JP2002097573A - Sliding member - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a sliding member having an abrasion-resistant hard coating thereon, which is formed at a low temperature without requiring high temperatures and thereby without a reduction of dimension accuracy due to heat deformation and of a hardness of a base material. SOLUTION: The sliding member is characterized by forming an amorphous hard carbon film composed of carbon and hydrogen as a main composition and a metallic oxide, on a relatively abutting or sliding part to an opponent member.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a sliding member for automobiles, home appliances, etc., on which an amorphous hard carbon film containing a metal oxide is formed. In the present invention, “hard” is in accordance with the general usage in tribology (for example, see “Tribologist, Vol. 44, No. 9, 1999, a small special issue, hard materials”). High quality, especially Hv1000 or more, more preferably Hv1
Refers to 500 or more. An application example of the amorphous hard carbon film is described in Tribologist, Vol 41, No. 9, 1996, pp. 760 to 771.

[0002]

2. Description of the Related Art Sliding members of an internal combustion engine for automobiles, for example, the outer peripheral surface, inner peripheral surface and side surfaces of a piston ring, vanes, and the outer peripheral surface of a fuel injection pump plunger are exposed to severe sliding conditions, so that they have high durability. Wear resistance is required.

Conventionally, in order to ensure sufficient sliding characteristics of these parts, particularly, abrasion resistance, a high-grade abrasion-resistant material is used, and a hard coating forming surface treatment such as nitriding or carburizing is performed. Abrasion resistance has been improved by increasing the function. However, in the conventional direction, the materials used are expensive, and the treatment at a high temperature of several hundred degrees to 1,000 degrees is required during the formation of the hard film. there were.

[0004] Since the fuel injection pump plunger slides in a gasoline environment having poor lubricity, a composite dispersion plating film in which hard particles are dispersed is applied. However, in order to obtain a predetermined film hardness, 400 ° C is required. Since a high degree of heat treatment is required, it is necessary to use a high quality material equivalent to SKD11 for the base material. Therefore, development of a treatment method for forming a wear-resistant hard film at a low temperature has been desired.

In Japanese Unexamined Patent Publication (Kokai) No. 3-240957, a thin film of silicon oxide (SiO ₂ ) formed on the surface of a mating material during sliding of an amorphous hardness carbon-hydrogen-silicon thin film is a so-called contamination due to gas adsorption or the like. It is disclosed that it exhibits lubrication and exhibits a relatively low coefficient of friction. The silicon oxide referred to here is one in which an amorphous hard carbon-hydrogen-silicon thin film containing silicon in advance is formed on the surface of a mating material by sliding with the mating material. The coefficient of friction of this thin film becomes low only after silicon oxide is formed on the surface of the mating material.

[0006]

SUMMARY OF THE INVENTION The present invention has been made in order to solve the above problems, and an object of the present invention is to provide a base material which does not require a high temperature for forming a wear-resistant hard film and which is thermally deformed. Without lowering of dimensional accuracy or lowering of hardness.
An object of the present invention is to provide a sliding member in which an amorphous hard carbon film containing a metal oxide is formed on a sliding portion by a method of forming a wear-resistant hard film at a low temperature. Further, the present invention provides an amorphous hard carbon film containing a metal oxide to obtain a stable low coefficient of friction from the beginning of sliding, which was impossible with a conventional amorphous hard carbon film. It is.

[0007]

DISCLOSURE OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and a metal member is contained in an amorphous hard carbon film containing carbon and hydrogen as main components to form a mating member. And achieves good wear resistance with a low coefficient of friction in sliding. The metal oxide is preferably an oxide of at least one element selected from the group consisting of Si, Ti, B and W. Further, the content of oxygen in carbon is preferably about 0.1 to 10 atomic%.

