Automotive automatic transmission

An automotive automatic transmission comprising:

• a primary transmission mechanism including:
• an input shaft connected to an engine;
• a planetary gear set having a sun gear, planetary gears and a ring gear, each of which is a helical gear, wherein one of said sun gear and said ring gear is connected to said input shaft and the other is connected to a stationary member via a one-way clutch and wherein a carrier for said planetary gears is connected to a primary output shaft;
• and
• an centrifugal clutch adapted to engage and release said input shaft with and from said primary output shaft in correspondence with a centrifugal force by a weight and a thrust force by said helical gear;
• a secondary transmission mechanism connected to said primary output shaft of said primary transmission, for controlling a gear-shift into two or more speed-changed conditions;
• and
• a gear shift controlling unit establishing a multiplicity of change-speed gears by selectively combining a released state and an engaged state of said centrifugal clutch of said primary transmission mechanism for each of said speed-changed conditions of said secondary transmission mechanism.