JPH08226541A - Piston ring for internal combustion engine - Google Patents

Abstract

PURPOSE: To improve wear resistance and scuffing resistance by forming ion plating films made of a mixture of CrN nitride chrome, oxygen, and Cr2 N nitride chrome on outer peripheral slide faces. CONSTITUTION: Three annular grooves 1a, 1b, 1c are provided in a piston 1, and ion plating films 2A, 4A made of a mixture of CrN nitride chrome, oxygen, and Vr2 N nitride chrome are formed on outer peripheral slide faces of a pressure ring 2 and an oil ring 4. Mixture component ratios of CrN nitride chrome and oxygen are 45.0 to 98.0weight%, and 0.01 to 20.0weight% respectively. Cr2 N nitride chrome is a residual part. Consequently, it is possible to improve wear resistance and scuffing resistance and satisfy the demand for high- performance engine.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a piston ring for an internal combustion engine, and more particularly to a surface-treated piston ring for an internal combustion engine.

[0002]

2. Description of the Related Art In recent years, as the performance of an internal combustion engine has increased, more and more severe conditions have been imposed on each functional component, and there has been a strong demand for extending the life of the internal combustion engine. The piston ring is also exposed to severe environments such as high rotation, high temperature, and high surface pressure more than ever before, and its durability is required to be improved. Furthermore, in order to improve engine performance and reduce size, a combination of three pressure rings and two oil rings, a combination of three pressure rings and one oil ring, a combination of two pressure rings and one oil ring, and a pressure Various combinations of piston rings for internal combustion engines, such as a combination of one ring and one oil ring, are used in diesel engines and gasoline engines. As a means for improving the durability of the piston ring, the sliding surface is subjected to wear resistance treatment such as hard chrome plating treatment or nitriding treatment.

[0003]

However, in the conventional piston ring having a chromium plating layer, the wear resistance is becoming insufficient, and the nitriding treatment has excellent wear resistance, so that it cannot be used under severe operating conditions. It has attracted attention as a surface treatment of the first pressure ring (top ring) used below, and it is often used recently. However, even the nitriding treatment adopted for the conventional piston ring is still insufficient in terms of wear resistance, scuffing resistance, and opponent attack resistance.

Therefore, the present invention provides a piston ring for an internal combustion engine, which has good wear resistance and scuffing resistance, and can reduce opponent attackability as much as possible (good opponent attack resistance). The purpose is to do.

[0005]

In order to achieve the above object, the present invention provides an ion plating on the outer peripheral sliding surface of a mixture of CrN-type chromium nitride, oxygen, and Cr ₂ N-type chromium nitride. A film is formed and the mixture composition ratio is Cr
N-type chromium nitride: 45.0-98.0% by weight, oxygen:
Provided is a piston ring for an internal combustion engine, which comprises 0.01 to 20.0% by weight, Cr ₂ N-type chromium nitride: the balance.

Further, according to the present invention, an ion plating film made of a mixture of CrN type chromium nitride, metal Cr, oxygen, and Cr ₂ N type chromium nitride is formed on the outer peripheral sliding surface, and the mixture composition ratio is CrN-type chromium nitride: 45.0-
98.0% by weight, Cr: 0.5 to 15.5% by weight, oxygen: 0.01 to 20.0% by weight, Cr ₂ N-type chromium nitride: balance, piston ring for internal combustion engine Are offered.

Further, in any of the above piston rings, the porosity of the ion plating film made of the mixture is preferably 0.5 to 20.0%.

[0008]

[Function] An ion plating film in which oxygen (O) is further contained in a mixture of CrN type chromium nitride and Cr ₂ N type chromium nitride in the above range, or CrN type chromium nitride and Cr
₂ A pressure ring or oil ring with an ion-plating film containing oxygen in a mixture of N-type chromium nitride and Cr formed on the outer peripheral sliding surface has wear resistance, scuffing resistance, and counterattack resistance It is possible to meet the demands for higher engine performance due to the heat resistance and peeling resistance.

