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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 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.

This paper describes the investigation into the contact pressure and incidental deformation on the contact surface of the piston skirt which comes in contact with the cylinder bore in operation. Focused on the single piston static tests in the first place, relationship between the contact pressure on said skirt and the strains developed inside the skirt, and the relationship between the deformation of skirt face and the strains inside the skirt were studied. Then, the dynamic contact pressure onto the skirt in operation and the amount of deformation were calculated based on the relationships mentioned above using the factor of dynamic strains measured on an engine in operation. The deformation of skirt calculated using said dynamic strains was verified by the direct measurement of the skirt deformation. It was demonstrated that the thrust side of a piston skirt was largely deformed due to enlarged contact pressure caused by the piston slap subsequent to firing top dead center.

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 paper reports the results of a study into a preview control that uses the displacement of the road surface in front of the vehicle to improve for front and rear actuator responsiveness delays, as well as delays due to calculation, communication, and the like. This study also examined the effect of a preview control using the eActive3 electric active suspension system, which is capable of controlling the roll, pitch, and warp modes of vehicle motion.

This paper describes and discusses the result of a comprehensive simulation analysis we have carried out to clarify the effects of gear dimensions, tooth surface modification, and manufacturing error on the static transmission error of automotive hypoid gears. Three representative factors have been analyzed contact ratio, crowning and pitch error because these characteristics play the most important role in tooth dimensions, tooth surface modification and manufacturing error. The analysis has clarified the effect of each factor on gear noise, making it possible to prepare a guideline for optimal design of gear dimensions and tooth surface modification under various conditions.

This paper describes the slip ring system for a new hybrid system using an electromagnetic torque converter or an electromagnetic coupling. The slip ring system, which enables electric power transmission between a winding rotor and an inverter fixed on a case, is a key component for establishing a new highly efficient hybrid system. Reducing the wear of the brushes in the slip ring system is a major topic of this research. To achieve this objective, brush wear characteristics were investigated using test-piece experiments that simulated the hybrid system environment. By clarifying these characteristics, the structure of a slip ring system for reducing brush wear was identified and a wear prediction method was constructed.

A CVT belt is composed of multiple elements and layered rings. Each of these component parts generates loss, including relative slippage caused by the geometrical relationship between the elements and innermost ring layer. An effective way of increasing CVT efficiency is to reduce this slippage. However, since the relative slippage also controls whether the rings transmit constant torque at all times, reducing the slippage will also have an effect on the torque transmission performance of the rings. Therefore, to improve CVT efficiency by reducing the relative slippage, it is first necessary to analyze the changes to torque transmission. However, this slippage is a phenomenon of the inner portion of the belt and it is extremely difficult to identify the internal thrust force when actual load is applied. This paper describes experiments carried out to analyze the changes in each torque transmission ratio when the relative slippage between the elements and innermost ring layer changes.

In this paper, we discuss vehicle directional stability and introduce advanced stability control (ASTC) to stabilize the vehicle during severe cornering. Vehicle behavior in a transient steering condition during severe cornering was analyzed by computer simulation. It was found that applying an external yaw moment makes the vehicle more stable. The effect of controlling the brake force response is also evaluated by simulation to determine the brake actuator response criteria. The actual vehicle test was performed with a pylon slalom using a hydraulic brake actuator. It is verified that the ASTC stabilizes the vehicle for transient steering maneuvers.

This study focuses on fluctuations in the aerodynamic load acting on a hatchback car model under steady-state conditions, which can lead to degeneration of vehicle motion performance due to excitation of vehicle vibrations. Large eddy simulations were first conducted on a vehicle model based on a production hatchback car with and without additional aerodynamic devices that had received good subjective assessments by drivers. The numerical results showed that the magnitudes of the lateral load fluctuations were larger without the devices at Strouhal numbers less than approximately 0.1, where surface pressure fluctuations indicated a negative correlation between the two sides of the rear end, which could give rise to yawing and rolling vibrations. Based on the numerical results, wind-tunnel tests were performed with a 28%-scale hatchback car model.

It is difficult to improve tire cavity noise since the pressure of cavity resonance acts as a compelling force, and its low damping and high gain characteristics dominate the vibration of both the suspension and body. For this reason, the analysis described in this article aimed to clarify the design factors involved and to improve this phenomenon at the source. This was accomplished by investigating the acoustic coupling vibration mode of the wheel, which is the component that transmits the pressure of cavity resonance at first. In addition, the vibration characteristic of suspension was investigated also. A speaker-equipped sound pressure generator inside the tire and wheel assembly was developed and used to infer that wheel vibration under cavity resonance is a forced vibration mode with respect to the cavity resonance pressure distribution, not an eigenvalue mode, and this phenomenon may therefore be improved by optimizing the out-of-plane torsional stiffness of the disk.

