Sliding element for a sliding bearing or segment for a sliding element and method for manufacturing a sliding element

Abstract

Sliding element (1) for a sliding bearing or segment for a made of a material comprising a thermoplastic with a chemically equivalent fiber reinforcement, wherein the fiber (3) of the fiber reinforcement has a chemically identical structure to an embedding matrix (2) of the thermoplastic, wherein the physical properties of the fiber (3) differ from those of the embedding matrix (2) of the thermoplastic, wherein a difference in the melting temperatures of the embedding matrix (2) and the chemically equivalent fiber (3) is increased by using thermoplastics with longer macromolecules and a higher molecular weight for the fiber (3).

Description

Exemplary embodiments relate to a sliding element for a sliding bearing or a segment for a sliding element and to a method for producing the same.Plain bearings are used in many fields of technology in which individual components, assemblies or components move with respect to other components, components or systems. Plain bearings can thus enable a corresponding relative movement of the relevant components with respect to one another. Thus, for example, with the aid of a slide bearing, a rotation or else an oscillation about, for example, an axis, a linear movement along, for example, a movement direction and / or a pivoting of the relevant components with respect to one another can be made possible. With regard to these movements or these movements, the slide bearing enables a comparatively low-friction movement thereof.With regard to other types of movement and / or directions of movement, on the other hand, the slide bearing can have a guiding effect. Thus, for example, during a movement with respect to which it does not allow any relative movement of the components coupled to it, the slide bearing can transmit a force or a torque from one component to the other. As a result, for example, a force or a moment can be transferred across the slide bearing and thus the one component can be guided with respect to the other. An example of this is joint bearings, for example radial joint bearings and joint heads.A sliding shell is often introduced between an inner ring and an outer ring of a sliding bearing, which may be manufactured from steel, for example, in order to enable low-friction sliding of the inner ring and the outer ring with respect to one another. The sliding shell can be introduced, for example, into an outer ring of a sliding bearing-for example by an injection molding method. Sliding shells often consist of a plastic material. Sliding shells made of fiber-reinforced plastic are also known. In this case, fibers are introduced into an embedding plastic matrix.A fiber can be, for example, an element or a component which has a substantially greater extension in one direction, for example a main extension direction, than in a second and in a third direction, wherein the three directions span a coordinate system between them. The extent of the fiber may be greater in the first direction by at least a factor of 10, 100, 1,000, 10,000 or 100,000 than in the other two directions. The fiber can have any cross section perpendicular to a main extension direction, i.e. the first direction, for example circle, rectangles, quadrilateral, oval or the like. The fiber can have a plurality of fiber sections along its main extension direction. A fiber portion may have, for example, any length equal to or less than the fiber length. Individual fiber sections of the fiber can optionally be arranged parallel to one another, cross one another or be shaped into a mesh. The fiber may be arranged as a single fiber or in a fiber bundle.For example, plain bearings may be made of a material comprising a thermoplastic with a carbon fiber reinforcement and / or a glass fiber reinforcement.Sliding bushes are also known for mounting axles or shafts. Slide bushes are suitable above all for bearings in which high loads have to be absorbed and rotational speeds of an axle or shaft mounted in the slide bush are relatively low. Sliding bushes are often made of a plastic material. Furthermore, sliding bushes made of fiber-reinforced plastic are known. In this case, fibers are introduced into an embedding plastic matrix. For example, sliding bushes may be made of a material comprising a thermoplastic with a carbon fibre reinforcement and / or a glass fibre reinforcement.Sliding elements can be provided in one piece or consist of several segments. Sliding elements, such as sliding bearings or sliding bushes made of a carbon fiber- or glass fiber-reinforced plastic, however, have a number of disadvantages.Glass fibers as well as carbon fibers are sharp-edged, for which reason sliding elements made of a carbon fiber- or glass fiber-reinforced plastic contain sharp-edged fiber ends. Particularly in the case of short glass fibers as well as carbon fibers in a fiber-reinforced plastic, a body sliding on the sliding element, e.g. an inner ring in a sliding bearing or a shaft supported in a sliding bushing, can be damaged and sometimes worn out to a great extent. Sliding elements formed from an endless fiber-reinforced plastic, e.g. a plastic reinforced with a textile