Lubricating method of lubrication system of engine

A lubricating method of a lubrication system of an engine, wherein

• an oil chamber (7) is arranged on a crankcase (6), a first check valve (8) with an oil circuit unidirectionally leading to the oil chamber (7) is arranged between a crankshaft chamber (5) and the oil chamber (7), a first lubricating oil circuit (14) is arranged between the oil chamber (7) and a cam chamber (3);
• the cam chamber (3) is communicated with an upper rocker aim chamber (1) through a tappet hole, an oil nozzle (18) is arranged on the first lubricating oil circuit (14);
• an oil return circuit that communicates the upper rocker arm chamber (1) and the crankshaft chamber (5) in the crankcase (6) is arranged on a cylinder (13), and a second check valve (17) which can unidirectionally lead to the crankshaft chamber (5) from the upper rocker arm chamber (1) is arranged in the oil return circuit;
• and
• when a piston (2) goes up, the pressure in the crankshaft chamber (5) is reduced, the first check valve (8) is closed, and oil mist in the upper rocker arm chamber (1) returns to the crankshaft chamber (5) through the oil return circuit and the second check valve (17);
• wherein threshold values of the first check valve and. the second check valve are set to 0.10 MPa;
• a cross-sectional area of the oil circuit from inside to an outlet of the oil nozzle (18) is gradually decreased;
• a minimum oil circuit cross-sectional area of the first lubricating oil circuit (14) is S1, a minimum oil circuit cross-sectional area of the oil nozzle (18) is S2, and an oil circuit cross-sectional area of an expansion port of the oil nozzle (18) is S3, wherein S1/S2 is greater than 1.5, S3/S2 is greater than 1.8.