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A monolithic type aluminum (Al) cylinder made of hypereutectic Aluminum-Silicon alloy has been widely used for motorcycle applications. It has a lightweight structure and a superior cooling ability owing to its material property and surface finishing. Usually the cylinder bore surface of the monolithic type Al cylinder is finished by an etching process or a honing process in order to expose silicon (Si) particles from aluminum (Al) matrix for the improvement of the tribological properties. The morphology of the cylinder bore surface including the exposure of Si particles is supposed to make an important effect on its tribological properties, especially on the anti-scuffing property. In this research, the anti-scuffing property of three kinds of cylinder bore finishing, an etched surface, a Si exposure honed surface and a conventional plateau honed surface is evaluated with using a reciprocated type wear tester. The experimental results are analyzed by using Weibull analysis.

This paper concerns a torque control of a rear wheel of a motorcycle equipped with a rubber/aramid belt electronically-controlled continuous variable transmission where a primary sheave position is controlled by an electric motor. In particular, the paper discusses a method to calculate a required engine torque and a required primary sheave position, given reference values of a rear-wheel torque and an engine rotational velocity. The method forms a foundation of a hierarchized traction control where a higher control layer decides an optimal motorcycle motion (rear-wheel torque and engine rotational velocity) and a lower control layer realizes the motion by actuators (engine torque and primary sheave position). Difficulties of the control are due to large mechanical compliance of the rubber/aramid belt, which leads to an inevitable lag from the primary sheave position to a speed reduction ratio.

This paper describes the development of a new concept two-wheel steering system for realizing motorcycle motion control. By considering the whole of the main frame as the rear-wheel steering axis, it was possible to move the rear-wheel steering system from the conventional installation position at the rear arm to the head pipe. As a result, the developed two-wheel steering system is both lightweight and compact. This two-wheel steering system was installed in a motorcycle, and starting and stopping tests were carried out with two people riding on the motorcycle. The test results confirmed that the two-wheel steering system is capable of changing the motion characteristics of the motorcycle in actual riding. Furthermore, by calculating the equivalent wheel alignment of this system, this paper also theoretically demonstrates that these changes in motion characteristics are caused by changes in caster and trail.

We introduce a research on steering dampers using MR fluid (Magnetorheological Fluid). In recent years, steering dampers have been used in on-road and off-road motorcycles. Steering dampers stabilize the front end of motorcycles. The advantage of a steering damper is increased stability, but hydraulic steering dampers give rise to the problem of ‘Heavy Steering’. In order to resolve this heavy steering, we need to set the restrictions on the maximum damping force and avoid it from interfering when the rider is steering. However only reducing the damping force will lead to insufficient damping force when the handle, unresponsive because of kickback, shakes. We solved this problem with the development of an electric control damper which generates sufficient damping force at low steering angle rates and also allows for mechanically limiting the maximum damping force.

A connecting rod made of titanium alloy is effective for lower fuel consumption and higher power output comparing to a steel one because the titanium connecting rod enables to reduce the weight of both of reciprocating and rotating parts in an entire engine substantially. But up to now, it has been adopted only to expensive and small-lot production models because a material cost is high, a processing is difficult and a wear on a sliding area should be prevented. In order to adopt the titanium connecting rods into a more types of motorcycles, appropriate materials, processing methods and surface treatment were considered. Hot forging process was applied not only to reduce a machining volume but also to enhance a material strength and stiffness. And the fracture-splitting (FS) method for the big-end of the titanium connecting rod was put into a practical use.

The Bonded Valve Seat System is the latest technology to realize drastic reduction in valve temperature in SI engines characterized by the good thermal conductivity of extremely thin valve seats bonded directly on the aluminum cylinder head. A unique and highly rationalized resistance bonding technique was developed to maintain adequate bonding strength and positioning precision in a short bonding period of around one second. Engineering data on optimization of bonding-section geometry, valve seat material and the surface treatment and bonding parameters were presented and discussed regarding the mechanism. The geometry of the bonding section of the cylinder head was optimized by FEM analysis so that the aluminum material should deform to embed the valve seat ring with the action of expelling the surface contamination and the oxide film. The bonding facility was modified so that the electrode axis should move flexibly according to distortion of the cylinder head during bonding.

