DE102020101230A1 - Piston ring, piston machine with a piston ring and method for producing a piston ring - Google Patents

Abstract

The present invention relates to a piston ring made of a fiber composite material with a matrix and fibers embedded therein, which piston ring defines an axis and comprises an inner circumferential surface, an outer circumferential surface radially spaced therefrom and an expansion opening, the piston ring being expandable in the circumferential direction of the axis by enlarging the expansion opening, wherein the fibers on the piston ring have different orientations in sections, the fibers having different orientations, at least at a deformation section arranged at a distance from the expansion opening, along a thickness direction of the piston ring radially from the inner circumferential surface to the outer circumferential surface. The invention also relates to a piston machine and a method for producing a piston ring.

Description

The present invention relates to a piston ring made of a fiber composite material with a matrix and fibers embedded therein.

The invention also relates to a piston machine with at least one such piston ring and a method for producing a piston ring.

The present disclosure further includes the use of at least one piston ring of the type mentioned above.

the WO 2018/234244 A1 describes different embodiments of piston rings, each made of a fiber composite material with a matrix and fibers embedded therein. These piston rings comprise a free carbon phase with a volume fraction of at least approx. 5%, as a result of which the respective piston ring itself has lubricating properties in order to support the lubricating properties of the engine. Delamination of the piston ring is effectively avoided by a high mechanical stability, in particular due to the carbides. The piston ring has a high temperature stability and is wear-resistant despite the lubricating properties.

In the WO 2018/234244 A1 processes for manufacturing the different piston rings are also described.

In addition, piston rings made of metallic ring structures are known which can be coated to increase wear resistance, for example with a so-called “diamond-like carbon” (DLC) coating. The disadvantage here is the brittle nature of the DLC layer, as a result of which it is susceptible to damage resulting in failure of the functional layer.

The object of the present invention is to provide a piston ring made of a fiber composite material, which piston ring has improved functional properties.

This object is achieved according to the invention by a piston ring made of a fiber composite material with a matrix and fibers embedded therein, which piston ring defines an axis and comprises an inner circumferential surface, an outer circumferential surface radially spaced therefrom and an expansion opening, the piston ring being expandable in the circumferential direction of the axis while enlarging the expansion opening The fibers on the piston ring have different orientations in sections, the fibers having different orientations along a thickness direction of the piston ring radially from the inner circumferential surface to the outer circumferential surface, at least at a deformation section arranged at a distance from the expansion opening.

The mechanical properties of the piston ring according to the present invention can be influenced in a targeted manner via the orientations of the fibers. For assembly, the piston ring must be widened by enlarging the expansion opening. The expansion opening can be delimited in particular facing end faces of the piston ring (“ring joint”), which are spaced at a greater distance relative to one another. As a result of the expansion, the piston ring is mechanically stressed, with the greatest stress occurring at the deformation section arranged at a distance from the expansion opening. According to the invention, provision is made for different orientations of the fibers to be provided at least on the deformation section, along the thickness direction from the inner circumferential surface to the outer circumferential surface. In particular, this gives the possibility that the piston ring, at least at the deformation section, has different stiffnesses radially on the inside, radially on the outside and / or in between. On the one hand, this gives the possibility of ensuring sufficient deformability for improved assembly. On the other hand, there is the possibility of providing sufficiently good frictional properties on the outer circumferential surface. Depending on the application and the properties to be achieved, the piston ring can be provided with a suitable rigidity.

It goes without saying that in the present case the orientations of the fibers are considered in the reference system of the piston ring, so to speak in the form of cylinder coordinates with an axial direction, a circumferential direction around the axis and a radial direction with respect to the axis.

In particular, it can be preferred if the deformation section of the expansion opening is in particular diametrically opposite with respect to the axis.

Alternatively, it can be provided that the deformation section has an angular distance from the expansion opening with respect to the axis that is less than 180 °.

The deformation section can cover, for example, an angular range of at least approximately 10 ° with respect to the axis, preferably at least approximately 20 ° and more.

More than just one deformation section can be provided.

It can be provided that an angle of the orientation of the fibers with respect to the Axial direction adjacent to the inner peripheral surface is larger than adjacent to the outer peripheral surface.

Alternatively, it can be provided that an angle of the orientation of the fibers with respect to the axial direction adjacent to the inner circumferential surface is smaller than on the outer circumferential surface.

Alternatively, it can be provided that an angle of the orientation of the fibers with respect to the axial direction adjacent to the inner circumferential surface is the same or essentially the same as on the outer circumferential surface.

• - ungefähr 10° bis 80°, vorzugsweise ungefähr 20° bis 70°, bevorzugt ungefähr 30° bis 60°, beispielsweise ungefähr 45°;
• - weniger als ungefähr 10° bis ungefähr 0°;
• - mehr als ungefähr 80° bis ungefähr 90°.

For example, it can be provided that an orientation of the fibers adjacent to the inner circumferential surface includes an angle with the axial direction that is one of the following:

• - about 10 ° to 80 °, preferably about 20 ° to 70 °, preferably about 30 ° to 60 °, for example about 45 °;
• - less than about 10 ° to about 0 °;
• - more than about 80 ° to about 90 °.

• - ungefähr 10° bis 80°, vorzugsweise ungefähr 20° bis 70°, bevorzugt ungefähr 30° bis 60°, beispielsweise ungefähr 45°;
• - weniger als ungefähr 10° bis ungefähr 0°;
• - mehr als ungefähr 80° bis ungefähr 90°.

Alternatively or in addition, it can be provided that an orientation of the fibers adjacent to the outer circumferential surface includes an angle with the axial direction that is one of the following:

• - about 10 ° to 80 °, preferably about 20 ° to 70 °, preferably about 30 ° to 60 °, for example about 45 °;
• - less than about 10 ° to about 0 °;
• - more than about 80 ° to about 90 °.

The rigidity of the piston ring can be varied through the angle of the fibers with respect to the axial direction. Accordingly, it can be provided that, during the production of the piston ring, the fibers are arranged with different orientations along the thickness direction at least on the deformation section. The manufacturing process will be discussed in detail below.

For the time being, however, it can be mentioned, for example, that the fibers can be applied to a core, for example by means of a winding process. It can be advantageous here if the fibers have a minimum angle radially on the inside and / or radially on the outside with respect to the axial direction which is greater than 0 ° due to the winding method used. In a corresponding manner, it can be provided that, due to the winding method used, an angle of the fiber orientation is not aligned exactly perpendicular to the axial direction, but rather different from 90 ° in order to simplify the winding process.

It can be provided that fibers of different properties are used along the thickness direction, at least at the deformation section. For example, the fibers differ from one another in terms of their thickness and / or tensile strength.

