IE42315B1 - Oil control piston ring - Google Patents

Description

The present invention relates to oil control piston rings for location in a groove of a piston which moves in a cylinder bore of an internal combustion engine.

The invention provides an oil control piston ring for location in a groove of a piston which moves in a cylinder bore of an internal combustion engine, said oil control piston ring comprising a steel strip having a split annular shape, said strip including a pair of sidewall portions and an intermediate wall portion defining a radially inwardly opening channel, said ring having at its outer periphery two axially spaced cylindrical surfaces for oil scraping engagement with said cylinder wall, said cylindrical surfaces each being located at the juncture of respective radially outwardly extending portions of said strip, said respective radially outwardly extending portions extending radially outwardly with respect to said intermediate wall por20 tion and forming two axially spaced oil scraping rims, said portions having an inner apex and having confronting inner surfaces which abut, said confront ing inner surfaces being in continuous abutting rela tion at the inner apex and as they extend from said *23χβ - 3 inner apex toward said intermediate wall, said abutting relation existing for at least part of the distance between said inner apex and the intermediate wall,said sidewall portions extending radially inwardly relative to said intermediate wall in a direction opposite from that of said portions, said intermediate wall, and said sidewalls being formed from a single steel strip.

In order that the invention may be well understood, q two embodiments thereof will now be described, by way of example only, with reference to the accompanying drawings in which:Fig.l is a partial view in elevation of the top of a piston of an internal combustion engine, the piston having circumferential grooves formed therein within which are disposed piston rings, including an oil control piston ring; Fig.2 is an enlarged sectional view taken along the line 2-2 of Fig.l; 0 Fig.3 is a partial perspective view of an assembly of an oil control ring together with an expander spring; Fig.4 is an enlarged view in cross section taken along lines 4-4 of Fig.3; Fig.5 is a plan view of the assembly of Fig.3; Fig.6 is a schematic block flow diagram of a process of making piston rings; u· 4 2313 - 4 Fig. 7 is a schematic side view of roll form equipment employed to carry out the roll form step schematically illustrated in Fig.6; Fig. 8 is a perspective view of a portion of 5 metal strip usable to make a piston ring; Fig. 9 is an end view in elevation of one of the roll stands of the equipment shown in Fig.7; Fig.10 is a plan view of another embodiment of 10 the piston ring; Fig.11 is a side view of the ring of Fig.10; Fig.12 is an enlarged section view along lines 12-1B. of Fig.10, and also shows an expander spring engaging the ring; Fig.13 is an enlarged partial section view along 15 line 11-U of Fig. 10; and Fig.14 corresponds to Fig.12 but shows a different type of expander spring.

Referring to Figs. 1 and 2 there is shown in partial view a piston IO containing a plurality of ring grooves 12,14 and 16 disposed circumferentially thereabout, ring groove 16 having disposed therein an oil control ring assembly 18. Compression rings 20, 22 are respectively disposed in circumferential groove 12,14. Piston 10 is dis posed within the cylinder 23 of an internal combustion engine, cylinder 23 having a cylinder wall surface 25.

Referring now to Figs. 3,4 and 5, the piston ring 423 15 - 5 is generally indicated at 24 assembled together with an expander spring 26. Oil control piston ring 24, as best seen with reference to Figs. 3,4 and 5 is of generally circular, split annular construction and has, 5 in cross section (Fig.4) generally a U-shape. A pair of opposed side walls 28a, 28b project inwardly of ring 24 (towards the center thereof) from, respectively, the uppermost and lowermost portions of intermediate wall 30.

