EP4073370A1 - Piston and method for producing same - Google Patents

Piston and method for producing same

Info

Publication number
EP4073370A1
EP4073370A1 EP20820892.6A EP20820892A EP4073370A1 EP 4073370 A1 EP4073370 A1 EP 4073370A1 EP 20820892 A EP20820892 A EP 20820892A EP 4073370 A1 EP4073370 A1 EP 4073370A1
Authority
EP
European Patent Office
Prior art keywords
piston
depressions
coating
along
friction
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Pending
Application number
EP20820892.6A
Other languages
German (de)
French (fr)
Inventor
Margrit Dannenfeldt
Carolin Kleinlein
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Federal Mogul Nuernberg GmbH
Original Assignee
Federal Mogul Nuernberg GmbH
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Federal Mogul Nuernberg GmbH filed Critical Federal Mogul Nuernberg GmbH
Publication of EP4073370A1 publication Critical patent/EP4073370A1/en
Pending legal-status Critical Current

Links

Classifications

    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02F—CYLINDERS, PISTONS OR CASINGS, FOR COMBUSTION ENGINES; ARRANGEMENTS OF SEALINGS IN COMBUSTION ENGINES
    • F02F3/00—Pistons 
    • F02F3/10—Pistons  having surface coverings
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02F—CYLINDERS, PISTONS OR CASINGS, FOR COMBUSTION ENGINES; ARRANGEMENTS OF SEALINGS IN COMBUSTION ENGINES
    • F02F3/00—Pistons 
    • F02F3/10—Pistons  having surface coverings
    • F02F3/105—Pistons  having surface coverings the coverings forming a double skirt
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02F—CYLINDERS, PISTONS OR CASINGS, FOR COMBUSTION ENGINES; ARRANGEMENTS OF SEALINGS IN COMBUSTION ENGINES
    • F02F3/00—Pistons 
    • F02F3/02—Pistons  having means for accommodating or controlling heat expansion
    • F02F3/027—Pistons  having means for accommodating or controlling heat expansion the skirt wall having cavities

