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For a numerical model of vibro-acoustic coupling analysis, such as a vehicle noise and vibration, both structural and acoustical dynamic characteristics are necessary to replicate the physical phenomenon. The accuracy of the analysis is not enough for substituting a prototype phase with a digital phase in the product development phases. One of the reasons is the difficulty of addressing the interior acoustical characteristics due to the complexity of the acoustical transfer paths, which are a duct and a small hole of trim parts in a vehicle. Those complex features affect on the nodal locations and the body coupling surface of acoustic mode shapes. In order to improve the accuracy of the analysis, the physical mechanisms of those features need to be extracted from experimental testing.

This study examined methods of machining a microsurface texture on the surface of the rolling elements of a toroidal continuously variable transmission (CVT) for improving the traction coefficient. The microsurface texture of the toroidal surfaces consists of tiny circumferential grooves (referred to here as micro grooves) and a mirror-like surface finish similar to the rolling surface of bearings. Hard turning with a cubic boron nitride (cBN) cutting tool, grinding with a cBN wheel and micro forming were applied to machine the micro grooves. The results made clear the practical potential of each method. A micro forming device was also developed for use in actual production. A mirror-like surface finish and micro crowning of the convex portions of the microsurface texture were simultaneously executed by superfinishing them with a fine-grained elastic superfinishing stone.

Since interior noise has a strong effect on vehicle salability, it is particularly important to be able to estimate noise levels accurately by means of simulation at the design stage. The use of sensitivity analysis makes it easy to determine how the analytical model should be modified or the structure optimized for the purpose of reducting vibration and noise of the structural-acoustic systems. The present work focused on a structural-acoustic coupling problem. As the coefficient matrices of a coupled structural-acoustic system are not symmetrical, the conventional orthogonality conditions obtained in structural dynamics generally do not hold true for the coupled system. To overcome this problem, the orthogonality and normalization conditions of a coupled system were derived by us. In this paper, our sensitivity analysis methods are applied to an interior noise problem of a cabin model.

A block-on-ring friction and wear testing machine (LFW-1) was used as a test method for making fundamental evaluations of the effect of the Belt-Drive Continuously Variable Transmission(B-CVT) fluid on the friction coefficient between the belt and pulleys. The results confirmed that this method can simulate the friction phenomena between the belt and pulleys of an actual transmission. The mechanism whereby ZDDP and some Ca detergents improve the torque capacity of a B-CVT was also investigated along with the effect of the deterioration of these additives on the friction coefficient. It was found that these additives form a film, 80-90 nm in thickness, on the sliding surface, which is effective in increasing the friction coefficient. The friction coefficient declined with increasing additive deterioration. The results of a 31P-NMR analysis indicated that the decline closely correlated with the amount of ZDDP in the B-CVT fluid.

Achieving a multi-cylinder engine with excellent noise/vibration character sties and low friction at the main bearings requires an optimal design not only for the crankshaft construction but also for the bearing support system of the cylinder block. To accomplish that, it is necessary to understand crankshaft system behavior and the bearing load distribution for each of the main bearings. Crankshaft system behavior has traditionally been evaluated experimentally because of the difficulty in performing calculations to predict resonance behavior over the entire engine speed range. A coupled crankshaft-block analysis method has been developed to calculate crankshaft system behavior by treating vibration and lubrication in a systematic manner. This method has the feature that the coupled behavior of the crankshaft and the cylinder block is analyzed by means of main bearing lubrication calculations. This paper presents the results obtained with this method.

Engines that not only produce less noise but also provide good sound quality have been in increasing demand recently. Discomforting noise can sometimes be heard, however, during acceleration as the engine reaches higher levels of power and speed. This paper presents the results of a study into the bending vibration of the crankshaft-flywheel system, which clarify the mechanism producing discomforting noise during acceleration. Based on that study, a flexible flywheel has been developed which effectively reduces crankshaft bending vibration that is closely related to the frequency range of the discomforting noise. As a result, acceleration sound quality is greatly improved.

