Search Results

This report will introduce a new engine sound design concept and propose a design process. In sound design for automotive development of popular vehicles, it is common to seek to enhance the state of the existing marketed vehicle in order to meet further demands from customers. For standout models such as sports vehicles and flagship vehicles, sound design commonly reflects the sound ideals of the manufacturer’s branding or engineers. Each case has common point that the sound direction is determined by itself clearly. However, in this way, it is difficult to create abstract concept sound. Because it is no direction for the sound. Therefore, this paper examines ways to achieve a new sound that satisfies a sound concept based on an unprecedented abstract concept “wood”. The reason why sound concept is “wood”, it is the difficult to make as a new engine sound and good study to reveal usefulness of new sound design process.

Crank rumble is an amplitude-modulation of engine noise perceived inside a car. It is common under full load acceleration but not under part load acceleration, so could cause concern. Honda and Ricardo carried out a program of work to research methods to reduce the perceived (subjective) level of crank rumble inside a vehicle under part load acceleration. Transfer Path Analysis (TPA) is a method of predicting vehicle interior noise by separating sources (the engine) and transfer paths (the vehicle body). TPA was applied in the time domain to allow subjective assessment of the different contributors to the interior sound quality. Subjective assessment was performed by a panel of listeners, to avoid bias caused by individual opinions. This approach identified key contributors to the perceived crank rumble, and allowed targets to be set. Computer Aided Engineering (CAE) was used to study a range of modifications to the engine.

It is known that lean combustion is effective as one of the ways which improves thermal efficiency of a gasoline engine. In the interest of furthering efficiency, the use of leaner mixtures is desired. However, to realize robust lean combustion it is necessary to reduce combustion cyclic variation while managing the emission nitrogen oxides. In this study, combustion analysis was carried out focusing on cyclic variations of the heat release of lean combustion. Since the initial flame kernel growth speed has a great effect on the indicated mean effective pressure, laminar flame speed (LFS) around the spark plug was analyzed. Infrared absorption spectrophotometry was used for the measurement of a fuel concentration around the spark plug. Moreover, a LFS predicting formula, which can be used in an area leaner than before, was drawn from detailed chemical reaction calculation results, and the LFS around the spark plug was also calculated through the use of this formula.

This paper summarizes the piston pin noise mechanism and show the way to reduce noise level of semi-floating system. A mechanism of piston pin noise of semi-floating system was clarified by measurement of piston and piston pin behavior and visualization of engine oil mist around piston and piston pin. Piston and piston pin behavior was measured by accelerometer and eddy current type gap sensor with linkage system at the actual engine running condition. Engine oil behavior was visualized and measured its flow vector by Particle Tracking Velocimetry (PTV). For PTV, engine oil mist particle image was taken by high speed camera with fiber scope attached to linkage system. From themeasurement, it was cleared that engine oil doesn't reach to piston hole from undersurface of piston land and come rushing out from piston broach via groove. The result shows that lacking of engine oil between piston and piston pin makes noise larger.

In practical lean burn engines used to date, the use of a stratified air-fuel configuration, with a comparatively rich mixture in the vicinity of the spark plugs, has resulted in the stable combustion of an overall lean mixture. However, because a comparatively rich mixture is burned during the first half of combustion, NOx emissions are not reduced sufficiently. This research focused on a form of lean burn with homogeneous premixture that would be able to balance low NOx emissions with combustion controllability. It is widely known that homogeneous lean premixed gas has poor flame propagation characteristics. To determine the dominant cause of this, this study investigated the combustion properties of a single-cylinder engine while changing the compression ratio and intake temperature. As a result, the primary cause of combustion fluctuation, the abnormal cycle has a low TDC temperature compared to that of other cycles.

