Engine Lubrication Method

Abstract

A four-cycle engine has a lightweight aluminum alloy engine block having a cylindrical bore and an enclosed oil reservoir formed therein. A crankshaft is rotatably mounted in the engine block for rotation about a crankshaft axis. A piston reciprocates within the bore and is connected to the crankshaft by a connecting rod. An oil pump driven by the cam gear, which mates with crank gear that is driven by crank shaft, inhales the oil from the oil reservoir and the valve chamber to splash lubricate into the cylinder bore. The engine is provided with a cylinder head assembly defining a compact combustion chamber having a pair of overhead intake and exhaust ports and cooperating intake and exhaust valves.

1 . A single-cylinder, four-stroke cycle, spark ignition internal combustion engine for mounting on a power tool comprising:
 a cylinder block having a cylinder, a cylinder head, a piston mounted for reciprocation in said cylinder, said cylinder head defining an air-fuel combustion chamber;   a lower case mating with said cylinder block by a plane perpendicular to the cylinder bore axis;   a crankshaft chamber formed by said cylinder block and said lower case;   an air-fuel mixture intake port and an exhaust gas port in said cylinder head;   a valve cover on said cylinder head defining a valve chamber;   an intake valve and an exhaust valve mounted in said intake and exhaust port, respectively, for reciprocation between port-open and port-closed positions;   a valve-actuating valve train in a valve chamber, said valve train including at least one rocker arm and at least one valve train push rod assembly extending therefrom within said valve chamber and engaging said rocker arm;   a crankshaft rotatably mounted in said crankshaft chamber, wherein said crankshaft includes a crank portion and at least one counterweight web and has an axis which is on the mating plane of said cylinder block and said lower case;   a connecting rod having articulated connections at one end thereof to said piston and at an opposite end thereof to said crank portion, thereby forming a piston-connecting rod crankshaft assembly;   a cam chamber having at least one earn being drivably connected to said crankshaft, said at least one cam having a cam gear and being driven at one-half crankshaft speed, the opposite end of said push rod assembly being drivably connected to said cam whereby said push rod assembly is actuated with a reciprocating motion upon rotation of said at least one cam, said cam chamber having communication means to the crankshaft chamber;   a lubrication oil reservoir formed below the lower case; and   an oil pump connected drivably to said cam gear-cam assembly, wherein said pump inhales lubrication oil from said oil reservoir and valve chamber and splashes the oil in parallel into the cylinder and into the cam chamber to lubricate the engine parts inside the cylinder and the cam chamber and the valve chamber.   
     
     
         2 . The engine set forth in  claim 1  further comprising an air cleaner box connected to said valve chamber via a first passage through which breathing oil mist gas flows, a second passage connecting the air cleaner box to the crankshaft chamber or cylinder block, and a valve being provided at the entrance of said passage into the crankshaft chamber, wherein the opening of the valve is controlled by reciprocating motion of said piston, and wherein said valve opens when pressure in the crankshaft chamber is negative and closes when the pressure in the crankshaft chamber is positive, thereby the oil mist flow control valve structure establishing a lubrication oil mist flow circuit from said valve chamber to said crankshaft chamber or said cylinder block through said air cleaner box. 
     
     
         3 . The engine set forth in  claim 1 , wherein said oil pump is integrally attached with the cam or the cam gear. 
     
     
         4 . The engine set forth in  claim 1 , wherein said oil pump is a trochoid pump. 
     
     
         5 . The engine set forth in  claim 1 , wherein said oil pump has two separated inlet cavities. 
     
     
         6 . The engine set forth in  claim 1 , wherein said oil pump has at least one relief passage which communicates between outlet cavity of the pump and the oil reservoir. 
     
     
         7 . The engine set forth in  claim 1 , wherein said lower case has a circular arc wall to separate said oil reservoir from said crankshaft chamber, said circular arc wall at least partially surrounding said web at a slight distance therefrom, and said circular arc wall having a drain hole and slits to communicate between said crankshaft chamber and oil reservoir. 
     
     
         8 . The engine set forth in  claim 1 , wherein said circular arc wall is shaped to be a 20 to 45 degree to said drain hole. 
     
     
         9 . A hand-held, transportable, or stationary power tool driven by the engine set forth in  claim 1 , wherein said power tool is driven by a horizontal or vertical or inclined power shaft. 
     
     
         10 . The engine set forth in  claim 1 , wherein said cylinder block has at least one oil recess to store oil when the engine is oriented to incline and to prevent oil in the crankshaft chamber from flowing into combustion chamber. 
     
     
         11 . The engine set forth in  claim 1 , wherein said lower case has at least one oil recess to store oil when the engine is oriented to incline and to prevent oil in the oil reservoir from flowing into said combustion chamber. 
     
     
         12 . The engine set forth in  claim 1 , wherein said lower case has at least one long pipe to prevent oil in the oil reservoir from flowing into said cam chamber or said valve chamber. 
     
     
         13 . The engine set forth in  claim 1 , wherein said intake and exhaust valves are inclined with respect to each other. 
     
     
         14 . The engine set forth in  claim 1 , wherein said cylinder block has at least one oil passage located near the intake valve to communicate between said valve chamber and said oil reservoir. 
     
     
         15 . The engine set forth in  claim 1 , wherein said cylinder block has at least one oil passage located near the intake valve to communicate between said valve chamber and said oil recess in the cylinder block. 
     
     
         16 . The engine set forth in  claim 15 , wherein said cylinder block has at least one long pipe to prevent oil in the oil recess from flowing into said valve chamber.