fabric formed from fibers, can also have sharp-edged fiber ends. The sharp-edged fiber ends are formed during use, for example, due to fiber breakage under high loads of the sliding element. The service life of a sliding element, such as a sliding bearing or a sliding bushing, can thereby be greatly reduced.The elongation at break of glass fibers and much stronger of carbon fibers compared to a surrounding plastic matrix is also reduced. The elongation at break is a specific material characteristic value which characterizes the deformability of a material in the plastic range (also called ductility) up to fracture. Usually, glass fibers have an elongation at break of less than 5%. In the case of a correct attachment of the surface of the glass fibers to the surface of the surrounding plastic matrix, the elongation at break of the composite material of fiber and surrounding plastic matrix is thus reduced. The impact strength, i.e., ability to absorb impact energy and impact energy without breaking, and the energy absorbing property of the composite material is thereby greatly lowered.Glass fibers are usually provided in the form of E-glass fibers (E= El). However, E-glass fibers have only very limited chemical resistance both in the basic and in the acidic range-in particular in the basic range. The strength of the fiber as well as of the composite of fiber and surrounding plastic matrix is thus reduced in the presence of acidic or basic substance. Furthermore, chemicals or water can pass through very fine capillaries between surfaces of the glass fibers and surfaces of the surrounding plastic matrix into the interior of the composite of fiber and surrounding plastic matrix, and thereby reduce the strength of the composite.A sliding element made of carbon fiber-reinforced plastic also has the disadvantage that carbon fibers or abrasion particles of the carbon fibers promote corrosion of the body due to high electrochemical voltage differences between the fibers and a body made of metal, e.g. steel, which slides on the sliding element.A good connection of the fiber surface to the surrounding plastic matrix is essential for the transmission of forces between fiber and surrounding matrix. Both of the aforementioned types of fibers have the disadvantage inherent that they require a special surface treatment for a good attachment of their fiber surface to the surrounding plastic matrix, which must be specially adapted to the respective plastic of the surrounding matrix. In the production of a sliding element, therefore, time-consuming and thus also cost-intensive steps are required for specific surface treatment of the fibers.Furthermore, sliding elements which are made of a glass fiber-reinforced or carbon fiber-reinforced plastic can be separated into their individual components only with great effort after use. Sliding elements are usually disposed of on the one hand by being placed in a landfill or thermal utilization, or on the other hand recycled to granules by grinding and subsequent extrusion. However, as a result of the grinding, the fiber length of the brittle glass or carbon fibers decreases significantly. A composite material formed from recycled material has lower strength and reduced impact strength due to the significantly reduced fiber length.Carbon fibers also have a relatively high price, so that the production costs for a sliding element made of a carbon fiber-reinforced plastic are relatively high.This invention relates to a water-lubricated support bearing, especially for ship shafts, having an elastic support element arranged in a bearing bushing.A plain bearing teaches a bearing which has a long life and can be used in a number of applications, for example in applications with high vibrations.Method and Apparatus for Making Slide or Support Bearings are taught.teaches a slide bearing or a slide bushing.Wilhelm Hermann Muller "Material Data Sheet PTFE Nature" describes the properties of PTFE Nature.There is therefore a need to provide a sliding element for a sliding bearing and a method for producing the same, which at least avoid the disadvantages mentioned above.Embodiments enable this by providing a sliding element for a sliding bearing or a segment for a sliding element of a material comprising a thermoplastic with a chemically equivalent fibre reinforcement. As a result, a sliding element with improved properties can be provided.According to some embodiments, the thermoplastic comprises polyamide, partially aromaticized polyamide, polyetheretherketone, polyethersulfone, polyetherimide, polyaryletherketone, polymethylmethacrylate, polyvinyl chloride, polyurethane, acrylonitrile butadiene styrene, polylactate, polycarbonate, polyethylene terephthalate, polyethylene, polypropylene, polystyrene, polyphthalamide, polyacetal, polyphenylene sulfide, polyimide, polyamideimide, polysulfone, polyphenylene ether, polyarylamide, polybenzimidazole, polytetrafluoroethylene, polyvinylidene fluoride, or liquid crystalline polymers.In some embodiments, the sliding element comprises a sliding shell or a sliding bushing.Embodiments provide a slide bearing with at least one slide element or a segment for a slide element according to the embodiments. A slide bearing according to the exemplary