JP2004068815A - Piston ring - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a piston ring to maintain a high aluminum agglutination preventing effect for a long period of time by forming a solid lubricant dispersed film with a material having high heat resistance and mechanical strength and low hygroscopicity as a heat resistant material on a piston ring side surface. <P>SOLUTION: The film made of the heat resistant material at least on one side surface of which the solid lubricant is dispersed is provided on the piston ring for an internal combustion engine, and the heat resistant material is formed of at least one kind of a polyamide-imide silicon dioxide hybrid material and a polyimide silicon dioxide hybrid material. <P>COPYRIGHT: (C)2004,JPO

Description

The present invention relates to a piston ring for an internal combustion engine coated with a resin film having a low coefficient of friction.

In an internal combustion engine, the reciprocation of the piston is repeated due to the explosion of fuel in the combustion chamber, and the collision between the piston ring groove and the piston ring is repeated accordingly. Due to the explosion, the temperature near the top ring of a gasoline engine is likely to rise to nearly 250 ° C, and it is expected that the temperature will rise further in a diesel engine. When the piston ring is hit at such a high temperature, the piston ring groove surface of the piston made of an aluminum alloy is fatigue-ruptured, causing surface peeling and aluminum pieces falling off. Further, a phenomenon occurs in which the dropped aluminum alloy piece or the aluminum alloy on the exposed surface due to the falling off adheres to the side surface of the piston ring. This is called aluminum adhesion. When this aluminum adhesion progresses, the piston ring sticks to the piston ring groove, the sealing performance of the piston ring is impaired, and a phenomenon called “blow-by” occurs in which high-pressure combustion gas flows out from the combustion chamber to the crank chamber. This causes a decrease in engine output. In addition, the oil seal function is lost, resulting in an increase in oil consumption.

In order to prevent such sticking between the piston ring groove and the top piston ring due to aluminum adhesion, a number of methods for preventing the top ring from directly contacting the aluminum alloy piston have been proposed.

As a countermeasure on the piston side, as disclosed in JP-A-63-170546, a method of subjecting the piston ring groove to anodizing treatment (alumite treatment) and further filling the micropores with a lubricating substance. No. Since a hard oxide film containing aluminum oxide as a main component is formed on the piston ring groove surface by the alumite treatment, the aluminum powder is prevented from falling off, and the adhesion to the piston ring does not occur. However, the alumite treatment of the piston has a disadvantage of high cost.

対 策 As a countermeasure on the piston ring side, there are the methods disclosed in Japanese Utility Model Laid-Open No. 60-82552 and Japanese Patent Application Laid-Open No. 62-233458. According to the method disclosed in Japanese Utility Model Application Laid-open No. 60-82552, a phosphate film or triiron tetroxide film is formed on the side surface of the piston ring, and a solid lubricant such as molybdenum disulfide, graphite, carbon, and boron nitride is formed thereon. A heat and abrasion resistant resin film of a dispersed tetrafluoroethylene resin or oxybenzoyl polyester resin is formed. In the method disclosed in JP-A-62-233458, a film in which a solid lubricant such as molybdenum disulfide is dispersed in a heat-resistant resin such as an epoxy resin, a phenol resin, a polyamide resin, or a polyimide resin is coated on the piston ring side. Formed. The content of molybdenum disulfide, which is a solid lubricant, is desirably 60 to 95% by mass, and the solid lubricant itself is cleaved to reduce the coefficient of friction between the piston ring groove and the side surface of the piston ring. However, since the heat-resistant resin which is the base material of the film is soft, even if the wear of the piston ring groove is reduced by the solid lubricant, the wear cannot be completely suppressed. For this reason, the piston ring manufactured by this method is effective in preventing the adhesion of aluminum at the initial stage, but has insufficient durability. In particular, in a high-power engine, the resin film is worn away in a relatively short period of time due to high temperature and strong tapping, and the aluminum alloy in the piston ring groove comes into contact with the side surface of the piston ring, so that aluminum adhesion proceeds.