In automobile development, steering vibrations caused by engine excitation force and suspension vibration input from the road surface are a problem. The conventional method of reducing vibrations and thereby securing marketability has been to dispose a dynamic damper inside the steering wheel. The resonance frequency of a steering system varies for each vehicle developed (as a result of the vehicle size, the arrangement of the stiff members of the vehicle body, and the like). As a result, the individual values of dynamic dampers that are used with vehicles must be adjusted for each developed vehicle type. To address this problem, we have developed a new structure in which, rather than using a conventional dynamic damper, we disposed a floating bush on the Supplemental Restraint System (SRS) module attachment section and used the SRS module itself as the weight for the dynamic damper.

It is a well-known fact that the exhaust emission characteristics of hydrogen fueled engines are extremely good. The external mixture formation - a hydrogen fuel supply method - has the merit of practically zero NOx emission level in the lean mixture range with the excess air ratio λ set at 2.0 or greater as well as the merits of simple mechanism and easy operation. However, the practical use of such engines has been impeded partly due to the occurrence of backfire where the excess air ratio λ is 2 to 3. In order to allow the practical use of the hydrogen fueled engines with external mixture formation, it is vital to determine the causes of backfire and to establish proper countermeasures. It is found through a recent study conducted on the mechanism of backfire that the abnormal electric discharge in the intake stroke is one of the causes of backfire.

Generally, pass-by noise levels measured outdoors vary according to the influence of weather conditions, background noise and the driver’s skill. Manufactures, therefore, are trying to reproduce proving ground driving conditions on a chassis dynamometer. The tire noise that occurs on actual road surfaces, however, is difficult to reproduce in indoor tests. In 2016, new pass-by noise regulations (UN R51-03) will take effect in Europe, Japan and other countries. Furthermore, stricter regulations (2dB) will take effect in 2020. In addition to the acceleration runs required under current regulations, UN R51-03 will require constant speed runs. Therefore, an efficient measurement methods are necessary for vehicle development. To solve the above mentioned issues, an indoor evaluation system capable of reproducing the tire noise that occurs on road surfaces has been developed.

Seat vibration when a vehicle is idling or in motion is an issue in automobile development. In order to reduce this vibration, dynamic damper or inertia mass is widely used. These countermeasures increases vehicle's weight and causes bad fuel-efficiency. Some new ways to reduce the vibration without weight increase are needed. One of that is the floating seat. Seat vibration has been reduced by controlling seat resonance frequencies. In order to control resonance frequency, the structures of the seat-mounting unit are replaced with floating structures using rubber bushings. It was demonstrated that partially replacing the mounting unit with floating structures makes it possible to control the resonance frequencies of the entire seat. The issue of balancing vibration reduction with strength and durability and crash safety performance caused by the fitting of rubber bushings to the seat-mounting unit was addressed using stopper structures optimized for each type of input.

This paper discussed the sound quality which assumed important factor in the development of outboard engines in the 183 to 257 kW class in the future. Many kinds of industrial product development dealt with sound quality, and there were many examples using sound quality index adapted customer requirements or products usage. In case of outboard engine development, there were examples of noise reduction and compliance with noise regulations, but there was almost no example of sound quality development. This research proceeded a questionnaire survey of 90 boat owners who were listening to several cruising engine sounds in main market, US. From this result, authors discussed customer trend and extracted 3 sound quality indexes, luxury, deep and sporty, which were demanded in our target class. Next step was that authors made simulation sounds referring 3 sound quality indexes to verify customer’s trend.

In order to efficiently enhance engine sound quality under acceleration, the authors have developed an evaluation method for primary judgment of the sound quality of engine combustion noise at the stage of advanced engine development before the prototype vehicle is built. This method is an application of an existing method for evaluating the sound quality of engine combustion noise in vehicle interiors to the evaluation of noise and vibration at an engine acoustic test bench. In this method, it is necessary to consider the air-borne and the structure-borne components separately. The analysis procedure for the air-borne component is as follows. First, the sound pressure at a point 1 m away from the engine and the in-cylinder pressure of each cylinder are measured simultaneously in a semi-anechoic engine dynamometer test chamber. Next, the signal correlated with engine combustion is extracted from the measured sound pressure using the time domain combustion noise separation method.