DE102021205408A1 - Process for coating a sliding element - Google Patents

Abstract

The present invention relates to a method for coating a base body (1) of a sliding element (2), in particular an engine component such as a piston (18) or a piston ring (3). achieved in that a hardenable matrix (6) is applied to the base body (1), surface particles (8) being applied to a matrix surface (7) before the matrix (6) hardens and the matrix (6) then being hardened.The The invention also relates to a sliding element (2) coated in this way.

Description

The present invention relates to a method for coating a sliding element having a base body, such as an engine or compressor component, in particular a piston or piston ring. The invention also relates to a sliding element coated in this way.

Sliding elements are those components which slide along another element during operation. In an internal combustion engine, for example, usually at least one piston and a piston ring accommodated in the piston are arranged in a cylinder in a stroke-adjustable manner, each of which forms a sliding element. In this case, an outer surface of the piston or of the piston ring and an inner surface of the associated cylinder face one another. High, sometimes contradictory, demands are placed on such sliding elements.

In the case of pistons and piston rings as sliding elements, it is desirable, for example, for the piston and piston ring to exhibit advantageous running-in behavior. This means that when new, the piston and the piston ring are worn down as quickly as possible in such a way that the piston or the piston ring and the cylinder fit together in such a way that a possible gap between the piston or the piston ring and the cylinder is kept as small as possible in order to to reduce the flow through the gap, for example by exhaust gas and/or lubricant. On the other hand, after running in, the resulting state should last as long as possible, i.e. no further abrasion should take place. At the same time, there should be as little friction and abrasion as possible between the cylinder and the piston or piston ring in order to be able to operate the associated internal combustion engine efficiently.

In order to meet these conflicting requirements, a base body of the sliding element can be coated.

From the DE 10 2016 207 592 A1 it is known to coat a base body of a skirt of a piston with an inner layer and an outer layer applied to the inner layer. The inner layer is first applied to the base body. The inner layer is hardenable and includes organic binders and solid lubricants. The outer layer comprises inorganic binders and is also curable. The outer layer is applied in liquid form to the hardened inner layer and then hardened in air.

From the WO 2005/056276 A1 it is known to apply a powder-based layer to a piston or a piston ring and then to cure it.

The present invention is concerned with the task of specifying improved or at least different embodiments for a method for coating a sliding element and for a sliding element coated in this way, which are characterized in particular by reduced wear and/or reduced friction in the run-in state.

According to the invention, this object is achieved by the subject matter of the independent claims. Advantageous embodiments are the subject matter of the dependent claims.

The present invention is based on the general idea of using a curable matrix for coating a sliding element, such as a piston or a piston ring, with particles being applied to the surface of the curable matrix before the matrix is cured, and the matrix then being cured. As a result, some of the applied particles penetrate the surface of the matrix and are fixed there by curing in such a way that some of them protrude beyond the matrix. When the sliding element runs in, i.e. when it is new, these particles are removed. As a result, cavities are formed on the surface of the matrix, which form collecting spaces for a lubricant between the sliding element and an associated element along which the sliding element slides during operation. In other words, the partial removal of the particles creates cavities on the surface of the matrix, each of which forms a reservoir for the lubricant. In addition to a rapid running-in phase, this results in reduced wear after the running-in phase.

In accordance with the idea of the invention, a base body of the sliding element is first provided for coating the sliding element. In this case, the base body has an outer surface which, during operation, faces an associated element along which the sliding element slides. This outer surface is also referred to below as the outer surface of the base body. The curable matrix is applied to the base body, said particles being applied to a surface of the matrix that faces away from the base body outer surface, hereinafter also referred to as matrix surface, before the matrix cures. These particles are also referred to below as surface particles. The matrix is then cured.

In principle, the sliding element can be any element that is Operation along an associated element, hereinafter also referred to as counter-sliding element slides.

