The utility model discloses a pin shaft assembly. The pin shaft assembly comprises a pin shaft body, a driving rod and a plug, wherein the pin shaft body is provided with a lubrication channel and a storing cavity used for storing a lubrication medium; one end of the driving rod is arranged in the storing cavity; the plug is detachably fixed on the end part of the pin shaft body, and is used for plugging the open end of the storing cavity; the driving rod is in transmission threaded connection with the plug, and the other end of the driving rod passes through the plug and extends out of the pin shaft body; one end of the lubrication channel is communicated with the storing cavity, and the other end of the lubrication channel extends to the peripheral wall of the pin shaft body; in a conventional state, the lubrication medium is stored in the lubrication cavity; during lubrication, an operator rotates the driving rod periodically; under the action of a transmission thread, the driving rod further goes deep into the storing cavity, and the lubrication medium in the storing cavity is pressed, so that the lubrication medium is driven to flow to the peripheral wall of the pin shaft body through the lubrication channel in order to lubricate a sliding bearing. Moreover, the utility model further discloses an articulation mechanism and an engineering machine.