US3645174A

US3645174A - Antiemissions compression piston ring

Info

Publication number: US3645174A
Application number: US88344A
Authority: US
Inventors: Herbert F Prasse
Original assignee: Ramsey Corp
Current assignee: SPX Corp
Priority date: 1970-11-10
Filing date: 1970-11-10
Publication date: 1972-02-29
Anticipated expiration: 1989-02-28

Abstract

A U-shaped cross section piston ring for use at the top of an internal combustion engine piston with one leg thereof received in a circumferential groove spaced from the top of the piston and the other leg thereof either overlying the top of the piston or coplanar therewith in a circumferential ledge at the top of the piston.

Description

ilnite States 1111 Prasse 1 Feb. 29, 11972 [54] ANTIEMISSIONS COMPRESSION 1,963,151 6/1934 Russell ..92/200 PISTON RING 2.074,581 3/1937 Frye ...277/178 X 2,367,030 1/1945 Jessup ..277/178 1 1 lnvemofi Herbert Pram, Town and Country, 2,614,899 10/1952 Phillips ..277/76 3,198,531 8/1965 Brenneke ..277/178 Assignee: Ramsey Corporation, St. Louis, MO. [221 Flled? 1970 468,830 5/1914 France ..92/182 [21] Appl. No.: 88,344 700,300 12/1940 Germany ..92/246 587,913 5/1947 Great Britain. .....92/246 Related [1.5. Application Data 792,922 4/1958 Great Britain ..277/208 [62] Division of Ser. No. 815,653, Apr. 14, 1969. Primary Exami"er EdgaI Geogmgan Assistant Examiner-Irwin C. Cohen [52] US. Cl ..92/193, 92/182, 92/246, Atm,ney Hi|L Sherman Meroni, Gross & Simpson 277/178, 277/208 [51] Int. Cl ..Fl6j l/00, Fl6j 9/06, F16j 9/20 57 ABSTRACT [58] Field of Search ..277/76,161,178, 207, 208,

277/216, 235 A; 92/200, 208, 193, 181, 182, 246 A U-shaped cross section piston ring for use at the top of an internal combustion engine piston with one leg thereof [56] References Cited received in a circumferential groove spaced from the top of the piston and the other leg thereof either overlying the top of UNlTED STATES PATENTS the piston or coplanar therewith in a circumferential ledge at the top of the piston. 1,868,075 7/1932 Reiland et a] ..92/193 1,903,396 4/1933 Bramberry ..92/208 X 7 Claims, 9 Drawing Figures g K 7 M Q 19 j E w 6 J 7 ANTIEMISSIONS COMPRESSION PISTON RING RELATED APPLICATIONS This application is a division of Herbert F. Prasse application entitled Antiemissions Compression Piston Ring," filed Apr. 14-, 1969, Ser. No. 815,653.

BACKGROUND OF THE INVENTION 1. Field of the Invention This invention relates to piston rings and more specifically to an antiemissions piston ring for mounting at the top of the piston.

2. Prior Art I Recent developments in internal combustion engine technology have emphasized the reduction of engine emissions. Such emissions may be caused to a great extent by failure to burn all of the fuel injected into the engine cylinders. Exhaust of such unburned hydrocarbons may greatly contribute to air pollution.

In a conventional piston and piston ring design, the top compression piston ring is positioned in a ring groove spaced axially from the top of the piston. This creates a circumferential crevice between the outer diameter of the piston and the cylinder wall in the area above the top compression ring. To the extent that the top compression ring does not fit snugly with the top radial wall of the ring groove, that area also forms a crevice. As the piston rises in the cylinder during the compression stroke, fuel can condense along the cylinder wall and be thrust into the above-mentioned crevices. Because of the small space involved, combustion may not take place in these crevices, allowing the formation of undesired emission products.

Attempts have been made to correct this by placing the top compression ring groove as close to the top of the piston as possible. However, placement of the ring groove is limited by the necessity of not weakening the top of the piston. If the ring groove is placed too close to the top of the piston, the groove may result in a peripheral weak point at the top of the piston. In addition, the top of the piston is the most hostile environment for a piston ring. That area is subjected to the greatest heat and pressure and extreme wear would be encountered utilizing a conventional ring in that area.

