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High frequency wind noise caused by turbulent flow around the front pillars of a vehicle is an important factor for customer perception of ride comfort. In order to reduce undesirable interior wind noise during vehicle development process, a calculation and visualization method for exterior wind noise with an acceptable computational cost and adequate accuracy is required. In this paper an index for prediction of the strength of exterior wind noise, referred to as Exterior Noise Power (ENP), is developed based on an assumption that the acoustic power of exterior wind noise can be approximated by the far field acoustic power radiated from vehicle surface. Using the well-known Curle’s equation, ENP can be represented as a surface integral of an acoustic intensity distribution, referred to as Exterior Noise Power Distribution (ENPD). ENPD is estimated from turbulent surface pressure fluctuation and mean convective velocity in the vicinity of the vehicle surface.

In this study, a new practical design method (tool) for engine sound quality in a car interior is proposed. The tool can automatically create the target interior sound using the psychoacoustic index ‘powerfulness’ based on subjective tests. Moreover, it can calculate the intake noise characteristic to create the target interior sound and select the suitable intake specification from the prepared database. By using this method sound engineering can be easily and effectively carried out without manufacturing an experimental car.

Statistical Energy Analysis (SEA) is a promising tool for developing an efficient sound package design for reducing airborne interior noise at high frequencies. The optimal sound package, however, is not directly predicted by using the SEA vehicle model alone and therefore requires parametric studies of sound package configurations. This paper describes an effective method for using SEA modeling to achieve the desired interior noise level targets. A mathematical model, expressed by one equation, is derived on the assumption that the directions of the power flows are known in the SEA model. This equation describes the relationship between sound package properties and the resulting interior noise level. Using the relationship between weight and performance of sound package, an efficient configuration can be determined. The predicted sound pressure level of the vehicle interior with the optimized sound package correlated well to the experimental data for the case presented in this paper.

Brake squeal is a phenomenon of self-induced vibration of the brake components during braking. There are many kinds of brake squeal cases whose mechanisms require acting on a various number of potential root causes. Brake squeal phenomena can be generally separated into 2 main mode types related to the direction of disc vibration involved: in-plane mode and out-of-plane mode. For out-of-plane mode, a number of existing countermeasures can be potentially applied after characterization of the squeal occurrence condition by direct experiment or simulation analysis[1,2,3,4]. However, as there are many possible mechanisms and root causes for the in-plane modes[5,6,7,8,9,10,11,12,13], it is generally necessary to perform a detailed analysis of the vibration mechanism before implementing a countermeasure.

Whinning gear noise(final gear noise), one of the causes for automobile interior noise is due to the exciting force of final gear kit and as a general countermeasure for this problem, a reduction of resonance level in transfer system and better meshing of gears have been utilized. However,vibration characteristics of final gear unit have not been considered much in this case. Authors have executed impacting test on final gear unit and confirmed its vibration characteristics. Based on this fact,vibration model consisting of bearings and gears spring system was constructed to evaluate vibration characteristics of final gear unit along with the results obtained from final gear unit of front engine,rear drive passenger car.

To analyze chain noise which occurs in transfers using silent chain, analysis considering the energy of the noise source is effective. We can simulate chain noise by calculating a dimensionless coefficient of “chain noise energy” consisting of two contributing factors: the energy of the collision when the chain meshes with the sprocket, and fluctuation in the chain speed.

A method for applying soap film geometry to an automobile body structure has been developed. Its curved surface reduce both interior noise and damping material application because of its high rigidity and uneven deformation mode. This paper demonstrates these mechanism, benchmarks their performance with conventional flat and bead panels and presents an application to the floor panel of an automobile body.

