Oil cylinders capable of expanding and retracting reliably and sequentially, multi-oil cylinder sequential telescopic mechanism and engineering machinery

The invention discloses oil cylinders capable of expanding and retracting reliably and sequentially, a multi-oil cylinder sequential telescopic mechanism and engineering machinery, and belongs to thetechnical field of fluid pressure executing mechanisms. A first piston rod is provided with a sixth oil port and a seventh oil port, the sixth oil port and the seventh oil port both communicate with the outer wall of the first piston rod, a first piston and the first piston rod are provided with an eighth oil port, the first piston rod is provided with an inner cavity, the inner cavity is providedwith a first oil passage pipe and a second oil passage pipe, the first oil passage pipe communicates with the eighth oil port and a third oil port, the second oil passage pipe communicates with the seventh oil port and a fourth oil port, a fifth oil port and the sixth oil port communicate with the inner cavity, the first piston rod is provided with a stroke control valve, the stroke control valvecontrols opening and closi