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Large motorcycles have a strong recreational aspect. Therefore, in addition to the sportiness that comes from the direct torque feel and the comfort that comes from the ease of operations, users demand improvements to fuel economy from the perspective of the environment and riding economics. In order to satisfy these needs, we have developed the world's first dual clutch transmission (hereinafter referred to as DCT) for motorcycles. In order to make the DCT more compact, we adopted a dual shaft construction for the main shaft, two hydraulic clutches arranged in-line, the basic structure of the gear shift mechanism carried over from a manual transmission (hereinafter referred to as MT) vehicle, a hydraulic circuit consolidated into the engine side cover, and shared use of engine oil for clutch actuation. Through these innovations, it became possible to carry over the die of the crankcase used on the MT vehicle as well as being able to load it onto the same frame as the MT vehicle.

Gear meshing noise is a common noise issue in manual transmission, its noise generation mechanism has been studied extensively [1, 2]. But most of time we have situations where multiple gear sets are connected in series and the noise and vibration behavior for a multi-stage gear can be quite different due to vibration inter-actions or interferences among multiple gear sets. In this paper, a two-stage gear driveline model was built using MSC ADAMS. Vibration order contents of a two-stage gear driveline were analyzed by both CAE simulation and theoretical calculations. In addition to gear meshing vibration orders of each gear set, the orders resulted from modulations between individual gear meshing and their harmonics were evident in the results. These special order contents were verified by experimental results, and also evidenced on transmission end of line tester results at transmission supplier GJT in Ganzhou, China.

A new CVT that is lighter in weight and more highly efficient than the previous CVT for use in compact vehicles has been developed and used in the 2014 model year FIT. The allowable torque capacity was expanded to that of the 1.8-L engine class, making this CVT usable in a greater number of vehicle models. The ratio coverage was also expanded and the transfer efficiency was increased to enhance fuel economy and drivability. Integration of hydraulic control system functional parts and reduction in the number of case component parts were carried out as structural modifications. Pulley side pressures were also reduced by the use of new CVT fluid so that the pulley could be made more compact and lighter in weight. Enhancements were made in CVT shift control, providing more acceleration considered from the driver's acceleration demand and more linearity between vehicle speed and engine speed than in previous models.

Pulley thrust control, changes in the trajectory of the belt as it winds around the pulleys, and the amount of friction transmission were focused on in order to reduce transmission loss and increase the transmission efficiency of CVT. In the case of pulley thrust control, making use of the linear relationship between the rotary speed fluctuation transfer characteristic and the torque transmission capacity between the pulleys and the belt, it was possible to reduce the excess safety factor of the torque transmission volume. Due to pulley tilt, the trajectory of the belt displays deviations with the theoretical geometrical winding radius. The structure of the pulleys was modified in order to reduce this deviation and increase transmission efficiency. Optimization of the additives in the CVT fluid increased the coefficient of friction, decreasing pulley thrust and increasing transmission efficiency.