A pair of scraping rims 32a, 32b, are displaced 10 out of the surface of the intermediate wall 30 and are formed of radially outwardly extending portions 3a, 4a, 3b and 4b which project from intermediate wall 30 outwardly of oil control ring 24. The portions 3a , 4a, 3b, and 4b will be seen in Fig.4 to have inner apices and confronting inner surfaces which abut along the lines 39a and 39b for at least part of the distance between the inner apices and the intermediate wall 30. Scraping rims 32a, 32b are each seen to have respectively, a cylindrical scraping face 34a, 34b tacing outwardly of the ring and extending circumferentially therearound. Both of the scraping rims 32a 32b have hard wear coatings, 36a, 36b, respectively, deposited thereover. The hard wear coatings 36a, 36b increase the wear resistance of scraping faces 34a, 34b against cylinder wall 25 and may comprise any suitable hard facing material such as chromium or molybdenum, to name but two possibilities. The coatings may be applied by plating from an electrochemical bath, by plasma or spray gun plating or any other suitable means. Due to the mode of applying the coating 36a,36b it usually extends beyond scraping faces 34a, 34b to other portions of intermediate wall 30. It will be understood that such hard facing materials are not always required. - 423 IS - 6 Expander spring 26 engages oil control ring 24 from the inside thereof. As best seen in Figs. 3 and *>, expander spring 26 is compressed somewhat between oil control piston ring 24 and the bottom wail 16c of circumferential oil control grooves 16 (Fig.2) so that» in use» expansion spring 26 forces oil control piston ring 24 outwardly so that the cylindrical faces of scraping rime 32a, 32b engage the cylinder wall 25 of engine cylinder 23 in scraping,sliding engagement therewith. Legs 28a, 28b may be formed with a very slightly outward flare as they extend from wall 30. A slight outward flare may improve the seal with the upper and lower surfaces 16a, 16b, respectively, of the groove 16. An inward flare (legs 28a, 28b X5 flared towards each other ) is normally not desired.

As is best seen with reference to Fig.4, oil control piston ring 24 is made from a single strip of metal, for example from flat, generally ribbon-shaped steel stock such as shown in Fig.8. Preferably 1050 2o carbon steel stock is used and annealed to make it ductile. After carrying out the various roll forming and other steps described in more detail hereinbelow, the piston ring rolled, coiled and cut from a strip such as that shown in Fig.d has the form shown, for example in Figs.3-5. Side walls 28a, 28b are formed from the respective longitudinally extending edge portions of the strip and intermediate wall 30 is formed from the longitudinally extending center portion of the strip with scraping rims 32a , 32b being formed from pleats folded in the longitudinally extending center portion of the strip, all as explained in more detail below. As is best seen in Fig.4 the pleats from which scraping rims 32a, 32b are formed are closed upon themselves to form generally rigid, solid multi-layer - 7 rims 32a, 32b. By multi-layer it is meant that the total rim thickness (measured parallel to intermediate wall 30) is formed of effectively a double layer of the original strip thickness for at least a portion of the depth by which the rims 32a, 32b extend from the base 31 of intermediate wall 30. The distal end of scraping rims 32a, 32b, i.e. the ends remote from base 31 of the intermediate wall 30, comprise apex folded portions 38a, 38b and the remainder of scraping rims 32a, 32b contain abutting surfaces indicated at 39a, 39b which extend into and through intermediate wall 30. Surfaces 39a , 39b are in tight abutting contact with each other for almost the entire length thereof, i.e. for at least the major portion thereof.

A plurality of vent openings 40 are provided in oil control piston ring 24 between scraping rims 32a, 32b along the circumference of the ring (Figs. 3 and 4). Sidp walls 28a, 28b have respective edge faces 33a, 33b. Intermediate wall 30 has an inside ” J surface 35.

Expanded spring 26 comprises (Fig.3) a perforated profiled spring of the garter spring, circumferentially expanding type which does not bottom on the bottom 16c of oil control circumferential ring groove 16. Expander spring 26 is composed of circumferentially spaced arcuate segments 41a disposed in two parallel extending rows with the segments of one row being staggered with relation to the segments of the other row. Each segment of one row is connected by one outstanding finger 41 to one segment of the other row and by its other finger 41 to an adjacent segment of the other row. The circumferentially outer 423 15 - 8 edges of arcuate segments 41a engage the inside surface 35 of ring 24 and, in use, thereby press thereagainst and urge piston ring 24 into scraping contact with cylinder wall 25 (Figs. 2 and 4). As best seen in Fig.4 the uppermost and lowermost portions of segments 41a are beveled to aid in reducing wear on ring 24.

It will be understood that any other suitable type of expander spring may be employed such as garter type springs of different configuration than that illustrated, coil type expander springs, etc.

For example, fingers 2fr may have axially projecting portions which engage, respectively, edge faces 33a, 33b of ring 24. It will be further apparent to those skilled in the art that the gap 44 of ring and expander assembly 18 shown in Fig.5 will, upon being compressed into position within groove 16, be reduced to a quite narrow slit 441 as seen in Fig.l.