embodiments has improved properties compared to known slide bearings.Embodiments further provide a method for producing a sliding element for a sliding bearing or a segment for a sliding element. The method thereby comprises providing a material comprising a thermoplastic with a chemically equivalent fibrous reinforcement, and forming the sliding element or the segment for a sliding element from the material. By the proposed method, a sliding element with improved properties can be provided.According to some embodiments, forming the sliding element or the segment for a sliding element comprises injection molding the sliding element or the segment for a sliding element.According to some embodiments, forming the sliding element or the segment for a sliding element comprises forming a tubular body by means of extrusion or by means of a winding process and clampingly processing the tubular body.In some embodiments, the material is provided in the form of a fiberized granulate or in the form of a fiber bundle or fabric of fibers impregnated with the thermoplastic.According to some embodiments, the forming of the sliding element or the segment for a sliding element comprises pressing one or more fabric layers of fibers impregnated with the thermoplastic under application of pressure and / or temperature.Preferred exemplary embodiments of the present invention are explained in more detail below with reference to the appended figures. The following are shown: FIG. 1 shows a schematic side view of a segment of an exemplary embodiment of a sliding element; and FIG. 2 shows a flow diagram of an exemplary embodiment of a method for producing a sliding element.FIG. 1 shows a side view of a segment of a sliding element 1. the sliding element 1 can be, for example, a sliding shell introduced into an inner or outer ring of a sliding bearing or a sliding bushing. The sliding element 1 is formed from a material comprising an embedding matrix 2 and a reinforcement in the form of a fiber 3. The embedding matrix 2 comprises a thermoplastic. The fiber 3 is chemically equivalent to the thermoplastic. Chemically equivalent means that the fiber 3 and the thermoplastic embedding matrix 2 have a chemically equivalent structure. In particular, the chemical properties of the fiber 3 and of the thermoplastic of the embedding matrix 2 are the same. The fiber 3 can be, for example, chemically identical to the thermoplastic of the embedding matrix 2, i.e. have a chemically identical structure to the thermoplastic of the embedding matrix 2. The physical state or physical properties of the fiber 3 may be different from those of the thermoplastic of the embedding matrix 2.The thermoplastic of the embedding matrix 2 may include, for example, polyamide, partially aromaticized polyamide, polyetheretherketone, polyethersulfone, polyetherimide, polyaryletherketone, polymethylmethacrylate, polyvinyl chloride, polyurethane, acrylonitrile-butadiene-styrene, polylactate, polycarbonate, polyethylene terephthalate, polyethylene, polypropylene, polystyrene, polyphthalamide, polyacetal, polyphenylene sulfide, polyimide, polyamideimide, polysulfone, polyphenylene ether, polyarylamide, polybenzimidazole, polytetrafluoroethylene, polyvinylidene fluoride, or liquid crystalline polymers. The fiber 3 can have a chemically identical structure to the thermoplastic of the embedding matrix 2, i.e. can comprise the same thermoplastic.Optionally, at least one lubricant or a lubricant additive can also be mixed into the material of the embedding matrix 2. Under certain circumstances, a plurality of lubricants or lubricant additives may also be mixed in. The lubricant can be a PTFE powder, graphite and / or MoS2(molybdenum disulfide) and / or inorganic nanoparticles. Accordingly, one or more lubricants can also be mixed with the fiber 3.A sliding bearing can have, for example, an inner ring and an outer ring made of steel, wherein a sliding element 1 in the form of a sliding shell is introduced into the outer ring made of steel. The sliding element 1 in the form of the sliding shell can form a sliding surface for a sliding surface of the inner ring, so that the inner ring and the outer ring can be moved relative to one another in a mediated manner via the at least one sliding surface of the inner ring and the sliding shell. A slide bearing can furthermore comprise, for example, a slide element 1 in the form of a slide bushing, with which a shaft or axle introduced into the slide bushing can be mounted so as to rotate with respect thereto.The sliding element 1 can be formed in one piece or from several segments.FIG. 2 shows a flow diagram of a method 10 for producing the sliding element 1. the method 10 comprises providing 11 a material comprising a thermoplastic with a chemically equivalent fibre reinforcement. Furthermore, the method includes forming 12 the sliding element 1 from the material.Alternatively, individual segments for a sliding element 1 can also be produced with the method 10 instead of a one-piece sliding element 1. A plurality of segments can be connected to one another to form a sliding element 1.The forming of the sliding element 1 can comprise, for example, an injection molding of the sliding element 1. The material can be provided, for