Recently, it has been very important to reduce the noise, especially the Squeak and Rattle noise, for improving customer appeal of passenger vehicles. The Squeak and Rattle noise occurring inside the car cabin during vehicle operation is an especially large problem. This paper describes a newly developed measurement technology that uses the developed signal processing using the Beam-forming method and vibration sensor to identify the Squeak and Rattle noise sources, making it possible to determine effective countermeasures quickly. This new technology is used to identify all Squeak and Rattle noises at a time among many different noises, for example Wind noise, Engine noise and Road noise occurring during vehicle operation, and is expected to shorten substantially the time needed for noise analysis and contribute to quality improvements.

Building a toroidal continuously variable transmission (CVT) with multiple power rollers arranged in parallel is an effective way to improve its torque capacity. However, that requires a method for synchronizing the operation of all of the power rollers. This paper describes a method of synchronizing the four power rollers in a toroidal CVT that we have researched and developed. It also presents the results of an analysis of the cause of power roller vibration, which was a serious issue encountered in the development process, and describes an effective method for preventing it. The methods described here achieve sufficient synchronization performance for practical use of the toroidal CVT on production vehicles.

A seat vibration prediction technique using a substructure synthesis method was developed for use in ride comfort evaluations. The human body was modeled as a vibration transfer matrix using the mean apparent mass of human subjects, based on data measured in advance. Seat vibration characteristics were measured with rigid masses on the seat. The measured data and vibration transfer matrix of the human body were synthesized using a substructure synthesis method, to predict vibration of the seat cushion and backrest in an occupant-loaded condition without actually using human subjects. Results showed that seat vibration predicted with this method was very similar to, and more repeatable than, that obtained experimentally with human subjects.

This paper describes a newly developed steel composition and surface modification methods for improving the rolling contact fatigue strength of parts used in transmission systems, especially continuously variable transmissions (CVTs) to increase their torque capacity. The mechanisms of two types of typical rolling contact fatigue phenomenon in case hardening steel were examined with the aim of improving rolling contact fatigue strength. One concerned white etching constituents (WEC) and the other one concerned peculiar microstructural changes caused by hydrogen originating from decomposition of the lubrication oil as a result of repeated rolling contact stress cycles. The rolling contact fatigue strength limit due to WEC has been improved markedly by dispersing fine M23C6 alloy carbides in the martensite matrix at the subsurface layer of parts.

Lock-up operation of an automatic transmission is known as one good method of improving fuel economy. However, locking up the transmission at low vehicle speeds can often cause undesirable vibration or booming noise. Slip control of the lock-up clutch can resolve these problems, but the speed difference of the lock-up clutch needs to be controlled at a certain value. This control system has to overcome large changes in the parameters of the lock-up system at low vehicle speeds and also changes with regard to the speed ratio in a continuously variable transmission (CVT). In this study, this complex non-linear system has been modeled as a first-order linear parameter varying (LPV) system. A robust control algorithm was applied taking various disturbances into account to design a new slip lock-up control system.

Diesel engines have attracted more attention in recent years as one means of reducing carbon dioxide (CO2) emissions from motor vehicles. One of the major issues for diesel engines is exhaust emissions performance. Diesel engines also face various difficulties in providing the driving force demanded by the driver because of their greater inertia than that of gasoline engines. Meanwhile, continuously variable transmissions (CVTs) have been popularized as gearboxes that execute ratio changes continuously without generating shift shock. The aim of this research is to achieve higher levels of drivability and exhaust emissions performance by mating a CVT to a diesel engine and making maximum use of the continuous ratio change capability. An integrated engine-CVT control algorithm that can freely set the driving force and also the engine operating conditions for generating that driving force has been developed through this study.

Eliminating squeal noise generated during braking is an important task for the improvement of vehicle passengers' comfort. Considerable amount of research and development works have been done on the problem to date. In this study, we focused on the analyses of friction self-excited vibration and brake part resonance during high frequency brake squeal. Friction self-excited vibration is caused by the dry friction between pads and rotor, and occurs as a function of their relative sliding velocities. Its vibration frequency can be calculated in relation to the mass and stiffness of the pad sliding surface. Frequency responses of the brake assembly were measured and the vibration modes of the pad, disc and caliper during squeal were identified through modal analysis. Further study led to the development of a computer simulation method for analyzing the vibration modes of brake parts. Analytical results obtained using the method agreed well with the corresponding experimental data.

