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EP1745205A2 - Method of coating a surface with a dry lubricating film - Google Patents

Method of coating a surface with a dry lubricating film

Info

Publication number
EP1745205A2
EP1745205A2 EP05762671A EP05762671A EP1745205A2 EP 1745205 A2 EP1745205 A2 EP 1745205A2 EP 05762671 A EP05762671 A EP 05762671A EP 05762671 A EP05762671 A EP 05762671A EP 1745205 A2 EP1745205 A2 EP 1745205A2
Authority
EP
European Patent Office
Prior art keywords
coating
lubricating film
film
dry lubricating
paste
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.)
Withdrawn
Application number
EP05762671A
Other languages
German (de)
French (fr)
Inventor
Jean-Michel Bordes
Christian Coddet
Hanlin Liao
Cornélis MEEKEL
Ga Zhang
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.)
PSA Automobiles SA
Original Assignee
Peugeot Citroen Automobiles SA
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
Priority claimed from FR0405059A external-priority patent/FR2870320B1/en
Priority claimed from FR0451707A external-priority patent/FR2873783B1/en
Application filed by Peugeot Citroen Automobiles SA filed Critical Peugeot Citroen Automobiles SA
Publication of EP1745205A2 publication Critical patent/EP1745205A2/en
Withdrawn legal-status Critical Current

Links

Classifications

    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B05—SPRAYING OR ATOMISING IN GENERAL; APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
    • B05D—PROCESSES FOR APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
    • B05D5/00—Processes for applying liquids or other fluent materials to surfaces to obtain special surface effects, finishes or structures
    • B05D5/08—Processes for applying liquids or other fluent materials to surfaces to obtain special surface effects, finishes or structures to obtain an anti-friction or anti-adhesive surface
    • 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
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B05—SPRAYING OR ATOMISING IN GENERAL; APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
    • B05D—PROCESSES FOR APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
    • B05D1/00—Processes for applying liquids or other fluent materials
    • B05D1/32—Processes for applying liquids or other fluent materials using means for protecting parts of a surface not to be coated, e.g. using stencils, resists

