Adjustable chair backrest mechanism

The utility model relates to the technical field of chair backrests, in particular to an adjustable chair backrest mechanism, which comprises a fixing plate, a backrest plate and a mounting rod, the side end face of the fixing plate is provided with mounting plates which are symmetrically distributed, a rotating shaft is rotatably mounted between the mounting plates, the side ends of the mounting plates are provided with round pipes, and the round pipes are connected with the backrest plate. A second spring is mounted in the round pipe, the mounting rod is mounted at the tail end of the second spring and penetrates through the mounting plate, a first gear is mounted on the mounting rod, connecting rods which are symmetrically distributed are mounted at the upper end of the rotating shaft, and the backrest plate is mounted at the upper ends of the connecting rods. Telescopic supporting rods distributed in an array mode are installed at the side end of the backrest plate, a supporting plate is installed at the