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A numerical calculation method, which enables the analysis of gear train behavior including non-linear elements in a motorcycle engine, was established. During the modeling process, it was confirmed that factors such as bearing distortion, radial bearing clearance and elastic deformation of a tooth flank could not be neglected because they effect the rotation behavior. To keep a high accuracy, those factors were included in the simulation model, after they were converted into the rigidity elements along the rotational direction of each gear model. In addition, the model was combined with a crankshaft behavior calculation model for a driving and excitation source. A time domain numerical integration method was used to perform the transient response simulation across a wide range of engine speeds. A jump phenomenon of response behavior of the driven gear was predicted that is a characteristic of non-linear response. The phenomenon was also observed in a physical test.

Variable-valve-actuation mechanism is considered to be one of the most suitable solutions to realize the compatibility between higher power output and performances in the practical speed range. A new variable-valve-actuation mechanism named “Shuttle Cam” was designed and studied. In this mechanism which was applied to a conventional motorcycle engine with rocker arms and gear-train-driven valve system, the cam gears move along the idler gear. And cam shafts simultaneously slide along the rocker-arm slipper surfaces which are concentric with the idler gear. Consequently valve lift varies continuously in accordance with the alteration in the rocker-arm lever ratio and the cam phasing changes simultaneously in accordance with the cam gear rotation. Result of the experiments has confirmed that the mechanism functions accurately even at high speeds up to 10,000 rpm and some improvements were achieved in power output, fuel consumption, idling quality, and exhaust-noise level.

To enable non-throttling operation of gasoline S.I. engine, we have manufactured engines equipped with a newly developed Hydraulic Variable-valve Train (HVT), which can vary its intake-valve closing-timing freely. The air-intake control ability of HVT engine is equivalent to conventional throttling engines. Combustion becomes unstable, however, under non-throttling operation at idling. For the countermeasure, newly designed combustion chamber has been developed. The reduction of pumping loss by the HVT depends on engine speed rather than load, and amounts to about 80 % maximum. A conventional engine-management system is not applicable for non-throttling operation. Therefore, new management system has been developed for load control.

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.

A Sports car's high performance, pursued as its major design point, forces the car to be as light as possible. Because of this, the NSX's body and chassis is build by making the best use of aluminum. This paper describes the development of aluminum for the NSX, and the forming and connecting technologies needed to achieve an all aluminum body.

Several processes, such as casting, forging, and pressing, were used in the manufacturing of the Honda NSX's aluminum chassis. For casting, a high grade method which utilizes program control of mold temperature was developed and put into practical use. For optimum forging, a selection of cold and hot processes were investigated and a process to save energy during processing was pursued. As a result, an overall weight reduction of approximately 50% was achieved.

An attempt was made to apply the index U* in detail analysis of load paths in structural joints under static load, using as examples coupling structures of two joined frames with hat-shaped sections, and T-beam joint structures each including spot welds, both of which are widely used in automotive body structures. U* is a load path analysis index that expresses the strength of connection between load points and arbitrary points on a structure. It was possible to identify areas making up load paths by means of the magnitude of U* values, and to clarify the areas that should be coupled in order to achieve effective load transfer to contiguous members. In addition, because it is possible to determine whether or not each section of a structure possesses the potential for load transfer using U* analysis, the research also demonstrated that U* could be used as an indicator of joint structures providing efficient load transfer.

The atomization of molten aluminum when injected during high-pressure die casting is analyzed to determine its effect in enhancing the strength of the product being cast. In the previously reported first step of this study, molten aluminum was injected into open space and its atomization was observed photographically. Now in the second step of the study, a simulation is conducted to determine how the molten aluminum becomes atomized at the injection nozzle (gate) and how this atomized material flows and fills the cavity. A new simulation method is developed based on large-eddy simulation coupled with the volume-of-fluid method. The simulation system is verified by comparing its output with photographs taken in the first step of the study. Simulations are then conducted using an approximation of a real cavity to visualize how it is filled by the atomized molten aluminum.