Alternatively or in addition, it can be provided that different densities of the fibers are arranged along the thickness direction, at least on the deformation section.

Practical investigations have shown that a crack in the piston ring can occur more frequently on the inner circumferential surface than on the outer circumferential surface. Therefore, a lower rigidity of the piston ring on the inner circumferential surface than on the outer circumferential surface can be preferred.

With regard to advantageous friction properties, it has been shown in practice that a high degree of rigidity of the piston ring on the outer circumferential surface can be advantageous.

It can therefore be advantageous if the rigidity of the piston ring, at least at the deformation section, is higher adjacent to the outer circumferential surface than adjacent to the inner circumferential surface, or that the rigidity adjacent to the inner circumferential surface is higher than adjacent to the outer circumferential surface.

In another advantageous embodiment of the piston ring according to the invention, it can be provided that the rigidity of the piston ring, at least at the deformation section, adjacent to the inner circumferential surface, is the same or essentially the same as adjacent to the outer circumferential surface, and / or in each case greater or in each case smaller than in a radial intermediate area of the piston ring. This can, for example, open up the possibility of counteracting the formation of cracks on the inner circumferential surface and at the same time achieving advantageous friction properties on the outer circumferential surface.

In another advantageous embodiment of the piston ring according to the invention, it can be advantageous if the rigidity of the piston ring, at least at the deformation section, adjacent to the inner circumferential surface, adjacent to the outer circumferential surface and radially in between, are different from one another.

It can be provided that the orientations of the fibers, along the thickness direction, differ from one another in the entire circumferential direction, in particular in order to form different stiffnesses of the piston ring. This can be done, for example, in the manufacture of the piston ring simplify, for example by means of a winding or braiding process.

It can be favorable if the piston ring has two or more layers adjoining one another or merging into one another along the thickness direction, the orientations of the fibers within a respective layer being identical or essentially identical, preferably along the entire circumferential direction. Within a layer, the orientations of the fibers are at least essentially the same, but the orientations of the fibers in different layers differ from one another.

The two or more layers can, for example, be provided in a simple manner in terms of production technology by means of a winding process, braiding process, by positioning woven fibers or fiber fleece in different webs.

It can be provided that the two or more layers have the same or essentially the same layer thicknesses. Alternatively, it can be provided that at least two layers have the same or essentially the same layer thicknesses and / or that at least two layers have different layer thicknesses.

It can be provided that within a respective layer there is only one orientation of the fibers or two or more orientations, in particular two orientations in the case of a fiber fabric or a fiber braid. For example, a first layer with two orientations oriented at an angle to one another, formed by a fabric or a braid, of fibers is provided. In a further layer, the fibers can have at least one orientation different therefrom. Here, for example, two different orientations aligned at an angle to one another can be provided, again formed by means of a braid or a fabric.

A particular orientation of the fibers within a layer can be a preferred direction of the fibers, for example when the piston ring is produced by means of a fiber fleece. The fiber fleece provided in webs can, for example, have a respective preferred direction in two or three dimensions, although deviations from this preferred direction can result within the web.

Alternatively, it can be provided that the respective orientation is identical for all fibers within a layer.

In a preferred embodiment of the piston ring according to the invention it can be provided that the orientations of the fibers vary continuously along the thickness direction. For example, by means of a winding or braiding process, fiber orientations can be continuously changed radially from the inside to the outside in superimposed layers.

It can prove to be particularly favorable if the fibers are each aligned in a lateral surface around the axis. This can in particular be understood to mean that the orientations have no or essentially no radial component. In particular, however, an axial component and / or a component can be provided in the circumferential direction.

The fibers can be, for example, wound fibers.

The fibers can form, for example, a fiber braid or a fiber fabric.

The fibers are arranged, for example, in layers radially one above the other with a respective orientation. As already mentioned, this can be achieved, for example, by providing a fiber fleece, for example a wet fleece, in webs. The sheets can be laid one on top of the other in different layers with different preferential directions. If fiber fleece is used for production, it can be, for example, a parallel fleece in which the fibers are oriented longitudinally or in which the fibers are oriented transversely. Alternatively, a cross-ply fleece with longitudinally or transversely oriented fibers that have at least two preferred directions can be used. The mechanical structural properties of nonwoven semifinished products such as strength, force-elongation behavior, elasticity and / or flexural rigidity can be influenced to a greater or lesser extent depending on the manufacturing process by aligning the fibers along at least one preferred direction. In the case of parallel webs with a production direction “MD” (machine direction), a preferred orientation MD: CD of, for example, approximately 5: 1 to 14: 1 can be achieved, with “CD” denoting the transverse direction “cross direction” transversely to the machine direction. In the case of cross-ply fleece, a strength MD: CD of up to approx. 1: 1, for example, can be achieved.

It can be provided in particular that the matrix comprises carbide and a free carbon phase and / or that the fiber composite material is C / C-SiC.

The nature of the fiber composite material can in particular be as it is in the WO 2018/234244 A1 is described by the same applicant. The content and disclosure of this Publication are fully incorporated into the present disclosure.

The fiber composite material preferably comprises fibers and a matrix, it being possible for the matrix to be formed from a carbon precursor (carbon-containing resin or the like) in which the fibers are embedded. The fibers can be pre-impregnated with the carbon precursor (pre-preg) or infiltrated (subsequently impregnated). The carbon precursor with the fibers can be hardened, for example by pressing and / or heating. Subsequent pyrolysis can carbonize the precursor and form a porous, near-net-shape body with a carbon-containing matrix, into which a carbide former can be introduced. The carbide former reacts with the carbon of the porous body to form carbide. Carbide regions can be formed around carbon portions of the matrix.

There is preferably the possibility of influencing the properties of the piston ring in a targeted manner through the carbide formation, in particular the free carbon phase can be influenced. The selection of the carbide former and the selection of the fiber material also make it possible to influence the mechanical stability, heat conduction and / or thermal expansion of the piston ring.

Different preferred carbide formers can be used. For example, silicon carbide, tungsten carbide or titanium carbide have proven to be advantageous.

It can be provided that the free carbon phase comprises a proportion of more than 5% by volume. This improves the lubricating properties of the piston ring.

For example, the free carbon phase can have a proportion of approx. 5% by volume to approx. 25% by volume, in a preferred embodiment preferably approx. 10% by volume to approx. 20% by volume.

