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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.

Oil film thickness is one of the most important issues for optimization of bearing design. A technique has been developed to measure oil film thickness by noting the change in capacitance between the shaft and a thin-film electrode of several micrometers thickness formed on the surface of a bearing. The authors applied this technique to the main journals of an automobile engine and measured the oil film thickness up to maximum speed and full load. The oil film thickness became thinner with increased engine load, and then turned thicker with increased engine speed.

The finite element method (FEM) is effective for analyzing brake squeal phenomena. Although FEM analysis can be used to easily obtain squeal frequencies and complex vibration modes, it is difficult to identify how to modify brake structure design or contact conditions between components. Therefore, this study deals with a practical design method using sensitivity analysis to reduce brake squeal, which is capable of optimizing both the structure of components and contact conditions. A series of analysis processes that consist of modal reduction, complex eigenvalue analysis, sensitivity analysis and optimization analysis is shown and some application results are described using disk brake systems.

The design of the newly developed Toyota AZ series 4 cylinder engine has been optimized through both simulations and experiments to improve heat transfer, cooling water flow, vibration noise and other characteristics. The AZ engine was developed to achieve good power performance and significantly reduced vibration noise. The new engine meets the LEV regulations due to the improved combustion and optimized exhaust gas flow. A major reduction in friction has resulted in a significant improvement in fuel economy compared with conventional models. It also pioneered a newly developed resin gear drive balance shaft.

The Vapor Reducing Fuel Tank System (Bladder Tank System) using a flexible plastic membrane (Bladder Membrane) was newly developed in order to reduce the amount of vaporized gasoline in a steel fuel tank. This Bladder Membrane is flexible to expand in proportion to a fuel volume and prevents the permeation of the vaporized gasoline. As a result of our initial study for various materials, we decided to apply a multi-layer plastic material which could achieve both low fuel permeability and good flexibility. This multi-layer material consists of polyethylene(PE) for structural material and polyamide(PA) for low permeability. The modulus of the PE needs to achieve a sufficient flexibility in order to keep the movement of the membrane. While PA material must have not only low fuel permeability but also strong adhesion with the structural material of PE. We also clarify the membrane design to keep a good flexibility and to reduce a strain.

In preparation for compliance with California's SULEV standard and Euro STAGE 4 standard, which will take effect in 2002 and 2005, respectively, we have developed a laminated planar oxygen sensor. The developed sensor has the following characteristics: high thermal conductivity and superior dielectric characteristic, due to direct joining of the heater element alumina substrate and the sensor element zirconia electrolyte; low heat stress at temperature rise, due to optimized heater design; superior sensor protection from water droplets, and improved sensor response, due to optimized arrangement of intake holes in the sensor cover. With these characteristics, the developed oxygen sensor can be activated in 10 seconds after cold start. This report describes the technologies we used to develop the early-activation oxygen sensor.

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.

A highly reliable all-mechanical air bag system has been developed with a production cost lower than the electrical air bag system. All components, such as the bag, inflator and sensor are integrated into the steering wheel. Regarding the sensor design, we first discussed the requirements of the sensor to optimize the driver's protection, and then we designed it using a simulation method. We have confirmed by crash tests that this method is correct, and have found that this system is effective for reducing facial injuries.

This paper analyzes the vibration of open-top cars known as lateral shake. The characteristics of the phenomenon were identified by means of road tests and a test method called the shake test was devised to reproduce these characteristics in order that the respective roles of the suspension, body and engine could be determined. On the basis of the analysis findings, a simple but practical simulation model was realized and used to investigate various methods of reducing lateral shake. The simulations indicated that although changing the natural frequency of the suspension has little effect, increasing the natural torsional frequency of the body and/or utilizing the engine as a dynamic damper results in a significant improvement. Further experiments conclusively demonstrated that by optimizing the body structure in accordance with FEM analysis results and optimizing the spring constant of the engine mounts, the level of lateral shake can be halved.

The SEA model of wind noise requires the quantification of both the acoustic as well as the turbulent flow contributions to the exterior pressure. The acoustic pressure is difficult to measure because it is usually much lower in amplitude than the turbulent pressure. However, the coupling of the acoustic pressure to the surface vibration is usually much stronger than the turbulent pressure, especially in the acoustic coincidence frequency range. The coupling is determined by the spatial matching between the pressure and the vibration which can be described by the wavenumber spectra. This paper uses measured vibration modes of a vehicle window to determine the coupling to both acoustic and turbulent pressure fields and compares these to the results from an SEA model. The interior acoustic intensity radiating from the window during road tests is also used to validate the results.