In diesel engines with a straight intake port and a lipless cavity to restrict in-cylinder flow, an injector with numerous small-diameter orifices with a narrow angle can be used to create a highly homogeneous air-fuel mixture that, during PCCI combustion, dramatically reduces the NOX and soot without the addition of expensive new devices. To further improve this new combustion concept, this research focused on cooling losses, which are generally thought to account for 16 to 35% of the total energy of the fuel, and approaches to reducing fuel consumption were explored. First, to clarify the proportions of convective heat transfer and radiation in the cooling losses, a Rapid Compression Machine (RCM) was used to measure the local heat flux and radiation to the combustion chamber wall. The results showed that though larger amounts of injected fuel increased the proportion of heat losses from radiation, the primary factor in cooling losses is convective heat transfer.

One primary result of the reduction of platinum group metals (PGM) within a catalytic converter is the decline in NOx conversion efficiency. This paper hypothesizes that the primary factor of this decline to be hydrocarbon (HC) poisoning. To maintain high NOx conversion efficiency as the PGM reduces, Rh activation improvement becomes significant to overcome the HC poisoning. Analysis of the Rh deterioration mechanism found that it is effective to separately arrange Rh and CeO2 on the converter, avoiding the Rh deactivation. By this improvement, we improved the catalyst activity at less than 25% of the original Rh loading.

A molded headliner made from polypropylene, which we developed for the first time in the world, was adopted in May 1987 for TOYOTA COROLLA. The new material with high stiffness and light weights, has a sandwich structure consisting of PP-sheets and a PP-foam sheet. We have thus succeeded in the production of the new headliner in which each layer is laminated without any adhesive. A unique resin used for PP-sheets as surface skins was developed with high impact, thermal and fire resistances. Further, a PP-form core sheet with soft-feel and good moldability was also developed. As a result, we established proper conditions of molding this material and succeeded in producing stable superior parts with high quality and short cycle-time. Finally new molded headliner is comparable to the suspended type headliner in respect to weight and production cost.

The new P710 hybrid transaxle for a mid-size 2.5-liter class vehicle was developed based on the Toyota New Global Architecture (TNGA) design philosophy to achieve a range of desired performance objects. A smaller and lighter transaxle with low mechanical loss was realized by incorporating a new gear train structure and a downsized motor. The noise of the P710 transaxle was also reduced by adopting a new damper structure.

When vehicles run on the flooded road, water enters to the engine compartment and sometimes reaches the position of the air intake duct and electrical parts and causes the reliability problems. Numerical simulation is an effective tool for this phenomenon because it can not only evaluate the water level before experiment but also identify the intrusion route. Recently, the gap around the engine cooling modules tends to become smaller and the undercover tends to become bigger than before in order to enhance the vehicle performance (e.g., aerodynamics, exterior noise). Leakage tightness around the engine compartment becomes higher and causes an increase of the buoyancy force from the water. Therefore the vehicle attitude change is causing a greater impact on the water level. This paper describes the development of a water level prediction method in engine compartment while running on the flooded road by using the coupled multibody and fluid dynamics.

Continuously variable transmission (CVT) and hybrid systems, which have metal belts and electrical units not found in conventional transmissions, are susceptible to extremely High Frequency belt and electromagnetic noise between 5 to 10 kHz. The evaluation and reduction of high frequency (HF) noise of 5 kHz and more is therefore a critical point for improving the quietness of vehicles installed with such systems. This article describes new sound source search technology capable of identifying sources of noise up to 15 kHz in the vehicle interior. Unlike conventional beamforming methods, this new system uses an improved microphone array provided with additional acoustic material. This article outlines the development of the system and its application to sound source identification of HF noise in a hybrid vehicle.

In this paper, the authors introduce the spark plug for misfire detection system by ion current. In order to realize high accuracy misfire detection, the signal of ion current must be larger than that of noise. For maintaining ion signal in all designed lifetime, the configuration and initial condition of spark position are derived by an experiment and consideration about degradation in use. Additionally, the cause of noise is determined by an observation and a theoretical study, and we indicate the method to inhibit noise efficiently. Finally, effect of the methods found by these two approaches is confirmed with an engine, and we propose specifications of spark plug satisfying the condition that realize high accuracy detection by ion current.

