Patent Application
20090013959
1. Field of Invention
The invention relates to four-stroke internal combustion engine (ICE) and more particularly to an improved lubrication system for a small lightweight four-stroke engine.
2. Description of Related Art
Portable power tools such as lawn movers, line trimmers, chain saws as mostly powered by two-stroke ICEs in earlier days. Gradually, two-stroke engines are phased out due to heavy harmful exhaust emissions (e.g., hydrocarbon (HC)). Nowadays, almost all such portable power tools are powered by four-stroke ICEs.
Lubrication becomes a very serious problem since portable power tools are required to operate in a wide range of orientations (i.e., being tilted or even upside down). There have been numerous suggestions in prior patents for solving this problem. For example, U.S. Pat. No. 7,287,508 discloses an engine lubrication method which is incorporated herein by reference. Thus, continuing improvements in the exploitation of lubrication system for a small lightweight four-stroke engine are constantly being sought.
It is therefore one object of the invention to provide a lubrication system for a small lightweight four-stroke engine and the lubrication system, provided with a weight at one end of a flexible oil tube inserted into an oil reservoir, is capable of providing a sufficient lubrication to the engine which may operate in a horizontal posture, a vertical posture, or any posture therebetween.
The above and other objects, features and advantages of the invention will become apparent from the following detailed description taken with the accompanying drawings.
Referring to
A crankcase 10 is provided. An oil reservoir 30 is provided. A check valve case 20 is provided in fluid communication with both the crankcase 10 and the oil reservoir 30. A first branch tube 60 is in fluid communication with both the check valve case 20 and a gaseous oil tube 42 which is connected to a cam actuation section 40. A first venturi 61 is provided proximate a joining portion of the cam actuation section 40 and the gaseous oil tube 42. Note that the number of the first venturi 61 may be more than one depending on applications. A second branch tube 70 is provided between the crankcase 10 and a camshaft case 41 of the cam actuation section 40 and is in fluid communication therewith. A second venturi 71 is provided in the second branch tube 70. The second branch tube 70 has a flexible oil tube 73 having a weight 731 at one end so that one end of the flexible oil tube 73 may be always immersed in the oil reservoir 30, and a tubing member 72 connected to the flexible oil tube 73 and being in fluid communication therewith.
The crankcase 10 comprises a crank casing 11 formed with a cylinder block 81 which has a cylinder bore (not numbered) with a piston 15 slidably provided therein. A passage 12 is provided on the bottom of the crankcase 10 and is in fluid communication with the check valve case 20. A crankshaft 13, provided in the crankcase 10, has two sets of bearings 131 and oil seals 132 at both ends. A connecting rod 14 is provided to interconnect the crankshaft 13 and the piston 15.
The check valve case 20 is provided below the crankcase 10. The check valve case 20 is connected to an oil mist return tube 22 which is extended from the bottom of the check valve case 20 into the oil reservoir 30. A check valve 21 is provided in the check valve case 20 and has a retaining plate 211 and an elastic plate 212 being on the top surface of the retaining plate 211. Oil mist from the crankcase 10 may deflect the elastic plate 212 to open the check valve 21 when the piston 15 moves downward. Hence, oil mist enters the check valve case 20. Finally, oil mist flows to the oil reservoir 30 via the oil mist return tube 22. At the same time, a small portion of oil mist enters the first branch tube 60 which is in fluid communication with the check valve case 20 (see
The oil reservoir 30 is provided below the check valve case 20 and is in fluid communication with the check valve case 20 via the oil mist return tube 22. Liquid lubricating oil is filled in the oil reservoir 30. The oil reservoir 30 has a volume great larger than that of the check valve case 20. Hence, flow rate of the oil mist may decrease greatly when it enter the oil reservoir 30. As a result, heavy liquid oil particles in the oil mist fall into the oil reservoir 30 and light gaseous oil particles in the oil mist are accumulated on the oil level of the oil reservoir 30. Further, gaseous oil may enter the gaseous oil tube 42. An open end of the oil mist return tube 22 is provided above the center of the oil reservoir 30.
The cam actuation section 40 comprises a lower camshaft case 41 and an upper space 431. Two spaced ports 432 are provided between the camshaft case 41 and the space 431. A pushing rod 43 passes through either port 432. In addition to the pushing rods 43, a camshaft 44 and a camshaft follower 45 are provided in the cam actuation section 40. The camshaft 44 comprises a cam 441 and a reduction gear 442 coaxially and integrally formed therewith. The camshaft 44 and the camshaft follower 45 are engaged. The reduction gear 442 is in mesh with a lower gear 46 which is fixed in the crankshaft 13. The cam actuation section 40 has a top end in fluid communication with a rocker arm case 50 and a bottom end provided with the gaseous oil tube 42. The gaseous oil tube 42 has a bottom end disposed above the oil level of the oil reservoir 30. Gaseous oil rather than liquid oil in the oil reservoir 30 may flow to the cam actuation section 40 via the gaseous oil tube 42 when the piston 15 moves downward. Oil mist in the camshaft case 41 is directed along an inner wall 411 of the camshaft case 41 to the ports 432 and a second branch tube inlet 701 when the reduction gear 442 rotates.