Japanese Patent Laid-Open No. 9-184079 discloses a coating for improving durability. This film has a coarser manganese phosphate undercoat than conventional ones, and the molybdenum disulfide particles dispersed in the undercoat have a particle size of 1 to 2 μm. Thus, adhesion of aluminum can be prevented for a long period of time. However, although the durability is improved, there is a problem that the aluminum adhesion preventing effect is low because the projections of the manganese phosphate base coat come into contact with aluminum early.

ポ リ ア ミ ド Polyamideimide (PAI) is the main binder that has been used for coatings to prevent aluminum adhesion. Polyamide imide is a resin having both excellent heat resistance and flexibility, but has high hygroscopicity because it is a polar molecule. For this reason, there is a possibility that moisture may be absorbed by coming into contact with steam generated at a high temperature in combustion of the hydrocarbon fuel in the engine. Polyamide imide that has absorbed moisture has extremely poor mechanical strength, flexibility, and adhesion to the substrate, etc. as compared to before absorbing moisture. It is easily broken or peeled off by sliding, and the film is worn away. The same applies to polyimide (PI). As described above, there is a possibility that the conventional resin film did not have sufficient durability due to moisture absorption of the binder.

ポ リ ア ミ ド In addition, since polyamideimide and polyimide are organic high molecular compounds, they are easily oxidized and decomposed at high temperatures. Therefore, there is a problem that the engine with high combustion temperature has poor durability, and it may not be possible to cope with the rise of the piston ring temperature due to the high top of the piston ring for the purpose of increasing the output of the engine and complying with strict exhaust gas regulations. There is.

Recently, organic-inorganic hybrid materials have attracted attention as a material having both advantages of organic compounds and inorganic compounds. JP-A-2001-240670 discloses a polyamideimide-silicon dioxide hybrid material having improved mechanical strength and heat resistance while maintaining the inherent flexibility and extensibility of polyamideimide. This polyamideimide-silicon dioxide hybrid material can be obtained by heat-treating a silane-modified polyamideimide resin prepared by grafting alkoxysilane to a polyamideimide having a carboxyl group (—COOH) or an acid anhydride group at a terminal. . "Polymer Preprint, Japan," Vol. 49, No. 14 (2000) states that the polyamide-imide-silicon dioxide hybrid material has a lower moisture absorption than the polyamide-imide itself.

"Plastics Age," Mar. 2002, 130-132, and "Polymer Preprint, Japan," Vol. 50, No. 11 (2001) describe the side chain of polyamic acid composed of pyromellitic acid and oxadianiline. It is described that a heat treatment of a silane-modified polyamic acid prepared by grafting methoxysilane gives a polyimide-silicon dioxide hybrid material having significantly higher breaking strength and tensile modulus than polyimide itself.

However, although the polyamideimide-silicon dioxide hybrid material and the polyimide-silicon dioxide hybrid material have excellent heat resistance and mechanical strength, the effect of preventing aluminum adhesion is not always satisfactory.

JP 2001-240670 A "Plastics Age", March 2002, pp.130-132

Therefore, an object of the present invention is to form a solid lubricant dispersion film having a high heat resistance and a high mechanical strength and a low hygroscopic property on a side surface of a piston ring as a binder, thereby achieving a high aluminum adhesion preventing effect over a long period of time. It is to provide a lasting piston ring.

As a result of intensive studies in view of the above problems, the present inventors have found that polyamideimide or polyimide, which has been used as a heat-resistant material in a conventional resin film, has at least a polyamideimide-silicon dioxide hybrid material and a polyimide-silicon dioxide hybrid material. By replacing with a heat-resistant material consisting of one, the heat resistance of the resin film, the mechanical strength, and the adhesion to the base are improved, and the moisture absorption is reduced, thereby reducing the wear rate of the resin film. As a result, the present inventors have found that aluminum adhesion to the side of the piston ring can be prevented for a long period of time, and arrived at the present invention.

That is, the piston ring for an internal combustion engine of the present invention has a film made of a heat-resistant material in which a solid lubricant is dispersed on at least one side surface, and the heat-resistant material is a polyamideimide-silicon dioxide hybrid material and a polyimide-silicon dioxide. It is characterized by comprising at least one kind of hybrid material.

