Masao Ishihama

Optimum design method for hydraulic engine mounts

This paper shows the optimum design method of the hydraulic engine mount. This engine mount has been developed recently to significantly reduce the vibration in car bodies emitted by engines. The resonance peak of conventional engine-mount system can not be suppressed sufficiently. Hydrauric engine mounts are able to suppress the resonance peak by using the fluid reaction effect of the fluid enclosed in the mount. The design was recently modified by trial and error experimentation. Du to the lack of information on a suitable design, its ability had not been effectively demonstrated. In this paper, after analyzing the mount, its optimum design formula is obtained in a very simple and useful manner similar to the design equation of dynamic absorbers, The effectiveness of the formula is confirmed theoretically and experimentally.

Training students on the TRIZ method using a patent database

The objective of this research is to develop a better method of teaching invention to young students with little engineering experience. The project used for this purpose was aimed at: 1) the creation of a new engine subsystem for better automobile fuel economy and 2) a feasibility study of a variable compression system. This project was conducted as an undergraduate thesis by three mechanical systems engineering students. Engineering design was chosen as the process tool for this project. At the conceptual design stage, students tried the TRIZ (Russian Theory of Inventive Problem Solving) method. Though TRIZ gave abstract solutions to the students, they could not find specialised solutions because of their poor engineering knowledge base. To solve this situation, inventions appearing in past patents were used to complement their paucity of experience. By this method, the students were able to get to specialised solutions easily. After this training, they invented a new type of ski vibration test stand.

Optimum design method for hydraulic engine mount.

This paper shows the optimum design method of the hydraulic engine mount. This engine mount has been developed recently to significantly reduce the vibration in car bodies emitted by engines. The resonance peak of conventional engine-mount system can not be suppressed sufficiently. Hydrauric engine mounts are able to suppress the resonance peak by using the fluid reaction effect of the fluid enclosed in the mount. The design was recently modified by trial and error experimentation. Du to the lack of information on a suitable design, its ability had not been effectively demonstrated. In this paper, after analyzing the mount, its optimum design formula is obtained in a very simple and useful manner similar to the design equation of dynamic absorbers, The effectiveness of the formula is confirmed theoretically and experimentally.

Ultrasonic Wave Propagation Analysis for In-Process Monitoring of Stamping

The servo press has high potential for producing high precision mechanical parts. However, small gaps between dies and workpieces tend to exist even in servo press stamping, and the potential of the servo press has not yet been fully utilized. The reason for this is conventional presses do not have feedback control systems, and the lack of a suitable method of sensing contact information in real time causes deterioration in the accuracy of products. If slide motion could be controlled by contact information, the small gaps could be removed. To solve this problem, the authors have developed a method of monitoring the contact states between dies and workpieces during the stamping process. The method uses ultrasonic wave reflection and transmission at the contact surfaces and was proved to be able to monitor contact pressure by using a simple geometry experimental die apparatus. Finite-difference time-domain (FDTD) numerical simulation was conducted in this study to obtain better understanding of wave propagation through dies and workpieces. The results obtained from this FDTD simulation visualized wave propagation that could not be experimentally measured. Some of the major results obtained are as follows. 1) When a thin metal sheet is pressed between dies that have inclined stamping surfaces, ultrasonic elastic waves are reflected and transmitted multiple times. 2) Modal conversion occurs at the die-workpiece boundary in such a way that normal waves with an inclined incident angle are transformed into normal and shear waves. 3) Elastic waves sent out from an ultrasonic transducer are mixtures of normal waves with flat wave fronts along the propagation path axis, normal waves with circular or spherical wave fronts expanding from both sides of the transducer, and shear waves. These results brought about much useful information for setting ultrasonic transducers and analyzing collected signals.

Modeling High-Frequency Tire Tread Vibration as a Group of Traveling Bending Waves

Tire noise is one of the major causes of road traffic noise. The high-frequency component dominates tire radiation noise, which is caused by tire tread bending vibration excited by rough road surface textures. As a result of such complicated phenomena, including very complicated tread vibration modes in the high-frequency range, heavy damping, and non-periodic patterns of the road surface texture, the modal analysis approach may appear to have a low potential for analyzing this problem. Based on the above considerations, we attempted to model the tread vibration phenomenon as a group of traveling bending waves excited at an array of pavement chippings. By setting the tread shoulders as reflecting lines, the interference effect of diagonally propagating direct and reflected waves is clarified. The vibration propagation speed and decay rate were estimated through shaker tests. The shape of the probability distribution function of the chippings intervals affects the traveling wave patterns. These observations will help engineers to develop less noisy tires.Copyright

A study of an effective development process to improve the engine performance of the passenger car

This paper describes a new method for efficiently developing engines that have innovative technologies. The proposed method considers both technological and managerial aspects based on the empirical experiences of the authors. With respect to technology, a conceptual engine that represents the functions of the main engine was proven to reduce the risks that accompany the adoption of new technology. With respect to management, the placement of a powerful project leader to manage a matrix-type development organisation as well as parts suppliers was confirmed to be essential.