SUMMARY My invention provides for a new piston ring which has a U- shaped cross section providing two radially extending axially spaced-apart legs and an outer diameter peripheral or bight section spanning the legs. The ring is used in connection with a piston which has an axially narrow ring groove positioned adjacent the top of the piston. This ring groove receives one of the legs of the ring. The other leg either overlies the top of the piston, or preferably, is received in a peripheral ledge formed in the top of the piston. The bight section of the ring engages the cylinder wall and functions as a compression or sealing 1% a preferred embodiment, an expander may be used in the ring channel to aid in expanding the periphery thereof into engagement with the cylinder wall. The ring may also utilize the expansive force created during the power stroke as an aid in both circumferential and axial sealing. The peripheral portion of the ring seals against the cylinder wall while the radial legs are sealed against radial walls of the groove or ledge.

It is therefore an object of this invention to provide a new antiemissions piston ring.

It is a further object of this invention to provide an antiemis sions piston ring having a U-shaped cross section adapted to be positioned at the top of the piston.

It is a further and more specific object of this invention to provide a U-shaped cross section compression piston ring having a radial leg adapted to overlie a portion of the top of the piston and a second radial leg adapted to be received in a ring groove spaced from the top of the piston.

It is yet another and more specific object of this invention to provide a U-shaped cross section antiemissions control ring adapted to be positioned at the top of the ring groove and having a periphery adapted to sealingly engage the cylinder wall and a radial configuration adapted to seal against a radial wall of the piston.

Other objects, features and advantages of the present invention will be readily apparent from the following detailed description of certain preferred embodiments thereof taken in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a fragmentary cross-sectional view of a piston received in a cylinder bore equipped with the antiemissions ring of this invention.

FIG. 2 is a plan view partially in section of the piston ring of this invention.

FIG. 3 is a fragmentary enlarged cross-sectional view of the top of a piston equipped with the piston ring of this invention during the power and compression strokes.

FIG. 4 is a view similar to FIG. 3 during the exhaust stroke.

FIG. 5 is a view similar to FIG. 4 during the intake stroke.

FIG. 6 is a view similar to FIG. 3 illustrating another embodiment of this invention.

FIG. 7 is a view similar to FIG. 3 illustrating a third embodiment of this invention.

FIG. 8 is a view similar to FIG. 3 illustrating a further embodiment of this invention.

FIG. 9 is a cross-sectional view of the ring of FIG. 8 taken along the lines VIIII-VIIII.

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a fragmentary cross-sectional view of a piston 10 received in the bore 11 of a cylinder 12. The piston head includes conventional piston ring grooves l3, l4 and I5. Compressions rings 16 and 17 are positioned in the

ring grooves

13 and 14 and a combination circumferential spacer-expander and dual rail oil control ring 18 is positioned in the ring groove 15. The ring groove 15 has an oil drainage bore 19 therein adapted to drain oil scraped by the oil control ring 18.

As is conventional, the top compression ring groove I3 is spaced axially below the top 20 of the piston head 10. Thus, a large area crevice 21 is provided between the wall 22 of the cylinder bore 11 and the outer diameter 23 of the piston head 10 above the ring 16. During the compression and power strokes, when the ring 16 is pressed against the bottom radial wall 24 of the ring groove 13, an additional crevice area is provided in the area 25 between the top radial wall 26 of the groove 13 and the top of the ring 16 and the areas between the back wall 27 of the groove 13 and the back of the ring I6. During compression, fuel injected into the cylinder is forced into the

crevices

21 and 25. In most internal combustion engines, the cylinder wall 22 is cooler than either the piston head 10 or the interior of the cylinder bore 11. This allows the injected fuel vapor to condense along the cylinder wall. The condensed fuel vapor can substantially fill the crevices 21 25.

These crevices may be too small to support combustion of the condensed fuel therein during the power stroke of the piston. This produces a quantity of unburned fuel during each cycle of the engine which can then form pollutant emissions which escape the engine through the exhaust. In addition, because the top compression ring 16 never reaches the top of the cylinder bore, carbon deposits can build up on the cylinder wall 22 and in the top ring groove 13. These carbon deposits adversely affect the operation of the engine and can, of themselves, add to the pollutant emissions of the engine.

In order to overcome these disadvantages and to reduce pollutants created by the operation of the internal combustion engine, this invention provides an emissions control ring 30 adjacent the top 20 of the piston head 10. The ring is substantially U-shaped in cross section and has top 31 and bottom 32 radially directed legs and an axially extending bight portion 33 connecting the

legs

31 and 32 at the outer periphery thereof.

The ring 30 may be either cast or rolled. The bight section 33 may be slightly rounded in an axial direction and may have a hard-faced coating on the outer periphery thereof to increase the life of the ring and reduce scuffing. The outer diameter of the bight 33 is adapted to contact the cylinder wall 22 in circumferential engagement therewith thereby preventing the formation of carbon deposits and condensed fuel buildup in the

crevices

21 and 25.