The solid lubricant is made of at least one of an inorganic compound, an inorganic simple substance and a fluororesin, and preferably has an average particle diameter of 0.1 to 20 μm. Specifically, the solid lubricant was selected from the group consisting of molybdenum disulfide, tungsten disulfide, boron nitride, graphite, polytetrafluoroethylene resin, and ethylene tetrafluoride / perfluoroalkyl vinyl ether copolymer resin. Preferably, it is at least one. Further, the content of the solid lubricant is preferably 5 to 80% by mass of the whole coating.

ピ ス ト ン In the piston ring having the coating, a nitride layer having a thickness of 3 to 120 μm may be formed on the surface of the piston ring base material.

The piston ring of the present invention is excellent in mechanical strength and flexibility, and has a low hygroscopic property, a polyamideimide-silicon dioxide hybrid material, a polyimide-silicon dioxide hybrid material, and a mixed material thereof as a binder of a solid lubricant dispersion film, The solid lubricant dispersed film is provided on at least one side of the piston ring. Therefore, the effect of preventing or delaying the aluminum adhesion generated between the top ring groove and the top ring is larger than that of the conventional aluminum anti-adhesion coating.

[1] Piston Ring Base Material The piston ring base material is not particularly limited, but is preferably made of a material having excellent durability. Preferred materials include steel, martensitic stainless steel, austenitic stainless steel, high-grade cast iron, titanium alloy and the like. In addition, the piston ring base material may be subjected to a treatment such as nitriding, phosphating, and plating in advance.

[2] Resin film The resin film contains a heat-resistant material composed of at least one of a polyamideimide-silicon dioxide hybrid material and a polyimide-silicon dioxide hybrid material, and solid lubricant particles sufficiently dispersed in the heat-resistant material.

(1) Heat resistant material The heat resistant material is made of at least one of a polyamideimide-silicon dioxide hybrid material and a polyimide-silicon dioxide hybrid material, and forms a resin film as a binder. The term "hybrid material" as used herein means a so-called organic-inorganic hybrid material in which an organic material and a metal oxide are complexed or bonded. The organic-inorganic hybrid material is not a simple mixture of an organic compound and an inorganic compound, but is a compound obtained by compounding both at the molecular level in the synthesis stage. As the hybrid material, a material obtained by heat-treating a silane-modified resin and oxidizing silane to silicon dioxide is preferable. The silane-modified resin is obtained by reacting a polyamideimide and / or a polyimide with a glycidyl ether group-containing alkoxysilane partial condensate. A film containing an organic-inorganic hybrid material as a heat-resistant material has low hygroscopicity, high heat resistance, high mechanical strength, and high adhesion to a substrate, and has high flexibility, and therefore has high durability. In order to obtain a film having excellent durability, the ratio of silicon dioxide contained in the hybrid material is preferably 0.2 to 30% by mass. When the amount is less than 0.2% by mass, it is difficult to obtain the effect of reducing the hygroscopicity and the effect of improving the mechanical strength.

(2) Solid Lubricant As the solid lubricant, it is preferable to use an inorganic solid lubricant and a fluororesin alone or in combination. Inorganic solid lubricants reduce the coefficient of friction of the film by cleaving themselves when the film slides, so the film in which these are dispersed has high wear resistance and prevents aluminum adhesion for a long time. Can be. Examples of the inorganic solid lubricant include inorganic compounds such as molybdenum disulfide, tungsten disulfide, and boron nitride, and inorganic simple substances such as graphite.

Fluororesin has low reactivity with other substances and low reactivity between fluororesins, and thus has a low friction coefficient and functions as a solid lubricant. Preferred examples include polytetrafluoroethylene (PTFE), which is a linear polymer of ethylene tetrafluoride (CF ₂ = CF ₂ ), and ethylene tetrafluoride / perfluoroalkyl vinyl ether copolymer resin (PFA). No. Polytetrafluoroethylene (PTFE) has particularly excellent solid lubrication function among fluororesins, and has a low coefficient of friction. Further, since the fluororesin has extensibility, it tends to spread on a sliding surface by being hit and sliding. For this reason, the film in which the fluororesin is dispersed has high wear resistance. In particular, when the fluororesin content is high, the thin film generated by spreading the fluororesin covers the entire film, so that the coefficient of friction is lower and the film has excellent durability, and the aluminum adhesion resistance effect can be maintained for a long time. it can.

