JPH109387A - Piston ring - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a piston ring excellent in the run-in operation at the initial stage, antiabrasiveness, and the productivity. SOLUTION: A combination oil ring 10 is composed of an oil ring 11 and coil expander 12. The oil ring 11 is made of steel having an approx. I-section, and PVD-processed skin films 16 and 17 consisting of hard skin films 20 and 21, inclined layers 22 and 23, and initial stage run-in layers 24 and 25 are provided on the peripheral surfaces of an upper and a lower rail 13 and 14. The hard skin films consist of Cr2 N or a mixture of Cr2 N and a Cr. Each run-in layer is formed as a Cr film in which 0.5-2.0wt.% nitrogen is included in the form of solid solution, wherein the hardness should be HV 300-800 while the thickness be 10μm or less. The inclined layers are formed in the middle in the process when the hard skin films and run-in layers are formed continuously by the PVD processing, in which the nitrogen concentration is decremental toward the surfaces, and the hardness lies between the hard skin film and run-in layer while the thickness lies 5μm or less.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a piston ring mounted on a piston of an internal combustion engine.

[0002]

2. Description of the Related Art In recent years, the load on a piston ring has been increasing with the increase in performance and output of an engine. Among them, the oil ring, from the viewpoint of reducing oil consumption,
There is a trend to increase the oil adjusting function by reducing the axial width, so that the sliding surface that comes into contact with the inner periphery of the cylinder has a high surface pressure, and the sliding conditions are more severe than before.
Also, from the viewpoint of reducing the amount of blow-by gas, there is a trend to reduce the width of the compression ring in the axial direction in order to improve the followability with the piston. And the sliding conditions are stricter than before. As described above, various strict requirements have been put on the piston ring.

For this reason, a Cr ₂ N film (Japanese Patent Laid-Open No. 1-156461) or a Cr ₂ N
A film in which N and Cr are mixed (Japanese Patent Publication No. 6-25597)
No.) is proposed. In addition, Cr ₂ N
There is also known a film configuration in which a CrN film is formed on a film in which Cr and Cr are mixed (Japanese Patent Application Laid-Open No. 62-228648).

[0004]

In order to reduce the amount of oil consumption and the amount of blow-by gas, it is desirable that the initial adaptation of the sliding surface be completed quickly and that the abrasion of the sliding surface does not progress as it is. However, even though the coating is advantageous for measures against abrasion, its initial conformability is insufficient, and it takes time until conformity with the cylinder is obtained.

[0005] As a means for imparting initial conformability, there is Ni-P-based composite plating, but there is a problem in productivity because continuous processing with a hard film by PVD processing cannot be performed.

An object of the present invention is to provide a piston ring which is excellent in initial conformability and abrasion resistance and which is excellent in productivity.

[0007]

According to the present invention, there is provided a method for producing a Cr ₂ N hard coating or a Cr ₂ N and C
In the piston ring on which the hard coating mixed with r is formed, an initial conforming layer is formed on the hard coating by PVD processing, and the initial conforming layer has a hardness of 300 to 800 (Vickers) in which nitrogen is dissolved. Hardness) C
It is characterized by being composed of an r film. The nitrogen content of the initial conforming layer is desirably 0.5 to 2.0% by weight.

[0008] PV between the hard coating and the initial conformable layer
It is desirable to form a gradient layer by D treatment. The gradient layer is formed in the middle of the process of continuously forming the hard coating and the initial conformable layer by PVD processing, and is a layer in which the nitrogen concentration is intermittently or continuously reduced toward the surface. And

When the hard coating is a Cr ₂ N coating, the composition of the gradient layer is such that Cr ₂ N, Cr ₂ N + Cr, Cr (N solid solution) or Cr ₂ N + Cr, Cr (N solid solution) is present on the surface side. And the nitrogen concentration decreases toward the surface. When the hard coating is a coating in which Cr ₂ N and Cr are mixed, Cr ₂ N + Cr, Cr (N solid solution)
Is a layer or Cr (N solid solution) toward the surface side, and the nitrogen concentration decreases toward the surface.

[0010] The initial conforming layer is compared with a mere Cr layer,
Since Cr has a desired hardness (HV 300 to 800) due to the solid solution of nitrogen in Cr, it is less liable to be worn out before sufficient adaptation, and adaptation can be obtained in a short time. .

