JP3059793B2 - piston ring - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

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 piston ring having excellent seizure resistance and good initial adaptability to a cylinder.

[0002]

2. Description of the Related Art In recent years,
As the engine becomes smaller and lighter, and its output becomes higher, the requirements for the piston ring become more and more severe, and higher levels of wear resistance, seizure resistance, and initial conformability are required. ing.

Conventionally, hard chromium plating, which has been often used for surface treatment of piston rings for internal combustion engines, has a problem in wear resistance when using high lead fuel or when operating in a corrosive atmosphere. As an alternative, thermal spraying has been applied. However, although the thermal spray coating is excellent in abrasion resistance, there are problems such as peeling or falling off of the coating during operation and abrasion of a mating material. Therefore, recently, a steel ring subjected to a nitriding treatment having excellent wear resistance has been put to practical use.

[0004] However, while the nitrided layer is excellent in abrasion resistance, it is inferior in seizure resistance as compared with the hard chromium plating layer and the thermal sprayed layer, and in some cases, scuffing occurs. Therefore, a piston ring having a nitrided layer on the outer peripheral sliding surface has a problem particularly when used under severe operating conditions.

As a piston ring which overcomes the above problems, Japanese Patent Laid-Open No. 1-15353 discloses a piston ring in which a nitrided layer is formed on an outer peripheral sliding surface and a composite dispersion plating layer is formed on the nitrided layer. Is disclosed. In this piston ring, a composite dispersion plating layer in which hard particles or solid lubricant particles are dispersed in a matrix of a nickel-based alloy containing cobalt and phosphorus is used. This piston ring not only has excellent wear resistance, but also has improved seizure resistance, but it does not have sufficient seizure resistance and initial conformability when used in internal combustion engines under severe conditions. It is difficult to say, and a piston ring having excellent seizure resistance and initial conformability is desired.

Accordingly, it is an object of the present invention to provide a piston ring which is excellent in seizure resistance and also excellent in initial conformability.

[0007]

Means for Solving the Problems In view of the above problems, as a result of intensive studies, the present inventors have found that a nitride layer and a cobalt-nickel
In a piston ring having a double structure layer with a composite dispersion plating layer in which particles are dispersed in a matrix of a phosphorus alloy, by using an alloy matrix having a specific metal composition ratio, excellent seizure resistance is obtained. At the same time, I discovered that a piston ring with excellent initial compatibility could be obtained,
The present invention has been completed.

That is, the piston ring of the present invention has a double-layered structure comprising a nitrided layer on at least the outer peripheral sliding surface thereof and a composite dispersion plating layer formed on the nitrided layer and having a thickness of 0.5 to 20 μm. Wherein the composite dispersed plating layer comprises 2 to 10% by weight of phosphorus and 10 to 5% of nickel.
In a matrix of a cobalt-nickel-phosphorus alloy comprising 40% by weight and 55 to 88% by weight of cobalt, particles having a particle size of 0.3 to 10 μm are dispersed in an area ratio of 5 to 30%. .

The present invention will be described in detail below. In the present invention, a nitride layer (first
Layer) and the cobalt-nickel-phosphorus alloy composite dispersed plating layer (second layer) are formed to have a double structure.

The base of the piston ring of the present invention is made of a steel material, and is not particularly limited as long as it is a steel material suitable for obtaining a nitrided layer exhibiting good wear resistance. A particularly preferred example is C: 0.
It is a steel material containing 6 to 1.5% by weight and Cr: 12 to 19% by weight, or a chromium steel containing Mo and / or V in a small amount.

The first nitrided layer can be obtained by a nitriding treatment with N ₂ gas. Preferably, 550-590 ° C
In 3-10 hours, subjected to a nitriding treatment in an N ₂ atmosphere at 1.0 to 1.1 atm. The preferred thickness of the nitrided layer is 80-130 μm. This nitrided layer has a high hardness and a high abrasion resistance.

[0012] The nitrided layer has a high hardness, and thus the piston ring subjected to the nitriding treatment has good wear resistance. However, since the seizure resistance and the initial conformability are inferior, to compensate for this defect,
A composite dispersion plating layer is formed on the first layer as a second layer.

The composite dispersed plating layer of the present invention is obtained by dispersing particles in a matrix of a cobalt-nickel-phosphorus alloy.

Cobalt in the alloy matrix improves the heat resistance and corrosion resistance of the matrix and also improves the crush fatigue strength of the coating. Further, under a use condition in which the piston ring temperature exceeds 300 ° C., such as in a diesel engine, cobalt on the surface is oxidized to produce tricobalt tetroxide. This forms an oxide layer having a low coefficient of friction, which is favorable for sliding friction. The amount of cobalt in the alloy matrix of this composite coating is
If the content is less than 55% by weight, the above effects cannot be obtained remarkably.
The effect does not change significantly when the amount exceeds 55% by weight.
To 88% by weight. The preferred cobalt content is 60-80
% By weight.