Definitions

  • the present invention relates to a piston for use in internal combustion engines. It also relates to a method for producing such pistons.
  • Pistons are used in internal combustion engines to drive a motor vehicle via a crankshaft.
  • the pistons move up and down within the cylinder of the internal combustion engine and are guided through the walls of the cylinder.
  • the pistons are in contact with these walls, there is friction between the piston and the walls. This leads to wear and tear and energy losses.
  • the piston is lubricated by oil and the piston surfaces that are in contact with the cylinder are provided with friction-reducing coatings. Examples of such coatings are described, for example, in DE 102005 057 754 B4.
  • a corresponding reduction in friction is intended to reduce the amount of exhaust gas from the vehicle, in this case primarily carbon dioxide, and other requirements are also to be met.
  • Further measures for reducing friction include the use of lower-friction coatings and the use of an oil with a lower viscosity.
  • solutions are also known in which friction is reduced by applying a patterned Coating is to be achieved. Dots, zigzag profiles and V profiles are known as patterns.
  • the present invention aims to reduce the friction of the pistons in the cylinder.
  • the invention is defined by the piston according to claim 1. It is further defined by the method according to claim 8. Preferred embodiments are defined in the dependent claims.
  • the piston is a piston for use in internal combustion engines.
  • they can be pistons for use in diesel, but also gasoline engines.
  • These pistons can be made of steel or aluminum / aluminum alloys. However, other materials are also conceivable.
  • the piston has a piston crown.
  • This piston crown often has a combustion chamber bowl and, when used, lies opposite the combustion chamber of the cylinder. During combustion, a force is exerted on this piston crown in the engine, which forces the piston in a direction that is directed outwards.
  • a piston skirt adjoins the piston crown.
  • the piston skirt has, at least in part, convex surfaces which, when the piston is used, bear against the cylinder wall. These surfaces recede with respect to a cylindrical surface on the edge surfaces of the contact surface. These spherical surfaces form the pressure walls or counterpressure walls and are also referred to as skirt walls.
  • the piston skirt also has box walls that have pin bosses for receiving piston pins. The convex surfaces are in use on the cylinder wall of the internal combustion engine.
  • the spherical surfaces usually have one or more friction-reducing coatings.
  • Polymer-bound coating materials that contain solid lubricants are used as coatings.
  • Polyamide imide or phenolic resin are often used as the polymer.
  • Graphite is often used as a solid lubricant, but MoSg or PTFE can also be used.
  • Other materials, as described in DE 10 2016 205 199 A1, can also be used. In interaction with the cylinder wall, these friction-reducing coatings show less friction than the piston material.
  • Depressions are provided in the coating, which are arranged such that the distance S between two directly adjacent depressions along the axial direction of the piston and the width L of the depressions along the axial direction of the piston satisfy the formula S> 2L. Accordingly, a distance between two depressions that are adjacent to one another in the axial direction is greater and in particular greater than twice as large as the width of the depressions.
  • the width L of the depression denotes the maximum width of the depression along the axial direction.
  • These depressions preferably cover at least 3%, more preferably at least 10% of the area of the coating.
  • pistons with corresponding distances between the depressions have particularly low friction, which was attributed to particularly good oil retention properties (without wishing to be limited to this theory). According to another theory, these effects can occur particularly in the case of slits, since the oil vortex formation is particularly pronounced there. For increasingly larger distances S, the friction-reducing one becomes Effect less pronounced. It is particularly preferred that the distance is less than 10% of the shaft height.
  • the depressions are preferably longer than they are wide, i.e. E> L. Such pistons have particularly reduced friction.
  • the fact that the depressions preferably cover at least 3%, more preferably at least 10% of the surface of the coating ensures that they have a significant influence on the oil retention behavior of the piston.
  • the length E should be smaller than the width of the coating E ', so that the depressions lie completely in the coating on at least one side.
  • the depressions are completely enclosed by the respective coating - in other words, the material of the coating completely surrounds the mostly rectangular depressions. This prevents oil from draining off.
  • depressions should be located in a row horizontally next to one another (i.e., aligned along the circumference).
  • the width of the webs of coating material between these aligned depressions i.e., the circumferential distance between the depressions
  • 0 e.g., greater than 1pm or greater than 100pm.
  • the thickness of the webs i.e. the layer thickness of the coating
  • the material of the coating has an essentially constant thickness over the entire coating.
  • This thickness of the coating material is preferably between 5 and 25 gm, more preferably between 10 and 15 gm. Such coatings can easily be produced by screen printing.
  • one depression is provided per 5 ° -30 °, particularly preferably 10 °, piston circumference and that this is provided Wells are provided in a row along the circumference.
  • the wells can also be of different lengths.
  • the depressions extend in at most 35% of the surface of the coating (ie that the area of the depressions in relation to the total area enclosed by the outer boundary of the coating is less than 35%) and it is preferably in the range of 20% of the total area enclosed by the outer boundary of the coating. In experiments, this led to a particularly strong reduction in friction.
  • the minimum indentation area is 3% of the total area, i.e. the indentations cover at least 3% of the total area of the coating.
  • the depressions preferably extend so deeply through the coating that they reach the material of the piston skirt and that their underside is therefore not formed by the material of the coating. Correspondingly deep depressions are particularly good oil reservoirs and therefore lead to good lubrication.
  • the boundary surfaces of the recess (s) preferably extend obliquely with respect to the coating and the material of the surfaces to which they adjoin.
  • the boundary surfaces are not completely perpendicular, but sloping. In this respect, they enclose an angle not equal to 90 ° with the material of the coating and the material of the surfaces to which they adjoin.
  • the depressions adjacent to one another in the axial direction are preferably offset from one another along the circumferential direction. Accordingly, the depressions are not lined up one behind the other in the axial direction, but have, for example, their centers offset along the circumferential direction.
  • a corresponding piston has a particularly low friction when used.
  • the fact that the depressions are enclosed implies that the extension length of at least some, preferably all of the depressions along the circumferential direction is shorter than the extension length along the circumferential direction of the coating in which they are formed. In other words, the depressions are so short that they do not extend from one side of the coating to the other side of the coating along the circumferential direction. Since the depressions are so short that they are completely embedded in the coating, they can serve as a reservoir for oil and thus significantly reduce the friction of the piston. This prevents them from acting as an oil drain, as the oil cannot drain through the depressions on the sides of the coating.
  • the depressions preferably have a substantially rectangular shape.
  • the ends of the depressions in the circumferential direction can also be rounded. Such a shape is easy to develop. Accordingly, a corresponding piston can be produced inexpensively.
  • the depressions preferably have a width L of less than 2 mm and particularly preferably in the range of 0.6-0.8 mm.
  • Correspondingly thin depressions have proven to be particularly advantageous for the retention behavior of oil, which may be due to the capillary forces, among other things, without being limited to this theory.
  • a method for producing a piston according to one of the preceding claims is according to the invention, in which the coating including the depressions is applied by means of a screen printing process.
  • Such a method is particularly easy to implement and also has sufficient accuracy, which is why the coatings with the depressions can be applied with it.
  • the precision of screen printing depends on various parameters from, although it has been shown that it is comparatively easy to control.
  • Figure 1 shows a piston according to the invention according to one embodiment.
  • FIG. 2 shows a detailed view of coatings of the piston according to the invention.
  • FIG. 3 shows a cross-sectional view of a recess in the piston according to the invention.
  • Figures 4a) and b) show different variants of a piston according to the invention.
  • Figures 4c and 4d) show a piston not according to the invention.
  • FIG. 1 shows a view of a piston 10 according to the invention according to the first embodiment of the invention.
  • the piston has a cylindrical shape with a cylinder axis A.
  • a piston skirt 14 adjoins a piston head 12 of the piston with annular grooves 13.
  • the piston skirt 14 has convex surfaces 16, which represent skirt walls, and box walls 17.
  • the cylindrical surfaces 16 lie against the cylinder wall of the internal combustion engine and have a friction-reducing coating 18 made of a graphite-containing polymer material.
  • the coating 16 is provided on only part of the spherical surface 16.
  • the spherical surface 16 adjoins the ring field with the ring grooves 13 of the piston.
  • the coating 18 extends along the circumference of the piston for a length E '.
  • Rectangular depressions 20 are provided in the coating 18 which extend through the coating material so that the material of the piston is exposed through the depressions 20.
  • the ends of the rectangular depressions can be rounded.
  • a plurality of depressions 20 are lined up along the circumferential direction. There are several such rows of lined up depressions 20, which are offset from one another along the circumferential direction, so that the axially adjacent depressions 20 are offset from one another along the circumferential direction.
  • the depressions 20 are shown in further detail in FIG. Several depressions 20 are shown here in two rows, which are offset from one another along the circumferential direction of the piston 10.
  • the recesses 20 have a rectangular shape in plan view and have a length E along the circumferential direction and a width L in the axial direction A.
  • the distance between two adjacent recesses 20 in the axial direction is defined as S. For the distance S, S> 2 L.
  • FIG. 3 shows a cross section through a depression 20 along the circumferential direction.
  • the boundary surfaces 17 of the recess are inclined with respect to the material of the spherical surfaces 16 and also include an angle with respect to the material of the coating 18.
  • the recess 20 is closed at the bottom, i.e. the underside of the recess 20 is formed by the material of the piston 16 and is closed so that it prevents oil from flowing off downwards.
  • a piston 10 configured as shown in FIGS. 1-3 has a friction reduced by up to 20%. This is because the depressions 20 have comparatively good oil retention properties. In this respect, oil collects in them and then reduces the friction. In contrast to depressions that extend over the entire width of the coating, the Oil retention properties improved because the oil cannot drain off. For the oil retention behavior, it is important that the slots are narrow and deep enough. Calculations that make this behavior plausible are described, for example, in the paper by M. Scholle, "Hydrodynamical modeling of lubricant friction between rough surfaces", Tribology International 40 (2007) 1004-1011.
  • FIG. 4 shows pistons according to the invention in FIGS. A) and b).
  • FIG. 4b) corresponds to the piston that is already shown in FIG. This piston is therefore not always discussed in detail.
  • FIG. 4a shows a piston 10 'according to a second embodiment of the invention with a coating 18' in which the coatings 20 'are arranged such that adjacent depressions 20' are lined up along the axial direction of the piston. Furthermore, on the side of the coating 18 'opposite the piston head 12', there is a surface 19 'of the coating in which no depressions 20' are provided. Even if such an arrangement of the depressions 20 ′ is less advantageous in comparison to the first embodiment with regard to the retention capacity for oil, a corresponding piston is improved in comparison to the prior art with regard to the oil retention properties and thus has less friction.
  • FIG. 4c) shows a further piston 10 ′′ which is not part of the invention.
  • This piston 10 ′′ also has a coating 18 ′′ which has depressions 20 ′′.
  • These depressions 20 ′′ extend along the circumferential direction of the piston 10 ′′ over the entire width of the coating 18 ′′ and are therefore not enclosed, as required by the invention.
  • the depressions 20, 20 'each only extend over a section of the coating 18, 18' along the circumferential direction, but not over the entire width of the coating 18, 18 '.
  • the depressions 20 ′′ extend over the entire width of the coating 18 ′′, oil can drain from them. This then leads to increased friction compared to pistons in which the depressions are enclosed.
  • FIG. 4d shows a piston 10 111 which is not according to the invention.
  • Essentially circular depressions 20 111 are provided here in a coating 18 111 , which are arranged in several rows along the circumferential direction of the piston 10 111 and which are offset from one another along the circumferential direction.
  • the depressions 20 - '-' - '- shown here do not meet the requirement that S> 2 L, but are arranged too closely.
  • E> L does not apply here.
  • the coatings 18 to 18 111 shown in FIGS. 4a) to 4d) can be produced by a screen printing process.