In order to optimize air-fuel mixture formation in a small DI diesel engine, studies were conducted into the effects of combustion chamber shape and fuel spray impingement. Based on the findings of these studies, the shape of the combustion chamber was modified to induce complex air motion with high turbulence and fuel injection was carefully controlled to achieve optimum impingement intensity. As a result, the mixture formation process was greatly improved with a consequent gain in terms of engine performance. To clarify the reasons for this improvement in combustion, a three-dimensional calculation of the in-cylinder air motion was made. The behaviour of the spray and flame was observed using an endoscope. The new combustion system, named TOYOTA Reflex Burn system (TRB) thus developed has been adopted in production engines since August 1988.

It is well known that pilot injection is an effective method of reducing diesel knock noise during idling, but no actual system has as yet been commercially produced. With the objective of developing a practicable pilot injection device, simulations were conducted of various simple mechanisms in order to determine the best specifications and analyze the fuel injection characteristics. Based on these results, a chamber expansion type pilot injection device, which enables the injection pump pressure chamber volume to be increased at a given moment during the fuel compression stroke, has been developed and has been found to remarkably decrease knock noise during cold idling. An investigation into the effects of this device on output power, exhaust emissions, cold startability and durability revealed that it is eminently suitable for practical application.

Low frequency interior wind noise is typically dominated by underfloor flow noise. The source mechanisms are fluctuating surface pressure loading from both flow turbulence and acoustic field levels developed in the semi-reverberant cavity between floor and road. Previous studies have used computation fluid dynamics (CFD) to estimate the aero-acoustic loading applied to a vibro-acoustic model, which is then used to predict the transmitted interior wind noise. This paper reports a new perspective in two respects. First it uses novel surface pressure microphone arrays to directly measure the underfloor aero-acoustic loading in the wind tunnel. Second, it considers two different underfloor aerodynamic configurations - with and without lightweight aero cover panels, which are installed primarily to reduce aerodynamic drag.

This paper describes a new method for objective evaluation of wind noise in the passenger compartment of a car. The loudness and direction of noise in each frequency band can be estimated by performing analyses based on human hearing properties. Therefore, those wind noise components that are annoying to the passengers or those wind noise components whose source location can be determined by the human listener can be identified objectively. Furthermore, the total loudness of wind noise can be estimated quite precisely by adding the loudness of the frequency bands for noise emanating from the direction of the side window.

It is difficult to improve tire cavity noise since the pressure of cavity resonance acts as a compelling force, and its low damping and high gain characteristics dominate the vibration of both the suspension and body. For this reason, the analysis described in this article aimed to clarify the design factors involved and to improve this phenomenon at the source. This was accomplished by investigating the acoustic coupling vibration mode of the wheel, which is the component that transmits the pressure of cavity resonance at first. In addition, the vibration characteristic of suspension was investigated also. A speaker-equipped sound pressure generator inside the tire and wheel assembly was developed and used to infer that wheel vibration under cavity resonance is a forced vibration mode with respect to the cavity resonance pressure distribution, not an eigenvalue mode, and this phenomenon may therefore be improved by optimizing the out-of-plane torsional stiffness of the disk.

With advancement of aeroacoustic wind tunnels and CAE technology, aeroacoustic cabin noise in steady flow has been improved. On the other hand, passenger comfort is also impacted by aeroacoustic noise in unsteady flow. There have been comparatively few studies into this area, and the mechanism remains unclear. Considering the future proliferation of autonomous driving, drivers will pay more attention to cabin noise than previously, and aeroacoustic noise is expected to become more prominent. Thus, the reduction of fluctuating aeroacoustic noise is important. Most of the previous research relied on road tests, which don’t provide reproducible conditions due to changing atmospheric and traffic conditions. To solve these problems, research using devices that generate turbulence are being conducted. However, the fluctuations of flow generated in previous studies were small, failing to simulate on-road conditions sufficiently.