DE102012013803A1 - Piston ring for combustion engine, has transition area forming sharp striking edge in contact area from lower flank area, while curved shell surface extending in direction of upper flank area is protruded from striking edge - Google Patents

Abstract

The piston ring (3) has a base body with a radially outer contact area (6), a radially inner peripheral area (7), and upper- and lower- flank areas (8,9), where the flank areas are extended between the outer contact area and inner peripheral area. The contact area is provided with a contour extending non-parallel to the inner peripheral area. A transition area (10) forms a sharp striking edge in the contact area from the lower flank area. A curved shell surface (12) extending in the direction of the upper flank area is protruded from a striking edge (11).

Description

The invention relates to a piston ring for an internal combustion engine according to the generic part of the first claim.

Pistons for internal combustion engines are often equipped with three axially superimposed piston rings, wherein the upper ring facing the combustion chamber acts as compression rings and the lower piston ring facing an oil chamber acts as an oil control piston ring.

Compression rings of the second groove have both the task, in addition to the (first) compression ring to seal the combustion chamber relative to the crankcase as well as together with the oil control ring (third ring) to regulate the lubricating film on the cylinder wall.

In order to ensure the oil wiping effect, the ring should float on the oil film during the upstroke and, on the downstroke, strip off the oil towards the oil chamber, usually defined by a crankcase.

The geometry of the piston ring is to be designed so that the functional behavior is consistently ensured under all operating conditions of the internal combustion engine.

Compression rings of the second groove are usually provided with minutes today or formed (in simple two-stroke engines) in a cylindrical shape. A distinction is made between minute and nasal minute rings. Both designs are characterized by a conical, d. H. rectilinear running surface, if necessary with partial cylindrical contact surface (so-called luffing).

The mentioned conicity ensures that during the upstroke the ring can float on the oil film.

It is also known that piston rings with a flat conicity generally tend to better float. For this reason, the tapering tends to be flatter. This, however, has the disadvantage that the gap opening on the top side (combustion chamber side) of the piston ring becomes ever smaller, so that the oil film can no longer completely penetrate into the formed wedge. In the operating state of the piston ring, this causes the piston ring on the combustion chamber side to push a lubricating film shaft in front of it.

The JP 2002-039384 A discloses a different tread geometry. Here is a, extending from the upper to the lower ring edge radius formed, being provided in the transition areas in the upper and lower flank surface curve radii different curvature.

The EP 2 045 488 B1 discloses a piston ring suitable for the piston of a reciprocating engine with a cylinder liner, wherein the outer peripheral surface of the piston ring has a curved surface of a circular arc with a predetermined radius of curvature in its axial region. The radius of curvature is 1.18 to 1.35 times the inside diameter of the cylinder liner in which the piston ring slides during use.

By the DE 39 40 301 A1 a piston ring has become known for gas sealing. The lower flank of the piston ring is relieved to the inside by other measures so far that the active or loaded active flank width, calculated from the tread, corresponds at most to the maximum active tread height and this active tread height is only so high that at 75% lift height in the At the rated speed, the compression stroke still does not result in overtopping and the tread portion above the active range is permanently removed from the system on the cylinder surface. The active tread part is - like the entire tread - processed symmetrically or asymmetrically spherical.

The invention has for its object to make a piston ring, in particular for the second groove of a piston for an internal combustion engine tread side so that with good Ölabstreif- and Abdichtwirkung in the downstroke an optimal floating of the ring is guaranteed under all operating conditions of the internal combustion engine.

The object is achieved in that the transition region from the lower flank region into the running surface forms a sharp scraper edge, from which a curved lateral surface extending in the direction of the upper flank region extends, such that between the scraper edge and the inlet region of the lateral surface into the upper flank region a gap with a maximum width ≤ 0.5 mm is formed.

Advantageous developments of the subject invention can be found in the dependent claims.

Due to this novel tread geometry, the functional behavior of the piston ring can be ensured consistently well under all operating conditions of the internal combustion engine.

While in a piston ring with an axial height of 2 mm and a tread-side taper of 2.0 °, an indentation gap of about 0.07 mm, a gap with a width ≤ 0.5 mm can be formed at the same height and selected curved lateral surface ,

The curvature here is to be designed so that it runs at the point of the lower sharp wiper edge quasi parallel to the cylinder wall of the surrounding cylinder and disproportionately away in the direction of the upper edge region of the cylinder wall.

The curvature may, for example, be circular, a parabola or an ellipse or have a different curved contour.

This design ensures that topside, d. H. on the combustion chamber side, a large gap opening is present, which can absorb the oil film. On the other hand, the gap angle towards the scraping edge becomes extremely small (towards 0), so that the best possible floating behavior of the ring on the lubricant film is ensured.

For example, by different radii of the tread you can meet different lubricant situations or axial heights of the piston ring.

The piston ring is executable both as a nose-shaped ring (with and without undercut) and without radial puncture.

