Extension tube-type vehicle-mounted back support

An extension tube-type vehicle-mounted back support, comprising a mounting rod and a mounting part mounted on the mounting rod for retaining a mobile device;

• the mounting rod including a connector and two connection tubes respectively connected to left and right ends of the connector, outer ends of the two connection tubes being connected with clamping parts respectively, at least one of the connection tubes being internally provided with a telescopic spring, a corresponding one of the clamping parts being biased by the telescopic spring to move left and right relative to the connection tube having the telescopic spring;
• wherein the mounting part includes a rotating rod mounted on the mounting rod, a ball joint assembly mounted on the rotating rod, and a brace mounted on the ball joint assembly;
• the rotating rod has a hollow rod body and a pivot interface connected to one side of the hollow rod body, the hollow rod body is fitted on the mounting rod, upper and lower sides of the pivot interface are provided with locking walls each having a first connecting hole;
• the ball joint assembly has a pivot seat, the pivot seat has a second connecting hole, the pivot seat is inserted into the pivot interface, a screw is inserted through the first connecting hole of the upper locking wall, the second connecting hole and the first connecting hole of the lower locking wall in sequence, and a lower end of the screw is fitted with an adjusting nut;
• wherein the connector has a middle limiting portion and two connecting shaft portions extending outward from two sides of the middle limiting portion;
• one of the connection tubes is fitted on an outer periphery of one of the connecting shaft portions, and the other connection tube is fitted on an outer periphery of the middle limiting portion, one end of the telescopic spring is fitted on an outer periphery of the other connecting shaft portion, another end of the telescopic spring is connected to the corresponding clamping part;
• one end of the hollow rod body extends radially inwardly to form an annular stop portion, the hollow rod body is fitted on an outer periphery of the other connection tube, and the annular stop portion is configured to limit an inner end of the other connection tube.