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Generally, automobiles have many performance requirements for comfort, of which noise, vibration and harshness are very important. Toyota Motor Corporation equipped several 2003 models with the second-generation Electronically Controlled Brake system (ECB2). These ECB2 actuator units adopted a new structure that reduced pumping noise by controlling the skew phenomena of needle roller bearings. Normally, needle roller bearings are advantageous over other bearings in cases where a large force is loaded on bearings, because the contact areas can be made larger. However, a thrust force arises from skew phenomena because of minute clearances among the component parts of needle roller bearings. As a result, axial vibration of the bearing shaft sometimes occurs due to the thrust force. This paper explains how the thrust force generated from the skew phenomena of needle roller bearings occasionally affects the pumping vibration level of equipped machinery such as the brake actuator unit.

The tire is one of the most important parts, which influence the noise, vibration, and harshness of the passenger cars. It is well known that effect of rotation influences tire vibration characteristics, and earlier studies presented formulas of tire vibration behavior. However, there are no studies of tire vibration including lateral vibration on effect of rotation. In this paper, we present new formulas of tire vibration on effect of rotation using a three-dimensional flexible ring model. The model consists of the cylindrical ring represents the tread and the springs represent the sidewall stiffness. The equation of motion of lateral, longitudinal, and radial vibration on the tread are derived based on the assumption of inextensional deformation. Many of the associated numerical parameters are identified from experimental tests.

This paper describes a steady vibration of an engine supported by rubber and hydraulic mounts at a relatively low frequency range, assuming an engine is a rigid body. We identify dynamic characteristics of a hydraulic mount with respect to frequency and amplitude. The equation of motion is solved numerically by the Newton-Raphson method, treating the mount characteristics as functions of frequency and amplitude. The excitation test to simulate an engine shake and an idling vibration was performed using a mass block instead of an actual engine. During the engine shake, we observed that the amplitude dependency of hydraulic mounts strongly influences the vibration, while idling, we investigated rolling vibration especially for the case where the torque axis does not pass through the engine's center of gravity. The theoretical predictions agree closely with the experimental results in both engine shake and idling vibration tests.

This paper presents a new application of a vehicle on-board battery charger utilizing high frequency Silicon Carbide (SiC) power devices. SiC is one of the most promising alternatives to Silicon (Si) for power semiconductor devices due to its superior material characteristics such as lower on-state resistance, higher junction temperature, and higher switching frequency. An on-board charger prototype is developed demonstrating these advantages and a peak system efficiency of 95% is measured while operating with a switching frequency of 250 kHz. A maximum output power of 6.06 kW results in a gravimetric power density of 3.8 W/kg and a volumetric power density of 5.0 kW/L, which are about 10 times the densities compared with the current Prius Plug-In Si charger. SiC technology is indispensable to eco-friendly PHV/EV development.

This paper proposes a novel method of verifying comprehensive driver model used for the evaluation of driving safety systems, which is achieved by coupling the traffic simulation and the driving simulator (DS). The method consists of three-step procedure. In the first step, an actual driver operates a DS vehicle in the traffic flow controlled by the traffic simulation. Then in the next step, the actual driver is replaced by a driver model and the surrounding vehicle maneuvers are replayed using the recorded data from the first step. Then, the maneuver by the driver model is compared directly with the actual driver's maneuver along the simulation time steps.

The development of electric vehicles has been progressed, rapidly, to achieve Carbon neutrality by 2050. There have been increasing concerns about Electromagnetic Compatibility (EMC) performance due to increasing power for power trains of vehicles. Because same power train system expands to some vehicles, we have developed numerical simulations in order to predict the vehicle EMC performances. We modeled a vehicle which has inverter noises by numerical simulation to calculate electric fields based on GB/T18387. We simulated the common mode noise which flows through the shielding braid of the high voltage wire harnesses. As a result, it is confirmed a correlation between the electric fields calculated by numerical simulation and the measured one.

