Development of Dual Clutch Transmission for Large Motorcycles

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. In order to achieve the smooth starts and gear shifts demanded of motorcycles, independent linear solenoid valves were positioned on each of the two clutches; this configuration makes it possible to control the clutch hydraulic pressure directly. At a standstill, no creep torque is applied. Then, by controlling the clutch hydraulic pressure rise characteristics immediately after starting launch controls, it is possible to start smoothly. Gear shifting by the two linear solenoid valves directly controlling hydraulic pressure makes it possible to control the clutch capacity of the driving side and the non-driving side with precision to realize smooth gear shifting with no drops in torque. A 5% improvement in fuel economy compared to the MT vehicle in WMTC mode was realized by optimizing the shift schedule.