Definitions

  • the present invention relates to a method for coating a surface, in particular a piston skirt of an internal combustion engine, with a dry lubricating film with high mechanical resistance and low coefficient of friction.
  • the object of the invention is mainly to reduce friction between the skirt of the piston and the cylinder. It is in fact known that the main function of the piston skirts is to guide the piston in the cylinder while avoiding any risk of seizure, the upper part of the piston being composed of ring holders which seal between the chamber and the lower part of the engine. The friction between the skirt and the resulting cylinder is therefore a source of noise, loss of energy and damage to the surfaces. In order to remedy these drawbacks, several solutions have been considered.
  • patent application EP0380415 describes a composite coating, based on a resin from the family of sulfonic polymers, which is fixed to the skirt of the piston by screwing, shrinking or gluing. This invention has the disadvantage of adding an assembly step between the piston skirt and the very restrictive coating in terms of manufacture and mechanical strength.
  • patent FR2808461 proposes a process for depositing pure polyaryietherketone by pure thermal spraying on the piston skirt, but it has the drawback of being restrictive in terms of equipment, since it requires the use of projection torches.
  • patent EP0614416 proposes a solution which consists in coating by transfer pad the piston skirt with a paste comprising a dry moistened lubricant then in drying the paste.
  • the dry lubricant is composed of a fluoropolymer or graphite or molybdenum disulphide mixed with a binder and a very volatile organic solvent such as acetone.
  • the object of the present invention is to propose a method for coating a surface, in particular a piston skirt of an internal combustion engine, with a dry lubricating film with high mechanical resistance and low coefficient of friction. overcoming all or part of the drawbacks noted in the prior art detailed above.
  • said process consists in: - coating the surface of a paste produced in an aqueous solvent and comprising a polymer with low coefficient of friction, - heating said film at a temperature T for a period t, of so that said film has an amorphous structure,
  • the step of coating the surface with the paste can be followed by a step of drying said paste so as to obtain a dry lubricating film.
  • the step of heating said film can be followed by a step of cooling said film so that said film largely retains its amorphous structure.
  • Said low friction polymer is preferably a polyaryiether ketone.
  • said paste can be produced from a mixture of water, a binder in the proportions of 2 to 5% by mass, a dispersant in the proportions of 1 to 3% by mass, of an anti-foaming agent in the proportions of 5 to 30 ppm, to which is added the polymer with a low coefficient of friction in the proportions of 60 to 80% by mass.
  • Said paste can also contain non-organic compounds with a lubricating property, and preferably in proportions of less than 10% by mass.
  • Said inorganic compounds are one or more of the following compounds: molybdenum disulphides, carbon, carbon nanotubes, silicon carbides or even graphite.
  • the step of coating the surface with said paste can be preceded by a step of preparing the surface which comprises at least a first step of cleaning said surface using a solvent or 'A detergent.
  • the temperature T is preferably between 350 ° C and 450 ° C.
  • the duration t is preferably between 5 s and 15 s.
  • the cleaning can be followed for example by a sandblasting operation which consists in spraying silica grains at high speed on the skirts 7a, 7b so as to create small impacts which favor the attachment of the film 3.
  • a sandblasting operation which consists in spraying silica grains at high speed on the skirts 7a, 7b so as to create small impacts which favor the attachment of the film 3.
  • this operation is optional insofar as the skirts 7a, 7b admit a base roughness of approximately 20 microns which allows sufficient attachment of the film 3 to said skirts.
  • the preparation of the dough is carried out from a mixture of water, a binder in the proportions of 2 to 5% by mass, a dispersant in the proportions of 1 to 3% by mass, of an anti-foaming agent in the proportions of 5 to 30 ppm, to which is added a polymer with a low coefficient of friction in the proportions of 60 to 80% by mass.
  • the proportions by percentage by mass refer to the total mass of the paste consisting of the mixture of water, binder, dispersant, anti-foaming agent, polymer with a low coefficient of friction.
  • the polymer with a low coefficient of friction is preferably a polyaryiether ketone sold under the name of Poly Ether Ether
  • Ketone PEEK TM. It is a semi-crystalline polymer, the basic formula of which is as follows: oxy-1, 4-phenylene-oxy-1, 4-phenylene-carbonyl-
  • Polyaryietherketone is a polymer with a low coefficient of friction which gives tribological properties to film 3 and which therefore makes it possible to significantly reduce the friction observed between the piston skirts and the cylinder. More precisely, compared with the results obtained with dry lubricating films comprising fluorinated polymers, graphite or molybdenum disulphide, a reduction of up to 20% in friction is observed in hydrodynamic lubrication regime, which allows a gain in consumption. in fuel of at least 1%. It was also chosen for its high chemical inertness and good mechanical performance, especially at high temperatures. In hydrodynamic regime, it indeed admits a surface energy at least twice lower than fluoropolymers, graphite and molybdenum disulfide.
  • the binder it is advantageous to use two ultra-fine powders of low viscosity, either with an average particle size of 25 ⁇ m, or with an average particle size of 10 ⁇ m.
  • RHODOVIOL 25/140 TM which is a polyvinyl alcohol obtained by hydrolysis of polyvinyl acetate. It helps to promote the adhesion of the paste on the surface to be coated.
  • anti-foaming agent it is advantageous to use the
  • BEVALOID 581 B TM It is a mixture of aliphatic hydrocarbons and nonionic surfactants. It avoids the foaming phenomena that appear when mixing PEEK TM powder in water. Regarding the dispersant, it is advantageous to use SINNOPAL OP11 TM. It is a non-anionic surfactant (Octylphenol ethoxyl), which avoids the settling of the PEEK TM powder in solution.
  • the preparation of the dough is carried out according to the same recommendations as those described in the first embodiment, except that one or more non-organic compounds with lubricating property are added in proportions less than 10% by mass.
  • the percentages by mass refer to the total mass of the paste made up of the water, binder, dispersant, anti-foaming agent, polymer with low friction coefficient, non-organic compounds with lubricating properties.
  • non-organic compounds with lubricating properties it is advantageous to use molybdenum disulphides, carbon nanotubes, carbon, silicon carbides or even graphite in proportions of less than 10% by mass.
  • These inorganic compounds are in the form of powder admitting an average particle size, G, in accordance with that specified in the table below:
  • the presence in the paste of one or more of these non-organic compounds is particularly desirable, insofar as they optimize the mechanical properties in terms of friction and of the wear resistance of the film 3.
  • the addition of molybdenum disulfide or carbon nanotubes in proportions of 10% by mass makes it possible to reduce by around 15% the coefficient of friction corresponding to a film obtained according to the first embodiment of the paste, that is to say with a paste produced from a mixture of water, a binder in the proportions of 2 to 5% by mass, a dispersant in the proportions of 1 to 3% by mass, an anti-foaming agent in the proportions of 5 to 30 ppm, and of the polyaryiether ketone in the proportions of 60 to 80% by mass.
  • the addition of molybdenum disulphides, carbon nanotubes, carbon, silicon carbides or even graphite in proportions of 10% by mass makes it possible to increase resistance to wear corresponding to a film obtained according to the first embodiment of the paste.
  • the process for depositing the dough on the skirt 7a, 7b can be carried out by a process of the screen printing type, which consists in rotating the piston 1 around its axis 2 and in bringing the skirt 7a, 7b into contact with a sieve, not shown in Figure 1, through which flows said dough.
  • a process of the screen printing type which consists in rotating the piston 1 around its axis 2 and in bringing the skirt 7a, 7b into contact with a sieve, not shown in Figure 1, through which flows said dough.
  • a thermal spraying process it is not necessary to mask the area of the grooves 5 of the piston 1 provided for the segments, to prevent the dough from being deposited there.
  • the piston 1 it is advantageous to heat the piston 1 to a temperature of approximately 200 ° C. in order on the one hand to dry the dough so as to obtain the dry lubricating film 3 and in order on the other part of avoiding the thermal shocks which result from the heat treatment which will follow and which is located at the level of said film 3 and not over the entire thickness of the skirt 7a, 7b.
  • a temperature T for a duration t.
  • the heating device can use YAG laser technology or C02 lasers with a power between 800 and
  • the temperature T is between 350 ° C and 450 ° C.
  • the duration t is between 5 s and 15 s. So that the film 3 largely retains its amorphous structure, it must then be cooled. Using the YAG laser heater as described above, simple cooling with ambient air results in a semi-crystalline structure. According to the method described above, the thickness of the film 3 is from 20 to 100 ⁇ m. According to an alternative sintering method, the film can be sintered by means of a heating device other than the laser, such as an induction heating device. The temperature T is then between 380 ° C and 450 ° C and the duration t is reduced to an interval of 4 to 8 s.
  • the cooling advantageously comprises a first air quenching intended to cool the surface of the skirt 7a, 7b to a temperature of approximately 260 ° C. then a second quenching with water, intended to bring the film 3 to the room temperature, while retaining an amorphous structure.

