JP3266439B2 - Piston ring and method of manufacturing the same - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a piston ring having excellent initial conformability.

[0002]

2. Description of the Related Art In recent years, high output and high speed engines have been developed.
As the service life of piston rings has become increasingly severe due to longer service life and compliance with exhaust gas regulations, very hard nitrided layers and hard PVD films have been formed on the outer sliding parts of piston rings. There are many examples. As a result, the wear characteristics of the piston ring are remarkably improved, and particularly, the life of the engine is extended.

[0003]

However, the nitrided layer and the hard PVD film have poor initial conformability in the initial operation state, and thus deteriorate the initial consumption of lubricating oil.

[0004] On the other hand, it has been proposed to coat Ti on a PVD film made of TiN (JP-A-Hei.
It is difficult to realize Ti because scuff resistance is very poor.

[0005] In some cases, Sn plating is applied to a piston skirt portion or the like in order to improve initial conformability and scuff resistance. This Sn plating has not been used recently because it wears too quickly for the outer peripheral surface of the piston ring.

SUMMARY OF THE INVENTION An object of the present invention is to provide a piston ring having a coating having excellent initial conformability and good scuff resistance, and a method for producing the same.

[0007]

SUMMARY OF THE INVENTION A piston ring according to the present invention comprises a nitrided layer or a hard PVD formed on an outer peripheral surface.
A film having a thickness of 1 to 15 μm is coated on the film,
This film is made of Mo and / or Cr.
8.0 to 99.5% by weight, with the balance being N, with a film hardness of 300 to 800 Vickers hardness (HV) and a crystal grain size of 1
less than μm.

In the above description, the lower limit of the film thickness is 5 μm.
m, and the upper limit is more preferably 10 μm.

The lower limit of the film hardness is 500 in Vickers hardness.
Is more preferred.

[0010] The grain size of the film forming the film is 0.1 mm.
Less than 1 μm is more preferred.

The above-mentioned film can be coated by a PVD method. Note that the PVD method includes a vapor deposition method, a sputtering method, and an ion plating method.

[0012]

In the above, if less than 98.0% by weight of either or both of Mo and Cr (N exceeds 2.0% by weight), the abrasion resistance is too good and it is not suitable as an initial conforming layer. On the other hand, if the content of Mo and / or Cr exceeds 99.5% by weight (N is less than 0.5% by weight), the hardness decreases and the abrasion resistance is too poor to be suitable as an initial conformable layer. Absent.

When the crystal grain size forming the film is 1 μm or more, the falling resistance of the sliding portion and the adhesion of the film are inferior.

Further, the film hardness is Vickers hardness 300
If it is less than 1, the abrasion resistance is too poor and it is not suitable as an initial conformable layer. If the Vickers hardness exceeds 800, the abrasion resistance is too good, so that it is not suitable as an initial conformable layer.

[0015]

FIG. 1A is a longitudinal sectional view showing a part of a piston ring according to an embodiment of the present invention. The piston ring 1 in the present embodiment is a rectangular cross-section ring made of steel, cast iron, titanium, a titanium alloy or the like.

A nitride layer 2 is formed on the entire surface of the piston ring 1. The nitride layer 2 is formed by gas nitriding, salt bath nitriding, gas soft nitriding, ion nitriding, or the like. In this embodiment, an example is shown in which a nitride layer is formed on the entire surface, but the nitride layer is formed at least on the outer peripheral surface.

Then, on the nitrided layer 2 on the outer peripheral surface,
Further, the coating 4 is coated by arc ion plating. The film 4 has a thickness of 1 to 15 μm,
98.0-9 for either or both of Mo and Cr
It consists of 9.5% by weight, the balance being N, and has a Vickers hardness of 300 to 800 and a crystal grain size of less than 1 μm.

FIG. 1B is a longitudinal sectional view showing a part of a piston ring according to another embodiment of the present invention. Figure 1 above
The difference from the piston ring of (a) is that instead of the nitrided layer 2, a hard PVD film 3 is coated on the outer peripheral surface of the piston ring 1, and the film 4 having a film thickness of 1 to 15 μm is formed thereon.
Is covered. The hard PVD film 3 is made of a hard PVD containing molybdenum nitride, chromium nitride, or the like.
It is a film.

The arc ion plating method is one type of ion plating in which a coating material of a cathode is vaporized and ionized by using vacuum arc discharge to form a coating on the surface of an object to be coated. . This arc ion plating method has a feature that the ionization rate of steam is high, and a dense and excellent coating film can be obtained.

