Back group of chain ware of bicycle

The utility model provides a back group of chain ware of bicycle, include one group of chain frame, a drive unit, a drive unit, an and buffer unit, drive unit has a frame fixing base, an interconnection moving part, an and outer interlock spare, it is interior, outer interlock spare pivot is located and is dialled between chain frame and the frame fixing base, drive unit has a motor, a nut seat, an and driving screw, frame fixing base and outer interlock spare are located to the motor pivot, the interconnection moving part is located to nut seat pivot, the motor is connected to the one end of driving screw, other end spiro union in the nut seat of driving screw, the buffer unit has one and keeps a seat and a bolster, just it keeps the hole to have one to keep an outer peripheral face of locating the motor, the bolster is located keep hole and the top that keep the seat and is supported in outer interlock spare, so the structure arrangement can let the buffer unit provide the protection effect to drive unit.