平均 The average particle size of the solid lubricant is preferably 0.1 to 20 μm, more preferably 0.1 to 10 μm. If it is less than 0.1 μm, the function as a solid lubricant is low, and if it is more than 20 μm, it easily falls off the film, and the wear of the film is accelerated.

(3) Other Additives A resin curing agent, a reinforcing material such as antimony trioxide or the like may be appropriately added to the resin film used for the piston ring of the present invention.

[3] Manufacture of piston ring
(1) Pretreatment It is preferable to perform pretreatment such as nitriding treatment and surfactant treatment on the piston ring base material. The nitriding process forms a hard nitrided layer on the surface of the base material, thereby improving the wear resistance of the outer peripheral surface of the piston ring and improving the scuff resistance between the mating material and the aluminum alloy cylinder. Can be. For the nitriding treatment, a method such as gas nitriding, ion nitriding, salt bath nitriding, sulphonitriding or the like can be used. The thickness of the nitrided layer is preferably formed to be 3 to 120 μm. If the thickness is less than 3 μm, sufficient wear resistance cannot be obtained, and if the thickness is more than 120 μm, the piston ring tends to break.

(4) After the nitriding treatment, if necessary, degreasing is performed with an alkali, a hydrocarbon or the like to remove oil on the surface. After degreasing, pretreatment such as pickling and phosphate treatment may be performed as necessary.

(2) Preparation of hybrid material The hybrid material can be prepared by a known method. For example, in the case of a silane-modified resin, the method described in JP-A-2001-240670, "Plastics Age," Mar. 2002, 130-132, "Polymer Preprint, Japan," Vol. 50, No. 11 (2001), etc. Preferably, it is used. For example, a glycidyl ether group-containing alkoxysilane partial condensate is produced by a dealcoholation reaction between a tetramethoxysilane partial condensate and glycid (glycidol), and a polyamideimide having a carboxyl group and / or an acid anhydride group at a molecular terminal and / or By reacting a polyimide with a glycidyl ether group-containing alkoxysilane partial condensate, a silane-modified polyamideimide resin and / or a silane-modified polyimide resin can be obtained.

Silane-modified polyamideimide and silane-modified polyimide also act as a silane coupling agent. Since silane is present uniformly in polyamideimide or polyimide molecules without excess or shortage, it is possible to obtain strong adhesion between the piston ring base material and the solid lubricating film without special pretreatment of the piston ring. Can be.

(3) Preparation of coating liquid A varnish prepared by dissolving a polyamideimide-silicon dioxide hybrid material and / or a polyimide-silicon dioxide hybrid material in a solvent containing N-methyl-2-pyrrolidinone or the like as a main component, and a solid lubricant or a dispersion thereof. The varnish can be mixed with the liquid to prepare a solid lubricant dispersed varnish (coating liquid). The amount of the solid lubricant added is preferably from 5 to 80% by mass, more preferably from 30 to 70% by mass of the film mass after drying. If it is less than 5% by mass, the coefficient of friction cannot be sufficiently reduced, so that the film tends to be worn. If it is more than 80% by mass, the solid lubricating material tends to fall off because the heat-resistant material cannot sufficiently retain the solid lubricating material. It becomes a film with poor abrasion.

(4) Formation of Resin Film The prepared coating solution can be applied to at least one of the upper and lower surfaces of the piston ring. In order to more effectively prevent aluminum adhesion caused by collision between the piston ring groove and the piston ring, it is preferable to apply the coating to both side surfaces of the piston ring or the entire piston ring. In addition, from the viewpoint of reinforcing the aluminum adhesion resistance, it may be applied only to a site where wear is particularly severe. For example, the application liquid may be applied only to the lower surface of a piston ring which is generally hit and severely worn.