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  • Engineering & Computer Science (AREA)
  • Chemical & Material Sciences (AREA)
  • Combustion & Propulsion (AREA)
  • Mechanical Engineering (AREA)
  • General Engineering & Computer Science (AREA)
  • Pistons, Piston Rings, And Cylinders (AREA)

Abstract

The present invention relates to pistons (10) for use in internal combustion engines, having: a piston crown (12) which is adjoined by a piston skirt (14), wherein the piston skirt (14) has surfaces (18) which lie against the cylinder wall during use of the piston, wherein the surfaces (16) have one or more friction-reducing coatings (18) and wherein depressions (20) are provided in the coating, which depressions (20) are arranged such that the spacing S between in each case two adjacent depressions (20) along the axial direction (A) of the piston and the width L of the depressions (20) along the axial direction (A) of the piston satisfy the formula S > 2 L.

Description

Kolben und Verfahren zur Herstellung desselben Piston and method of making the same
Technisches Gebiet Technical area
Die vorliegende Erfindung betrifft einen Kolben zur Verwendung in Verbrennungsmotoren. Sie betrifft ferner ein Verfahren zur Herstellung solcher Kolben. The present invention relates to a piston for use in internal combustion engines. It also relates to a method for producing such pistons.
Stand der Technik State of the art
Kolben werden in Verbrennungsmotoren verwendet, um über eine Kurbelwelle ein Kraftfahrzeug anzutreiben. Die Kolben bewegen sich innerhalb des Zylinders des Verbrennungsmotors auf und ab und werden durch die Wände des Zylinders geführt. Pistons are used in internal combustion engines to drive a motor vehicle via a crankshaft. The pistons move up and down within the cylinder of the internal combustion engine and are guided through the walls of the cylinder.
Durch das Anliegen der Kolben an diesen Wänden gibt es zwischen dem Kolben und den Wänden Reibung. Diese führt zu Verschleiß und Energieverlusten. Aus diesen Gründen wird der Kolben durch Öl geschmiert und werden die Kolbenoberflächen, die mit dem Zylinder in Kontakt stehen, mit reibungsreduzierenden Beschichtungen versehen. Beispiele solcher Beschichtungen sind zum Beispiel in der DE 102005 057 754 B4 beschrieben. Because the pistons are in contact with these walls, there is friction between the piston and the walls. This leads to wear and tear and energy losses. For these reasons, the piston is lubricated by oil and the piston surfaces that are in contact with the cylinder are provided with friction-reducing coatings. Examples of such coatings are described, for example, in DE 102005 057 754 B4.
Durch eine entsprechende Reibungsreduzierung soll die Abgasmenge des Fahrzeugs, hier vor allem Kohlendioxid, reduziert werden und sollen auch andere Vorgaben erfüllt werden. Als weitere Maßnahmen zur Reibungsreduzierung kommen unter anderem ein Einsatz von reibungsärmeren Beschichtungen und der Einsatz eines Öls mit geringerer Viskosität in Frage. Auch sind, wie zum Beispiel in der DE 102005 057754 B4 beschrieben, Lösungen bekannt, bei denen eine Reibungsreduzierung durch das Aufbringen einer gemusterten Beschichtung erzielt werden soll. Als Muster sind Punkte, Zickzack-Profile und V-Profile bekannt. A corresponding reduction in friction is intended to reduce the amount of exhaust gas from the vehicle, in this case primarily carbon dioxide, and other requirements are also to be met. Further measures for reducing friction include the use of lower-friction coatings and the use of an oil with a lower viscosity. As described for example in DE 102005 057754 B4, solutions are also known in which friction is reduced by applying a patterned Coating is to be achieved. Dots, zigzag profiles and V profiles are known as patterns.
Darstellung der Erfindung Presentation of the invention
Den Erfindern ist jedoch aufgefallen, dass diese Lösungen noch weiter optimiert werden können, was die Reibungsreduzierung angeht. However, the inventors have noticed that these solutions can be optimized even further in terms of reducing friction.
Die vorliegende Erfindung zielt darauf ab, die Reibung der Kolben im Zylinder zu reduzieren. Die Erfindung wird durch den Kolben nach Anspruch 1 definiert. Sie wird ferner durch das Verfahren nach Anspruch 8 definiert. Bevorzugte Ausführungsformen werden in den abhängigen Ansprüchen definiert . The present invention aims to reduce the friction of the pistons in the cylinder. The invention is defined by the piston according to claim 1. It is further defined by the method according to claim 8. Preferred embodiments are defined in the dependent claims.
Erfindungsgemäß handelt es sich bei dem Kolben um einen Kolben zur Verwendung in Verbrennungsmotoren. Insbesondere kann es sich um Kolben zur Verwendung in Diesel-, aber auch Benzinmotoren handeln. Diese Kolben können aus Stahl oder Aluminium/Aluminiumlegierungen bestehen. Es sind jedoch auch andere Materialien denkbar. According to the invention, the piston is a piston for use in internal combustion engines. In particular, they can be pistons for use in diesel, but also gasoline engines. These pistons can be made of steel or aluminum / aluminum alloys. However, other materials are also conceivable.
Der Kolben weist einen Kolbenboden auf. Dieser Kolbenboden weist oft eine Brennraummulde auf und liegt bei Verwendung dem Brennraum des Zylinders gegenüber. Auf diesen Kolbenboden wird im Motor bei der Verbrennung eine Kraft ausgeübt, die den Kolben in eine Richtung drückt, die nach außen gerichtet ist. An den Kolbenboden schließt sich ein Kolbenschaft an.The piston has a piston crown. This piston crown often has a combustion chamber bowl and, when used, lies opposite the combustion chamber of the cylinder. During combustion, a force is exerted on this piston crown in the engine, which forces the piston in a direction that is directed outwards. A piston skirt adjoins the piston crown.
Der Kolbenschaft weist zumindest in Teilen ballige Flächen auf, die bei Verwendung des Kolbens an der Zylinderwand anliegen. Diese Flächen weichen bezüglich einer Zylinderfläche an den Randflächen der Kontaktfläche zurück. Diese balligen Flächen bilden die Druckwände bzw. Gegendruckwände und werden auch als Schaftwände bezeichnet. Der Kolbenschaft weist auch Kastenwände auf, die Bolzennaben zur Aufnahme von Kolbenbolzen aufweisen. Die balligen Flächen liegen bei Verwendung an der Zylinderwand des Verbrennungsmotors an. The piston skirt has, at least in part, convex surfaces which, when the piston is used, bear against the cylinder wall. These surfaces recede with respect to a cylindrical surface on the edge surfaces of the contact surface. These spherical surfaces form the pressure walls or counterpressure walls and are also referred to as skirt walls. The piston skirt also has box walls that have pin bosses for receiving piston pins. The convex surfaces are in use on the cylinder wall of the internal combustion engine.