• - Kohlenstofffasern;
• - metallische Fasern, beispielsweise Wolframfasern oder Molybdänfasern, oder Fasern aus oder basierend auf einer Metalllegierung, beispielsweise einer Wolframlegierung oder einer Molybdänlegierung;
• - oxidische Fasern, beispielsweise aus Aluminiumoxid oder Zirkonoxid;
• - Fasern aus einem Carbidmaterial, beispielsweise aus Siliziumcarbid.

The fiber composite material can withstand high mechanical loads due to the fibers embedded in the matrix. The fibers are or include, for example, one of the following:

• - carbon fibers;
• metallic fibers, for example tungsten fibers or molybdenum fibers, or fibers made of or based on a metal alloy, for example a tungsten alloy or a molybdenum alloy;
• - oxide fibers, for example made of aluminum oxide or zirconium oxide;
• - Fibers made of a carbide material, for example silicon carbide.

In an advantageous embodiment of the piston ring according to the invention, the fiber composite material is C / C-SiC. To form it, carbon fibers, for example, are pre-impregnated with a carbon precursor or infiltrated and shaped. The fiber matrix material is cured. In the present case, “hardening” can be viewed in particular as hardening by pressing and / or the action of temperature, including pyrolysis, to form a porous body with a carbon-containing matrix. Siliconization with liquid silicon forms silicon carbide, which forms areas around the free carbon to increase the mechanical strength.

The piston ring can be designed in one piece or in several pieces.

The piston ring can have ring joints of different properties at the expansion opening. This will be discussed below.

It can be favorable if the piston ring has at least one groove running at least partially in the circumferential direction to form a labyrinth seal with a piston receptacle on the outer circumferential surface.

Additionally or alternatively, at least one oil control groove can be provided on the outer circumferential surface.

It can prove to be advantageous if at least one recess for forming a labyrinth seal with a corresponding end face of the piston ring is provided on at least one end face of the piston ring that delimits the expansion opening. This labyrinth seal can in particular reduce the so-called “blow-by” in the area of the ring joint.

As mentioned at the outset, the present invention also relates to a piston machine. The piston machine according to the present invention has at least one piston which can be reciprocated in a piston receptacle and on which at least one piston ring of the aforementioned type is arranged.

An advantageous embodiment of the piston machine can be a motor or comprise a motor, in particular a free-piston motor. The piston of the engine can in particular be a combustion piston.

In another type of advantageous embodiment, the piston machine is or comprises a compressor.

The present disclosure also relates to a use. A piston ring of the aforementioned type is used in a piston machine, for example an engine, in particular a free piston engine of a free piston device.

• - Anordnen von Fasern zur Bildung eines Körpers in Form eines insbesondere senkrechten, eine Achse definierenden Kreiszylinders derart, dass radial bezüglich der Achse zumindest zwei Lagen von Fasern angeordnet werden und die Fasern in Umfangsrichtung der Achse über einen vorgegebenen oder vorgebbaren Winkelbereich entlang einer Radialrichtung unterschiedliche Orientierungen aufweisen;
• - Bereitstellen und Aushärten einer Matrix für die Fasern.

A method according to the invention for producing a piston ring according to the invention comprises the following steps:

• Arranging fibers to form a body in the form of a particularly vertical circular cylinder defining an axis in such a way that at least two layers of fibers are arranged radially with respect to the axis and the fibers have different orientations in the circumferential direction of the axis over a predetermined or predeterminable angular range along a radial direction exhibit;
• - Providing and curing a matrix for the fibers.

The advantages that have already been mentioned in connection with the explanation of the piston ring according to the invention can likewise be achieved using the method and the piston machine and using the use. In this regard, reference can be made to the statements above. Advantageous embodiments of the method according to the invention, the piston machine according to the invention and the use according to the invention result from advantageous embodiments of the piston ring according to the invention. In this regard, too, reference can be made to the statements above.

In the method of the invention, the fibers are arranged to form a body. This can be a near net shape body for forming the piston ring itself. Alternatively, for example, an elongated cylindrical body can be formed which, as explained below, is divided axially into individual segments to form respective piston rings. At least two layers have fibers with different orientations - at least over a predefined or predefinable angular range which corresponds to the subsequent deformation section.

In the piston ring according to the invention, the fibers of the body are embedded in a matrix. In the process, the matrix is provided and cured, as a result of which the body can be cured and prepared for any further process steps.

The fibers can be arranged, for example, by winding the fibers onto a core, the fiber orientation being changed via an angle at which the fibers are wound onto the core.

The fibers can be arranged, for example, by braiding the fibers on a core, the fiber orientation being changed via an angle at which the fibers are braided onto the core. A respective braid has in particular two fiber directions arranged crosswise to one another.

The fibers can be arranged, for example, by providing two or more layers of fiber fabric, in particular woven crosswise. The layers can be placed on the core, with superimposed layers being placed on the core at different angles.

The fibers can be arranged, for example, by providing two or more layers of fiber felt which have a respective preferred orientation of the fibers contained therein. This can be, for example, the above-mentioned parallel fleece oriented longitudinally or transversely, or the cross-layer fleece oriented longitudinally and transversely.

The fibers can be arranged, for example, by means of 3D printing of matrix material containing fibers.

The fibers can be arranged, for example, by arranging and specifically positioning individual fibers on a core using tailored fiber placement (TFP).

The fibers can be arranged, for example, by providing and positioning fiber strands on the core by means of a pultrusion device.

The fibers can be arranged, for example, by means of an injection molding process, the fibers being embedded in matrix material.

In the method it can be provided that the fibers are provided pre-impregnated with matrix material in the step of arranging (prepreg). Alternatively, it can be provided that the fibers are infiltrated with a matrix material after they have been arranged.

Provision can be made for the body to be axially divided into a plurality of rings after the matrix material has hardened. Alternatively, the body already has the shape of the piston ring that is near net shape or identical to net shape.

For example, after curing or when arranging the fibers, an expansion opening and, accordingly, an annular joint can be formed on the body.

The body or the piston ring can be reworked, for example. In particular, reworking can be carried out by grinding the outer circumferential surface in particular. Further options for post-processing include, for example, the introduction of at least one groove on the outer circumferential surface and / or the introduction of at least one recess on an end face delimiting the expansion opening.

To the already referenced WO 2018/234244 A1 reference is made again with regard to the introduction of a carbide former into a carbon-containing matrix. The steps described in this publication for carbidizing and providing a free carbon phase of the piston ring can also be used in the present case in preferred exemplary embodiments of the method according to the invention.