The sliding element can be a component of a motor, for example an internal combustion engine. The sliding element can therefore be a piston or a piston ring. Likewise, the sliding element can be a connecting rod, a bearing shell, a crankshaft or a component of a valve train, such as a camshaft or a valve stem. Likewise, the sliding element can be a component of an electric motor.

The sliding element can also be a component of a compressor, e.g. for an air conditioning system, for a brake system, for a waste heat recovery (WHR) system and the like.

If both the piston and the piston ring are coated in this way, it is also conceivable to coat them together. This can be done, for example, when the piston ring is in the piston.

The matrix can be cured both actively and passively.

During active curing of the matrix, a temperature increase is actively brought about.

When the matrix is passively cured, there is no active increase in temperature. In particular, the matrix can cure at ambient temperature.

In principle, the base body can be made of any materials.

The base body is advantageously made from a metal or a metal alloy, in particular from steel, cast iron or an aluminum alloy.

It is advantageous if the coating is applied to a skirt of the piston in the case of a piston as a sliding element. This means that the shaft has the base body or forms it.

In advantageous embodiments, the coating is carried out in such a way that the matrix surface with the surface particles forms an outer run-in surface of the sliding element. In other words, the running-in surface is in direct contact with the counter-sliding element in the running-in phase. In the case of a piston or a piston ring, the run-in surface is in direct contact with an associated cylinder. This reduces the break-in period. Furthermore, said reservoirs for the lubricant are created in this way within a shorter run-in period. As a result, in addition to a faster running-in period, the reduced wear begins more quickly.

In principle, it is possible to provide at least one additional layer on the entry surface.

It is preferred if the run-in surface forms the outermost surface of the sliding element.

It goes without saying that at least one further layer can be applied below the matrix, that is to say between the matrix and the outer surface of the base body, this layer also being referred to below as an intermediate layer. In particular, at least one intermediate layer can serve as an adhesive layer between the matrix and the outer surface of the base body.

In principle, the surface particles can be particles of any type.

In advantageous embodiments, the surface particles are at least partially hard particles. These include, for example, ceramic particles, in particular carbide ceramics and/or nitride ceramics. The hard particles also include metal particles. It is thus possible, for example, to produce grooves on an inner surface of the associated counter-sliding element facing the run-in surface, which grooves can also serve as a reservoir for the lubricant.

In a preferred embodiment, the surface particles can also contain fibers such as aramid fibers, e.g. Kevlar, or carbon fibers. Such elongate particles can further reduce wear on the sliding element and counter-sliding element and/or on the counter-sliding element.

Alternatively or additionally, solid lubricant particles can be used as surface particles. These include, for example, graphite, polytetrafluoroethylene or PTFE for short, boron nitride, in particular h-boron nitride, and molybdenum sulfite. In this way it is possible in particular to reduce the friction and wear between the sliding element and the counter-sliding element, in particular between the inner surface of the cylinder and the piston or the piston ring.

Alternatively or additionally, it is conceivable to use those with color pigments as surface particles. As a result, the surface of the sliding element that is visible when new is marked in color. This results in simplified assembly, in particular a reduced risk of using unsuitable sliding elements in an associated application, for example a reduced risk of using unsuitable pistons or col benringe in an associated cylinder. In addition, the at least partial removal of the color pigments that has taken place in the running-in phase provides an indicator of the removal that has taken place in the running-in phase and/or of the wear of the sliding element. In other words, in this way the degree of wear and/or the degree of removal can be visually identified in a simplified manner.

In principle, the curable matrix can have any composition as long as it is curable.

The matrix is preferably liquid or viscous and can therefore be cured. The matrix is expediently applied to the base body in the liquid state and cured after the application of the surface particles.

The matrix advantageously has polyamideimides. In particular, the matrix can consist of polyamideimides.

Alternatively or additionally, the matrix contains epoxides, in particular epoxy resins. In particular, the matrix can consist of epoxides, in particular epoxy resins.