Landscapes

  • 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 invention relates to a method of coating a surface, such as the skirt (7a, 7b) of a piston (1) of an internal combustion engine, with a dry lubricating film (3) which has a high mechanical strength and a low friction coefficient and which is intended to reduce friction between the skirt (7a, 7b) of the piston (1) and the cylinder. The inventive method comprises the following steps consisting in: coating the surface (7a, 7b) with a paste which is disposed in an aqueous solvent and which comprises a polymer having a low friction coefficient and, optionally, non-organic compounds; and heating the film (3) to a temperature T for a time t, such that said film (3) assumes an amorphous structure.

Description

PROCEDE POUR REVETIR D'UN FILM LUBRIFIANT SEC UNE SURFACE La présente invention a pour objet un procédé pour revêtir une surface , notamment une jupe de piston d'un moteur à combustion interne, d'un film lubrifiant sec à haute résistance mécanique et à faible coefficient de frottement. Le but de l'invention est principalement de réduire les frottements entre la jupe du piston et le cylindre. Il est en effet connu que les jupes de piston ont pour fonction principale d'assurer le guidage du piston dans le cylindre en évitant tout risque de grippage, la partie supérieure du piston étant composée de porte-segments qui assurent l'étanchéité entre la chambre de combustion et la partie inférieure du moteur. Les frottements entre la jupe et le cylindre qui en résultent sont dès lors sources de bruit, de perte d'énergie et d'endommagement des surfaces. Afin de remédier à ces inconvénients, plusieurs solutions ont été envisagées. L'introduction d'un jeu de plusieurs microns entre la jupe et le cylindre accompagné d'un lubrifiant tel que de l'huile permet en effet d'éviter les problèmes de grippage mais crée une consommation d'huile importante. D'autres solutions consistant à revêtir la jupe d'un revêtement résistant au grippage et doté d'un faible coefficient de frottement semblent avoir été la piste privilégiée des constructeurs automobiles et des équipementiers. Ainsi, la demande de brevet EP0380415 décrit un revêtement composite, à base d'une résine de la famille des polymères sulfoniques, qui est fixé à la jupe du piston par vissage, frettage ou collage. Cette invention présente l'inconvénient d'ajouter une étape d'assemblage entre la jupe de piston et le revêtement très contraignante en terme de fabrication et de tenue mécanique. De même, le brevet FR2808461 propose un procédé de dépôt de polyaryiethercetone pur par projection thermique pur sur la jupe de piston, mais celui-ci présente l'inconvénient d'être contraignant en terme d'équipements, puisqu'il nécessite l'emploi de torches de projection. Enfin, le brevet EP0614416 propose une solution qui consiste à enduire par tampon de transfert la jupe de piston d'une pâte comportant un lubrifiant sec humidifié puis à sécher la pâte. Le lubrifiant sec est composé d'un polymère fluoré ou de graphite ou de bisulfure de molybdène mélangé à un liant et à un solvant organique très volatile tel que l'acétone. Ce procédé présente l'avantage d'être simple de mise en œuvre, puisqu'il repose essentiellement sur l'étape d'enduction par tampon de transfert, mais présente l'inconvénient d'utiliser un solvant organique très volatile, qui nécessite l'emploi d'accessoires de dépollution lourds à gérer dans une chaîne de production. De plus, si les polymères fluorés, le graphite et le bisulfure de molybdène confèrent au revêtement un bon coefficient de frottement, ils ne donnent pas pour autant satisfaction en terme de résistance mécanique. C'est pourquoi, le but de la présente invention est de proposer un procédé pour revêtir une surface, notamment une jupe de piston d'un moteur à combustion interne, d'un film lubrifiant sec à haute résistance mécanique et à faible coefficient de frottement palliant tout ou partie des inconvénients relevés dans l'art antérieur détaillé ci-avant. Ce but est atteint par le fait que ledit procédé consiste à : - Enduire la surface d'une pâte réalisée dans un solvant aqueux et comportant un polymère à faible coefficient de frottement, - Chauffer ledit film à une température T pendant une durée t, de manière à ce que ledit film admette une structure amorphe,The present invention relates to a method for coating a surface, in particular a piston skirt of an internal combustion engine, with a dry lubricating film with high mechanical resistance and low coefficient of friction. The object of the invention is mainly to reduce friction between the skirt of the piston and the cylinder. It is in fact known that the main function of the piston skirts is to guide the piston in the cylinder while avoiding any risk of seizure, the upper part of the piston being composed of ring holders which seal between the chamber and the lower part of the engine. The friction between the skirt and the resulting cylinder is therefore a source of noise, loss of energy and damage to the surfaces. In order to remedy these drawbacks, several solutions have been considered. The introduction of a play of several microns between the skirt and the cylinder accompanied by a lubricant such as oil indeed makes it possible to avoid the problems of seizing up but creates a significant consumption of oil. Other solutions consisting in coating the skirt with a coating resistant to seizing and provided with a low coefficient of friction seem to have been the preferred track of the automobile manufacturers and the equipment manufacturers. Thus, patent application EP0380415 describes a composite coating, based on a resin from the family of sulfonic polymers, which is fixed to the skirt of the piston by screwing, shrinking or gluing. This invention has the disadvantage of adding an assembly step between the piston skirt and the very restrictive coating in terms of manufacture and mechanical strength. Similarly, patent FR2808461 proposes a process for depositing pure polyaryietherketone by pure thermal spraying on the piston skirt, but it has the drawback of being restrictive in terms of equipment, since it requires the use of projection torches. Finally, patent EP0614416 proposes a solution which consists in coating by transfer pad the piston skirt with a paste comprising a dry moistened lubricant then in drying the paste. The dry lubricant is composed of a fluoropolymer or graphite or molybdenum disulphide mixed with a binder and a very volatile organic solvent such as acetone. This method has the advantage of being simple to implement, since it is essentially