Development of Technologies for Eliminating High-Level Noise Emitting Vehicles on Japanese Roads

The purpose of the present study is to improve the on-street exhaust noise measurement technique for regulating vehicles that emit unacceptably large exhaust noise. The method under development uses racing operation of engines with a wide-open throttle on a standing vehicle. In contrast, the engine operation condition considered in the conventional on-street measurement technique considers operation at 75% of rated power followed by the throttle valve being released to its original position. The current regulation considers the maximum noise level during this engine operation condition. Accordingly, the engine is not loaded during testing. This loading condition provides unsatisfactory correlation between the exhaust noise level measured by the on-street method and the ISO vehicle acceleration noise under the wide-open throttle condition. The present paper reports the advantages of the proposed method as well as some important factors in the proper application of the newly proposed method. In the present study, we perform noise measurement along highways, a vehicle experiment in an anechoic chassis dynamometer, and computer simulations. The results revealed that the proposed on-street measurement method can be used to approximately determine the exhaust noise level during full acceleration for most vehicle types. In addition, the sensitivities of the measured noise levels for the testing conditions were clarified. The second item in this study is efficient engine speed measurement using exhaust sound signal only without electric wire harnessing. A survey of the measurement systems proposed by three different companies revealed that the measurement principles of two of these systems have potential application to on-street exhaust measurement. The last item investigated herein is better indices of exhaust noise evaluation. Loudness defined by ISO was found to be much better than the conventional dB(A) scale in terms of correlation with subjective evaluation results.Copyright

Tire Sound Quality Evaluation Tool Using Sound Synthesis With Physical Modeling

A computer aided tool for tire sound quality evaluation was developed. Automotive engineers can evaluate a tire structure by listening to synthesized sound that the tire would radiate when it rolls on a specific type of road surface. Among three kinds of tire sound, this study dealt with only the tire sound that radiates through its structural vibration caused by road surface texture excitation. The tool can be used on personal computers. To make it happen, tire sound radiation process is modeled into two parts. One is excitation. Tire deformation at the contact patch was calculated from road surface texture database by rolling contact analyses using multi-body dynamics simulation software. The model includes rolling tire structure model with contact compliance and simple suspension system for the wheel axle. Observation of the calculation results gives such an insight that excitation waveforms from road surface have prominent peaks that occur only at high peaks isolated from others, and do not have dips. This transformation process from road surface waveform to excitation is more accurate than tire envelope model and also not prohibitive considering today’s low-price computing power. The other process is tire structure vibration response. By limiting the usage of tire structure models just in representing over all vibration modal responses to road surface excitations in relatively low frequency range, a simple structural finite element model (FEM) was created. In this FEM, tire wall composite structures are modeled as assembly of solid elements with uniform material properties. The trick in using this FEM model lies in its boundary condition setting. By measuring vibration transfer functions from many points on a contact patch to tire tread and sidewalls, excitation in the middle of the contact patch was found to be blocked to travel to the sidewalls in higher frequency range due to the contact restriction on the periphery of the patch. This finding is essential in giving suitable boundary conditions to the FEM model and choosing the excitation points. To make the computing time minimum for synthesis, the vibration responses of the tire are represented by infinite impulse response (IIR) digital filter banks. The waveform obtained by applying the measured road texture waveforms to the IIR filter, was transferred to sound waves by the sound command of Matlab. By modifying the IIR filter, automotive engineers can judge the effect of tire structural design changes.Copyright

Motor Vehicle Exterior Sound Quality Improvement for Indoors

The objectives of this study are these three items. 1) To find better indices than dB(A) for representing annoyances caused by motor vehicle traffic noise along highways. 2) To find the frequency range of motor vehicle exterior noise that should primarily be controlled to achieve better indoor sound environment along highways. 3) To find suitable vehicle driving conditions for evaluating indoor sound environment. To obtain the desired results psycho-acoustic experiments were conducted. Firstly, sound samples were collected with microphones placed at such locations as on a sidewalk, in front of a small house and at the center of a room inside of the house. The number of test vehicles was fifteen, consisting of six motorcycles and nine passenger cars. The driving conditions were full acceleration and mild acceleration usually found in normal traffic flow. Secondly, semantic differentiation method was used. Ten pairs of adjectives were used to scale the impressions of each sound sample. Finally, physical characters of the sound samples and their subjective evaluations were compared. The results were obtained as follows. 1) Six sound samples got more uncomfortable impression at indoors. These sound samples were collected by vehicles with sport-type mufflers. 2) The samples that indoor sound quality is degraded than outdoor contain high power in low frequency range below 200 Hz. These low frequency components penetrate through the housing walls more easily than higher frequency components. 3) The degradation of comfort impression was found in mild acceleration conditions. The low frequency components of sound samples for mild acceleration are larger than those for full acceleration. Though the throttle is not fully open in mild acceleration, low engine speed generates low frequency components, and eventually increased indoor sound power in the frequency range. The conclusions drawn from these results are, 1) Indoor sound samples should be included for evaluating sound environment along highways. 2) Mild acceleration is a better driving condition for evaluating indoor sound environment along highways. In this condition, very low engine speed causes low frequency component emission that penetrate into housing more than in heavy accelerating conditions. 3) Engine exhaust systems that emit very loud low-frequency components should be focused upon in regulating traffic noise. 4) Extensive collection and analysis of housing sound insulation, absorption and resonance data along highways are necessary for further investigations. 5) Better psycho-acoustic experiment methods should be developed for investigating sound context effects on panelists.Copyright

Vibro-Acoustic Study of Flat Panel Speakers for Better In-car Entertainment

One potential method by which to realize better acoustic in-car entertainment with a minimum of space is to adopt very thin Flat-Panel Speakers (FPSs), which use a combination of an array of coils printed on a flexible thin plastic film and permanent magnets. In the present report, the optimal panel material was investigated through experimental modal analysis. The optimal driving unit placement over the board was then determined using FEM based modal analyses. Finally, structural modifications to the sound radiating board in order to obtain a wider efficient frequency range were investigated experimentally. Among several design alternatives, satisfactory results were obtained by either dividing the sound radiating board into virtually independent sub-panels or adding resilient damping material supported by a restraining material.