The basic configuration of the arc ion plating apparatus will be described with reference to FIG. A cathode (evaporation source) 11 made of a material for forming a film is placed in a vacuum chamber 10.
And a coating object 12 on which a film is formed is provided. The cathode (evaporation source) 11 is connected to an arc supply source 13 installed outside the vacuum chamber 10,
An anode (not shown) is connected to the arc supply source 13.
The coating object 12 is configured so that a negative bias voltage is applied by a bias voltage supply source 14. The vacuum chamber 10 is provided with a gas inlet 15 connected to a process gas supply source and an exhaust port 16 connected to a pump.

Therefore, when an arc discharge is generated between the cathode (evaporation source) 11 and the anode in the vacuum chamber 10, the arc forms an arc spot on the surface of the cathode (evaporation source) 11 and the cathode (evaporation source). It moves on the surface of the evaporation source 11 at random and at high speed. Due to the energy of the arc current (tens to hundreds of amps) concentrated on the arc spot,
The material of the cathode (evaporation source) 11 evaporates instantaneously and becomes metal ions 17 at the same time, and jumps out into a vacuum. On the other hand, when the bias voltage is applied to the object to be coated 12, the metal ions 17 are accelerated and adhere to the surface of the object to be coated 12 together with the reaction gas particles 18, so that a dense film is generated.

In the present invention, Mo 98.0-99.5
In the case of forming a film consisting of weight% and residual N, a cathode (evaporation source) is used in the arc ion plating apparatus.
Eleven, Mo metal is used, and nitrogen gas is used as a process gas.

When forming a coating consisting of 98.0 to 99.5% by weight of Cr and the remaining N, Cr metal is used as the material of the cathode (evaporation source) 11 in the arc ion plating apparatus, and the process is performed. Nitrogen gas is used as the gas.

Further, 98.0-9 for both Mo and Cr
When forming a film consisting of 9.5% by weight and the remaining N, in the above arc ion plating apparatus, a Mo—Cr alloy is used as a material of the cathode (evaporation source) 11, and a nitrogen gas is used as a process gas. You.

It should be noted that both Mo and Cr are 98.0-9.
When forming a film consisting of 9.5% by weight and the remaining N, M
a cathode made of o metal, a cathode made of Cr metal, and M
At least two of the cathodes made of an o-Cr alloy may be provided, and nitrogen gas may be used as a process gas.

As for the film hardness, the nitrogen flow rate is reduced and the hardness is set to 300 to 800 HV. The hardness can be adjusted by controlling the bias voltage at the time of ion plating. As the bias voltage increases, the hardness increases.

In order to evaluate the initial conformability of the coating 4,
A wear test was performed using a reciprocating friction tester shown in FIG.

An outline of the reciprocating friction tester shown in FIG. 3 will be described. A pin-shaped upper test piece 2 corresponding to a piston ring is described.
Numeral 0 is held by the fixed block 21, a downward load is applied from above by the hydraulic cylinder 22, and is pressed against a lower test piece 23 described later. On the other hand, the lower test piece 23 having a rectangular flat plate shape corresponding to the cylinder is held by the movable block 24 and reciprocated by the crank mechanism 25. 26 is a load cell.

The test conditions are as follows. 1. Test sample A. Lower specimen: Cast iron for cylinder block (FC250
Equivalent material) A test surface of a flat plate (dimensions: length 70 mm, width 17 mm, thickness 14 mm) is buff-polished to have a surface roughness of 0.1 μm.
What you did below. Note that hardness Rockwell hardness (H _R
B) is 90. B. Upper specimen: Steel rod for piston ring (Dimension: 8m in diameter)
(m, 23 mm in length) with a spherical finish of 18 mmR. The steel rod was a martensitic 17Cr stainless steel, and the surface of the steel rod was coated with the coating shown in Table 1. Except for Comparative Examples 1, 3, and 4, a nitrided layer was formed on the surface of the steel rod, and the coating (film thickness: 5 μm) described in Table 1 was formed thereon.
m) is coated. Comparative Example 1 was a Cr plating film (film thickness:
5 μm), in Comparative Example 3, the surface of the steel rod was coated with a PVD film made of TiN, and a Pd film made of Ti was formed thereon.
A VD film (film thickness: 5 μm) was coated, and Comparative Example 4 was only a nitride layer. Comparative Examples 9 and 10 were processed in a vacuum (0.1 mTorr) without introducing nitrogen. In addition,
The crystal grain size forming the PVD film was less than 0.1 μm.

[0030]

(Note 1) The hardness of Comparative Example 2 was 5 g HV.
f and others are HV 100 gf. (Note 2) In Comparative Example 7 and Example 1, the component in the film was Mo.
And N, and N is dissolved in the metal Mo. (Note 3) In Comparative Example 8 and Example 2, the component in the coating was Cr.
And N, and N is dissolved in metal Cr. (Note 4) In Examples 3 and 4, the components in the film were Mo, Cr, and N.
And N is dissolved in the Mo—Cr alloy (Cr—Mo alloy). (Note 5) In the Mo-Cr alloys (Cr-Mo alloys) of Examples 3 and 4, the ratio of Mo to Cr is a weight ratio.

