Patent Application
20070246026
These and other aspects, features and advantages will become readily apparent to those skilled in the art in view of the following detailed description of the presently preferred embodiments and best mode, appended claims, and accompanying drawings, in which:
Referring in more detail to the drawings,
The material 34 inhibits the flow of fluid and gases thereby, thus, reducing the amount of oil expelled via “oil-scrape” or “throw-off” (results from oil above the upper most piston ring being thrown upwards by the piston 20 and/or piston ring 24 during an upstroke of the piston) upwards into the exhaust emissions, while also acting to provide a labyrinth to combustion gases flowing toward the uppermost piston ring 24. Accordingly, any localized formation of oxidized lubrication is inhibited from building up on a back of the piston ring groove 22, which in turn, acts to prevent a condition know as “carbon jacking” of the rings 24, or “sticking” of the rings 24. Further, the material 34 acts to remove or scrape carbon buildup from an upper land portion 36 of the piston 20, wherein the upper land portion 36 is defined generally between the uppermost ring 24 and a crown 38 of the piston 20. This is particularly true after some use of the engine has occurred, wherein some desirable amount of carbon buildup (
The material 34 on the upper portion 32 of the liner 10 is preferably formed to provide a cold radial clearance (r) with the upper land 36 of the piston 20, down to about 0.100 mm. Generally, the material 34 is formed to the reduced inner diameter d1 over at least a section of the upper portion 32 by about 0.5-1.5% relative to the inner diameter D of the lower portion 30. The width (w) of the material 34 extends axially along the central axis 21, and can be varied in length of coverage, as desired, however, it preferably extends to an area of the cylinder upper portion 32 immediately adjacent the imaginary TDC plane 28. As such, scraping of the upper land 36 of the piston 20 is facilitated in use, as shown in
The cylinder liner 10, with the material 34 formed on the upper portion 32, can be further processed, such as machined, heat treated, whether cased hardened or through hardened, without any additional challenges. However, given that the inner diameter d1 of the upper portion 32 is reduced from the inner diameter D of the lower portion 30, it is generally preferred, and in some cases necessary to assemble the piston 20, with rings 24 assembled thereon, into the cylinder liner 10 from its underside, with the piston 20 being linked to the connecting rod (not shown), prior to assembling the cylinder block 12 to the engine block.
The material 34 extending radially inwardly from the inner wall 16 can be formed by one of several mechanisms. For example, the material 34 can be formed in an extruding process wherein the material of the inner wall 16 is extruded or knurled from the material of the cylinder liner to produce peaks 40 (
In use, the material 34 formed on the upper surface 32 acts to benefit operation of the engine in a number of ways. Initially, the material 32 provides a labyrinth to inhibit the downward flow of hot combustion gases and fluid toward the upper most piston ring 24 and groove 22. As such, the ingress of hot gases and fluid from the combustion chamber past the upper most piston ring 24 is inhibited, thereby retarding local oxidation of lubricant and diminishing carbon formation within and on the back side of the groove 22, thereby promoting proper functioning of the piston rings 24. As mentioned, this acts to reduce the likelihood of ring jacking or sticking from occurring, and thus, the useful life and efficiency of the engine between servicing is enhanced.
As use of the engine continues over time, the radially inwardly extending material 34 acts to attract and accumulate a desired amount of build up (
The mechanical barrier 44 formed by carbon build-up, which is facilitated by the material 34, thus, performs at least two important roles in increasing the running performance of the engine. First, it inhibits gas and fluid penetration downwards, and second, it inhibits oil scrape and throw-off upwards. The first of which acts to increase the useful life of the engine, such as by preventing the onset of ring jacking and sticking, while the second acts to improve the oil consumption of the engine and reduce exhaust emissions.
Accordingly, a cylinder liner 10 constructed within the scope of the present invention, as defined by the claims, provides at least the benefits of the bands discussed in the background section above, which, as mentioned, require complex and precise machining and secondary installation, without having to incur the negative aspects associated therewith. Further, it is believed that the useful life of the engine between servicing can be further enhanced relative to the useful life attainable through the use of the aforementioned bands. Also, cylinder liners of any size and thickness can benefit from the invention herein, unlike the use of separate bands, which require that the cylinder liners are of suitable thickness to form the radially outwardly extending grooves or recess for their receipt therein.
It is to be understood that other embodiments of the invention which accomplish the same function are incorporated herein within the scope of any ultimately allowed patent claims.
This application claims the benefit of U.S. Provisional Application Ser. No. 60/794,363, filed Apr. 24, 2006, which is incorporated herein by reference in its entirety.
| Number | Date | Country | |
|---|---|---|---|
| 60794363 | Apr 2006 | US |