As a coating method, it is preferable to use a known method such as spray coating, dip coating, spin coating, roll coating, electrostatic coating, or printing. From the viewpoint of suppressing the occurrence of spots and improving the solvent removal efficiency, it is more preferable to use spray coating. Further, from the viewpoint of high coating efficiency and high accuracy and low environmental pollution, it is more preferable to use a printing method such as screen printing.

皮膜 A film can be formed by performing a curing treatment after application. Curing conditions vary depending on the type of heat-resistant material resin, but in the case of a film using a polyamideimide-silicon dioxide hybrid material as a heat-resistant material, it is preferable to carry out curing by heating at 170 to 300 ° C. for 30 to 120 minutes. If the curing temperature is lower than 170 ° C, the curing reaction will not be performed sufficiently, so the original mechanical strength and moisture absorption resistance of the heat-resistant material will not be obtained, and if it is higher than 300 ° C, the formed film will be oxidized and decomposed. Quality degrades. If the curing time is shorter than 30 minutes, the curing reaction is not performed sufficiently, so that the original mechanical strength and moisture absorption resistance of the heat-resistant material cannot be obtained. Does not proceed, wasting time and energy.

The resin film is preferably formed to have a thickness of 3 to 40 µm, more preferably 5 to 15 µm. If it is less than 3 μm, the abrasion resistance is insufficient, and if it exceeds 40 μm, it becomes difficult to mount it in the piston ring groove. .

As described above, a film in which a solid lubricant is dispersed in a heat-resistant resin using a heat-resistant resin made of at least one of a polyamideimide-silicon dioxide hybrid material and a polyimide-silicon dioxide hybrid material as a binder, at least on a side surface of the piston ring. By forming the piston ring, it is possible to obtain a piston ring effective for preventing aluminum adhesion generated between the piston ring and the piston ring groove.

The present invention will be described in more detail with reference to the following examples, but the present invention is not limited thereto.

Example 1
(1) Pretreatment The surface of the top ring base material made of martensitic stainless steel was nitrided by a gas nitriding method, and then degreased with a commercially available alkaline degreaser. Then, it was washed with water and then dried sufficiently.

(2) Preparation of coating solution As a heat-resistant material, silane modification was performed in a solvent in which N-methyl-2-pyrrolidone and xylene were mixed at a mass ratio of 80:20 so that the total concentration of polyamideimide and silicon dioxide was 30% by mass. Content of molybdenum disulfide with an average particle size of 5 μm and graphite with an average particle size of 4 μm as solid lubricant in a varnish (Compocellan H901, manufactured by Arakawa Chemical Industries, Ltd.) in which a polyamideimide resin was dissolved. Was added so as to be 30% by mass and 10% by mass, respectively, and sufficiently stirred to prepare a coating liquid in which the solid lubricant was uniformly dispersed. Next, the mixture was diluted with a mixed solution containing N-methyl-2-pyrrolidone and xylene as main components and stirred to prepare a coating solution for spraying.

(3) Formation of resin film After applying the obtained coating solution to one side of the pretreated top ring base material by spraying, it was cured at 250 ° C for 1 hour, and the polyamide imide in which the solid lubricant was dispersed Forming a resin coating of silicon dioxide hybrid material; Table 1 shows the composition and thickness of the cured film.

Example 2
A varnish prepared by dissolving a silane-modified polyimide resin in a solvent in which N-methyl-2-pyrrolidone and xylene are mixed at a mass ratio of 80:20 so that the total concentration of polyimide and silicon dioxide is 18% by mass (Arakawa Chemical Industries, Ltd.) A coating liquid is applied to one side of the top ring base material, cured, and a solid lubricant is dispersed in the same manner as in Example 1 except that the curing treatment temperature is set to 300 ° C. using Composeran H800). Forming a resin coating of silicon dioxide hybrid material; Table 1 shows the composition and thickness of the cured film.

