1. Field of the Invention
The present invention relates generally to internal combustion engines having at least one reciprocating piston within a cylinder, and more particularly to seals between the reciprocating piston and a cylinder wall.
2. Related Art
Typical internal combustion engines are provided with at least one piston body which reciprocates within a cylinder of an engine block. In general, each piston body includes a plurality of ring grooves, each of which receives and operably supports a piston ring. In operation, the piston rings remain in the ring grooves and travel with their respective piston bodies in a reciprocating motion within cylinders of an engine block. Among other things, the pistons rings function to seal combustion gasses in a combustion chamber above the piston body, to transfer heat from the piston body to the cylinder wall, to restrict the passage of oil from the crank case to the combustion chamber and to provide a generally uniform oil film on the cylinder wall. Such piston rings are typically biased with a spring force in a radially outward direction against the cylinder wall to establish the seal between the piston body and the cylinder wall.
One aspect of the present invention provides for a piston assembly including a piston body having a skirt. At least a portion of the skirt extends circumferentially continuously and has a skirt diameter. The piston assembly also includes a piston ring having a ring body with a generally helical shape and having an inner face. The ring body extends through at least one full revolution when in a relaxed condition. When in a relaxed condition, the inner face of the ring body presents a ring diameter that is less than the skirt diameter. The ring body circumferentially surrounds the skirt of the piston body, causing the inner face to be biased into engagement with the outer surface of the circumferentially continuous portion of the skirt to establish a dynamic seal between the ring body and the piston body.
The piston ring may be seated in a channel of a cylinder wall to establish the seal between the cylinder wall and the piston body. As such, the piston ring remains generally stationary and does not move relative to the cylinder wall during operation of the engine. This location allows for increased stability of the piston body as it reciprocates in the cylinder of the engine without compromising the length of the skirt, i.e. the skirt may extend downwardly past the cylinder wall when the piston body is in a bottom dead center position. The piston ring is also resistant to blow by.
Another aspect of the present invention provides for a power cylinder assembly. The power cylinder assembly includes a cylinder wall having a circumferentially continuous channel formed therein. The power cylinder assembly also includes a piston body with a skirt, and at least a portion of an outer surface of the skirt extends substantially continuously around a circumference. This portion of the skirt has a generally continuous skirt diameter. The power cylinder assembly further includes a piston ring which is disposed in the channel of the cylinder wall. The piston ring has a ring body which extends through at least one full revolution in a generally helical shape when the ring body is in a relaxed condition. When in the relaxed condition, the ring body has an inner face which presents an inner diameter that is less than the skirt diameter of the piston body. The ring body circumferentially surrounds the skirt of the piston body, and the inner face is biased into engagement with the outer surface of the circumferentially continuous portion of the skirt to establish a seal between the cylinder wall and the piston body.
Yet another aspect of the present invention is a piston ring for sealing a cylinder wall to a piston body. The piston ring has a ring body with a generally helical shape that extends through at least one revolution when in a relaxed condition. The ring body has an inner face that is rounded or chamfered to dynamically engage a piston 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:
Referring to the Figures, wherein like numerals indicate corresponding parts throughout the several views, an exemplary embodiment of a piston ring 20 for sealing a piston body 22 to a cylinder wall 24 of a power cylinder assembly 26 of an internal combustion engine is generally shown in
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To install the ring body 42 onto the skirt 36 of a piston body 22, the ring body 42 must be spread, or unwound, partially to elastically deflect the material of the ring body 42, thereby temporarily increasing the ring diameter DR to greater than the skirt diameter Ds. The ring body 42 is then inserted over the skirt 36 of the piston body 22 and relaxed, thereby causing the inner face 44 to be biased with a spring force internal to the ring body 42 against the outer surface of the piston body 22.
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The ring body 42 may be formed through any desirable manufacturing process and may be of any suitable spring-like material including, for example, spring steel. The ring body 42 may also either be uncoated or may have a wear resistant coating (such as chromium, chromium with aluminum oxide ceramic [CKS], chromium with microdiamond [GDC], etc.) applied to the inner face 44. The material and geometry of the ring body 42 are preferably chosen to provide a gas and oil tight seal between the cylinder wall 24 and the piston body 22 while minimizing the friction between the ring body 42 and the piston body 22.
The exemplary description of the embodiment is meant to be illustrative and not limiting of the invention. Variations and modifications to the disclosed embodiment may become apparent to those skilled in the art and come within the scope of the invention.
This application claims the benefit of application Ser. No. 61/600,216 filed Feb. 17, 2012.
Number | Date | Country | |
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61600216 | Feb 2012 | US |