Primary-secondary hinge

The utility model discloses a primary-secondary hinge which comprises a secondary hinge and a primary hinge, a first sleeve is arranged on the primary hinge, a second sleeve is arranged on the secondary hinge, and a connecting piece which penetrates through the first sleeve and the second sleeve to enable the secondary hinge and the primary hinge to be rotatably connected is arranged between the secondary hinge and the primary hinge. The connecting piece comprises a center shaft penetrating through the first sleeve and the second sleeve, the center shaft comprises a first end and a second end which extend out of the two ends of the first sleeve respectively, and the first end and the second end are fixed to the two ends of the first sleeve to limit rotation of the first sleeve relative to the center shaft. A lubricating channel capable of storing lubricating oil is formed in the center shaft, a gap between the center shaft and the second sleeve can be lubricated through a lubricating hole, friction generated