based on the step of coating with a transfer buffer, but has the disadvantage of using a very volatile organic solvent, which requires the use of heavy pollution control accessories to manage in a production chain. In addition, if the fluoropolymers, graphite and molybdenum disulphide give the coating a good coefficient of friction, they are not satisfactory in terms of mechanical strength. This is why, the object of the present invention is to propose a method for coating a surface, in particular a piston skirt of an internal combustion engine, with a dry lubricating film with high mechanical resistance and low coefficient of friction. overcoming all or part of the drawbacks noted in the prior art detailed above. This object is achieved by the fact that said process consists in: - coating the surface of a paste produced in an aqueous solvent and comprising a polymer with low coefficient of friction, - heating said film at a temperature T for a period t, of so that said film has an amorphous structure,
Selon d'autres caractéristiques : L'étape d'enduction de la surface par la pâte peut être suivie par une étape de séchage de ladite pâte de manière à obtenir un film lubrifiant sec. L'étape de chauffage dudit film peut être suivie par une étape de refroidissement dudit film de manière à ce que ledit film conserve en grande partie sa structure amorphe Ledit polymère à faible coefficient de frottement est de préférence un polyaryiethercetone. Selon un mode préféré de l'invention, ladite pâte peut être réalisée à partir d'un mélange composé d'eau, d'un liant dans les proportions de 2 à 5 % en masse, d'un dispersant dans les proportions de 1 à 3 % en masse, d'un agent anti-moussage dans les proportions de 5 à 30 ppm, auquel est ajouté le polymère à faible coefficient de frottement dans les proportions de 60 à 80 % en masse. Ladite pâte peut comporter en outre des composés non organiques à propriété lubrifiante, et de préférence dans des proportions inférieures à 10 % en masse. Lesdits composés non organiques sont un ou plusieurs des composés suivants : des bisulfures de molybdène, du carbone, des nanotubes de carbone, des carbures de silicium ou bien du graphite.According to other characteristics: The step of coating the surface with the paste can be followed by a step of drying said paste so as to obtain a dry lubricating film. The step of heating said film can be followed by a step of cooling said film so that said film largely retains its amorphous structure. Said low friction polymer is preferably a polyaryiether ketone. According to a preferred embodiment of the invention, said paste can be produced from a mixture of water, a binder in the proportions of 2 to 5% by mass, a dispersant in the proportions of 1 to 3% by mass, of an anti-foaming agent in the proportions of 5 to 30 ppm, to which is added the polymer with a low coefficient of friction in the proportions of 60 to 80% by mass. Said paste can also contain non-organic compounds with a lubricating property, and preferably in proportions of less than 10% by mass. Said inorganic compounds are one or more of the following compounds: molybdenum disulphides, carbon, carbon nanotubes, silicon carbides or even graphite.
Selon d'autres caractéristiques : L'étape d'enduction de la surface par ladite pâte peut être précédée d'une étape de préparation de la surface qui comporte au moins une première étape de nettoyage de ladite surface au moyen d'un solvant ou d'une lessive. La température T est comprise de préférence entre 350°C et 450°C. La durée t est comprise de préférence entre 5 s et 15 s. Un autre but de l'invention est de proposer deux jupes de piston de moteur à combustion interne revêtue d'un film lubrifiant sec suivant le procédé décrit ci-avant. L'invention sera mieux comprise à la lecture de la description qui suit et qui est rédigée à titre d'exemple non limitatif, et à l'unique figure annexée qui représente la partie supérieure d'un piston 1 de moteur à combustion interne comportant deux jupes 7a, 7b revêtues d'un film lubrifiant sec 3 conformément à l'invention. Préalablement au dépôt du film 3 sur les jupes 7a, 7b, la surface extérieure du piston 1 est nettoyée au moyen d'une lessive ou d'un solvant afin d'éliminer les impuretés ainsi qu'un éventuel revêtement protecteur appliqué pour protéger le piston 1 lors de son transport. Afin d'augmenter la rugosité des jupes 7a, 7b, le nettoyage peut être suivi par exemple par une opération de sablage qui consiste à projeter à grande vitesse des grains de silice sur les jupes 7a, 7b de manière à créer de petits impacts qui favorisent l'accrochage du film 3. Toutefois, cette opération est facultative dans la mesure où les jupes 7a, 7b admettent une rugosité de base de 20 microns environ qui permet un accrochage suffisant du film 3 sur lesdites jupes. Selon un premier mode de réalisation, la préparation de la pâte, non représentée sur la figure 1 , est réalisée à partir d'un mélange composé d'eau, d'un liant dans les proportions de 2 à 5 % en masse, d'un dispersant dans les proportions de 1 à 3 % en masse, d'un agent anti- moussage dans les proportions de 5 à 30 ppm, auquel est ajouté un polymère à faible coefficient de frottement dans les proportions de 60 à 80 % en masse. Les proportions en pourcentage en masse se réfèrent à la masse totale de la pâte constituée du mélange eau, liant, dispersant, agent anti-moussage, polymère à faible coefficient de frottement. Le polymère à faible coefficient de frottement est de préférence un polyaryiethercetone commercialisé sous le nom de Poly Ether EtherAccording to other characteristics: The step of coating the surface with said paste can be preceded by a step of preparing the surface which comprises at least a first step of cleaning said surface using a solvent or 'A detergent. The temperature T is preferably between 350 ° C and 450 ° C. The duration t is preferably between 5 s and 15 s. Another object of the invention is to provide two piston skirts of an internal combustion engine coated with a dry lubricating film according to the method described above. The invention will be better understood on reading the description which follows and which is drawn up by way of nonlimiting example, and in the single figure annexed which represents the upper part of a piston 1 of an internal combustion engine comprising two skirts 7a, 7b coated with a dry lubricating film 3 in accordance with the invention. Before depositing the film 3 on the skirts 7a, 7b, the external surface of the piston 1 is cleaned using a detergent or a solvent in order to remove the impurities as well as any protective coating