Die balligen Flächen weisen meist eine oder mehrere reibungsreduzierende Beschichtungen auf. Als Beschichtungen werden polymergebundene Beschichtungsmaterialien verwendet, die Festschmierstoffe aufweisen. Als Polymer werden oft Polyamidimid oder Phenolharz verwendet. Als Festschmierstoff wird oft Graphit eingesetzt, aber auch MoSg oder PTFE kann verwendet werden. Andere Materialien, wie sie in der DE 10 2016 205 199 Al beschrieben werden, können auch Anwendung finden. Diese reibungsreduzierenden Beschichtungen zeigen im Zusammenspiel mit der Zylinderwand weniger Reibung als das Kolbenmaterial . The spherical surfaces usually have one or more friction-reducing coatings. Polymer-bound coating materials that contain solid lubricants are used as coatings. Polyamide imide or phenolic resin are often used as the polymer. Graphite is often used as a solid lubricant, but MoSg or PTFE can also be used. Other materials, as described in DE 10 2016 205 199 A1, can also be used. In interaction with the cylinder wall, these friction-reducing coatings show less friction than the piston material.
In der Beschichtung sind Vertiefungen vorgesehen, die so angeordnet sind, dass der Abstand S zwischen je zwei direkt benachbarten Vertiefungen entlang der Axialrichtung des Kolbens und die Breite L der Vertiefungen entlang der Axialrichtung des Kolbens der Formel S > 2L genügen. Demgemäß ist zwischen zwei zueinander in der Axialrichtung benachbarten Vertiefungen ein Abstand größer und insbesondere größer als zweimal so groß wie die Breite der Vertiefungen.Depressions are provided in the coating, which are arranged such that the distance S between two directly adjacent depressions along the axial direction of the piston and the width L of the depressions along the axial direction of the piston satisfy the formula S> 2L. Accordingly, a distance between two depressions that are adjacent to one another in the axial direction is greater and in particular greater than twice as large as the width of the depressions.
Im Fall von ungleichmäßig ausgebildeten Vertiefungen bezeichnet die Breite L der Vertiefung die maximale Breite der Vertiefung entlang der Axialrichtung. Diese Vertiefungen decken bevorzugt wenigstens 3%, stärker bevorzugt wenigstens 10% der Fläche der Beschichtung ab. In the case of unevenly formed depressions, the width L of the depression denotes the maximum width of the depression along the axial direction. These depressions preferably cover at least 3%, more preferably at least 10% of the area of the coating.
Den Erfindern ist aufgefallen, dass Kolben mit entsprechenden Abständen zwischen den Vertiefungen besonders reibungsarm sind, was auf besonders gute Ölrückhalteeigenschaften zurückgeführt wurde (ohne auf diese Theorie beschränkt sein zu wollen). Diese Effekte können nach einer anderen Theorie besonders bei Schlitzen auftreten, da dort die Ölwirbelbildung besonders ausgeprägt ist. Für zunehmend größer werdende Abstände S wird der reibungsreduzierende Effekt weniger ausgeprägt. Besonders bevorzugt wird, dass der Abstand kleiner als 10% der Schafthöhe ist. The inventors noticed that pistons with corresponding distances between the depressions have particularly low friction, which was attributed to particularly good oil retention properties (without wishing to be limited to this theory). According to another theory, these effects can occur particularly in the case of slits, since the oil vortex formation is particularly pronounced there. For increasingly larger distances S, the friction-reducing one becomes Effect less pronounced. It is particularly preferred that the distance is less than 10% of the shaft height.
Die Vertiefungen sind bevorzugt länger als sie breit sind, d.h. E>L. Solche Kolben sind besonders reibungsreduziert. Dadurch, dass die Vertiefungen bevorzugt wenigstens 3%, stärker bevorzugt wenigstens 10% der Fläche der Beschichtung abdecken, wird sichergestellt, dass diese einen signifikanten Einfluss auf das Ölrückhalteverhalten des Kolbens haben. The depressions are preferably longer than they are wide, i.e. E> L. Such pistons have particularly reduced friction. The fact that the depressions preferably cover at least 3%, more preferably at least 10% of the surface of the coating ensures that they have a significant influence on the oil retention behavior of the piston.
Die Länge E soll kleiner als die Breite der Beschichtung E' sein, so dass die Vertiefungen zumindest an einer Seite komplett in der Beschichtung liegen. Die Vertiefungen sind rundum von der jeweiligen Beschichtung umschlossen - anders gesagt umgibt das Material der Beschichtung vollständig die meistens rechteckigen Vertiefungen. Dies verhindert ein Abfließen von Öl. The length E should be smaller than the width of the coating E ', so that the depressions lie completely in the coating on at least one side. The depressions are completely enclosed by the respective coating - in other words, the material of the coating completely surrounds the mostly rectangular depressions. This prevents oil from draining off.
Bevorzugter sollen sich mehrere Vertiefungen in einer Reihe horizontal nebeneinander (d.h. entlang des Umfangs fluchtend) befinden. Die Breite der Stege aus Beschichtungsmaterial zwischen diesen fluchtenden Vertiefungen (d.h. der Abstand entlang des Umfangs zwischen den Vertiefungen) muss größer als 0 sein (z.B. größer als lpm oder größer als lOOpm). More preferably, several depressions should be located in a row horizontally next to one another (i.e., aligned along the circumference). The width of the webs of coating material between these aligned depressions (i.e., the circumferential distance between the depressions) must be greater than 0 (e.g., greater than 1pm or greater than 100pm).
