JP2003148242A - Piston ring and combination of piston ring and ring channel - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a piston ring for an internal combustion engine capable of effectively preventing the agglutination of aluminum from a ring channel of a piston made of an aluminum alloy. SOLUTION: Lubricant particles are jetted on the surface of at least the lower face of the piston ring for the internal combustion engine to form a lubricant film. As a lubricant particle, molybdenum disulfide particle, tungsten disulfide particle, metallic tin particle, etc., are preferable. Moreover, it is preferable to obtain a first pressure ring using the piston ring. Furthermore, the lubricant film formed by jetting lubricant particles on the lower face of the piston ring channel may be formed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a piston ring suitable as a piston ring for an internal combustion engine, and more particularly to improving the aluminum adhesion resistance of the piston ring mounted on an aluminum alloy piston.

[0002]

2. Description of the Related Art In recent years, from the viewpoint of conservation of the global environment,
There is a demand for weight reduction of automobile bodies. Due to such a demand for weight reduction, in recent automobiles, engines are mainly made of aluminum alloys, and pistons are also made of aluminum alloys. On the other hand, with the demand for higher engine output, the engine is exposed to a higher temperature combustion environment, and therefore, strict quality requirements are also placed on the piston ring.

When a piston ring is mounted in the piston ring groove of an aluminum alloy piston, the engine ring is exposed to high temperature as the engine speed and output are increased, and the upper and lower surfaces of the piston ring groove are hit by the piston ring. Aluminum adhesion of piston material Al on the lower surface of the piston ring (hereinafter also referred to as Al adhesion) and roughness of the piston ring groove lower surface due to adhesion of piston material Al to the piston ring (hereinafter, (Also referred to as groove roughening). When such aluminum adhesion and groove roughening occur, the sealing performance on the upper and lower surfaces of the piston ring deteriorates, and combustion gas blows through the gap between the ring groove and the lower surface, increasing the so-called blow-by, which lowers the engine output. Cause.

In order to prevent such Al adhesion and groove roughening on the piston ring, the piston has conventionally been subjected to a hard alumite treatment by anodic oxidation as a countermeasure for the piston. However, the hard alumite treatment has a problem that the treatment cost is high and the manufacturing cost is increased. On the other hand, as a countermeasure for the piston ring, for example, in Japanese Utility Model Publication No. 60-82552, a phosphate coating or a ferrosoferric oxide coating is provided as a base coating on at least the lower surface of the piston ring, and a solid coating is formed thereon. A piston ring having a heat-resistant and wear-resistant resin film containing a lubricant has been proposed. However, in addition to the problem that the fatigue resistance of the piston ring decreases when the formation process of the base film is performed,
There is also a problem that the solid lubricant contained in the heat-resistant and wear-resistant resin film is worn out or comes off, causing Al adhesion.

In order to solve such a problem, Japanese Unexamined Patent Publication No.
No. 307568 discloses a piston ring in which a nitride layer is formed on at least the lower surface of the piston ring, and a heat-resistant and abrasion-resistant resin film containing a solid lubricant is further formed on the lower surface of the nitride layer. Proposed. However, even with a piston ring manufactured by the technique described in Japanese Patent Application Laid-Open No. 1-307568, the solid lubricant retained in the heat-resistant and wear-resistant resin film may be worn away or fall off. There was also the problem of adhesion. Also,
Since coating and baking treatments are required to form a heat-resistant and abrasion-resistant resin film, there is also a problem that the hardness of the nitride layer is reduced and the fatigue resistance is reduced.

Further, Japanese Patent Laid-Open No. 9-184079 discloses a first coating layer formed by a phosphate chemical conversion treatment and a second coating layer formed of a heat and abrasion resistant resin containing solid lubricant particles. A wear-resistant member having a laminated structure, in which gaps are formed between the crystal grains on the outermost surface of the phosphate chemical conversion treatment film, and the gap has a width and a depth to bury the particles of the solid lubricant, is proposed. Has been done. In the wear resistant member described in Japanese Patent Laid-Open No. 9-184079, solid lubricant particles are less likely to fall off, the lubricating function is maintained for a long time, and the occurrence of adhesive wear is prevented.