The physical properties of Cr ₂ N and CrN are shown in the table below.
From this, it can be seen that Cr ₂ N and CrN alone are hard and brittle.

Cr ₂ N CrN theoretical density (g / cm ³ ) 6.51 6.14 hardness Hv (kg / mm ² ) 1800 to 2500 1500 to 2200 elastic modulus (kg / mm ² ) about 35,000 about 25,000

Therefore, when each single ion plating film produced by the PVD method is used alone,
Due to poor workability during grinding / polishing, chipping and peeling occur frequently, and the yield rate is significantly reduced. In addition, when the finished product is used in an internal combustion engine, it is extremely weak against dynamic shock and thermal shock and easily breaks, and its excellent wear resistance and scuffing resistance are sufficient. Cannot be utilized.

On the other hand, in the mixed ion plating film in the above composition range, CrN having a low hardness and a low elastic modulus is contained in an amount of more than 45% by weight,
By making the balance Cr ₂ N, Cr ₂ N (hexagonal) C
rN (cubic crystal) crystals are also effective in that they have different crystal systems,
Ion plating film is formed while intricately interlocking with each other. Furthermore, by adding oxygen to this, the hardness of the film is slightly increased and the best wear resistance,
It does not impair the wear resistance and scuffing resistance equivalent to the ion plating film consisting of CrN alone, which has scuffing resistance, but rather improves the various properties by adding oxygen, while improving impact resistance and toughness. It is possible to obtain an excellent sliding member that is improved and has overcome chipping, peeling, breakage, and the like.

However, as compared with the wear resistance of the ion plating film of CrN alone, that of the ion plating film of Cr ₂ N alone is low, so that in the mixed ion plating film in which CrN is 45% by weight or less, Abrasion resistance drops sharply and film adhesion is extremely low. Even if CrN is mixed in an amount of 98.0% by weight or more, a sharp increase in wear resistance and coating adhesion is not expected.

On the other hand, if the oxygen content is less than 0.01% by weight, the film hardness cannot be increased, and the content is 20.0% by weight.
Above, the film strength becomes brittle. Further, by including 0.5 to 15.0% by weight of Cr in this mixed ion plating film, that is, by interposing a metal (Cr) in the crystal grain boundary of ceramics, the adhesion between crystal grains can be improved. It is possible to strengthen the force and improve the toughness of the ion plating film. This caused the chip,
Further effects can be exerted in overcoming peeling, breakage, and the like. However, if the Cr content is 0.5% by weight or less, there is no effect, and if it exceeds 15.0% by weight, the scuffing resistance is deteriorated.

The toughness of the ion plating film is greatly influenced by the porosity of the film. Therefore, the porosity of the ion plating film is 0.5 to 20.0.
%, It is possible to exert a further effect in overcoming chipping, peeling, breakage, and the like. However, when the porosity is 0.5% or less, the denseness of the coating becomes high and the coating becomes brittle, and chipping, peeling and the like are likely to occur. On the contrary, when the porosity exceeds 20.0%, the strength of the ion plating film itself decreases,
Corruption tends to occur and wear resistance decreases.

[0016]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A piston ring for an internal combustion engine according to the present invention will be described with reference to FIGS. FIG. 1 shows a piston ring for an internal combustion engine according to an embodiment of the present invention. The piston 1 is provided with three annular grooves 1a, 1b, 1c, and a first pressure ring 2 (top ring), a second pressure ring 3, and an oil ring 4 are mounted in order from the combustion chamber. Oil ring 4
Is a combination oil ring and is composed of a side rail 4a and a spacer expander 4b.

The base material of the pressure rings 2 and 3 is made of stainless steel (17Cr stainless steel), and the base material of the side rail 4a of the oil ring 4 is also stainless steel (13Cr stainless steel). The outer peripheral sliding surfaces of the rings 2, 3, 4 are in sliding contact with the cylinder liner 5. Ion plating films 2A and 4A are formed on the outer peripheral sliding contact surfaces of the first pressure ring 2 and the oil ring 4, respectively. Since the first pressure ring 2 has the most remarkable wear,
An ion plating film 2A is formed on the outer peripheral sliding surface for the purpose of improving scuffing resistance and opponent attack resistance. Also, with respect to the oil ring 4, when it wears, the oil scraping action is lost and the oil rise increases, so that the consumption of the lubricating oil increases and the lubricating oil flows into the combustion chamber, which adversely affects the combustion state. Therefore, the ion plating film 4A is also formed on the outer peripheral sliding surface of the oil ring 4.