In addition or as an alternative, the matrix can contain silicone, polyetheretherketone or, for short, PEEK, PEAK and the like. In particular, the matrix can consist of silicone, PEEK, PEAK and the like.

Embodiments are advantageous in which the matrix has particles distributed within the matrix and thus suspended, which are also referred to below as suspension particles. This means that the matrix with suspension particles distributed in the matrix is applied to the base body. Then, before the matrix hardens, the surface particles are applied to the matrix surface. Thus, the matrix is functionally expanded.

The suspension particles can be hard particles, solid lubricants, fibers and the like.

In principle, the suspension particles and the surface particles can be at least partially identical.

The suspension particles and the surface particles are advantageously different.

In a preferred embodiment, the suspension particles at least predominantly include hard particles, while the surface particles contain at least predominantly solid lubricants. As a result, solid lubricant from the surface particles that has been removed during entry can be deposited in depressions on the surface of the counter-sliding element, such as a cylinder, and contribute to reducing friction and wear during further operation.

It goes without saying that, in addition to the method for coating the sliding element, a sliding element coated in this way also belongs to the scope of this invention.

Further important features and advantages of the invention result from the dependent claims, from the drawings and from the associated description of the figures with reference to the drawings.

It goes without saying that the features mentioned above and those still to be explained below can be used not only in the combination specified in each case, but also in other combinations or on their own, without departing from the scope of the present invention.

Preferred exemplary embodiments of the invention are illustrated in the drawings and are explained in more detail in the following description, with the same reference symbols referring to identical or similar or functionally identical components.

• 1 einen Schnitt durch einen Grundkörper eines Gleitelements mit einer Beschichtung im Neuzustand,
• 2 die Ansicht aus 1 nach einer Einlaufphase,
• 3 die Ansicht aus 1 bei einem anderen Ausführungsbeispiel,
• 4 die Ansicht aus 1 bei einem weiteren Ausführungsbeispiel.

Show it, each schematically

• 1 a section through a base body of a sliding element with a coating when new,
• 2 the view off 1 after a running-in phase,
• 3 the view off 1 in another embodiment,
• 4 the view off 1 in another embodiment.

the 1 until 4 each show a section through a base body 1 of a sliding element 2, for example a piston 18 or a piston ring 3, including the associated coating 4. The coating 4 is applied to an outer surface 5 of the base body 1, which is also referred to below as the base body outer surface 5. During operation, the base body outer surface 5 faces a counter-sliding body (not shown), in the case of the piston 18 or piston ring 3 a cylinder of an internal combustion engine (not shown).

According to the figures, a matrix 6 which can be hardened is applied to the outer surface 5 of the base body. The matrix 6 includes, for example, polyamideimides and/or epoxides, in particular epoxy resins.

According to the 1 as well as 3 and 4, particles 8 are applied to a surface 7 of the matrix which faces away from the outer surface 5 of the base body, also referred to below as matrix surface 7, which are also referred to below as surface particles 8. The surface particles 8 are applied before the matrix 6 hardens. As a result, the surface particles 8 dip at least partially into the matrix 6 via the matrix surface 7 . Like the 1 , 3 and 4 can be removed, at least part of the surface particles 8 protrudes from the matrix surface 7 . Like the 1 3 and 4, the matrix surface 7 together with the surface particles 8 protruding from the matrix surface 7 forms a run-in surface 9 of the sliding element 2 which, when new, interacts with an associated counter-sliding element (not shown). In the case of a piston 18 or a piston ring 3 as the sliding element 2, the inlet surface 9 interacts, for example, with an inner surface of the associated cylinder (not shown). In the exemplary embodiments shown, the run-in surface 9 forms the outermost surface of the sliding element 2. However, it would also be conceivable to apply a further layer, not shown, to the run-in surface 9.