[0007]

However, even in the technique disclosed in Japanese Patent Laid-Open No. 9-184079, it is necessary to heat in order to form the heat resistant and abrasion resistant resin coating layer containing solid lubricant particles. . This heating has left the problem that the hardness of the Cr plating film is lowered and the fatigue resistance is lowered.

The present invention advantageously solves the above-mentioned problems of the prior art, and can effectively prevent Al adhesion from the ring groove of the aluminum alloy piston without deteriorating the characteristics of the piston ring. An object of the present invention is to provide a piston ring for an internal combustion engine having excellent adhesion and a combination of the piston ring and the piston ring groove.

[0009]

DISCLOSURE OF THE INVENTION The present inventors have diligently studied a method for improving aluminum adhesion resistance of a piston ring without forming a heat and abrasion resistant resin coating layer. As a result, by injecting lubricant particles onto the piston ring surface at high speed, Al from the piston ring groove is not deteriorated without deteriorating various characteristics of the piston ring such as fatigue resistance.
It was found that a lubricant film capable of effectively preventing adhesion can be formed, and that this film is durable.

The present invention has been completed on the basis of the above findings and further studies. That is, the present invention is as follows. (1) A piston ring for an internal combustion engine, which has a lubricant coating formed by spraying lubricant particles on at least the lower surface of the piston ring, and has excellent aluminum adhesion resistance Piston ring for engines. (2) The piston ring for an internal combustion engine according to (1), wherein the lubricant particles are one kind selected from molybdenum disulfide particles, tungsten disulfide particles, and metal tin particles. (3) The piston ring for an internal combustion engine as described in (1) or (2), wherein the lubricant coating is formed as an upper layer of a hard coating. (4) In (3), the piston ring for an internal combustion engine, wherein the hard coating is a nitride coating. (5) In any one of (1) to (4), a piston ring for an internal combustion engine, characterized in that it has a hard coating on the outer peripheral surface of the piston ring. (6) In (5), the hard coating is a nitride coating, Cr
A piston ring for an internal combustion engine, which is a plating film or an ion plating film. (7) A pressure piston ring for an internal combustion engine, wherein the piston ring for an internal combustion engine according to any one of (1) to (6) is a pressure piston ring. (8) A combination of a piston groove of an aluminum alloy piston of an internal combustion engine and a piston ring mounted in the piston groove, wherein lubricant particles are provided on at least a lower surface of the piston groove or at least a lower surface of the piston ring. A combination of a piston ring and a piston groove having excellent aluminum adhesion resistance, which has a lubricant film formed by spraying. (9) In (8), the lubricant particle is one kind selected from molybdenum disulfide particles, tungsten disulfide particles, and metal tin particles, and a combination of a piston ring and a piston groove. .

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION The piston ring for an internal combustion engine of the present invention has a lubricant coating formed by spraying lubricant particles on at least the lower surface. In the present invention, the material of the piston ring is not particularly limited, and any conventionally known material can be suitably used, but it is preferably made of steel.

The piston ring for an internal combustion engine is usually composed of two pressure rings and one oil ring. The first pressure ring, which has a high surface pressure and is used in harsh environments, has a cast iron ring, but has a higher Si content.
From the viewpoint of durability, it is preferable to use a steel piston ring made of Si-Cr steel or steel having Cr increased to 10% or more.
For the first pressure ring, it is preferable to subject the sliding surface to a hard surface treatment such as gas nitriding treatment, hard chrome plating treatment, composite plating, or ion plating (PVD treatment) in order to improve durability. .

