CA1088971A

CA1088971A - Piston ring

Info

Publication number: CA1088971A
Application number: CA290,229A
Authority: CA
Inventors: Raymond L. Grimm
Original assignee: SKF Automotive Products Inc
Current assignee: SKF Automotive Products Inc
Priority date: 1976-11-05
Filing date: 1977-11-04
Publication date: 1980-11-04
Also published as: IT1113668B; FR2370178A1; DE2748888A1; JPS5392076A; FR2370178B1; DE2748888C2; GB1583010A; JPS5911055B2

Abstract

ABSTRACT OF THE DISCLOSURE
An improved piston ring has at least one pumping means including a hydrodynamic cavity in a lower face of the ring. The hydrodynamic cavity traps oil, and the pumping means forces the oil to the underside of the ring and out of the ring groove to the clearance space between the piston and the engine cylinder bore, minimizing the amount of oil permitted to reach the combustion chamber.

Description

This invention relates to piston rings for use in internal combustion engines~ which piston rings are shaped so as to minimize oil consumption.
Piston rings are annular members designed to fit in a groove in a piston. Various ring configurations have been proposed to provide pistons which properly seal the comhustion chamber of the internal combus-tion engine. Some examples of commonly used piston ring configurations are shown in Figure 4, Section 35.38 of the 1976 Society of Automotive Engineers Handbook.
Gne specific ring configuration is disclosed in United States Patent 1,579,043. This patent shows a piston ring with an undercut scraper groove having a triangular groove along the entire length of the lower surface, two vertically spaced base planes and a channel which connects the groove to the ring's inner diameter.
A more recent ring design is disclosed in United States Patent 3,781,022. This patent shows a ring having a multiplicity of minute indentations formed on the sliding surface of the ring. The indentations are arranged in a Geometric pattern to form oil-retaining means on the 'sliding surface.
In operation, the piston ring and cylinder bore wear as the engine is run until the bore takes on a tapered configuration. As the piston moves longitudinally along the bore, the piston ring will oscillate or rock back and forth in its groove. This oscillation destroys the sealing ability of the piston ring and results in increasing oil consumption.
The present invention provides a piston ring adapted to be mounted in a ring groove formed in the peripheral side wall of a piston for an internal combustion engine and disposed adjacent one :
axial end face of the piston facing the combustion chamber, said ring including upper and :lower generally parallel axial side faces and radially spaced inner and outer circumferential surfaces, the outer surface confronting and contacting the cylindrical bore for the piston to provide a tight seal between the ring and bore, hydrodynamic and pumping , 7~

means in the form of at least one circumferential groove in the lower axial side face of said ring remote from the combustion chamber disposed completely between said inner and outer surfaces, said groove operable during reciprocating movement of the p;ston to impede the flow of a lubricant past the lower side face of the ring to the combustion chamber ~y entrapping lubrïcant therein and the edges of the groove hydrodynami-g~O~Q
cally dischargîng lubricant from the g~eff~ upon radial oscillating move-ment of the ring.
In the accompanying drawing:
Figure 1 shows a cross section of a piston ring of this invention in the piston groove; and Figure 2 shows an enlarged view of a modified piston ring.
In the accompanying drawing, a section of a piston lO has a piston ring 12 contained within a groove 14. The ring 12 has a pumping means in the form of a plurality of triangular shaped grooves 16 machined in the lower surface of the ring 12. As the piston 10 moves up and down a piston bore (not shown), the ring 12 will oscillate in the groove 14.
The ring 12 will move toward the back wall 18 of groove 14 when the bore of the cyl;nder bore is at a minimum and move away from the wall when the cylinder bore is at a maximum. As the ring oscillates, the trailing edge 20 of the grooves 16 will scrape and force any oil present towards the outer diameter of the piston where the ring can scrape the oil downward into the crankcase. The scraping action prevents or minimizes the migration of oil around the ring from the crankcase to the combustion chamber.
Figure 2 shows a second embodiment of this invention wherein a ring 22 has a plurality of cavities 24 on the underside of the ring, the cavities having a partially rounded configuration. As shown, the grooves have a trailing edge 26 which will scrape oil towards the narrowed side ---` 11)1918~'7~L

of the cavity and then to the underside of the ring.
The drawing shows triangular or substartially triangular grooves - formed into the ring's surface but other shapes can be employed. Function-ally, the piston rings of this invention have hydrodynamic means on one surface of the ring to move oil away from the combustion chc~mber towards an oil reservoir.
In general, with the triangular shaped groove shown in the drawing, the trailing edge will form an oblique angle or incident angle with the edge of the piston groove.

lo Example The following test results of an engine run with various face groove configurations indicate the invention~s effectiveness.
A single cylinder air cooled, L,head engine having:
3.5 in bore;
3.25 in stroke;
31.3 cid; and 6.5 to 1 compression ratio was tested using compression rings shaped according to this invention and also normal rings.
The grooved compression rings tested had 1, 3, or 5 grooves having essentially a triangular cross section similar in shape to that shownLiin the drawings. The vertical side of the groove was about 0.002 to 0.007 inch averaging about .005 inch, and the horizontal open side measured about 0.015 inch. The angle between the leading edge of the triangular groove and the cylinder was about 18 degrees.
The engine was run in for 1-1/4 hours before each test, using an increasing load and rpm, followed by a 1 hour run at 3,000 rpm at 3/4 throttle.
The engine was then tested by running at 3,000 rpm and 3/4 throttle for three (3) cycles lasting eight hours.

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The oil consumption was measured after each eight hour interval ard the overall average oil economy calculated. The averages are tabulated in Table 1.

Number of Grooves Hours/Qt of oil none 33.7 1 26~5 38.1 52.5 The example shows that using a second compression ring with a plurality of grooves decreases the amount of oil consumed by the engine during operation.
From the foregoing example and description, it is apparent that a new improved piston ring configuration has been disclosed. The ring makes efficient use of the ring's radial motion within the piston groove caused by cylinder taper due to engine wear ~nd reduces oil v consumption.

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Claims

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE PROPERTY OR
PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. A piston ring adapted to be mounted in a ring groove formed in the peripheral side wall of a piston for an internal combustion engine and disposed adjacent one axial end face of the piston facing the combustion chamber, said ring including upper and lower generally parallel axial side faces and radially spaced inner and outer circumferential surfaces, the outer surface confronting and contacting the cylindrical bore for the piston to provide a tight seal between the ring and bore, hydrodynamic and pumping means in the form of at least one circumferential groove in the lower axial side face of said ring remote from the combustion chamber disposed completely between said inner and outer surfaces, said groove operable during reciprocating movement of the piston to impede the flow of a lubricant past the lower side face of the ring to the combustion chamber by entrapping lubricant therein and the edges of the groove hydrodynamically discharging lubricant from the groove upon radial oscillating movement of the ring.

2. A piston ring as claimed in Claim 1 including a plurality of radially spaced circumferential grooves in said lower axial side face.

3. A piston ring as claimed in Claim 1 wherein said circumferential groove in said lower axial side face is of generally triangular cross section.

4. A piston ring as claimed in Claim 1 wherein an edge of said circumferential groove is oblique with respect to a wall of the groove.

5. A piston ring as claimed in Claim 1 wherein said circumferential groove is of triangular cross section, the vertical side of said groove measuring between about 0.002 to 0.007 inches and the horizontal open side is about 0.015 inches.

6. A piston ring as claimed in Claim 5 wherein the angle between the leading edge of said triangular groove and the lower axial side face is about 18°.