Automatic transmission for electric vehicle hub

An automatic transmission for an electric vehicle hub, comprising:

• an external motor rotor fixedly connected with a motor shaft;
• a sun gear;
• at least three first planet gears which are arranged circumferentially around the sun gear;
• and
• at least three corresponding second planet gears coaxially fixed with the respective first planet gears;
• wherein the first and the second planet gears are respectively engaged and transmitted along with first and second internal gears, and the second internal gear has a diameter greater than that of the first internal gear;
• and
• wherein a rotating disk is arranged between external circumferential surface of the first internal gear and internal circumferential surface of the second internal gear, and a hub is fixed to exterior of the rotating disk;
• and
• the automatic transmission further comprising:
• a clutch device, making the rotating disk and the external circumferential surface of the first internal gear contact with each other for a transmission of slower rpm, and when the rpm reaches critical, making the rotating disk and the internal circumferential surface of the second internal gear contact with each other at a high-speed rotation.