Von Vorteil ist jedoch, dass die Dicke der Stege (d.h. die Schichtdicke der Beschichtung) gleich der Schichtdicke der Schicht im Bereich des Abstands S ist - anders gesagt hat das Material der Beschichtung eine im Wesentlichen konstante Dicke über die gesamte Beschichtung. Diese Dicke des Beschichtungsmaterials beträgt bevorzugt zwischen 5 und 25 gm, stärker bevorzugt zwischen 10 und 15 gm. Solche Beschichtungen lassen sich gut durch Siebdruck erstellen. However, it is advantageous that the thickness of the webs (i.e. the layer thickness of the coating) is the same as the layer thickness of the layer in the area of the distance S - in other words, the material of the coating has an essentially constant thickness over the entire coating. This thickness of the coating material is preferably between 5 and 25 gm, more preferably between 10 and 15 gm. Such coatings can easily be produced by screen printing.
Bevorzugt wird, dass eine Vertiefung pro 5°-30°, besonders bevorzugt 10°, Kolbenumfang vorgesehen ist und dass diese Vertiefungen in einer Reihe entlang des Umfangs vorgesehen sind. Die Vertiefungen können auch unterschiedlich lang sein. It is preferred that one depression is provided per 5 ° -30 °, particularly preferably 10 °, piston circumference and that this is provided Wells are provided in a row along the circumference. The wells can also be of different lengths.
In diesem Zusammenhang wird besonders bevorzugt, dass sich die Vertiefungen in höchstens 35 % der Fläche der Beschichtung erstrecken (d.h. dass die Fläche der Vertiefungen in Bezug auf die Gesamtfläche, die durch die äußere Begrenzung der Beschichtung umschlossen wird, weniger als 35% beträgt) und sie bevorzugt im Bereich von 20% der Gesamtfläche, die durch die äußere Begrenzung der Beschichtung umschlossen wird, liegt. Dies führte in Experimenten zu einer besonders starken Reibungsverminderung. Die minimale Vertiefungsfläche liegt bei 3% der Gesamtfläche, d.h. die Vertiefungen decken mindestens 3% der Gesamtfläche der Beschichtung ab. In this context, it is particularly preferred that the depressions extend in at most 35% of the surface of the coating (ie that the area of the depressions in relation to the total area enclosed by the outer boundary of the coating is less than 35%) and it is preferably in the range of 20% of the total area enclosed by the outer boundary of the coating. In experiments, this led to a particularly strong reduction in friction. The minimum indentation area is 3% of the total area, i.e. the indentations cover at least 3% of the total area of the coating.
Bevorzugt erstrecken sich die Vertiefungen so tief durch die Beschichtung, dass sie das Material des Kolbenschaftes erreichen und dass somit ihre Unterseite nicht durch das Material der Beschichtung ausgebildet ist. Entsprechend tiefe Vertiefungen sind besonders gute Ölreservoirs und führen daher zu einer guten Schmierung. The depressions preferably extend so deeply through the coating that they reach the material of the piston skirt and that their underside is therefore not formed by the material of the coating. Correspondingly deep depressions are particularly good oil reservoirs and therefore lead to good lubrication.
Bevorzugt erstrecken sich die Begrenzungsflächen der Vertiefung (en) schräg bezüglich der Beschichtung und des Materials der Flächen, an das sie angrenzen. D. h. die Begrenzungsflächen sind nicht vollständig senkrecht, sondern schräg. Insofern schließen sie einen Winkel ungleich 90° mit dem Material der Beschichtung und dem Material der Flächen ein, an welche sie angrenzen. The boundary surfaces of the recess (s) preferably extend obliquely with respect to the coating and the material of the surfaces to which they adjoin. I. E. the boundary surfaces are not completely perpendicular, but sloping. In this respect, they enclose an angle not equal to 90 ° with the material of the coating and the material of the surfaces to which they adjoin.
Bevorzugt sind die zueinander in der Axialrichtung benachbarten Vertiefungen entlang der Umfangsrichtung zueinander versetzt. Demgemäß sind die Vertiefungen nicht in der Axialrichtung hintereinander aufgereiht, sondern haben zum Beispiel ihre Mittelpunkte entlang der Umfangsrichtung versetzt. Ein entsprechender Kolben hat bei Verwendung eine besonders niedrige Reibung. Durch das Umschlossen Sein der Vertiefungen wird impliziert, dass die Erstreckungslänge zumindest einiger, bevorzugt aller Vertiefungen entlang der Umfangsrichtung kürzer ist als die Erstreckungslänge entlang der Umfangsrichtung der Beschichtung, in der diese ausgebildet sind. Anders gesagt sind die Vertiefungen so kurz, dass sie sich nicht von einer Seite der Beschichtung zur anderen Seite der Beschichtung entlang der Umfangsrichtung erstrecken. Da die Vertiefungen somit so kurz sind, dass sie vollständig in die Beschichtung eingebettet sind, können diese als ein Reservoir von Öl dienen, und verringern somit die Reibung des Kolbens signifikant. Somit wird verhindert, dass sie als Öldrainage wirken, da das Öl nicht über die Vertiefungen an den Seiten der Beschichtung abfließen kann. The depressions adjacent to one another in the axial direction are preferably offset from one another along the circumferential direction. Accordingly, the depressions are not lined up one behind the other in the axial direction, but have, for example, their centers offset along the circumferential direction. A corresponding piston has a particularly low friction when used. The fact that the depressions are enclosed implies that the extension length of at least some, preferably all of the depressions along the circumferential direction is shorter than the extension length along the circumferential direction of the coating in which they are formed. In other words, the depressions are so short that they do not extend from one side of the coating to the other side of the coating along the circumferential direction. Since the depressions are so short that they are completely embedded in the coating, they can serve as a reservoir for oil and thus significantly reduce the friction of the piston. This prevents them from acting as an oil drain, as the oil cannot drain through the depressions on the sides of the coating.
Bevorzugt haben die Vertiefungen eine im Wesentlichen rechteckige Form. Die Enden der Vertiefungen in der Umfangsrichtung können auch abgerundet sein. Eine solche Form ist leicht auszubilden. Demgemäß ist entsprechender Kolben kostengünstig herstellbar. The depressions preferably have a substantially rectangular shape. The ends of the depressions in the circumferential direction can also be rounded. Such a shape is easy to develop. Accordingly, a corresponding piston can be produced inexpensively.