Further, in the diesel engine, since the environment exposed to combustion is severe, the piston ring groove is mainly formed in the first pressure ring groove by the piston resister made of Ni-resist cast iron. Therefore, Al adhesion does not occur in the first pressure ring groove. Therefore, in a diesel engine, the second pressure ring without a piston trailer is required to have aluminum adhesion resistance. Therefore, the piston ring of the present invention having a lubricant coating formed thereon should be used as the second pressure ring of the diesel engine. Is preferred.

In the present invention, as shown in FIG. 1, lubricant particles are applied at a high speed to at least the lower surface of the piston ring 1, which is a hitting surface, preferably the lower surface of the steel piston ring 1, or even the upper surface thereof. The lubricant film 2 is formed by spraying. By injecting the lubricant particles at a high speed, it is possible to form a dense and highly adherent lubricant film without using a binder.

FIG. 1A shows an example in which a lubricant coating 2 is formed on the lower surface of the piston ring 1. FIG. 1B is an example in which the lubricant coating 2 is formed on the upper and lower surfaces of the piston ring 1. FIG. 1C shows an example in which the lubricant coating 2 is formed on the upper and lower surfaces of the piston ring 1 as the upper layer of the hard coating 3. FIG. 1D shows an example in which the hard coating 3 is formed on the outer peripheral sliding surface of the piston ring 1 and the lubricant coating 2 is formed on the upper, lower and outer peripheral surfaces of the piston ring 1 as the upper layer of the hard coating 3. is there. Although not shown, the hard coating 3 is formed on the outer peripheral sliding surface of the piston ring, the hard coating 3 is formed at least on the lower surface of the piston ring, and the lubricating coating 2 is formed only on the lower surface of the piston ring as the upper layer of the hard coating 3. You may.

By forming the lubricant film 2 on at least the lower surface of the piston ring, it is possible to remarkably prevent Al adhesion from the ring groove of the aluminum alloy piston. The hard coating formed on the outer peripheral sliding surface of the piston ring, if necessary, is preferably a nitride coating, a Cr plating coating, or an ion plating coating. As the nitride film, any film formed by a known nitride film forming method can be applied. Further, there is no problem even if the Cr plating film is a laminated Cr plating film. There is no problem even if the ion plating film is a Cr-N-based film, a Cr-B-N-based film or a Ti-N-based film. There is no problem even if the lubricant coating 2 is formed on the outer peripheral sliding surface of the piston ring.

As the method for injecting the lubricant particles, any of the injection methods utilizing a generally known shot blasting device is suitable. Among them, it is preferable to use a direct pressure type injection device, a gravity type injection device or the like, but the present invention is not limited to this. The lubricant coating formed on the surface of the piston ring preferably has a thickness of 1 to 20 μm. When the film thickness is less than 1 μm, the film thickness is too thin, the lubricating effect is small, the Al adhesion preventing effect from the piston ring groove is small, and the durability is reduced. On the other hand, when it exceeds 20 μm, there is a problem that the film thickness is too thick and the adhesiveness is deteriorated and the film peels off in a short time. Further, although the lubricant film in the present invention is firmly adhered and formed on the surface of the piston ring, there is no diffusion and penetration of the lubricant (Mo, S) into the piston ring base material, and the piston ring characteristics such as fatigue resistance. It has the characteristic that there is no change. It can be understood from FIG. 2 that there is no diffusion and penetration of the lubricant into the piston ring base material. Figure 2
Is a schematic concentration curve that analyzes the concentration of Fe, Mo, and S in the depth direction from the surface to the piston ring base metal including the boundary surface on the cross section of the piston ring with the lubricant coating formed on the surface. It is the explanatory view shown. 2 (a) is Fe,
(B) shows the concentration curve of Mo and (c) shows the concentration curve of S. Both elements show significant changes at the interface between the lubricant coating and the base material. Therefore, it can be said that the lubricant (Mo, S) does not diffuse and penetrate into the piston ring base material.