The design of the piston ring is basically independent of the base material of the piston ring. The curved surface of the tread can be both uncoated and coated (completely or partially).

The subject invention is illustrated by means of an embodiment in the drawing and will be described as follows. Show it:

1 Compression piston ring, in particular used in the second groove of a piston, which is provided with a tread contour according to the invention;

2 Nose ring, which is provided with a tread contour according to the invention.

1 shows one, in a groove 1 a piston 2 used piston ring 3 , The piston 2 is radially, for example, a cylinder or a cylinder liner 4 with a cylinder wall 5 across from. So that the subject invention can be better illustrated, the proportions are oversubscribed. The piston ring 3 has a radial outer tread 6 , a radially inner peripheral surface 7 , a combustion chamber B facing upper flank area 8th and a, an oil chamber O facing lower flank area 9 , In the transition area 10 from the lower flank area 9 in the tread 6 becomes a sharp scraping edge 11 educated. From the wiper edge 11 starting, extending in the direction of the upper flank area 8th a curved circumferential surface 12 , which is provided in this example circularly with a predetermined radius R. In a piston ring 3 with an axial height of 2.0 mm and a radius of 10 mm would be in the transition region of the tread 6 in the upper flank area 8th set a gap S ≤ 0.3 mm. Of importance in the subject invention that the wiper edge 11 directly with the cylinder wall 5 is in active connection. With regard to the small radius R is the curvature of the lateral surface 12 designed so that they are at the point of the lower wiper edge 11 almost parallel to the cylinder wall 5 runs and moves in the direction of the upper flank area 8th disproportionately from the cylinder wall 5 away.

2 shows an alternative to 1 , Identical components are provided with the same reference numerals. The piston ring 3 is designed as a nose ring, recognizable by the fact that the sharp wiper edge 11 due to the recess 13 , between lower flank area 9 and tread 6 axially slightly higher than at 1 is scheduled. Starting from the sharp scraping edge 11 Here is a curved outer surface 12 given, extending in the direction of the upper flank area 8th extends. The curved shell surface 12 can be executed as an ellipse or parabola in this example. In analogy to 1 Here is a defined gap S between the wiper edge 11 , respectively the cylinder wall 5 , and the inlet area 14 the curved lateral surface 12 in the upper flank area 8th educated.

The piston ring 3 according to 1 and or 2 For example, as a compression ring in the second groove of a piston 2 be used.

The inventive tread contour ensures that in the upper flank area 8th a large gap opening S is present, which can absorb an oil film. On the other hand, the gap angle direction wiping edge 11 extremely low, ie it moves towards 0, so that the best possible Aufschwimmverhalten of the piston ring 3 can be ensured on the oil film. Through different radii of the tread 6 You can different lubricant situations or axial heights of the piston ring 3 satisfy.

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• JP 2002-039384A [0009]
• EP 2045488 B1 [0010]
• DE 3940301 A1 [0011]

Claims (8)

Piston ring for an internal combustion engine, having a base body, comprising a radially outer running surface ( 6 ), a radially inner peripheral surface ( 7 ), upper ( 8th ) as well as lower ( 9 ) between tread ( 6 ) and inner peripheral surface ( 7 ) extending flank areas, wherein the tread ( 6 ) with a non-parallel to the inner peripheral surface ( 7 ) extending contour, characterized in that the transition region ( 10 ) from the lower flank area ( 9 ) in the tread ( 6 ) a sharp wiper edge ( 11 ), starting from which one, in the direction of the upper flank area ( 8th ) extending curved lateral surface ( 12 ) extends in such a way that between the wiper edge ( 11 ) and the inlet area ( 14 ) of the lateral surface ( 12 ) in the upper flank area ( 8th ) a gap (S) having a maximum width ≤ 0.5 mm is formed. Piston ring according to claim 1, characterized in that the curved lateral surface ( 12 ) has a contour in which, based on the axial height of the piston ring ( 3 ), at least three measuring points are not arranged on a line. Piston ring according to claim 1 or 2, characterized in that the curved lateral surface ( 12 ) is formed as a circular arc section with predeterminable radius (R). Piston ring according to claim 1 or 2, characterized in that the curved lateral surface ( 12 ) has the contour of a parabola or an ellipse. Piston ring according to one of claims 1 to 3, characterized in that the gap (S) has a width ≤ 0.3 mm. Piston ring according to one of claims 1 to 3, characterized in that in a base body having an axial height ≤ 2.0 mm, a circular arc portion is given with a radius of about 10 mm. Piston ring according to one of claims 1 to 6, designed as a nose-shaped ring, in particular insertable in the second groove of a piston ( 2 ) of the internal combustion engine. Piston ring according to one of claims 1 to 7, characterized in that the lateral surface ( 12 ), respectively the tread ( 6 ), at least partially provided with a wear-reducing coating.

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