The cylindrical scraping faces 34a, 34b and their respective cylindrical, hard wear coatings 36a, 36b thereover provides an oil scraping surface of excellent characteristics for scraping oil from the surface 24Γ of cylinder 23. The cylindrical surface is a distinct advantage over prior rolled steel oil control rings which provided but a rounded contact surface against cylinder wall 2/: The cylindrical surfaces provide by virtue of its scraping edges 37a and 37a1 and 37b and 37b1 knife-like edges to scrape oil from the surface and move it ahead of the traveling piston ring.

Fig. 6 shows a block flow diagram of a typical process for manufacturing piston rings. Metal strip la fed to a roll form operation Indicated by the block 1. The roll form operation may be one such as schematically shown In Fig.7. During the roll form operation the metal strip Is formed into the profiled strip having the scraper rims formed thereon from which the piston rings are made. After the roll form operation the profiled strip is then sent to a punching or other suitable operation Indicated by the block 2 in which suitable vent openings are punched in the strip. As indicated by the block 3 in Pig.6, this may be followed by suitable heat treatment and drawing operation to harden the strip. This may be accomplished in the known manner by passing the i strip through induction coil heaters, spray quenches and wire drawing apparatus. After the heat treatment operation exemplified by block 3, the profiled strip is passed to a coiling operation in which a permanent set is applied to the strip to provide a permanently coiled strip. This may be accomplished in any suitable manner, usually by colling the strip about a mandrel and heat setting the strip to a permanent set on the mandrel . This is shown by the coil and set block indicated by the numeral 4 in Fig.6. The coils are then severed to any convenient length of coll in the coil severing step indicated by blo-?k 5. With the coil severed to convenient coil lengths, they are then passed to a surface finishing operation. This may include any suitable step such as phosphate treating the coiled metal to impart a suitable surface thereto, and optionally applying a hard, wear resistant facing on the coil, at least to the intermediate wall or the scraping rims or scraping rim faces thereof. The wear resistant coating may be a chromium coating, a molybdenum or molybdenum alloy coating or any other suitable coating applied by any appropriate method such as electro-plating, plasma or flame spraying, etc. The 423 15 - 10 surface finishing step is generally indicated by block in Fig.6. After the surface finishing step is completed the cut coils are severed lengthwise, i.e. longitudinally with respect to the coil so that individual gapped rings are severed from the coil. This is illustrated in block of Fig.6. It will be appreciated that the particular sequence illustrated in Fig.6 may be varied, for example, at any suitable point thereof, stock may be withdrawn from the process and placed into storage and then reintroduced into the process later on.

Referring now to Fig.7, there is shown in schematic view roll form equipment utilizable to produce the rolled metal piston ring. A coil 46 of metal strip 50 is unwound in the direction indicated by the arrows 48 of Fig.7 to pass metal strip 50 through a series of roll stands 60, 70, 80, 90, 100, 110 and 120.

Referring to Fig.8 , there is shown a perspective hroken-away view of a portion of metal strip 50 which is seen to be generally of a flat, ribbon-shape having a first major surface 51 and an oppositely-facing second major surface 52, the major surfaces being bounded by longitudinally extending edges 53, 54. Dotted lines A, B are superimposed on strip 50 ir. Fig.8 to indicate edge portions 50a, and 50a of strip 50 and central portion 50b. Edge portions 50a and 50a^ are of equal width and indicate longitudinally extending segments of strip 50 adjacent to, respectively, edges 53 and 54. Central portion 50b indicates the longitudinally extending section which is intermediate end sections 50a and 50a. It will be appreciated that the divisions of strip 50 into longitudinally extending end portions and a central portion is done for ease of description. Generally, side walls 28a and 28b of oil control piston ring 24 are made from end sections 50a 4231 - 11 and 50a^ and intermediate wall 30 (and scraping rims 32a and 32b folded therefrom) are made from central portion 5Ob. However, it is to be understood that the portions of strip 50 described as the edge portions do not necessar ily have to coincide exactly with side walls 28a, 28b, since the edge portion confined between opposed form rolls in the initial stages of the roll form step may be somewhat more or somewhat less than the amount of strip 50 which is ultimately turned over to form side walls 28a, 28b.

A series of seven roll form stands are shown in fig.7, through which metal strip 50 is fed. In the embodiment illustrated, the first six roll form stands 60, 70, 80, 90, 100 and 110, each contain a set of two opposed vertical roll forms which are profiled to define a metal working space between them at the region of tangential confluence of the two rolls. The seventh and last roll form stand 120 contains opposed horizontal xOllers as well as opposed vertical rollers, all of which sets of opposed horizontal and vertical rollers cooperate to form the metal work space at their point of confluence.