• 1: eine perspektivische schematische Darstellung eines erfindungsgemäßen Kolbenrings;
• 2: den Kolbenring in Draufsicht axial in einem unaufgeweiteten Zustand;
• 3: eine Darstellung entsprechend 2, wobei der Kolbenring aufgeweitet ist;
• 4A bis 4C: schematische Darstellungen von radial übereinander angeordneten Schichten des Kolbenrings aus 1, wobei diese in der Zeichnung übereinander dargestellt sind und Orientierungen der Fasern des Kolbenrings schematisch gezeigt sind, wobei die Schichten durch Ausbreiten der Mantelfläche in einer Ebene gezeigt sind;
• 5: eine vergrößerte Detaildarstellung von Detail A in 4;
• 6A bis 6C: eine Darstellung entsprechend den 4A bis 4C bei einem andersartigen erfindungsgemäßen Kolbenring in einer Detailansicht;
• 7: eine schematische vergrößerte Darstellung von Detail B in 6A;
• 8A bis 8C: eine Darstellung entsprechend den 4A bis 4C bei einem andersartigen erfindungsgemäßen Kolbenring in einer Detailansicht;
• 9A bis 9C: eine Darstellung entsprechend den 4A bis 4C bei einem andersartigen erfindungsgemäßen Kolbenring in einer Detailansicht;
• 10A bis 10C: eine Darstellung entsprechend den 4A bis 4C bei einem andersartigen erfindungsgemäßen Kolbenring in einer Detailansicht;
• 11A bis 11C: eine Darstellung entsprechend den 4A bis 4C bei einem andersartigen erfindungsgemäßen Kolbenring in einer Detailansicht;
• 12A bis 12C: eine Darstellung entsprechend den 4A bis 4C bei einem andersartigen erfindungsgemäßen Kolbenring in einer Detailansicht;
• 13A bis 13C: eine Darstellung entsprechend den 4A bis 4C bei einem andersartigen erfindungsgemäßen Kolbenring in einer Detailansicht;
• 14A und 14B: schematische Darstellungen von zwei radial übereinander angeordneten Schichten des Kolbenrings aus 1, wobei diese in der Zeichnung übereinander dargestellt sind und Orientierungen der Fasern des Kolbenrings schematisch gezeigt sind, wobei die Schichten durch Ausbreiten der Mantelfläche in einer Ebene gezeigt sind;
• 15 und 15B: eine Darstellung entsprechend den 14A bis 14C bei einem andersartigen erfindungsgemäßen Kolbenring in einer Detailansicht;
• 16 bis 27: beispielhafte Darstellungen für unterschiedliche Ausführungsformen von Ringstößen eines erfindungsgemäßen Kolbenrings, wobei in den 16 bis 23 und 27 jeweils oben eine Seitenansicht des Kolbenrings und jeweils unten eine Draufsicht auf den Kolbenring in axialer Richtung gezeigt ist;
• 28 bis 30: schematische vergrößerte Darstellungen einer Außenumfangsfläche eines erfindungsgemäßen Kolbenrings angrenzend an eine Kolbenaufnahme;
• 31: eine schematische vergrößerte Darstellung eines Ringstoßes mit einer Aufweitöffnung eines erfindungsgemäßen Kolbenrings;
• 32: eine Schnittansicht einer Freikolbenvorrichtung in einer Teildarstellung, wobei die Freikolbenvorrichtung eine als Freikolbenmotor ausgebildete erfindungsgemäße Kolbenmaschine umfasst;
• 33: eine Darstellung zur Illustration des erfindungsgemäßen Verfahrens, bei dem Fasern auf einen Kern gewickelt werden;
• 34: eine Darstellung entsprechend 33, bei der Fasern auf einen Kern geflochten werden;
• 35: schematisch die Anordnung übereinanderliegender Lagen mit Fasern auf einem Kern;
• 36: eine schematische Detaildarstellung eines längsorientierten Parallelvlieses mit Fasern;
• 37: eine schematische Darstellung eines querorientierten Parallelvlieses mit Fasern; und
• 38: eine schematische Darstellung eines längs und quer orientierten Kreuzlagenvlieses mit Fasern.

The following description of preferred embodiments of the invention is used in conjunction with the drawing to explain the invention in greater detail. Show it:

• 1 : a perspective schematic representation of a piston ring according to the invention;
• 2 : the piston ring in plan view axially in an unexpanded state;
• 3 : a representation accordingly 2 wherein the piston ring is expanded;
• 4A until 4C : schematic representations of layers of the piston ring arranged radially one above the other 1 These are shown one above the other in the drawing and orientations of the fibers of the piston ring are shown schematically, the layers being shown by spreading out the lateral surface in one plane;
• 5 : an enlarged detail view of detail A in 4th ;
• 6A until 6C : a representation corresponding to the 4A until 4C in a different type of piston ring according to the invention in a detailed view;
• 7th : a schematic enlarged representation of detail B in 6A ;
• 8A until 8C : a representation corresponding to the 4A until 4C in a different type of piston ring according to the invention in a detailed view;
• 9A until 9C : a representation corresponding to the 4A until 4C in a different type of piston ring according to the invention in a detailed view;
• 10A until 10C : a representation corresponding to the 4A until 4C in a different type of piston ring according to the invention in a detailed view;
• 11A until 11C : a representation corresponding to the 4A until 4C in a different type of piston ring according to the invention in a detailed view;
• 12A until 12C : a representation corresponding to the 4A until 4C in a different type of piston ring according to the invention in a detailed view;
• 13A until 13C : a representation corresponding to the 4A until 4C in a different type of piston ring according to the invention in a detailed view;
• 14A and 14B : schematic representations of two layers of the piston ring arranged radially one above the other 1 , these being shown one above the other in the drawing and orientations of the fibers of the piston ring being shown schematically, the layers being shown by spreading out the lateral surface in one plane;
• 15th and 15B : a representation corresponding to the 14A until 14C in a different type of piston ring according to the invention in a detailed view;
• 16 until 27 : Exemplary representations for different embodiments of ring joints of a piston ring according to the invention, wherein in the 16 until 23 and 27 a side view of the piston ring is shown at the top and a plan view of the piston ring in the axial direction is shown at the bottom;
• 28 until 30th : schematic enlarged representations of an outer circumferential surface of a piston ring according to the invention adjoining a piston receptacle;
• 31 : a schematic enlarged illustration of a ring joint with an expansion opening of a piston ring according to the invention;
• 32 : a sectional view of a free piston device in a partial representation, the free piston device comprising a piston machine according to the invention embodied as a free piston engine;
• 33 : a representation to illustrate the method according to the invention, in which fibers are wound on a core;
• 34 : a representation accordingly 33 , in which fibers are braided on a core;
• 35 : schematically the arrangement of superimposed layers with fibers on a core;
• 36 : a schematic detailed representation of a longitudinally oriented parallel fleece with fibers;
• 37 : a schematic representation of a transversely oriented parallel fleece with fibers; and
• 38 : a schematic representation of a longitudinally and transversely oriented cross-ply fleece with fibers.

the 1 until 3 show schematic representations of a whole with the reference number 10 occupied piston ring according to the invention in a preferred embodiment. The piston ring 10 is made of a fiber composite material that has a matrix 12th and fibers embedded therein 14th includes. The fiber composite material is preferably C / C-SiC and preferably has a free carbon phase of, for example, at least 5%. The nature of the fiber composite material and its production has already been mentioned above with reference to the WO 2018/234244 A1 received.

