Train door uncoupling cylinder

The utility model discloses a train door uncoupling cylinder which comprises a cylinder base, a cylinder cover, a seal ring, a piston and a piston rod, wherein the middle of the cylinder base is provided with a cylinder tube; the bronzine cylinder cover is plugged at the upper part of the cylinder tube; a sealed cylinder chamber is formed by the cylinder cover and the interior of the cylinder tube; the middle of the cylinder cover is provided with a perforated inner hole; the piston rod stretches into the cylinder chamber from the inner hole; the piston is arranged at the tail end, which is positioned in the cylinder chamber, of the piston rod; the seal ring is sleeved outside the piston, so that the piston and the side wall of the cylinder chamber are sealed, and the section of the seal ring is of an inverted Y shape; the side wall, which is contacted with the piston rod, of the inner hole is provided with an oil storage tank; the oil storage tank is internally provided with a lubricant grease; a clearance b