An analytic technology able to rapidly and accurately predict oil flows and churning torque in a transmission has been developed. The new method uses the finite difference method for analysis; with regard to wall boundaries it reproduces the shapes of physical objects by imparting boundary information to cells. This has made it a simple matter to treat the rotation and meshing of the gears, which form oil flows, and has also reduced the calculation cost. Tests of single-phase and multi-phase flows and churning torque were conducted in order to verify the accuracy of the new method. Calculation results for the flow velocity fields produced by rotating bodies, the trajectory of oil, and the behavior of the surface of the fluid displayed a good correlation with test results. Considering air entrainment in the oil, the ability of the method to reproduce these phenomena at high speeds of rotation was also increased.

This paper will discuss the stress reduction of the worm wheel for an electric power steering (EPS) system. The research discussed in this paper focused on the worm wheel, the EPS component that determines the maximum diameter of the system. If the stress of the worm wheel could be reduced without increasing in size, it would be possible to reduce the size of the worm wheel and EPS system. In order to reduce the stress of the worm wheel, the conventional design method has extended the line-of-action toward outside of the worm wheel to increase the contact ratio of the gears and these method lead to an increase in the outer diameter. In order to address this issue, past research proposes the basic concept to extend line-of-action toward the inside of the worm wheel. And this new meshing theory was named MUB (Meshing Under Base-circle) theory. In this paper, characteristics of meshing of the gear formed by MUB theory are determined in more detail.

Gas shielded metal arc welding is generally applied to automobile chassis parts. However, the weld parts with the E-coat show poor corrosion resistance. Therefore, the corrosion mechanism of the weld parts was investigated. The results found two reasons why the weld parts corroded faster than the non weld parts:(1)inadequate phosphating (2)defects in the E-coat. After detailed investigation, it was clarified that the major cause of poor corrosion resistance was the defects in the E-coat caused by slags formed on the surface of the weld bead. Therefore the amount of slag has to be decreased to improve the corrosion resistance. The effect of shielding gas composition on the amount of slag was then investigated. In the case of Ar and oxidizing gas mixture, the corrosion resistance improved as the oxidizing gas content decreased. This was due to the reduction of slags.

Recently, it has been widely practiced in motorcycle developments that the same type of engine is commonly applied to various vehicle categories. Accordingly, it is drawing more attention to develop the methodology for creating the best suitable sound for each individual vehicle category regardless of restriction from the engine configurations. In our study, we aimed to establish a procedure to control exhaust sounds beyond the borders across the inherent sound qualities originated from their engine configurations. Firstly, we conducted subjective tests in order to extract essential factors, depicted by adjectives that appear in verbal expressions commonly used to illustrate sound qualities in general. The results enabled us to conduct quantitative evaluations of the exhaust sound qualities of various motorcycles. Next, we clarified the relationships among the individual factors of sound qualities under our study and physical parameters in waveforms of the sounds.

1 Many different bolts are employed in automobiles for different purposes and uses, and their strength generally ranges from 700 N/mm2 to 1200 N/mm2. Automobiles face the issue of making improvements in fuel economy as an environmental measure, and there is consequently a requirement to lighten component parts. The creationof higher-strength bolts is an important factor in achieving lighter weight. Increasing the strength, however, can also bring about an increased incidence of delayed fracture, and the conventional solution used to require the application of special steels such as expensive maraging steel. The present development addressed this issue by focusing on high carbon steel rod, which had been considered less susceptible to delayed fracture, although heading was also considered to be difficult. Heading techniques were therefore devised that made it possible not only to form bolts from this material, but also to provide satisfactory strength.

A compact, low-cost fuel pump module has been developed for use in motorcycles with a small-displacement engine. Various considerations are given to make the module as compact as possible. The pump motor, which is one of the major component parts, is down-sized specifically for applications to small-displacement engines. The pressure regulator uses a simple construction consisting only of a ball and a spring without a diaphragm. Especially noteworthy is that with the volume reduced by approximately 40% from the conventional pressure regulator while using the construction that reduces self-excited vibrations caused by fuel pressure pulsations, the pressure regulator contributes significantly to the down-sizing and cost reduction of the module. Furthermore, the down-sized module remarkably reduces the size of fuel pump mount surface, allowing a modification from the flat-surface sealing to the radial sealing.

