Lubricating device for piston of cold air relief valve

The utility model discloses a lubricating device of a cold air vent valve piston, which comprises a cylinder body, a vent piston matched with the cylinder body is arranged in the cylinder body, a cast iron piston ring is arranged at the bottom of the vent piston, a cylinder cover is arranged at the top of the cylinder body, a small oil pocket is arranged at the top of the cylinder cover, a plurality of groups of oil dripping pipes are connected onto the small oil pocket, and the small oil pocket is connected with a large oil pocket through a connecting pipe. The left side of the top of the large oil pocket is connected with a nitrogen pipeline, the nitrogen pipeline is provided with a second ball valve, and the right side of the top of the large oil pocket is connected with an oil supplementing pipe. Flame-retardant hydraulic oil can be added into the large oil pocket half an hour before the valve acts, the hydraulic oil is fed into the small oil pocket through nitrogen pressure, the hydraulic oil is dropped