Swing hydraulic cylinder with bidirectionally adjustable rotation angle for electro-hydraulic actuator

According to the swing hydraulic cylinder, a gear is arranged in a gear box, a cylinder barrel is installed above the gear box, a rack is arranged in the cylinder barrel, the rack is meshed with the gear, cylinder covers are arranged at the two ends of the cylinder barrel respectively in a sealing mode, sealing rings are arranged at the two ends of the rack respectively, and the two ends of the cylinder barrel are meshed with the gear. A first cavity is reserved between the rack and each cylinder cover, a first oil way is arranged on each cylinder cover, a barrel is arranged on the outer side of each cylinder cover, each cylinder cover is sealed at the inner end of the barrel, a barrel cover covers the outer end of each barrel, a second oil way is arranged on each barrel cover, and a piston is arranged in each barrel. Each piston divides the barrel into a second cavity and a third cavity, each first oil way is communicated with the corresponding second cavity, each second oil way is communicated with the thir