applied to protect the piston 1 during transport. In order to increase the roughness of the skirts 7a, 7b, the cleaning can be followed for example by a sandblasting operation which consists in spraying silica grains at high speed on the skirts 7a, 7b so as to create small impacts which favor the attachment of the film 3. However, this operation is optional insofar as the skirts 7a, 7b admit a base roughness of approximately 20 microns which allows sufficient attachment of the film 3 to said skirts. According to a first embodiment, the preparation of the dough, not shown in Figure 1, is carried out from a mixture of water, a binder in the proportions of 2 to 5% by mass, a dispersant in the proportions of 1 to 3% by mass, of an anti-foaming agent in the proportions of 5 to 30 ppm, to which is added a polymer with a low coefficient of friction in the proportions of 60 to 80% by mass. The proportions by percentage by mass refer to the total mass of the paste consisting of the mixture of water, binder, dispersant, anti-foaming agent, polymer with a low coefficient of friction. The polymer with a low coefficient of friction is preferably a polyaryiether ketone sold under the name of Poly Ether Ether
Ketone (PEEK ™). Il s'agit d'un polymère semi-cristallin dont la formule de base est la suivante : oxy-1 ,4-phénylène-oxy-1 ,4-phénylène-carbonyle-Ketone (PEEK ™). It is a semi-crystalline polymer, the basic formula of which is as follows: oxy-1, 4-phenylene-oxy-1, 4-phenylene-carbonyl-
1 ,4-phénylène, représentée sur la figure ci-après :1, 4-phenylene, shown in the figure below:
Le polyaryiethercetone est un polymère à faible coefficient de frottement qui confère les propriétés tribologiques au film 3 et qui permet par conséquent de diminuer de manière significative les frottements observés entre les jupes de piston et le cylindre. Plus précisément, par rapport aux résultats obtenus avec des films lubrifiants secs comportant des polymères fluorés, du graphite ou du bisulfure de molybdène, on observe une réduction jusqu'à 20 % des frottements en régime de lubrification hydrodynamique, ce qui autorise un gain de consommation en carburant d'au moins 1%. Il a également été choisi pour sa grande inertie chimique et ses bonnes performances mécaniques notamment à hautes températures. En régime hydrodynamique, il admet en effet une énergie de surface au moins deux fois plus faible que les polymères fluorés, le graphite et le bisulfure de molybdène. Pour l'invention, il est avantageux d'utiliser deux poudres ultra-fines de faible viscosité, soit de granulométrie moyenne de 25μm, soit de granulométrie moyenne 10μm. Concernant le liant, il est avantageux d'employer le RHODOVIOL 25/140 ™ qui est un alcool polyvinylique obtenu par hydrolyse de l'acétate de polyvinyle. Il permet de favoriser l'adhérence de la pâte sur la surface à revêtir. Concernant l'agent anti-moussage, il est avantageux d'employer le Polyaryietherketone is a polymer with a low coefficient of friction which gives tribological properties to film 3 and which therefore makes it possible to significantly reduce the friction observed between the piston skirts and the cylinder. More precisely, compared with the results obtained with dry lubricating films comprising fluorinated polymers, graphite or molybdenum disulphide, a reduction of up to 20% in friction is observed in hydrodynamic lubrication regime, which allows a gain in consumption. in fuel of at least 1%. It was also chosen for its high chemical inertness and good mechanical performance, especially at high temperatures. In hydrodynamic regime, it indeed admits a surface energy at least twice lower than fluoropolymers, graphite and molybdenum disulfide. For the invention, it is advantageous to use two ultra-fine powders of low viscosity, either with an average particle size of 25 μm, or with an average particle size of 10 μm. Regarding the binder, it is advantageous to use RHODOVIOL 25/140 ™ which is a polyvinyl alcohol obtained by hydrolysis of polyvinyl acetate. It helps to promote the adhesion of the paste on the surface to be coated. Regarding the anti-foaming agent, it is advantageous to use the
BEVALOID 581 B ™. Il s'agit d'un mélange d'hydrocarbures aliphatiques et de tensioactifs non ioniques. Il permet d'éviter les phénomènes de moussage qui apparaissent quand on mélange la poudre de PEEK ™ dans l'eau. Concernant le dispersant, il est avantageux d'employer le SINNOPAL OP11 ™. Il s'agit d'un tensioactif non anionique (Octylphénol ethoxyle), qui permet d'éviter la décantation de la poudre de PEEK ™ en solution. Selon un second mode de réalisation, la préparation de la pâte s'effectue suivant les mêmes préconisations que celles décrites dans le premier mode de réalisation, si ce n'est que l'on ajoute un ou plusieurs composés non organiques à propriété lubrifiante dans des proportions inférieures à 10 % en masse. Les proportions en pourcentage en masse se réfèrent à la masse totale de la pâte constituée du mélange eau, liant, dispersant, agent anti-moussage, polymère à faible coefficient de frottement, composés non organiques à propriété lubrifiante. Concernant les composés non organiques à propriété lubrifiante, il est avantageux d'utiliser des bisulfures de molybdène, des nanotubes de carbone, du carbone, des carbures de silicium ou bien du graphite dans des proportions inférieures à 10 % en masse. Ces composés non organiques se présentent sous la forme de poudre admettant une granulométrie moyenne, G, conforme à celle spécifiée dans le tableau ci- après :BEVALOID 581 B ™. It is a mixture of aliphatic hydrocarbons and nonionic surfactants. It avoids the foaming phenomena that appear when mixing PEEK ™ powder in water. Regarding the dispersant, it is advantageous to use SINNOPAL OP11 ™. It is a non-anionic surfactant (Octylphenol ethoxyl), which avoids the settling of the PEEK ™ powder in solution. According to a second embodiment, the preparation of the dough is carried out according to the same recommendations as those described in the first embodiment, except that one or more non-organic compounds with lubricating property are added in proportions less than 10% by mass. The percentages by mass refer to the total mass of the paste made up of the water, binder, dispersant, anti-foaming agent, polymer with low friction coefficient, non-organic compounds with lubricating properties. With regard to non-organic compounds with lubricating properties, it is advantageous to use molybdenum disulphides, carbon nanotubes, carbon, silicon carbides or even graphite in proportions of less than 10% by mass. These inorganic compounds are in the form of powder admitting an average particle size, G, in accordance with that specified in the table below:
