Transmission assembly, speed reducer and industrial robot

The utility model discloses a transmission assembly, a speed reducer and an industrial robot. The transmission assembly comprises a first transmission part and a second transmission part, the first transmission part is provided with a gear pin, the second transmission part is provided with a gear groove, and the first transmission part and the second transmission part can perform transmission through mutual meshing of the gear pin and the groove wall of the gear groove; according to the configuration of the transmission assembly, the size of a gap formed by meshing of the gear pin and the groove wall of the gear groove is within a first preset range, and the first preset range can be determined through the radius of the gear pin and the radius of the groove wall of the gear groove. According to the transmission assembly, the design range of the gap when the gear pin and the gear groove are meshed is determined according to the radiuses of the gear pin and the gear groove, so that the gear pin and the gear groove are more reasonable in size matching, lubricating oil can achieve a good lubricating effect between the gear pin and the gear groove, stress concentration of the gear pin and the gear groove can be avoided, and the service life of the gear pin and the gear groove is prolonged. And the service life of the whole transmission structure is prolonged.