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This research investigated the mechanism of the effects of hydraulic dampers, which are attached to vehicle body structures and are known by experience to suppress vehicle body vibration and enhance ride comfort and steering stability. In investigating the mechanism, we employed quantitative data from riding tests, and analytical data from simplified vibration models. In our assessment of ride comfort in riding tests using vehicles equipped with hydraulic dampers, we confirmed effects reducing body floor vibration in the low-frequency range. We also confirmed vibration reduction in unsprung suspension parts to be a notable mechanical characteristic which merits close attention in all cases. To investigate the mechanism of the vibration reduction effect in unsprung parts, we considered a simplified vibration model, in which the engine and unsprung parts, which are rigid, are linked to the vehicle body, which is an elastic body equipped with hydraulic dampers.

While there has been an empirical rule telling suspension designers that a slight rearward inclination of the wheel travel locus could improve ride harshness performance, there has not been any quantitative proof on it, to the extent of authors' knowledge. The authors planned to analyze the phenomenon by quantitatively measuring the force transmission via suspension, to find out that the amplitude of longitudinal force transmission to the sprung mass changes significantly depending on the above inclination angle. Further investigation has lead to a conclusion that the force transmission from ground to tire has a sharp directivity. And that the relationship between this direction and the direction of wheel travel is a dominant factor, which decides the magnitude of longitudinal force transmission to the sprung mass. In order to make use of the finding, the optimal wheel center locus inclination in side view has been studied, to minimize the longitudinal force transmission.

The popularity of AWD passenger vehicles presents a challenge to provide car-like drive-train NVH within a relatively small package space. This paper describes a drive-train NVH case study in which analysis and test were used, in conjunction, to solve an NVH problem. Also, it details a systematic process of using the analytical model to identify and resolve similar problems. The particular problem for this case study is a noise and vibration issue occurring at 75 MPH primarily in the middle seat of an all-wheel drive vehicle. Tests indicated that it may be due to propeller shaft imbalance. Analysis results showed good correlation with the tests for that loading condition. Several solutions were identified, which were confirmed by both test and analysis. The most cost-effective of these solutions was implemented.

Operational analysis of automotive engines using flexible multi-body dynamics is increasingly important from the viewpoint of multi-objective optimization as it can predict not only vibration, but also stress and friction at the same time. Still, the finite element (FE) models used in this analysis have large degrees-of-freedom, so iterative calculation takes a lot of time when there is form change. This research therefore describes a technique that applies a modal differential substructure method (a technique that reduces the degrees of freedom in a FE model) that can simulate form changes in FE models by changing modal mass and modal stiffness in reduced models. By using this method, non-parametric form change in FE model can be parametrically simulated, so it is possible to speed up repeated vibration calculations. In the proposed method, FE model is finely divided for each form change design area, and a reduced model of that divided structure is created.

When the belt contacts a pulley in a pushing belt-type CVT, vibration is generated by frictional force due to rubbing between the individual elements that are components of the belt, which is said to increase wear and noise. The authors speculated that the source of that vibration is misalignment of the secondary pulley and primary pulley V-surfaces. To verify that phenomenon, a newly developed micro data logger was attached to an element of a mass-produced metal pushing V-belt CVT and the acceleration was measured at rotations equal to those at drive (1000 to 2500 r/m). In addition, the results of calculations using a behavior analysis model showed that changes in pulley misalignment influence element vibration, and that the magnitude of the vibration is correlated to the change in the metal pushing V-belt alignment immediately before the element contacts the pulley.

In engines having an inline four cylinder DOHC configuration, the rotational vibrations of camshaft increase at high engine speeds above 10000 rpm, causing an increase of tension in the cam chain. It is therefore difficult to realize an optimum designing of a cam chain system when the durability has to be taken into considerations. Using the simulation we analyzed in this research how the rotational vibrations and tension increase at high engine speeds in an inline four cylinder DOHC engine. As its consequent, it is understood that the increases of rotational vibrations and tension caused by the resonance of the spring mass vibration system in which the cam chain serves as springs and the camshafts as the equivalent masses. Also it is found out that the vibration system is of a unique non-linear type in which the resonance of the fourth order frequency is also excited by the crankshaft torque fluctuations of the second order frequency.