Example 3
The silane-modified polyamideimide resin used in Example 1 and the silane-modified polyamide resin used in Example 2 so that the mass ratio of the polyamideimide-silicon dioxide hybrid material and the polyimide-silicon dioxide hybrid material after the curing treatment becomes 1: 1. Using a varnish obtained by dissolving a polyimide resin in a solvent obtained by mixing N-methyl-2-pyrrolidone and xylene in a mass ratio of 80:20, and setting the curing temperature to 300 ° C., in the same manner as in Example 1, except that the top ring base material was used. A coating liquid was applied to one side surface of the sample, and a curing treatment was performed to form a resin film made of a mixed material of a polyamideimide-silicon dioxide hybrid material and a polyimide-silicon dioxide hybrid material in which a solid lubricant was dispersed. Table 1 shows the composition and thickness of the cured film.

Comparative Example 1
(1) Pretreatment The surface of a top ring base material made of martensitic stainless steel was nitrided by a gas nitriding method, and then degreased with a commercially available alkaline degreaser. Next, after washing with water and drying sufficiently, washing with trichloroethylene was further performed.

(2) Forming a resin film Topping a commercially available solid lubricant dispersion resin solution (Kawamura Laboratories, Defric HMB-2) in which a solid lubricant mainly composed of molybdenum disulfide and graphite is dispersed in polyamideimide. After being applied to one side of the base material by a spray method, a curing treatment was performed at 190 ° C. for 1 hour to form a resin film. Table 1 shows the composition and thickness of the cured film.

Comparative Example 2
A resin film was formed on one side of the top ring base material in the same manner as in Example 1 except that polyamideimide was used as the heat resistant material. Table 1 shows the composition and thickness of the cured film.

Comparative Example 3
A resin film was formed on one side surface of the top ring base material in the same manner as in Example 3 except that polyimide was used as the heat resistant material. Table 1 shows the composition and thickness of the cured film.

Comparative Example 4
A coating solution was applied to one side of the top ring base material in the same manner as in Example 1 except that a mixture of polyamideimide and polyimide (mass ratio 1: 1) was used as a heat-resistant material, and the curing temperature was set to 300 ° C. . Table 1 shows the composition and thickness of the cured film.

注： (1) 括弧内の数値は、耐熱性材料中のSiO₂の含有量（質量％）。
(2) 樹脂皮膜全体を100質量％としたときの割合（質量％）。
(3) 皮膜Aについては、作製後すぐにアルミニウム凝着試験を行った。
(4) 皮膜Bについては、吸湿試験後にアルミニウム凝着試験を行った。
(5) データなし。

Note: (1) The figures in parentheses indicate the content (% by mass) of SiO _{2 in} the heat-resistant material.
(2) Ratio (% by mass) when the entire resin film is taken as 100% by mass.
(3) The coating A was subjected to an aluminum adhesion test immediately after the preparation.
(4) Coating B was subjected to an aluminum adhesion test after the moisture absorption test.
(5) No data.

The following tests were performed on the resin films of Examples 1 to 3 and Comparative Examples 1 to 4.

[A] Moisture Absorption Test The top ring base materials used in Examples 1 to 3 and Comparative Examples 1 to 4 were stored for 24 hours in a thermostat at a temperature of 25 ° C. and a relative humidity of 30% before forming the film. Thereafter, it was weighed by an electronic balance. The mass at this time is defined as m ₁ . Next, after applying the coating solution, the solution was stored in a thermostat at a temperature of 25 ° C. and a relative humidity of 30% for 24 hours, and then weighed by an electronic balance. The mass at this time is defined as m ₂ . Further, each top ring was stored in a thermostat at a temperature of 50 ° C. and a relative humidity of 90% for 24 hours, and then weighed by an electronic balance. The mass at this time is defined as m ₃ . According to a calculation formula: a = 100 × (m ₃ −m ₂ ) / (m ₂ −m ₁ ), the moisture absorption a of each film was calculated.