As in particular from the 2 and 3 emerges, defines the piston ring 10 an axis 16 . A circumferential direction with respect to the axis 16 is with the reference number 18th marked. A radial direction with respect to the axis 16 which radial direction is a thickness direction of the piston ring 10 is with the reference symbol 20th marked.

In an exemplary implementation in practice when used in internal combustion engines of motor vehicles, the piston ring 10 for example a diameter of less than 100 mm. For example, about 80 mm is common. A height of the piston ring 10 in the axial direction can be, for example, less than approximately 5 mm, approximately 1 mm being common. A thickness of the piston ring 10 in the radial direction 20th can be, for example, less than about 5 mm, with about 3 mm being common, for example.

It goes without saying that the dimensions of the piston ring according to the invention can deviate from the values mentioned above, for example when used in ship engines or compressors.

As in particular from the 2 and 3 shown includes the piston ring 10 a ring joint 22nd with an expansion opening 24 , the opposite end faces 26th of the piston ring 10 is limited.

The piston ring can be used for assembly 10 with enlargement of the expansion opening 24 be widened. This is in 3 shown.

When expanding, the piston ring 10 in particular at a deformation section 28 claimed in a special way. In the present example, the deformation section lies in the expansion opening 24 with respect to the axis 16 opposite to.

A range of angles 30th of the deformation section 28 can for example be approximately more than 10 °, approximately more than 20 ° and above.

Stresses as a result of the deformation can, however, in particular along the entire circumference of the piston ring 10 appear.

According to the present invention it is provided that the fibers 14th of the piston ring 10 have different orientations. There is a variation in the orientations at least at the deformation section 28 along the thickness direction 20th from an inner peripheral surface 32 to an outer peripheral surface 34 of the piston ring 10 .

By varying the orientations of the fibers 14th can the piston ring 10 especially at the deformation section 28 be equipped with such a rigidity that, on the one hand, easier assembly is possible and, on the other hand, sufficient stability is ensured at which crack formation can be avoided.

In addition, by providing the orientations of the fibers that are along the thickness direction 20th at least at the deformation section 28 differ from each other, especially on the outer peripheral surface 34 the best possible friction properties with adequate wear resistance are given for the respective application.

It is beneficial if the rigidity of the piston ring 10 along the entire circumferential direction 18th , and not just at the deformation section 28 , is constant.

To achieve different stiffnesses due to different orientations of the fibers in the thickness direction 20th it is preferably provided that the piston ring 10 having radially superimposed layers. The ones in the 1 until 4C The illustrated embodiment has, for example, three layers 36 , 38 and 40 radially from the inside to the outside.

It can be provided that the piston ring according to the invention 10 has only two layers. On the other hand, provision can be made for more than three layers to be provided.

Within a respective layer, the fibers point 14th preferably an identical or substantially identical orientation, the orientations of the fibers 14th differ from each other by at least two layers.

In the drawing are the fibers 14th only partially shown in the respective layers so that they and the orientations are better recognizable. Areas free from fibers 14th and / or the distances between the fibers shown in the drawing 14th , the density of the fibers 14th and the docking of the fibers 14th are therefore not representative. The piston ring 10 Depending on requirements, areas can be free of fibers 14th exhibit.

The fibers 14th preferably point along the entire circumferential direction 18th , not just at the deformation section 28 , an identical or substantially identical orientation. As explained above, the orientations of the fibers 14th while in the reference system of the piston ring 10 considered, so to speak in cylindrical coordinates. Accordingly, the orientations can have an axial component along the axis 16 , a component in the circumferential direction 18th and / or a component in the radial direction 20th exhibit.

It can be particularly advantageous if the orientations of the fibers 14th within only the respective layers in a lateral surface around the axis 16 run around and in particular no radial component in the radial direction 20th is provided.

In a preferred embodiment of the piston ring according to the invention it can be provided that the orientations of the fibers 14th in the thickness direction 20th , at least at the deformation section 28 , vary continuously, deviating from the layer-by-layer variation of the orientations of the fibers discussed below 14th .

In the following, with reference to the groups of figures 4, 6, 8, 9, 10, 11, 12, 13, 14 and 15, exemplary orientations of fibers 14th referenced depending on the respective layer. In the groups of figures 4, 6, 8 to 13, the three layers are exemplary and non-limiting for the present invention 36 , 38 and 40 intended. In the embodiments of the groups of figures 14th and 15 are merely a radially inner layer 36 and a radially outer layer 40 intended.

In the groups of figures mentioned above, an arrow indicates 42 in each case the axial direction, an arrow 44 each the circumferential direction. The radially inner layer in each case 36 is shown above, the radially outer layer in each case 40 is shown below.

the 4A until 4C show that the layer 36 Fibers 14th with orientation running essentially in the axial direction. The middle layer 38 exhibits fibers 14th which are inclined at an angle of approximately 45 ° with respect to the axial direction. The same applies to the layer 40 , with the slope of the fibers 14th however, the slope of the fibers 14th in the shift 38 is opposite with respect to the axial direction.

With such an orientation of fibers 14th can the piston ring 10 for example, radially inwardly rather less stiff and radially in the middle as well as outwardly rather more rigidly in relation to this.

5 shows an enlarged view of a detailed view of 4A . It can be seen that the orientation of the fibers is preferred 14th doing an angle 46 with respect to the axial direction, which is different from 0 °. This simplifies the manufacture of the piston ring 10 , in particular by means of a winding process. The angle 46 can for example be about -5 ° to 5 ° to about -10 ° to 10 °.

The same applies to the following embodiments, in which a course of the fibers is shown in the drawing 14th is shown in the axial direction for convenience of explanation.

In the embodiment according to 6A , 6B and 6C are the fibers 14th in the shift 36 radially inward approximately in the circumferential direction 18th aligned. In the shift 38 in the middle are the fibers 14th about 45 ° with respect to the axis 16 (and with respect to the circumferential direction 18th ) inclined. In the shift 40 The fibers are radially outside 14th aligned approximately in the axial direction.

