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Designing a lightweight and durable engine is universally important from the standpoints of fuel economy, vehicle dynamics and cost. However, it is challenging to theoretically find an optimal solution which meets both requirements in products such as the cylinder head, to which various thermal loads and mechanical loads are simultaneously applied. In our research, we focused on “non-parametric optimization” and attempted to establish a new design approach derived from the weight reduction of a cylinder head. Our optimization process consists of topology optimization and shape optimization. In the topology optimization process, we explored an optimal structure with the theoretically-highest stiffness in the given design space. This is to provide an efficient structure for pursuing both lightweight and durable characteristics in the subsequent shape optimization process.

Vehicles are required durability in various environments all over the world. Especially water resistance on flooded roads is one of the important issues. To solve this kind of problem, a CFD technology was established in order to predict the water resistance performance of the vehicle at the early development stage. By comparison with vehicle tests on flooded roads, it is clarified the following key factors are required for accurate prediction; the vehicle velocity change, the vehicle height change and the air intake flow rate. Moreover, these three key factors should be appropriately determined from vehicle and engine specification to predict water intrusion for flooded roads at the early stage of development. In this paper, a methodology which determines appropriate analysis conditions mentioned above for flooding simulation from vehicle and engine specification is described. The methodology enables us to determine whether the vehicle provides sufficient waterproofness.

A hybrid simulation model in the transient bench was developed to realize the characteristics of the transient behavior and the fuel economy equivalent to that of a real vehicle. The motors and the batteries that were main components of the hybrid vehicle system were simulated as constructive modules, the functions of which have the integrated control and the input/output (I/O) function with real components. This model enabled us to accommodate a variety of auxiliary (AUX) I/O flexibly. The accuracy of the model was verified by the transient characteristics of the engine and the fuel economy result through correlation with a mass-produced vehicle. Furthermore, the flexibility of the model to a variety of AUX I/O was examined from the simulation test of the vehicle equipped with the waste heat recovery (WHR) system.

The effects of aerodynamic coefficients on handling response and flat ride were quantified. For handling response, the aerodynamic effect was quantified by analysis with linear representation and a two-wheel simulation model, using aerodynamic coefficients obtained from a full scale car wind tunnel. The correlation of aerodynamic coefficients and handling response with driving feel was also ascertained. Aerodynamic yaw moment and side-force were also converted to equivalent front and rear lift to standardize aerodynamic indexes and improve aerodynamic development efficiency. For flat ride, steady and unsteady aerodynamic effects were quantified by analysis with a two-degree-of-freedom mass-spring-damper simulation model and aerodynamic coefficients obtained from a 35% scale model wind tunnel and towing tank test. Unsteady aerodynamic force occurrence mechanism was ascertained by unsteady CFD using dynamic mesh.

A new brake system, able to make efficient use of regenerative braking while maintaining excellent brake feel, has been developed to increase the fuel economy of hybrid vehicles. A hydraulic servo was used as a base to enable mechanical operation of the service brakes; solenoid valves and brake fluid pressure sensors were added to this base to make it possible to control brake line pressure as demanded. The use of a stroke simulator in the hydraulic servo prevents brake feel from being affected by the control of the brake pressure. In addition, high-accuracy brake pressure control that functions cooperatively with the regenerative brakes is enabled, resulting in stable braking effectiveness.

Super-sport motorcycles have shorter wheelbases than other category motorcycles. Due to this, strong braking occasionally causes large pitching motions to occur, including rear-wheel-lift. In order to reduce such pitching motions and achieve an effective braking force, the authors have developed a brake-by-wire system that uses a pressure sensor to detect the braking input pressure and an electric actuator to variably control the hydraulic pressure. This system makes it possible to precisely control the braking force compared with the previous ABS. Large pitching control was performed by the distribution of a front wheel and a rear-wheel braking forces, CBS (Combined Brake System), by using electronic control, and Brake-by-Wire has been suitable for sport riding. As a result, stable braking performance could be obtained without spoiling the handling characteristics of super-sport motorcycles.