Table 2 shows the results of the moisture absorption test using the top rings of Examples 1 to 3 and Comparative Examples 1 to 4. It can be seen that the polyamideimide-silicon dioxide hybrid material, the polyimide-silicon dioxide hybrid material, and the film using the mixed material thereof as a binder have a clearly lower moisture absorption than the film using the polyamideimide, polyimide, or a mixture thereof as a binder.

[B] Adhesion test The same material as that applied to the top ring base material described in Examples 1 to 3 and Comparative Examples 1 to 4 was used, and a film was formed by the same treatment. A plate of × 30 mm × 1 mm was boiled for 24 hours, dried sufficiently at 100 ° C., allowed to stand at room temperature for 24 hours, and then the adhesion of the film was measured by a grid tape test. Table 3 shows the results of the adhesion test.

[C] Aluminum adhesion test The aluminum adhesion test of the top rings produced in Examples 1 to 3 and Comparative Examples 1 to 4 was performed using the aluminum adhesion tester shown in FIG. In the aluminum adhesion test, a thermocouple 5 is inserted into the piston material 2, and the piston material 2 heated by the heater 1 is reciprocated up and down while being controlled by the temperature controller 4, and the side surface of the top ring 3 on which the resin film is formed is removed. Tapping was performed, and the top ring 3 was further rotated at a constant speed to provide sliding. The piston material 2 was a disk (diameter: 100 mm) made of an aluminum alloy [JIS AC8A (T6)], and the top ring 3 had an outer diameter of 75 mm. The rotation speed at the outer periphery of the top ring was 3.3 mm / s, the surface pressure at the time of hitting was 0.57 MPa, and the hitting cycle was 3.3 Hz. No lubricating oil was used.

FIG. 2 shows the number of hits before aluminum adhesion occurs on the top rings of Examples 1 to 3 and Comparative Examples 1 to 4. As apparent from FIG. 2, polyamideimide, polyimide and polyamideimide + polyimide from rings of Comparative Example 1 to Comparative Example 4 formed a solid lubricant dispersed coating that the binder, PAI-SiO ₂ hybrid material, PI-SiO The top rings of Examples 1 to 3 in which a solid lubricant dispersion film was formed using a _two- hybrid material and a mixed material thereof as a binder had higher aluminum adhesion resistance.

In the rings of Comparative Examples 1 to 4, the number of taps (adhesion resistance to aluminum) before adhesion after moisture absorption was reduced from 1/2 before moisture absorption to 2/3, whereas Examples 1 to 4 were performed. In the top ring of Example 3, almost no decrease in aluminum adhesion resistance due to moisture absorption was observed. Therefore, it can be said that the rings of Examples 1 to 3 have better water resistance than the rings of Comparative Examples 1 to 4.

It is an outline sectional view showing an adhesion test machine. It is a graph which shows the number of times of hit until aluminum adhesion occurs in the top ring with each resin film.

Explanation of reference numerals

DESCRIPTION OF SYMBOLS 1 ... Heater 2 ... Piston material 3 ... Piston ring 4 ... Temperature controller 5 ... Thermocouple

Claims (5)

At least on one side, a piston ring for an internal combustion engine having a coating made of a heat-resistant material in which a solid lubricant is dispersed, wherein the heat-resistant material is at least one of a polyamideimide-silicon dioxide hybrid material and a polyimide-silicon dioxide hybrid material. A piston ring comprising: The piston ring according to claim 1, wherein the solid lubricant is made of at least one of an inorganic compound, an inorganic simple substance, and a fluororesin, and the solid lubricant has an average particle size of 0.1 to 20 μm. . The piston ring according to claim 2, wherein the solid lubricant is formed from molybdenum disulfide, tungsten disulfide, boron nitride, graphite, polytetrafluoroethylene resin, and ethylene tetrafluoride / perfluoroalkyl vinyl ether copolymer resin. A piston ring characterized by at least one selected from the group consisting of: The piston ring according to any one of claims 1 to 3, wherein a content of the solid lubricant is 5 to 80% by mass of the entire coating. The piston ring according to any one of claims 1 to 4, wherein a nitride layer having a thickness of 3 to 120 µm is formed on a surface of the piston ring base material.

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