Harmonic speed reducer

The utility model discloses a harmonic speed reducer, which relates to the technical field of harmonic speed reducers and comprises a flexible gear, a wave generator and a rigid gear. The surface hardness of the first nitriding layer arranged on the surface of the flexible gear ranges from 550 HV to 750 HV, so that the flexible gear has better abrasion resistance, the abrasion resistance of the first tooth part and the first inner hole is better, the abrasion loss generated when the flexible gear is meshed with the second tooth part of the rigid gear is reduced, and the service life of the flexible gear is prolonged. The surface hardness of the first nitriding layer of the rigid wheel ranges from 450 HV to 650 HV, so that the rigid wheel has certain strength and wear resistance. The hardness of the first nitriding layer is larger than that of the second nitriding layer, the abrasion condition of the flexible gear can be effectively improved, the service life of the flexible gear is prolonged, and the replacem