To reduce interior noise effectively in the vehicle body structure development process, noise and vibration engineers have to first identify the portions of the body that have high sensitivity. Second, the necessary vibration characteristics of each portion must be determined, and third, the appropriate body structure for achieving the target performance of the vehicle must be realized within a short development timeframe. This paper proposes a new method based on the substructure synthesis method which is effective up to 200Hz. This method primarily utilizes equations expressing the relationship between driving point inertance change at arbitrary body portions and the corresponding sound pressure level (SPL) variation at the occupant's ear positions under external force. A modified system equation was derived from the body transfer functions and equation of motion by adding a virtual dynamic stiffness expression into the dynamic stiffness matrix of the vehicle.

Trivalent chromate coating is replacing the conventional hexavalent chromate coating applied on zinc plating. Zinc plating uses one of three types of plating baths (zincate, cyanide and chloride) according to the characteristics required of subject parts. It has been recognized that trivalent chromate coating provides different corrosion resistance depending on the type of zinc plating bath used. Zinc plating with chromate coating were analyzed to clarify the cause of the corrosion resistance variation with the type of zinc plating bath. It has been revealed that the chromate coating thickness and the condition of top SiO2 layer vary with the type of zinc plating bath, resulting in corrosion resistance variation.

This paper describes the development and achievement of a target engine sound for a V6 SUV in consideration of the sound quality preferences of customers in the U.S. First, a simple definition for engine sound under acceleration was found using order arrangement, frequency balance, and linearity. These elements are the product of commonly used characteristics in conventional development and can be applied simply when setting component targets. The development focused on order arrangement as the most important of these elements, and sounds with and without integer orders were selected as target candidates. Next, subjective auditory evaluations were performed in the U.S. using digitally processed sounds and an evaluation panel comprising roughly 40 subjects. The target sound was determined after classifying the results of this evaluation using cluster analysis.

In recent years, the automotive manufacturers have been working to reduce fuel consumption in order to cut down on CO2 emissions, promoting weight reduction as one of the fuel saving countermeasures. On the other hand, this trend of weight reduction is well known to reduce vehicle stability in response to disturbances. Thus, automotive aerodynamic development is required not only to reduce aerodynamic drag, which contributes directly to lower fuel consumption, but also to develop technology for controlling unstable vehicle behavior caused by natural wind. In order to control the unstable vehicle motion changed by external contour modification, it is necessary to understand unsteady aerodynamic forces that fluctuating natural wind in real-world environments exerts on vehicles. In the past, some studies have reported the characteristics of unsteady aerodynamic forces induced by natural winds, comparing to steady aerodynamic forces obtained from conventional wind tunnel tests.

We have developed a novel engine cycle simulation program (UniDES: universal diesel engine simulator) to reproduce the diesel combustion process over a wide range of engine operating parameters, such as the amount of injected fuel, the injection timing, and the EGR ratio. The approach described in this paper employs a zoning model, where the in-cylinder region is divided into up to five zones. We also applied a probability density function (PDF) concept to each zone to consider the effect of spatial non-homogeneities, such as local equivalence ratios and temperature, on the combustion characteristics. We linked this program to the commonly used commercial GT-Power® software (UniDES+GT). As a result, we were able to reproduce transient engine behavior very accurately.

This paper presents a modeling method for prediction of low-frequency road noise in a steady-state condition where rotating tires are excited by actual road profile undulation input. The proposed finite element (FE) tire model contains not only additional geometric stiffness related to inflation pressure and axle load but also Coriolis force and centrifugal force effects caused by tire rotation for precise road noise simulation. Road inputs act on the nodes of each rib in the contact patch of the stationary tire model and move along them at the driving velocity. The nodes are enforced to displace in frequency domain based on the measured road profile. Tire model accuracy was confirmed by the spindle forces on the rotating chassis drum up to 100Hz where Coriolis force effect should be considered. Full vehicle simulation results showed good agreement with the vibration measurement of front/rear suspension at two driving velocities.

In order to reduce CO₂, Electric Vehicles (EV) and Hybrid Vehicles (HV) are effective. Those types of vehicles have powertrains from conventional vehicles. Those new powertrains drastically improve their efficiency from conventional vehicles keeping the same or superior power performance. On the other hand, those vehicles have an issue for thermal energy shortage during warming up process. The thermal energy is very large, and seriously affects the fuel economy for HV and the mileage for EV. In this paper, we propose VHDL-AMS multi-domain simulation technique for the estimation of the vehicle performance at the concept planning stage. The VHDL-AMS is IEEE and IEC standardized language, which supports not only multi-domain (physics) but also encryption. The common modeling language and encryption standard is indispensable for full-vehicle simulation.