example, in the form of granules interspersed with fibers 3. The fibers 3 have a high orientation of their macromolecules, which is produced in the production process of the fibers by means of stretching. The fibers are deformed in a defined manner, for example, fibers made of a plastic are placed under tensile stress, so that disordered polymers and partially crystalline regions align approximately parallel to the direction of tension. As a result, contact areas between the macromolecules of the fiber become larger and distances between the macromolecules become smaller. Secondary bonds between the macromolecules of the fiber are correspondingly stronger, for which reason the fiber has a higher melting temperature than the surrounding matrix material provided in the form of the granulate. The difference in melting temperatures of embedding matrix 2 and chemically equivalent fiber 3 can be further increased, for example, by using thermoplastics with longer macromolecules and higher molecular weight for fiber 3. Due to the higher melting point of the fibers, the granulate for the embedding matrix can therefore be heated and melted, for example, in an injection molding process, while the chemically equivalent fibers are retained, i.e. do not melt. The sliding element 1 can thus be easily formed in a tool, for example by injection molding.Also, forming the sliding member 1 may include, for example, manufacturing a tubular body. For example, the tubular body can be produced by extrusion of a granulate interspersed with fibres 3. Alternatively, the tubular body can be produced in a winding process in which fiber bundles of fibers 3, which are also known as rovings, or a woven fabric of fibers 3, are impregnated with a chemically equivalent matrix powder and are then wound onto a core under exposure to temperature. The sliding member 1 can be obtained by subsequent clamping processing of the tubular body.Also, forming the sliding element 1 may comprise, for example, hot pressing fabric layers of fibres 3 impregnated with a matrix 2. In general, the forming of the sliding element can comprise pressing one or more fabric layers under application of pressure and / or temperature.When the sliding element 1 formed, for example, in an injection molding process is cooled, the surface of the fiber 3 chemically equivalent to the thermoplastic can additionally act nucleatingly, in particular strongly nucleatingly, on the still liquid melt of the embedding matrix 2, since the fibers 3 and the thermoplastic are chemically equivalent to the embedding matrix 2-in particular can have a chemically identical structure. The fiber 3 chemically equivalent to the thermoplastic of the embedding matrix 2 thus promotes the release of germ cells for a crystallization of the cooling melt of the embedding matrix 2. the formation of transcrystalline regions around the fibers 3 can thereby be achieved, in particular so-called shish kebab structures can be achieved. A shish-kebab structure is a dumbbell-shaped structure, wherein the inner part (core) consists of largely elongated chains arranged in parallel, while the dumbbells are constructed from folded lamellae. The mechanical properties as well as the tribological properties of such a sliding element can be improved compared to conventional sliding elements. Due to the nucleating effect of the surface of the fiber 3, a rate of crystallization of the melt of the embedding matrix 2 surrounding the fiber 3 can also be increased. Thus, for example, sliding elements 1 produced in an injection molding process can be ejected more quickly, i.e. can be released more quickly from an injection mold. Cycle times of an injection molding tool and thus also the production costs of a sliding element 1 according to the exemplary embodiments can thus be reduced.By avoiding expensive carbon fibers in the sliding member 1 according to the embodiments, the manufacturing cost of the sliding member 1 can be further reduced compared to conventional sliding members made of a carbon fiber reinforced plastic.Fibers made of a plastic have an increased elongation at break compared to glass or carbon fibers. By using fibers 3 chemically equivalent to the thermoplastic of the embedding matrix 2, the impact resistance and the energy absorption capacity of a sliding element 1 according to the exemplary embodiments can thus be increased compared to sliding elements made of carbon- or glass-fiber-reinforced plastics. The risk of breakage of a sliding element 1 according to the exemplary embodiments, for example in the event of an impact load, can thus be reduced compared to conventional sliding elements made of carbon- or glass-fibre-reinforced plastics.Due to the chemical equivalence of the fibers 3 and the thermoplastic of the embedding matrix 2, a good bonding of the fiber surfaces to the surrounding surfaces of the embedding matrix 2 is provided. A special surface treatment of the fibers 3 to achieve a good bonding can therefore be avoided in comparison with a carbon- or glass-fiber-reinforced plastic. Pulling out fibers 3 from the embedding matrix 2 as a result of the action of large external forces or loads is made more difficult, and therefore a composite strength of the composite of fiber 3 and embedding matrix 