Knowledge of the loads experienced by a leaf spring suspension is required for the optimal design of the suspension components and frame. The most common method of representing leaf springs is the SAE 3 link model, which does not give good results in the lateral direction. In this paper, a beam element leaf spring model is developed. This model is validated using data obtained from laboratory tests done on leaf spring assemblies. The model is then subjected to actual road load data measured on the Proving Ground. Lastly, results from the beam element model are presented and compared with results obtained from proving ground tests. Overall, the beam element model gives good results in all directions except in situations where it is subjected to high fore/aft acceleration and high reverse braking events.

Mode management is an essential part of the design process for NVH performance. System resonances must be sufficiently separated to minimize interaction from source inputs and each other [1]. Such resonances are typically determined through experimental modal testing conducted in a lab environment under controlled and repeatable conditions. Global vehicle and suspension system response demonstrate soft nonlinear behavior, however. Their resonant frequencies may thus decrease under on-road input not reproducible in a lab environment. Subsequently, mode management charts derived from lab testing may not be representative of the vehicle's on-road dynamic response. This paper presents modal model determination methodologies, and examines suspension system and vehicle global dynamic response under lab modal test and operating conditions. Vehicle suspension modes measured under static and dynamic (rolling) conditions will be compared.

This paper summarizes the development of a predictive vibro-acoustic full vehicle model of a mid-size sedan and focuses on the engineering analysis procedures used to evaluate the design performance related to engine induced noise and vibration. The vehicle model is build up from a mixture of test-based and finite element component models. FRF Based Substructuring is used for their assembly. The virtual car model is loaded by engine forces resulting from indirect force identification. This force-set includes combustion, inertia, piston slap and crank bearing forces, for engine harmonics from 0.5 to 10th order. Such forced response analysis yields vibration levels at every component, at every interface between components, and interior noise predictions. The target is to provide the vehicle NVH manager with the insight required to identify major causes for peak noise levels and to set targets and develop an action plan for every component design team.

This paper describes a new approach and specific design procedure for more lightweight automotive Body in White (BIW) design. For a BIW structure with a target value for static stiffness, joints with high stiffness sensitivity are selected and a lightweight BIW joint design chart is produced from calculations combining topology optimization and thickness optimization. Using this chart made it possible to theoretically assign an optimum spring value to the BIW structure for the purpose of lightweight design, enabling substantial weight reduction in the base model while maintaining the same stiffness performance.

By optimizing parameters related to damping performance and adopting a layout that incorporates the turbine into the damper components, a “Turbine Twin-Damper” lock-up damper was developed that achieves both damping performance and compactness. To reduce losses in the fluid flow channel, a smaller torus was developed that reduce the width of the torus by about 30%.Through the combination of this Turbine Twin-Damper and smaller torus, attenuation of the torque fluctuation transmitted to the transmission to 1/2 or less compared to a conventional product was achieved without increasing the overall width of the torque converter. As a result, the engine speed at cruise fell by 400rpm, and fuel economy improved.

This paper dis cusses the development of a nonlinear shock absorber model for low-frequency CAE-NVH applications of body-on-frame vehicles. In CAE simulations, the shock absorber is represented by a linear damper model and is found to be inadequate in capturing the dynamics of shock absorbers. In particular, this model neither captures nonlinear behavior of shock absorbers nor distinguishes between compression and rebound motions of the suspension. Such an inadequacy limits the utility of CAE simulations in understanding the influence of shock absorbers on shake performance of body-on-frame vehicles in the low frequency range where shock absorbers play a significant role. Given this background, it becomes imperative to develop a shock absorber model that is not only sophisticated to describe shock absorber dynamics adequately but also simple enough to implement in full-vehicle simulations. This investigation addresses just that.

We succeeded in creating of a very small wiper system for a CCD camera. The source of driving force of it is a vibration phenomenon of a piezoelectric element. In this paper, we will describe the structure and motion of our newly proposed wiper system and the fundamental motion of a piezoelectric element in it. And in order to clarify the driving principle, we carried out a theoretical analysis using the Principle of Hamilton. As a result, a driving mechanism was found, that is, when the blade displaces at a high angular velocity into one direction, the shaft rotates in the opposite direction. We were able to confirm the driving mechanism also by experiments.