The muffler layout in the exhaust system has been optimized for the attenuation of exhaust noise which has not been studied much to this date. As a result, “Exhaust Manifold Muffler” has been developed. This unit is capable of efficiently muffling the primary and secondary componemts of the engine explosion stroke noise. Such task is achieved without deterioration of engine performance by allocating the volume at the junction of the exhaust manifold branch pipes. Acoustic characteristics of “Exhaust Manifold Muffler” have been analyzed by FEM and experimental methods, which have shown that not only does the volume placed at the junction of the exhaust manifold branch pipes work as a conventional muffler, but also prevents the exhaust manifold branch pipes from amplifying exhaust noise. This is the reason why “Exhaust Manifold Muffler” can muffle more efficiently than the conventional muffler.

Finite element aodels have been developed to analyze drive line and suspension vibration. For the analysis of booming noise, we have addressed the optimization of the differential gear carrier mounting system by using a virtual system and realization of it considering many constraints. To reduce the differential whine noise, a simulation method considering the transmitting error of the differential gear was applied. And we have approached for the subtle arrangements of many structural resonances with detail research of the drive line and suspension. For the reduction of road noise, we adopted the approach of shifting the node of the rear suspension member mode.

A practical shape optimization technique is presented. We employed the basis vector method to parameterize the shape of the structural domain that is usually discretized by the finite element method. VMA/GENESIS software, the optimization system with finite element analysis, sensitivity analysis, and numerical optimization capabilities, was used for this study. Various design problems such as body, chassis, and engine parts design are solved to demonstrate the effectiveness and the robustness of the present approach for automotive applications.

In order to reduce the interior noise of a vehicle with a four-cylinder engine, investigations were made using finite element and vector methods, acoustic intensity testing and holography technique. The investigation resulted in inclination of the engine mounting, design changes to the front suspension member, a shock absorber engine mounting, structural modifications to reduce body panel vibration and a new engine mounting to insulate high frequency engine vibration.

In a two-loudspeaker stereophonic reproduction system of a passenger car, the geometrical configuration of the right and left loudspeakers has the disadvantage of being asymmetrical to the listener. For this system, we have made both theoretical and experimental verifications of the effects of strongly reflected sounds on the sound pressure level difference and phase difference between two ears which determine the location of sound image in a small compartment of a passenger car. On the basis of these verifications, we have developed a new sound localization control system. With this system, acoustical effects such as sound expansion and ambience have been greatly improved in a passenger car. In this system, input signals to the loudspeakers are controlled so that the sound image produced by the loudspeaker nearer to the listeners may acoustically move so as to position itself symmetrically with the other loudspeaker with regard to the listeners.

This paper describes an objective evaluation method for the engine sound quality in a car interior during acceleration. Two principal factors, pleasantness and raciness, of the engine sound quality were found with a subjective evaluation test in a laboratory. Psycho-acoustic indexes corresponding to these factors were revealed by investigating the correlation among subjective ratings and acoustic characteristics. The index of raciness was originally proposed for the assessment of sound that makes driving fun when the sound is emphasized. We propose that the design of engine sound is required with consideration of the balance between pleasantness and raciness.

One of the key elements of vehicle safety requires a constantly uninterrupted visible view especially during unexpected weather conditions. Our present development of a light reflection type rain sensor is a key device of our automatic windshield wiper system. The design concept of the sensor is based on the quantification on both detected rainfalls and wiping modes in order to match the wiping mode in an operator's mind by optimizing the optical sensing system and establishing an algorithm for controlling wiping. In addition, auto-initialization of the system has been achieved first in the world.

This paper presents an improvement in the accuracy of NOx sensors at high NOx concentration regions by optimizing the manufacturing process, sensor electrode materials and structure, in order to suppress the deterioration mechanism of sensor electrodes. Though NOx sensors generally consist of Pt/Au alloy based oxygen pump electrodes and Pt/Rh alloy based sensor electrodes, detailed experimental analysis of aged NOx sensors showed changes in the surface composition and morphology of the sensor electrode. The surface of the sensor electrode was covered with Au, which is not originally contained in the electrode, resulting in a diminished active site for NOx detection on the sensor electrode and a decrease in sensor output. Theoretical analysis using CAE with molecular dynamics supported that Au tends to be concentrated on the surface of the sensor electrode.

The noise generation mechanism of a direct-acting valve train such as used in sporty and luxury cars was determined for both mechanical and hydraulic tappets through measurements of sound pressure levels and vibrations and the use of computer graphics to observe actual valve and tappet movement. Two phenomena were clarified: chatter at low engine speeds and a mechanical noise at high engine speeds. Further experiments established that the noise of a mechanical tappet can be greatly reduced and its tonal quality improved by optimizing the cam profile and by increasing the acoustic damping ratio of the tappet.