Search Results

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.

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.

This paper presents an approach for efficiently evaluating motorcycle main frame strength using external loads predicted from measured strain data in our development process. The loads are calculated by simple matrix inversion, and can be used as boundary conditions of static analysis that resembles actual phenomena. The advantage of this method is that it allows relatively precise reproduction of actual boundary conditions without the data usually needed for dynamic simulation such as tire and suspension characteristics which often take large amount of time and man-hour to obtain. Although this approach is simple and common practice, there are a lot of things to be concerned for gaining useful results in a broad range of stages in the motorcycle main frame development process. How we effectively make use of this approach is going to be introduced here.

Generally, the gearshift mechanism for outboard motors shifts into forward or reverse gear without using the synchromesh arrangement (dog clutch engagement)(See Fig.1). This type of shift mechanism has advantages in simple structure and in saving space and cost, but at the same time, this is often the source of problem due to the abrasion caused by the hitting of gear against the dog clutch before the engagement, as well as large gearshift shock and noise. In addition, the outboard motor horsepower is getting bigger in recent years. As they are equipped with bigger and heavier engines and propellers, the shifting shock and noise tend to become more severe. For this reason, the improvement in this aspect is required. We looked into the way to reduce the shock and noise by means of propellers, because the propeller can be mounted and replaced easily, which allows the effective improvement to be spread to the outboard motors already in the market.

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.

In this paper, we introduce a research of Steering Damper using MR fluid (Magnetorheological Fluid). In recent years, Steering Dampers have been used in motocross races on off road courses. Steering Dampers stabilize the front end of motocross bikes that are used in competitive races held on rough terrain. The advantage of a Steering Damper is increased stability, however hydraulic Steering Dampers give rise to the problem of ‘Heavy Steering’. In order to solve this problem, we used MR Fluid and developed an Electronic Control Steering Damper that does not use a valve like hydraulic damper. The damper design uses “Direct Shear Mode” and features a steering angle sensor built into the damper, which results in easier, smoother steering. To test the effectiveness of our new design, we installed our new Steering Damper on the YZ 450F (Yamaha's competition model). We then asked for feedback from riders both in Japan and overseas.

Yamaha Motor Co., Ltd. has been developing 1kW generator system of direct methanol fuel cell (DMFC). The performance and durability characterization of a 1kW DMFC stack that the weight of the stack was decreased 20% in comparison with that of previous stack was evaluated. The DMFC operation condition was optimized from the design of experiment and the results of the net output. The overall system efficiency of the Yamaha DMFC system using the stack became a maximum in current 20A, was 30%. The stack was generated at 20A under the Daily Start up and Shutdown (DSS) condition for 1500h. This report describes some latest results concerning the durability characterization, which were obtained in the NEDO's project.

This paper describes an experimental method to predict the rolling contact fatigue life of a crankpin in a market vehicle engine. The fatigue life up to pitting was evaluated by two laboratory tests including a fatigue life measurement using a ball-on-disk test machine and a crankpin durability measurement by an engine bench test. The surface observation after the tests revealed that the surface dent triggers pitting in both tests. The Weibull plot of the percent failure vs. cycle to failure as a function of the contact stress was presented. In order to directly evaluate the effect of the contact stress on the lifetime, the lifetime values measured at L50 are plotted in the diagram showing the contact stress vs. cycle to failure. The obtained relation can predict the lifetime under the controlled condition in which the number of maximum torque points is countable.

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.

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.

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.

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.

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.

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.

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.

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.