Universal joint of intelligent internal detector for small-caliber oil and gas pipeline and intelligent internal detector

The invention provides a universal joint of an intelligent internal detector for a small-caliber oil and gas pipeline and the intelligent internal detector. The universal joint comprises a connecting rod and two rotary connecting pieces hinged to the two ends of the connecting rod, the end, away from the connecting rod, of each rotary connecting piece is arranged to be hinged to the functional joint, and the hinged shafts, hinged to the connecting rod, of the two rotary connecting pieces intersect in space. The length L of the connecting rod is equal to k1 * D1, the diameter D2 of the connecting rod is equal to k2 * L, the length L1 of each rotary connecting piece is equal to k3 * L, k1 ranges from 0.5 to 1.2, k2 ranges from 0.12 to 0.18, k3 ranges from 0.22 to 0.28, and D1 is not larger than DN100. When the universal joint is applied to the intelligent internal detector to detect internal defects of a small-caliber oil and gas pipeline, adjacent functional joints of the intelligent internal detector are hing