[0011] The gradient layer is a layer that complements the initial conforming layer,
Since the hardness is in the range between the hard coating and the initial conformable layer, the hardness is higher than that of the initial conformable layer, and it is hard to be worn away. On the other hand, the wear rate of the initial conforming layer is high at both high and low surface pressures, whereas the inclined layer progresses rapidly at high surface pressures, but has little progress at low surface pressures. Therefore, if the inclined layer is exposed at a place where the initial adaptation layer is worn out before the adaptation occurs, the exposed portion is slid at a high surface pressure, so that abrasion proceeds and adaptation can be obtained in a short time. Also,
In the portion where the adaptation occurs before the initial adaptation layer is worn out, the sliding with low surface pressure is performed, so that the abrasion of the inclined layer is little progressed and the opening gap is prevented from expanding.

The initial conforming layer is 10 μm or less, and the gradient layer is 5 μm.
When the thickness is equal to or less than μm, the expansion of the gap between the rings after each layer is worn can be suppressed to be low, and the oil consumption and the blow-by gas amount can be suppressed from expanding.

The hard coating, the gradient layer and the initial conforming layer are made of PVD
The film can be formed by continuous processing, so that the productivity of film formation is excellent.

[0014]

FIG. 1 is a longitudinal sectional view showing one embodiment of the present invention and showing a combined oil ring mounted on an oil ring groove of a piston inserted into a cylinder. In FIG. 1, 1 is a piston, 2 is a cylinder, and a combined oil ring 10 is mounted in an oil ring groove 3 formed on the outer peripheral surface of the piston 1. The combination oil ring 10 is a two-piece steel combination oil ring, and includes an oil ring 11 and a coil expander 12.

The oil ring 11 is a steel ring having an abutment and having a substantially I-shaped cross section, and a pair of upper and lower rails 13 and 14 extending in the circumferential direction, and the pair of rails 13 and 14 extending in the circumferential direction. Thin straight web 15 connecting
It consists of PVD coatings 16 and 17 are formed on the outer peripheral surfaces of the upper and lower rails 13 and 14, respectively, and sliding surfaces that come into contact with the inner peripheral surface 4 of the cylinder 2 and scrape oil from the inner peripheral surface 4 of the cylinder 2. 18 and 19 are constituted.
Each of the PVD coatings 16 and 17 is composed of hard coatings 20 and 21, inclined layers 22 and 23, and initial adaptation layers 24 and 25, which are sequentially laminated toward the surface. The axial width of the sliding surfaces of the upper and lower rails 13 and 14 is 0.4 mm or less.

The hard films 20 and 21 are Cr ₂ N films or films in which Cr ₂ N and Cr are mixed, the nitrogen content in the films is 11 to 17% by weight, and the Vickers hardness of the films. Is in the range of HV1300-2000. The thickness of the hard coatings 20, 21 may be about 50 μm at the maximum, and is preferably 3 μm or more from the viewpoint of abrasion resistance.

The initial conforming layers 24 and 25 are formed by adding 0.5% of nitrogen.
It is a Cr film having a solid solution of ２．０2.0% by weight, and has a Vickers hardness in the range of 300 to 800 HV. The thickness of the initial conformable layers 24 and 25 is 10 μm or less.

The inclined layers 22 and 23 are formed in the middle of the process of continuously forming the hard coatings 20 and 21 and the initial conforming layers 24 and 25 by the PVD process, and the nitrogen concentration is intermittent or continuous toward the surface. The hardness is in the range between the hard coatings 20,21 and the initial conformal layers 24,25. The thickness of the inclined layers 22 and 23 is 5 μm or less.

An outer circumferential groove 26 formed by the web 15 and the projecting portions on the outer circumferential sides of the upper and lower rails 13 and 14 is an oil receiving groove, and is formed by sliding surfaces 18 and 19 of the upper and lower rails 13 and 14 inside the cylinder 2. Oil scraped from the peripheral surface 4
6 through a plurality of oil holes 27 formed in the web 15 at equal intervals in the circumferential direction.
1 and is dropped into an oil pan through a plurality of oil escape holes (not shown) formed in the bottom surface 5 of the oil ring groove 3 of the piston 1.