La présence dans la pâte d'un ou plusieurs de ces composés non organiques est particulièrement souhaitable, dans la mesure où ils optimisent les propriétés mécaniques en terme de frottement et de résistance à l'usure du film 3. En effet, l'addition de bisulfure de molybdène ou de nanotubes de carbone dans des proportions de 10% en masse, permet de diminuer d'environ 15 % le coefficient de frottement correspondant à un film obtenu selon le premier mode de réalisation de la pâte, c'est à dire avec une pâte réalisée à partir d'un mélange composé d'eau, d'un liant dans les proportions de 2 à 5 % en masse, d'un dispersant dans les proportions de 1 à 3 % en masse, d'un agent anti-moussage dans les proportions de 5 à 30 ppm, et du polyaryiethercetone dans les proportions de 60 à 80 % en masse. De même, l'addition de bisulfures de molybdène, des nanotubes de carbone, du carbone, des carbures de silicium ou bien du graphite dans des proportions de 10% en masse, permet d'augmenter jusqu'à 75% la résistance à l'usure correspondant à un film obtenu selon le premier mode de réalisation de la pâte. Le procédé de dépôt de la pâte sur la jupe 7a, 7b peut être effectué par un procédé du type sérigraphie, qui consiste à faire tourner le piston 1 autour de son axe 2 et à mettre en contact la jupe 7a, 7b avec un tamis, non représenté sur la figure 1 , au travers duquel s'écoule ladite pâte. Avantageusement, et contrairement à un procédé de projection thermique, il n'est pas nécessaire de masquer la zone des gorges 5 du piston 1 prévues pour les segments, pour éviter que la pâte ne s'y dépose. Une fois la jupe 7a, 7b ainsi revêtue, il est avantageux de chauffer le piston 1 à une température d'environ 200 °C afin d'une part de sécher la pâte de manière à obtenir le film lubrifiant sec 3 et afin d'autre part d'éviter les chocs thermiques qui résultent du traitement thermique qui va suivre et qui est localisé au niveau dudit film 3 et non sur toute l'épaisseur de la jupe 7a, 7b. En effet, afin que ledit film 3 admette une structure amorphe, il est nécessaire de le fritter, c'est à dire de le chauffer à une température T pendant une durée t. Le dispositif de chauffage peut utiliser la technologie des lasers YAG ou des lasers au C02 de puissance comprise entre 800 etThe presence in the paste of one or more of these non-organic compounds is particularly desirable, insofar as they optimize the mechanical properties in terms of friction and of the wear resistance of the film 3. In fact, the addition of molybdenum disulfide or carbon nanotubes in proportions of 10% by mass, makes it possible to reduce by around 15% the coefficient of friction corresponding to a film obtained according to the first embodiment of the paste, that is to say with a paste produced from a mixture of water, a binder in the proportions of 2 to 5% by mass, a dispersant in the proportions of 1 to 3% by mass, an anti-foaming agent in the proportions of 5 to 30 ppm, and of the polyaryiether ketone in the proportions of 60 to 80% by mass. Likewise, the addition of molybdenum disulphides, carbon nanotubes, carbon, silicon carbides or even graphite in proportions of 10% by mass, makes it possible to increase resistance to wear corresponding to a film obtained according to the first embodiment of the paste. The process for depositing the dough on the skirt 7a, 7b can be carried out by a process of the screen printing type, which consists in rotating the piston 1 around its axis 2 and in bringing the skirt 7a, 7b into contact with a sieve, not shown in Figure 1, through which flows said dough. Advantageously, and unlike a thermal spraying process, it is not necessary to mask the area of the grooves 5 of the piston 1 provided for the segments, to prevent the dough from being deposited there. Once the skirt 7a, 7b thus coated, it is advantageous to heat the piston 1 to a temperature of approximately 200 ° C. in order on the one hand to dry the dough so as to obtain the dry lubricating film 3 and in order on the other part of avoiding the thermal shocks which result from the heat treatment which will follow and which is located at the level of said film 3 and not over the entire thickness of the skirt 7a, 7b. In fact, in order for said film 3 to have an amorphous structure, it is necessary to sinter it, that is to say to heat it to a temperature T for a duration t. The heating device can use YAG laser technology or C02 lasers with a power between 800 and
5000 Watt. Avantageusement, la température T est comprise entre 350°C et 450°C. Avantageusement, la durée t est comprise entre 5 s et 15 s. De manière à ce que le film 3 conserve en grande partie sa structure amorphe, il faut ensuite procéder à son refroidissement. En utilisant le dispositif de chauffage au laser YAG comme décrit ci-dessus, un simple refroidissement à l'air ambiant permet d'obtenir une structure semi-cristalline. Suivant le procédé décrit précédemment, l'épaisseur du film 3 est de 20 à 100μm. Suivant un mode de frittage alternatif, on peut fritter le film au moyen d'un autre dispositif de chauffage que le laser, tel qu'un dispositif de chauffage par induction. La température T est alors comprise entre 380°C et 450°C et la durée t est réduite à un intervalle de 4 à 8 s. Le refroidissement comporte avantageusement une première trempe à l'air destinée à refroidir la surface de la jupe 7a, 7b jusqu'à une température d'environ 260°C puis une seconde trempe à l'eau, destinée à ramener le film 3 à la température ambiante, tout en lui conservant une structure amorphe. 5000 Watt. Advantageously, the temperature T is between 350 ° C and 450 ° C. Advantageously, the duration t is between 5 s and 15 s. So that the film 3 largely retains its amorphous structure, it must then be cooled. Using the YAG laser heater as described above, simple cooling with ambient air results in a semi-crystalline structure. According to the method described above, the thickness of the film 3 is from 20 to 100 μm. According to an alternative sintering method, the film can be sintered by means of a heating device other than the laser, such as an induction heating device. The temperature T is then between 380 ° C and 450 ° C and the duration t is reduced to an interval of 4 to 8 s. The cooling advantageously comprises a first air quenching intended to cool the surface of the skirt 7a, 7b to a temperature of approximately 260 ° C. then a second quenching with water, intended to bring the film 3 to the room temperature, while retaining an amorphous structure.