Fig.9 shows an end view along view line IX-IX and is typical of the construction of the other roll form stands, except for the provision of horizontal, as well as the vertical,roll forms in roll form stand 120.

Referring to Fig.9, roll form stand 120 comprises a roll form stand base 122 having a pair of opposed stanchions 123a and 123b from which protrude upper journal posts 124a, 124b and lower journal posts 125a, 125b. A vertical top roll 126 and a vertical bottom roll 127 are journaled, respectively, in journal posts 124a, 124b and 125a, 125b. Horizontal top rolls 128a,128b are each journaled, respectively, in journal post 124a, 125a and 124b, 125b. The rollers are mounted by means of journal shafts (unnumbered) as shown. Roll form stand 120 is affixed to support base 130 by mounting bolts 131.

Roll form stands 60, 70, 80, 90, 100 and 110 are generally similar to roll form stand 120, except that they carry only a pair of opposed vertical rolls and no horizontal rolls.

Accordingly, roll form 60 comprises a roll form support. 62 which includes upright stanchions 63a and 63b. Vertical top roll 66 and vertical bottom roll 67 are journaled between stanchions 63a and 63b. Corresponding parts of the other roll forms are correspondingly numbered. The direction of rotation of the respective top and bottom rolls are indicated by the curved arrows associated therewith. In each case,the stanchion shown in the foreground of Fig.7 (that carrying the a designator) is partially broken away to better show the top and bottom vertical rolls (vertical and horizontal rolls in the case of roll form support 120 only).

After emerging from roll stand 120, shown in Fig.7, vent holes as required may be punched In the strip and the strip subjected to other operations such as heat tempering and drying, coiling, severing,etc. as indicated by the block flow diagram of Fig.6, explained hereinabove.

In the embodiment of Figs. 10-14 parts corree30 ponding to those of the embodiment of Figs. 3-5 are identically numbered. Thus, an oil control piston ring 24 is X □ generally circular In plan view and has a gap 44 therein. A pair of opposed side walls 28a, 28b project Inwardly of ring 24. A pair of scraping rims 32a, 32b project from ring 24,which is provided with vent openings 40 (shown in dotted lines in Fig. 10). Typical dimensions for ring 24 of Fig. 10 are 0.134 inches radial wall thickness (dimension R-R in Fig. IO) and 0.187 inches ring width (dimension W-W in Fig. 11). Ring 24 may be made of a metal strip, for example, a steel strip of 0.0175 to 0.0185 inch thickness (dimension t-t in Figs. 12 and 14). The ring of Figs. 10-13 may be made, for example, from C-1050 steel which has been given a black oxide surface treatment. Chrome plating 36a, 36b may be applied, for example, by electro15 plating.

Typical tolerances attainable by producing rings are that scraping faces 34a, 34b must show 360° continuous line contact at gauge diameter of the ring (dimension G-G in Fig. 11). The maximum allowable deviation measured from the true gauge diameter i9 .0003 Inches.

The scraping faces 34a, 34b must also be in 360° alignment with each other to within .0004 inches maximum with reference to the cylindrical plane of the ring.

Side walls 28a and 28b must not exceed .0003 inch maximum deviation about 360° from a flat surface measured circumferentially on surfaces 28a1, 28b1 (e.g. Figs. and 14) at a point from .010 to .020 Inches from the inside diameter of the ring, i.e. from end faces 33a, 33b. The small flare (dimensions f-f in Fig. 13) imparted to the ring is held to a maximum of .00015 inches over a length of .050 inches of the side walls, measured at a point (line p-p in Fig. 13) which is .020 inches from the ring inside diameter, i.e. end faces 2 315 - 14 33α, 33b. An exaggerated portrayal of the position of the surfaces of side wall 28a is shown by F (outward flare) and F* (Inward flare).

The extrusion forces imposed on the ring insure 5 that surfaces, or more properly, interfaces, 39a, 39b formed by the pressed-together abutting portions of intermediate wall 30 provide a ring whose strength, rigidity and durability could not be matched for example, by forming scraping rims 32a, 32b as hollow ridges, even if thereafter the hollow was filled with metal or other material which, in any event, might tend to separate from the ring in use. It will be noted that the abutting surfaces 39a, 39b extend from the inner apices 39a1 and 39b1 toward the inner surface of the channel formed by the sidewalls 28a and 28b and intermediate wall 30. Inner apices 39a1 and 39b1 are formed at the intersection of the inner surfaces of Vshaped portions by rolling the rims 32a and 32b out of ths plane of the strip 50 b, the apparatus shown in Fig. 7. The outer surfaces of the V-shaped portions converge to an outer end or apex at which the cylindrical surfaces 34a and 34b, respectively, are formed by the roll 126 (Fig.9).

