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Recently, there have been many reports about development of Human Machine Interface (HMI) which used a visual or auditory display to improve driver assist. For a motorcycle, it is suitable to use a haptic display for rider assist, since there are many disturbances in open-air situation such as sunshine and surrounding noise. Therefore, a test vehicle based on a large motorcycle equipped with the haptic throttle grip that is connected to a motor by gear, an original ECU to control the motor, and a lean angle sensor to calculate the lateral force of the motorcycle was developed. To inform surplus driving force warning, the throttle grip, a haptic display outputs additional return torque estimated by the friction circle and ellipse with the lateral force of the motorcycle.

The main evaluation methods of two-stroke engine oil were standardized as the JASO (JASO: Japanese Automobile Standard Organization) method in 1993(1). After the establishment of the JASO specification, the authors executed an evaluation of various oils. As a result, it has been determined that an examination method that also evaluates the differences in demands on oil caused by regional characteristics and use conditions of the engine is necessary. Thus, the three following methods were developed. The first is a method of low-temperature detergency examination. The second is a method of low-temperature start-ability examination. The third is an exhaust port carbon blocking examination. These three examination methods are explained in full in this paper.

This paper gives a report on ergonomic approaches we tried to scooters for improvements in their riding comfort. First we conducted investigations into riding postures that offer a comfortable scooter ride. That is, we picked out major items for the evaluation of scooter riding postures and investigated a correlation between those items and their physical quantities. Our investigation revealed that room for leg and arm movements played a major role in a scooter riding posture. We further found out a high correlation between the evaluation items for legroom and the knee angles and also high correlation between the evaluation items for legroom and the ankle angle. Next we report on the result of the attempt we made at improved riding comfort by equipping the scooter seat with a backrest. To check the effects of backrest, we measured the seating pressure distribution, myogenic potential, and cardiogenic potential.

This paper reports the new design method of vibration isolation mount for the scooter powerunit. In the conventional design, while the engine vibration is efficiently isolated by the link mechanism, the time lag induced by the movement of the link mechanism spoils the riding quality when the rider operates the steering or the throttle. To solve the problem, a new design without the link mechanism was proposed. The optimized combination of the crank balance and the single-axis balancer was used to control the orbit of the powerunit vibration. First, the new equations were introduced to balance the inertial forces and moments at the target position by optimizing the amount and the phase of the crank balance and the balancer. Then, some results from the experimental tests were reported to validate the numerically optimized design. Using this new design method, the riding pleasure can be enhanced without unpleasant mechanical vibration.

Today, environmental issues have become major global issues. Under these social circumstances, restrictions on vehicles powered by internal-combustion engines have become increasingly stringent. While, many models of motorcycle are intended for hobbyists, and enjoyment is a major factor in the appeal of these products. So it is necessary to simultaneously realize improved environmental performance and heightened enjoyment. Therefore, the authors focused on controlling the richness of the mixture, the air-fuel ratio. In the case of intake port-injection engines, it is common these days to control fuel injection using a fuel model that takes fuel adhered in the intake port into consideration, in order to control the air-fuel ratio. When this method of control is used, it is necessary to derive the ratio of injected fuel that adheres inside the intake pipe and the ratio of adhered fuel that is drawn into the cylinder.