[0015] By including nickel in the alloy matrix, the heat resistance, corrosion resistance and toughness of the matrix are improved, and the strength of the coating is also improved. If the amount of nickel is less than 10% by weight, the above effect cannot be obtained remarkably, and if it exceeds 40% by weight, the effect is not significantly changed. Therefore, the amount of nickel is set to 10 to 40% by weight. The preferred nickel content is 25-35% by weight.

Further, by incorporating phosphorus into the alloy matrix, the hardness of the matrix is increased and an effect of excellent wear resistance is exhibited. If the amount of phosphorus is less than 2% by weight, the hardness does not increase,
The effect of improving the wear resistance is small. If the content exceeds 10% by weight, the hardness increases, but the plating layer is rather brittle, the impact strength is weakened, and the adhesion of the plating layer is also deteriorated. Therefore, the amount of phosphorus is 2 to 10% by weight. The preferred phosphorus content is 3-8% by weight.

By dispersing the particles in the alloy matrix, the wear resistance of the plating layer is improved. It is preferable to use hard particles and / or solid lubricant particles as the particles. As the hard particles, metal carbides such as TiC, SiC, Cr ₃ C ₂ , metal nitrides such as TiN, Si ₃ N ₄ , Cr ₂ N,
Alternatively, a metal oxide such as Al ₂ O ₃ , TiO ₂ , or Cr ₂ O ₃ can be used. As the solid lubricant particles, molybdenum disulfide, tungsten disulfide, boron nitride or the like can be used.

The amount of dispersion and the particle size of the particles are also related to the plating thickness to be formed. However, if these are excessively large or large, the film becomes brittle and the wear of the sliding partner material is increased, which is not preferable. . When the amount of dispersion is small or the particle size is small, the effect is small. Accordingly, the dispersion amount of the particles is in the range of 5 to 30% by area ratio, and the particle size is 0.3 to 10 μm. Preferably, the dispersion amount of the particles is in the range of 10 to 20% by area ratio, and the particle size is 0.5 to 5.0 μm.

Regarding the thickness of the composite dispersed plating layer, if it is excessively thin, the composite dispersed plating layer disappears before a sufficient initial running-in state is achieved, and the expected effect cannot be obtained. Must be 0.5 μm or more. On the other hand, if the composite dispersion plating layer is too thick, peeling of the plating layer is likely to occur, and the outer peripheral wear until reaching a state where good wear resistance of the nitrided layer is used increases, and the ring joint is increased. The increase of the gap proceeds early, and the phenomenon of deterioration of the airtightness of the piston ring occurs early. Therefore, the thickness of the plating layer must be 20 μm or less. Therefore, the thickness of the composite dispersed plating layer is 0.5 to 20 μm, preferably 5 to 10 μm.

[0020]

The present invention will be described in more detail with reference to the following examples. Example 1 Alloy steel SUS440B (C: 0.75-0.95% by weight, Si: 1.0% or less, Mn: 1.0% or less, P: 0.04% or less, Ni: 0.60% or less,
Cr: 16.0 to 18.0%, Mo: 0.75% or less), after forming a nitrided layer, 5% by weight of phosphorus, 30% by weight of nickel and 65% by weight of cobalt
To form a 10% dispersion composite dispersion plating layer at a weight percent from consisting alloy base during particle size 0.3 5 .mu.m of silicon nitride (Si ₃ N ₄₎ particles and the area ratio (specimen A).

Example 2 After forming a nitride layer on the same alloy steel as in Example 1, 5% by weight of phosphorus was used.
And a composite dispersion plating layer in which molybdenum disulfide having a particle size of 0.3 to 5 μm was dispersed at an area ratio of 10% in an alloy matrix composed of 30% by weight of nickel and 65% by weight of cobalt (test piece B).

Comparative Example 1 The same alloy steel as in Example 1 was subjected to only conventional hard chromium plating (test piece C).