Bevorzugt haben die Vertiefungen eine Breite L von weniger als 2mm und besonders bevorzugt im Bereich von 0,6-0,8 mm. Entsprechend dünne Vertiefungen haben sich als besonders vorteilhaft für das Rückhalteverhalten von Öl herausgestellt, was unter anderem an den Kapillarkräften liegen kann, ohne auf diese Theorie beschränkt zu sein. The depressions preferably have a width L of less than 2 mm and particularly preferably in the range of 0.6-0.8 mm. Correspondingly thin depressions have proven to be particularly advantageous for the retention behavior of oil, which may be due to the capillary forces, among other things, without being limited to this theory.
Weiterhin ist ein Verfahren zur Herstellung eines Kolben nach einem der vorhergehenden Ansprüche erfindungsgemäß, bei dem die Beschichtung einschließlich der Vertiefungen mittels eines Siebdruckverfahrens aufgebracht wird. Ein solches Verfahren ist besonders einfach zu implementieren und hat auch eine ausreichende Genauigkeit, weshalb man damit gut die Beschichtungen mit den Vertiefungen aufbringen kann. Die Präzision des Siebdrucks hängt von verschiedenen Parametern ab, wobei es sich jedoch gezeigt hat, dass sie vergleichsweise gut kontrollierbar ist. Furthermore, a method for producing a piston according to one of the preceding claims is according to the invention, in which the coating including the depressions is applied by means of a screen printing process. Such a method is particularly easy to implement and also has sufficient accuracy, which is why the coatings with the depressions can be applied with it. The precision of screen printing depends on various parameters from, although it has been shown that it is comparatively easy to control.
Kurze Beschreibung der Zeichnungen Brief description of the drawings
Figur 1 zeigt einen erfindungsgemäßen Kolben nach einer Ausführungsform. Figure 1 shows a piston according to the invention according to one embodiment.
Figur 2 zeigt eine Detailansicht von Beschichtungen des erfindungsgemäßen Kolbens. FIG. 2 shows a detailed view of coatings of the piston according to the invention.
Figur 3 zeigt eine Querschnittsdarstellung einer Vertiefung des erfindungsgemäßen Kolbens. FIG. 3 shows a cross-sectional view of a recess in the piston according to the invention.
Figuren 4a) und b) zeigen verschiedene Varianten eines erfindungsgemäßen Kolbens. Figuren 4c und 4d) zeigen einen nicht erfindungsgemäßen Kolben. Figures 4a) and b) show different variants of a piston according to the invention. Figures 4c and 4d) show a piston not according to the invention.
Detaillierte Beschreibung der Figuren Detailed description of the figures
Figur 1 zeigt eine Ansicht eines erfindungsgemäßen Kolbens 10 gemäß der ersten Ausführungsform der Erfindung. Der Kolben hat eine zylindrische Form mit einer Zylinderachse A. An einen Kolbenboden 12 des Kolbens mit Ringnuten 13 schließt sich ein Kolbenschaft 14 an. Der Kolbenschaft 14 weist ballige Flächen 16, welche Schaftwände darstellen, und Kastenwände 17 auf. FIG. 1 shows a view of a piston 10 according to the invention according to the first embodiment of the invention. The piston has a cylindrical shape with a cylinder axis A. A piston skirt 14 adjoins a piston head 12 of the piston with annular grooves 13. The piston skirt 14 has convex surfaces 16, which represent skirt walls, and box walls 17.
Die zylindrischen Flächen 16 liegen bei Verwendung des Kolbens an der Zylinderwand des Verbrennungsmotors an und weisen eine reibungsreduzierende Beschichtung 18 aus einem graphithaltigen Polymermaterial auf. Die Beschichtung 16 ist nur auf einem Teil der balligen Fläche 16 vorgesehen. Die ballige Fläche 16 schließt sich an das Ringfeld mit den Ringnuten 13 des Kolbens an. Die Beschichtung 18 erstreckt sich entlang des Umfangs des Kolbens über eine Länge E'. In der Beschichtung 18 sind rechteckige Vertiefungen 20 vorgesehen, die sich durch das Beschichtungsmaterial hindurch erstrecken, sodass das Material des Kolbens durch die Vertiefungen 20 freigelegt wird. Die Enden der rechteckigen Vertiefungen können abgerundet sein. Mehrere Vertiefungen 20 sind entlang der Umfangsrichtung aufgereiht. Es gibt mehrere solche Reihen aus aufgereihten Vertiefungen 20, die entlang der Umfangsrichtung zueinander versetzt sind, sodass die axial benachbarten Vertiefungen 20 zueinander entlang der Umfangsrichtung versetzt sind. When the piston is used, the cylindrical surfaces 16 lie against the cylinder wall of the internal combustion engine and have a friction-reducing coating 18 made of a graphite-containing polymer material. The coating 16 is provided on only part of the spherical surface 16. The spherical surface 16 adjoins the ring field with the ring grooves 13 of the piston. The coating 18 extends along the circumference of the piston for a length E '. Rectangular depressions 20 are provided in the coating 18 which extend through the coating material so that the material of the piston is exposed through the depressions 20. The ends of the rectangular depressions can be rounded. A plurality of depressions 20 are lined up along the circumferential direction. There are several such rows of lined up depressions 20, which are offset from one another along the circumferential direction, so that the axially adjacent depressions 20 are offset from one another along the circumferential direction.
Die Vertiefungen 20 sind weiter im Detail in der Figur 2 dargestellt. Mehrere Vertiefungen 20 sind hier in zwei Reihen dargestellt, die zueinander entlang der Umfangsrichtung des Kolbens 10 versetzt sind. Die Vertiefungen 20 haben eine rechteckige Form in der Draufsicht und haben eine Länge E entlang der Umfangsrichtung und eine Breite L in der Axialrichtung A. Der Abstand zwischen zwei benachbarten Vertiefungen 20 in der Axialrichtung ist als S definiert. Für den Abstand S gilt S > 2 L. The depressions 20 are shown in further detail in FIG. Several depressions 20 are shown here in two rows, which are offset from one another along the circumferential direction of the piston 10. The recesses 20 have a rectangular shape in plan view and have a length E along the circumferential direction and a width L in the axial direction A. The distance between two adjacent recesses 20 in the axial direction is defined as S. For the distance S, S> 2 L.
In Figur 3 ist ein Querschnitt durch eine Vertiefung 20 entlang der Umfangsrichtung gezeigt. Wie aus dieser Figur zu sehen ist, sind die Begrenzungsflächen 17 der Vertiefung bezüglich des Materials der balligen Flächen 16 geneigt und schließen auch einen Winkel bezüglich des Materials der Beschichtung 18 ein. Die Vertiefung 20 ist unten geschlossen, d.h. die Unterseite der Vertiefung 20 wird durch das Material des Kolbens 16 gebildet und ist geschlossen, so dass sie verhindert, dass Öl nach unten abfließt. FIG. 3 shows a cross section through a depression 20 along the circumferential direction. As can be seen from this figure, the boundary surfaces 17 of the recess are inclined with respect to the material of the spherical surfaces 16 and also include an angle with respect to the material of the coating 18. The recess 20 is closed at the bottom, i.e. the underside of the recess 20 is formed by the material of the piston 16 and is closed so that it prevents oil from flowing off downwards.