The coil expander 12 is mounted in an inner circumferential groove 28 formed by the inner circumferential projections of the upper and lower rails 13 and 14 and the web 15. The coil expander 12 is formed by winding a wire having a circular cross section in a coil shape, grinding the outer peripheral surface of the coil into a ring shape, and the cross section of the wire is formed in a shape in which the outer peripheral side of the circle is cut away in the figure. ing. The cross-sectional shape of the wire forming the coil expander 12 is not limited to the above, and may be, for example, a circle. The coil expander 12 is mounted in a state where both ends of the opening are abutted and contracted, and is configured to generate a radially outward expanding force. By pressing the oil ring 11 radially outward, Then, the sliding surfaces 18 and 19 of the oil ring 11 are brought into close contact with the inner peripheral surface 4 of the cylinder 2.

FIG. 2 shows another embodiment of the present invention.
And the combination oil ring is different. The combination oil ring 30 of this embodiment is a three-piece steel combination oil ring, and a pair of upper and lower side rails 31, 32.
And a spacer expander 33.

The pair of side rails 31 and 32 are made of steel.
It is a ring having a rectangular section with a mouth and extending in the circumferential direction.
The outer peripheral surfaces of the side rails 31 and 32 are formed with PVD coatings 34 and 35, respectively, and are sliding surfaces that come into contact with the inner peripheral surface 4 of the cylinder 2 and scrape off the oil on the inner peripheral surface 4 of the cylinder 2. 36 and 37 are configured. Each side rail 3
The axial width of the sliding surfaces 1 and 32 is 0.6 mm or less.
The PVD coatings 34 and 35 are the same as the PVD coatings 16 and 17 formed on the outer peripheral surface of the oil ring 11 of the two-piece steel combined oil ring 10.

The spacer expander 33 is formed as follows. In FIG. 3, the material 50 has a symmetrical shape with respect to the center line in the longitudinal direction, and a plurality of tortoise-shaped holes 51 serving as oil holes are arranged at regular intervals in the longitudinal direction of the thin steel strip. Substantially V-shaped notches 52 are formed on both sides of the thin steel strip between 51. This material 50 is bent symmetrically. That is, both sides in the width direction are bent at the same width and 90 degrees in the same direction along the bending lines AA and BB.
Next, the upper and lower ends are obliquely bent at the same width along the bending lines CC and DD to stand up, and then the bending line E-
The ends of the upper and lower standing pieces are horizontally bent at the same width along E and FF. After bending the material 50 as above,
It is completed through ring forming, joint cutting, surface treatment process and the like.

That is, the spacer expander 33 is
The cross section is substantially U-shaped, and a pair of horizontal upper and lower pieces 3
8 and 39 and an upright piece 40 for connecting them,
8 and a plurality of side rail pressing pieces 41, 42 erected obliquely inward in the radial direction are formed on the inner circumference of the lower piece 39 at equal intervals in the circumferential direction. , 42 are further provided with inner pieces 43, 4 extending horizontally.
4 are formed. A large number of oil holes are formed in the upper piece 38, the upright piece 40, and the lower piece 39 at equal intervals in the circumferential direction.

The spacer expander 33 includes a piston 1
Are fitted in the oil ring groove 3 in a state where both ends are abutted and contracted to generate a radially outward expanding force, and a pair of side rails 31 and 3 are provided.
2 is vertically separated (axially) held by upper and lower pieces 38, 39,
The upper and lower side rail pressing pieces 41 and 42 respectively press the inner peripheral surfaces of the pair of side rails 31 and 32, so that the sliding surfaces 36 and 37 of the side rails 31 and 32 are attached to the inner peripheral surface 4 of the cylinder 2. At the same time, the inner peripheral ends of the side rails 31 and 32 are brought into close contact with the side surfaces 3 a and 3 b of the oil ring groove 3.

Sliding surface 3 of upper and lower side rails 31 and 32
The oil scraped from the inner peripheral surface 4 of the cylinder 2 at 6, 37 moves to the inner peripheral side through a plurality of oil holes of the spacer expander 33 and is formed on the bottom surface 5 of the oil ring groove 3 of the piston 1. Through a plurality of oil escape holes (not shown).