The U-shaped cross section of the ring 30 allows the ring to be placed at the top of the piston head while at the same time providing for a more complete sealing than can be achieved with a solid ring.

As best illustrated in FIG. 3, the ring30 is located at the top of the piston head having upper radial leg 31 lying adjacent the top 20 and the lower radial leg 32 received in a radial ring groove 33 spaced axially from the top 20 of the piston head. The ring is split having circumferential ends and 36. The ring is designed to be installed in a cylinder bore in a circumferentially compressed condition where it will expansibly engage the cylinder wall 22.

The ring groove 33 is dimensioned to receive the radial leg 32. Preferably the groove 33 has an axial height slightly greater than the axial height of the leg 32 so as to allow free movement of the leg therein. Further, the groove 33 has a radial depth sufficient to allow the leg 32 to be received therein in a nonbottoming relation. While the groove 33 may be located axially below the top 20 of the piston head 10 by a distance which will allow the leg 31 to overlie the top 20, it is preferable to have it dimensioned so that the top radial wall 34 of the top leg 31 is substantially coplanar with the top 20 of the piston head 10.

A peripheral ledge 35 is provided around the top of the piston head 10 to receive the leg 31. The ledge 35 has an axial wall 36 which is slightly longer than the axial width of the leg 31 and a radial wall 37 which extends radially into the piston head 10 by a dimension which is greater than the operating radial penetration of the leg 31 from the side 23 of the piston head 10. Thus, the leg 31 is nonbottoming against the axial wall 36 and a space 38 is provided between the inner diameter 39 of the leg 31 and the wall 36 of the ledge 35.

A second ledge 40 may be provided adjacent the outer diameter of the ledge 35 and consists of a radial wall 41 and an axial wall 42. The ledge 40 provides a seat for an expansion spring 43 which acts against the inner periphery 44 of the bight section 33 of the ring 30. The expansion spring 43 is illustrated as being of the wave type wherein the inner diameter of the convolutions bottom against the wall 42 of the groove 40 and the outer diameter convolutions bottom against the inner diameter 44 of the bight 33 of the ring, thus circumferentially expanding the ring into tight sealing engagement with the wall 22 of the cylinder bore 11. The outer diameter of the bight 33 has a wear and scuff resistant coating 45 thereon.

The U-shaped cross section construction of the ring 30 cooperates with the dimensioning of the groove 33 and of the ledge 35 to aid in sealing the firing area 46 of the cylinder bore 11 above the top 20 of the piston 10. FIG. 3 illustrates the sealing effect during the power and compression strokes. The arrowed lines illustrate the effect of the expanding combusted gases during the power stroke as well as the compressed vapors during the compression stroke. The depth of the axial wall 36 of the ledge 35 is preferably great enough so that the axial force of the gases illustrated by the arrowed lines 47 on the top leg 31 of the ring 30 is not sufficient to cause the leg 31 to be deflected into sealing contact with the radial wall 37 of the ledge. Therefore, some of the pressurized gases will escape through the space 38 between the back wall 39 of the leg 31 and the axial wall 36 of the ledge into the area 48 between the piston 10 and the inner diameter 44 of the bight area of the pression stroke to the same extent that it would condense upon contact with the cold cylinder wall 22.

During both the compression and power strokes, the fuel vapor is therefore contained to the area above the top 20 of the piston head 10 except for that small amount of vapor which is allowed to act against the ring 30 radially inwardly of the outer diameter thereof.

Because the piston ring 30 is located at the top of the piston, and because it uses both the compressed and combusted gases to aid in sealing the cylinder wall, sealing is more effective than in a conventional top compression ring such as the ring 16. The gases do not have as far to travel before exerting their sealing pressure on the ring, thus reducing the time lapse between combustion and sealing. Therefore, the amount of blowby past the ring is minimized.

FIG. 4- illustrates the gas flow and ring positioning during the exhaust stroke. Due to the upward movement of the piston head 10 during the exhaust stroke, as well as due to the existence of pressured gases in the cavity 48, the bottom radial wall of the legs 32 of the rings 30 is retained in sealing contact with the bottom wall 50 of the groove 33. Because the majority of the fuel vapor in the space 48 is not condensed due to the heat of the piston head 10, that vapor, assuming it is not combusted, is free to escape the space 48 through the space 38 in view of the decrease in pressure in the firing area 46. The vapor thus will combine at an early stage with the hot combustion gases and be combusted. It can thus be seen that the area below the ring is sealed from the area 46 due to the sealing contact between the outer periphery of the ring 30 and the cylinder wall 22 and the sealing engagement between the bottom leg 32 and the bottom radial wall 50 of the groove 33 during the exhaust stroke. However, because the vapor does not condense in the space 48, it can combust therein during the power stroke and the gases thus produced will escape during the exhaust stroke.