Es wurde festgestellt, dass ein wie in Figuren 1-3 dargestellt ausgestalteter Kolben 10 eine um bis zu 20% reduzierte Reibung aufweist. Dies liegt daran, dass die Vertiefungen 20 vergleichsweise gute Ölrückhalteeigenschaften haben. Insofern sammelt sich in ihnen Öl an und verringert dann die Reibung. Im Gegensatz zu Vertiefungen, die sich über die gesamte Breite der Beschichtung erstrecken, sind die Ölrückhalteeigenschaften verbessert, da das Öl nicht abfließen kann. Für das Ölrückhalteverhalten ist es wichtig, dass die Schlitze schmal und tief genug ausgebildet sind. Berechnungen, die dieses Verhalten plausibel machen, sind zum Beispiel in dem Paper von M. Scholle, „Hydrodynamical modelling of lubricant friction between rough surfaces", Tribology International 40 (2007) 1004 - 1011 beschrieben. It was found that a piston 10 configured as shown in FIGS. 1-3 has a friction reduced by up to 20%. This is because the depressions 20 have comparatively good oil retention properties. In this respect, oil collects in them and then reduces the friction. In contrast to depressions that extend over the entire width of the coating, the Oil retention properties improved because the oil cannot drain off. For the oil retention behavior, it is important that the slots are narrow and deep enough. Calculations that make this behavior plausible are described, for example, in the paper by M. Scholle, "Hydrodynamical modeling of lubricant friction between rough surfaces", Tribology International 40 (2007) 1004-1011.
Figur 4 zeigt in Figuren a) und b) erfindungsgemäße Kolben. Hierbei entspricht Figur 4b) dem Kolben, der bereits in Figur 1 dargestellt ist. Auf diesen Kolben wird somit nicht immer im Detail eingegangen. FIG. 4 shows pistons according to the invention in FIGS. A) and b). Here, FIG. 4b) corresponds to the piston that is already shown in FIG. This piston is therefore not always discussed in detail.
Figur 4a) zeigt einen Kolben 10' gemäß einer zweiten Ausführungsform der Erfindung mit einer Beschichtung 18', in der Beschichtungen 20' so angeordnet sind, dass benachbarte Vertiefungen 20' entlang der Axialrichtung des Kolbens aufgereiht sind. Ferner befindet sich an der dem Kolbenboden 12' gegenüberliegenden Seite der Beschichtung 18' eine Fläche 19' der Beschichtung, in der keine Vertiefungen 20' vorgesehen sind. Auch wenn eine solche Anordnung der Vertiefungen 20' im Vergleich zu der ersten Ausführungsform weniger vorteilhaft ist, was das Rückhaltevermögen für Öl angeht, ist ein dementsprechender Kolben im Vergleich zum Stand der Technik in Bezug auf die Ölrückhalteeigenschaften verbessert und weißt somit weniger Reibung auf. FIG. 4a) shows a piston 10 'according to a second embodiment of the invention with a coating 18' in which the coatings 20 'are arranged such that adjacent depressions 20' are lined up along the axial direction of the piston. Furthermore, on the side of the coating 18 'opposite the piston head 12', there is a surface 19 'of the coating in which no depressions 20' are provided. Even if such an arrangement of the depressions 20 ′ is less advantageous in comparison to the first embodiment with regard to the retention capacity for oil, a corresponding piston is improved in comparison to the prior art with regard to the oil retention properties and thus has less friction.
Figur 4c) zeigt einen weiteren Kolben 10'', der nicht Teil der Erfindung ist. Auch dieser Kolben 10'' hat eine Beschichtung 18'', die Vertiefungen 20'' aufweist. Diese Vertiefungen 20'' erstrecken sich jedoch entlang der Umfangsrichtung des Kolben 10'' über die gesamte Breite der Beschichtung 18'' und sind damit nicht, wie dies die Erfindung verlangt, umschlossen. In den vorhergehenden Ausführungsformen der Figuren 4a) und 4b) erstrecken sich die Vertiefungen 20, 20' jeweils nur über einen Abschnitt der Beschichtung 18, 18' entlang der Umfangsrichtung, nicht aber über die gesamte Breite der Beschichtung 18, 18'. Dadurch, dass sich die Vertiefungen 20'' über die gesamte Breite der Beschichtung 18'' erstrecken, kann Öl aus ihnen abfließen. Dies führt dann zu einer im Vergleich zu Kolben, bei denen die Vertiefungen umschlossen sind, erhöhten Reibung. FIG. 4c) shows a further piston 10 ″ which is not part of the invention. This piston 10 ″ also has a coating 18 ″ which has depressions 20 ″. These depressions 20 ″, however, extend along the circumferential direction of the piston 10 ″ over the entire width of the coating 18 ″ and are therefore not enclosed, as required by the invention. In the previous embodiments of FIGS. 4a) and 4b), the depressions 20, 20 'each only extend over a section of the coating 18, 18' along the circumferential direction, but not over the entire width of the coating 18, 18 '. Thereby, that the depressions 20 ″ extend over the entire width of the coating 18 ″, oil can drain from them. This then leads to increased friction compared to pistons in which the depressions are enclosed.
Figur 4d) zeigt einen Kolben 10111, der nicht erfindungsgemäß ist. Hier sind in einer Beschichtung 18111 im Wesentlichen kreisförmige Vertiefungen 20111 vorgesehen, die in mehreren Reihen entlang der Umfangsrichtung des Kolbens 10111 angeordnet sind und die zueinander entlang der Umfangsrichtung versetzt sind. Die hier gezeigten Vertiefungen 20-'--'--'- erfüllen nicht das Erfordernis, dass S > 2 L, sondern sind zu eng angeordnet. Zudem gilt hier nicht E > L. FIG. 4d) shows a piston 10 111 which is not according to the invention. Essentially circular depressions 20 111 are provided here in a coating 18 111 , which are arranged in several rows along the circumferential direction of the piston 10 111 and which are offset from one another along the circumferential direction. The depressions 20 - '-' - '- shown here do not meet the requirement that S> 2 L, but are arranged too closely. In addition, E> L does not apply here.
Die in Figur 4a) bis 4d) gezeigten Beschichtungen 18 bis 18111 können durch ein Siebdruckverfahren hergestellt werden. The coatings 18 to 18 111 shown in FIGS. 4a) to 4d) can be produced by a screen printing process.