7th shows an enlarged illustration according to FIG 6A . It is shown how between the orientation of the fibers 14th and the circumferential direction 18th an angle 48 may be present. For example, the angle is 48 about -5 ° to 5 ° to about -10 ° to 10 °. Corresponding to the above embodiments with respect to FIG 5 For example, a winding of the fibers turns out to be 14th as advantageous if this is not exactly along the circumferential direction 18th run, but relative to this at an angle 48 inclined. The same applies to the following explanations with regard to the further embodiments in which the orientation of the fibers 14th along the circumferential direction 18th are shown to simplify the explanations.

In the variant according to the 6A until 6C can be in the shift 36 high rigidity can be achieved, in the middle a lower stiffness and in the layer 40 an even lower rigidity.

In the embodiments according to 8A until 8C are the fibers 14th in the shift 36 radially on the inside by approximately 45 ° with respect to the axis 16 inclined. In the shift 38 in the middle are the fibers 14th at a smaller angle with respect to the axis 16 inclined, for example about 25 °. In the shift 40 are the fibers 14th aligned approximately in the axial direction.

In the variant according to the 9A until 9C it is the same for the orientation in the layers 36 and 38 equally. In the shift 40 The fibers are radially outside 14th roughly along the circumferential direction 18th aligned.

In the variant according to the group of figures 8, the piston ring 10 one of the inner peripheral surface 32 to the outer peripheral surface 34 decreasing stiffness. In the variant according to the group of figures 9, the piston ring 10 one in the middle (layer 38 ) opposite the layer 36 lower rigidity. In the shift 40 The stiffness is highest on the radial outside.

The variants according to the groups of figures 10 and 11 are with regard to the orientation of the fibers 14th designed in exactly the opposite way to the variants according to the groups of figures 8 and 9, respectively.

In the variant according to 10A are the fibers 14th in the shift 36 approximately axially aligned in the slice 38 relative to the axis 16 inclined (e.g. about 25 °) and in layer 40 by about 45 ° with respect to the axis 16 inclined.

The variant according to the 11A until 11C differs from the latter variant in that in the layer 36 the fibers 14th an orientation approximately in the circumferential direction 18th exhibit.

In the variant according to the group of figures 10, the piston ring 10 one of the inner peripheral surface 32 to the outer peripheral surface 34 increasing stiffness. In the variant according to the group of figures 11, the piston ring 10 one in the middle (layer 38 ) opposite the layer 40 lower rigidity. In the shift 36 The stiffness is highest radially on the inside.

While the fibers explained so far with reference to the groups of figures 4, 6 and 8 to 11 14th have only one orientation within each layer and are produced, for example, by winding, the variants of the groups of figures 12 and 13 now explained have fibers within each layer 14th with two different orientations. Here are the fibers 14th for example made by a braid or a fabric.

The variant of the 12A until 12C points in the shift 36 a fabric or braid 50 with fibers 14th whose orientations run approximately in the axial direction and approximately in the circumferential direction. In the shift 38 are the respective orientations relative to the axis 16 or the circumferential direction 18th inclined, for example by about 25 °. In the shift 40 are the respective orientations at approximately 45 ° with respect to the axis 16 and the circumferential direction 18th inclined.

The piston ring having such fiber orientations 10 is radially inward along the inner peripheral surface 32 particularly stiff, less stiff in the middle and radially on the outside along the outer circumferential surface 38 less stiff.

The opposite is true for the piston ring 10 according to the 13A until 13C . Here are the respective orientations of the fibers 14th within the layers 36 until 40 compared to the variant according to 12A until 12C radially inside and radially outside exactly opposite. The piston ring made in this way 10 thereby points on the outer circumferential surface 34 has high rigidity, lower rigidity in the middle, and on the inner peripheral surface 32 an even lower rigidity.

The groups of figures show by way of example 14th and 15 variants of the piston ring 10 where, as explained, only two layers 36 and 40 available. Another difference to the variants described so far is that in one layer 36 or 40 Fibers 14th with two different orientations are present, being in the other layer 40 or. 38 Fibers 14th are available with only one orientation.

To produce these piston rings, for example, a fiber braid or fabric can be combined with a fiber winding.

The embodiment according to 14A and 14B has fibers aligned radially on the inside in two orientations (essentially axially and in the circumferential direction) 14th on, causing the piston ring 10 on the inner peripheral surface 32 has a high rigidity. In the shift 40 The fibers are radially outside 14th approximately at an angle of 45 ° with respect to the axis 16 aligned so that the piston ring 10 in the outer peripheral surface 34 is less stiff.

In the embodiment according to 15A and 15B are the fibers 14th in the shift 36 approximately axially aligned in the slice 40 are two kinds of orientations with inclination with respect to the axis 16 of approximately 45 ° each.

In this way, for example, a piston ring 10 be produced, which is stiffer radially on the outside than radially on the inside.

In all variants of the piston ring according to the invention described here 10 can the ring joint 22nd be designed, for example, in one of the ways described below.

For example, a straight ring joint 22nd according to 16 intended.

For example, there are oblique ring joints 22nd in right-hand version or in left-hand version according to the 17th or. 18th intended.

For example, there is an annular joint that is overlapped in the axial direction 22nd according to 19th intended.

For example, a gas-tight ring joint 22nd with overlap in the axial and in the radial direction according to 20th intended.

For example, a ring joint 22nd as with a compression ring with tangential impact according to 21 intended.

For example, a ring joint as in the case of a compression ring with a gas-tight, hooked joint is shown in FIG 22nd provided with an overlap in the circumferential direction 18th , the radial direction 20th and an additional hook is provided.

For example, a ring joint 22nd as in the case of a gas-tight joint with a rectangular recess in accordance with 23 intended. For example, an overlap is provided in the axial direction and in the radial direction.

For example, the butt ends are on the front sides 26th according to the 24 until 26th free worked.

For example, a ring joint 22nd as with a compression ring with a hooked joint according to 27 provided, in which there is an overlap in the axial direction.

the 28 until 30th schematically show sections of the outer circumferential surface 34 adjacent to a piston seat 52 , for example in the form of a piston liner 54 . In the piston liner 54 can be a piston, not shown in the drawing, the piston ring 10 surrounds, are axially reciprocated.

The piston ring 10 shows in the variants according to 28 until 30th along the outer peripheral surface 34 preferably grooves throughout 56 on. The grooves 56 can have different cross-sections, for example rectangular, triangular or (not shown) rounded cross-sections.

About the grooves 56 can between the piston ring 10 and the piston liner 54 a labyrinth seal can be provided.

The piston ring 10 can, as with the variant according to 30th shown, at least one oil control groove 58 exhibit.