FIG. 5 illustrates the positioning of the ring during the intake stroke. At this point, the piston head 10 is moving downwardly to draw fuel vapor into the combustion area 46. Insufiicient gas will remain in the space 48 to press the bottom leg 32 of the ring 30 against the wall 50 of the groove 33. However, the downward movement of the piston head coupled with the inertia of the ring and the presence of a reduced pressure area in the combustion space 46 will combine to lift the ring 30 with respect to the piston head 10 until the top of the leg 32 has contacted the top wall 51 of the groove 33 and is sealed thereagainst. Whatever vapor remains in the space 48 will be allowed to escape through the space 38 to recombine with the vapor in the combustion area 46.

Therefore, the ring 30 seals the combustion area 46 not only during the power stroke, but also during the exhaust intake and compression strokes. Further, the ring 30 acts to reduce to a minimum the area in which fuel vapors may remain uncombusted throughout the firing cycle of the engine. The ring 30 acts as both a compression ring and as an emissions control rmg.

FIG. 6 illustrates a modification of the ring of the prior figures. The piston head is provided with a single ledge 60 which terminates in a radially outer wall 61 which has an outer diameter less than the outer diameter 62 of the remainder of the piston head. The wall 61 extends from the radial wall 63 of the ledge 60 to the groove 33. An elastomeric expander 65 is provided between the wall 61 and the inner diameter of the ring 30. The elastomeric and the inner diameter of the ring thereby providing blockage in the axial direction around the inner periphery of the ring. This further reduces the crevice area in the interior of the ring. Thus, the fuel vapors are restricted to the area 66 below the top leg 31 of the ring 30 and above the wall 63 of the ledge 60 and the elastomer expander 65.

Because of the ability of the gases in the combustion urea 46 to act against the back 38 of the top leg 31 of the ring 30 against a portion of the inner diameter of the bight 33, sealing will be accomplished in the samemanncr as in the prior embodiment with the exception that the gases will not act against the bottom leg 32 of the ring except through compression of the elastomeric expander.

FIG. 7 illustrates a further modification of the ring of this invention. The ring 70 is of substantially U-shaped cross section having a top radial leg 71 and a bottom radial leg 72 axially spaced apart by an outer peripheral bight section 73. The piston has a radially extending ring groove 74 axially spaced from the top 20 of the piston head 10. A peripheral ledge 75 extends around the top of the piston head 10. The ledge 75 has an axial wall 76 having a length approximately equal to the width of the radial leg 71 of the ring 70. A radial wall 77 of the ledge 75 extends outwardly from the axial wall 76 to a radial wall 78 which has an outer diameter less than the outer diameter 79 of the majority of the piston head. The wall 78 extends from the wall 77 of the ledge 75 to the ring groove 74. Therefore, a land 80 is defined by the radial wall 77, the axial wall 78, and the ring groove 74. The land 80 has an axial length substantially equal to the distance between the

radial legs

71 and 72 of the ring 70, so that the ring 70 may be interfitted with the land 80 in an interference fit relation, the land 80 acting as a male member and the inwardly opening channel of the ring 70 acting as a female member.

An expander spring 81, illustrated as being of the wave type, is positioned between the axial wall 78 and the inner diameter of the bight section 73 of the ring 70 to circumferentially urge the outer diameter of the ring into sealing engagement with the wall 22 of the cylinder bore. Because the ring 70 is receivedon the land 80 in an interference fit therewith, the bottom wall 82 of the leg 71 is in sealing engagement with the radial wall 77 of the ledge 75 and will remain therein throughout the cycle of the engine.

In this manner, the clearance behind the ring 70 is not vented to the combustion chamber and fuel vapor will not be entrapped therein. Further, the ring 70 has a minimum of operating friction because the combustion gases will operate against only the leg 71 of the ring as compared with the total back side operation of the gases in the ring of FIG. 3.

To prevent pressure from building up behind the inner diameter of the ring due to leakage at the seal between the leg 71 and the wall 77, a vent 85 may be provided to vent the clearance space to the lower pressure area axially below the ring 70.

To further minimize friction and to offset the action of the gases against the ring 71, increased diameter sealing beads 86 may be provided on the outer diameter of the bight 73. The beads 86 may be coated as indicated at 87 with a hard-wearing scuff-resistant material. The beads 86 are preferably axially spaced and are either continuously circumferential or segmented. In those instances where the beads are continuously circumferential, in order to prevent leakage pressure buildup in the space 88 between the axially spaced beads, a vent 89 can be provided to vent the space 88 to the clearance space behind the inner diameter of the bight where the gas may thereafter escape through the vent 85.

