Single-joint flexible joint

The invention belongs to the field of petroleum logging instruments, and particularly relates to a single-joint flexible joint. The flexible joint comprises an upper connector assembly, a skin balancing assembly, a joint flexible assembly and a lower connector assembly, wherein the skin balancing assembly comprises a pressure-bearing plug, a balancing main shaft, an isolation cover, a rubber sleeve and a locking steel wire and can balance the external pressure borne by an instrument so as to realize zero difference between internal pressure and external pressure difference of the instrument; and the joint flexible assembly comprises a pressure-resistant hose, a spherical bearing, a connecting shaft, a connecting key, a spherical shaft, a spherical sleeve and a central spindle and can not only realize axial bending of the upper and lower sections of the instrument, but also realize relative rotation of the upper and lower sections of the instrument. According to the flexible joint, theproblem that an instrumen