It is well known that the self-aligning torque decreases before lateral force is saturated. Focusing on this self-aligning torque change, an estimation method has been developed to detect the friction condition between steered wheels and road surface before the lateral force reaches the friction limit. The lateral grip margin (LGM) is defined based on the self-aligning torque change, which is obtained using the EPS torque and motor current information. The LGM is theoretically analyzed based on the tire model and experimentally verified through the full-scale vehicle test. Moreover, the estimated LGM is applied for the chassis control systems to improve the vehicle dynamics performance.

The frequency response of steering effort torque changes according to the influence of vehicle dynamics. To help enhance feel, a new electronic power steering (EPS) control has been constructed. As the control can be achieved by the addition of a viscosity control with a filter to existing EPS systems, its structure is simple and easily installed. Actual vehicle tests have been performed to verify that the control is capable of enhancing convergence without adversely affecting response during steering.

The research described in this paper aimed to study the cornering resistance and dissipation power on the tire contact patch, and to develop an efficient direct yaw moment control (DYC) during acceleration and deceleration while turning. A previously reported method [1], which formulates the cornering resistance in steady-state cornering, was extended to so-called quasi steady-state cornering that includes acceleration and deceleration while turning. Simulations revealed that the direct yaw moment reduces the dissipation power due to the load shift between the front and rear wheels. In addition, the optimum direct yaw moment cancels out the understeer augmented by acceleration. In contrast, anti-direct yaw moment optimizes the dissipation power during decelerating to maximize kinetic energy recovery. The optimization method proved that the optimum direct yaw moment can be achieved by equalizing the slip vectors of all the wheels.

Electric vehicles (EVs) are attracting attention due to growing awareness of environmental issues such as fossil fuel depletion and global warming. In particular, a wide range of research has examined how direct yaw moment controls (DYCs) can enhance the handling performance of EVs equipped with multiple in-wheel motors (IWMs) or the like. Recently, this research has focused on reducing energy consumption through driving force distribution control. The first report proposed a method to minimize energy consumption through an efficient DYC for extending the cruising range of a vehicle installed with four IWMs, and described the vehicle behavior with this control. Since motors allow high design flexibility, EVs can be developed with a variety of drive systems. For this reason, various driving force distribution control methods can be considered based on the adopted system.

A vehicle parking manoeuvre is characterized by low or zero speed, small turning radius and large yaw velocity of the steered wheels. To predict the forces and moments generated by a wheel under these conditions, the Pacejka Magic Formula model has been extended to incorporate the effect of spin (turn slip model) in the past years. The extensions have been further developed and incorporated in the MFTyre/MF-Swift 6.2 model. This paper describes the development of a method for the identification of the turn slip parameters. Based on the operating conditions of a typical parking manoeuvre, the dominant parameters of the turn slip model are firstly defined. At an indoor test facility, the response of a tyre under the identified operating conditions is measured. An algorithm is developed to identify the dominant turn slip parameters from the measured responses.

In anticipation of the increased needs to further reduce exhaust gas emissions and improve fuel consumption, a new brake-by-wire system called an “Electronically Controlled Brake” system (hereafter referred to as “ECB”) has been developed. With this brake system, which is able to smoothly control the hydraulic pressure that is applied to each of the four wheel cylinders on an individual basis, functional enhancements can be added by appropriately modifying its software. This paper discusses the necessity of the ECB, the system configuration, and the results of its application on hybrid vehicles.

As a process that enables the high-speed and continuous forming of lengthy materials with a constant cross-sectional configuration, roll forming offers much higher productivity than the stamping process. However, in case a change must be made to the shape of the cross section, the material must normally be stamped or joined with a part containing a separate shape. This affects productivity, increases the number of pieces, and degrades the material's appearance. This report describes the roll-forming technology that we developed, in which the cross section of the material can be changed gradually. This method adopts a system which uses a movable and rotatable roll-stand that enables high-speed, continuous roll-forming processes.

In fatal accidents due to heavy duty trucks, the fatalities of occupants in passenger cars in which rear-end collision occur account for the largest percent. Collisions to the vehicles in traffic jams and collision to other accidents scenes on express ways can result in serious repercussions. Therefore the system which reduces the damage of collisions has long been demanded and here the world-first Pre-crash Safety (PCS) System for heavy duty trucks was developed. This system gives warning to the driver in case there is a possibility of collision with preceding vehicles, and activates the brakes to mitigate damage in case there is a higher possibility of collision. In order to get the maximum effect on the express ways where the trucks are in high speed, it is necessary to give warning and activate the brakes with relatively early timing.