The subcomponent of the amorphous hard carbon film according to the present invention is mainly an oxide, and is used as a raw material such as fluorine, bromine and chlorine in addition to a small amount of oxygen and metal element which are not bonded as an oxide. Including substances caused by. In the present invention, the substance composed of carbon and hydrogen as main components has an amorphous structure detected by Ar laser Raman spectroscopy, thereby exhibiting excellent sliding characteristics. On the other hand, the oxide may be crystalline or amorphous.

In the present invention, the mating member is a cylinder or a cylinder liner made of cast iron or an aluminum alloy when the sliding member is a piston ring, and is made of an aluminum alloy when the sliding member is a compressor vane. Alternatively, when the sliding member is a fuel injection plunger which is an iron rotor and a housing, the material is equivalent to SKD11. These are examples, and the sliding member and the counterpart material of the present invention are applied to all members that can utilize the characteristics of the amorphous hard carbon film.

The hardness of the amorphous hard carbon film according to the present invention is mainly determined by the hydrogen content in the film. When the Vickers hardness is 1800 or less, the abrasion resistance is poor, and when the Vickers hardness is 2500 or more, the film is easily chipped. Therefore, Hv1800-25
00 is preferred. More preferably Hv1 with Vickers hardness
A range of 900 to 2400 is desirable. If the thickness of the film is less than 2 μm, sufficient abrasion resistance cannot be obtained.
Above, it is easy to peel off due to the stress of the film.
0 μm is preferred. Subsequently, the film formation site for each sliding member is at least one of an outer peripheral surface, an inner peripheral surface, a side surface, and a spacer ear portion in the case of a piston ring, and at least a tip of the vane in the case of a compressor vane. At least one of the R surface and the side surface, and in the case of a plunger for a fuel injection pump, at least the outer peripheral surface of the plunger. The base material such as the piston ring, the vane and the plunger may be a conventionally used material. When the amorphous hard carbon film is formed at a necessary portion of the sliding member, the amorphous hard carbon film may be formed directly on the underlying metal, or may be formed of a Ni— layer in which hard particles such as a nitride layer, a Cr plating film, and silicon nitride are dispersed. It can also be formed on a Co-P-based composite dispersion plating film, an ion plating film of CrN, TiN, or the like.

Such an amorphous hard carbon film containing carbon and hydrogen as main components and a metal oxide can be obtained by introducing a carbon material, a metal-containing material and an oxygen material into a vacuum chamber in which a sliding member is installed. It can be formed on the surface of the sliding member. Examples of the film forming method include an RF plasma CVD method, an ion beam evaporation method, an ion plating method, and a vacuum arc method. Hereinafter, an example of the RF plasma CVD method will be described.

As the carbon source gas, a hydrocarbon gas such as methane and acetylene can be used. Examples of the metal-containing source gas include tetramethylsilane, tetraethylsilane, tetramethoxysilane, tetraethoxysilane, triethoxyboron, boron trifluoride, and tetra-i.
-Titanium propoxy, tungsten hexafluoride or the like can be used. Note that the sliding member is not heated during the film formation. The temperature of the sliding member rises due to exposure to the plasma, but is 200 ° C. or less.

[0013]

The amorphous carbon film containing the metal oxide formed on the surface of the sliding member in this manner has good adhesion to the sliding member, high hardness and low friction coefficient. Also shows excellent performance in abrasion resistance in sliding with materials. By forming such an amorphous hard carbon film containing a metal oxide at a position where the sliding member comes into contact with or slides against a mating material, sufficient wear resistance can be ensured even under severe sliding conditions. Can be.

In particular, the amorphous hard carbon film according to the present invention has a feature that, unlike the conventional amorphous hard carbon film, it contains a metal oxide, so that a friction coefficient lower than that of the conventional hard carbon film can be obtained. This property was considered as follows.
For example, in a conventional amorphous hard carbon film containing silicon, the film hardness and the friction coefficient are considered to depend on the amount of carbon in the film and the bonding state and the bonding state depending on the hydrogen concentration in the film. We focused on the bonding state of Carbon forms sp2 bonds (graphite structure) and sp3 bonds (diamond structure) by bonding with each other or with hydrogen. The amorphous hard carbon film according to the present invention has a broad G around 1550 cm −1 as measured by Ar laser Raman spectroscopy.
(Graphite) has been confirmed to have structural features with the peak as a sub-peak, including sp2 and sp3 bonds,
That is, the structure has a mixture of a graphite structure and a diamond structure.