In recent years, the increased use of electric power steering in vehicles has increased the importance of issues such as making systems more compact and lightweight, and dealing with increased development man-hours. To increase development efficiency, the use of a “Hardware in the loop simulator” (HILS) is being tested to shift from the previous development method that relied on a driver's subjective evaluation in an actual vehicle test to bench-test development. Using HILS enables tasks such as specification studies, performance forecasts, issue identification and countermeasure proposals to be performed at an early stage of development even when there is no prototype vehicle. This report describes a case study of using HILS to solve the issues of reducing the load by adjusting the geometric specifications around the kingpin and eliminating the tradeoff by adding a new EPS control algorithm in order to make the electric power steering (EPS) more compact and lightweight.

HONDA completed research and development of the Metal V-Belt for CVTs in-house for the purpose of reducing the minimum pitch radius. The newly developed belt is essential to the compactness of a CVT and increases the speed ratio range. Increase of ring stress caused by reducing the minimum pitch radius is treated by improvement of element shape, optimizing clearance between elements and between element and ring and improving materials.(1) In this paper, the optimization of clearance between elements, heat treatment of elements and optimization of ring material are described in detail. Optimum total clearance between elements for a virgin belt is defined by test results during operation using a specially engraved gap sensor and a telemeter system. Tolerance and conditions of heat treatment for elements are optimized concerning fatigue strength of the element nose.

The Vehicle Stability Assist (VSA) system can generate sufficient forces to rapidly change the vehicle's motion. We can use this capability to effectively control the vehicle's behavior, but we must pay careful attention to ensure its reliability. The VSA system should be precisely tuned for each vehicle's characteristics in order to satisfactorily control performance without any unnecessary intervention or any excessive warnings. Usually extensive field tests are necessary to precisely tune the VSA system. This paper presents a practical method to tune the VSA system with Hardware-In-the-Loop (HIL) simulations in the final stage of its development. Due to the application of this procedure, both high control capabilities and reliability of the VSA system can be achieved.

In the consideration of safety to health, many countries have recently been enforsing regulations on the use of asbestos. To keep abreast of this trend, it has become necessary to replace the gasket materials currently used in the cases and the covers of motorcycle engines with non-asbestos materials. The gaskets used in motorcycles are subjected to extremely severe sealing loads and temperature in the small and high performance engines. They are required to have excellent sealability and creep relaxation characteristics at high temperature. Under such conditions, it is extremely difficult to substitute non-asbestos materials for asbestos which has superb material characteristics such as higher heat resistance and greater aspect ratio (length of fiber/dia.).

In motorcycles traveling at medium to high speed, roll stability is usually maintained by restoration forces generated by a self-steering effect. However, when the vehicle is stationary or traveling in low speed, sufficient restoring force does not occur because some of the forces, such as centrifugal force, become small. In our study, we aimed at prototyping a motorcycle having roll stability when the vehicle is stationary or at low speed with a steering control for self-standing assist, while maintaining stability properties in medium to high speed. A model was built to represent dynamics of roll motion, which is composed of a fixed point mass located above the vehicle’s center of gravity and another movable point mass below that gravity center. According to the model, when steered, the roll moment direction generated by the shift of the movable point mass becomes the same as the direction generated by the ground contact point shift of the front tire.

This paper summarizes the piston pin noise mechanism and show the way to reduce noise level of semi-floating system. A mechanism of piston pin noise of semi-floating system was clarified by measurement of piston and piston pin behavior and visualization of engine oil mist around piston and piston pin. Piston and piston pin behavior was measured by accelerometer and eddy current type gap sensor with linkage system at the actual engine running condition. Engine oil behavior was visualized and measured its flow vector by Particle Tracking Velocimetry (PTV). For PTV, engine oil mist particle image was taken by high speed camera with fiber scope attached to linkage system. From themeasurement, it was cleared that engine oil doesn't reach to piston hole from undersurface of piston land and come rushing out from piston broach via groove. The result shows that lacking of engine oil between piston and piston pin makes noise larger.

