Honda-original, rubber-belt-type, electronically-controlled CVT

In the development of the S Matic system, Honda set the following three goals.

(1) Compact and light weight
(2) Shift characteristics that allow attainment of fuel economy, exhaust emissions, quietness and driving performance.
(3) The control system shall not be complex.

In the system applied to the 2004 FORZA, the manual mode has been added to the two kinds of automatic modes. From the standpoint of providing additional riding fun rather than purly the pursuit of efficiency, the system permits the rider’s active choice of shifting in 6 speeds.

While the unsprung, unit-swing engine configuration is common in scooters, as the engine weight is very influential to the dynamic performance of the vehicle, the unit has to be as light as possible. To maintain the virtue of the conventional belt-type CVT, as well as employing the rubber belt, the pulleys are made of die-cast aluminum alloy.
The boss of the movable drive face is made of steel and cast in the aluminum alloy pulley to reduce the pitch diameter to allow for a wide-range reduction ratio.

Honda S Matic system overview
 Honda S Matic system overview

Outlines of system
The sensors are incorporated to detect the drive pulley revolutions, the driven pulley revolutions, the pulley position, the vehicle speed, and the throttle opening. Referring to the inputs from those sensors and switches, the reduction ratio control unit determines items to control, and controls the pulley position by controlling the drive motor.
The control current occurs in the motor, the motor spins, and the rotation is transmitted to the movable gear via the reduction gear. The feed thread in the movable gear changes the rotating force into an axial force that moves the movable drive face for shifting of the reduction ratio.
The guide key is employed to allow the movable drive face to slide and transmit the engine torque. As the gears in the shifting mechanism are of no lubrication type, some gears are made of plastic to reduce wear and weight. The guide key, which transmits torque, and a part of the feed thread are grease-lubricated to ensure smooth operations.
In addition to the above-mentioned, the outside air is introduced in the belt housing to lower the belt temperature and extend belt life. Also, careful measures are taken to prevent dust entry into the housing. Although the construction in the driven side is similar to that of a conventional belt-type CVT, the rotor has been added to detect the pulley revolutions.


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