The ion plating films 2A and 4A of the above-mentioned embodiment are formed by a known reactive ion plating method. In this method, Cr is evaporated in a reaction gas such as nitrogen, ionized in a gas phase, and a reaction product of the reaction gas and vaporized material ions, that is, CrN and Cr ₂ A surface treatment method in which a mixture of N or a mixture of CrN, Cr ₂ N and Cr is formed.

Next, the wear resistance test and the cylinder liner attack test of the internal combustion engine piston ring will be described. First, the characteristics of the ion-plated film of Cr ₂ N type alone, the ion-plated film of mixed Cr ₂ N type and CrN type, and the one of ion-plated film of Cr N type alone were tested. . Specifically, a pressure ring sample and an oil ring sample having sizes compatible with the engine were prepared. The number of pressure rings and oil rings per cylinder is 1 each.
Is. Further, the cylinder bore is cast iron, and specifically, F
It is equivalent to C25.

The base material of the pressure ring is stainless steel containing 17% chromium and the side rails are stainless steel containing 13% chromium. Sample I is Cr ₂ N type with a thickness of 30 μm on the peripheral surface of the ring base material. one treated by an ion-plating coating, sample II are those subjected to ion-plating coating Cr ₂ N-type and CrN-type thickness 30μm on the ring substrate outer circumferential sliding surface are mixed, Cr ₂ N-type And the CrN type content ratio is 50:50. Sample III has a 30 μm thick CrN-type ion plating film on the outer peripheral sliding surface of the ring base material.

The above sample was used as a 4-cycle water-cooled 4-cylinder cylinder 1.
It was installed in a 600 cc gasoline engine, and a durability test was performed for 200 hours under full load operation. FIG. 2 is a graph showing the wear amount of the side rails of the pressure ring and the oil ring and the wear amount data near the top dead center of the mating cylinder. Figure 2
Therefore, the pressure ring and the oil ring are better than the Cr ₂ N type ion plating film.
It was found that the one having the ion plating film of the Cr ₂ N type and the CrN type mixed and the one having the ion plating film of the CrN type alone had excellent wear resistance.

Although not shown in the figure, when the wear amount of the normal nitriding ring is set to "1", the wear amount of the CrN type ion-plated coating ring is about ⅕ that of Cr ₂ N _2. It is about 1/10 in the ring with ion plating film (Sample B) of mixed type and CrN type, so the ion plating film is applied as compared with the pressure ring or oil ring that is subjected to normal nitriding treatment. The amount of wear of the ring is extremely small.

Regarding the aggression to the cylinder, 2
The amount of wear of the cylinder after running for 00 hours was measured. The wear amount of the cylinder that had a sliding relationship with Sample I was 1.
5 μm, and the wear amount of the cylinder having a sliding relationship with Sample II was 1.0 μm.
The wear amount is 1.0μ for the cylinder that has a sliding relationship with
It was m. In particular, it was found that the sample II coated with the Cr ₂ N type and CrN type mixed ion plating film has a good resistance to the opponent attack, similarly to the sample III coated with the CrN type ion plating film.

Next, in order to confirm the excellence of the single ring of the internal combustion engine piston ring according to the present invention, various surface treatments were applied to the test pieces and various tests were conducted. The base material of the test pieces is stainless steel, and their surface treatments are shown in Table 1.

[0025]

[Table 1]

Samples 1 to 8 have an ion plating layer having a thickness of 50 μm, and sample 9 has a chromium plating layer having a thickness of 50 μm.