Claims

REVENDICATIONS
1. Procédé pour revêtir d'un film lubrifiant sec (3) une surface (7a, 7b) caractérisé en ce qu'il consiste à : a) Enduire la surface (7a, 7b) d'une pâte réalisée dans un solvant aqueux et comportant un polymère à faible coefficient de frottement, b) Chauffer ledit film (3) à une température T pendant une durée t, pour induire une structure amorphe,1. Process for coating a surface (7a, 7b) with a dry lubricating film (3), characterized in that it consists in: a) coating the surface (7a, 7b) with a paste produced in an aqueous solvent and comprising a low friction polymer, b) heating said film (3) at a temperature T for a period t, to induce an amorphous structure,
2. Procédé pour revêtir d'un film lubrifiant sec (3) une surface (7a, 7b), selon la revendication 1 , caractérisé en ce que l'étape d'enduction de la surface (7a, 7b) par la pâte est suivie par une étape de séchage de ladite pâte de manière à obtenir un film lubrifiant sec (3).2. Method for coating with a dry lubricating film (3) a surface (7a, 7b), according to claim 1, characterized in that the step of coating the surface (7a, 7b) with the paste is followed by a step of drying said paste so as to obtain a dry lubricating film (3).
3. Procédé pour revêtir d'un film lubrifiant sec (3) une surface (7a, 7b), selon l'une quelconque des revendications précédentes, caractérisé en ce que l'étape de chauffage du film est suivie par une étape de refroidissement dudit film (3) de manière à ce que ledit film (3) conserve en grande partie sa structure amorphe.3. Method for coating with a dry lubricating film (3) a surface (7a, 7b), according to any one of the preceding claims, characterized in that the step of heating the film is followed by a step of cooling said film (3) so that said film (3) largely retains its amorphous structure.
Procédé pour revêtir d'un film lubrifiant sec (3) une surface (7a, 7b), selon l'une quelconque des revendications précédentes, caractérisé en ce que le polymère à faible coefficient de frottement est un polyaryiethercetone.Method for coating a surface (7a, 7b) with a dry lubricating film (3) according to any one of the preceding claims, characterized in that the low-friction polymer is a polyaryietherketone.
5. Procédé pour revêtir d'un film lubrifiant sec (3) une surface (7a, 7b), selon l'une quelconque des revendications précédentes, caractérisé en ce que ladite pâte est réalisée à partir d'un mélange composé d'eau, d'un liant dans les proportions de 2 à 5 % en masse, d'un dispersant dans les proportions de 1 à 3 % en masse, d'un agent anti-moussage dans les proportions de 5 à 30 ppm, auquel est ajouté le polymère à faible coefficient de frottement dans les proportions de 60 à 80 % en masse. 5. Method for coating with a dry lubricating film (3) a surface (7a, 7b), according to any one of the preceding claims, characterized in that said paste is produced from a mixture composed of water, of a binder in the proportions of 2 to 5% by mass, of a dispersant in the proportions of 1 to 3% by mass, of an anti-foaming agent in the proportions of 5 to 30 ppm, to which the polymer with low coefficient of friction in the proportions of 60 to 80% by mass.
6. Procédé pour revêtir d'un film lubrifiant sec (3) une surface (7a, 7b), selon l'une quelconque des revendications précédentes, caractérisé en ce que la pâte comprend de plus des composés non organiques à propriétés lubrifiantes.6. Method for coating with a dry lubricating film (3) a surface (7a, 7b), according to any one of the preceding claims, characterized in that the paste also comprises non-organic compounds with lubricating properties.
7. Procédé pour revêtir d'un film lubrifiant sec (3) une surface (7a, 7b), selon la revendication 6, caractérisé en ce que la pâte comprend des composés non organiques dans des proportions inférieures à 10 % en masse.7. Method for coating with a dry lubricating film (3) a surface (7a, 7b), according to claim 6, characterized in that the paste comprises non-organic compounds in proportions of less than 10% by mass.
8. Procédé pour revêtir d'un film lubrifiant sec (3) une surface (7a, 7b), selon l'une quelconques des revendications 6 à 7, caractérisé en ce que les composés non organiques sont choisis dans le groupe de composés constitué par les bisulfures de molybdène, le carbone, les nanotubes de carbone, les carbures de silicium, le graphite, et le mélange desdits composés.8. Method for coating a surface (7a, 7b) with a dry lubricating film (3), according to any one of claims 6 to 7, characterized in that the inorganic compounds are chosen from the group of compounds consisting of molybdenum disulphides, carbon, carbon nanotubes, silicon carbides, graphite, and the mixture of said compounds.