The grooves 56 and 58 can on the piston ring 10 be formed for example in the course of a post-processing by grinding or milling.

31 shows a schematic representation of a variant of the piston ring 10 , at the one at the ring joint 22nd on the front sides 26th grooves in each case 60 are formed. There are the grooves 60 on the opposite end faces 26th arranged so that at the ring joint 22nd a labyrinth seal to reduce blow-by can be achieved. The grooves 60 can for example have a right-shaped, a triangular or a (not shown) round cross-section.

The grooves too 60 can, for example, by means of post-processing by grinding or milling the piston ring 10 are manufactured.

the 32 shows in a schematic partial representation one with the reference number 62 documented advantageous embodiment of a free piston device according to the invention. The free piston device 62 includes a free piston engine 64 , which is an advantageous embodiment of a piston machine according to the invention 66 acts. The free piston engine 64 includes, for example, the piston mount 52 , designed as a piston liner 54 .

In the piston seat 62 is a combustion piston 68 added, on which at least one piston ring according to the invention 10 is arranged.

The combustion piston 68 is along an axis 70 that with the axis 16 coincides with the piston mount 52 reciprocating. The combustion piston 68 limited by a piston area 72 a combustion chamber 74 . In the combustion chamber 74 a fuel-air mixture can be ignited with expansion, causing the combustion piston 68 is moved.

It is advantageous to use a C / C-SiC piston ring as a compression-compression ring with a relatively small ring joint 22nd that a sufficiently good seal of the combustion chamber of a piston engine can be achieved. In particular, a second compression ring can preferably be saved. An oil control ring, possibly also made of C / C-SiC, can be designed in such a way that only the smallest possible amount of oil is still present on the piston receptacle, due to the lubricating properties of the free carbon phase of the piston ring. As a result, it can be provided that the frequent secondary function of the usually second compression ring, fine adjustments of the oil quantity, is no longer necessary.

With such a configuration, there is the advantage that the piston can be made shorter and is lighter. The free inertia forces can be reduced, and the engine can be built with less space requirement. Such an engine can have a lower weight, and the engine's center of gravity can be lowered (for example in a motor vehicle). This can include advantages, for example, in the crash behavior of a vehicle. Overall, the entire vehicle structure can be designed to be lighter, as a result of which a secondary saving in fuel is possible.

The piston ring according to the invention can be designed in one part or in several parts. A multi-part design is advantageous, for example, in an application when the widening of the piston ring during assembly also takes place with the relative orientation of the fibers causing the “lowest” rigidity 14th could not be sufficiently guaranteed. For example, in this case of a multi-part piston ring, it can be provided that the deformation section 28 the expansion opening 24 not with respect to the axis 16 diametrically opposite, but depending on the extent of the individual segments of the piston ring along the circumferential direction 18th has an angular distance of less than 180 °. This is expressly reserved for the present invention, in particular also in the case of a one-piece piston ring.

For a more detailed explanation of the manufacturing process for the piston ring according to the invention, reference is first made to 33 referenced. This shows you around an axis 76 rotatable core 78 and a winding device 80 , with the fibers 14th can be provided as an endless material, for example by means of a roving. An angle at which the fiber 14th on the rotating core 78 can be applied can be varied. By moving the winding device 80 parallel to the axis 76 can fibers 14th to form a body 82 in the form of a vertical circular cylinder with the axis 16 to be ordered. In the circumferential direction of the axis 16 can have different orientations of the fibers at least over a predefined or predefinable angular range 14th , along the radial direction 20th can be achieved by varying the angle at which it is wound.

When winding, for example, a first, inner layer is created 36 with a given orientation of the fibers 14th educated. Then at least one second layer can be placed radially on the outside with a different orientation of the fibers 14th are formed.

Matrix material for forming the matrix 12th for the fibers 14th can be provided by the body 12th is soaked after the winding process. Alternatively, pre-soaked fibers can be provided.

After the matrix has hardened 12th can the body 32 axially divided into individual rings. If necessary, ring joints can 22nd with the expansion openings 24 are formed.

It is conceivable that the body 82 after the matrix has hardened 12th or the individual rings resulting from segmentation or the piston rings with an existing ring joint 22nd be reworked. The outer circumferential surface, in particular, can be used during post-processing 34 be sanded. Alternatively or in addition, for example, the grooves 56 , 58 or 60 be formed.

34 shows one of the 33 similar device in which a further winding device 84 is used. This gives the opportunity to get to the core 78 Apply a braid by using each winding device 80 , 84 Fibers 14th with different orientations towards the core 78 to be wrapped. At least one of the fiber orientations can then be changed in a further layer.

35 shows schematically a core 86 , the one axis 88 having. Multiple lanes 90 a fiber material 92 can be superimposed on the core 86 be applied that layers with different orientations or even several different orientations of the fibers 14th develop.

At the railways 90 it can be, for example, a fabric made of fibers, as shown in the WO 2018/234244 A1 are described.

If the production is different, there are webs 90 made of fiber fleece 94 for use. the 36 until 38 show examples of related nonwovens 94 .

36 shows a fiber fleece, designed as a parallel fleece 94 with longitudinally oriented fibers. The fiber directions can differ within the fleece. However, the nonwoven fabric 94 one with an arrow 96 symbolized preferred direction.

37 shows a nonwoven fabric 94 , which is a parallel fleece with transverse orientation. Arrows 98 and 99 indicate preferred directions of the fibers 14th within the fiber fleece 94 .

38 shows a nonwoven fabric 94 , designed as a cross-ply fleece with longitudinal and transverse orientation. The fibers 14th can, for example, have preferred directions indicated by the arrows 96 , 98 and 99 Marked are.

Depending on the orientation of the lanes 90 In particular, different layers of fibers can be placed one on top of the other 14th with different orientations along the thickness direction 20th at the piston ring 10 be achieved.

It goes without saying that when winding, braiding, use of woven fiber material 92 and / or woven fiber fleece 94 more than one layer of fibers at a time 14th can be used with an identical orientation for production, in which case several layers together form one of the layers.

List of reference symbols

10

Piston ring

12th

matrix

14th

fiber

16

axis

18th

Circumferential direction

20th

radial direction / thickness direction

22nd

Ring joint

24

Expansion opening

26th

Front side

28

Deformation section

30th

Angular range

32

Inner peripheral surface

34

Outer peripheral surface

36, 38, 40

layer

42

Arrow axial direction

44

Arrow circumferential direction

46, 48

angle

50

Fabric / braid

52

Piston seat

54

Piston liner

56

Groove

58

Oil control groove

60

Groove

62

Free piston device

64

Free piston engine

66

Piston engine

68

Combustion piston

70

axis

72

Piston area

74

Combustion chamber

76

axis

78

core

80

Winding device

82

body

84

Winding device

86

core

88

axis

90

rail

92

Fiber material

94

Non-woven fabric

96, 98, 99

Arrows preferred direction

QUOTES INCLUDED IN THE DESCRIPTION

This list of the documents listed by the applicant was 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.