2. Abrasion test conditions Test: 5 kg x 200 cpm Lubrication: 10 w diesel engine oil

Under the above conditions, each film was rubbed by a reciprocating friction tester, and the abrasion state of the film was observed every minute. For the film which did not wear, the test was continued to measure the abrasion time of the film. FIG. 4 shows the time until each coating wears out.

From the test results shown in FIG. 4, it can be seen that Comparative Examples 2, 3, 9, and 10 take a shorter time until the film is worn.
However, in Comparative Examples 3, 9, and 10, scuff marks were observed on the sliding surface of the film, and thus, they were not suitable as the initial conformable layer. Further, Comparative Example 2 is insufficient for a piston ring because the wear is too fast. On the other hand, in Examples 1, 2, 3, and 4, the time until the film was worn was good, and the scuff resistance was also good.

Next, the piston ring whose outer surface was coated with the coating shown in Table 1 was subjected to an engine test. That is,
The piston ring was assembled in an in-line 4-cylinder gasoline engine of φ81 mm, and an initial lubricating oil consumption test was performed under the condition of 6000 rpm × WOT.

FIGS. 5 and 6 show the results of the lubricating oil consumption test. FIG. 5 shows the relationship between the operating time and the amount of lubricating oil consumption for Comparative Examples 1 and 4 and Example 1. FIG. 6 shows the amount of lubricating oil consumption after 10 hours of operation for each Comparative Example and Example. It is shown.

As shown in the test results of FIGS. 5 and 6, it can be seen that the piston ring of this embodiment consumes a small amount of lubricating oil in the initial stage.

[0038]

As described above, since the piston ring of the present invention has excellent initial conformability, the initial consumption of lubricating oil can be reduced.

[Brief description of the drawings]

FIGS. 1A and 1B are longitudinal sectional views each showing a part of a piston ring according to an embodiment of the present invention.

FIG. 2 is a diagram illustrating a configuration of an arc ion plating apparatus.

FIG. 3 is a front view showing an outline of a reciprocating friction tester.

FIG. 4 is a graph showing the time until the coating is worn in a reciprocating friction test.

FIG. 5 is a graph showing lubricating oil consumption with respect to operating time in an engine test of a piston ring coated with a film.

FIG. 6 is a graph showing consumption of lubricating oil after 10 hours of operation in an engine test of a piston ring coated with a film.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Piston ring 2 Nitride layer 3 Hard PVD coating 4 Coating 10 Vacuum chamber 11 Cathode (evaporation source) 12 Coating object 13 Arc supply source 14 Bias voltage supply source 15 Gas inlet 16 Exhaust port 17 Metal ion 18 Reactive gas particles 20 Test piece 21 Fixed block 22 Hydraulic cylinder 23 Lower test piece 24 Movable block 25 Crank mechanism 26 Load cell

──────────────────────────────────────────────────続 き Continuation of the front page (51) Int.Cl. ⁷ Identification code FI F02F 5/00 F02F 5/00 N (56) References JP-A-2-134468 (JP, A) JP-A-3-255271 ( JP, A) JP-A-6-94130 (JP, A) JP-A-3-79863 (JP, A) JP-A-63-289374 (JP, A) JP-A-3-277870 (JP, A) JP JP-A-4-4361 (JP, A) JP-A-5-215239 (JP, A) JP-A-4-34268 (JP, A) JP-A-5-78821 (JP, A) (58) .Cl. ⁷ , DB name) F16J 9/26 C23C 14/14 F02F 5/00

Claims (3)

(57) [Claims] [Claim 1] A film thickness is the film of 1~15μm coated on a nitride layer formed on an outer peripheral surface, the coating M
98.0-99. for either or both of o and Cr.
5% by weight, balance N, Vickers hardness 3
A piston ring having a crystal grain diameter of from 00 to 800 and less than 1 μm. 2. A hard PVD skin formed on an outer peripheral surface.
Thickness on the film has been coated film of 1 to 15 m, this
The coating 98 on either or both of Mo and Cr.
A piston ring comprising 0 to 99.5% by weight, the balance being N, having a Vickers hardness of 300 to 800 and a crystal grain size of less than 1 μm. 3. The method for manufacturing a piston ring according to claim 1 , wherein the coating having a thickness of 1 to 15 μm is formed by PV.
A method for producing a piston ring, wherein the piston ring is coated by a D method.