Claims

Ansprüche Expectations
1. Kolben (10) zur Verwendung in Verbrennungsmotoren mit: einem Kolbenboden (12), an den sich ein Kolbenschaft1. Piston (10) for use in internal combustion engines, comprising: a piston head (12) to which a piston skirt is attached
(14) anschließt, wobei der Kolbenschaft (14) Flächen (18) aufweist, die bei Verwendung des Kolbens an der Zylinderwand anliegen, wobei die Flächen (16) eine oder mehrere reibungsreduzierende Beschichtungen (18) aufweisen und wobei in der Beschichtung Vertiefungen (20) vorgesehen sind, die so angeordnet sind, dass der Abstand S zwischen je zwei benachbarten Vertiefungen (20) entlang der Axialrichtung (A) des Kolbens und die Breite L der Vertiefungen (20) entlang der Axialrichtung (A) des Kolbens der Formel S > 2 L genügen, wobei eine oder mehrere, bevorzugt alle, Vertiefungen (20) von der Beschichtung (18), in der sie ausgebildet sind, umschlossen sind, wobei mehrere der Vertiefungen (20) entlang des Umfangs des Kolbens (10) fluchtend in einer der einen oder mehreren Beschichtungen (18) vorgesehen sind. (14) adjoins, the piston skirt (14) having surfaces (18) which, when the piston is used, bear against the cylinder wall, the surfaces (16) having one or more friction-reducing coatings (18) and recesses (20 ) are provided, which are arranged such that the distance S between each two adjacent depressions (20) along the axial direction (A) of the piston and the width L of the depressions (20) along the axial direction (A) of the piston of the formula S> 2 L suffice, with one or more, preferably all, depressions (20) being enclosed by the coating (18) in which they are formed, with several of the depressions (20) aligned along the circumference of the piston (10) in a the one or more coatings (18) are provided.
2. Kolben nach Anspruch 1, wobei sich die Vertiefungen (20) durch die Beschichtung (18) erstrecken, so dass sie das2. Piston according to claim 1, wherein the recesses (20) through the coating (18) extend so that they
Material des Kolbenschafts (14) erreichen. Reach the material of the piston skirt (14).
3. Kolben nach Anspruch 1 oder 2, wobei sich die Begrenzungsflächen (17) der Vertiefungen (20) schräg bezüglich der Beschichtung (18) und dem Material der Flächen (16), an das sie angrenzen, erstrecken. 3. Piston according to claim 1 or 2, wherein the boundary surfaces (17) of the depressions (20) extend obliquely with respect to the coating (18) and the material of the surfaces (16) which they adjoin.
4. Kolben nach einem der vorhergehenden Ansprüche, wobei die Erstreckungslänge E zumindest einiger, bevorzugt aller Vertiefungen (20) entlang der Umfangsrichtung kürzer ist als die Erstreckungslänge E' entlang der Umfangsrichtung der Beschichtung (18), in der diese ausgebildet sind. 5. Kolben nach Anspruch 4, wobei zueinander in der Axialrichtung benachbarte Vertiefungen (20) entlang der Umfangsrichtung zueinander versetzt sind. 4. Piston according to one of the preceding claims, wherein the extension length E of at least some, preferably all of the depressions (20) along the circumferential direction is shorter than the extension length E 'along the circumferential direction of the coating (18) in which they are formed. 5. Piston according to claim 4, wherein recesses (20) which are adjacent to one another in the axial direction are offset from one another along the circumferential direction.
6. Kolben nach einem der vorhergehenden Ansprüche, wobei die Vertiefungen (20) eine im Wesentlichen rechteckige Form aufweisen . 6. Piston according to one of the preceding claims, wherein the recesses (20) have a substantially rectangular shape.
7. Kolben nach einem der vorhergehenden Ansprüche, wobei die Vertiefungen (20) eine Breite L von weniger als 2 mm und bevorzugt im Bereich von 0,6-0,8 mm haben. 7. Piston according to one of the preceding claims, wherein the recesses (20) have a width L of less than 2 mm and preferably in the range of 0.6-0.8 mm.
8. Verfahren zur Herstellung eines Kolbens nach einem der vorhergehenden Ansprüche, wobei die Beschichtung (18) einschließlich der Vertiefungen (20) mittels eines Siebdruckverfahrens aufgebracht wird. 8. A method for producing a piston according to any one of the preceding claims, wherein the coating (18) including the depressions (20) is applied by means of a screen printing process.
EP20820892.6A 2019-12-12 2020-12-07 Piston and method for producing same Pending EP4073370A1 (en)

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