FR2523215A1 - PISTON RING - Google Patents

Abstract

THE INVENTION RELATES TO A SPLIT PISTON SEGMENT WITH A WEAR-RESISTANT COATING. THE WEAR-RESISTANT COATING STRIP 38 IS LOCKED IN A THROAT IN THE BENT OUTSIDE PERIPHERAL SURFACE OF THE SEGMENT 20, BETWEEN TWO FLANGES 40, 42 OF WHICH ONE 40 IS WIDER THAN THE OTHER 42. A COVERED JOINT IS SHAPED BY MACHINING THE OPPOSITE ENDS OF SEGMENT 20. FIELD OF APPLICATION: INTERNAL COMBUSTION ENGINES, ESPECIALLY OF THE DIESEL TYPE.

Description

The invention relates to the piston rings, and more particularly to a

  annulus segment and piston slit bearing a coating or a wear-resistant layer on its bearing surface, and a seal-type seal at its hyphenation.

  So far, it is known that annulled segments

  slits with a wear coating on their

  radial outer layer can be used

  advantageously as upper segments or segments of

  Examples of such segments are described in U.S. Patent Nos. 3,133,739 and 2,266,692 Tl. It has also been found desirable to provide lap seals. to the

  breaking of piston compression rings in order to improve

  improve the sealing of this break with, as a result, a decrease in the leakage of combustion gases Examples of such types of seals are described

  in U.S. Patent No. 615,902.

  However, it has become apparent that the overlap-type breakaway gaskets proposed so far to provide effective sealing can not be used with conventionally designed wear-coated segments.

  without risk of flaking and deterioration of the coating

  wear in the joint area during the manufacture of the segment It has been proposed not to overfill the joint area, but the result is a lack of

  sealing and deterioration of the engine.

  The subject of the invention is therefore an annulled segment

  advanced split piston tube that combines the advantageous features of wear-coated piston rings with advanced features

  leak-tightness of joints of the overlap type

  segment in which the wear coating extends over the entire circumference of the bearing surface of said segment. The invention will be described in more detail with reference to the accompanying drawings by way of non-limiting example and in which: FIG. 1 is a top view of a piston ring produced in accordance with the invention; FIG. partial vertical section along line 2-2 of Figure 1; Figure 3 is a partial vertical section of a detail of the segment of Figure 2, but shown on an even larger scale Figure 4 is a partial vertical section in the direction of the arrow A of Figure 1; Figure 5 is a partial vertical section taken along line 5-5 of Figure 1; Figure 6 is a partial top view showing the separated ends of the segment in the free state, the spacing being exaggeratedly represented; Figure 7 is a partial bottom view similar to that of Figure 6; Figure 8 is a partial perspective view of the separated ends of the upper surface of the segment; Figure 9 is a partial perspective view showing the separated ends of the lower surface of the segment; and FIG. 10 is a partial section, similar to that of FIG. 3, of a part of another form of

  embodiment of the piston ring according to the invention.

  FIG. 1 shows the piston segment 20 according to the invention in a preferred embodiment indicated by way of example, this segment being intended for use as an upper compression segment in a diesel engine. comparison of FIGS. 1 to 4, segment 20 is of the type presenting

  a curved outer circumferential surface 22, i.e.

  that the outer peripheral surface 22 of the segment has a uniform curvature of radius R (FIG. 2). The sectional configuration of the segment 20 is of the keystone type, that is, the upper and lower sides. 24 and 26, respectively, of the segment 20 are inclined so as to converge towards each other and towards the inside of the segment.

  segment 20 extends parallel to its axis.

  As best seen in Figures 3 and 4, the outer face 22 of the segment has a circumferential groove defined by a bottom surface 32 and upper and lower edge surfaces 34 and 36,

  respectively This groove is filled, by techniques

  known, for example by plasma spraying, of a hard, wear-resistant material, for example

  chromium, to form a surrounding circumferential band 38

  The segment body 20 is made by conventional methods, for example by centrifugal casting, and it consists of

  of a ferrous metal such as graphite cast iron spheron

dal or steel.

  In accordance with one embodiment of the invention,

  vention, the wear band is shifted axially from the

  segment 20 so that its center is arranged slightly

  below a central plane P of the segment (FIGS. 2 and 3) to form upper and lower ferrous edges 40 and 42, respectively (FIGS. 3 and 4) of unequal width (measured axially at segment 20). ray R is centered on plane B It appeared that the

  upper rim 40 and the lower rim 42 are suf-

  In such an embodiment, in such an embodiment, narrowly to minimize any tendency to friction between the flanges and the cylinder bore of an associated motor (not shown), the aforesaid convex face 22 further reduces any friction by placing the flanges 40 and 42 to

  a certain distance from the wall of the cylinder

sant face (not shown).