Focusing on the bonding state of the elements in the film, it is considered that elemental silicon bonds with carbon to form a stable carbide, but partially unbonded electrons may remain as dangling bonds. It is considered that the film becomes unstable structurally and affects the hardness and the coefficient of friction of the film. If there is a dangling bond inside the film, the abrasion proceeds by sliding and the inside of the film is exposed to the atmosphere, and when exposed to the atmosphere, a chemical reaction due to interaction with the atmosphere, for example, the oxidation reaction of the surface proceeds in an oxidizing atmosphere, It is believed that the reaction proceeds until the surface reaches a chemically stable state. Therefore, in the present invention, a small amount of oxygen is introduced when an amorphous hard carbon film to which a metal element is added is generated from plasma in a vacuum, and a metal element that has not become a safe carbide is combined with oxygen to form an oxide. The focus was on achieving a stable binding state by performing the following. Although the example of the silicon oxide has been described above, in the case of Ti or the like, the same effect can be expected by using Ti which is not combined with carbon as the oxide as TiC.

As described above, the amorphous hard material having both the low friction property due to the graphite structure and the hard property due to the diamond structure and the Si—C bond, and having a stable bonding state by adding a small amount of oxygen. The present inventors have devised an amorphous hard carbon film containing a metal oxide according to the present invention as a film capable of obtaining stable low friction with a carbon film.

FIG. 7 shows the effect of reducing the coefficient of friction of a film obtained by adding oxygen during the formation of an amorphous hard carbon film containing silicon. By adding a small amount of oxygen,
It can be seen that the coefficient of friction has been reduced. As a result of examining the silicon content and the state of the film by X-ray photoelectron spectroscopy (XPS) for such a film, silicon is less than 4 atomic% and is mainly bonded to carbon to form a Si—C bond. It was confirmed that some silicon was bonded to oxygen to form an oxide of SiOx. In other words, from this fact, the silicon that is not stable carbide in the amorphous hard carbon film containing silicon is converted into an oxide by adding oxygen to form a stable bonding state, whereby the friction is increased. It was shown that the coefficient was reduced.

[0018]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a film forming method for a piston ring and a vane will be described.

Embodiment 1 (Piston Ring) FIG. 1 shows an embodiment in which the present invention is applied to a piston ring. As described above, the hatched portions of the outer peripheral surface 1a, the inner peripheral surface 1b, and the side surface 1c of the rail 1
An amorphous hard carbon film 2 containing a metal oxide is formed by a plasma CVD method. Also, an amorphous hard carbon film 2 containing a metal oxide is formed on a lug 4 where the spacer 3 is in contact with the rail 1.

In order to form the amorphous hard carbon film according to the present invention on the piston ring, the piston ring 42 which has been nitrided and cleaned in a vacuum chamber 41 (FIG. 41) is subjected to RF.
An exhaust port 4 is provided on an electrode plate 44 connected to a power supply 43.
Vacuum chamber 1 by a vacuum pump (not shown) connected to
The inside was evacuated to about 5.25E-8Pa. Next, while continuously exhausting the inside of the vacuum chamber 41, Ar gas is introduced from the gas inlet 46 to adjust the pressure in the vacuum chamber 41 to about 7.5E-5Pa, and RF power is supplied from the RF power supply 43 to the piston. The plasma discharge was excited in addition to the ring 42 to clean the piston ring surface. Subsequently, the flow of Ar gas is stopped, a carbon source gas, a metal-containing source gas, and an oxygen source gas are introduced into the vacuum chamber 41, and RF power is applied again to excite plasma discharge, thereby nitriding the piston ring surface. An amorphous hard carbon film containing a metal oxide was formed on the layer to a thickness of 10 μm. Acetylene is used as the carbon source gas,
Tetramethylsilane was used as the metal-containing source gas. Table 1 shows film forming conditions including a comparative example.