Patent literature cited

• WO 2018/234244 A1 [0004, 0005, 0042, 0075, 0077, 0152]

Claims (20)

Piston ring made of a fiber composite material with a matrix (12) and fibers (14) embedded therein, which piston ring (10) defines an axis (16) and comprises an inner circumferential surface (32), an outer circumferential surface (34) radially spaced therefrom and an expansion opening (24), wherein the piston ring (10) with enlargement of the expansion opening (24) in the circumferential direction ( 18) of the axis (16) is expandable, wherein the fibers (14) on the piston ring (10) have different orientations in sections, wherein the fibers (14), at least at a deformation section (28) arranged at a distance from the expansion opening (24), have different orientations along a thickness direction (20) of the piston ring (20) radially from the inner circumferential surface (32) to the outer circumferential surface (34) . Piston ring after Claim 1 , characterized in that the deformation section (28) lies opposite the expansion opening (24) with respect to the axis (16). Piston ring after Claim 1 or 2 , characterized in that an angle (46, 48) of the orientation of the fibers (14) with respect to the axial direction adjacent to the inner circumferential surface (32) is greater than adjacent to the outer circumferential surface (34), is smaller than on the outer circumferential surface (34), or is the same size or essentially the same size as on the outer circumferential surface (34). Piston ring according to one of the preceding claims, characterized in that an orientation of the fibers (14) adjacent to the inner circumferential surface (32) and / or adjacent to the outer circumferential surface (34) includes an angle (46, 48) with the axial direction that is one of the The following is: approximately 10 ° to 80 °, preferably approximately 20 ° to 70 °, preferably approximately 30 ° to 60 °; - less than about 10 ° to about 0 °; - more than about 80 ° to about 90 °. Piston ring according to one of the preceding claims, characterized in that the rigidity of the piston ring (10), at least at the deformation section (28), adjacent to the outer circumferential surface (34) is higher than adjacent to the inner circumferential surface (32), or that the rigidity is adjacent to the inner peripheral surface (32) is higher than adjacent to the outer peripheral surface (34). Piston ring according to one of the preceding claims, characterized in that the rigidity of the piston ring (10), at least at the deformation section (28), adjacent to the inner circumferential surface (32) is the same or essentially the same as adjacent to the outer circumferential surface (34) or different therefrom , and / or each larger or each smaller than in a radially intermediate region of the piston ring (10). Piston ring according to one of the preceding claims, characterized in that the orientations of the fibers (14), along the thickness direction (20), differ from one another in the entire circumferential direction (18), in particular to form different stiffnesses of the piston ring (10). Piston ring according to one of the preceding claims, characterized in that the piston ring (10) has two or more layers (36, 38, 40) adjacent or merging into one another along the thickness direction (20), the orientations of the fibers (14) within a respective one Layer (36, 38, 40) are identical or substantially identical, preferably along the entire circumferential direction (18). Piston ring after Claim 8 , characterized in that within a respective layer (36, 38, 40) there is only one orientation of the fibers (14) or two or more orientations, in particular two orientations in the case of a fiber fabric (50) or fiber braid (50). Piston ring after Claim 8 or 9 , characterized in that the respective orientation of the fibers (14) is a preferred orientation of fibers or that the respective orientation for all fibers (14) within a layer (36, 38, 40) is identical. Piston ring according to one of the Claims 1 until 7th , characterized in that the orientations of the fibers (14) vary continuously along the thickness direction (20). Piston ring according to one of the preceding claims, characterized in that the fibers (14) are each aligned in a lateral surface around the axis (16). Piston ring according to one of the preceding claims, characterized in that at least one of the following applies: - the fibers (14) are wound fibers (14); - The fibers (14) form a fiber braid (50) or a fiber fabric (50); - The fibers (14) are arranged in layers (36, 38, 40) lying radially one above the other with a respective orientation. Piston ring according to one of the preceding claims, characterized in that the matrix (12) comprises carbide and a free carbon phase and / or that the fiber composite material is C / C-SiC. Piston ring according to one of the preceding claims, characterized in that the piston ring (10) on the outer circumferential surface (34) has at least one groove (56, 60) running at least partially in the circumferential direction (18) to form a labyrinth seal with a piston receptacle (52). Piston ring according to one of the preceding claims, characterized in that at least one recess for forming a labyrinth seal with a corresponding end face (26) of the piston ring (10) is provided on at least one end face (26) of the piston ring (10) delimiting the expansion opening (24) . Piston machine, comprising at least one piston which can be reciprocated in a piston receptacle (52) and on which at least one piston ring (10) according to one of the preceding claims is arranged, wherein the piston machine is in particular a motor or a compressor or comprises one. Method for producing a piston ring according to one of the Claims 1 until 16 The method comprising: Arranging fibers to form a body in the form of a particularly vertical circular cylinder defining an axis in such a way that at least two layers of fibers are arranged radially with respect to the axis and the fibers are arranged in the circumferential direction of the axis over a predefined or predefinable angular range have different orientations along a radial direction; - Providing and curing a matrix for the fibers. Procedure according to Claim 18 characterized in that the fibers are arranged via at least one of the following: winding the fibers onto a core, the fiber orientation being changed via an angle at which the fibers are wound onto the core; Braiding the fibers on a core, the fiber orientation being changed over an angle at which the fibers are braided onto the core; Providing two or more layers of fiber fabric which are placed on the core, with superimposed layers being placed on the core at different angles; - Provision of two or more layers of fiber felt which have a respective preferred orientation of the fibers contained therein; - 3D printing of matrix material containing fibers; - Arrangement and targeted positioning of individual fibers on a core using tailored fiber placement (TFP); - Provision and positioning of fiber strands by means of a pultrusion device; - Provision by means of an injection molding process, with fibers being embedded in matrix material. Procedure according to Claim 18 or 19th , characterized in that the method comprises at least one of the following steps: the fibers are provided pre-impregnated with matrix material in the step of arranging, or the fibers are infiltrated with a matrix material after arranging; the body is divided axially into a plurality of rings after the matrix material has hardened; - a widening opening is formed on the body after curing or when arranging the fibers; The body or the piston ring are reworked, in particular reworking takes place by grinding and / or making at least one groove on the outer circumferential surface and / or making at least one recess on an end face delimiting the expansion opening.

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