  According to another feature of the present invention, the segment 20 has an oblique-type lap seal at the break of the segment, to reduce leakage causing engine crankcase ventilation. The seal design is a modified form of the overall type. represented in FIGS. 6 and 7 of the aforementioned US Pat. No. 615,902. As can best be seen in FIGS. 6 to 9, one of the ends cut off

  segment 20 has a tongue 50 which extends beyond

  conferring an extreme face 51 extending

  radially and axially towards the other end

  The other severed end of the segment has a recess 54 (FIG. 8) for receiving the tongue, which is inclined in a complementary manner. When the segment 20 is compressed to its working diameter, for example when it is placed in a position of job

  in the corresponding groove for the upper segment

  When a piston is compressed and the latter is mounted in the bore of the associated cylinder of a motor, the tongue 50 extends above and slides on the opposite cut end 54 of the segment 20.

  1, 4 and 5 represent this normal overlap corresponding to

in the working position.

  FIG. 10 shows another preferred embodiment of the piston ring according to the invention, this segment being indicated at 90. The segment 90 is of the type having a curved outer peripheral surface 91 having a uniform curvature of radius R '(FIG. 10). which, unlike the face 22 of the segment 20 shown in FIG. 3, the radius of curvature R of which is centered on the plane P, is not centered on a central plane P 'of the segment

  90 In the latter, a wear band 92 of resistant material

  the wear is axially offset from the central plane P ';

  its central axis included in a plane C is arranged slightly

  below the central plane so that the courier radius

  The maximum outer diameter of the segment 90 thus falls on the center, considered axially at the segment 90, of the wear strip 92. The flanges 93 and 94 made of cast iron, forming the upper limits

  and lower, respectively, of the band 91, are realized

  at unequal widths (measured axially at segment 90) and, for example, have dimensions substantially equal to those previously indicated for segment 20 shown in FIG. 3. Similarly, upper and lower sides 95 and 96, respectively, and all the others 5.

  characteristics of segment 90 are substantially identical

  to those of the segment 20 as described above and as also described hereinafter It has been found that a preferred embodiment of the piston ring according to the invention, having an offset convex face, as

  this is the case of segment 90, it is particularly

  to reduce the leakage of flue gases

  which is called crankcase ventilation, in use, and may also unexpectedly have good wear resistance, since this characteristic tends to constantly ensure that the belt is kept in contact with the material resistant to wear. wear with the wall of

engine cylinder.

  Referring again to FIG. 9, it can be seen that the oblique seal of the segment 20 can be made by a conventional milling operation which cuts off the material from the end of the segment.

  to form the tongue 50, the milling cutter

  at the same time the inclined top surface 52 of

  the tongue 50 and the end surface 51 extending radially

  The upper end of the surface 52 terminates in a circumferential edge 56 which is located approximately in the middle of the upper flange 40 of the end of the segment having the tongue. The lower and inner end of the inclined surface 52 terminates. at an edge 58 extending circumferentially to the segment, in proximity, but radially, outside the inner edge 60 of the inner peripheral surface 31 of the segment. The wear-resistant strip 38 extends completely to the outer edge. 62, extending axially, of the tongue 50, and the end face 64 of this tongue 50 is located

  in a radial plane parallel to the axis of the segment 20.

  The recess 54 in the other severed end of the segment 20 may be formed in the same manner by a milling operation to produce an inclined surface 70 and an associated lateral face 72 of the recess 54 (FIG. outer superior 74

  of the surface 70, as well as the edge 56, extend

  conferringly in the middle of the upper rim 40 (FIG.

  8) The lower edge 76, radially inwardly

  of the surface 70 also extends circumferentially

  20 and is disposed approximately contiguous to the edge 58, having the same extent as the latter, in the position of overlap of the segment seal (FIG). The end face 78 (FIGS. 6-8) of FIG. recessed end of the segment extends substantially parallel to the face 51 to which it is juxtaposed when the segment 20 is in the working position in which its

ends overlap.

  The presence of the upper flange 40, of greater width, of the segment 20, the edge cut by the oblique seal, to the outer peripheral surface of the segment 20, at the location of the edges 56 and 74 (FIG.

  8), leaves an extension 40a of the upper rim

  extending along the tongue 50 from the outer edge of the face 51, to the end face 64 (Figure 7), and an extension 40b of the upper flange

  extending along the outer periphery of the

  of the segment, between the faces 72 and 78 of pre-

  the extension 40a of the rim has a dimension

  axial dimension substantially between one and two times the axial dimension of the extension 40 b of the flange It is also preferable that the extension 40 b of the flange (FIG. 8) is at least equal to or slightly greater, in

  axial dimension, at the lower edge 42 of the segment 20.

  The surfaces 52 and 70 (FIGS. 5, 8 and 9) extend in planes forming an acute angle with the plane P and oriented substantially diagonally with respect to the section of the plane.

segment body.

  When manufacturing segment 20, after

  the oblique seal has been milled in the

  severed half of the segment, several of these segments are mounted on a tree and coated, by spraying

  plasma, hard material, wear-resistant

  The spray coated faces are then ground to expose the flanges 40 and 42 separated by the web 38. The edges 74 and 56 of the extensions 40a and b are then placed outside the portion of the web.

  the surface of the segment filled with pulverized metal.

  an expansion force is applied to the spray-coated segments to separate the ends, the only area in which flaking may occur

  of the wear resistance strip 38 is located near

  The effect of this flaking along the axial edges 62 and 80 is minimized or eliminated during

  a subsequent hyphenation rectification operation.