Composition: Determined by the reflection intensity ratio of each composition of the X-ray diffraction pattern Porosity: Calculated from image processing of the cut specimen surface of the speculum in the cross-sectional direction Abrasion resistance test Abrasion test gas: Amsler abrasion tester Rotating piece (outer diameter: 40 mm, inner diameter: 16 mm, thickness: 10
mm) Fixed piece (18 mm × 15 mm × 5 mm): Various coating materials (thickness = 50 μm) on the contact surface side peripheral speed: 1 m / sec, lubricating oil: 10W30, oil temperature: 80
℃ load: 150kg, time: 7 hours

A wear resistance test was conducted under the above test conditions. The material of the rotating piece is cast iron for cylinder liner (C: 3.2
% By weight, Si: 2.1% by weight, Mn: 0.8% by weight,
P: 0.3% by weight, Cu: 0.4% by weight, Mo: 0.2
% By weight, B: 0.1% by weight, Fe: balance) were used. The results are shown in FIG. 3 in which the wear amount of Sample 9 is 100.

As is apparent from FIG. 3, when the conventional chromium plating is set to 100, the wear amount index of the samples 3, 5 and 7 of the examples is 35 to 40, and the wear resistance is higher than that of the sample 9 plated with chromium. It turns out that it has excellent properties. In addition, the wear amount index of the mating material (rotating material) of Example samples 3, 5, and 7 is 40 to
It is as low as 53 and it can be seen that it has resistance to opponent attack.
Sample 2 is CrN 50%, Cr ₂ N 50%, Cr,
The composition does not contain O. The wear index of sample 2 is 40, 5
It was 0, and the result was better than that of sample 9 plated with chromium. The wear index of the sample 1 having a composition not containing Cr and O is 80 and 95, and the wear index of the sample 4 having a composition of O of 25% is 60 and 100, which are comparable or slightly better than those of the sample 9. there were. The wear index of Sample 6 having a Cr composition of 20% and Sample 8 having a porosity of 25% is 100.
It can be seen that the deterioration was worse than that of Sample 9 plated with chrome.

Scuffing resistance test Abrasion tester: Amsler type abrasion tester Rotating piece (outer diameter: 40 mm, inner diameter: 16 mm, thickness: 10
mm) Fixed piece (18 mm × 15 mm × 5 mm): Various coating materials on the contact surface side (thickness = 50 μm) Peripheral speed: 5 m / sec Lubricating oil: SAE30 + white kerosene (1: 1) Oil temperature: 50 ° C Oil amount : 0.2L / min Load: Until scuffing

A scuffing resistance test was conducted under the above test conditions. This test is a rotating piece made of the same material as the wear test,
The fixing pieces of the same various coating materials were used. First of all, in order to make the sliding surface of the test piece familiar, fix the test piece,
While the lubricating oil was supplied for 20 minutes at a load of 25 kg / cm ^{2, the} rotating piece was rotated while pressingly contacting the fixed piece. Next, the surface pressure is increased to 30 kg / cm ² , and the surface pressure is increased to 5 kg every 2 minutes.
/ Cm ² increments an elevated scuffing was determined as a limit surface pressure load when produced. The results are shown in FIG. 4 with the surface pressure of scuffing of chrome plating being 100.

As is apparent from FIG. 4, assuming that the conventional chrome plating has an anti-scuffing property of 100, Sample 1
In the cases of ~ 5 and 7, it is clear that the anti-scuffing property is superior to the chrome plating. In particular, Example samples 3, 5, and 7
Had high scuffing surface pressure indexes of 138, 140 and 145. On the other hand, sample 6 containing 20% Cr
It can be seen that Sample 8 having a porosity of 25% has a scuffing surface pressure index of 65 to 70 and is inferior in scuffing resistance to Sample 9 plated with chromium.

Finally, an evaluation test was conducted on the adhesion of the ion plating film to the base material. 90m diameter
Nine m of piston rings were prepared, and the same coatings as those used in the wear resistance and scuff resistance tests were provided on the outer peripheral surfaces thereof. The thickness of each film was 50 μm. The adhesion evaluation test was carried out using a twist peel tester as shown in FIG.

