PATENT OF THE WEEK – CONTINUOUSLY VARIABLE TRANSMISSION

The Continuously Variable Transmission was invented by Akihiko Kita on December 18, 2007 bearing patent number US7309067B2.

A belt type (CVT type) continuously variable automatic transmission (hereinafter referred to as a “continuously variable transmission”) mounted in, for example, a vehicle, typically includes a forward-reverse switching mechanism for switching the input rotation between forward rotation and reverse rotation, and a speed change unit for freely changing the speed ratio.

An input shaft, a stepless speed change unit, a forward-reverse switching mechanism, and an output shaft are arranged in that order in a power transmitting path of a continuously variable transmission. The forward-reverse switching mechanism includes i) a gear mechanism having a sun gear which rotates in the same direction as the rotation output from the stepless speed change unit, a carrier which is always fixed (stationary), and a ring gear which rotates in the reverse direction, ii) a clutch between the sun gear and the output shaft, and iii) a clutch between the ring gear and the output shaft. This structure enables the transmission of power between the gear mechanism and the stepless speed change unit and the vehicle drive wheels to be interrupted by the clutches when the vehicle is being towed or is stopped suddenly, and also obviates the need for a brake able to withstand a large amount of torque.