  This is made possible by dimensional tolerances

  relatively large that can be admitted for the dimensions

  free hyphenation, which allows, therefore, to remove

  metal worm surfaces 64 and 72 (and edges 62 and 80

  coating) without exceeding the break-even tolerances.

  In previous attempts to use a seal of

  slanting overlapping slenderness in coated segments

  Since the wear edges 56 and 74 were disposed within the hard coating metal, the oblique surfaces 70 and 52 could not be machined to eliminate flaking, while maintaining minimum play conditions between the surfaces 52 and 70 to limit the leakage of gas by the lap joint break In general, in the segments mentioned above by way of example, the game inti ent these overlapping surfaces is maintained

  within the limits of 0.03 to 0.13 mm.

  It should be noted that the oblique type seal effectively seals in a direction directed from the upper side of the segment to the lower side, the upper side being normally marked by the letter "H" and by a "dash". machining "84 (Figure 6) to be oriented,

  during assembly, to the combustion zone of the cylinder

  Thus, with the upper side of the segment 20 facing upwards towards the top of the piston, the seal provided by the segment seal is in the up-down direction. It should also be noted that the upper flange is preferably made at a greater width than the lower flange 42 to allow the oblique seal to bite into the flange 40, while leaving extensions 40a and 40b of this flange of sufficient width to ensure the strength Nevertheless, and although not currently preferred, the bottom flange 42 may be made at a width equal to that of the top flange 40 under appropriate circumstances although the invention has been described in its application to charged segments. of chromium, the principles of the invention can also be applied to segments carrying other wear-resistant materials that fill the groove, for example molybdenum, ceramics, aluminum oxide, chromium oxides,

  chromium carbide or titanium carbide.

  In the above description, the terms

  'up', 'down', 'upper' and 'lower' are used

  indicative and not limiting, with reference to the

  preferred and previously indicated the segment relative to the associated piston, in an application where the piston performs a reciprocating vertical movement and the segment is used as an upper seal or compression seal. It goes without saying that many modifications can be made to the piston segment described and

  shown without departing from the scope of the invention.

Claims (8)

  Piston ring, characterized in that it comprises a split annular metal body having axial side walls (24, 26) enabling it to be housed in a segment groove, and a peripheral surface.   outside (22) which, in all its   a groove delimited in part by axially spaced flanges (40, 42) on the circumferential surface, a band (38) of wear-resistant material, accommodated in the groove, for sealing a cylinder wall, the flanges being respectively adjacent to opposite axial edges of   the strip, a lap joint being formed at the ends   severed menses of the segment and having opposed planar surfaces (52, 70) which extend substantially diagonally with respect to the segment body, said surfaces being inclined to form an acute angle with the plane of the segment and said surfaces terminating at said   outer peripheral surface in one (40) flanges.   Piston ring according to claim 1 for use as a compression ring on a piston in a reciprocating piston engine,   characterized in that it has reference marks (H, 84)   to indicate the orientation in which the segment is placed in a piston groove so that said flange   (40) is oriented towards the combustion zone of the cylinder.   Piston ring according to Claim 2,   characterized in that the flat surfaces of the joint   at their radially inner ends (58, 76),   in said sidewall remote from said flange (40).   Piston ring according to claim 3, characterized in that the seal surfaces extend circumferentially from an associated end wall (64, 78), defining a first radial face of the break of the segment, to another wall. associated end (51, 72) defining the other radial face of the break, said groove extending over the entire circumference of the peripheral surface and the band having extreme edges (62,   ) oriented axially and appearing at the hyphenation.   Piston ring according to any one of   Claims 1, 2 and 4, characterized in that the surface   circumferential contour such that the maximum outer diameter of the segment is on the outer surface   wear of the metal strip.   6 Piston ring according to any one of   Claims 1, 2 and 4, characterized in that one (40)   flanges are wider than the other flange (42).   7 Piston ring according to any one of   Claims 1, 2 and 4, characterized in that it has   in section, a keystone profile.   Piston ring according to Claim 5, characterized in that the center of the axial dimension of the strip is offset from the central plane (P) of the body of the piston.   segment, towards the side wall of the outermost segment said flange (40).   9 Piston ring for a combustion engine   internal displacement with reciprocating pistons,   characterized in that it comprises a split annular metal body having an outer peripheral surface (22), a strip (38) of wear-resistant material which extends around the periphery of the outer peripheral surface and which is intended to to make a sealing contact with a cylinder wall, this strip having a dimension, in the axial direction of the segment, smaller than that of the outer peripheral surface, and being axially offset from the plane of said segment so that said outer peripheral surface comprises flanges (40, 42) of unequal axial dimensions made of a single   piece with the body and arranged in full -on the   the axially opposite edges of the strip, the ends   severed menses of the joint-forming segment   which has opposite flat surfaces (52, 70)   extending diagonally to the section of the segment and   on the outer peripheral surface in the area   the rim having the largest axial dimension.   Piston ring according to claim 8, characterized in that the circumferential surface has an offset curved profile so that the maximum outer diameter of the segment falls on the center of the axial dimension of the strip.