A unique "dual input" shaft allows the separate clutches to be stacked in the same location as a conventional clutch, reducing bulk and weight.
Much of the electro-hydraulic circuitry for the Honda Dual Clutch system is located directly on the engine or internally, reducing overall bulk.
The Honda Dual-Clutch system is fully integrated into the EFI's ride-by-wire control, meaning downshifts should be similarly seamless, with the system most likely keeping one or two of the throttle butterfly valves cracked open to bleed off engine vacuum and reduce backtorque.
A version of
Honda’s new VFR1200
sport-tour
motorcycle will come equipped with the world’s first semi-automatic dual clutch transmission, according to information recently released by Honda Japan. Unlike previous “semi-automatic” designs that have recently made their way into motorcycling, the new Honda unit is not a CVT transmission such as that used on the Aprilia Mana and even Honda’s own DN-01 (basically the same as those used in most automobiles, relying on a heavy and inefficient torque converter to function as a clutch) nor is it just a electro-hydraulically-operated conventional clutch as found on the now-discontinued Yamaha FJR1300 AE. The new dual clutch transmission is basically very similar in function to the semi-automatic gearboxes used by Formula One and World Rally Championship racecars, allowing seamless, lightning-quick gearshifts with none of the inefficiency or quirkiness of previous motorcycle-
specific units.
Why two clutches? One of the disadvantages of the constant-mesh transmission is that engaging the next gear involves connecting one set of gears that are already spinning to a set of gears that aren’t rotating. This requires interrupting the power being applied so that the gearsets can disengage and slide over to engage another; the gears’ engagement dogs (male/female slotted connectors on the inner portion of each gear ring) are made to stay connected under power for obvious reasons. The interruption not only wastes power that could be used for acceleration, but it also upsets the chassis and suspension due to the sudden torque pull on the chain or driveshaft when the power is stopped and then re-applied.
The multiple clutch system works by having each clutch work a specific set of gears; in the Honda’s case, one clutch works with odd-numbered gears (1st, 3rd, 5th) while the other handles the even-numbered ones (2nd, 4th, 6th). The two clutches operate independently and alternately to perform gear changes. For example, when changing from 1st to 2nd gear, the engine’s ECU detects the upshift and engages 2nd gear, then releases the clutch controlling 1st gear while simultaneously engaging the clutch handling 2nd gear. So instead of having to take the time to connect a spinning gear to a stationary one as in a conventional transmission, the dual clutch system basically already has the gear engaged. Because there is virtually no interruption of power and the clutches are electro-hydraulically controlled, the gearchanges are not only seamless but are also accomplished far quicker than any human can.
The unique aspect of the Honda dual clutch transmission is that it features a light, compact design that allows the system to be combined with existing motorcycle engines without requiring a complete revamp of the engine’s layout. The new system employs dual input shafts and a patented inline clutch design, and concentration of hydraulic circuitry beneath the engine cover to reduce mass. The shift mechanism design is based on that of a conventional motorcycle shift drum, so it isn’t overly bulky or heavy.
In order to respond to rider demands in a broad range of situations, the transmission is equipped with three operating modes: two fully automatic modes (D-mode for regular operation and S-mode for “sporty riding”), and a 6-speed manual mode that the rider operates by paddles on the left handlebar. Optimized shift scheduling in the auto modes achieves fuel economy equal to or better than that of a fully manual transmission, enabling the Honda Dual Clutch Transmission to deliver both performance and economy combined.
One very interesting aspect of the Honda announcement was the company “intends to gradually expand the deployment of the new transmission to more and more of its large-displacement motorcycles, particularly sports models destined for use in developed countries.” In other words, don’t be surprised to see this dual clutch semi-automatic transmission on the CBR1000RR (and maybe the 600RR?) in the future.
