Reduction gear and electromechanical device

A reduction gear, comprising a motor and a speed reduction assembly, wherein the motor comprises:

• a first rotary shaft and a second rotary shaft which rotate around a central axis,
• a second rotor and a first rotor which are disposed on radial outer sides of the second rotary shaft and the first rotary shaft respectively,
• a stator disposed between the second rotor and the first rotor, and
• a first motor housing disposed on an axial side, away from the stator, of the first rotor;
• the speed reduction assembly comprises
• a first gear disposed on one side, away from the first rotor, of the second rotor,
• a second gear and a third gear which mesh with the first gears, and
• an output shaft driven by the third gear;
• and
• the motor further comprises:
• a first bearing disposed on a radial inner side of the first rotary shaft, and
• a second bearing disposed on a radial inner side of the second rotary shaft or the output shaft,
• the first bearing and the second bearing are located on two sides of the stator in an axial direction, and
• the first gear is located on one side, away from the stator, of the second rotor,
• wherein the second bearing is disposed on the radial inner side of the first gears, the second gear and the third gear, and at least a part of the second bearing overlaps with the first gear in a radial direction of the reduction gear.