Crankcase Scavenging Mechanism for a Four-Stroke Engine

Abstract

A crankcase scavenging mechanism for a four-stroke engine is disclosed. A valve operating chamber is assembled from a cylinder head and a cylinder head cover and is communicated with a crankcase. The cylinder head cover is arranged on the top of the cylinder head and is provided with a gas-oil separating cavity on the top thereof. A passage is communicated with the valve operating chamber. The gas-oil separating cavity is connected with a partition plate to form an oil-gas separation chamber. The oil-gas separation chamber is provided with a one-way valve thereon. The one-way valve is installed in a one-way valve hole. A passage above the one-way valve is provided with an inclined orifice, one end of which is blocked by a plug, the other end of which is communicated with the cylinder head and is further communicated with a suction tube through a cylinder head communication passage. An oil-returning hole is formed between the inclined orifice of the passage and the oil-gas separation chamber.

1 . A crankcase scavenging mechanism for a four-stroke engine wherein a main body of the engine comprises a casing, a cylinder sleeve and a cylinder head; a crankcase the engine is assembled from the casing and a crankcase cover, the crankcase being provided with a crankshaft therein and containing lubricating oil; a valve operating chamber is assembled from the cylinder head and a cylinder head cover and is communicated with the crankcase; a piston is connected to a crankpin of the crankshaft via a connecting rod; the cylinder head is communicated with a combustion chamber; a suction system is held on the cylinder head to communicate with a gas inlet of the cylinder head; the cylinder head cover is arranged on the cylinder head; wherein the cylinder head cover is provided with a gas-oil separating cavity on the top thereof, the gas-oil separating cavity being communicated with the valve operating chamber via a passage and being connected with a partition plate to form the oil-gas separation chamber; the oil-gas separation chamber is provided with a one-way valve thereon, the one-way valve being installed in a one-way valve hole; a passage above the one-way valve is provided with an inclined orifice one end of which is blocked by a plug, the other end of which is communicated with the cylinder head and is further communicated with a suction tube through a cylinder head communication passage; and an oil-returning hole is formed between the inclined orifice of the passage and the oil-gas separation chamber. 
   
   
       2 . The crankcase scavenging mechanism for a four-stroke engine according to  claim 1 , wherein the gas-oil separating cavity is of labyrinth formed by three labyrinth-forming walls. 
   
   
       3 . The crankcase scavenging mechanism for a four-stroke engine according to  claim 1 , wherein the one-way valve comprises a valve seat, a plastic ball within the valve seat, a cylindrical pin, and a seal ring within the valve seat. 
   
   
       4 . The crankcase scavenging mechanism for a four-stroke engine according to  claim 2 , wherein the one-way valve comprises a valve seat, a plastic ball within the valve seat, a cylindrical pin, and a seal ring within the valve seat.