The lubricant particles used for forming the lubricant film are preferably one kind selected from molybdenum disulfide, tungsten disulfide and metallic tin. The lubricant particles used are preferably powders having an average particle size of 0.4 to 50 μm. The average particle size of the injected lubricant particles is 0.4 μ
If it is less than m, the desired collision energy cannot be obtained, and there is a problem that it falls off in the formation of the lubricant film. On the other hand, if the average particle size exceeds 50 μm, a dense and highly adherent lubricant film cannot be formed.

The average particle size used in the present invention is JIS R
The value measured in accordance with the regulations of 6001 shall be used.
It is preferable that the injection speed or the injection pressure when the above-mentioned lubricant particles are injected onto the piston ring surface is appropriately determined according to the desired lubricant film characteristics. For example, when using a direct pressure injection device, the injection speed is 100
A high speed of not less than m / s, preferably not more than 250 m / s is preferable. If the jet speed is less than 100 m / s, the adhesion of the formed film deteriorates, the surface roughness becomes rough, and the durability of the film decreases. On the other hand, increasing the injection speed over 250 m / s has a problem that the air pressure becomes too high, but the apparatus becomes large and it is not economical.

The lubricant particles sprayed onto the surface of the piston ring at a high speed of 100 m / s or more collide with the surface of the piston ring, are decelerated, and firmly adhere to the surface. When the jetting speed is low, the adhesive strength is reduced, and the coating is peeled off and the durability of the coating is insufficient. The injection pressure may be used instead of the injection speed. The injection pressure is 0.3 MPa or more, preferably 1.5 MPa or less.

Except for degreasing, the lubricant film may be formed as it is on the surface of the piston ring base material without any special pretreatment, or may be formed after a hard surface treatment such as a nitride film. Good. Further, it is more effective to improve the aluminum adhesion resistance by forming the lubricant film without performing the hard surface treatment. Therefore, the piston ring having the lubricant coating of the present invention is more preferably used for the first pressure ring.

Further, by forming a lubricant film on at least the lower surface of the piston ring, Al adhesion from the piston ring groove can be sufficiently prevented, but at least the lower surface of the piston ring, or at least the lower surface of the piston ring groove, The combination of the piston ring and the piston ring groove, both of which have a lubricant coating formed by spraying lubricant particles, will further prevent Al adhesion to the piston ring and prevent the piston ring from becoming aluminum-resistant. Wearability is remarkably improved. The lubricant film formed in the piston ring groove may be the same as the film formed on the piston ring in terms of film thickness, forming method, and the like.

[0023]

EXAMPLE A steel material (wire material) having a composition shown in Table 1 was processed into a predetermined shape and then heat-treated to obtain a desired strength to obtain a steel piston ring (product). In addition,
Some piston rings were hard surface-treated to form a hard coating. The hard coating is a nitride coating (hardness: Hv 1050
) And a gas nitriding treatment. A Cr plating film or an ion plating film was formed on the outer peripheral sliding surface of some piston rings. The Cr plating film was formed by a Cr plating treatment using a known fluoride bath. The ion plating coating was a Cr-N coating and was formed by a known method.

Lubricant coatings were formed on these steel piston rings under the conditions shown in Table 2. The lubricant particles shown in Table 2 were used, and the lubricant particles were sprayed onto the piston ring surface under the conditions shown in Table 2 to form a lubricant film. As a conventional example, molybdenum disulfide particles were mixed with a polyamide resin, and a coating solution prepared by dissolving the solvent in a solvent was applied to the surface of the piston ring and baked to form a resin film containing a lubricant.