A twist test was conducted using a twist peel tester. In the twist test, the facing end portions of the facing port 21a of the piston ring 2 are held by the grippers 32a, 32.
hold the gripping tool 32a with the gripping tool 32b.
21b on the opposite side of the abutment in the diametrical direction of the piston ring 2
The piston ring 2 is twisted at a predetermined twist angle by rotating it about the axis as indicated by the alternate long and short dash line. After twisting, the opposite side 21b of the piston ring 2 was cut, and the presence or absence of peeling of the coating layer on the cut surface (fracture surface) from the ring base material was visually observed. The result is shown in FIG. 5 with the peeling angle of the comparative example sample 9 of chrome plating being 100.

As is apparent from FIG. 5, when the breakage resistance of the conventional chromium-plated sample is set to 100, the comparative sample 2,
In the case of 6 and Example samples 3, 5, and 7, the peeling angle index is 1
It is clear that it is 10 to 145, which is superior to chrome plating. On the other hand, comparative sample 1 having a composition not containing Cr and O
Comparative sample 4 having a composition of 25% O and comparative sample 8 having a porosity of 25% had a peeling angle index of 60 to 75 and were inferior in breakage resistance to sample 9 plated with chromium. The comparative sample 6 has an index of 140 with respect to chromium plating and is excellent in breakage resistance, but is not suitable for use because it does not have the wear resistance and scuffing resistance of FIGS. 3 and 4 at the same time.

[0036]

As described above, in the piston ring for an internal combustion engine of the present invention, CrN-type chromium nitride of 45.
0 to 98.0% by weight, oxygen 0.01 to 20.0% by weight, the balance being an ion plating film made of a mixture of Cr ₂ N-type chromium nitride, or CrN-type chromium nitride 45.0 to 98. 0% by weight, metallic chrome 0.5-1
5.0% by weight, 0.01 to 20.0% by weight of oxygen, and the balance being an ion plating film made of a mixture of Cr ₂ N-type chromium nitride, so that abrasion resistance, scuffing resistance, and attack resistance against opponents Not only is it excellent in peeling property, but also has a remarkable effect that the peeling resistance is remarkably improved by a synergistic effect.

[Brief description of drawings]

FIG. 1 is a sectional view showing an embodiment of a piston ring for an internal combustion engine according to the present invention.

FIG. 2 is a graph showing the amount of wear of a pressure ring and an oil ring and the amount of wear of a cylinder as a mating material in an actual engine test.

FIG. 3 is a graph showing wear resistance of a test piece subjected to various surface treatments and a mating material.

FIG. 4 is a graph showing the scuffing resistance of test pieces that have been subjected to various surface treatments.

FIG. 5 is a graph showing the film adhesion of test pieces that have been subjected to various surface treatments.

FIG. 6 is a schematic diagram showing a test device for an adhesion test.

[Explanation of symbols]

 2, 3 Pressure ring 4 Oil ring 5 Cylinder liner 2A, 4A Ion plating film

Claims (3)

[Claims] 1. A CrN-type chromium nitride on the outer peripheral sliding surface,
An ion plating film made of a mixture of oxygen and Cr ₂ N type chromium nitride is formed, and the mixture composition ratio is C.
rN-type chromium nitride: 45.0-98.0% by weight, oxygen:
0.01-20.0% by weight, Cr ₂ N-type chromium nitride: The balance is a piston ring for an internal combustion engine. 2. A CrN-type chromium nitride on the outer peripheral sliding surface,
An ion plating film made of a mixture of metal Cr, oxygen, and Cr ₂ N-type chromium nitride is formed, and the mixing composition ratio is CrN-type chromium nitride: 45.0 to 98.0 wt%, Cr: 0.5. ~ 15.5% by weight, oxygen: 0.01 ~
20.0% by weight, Cr ₂ N-type chromium nitride: The balance is a piston ring for an internal combustion engine. 3. The piston ring for an internal combustion engine according to claim 1, wherein the ion plating film made of the mixture has a porosity of 0.5 to 20.0%.