A high-quality die-casting technology has been developed for lightweight aluminum frame structures that produces high-strength aluminum parts that are also weldable. This new technology has been used in casting frames for motorcycles and snowmobiles and has enabled improved frame designs with far fewer component parts than was possible before. This die-casting technology also results in a significant reduction in energy consumption during the manufacturing process.

1 Research was conducted on reduction of circuit inductance for the purpose of reducing the surge voltage generated during switching by FET (field effect transistor / semiconductor device) in the power modules of motor controllers for golf carts (Fig. 1) and other electric vehicles. The motor control system is composed of the battery, the motor controller, the motor, and the wirings that connect them, and the inductance exists in them altogether. It became clear from simulation analysis and measurements from a prototype that only the inductance within the motor controller among these composition parts influences the surge voltage. And it became clear that there is a correlation between surge voltage and the sum of the inductance of the electrolytic capacitor inside the power module and the inductance of the circuit by which current is supplied from the electrolytic capacitor to the FET.

A mathematical model to estimate the shape of a brake hose has been developed. A few papers applying Finite Element Methods (FEM) to this problem have been reported. However, the solutions require a large amounts of computational time even if a super computer is used. A brake hose is made of a flexible material such as rubber, and exhibits large scale deformation when it is mounted on a chassis. Element node displacements are chosen as the independent variables for FEM, so the method becomes a successive iteration of hose shape modifications based on displacements of the nodes. The developed model is approached from the standpoint of mechanical dynamics. A brake hose is divided into small beam elements and particles. The particles are driven by element forces and move around in three-dimensional space.

Connecting rod design factors, such as geometric shape, capscrew torque and materials can significantly affect bore distortion and assembly stress. In this paper, experiments using different materials were conducted on several connecting rod big-ends with various shapes, bosses and bolts. The results show that the distortion of the big-end bore and the bolt stress are influenced considerably by the big-end shape, the bolt axial tension and the material under inertia force. It was also observed that the bolt bending stress and the load separating the big-end joint surface could be calculated with high accuracy using three-dimensional FEM in the initial connecting rod design.

We compared motoring friction loss, output performance at WOT (wide open throttle) and specific fuel consumption of big-end bearings on engines having identical specifications between the case of using plain bearings and rolling bearings to investigate the effect of the lubricating oil supply rate on these parameters in an attempt to improve output through reduction of friction loss for big-end bearings of small, high-output motorcycle engines. Testing was performed using a 125 cc, 4-cycle, single cylinder engine at high engine speeds mainly above 10,000 rpm.

YAMAHA MOTOR CO., LTD. has developed the YCLS system described in this report. The YCLS provides electrical support for a mechanical oil pump to offset its disadvantage. This system can reduce oil consumption at low engine speeds. As a result, it achieves its aim of reducing exhaust smoke, thus improving the dirty image of 2-stroke gasoline engines. Since the system reduces oil consumption in actual operation, it can be said that the technology contributes to resource saving.

The propeller blade hydrofoil section is one of the factors that determines the propeller performance. In the development of the hydrofoil, repeatedly performed experiments using many foil models and the cavitation tunnel involve extended time and high cost. This is why there are expectations for the numerical simulation to realize shorter development time and cost cutback. On the other hand, a technique for reproducing the hydrofoil characteristics taking account of the cavitation effect using CFD (Computational Fluid Dynamics) has hardly been established. There is no example of performance prediction especially for a hydrofoil section of the outboard motor propellers in which the trailing edge is cut off. This paper describes the results of the prediction of hydrodynamic characteristics performed in regard to the two differently shaped outboard motor propeller blade hydrofoil sections taking account of the cavitation effect.

