbling noise in an engine structure and several investigations to reduce rumbling noise. Some new approaches have been introduced to evaluate the influence of an combustion impact, the movement of a crankshaft, timing of rumbling noise and so on. The result shows that the primary cause of rumbling noise is the movement of a crankshaft due to the impact of combustion and next is the vibration characteristics of the engine-transmission assembly (power plant). Finally superior engine sound quality is achieved by increasing counterweights and stiffness of a crankshaft and also by optimizing the spark advance and improving vibration characteristics of various engine parts.