TH36967A - Lubrication system in 4-stroke engines - Google Patents

Abstract

The oil reservoir, crankcase, and valve working chamber are located within the engine. The oil reservoir and crankcase are in contact with each other through orifices, and the crankcase and valve working chamber are in contact with each other through one-way valves that open during pressure build-up in the crankcase. The valve working chamber and oil reservoir are in contact with each other through orifice holes. Actuated by pressure build-up in the crankcase, the oil mist generated in the oil reservoir recirculates from the oil reservoir to the crankcase, valve working chamber, and oil reservoir. Therefore, at any operating height of the engine, the lubricating oil can recirculate without the need for a separate oil pump.

Claims (12)

1. The lubrication system for a four-stroke engine consists of an oil reservoir (22) which holds the lubricating oil (0) and contains an oil mist production pathway (25) for producing oil mist from the lubricating oil; a crankcase (23) which contains the crankshaft section (13a) (13); and an operating valve chamber (24) which contains the operating valve device (31). The aforementioned oil reservoir (22), the aforementioned crankcase (23), and the aforementioned operating valve chamber (24) are supplied to the engine body (1). The aforementioned oil reservoir (22) and the aforementioned crankcase (23) are in contact with each other through a through hole (46) located above the oil level in the oil reservoir (22). The aforementioned crankcase (23) and the aforementioned operating valve chamber (24) are in contact with each other through control valves (49, 71) which open during boosting. The crankcase pressure is reduced (23) and the valve is closed when the crankcase pressure is reduced (23). The working valve chamber (24) is in contact at the top with the atmosphere and at the bottom with the oil reservoir (22) through the orifice (51), and the following relationship occurs during engine operation: Pc less than or equal to Po less than Pv, where Pc is the crankcase pressure (23); Po is the oil reservoir pressure (22); and Pv is the working valve chamber pressure (24). 2. The lubrication system for the four-stroke engine under claim 1 also consists of an uppermost chamber (56) which occupies the position above the working valve chamber (24) and is in contact with the working valve chamber (24) through the orifice (57) and is also in contact with the aforementioned oil reservoir (22) or the aforementioned crankcase (23) through the oil passage (58) and the following relationship occurs during engine operation: Pc less than or equal to Po less than or equal to Pt less than or equal to Pv, where Pt is the pressure in the uppermost chamber (56). 3. A system for lubricating a four-stroke engine under either claim 1 or 2, in which the oil mist production pathway consists of an oil crankshaft (25) which is rotated by the aforementioned crankshaft (13) to agitate and distribute the lubricating oil (0) to the aforementioned oil reservoir (22) at all times, regardless of the engine's tilt state. 4. A system for lubricating a four-stroke engine according to claim No. 1, in which the aforementioned control valves consist of a one-way valve (49) of the pressure-responsive type. 5. A system for lubricating a four-stroke engine according to claim 1, in which the aforementioned control valves consist of a rotary valve (71) which opens during the downward movement of the piston (8) in conjunction with the rotation of the crankshaft (13) and closes during the upward movement of the piston (8). 6. A lubrication system for a four-stroke engine according to claim number 5, in which the opening time of the aforementioned rotary valve (71) is approximately 180 degrees in terms of crank angle, and the starting point of the opening of the aforementioned rotary valve (71) is determined in the range from the center point (p) between the top dead center and bottom dead center of the piston (8) to the piston drop position at 45 degrees of the aforementioned piston (8) in terms of crank angle. 7. A system for lubricating an air-cooled four-stroke engine according to any of the claims 1 through 6, whereby the engine is also comprised of a shield (69) that covers the outer circumference of the cylinder block (6) and defines the cooling air passage (68) between the shield (69) and the outer circumference of the cylinder block (6); a cooling fan (60) mounted at one end of the crankshaft (13) supported in the cylinder block (7) for feeding cooling air into the cooling air passage (68); and a recoil starter (70) mounted to the cylinder block (7) to extend outward of the shield (69) and which can act as a crankshaft at the other end of the crankshaft (13) where such oil chamber (22) is built into the crankcase (7) and between the recoil starter (70) and the crankcase (23) in the crankshaft section (7) and the oil mist that Produced in the oil reservoir (22), it is fed to the crankcase (23) and other parts of the engine. 8. The lubrication system for a four-stroke engine consists of a crankcase (132) containing the crankshaft section (108a) of the crankshaft (108) which holds the lubricating oil (0) in it, and a working valve chamber (116) containing the working valve device (115). The aforementioned crankcase (132) and the aforementioned working valve chamber (116) are supplied to the engine body (101). The oil mist production pathway (135) is supplied to the aforementioned crankcase (132) to produce oil mist from the lubricating oil. The aforementioned crankcase (132) and the working valve chamber (116) are in contact with each other above the lubricating oil level (0) in the crankcase (132) through a control valve (139) which opens when the pressure in the aforementioned crankcase (132) increases and closes when the pressure in the aforementioned crankcase decreases. The working valve chamber (116) is in contact at the top with the atmosphere and at the bottom with the The previously mentioned crankcase pressure (132) passes through the orifice (138) and the following relationship occurs between the engine operating pressure Pc less Pv, where Pc is the pressure in the previously mentioned crankcase and Pv is the pressure in the operating valve chamber. 9. The lubrication system for the four-stroke engine under claim number 8 also consists of an uppermost chamber (164) provided to the engine body (101) to occupy a position above the aforementioned working valve chamber (116) located higher and to contact the aforementioned working valve chamber through the orifice (165) and also to contact the aforementioned crankcase (136) through the oil recirculation passage (166) and the following relationship occurs: Pc ≤ or equal to Pt ≤ Pv, where Pt is the pressure in the uppermost chamber (164). 10. A system for lubricating a four-stroke engine according to claim number 8, in which the aforementioned control valve shall be incorporated with a rotary valve (139) which opens during the downward movement of the piston (110) in conjunction with the rotation of the crankshaft (108) and closes during the upward movement of the piston. 11. A lubrication system for a four-stroke engine according to claim 10, in which the opening time of the aforementioned rotary valve (139) is approximately 180 degrees in terms of crank angle, and the opening point of the aforementioned rotary valve is set in or from the center (P) between the top dead center and bottom dead center of the piston to reduce the piston position (110) to the bottom position of the piston at 45 degrees in terms of the aforementioned piston angle. 12. The lubrication system for the four-stroke engine according to claim number 8, in which the crankcase mentioned (132) is made up of an inner chamber (132a) in which the crankshaft section (108a) of the crankshaft (108) is placed, and an outer chamber (132b) is located near the opposite side of the inner chamber mentioned (132a) on the opposite side of the bulkhead (134) and in contact with the bottom of the inner chamber mentioned, and in which the majority of the lubricating oil (0) in the crankcase mentioned (132) is received in the outer chamber mentioned (132b) when the engine (10E) falls to its side or is inverted.