Fig. 12 shows the piston ring which has dimensions as exemplified above engaged with an expansion ring 26 similar in shape, but radially proportionally wider, to that shown in Fig. 4, and made of material relatively thicker than the ring. Expansion sprinq 26 of Fig. 12 may exert an expansion force of 275 psi. No significant outward deflection of sidewalls 28a, 23b is caused thereby.

Fig.14 shows another embodiment of an expander spring wherein the spring is formed somewhat T-shaped in cross section by having axially projecting knobs 2315 - 15 ~ 45a and 45b, which engage the piston ring at the edge faces 33a, 33b thereof.

When hard alloy steel such as chromium alloy steels containing sufficient carbon so that a chromium carbide constituent is formed in the alloy of the steel is employed, the necessity of a hard facing alloy such as chromium or molybdenum may be avoided, at least in certain applications. In other applications, such as heavy duty diesel engines, the provision of a hard facing such as chromium or molybdenum or any other suitable facing is highly desirable.

It will be' appreciated that there has been described an oil control piston ring which has closely controlled dimensional variations and is of rigid con15 struction, being made from relatively heavy strip to impart the desired rigidity and improved scraping action.

Claims (7)

1. An oil control piston ring for location in a groove of a piston which moves in a cylinder bore of an internal combustion engine, said oil control piston ring 5 comprising a steel strip having a split annular shape, said strip including a pair of sidewall portions and an intermediate wall portion defining a radially Inwardly opening channel, said ring having at its outer periphery two axially spaced cylindrical surfaces for oil scraping 10 engagement with said cylinder wall, said cylindrical surfaces each being located at the juncture of respective radially outwardly extending portions of said strip, said respective radially outwardly extending portions extending radially outwardly with respect to said intermediate 15 wall portion and forming two axially spaced oil scraping rims, said portions having an inner apex and having confronting inner surfaces which abut, said confronting inner surfaces being in continuous abutting relation at the inner apex and as they extend from said inner apex toward 20 said intermediate wall, said abutting relation existing for at least (art of the distance between said inner apex and the intermediate wall, said sidewall portions extending radially inwardly relative to said intermediate wall in a direction opposite from that of said portions, 25 said intermediate wall, and said sidewalls being formed from a single steel strip.

2. An oil control piston ring as claimed in claim 1, wherein the inner surfaces of the sidewalls intersect the intermediate wall at substantially a right angle 30 with an inward or outward flare not exceeding .00015 measured over .050 of the sidewalls from a point .020” from the radially innermost extent of said sidewall portions . - 17 3. An oil control piston ring as claimed in claim 1 or 2, wherein the inner surfaces of the portions forming said oil scraping rime extend radially from said channel and abut for substantially all of the radial extent thereof. 54. An oil control piston ring as claimed in any one of the preceding claims, wherein said cylindrical surfaces comprise a wear resistant coating material.

3. 5. An oil control piston ring as claimed in claim 4 wherein said wear resistant material is chromium. 10

4. 6. An oil control piston ring as claimed in any one of the prceding claims, wherein said steel is a carboncontaining chromium alloy steel.

5. 7. An oil control piston ring as claimed in any one of the preceding claims, including vent openings in the 15 intermediate wall disposed between the rims.

6. 8. An oil control ring as claimed in any of tlie preceding claims, in combination with an expander ring having leg portions and an intermediate base portion forming an outwardly opening channel and dimensioned to fit 20 within said inwardly opening channe 1 of said oil control piston ring with the leg portions extending radially outwardly and the base portion forming the innermost portion of the expander ring, the outer extremities of the leg portions being positioned to engage the inner surface of the 25 intermediate wall of said oil control piston ring next to the intersection of the sidewall portions with said intermediate wall to exert a radially outwardly directed expanding force on said oil control ring and maintain said cylindrical surfaces in oil scraping relation with said cylindric30 al bore.

7. 9. A combination as claimed in claim 8 wherein the outer upper edge of the upper leg of the expander ring and the outer lower edge of the lower leg of the expander ring are each bevelled. 5 10. Either of the oil control piston rings substantially as herein described with reference to Figs. 1-5 and