Digital signal processors (DSPs) are being used widely for sound field reproduction. However, it is difficult to apply a DSP to a car audio system because of the complicated acoustic characteristics of the passenger compartment. The authors have developed a new car audio system which employs special DSP software and a new speaker layout to provide excellent presence. The DSP has five output channels to generate stereophonic reflection from the front and rear speakers. The DSP software is programmed for each individual car model. A center speaker and A-pillar tweeters are used to produce a natural sound field in front through effective utilization of reflection from the windshield. This system is featured in 1992 Nissan models.

The Hybrid FE-SEA method has been used to create fast/efficient model of structure-borne noise in a fully trimmed vehicle from 200Hz to 1kHz. A joint paper is presented which highlights the method and modelling process along with extensive validation results. This paper describes the use of the model to analyze structure borne noise in the full vehicle, design and evaluate the impact of counter-measures. One of the key attributes of the Hybrid FE-SEA method is the ability to predict noise transfer paths in the vehicle. First, results from a Noise Path Analysis are used to identify key contributors to interior noise in the 200Hz-1kHz frequency range. Next potential design strategies for reducing interior noise are introduced along with implications on the model. Finally, sample prediction results illustrating the impact of design changes on interior noise levels are shown along with preliminary experimental validation results.

This paper describes the results of an investigation into the controllability of a traction-drive type half toroidal CVT, built with traction-drive elements. One feature of this CVT is that it provides better power transmission efficiency at its rolling contact points than other traction-drive CVTs developed previously. Another feature is that ratio changes can be effected with only a slight power input. A third feature is that it does not require any special hydraulic system to engage the contact points of rolling elements because it is designed to generate engaging force spontaneously in proportion to the torque input. The first half of the paper presents an analysis of the shifting mechanism. The characteristics of ratio changes effected by slight displacements of the power rollers were analyzed theoretically. A simplified CVT model was then examined experimentally and found to provide good response characteristics.

This paper describes a new 4.5-liter V8 engine, VH45DE, which was developed for use in the INFINITI Q45 sporty luxury sedan that was released in the U.S. and Japanese markets in November 1989. The many V8 engines in use around the world can be broadly devided into two categories. One category is characterized by ample torque at low engine speed and relatively large engine displacement. The other category is characterized by enhanced performance at relatively high engine speeds. The VH45DE engine is a new-generation V8 powerplant that delivers smooth power output at top-end speed and also generates ample torque at low engine speed to maintain good idle stability, and accomplishes it all with the smallest possible displacement. Development efforts were focused on two main goals. The first was to achieve efficient intake air charging. This has been accomplished the intake air resonant point at a relatively high engine speed through appropriate intake branch and collector tuning.

Technologies for reducing fuel consumption have attracted strong interest in recent years amid the heightened concern about global environmental protection. At Nissan, we have been focusing on the development of electronically controlled continuously variable transmissions (CVTs) since the early 1980s as a promising technology for reducing fuel consumption. That work has led to the commercialization of the world's first belt-drive CVT that is suitable for application up to 2.0-liter class passenger cars. The practical use of CVTs has so far been limited to cars mounted with small displacement engines of the 1.6-liter class. The belt-drive CVT described here incorporates new technology for transmitting greater torque and also has product attributes suitable for use on upscale passenger cars, making it applicable to 2.0-liter class models.

This paper presents Nissan's new four-valve-per-cylinder direct injection (DI) diesel engine series consisting of a 2-liter class and 3-liter class. These engine series provide substantially improved power output along with lower noise and vibration levels, which have been traditional drawbacks of DI diesel engines. Nissan developed this engine series in response to the heightened need in recent years for passenger-car DI diesel engines with superior thermal efficiency, a characteristic advantageous for reducing CO2 emissions.

The purpose of this study was to develop a simple optimization method for use in designing vibration insulators. With this method, stiffness, location and inclination of each insulator are used as design parameters. A performance index consisting of vehicle modal parameters expressed as eigenvalues and eigenvectors has been constructed to evaluate low-frequency idle/shake performance and higher frequency vibration performance involving road/engine inputs. Using this performance index and the sensitivity of the modal parameters, a designer can easily find a suitable direction for optimizing mount performance and thereby obtain a stable solution. The new method was employed to optimize an engine mount system. Experimental data obtained on the system validated the accuracy of the calculated results and showed an improvement in idle/shake performance. This method is a useful tool in designing optimum vibration insulators.