2 shows the embodiment of 1 in a state during or after the run-in phase. Accordingly, the surface particles 8 protruding from the matrix surface 7 are removed in the running-in phase through the interaction with the associated counter-sliding element. As a result, cavities 10 are formed on the matrix surface 7, which are used during operation to store a lubricant (not shown) between the counter-sliding element and the sliding element 2. In addition to a rapid running-in phase, there is a long-lasting reduced wear between the sliding element and the counter-sliding element.

The coating 4 is preferably applied to a piston skirt 11 in the case of the piston 18 as the sliding element 2 . In this case, the base body 1 is the base body 1 of the piston shaft 11 of the piston 18.

The surface particles 8 can be hard particles 12, for example made of ceramics and/or carbide ceramics and/or nitride ceramics and/or metals. Alternatively or additionally, the surface particles 8 can be solid lubricant particles 13, for example made of graphite, molybdenum sulfite, PTFE, boron nitride, in particular h-boron nitride, and the like. Alternatively or additionally, at least some of the surface particles 8 can be or contain color pigments. Alternatively or additionally, the surface particles 8 can contain fibers such as aramid fibers, e.g. Kevlar, or carbon fibers

As 3 can be removed, particles 15 distributed and thus suspended within the matrix 6 can be provided, which are also referred to below as suspension particles 15 . In the 3 the suspension particles 15 are smaller than the surface particles 8 for better differentiation and have a different shape. In principle, the suspension particles 15 can be of any type. In particular, the suspension particles 15 can be different from the surface particles 8 or at least partially correspond to them. The suspension particles 15 are advantageously at least predominantly hard particles 12, while the surface particles 8 are at least predominantly solid lubricant particles 13. As a result, solid lubricant particles 13 removed in the run-in phase on the surface of the counter-sliding element, such as the cylinder, in depressions contribute to reducing friction and wear during further operation.

How in particular 4 can be seen, it is also conceivable to apply a further layer 16 between the base body outer surface 5 and the matrix 6, which is also referred to below as an intermediate layer 16. at in 4 shown embodiment, only such an intermediate layer 16 is provided. Consequently, the intermediate layer 16 is applied to the outer surface 5 of the base body and the matrix 6 to the intermediate layer 16 . The intermediate layer 16 can be an adhesive layer 17, for example.

QUOTES INCLUDED IN DESCRIPTION

This list of documents cited 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

• DE 102016207592 A1 [0005]
• WO 2005/056276 A1 [0006]

Claims (10)

Method for coating a sliding element (2), in particular a piston (18) or a piston ring (3), which has a base body (1) with an outer surface (5) of the base body which faces a counter-sliding element during operation, - a hardenable matrix (6) being applied to the base body (1), - before the matrix (6) hardens, surface particles (8) are applied to a matrix surface (7) of the matrix (6) facing away from the outer surface (5) of the base body, - The matrix (6) is then cured. procedure after claim 1 , characterized in that the coating takes place in such a way that the matrix surface (7) with the surface particles (8) forms an inlet surface (9) of the sliding element (2). procedure after claim 1 or 2 , characterized in that at least partially hard particles (12) are used as surface particles (8). Procedure according to one of Claims 1 until 3 , characterized in that at least some solid lubricant particles (13) are used as surface particles (8). Procedure according to one of Claims 1 until 4 , characterized in that at least some of the surface particles (8) used are those with color pigments (14). Procedure according to one of Claims 1 until 5 , characterized in that at least some of the surface particles (8) used are those with fibers. Procedure according to one of Claims 1 until 6 , characterized in that at least some polyamideimides and/or epoxides are used as the matrix (6). Procedure according to one of Claims 1 until 7 , characterized in that the matrix (6) with in the matrix (6) distributed suspension particles (15) is applied. procedure after claim 8 , characterized in that the suspension particles (15) are different from the surface particles (8). Sliding element (2), in particular piston (18) or piston ring (3) for an internal combustion engine, according to the method of one of Claims 1 until 9 is coated.

Images