Patent Application
20200284344
The present invention is related generally to piston rings and methods of manufacturing piston rings.
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. Improvements to piston ring performance is desired.
One aspect of the present invention provides a piston ring for a piston of an internal combustion engine. The piston ring provides for improved performance, specifically a reduction in blowby gases and improved oil control. The piston ring includes a wire formed of a metal material extending circumferentially around a center axis. The wire presents a wire outer diameter surface which includes a recess. The piston ring also includes a rail formed of steel extending circumferentially around the center axis and disposed in the recess of the wire. The rail presents a rail outer diameter surface. A coating including diamond-like carbon is disposed on the rail outer diameter surface.
Another aspect of the invention provides a method of manufacturing a piston ring. The method comprises providing a rail formed of steel and extending circumferentially around a center axis, the rail presents a rail outer diameter surface. The method also includes disposing a coating including diamond-like carbon on the rail outer diameter surface. The method further includes providing a wire formed of a metal material and extending circumferentially around a center axis, and the wire presents a wire outer diameter surface which includes a recess. The method further includes disposing the rail in the recess of the wire.
Yet another aspect of the invention provides a piston assembly. The piston assembly comprises a piston body portion. At least one piston ring is disposed on the piston body portion. Each of the at least one piston ring includes a wire and a rail. The wire is formed of a metal material extending circumferentially around a center axis. The wire presents a wire outer diameter surface which includes a recess. A rail formed of steel extends circumferentially around the center axis and is disposed in the recess of said wire. The rail presents a rail outer diameter surface. A coating including diamond-like carbon is disposed on the rail outer diameter surface.
Another aspect of the invention includes a method of manufacturing a piston assembly. The method comprises providing a piston body portion; and disposing at least one piston ring on the piston body portion. Each of the at least one piston ring includes a wire formed of a metal material extending circumferentially around a center axis. The wire presents a wire outer diameter surface which includes a recess. A rail formed of steel and extending circumferentially around the center axis is disposed in the recess of the wire. The rail presents a rail outer diameter surface. The method further includes disposing a coating including diamond-like carbon on the rail outer diameter surface.
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 wire 12 is formed of a metal material and extends circumferentially around a center axis A between opposite wire ends 20. A wire gap 26 is located between the wire ends 20. The wire 12 presents a wire outer diameter surface 22 which includes the recess 16.
The rail 14 is formed of steel and extends circumferentially around the center axis A between opposite rail ends 24. A rail gap 27 is located between the rail ends 24. Preferably, the rail ends 24 are circumferentially misaligned aligned with the wire ends 20, and the rail gap 27 is circumferentially misaligned with the wire gap 26. For example, as shown in
The coating 18 which includes diamond-like carbon can be referred to as a DLC coating. According to a preferred embodiment, the coating 18 is free of hydrogen. The coating 18 is disposed on the rail outer diameter surface 28, and the coating 18 presents a coating outer diameter surface 30. The coating 18 is preferably not disposed on the wire outer diameter surface 22 and thus a smaller axial higher of the ring 10 is coated, compared to rings with a coating on an entire outer diameter surface, which can increase the capacity of the DLC furnace.
As best shown in
The wire 12 also presents an upper ring surface 36 and a lower ring surface 38 opposite the upper ring surface 36. An upper corner 40 is located between the upper ring surface 36 and the upper portion 32 of the wire outer diameter surface 22, and a lower corner 42 is located between the lower ring surface 38 and the lower portion 34 of the wire outer diameter surface 22. The upper and lower corners 40, 42 of the wire 12 are sharp.
The coating 18 is not disposed on the corners 40, 42 of the wire 12. Thus, the upper and lower corners 40, 42 remain exposed. Preferably, the coating 18 is spaced from the upper corner 40 by the upper portion 32 of the wire outer diameter surface 22, and the coating 18 is spaced from the lower corner 42 by the lower portion 34 of the wire outer diameter surface 22. When the piston ring 10 is used in an internal combustion engine, the exposed and uncoated sharp corners 40, 24 help to control the oil consumption and reduce blowby gases during operation.
To improve wear resistance, a layer 43 of chrome can be disposed on the lower ring surface 38, as shown in
Another aspect of the invention provides a method of manufacturing the piston ring 10. The method generally comprises the steps of providing the rail 14; disposing the coating 18 on the rail outer diameter surface 28; providing the wire 12; and disposing the rail 14 in the recess 16 of the wire 12. The method can also include applying the layer 43 of chrome to the lower ring surface 38, or nitriding all surfaces of the wire 12.
Yet another aspect of the invention provides a piston assembly 44 including the two-piece DLC coated piston ring 10. An example of the piston assembly 44 is shown in
Another aspect of the invention provides a method of manufacturing the piston assembly 44. The method includes providing the piston body portion 46, disposing at least one of the piston rings 10 on the piston body portion 46; and disposing the coating 18 including diamond-like carbon on the rail 14.
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.