[0021]

[Table 1]

The piston ring was not heated during the film formation. When the piston ring is exposed to the plasma, the temperature of the piston ring rises due to the impact of the collision of electrons and ions in the plasma.
It was not heated to a temperature above ° C. In the case of FIG. 4 in which the piston rings 42 are stacked and placed on the electrode plate 44, an amorphous hard carbon film is formed only on the outer peripheral surface of the piston ring. On the other hand, when a plurality of piston rings 42 are arranged at regular intervals on a cylindrical jig 50 as shown in FIG. 5, an amorphous hard carbon film must be formed on the outer peripheral surface and side surfaces of the piston ring. Can be. In addition, as shown in FIG. 6, when the plurality of piston rings 42 are disposed so as to be supported from the inner peripheral side by three support rods 60 at regular intervals,
An amorphous hard carbon film can be formed on the outer peripheral surface, the side surface, and the inner peripheral surface (excluding a portion shaded by the support rod) of the piston ring.

As shown in FIG. 4, the piston rings were stacked, and an amorphous hard carbon film was formed on the outer peripheral surface under the conditions shown in Table 1. The friction loss of the piston ring thus surface-treated was measured by a motoring test. The mating material is a FC250 cylinder liner with a rotation speed of 100 rpm. Oil is low viscosity oil (40 ℃, 5cS
t). The result is shown in FIG.

Comparative Example 1 For comparison, the friction loss was measured under the same conditions as in Example 1 without using any film-forming surface treatment on the same nitrided piston ring used in Example 1. The results are also shown in FIG.

Comparative Example 2 For comparison, a friction loss was compared under the same conditions as in Example 1 except that a chromium plating layer was formed on the same nitrided piston ring used in Example 1 to a thickness of about 20 μm. .
The results are also shown in FIG.

Comparative Example 3 For comparison, an amorphous hard carbon film containing only silicon as a carbide without adding oxygen during film formation was formed on the outer peripheral surface of the piston ring to a thickness of about 10 μm. FIG. 8 also shows the result of measuring the friction loss of the piston ring having such a film formed thereon. As is clear from FIG. 8, the piston ring according to the first embodiment has a 11.6% reduction in friction loss as compared with the comparative example 1 having only the nitrided layer. This value is about 8% lower than that of the nitride + chromium plating of Comparative Example 2. Also, the friction loss of the first embodiment is reduced by about 3.2% with respect to the amorphous hard carbon film of the third comparative example in which silicon is present only as a carbide without adding oxygen. That is, from this result, by adding a small amount of oxygen to an amorphous hard carbon film containing silicon, structurally unstable silicon that is not completely carbide in the film is converted into an oxide, and more stable silicon is obtained. Since the amorphous hard carbon film of the present invention in the form of an oxide and in a more stable bonding state can realize a lower friction coefficient, the friction loss can be reduced as compared with the amorphous hard carbon film in which the oxide is not formed. It was shown that.

Embodiment 2 (Vane) FIG. 2A is a perspective view of a compressor vane 20 (base material is SKH51). FIG. 2 (B) shows the vane 20.
The amorphous hard carbon film 2 containing silicon oxide was formed on the tip R surface 20b and four side surfaces by RF plasma CVD in the same manner as described above. Table 2 shows the manufacturing conditions of Example 2 and Comparative Example.

[0028]

[Table 2]

As shown in FIG. 2B, when an amorphous hard carbon film is formed on the surface of the vane 20 except for the bottom surface 20c, the vane is placed on the electrode plate 44 in the apparatus shown in FIG. Stand vertically at regular intervals. An abrasion resistance evaluation test of a vane in which an amorphous hard carbon film containing a metal oxide was coated on the tip R surface 20b and four side surfaces as shown in FIG. 2 was performed. The partner material is FC250 material, load 9
8.1 N / mm, sliding speed 0.5 m / sec. For 4 hours. FIG. 9 shows the result.

