The present invention relates to internal combustion engines. In particular, the present invention relates to oil drainback systems for internal combustion engines.
Internal combustion engines require oil, or some other form of lubricant, to lubricate the various moving parts of the engine. In standard internal combustion engines, this is accomplished by storing the oil in a crankcase and supplying oil from the crankcase to the various moving parts through some type of distribution system. The oil from the various parts of the engine is then returned to the crankcase via some type of drainback system, such as a drainback passage.
For example, oil from the crankcase of a standard internal combustion engine is supplied from the crankcase to the valve train to lubricate the valves, rocker arms, and other parts of the valve train. The oil from the valve train passes through the cylinder head of the engine and back to the crankcase through a drainback passage.
However, under certain operating conditions, this standard drainback system poses some drawbacks. For example, under conditions when high crankcase pressure exists, oil from the crankcase can be forced backwards through the drainback passage, possibly filling the cylinder head and valve box with oil. Similarly, if the engine were operated at an elevated angle (e.g. tilted backwards), oil from the crankcase could flow backwards through the drainback passage, again possibly filling the cylinder head and valve box with oil. If the cylinder head and valve box were filled with oil, the operation of the air intake, air exhaust, and spark plug, which are located in the cylinder head, could be interrupted and oil could possible flow through the valves into the cylinder.
It would therefore be advantageous if an internal combustion engine could be designed that prevented oil from the crankcase from filling the cylinder head and/or valve box of the engine. In particular, it would be advantageous if the oil drainback system of the internal combustion engine could be designed to allow the flow of oil through the drainback passage from the valve box to the crankcase during normal operation and to prevent the flow of oil through the drainback passage from the crankcase to the valve box during certain operating conditions, such as when high pressure is present in the crankcase or during operation at an elevated angle.
One aspect of the present invention is an internal combustion engine having a crankcase that has walls that define an interior volume for containing oil. A cylinder head has a proximal end that is fastened to the crankcase and extends laterally outward from the crankcase and terminates at a distal end. A rocker arm cover is fastened to the distal end of the cylinder head and defines a cavity that forms a valve box. A drainback passage interconnects the interior volume of the crankcase and the valve box to enable the flow of fluid from the valve box to the interior volume of the crankcase. A check valve is located within the drainback passage and allows the flow of fluid from the valve box to the interior volume of the crankcase and prevents the flow of fluid from the interior volume of the crankcase to the valve box.
This allows oil from the valve box to drain back to the crankcase during normal operation and prevents oil from traveling backwards through the drainback passage (into the valve box) when the pressure in the crankcase is increased or the angle of operation of the engine increases.
Another aspect of the present invention is an internal combustion engine where the cylinder head has a bore formed therethrough that extends from the proximal to the distal end. The crankcase has a cylinder that has a cylinder wall integrally formed in one of the walls of the crankcase. The cylinder wall has a bore formed therethough that extends from an interior surface of the cylinder wall, which communicates with the interior volume of the crankcase, to an exterior surface of the cylinder wall, which engages the proximal end of the cylinder head. The bore in the cylinder head and the bore is the cylinder wall together define the drainback passage. In addition, the bore in the cylinder wall is enlarged at one end to form a cavity in the exterior surface of the cylinder wall and a check ball is disposed within the cavity. The cavity and the check ball together define the check valve. The check ball seats against the bore at the proximal end of the cylinder head to prevent the flow of fluid from the interior volume of the crankcase to the valve box when there is high pressure present within the crankcase or when the engine is operated at an elevated angle.
a is an enlarged view of the check valve of
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As is well known in the art, during operation of the engine 100, a piston 210 (see
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The cylinder 160 has a cylindrical cylinder wall 405 integrally molded into one of the crankcase walls 400. The cylinder wall 405 defines a cavity within the cylinder 160 that forms a cylinder cavity 165, which receives the piston (not shown). The cylinder wall 405 below the cylinder cavity 165 presents an interior surface 460 that communicates with the interior volume 380 of the crankcase 110 and an exterior surface 465 that engages the sealing surface 185 on the cylinder head 170.
A cylindrical bore 530 is formed in the cylinder wall 405 below the cylinder cavity 165 and it extends from the cylinder wall interior surface 460, where it communicates with the crankcase interior volume 380, to the cylinder wall exterior surface 465, where it aligns with and couples to the bore 550 in the cylinder head 170. The bore 550 in the cylinder head and the bore 530 in the cylinder wall 405 together define an oil drainback passage that enables oil collected in the valve box to flow back to the crankcase interior volume 380.
