Hydraulic automatic pressure-relief device for starting of diesel engine

The utility model relates to a hydraulic automatic pressure-reducing device for the starting of a diesel engine. The device comprises a cylinder head cover and a pressure-relief shaft; an oil inlet passage is arranged on the cylinder wall of the cylinder head cover on one side of an intake rocker; one side of the pressure-relief shaft is hermetically connected with the oil inlet passage of the cylinder head cover, the other side is supported in the cylinder head cover through an elastic component; a tapered lug boss on the pressure-relief shaft is connected with an exhaust rocker or the intake rocker; and the small taper surface of the tapered lug boss faces to one side of the oil inlet passage of the cylinder head cover. The utility model utilizes the lubrication system in the diesel, adopts lubricant as the power to control the axial movement of the pressure-relief shaft, and has the characteristics of reasonable and simple structure and capability of protecting the diesel engine.