2 is increased overall.The good bonding of the fiber surfaces to the surrounding surfaces of the embedding matrix 2, which is realized on account of the chemical equivalence of the fibers 3 and of the thermoplastic of the embedding matrix 2, additionally effectively prevents the formation of capillaries between surfaces of the fiber 3 and the embedding matrix 2.Fibers made of a plastic are not sharp-edged per se in contrast to glass fibers, so that a surface of a body sliding on a sliding element 1 is not damaged or worn. A sliding element 1 according to the exemplary embodiments can thus reduce the wear of bodies sliding thereon compared to conventional sliding elements made of a carbon fiber or glass fiber-reinforced plastic.In summary, sliding elements according to the exemplary embodiments can thus extend the service life of the sliding bearing when used in sliding bearings. Furthermore, maintenance intervals for the slide bearing can be increased due to the advantageous properties of the slide elements according to the exemplary embodiments. Thus, the cost and effort over the cycle of use of a sliding member can be reduced.In addition, a sliding element 1 according to the embodiments can be recycled better, since the fiber 3 and the thermoplastic are chemically equivalent to the embedding matrix 2. In particular, the fiber 3 and the thermoplastic of the embedding matrix 2 may have a chemically identical structure, i.e. comprise a same thermoplastic. When recycling a sliding element according to the exemplary embodiments, the fibers 3 thus do not have to be separated from the embedding matrix 2, but can be ground to a granulate, for example. The granulate obtained in this way can be used, for example, in a further process for producing technically high-quality parts, in particular for producing sliding elements.List of reference characters1 Sliding element 2 embedding matrix 3 fiber 10 method 11 providing a material comprising a thermoplastic with a chemically identical fiber reinforcement 12 forming the sliding element from the material

Claims

Sliding element (1) for a sliding bearing or segment for a one made of a material comprising a thermoplastic with a chemically equivalent fibre reinforcement, wherein the fibre (3) of the fibre reinforcement has a chemically identical structure as an embedding matrix (2) of the thermoplastic of the latter, wherein the physical properties of the fibre (3) are different from those of the embedding matrix (2) of the thermoplastic of the latter, wherein a difference in the melting temperatures of embedding matrix (2) and chemically equivalent fibre (3) is increased by using thermoplastics with longer macromolecules and higher molecular weight for the fibre (3).The sliding element (1) for a sliding bearing or segment for one of claim 1, wherein the thermoplastic comprises polyamide, partially aromaticized polyamide, polyetheretherketone, polyethersulfone, polyetherimide, polyaryletherketone, polymethylmethacrylate, polyvinyl chloride, polyurethane, acrylonitrile-butadiene-styrene, polylactate, polycarbonate, polyethylene terephthalate, polyethylene, polypropylene, polystyrene, polyphthalamide, polyacetal, polyphenylene sulfide, polyimide, polyamideimide, polysulfone, polyphenylene ether, polyarylamide, polybenzimidazole, polytetrafluoroethylene, polyvinylidene fluoride, or liquid crystalline polymers.A sliding element (1) for a sliding bearing or segment for one according to claim 1 or claim 2, wherein the sliding element comprises a sliding shell or a sliding bushing.Sliding bearing having at least one sliding element (1) or a segment for a sliding element according to one of Claims 1 to 3.A method (10) of making a sliding element for a sliding bearing or a segment for one comprising: providing (11) a material comprising a thermoplastic with a chemically equivalent fibre reinforcement, wherein the fibre (3) of the fibre reinforcement has a chemically identical structure to an embedding matrix (2) of the thermoplastic of the lead, wherein the physical properties of the fibre (3) are different from those of the embedding matrix (2) of the thermoplastic, wherein a difference of the melting temperatures of embedding matrix (2) and chemically equivalent fibre (3) is increased by using thermoplastics with longer macromolecules and higher molecular weight for the fibre (3); and forming (12) the segment or segments for a sliding element from the material.The method (10) of claim 5, wherein the forming (12) of the segment or segments comprises injection molding the segment or segments for one.The method (10) according to claim 5, wherein the forming (12) of the segment or segments comprises forming a tubular body by extrusion or by a winding process and clampingly working the tubular body.The method (10) according to any of the preceding claims, wherein the material is provided in the form of a fiber-interspersed granulate or in the form of a fiber bundle or fabric of fibers impregnated with the thermoplastic.The method (10) of claim 5, wherein forming (12) the segment or segments comprises compressing one or more layers of fibers impregnated with the thermoplastic under pressurization and / or temperature.

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