Patent Application
20200191269
The present invention is related generally to piston rings, piston assemblies including piston rings, and methods of manufacturing the same.
Internal combustion engine manufacturers are encountering increasing demands to improve engine efficiencies and performance, including, but not limited to, improving fuel economy, improving fuel combustion, reducing oil consumption, increasing the exhaust temperature for subsequent use of the heat, increasing compression loads within the cylinder bores, decreasing weight and making engines more compact. In order to satisfy one or more of these demands, many engine manufacturers have been employing advanced technologies to increase the temperature and pressure loads within the combustion chambers of their engines. Consequently, such pistons must be sealed to their respective cylinder bores with piston rings that are designed to withstand the increasingly extreme environment.
Most pistons are sealed against their respective cylinder walls with three piston rings which are axially spaced from one another, and each piston ring is optimized to perform a specific task. Traditionally, the top ring is a compression ring optimized for sealing combustion gasses in the combustion chamber above the piston. The bottom ring is typically an oil control ring which is optimized for scraping the cylinder wall and keeping oil from passing into the combustion chamber. The second, or intermediate, ring typically serves the dual purposes of assisting the top compression ring in sealing the combustion gasses in the combustion chamber and also scraping any oil that made it past the oil control ring.
One aspect of the present invention provides an oil ring for a piston of an internal combustion engine capable of reducing friction while maintaining good control of an oil film along a cylinder during operation in the engine. The oil ring comprises a ring body extending circumferentially around a center axis between opposite ends. The ring body presents an outer diameter surface and an inner diameter surface spaced from one another by a top surface and a bottom surface. The piston body includes an inner land extending radially from the bottom surface toward the center axis and forming a portion of the inner diameter surface. The inner diameter surface presents a counterbore between the inner land and the top surface of the ring body. The ring body includes an outer lower land extending radially outwardly from the bottom surface and away from the center axis and an outer upper land extending radially outwardly from the top surface and away from the center axis. The outer lower land and the outer upper land present a portion of the outer diameter surface. The outer diameter surface presents an oil groove between the outer lower land and the outer upper land.
Another aspect of the invention provides a piston assembly including a piston and oil ring capable of reducing friction while maintaining good control of an oil film along a cylinder during operation in the engine. The piston comprises a piston body including a combustion surface and a ring belt depending from the combustion surface and extending circumferentially around a center axis. The ring belt includes a plurality of ring grooves spaced from one another by piston lands. The oil ring is disposed in one of the ring grooves. One of the piston lands which is located above the one ring groove containing the oil ring includes a plurality of holes. The holes extend radially inwardly to the ring groove containing the oil ring. The oil ring includes a ring body extending circumferentially around the center axis between opposite ends. The ring body presents an outer diameter surface and an inner diameter surface spaced from one another by a top surface and a bottom surface. The ring body includes an inner land extending radially from the bottom surface toward the center axis and forming a portion of the inner diameter surface; and the ring body includes a counterbore between the inner land and the top surface of the ring body.
Another aspect of the invention provides a method of manufacturing the oil ring. The method includes providing a ring body extending circumferentially around a center axis between opposite ends. The ring body presents an outer diameter surface and an inner diameter surface spaced from one another by a top surface and a bottom surface. The ring body includes an inner land extending radially from the bottom surface toward the center axis and forming a portion of the inner diameter surface. The inner diameter surface presents a counterbore between the inner land and the top surface of the ring body. The ring body includes an outer lower land extending radially outwardly from the bottom surface and away from the center axis and an outer upper land extending radially outwardly from the top surface and away from the center axis. The outer lower land and the outer upper land present a portion of the outer diameter surface. The outer diameter surface presents an oil groove between the outer lower land and the outer upper land.
Yet another aspect of the invention provides a method of manufacturing a piston assembly, comprising the steps of: providing a piston body including a combustion surface and a ring belt depending from the combustion surface and extending circumferentially around a center axis, the ring belt including a plurality of ring grooves spaced from one another by lands; and disposing an oil ring in one of the ring grooves of the piston body, wherein one of the lands which is located above the one ring groove containing the oil ring including a plurality of holes, and the holes extending radially inwardly to the ring groove containing the oil ring. The oil ring includes a ring body extending circumferentially around the center axis between opposite ends. The ring body presents an outer diameter surface and an inner diameter surface spaced from one another by a top surface and a bottom surface. The ring body includes an inner land extending radially from the bottom surface toward the center axis and forming a portion of the inner diameter surface, and the ring body includes a counterbore between the inner land and the top surface of the ring body.