COMPARATIVE EXAMPLE 4 For comparison, a vane without the surface treatment for film formation was prepared on the same SKH51 as used in Example 2, and the wear resistance was compared. The results are also shown in FIG.

Comparative Example 5 For comparison, a vane having a CrN film formed to a thickness of about 5 μm on the same SKH51 as used in Example 2 by an ion plating method was prepared, and the wear resistance was compared. The results are also shown in FIG.

COMPARATIVE EXAMPLE 6 For comparison, an amorphous hard carbon film containing only silicon as a carbide without adding oxygen during film formation was applied to a vane by about 10 μm.
It was formed in thickness. FIG. 9 also shows the results of comparative evaluation of the wear resistance of the vane on which such a film was formed.

As is clear from FIG. 9, unprocessed SKH5
1 (Comparative Example 4) had the largest abrasion loss, and the oxygen hardened amorphous hard carbon film (Comparative Example 6) had the second largest abrasion loss. Example 2 was based on the ion plating of Comparative Example 5. It can be seen that the wear amount is very small, equivalent to that of the CrN film. Further, focusing on the friction coefficient as shown in Table 2, Example 2 has a lower friction coefficient than the comparative example. That is, from this result, by adding a slight amount of oxygen to the amorphous hard carbon film containing silicon, the structurally unstable silicon that is not completely carbide in the film is converted into an oxide, and a more stable It was shown that the amorphous hard carbon film in the bonded state exhibited better wear resistance than the amorphous hard carbon film on which no oxide was formed, and in addition, a low friction coefficient could be realized.

Embodiment 3 (Plunger) FIG. 3 is a sectional view of a fuel injection pump plunger (material equivalent to SKD11). RF plasma C is applied to the outer peripheral portion 30a of the plunger 30 in the same manner as described above.
Amorphous hard carbon film 2 containing silicon oxide by VD method
Was formed. With the device shown in FIG. 4, one end of the plunger is held and a plurality of the plungers are aligned on the electrode plate 44 at a constant interval. Amorphous hard carbon film with a thickness of 10
μm was formed. A test for evaluating seizure resistance under gasoline lubrication was performed using such a plunger. Sliding speed 8m /
The operation was performed up to a load condition of max. Table 3
Showed the result.

[0035]

[Table 3]

COMPARATIVE EXAMPLE 7 For the purpose of comparison, the same seizure resistance of the plunger which was not subjected to the film-forming surface treatment on SKD11 used in Example 2 was tested in the same manner as in Example 2. The results are shown in Table 3.

Comparative Example 8 For the purpose of comparison, the seizure resistance of a plunger made of a Ni-Co-P-based plating film containing boron on the same SKD11 used in Example 3 by a composite dispersion plating method was implemented. Tested in the same manner as in Example 3. The results are shown in Table 3.

Comparative Example 9 For comparison, an amorphous hard carbon film in which silicon was present only as a carbide without adding oxygen during film formation was formed in a plunger to a thickness of about 10 μm. Table 3 also shows the results of comparative evaluation of the seizure resistance of the plunger having such a film formed thereon.

As is clear from the seizure load values shown in Table 3, SKD1 without any film-forming surface treatment was used.
With the plunger No. 1, burn-in occurs near 10 MPa. Further, in a Ni—Co—P plating film containing boron, image sticking occurs at about 20 MPa. Further, in the amorphous hard carbon film containing no silicon oxide, seizure occurs at about 22 MPa, but in the amorphous hard carbon film containing silicon oxide, no seizure occurred up to the maximum load of 25 MPa. In other words, from this fact, by adding a small amount of oxygen to an amorphous hard carbon film containing silicon, structurally unstable silicon that is not completely carbide in the film is converted into an oxide, and a more stable bonding state is obtained. It has been shown that the amorphous hard carbon film of the present invention can achieve better seizure resistance than an amorphous hard carbon film having no oxide formed.

