Speed reducer assembling unit and speed reducer assembling module

The utility model belongs to the technical field of speed reducer assembly, and discloses a speed reducer assembly unit which comprises a fixed part and a movable part. The fixed part comprises a fixed frame, a cam rotationally supported on the fixed frame, a rotary driver for driving the cam to rotate, a limiting seat located above the cam and a lifting driver for driving the limiting seat to lift, the rotation center line of the cam is in the vertical direction, and the limiting seat is provided with a vertically-through speed reducer limiting cavity; the movable part comprises a supporting plate and a positioning seat arranged on the supporting plate in a sliding mode, the sliding direction is consistent with the large-diameter direction of the cam, and a limiting assembly is arranged between the supporting plate and the positioning seat. The limiting assembly comprises two fixed blocks and a movable block arranged between the two fixed blocks, a spring is arranged between the movable block and any fixed b