In the present invention, in the above two embodiments, the PVD-treated film has the structure of the hard film, the gradient layer, and the initial conformable layer. The configuration can also be adopted.

In the above embodiment, a gas nitride layer (not shown) is formed under the PVD coating.

In the above embodiment, the PVD process can use ion plating, vacuum deposition, sputtering, or the like.

Hereinafter, an oil consumption test for confirming the effect of the present invention will be described.

In the two-piece steel combined oil ring 10 described in the above embodiment, the outer peripheral surfaces of the rails 13 and 14 above and below the oil ring 11 are subjected to PVD treatment using an arc ion plating apparatus under the following conditions. A film was formed and subjected to an actual test of oil consumption. The outer peripheral surface is subjected to a gas nitriding treatment before the PVD treatment.

(1) Conditions for forming PVD coating film Degree of vacuum in the processing chamber: 10 ^-5 to 10 ^-6 Torr Evaporation source: Cr Reactive gas: Nitrogen gas Bias voltage: 20 V constant

(Comparative Example 1) An arc ion plating process is performed at a pressure of 2 mTorr, a film forming speed of 2.7 nm / s, and a film forming time of 3 hours after introducing nitrogen. (Comparative Example 2) Only gas nitriding treatment and no arc ion plating treatment. (Comparative Example 3) Arc ion plating is performed at a pressure of 2 mTorr, a deposition rate of 2.7 nm / s, and a deposition time of 4 hours after the introduction of nitrogen. While maintaining the same deposition rate continuously in the same processing chamber,
While gradually reducing the amount of nitrogen introduced (0.05 for 30 minutes)
pressure is reduced to mTorr), and an arc ion plating process is performed. An arc ion plating process is performed for one hour at the above-mentioned final pressure (0.05 mTorr) and the same film forming rate. (Comparative Example 4) An arc ion plating process is performed at a pressure of 2 mTorr, a deposition rate of 2.7 nm / s, and a deposition time of 4 hours after the introduction of nitrogen. While maintaining the same deposition rate continuously in the same processing chamber,
While gradually reducing the amount of nitrogen introduced (0.9 m
Pressure is reduced to Torr) and arc ion plating is performed. An arc ion plating process is performed for 1 hour at the final pressure (0.9 mTorr) and the same film forming rate.

Example 1 An arc ion plating process is performed at a pressure of 2 mTorr, a deposition rate of 2.7 nm / s, and a deposition time of 4 hours after the introduction of nitrogen. In the same processing chamber, the amount of nitrogen introduced was 0.6 mT within a few seconds.
Reduce pressure to orr. An arc ion plating process is performed for one hour at the above set pressure (0.6 mTorr) and at the same film forming speed. (Example 2) Arc ion plating is performed at a pressure of 2 mTorr, a deposition rate of 2.7 nm / s, and a deposition time of 4 hours after the introduction of nitrogen. While maintaining the same deposition rate continuously in the same processing chamber,
While gradually reducing the amount of nitrogen introduced (0.1 m
Pressure is reduced to Torr) and arc ion plating is performed. The arc ion plating process is performed for one hour at the final pressure (0.1 mTorr) and the same film forming speed. Example 3 An arc ion plating process is performed at a pressure of 2 mTorr, a film formation speed of 2.7 nm / s, and a film formation time of 4 hours after introducing nitrogen. While maintaining the same deposition rate continuously in the same processing chamber,
While gradually reducing the amount of nitrogen introduced (0.6 m in 30 minutes)
Pressure is reduced to Torr) and arc ion plating is performed. An arc ion plating process is performed for one hour at the final pressure (0.6 mTorr) and the same film forming speed. Example 4 An arc ion plating process is performed at a pressure of 2 mTorr, a film formation speed of 2.7 nm / s, and a film formation time of 4 hours after the introduction of nitrogen. While maintaining the same deposition rate continuously in the same processing chamber,
While gradually reducing the amount of nitrogen introduced (0.8 m
Pressure is reduced to Torr) and arc ion plating is performed. An arc ion plating process is performed for one hour at the final pressure (0.8 mTorr) and the same film forming speed.

