Honda developed the world’s first Dual Clutch Transmission for motorcycles with the intent of affording more users than ever the sporty enjoyment of manual shifting combined with easy, carefree operation.
This new transmission utilizes Honda's proprietary dual-clutch transmission technology to provide fully automatic operation in a conventional manual motorcycle transmission.
In addition to its lightweight and compact construction, this new system boasts numerous features that heighten sports riding enjoyment while taking both the direct manual transmission control with the convenience afforded by an automatic transmission to a new level.
On conventional transversely mounted automotive dual-clutch transmissions, it is difficult to shorten dimensions along the length of the transmission shaft, so multiple output shafts are often used. Just as with automobiles, the application of a dual-clutch transmission with its complex assembly to a transversely mounted motorcycle engine was exceedingly problematic, requiring careful consideration of the motorcycle’s bank angle and potential interference with the rider's legs in a severely restricted layout.
Based on existing manual transmissions, Honda’s new Dual Clutch Transmission solves many of these problems thanks to its dual input shafts, exclusive in-line clutch design, and concentration of hydraulic circuitry beneath the engine cover.
Honda packages this transmission in a motorcycle chassis by minimizing dimensions along the length of the transmission shaft. Also, a shift mechanism simpler than the independently operating shifters of automotive systems is developed based on a conventional motorcycle shift drum.
The Dual Clutch Transmission main shaft is actually comprised of two coaxial shafts in one: an inner shaft for odd-numbered gears (1st, 3rd, 5th) and an outer shaft for even-numbered gears (2nd, 4th, 6th).
Both the inner and outer shafts are connected to mutually independent clutches, which operate alternately to achieve fast, seamless gear changes with constant, uninterrupted power application.
The in-line layout of these two clutches along the transmission axle, together with the hydraulic control piston installed on the inner face of the clutch disc, results in a more compact configuration which also minimizes lateral intrusions in the direction of the transversely mounted engine.
A more compact and lightweight construction was achieved by concentrating the linear solenoid valves and other clutch control devices and hydraulic circuits under the clutch cover.
Two control devices are independently used for optimized control of the two clutches, achieving smoother acceleration and shock-free gear changes.
Much like a conventional manual transmission, the shift mechanism uses a rotating shift drum to actuate the shifter. However, unlike conventional transmissions, the shift drum is motor-driven for optimized control. Alternating operation of the two clutches is performed using this single shift drum.
A basic construction essentially identical to conventional manual transmissions was used to create a simple, lightweight, and compact system. When the computer-controlled shift system determines the optimum time to shift from 1st to 2nd gear, it prepares to shift gears by releasing the clutch for the even-numbered gears and selecting 2nd gear. The next step is to release the clutch for the odd-numbered gears while simultaneously reengaging the clutch for the even-numbered gears, thereby effecting a smooth shift with no interruption of power.
The Honda Dual Clutch Transmission features two operating modes which can be controlled with a convenient switch located on the handlebars.
In AT mode, all gear shifts are performed automatically by the computer in response to driving conditions; in MT mode, the rider uses the shift switch to select gears. In either mode, start up is performed automatically.
In addition, the AT mode features two sub-modes — D-mode and S-mode — which can be used to select either of two shift schedule maps applied in accordance with the vehicle design concept. For example, D-mode could feature a shift schedule that prioritizes fuel economy even while accommodating sporty performance at a higher pace. The S-mode, in contrast, could be designed to maintain higher engine speeds for sportier performance throughout the power curve.
The clutch and transmission are electronically controlled in accordance with a programmed schedule. When in gear (other than neutral), the driver can switch between D and S modes.
The driver can shift up or down one gear at a time simply by operating a switch. If the rider operates this switch while in AT modes, the motorcycle also automatically goes into MT mode. The bike automatically goes into 1st gear when stationary. The rider can return to AT mode by operating a switch.