These and other features and advantages of the present invention will be readily appreciated, as the same becomes better understood by reference to the following detailed description when considered in connection with the accompanying drawings wherein:
As shown in
The oil ring comprises a ring body 18 extending circumferentially around a center axis A between opposite ends 20. The ring body of the oil ring is formed of metal, such as steel or aluminum, and the ring body is free of holes for draining oil. As shown in
Also shown in
The inner diameter surface of the oil ring includes a first inner flat area 48 extending from the top surface to the inner land. The inner diameter surface then extends radially inwardly along the inner land toward the center axis and at an angle from the first inner flat area to a second inner flat area 50 which presents an innermost point of the ring body. The second inner flat area extends to the bottom surface of the ring body.
As shown in
As shown in
As best shown in
The piston ring and piston assembly have several advantages during operation in the internal combustion engine. During operation, the oil ring will be energized during the power stroke by channeling combustion pressure from the piston land above the oil ring to the area in the ring groove behind the oil ring. The pressure will pass through the series of holes placed around the piston land to the back of the oil ring groove. The same results may be obtained by suitably dimensioning the piston land and ring groove geometry and clearances, as those skilled in the art will recognize. The oil ring is not energized during the remaining strokes, which results in a reduction of oil ring friction while still maintaining oil film control.
The features of the counterbore on the top inner diameter corner of the cross-section of the oil ring, combined with no oil drain slots or holes in the oil ring, allow the combustion pressure from the piston land above to build behind the oil ring during the power stroke. The pressure will apply forces to the inner diameter surface or profile of the oil ring, pushing the oil ring against the bottom of the ring groove and to the cylinder thus sealing oil from moving upward past the oil ring. The oil ring has a very low tangential force because the free gap is minimized and there is no coil spring or expander to supply external force. The friction will be greatly reduced during the intake, compression, and exhaust strokes. The outer lands of the oil ring are spaced far enough apart to allow for the wide, deep outer diameter groove that will accumulate oil scraped by the outer upper land of the oil ring. The scraped oil should be effectively drained. Thus, the spacing of the outer lands on the oil ring, along with the low ring tangential tension and the hydrodynamic forces, will increase the oil film thickness between the outer lands of the oil ring and the cylinder bore on the compression and exhaust strokes. This, along with suitable piston features, will allow oil accumulated in the outer diameter groove of the oil ring to exit below the oil ring. Another option to drain oil from the outer diameter groove of the oil ring is to include the scallops cutout through the outer would be to add scallop cutouts through the outer lower land of the oil ring.
The piston assembly does not include a coil ring or expander. Thus, the oil seal is maintained by the combustion pressure alone. In addition, since there are no oil drain slots or holes in the oil ring, the combustion pressure behind the ring is sealed. The oil ring alone has little or no tangential force. The outer diameter groove of the oil ring is deep and wide enough to accumulate greater quantities of oil.
Another aspect of the invention provides a method of manufacturing the piston ring and the piston assembly including the piston and piston ring. The method of manufacturing the piston ring can include forming the ring body by casting, forging, machining, and/or other methods known in the art. The method of manufacturing the piston for the piston assembly includes providing the piston body including the combustion surface and the ring belt depending from the combustion surface and extending circumferentially around the center axis, wherein the ring belt includes a plurality of the ring grooves spaced from one another by the lands, and disposing the oil ring in one of the ring grooves of the piston body, wherein one of the lands which is located above the one ring groove containing the oil ring includes a plurality of holes, and the holes extend radially inwardly to the ring groove containing the oil ring. The piston can also be formed by casting, forging, machining, and/or other methods known in the art.
Obviously, many modifications and variations of the present invention are possible in light of the above teachings and may be practiced otherwise than as specifically described while within the scope of the claims. It is contemplated that all features described and of all embodiments can be combined with each other, so long as such combinations would not contradict one another.