The engine may be implemented as an overhead valve (OHV) engine in the embodiment. Alternatively, the engine may be implemented as an overhead camshaft (OHC) engine equipped with a cam 443, upper and lower pulleys 444 in which one of the pulleys 444 is secured to the cam 443, and a belt 47 passing around the pulleys 444 in another embodiment (see
The rocker arm case 50 is provided in a plastic cylinder head cover 80 which is affixed to the cylinder block 81. In the rocker arm case 50 a rocker arm mechanism 51 is provided. The rocker arm mechanism 51 comprises a rocker arm 511, a valve 512, and a compression spring 513. The cam 441 may rotate to actuate the rocker arm mechanism 51 via the camshaft follower 45 and the pushing rods 43.
A small portion of oil mist in the check valve case 20 enters the first venturi 61 via the first branch tube 60. Liquid oil particles in the oil mist are nebulized by the first venturi 61. As an end, oil mist with a small amount of liquid oil enters the camshaft case 41.
The second branch tube 70 has a second branch tube inlet 701 provided in the camshaft case 41 near the port 432. Excess oil mist in the cam actuation section 40 may enter the crankcase 10 via the second branch tube 70 when the piston 15 moves upward. As a result, excess oil mist and liquid oil are prevented from remaining in the cam actuation section 40 and the rocker arm case 50. This has the benefit of reducing the consumption of lubricating oil.
The number of the second branch tube 70 may be more than one depending on applications. Excess oil mist enters the second branch tube 70 when the piston 15 moves upward. Also, lubricating oil in the oil reservoir 30 flows to the second branch tube 70 via the flexible oil tube 73 and the tubing member 72. Oil mist in the second branch tube 70 and liquid oil in the tubing member 72 are mixed in the second venturi 71. Further, the nebulized oil mist enters the crankcase 10 when the piston 15 moves upward.
An oil return section 83 is provided on the top of the cylinder head cover 80 and is separated from the rocker arm case 50 therebelow. The oil return section 83 comprises two oil return reservoirs 831 being in fluid communication with each other, and a plurality of channels 832 interconnecting the oil return section 83 and the rocker arm case 50. Excess oil mist and liquid oil may enter at least one of the channels 832 irrespective of the posture of the engine (i.e., horizontal posture, vertical posture, or any posture therebetween). Therefore, the purpose of returning lubricating oil in the rocker arm case 50 can be achieved.
One end of the oil return section 83 is provided with an oil return line 84 which has one end in fluid communication with the crankcase 10 so that the oil return section 83 can communicate with the crankcase 10. Excess oil mist and liquid oil in the rocker arm case 50 may return to the oil return section 83 via the channels 832. Next, the excess oil mist and liquid oil are inhaled into the crankcase 10 via the oil return line 84.
A liquid oil and gaseous oil separation chamber 85 is provided between the oil return section 83 and the rocker arm case 50. A porous plate 851 for absorbing lubricating oil is provided on the top of the liquid oil and gaseous oil separation chamber 85. A plurality of apertures 852 are provided on the bottom of the liquid oil and gaseous oil separation chamber 85 and are in fluid communication with the rocker arm case 50. Thus, excess oil mist may enter the liquid oil and gaseous oil separation chamber 85 via the apertures 852. Liquid oil particles in the oil mist are absorbed by the porous plate 851. Next, the absorbed liquid oil is inhaled into the oil return section 83 via the channels 832. Finally, it is sent to the crankcase 10 via the oil return line 84. Gaseous oil is separated by the liquid oil and gaseous oil separation chamber 85 to form blow-by gas which is sent to an air filter (not shown) via a breather pipe 86. Blowby gas with clean air passing through the air filter is inhaled into a combustion chamber 87 in an air intake cycle of the engine (see
As shown
As shown in
Oil mist and liquid oil in the crankcase 10 will flow to the check valve case 20 when the piston 15 moves downward.
While the invention herein disclosed has been described by means of specific embodiments, numerous modifications and variations could be made thereto by those skilled in the art without departing from the scope and spirit of the invention set forth in the claims.
| Number | Date | Country | Kind |
|---|---|---|---|
| 096125988 | Jul 2007 | TW | national |
