Low speed gear module

A low speed gear module, comprising:

• a fixed cylinder part, comprising a first inner gear;
• a rotating cylinder, arranged corresponding to the fixed cylinder part, rotatable relative to the fixed cylinder part, comprising a second inner gear, and an accommodating space jointly defined between the first inner gear and the second inner gear;
• a first planetary gear set, accommodated in the accommodating space, and comprising a fixing plate, a plurality of first planetary gears fixedly coupled to a side of the fixing plate, and a driven gear fixedly coupled to another side of the fixing plate;
• a sun gear, installed between the first planetary gears, each first planetary gear engaged with the sun gear at one side thereof and engaged with the first inner gear at another side thereof to drive the driven gear to rotate with the first planetary gears;
• a second planetary gear set, installed on a periphery of the driven gear, comprising a positioning frame and a plurality of second planetary gears pivotally coupled to the positioning frame, each second planetary gear engaged with the driven gear at one side thereof and engaged with the first inner gear and the second inner gear at another side thereof to drive the rotating cylinder to rotate with the driven gear, and the positioning frame comprising a through hole defined on one side thereof for the driven gear to be inserted;
• a concave-convex structure, comprising a convex column extended from the rotating cylinder or another side of the positioning frame and a concave hole defined on another one of the rotating cylinders and another side of the positioning frame, and the convex column inserted in the concave hole;
• and
• a limit bearing set, comprising a first ball bearing adapted to sheathe the driven gear and mounted between the driven gear and inner surface of the through hole, and a second ball bearing adapted to sheathe the convex column and mounted between the convex column and inner surface of the concave hole.