A motor-assist system has been developed and employed for the "Insight' hybrid car. The system consists of an internal combustion engine as the primary power source, with an electric motor placed around the engine's crankshaft. Such construction reduces the system's volume significantly and offers more flexibility for the power plant layout. The system's functions include regeneration during braking, an idle stop mechanism, driving power assistance, and power supply for the 12V electrical system. A proper energy management method for various driving modes has been established by combining these functions, and fuel economy is significantly improved as a result. As another control feature, an active motor vibration control system compensates the idling vibration that is unique to three-cylinder engines.

This paper describes the double wishbone suspension used in the Honda Prelude. This system is designed to improve handling and anti-dive performance via the layout of the suspension arms and the springs and dampers. It also allows a low hood line over the transverse mounted engine for this sports-type vehicle.

In this research, a new wire material made using surface-reforming heat treatment was developed in order to enhance the corrosion fatigue resistance of suspension springs. The aim of surface reforming is to improve hydrogen embrittlement characteristics through grain refinement and to improve crack propagation resistance by partial softening of hardness. The grain refinement method used an α'→γ reversed transformation by rapid short-term heating in repeated induction heating and quenching (R-IHQ) to refine the crystal grain size of SAE 9254 steel spring wire to 4 μm or less. In order to simultaneously improve the fatigue crack propagation characteristics, the possibility of reducing the hardness immediately below the spring surface layer was also examined. By applying contour hardening in the second IHQ cycle, a heat affected zone (HAZ) is obtained immediately below the surface.

A 50 Hz Solid-State Relay (SSR) was used to provide pulse-width-modulated power to engine cooling fans for continuous speed control, to reduce airflow noise and improve efficiency. However, this caused the cooling fans to vibrate at the switching frequency and harmonics, thus degrading vehicle NVH performance. This paper describes the problem associated with SSR- powered cooling fans, including root-cause analysis, and identification of areas sensitive to vibration affected by the switching power supply. Based on our analysis, we found several solutions to the problem. Our production solution and some generic recommendations for shroud design are presented in the paper.

Pulse feeling is an important factor concerning ride pleasure for V-twin engine, American-type motorcycles. Depending on sensory evaluation, estimating the pulse feeling varies widely from person to person. Therefore, it takes a large amount of time to determine specifications. To resolve this problem, a quantitative evaluation method was established. To determine the process, sensory evaluation testing for Japanese and American riders was conducted to verify how they feel the pulse. Both sets of riders drew the same conclusion that seat vibration is the most dominant factor for the pulse feeling. With this in mind, a pulse intensity indicator was introduced into the evaluation indicators for vibration feeling to quantify the seat vibration pulse. Furthermore, a time domain response analysis was applied to a newly created complete motorcycle analysis model. The output conveyed good correlation with the actual data.

This paper deals with low-frequency squeal phenomena generated in floating type of car disc brake units. First, the vibration characteristics of low-frequency squeal (about 2 kHz) were investigated. Here, in order to reproduce the squeal, a bench-test apparatus consisting of an actual automotive disc brake unit was utilized, itself comprising a disc, pad, and caliper. With this, the associated frequency characteristics were experimentally determined. It was found that the squeal is caused by coupled out-of-plane vibration modes among the disc and caliper due to Coulomb friction. As an experimental countermeasure, a dynamic absorber was applied to the leading side or the trailing side of the inner caliper. It was found that squeal can be suppressed when the natural frequency of the dynamic absorber is tuned so as to be near the frequency of the squeal, and that squeal can be suppressed even without viscous damping of the dynamic absorber.

In recent years, the number of reported traffic accidents due to sudden deterioration in driver’s physical condition has been increasing, it is expected to develop a system that prevents accidents even if physical condition suddenly changes while driving, or reduces damage through vehicle body control. For this purpose, it is necessary to detect sudden changes of the driver’s physical condition, and research is being conducted widely. Among them, it is reported that some of such changes may appear in the heartbeat interval. In other words, by acquiring the driver’s heartbeat interval in real time, it may be possible to detect the sudden changes, and reduce traffic accident. Even if a traffic accident occurs, the damage can be reduced by emergency evacuation immediately after detecting sudden changes.