[0040]

The sliding member used for severe sliding conditions for automobiles and home appliances does not use an expensive heat-resistant material such as a Ni or Co material and can be used as a mating material for the sliding member. By forming an amorphous hard carbon film containing a metal oxide in a low-temperature atmosphere near room temperature at the site where it contacts or slides,
There is no decrease in dimensional accuracy due to thermal deformation of the base material, and it is possible to easily form a uniform, high-adhesion film with good adhesion.
This greatly improves the wear resistance and seizure resistance of the sliding member, and reduces the friction loss by coating the sliding part of the piston ring, vane, and plunger with a film with low friction coefficient and high hardness. Reduced, abrasion and seizure resistance are improved, and durability is improved. In addition, since a metal oxide that reduces the coefficient of friction is contained in the film in advance, a low coefficient of friction can be obtained even in an oxidizing atmosphere or in a vacuum.

[Brief description of the drawings]

FIG. 1 is a sectional view of a piston ring to which the present invention is applied.

FIG. 2A is a perspective view of a compressor vane to which the present invention is applied, and FIG. 4B is a cross-sectional view of the vane.

FIG. 3 is a sectional view of a plunger for a fuel injection pump to which the present invention is applied.

FIG. 4 is a view showing an outline of an RF plasma CVD apparatus for forming an amorphous hard carbon film according to the present invention.

FIG. 5 shows an outer peripheral surface of a piston ring to which the present invention is applied;
FIG. 4 is a diagram showing a method in a case where an amorphous hard carbon film is formed on a side surface.

FIG. 6 is a view showing a method of forming an amorphous hard carbon film on the outer peripheral surface, the side surface, and the inner peripheral surface of the piston ring to which the present invention is applied.

FIG. 7 is a graph showing a relationship between an oxygen flow rate and a friction coefficient.

FIG. 8 is a graph showing frictional losses of Examples and Comparative Examples.

FIG. 9 is a graph showing the amount of vane wear in Examples and Comparative Examples.

[Explanation of symbols]

 1. Rail 2. Amorphous hard carbon film containing metal oxide 3. Spacer 4. Ears 20 Vane 30 Plunger

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) // F02F 5/00 F04B 21/04 C F-term (Reference) 3G066 AA07 AB02 BA00 BA49 CA09 CD15 CD21 3H040 AA03 BB11 CC14 DD11 DD36 DD40 3H071 BB02 CC26 DD01 EE05 EE06 3J011 DA01 QA04 SE02 SE10 4K030 AA06 AA09 BA27 BB05 CA02 FA03 JA01 JA06 LA23

Claims (7)

[Claims] 1. A sliding member characterized in that an amorphous hard carbon film containing carbon and hydrogen as main components and a metal oxide is formed on a portion which is relatively in contact with or slidingly contacts with a counterpart member. 2. The method according to claim 1, wherein the metal oxide is Si, Ti, B and W.
The sliding member according to claim 1, wherein the sliding member is an oxide of at least one element selected from the group consisting of: 3. The sliding member according to claim 1, wherein the amorphous hard carbon film has a Vickers hardness of 1800 to 2500. 4. The amorphous hard carbon film having a thickness of 2 to 15
The sliding member according to any one of claims 1 to 3, wherein the thickness of the sliding member is μm. 5. The amorphous hard carbon film according to claim 1, which is formed on at least one of an outer peripheral surface, an inner peripheral surface, a side surface, and a spacer ear of a piston ring. A piston ring characterized by the above-mentioned. 6. An amorphous hard carbon film according to any one of claims 1 to 4, wherein at least a tip R
A compressor vane formed at one or more locations on a surface and a side surface. 7. A plunger for a fuel injection pump, wherein the amorphous hard carbon film according to any one of claims 1 to 4 is formed at least on an outer peripheral surface.