The Rx400h, which was put on the market in 2005, realized overwhelming power performance with the adoption of a high-voltage system, high-power output motor, and 3-motor type 4WD. Toyota has been working on a solution to increase the output power of the motor, i.e., the development of system stabilization technology. This paper introduces high-speed power balance control, which keeps the balance of power constant regardless of rapid changes in the number of motor rotations resulting from slipping tires or other factors, along with sensor error compensation control, which suppresses cyclic power fluctuation resulting from errors in the position sensor of the motor.

The unsteady aerodynamic loads produced due to vehicle dynamic motions affect vehicle dynamic performance attributes such as straight-line stability or handling characteristics. To improve these dynamic performances, understanding the detailed mechanisms by which unsteady aerodynamic loads are caused during dynamic motions and the effects of unsteady aerodynamic loads on vehicle dynamic performance are needed. This paper describes the numerical study of unsteady aerodynamics of a 1/4 scale car model in dynamic pitching motion to clarify the detailed mechanisms by which unsteady aerodynamic loads are caused during the motion. Vortical structures around front wheelhouse and front under side of the body are analyzed by introducing schematic views to understand the mechanisms of unsteady flow fields. Furthermore, effects of aerodynamic devices devised based on the analyses on unsteady aerodynamics are discussed.

Replacing the metal car roof with conventional solar modules results in the increase of total car weight and change of center of mass, which is not preferable for car designing. Therefore, weight reduction is required for solar modules to be equipped on vehicles. Exchanging glass to plastic for the cover plate of solar module is one of the major approaches to reduce weight; however, load bearing property, impact resistance, thermal deformation, and weatherability become new challenges. In this paper a new solar module structure that weighs as light as conventional steel car roofs, resolving these challenges is proposed.

This article proposes a rubber suspension bushing model considering amplitude dependence as a useful tool at the initial design phase. The purpose of this study is not to express physical phenomena accurately and in detail and to explore the truth academically, but to provide a useful design method for initial design phase. Experiments were carried out to verify several dynamic characteristics of rubber bushings under vibration up to a frequency of 100 Hz, which is an important frequency range when designing ride comfort performance. When dynamic characteristic theory and the geometrical properties of the force-displacement characteristic curve were considered using these dynamic characteristics as assumptions, an equation was derived that is capable of calculating the dynamic stiffness under an arbitrary amplitude by identifying only two general design parameters (dynamic stiffness and loss factor) under a reference amplitude.

To reduce tire/road noise, it is important to examine the noise generation mechanism. Noise generated by a rolling tire is mainly emitted from the tread block. However, it has recently been reported that smooth tires also generate noise recently. This paper remarks on a smooth tire vibration by rolling on the road. The vibration of a rolling smooth tire is mainly vibration excited from the road surface. It is difficult to measure the input from the road surface, so we measured the tire's vibration at the leading and trailing edges. Scan Laser Doppler Vibrometers were employed to measure the vibration of the tire tread.

As part of efforts to address climate change and improve energy security, researchers have improved the thermal efficiency of engines by expanding the lean combustion limit. To further expand the lean combustion limit, the authors focused not only on engine technology but the chemical reactivity of various fuel molecules. Furan and anisole were among the fuel molecules selected, based on the idea that promising candidates should enhance the flame propagation speed and have good knocking resistance. Engine testing showed that the lean limit can be expanded by using fuels with the right molecular structures, resulting in higher thermal efficiency.

Recently, the development stage of agricultural vehicles such as the tractor has focused on new demands to improve the cabin environment. Especially the ride comfort has become increasingly important. For this purpose, rubber bushes have been installed the tractor to reduce road vibration to the driver in the cabin. However, this device does not sufficiently suppress vibration. This paper presents a method of vibration reduction that installs a semi-active suspension in the lateral and vertical directions at the cabin mount position of the tractor. In numerical simulation, the tractor model installed with a semi-active suspension is superior in performance to the conventional tractor model.