In two-stroke engines, the exhaust port timing has a great effect on engine performance characteristics. If the exhaust port timing can be varied in response to variations in the engine speed, an extensive improvement of performance can be realized. The Yamaha Power Valve System (YPVS) increases engine output with a valve which operates in the exhaust passage; this valve controls exhaust port timing in response to engine speed, despite the extremely high thermal load encountered in the exhaust passage. This literature deals with the construction and operation principles of YPVS and its effect on the increase of engine output. Also discussed is a series of tests and measurements made on the delivery ratio and trapping efficiency in order to elucidate why engine output is increased.

All the primary inertia forces and/or moments generated by engines having three cylinders or less are not normally in balance by themselves and thus may be a great source of vibration for the frame supporting the engine. If the mass distribution of the crankwebs is selected in a proper manner, it is possible to determine arbitrarily the directions and the length ratio of principal axes of ellipses, which are obtained as Lissajous diagrams of inertia force and moment. This method can be effectively applied to reduce vibration in the frames. In this paper the appropriate inertia force and moment ellipse equations are developed and the analysis is outlined for optimizing the engine balance. Also the fundamental properties of the linear vibration systems excited by the elliptical forces as well as some experimental examples of elliptical excitation are detailed.

A laser Doppler velocimeter is used to measure in real time the velocities of pipe flows in a crankcase-scavenged small two-cycle engine with piston and reed valves. Consequently the optical windows in each pipe must be exchanged instantly by using rotary window systems. The flows in both the inlet and exhaust pipes show different patterns in the motored and firing conditions, but the flows in the scavenging pipe are in a similar pattern regardless of the operating conditions.

Abnormal valve gear vibration is a perennial problem confronting the designer of high-performance 4-stroke engines. It would shorten time and reduce costs if an analytical method could be applied to the prediction of engine valve behavior. This paper describes a method of valve motion simulation for both SOHC and DOHC valve gears through interactive calculation and using computer graphics. The authors tried to set up as simple a simulation model as possible by using modal analysis and modeling techniques. Through setting simulation model parameters and experimental damping factors, a close correlation between calculated and actually measured results was found.

THE MULTI-VALVE FOUR STROKE CYCLE engine design trend is Coward increased engine power and higher fuel efficiency. While a four-valve system is the most common direction, problems occur when the valve area is widened by increasing the cylinder bore for a higher engine output. The layout of four larger valves causes the combustion chamber shape to flatten and the combustion time period to increase. In pursuit of the optimum multi-valve engine we have studied four, five, six and seven-valve per cylinder design. Performance targets and design constraints led us toward the successful five-valve engine technology. This technology develops high engine torque and efficient combustion over a wide range of engine speeds.

Carburized and quenched materials with high fatigue strength are often used for motorcycle engine parts. Nitrided materials exhibit less deformation during heat treatment than carburized and quenched materials, so if the same or higher fatigue strength can be achieved with nitrided materials as with carburized and quenched materials, the geometric precision of parts can be increased and we can reduce engine noise as well as power loss. When the fatigue strengths of a nitrided material with its compound layer surface put into γ’ phase through nitriding potential control (hereafter, G), and a nitrided material put into ε phase (hereafter, E) were measured, the results showed the fatigue strength of the G to be about 11% higher than that of carburized and quenched materials. It was inferred that the strength of the compound layer determines fatigue strength.

In recent years, global warming, depletion of fossil fuels, and reducing pollution have become increasingly prominent issues, resulting in demand for environmentally-friendly two-wheeled vehicles capable of reducing CO2 emissions. However, it remains necessary to meet customers’ expectations by providing smaller drivetrains, lighter vehicles, and support for long-distance riding, among other characteristics. In the face of this situation, hybrid electric vehicle (HEV) systems are considered to be the most realistic method for creating environmentally-friendly powertrains and are widely used. This research introduces a hybrid electric two-wheeled vehicle fitted with an electrical variable transmission (EVT) system, a completely new type of electrical transmission that meets the aforementioned needs, achieving enhanced fuel efficiency with a compact drivetrain. The EVT system comprises double rotors installed inside the stator.