In general, welding of high-pressure die casting (DC) parts has been difficult due to gases trapped in the castings. This is a result of the high-speed turbulent flow condition of the DC process. These gases are liberated during welding and produce porosity in the weld joint. The Author had found the range where an enough welding quality was obtained without great drop in castability to the middle of the laminar flow and turbulent flow. This range has been defined as the transition zone. Moreover high strength Al-Mg-Ni alloy was developed by non-heat-treatment. The Transition Flow Filling Method(TFFM) has been developed, that can not only reduce the amount of trapped gases but also is applicable to standard high pressure die casting equipment. With this method, high quality DC parts can be produced that are weldable, strong and have high toughness.

A new DC brushless motor, which has an almost equivalent driving performance to a 50 cm₃ scooter engine, has been developed to be used in a new electric motorcycle for business. The traction motor is compact enough to be mounted close to the driveshaft of the transmission, which helps reduce friction in the drive train. Consequently, in the downsized motor, by mounting the drive train unit with the PDU (Power Drive Unit) on the wheel side by applying reduction gears, it enables the reduction of maximum motor torque requirement. It also enables other parts of the drive system to be integrated into one unit. In this motor, IPM (Interior Permanent Magnet) structure has been implemented to cope with the high rotation of the motor, and the concentrated winding stator coil has been implemented for downsizing. As for the rotor, the magnets were placed in sections and the yoke shapes were improved to achieve higher rotation speeds that provide the higher power.

Honda developed a 750cm3 V-4 engine adopting an elliptical piston, and began selling the “NR” motorcycle with the engine installed in 1992. The adoption of an elliptical piston and cylinder achieved a compact layout of eight valves, which consists of four intake valves and four exhaust valves per cylinder. This paper explains the features of an engine with such a layout, focusing on the following: 1) Multiple valves and short-stroke enable the 750cm3 engine to achieve 15,000rpm. 2) The engine is more compact and lightweight than an engine having the same displacement, and more powerful than one with twice as many cylinders (8 cylinders). Also, this paper describes the techniques giving improved blowby gas and oil consumption characteristics as related to the sealing property of the piston, cylinder and piston ring and achieving performance equivalent to a conventional motorcycle engine.

In this research, a simulation method was developed in which it was able to estimate, in the early stage of design, the strains that potentially lead to damages to motorcycle engine parts when tipped over from a stationary state. Splitting a series of phenomena from the start of tilting of motorcycle from the upright position up to the end of collision of engine parts after the contact on the ground to two groups by before and after the contact of engine parts on the ground, we applied the multi body dynamics analysis to the first group, and the elastro-plastic FEM analysis to the latter one. In the computer simulation of collision using the elastro-plastic FEM analysis, we minimized the FEM models from the entire motorcycle models and treated others as a solid model to shorten the computation period. It is also realized that the strains occurring in the engine parts can be simulated by considering only the mass of the parts which are rigidly mounted on the engine.

SUS301-EH is widely used as a material for exhaust system gaskets, however, at temperatures in excess of 400°C, it can not be used as gas-seal ability of the material declines due to its reduced hardness. The following methods were found to be effective in controlling the softening of stainless steel at high temperatures: (1) The addition of a nitrogen component; (2) Stabilization of the austenite structure; (3) The addition of a molybdenum component. The addition of 0.5% nitrogen to austenitic stainless steel containing molybdenum has enabled the speed of softening at high temperatures to be significantly reduced, due to strain aging by solid nitrogen below 600°C and the combined effects of precipitation hardening and control of growth of recrystallized grains through the precipitation of fine Cr2N on the dislocations and the grain boundary above 600°C.

Using sand cores, the weld-able, hollow die-cast parts have been developed. For casting, the transition flow filling method is applied to reduce gas containment and to minimize damages to the core. In designing the products, the newly developed core stress prediction system by melt pressure distribution and the newly developed in-product gas containment prediction system have been applied. The hollow die-cast frame made by the new method attains a 30% increase in rigidity and 1kg reduction of weight.