Test pieces were taken from the piston ring having these lubricant coatings formed on the surface thereof, and a hitting test was carried out as the ring material 12 using the tester shown in FIG. As the piston side member 13, an AC8A plate, which is a material of the aluminum alloy piston, was used. The hit test is the piston side material
13 is fixed to the testing machine 11 so as not to move in the axial direction, and the ring material 12 as a test material is concentrically attached to the piston side material 13,
This is a test in which the circular rod 15 provided on the inner peripheral surface side of the ring member 12 is reciprocated in the axial direction to give the ring member 12 an action of striking the piston side member 13 while rotating. After the test
The ring material was taken out, and the presence or absence of Al adhesion on the surface, the wear amount of the ring material, and the wear amount of the piston side material were investigated. The tester 11 has a heater, which can increase the temperature of the test material and reproduce the environment inside the engine.

The test conditions for the hitting test are as follows. Piston side temperature: 240 ℃, 260 ℃ Repetition number: 500 times / min Rotation number (ring material): 3.0 rpm Test time: 2h Table 3 shows the obtained results.

[0027]

[Table 1]

[0028]

[Table 2]

[0029]

[Table 3]

In each of the examples of the present invention, Al adhesion was not observed, the amount of wear was small, and the aluminum adhesion resistance of the piston ring was remarkably improved. On the other hand, in the conventional example, the adhesion of Al was observed at the piston side temperatures of 240 ° C. and 260 ° C., and the wear amount was further increased.

[0031]

According to the present invention, Al adhesion from the ring groove of the aluminum alloy piston can be effectively prevented without forming a resin coating containing a lubricant, and the durability of the piston ring for an internal combustion engine can be improved. It is remarkably improved and has a remarkable effect on the industry.

[Brief description of drawings]

FIG. 1 is a sectional view schematically showing an example of forming a lubricant film on the surface of a piston ring of the present invention.

FIG. 2 is an explanatory diagram showing an example of analysis of elements in the vicinity of the boundary surface between the base material of the piston ring and the lubricant film of the present invention.

FIG. 3 is a partially cutaway perspective view of a testing machine that performs a hitting test.

[Explanation of symbols]

1 piston ring 2 Lubricant coating 3 hard coating 11 Testing machine 12 Ring material (piston ring) 13 Piston side material 14 heater 15 yen bar

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Takahiro Okazaki             5-2-6 Honmachi Nishi, Saitama City, Saitama Prefecture             Nippon Piston Ring Co., Ltd. inside the Yono factory F term (reference) 3J044 AA02 BA03 BA04 BB06 BB16                       BB23 BB28 BB36 BB39 BC03                       BC06 BC07 BC08 CA06 CB02                       CB11 DA09 DA16

Claims (9)

[Claims] 1. A piston ring for an internal combustion engine, comprising:
A piston ring for an internal combustion engine having excellent aluminum adhesion resistance, which has a lubricant coating formed by spraying lubricant particles on at least the lower surface of the piston ring. 2. The piston ring for an internal combustion engine according to claim 1, wherein the lubricant particles are one kind selected from molybdenum disulfide particles, tungsten disulfide particles, and metal tin particles. . 3. The piston ring for an internal combustion engine according to claim 1, wherein the lubricant film is formed as an upper layer of a hard film. 4. The piston ring for an internal combustion engine according to claim 3, wherein the hard coating is a nitride coating. 5. The piston ring for an internal combustion engine according to claim 1, wherein a hard coating is provided on a surface of an outer peripheral sliding surface of the piston ring. 6. The piston ring for an internal combustion engine according to claim 5, wherein the hard coating is a nitride coating, a Cr plating coating, or an ion plating coating. 7. A pressure piston ring for an internal combustion engine, wherein the piston ring for an internal combustion engine according to claim 1 is a pressure piston ring. 8. A combination of a piston groove of an aluminum alloy piston of an internal combustion engine and a piston ring mounted in the piston groove, wherein at least a lower surface of the piston groove or at least a lower surface of the piston ring is lubricated. A combination of a piston ring and a piston groove having excellent aluminum adhesion resistance, which has a lubricant film formed by spraying agent particles. 9. The piston ring and the piston groove according to claim 8, wherein the lubricant particles are one kind selected from molybdenum disulfide particles, tungsten disulfide particles, and metal tin particles. In combination with.