FIG. 8 illustrates a modification of the ring of FIG. 7 where the land 80 is chamfered as at 91 and 92 along its radially outer and axially top and bottom peripheries to reduce the contact area between the land and the

legs

71 and 72 of the piston ring 70. This provides for greater radial response of the ring 70 while at the same time maintaining the seal between the leg 71 and the radial wall 77 of the ledge 75. The

chamfers

91 and 92 also provide for ease of insulation of the ring.

In those instances where the cylinder bore 11 is provided with an installation chamfer as indicated at 93, the top bead 86 may be moved axially downwardly to position as indicated at 94 to allow the bead to run clear of the insulation chamfer 93 when the piston head 10 is at the top of its stroke. The lower bead 95 may be positioned anywhere below the upper bead 94 which will optimize the balancing of the ring against the wall 22 of the cylinder bore 11.

As has been mentioned, the ring of the invention may be a cast ring or may be rolled into its U-shaped cross section. The

reduced thickness of the ring in comparison to standard compression rings allows greater response of the ring to engine operating conditions. Because of the extreme heat encountered at the top of the piston, normal compression rings encounter extreme wear. For this reason, the rings of this invention are preferably flame-spray coated with molybdenum or the like metals or plasma-coated with refractory alloy metals as is taught in my US. Pat. application, Ser. No. 696,645, the teachings of which are expressly incorporated herein by reference.

It can therefore be seen that my invention provides for a new piston ring having a substantially U-shaped cross section adapted to be positioned at the top of the piston to reduce blowby and carbon formation while effectively preventing the formation of unburned hydrocarbons created by condensation of fuel vapor against the cylinder wall and entrapment thereof in crevice spaces between the piston head and cylinder wall.

Although the teachings of my invention have herein been discussed with reference to specific theories and embodiments, it is to be understood that these are by way of illustration only and that others may wish to utilize my invention in different designs or applications.

I claim as my invention:

1. As internal combustion engine piston and piston ring combination comprising: a piston having a top, said piston having a circumferential ring groove with top and bottom radial walls closely axially spaced from the top of the piston, an emissions control ring having axially spaced radially directed substantially parallel flat legs interconnected by an outer peripheral bite section, said bite section adapted to ride against the wall of a cylinder in which the piston is received, said ring positioned around the outer periphery of the piston at the top thereof with a radial clearance between the inner diameter of the bite portion of the ring and the piston outer diameter and one leg of the ring received atop the piston top in sealed contact therewith and the other leg received in the said ring groove in sealed contact with the top radial wall thereof whereby the said ring enclamps the land between the top radial wall of the ring groove and the top of the piston in sealing relation therewith, a plurality of circumferentially spaced scrapping beads positioned around the outer diameter of the bite section in axially spaced relation to one another, the said beads increasing the diameter of the ring in the area of the said beads, the said beads being the portion of the bite section adapted to ride against the wall of the cylinder, a vent in said ring porting the area between the axially spaced beads to the radial clearance between the inner diameter of the bite portion of the ring and the piston outer diameter, and an additional vent in said ring porting the said radial clearance to the area between the piston and the outer diameter of the beads axially below the beads.

2. The combination of claim 1 wherein an expansion ring is entrapped between the inner diameter of the bite section and the outer diameter of the piston to circumferentially expand the piston ring.

3. The combination of claim I wherein the said beads are positioned circumferentially around the ring axially spaced from the top and bottom thereof.

4. The combination of claim 1 wherein one of the said beads is positioned adjacent the top of the said ring circumferentially therearound and another of said beads is positioned intermediate the top and bottom thereof, the ring having only two beads.

5. The combination of claim 1 wherein the said beads have their outer diameter coated with a refractory metal alloy.

6. The combination of claim 1 where at least one of the said beads is circumferentially segmented.

7. The combination of claim I wherein the top of the piston has a circumferential depressed ledge around the periphery of the piston at the top thereof, and the top leg of the ring overlies the said ledge in sealing relation with a top surface of the said ledge, the inner diameter of the said ring having a radial clearance between it and the inner diameter wall of the said ledge.

Claims

3. The combination of claim 1 wherein the said beads are positioned circumferentially around the ring axially spaced from the top and bottom thereof.

7. The combination of claim 1 wherein the top of the piston has a circumferential depressed ledge around the periphery of the piston at the top thereof, and the top leg of the ring overlies the said ledge in sealing relation with a top surface of the said ledge, the inner diameter of the said ring having a radial clearance between it and the inner diameter wall of the said ledge.