Comparative Example 2 Only the nitride layer was formed on the same alloy steel as in Example 1 (test piece D). (1) Seizure resistance test The above specimens A to D were subjected to a seizure resistance test using the following apparatus and method. FIG. 1 is a partial cross-sectional view showing a main part of the test apparatus, and FIG. 2 is a view taken along line XX in FIG. An 80 mm diameter disk 3 made of cast iron material FC25 used as a cylinder material and having a honing finish on the sliding surface 2 is provided on the stator holder 1.
Is mounted detachably, and lubricating oil is supplied to the center thereof through the lubrication hole 4 from the back side. Here, a hydraulic device (not shown) is provided on the stator holder 1.
Accordingly, a pressing force (P) is applied at a predetermined pressure toward the right in FIG. The test piece holder 6 mounted on the rotor 5 facing the disk 3 is provided with four mounting holes at equal intervals on a circumference concentric with the rotation axis. Is attached. The 5 mm × 5 mm tip surface of the test piece 7 which has been subjected to a predetermined surface treatment comes into contact with the sliding surface 2 of the disk 3 and is rotated at a predetermined speed by a driving device (not shown).

Using the above-described apparatus, a test was performed while lubricating oil at a constant temperature was supplied to the sliding surface from the lubrication hole 4 on the stator side. When the rotor 5 is rotated, the friction between the test piece 5 and the disk 3 causes a torque F (see FIG.
The torque F was detected by the load cell 9 via the spindle 8, and the change in the torque F due to the change in the pressing force was read by the dynamic strain meter 10. When seizure occurs, the torque F sharply increases, and the pressing force at that time was used as the seizure resistance of the test piece.

The test conditions were as follows. . Friction Speed: 8m / Sec lubricant: no additives motor oil # 30 oil temperature: 80 ° C. oil absorption: 400 cc / min contact pressure; 40 kg / cm ² than to baking generator 10 kg / cm
FIG. 3 shows the test results of increasing the pressure by ^{2 and} maintaining each surface pressure for 3 minutes.

As is clear from FIG. 3, the test pieces A and B on which the composite dispersed plating layer of the present invention is formed are the same as the test piece C on which the hard chromium plating layer is formed and the test piece D on which only the nitride layer is formed. In comparison, the seizure resistance is greatly improved.

(2) Actual machine test Steel (nominal diameter × width × thickness 86.0 mm × 2.0 mm × 3.6 mm) (SUS
440B) was subjected to the same surface treatment as the test pieces A to D used in the above-described seizure resistance test, and the test pieces A ′ to D ′ were respectively formed. These are bore diameters respectively.
86mm, 4 cycle water-cooled 4-cylinder 2600cc engine cast iron (F
The above-described piston ring was assembled in an engine cylinder manufactured by C-25), and a bench test was performed using light oil as fuel at 6500 rpm under a full load for 100 hours to measure oil consumption. The test results are shown in FIG.

As is apparent from FIG. 4, the piston ring [test piece A ', B'] of the present invention having the composite dispersed plating layer formed on the upper layer has a low oil consumption from the initial stage. I understand.

No scuffing was observed in the piston rings of the present invention [test pieces A 'and B']. However, light scuffing was observed on the test piece D '.

[0030]

As described in detail above, the piston ring of the present invention having a nitrided layer and a cobalt-nickel-phosphorus alloy composite dispersed plating layer having a specific metal composition ratio on the outer peripheral sliding surface is provided by the composite dispersed plating. The layer has excellent seizure resistance and excellent initial conformability.

[Brief description of the drawings]

FIG. 1 is a partial cross-sectional view showing a main part of a test device for a seizure resistance test.

FIG. 2 is a view as viewed in the direction of arrows XX in FIG. 1;

FIG. 3 is a graph showing the results of a seizure resistance test.

FIG. 4 is a graph showing a relationship between a test time and an oil consumption obtained from an actual machine test.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Stator holder 2 ... Sliding surface 3 ... Disc 4 ... Lubrication hole 5 ... Rotor 6 ... Test piece holder 7 ... Test piece 8 ... Spindle 9・ ・ ・ Load cell 10 ・ ・ ・ Dynamic strainmeter

Continuation of the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) F16J 1/00-1/24 F16J 7/00-10/04 C23C 30/00 F02F 5/00 C25D 15/02

Claims (2)

(57) [Claims] 1. A nitride layer on at least the outer peripheral sliding surface,
In a piston ring having a double structure layer composed of a composite dispersion plating layer having a thickness of 0.5 to 20 μm formed on the nitrided layer, the composite dispersion plating layer is composed of 2 to 10% by weight of phosphorus and nickel 10%. In a matrix of a cobalt-nickel-phosphorus alloy consisting of about 40% by weight and 55-88% by weight of cobalt,
A piston ring characterized by a layer in which particles of 0.3 to 10 μm are dispersed in an area ratio of 5 to 30%. 2. The piston ring according to claim 1, wherein said particles are hard particles selected from metal nitrides, carbides and oxides and / or tungsten disulfide, molybdenum disulfide and boron nitride. A piston ring characterized by selected solid lubricant particles. [0001]