A multi-body simulation coupled with a tire model enables the prediction of forces generated on a vehicle when driven over a rough road profile. As the durability of a vehicle depends on these generated forces, the accuracy of the predicted forces is a crucial factor in assessing durability. A new test setup has been used to evaluate the accuracy of the simulation. Due to good reproducibility, the results from physical testing and simulation can be compared in the time domain. This time domain comparison makes it possible to detect any problems associated with the simulation which need to be improved. This new evaluation method is very suitable to full vehicle simulations involving rough road profiles. It was also confirmed that the suspension model with tire model evaluated in this project had an adequate capability for curb strike simulation by a full vehicle.

Lane departure prevention systems are able to detect imminent departure from the road, allowing the driver to apply control to prevent lane departure. These systems possess enormous potential to reduce the number of accidents resulting from road departure, but their effectiveness is highly reliant on their level of acceptance by drivers. The effectiveness of the systems will depend on when they are providing driving assistance, what level of laxness in terms of maintaining contact with the steering wheel is allowed on the part of the driver, and what level of assistance the system provides. This paper will discuss research on the minimum necessary contact and contact strength with the steering wheel on the part of the driver when a lane departure prevention system is in operation.

A multi-use road simulator for reproducing various road loads on motorcycles and buggies has been developed on a test bench by using computer-controlled hydraulic actuators. The device is controlled by a low-priced personal computer and an interface system with custom software. An unique feature is the capability to simulate loads related to such phenomena as the bottoming of suspension and the movement of a telescopic type front fork on the road.

Using stabilizing yaw-moment diagrams, the authors analyzed three methods of active chassis control for their effect and effective ranges during cornering maneuvers. The following results were obtained: controlling the transverse distribution of driving and braking forces cancels the changes in a vehicle's dynamic characteristics caused by acceleration and deceleration. Controlling the distribution of roll stiffness is only effective in ranges with high lateral acceleration, and the effect varies depending on the longitudinal weight distribution. Controlling the rear wheel steering angle is most effective in a range with a small side slip angle, but this effect decreases with an increase in the angle, especially during deceleration.

Four forces act in rings for a metal pushing V-belt. These forces are: two kinds of intercepting forces which prevent blocks from going outside of pulleys (one caused by pulley thrust, the other caused by centrifugal force), frictional force acting between the rings and the blocks, and bending force in longitudinal direction. In the previous paper (1)(2)(3)(5), distribution of three forces, excluding centrifugal force, were presented at low belt speed. We successfully measured all four kinds of forces including centrifugal force continuously at practical operation conditions for layered rings. In this paper, distribution of these four forces on the innermost ring is described at steady states.

The moment of inertia of the crankshaft cannot be ignored when analyzing the dynamics of a motorcycle. In this research, the tire friction force (calculated by drag and tire side force) was used as an index of the drive performance. The ratio of roll rate and steering torque (here after referred to as a roll rate gain) was used as an index of the cornering performance, and it was analyzed as the influence of the moment of inertia of a crankshaft on the drive performance as well as cornering performance. As a result, the influence on drive performance and cornering performance by the moment of inertia has been found.

Predicting fuel consumption and performance of an outboard motor for a high speed small planing boat are numerically challenging. The propeller is one of the most popular propulsion systems used for outboard motors. We focused our attention on the fact that the thrust performance of a propeller has a major impact on cruising fuel consumption and performance. We believe that we can numerically predict cruising fuel consumption, which has conventionally been estimated through experiential means, using accurate thrust performance measurements via CFD simulation without cavitations model. This study aims to develop a simulator that could quantitatively predict cruising fuel consumption and performance of an outboard motor used for a high speed small planing boat. After comparing the CFD simulation of propellers against the results of model tests, the simulated results are in good agreement with the experimental results.

5 belt wind tunnels are the most common facility to conduct the experimental aerodynamics development for production cars. Among aerodynamic properties, usually drag is the most important development target, but lift force and its front/rear balance is also important for vehicle dynamics. Related to the lift measurement, it is known that the “pad correction”, the correction in the lift measurement values for the undesirable aerodynamic force acting on wheel belt surface around the tire contact patch, must be accounted. Due to the pad correction measurement difficulties, it is common to simply subtract a fixed amount of lift values from measured lift force. However, this method is obviously not perfect as the pad corrections are different for differing vehicle body shapes, aerodynamic configurations, tire sizes and shapes.