Table 1 shows the composition of the PVD coating and the hardness of the initial conformable layer. (Note 1) Regarding the composition of each gradient layer, Cr ₂ N, Cr ₂ N + Cr, and Cr (N solid solution) are laminated toward the surface side, and the nitrogen concentration decreases toward the surface.

(2) Actual machine test conditions The above-described combined oil ring was used for a cylinder bore diameter φ75 mm.
Built into a 4-cylinder gasoline engine, with full load durability of 25
The oil consumption (g / Hr) was measured at an operation time of 1 hour (initial) and 250 hours (durability) when the actual machine was operated under the condition of 0 hour.

Table 2 shows the test results.

Table 2 shows the following. That is,
The hard coating (Cr ₂ N) and gas nitriding of Comparative Examples 1 and 2 have poor initial conformability. Moreover, even with a film structure having the same structure as the present invention, initial break layer of Comparative Example 3, 4 (Cr, N solid solution), the hardness of HV270 or HV850, initial conformability gas nitriding or hard film (Cr ₂ N ) Is not much improved.

On the other hand, in the coating composition of the present invention having no inclined layer and the hardness of the initial adaptation layer (solid solution of Cr and N) of HV600, the initial adaptability is gas nitriding or Improved compared to hard coating (Cr ₂ N). further,
In Examples 2, 3 and 4 in which the hardness of the initial conformable layer (solid solution of Cr and N) is 300 to 800 in the coating composition of the present invention having the gradient layer, the initial conformability is further improved. I understand.

The oil consumption after the endurance is all good.

The present invention can be applied not only to an oil ring but also to a compression ring.

[0042]

As described above, according to the present invention, it is possible to provide a piston ring which is excellent in initial conformability and abrasion resistance even under severe conditions in an internal combustion engine and is excellent in productivity.

[Brief description of the drawings]

1A and 1B show an embodiment of the present invention, wherein FIG. 1A is a longitudinal sectional view showing a combined oil ring mounted in an oil ring groove of a piston inserted into a cylinder, and FIG. It is an enlarged view.

FIG. 2 is a longitudinal sectional view showing another embodiment of the present invention and showing a combined oil ring mounted in an oil ring groove of a piston inserted into a cylinder.

FIG. 3 is a plan view showing a part of a material of a spacer expander.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Piston 2 Cylinder 3 Oil ring groove 3a, 3b Groove side surface 4 Cylinder inner peripheral surface 10 Combined oil ring 11 Oil ring 12 Coil expander 13 Upper rail 14 Lower rail 15 Web 16, 17 PVD processing film 18, 19 Sliding surface 20 , 21 Hard coating 22, 23 Gradient layer 24, 25 Initial conforming layer 26 Outer groove 27 Oil hole 28 Inner groove 30 Combined oil ring 31 Upper side rail 32 Lower side rail 33 Spacer expander 34, 35 PVD processing film 36, 37 Sliding surface 38 Upper piece 39 Lower piece 40 Upright piece 41,42 Side rail pressing piece 43,44 Inner piece 50 Material 51 Tortoise-shaped hole 52 Substantially V-shaped notch

Claims (5)

[Claims] 1. The outer peripheral sliding surface is made of Cr ₂ N by PVD processing.
In a piston ring on which a hard film or a hard film in which Cr ₂ N and Cr are mixed is formed, an initial conformable layer formed by PVD processing is formed on the hard film, and the initial conformable layer has a solid solution of nitrogen. Hardness HV30
A piston ring comprising a 0 to 800 Cr film. 2. The method according to claim 1, wherein the nitrogen content of the initial conformable layer is 0.5.
2. The piston ring according to claim 1, wherein the amount is from 2.0 to 2.0% by weight. 3. The piston ring according to claim 1, wherein the thickness of the initial conformable layer is 10 μm or less. 4. Between the hard coating and the initial conforming layer, P
A gradient layer formed by a VD process, wherein the gradient layer is formed in the middle of the process of continuously forming the hard coating and the initial conformable layer by a PVD process, and the nitrogen concentration decreases toward the surface; The piston ring according to claim 1, 2, or 3, wherein 5. The piston ring according to claim 4, wherein the thickness of the inclined layer is 5 μm or less.