The outer end of the bore 530 is enlarged to form a cavity 560 in the cylinder wall exterior surface 465. A check ball 620 is received in this cavity 560 to form a check valve, which enables oil to flow out of the valve box through the bore 550 during normal engine operation, but prevents oil from flowing from the crankcase bore 530 back to the valve box during certain circumstances, such as times when increased crankcase pressure is present or operation at an elevated angle, as described in more detail below.
The check ball 620 is preferably made of a fluorocarbon material, which is able to withstand high temperature and is highly resistant to oil absorption and wear. However, the check ball 620 can also be made of any other material that can perform the sealing required, as described below. Alternatively, the check valve could also be a reed valve, a check disk, a ball valve, or any other type check valve or similar type one-way flow sealing device located within the oil drainback passage that would allow the flow of oil from the valve box to the interior volume 380 of the crankcase 110 during normal operation of the engine 100 and prevent the flow of oil from the interior volume 380 of the crankcase 110 to the valve box during certain operating conditions, such as when high pressure is present in the crankcase or during operation at an angle.
A head gasket 175 is disposed between the crankcase 110 and the cylinder head 170 to prevent the leakage of oil from between the cylinder wall exterior surface 465 and the cylinder head sealing surface 185. The head gasket 175 has an aperture 540 that is aligned with the bores 530, 550 to allow oil to flow through the head gasket 175.
In alternate embodiments of the invention, the drainback passage does not have to be integral to the cylinder head and crankcase as described above. The drainback passage could connect the valve box to the internal volume of the crankcase in any manner, such as externally via a hose, tube, or other method, and have some type of check valve therein.
During normal operation of the engine 100 (i.e. at times in the engine cycle where low crankcase pressure exists and the engine is not being operated at an elevated angle) the check ball 620 floats within the cavity 560 allowing oil to flow through the cavity 560 and past the check ball 620. This allows oil from the valve box to flow through the bore 550 in the cylinder head 170, through the aperture 540 in the head gasket 175, around the check ball 620, and through the bore 530 in the side wall 400 back to the crankcase 110.
At times in the engine cycle where high crankcase pressures exist, the pressure in the crankcase bore 530 increases and forces the check ball 620 towards the cylinder head 170. When this occurs, the check ball 620 passes through the aperture 540 in the head gasket 175 and seats against the bore 550 at the seating surface 185 of the cylinder head 170. Similarly, if the engine 100 is operated at an elevated angle, the check ball 620 moves towards the cylinder head 170. When this occurs, the check ball 620 again passes through the aperture 540 in the head gasket 175 and seats against the bore 550 at the sealing surface 185 of the cylinder head 170. The seating of the check ball 620 against the bore 550 closes the oil drainback passage and prevents the oil form flowing backwards through the bore 550. This allows the engine 100 to operate during times where high crankcase pressures exist and at elevated angles without the valve box filling with oil.
In the preferred embodiment of the present invention, the check ball 620 prevents the flow of oil backwards through the bore 550 in the cylinder head 170 by seating against the bore 550 at the distal end of the cylinder head 170. However, the check ball 620 could seat against any surface anywhere along the oil drainback path. For example, if the aperture 540 in the head gasket 175 were made smaller the check ball 620 would seat against the head gasket 175 rather than passing through, thereby preventing oil from flowing backwards through the bore 550 back into the valve box.
In the present embodiment, the engine 100 is a vertical shaft engine capable of outputting 15–20 horsepower for implementation in a variety of consumer lawn and garden machinery such as lawn mowers. In alternate embodiments, the engine 100 can also be implemented as a horizontal shaft engine, be designed to output greater or lesser amounts of power, and/or be implemented in a variety of other types of machines, e.g., snow-blowers. Further, in alternate embodiments, the particular arrangement of parts within the engine 100 can vary from those shown and discussed above. For example, in one alternate embodiment, the cams 360 could be located above the gears 320 rather than underneath the gears.
While the foregoing specification illustrates and describes the preferred embodiments of this invention, it is to be understood that the invention is not limited to the precise construction herein disclosed. The invention can be embodied in other specific forms without departing from the spirit or essential attributes of the invention. Accordingly, reference should be made to the following claims, rather than to the foregoing specification, as indicating the scope of the invention.
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Number | Date | Country | |
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20050034697 A1 | Feb 2005 | US |