9. Procédé pour revêtir d'un film lubrifiant sec (3) une surface (7a, 7b), selon l'une quelconques des revendications précédentes, caractérisé en ce que l'étape d'enduction de la surface par ladite pâte est précédée d'une étape de préparation de la surface (7a, 7b) qui comporte au moins une première étape de nettoyage de ladite surface (7a, 7b) au moyen d'un solvant ou d'une lessive,9. Method for coating a surface (7a, 7b) with a dry lubricating film (3), according to any one of the preceding claims, characterized in that the step of coating the surface with said paste is preceded by 'a step of preparing the surface (7a, 7b) which comprises at least a first step of cleaning said surface (7a, 7b) using a solvent or a detergent,
10. Procédé pour revêtir d'un film lubrifiant sec (3) une surface (7a, 7b), selon la revendication précédente, caractérisé en ce que l'étape de préparation de la surface (7a, 7b) comporte une seconde étape permettant d'augmenter la rugosité de ladite surface,10. Method for coating a dry lubricating film (3) on a surface (7a, 7b), according to the preceding claim, characterized in that the step of preparing the surface (7a, 7b) comprises a second step allowing d 'increase the roughness of said surface,
11. Procédé pour revêtir d'un film lubrifiant sec (3) une surface (7a, 7b), selon l'une quelconque des revendications précédentes, caractérisé en ce que la température T est comprise entre 350°C et 450°C, 11. Method for coating a surface (7a, 7b) with a dry lubricating film (3), according to any one of the preceding claims, characterized in that the temperature T is between 350 ° C and 450 ° C,
12. Procédé pour revêtir d'un film lubrifiant sec (3) une surface (7a, 7b), selon l'une quelconque des revendications précédentes, caractérisé en ce que la durée t est comprise entre 5 s et 15 s,12. Method for coating a surface (7a, 7b) with a dry lubricating film (3), according to any one of the preceding claims, characterized in that the duration t is between 5 s and 15 s,
13. Jupe (7a, 7b) de piston (1 ) de moteur à combustion interne, caractérisée en ce qu'elles sont revêtues d'un film lubrifiant sec (3) suivant le procédé conformément à l'une des revendications précédentes. 13. Skirt (7a, 7b) of piston (1) of internal combustion engine, characterized in that they are coated with a dry lubricating film (3) according to the method according to one of the preceding claims.
EP05762671A 2004-05-11 2005-05-11 Method of coating a surface with a dry lubricating film Withdrawn EP1745205A2 (en)

Applications Claiming Priority (3)

Application Number Priority Date Filing Date Title
FR0405059A FR2870320B1 (en) 2004-05-11 2004-05-11 METHOD FOR COATING DRY LUBRICANT FILM WITH CONVEX SURFACE
FR0451707A FR2873783B1 (en) 2004-07-29 2004-07-29 PROCESS FOR COATING DRY LUBRICANT FILM WITH CONVEX SURFACE
PCT/FR2005/050312 WO2005114038A2 (en) 2004-05-11 2005-05-11 Method of coating a surface with a dry lubricating film

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JP6286527B2 (en) 2013-03-15 2018-02-28 マーレ インターナショナル ゲゼルシャフト ミット ベシュレンクテル ハフツングＭＡＨＬＥ Ｉｎｔｅｒｎａｔｉｏｎａｌ ＧｍｂＨ Anti-friction coating for piston assembly
JP6259585B2 (en) * 2013-04-30 2018-01-10 日野自動車株式会社 Piston sliding part lubrication structure

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DE2655712B2 (en) * 1976-12-09 1979-06-21 Mahle Gmbh, 7000 Stuttgart , Piston with coated sliding surface for internal combustion engines
US5174193A (en) * 1990-06-23 1992-12-29 T&N Technology Limited Pistons for engines or motors
US5266142A (en) * 1991-11-01 1993-11-30 Decc Technology Partnership A Limited Partnership Coated piston and method and apparatus of coating the same
JPH06316686A (en) * 1992-10-30 1994-11-15 Nikken Toso Kogyo Kk Pfa-peek composite coating film
JP2881633B2 (en) * 1995-02-01 1999-04-12 大同メタル工業株式会社 Wet multi-layer bearing for compressor and method of manufacturing the same
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FR2808461B1 (en) * 2000-05-04 2003-02-28 Peugeot Citroen Automobiles Sa PROCESS FOR REDUCING FRICTION BETWEEN AT LEAST TWO METAL PARTS AND PISTON OBTAINED BY THE PROCESS

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